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048636789	claims	1. A pressurized water reactor vessel, the vessel defining a predetermined axial direction of the flow of coolant therewithin and having plural spider assemblies supporting, for vertical movement within the vessel, respective clusters of rods in spaced, parallel axial relationship, parallel to the predetermined axial direction of coolant flow, and a rod guide for each spider assembly and respective cluster of rods, the rod guide having horizontally oriented support plates therewithin, each plate having an interior opening for accommodating axial movement therethrough of the spider assembly and respective cluster of rods, the opening defining plural radially extending channels and corresponding parallel interior wall surfaces of the support plate, the spider assembly comprising: a hub of elongated configuration and defining a central axis, for positioning parallel to the predetermined axial direction of coolant flow; control rod mounts for the respectively corresponding control rods of the cluster; and a vane assembly integrally connecting the control and mounts to the hub, the vane assembly comprising plural, planar vane elements, at least a predetermined number thereof being affixed to and extending radially from the hub and oriented so as to be received through respectively corresponding channels in each support plate, each said radially extending vane element having parallel, spaced major planar surfaces which are contiguous to the respective interior wall surfaces of the support plate defined by the radially extending channels when the vane element is received therewithin, said parallel, spaced major planar surfaces defining a plane of symmetry therebetween parallel to the central axis of the hub and each said vane element having a leading edge and a trailing edge relative to and extending transversely of the axial direction of coolant flow, the leading edge having a cross-sectional configuration in a plane perpendicular to the major parallel planar surfaces which is non-symmetrical relative to the plane of symmetry, the respective flow stagnation lines of the radially extending vane elements being off-set from the respective planes of symmetry thereof in a commonly oriented direction and producing in response to the coolant flow thereover a torsional load bias on the hub in a predetermined orientation for engaging the commonly oriented, spaced, major planar surfaces of the plural radially extending vanes against the respective, commonly oriented and contiguous interior wall surfaces of the support plate defined by the corresponding channels. 2. A pressure vessel having plural spider assemblies as recited in claim 1, wherein the trailing edge of each vane element of each spider assembly is of square cross-sectional configuration in a plane transverse to the major planar surfaces thereof and parallel to the direction of coolant flow. 3. A pressure vessel having spider assemblies as recited in claim 1, wherein each vane element leading edge of each spider assembly is of a non-symmetrical, convex cross-sectional configuration. 4. A pressure vessel having spider assemblies as recited in claim 1, wherein each vane element leading edge of each spider assembly cross-section defines a single acute angle with respect to one of the major planar surfaces thereof. 5. A pressure vessel having spider assemblies as recited in claim 1, wherein each vane element leading edge of each spider assembly cross-section defines double acute angles with respect to the respective planar surfaces. 6. A pressure vessel having spider assemblies as recited in claim 1, wherein each vane element leading edge of each spider assembly cross-section defines a truncated acute angle with respect to one of the major planar surfaces thereof.
	summary
	abstract	A method of manufacturing an integrated circuit (IC) device includes forming a photoresist layer on a substrate, and exposing the photoresist layer to light by using a photolithographic apparatus including a light generator. The light generator includes a chamber having a plasma generation space, an optical element in the chamber, and a debris shielding assembly between the optical element and the plasma generation space in the chamber, and the debris shielding assembly includes a protective film facing the optical element and being spaced apart from the optical element with a protective space therebetween, the protective space including an optical path, and a protective frame to support the protective film and to shield the protective space from the plasma generation space.
050857096	abstract	Natural gas processing equipment and sorption media such as charcoal, silica or alumina, contaminated with adherent scale deposits of alkaline earth metal sulfates may include radioactive components, especially radium sulfate and thorium sulfate, which render the equipment radioactive. The scale is removed from the processing equipment by washing with an aqueous chemical composition including a polyaminopolycarboxylic acid such as EDTA or DEPA as a chelant in combination with a synergist, preferably oxalate or monocarboxylate acid anion such as salicylate. The washing may be carried out with the equipment in place or by immersion of the equipment in a body of the solution in a suitable treatment tank.
	claims	1. A wavefront information obtaining method comprising:receiving intensity information of a first periodic pattern and intensity information of a second periodic pattern having a phase shifted with respect to a phase of the first periodic pattern; andobtaining wavefront information,wherein the obtaining of the wavefront information obtains the wavefront information for one pixel by using:intensity information at a first pixel of the first periodic pattern;intensity information at a second pixel of the first periodic pattern, the second pixel being positioned within three pixels from the first pixel; andintensity information at the first pixel of the second periodic pattern. 2. The wavefront information obtaining method according to claim 1, wherein the obtaining of the wavefront information obtains the wavefront information by applying:the intensity information at the first pixel of the first periodic pattern;the intensity information at the second pixel of the first periodic pattern; andthe intensity information at the first pixel of the second periodic pattern,to a formula based on a phase shifting method on condition that those pieces of intensity information are regarded as pieces of intensity information at the first pixel of different periodic patterns. 3. The wavefront information obtaining method according to claim 1, wherein the obtaining of the wavefront information obtains the wavefront information by applying:the intensity information at the first pixel of the first periodic pattern;the intensity information at the second pixel of the first periodic pattern; andthe intensity information at the first pixel of the second periodic pattern,to a formula based on a phase shifting method on condition that those pieces of intensity information are regarded as pieces of intensity information at the first pixel or the second pixel of different periodic patterns. 4. The wavefront information obtaining method according to claim 3, wherein the obtaining of the wavefront information obtains wavefront information for one pixel by using:the intensity information at the first pixel of the first periodic pattern;the intensity information at the second pixel of the first periodic pattern;the intensity information at the first pixel of the second periodic pattern; andintensity information at the second pixel of the second periodic pattern. 5. The wavefront information obtaining method according to claim 3, wherein the first pixel and the second pixel are adjacent to each other in the first and second periodic pattern. 6. The wavefront information obtaining method according to claim 1, wherein the obtaining of the wavefront information obtains the wavefront information by taking Fourier transform of a composite periodic pattern of an intensity distribution having:an intensity at the first pixel of the first periodic pattern;an intensity at the second pixel of the first periodic pattern; andan intensity at the first pixel of the second periodic pattern. 7. The wavefront information obtaining method according to claim 6, wherein, in the composite periodic pattern,the intensity at the first pixel of the first periodic pattern andthe intensity at the first pixel of the second periodic pattern are positioned within three pixels. 8. The wavefront information obtaining method according to claim 1, wherein the wavefront information is information regarding at least one of a phase, a differential phase, an amplitude, and scattering of a wavefront of light which forms the first and second periodic pattern. 9. The wavefront information obtaining method according to claim 1,wherein the obtaining of the wavefront information obtains wavefront information for a plurality of pixels. 10. The wavefront information obtaining method according to claim 9, further comprisingtransmitting, to a display apparatus, image data of the wavefront information for a plurality of pixels. 11. The wavefront information obtaining method according to claim 1, wherein the periodic pattern is an interference pattern or a moiré. 12. The wavefront information obtaining method according to claim 1, wherein the periodic pattern is an X-ray periodic pattern. 13. A non-transitory computer-readable medium storing a program for causing a computer to execute the wavefront information obtaining method according to claim 1. 14. A wavefront information obtaining method comprising:receiving intensity information of a first periodic pattern, a second periodic pattern having a phase shifted in a first direction with respect to a phase of the first periodic pattern, and a third periodic pattern having a phase shifted in a second direction with respect to the phase of the first periodic pattern, the second direction crossing the first direction;obtaining shearing wavefront information in the first direction; andobtaining shearing wavefront information in the second direction,wherein the obtaining the shearing wavefront information in the first direction obtains the shearing wavefront information in the first direction for one pixel by using:intensity information at a first pixel of the first periodic pattern;intensity information at the first pixel of the second periodic pattern; andintensity information at a second pixel of the first periodic pattern or the second periodic pattern, the second pixel being positioned within three pixels from the first pixel, andwherein the obtaining the shearing wavefront information in the second direction obtains the shearing wavefront information in the second direction for one pixel by using:the intensity information at the first pixel of the first periodic pattern;intensity information at the first pixel of the third periodic pattern; andintensity information at a third pixel of the first periodic pattern or the third periodic pattern, the third pixel being positioned within three pixels from the first pixel. 15. A non-transitory computer-readable medium storing a program for causing a computer to execute the wavefront information obtaining method according to claim 14. 16. A computation apparatus configured to obtain wavefront information comprising:a unit configured to receive intensity information of a first periodic pattern and intensity information of a second periodic pattern having a phase shifted with respect to a phase of the first periodic pattern; anda unit configured to obtain wavefront information for one pixel in wavefront information distribution by using:intensity at a first pixel of the first periodic pattern;intensity at a second pixel of the first periodic pattern, the second pixel being positioned within three pixels from the first pixel; andintensity at the first pixel of the second periodic pattern.
053751507	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Outline of Contents I. Overview Description of Control Complex PA1 II. Panel Overview PA1 III. DIAS PA1 IV. DPS PA1 V. Control Room Integration PA1 VI Panel Modularity PA1 APPENDIX (Validity Algorithm) PA1 Pump A hollow pump indicates that the pump has been activated by the operator to automatic control signal. A solid pump indicates that the pump has been deactivated by the operator or automatic control signal. PA1 Valve A hollow valve indicates that the valve is fully open and a solid valve indicates that the valve is fully closed. A valve not fully open or closed has a mixed solid/hollow shape, i.e., left side solid/right ride hollow. PA1 Valve Open and Operable--Red Color Coding. PA1 Valve Closed and Operable--Green Color Coding. PA1 Non-Instrumented Valve--Grey Color Coding (Position is Operator Inputted). PA1 Valve Not Operable--Grey Color Coding with Alarm Coding. PA1 Loss of Indication--Grey Color Coding with Alarm Coding and mixed hollow/solid shape. PA1 Level 1 Display Page--"Critical Functions: this page provides more detail on the critical function matrix presented on IPSO. Specifically, more detail on alarm conditions (descriptor, priority). This will help guide the operator to the appropriate level two critical function display page. PA1 The critical function information provided on the 1st level display page that is associated with the critical function. PA1 Information related to success path availability and performance of the success paths that can support that critical function. PA1 High level information presented using a mimic format with the critical function/success path related information. PA1 A time trend of the most representative critical function parameter. PA1 1. RCP 1A PA1 2. RCP 1B PA1 3. RCP 2A PA1 4. RCP 2B PA1 5. RCP SealBleed PA1 6. RFCS PA1 7. .sup.T hot PA1 8. .sup.T cold PA1 9. Pressurizer Pressure PA1 10. Pressurizer Level PA1 1. When validation fails and a "FAULT SELECT" sensor is selected for the "process representation". PA1 2. When the "Valid" output does not correlate to the PAMI sensor(s). PA1 1. The "process representation" is always displayed on the applicable DIAS display and/or CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. Each plant process parameter will be evaluated individually to determine the type of display required and location (DIAS and CRT or CRT only). PA1 2. The "process representation" is always a "valid" value unless there is a: PA1 3. The "process representation" is always used for alarm calculations and trending (where a single value is normally trended). This can be "valid", "fault select" or "operator select" data, depending on the results of the algorithm calculations as described below. PA1 4. Using a menu on DIAS or the CRT, the operator may view any of the values (A, B, C, D or calculated output) without changing the "process representation". PA1 5. A "Fault Select" value will be displayed automatically as the "process representation" when the validation algorithm is unable to yield "valid" data. The "fault select" value is the output of the sensor closest to the last "valid" signal at the time validation initially failed. On DIAS (if applicable), this information will be labeled "fault select". On the CRT(s) graphic pages, this information is preceded by an asterisk () to indicate suspect data. The "fault select" "process representation" is automatically returned to a "valid" "process representation" when the validation algorithm is able to calculate "valid" data. PA1 6. An "operator select" sensor may be selected for the "process representation" only when there is a: PA1 The "operator select" "process representation" will replace the "valid" or "fault select" "process representation". On DIAS (if applicable), this information will be labeled "operator select". On the CRT(s), this information will be preceded by an asterisk () on graphic displays and labelled "operator select" in the data base. The "operator select" "process representation" is automatically replaced by the calculated "valid" signal when both the "Validation Fault" and the "PAMI Fault" clear. PA1 1. Conditions that may cause a trip in less than 10 minutes. PA1 2. Conditions that may cause major equipment damage. PA1 3. Personnel/Radiation hazard. PA1 4. Critical Safety Function violation. PA1 5. Immediate Technical Specification Action Required. PA1 6. First-Out Reactor/Turbine Trip. PA1 1. Conditions that may cause a trip in greater than 10 minutes. PA1 2. Technical specification action items that are not Priority 1. PA1 3. Possible equipment damage. PA1 1. Sensor deviations. PA1 2. Equipment status deviations. PA1 3. Equipment/process deviations not critical to operation. PA1 1. Normal operation PA1 2. Heatup/cooldown. PA1 3. Cold shutdown/refueling. PA1 4. Post-trip. PA1 1. Unacknowledged Alarm--If there is an unacknowledged alarm associated with an alarm tile, the alarm tile will flash at a fast rate (i.e., 4 times/sec using a 50/50 duty cycle as depicted by the long rays in FIG. 9). This condition takes precedence over all other alarm tile states for group alarms. PA1 2. Cleared Alarm/Return to Normal (Reset Alarm)--When an alarm condition clears, the corresponding alarm tile flashes at a slow rate (i.e., 1 time/sec using a 50/50 duty cycle as depicted by the short rays in FIG. 9) until this condition has been acknowledged. This condition takes precedence over the remaining two states for grouped alarms. PA1 3. Alarm--If an alarm condition exists and alarm states 1 and 2 above do not exist, then the alarm tile is lit without flashing (as depicted by the absence of rays in FIG. 9). PA1 4. No Alarm--If thee is no alarm condition associated with an annunciator tile, then the alarm tile is not lit (not depicted in FIG. 9). To indicate that the alarm tile's bulb is functioning, a lamp test feature is provided. PA1 A) First Level Display Page Set (Major Plant System/Function Groupings 142) PA1 B) Control Room Workstation 144 PA1 C) Alarm tiles 146 PA1 1) The operator selects the "Alarm List" menu option 140 (FIG. 4) followed by the "Elec." menu option 148 (FIG. 12). This accesses the categorized alarm listing of the type shown in FIG. 14 beginning with the electrical alarms. PA1 2) If the operator wishes to view alarms associated with a specific alarm, e.g., RCP1A, he selects the following menu options from page 84 (FIGS. 4 and 12): PA1 A. Categorized Alarm List--The operator selects "Alarm List" followed by the tile, e.g., "RCP1A", menu option. The categorized alarm list is accessed with RCP1A alarms at the top of the page. PA1 B. Alarm Messages--The operator can use the alarm tile menu options in the same method that the control panel alarm tiles are used. The selection of an alarm tile menu option provides the alarm message and a menu with display pages that can provide supporting information about the alarm condition. PA1 1) Alarm acknowledgement via the annunciator tiles--Alarms can be acknowledged by depressing alarming/unacknowledged annunciator tiles or a CRT annunciator tile representation. This action changes the annunciator tile from a flashing condition to a solid condition when all alarm conditions associated with the tile have been acknowledged and silences any audible sound (described later) associated with the alarm condition. Alarm messages are viewed in the message window (when using the physical tile) and the workstation's CRT message line (see FIG. 16). PA1 2) Alarm acknowledgement using alarm listing pages--Alarms can be acknowledged on the categorized listing by touching alarm tile touch targets associated with the alarm tile categories (see FIG. 14). Upon touching the alarm tile's representation, all alarms associated with that tile are acknowledged. This means of alarm acknowledgement may be the most useful for acknowledging multiple alarms remote to the operator's location. PA1 1. Unacknowledged Priority 1 or 2 Alarms. PA1 2. An Alarm Reminder Tone for Priority 1 or 2 Unacknowledged or Cleared Conditions. PA1 3. Cleared Priority 1 Alarms, or Cleared Priority 2 Alarms. PA1 All new/unacknowledged priority 2, 3 and operator aid features change from a fast flash rate to a steady highlighted condition, i.e., tiles and CRT alarm representations. PA1 Any cleared alarm conditions, i.e., slow flash rate, are not presented as alarm information. PA1 Any new alarm condition or cleared alarm condition coming in after the "STOP FLASH" button has been activated, is normally displayed to the operator (i.e., flashing). However, the operator may redepress the alarm "STOP FLASH" button to suppress these conditions. PA1 1) Primary Systems (example, see FIG. 19) PA1 2) Secondary Systems PA1 3) Power Conversion PA1 4) Electrical Systems PA1 5) Auxiliary Systems PA1 6) Critical Functions PA1 1) The next higher level (when applicable display page in the hierarchy, item (c). This feature is more meaningful on a 3rd level display page since the next higher level page is a level 2 display page which is not normally on the menu. PA1 2) Display pages of systems that are connected to or support the process of the presently displayed page (h,i). PA1 3) All six fist level display pages (b, c, d, e, f, g). PA1 4) The IPSO display page (a). PA1 5) The last page viewed on the monitor (j). PA1 (1) Display Page Access Using Alarm Tiles--This mechanism for display page access may be most useful for obtaining display pages associated with the workstation's process. By pressing a workstation alarm tile from display 78, such as 80 (FIG. 15), region 4 of the workstation CRT's display page menu changes to a new menu with display page options associated with the alarm tile's descriptor. For example, as shown in FIG. 23 an RCP1A alarm tile provides menu options associated with RCP 1A. The desired display page will then be a direct access menu option. PA1 (2) Accessing CRT Information from the Discrete Indicators--Each discrete indicator 82 such as shown in FIG. 7, has a CRT access touch target 158. This button provides for access to supporting information for the process parameter that is presently displayed on the discrete indicator. By touching the CRT target on the discrete indicator, region 4 of the menu options on the workstation's CRT changes to menu options containing display pages with supporting and diagnostic information associated with the process parameter. PA1 (3) Display Page Access Using a Display Page Directory--Any display page of the display page hierarchy can be accessed using the presently displayed menu. For example, if the operator is viewing the Feedwater System display page and wants to access the CVCS display page, the following sequence takes place (refer to FIGS. 22 and 4): The operator selects "by touch" the "DIRECTORY" menu option (option 1 in region 2 on FIG. 22) followed by the "PRIMARY" menu option (option b in region 3 on FIG. 22). This accesses the primary section of the display page hierarchy from the display page library (see FIG. 4). Each display page within the primary section of the display page within the primary section of the display page hierarchy is a touch target on this display page, and now the operator can select the CVCS display page. Any page in the display page hierarchy can be accessed using this feature. The "DIRECTORY" menu option is followed by the desired hierarchy associated with one of the six fist level display pages, menu options b, c, d, e, f or g on FIG. 22. PA1 Failure to satisfy the safety function status checks, (post-trip). PA1 Poor performance of a success path/system that is being used to support a critical function. PA1 An undesirable priority 1 deviation in a power production function (pre-trip). PA1 Unavailability of a safety system (less than minimum availability as defined by Reg. Guide 1.47). PA1 (a) Feedwater and Condensate System Status Information (i.e., operational status, alarm status) PA1 (b) Steam Generator Levels, Dynamic Representation PA1 (c) Steam Generator Safety Valve Status PA1 (d) Atmospheric Dump Valve Status PA1 (e) Main Steam Isolation Valve Status PA1 (f) Turbine Bypass System Status PA1 (a) Plant net electric output, digital value. PA1 (b) Alarm information for deviations in important processes associated with the main turbine and turbine generator. PA1 (c) Power distribution operational and alarm status to the plant busses and site grid. PA1 (a) Circulation water system status. PA1 (b) Alarm information for critical deviations in condenser pressure conditions. PA1 Containment Isolation Actuation PA1 Safety Injection Actuation PA1 Main Steam Isolation PA1 Containment Pure Isolation PA1 High Containment Airborne Radiation PA1 High Activity Associated, with Any Release Path PA1 High Coolant Activity PA1 (a) Diesel Generator Status PA1 (b) Status of Power Distribution within the Power Plant PA1 (c) Instrument Air System Status PA1 (d) Service Water System Status PA1 (e) Component Cooling Water System Status PA1 CCW--Component Cooling Water PA1 CD--Condensate PA1 CI--Containment Isolation PA1 CS--Containment Spray PA1 CW--Circulating Water PA1 EF--Emergency Feedwater PA1 FW--Feedwater PA1 IA--Instrument Air PA1 SDC--Shutdown Cooling PA1 RCS--Reactor Coolant PA1 SI--Safety Injection PA1 SW--Service Water PA1 TB--Turbine Bypass PA1 Yes, go to step 2 PA1 No, go to step 5 PA1 If all deviation checks are satisfactory do the following: PA1 If any deviation checks are unsatisfactory, the following occurs: PA1 * If the first pass, the algorithm is repeated, beginning at step 1. PA1 * If the second pass validation fails, go to step 5. PA1 Does the "valid" signal deviation check against the PAMI sensor(s). PA1 a. Yes, Output the "PAMI" message and if not previously present, remove the "PAMI Fault Operator Select Permissive", clear the "PAMI Fault" alarm if present, go to step 6. PA1 b. No, Perform the following: PA1 If the previous scan was not "fault select", a "validation fault" has just occurred. Do the following: PA1 If the previous scan was "fault select", validation had failed previously and already picked a "fault select" sensor. Continue to output the "fault select" sensor as the "calculated signal", go to step 6. PA1 If there is no Operator Select permissive, output the "calculated signal", as the "process representation", go to step 9. PA1 If there is an Operator Select permissive, go to step 7. PA1 Yes, output the signal from the selected sensor as the "process representation", go to step 8. PA1 No, output the "calculated signal" as the "process representation", go to step 9. PA1 Yes, output the "PAMI" message on the "process representation" display. PA1 No, remove the "PAMI" message on the "process representation" display. PA1 No, go to step 10 ("bad" sensor evaluations are not performed when the "process representation" is from a "fault select" sensor). PA1 Yes, Deviation check all "bad" sensors (A, B, C, D) against the "valid", or "operator select" signal by the following methods: PA1 Yes, Output the message "Out-of-Range" along with the "process representation" signal. On the CRT place an asterisk () preceding the "process representation". Go to step 1 and repeat the algorithm. PA1 No, go to step 1 and repeat the algorithm. PA1 1. Different numbers of sensors PA1 2. Multiple sensors ranges PA1 3. Data reduction in related process measurements. PA1 1. Determine a "process representation" temperature in each of the 4 cold legs (1A, 1B, 2A, 2B) through a combination of deviation checking and averaging (the details are described later). PA1 2. From the results in step 1 determine a T.sub.cold "process representation" for each RCS loop (loop 1 and loop 2) by averaging the corresponding A, B data. PA1 3. From the results in step 2determine a RCS T.sub.cold "process representation" for normal display and alarms by averaging loop 1 and 2 data. PA1 1. The leg 1A, 1B, 2A, 2B, loop 1, 2 and RCS T.sub.cold "process representation" shall always be displayed on the applicable DIAS display and/or CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. PA1 2. The T.sub.cold algorithm and display processing is identical to the generic validation algorithm with the following modifications: PA1 Note: To simplify the discussion of sensor tag numbers, the following letters will be used to designate sensors in a cold leg. PA1 The algorithms described below are calculated and displayed independently by both DPS and DIAS. PA1 1. Determination of "calculated signal" and faults, as described below (steps 1-8): PA1 2. "Process Representation" selection (steps 9, 10) (similar to steps 6 and 7 of the generic validation algorithm). PA1 3. PAMI Check of "operator select" sensor (Step 11) (identical to step 8 of the generic validation algorithm). PA1 4. Bad Sensor Evaluation and Range Check (step 12, 13) (similar to steps 9, 10 of the generic validation algorithm). PA1 Yes, go to step 2 PA1 No, go to step 5 PA1 2. The algorithm averages A and B, go to step 3. PA1 3. Deviation check both "good" narrow range sensors (A and B) against the average (within sum of 1/2 narrow range uncertainty and expected process variation). PA1 The average or selected sensor goes in-range at 96% and 4% of narrow range. PA1 The average or selected sensor goes out-of-range at 98% and 2% of narrow range. PA1 If in-range, clear the "Validation Fault" alarm, if present, disable the "Validation fault Operator Select Permissive", and output the average or selected narrow range sensor as the "valid" "calculated signal". Go to step 6. PA1 If out-of-range, attempt the wide range validation, go to step 7. PA1 If either sensor A or B passes the deviation check, the algorithm selects the sensor (A or B) that is closest to C. This sensor is selected of further checks. The sensor that deviates the most from sensor C is flagged as a "bad" sensor, if not previously "bad" and its associated sensor deviation alarm is generated if not previously generated. Go to step 4. PA1 If both A and B do not deviation check against C, go to step 7 and attempt wide range validation. PA1 If satisfactory, do the following: PA1 If unsatisfactory, do the following: PA1 If the deviation check is satisfactory, select C sensor as "valid", "calculated signal" and do the following: PA1 If the deviation check is unsatisfactory, validation fails, go to step 8. PA1 If the previous scan was not "fault select", a validation fault has just occurred. Do the following: PA1 If the previous scan was "fault select", validation had failed previously and the algorithm has already picked a "fault select" sensor. Continue to output the signal from the "fault select" sensor as the "calculated signal", go to step 9. PA1 If the deviation checks are satisfactory, clear the "T.sub.c Cold Leg (1A/1B or 2A/2B) Temp Deviation" alarm, if present, go to step 6. PA1 If either deviation check is unsatisfactory, generate the "T.sub.c Cold Leg (1A/1B or 2A/2B) Temp Deviation" alarm, go to step 6. PA1 Yes, output the average as narrow range, go to step 7. PA1 No, output the average as wide range, go to step 7. PA1 If either or both are out-of-range, output this T.sub.c loop "process representation" signal with the message "out-of-range", go to step 8. PA1 If both are in-range, this T.sub.c loop "process representation" is not output with the message, "out-of-range", go to step 8. PA1 Yes, output the "PAMI" message with the loop (1 or 2) T.sub.c "process representation", the loop T.sub.c algorithm is repeated, go to step 1. PA1 No, do not output the "PAMI" message with the loop (1 or 2) T.sub.c "process representation", the loop T.sub.c algorithm is repeated, go to step 1. PA1 The RCS T.sub.cold "process representation" will be calculated by averaging the "process representation" inputs from loop 1 and 2 T.sub.cold. PA1 No, output the "process representation" from step 2 as "fault select", go to step 6. PA1 Yes, output the "process representation" from step 2 as "fault select", go to step 6. PA1 No, output the "process representation" from step 2 as "operator select", go to step 6. PA1 These selections include the following: PA1 Yes, go to step 2 PA1 No, go to step 5 and attempt (0-1600 psig range validation) PA1 If all deviation checks are satisfactory, go to step 4 to see if the average is in range. PA1 If any deviation checks are unsatisfactory, the following occurs: PA1 The average goes in-range at 96% and 4% of narrow range. PA1 the average goes out-of-range at 98% and 2% of narrow range. PA1 If in-range, do the following: PA1 If out-of-range, attempt the (0-1600 psig) range validation, go to step 5. PA1 Yes, go to step 6. PA1 If all deviation checks are satisfactory, go to step 8to see if the average is in range. PA1 If any deviation checks are unsatisfactory, the following occurs: PA1 The average goes in-range at 96% and 4% of the 0-1600 psig range. PA1 The average goes out-of-range at 98% and 2% of the 0-1600 psig range. PA1 If in-range, do the following: PA1 If out-of-range, attempt the 0-4000 psig range validation, go to step 9. PA1 Yes, go to step 10. PA1 No, (0-4000 psig) range validation is not possible, go to step 13. PA1 If both deviation checks are satisfactory, do the following: PA1 If either deviation check is unsatisfactory, go to step 13. PA1 Yes, do the following: PA1 No, do the following: PA1 If the previous scan was not "fault select", a validation fault has just occurred, do the following: PA1 Yes, Output the message "Out-of-Range" along the "process representation" signal. On the CRT place an asterisk () preceding the "process representation". Go to step 1 and repeat the algorithm. PA1 No, go to step 1 and repeat the algorithm. A. Alarm and Messages PA2 B. Indicator PA2 C. CRT PA2 D. Controller PA2 E. Display Formats PA2 F. Display Integration PA2 A. Discreet Indicators PA2 B. Validity Algorithm Summary PA2 C. Alarm Processing and Display PA2 5. Determining Alarm Conditions PA2 6. Acknowledging Alarms PA2 A. CRT PA2 B. IPSO PA2 a. "Fault Select" value of PA2 b. "Operator Select" value. PA2 a. "Validation Fault" or PA2 b. "PAMI Fault". PA2 "Alarm Tiles 150" PA2 "Primary, 152" PA2 a. Clear the "Validation Fault" alarm, if previously present PA2 b. Clear the permissive that allows the operator to select a sensor after a validation fault (i.e., "Validation Fault Operator Select Permissive"), if previously present. PA2 c. Declare any "suspect" sensor "bad" and output a sensor deviation alarm on that sensor. PA2 d. Output the average as the "valid" "calculated signal". PA2 e. Go to step 4. PA2 a. The sensor with the greatest deviation from the average is flagged as "suspect", then the algorithm checks to see if this is the first or second pass on this scan. PA2 Remove the "PAMI" message PA2 Generate a "PAMI" Fault" alarm PA2 Enable the "PAMI Fault Operator Select Permissive" PA2 Go to step 6. PA2 a. Generate a "Validation Fault " alarm PA2 b. Declare all "suspect" sensors "good". PA2 c. Enable the permissive for the operator to select an individual sensor output for "process representation", the ("Validation Fault Operator Select Permissive"). PA2 d. Deviation check all sensors against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA2 e. Output the signal from the "fault select" sensor as the "calculated signal". PA2 f. Go to step 6. PA2 Deviation check "bad" sensors to be (within sum of instrument range uncertainty and expected process variation). PA2 a. Steps 1-5 (Determination of "Calculated Signal" and Faults) of the generic validation algorithm are modified to account for the following (steps 1-8 perform these functions): PA2 b. The (Determination of "Calculated Signal" and Faults) and the remainder of the generic validation algorithm (steps 6-10) are performed independently for each of the cold legs (1A, 1B, 2A, 2B). PA2 c. Two additional algorithms were added: PA2 A--1st arrow range sensor (safety) (465.degree.-615.degree. F.) PA2 B--2nd narrow range sensor (safety) (465.degree.-615.degree. F.) PA2 C--wide range sensor (PAMI) (50.degree.-750.degree. F.) PA2 D--wide range sensor in opposite cold leg (i.e., when discussing loop 1A, this will be the wide range sensor in loop 1B, PAMI) (50.degree.-750.degree. F.) PA2 Cold leg 1A, 1B, 2A and 2B temperature "calculated signal" will be calculated using sensors A, B, C. A validation attempt will be made using narrow range sensors, if that is unsuccessful, the cold leg "calculated signal" will be validated using wide range sensors. In the event that validation fails using both narrow and wide range sensors, the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "calculated signal". PA2 If both deviation checks are satisfactory, go to step 4 to see if the average is in range. PA2 If any deviation checks are unsatisfactory, go to step 5. PA2 a. Disable the "PAMI fault operator select permissive" PA2 b. Output the "PAMI" message with the "valid" "calculated signal". PA2 c. Clear the "PAMI Fault" alarm, if present. PA2 d. Go to step 9. PA2 a. Remove the "PAMI" message. PA2 b. Enable the "PAMI Fault Operator Select Permissive". PA2 a. Clear the "Validation Fault" alarm, if present PA2 b. Disable the "Validation Fault Operator Select Permissive", if it was enabled. PA2 c. Go to step 9. PA2 a. Generate a "validation fault" alarm. PA2 b. Enable the "Validation Fault Operator Select Permissive". PA2 c. Deviation check all sensors (A, B, C) against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA2 d. Output the signal from the "fault select" sensor as the leg T.sub.c "calculated signal". PA2 e. Go to step 9. PA2 Yes, output average as "valid", go to step 5. PA2 No, go to step 3. PA2 Yes, go to step 4. PA2 No, output the average as "fault select", go to step 5. PA2 Yes, output the average as "fault select", go to step 5. PA2 No, output the average as "operator select", go to step 5. PA2 a. Steps 1-5 (determination of "Calculated Signal" and Faults) of the generic validation algorithm are modified to account for the following. PA2 b. The remainder of the generic algorithm (steps 6-10) are renumbered to account for additional steps in the (Determination of "Calculated Signal" and Faults). They are almost identical with the minor modifications described with each step. PA2 The sensor with the greatest deviation from the average is flagged as a "suspect" sensor, then the algorithm checks to see if this the first or second pass on this scan. PA2 * If the first pass, the algorithm is repeated, beginning at step 1. PA2 * If it is the second pass, the (1500-2500) range validation fails, go to step 5 to attempt 0-1600 psig range validation. PA2 a. Clear the "Validation Fault" alarm, if previously present. PA2 b. Remove the "Validation Fault Operator Select Permissive". PA2 c. Output the average as the "valid" "calculated signal". PA2 d. Go to step 12. PA2 No, go to step 9 and attempt (0-4,000 range validation). PA2 The sensor with the greatest deviation from the average is flagged as a "suspect" sensor, then the algorithm checks to see if this is the first or second pass on this scan. PA2 * If the first pass, the 0-1600 psig range algorithm is repeated, beginning at step 5. PA2 * If it is the second pass, the 0-1600 psig range validation fails, go to step 9 to attempt 0-4000 psig range validation. PA2 Hysteresis prevents frequent range shifts. Out-of-range occurs at 98% and 2% to ensure that no out-of-range sensors are used to calculate a "valid" output (i.e., worst case sensors would read 100% or 0%). PA2 a. Clear the "Validation Fault" alarm if previously present. PA2 b. Remove the "Validation Fault Operator Select Permissive". PA2 c. Output the average as the "valid" "calculated signal". PA2 d. Go to step 12. PA2 a. Clear the "validation fault" alarm, if previously present. PA2 b. Remove the "Validation Fault Operator Select Permissive", If previously present. PA2 c. Go to step 12. PA2 a. Output the "PAMI" message, if not previously present. PA2 b. Remove the "PAMI Fault Operator Select Permissive", if previously present. PA2 c. Go to step 14. PA2 a. Remove the "PAMI" message, if previously present. PA2 b. Generate a "PAMI Fault" alarm, if not previously present. PA2 c. Enable the "PAMI Fault Operator Select Permissive". PA2 d. Go to step 14. PA2 a. Generate a "Validation Fault" alarm. PA2 b. Deviation check all sensors (A, B, C, D, E, F, G, H, I, J, K, or L) against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA2 c, Output the signal from the "fault select" sensor as the pressurizer pressure "calculated signal". PA2 d. Enable the "Validation Fault Operator Select Permissive". PA2 e. Go to step 14. 1. Mode and Equipment Dependence PA3 2. Subfunction Grouping PA3 3. Shape and Color Coding PA3 4. Alarms on CRT PA3 a. Remove "bad" data flags and make them "good" on all sensors passing the deviation check, if present and clear its associated sensor deviation alarm. PA3 b. Maintain "bad" data flags on all sensors failing the deviation check. PA3 c. Go to step 10. PA3 1. Only 3 cold leg sensors. PA3 2. There are wide and narrow range temperature sensors in the same cold leg. PA3 1. An algorithm that averages the 2 cold leg "process representation" to get a loop T.sub.cold "process representation" (1A ad 1B for loop 1 and 2A and 2B for loop 2). PA3 2. An algorithm that averages the 2 cold loop "process representation" to get an RCS T.sub.cold "process representation" (loop 1 and loop 2). PA3 3. Using a menu (as described in the generic validation algorithm) on DIAS or the CRT the operator may view any of the 12 sensor values of 7 "calculated signals". These selections include the following: PA3 Validation Algorithms PA3 1. Three sensor ranges 0-1600 psig), (1500-2500 psig) and (0-4000 psig). I. Overview Description of Control Complex FIG. 1 shows a control room complex in accordance with the preferred embodiment of the present invention. The heart of the main control room 10 is a master control console 12 which allows one person to operate the nuclear steam supply system from the hot standby to the full power condition. It should be appreciated that the control room, equipment and methods described herein, may be advantageously used with light water reactors, heavy water reactors, high temperature gas cooled reactors, liquid metal reactors and advanced passive light water reactors, but for present purposes, the description will proceed on the basis that the plant has a pressurized water NSSS. For such an NSSS, the master control console 12 typically has five panels, one each for the reactor coolant system (RCS) 14, the chemical volume and control system (CVCS) 16, the nuclear reactor core 18. The feed water and condenser system (FWCS) 20, and the turbine system 22. As will be described more fully below, the monitoring and control for each of these five plant systems, is accomplished at the respective panel in the master control console. Immediately overhead behind the core monitoring and control panel 18, is a large board or screen 24 for displaying the integrated process status overview (IPSO). Thus, the operator has five panels and the overhead IPSO board within easy view while sitting or standing in the center of the master control console 12. To the left of the master control console is the safety related console 26, typically including modules associated with the safety monitoring, engineered safeguard features, cooling water, and similar functions. To the right of the master control console is the auxiliary system console 28 containing modules associated with the secondary cycle, auxiliary power and diesel generator, the switch yard, and the heating and ventilation system. Preferably, the plant computer 30 and mass data storage devices 32 associated with the control room are located in distributed equipment rooms 31 to improve fire safety and sabotage protection. The control room complex 10 also has associated therewith, a shift supervisor's office 34, which has a complete view of the control room, an integrated technical support center (TSC) 36 and viewing gallery outside the control area, and other offices 38 in which paper work associated with the operation of the plant may be performed. Similarly, desk, tables, and the like 40 are located on the control room flour for convenient use by the operators. A remote shut-down room 42 (FIG. 2) is also available on site for post-accident monitoring purposes (PAM). FIG. 2 is a schematic of the information links between the plant components and sensors, which for present purposes are considered conventional, and the various panels in the main control room. It is evident from FIG. 2 that information flows in both directions through the dashed line 46 representing the nuclear steam supply system and turbo generating system boundary. NSSS status and sensor information 48 that is used in the plant protection system 50 and the PAMS 58, passes directly through the NSSS boundary 46. Control signals 52 from the power control system pass directly through the NSSS boundary. Other control system signals 60, 62 from the engineered safeguard function component control system 56 and the normal process component control system 64, are interfaced through the NSSS boundary via remote multiplexors 6. Each of the plant protection system, ESF component control system, process component control system, power control system and PAMs, is linked to the main control room 42, to each other, to the data processing system (DPS) 70 and to the discrete indication and alarm system (DIAS) 72. FIG. 2 illustrates one significant aspect of the present invention, namely, the integration of monitoring, control and protection information, during both normal and accident conditions, so that the operator's task in determining an appropriate course of action is considerably simplified. The way in which this is accomplished will be described in the following sections. II. Panel Overview FIGS. 3(a) and 3(b) are schematics of a sit/stand panel such as the reactor coolant system panel 14 from the master control console 12 in accordance with one embodiment of the invention. FIGS. 3(c) and 3(d) show an alternative embodiment for stand up only. The substantially flat upper portion or wall 74 of the panel is vertically oriented and the substantially flat lower or desk portion 76 is substantially horizontal, with the monitoring and alarm interfaces carried by the upper portion, and the control interfaces carried on the lower portion. A. Alarm and Messages The alarm functionality (see FIGS. 9, 15-18) includes alarm interface 78 having a multiplicity of tiles 80 each having a particular acronym or similar cue 81 associated therewith, whereby an alarm and message (A&M) condition is indicated by the illumination of that tile and the generation of an accompanying audible signal. The operator is required to acknowledge the alarm by either pushing the tile or some other interface provided for that purpose. The number of tiles associated with a particular panel is dependent on the number of different alarm conditions that can arise with respect to the monitored system, e.g., the reactor coolant system. Typcially, hundreds of such tiles are associated with each panel. The alarms are prioritized into three (3) alarm classes (Priority 1, Priority 2, and Priority 3, prompting immediate action, prompt action and cautionary awareness). This RCS panel alarms are equipment status and mode dependent (Normal RCS, Heatup/Cooldown, Cold Shutdown/Refueling and Post Trip). When a high priority alarm actuates coincidentally with a low priority alarm on the same parameter, the lower priority alarm is automatically cleared. On improving conditions, the higher priority alarm will flash and sound a reset tone. The operator will acknowledge that the higher priority alarm has cleared. If the lower priority alarm still exists, its alarm window or indicator will turn on in the acknowledged state after the operator acknowledges that the higher priority alarm has cleared. B. Indicator The second monitoring interface are the process variable indicators, for example reactor coolant hot and cold leg temperatures, pressurizer level and pressure, and other RCS parameters. Discrete indicators 82 (see also FIGS. 7 and 8) provide an improved method of presenting the RCS panel parameters. Some RCS panel parameters require continuous validated display and trending on the master control console. Plant process and category 1 parameters like pressurizer level and RCS cold leg temperature fall into this category. Other RCS panel parameters are used less frequently. The discrete indicators 82 provide indication on parameters needed for operation when the Data Processing System (CRT information displays) is unavailable. These include Regulatory Guide 1.97 category 1 and 2 parameters, parameters associated with priority 1 or priority 2 alarms, other parameters needed for operation due to inaccessibility of local gages and parameters that the operator must view for surveillance when the Data Processing System is unavailable for a period of up to twenty-four (24) hours. These less frequently viewed parameters would be available on discrete indicators, with a menu available by operator selection. The menu would show alphanumeric listings of available data points. Lastly, parameters displayed on process controllers need not be available on discrete indicators. C. CRT Additionally, a CRT display 84 generates an image of the major vessels, pipes, pumps, valves and the like associated with, e.g., the reactor coolant system, and displays the alarms and values of the parameters which may be shown in bar, graph, trend line or other form on the other displays 78, 82 (see FIGS. 4-6, 10, 12-14 and 19-23). From this CRT, the operator has access to all NSSS information. The information is presented in a three level structured hierarchy that is consistent with the operator's system visualization. FIG. 4 illustrates the NSSS primary side page directory 84, which accesses all CRT pages related to the functions of the RCS panel. D. Controller In the control portion 76 of the panel 14, a plurality of discrete, on-off switches 86 are provided at the left, for example, each switch pattern being associated with a particular reactor cooling pump whose operating parameters are displayed immediately above it, and analog control interfaces which can be in the form of conventional dials or the like (not shown), or touch screen discrete control as indicated at 88. Process controllers are provided on the RCS panel to provide the operators with the ability to automatically or manually control process control loops. The process controllers allow control of throttling or variable position devices (such as electro-pneumatic valves) from a single control panel device. Process controllers are used for closed loop control of the following RCS panel process variables: pressure level, pressurizer pressure, RCP Seal Injection Flow and RCP Seal Injection Temperature. Process controllers are designed for each specific control loop utilizing a consistent set of display and control features. In a conventional control room, each process control loop has its own control device, usually referred to as a MANUAL/AUTO Station. For example, the RCP Seal Injection Sub-System has five process control loops, a seal injection flow control loop for each o the four RCPs and a seal injection temperature control loop for the entire sub-system. These five control loops each have their own MANUAL/AUTO station which occupy a large amount of control panel space and make cross loop comparisons cumbersome. Although these five process loops are controlled independently, process variations in one controlled parameter affect the other four process parameters. Conventional MANUAL/AUTO stations make it difficult for the operator to simultaneously interact with the five MANUAL/AUTO stations. The RCS panel process controllers for similar processes (related by function or system) are operated from a single control station, called a process controller. This single control station saves panel space, accommodates convenient cross channel checking and allows easier control loop interaction for multiple related controls. Component control features (i.e., actuation of switches controls) provide the primary method by which the operator actuates equipment and system on the RCS panel. The RCS panel has forty-three components controlled from momentary type switches. Each switch contains a red status indicator for active or open and a green status indicator for inactive or closed. Blue status indicator lights/switches are used to indicate and select automatic control or control via a process controller. In addition to color coding, the red switch is always located above the green switch to reinforce color distinction. Each switch generates an active control signal when depressed and is inactive when released. Each switch is backlit to indicate equipment status/position. E. Display Formats Process display formats use standard information placement for similar processes and equipment. Fluid system piping representations are where possible standardized, top to bottom, left to right, with avoidance of crossovers. Incoming and outgoing flow path connections are placed at the margins. Related data are grouped by task and analysis specifications for comparison, sequence of use, function, and frequency. Process representations/layout are based on the operator's process visualization to maximize the efficiency of his data gathering tasks. The operator's visualization of a system is often based on diagrams used with learning materials and plant design documentation associated with system descriptions. Graphic information is presented on display page formats to aid in rapid operator comprehension of processes. Graphic information includes the use of bar graphs, flow charts, trends, and other plots, (e.g., Temp. vs. Press.). Bar graphs are primarily used to represent flows, pressures and levels. Since level corresponds to a tank, the bar graph is placed with consistent spatial orientation with respect to the tank symbol. Level bar graphs are oriented vertically. Flow bar graphs when used are oriented horizontally. Bar graphs are also helpful for comparison of numeric quantities. Flowcharts are used when they aid in the operator's process visualization. Flowcharts are helpful for understanding control system processes such as the Turbine Control System. Operator's learning materials for process control systems are frequently in a flowchart format, and thus a similar format on a display page is easy to comprehend. Trends are used on display page formats when task analysis indicates that the operator should be informed about parameter changes over time. Additionally, the operator is able to establish tends of any data base points in the plant computers data base. In some situtations, task analysis may indicate that more than one trend is important to monitor process comparisons. In other situations such as heatup/cooldown curvers, two parameters may be placed on the different ordinate axis of a graph. When more than one trend curve occupies the same coordinate axes, two ordinate vertical axes can be used for parameters that have different units. Scale labels are divisible by 1, 2, 5 or 10. Tick marks between scale labels are also divisible by 1, 2, 5 or 10. Trended information is typically presented on display pages with a scale of 30 minutes. However, the operator is able to adjust the scale to suit his needs. Logarithmic axes may be established using multiples of 10. If full range is less than 10, an intermediate range label is located to fall near the middle of the scale. Different colors are used for trends occupying the same coordinates. When multiple curves use a common scale, the scale is grey and the curves are color coded. When multiple ordinate scales are used, they are color coded in correspondence to the curve. The colors used for trends will not include the alarm color or normal status color to avoid associating process parameter with normal or alarm conditions. Color is used to aid the operator in rapidly discriminating between different types of information. Since the benefits of color coding are more pronounced with fewer colors, coding on informational displays (i.e., IPSO, CRTs, alarm tiles) is limited to seven colors. In addition, color coded information has other representational characteristics to aid in discrimination of data and discrimination by color deficient observers. The following colors are used in the information display to represent the following types of information. The colors used have been carefully selected to yield satisfactory contrast for red-green deficient color observers. ______________________________________ Color Representation Characteristics ______________________________________ Black Background color. Green Component Off/Inactive, Valve Closed and Operable. Red Component On/Activated, Valve Open and Operable. Yellow Alarm Status-Good attention-getting color. Grey Text, labels, dividing lines, menu options, piping, inoperable and non-instrumented valves, graph grids, and other applications not covered by other coding conventions. Light Blue Process parameter values. White System's response to operator touch, e.g., menu selection until appropriate system response occurs. ______________________________________ Shape coding is used in the information system to aid the operator to identifying component type, operational status, and alarm status. Component shape coding is based on symbology studies which included shape coding questionnaires given to nuclear power plant personnel. FIGS. 5 and 6 show the shapes used to represent components in the control room. An attribute of shape, hollow/solid, is reflective of the status of the component. Hollow shape coding indicates that the component is active, whereas solid shape coding is used to represent inactive components. An example of shape coding for a pump and valve is described as follows. Information coding on valves is provided by these additional characteristics/representations: F. Display Integration Information associated with safety related concerns is integrated as a part o the control room information to allow the operator to use safety related information, where possible, during normal operation. This is a better design from a human factors view than that of previous control rooms because in stressful situations, people tend to use information that they are most familiar with. In many situations, safety related parameters are only a subset of the parameters that monitor a particular process variable. Operators of present control room designs typically use control or narrow range indications during process control and should use separate safety related indications when monitoring plant safety concerns. In this invention, the parameters typically used for monitoring and control are validated for accuracy against the safety related parameter(s), where available. If a parameter deviates beyond expected values from the associated safety related information, a validation alarm is presented to the operator. In response to an alarm condition, the operator can review the individual channels associated with the parameter on either a diagnostic CRT page or the discrete indicator displaying that parameter. At this time, he can select the most appropriate sensor for display. The operator is informed when the validation algorithm is able to validate the data. The resultant output of the validation algorithms are used on IPSO, the normally displayed format of a discrete indicator, and the higher level display pages on the CRT display system that contain the parameter. The Regulatory Guide 1.97 category 1 information is also displayed, by discrete indication display, at a single location on the safety monitoring panel. Critical Function and Success Path (availability and performance) information is accessible throughout the information hierarchy (see FIGS. 10, 24, 25, 26, 27, 32-35). Alarms provide guidance to unexpected deviation in critical functions as well as success path unavailability or performance problems. Priority 1 alarms alert the operator to the inability to maintain a critical function as well as the inability of a success path to meet minimum functional requirements. Lower priority alarms provide subsystem/train and component unavailability or poor performance. IPSO provides overview information that is most useful for operator assessment of the Critical Functions. Priority 1 alarms associated with the Critical Functions or Success Paths supporting the critical function are presented on IPSO critical function matrix. Supporting information relating to these alarm conditions is available by using the alarm tiles or the critical function section of the CRT display page hierarchy. The critical function section of the display page hierarchy contains the following information: A 2nd level page exists for each of the 12 critical functions. Each page contains: The 3rd level display pages in the critical function hierarchy are a duplicate of display page existing elsewhere in the hierarchy. For example, a safety injection display page display page under Inventory Control also exists within the primary section of the display page hierarchy. III. DISCRETE INDICATOR AND ALARM SYSTEM A. Discrete Indicator The discrete indicator 82 provide an improved method of presenting safety related parameters. Major process parameters such as Regulatory guide 1.97 Category 1, require continuous validated display and trending on the master control console. The discrete indicators also provide indication and alarms on parameters needed for operation when the Data Processing System (DPS) is unavailable. These include Regulatory Guide 1.97 Category 1, 2 and 3 parameters, parameters associated with priority 1 or priority 2 alarms, and other surveillance related parameters. Though the DPS is a highly reliable and redundant computer system, its unavailability is considered for a period of up to twenty-four hours. The less frequently viewed parameters are available on discrete indicators, with a menu available by operator selection. Each discrete indicator has the capability to present a number of parameters associated with a component, system, or process. The discrete indicators present various display formats that are based on fulfilling certain operator information requirements. When monitoring or controlling a process such as pressurizer pressure, it is desirable that the operator use a "process representation" value in the most accurate range. For this type of information, the discrete indicator 82, such as shown in FIGS. 7 and 8, presents a bold digital value 90 in field 92 and an analog bar graph 94 of the validated average of the sensors in the most accurate range. The preferred validation technique is described in the Appendix, and validated status is indicated in field 96. This validation data is checked against post-accident monitoring indication (PAMI) sensors when applicable. When in agreement with the PAMI, as shown at field 98 the indicator ay be used for post-accident monitoring. This has the advantage of continuing to allow the operator to utilize the indicator he is most familiar with and uses on a day-to-day basis. The operator, upon demand, can display any individual channel on the discrete indicator digital display by touching a sensor identification such as 102. The use of validated parameters is a benefit to operators by reducing their stimulus overload and task loading resulting from presentation of multiple sensor channels representing a single parameter. When the parameter cannot be validated, the discrete indicator displays the sensor reading that is closest to the last validated value. A validation alarm is generated for this condition. The discrete indicator continues to display this sensor's value until the operator selects another value for indication. The field 96 on the discrete indicator that usually read "VALID" displays "FAULT SEL" in reverse image. This indicates that the value is not validated and has been selected by the computer. In this circumstance, the operator should review the available sensors that can be used for the "process representation". If the operator makes a sensor selection (which is enabled by a validation fault or failure of the "VALID" signal to agree with PAMI), the field 96 the "FAULT SEL" will be replaced by the message"OPERATOR SELECT", which is displayed in reverse image. When the validation algorithm can validate the data and all faults have cleared, the validation fault alarm will clear and the algorithm will replace the "FAULT SELECT" or "OPERATOR SELECT" "process representation" in field 92 with the "VALID" "calculated signal". Parameters that are required for monitoring the overall performance of plant processes ore responding to priority 1 or 2 alarms are provided on discrete indicators. The most representative process parameter is the normally displayed value. Through menu options, the operator can view the other process related parameters. There are ten discrete indicators provided for the RCS panel. The indicators are: FIG. 7 illustrates that two related discrete indicators can be shown on a single display 82. On the left side of the display 82 validated pressurizer pressure is shown whereas at the right, pressurizer level is shown. The pressure display includes the following: digital "process representation" value 90 with units of measurement (2254 psig), quality 96 of the display (VALID), indication 98 that the display is acceptable for post accident monitoring (PAMI), bar chart 94 with the process value, a 30 minutes tend 104, normal operating range (NORMAL) 106, instrument range (1500-2500) and units of measurement for the bar chart (psig). In the upper right hand corner of the PRESS display, there are two buttons, "CRT" and "MENU". When touched, the selected button backlights, indicating selection. When the operator removes his hand, the actual selection is processed. The "CRT" button changes the CRT 84 menu options on the CRT located at the same panel as the discrete indicator where the button is pushed, e.g., RCS panel 14 as shown in FIG. 3. This "CRT" option identifies the CRT pages most closely associated the parameters on the discrete indicator. The "MENU" button selects the discrete indicator menu (FIG. 8). The upper section of the menu page is nearly identical to the normal display. It contains the digital "process representation" value 90 with units of measurement (2254 psig), quality of display (valid), indication that the display is acceptable for post accident monitoring (PAMI), CRT and MENU buttons. The lower section of the menu page contains selector buttons, such as 102, for all sensor inputs and "calculated signals" of this discrete indicator. The selector buttons 102 backlight when touched, indicating selection. When the operator removes his finger, the actual processing of the selection takes place. There are 13 buttons for pressure: four for 0-1600 psig pressurizer pressure: P-103, P-104, P-105 and P-106; six of 1500-2500 psig pressure: P-101A, P-101B, P-101C, P-101D, P-100X and P-100Y; two for 0-4000 psig RCS pressure: P-190A and P-190B; and one for the "calculated signal" pressure: CALC PRESS. When selected, the "CALC PRESS" button displays the "calculated signal" (i.e., the output of the algorithm). The "calculated signal" of the algorithm can be a "valid" signal. If the algorithm were to fail and select an individual sensor for the "calculated signal", the "valid" message would be replaced by the message "fault select". This message"fault select" would be displayed in reverse image on the discrete indicator. This message would be displayed on the discrete indicator any time "CALC PRESS" is selected until the algorithm outputs a "VALID" signal to replace the "FAULT SELECT" sensor. To change the display, the operator would touch the button containing the sensor he wished to view. For example: by touching the button marked "P-103", the digital display would display the output from the 0-1600 psig range sensor P-103. The message "VALID" below the digital value would be replaced by the message "P-103". Additionally, the "PAMI" message would be removed because P-103 is not a PAMI sensor. The button "ANAL/ALARM OPER SEL" selects the signal used for the "process representation" in DIAS. It selects whatever sensor is displayed on the digital display. The signal select button gives the operator the option to "operator select" any of the sensor for analog display and alarm processing when a fault exists, such as: If a fault were present and the operator elected to select P-103 for the "process representation", he would select the menu, select P-103 or display and then touch the "ANAL/ALARM OPER SEL" button. The message in field 96 below the digital display would read "P-103 OP SEL" in reverse image. Any time P-103 was selected for display, it would have the message "OP SEL" displayed in reverse image, indicating that the output from P-103 is being used for the "process representation". After selecting an "operator select" sensor for the "process representation", it is expected that the operator will depress the button marked "ANALG DISPLAY". This would return to the analog 94 and trend display 104 (FIG. 7) for the operator selected sensor with the message "OP SEL" in reverse image. The "ANAL/ALARM OPER SEL" button is not normally displayed on the discrete indicator menu page; it automatically displays when the "operator select permissive" is enabled after a fault. The "ANAL/ALARM OPER SEL" button is removed from the menu page when the "operator select permissive" is disabled after all faults are corrected. The button "ANALOG DISPLAY" removes the menu page and replaces it with the bar graph (analog) and trend display for whatever sensor or "calculated signal" is currently selected as the "process representation" (normally the "valid" "calculated signal" output). Other validated process parameter discrete indicators operate in an identical manner. Menu driven discrete indicators contain all level 1 and 2 displays for a functional group of indication. B. Validation Algorithm Summary To reduce an operator's task loading and to reduce his stimulus overload, a generic validation algorithm is used. This algorithm takes the outputs of all sensors measuring the same parameter and generates a single output representative of that parameter, called the "Process Representation". A generic validation approach is used to ensure that it is well understood by operators. This avoids an operator questioning the origin of each valid parameter. This generic algorithm averages all sensors [(A, B, C and D) (sensor quantity may be parameter specific)] and deviation checks all sensor against the average. If the deviation checks are satisfactory, the average is used as the "Process Representation" and is output as a "valid" signal. If any sensors do not successfully pass the deviation check against the average, the sensor with the greatest deviation from the average is taken out and the average is recalculated with the remaining sensors. When all sensor used to generate the average deviation check satisfactorily against the average, this average is used as the "valid process representation". This "valid process representation" is then deviation checked against the post-accident monitoring system sensors (if present). If this second deviation check is satisfactory, the "process representation" is displayed with the message "Valid PAMI" (Post-Accident Monitoring Indication), indicating that this signal is suitable for monitoring during emergency conditions, since it is in agreement with the value as determined by the PAMI sensors. As long as agreement exists, this indicator may then be utilized for post-accident monitoring rather than utilizing the dedicated PAMI indicator. This provides a Human Factors Engineering advantage of allowing the operator to use the indicator he normally uses for any day-to-day work and which he is most familiar with. The validation process, as described, reduces the time an operator takes to perform the tasks related to key process related parameters. To ensure timely information, all validated outputs are recalculated at least once every two seconds. Additionally, redundancy and hardware diversity are provided in the calculating devices insuring reliability. The following section describes the algorithm and display processing on the DIAS and CRT displays. Both of these are explained below. It should be appreciated that the discrete validation is accomplished using a generic algorithm that is applicable to different parameters. In this manner, the operators understand how the validated reading has been determined for every parameter and, again, this reinforces their confidence. This algorithm always has an output and allows the operator selection for display when validation is not possible. The discrete indicators continuously display all vital information yet allow easy access via a function or organized menu system to enable the operator to access less frequently needed information. There is no need for separate backup displays, since the backups are integrated in the subsidiary levels of retrieval. Such displays vastly reduce the amount of indicator locations required on the panel and yet provide all vital indication in a easy to use format, thereby reducing stimulus overload. The Appendix in conjunction with FIGS. 37 and 38 provide additional details on the preferred implementation of the algorithm. C. Alarm Processing and Display: Another feature of the monitoring associated with each panel, is the reduction of the number of alarms that are generated, in order to minimize the operator information overload. Cross channel signal validation is accomplished prior to alarm generation, and the alarm logic and set points are contingent on the applicable plant mode. The alarms are displayed with distinct visual cueing in accordance with the priority of the required operator response. For example, priority 1 dictates immediate action, priority 2 dictates prompt action, priority 3 is cautionary, and priority 4, or operator aid, is merely status information. The types of alarm conditions that exist within each category are described below: Priority 1 Priority 2 Priority 3 The alarms are displayed using techniques that help the operator quickly correlate the impact of the alarm on plant safety or performance. These techniques include grouping of displays which highlight the nature of the problem rather than the symptom denoted by the specific alarm condition. Another is the fixed spatial dedication off alarm displays allowing pattern recognition. Another is the plant level pictorial overview display on the IPSO board which shows success paths and critical functions impacted by the priority 1 alarms. To ensure that all alarms are recognized by the operator without task overload, all alarms can be either individually acknowledged, or acknowledged in small functionally related groups. All alarms can be acknowledged at any control panel. Momentary audible alerts for alarm state changes require no operator action to silence. Periodic momentary audible reminders are provided for unacknowledged conditions. The operator can affectuate a global alarm stop flash which will automatically resume in time, to allow for deferred acknowledgement. In addition to alarms, an information notification category "Operator Aids" has been established for information that may be helpful for operations but is not representative of deviations from abnormal conditions. Conditions classified as "Operator Aids" include: channel bypass conditions, approach to interlocks and equipment status change permissive. Some parameters have more than one alarm on the same parameter (i.e., Seal Inlet Temperature Hi Hi and Hi). To limit the operator's required response, the lower priority is automatically cleared without a reset tone or slow flash rate when the higher priority alarm actuates after actuation of the lower priority alarm. The Hi Hi alarm will be acknowledged by the operator; therefore, the operator acknowledgement f the cleared lower priority alarm is unnecessary. When the condition improves to the point where the higher priority alarm clears, the condition will sound a reset tone and the alarm window will flash slowly. The operator will acknowledge that the higher priority alarm has cleared. If the lower priority alarm condition still exist, its alarm tile or indicator will turn on in the acknowledged state after the operator acknowledges that the higher priority alarm has cleared. If the condition improves such that is clears both the high and low priority alarms before operator acknowledgement, then operator acknowledgement of the cleared high priority alarm will also clear the lower priority condition. 1. Mode and Equipment Dependency A key feature of the alarm system is its mode dependent and equipment status dependent logic. These features combine to greatly reduce the number of alarms received during significant events and limit those alarms to conditions that actually represent process or conditions that actually represent process or component deviations pertinent to the current plant state. Mode and equipment dependency is implemented both through alarm logic changes and setpoint changes. An alarm of mode dependency is the reduction in the low pressurizer alarm setpoint to avoid a nuisance alarm on a normal reactor ring. Equipment dependent logic is used to actuate a low flow alarm only when an upstream pump is supposed to be operating. Four modes have been selected which correspond to significant changes in the alarm logic based on the plant state. These modes are: The alarm models are manually entered by the operator with the exception of the post-trip mode. Upon a reactor trip, the alarm logic automatically switches to the post-trip mode with no operator action required. All equipment dependent alarm features are actuated automatically without operator action. 2. Subfunction Grouping The RCS panel has over 200 conditions that can cause an alarm. To reduce the operator's stimulus overload due to the quantity of alarms and improve his alarm comprehension, many alarms are grouped into subfunctional groups 108, 110, 112 (FIG. 15). The subfunctional group alarm tiles have a variety o related subfunctional group alarm messages that are read on the panel alarm message window 114 (adjacent to the alarm tile) o CCRT. In cases where key process related parameters are alarmed, there is a single alarm message of each alarm tile (i.e., RCS Pressure Low). This single alarm message allows the operator to quickly identify the specific process related problem. As shown in FIG. 16, some alarms are grouped by similar component rather than process function, and are augmented by a message such as 116. As shown in FIG. 9, each alarm tile can be in one of the following states: 3. Shape and Color coding Alarm information is identified by a unique tile color, preferably yellow 118. The parameter-component descriptor or concise message 120 within the tube is shown in blue. Grey color coding is used for the tile color 122 for Return to Normal conditions. Shape coding is used to identify alarm priority, i.e., 1, 2, or 3. A single bright color is used for alarm information to maximize the attention-getting quality of this information. The shape coding used for identifying alarm priorities uses representational features of decreasing levels of salience. Shape coding of alarm priorities also allows retention of priority information for Return to Normal conditions. For priority 1 alarms, the alarm tiles, mimic diagram components, symbols, process parameters, and menu option fields have their descriptor presented in reverse image (i.e., blue letters 12 on a yellow 118 solid rectangular background 124) using the alarm color coding. The descriptor is presented in blue to provide good contrast of readability. In addition, the alarm tiles and menu option fields on the CRT use the same representation. For priority 2 alarms, the alarm tiles, mimic diagram parameters, components, menu options, and symbols have a thin (1 line) box 126 using the yellow alarm color code 118 around their descriptor, which is blue. For priority 3 alarms, the alarm tiles, mimic diagram parameters, components, menu options, and symbols have brackets 128 around their descriptors 120. For all alarms, English Descriptors on the CRT's message line are also represented with the alarm representation formats when they are in alarm. 4. Alarms on CRT Each CRT page in the data processing system provides the operator with an overview of the existence of any unacknowledged alarm conditions and a general overview of where they exist within the plant. The standard menu provided with each display page contains the IPSO and all fist level display pages as menu options (see FIG. 10 menu region 130). These menu option fields provide the existence of unacknowledged alarms in their sector of the display page hierarchy and their alarm status/priority by using the alarm highlighting feature as described above. If an alarm tile (i.e., in the DIAS) is in alarm, a fist level display page menu option field, such as 132, in the menu options 130 shows that an alarm condition exists in an associated area of the display page hierarchy. The alarm tiles in menu 130 are categorized into the fist level display page set corresponding to the console groupings or by critical function as shown in FIG. 11. In addition to alarm information represented on the fist level display page menu options, the following display page features are also used to represent the existence of alarms. Display page menu options 134 that provide access to levels 2 and 3 display pages are lit with the above described alarm representation if information on the corresponding page is in alarm (e.g., if an unacknowledged alarm exists, the display page menu option is highlighted to show the highest priority unacknowledged condition). The operator can be selecting option 136, call up a level 2 display page directory containing a pictorial diagram of the level 3 display pages in a hierarchical format associated with a first level display page (see FIGS. 12 and 15). Each of the level 2 and 3 display pages represented on this diagram provide alarm notification if information on that display page is in an unacknowledged alarm state. This alarm information is most useful or determining where alarms exist within an area of the display page hierarchy. For example, the operator would be notified by the display page menu 130 (FIG. 10) that an unacknowledged alarm(s) exists in the auxiliary systems by grey alarm shape coding (return to normal) and slow flashing of alarm coding on the "PRI" menu option field. He can then access that directory/hierarchy to see what page(s) contains alarm information by touching the menu option "DIRECTORY 136" followed by "PRI". When the Primary display directory comes up (FIG. 12), the field(s) representing the display page(s) that contains the alarm condition(s) (such as PZR LEVEL 138) will be highlighted. The desired page that contains the alarm information (similar to FIG. 15) is accessed by touching the flashing field. The descriptors of components and plant data on the process display pages of the CRT (FIG. 13) are alarm coded and flashed to provide indication of alarms and their acknowledgement status. A component's descriptor can provide this alarm information if a parameter associated with the component is in alarm. This is true even if the parameter in alarm is not represented on the display pages, e.g., low pump lube oil pressure is represented by alarm coding of the associated component's symbol. To view the exact information that is in alarm, the operator can access a lower level display page, or use the alarm system features that are described later. 5. Determination Alarm Conditions and Acknowledging Alarms With reference again to FIG. 16, each category 1 and 2 alarm annunciator tile in the DIAS may notify the operator of more than one possible alarm condition. To quickly determine the actual alarm condition, a message window 114 is provided in the display area 78 on the panel. By depressing an unacknowledged alarming annunciator tile such as 134, an English description 116 of the specific alarm condition is provided on the message window 114. The alarm tile 134 remains flashing until all alarm conditions associated with the alarm tile have been acknowledged. The English descriptors of additional alarms can be accessed by redepressing the alarm tile 134. At the same time that a message appears on the message window of a DIAS alarm display 78, an alarm message is presented on another field 132 at the bottom of the display page 84 on the panel CRT (see FIG. 13). The CRT alarm message contains the following information: Time, Priority, Severity (e.g., Hi, Hi-Hi), Descriptor, Setpoint, and real time process value (coded as described to show the alarm priority and alarm condition). If additional unacknowledged alarms exist that are associated with the tile, the number of additional unacknowledged alarms is specified within a circle 136 at the right hand side of the message area (see FIG. 13). In addition to this alarm message, menu options/fields appear on the display page menu (Region 4) and provide direct access to the display pages that can be used to obtain supporting or diagnostic information of the alarm condition. The display regions are shown in FIG. 22. The alarm tiles that are in alarm on the DIAS display 78 of a given panel an be accessed and acknowledged on any CRT panel by procedure similar to accessing and acknowledging the alarms via the alarm tiles. By selecting the "Alarm Tiles" menu option followed by an alarming display page menu option, i.e., first level display page set (region 3), the alarm tiles that are in alarm, that are associated with the display page, are provided in region 4 of the display page menu. One tile is depicted and is a touch target that provides access to other tiles. The operator acknowledges and reviews these CRT alarm tiles by touch and obtains alarm messages and supporting display page touch targets in the same format as described above. This means of responding to alarming alarm tiles is most useful for responding to alarms at workstations that are remote to the operator's location. All alarm conditions associated with an annunciator tile in the DIAS display are held in a buffer. The buffer containing alarm conditions is arranged in the following format: ______________________________________ 1. First-In Unacknowledged 2. . . . . . N Last-In Unacknowledged N+1 First-In Cleared/Return to Normal N+2 . . . . . . . n Last-In Cleared/Return to Normal n+.sup.1 Acknowledged Alarms n+2 . . . . . ______________________________________ Depressing an alarm tile provides access to the alarm condition that is at the top of the buffer. Acknowledging unacknowledged alarms moves these alarm conditions to the bottom of the buffer. Acknowledging cleared alarms drops them from the buffer. Previously acknowledged alarm(s) (n+1, n+2, . . . ) can be reviewed when thee are no unacknowledged or cleared unacknowledged alarm conditions present. Upon reviewing these alarms, they move to the bottom of the buffer. Alarm messages for priority 3 alarms and operator aids are only generated by the computer and only appear on the message line 132 of the CRT page (FIG. 3); there will be no English descriptor provided on the message window of the DIAS display 78. One annunciator tile is provided at each annunciator workstation for all priority 3 alarms and 1 alarm tile is provided on the workstation for operator aids that are associated with these workstation. when an alarm condition changes priority, the following changes occur in the alarm handling system. When a higher priority alarm comes in on the same parameter, the previous alarm is automatically cleared (i.e., no operator acknowledgement necessary since he will need to acknowledge the higher priority condition) without a reset tone or slow flash rate. When an alarm condition improves to the point where the high priority alarm clears, the operator will need to acknowledge that the higher priority alarm has cleared; however, if the lower priority alarm still exists, it will turn on (upon operator acknowledgement of the higher priority cleared condition) and automatically go to the acknowledged state (i.e., no operator action required). The new lower priority alarm condition will be observed by the operator when reading the alarm message in response to clearing the highest priority alarm. The invention provides a means of listing and categorizing alarms, and accessing supporting display pages accessible from the fields 138 of the DIAS display 78 and 140 of the CRT display 84 shown in FIGS. 15 and 13, respectively. In this system, alarms are provided on alarm listing display pages. The categories of alarms in this listing are as follows (see FIG. 14): A workstation's alarm tiles in alarm are listed by priority. Alarms associated with the alarm tiles are listed as they are contained in the alarm tile's alarm buffer. These alarm categories provide alarm data consistent with operator's information needs in response to alarm conditions. When accessing the Categorized Alarm Listing 78 via page 84 (FIGS. 4 and 12), the operator can easily select the data in the category he wishes to see. Using the "Alarm List" menu option 14 (FIG. 4) followed by a display page feature that represents alarm condition(s) (FIG. 12), the operator can view the specific alarm conditions that he is interested in (FIG. 14). Three examples of accessing alarm data in the categorized list from page 84 (FIG. 4) follow. The display page's menu changes to a representation of the alarm tiles that are in alarm and are associated with the Primary Systems (see FIG. 14). At this time, the operator can request one of two different types of information formats associated with the displayed alarm tiles: Alarm information is also provided on all process display mimic diagrams which contain a component or parameter which is in an alarm condition. Color, and shape coding is used to indicate alarm conditions, as described earlier. Parameters in alarms that are associated with a component can cause the represented component's descriptor to be highlighted to indicate an alarm condition if the parameter is not visible on the display page, e.g., pump lube oil pressure may not be listed on a level two display page, so the pump's descriptor may be alarm coded. If the operator desires to see the exact alarm condition associated with a component, he would access the appropriate lower level display page. Alternatively, he could touch the "Alarm Tiles" menu option followed by touching the component's descriptor and respond to the alarm using alarm tile representations. This action also accesses menu options associated with display pages that provide more detail about the component. the following means of alarm acknowledgement is provided with the invention. Each of these methods of alarm acknowledgement clears unacknowledged alarm indicators in the other alarm formats. When an alarm condition clears, the operator needs to be notified. Notification is accomplished by flashing the annunciator tiles and associated process display page information at a slow rate. Acknowledging or resetting the cleared alarm indications takes place in a mechanism similar to acknowledgement of new alarms, i.e., touching an alarm tile or CRT alarm representation/feature. Distinct sounds/tones are provided in the control room to indicate the following alarm information: An audible alarm, tone 1 or 3, is only present for 1 second and tone 2 will repeat periodically, once every minute, until all new or cleared alarms are acknowledged. In situations where multiple unacknowledged alarms exist, the operator needs to direct his attention at the highest priority new alarm conditions. In this situation, all other unacknowledged alarms, i.e., new priority 2, 3 and all cleared alarm conditions, are added noise that distracts the operator from most important alarm conditions. In the control room, a "STOP FLASH" and "RESUME" button exists at the MCC, ACC and ASC. When the "STOP FLASH" button is depressed, the alarm system's behavior exhibits the following characteristics: The alarm reminder tone informs the operator about any unacknowledged new or cleared alarm conditions that exist. To identify these conditions for acknowledgement, the operator selects a "resume" button which returns all unacknowledged and cleared conditions to their normal representational alarm status. The alarm suppression button is backlit after selection to show that the alarm suppression feature is active. So that the operator can provide quick, direct access to supporting information thereby enhancing the operator response to alarm conditions, a single operator action provides alarm acknowledgement, display of alarm parameters, and selection options for CRT display pages appropriate for the alarm condition. The invention provides redundancy and diversity in alarm processing and display such that the operators have confidence in intelligent alarm processing techniques and such that plant safety and availability are not impacted by equipment failures. Priority 1 and 2 alarms are processed and displayed by two independent systems. Two-system redundancy is invisible to the operators through continuous cross-checking and integrated operator interfaces. FIGS. 16-18 show a schematic alarm response using the tiles in accordance with the invention. The illustrated group of tiles is associated with the reactor coolant pump seal monitoring in the reactor cooling system panel shown in FIG. 3. The priority 2 seal/bleed system trouble alarm is illuminated to alert the operator, who then can read a more complete message in the message window, which indicates a high control bleed-off pressure. Such a message is provided for priority 1 and 2 alarms. The same message in more complete form is displayed on the panel CRT. The CRT also identifies menu options that indicate useful supporting display pages. Alternatively, the operator may directly access a listing of all the alarms in a particular group. Thus, overview of the alarm conditions is provided with the tiles, and the detail is provided with the associated messages. A given alarm is rendered more or less important at a particular point in time, depending on the equipment status and the mode of operation of the NSSS. Alarm handling is reduced by validation of the parameter signals, and clearing automatically lower priority alarms when one of the higher priority alarms is actuated on the same condition. IV. DATA PROCESSING SYSTEM A. The CRT Display The CRT shown 84 in the center of the panel in FIG. 3 is part of the data processing system which processes and displays all plant operational data. Thus, it is linked to all other instrumentation and control system in the control room. FIGS. 2, 28 and 30 schematically show the relationship of the data processing system with the control system, plant protection system, and discrete indication and alarm system. The data processing system 70 receives from the control system 64, the same sensor data that is used by the control system for executing the control logic. Likewise, it receives from the discrete indication and alarm system 72 the validated sensor data that is used by the discrete indication and alarm system for generating the discrete alarms and displays. The plant protection system 50 does not use internally validate data for its trip logic, and this "raw" signal is for each channel passed along to the data processing system 70 which performs its own signal validation logic 154 on the plant protection system signals, and passes on the internally validated signal to the validated signal comparison logic 156. In that functional area, the validated signals from the control system 64, the plant protection system 50 and the discrete indication and alarm system 72 are compared and displayed on the CRT 84. It should be appreciated that both the validated signal from the comparison logic 156 and the validated signal from the plant protection system are available for display on the CRT 84. Thus, the CRT display within each panel includes signal validation and all CRTs in the plant are capable of accessing any information available to the other CRTs in the plant. Moreover, on any given CRT, the alarm tile images from any other panel may be generated and the alarms acknowledged. Detailed display indicator windows may be accessed as well. The CRTs have a substantially real time response, with at most a two-second delay. The CRT display pages contain all the power plant information that is available to the operator, in a structured, hierarchic format. The CRT pages are very useful for information presentation because they allow graphical layouts of power plant processes in formats that are consistent with operator visualization. In addition, CRT formats can aid operational activities, where appropriate, by providing trends, categorized listing, messages, operational prompts, as well as alert the operator to abnormal processes. The primary method the operator obtains information formats on the CRTs is through a touch screen interface which operates in a known manner. The touch screens are based on infrared beam technology. Horizontal and vertical beams exist in a bezel mounted around the face of each color monitor. When the beams are obstructed by the user, the coordinates are cross-referenced with the display page data base to determine the selected information. Messages and Supporting Display page option touch targets can be accessed onto panel CRTs by touching other panel features, e.g., discrete indicators and alarm tiles. IPSO is available as a display page and forms the apex of the display page hierarchy (See FIGS. 10, 22 and 24). Three levels exist below IPSO, where each level of the hierarchy provides consistent information content to satisfy particular operational needs. The structure of the hierarchical format is based on assisting the operator in the performance of his tasks as well as providing quick and easy access to all information displayed via the CRTs. The display formats on the top level provide information for general monitoring activities, while the lowest level formats contain information that is most useful for supporting diagnostic activities. Level 1 display pages provide information that is most useful for general monitoring activities associated with a major plant process. These display pages inform the operator of major system performance and major equipment status and provide direction to lower level display pages for supportive or diagnostic information. The level 1 display pages are as follows: Level 2 display pages provide information that is most useful of controlling plant components and systems. These pages contain all information necessary to control the system's processes and functions. Parameters which must be observed during controlling tasks appear on the same display, even though they may be parts of other systems. Proposed operating procedures or guides for controlling components are utilized for determining which parameters to display. FIG. 20 is a sample display for Reactor Coolant Pump 1A and 1B Control. The operator would normally monitor the "Primary System" display page to assess RCS performance. If the operator wishes to operate or adjust RCP 1A or 1B, the operator would access the control display page. All information for Reactor Coolant Pump control is on the control display to preclude unnecessary jumping between display pages. Level 3 display pages provide information that is most useful for diagnostic activities of the component and processes represented in level 2 display pages. Level 3 display pages provide data useful for instrument cross-channel comparisons, detailed information for diagnosing equipment or system malfunctions, and trending information useful for determining direction of system performance changes, degradation or improvement. FIG. 21 shows a diagnostic display of the Seal and Cooling section of RCP1A; the pump portion, the supporting oil system, and the motor section are presented on a separate display page due to display page information density limits. Display page access is accomplished though the use of menus placed on the bottom of the display pages. Each display page contains one standard menu format that provides direct, i.e., single touch, access to all related display pages in the information hierarchy. The menu has fields (see FIG. 10) where display page title are listed. By selecting a field (a thru j), the specified display page is accessed. The menu option fields associated with a display page includes the following (see FIG. 22). To access a display page described by a menu option, the operator would select the menu option (a-k) by touching the desired menu option field on the monitor. The menu option is highlighted (using black letters on a white background) until the display page appears. Since the menu options provide direct access to a minimum set of display pages in the display page hierarchy, alternate means are available for quickly accessing other display pages. Three options are available to the operator: In addition to the menu options described above, menu options exist for "LAST PAGE", "ALARM LIST", "ALARM TILES", "OTHER", and horizontal paging options ("Keys"). The "LAST PAGE" (option j on FIG. 22) provides direct access to the last page that was on the monitor. This is very useful to operators for comparison of information between two display pages, or retrieval of information that the operator was previously involved with. The "ALARM LIST" (option n on FIG. 22) provides for quick access to the alarm listing display pages. The access toi alarm tile representations of active alarm tiles in the area above Region 4 (see FIG. 23) of the workstation's CRT menu. This allows an operator to access alarm information associated with specific tiles on any workstation's CRT. This method of alarm access is further described in Section 5 of this document. The "OTHER" (option k on FIG. 22) provides access to display pages or information that does not fall into the categories of information described by the presently displayed menu options. B. IPSO Another part of the data processing system is the integrated process status overview (IPSO board) 24. Although the number of displays and alarms stimulating the operator at any one time can be considerably reduced using the panels having the discrete alarm, discrete display, and CRT displays described above, the number of stimuli is still relatively high and, particularly during emergency operations, may cause delay in the operator's understanding of the status and trends of the critical systems of the NSSS. A single display is needed that presents only the highest level concerns to the operator and helps guide the operator to the more detailed information as it is needed. Although some attempts have been made in the past to present a large board or display to the operator, such displays to date have not included a significant consolidation of information in the nature to be described below. The IPSO board presents a high level overview of all high level concerns including overview of the plant state, critical safety and power functions, symbols representing key systems and processes, key plant data, and key alarms. IPSO information includes trends, deviations, numeric values of must representative critical function parameters, and the existence and system location of priority 1 alarms including availability and performance status for systems supporting the critical functions. This is otherwise known as success path monitoring. The IPSO board also can identify the existence and plant area location of other unacknowledged alarms. Thus IPSO bridges the gap between an operator's tendency toward system thinking and a more desirable assessment of critical functions. This compensates for reduction in the dedicated displays to help operators maintain a field plant conditions. It also helps operators maintain a field plant conditions. It also helps operators maintain an overview of plant performance while being involved in detailed diagnostic tasks. IPSO provides a common mental visualization of the plant process to facilitate better communication among plant personnel. In FIG. 25, the condition illustrated is a reactor trip. At the instance illustrated, the temperature rise in the reactor is 27.degree. and the average temperature rise is higher than desired and rising as indicated by the arrow and "+". The pressurizer pressure is higher than desired, but it is falling. Likewise, the steam generator water level is higher than desired but falling. FIG. 24 shows a CRT display page hierarchy wherein the IPSO is at the apex, the first level display page set contains generic monitoring information for each of the secondary, electrical, primary, auxiliary, power conversion and critical function systems, the second level of display pages relates to system and/or component control, and the third level of display pages provides details and diagnostic information. IPSO is a continuous display visible from any control room workstation, the shift supervisor's office, and Technical Support Center. The IPSO is centrally located relative to the master control console. The IPSO also exists as a display page format that is accessible from any control room workstation CRT as well as remote facilities such as the Emergency Operations Facility. The IPSO large panel format is 4.5 feet high by 6 feet wide. Its location, above and behind the MCC workstation, is approximately 40 feet form the shift supervisor's office (the furthest viewable point). One of the beneficial aspects of IPSO is the use of IPSO information to support operator response to plant disturbances, particularly when a disturbance effects a number of plant functions. IPSO information supports the operator's ability to respond to challenges in plant power production as well as safety-related concerns. IPSO supports the operator's ability to quickly assess the overall plant's process performance by providing information to allow a quick assessment of the plant's critical safety functions. The concept of monitoring plant power and safety functions allows a categorization of the power and safety-related plant processes into a manageable set of information that is representative of the various plant processes. The critical functions are: Critical To: ______________________________________ Function Power Safety ______________________________________ 1. Reactivity Control X X 2. Core Heat Removal X X 3. RCS Heat Removal X X 4. RCS Inventory Control X X 5. RCS Pressure Control X X 6. Steam/Feed Conversion X 7. Electric Generation X 8. Heat Rejection X 9. Containment Environment Control X 10. Containment Isolation X 11. Radiological Emissions Control X X 12. Vital Auxiliaries X X ______________________________________ A 3.times.4 alarm matrix block 160 containing a box 162 for each critical function exist in the upper right hand corner of IPSO (see FIG. 25 and the CRT display of IPSO in FIG. 10). The matrix provides a single location for the continuous display of critical function status. If a priority 1 alarm condition exists that relates to a critical function, the corresponding matrix box 164 will be highlighted in the priority 1 alarm presentation technique. Critical Function alarms are representative of one of the following priority 1 conditions: The 3.times.4 matrix representation is an overview summary of the 1st level critical function display page information (FIG. 22). The operator obtains the details associated with critical function and Success Path alarms in the Critical Function section of the display page. Each critical function can be maintained by one or more plant systems. Information on IPSO is most representative of the ability of supporting systems to maintain the critical functions. For some critical functions, the overall status of the critical function can be assessed by a most representative controlled parameter(s). For these critical functions, the process parameter's relationship to the control setpoint(s) and indication of improving or degrading trends is represented on IPSO to the right of the parameter's descriptor. An arrowhead as explained in FIG. 26 is used if the integral of the parameter's value is greater than an acceptable narrow band control value, indicating that the parameter is moving toward or away from the control setpoint. The arrowhead's direction, up or down, indicates the direction of change of the process parameter. If these parameters deviate beyond normal control bounds, a plus or minus sign is placed above or below the control setpoint representation. The following bases were used for the selection of parameters or other indications that are used on IPSO to provide the monitoring of the overall status of the critical functions. 1. Reactivity Control Reactor power is the only parameter displayed on the IPSO as a means of monitoring reactivity. Using Reactor Power, the operator can quickly determine if the rods have inserted. He can also use Reactor Power to determine the general rate and direction of reactivity change after shutdown. Reactor Power is displayed on IPSO with a digital representation 166 because a discrete value of this parameter is most meaningful to both operators and administrative personnel. The IPSO also provides an alarm representation on the reactor vessel if there is a priority 1 alarm condition associated with the Core Operating Limit Supervisory System. 2. Core Heat Removal A representative Core Exit Temperature 168 and Subcooled Margin 170 are the parameters presented on IPSO for determining if Core Heat removal is adequate. If Core Exit Temperature is within limits, then the operator can be assured of maintaining fuel integrity. The Subcooling Margin is used because it gives the operator the temperature margin to bulk boiling. Core Exit Temperature is represented on IPSO by using a dynamic representation (i.e., trending format), since there is a distinct upper bound that defines a limit to core exit temperature, and setpoints for representational characteristics can be easily defined. Subcooled Margin is also represented on IPSO using a dynamic representation since there is a lower bound which defines an operational limit for maintaining subcooling. 3. RCS Heat Removal T.sub.H, T.sub.C, S/G Level 172, and T.sub.ave 174 are used on IPSO to provide the operator the ability to quickly assess the efffectiveness of the RCS Heat Removal Function. In order to remove heat from the Reactor Coolant, S/G Level must be sufficiently maintained so that the necessary heat transfer can take place from the RCS to the steam plant. A dynamic representation is used so the operator can observe degradations of improvements in deviant condition at a glance. T.sub.H and T.sub.C are used on IPSO because they are needed by the operator to determine how much heat is being transferred from the reactor coolant to the secondary system. A digital value of these parameters is used since a quick comparison ofthese parameters is desired for observing the delta T. IN addition, an indication of their actual values are used often and would be helpful to an operator in locations where the discrete indicator displaying T.sub.h and T.sub.c is not easily visible. T.sub.ave is presented on IPSO using a dynamic representation to allow quick operator assessment of whether this controlled parameter is within acceptable operating bounds. 4. RCS Inventory Control Pressurizer Level 176 is presented on the IPSO using a dynamic representational indication to allow the operator to quickly access if the RCS has the proper quantity of coolant and observe deviations in level indicative of improving or degrading conditions. 5. CS Pressure Control Pressurizer Pressure 178 and Subcooled Margin is used as the indications on IPSO to determine the RCS Pressure Control. A dynamic representation is used on IPSO to notify the operator of changing pressure conditions that may indicate RCS depressurization or over pressurization. A dynamic representation is used on IPSO for saturation margin. A saturation condition in the RCS can adversely affect the ability to control pressure by the pressurizer. Also, if pressure is dropping, the subcooled margin monitor representation on IPSO depicts a decrease in the margin to saturation. 6. Steam/Feed Conversion The processes associated with Steam/Feed Conversion can be quickly assessed by providing the following information on IPSO: 7. Electric Generation The processes associated with Electric Generation can be quickly assessed by providing the following information on IPSO: 8. Heat Rejection The processes associated with heat rejection can be quickly assessed by providing the following information on IPSO: 9. Containment Environment Control Containment Pressure and Containment Temperature are the parameters which are used on the IPSO to monitor the control of the Containment Environment. These are presented on IPSO using a dynamic representation to allow assessment of trending and relative values. The Containment Pressure variable is used on the IPSO to warn the operator about an adverse overpressure situation which could be the result of a break in the Reactor Coolant System. The Containment Temperature also helps indicate a possible break in the Reactor Coolant System; it also can indicate a combustion in the Containment Building. 10. Containment Isolation The Containment Isolation Safety function is monitored on the IPSO with a Containment Isolation system symbol representation. This symbol will be driven by an algorithm which presents the effectiveness of the following containment isolation situations when the associated conditions warrant containment isolation: 11. Radiological Emissions Control Radiation symbols exist on IPSO which presents notification of high radioactivity levels such as inside containment, and (2) radiation associated with radioactivity release paths to the environment. These symbols will only be presented on IPSO when high radiation levels exist. These indications are presented in the alarm color in a location relative to the sensor in any of the following situations occurs: 12. Vital Auxiliaries Vital Auxiliaries are monitored on IPSO by providing the following information: The systems represented on IPSO are the major heat transport path systems and systems that are required to support the major heat transport process, either power or safety related. These systems include systems that require availability monitoring per Reg. Guide 1.47, and all major success paths that support the plant Critical Functions. The following systems have dynamic representations on IPSO: System Information presented on IPSO includes systems operational status, change in operational status (i.e., active to inactive, or inactive to active) and the existence of a priority one alarm(s) associated with the system. Alarm information on systems can also help inform an operator about success path related Critical Function alarms. Priority 1 alarm information is also presented on IPSO by alarm coding the descriptors of the representative features on IPSO as described above. V. INTEGRATION OF CONTROL ROOM FIG. 27 presents an overview of the integrated information presentation available to the operator in accordance with the invention. From the integrated process status overview or board, the operator may observe the high priority alarms. If the operator is concerned with parameter trends, he may view the discrete indicators. If he is interested in the system and component status, he may view the settings on the system controls. Thus, the IPSO information is displayed either on the board or at the panel CRT, and the other information from the operator's panel or any other panel, is available to the operator on his CRT. From the IPSO overview, the operator may navigate through the CRT or DIAS display pages. Moreover, the operator has direct access to either of these types of information from any of the control panels and when a system control is adjusted or set, the results are incorporated into the other alarm and display generator in the other panels. As shown in FIGS. 2 and 28-31, in general overview, the integration of the system means that each panel including the main console, the safety console, and the auxiliary console, includes a CRT 84 which is driven by the data processing system 70. The data processing system utilizes the plant main computer and, although being more powerful, it is not as reliable as the DIAS 72 computers (which may be distributed microprocessors-based or mini-computer based). Also, it is slower because it is menu driven and performs many more computations. It is used primarily for conveying the most important information to the operator and thus important alarm tiles can be viewed on each CRT and acknowledged from any CRT. Any information available on one CRT is available at every other CRT. The indicator and alarm system 72 for a given panel is related to the controls, but the discrete (i.e., quick and accurate) aspects of the alarms and indicator displays 78, 82, and controls of that panel are not available at any other panel. Basically, information is categorized in three ways. Category 1 information must be continuously displayed at all times and this is accomplished in DIAS 72. Category 2 information need not be continuously available, but it must nevertheless be available periodically and this is also the responsiblity of DIAS 72. Category 3 information is not needed rapidly and is informational only, and that is provided by the DPS 70. In the event of the failure of DPS, some essential information is provided by DIAS. The DPS and DIAS are connected to the IPSO board by a display generator 180. From the IPSO, the operator can obtain detailed information either by going to the panel of concern, or paging through the CRT displays. It should be appreciated that DIAS and DPS do not necessarily receive inputs for the same parameters, but, to the extent they do receive information from common parameters, the sensor for these parameters are the same. Moreover, the validation algorithms used in DIAS and DPS are the same. Furthermore, the algorithms used for the discrete alarm tiles and the discrete indicators include as part of the computation of the "representative" value, a comparison of the DIAS and DPS validated values. FIG. 29 is a block diagram representing the discrete indicator and alarm system in relation to other parts of the control room signal processing. The DIAS system preferably is segmented so that, for example, all of the required discrete indicator and discrete alarm information for a given panel N is processed in only one segment. Each segment, however, includes a redundant processor. The information and processing in DIAS 1 is for category 1 and 2 information which is not normally displayed directly on IPSO. IPSO normally receives its input from the DPS. However, inn the event of a failure of DPS, certain of the DIAS information is then sent to the IPSO display generator for presentation on the IPSO board. It should also be appreciated that both DIAS and the DPS utilize sensor output from all sensors in the plant for measuring a given parameter, but that the number of sensor in the plant for a given parameter may differ from parameter to parameter. For example, the pressurizer pressure is obtained from 12 sensors, whereas another parameter, for example, from the balance of plant, may only be measured by two or three sensors. Some systems, such as the plant protection system, do not employ validation because they must perform their function as quickly as possible and employ, for example, a 2 out of 4 actuation logic from 4 independent channels. In the event the validation for a given parameter differs as determined within two or more systems, an alarm or other cue will be provided to the operator through the CRT. One of the significant advantages of the present invention is that the DPS need not be nuclear qualified, yet it can be confidently used because it obtains parameter values from the same sensors as the nuclear qualified DIAS. These are validated in the same manner and a comparison is made between the validated DPS parameters and the validated DIAS parameters, before the DPS information is displayed on the CRTs or the IPSO. The nuclear qualification of the alarm tiles and windows, and the discrete indicator displays in the DIAS are preferably implemented using a 512.times.256 electroluminescent display panel, power conversion circuitry, and graphics drawing controller with VT text terminal emulation, such as the M3 electroluminescent display module available from the Digital Electronics Corporation, Hayward, Calif. The control function of each panel is preferably implemented using discrete, distributed programmable controllers of the type available under the trademark "MODICON 984" from the AEG Modicon Corporation, North Andover, Mass. U.S.A. Thus, the computational basis of the DIAS is with either distributed, discrete programmable microprocessors or mini computers, whereas the computational basis of the DPS is a dedicated main frame computer. The ES control system and the process component control system are show schematically in FIG. 31, whereas the plant protection system is preferably of the type based on the "Core Protection Calculator" system such as described in U.S. Pat. No. 4,330,367, "System and Process for the Control of a Nuclear Power System", issued on May 18, 1982, to Combustion Engineering, Inc., the disclosure of which is hereby incorporated by reference. Another aspect of integration is the capability to display the critical functions and success path in IPSO as described above. Since the major safety and power generating signal and status generators are connected to both DIAS and DPS, the operator may page through the critical functions in accordance with the display page hierarchy shown in FIGS. 32 through 35. In FIG. 33, the operator is informed that the emergency feed is unavailable in the reactant coolant system. In FIG. 34, the operator is informed that the emergency feed is unavailable and the reactor is in a trip condition. Under these circumstances, the operator must determine an alternative for removing heat from the reactor core and by paging to the second level of the critical function display page which, although shown for inventory control (FIG. 35), would have a comparable level of detail for heat removal. This type of information with this level of detail and integration is available for all critical functions under substantially all operating conditions, not only during accidents. VI. PANEL MODULARITY It should be appreciated that, as mentioned above, the discrete tile and message technique significantly reduces the surface area required on the panel to perform that particular monitoring function. Similarly, the discrete display portion of the monitoring function, including the hierarchical pages, is condensed relative to conventional nuclear control room systems. The control function on a given panel can be consolidated in a similar fashion. Thus, a feature of the present invention is the physical modularity of each panel constituting the master control console, and more generally, of each panel in the main control room. In essence, the space required for effective interface with the operator for a given panel, becomes independent of the number of alarms or displays or controls that are to be accessed by the operator. For example, as shown in FIG. 3, six locations on each side of the CRT may be allocated for alarm and indicator display purposes. Preferably, the top two on each side are dedicated to alarms 78 and the other four on each side dedicated to the indicator display 82. An identical layout is provided for each panel in the control room. This permits significant flexibility and cost savings during the construction phase of the plant because the hardware can be installed and the terminals connected early in the construction schedule, even before all system functional requirements have been finalized. The software based systems are shipped early with representative software installed to allow preliminary checking of the control room operations. Final software installation and functional testing are conducted at a more convenient point in the construction schedule. This method can accelerate plant construction schedules for the instrumentation and control systems significantly. Since the instrumentation and control requirements for a given plant are often not finalized until late in the plant design schedule, the present invention will in almost every case significantly reduce costly delays during construction. This is in addition to the obvious cost savings in the ability to fabricate uniform panels, both in the engineering phase normally required to select the locations of and lay out the alarms and displays, and in the material savings in fabricating more compact panels. Furthermore, such modularity in the plant facilitates the training of operators and, when operators are under stress during emergencies, should reduce operator error because the functionality of each panel is spatially consistent. Thus, each modular control panel has spatially dedicated discrete indicators and alarms, preferably at least one spatially dedicated discrete controller at 88, a CRT 84, and interconnections with at least one other modular control panel or computer for communication therewith. For example, communication via the DPS includes, among other things, the ability to acknowledge an alarm at one panel while the operator is located at another panel, and the automatic availability at every other panel of information concerning the system controlled at one panel. FIG. 36(a) illustrates the conventional sequence for furnishing instrumentation and control to a nuclear power plant and 36(b) the sequence in accordance with the invention. Conventionally, the input and outputs are defined, the necessary algorithms are then defined, and these specify the man machine interface. Fabrication of all equipment then begins and all equipment is installed in the plant at substantially the same time before system testing can begin. In contrast, the modularity of the present invention permits fabrication of hardware to begin immediately in parallel with the definition of the input/output. Likewise, the hardware can be installed and generically tested in parallel with the definition of the man machine interface and the definition of the algorithms that are plant specific. The hardware and software are then integrated before final testing. In a conventional nuclear installation, the equipment is installed during the fourth year of the entire instrumentation and control activity, whereas with the present invention, equipment can be installed during the second or third year. With further reference to FIG. 2, the process component control system and the engineered safety features component control system 56 use programmable logic controllers similar to the Modicon equipment mentioned above including input and output multiplexors and associated wires and cabling, all of which can be shipped to the plant before the plant specific logic and algorithms have been developed. The equipment is fault tolerant. The data processing system 70 uses redundant plant main frame computers, along with modular software and hardware and associated data links. such hardware can be delivered and the modular software that is specific to the plant installed, just prior to integration and system testing. The DIAS 72 also uses input/output multiplexors and a fault tolerant arrangement, with programmable logic processors or mini-computers, with the same advantages as described with respect to the process control and engineered safety features control systems. APPENDIX DETAILED EXAMPLES OF VALIDATION ALGORITHM This Appendix describes the details of the generic validation and display algorithm implemented in the DPS and DIAS. Definition of Terms Used in Discussion PAMI--Post Accident Monitoring Instrumentation. Instrument Uncertainty--The performance accuracy of a sensor and its transmitter (i.e., if accuracy is .+-.1%, the instrument uncertainty is 2%). Expected Process Variation--The difference in temperature (or other unit of measurement) between sensors measuring the same process parameter due to expected variation in the process temperature (or other unit of measurement) at different sensor locations. Calculated Signal--A single signal that the algorithm calculates to represent all sensors measuring the same parameter. Process Representation--A single signal that is output for displays and alarms where a single value is needed as opposed to multiple sensor values. The "process representation" will always be the "calculated signal" unless a failure has occurred. After a failure it may be the output of a single sensor selected by the operator or algorithm. Valid--A "calculated signal" that has been verified too be accurate by successfully deviation checking all of its inputs with their average. Valid PAMI--A "valid" "process representation" that deviation checks successfully against the "PAMI" sensors. Validation Fault--A failure of the validation and display algorithm to calculate a "Valid" "Calculated Signal". PAMI Fault--A failure of the "Calculated Signal" to deviation check successfully against the "PAMI" sensors. Fault Select--The "calculated signal" that is the output of the sensor closest to the last "valid" signal at the time validation initially failed. Operator Select--A "process representation" that is the output of the sensor that the operator has selected after a "PAMI Fault" or a "Validation Fault". Good--A label given to a sensor that deviation checks successfully against the "Operator Select" or "Valid" "Process Representation". Bad--A label give to a sensor that fails to deviation check successfully against the "Valid" "Process Representation". Suspect--A label given to the "good" sensor that deviates the most from the average "calculated signal" when any deviation check fails. "Validation Fault Operator Select Permissive"--The permissive that allows the operator to select an individual sensor as the "Process Representation" when the algorithm is unable to calculate a "valid" signal. "PAMI Fault Operator Select Permissive"--The permissive that allows the operator to select an individual sensor as the "Process Representation" when the "valid" "calculated signal" does not deviation check successfully against "PAMI" indication. Validation and Display Algorithm The sensor inputs (A, B, C, D) are all read ad stored at the time the algorithm begins. The algorithm uses these stored inputs to perform all steps (1-10), which comprise a scan. When the algorithm is repeated (after step 10), the sensor inputs are read and stored again, for use on the new scan. Determination of "Calculated Signal" and Faults (steps 1, 2, 3, 4, 5) Validation Attempts (steps 1, 2, 3) 1. The algorithm checks to see if there are 2 or more "good" sensors. Note: A sensor is "good" if it was not declared a "bad" sensor on the previous scan or a "suspect" sensor on a previous pass. 2. The algorithm average all "good" sensors (A, B, C, D). Go to step 3. 3. Deviation checks all good sensors against the average (within sum of 1/2 instrument uncertainty and expected process variation). Note: if the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. Note: Failing to pass the deviation check on the second pass indicates that there are two or more simultaneous sensor failures. The algorithm cannot be sure to correctly eliminate only the bad sensors, therefore the algorithm must fail. This ensures that the algorithm does not calculate an incorrect "valid" signal for this case. Normally without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. Valid--PAMI Check (step 4) 4. (Step applicable if process has a Category 1 PAMI Sensor). If there is no PAMI sensor(s) in this process, the step is not performed, go to step 6. Note: The "PAMI Fault Operator Select Permissive" allows the operator to select any sensor for the "process representation" when the "calculated signal" (i.e., algorithm's "valid" output) does not agree with the PAMI sensor(s). Failed Validation (step 5) 5. The algorithm checks to see if the "calculated signal" on the previous scan was a "Fault Select" sensor. Note: this step ensures that the algorithm will attempt to validate using all sensors not previously determined "bad" on the next validation attempt. Note: It is important that the sensor initially fault selected be retained since over time other failed sensors may erroneously appear more accurate. "Process Representation" Selection (steps 6, 7) 6. The algorithm checks to see if there is either the "Validation Fault Operator Select Permissive" or the "PAMI Fault Operator Select Permissive". Note: A validation fault enables one Operator Select Permissive and failure of the "valid" algorithm output to deviation check satisfactorily against "PAMI" gives the other Operator Select Permissive. 7. Check to see if the operator has selected a sensor as the "process representation". Note: This step outputs the "calculated signal" as the "process representation" when the operator has the option to select a sensor, but does not use that option. PAMI Check of "Operator Select" Sensor (step 8) 8. Does the "operator select" sensor deviation check against the PAMI sensor (within sum of PAMI instrument uncertainty and expected process variation). Bad Sensor Evaluation (step 9) 9. Is the "process representation" "valid" or "operator select". Range Check (step 10) 10. The algorithm checks to see if the "process representation", is at or above the maximum numerical range, or at or below the minimum numerical range for the sensors. Note: "Out-of-range" informs the operator that the actual process value may be higher or lower than the sensor is capable of measuring. In the case of process measurements with multiple ranges of sensors this check will cause the selection of sensors in a new range. Note: On the RCS panel, RCP Differential Pressure, SG Differential Pressure and Pressurizer Level Reference Leg Temperature use this generic validation algoirthm directly. The T.sub.cold, T.sub.hot, Pressurizer Level and Pressurizer Pressure algorithms this generic algorithm with additional steps and minor modifications to accommodate: T.sub.cold Validation Algorithm (FIG. 37) There are 12 sensors used to measure cold leg temperatures in the RCS. During most operational sequences, the operator is looking for a single "process representation" of all cold leg temperatures in the RCS. This value will be provided in the DIAS with a display labeled "RCS T.sub.cold ". For consistency, this value, which is determined by DIAS, is also used on the Integrated Process Status Overview (IPSO) board. To ensure reliability, DPS compares DIAS's RCS T.sub.cold "process representation" with its own RCS T.sub.cold and alarms any deviations (DPS/DIAS RCS T.sub.c Calculation Deviation). A three step validation algorithm is used to determine this value: The three step process determines "valid" "process representation" temperatures for cold legs 1A, 1B, 2A and 2B, cold loop 1 ad 2 and RCS T.sub.c. For situations when a "valid" cold leg "process representation" temperature cannot be calculated the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "process representation" temperature. This automatic fault selection ensures a continuous output of the RCS T.sub.cold "process representation" for display and alarms. After a failure the operator may select an individual sensor for that cold leg (1A, 1B, 2A, 2B) "process representation". This selection will allow calculation of loop 1, loop 2 and RCS T.sub.cold "process representation", with "operator select" data. The following section describes the algorithm and display processing on the DIAS and CRT displays. ______________________________________ T-112CA/122CA 465-615.degree. F. T.sub.cold Loop 1A/2A T-112CB/122CB 465-615.degree. F. T.sub.cold Loop 1B/2B T-112CC/122CC 465-615.degree. F. T.sub.cold Loop 1A/2A T-112CD/122CD 465-615.degree. F. T.sub.cold Loop 1B/2B T-111CA/111CB/ 50-750.degree. F. T.sub.cold Loop 1A/1B/ 123CA/123CB 2A/2B, PAMI Loop 1A Tc Calculated Signal Loop 1B Tc Calculated Signal Loop 2A Tc Calculated Signal Loop 2B Tc Calculated Signal Loop 1 Tc Calculated Signal Loop 2 Tc Calculated Signal RCS Tc Calculated Signal ______________________________________ Method to Determine Cold Leg 1A, 1B, 2A, or 2B T.sub.cold "Process Representation" The determination of the Cold Leg "Process Representation" will be performed in four parts: Cold Leg (1A, 1B, 2A or 2B Validation and Display Algorithm Determination of "Calculated Signal" and Faults (steps 1-8) Narrow range Validation Attempt (Steps 1-5) 1. The algorithm checks to see if there are two "good" narrow range sensors (A and B). Note: A sensor is "good" if it was not declared a "bad" sensor on the previous scan. Range Selection (Step 4) 4. The algorithm checks to see if the average or selected narrow range sensor is in-range. Note: Hysteresis is needed to prevent frequent shifts at end-of-range. Out-of-range occurs at 98% and 2% to ensure that no out-of-range sensors are used to calculate a "valid" output (i.e.: worst case sensors would read 100% or 0%). 5. The algorithm deviation checks narrow range sensors (A and B) against sensor C (within sum of wide range instrument uncertainty and expected process variation). Valid PAMI Check (step 6) 6. The algorithm checks to see if the "valid" average or selected sensor deviation checks satisfactorily against the PAMI sensor (C). (Within sum of 1/2 wide range uncertainty and expected process variation). Note: this feature allows the operator to select another sensor for the cold leg "process representation" when the algorithm's "valid" output does not correlate with postaccident monitoring indication (sensor c). Wide Range Validation Attempt (Step 7) 7. Deviation check C against D (within sum of wide range instrument uncertainty and expected process validation). Note: to validate the signal wide range sensor in a cold leg, the algorithm deviation checks it against the wide range sensor in the other cold leg of that loop (i.e., if in loop 1, 1A wide range sensor is deviation checked against the 1B wide range sensor). Failed Validation (step 8) 8. The algorithm checks to see if the "calculated signal" on the previous scan was a "fault select" sensor. T.sub.c Leg (A or B) "Process Representation" Selection (Steps 9, 10) 9. Step 9 is identical to step 6 of the generic validation algorithm. 10. Step 10 is identical to step 7 of the generic validation algorithm except for the following. The operator may select any sensor A, B or C from that cold leg or A, B, C from the opposite cold leg (A or B) as the "process representation". PAMI Check of "Operator Select" Sensor (Step 11) 11. This step is identical to step 8 of the generic validation algorithm. Bad Sensor Evaluation (Step 12) 12. This step is identical to step 9 of the generic validation algorithm except that wide range instrument uncertainties are used on all deviation checks except when narrow range sensors are being deviation checked against a narrow range signal, in this case narrow range instrument certainties will be used. Range Check (Step 13) 13. This step is identical to step 10 of the generic validation algorithm. Method to Determine Loop 1 and 2 T.sub.cold "Process Representation" The loop 1 and 2 T.sub.c "process representation" will be calculated by averaging the "process representation" from the A and B cold legs (1A and 1B for loop 1), (2A and 2B for loop 2). Note: to simplify the discussion of the cold leg (1A, 1B, 2A or 2B) "process representation" inputs to the loop 1 or loop 2 algorithm, A will designate the input from leg 1A or 2A and B will designate the input from leg 1B or 2B leg T.sub.c. 1. The algorithm averages the "process representation" inputs from the A and B cold legs and outputs the average as the loop (1 or 2) T.sub.c "process representation". 2. The algorithm checks to see if A and B are "valid". 3. The algorithm checks to see if A or B is "operator select". 4. The algorithm checks to see if A or B is "fault select". 5. Deviation check A and B against the average. (within sum of 1/2 wide range instrument uncertainty and expected process variation). 6. The algorithm checks to see if A and B are narrow range. 7 . The algorithm checks to see if either or both inputs is out-of-range. 8. The algorithm checks to see if A and B inputs are PAMI. Method to Determine RCS T.sub.cold 5. The algorithm checks to see if signal 1 or 2 is "fault select". Range Check 6. This step is identical to step 10 of the generic validation algorithm. Go to step 1 and repeat the algorithm. Pressurizer Pressure Validation Algorithm (FIG. 38) There are 12 sensors used to measure pressurizer and RCS pressure. During most operational sequences, the operator is looking for a single "process representation" of all pressurizer/RCS pressure readings. This value will be provided in DIAS with a display labeled "PRESS". For consistency, this value, which is determined by DIAS, is also used on the IPSO board. To ensure reliability, DPS compares DIAS's Press "process representation" with its own Press "process representation" and alarms any deviations (DPS/DIAS Press Calculation Deviation). The algorithm determines a "valid" "process representation" for pressurizer/RCS pressure. For situations when a "valid" signal as the "fault select" "process representation" pressure. This automatic fault selection ensures continuous output of the pressurizer/RCS "process representation" pressure for displays and alarms. After a failure the operator may select an individual sensor for the pressure "process representation" as the "fault select" "process representation". The following section describes the algorithm and display processing on the DIAS and CRT displays. 1. The "process representation" pressure shall always be displayed on the applicable DIAS display and/or the CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. 2. The pressure algorithm and display processing is identical to the generic validation algorithm with the following modifications: 3. Using a menu (as described in the generic validation algorithm) the operator may view any of the 12 sensor values or signal "calculated signal". ______________________________________ P-103, 104, 105, 106 0-1600 psig Pressurizer Pressure P-101A, 101B, 101C, 1500-2500 psig Pressurizer Pressure 101D, 100X, 100Y P-190A, 190B 0-4000 psig RCS Pressure, PAMI CALC PRESS Calculated Signal ______________________________________ Validation Algorithm To simplify the discussion of sensor tag numbers, the following letters will be used to designate pressure sensors: ______________________________________ P - 101A - A P - 101B - B P - 101C - C P - 101D - D P - 100X - E P - 100Y - F P - 103 - G P - 104 - H P - 105 - I P - 106 - J P - 190A - K P - 190B - L ______________________________________ The algorithm described below is calculated and displaced independently by both DPS and DIAS. The pressurizer pressure "calculated signal" will be calculated using sensors A, B, C, D, E, F, G, H, I, J, K and L. An attempt will be made to use the narrow 1500-2500 psig range sensors (A, B, C, D, E and F) (pressure is normally in this range). If pressure is outside the 1500-2500 psig range, the 0-1600 psig range sensors (G, H, I and J) will be used. If pressure cannot be calculated using these sensors, the 0-4000 psig range sensors (K and L) will be used. In the event that the validation fails all of these three ranges, the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "calculated signal". this "fault select" "calculated signal" will be used as the "process representation" until the operator selects an "operator select" sensor to replace it or the algorithm is able to validate data. Pressurizer Pressure Validation and Display Algorithm Determination of Calculated Signal and Faults (steps 1-13) 1500-2500 psig Range Validation Attempt (steps 1-4) 1. The algorithm checks to see if there are 2 or more "good" (1500-2500 psig narrow range) sensors. Note: A sensor is "good" it was not declared a "bad" sensor on the previous pass or a suspect sensor on a previous pass. 2. The algorithm averages all "good" (1500-2500) range sensors (A, B, C, D, E and F). Go to step 3. 3. Deviation check all "good" (1500-2500) range sensors against the average (within sum of 1/2 narrow range uncertainty and expected process variation). Note: If the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. Note: Failing to pass the deviation check on the second pass indicates that there are two or more simultaneous (1500-2500) range sensor failures. The algorithm cannot be sure to correctly eliminate only the bad sensors, therefore the (1500-2500) range validation must fail. The 0-1600 psig range validation is attempted. This ensures that the algorithm does not calculate an incorrect signal for this case. Normally without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. Range Selection (step 4) 4. The algorithm checks to see if the average is in-range. Note: Hysteresis prevents frequent range shifts. Out-of-range occurs at 98% and 2% to ensure that no out-of-range sensors are used to calculate a "valid" output (i.e., worst case sensors would read 100% and 0%). 0-1600 psig Range Validation Attempt (steps 5-8) 5. The algorithm checks to see of there are 2 or more "good" 0-1600 psig range sensors (G, H, I and J). 6. The algorithm averages all "good" 0-1600 psig range sensors (G, H, I and J). Go to step 7. 7. Deviation check all "good" 0-1600 psig range sensors against the average (within sum of 1/2 of the 0-1600 psig range uncertainty and expected process variation). Note: If the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. Note: Failing to pass the deviation check on the second pass indicates that there are two or more simultaneous 0-1600 psig range sensor failures. The algorithm cannot be sure to correctly eliminate only the bad sensors, therefore the 0-1600 psig rage validation must fail. The 0-4000 psig range is attempted. This ensures that the algorithm does not calculate an incorrect signal for this case. Normally, without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. Range Selection (step 8) 8. The algorithm checks to see if the average is in-range. 0-4000 psig Range Validation Attempt (steps 9, 10, 11) 9. The algorithm checks to see if both of the 0-4000 psig range sensors (K and L) are "good". 10. The algorithm averages K and L, the 0-4000 psig range sensors. Go to step 11. 11. Deviation check K and L against the average (within sum of 1/2 0-4000 psig range uncertainty and expected process variation). Valid-PAMI Check (step 12) 12. Does the "valid" "calculated signal" deviation check against the PAMI sensors. Use a method a. If the "valid" "calculated signal" is in the 1500-2500 psig or 0-1600 psig range, and method b. If in the 0-4000 psig range. Method (a) (within sum of 1/2 0-4000 psig range instrument uncertainty, plus process variation, plus instrument position constant). Method (b) (within sum 1/2 0-4000 psig range instrument uncertainty, plus process variation). Note: The (0-4000 psig) wide range sensors (K and L) are not located on the pressurizer, as are the other pressure sensors. The K and L sensors are positioned at the discharge of the reactor coolant pumps (RCPs) where they measure RCS pressure. During normal operation the pressure at this location is much higher (approximately 110 psi for a System 80 plant) than at the pressurizer, where sensors (A, B, C, D, E, F, G, H, I and J) are located. An additional deviation acceptance criteria (called instrument position constant) will be used when deviation checks are made with or against the K and L (0-4000 psig range) sensors. Failed Validation (step 13) 13. The algorithm checks to see if the "calculated signal" output of the previous scan was a "fault select" sensor. Pressurizer Pressure "Process Representation" Selection (steps 14, 15) 14. Step 14 is identical to step 6 of the generic validation algorithm. 15. Step 15 is identical to step 7 of the generic validation algorithm. PAMI Check of "Operator Select" Sensor (step 16) 16. Step 16 is identical to step 8 of the generic validation, except that the deviation criteria are the same as those specified in step 12 of this pressurizer pressure validation and display algorithm. Bad Sensor Evaluation (step 17) 17. This step is identical to step 9 of the generic validation algorithm, except that the deviation criteria checks are the same as those specified in step 12 of this pressurizer pressure validation and display algorithm. Range check (step 18) 18. The algorithm checks to see if the "process representation" is at or above the maximum numerical range (1600 psig for the 0-1600 psig sensors, 2500 psig for the 1500-2500 psig sensors and 4000 psig for the 0-4000 psig sensors) or at or below the minimum numerical range (0 psig for the 0-1600 psig and 15-4000 psig sensors and 1500 psig for the 1500-2500 psig sensors). Note: "Out-of-range" informs the operator that the actual pressure may be higher or lower than the sensor is capable of measuring.
054229200	claims	1. A method for estimating crystal grain sizes of nuclear fuel pellets comprising: (a) heating a plurality types of UO.sub.2 powders of a predetermined amount at a predetermined temperature raising speed in dry air of a constant flow amount, thereby measuring weight change ratios occurring due to the oxidation of each of the UO.sub.2 powders; (b) determining for each kind of UO.sub.2 powders a temperature at which a composition of the powder arrives at from the UO.sub.2+x phase to the U.sub.3 O.sub.7 phase, on the basis of a change in the weight change ratios; (c) producing UO.sub.2 sintered pellets from the plurality types of UO.sub.2 powders in which the arrival temperatures are known; (d) measuring the crystal grain sizes of the plurality types of the sintered pellets produced in the (c); (e) recognizing a correlation between the U.sub.3 O.sub.7 phase arrival temperature determined in the (b) and the crystal grain size of the sintered pellet measured in the (d); (f) determining a U.sub.3 O.sub.7 phase arrival temperature of a UO.sub.2 powder of a test sample under the same conditions as those in the (a) and (b); and (g) estimating a crystal grain size of the UO.sub.2 powder of the test sample upon production into a sintered pellet, according to the U.sub.3 O.sub.7 phase arrival temperature determined in the (f) and the correlation determined in the (e). 2. The method for estimating crystal grain sizes of nuclear fuel pellets according to claim 1 wherein the value at which the weight change ratio changes in said (b) is determined, after drawing an oxidation curve of the UO.sub.2 powder, from an inflection point of the curve. 3. The method for estimating crystal grain sizes of nuclear fuel pellets according to claim 1 wherein the measurement of the crystal grain size of the sintered pellet in said (d) is performed such that a cross section of the UO.sub.2 sintered pellet is polished, thereafter an etching treatment is performed to expose crystal grain boundaries, and image information obtained by an optical microscope or a scanning type electron microscope is used by means of a cross-sectional method.
039487245	summary	This invention relates to a device for handling rod-shaped members of a nuclear reactor and more particularly refers to a new and improved traveling device for transfer of rod-shaped members in and from a nuclear reaction vessel. Devices for handling rod-shaped elements in nuclear reactors usually have a hoisting unit which together with a gripping device operates via a number of connecting members such as rods, ropes, chains and the like to move fuel, breeder or absorber rods in and out of the reactor. To be effective, it is necessary to place the gripping device and of course the hoisting unit into a position perpendicular above the rod-shaped member to be moved. In the known devices of this type, this is accomplished via construction involving a main rotary cover with a second smaller rotary cover arranged eccentrically within the main rotary cover, and a hoisting unit disposed on the second smaller rotary cover. Through rotating motions of both rotary covers relative to each other and to the reactor vessel, the hoisting unit may be transported into position above the fission zone of the reactor. Other additional auxiliary equipment must also be affixed to the rotary cover. To accommodate the additional auxiliary equipment and the handling device without interfering with one another during rotary movements of the covers, it becomes necessary to employ large reactor containers with large rotary covers to properly space the appliances. This results in appreciably increased costs which are magnified by the presence of a plurality of rotary covers and their complicated drives. It is accordingly an object of the invention to provide a device for handling rod-shaped members in a nuclear reactor employing a single rotary cover. Another object of the present invention is to provide a handling device in conjunction with a small reaction vessel of a diameter not substantially greater than the fission zone which it encompasses. With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for handling rod-shaped members of a nuclear reactor comprising a reaction vessel, a reactor core containing rod-shaped members in the reaction vessel, a rotary cover on the reaction vessel, means for rotating the rotary cover, a slot in said rotary cover, a hoisting unit arranged on said rotary cover, means for moving said hoisting unit along said slot, a grip for grasping a rod-shaped member, transmission means interconnected with said hoisting unit for movement of said grip in the slot, whereby through rotation of said rotary cover and movement of said hoisting unit along the slot, said grip may be moved into position for transfer of any desired rod-shaped member. In accordance with the invention, the device for handling rod-shaped members is provided with a rotary cover having a slot therein and the hoisting unit disposed on the rotary cover moves along the slot situated in the rotary cover. The intermediate transmission elements connected to the remote control grip move in this slot. The slot may extend over the entire rotary cover or only over a portion thereof, depending on whether the handling device is to be used only for relocating rod members within individual positions of the fission zone or depositing positions adjacent thereto or whether the entire cross section of the reactor vessel is to be accessible. In a preferred embodiment, the slot is arranged radially in the rotary cover thus obtaining a favorable relation between the length of the slot and the area which is swept by the slot during the rotation of the rotary cover. gas from shielding box or gas-tight hood is disposed on the rotary reactor cover sealed to the cover to prevent emission of radioactive radiation or protective from the reaction vessel and to prevent penetration of air thereinto. The shielding box should be of ample size to ensure the free mobility of the hoisting unit in its interior. Movement of the hoisting unit along the slot may be accomplished by means of a carriage or cart on which the hoisting unit rests. To prevent exposure of the hoisting unit and the gripping device to the corrosive effects of the reactor atmosphere particularly from reactors cooled with liquid metal, provision is made for preventing the gaseous atmosphere from the reactor vessel passing up through the slot into the area of the hoisting unit by means of two expansion members such as bellows or other pleated members, connected at one end with the wall of the shielding box and at the other end with the carriage which carries the hoisting unit. The bellows, by acting as a barrier to convection of gaseous currents from the atmosphere of the reaction vessel, protects the hoisting unit against impurities stemming from the reactor atmosphere, which contains for example gas, steam or coolant particles of metal. Another feature of the invention is the provision of a shielding block inserted from the side to seal the slot thereby making the hoisting unit and the bellows, following the removal of the shielding box, accessible for repair and maintenance work. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a device for handling rod-shaped members of a nuclear reactor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
	claims	1. A storage rack arrangement for the storage of nuclear fuel elements in a storage pool, wherein the storage rack arrangement (10) includes at least two storage racks (1, 1.1-1.3) which each contain a plurality of vertical channels (9) arranged next to one another for the reception of the fuel elements, and wherein positioning elements (6) are provided at the storage racks at the bottom, characterized in that storage racks (1, 1.1-1.3) arranged next to one another are connected to one another at the top; and in that the storage rack arrangement (10) additionally includes one or more base plates (2.1-2.3) which are provided with positioning members (8) which fit with the positioning elements (6) of the storage racks (1, 1.1-1.3) and which, together with the positioning elements, position the storage racks with respect to the base plate or base plates to prevent lateral movement of the storage racks relative to the base plate or plates. 2. A storage rack arrangement in accordance with claim 1, wherein the positioning elements (6) are made as support elements on which the storage racks (1, 1.1-1.3) are supported, and wherein the positioning members (8) are made as seats in the base plate or plates (2.1-2.3) or as projecting parts on the base plate or plates. 3. A storage rack arrangement in accordance with claim 1, wherein the support elements (6) are each provided with support members (6a), in particular with vertically adjustable support members, to support the storage racks (1, 1.1-1.3) on the base plate or plates (2.1-2.3) or on the floor 12 of the storage pool. 4. A storage rack arrangement in accordance with claim 1, wherein the positioning element (6) are each made, together with the associated positioning member (8),as a plug connection or as a holder with a part to be held. 5. A storage rack arrangement in accordance with claim 1, wherein the base plate or base plates (2.1-2.3) are displaceable on the floor (12) of the storage pool. 6. A storage rack arrangement in accordance with claim 1, wherein storage racks (1.1, 1.2) arranged next to one another are each positioned with or connected to at least one common base plate (2.1-2.3). 7. A storage rack arrangement in accordance with claim 1, wherein the base plates (2.1-2.3) are arranged at the periphery of the storage racks (1, 1.1-1.3), or wherein base plates are substantially arranged at the total periphery of the storage racks. 8. A storage rack arrangement in accordance with claim 1, wherein the base plate or base plates (2.1-2.3) extend over at least 80% of the base area of the storage rack arrangement (10) or substantially over the total base area of the storage rack arrangement. 9. A storage rack arrangement in accordance with claim 1, wherein the base plate or base plates (2.1-2.3) are larger than the base area of a storage rack (1, 1.1-1.3). 10. A storage rack arrangement in accordance with claim 1, wherein the base plate or base plates (2.1-2.3) project with respect to the storage racks (1, 1.1-1.3). 11. A storage rack arrangement in accordance with claim 1, wherein the base plates (2.1-2.3) are connected to one another independently of the connection of the storage racks (1, 1.1-1.3). 12. A storage rack arrangement in accordance with claim 1, wherein the storage racks (1, 1.1-1.3) are each provided with lateral braces (4.1-4.4, 4.1′, 4.1″, 4.2′, 4.2″). 13. A storage rack arrangement in accordance with claim 12, wherein the braces (4.1, 4.2; 4.3, 4.4) of adjacent storage racks (1.1-1.3) are connected to one another at an upper section of the storage racks (1.1-1.3). 14. A storage rack in accordance with claim 13, wherein the braces (4.1, 4.2; 4.3, 4.4) of adjacent storage racks (1.1-1.3) are each connected to one another by means of a screw connection (5, 5.1, 5.2). 15. A storage rack arrangement in accordance with claim 1, wherein the storage racks (1, 1.1-1.3) are provided on each side with at least three substantially vertically extending braces (4.1′, 4.1″, 4.2′, 4.2″). 16. A storage rack arrangement in accordance with claim 1, wherein the positioning elements (6) and the positioning members (8) are configured to collectively fix the storage racks (1, 1.1-1.3) within a prescribed horizontal position with respect to the base plate (2.1-2.3). 17. A storage rack arrangement in accordance with claim 1, wherein the base plate (2.1-2.3) and storage racks (1, 1.1-1.3) are configured to be interconnected independent of a fixed connection therebetween. 18. A storage rack arrangement for the storage of nuclear fuel elements in a storage pool, the storage rack arrangement (10) comprising:at least two storage racks (1, 1.1-1.3) connected to each other, each storage rack including:a plurality of vertical channels (9) arranged next to one another for the reception of the fuel elements; anda plurality of positioning elements (6) coupled to the storage racks and selectively positional thereon;at least one base plate (2.1-2.3) including positioning members (8) sized and configured to fit with the positioning elements (6) of the storage racks (1, 1.1-1.3) to collectively position the storage racks (1, 1.1-1.3) with respect to the at least one base plate (2.1-2.3) to prevent lateral movement of the storage racks (1, 1.1-1.3) relative to the base plate (2.1-2.3). 19. A storage rack arrangement in accordance with claim 18, wherein the positioning elements (6) and the positioning members (8) collectively fix the storage racks (1, 1.1-1.3) within a prescribed horizontal position with respect to the base plate (2.1-2.3). 20. A storage rack arrangement in accordance with claim 18, wherein the base plate (2.1-2.3) and storage rack (1, 1.1-1.3) are configured to be interconnected independent of a fixed connection therebetween.
	claims	1. A system for measuring the polarization and intensity of extreme ultraviolet, soft x-ray, and x-ray radiation produced by a source, comprising: (A) a reflective surface, the reflective surface being adapted to reflect the radiation produced by the source, wherein the reflecting surface is adapted to rotate around an axis, the axis being substantially parallel to an incoming path of the radiation reflected by the reflective surface; (B) a capillary array being adapted to transmit the radiation, the capillary array comprising: (a) a receiving end positioned to receive the radiation reflected by the reflective surface; and (b) an emitting end; and (C) a detector positioned to receive radiation emitted by the emitting end of the capillary array, the detector being adapted to measure the intensity of the emitted radiation. 2. The system of claim 1 wherein the reflecting surface comprises a concave shape. claim 1 3. The system of claim 1 wherein the reflecting surface is a multi-layer mirror. claim 1 4. The system of claim 1 wherein the reflecting surface is a crystal. claim 1 5. The system of claim 1 wherein the capillary array and the detector are adapted to rotate around the axis, wherein the reflective surface, the capillary array, and the detector may be maintained in the same angular position relative to each other when the reflective surface is rotated around the axis. claim 1 6. The system of claim 1 wherein the capillary array is adapted to rotate around an axis, the axis being substantially parallel to an incoming path of the radiation reflected by the reflective surface. claim 1 7. The system of claim 1 wherein the capillary array comprises at least one hollow capillary, the capillary having an inner diameter, the inner diameter gradually decreasing from the receiving end of the capillary array to the emitting end of the capillary array, wherein the flux density of the radiation is increased as the radiation is transmitted by the capillary array. claim 1 8. The system of claim 1 wherein the capillary array comprises a substantially conical shape. claim 1 9. The system of claim 1 wherein the capillary array comprises a substantially arced shape. claim 1 10. The system of claim 1 further comprising a filter positioned between the source and the reflective surface, the filter being adapted to prevent unwanted radiation from falling on the reflective surface. claim 1 11. The system of claim 1 , wherein the capillary array has a plurality of capillaries, each capillary arced in the same direction. claim 1 12. A system for measuring the polarization and intensity of extreme ultraviolet, soft x-ray, and x-ray radiation produced by a source, the system comprising: (A) reflector means for reflecting radiation from the source; (B) capillary array means for transmitting radiation from the reflector means; (C) detector means for measuring the intensity of the radiation transmitted from the capillary array means in a plurality of angular positions relative to an incoming path of the radiation, whereby the detector means can measure the intensity of radiation in a plurality of planes of vibration of the radiation; and (D) means for rotating the capillary array means and the detector means around an axis that is substantially parallel to the incoming path of radiation. 13. The system of claim 12 further comprising means for increasing flux density of the radiation as the radiation is transmitted by the capillary array means. claim 12 14. The system of claim 12 further comprising means for rotating the reflector means around an axis that is substantially parallel to the incoming path of radiation. claim 12 15. The system of claim 12 , wherein the capillary array means has a plurality of capillaries, each capillary arced in the same direction. claim 12 16. A method of measuring the polarity and intensity of extreme ultraviolet, soft x-ray, and x-ray radiation, the method comprising the following steps: (A) reflecting the radiation on to a capillary array; (B) using the capillary array to transmit the radiation to a detector; and (C) measuring the intensity of the radiation using the detector, the detector being in a first angular position relative to the incoming path of the radiation. 17. The method of claim 16 further comprising the following steps: claim 16 (A) rotating the capillary array and the detector relative to an axis that is substantially parallel to the incoming path of radiation, wherein the capillary array and the detector are positioned in a second angular position relative to the incoming path of the radiation; (B) measuring the intensity of the radiation using the detector in the second position. 18. The method of claim 17 further comprising the step of comparing the intensity of the radiation in the first and second positions. claim 17 19. The method of claim 16 further comprising the step of increasing the flux density of the radiation before measuring the intensity of the radiation. claim 16 20. The method of claim 17 further comprising the step of rotating the reflective surface relative to the incoming path of the radiation. claim 17
047626763	claims	1. A top nozzle adapter plate for use in a fuel assembly of a nuclear reactor, said fuel assembly having a plurality of elongated structural members and a multiplicity of fuel rods disposed in a predetermined array, said fuel rods being supported in a manner which permits the possibility of upward movement thereof from said fuel assembly when acted upon by hydraulic forces occurring in upward coolant flow through said fuel assembly in said reactor, said adapter plate comprising: (a) an upper structural component capable of rigid connection to said elongated structural members; and (b) a lower functional component connected to said upper structural component and including a grid composed of a plurality of spaced and interleaved straps which extend in vertical planes generally parallel to the direction of coolant flow through the grid and cross one another to form intersections aligned with individual fuel rods in said array thereof, said strap intersections being capable of restraining movement of fuel rods upward from said fuel assembly while defining open channels through said grid which are capable of allowing passage of coolant flow therethrough, said lower component also including adjustable coolant flow directing means being operable to establish a predetermined desired pressure drop across said top nozzle of said fuel assembly. said upper component includes a plurality of open flanges connected to and extending outwardly of said hubs; and said grid includes upstanding corner strips for attachment to said flanges of said upper component. (a) an upper structural component including a plurality of spaced and interconnected hubs and ligaments arranged to define substantial open areas for coolant flow therethrough while providing a rigid framework capable of transmitting lifting loads imposed by said fuel assembly, said hubs being connected to said elongated structural members of said fuel assembly; and (b) a lower functional component connected to said upper structural component and including a grid composed of a plurality of spaced and interleaved straps which extend in vertical planes generally parallel to the direction of coolant flow through the grid and cross one another to form intersections aligned with individual fuel rods in said array thereof, said strap intersections being capable of restraining movement of fuel rods upward from said fuel assembly while defining open channels through said grid which are capable of allowing passage of coolant flow therethrough, said grid also including void areas through which said hubs of said upper component extend, said lower component also including adjustable coolant flow directing means being operable to establish a predetermined desired pressure drop across said top nozzle of said fuel assembly. said upper component includes a plurality of open flanges connected to and extending outwardly of said hubs; and said grid includes upstanding corner strips attached to said flanges of said upper component. (a) an upper structural component capable of rigid connection to said elongated structural members; and (b) a lower functional component connected to said upper structural component and including a grid composed of a plurality of spaced and interleaved straps which are capable of restraining movement of fuel rods upward from said fuel assembly while defining open channels through said grid which are capable of allowing passage of coolant flow therethrough, said lower component also including coolant flow directing means being operable to establish a predetermined desired pressure drop across said top nozzle of said fuel assembly; (c) said coolant flow directing means being in the form of a plurality of tabs connected to predetermined ones of said grid straps and extending outwardly therefrom, said tabs being adjustable into various desired positional relationships with respect to said grid channels for controlling coolant flow therethrough. said upper component includes a plurality of open flanges connected to and extending outwardly of said hubs; and said grid includes upstanding corner strips for attachment to said flanges of said upper component. (a) an upper structural component including a plurality of spaced and interconnected hubs and ligaments arranged to define substantial open areas for coolant flow therethrough while providing a rigid framework capable of transmitting lifting loads imposed by said fuel assembly, said hubs being connected to said elongated structural members of said fuel assembly; and (b) a lower functional component connected to said upper structural component and including a grid composed of a plurality of spaced and interleaved straps which are capable of restraining movement of fuel rods upward from said fuel assembly while defining open channels through said grid which are capable of allowing passage of coolant flow therethrough, said grid also including void areas through which said hubs of said upper component extend, said lower component also including coolant flow directing means being operable to establish a predetermined desired pressure drop across said top nozzle of said fuel assembly; (c) said coolant flow directing means being in the form of a plurality of tabs connected to predetermined ones of said grid straps and extending outwardly therefrom, said tabs being adjustable into various desired positional relationships with respect to said grid channels for controlling coolant flow therethrough. said upper component includes a plurality of open flanges connected to and extending outwardly of said hubs; and said grid includes upstanding corner strips for attachment to said flanges of said upper component. 2. The adapter plate as recited in claim 1, wherein said coolant flow directing means is in the form of a plurality of tabs connected to predetermined ones of said grid straps and extending outwardly therefrom, said tabs being adjustable into various desired positional relationships with respect to said grid channels for controlling coolant flow therethrough. 3. The adapter plate as recited in claim 1, wherein said coolant flow directing means is in the form of a thin flat plate having holes of predetermined desired sizes and shapes formed therein, said plate extending along said interleaved straps of said grid with its holes generally aligned with said open channels of said grid. 4. The adapter plate as recited in claim 1, wherein said upper structural component includes a plurality of spaced and interconnected hubs and ligaments arranged to define substantial open areas for coolant flow therethrough while providing a rigid framework capable of transmitting lifting loads imposed by said fuel assembly, said hubs being capable of connection to said elongated structural members of said fuel assembly. 5. The adapter plate as recited in claim 4, wherein said grid includes void areas through which said hubs of said upper component extend when said grid is connected to said upper component. 6. The adapter plate as recited in claim 4, wherein: 7. In a fuel assembly having a plurality of elongated members, top and bottom nozzles attached to upper and lower ends of said members, a multiplicity of fuel rods extending between said nozzles, a liquid coolant flow upwardly through said fuel assembly along said fuel rods thereof and support means for disposing said fuel rods in a generally side-by-side predetermined spaced relation to one another and to said elongated members, said support means permitting the possibility of upward movement of said fuel rods toward said top nozzle when acted upon by hydraulic forces, said top and bottom nozzles and elongated members together forming a rigid structural skeleton of said fuel assembly, an adapter plate in said top nozzle comprising: 8. The adapter plate as recited in claim 7, wherein said coolant flow directing means is in the form of a plurality of tabs connected to predetermined ones of said grid straps and extending outwardly therefrom, said tabs being adjustable into various desired positional relationships with respect to said grid channels for controlling coolant flow therethrough. 9. The adapter plate as recited in claim 7, wherein said coolant flow directing means is in the form of a thin flat plate having holes of predetermined desired sizes and shapes formed therein, said plate extending along said interleaved straps of said grid with its holes generally aligned with said open channels of said grid. 10. The adapter plate as recited in claim 7, wherein: 11. A top nozzle adapter plate for use in a fuel assembly of a nuclear reactor, said fuel assembly having a plurality of elongated structural members and a multiplicity of fuel rods disposed in a predetermined array, said fuel rods being supported in a manner which permits the possibility of upward movement thereof from said fuel assembly when acted upon by hydraulic forces occurring in upward coolant flow through said fuel assembly in said reactor, said adapter plate comprising: 12. The adapter plate as recited in claim 11, wherein said interleaved straps of said grid cross one another to form intersections capable of alignment with individual fuel rods in said array thereof. 13. The adapter plate as recited in claim 11, wherein said upper structural component includes a plurality of spaced and interconnected hubs and ligaments arranged to define substantial open areas for coolant flow therethrough while providing a rigid framework capable of transmitting lifting loads imposed by said fuel assembly, said hubs being capable of connection to said elongated structural members of said fuel assembly. 14. The adapter plate as recited in claim 13, wherein said grid includes void areas through which said hubs of said upper component extend when said grid is connected to said upper component. 15. The adapter plate as recited in claim 13, wherein: 16. In a fuel assembly having a plurality of elongated members, top and bottom nozzles attached to upper and lower ends of said members, a multiplicity of fuel rods extending between said nozzles, a liquid coolant flow upwardly through said fuel assembly along said fuel rods thereof and support means for disposing said fuel rods in a generally side-by-side predetermined spaced relation to one another and to said elongated members, said support means permitting the possibility of upward movement of said fuel rods toward said top nozzle when acted upon by hydraulic forces, said top and bottom nozzles and elongated members together forming a rigid structural skeleton of said fuel assembly, an adapter plate in said top nozzle comprising: 17. The adapter plate as recited in claim 16, wherein said interleaved straps of said grid cross one another to form intersections aligned with individual fuel rods in said array thereof. 18. The adapter plate as recited in claim 17, wherein:
	summary
	claims	1. A base portion for use in a bottom nozzle of a fuel assembly in a nuclear reactor, the base portion comprising:a top surface;a bottom surface;a plurality of vertical walls extending between the bottom surface and the top surface, wherein the plurality of vertical walls define a plurality of non-circular passages passing between the bottom surface and the top surface through the base portion; anda plurality of debris filters extending from the top surface and spanning across a respective one of the plurality of non-circular passages, wherein each debris filter comprises a lattice structure, and wherein the plurality of debris filters are configured to extend alongside a substantial portion of a bottom of a plurality of fuel rods of the fuel assembly and in between the plurality of fuel rods of the fuel assembly. 2. The base portion of claim 1, further comprising:a plurality of thickened areas, wherein each thickened area is defined by intersecting portions of the vertical walls, wherein a thickness of the intersecting portions is greater than a thickness of the vertical walls; anda plurality of flow holes, each disposed in a respective thickened area. 3. The base portion of claim 2, wherein each flow hole comprises a tapered inlet at the bottom surface of the base portion and a tapered outlet at the top surface of the base portion. 4. The base portion of claim 3, further comprising a plurality of spring members, each spring member extending upward from a top edge of a respective vertical wall a height, wherein each spring member is structured to be engaged by two fuel rods of the fuel assembly. 5. The base portion of claim 4, wherein each spring member includes a first biasing portion which is structured to engage one of the two fuel rods and a second biasing portion which is disposed opposite the first biasing portion and which is structured to engage a second one of the two fuel rods. 6. The base portion of claim 5, wherein each of the first biasing portion and the second biasing portion are an arcuate shape. 7. The base portion of claim 1, wherein each debris filter comprises a hollow pyramid or hollow cone structure. 8. The base portion of claim 1, wherein when viewed from directly above the base portion or directly below the base portion the lattice structure of each debris filter is arranged so as to form a pattern. 9. The base portion of claim 1, further comprising a plurality of spring members, each spring member extending upward from a top edge of a respective vertical wall a height, wherein each spring member is structured to be engaged by two fuel rods of the fuel assembly. 10. The base portion of claim 9, wherein each spring member includes a first biasing portion which is structured to engage one of the two fuel rods and a second biasing portion which is disposed opposite the first biasing portion and which is structured to engage a second one of the two fuel rods. 11. The base portion of claim 10, wherein each of the first biasing portion and the second biasing portion are an arcuate shape. 12. The base portion of claim 4, wherein the plurality of spring members are integrally connected with a respective top edge of the respective vertical wall. 13. The base portion of claim 1, wherein the plurality of debris filters are integrally connected with the top surface. 14. The base portion of claim 9, wherein the plurality of debris filters are integrally connected with the top surface and the plurality of spring members are integrally connected with a respective top edge of the respective vertical wall. 15. A bottom nozzle assembly for use in a fuel assembly in a nuclear reactor, the bottom nozzle assembly comprising:a rectangular skirt portion; anda base portion as recited in claim 1 coupled to the rectangular skirt portion. 16. A fuel assembly for use in a nuclear reactor, the fuel assembly comprising:the bottom nozzle assembly of claim 15;a top nozzle;a number of guide tubes which extend longitudinally between, and are coupled to, the bottom nozzle assembly and the top nozzle; andan array of elongated fuel rods extending between the top nozzle and the bottom nozzle assembly.
047529474	abstract	A primary radiation diaphragm for X-ray examination devices has at least one pair of diaphragm plates movable in opposite directions relative to each other for gating an X-ray beam. The diaphragm plates are displaceably mounted in spaced planes and the respective adjustment limits are selected such that each diaphragm plate can selectively limit the X-ray beam with one of two edges disposed perpendicular to the path of adjustment movement. The edges may have different shapes for adapting the gated field to the shape of the body organ under examination.
044343710	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an electron beam lithography machine 10 having a Gaussian electron beam 12. The electron beam emitted from electron source 14 passes through blanking aperture 16 and then through blanking deflector 18. Beam 12 is focused by lenses 20 and 22 and is demagnified by lens 24 onto target 26. Lens 24 contains the final beam aperture, virtual image 25 of which exits at plane 28 imaged by lens 22 and virtual image 29 at plane 30 imaged by lens 20. The equivalent virtual source is indicated at 31. In order to achieve blanking, the beam 12 must be deflected sufficiently far to miss the aperture hole in the blanking aperture 16. Typical Gaussian beam systems require deflection angles near 2.10.sup.-3 radians. With high-speed Gaussian beams, blanking times are in the range of 1 to 10 nanoseconds. Blanking is accomplished by applying beam deflecting energy to blanking deflector 18. In the blanked position, the equivalent ray path is shown in dashed lines. The dashed ray paths shown below aperture 16 are "virtual" and serve to indicate where the blanked beam would have to go if it were to pass through the final aperture (in plate 24). FIG. 2 is a schematic ray trace diagram of an electron beam machine 32 which provides a shaped beam to the target. Electron source 34 delivers electron beam 36 through lens 38 which focuses the beam toward beam shaper aperture 40. The beam 36 from source 34 is not as finely defined as in the Gaussian system, but the beam shaper aperture cuts off the sides of the beam so that the resultant electron beam below shaped aperture 30 is of selected shape and has well defined edges. Blanking deflector 42 is positioned down the beam path to apply lateral force to the beam to direct it away from the target. Lenses 44 and 46 are sequentially positioned along the beam path toward 48, and the aperture in lens 46 acts as the blanking aperture. The dot-dashed lines below blanking deflector 42 indicate the virtual source 35 and virtual paths 37 of the deflected electron beam. In shaped beam electron beam lithography machines spot exposure times are on the order of 10 to 1,000 nanoseconds, and blanking times must be approximately one order of magnitude shorter than the exposure time so that the spot edge definition is not reduced. Thus, blanking times for shaped beam systems should be in the range of 1 to 100 nanoseconds. This is the time from the beginning of the blanking pulse to the completion of beam swing out of the blanking aperture. The deflection angle in a typical shaped beam electron beam machine is about 1.10.sup.-3 radians. The blanking deflectors 18 and 42 can be electrostatic plates. For a set of electrostatic deflection plates of reasonable size, the deflection angle given above for Gaussian beams and a beam energy of 20 thousand volts, the required driving voltage becomes 20 volts which exceeds the capability of state of the art drivers with nanosecond rise time. Thus, electrostatic deflection is not practical. If blanking is to be achieved by magnetic deflection, and if a single turn coil is considered to minimize self inductance, a coil of reasonable dimensions requires a coil current of approximately one ampere, which exceeds the capability of state of the art amplifiers which have nanosecond rise time. One of the problems of electrostatic deflection is that the electrostatic plates are subject to voltage pulse reflections since they fail to provide a termination which matches the transmission line impedance. The reflected waves travel back and forth between the driver and the plates in tens of nanoseconds so that they can lead to periodic unblanking pulses until the wave energy has become dissipated. In accordance with this invention, the blanking deflectors 18 and 42 are each shaped so that each provides electrostatic as well as magnetic deflection and also serves as a line termination. FIGS. 3 and 4 illustrate the preferred embodient of the blanking apparatus 50. The blanking apparatus 50 is the same in both of these figures, and is the apparatus 18 in FIG. 1 and is the apparatus 42 in FIG. 2. In FIG. 3 apparatus 50 is shown as being connected to the output of one driver amplifier 52 through coaxial cable 54. In FIG. 4, blanking apparatus 50 is shown as being connected to differential twin driver amplifiers 56 and 58 respectively through coaxial cables 60 and 62. As seen in FIGS. 3 and 4, upper plate 64 has a beam opening 66 for passage of the electron beam 67, which is the same as beams 12 and 36. The beam 67 is to be deflected away from the blanking aperture to cut off the beam. Upper plate 64 is preferably normal to the beam path, as is lower plate 68 with its beam opening 70. In FIG. 3, upper plate 64 is connected at its adjacent edge to center conductor 72 of coaxial cable 54, while lower plate 68 is connected at its adjacent edge to outer conductor 74 of the coaxial cable 64. Secured to the outer edge of upper plate 64 and extending substantially parallel to the beam path 67 is outer deflection plate 74. Inner deflection plate 76 is substantially parallel to outer deflection plate 74 and on the opposite side of the beam path. Inner deflection plate 76 is connected to the inner edge of lower plate 68. In addition, resistor 78 interconnects the outer edges upper plate 64 and lower plate 68. As indicated in FIGS. 3 and 4, tab 80 is formed extending to the right of outer deflection plate 74 to hold resistor 78 away from plate 74. Similarly, plate 68 extends to the right of the plane defined by deflection plate 74, for resistor connection. The structure in FIG. 3 is configured to produce both electrostatic and magnetic deflection. A one turn magnetic deflection coil is composed of conductor 72, upper plate 64, resistor 78 with its connections, lower plate 68 and outer conductor 73. This one turn magnetic deflection coil is a loop which is positioned in a plane substantially parallel to the beam path 67. When driver-amplifier 52 drives current around that single loop, a magnetic field is generated which causes deflection of beam 68. The deflection due to this magnetic field is in the direction normal to deflector plates 74 and 76, that is generally left to right in FIGS. 3 and 4. At the same time, the current charges up deflection plates 74 and 76 which act as capacitive deflection plates which deflect the beam 68 in the same direction as the magnetic deflection. Resistor 78 is chosen so that the reactance of the blanking apparatus 10 matches the impedance of coaxial feedline 54, which in turn matches the output impedance of driver-amplifier 52. By combining the effect of capacitance and magnetic deflection, the drive current and voltage levels can be significantly reduced as compared to individual magnetic or capacitive deflection. In addition, unwanted pulse reflections can be avoided. These improvements are achieved by employment of the following concepts: first, reflections are minimized by sending the drive pulses through transmission lines and by using deflection elements which terminate the lines with their own characteristic impedance. The simplest approach to such impedance matching is to employ a coaxial cable 54 as indicated, in combination with the termination, impedance matching resistor 78. The upper limit of blanking frequency is where the reactive impedance of the blanking apparatus 50 becomes comparable to the impedance of resistor 78. With a 50 ohm cable 54, this occurs at about 500 megahertz. The upper frequency limit is thus about twice that of untuned capacitive or magnetic deflection systems. The effects of the electrostatic and magnetic deflection on the beam are approximately equal. In theory, the electrostatic deflection would be about three times the magnetic deflection, but the large unavoidable stray capacitance brings the effect of electrostatic deflection approximately equal to the magnetic deflection. FIG. 4 illustrates twin differential driver-amplifiers 56 and 58 respectively connected through coaxial cables 60 and 62 to the inner corners of plate 68 and 64. By the use of twin differential driver-amplifiers as indicated, either their deflection amplitude or the deflection speed for blanking can be increased by a factor of 2. In summary, the blanking apparatus 50 and its drive permits either a reduction in the drive requirements (per driver-amplifier) by a factor of 4 or an increase in blanking speed by a factor of 4 over conventional approaches. For example, with a pair of ultra-fast, commercially available operational amplifiers, Gaussian beams can be blanked at about 1 nanosecond. Such amplifiers are available from National Semiconductor and are identified as type LH0063. Such amplifiers have outputs in the order of 5 to 10 volts into 50 ohm loads and possess slew rates as high as 6,000 volts per microsecond. Such amplifiers are suitable for this application. This invention has been described in its presently contemplated best mode and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.
	description	This present application is a continuation of, and claims priority to, U.S. patent application Ser. No. 13/213,604, entitled “Double Helix Conductor,” filed Aug. 19, 2011, which claims priority to U.S. Provisional Patent Application Ser. No. 61/464,449, entitled “Novel Electromagnetic Coil With Structure Similar To DNA,” filed Mar. 3, 2011. These related applications are hereby incorporated by reference into the present application in their entirety. The invention relates to bodies structured as helically wound runners around which one or more conductive wires may be wound, electrical devices and/or systems configured to include such bodies, and the manufacture of such bodies and/or such electrical devices and/or systems. The invention also relates to methods of operation of these devices and systems, and applications thereof. It is known that spirally wound electrical conductors may exhibit certain electromagnetic properties and/or generate particular electromagnetic fields. For example, it is known that an electromagnetic coil may act as an inductor and/or part of a transformer, and has many established useful applications in electrical circuits. An electromagnetic coil may be used to exploit the electromagnetic field that is created when, e.g., an active current source is operatively coupled to both ends of the coil. One aspect of the invention relates to an electrical system comprising a body and one or more conductive wires. The body may include two intertwined helically wound runners. A first runner is coupled to the second runner by struts. The body is arranged in a toroidal shape. The one or more conductive wires may be spirally wound around at least one runner of the body. These and other objects, features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related components of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the any limits. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. FIG. 1 illustrates a side view of an exemplary body 15. Body 15 may include two or more intertwined helically wound runners—runner 16 and runner 17. Runner 16 and runner 17 may be coupled by struts 18. Body 15 include two ends—end 20 and end 21—disposed at opposite sides of body 15. Runners 16 and/or 17 may be arranged in the shape of a three-dimensional curve similar to or substantially the same as a helix. A helix may be characterized by the fact that a tangent line at any point along the curve has a constant angle with a (fixed) line called the axis. The pitch of a helix may be the width of one 360 degree helix turn (a.k.a. revolution), e.g. measured parallel to the axis of the helix. Intertwined helically wound runners may share the same axis, be congruent, and/or differ by a translation along the axis, e.g. measuring half the pitch. The two runners shown in FIG. 1 may share the same axis 22, extending horizontally for approximately three complete revolutions. The length of body 15, as measured along axis 22 from end 20 to end 21, may thus be approximately three times the length of pitch 23. A helical shape may have constant pitch, constant radius (measured in the plane perpendicular to the axis), constant torsion, constant curvature, constant ratio of curvature to torsion, and/or a straight axis. In FIG. 1, the radius of body 15 may be half of diameter 24. It is noted that the shape of body 15 resembles the general shape of DNA. The shape of the cross-section of a runner may include one or more of a circle, an oval, a square, a triangle, a rectangle, an angular shape, a polygon, and/or other shapes. The width and height of the cross-section of a runner may be limited to a maximum of half the pitch for practical purposes. The shape and/or size of the cross-section of a runner may change along the length of the runner. The relation of the width of a runner to the pitch of the helical shape may define a characteristic measurement/feature of body 15. This relation may be constant along the length of body 15, e.g. from end 20 to end 21. In FIG. 1, the shape of cross-section of runner 16 and runner 17 may be a rectangle that is approximately three times wider than it is tall. Furthermore, the width of runner 16 or runner 17 may be approximately 1/13th of the pitch of said runner of body 15. As a result, runner 17 of body 15 resembles a ribbon having an inner surface 25 (facing axis 22 of the helical shape) and an outer surface 26 (facing the opposite way as inner surface 25). Runner 16 of body 15 resembles a ribbon having an inner surface 27 (facing axis 22 of the helical shape) and an outer surface 28 (facing the opposite way as inner surface 27). Note that embodiments of this disclosure are not intended to be limited by any of the given examples. Struts 18 coupling the runner 16 and runner 17 may be substantially straight, curved, the shape of an arc, twisted, and/or other shapes. In FIG. 1, struts 18 may be substantially straight. Struts 18 may be arranged substantially perpendicular to axis 22, and/or substantially parallel to others of struts 18. The shape of a cross-section of a strut may include one or more of a circle, an oval, a square, a triangle, a rectangle, an angular shape, a polygon, and/or other shapes. The shape and/or size of the cross-section of one of struts 18 may change along the length of the strut. In FIG. 1, the shape of the cross-section of struts 18 may be a circle. In FIG. 1, all or most struts may have substantially the same length. The number of struts per revolution may not be constant. In FIG. 1, body 15 includes approximately 10 struts per complete revolution of 3 runner. As shown in FIG. 1, the diameter of each strut may be smaller than the width of a runner as measured e.g. at inner surface 25 of runner 17 at the point of engagement 19 with one of struts 18. The diameter of one strut may not be constant. The diameters of multiple adjacent struts may not be the same. Runner 16, runner 17 and/or struts 18 may be manufactured from one or more of plastic, plastic plated with metals including copper, nickel, iron, soft iron, nickel alloys, and/or other metals and alloys, and/or other materials. In some embodiments, runner 16, runner 17 and struts 18 are manufactured from non-conductive material. Runner 16, runner 17, and struts 18 may be manufactured from different materials. Runner 16, runner 17, and struts 18 may be manufactured through integral construction or formed separately prior to being assembled. FIG. 2 illustrates an isometric view of an exemplary body 15 including two intertwined helically wound runners—runner 16 and runner 17—coupled by struts 18. Body 15 is shown here with axis 22 of both helically wound runners extending vertically. FIG. 3 illustrates a top-down view of an exemplary body 35 including two intertwined helically wound runners—runner 36 and runner 37—sharing the same circular axis 42, both runners coupled by struts 38. The resulting shape of body 35 may be referred to as toroidal. Body 35 may be formed the same as or similar to body 15, though comprising more revolutions, by arranging the body in a planar circular shape and joining both ends—end 20 and end 21 in FIG. 1—together. The preceding statement is not intended to limit the (process of) manufacture of bodies similar to or substantially the same as body 35 in any way. Note that the shape of the cross-section of both runner 36 and runner 37 in FIG. 3 may be circular, whereas it may be rectangular for body 15 in FIGS. 1 and 2. Referring to FIG. 3, the diameter 44 of the circular axis of body 35, as well as the number of complete revolutions per runner required to completely extend along the entire circular axis 42 may be characteristic measurements/features of body 35. For example, as shown in FIG. 3, runner 36 and runner 37 of body 35 may require approximately eight complete revolutions around circular axis 42 of body 35, or some other number of rotations. Note that one or more struts 38 of body 35 in FIG. 3 include a center-strut element 39, which is lacking from struts 18 of body 15. Center-strut element 39 may be associated with a particular strut of body 35. The shape of the cross section of a center-strut element may include one or more of a circle, an oval, a square, a triangle, a rectangle, an angular shape, a polygon, and/or other shapes. The shape and/or size of the cross-section of one of center-strut elements 39 may change along the length of center-strut element 39. One or more struts 38 of body 35 may include a center-strut element 39, which may have a different shape than a center-strut element 39 of another one of struts 38. In FIG. 3, the shape of the cross-section of center-strut element 39—nay be circular, such that center-strut element 39 may have a cylindrical shape, in which the axis of the cylindrical shape of a given center-strut element 39 may coincide with the associated strut 38. In FIG. 3, struts 38 include center-strut element 39, having substantially the same shape. A center-strut element may enhance structural integrity and/or serve other purposes. FIG. 4 illustrates an isometric view of an exemplary body 35 including two intertwined helically wound runners—runner 36 and runner 37—sharing the same circular axis, both runners coupled by struts 38. Note that, as in FIG. 3, the struts of body 35 in FIG. 4 may include a center-strut element 39, which may be lacking from struts 18 of body 15. FIG. 5 illustrates a top-down view of an exemplary body 55 including two intertwined helically wound runners—runner 57 and runner 58—sharing the same circular axis 62 and having wire guides 56, both runners coupled by struts 59. Though the shape of the cross-section of runner 57 and runner 58 in FIG. 5 may be circular, a runner may still have an inner surface (the half of the surface of a runner for which normal vectors are directed approximately inward toward body 55) and an outer surface (the half of the surface of a runner for which normal vectors are directed approximately outward, away from body 55). Any part of runner 57 or runner 58 may include wire guides 56. Wire guides 56 may include grooves, notches, protrusions, slots, and/or other structural elements disposed on and/or in runner 57 or runner 58 and configured to guide a wire along at least a part of the surface of runner 57 or runner 58, generally in a direction substantially perpendicular to the direction of runner 57 or runner 58 at the point of engagement between one of wire guides 56 and runner 57 or runner 58. In FIG. 5, one of wire guides 56 of runner 58 may include a protrusion disposed on the outer surface of runner 58, arranged such that wire guide 56 may guide a wire arranged in a helical shape around runner 58, wherein the helical shape has an axis that coincides with runner 58. Such a wire, as any wire listed in any figure included in this description, may be insulated, uninsulated, or partially insulated and partially uninsulated. As shown in FIG. 5, wire guides 56 may be disposed in an intermittent pattern rather than a continuous pattern, e.g. such that no protrusion is disposed on the surface of runner 57 or runner 58 approximately nearest to (or directly opposite to) one of points of engagement 63 between runner 57 or runner 58 and of one struts 59. The number of wire guides per complete revolution of a runner and/or the number of wire guides between adjacent struts may be characteristic measurements/features of body 55. The size, shape, position, and/or pattern of disposition of wire guides 56 may be characteristic measurements/features of body 55. FIG. 6 illustrates an isometric view of an exemplary body 55 including two intertwined helically wound runners—runner 57 and runner 58—sharing the same circular axis and having wire guides 56, both runners coupled by struts 59. FIG. 7 illustrates a top-down view of an exemplary body 75 including two intertwined helically wound runners—runner 76 and runner 77—sharing the same elliptical axis 78, both runner coupled by struts 79. A body including two (or more) intertwined helically wound runners sharing the same axis may be arranged in any planar shape, including a circle, an oval, a triangle, a square, a rectangle, an angular shape, a polygon, and/or other planar shapes. Alternatively, and/or simultaneously, such a body may be arranged in a three-dimensional curve (a.k.a. space curve). In FIG. 7, body 75 may be formed from a body similar to body 15, though comprising more evolutions, by arranging the body in an planar elliptical shape and joining both ends—end 20 and end 21 in FIG. 1—together. The preceding statement is not intended to limit the (process of) manufacture of bodies similar to or substantially the same as body 75 in any way. FIG. 8 illustrates a top-down view of an exemplary body 85 including two intertwined helically wound runners—runner 88 and runner 89—sharing the same circular axis, coupled by struts 90 and having conductive wires—wire 86 and wire 87—spirally wound therearound. Wire 86 and wire 87, as any wire listed in any figure included in this description, may be insulated, uninsulated, or partially insulated and partially uninsulated. The shape of body 85 may be similar to the shape of body 35 in FIG. 3. Runner 88 and runner 89 of body 85 may form cores around which wire 86 and wire 87 are spirally wound, respectively. As such, wire 86 and wire 87 may be arranged in a helical shape having axes that coincide with runner 88 and runner 89, respectively. As shown in FIG. 8, wire 86 and 87 may be wound such that they go around any of struts 90 of body 85 and/or around any points of engagement between one of struts 90 and one of runners 88 and 89. The number of wire turns per complete revolution of a runner and/or the number of wire turns between adjacent struts may be characteristic measurements/features of body 85. In FIG. 8, wire 86 and wire 87 may be arranged to make approximately five turns between adjacent struts associated with runner 88 and runner 89, respectively, and/or some other number of turns. Wire 86 may include two leads—lead 86a and lead 86b. Wire 87 may include two leads—lead 87a and lead 87b. Wire 86 and wire 87 may be conductive. Body 85 may be used in an electrical system having one or more power sources and/or current sources arranged such that electrical coupling with one or both of wire 86 and wire 87 may be established, e.g. through coupling with lead 86a and 86b of wire 86 and through coupling with lead 87a and 87b of wire 87. The current supplied to wire 86 may be a direct current or an alternating current. The current supplied to wire 87 may be a direct current or an alternating current. The currents supplied to wire 86 and wire 87 may flow in the same direction or the opposite direction. For alternating currents, operating frequencies ranging from 0 Hz to 40 GHz are contemplated. The operating frequencies for wire 86 and wire 87 may be the same or different. Other electrical operating characteristics of current supplied to wire 86 and wire 87, such as phase, may be the same or different. The electrical system may be used to exploit the electromagnetic field that is created when electrical power is supplied to one or more wires of body 85. Some embodiments of an electrical system including a body similar to or substantially the same as body 85 in FIG. 8, thus including wire 86 and wire 87, may be configured to have a current in wire 86 flowing in the opposite direction as the current in wire 87. In some embodiments the current supplied to one wire may be a direct current, whereas the current supplied to another wire may be an alternating current. FIG. 9 illustrates a top-down view of an exemplary body 95 including two intertwined helically wound runners—runner 97 and runner 98—sharing the same circular axis, both runner coupled by struts and having a wire 96 spirally wound around both runners of body 95. Wire 96, as any wire listed in any figure included in this description, may be insulated, uninsulated, or partially insulated and partially uninsulated. Wire 96 may include two leads—lead 86a and lead 86b. The resulting shape of body 95 with wire 96 may be referred to as a helicoidal shape. Wire 96 may be conductive. Body 95 may be used in an electrical system having a power source and/or a current source arranged such that electrical coupling with wire 96, e.g. through leads 96a and 96b, may be established. The electrical power supplied to wire 96 may include a direct current or an alternating current. Operating frequencies for an alternating current flowing through wire 96 are contemplated to range from 0 Hz to 40 GHz. The electrical system may be used to exploit the electromagnetic field that is created when electrical power is supplied to wire 96 of body 95. Any of the bodies shown in FIGS. 1-9 may be used in an electrical system. Conductive wires may be spirally wound around one or more runners, one or more struts, and/or any combination thereof to produce electrical systems having specific electromagnetic properties when electrical power is supplied to one or more of the conductive wires. These conductive wires may be insulated, uninsulated, or partially insulated and partially uninsulated. A (magnetic) core may be disposed in the space between multiple runners, such that the runners helically wound around the (magnetic)—core. Alternatively, and/or simultaneously, relative to any body described herein, a (magnetic) core may be moved along a straight line, along any curve of the body, along a strut, along a runner, along any axis of the body, or along any surface of the body, in any three-dimensional relation to the body. For example, a magnet may be moved along a line perpendicular to the planar shape of body 85, in the center of the circular axis of body 85, a.k.a. through the “donut-hole.” Applications for any of the electrical systems described herein may include affecting growth and/or growth rate of plants and/or other organisms. Applications for any of the electrical systems described herein may include therapeutic applications. Applications for any of the electrical systems described herein may include energy production, conversion, and/or transformation. Applications for any of the electrical systems described herein may include ATP production, transfer, and/or processing. In some embodiments, an electrical system including any of the bodies shown in FIGS. 1-9 may be used as a component in an electrical circuit, performing one or more functions and/or applications including a (tunable) inductor, a (Tesla) coil, a transformer, a transducer, a transistor, a resistor, a solenoid, a stator for an electrical motor, an electromagnet, an electromagnetic pulse generator, an electromagnetic actuator, an energy conversion device, a position servomechanism, a generator, a stepping motor, a DC motor, a (contact-free) linear drive, an axial flux device, a measurement device for magnetic permeability, a dipole magnet, and a device to alter electron and/or particle trajectory. Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.
	abstract	A transfer cask system for cooling spent nuclear fuel during the transfer from a spent nuclear fuel pool to a storage or transfer cask is disclosed. A canister containing spent nuclear fuel is inserted into a transfer cask. The transfer cask includes spacing components which define an annular region between the transfer cask and the canister. The transfer cask includes air inlets near a bottom end that permit air to flow through the defined annular region and exit at the open top of the transfer cask, thereby cooling the fuel within the canister. The transfer cask further comprises a neutron shield configured to absorb additional heat and shield radiation that may be generated within the canister. The transfer cask includes a transfer door that can open and close and has support rails that can support a spent nuclear fuel canister located in the transfer cask.
	summary
	claims	1. A nuclear waste cask with impact protection comprising:a longitudinal axis;a longitudinally elongated cask body including a top end, a bottom end, and a sidewall extending between the ends, and a cavity configured for holding a nuclear waste canister; andan impact limiter coupled to the top end of the cask body, the impact limiter comprising an annular perforated sleeve having a body including a central opening and a circumferential array of elongated longitudinal passages formed therethrough around the central opening. 2. The cask according to claim 1, wherein the longitudinal passages are oriented parallel to each other and extend between a top surface and a bottom surface of the perforated sleeve. 3. The cask according to claim 2, wherein the longitudinal passages are oriented parallel to the longitudinal axis of the cask. 4. The cask according to claim 2, wherein e longitudinal passages have a circular transverse cross section. 5. The cask according to claim 4, wherein the longitudinal passages each have a longitudinal length which is greater than their respective diameter. 6. The cask according to claim 5, wherein the longitudinal passages each have a length greater than at least two times their respective diameter. 7. The cask according to claim 4, wherein the array of longitudinal passages are dispersed in a full 360 degree pattern around an entirety of the perforated sleeve. 8. The cask according to claim 5, wherein the array of longitudinal passages comprises multiple concentric rings of longitudinal passages which extend circumferentially around the perforated sleeve. 9. The cask according to claim 8, wherein the longitudinal passages in each ring have progressively larger diameters moving outwardly from the central opening. 10. The cask according to claim 9, wherein the longitudinal passages of an outermost ring each have larger diameters than the longitudinal passages of an innermost ring. 11. The cask according to claim 8, wherein the longitudinal passages are arrayed in a staggered pitch pattern. 12. The cask according to claim 11, wherein the perforated sleeve includes at least three concentric rings of longitudinal passages. 13. The cask according to claim 11, wherein each longitudinal passage is separated by a solid web of material of the perforated sleeve which is smaller in radial thickness than a largest diameter of the longitudinal passages. 14. The cask according to claim 1, wherein the longitudinal passages are closely packed such that a radial reference line drawn outwards from a geometric center of the perforated sleeve through any portion of the perforated sleeve intersects at least one longitudinal passage. 15. The cask according to claim 1, wherein the body of the perforated sleeve has a solid monolithic unitary structure which defines the central opening and longitudinal passages. 16. The cask according to claim 15, wherein the body of the perforated sleeve is formed of metal. 17. The cask according to claim 16, wherein the body of the perforated sleeve is formed of a soft isotopic metallic material comprising aluminum or aluminum alloy. 18. The cask according to claim 16, wherein the body of the perforated sleeve is collectively formed by multiple metallic ring segments stacked together, each ring segment defining a portion of the central opening and longitudinal passages which are concentrically aligned in each ring segment. 19. The cask according to claim 1, wherein the impact limiter further comprises an outer cap shell including a circular end wall and a sidewall extending longitudinally from the end wall, the perforated sleeve being nested inside the cap shell. 20. The cask according to claim 19, wherein the impact limiter includes a centrally-located internal annular collar which defines a receptacle which slideably receives a top end forging on the top end of the cask. 21. The cask according to claim 20, wherein the collar is spaced radially inwards from the sidewall of the end cap to define an annulus, the perforated sleeve being nested in the annulus. 22. The cask according to claim 19, wherein the outer cap shell defines an end cavity of the impact limiter, the end cavity containing an energy absorbing material. 23. The cask according to claim 22, wherein the energy absorbing material is a corrugated aluminum panel honeycomb structure or a polymeric foam material. 24. The cask according to claim 1, wherein the perforated sleeve defines a longitudinally-extending annular load transfer surface arranged to transmit an external impact force on the impact limiter to a corresponding annular impact load bearing surface formed by a diametrically reduced stepped portion of the top end of the cask. 25. The cask according to claim 1, wherein the impact limiter protrudes radially outward beyond the sidewall of the cask. 26. The cask according to claim 1, further comprising a second impact limiter coupled to the bottom end of the cask body, the second impact limiter comprising an annular perforated sleeve having a body including a central opening and a circumferential array of elongated longitudinal passages formed therethrough. 27. The cask according to claim 1, wherein the perforated sleeve has a solidity ratio less than 0.5 resulting in an open area of the sleeve collectively formed by the longitudinal passages being greater than 50 percent. 28. The cask according to claim 1, wherein the longitudinal passages are arranged in a triangular staggered 60 degree hole pattern. 29. The cask according to claim 1, wherein the perforated sleeve comprises an outer circumferential wall and an inner circumferential wall extending longitudinally between opposing major end surfaces of the perforated sleeve. 30. The cask according to claim 1, wherein the top end of the cask comprises an end forging defining an outward facing annular bearing surface which is radially aligned with an inwardly facing annular load transfer surface of the perforated sleeve.
	description	This application is the National Stage of International Application No. PCT/US2005/046834, filed Dec. 21 2005, which claims the benefit of U.S. Provisional Application No. 60/638,870, filed Dec. 22, 2004, the disclosure of which is incorporated herein by reference in its entirety. This work is partly supported by the Department of Health and Human Services, the National Institute of Health, and the Department of Defense, under contract numbers NIH CA78331 and DOD PC030800, respectively. Accordingly, the Government may have rights in these inventions. The present invention pertains to superconducting electromagnet systems for manipulating charged particles. The present invention also pertains to providing high energy positive ions for radiation therapy. In radiation therapy, the use of proton beams provides the possibility of better dose conformity to the treatment target and normal tissue sparing compared to commonly used photon beams because of the lower entrance dose, sharper penumbra and rapid fall off beyond the treatment depth, which result from the Bragg peak in the dose distribution. Despite the dosimetric superiority and some encouraging clinical results for well-localized radio-resistant lesions, the utilization of proton therapy has lagged behind therapies using photons and electrons because the facilities of proton therapy employing cyclotron and synchrotron technology are expensive and complex. As a result, proton therapy has not been a widespread modality in radiation therapy. This situation can be improved if a compact and economical laser-proton therapy unit is available. Laser-proton systems for radiation therapy are currently being developed at the Fox Chase Cancer Center, Philadelphia, Pa. by the present inventors. A typical laser-proton system design includes three types of components: (1) a compact laser-proton source to produce high-energy protons, (2) a compact particle selection and beam collimating device for accurate beam delivery, and (3) a treatment optimization algorithm to achieve conformal dose distributions using laser-accelerated proton beams. Laser acceleration of particles was first proposed in 1979 for electrons. Rapid progress has been made in laser-electron acceleration in the 1990s since the advent of chirped pulse amplification (CPA) and high fluence solid-state laser materials such as Ti:sapphire. Recently, there have been a number of experimental investigations, which observed protons with energies of several tens of MeV. A recent experiment conducted at Lawrence Livermore National Laboratory reported particles with a maximum energy of 58 MeV. The mechanism for laser-proton acceleration is under study. It has been long linked to the longitudinal electric field created as a result of laser-matter interaction. Recent experimental investigations as well as the results of computer simulations (specifically particle in cell) of the laser-plasma interaction for proton acceleration have shown that laser-accelerated proton beams have broad energy and angular distributions and cannot be directly used in therapy. A spectrometer-like particle selection and beam modulation system is described by several of the present inventors in which a magnetic field distributed as a step function was used to spread protons in space according to their energies and emitting angles. A particle selection and beam modulation system has been disclosed in International Patent Application No. PCT/US2004/017081, filed Jun. 2, 2004, entitled “High Energy Polyenergetic Ion Selection Systems, Ion Beam Therapy Systems, and Ion Beam Treatment Centers”, the entirety of which is incorporated by reference herein. Subsequently, the proton beams are retrieved with resultant energies, which can be used to generate modulated energy distributions that will deliver the spread-out Bragg Peaks (SOBP). Therefore, the earlier proposed particle selection system constitutes a selection device, which is based on the ideal step field configuration. As a step field distribution is difficult to achieve, further improvements to-particle selection systems that incorporate non-ideal step field configurations are presently needed. Also because non-step field configurations arise from the use of typical electromagnet systems, improvements in the electromagnet systems are currently sought for the efficient and compact separation of laser-accelerated polyenergetic positive ions. The present invention provides compact superconducting electromagnet systems capable of producing a step-like magnetic field distribution, which can be useful for proton beam selection. One design of the superconducting electromagnet system can be obtained from an analytical calculation of the magnetic field for rectangular coils, which provides a three dimensional magnetic field distribution, thus accounting for such boundary effects as edge focusing due to the influence of the flinging field patterns at the edge of the coils. The simulation of proton trajectories can be used to test the electromagnet system and optimize the design for certain criteria. In certain embodiments, the electromagnets of the invention are capable of producing a step-like magnetic field for use in a high energy polyenergetic positive ion beam selection mechanism. The present invention also provides superconducting electromagnet systems that produce step-like fields distributed in rectangular regions. The field distributions are useful for proton transport in particle selection systems. Proton dose distributions are calculated and compared to the results for the ideal step field and the field that can be generated by the designed superconducting electromagnet system. The present invention provides for ion selection systems for high energy polyenergetic ion beams composed of a plurality of high energy polyenergetic positive ions. These systems are composed of a beam collimator, a first magnetic field source capable of spatially separating said high energy polyenergetic positive ions according to their energy levels, an aperture capable of modulating the spatially separated high energy polyenergetic positive ions, and a second magnetic field source capable of recombining the modulated high energy polyenergetic positive ions, where the first and second magnetic field sources are superconducting electromagnets capable of providing a magnetic field of about 0.1 to about 30 Tesla. There are also provided methods of forming a high energy polyenergetic positive ion beam comprising the steps of forming a laser-accelerated high energy polyenergetic ion beam composed of a plurality of high energy polyenergetic positive ions characterized as having a distribution of energy levels, collimating the laser-accelerated ion beam using a collimation device, spatially separating the high energy positive ions according to their energy levels using a first magnetic field provided by a first superconducting electromagnet having a magnetic field of about 0.1 to 30 Tesla, modulating the spatially separated high energy polyenergetic positive ions using an aperture; and then recombining the modulated high energy polyenergetic positive ions using a second magnetic field provided by a second superconducting electromagnet having a magnetic field of at least about 0.1 to about 30 Tesla. Also provided are laser-accelerated high energy polyenergetic positive ion therapy systems. These systems comprise a laser-targeting system, comprising a laser and a targeting system capable of producing a high energy polyenergetic ion beam, an ion selection system capable of producing a therapeutically suitable high energy polyenergetic positive ion beam from a portion of said high energy polyenergetic positive ions, said ion selection system comprising at least two superconducting electromagnets each capable of providing a magnetic field of about 0.1 to about 30 Tesla, and an ion beam monitoring and control system. The high energy polyenergetic ion beam in these systems can be comprised of high energy polyenergetic positive ions having energy levels of at least about 50 MeV, with the high energy polyenergetic positive ions being spatially separated based on energy level. The present invention also provides methods of treating a patient with a laser-accelerated high energy polyenergetic positive ion therapy system. These methods of treatment comprise the steps of identifying the position of a targeted region in a patient, determining the treatment strategy of the targeted region, with the treatment strategy comprised of determining the dose distributions of a plurality of therapeutically suitable high energy polyenergetic positive ion beams for irradiating the targeted region, forming said plurality of therapeutically suitable high energy polyenergetic positive ion beams from a plurality of high energy polyenergetic positive ions, that are spatially separated based on energy level using one or more superconducting electromagnets each capable of providing a magnetic field of about 0.1 to about 30 Tesla, and delivering the plurality of therapeutically suitable polyenergetic positive ion beams to the targeted region according to the treatment strategy. Also provided are laser-accelerated high energy polyenergetic positive ion beam treatment centers. These centers comprise a location for securing a patient and a laser-accelerated high energy polyenergetic positive ion therapy system capable of delivering a therapeutically suitable high energy polyenergetic positive ion beam to a patient at said location This ion therapy system can be comprised of a laser-targeting system, said laser-targeting system comprising a laser and a target assembly capable of producing a high energy polyenergetic ion beam, comprising high energy polyenergetic positive ions having energy levels of at least about 50 MeV, an ion selection system capable of producing a therapeutically suitable high energy polyenergetic positive ion beam using said high energy polyenergetic positive ions, the high energy polyenergetic positive ions being spatially separated based on energy level using superconducting electromagnets each capable of providing a magnetic field of about 0.1 to about 30 Tesla, and a monitoring and control system for the therapeutically suitable high energy polyenergetic positive ion beam. Further, there are provided compact superconducting electromagnet systems for magnetically separating a polyenergetic positive ion beam. These systems comprise a series of two or more superconducting coils in fluidic communication. Each of the superconducting coils can be individually capable of providing a magnetic field of about 0.1 to about 30 Tesla and at least two of the magnetic fields are provided in opposite directions to each other. These and other aspects of the present invention will be readily be apparent to those skilled in the art in view of the following drawings and detailed description. The summary and the following detailed description are not to be considered restrictive of the invention as defined in the appended claims and serve only to provide examples and explanations of the invention. The present invention may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. When a range of values is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. All ranges are inclusive and combinable. It is to be appreciated that certain features of the invention which are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges include each and every value within that range. As used herein, the term “protons” refers to the atomic nuclei of hydrogen (H1) having a charge of +1. As used herein, the term “positive ions” refers to atoms and atomic nuclei having a net positive charge. As used herein, the term “polyenergetic” refers to a state of matter being characterized as having more than one energy level. As used herein, the term “high energy” refers to a state of matter being characterized as having an energy level greater than 1 million electron volts (“MeV”). As used herein, the term “beamlet” refers to a portion of a high energy polyenergetic positive ion beam that is spatially separated, or energetically separated, or both spatially and energetically separated. The terms “primary collimator”, “primary collimation device”, “initial collimator”, and “initial collimation device” are used interchangeably herein. The terms “energy modulation system” and “aperture” are used interchangeably when it is apparent that the aperture referred to is capable of modulating a spatially separated high energy polyenergetic positive ion beam. The phrase “fluidic communication” is meant that two or more electromagnetic coils are arranged such that one or more ion beams is capable of passing through the magnetic field generated within each of the coils, such as illustrated in FIG. 2. The ion selection systems for high energy polyenergetic ion beams are composed of a beam collimator, a first magnetic field source capable of spatially separating said high energy polyenergetic positive ions according to their energy levels, an aperture capable of modulating the spatially separated high energy polyenergetic positive ions, and a second magnetic field source capable of recombining the modulated high energy polyenergetic positive ions, where the first and second magnetic field sources are superconducting electromagnets capable of providing a magnetic field of about 0.1 to about 30 Tesla. Laser-accelerated proton therapy systems use high intensity laser pulses to generate plasmas in a high density material, and accelerate the protons to high kinetic energies. Examples of laser-accelerated proton therapy systems that can be adapted for use in the present invention are described in further detail in “High Energy Polyenergetic Ion Selection Systems, Ion Beam Therapy Systems, and Ion Beam Treatment Centers”, WO2004109717, U.S. application Ser. No. 10/559058, claiming priority to U.S. App. No. 60/475,027, filed Jun. 2, 2003, the portion of which pertaining to laser-accelerated proton therapy systems is incorporated by reference herein. Examples of methods of modulating laser-accelerated protons for radiation therapy that can be adapted for use in the present invention are described in further detail in “Methods of Modulating Laser-Accelerated Protons for Radiation Therapy”, WO2005057738, U.S. application Ser. No. 11/445850, claiming priority to U.S. App. No. 60/475,027, filed Jun. 2, 2003, and U.S. App. No. 60/526,436, filed Dec. 2, 2003, the portion of which pertaining to methods of modulating laser-accelerated protons for radiation therapy is incorporated by reference herein. The compact superconducting electromagnet systems for magnetically separating a polyenergetic positive ion beam in some embodiments include a series of two or more superconducting coils in fluidic communication. Each of the superconducting coils is individually capable of providing a magnetic field of between about 0.1 and about 30 Tesla, and at least two of the magnetic fields are provided in opposite directions to each other. In some embodiments, the compact superconducting electromagnet systems include two outer electromagnets each capable of providing a magnetic field in the same direction, and two inner electromagnets each capable of providing a magnetic field in the same direction to each other and opposite the direction of the magnetic field of the outer electromagnets. In these embodiments, the magnetic fields of the inner electromagnets may by different in strength, or they may have about the same strength. In related embodiments, the two inner electromagnets can be adjacent to each other or separated by a gap. When separated, a suitable gap is typically in the range of from about 0.2 cm to about 5 cm, and more suitably in the range of from about 0.5 to about 2 cm. In certain preferred embodiments, the two inner electromagnets are separated by a gap of about 1 cm. In certain embodiments, a series of collimators each having an aperture size in the range of from about 0.02 cm to about 2 cm. Strong magnetic fields can be generated using the superconducting electromagnet systems. Compact superconducting electromagnet systems can include electromagnets that are variously shaped to control the magnetic field distribution. In certain embodiments the superconducting electromagnetic coils are preferably shaped to produce uniformly distributed fields. Suitable superconducting electromagnets are rectangularly shaped. Rectangularly shaped superconducting electromagnets are capable of producing magnetic fields that are more uniformly spatially distributed than magnetic fields arising from circularly shaped electromagnets. Suitable magnetic field sources for this and various embodiments of the present invention include superconducting electromagnets having a magnetic field strength in the range of from about 0.1 to about 30 Tesla, more suitably in the range of from about 0.2 to 20 Tesla, or even from about 0.5 to about 10 Tesla, and more suitably in the range of from about 0.5 to about 5 Tesla. In some embodiments, the maximum magnetic field of each of the electromagnets can be less than about 5 Tesla. In certain embodiments, superconducting electromagnets having from about 1,000 to about 100,000 turns, preferably from about 5,000 to about 20,000 turns, and even more preferably about 10,000 turns are suitable for the present invention. Suitable superconducting electromagnet can be made by winding a long wire by multiple turns. Two or more such superconducting electromagnets can be connected together, which provide a gap, d, between, where a somewhat uniform magnetic field can be provided and protons will pass therethrough. The dimensions of a single superconducting electromagnet can be determined with both the laser-proton system design and the selection of the material of the wire in mind. A compact laser-proton system can include a compact electromagnet system. In some embodiments, the dimensions of the superconducting electromagnets can be rectangular in over all shape, having rectangular dimensions in the range of from about 5 cm to about 100 cm, more preferably in the range of from about 10 cm to about 75 cm, and even more preferably in the range of from about 15 cm to 50 cm. In one embodiment of the present invention, the upper limit on the dimensions of a single superconducting electromagnet can be set to about 20×40×25 cm3 (Lx×Ly×Lz). As used herein, the mathematical symbol tilde (“˜”) used in front of a number means “about”. If a conventional copper wire is used, which can carry a current with a density of ˜103 A/cm2, the cross sector of the electromagnet coil wound with the copper wire should be ˜103 cm2 to get a total current of ˜106 A to achieve a magnetic induction of ˜4.4 T (see Appendix). Thus, a thickness (T) of about 40 cm for a conventional non-superconducting electromagnet with a length (Lz) of about 25 cm can be used to meet the cross section, which makes the width in both x- (Lx) and y-direction, (Ly) much greater than about 80 cm. While such electromagnets can be used in the present invention, it may be desirable to use even smaller electromagnets. The size of the electromagnet can be significantly reduced by utilizing superconducting wires instead of copper because a superconducting wire can carry a very high current density. Another advantage of using superconducting wires can be saving power. The power consumption for a superconducting electromagnet is only about 1% to about 10% of that for a comparable conventional electromagnet. Superconducting wires are commercially available and have been widely used in high energy accelerators to produce strong magnetic fields. A suitable superconducting wire can be NbTi, which has a critical current density of ˜4.25×105 A/cm2 at 4.2 K for a field of ˜4.4 T. Another commercially available superconducting wire, Nb3Sn, can also be used. Other types of superconducting wires, including those made from high temperature superconductors, can be used. Suitable high temperature superconducting wires have a critical temperature above about 77 K, examples of which include YBCO (e.g., YBa2Cu3O7-x) and BSCCO (e.g., Bi2Sr2Ca2Cu3O10 or Bi2Sr2Ca1Cu2O8) materials. Suitable high temperature superconducting wires are commercially available from the American Superconductor, Westborough, Mass., (http://www.amsuper.com/index.cfm). Suitable superconducting wires, such as NbTi wires, are commercially available in widths of from about 10 micron to 250 micron diameter form Japan Superconducting Technology, Inc. Tokyo, Japan, (http://www.jastec.org/eg/index.html). The actual current can be less than the critical current, otherwise, the superconducting state can be broken and the wire will function in the conventional conducting state. In one embodiment, four electromagnets can be used to achieve a step-like field distribution. The electromagnets are placed parallel along the x-axis (beam axis) with the first and the fourth electromagnet field pointing to −z, and the second and third magnetic field pointing to z. The first electromagnet produces the magnetic field with the Lorentz force that pushes protons up, then the second and the third produce the field that pulls the protons down, and the field from the last one puts the protons back to the original direction. Such a superconducting electromagnet system can be shorter than about 100 cm in the dimension along the beam axis. Suitable cryogenics for the superconducting electromagnets used in the present invention may include any of the cryogenic systems know to those skilled in the art, which are readily fashioned from commercially available components for superconducting electromagnets. A suitable cryostat can be designed and implemented together with the electromagnet system. In various embodiments, an initial collimator defines the angular spread of the incoming beam entering the first magnetic field. The tangent of the angle of the beam spread of the beam exiting the initial collimator can be about the ratio of one half the distance of the initial collimator exit opening where the beam exits the collimator to the distance of the collimator exit opening to the proton beam source (i.e., the plasma target). This angle can be less than about 1 radian. The emitting angle is the angle of the initial energy distribution exiting the target system (i.e., target and initial collimation device). Electrons can be deflected in the opposite direction from the positive ions by the first magnetic field and absorbed by a suitable electron beam stopper. Suitable electron stoppers include tungsten, lead, copper or any material of sufficient thickness to attenuate the electrons and any particles they generate to a desired level. The aperture can be used to select the desired energy components, and the matching magnetic field setup (in one embodiment, the second magnetic field) can be selected that is capable of recombining the selected protons into a polyenergetic positive ion beam. Suitable apertures can be made from tungsten, copper or any other materials of sufficient thickness that are capable of reducing the energy levels of positive ions. This energy level reduction can be carried out to such a degree that the positive ions can be differentiated from those ions that do not go through the aperture. In various embodiments of the present invention, the aperture geometry can be a circular, rectangular, or irregular-shaped opening or multiple openings on a plate or slab, which when placed in a spatially separated polyenergetic ion beam, is capable of fluidically communicating a portion of the ion beam therethrough. In other embodiments, the aperture can be made from a plate that has multiple openings that are controllably selected, such as by physical translation or rotation into the separated ion beam to spatially select the desirable energy level or energy levels to modulate-the separated ion beam. The modulation of the ion beam gives rise to a therapeutically suitable high energy polyenergetic positive ion beam as described herein. Suitable apertures include multi-leaf collimators. In addition to controllably selecting the spatial position of the openings that fluidically communicate the spatially separated ion beams, the aperture openings may also be controllably shaped or multiply shaped, using regular or irregular shapes. Various combinations of openings in the aperture are thus used to modulate the spatially separated ion beam. The spatially separated positive ions are subsequently recombined using the second magnetic field. The high and low energy positive ion (e.g., proton beam) stoppers can eliminate unwanted low-energy particles and high-energy particles (not shown). Because of the broad angular distribution of the accelerated protons (which depends on a given energy range), there can be a spatial mixing of different energy positive ions after they pass through the first magnetic field. For example, a portion of the low energy protons may go to regions where the high energy particles reside, and vice versa. Reducing the spatial mixing of protons can be carried out by introducing a primary collimation device, such as the initial collimation device. A primary collimation device can be used to collimate protons to the desired angular distribution. To reduce the unwanted protons, as well as to collimate them to a specific angular distribution, a primary collimation device can be provided. Its geometrical size and shape can be tailored to the energy and angular proton distributions. For example, in one embodiment of the present invention there can be provided a 5 cm long tungsten collimator that absorbs the unwanted energy components. Because of its density and the requirement for the compactness of the selection system, tungsten is a favorable choice for collimation purposes. A suitable primary collimator opening provides a 1×1 cm2 field size defined at 100 cm SSD. Protons that move into an angle larger than this can be blocked. The magnetic field spreads the polyenergetic protons into spatial regions according to their energy and angular distributions. Their spatial distribution can be such that the lower energy particles are deflected at greater distances away from the central axis, and as the proton energy increases the spatial deflection decreases. Therefore, the contribution of both the magnetic field and the primary collimator (with a specific collimator opening) creates such a spatial proton distribution that allows the energy selection or proton energy spectrum reformation, using an aperture. The geometric shape of an aperture can determine the energy distribution of the therapeutic protons. One embodiment of the present invention provides an ion-selection system in which a magnetic field is used to spread the laser-accelerated protons spatially based on their energy levels and emitting angles, and apertures of different shapes are used to select protons within a therapeutic window of energy and angle. Such a compact device eliminates the need for the massive beam transportation and collimating equipment that is common in conventional proton therapy systems. The laser-proton source and the ion selection and collimating device of the present invention can be installed on a treatment gantry (such as provided by a conventional clinical accelerator) to form a compact treatment unit, which can be installed in a conventional radiotherapy treatment room. In certain embodiments of the invention, a secondary monitor chamber measures the intensity of each energy component. A primary monitor chamber can be also provided. Various ways of monitoring ion beams and control systems are disclosed in U.S. patent application Ser. No. 09/757,150 filed Jan. 8, 2001, Pub. No. U.S. 2002/0090194 A1, Pub. Date Jul. 11, 2002, “Laser Driven Ion Accelerator”, the portion of which pertaining to monitoring ion beams and control systems is incorporated by reference herein. One embodiment of a suitable compact geometry provides dimensions of less than 50 cm in length and less than 40 cm in diameter. Since different laser-protons have different angular distributions, a collimator can be used to define the field size. When the initial collimator has a square opening, and the polyenergetic collimated protons of different energy levels have passed through the electromagnet fields, the collimated protons will reach different transverse locations. Because of the finite size of the initial collimator there can be some overlap of proton energy levels, which can depend on the size of the initial collimator, the magnetic field strength and the distance from the energy plane to the initial collimator. For selecting the desired energy of this embodiment, a second collimator can be used, which can be positioned at the corresponding transverse location. For example, a square aperture can be used to select a 50, 150 or the 250 MeV field of protons. Multiple laser pulses can be provided to produce a combination of protons to provide a desired spectrum. The desired proton energy spectrum can be used to produce a therapeutically high energy polyenergetic positive ion beam, which provides uniform dose distributions over a desired depth range. Another embodiment of the ion selection system of the present invention is to use variable aperture sizes at the energy space (plane) to select both an energy and the total number of protons of that energy (intensity) simultaneously. This embodiment uses fewer laser pulses to achieve a desired proton spectrum compared to the preceding embodiment. This variable aperture size embodiment preferably uses an elongated aperture at the energy space with variable widths at different transverse (energy) locations. Without being bound by a particular theory of operation, this design allows for energy and intensity selection simultaneously from the same laser pulse. This appears to be a highly efficient way to use a polyenergetic laser-proton beam to achieve a uniform dose over a depth range for radiation therapy. A variable energy aperture size can use a subsequent differential magnetic system to recombine the fields of different proton energy levels to a similar field size. In certain embodiments, a secondary collimation device can be provided to define the final field size and shape of the positive ions that form the therapeutically suitable high energy polyenergetic positive ion beam. Small shaped beams (e.g., squares, circles, rectangles, and combinations thereof) can be provided by modulating the intensity of individual beamlets so that a conformal dose distribution to the target volume can be achieved. In this embodiment, there is provided a modulatable secondary collimation device that is capable of modulating the spatially separated beam. The modulatable secondary collimation device may have a variable shape, which can be realized using an aperture, as described earlier, such as a multileaf collimator (MLC). A number of laser pulses can be provided using this embodiment to treat a target volume. While the aperture that modulates the energy levels can move in the transverse direction to select a desired energy spectrum to cover the depth range of at least a portion of the entire target volume, the modulatable secondary collimation devices (e.g., the MLC) are capable of changing the field shape of the recombined beam to enclose at least a portion of the cross-section of the target volume at the corresponding depths. The methods described herein for the ion selection systems of the present invention may suitably be performed using the devices and instrumentalities described herein. Because the proton beams can be small in cross-section, it is possible to establish a high magnetic field within a small space. Certain embodiments of the present invention do not require strict B-field spatial distribution, rather, the magnetic fields may have a slow gradient, they may be spatially overlapping, or both. Suitable embodiments of the present invention will include at least two magnetic field sources that have matching, opposite, B-fields. The geometry may be further reduced in the beam direction by using higher magnetic fields, smaller photon beam stoppers, or both. Various alternate embodiments of the present invention include embodiments of an ion selection system composed of a collimation device capable of collimating a laser-accelerated high energy polyenergetic positive ion beam, the laser-accelerated high energy polyenergetic ion beam having a plurality of high energy polyenergetic positive ions; a first magnetic field source capable of spatially separating the high energy polyenergetic positive ions according to their energy levels; an aperture capable of modulating the spatially separated high energy polyenergetic positive ions; and a second magnetic field source capable of recombining the modulated high energy polyenergetic positive ions, wherein the first and second magnetic field sources are provided are superconducting electromagnets capable of providing a magnetic field between about 0.1 and about 30 Tesla. Another embodiment of an ion selection system similar to that provided above further includes a third magnetic field source, the third magnetic field source capable of bending the trajectories of the spatially separated high energy polyenergetic positive ions towards the aperture. Preferably the third magnetic field source is a superconducting electromagnet. Additional embodiments include an ion selection system similar to the above but with the aperture placed inside the magnetic field of the third magnetic field source or alternatively, with the aperture being placed outside of the magnetic field of the third magnetic field source, where the third magnetic field source is separated into two portions. In other embodiments of the invention, the magnetic field of the third magnetic field source is capable of bending the trajectories of the modulated high energy polyenergetic positive ions towards the second magnetic field source. In certain embodiments, the second magnetic field source is capable of bending the trajectories of the modulated high energy polyenergetic positive ions towards a direction that is not parallel to the direction of the laser-accelerated high energy polyenergetic ion beam. Other embodiments have a second magnetic field source that is capable of bending the trajectories of the modulated high energy polyenergetic positive ions towards a direction that is parallel to the direction of the laser-accelerated high energy polyenergetic ion beam. Certain embodiments of the invention have a secondary collimation device capable of fluidically communicating a portion of the recombined high energy polyenergetic positive ions therethrough. In certain embodiments, the secondary collimation device is capable of modulating the beam shape of the recombined high energy polyenergetic positive ions. In certain embodiments, a rotatable wheel with an aperture having a plurality of openings, each of the openings capable of fluidically communicating high energy polyenergetic positive ions therethrough, can be used. Another suitable aperture is a multileaf collimator with openings that are capable of passing low energy ions, high energy ions, respectively, or a combination thereof. In accordance with certain embodiments of the invention, a laser-accelerated high energy polyenergetic ion beam including a plurality of high energy polyenergetic positive ions is collimated using a collimation device, and the positive ions are spatially separated according to their energy levels using a first magnetic field. The spatially separated high energy polyenergetic positive ions are modulated using an energy selection aperture and the modulated high energy polyenergetic positive ions are recombined using a second magnetic field. In certain embodiments, a portion of the positive ions are transmitted through the aperture, e.g., having energy levels in the range of from about 50 MeV to about 250 MeV, and other portions are blocked by the energy selection aperture. In this embodiment magnetic fields of strength between about 0.1 and about 30 Tesla are provided using superconducting electromagnets. In certain embodiments, the magnetic field is between about 0.2 and about 20 Tesla. In certain embodiments, the trajectories of the positive ions are bent in a direction away from the beam axis of the laser-accelerated high energy polyenergetic ion beam using the first magnetic field. In other embodiments, the trajectories of the spatially separated positive ions are further bent in a direction towards the aperture using the third magnetic field. The third magnetic field, in some embodiments, bends the trajectories of the spatially separated high energy polyenergetic positive ions towards the second magnetic field. This embodiment can further include the bending of the trajectories of the ions by the second magnetic field toward a direction parallel to the direction of the laser-accelerated high energy polyenergetic ion beam. Preferably, the first second and third magnetic fields are supplied by superconducting electromagnets. In certain embodiments, the spatially separated high energy positive ions are modulated by energy level using a location-controllable opening in an aperture. In some embodiments, the spatial separation of the high energy polyenergetic positive ions is over distances up to about 50 cm with these distances measured perpendicularly to the beam axis of the laser-accelerated ion beam as it enters the first magnetic field. The present invention also provides methods of producing radioisotopes using the laser-accelerated high energy polyenergetic ion beams provided herein by irradiating a radioisotope precursor with the recombined spatially separated high energy polyenergetic positive ions. The production of 2-deoxy-2-18F fluoro-D-glucose (“[18F]FDG”) is carried out by proton bombardment of the chemical precursors leading to the radioisotopes. These processes use proton beams generated using traditional cyclotron and synchrotron sources. For example, J. Medema, et al. [http://www.kvi.nl/˜agorcalc/ecpm31/abstracts/medema2.html] have reported on the production of [18F] Fluoride and [18F] FDG by first preparing [18F] fluoride via the 18O (p, n) [18F] nuclear reaction in 18O enriched water, and producing the [18F]FDG by recovering the [18F]fluoride via the resin method and the cryptate drying process. The present invention provides high energy polyenergetic ion beams suitable for use in this process of preparing radioisotopes. Thus, the process of producing radioisotopes includes the steps of forming a high energy polyenergetic proton beam as described herein to provide an appropriate particle, target and beam current. A target precursor is filled with H218O. The high energy polyenergetic proton beam irradiates the target precursor until a preselected integrated beam current or time is reached. The target pressure can be monitored by a pressure transducer. When the integrated beam current or the time is reached the [18F]fluoride is used for chemically synthesizing [18F] FDG. The final product is isotonic, colorless, sterile, and pyrogen free and is suitable for clinical use. The ion selection systems in various embodiments as described can be used as components of laser-accelerated high energy polyenergetic positive ion therapy systems. In one embodiment of the present invention there is provided a compact, flexible and cost-effective proton therapy system. This embodiment relies on three technological breakthroughs: (1) laser-acceleration of high-energy polyenergetic protons, (2) compact system design for ion selection and beam collimation using superconducting electromagnets, and (3) treatment optimization software to utilize laser-accelerated proton beams. An important component of a laser proton radiotherapy system is a compact ion selection and beam collimation device, which is coupled to a compact laser-proton source to deliver small pencil beams of protons of different energy levels and intensities. Typically, the laser and the treatment unit are placed on the same suspension bench to ensure laser beam alignment (negligible energy loss due to the small distance). This also aids in keeping the whole system compact. In this embodiment, the target assembly and the ion selection device are placed on a rotating gantry and the laser beam is transported to the final focusing mirror through a series of mirrors. The distances between the mirrors are adjusted to scan the proton beam along x- and y-axis, respectively, which generates a parallel scanned beam. An alternative method is to swing the target and ion selection device about the laser beam axis defined by the mirrors to achieve a scan pattern. This generates a divergent scan beam. The treatment couch in the treatment system can be adjusted to perform coplanar and noncoplanar, isocentric and SSD (source-to-surface distance) treatments. One embodiment of an ion therapy system includes a laser-targeting system, the laser-targeting system comprising a laser and a targeting system capable of producing a high energy polyenergetic ion beam, the high energy polyenergetic ion beam including high energy polyenergetic positive ions having energy levels of at least about 50 MeV. In this embodiment, the high energy polyenergetic positive ions are spatially separated based on energy level and an ion selection system capable of producing a therapeutically suitable high energy polyenergetic positive ion beam from a portion of the high energy polyenergetic positive ions is provided. Also provided is a differential chamber and an integration chamber. Positive ions of different energies will typically pass through different parts of the differential chamber that measure the differences in energies of the ions and monitors the energy of the selected ions. Typically, the differential chamber does not control the energy selection aperture. The integration chamber is provided to generate a signal that is analyzed (e.g., by a computer or suitable data processor) to determine the position of the aperture and the aperture openings. One embodiment of the treatment system provides an ion-selection system in which a magnetic field is used to spread the laser-accelerated protons spatially based on their energy levels and emitting angles, and apertures of different shapes are used to select protons within a therapeutic window of energy and angle. To reduce the size of the ion-selection system, the magnetic field is supplied by superconducting electromagnets. The magnetic fields are typically in the range of about 0.1 and about 30 Tesla. Further embodiments use fields between about 0.2 and about 20 Tesla, about 0.5 and about 10 Tesla, and about 0.8 and about 5 Telsa. Using superconducting electromagnets results in a compact device that eliminates the need for the massive beam transportation and collimating equipment that is common in conventional proton therapy systems. The laser-proton source and the ion selection and collimating device of this embodiment are typically installed on a treatment gantry (such as provided by a conventional clinical accelerator) to form a compact treatment unit, which can be installed in a conventional radiotherapy treatment room. A laser-accelerated high energy polyenergetic positive ion therapy system in the various embodiments described above can be used in a method of treating a patient. For example, the proton selection systems provided by the various embodiments of the present invention open up a way for generating small beamlets of polyenergetic protons that can be used for inverse treatment planning. Due to the dosimetric characteristics of protons, the energy and intensity modulated proton therapy can significantly improve the conformity of the dose to the treatment volume. In addition, healthy tissues are spared using the methods of the present invention compared to conventional treatments. Overall results suggest that the laser accelerated protons together with the ion selection system for radiation treatments will help treat cancer. Radiation therapy is one of the most effective treatment modalities for prostate cancer. In external beam radiation therapy, the use of proton beams provides the possibility of superior dose conformity to the treatment target and normal tissue sparing as a result of the Bragg peak effect. While neutrons and photons (X-rays) show high entrance dose and slow attenuation with depth, monoenergetic protons have a very sharp peak of energy deposition as a function of the beam penetration just before propagation through tissue stops. As a consequence, it is possible for almost all of the incident proton energy to be deposited within or very near the 3D tumor volume, avoiding radiation-induced injury to surrounding normal tissues. Protons have a higher linear energy transfer component near the end of their range, and are more effective biologically for radiotherapy of deep-seated tumors than conventional medical accelerator beams or cobalt-60 sources. In spite of the dosimetric superiority characterized by the sharp Bragg peak, utilization of proton therapy has lagged far behind that of photons for prostate treatment. This is because the operating regime for proton accelerators is at least an order of magnitude higher in cost and complexity, which results in their being too expensive for widespread clinical use compared to electron/photon medical accelerators. Conventional proton accelerators are cyclotrons and synchrotrons, of which only two such medical facilities exist in the U.S., those of Massachusetts General Hospital (MGH) and Loma Linda University Medical Center (LLUMC). Both occupy a very large space (entire floor or building). Although they are growing in number, only several such clinical facilities exist in the world. Despite a somewhat limited number of clinical cases from these facilities, treatment records have shown encouraging results particularly for well-localized radio resistant lesions. The degree of clinical effectiveness for a wide variety of malignancies has not been quantified due to limited treatment experience with this beam modality. This situation will be greatly improved by the availability of a compact, flexible, and cost-effective proton therapy system, as provided by the present invention. The present invention enables the widespread use of this superior beam modality and therefore bring significant advances in the management of cancers, such as brain, lung, breast and prostate cancers. The method of treating a patient with a laser-accelerated high energy polyenergetic positive ion therapy system includes the step of determining the treatment strategy of the targeted region in the patient. The treatment strategy includes determining the dose distributions of a plurality of therapeutically suitable high energy polyenergetic positive ion beams for irradiation of the targeted region. Dose calculation is performed in treatment optimization for laser accelerated proton beam therapy because the dose distributions of small proton beamlets are significantly affected by the beam size and heterogeneous patient anatomy. Patient dose calculations are estimated using the GEANT3 system. The code is designed as a general purpose Monte Carlo simulation. For accelerating dose calculation, a fast proton dose calculation algorithm has been developed based on conventional photon and electron Monte Carlo dose calculation algorithms. Various variance reduction techniques have been implemented in the code to speed up the Monte Carlo simulation. These include “deterministic sampling” and “particle track repeating,” which are very efficient for charged particle simulations. The implementation of this fast Monte Carlo code is tested using the GEANT3 code. The source models are also implemented to reconstruct the phase-space parameters (energy, charge, direction and location) for the proton pencil beams emerging from the laser proton therapy device during a Monte Carlo dose calculation. Suitable software is available that can be adapted for use in treating patients with laser-accelerated polyenergetic positive ions. Such software first converts the patient CT data into a simulation phantom consisting of air, tissue, lung and bone. Based on the contours of the target volume and critical structures, the software computes the dose distributions for all the beamlets of different spectra, incident angles (e.g., gantry angles specified by the planner), and incident locations (e.g., within a treatment port/field). The final dose array for all the beamlets is provided to the treatment optimization algorithm, as described further below. In certain embodiments, improved treatment optimization tools for EIMPT are also provided. A treatment optimization algorithm has been developed based on typical polyenergetic proton beams generated from a typical laser proton accelerator and actual patient anatomy. Commonly used “inverse-planning” techniques include computer simulated annealing, iterative methods, filtered back projection and direct Fourier transformation. Considering the calculation time and the possible complexity with proton beams, the iterative optimization approach (based on a gradient search) is suitably adopted. This is based on iterative optimization algorithms for photon and electron energy- and intensity-modulation. Improved algorithms for energy- and intensity-modulated proton beams are tested. Further improvements of the algorithm is carried out in view of the special features of the realistic proton beams. The “optimizer” performs the following tasks: (1) takes the beamlet dose distributions from the dose calculation algorithm (see above), (2) adjusts the beamlet weights (intensities) to produce the best possible treatment plan based on the target/critical structure dose prescriptions, and (3) outputs the intensity maps (beamlet weighting factors) for all the beam ports and gantry angles for beam delivery sequence studies. In accordance with an embodiment of the invention, a method of treating a patient includes the steps of identifying the position of a targeted region in a patient, determining the treatment strategy of the targeted region, the treatment strategy comprising determining the dose distributions of a plurality of therapeutically suitable high energy polyenergetic positive ion beams for irradiating the targeted region (e.g., determining the energy distribution, intensity and direction of a plurality of therapeutically suitable high energy polyenergetic positive ion beams); forming the plurality of therapeutically suitable high energy polyenergetic positive ion beams from a plurality of high energy polyenergetic positive ions, the high energy polyenergetic positive ions being spatially separated based on energy level using a superconducting electromagnet; and delivering the plurality of therapeutically suitable polyenergetic positive ion beams to the targeted region according to the treatment strategy. In a related invention to the ion therapy system, the laser-accelerated high energy polyenergetic positive ion therapy system as described above in various embodiments can form the basis of a laser-accelerated high energy polyenergetic positive ion beam treatment center. In a laser-accelerated high energy polyenergetic positive ion beam treatment center, there is provided a main laser beam line that is reflectively transported using a series of beam reflectors, e.g., mirrors, to a target and ion selection system. The target and ion selection system includes the target system for generating high energy polyenergetic ions and an ion separation system. In one embodiment, the proton beam exiting the target and ion selection system includes therapeutically suitable high energy polyenergetic positive ions that are generated as described above. In this embodiment, the proton beam exiting the target and ion selection system are directed in the direction parallel to the direction of the laser beam entering the target and ion selection system. The ion beam in the treatment center is directed towards a couch, which locates the patient and the patient's target. In certain embodiments, the mirrors and target and ion selection system are capable of being rotated, for instance in the x-z plane, with the z direction being perpendicular to the x-y plane, around the axis of the main laser beam line using a gantry. In some embodiments, the final mirror from which the laser beam is reflected into the target and ion selection system is fixed to the target and ion selection system. The distance between the final mirror and mirror and ion selection system is shown adjustable along the y direction to permit scanning of the ion beam along the y direction. Suitable target and ion selection systems are compact (i.e., less than about 100 to 200 kg in total mass, and less than about 1 meter in dimension, and incorporating superconducting electromagnets). The compactness of the target and ion selection systems permit their positioning with robotically-controlled systems to provide rapid scanning of the ion beam up to about 10 cm/s. In one embodiment, treatment centers can use a proton ion beam. But treatment centers using other positive ions are also envisioned. Embodiments directed towards treatment centers using other light ions, for example lithium, beryllium, boron, or carbon, or any combination thereof, are also envisioned. The high energy polyenergetic positive ions typically have energy levels of at least about 50 MeV. These high energy polyenergetic positive ions are spatially separated based on energy level using superconducting electromagnets which are capable of providing a magnetic field of between about 0.1 and about 30 Tesla. In further embodiments, the magnetic field can be between about 0.2 and about 20 Tesla, about 0.5 and about 10 Tesla, or about 0.8 and about 5 Tesla. In other embodiments of a laser-accelerated high energy polyenergetic positive ion beam treatment center, the center includes at least one of the ion therapy systems described above and at least one location for securing a patient, for example a couch. For example, a suitable treatment center of this type includes a laser beam that is reflectively transported to the target assembly using a plurality of mirrors. This treatment center can further include an optical monitoring and control system for the laser beam. Further embodiments include at least one beam splitter or mirror that is provided to split the laser beam into split or reflected laser beams to each of at least two target assemblies or to reflect the laser beam to one of the target assemblies. A suitable treatment center can have, for example, a laser-targeting system having two target assemblies and two ion selection systems each capable of individually producing a therapeutically suitable high energy polyenergetic positive ion beam from each of the individual high energy polyenergetic positive ion beams. Other embodiments can contain additional target assemblies and ion selection systems. An individual polyenergetic ion beam monitoring and control system is also provided for each of the therapeutically suitable high energy polyenergetic positive ion beams. One embodiment may include a mirror that is capable of being positioned in and out of the main laser beam to direct the beam to one of the ion therapy systems. Alternatively, a beam splitter can be used when a sufficiently powerful laser beam is provided so that split beams can be used simultaneously by two or more ion therapy systems. For providing patient privacy, typical ion therapy centers having two or more ion therapy systems will have an individual treatment room for each of the ion therapy systems. In such embodiments, the laser beam source is suitably located in a separate room or building. In embodiments with an optical monitoring system, the operator can know, and control, which of the ion therapy systems is being activated. One embodiment of the high energy polyenergetic positive ion beam radiation treatment centers of the present invention also includes a suitable laser and a system for monitoring and controlling the therapeutically suitable high energy polyenergetic positive ions. Suitable lasers are typically housed in a building, such as in the same building as the positive ion beam treatment center, or possibly in a nearby building connected by a conduit for containing the laser beam. The main laser beam line is typically transported through the building within shielded vacuum conduit using a series of mirrors to direct the laser beam to the target and ion selection system. The target and ion selection system is typically mounted on a gantry, which is placed in a treatment room. In additional embodiments of the present invention, the main laser beam is split using a beam splitter into a plurality of laser beams emanating from a single laser. Each of the laser beams emanating from the beam splitter is directed to an individual target and ion selection system for treating a patient. In this fashion, high energy polyenergetic positive ion radiation treatment centers are provided using one laser source and a plurality of ion therapy systems to treat a plurality of patients. In certain embodiments of the high energy polyenergetic positive ion radiation treatment centers of the present invention, there are provided a plurality of treatment rooms, each treatment room having an individual target and ion selection system, a location for a patient, and a proton beam monitoring and controlling system. A plurality of treatment rooms equipped this way enables a greater number of patients that can be treated with the investment of one high power laser for providing therapeutically suitable high energy polyenergetic positive ions. Particle selection mechanism for a laser-proton accelerator. A laser-accelerated proton therapy system uses high intensity laser pulses to generate plasmas in a high density material, and accelerate the protons to high kinetic energies. One embodiment of a system design is shown in FIG. 1. The laser beam produced by a table-top-scale laser system (not drawn) is sent to the treatment unit through vacuum beam pipelines. The target assembly and the particle selection device is placed in the rotating gantry (not drawn). The laser beam is guided by a system of mirrors (a-e) as shown. The distances between mirrors are adjusted to scan the proton beam along the y- and z-axes and to generate a parallel scan beam. Alternatively, the target and the particle selection device are moved about the laser beam to achieve a parallel scan pattern. A compact particle selection and beam collimation device is used to deliver small pencil beams of protons of different energies and intensities, as schematically described in one embodiment in FIG. 2. The particles produced by the laser include not just protons, but may also include various unwanted species such as photons, neutrons, and electrons. The protons coming from the target are mainly accelerated forward along the x-axis, which can be the beam axis. A step magnetic field, (see, e.g., FIG. 3) distributed in four separated regions, can be used to deflect protons and electrons. In the first region (a), the magnetic field points into the plane or −z-direction, and the protons are pushed up. When they enter into the second (b) and the third (c) region, the field is flipped to the z-direction, and the protons are pulled down. The field in the last region (d) puts the protons back to the original beam axis. As shown in FIG. 2 a beam stopper can be placed on the beam axis to block the photons and neutrons as well as high energy protons. The electrons are deflected downward by the magnetic field and are absorbed by an electron stopper placed in the lower part of the device. Other unwanted particles missed by the stoppers can be absorbed by the shielding surrounding the particle selection device. The deflection of protons depends on the proton energy. The protons with low energies are more deflected than those with high energies. Thus, particles with different energies are spatially separated in the y-direction. A collimator aperture is placed near the center of the system at certain position on the y-axis, where the protons of given energy pass through its opening; the particles with other energies are stopped by the collimator. In one embodiment, two more collimators are used to control proton beam size; one is at the beginning of the magnetic field (primary collimator), and the other (secondary collimator) is at the end. A non-step magnetic field can be used to model the performance of this embodiment of the present invention. Calculation of the magnetic field produced by rectangular loops. A strong magnetic field can be generated by a cylindrical winding of conventional metal wire, and preferably superconducting wire. The calculation of the complete field distribution is electromagnet dependent and very complicated. Analytical solutions can be quite difficult to obtain, except for very few special points. A superconducting electromagnet can be treated as a stack of current loops. An analytical calculation of magnetic field distribution for a single rectangular loop can be performed using the Biot-Savart law. Thus, a complete 3-D field distribution for the superconducting electromagnet can be obtained by summing up the fields for each loop. A single rectangular loop carrying a current I is shown in FIG. 4, and the three components of the magnetic field strength, Bx, By, Bz, are analytically calculated and given in the Appendix, below. The field for multiple loops is the superposition of the fields for individual loops. B x , y , z = ∑ i = 1 n ⁢ B x , y , z ⁡ ( ( i - 1 ) ⁢ Δ ⁢ ⁢ z + z 1 ) , ( 1 ) where Δz is the distance between two adjacent loops, z1 the position of the first loop, and n the total number of loops. The electromagnet coil can be treated as multiple current loops assuming the uniform current density in the coil. A computer code was written to simulate the magnetic field of the rectangular loop based on the calculation. The field distribution along the x-axis or the beam axis for the single loop is plotted in FIG. 5. As can be seen, Bz is not uniformly distributed in the x-axis. Two peaks appear at the edge of the loop. Also, Bz has big variation in either the y- or z-directions as shown in FIGS. 5 (a) and (b). A comparison among the three components of the field in (c) shows that Bx dominates over Bz at the edges of the loop and will significantly change the total field around the edges, while By can be ignored. Thus, more than one loop can be used to produce a uniform magnetic field. Another loop with the same size and current in parallel along the z-axis can be added. This is similar to the circular Helmhotz coil. The distance between the two loops in this example is about 4 cm. The field distribution for the double loop is not much different from the distribution of the single loop. The peaks are still present, although the peaks of Bx have been somewhat reduced. This indicates that adding loops in the z-direction can reduce the peaks and flatten out the field distribution. Superconducting Electromagnet Embodiments. As mentioned above, more loops can be used to stack vertically along the z-axis to reduce the peaks and smooth the field distribution. Loops can be stacked to make electromagnets; a superconducting electromagnet can be made by winding a long wire by multiple turns that are magnetically equivalent to a stack of loops as shown in FIG. 6. Two such superconducting electromagnets can be connected together, which provide a gap, d, between, where a somewhat uniform magnetic field is provided and protons will pass therethrough. The dimensions of a single superconducting electromagnet can be determined with both the laser-proton system design and the selection of the material of the wire in mind. A compact laser-proton system can include a compact electromagnet system. In one embodiment of the present invention, the upper limit on the dimensions of a single superconducting electromagnet is set to about 20×40×25 cm3 (Lx×Ly×Lz). As used herein, the mathematical symbol tilde (“˜”) used in front of a number means “about”. If a conventional copper wire is used, which can carry a current with a density of ˜103 A/cm2, the cross section of the electromagnet coil wound with the copper wire should be ˜103 cm2 to get a total current of ˜106 A to achieve a magnetic induction of ˜4.4 T (see Appendix). Thus, a thickness (T) of about 40 cm for a conventional non-superconducting electromagnet with a length (Lz) of about 25 cm can be used to meet the cross section, which makes the width in both x- (Lx) and y-direction, (Ly) much greater than about 80 cm. While such electromagnets can be used in the present invention, it is desirable to use even smaller electromagnets. The size of the electromagnet can be significantly reduced by utilizing superconducting wires instead of copper because a superconducting wire can carry a very high current density. Another advantage of using superconducting wires is saving power. The power consumption for a superconducting electromagnet is only about 1% to about 10% of that for a comparable conventional electromagnet. Superconducting wires are commercially available and have been widely used in high energy accelerators to produce strong magnetic fields. A suitable superconducting wire is NbTi, which has a critical current density of ˜4.25×105 A/cm2 at 4.2 K for a field of ˜4.4 T. Another commercially available superconducting wire, Nb3Sn, can also be used. Other types of superconducting wires, including those made from high temperature superconductors, can be used. Suitable high temperature superconducting wires are commercially available from the American Superconductor, Westborough, Mass. (http://www.amsuper.com/index.cfm). Suitable superconducting wires, such as NbTi wire, is commercially available in widths of from about 10 micron to 250 micron diameter form Japan Superconducting Technology, Inc. Tokyo, Japan, (http://www.jastec.org/eg/index.html). The actual current can be less than the critical current, otherwise, the superconducting state can be broken and the wire will function in the conventional conducting state. In one embodiment, to generate a magnetic field of ˜4.4 T, a suitable super-conducting wire, such as NbTi wire of about 0.2 mm in diameter, which carries a current of about 85 A, is wound 10000 turns to make a rectangular superconducting electromagnet of about 20 cm in length (Lz) and about 0.2 cm in thickness. Thus, a pair of such superconducting electromagnets will be about 40 cm long, including a gap (d) of about 1 cm. The coil cross section in the superconducting electromagnet is about 20 cm×0.2 cm, so the current density is only about 2×105 A/cm2, which is less than the critical current density and therefore can be used for maintaining the superconductivity. As a result, the electromagnet size can be reduced by a factor of ˜200 using superconducting wires. Suitable superconducting wires can have a thickness in the range of from about 10 nanometers (“nm”) to about 5 mm. In one embodiment, suitable superconducting wires can have a thickness of about 0.2 cm, and are coiled in a rectangular fashion to provide dimensions of width of about 15 cm in the x-axis, and a width of about 20 cm in the y-axis. Such superconducting electromagnets are suitable and produce a smooth magnetic field, as shown in FIG. 7. The edge peaks of Bz are substantially removed and Bx has only small peaks at the edges. In one embodiment, four electromagnets are used to achieve a step-like field distribution (see FIG. 3). The electromagnets are placed parallel along the x-axis (beam axis) with the first and the fourth electromagnet field pointing to −z, and the second and third magnetic field pointing to z. The first electromagnet produces the magnetic field with the Lorentz force that pushes protons up, then the second and the third produce the field that pulls the protons down, and the field from the last one puts the protons back to the original direction. This superconducting electromagnet system only takes about 80 cm along the beam axis, which is comparable in size to a photon and electron accelerator. A smooth step-like field distribution (see FIG. 8) is produced with I=85 A and B=Bz˜4.4 T. Bx and By are small and can be ignored. In this embodiment B≈Bz. The following description is directed to the dynamics of protons, as one illustrative embodiment Additional embodiments directed to other positive ions in addition to protons are also envisioned. Other embodiments directed towards lithium, beryllium, boron, carbon, or other light ions, or any combination thereof are also envisioned. Proton transport and optimization of the electromagnet system. One embodiment of the superconducting electromagnet system of the present invention can be tested by studying proton transport in the magnetic field produced by the system. The magnetic field can separate protons with different energies in their trajectories and returns substantially all of the desired protons moving initially along the beam axis to the beam axis. The proton's dynamics can be described by the equation of motion ⅆ p ⅆ t = qv × B ( 2 ) where p is the momentum of the proton, q is the charge of the proton, and v is the velocity of the proton. Based on a symplectic algorithm, a simulation code has been written to give a numerical solution for proton trajectories. A number of factors are discussed, which can influence the field distribution and affect the proton beams. Those parameters can be fine tuned to optimize a electromagnet system. Beam collimation. In this embodiment, a PIC simulation has shown that, for the given laser-plasma parameters, the protons can have an energy spectrum that is much wider than needed in clinical applications. Collimators can be introduced to block or slow the unwanted protons and collimate the desired particle beams. In the proton collimation, the beam size and its energy spread can be considered. The beam size can be selected by the treatment plan, and determined by the primary collimator in the beginning and the secondary collimator in the end. For instance, for intensity modulated proton therapy, a pencil beam with a 1×1 cm2 field at SSD of 100 cm can be used. The primary collimator opening is usually not arbitrarily large, since it directly controls the energy spread of the resultant beam. The primary collimator aperture can be chosen in various embodiments of the present invention to be such that particles that subtend an angle of about 2*arctan(0.025/5.0) are permitted to go through, thus giving a beam size of about 1×1 cm2 at about 100 cm SSD. In one embodiment, the middle collimator is used to shape the energy spectrum of the spread out protons to obtain clinically useful beams. The results in FIG. 9 show that a 0.40-cm aperture opening can be used to collect substantially all 250-MeV particles with a less than 30 MeV energy spread, not accounting for the angular distribution. Considering that the protons have an inherent angular spread originating from the laser interaction with the solid structure, more divergent proton beams and broader energy spread for each beam can arise for similar collimation parameters given above. Thus, the aperture size can be slightly reduced to control the energy spread in the beam. An about 0.3-cm aperture has been used in the following embodiment. A secondary collimator is also introduced in this embodiment to establish a suitable beam size and filter out remaining unwanted particles. Field strength. In this embodiment, the maximum deviation of the proton beam from the central axis ym can increase with the magnetic field strength B. This deviation can determine the size of the selection system. The spatial separation of two proton beams with adjacent characteristic energies at the point of their maximum deviation ym can be related to the deviation itself, as shown in FIG. 9. The lower ym can result in the smaller spatial separation, thus larger resultant energy spread in the proton beam. Maintaining a reasonably small energy spread can be established by using a small value of ym. The absolute value of the magnetic field is usually not too small. FIG. 10 shows the effect of the magnetic field strength. For a small field of 0.8 T, the electromagnet width in the y-axis can be reduced to less than 2.5 cm, but the energy spread for protons with characteristic energy higher than 160 MeV can be too large to be acceptable as shown in FIG. 14(b). These results indicate that a field strength of about B=4.4 T and a electromagnet width in the y-direction of about Ly=20 cm provides a suitable compact selection system with acceptable energy spread in the final proton beam. Gap between the paired electromagnets. In certain embodiments, the protons traversing the magnetic field can refocus on the beam axis where the secondary collimator is placed. However, since the magnetic field is not always step-distributed, the y-position of the protons at the secondary collimator, ys, can deviate from 0. In certain embodiments, ys can be affected by the field strength and the field shape, both of which are related to the gap between the two paired superconducting electromagnets. Usually, ys varies with different energies. Thus, the secondary collimator can be moved along the y-axis to collect the proton beams with different energies. However, the position of the secondary collimator is usually fixed for all energies in order to avoid the uncertainties caused by moving the collimator. In order to achieve this, the gap can be tuned to shape the field in such a way as to allow the required protons with different energies to focus on the same point ys, which is close to 0. FIG. 11 shows the trajectories of a proton for d=0.5, 1, 2, 4 cm. For d=1.0 cm, the difference of ys for different energies is minimum and the closest to zero, thus, a 1.0-cm gap is used in certain embodiments of the invention. Width of the middle electromagnets. In certain embodiments, the trajectories of the protons can be very sensitive to the width of the middle electromagnets in the x-direction (i.e., the beam direction), Lx. In an alternate variation, the width for all four electromagnets was set as 15 cm to be consistent with the step field distribution. With this configuration, the protons usually did not return to the x-axis and diverge at x=80 cm for different energies as shown in FIG. 12 (a). Using 17 cm in a different variation also led to protons not returning to the x-axis, as shown in FIG. 12(b). Without being bound to a specific theory of operation, it is believed that the protons are not returning to the x-axis because the field strength for the second and third electromagnet is lower than that for the first and fourth, as shown in FIG. 8. These examples show that Lx=16.3 cm leads to the best results in this embodiment (see FIG. 11(b)). These results show that the importance of the design parameters of a suitable electromagnet system for a polyenergetic positive ion beam selection device for use in laser-accelerated proton beam therapy. The parameters of the electromagnet system are readily determined with the system design and the simulation of proton transport, as provided in the various aspects of the present invention. FIG. 13 compares the proton trajectories in the electromagnet-generated field and the ideal step field. The trajectories in the former case are shifted up in the y-direction. This appears to result from the field strength in the first and the fourth region being larger than that in the middle to balance the asymmetry of the field distribution, while the field strength for all four regions is the same in the latter case. Energy spectrum and dose distribution. Without being bound by any particular theory of operation, it is believed that the energy spread of a proton beam comes from the broad energy and angular distribution of the laser-accelerated protons. The resulting polyenergetic proton beams are clinically useful for irradiating tumors. With an ideal step magnetic field, preliminary results have shown that although each polyenergetic laser-accelerated proton beam results in a less sharp depth-dose falloff, nonetheless it can be combined and modulated to generate a spread-out Bragg peak (SOBP) with a well-conformal coverage of the target. The energy spectra and the corresponding dose distributions can be recalculated in the presence of the magnetic field produced by a superconducting electromagnet system of the present invention. To calculate the energy spread centered around the characteristic energy E, ym(E), the y-position of the proton with energy E, when the proton reaches xm, the x-position where the particle selection aperture is placed is determined. Then, the aperture center is moved to ym(E), with a width of 3 mm, and the protons which pass through the aperture are counted. Thus, a proton beam with an energy spread peaked around E is obtained. The energy spectra for three beams are shown in FIG. 14. Lower energy proton beams have smaller energy spread in their distributions, whereas the high energy beams have larger energy spread. Without being bound by a particular theory of operation, this result is apparently due to the fact that the higher energy protons are less deflected by the magnetic field and thus are less divergent than the lower energy protons. FIG. 14(b) shows the energy spread increases with the decrease of the field strength. For B=0.8 T, the energy spread is larger than 100 MeV for the characteristic energy higher than 160 MeV. This energy spread is not optimally desirable for certain embodiments of the invention. The dose distributions for the polyenergetic proton beams can be calculated using the GEANT3 Monte Carlo code. Since the energy spread tends to spread out the Bragg peak, the wider energy distribution typically gives rise to a flatter Bragg peak, as is shown in FIG. 15. FIGS. 14 and 15 compare the energy spectra and associated depth-dose distributions calculated using the ideal step magnetic field distribution and that for the electromagnet-produced system. The proton energy spectra for the electromagnet-generated field are somewhat shifted to lower energy regions, which appears to be consistent with FIG. 13. One embodiment of the invention provides a compact superconducting electromagnet system capable of producing a step-like magnetic field distribution, which is useful for proton beam selection. One design of the superconducting electromagnet system is obtained from the analytical calculation of the magnetic field for rectangular coils, which provides a three dimensional magnetic field distribution, thus accounting for such boundary effects as edge focusing due to the influence of the fringing field patterns at the edge of the coils. The simulation of proton trajectories is used to test the electromagnet system and optimize the design for certain criteria. These results indicate that clinically acceptable quality proton beams can be produced with an embodiment of a suitable magnetic selection system using the following parameters: The dimensions of a single electromagnet can be about Lx=15 cm (outer), 16 cm (inner), Ly=30 cm, and Lz=20 cm. An average magnetic induction of about 4 to 5 T, is provided using a loop current of about I=85 A with about 10000 turns of a suitable superconducting wire, such as NbTi wire. The current can vary between 60 A and 600 A depending on the fabrication of superconducting wires and the use of power supply. The gap between the paired electromagnets can be about 1 cm The aperture size for the three collimators can be set to about 0.05 cm for the primary, 0.3 cm for the selection aperture, and 0.8 cm for the secondary. Using the electromagnet system of this embodiment, energy spectra are obtained for different selected characteristic energies. Compared with the energy spectra obtained with the ideal step field distribution, they have a small shift to low energy regions, but they both have almost the same spreads. This agrees with the dose distribution pattern obtained with those energy spectra. The superconducting electromagnet systems of the present invention are useful in the particle selection mechanism of our related invention, International Patent Application No. PCT/US2004/017081, filed Jun. 2, 2004, entitled “High Energy Polyenergetic Ion Selection Systems, Ion Beam Therapy Systems, and Ion Beam Treatment Centers”, the entirety of which is incorporated by reference herein. Accordingly, the superconducting electromagnet systems provided herein can be used for producing clinically usable proton beams. These systems can be modeled using Monte Carlo calculations of dose distributions based on real patient geometry. We apply the Biot-Savart law to the rectangular current loop shown in FIG. 4 B = ∮ C ⁢ μ 0 ⁢ I ⁢ ⅆ l × r 4 ⁢ ⁢ π ⁢ ⁢ r 3 = ∑ i = 1 4 ⁢ ⁢ ∫ Li ⁢ μ 0 ⁢ I ⁢ ⅆ l × r i 4 ⁢ ⁢ π ⁢ ⁢ r i 3 ⁢ , ( I ) where B is magnetic induction, μo the permeability of free space, which is equal to 4π×10−7 NA−2. I is the current carried by the loop, and ri is the distance between the current element of the i-th side of the loop and the point (x, y, z) and given by:ri=((x−xi)2+(y−yi)2+(z−zi)2)1/2, i=1,2,3,4.Integrating Eq. (I) over the loop, we obtain the three components of the magnetic field B x = - μ 0 ⁢ I ⁡ ( y - b / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x + a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( y - b / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x - a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( y + b / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x + a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( y + b / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x - a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 , ( II ) B y = μ 0 ⁢ I ⁡ ( x + a / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( x + a / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( z + c / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 , ⁢ and ( III ) B z = μ 0 ⁢ I ⁡ ( x + a / 2 ) ⁢ ( y + b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( y - b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( y + b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( y - b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( x + a / 2 ) ⁢ ( y - b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x + a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( y - b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x - a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 - μ 0 ⁢ I ⁡ ( x + a / 2 ) ⁢ ( y - b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x + a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x + a / 2 ) 2 + ( y - b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 + μ 0 ⁢ I ⁡ ( x - a / 2 ) ⁢ ( y + b / 2 ) 4 ⁢ ⁢ π ⁡ [ ( x - a / 2 ) 2 + ( z + c / 2 ) 2 ] ( ( x - a / 2 ) 2 + ( y + b / 2 ) 2 + ( z + c / 2 ) 2 ) 1 / 2 . ( IV ) For a special point (0, 0, −c/2), the center of the loop, the z-component of the magnetic field is reduced to a known expression, (N. Ida and J. Baotos, Electromagnetics and Calculation of Fields, Springer-Verlag, 1992) B z = - 2 ⁢ ⁢ μ 0 ⁢ I π ⁢ a 2 + b 2 ab . ( V ) Eq. (V) can be used to estimate roughly what current is needed for a given magnetic field strength. For Bz=4.4 T, a=0.15 m, and b=0.3 m, the required current is I = ⁢ π ⁢ ⁢ B z 2 ⁢ ⁢ μ 0 ⁢ ab a 2 + b 2 = ⁢ π × 4.4 × 0.15 × 0.3 2 × 4 ⁢ ⁢ π × 10 - 7 ⁢ 0.15 2 + 0.3 2 = ⁢ 7.4 × 10 5 ⁢ ⁢ A . Thus, in order to produce a field of ˜4.4 T close to the plane of the loop, the current I has to be ˜106 A.
	claims	1. A repair apparatus for repairing a shroud in a nuclear reactor pressure vessel, the reactor pressure vessel comprising a core shroud having a plurality of shroud lugs around the circumference of a first end of the core shroud, a shroud support structure arranged to support the core shroud inside the reactor pressure vessel so that the shroud and a side wall of the reactor pressure vessel define an annulus therebetween, a second end of the shroud is coupled to the shroud support structure, said shroud repair apparatus comprising: an upper stabilizer assembly configured to couple to a shroud lug, said upper stabilizer comprising a stabilizer block and an upper stabilizer wedge slidably coupled to said upper stabilizer block; a lower stabilizer assembly, said lower stabilizer comprising a stabilizer block and an lower stabilizer wedge slidably coupled to said lower stabilizer block, said lower stabilizer block configured to engage the shroud; and a tie rod having an outer surface, said tie rod extending between and coupled at a first end to said upper stabilizer assembly and at a second end to said lower stabilizer assembly. 2. A repair apparatus in accordance with claim 1 wherein said upper stabilizer assembly further comprises a jack bolt, said jack bolt extending through a jack bolt opening in said upper stabilizer wedge and threadedly engaging a jack bolt opening in said upper stabilizer block. claim 1 3. A repair apparatus in accordance with claim 2 wherein said lower stabilizer assembly further comprises a jack bolt, said jack bolt extending through a jack bolt opening in said lower stabilizer wedge and threadedly engaging a jack bolt opening in said lower stabilizer block. claim 2 4. A repair apparatus in accordance with claim 3 wherein said upper stabilizer wedge and said lower stabilizer wedge each further comprise a ratchet lock spring configured to engage said corresponding jack bolt. claim 3 5. A repair apparatus in accordance with claim 1 wherein said lower stabilizer wedge further comprises a horizontal stabilizing spring configured to engage the side wall of the reactor pressure vessel. claim 1 6. A repair apparatus in accordance with claim 1 wherein said upper stabilizer wedge further comprises an integral leaf spring portion configured to engage the side wall of the reactor pressure vessel. claim 1 7. A repair apparatus in accordance with claim 1 wherein said tie rod is attached to said upper stabilizer block with a tie rod nut and a spring washer, said spring washer positioned between said tie rod nut and said upper stabilizer block. claim 1 8. A repair apparatus in accordance with claim 1 wherein said tie rod comprises a plurality of longitudinal grooves in said outer surface. claim 1 9. A repair apparatus in accordance with claim 1 wherein said tie rod comprises a sleeve attached to said tie rod outer surface, said sleeve comprising an outer surface having longitudinal fins, said sleeve covering at least a portion of said outer surface of said tie rod. claim 1 10. A repair apparatus in accordance with claim 1 wherein said tie rod further comprises a limit stop at said first end, said limit stop configured to engage the shroud, said limit stop comprising at least one shear pin configured to engage mating holes in a bottom surface of said upper stabilizer block. claim 1 11. A nuclear reactor pressure vessel comprising: a core shroud comprising a plurality of shroud lugs around the circumference of a first end of said core shroud; a shroud support structure arranged to support said core shroud inside said reactor pressure vessel so that said shroud and a side wall of said reactor pressure vessel define an annulus therebetween, a second end of said shroud is coupled to said shroud support structure; and at least one shroud repair apparatus positioned in said annulus, each said shroud repair apparatus comprising: an upper stabilizer assembly coupled to a shroud lug, said upper stabilizer comprising a stabilizer block and an upper stabilizer wedge slidably coupled to said upper stabilizer block; a lower stabilizer assembly, said lower stabilizer comprising a stabilizer block and an lower stabilizer wedge slidably coupled to said lower stabilizer block, said lower stabilizer block engaging said shroud; and a tie rod having an outer surface, said tie rod extending between and coupled at a first end to said upper stabilizer assembly and at a second end to said lower stabilizer assembly. 12. A nuclear reactor pressure vessel in accordance with claim 11 wherein said upper stabilizer assembly further comprises a jack bolt, said jack bolt extending through a jack bolt opening in said upper stabilizer wedge and threadedly engaging a jack bolt opening in said upper stabilizer block. claim 11 13. A nuclear reactor pressure vessel in accordance with claim 12 wherein said lower stabilizer assembly further comprises a jack bolt, said jack bolt extending through a jack bolt opening in said lower stabilizer wedge and threadedly engaging a jack bolt opening in said lower stabilizer block. claim 12 14. A nuclear reactor pressure vessel in accordance with claim 13 wherein said upper stabilizer wedge and said lower stabilizer wedge each further comprise a ratchet lock spring configured to engage said corresponding jack bolt. claim 13 15. A nuclear reactor pressure vessel in accordance with claim 11 wherein said lower stabilizer wedge further comprises a horizontal stabilizing spring configured to engage said side wall of said reactor pressure vessel. claim 11 16. A nuclear reactor pressure vessel in accordance with claim 11 wherein said upper stabilizer wedge further comprises an integral leaf spring portion configured to engage said side wall of said reactor pressure vessel. claim 11 17. A nuclear reactor pressure vessel in accordance with claim 11 wherein said tie rod is attached to said upper stabilizer block with a tie rod nut and a spring washer, said spring washer positioned between said tie rod nut and said upper stabilizer block. claim 11 18. A nuclear reactor pressure vessel in accordance with claim 11 wherein said tie rod comprises a plurality of longitudinal grooves in said outer surface. claim 11 19. A nuclear reactor pressure vessel in accordance with claim 11 wherein said tie rod comprises a sleeve attached to said tie rod outer surface, said sleeve comprising an outer surface having longitudinal fins, said sleeve covering at least a portion of said outer surface of said tie rod. claim 11 20. A nuclear reactor pressure vessel in accordance with claim 11 wherein said tie rod further comprises a limit stop at said first end, said limit stop configured to engage said shroud, said limit stop comprising at least one shear pin configured to engage mating holes in a bottom surface of said upper stabilizer block. claim 11
048511838	abstract	A nuclear reactor for generating electricity is disposed underground at the bottom of a vertical hole that can be drilled using conventional drilling technology. The primary coolant of the reactor core is the working fluid in a plurality of thermodynamically coupled heat pipes emplaced in the hole between the heat source at the bottom of the hole and heat exchange means near the surface of the earth. Additionally, the primary coolant (consisting of the working flud in the heat pipes in the reactor core) moderates neutrons and regulates their reactivity, thus keeping the power of the reactor substantially constant. At the end of its useful life, the reactor core may be abandoned in place. Isolation from the atmosphere in case of accident or for abandonment is provided by the operation of explosive closures and mechanical valves emplaced along the hole. This invention combines technology developed and tested for small, highly efficient, space-based nuclear electric power plants with the technology of fast-acting closure mechanisms developed and used for underground testing of nuclear weapons. This invention provides a nuclear power installation which is safe from the worst conceivable reactor accident, namely, the explosion of a nuclear weapon near the ground surface of a nuclear power reactor.
	abstract	Systems and apparatuses for providing particle beams for radiation therapy with a compact design and suitable to a single treatment room. The radiation system comprises a stationary cyclotron coupled to a rotating gantry assembly through a beam line assembly. The system is equipped with a single set of dipole magnets that are installed on the rotating gantry assembly and undertakes the dual functions of beam energy selection and beam deflection. The energy degrader may be exposed to the air pressure. The beam line assembly comprises a rotating segment and a stationary segment that are separated from each other through an intermediate segment that is exposed to an ambient pressure.
	summary
051715201	summary	BACKGROUND OF THE INVENTION This invention relates generally to nuclear fuel elements. More particularly, this invention relates to fuel elements which employ a cladding tube containing a fuel pellet of fissionable material for use in a nuclear reactor. One form of a fuel rod typically employed in nuclear reactors comprises a fuel pellet which is contained in a cladding tube. The cladding tube is typically manufactured from zirconium-alloy or various metal-alloy materials. The fuel rods, in conventional reactor configurations, are mounted to a support grid. The lower portions of the rods below the grid are disposed in regions where debris may be entrapped. The zirconium-alloy fuel cladding has a useful life which is subject to debris fretting. The zirconium-alloy fuel rods employed in nuclear reactors are exposed to high temperature water which is typically in the range 300.degree. C. to 400.degree. C. The water is subjected to high pressures and frequently contains metal particles of stainless steel or Inconel-alloy steel which originate at reactor locations remote from the fuel rods themselves. The metallic particles tend to collect near the bottom of the fuel rods and are entrapped by the first support grid for the fuel rods. The metallic debris may be maintained in a quasi-suspensive state due to vibration and movement of the water through the reactor. The metallic particles which form the debris may be hardened by radiation. The hardened metallic state tends to rapidly accelerate the wear or erosion of the cladding tubes of the fuel rods. The resultant tube fretting may be sufficient so as to ultimately result in penetration of the cladding tube wall, thereby resulting in failure of the cladding. Thus, the long term integrity of the fuel cladding is a direct function of resistance to debris fretting. The hostile environment of the reactor dictates that any structural modification or enhancement to the cladding tube satisfy a number of constraints. First, any wear resistant structure must be significantly harder than the metallic debris particles to effectively resist abrasion from the particles. Any coating applied to the cladding tube must have excellent long term adhesive qualities, be fully compatible with the thermal expansion of the cladding tube and also form a strong bond with the tube. In addition, any coating must be resistant to the chemical environment in the reactor which characteristically includes hot water at a pH of approximately 7. The thickness of any coating applied to the cladding tubes must be relatively thin so that the flow of water around the fuel rods is not significantly impeded by the coating and that the coating not function as a thermal barrier. Any coating is preferably capable of application in a process which does not require heating of the cladding tube above 400.degree. C. In addition, it is also desirable that the coating be inexpensive and be suitable for mass production. Coatings of various forms and functions have been applied to the inside surfaces of cladding tubes for nuclear reactors. For example, U.S. Pat. Ser. No. 07/211/182 assigned to the assignee of the present invention discloses a fuel element for a nuclear reactor having a zirconium-tin alloy cladding tube. A thin coating of an enriched boron-10 glass containing burnable poison particles is deposited on the inside of the cladding tube from a liquid sol-gel. The coating includes a glass binder which is applied on the inside of the zirconium-alloy cladding tube. U.S. Pat. No. 3,625,821 discloses electroplating the inside surface of a tube with coating of a matrix metal and boron compound of, for example, nickel, iron manganese or chrome. Boron compounds such as boron nitride, titanium boride and zirconium boride are electroplated onto a Zircaloy substrate. U.S. Pat. No. 4,695,476 discloses a vapor deposition of volatized boron compounds on the inside of fuel rod cladding. SUMMARY OF THE INVENTION Briefly stated, the invention in a preferred form is a wear resistant coating which is applied to a cladding tube for a fuel element employed in a nuclear reactor. The coating is applied to the outside surface of the cladding tube and comprises a matrix of ceramic material and glass. The glass acts as a binder to bond the ceramic material to the cladding tube. The coefficient of thermal expansion of the ceramic material and the glass is approximately equal to the coefficient of thermal expansion of the cladding tube material. The cladding tube may be substantially formed from a zirconium-alloy. Zircon may be employed as the ceramic material. The glass may be calcium zinc borate, calcium magnesium aluminosilicate or sodium borosilicate. The coating in one embodiment has an outside surface which substantially consists of the ceramic material and the coating has a thickness of approximately 5 mil. The ceramic material and glass is premixed to form a coating mixture. The ceramic material and glass is mixed in ratios sufficient to ensure bonding the ceramic material to the cladding tube. The cladding tube is preheated to a temperature between 300.degree. C. to 400.degree. C. The coating mixture is then flame sprayed onto the outside surface of the tube to form the wear resistant matrix. The flame spraying is conducted under conditions wherein the glass particles are transformed to a semi-molten state while the ceramic particles remain in a non-molten state. The outside surface of the matrix is etched to remove glass material to form an exposed outside surface which substantially consists of the ceramic material. Normally, the coating mixture is only applied to the surface of the one end of each rod that will be retained in the vicinity of the lower support grid. An object of the invention is to provide a new and improved fuel cladding having an enhanced resistance to wear from metallic debris surrounding the fuel rods of a nuclear reactor. Another object of the invention is to provide a new and improved coating which may be applied in an efficient and cost effective manner to enhance the wear resistance of a fuel rod cladding. A further object of the invention is to provide a new and improved method for manufacturing a cladding tube having enhanced wear resistant properties. Other objects and advantages of the invention will become apparent from the drawings and the specification.
	description	1. Field of the Invention The invention relates to a microlithography objective that provides a light path for a light bundle from an object field in an object plane to an image field in an image plane, a projection exposure apparatus with such an projection exposure objective and a usage of such a projection exposure system for processing of chips. 2. Description of the Prior Art Lithography with wavelengths of <193 nm, particularly EUV lithography with λ=11 nm or λ=13 nm are discussed as possible techniques for imaging of structures of <130 nm, and more preferably of <100 nm. The resolution of a lithographic system is described by the following equation: RES = k 1 · λ NA wherein k1 denotes a specific parameter of the lithography process, λ denotes the wavelength of the incident light and NA denotes the numerical aperture of the system on the image side. For imaging systems in the EUV range, reflective systems with multilayers are used substantially as optical components. Preferably, Mo/Be systems are used as multilayer systems for λ=11 nm and Mo/Si systems are used for λ=13 nm. The reflectivity of the multilayer systems used currently lies in the range of approximately 70%. Therefore a projection objective for EUV microlithography should have as few optical components as possible to achieve a sufficient light intensity. In order to achieve a resolution that is as high as possible, on the other hand, it is necessary that the system has an aperture that is as large as possible on the image side. For lithography systems, it is advantageous if the beam path or so called light path within a projection objective is free of shadows or obscurations. The projection objectives should have no mirrors with transmissive areas, especially openings, since transmissive areas lead to shading. If the objective does not have mirrors with transmissive areas, then the objective has an obscuration-free beam path and the exit pupil of the objective is free of shading and free of obscurations. Furthermore, the aperture diaphragm of such an objective does not need to have a shading device. A disadvantage of systems with an exit pupil shaded, e.g., a so-called Schwarzschild mirror systems, is that structures of specific size can be imaged only with restrictions. The exit pupil is defined as the image of the aperture diaphragm formed by the optical elements arranged in the light path of the objective between the aperture diaphragm and the image plane. 4-Mirror systems for microlithography have become known, for example, from U.S. Pat. No. 5,315,629 or EP 0 480,617 B1. Such systems, however, permit a numerical aperture only of NA=0.1 on the image side with a sufficient field size of at least 1.0 mm scanning slit width. The limit of resolution lies in the range of 70 nm with the use of x-ray light with a wavelength of 10 to 30 nm. 6-Mirror systems for microlithography have been made known from the publications U.S. Pat. No. 5,153,898; EP-A-0 252,734; EP-A-0 947,882; U.S. Pat. No. 5,686,728; EP 0 779,528; U.S. Pat. No. 5,815,310; WO 99/57606; and U.S. Pat. No. 6,033,079. Such 6-mirror systems have a numerical aperture of <0.3 on the image side, which leads to a resolution limit in the range of 30 nm with the use of x-ray light with a wavelength of 10-30 nm. Another disadvantage of both 4-mirror and 6-mirror systems is the fact that they provide only a few possibilities for correction of imaging errors. A projection objective for microlithography with eight mirrors has become known from U.S. Pat. No. 5,686,728. This projection objective has a high numerical aperture of NA=0.55 on the image side. Of course, a projection objective as it is known from U.S. Pat. No. 5,686,728 is suitable only for wavelengths longer than 126 nm, since, for example, the angle of incidence of the chief ray of the field point, which lies on the axis of symmetry in the center of the object field, is so large that this 8-mirror system cannot be operated in the EUV wavelength region of 10 to 30 nm. Another disadvantage of the system according to U.S. Pat. No. 5,686,728 is the fact that all eight mirrors are made aspheric and that the angle of the chief ray at the object has a value of 13° with a numerical aperture of 0.11 on the object side. There is provided a projection objective that provides a light path for a light bundle from an object field in an object plane to an image field in an image plane. The projection objective includes a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, a sixth mirror, a seventh mirror, and an eighth mirror. The light path is provided via the eight mirrors and is free of obscuration. The light bundle includes light with a wavelength in a range of 10-30 nm. The object field represents a segment of a ring field with an axis of symmetry that is perpendicular to an optical axis. The light bundle has a chief ray of a field point that lies on an axis of symmetry and in a center of the object field. The projection objective has therein a right-handed coordinate system with an x axis, a y axis and a z axis. The z axis runs parallel to the optical axis and the z axis points from the object field to the image field. The y axis runs parallel to the axis of symmetry and the y axis points from the optical axis to the object field. For each of the eight mirrors i (i=1 to 8) there is a characteristic quantity Ci, which is defined as a scalar product of a unit vector x in a direction of the x axis and a vector product between one unit vector nibefore, which has a direction of the chief ray striking an ith mirror, and a unit vector niafter, which has a direction of the chief ray reflected at the ith mirror, thus Ci=x (nibefore×niafter). Where C1>0 applies to the first mirror, C2<0 applies to the second mirror, C5<0 applies to the fifth mirror, and C6>0 applies to the sixth mirror. There is also provided another projection objective that provides a light path for a light bundle from an object field in an object plane to an image field in an image plane. The projection objective includes a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, a sixth mirror, a seventh mirror, and an eighth mirror. The light path is provided via the eight mirrors and is free of obscuration. The light bundle includes light with a wavelength in a range of 10-30 mm. The projection objective has a drift path that is formed between two of the eight mirrors. The drift path is longer than 70% of a structural length of the projection objective. There is further provided yet another projection objective that provides a light path for a light bundle from an object field in an object plane to an image field in an image plane. The projection objective includes a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, a sixth mirror, a seventh mirror, and an eighth mirror. The light path is provided via the eight mirrors and is free of obscuration. The light bundle includes light with a wavelength in a range of 10-30 nm. The projection objective has a drift path that is formed between two of the eight mirrors. The drift path is longer than 70% of a structural length of the projection objective. A first object of the invention is to provide a suitable projection objective for lithography with short EUV wavelengths in the range of 10 to 30 nm, which is characterized by a large numerical aperture and improved possibilities of imaging correction when compared with previously known projection systems for EUV microlithography. Another object of the invention consists of indicating a microlithography projection objective for lithography with wavelengths of ≦193 nm, which has both a large aperture and which can be manufactured in a simple manner. According to the invention, the first object is solved by a microlithography projection objective for EUV lithography with a wavelength in the range of 10-30 nm by the fact that the microlithography projection objective has eight mirrors instead of four or six mirrors. The inventors have recognized surprisingly that such an objective makes available both a sufficient light intensity as well as a sufficiently large numerical aperture in order to meet the requirements for high resolution as well as to make available sufficient possibilities for imaging correction. In order to achieve a resolution as high as possible, in an advantageous embodiment, the numerical aperture of the projection objective on the image side is greater than 0.2. In order to minimize the angle of incidence of the chief ray of the field point, which lies on the axis of symmetry and in the center of the object field, advantageously, the numerical aperture on the image side of the projection system according to the invention is limited to NA<0.5. In order to force a bundle of light rays in the direction of the optical axis (HA) and to avoid off-axis segments of the mirrors having a large distance to the optical axis (HA) in a particular advantageous embodiment the projection objective is designed in such a way that at least one intermediate image of the object field is formed in the beam path of the projection objective between object field and image field. In the present application, that part of a mirror on which the light rays that are guided through the projection objective impinge is denoted as the off-axis segment of a mirror. The distance of the off-axis segment from the optical axis (HA) in the present application is the distance of the point of incidence of the chief ray of the central field point onto the off-axis segment of the mirror from the optical axis (HA). In order to minimize the angle of incidence on the first mirror of the projection objective according to the invention, in a particularly advantageous embodiment of the invention, a diaphragm, which is preferably circular or nearly circular, is arranged in the light path between first and second mirrors, preferably on or in the vicinity of the first mirror or on or in the vicinity of the second mirror. “In the vicinity” in the present Application is understood as the distance of the diaphragm from the closest mirror that is less than 1/10th of the distance from the preceding mirror to the mirror in the vicinity of the diaphragm. For example, “in the vicinity of S2” means that the following applies: BS2< 1/10 S1S2,wherein BS2 denotes the distance of the diaphragm to the second mirror and S1S2 denotes the distance between the first and second mirrors. Such an arrangement permits a minimal separation of the beam bundles which reduces the angles of incidence on the first, second and third mirrors in the front part of the objective. In addition, such an arrangement of the diaphragm yields a configuration where the off-axis segment of the third mirror lies directly below the optical axis and is nearly in a mirror image of the off-axis segment of the first mirror S1. Furthermore, the angles of incidence on the fourth and fifth mirrors are also reduced, since the distance of the bundle of light rays from the optical axis is minimal between the fourth and fifth mirrors. In order to produce small angles of incidence on the mirrors, it is further of advantage, if the distances of the off-axis segment of the mirrors to the optical axis (HA) are kept small. Since these distances can be varied randomly by an appropriate scaling, they are characterized by their size ratio relative to the structural length of the objective in the present application. It is particularly advantageous, if the following relation is fulfilled: the distance of the off-axis segment of each mirror to the optical axis (HA) is smaller than 0.3structural length of the projection objective, and preferably: the distance of the off-axis segment of each mirror to the optical axis (HA) is smaller than 0.25structural length of the projection objective. In a further embodiment of the invention, the radius of curvature of at least one mirror is larger than the structural length of the projection objective. In this application the distance of the off-axis segment of a mirror to the optical axis (HA) is the distance between that point of the off-axis segment onto which the chief ray (CR) of a light bundle emerging form a field point, that lies on an axis of symmetry and in a center of an object field, impinges, and the optical axis (HA). The distance from the object to be imaged up to its image is understood as the structural length of the projection objective in the present application. In more detail this means the structural length is the distance between the object plane and the image plane along the optical axis (HA) of the projection objective. It is particularly advantageous, that the aforementioned condition for radius of curvature applies to the second, third and fourth mirrors, so that the paths of the light bundles from the first to the second mirror and from the third to the fourth mirror are nearly parallel. With such a configuration a minimal separation of the ray bundles and large drift paths are achieved. In the present application, the distance between the vertexes of two sequential mirrors in the light path of the light traveling through the objective is to be understood as the drift path. The aforementioned conditions contribute to small angles of incidence on the mirrors. The projection objective can be further characterized from the sum of (a) the lengths of all drift paths between pairs of sequential mirrors in said light path, (b) the length from said object plane to a vertex of said first mirror (S1) in said light path, and (c) the length from a vertex of said eighth mirror (S8) to said image plane in said light path, as indicated in the following formula:sum =length of drift pathS1S2+length of drift pathS2S3+length of drift pathS3S4+length of drift pathS4S5+length of drift pathS5S6+length of drift pathS6S7+length of drift pathS7S8+length from object plane to vertexS1+length from vertexS8 image plane. In a preferred embodiment, this sum is at least 2.5 times the structural length of the projection objective. The projection objective is preferably further characterized in that at least one drift path is longer than 70% of the structural length of the projection objective. In another embodiment of the invention, the microlithography projection objective is designed such that the sine of the angle of the chief ray at the object is smaller than twice the value of the object-side aperture (NAO). This is an advantage, since obscuration or shading effects on the masks are reduced thereby. It is a particular advantage if the projection objective has two intermediate images. The first intermediate image in a system with two intermediate images is formed preferably between the second and third mirrors. This leads to the fact that the first, second, third and fourth mirrors have off-axis segments in the vicinity of the axis. In order to assure that the off-axis segments of the mirrors are near to the axis for as many mirrors as possible in the objective part comprising the fifth, sixth, seventh and eighth mirrors, the projection objective is designed in such a way that the second intermediate image is formed in the beam path between the sixth and seventh mirrors. It is particularly preferred, if the angle of incidence of the chief ray of the field point, which lies on the axis of symmetry in the center of the object field, is smaller than 20° on all mirrors, in the case of a system with two intermediate images. In a preferred embodiment with two intermediate images, at least one of the eight mirror surfaces is made spherical. It is particularly advantageous if those mirrors of the objective with the largest distance of the off-axis segment are made spherical, since interferometric testability of off-axis aspheric profiles becomes difficult with an off-axis segment having a large distance to the optical axis. In a system with two intermediate images between the second and third mirrors as well as between the sixth and seventh mirrors, the sixth mirror is the mirror with the largest distance from the optical axis. In such an embodiment, preferably the sixth mirror is formed spherical for the sake of interferometric testability. In addition to the projection objective, the invention also makes available a projection exposure system, wherein the projection exposure system comprises an illumination device for illuminating a ring field as well as a projection objective according to the invention. FIG. 1 shows what is to be understood as the off-axis segment of a mirror and the diameter of such an off-axis segment in the present application. FIG. 1 shows a kidney-shaped field as an example for a projected field 1 on a mirror of the projection objective. Such a shape is expected for the off-axis segments in an objective according to the invention, if used in a microlithography projection exposure system. The enveloping circle 2 completely encloses the kidney shape and coincides with edge 10 of the kidney shape at two points 6, 8. The enveloping circle is always the smallest circle that encloses the off-axis segment. Diameter D of the off-axis segment then results from the diameter of the enveloping circle 2. In FIG. 2, the object field 11 of a projection exposure system is shown in the object plane of the projection objective, which is imaged by means of the projection objective according to the invention in an image plane, in which a light-sensitive object is arranged, for example, a wafer. The shape of the image field corresponds to that of the object field 11. With reduction objectives as frequently used in microlithography, the image field is reduced by a predetermined factor relative to the object field. The object field 11 has the configuration of a segment of a ring field. The segment has an axis of symmetry 12. The image field represents a segment of a ring field. The segment has an axis of symmetry and an extension perpendicular to the axis of symmetry and the extension is at least 20, preferably at least 25 mm. In addition, the axes that span the object and image planes, namely the x axis and the y axis are depicted in FIG. 2. As can be seen from FIG. 2, the axis of symmetry 12 of ring field 11 runs in the direction of the y-axis. At the same time, the y axis coincides with the scanning direction of an EUV projection exposure system, which is designed as a ring-field scanner. The x-direction is then the direction that runs perpendicular to the scanning direction, within the object plane. Additionally, the unit vector x in the direction of the x axis is depicted in FIG. 12. The optical axis HA of the projection objective extends in the z direction. A first example of embodiment of a projection objective, which can be utilized in the EUV range with λ=10-30 nm and is characterized by small angles of incidence on all mirrors, is shown in FIG. 3. The object in object plane 100 is imaged by means of the projection objective in the image plane 102, in which, for example, a wafer can be arranged. The projection objective according to the invention comprises a first mirror S1, a second mirror S2, a third mirror S3, a fourth mirror S4, a fifth mirror S5, a sixth mirror S6, a seventh mirror S7 as well as an eighth mirror S8. In the example of embodiment shown in FIG. 3, all mirrors S1, S2, S3, S4, S5, S6, S7 and S8 are formed as aspheric mirrors. The system comprises one intermediate image Z1 between the fifth S5 and the sixth S6 mirrors. The y and z directions of the right-handed x, y and z coordinate system are also depicted in FIG. 3. The z axis runs parallel to the optical axis HA and the orientation of the z axis points from the object plane 100 to the image plane 102. The y axis runs parallel to the axis of symmetry 12 of the object field 11. The object field 11 is shown in FIG. 2. The orientation of the y-axis is from the optic axis HA to the object field 11 as shown in FIG. 2. Additionally, the unit vectors n1before and n1after, which indicate the direction of the chief ray CR before and after the reflection at the first mirror, are depicted in FIG. 3 for the first mirror S1. The chief ray CR emerges from an object point on the axis of symmetry 12 in the center of the object field 11 shown in FIG. 2 and runs in a direction to the image field. The unit vectors result analogously for the other mirrors S2 to S8. The system is centered relative to the optical axis HA and is telecentric on the image side, i.e., in the image plane 102. Image-side telecentry is understood to mean that the chief ray CR impinges onto the image plane 102 at an angle close to or approximately 90°. The chief ray CR is reflected at the fourth mirror S4 in such a way that it runs in a direction away from the optical axis to the fifth mirror S5. The following inequalities result as characteristic quantities Ci for the mirrors: C1>0, C2<0, C3>0, C4<0, C5<0, C6>0, C7<0, C8>0. The characteristic quantities are defined as the scalar product between the unit vector x in the direction of the x axis and the vector product between one unit vector nibefore, which has the direction of the chief ray impinging onto the ith mirror, and a unit vector niafter, which has the direction of the chief ray reflected at the ith mirror, thusCi=x*(nibefore×niafter). The quantity Ci provides clear information of whether a chief ray CR impinging onto a mirror is reflected in the positive or negative y direction, whereby it is important whether the chief ray CR enters from the direction of the object plane 100 or from the direction of the image plane 102. It follows that Ci>0 applies if the chief ray impinges onto the mirror from the direction of the object plane 100 and is reflected in the direction of the negative y axis. Ci<0 applies if the chief ray impinges the mirror from the direction of the object plane 100 and is reflected in the direction of the positive y axis. Ci>0 applies if the chief ray impinges the mirror from the direction of the image plane 102 and is reflected in the direction of the positive y axis, and Ci<0, applies if the chief ray impinges the mirror from the direction of the image plane 102 and is reflected in the direction of the negative y axis. Within the mirror system, in order to keep light losses as well as coating-induced wavefront aberrations as small as possible, the angle of incidence of the chief ray CR of the central field point on the respective mirror surface is smaller than 26° in the example of embodiment according to FIG. 3. The angles of incidence of the chief ray of the central field point are reproduced in the following Table 1: TABLE 1Angles of incidence of the chief ray of the centralfield point for the example of embodiment of FIG. 3.MirrorAngle of incidence110.5°215.0°314.9°411.0°510.6°625.6°715.7°84.7° The 8-mirror objective shown in FIG. 3 has an image-side aperture of NA=0.4 and a scanning slit width of 1 mm. The following measures were taken in order to minimize the angle of incidence on the individual mirrors: The angle of the chief ray at object 100 is minimized, whereby the aperture on the object side NAO=0.1. The angle of incidence on the first mirror is minimized in this way. The maximal chief-ray angle at the object amounts to only 6.1° with the indicated numerical aperture NAO of 0.1 on the object side and is thus substantially smaller than the maximal chief-ray angle of 13° at the object according to U.S. Pat. No. 5,686,728. The physical diaphragm (B) is localized on the second mirror S2. This permits a minimal separation of the beam bundles in the front part of the objective, which reduces the angles of incidence on S1, S2 and S3. Additionally, this brings about the circumstance that the off-axis segment of mirror S3 lies directly under the optical axis and nearly in a mirror image to the off-axis segment of mirror S1, in contrast, for example, to the 8-mirror objective for wavelengths of >126 nm shown in U.S. Pat. No. 5,686,728. Based on this measure, the angles of incidence on S4 and S5 are smaller, since the distance of the beam bundle from the optical axis is minimal between S4 and S5. The off-axis segments of the individual mirrors are shown in FIGS. 4A-4H. The off axis segment of each mirror in FIGS. 4A-4H are depicted in the x-y-plane as the ring field shown in FIG. 2 is. Therefore, the x-axis and their direction as well as the y-axis and their direction are the same as in FIG. 2. The optical axis (HA) of the projection objective runs along the z-axis and is situated in the x-y-plane in the orgin (0,0) of the coordinate system. The distance of the off-axis segment of a mirror to the optical axis (HA) is the distance between that point of the off-axis segment onto which the chief ray (CR) of a light bundle emerging from a field point, that lies on an axis of symmetry and in a center of an object field, impinges, and the optical axis (HA). FIG. 4A shows the off-axis segment on mirror S1, FIG. 4B shows the off-axis segment of mirror S2, FIG. 4C shows the off-axis segment of mirror S3, FIG. 4D shows the off-axis segment of mirror S4, FIG. 4E shows the off-axis segment of mirror S5, FIG. 4F shows the off-axis segment of mirror S6, FIG. 4G shows the off-axis segment of mirror S7 and FIG. 4H shows the off-axis segment of mirror S8 of the embodiment of an 8-mirror objective according to FIG. 3. As can be seen clearly from FIGS. 4A-4H, all off-axis segments of mirrors S1 to S8 are free of shadows or obscurations. This means that the beam path of a light bundle, which passes through the objective from the object plane to the image plane, and which images the object field in the object plane into the image field in the image plane is free of shadows and obscurations. In addition, the radii of curvature of at least one of mirrors S2 to S4 is selected as large, preferably larger then the structural length of the projection objective, so that drift paths that are as large as possible are formed, and the paths of the beam bundles from S1 to S2 and from S3 to S4 lie nearly parallel. The same applies to the paths of the beam bundles from S2 to S3 and from S4 to S5. A minimal separation of the beam bundles also results from this. The wavefront has a maximal rms value of less than 0.030λ. Distortion is corrected via the scanning slit to a maximal value of 1 nm and has the form of a third-degree polynomial, so that the dynamic distortion mediated by the scanning process is minimized. The curvature of the image field is corrected by considering the Petzval condition. The exact data of the objective according to FIG. 3 are shown in Code V format in Table 2 in the FIG. 8. FIG. 5 shows a second embodiment of an 8-mirror objective according to the invention with mirrors S1, S2, S3, S4, S5, S6, S7 and S8. The same components as in FIG. 3 are given the same reference numbers. In particular, the x axis, the y axis and the z axis as well as the characteristic quantities are defined as in the description to FIG. 3. In FIG. 5, the physical diaphragm (B) is localized on the first mirror S1. The following apply to the characteristic quantities Ci, as defined in the description to FIG. 3:C1>0, C2<0, C3<0, C4>0, C5<0, C6>0, C7>0, C8<0. In order to achieve a production of an 8-mirror objective with the smallest possible expenditure and to assure an interferometric testability, it is provided in the case of this objective to make the mirror with a off-axis segment having the largest distance to the optical axis spherical. In order to minimize the angles of incidence and to compel the beam bundle in the direction of the optical axis and thus to limit the occurrence of off-axis segments far from the axis, the embodiment according to FIG. 5 has two intermediate images Z1, Z2. A first subsystem (i.e., mirrors S1 and S2) images an object field into the first intermediate image (Z1). A second subsystem (i.e., mirrors S3, S4, S5 and S6) images the first intermediate image (Z1) into the second intermediate image (Z2). A third subsystem (i.e., mirrors S7 and S8) images the second intermediate image (Z2) into an image field. In the example of embodiment shown in FIG. 5 with two intermediate images, mirrors S1, S2, S3, S4, S5 as well as S7 and S8 are aspheric, while mirror S6 which has a off-axis segment having the largest distance to the optical axis, in contrast, is spherical. The system has an aperture of NA=0.4 on the image side. Based on the example of embodiment in FIG. 5, it is clear that the first intermediate image between S2 and S3 provides for the fact that the first four mirrors S1, S2, S3, S4 have off-axis segments in the vicinity of the axis. This cannot be assured to the same extent in the back high-aperture part of the objective by the second intermediate image Z2 alone. The sixth mirror S6 thus has a off-axis segment with a large distance to the axis. If mirror S6 is formed aspheric, then it would be difficult to test it only with on-axis test optics. Thus, it is made spherical according to the invention. The angles of incidence of the chief ray of the central field point are reproduced in the following Table 3: TABLE 3Angles of incidence of the chief ray of the centralfield point for the example of embodiment of FIG. 5.MirrorAngle of incidenceS17.5°S24.4°S34.6°S410.5°S519.4°S64.6°S714.0°S84.2° The off-axis segments of the individual mirror segments are shown in FIGS. 6A-6H. The off axis segment of each mirror in FIGS. 6A-6H are depicted in the x-y-plane as the ring field shown in FIG. 2 is. Therefore, the x-axis and their direction as well as the y-axis and their direction are the same as in FIG. 2. The optical axis (HA) of the projection objective runs along the z-axis and is situated in the x-y-plane in the orgin (0,0) of the coordinate system. The distance of the off-axis segment of a mirror to the optical axis (HA) is the distance between that point of the off-axis segment onto which the chief ray (CR) of a light bundle emerging from a field point, that lies on an axis of symmetry and in a center of an object field, impinges, and the optical axis (HA). Thus, FIG. 6A shows the off-axis segment on mirror S1, FIG. 6B shows the off-axis segment of mirror S2, FIG. 6C shows the off-axis segment of mirror S3, FIG. 6D shows the off-axis segment of mirror S4, FIG. 6E shows the off-axis segment of mirror S5, FIG. 6F shows the off-axis segment of mirror S6, FIG. 6G shows the off-axis segment of mirror S7, and FIG. 6H shows the off-axis segment of mirror S8 of the embodiment of an 8-mirror objective according to FIG. 5. As can be seen clearly from FIGS. 6A-6H, all off-axis segments of mirrors S1 to S8 are free of shadows or obscurations. This means that the beam path of a light bundle, which passes through the objective from the object plane to the image plane, and which images the object field in the object plane into the image field in the image plane, is free of shadows and obscurations. The exact data of the objective according to FIG. 5 are shown in Code V format in Table 4 in FIG. 9. In the two forms of embodiment of the invention, the distances of the off-axis segments of the mirror are advantageously minimized in order to produce small angles of incidence on the mirrors. Since these distances can be varied randomly by an appropriate scaling, they are characterized by their existing ratio of size relative to the structural length of the objective. The ratios of the distance values of the off-axis segments to the optical axis (HA) divided by structural length are listed in Table 5 below for all mirrors of the two examples of embodiment. TABLE 5Ratio of distances of the off-axis segmentsdivided by the structural lengthExample of embodimentExample of embodimentMirroraccording to FIG. 3according to FIG. 510.0780.00020.0000.04030.0620.05440.1330.00250.2210.04660.1290.17970.0250.01080.0280.016 The projection objective of the present invention can be employed in a projection exposure system. In addition to the projection objective, such a system should include an EUV radiation source, an illumination device that partially collects the radiation and further conducts the radiation to illuminate a ring field, a mask that bears a structure or pattern on a support system, wherein the mask is arranged in a plane of the ring field, and wherein the projection objective images an illuminated part of the mask in the image field, and a light sensitive substrate arranged in a plane of the image field. FIG. 7 shows a projection exposure system for microlithography with an 8-mirror projection objective 200 according to the invention. The illumination system 202 may be formed, as described, for example, in EP 99-106348.8 with the title “Illumination system, particularly for EUV lithography” or U.S. Ser. No. 09/305,017, now U.S. Pat. No. 6,198,793, with the title “Illumination system particularly for EUV-Lithography”, the disclosure content of which is fully incorporated in the present Application. Such an illumination system contains an EUV light source 204. The light of the EUV light source is collected by collector mirror 206. The reticle 212 is located on a support structure 213, and illuminated by means of a first mirror 207 comprising raster elements or so-called field raster elements, and a second mirror 208 also comprising raster elements or so-called pupil raster elements, as well as a mirror 210. The light reflected by reticle 212 is imaged onto a light-sensitive layer 215, which is situated on a carrier 214, by means of the projection objective according to the invention. The projection exposure system of FIG. 7 can be used or the manufacturing of chips, e.g. integrated circuits. Such a method includes the step of (a) employing the projection exposure system to provide a projection beam from the EUV radiation source and the illumination system, (b) providing a substrate that is at least partially covered by a layer of radiation sensitive material, (c) using a mask to endow the projection beam with a pattern in its cross section and (d) using the projection objective to project the patterned beam onto a target portion of the layer of radiation sensitive material. A projection objective with eight mirrors is thus indicated for the first time by the invention, which is characterized by an applicability in the EUV wavelength region with λ=11 to 30 nm and represents a particularly advantageous, compact projection objective from the constructional and manufacturing points of view. The projection objective that has been presented is also characterized by a large aperture with a simultaneous shadow-free or obscuration-free beam path. This leads to a shadow-free exit pupil. It should be understood by a person skilled in the art, that the disclosure content of this application comprises all possible combinations of any element(s) of any claims with any element(s) of any other claim, as well as combinations of all claims amongst each other.
	abstract	A flame-retardant and electromagnetic wave-shielding thermoplastic resin composition is provided, which comprises 100 parts by weight of a thermoplastic resin (A); from 0.5 to 30 parts by weight of a flame retardant of a halogen-free phosphate (B) represented by the following general formula (1):
052251462	summary	BACKGROUND OF THE INVENTION The present invention relates generally to a method for increasing energy confinement and controlling transport in the plasma of a tokamak. More particularly, the present invention relates to a method of creating and sustaining a radial electric field throughout a substantial portion of the cross-section of the plasma by injecting electrons from an external source into the plasma. The apparatus for toroidal magnetic confinement that is most popular in controlled fusion research today is the tokamak device. To date, the experiments that have been performed with tokamaks to create high temperature plasmas have been of short duration. The duration and energy confinement of the tokamak plasma must be increased to produce useful amounts of energy with this device. A radial electric field within the plasma of a tokamak has been experimentally shown to increase energy and particle confinement. Theoretical work has been the basis of the proposition that radial electric fields can reduce particle and energy loss from tokamak plasmas. Experimental results reported by Oren et al, J. of Nuclear Materials 111 & 112, 34, (1982) demonstrated that overall confinement time would increase by a factor of 10 when a radial electric field was created in the plasma of a tokamak by a cold cathode or a tungsten filament. Particle and energy confinement are known to be closely related. The radial electric field that was created in the plasma by this method was of significant magnitude only at the extreme edges of the plasma. A problem which arises from longer duration plasmas is the accumulation of impurities and if fusion is occurring, fusion waste products such as helium ash. Impurity accumulation within the plasma was demonstrated by Oren et al. when a negative potential was induced within the plasma. The accumulation approached a constant value as the radial electric field decreased. M. Ono et al., Phys. Rev. Letters 60, 294 (1988) reported improvements in both energy and particle confinement times associated with radial electric fields produced by radiofrequency heating of a tokamak plasma. The magnitude of internal turbulence was observed to be greatly reduced in the presence of the radial electric field, and energy confinement times improved by 30%. Itoh and Itoh, Phys. Rev. Letters 60, 2276 (1988) and Shaing et al., Comments Plasma Phys. Controlled Fusion 12, 69 (1988) present theories which claim that radial electric fields will influence the transport of particles in tokamak plasmas and will thus affect confinement of both particles and energy. The method postulated is that a resonant interaction between the magnetic structure and particles of a particular velocity causes rapid transport of those particles to the edge of the plasma. The application of a radial electric field shifts the resonant velocity from one that many particles possess to one shared by only a few. Hence, only a few particles then participate in transport. In particular, Shaing et al. suggest that producing a negative radial electric field will reduce transport and improve confinement. Recent work by R. J. Taylor et al., Phys. Rev. Letters, 63, 2365 (1989) suggest that radial electric fields in tokamak plasmas can have a substantial beneficial effect upon energy and particle confinement. In particular, Taylor et. al's biasing of the plasma center negative with respect to the wall seemed to reproduce many features of the "H-mode" regime of plasma confinement. This was demonstrated by inserting a material electrode into a tokamak plasma and applying a negative bias. For higher temperature plasmas, experimentation with radial electric fields would require a non-invasive biasing technique. The transition of a plasma into the H-mode is marked by a sudden decrease in the hydrogenic light emission from the plasma edge, followed by a prolonged increase in the plasma density. The reduction of hydrogen light (H.sub..alpha. or H.sub..beta.) indicates that the incoming neutral particle flux is reduced, presumably because of a decrease of the outgoing plasma flux, leading to a reduction in "recycling." The improvement in the energy confinement is generally less than the increase in particle confinement. H-mode measurements also reveal the formation of sharp density and temperature gradients inside the last closed magnetic surfaces, which represents a transport barrier. Despite the magnitude of the effort aimed at modeling the H-mode, no clear mechanism has been identified, although radial electric fields are thought to play a role. Accordingly, it is an object of the present invention to provide a method and apparatus for controlling transport in a tokamak plasma. Another object of the present invention is to provide a method and apparatus for stabilizing highly perpendicular velocity electrons against kinetic instabilities in a tokamak. A further object of the present invention is to provide a non-invasive biasing technique for creating radial electric fields in a tokamak. Yet a further object is to provide an arrangement for trapping electrons in the interior of a tokamak plasma and charging it negative with respect to the edge to improve confinement properties. SUMMARY OF THE INVENTION This invention includes a method for improving confinement properties of a plasma of a tokamak by providing a ripple field region in the plasma; injecting electrons having predominantly perpendicular energy into the ripple field region for trapping the electrons into the plasma; and, negatively charging the plasma center with respect to the edge by allowing the electrons to grad-B drift vertically toward the plasma interior until they are detrapped, thereby creating a radial electric field at the edge of the plasma. The electrons are injected from an electron source exterior of the plasma. Preferably, the electrons have a perpendicular to parallel energy ratio of greater than 1 and are injected by a flat cathode containing an electro-cyclotron-heating (ECH) cavity. The ripple field is created by poloidal bending magnets locally placed around the torus of the tokamak. The cathode includes a LaB.sub.6 electron emitting faceplate. An electron injector for improving confinement properties of a tokamak plasma includes an external cathode adjacent to the tokamak for emitting electrons into the plasma; means for accelerating the electrons by radiofrequency waves at the electron cyclotron frequency; and a plurality of magnetic coils located around the torus of the tokamak for creating a local magnetic field ripple for trapping the electrons. In this manner, the electrons drift and move toward the interior of the plasma until they are detrapped, thereby creating a radial electric field at the edge of the plasma. The means for accelerating the electrons by radio frequency waves includes an electro cyclotron heating waveguide cavity and an electro cyclotron heating acceleration region adjacent to the cathode. The electrode includes a carbon heater and a LaB.sub.6 emitting faceplate.
043426204	summary	BACKGROUND OF THE INVENTION This invention relates to nuclear fuel storage and in particular to an apparatus for storing fuel assemblies in a pool. U.S. Pat. No. 4,177,385 issued on Dec. 4, 1979 to Frank Bevilacqua for "Nuclear Fuel Storage" discloses an apparatus and method for storage of fuel in a stainless steel, egg-crate frame within a storage pool. Fuel is initially stored in a checkerboard pattern or in each opening if the fuel is of low enrichment. Additional fuel (or fuel of higher enrichment) is later stored by adding box inserts within each opening in the frame, thereby forming flux-traps between the openings. Still higher enrichment fuel is later stored by adding poison material around the boxes. The method and apparatus described in the Bevilacqua patent can be significantly improved by simplifying the structure of the box inserts and the manner in which poison is added thereto. SUMMARY OF THE INVENTION It is an object of the invention to provide such a simplified box insert which can be shipped to the reactor plant in a form that is convenient and easy to handle, and which may thereafter be fabricated quickly and inserted into the frame. Another advantage of the invention is that the box inserts may be formed by very thin plates of stainless steel without sacrificing structural rigidity. In the preferred embodiment the poison material is provided directly on the box inserts. This permits a thinner overall box dimension so that a larger water gap between poison boxes can be maintained in the frame. The increased water gap enhances the flux-trap effect and accordingly provides a less reactive, safer storage facility. The inventive box insert comprises a plurality of vertically extending plates arranged as a open-ended polygonal container having a smaller cross-sectional area than the opening in the frame. Each plate has a flat portion forming a respective side of the container and an integral tab portion rigidly projecting outwardly from the longitudinal edge of the container. The adjacent tabs of each plate are connected, thereby giving the container rigidity and providing the container with a plurality of outwardly projecting ribs. The box may then be slidingly inserted into the frame so that the ribs fit into the corners of the frame defining the opening. Thereafter a fuel assembly may be lowered into the box portion of the container, which is rigidly maintained in spaced relation from the frame by the ribbed portions of the box.
	description	This application claims priority to U.S. Provisional Application Ser. No. 62/629,146 filed on Feb. 12, 2018, the disclosure of which is expressly incorporated herein by reference. The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used and licensed by or for the United States Government for any governmental purpose without payment of any royalties thereon. This invention (Navy Case 200,491 and 200,507) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Portsmouth Naval Shipyard legal office or Technology Transfer Office, Naval Surface Warfare Center Crane, email: [email protected]. The present invention relates to systems and methods for securely storing radioactive source materials with elements including visual and automated inventory, security, alerting, and stabilization design elements. Various embodiments enable inventory tasks, prevent storage structures from being negligently left open or unlocked, ensure stabilization of storage structures in a moving mobile structure, and provide an alerting system for warning staff of an unsecure or unlocked condition of such storage structures. Various regulations and laws require organizations that store or use radiological sources to meet a variety of regulatory requirements including ones related to security. For example, such regulations require organizations licensed to possess radiological sources to ensure that all radioactive check sources and standards are properly stored. A variety of problems have been encountered by such organizations in complying with these requirements. For example, users of such sources or standards have negligently left radiological source storage containers open or unlocked and triggered a reporting requirement under such regulations. Another problem was that existing products available on the market are not suitable for storing such radiological materials for a variety of reasons. For example, combustible material cannot be used in construction of such a container. Also, embodiments of this system needed to be used in confined spaces such as within a submarine where entry/egress into the submarine is limited to specific hatches. Another difficulty in this design effort was that this invention had to be usable in a moving structure such as a ship or submarine which can take on a significant degree of roll, pitch and yaw during movement. Another problem arose from a need to conduct inventory activities without a need to open the storage container which creates additional risks of negligence with respect to security or distracting crews from other high criticality missions. Human factors and lack of design to address such human factors were also a major problem given root cause for a variety of security violations. For example, hasp locks were found to be unusable given movement conditions and negligence of users to secure/use the hasp locks. Another design problem was encountered by existing cabinets due to designs susceptible to a condition where the cabinet appeared locked but it was not in fact locked because its door was not fully seated up against the cabinet body. Existing cabinets' door lock designs resulted in a case where the lock appeared to be in a locked position but was not actually engaged with the cabinet's frame. Another difficulty was a lack of system that was suitable for securing internally stored containers placed therein from movement. Ship movements created risks of damage or contamination particularly with regard to hazardous materials. Exemplary embodiments that address these problems and needs include an apparatus for securely storing one or more radioactive sources in source containers. Such an embodiment can include an enclosure with removable or moveable shelves coupled or fixed within the enclosure, a hinge coupled to an edge section of sides of the enclosure, and a door coupled to the hinge. The exemplary door can include a frame and a transparent section (e.g., a Plexiglas sheet with a thickness that prevents heavy objects from breaking the sheet). The transparent section is sized to enable external view of objects stored on each removable or moveable shelves from a wide field of view eternal to the enclosure and door. The exemplary apparatus further can include a locking mechanism coupled to the door section and that includes a latching mechanism that selectively engages with a side section of the enclosure adjacent to the door. In at least one embodiment, the exemplary locking mechanism is formed to automatically lock and engage with the enclosure when the door section is rotated to abut a door jamb section of the enclosure. The exemplary locking mechanism can include a key reader and a key etched with a pattern encoded or etched by a laser or another etching machine. The exemplary apparatus can further include a door handle coupled to the door section, a magnet coupled to a section of the enclosure disposed so it magnetically engages the door section to pull the door section against the enclosure when the door section is within a magnetic field of the magnet to thereby reduce potential for failure to engage the lock in a perceived closed position. The exemplary apparatus includes an alarm mechanism system includes an alarm field magnet that couples or mounts with the door section. The alarm system further includes a main alarm body coupled to the enclosure where the alarm system includes a magnetic flux field detection section coupled with an alarm activation section that activates an audible alarm when the alarm field magnet is not adjacent to or within detection range of the magnetic flux field detection section. The exemplary apparatus further includes a tether or tipping prevention section that fixes or tethers the apparatus with respect to an adjacent structure such as a wall. Additional optional features also addressed a need for automating check in and checkout of radiological sources as well as automating warnings of potential unsafe or unsecure conditions based on an automated system that detects a variety of conditions such as check out time and elapsed time since checkout exceeding various parameters associated with maximum time of use of such radiological sources or materials. Sizing of internal storage structures was also a problem given existing products could not accommodate size of various source containers within the overall storage cabinets shelves. A variety of methods are used with respect to various embodiments of the invention. For example, various methods including providing an embodiment of an exemplary radiological source cabinet such as disclosed below to include installing the cabinet onto a ship or submarine and tethering the cabinet to a mounting point in the ship or submarine. The ship or submarine then gets under way and begins to move or change orientation in relation to a water body the ship or submarine is operating in and thereby result in force or movement forces being applied to the cabinet which otherwise would cause the cabinet to move but for the tether attaching the cabinet to the chip or submarine's internal spaces. Next, a user would operate various elements of the cabinet to include using a key that is difficult to copy to unlock a spring loaded locking mechanism that is spring loaded to a locking position, opening a door of the cabinet that includes a door alarm which has a protective structure that prevents turning off the door alarm, installing or removing a radioactive source from the cabinet, closing the door to proximity to a door closing assistance magnet that prevents the door from being in physical contact with the cabinet enclosure or jamb area, silencing the door alarm when the door alarm sensor comes into contact or sensing proximity with a door alarm magnet attached to the door, then releasing the key, extracting it which results in the door locking mechanism automatically locking due to a spring loaded lock. Next, an inventory of the radiological sources is conducted by viewing the sources through a transparent section of the cabinet's door, noting a presence or absence of a particular radiological source container that has a predesignated location on shelves inside of the cabinet. Personnel assigned to inventory tasks then inspects the radiological source containers by comparing locations of such sources on an inventory list to predetermined or pre-designated assigned locations on the cabinet's shelves. A variety of additional features or steps can be added including use of automation, detection, additional alarms, tracking, and additional structures such as locking or retention mechanisms that are adapted to receive a uniquely shaped radiological source container (e.g., a uniquely shaped base fits into a correspondingly shaped receiving structure mounted on the shelves). Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived. The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention. Referring to FIGS. 1 and 2, an exemplary secure radioactive source locker assembly 1 in accordance one embodiment of the invention is shown. The exemplary assembly 1 is formed with enclosing top, bottom, back and side walls and an open front side defined by edges of the left side, right side, and top/bottom walls opposing on a front side opposing the back side. A first attachment/tether structure 3 is coupled to an adjacent structure, in this exemplary case a wall of a submarine (not shown). A second attachment/tether structure 7 is coupled to an external section of the locker assembly 1. An anti-tip chain/tether 5 is coupled on one side to the first attachment/tether structure 3 and on an opposing side to the second attachment/tether structure 7. Alternative mounting systems can be provided such as via bolting of the locker assembly 1 to a floor or wall. A door structure 17 is coupled to a side of the locker assembly 1 using a hinge 19, e.g., a piano hinge, which is operable to enable the door structure 17 to pivot on the hinge 19 and allow access to interior areas of the locker assembly 1. The door structure 17 covers or seals the opening of the locker assembly 1. A door handle 9 is coupled to the door structure 17. The door structure 17 is formed with a transparent Plexiglas, e.g., polycarbonate material, Lexan®, etc transparent material viewing window 11 which is secured within a door frame which the hinge 19 is attached to. The exemplary locker assembly 1 is further provided with moveable or repositionable interior shelves 13. Embodiments can include securing structures (not shown) which fix or lock into position radiological storage containers on the shelves so they do not move when in a mobile structure, e.g., ship is in motion due to maneuvering or sea wave action. A locking structure and key system 15, e.g., MUL-T-Lock® lock and key system, such as for example shown in U.S. Pat. Nos. 5,839,308, 5,784,910, or 5,520,035, is coupled to the door structure 17 which selectively engages and locks with a side section, e.g., right side, of the locker assembly 1. The exemplary locking structure and key system 15 is designed to automatically lock (e.g., spring loaded to a locked position even when a key is inserted) particularly when the door is closed/positioned adjacent to a corresponding side (e.g., right side in this figure when facing the door structure 17) of the locker assembly 1. A magnetic door catch or retaining structure 70 is provided to ensure the door structure 17 is fully seated in a closed position and thereby aid in avoiding a case where the door appears to be locked and secured but is in fact in close proximity to the locker assembly 1 sides but without the locking structure 15 actually engaged and locking onto the locker assembly 1 enclosure frame or side. The exemplary handle 9 can be mounted to the door below the lock with a magnet installed inside the locker to ensure that the door does not move when closed. Embodiments of this disclosure can include a radiation detection or hazardous material detection system (not shown). This detections system includes detection systems that identify leaks or exposure of hazardous material or radioactive material storage structures within the locker assembly 1. For example, exemplary radiation detection systems can include Gas-filled detectors including Geiger-Muller counters, ionization chambers, radiation survey meters, or proportional counters. The radiation detection system includes a warning system that can emit an audible alarm or transmit a warning signal to an external control station (not shown) which then shows or displays a warning to an operator. An exemplary system can further include automated reader instruments, electronic radiation measuring instruments, alarm badges, or thermoluminescent dosimeters (TLD). Another exemplary embodiment can further include optically stimulated luminescence (OSL) based systems that provide higher accuracy for measurement of low levels of radioactivity. Exemplary embodiments can further include an additive or coating to the door section's transparent section that provide radiation protection. Alternatively, the transparent section can be formed of leaded glass that has a transparent reinforcing coating, such as a plastic coating, that provides protection against breakage of the leaded glass that leaves an opening in the transparent section. In various embodiments, outer dimensions and shelf heights are at the discretion of a user or requester to accommodate different radiological sources being stored in the exemplary locker assembly 1. In at least one embodiment, a lip or edge 21A of the door structure 17 can be designed to have a minimum of 1″ in order to accommodate the locking structure 15 and alarm mechanism 26. The exemplary locker assembly 1 is formed with a door frame section which is formed with an inset section that receives and encloses the door structure 17 so that an outer face of the door section 17 is flush with the door frame section. The exemplary door frame section is also formed with a step or shoulder that the door structure 17 abuts when the door structure 17 is in a closed position within the inset section. The exemplary selected locking structure 15 (e.g., MUL-T-LOCK® drawer latch lock with different keying) that in at least one embodiment removes a need for a lock hasp and staple. The exemplary locking structure 15 function in this embodiment includes a self-locking structure. The key in this embodiment is a laser encoded key with “key card” that has anti-copy design so that unauthorized copies cannot be created. (e.g. see FIG. 5) In this example, a “key card” with key code is issued for each laser encoded key. That key code is associated with a stored laser encoding pattern that must be presented to a secure key production facility to produce and receive another key. In at least some embodiments, the self-locking lock ensures that once the door is closed the locker will be locked. The exemplary locking structure 15 will not allow removal of the key without the locking device being engaged, meaning that the key cannot be removed without the lock being in the locked position. Exemplary alarm 69A can have alkaline batteries that are replaced periodically, e.g., every 6 months, during the biannual inventory of radiological sources to ensure that the battery life is not a limiting factor. Exemplary alarm system 69A can remain on while the locker is installed and in use. A lockable protective bracket 69C can be installed with respect to alarm 69A to ensure that the alarm will remain in place and the on/off switch cannot be accessed. An exemplary alarm can be used to provide an immediate indication that the door structure 17 remains open, and that the sources are not properly stored. An alarm mechanism 69A is provided, in this case a proximity alarm that detects proximity to a magnetic structure 69B (not visible) coupled with a side section (in this case right side facing the door structure 17). A low battery alarm system can also be included to warn users that the alarm battery is in a low energy state and therefore should be replaced. Such warnings can be a light or audible alarm or notification system. FIG. 3 shows a high level or simplified hierarchical block diagram of various components of an embodiment of the invention. An apparatus for securely storing radioactive source materials assembly 1 is provided (e.g., such as in FIGS. 1-2). A locker body is provided with top, bottom, vertical sides coupled to the top and bottom forming an enclosure with an open side (e.g., front side). The locker body can be constructed using sheet metal and solid welds to ensure a solid body enclosure. A door structure 17 is provided coupled to a side of the door body. Locking mechanism 15: Ensures controlled access to the locker 1. This exemplary locking mechanism does not allow the key to be removed while in the open position, automatically locks, and has methods and designs to ensure keys cannot be copied except by an authorized entity. The exemplary enclosure is coupled with door structure 17 with hinge 19. The enclosure is constructed using sheet metal with a full piano hinge 19 welded on both ends to ensure the door does not lift. Transparent components 11: Constructed of 1″ deep aluminum walls that holds a Plexiglas viewing window. Plexiglas allows for immediate viewing of contents, as well as providing a non-combustible barrier. Magnet 70: installed on door structure 17 and a frame section or shelves 13 located within the body of the locker assembly. Magnet 70 ensures that the door will close, and not flex while closed. Alarm 69: A proximity alarm 69 ensures close personnel are aware that the locker assembly 1 is open. The alarm 69 can include a self-contained power source. This exemplary alarm 69 is not accessible by a person opening the locker assembly 1 when in the installed position using, e.g., a lockable/removable cover bracket that blocks access to a person accessing the assembly 1 without a cover bracket key. An optional section can include a radiological source tracking system (RSTS) 81 (not shown). The RSTS 81 system can include one or more of an RFID or optical bar code scanner section 83. The RFID or optical bar code scanner section 83 can detect identifier information associated with materials placed into or removed from the enclosure or locker assembly 1. The RSTS 81 can also include a controller with machine instructions for controlling the RSTS 81 and various elements of the system. The RSTS 81 can further include a triggered alarm 87 which can include a pressure pad or motion detection system placed in front of the cabinet or locker assembly 1 which activates an alarm with a person is in proximity to the assembly 1. The exemplary RSTS 81 can further include a movement and object/feature detection section 89 that has a camera system. The RSTS 81 can include a control system which is either located in the locker assembly 1 or is disposed remotely in communication with the camera system object/feature detection system with, e.g., a neural network feature or object classifier with an associated library of features associated with different objects (e.g., source containers, bar codes or other identifiers associated with particular source containers, access authorization badges or tokens, and facial features of authorized persons who are authorized to unlock the locker assembly 1 and remove source containers) that is adapted to detect movement and object/feature recognition of sources moved into and out of the cabinet or locker assembly 1. The movement and object/feature detection section 89 can further include facial recognition systems which identify persons who are in proximity with or are removing radioactive sources from the automatic locking radioactive source locker assembly 1 then log detected identity information with removal or access actions associated with the radioactive sources. RSTS 81 can further include inventory/removal/access action tracking systems which monitor time elapsed since an object such as a radiation source has been removed or left out of the locker assembly 1. The RSTS 81 can further set off an alarm which causes a search for the removed radiation source that has not been returned to the locker assembly 1 in a predetermined time period. A card reader can also be provided or used to determine if an authorized person or unauthorized person is attempting to open the locker assembly 1. The card reader can be coupled with alarm 69A so that the alarm 69A or the RSTS 81 activates an unauthorized access alarm if the assembly 1 is opened with even with the key. FIG. 4A shows an exemplary method in accordance with one embodiment of the invention. Step 101: Install automatic locking radioactive source or material storage locker or container into an interior section of a ship or submersible vessel to include tethering the automatic locking radioactive source or material storage locker to a tether mounting section of the ship or vessel such as shown in, e.g., FIGS. 1-3, with audible alarm that activates when the door is opened. At Step 102: Get ship or submersible vessel under weigh whereby the ship or submersible vessel will begin to move in response to ship control inputs or wave motion. At Step 103: Insert a key into the locking mechanism and turn ½ turn to the left and thereby disengage the locking mechanism from engaging with the locker enclosure; Step 105: Pull the door handle (while maintaining light pressure to keep key engaged/rotated) to open door. Once door is opened, the alarm's magnet will move out of detection proximity with the alarm's magnetic flux field detector and an audible alarm will sound (this audible alarm will continue until the locker's door is securely closed and locked); Step 107: Place radioactive sources inside the container on designated shelves (RFID tags may be used for tracking to ensure: proper location, radiological source returned in a timely manner, correct radiological source removed from container); Step 109: Close door, release pressure on key and remove key from lock (this will ensure the door is closed/locked properly). FIG. 4 B shows a method that is executed once a user is ready to check out a source for daily source check that includes the following steps: Step 121: Sign key out of designated key locker; Step 123: Insert key into locking mechanism and turn ½ turn to the left, this will disengage the lock; Step 125: Pull the door handle (while maintaining light pressure to keep key engaged/rotated) to open door. Once door is opened, the magnet will disengage and an audible alarm will sound (this audible alarm will continue until the door is securely closed and locked); Step 127: Remove and sign out the radioactive source(s) from their designated shelves inside the container. (RFID tags may be used for tracking to ensure: proper location, source returned in a timely manner, correct source removed from container); Step 129: Close door, release pressure on key and remove key from lock (this will ensure the door is closed/locked properly); Step 131: Use the source for a daily check and return radioactive source or sources back to the automatic locking radioactive material storage container with audible alarm by repeating the method at FIG. 4A. FIG. 4C shows a method of inspecting for presence or inventorying of the radioactive sources as described herein. At Step 151: Obtain a list of radioactive source containers which are stored in the automatic locking radioactive source or material storage locker such as shown herein (e.g., FIGS. 1-3). At Step 153: conduct a visual inspection of the radioactive source containers in the automatic locking radioactive source or material storage locker through the transparent section of the locker's door by comparing the list of radioactive source containers with the radioactive source containers visible through the transparent section. Step 155: Identify missing radioactive source containers, if any, and create an inspection record that includes records of radioactive source containers that are present or missing. Alternative embodiments can include processing steps that include operating RSTS 81 as discussed above. For example, processing steps can include execution of steps such as disclosed with respect to FIGS. 4A-4C where RSTS 81 systems can detect or identify specific radiological sources which are placed into the automatic locking radioactive source or material storage locker assembly 1 and detect when the assembly 1 door has been closed. The RSTS 81 can also track identity as discussed above of persons who perform inventory actions, or access/remove radioactive sources with respect to the locker assembly 1. An additional processing step can include RSTS 81 sending reports of access, inventory, removal, return, unauthorized access, and failure to return radioactive sources to the locker assembly 1 within predetermined time periods warnings to another computer system via a network or wireless connection (not shown) which tracks, reports, and displays status or alarms associated with FIG. 5 shows an exemplary etched key 15A used with at least one embodiment of the invention. An etched section is shown 15B which is associated with a stored etching pattern maintained by a key manufacturing facility via a control number not shown on the key 15A. An alternative embodiment can include an optional radio frequency identification (RFID) or optical bar code scanner, controller with machine instructions including system for detecting movement of radiological sources into or out of the cabinet and triggering alarms when various conditions are determined (e.g., maximum time period elapsed between removal and return of radiological sources based on RFID or bar code). Various embodiments can also include shelves that include specific receiving structures that are unique to each of the source containers or are designed for each object/radioactive source. For example, a base of each radiological source container can have a different shape so that the base shape corresponds to a specific radiological source container receiving structure (e.g., square bottom, circular, rectangular, a shape with keyway structures (e.g., one keyway, two keyways, three keyways) that do not permit the wrong structure to be inserted into the source container receiving structure. Various embodiments enable a quick check to ensure all contents are present, the correct source container is in a specific structure or location and thereby prevents a need to go searching around the locker to try to find it. The door's transparent section enables needed visibility that allows for a full check of all information displayed on the objects/radioactive sources. Verification of in-depth inventory and tracking information without accessing the sources is achieved with various embodiments of the invention. Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.
	summary
	abstract	Disclosed is a radiation logging tool, comprising a tool housing; a compact generator that produces radiation; a power supply coupled to the compact generator; and control circuitry. Embodiments of the compact generator comprise a generator vacuum tube comprising a source generating charged particles, and a target onto which the charged particles are directed; and a high voltage supply comprising a high voltage multiplier ladder located laterally adjacent to the generator vacuum tube. The high voltage supply applies a high voltage between the source and the target to accelerate the charged particles to a predetermined energy level. The compact generator also includes an electrical coupling between an output of the high voltage supply and the target of the generator vacuum tube to accommodate the collocated positions of the generator vacuum tube and the high voltage power supply.
051735199	claims	1. A method of forming a conductive metal-filled composite, comprising a. an intermingling step of intermingling at least 2 vol. % of oxide-covered copper or nickel metal particles in an engineering plastic; b. a contacting step of contacting the metal particles with an effective amount of a developing agent selected from the group of amine or ammonium compounds having at least one alkyl, alkenyl or acyl group of from 8 to 20 carbon atoms and having at least one further group carrying a coordinative functional substituent, the amine or ammonium nitrogen atom and the functional substituent being separated by from two to six other atoms; c. a heating step of subjecting the metal particles and the developing agent in the substantial absence of oxygen to improve the conductivity of the metal-filled substrate. 2. The method of claim 1, wherein said heating step takes place at or above the softening point of the engineering plastic. 3. The method of claim 1, wherein said developing agent is incorporated in the engineering plastic. 4. The method of claim 2, wherein said developing agent is incorporated in the engineering plastic during said intermingling step. 5. The method of claim 1, wherein the engineering plastic is selected from the group of polyamides, polyesters, polyphenylene ethers, and ABS resins. 6. The method of claim 1, wherein said coordinative functional substituent is selected from the group of hydroxy, amino, and mercapto. 7. The method of claim 1, wherein said at least one further group carrying a coordinative functional substituent is selected from the group of hydroxyalkyl, aminoalkyl and mercaptoalkyl groups. 8. The method of claim 1, wherein said developing agent has two further groups carrying a coordinative functional substituent. 9. The method of claim 8, wherein the developing agent is selected from the group of bis (2-hydroxyethyl) and bis (2-hydroxypropyl) C.sub.8 -C.sub.20 -alkyl amines. 10. The method of claim 8, wherein the developing agent is selected from the group of N,N-bis (2-hydroxyethyl) and N,N-bis (2-hydroxypropyl) C.sub.8 -C.sub.20 - alkyl amides. 11. A conductive metal-filled substrate produced by the method of claim 1. 12. A method of shielding a space from a source of EMI by placing the conductive metal-filled substrate of claim 11 between the source of EMI and the space to be shielded.
	description	1. Field Example embodiments generally relate to Boiling Water Reactors (BWRs) and assemblies and methods for reinforcing piping for coolant spray within such reactors. 2. Description of Related Art Generally, BWRs include a reactor core surrounded by a shroud and a shroud support structure. Piping typically penetrates this shroud to deliver emergency coolant water to the core in the event of an emergency involving a loss of coolant or where coolant is otherwise unavailable to the core. As shown in FIG. 1, such piping includes core spray piping 10 and spargers used to deliver coolant water to the reactor core. The core spray cooling water is typically supplied to the reactor core region through a sparger T-box 15 that penetrates the shroud wall. The distal end of the T-box 15 is inside the shroud, while the proximal end extends outside the shroud. The sparger T-box typically intersects two sparger pipes 10 to form a piping “T.” The sparger pipes 10 are typically welded to the sparger T-box 15. The distal end of the T-box 15 may be capped by a flat cover plate 20 welded to the T-box 15. While only a lower sparger T-box 15 is shown in FIG. 1, upper sparger T-boxes are typically present as well and roughly match the configuration of the lower sparger T-box in the upper configuration. Lower T-boxes typically intersect sparger pipes 10 at a center vertical displacement such that the pipes 10 mate symmetrically with the upper and lower halves of the lower T-box 15. Upper sparger T-boxes may not intersect the sparger pipes 10 at a center vertical offset due to other structural placement and thus sparger pipes 10 may not symmetrically mate with the upper sparger T-box. The cover plate weld 25 and sparger pipe welds 26 are susceptible to cracking due to the high temperature, high pressure, and variable chemistry water flowing around the T-box 15. Resulting damage to welds 25 and 26 may be accessible for repair and inspection within a BWR only during scheduled plant outages for refueling and repair. These outages typically occur at several month intervals, and thus components within the core, including welds 25 and 26, must remain intact for lengthy periods before being inspected and/or repaired. Further, BWR core operating conditions include high levels of radioactivity due to fission occurring in the fuel rods. Radioactivity, particularly the neutron flux generated in an operating nuclear reactor core, degrades the material strength and elasticity of core components over time. Components within the core, including welds 25 and 26, are thus subject to premature brittling and cracking due to this radiation exposure. Accordingly, flow-induced vibration, lengthy operating cycles, and demanding water conditions coupled with radiation can cause the welds 25 and 26 to crack, particularly, by intergranular stress corrosion cracking. If cracks in welds 25 and 26 propagate circumferentially so as to completely disunion either the cover plate 20 or the sparger pipes 10 from the sparger T-box 15, uncontrolled cooling water leakage may result. Further compounding the precarious nature of the sparger T-box welds 25 and 26 is their arrangement within the shroud among other components. Even during repair phases, workers may have only remote access to the sparger T-box 15 inside the shroud, and locating and repairing welds on the T-box may require increased expense, removal of other components, and worker hazards. Related art sparger T-box repairs and clamps may use clamping mechanisms to relieve stress on welds 25 and 26 and provide redundant security in the case of weld failure. Sparger T-boxes 15 may have various physical configurations based on their particular plant installation and repair history. Related art repair mechanisms are generally configured for only a single sparger T-box in a particular BWR and are incompatible with other sparger T-boxes in other BWRs. Example embodiments are directed to core spray sparger T-box repairs, specifically, to universal core spray sparger T-box weldless clamps having remote-friendly operation and methods of using universal core spray sparger T-box weldless clamps. Example embodiment clamps may be secured without welding to a variety of upper and lower sparger T-box configurations. Example embodiment clamps may be configured to simultaneously engage a sparger T-box in multiple dimensions to allow a universal fit. Further, example embodiment clamps may be accessed, installed, or removed by interacting only with a front side of the example embodiment clamps, thus potentially reducing difficulty and cost in remote access repairs to example clamps. FIGS. 2 and 3 are isometric views of example embodiment core spray sparger T-box clamp assemblies 100 and 200 that may attach to the lower and upper sparger T-boxes 15 and 16, respectively, and sparger pipes 10 on either side of each sparger T-box. Example embodiment clamp assemblies 100 and 200 may reinforce and provide redundancy to the welds 25 and 26 (shown in FIG. 1) between the T-box and the cover plate and sparger pipes. The example embodiment clamp assemblies 100 and 200 may hold the pipes 10 and the cover plate 20 (shown in FIG. 1) to the sparger T-boxes 15 and 16 and thus relieve stress on welds 25 and 26 (shown in FIG. 1) and prevent or minimize coolant leakage from the welds 25 and 26 in the event of a full circumferential crack. Example embodiments are described hereinafter with respect to the lower core spray sparger T-box clamp assembly 100. Upper clamp assembly 200 may have shared characteristics with the lower clamp assembly 100, and thus redundant descriptions are omitted. FIG. 4 is an exploded view of the example embodiment clamp assembly 100 in FIG. 2. As shown in FIG. 4, the example clamp assembly 100 includes an anchor plate 110 between two sparger pipe supports 115 and 116. The anchor plate 110 may be in front of the sparger T-box 15 (as shown in FIG. 2) and shaped to substantially match and cover and/or overlap the sparger T-box 15 and cover plate 20 (shown in FIG. 1). The sparger pipe supports 115 and 116 engage and support the left and right sparger pipes 10 on either side of the sparger T-box 15 via, for example, inner and outer T-bolts 121 and 122. The anchor plate 110 and sparger pipe supports 115 and 116 may be located in any relative position to match the configuration of various sparger T-boxes. For example, upper sparger T-boxes may be vertically offset from the sparger pipes 10, and the anchor plate 110 and sparger pipe supports 115 may be similarly offset to match the upper sparger T-box in that case. The anchor plate 110 and sparger pipe supports 115 and 116 are connected by a dovetail joint that permits the sparger pipe supports 115 and 116 to translate relative to the anchor plate in an axial direction but prevents translation in a transverse direction along the length of the pipe supports 115 and 116. In this way, the anchor plate 110 and pipe supports 115 and 116 may be secured independently against the sparger T-box and sparger pipes, respectively. Further, the dovetail joints allow the anchor plate 110 and pipe supports 115 and 116 to be installed at different displacements in the axial direction to accommodate different sparger T-box and pipe configurations. First described are example structures for attaching example embodiment clamps to the sparger pipes, specifically, for attaching the sparger supports 115 and 116 to the sparger pipes 10. In an example embodiment, the sparger pipe supports 115 and 116 may be attached to the sparger pipes 10 by inner and outer T-bolts 121 and 122, which may be secured to the supports 115 and 116 by T-bolt nuts 131 and 132. The T-bolts 121 and 122 may extend through apertures 50 (shown in FIG. 12) created in the sparger pipes 10 by, for example, electric discharge machining. A threaded end of each T-bolt 121 and 122 may extend through the pipe support 116. Sealing collars 141 and 142 may interface with the sparger pipe around the aperture 50 in order to prevent leakage of coolant through the aperture 50. The T-bolt nuts 131 and 132 may screw onto the threaded ends of corresponding T-bolts 121 and 122. The head of each T-bolt 121 and 122 may have a keyed shape, for instance a rectangular shape, that allows the T-bolt to slide into a corresponding aperture 50. The T-bolt may then be rotated and thus locked in the sparger pipe 10. Sealing collars 141 and 142 may be placed on the T-bolts 121 and 122 such that as the T-bolt nuts 131 and 132 are tightened, the collars 141 and 142 may be seated against the exterior curved surfaces of the sparger pipes 10. The sparger pipe support 115 and 116 may have recesses and holes to allow the T-bolts 121 and 122, T-bolt nuts 131 and 132, and sealing collars 141 and 142 to pass through the pipe supports 115 and 116 and/or seat against them. Ratchet springs 125 may be placed into adjoining slots in the sparger pipe supports 115 and 116 to allow only one-way rotation of the T-bolt nuts 131 and 132. For example, ratchet springs 125 may allow only tightening of the T-bolt nuts 131 and 132. The ratchet springs 125 may be keyed to allow disengagement from the T-bolt nuts 131 and 132 and permit two-way rotation of the nuts 131 and 132. For example, the ratchet springs 125 may be keyed to disengage and allow removal of the sparger pipe supports 115 and 116. Although example embodiments and example structures for attaching example embodiment clamps to sparger pipes have been described as having sparger pipe supports 115 and 116 joined to sparger pipes 10 through a T-bolt 121, T-bolt nut 131, and sealing collar 141, other fastening structures are useable with example embodiments. For example, the sparger pipe supports may be attached to the sparger pipes by welding and/or gripping fasteners around the circumference of a sparger pipe as would be known to one skilled in the art. Second described is a unique example clamp for securing example embodiment clamp assemblies to sparger T-boxes of varying configurations. Because example embodiment assembly clamp assemblies include dovetail joints that permit axial movement between the anchor plate 110 and sparger pipe supports 115 and 116, the anchor plate 110 is independently clamped to the sparger T-box. Sparger T-boxes may have variety of configurations and front plate structures, and example embodiments provide a unique universal, front-accessible clamping mechanism for attaching to sparger T-boxes despite diverse front and dimensional characteristics. As shown in FIG. 4, example clamp assemblies include a central post 151, a ratchet nut 152, a slider wedge 153, a ratchet nut lock 154, a pair of slide latches 155, and/or four flat-head screws 156. These structures allow example embodiment clamp assemblies to engage a variety of sparger T-boxes securely and removably. FIGS. 5 and 6 illustrate the latching structures described in FIG. 4. FIG. 6 is a cross-section along the line V-V in FIG. 5. As shown in FIG. 6, the anchor plate 110 may have a rectangular recessed area 111 that accommodates a rectangular end of the central post 151. The central post 151 may be prevented from rotating within the recessed area 111 due to the rectangular shape. The recessed area 111, however, may permit the central post 151 to translate within the recessed area 111 and thus re-center the anchor plate 110 to accommodate irregular T-box geometries. Such accommodation is discussed below in greater detail. The ratchet nut 152 and ratchet nut lock 154 are placed on the other end of the central post 151 opposite the rectangular end. The outer surface of the ratchet nut 152 engages the inner surface of the ratchet nut lock 154 so as to permit rotation of the ratchet nut 152 in one direction only. As the ratchet nut 152 rotates, its inner surface engages threads on the end of the central post 151, drawing the ratchet nut 152 along the central post 151 in an axial direction. For example, the ratchet nut lock 154 may permit rotation of the ratchet nut 151 only in a direction corresponding to the ratchet nut 151 tightening down onto the central post 151 axially. The ratchet nut lock 154 may include a release 158, which may be a hole permitting a tool to be passed into it that disengages the ratchet nut lock 154 from the ratchet nut 152, allowing rotation of the ratchet nut 152 in any direction, including tightening and loosening along the central post 151. The slider wedge 153 is within, but not completely confined by, the ratchet nut 152, and the central post 151 passes through the slider wedge 153. The slider wedge 153 is not rigidly attached to the ratchet nut 152. Instead, the slider wedge 153 and ratchet nut lock 154 are rigidly fixed together by, for example, flat-head screws 156 passing through the ratchet nut lock 154 and slider wedge 153. The slider wedge 153 and ratchet nut lock 154 may be held stationary by slide latches 155 that are mated with the stationary sparger T-box. In this way the ratchet nut 152 may rotate and move axially along the central post 151, but the ratchet nut lock 154 and slider wedge 153 translate only axially, and do not rotate, with the ratchet nut 152. FIG. 7 is an isometric view of a slider wedge 153 useable in example embodiments. FIG. 8 is an isometric view of slide latches 155 useable in example embodiments. As shown in FIG. 8, slide latches 155 may have an angled end 165 and a conical end 166. The angled end 165 may mate with the angled inner surface 163 of the slider wedge 153 shown in FIG. 7. As shown in FIG. 6, the angled ends 165 may fit within the angled inner surface 163 and prevent rotation of the slider wedge 153 as long as the slide latch 155 cannot rotate. As the slider wedge 153 is translated axially along the central post 151, the slide latches 155 may be drawn inward radially due to the mating of the angled inner surface 163 and the angled ends 165. As the conical ends 166 are held stationary and/or impeded from further radial movement, the slider wedge 153 may not move the slide latches 155 inward radially any further, and the slider wedge 153 and ratchet nut 152 may not be further tightened along the central post 151. FIG. 9 shows the anchor plate 110 in greater detail, including a T-shaped slot 112 across the face of the anchor plate 110. The slot 112 allows the slide latches 155 to be fixed with the anchor plate 110 and prevents rotation of the slide latches 155, the ratchet nut lock 154, and/or slider wedge 153 to which the ratchet nut lock 154 is mated. The slot 112, however, permits the slide latches 155 to move radially inward and outward as they are tightened against the sparger T-box. Further, the direction of the slot 112 may match an orientation of the recessed area 111 on the opposite side of the anchor plate 110 (shown in FIGS. 5 and 6). In this way, the central post 151 may translate relative to the recessed area 111 only in a direction corresponding to the slot 112 direction and slide latch 155 orientation. Thus, if the anchor plate 110 and central post 151 are not initially centered between the exterior of a sparger T-box, the central post can translate due to clamping force from the slide latches 155 to a position centered between the slide latches 155. In this way example embodiment clamp assemblies may accommodate different or uneven outer geometries of sparger T-boxes without unevenly attaching to the sparger T-box. FIG. 10 shows the same example embodiment clamp assembly as FIGS. 5 and 6, but with the ratchet nut 152, ratchet nut lock 154, and slider wedge 153 advanced further axially along the central post 151. As shown in FIG. 10, the slide latches 155 have been drawn radially inward due to the axial translation of the slider wedge 153. The conical end 166 of slide latch 155 may engage a hole 60 in the sparger T-box 15 (shown in FIG. 12). The hole 60 may be formed by any known method including, for example, electric discharge machining. Once the conical end 166 is fully seated into the hole 60, the latch may not be translated inward radially further, and tightening of the ratchet nut bolt may be impeded or stopped. Example clamps for securing example embodiment clamp assemblies to sparger T-boxes of varying configurations having been described, it will be apparent to those skilled in the art that departure from these examples by routine experimentation to accommodate other configurations is possible. For example, the shape of ends 166 of slide latches 155 need not be conical or engage T-boxes in a single area; rather, any equivalent structure that allows the slide latches 155 to engage the sparger T-box may be substituted. Similarly, screws need not be used to secure the slider wedge to the ratchet nut lock and T-shaped slots are not required to prevent the slide latches from rotating. Rather, any structure for mating the slider wedge, ratchet nut lock, and slide latches may be implemented. These example structures offer an example embodiment clamp assembly may be secured to the body of the sparger T-box of divergent configuration, and how installation and removal may be achieved through a single face-accessible nut structure. Thirdly, example embodiment clamp assemblies may also include structures that seat against the cover plate 20 to provide support to weld 25 and prevent potential coolant leakage should weld 25 fail. As shown in FIG. 4, example embodiment clamp assemblies may include a bearing plate 160, bearing plate bolts 161, and latch springs 162. The bearing plate 160 may be biased against the cover plate 20 and may secure the cover plate 20 in the event weld 25 fails. The bearing plate 160 may be connected to the anchor plate 110 by bearing plate bolts 161 that extend through threaded holes 113 in the anchor plate 110 (shown in FIG. 9). The bearing bolts 161 may rotate to move the bearing plate 160 toward the T-box cover plate 20. Latch springs 162 may lock the rotational position of the bearing plate bolts 161 to ensure that force applied to the cover plate 20 by the bearing plate 160 does not lessen over a prolonged operation period. The latch springs 162 may seat in respective slots on the face of the anchor plate 110 and may be disengaged by a key structure that disengages the latch springs 162 from the bolts 161 to allow rotation of the bolts in either direction. Example methods for operating core spray sparger T-box clamp assemblies are described with reference to FIGS. 11 and 12. FIG. 11 is a flow chart of an example method for operating a core spray sparger T-box clamp. As shown in FIG. 11, in optional step S10, slots and holes may be formed in existing sparger pipes and sparger T-boxes. The slots and holes may be placed in any configuration so as to permit a clamp assembly to engage and clamp to sparger pipes and sparger T-boxes. For example, slots may be machined into the sparger pipes and holes may be machined into opposite sides of the sparger T-box. Any known process of forming these holes and slots may be used, including electric discharge machining. FIG. 12 shows an example of step S10 with slots 50 and holes 60 machined into the sparger pipes 10 and sparger T-box 15, respectively. As shown in step S20, an anchor plate may be clamped to the sparger T-box. Such clamping may be performed solely by rotational tightening on the face of the clamping mechanism and may accommodate a wide variety of sparger T-box configurations. The clamping may also center the clamping assembly between the clamped areas of the sparger T-box. As shown in step S30, sparger pipe supports may be attached to the sparger pipes so as to secure the sparger pipe supports to the sparger pipes. The supports may secure the sparger pipes in transverse directions parallel to the supports only. Securing the sparger pipe supports may include tightening the sparger pipe supports on only the face of the sparger supports. The clamp assembly may be secured against the sparger T-box cover by tightening on the face of the anchor plate. As such, all example methods require only access to the face of clamping assemblies in order to operate the clamping assemblies; however, access to other sides and/or aspects of clamping assemblies may be allowed by example methods. As shown in step S40, a bearing plate may then be biased against a cover plate of the sparger T-box. Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments and example methods may be varied through routine experimentation and without further inventive activity. Variations are not to be regarded as departure from the spirit and scope of the exemplary embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
048246336	abstract	A method and an apparatus for controlling a reactor refuelling machine including a plurality of grippers comprised of a plurality of telescopic bars which are telescopically actuatable independently of each other and at least one gripping member mounted to each telescopic bar. A decision is made as to whether the movement of a particular gripper in the Z direction is constrained by a status of the movement of a different gripper. The parallel operation is performed when the movement of the particular gripper in the Z direction is not constrained and when constrained, the particular gripper is placed in condition for waiting.
	claims	1. A method of operating a nuclear fission reactor fuel assembly, comprising the step of disposing an enclosure in a nuclear reactor vessel, said enclosure sealingly enclosing a nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 2. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a nuclear fuel foam defining a plurality of spatially distributed open-cell voids within the nuclear fuel foam to facilitate transport of volatile fission products generated by the nuclear fuel foam. 3. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a nuclear fuel foam defining a plurality of spatially distributed open-cell voids within the nuclear fuel foam to permit expansion of the nuclear fuel foam. 4. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a fissile nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 5. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a fertile nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 6. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a thorium nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 7. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a uranium nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 8. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a mixture of fissile and fertile nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 9. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose an uncoated nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 10. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose an oxide nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 11. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a nitride nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 12. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so that the enclosure is capable of being disposed in a fast neutron nuclear reactor and is capable of sealingly enclosing a nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam. 13. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a nuclear fuel foam having a polygonal-shaped geometry in transverse cross-section. 14. The method according to claim 1, wherein the step of disposing the enclosure comprises disposing the enclosure so as to sealingly enclose a nuclear fuel foam having a parallelepiped geometry. 15. The method according to claim 1, further comprising the step of associating a heat absorber with said enclosure, the heat absorber adapted to be in heat transfer communication with the nuclear fuel foam for absorbing the heat generated by the nuclear fuel foam. 16. The method according to claim 15, wherein the step of associating the heat absorber comprises associating the heat absorber that is a flowing fluid. 17. The method according to claim 1, wherein the step of associating the heat absorber comprises associating the heat absorber that is a phase-changing composition. 18. The method according to claim 1, wherein the step of associating the heat absorber comprises associating the heat absorber that is a thermo-electric material. 19. The method according to claim 15, wherein the step of associating the heat absorber with the enclosure comprises extending a heat absorber conduit through the nuclear fuel foam, the heat absorber conduit being capable of carrying a cooling fluid therealong in heat transfer communication with the nuclear fuel foam for absorbing the heat generated by the nuclear fuel foam. 20. A method of operating a nuclear fission reactor fuel assembly, the method comprising:fissioning with a nuclear fission reactor fuel assembly having nuclear fuel foam sealingly disposed therein, the nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam;generating volatile fission products by the nuclear fuel foam; andtransporting, in the plurality of interconnected open-cell voids within the nuclear fuel foam, the volatile fission products generated by the nuclear fuel foam. 21. A method of operating a nuclear fission reactor fuel assembly, the method comprising:fissioning with a nuclear fission reactor fuel assembly having nuclear fuel foam sealingly disposed therein, the nuclear fuel foam defining a plurality of interconnected open-cell voids within the nuclear fuel foam;generating volatile fission products by the nuclear fuel foam; andexpanding the nuclear fuel foam into the plurality of interconnected open-cell voids within the nuclear fuel foam.
	description	The present invention relates to a 3-dimensional image construction method and apparatus, particularly to a 3-dimensional image construction method and apparatus using a refraction contrast. An X-ray CT (computed tomography) of the inner structure of an object is a very powerful tool for the nondestructive observation. Since the development in early 1970's, it has found numerous applications in many fields of science, technology and medicine. Most of the methods which utilize the principal scheme of the CT are based on an X-ray absorption contrast. For example, a 3-dimensional medical image based on an X-ray absorption contrast considerably contributes to a medical diagnosing in addition to an ultrasonic image and an MRI (magnetic resonance imaging) in a medical field. However, in recent years, X-ray imaging techniques have rapidly been developing and utilized a new kind of contrasts. One of the contrasts is a refraction contrast (i.e., the distribution of the X-ray intensity dependent on the refraction of the X-ray penetrated through an object). In general, the refraction contrast may be any kind of the X-ray images with the intensity distribution thereof being a function of a refraction angle. Main advantages of the refraction contrast are the possibility to observe tiny cracks and deformations invisible in other types of contrasts and better sensitivity to the low Z materials. This is of great importance in medical imaging. The CT-reconstruction based on the refraction contrast has been expected to possess the same advantages. The inventors of the present application have studied the contrast diagnosing for a coronary artery by injecting a contrast medium into a vein since 1997, and have recognized that there are many internal organs which are invisible or have problems in image quality by the ordinary absorption contrast. The inventors have intended to make these internal organs visible, become there have been a possibility such that a visible 3-dimensional image of the internal organs invisible by the conventional absorption contrast method may be constructed. A CT-reconstruction by the refraction contrast has been attempted until now, but the reliable image of an object has not been realized. The object of the present invention is to provide a method and apparatus for constructing a 3-dimensional image of the internal organs invisible by the conventional method. The X-ray CT-reconstruction technique has been widely used in many fields of research. In general, the CT-reconstruction is based on the absorption contrast described above. Recently, the methods for generating another contrasts have been developed. One of the contrasts is the refraction one due to the change of propagating direction of the X-ray beam when the parallel X-ray beam penetrates through an object. The refraction contrast has advantages such that portions invisible by the absorption contrast may be observe. Therefore, the CT-reconstruction method based on the refraction contrast has also the same advantages described above. However, this method requires a new mathematical algorithm and software. The present invention solved the problems including establishment of a theoretical formula for a mathematical model which is the base for a computer modeling and experimental realization of technique. A first aspect of the present invent is an apparatus for constructing a 3-dimensional image of an object. The apparatus comprises: generating means for generating a monochromatic and parallel X-ray beam from an X-ray beam; an angle analyzer for reflecting or transmitting the monochromatic and parallel X-ray beam passing through the object positioned on a rotatable goniometer in the monochromatic and parallel X-ray beam; an imaging device for generating a refraction angle data by receiving the monochromatic and parallel X-ray beam reflected on or transmitted through the angle analyzer to defect the intensity thereof and output a refraction angle data; and an arithmetic device for constructing the 3-dimensional image by carrying out an arithmetical operation for the refraction angle data from the imaging device; wherein the arithmetic device extracts, from the refraction angle data, a refraction angle distribution Δα(,t), herein is a rotation angle of the object and t is a projection coordinate perpendicular to the X-ray beam, and reconstructs a refraction index gradient ∇ñ from the extracted refraction angle distribution Δα(,t), and the reconstruction of the refraction index gradient ∇ñ is carried out by an algorithmΔα(Θ,t)eiΘ=∫S\|∇ñ(r)\|eiφ(r)dr herein ñ (r) is a local refraction index which has a relation to the refraction index n(r) in portion r as ñ=1−n, φ(r) is the angle between the direction of the X-ray beam and the refraction index gradient ∇ñ (r), and S is an integration path. A second aspect of the present invention is a method for constructing a 3-dimensional image of an object. The method comprises the steps of: generating a monochromatic and parallel X-ray beam from an X-ray beam by a monochromator-collimator; reflecting or transmitting the monochromatic and parallel X-ray beam passed through the object positioned on a rotatable goniometer in the monochromatic and parallel X-ray beam, and receiving the monochromatic and parallel X-ray beam reflected on or transmitted through the angle analyzer by an imaging device to acquire a refraction angle data; and constructing the 3-dimensional image by carrying out an arithmetical operation for the refraction angle data from the imaging device; wherein the arithmetical operation includes the steps of, extracting a refraction angle distribution Δα(,t), herein is a rotation angle of the object and t is a projection coordinate perpendicular to the X-ray beam, reconstructing a refraction index gradient ∇ñ from the diffraction angle distribution Δα(,t), and converting the reconstructed refraction index gradient ∇ñ to a scalar field ñ (r). In accordance with the present invention, the problems for a mathematically correct algorithm of the CT-reconstruction based on the X-ray refraction contrast has been solved. The software prepared by this algorithm has showed good results. Also, the 3-dimensional image construction method and apparatus have following advantageous effects; (1) A cartilage may be imaged, and (2) Breast cancer cell, connective tissue, stroma, milk duct(ductus lactiferi), blood vessel, collagenous fiber of stroma, and the like may be imaged. A refraction contrast is based on the distribution of an X-ray intensity due to the refraction of an X-ray beam which penetrates through an object. In most cases, the refraction contrast is mixed with an absorption cons Fortunately, by the current technique, the information on a refraction angle distribution can be extracted from the mixture of the refraction and absorption contrasts. The refraction angle Δα of the X-ray beam penetrating through an object is calculated as the integral over the x-ray beam path S with the elemental refraction as the integrand:Δα=∫S\|∇ñ(r)\| sin φ(r)dr (1)where ñ (r) is a local refraction index which has a relation to the refraction index n(r) in position r as ñ=1−n, φ (r) is the angle between the X-ray beam direction and the refraction index gradient ∇ñ (r), i.e., the angle between the X-ray beam direction and the differentiation of the local refraction index ñ. In this integral, the X-ray beam path S inside the object may be approximated by a straight line taking into account the fact that ñ≦10−5 in the X-ray region. The equation (1) is not enough for the CT-reconstruction, because it has two unknown functions: the absolute value of the refraction index gradient \|∇ñ\| and the angle φ (r) both of which may not be obtained independently. Since the values of the refraction index ñ are equal on both sides of the object, the difference between them has always zero value:0=∫S\|∇ñ(r)\| cos φ(r)dr (2) Equations (1) and (2) may be written in the complex form, if the equation (2) is multiplied with complex unity i and is added to the equation (1)Δα=−i∫S\|∇ñ(r)\|eiφ(r)dr (3) This equation serves as the base for the CT-reconstruction equation. FIG. 1 shows a basic CT geometry. An object 12 is positioned on a rotatable goniometer in an X-ray beam 8. Herein, is the angle between the initial position and present position (designated by a dotted line, t is the projection coordinate perpendicular to the X-ray beam 8, and a refraction angle distribution Δα(,t) is the projection with the information about the refraction angle. According to the general CT method, it is needed to acquire the information on the refraction angle as the information on the angular position of the object and the space coordinate t. Therefore, after mathematical manipulations with the equation (3), the algorithm for the CT-reconstruction may be written as follows:Δα(Θ,t)eiΘ=∫S\|∇ñ(r)\|eiφ(r)dr (4) with the integration path S being the straight line x cos +y sin =t. The equation (4) denotes that the result of the CT-reconstruction is the gradient of the field of refraction index. One can note that the equation (4) is very similar to the equation for the absorption contrast based CT-reconstruction. The difference is in the input fractions (they are Δα(,t) exp (i) for the refraction contrast and log(,t)/I0) for the absorption contrast, and in the functions to be reconstructed (they are \|∇ñ (r)\|expiφ (r) for the refraction contrast and μ(r) for the absorption contrast). However, there is one important difference between theses cases of refraction contrast and absorption contrast. In the equation for the absorption contrast based CT-reconstruction, both input and output functions are in the real number space, while the refraction contrast based CT-reconstruction utilizes the functions in the complex number space. This means that the absorption contrast based CT algorithm may not be adopted for the case of the refraction contrast and its own original algorithm and software are required. Due to the structure of the equation (4), the mathematical formalism of the refraction contrast based CT algorithm is the same as that is used for the case of absorption contrast (so called Filtered Backprojection method). Basically, the mathematical formalism consists of the following four steps. i) Fourier transform of the input function Δα(,t) exp i (which is often called “sinogram”):PΘ(ω)=∫−∞∞Δα(Θ,t)expiΘe−2πiωtdt. (5) ii) Filtering of the transformed function PΘ(ω):SΘ(ω)=PΘ(ω)b(ω) (6)Herein, b(ω) is a filtering function. There are a lot of filtering functions used in the CT-reconstruction. However, the filtering functions usually used in the absorption abstract based CT-reconstruction are hardly applicable in the refraction contrast, because all of the filtering functions suppress high frequency components emphasizing low frequency ones. It is reasonable in case of absorption contrast, because most useful information is contained in the low domain, while high frequency components mostly consists of noise. Contrastingly, in case of refraction contrast, higher Fourier components play important role and should not be suppressed by the filtering function. iii) Backward Fourier transform of the filtered function:QΘ(t)=∫−∞∞SΘ(ω)\|ω\|e2πiωdω. (7)The resulting function QΘ(t) is known as the filtered sinogram. iv) Backprojecting of the filtered sinogram to the real space.\|∇ñ(x)=expiφ(r)=∫0πQΘ(t)dΘ (8)Herein, r≡(x, y) corresponds to t as t=x cos +y sin . This algorithm is presented for the continuous form of the equations. However, in any practical application, the function Δα(,t) is known only in a certain points m and tn. Therefore, the discrete form of the algorithm must be used in actual calculations. The refraction contrast based CT equation (4) shows that the reconstructed function is the gradient of the refraction index Δñ (r), while most users would prefer the results in the form of the real physical values ñ (r) rather than its gradients. In order to calculate the real physical values, the CT-reconstruction is first performed, and then the scalar field ñ (r) is built from the gradient ∇ñ (r) using the property of the scalar field gradientñ(r0)=∫∞r0∇ñ(r)dr. (9) However, the basic equality ∇×(∇ñ (r))≡0 is not fulfilled strictly due to the arithmetical error in step (iv) of the CT-reconstruction algorithm (see the equation (8)). This means that the value of the scalar field ñ (r0) depends on the choice of the integration path so that it is needed to calculate two or more integral equations (9) along the different trajectories and then use that average thereof as the most realistic result. In order to avoid this problem, another way is used to reconstruct the value ñ. The gradient-to-field conversion may be done before the backprojecting of the filtered projection equation (8), since the physical meaning of the filtered sinogram Q(t) is the projection of the gradient ∇ñ (r). Then, in the fourth step (iv) of the reconstruction algorithm, the new functionQΘintegrated(t)=∫∞tQΘ(r)dr (10)is used instead of the function QΘ(t). After this transformation, the reconstructed function is the equation (8) is not the gradient, but the refraction index itself. The gradient-to-field conversion built in inside the reconstruction algorithm has certain advantages over the conversion performed after the reconstruction. First of all, the integral equation (10) is one-dimensional contrastingly to the integral equation (9) which is performed over a curve on the surface (x,y). This makes the integration mathematically easier and computationally cheaper. Secondary, the equality ∇×(∇ñ (r))≡0 holds true strictly before the fourth step of the algorithm due to the member \|ω\| in the integrand of the equation (7) which grantees the mean value of the function QΘ(t) equal to zero. An embodiment of the 3-dimensional image construction method and apparatus in accordance with the present invention will now be described. The problem of the experimental derivation of the function Δα(,t) is the equation (4) is not obvious and different techniques have been proposed until now. The most reliable one of them is the diffraction enhanced imaging (DEI) method presented in 1997. The schematics of the experiment performed in accordance with the DEI method is presented in FIG. 2. Reference numeral 10 designates an asymmetrical monochromator which makes the X-ray from the X-ray source (not shown in the figure) to a monochromatic parallel beam (plane wave), and reference numeral 12 an object (or sample) under investigation. The rotation axis for the CT scanning over the angle is perpendicular to the image plane. Reference numeral 14 designates a reflection-type angle analyzer, and 16 a CCD (solid imaging device) camera. The diffraction angle data from the CCD camera 16 is transferred to a computer 18 which is an arithmetic device. Photon energy used in the embodiment was 11.7 keV. Both the monochromator 10 and angle analyzer 14 used Si(220) which was diffraction type and was asymmetrically cut with 9.5°. At these conditions, Bragg angle B=16.0° and a asymmetry factor b=3.8. The CCD camera used had a view area of 10.0 mm (width)×7.5 mm(height) with 1384×1032 pixels. The horizontal and vertical dimensions of view area are different due to the asymmetrical reflection. The choice of the asymmetrically cut crystals was done reasoning from the size of the object, the view area of the CCD camera, and the width of reflective curve, i.e., rocking curve of the angle analyzer 14. However, the monochromator 10 and angle analyzer 14 are not limited to a asymmetrically cut Si crystal. The present embodiments was performed at the vertical wiggler beamline BL14B at a synchrotron radiation facility (Photon Factory) of High Energy Accelerator Research Organization. The X-ray beam (lane wave) 8 reflected from the asymmetrical monochromator 10 passes through the object 12, and is incident on the angle analyzer 14 to be analyzed in angle. At this time, two reflecting positions of the angle analyzer 14, i.e., the positions on the left and right slopes from the reflecting peak of the rocking curve are selected. The X-ray beam reflected on the angle analyzer 14 is acquired by the CCD camera 16 to generate the refraction contrast. The rocking curve of the angle analyzer 14 is shown in FIG. 3. In order to extract the refraction angle data in accordance with the DEI method, it is required that two pictures of the same object at two positions of the analyzer 14 are taken. In FIG. 3, these two positions of the analyzer 14 (reflecting points where angle information may be extracted to a maximum extent from the contrasts) are denoted as positions L and H. The position L is on the left slope from the reflecting peak of the rocking curve, and the position L on the right slope. In the figure, each of the positions L and H designates the height of half-width. The positions L and H may be varied in their height on condition that they have the same height. Series of images for reconstruction are taken in the points L and H of the rocking curve. The reflectivity in both L and H points is 0.5. The refraction angle may be calculated according to the equation (6b) disclosed in the reference “D. Chapman, W. Thomlinson, R. E. Johnston, D. Washburn, E. Pisano, N. Gmür, Z. Zhong, R. Menk, F. Arfelli and D. Sayers, Phys. Med. Biol. 42, 2015 (1997)”. However, the theoretical model used in the above reference utilizes the Taylor expansion of the rocking curve and therefore it is suitable only in limited ranges. In order to increase the degree of accuracy, the rocking curve of the analyzing crystal is utilized instead of its Taylor approximation. The result of the refraction angle extraction is shown in is FIGS. 4A, 4B and 4C. The sample presented in these figures is a fragment of the refill for the ball point pen deformed by fire. This sample was chosen because (i) it has no central symmetry, (ii) absorption contrast is low at 11.7 keV, and (iii) it consists of different substances (plastic body with ink and air spaces inside). A method for constructing a 3-dimensional image by utilizing the sample will now be described in every step. (1) The monochromator 10 and angle analyzer 14 are positioned as shown in FIG. 2. The angle analyzer 14 is rotated to obtain a reflection curve (rocking curve). (2) The reflection position is adjusted to the point L of the rocking curve. (3) The sample 12 is set. (4) The transmitted X-ray and refracted X-ray through the sample 12 are reflected on the angle analyzer 14 and are incident on the CCD camera 16. The refraction angle data from the CCD camera 16 is input into the computer 18. (5) The sample 12 is removed. (6) In the condition of no sample 12, a plane wave is reflected on the angle analyzer 14 and is input into the CCD camera 16. The refracted angle data is input into the computer 18. (7) In the computer 18, the refracted angle data acquired in the step 6 is subtracted from the refracted angle data acquired in the step 4. (8) The sample 12 is set again and the sample is rotated to a subsequent angle. (9) The operations in the step 4-7 are repeated. (10) The same operations are continued until the rotating angle of the sample is reached 180°. (11) The reflection position is adjusted to the point H of the rocking curve. (12) The operations in the steps 3-10 are repeated. (13) The refraction angle is extracted by computing two kinds of data acquired in step 7 for two reflecting positions of the angle analyzer. (14) The image is extracted due to the Filtered Backprojection method by utilizing the equation (4). FIGS. 4A and 4B show the original images in L and H positions of the rocking curve of the angle analyzer 14, respectively. In these images, noises are subtracted, i.e., the background image without the sample is subtracted from the image with sample. FIG. 14C shows the extracted refraction angle Δα proportional to the intensity of the gray scale with zero deflection corresponding to the middle gray. According to the above described description, the refraction contrast based reconstruction process consists of the following steps: (i) Taking set of images at different m=mΔ (with m an integer varying in ranges from 0 to M and Δ=180°/M) in the L point of the rocking curve (see FIG. 4A). (ii) Taking set of images at different m=mΔ (with m an integer varying in ranges from 0 to M and Δ=180°/M) in the H point of the rocking curve (see FIG. 4B). (iii) Extracting Δα(m, t) from the sets of images according to the modified DEI method (see FIG. 4C for the extracted data). (iv) CT-reconstruction of a slice on the basis of Equation (4). As a result of T-reconstruction, the gradient Δñ is obtained. (v) Transformation of the gradient Δñ to the more suitable local refraction index. The number of projections of the object in the embodiment was M=360 which gives Δ=0.5°. The reconstructed two-dimensional image of the slice marked in FIG. 4C with the dotted line are shown in FIGS. 5A, 5B and 5C. FIG. 5A shows the reconstruction Δñ in the form of \|∇ñ\| for the slice (a 2-dimensional slice image), FIG. 5B the reconstruction Δñ is the form of \|∇ñ sin φ\| for the slice (a 2-dimensional slice image), and FIG. 5C the result of \|∇ñ\|→\|ñ\| transformation (a 2-dimensional slice image). It is noted that the object on the reconstructed imaged has fuzzy edge. This is the consequence of the X-ray optics limitations which appears mainly due to the Borrmann fin effect, the source size, and the propagation-interference contrast. It is expected that the edge fuzziness can be partially suppressed with the decrease of the object-to-detector distance (it was 138 cm in the embodiment). The 2-dimensional slice image shown in FIG. 5C proves to be very interesting, because it shows all three materials (plastic body, ink, air inside). All three materials are distinguishable in contrast. The refraction index of the ink proved to be larger than that of the plastic body. This is because black ink is made using carbon black and has inclusions of pigments such as titanium dioxide. A 3-dimensional image is acquired by constructing all of the reconstructed 2-dimensional slice images. The 3-dimensional representation of the object is displayed in FIG. 6. They are realistic representation of the sample. One more artifact comes from ∇ñ→ñ transformation and can be recognized as a netlike contrast of pixel size in FIG. 5C. It is possible to erase this unwanted contrast but it takes one order longer computation time and for most cases may be left as is since it does not distort the image strongly. FIG. 7A shows an example of the 3 dimensional image for sample piece of micropapillary carcinoma. The 2-dimensional slice images of the 3-dimensional image are shown in FIGS. 7B, 7C and 7D, respectively. FIG. 7B shows the 2-dimensional slice image in an X-plane, FIG. 7C the 2 dimensional slice image in a Y-plane, and FIG. 7D the 2-dimensional slice image in a Z-plane, respectively. These 2-dimensional slice images show three milk ducts designated by numerals 1, 2 and 3. A high contrast area is observed in the center of the breast duct. The high contrast area is recognized as calcification. A low contrast area is observed in proximity to the calcified area. The low contrast area is recognized as a necrotic area A higher contrast area surrounds the low contrast necrotic area. The higher contrast area is recognized as a cancer cell tissue. A high contrast linear area or net area is observed outside the breast duct. This area is recognized as an invasive cancer cell tissue. In particular, the breast duct 3 observed in FIG. 7D is substantially occluded. Furthermore, it is easily recognized that almost of breast ducts have a white edge surrounding the breast duct, respectively. The white edge region denotes a higher density of electrons. Even irregular shape of spreading invasive malignant tumor may be observed clearly. FIG. 8 shows a dyed pathological view corresponding to the 2-dimensional slice image in FIG. 7D. This dyed pathological view has extremely good correspondence to the 2-dimensional slice image formed by the 3-dimensional image construction apparatus in accordance with the present invention, so that there is a possibility such that the refraction contrast based CT image according to the present invention may be replaced by the dyed pathological view. In order to find out a breast cancer as early as possible, a mammography is particularly useful. The current mammography uses the X-ray absorption contrast. The best space resolution in the current mammography based on the X-ray absorption contrast is at most 50 μm, while the 3-dimensional image construction apparatus based on a refraction contrast according to the present invention has realized a space resolution in the range of 5-10 μm. Thereby, an X-ray pathological diagnosis would be developed. While the reflection-type angle analyzer is used in the embodiment 1, a transmission-type angle analyzer may be used. FIG. 9 shows a 3-dimensional image construction apparatus using a transmission type angle analyzer 20. In the figure, the same components as that in FIG. 2 are designated by the same reference numerals. The transmittance curve of the transmission-type angle analyzer 20 is shown in FIG. 10. An offset angle at which the angle analyzer 201 with the direction perpendicular to the X-ray beam is set so that the transmittance becomes one. The refracted X-ray beam 22 and transmitted X-ray beam 24 are emitted from the angle analyzer 20. A CCD camera 16 receives the refracted X-ray beam 22. In this case, a dark field image is taken in the CCD camera 16. The output data from the CCD camera 16 is input into a computer 18. The CT-reconstruction process is the same as that in the embodiment 1. The method for constructing a 3-dimensional image is conducted according to the following steps. (1) The sample 12 is set. (2) The refracted X-ray beam through the sample 12 is transmitted through the angle analyzer 20 and is incident on the CCD camera 16. The refracted angle data from the CCD camera 16 is inputted into the computer 18. (3) The sample is rotated to a subsequent angle, and the step (2) is carried out. (4) The same operations are continued until the rotating angle of the sample is reached 180°. (5) The image is extracted due to the Filtered Backprojection method by utilizing the equation (4). In the step (4), the axis at which the sample 12 is rotated is perpendicular to the image plane of FIG. 9, while any rotational axis may be selected. As described in the embodiments 1 and 2, the problems in the CT-reconstruction based on a refraction contrast are solved successfully. The theory described above serves as a basis for the programming algorithm prepared and tested in the embodiments. It has been proved that the result of reconstruction is reliable. The 3-dimensional image construction method and apparatus in accordance with the present invention may be utilized for an X-ray pathological diagnosis and contribute to the progress thereof.
	summary
	description	This application is a Continuation of U.S. patent application Ser. No. 14/303,227, filed Jun. 12, 2014, which application is a Continuation of U.S. patent application Ser. No. 13/607,329, filed Sep. 7, 2012, and issued as U.S. Pat. No. 8,766,213. Both prior applications are hereby incorporated by reference. The present invention relates to charged particle beam systems, more specifically to a system and method for laser beam alignment within charged particle beam systems. Charged particle beam systems are used in a variety of applications, including the manufacturing, repair, and inspection of miniature devices, such as integrated circuits, magnetic recording heads, and photolithography masks. Charged particle beams include ion beams and electron beams. Ions in a focused beam typically have sufficient momentum to micromachine by physically ejecting material from a surface. Because electrons are much lighter than ions, electron beams are typically limited to removing material by inducing a chemical reaction between an etchant vapor and the substrate. Both ion beams and electron beams can be used to image a surface at a greater magnification and higher resolution than can be achieved by the best optical microscopes. Since ion beams tend to damage sample surfaces even when used to image, ion beam columns are often combined with electron beam columns in dual beam systems. Such systems often include a scanning electron microscope (SEM) that can provide a high-resolution image with minimal damage to the target, and an ion beam system, such as a focused or shaped beam system, that can be used to alter workpieces and to form images. Dual beam systems including a liquid metal focused ion beam and an electron beam are well known. Focused ion beam milling in many instances are unacceptably slow for some micromachining applications. Other techniques, such as milling with a femtosecond laser can be used for faster material removal but the resolution of these techniques is lower than a typical LMIS FIB system. Lasers are typically capable of supplying energy to a substrate at a much higher rate than charged particle beams, and so lasers typically have much higher material removal rates (typically up to 7×106 μm3/s for a 1 kHz laser pulse repetition rate) than charged particle beams (typically 0.1 to 3.0 μm3/s for a Gallium FIB). Laser systems use several different mechanisms for micromachining, including laser ablation, in which energy supplied rapidly to a small volume causes atoms to be explosively expelled from the substrate. All such methods for rapid removal of material from a substrate using a laser beam will be collectively referred to herein as laser beam milling. The combination of a charged particle beam system with a laser beam system can demonstrate the advantages of both. For example, combining a high resolution LMIS FIB with a femtosecond laser allows the laser beam to be used for rapid material removal and the ion beam to be used for high precision micromachining in order to provide an extended range of milling applications within the same system. The combination of an electron beam system, either alone or in conjunction with a FIB, allows for nondestructive imaging of a sample. FIG. 1 shows a prior art dual beam system 100 having a combination charged particle beam column 101 and laser 104. Such a dual beam system is described in U.S. Pat. App. No. 2011/0248164 by Marcus Straw et al., for “Combination Laser and Charged Particle Beam System,” which is assigned to the assignee of the present application, and which is hereby incorporated by reference. U.S. Pat. App. No. 2011/0248164 is not admitted to be prior art by its inclusion in this Background section. As shown in the schematic drawing of FIG. 1, the laser beam 102 from laser 104 is focused by lens 106 located inside the vacuum chamber 108 into a converging laser beam 120. The laser beam 102 enters the chamber through a window 110. A single lens 106 or group of lenses (not shown) located adjacent to the charged particle beam 112 is used to focus the laser beam 120 such that it is either coincident and confocal with, or adjacent to, the charged particle beam 112 (produced by charged particle beam focusing column 101) as it impacts the sample 114 at location 116. Integrating a laser beam system with a charged particle beam system provides significant challenges. Problems may arise in spatially stabilizing the laser beam that is used in conjunction with a charged particle beam. The stability of the laser is determined by its ability to precisely maintain its direction as well as its initial position with the output aperture. The laser beam position may drift, however, over time with variations in temperature, mechanical vibrations inside the laser, and other environmental conditions. Periodic re-alignment of the laser beam is therefore required to compensate for the drift. Aligning a laser beam within a charged particle beam system is currently a very tedious and time consuming manual process and requires significant expertise. Automated beam positioning in laser beam systems is well known. See “Automatic beam alignment system for a pulsed infrared laser”, Review of Scientific Instruments 80, 013102 (2009). Past systems usually use a controller that receives signals from beam position detectors, and consequently issue commands for motorized optical elements (e.g., adjustable mirrors) in order to maintain proper alignment of the beam. Unfortunately, other than aligning the laser beam manually, there is currently no practical system that allows for the convenient alignment of the laser beam positioning in charge particle beam systems. The small sample chamber of a charged particle beam system makes it difficult to house components needed for beam alignment systems. What is needed is a method and apparatus for a convenient way to align a laser beam within a charged particle beam system without the need for performing the alignment manually. An object of the invention is to provide a method and apparatus to perform an alignment of a laser beam within a charged particle beam system that is done in conjunction with an electron beam or focused ion beam that provides coincident alignment with the system's eucentric point. According to a preferred embodiment of the present invention, a beam positioning system may be used to provide this type of alignment. Another object of the invention is to provide a system having a vacuum chamber, a workpiece support within the vacuum chamber, a charged particle beam system for generating a beam of charged particles, a laser beam system for generating a laser beam, and a laser beam alignment system for aligning the laser beam, wherein the laser beam alignment system has a laser beam position detector in the vacuum chamber. The system will have a second beam position detector outside the vacuum chamber and beam steering mirrors to make adjustments to the laser beam so that the laser beam is aligned to the eucentric point of a charged particle beam system. Another object of the invention is to provide a method of making adjustments to a laser beam comprising a charged particle beam source capable of generating a charged particle beam, providing a vacuum chamber, providing a laser beam source capable of generating a laser beam, providing a laser beam alignment system that allows the laser beam source to be aligned to the eucentric point of a charged particle beam system. Another object of the invention is to provide a method of using a laser system with a charge particle beam system, wherein the steps include generating a charged particle beam to be used on a workpiece, generating a laser beam to be used on the workpiece, wherein the laser beam is aligned eucentrically to the workpiece. The aligning process of the laser beam is performed using an alignment detector that is located within the vacuum chamber of the system, as well as an alignment detector that is located outside the detector. The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. The incorporation of a laser beam system with a charged particle system involves difficulties with the amount of time and expertise required to align the laser beam. The common methods for aligning a laser beam inside a vacuum chamber are very tedious and time consuming manual processes. Embodiments of the present invention provide advantages over common methods of manually aligning a laser beam within a charged particle beam system. Some embodiments of the present invention provide a system for the alignment of a laser beam within a charged particle beam system using laser position sensors. FIG. 2 shows a schematic view of a laser beam alignment system 201 according to a preferred embodiment that is used in charged particle beam system. A laser beam source 205 generates a laser beam 204. Two fast steering mirrors 202, 203 are positioned to control the direction of the laser beam 204. Fast steering mirrors (FSM) have the ability to mechanically tilt the mirror in order to control the direction of the laser beam. FSMs are well known to those having skill in the art, and need not be described further herein. Other types of beam steering mirrors are well known in the art, including scanning mirrors. A galvanometer based scanning mirror can be used in place of FSMs and are also well known to those having skill in the art. Fast steering beam mirrors 202 and 203 are connected by lines 207 and 208 to fast steering mirror controllers 206 and 213. Voice coils, or devices that are galvanometers or act like galvanometers, are used in fast steering mirrors to use the electrical signals it receives from the controllers. Fast steering mirror controllers 206 and 213 control the fine pointing and tracking of the laser beams. Fast steering mirror 202 is coupled to the quad cell detector 210 via the controller 206. Quad cell detector 210 is located outside the chamber wall 209 of the charged particle beam system 201. Chamber wall 209 separates the vacuum chamber of the charged particle beam system 201 from the outside. As laser beam 204 reflects off of fast steering mirror 202 and 203, laser beam 204 is split with a beam sampler, or beam splitter 211, to form a second beam 223. Beam splitter 211 is a conventional beam splitter that separates the beam into two component beams. The power splitting between the two component beams is determined by the reflection and transmission coefficients of the beam splitter. Second beam 223 is directed to quad cell detector 210. Generally, second beam 223 is the weaker beam of the two split beams. Quad cell detector 210 and quad cell detector 215 can be conventional alignment detectors that are capable of detecting the alignment, or the position, of a laser beam source. A position sensitive detector (PSD) is another type of an alignment detector. A PSD can be generally a photoelectric device that converts an incident light, or laser beam, into continuous position data. In other words, a PSD can detect and record the position of incident light beams. A PSD can have various configurations, including a quadrant detector configuration or a dual axis lateral effect detectors. The purpose of these two types is to sense the position of the beam centroid in the X-Y plane orthogonal to the optical axis. In order to measure the X and Y position from the PSD, four electrodes are attached (not shown) to the detector and an algorithm then processes the four currents generated by photoabsorption. Quad cell detector 210 is generally fixed and provides the positional data of laser beam 204 to FSM controller 206. It then makes the adjustments in the fast steering mirror 202 so that the laser beam comes to an alignment point 220. Laser beam 204 enters the vacuum chamber via window 212 where the laser beam is focused using objective lens 214. Quad cell detector 215 is coupled to controller 213 and fast steering mirror 203. Quad cell detector 215 is located inside the chamber wall 209 within the vacuum chamber. Quad cell detector 215 works with the fast steering mirror controller 213 and fast steering mirror 203 to mechanically align the laser beam 204 to an alignment point 221. The in-chamber quad cell detector 215 is able to be positioned remotely with relatively good positional accuracy and high repeatability. Other types of alignment detectors can perform the detection of the laser alignment or position detection. A quad cell detector is generally a uniform disk with two gaps across its surface. It generates four signals from each quadrant of the disk. The laser beam is varied on the disk until the signal strength of each quadrant of the disk is equal. The in-chamber quad cell detector 215 is capable of being retracted or moved to clear the path for laser beam 204 with retractor 222. Retractor 222 can be controlled remotely from outside the vacuum chamber 360 and can be any mechanism that can move the quad cell detector 215 from its alignment position to a position away from laser beam pathway. The mechanism can be a lever that is manually adjusted in the X-Y-Z direction, or the mechanism can be an electronic component that can electronically adjust the quad cell detector 215 in the X-Y-Z direction. The mechanism must allow the retractor 222 to move the quad cell detector 215 in and out of the proper position accurately and repeatedly. The retractor 222 is aligned to the optical axis of the objective lens 214. In one embodiment of the invention, the objective lens 214 provides a hard stop for the quad cell detector 215 (not shown). It would include an electronically controlled actuator arm that slides the quad cell detector 215 in and out of the proper aligned position. FIG. 3 shows a system 300 according to a preferred embodiment of the present invention that combines a focused laser beam 216 (produced by a laser 306) for rapid material removal with a focused ion beam (FIB) 352 (produced by a FIB column 304) for further material processing and an electron beam 350 (produced by a SEM column 302) for monitoring the material removal process. A laser 306 directs a laser beam 308 towards a first steering mirror 202, which reflects the laser beam 308 to form a first reflected beam 312. First reflected beam 312 is directed towards a second steering mirror 203, which reflects the first reflected beam 312 to form a second reflected beam 322 which is directed through transparent window 212 in vacuum chamber 360. By “transparent” it is meant that the window is transparent to wavelengths of the particular type of laser being used. Steering mirrors 202 and 203 (or a similar reflecting elements) are used to adjust the position of the laser beam 216 on the sample 320. An objective lens 214 focuses the laser beam 322 (which may be substantially parallel) into a focused laser beam 216 with a focal point at or near to the surface of a sample 320. In some embodiments, laser beam 216 is preferably capable of being operated at a fluence greater than the ablation threshold of the material in sample 320 being machined. Preferred embodiments of the invention could use any type of laser, now existing or to be developed, that supplies sufficient fluence. A preferred laser provides a short, nanosecond to femtosecond, pulsed laser beam. Suitable lasers include, for example, a Ti:Sapphire oscillator or amplifier, a fiber-based laser, or an ytterbium- or chromium-doped thin disk laser. Other embodiments may use a laser having less fluence that reacts with the workpiece without ablation, such as thermally induced chemical desorption processes using a laser or the process of laser photochemistry. The current system allows for the manipulation of the fast steering mirrors 202 and 203 to be precisely controlled with the adjustments calculated by the reading of the quad cell detectors 210 and 215 so that the alignment of the laser beam can be made through the center of the objective lens 214 and ultimately, targeting the eucentric point of the target 320. Quad cell detector 214 is located as close to the output of the objective lens 214 as practically possible to provide better precision of the laser beam and to prevent damage to the detector induced by the focused laser beam. Sample 320 is typically positioned on a precision stage (not shown), which preferably can translate the sample in the X-Y plane, and more preferably can also translate the work piece in the Z-axis, as well as being able to tilt and rotate the sample for maximum flexibility in fabricating three-dimensional structures. System 300 optionally includes one or more charged particle beam columns, such as an electron beam column 302, an ion beam column 304, or both, which can be used for imaging the sample to monitor the laser ablation process, or for other processing (such as FIB-milling) or imaging tasks. Ion beam column 304 typically forms a beam of ions 352 which may be focused onto the sample surface 320 at or near the focal point of the laser beam 318. FIB column 304 may also be capable of scanning ion beam 352 on the substrate surface to perform imaging and/or FIB milling. System 300 may also include a gas injection 330 system for supplying a precursor gas that reacts with the substrate 320 in the presence of the electron beam 350 or focused ion beam 352. As is well-known in the prior art, the electron beam column 302 comprises an electron source (not shown) for producing electrons and electron-optical lenses (not shown) for forming a finely focused beam of electrons 350 which may be used for SEM imaging of the sample surface 320. The beam of electrons 350 can be positioned on, and can be scanned over, the surface of the sample 320 by means of a deflection coil or plates (not shown). Operation of the lenses and deflection coils is controlled by power supply and control unit (not shown). It is noted that the lenses and deflection unit may manipulate the electron beam through the use of electric fields, magnetic fields, or a combination thereof. Sample chamber 360 preferably includes one or more gas outlets for evacuating the sample chamber using a high vacuum and mechanical pumping system under the control of a vacuum controller (not shown). Sample chamber 360 also preferably includes one or more gas inlets through which gas can be introduced to the chamber at a desired pressure. FIG. 4 is a flowchart showing the steps of an algorithm for the alignment of the laser beam system 300 of FIG. 3 in accordance with one of the embodiments. Before the algorithm is begun, in step 401, the beam must be coarsely focused and aligned so that the laser beam is aligned to point 220. This step should be done with the system vented and the isolation table, if any, floated. Laser beam 204 is further positioned so that it passes through the laser injection port (LIP) window 214 and into the vacuum chamber 360. Adequate coarse focus will generally result in the formation of visible plasma when the vacuum chamber is open. The optical emission from the plasma will enable the user to roughly position the focus of the laser beam close to the eucentric point of the column (the LIP window 214 is capable of being manually translated in X, Y, and Z from outside the chamber). The LIP window 214 can be shifted in the X and Y directions, which positions the beam on the sample. The LIP window 214 can be moved in and out in the Z axis so that that focus of the beam can be directed to a desired location, e.g., so that the beam is aligned with the eucentric point of the system. After the manual coarse focus and positioning of the beam, the system 300 is pumped down and the electron beam turned on. Generally, the manual manipulation for coarse focusing will only need to be done the first time the laser is aligned with system 300. In step 402, quad cell 215 is moved to its pre-aligned position in the laser beam pathway. In step 403, the position of the laser beam 204 on the beam splitter 211 is monitored at quad cell detector 210. Beam position information from quad cell detector 210 is converted to a usable signal (via the fast steering mirror 202 and controller 206). In steps 404 and 411, controller 206 works with the voice coils of fast steering mirror 202, which provides the precision adjustments needed to steer the beam to be coincident with point 220. Steps 404 and 411 are performed repeatedly until the beam is aligned properly to point 220. Once the beam is aligned properly to point 220, in step 405, the position of the beam at the objective lens 214 is monitored by quad cell detector 215. As with quad cell detector 210, beam position information from quad cell detector 215 is converted to a voltage (via the fast steering mirror 203 and controller 213) that is applied to the voice coils of fast steering mirror 203. The adjustments made to fast steering mirror 203 with controller 213 is repeatedly, sequentially, and iteratively made until the beam is coincident with point 221 in step 407. If the beam is targeted properly on point 221, in step 408, the beam position is once again monitored at beam splitter 211 with quad cell detector 210. In step 409, the beam is monitored to be targeted on point 220. The whole process is repeated until the beam is aligned with both points 220 and 221. Once alignment of beam is made to be coincident with points 220 and 221, the beam enters LIP window 212. The location of the beam is checked on fast steering mirror 203. It is necessary to use fast steering mirror 203 to direct the beam so that it is centered on sample 320 because the fast steering mirror 203 is used to scan the beam on sample 320. If the beam is not centered on the fast steering mirror 203, the scan may not be linear across the scan field. Not having it centered may also limit the extent of the scan in one direction. In cases where fast steering mirror 203 is not centered on sample 320, the entire mirror assembly is moved in the X/Y directions in step 410 as needed to center the beam. In this process, the angle of the mirror is generally not changed. Once the laser beam is aligned to be coincident with the system's eucentric point, a retractor 222 is used to move quad cell detector 215 out of the beam path to allow the beam to be incident with the sample. In use, the laser beam is focused to the eucentric point of the charged particle system. The eucentric point is typically a prior known distance from the end of the electron column 302. The focus of electron beam 350 is adjusted such that the focus distance is the same as the eucentric point of the system and the workpiece height is adjusted until the sample comes into focus. A laser spot is then machined on the sample and compared to the system's eucentric point. If the laser spot is not positioned at the eucentric point, the LIP window 212 is manually adjusted until the correct position is achieved. The alignment procedure detailed above is repeated and the manual positioning of the laser spot is performed again. The whole process is iterated until the beam is aligned and positioned at the eucentric point and the electron beam 350 is aligned to the eucentric point. Once the alignment is set, LIP window 212 position is fixed. The invention described above has broad applicability and can provide many benefits as described and shown in the examples above. The embodiments will vary greatly depending upon the specific application, and not every embodiment will provide all of the benefits and meet all of the objectives that are achievable by the invention. For example, in a preferred embodiment TEM samples are created using a gallium liquid metal ion source to produce a beam of gallium ions focused to a sub-micrometer spot. Such focused ion beam systems are commercially available, for example, from FEI Company, the assignee of the present application. However, even though much of the previous description is directed toward the use of FIB milling, the milling beam used to process the desired TEM samples could comprise, for example, an electron beam, a laser beam, or a focused or shaped ion beam, for example, from a liquid metal ion source or a plasma ion source, or any other charged particle beam. Further, although much of the previous description is directed at semiconductor wafers, the invention could be applied to any suitable substrate or surface. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made to the embodiments described herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
	description	The present invention relates in general to methods for controlling the positions of nuclear fuel assemblies inside a nuclear reactor core. The core of a nuclear reactor typically comprises of a plurality of prism shaped nuclear fuel assemblies, supported on a core support plate. Placed above the assemblies is an upper core plate (UCP) designed for, among other things, locking into position the top nozzles of the nuclear fuel assemblies. Each of the top nozzles of the nuclear fuel assemblies typically includes two holes, called “S shaped hole”, intended for cooperating with the centering pins of the upper core plate. The centering pins protrude under the upper core plate and is each engaged in an S shaped hole. It is important for the nuclear fuel assemblies to be positioned properly inside the nuclear reactor core. Indeed, during core loading operations, the nuclear fuel assemblies are first set in place inside the reactor core, and then the upper core plate and other reactor internals are replaced. During the setting in place of the upper core plate (UCP), the pins are engaged in the S shaped holes. If the pins and the S shaped holes of some assemblies are in an offset position relative to each other, the pins of the UCP can be entered with force in some S shaped holes. This does not in any way interfere with the operation of the reactor, but during the subsequent shut down of the reactor, when the UCP is extracted out of the core, there is a risk of the nuclear fuel assemblies remaining attached to the upper plate of the core during the lifting of the UCP. Such a situation is particularly problematic. Thus, it is necessary carry out a highly reliable control of the positions of the nuclear fuel assemblies of the core in relation to the upper core plate, after loading of the assemblies into the core and before setting in place the upper core plate. It is an object of the present invention to provide a method for controlling the positions of a plurality of nuclear fuel assemblies in relation to the upper core plate, which is quick and reliable. The present invention provides a method for controlling the positions of a plurality of nuclear fuel assemblies in relation to an upper core plate in a nuclear reactor core, the method comprising of the following steps: choosing a reference point in the reactor internals or in a reactor vessel; determining the positions of the S shaped holes of the nuclear fuel assemblies relative to the reference point, each S shaped hole being intended to cooperate with a corresponding centering pin of the upper core plate; acquiring the positions of the centering pins of the upper core plate relative to the reference point; comparing the positions of the S shaped holes and the positions of the pins and deducing therefrom whether the nuclear fuel assemblies are correctly positioned in relation to the upper core plate. The method may further include one or more of the following characteristic features, considered individually or in accordance with any technically possible combinations: the reference point is a guide pin integrally attached to a lining of the core, the guide pin being adapted so as to cooperate with a notch of the upper core plate in order to position the upper core plate in relation to the lining of the core, the positions of the S shaped holes relative to the reference point are determined by taking images of the nuclear fuel assemblies, and determining with the aid of said images the positions of the S shaped holes relative to the reference point, each image is adapted to provide the positions of the S shaped holes of at least one given nuclear fuel assembly and at least one S shaped hole of a nuclear fuel assembly adjacent to the given nuclear fuel assembly, an overall image of the plurality of nuclear fuel assemblies is developed from the various images of the nuclear fuel assemblies, the overall image providing the positions of all the S shaped holes of the plurality of nuclear fuel assemblies, the comparison of the positions of the S shaped holes and the positions of the pins is carried out by comparing the overall image of the plurality of nuclear fuel assemblies to a theoretical image of the upper core plate providing the positions of all of the centering pins corresponding to all the S shaped holes of the plurality of nuclear fuel assemblies, each nuclear fuel assembly is considered to be correctly positioned in relation to the upper core plate if the comparison of the position of each S shaped hole of said nuclear fuel assembly with the position of the corresponding pin indicates that the S shaped hole and the pin have a distance between them that is less than a predetermined limit, for example 8 millimeters, the images are taken by means of a digital image capturing apparatus, moved by a machine for loading nuclear fuel assemblies, the plurality of nuclear fuel assemblies comprise at least one quarter of the nuclear fuel assemblies of the core, and preferably at least half of them. The invention relates to a second aspect of an assembly for controlling the positions of a plurality of nuclear fuel assemblies in relation to an upper core plate in a nuclear reactor core, comprising of the following: a device suitable for determining the positions of S shaped holes of nuclear fuel assemblies relative to a reference point, each S shaped hole being provided to cooperate with a corresponding centering pin of the upper core plate, the reference point being chosen in the reactor internals or in a reactor vessel, a device suitable for determining the positions of the centering pins of the upper core plate (3) relative to the reference point, a device suitable for comparing the positions of the S shaped holes and the positions of the pins, and deducing therefrom whether the nuclear fuel assemblies are correctly positioned relative to the upper core plate. As indicated above, the method of the invention aims to control the positions of a plurality of nuclear fuel assemblies 1 in relation to an upper core plate 3 in the core 5 of a nuclear reactor. The core 5 of a nuclear reactor is shown partially in a schematic representation in FIGS. 1 and 2. The core 5 includes a large number of nuclear fuel assemblies 1, that are prism shaped. Each assembly 1 has an elongated shape along the central X axis of the nuclear reactor core. The assemblies 1 are positioned in the core of the nuclear reactor adjacent to each other, in a manner such that the lateral side faces 6 of two adjacent assemblies are opposite one another and in immediate proximity to one another. Each assembly comprises a framework inside which the nuclear fuel rods are placed. The framework includes, among other things, a top nozzle and a bottom nozzle. The assemblies 1 are supported by their bottom nozzles on a core base plate, not shown. The upper core plate 3 is axially positioned immediately above the assemblies 1. The core also has a core lining 7 substantially cylindrical, coaxial with the X axis. The lining 7 helps to channel the circulation of the primary fluid in the reactor core. The partition 9 is placed around the fuel assemblies 1, between the assemblies 1 and the lining 7 of the core. The partition 9 performs the function of locking the assemblies 1 in position, and helps to channel the circulation of the primary fluid through the assemblies. The assemblies are positioned in the core in a regular manner, for example based on a square mesh grid. The upper core plate 3, as shown in FIG. 3, is a substantially circular plate with outer diameter substantially corresponding to the internal diameter of the core lining 7. It is centred on the X axis and is substantially perpendicular to the X axis. It has a plurality of orifices 11, for example provided for the passage of the guide tubes of the reactivity control rod clusters of the reactor, or for the circulation of the primary fluid. Only one portion of the orifices 11 is shown in FIG. 3. The core support plate 3 is locked in position angularly around the central X axis relative to the core lining 5 by pins 13 rigidly fixed to the core lining. The pins 13 protrude radially towards the interior of the core lining 7 relative to the radially inner surface 15 of the core lining (FIGS. 2, 4, 5). They cooperate with the notches 17, formed at the periphery of the upper core plate 3. As seen in FIGS. 4 and 5, the notches 17 each have a circumferential width that is slightly greater than that of the guide pins 13. The notches 17 extend axially across the entire thickness of the upper core plate. The pins 13 are engaged in the notches 17, the upper core plate 3 being thus locked in rotation relative to the core lining 5 and axially free in relation to the latter. The upper core plate 3 has on its underside surface 19 facing towards the nuclear fuel assemblies 1 a plurality of centering pins 21 (FIG. 6). The pins 21 protrude from the underside surface 19 towards the fuel assemblies. Each of the top nozzles 23 of the fuel assemblies typically have two holes 25 each meant for receiving a pin 21, called S shaped holes. As shown in FIG. 8, seen in cross sectional view perpendicular to the X axis, the top nozzles 23 have a square cross section, the S shaped holes 25 being located at two opposite corners of said section. The S shaped holes 25 are open at the top, that is to say, towards the upper core plate, as shown in FIG. 6. The pins 21 each perform the function of maintaining in position the top nozzle of an assembly 1. The control method of the invention, the main steps of which are identified in FIG. 9, is aimed at verifying that the nuclear fuel assemblies, after loading in the core, are well positioned relative to the upper core plate 3. More specifically, the method is designed to determine whether the S shaped holes 25 of the nuclear fuel assemblies are correctly positioned relative to the pins 21 of the upper core plate. The method comprises the following steps: choosing a reference point in the reactor internals or in a reactor vessel; determining the positions of the S shaped holes 25 of the nuclear fuel assemblies relative to the reference point; acquiring the positions of the centering pins 21 of the upper core plate relative to the reference point; comparing the positions of the S shaped holes 25 and the positions of the pins 21; deducing therefrom whether the nuclear fuel assemblies are correctly positioned in relation to the upper core plate. The reference point is preferably an element whose position is known with good precision in relation to the upper core plate. Typically, the reference point is one of the guide pins 13 that enable the indexing of the upper core plate in position relative to the core lining. Typically, the uncertainty with respect to the positions of the pins 21 relative to the centering pins 13 is of the order of 1 millimeter. Determination of the positions of the S shaped holes 25 of the nuclear fuel assemblies in relation to the reference point is carried out by taking images of the assemblies 1, and determining with the aid of said images the positions of the S shaped holes relative to the reference point. More specifically, an image is acquired for each fuel assembly 1. The image capturing device is placed above the top nozzle 23 of the assembly to be photographed, the optical axis of the image capturing apparatus being substantially parallel to the central X axis. Each acquired image is of an appropriate size so as to allow the identification on the said image of the S shaped holes of the assembly photographed, and of at least one S shaped hole 25 of a nuclear fuel assembly adjacent to the assembly photographed. As shown in FIG. 8, when the assemblies are arranged in a square mesh grid, each assembly 29 is surrounded by eight adjacent assemblies 31. The top nozzle of each assembly has two S shaped holes 25 disposed at two corners of the nozzle situated along a diagonal. Typically, all of the assemblies are arranged based on the same orientation, in a manner such that the S shaped holes 25 of the different assemblies S are located along the same diagonal. Thus, several of the assemblies 31 adjacent to the assembly 29 have one S shaped hole 25 on the edges adjoining the assembly 29. In the example shown in FIG. 8, six of the assemblies adjacent to the assembly 29 have one S shaped hole 25 adjoining the assembly 29. Thus, in this example, the image of the assembly 29 allows not only the identification of the two S shaped holes of the assembly 29, but also of one S shaped hole for six of the adjacent assemblies. As shown in FIG. 7, images are acquired on an assembly by assembly basis, following a predefined order. For example, the assemblies are processed row by row. Getting through a first row thus involves starting from the assembly situated at a first end of the row. The adjacent assembly is subsequently photographed, and this is continued through the row right until the assembly situated at the second end of the row. The adjacent row is then processed, for example in the opposite direction. Such an S oriented path helps to minimise the travel time of the image capturing apparatus from one assembly to another. Once the images of each of the nuclear fuel assemblies have been acquired, a comprehensive overall image of all the nuclear fuel assemblies is created from the previously acquired images. The overall image provides the positions of all the S shaped holes of all the nuclear fuel assemblies in relation to each other. The overall image is computationally created by merging the acquired images. The positions in the various images in relation to each other may be adjusted with precision due to the fact that each image includes S shaped holes 25 that also appear in other images, as indicated here above. The positions of the S shaped holes relative to the reference point is then determined from the overall image. In order to do this, it is necessary to know with precision the position of at least one S shaped hole 25 relative to the reference point. This position may be determined in multiple ways. For example, it is possible to acquire an additional image, showing both the guide pin serving as a reference point and the holes 25 of an assembly located in the proximity of the pin 13. Alternatively, it is possible to acquire an image showing the position of the holes 25 of an assembly in relation to an element of the core whose position relative to the guide pin is accurately known. This element can for example be an element of the partition 9. It is also possible to use for this purpose one of the images acquired for an assembly located next to the partition. Comparison of the positions of the S shaped holes and the positions of the pins is carried out by comparing the previously developed overall image with a theoretical image of the upper core plate providing the positions of the different centering pins in relation to the reference point. This image is typically a predetermined digital image, stored in a database. For example, it is reconstructed from the manufacturing drawings of the elements of the nuclear reactor core, in particular the manufacturing drawings for the lining of the core and the upper core plate. The comparison is done by superimposing the overall image on the theoretical image of the upper core plate. The superimposing is automatically performed on a computer. As a variant, the superimposing is done manually, by an operator. Subsequently, for each S shaped hole 25 of each assembly, the gap between the S shaped hole and the corresponding pin 21 of the upper core plate 3 is determined. To do this, for example, the distance between the centre of the S shaped hole 25 and the centre of the corresponding pin 21 in the superimposition is considered, as it is derived from the superimposition of the theoretical image and the overall image. Said positions correspond to the positions in a plane substantially perpendicular to the central X axis of the reactor core. The gap corresponds to the distance between the two centres in said plane perpendicular to the X axis. The gap distance is calculated automatically, or determined graphically by an operator. Subsequently, the distances found for each S shaped hole are compared to a predetermined limit. The limit is for example equal to 8 millimeters, preferably equal to 4 millimeters, and more preferably equal to 2 millimeters. If the distance found for one of the S shaped holes of an assembly is greater than the limit, the assembly is considered to be badly positioned relative to the upper core plate. If instead the distances found for all the S shaped holes of an assembly are less than the limit, the assembly is considered to be well positioned relative to the upper core plate. The method makes it possible to provide a list of all the S shaped holes 25 which are out of tolerance, that is to say for which the calculated distances are greater than the predetermined limit. The method also makes it possible to provide a list of badly positioned assemblies, possibly with the identification numbers of the badly positioned assemblies. The method can also provide the gaps between assemblies, calculated from the positions of the S shaped holes 25 of the various assemblies. The method described here above can be implemented by means of the device shown schematically in FIG. 1. The device 33 comprises an image capturing device 35, and a computer 37. The image capturing device 35 comprises a support 39, the illumination means 41 fixed to the support 39, a sealed housing 43 fixed on the support 39, and a digital image capturing apparatus 45 disposed in the interior of the sealed housing. The image capturing device 35 is designed to be moved by the machine 47 for loading nuclear fuel assemblies in the reactor core. In order to do this, the support 39 comprises a coupling member provided to cooperate with the mast 49 of the loading machine 47. The device 33 has been designed in order that the lighting power intensity 41 may be adjusted from the computer 37, for example depending on the surface condition of the nuclear fuel assemblies. The image capturing apparatus is for example a digital photographic apparatus, for example having a resolution of 18 million pixels, allowing for a resolution of 0.1 millimeter per pixel in the operating conditions envisaged. These conditions are as follows: field of view for each image of approximately 300 millimeters/400 millimeters; a distance of about 2 meters between the lens of the camera 45 and the top nozzle of the assembly to be photographed; a focal length of around 100 millimeters. The apparatus could also be a digital camera. The photographic apparatus 45 is connected to the computer 37 via a digital connection, allowing for the exchange of data between the computer and the photo apparatus. This link is for example of the Ethernet connection type. The device is adapted so as to allow remote control of the photographic apparatus by means of the computer 37 and the feeding back of images from the photographic apparatus 45 to the computer 37. The housing 43 is connected to a ventilation system, not shown, and maintained at an internal pressure of 2 bar. The computer 37 is programmed for the following: controlling the acquisition of images by the photographic apparatus for each nuclear fuel assembly; from the acquired images, merging of the images in a manner so as to form the overall image of the nuclear fuel assemblies; determining the positions of the S shaped holes relative to the reference point, from the overall image and, for example, from an image giving the position of at least one S shaped hole relative to the reference point; storing the theoretical image of the upper core plate; superimposing the overall image over the theoretical image of the upper core plate; comparing the previously determined positions of the S shaped holes to the positions of the pins deriving from the theoretical image of the upper core plate; determining the gap distances between each S shaped hole and the corresponding pin; comparing the gap distances determined to the predetermined limit; providing a list of S shaped holes that are badly positioned relative to the corresponding pins, the list of assemblies that are badly positioned relative to the upper core plate, possibly the identification details of the badly positioned nuclear fuel assemblies, and possibly calculating the gaps between assemblies. Since the control method includes a step for determining the positions of the S shaped holes of the nuclear fuel assemblies relative to a reference point in the internals or in the reactor vessel, and a step for acquiring the positions of the centering pins of the upper core plate relative to the same point reference, it is possible to perform a very precise comparison of the positions of S shaped holes and the positions of the corresponding pins. The use as a reference point of the guide pin of the upper core plate is particularly well suited, because the position of the upper core plate relative to this pin is known in a precise manner. The positions of the S shaped holes relative to the reference point can be determined in a rapid and convenient manner by taking images of the assemblies with the help of appropriate equipment. The use of an overall image of the nuclear fuel assemblies, developed by merging the various images taken with the help of the image capturing device, makes it possible to perform a quick and accurate comparison with the position of the pins of the upper core plate. This allows for accelerating the process. The overall image can be constructed with a good degree of accuracy if each image taken with the image capture device not only gives the positions of the S shaped holes of a particular assembly, but also of at least one S shaped hole of another assembly, serving as a benchmark for the juxtaposition of the different images. The method is particularly rapid, the time necessary for implementation being for example about four hours for the entire nuclear reactor core. This is particularly important because controlling the position of nuclear fuel assemblies in relation to the upper core plate is on the critical path during unloading and reloading of nuclear fuel assemblies in the reactor core. Due to the fact that the positions of the S shaped holes relative to the pins are accurately determined, the risk of the nuclear fuel assemblies getting stuck during the lifting of the upper core plate is minimised. In any event, for reasons of economy, the method is applied to at least a quarter of the nuclear fuel assemblies of the core, and preferably to at least half of the nuclear fuel assemblies of the core, and more preferably to the entire amount of nuclear fuel assemblies of the core. By way of a variant, the size of each image can be adapted in order to allow the viewing of two adjacent assemblies, and thus to enable the determination of positions of the S shaped holes of the two assemblies. The size of the images may also be adapted in order to allow the viewing of four or more assemblies, provided that the resolution of the image capturing apparatus is sufficient for this purpose.
	abstract	The present invention relates to systems and methods for diagnosing undesirable events or the lack of desirable events representing product or process malfunctions. One aspect of the invention includes a method for determining a cause of a malfunction event in a prototype or production product or process. Another aspect of the invention includes a method for identifying evidence of deviation from a specification for a product or process. Still another aspect of the invention includes a method for ascertaining the reliability of a product or process. The present invention also provides a diagnostic computer system and computer program code for performing various methods embodying different aspects of the present invention. A computer system for training a user to diagnose and apply corrective action to a malfunctioning product or process is also provided.
044735286	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, a passive containment system for a four-loop pressurized water reactor is disclosed. Basically, the system includes a plurality of interconnected steel cells located within the concrete housing, the steel cells enclosing the reactor coolant system and the engineered safety system components. Centrally, the reactor vessel cell 101 houses the reactor vessel 102. Four steam generator cells 103 each house a steam generator 104, and four reactor coolant pump cells 105 each house a reactor coolant pump 106. A pressurizer cell 107 confines the reactor coolant pressurizer 108 and a surge line 109 interconnects the pressurizer to the reactor system. A regenerative heat exchanger cell 110 houses a high-pressure regenerative heat exchanger, which is not shown. Pipe cells 111 enclose the reactor coolant system piping which is indicated at 112. The engineered safety components include four refill tank cells 113 which each enclose a reactor vessel refill tank 114. Four deluge tank cells 115 each encompass a deluge tank 116, and four quench tank cells 117 each house a quenchtank 118. The aforedescribed interconnected steel cells form a leak-proof structure for the reactor coolant system and this system of cells is designated as the primary reactor containment 119. During reactor operation the free space within the containment 119 is maintained at a high vacuum to eliminate the need for thermal insulation at the exterior surface of the reactor coolant system. During reactor shutdown for maintenance operations, air at atmospheric pressure is circulated within the containment 119. The cells for the various components are encased within a concrete housing or structure, generally indicated at 120, except at the upper end of the reactor vessel. The concrete structure 120 provides structural support for both the containment cells and the components therein, and a sufficient thickness of structural concrete is provided to serve as biological shielding. The refueling enclosure above the reactor vessel is filled with water for shielding purposes, and protection against penetrating radiation is therefore provided to the occupants within the reactor building for both normal reactor operation and for all postulated accidents within the containment including the LOCA. A number of compartments are provided for portions of the reactor coolant system components. A compartment is formed by a steel shroud 121 that encloses the control rod drive thimbles. A steel diaphragm seal 122 bridges the annular space between the reactor vessel flange 123 and the reactor vessel cell 101. Each pump cell 105 includes a pump motor compartment 124. A steel diaphragm seal 127 bridges the annular space between the pump casing and the pump cell 105. A pressurizer compartment 126 is provided, and a steel diaphragm seal 125 bridges the annular space between the lower head of the pressurizer 108 and the pressurizer cell 107. The compartments can be supplied with either an air or inert gas atmosphere for ventilation or cooling, and at the same time the rest of the free space in the containment can be maintained at a high vacuum or at atmospheric pressure. The water filled tanks, which comprises the components of the engineered safety systems, are elevated for functional purposes. The refill tanks 114, and the deluge tanks 116, and preferably, the quench tanks 118, contain neutron poison in solution. The contents of the tanks are maintained at a low temperature by mechanical refrigeration units, not shown. A sufficient amount of cooling liquid is provided within the refill tanks 114 to quench the steam in the steam generator 104 secondary systems and to overflow through the postulated pipe break in the LOCA. The deluge tanks 116 contain a sufficient amount of fluid to quench the steam carryover from the containment in the LOCA, and then fill the containment 119 free volume to an elevation above the postulated reactor coolant system pipe break. The fluid in the quench tanks 118 provide sufficient heat sink capacity to prevent containment over pressure during the term of the LOCA. The combined heat sink capacity of the deluge and quench tanks enable reactor cool down to a cold shutdown condition on turbine trip or on the loss of the offsite electric power. The liquid within the refill tanks 114 is utilized for emergency reactor core cooling in the LOCA. The steam line 128 communicating with the associated steam generator 104 through an isolation valve enters the associated refill tank where it is branched to a number of refill steam jet injectors 129 defined in the refill tank. The injector nozzles are so positioned at a tube sheet 130 to enable pressurization of the cooling liquid below the tube sheet by the steam flow through the injectors 129, and this pressurized fluid is in communication with a high pressure injection pipe 131 communicating with the lower region of the associated refill tank, and the pipe 131 communicates with the cold "leg" of the reactor coolant system. Each pipe 131 has one or more check valves 132, FIG. 10, and isolation valves 133 for operational purposes. Each steam line 128 also includes one or more check valves 134 and isolation valves 135. The isolation valves 133 and 135, and valves subsequently designated by similar terms, are preferably of the electrically operated type. The cooling liquid within the deluge tanks 116 is utilized for various selective purposes, such as quenching steam within the containment system in the event of a LOCA, thermal absorption by steam quench in the event of overpressure discharge from the pressurizer relief valves 136 and safety valves 137, and for steam quenching purposes in the event of an overpressure discharge from the associated steam generator relief valve 138, FIG. 11. Each deluge tank has twelve or more 12 inch vent pipes 139 that penetrate the tank top head and extend almost the full length, or depth, of the tank. The vent pipes 139, within the tank, are perforated by thousands of small orifices submerged within the cooling liquid to facilitate an immediate quench of steam entering the vent pipes 139 by the chilled water within the tanks. Each vent pipe is encircled by a spaced shroud pipe 140 which promotes thermal circulation past the vent pipe orifices within the tank in that the shroud pipes produce a "chimney" effect and the thermal circulation of the cooling liquid past the orifices tends to "scrub" the orifices with cooling liquid to improve the heat transfer between the steam entering the cooling liquid, and the cooling liquid. Each deluge tank is additionally provided with vent pipes 139' which are connected to the discharge from the pressurizer relief valves 136 or the pressurizer safety valves 137, or to the relief valves 138 communicating with the associated steam generator secondary. In FIG. 11 the vent pipe 150 is that conduit which communicates the associated steam generator secondary relief valve 138 with the deluge tank 116. In the four-loop system disclosed, the pressurizer includes two relief valves 136 and two safety valves 137, and the discharge from two of the relief valves 136 is connected to the vent pipes 139' of two separate deluge tanks, while the two pressurizer safety valves 137 are each connected to the remaining two deluge tanks vent pipes 139' wherein each of the relief and safety valves of the pressurizer are associated with a different deluge tank, and this relationship permits the thermal energy within the reactor coolant system to be distributed between the four deluge tanks of the four-loop system in the event of reactor coolant overpressure. Each deluge tank 116 includes an injection pipe 141 communicating with the lower region of the tank, and is illustrated in FIG. 10, the pipe 141 communicates with the refill tank discharge pipe 131 through one or more check valves 142 and an isolation valve 143. The presence of the pipe 141 permits the cooling liquid within the deluge tank to be selectively supplied to the reactor coolant system upon the pressure within the reactor coolant system being less than the static head pressure of the deluge tank within pipe 141. The liquid within the quench tanks 118 is used to quench a portion of the steam resulting from reactor coolant blowdown in a LOCA. The balance of the heat sink capacity of the quench fluid is retained for protection against containment over pressure and the quench tank provides a vented containment for this purpose. Each quench tank has one or more 12 inch vent pipes 139" that penetrate the tank top head and extend almost the depth of the tank. The vent pipes 139" are identical to the vent pipes 139 of the deluge tanks, and include many small perforations submerged in the cooling liquid to facilitate an immediate quench of the steam carryover within the containment by the chilled water in the event of a LOCA. Each vent pipe 139" is encircled by a shroud pipe 140' to promote thermal circulation past the orifices, as previously described. The number of vent pipes 139" in the quench tanks are considerably less than the number of vent pipes 139 in the deluge tanks, and comparatively, the vent area in a quench tank is a fraction, approximately 1/12, of the vent area in the deluge tanks. Thus, the quench tanks retain heat sink capacity for the term of the LOCA duration. In addition to the vent pipes 139", each quench tank is provided with apparatus for serving as a heat sink to absorb steam blow-off from the associated steam generator relief valves 138 or safety valves 144. For this purpose the conduits 151 connect to the steam generator steam line 146 through valves 138 and 144, FIG. 11, and each quench tank is also provided with a steam supply line 152 which communicates with generator secondary steam line 146 through an isolation valve 138 wherein steam may be supplied to an injector 145 located within the quench tank having a discharge conduit communciating with the steam generator secondary feedwater line 147 through a check valve, FIG. 11. Thus, the entrance of steam within conduit 152 permits coolant to be removed from the associated quench tank 118 through an injector 145 wherein the coolant may be used as an auxiliary feedwater source for the steam generator in the event of emergency conditions. The primary steam generator steam line 146 includes an isolation valve 148, while the supply of feedwater to conduit 147 is normally controlled by isolation feed valve 149. With reference to FIGS. 10 and 11, it is to be appreciated that the systems disclosed in these figures are schematic and do not fully disclose all of the venting or thermal absorption structure associated with each deluge and quench tank. For instance, in FIG. 10 only the containment venting pipes are shown for the deluge and quench tanks, while in FIG. 11 steam generator relief venting operation is disclosed with respect to deluge tank 116, while in FIG. 11 the thermal absorption venting means connected to the steam line 146 are illustrated, as is the steam supply conduit 152, the injector 145 and the generator feedwater pipe 147. The passive engineered safety features in the disclosed pressurized containment system offer flexibility for plant operation. One arrangement for normal operation is described for the four-loop pressurized water reactor. Two of the four steam generators 104 are used for high-pressure safety injection in the event of a LOCA and this requires that two of the isolation valves 135 on the steam lines 128 be locked open, and two are locked closed. In the postulated LOCA this arrangement provides continued high-pressure safety injection utilizing the stored energy in two steam generators. The other two steam generators remain available for decay heat removal from the core heat and secondary system and reactor coolant system cooldown. General Operation The response of the passive containment system to a LOCA is described for a containment design for about 75 psia back pressure. A four-loop pressurized water reactor and normal operation generating 1000 megawatts of electricity is selected for illustrative purposes. The design values specified are in the design range typical for the nuclear plant selected. Similar evaluations of the passive containment system can be made for all pressurized water reactors including the two and three-loop designs, as well as for all boiling water reactors. In the reactor system selected, the coolant absorbs heat on passage through the reactor vessel 102, releases the heat to generate steam in passage through the steam generators 104, and is recirculated through these components by the reactor coolant pumps 106. The pressurizer 108 maintains the reactor coolant at about 2250 psia pressure to suppress boiling. The reactor coolant system is interconnected by piping 112, and contains approximately 540,000 pounds of coolant with about 314,000,000 British thermal units (BTU) of stored energy in the coolant at a weighted average temperature of 578.degree. F. The primary containment 119 is designed with a free volume of approximately 250,000 cubic feet, and the air within this space is initially substantially removed by steam ejectors, or other vacuum producing apparatus, and maintained at less than 2 psia total pressure by a vacuum pump. The four deluge tanks 116 within the primary container together hold about 3,330,000 pounds of fluid maintained at 50.degree. F. A total free board, slightly in excess of 5000 cubic feet in the deluge tanks, is maintained at less than 2 psia. The four quench tanks 118 altogether contain about 3,330,000 pounds of fluid maintained at 50.degree. F. A total free board slightly in excess of 5000 cubic feet in the quench tanks is maintained at less than 2 psia total pressure. The four refill tanks 114 together contain approximately 1,450,000 pounds of treated water maintained at 50.degree. F. and 1000 psia hydrostatic pressure. The secondary systems of the four steam generators 104 contain approximately 400,000 pounds of fluid with an energy content approaching 550,000,000 BTU. The steam generators operate in the 1000 psia range at rated load. The unique engineered safety system components within the pressurized containment system are designed to be possibly responsive in providing inherent safety to the public during accidents that could endanger public health. As a basis of design for a nuclear power plant, it is postulated that a spectrum of pipe breaks can occur in the reactor coolant system, or in the secondary system and be controlled in the manners set forth below. OPERATION IN THE EVENT OF ACCIDENT Design Basis Loss of Coolant Accident In the design basis LOCA the largest pipe 112 at the reactor coolant system ruptures. A free blow-down of coolant from the two open ends of the ruptured pipe occurs and the bulk of the coolant blow-down occurs in less than 10 seconds, and the blow-down is complete within about 27 seconds. Decompression of the reactor coolant through the break results in the flashing of a portion of the coolant blow-down into steam. The steam pressurizes the evacuated containment 119 free volume, and within a very short time, such as one second, after the break steam pressure within the containment of about five psia forces the water in the deluge and quench vent pipes 139 and 139" to flow through the associated submerged vent orifices wherein the water within the vents is replaced by the steam from within the containment and this steam from the containment is quenched by the chilled water within the deluge and quench tanks. Maximum steam carryover occurs at about 4 seconds into the accident with about 13,300 pounds per second of steam representing 15.7 million BTU's per second of energy, quenched by the stored water. Initially, the steam flashing rate from the coolant blow-down exceeds the rate of steam carryover into the deluge and quench tanks. As the containment 119 pressure increases the steam flow rate through the vent pipes 139 and 139" increases until a choked flow condition occurs. As the coolant system is depressurized, the rate of blow-down and steam flashing decreases. The containment pressure peaks at about the time that the rate of steam carryover equals the rate of steam flashing. The steam carryover increases the liquid volume and temperature within the deluge and quench tanks. With initial vacuum conditions, both in the containment free volume and at the deluge and quench tanks free board, the liquid volume and temperature increase as the result of steam carryover does not impose an appreciable back pressure on the containment for the post accident period. The post accident free board and the deluge tanks is at a pressure of 2.1 psia, the saturation pressure of the 128.degree. F. water. The evacuated containment 119 and steam carryover into the deluge and quench tanks has a decided beneficial effect on the LOCA. A curve of the containment pressure response to the pump suction break is shown in FIG. 12. The containment pressure peaks at about 75 psia, and at this point in time the amount of energy in the steam flowing into the deluge and quench tanks, plus the energy being retained in the saturated water in the containment, starts to exceed the coolant blow-down energy and the containment pressure reduces. By the end of the blow-down, approximately 27 seconds into the accident, the containment pressure has decreased to sub-atmospheric pressure, and at 32 seconds into the accident the containment has depressurized to about 9.5 psia. During depressurization of the reactor coolant system from 2250 to 1900 psia at less than 0.2 seconds into the LOCA, an automatic closure of the isolation valves 148 and 149 at the steam line 146 and feedwater line 147 occurs. With the steam generator secondary isolated, the steam pressure increases at a result of continued energy flow, and thermal energy is transferred by thermal convection and conduction from the reactor system into the generator secondary system. In less than 7 seconds the coolant blow-down depressurized the reactor system below that in the steam generator secondary, and the meantime, the secondary system pressure has increased above the normal 1000 psia range with the automatic closure of the isolation valve. Depressurization of the reactor coolant system below a generator secondary system pressure passively initiates emergency core cooling, i.e. emergency coolant flow into the reactor system from the refill tanks 114. The check valve 132 positioned in the series at the piping 131 interconnected the refill tanks to the reactor coolant system automatically open as soon as the reactor coolant system depressurizes below the hydrostatic pressure in the refill tanks. Safety injection flow from the refill tanks in turn automatically initiates steam flow from the steam generator 104 with open isolation valve 135 in the interconnecting steam line 128. Secondary steam flow through the injectors 129 within the refill tanks entrains the borated water providing rapid safety injection at a high-pressure into the reactor system. The emergency core cooling system designed is based on a core reflood rate equivalent to about 1.5 inches per second from a refill tank at 100 psia reactor coolant back pressure. This core reflood rate is adequate for the emergency cooling of the fuel elements. The high turbulance resulting from reactor coolant blow-down increases the energy transfer from the fuel, and this continues with the rapid injection of emergency cooling water. With high borated refill water starting to refill the reactor vessel 102 and reflood the core within 7 seconds after the LOCA, the fuel is rapidly quenched preventing an excessive temperature increase. The aforementioned describes the primary side decay heat removal system, which is now operational. The steam generators 104 secondaries contains an adequate amount of stored energy in the form of steam for safety injection, and refill tanks 114 have an adequate supply of borated water for core reflood and an overflow through the pipe break. Before the steam pressure in the steam generator secondary being utilized is expended the isolation valves 135 on the other steam lines 128 can be automatically or manually opened to continue the decay heat removal from the quenched fuel with the other standby refill systems in sequence. After the refill systems in tanks 114 are expended, about four minutes into the accident, decay heat removal automatically continues with gravity flow of borated water from the four deluge tanks 116. The deluge tank water, heated from 50.degree. F. to about 130.degree. F. by steam carryover from the containment, has over 50 feet of static head. In that the containment free volume and the deluge tank free board are approximately at the same pressure, the driving force continuing decay heat removal is in excess of 20 psia. The stored coolant mass in the deluge tanks continues passive decay heat removal for about four hours into the accident. During this time, the containment 119 is flooded with borated water to an elevation above any postulated pipe break in the reactor coolant system. After about four hours into the LOCA the passive engineered safety system inter-operations continue: (a) The contaiment 119 is maintained below atmospheric pressure; PA1 (b) Decay heat removal via gravity flow from the deluge tanks is becoming depleted; and, PA1 (c) The containment free volume is flooded above the postulated pipe break location. The temperature of the water flooding the containment is less than 200.degree. F. and the free volume above flood level is below atmospheric pressure. The stored water in the quench tanks 118 continues to provide a heat sink for steam carry-over preventing the containment from being pressurized above atmospheric pressure. Within the four hour post-accident time period active systems can be made functional for continued decay heat removal. Small Loss of Coolant Accident In the spectrum of reactor coolant system pipe breaks, a small LOCA is one in which the charging pumps, i.e., the normally operating make-up pumps, are able to maintain an adequate supply of coolant in the reactor system for safe cooldown and cold shutdown. At the start of cooldown, the reactor and turbine are shut down. The secondary system of the steam generator is isolated by closing valves 148 and 149 on the generator main steam line and feedwater line 146 and 147, respectively. After shut down, the reactor coolant system temperature is decreased at a rate of 50.degree. F. per hour. For this cooldown, a secondary side-decay heat removal system becomes operational. The steam generator secondaries with closed isolation valves 135 on the steam lines 128 are used to tranfer heat from the reactor system to the associated quench tank 118. This secondary side-decay heat removal system utilizes the apparatus schematically illustrated in FIG. 11. Decay heat from the reactor core and sensible heat from the reactor system is transferred to the steam generator secondary by utilizing the reactor coolant pump 106, or by natural thermal convection. This heat, transferred to the secondary system, is in turn transferred to the quench tanks 118 by directed blow-down of steam through the relief valves 138 and pipes 151. Also, a portion of the steam blow-down may be directed through relief valve 138 associated with pipe 152 wherein make up steam injectors 145 inject emergency feedwater into the steam generator secondary through feedwater pipe 147. During reactor cooldown, as soon as the reactor coolant system pressure decreases below 1000 psia, the refill system with open isolation valves 135 routed from the steam generator secondary to the refill tanks 114, is utilized for injecion of the reactor coolant makeup at a controlled rate, such steam generators being used for refill which were not used for secondary side decay heat removal. The reactor vessel refill system, FIG. 10, and the secondary side-decay heat removal system of FIG. 11, are operative for the balance of the cooldown to cold shutdown. The steam from the steam generator secondaries transfers the decay heat to the quench tanks. The normally provided active residual heat removal system can be placed into operation at any time after the reactor coolant system pressure is reduced below 300 psia. In the small LOCA, sump pumps and vacuum pumps, not shown, are effective in the removal of the coolant leaking into the containment 119. Cold traps in the vacuum system condense the leakage fluid carried over as a vapor that is condensed into the liquid in cold traps. The liquid collected is transferred to the radioactive liquid storage tanks, not shown. Intermediate LOCA An intermediate size LOCA results in a loss of coolant that is beyond the capacity of the charging pumps, and also, the reactor coolant system is not depressurized rapidly enough for the pressurized containment system refill system to become operative before the active high pressure injection system is automatically activated. In an intermediate size LOCA the active injection system is operative for that period of time required to depressurize the reactor coolant system below secondary system pressure. The passive refill system and the primary side-decay heat removal system of FIG. 10 are effective for the balance of the cooldown to cold shutdown. Decompression of the reactor coolant through the pipe break results in the pressurization of the containment 119. Steam pressure within the containment forces the water in the vent pipes 139 and 139" to flow through submerged orifices into the free board space in the deluge and quench tanks. The containment peaks at a lower pressure than in the design basis LOCA because of the lower blow-down rate through the smaller pipe break. After the secondary system energy is expended by the safety injection of the borated water from the refill tank 114, core decay heat removal automatically continues with gravity flow of borated water from the four deluge tanks. The containment 119 is flooded with the borated water to an elevation above any postulated intermediate pipe break in the reactor coolant system. Steam Generator Tube Rupture A postulated steam generator tube rupture is an intermediate sized LOCA. On a tube rupture, it is most desirable to cooldown the reactor to a cold shutdown condition as rapidly as possible. With the pressurized containment system disclosed a rapid cooldown is accomplished through secondary system steam relief to the deluge and quench tanks 116 and 118, respectively. Reactor coolant blowdown through the tube rupture rapidly reduces the liquid mass and pressure in the reactor system, thus automatically actuating the charging pumps and the high-pressure injection pumps. Increased steam flow on the secondary side resulting from the tube rupture causes a steam flow/feed water flow mismatch tripping the turbine. Low pressurizer pressure actuates reactor trip, and the main steam generator steam line and feedwater isolation valve 148 and 149 close automatically. The secondary side-decay heat removal system of FIG. 11 becomes operational. A termination of the main feed water flow automatically actuates relief valves 138 on steam line 146 at the steam generator secondary. Steam flow through the relief valve is directed to injector 145 at the quench tank 118. Chilled, demineralized water from the quench tanks is entrained by the steam flow through the injectors. The mixed fluid entering the steam generator secondaries through the feed water lines 147, and a portion of the secondary system steam blow-down is through relief valve 138, routed directed into the deluge and quench tanks through pipes 150 and 151. During the reactor cooldown, the water in the steam generator with a faulty tube rises at a faster rate than the level in the other steam generators. The operator should terminate make up to the faulty steam generator in order to maintain as high a secondary pressure as possible, without opening the safety valves, to reduce continued reactor coolant blow-down through the rupture. The injected makeup flow from the quench tanks and steam blow-down to the deluge and quench tanks from the steam generators' secondary maintains the design rate of cooldown for the reactor coolant system. It is noted that on a steam generator tube rupture the radioactive contamination resulting from reactor coolant blow-down from the faulted steam generator is restricted to the associated deluge and quench tanks 116 and 118. After the reactor coolant system pressure is reduced below secondary system pressure, the reactor vessel refill system is operative along with the decay heat transfer system of FIG. 11 utilizing the heat sink capacities of the deluge and quench tanks. One or more steam generator secondaries are used for refill, and the other secondary systems are used for decay heat transfer. Open Pressurizer Relief Valve The passive containment system of the invention responds even more immediately to another intermediate LOCA, i.e., when a pressurizer relief valve doesn't reseat. The overpressure relief is quenched by the chilled water in a deluge tank such as through a pipe 139', and a deluge tank is not limited in heat sink capacity or free board for the mass carryover. As in the case of a steam generator tube rupture, the high pressure injection pump maintain the required reactor coolant system inventory and reduce pressure until the passive refill system and the primary side-decay heat removal system of FIG. 10 is operative. One or more steam generator secondaries are utilized in the passive refill system, and the others are utilized for the secondary side-decay heat removal system of FIG. 11 to transfer the decay heat to the heat sink provided at the quench and deluge tanks. Main Steam Or Feed Water Line Break A break in the main steam line 146 of a generator causes a rapid increase in the steam rate flow from the affected steam generator 104 and a sudden reduction in its pressure and temperature. With the pressure in the affected steam generator reduced, backflow from the other steam lines through the break is prevented by self-actuated check valves, not shown. The high steam flow from the affected steam generator, coincident with low steam line pressure, signals the isolation valves 148 and 149 for each steam generator to close. Thus, the steam blow-down is practically limited to the affected steam generator 104. For a break outside the primary reactor containment, the closure of the steam line isolation valve 148 limits the blow-down to about ten seconds. For a break inside of the primary reactor containment 119 the rapid blow-down increases the heat transfer rate, causing a sudden transient in the reactor coolant system significantly reducing the temperature, pressure, liquid volume and core shutdown margin. The transient automatically initiates an overpower reactor trip and actuates the safety injection system to prevent fuel damage. The borated water injected maintains sufficient coolant volume inventory and shut-down reactivity. Assuming that the entire mass and energy from the affected steam generator carries over into the four deluge tanks 116 through the vertical vent pipes 139, the temperature of the stored water in the tanks increases from an initial 50.degree. F. to about 65.degree. F. This assumption on steam carryover into the deluge tanks is most conservative. It neglects the mass and energy that remains in the steam generator secondary. No credit is taken for mass and energy carryover into the four quench tanks 118. Also, a great portion of the mass and energy is retained within the primary reactor containment free volume. A pressure transient occurs in the confines of the break location. The pressure peaks during vent pipe 139 clearance of water, and it is anticipated that this pressure transient does not exceed 25 psia. At the end of the blow-down the containment pressure is less than 5 psia. In the post-accident time period the secondaries in the unaffected steam generators are available for the dissipation of core decay heat utilizing the secondary side-decay heat removal system apparatus shown in FIG. 11. This heat is transferred from the reactor coolant to the secondary system by natural convection and conduction. Steam blow-down from the secondary system through relief valves 138 is quenched by the water in the deluge and quench tanks 116 and 118. Steam flow is also directed through steam injectors 145 to provide emergency feedwater for continued decay heat transfer. The heat capacity of the deluge and refill tanks 116 and 114 enables cold shut-down of the reactor system without the need for the transfer of heat outside of the containment 119. Thus, the passive containment system retains the mass and energy from a postulated spectrum of steam and feedwater line breaks. There is no release of mass, energy or radioactivity to the environment except for the ten second release of a steam line break outside of the primary reactor containment 119. Loss Of External Electric Load Or Turbine Trip A number of events resulting in a decrease in heat removal by the steam generator secondary systems are postulated. Beside (1) the loss of external electric load and (2) turbine trip, these events include; (3) steam pressure regulator malfunction or failure that results in decreasing steam flow, (4) inadvertent closure of main steam isolation valves, (5) loss of condenser vacuum, (6) coincident loss of onsite and external (offsite) a.c. power such as a station blackout, (7) loss of normal feed water flow, and (8) feedwater piping break. The alternate decay heat removal system is responsive in these events permitting safe reactor cooldown to a cold shut down condition. On a loss of external electrical load the turbine is subject to being tripped. With a turbine trip the reactor is also subject to being tripped. A heat sink is required for the core decay heat to prevent overpressure in the secondary system of the steam generator as well as in the reactor coolant system. The secondary side-decay heat removal system shown in FIG. 11 provides this function. The chilled water within the deluge and quench tanks 116 and 118, respectively, provide a heat sink for the core decay heat via the reactor coolant system and the secondary system. On reactor trip the steam generator relief valves 138 on the steam lines 146 are automatically actuated relieving secondary system steam into the deluge and quench tanks. The discharge from a number of relief valves is directed to steam injectors 147 that entrain water from the quench tanks 118 providing emergency feed water to the steam generators 104. At the reactor coolant system thermal circulation of the primary coolant transfers the decay heat from the core to the secondary system. The response of the primary containment system of the invention to the above eight postulated events resulting in a decrease in heat removal by the secondary system is similar to that for a loss of normal feed water. Effectively, the core decay heat and the stored energy in the reactor coolant system and the secondary system are in the same range for the eight postulated events. Overpressure protection is also provided. The relief valve 136 and the safety valve 137 on the pressurizer 108 relieves any overpressure within the reactor coolant system by the discharge of these valves into the deluge tanks, the discharge conduits of the relief and safety valves communicating with steam vents of different deluge tanks whereby all four deluge tanks may be utilized in the absorption of thermal energy from the reactor coolant system through the pressurizer. Also, the safety valves on the steam lines 146 relieve overpressure in the steam generator secondaries to the quench tanks. Loss Of Normal Feed Water The passive containment system of the invention offers an alternate core decay heat removal system whenever the normal feed water sources are unavailable. This alternate system also enables reactor coolant system cooldown at 50.degree. F. per hour. Emergency feedwater is automatically injected into the steam generator secondary systems from the quench tanks 118, along with steam blow-down to the contained heat sink, i.e. quench and deluge tanks. Decay heat is transferred by conduction and natural convection from the core elements to the secondary system for rejection from the reactor coolant system and the secondary side-decay heat removal system using the apparatus of FIG. 11 provides this function. On a loss of normal feed water flow, relief valve 138 at two steam generators automatically open on high pressure or on the loss of feedwater. One set of valves initiates steam blowdown to the associated deluge and quench tanks, and valve 138 initiates steam flow through pipe 152 which activates injector 145 for forcing feedwater from the associated quench tanks 118 into the feedwater line 147. Steam flow to the deluge and quench tanks absorbs the energy resulting from decay heat rejection, sensible energy flow (50.degree. F. per hour) from the reactor coolant system cooldown, and secondary system temperature and pressure reduction. The latter enables continued thermal conduction and natural convection of energy from the reactor coolant system to the steam generator secondary systems. The initial mass flow of steam into the deluge and quench tanks is in the range of 80 pounds per second absorbing 95,000 BTUs per second. The steam is dissipated in the chilled water to the small orifices within vent pipes 139 and 139". Steam flow to the injectors 145 positioned within the quench tanks 118 is used to replenish the mass lost through secondary systems steam blow-down and the added amount required for the change in the specific volume during steam generator cooldown. Steam flow through the injectors retains the chilled water, and develops a velocity head with sufficient resultant pressure to open the downstream check valves for emergency feedwater injection into the adjacent feed water lines. Initially, the high pressure steam entrains at least 1.24 pounds of water per pound of steam. The starting feedwater flow rate is in the range of 1000 pounds per second. As the secondary system pressure decreases, the economy of the injector improves. In this application the steam pressure and secondary system back pressure decrease simultaneously, and the temperature of the intake water increases as a result of the steam blow-down. From the above description it will be appreciated that the passive containment system described above permits a wide variety of nuclear reactor accidents to be confined and controlled. The use of the refill, deluge and quench tanks in conjunction with the electrically operated isolation valves associated therewith, permits replacement reactor coolant to be directly introduced into the reactor coolant system, and the capacity of the deluge tanks permits the reactor to be flooded above the point of a break, in the event of a major LOCA. The deluge and quench tanks readily absorb the steam within the containment system during a major LOCA, and the design of the quench tank is such as to permit the necessary heat absorption over an extended period of time for lengthy heat decay purposes. Utilizing the secondary heat decay system employing the apparatus shown in FIG. 11 the deluge and quench tanks provide sufficient heat sink capacity to cool the steam generator secondary to achieve control of the reactor, and the quench tank injector provides a source for feedwater in those situations where additional feed water is needed for heat decay and control purposes. The presence of both deluge and quench tanks provides a versatility for heat sink purposes not heretofore available, and by controlling the utilization of steam energy within preselected steam generators the source of energy within the steam generators may be allocated between reactor coolant refill and heat decay functions as desired to most effectively bring the reactor assembly to a cooldown. Various modifications to the inventive concepts may be apparent to those skilled in the art without departing from the spirit and scope of the invention. For instance, the deluge and quench tanks of a common loop could be mounted in a common cell, one above the other, and other physical relationships could be modified from the disclosed embodiment within the concepts of the invention.
	claims	1. A nuclear power system, comprising:a reactor vessel defining a volume;a reactor core positioned within the volume, the reactor core including one or more nuclear fuel assemblies configured to generate a nuclear fission reaction;a containment vessel sized to enclose the reactor vessel such that an open volume is defined between the containment vessel and the reactor vessel; anda boron injection system positioned in the open volume and comprising an amount of boron in solid form sufficient to stop the nuclear fission reaction or maintain the nuclear fission reaction at a sub-critical state, wherein the boron injection system comprises a boron container sized to hold or enclose the amount of boron in solid form, wherein the boron container is configured to release the amount of boron in solid form directly into the open volume in response to at least one of a predetermined temperature and pressure within the open volume, and wherein the amount of boron in solid form is configured to go into solution upon mixing with primary coolant in the open volume such that the solution is in fluid communication with an inner surface of the containment vessel. 2. The nuclear power system of claim 1, wherein the boron container includes a latch actuatable by the at least one of the predetermined temperature and pressure to open the boron container such that the amount of boron in solid form is delivered directly into the open volume. 3. The nuclear power system of claim 1, wherein the reactor vessel further comprises at least one valve openable to fluidly couple the volume of the reactor vessel with the open volume. 4. The nuclear power system of claim 3, wherein the at least one valve comprises:a reactor vent valve configured to vent the primary coolant in vapor form from the volume of the reactor vessel to the open volume; anda reactor recirculation valve configured to circulate at least a portion of the solution to the reactor core. 5. The nuclear power system of claim 4, wherein the amount of boron in solid form is configured to go into solution with a condensed form of the primary coolant vented into to the open volume. 6. The nuclear power system of claim 4, wherein at least a portion of the boron container that holds the amount of solid boron is meltable or dissolvable, and wherein the reactor vent valve is configured to vent the primary coolant in vapor form at the predetermined temperature that is sufficient to melt or dissolve the portion of the boron container to release the amount of boron in solid form into the open volume. 7. The nuclear power system of claim 1, wherein the amount of boron in solid form is in granular form. 8. The nuclear power system of claim 1, wherein the nuclear power system does not include any control rod assemblies positionable within the reactor vessel. 9. A method for controlling a nuclear fission reaction, comprising:operating a nuclear power system to generate a nuclear fission reaction, the nuclear power system comprising:a reactor vessel defining a volume;a reactor core positioned within the volume, the reactor core comprising one or more nuclear fuel assemblies configured to generate the nuclear fission reaction,a containment vessel sized to enclose the reactor vessel such that an open volume is defined between the containment vessel and the reactor vessel, anda boron injection system positioned in the open volume and comprising an amount of boron in solid form, wherein the boron injection system comprises a boron container sized to hold or enclose the amount of boron in solid form, and wherein the boron container is configured to release the amount of boron in solid form directly into the open volume;initiating an emergency operation of the nuclear power system based on a loss of a primary coolant from the volume of the reactor vessel to the open volume;based on the emergency operation, releasing the amount of boron in solid form into the open volume of the containment vessel in response to at least one of a predetermined temperature and pressure within the open volume such that the amount of boron in solid form goes into solution upon mixing with the primary coolant in the open volume and (b) the solution is in fluid communication with an inner surface of the containment vessel;circulating the solution from the open volume of the containment vessel to the reactor core; andwith the solution, stopping the nuclear fission reaction or maintaining the nuclear fission reaction at a sub-critical state. 10. The method of claim 9, wherein releasing the amount of boron in solid form from the boron container comprises actuating a latch on the boron container by the at least one of the predetermined temperature and pressure in the open volume. 11. The method of claim 9, wherein releasing the amount of boron in solid form from the boron container comprises melting or dissolving at least a portion of the boron container based on the predetermined temperature in the open volume. 12. The method of claim 10, further comprising, based on the emergency event, opening at least one valve on the reactor vessel to fluidly couple the volume of the reactor vessel with the open volume. 13. The method of claim 12, wherein opening at least one valve on the reactor vessel comprises:opening a reactor vent valve to vent the primary coolant in vapor form from the volume of the reactor vessel to the open volume; andopening a reactor recirculation valve to circulate the solution to the reactor core. 14. The method of claim 13, wherein the amount of boron in solid form goes into solution with a condensed form of the primary coolant vented into the open volume. 15. The method of claim 13, wherein the primary coolant in vapor form is at the at least one of the predetermined pressure and temperature that is sufficient to actuate the latch to release the amount of boron in solid form from the boron container into the open volume. 16. The method of claim 9, wherein the boron in solid form is in granular form. 17. The method of claim 9, further comprising operating the nuclear power system to generate the nuclear fission reaction without any operation of control rod assemblies.
048184691	abstract	The seal for turning valve bodies, in particular for valves in radioactive lants, is composed of a molded element of flexible graphite which is coated with a thin, flexible tantalum layer. The tantalum enclosure surrounds the graphite molded element, preferably all around. The tantalum layer is sufficiently thin so that it remains flexible.
062122541	summary	BACKGROUND OF THE INVENTION This invention relates generally to the observation of a structural feature of an object utilizing penetrating radiation such as x-rays. More particularly, but not exclusively, the invention relates to x-ray phase-contrast recordal, e.g. imaging, of internal boundary features. The present applicant's international patent publication WO95/05725 (PCT/AU94/00480) and provisional patent application PN5811/95 disclose various configurations and conditions suitable for differential phase-contrast imaging using hard x-rays. Other disclosures are to be found in Soviet patent 1402871 and in U.S. Pat. No. 5,319,694. It is desired that relatively simpler conditions and configurations more closely related, at least in some embodiments, to traditional methods of absorption-contrast radiography, may be utilised for differential phase-contrast imaging with hard x-rays. In accordance with the present invention there is provided a method of obtaining an image of a boundary of an object, said boundary representing a refractive index variation, said method including: irradiating said boundary with penetrating radiation having high lateral spatial coherence and a propagation component transverse to said refraction index variation; and PA1 receiving at least a portion of said radiation on an image plane so as to form said image, said radiation having been refracted by said boundary such that said boundary is represented on said image by a corresponding intensity variation. PA1 a source for irradiating said boundary with penetrating radiation having high lateral spatial coherence and a propagation component transverse to said refraction index variation; and PA1 a detector for receiving at least a portion of said radiation so as to form said image, said radiation having been refracted by said boundary such that said boundary is represented on said image by a corresponding intensity variation. PA1 irradiating the boundary with penetrating radiation having a propagation direction such that there is a significant component of the propagation vector transverse to the direction of said refractive index variation or in the direction of said thickness variation, and further having a lateral spatial coherence sufficiently high for the variation in refractive index or thickness to cause a detectable change in the local direction of propagation of the radiation wavefront at the boundary; and PA1 detecting and recording at least a portion of said radiation after it has traversed said boundary in a manner whereby an effect of said change in the local direction of propagation is observable and thereby recorded as a local diminution or rapid variation of intensity of the radiation which thereby substantially images the boundary. PA1 means to irradiate the boundary with x-ray radiation having a propagation direction such that there is a significant component of the propagation vector transverse to the direction of said refractive index variation or in the direction of said thickness variation, and further having a lateral spatial coherence sufficiently high for the variation in refractive index or thickness to cause a detectable change in the local direction of propagation of the radiation wavefront at the boundary; and PA1 means to detect and record at least a portion of said radiation after it has traversed said boundary in a manner whereby an effect of said change in the local direction of propagation is observable and thereby recorded as a local diminution or rapid variation of intensity of the radiation which thereby substantially images the boundary. PA1 irradiating said boundary with penetrating radiation having high lateral spatial coherence and a propagation component transverse to said refraction index variation; and PA1 receiving at least a portion of said radiation on an image plane so as to form said image, said radiation having been Fresnel diffracted by said boundary such that said boundary is represented on said image by a corresponding intensity variation. PA1 a source for irradiating said boundary with penetrating radiation having high lateral spatial coherence and a propagation component transverse to said refraction index variation; and PA1 a detector for receiving at least a portion of said radiation so as to form said image, said radiation having been Fresnel diffracted by said boundary such that said boundary is represented on said image by a corresponding intensity variation. The present invention further provides an apparatus for obtaining an image of a boundary of an object, said boundary representing a refractive index variation, said apparatus including: The present invention also provides a method of deriving a phase-contrast record of an internal boundary having a sharp refractive index variation or defined by a thickness variation, comprising: The present invention further provides an apparatus for deriving a phase-contrast record of an internal boundary having a sharp refractive index variation or defined by a thickness variation, comprising: The present invention also provides a method of obtaining an image of a boundary of an object, said boundary representing a refractive index variation, said method including: The present invention further provides an apparatus for obtaining an image of a boundary of an object, said boundary representing a refractive index variation, said apparatus including: The present invention also provides a method of determining the phase of an image, including processing phase-contrast image data of said image. The intensity effect of a change in the local direction of propagation is preferably observable in an image comprising the record. The record and therefore the image may be photographic or electronic. The term "image" may thus refer, for example, to an observable effect in a set of intensity data, for example a table or other stored record of intensity values: the term is not confined to a visual context. The recording medium may comprise a two-dimensional pixilated detector, e.g. an electronic detector such as a charge-coupled device (CCD) array. The irradiating means preferably includes a source of x-rays of diameter 20 micron or less, where diameter refers to the full width of intensity distribution of the source at half maximum intensity. The apparatus may advantageously further include a suitable stage or holder for samples containing the internal boundary being imaged. The penetrating radiation, e.g. x-ray radiation, may be polychromatic and is preferably in the hard x-ray range, i.e. in the range 1 keV to 1 MeV. The separation of the boundary and the detecting means is preferably selected to enhance the resolution of the image. For example, it has been observed that a sharper image, i.e. one with better contrast, is achieved by increasing separation. For instance contrast is improved at least for a separation of about 1 m relative to a separation of 0.4 m. This may partly be because background noise is diminished with increasing separation but the intensity variation effect arising from the change in the local direction of propagation is substantially preserved. The term "lateral spatial coherence" herein refers to the correlation of the complex amplitudes of waves between different points transverse to the direction of propagation of the waves. Lateral spatial coherence is said to occur when each point on a wavefront has a direction of propagation which does not change over time. In practice, high lateral spatial coherence may, for example, be achieved by using a source of small effective size or by observing the beam at a large distance from the source. For example, for 20 keV x-rays a source size of 20 .mu.m diameter or less would typically be appropriate. The smaller the source size the better for the purposes of this invention, provided total flux from the source is sufficient. Lateral spatial coherence may need to be preserved by careful selection of the x-ray window of the source, e.g. such that it is of highly uniform thickness and homogeneity.
047599022	claims	1. The method of determining the long-term radiation levels of a water-cooled nuclear reactor cooling system, comprising the steps of: (a) Inserting a dual-electrode electrochemical potential measuring device, including an unprefilmed measuring electrode and a secondary standard electrode, into a continuously flowing sample line from any selected point in the plant cooling system; (b) Wherein said electrochemical potential measuring device utilizes at least one unprefilmed measuring electrode fabricated from the same metal as the cooling system; (c) Collecting electrochemical potential data beginning immediately after the electrode insertion and continuing over a predetermined measurement period; (d) Determining the normalized electrochemical potential fractions by dividing each electrochemical potential measurement result by the measured or interpolated electrochemical potential after a prescribed short exposure period; (e) Determining the slope of the straight line through the data points created by plotting the normalized electrochemical potential fractions versus the logarithm of time in hours; (f) Dividing the average of the measured values of the Co-60 concentration in the cooling water by the slope determined in step e; and (g) Determining the expected long-term dose rate by using the standard curve of the type shown in FIG. 11 prepared from the data in the prior art and prepared using the said prescribed short exposure period used in step d. (a) Inserting a dual-electrode electrochemical potential measuring device, including an unprefilmed measuring electrode and a secondary standard electrode, into a continuously flowing sample line from any selected point in the plant cooling system; (b) Wherein said electrochemical potential measuring device utilizes at least one unprefilmed measuring electrode fabricated from the same metal as the cooling system; (c) Collecting electrochemical potential data beginning immediately after the electrode insertion and continuing over a predetermined measurement period; (d) Determining the normalized electrochemical potential fractions by dividing each electrochemical potential measurement result by the measured or interpolated electrochemical potential after a prescribed short exposure period; (e) Determining the slope of the straight line through the data points created by plotting the normalized electrochemical potential fractions versus the logarithm of time in hours; (f) Dividing the average of the measured values of the Co-60 concentration in the cooling water by the slope determined in step e; and (g) Determining the expected long-term dose rate by using the standard curve of the type shown in FIG. 11 prepared from the data in the prior art and prepared using the said prescribed short exposure period used in step d. (a) Changing temporarily the water chemistry and reactor operational parameters to reflect the proposed changes; (b) Inserting as dual-electrode electrochemical potential measuring device, including an unprefilmed measuring electrode and a secondary standard electrode, into a continuously flowing sample line from any selected point in the plant cooling system; (c) Wherein said electrochemical potential measuring device utilizes at least one unprefilmed measuring electrode fabricated from the same metal as the cooling system; (d) Collecting electrochemical potential data beginning immediately after the electrode insertion and continuing over a predetermined measurement period; (e) Determining the normalized electrochemical potential fractions by dividing each electrochemical potential measurement result by the measured or interpolated electrochemical potential after a prescribed short exposure period; (f) Determining the slope of the straight line through the data points created by plotting the normalized electrochemical potential fractions versus the logarithm of time in hours; (g) Dividing the average of the measured values of the Co-60 concentration in the cooling water by the slope determined in step f; and (h) Determining the expected long-term dose rate by using the standard curve of the type shown in FIG. 11 prepared from the data in the prior art and prepared using the said prescribed short exposure period used in step e. 2. The method of determining the effects due to controlled or uncontrolled changes that may have occurred in the water chemistry of a nuclear reactor on the long-term radiation levels from the cooling system of that reactor, comprising the steps of: 3. The method of determining the effects due to proposed changes in water chemistry and reactor-operational parameters on the long-term radiation levels from a water-cooled nuclear reactor cooling system, comprising the steps of: 4. The methods of claims 1, 2, or 3 where the nuclear reactor uses a direct-cycle cooling system with neutral-pH water such as a boiling water reactor. 5. The methods of claims 1, 2, 3, or 4 where the nuclear reactor cooling system is fabricated from type-304 stainless steel, type-316 stainless steel, or low-alloy carbon steel. 6. The methods of claims 1, 2, 3, 4, or 5 where the sample line comes from the recirculation system portion of the cooling system of the nuclear reactor. 7. The methods of claims 1, 2, 3, 4, or 5 where the sample line comes from the reactor water clean-up system portion of the cooling system of the nuclear reactor.
051184680	summary	The invention concerns a method of making a neutron absorbing element, for use e.g. as a component of a control rod for a nuclear reactor using water, and the neutron absorbing element obtained. The article "Development of Zircaloy Clad Hafnium Rods for BWR Long Life Neutron Absorbers", by R. KUWAE-M.OBATA-K.SATO-S.SHIMA-J of Nuclear Science and Technology, 23(2), pages 185-187 (Feb. 1986), describes the manufacture of zircaloy clad hafnium rods to replace neutron absorbers based on boron carbide and reminds the reader that Hf is a more durable neutron absorber than boron carbide. The manufacture of a hafnium rod is a complex process, starting with fusion under vacuum and continuing with hot then cold finishing processes, with heat treatments. The cladding of such a rod with zircaloy 2, described in the above article, is also complicated and expensive. Applicants have sought to develop a hafnium based absorbing element which is simpler to produce and more economical. DESCRIPTION OF INVENTION The first subject of the invention is a method of making a metal, neutron absorbing element for use in a control arrangement of a nuclear reactor, the element comprising hafnium and being covered with a cladding which is hardly absorbent or non-absorbent to said neutrons. According to the invention the method comprises the following operations: a) preparing metal products comprising (weight %) per type of element or alloy: PA0 b) introducing at least some of these products into a metal container with an open end; PA0 c) compressing said products in the container, or compressing them before putting them into the container; PA0 d) if necessary repeating the introduction and compression of the products until the container is at least 95% full, with the apparent density of the compressed products at over 80% of their density in the solid state; PA0 e) closing the open end of the container by welding on a metal lid or plug and providing an internal air vacuum better than 1.3 Pa (=10.sup.-2 mm of mercury), by a method such as electron bombardment, laser welding or arc welding under argon with sealing, with the inside of the container put under vacuum or under a neutral gas such as helium. PA0 either before insertion in the cladding container: in this case the compactable products have been mixed, homogenised if appropriate, and compressed e.g. in pellet form; they can be put into the container with a slight clearance, typically less than 0.5 mm of the diameter; PA0 or after insertion in the container, generally in a plurality of stages; in which case compression is generally effected at least twice with an instrument passed into the container, preferably with a small clearance. PA0 by preparing pellets from batches of products which differ in their hafnium content, and by piling them into the container to give a hafnium content which varies discretely along the element formed by the closed container. PA0 by placing hafnium and possibly alloy containing hafnium in the container in one or more sequences, in quantities which increase continuously from one end of the container to the other, while at the same time inserting decreasing quantities of metal or alloy containing less hafnium, and by compressing them together after each inserting sequence or at the end of the operation before closing the end of the container. The content or surface density of hafnium is thus made to vary continuously along the absorbing element. PA0 preferred use of pure Hf (electrolytic crystals) without any complex and expensive conversion; PA0 flexibility with regard to sources of metals or alloys; PA0 ease in adjusting the weight of Hf; PA0 possibility of varying the Hf content along the element: PA0 possibility of modifying the total mass for a given mass of Hf contained; PA0 simple manufacturing process. Hf--at least 25% PA1 Zr and/or Zr alloys=0 to 75% PA1 Ti and/or Ti alloy=0 to 75% PA1 Hf-Zr alloys containing <55% Zr=0 to 75% PA1 Hf-Ti alloys containing <55% Ti=0 to 75% PA1 neutron absorbing metal elements melting at over 400.degree. C.: <0.2% and preferably less than 0.1% PA1 other metal elements melting at over 400.degree. C.: 0 to the balance, the balance being less than 5%; The absorbing elements according to the invention are thus entirely metallic. The compactable metal products particularly comprise crystals and/or chips and/or sponge. The term "crystals" here refers to electrolytic metal deposits, the term "chips" to metal fragments formed in machining operations such as turning, milling or boring and possibly small scrap with a unit volume generally less than 1 cubic cm, while the term "sponge" refers to products obtained by magnesium reduction or Kroll reduction in the case of Hf, Zr and Ti. The hafnium used preferably comprises electrolytic crystals representing at least 25% of the total weight of products and with a mean H content and a mean Cl content of respectively less than 40 ppm and 50 ppm. The products used may further comprise electrolytic crystals of Zr and/or Ti, again with a hydrogen and a chlorine content of respectively less than 40 ppm and 50 ppm, possibly in addition to the electrolytic Hf crystals. The electrolytic Hf crystals deserve special attention, since they preferably make up all or an important part of the charge forming the interior of the neutron absorbing element of the invention. They typically have a settled apparent density of from 2 to 6 g/cm.sup.3, with a variable individual size of from 0.1 mm to 3 mm or 4 mm, with a solid or needle like appearance according to the electrolytic conditions. They are often grouped in aggregates, representing the simultaneous growth of dendrites or needles along a plurality of crystallographic axes. The size of these aggregates is then typically from 3 mm to 2 cm. The largest aggregates are either removed for this use or fragmented, e.g. by grinding, to return to a smaller size, typically less than 0.5 to 0.3 times the diameter or thickness of the compacted product to be obtained. On leaving the electrolytic process, which typically took place in a bath of molten chlorides, the hafnium crystals are usually washed and dried. Their H and Cl content at this stage, generally respectively less than 40 and 50 ppm, may be lowered to less than 25 to 30 ppm by carefully controlling the electrolytic conditions and possibly also by more extensive drying than drying in ambient air: they may be dried at from 150.degree. to 300.degree. C. in a vacuum higher than 1.3 Pa or in an inert gas. The purification from H and Cl can be taken still further by subjecting the electrolytic crystals to treatment for 8 to 48 hours at from 1000.degree. to 1250.degree. C. and typically for 16 to 32 hours at from 1050.degree. to 1150.degree. C., at a vacuum higher than one mPa instead of the treatment at from 150.degree. to 300.degree. C. the residual content of H and Cl is then respectively less than 20 ppm and less than 10 ppm. The same treatments may be applied separately or simultaneously when electrolytic crystals of Zr and/or Ti are also used. Various pure metals and alloys may be chosen to form the charge, according to the required linear density of Hf and the desired weight of the element and also dependent on availability. Thus the inside of the element may contain from 25 to 100% Hf, and the element may, for example, be made as light as possible by using crystals or chips of Ti or alloy. Electrolytic hafnium crystals are particularly suitable for compression, mainly because of the high proportion of cavities in them, resulting in a low settled apparent density. Compression may be carried out at two possible stages: When pellets are used, the pellets placed in the container may be recompressed. The filling of the container and compression are generally controlled so that a free internal height of less than 3 mm and preferably less than 1 mm is left when the plug or lid to be welded onto the container is put into position. The apparent density of the compressed products is over 80% of their mean density in the solid state and typically from 85 to 95% thereof. The products are usually mixed before being compressed or placed in the metal container. In this way the variations in the weight of hafnium per unit length or per unit useful surface area along the closed container or element are less than 2 relative percent or even less than one relative percent. The content or density of hafnium may vary along the absorbing element when this is desirable. This can be provided for by one of the two following methods; The metal container and its lid are made of any metal alloy which will have sufficient corrosion resistance in the reactor at about 350.degree. C. A stainless steel, preferably a low carbon or stabilised austeno-ferritic steel, for example an AISI 316L, is particularly appropriate in its corrosion resistance, weldability and suitability for shaping as a container. The metal or alloy for the container can also be selected by reference to the metal or alloy used in the structure of the control arrangement, according to the fixing method envisaged for the absorbing element according to the invention. It will be noted that the nature of the container and its contents make it possible to change the shape of the absorbing element formed by the filled and closed container, by moderate cold shaping or warm shaping at less than 250.degree. C. This may e.g. lengthen the container by less than 30% or change its width so that it can be fixed on the control arrangement. The second subject of the invention is the metal, neutron absorbing element obtained; it is filled with compacted metal products comprising at least 25% of electrolytic Hf crystals of easily recognised shapes. The local hafnium content may vary in steps along the element; alternatively it may vary continuously from one end to the other, typically by at least 10 relative percent. In addition to the hafnium crystals and possibly chips, and e.g. as a means of adjusting the weight, the element may also contain at least 20% of crystals or chips of Zr or alloy and/or Ti or alloy. A portion of the Hf, Ti and/or Zr elements may be in sponge form. ADVANTAGES OF INVENTION There are many:
051679116	claims	1. A fuel assembly comprising a plurality of fuel rods in which nuclear fuel material is contained hermetically, a lower tie plate, which holds a lower end of the fuel rods and has a coolant flow path formed inside for leading the coolant to a gap between said fuel rods, and a channel box which encloses a bundle of said fuel rods: characterized in a means of resistance, of which pressure loss coefficient is dependent on flow velocity of the passing coolant, installed in a through hole which is provided at a side wall of the lower tie plate to lead a portion of coolant to outside of said fuel assembly from the coolant flow path in the lower tie plate without supplying the portion of coolant to the gap between said fuel rods by connecting to the lower tie plate. said means of resistance have a plurality of coolant flow paths in which a throat portion is formed respectively, and cross sectional area of each of the coolant flow paths increases continuously from the throat portion toward both of upper stream side and down stream side, and encountered side walls of the coolant flow path are formed with continuous smooth planes from the upper stream side to the down stream side of the throat portion. a plurality of the coolant flow paths are formed between the adjacent resistant members mutually, and the encountered side walls of the coolant flow path are a surface of the resistant members. the resistant members are round rods. the side wall of the lower tie plate has four side planes, and said means of resistance are installed at two side planes, which are adjacent to the same corner portion, out of the four side planes. the side wall of the lower tie plate has four side planes, and said means of resistance are installed at two side planes, which are adjacent to the same corner portion, out of the four side planes, while said means of resistance is not installed in the through hole at each of other two side planes. a fuel supporting portion to support lower end of a plurality of fuel rods, and a cylindrical side wall portion, in which a coolant flow path is formed, connecting to the fuel supporting portion: characterized in a means of resistance, of which pressure loss coefficient is dependent on velocity of passing coolant, installed in a through hole, which is provided at the side wall, to lead a portion of coolant from the coolant flow path to outside of the lower tie plate by connecting to the side wall. said means of resistance have a plurality of coolant flow paths in each of which a throat portion is formed, and cross sectional area of each of the coolant flow paths increases continuously from the throat portion toward both of upper stream side and down stream side, and encountered side walls of the coolant flow path are formed with continuous smooth planes from the upper stream side to the down stream side of the throat portion. a plurality of fuel assemblies each of which comprises a plurality of fuel rods which contain nuclear fuel material inside hermetically, a lower tie plate holding a lower end of the fuel rods, in which a coolant flow path to lead coolant to a gap between the fuel rods is formed inside, and a channel box which encloses a bundle of the fuel rods, wherein the fuel assemblies are arranged to form a gap region to flow the leak current between each of adjacent fuel assemblies, characterized in a means of resistance, in which coolant flow from the lower tie plate to the gap region flows through inside and of which pressure loss coefficient is dependent on velocity of passing coolant, installed at the side wall of the lower tie plate. said means of resistance have a plurality of coolant flow paths in which a throat portion is formed, and cross sectional area of each of the coolant flow paths increases continuously from the throat portion toward both of upper stream side and down stream side, and encountered side walls of the coolant flow path are formed with continuous smooth planes from the upper stream side to the down stream side of the throat portion. said means of resistance comprises a plurality of resistant members, and a plurality of the coolant flow paths are formed between the adjacent resistant members mutually, and the encountered side walls of the coolant flow path are a surface of the resistant members. said gap region includes the first gap region and the second gap region which locates at a cross point with the first gap region, the second gap region being wider than the first gap region, and each of the fuel assemblies are arranged so as to touch a portion of the side plane to the first gap region and to touch the rest portion of the side plane to the second gap region, and a through hole which leads coolant from inside of the lower tie plate to the first gap region is provided at the side plane of the lower tie plate which faces to the first gap region, and said means of resistance is installed at the side plane of the lower tie plate which faces to the second gap region. a reactor vessel, a plurality of fuel assemblies which are loaded in a reactor core in the reactor vessel, and a reactor core support plate to support the fuel assembly, characterized in a means of resistance, in which coolant flow from the lower portion than the reactor core support plate to the gap region flows through inside and of which pressure loss coefficient is dependent on velocity of passing coolant, installed at the reactor core support plate. said means of resistance have a plurality of coolant flow paths in which a throat portion is formed, and cross sectional area of each of the coolant flow paths increases continuously from the throat portion toward both of upper stream side and down stream side, and encountered side wall of the coolant flow path are formed with continuous smooth planes from the upper stream side to the down stream side of the throat portion. said means of resistance comprises a plurality of resistant members, and a plurality of the coolant flow paths are formed between the adjacent resistant members mutually, and the encountered side walls of the coolant flow path are surface of the resistant members. 2. A fuel assembly as claimed in claim 1, wherein 3. A fuel assembly as claimed in claim 2, wherein said means of resistance comprises a plurality of resistant members, and 4. A fuel assembly as claimed in claim 3, wherein 5. A fuel assembly as claimed in claim 1, wherein 6. A fuel assembly as claimed in claim 1, wherein 7. A lower tie plate comprising 8. A lower tie plate as claimed in claim 7, wherein 9. A reactor core of a boiling water reactor comprising 10. A reactor core of a boiling water reactor as claimed in claim 9, wherein 11. A reactor core of a boiling water reactor as claimed in claim 10, wherein 12. A reactor core of a boiling water reactor as claimed in claim 9, wherein 13. A nuclear reactor comprising 14. A nuclear reactor as claimed in claim 13, wherein 15. A nuclear reactor as claimed in claim 14, wherein
	description	The present application is a divisional of U.S. application Ser. No. 10/842,463, filed May 11, 2004, the disclosure of which is herewith incorporated by reference in its entirety. 1. Field of the Invention The present invention relates to a particle beam treatment system, and more particularly to a particle beam irradiation apparatus for treating an affected part by irradiating it with charged particle beams comprising proton ions, carbon ions, or the like, and a treatment planning unit using this particle beam irradiation apparatus, and a particle beam irradiation method. 2. Description of the Related Art A treatment method for treating a patient with cancer or the like by irradiating the affected part of the patient with charged particle beams such as proton beams is known. The treatment system used for this treatment includes a charged particle beam generating unit, beam transport system, and treatment room. The charged particle beam accelerated by the accelerator of the charged particle beam generating unit reaches the beam delivery apparatus beam delivery apparatus in the treatment room through the beam transport system, and after being scanned by scanning electromagnets provided in the beam delivery apparatus beam delivery apparatus, the charged particle beam is applied from a nozzle to the affected part of the patient. A treatment method using such a treatment system is known that includes the steps of: stopping the output of the charged particle beam from the beam delivery apparatus; and in a state where the output of the charged particle beam is stopped, controlling the scanning electromagnets to change the irradiation position (spot) of the charged particle beam (so-called “scanning”) and to start the output of the charged particle beam from the beam delivery apparatus after the aforementioned change (see, for example, European Patent Application No. 0779081A2 [FIG. 1 and the like]). In the above-described conventional particle beam treatment system, in order to reduce to a minimum the exposure of normal tissue to radiation and perform a proper treatment with neither too much nor too little irradiation, the beam delivery apparatus has an irradiation dose monitor and/or beam position monitor for estimating the irradiation dose distribution, located at the downstream side of the electromagnets and immediately in front of a patient to be irradiated. In many cases, this monitor is of a type that accumulates charges ionized by the passage of beams in a capacitor, and that reads the voltage induced by the capacitor after spot irradiation. The capacity of this capacitor is determined so as to permit the amount of ionized charges by the spot subjected to a largest irradiation dose. For the above-described capacitor, as the capacity decreases, the output voltage increases, thereby enhancing the resolution. Conversely, as the capacitor increases, the resolution decreases. Such being the situation, if the difference in irradiation dose between the spot subjected to the largest irradiation dose and that subjected to the smallest irradiation dose can be reduced, the capacity of the capacitor could be correspondingly reduced to enhance the resolution. This would effect the possibility of detecting more correctly an actual irradiation dose. However, the aforesaid conventional art does not particularly give consideration to the above-described reduction of the difference in irradiation dose, thus leaving room for improvement in the detection accuracy with respect to the actual irradiation dose. Meanwhile, when performing irradiation to each spot, a target irradiation dose is set on a spot-by-spot basis. Once an integrated value of irradiation dose detected by the irradiation dose monitor has reached the target value, a beam stop command is outputted to the accelerator, and in response to it, the accelerator stops the output of a charged particle beam. With typical accelerator such as a slow cycling synchrotron or a cyclotron, even if the beam stop command is inputted as described above, strictly speaking, it is not impossible that some amount of response delay occurs rather than the output of the charged particle beam immediately stops. In such a case, even after the aforementioned target value was reached, the charged particle beam continues to be applied to the pertinent spot for the time period during the response delay time. This leaves room for improvement in the control accuracy with respect to the irradiation dose of the charged particle beam. Since the irradiation dose monitor is an machine, it is difficult to perfectly eliminate the possibility that the irradiation dose monitor causes a malfunction or failure. Also, since the target irradiation dose for each spot is usually a value transmitted from a data base or a value calculated based on the transmitted value, it is not impossible that an improper value is inputted at the stage of the transmission or the calculation. However, the above-described conventional art does not particularly give consideration to such a monitor abnormality or an input error. This leaves room for improvement in the prevention of excessive irradiation of charged particle beams due to the aforementioned monitor abnormality or input error. Furthermore, when performing irradiation to each spot, a target irradiation dose is set on a spot-by-spot basis. Once the integrated value of irradiation dose by the irradiation dose monitor has reached the target value, a beam stop command is outputted to the accelerator, and in response to it, the accelerator stops the output of the charged particle beam. Regarding such a beam stopping function, it is not impossible that equipment associated with this function causes a malfunction or failure, as well. However, the above-described conventional art does not particularly take a malfunction of such a beam stopping function into consideration. This leaves room for improvement in the prevention of excessive irradiation of charged particle beams due to the above-described malfunction or failure of the beam stopping function. Accordingly, it is a first object of the present invention to provide a particle beam irradiation apparatus, treatment planning unit using this, and particle beam irradiation method that are capable of improving the detection accuracy with respect to an actual irradiation dose during treatment using charged particle beams. It is a second object of the present invention to provide a particle beam irradiation apparatus and particle beam irradiation method that are capable of enhancing the control accuracy with respect to the irradiation dose of charged particle beams. It is a third object of the present invention to provide a particle beam irradiation apparatus and particle beam irradiation method that are capable of reliably preventing the excessive irradiation of charged particle beams due to a monitor abnormality, input error, or the like. It is a fourth object of the present invention to provide a particle beam irradiation apparatus and particle beam irradiation method that are capable of reliably preventing the excessive irradiation of charged particle beams due to a malfunction or the like of a beam stopping function. It is a fifth object of the present invention to provide a particle beam irradiation apparatus and particle beam irradiation method that are capable of reducing the treatment time when performing irradiation of charged particle beams for each of a plurality of layer regions in a target. To achieve the above-described first object, the present invention provides a particle beam irradiation apparatus that includes an accelerator for extracting a charged particle beam; an beam delivery apparatus having a charged particle beam scanning unit and outputting the charged particle beam extacted from the accelerator; and a controller that stops the output of the charged particle beam from the beam delivery apparatus, and that, in a state where the output of the charged particle beam is stopped, controls the charged particle beam scanning unit to change the irradiation position of the charged particle beam, start the output of the charged particle beam from the beam delivery apparatus after the above-described change, and perform irradiations of the charged particle beam with respect to at least one irradiation position a plurality of times based on treatment planning information. In the present invention, the controller controls the charged particle beam scanning unit to perform irradiations of the charged particle beam with respect to at least one irradiation position a plurality of times. By virtue of this feature, regarding an irradiation position subjected to too much irradiation dose by one-time ion irradiation, it is possible to perform a divided irradiation so as to reduce an irradiation dose for each radiation. This allows the difference in irradiation dose between the irradiation position subjected to the largest dose and that subjected to the smallest dose to be reduced, thereby leveling off irradiation dose. As a result, the capacity of the capacitor of a position monitor can be correspondingly reduced to enhance the resolution, and therefore, the actual irradiation dose during treatment can be detected further correctly. To achieve the above-described second object, the present invention provides a particle beam irradiation apparatus including a controller that controls the irradiation of the charged particle beam to the irradiation position so that the irradiation dose applied to the irradiation position becomes a set irradiation dose, in a state where the irradiation dose applied to the irradiation position during the time period from the outputting of a beam extraction stop signal at the time when the irradiation dose detected by the irradiation dose detector reaches the set irradiation dose up to the extraction stop of the charged particle beam from the accelerator, is added. Even if the beam stop command is inputted, strictly speaking, it is not impossible that some amount of response delay occurs rather than the extraction of the charged particle beam from the accelerator immediately stops. In the present invention, the controller can perform an irradiation of the charged particle beam to an irradiation position so that the irradiation dose at the irradiation position becomes a set irradiation dose, in a state where the irradiation dose applied to the irradiation position during the time period from the outputting of a beam extraction stop signal up to the extraction stop of the charged particle beam from the accelerator, is added. This allows the irradiation dose at each irradiation position to become substantially the set irradiation dose, thereby enabling the charged particle beam to be applied to each irradiation position with high accuracy. To control the irradiation dose, even if there is time delay between the outputting of the beam extraction stop signal and the extraction stop of the charged particle beam from the accelerator, the irradiation dose at each irradiation position can be made to be a set irradiation dose, allowing for the irradiation dose for the time period during the time delay. This makes it possible to irradiate, with high degree of accuracy, any irradiation position with charged particle beams of a dose substantially equal to the set irradiation dose. To achieve the above-described third object, the present invention provides a particle beam irradiation apparatus including a controller that stops the output of the charged particle beam from the beam delivery apparatus, that, in a state where the output of the charged particle beam is stopped, controls the charged particle beam scanning unit to change the irradiation position of the charged particle beam and to start the output of the charged particle beam from the beam delivery apparatus after the above-described change, and that determines the occurrence of an abnormality based on an elapsed time from the irradiation start of the charged particle beam with respect to one irradiation position. In the present invention, the controller determines the occurrence of an abnormality based on an elapsed time from the irradiation start of the charged particle beam with respect to one irradiation position. Therefore, even if the irradiation time of the charged particle beam is likely to abnormally elongate due to the occurrence of a malfunction or failure of the irradiation dose detector, or an improper input value, the irradiation of the charged particle beam can be stopped after a certain time has elapsed. This reliably prevents an excessive irradiation to a target, and further improves the safety. To achieve the above-described fourth object, the present invention provides a particle beam irradiation apparatus including a controller that stops the output of the charged particle beam from the beam delivery apparatus, that, in a state where the output of the charged particle beam is stopped, controls the charged particle beam scanning unit to change the irradiation position of the charged particle beam and to start the output of the charged particle beam from the beam delivery apparatus after the above-described change, and that determines the occurrence of an abnormality using the irradiation dose detected by the irradiation detector and a second set irradiation dose larger than respective first set irradiation doses with respect to a plurality of irradiation positions in the target. In the present invention, the controller determines the occurrence of an abnormality, using the irradiation dose detected by the irradiation dose detector and the second set dose larger than respective first set doses with respect to a plurality of irradiation positions in the target. Therefore, even if, due to a malfunction or the like of the beam stopping function, the charged particle beam does not readily stop and the irradiation dose is likely to abnormally increase, the irradiation can be stopped at a certain upper limit irradiation dose, thereby reliably preventing an excessive irradiation to the target. This further enhances the safety. To achieve the above-described fifth object, the present invention provides a particle beam irradiation apparatus including a controller that performs control to decelerate the charged particle beam in the accelerator when the irradiation of the charged particle beam with respect to one of a plurality of layer regions that are different in irradiation energy from each other in a target to be irradiated with the charged particle beam from the beam delivery apparatus, has been completed. In the spot scanning irradiation according to the present invention, as the size of a target changes, the number of spots in a layer changes, and consequently, the time required to complete an irradiation to all spots in the layer changes. Regarding the allowable extraction period of the synchrotron, if it is set to be long with a large target assumed, the irradiations to all layers takes much time to complete, thereby elongating the treatment time for a patient. In the present invention, after the irradiation in a layer region has been completed, the charged particle beam in the accelerator is decelerated, and therefore, the allowable extraction period of the charged particle beams in the accelerator can be earlier terminated. As a result, even when it is necessary to irradiate a plurality of layer regions with charged particle beams, the treatment time can be made short. Hereinafter, a particle beam treatment system having a particle beam irradiation apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, a proton beam treatment system, which is a particle beam treatment system according to this embodiment, includes a charged particle beam generating unit 1 and a beam transport system 4 connected to the downstream side of the charged particle beam generating unit 1. The charged particle beam generating unit 1 comprises an ion source (not shown), a pre-stage charged particle beam generating unit (linear accelerator (linac)) 11, and a synchrotron (accelerator) 12. The synchrotron 12 includes a high-frequency applying unit 9 and acceleration unit 10. The high-frequency applying unit 9 is constructed by connecting a high-frequency applying electrode 93 disposed on the circulating orbit of the synchrotron 12 and a high-frequency power source 91 by an open/close switch 92. The acceleration unit (second element; charged particle beam energy changing unit) 10 comprises a high-frequency accelerating cavity (not shown) disposed on the circulating orbit thereof, and a high-frequency power source (not shown) for applying a high-frequency power to the high-frequency accelerating cavity. Ions generated in the ion source, e.g., hydrogen ions (protons) or carbon ions, are accelerated by the pre-stage charged particle beam generating unit (e.g., linear charged particle beam generating unit) 11. The ion beam (proton beam) emitted from the pre-stage charged particle beam generating unit 11 is injected into the synchrotron 12. In the synchrotron 12, this ion beam, which is a charged particle beam, is given energy and accelerated by the high-frequency power that is applied to the ion beam through the high-frequency accelerating cavity from the high-frequency power source 91. After the energy of the ion beam circulating through the synchrotron 12 has been increased up to a set energy (e.g., 100 to 200 MeV), a high frequency for emission from the high-frequency power source 91 reaches the high-frequency applying electrode 93 through the open/close switch 92 in a closed state, and is applied to the ion beam from the high-frequency applying electrode 93. The application of this high-frequency causes the ion beam that is circulating within a stability limit to shift to the outside of the stability limit, thereby extracting the ion beam from the synchrotron 12 through an extraction deflector 8. At the extraction of the ion beam, currents supplied to quadrupole electromagnets 13 and bending electromagnets 14 are held at set values, and the stability limit is held substantially constant. Opening the open/close switch 92 to stop the application of the high frequency power to the high-frequency applying electrode 93, stops the extraction of the ion beam from the synchrotron 12. The ion beam extracted from the synchrotron 12 is transported to the downstream side of the beam transport system 4. The beam transport system 4 includes quadrupole electromagnets 18 and a deflection electromagnet 17; and quadrupole electromagnets 21 and 22, and deflection electromagnets 23 and 24 that are sequentially arranged on a beam path 62 communicating with the beam delivery apparatus 15 provided in a treatment room from the upstream side toward the beam traveling direction. Here, the aforementioned electromagnets each constitute a first element. The ion beam introduced into the beam transport system 4 is transported to the beam delivery apparatus 15 through the beam path 62. The treatment room has the beam delivery apparatus 15 affixed to a rotating gantry (not shown) provided therein. A beam transport unit having an inverse U-shape and including a part of the beam path 62 in the beam transport system 4, and the beam delivery apparatus 15 are disposed in a rotating drum (not shown) with a substantially cylindrical shape, of the rotating gantry (not shown). The rotating drum is configured so as to be rotated by a motor (not shown). A treatment gauge (not shown) is formed in the rotating drum. The beam delivery apparatus 15 has a casing (not shown) affixed to the rotating drum and connected to the aforementioned inverse U-shaped beam transport unit. Scanning electromagnets 5A and 5B for scanning a beam, a dose monitor 6A, a position monitor 6B and the like are disposed in the casing. The scanning electromagnets 5A and 5B are used for deflecting a beam, for example, in directions orthogonally intersecting each other (an X-direction and Y-direction) on a plane perpendicular to the beam axis, and moving an irradiation position in the X-direction and Y-direction. Before an ion beam is applied from the beam delivery apparatus 15, a bed 29 for treatment is moved by a bed drive unit (not shown) and inserted into the aforementioned treatment gauge, and the positioning of the bed 29 for irradiation with respect to the beam delivery apparatus 15 is performed. The rotating drum is rotated by controlling the rotation of the motor by a gantry controller (not shown) so that the beam axis of the beam delivery apparatus 15 turns toward the affected part of a patient 30. The ion beam introduced into the beam delivery apparatus 15 from the inverse U-shaped beam transport unit through the beam path 62 is caused to sequentially scan irradiation positions by the scanning electromagnets (charged particle beam scanning unit) 5A and 5B, and applied to the affected part (e.g., occurrence region of cancer or tumor) of the patient 30. This ion beam releases its energy in the affected part, and forms a high dose region there. The scanning electromagnets 5A and 5B in the beam delivery apparatus 15 are controlled by a scanning controller 41 disposed, for example, in the gantry chamber in a treatment unit. A control system included in the proton beam treatment system according to this embodiment will be described with reference to FIG. 1. This control system 90 comprises a central control unit 100, storage unit 110 storing treatment planning database, scanning controller 41, and accelerator and transport system controller 40 (hereinafter referred to as an “accelerator controller”). Furthermore, the proton beam treatment system according to this embodiment has a treatment planning unit 140. While the aforementioned treatment planning data (patient data) stored in the storage unit 110 on a patient-by-patient basis is not particularly shown, the treatment planning data includes data such as patient ID numbers, irradiation doses (through a treatment and/or per fraction), irradiation energy, irradiation directions, irradiation positions, and others. The central control unit 100 has a CPU and memory 103. The CPU 100 reads the above-described treatment planning data concerning patients to be treated from the storage unit 110, using the inputted patient identification information. The control pattern with respect to the exciting power supply to each of the above-described electromagnets is determined by the value of irradiation energy out of the treatment planning data on a patient-by-patient basis. The memory 103 stores a power supply control table in advance. Specifically, for example, in accordance with various values of irradiation energy (70, 80, 90, . . . [MeV]), values of supply exciting power or their patterns with respect to a quadrupole electromagnet 13 and deflection electromagnet 14 in the charged particle beam generating unit 1 including the synchrotron 12; and the quadrupole electromagnets 18, deflection electromagnet 17, the quadrupole electromagnets 21 and 22, and deflection electromagnets 23 and 24 in the beam transport system 4, are preset. Also, using the above-described treatment planning data and power supply control table, the CPU 101 as a control information producing unit, produces control command data (control command information) for controlling the electromagnets provided on the charged particle beam generating unit 1 and the beam paths, regarding a patient to be treated. Then, the CPU 101 outputs the control command data produced in this manner to the scanning controller 41 and accelerator controller 40. One of the features of this embodiment lies in that, based on the treatment planning data created by the treatment planning unit 140, the central control unit 100, scanning controller 41, and accelerator controller 40 performs control operations in close liaison with one another as follows: (1) they stops the output of an ion beam from the beam delivery apparatus 150, and in a state where the output of the ion beam is stopped, they control the scanning electromagnets 5A and 5B to change the irradiation position (spot) of the ion beam and to start the output of the ion beam from the beam delivery apparatus 15 after the aforementioned change (so-called “scanning”); (2) in order to reduce variations in irradiation dose at a spot, they control the synchrotron 12 and beam delivery apparatus 15 to divide an irradiation of an ion beam with respect to at least one identical irradiation position (spot) at which the dose otherwise would exceed a division reference irradiation dose (discussed below), into a plurality of times of irradiations. Hereinafter, detailed explanation thereof will be provided with reference to FIGS. 2 to 18. First, the creation of a treatment plan by the treatment planning unit 140 is explained. The treatment planning unit 140 is, for example, constituted of a personal computer. While its illustration is omitted, the treatment planning unit 140 includes an input unit (e.g., keyboard) which can be operated by an operator and with which the operator can input; a computing unit (e.g., CPU) that performs a predetermined arithmetic processing based on an input result by the aforementioned input means and operation means; an input/output interface that performs the input/output of information, such as the input of external image data and the output of treatment planning data created by this computing unit; and a display unit. FIG. 2 is a flowchart showing arithmetic processing steps executed by the aforementioned computing means of the treatment planning unit 140. In FIG. 2, if an operator (usually a doctor or medical staff) inputs identification information (e.g., a name, ID number) about a patient to be treated via the input unit, the determination in step 101 is satisfied, and the processing advances to step 102, where a patient image file (file previously taken by extra imaging means such as CT scanner and stored in the database of the storage unit 110) of a pertinent patient is read. Here, the patient image file is tomography image information. Thereafter, in step 103, the read patient image file is outputted on a display unit as display signals, and a corresponding display is made. If the operator performs specification by filling in a target region to be irradiated with an ion beam via the input unit while watching the displayed patient image file, the determination in step 104 is satisfied, and the processing advances to step 105, where recognition processing is three-dimensionally performed regarding the filled-in region. In this situation, if the operator inputs a target dose to be applied to a corresponding target region via the input unit, the determination in step 106 is satisfied. Furthermore, if the operator inputs an irradiation direction of the ion beam, the determination in step 107 is satisfied, and the processing advances to step 108. Moreover, if the operator inputs, via the input unit, a division reference irradiation dose, which is a reference irradiation dose such that a divided irradiation is to be performed if an irradiation dose per unit spot exceeds this reference irradiation dose, the determination in step 108 is satisfied, and the processing advances to step 110. Here, description will be made of the relationship between the depth of a target and energy of an ion beam. The target is a region, including an affected part, to be irradiated with an ion beam, and is somewhat larger than the affected part. FIG. 3 shows the relationship between the depth of the target in a body and the irradiation dose of ion beam. The peak of dose as shown in FIG. 3 is referred to as a “Bragg peak”. The application of an ion beam to the target is performed in the position of the Bragg peak. The position of Bragg peak varies depending on the energy of ion beam. Therefore, dividing the target into a plurality of layers (slices) in the depth direction (traveling direction of ion beam in the body), and changing the energy of ion beam to the energy in correspondence with a depth (a layer) allows the ion beam to be irradiated throughout the entire target (target region) having a thickness in the depth direction as uniformly as possible. From this point of view, in step 110, the number of layers in the target region to be divided in the depth direction is determined. One possible determination method for determining the number of layers is to set the thickness of a layer, and to automatically determine the number of layers in accordance with the aforementioned thickness and a thickness of the target region in the depth direction. The thickness of layer may be a fixed value irrespective of the size of the target region, or alternatively may be automatically determined appropriately to the maximum depth of the target region. Still alternatively, the thickness of layer may be automatically determined in accordance with the spread of the energy of ion beam, or simply, the number itself of layers may be inputted by the operator via the input unit instead of determining the thickness of layer. FIG. 4 is a diagram showing an example of layers determined in the above-described manner. In this example, the number of layers is four: layers 1, 2, 3, and 4 in this order from the lowest layer. The layers 1 and 2 each have a spread of 10 cm in the X-direction and a spread of 10 cm in the Y-direction. The layers 3 and 4 each have a spread of 20 cm in the X-direction and a spread of 10 cm in the Y-direction. FIG. 3 represents an example of dose distribution in the depth direction as viewed from the line A–A′ in FIG. 4. On the other hand, FIG. 5 represents an example of dose distribution in the depth direction as viewed from the line B–B′ in FIG. 4. After the number of layers has been determined in this manner, the proceeding advances to step 111, where the number (and positions) of spots that divide each layer (target cross section) in the direction perpendicular to the depth direction, is determined. On this determination, like the above-described layers, one spot diameter is set, and the number of spots is automatically determined in accordance with the size of the spot and the size of the pertinent layer. The spot diameter may be a fixed value, or alternatively may be automatically determined appropriately to the target cross section. Still alternatively, the spot diameter may be automatically determined appropriately to the size of ion beam (i.e., the beam diameter), or simply, spot positions themselves or the distances themselves between spot positions may be inputted by the operator via the input unit instead of determining the spot size. After step 111 has been completed, the processing advances to step 120, where the irradiation dose at each spot in all layers is determined. FIG. 6 is a flowchart showing detailed procedure in the aforementioned step 120. As described above, basically, the application of an ion beam to the target is performed in the position of the Bragg peak, and it is desirable that the ion beam be irradiated throughout the entire target (target region) having a thickness in the depth direction as uniformly as possible. On the determination in the irradiation dose at each spot, therefore, it is necessary to ultimately secure a uniform irradiation throughout the entire target region. In light of the above, in steps 121–123, firstly initial condition are determined in step 121. Specifically, by the accumulation of past calculation examples, the utilization of simple models or the like, the irradiation doses with respect to all spots on layer-by-layer basis that are deemed to correspond to the target doses, the irradiation direction of ion beam, and the numbers of layers that were inputted or determined in steps 106 to 111, are determined as temporary values. Thereafter, the processing advances to step 122, where, using a known method, a simulation calculation is performed as to how the actual dose distribution in the entire target region becomes, if an irradiation is performed using the values of irradiation doses with respect to all spots, the doses having been determined in step 121. Then, in step 123, it is determined whether the aforementioned calculated dose distribution is uniform throughout substantially the entire region of the target, namely, whether variations remain within a given limit. If not so, the processing advances to step 124, where a predetermined correction is made. This correction may be such that the irradiation doses at spots somewhat outstandingly higher/lower than an average dose value are automatically lowered/raised with a correction width, and that the correction width may be set by a manual operation. After such a correction, the processing returns to step 121 and the same procedure is repeated. Therefore, the correction in step 124 and the dose distribution calculation in step 122 are performed until the irradiation dose distribution becomes uniform to a certain extent. Thus, ultimately, the irradiation doses with respect all spots that allow substantially uniform dose distribution to be implemented in the entire target region, are determined. Thereafter, the processing advances to step 130. In this stage, although the irradiation doses to all spots have each been determined, each of all these spots is set to be irradiated with a pertinent allocated irradiation dose at one time. In step 130, if there are any irradiation doses exceeding the division reference irradiation dose inputted before in step 108, out of the irradiation doses determined with respect to all spots, the ion beam irradiation to each of such spots is not performed at one time, but is performed in the form of irradiations divided into a plurality of times (at least two times). Here, we assume the number N of irradiations to be a minimum natural number n that satisfies the relationship: n≧R/Rs, where R and Rs, respectively, denote the irradiation dose and the division reference irradiation dose at a pertinent spot. In other words, the number N of irradiations is assumed to be a value obtained by rounding-up the decimal places of R divided by Rs. Therefore, if N=1, then R≦Rs, and hence a plurality of times of divided irradiations are not performed (namely, the irradiation is performed at one time). If N=2, then R>Rs, and hence it is planned that irradiations divided into a plurality of times are performed. FIG. 7 shows an example (layers 1 to 4) of divided irradiations as described above with reference to FIGS. 4 and 5. In this example, the division reference dose is assumed to be 10 (a relative value without unit; the same shall apply hereinafter). As shown in FIG. 7, regarding the layer 1, before division processing (i.e., when the irradiation is performed at one time), the irradiation dose at each spot was 70. Such being the situation, it is planned that irradiations divided into seven times are performed, the irradiation dose for each divided irradiation being 10. Likewise, regarding the layers 2, 3, and 4, the irradiation doses at each spot before division processing were 25, 17.9, and 12.6, respectively. Accordingly, in the layers 2, 3, and 4, respectively, it is planned that irradiations divided into three, two, and two times were performed, the irradiation dose for each divided irradiation being 8.3, 9, and 6.3, respectively. More specific explanations of the above will be provided with reference to FIG. 8. As described above, regarding the layer 1 (the region corresponding to the right half of the layer 1 shown in FIG. 8; here, the right-left direction in FIG. 8 corresponds to that in FIG. 4), irradiations divided into seven times are performed, and it is planned that an irradiation with irradiation dose of 10 is repeated in each of the first-time to seventh-time irradiations. Regarding the layer 2 (the region corresponding to the right half of the layer 2 shown in FIG. 8), it is planned that an irradiation with irradiation dose of 8.3 is repeated three times. Regarding the layer 3, with respect to the region shown in the right half in FIG. 8, it is planned that an irradiation with irradiation dose of 9.0 is repeated two times, while with respect to the region shown in the left half in FIG. 8, it is planned that an irradiation with irradiation dose of 10 is repeated seven times. Regarding the layer 4, with respect to the region shown in the right half in FIG. 8, it is planned that an irradiation with an irradiation dose of 6.3 is repeated two times, while with respect to the region shown in the left half in FIG. 8, it is planned that an irradiation with irradiation dose of 8.3 is repeated three times. After step 130 has been completed, the processing advances to step 131, where the order of the irradiation with respect to spots in each of the layers is determined. Specifically, in the proton beam treatment system according to this embodiment, as described above, the output of an ion beam from the beam delivery apparatus 15 is stopped, and in the state the output of the ion beam is stopped, a scanning irradiation to change the irradiation position (spot) is performed. In step 131, it is determined how the ion beam is to be moved with respect to each spot in the scanning irradiation. Here, the ion beam to be applied to the target is narrow, and its diameter is a little larger than that of the spot diameter. FIGS. 9 and 10 each show an example of the setting of the order of spot irradiation. This order of spot irradiation order corresponds to the example described with reference to FIGS. 4, 3, 5, 7, and 8. FIG. 9 shows the setting of irradiation orders in both the layers 1 and 2 in a combined and simplified manner. As shown in FIG. 9, for each of the layers 1 and 2, 100 spots in total are set in a lattice shape of 10 rows and 10 columns. The application of an ion beam to the target (the square region in FIG. 9) of the layers 1 and 2 is performed, for example, in a manner as follows: an irradiation is performed on a spot-by-spot basis from one end (the left lower corner in FIG. 9) in the spot row (including ten spots) situated at one end of these layers toward the other end (the right lower corner in FIG. 9) of this spot row, i.e., from the left toward the right in FIG. 9. After the irradiation to the other end has been completed, the irradiation is performed on a spot-by-spot basis from one end (the right lower end in FIG. 9) in another spot row adjacent to the aforementioned spot row toward the other end (the left end in FIG. 9) of the other row, i.e., from the right toward the left in FIG. 9. After the irradiation to the other end in the other row has been completed, the ion beam moves to a next other spot row adjacent. In this manner, in this embodiment, it is planned that, in the horizontal surface of each of the layers 1 and 2, the ion beam is moved by inversing its traveling direction (i.e., by causing the ion beam to meander) for each of the adjacent spot rows, until the ion beam reaches the last spot (the left upper corner in FIG. 9) in the last spot row, thus completing an irradiation operation (one of a plurality of times of scanning operations) with respect to the layers 1 and 2. Regarding the layer 1, the irradiation dose at each of the total of 100 spots is 10 for each divided irradiation, and as described above, one meandering scanning operation for each of the spot rows is repeated seven times. From the first-time through seventh-time scanning operations, the same irradiation order setting may be applied. Alternatively, however, in order to speed up an irradiation, for example, the second-time scanning may be performed from the left upper corner toward the left lower corner in FIG. 9 along the reverse route (the same shall apply hereinafter). Also, regarding the layer 2, as described with reference to FIG. 8, it is planned that the irradiation dose at each of the total of 100 spots is 8.3 for each divided irradiation, and it is planned that one meandering scanning operation as described above is repeated three times. FIG. 10 shows the setting of irradiation orders in both the layers 3 and 4 in a combined and simplified manner, although this is an example of the first-time and second-time scanning operations. As shown in FIG. 10, for each of the layers 1 and 2, 200 spots in total are set in a lattice shape of 10 rows and 20 columns. The application of an ion beam to the target (the rectangular region in FIG. 9) of the layers 3 and 4 is performed, as is the case with the layers 1 and 2, for example, in a manner as follows: an irradiation is performed on a spot-by-spot basis from one end (the left lower corner in FIG. 10) in the spot row (including twenty spots) situated at one end of these layers toward another end (the right lower corner in FIG. 10) in this spot row. After the irradiation to the other end has been completed, the irradiation is performed from one end (the right lower end in FIG. 10) in another spot row adjacent to the aforementioned spot row toward the other end (the left end in FIG. 10) of the other row. After the irradiation to the other end in the other row has been completed, the ion beam moves to a next other spot row adjacent. In this way, in this embodiment, also for each of the layers 3 and 4, it is planned that, in the horizontal surface, the ion beam is moved by causing the ion beam to meander for each of the adjacent spot rows, and that one irradiation operation (one of two scanning operations) with respect to the layers 3 and 4 is completed. In the layer 3, as shown in FIG. 8, the irradiation dose for each divided irradiation with respect to each of the total of 200 spots is 9 for each of the 100 spots in the right half region in FIG. 10, and 10 for each of the 100 spots in the left half region in FIG. 10. It is planned, therefore, that one scanning operation that meanders for each of the spot rows while changing an irradiation dose at a midpoint in a spot row, is repeated two times. Likewise, in the layer 4, the irradiation dose for each divided irradiation with respect of each of the total of 200 spots is 6.3 for each of the 100 spots in the right half region in FIG. 10, and 8.3 for each of the 100 spots in the right half region in FIG. 10. It is planned, therefore, that one scanning operation that meanders for each of the spot rows while changing an irradiation dose at a midpoint in a spot row, is repeated two times. Regarding each of the layers 3 and 4, in irradiations at the third time and afterward, the irradiation to the 100 spots in the right half in FIG. 10 do not need, and the irradiation to the 100 spots in the left half alone is performed (see FIG. 8). Regarding the irradiation order then, although it is not particularly illustrated, for example, performing like the layers 1 and 2 shown in FIG. 9 suffices for the layers 3 and 4. Regarding the layer 3, the irradiation dose with respect of each of its 100 spots is 10 for each divided irradiation, and it is planned that in the left half region alone, for example, one meandering scanning operation is performed five times (in the third-time to seventh-time scanning operations). Likewise, in the layer 4, the irradiation dose with respect of each of its 100 spots is 8.3 for each divided irradiation, and it is planned that in the left half region alone, for example, one meandering scanning operation is performed (in the third-time scanning). After the spot irradiation order has been determined as described above, the processing advances to step 132, where the dose distribution at a target area that is estimated when irradiations are performed with the irradiation dose with respect to all layers and all spots and in the spot irradiation order that were each determined as described above, is calculated using a known method. This simulation uses a method with higher accuracy and requiring a little longer calculation time than a simplified method as shown before in FIG. 6. Hereafter, the processing advances to step 133, where the estimated dose distribution result calculated in step 132 is outputted on the display unit as display signals, together with a planning result. The display then may be, for example, a summary including a dose volume histogram (DVH) or the like. Preferably, a comment about influences on normal organs, and others can be displayed together. If the operator determines that this display is insufficient (improper) upon watching this display, he/she does not input “OK”, and hence, the processing returns to step 107 based on the determination by step 134. Until the determination in step 134 becomes “YES”, the processing of steps 107 to 134 is repeated. If the operator determines that the created treatment planning information is proper, he/she inputs “OK”, thereby satisfying the determination in step 134. Thereafter, the operator performs a registration instruction input (via a button on the screen display or keyboard) to permit the registration in the treatment planning information, thereby satisfying the determination in step 135. Then, in a next step 136, the operator performs registration processing for the treatment planning information at the storage unit 110, thus completing the processing shown in FIG. 2. Next, the central control unit 100 reads the treatment planning information, in which divided irradiations are planned as described above and which has been stored in the storage unit 110, and stores it into the memory 103. The CPU 101 transmits, to the memory 41M of the scanning controller 41, the treatment planning information stored in the memory 103 (i.e., information such as the number of layers, the number of irradiation positions (the numbers of spots), the irradiation order with respect to irradiation positions in each of the layers, a target irradiation dose (set irradiation dose) at each irradiation position, and current values of the scanning electromagnets 5A and 5B with respect to all spots in each of the layers). The scanning controller 41 stores this treatment planning information into the memory 41M. Also, the CPU 101 transmits, to the accelerator controller 40, all data of acceleration parameters of the synchrotron 12 with respect to all layers out of the treatment planning information. The data of acceleration parameters includes the value of an exciting current for each of the electromagnets for the synchrotron 12 and beam transport system, and the value of high-frequency power to be applied to the high-frequency accelerating cavity, which are each determined by the energy of ion beam applied to each of the layers. The data of these acceleration parameters is classified, for example, into a plurality of acceleration patterns in advance. FIG. 11 shows a part of the treatment planning information stored in the memory 41M of the scanning controller 41. The part of the information comprises irradiation parameters, that is, information on the irradiation index number (layer number and irradiation number), information on the X-direction position (X-position) and the Y-direction position (Y-position) of an irradiation position (spot), and information on a target irradiation dose (irradiation dose) for each divided irradiation. Furthermore, the irradiation parameters includes layer change flag information. The information on the irradiation number, for example, “2-2” means a “second-time irradiation in the layer 2, “2-3” means a “third-time irradiation in the layer 2”, and “3-1” means a “first-time irradiation in the layer 3”. The information on a X-direction position and Y-direction position is represented by current values of the scanning electromagnets 5A and 5B for scanning an ion beam to the irradiation position specified by the pertinent X-position and Y-position. Spot numbers j (described later) are given, in the irradiation order, to all divided irradiations with respect to the layer 2, i.e., “2-1” (not shown), “2-2”, and “2-3”. Likewise, spot numbers are given to all divided irradiations with respect to the other layers 1, 3, and 4. Next, with reference to FIG. 12, specific descriptions will be made of respective controls by the scanning controller 41 and the accelerator controller 40 in performing the spot scanning in this embodiment. If an irradiation start instructing unit (not shown) disposed in the treatment room is operated, then in step 201, the accelerator controller 40 correspondingly initializes an operator i denoting a layer number to 1, as well as initializes an operator; denoting a spot number to 1, and outputs signals to that effect. Upon being subjected to the initialization in step 201, the accelerator controller 40 reads and sets the accelerator parameters with respect to the i-th layer (i=1 at this point in time) out of the acceleration parameters of a plurality of patterns stored in the memory, in step 202. Then, in step 203, the accelerator controller 40 outputs it to the synchrotron 12. Also, in step 203, the accelerator controller 40 outputs exiting current information with respect to the electromagnets that is included in the i-th accelerator parameters, to the power source for each of the electromagnets of the synchrotron 12 and beam transport system 5, and controls a pertinent power source so that each of the electromagnets is excited by a predetermined current using this exiting current information. Furthermore, in step 203, the accelerator controller 40 controls the high-frequency power source for applying a high-frequency power to the high-frequency cavity to increase the frequency up to a predetermined value. This allows the energy of an ion beam circulating through the synchrotron 12 to increase up to the energy determined by the treatment plan. Thereafter, the processing advances to step 204, where accelerator controller 40 outputs an extraction preparation command to the scanning controller 41. Upon receipt of the information on initial setting in step 201 and the extraction preparation command in step 204 from the accelerator controller 40, in step 205, the scanning controller 41 reads and sets current value data and irradiation dose data of the j-th spot (j=1 at this point in time) out of the current value data (data shown in the “X-position and Y-position” columns in FIG. 11) and the irradiation dose data (data shown in the “irradiation dose” column in FIG. 11), which are already stored in the memory 41M as described above (see FIG. 13 shown later). Similarly, regarding the aforementioned target count number stored in the memory 41M, the scanning controller 41 reads and sets data of the j-th spot (j=1 at this point in time) as well. Here, the scanning controller 41 controls a pertinent power so that the electromagnets 5A and 5B are excited by the current value of the j-th spot. After the preparation for the irradiation to the pertinent spot has been completed in this manner, the scanning controller 41 outputs a beam extraction start signal in step 300, and controls the high-frequency applying unit 9 to extract an ion beam from the synchrotron. Specifically, the open/close switch 92 is closed by the beam extraction start signal passing through the accelerator controller 40 and a high frequency is applied to the ion beam, whereby the ion beam is extracted. Because the electromagnets 5A and 5B are excited so that the ion beam reaches the first spot position, the ion beam is applied to the first spot in a pertinent layer by the beam delivery apparatus 15. When the irradiation dose at the first spot reaches a pertinent target irradiation dose, the scanning controller 41 outputs a beam extraction stop signal in step 300. The beam extraction stop signal passes through the accelerator controller 40 and opens the open/close switch 92, thereby stopping the extraction of the ion beam. At this point in time, only the first-time irradiation to the first spot in the layer 1 has been completed. Since the determination in step 208 is “No”, the processing advances to step 209, where 1 is added to the spot number j (i.e., the irradiation position is moved to the next spot adjacent). Then, the processing of steps 205, 300, and 208 are repeated. Specifically, until the irradiation to all spots in the layer 1 is completed, the irradiation (scanning irradiation) of ion beam is performed while moving the ion beam to adjacent spots one after another by the scanning electromagnets 5A and 5B and stopping the irradiation during movement. If all divided irradiations to all spots in the layer 1 (seven-time irradiations in the above-described example) have been completed, the determination in step 208 becomes “Yes”. At this time, the scanning controller 41 outputs a layer change command to the CPU of the accelerator controller 40. Upon receipt of the layer change command, the CPU of the accelerator controller 40 adds 1 to the layer number i (i.e., changes the object to be irradiated to the layer 2) in step 213, and outputs a remaining beam deceleration command to the synchrotron 12 in step 214. By the output of the remaining beam deceleration command, the accelerator controller 40 controls the power source for each of the electromagnets in the synchrotron 12 to gradually reduce the exciting current of each of the electromagnets until it becomes the predetermined current such as the current appropriate for the beam injection from the pre-stage accelerator. This decelerates an ion beam circulating through the synchrotron 12. As a result, the time period during which a beam can be extracted varies depending on the number of spots and irradiation dose. At the point in time, since only the irradiation with respect to the layer 1 has been completed, the determination in step 215 becomes “No”. In step 202, the accelerator parameters for the second layer (layer 2) is read from the memory for the accelerator controller 40 and is set. Hereinafter, the processing of steps 203 to 215 is performed with respect to the layer 2. Also, until all divided irradiations to all spots in the layer 4 is completed, the processing of steps 202 to 215 is performed. If the determination in step 215 becomes “Yes” (i.e., if predetermined irradiations to all spots in all layers in the target of a patient 30 have been completed), the CPU of the accelerator controller 40 outputs an irradiation end signal to the CPU 101. As described above, under the acceleration by the synchrotron 12, an ion beam extracted from the synchrotron 12 is transported through the beam transport system. Then, the ion beam is applied to the target of the pertinent patient in an optimum mode as planned by a treatment plan, via the beam delivery apparatus 15 in the treatment room in which the patient to be irradiated is present. At this time, a detection signal of the dose monitor 6A provided in the nozzle of the beam delivery apparatus 15 is inputted to the scanning controller 41. Other features of this embodiment are: by using this detection signal, (1) to clear the integrated value of irradiation doses simultaneously with a beam-off signal; (2) to determine the occurrence of an abnormal operation in accordance with an elapsed time after beam extraction is started; and (3) to determine the occurrence of an abnormal operation based on the comparison between the integrated value of irradiation doses and a predetermined regulated value. More detailed explanations thereof will be provided below with reference to FIGS. 13 to 18. FIG. 13 is a detailed functional block diagram showing the functional construction of the scanning controller 41. As shown in FIG. 13, the scanning controller 41 comprises a preset counter 41a, recording counter 41b, and maximum dose counter 41c as ones related to the detection of an irradiation dose, and for controlling these counters, comprises a preset counter control section 41A, recording counter control section 41B, and maximum dose counter control section 41C. Here, the dose monitor 6A is a known one, and of a type that outputs pulses in accordance with the amount of electrical charges ionized by the passage of beam. Specifically, the dose monitor 6A outputs one pulse for each predetermined minute charge amount. The preset counter 41a and recording counter 41b determine the irradiation dose by counting the number of pulses outputted from the dose monitor 6A. Besides the above-described preset counter 41a, the preset counter control section 41A includes a spot timer 41Aa, difference calculating section 41Ab, determination section 41Ac, OR circuits 41Ad and 41Ae. The preset counter 41a includes a pulse input section 41aa, set value input section 41ab, initialization (clear) signal input section 41ac, operation start (START) signal input section 41ad, count value reading section 41ae, and set value comparison result output section 41af. Besides the above-described recording counter 41b, the recording counter control section 41B includes a first delay timer 41Ba, second delay timer 41Bb, first register 41Bc, second register 41Bd, difference calculating section 41Be, determination section 41Bf, NOT circuit 41Bg, and OR circuit 41Bh. The recording counter 41b includes a pulse input section 41ba, initialization (clear) signal input section 41bc, operation start (START) signal input section 41bd, and count value reading section 41be. As described above, the maximum dose counter control section 41C has a maximum dose counter 41c, which includes a pulse input section 41ca, set value input section 41cb, initialization (clear) signal input section 41cc, operation start (START) signal input section 41cd, and set value comparison result output section 41cf. Furthermore, the scanning controller 41 has a memory 41M and beam extraction start/stop signal producing section 41S. FIG. 14 is a flowchart showing the detailed procedures in steps 205 and 300 in FIGS. 12 executed by the scanning controller 41 with the above features. As described above, the operator i is initialized to 1, and the operator j is initialized to 1, in advance. In step 301, the scanning controller 41 outputs a preset count setting command corresponding to the target count number of the preset counter 41a already stored in the memory 41M, to the preset counter set value input section 41ab of the preset counter control section 41A. In step 302, the scanning controller 41 sets a target count number at the first spot in the layer 1 in accordance with the aforementioned set command. Here, the “target count number” refers to a value corresponding to the target irradiation dose of a pertinent spot in a pertinent layer in the column “radiation dose” shown in FIG. 11. This target count number is calculated by the scanning controller 41 based on the above-described target irradiation dose, before the start of ion beam irradiation. The calculation of the target count number using the target irradiation dose may be performed immediately after the preset counter control section 41A receives the aforementioned set command, or alternatively may be performed before the central control unit 100 transmits data to the scanning controller 41 if the central control unit 100 performs the calculation. Likewise, at this time, the scanning controller 41 outputs a maximum spot or layer dose counter setting command corresponding to the target count number (maximum dose count number) of the maximum dose counter 41c stored in the memory 41M, to the maximum dose counter set value input section 41cb of the maximum dose counter control section 41C. More details thereof will be described later. Upon completion of step 301, the processing advances to step 303, where the scanning controller 41 outputs a current setting command with respect to the electromagnets 5A and 5B regarding a pertinent spot, i.e., current data corresponding to each of X-position and Y-position in FIG. 11, to the power source for the electromagnets 5A and 5B. The electromagnets 5A and 5B generate a deflection electromagnetic force with pertinent current values, and output a current setting completion signal indicating that such a state has been accomplished, to the scanning controller 41. In step 304, this current setting completion signal is inputted to the beam extraction start/stop signal producing section 41S. On the other hand, in the preset counter control section 41A, when the target count number is set in step 302 as described above, this set value is inputted not only to the aforementioned preset counter set value input section 41ab but also to the difference calculation section 41Ab. Furthermore, the count number counted at this point in time (i.e., the count number at setting) is read from the preset counter count value reading section 41ae, and this is also inputted to the difference calculation section 41Ab. The difference calculation section 41Ab calculates the difference between these values: (count number at setting)—(target count number), and inputs it to the determination section 41Ac. In step 302A, the determination section 41Ac determines whether this difference is negative, namely, whether the count value at setting is less than the target count number. If this determination is satisfied, the determination section 41Ac outputs a target count number setting OK signal to the beam extraction start/stop signal producing section 41S. In step 305, the scanning controller 41 outputs a beam extraction (radiation) start signal from the beam extraction start/stop signal producing section 41S on the conditions that the target count number setting OK signal from the determination section 41Ac of the preset counter control section 41A, the current setting command in step 303, and the current setting completion signal from the scanning electromagnets 5A and 5B have been inputted. The beam extraction start signal passes through the accelerator controller 40 and closes the open/close switch 92. An ion beam is extracted from the synchrotron 12, and the ion beam is applied to a pertinent spot (e.g., the first spot in the layer 1). Next, the processing advances to step 306, where the beam extraction start/stop signal producing section 41S outputs a timer start command signal for starting the spot timer 41Aa of the preset counter control section 41A. If the elapsed time after this start that is measured by the spot timer 41Aa becomes a predetermined set time or more, (namely, if the beam extraction is performed for a predetermined time or more without being reset, as described later), a time excess signal is issued in step 307. In step 308, on the conditions that the time exceed signal has occurred and the timer start command signal has been inputted, a first abnormality signal is outputted to the central control unit 100. Upon receipt of the first abnormality signal, the central control unit 100 performs a predetermined abnormality processing, for example, an immediate forced stop with respect to beam extraction from the synchrotron 12, and recording to that effect through the intermediary of the scanning controller 41 and accelerator controller 41 (or alternatively, not through the intermediary thereof). On the other hand, when a beam irradiation is started by the output of the beam extraction start signal in step 305, detection signal of the dose monitor 6A is converted into a train of dose pulses by a current-frequency converter (i.e., I-F converter; not shown), and thereafter they are inputted to the preset counter pulse input section 41aa, recording counter pulse input section 41ba, maximum dose counter pulse input section 41ca of the scanning controller 41. These counters 41a, 41b, and 41c simultaneously count the pulses. This count number represents the irradiation dose from the start of counting. If the count value based on the input pulses from the pulse input section 41aa becomes a value of no less than the set value of the target count number set in step 302, the preset counter 41a issues an irradiation dose excess signal in step 309. In step 310, on the conditions that the irradiation dose excess signal has occurred and the target count number set in step 302 has been inputted, the preset counter 41a outputs a trigger signal from the set value comparison result output section 41af. As a first reset signal, this trigger signal is inputted to the initialization (clear) signal input section 41ac and operation start (START) signal input section 41ad of the preset counter 41a via the OR circuits 41Ad and 41Ae, and in step 311, the count number of the preset counter 41a is reset to start recounting. In step 312, based on the above-described trigger signal, the beam extraction start/stop signal producing section 41S of the scanning controller 41 produces a beam extraction start/stop signal and outputs it to the accelerator controller 40. The beam extraction start/stop signal passes through the accelerator controller 40 and reaches the open/close switch 92. Substantially by the beam extraction start/stop signal, the scanning controller 41 controls the open/close switch 92 to open. This stops the extraction of the ion beam from the synchrotron 12, and stops application of the ion beam to a patient. With the stoppage of the irradiation, the beam extraction start/stop signal producing section 41S outputs a command signal to stop or reset the spot timer 431Aa in step 313. The recording counter control section 41B of the scanning controller 41 has a first and second delay timers 41Ba and 41Bb. In step 314, the above-described beam extraction start/stop signal outputted by the beam extraction start/stop signal producing section 41S is inputted as a command signal for starting the first delay timer 41Ba in the form of converting beam ON→OFF switching into OFF→ON switching via the NOT circuit 41Bg. If the elapsed time after this start becomes a predetermined set time (i.e., first delay time, corresponding to the “delay” in FIG. 16 shown later), a first time arrival signal is sent to the first register 41Bc of the recording counter control section 41B, in step 315. In step 316, on the conditions that the first time arrival signal and a first delay timer start command signal have been inputted, a recording counter reading signal is outputted from the first register 41Bc to the recording counter 41Bc, and the count value then is inputted from the recording counter count value reading section 41be to the first register 41Bc. While not shown in FIG. 14 for the sake of simplification, the above-described time arrival signal is inputted as a signal for starting the second delay timer 41Bb. As in the case of the first delay timer, if the elapsed time after the start becomes a predetermined set time (i.e., a second delay time), a second time arrival signal is sent to the second register 41Bd of the recording counter control section 41B. On the conditions that the second time arrival signal and second delay timer start command signal have been inputted, a recording counter reading signal is outputted from the second register 41Bd to the recording counter 41b, and the count value then is inputted from the recording counter count value reading section 41be to the second register 41Bd. The count values at the first and second registers 41Bc and 41Bd are inputted to the difference calculation section 41Be, and after the difference therebetween is calculated, the difference is inputted to the determination section 41Bf. In step 317, the determination section 41Bf of the recording counter control section 41B determines whether the recording count value is a normal value, i.e., whether the above-described difference is within a predetermined proper range, and if the determination section 41Bf determines that the difference is an abnormal value, it outputs a second abnormality signal to the central control unit 100 in step 318. Upon receipt of the second abnormality signal, the central control unit 100 executes the predetermined abnormality processing as described above. If it is determined that the difference is a normal value in step 317, the determination section 41Bf inputs a second reset signal for resetting the recording counter 41b to the initialization (clear) signal input section 41bc and operation start (START) signal input section 41bd of the recording counter 41b via the OR circuit 41Bb, and after the resetting, starts recounting in step 319. Also, the count value then is outputted as an actual dose record from the determination section 41Bf to the central control unit 100. Furthermore, in step 320, the determination section 41Bf outputs a third reset signal for resetting the maximum dose counter control section 41C to the initialization (clear) signal input section 41cc and operation start (START) signal input section 41cd of the maximum dose counter 41c via the OR circuit 41Bb. On the other hand, based on the third reset signal inputted to the initialization (clear) signal input section 41cc and operation start (START) signal input section 41cd, the maximum dose counter 41c clears the count value and then starts recounting in step 321. If the beam extraction start signal is outputted in step 305, the maximum dose counter 41c counts pulses as a detection signal of the dose monitor 6A inputted to the pulse input section 41ca of the maximum dose counter 41c. This counter number represents the irradiation dose from the start of counting. In this time, in step 323, the maximum dose counter 41c has set a target count number (maximum dose count number) in a pertinent spot to be irradiated, in accordance with a maximum dose counter setting command inputted to the set value input section 41cb in the above-described step 301. If the above-described integrated value of irradiation dose becomes a value of no less than the set value of the target maximum count number set in the above step 323, the maximum dose counter 41c produces a count excess signal in step 322. Then, in step 324, on the conditions that the set target maximum count number (step 323) and the count excess signal has been inputted, the maximum dose counter 41c outputs a third abnormality signal from the set value comparison result output section 41cf to the central control unit 100 in step 324. Upon receipt of the third abnormality signal, the central control unit 100 executes the above-described predetermined abnormality processing. The target maximum count number refers to an irradiation dose set so as to be a little larger than the largest target dose in respective target irradiation doses with respective to all irradiation positions (all spots) in a target. FIG. 15 is a timing chart showing a series of operations of the preset counter 41a and recording counter 41b as described above. According to the particle beam treatment system of this embodiment with the above-described features, the following effects are provided. (1) Resolution Enhancing Effect by Divided Irradiations In general, the position monitor 6B is of a type that accumulates electric charges ionized by the passage of an ion beam in a capacitor and that reads a voltage induced in the capacitor after the spot irradiation. The capacity of this capacitor is determined so as to permit the amount of ionized electric charges by the spot subjected to the maximum irradiation dose. Regarding this capacitor, as the capacity decreases, the output voltage increases and the signal-to-noise ratio becomes higher, thereby enhancing the position measurement resolution. Conversely, as the capacity increases, the resolution decreases. Accordingly, in this embodiment, in a treatment plan using the treatment planning unit 140, it is planned that the irradiation to each spot in a layer is performed by dividing it into a plurality of times of irradiations (for example, in the example shown in FIG. 7, irradiations are performed seven times in the layer 1, three times in the layer 2, two times in the layer 3, and two times in the layer 4). The central control unit 100, accelerator controller 40, and scanning controller 41 control the synchrotron 12 and beam delivery apparatus 15 by using treatment information obtained by the above treatment plan. By virtue of this feature, regarding an irradiation position subjected to too much irradiation dose by one-time ion beam irradiation, it is possible to perform a divided irradiation so as to reduce an irradiation dose for each divided irradiation. This allows the difference in irradiation dose between the irradiation position subjected to the maximum dose and that subjected to the minimum dose to be reduced, thereby leveling off irradiation dose. In the example in FIG. 7, the maximum radiation dose is 10 at the spots in the layer 1, while the minimum radiation dose is 6.3 at the spots in the layer 4. As a result, the capacity of the capacitor of the position monitor 6B can be correspondingly reduced to enhance the resolution. This makes it possible to further correctly detect an actual beam position during treatment. (2) High-Accuracy Irradiation Effect by Preset Counter Clear In this type of particle beam irradiation apparatus, in order to reduce the exposure of normal tissue to radiation to a minimum and perform a proper treatment with neither too much nor too little irradiation, there is usually provided an irradiation dose monitor for measuring the irradiation dose of ion beam. When performing irradiation to each spot, a target irradiation dose is set on a spot-by-spot basis. Once the integrated value of irradiation doses detected by the dose monitor has reached the target value, a beam extraction stop command signal (beam stop command) is outputted to the accelerator, and in response to it, the accelerator stops the extraction of charged particle beam. With typical accelerator such as a slow cycling synchrotron or a cyclotron, even if the beam stop command is inputted, strictly speaking, it is not impossible that some amount of response delay occurs rather than the output of the charged particle beam immediately stops. In view of the above problem, in this embodiment, once the irradiation dose detected by the dose monitor 6A and counted by the preset counter 41a has reached a predetermined value, i.e., a target value (see step 309), the preset counter control section 41A outputs a trigger signal for triggering the scanning controller 41 to output the beam extraction stop signal to the high-frequency applying unit 9 (see step 312), and in step 311, clears the integrated count number of the preset counter 41a to restart integration, without waiting for the actual stop of the beam from the accelerator. FIG. 16 is a time chart showing the operations at this time. As shown in FIG. 16, a response delay can occur between the outputting of the beam extraction stop signal and the actual stoppage of the ion beam extraction from the synchrotron 12. During this response delay, the irradiation dose of ion beam extracted from the synchrotron 12 is integrated after the aforementioned clearing. After the extraction of ion beam has been actually stopped, the irradiation position is changed to a next irradiation position (spot) by the processing in steps 209 and 205 (see FIG. 12), and in step 302, the target count number is changed (in FIG. 16, for example, a change from the condition 1 (the target irradiation dose to be applied to the spot situated at a position) to the condition 2 (the target irradiation dose to be applied to the next spot) is made). Here, the target count number is a count number corresponding to a target irradiation dose. In step 303, the scanning electromagnets 5A and 5B are subjected to control, and in 305, the extraction of ion beam from the synchrotron 12 is restarted. At this time, the irradiation dose at the aforementioned next spot after the beam has moved there is detected by the dose monitor 6A and integrated by the preset counter 41a, like the foregoing. The integration of count number then includes previously, as an initial value, the count number with respect to an immediately preceding spot during the time period of the response delay of the accelerator, and the irradiation dose at the spot subsequent to the aforementioned spot is added to this initial value (see the part “condition 2 setting” in FIG. 16). As a result, irradiating the above-described subsequent spot with ion beam extracted from the synchrotron 12 until a target irradiation dose is reached, means irradiating this spot with the irradiation dose obtained by subtracting the aforementioned initial value from the target irradiation dose at this spot (i.e., the irradiation dose shown in “condition 2” in FIG. 16). Once the irradiation dose at this spot after the movement has reached a target irradiation dose, the preset counter control section 40A outputs a trigger signal for triggering the scanning controller 41 to output the beam extraction stop signal to the high-frequency applying unit 9, and clears the count number of the preset counter 41a, like the foregoing. The irradiation dose during the time period of the response delay of the synchrotron 12 is added as an initial value in irradiating the spot after a further subsequent movement, and the same is repeated hereinafter. Because the scanning controller 41 performs the above-described control, when attempting to irradiate each spot, an ion beam is always applied to the spot until the target dose of the spot is reached, on the assumption that an irradiation dose for the time period during a response delay of the synchrotron 12 occurring at irradiation to a spot is a part of irradiation dose at a subsequent spot. If irradiation dose control is performed without giving consideration to the response delay, an excessive irradiation corresponding to response delay is performed. This raises the possibility that the irradiation dose becomes, e.g., 1.2 at all spots (the intended irradiation dose is represented by 1.0 as shown in FIG. 17). In contrast, in this embodiment, by performing the above-described control, an ion beam dose (nearly equals 1.0) substantially equal to the target irradiation dose set with respect to a pertinent spot can be applied to all spots except the first spot to be irradiated (i.e., the spot at the left end in FIG. 18) with high accuracy, without an excessive irradiation corresponding to a response delay. In this embodiment, based on the assumption that the irradiation dose corresponding to a response delay of the synchrotron 12 occurring when irradiating a pertinent spot is a part of the irradiation dose at a next spot, an ion beam is applied to the pertinent spot until the target dose at the pertinent spot is reached. However, the same effect can be obtained using the following methods (1) and (2), as well. (1) To output a trigger signal in step 310 based on the conditions that, in step 309 in the preset counter control section 41A, when, from the target irradiation dose at a spot, the irradiation dose corresponding to the response delay occurring when irradiating immediately preceding spot is subtracted, and further when from the remaining irradiation dose, the count number with respect to the spot during irradiation is subtracted, remaining irradiation dose has become zero, and that the set target count number has been inputted in step 302. (2) To set the irradiation dose obtained by, from the target irradiation dose on a spot, subtracting the irradiation dose corresponding to the response delay occurring at the time of irradiating immediately preceding spot, as the target count number set in step 302 in the preset counter control section 41A.(3) Safety Enhancing Effect by Spot Timer Since the dose monitor 6A is an machine, it is difficult to perfectly eliminate the possibility that the irradiation dose monitor causes a malfunction or failure. Also, since the target irradiation dose for each spot is usually a value transmitted from a data base or a value calculated based on the transmitted value, it is not impossible that an improper value is inputted at the stage of the transmission or the calculation. In light of the above, in this embodiment, the scanning controller 41 has a spot timer, and determines whether an abnormal operation has occurred in accordance with the elapsed time after an ion beam started to be extracted to one spot (see steps 306 and 307 in FIG. 14). If the elapsed time after the extraction start becomes no less than a predetermined time, the scanning controller 41 outputs an abnormality signal for indicating the occurrence of an abnormal operation (the first abnormality signal) in step 308. Therefore, even if the extraction time of the charged particle beam is likely to abnormally elongate due to a malfunction or an occurrence of failure of the dose monitor 6A, or improper input value, the extraction of ion beam can be stopped after a certain time has elapsed. This reliably prevents excessive irradiation to an affected part, and further improves the safety. (4) Safety Enhancing Effect by Maximum Dose Counter Regarding the function of stopping the output of ion beam when the irradiation dose detected by the dose monitor reaches the target value, it is not impossible that equipment associated with this function causes a malfunction or failure. Also, it is not impossible that an error occurs in the setting of irradiation data. In view of the above problems, in this embodiment, the maximum dose counter control section 41C in the scanning controller 41 determines whether any abnormal operation has occurred (see steps 322 and 323 in FIG. 14) in accordance with the magnitude relation between the count number detected by the dose monitor 6A and integrated by the maximum dose counter control section 41C and a predetermined regulated value. If the count number becomes no less than a predetermined regulated value, the scanning controller 41 outputs a third abnormality signal in step 324. Therefore, even if the ion beam does not readily to stop due to a malfunction or the like of the beam stopping function and the irradiation dose is likely to abnormally increase, the irradiation can be stopped at a certain upper limit irradiation dose, thereby reliably preventing an excessive irradiation to an affected part. This further enhances the safety. Also, even if a target irradiation dose abnormally increases due to a malfunction or the like of data communications when an operator directly manually makes a regulated value a set value using, e.g., a hard switch, and the charged particle beam does not readily stop due to a malfunction or the like of the beam stopping function and the irradiation dose is likely to abnormally increase, the irradiation can be stopped at a certain upper limit irradiation dose, thereby reliably preventing an excessive irradiation to an affected part. This further enhances the safety. (5) Deceleration Effect of Ion Beam Remained in Synchrotron at Completion of Irradiation to All Spot in Layer In the spot scanning irradiation according to the present invention, as the size of a target changes, the number of spots in a layer changes, and consequently, the time required to complete an irradiation to all spots in the layer changes. Regarding the allowable extraction period of synchrotron, if it is set to be long with a large target assumed, the irradiation to all layers takes much time to complete, thereby elongating the treatment time for a patient. In view of the above, in this embodiment, after the irradiation to all spots in a layer has been completed, the charged particle beam in the accelerator is decelerated, quickly outputs a remaining beam deceleration command, thereby decelerating ion beams in the synchrotron. This terminates the allowable extraction period of the synchrotron. As a result, the allowable extraction period is controlled to a requisite minimum, thereby making the treatment time with respect to a patient short. The above-described ion beam irradiation by spot scanning can be applied to a proton beam treatment system using a cyclotron serving as an accelerator. This proton beam treatment system will be explained with reference to FIG. 19. The proton beam treatment system according to this embodiment has a construction where, in the proton beam treatment system shown in FIG. 19, the synchrotron is changed to a cyclotron 12A, and an energy changing unit (a second element and a charged particle beam energy changing unit) 42 is newly added. A charged particle beam generating unit 1A has a cyclotron 12A, which accelerates ion beams of the fixed energy. The cyclotron 12A has an acceleration unit 10A. The charged particle beam energy changing unit 42 is installed to a beam transport system 4 in the vicinity of the cyclotron 12A. The energy changing unit 42 comprises a plurality of planar degraders (not shown) for passing ion beams therethrough to cause the ion beams to lose energy, bending electromagnets (not shown) for deflecting the ion beams, which have been reduced in energy, and an aperture (not shown) for cutting out a part of the ion beams after passing the bending electromagnets. The energy changing unit 42 further includes a plurality of energy adjusting plates having thicknesses different from each other for changing energy value. Ion beams are changed in energy value by passing through the degraders. The plurality of degraders are made different in thickness from each other in order to obtain a plurality of energy values. As in the case of the embodiment shown in FIG. 1, the CPU 101 in the central control unit 100 reads the treatment planning information (see FIG. 11) stored in the memory 103 from the storage unit 110, and causes the memory (not shown) in the scanning controller 41 to store it. The CPU 101 transmits to an accelerator controller 40A all of data of operational parameters concerning all layers out of the treatment planning information. Here, the data of operational parameters comprises degrader numbers and an exciting current value of each electromagnets in the beam transport system, which are determined by the energy of ion beams applied to each of the layers. The control by the scanning controller 41 during the spot scanning according to this embodiment is performed similarly to the control illustrated in FIGS. 12 and 14 in the embodiment shown in FIG. 1. The control by the accelerator controller 40A is the control by the accelerator controller 40 shown in FIG. 12 except for step 214. Therefore, the accelerator controller 40A executes step 215 after step 213. Here, out of the control by the accelerator controller 40A, the control specific to this embodiment will be chiefly explained. In step 202, the aforementioned data of operational parameters with respect to an i-th layer (e.g., the layer 1) is set. In step 203, the accelerator controller 40A outputs degrader numbers to the energy changing unit 42, and outputs each exciting current value to a respective one of electromagnet power sources in the beam transport system 4. Specifically, the accelerator controller 40A performs control to insert a predetermined degrader in the energy changing unit 42 into beam path 62 based on the degrader number, and based on each of the exciting current values control, it perform to cause corresponding electromagnet power sources to excite a respective one of electromagnets (first element) in the beam transport system 4. The entrance of ion beam into the cyclotron 12A is performed by an ion source 11A. The beam extraction start signal outputted from the scanning controller 41 in step 300, and more specifically in step 305 (see FIG. 14), is inputted to the power source for the ion source 11A through the accelerator controller 40A. Based on the beam extraction start signal, the scanning controller 41 activates the ion source 11A to apply ion beams to the cyclotron 12A. When the beam extraction start signal passes through the inside of the accelerator control unit 40A, the accelerator control unit 40A outputs a predetermined high-frequency power set value to the high-frequency power source (not shown) of the acceleration unit 10A. Then, the ion beam in the cyclotron 12 is accelerated to the predetermined energy and extracted from the cyclotron 12A through an extraction deflector 8. The energy of the ion beam is reduced to the set energy by the degrader provided in the beam path 62, and reaches the beam delivery apparatus 15 through the beam path 62. These ion beam is applied to the pertinent spot in a pertinent layer in the target region of a patient 30 by scanning of the scanning electromagnets 5A and 5B. When the irradiation dose measured by the dose monitor 6A reaches a target dose of the pertinent spot, the scanning controller 41 outputs a beam extraction stop signal in step 300, and specifically in step 312 (see FIG. 14). The beam extraction stop signal is inputted to the power source for the ion source 11A through the accelerator controller 40A. Based on the beam extraction stop signal, the scanning controller 41 performs control to stop the ion source 11A and stop the application of the ion beam to the cyclotron 12A. When the beam extraction start signal passes through the inside of the accelerator control unit 40A, the accelerator control unit 40A controls the high-frequency power source for the acceleration unit 10A to stop the application of a high-frequency power to the acceleration unit 10A. This terminates the irradiation of ion beam with respect to the pertinent spot. Hereinafter, the irradiation of ion beam with respect to a subsequent spot is performed in the same manner as in the embodiment shown in FIG. 1. According to this embodiment, the effects (1) to (4) produced in the embodiment shown in FIG. 1 can be achieved. As is evident from the foregoing, according to the present invention, the detection accuracy with respect to an actual irradiation dose during treatment using charged particle beams can be enhanced. Also, according to the present invention, the control accuracy with respect to irradiation dose of charged particle beams can be improved. Furthermore, according to the present invention, the excessive irradiation of charged particle beams due to a monitor abnormality, input error, or the like can be reliably prevented. Moreover, according to the present invention, the excessive irradiation of charged particle beams due to a malfunction of a beam stopping function, or the like can be reliably prevented. Besides, according to the present invention, the treatment time with respect to a patient can be reduced.
	summary
	abstract	The present invention is directed to a switch circuit and method to quickly enable or disable the ion beam to a wafer within an ion implantation system. The beam control technique may be applied to wafer doping repaint and duty factor reduction. The circuit and method may be used to quench an arc that may form between high voltage electrodes associated with an ion source to shorten the duration of the arc and mitigate non-uniform ion implantations. The circuit and method facilitates repainting the ion beam over areas where an arc was detected to recover dose loss during such arcing. A high voltage high speed switching circuit is added between each high voltage supply and its respective electrode to quickly extinguish the arc to minimize disruption of the ion beam. The high voltage switch is controlled by a trigger circuit which detects voltage or current changes to each electrode. Protection circuits for the HV switch absorb energy from reactive components and clamp any overvoltages.
	abstract	An electromagnetic-wave suppressing material is provided. The electromagnetic-wave suppressing material includes an ionic liquid and nanometer-order particles mixed with the ionic liquid, where 10 wt % or more of the nanometer-order particles is mixed with respect to 100 wt % of the ionic liquid.
	description	The present invention relates to a method for manufacturing a long-term storage container for storage of radioactive material to inhibit radioactive radiation therefrom to the outside of the container, said container having a bottom and upright wall extending therefrom, the top of said container to be closed by a screw-on lid, said container having an integral inner container part of a first material, e.g. plastic material, with a bottom and upright wall, an integral outer container of a second material, e.g. plastic material with a bottom and upright wall, and radioactive radiation inhibiting material in an inter-space between the walls and bottoms of said inner and outer containers. The invention also relates to a long-term storage container for storage of radioactive material to inhibit radioactive radiation therefrom to the outside of the container. Further the invention relates to a method for manufacturing a radioactive radiation inhibiting lid suitable for fitting onto a top region of a long-term storage container for storage of radioactive material and inhibiting radioactive radiation therefrom to the outside of the lid. Also, the invention relates to a lid for use with such long-term storage container. Finally, the invention also relates to a moulding apparatus for manufacturing the storage container. Long-term storage of radioactive material in a safe manner is an ever increasing environmental problem. Attempts have been made to have such material stored in metal barrels, but these are subject to rust or corrosion and therefore prone to leakage of the radioactive material. To overcome such deterioration and possible leakage problems, there has been proposed to provide long-term storage containers of the type mentioned in the introductory part. Such container was essentially attempted to be made by inserting space members between the inner and outer container parts, and thereafter filling in liquid form the inter-space with In recognition of such defective manufacturing method, and also the urgent need for safer, long-term storage containers which are ready to use after manufacturing without necessity of subsequent radioactive radiation leakage tests, the present invention provides for a method and container having properties of an inter-space container part made from a void free radioactive radiation inhibiting material, and being safe and simple to manufacture, thus providing a safe, reliable storage container not requiring subsequent reliability tests. In accordance with the invention the manufacturing method of such container is characterised by the features as stated in the relevant independent method claims and further features thereof are stated in their respective sub-claims. Suitably, the inner and outer container parts are made from a plastic material such as e.g. high density polyethylene, and the inter-space container part between the inner and outer container parts is moulded from a radioactive radiation inhibiting material which is selectable from one of: lead, lead alloy, tin and tin alloy. According to the invention the method for manufacturing the radioactive radiation inhibiting lid comprises the features as stated in the relevant independent method claims. Further embodiments thereof are stated in the related sub-claims. Characteristic features of the storage container are defined in the in the independent article claim and further features thereof are defined in its sub-claim. Characteristic features of the lid for use with the container are defined in the relevant independent claim and further features thereof are defined in its sub-claims. The inventive method preferably makes use of a moulding apparatus for manufacturing the storage container, as defined in the introductory part, as the characteristic features of the apparatus appear from the relevant independent claim. A further feature of the apparatus appears from its sub-claim. It is important in a safe manner to be able to lift the storage container with its contents, and according to an embodiment of the lid there is at a lower end of the lid skirt provided a lifting or engagement face suitable to co-operate with a container lifting device when such device is made to engage a container having a fitted lid. As soon as a storage container has been fully filled by radioactive substances and other material, it is important to be able to safeguard against the lid when fully screwed onto the storage container being removable from the container. Therefore, the step of casting said lid threads includes providing a locking member for non-releasable engagement with locking means on the outside of the storage container when the lid is fully screwed onto the container. Suitably, said plastic material in the lid is high density polyethylene, and said radioactive radiation inhibiting material is selected from lead, lead alloy, tin and tin alloy. The storage container thus comprises an integral inner container part of plastic material with a bottom and upright wall, an integral outer container part of plastic material with a bottom and upright wall, and a radioactive radiation inhibiting material in an inter-space between the walls and bottoms of said inner and outer storage container part, respectively. According to the invention, the radioactive radiation inhibiting material is in the form of an injection or pressure moulded, integral inter-space container having a bottom and an upright wall extending therefrom. In a preferred version the outer container part is thus a storage container part moulded onto the outside of the inter-space container when the inter-space container is fitted onto the outside of the inner container. The storage container has on an outside face of the outer container part threads configured to engage threads on said lid, and the outer container part has locking means for non-releasable locking engagement with a locking member on said lid when said lid is fully screwed onto the storage container. FIG. 1 shows in vertical section and perspective view a half of storage container 1 according to the invention, having an inner container part 2, an outer container part 3, and an inter-space container part 4. It is noted that the inner container part 2 has integral bottom and upright wall. Also, the outer container part 3 has integral bottom and upright wall. An inter-space between the inner container part 2 and the outer container part 3 is defined by an inter-space container part 4 having a bottom and upright wall integrally made from a radioactive radiation inhibiting material through injection moulding or pressure moulding. The inner and outer container part 2, 3 are suitably made from a plastic material, e.g. high density polyethylene, through injection moulding, and the radioactive radiation inhibiting material is suitably one of: lead, lead alloy, tin and tin alloy. As shown on FIGS. 2a and 3 there is at an upper, outside region of the outer container part 3 is provided threads 5 configured to engage threads 6 on a lid 7, and wherein the outer container part has locking means 8 for non-releasable locking engagement with a locking member 9 on said lid when said lid is fully screwed onto the storage container. Said locking means and locking member are merely indicated without illustrating any details. However, it will be visualized that a resilient member and a hook-like member could provide such locking, i.e. a sort of snap function. The lid 7 has an injection moulded, integral first lid member 7′, 7″; 7′″ of plastic material in the form of a top part 7′ and a skirt 7″ depending therefrom, an inside of said skirt 7″ having said threads 6 to enable fitting engagement with the external threads 5 on the storage container. There is in addition at least one recess 10; 11 in said top part, and a second lid member 12; 13 is provided in the form of a solidified radioactive radiation inhibiting material located in an inside region of said first lid member and said at least one recess, said material retained in said at least one recess 10; 11 providing for non-releasable locking of the second lid member 12; 13 to the first lid member 7′, 7″; 7′″. A bottom end 14; 15 portion of the skirt portion of said first lid member 7′, 7″; 7′″ configured to be able to engage a container lifting device (not shown). Similarly to the storage container parts 2 and 3, the first lid member 7′, 7″; 7′″ is suitably made of a plastic material, e.g. high density polyethylene. The manufacturing of the first lid member is suitably through an injection moulding process. The radioactive radiation inhibiting material is suitably one of lead, lead alloy, tin and tin alloy. From FIG. 2b it will be noted that the lid is provided with an inner liner 7″″. It will be appreciated that such inner liner is suitably be applied to the embodiments of FIGS. 2a and 3 through post-installing the liner after providing the assembly of the two lid parts. Such post-installing can e.g. be made through use of snap-engagement of the liner with the lid assembly or by letting the liner simply rest on an upper edge portion of the inner container. It may also be considered to have inside the inner container an internal lid to be placed on top of the radioactive material located inside the inner container. FIG. 4 shows the major steps of the method for manufacturing the long-term storage container for storage of radioactive material to inhibit radioactive radiation therefrom, as disclosed in connection with FIGS. 1, 2 and 3. The method comprises: in step 21 integrally casting in a first mould 31, 31′, 32 (FIG. 5a) through injection moulding via an inlet 33 (FIG. 5a) a first container part 34 (FIG. 5a) having a bottom 34′ and a wall 34″; in step 22 integrally casting in a second mould 35, 36 (FIG. 5b) through injection or pressure moulding via an inlet 37 (FIG. 5b) an inter-space container part 38 of said radioactive radiation inhibiting material, said inter-space container part 38 having a bottom and a wall and forming a second container part; in step 23 (FIG. 5c) removing a first part 32 (FIG. 5a) of the first mould 31, 31′, 32 (FIG. 5a) which formed a first side wall face 34′ (FIG. 5a) and a first bottom face 34″ (FIG. 5a) of the first integral container part 34 (FIG. 5c); in step 24 (FIG. 5d) removing said inter-space container part 38 from the second mould 35, 36, in step 25 (FIGS. 5c and 5d combined) placing said inter-space container part 38 in fitting engagement with said first wall face 34′ (FIG. 5a) and said first bottom face 34″ (FIG. 5a) of the first container part 34 (FIG. 5c) to form a first assembly of container parts 34, 38, and with the first container part in engagement with a portion 31′ of a second part 31, 31′ of the first mould; in step 26 (FIG. 5e) locating in a third mould 39 (FIG. 5c); 52, 53 (FIG. 6c) the first assembly of container parts 34, 38 (FIG. 5e) with said inter-space container part 38 in spaced relationship to a mould member 40 (FIG. 5c) of the third mould 39, so as to form a cavity 41 between the member 40 and the inter-space container part 38, the second part 31, 31′ of the first mould having a portion 31′ inside the first container part 34 to support it during moulding of the third container part, and a top 31 of the second part of the first mould closing off an open end of said third mould member 40; in step 27 (FIG. 5f) through injection moulding via inlet 42 into said cavity 41 integrally casting a third container part 43 (FIG. 5f) having a side wall and a bottom; and in step 28 (FIG. 5g) releasing a second assembly of container parts formed by the first, second and third container parts 34, 38, 43 (FIG. 5g) from the said third mould 39 (FIG. 5c), however noting that also the mould member 31, 31′ is removed. It is observed that in FIG. 5 the first container part 34 is said inner container part, and that the inter-space container part 38 forms the second container part and fits onto the outside of the container part 34. Suitably in the injection moulding process of the inner and outer container parts there is used a plastic material which is e.g. high density polyethylene. The inter-space container part 38 forming the second container part is moulded from a radioactive radiation inhibiting material selectable from one of: lead, lead alloy, tin and tin alloy. Following the procedure according to FIG. 5, step 27 (FIG. 5f) in addition provides for threads 5 on the outside of said outer container part, said threads dimensioned to enable fitting engagement with threads on a lid to be fitted by screwing onto the storage container. Further, the provision of threads on the outer container part also includes provision of locking means configured for non-releasable engagement with a locking member on said lid when said lid is fully screwed onto the container. With reference to FIG. 6a the method for manufacturing the radioactive radiation inhibiting lid which is suitable for fitting onto a top region of a storage container for long term storage of radioactive material and inhibiting radioactive radiation therefrom, comprises: in step 51 casting in a first mould through injection moulding of a plastic material, e.g. high density polyethylene, an integral first lid member with a top part 7′ and a skirt 7″; 7′″ depending therefrom, said casting providing on an inside of said skirt threads 6 to enable fitting engagement with external threads 5 on said storage container 1, said casting further providing in said top part at least one recess 10; 11, in step 52 releasing from the first mould said first lid member 7′, 7″; 7′″ in step 53 filling in liquid form a radioactive radiation inhibiting material in an inside region of said first lid member and said at least one recess, and in step 54 allowing said radioactive radiation inhibiting material, suitably selected from lead, lead alloy, tin and tin alloy, to solidify to form the second lid member 12; 13, material retained in said at least one recess 10; 11 non-releasable locking the second lid member to the first lid member. The first mould is configured to provide at a lower end 14; 15 of the skirt a lifting or engagement face suitable to cooperate with a container lifting device (not shown) when such device is made to engage a container having a fitted lid. Step 51 also includes in casting said threads 6 provision of a locking member 9 for non-releasable engagement with locking means 8 on the outside of the storage container when the lid is fully screwed onto the container. As an alternative to the method depicted in FIG. 6a, the following steps could be made as depicted on FIG. 6b, viz.: in step 55 providing a pre-cast second lid member 12 made from radioactive radiation inhibiting material, suitably selected from lead, lead alloy, tin and tin alloy, in step 56 placing the second lid member in a mould for moulding around at least one face and the edges thereof a first and integral lid member through injection moulding of a plastic material, e.g. high density polyethylene, said integral first lid member provided with a top part 7′ and a skirt 7″; 7′″ depending therefrom, said casting providing on an inside of said skirt threads 6 to enable fitting engagement with external threads 5 on said storage container 1, said second lid member 7 further providing in said top part at least one recess 10; 11 in which said second lid member 12 is located, and in step 57 releasing from the first mould said first lid member 7′, 7″; 7′″ with the second lid member 12 in non-releasable engagement the first lid member. FIGS. 7a-7d show in more detail practical aspects of the manufacturing steps in accordance with the invention. FIG. 7a shows the moulding apparatus 61 closed and ready for moulding the inner container part 62 through injection moulding 63 via e.g. a screw conveyor 63′. The hot flow of plastic material to the cavity dedicated to casting of the outer container part has been shut off by a valve 64 located in a hot channel system 65. FIG. 7b shows the inner container part 62 after having being cast, the moulding apparatus 61 has been opened and the inner container part 62 is ready to be removed from one mould core 66 to another mould core 67 of the apparatus, the mould core 67 being located in the part of the apparatus intended for casting the outer container part. Thus, FIG. 7b also illustrates removal of the inner container part 62 from the mould core 66 to the core 67, and such movement is suitably made by means of a robot (not shown). The cores 66, 67 are suitably located on an apparatus slide 61′ and movable by a powered extendable and retractable device, e.g. a hydraulic or pneumatic cylinder and piston device. FIG. 7c shows the inner container part 62 located on the core 67 and with the separately made inter-space container part 68 of radioactive radiation inhibiting material fitted onto the outside of the inner container part 62. The container part 68 is suitably moved and positioned into engagement with the container part 62 through use of a dedicated robot (not shown). The inter-space container part 68 which is to inhibit radioactive radiation from spreading from the inside of the storage container to the environment outside the container is suitably made from a radioactive radiation inhibiting material, such as e.g. lead, lead alloy, tin or tin alloy, to form to the extent possible a nuclear radiation barrier. The inter-space container part should be of a unitary structure in order to avoid any leaks therethrough of any highly radioactive material to be retained by the container. The inter-space container part has to be cast in a separate mould, in connection with the disclosure of FIGS. 4 and 5 denoted as the second mould. In one aspect of its manufacturing process, the inter-space container 68 could be made or cast at the same manufacturing plant as the inner and outer container parts are injection moulded, but in a separate moulding apparatus located thereat. However, in another aspect the inter-space container could be made by a different manufacturer and delivered as just-in-time (JIT) delivery at the location where the injection moulding of the inner and outer container parts of plastic material takes place. As indicated on FIG. 7d supply 63′ of hot injection material is enabled, and when the mould is in closed position as indicated, the outer container part 69 is moulded at the same time as a further inner container part 62′ is moulded. After completed cooling-down-time, the moulding apparatus 61 then opens and the complete storage container having inner 62, inter-space 68 and outer 69 container parts is removed from the moulding apparatus 61. Further, the inner container part 62′ is moved from the core 66 to the core 67 as depicted on FIG. 7b, and the cycle just described for making the complete container 62, 68, 69 and a further inner container part 62′ is repeated. It will be recognized that in the context of FIG. 4 and with reference to FIG. 7, the first mould is to be construed as that enabling the casting of the inner container part, i.e. the cavity where the core 66 is located. Likewise, the third mould is to be construed as that enabling the outer container part 69 to be cast, i.e. in the cavity where the core 67 is located and where the inner container part 62 and the inter-space container part 68 are supported by the core 67. The second mould is in this context and with reference to FIG. 4 a mould used for casting the inter-space container part, whether at the plant nearby the first and third mould or at some remote place. The container 62, 68, 69 is suitably made as a circular container having a volume of e.g. 200 litres, although larger or smaller volume contents are conceivable without departing from the concept of the invention. As indicated earlier, the lid and its inner liner are made separately. The container comprises the inner container part and the outer container part made from a plastic material, suitably polyethylene such as e.g. PEH (HDPE), although other plastic materials may be suitable. An important aspect of the making of the inter-space container part 68 as a separate is that it will be possible to inspect it properly before it is fitted into the moulding apparatus as shown on FIG. 7c. The same of course to the approach indicated on FIG. 5, and FIGS. 5b and 5d in particular. As the inter-space container part is crucial to inhibit unwanted radioactive radiation from radioactive material to be stored in the container, a visual inspection and also measurement based detection of any damages or production flaws will be important to establish prior to the fitting of this container part 68 on the inner container part 62 and the subsequent casting of the outer container part 69. The invention provides for a better engagement between the container parts, more easily made container parts and assembly thereof, and highly improved safeguard against unintended leakage of radioactive radiation from the inside to the outside of the container. Further, the invention provides for a more permanent storage of the radioactive material, thereby avoiding having to change storage containers at a later stage. The invention provides for a storage container which has a storage capacity substantially larger than that of any currently available storage container for known types of nuclear medium and high radioactive material. The invention therefore yields reduced need for transportation and replacement of storage containers, as well as reduced volumetric requirements compared to the requirements linked to the currently used containers. The thickness of the inter-space container part will be determined by type of radioactive material to be contained by the container. Highly radioactive material may over time have a tendency to deteriorate a plastic material, and in this context the inter-space container part serves not only to protect against radioactive radiation to the outside of the container, but also serves to protect the outer container part against deterioration over time due to radiation from the radioactive waste contained by the storage container. The inner container part 62 may not need to be thick-walled as the outer container part 69, but the outer container part will need to have walls that are sufficiently strong to also withstand stress caused upon lifting and handling of the heavy containers. In some cases handling of the containers may necessitate that straps can be attached around the container to lift and move it. If the radioactive material to be contained is extremely radioactive or chemically aggressive, an inner liner inside the inner container part may be desirable, suitable made of a chemically inert material which provides some resistance to deterioration caused by radiation. However, in most cases the inner container part is made of a chemically inert and to the best possible extent also durable against radioactive radiation, above all to protect the inter-space layer. Apart from PEH/HDPE as possible materials for the inner container part and any possible extra inner liner, it could be considered using materials like concrete or ceramic materials. The outer container part is suitably made from a chemically inert material which inherently protects not only the inter-space container part, but also the inner container part and the nuclear waste against physical damage, while simultaneously preserving the integrity of the container over time to prevent escape of its contents. Although the sufficient overall physical strength of the storage container will primarily be contributed to by the outer container part and the lid structure fitted thereto, it is also conceivable to have the main strength of the container related to two or all three of the inner, the outer and the inter-space container parts. It will be appreciated that if a twin mould apparatus as shown on FIG. 7 is used for casting the inner 62; 62′ and outer 69 container parts, the apparatus must be large enough for casting both such parts. However, it lies within the invention that both the inner container part 62; 62′ and the outer container part 69 could each be made in a separate injection moulding apparatus instead of a common one as shown on FIG. 7. Thus, there could be either two moulding apparatuses with a dedicated mould in each for casting an inner and an outer container part, respectively, or a single moulding apparatus, as shown on FIG. 7 of a size capable of containing a replaceable mould for casting either the inner or the outer container part. In the latter case, it could be visualized to cast a specific number of inner container parts in a dedicated mould, then replacing that mould by one for making the outer container part, and thus using the pre-made inner container parts and inter-space container parts when making the outer container parts and thereby the final assembled container, as disclosed above. In the practical, though not limitative embodiment of FIG. 7, the twin-cavity moulding apparatus is a currently preferred embodiment, thus enables casting of both the inner container part and outer container part in a single operation. Thereby, the need for another, separate moulding apparatus for casting the inner container part will be avoided. As shown and disclosed above in connection with FIG. 7a, as a process start, only the inner container part is cast. It will be appreciated by the expert in the art that the closure valve 64 is suitably associated with the injection channel 65 for the hot, melted plastic material to be injected, so that just the inner container part 62 is cast at the start of a production start, whereby the next mould cavity having the core 67 at that stage is inoperative as regards casting. This implies that at the end of the production cycle only the mould cavity for casting the outer container part is operative, whereas the mould cavity for casting an inner container part is inoperative as regards casting. Thus, between the production start stage and the production end stage of a production series, both the first and the next mould cavities in the moulding apparatus will be operative to receive injection of plastic material. In view of the in particular the heavy weights of the container parts and above all the radioactive radiation inhibiting material related the container as well as the lid, it will be required to have available robots or other handling equipment to move the various parts in and out of the moulding apparatus. Thus, the completed, heavy storage container when removed from the moulding apparatus subsequent to the step of FIG. 7d and when the moulding apparatus is fully opened, will be removed through aid from the robot. Further, a production plant will need to have required equipment related to moulding process, such as e.g. hydraulic or pneumatic units, basic moulding apparatus with pressure cylinders, valves etc. in addition to the mould or moulds, a supply of plastic material, any required grinder for such material, conveyors, material injectors, material heating equipment, as well as tools for maintenance, storage etc. Furthermore, the casting of the lid part, including the radioactive radiation inhibiting material therein, will have to be made in a moulding apparatus which is preferably separate from that making the inner and outer container parts, in order not to complicate operations. The lid, suitably made from the same plastic material, will also comprise a nuclear radiation barrier made from lead material.
042971683	claims	1. For use in a nuclear reactor, an oxide composition nuclear fuel material in compacted pellet form containing at least one fissionable isotope and an amount of an oxide selected from the group consisting of V.sub.2 O.sub.4 and V.sub.2 O.sub.5 and mixtures thereof effective to immobilize cadmium resulting from nuclear fission chain reactions of the nuclear fuel material through a reaction between the said cadmium and the said oxide and thereby prevent cadmium embrittlement of nuclear fuel cladding at reactor operating temperatures. 2. The composition of claim 1 in which the nuclear fuel material comprises compounds selected from the group consisting of uranium oxide compounds, plutonium oxide compounds, thorium oxide compounds and mixtures thereof. 3. The composition of claim 1 in which the nuclear material comprises uranium oxide compounds. 4. The composition of claim 1 in which the immobilizing additive is V.sub.2 O.sub.5. 5. The composition of claim 1 in which the immobilizing additive is V.sub.2 O.sub.4. 6. The composition of claim 1 in which the immobilizing additive is present in the nuclear fuel in an amount between about 0.0025 and 0.025 weight percent on the basis of the nuclear material. 7. The composition of claim 1 in which the immobilizing additive-content of the nuclear fuel is about 0.0075 weight percent on the basis of the nuclear material. 8. The method of immobilizing fission product cadmium generated in nuclear fuel material of oxide composition in pellet form containing at least one fissionable isotope which comprises the step of providing in contact with the nuclear fuel material an amount of a substantially stoichiometric oxide selected from the group consisting of V.sub.2 O.sub.4 and V.sub.2 O.sub.5 and mixtures thereof effective to immobilize the cadmium generated in the nuclear fission chain reaction of the nuclear fuel material through a reaction between the said cadmium and the said vanadium oxide and thereby prevent cadmium embrittlement of nuclear fuel cladding at reactor operating temperatures. 9. The method of claim 8 in which the additive is mixed with and distributed through the nuclear fuel material. 10. The method of claim 8 in which the additive is disposed in contact with the pellet of nuclear fuel material.
	summary
062787640	description	DETAILED DESCRIPTION OF THE INVENTION The present invention involves high-efficiency replicated x-ray optics and a method of fabrication. A replicated optic having a tubular shape open at both ends with an interior surface that is highly reflective to x-rays within a wavelength band of interest is fabricated by dc or rf sputter deposition of reflecting layers onto a super-polished reusable mandrel. The reflecting layer or layers are strengthened by a supporting multilayer deposited thereon, and an outer mechanical supporting layer. The supporting multilayer structure results in stronger stress-relieved reflecting surfaces that do not deform during separation from the mandrel, and consequently produce super-smooth surfaces comparable in smoothness to the initial mandrel surface (i.e., <12 .ANG., and as low as 3-5 .ANG. rms). The increased strength of the reflecting layer enhances the ability to part the replica from the mandrel without degradation in surface roughness and performance. In addition, a parting layer is typically first sputter deposited on the mandrel to ease removal of the optic from the mandrel and to maintain its surface smoothness. Upon separation of the layered device from the mandrel, the formed tubular shell has an inner surface with the shape and surface smoothness of the master mandrel. In operation, a beam of x-rays enters one end of the tubular shell, undergoes a single reflection at the interior surface, and exits from the other end with a different direction of travel. The shape of the optics is unlimited since the optical device mimics or replicates the shape of the mandrel. The optics may be truncated paraboloidal, ellipsoidal, hyperboloidal, or polynomial shells of revolution. The optics can be used singly or in combinations to form a range of x-ray optical systems. Depending on the shape, x-rays are focused, collimated, or otherwise manipulated when they are allowed to enter one end of the shell, reflect from the inner mirrored surface, and then exit in a new direction. The inner reflecting layer may be either a single layer grazing reflection mirrored surface or, alternatively, a multilayer resonance reflection mirrored surface. The wavelength bandpass of the multilayer mirror can be used to select a specific range of x-ray energies. High efficiency results from the high quality of the mirror, large reflection angles (especially for resonant mirrors), and the large collection solid angle of the tubular structure compared to more conventional open geometry x-ray optics. These optics have a number of applications, including static and scanning collimators for x-ray lithography, one and two element collection and focusing optics for x-ray crystallography, collection and concentration optics for x-ray fluorescence analysis, Wolter and zone-plate x-ray microscopes; x-ray radiographic systems and tomography. FIG. 1 illustrates an embodiment of a collimator generally indicated at 10 comprising a collimator housing 11, an opening 12 extending therethrough, in which is located a cone 13 having a tapered inner surface in which is positioned a tapering tubular member 14 having a multilayer reflector shell 15 on the inner surface thereof. A beam block 16 may be located in an open end 17 of tubular shell 14. Thus, a beam of x-rays from a source 18 is directed, as indicated at 19, through the open end 17 and reflected by multilayer reflector shell 15 so as to leave the tubular member 14 in a different direction as indicated by arrows 19'. The direct unreflected x-rays indicated at 20 may be stopped by the beam block 16. This optic is therefore capable of taking a radially diverging radiation pattern produced by a point x-ray source and converting it to a parallel annular beam suitable for semiconductor proximity lithography. Typical optics that serve as collimators for proximity x-ray lithography optics have been fabricated with a length of approximately 10 cm, a large end diameter of 3-4 cm, and a small end diameter of 2-3 cm. The small end of the optic is typically placed 3-5 cm from an x-ray point source. For lithography applications, a beam block is used to stop the direct unreflected x-rays from exiting the optic as shown in FIG. 1. The optical structures are made by sputter depositing layers of materials onto a super-smooth mandrel, thus forming the optic from the inside out. When the mandrel is separated from the sputtered shell, the innermost layer replicates the mandrel shape and smoothness and serves as the reflecting surface for the mirror. A cross-sectional view of a reflecting optic deposited on a mandrel is shown in FIG. 2. Referring to FIG. 2, the mandrel 22 is typically made of glass, ceramic, or a metal such as aluminum. Superpolished electroless nickel coated aluminum mandrels have been used as forms for x-ray collimators. A parting layer 23 may be sputter deposited on the mandrel. Although the parting layer may not be required in some applications, it is preferred. The parting layer is made of a non-wetting and non-chemically interacting material that maintains or improves the mandrel surface quality. Suitable materials include amorphous carbon and carbides such as boron carbide. The reflecting layer or multilayers 24 are sputter deposited (e.g., by dc magnetron) on the parting layer 23. A single layer forms a grazing incidence mirror; a multilayer is used for resonant multilayer reflectors. A supporting multilayer 25 is then deposited on the reflecting layer(s) 24. An outer supporting layer 26 is then typically electrodeposited on the supporting multilayer 25 for handling purposes. For a single layer specularly reflecting surface, the reflecting layer typically has a thickness of about 250-600 .ANG. (made of layers about 20 .ANG. thick). The reflecting layer is typically made of materials such as gold, platinum, rhodium, nickel, nickel alloys, rhenium, or alloys of rhenium. A tungsten-rhenium alloy (W.sub.3 Re) is a common material used to make grazing reflection mirrors. Alternatively, a series of layers are initially deposited that constitute a multilayer resonant mirror. Multilayer mirrors are typically 1000-3000.ANG. thick and are made of alternating layers of high and low atomic number materials, such as boron carbide (B.sub.4 C) and W.sub.3 Re. Multilayer mirrors are capable of much larger reflection angles and thus in many applications can occupy a larger solid angle and thus collect a larger fraction of x-rays. There are several considerations in the choice of materials for the reflecting surface. If the reflection process is to be specular total external reflection, then the reflecting surface material must have the best optical properties for the wavelengths of interest and be capable of being fabricated with low surface roughness. The specularly reflecting surface material(s) must have good stability in the ambient atmosphere of the exposure system and exhibit good shelf life without extraordinary measures. It should also be possible to clean the reflecting surface of general contaminants that degrade the reflectivity without increasing surface roughness. The optic must have an excellent finish on its internal surface, must have a highly uniform reflective coating, must be true to the desired figure, and must have good mechanical stability. In order to strengthen the initial reflecting layer, a short period supporting multilayer (d=20 to 30 .ANG.) is deposited having a total thickness of about one micron. The supporting multilayer is made of alternating layers of the reflecting material (e.g., Au, Pt, Ni, Ni alloys, Rh, Re, W.sub.3 Re) and a metal such as copper, copper-nickel alloy, gold, or silver. The layers of the two materials are of equal thickness (about 1-2 nm each). Alternating layers of materials such as W.sub.3 Re and copper (Cu) give the structure unusually large tensile and hoop strength (much greater than is possible using a single material), and thus the robust ability to retain the original mandrel surface smoothness. These multilayer structures have exceptional strength with yield stresses in excess of 300,000 psi, which is greater than either material alone. These multilayer structures have a total thickness of one micrometer and provide a "strong back", which suppresses deformation of the reflecting layer during parting of the mandrel, making possible the production of reflecting surfaces with roughness of 3-5 .ANG. rms. The deposition of copper is typically continued to form a copper layer approximately 4 micrometers thick to enable electrodeposition of a low residual stress mechanical supporting layer approximately 1 mm thick or greater to improve the sturdiness of the part. This outer layer is made of a material that can be electroplated easily, such as nickel, nickel-copper alloys, copper, stainless steel, iron-nickel alloys, copper-tin alloys, and other copper-based alloys (brass). This outer layer protects the underlying layers from mechanical deformation and contamination, and facilitates the handling of the optical device. The special parting layer is sputter deposited on the mandrel surface prior to deposition of the reflecting structure and is typically made of amorphous or glassy carbon, or a carbide such as boron carbide. The thickness of the layer is typically 2-5 nm. After separation, any carbon remaining on the optical device does not affect its performance. The mandrel is cleaned of any carbon before being reused, when a new parting layer is deposited. The parting layer provides two specific characteristics to the mandrel surface of critical importance to the parting of the replica structure from the mandrel. First, adhesion to a polished mandrel surface is not uniform and varies over that surface due to cleanliness and the natural bonding of two clean metal surfaces. This non-uniform adhesion results in shear stresses during parting that deform the reflecting layer. This significantly increases surface roughness and degrades performance. Sputter deposition of an amorphous carbon layer that does not react with the reflecting layer material and has low adhesion with the reflecting material enables parting while maintaining a 3-5 .ANG. rms surface finish. In addition, this amorphous carbon layer improves the smoothness of the mandrel itself prior to deposition of the reflecting layer. The presence of a parting layer maintains or enhances the smoothness of the mandrel, provides uniform adhesion, and substantially decreases the adhesion of the reflecting surface material to the mandrel, which reduces the forces required to part the replica structure and thus the potential for increased surface roughness. The low stress required to part the replica from the mandrel has made possible the maintenance of the surface figure of the mandrel in the replicated part and minimized the potential for damage to the mandrel during parting so that multiple replicas can be manufactured from a single mandrel. In a specific embodiment, a prototype collimator structure consists of a carbon parting layer deposited directly on the mandrel surface, followed by a W.sub.3 Re x-ray reflecting layer, then a W.sub.3 Re/Cu multilayer, a thick Cu film, and finally a thick Ni film. All layers were sputtered except for the nickel, which is electroplated. The purpose of the thick copper film is to protect the reflecting surface and supporting multilayer from atmospheric contamination during transport from the sputtering apparatus to the plating apparatus and to enhance the electroplating of the mandrel. The W.sub.3 Re/Cu multilayer provides a good thermal coefficient of expansion match between the copper protective layer and the W.sub.3 Re reflective layer. The low residual stress, thick plated nickel layer makes the coating mechanically robust after parting from the mandrel and is also relatively corrosion-resistant. Production of these optics involved changes to an existing sputtering system and an electroplating apparatus. A special collimator mount was constructed for the sputtering system that allows the mandrel to be rotated around its long axis during deposition. In addition, shields were installed to prevent deposition of sputtered material onto the mandrel at an oblique angle, which could cause columnar film growth and surface finish degradation or co-deposition from the two sources used. This made high quality layering possible. Thus, the exposed mandrel surface looked nearly flat from the point of view of the sputter guns during deposition. The sputter guns used are arrayed on a circle in opposition, concentric with the long axis of the mandrel. Each sputter gun is individually shuttered so that layer deposition is initiated by the opening of the shutters. Layering is achieved as a point on the mandrel surface rotates through the masking apertures of the sources, sputtering Material A and Material B in an alternating sequence: A-B-A-B-A-B. In the electroplating system, the mandrel, which already has the sputter deposited coating, is suspended from a motor, which rotates it in the bath during deposition. The plating current is supplied by a dc power supply, and a computer controls the entire system. The plating current is also measured by the computer, making possible real-time monitoring of the deposition rate and improved layer thickness control. This makes possible the control of the deposition rate and the residual stress in the nickel deposit. The electro-deposition process parameters are controlled to produce a very low residual stress Ni deposit that makes it substantially easier to maintain the optic figure and to separate it from the mandrel. Reflectivity measurements performed on W.sub.3 Re single films deposited onto flat substrates using the same apparatus as is used to make the optics show excellent agreement with a calculation of the ideal grazing-incidence reflectivity for a single W.sub.3 Re film, demonstrating the high quality of the film. The grazing angles of incidence are typically small, thus strongly limiting the solid angle of the optic relative to the radiation-emitting source. This limitation can be partially overcome by the use of multilayer coated resonance reflectors that will function at larger reflection angles increasing the usable source emitted/collected radiation by more than a factor of five. The replication based manufacturing process for producing x-ray optic surfaces/multilayer structures has multiple steps, depending on the physics of the reflection process and complexity of the reflecting surface structures. The general outline of the manufacturing process steps follows. 1. Selection of materials for specularly reflecting surface or multilayer structure, which provide the needed reflection efficiencies in the spectral ranges of the technical application. PA1 2. Deposition of these materials on super-polished flat surfaces to demonstrate that the required reflection efficiencies are attainable under standard short wavelength reflection optic development conditions. PA1 3. Evaluation of the stability of the structures deposited on the super-polished flats under simulated conditions for the application. PA1 4. If the structures are stable and exhibit acceptable performance, then deposition calibration parameters for the magnetron sputter deposition processes for deposition on the doubly curved replication mandrel surfaces are established. PA1 5. In principle, single layer specularly reflecting surfaces only require that the total thickness of the single reflecting media layer be controlled for effective reflection performance to be achieved. In practice, it is necessary to maintain surface roughness and composition at levels that are technically required for effective performance. Calibration, in this case, requires only a semi-quantitative knowledge of the layer thickness deposited on the replication mandrel surface under specified deposition source and replication mandrel motion conditions. Typical specular reflecting material structures are 25-60 nm thickness. PA1 6. Multilayer resonance reflectors are wavelength dispersive, so if a known wavelength or band of wavelengths is needed for a given application, a specific angle of incidence and multilayer periodicity must be used. The relationship between wavelength, angle of incidence and multilayer periodicity is given by the classic simple Bragg equation: n.lambda.=2d sin .theta., where .lambda. is the radiation wavelength (nm), d the multilayer period (d[nm]=t.sub.A +t.sub.B), and .theta. is the grazing angle of incidence on the optic surface. The thicknesses of the two sputtered materials A and B are given by t.sub.A and t.sub.B. A correction for refraction of the x-rays by the multilayer is also made, though the principle of operation is shown by the simple Bragg equation. Since the angle of incidence onto the collimator surface varies along the axis of the collimator, the multilayer period must also vary in a manner defined and controllable during optic manufacture so as to maintain the Bragg condition. This is accomplished by accurate masking of the deposition source profile to generate the desired thickness profile, i.e., longitudinal variation in multilayer period. PA1 7. Preparation of a superpolished (rms<0.3-0.5 nm) master mandrel using metal, glass, or ceramic materials. Surface quality relative to roughness, mid-range figure, and figure in general are shown to be largely determined in this step. PA1 8. Exact replication of the master mandrel surface and figure requires that there be no distortions of the mandrel form introduced by the replication process. The first issue to be considered in achieving this end is the maintenance of surface smoothness. In many cases, the reflecting surfaces are low strength noble metals (e.g., Au), which are easily plastically deformed. Thus, though the mandrel surface may have a smoothness that is nearly atomic (rms<0.2 nm), roughness is introduced as a result of adhesion forces during the parting of the replica from the mandrel. It is also possible that contamination of the uncoated mandrel surface will introduce "roughness" into the parted surface, even though the mandrel itself has a very high surface quality. PA1 9. Manufacture of supporting structure or substrate for the replicating structure. The electroforming process starts with the careful preparation of the plating solution. An exemplary solution contains 300 g/L nickel sulfamate hexahydrate, 40-g/L boric acid, and 2-g/L nickel chloride to aid in anode corrosion. Anodes are composed of sulfur depolarized nickel rounds. The rounds are suspended in titanium baskets enclosed in polyethylene anode bags to prevent any particulate matter from entering the solution. The solution is continuously filtered through a 10-micron cartridge at a flow rate of 1200 liters per hour. PA1 10. Separation of the super-polished master mandrel and replicated collimator shell structure. An apparatus specifically designed to fit the diameters of the electroplated nickel at the ends of the collimator/mandrel assembly was developed. This made possible kinematic axial loading of the collimator/mandrel assembly to apply a shear load at the mandrel/collimator interface. The system is arranged with the large diameter end of the collimator structure up in this vertical apparatus. A structure to maintain axial alignment of the parted collimator structures is implemented to eliminate damage to the superpolished mandrel or to the inner surface of the parted collimator cone by touch or impact upon release of the collimator structure from the mandrel. All these operations are carried out at room temperature under moderate clean environment conditions. It may be necessary in some instances to introduce a depth variation in multilayer period for the sputter deposited material. This is accomplished by changing the rotation period of the mandrel in the deposition system or by changing the deposition rates of the two sputtered materials (A, B) that comprise the multilayer. This increases the bandwidth of the multilayer at a particular angle of incidence, which is advantageous in some cases. In the process described herein, a parting layer of a non-wetting and non-chemically interacting material that maintains or improves the mandrel surface quality is deposited first. The reflecting surface material is deposited on this parting layer. This process refines the grain size of the reflecting layer material and increases its tensile strength. The next sputter deposited structure is a multilayer of copper and the reflecting surface material. This multilayer structure is approximately one micron thick and will typically have a tensile strength greater than 2 GPa. A third layer comprised of copper is then deposited as 4 nm layers, with a total thickness of 4000 nm. This copper layer has a tensile strength of about 0.65 GPa and provides an ideal bonding matrix for the electroplated nickel used to provide macroscopic mechanical integrity. After chemical analysis and adjustment to optimal parameters, the samples are processed to determine the deposit internal stress. The method of measurement is a "spread leg" strip. This strip is comprised of beryllium copper (0.2 mm in thickness) with one face of each leg masked off with a polymeric coating. By plating a known thickness of material on the strip and measuring the deflection of each leg from the perpendicular with a calibrated scale, stress values can be determined to .+-.300 psi. Values of high stress can be reduced either by chemical additives or by low pH/high current density plating on a sacrificial panel. Plating stress is also influenced by current density, solution temperature, substrate composition, and deposit thickness. Because the substrate and deposit thicknesses were predetermined, solution temperature and current density were the only variables available for modification to reduce internal stress. A careful study of the required thickness and desired internal stress determined a current density of 20 amps per square foot. This produced a deposit rate of 0.025 mm/hr. Deposit thickness on the completed cone is 1.5-1.625 mm, which required 72 hours in the plating tank. Thickness variation from end to end is less than 5%. A special fixture was designed to minimize any current density variations due to field effects near the ends of the mandrel. Essentially this "burn guard" extends the conical mandrel several inches on each end, and allows for the connection to a rotating fixture. A neoprene washer is fitted between the mandrel and the burn guard to prevent the joining of the two surfaces with the electrodeposited nickel. The rotating fixture uses a special mercury filled contact that allows rotation of the mandrel while passing the DC current and also prevents any ripple or current variations that would be detrimental to the coating properties. Because the mandrel is vacuum coated, it remains free of any soils, oils, or other material that would reduce adhesion of the electrodeposit or cause inferior deposits. The only pretreatment required is to immerse the mandrel into the plating solution for 30 seconds prior to the initiation of current. This allows the mandrel to rise to the temperature of the plating bath, and the small amount of chloride present removes any oxides that may have formed. After the electroforming is completed, the mandrel is rinsed and dried, and the removal of the mandrel only requires a small amount of force to the large diameter end to release it from the electroformed mirror assembly. The mandrel and the replication shell are now removed from the parting apparatus and stored under clean conditions. The primary degradation mechanism for the mandrel appears to be chemical corrosion of the superpolished electroless nickel by the plating electrolyte at the ends of the mandrel. These areas have limited impact on performance and thus, little effect on the operation of the optics. Three collimator structures have been successfully replicated from a single high quality mandrel, and additional structures can be fabricated with the same mandrel structure. The tubular optical devices fabricated according to the present invention can be used for many applications, and designs for several specific applications are described below. X-ray proximity lithography is a leading candidate for advanced semiconductor manufacturing when optical lithography techniques are no longer able to meet the resolution requirements for future generations of devices. The resolution limit is determined by diffraction of the illumination source, by the features of the mask, and by the ability of the non-linear photoresist to accentuate variations in the exposure dose (contrast enhancement). X-ray lithography technology and infrastructure has been under development for a number of years. Under DARPA sponsorship, x-ray masks and aligners have been produced and have demonstrated capabilities suitable for 0.13 .mu.m device fabrication. Electron storage rings (synchrotrons) have been used as powerful sources of collimated x-ray radiation with an optimum wavelength in the range from 8-11 .ANG.. It appears technically feasible to extend this technology to 0.13 .mu.m devices and beyond. However, for some applications, the complexity of a multi-beam fabrication facility based on a synchrotron source is not cost-effective. Such applications include low volume manufacturing of application specific integrated circuits (ASIC's) for commercial and military markets, prototype and process development markets, and mask replication. These markets demand a high degree of flexibility from the lithography tool, and this can only be achieved in a granular (small, inexpensive) system. Thus, there is a need for a compact x-ray source operating at a wavelength around 11 .ANG., with sufficient brightness (power per area per unit solid angle) to achieve sub-0.13 .mu.m resolution and acceptable wafer throughput. The first x-ray collimators for proximity lithography fabricated at the Lawrence Livermore National Laboratory (LLNL) was near-conical polynomial shaped structures having highly reflective interior surfaces. The shape of the reflecting surface is designed to transform a portion of the spherical radiation pattern produced by a point source into a quasi-parallel beam of x-rays, capable of illuminating a full print field at near normal incidence angles. FIG. 3 shows an optic having a grazing reflection mirror, a circular cross-section, and a polynomial shape described by a sixth order polynomial. The coefficients of the polynomial are chosen to produce a relatively uniform intensity distribution over the illuminated field by accounting for the differential solid angle of incoming rays, the angular dependent reflectivity, and the direction of the exiting rays. A beam block stops direct irradiation of the mask by unreflected rays, as in FIG. 1. These initially fabricated optics were single reflection designs that were fabricated using replica optics techniques to produce high quality surfaces. The fabrication technique uses an aluminum mandrel coated with electroless Ni, diamond turned, and flow polished to a 3-5 .ANG. roughness. The mandrel is then dc sputter coated with a carbon parting layer, followed by a 300 .ANG. gold mirror layer, and then a 1.2 mm thick substrate multilayer of W.sub.3 Re and Cu. These layers are overcoated by a 1-mm thick electroplated Ni sealing layer. The debris shield/beam block structure, such as shown at 16 in FIG. 1, consists of a 2 .mu.m thick polypropylene film disk with a 5 mil thick 6.35 mm diameter lead disk attached to the center of the disk and then mounted coaxially with, and immediately in front of, the source end of the collimator. The lead disk serves as the beam block to prevent direct irradiation of the mask, and the film serves to both support the beam block and to prevent debris contamination of the collimator. This initial collimator was able to fully illuminate a 36.times.36-mm print field and consequently produces a 51-mm diameter circular illumination field. The global divergence at the outer edge of the illumination field was designed to be 28 mrad (20 mrad at the print field edge) and -10 mrad at the center. Although this collimator has many useful characteristics, a divergence defect at the center of the print field prevents useful features from printing in that region. Rays arrive at the mask from different points on the collimator mirror and therefore are incident at substantially different angles. The advanced scanning design of FIG. 4 uses a paraboloidal reflector that produces a ring shaped illumination field, which is then scanned across the print field and thus avoids the central defect. The performance of this collimator was analyzed using an x-ray CCD camera in the geometry shown in FIG. 4. The gain was determined by comparing the x-ray intensity measured by the CCD both with and without the collimator in place. For measurements of the global and local divergence, a pinhole array was interposed between the collimator and the camera, and the location of the projected images were compared to corresponding pinhole location (modified Hartmann test). The experimental apparatus of FIG. 4 comprises an x-ray source 30, a collimator 31 having a tubular optic therein and having a debris filter and beam block support 32 retaining a beam block 33 located at the entrance or source end of collimator 32, a pinhole array 34, and a CCD camera 35 with a UV filter 36. A radial average of the 2D x-ray distribution for the image, produced by the CCD camera of FIG. 4, was measured as a function of gain (increase in delivered intensity) and compared to the gains from a series of Monte Carlo ray trace simulations that incorporate the experimental geometry but with different assumed rms surface roughness. The experimental curves fall mainly between the 5 .ANG. and 10 .ANG. roughness curves, providing strong evidence that the present method is capable of producing very smooth and therefore highly reflective and efficient x-ray optics. In addition, fabricated optics have been measured using AFM and shown to have a surface roughness <6.5 .ANG. rms. Using a pinhole array such as shown in FIG. 4, images were obtained. The global divergence (incident angles on the array) as a function of radial position can be determined by comparing the centroid of each of the small pinhole images to the known location of the pinhole. The results of the global divergence determinations showed that the measured values compared well with values expected from an analytic determination of global divergence using the experimental geometry and the theoretical optic shape, thus confirming excellent figure control. By using the same pinhole array images, the local divergence (spread of incident angles) as a function of radial position can be estimated from the ratio of the FWHM of the spot cast by each pinhole and the distance between the pinhole array and the camera image plane. A typical pinhole image indicated values of about 1 mrad except in the center where the values reach 2 mrad. These values are very close to lithography specifications (2-5 mrad for the 3.sigma. width). FIG. 5 shows an optical device using a scanning paraboloidal shell x-ray collimator optic to increase by about 10 times the number of x-rays delivered to a mask of an x-ray lithography system. The optic consists of a truncated paraboloidal shell with an interior surface that is an x-ray multilayer mirror. When positioned such that the point source is at the focus of the parabolic shape, rays emanating from the source enter the small end of the optic, are reflected by the mirrored surface, and exit the optic in a parallel beam. Rays from the source are prevented from passing directly through the optic by a beam block placed at the entrance to the optic. The beam block consists of 2 mil lead foil that is capable of totally absorbing the incident x-ray radiation. The beam block can be supported by a thin polypropylene film that has been affixed to a mechanical ring support. The lead foil is attached to the film using epoxy. The film further serves to block target debris generated by the source and prevents debris contamination of the x-ray mirror surface. The film can also be coated with a thin metal layer, typically aluminum, and then serves to block ultraviolet radiation from the source that would otherwise have the potential of damaging the mask surface. Because the central portion of the optic is blocked, the collimator produces an annular or ring field. To uniformly illuminate the print field, the ring field is scanned across the print field by either moving the source and collimator or by scanning the wafer. In either case, a uniform intensity distribution is obtained by using a shaped beam block or obscuration. One advantage of a scanning collimator is that imperfections of the reflecting surface that would produce intensity non-uniformities are to a significant extent averaged out by the scanning process. Thin struts oriented perpendicular to the direction of motion can be used to support the thin UV/debris filter because the scanning process will minimize any shadowing effect caused by these struts. As seen in FIG. 5, the optic 40 has a beam block 41, a support/flat field mask 42, and a pair of thin filter supports 43. As a beam indicated by arrow 44 passes the print field 45 as indicated by the illumination pattern 46. The print field 45 is uniformly exposed even though a central spot 47 is not illuminated. FIG. 6 is a schematic of a possible scanning collimator system where the focusing lens, laser target, and collimator are all scanned on a single stage. Alternatively, the collimator and source assembly can remain fixed and the mask scanned past the collimated beam by a scanning stepper. As shown in FIG. 6, the scanning collimator system comprises a stepper 50, and a scanning stage 51 having therein a focusing lens 52 for laser beam 53, a target tape drive 54 and a collimator 55, which produces a collimated x-ray beam 56 that is directed onto a mask 57 located on the stepper 50. Because the scanning process overlays rays reflected from different places on the collimator mirror onto a single point on the mask, it is necessary that the collimator have zero global divergence everywhere (i.e., the average incident angle of rays on the mask must be perpendicular to the mask surface). The collimator shape that produces the required x-ray beam of parallel rays is a truncated paraboloid of revolution, with the source placed at the focus. An example of this class of collimator is shown in FIG. 7. Efficient scanning systems must use resonance reflection mirrors. These mirrors would consist of 40-50 alternating layers of W.sub.3 Re or Rh and B.sub.4 C with d-spacings ranging from about 28 to 56 .ANG.. At the central wavelength of the bandpass (11 .ANG.), this range of d-spacings corresponds to reflection angles of 5.5.degree. to 11.degree.. These angles are significantly greater than those possible with grazing reflection (<3.5.degree.), and thus the collection solid-angle is substantially increased. To correctly predict gains of these collimators, account must be taken of the finite bandpass of the mirror, which is narrower than the spectral width of a typical laser produced copper plasma. Nevertheless, gains using these systems can be significant. See Table 1. Three parameters will define a paraboloidal collimator geometry: the shape given by f, the entrance position (z-coordinate), and the exit position (z-coordinate). The integrated dose given will have a minimum at some y-value on the mask. The mask is assumed to be scanned in the x direction. For a uniform exposure, a shaped obscuration must be used to attenuate the intensity at other values of y to match this minimum. It is therefore this minimum dose point that determines the overall dose and the gain. By maximizing the minimum dose value through variation of these three parameters, the optimum collimator design can be achieved. Other subsidiary constraints must also be considered. These include limiting the source-to-collimator distance to no less than 2 cm, and limiting the variation in local divergence to 5 mrad or less. By using this optimizing procedure and then determining the gain by comparing the dose with and without a collimator (with the mask at the relevant distance), a table of gain values can be determined for different field sizes, as shown in Table 1. TABLE 1 Calculated gain values for resonance reflection collimators print field size (mm) 20 .times. 20 25 .times. 25 25 .times. 36 25 .times. 50 gain (20 mrad, no He) 6.7 4.5 6.6 8.9 gain (20 mrad, 1 atm He) 9.0 6.6 11.7 19.8 gain (5 mrad, 1 atm He) 393 370 1135 3863 In Table 1, three gain values are given for each of four field sizes. The first gain assumes that the maximum global divergence at the edge (not the corner) of the print field is 20 mrad and that there is no He absorption. The second gain value includes the effect of He absorption, and the third gain value assumes the maximum global divergence is 5 mrad and the effect of He is included. The gains depend on the allowed maximum global divergence, but in all cases the gains are significant. For certain applications, high-brightness rotating anodes can be used as x-ray sources instead of laser produced plasmas for low-throughput lithography applications. The collimator may have to be placed more than 2 cm from the source so as not to interfere with the optics of the electron beam. In order to capture the same large solid angle as described in the previous section, the optic must have a larger diameter. The resultant ring field is now substantially larger than the print field to be illuminated and is inefficient at delivering x-rays to the mask. This difficulty may be remedied by a two-element axicon system. The first element is a replicated optic having a multilayered mirrored interior that serves to collect the source x-rays and redirects them towards the optical axis. The second optic has a reflecting exterior surface that serves to produce a collimated ring beam having an outer diameter that is only slightly larger than the print field. This second optic is long, has a small diameter, uses grazing reflection, and can be made by standard exterior surface polishing techniques. At least two configurations are possible. The first configuration is the well-known Wolter III telescope (see Michette, `Optical Systems for Soft X-Rays`, Plenum 1986). In this case, the first optic having a mirrored interior is a truncated ellipsoid of revolution with the source at one focus. This optic refocuses x-rays from a point source at the first focus to a point at the second focus. The second optic is a truncated paraboloid of revolution having its focus coincident with the second focus of the ellipsoid. The paraboloid having a reflective exterior surface reflects the converging rays to produce a small diameter collimated ring beam. A second configuration uses a `tilted` truncated paraboloid of revolution as the first optic is shown in FIG. 8. As with the previous configuration, this element has a mirrored interior surface and is made using the replica techniques disclosed herein. This element serves to form a collimated ring beam, but because of the tilted nature of the paraboloidal shape, the beam is directed towards the optical axis. The second optic in this configuration is a linear cone having a grazing reflection exterior mirror that turns the converging ring beam to form a small diameter collimated ring beam traveling parallel to the axis. To maximize the collection solid angle, the first element uses a multilayer mirror. When used with narrow-band characteristic x-rays produced by rotating anode x-ray tubes, scanning axicon collimators of the type disclosed can produce very large gains of 25-50. Many other optical configurations for lithography are possible using reflective optics of the type described here. These optics can be used in projection lithography systems in addition to the proximity lithography applications described above. For projection lithography, similar systems would be used, but only a portion of the annular beam is used, or alternatively a portion of the annular beam is scanned across the print field. The principal tool used to determine the detailed structure of macromolecules is x-ray crystal diffraction. Although high x-ray fluences can be obtained at synchrotron facilities, most structural determinations are made using smaller and more convenient systems based on rotating anode x-ray generators. Academic, biomedical, and pharmaceutical laboratories worldwide have these or similar systems. For large macromolecules, the typical time required to obtain a data set from one crystal sample is one week; it can take more than a day to determine that a sample is unsuitable for measurement. A typical state-of-the-art system consists of a high-brightness 5 kW rotating copper anode source and two orthogonally oriented nickel mirrors used for focusing and wavelength selection. Monte Carlo ray-trace simulations of this system indicate only 10.sup.-8 of the in-band source photons reach the sample. X-ray optics produced by the replication technology disclosed herein are capable of dramatically improving the x-ray fluence delivered to the sample in current x-ray diffraction systems. FIG. 9 shows a two-element ellipsoidal focusing optic (modified Wolter microscope) having a graded layer thickness resonance mirror. Graded d-spacing multilayer resonance reflectors provide wavelength selection and high reflectivities at relatively large reflection angles (up to 1.8 degrees compared to 0.3 degrees for grazing reflection at 1.5 .ANG. Cu-K wavelength). These larger reflection angles and the geometry of the optic provide a much larger collection solid angle than present mirrors. Simulations indicate that a 10-to-100-fold improvement in x-rays delivered to a sample could be obtained leading to a proportionally reduced measurement time. Monte Carlo ray-trace codes were used to produce a novel axicon design capable of delivering 10.times. to 100.times. the current x-ray fluence to the sample. The design shown in FIG. 9 uses a collecting optic that is a truncated ellipsoid of revolution with a reflecting interior surface. The source is positioned at one focus. The second optic is a truncated hyperboloid of revolution with a reflecting exterior surface. The appropriate focus of the hyperboloid is coincident with the second focus of the ellipsoid. The second element acts to partially collimate the converging rays gathered by the ellipsoid and direct then to the sample. The hyperboloidal shape of the second element can be approximated by a linear cone with little loss in focused fluence. The two element multilayer mirror system, as shown in FIG. 9 and generally indicated at 60, comprises an ellipsoidal internal mirror 61 and a conoidal external mirror 62. Energy 63 from a source 64 is reflected by internal mirror 61 onto external mirror 62 to a sample 65. Mirrors made of alternating layers of low and high-Z materials are able to efficiently reflect at much larger angles. Because the average reflection angle varies with axial position on the optic, the d-spacing must also vary. These mirrors comprise 40-50 alternating layers of W.sub.3 Re and B.sub.4 C with d-spacings ranging from 25 to 100 .ANG.. At the central wavelength of the bandpass (1.5 .ANG.), this range of d-spacings corresponds to reflection angles of 1.8.degree. to 0.5.degree. with peak reflectivities of greater than 50%. The wavelength bandpass at any given resonant angle is sufficiently narrow to discriminate between the Cu K.alpha. and K.beta. x-rays, allowing only the desired wavelengths to reach the sample. For the case in which the collection optic can be placed sufficiently close to the source, a single element ellipsoidal mirror system can be used. In this case, the source is placed at the first focus of the truncated ellipsoid of revolution and the sample is placed at the second focus. This optic has a mirrored interior and is made using the replica techniques described herein. To provide a larger collection solid angle, the optic can be made as two sections as shown in FIG. 10. The optic is generally indicated at 70 and has two internal mirror sections 71 and 72 with a source 73 located at a first focus point and a sample 74 placed at the second focus point. Maximum efficiency is most often achieved with the large reflection angles produced by multilayer mirrors. This optic is relevant for applications where it is desirable to concentrate x-rays from a small source to spot on the sample. Common applications include crystallography and x-ray microfluorescence. In certain x-ray fluorescence or spectroscopic measurements, it is desirable to efficiently collect x-rays from the source region, selecting a narrow band of those x-rays for detection or analysis. This can be accomplished with a single element or multi-element x-ray optical system. For instance, certain microfluorescence analysis systems use a well-focused beam of x-rays or electrons to excite the atoms in a small region of the sample being analyzed. The characteristic x-rays emitted from this region can be used quantify the elemental constituents of the sample. A single focusing element such as an ellipsoidal optic could be used to collect the emitted characteristic x-rays. In this case, the optic gives significantly greater x-ray collection and therefore higher instrumental sensitivity. If the collecting optic uses a multilayer reflector, it is capable of selecting a specific wavelength to analyze. In another case, the collecting optic could use a grazing reflection surface so a broad range of wavelengths are reflected to a energy dispersive detector, which is capable of distinguishing the different characteristic x-ray energies. Many other optical configurations for focusing or efficiently collecting x-rays are possible using these optics. Another such system for collecting and analyzing x-rays comprises a paraboloidal collector using grazing incidence reflection that produces a collimated beam of collected x-rays, followed by a second element that is a flat narrow band-pass multilayer mirror. The collimated beam allows the multilayer reflector to be formed by a simple constant d-spacing flat mirror. The reflected x-rays are directed to an area detector or detector array as shown in FIG. 11. Alternatively, a second parabolic mirror can be used after the flat multilayer mirror to refocus the parallel beam to a small region. The embodiment shown in FIG. 11, generally indicated at 80, comprises a grazing reflection parabolic mirror 81 and a flat multilayer mirror 82, with a beam block 83 therebetween. X-rays indicated at 84 from a source 85 are reflected by mirrors 81 and 82 onto a detector 86. The beam block can be used to stop unreflected uncollimated source x-rays. The paraboloidal mirror is made using the replica methods previously described. Wolter microscopes are used to efficiently produce high quality x-ray images of small emitting or illuminated samples. These two-element systems, such as shown in FIG. 12, consist of a truncated hyperboloid 90 of revolution followed by a truncated ellipsoid 92 of revolution. FIG. 12 illustrates an x-ray microscope system that consists of a two-element paraboloidal condenser and the two-element hyperboloidal-ellipsoidal Wolter objective. Conventional high quality microscopes consist of diamond turned and repetitively polished elements that cost several million dollars to fabricate. The replica techniques described herein will produce similar quality optics for a small fraction of the present cost. This is important in many areas of research where x-ray microscopy is used, including biological imaging and inertial confinement fusion. By obtaining multiple views of the same object, these microscopes can also be used to produce tomographic images used to obtain 3-D images of semiconductor devices for failure analysis and quality control. Zone plate microscopes typically consist of a condenser/monochromator that illuminates a sample with x-rays. Transmitted x-rays from a small region of the sample are then focused by an objective zone plate onto a detector. The sample is usually scanned to form the complete image. The present invention allows less expensive and more efficient microscopes to be made using the appropriate replica optic to serve as the condenser (a paraboloid for focusing a collimated beam or an ellipsoid for focusing x-rays from a diverging point source). It has been shown that the present invention provides a new class of x-ray optical devices that have a tubular shape, open at both ends, with the interior surface being highly reflective to x-rays within a wavelength band of interest. The tubular shaped x-ray optical devices are fabricated using a super-polished mandrel on which is sputter deposited layers of reflecting material, thus forming the optic from the inside out. Applications of these x-ray optics include x-ray proximity or projection lithography for semiconductor manufacturing, x-ray crystallography for macromolecular structural determinations, x-ray fluorescence analysis for material studies and semiconductor manufacturing process control, x-ray microscopy and radiography for biological imaging, tomography, semiconductor device failure analysis and quality control, and x-ray microscopes used in inertial confinement fusion studies. While particular embodiments, materials, and parameters have been described and/or illustrated to exemplify and teach the principles of the invention, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.
	abstract	A solid-state high energy-density micro radioisotope power source device including a dielectric and radiation shielding body having an internal cavity, a first electrode disposed a first end of the cavity, and a second electrode disposed at an opposing second end of the cavity and spaced apart from the first electrode such that a micro chamber is provided therebetween. The device further includes a solid-state composite voltaic semiconductor disposed within the micro chamber fabricated by combining at least one semiconductor material with at least one radioisotope material to provide a pre-voltaic semiconductor composition; depositing the pre-voltaic semiconductor composition into the micro chamber; heating the body to liquefy the pre-voltaic semiconductor composition within the micro chamber such that the semiconductor and radioisotope materials are uniformly mixed; and cooling the body and liquid state composite mixture such that liquid state composite mixture solidifies to provide the solid-state composite voltaic semiconductor.
047566566	abstract	Apparatus for remotely handling a device in an irradiated underwater environment includes a plurality of tubular sections interconnected end-to-end to form a handling structure, the bottom section being adapted for connection to the device. A support section is connected to the top tubular section and is adapted to be suspended from an overhead crane. Each section is flanged at its opposite ends. Axially retractable bolts in each bottom flange are threadedly engageable with holes in the top flange of an adjacent section, each bolt being biased to its retracted position and retained in place on the bottom flange. Guide pins on each top flange cooperate with mating holes on adjacent bottom flanges to guide movement of the parts to the proper interconnection orientation. Each section carries two hydraulic line segments provided with quick-connect/disconnect fittings at their opposite ends for connection to the segments of adjacent tubular sections upon interconnection thereof to form control lines which are connectable to the device and to an associated control console.
	abstract	The invention relates to an apparatus and methods for operation in relatively high radiation fields to remotely switch signal devices through a shared single main umbilical signal cable. The invention is particularly suitable for use in a nuclear reactor, such as a boiling water reactor, and in difficult to access areas in the reactor pressure vessel. One or more main umbilical cables connect a control station to an enclosure housing a signal switching device. The signal switching device allows several signal generating/receiving devices, such as cameras and ultrasonic probes, to be controlled by the one or more main umbilical cables.
048200581	claims	1. In a nuclear reactor including at least one guide thimble and at least one control rod received in said guide thimble and supported for movement relative thereto, the improvement which comprises: an end plug having a central axis and an imperforate asymmetrical tip configuration attached to an end of said control rod, said asymmetrical tip configuration defining a lower terminal end on said end plug which is offset to one side of said central axis and produces, in response to axial flow of coolant along said control rod and within its respective guide thimble, a non-symmetric coolant flow velocity pattern about said end plug and a lateral substantially steady state force on said control rod which presses said control rod end plug against a wall of said guide thimble so as to substantially prevent lateral vibration of said control rod due to said axial flow of the coolant. 2. The nuclear reactor as recited in claim 1, wherein said asymmetrical tip configuration includes a flat formed on a side of a generally tapered outer surface of said end plug tip so as to begin at an upper portion of said end plug on an opposite end of said central axis, intersect said central axis and terminate at said lower terminal end on said one side of said central axis. 3. The nuclear reactor as recited in claim 1, wherein said asymmetrical tip configuration includes a pair of flats formed on opposite sides of a generally tapered outer surface of said end plug, one of said flats intersecting said central axis of said end plug and meeting said other of said flats at said lower terminal end on said one side of said central axis. 4. The nuclear reactor as recited in claim 1, wherein said asymmetrical tip configuration includes a pointed conical surface which terminates at said offset lower terminal end of said end plug. 5. The nuclear reactor as recited in claim 1, wherein said asymmetrical tip configuration includes a concave surface formed on a side of a generally tapered outer surface of said end plug so as to begin at an upper portion of said end plug on an opposite side of said central axis, intersect said central axis and terminate at said lower terminal end on said one side of said central axis.
	abstract	A nuclear fuel rod end distance adjusting device includes an insertion rod, a housing having a hollow space, insertion power means installed inside the housing, a connector connected between the insertion power means and the insertion rod, and an anti-rotation tool installed between the insertion power means and the connector. The insertion rod includes nuclear fuel rod tongs and configured to linearly move forward and backward. The insertion power means is configured to move in a longitudinal direction of the housing by converting a rotational motion into a linear motion. The anti-rotation tool is configured to move in the longitudinal direction of the housing by being interlocked with the linear motion of the insertion power means, but preventing rotational force of the insertion power means from being transmitted to the connector. Thereby, movement and end distance of the fuel rods can be more minutely and stably adjusted.
	claims	1. A modular photon emitter, comprising:a spring;a disk including a Beta source;a plastic scintillator disk adjacent said Beta source;a neutral density filter over said scintillator disk; anda bottom cap and a capsule securable together to define a cylindrical chamber with an opening in said capsule on one end;wherein said spring, Beta source disk, plastic scintillator disk, and filter are encapsulated in said cylindrical chamber with said filter adjacent said opening on one end of said capsule and said spring biasing said Beta source disk and said scintillator disk toward said opening. 2. The photon emitter of claim 1, wherein the surface of said scintillator disk adjacent said Beta source disk is roughened. 3. The photon emitter of claim 1, wherein said Beta source is C14. 4. The photon emitter of claim 1, wherein said capsule includes an annular face surrounding said opening, and said filter is secured against said face.
052020843	summary	TECHNICAL FIELD This invention relates generally to nuclear reactors, and, more particularly, to a reactor having improved fuel arrangements in a reactor core. BACKGROUND ART Fission reactors rely on fissioning of fissile atoms such as uranium isotopes (U.sup.233, U.sup.235) and plutonium isotopes (Pu.sup.239, Pu.sup.241). Upon absorption of a neutron, a fissile atom can disintegrate, yielding atoms of lower atomic weight and high kinetic energy along with several high-energy neutrons. The kinetic energy of the fission products is quickly dissipated as heat, which is the primary energy product of nuclear reactors. Some of the neutrons released during disintegration can be absorbed by other fissile atoms, causing a chain reaction of disintegration and heat generation. The fissile atoms in nuclear reactors are arranged so that the chain reaction can be self-sustaining. To facilitate handling, fissile fuel is typically maintained in modular units. These units can be bundles of vertically extending fuel rods. Each rod has a cladding which encloses a stack of fissile fuel pellets. Generally, each rod includes a space or "plenum" for accumulating gaseous byproducts of fission reactions which might otherwise unacceptably pressurize the rod and lead to its rupture. The bundles are arranged in a two-dimensional array in the reactor to form a "core". Neutron-absorbing control rods are inserted between or within fuel bundles to control the reactivity of the core. The reactivity of the core can be adjusted by incremental insertions and withdrawals of the control rods. Both economic and safety considerations favor improved fuel utilization, which can mean less frequent refueling and less exposure to radiation from a reactor interior. In addition, improved fuel utilization generally implies more complete fuel "burnups", or fissioning. A major obstacle to obtaining long fuel element lifetimes and complete fuel burnups is the inhomogeneities of the neutron flux both radially and axially throughout the core. For example, fuel bundles near the center of the core are surrounded by other fuel elements. Accordingly, the neutron flux at these central fuel bundles exceeds the neutron flux at peripheral fuel bundles which have one or more sides facing away from the rest of the fuel elements. Therefore, peripheral fuel bundles tend to burn up more slowly than do the more central fuel bundles. The problem of flux density variations with radial core position has been addressed by repositioning fuel bundles between central and peripheral positions. This results in extended fuel bundle lifetimes at the expense of additional refueling operations. Variations in neutron flux density occur in the axial direction as well as the radial direction. For example, fuel near the top or bottom of a fuel bundle is subjected to less neutron flux than is fuel located midway up a fuel bundle. These axial variations are not effectively addressed by radial redistribution of fuel elements. In addition to the variations in neutron flux density, variations in spectral distribution affect burnup. For example, in a boiling-water reactor (BWR), neutrons released during fissioning move too quickly and have too high an energy to readily induce the further fissioning required to sustain a chain reaction. These high energy neutrons are known as "fast" neutrons. Slower neutrons, referred to as "thermal neutrons", most readily induce fission. In BWRs, thermal neutrons are formerly fast neutrons that have been slowed primarily through collisions with hydrogen atoms in the water (moderator) used as the heat transfer medium. Between the energy levels of thermal and fast neutrons are "epi-thermal" neutrons. Epithermal neutrons exceed the desired energy for inducing fission but promote resonance absorption by many actinide series isotopes, converting some "fertile" isotopes to "fissile" (fissionable) isotopes. For example, epithermal neutrons are effective at converting fertile U.sup.238 to fissile Pu.sup.239. Within a core, the percentages of thermal, epithermal and fast neutrons vary over the axial extent of the core. Axial variations in neutron spectra are caused in part by variations in the density or void fraction of the water flowing up the core. In a boiling-water reactor (BWR), water entering the bottom of a core is essentially completely in the liquid phase. Water flowing up through the core boils, so most of the volume of water exiting the top of the core is in the vapor phase, i.e., steam. Steam is less effective than liquid water as a neutron moderator due to the lower density of the vapor phase. Therefore, from the point of view of neutron moderation, core volumes occupied by steam are considered "voids"; the amount of steam at any spatial region in the core can be characterized by a "void fraction". Within a fuel bundle, the void fraction can vary from about zero at the base to about 0.7 near the top. Continuing the example for the BWR, rear the bottom of a fuel bundle, neutron generation and density are relatively low, but the percentage of thermal neutrons is high because of the moderation provided by the low void fraction water at that level. Higher up, neutron density reaches its maximum, while void fraction continues to climb. Thus, the density of thermal neutrons peaks somewhere near the lower-middle level of the bundle. Above this level, neutron density remains roughly stable while the percentages of epithermal and fast neutrons increase. Near the top of the bundle, neutron density decreases across the spectrum since there are no neutrons being generated just above the top of the bundle. The inhomogeneities induced by this spectral distribution can cause a variety of related problems. Focusing on the upper-middle section, problems of inadequate burnup and increased production of high-level transuranic waste are of concern. Since the upper-middle section has a relatively low percentage of thermal neutrons, a higher concentration of of fissile fuel is sometimes used to support a chain reaction. If the fuel bundle has a uniform fissile fuel distribution, this section could fall below criticality (the level required to sustain a chain reaction) before the other bundle sections. The fuel bundle would have to be replaced long before the fissile fuel in all sections of the bundle were depleted, wasting fuel. The problem with waste disposal is further aggravated at this upper-middle section since the relatively high level of epithermal neutrons results in increased production of actinide-series elements such as neptunium, plutonium, americium, and curium, which end up as high level-waste. One method of dealing with axial spectral variations is using a control rod. For the BWR, control rods typically extend into the core from below and contain neutron-absorbing material which robs the adjacent fuel of thermal neutrons which would otherwise be available for fissioning. Thus, control rods can be used to modify the distribution of thermal neutrons over axial position to achieve more complete burnups. However, control rods provide only a gross level of control over spectral density. More precise compensation for spectral variations can be implemented using enrichment variation and burnable poisons. Enrichment variation using, for example, U.sup.235 enriched uranium, can be used near the top of a fuel bundle to partially compensate for a localized lack of thermal neutrons. Similarly, burnable poisons such as gadolinium oxide (Gd.sub.2 O.sub.3), can balance the exposure of bundle sections receiving a high thermal neutron flux. Over time, the burnable poisons are converted to isotopes which are not poisons so that more thermal neutrons become available for fissioning as the amount of fissile material decreases. In this way, fissioning can remain more constant over time in a section of the fuel bundle. By varying the amount of enrichment and burnable poisons by axial position along a bundle, longer and more complete burnups can be achieved. In addition, the enrichment and poison profiles can be varied by radial position to compensate for radial variations in thermal neutron density. Nonetheless, taken together, the use of control rods, radial positional exchange of bundles, selective enrichment and distribution of burnable poisons still leave problems with axial variations in burn rates and neutron spectra. Furthermore, none of these employed methods effectively address the problem of the high level of fissile material produced and left in the upper-middle sections of the bundle due to the high level of epithermal neutrons and the low level of thermal neutrons. What is needed is a system that deals more effectively with axial spectral variations in neutron flux so that higher fuel burnups are provided and so that high-level waste is minimized. Furthermore, since water is used as the coolant in a conventional BWR, it becomes contaminated with impurities, or crud, as it is circulated through the reactor, piping, and the typical steam turbine being powered by the steam generated by the BWR. The crud is undesirable in the reactor since it may accumulate on the fuel rod cladding and decrease heat transfer rates between the rods and the coolant water flowable thereover. The decreased heat transfer rate allows the fuel temperature to rise which decrease reactivity. Furthermore, increased clad temperatures can lead to a shorter mechanical lifetime of the fuel rods. Accordingly, the reactor should include suitable means to ensure that the crud may be removed from the coolant for reducing or preventing crud buildup on the fuel bundles. OBJECTS OF THE INVENTION A major object of the present invention is to provide for more thorough fuel burnups to enhance fuel utilization and minimize active waste products. Another object of the present invention is to provide a new and improved reactor effective for using axial variations in neutron flux density and in a neutron spectral distribution for both converting fertile fuel to fissile fuel, and providing more uniform and complete fuel fissioning during the life of the fuel in the reactor core. Another object of the present invention is to provide a new and improved reactor having a bi-level core in the form of an axially stacked steam cooled reactor (SCR) and a boiling water reactor (BWR) including means for removing crud from the reactor coolant. DISCLOSURE OF INVENTION In accordance with the present invention, a nuclear reactor with a recirculating heat transfer fluid has a bi-level core which provides enhanced flexibility in fuel arrangement. The bi-level core includes a first core, a plurality of steam separators disposed above the first core, and a second core disposed above the steam separators all inside a single pressure vessel. The steam separators receive a steam and water mixture from the first core and separate the water from the steam. The separated steam is channeled to the second core which cools the second core resulting in the generation of superheated steam. Preferably, fuel bundles of the second core are arranged in vertical alignment with the interposed steam separator and fuel bundles of the first core. This permits a fuel bundle of the first core to be accessed by removing all three elements as a single assembly. During refueling operations, fuel bundles can be shifted from one core to the other, providing additional flexibility in arranging units at various stages of burnup. The bi-level core allows fuel to be initially positioned in the second core for conversion of fertile fuel to fissile fuel, and then repositioned to the first core for more complete axial burnup. The steam separators disposed between the first and second cores control the quality of steam channeled into the second core, and allow crud to remain in solution in the separated water for being removed during operation by a reactor water cleanup system without buildup in either core.
	claims	1. An X-ray imaging apparatus for carrying out scanning X-ray imaging, the X-ray imaging apparatus comprising: an X-ray source ( 5 ) in front of the object being imaged for generating X-ray radiation, a primary collimator ( 6 ) for forming an X-ray beam ( 11 ) of the X-ray radiation generated and for directing the X-ray beam through the object being imaged, and X-ray radiation receiving means ( 15 ) located behind the object being imaged for receiving X-ray radiation, characterised in that the X-ray imaging apparatus comprises X-ray radiation identifying means ( 20 - 22 ) for producing a control signal, on the basis of which control signal, the position of the X-ray beam emitted from the X-ray source ( 5 ) with respect to the X-ray radiation receiving means ( 15 ) can be located and, if necessary, the ray beam can be directed inside the imaging area of the radiation receiving means and on the basis of which control signal, the movements of the apparatus required by scanning imaging can be adjusted so as to be synchronised with each other. 2. An apparatus as claimed in claim 1 , characterised in that the radiation receiving means comprise a digital imaging detector ( 15 ). claim 1 3. An apparatus as claimed in claim 1 , characterised in that the apparatus is used as scanning cephalometric imaging apparatus, which comprises a line detector camera ( 8 ) equipped with a digital imaging detector ( 15 ) and a secondary collimator ( 9 ) in the vicinity of the line detector camera ( 8 ), and that the identifying means ( 20 - 22 ) produce a control signal by means of which the movements of the apparatus required by scanning cephalometric imaging are mutually synchronised and/or maintained synchronised. claim 1 4. An apparatus as claimed in claim 3 , characterised in that as identifying means is used at least one identifying detector ( 20 - 22 ) located on that surface of the secondary collimator ( 9 ), which is on the X-ray source ( 5 ) side. claim 3 5. An apparatus as claimed in claim 4 , characterised in that the said at least one identifying detector is located at the slot ( 19 ) of the secondary collimator ( 9 ). claim 4 6. An apparatus as claimed in claim 1 , characterised in that as the apparatus is used an intraoral imaging apparatus. claim 1 7. An apparatus as claimed in claim 1 , wherein the radiation receiving means is a digital imaging detector, characterised in that as identifying means are used such pixels inside ( 15 B) the active imaging area of the imaging detector ( 15 ), which are normally arranged to be radiation-free and to give out an identifying signal when radiation meets them. claim 1 8. An apparatus as claimed in claim 1 , wherein the radiation receiving means is a digital imaging detector, characterised in that as identifying means are used such pixels inside ( 15 A) the active imaging area of the imaging detector ( 15 ), which are normally arranged to be in the field of rays and to provide information on radiation meeting the detector. claim 1
052805069	abstract	A main steam isolation valve of a reactor power plant comprises a valve body provided with inlet and outlet portions through which a steam flows, a cylindrical valve disk accommodated in the valve body to be reciprocatingly movable therein along an inner peripheral surface of the valve body for opening and closing the steam flow inlet portion and a driving mechanism secured to the valve body and operatively connected to the valve disk for reciprocatingly moving the valve disk in the valve body. A coupling member is applied to an end opening of the valve body for holding the valve disk when the valve disk is shifted to a position fully opening the inlet portion. A tubular wall member is integrally formed with the valve body so as to surround the valve disk with a gap therebetween when the valve disk is fully opened. A guide rib is further disposed to the valve body for causing asymmetric steam flow in the inlet portion of the steam flow of the valve body.
047924292	abstract	An upper end fitting 14 of a nuclear fuel assembly is provided at two of its opposite corners with spring retention caps 12 having a hook-like structrue defined by an inwardly directed flange 50 engaging a slot 56 in the top nozzle or end fitting 14. The spring packs 20 are retained within the spring retention caps 12 even if one or both spring retention screws 34 break and both the broken screw portions and the springs are maintained in operative position by the cap 12 until reconstitution.
050935798	claims	1. A substrate holding device for holding a substrate for exposure thereof with radiation, said apparatus comprising: a holding table including a reduced pressure passageway; a pressure gauge for measuring a value related to the pressure in said reduced pressure passageway; a pump for producing a pressure difference between a first surface of the substrate to be attracted to said holding table and a second surface of the substrate not to be attracted to said holding table; a valve which can be opened/closed for control of the pressure in said reduced pressure passageway; pressure control means for controlling the opening/closing of said valve during exposure of the substrate with radiation, on the basis of an output corresponding to the valve measured by said pressure gauge, such that the substrate is held on said holding table during the exposure by a controlled pressure difference; and temperature control means for controlling the temperature of said holding table. a holding table including a reduced pressure passageway; a pressure gauge for measuring a value related to the pressure in said reduced pressure passageway; a pump for producing a pressure difference between a first surface of the substrate to be attracted to said holding table and a second surface of the substrate not to be attracted to said holding table; a tank for containing gas to be supplied to said reduced pressure passageway; a first valve provided between said reduced pressure passageway and said pump; a second valve provided between said reduced pressure passageway and said tank; and pressure control means for controlling opening/closing of said first and second valves during exposure of the substrate with the radiation, on the basis of an output corresponding to the value measured by said pressure gauge, so as to provide a predetermined pressure in said reduced pressure passageway, such that the substrate is held on said holding table during exposure by a controlled pressure difference. a holding table including a reduced pressure passageway; a pressure gauge for measuring a value related to the pressure in said reduced pressure passageway; a pump for producing a pressure difference between a first surface of the substrate to be attracted to said holding table and a second surface of the substrate not to be attracted to said holding table; a valve which can be opened/closed for control of the pressure in said reduced pressure passageway; and pressure control means for controlling the opening/closing of said valve during the exposure of the substrate with the radiation, on the basis of an output corresponding to the value measured by said pressure gauge, so as to provide a predetermined pressure in said reduced pressure passageway, such that the substrate is held on said holding table during the exposure by a controlled pressure difference. a holding table including a reduced pressure passageway; a pressure gauge for measuring a value related to the pressure in said reduced pressure passageway; a pump for producing a pressure difference between a first surface of the substrate to be attracted to said holding table and a second surface of the substrate not to be attracted to said holding table; a valve which can be opened/closed for control of the pressure in said reduced pressure passageway; and pressure control means for controlling the opening/closing of said valve during the exposure of the substrate with the radiation, on the basis of an output corresponding to the value measured by said pressure gauge, such that the substrate is held on said holding table during the exposure by a controlled pressure difference and with a predetermined contact thermal resistance between the substrate and said holding table. a holding table including a reduced pressure passageway; a pressure gauge for measuring a value related to the pressure in said reduced pressure passageway; pressure difference producing means for producing a pressure difference between a first surface of the substrate to be attracted to said holding table and a second surface of the substrate not to be attracted to said holding table; pressure control means for controlling the pressure in said reduced pressure passageway during the exposure of the substrate with the radiation, on the basis of an output corresponding to the value measured by said pressure gauge, such that the substrate is held on said holding table during the exposure by a controlled pressure difference; and temperature control means for controlling the temperature of said holding table. a holding table for holding the substrate thereon, said holding table including a reduced-pressure passageway; exposing means for exposing the substrate, held by said holding table, with radiation; a chamber for surrounding said holding table with a predetermined reduced-pressure ambience; a pressure gauge for measuring a level related to the pressure in said reduced-pressure passageway; pump means for producing through said reduced-pressure passageway a pressure difference between a first surface of the substrate facing said holding table and a second surface on the opposite side of the substrate, such that the substrate is held on said holding table by the produced pressure difference; valve means to be opened/closed for control of the pressure in said reduced-pressure passageway; and control means for controlling the opening/closing of said valve means during exposure of the substrate with radiation on the basis of the measurement by said pressure gauge, such that during exposure of the substrate with the radiation the substrate is held on said holding table with a controlled pressure difference and with a controlled contact thermal resistance between the substrate and said holding table. placing the substrate on a holding table in a chamber; applying pressure to one of a first surface of the substrate placed on the holding table facing the holding table and a second surface of the substrate opposite the first surface, through a passageway with valve means so as to produce a pressure difference between the first surface and the second surface of the substrate; measuring a level related to the pressure in the passageway; exposing the substrate on the holding table with radiation to form the pattern on the substrate; and controlling, during the exposure of the substrate, the opening/closing of the passageway by the valve means on the basis of the measured level so as to control the pressure difference between the first surface and the second surface of the substrate to continuously hold the substrate during the exposure by a controlled pressure difference between the first and second surfaces and with a controlled contact thermal resistance between the substrate and the holding table. 2. A device according to claim 1, wherein said temperature control means supplies constant temperature water to said holding table. 3. A device according to claim 1, wherein said pressure control means controls said valve so as to provide a predetermined contact thermal resistance between the substrate and said holding table. 4. A substrate holding device for holding a substrate for exposure thereof with radiation, said apparatus comprising: 5. A device according to claim 4, wherein said pressure control means controls said first and second valves so as to provide a predetermined contact thermal resistance between the substrate and said holding table. 6. A substrate holding device for holding a substrate for exposure thereof with radiation, said apparatus comprising: 7. A substrate holding device for holding a substrate for exposure thereof with radiation, said apparatus comprising: 8. A device for holding a substrate on which a pattern formed on an original is to be printed by exposure of the substrate with radiation, said device comprising: 9. A device according to claim 8, wherein said temperature control means controls the temperature of each of the original and the substrate, through said holding table. 10. A device according to claim 8, wherein said pressure control means controls the pressure in said reduced pressure passageway so as to provide a predetermined contact thermal resistance between the substrate and said holding table. 11. A device according to claim 8, further comprising a chamber for surrounding the original and the substrate with a predetermined ambience. 12. A device according to claim 8, wherein said device is used with an exposure apparatus having a chamber, for exposing the original and the substrate with radiation, and wherein said holding table is accommodated in the chamber. 13. An exposure apparatus for exposing a substrate with radiation to form a pattern on the substrate, said apparatus comprising: 14. An apparatus according to claim 13, further comprising temperature controlling means for controlling the temperature of said holding table. 15. A method of exposing a substrate with radiation to form a pattern on the substrate, said method comprising the steps of: 16. A method according to claim 15, further comprising holding the substrate on the holding table only by the controlled pressure difference during the exposure.
	summary
052395669	claims	1. A multi-layered mirror comprising: a substrate; first layers of a first substance; and second layers of a second substance; wherein said first layers and said second layers are alternately laminated on said substrate; the difference in refractive index in the soft X-ray region of said first substance from vacuum is larger than that of said second substance; and said first substance is a nickel-chromium alloy containing chromium in a proportion of 5% by weight or larger, or of pure chromium. a substrate; first layers of a first substance; and second layers of a second substance; wherein said first layers and said second layers are alternately laminated on said substrate; the difference in refractive index in the soft X-ray region of said first substance from vacuum is larger than that of said second substance; and said first substance is a nickel-chromium alloy containing chromium in a proportion of 5% by weight or larger. an ellipsoidal multi-layered condenser mirror including a substrate, first layers of a first substance, and second layers of a second substance, with said first layers and said second layers being alternately laminated on said substrate, the difference in refractive index in the soft X-ray region of said first substance from vacuum being larger than that of said second substance, and said first substance being a nickel-chromium alloy containing chromium in a proportion of 5% by weight or larger; an X-ray source and a specimen positioned respectively on two focal points of said condenser mirror; an imaging optical system capable of focusing X-rays; and a detector for detecting X-rays irradiating the specimen. a substrate; first layers of a first substance; and second layers of a second substance; wherein said first layers and said second layers are alternately laminated on said substrate; the difference in refractive index in the soft X-ray region of said first substance from vacuum is larger than that of said second substance; and said second substance is vanadium oxide. a substrate; first layers of a first substance; and second layers of a second substance; wherein said first layers and said second layers are alternatively laminated on said substrate; the difference in refractive index in the soft X-ray region of said first substance from vacuum is larger than that of said second substance; and said second substance is vanadium oxide. an ellipsoidal multi-layered condenser mirror including a substrate, first layers of a first substance, sand second layers of a second substance, with said first layers and said second layers being alternately laminated on said substrate, the difference in refractive index in the soft X-ray region of said first substance from vacuum being larger than that of said second substance, and said second substance being vanadium oxide; an X-ray source and a specimen positioned respectively on two focal points of said condenser mirror; an imaging optical system capable of focusing X-rays; and a detector for detecting X-rays irradiating the specimen. 2. A multi-layered mirror according to claim 1, wherein said second substance is selected from the group consisting of vanadium oxide, silicon oxide and carbon. 3. An ellipsoidal multi-layered condenser mirror comprising: 4. A multi-layered condenser mirror according to claim 3, wherein said second substance is selected from the group consisting of vanadium oxide, silicon oxide and carbon. 5. An X-ray microscope comprising: 6. An X-ray microscope according to claim 5, wherein said second substance is selected from the group consisting of vanadium oxide, silicon oxide and carbon. 7. An X-ray microscope according to claim 6, wherein said imaging optical system includes a zone plate. 8. An X-ray microscope according to claim 5 wherein said imaging optical system includes a zone plate. 9. A multi-layered mirror comprising: 10. A multi-layered mirror according to claim 9, wherein said first substance is chromium alloy. 11. An ellipsoidal multi-layered condenser mirror, comprising: 12. An ellipsoidal multi-layered condenser mirror according to claim 11, wherein said first substance is chromium alloy. 13. An X-ray microscope comprising: 14. An X-ray microscope according to claim 13; wherein said first substance is chromium alloy. 15. An X-ray microscope according to claim 14, wherein said imaging optical system includes a zone plate. 16. An X-ray microscope according to claim 13, wherein said imaging optical system includes a zone plate.
052157059	abstract	To measure fuel rod-centering forces exerted by double-acting springs assembled with different pairs of ferrules in a nuclear fuel bundle spacer, a gauge is provided to include an alignment rod and a probe carried by a handle for insertions into the ferrules of a ferrule pair. The alignment rod loads the side of the spring acting in its ferrule, while the other spring side exerts its fuel rod-centering force on a plunger mounted in the probe. The plunger is mechanically linked to a load cell which provides an electrical readout of the spring force.
	claims	1. A security entrance system for preventing entry of forbidden articles and/or substances from a surrounding area to a protected one comprising:a partitioning separating a protected area from an unprotected one;at least one walk-gate made in said partitioning;an information control-and-processing device and a detector of forbidden articles and/or substances,wherein said detector of forbidden articles and/or substances comprises an X-ray radiation source to provide examination of a person passing through at least one walk-gate;wherein an X-ray receiver of said detector is made as a vertical linear X-ray receiver built-in into a walk-gate element opposite to said X-ray radiation source; andwherein said walk-gate element with said built-in X-ray receiver is a movable door with a drive mechanism of said door made so that it maintains a predefined ratio of a door motion speed and of a scanning rate of the X-ray radiation source. 2. The security entrance system as in claim 1, wherein at least one walk-gate in said partitioning is supplied with at least one door having a respective drive mechanism connected to a signal output of the information control-and-processing device. 3. The security entrance system as in claim 1, wherein said detector of forbidden articles and/or substances is comprised of an X-ray scanning radiation source and of an X-ray receiver that is co-linear to said X-ray radiation and is connected to information inputs of the information control-and-processing device. 4. The security entrance system as in claim 3, wherein said detector of forbidden articles and/or substances further comprises a horizontal linear X-ray receiver disposed under a walk-gate floor provided with at least one X-ray transparent portion or built-in into said walk-gate floor. 5. The security entrance system as in claim 3, wherein said detector of forbidden articles and/or substances further comprises a horizontal linear X-ray receiver built-in into a walk-gate floor. 6. The security entrance system as in claim 3, wherein said detector of forbidden articles and/or substances further comprises a horizontal linear X-ray receiver disposed above a walk-gate ceiling provided with at least one X-ray transparent portion. 7. The security entrance system as in claim 3, wherein said detector of forbidden articles and/or substances further comprises a horizontal linear X-ray receiver built-in into a walk-gate ceiling. 8. The security entrance system as in claim 1, wherein said X-ray radiation source of said detector of forbidden articles and/or substances is made to generate a flat fan-shaped X-ray beam in a walk-gate plane and can be disposed behind a bottom part of one of the walk-gate side walls provided with at least one X-ray transparent portion. 9. The security entrance system as in claim 1, wherein said X-ray radiation source of said detector of forbidden articles and/or substances is made to generate a flat fan-shaped X-ray beam in a walk-gate plane and is built-in into a bottom part of one of the walk-gate side walls. 10. The security entrance system as in claim 1, wherein said walk-gate is additionally supplied with a sensor to define a presence of a person ready to pass through said walk-gate with an output of said sensor being connected to an input for activating the X-ray radiation source.
051480328	abstract	In a radiation emitting device, particularly in a radiation therapy device, isodose curves are adjusted both by a moveable plate that is controlled during irradiation and by varying the dose rate of the radiation beam during irradiation. By superimposing the effects of moving the plate and varying the dose rate of the radiation beam, it is possible to vary the isodose curve in the object of irradiation, so that a wide range of variation in the possible isodose curves is obtained. If the plate is moved at a constant speed, e.g. various wedge-shaped isodose curves can be easily achieved.
	claims	1. An apparatus comprising:a heat exchanger, the heat exchanger including at least a first surface;a mirror assembly, the mirror assembly including a first mirror block having a first mirrored surface, the mirror assembly having at least a first well defined therein, wherein the heat exchanger is separated from the mirror assembly; anda first liquid metal interface, the first liquid metal interface including liquid metal, the liquid metal being contained in the at least first well, wherein the first surface is in contact with the liquid metal to transfer heat from the first mirror block to the heat exchanger and wherein the first surface of the heat exchanger is immersed in the liquid metal within the first well. 2. The apparatus of claim 1 wherein the mirror assembly further includes a base plate, the base plate being coupled to the first mirror block. 3. The apparatus of claim 2 wherein the at least first well is defined in the first mirror block. 4. The apparatus of claim 2 further including:an optical element, wherein the optical element is coupled to the base plate. 5. The apparatus of claim 2 wherein the base plate includes a first structure and the first mirror block includes a second structure, the first structure and the second structure being arranged to couple the base plate to the first mirror block. 6. The apparatus of claim 5 wherein the second structure is a rib or a round boss. 7. The apparatus of claim 2 further including:a second liquid metal interface including the liquid metal, wherein the mirror assembly further includes a second mirror block coupled to the base plate, the second mirror block having at least a second well defined therein, the liquid metal of the second liquid metal interface being contained in the at least second well. 8. The apparatus of claim 2 wherein the base plate and the first mirror block are coupled at an interface, the interface being a quasi-kinematic mount. 9. The apparatus of claim 1 wherein the heat exchanger includes at least a first prong, the first prong including the first surface, and wherein the first prong being at least partially positioned within the first well. 10. The apparatus of claim 1 wherein the liquid metal is a gallium alloy. 11. The apparatus of claim 1 wherein the liquid metal has an associated temperature gradient, wherein the temperature gradient is approximately normal to the first mirrored surface. 12. The apparatus of claim 1 further including:an optical element, the optical element being coupled to the mirror assembly. 13. The apparatus of claim 1 wherein the apparatus is an extreme ultraviolet (EUV) lithography system. 14. A device manufactured with the EUV lithography system of claim 13. 15. The apparatus of claim 1 wherein the heat exchanger is not in direct contact with the mirror assembly. 16. The apparatus of claim 1 wherein the first liquid metal interface is an interface between the heat exchanger and the mirror assembly. 17. The apparatus of claim 1 wherein the first mirrored surface faces downwardly towards the heat exchanger. 18. The apparatus of claim 1 wherein the at least first well has a bottom surface, and wherein the first liquid metal interface is formed between the first surface of the heat exchanger and the bottom surface. 19. A method for assembling a cooling apparatus in an extreme ultraviolet (EUV) lithography system, the method comprising:obtaining a mirror assembly, the mirror assembly having at least one cavity defined therein;at least partially filling the at least one cavity with a liquid metal; andpositioning at least one surface of a heat exchanger in the at least one cavity, wherein positioning the at least one surface of the heat exchanger in the at least one cavity includes causing the at least one surface to contact the liquid metal, wherein the heat exchanger is separated from the mirror assembly. 20. The method of claim 19 wherein the mirror assembly includes a base plate and a mirror block, the base plate being coupled to an optical arrangement, the at least one cavity being defined in the mirror block. 21. The method of claim 20 further including:assembling the mirror block to the base plate after at least partially filling the at least one cavity with the liquid metal. 22. The method of claim 21 wherein the at least one surface of the heat exchanger is associated with at least one prong of the heat exchanger, the at least one prong of the heat exchanger being arranged to pass through the base plate and into the at least one cavity. 23. The method of claim 19 wherein the heat exchanger is not in direct contact with the mirror assembly. 24. The apparatus of claim 19 wherein the mirror assembly includes a mirrored surface, the mirrored surface being arranged to face downwardly towards the heat exchanger. 25. A method for cooling a mirror arrangement in a lithography device, the method comprising:transferring a heat load from a mirrored surface of the mirror arrangement to a liquid metal interface, the liquid metal interface being arranged between the mirror arrangement and a heat exchanger; andtransferring the heat load from the liquid metal interface to at least a first surface of the heat exchanger, wherein the first surface of the heat exchanger is immersed in the liquid metal interface within a first well. 26. The method of claim 25 wherein the first surface of the heat exchanger is associated with a prong of the heat exchanger and the liquid metal interface is arranged in a cavity defined in the mirror arrangement. 27. The method of claim 26 wherein the heat exchanger is not in direct contact with the mirror assembly, and wherein the prong of the heat exchanger is positioned within the cavity defined in the mirror arrangement. 28. The apparatus of claim 25 wherein the mirrored surface faces downwardly towards the heat exchanger.
	summary
	description	This application claims the benefit of Chinese Application No. 2003-10124909.X filed Dec. 29, 2003. The present invention relates to a collimator, as well as an X-ray irradiator and an X-ray apparatus. Particularly, the invention is concerned with a collimator for restricting an irradiation range of X-ray, as well as an X-ray irradiator and an X-ray apparatus both provided with such a collimator. In an X-ray irradiator there is used a collimator for restricting an irradiation range of X-ray. The collimator has an aperture permitting X-ray to pass therethrough and has a structure such that X-ray cannot pass through the collimator except through the aperture. With this structure, the irradiation range of X-ray can be adjusted. A collimator having a variable aperture is provided with movable plate members, namely, blades having X-ray absorbability. As the blades there are used a pair of blades opposed to each other at respective end faces. The pair of blades are movable in directions opposite to each other in a plane parallel to their surfaces. For expanding the aperture, the pair of blades are moved in directions away from each other, while for narrowing the aperture, the blades are moved toward each other. Two pairs of such blades are combined perpendicularly to each other to afford a collimator wherein the size of aperture can be changed in two directions perpendicular to each other. In such a collimator, by making all of the blades adjustable independently, it is possible to adjust not only the size of aperture but also a two-dimensional position thereof (see, for example, Patent Literature 1). [Patent Literature 1] Japanese Published Unexamined Patent Application No. 2002-355242 (pages 2 to 3, FIGS. 1 to 2) In the above collimator, in order to make all of the blades adjustable independently, it is necessary to use special blades and a drive mechanism for the blades. Therefore, it is an object of the present invention to provide a collimator having a high degree of freedom for adjusting an aperture without the need of any special blades and drive mechanism, as well as an X-ray irradiator and an X-ray apparatus both provided with such a collimator. (1) The present invention, in one aspect thereof for solving the above-mentioned problem, resides in a collimator comprising: a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; a second plate member disposed spacedly from the first plate member in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members; a pair of third plate members disposed spacedly from the first and second plate members in a direction perpendicular to the surfaces of the first and second plate members, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by the spacing between respective end faces opposed to each other; and a fourth plate member disposed spacedly from the first, second and third plate members in a direction perpendicular to the surfaces of the first, second and third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members. (2) The present invention, in another aspect thereof for solving the above-mentioned problem, resides in an X-ray irradiator comprising an X-ray tube and a collimator for collimating X-ray generated from the X-ray tube, the collimator comprising: a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; a second plate member disposed spacedly from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members; a pair of third plate members disposed spacedly from the first and second plate members in a direction perpendicular to the surfaces of the first and second plate members, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by the spacing between respective end faces opposed to each other; and a fourth plate member disposed spacedly from the first, second and third plate members in a direction perpendicular to the surfaces of the first, second and third plate members, having X-ray absorbability, and being movable in a direction parallel to the moving direction of the third plate members. (3) The present invention, in a further aspect thereof for solving the above-mentioned problem, resides in an X-ray apparatus comprising an X-ray tube, a collimator for collimating X-ray generated from the X-ray tube and applying the collimated X-ray to an object to be radiographed, and a detector means for detecting the X-ray which has passed through the object to be radiographed, the collimator comprising: a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; a second plate member disposed spacedly from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members; a pair of third plate members disposed spacedly from the first and second plate members in a direction perpendicular to the surfaces of the first and second plate members, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; and a fourth plate member disposed spacedly from the first, second and third plate members in a direction perpendicular to the surfaces of the first, second and third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members. In the invention in each of the above aspects, the first and third plate members, which are combined perpendicularly to each other to form a quadrangular aperture, are further combined with the second and fourth plate members which are perpendicular to each other and which are adapted to operate independently of each other, whereby it is possible to adjust the aperture at a high degree of freedom without the need of using any special blades and drive mechanism. For enhancing the degree of freedom in forming the aperture it is preferable that the second plate member and the fourth plate member be movable independently of each other. For facilitating the assembly of the collimator it is preferable that the first and second plate members be constructed as a unitized combination and that the third and fourth plate members be constructed as a unitized combination. For making it possible to combine sub-units according to purposes of use it is preferable that the combined unit of the first and second plate members be subunitized for each of the plate members and that the combined unit of the third and fourth plate members be subunitized for each of the plate members. According to the present invention, it is possible to provide a collimator having a high degree of freedom for adjusting an aperture without the need of any special blades and drive mechanism, as well as an X-ray irradiator and an X-ray apparatus both provided with such a collimator. Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. An embodiment of the present invention will be described in detail hereinunder with reference to the drawings. FIG. 1 illustrates a schematic construction of an X-ray apparatus. This apparatus is an example of a mode for carrying out the invention. With the construction of this apparatus there is shown an example of a mode for carrying the invention with respect to the apparatus thereof. In this X-ray apparatus, as shown in the same figure, X-ray generated from an X-ray tube 1 is diaphragmed by an X-ray diaphragm 3 and is collimated by a collimating plate 500 disposed within a collimator 5, then the collimated X-ray is applied toward an object 7 to be radiographed and transmitted X-ray is detected by a detector 9. The X-ray tube 1 is an example of a mode for carrying out the invention with respect to the X-ray tube defined herein. The collimator 5 is an example of a mode for carrying out the invention with respect to the collimator of the invention. The detector 9 is an example of a mode for carrying out the invention with respect to the detector means defined herein. The portion comprising the X-ray tube 1, X-ray diaphragm 3 and collimator 5 is an example of a mode for carrying out the invention with respect to the X-ray irradiator of the invention. With the construction of this apparatus there is shown an example of a mode for carrying out the invention with respect to the X-ray irradiator of the invention. The collimator 5 is an example of a mode for carrying out the invention with respect to the collimator of the invention. With the construction of this apparatus there is shown an example of a mode for carrying out the invention with respect to the collimator of the invention. The X-ray tube 1 has an anode 101 and a cathode 103, and X-ray is generated from a point of collision (focus) of electrons which are emitted from the cathode 103 toward the anode 101. The X-ray thus generated is applied to the object through the X-ray diaphragm 3 and the collimator 5. The X-ray diaphragm 3 is constructed of an X-ray absorbing material such as lead for example. The collimating plate 500 in the collimator 5 is also constructed of an X-ray absorbing material such as lead for example. The X-ray diaphragm 3 shapes the X-ray generated from the X-ray tube 1 so that the X-ray becomes a quadrangular pyramid-like beam with an X-ray focus on the anode 101 as a vertex. The collimator 5 defines an X-ray irradiation field V by an aperture which is formed by the collimating plate 500. The aperture is variable to adjust the X-ray irradiation field V. Reference will be made to the collimating plate 500 in the collimator 5. FIG. 2 shows the construction of a principal portion of the collimating plate 500. As shown in the same figure, the collimating plate 500 comprises two vertical stages of collimating plates which are an upper collimating plate 510 and a lower collimating plate 520. In the same figure, three mutually perpendicular directions are assumed to be x, y, and z directions, z being the vertical direction. The X-ray is radiated from above. The upper collimating plate 510 has a pair of symmetric blades 512, 512′ and a single blade 514, which are all rectangular plates and are constructed of an X-ray absorbing material such as lead for example. The symmetric blades 512 and 512′ lie on the same plane and their long sides are parallel to each other, while their short sides corresponding to each other lie on the same straight lines respectively. The symmetric blades 512 and 512′ are displaceable in their short side direction (x direction), whereby a distance “a” between their mutually opposed end faces can be adjusted. The symmetric blades 512 and 512′ are an example of a mode for carrying out the invention with respect to the first plate members defined herein. The single blade 514 lies on a horizontal plane positioned above the symmetric blades 512 and 512′ and its long and short sides are parallel respectively to the long and shorts sides of the symmetric blades 512 and 512′. The single blade 514 is also displaceable in its short side direction (x direction). The single blade 514 is an example of a mode for carrying out the invention with respect to the second plate member defined herein. The symmetric blades 512 and 512′ are position-adjustable in x direction independently of each other. A schematic construction of a drive mechanism which permits such a positional adjustment is shown in FIG. 3. As shown in the same figure, the symmetric blades 512 and 512′ have arms 612 and 612′, respectively, which extend in y direction. The arms 612 and 612′ are engaged at end portions thereof with a shaft 712. The shaft 712, which extends in x direction, is threaded throughout the overall length thereof so that the threads are reverse right and left with a mid portion of the shaft 712 as a boundary. The end portions of the arms 612 and 612′ engaged with the shaft 712 are internally threaded correspondingly to the threads on the shaft 712. A motor 716 is mounted on one end of the shaft 712. The motor 716 is a reverse-rotatable motor and is controlled by a control means (not shown). With rotation in one direction of the motor 716, the symmetric blades 512 and 512′ are displaced toward each other, while with rotation in the opposite direction of the motor, the symmetric blades 512 and 512′ are displaced away from each other. That is, the symmetric blades 512 and 512′ are displaced symmetrically with each other. The position of the single blade 514 is adjustable in x direction. A schematic construction of a drive mechanism which permits such position adjustment is shown in FIG. 4. As shown in the same figure, the single blade 514 has an arm 614 extending in y direction. An end portion of the arm 614 is engaged with a shaft 714. The shaft 714, which extends in x direction, is threaded throughout the overall length thereof. The end portion of the arm 614 engaged with the shaft 714 is internally threaded correspondingly to the threads on the shaft 714. A motor 718 is mounted on one end of the shaft 714. The motor 718 is a reverse-rotatable motor. With rotation in one direction of the motor 718, the single blade 514 is displaced in one direction along the shaft 714, while with rotation in the opposite direction of the motor, the single blade 514 is displaced in the opposite direction. The motor 718 is controlled independently of the motor 716 by a control means (not shown). The lower collimating plate 520 is of the same construction as the upper collimating plate 510. That is, the lower collimating plate 520 has a pair of symmetric blades 522, 522′ and a single blade 524. The symmetric blades 522, 522′ and the single blade 524 are all rectangular plates and are formed of an X-ray absorbing material such as lead for example. A horizontal plane where the symmetric blades 522, 522′ and the single blade 524 are present is positioned below the horizontal plate where the symmetric blades 512 and 512′ of the upper collimating plate 510 are present. The long-side direction of the symmetric blades 522, 522′ and the single blade 524 is perpendicular to the long-side direction of the symmetric blades 512 and 512′ of the upper collimating plate 510. The symmetric blades 522 and 522′ are displaceable in the short-side direction (y direction), thereby permitting adjustment of the distance “b” between their end faces opposed to each other. Position adjustment of the symmetric blades 522 and 522′ is made by a drive mechanism which is the same as the drive mechanism shown in FIG. 3. The drive mechanism for the symmetric blades 522 and 522′ is independent of the drive mechanism for the symmetric blades 512 and 512′. The symmetric blades 522 and 522′ are an example of a mode for carrying out the invention with respect to the third plate members defined herein. The single blade 524 is also displaceable in its short-side direction (y direction). Position adjustment of the single blade 524 is made by a drive mechanism which is the same as the drive mechanism shown in FIG. 4. The drive mechanism for the single blade 524 is independent of the drive mechanism for the single blade 514. The single blade 524 is an example of a mode for carrying out the invention with respect to the fourth plate member defined herein. With the collimating plate 500 of such a construction, there is formed a quadrangular aperture for the X-ray emitted from the X-ray tube 1. FIGS. 5 to 14 illustrate in what state the aperture is formed. FIG. 5 shows a state in which an aperture is formed by only the four symmetric blades 512, 512′, 522, and 522′. In this case, the single blades 514 and 524 are in their retracted positions, not participating in the formation of aperture. The center of the aperture a×b formed by only the symmetric blades 512, 512′, 522, and 522′ coincides with the center C of the collimator, whereby X-ray is radiated symmetrically with respect to the collimator center C. Such an aperture will hereinafter be referred to “symmetric aperture”. The shape of the symmetric aperture is square or rectangular. The size a×b of the symmetric aperture can be changed as desired by adjusting the positions of the symmetric blades 512, 512′, 522, and 522′. It is FIG. 6 that shows a maximum state of the aperture. By adjusting the positions of the single blades 514 and 524 with the symmetric blades 512, 512′, 522, and 522′ fixed to the respective positions corresponding to the maximum aperture, there can be formed such an aperture as shown in FIG. 7. As shown in the same figure, the aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512′, 522′. By doing so, the X-ray is asymmetrically applied with respect to a collimator center C. Such an aperture will hereinafter be referred to as “asymmetric aperture”. The size a×b of the asymmetric aperture can be changed as desired by adjusting the positions of the single blades 514 and 524. The shape of the asymmetric aperture is square or rectangular. The asymmetric aperture can also be formed as in FIGS. 8 to 10. In FIG. 8, an aperture is formed by mutually opposed end faces of the single blade 514, 524 and the symmetric blades 512, 522′. In FIG. 9, an aperture is formed by mutually opposed end faces of the single blade 514, 524 and the symmetric blades 512, 522. In FIG. 10, an aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512′, 522. By adjusting all of the positions of the symmetric blades 512, 512′, 522, 522′ and the single blades 514, 524 it is possible to form such an aperture as shown in FIG. 11. As shown in the same figure, an aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512′, 522′, whereby X-ray is radiated eccentrically from the collimator center C. Such an aperture will hereinafter be referred to “eccentric aperture”. The size a×b of the eccentric aperture can be changed as desired by adjusting the positions of the symmetric blades 512, 512′, 522, 522′ and the single blades 514, 524. The shape of the eccentric aperture is square or rectangular. It is also possible to form such eccentric apertures as shown in FIGS. 12 to 14. In FIG. 12, an aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512, 522′. In FIG. 13, an aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512, 522. In FIG. 14, an aperture is formed by mutually opposed end faces of the single blades 514, 524 and the symmetric blades 512′, 522. Thus, the collimating plate 500 has the single blades 514 and 524 in addition to the symmetric blades 512, 512′, 522, and 522′, so by adjusting the positions of these blades it is possible to obtain any of symmetric aperture, asymmetric aperture and eccentric aperture. Besides, since the collimating plate 500 is composed of simple plate members and a linear feed mechanism, any special blades and drive mechanism are not needed. As shown in FIG. 15, the upper collimating plate 510 and the lower collimating plate 520 may be constructed respectively as unitized combinations together with their drive mechanisms. In this case, it is preferable that the symmetric blade portion and the single blade portion of each unit be separated from each other as sub units, as indicated with dotted lines. By so doing, it becomes possible to make various combinations of sub units. For example, when only a symmetric aperture is needed, it is possible to construct a waste-free collimating plate 500 suited to the purpose of use, for example, by omitting sub units 518 and 528 and using only sub units 516 and 526. Many widely different embodiments of the present invention may be configured without departing from the spirit and the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.
	claims	1. A UV LED lamp, comprising: a pair of end caps; a heat sink mounted between said end caps; a LED segment with a first plurality of LED subassembly packages, said LED segment having a heat transfer plate, a thermal interface material contacting said heat transfer plate, said LED subassembly packages contacting said thermal interface material, said heat transfer plate contacting a first surface of said heat sink; anda first reflector positioned to reflect and focus radiation from the LED subassembly packages onto a substrate,wherein said first plurality of LED subassembly packages is varied in number to accommodate a variable width or length of said substrate. 2. The UV LED lamp of claim 1, further comprising another LED segment and a second reflector, said other LED segment with a second plurality of LED subassembly packages mounted to a second surface of said heat sink,wherein said second plurality of LED packages is varied in number to accommodate said variable width or length of said substrate, said second reflector positioned to reflect and focus radiation from the second plurality of LED subassembly packages onto said substrate. 3. The UV LED lamp of claim 2, wherein said second plurality of LED subassembly segments emits a radiation wavelength differing from a radiation wavelength of said first plurality of LED subassembly segments. 4. A method of curing materials deposited on a substrate, said materials having UV photoinitiators, such method comprising directing UV radiation at said substrate, said UV radiation originating from the UV LED lamp of claim 2. 5. The method of claim 4, wherein a different material is cured by each of said subassemblies, such subassemblies emitting differing wavelengths of UV radiation. 6. The method of claim 4, further comprising cooling said UV subassembly segments. 7. The method of claim 6, wherein said UV subassembly segments are cooled by circulating coolant through a pair of coolant passages located in said heat sink. 8. The UV LED lamp of claim 1, further comprising a plurality of alignment pins extending from one of said end caps. 9. The UV LED lamp of claim 1, further comprising a pair of fluid valves for admitting coolant to ingress and egress said heat sink. 10. The UV LED of claim 9, wherein said heat sink defines a pair of coolant passages, wherein one of said coolant passages admits coolant ingressing said heat sink and wherein the other of said coolant passages admits coolant egressing said heat sink. 11. The UV LED of claim 10, wherein each of said coolant passages is bounded by fin features protruding into said liquid coolant. 12. A method of curing materials deposited on a substrate, said materials having UV photoinitiators, such method comprising directing UV radiation at said substrate, said UV radiation originating from the UV LED lamp of claim 1.
	description	This application claims priority of German patent application no. 10 2008 037 698.1, filed Aug. 14, 2008, the entire content of which is incorporated herein by reference. The invention relates to a particle beam apparatus having an annularly-shaped illumination aperture, especially for viewing or image recording in transmission. With this particle beam apparatus images can be generated with phase contrast. U.S. Pat. No. 6,797,956 discloses a phase contrast electron microscope having phase contrast imaging. By utilizing an annularly-shaped illuminating aperture, no small components are needed for the phase-shifting element which are critical with respect to electrostatic charging and contamination compared to other phase contrast systems. However, more detailed analysis has shown that the phase shift in this known system is achieved essentially by the intense spherical aberration of the einzel lens in the peripheral region. Additional systems for generating phase contrast in a transmission electron microscope are disclosed in United States patent application publications 2008/0296509 and 2007/0284528 and U.S. Pat. Nos. 5,814,815 and 6,797,956. It is the object of the invention to improve the contrast generation in a particle beam apparatus having an annularly-shaped illuminating aperture compared to the known systems. The particle beam apparatus of the invention according to a first embodiment defines an optical axis and includes: an illuminating system for illuminating an object to be positioned in an object plane with a beam of charged particles which splits into a null beam and higher diffraction orders at the object; an objective arranged along the optical axis for imaging the object illuminated by the illuminating system; the illuminating system being configured to generate, during operation, an annularly-shaped illuminating aperture in a plane fourier transformed to the object plane; the objective having a focal plane facing away from the object plane; a phase-shifting element mounted in the focal plane or a plane conjugated thereto; the phase-shifting element including an einzel lens having first and second outer electrodes arranged along the optical axis and an inner electrode arranged therebetween; and, the electrodes being arranged and charged with electrical potential, during operation, so as to cause the potential at the optical axis to correspond to the potential at the first and second outer electrodes of the einzel lens. A second embodiment of the particle beam apparatus of the invention defines an optical axis and includes: an illuminating system for illuminating an object to be positioned in an object plane with a beam of charged particles which splits into a null beam and higher diffraction orders at the object; an objective arranged along the optical axis for imaging the object illuminated by the illuminating system; the illuminating system being configured to generate, during operation, an annularly-shaped illuminating aperture in a plane fourier transformed to the object plane; the objective having a focal plane facing away from the object plane; a phase-shifting element mounted in the focal plane or a plane conjugated thereto; the phase-shifting element including a carrier; and, an annularly-shaped electrode accommodated in the carrier; the annularly-shaped electrode having a side facing away from the optical axis in a radial direction; the electrode having an edge on the side thereof; and, the edge and the carrier conjointly defining an annular gap therebetween. In one embodiment of the invention, the electrodes of the phase-shifting element are so arranged and charged with electrical potential during operation that the potential on the optical axis corresponds to the potential of the outer electrodes of the einzel lens. With this measure, it is ensured that electrons whose paths run further away from the optical axis run through a different potential difference than electrons whose paths run closer to the optical axis. The null beam runs in the proximity of the edges of the electrodes of the einzel lens. For this reason, it is ensured in this way that the null beam experiences another phase shift than the electrons diffracted toward the optical axis at the object. Especially, a large-area potential distribution central to the optical axis can be brought about on the potential of the outer electrodes or on the potential of the electron optical column forward and rearward of the phase-shifting element. In this way, an intensely localized potential drop is achieved in the proximity of the edges of the inner electrode, that is, in the region wherein the null beam runs. In a special embodiment, the particle beam apparatus has an optical axis, an illuminating system for illuminating an object to be positioned in an object plane with a beam of charged particles and an objective for imaging the illuminated object. The beam of charged particles is split on the object into a null beam and higher diffraction orders. The illuminating system can be so configured that it generates an annularly-shaped illuminating aperture during operation in a plane which is Fourier transformed to the object plane. A phase-shifting element can be mounted in a focal plane of the objective, which faces away from the object plane, or in a plane conjugated thereto. The phase-shifting element can have an einzel lens (viewed in the direction of the optical axis) having two outer electrodes and one or several inner electrodes lying therebetween. Furthermore, the phase-shifting element can have an additional electrode on or in the proximity of the optical axis. With the additional electrode on the optical axis or in the proximity of the optical axis, this electrode can be charged with a further electrical potential which deviates from the electrostatic potential of the inner electrode of the einzel lens. In this way, it is achieved that a defined electrostatic potential is present in the central region lying closer to the optical axis which deviates in a defined manner from the electrostatic potential in the peripheral region, that is, closer to the electrodes of the einzel lens. In this way, in turn, it can be achieved that the phase shifts, which the rays experience (which rays run at different radial distances from the optical axis), deviate more intensely and with more definition from each other. In a special embodiment, the additional electrode can be charged with the potential of the outer electrodes of the electrostatic lens. Alternatively, a separate voltage source can, however, be provided via which the additional electrode is charged with a potential deviating from the electrostatic potential of the outer electrodes of the einzel lens. In another embodiment of the invention, the additional electrode can be accommodated on a manipulator and positioned perpendicular to the direction of the optical axis. In a further special embodiment, the phase-shifting element can be so configured that it, during operation, imparts a phase shift to the null beam relative to the radiation diffracted at the object into higher diffraction orders and the phase-shifting element can be further configured in such a manner that it does not influence or only slightly influences the phase of the radiation diffracted at the object into higher diffraction orders with this beam running in radial direction closer to the optical axis than the null beam. Alternatively, the phase-shifting element can be so configured that it, during operation, imparts a phase shift to the radiation, which is diffracted into higher diffraction orders at the object, with respect to the null beam and the phase-shifting element can be so configured that it does not or hardly influences, during operation, the phase of the null beam. In a further embodiment of the invention, the inner electrode has two or more segments of which two segments, which lie opposite to each other with reference to the optical axis, are charged, during operation, with potentials of mutually opposite polarities. The segments have edges facing toward the optical axis and two segments lying opposite each other with respect to the optical axis can have different distances in radial direction from the optical axis. In another embodiment of the invention, a deflection system can be mounted in a source side plane conjugated to the object plane. This deflection system is for a time sequential generation of the annularly-shaped illuminating aperture and a supply voltage can be provided which is so configured that the segments are charged with potential alternately or rotatingly. In a further embodiment, the einzel lens can be accommodated on a carrier. The electrodes of the einzel lens can have edges on the side facing in radial direction away from the optical axis and an annularly-shaped or annularly-segmented shaped gap can be provided between the edges of the electrodes of the einzel lens and the carrier. The inner electrode of the einzel lens can have a first annularly-shaped or annularly-segmented shaped electrode and a second annularly-shaped or annularly-segmented shaped electrode and the first annularly-shaped or annularly-segmented shaped electrode can be electrically insulated with respect to the second ring-shaped or ring-segmented shaped electrode. The second annularly-shaped or annularly-segmented shaped electrode can be mounted in radial direction outside of the first annularly-shaped or annularly-segmented shaped electrode and the second annularly-shaped or annularly-segmented shaped electrode can be charged during operation with the electric potential of the carrier. Furthermore, a voltage supply can be provided with which the first annularly-shaped or annularly-segmented shaped electrode can be charged with a potential deviating from the potential of the carrier. In a special embodiment, the first annularly-shaped or annularly-segmented shaped electrode can have several annular segments and a deflection system can be mounted in a source side plane conjugated to the object plane with this deflection system being for a time sequential generation of the annularly-shaped illuminating aperture. Furthermore, a voltage supply can be provided which is so configured that the annular segments are charged with a potential alternately or rotatingly. In a particle beam apparatus of the invention, the phase contrast can be generated very similarly to the generation of the phase contrast in the light microscopy. The illuminating system of the particle beam apparatus generates an annularly-shaped illuminating aperture in a plane Fourier transformed to the object plane to be imaged. As in the phase contrast light microscopy, the illumination of the object, which is to be imaged, can take place with a hollow conically-shaped beam. A phase-shifting element is mounted in the plane, which is Fourier transformed to the object plane, or in a plane conjugated thereto. The phase-shifting element can impart a phase shift to the radiation, which is undiffracted at the object (that is, the null beam), relative to the radiation diffracted at the object into higher diffraction orders. At the same time, the phase-shifting element can leave the phase of the radiation diffracted at the object into higher diffraction orders uninfluenced or only slightly influenced, which radiation runs in radial direction closer to the optical axis than the null beam. In another embodiment, and as with phase contrast in the light microscopy, a phase shift is imparted by the phase-shifting element to the radiation, which is diffracted at the object relative to the beam undiffracted at the object. The radiation, which is diffracted at the object into higher diffraction orders and which runs closer to the optical axis in the plane of the phase-shifting element in radial direction than the radiation, which is undiffracted at the object, is not influenced by the phase-shifting element. A corresponding phase-shifting element can therefore be configured to be annularly-shaped with a central aperture. Such an annularly-shaped phase-shifting element can accordingly be held at its outer periphery so that no cantilevered or almost cantilevered structures are needed. The phase-shifting element even supplies particle-optical advantages when the phase-shifting element or a holding structure of the phase-shifting element masks out the higher diffraction orders lying further from the optical axis than the null beam in radial direction. In this way, the negative influence of the off axis aberrations of the objective is reduced. Furthermore, the phase-shifting element influences not only the phase of the null beam but simultaneously attenuates the intensity of the null beam via a corresponding absorption. Overall, a contrast improvement is achieved via the thereby achievable intensity adaptation between the null beam and the higher diffraction orders. A very stable configuration of the phase-shifting element can be realized from a combination of the phase-shifting element with an aperture diaphragm. The radiation of higher order, which is diffracted toward the optical axis, can pass unhindered through the central opening of the phase-shifting element while the radiation, which is diffracted in radial direction away from the optical axis, is masked out. However, with this masking out, no information is lost because the illuminating beam, which is rotated by 180° with respect to the optical axis, contains the complementary information as to the masked orders of diffraction. A corresponding phase-shifting element is technologically simple to realize. Because of its unhindered passthrough through the phase-shifting element, the diffracted radiation of higher order, which carries the information, experiences no negative influencing either by the configuration of the phase-shifting element or because of its holder. This negative influence could be, for example, an attenuation or additional phase shift. Furthermore, no radiation, which is diffracted in specific spatial directions, is completely masked by the holding structures. The corresponding phase-shifting element can, rather, be configured as being rotationally symmetrical to the optical axis. Furthermore, small holes can be avoided in the phase-shifting element through which the primary beam must pass through. Negative influences from contamination effects which otherwise occur with small holes can be substantially precluded thereby; and, when only the radiation of zero diffraction order, which carries no information as to the object, passes through the phase-shifting element, the variations of the phase shift statistically cancel out because of local thickness fluctuations of the phase-shifting element. In a further embodiment of the invention, the phase-shifting element is configured as an annular electrode whose electrostatic potential can be varied. To generate the annularly-shaped illuminating aperture, a deflection system can be mounted in a plane conjugated to the object plane. In this embodiment, the annularly-shaped illuminating aperture is generated time sequentially by a variation of the deflection angle. An alternate generation of the annularly-shaped illuminating aperture is possible via a corresponding diaphragm having a central cropping in the illuminating beam path. Furthermore, and especially with thermal emitters as electron sources, it is possible to image the unheated cathode image (hollow beam) (which already has an annularly-shaped emission distribution with a weak central maximum) into the forward focal plane of the condenser-objective single-field lens and to mask the central emission spot in order to generate the annularly-shaped illuminating aperture. The transmission electron microscope in FIG. 1 is shown as an example of a particle beam apparatus of the invention. The transmission electron microscope includes a beam generator 1 and a three-stage condenser (2, 3, 6). The beam generator 1 is preferably a field emission source or a Schottky-emitter. The first condenser lens 2 generates a real image 12 of the crossover 11 of the beam generator 1. This real crossover image 12 is imaged real by the follow-on second condenser lens 3 into the source-end focal plane 13 of the third condenser lens 6. The third condenser lens 6 is a so-called condenser-objective single-field lens having a prefield functioning as a condenser lens and a back field functioning as an objective lens. In the third condenser lens 6, the object plane 7 lies at the center of the pole piece gap of the condenser-objective single-field lens 6. The object plane 7 is illuminated by a particle beam aligned parallel to the optical axis because of the imaging of the crossover 11 of the particle beam generator 1 into the source-end focal plane 13 of the condenser-objective single-field lens 6. The corresponding illuminating beam path is shown by broken lines in FIG. 1. A field diaphragm 5 and a deflection system 4 or a tilt point of a double deflection system are arranged in the source-end plane conjugated to the object plane 7. Because of the deflection system 4, the particle beam is tilted by the same angle to each point 14, which is conjugated to an object point, in the plane of the field diaphragm 5. A corresponding tilting of the particle beam in the object plane 7 is generated because of this deflection or tilting of the particle beam. Because of a charging of the deflection system 4 in two mutually perpendicular directions corresponding to a sine function in one direction and a cosine function in the direction perpendicular thereto with an amplitude constant in time and identical in both mutually perpendicular directions, a rotating beam results in the object plane 7 which corresponds to a time sequential hollow conically-shaped illuminating aperture. The inner diameter of the annularly-shaped illuminating aperture is determined and can be adjusted by setting the amplitude of the deflection generated by the deflection system 4. The annular diameter of the annularly-shaped illuminating aperture is, in contrast, determined by the imaging scale with which the crossover 11 of the particle beam generator 1 is imaged in the source-end focal plane 13 of the condenser-objective single-field lens 6. Because of the back field or imaging field of the condenser-objective single-field lens 6, the beam cone is focused into the intermediate image plane 10 with a time-sequential hollow cone-shaped illuminating aperture so that, in the intermediate image plane 10, a real image of the object plane 7 arises. In the rearward, intermediate image end focal plane 15 of the condenser-objective single-field lens, the annularly-shaped phase-shifting element 9 is accommodated in the region of the central opening of an aperture diaphragm 8. This annularly-shaped phase-shifting element has a large central opening 19 through which the diffracted radiation of higher order 51 can pass unhindered. This diffracted radiation of higher order 51 is diffracted relative to the undiffracted beam (null beam) 50 in the direction toward the optical axis OA. The central opening 19 has a diameter of several 10 μm, preferably, at least 30 μm. At the same time, the phase-shifting element 9 imparts a phase shift of preferably n/2 to the radiation, which is not diffracted at the object, that is, to the null beam 50. At the intermediate plane 10, a superposition of the phase-shifted null beam 50 takes place with the radiation 51 diffracted in the direction onto the optical axis. Those higher diffraction orders 52 diffracted at the object are, in contrast, absorbed by the aperture diaphragm 8. The higher diffraction orders 52 run further away from the optical axis in the plane of the phase-shifting element 9 relative to the undiffracted radiation. Reference can be made to FIG. 2 with respect to the positions of the different diffraction orders relative to the phase-shifting element 9 and the operation of the arrangement of the invention resulting therefrom. In FIG. 2, the solid lines are the two null beams 50 and the dashed lines are the two plus first diffraction orders and the dotted lines are the two minus first diffraction orders of the two drawn in illumination beams. The plus first diffraction order and the minus first diffraction order 51 pass uninfluenced through the central aperture 19 in the phase-shifting element 9. The plus first diffraction order and the minus first diffraction order are closer to the optical axis in the plane of the phase-shifting element than the null beams. The null beam, which is undiffracted at the specimen, experiences the desired phase shift and the likewise desired attenuation at the annularly-shaped phase-shifting element 9 whereas both axis-remote higher diffraction orders 52 are eliminated completely by the diaphragm 8. As shown in FIGS. 1 and 2, each point in the object plane 7 is illuminated by an electron beam which has a hollow conically-shaped illuminating aperture. The tip of illuminating beam cone lies in the object plane 7. The beam, which emanates again from the object plane, has a divergent hollow conically-shaped illuminating aperture and is imaged by the back field of the condenser-objective single-field lens 6 into the intermediate image plane 10. The higher diffraction orders 51 pass through the central opening 19 of the phase-shifting element 9. Because of the interference of these higher diffraction orders 51 with the null beam 50, which is phase shifted by the phase-shifting element, there occurs, in the intermediate image plane 10, a phase contrast image of the specimen disposed in the object plane 7. The illumination beams, which lie diametrically opposite each other, supply the diffraction information of the complementary half space. For this reason, the diffraction information as to the specimen is complete and the masking of the higher diffraction orders, which are diffracted away from the optical axis, leads only to an intensity loss by a factor of ½. This intensity loss is, however, relatively non-critical and is overcompensated by the remaining advantages of the present invention. A first embodiment for a phase-shifting element is shown in FIG. 3a in section and in plan in FIG. 3b. The embodiment includes an einzel lens including two outer annularly-shaped electrodes (101, 102) and an inner annularly-shaped electrode 103 lying therebetween. The outer annularly-shaped electrodes (101, 102) are arranged one behind the other in the direction of the optical axis OA. The two outer electrodes (101, 102) are at the same electrostatic potential which corresponds to the potential in the beam tube forward and rearward of the phase-shifting element so that an electron beam, which propagates along the optical axis OA, experiences no change of energy when passing through the phase-shifting element. In the embodiment shown in FIGS. 3a and 3b, it was assumed that the electron column in the region of the phase-shifting element lies at ground potential and, accordingly, the two outer electrodes are likewise at ground potential. Furthermore, an additional electrode 105 is provided on the optical axis. In the embodiment shown in FIGS. 3a and 3b, the additional electrode 105 is accommodated on a strut 104 on one of the outer electrodes 101. The inner electrode 103 lies at an electrostatic potential Vph which deviates from the electrostatic potential of the outer electrodes (101, 102) and generates the desired phase shift. The additional electrode 105 extends in the direction of the optical axis OA over almost the entire length of the einzel lens. With this additional electrode 105, it is ensured that electrons, whose paths run closer to the optical axis OA, pass through a different electrostatic potential than electrons whose paths run in the outer region of the passthrough opening 106. In this way, the electrons, which are diffracted at the object, experience the desired phase shift relative to the null beam. Electrons diffracted by the object run closer to the optical axis OA relative to the null beam because of the diffraction. Because of the additional electrode 105, information is masked, but this is non-critical because this affects only very high spatial frequencies. The additional electrode 105 is accommodated on the outer electrode 101 via the strut 104. The strut 104 does cause additional information to be masked even at lower spatial frequencies; this, however, is not critical as long as the complementary range of diffraction angles is not also simultaneously cropped because then, the masked information can be reconstructed. FIG. 4 shows, in section, a further embodiment of a phase-shifting element which is very similar to the embodiment shown in FIGS. 3a and 3b. Those components in FIG. 4 which correspond to the components in FIGS. 3a and 3b are identified by corresponding reference numerals increased by 100. With respect to these components of FIG. 4, which correspond to those in FIGS. 3a and 3b, reference can be made to the above description of FIGS. 3a and 3b. In the embodiment of FIG. 4, the additional electrode 205 is accommodated via an insulator 208 on a manipulator 207. A potential can be applied to the additional electrode 205 by a voltage source 209 and this potential deviates from the potential on the outer electrodes (201, 202). The additional electrode can be positioned by the manipulator 207 in two mutually perpendicular directions perpendicular to the optical axis OA as well as in the direction of the optical axis OA. In this way, the additional electrode 205 can be centered relative to the outer electrodes (201, 202) and the inner electrode 203. A further embodiment for a phase-shifting element is shown, in section, in FIG. 5b. FIG. 5a shows a plan view of the inner electrode of this phase-shifting element. The phase-shifting element or the phase plate contains, in turn, an einzel lens of two outer electrodes (301, 302) and an inner electrode 303 lying therebetween. In this embodiment, the inner electrode 303 is segmented and comprises four segments (303a, 303b, 303c, 303d) which are electrically insulated one from the other. Two segments (303a, 303c) lie opposite each other with respect to the optical axis OA and electrical potentials are applied thereto which have a polarity inverse compared to the potential of the outer electrodes (301, 302). When the outer electrodes are at ground potential, then a segment 303a is, for example, at +Vph and the segment 303c, which lies opposite relative to the optical axis OA, is at the same potential in magnitude but is at a negative potential −Vph. By applying inverse potentials to the opposite-lying segments, the situation is achieved that, as in the embodiment of FIGS. 3a and 3b, a zero crossover is imparted to the electrostatic potential at the optical axis. Compared to the embodiment in FIGS. 3a and 3b, this embodiment affords the advantage that carrier elements and electrodes, which project into the interior space 306 of the einzel lens and mask information, can be avoided. The potential distribution, which is generated with a segmented inner electrode 303, causes, in the case of a static illumination cone, that the electrons, which are scattered in various half spaces, experience an inverse phase shift with respect to each other. For example, electrons scattered in the positive half space experience a positive phase shift; whereas, electrons scattered in the negative half space experience a negative phase shift. In this way, a differential interference contrast (DIC) or a Hilbert phase contrast arises which generates a plastic image impression. The true image can be obtained again with the aid of an image reconstruction. FIG. 6 shows a plan view of an inner electrode of an embodiment for a phase-shifting element wherein the inner electrode has two segments (403a, 403b) electrically insulated from each other. The inner edge 404a of a segment 403a is spaced further away from the optical axis OA than the inner edge 404b of the other segment 403b. Potentials inverse to each other are, in turn, applied to the two segments (403a, 403b). Relative to the outer electrodes (not shown in FIG. 6) a positive potential is applied to the segment 403b whose inner edge lies closer to the optical axis. Since the annularly-shaped illuminating beam 405 in the half space next to the positive electrode runs closer to the electrode than in the half space, which is next to the negative electrode 403a, the null beam experiences a greater phase shift in the half space next to the positive electrode 403b than in the half space next to the negative electrode 403a. A Zernicke phase contrast arises when the phase shift, which is defined by the respective potentials, is so adjusted that the phase shift, which the null beam experiences, amounts to 3π/2 in the half space which is adjacent the positive electrode 403b and amounts to π/2 in the half space next to the negative electrode 403a. The remaining configuration of the phase-shifting element corresponds to the embodiment shown in FIG. 5b, that is, the inner electrode is mounted between two outer electrodes which lie at the electrical potential of the electron column forward and rearward of the einzel lens. FIG. 7 shows a plan view of an inner electrode of an embodiment wherein the inner electrode has a greater number of mutually electrically insulated segments (503a to 503h). With this electrode too, inverse electrical potentials +Vph and −Vph are applied to segments (503e, 503f, 503a, 503b) lying opposite each other with reference to the optical axis OA. The potentials applied to the individual segments are such that the potential charge runs about in a circle in the direction of arrow 504. The rotation frequency for the application of potential to the inner electrode is identical to the rotation frequency of the hollow conical illumination when this is generated dynamically and the electron beam is guided sequentially along a hollow cone by means of a deflection system. A rotating phase plate results from the circulating or rotating application of potential. The phase shift imparted by the phase plate to the unscattered beam (which ideally amounts to n/2) rotates in a circle synchronously to the movement of the null beam 505. Because of the inverse application of potential to opposite-lying segments, there results, in turn, the situation that the potential has a zero crossover at the optical axis OA. The remaining configuration of the phase-shifting element corresponds to the embodiment of FIG. 5b, that is, the inner electrode is mounted between two outer electrodes which are at the same electrical potential as the electron column forward and rearward of the einzel lens. It is here noted that the phase plates can also be used when the electron-optical column in the region of the phase plate should lie at an electrical potential Vo deviating from ground potential. In this case, the outer electrodes lie at this potential forward and rearward of the phase plate and this constant potential Vo is supplied to the rotating potential charge as an offset so that the segments (503a, 503b) as well as segments (503e, 503f), which lie opposite each other with reference to the optical axis OA, are charged with the potential Vo+Vph and Vo−Vph and the remaining segments (503c, 503d, 503g, 503h) are charged with the potential Vo. The null beam experiences a phase shift even with the use of this phase-shifting element while the phase of the radiation, which is diffracted at the object, remains entirely or virtually uninfluenced. In the embodiments described above, the phase-shifting element imparts a phase shift in each case to the null beam while the radiation, which is diffracted at the object remains substantially uninfluenced by the phase plate. However, for the generation of the phase contrast, only the relative phase shift between the null beam and the radiation diffracted at the object is relevant. For this reason, the diffracted radiation also can be shifted in the phase while the null beam remains uninfluenced or experiences only a slight phase shift. FIG. 8 is a perspective view, in section, of an embodiment for a phase-shifting element which imparts a phase shift to the radiation diffracted at the object. It includes an einzel lens having two outer electrodes (601, 602) and an inner electrode 603 mounted therebetween. The inner electrode 603 is electrically insulated relative to the two outer electrodes (601, 602) and lies at the potential Up which is necessary for phase shifting relative to the outer electrodes (601, 602). The einzel lens is mounted within a circularly-shaped hole of a plate 600 of electrically conductive material via an annularly-shaped air gap 605. The plate 600 and the two outer electrodes 601 and 602 of the einzel lens lie at the same potential. The einzel lens is accommodated on the plate 600 via one or several holding struts 604 via which also the potential supply takes place for the inner electrode 603. The inner clear diameter of the einzel lens should be approximately 50 to 100 μm. The annularly-shaped electrodes of the einzel lens should be as thin as possible and be at most 1 μm thick and the annularly-shaped gap 605 should have a gap width of below 0.5 μm. The outer electrodes (601, 602) of the einzel lens lie at the same potential as the plate 600. For this reason, the annularly-shaped gap is free of potential. The null beam, which passes through the gap 605, therefore experiences no phase shift. The radiation, which is diffracted at the object and diffracted in the direction of the optical axis and runs through the interior of the electrostatic einzel lens, is, in contrast, shifted in phase by the potential of the inner electrode 603. Compared to the embodiments wherein the null beam is shifted in phase, this arrangement has the disadvantage that shading of a spatial frequency range unavoidably takes place because of the electrodes (601, 602, 603) of the einzel lens. The inner electrode 603 can also be segmented in the embodiment of FIG. 8 and the individual segments can be charged with a rotating potential distribution so that this system too can be used with a dynamic hollow conical illumination wherein the potential applied to the inner electrode is identical to that of the rotation of the hollow cone illumination. Because of the rotating potential charging, there results, in turn, a rotating phase plate. A further embodiment of a phase plate is shown, in section, in FIG. 9a and a plan view is shown in FIG. 9b. The embodiment of FIGS. 9a and 9b also includes a plate 700 having a circularly-shaped hole 704 as in the embodiment of FIG. 8. Two annularly-shaped electrodes (701, 702) are accommodated in the hole 704 via one or several holding struts 705. The electrodes (701, 702) are arranged mutually coaxially to the optical axis OA and are insulated with respect to each other by an insulating layer 703. A clear annularly-shaped gap 706 is disposed between the two annularly-shaped electrodes (701, 702) and the plate 700 for the passthrough of the null beam. The outer one of the two annularly-shaped electrodes 701 lies at the same electrical potential as the plate and the inner annularly-shaped electrode 702 lies at the potential Up which deviates relative thereto and which functions for the phase shift of the electron beams diffracted at the object at higher diffraction orders. As in the embodiment of FIG. 8, the annularly-shaped gap 706 is free of potential so that the null beam experiences no phase shift. The insulating layer 703 does not have to be completely annularly-shaped and can, instead, comprise also an air gap. Only for reasons of stability, solid insulators should be used at some locations. The number or the size of the solid insulators should be as small as possible because the insulators can easily become charged. Also in this embodiment of the phase plate, the radiation, which is deflected toward the optical axis in higher diffraction orders, experiences a phase shift whereas the null beam, which passes through the annularly-shaped gap 706, is entirely or at least substantially uninfluenced by the phase plate. Based on the embodiments, the invention was explained herein in the context of an example of an electron microscope. The invention can also be utilized for particle beam apparatus having positively charged particles such as ions or positrons, for example, helium ions. The invention is especially usable in a transmission ion microscope. In FIG. 1, the magnetic lenses would then be replaced with electrostatic lenses. At the same time, the electron source would be replaced by an ion source such as a field ion source and the acceleration potentials would be correspondingly inverted. The phase plates shown in FIGS. 3a and 9b can, in contrast, remain unchanged also for a use in an ion microscope or a positron microscope. It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
	summary
049892266	abstract	A method of treating a substrate having first and second sides with corresponding oppositely facing first and second surfaces, to produce curvature in the first surface. The method includes the steps of removing material, according to a predetermined pattern, from the second side of the substrate, and applying a stress-producing film of material to at least one surface of the substrate to thereby cause the substrate to bend to produce the desired curvature in the first surface.
	abstract	A cerium activated lutetium borate phosphor of the following formula (I):(Lux,Lny)BO3:aCe,bA (I)
	claims	1. A reactor core, the reactor core comprising:a solid neutron moderator comprising at least one hole;a liquid neutron moderator; andat least one module, each module of the at least one module comprising:a module casing;thermal insulation positioned within the module casing;one heat pipe having an evaporation area, the one heat pipe comprising a heat pipe casing and a wick and containing a heat pipe coolant; andat least one fuel element comprising nuclear fuel and a can;each module of the at least one module being arranged within a respective hole of the at least one hole of the solid neutron moderator;the one heat pipe being located inside the module casing;the at least one fuel element being located along the evaporation area of the one heat pipe, around the heat pipe casing, in heat contact with the heat pipe casing, and enclosed in the can;the thermal insulation being arranged between the can and the module casing; andthe space between the module casing and the solid neutron moderator being filled with the liquid neutron moderator. 2. The reactor core according to claim 1, characterized in that each module of the at least one module comprises a vacuum located in the module casing. 3. The reactor core according to claim 1, characterized in that the reactor core comprises an inert gas and the module casing of each module of the at least one module is filled with the inert gas. 4. The reactor core according to claim 1, characterized in that the heat pipe coolant is at least one liquid metal. 5. The reactor core according to claim 1, characterized in that the liquid neutron moderator is water. 6. The reactor core according to claim 1, characterized in that the liquid neutron moderator is at least one non-freezing liquid at minus 40° C. 7. The reactor core according to claim 6 characterized in that the nonfreezing liquid is an aqueous alcohol solution. 8. The reactor core according to claim 3 characterized in that the inert gas is xenon. 9. The reactor core according to claim 4 characterized in that the at least one liquid metal is selected from the group consisting of lithium, calcium, lead, and silver. 10. The reactor core according to claim 4 characterized in that the at least one liquid metal comprises a plurality of liquid metals. 11. The reactor core according to claim 10 characterized in that the plurality of liquid metals comprises metals selected from the group consisting of lithium, calcium, lead, and silver. 12. The reactor core according to claim 1 characterized in that the at least one module comprises a plurality of modules and the at least one hole comprises a plurality of holes, each module of the plurality of modules being positioned within a respective hole of the plurality of holes. 13. The reactor core according to claim 12 characterized in that the at least one fuel element of each module of the at least one module is one fuel element. 14. The reactor core according to claim 13 characterized in that the one fuel element comprises a cavity for gaseous fission products of the respective nuclear fuel of the fuel element.
	summary
047215968	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is in the field of nuclear waste control and is particularly directed toward the elimination of long-lived radioactive nuclides of nulcear reactor waste. 2. Description of the Prior Art The difficulties encountered in attempting to safely dispose of radioactive wastes generated by the fission process in nuclear reactors is probably the largest single cause of public resistance to the construction of nuclear power stations. A decade ago it was liberally estimated that 200,000 megawatts of nuclear generated electricity would be available by 1980. Today this expectation is down by one half. A major argument against permitting the further spread of nuclear power involves concern over methods proposed for disposal of the nuclear waste products. Present methods of disposal of nuclear waste, which may be in the gaseous, liquid or solid state consist either of dilution and dispersion or storage. In the first approach radioactive gases or liquids are diluted with large volumes of air or water to reduce the activity per unit volume to an allegedly safe level and released into the environment. In the second use, radioactive materials are stored in the containers in the ground or under the sea. With adequate safeguards, storage for about 30 years suffices to remove the harm from relatively short-lived radioactive nuclides, but the situation is quite different for the long lived wastes. Fortunately, the majority of the fission wastes have half-lives less than one year, which means that at worst they must be stored for 33 years to be reduced to 10.sup.-10 of their original amount. However, eighteen fission waste products as well as all the actinide waste products have half-lives greater than one year, but less than 10.sup.10 years, and it is these products that pose the long term storage problem. To ensure that long lived waste products are kept out of the biosphere until they become harmless--involving periods of hundreds of thousands or millions of years--present proposals involve burial in geological salt formations or other formations such as granite, quartzite, tuff (welded volcanic ash) and shale. The burial solution to the waste problem is based on the assumption that the geological formation will remain stable for the necessary containment period. While this assumption is reasonable for plutonium, for example, it is not evident for the longer lived wastes including the fission products Pd.sup.107, Tc.sup.99, I.sup.129, CS.sup.135, and Zr.sup.93, as well as the actinides. In view of the extreme hazard that would be created if these materials were to be released into the biosphere, there is a strong and growing resistance to the "bury it and forget it" philosophy, and this opposition has now developed to the point of significantly slowing the growth of nuclear power. It is therefore most desirable if a method could be found to completely eliminate the noxious radioactive wastes from the environment. Two methods have been suggested for such a final solution to the waste problem. Extraterrestrial disposal would permanently remove the wastes by transportation by rocket into the sun. Two major problems face this technique. First the cost, and second, but more significant, there is the possibility of vehicle failure within the atmosphere leading to a highly dangerous level of radioactive contamination. A more attractive technique involves the direct transmutation of the dangerous waste materials by neutron bombardment into innocuous materials, or at worst short lived radioactive species. Such a transmutation can be achieved, for example, by recycling waste products back into the reactor which produced them. Such nuclear transformations have been discussed in the literature but have been found only applicable for effective elimination of the actinides produced by neutron capture, e.g., "Advanced Waste Management Studies Progress Report", 8, BNWL-B-223 (1973); H. C. Claiborne, "Neutron Induced Transmutation of High-Level Radioactive Wastes", ORNLTM-3964, 1, 24; and "High-Level Radioactive Waste Management Alternatives", 4, 9, BNWL 1900 (1974). The applicability of transmuting long-lived fission products as well as the actinides by neutron capture in reactors has not been regarded as practical since such a procedure reputedly produces more long term waste than it removes. SUMMARY OF THE INVENTION It is therefore a general object of the invention to reduce to amount of radioactive waste and in particular fission products in nuclear reactors so that time storage requirements may be reduced from those required for natural radioactive decay. The invention may be characterized as a method of increasing the rate of transmutation of radioactive nuclear waste materials in excess of their natural decay rates for the more rapid conversion to stable nuclides. The method comprises the steps of (a) extracting the nuclear waste from the reactor fuel, either continuously or periodically, (b) separating the waste into selected components of different constituents, (c) storing those components composed of stable nuclides or of short lived nuclides which naturally decay into stable nuclides, (d) exposing those components containing long lived high risk potential nuclides to a high flux of thermal neutrons in order to induce nuclear transmutations, (e) further separating of the waste after exposure to the neutrons, and repetition of steps c, d, and e for transmutation of the long lived radioactive waste into stable nuclides, or to short lived nuclides which rapidly decay to stable nuclides.
	summary
047055774	description	EXAMPLE 7.6 g uranium powder having an average particle size of 30 /.mu. and 5.6 g aluminum powder having an average particle size of 50 /.mu. were mixed for more than an hour in a tumbling mixer equipped with plastic or ceramics inserts and rotating at 70 rpm. Due to the pyrophorosity of the U powder the work was performed in a gas purification box. The powder mixture was then pressed at 300 MPa and room temperature into a plate of 2.5 mm thickness. Thereafter, the pressed body was inserted into an Al frame together with Al bottom and cover foils (sheaths, each with a thickness of 2.4 mm) and was welded to the frame in vacuo in a welding box. Rolling took place in three passes, a reduction in thickness of 1 mm of the combination of plate, frame and foils was realized in each of the first and second passes and an additional reduction in thickness of 15% was realized in the third roll pass. Thereafter the thickness of the plate was 1.3 mm. The rolling temperature was near 800.degree..+-.25 K., with the picture frame being heated for about 10 minutes before the first rolling pass. After the third rolling pass, the plate together with the frame was placed onto a sheet of molybdenum, was covered at its upper surface with a further sheet of molybdenum. In a steel clamping device the two molybdenum sheets were then fixed to the steel plate of the device and the said combination was subjected to a heat treatment of 800.degree..+-.25 K. for 100 hours. Radiographs and glow images of the plate indicated a uniform and homogeneous macroscopic structure without the formation of macroscopic cracks or bubbles. It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of appended claims.
	abstract	A system for implanting a substrate. The system includes a substrate holder disposed within a process chamber of the system and coupled to ground. The system also includes an electrode disposed within the process chamber and coupled to a power source, the power source configured to supply voltage to the electrode as an unbalanced voltage pulse train, wherein a negative peak voltage during a negative voltage pulse period of the unbalanced voltage pulse train is higher than a positive peak voltage during a positive voltage pulse period of the unbalanced pulse train. The system further includes a movable mask, wherein the movable mask is configured to move between a first position proximate the substrate holder, and a second position proximate the driven electrode.
051587386	description	DESCRIPTION OF A PREFERRED EMBODIMENT The example of implementation of the invention which will now be described may be considered as representative of applying the method to a pressurized water power reactor having, for example, a power of 1300 MW, whose core is formed by juxtaposed fuel assemblies of hexagonal cross-section. The general construction of the reactor will not be described here since it may be similar to that of pressurized water reactors now under development, such as that described in EP-A-0,231,710, although the invention is also applicable to a core having a square array of fuel assemblies. Reference may also be made to European patent application No. 0,097,488, already mentioned, for finding a description of a complete plant incorporating a reactor to which the invention is applicable. The core may be regarded as comprising six angular sectors all having the same construction and, for that reason, two sectors only are shown completely in FIG. 1. As shown, each sector comprises thirty-nine fuel assemblies (not counting the central assembly of the core) over each of which is mounted a control bar insertion mechanism. The eight positions 10, shown as white hexagons, are intended to receive shut-down bars, called "black" bars because they have a high neutron absorption or high anti-reactivity worth. The reactor consequently comprises forty-eight shut-down bars in all, sufficient alone for shutting down the reactor when at its normal operating temperature. They are each formed of a cluster of rods for insertion in guide tubes of the corresponding fuel assembly, each rod having a sheath containing pellets of neutron absorbing material. It can be seen that the reactor has, in all, forty-nine shut-down clusters, completely removed from the core (i.e., contained in the upper internals of the reactor) during normal operation of the latter. Each sector further has twenty fuel assembly locations 12 adapted to receive bars which are removed from the core after an operation period representing a fraction of the total duration of a cycle. The bars provided at the twenty locations 12 contain burnable neutronic poison, whose progressive consumption compensates for depletion of the fuel during an initial operating phase. Such bars are not necessarily all raised simultaneously. Depending on the degree of depletion of the fuel, a first set of bars (clusters of rods) is raised, then a second set of clusters is raised after a shorter or longer period. The sets of clusters are selected so as not to disturb the radial power distribution. The degree of insertion of the consumable poison clusters 12 is independent of fuel management and may be chosen so as to keep the radial power distribution as constant as possible. The method of controlling these clusters may be conventional and will not be described. It should only be mentioned that they also make it possible to modify the neutron energy spectrum: when they are removed from the core, the guide tubes which previously received them are invaded by water, which increases the moderation ratio of the core. This effect of variation of the neutron spectrum towards the lower energies is reinforced if the clusters contain fertile material, as described, for example, in EP-A-0,231,710. Finally, the positions 14 shown by hatched hexagons in FIG. 1 are intended to receive control bars. These bars are again formed of absorbent rod clusters. To reduce the number of through passages in the lid for controlling the necessary displacements of the bars, it is of advantage to provide two mutually independent bars at each position 14 and to control the two bars with two mechanisms placed coaxially or side by side. Devices are already known for independently moving two control bars occupying a same fuel assembly location in the core. Some arrangements make complete displacement independence possible. More often, for reasons of simplification, the arrangement involves a constraint: one of the two bars, determined by construction, always has a smaller (or at least not a greater) insertion in the core than the other bar (or even may only be lowered when the other is completely inserted in the core). As shown in FIG. 1, each sector of the core comprises six evenly distributed locations 14, one each for a set of two control bars. FIG. 2 illustrates an example of maximum total anti-reactivity variation in the core to be achieved by insertion or removal of the control bars. FIG. 2 corresponds to a case where the total anti-reactivity to be provided is broken down in the following way, for a new core at the beginning of its life: ______________________________________ Combustion reserve (after deduction of 1000 pcm the effect of the consumable poison): 1000 pcm Control margin: 500 pcm Power operation margin: 2000 pcm Compensation of the xenon effect: 2000 pcm ______________________________________ The combustion reserve of 1000 pcm, which permits to operate the reactor at 100% of its rated power, is absorbed when the core is new, by the 6.times.20 consumable poison clusters placed at locations 12. When the core is new, there is no xenon poisoning and then the control clusters situated at locations 14 must supply an anti-reactivity corresponding to the maximum possible amount of xenon poisoning. Consequently, the control clusters must have an anti-reactivity at least equal to 5500 pcm when fully inserted. FIG. 2 shows, by way of example, a typical evolution likely to take place in time and according to which there is successively: operation at 100% rated power with xenon saturation (point A); passage to 50% of the rated power (point B); steady operation at 50% of rated power (accompanied by a variation of the anti-reactivity due to xenon (point C); return to 100% of rated power without modification of the xenon content (point D); progressive decrease of the xenon anti-reactivity (point E). Referring to FIGS. 3A, 3B, 3C, implementation of a control method in accordance with the invention will be described assuming that it aims at maintaining: a control parameter, formed by the difference between the actual temperature at the outlet of the core and a reference temperature, within a dead range of +/-3.degree. C.; the difference between the actual axial offset and a reference offset in a range of +/-3.degree. % (FIG. 3A); the enthalpy increase factor F.DELTA.H at a value which is minimum and in any case less than 1.3 (FIG. 3B). The enthalpy increase .DELTA.H may be calculated either for an individual fuel assembly, or for a fraction of the core, or even for the whole core. For the unit under consideration (fuel assembly, fraction of the core or whole core), the enthalpy increase .DELTA.H may be calculated from the water inlet and outlet temperatures as a second or third degree polynomial function of the temperatures, depending on the desired accuracy. The inlet and outlet temperatures which are compared are not necessarily those measured at the same time, when it is desired to take into account the transit time of the cooling water in the assembly under consideration. FIG. 3C shows (assuming that the control process is to be carried out to maintain the axial offset difference or deviation at a value less than +/-3%) possible variations of the anti-reactivity inserted in the core, in a case where the clusters constituting the control bars have the distribution shown in FIG. 1. In FIG. 1, the six control cluster locations are designated by the numbers 1 to 6 also found in FIG. 3C. These numbers are given index a for designating the bars more fully inserted in the core and index b for designating the bars less fully inserted in the core in a set of two bars. It can be seen that only bars a are inserted when the anti-reactivity to be inserted does not exceed 2000 pcm. Beyond this, it is necessary to use bars a and b to maintain the axial offset difference between 17% and 20%: the variations of this difference are then as shown in FIG. 3A. In FIG. 3A, for an anti-reactivity of about 3000 pcm, a discontinuous evolution of the axial deviation difference can be seen, necessary for maintaining the enthalpy increase factor F.DELTA.H at a substantially minimum value and, in any case, less than 1.3 (FIG. 3B). An example illustrating how the method of the invention may be used to operate a reactor whose core has the construction shown schematically in FIG. 1 will now be described, assuming that control takes place independently for each of six sectors and the conditions to be respected are those already defined in connection with FIGS. 3A and 3B. For a given reactor, a relation may be defined for each fuel assembly, between the enthalpy increase factor and the position of the bars in the respective sector. In particular, an enthalpy increase factor E=F.DELTA.H of the hottest fuel assembly may be defined by a relation which is a linear combination of pre-computed "influence functions" f.sub.ij : EQU E.sub.j =E.sub.0j +.SIGMA..sub.i f.sub.ij).times.(r.sub.i) (1) where: E.sub.0j designates the starting enthalpy increase factor F.DELTA.H; each of the functions f.sub.ij represents the contribution of bar i to E.sub.j for the starting condition E.sub.0j ; the terms r.sub.i are the anti-reactivity variations caused by displacements of bars i, with i=1a, 1b, . . . , 6b, E.sub.j designates the factor F.DELTA.H after displacements of the clusters causing the variations r.sub.i, such clusters being designated hereafter, for the sake of convenience, as 1a, 1b, . . . , 6b. It may be necessary to update the influence functions when the state of the reactor has varied a great deal. A three dimensional in-line power distribution calculation may be used for this purpose. As mentioned above, the control method according to the invention, reacts to any evolution of the control parameter, i.e., it causes it to depart from the dead band by modifying the position of at least one of the control bars, the amplitude and the direction of displacement of this bar at least being determined so as to: bring the control parameter back within the dead band, maintain (or bring back) the axial offset difference in the authorized range (FIG. 3A), optimize the enthalpy increase factor. The first operation to be carried out consists in calculating the reactivity variations necessary for bringing the mean output temperature of the sector back to the reference or set value; then, a simulation procedure is used for selecting a bar (or bars) whose displacement will achieve this variation while optimizing F.DELTA.H. For this purpose, the strategy shown by the flowchart of FIG. 6 may be adopted. This strategy implies going through several control loops until the difference between the predicted reactivity variation and the necessary variation is less than a given value. 1. The first operation consists in drawing lots for randomly selecting: one bar from the six, or more generally n, bars of a sector (assuming for the moment that the six mutually corresponding bars in the six sectors will be re-positioned by the same amount); a displacement among all the displacements (including zero) of such an amplitude that they would cause a reactivity variation within a given range about the required reactivity variation: for example, in the case (illustrated in FIG. 6) of a required variation of -5 pcm, the displacement may be any one of all those which cause a variation between (-5+10)=+5 pcm and (-5-10)=-15 pcm. Then it is verified by a computation that the selected displacement does not cause the axial offset difference to depart from the authorized range. If the condition is not fulfilled, the attempted displacement is waived and lots are again cast for selecting another bar and/or another displacement. The computation is carried out again and the operations are repeated until the axial distribution conditions are respected. 2. When the axial distribution condition is fulfilled, the evolution (F.DELTA.H) of the enthalpy increase factor caused by the attempted displacement is calculated in accordance with formula (1). If, for example, the initial state is E0, if cluster 2a has been chosen and if the simulated displacement of cluster 2a changes the anti-reactivity from (2a) to (2a mod), a state E1 is obtained for the hottest assembly: EQU E1=E0+F.sub.1a (1a)+. . . +f.sub.2a (2a mod)+. . . +f.sub.6b (6b) a) If E1-E0=.DELTA.(F.DELTA.H) is negative or zero, the displacement is considered as satisfactory and it is stored. b) If .DELTA.(F.DELTA.H) is positive, a probability P between 0 and 1 is assigned to the displacement, depending on the absolute value of .DELTA.(F.DELTA.H): EQU P=exp[-.DELTA.(F.DELTA.H)/kT] Probability P is a function derived from Boltzman's law on the distribution of energies as a function of temperature and, for this reason, the constant denominator of the exponential function is designated by kT. On initialization of the method, kT is given a very high value, so that the negative exponential which represents P has a value close to 1 whatever .DELTA.(F.DELTA.H). Once the value of P has been determined by calculation for the value .DELTA.(F.DELTA.H)=E1-E0 to which the attempted displacement leads, any number between 0 and 1 is selected at random; the mean proportion of favorable draws, i.e., of draws between O and P, is equal to probability P. If the drawing of lots has a positive result, i.e., if the value chosen at random is less than P, value E1 will be considered the rated value. In the opposite case, the result is not taken into account, i.e., the attempted bar and amount of displacement are abandoned, and another bar and/or another displacement are selected at random, which corresponds to passing through the first loop again in FIG. 6. When the system is in initial condition with the probability close to 1, almost all numbers drawn by lots between 0 and 1 give a positive result. The method advantageously uses a computing circuit or program which computes the ratio between the number of positive draws and the total number of attempted displacements. If the result is too often favorable (e.g., greater than 90% of the attempts), kT is decreased by a given increment; if, on the other hand, the probability is too low (e.g., less than 70%), kT is increased by the same or another increment; a satisfactory value of P in the long run is about 0.8. The operation is repeated until a bar and a displacement are selected; the values selected and the corresponding anti-reactivity variation are then stored. Sometimes, it is necessary to accept repositioning of bars by moving them in a direction which will increase F.DELTA.H: since, in some situations, no displacement will further reduce F.DELTA.H. Attempting modifications which, a priori, do not seem to go in the right direction, make it possible to cause the system to depart from a secondary minimum of the function (such as those which appear in FIG. 5) to find a better minimum. 3. The simulation process is repeated until the sum of the stored displacements (the number of bars concerned going from 1 to 6 in the case of the example considered, in the same sector) supplies the required reactivity variation, with a predetermined tolerance. All displacements are then carried out by energizing bar actuators. FIG. 5 shows that, for each fuel assembly, the curve of variation of the enthalpy increase factor .DELTA.(F.DELTA.H) as a function of .DELTA.H has a plurality of successive minima. The method of the invention makes it possible to select displacements toward a minimum, which is not necessarily the lowest possible value of .DELTA.(F.DELTA.H). FIG. 4 shows, by way of example, typical bar arrangements for several inserted anti-reactivities. Numerous modifications of the flow diagram of FIG. 6 are possible. In particular, the diagram of FIG. 7 may be adopted in which calculation of the expected effect of the repositioning of the clusters on the amount of axial offset is only effected after random selection of bars and displacements which achieve the required anti-reactivity variation with an acceptable effect on F.DELTA.H. The flow diagram of FIG. 7 will not be described in detail since it is quite similar to that of FIG. 6. The flow diagram corresponds to the case where a first calculation has shown that the total reactivity variation to be obtained is x pcm; a, h, Nm and Np are adjustable parameters whose values are determined beforehand by dimensioning studies. The abbreviations designate: A0: axial deviation PA0 FDH: enthalpy increase factor PA0 abs: absolute value. It has been assumed up to now that all the bars belonging to the same group, for example bars 2a in all six sectors, are displaced simultaneously by the same amount after the calculation. This method of operation does not take into account possible azimuthal or radial offsets or imbalances of the power distribution. Such imbalances, of low value, may occur due to mechanical or geometric irregularities or (particularly when the bars are controlled by hydraulic mechanisms which have leaks) due to slow drifts of one or more bars. Reactors are, as a general rule, provided with thermocouples for measuring the temperature of the pressurized water where it flows out of the individual assemblies and with ion chambers placed outside the core and making it possible to measure the neutron flux. From the measurements delivered by these sensors, the azimuthal imbalances may be calculated with known codes, such as the "PROSPER" code available from the assignee of the present application. The imbalances can be represented by harmonics whose amplitude gives the amount of offset and whose phase makes it possible to determine the central axis of the imbalance. By slightly modifying the degree of insertion of one cluster or of several clusters placed close to the axis of imbalance, the amount of imbalance can be reduced below a tolerance threshold. FIG. 8 is a diagram showing a method of controlling the bars for attenuating the azimuthal imbalances. In FIG. 8, reference 20 designates a computer for determining, using the algorithms of FIG. 6 or FIG. 7, the displacements to be given to bars belonging to groups 1 to 6 (or 1 to 12 in the case of double bars). Instead of directly applying the control instructions delivered by outputs 1 to 12 (each instruction to all bars of the same group in different sectors), the computer sends the instructions, formed by an amplitude indication and a direction indication, to a circuit 22 which computes the individual displacements to be given to the bars, responsive to an azimuthal imbalance information delivered to inputs 24. In a simple embodiment, the inputs 24 simply deliver six coefficients for distributing, between the bars of the same group, deviations with respect to the nominal displacement calculated by computer 20 while complying with the condition of maintaining the required anti-reactivity modification unchanged. In a more elaborate embodiment, input 24 receives a correction coefficient matrix with 6.times.6 (or 6.times.12) terms, for improving the result. The matrix of coefficients may be supplied by a separate computer (not shown) using an existing computation code. In this case, circuit 22 must carry out a matrix multiplication of the displacement matrix delivered by computer 20 for the thirty-six (or seventy-two) bars and of the matrix of coefficients. Whatever the solution adopted, circuit 22 delivers, at thirty-six outputs (in the case of single bars) or seventy-two outputs (in the case of double bars) individual direction and amplitude data which are sent to respective control mechanisms 26. If the mechanism 26 is hydraulic, it generally comprises a cylinder whose piston supports the bar and a reciprocating hydraulic actuator, each actuation of the actuator displacing the cylinder by one step of predetermined amplitude. Since the cylinder is likely to have leaks which result in a slow downward drift of the bar, a reset system may be provided for compensating the drift. In the embodiment shown in FIG. 8, this system comprises means 28 for detecting the position of the bar when it is at any one of several positions, a counter 30 which receives the energy signals sent to mechanism 26 and works out, from the individual signals, the theoretical or set position of the bar and finally a comparator 32 which is tripped whenever the bar (or its control mechanism) passes in front of a measuring point of the position detection means 28. The comparator computes the difference between the theoretical position, given by counter 30, and the actual position, represented by the respective reference point and which is known by construction. If the difference is greater than one operating step of the actuator and cylinder, comparator 32 sends to the actuator of the bar an "up" order causing a number of steps to be effected for compensating the drift. Numerous other structural modifications are possible. The number of bars per sector could often be reduced, e.g., by omitting group 5 which is of little use. The use of double clusters, rather than single clusters, is necessary only for power start-up after a shut-down of long duration, sufficient for the xenon content to have decreased. Other parameters could be used, for example for reducing the maximum power per unit length of the fuel rods, taking into account chemical interactions between the sheath of the rods and the fuel pellets.
	description	This application is related to and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/653,400 filed on 16, Feb. 2005, the entire contents of which are herein incorporated by reference. This application is also related to and claims the benefit of Luxembourg Patent Application Ser. No. 91 158 filed on 25 Mar. 2005, the entire contents of which are herein incorporated by reference. The invention provides a head-end process for the reprocessing of reactor core material, which is suitable for a hot cell environment and industrially relevant material streams. The present invention relates to a head-end process for the reprocessing of reactor core material, more particularly to the fragmenting of coated fuel particles and nuclear fuel elements comprising coated fuel particles embedded in a matrix material. The reprocessing of coated particle fuel e.g. from high temperature gas-cooled reactors (HTGR) is useful in many cases to maximize the use of the fuel. It is even mandatory for the U-Pu (fast reactor) and for the Th-U fuel cycle as well as for the incineration of minor actinides in these reactors. Coated fuel particles are characterized by their high resistance against mechanical impact and chemical attack, which makes them safe, rather proliferation-resistant and suitable for direct disposal, yet difficult to reprocess. For use in a reactor, the fuel particles are generally embedded in the matrix material (e.g. graphite, carbide or ceramic) of a fuel element. About 10 000 fuel particles are e.g. contained in a spherical fuel element (pebble) of type AVR GLE-4, fabricated by NUKEM for the German High Temperature Reactor (HTR). The following table summarises the nominal characteristics of AVR GLE-4 pebbles and the embedded particles. Coated Fuel ParticleParticle batchHT 354-383Kernel compositionUO2Kernel diameter [μm]501Enrichment [U-235 wt. %]16.75Thickness of coatings [μm]:buffer92inner PyC38SiC33outer PyC41Particle diameter [μm]909PebbleHeavy metal loading [g/pebble]6.0U-235 contents [g/pebble]1.00 ± 1%Number of coated particles per pebble9560Volume packing fraction [%]6.2Defective SiC layers [U/Utot]7.8 × 10−6Matrix graphite gradeA3-3Matrix density [kg/m3]1750Temperature at final heat treatment [° C.]1900 For the reprocessing of coated fuel particles, i.e. the fuel kernel with multiple ceramic coatings, or fuel elements containing such fuel particles, one option is to isolate these particles from the matrix material (e.g. graphite) of the fuel elements, which may have the shape of spheres, rods, plates or other. Then the coatings of the fuel particles must be cracked to make the fuel kernel accessible to chemical reprocessing. Another option is to fragment the fuel elements and the coated particles together. A direct dissolution of the fuel element or of the coated particles is currently considered extremely difficult as in particular the often used SiC coating is resistant against dissolution in common nitric acid solutions. A mechanical cracking of the coatings is equally problematic due to the high mechanical resistance of the coatings and their questionable suitability for use in a hot cell environment. In “An Overview of HTGR Fuel Cycle”, Report ORNL-TM-4747, 1976, K. J. Notz describes examples of mechanical fracturing applied to ceramic nuclear fuel, such as grinding by hammers (coal mill type) or grinding between disks (wheat mill type). U.S. Pat. No. 4,323,198 discloses the fragmentation by sandblasting against a hard surface for the reprocessing of nuclear particle fuel. The known mechanical methods however suffer from several shortcomings: low efficiency and high energy consumption; potential use of pressurized gases as in the case of sandblasting; production of toxic or explosive dust causing safety problems; high noise level and vibrations; pollution of the matter to be fragmented by non-negligible quantities of abrasion products; high wear and tear of the impact material by abrasion, limited lifetime, high investment and operation costs. It can thus be concluded that mechanical methods are rather unsuited for use in hot cell environment as they are e.g. not compatible with the safety standards of the latter. High overall costs inhibits the industrial applicability of the mechanical methods. In “The Reprocessing Issue for HTR Spent Fuels”, Proc ICAPP'04, Grenéche et al. discuss the pulsed high voltage discharge technique for separating coated particles from their graphite matrix. Experimental results show that graphite can be fragmented, and that the grain size distribution is a function of the number of applied pulses. The high voltage technique is known e.g. from Bluhm et al. “Application of HV Discharges to Material Fragmentation and Recycling”, IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 7 No. 5, 2000. The cracking of coated fuel particles for reprocessing is, however, considered a so far unresolved problem. Furthermore, when nuclear reactors of certain types (e.g. block-type reactors) are loaded, the fuel elements comprising the fuel particles are inserted into a support material of the reactor core. The support material depends on the reactor type and may e.g. comprise graphite, carbide or nitride. After operation, the extraction of the fuel elements and the radioactive material is difficult, because during operation of the nuclear reactor, the support material and the fuel elements may be subject to deformations. The fuel elements can be literally stuck in the surrounding support material. Traditional methods for recovering the used nuclear fuel suffer from the disadvantage that the separation of the materials is not complete and that the support material remains contaminated with the nuclear fuel. Recycling of the support material thus is difficult. It is an object of the present invention to provide a head-end process for the reprocessing of reactor core material, which is suitable for a hot cell environment and industrially relevant material streams. In a head-end process for the reprocessing of reactor core material comprising fuel particles, reactor core material is arranged in a reactor containing a fluid (e.g. water). The reactor comprises a voltage discharge installation in the fluid. Voltage discharges are applied through the fluid for fragmenting the fuel particles into fragmentation products and the fragmentation products are segregated. According to the invention, the fuel particles are fractured by applying voltage discharges through the fluid contained in a reactor. The process is energy-efficient and power consumption is relatively low. The process does not suffer from the shortcomings of the mechanical methods discussed above, which makes it suitable for a hot cell environment with industrially relevant quantities. After fragmentation of the fuel particles, the fragmentation products can be directly fed into classical aqueous reprocessing. At the moment of introducing the fuel particles into the reactor, the fuel particles can be comprised in said reactor core material. The head-end process proposed is particularly well suited for fuel particles, which comprise each a fuel kernel and several coatings enclosing the fuel kernel. By application of voltage discharges, the coatings of the fuel particles are fragmented. In a preferred embodiment of the invention, the reactor core material further comprises matrix material, which are embedded in the matrix material; both the matrix material and the coatings may be fragmented by the application of voltage discharges. If necessary, the reactor core material is cut or pre-fragmented so that the pieces fed into the reactor have a suitable size, typically of the order of a few centimeters. The fragmentation of the matrix material and the coatings may be achieved in separate process steps. Alternatively, the fragmentation of the matrix material and the coating may be achieved in a single step. The matrix material may comprise the support material of the reactor core and the fuel element material, in which the fuel particles are embedded. As will be appreciated, the reactor core material with the fuel elements carrying the fuel particles can be fed into the present head-end process. Hence, there is no need for removing the nuclear fuel elements from the support material prior to fragmentation. The separation of the fuel kernel material and the matrix material of the support material and the fuel element can be achieved after the fragmentation by voltage discharges. The amount of fuel kernel material remaining in the matrix material is lower, which facilitates the recycling of the latter and thus potentially saves resources. The matrix material (e.g. graphite, nitride, carbide or other ceramic material) can also be further fragmented to facilitate decontamination and to obtain a powder as the starting product for possible re-fabrication of fuel, moderator or reflector. The matrix material, contaminated after its use, would consume excessive storage space if disposed of directly. Also, graphite of sufficient quality is a scarce resource, in particular when considering the possible deployment of a relatively large number of HTGRs worldwide. The segregation of the fragmentation products, e.g. coating shells, matrix material and/or fuel kernels can be achieved in any suited process step, like dissolving the fuel kernels or sieving. Sieving can e.g. comprise several sieving steps with sieves of different hole sizes. If the fuel kernel is to be dissolved e.g. in nitric acid, the coatings need not to be completely removed from the fuel kernels: it is sufficient that a crack in the coatings allows the acid to penetrate to the fuel kernel. According to a preferred embodiment of the invention, it is proposed a head-end process for the reprocessing of reactor core material wherein the reactor core material is arranged in a reactor containing a first volume of a fluid, the reactor being provided with a voltage discharge installation in the fluid. First voltage discharges are applied through the first volume of fluid so as to primarily fragment the matrix material. The so-obtained fragmentation products are segregated so as to retrieve residua fragments containing the nuclear fuel kernels and possibly some residual matrix material The residual fragments are arranged in the same or another reactor containing a second volume of fluid and second voltage discharges are applied through the second volume of fluid so as to fragment the coatings and the residual matrix material contained in the residual fragments. After fragmentation, the fuel kernels are segregated from the coatings and/or the residua matrix material. The electric parameters for applying the first and the second voltage discharges can be adapted so that in the first fragmentation step mainly matrix material is fragmented, while in the second fragmentation step the coatings of the fuel particles are cracked. The electric power can be chosen significantly higher in the second fragmentation step in order to achieve an increased power density in the liquid. Alternatively or additionally, the second volume can be chosen substantially smaller than the first volume, which also leads to an increased power density. Preferably the applied voltage ranges from 40 to 400 kV. At least one of the segregation steps preferentially comprises sieving and/or dissolving the fuel kernels. The first segregation step may comprise sieving with a sieve having holes, the size of which may e.g. be comprised between 0.7 and 0.95 times the fuel particle diameter. Alternatively, the hole size may e.g. be comprised between 0.7 and 0.95 times the fuel kernel diameter. If a sieve is used in the second segregation step, the holes have preferably a width comprised between 0.7 and 0.95 times the fuel kernel diameter. In practice, the reactor core material is advantageously arranged on a sieve or in a closed cup in the reactor, and the voltage discharges are caused by applying potential differences between two electrodes arranged in said reactor. One of the electrodes may be the sieve, resp. the closed cup. One of the electrodes may be grounded. If a sieve is used in the first fragmentation step, one may use a sieve with a hole size comprised between 2 and 4 times the size of the fuel particles and more preferably a sieve with a hole size corresponding to approximately 3 times the diameter of the fuel particles. It may furthermore prove useful if the electrode plunges into the reactor core material, fuel element pieces, fuel particles, or residual fragments. The invention will be more apparent from the following description of not limiting embodiments with reference to the above-mentioned drawings. FIG. 1 shows the structure of a fuel particle 10. Without prejudice to the general concepts of the invention, we will assume in the following that the nuclear fuel (Uranium, Plutonium, Thorium, minor actinides or mixtures of them) is present as ceramic kernel 12 in spherical shape with a diameter of approximately 0.5 mm. This fuel kernel 12 is covered with several successive coating layers: an inner carbon buffer layer 13, a pyrolytic carbon layer 14, a silicon-carbide layer 15 and an outer pyrolytic carbon layer 16. The fuel kernel forms, together with the coatings the fuel particle 10 with a typical diameter of approximately 1 mm. Thousands of these particles are contained in the matrix (made e.g. from graphite, carbide, or other ceramics) of a fuel element, which may have any suitable form, such as e.g. spherical, cylindrical or other. The process enables the separation of the fuel particles from their matrix material with the consecutive fragmentation or complete removal of the coatings to make the fuel kernel accessible to chemical dissolution for further reprocessing. The process can be used for fully separating the coatings and the matrix material from the kernels. This separation of kernels and coatings, however, is not even mandatory if the nuclear fuel of the kernels is chemically dissolved, so that a large fracture in the coating is deemed sufficient for this purpose. FIG. 2 shows an illustration of a small fragment 20 of a nuclear fuel element. Fuel particles 10 are embedded in a matrix material 22. If necessary, the fuel elements are mechanically cut or fragmented into pieces such that the dimensions of these primary fragments are such that the latter can be easily manipulated and fed into the subsequent process steps. Dimensions of the order of several centimeters may be convenient for the purpose of the invention. The embedded fuel particles themselves remain undamaged thanks to their high mechanical resistance. The fuel element pieces are brought into a reactor 30 filled with a volume V1 of water. The reactor vessel shown in FIG. 3 comprises a steel container 32, the inner wall of which is lined with an electric insulator 34 (e.g. plastic). A massive-steel high voltage electrode 36 is arranged in an electrically insulating cover block 37 and plunges into the water. A sieve 38 is located in the middle of the volume V1. A second electrode 40 is arranged at the bottom of the reactor an is electrically insulated from the steel container 32. The holes of the sieve 38 have a diameter of approximately three times the fuel particle diameter, in this case 3 mm. A pulse generator 42 periodically charges the top electrode 36 with voltages of 40-400 kV with respect to the bottom electrode 40. The distance between the high voltage electrode 36 and the sieve 38 is chosen such that the top electrode 36 has a suitable distance from the fragments 44 (e.g. of the order of one or several centimeters) and that discharges through the water are obtained. The discharges cause electro-hydraulic shock waves in the water, which fragment the matrix graphite. The maximum discharge currents are of the order of 10 kA. By correctly choosing the volume V1, damage to the fuel particles 10 can be avoided with these electric discharge parameters. For energy-optimised fragmentation, the diameter of the holes in the sieve 38 is adapted to the size of the fuel particles. If the holes are too large, the fuel particles remain in the matrix material, if they are too small, the matrix material will be fragmented to unnecessarily fine grains before falling through the holes of the sieve 38. The maximum of the statistical fragment size distribution is approximately 1.5 mm. If holes of 3 mm are selected, the fuel particles can thus be separated from the matrix in the material fraction 46, which has fully passed the sieve. The fuel particles, which have dropped through the sieve are contained in the sieve fraction containing the fragments with a minimal size of 1 mm. The quantity of material to be processed in further steps can be reduced by segregating out a fraction of the matrix material. This can be done by sieving the fragments obtained in the preceding step. The quantity of removed matrix material depends on the size of the holes in the sieve: if the hole diameter is only slightly smaller than the fuel particles, the residual material to treat further mainly comprises fuel particles; if the hole diameter is chosen substantially smaller than the fuel particles the fraction of residual matrix material is larger. If one chooses the hole diameter slightly smaller than the fuel kernel, one assures that possible cracked fuel particles are subject to further treatment. In a subsequent process step the residual fragments of the preceding step are treated with high voltage discharges in a liquid-containing reactor in order to crack the coatings of the fuel particles. There are two options: high voltage discharges over a closed cup or high voltage discharges over a sieve with a hole diameter slightly smaller than the fuel kernels (here 0.4 mm). The electric parameters can be identical to those mentioned above, the reaction volume V2 is however significantly smaller than the first volume V1. The electrode can plunge into the material fragments to be treated. The volume reduction yields an increased power density of the created shock waves, which make the coatings burst and which may remove them from the fuel kernel. Contrary to the oxide kernel, the coating shells and possibly residual matrix material are further fragmented. Once coatings and matrix material are sufficiently fragmented, they will drop through the sieve, or, when a closed cup is used, the fragmentation products can be sieved in a consecutive step. FIG. 4 shows a picture of separated coating shells and FIG. 5 shows fuel kernels together with their fragmented coating shells. Another option would be to dissolve the fragmentation products collected in a closed cup directly in nitric acid to maximize the recovery of nuclear material including the fraction that may have penetrated into the coating shells. It will be appreciated that fragmentation by voltage discharges can also be used for coated fuel particles, which are not embedded in matrix material. In this case, the fuel particles are arranged in a reactor containing a fluid or liquid (e.g. water), either on a sieve or in a closed cup. If a sieve is used, the latter preferentially has holes with a diameter slightly smaller than the diameter of the fuel kernels. Voltage discharges are provoked by application of high voltage pulses between the sieve and an electrode arranged in the reactor. The electrode may plunge into the fuel particles. The shock waves created by the discharges make the coatings burst. Small pieces of coating material can drop through the holes of the sieve, while intact fuel kernels remain on top of the sieve. When using a closed cup for fragmentation, high voltage pulses are applied between the cup and an electrode, which is arranged in the reactor at a suitable distance. The electrode may also plunge into the fuel particles. When the coatings are sufficiently fragmented, the fragments can be sieved to retrieve the fuel kernels and/or the fuel kernels can be dissolved, e.g. in nitric acid. Several proof-of-principle tests were performed with dummy particles. The following material was used for the experiments: a) Coated particles: ca. 90 g with yttrium-stabilized zirconia kernel and triple coating, dummy particles obtained from the French Atomic Energy Commission CEA, Grenoble, France. b) Several cylindrical pieces of typical commercial reactor graphite type SGL R6650. The tests were performed in suitably modified high voltage discharge installations known e.g. from Bluhm et al. between November 2003 and April 2004. Successful results are reported in the following. In the used laboratory equipment, the required electric energy for fragmenting the matrix graphite in the first fragmentation step was approximately 2000-5000 kWh/t depending on type and shape of the matrix graphite. The electric energy required for the fragmentation of the coatings was approximately 8000 kWh/t. The measured energy consumption for the tests is deemed conservative as the tests were run with laboratory installations and small amounts of material to be fragmented. Fragmentation of Dummy Particles Used material: 10 g dummy particles Ø1 mm. Reaction vessel: reduced volume with polyethylene insert Ø120×15 mm, bottom reinforced. Closed cup filled with water. Marx Generator: 7 stage 7×140 nF without additional inductivity, electrode distances 11, 12, 12, 12, 12, 12, 12 mm; charge current 120 mA at 60 kV. Distance between electrodes: 30 mm Number of pulses: 200 Sieve analysis of reaction product: particle diameterrecovered mass [g]>900 μm0 5005.65 2501.42<2501.75total8.82(i.e. 1.18 g handling loss) The analysis shows that all inserted fuel particles were fragmented and that all fuel kernels have remained intact. Fragmentation of Graphite Pieces Used material: 3 graphite cylinders approx. Ø44×35 mm, 282 g total Reaction vessel: Sieve bottom 3 mm, graphite cylinders symmetrically arranged around electrode. Marx Generator: 7 stage 7×140 nF without additional inductivity, electrode distances 11, 12, 12, 12, 12, 12, 12 mm; charge current 150 mA at 60 kV. Distance between electrodes: 50 mm Number of pulses: 2000. After 2000 pulses, almost all of the created graphite particles had dropped through the sieve.Fragmentation of Graphite Pieces Together with Coated Particles This test demonstrated that representative mixtures of graphite and coated particles can be fragmented together. Used material: graphite fragments <3 mm, 187 g (wet) with 1 g coated particles Reaction vessel: Closed cup Marx Generator: 7 stage 7×140 nF without additional inductivity, electrode distances 11, 12, 12, 12, 12, 12, 12 mm; charge current 150 mA at 60 kV. Distance between electrodes: 20 mm Number of pulses: 1600 total Sieve analysis of reaction product: particle diameterrecovered mass [g]>4mm02-4mm8.91.12-2mm29.90.9-1.12mm8.80.5-0.9mm14.50.25-0.5mm8.10.125-0.25mm5.7<0.125mm4.7 This test under not optimized conditions shows that at least a significant fraction of the coated particles can be fragmented with simultaneous presence of graphite fragments.
048329029	claims	1. Apparatus for refueling a nuclear reactor, said reactor being disposed for refueling under water in a pit in a containment, the said apparatus including a bridge to be mounted moveably over said pit on said containment, first means connected to said bridge, for moving said bridge forward and backward on said containment over said pit along a first path, a first pulse generator, connected to said moving means, responsive to the movement of said bridge, for producing pulses, means, connected to said generator, for counting said pulses, the count of said pulses being dependent on the distance of the movement of said bridge, a trolley mounted moveably on said bridge, second means, connected to said trolley, for moving said trolley forward and backward on said bridge along a second path at an angle to said first path, a second pulse generator, connected to said second moving means, responsive to the movement of said trolley, for producing pulses, means, connected to said second generator, for counting said last-named pulses, the count of said last-named pulses being dependent on the distance of movement of said trolley, a mast assembly suspended from said trolley including parts moveable vertically with reference to said trolley, third means, connected to said parts, for moving said parts upwardly or downwardly, a third pulse generator, connected to said third moving means for producing pulses, and means, connected to said third generator, for counting said last-named pulses, the count of said pulses being dependent on the distance of movement of said parts, the count of the pulses produced by said first, second and third pulse generators determining the position of said parts relative to said reactor. 2. The apparatus of claim 1 wherein the position-determining means, connected to said first, second and third pulse generators includes means for assigning a polarity to the numbers of the pulses of each which is dependent on the direction of movement of the bridge, trolley and parts each with respect to a reference point. 3. Apparatus for refueling a nuclear reactor, said reactor being disposed for refueling under water in a pit in a containment, the said apparatus including a bridge to be mounted on said containment moveably over said pit, first means, connected to said bridge, for moving said bridge forward and backward on said containment over said pit along a first path, a first pulse generator, connected to said moving means, responsive to the movement of said bridge, for producing pulses, first counting means, connected to said first pulse generator, for counting said pulses, means, connected to said first counting means, for setting the polarity of the counts of said first counting means so that counts for the forward movement are of opposite polarity to counts of the backward movement, whereby the net count of said first counter is a measure of the distance of movement of said bridge from a predetermined reference point, a trolley mounted moveably on said bridge, second means, connected to said trolley, for moving said trolley forward and backward on said bridge along a second path at an angle to said first path, a second pulse generator, connected to said second moving means, responsive to the movement of said trolley, for producing pulses, second counting means, connected to said second pulse generator for counting said last-named pulses, means, connected to said second-counting means, for setting the polarity of its counts so that its counts for the forward movement of said trolley are of opposite polarity to its counts for the backward movement of said trolley, whereby the net count of said second counter is a measure of the distance of said trolley from a second predetermined reference point, and a refueling mast assembly suspended from said trolley moveable therewith, said first and second path defining a coordinate system whose points define the position of said mast with reference to said nuclear reactor. 4. Apparatus for refueling a nuclear reactor, said reactor being disposed for refueling under water in a pit in a containment, the said apparatus including a mast assembly for engaging, raising and lowering selected ones of component assemblies of said reactor of at least one type, a trolley, means on said trolley, connected to said mast assembly, for raising or lowering said mast assembly, first switch means having parts on said trolley and on said mast assembly which cooperate to actuate said switch means when said mast assembly reaches a predetermined first position, said first position being definable by a first coordinate, whose magnitude is measured from a predetermined reference point along said mast, a bridge, a first track on said bridge for said trolley, first drive means, connected to said trolley for moving said trolley forward and backward along said track, a second track for said bridge, said second track to extend along said containment so that said bridge and trolley are movable over said pit on said second track, second drive means connected to said bridge for moving said bridge forward and backward along said second track, said first and second tracks to extend along non-parallel paths, so that the movement of said bridge along said second track moves said mast assembly in a first direction along said second track and the movement of said trolley moves said mast assembly in a second direction along said first track at an angle to said first direction, the positions of said mast assembly, to which it may be moved along said tracks, being definable by a system of coordinates, each position of said mast assembly being definable by a second coordinate whose magnitude measures the distance, from a reference point, of a position of said mast assembly along said first track and a third coordinate whose magnitude measures the distance, from a reference point, of a position of said mast assembly along said second track, second switch means having parts on said trolley and at a predetermined second reference position, defined by a predetermined of said second coordinates, on said first track, said parts being cooperative to actuate said second switch means when said trolley moves through said second position, third switch means having parts on said bridge and at a predetermined third position, defined by a predetermined of said third coordinates, on said second track, actuable when said bridge moves through said third position, control means, said control means containing intelligence of reference magnitudes of first, second and third coordinates measuring the first, second and third positions where the first, second and third switch means would be actuated if the calibration of said apparatus were maintained, means, connecting said first, second and third switch means to said control means, for impressing on said control means the actual magnitudes of said first, second and third coordinates, and means, responsive to any deviation of a said actual magnitude from a said reference magnitude, for correcting the coordinate settings of said mast assembly to compensate for said deviation. 5. The apparatus of claim 4 wherein the mast assembly is raised and lowered by a hoist including a rotating member, the bridge is moveable along the tracks on the containment on wheels and the trolley is moveable along the tracks on the bridge on wheels, the said apparatus including a first pulser, connected to the rotating member, for producing a first train pulses responsive to the rotation of said rotating member, a second pulser, connected to at least one wheel of the bridge for producing a second train of pulses responsive to the rotation of said one wheel, and a third pulser connected to at least one wheel of said trolley, for producing a third train of pulses responsive to the rotation of said last-named one wheel, the said apparatus also including counting means for counting the pulses of each of said train of pulses, the positions of said mast, bridge and trolley from respective starting positions being determined by the respective counts of the first, second and third trains of pulses produced by said first, second and third pulsers respectively as the mast, bridge or trolley moves from a starting position to any position displaced from the starting position, a one-to-one relationship being maintained between the count of first, second or third trains of pulses and any position of the mast, bridge or trolley including the positions where the first, second or third switch means are actuable, the control means including a first, second and third reference count corresponding to the positions of said first, second and third switch means respectively, the deviation of the actual magnitude of a coordinate from a reference magnitude being the difference between the reference count and the actual count for the positions of the first, second and third switch means. 6. The apparatus of claim 4 wherein the raising or lowering means for the mast includes a first pulser for producing a first train of pulses responsive to the upward or downward movement of said mast, the first drive means includes a second pulser for producing a second train of pulses responsive to the forward or backward movement of the bridge and the second drive means includes a third pulser for producing a third train of pulses responsive to the forward or backward movement of said trolley, the said apparatus also including counting means for counting the pulses of each of said train of pulses, the positions of said mast, bridge and trolley from respective starting positions being determined by the respective counts of the first, second and third trains of pulses produced by said first, second and third pulsers respectively as the mast, bridge or trolley moves from a starting position to any position displaced from the starting position, a one-to-one relationship being maintained between the count of first, second or third trains of pulses and any position of the mast, bridge or trolley, including the positions where said first, second or third means are actuable, the control means including a first, second and third reference count corresponding to the positions of the first, second and third switch means respectively, the deviation of the actual magnitude of a coordinate from a reference magnitude being the difference between the reference count and the actual count for the positions of the first, second and third switch means. 7. Apparatus for refueling a nuclear reactor, said reactor being disposed for refueling under water in a pit in a containment, the said apparatus including a mast assembly for engaging, raising and lowering selected ones of component assemblies of said reactor of at least one type, a trolley, means on said trolley, connected to said mast assembly for suspending said mast assembly, a bridge, a first track on said bridge for said trolley, first drive means connected to said trolley for moving said trolley forward and backward along said first track, a second track for said bridge, said second track to extend along said containment so that said trolley and bridge are movable over said pit on said second track, second drive means, connected to said bridge, for moving said bridge forward and backward along said second track, said first and second tracks extending along non-parallel paths, so that the movement of said trolley along said first track moves said mast assembly in a first direction along said first track and the movement of said bridge along said second track moves said mast assembly in a second direction at an angle to said first direction, the positions of said mast assembly, to which it may be moved being definable by a system of coordinates, each position of said mast assembly being definable by a first coordinate whose magnitude measures the distance, from a reference point, of a position of said mast assembly along said first track (trolley track) and a second coordinate whose magnitude measures the distance, from a reference point, of a position of said mast assembly along said second track (bridge track), control means, means, connected to said trolley and to said bridge, for impressing on said control means the magnitudes of the first and second coordinates defining each position of said mast, first switch means having parts on said trolley and at a predetermined first reference position, defined by a predetermined of said first coordinates, on said first track, said parts being cooperative to actuate said first switch means when said trolley moves through said first position, second switch means having parts on said bridge and at a predetermined second reference position, defined by predetermined of said second coordinates, on said second track, actuable when said bridge moves through said second position, the said control means containing intelligence of reference magnitudes of said first and second coordinates measuring the first and second positions where the first and second switch means would be actuated if the calibration of the positions of said bridge and trolley were maintained, means, connecting said first and second switch means to said control means, for impressing on said control means the actual magnitude of said first and second coordinates, and means, responsive to any deviation of said actual magnitude from said reference magnitudes, for correcting the coordinate settings of said mast assembly to compensate for said deviations. 8. The apparatus of claim 7 wherein the first track and the second track are linear and extend at right angles to each other and the coordinate system is a Cartesian coordinate system. 9. The apparatus of claim 8 wherein the part of the first switch means on the trolley is a first limit switch and the part of the first switch means in the first track is a first cam which actuates the first limit switch where the trolley passes over the first cam and the part of the second switch means on the bridge is a second limit switch and the part of the second switch means on the second track is second cam which actuates the second limit switch when the bridge passes over the second cam. 10. The apparatus of claim 7 wherein the means for impressing on the control means, the magnitudes of the first and second coordinates defining the positions of the mast assembly includes a first means, connected to the first drive means (for the trolley) for producing a first train of pulses whose number measures, on one-to-one relationship, the first coordinate for each position, including the position of the first switch means, of the mast assembly along the first track and second means, connected to the second drive means (for the bridge) for producing a second train of pulses whose number measures, in one-to-one relationship, the second coordinate for each position including the position of the second switch means, of the mast assembly along the second track, the reference magnitudes being a number each for the first and second coordinates which, if the calibration is maintained, is equal to the number of the corresponding train of pulses at the positions of the first and second switch means respectively. 11. The apparatus of claim 10 wherein the drive means includes wheels on the trolley and bridge, the first pulse-train-producing means including a first pulser, connected to at least one wheel of the trolley, to be actuated thereby to produce the first train of pulses in accordance with the rotation of said one wheel and the second pulse-train-producing means including a second pulser, connected to at least one wheel of the bridge, to be actuated thereby to produce the second train of pulses in accordance with the rotation of said last-named one wheel.
	claims	1. A method of reprocessing spent nuclear fuel, the method comprising:adding the spent nuclear fuel to an electro-reduction cell, wherein the electro-reduction cell comprises a halide salt electrolyte, and anode, and a cathode comprising an alloy of uranium and a first metal forming a low melting point alloy with uranium, the first metal being one or more of:iron;chromium;nickel;manganese; andcobalt;wherein the spent nuclear fuel comprises uranium oxide, plutonium and other actinides having a higher atomic number than uranium, and at least 1 mol of lanthanides per tonne of uranium in the spent nuclear fuel wherein the electro-reduction cell is operated at a temperature above the melting point of the alloy;the method further comprising:electrochemically reducing the spent nuclear fuel at a potential sufficient to reduce plutonium and lanthanides in the spent nuclear fuel, in order to form a molten alloy of the first metal, uranium and the other actinides having a higher atomic number than uranium present in the spent nuclear fuel; andextracting the molten alloy from the electro-reduction cell, during the step of electrochemically reducing the spent nuclear fuel, and while uranium oxide is still present in the electro-reduction cell. 2. The method according to claim 1, wherein the lanthanides in the spent nuclear fuel comprise cerium or neodymium, and the potential is sufficient to reduce at least 5% of the cerium or neodymium in the spent fuel simultaneously with the uranium. 3. The method according to claim 1, and comprising:withdrawing a portion of the halide salt electrolyte from the electro-reduction cell;performing exchange between the withdrawn portion of the halide salt electrolyte and a molten second metal which is less reactive than the uranium, plutonium, and other actinides having a higher atomic number than uranium present in the spent nuclear fuel, the molten second metal having dissolved within it a third metal which is more reactive than the uranium, plutonium, andother actinides having a higher atomic number than uranium present in the spent nuclear fuel, in order to provide an electrolyte having a reduced level of actinides, and an alloy of the second metal and the actinides. 4. The method according to claim 3, and comprising returning the alloy of the second metal and the actinides to the electro-reduction cell. 5. The method according to claim 4, wherein the second metal volatilises at the operating temperature of the electro-reduction cell, and comprising collecting the second metal via an off-gas condenser system. 6. The method according to claim 1, and comprising extracting the other actinides having a higher atomic number than uranium from the extracted alloy by contact with a molten salt comprising a metal halide where the metal has a higher electronegativity than uranium. 7. The method according to claim 6, and comprising performing first and second rounds of extraction, each round of extraction comprising the step of extracting the other actinides having a higher atomic number than uranium, and each round of extraction further comprising withdrawing the molten salt. 8. The method according to claim 7, and comprising reserving the molten salt from the second round of extraction, and wherein the molten salt used for the first round of extraction is molten salt that has been used for a previous second round of extraction on a previously processed withdrawn alloy. 9. The method according to claim 6, and comprising:contacting the molten salt with the extracted alloy at a temperature above the melting point of the extracted alloy;reducing the temperature to a temperature below the melting point of the extracted alloy and above the melting point of the molten salt;withdrawing the molten salt. 10. The method according to claim 9, and comprising tilting the extracted alloy following the reduction of temperature and prior to withdrawal of the molten salt.
052710513	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS The components of a pressurized water reactor (PWR) nuclear power plant relevant to the present invention are illustrated schematically in the figure. The PWR 1 includes a reactor vessel 3 having a core 5 containing a matrix of fuel assemblies 7. The reactor coolant system 9 includes a hot leg 11 connected to the primary side of steam generator(s) (not shown), a cold leg 13 also connected to the steam generator and pumps (also not shown) which circulate coolant in the form of light water through the reactor core 5 over the fuel assemblies 7, through the hot leg 11 to the steam generator(s) and back through the cold leg 13. Heat generated by fission of the fuel in the fuel assemblies 7 heats the coolant which is used by the steam generator to generate steam in a secondary loop to drive a turbine generator (also not shown). Periodically, the reactor core 5 is refueled by filling a refueling cavity 15 surrounding the head 17 of the reactor vessel with coolant from an in containment refueling water storage tank 19. During refueling, the head 17 is removed from the reactor vessel 3 and the fuel assemblies 7 to be replaced are raised by a refueling machine (not shown) into the refueling cavity 15 where they remain submerged in coolant. The removed fuel assemblies 7 are rotated to a horizontal position and passed through a fuel transfer tube having a normally open manual valve 23 to a fuel transfer canal 25. The fuel transfer tube 21 passes through containment 27. All of the components to the left of 27 in the figure are in containment while all those to the right of 27 are outside of containment. The spent fuel assemblies are conveyed through the fuel transfer canal 25 under coolant and passed through a normally open gate 29 into the spent fuel pit 31 where the spent fuel assemblies are stored under cover of coolant. Typically, the reactor 3 is refueled about every 18 months. During each refueling, about one third of the fuel assemblies are removed and transferred to the spent fuel pit. Typically, the spent fuel pit is designed to hold ten years worth of spent fuel assemblies. The spent fuel pit 31 must have the capability of removing the decay heat from the stored spent fuel assemblies. It is also necessary to purify the coolant in the spent fuel pit to maintain good clarity so that the fuel assemblies can be observed. In accordance with the invention, a combined cooling and purification system 33 is provided to perform these functions simultaneously. A unique aspect of the invention is that the spent fuel pit 31 has a volume of coolant sufficient to absorb the decay heat from a full ten-year accumulation of spent fuel assemblies without operation of the combined cooling and purification system 33 for a period of time sufficient to permit remedial action. In the exemplary system, this is a period of at least 72 hours. This implements the new concept of passive safety systems for PWRs. By passive, it is meant that the system maintains the plant in a safe condition following a disturbance such as an accident, loss of power or an earthquake without intervention by an operator, and without the use of equipment that requires electrical power. Thus, in the case of the spent fuel pit, if the combined cooling and purification system should fail or lose power, the spent fuel pit will maintain in a safe condition for at least 72 hours in which restoration of the combined cooling and purification system can be accomplished or temporary cooling means can put into operation. The combined cooling and purification system 33 includes two branches 35 and 37. The two branches 35 and 37 are served by first piping 38 including common suction piping 39 which draws coolant from the spent fuel pit 31 through an intake filter 41. Both branches 35 and 37 discharge coolant into the spent fuel pit 31 through common discharge piping 43. Each of the branches 33 and 35 of the combined cooling and purification system 33 includes a heat exchanger 45. Heat removed from coolant passed through the primary side of the heat exchanger 45 is removed by component cooling water passed through the secondary. The branches 35 and 37 of the combined cooling and purification system 33 also include purification apparatus 47 which includes a demineralizer 49 in series with a filter 51. Valves 53 can be used to isolate the demineralizer and filter. In parallel with the demineralizer 49 and filter 51 is an orifice 55 which sets the proportion of the flow through the branch which passes through the demineralizer and filter. In the exemplary system, about one third of the flow is purified and two thirds is by-passed by the orifice 55. Finally, each branch 35 and 37 includes a pump 57. As the spent fuel pit provides passive cooling of the spent fuel assemblies, the combined cooling and purification system 33 does not have to be safety rated, and thus the pumps do not have be powered by a safety rated bus. However, an auxiliary non-safety rated auxiliary power unit (not shown) can be provided for the pumps 57. Manual valves 59 and 61 in the common suction piping 39 control flow of coolant from the spent fuel pit 31 to the branches 35 and 37, respectively, of the combined cooling and purification system 33. Similarly, stop valves 63 and 65 in the common discharge piping 43 control the flow of coolant from the branches 35 and 37, respectively back to the spent fuel pit 31. Each of the branches 35 and 37 of the combined cooling and purification system have the capacity to provide the required cooling and purification for the spent fuel pit. The redundant branches, however, increase the availability of cooling and purification. Normally, the valves 59, 61, 63 and 65 for both branches are open, but only the pump 57 in a selected branch is run at any time. With these valves always open, transfer between the branches can be affected rapidly merely by switching active pumps 57. The invention further includes providing skimmers 67 connected by a line 69 to the common suction piping 39 for removing surface debris from coolant in the spent fuel pit 31. This eliminates the current need for separate skimmer circuits with their own pumps. As another aspect of the invention, the combined cooling and purification system 33 can also be used for cooling and purifying coolant in the refueling cavity 15. Thus, second piping 70 including suction piping 71 with isolation valves 73 and discharge piping 75 with isolation valves 77 connect the refueling cavity 15 in a loop with the combined cooling and purification system 33. Additional motor operated isolation valves 79 and 81 are provided inside reactor containment 27 and motor operated valve 83 and check valve 85 are provided outside a containment 27. The refueling cavity coolant is passed through one of the branches 35 and 37 of the combined cooling and purification system 33 by operation of the inlet valves 87 and 89 and outlet valves 91 and 93. By appropriate operation of the valves 59-65 and 87-93, one of the branches 35 and 37 of the combined cooling and purification system 33 can be connected to cool and purified coolant from the spent fuel pit 31 while the other branch is providing cooling and purification of coolant from the refueling cavity 15. Thus, the combined cooling and purification system 33 can be used as a supplement to, or in place of, the reactor heat removal system (RHR), previously used to cool refueling cavity coolant during refueling operations. The present invention removes the necessity for bringing in temporary equipment to clarify coolant in the refueling cavity 15. In addition, skimmers 95 are provided on the intakes of the suction piping 71 to remove surface debris from the coolant in the refueling cavity. Again, this eliminates the need to bring in temporary skimming equipment with a separate hydraulic circuit and pump. It is also an aspect of the invention that the combined cooling and purification system 33 can be used to clarify the coolant in the refueling water storage tank 19. Thus, third piping 96 including suction piping 97 and discharge piping 99 with their respective selection valves 101 and 103 are used in connection with the valves 59-63 and 87-93 to selectively connect the refueling water storage tank 19 in a loop with one of the branches 35-37 of the combined cooling and purification system 33. As another important aspect of the invention, the combined cooling and purification system 33 can be utilized to transfer coolant between the refueling water storage tank 19 and the refueling cavity 15 for refueling by opening valves 101 and 77 and closing valves 103 and 73. This effects a filling of the refueling cavity 15 with coolant from the refueling water storage tank 19 without having the coolant pass through the reactor core 5 as has been past practice. Thus, the coolant transferred to the refueling cavity 15 does not pick up debris and sediment from the reactor core 5. Furthermore, by passing through the purification apparatus 47, the clarity of the coolant delivered to the refueling cavity 15 is improved. In accordance with the invention, in the period prior to refueling, the coolant in the refueling water storage tank 19 is circulated through the combined cooling and purification system 33 to prepare it for refueling. As can be appreciated from the above description, the invention offers many advantages. First, it provides passive spent fuel pit cooling. It also provides a spent fuel pit cooling system which does not have to be safety rated. It reduces the amount of apparatus required for spent fuel pit cooling and purification by combining these systems in a single loop which can have redundant branches for increased availability and for simultaneously cooling and purifying refueling cavity coolant and purifying refueling water storage tank coolant while cooling and purifying spent fuel pit cooling. The invention also eliminates the need for separate skimmer circuits for the spent fuel pit and the need for bringing into containment temporary clarification and skimmer apparatus for the refueling cavity. Another important advantage offered by the invention is that it permits transfer of coolant from the refueling water storage tank to the refueling cavity without the need for the coolant to pass through the reactor core, and even provides for improving the clarity of the coolant while it is being transferred to the refueling cavity. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	claims	1. A method for repairing a nuclear fuel assembly, comprising:first providing a repair sleeve, the repair sleeve having a shaft with a first end, a second end, and a diameter, the diameter configured to fit into a guide thimble in a guide thimble opening of a top nozzle of the fuel assembly, the guide thimble connected to the top nozzle, wherein the diameter of the shaft is dimensioned such that an exterior of the shaft fits into the guide thimble in the guide thimble opening, wherein the shaft has at least two openings, each opening having a first closed end, oriented towards the shaft first end, and a second closed end, oriented towards the shaft second end, and a tendon connecting the first closed end and the second closed end of each opening, such that the tendon bridges the first and second closed ends of each opening, dividing each opening into two portions, the tendons configured to deflect in an instance of a horizontal load on the tendon during insertion, each of the tendons having at least one projection configured to be inserted into a dimple of a guide thimble sleeve, and the repair sleeve having a lapped edge for installation on the top of the top nozzle of the nuclear fuel assembly; andthen inserting the second end of the shaft of the provided repair sleeve into the guide thimble in the guide thimble opening in the top nozzle of the nuclear fuel assembly, the guide thimble connected to the top nozzle, such that the second ends of the tendons, the projections of the tendons, and the second ends of the openings are inserted into the guide thimble before the first ends of the tendons and the first ends of the openings are inserted into the guide thimble, and the projections of the tendons project into the dimples of the guide thimble sleeve; andinserting a thimble insert assembly into an interior of the provided repair sleeve. 2. The method according to claim 1, wherein the step of inserting the thimble insert assembly into the interior of the repair sleeve prevents further deflection of the repair sleeve in a horizontal direction. 3. The method according to claim 1, wherein the shaft has two openings and two tendons extending through the openings, each of the tendons having one projection. 4. The method according to claim 2, wherein the shaft has two openings and two tendons extending through the openings, each of the tendons having one projection. 5. The method according to claim 1, wherein the at least one projection is configured in a trapezoidal shape or a hemispherical shape. 6. The method according to claim 5, wherein the at least one projection is configured in a trapezoidal shape. 7. The method according to claim 5, wherein the at least one projection is configured in a hemispherical shape. 8. The method according to claim 2, wherein the at least one projection is configured in a trapezoidal shape or a hemispherical shape. 9. The method according to claim 8, wherein the at least one projection is configured in a trapezoidal shape. 10. The method according to claim 8, wherein the at least one projection is configured in a hemispherical shape. 11. The method according to claim 3, wherein the projection is configured in a trapezoidal shape or a hemispherical shape. 12. The method according to claim 11, wherein the at least one projection is configured in a trapezoidal shape. 13. The method according to claim 11, wherein the at least one projection is configured in a hemispherical shape.
052992411	abstract	In a transuranium elements transmuting reactor core in which a reactor is charged with a plurality of fuel assemblies at a core and an amount of a transuranium element to be added is controlled so as to prevent a fuel element contained in the fuel assemblies from melting, the amount of the transuranium elements to be added to the fuel element is controlled so as to keep an excess reactivity of the reactor substantially zero through an operation of the reactor. A charging density of minor actinides is set to lessen outwards of a core central portion in a core area where a plutonium content is made even. The charging density of minor actinides is set high accordingly in an area where a plutonium is enriched high at the core of a plutonium enriched area where a plutonium content varies. A transuranium elements transmuting fuel pin is formed by charging a transuranium fuel material in a fuel clad and the transuranium fuel material includes at least one of fuel materials consisting of an enriched uranium and an uranium-plutonium mixed fuel and a fertile material consisting of a natural uranium and a depleted uranium contain transuranium elements. In a transuranium elements transmuting assembly including a wrapper tube and a plurality of fuel pins enclosed in the wrapper tube, each of said fuel pin including a fuel clad. At least one part of the fuel pins are formed by charging a transuranium fuel material in the fuel clad with a transuranium fuel material inside.
055090397	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to a pellet stack length recording system, and more particularly to a nuclear fuel pellet stack segment length recording switch for automatically triggering a length measurement by the recording system. 2. Background Information A nuclear fuel rod contains fissile material in the form of a plurality of generally cylindrical nuclear fuel pellets maintained in a row or stack thereof in the rod. One type of nuclear fuel rod, for example, is a zoned fuel rod which contains short lengths of "blanket" pellets at each end. Other fuel rod designs additionally have fuel pellets stacked in three or more zones of different pellet types including end zones of the blanket pellets. The different types of the fuel pellets include natural, enriched and enriched coated. Fuel stacks for nuclear fuel rods may be collated by an automatic or a manual system. An example of an automatic system is disclosed in U.S. Pat. No. 4,842,808 issued Jun. 27, 1989 to Stuart L. Rieben et al. entitled "Nuclear Fuel Pellet Collating System" and assigned to the assignee of the present invention, which is herein incorporated by reference. The manual collating system consists of an operator work area for handling pellets, input pellet trays, and output pellet trays. The manual collating system further consists of linear measuring equipment having a linear scale, a standard commercial weight scale, a barcode reader, and a local data collection computer. The operator work area includes an angled table about which is conveniently mounted the input pellet tray, the output pellet tray, the linear measuring equipment, and the weight scale. The linear measuring equipment includes a support frame having an X-Y positioning device and a digital scale. The X-Y positioning device supports a measuring arm, a measuring head and a measuring probe. The operator positions the measuring probe in order to obtain measurements from the digital scale. The digital scale records the X coordinate length and transmits the length measurement to the local data collection computer. The weight scale includes a fixture for supporting the output pellet tray during a weighing operation. The weight scale transmits the weight measurement to the local data collection computer. The barcode reader is connected to the local dam collection computer and provides an error free identification of the input material (e.g., the pellets). The corrugated metal input pellet trays hold the pellets and include barcode identification labels. Whenever the identification labels are scanned by the barcode reader, the reader transmits the identification of the input material to the local data collection computer in order to verify the type of material prior to use at the operator work area. The local data collection computer, such as a desk top IBM compatible personal computer, prompts the operator during the collating process, records and verifies the pellet stack segment length and weight measurements which are taken by the operator during the stack building process, and communicates the pellet and fuel rod data to an historical data collection computer. Accurate pellet stack segment length measurements are essential for proper quality control and nuclear fuel rod operation. In the manual system, the length measurements are provided by the linear measuring equipment which includes the manually positioned measuring probe and the digital scale. Pellet stacks typically are assembled for a lot of 25 fuel rods at a time. The pellets for each lot are contained in special trays in a container or cassette. Due to the length of the cassette trays, each stack may consist of 9 or more segments. A typical 25 fuel rod lot, or one cassette, having 11 segments, requires 11 measurements to be recorded per rod, or 275 individual length measurements per cassette. Pellets are separated on an input tray for the zone, or a segment of the zone, row by row for each of 25 rows on the tray. Each row represents a segment of a fuel stack. The pellets, separated for the zone or segment, are measured and recorded row by row, starting with the front row and moving to the rear row. The accuracy of the pellet stack segment linear measuring equipment is provided by a spring preload device which compresses the pellet stack segment, in order to eliminate gaps between pellets, and by a zero length check of the digital scale before and after a group of measurements. Whenever measurements are taken, the operator positions the measuring probe against an individual pellet stack segment, which compresses the spring preload device. Then, the operator actuates a foot switch, in order to signal the digital scale to transmit the length of the pellet stack segment to the local data collection computer. Although the system provides the capability for accurate length measurements, there is room for improvement. During manual operation, the operator may become overly familiar with the function of the manual system and quickly move through a relatively large number of pellet stack segment length measurements. In particular, the operator's hand - foot coordination may become non-synchronized and, hence, the spring preload device may not be fully compressed before the foot switch is depressed. Accordingly, measurement errors may result. Although these errors are detected by subsequent quality control inspections, rework, such as remeasurement of the pellet stack segments, is required. There is a need, therefore, for a manual pellet stack segment measurement system that operates independently of the hand - foot coordination of an operator. There is a more particular need for such a manual measurement system that consistently provides accurate pellet stack segment length measurements. SUMMARY OF THE INVENTION These and other needs are satisfied by the invention which is directed to a pellet stack segment length recording switch for automatically triggering a length measurement by a length measurement system. The measurement system includes a digital length scale having a manually positioned measuring arm and head, a spring loaded slider block slidably attached to the measuring head and having an adjustable sensor pin, a spring having a predetermined compression force for resisting movement of a leg of the measuring head toward the slider block, a measuring probe attached to the slider block for compressing the pellet stack segment, and a high resolution fiber optic sensor for sensing a position of the sensor pin. The measuring arm is manually positioned, in order to jointly move the measuring head, the spring and the slider block, and to position the measuring probe at an end of the pellet stack segment. Whenever the measuring probe contacts the end of the pellet stack segment, any manual compression force applied to the measuring arm moves the measuring head, the spring, the slider block and the measuring probe, and compresses the end of the pellet stack segment. Whenever a sufficient force, which is smaller than the predetermined compression force of the spring, is manually applied, the pellet stack segment is compressed and any gaps between the pellets are eliminated. As such smaller force is applied, the measuring head compresses the spring and moves toward the slider block. Then, whenever the predetermined compression force is applied, the measuring head further compresses the spring and moves closer to the slider block. The position of the sensor pin of the slider block is adjusted, in order that whenever the predetermined compression force of the spring is applied, the fiber optic sensor detects the position of the sensor pin, with respect to the measuring head. The fiber optic sensor, in turn, triggers the digital length scale, in order to transmit the length of the pellet stack segment to a data collection computer. In this manner, any operator hand - foot coordination error is eliminated from the length measurements. Accordingly, accurate and consistent length measurements are provided by the length measurement system.
	abstract	A cartridge-based cryogenic imaging system includes a sample handling system. This system uses a kinematic base and cold interface system that provides vertical loading to horizontally mounted high-precision rotation stages that are able to facilitate automated high-resolution three-dimensional (3D) imaging with computed tomography (CT). Flexible metal braids are used to provide cooling and also allow a large range of rotation. A robotic sample transfer and loading system provides further automation by allowing a number of samples to be loaded and automatically sequentially placed on the sample stage and imaged. These characteristics provide the capability of high-throughput and highly automated cryogenic x-ray microscopy and computed tomography.
056423896	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawing in detail and first, particularly, to FIGS. 1 and 2 thereof, there is seen a passively operating safety device including a switching vessel or container 1 in the form of a pressure vessel with a fluid space 1.1 and a gas cushion space 1.2 located above it. Submerged in the fluid space 1.1 are heat exchanging pipes 2 having one end 2a which communicates with a steam or vapor space 3 of a reactor pressure vessel 4 and, under normal operating conditions or when an initial level range FI is present, another end 2b of these tubes communicates with a reactor water column 5. The reactor pressure vessel 4 is essentially a hollow cylindrical pressure vessel in a vertical configuration which has a pressure-tight, domed cover 4.1 flanged onto it, a likewise domed bottom calotte or cup 4.2, and a shell or jacket 4.3. A reactor core 6, including individual non-illustrated fuel assemblies, is located in the lower half of the interior of the reactor and control rods 7 with their non-illustrated absorber blades can be inserted into the gaps between the fuel assemblies. In this way, reactor power can be decreased by means of deeper insertion of the absorber blades into the core and reactor power can be increased by means of shallower insertion or removal of the absorber blades. Heat generated by controlled fission in the core is transferred to reactor water 5'. With medium-output boiling water reactors (i.e. in the order of magnitude of up to approximately 1000 MWe), this water circulates naturally, i.e. without special circulation pumps. The generated live steam is passed through live steam lines, which are not shown in FIG. 1, to non-illustrated steam turbines. The switching vessel 1 is thus equipped to initiate condensation in its heat-exchanging pipes 2 if there is a flow of steam in the direction of arrows f1 from the reactor interior into the heat exchanging pipes 2 through their one end 2a, when dropping below the initial level range FI of the reactor water 5'. The in-flowing wet steam is cooled because the heat exchanging tubes 2 are themselves cooled by the fluid bath or space 1.1. Therefore the steam condenses and flows back into the fluid column 5 or the reactor water 5' through the other ends 2b of the heat exchanging pipes which empty into the interior of the reactor. Due to the condensation process, the water bath 1.1 absorbs the condensation heat and a resultant increase of pressure in the switching vessel 1 is a derived actuation criterion for passive actuation of pilot fittings 8 and/or main fitting 9 by reporting the increased control pressure in the switching vessel 1 through a pressure control line 1.3 to the pilot fitting 8. A non-illustrated direct actuation of the main fitting 9 would also be possible. Such a main fitting 9 can, for example, be used to blow off steam in a condensation chamber to purposefully depressurize the reactor pressure vessel and/or a primary loop. Other possibilities are to use the pilot fittings and/or main fittings to actuate a reactor scram, i.e. insertion or fast insertion of the control rods into the core, or to close penetration fittings of the live steam lines, one of which (a fitting 9B) is shown in FIG. 2. This will be discussed below in greater detail. The fluid lines for transmission of the actuation criterion are therefore the heat exchanging pipes 2 (seen in FIG. 1) including their feed 2a and drain 2b (seen in FIG. 2). FIG. 2 shows a normally closed first main fitting 9A, through which primary medium or reactor steam arriving through lines 10, 11 can be blown-off in a condensation chamber 12 with a water bath 13 through a nozzle pipe 14. Actuation of the main fitting 9A is carried out by means of a pilot fitting 8A, which itself can be actuated from the switching vessel 1 through a pressure control line 1.3, 1.31. A second main fitting 9B is shown in an open position. Sections of pipe 15 and 11 attached to the main fitting 9B belong to a live steam line 16, so that live steam can be directed to a non-illustrated steam turbine through the live steam line 16 originating from the main fitting 9B. On the other side of a wall entrance or bushing 160 passing through a non-illustrated wall of a containment C (seen in FIG. 6), there is an additional penetration fitting in series with the main fitting 9B, which penetration fitting is actuated in the same manner as the fitting 9B. In the case of the malfunction discussed herein, i.e. if the level drops out of the initial or normal level range FI to a lower level range FII due to a transient or the like, a pilot fitting 8B is actuated by the switching vessel 1 through pressure control lines 1.3, 1.32, and the pilot fitting then brings the main fitting 9B into its closed position. As shown, the live steam pressure in the reactor pressure vessel 4 can serve as the control pressure in pressure control line 1.4. As can be recognized, the illustrated control is provided by means of passively operating safety devices without requiring any fittings to be actively actuated. Thus, a significant increase of the inherent safety can be achieved. It is possible to advantageously position the illustrated switching vessels 1 with their heat exchanging pipes 2 of FIGS. 1 and 2 on a level line, for example, that is "barely" below the normal or initial level range FI of the reactor pressure vessel 4 in a non-illustrated manner, so that the increased control pressure in the switching vessel 1 is available at a value above the level range FII for a relatively short time (in comparison to the illustrated position of the switching vessel 1) following a reduction in level from the level range FI. This is of particular advantage for the actuation of a reactor scram and for closing the penetration fittings. However, the automatic depressurization of the reactor pressure vessel 4 by means of the blow-off, discharge or drain off unit 9A, 12, 13, 14 should only be actuated at a lower level, such as the level range FII or preferably even lower, such as is permitted with the illustrated switching vessels 1 (or separate non-illustrated switching vessels which are located even lower). The actuating level FII is normally not reached if there is an emergency condenser 30 such as is shown in FIGS. 4 and 5 (but not in FIGS. 1 and 2) and if there is no other loss of coolant. In the previous embodiment of a safety device, as mentioned, the fluid lines for the automatic reporting of an actuation criterion (level below the initial or normal level FI) were provided as pipes 2 or as inlet pipes and drainage pipes with reference to the heat exchanging pipes 2, whereby in the case of the lower level FII, there is a derived actuation criterion in the form of an increased control pressure. With the second embodiment of a safety device according to the invention as disclosed in FIG. 3, the passively operating safety device is realized as an open flooding reservoir or well 18 having water 17 with a level which is geodetically higher than the reactor water column 5 and is located outside of the reactor pressure vessel 4. An interior 4.0 of the reactor pressure vessel 4 communicates with the flooding water column 17 in the flooding reservoir 18 through at least one connecting line 19 which acts as a fluid line, so that under normal operation of the reactor and within the indicated initial range of the level FI of the reactor water 5', a non-return or check fitting 25 is held in its closed position by means of a reactor-side overpressure (approximately 70 bar+ hydrostatic pressure due to the level FI). It is only when the level reaches or drops below the second level range (see FIG. 1) of the reactor water column, which lies below the initial level range FI, after pressure in the pressure vessel drops to a value which approaches the containment pressure (such as by means of the blow-off unit 9A, 12, 13, 14 as shown in FIG. 2), that the non-return fitting 25 can open due to the pressure equalization and flooding water can be added to the reactor pressure vessel 4 through the connecting line 19. It is preferable that the flooding reservoir 18 be located above a condensation chamber 20, which is used for blowing off excess reactor steam. For example, this chamber can be a toroidal or ring chamber, whereby in the left part of the condensation chamber 20 there is seen a condensation pipe 22 which branches off from a live steam line through a blow-off valve 21. This pipe has a nozzle head 23 on its lower end which is submerged in a water bath 24 of the condensation chamber 20. The flooding reservoir 18, which is open toward the top, can also be ring-shaped, corresponding to the condensation chamber 20, so that in this manner a very large water reservoir is available. As mentioned above, the opening of the connecting line 19 can be closed by the non-return fitting 25, which opens if the above-described pressure equalization occurs. The non-return fitting can be constructed as a valve or a flap. The connecting line 19 is curved in such a manner that its upper end 19a is connected to the lower region of the flooding reservoir 18, and its lower end 19b is connected to the reactor pressure vessel 4 at a point above the upper edge of the reactor core 6, as shown. The reactor core thus always remains covered by the reactor water 5' or by the water 17 from the flooding reservoir. It is important that a section 19.1 of the connecting line 19 between the pressure vessel 4 and the non-return fitting 25 be sloped downward (as a heat trap), as shown. In this manner, a transfer of heat by convection from the reactor water 5' to the interior of the line section 19.1 is prevented. A line section 19.2 between the non-return fitting 25 and the flooding reservoir 18, and the line section 19.1, are approximately S-shaped. In the very unlikely event that the connecting line 19 should crack, the contents of the flooding reservoir 18 would flow through non-illustrated redundant lines into the reactor pressure vessel 4, and the remaining portion would flow through the crack into a reactor pit 26. The water supply in the flooding reservoir 18 is large enough to ensure that even in this case, the level of water in the reactor pit in the event of the abnormal occurrence mentioned above is still higher than the upper edge of the core 6, so that the core 6 always remains covered in this manner, as well. The passively operating safety device as shown in FIGS. 4 and 5 includes the emergency condenser 30 having heat exchanging pipes 27 in water 28 of a water reservoir 29. In normal operation of the reactor 4 the condenser 30 communicates with the steam space 3 through an inlet pipe configuration 31, and with a lower region of the reactor water column 5 at a point above the reactor core 6 through a drainage pipe configuration 32. The location of the emergency condenser 30 is chosen in such a way that its heat exchanging pipes 27 are filled with condensate during normal operation of the reactor, i.e. they are in communication with the water column 5. In this manner, the water found in the pipe system 27, 31, 32 of the emergency condenser 30 stagnates during normal operation. If, however, the level of the reactor water 5' drops to the second level FII below the initial level FI, reactor steam flows through the inlet pipe configuration 31 into the heat exchanging pipes 27 of the emergency condenser 30 and condenses there because the pipes 27 are cooled by the water bath 28. The condensate flows through the drainage pipe configuration 32 back into the reactor pressure vessel 4. This means that a transfer of heat from the steam to the water bath 28 through the heat exchanging pipes 27 begins automatically. The output of the emergency condenser 30 increases up to a maximum value as the level in the pressure vessel 4 falls. The fluid lines according to the invention are therefore the lines 31, 27 and 32. It is preferable for the water reservoir 29 to be located above the condensation chamber 20 for blowing off excess reactor steam and for this reservoir, like the condensation chamber, to also be ring shaped. As is explained below in greater detail with reference to FIG. 6, it is preferred that the water reservoir 29 be constructed as a flooding reservoir 18 (seen in FIG. 3). FIG. 4 shows that the inlet pipe configuration 31 slopes downward from an inlet 31a thereof to a connection 31b with the heat exchanging pipes 27 of the emergency condenser. Similarly, the drainage pipe configuration 32 slopes downward from a connection 32b with the heat exchanging pipes 27 to an outlet 32a thereof. The drainage pipe configuration 32, which can be referred to as a condensate return line, preferably ends in a non-illustrated flow limiter, which offers the least possible resistance in the specified flow direction but, in the (very unlikely) event of a rupture of the return line 32, effectively prevents outflow from the pressure vessel. In coordination with this layout of the inlet and drainage pipe configurations, the heat exchanging pipes 27 of the emergency condenser 30 are formed of first and second legs 27.1, 27.2 and a reversing bend 27.3 and are essentially hairpin shaped with an upward or downward slope, wherein the first leg 27.1 is connected to the inlet pipe configuration 31 and the second leg 27.2 is connected to the drainage pipe configuration 32. FIG. 5 shows that there is a downward sloping, hairpin-shaped pipe bend 33 located on a section of the drainage pipe configuration 32 in the space between the reactor pressure vessel 4 and the water or flooding reservoir 29. The pipe bend 33 forms a circulation block or siphon during normal operation. Since this depends on the height relationship, the height relationships are drawn in as a scale next to a dot-dash reactor axis line 34. The circulation block 33 with its hairpin-shaped bends is larger than shown. These bends extend, for instance, over a height difference of 0.5 to 1 m. The circulation block is also to be advantageously provided in the example according to FIG. 4 or according to FIGS. 1 and 2 and is actually in the respective drain or return side branch 32 or the drain 2b in a non-illustrated manner. FIG. 6 shows a section of a concrete structure of a reactor building which is designated with reference symbol RG and has vertical and horizontal concrete walls and ceilings 35, 36, wherein the reactor pressure vessel 4 is mounted by means of support brackets 37 to a bearing structure 36a and is located in a safety vessel C (containment). Reference numeral 26 again represents the reactor pit. The flooding reservoir 18 which was explained with reference to FIG. 3 can also be seen above the condensation chamber 20 in FIG. 6. Additionally shown is the emergency condenser 30 which, with its hairpin shaped heat exchanging pipes 27, is submerged in the water column 17 of the open flooding reservoir 18. The curved connecting line 19 leads from the flooding reservoir 18 into the reactor pressure vessel 4. A chamber 38 above the reactor pressure vessel 4 is constructed as an additional water reservoir. An opening 39 in a ceiling slab 36b (which is used for removing the cover 4.1, for removing a steam dryer and water separator 390 and for exchanging fuel assemblies, etc.) is sealed by a calotte or cup-shaped cover 40. A containment condenser 41 for the condensation of steam in the containment C is connected to the water reservoir 38 by means of an inlet line 42a and a return line 42b, wherein these lines 42a, 42b are passed with a tight seal through the ceiling 36b. The steam condensed by the containment condenser 41 drips into the flooding reservoir 18 located below this condenser 41. During operation of this condenser 41, a natural circulation is established from the reservoir 38, through the pipes 42a, through heat exchanging pipes of the condenser 41 and back through the pipes 42b into the reservoir. Through the use of this apparatus, forced condensation of steam in the containment can be achieved, thus effectively limiting the containment pressure and also removing the afterheat from the containment. FIG. 6 also shows a fragmentary illustration of the condensation pipe 22, which is submerged with its nozzle head 23 in the water bath of the condensation chamber 20. The switching vessel 1 is not shown in FIG. 6. However, its use is advantageous as explained above. A particular advantage of the emergency condenser 30 (see FIGS. 4 and 5) is that just like the switching vessel 1 according to FIGS. 1 and 2, it is not sealed, it is ready for use and it is merely activated by a drop in the level FI in the pressure vessel 4, thus ensuring completely passive safety.
055703992	claims	1. A control rod and fuel supporting member gripping apparatus for gripping a fuel supporting member and a control rod, the fuel supporting member being mounted on a core supporting plate located below an upper lattice plate within a reactor pressure vessel and having fuel assembly supporting engagement holes in which bottom portions of a plurality of fuel assemblies are inserted to support the fuel assemblies and an insertion hole through which a control rod is passed, the control rod being detachably connected with a control rod driving mechanism by means of a bayonet coupling and being passed through a control rod passage so as to be lifted up and down in order to remove the fuel supporting member and the control rod from the core supporting plate and the control rod driving mechanism, said control rod and fuel supporting member gripping apparatus comprising: a gripping apparatus body hoisted vertically liftably in an installed state within the reactor pressure vessel; a fuel supporting member gripping device disposed at a portion below the gripping apparatus body for supporting the fuel supporting member fixedly in its axial direction but supported to be liftable; a control rod gripping device disposed at a portion below the gripping apparatus body to be liftable up and down and rotatable with respect to the gripping apparatus body; means for rotating the control rod gripping device with respect to the gripping apparatus body; and means for withdrawing the fuel supporting member and the control rod from an upper portion of the reactor pressure vessel substantially at the same time such that the fuel supporting member is raised to a height above the control rod and held at said height. taking out the fuel supporting member from the core supporting plate and lifting the fuel supporting member upward from the core supporting plate by a predetermined distance to a portion where a bottom portion of the fuel supporting member is maintained above an upper portion of a control rod handle; rotating the control rod in an axial direction to separate the control rod from the control rod driving mechanism; and withdrawing the fuel supporting member and the control rod from an upper portion of the reactor pressure vessel substantially at the same time, wherein the fuel supporting member is raised to a height above the control rod and held at said height, the fuel supporting member is prevented from axially rotating and the control rod is thereafter rotated. 2. A control rod and fuel supporting member gripping apparatus according to claim 1, wherein said fuel supporting member gripping device includes a detection means for detecting a fact of settlement of the gripping apparatus body on the fuel supporting member gripping device. 3. A control rod and fuel supporting member gripping apparatus according to claim 1, further comprising a detection means for detecting a fact that a rotation angle of said control rod gripping device is rotated by an angle over a predetermined angle. 4. A control rod and fuel supporting member gripping apparatus according to claim 1, wherein an upper lattice plate is disposed above said gripping apparatus body at an upper portion of the reactor pressure vessel and an upper plate is disposed on the upper lattice plate through a gripping apparatus body lifting device for lifting up and down the gripping apparatus body with respect to the upper lattice plate. 5. A control rod and fuel supporting member gripping apparatus according to claim 4, wherein said control rod gripping device comprises a hook means which is hung by a rotating member rotatably fixed to the upper plate in order to releasably grip a handle of the control rod, a first driving means for driving said control rod gripping device for making the hook perform gripping and releasing operations, a second driving means for lifting up and down the control rod lifting mechanism by raising the hook means, a third driving means having a reciprocal piston rod for driving a winding means, and a rotating device for rotating the rotating body clockwise or counterclockwise by connecting both ends of the winding means attached to a rotating member in rotational association with the rotating body to both ends of the reciprocal piston rod of the third driving means. 6. A control rod and fuel supporting member gripping apparatus according to claim 5, wherein said first, second and third driving means are air cylinder assemblies. 7. A control rod and fuel supporting member gripping apparatus according to claim 5, wherein said first driving means includes a biasing means for maintaining the gripping operation of the hook means when a supply of fluid is eliminated. 8. A control rod and fuel supporting member gripping apparatus according to claim 7, wherein said biasing means is a spring. 9. A control rod and fuel supporting member gripping apparatus according to claim 5, wherein said first driving means is connected to a rope means for releasing the hook means at a time when the rope means is pulled to thereby forcibly perform the releasing action. 10. A control rod and fuel supporting member gripping apparatus according to claim 1, wherein said fuel supporting member gripping device comprises a first driving source which makes a pair of retractable gripping plungers protrude from the inside of the fuel supporting member into a pair of side holes communicating with the respective fuel assembly supporting engagement holes of the fuel supporting member and facing each other in a direction of a diameter thereof in order to grip the fuel supporting member, and a second driving source which grips the fuel supporting member by means of the gripping plungers and which hoist the fuel supporting member. 11. A control rod and fuel supporting member gripping apparatus according to claim 10, wherein the fuel supporting member gripping portion comprises a locking mechanism for holding the first driving source in the gripping position when said fuel supporting member is gripped by means of the first driving source and hoisted by means of a lifting mechanism in order to prevent the gripped fuel supporting member from being released. 12. A control rod and fuel supporting member gripping apparatus according to claim 11, wherein said first driving source includes a gripping state holding mechanism for maintaining the gripping state of the fuel supporting member when a driving supply is eliminated. 13. A control rod and fuel supporting member gripping apparatus according to claim 11, wherein said first driving source is connected to a rope and a pair of plungers are retracted from a pair of side holes to an inside of said fuel supporting member, when said rope is pulled, in order to forcibly release the fuel supporting member. 14. A method of withdrawing a control rod and fuel supporting member from a reactor pressure vessel, in which the fuel supporting member is mounted on a core supporting plate located below an upper lattice plate within a reactor pressure vessel and has fuel assembly supporting engagement holes in which bottom portions of a plurality of fuel assemblies are inserted to support the fuel assemblies and an insertion hole through which a control rod is passed, and the control rod is connected to a control rod driving mechanism by means of a bayonet coupling and is passed through a control rod passage so as to be lifted up and down freely in order to remove the fuel supporting member and the control rod from the core supporting plate and the control rod driving mechanism, the method comprising the steps of:
	claims	1. A molten glass discharging device provided in a bottom of a melting furnace so as to control discharging of a molten material from the melting furnace, the molten glass discharging device comprising:an induction heating unit having a discharging passage along a discharging port that is formed in the bottom of the melting furnace;an induction coil provided outside the induction heating unit;a cooling unit supporting the induction heating unit and having a first cooling conduit through which a cooling fluid circulates; anda magnetic field shielding element provided outside the induction coil for shielding magnetic field,wherein the magnetic field shielding element is provided with a second cooling conduit through which a cooling fluid circulates. 2. The molten glass discharging device as set forth in claim 1, wherein the induction heating unit comprises two or more cylindrical heating elements that are symmetrically arranged along the discharging passage. 3. The molten glass discharging device as set forth in claim 1, wherein the cooling unit comprises a pair of cooling units that are symmetrically arranged on opposite lengthwise ends of the induction heating unit so that the cooling units are parallel to each other in directions perpendicular to the induction coil. 4. The molten glass discharging device as set forth in claim 1, wherein the magnetic field shielding element comprises a ferrite core.
050009087	claims	1. An improved method of draining down contained reactor-coolant water from the inverted vertical U-tubes of at least one vertical-type steam generator in which the upper inverted U-shaped ends of said tubes are closed and the lower ends thereof are open, said steam generator having a channel head at its lower end including a vertical dividing wall defining a primary water inlet side and a primary water outlet side of the generator, said steam generator having chemical volume control system means and residual heat removal system means, and said steam generator being part of a nuclear-powered steam generating system wherein said reactor-coolant water is normally circulated from and back into the reactor via a loop comprising said steam generator and inlet and outlet conduits connected to the lower end of said steam generator, and said reactor being in communication with pressurizer means and comprising the steps of introducing a gas which is inert to the system and which is under pressure above atmospheric pressure into at least one of the downwardly facing open ends of each of said U-tubes from below the tubesheet in which the open ends of said U-tubes are mounted adjacent the lower end of said steam generator while permitting said water to flow out from said open ends of the U-tubes, the improvement in combination therewith for substantially increasing the effectiveness and efficiency of such water removal from said tubes, which improved method comprises the additional steps of: (A) determining the parameters effecting a first average volumetric rate of removal for a predetermined period of time, said period of time being substantially coincident with the period of time in step (B), infra, of the reactor-coolant water from said inverted vertical U-tubes, the specific unit for said first average volumetric rate expressing properties identical with the properties expressed in a second average volumetric rate maintained in a later mentioned step; (B) determining the parameters effecting a second average volumetric rate of introduction of said gas, which is under said pressure above atmospheric pressure and which is introduced into at least one of the downwardly facing open ends of each of said U-tubes, at a predetermined value and at least for a portion of the period of time during said draining down in which the reactor-coolant water level, in the portion of the reactor cooling system external to said tubes and including said pressurizer means, is lowered to about the elevation of said tubesheet, said at least one of the downwardly facing open ends of each of said U-tubes being in communion with said primary water outlet side in the channel head of said steam generator and effecting a standing water column therein; and (C) maintaining a ratio of said second average volumetric rate of introduction of said gas to said first average volumetric rate of removal of the reactor-coolant water from said inverted vertical U-tubes in the range from about 1.2:1 to about 0.8:1; t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ; t.sub.1 '=(.sqroot.p.sub.1 /.sqroot.p.sub.2)t.sub.1 wherein p.sub.3 is a second preselected pressure of gas introduction which is in excess of p.sub.1, but is less than the critical pressure (p.sub.t) of said gas; p.sub.t .apprxeq.0.53p.sub.1 and p.sub.t is less than p.sub.3, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and t.sub.2 '=(1-t') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period. t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure to beneath said tubesheet of p.sub.1 ; t.sub.1 '=(4.472/.sqroot.p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1, but is less than the critical pressure (p.sub.t) of said gas; p.sub.t .apprxeq.0.53p.sub.2 and p.sub.t is less than ps, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and t.sub.2 '=(2-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period. t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ; t.sub.1 '=(p.sub.1 /p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1. and is greater than the critical pressure (p.sub.t) of said gas; p.sub.t .apprxeq.0.53p.sub.2 and p.sub.t is greater than p.sub.3 , wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period. t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure to beneath said tubesheet of p.sub.1 ; t.sub.1 '=(20/p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1, and is greater than the critical pressure (p.sub.t) of said gas; P.sub.1 .apprxeq.0.53p.sub.2 and p.sub.t is greater than p.sub.3, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period. t=the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ; t.sub.1 '=(.sqroot.p.sub.1 /.sqroot.p.sub.2)t.sub.1 wherein p.sub.2 is a second and intermediate preselected pressure of gas introduction which is in excess of p.sub.1 and less than p.sub.3 ; p.sub.t .apprxeq.0.53p.sub.2 is less than p.sub.4, wherein p.sub.t represents the critical pressure (p.sub.t) of said gas and wherein p.sub.4 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period; t.sub.21 =t.sub.1 '; t.sub.21 '=(.sub.2 /p.sub.3)t.sub.21 wherein p.sub.3 is the final preselected pressure of gas introduction which is in excess of p.sub.2 ; p.sub.t '.apprxeq.0.53p.sub.3, p.sub.t ' is greater than p.sub.4 and represents the critical pressure (p.sub.t ') of said gas at introduction pressure ps; t.sub.22 '=(1-t.sub.21 ') and represents the final pulse time-off period, with t.sub.21 ' representing the final pulse time-on period. 2. The method according to claim 1, wherein said gas is nitrogen. 3. The method according to claim 2, wherein said ratio of said second average volumetric rate of introduction of said gas to said first average volumetric rate of removal of the reactor-coolant water is maintained in the range of from about 1.1:1 to about 0.9:1. 4. The method according to claim 3, wherein said ratio is maintained at about 1:1. 5. The method of claim 1 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals. 6. The method of claim 3 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals. 7. The method of claim 4 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals. 8. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of as introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein: 9. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein: 10. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig, and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off ranging from about 0.075:1 to about 0.05:1. 11. The method according to claim 3, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig, and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off ranging from about 0.07:1 to about 0.057:1. 12. The method according to claim 4, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig. and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about 0.0634:1. 13. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ',and wherein: 14. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein: 15. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio as introduction final pulse time-on to gas introduction final pulse time-off of about t.sub.21 ':t.sub.22 ',and wherein: 16. The method according to claim 13, wherein p.sub.2 ranges upwards from said p.sub.t to about 400 psig. 17. The method according to claim 14, wherein p.sub.2 ranges upwards from said p.sub.t to about 400 psig. 18. The method according to claim 5, wherein said channel head has flow openings and wherein said gas is introduced via one of the flow openings for said water through the channel head adjacent to the lower end of said steam generator. 19. The method according to claim 5, wherein said gas is introduced through an opening in a manway attached to said channel head adjacent to the lower end of said steam generator. 20. The method according to claim 5, wherein said nuclear-powered steam generating system includes respective flow transmitters for detecting flow of said coolant water through said outlet conduit of each said steam generators, each said flow transmitter having a high-impulse reference tube and a low-impulse reference tube, both of which are attached to said outlet conduit of the steam generator, and wherein said gas is introduced via one of said flow transmitter impulse reference tubes associated with each said steam generator.
	description	The present invention relates generally to ion implantation systems, and more particularly to low energy, high current ion implantation systems and methods. Ion implantation systems are used to dope semiconductors with impurities in integrated circuit manufacturing. In such systems, an ion source ionizes a desired dopant element, which is extracted from the source in the form of an ion beam of desired energy. The ion beam is then directed at the surface of a semiconductor wafer in order to implant the wafer with the dopant element. The ions of the beam penetrate the surface of the wafer to form a region of desired conductivity, such as in the fabrication of transistor devices in the wafer. A typical ion implanter includes an ion source for generating the ion beam, a beamline assembly including a mass analysis apparatus for mass resolving the ion beam using magnetic fields, and a target chamber containing the semiconductor wafer or workpiece to be implanted by the ion beam. In order to achieve a desired implantation for a given application, the dosage and energy of the implanted ions may be varied. The ion dosage controls the concentration of implanted ions for a given semiconductor material. Typically, high current implanters are used for high dose implants, while medium current implanters are used for lower dosage applications. The ion energy is used to control junction depth in semiconductor devices, where the energy levels of the beam ions determine the degree to which ions are implanted or the depth of the implanted ions in the workpiece. The continuing trend toward smaller and smaller semiconductor devices requires a mechanism, which serves to deliver high beam currents at low energies. The high beam current provides the necessary dosage levels, while the low energy permits shallow implants. The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. The present invention is directed towards systems and methods for generating low energy, high current ion beams by scaling beamline dimensions and employing multiple beamlines. An array of beamlets is generated by an ion source. The beamlets then pass through a mass analysis module that permits selected ions to pass while blocking other ions and/or particles. The selected ions can then be accelerated to a desired energy level. Subsequently, the beamlets are diverged in horizontal and/or vertical directions to form a single low energy, high current ion beam. In accordance with one aspect of the present invention, a multi-channel ion implantation system is disclosed. The system comprises a beam source that generates a beamlet array and a beamline assembly that processes beamlets within the array. The beamline assembly comprises a mass analyzer module that operates on the beamlet array to remove ions having a non-selected mass energy product and permit selected ions, which are ions having a selected mass energy product, to pass through. The beamline assembly also comprises a beam formation component that causes the beamlets to sufficient diverge in one or both directions and form a single low energy, high current ion beam. To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. The present invention will now be described with reference to the drawings wherein like reference numerals are used to refer to like elements throughout. The illustrations and following descriptions are exemplary in nature, and not limiting. Thus, it will be appreciated that variants of the illustrated systems and methods and other such implementations apart from those illustrated herein are deemed as falling within the scope of the present invention and the appended claims. Many ion implantations performed in current semiconductor or other fabrication processes are shallow and/or ultra-shallow implants that form shallow and/or ultra-shallow junction depths in formed devices. These shallow and/or ultra-shallow implants typically employ low energies (e.g., 1 keV), but require relatively high beam current (e.g., 20 to 30 milli amps). Generally, it is appreciated that high current, low energy ion beams are obtained by extracting the ion beam from an ion source at a relatively high energy. Then, the ion beam is mass analyzed/purified and transported to a position relatively close to a target wafer. Subsequently, the ion beam is decelerated to a selected low energy level and is then transported to the target wafer or workpiece. Conventional low energy ion implantation devices can have difficulty providing relatively high ion beam current at low energies. Problems, such as increased space charge, energy contaminants, and the like, have a negative impact on the productivity of the conventional low energy implanters. Some conventional techniques have been employed that attempt to mitigate the problems, but some fundamental limitations remain and achievable beam currents for single ion beams may not satisfy the requirements of next generation semiconductor processes. The present invention facilitates low energy ion implantation by employing arrays of scaled beamlines that collectively provide a low energy, high current ion beam. The individual scaled beamlines are not subject to all of the difficulties and/or problems, such as those identified above, that can impact a conventional single ion implantation device. The present invention exploits the scaling laws of the processes that govern the formation and transport of ion beams in order to generate a collective ion beam without the above problems. The inventor of the present invention appreciates that ion beam trajectories, from the formation at a plasma boundary, to the final target are substantially scale independent. For example, the equations relevant for ion beam transport, Maxwell's equations (1), motion (2), and charge distribution (3), shown below are scale independent. ∇ 2 ⁢ V = - J ɛ o ⁢ v , ∇ 2 ⁢ A _ = - ⁢ J _ μ o , V , A _ , J _ , v _ ⁡ ( x , t ) ( 1 ) e ⁡ ( - ∇ · V + v _ ⊗ ∇ ⊗ A _ ) = m ⁢ ∂ ⁢ v _ ∂ t ( 2 ) n e / n 0 = e - KT e V - V 0 ( 3 ) As a result, the scale of a beamline (e.g., beam size, beamline length, bending radius, and the like) can be arbitrarily adjusted up or down while preserving ion beam current, voltages, and shape. Thus, the present invention employs arrays of scaled (reduced) beamlines that together provide a low energy, high current ion beam. Generally, voltages, currents, and vector potentials are maintained constant. Physical component and path dimensions can be scaled, while frequencies scale inversely to dimensions. Some exceptions are non-linear mediums, loss processes, and relativistic motions. Some items that change linearly (inversely) with scaling include electric fields, magnetic fields, and neutral pressure. Some items that change with square of scaling (inversely) include current densities and charge densities. Referring initially to FIG. 1, a multi-beamline ion implantation system 100 in accordance with an aspect of the present invention is depicted in block diagram form. The system 100 employs a beamlet array 104 comprised of a plurality of beamlets, which are scaled down ion beams. The system 100 performs mass analysis and possibly other transport operations on the beamlets individually in order to mitigate typical problems encountered with conventional low energy ion beam implanters. Generally, the beamlets are a fraction of a desired beam (e.g., 1/10) and, as a result, dimensions of components within the system are also that fraction of a conventional or single beamline ion beam implantation system. The system 100 includes an ion source 102 for producing a beamlet array 104 by using triode extraction, for example. The ion beam source 102 includes, for example, a plasma source 106 with an associated power source 108. The plasma source 106 may, for example, comprise a relatively long plasma confinement chamber from which the beamlet array 104 is extracted. The beamlet array 104 is comprised of a plurality of beamlets of similar size and with a spacing. Typically, the beamlet array 104 comprises a number of horizontal rows of beamlets. Elongated horizontally slits (not shown) can be employed to form beamlets elongated in the horizontal direction, which can facilitate horizontal merging of the beamlets. A beamline assembly array 110 is provided downstream of the ion source 102 to receive the beamlet array 104 therefrom. The beamline assembly array 110 includes a mass analyzer module 112 and beam formation component 114. Other components may be present therein and still be in accordance with the present invention. The beamline assembly array 110 is situated along the path to receive the beamlet array 104 and generates a single low energy, high current ion beam 116 at full scale. The mass analyzer module 112 comprises an array of mass analyzers having channels therein that allow individual beamlets to pass there through. Generally, the mass analyzers respectively comprise a pair of permanent magnets that form a channel there between. Adjacent channels typically share one of the pair of magnets. However, it is appreciated that the mass analyzer module 112 can have other configurations of mass analyzers, such as including multiple pairs of magnets per beamlet, an example of which is described in later figures. As stated above, scaling dimensions of beamline components requires an inverse scaling in magnetic fields. For example, a 1/10 scaling in dimensions (e.g., beamline length, bending radios, beam size, and the like) requires a 10× increase in magnetic fields for the mass analyzers. Consequently, permanent magnets can be required for small dimensions in order to provide a sufficient and consistent magnetic field. The channels within the mass analyzer module can be physically maintained by using beamguide spacers (not shown), which prevent individual magnets from physically moving and occupying the channels. The dimensions of the permanent magnets employed are relatively small, which may cause other separation mechanisms to be difficult to employ. Each magnet has a north and south pole that can attract neighboring magnets. Without a sufficient separation mechanism, such as beamguide spacers, the channels can become collapsed. The respective mass analyzers of the module 112 provide a magnetic field across the channels such that the paths of ions having a selected mass energy product is curved and passes through the respective channels. One or more slits or apertures may be present that block ions or particles having non-selected mass energy products. As a result, the mass analyzer module 112 substantially removes ions or particles from the beamlet array 104 that do not have the selected mass energy product. The selected mass energy product of the mass analyzer module 112 is generally fixed due to using permanent magnets, which provide a fixed, non-varying magnetic field. However, the present invention contemplates employing replaceable modules of permanent magnets that can be employed to obtain different magnetic fields, and as a result, different mass energy products for mass analysis of different dopant species. A beam formation component 114 is located downstream of the mass analyzer array 112 and forms a single beam 116 from the mass analyzed beamlet array 104. The beam formation component 114 causes the beamlets within the array 104 to diverge in horizontal and/or vertical directions so as to form the single beam 116. The optical properties of the extraction and the magnets, are such that the beamlets enter the post resolving drift space with some divergence. The divergence causes the beam to expand throughout the drift space. Additionally, because of the space-charge force, the lateral spread of an ion beam is proportional to:(√{square root over (m)}/√{square root over (q)})×(Iz2/U3/2) where m is an ion mass, q is an ion charge, I is a beam current, U is beam energy, and z is the traveling distance of the ion beam, assuming that the ion beam is uniform and has a circular cross section. The beam formation component 114 can employ these lateral spreads and the traveling distance to sufficiently diverge the beamlets in one or both directions. Alternately, the beam formation component can employ deflection plates to enhance divergence. Such deflection plates are located on horizontal and/or vertical planes and are biased to enhance deflection in a single axis. Another mechanism that can be employed by the beam formation component 114 is to perform mechanical scanning. The beamline assembly 110 and/or a target are moved in horizontal and/or vertical directions in order to spread coverage of a generated beam across a workpiece. In one example, the beam formation component 114 causes the beamlets to diverge in a horizontal direction by employing a drift region wherein the ions within the beamlets diverge sufficiently to cause rows of beamlets to merge together. The beam formation component 114 also employs a mechanism to cause the beamlets to diverge in the vertical direction. As with the horizontal direction, a drift region can also be used to allow sufficient divergence of the beamlets in the vertical direction. However, the beamlets may be shaped to widen more in the horizontal direction (horizontally elongated). In such a case, a suitable drift region could require relatively long length thereby making employment of a drift region for vertical divergence impractical. Alternately, vertical deflection plates, which lie in horizontal planes between paths of rows of beamlets, can be employed and biased so as to enhance divergence in the vertical direction. In one example, the vertical deflection plates are alternately biased positive and negative values. An end station 118 is also provided in the system 100 to receive the resultant single ion beam 116 from the beamline assembly 110. The end station 118 supports one or more workpieces such as semiconductor wafers (not shown) along the beam path for implantation using the mass analyzed decontaminated ion beam 116. The end station 118, in one example includes a target scanning system 120 for translating or scanning one or more target workpieces and the ion beam 104 relative to one another. The target scanning system 120 may provide for batch or serial implantation, for example, as may be desired under given circumstances, operating parameters and/or objectives. It is appreciated that the system 100 of FIG. 1 is described at a high level in order to facilitate a greater understanding of the present invention. Further details of suitable components that can be employed in the system 100 are described infra. Variations in the components described above as well as additional components can be employed in accordance with the present invention. As an example, consider a typical low energy ion beam of 100 eV, which has a beam current of about 30 microamps. Scaling the beamline by 1/10, including beam size, beamline length, and bending ratios, increasing the magnetic fields and background pressure by a factor of 10 still results in a beam current of 30 microamps. Continuing the example, if 700 of these scaled beamlets are employed in the system 100, a total beam current of about 20 milliamps at the low energy can be obtained. FIG. 2 is a vertical or plan view of a multi-channel, multi-beamline ion implantation system in accordance with an aspect of the present invention. The system is a multi-channel, multi-beamline ion implantation system that generates a beamlet array that, after passing through the multiple channels, is formed into a single beam. The system comprises an ion source 202, a triode extraction assembly 204, a first magnet module 206, a second magnet module 208, a post acceleration assembly 210, and a single axis deflector array 212. The ion source 202 comprises, in one example, a plasma source and a power source. The plasma source can comprise a relatively long plasma confinement chamber. The triode extraction assembly 204 is positioned downstream of the ion source 202 and extracts a beamlet array from the ion source 202. The n×m beamlet array comprises n horizontal rows and m vertical columns of beamlets. Slits, which may be part of the triode extraction assembly 204, are typically employed to form and shape the beamlets of the array. In one example, the slits are elongated in the horizontal direction, which generates beamlets elongated in the horizontal direction and allows for quicker overlap between beamlets of the array in the horizontal direction. The first magnet module 206 receives the beamlet array from the triode extraction assembly 204 and performs a first mass analysis on the beamlet array. The first magnet module 206 comprises an array of channels in between pairs of permanent magnets that permit passage of individual beamlets there through. The pairs of magnets cause ions having a selected mass energy product to bend at a first angle (e.g., 45 degrees) in a horizontal direction. Other ions and particles having differing mass energy products bend at other angles and can impact sides of the channels. In addition, an array of slits can be positioned after the first magnet module 206 to block ions and/or particles having non-selected mass energy products. Consequently, the first magnet module 206 operates as a first pass or first order mass energy product filter that substantially “purifies” the ion beam. The second magnet module 208 is positioned downstream of the first magnet module 206, receives the beamlet array and performs a second mass analysis on the beamlet array. The second magnet module 208 also comprises an array of channels in between pairs of permanent magnets that permit passage of individual beamlets there through. The pairs of magnets cause ions having a selected mass energy product to bend at a second angle (e.g., 45 degrees) in a horizontal direction, typically opposite the first angle. Other ions and particles bend at other angles and can impact sides of the channels. In addition, a second array of slits can be positioned after the second magnet module 208 to block ions and/or particles having non-selected mass energy products. The second magnet module 208 acts as a second pass mass energy product filter to further purify the beam. The post acceleration assembly 210 is positioned downstream of the second magnet module 208 and serves to accelerate (includes accelerating and decelerating) the beamlet array to a final energy value. The post acceleration assembly 210 comprises a number of electrodes positioned along a path of the beamlet array. The electrodes are biased so as to accelerate to the final energy value. A single axis deflector array 212 is positioned downstream of the post acceleration assembly 210 operates to diverge the beamlet array in the vertical direction. Generally, a number of deflection plates on horizontal planes associated with the n rows of beamlets are employed. Plates are positioned in between the horizontal rows of beamlets. The deflection plates are alternately biased such that adjacent plates have an opposite polarity. The magnitude and/or frequency of biasing controls the amount of vertical divergence to be obtained. As a result, the biased plates cause the beamlets to diverge in a vertical direction such that columns of beamlets form together. Alternately, a drift region could be employed. A drift region (not shown) is present that sufficiently diverges the beamlet array in a horizontal direction (x). As described above, ions within a beam tend to diverge as they travel. Low energy beams tend to diverge more so than higher energy beams over a given distance. As a result, a particular length or drift region length is employed to provide sufficient horizontal divergence. This length of the drift region can be relatively short, particularly if the beamlets are elongated in the horizontal direction, thereby facilitating quicker overlap of beamlets in the horizontal direction. Thus, horizontal rows of beamlets form into a single beam. The drift region, in combination with the single axis deflector array 212 causes the beamlet array to form into a single low energy, high current ion beam 216. A target 214, such as a wafer, multiple wafers, arrangement for a flat panel implantation, and the like is present at an end station and the ion beam is directed towards it to perform ion implantation. FIG. 3 is a perspective view of a single channel 302 through which an individual ion beamlet 304 passes in accordance with an aspect of the present invention. The beamlet 304 is part of an array of beamlets (not shown) that are employed to later form a single low energy, high current ion beam. A first magnet pair 306 and a second magnet pair 310 are shown with the channel 302 passing there through. The first magnet pair 306 deflects the beamlet 304 by a first angle in a horizontal (x) direction. Ions within the beamlet 304 having a selected mass energy product pass through the first magnet pair. Other ions within the beamlet 304 can be blocked by a first slit (not shown), but positioned at 308. Continuing, the second magnet pair 310 deflects the beamlet 304 by a second angle in a horizontal direction. Generally, the second angle is opposite, but equal to the first angle. Ions within the beamlet 304 having the selected mass energy product pass through the second magnet pair. Other ions within the beamlet 304 can be blocked by a second slit (not show), positioned at 312. Generally, the second slit has a higher mass resolution than the first slit. The first magnet pair 306 and the second magnet pair 310 are depicted as having trapezoidal cross sections in FIG. 3. This shape can facilitate passage of the beamlet 304 through the channel. However, it is appreciated that the present invention includes other shapes for the pairs of magnets and that the shape depicted in FIG. 3 is exemplary in nature. Additionally, the first magnet pair 306 and the second magnet pair 310 are generally permanent magnets in order to generate a sufficient magnetic field. FIG. 4A is a perspective view of a mass analyzer module 400 in accordance with an aspect of the present invention. The view depicts the module 400 as including an array of channels between pairs of permanent magnets through which an array of beamlets pass. More particularly, the view depicts a beamlet 402 passing through the mass analyzer module 400. The module 400 comprises a first array of magnets 404 and a second array of magnets 406. Due to the size of the arrays, channels, and beamlets, the magnets are typically permanent magnets in order to generate a sufficient magnetic field. The beamlet 402 is shown passing through a channel in the first array 404 and on through the second array 406. Beamguide spacers 408, in one example, are positioned 409 in between the columns of permanent magnets in order to properly position the magnets within the arrays. The spacers 408 are comprised of a non-magnetic material, such as aluminum, that is structurally sufficient to prevent magnets from physically moving. As a result, the spacers 408 permit the sufficient magnetic field to be generated in a non-varying manner between pairs of magnets. The beamguide spacers 408 have channels formed therein (in a z direction) through which the beamlets may pass. The channels can be formed in a number of suitable ways, such as by drilling from opposite ends of the spacers 408. The size and shape of the channels formed therein can also block ions and/or particles having non-selected mass energy products from passing through the arrays and channels. FIG. 4B is another enlarged view of the beamguide spacers 408 in accordance with an aspect of the present invention. In this view, attention is drawn toward a single channel 410 formed within a single spacer. The channel 410 can be formed, in this example, by drilling through spacer material at 412 and 414 in order to form the channel 410 continuously through the spacer. It is appreciated that the channel 410 is exemplary in nature and that the present invention contemplates other size and shapes of channels formed within spacer material. FIG. 5 is a perspective view of another mass analyzer module 500 that includes partition strips 508 in accordance with an aspect of the present invention. The view depicts the module 500 as including an array of channels between pairs of permanent magnets through which an array of beamlets pass. The module 500 is similar to the module 400 described in FIG. 4, but additionally includes the partition strips 508 to block cross-channel transport. The module 500 comprises a first array of magnets 504 and a second array of magnets 506. Due to the size of the arrays, channels, and beamlets, the magnets are typically permanent magnets in order to generate a sufficient magnetic field. The beamlet 502 is shown passing through a channel in the first array 504 and on through the second array 506. One potential problem that can occur with the first array of magnets 504 is that ions and/or particles with non-selected mass energy products may be prevented from continuing through a current channel through the second array 506, but may deflect so much that they pass through another channel, such as one above or below it. As a result, horizontal partition strips 508 are employed to mitigate or stop this cross channel transport. The partition strips 508 are typically comprised of an electrically neutral material so as not to interfere with the beamlets traveling through the channels. However, as described below, an alternate aspect of the present invention employs electrodes formed on upper and lower surfaces of the partition strips that can be employed to enhance uniformity of a generated single ion beam, as will be discussed in greater detail infra. FIG. 6 is a perspective view of yet another mass analyzer module 600 that includes deflection plates 610 in accordance with an aspect of the present invention. The view depicts the module 600 as including an array of channels between pairs of permanent magnets through which an array of beamlets pass. The module 600 is similar to the module 500 described in FIG. 5, but additionally includes the deflection plates 610 in order to sufficiently diverge the array of beamlets in a vertical direction (y). The module 600 comprises a first array of magnets 604 and a second array of magnets 606. Due to the size of the arrays, channels, and beamlets, the magnets are typically permanent magnets in order to generate a sufficient magnetic field. The beamlet 602 is shown passing through a channel in the first array 604 and on through the second array 606. Horizontal partition strips 608 are employed between the first array of magnets 604 and the second array of magnets 606 in order to mitigate or stop cross channel transport. The partition strips 608 are typically comprised of an electrically neutral material so as not to interfere with beamlets traveling through the channels. The vertical deflection plates 610 are positioned downstream of the second array of magnets 606. Individual plates separate rows of generated beamlets and are biased with an opposite polarity of adjacent plates. As a result, the vertical deflection plates 610 cause beamlets, including the beamlet 602, to sufficiently diverge (or scan) in the vertical direction so as to form continuous ion beams, in the vertical direction. Typically, a drift region is employed to provide sufficient divergence in a horizontal (x) direction. As a result, a single, continuous low energy, high current ion beam can be formed at the workpiece. FIG. 7 is a diagram of a partition plate 702 with uniformity correction electrodes in accordance with an aspect of the present invention. The partition plate 702 is typically employed between the mass analyzer modules, such as those described above, to prevent or mitigate cross channel transport. The partition plate 702 is exemplary in nature and is provided as an example to facilitate a better understanding of the invention. A single side of the partition plate 702 is shown with four separate beamlet regions, 704, 706. 708, and 710, near which beamlets pass from one array of magnets to another. Generally, the number of regions would correspond to the number of columns m. Each of the beamlet regions has an associated electrode 714, 716, 718, and 720 formed therein. The electrodes, in one example, are individually controllable. An adjacent plate (not shown) above or below the plate 702 is also present and similarly configured with electrodes. By selectively applying potentials to the electrodes on the plate 702 and the adjacent plate, electric fields specific to individual beamlets can be generated. A controller or other mechanism can control the fields through which the individual beamlets pass in order to adjust the beam current of individual beamlets. For example, by applying a positive voltage to the electrode 714 and a lower voltage to a corresponding electrode on the adjacent plate, beam blow up for that beamlet occurs thereby reducing its current after it passes through the second array of magnets. The applied voltages can also be time varying with selectable duty cycles in order to more fully control generated beam current. As a result, beam current of a generated low energy, high current ion beam can be measured at a target (e.g., wafer, multiple wafers, flat panel arrangement, and the like) or end station and analyzed. Subsequently, the controller can employ electrodes on the plates to modify and/or control beam current uniformity. In view of the foregoing structural and functional features described supra, methodologies in accordance with various aspects of the present invention will be better appreciated with reference to the above figures and descriptions. While, for purposes of simplicity of explanation, the methodologies described below are depicted and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that depicted and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect the present invention. Referring now to FIG. 8, a flow diagram illustrating a method 800 for generating a low energy, high current ion beam in accordance with an aspect of the present invention is disclosed. The method 800 generates an array of beamlets, performs beamline operations on individual beamlets, and then combines the beamlets to form a single low energy, high current ion beam. As stated previously, voltages, currents, vector potentials, and the like employed in beamline assemblies are scale independent. As a result, dimensions of ion beams can be reduced and yet still produce smaller ion beams, referred to as beamlets that have the same beam current as without reduction. Subsequently, these beamlets can be combined together adding beam currents for the beamlets into a relatively high current, low energy single ion beam. The method 800 begins at block 802, wherein an array of beamlets is generated. A plasma source and power source are employed with an extraction assembly to generate the array of beamlets. Horizontal slits, which are elongated in a horizontal direction, can be employed to shape the beamlets so that they are themselves elongated in the horizontal direction. The array of beamlets is comprised of a number of rows and columns and is substantially comprised of a selected ion species, such as boron or phosphorous, traveling with a selected energy. As a result, the selected ion species has a mass energy product. Individual beamlets are generally, but not necessarily, shaped wider or elongated in a horizontal direction. A first mass analysis of the array of beamlets is performed at block 804, wherein the beamlets are subjected to a magnetic field that causes the selected ions, having the desired mass energy product, to deflect at a first angle (e.g., 45 degrees, 30 degrees, and the like) in a horizontal direction. Other ions and/or particles either fail to deflect or deflect at an angle other than the first angle. The other ions and/or particles are substantially blocked at 806 by a blocking mechanism, which blocks ions and/or particles that deflect at angles other than the first angle for the beamlets within the array. The blocking mechanism can include a size and/or shape of channels formed through beamguide spacer materials and/or an appropriately sized slit, as described above. A second mass analysis of the array of beamlets is performed at block 808, wherein the beamlets are subjected to a second magnetic field that causes the selected ions, having the desired mass energy product, to deflect at a second angle in the horizontal direction. Other ions and/or particles either fail to deflect or deflect at an angle other than the second angle. The second angle is generally opposite, but equal to the first angle. The other ions and/or particles are again substantially blocked at 810 by a second blocking mechanism, which blocks ions and/or particles that deflect at angles other than the second angle for the beamlets within the array. The blocking mechanism can include a size and/or shape of channels formed through beamguide spacer materials and/or an appropriately sized slit, as described above. The array of beamlets are diverged or scanned in a vertical direction at block 812, wherein columns of beamlets are merged into single column beams. Typically, deflection plates are employed to cause sufficient deflection. Alternately, a suitably long drift region can be employed to obtain sufficient deflection. Additionally, mechanical scanning of an end station and/or target in the vertical direction can also be employed. The array of beamlets are diverged in a horizontal direction at block 814, wherein rows of beamlets are merged in single row beams and, a single low energy, high current ion beam. Generally, a suitably long drift region can be employed to obtain sufficient deflection in the horizontal direction, due to the shape of the beamlets. However, vertical deflection plates and/or mechanical scanning in the horizontal direction can also be employed. It is appreciated that alternate aspects of the method 800 are contemplated that include other functionality discussed with respect to other figures, such as mitigating cross channel transport, accelerating the beamlets, and the like. Additionally, variations of the method 800 are permitted in accordance with the present invention, such as performing only a single mass analysis or more than to mass analysis. Although the invention has been illustrated and described above with respect to a certain aspects and implementations, it will be appreciated that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated exemplary implementations of the invention. In this regard, it will also be recognized that the invention may include a computer-readable medium having computer-executable instructions for performing the steps of the various methods of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “including”, “has”, “having”, “with” and variants thereof are used in either the detailed description or the claims, these terms are intended to be inclusive in a manner similar to the term “comprising”. Also, the term “exemplary” as utilized herein simply means example, rather than finest performer.

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