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description | This application is related to application Ser. No. 15/447,687, filed Mar. 2, 2017, now U.S. Pat. No. 10,008,299. The embodiments of the present disclosure generally relate to safely storing radioactive debris, such as corium, nuclear fuel rod assemblies, and parts thereof, etc. The Fukushima Daiichi Nuclear Power Plant (IF) Unit I to 3 in Japan, owned and operated by Tokyo Electric Power Company (TEPCO), suffered tremendous damage from the East Japan Great Earthquake that occurred on Mar. 11, 2011. It is assumed that nuclear fuels in the 1F reactors experienced melting and, as a result, dropped to the bottom of the Reactor Pressure Vessel (RPV) and/or Pressure Containment Vessel (PCV), solidifying there as fuel debris after being fused with reactor internals, concrete structures, and other materials. In order to pursue decommissioning of 1F, it is necessary to remove the fuel debris from the RPV/PCV using appropriate and safe Packaging, Transfer and Storage (PTS) procedures. Fuel debris retrieval procedures are expected to be started within 10 years' time and completed in 20 to 25 years' time. It is planned that after 30-40 years the fuel debris will all be placed in interim storage. Embodiments of containers and methods are provided for safely removing and storing radioactive debris. One embodiment, among others, is the container containing radioactive debris. The container comprises an overpack having an elongated cylindrical body extending between a top end and a bottom end, a planar bottom part at the bottom end, and a circular planar lid at the top end. The container further includes a basket situated inside of the overpack, and a plurality of elongated cylindrical canisters that are maintained in parallel along their lengths by the basket. Each of the canisters has an elongated cylindrical body extending between a top end and a bottom end, a planar bottom part situated at the bottom end, and a circular planar lid situated at the top end. Furthermore, an elongated perforated columnizing insert is situated inside of at least one of the canisters. The insert has a plurality of elongated cylindrical tubes that are parallel along their lengths inside of the at least one canister. Each of the tubes has a side wall extending between a top end and a bottom end and has a plurality of perforations. Screening is associated with the side wall of each tube to delimit the perforations. A plurality of columns of the radioactive debris is situated in and is essentially created by respective tubes of the insert. The columns of the radioactive debris contain an amount of uranium dioxide (UO2) fuel. The perforations and the screening, in combination, enable gas flow through the side wall to enable evaporation of liquid from the radioactive debris, while adequately confining the columns of debris within the tubes. Another embodiment, among others, is a canister containing radioactive debris. The canister comprises an elongated cylindrical body extending between a top end and a bottom end, a planar bottom part situated at the bottom end, and a circular planar lid situated at the top end. An elongated columnizing insert is situated inside of the body of the canister. The insert has an elongated cylindrical body extending between a top end and a bottom end. The insert has a plurality of elongated cylindrical tubes that are parallel along their lengths inside of the canister. Each of the tubes has a side wall extending between a top end and a bottom end. The side wall has a plurality of perforations. Screening is associated with the side wall of each tube to delimit the perforations. A plurality of columns of the radioactive debris is situated in and is essentially created by respective tubes of the insert. The columns of the radioactive debris containing an amount of UO2 fuel. The perforations and the screening, in combination, enable gas flow through the side wall to enable evaporation of liquid from the radioactive debris, while adequately containing the columns of debris within the tubes. Yet another embodiment, among others, is a perforated columnizing insert containing radioactive debris and that is designed for insertion into a canister. The insert comprises an elongated cylindrical body extending between a top end and a bottom end. The insert has a plurality of elongated cylindrical tubes that are parallel along their lengths inside of the canister. Each of the tubes has a side wall extending between a top end and a bottom end. The side wall has a plurality of perforations. Screening is associated with the side wall of each tube to delimit the perforations. A plurality of columns of the radioactive debris is situated in and is essentially created by respective tubes of the insert. The columns of the radioactive debris contain an amount of UO2 fuel. The perforations and the screening, in combination, enable gas flow through the side wall to enable evaporation of liquid from the radioactive debris, while adequately containing the columns of debris within the tubes. Other apparatus, methods, apparatus, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. In order to establish PTS systems for IF fuel debris, procedures need to be formulated based on the nuclear fuel debris conditions, regulatory requirements, and Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) internal conditions. This entails full consideration of criticality prevention when handling nuclear fuel materials, the prevention of hydrogen explosion, and the evaluation of all other relevant safety-related functions. It is planned that fuel debris retrieval procedures will be implemented with the PCV filled with water, in order to shield against radiation and to prevent the dispersion of radioactive materials. To maintain sub-criticality during PTS procedures, IF fuel debris will be secured in canisters having a controlled internal diameter. Once fuel debris has been packaged securely in a fuel debris canister, some water also may be contained within the canister. Hydrogen generation through radiolysis of the water therefore is possible. To prevent a hydrogen explosion when handling fuel debris canisters, the canister includes a mesh type filter to allow the release of any hydrogen so generated in the canister. It is considered possible that nuclear fissile materials from fuel debris may be released along with the hydrogen from this filter. The fuel debris canister with filter must be designed to maintain sub-criticality (e.g., in a wet pool environment) even if nuclear fissile materials are released from the canister. The deployment of equipment to take away hydrogen and nuclear fissile materials released from the canisters also is a possibility. The following is an overview of the debris packaging and subsequent management of the loaded debris canisters. 1. Canister Loading The loading of fuel debris into the canisters will be performed adjacent to the reactor pressure vessel. After filling, a lid will be placed on the canister (not bolted) and then it will be transferred through the existing water channel to the reactor spent fuel pool. Neutron monitors located adjacent to the canister loading station will be available, if necessary, to infer reactivity of the canister during loading, to ensure that loading of debris does not violate the specified margin to criticality. Also, a portable weighing platform should be available, so that loading of debris can be halted if the specified weight limit otherwise would be violated. Filled canisters will be received in the reactor spent fuel pool and located in racks that will hold five canisters. These racks will be the baskets to be used inside a metal overpack, which later will be loaded first into a transfer cask, even later potentially into a transport cask and, ultimately, into a ventilated concrete dry storage cask for long-term interim storage. At this point, the debris inside the canister will be fully immersed in water and hydrolysis will result in the generation of hydrogen. The canisters will include a ventilation pipe to allow the release of such hydrogen, and this will enable the connection of the canister to an external hydrogen/off-gas processing and collection equipment. There should be sufficient floor space to locate such equipment adjacent to the reactor spent fuel pool and its primary functions will be as follows: (a) gases and moisture vapor from the canisters first will enter a Cyclone Moisture Separator; (b) the remaining gases will be directed to a Duplex Filter Monitoring Assembly (DFMA); (c) the filtered gases will be collected in a Gas Collection Header (GCH); and (d) collected gases will be discharged to a Plant Ventilation System (PVS). The debris canister will include a second penetration line for use in draining and/or purging the canister. During this initial period of storage this second line will enable a purge with helium gas should the hydrogen generation, for any reason, increase beyond the Lower Explosive Limit (LEL) concentration. Each line from the canisters will be monitored in order to provide an alert to any unacceptable operating conditions. 2. Reactor Spent Fuel Pool: Draining and Drying of the Debris Canisters As and when it is deemed appropriate, each basket holding five debris canisters will be transferred to another location in the reactor spent fuel pool (the canister processing station) where the group of five canisters will be connected to an external canister processing system. This will drain the water out of each canister and then will purge each canister with helium at approximately 150° Celsius, in order to drive out almost all of the moisture. Once this has been achieved, if necessary the basket of five canisters can be returned to its original storage location in the pool, where it can be connected again to the external gas removal and processing system. It can remain there until such time as transfer to another storage location is implemented. In this relatively dry condition, the generation of hydrogen through hydrolysis will have been reduced substantially. Alternatively, the canisters can be immediately packaged in an over-pack and transfer cask to remove the debris canisters from the reactor spent fuel pool. 3. Transfer Out of the Reactor Spent Fuel Pool Prior to transfer out of the reactor pool, the basket will be loaded into a metal overpack that itself already has been loaded into a transfer cask. At this point, the overpack will be fitted with a temporary shielding lid. Via penetrations in this temporary lid, the drain line on the canister will be closed off, and an external filter will be attached to the off-gas penetration line. The temporary lid will be replaced by a final closure lid, of either bolted or welded design, depending on the expected next stage in the management of the debris. If the intention is to make an on-site transfer to, for example, a common AFR (away from reactor) wet pool, then the closure lid would be bolted. If the intention is to transfer directly to AFR (off-site) interim dry storage, then the closure lid would be welded. The welded closure would include a simple closure plate for the period of off-site transportation. Once at the storage location, this would be replaced by an external filter. The bolted closure could include just a simple cover plate if the canisters were to be taken out of the over-pack and stored again in a wet pool environment. Alternatively, if there was concern that a significant time interruption might occur during the transfer, it also could include an external filter. The metal overpack will be drained and dried prior to moving on to the next phase of operations (wet pool or dry storage). 4. Key Features of the Debris Canister Two canister variants are disclosed. The first is an open structure with no internal subdivision to facilitate loading with debris and ultimately an expected higher packing density compared with what would be achieved with a smaller diameter canister. The second includes a cruciform internal sub-divider, in case any substantively intact fuel assemblies are recovered from the reactor core; (the sub-divider will help to facilitate ease of loading for up to four such intact or partially intact fuel assembly pieces) and/or to deal with debris that may have a concentration of enriched uranium that is higher than the estimated average debris mixture, which may not be subcritical in the open canister design. It is noted that the open structure may utilize a perforated columnizing insert for extremely fine debris. Full details of the basis for the proposed canister size and how sub-criticality can be assured, are provide later in this document. Prior to the canisters being drained, dried and packaged in an overpack, they will not include any sort of integral filter. During these phases of debris management, externally fitted filters will be utilized, exclusively, as and when appropriate. The canisters may incorporate hydrogen absorption material or other hydrogen control device. Any such hydrogen getter would be evaluated for management of hydrogen release from the debris and incorporated as needed. The quantities of various materials that will be contained in the mixed debris to be recovered and loaded into canisters has been estimated. For debris that may still be located inside the pressure vessel, this will tend to be mainly uranium mixed with some metallic structural materials (fuel cladding, BWR channel, BWR assembly components, possibly control rod blades and potentially some reactor structural materials). For debris that has penetrated the pressure vessel and fallen onto the base of the concrete containment, the mixture is expected to include concrete and some additional steel and other metals (from things like the pressure vessel, the lower core plate and the control rod drive mechanisms below the pressure vessel). In order to perform the best calculations, it would be necessary to take samples from the core debris, which could be analyzed to provide accurate information about the typical composition, or range of compositions that might be expected. In the absence of such information, preliminary calculations have been performed based on an assumed mixture of UO2 with carbon steel in various plausible ratios, based on the approximate information presented in Table A. TABLE AMaterialkgUO2 in Fuel Bundle200Components per Bundle (including channel)90Portion of control rods (100 kg each and 1 per 4 bundles25Miscellaneous other materials in the debris mix50Total per initial fuel assembly bundle365Percentage UO2 in Total Debris Material55% The average enrichment of the uranium in the core at the time of the accident is assumed to have been 3.7 percent U235. This is the typical average assembly enrichment for fresh assemblies loaded into the core. Individual rods and pellets will have had initial enrichments up to 4.95 percent U235. In practice some of the fuel in the core will have experienced significant burnup, so the assumption of an average of 3.7 percent is considered to be a conservative assumption in respect of evaluating reactivity. Initial criticality calculations have been performed assuming the extremely conservative assumption of a homogeneous mixture of uranium and other materials in various ratios. A Keff value of 0.95 is used as the maximum allowed reactivity at the +2a level. With UO2 content of 55 percent, under these conservative conditions, reactivity reaches a peak value just below the limit of Keff=0.95 when about 250 litres of debris has been loaded into the canister. As more debris is added, expelling water (moderator), reactivity then reduces slightly. If, however, the portion of UO2 in the debris mix is increased to 60 percent, then the 0.95 limit is estimated to be exceeded when about 200 liters of debris has been loaded in the canister. This would not be acceptable, even if the reactivity coefficient would reduce as the canister was filled up more. Since the estimated portion of 55 percent UO2 is subject to large uncertainty, clearly this preliminary criticality assessment leaves corresponding uncertainty regarding the ability to fill up the canister with 1F debris. In reality, however, the debris recovered and submitted for loading in the canisters is expected to be in the form of relatively large pieces of material that have been fused at high temperature. In other words, the debris/water mix in the canister will be highly heterogeneous. Accordingly, calculations have been performed assuming a heterogeneous mixture of debris and water, with pieces of debris in various physical forms. With these more realistic assumptions, it has been calculated that the canister can be fully loaded with UO2 and other material in any ratio from about 55:45 to about 70:30 and Keff reaches no more than about 0.5, far below the 0.95 limiting value. It is recognized however that debris with an enriched uranium concentration higher than the average for all debris could be recovered and submitted for loading into an individual canister. In the limit there could be hot-spots of entirely enriched uranium material. For pure enriched uranium, the maximum amount that could be loaded into the canister without violating reactivity limits would be small. This would be picked up by the proposed neutron monitoring equipment providing an alert for the operators. At this point, a decision would be required on how to proceed. One option would be to load only the relatively small quantity of high uranium content debris, meaning that the canister volume would be underutilized. This would be acceptable technically, but an economic penalty would be incurred (more canisters to purchase, handle, transport and store). An alternative would be to load such material into a canister of a modified design, as described hereinafter as the cruciform design. FIG. 1A is a perspective view of a first embodiment (open design) of a canister 10 of the present disclosure and is generally denoted by reference numeral 10a. The canister 10a has an elongated cylindrical body 11 extending between a top end 13 and a bottom end 15. There is a planar bottom part welded to the body 11 at the bottom end 15. The open top at the top end 13 is designed to receive a circular planar lid 17, which can be welded or bolted to the body 11. In the preferred embodiment, the closure lid is a single piece lid design that is secured to the canister 10a using cone bolts, which can be operated using long handled underwater tools. The closure lid 17 is engaged and handled using a grapple tool that can also be used to handle the canister 10a. Once the closure lid 17 is fully installed and all of the bolts are properly torqued, the closure lid 17 can be engaged with the grapple tool to facilitate handling of the loaded canister. The closure lid 17 is sealed to the upper head by use of an o-ring suitable for the designed configuration. The canister 10a accommodate the continuous passage of off-gases from the contained fuel debris. Accordingly, a traditional leak tight sealing configuration is not required. However, due to the fact that the canister 10a will be in underwater storage, a water tight configuration is needed. The canister 10a has a diameter that is no greater than about 49.5 cm, or about 19.5 inches, and an interior axial length that is no greater than about 381.0 cm, or about 150.0 inches, so that the radioactive debris cannot achieve nuclear criticality (or an undesirable nuclear reaction). In other words, the fuel debris is cut into small pieces and the pieces must be small enough to fit into the canister 10a, which ensures that they will not achieve unwanted nuclear criticality. Furthermore, it is assumed that the radioactive debris in each canister 10a contains an amount of uranium dioxide (UO2) fuel that is no greater than about 100 (kg, and an initial enrichment of the UO2 fuel is not greater than about 3.7 percent. It is further assumed that the canister 10a is fully loaded with the UO2 fuel and one or more other nonradioactive materials (e.g., carbon steel) in any volumetric ratio from 55:45 to 70:30, respectively. Further note that no nuetron absorber is needed in the first embodiment of the canister 10 to avoid unwanted nuclear criticality. FIG. 1B is a perspective view of a second embodiment (cruciform, or segmented, design) of a canister 10 of the present disclosure and is generally denoted by reference numeral 10b. The canister 10b has an elongated cylindrical body 11 extending between a top end 13 and a bottom end 15. There is a planar bottom part welded to the body 11 at the bottom end 15. The open top at the top end 13 is designed to receive a circular planar lid 17, which is bolted to the body 11. Unlike the canister 10a of FIG. 1A, the canister 10b further includes a flux trap 19 that has a plurality of spokes 20 with internal channels 21, or pockets, extending outwardly from a central elongated hub support 23. These channels 21 are filled with water when the canister 10b is in water and filled with air when the canister 10b is removed from the water and permitted to drain. The flux trap 19 has a cross-shaped cross-section, as is shown in FIG. 2. The cross-sectional width, or gap, of the rectangular channels 21 is preferably no less than about 2.54 cm, or about 1.0 inch. Reducing the gap down to about 0.75 inch produces a max Keff of about 0.938. A nominal gap of 1 inch produces a max Keff of about 0.907. Furthermore, the interior walls of the spokes includes a neutron absorber (FIG. 6). The combination of the gap and neutron absorber accommodate full loading of fuel debris, even if it were assumed to be all uranium material with 3.7 percent U235 in an optimal ratio of uranium to water (i.e., maximum reactivity configuration). Thus, in this embodiment, the canister 10b can contain radioactive debris with any amount of uranium dioxide (UO2) fuel at any initial enrichment and at any volumetric ratio with one or more other materials. In essence, the flux trap 19 and neutron absorber slow down neutrons so that the neutrons are too slow to meaningfully affect the fission process in a non-thermalized condition. The flux trap 19 is particularly important when the canister 10b is in water. As a result of the flux trap 19, the canister 10b has four sectors, each of which can receive fuel debris, such as corium, or in the alternative, up to four nuclear fuel rod assemblies in whatever condition (unlike the first embodiment, which is not designed to contain such assemblies). The canister 10b has a diameter that is no greater than about 49.5 cm, or 19.5 inches, and an interior axial length that is no greater than about 381.0 cm, or about 150.0 inches, so that the radioactive debris cannot achieve unwanted nuclear criticality. FIG. 2 is a top view of the canister 10 of respective FIG. 1 with its lid 17. FIG. 3 is a cross-sectional view of the second embodiment of the canister 10b of FIG. 1B with its lid 17. The first embodiment of the canister 10a would look similar except that it would not include the flux trap 19. FIG. 4 is a cross-sectional view of the second embodiment of the canister 10b of FIG. 1B taken along sectional line F-F of FIG. 3. FIGS. 5 and 6 are a cross-sectional views of the first and second embodiments of the canister 10 of FIG. 1A and FIG. 1B taken along sectional line G-G of FIG. 3. FIG. 7 is a cross-sectional view of detail H-H of FIG. 5 showing a debris screen. As shown in FIG. 1B, the flux trap 19 associated with the canister 10b may optionally include a neutron absorber on its interior walls of channels 21 that is held in place by a suitable retainer. FIG. 8 is a cross-sectional view of detail Hof FIG. 2 showing a debris seal. FIG. 9 is a cross-sectional view of detail J-J of FIG. 2 showing a recess for a canister grapple. Details of an upper closure head 18 engaged with the lid 17 is shown in FIG. 10. The inner and outer shells are sealed at the top end 13 by an upper head ring. The space between the inner and outer shells provides a means to install the vent and drain connections. The vent connection is necessary to process off-gasses and to connect the canister 10 to monitoring equipment. The vent permits hydrogen to escape from the canister 10 while preventing radioactive gases, for example, krpton (Kr), iodine (12), etc., from escaping. The escaping gases enter the overpack 61 (FIG. 17), and then escape the overpack 61 via a filter 92 (FIG. 24). This vent port 19a is configured so as to minimize radiation streaming while ensuring the upper most portion of the canister 10 is being accessed by processing or monitoring equipment. The drain port 19b extends to the bottom of the canister 10, to facilitate draining of water. The upper closure head 18 provides a seating surface for the thick bolted closure lid 17, which in the preferred embodiment, is 8.38 cm, or 3.3 inches. Details of a lower closure head 25 is shown in FIG. 11. The canister inner shell incorporates 12 screened holes in its bottom plate, to allow liquid drainage yet still retains fine debris particles. The screen material to be fitted to these holes will retain materials exceeding 250 microns in size, which is a typical screen size for this type of application. The escaping liquid enters the overpack 61 (FIG. 17), and then is drained from the overpack 61. Any smaller particulate matter that passes through these screens will be captured and processed in external equipment that will be connected to the canisters 10 while they are in pool storage. Access to the internal cavity of the canister 10 is controlled by vent and drain port fittings that are completely independent from the bolted closure lid 17. Each port fitting is a spring loaded poppet-style fitting 27, as illustrated in FIG. 14, which has been used in underwater applications where specially designed quick couplings play a vital role. Examples of this application are in oil, gas, and other deep water projects, as well as quick disconnects that have operated on space vehicles, beginning with the earliest NASA programs. Upon completion of draining and drying of the canister 10 and just prior to installation into the overpack 61 (FIG. 17), a filtered cap assembly will be installed on both the vent and drain port fittings. This type of filter assembly ensures that any particulate material (less than 1 micron) will be retained within the canister 10, while allowing any hydrogen or other off gas to escape the canister 10. FIG. 13 is a perspective view of a basket 30 that corrals and confines a plurality of the canisters 10 of FIG. 1 in a parallel configuration along their lengths. In FIG. 3, as a non-limiting example, the basket 30 is shown to have three canisters 10a and two canisters 10b. The basket 30 has a plurality of spaced parallel corral plates 31 that confine the plurality of elongated cylindrical canisters 10. Each of the corral plates 31 has a plurality of circular apertures to receive a respective canister 10 through it, except for the bottom plate 33, which is without the apertures. A plurality of elongated lifting bars 35 are distributed equally around a periphery of the basket 30 and extend along the plurality of elongated cylindrical canisters 10. Each of the lifting bars 35 has a top end 37 and a bottom end 39. Each of the lifting bars 35 has an eye hook 41 located at the top end 37. The bars 35 are attached to the plates 31 and 33. FIG. 15 is a perspective view of a four legged canister grapple 29 that can be used to move the canister 10 as well as the lid 17. The canister grapple 29 has a plurality of legs 41, which total four in this example and which extend downwardly from a circular planar body 42. Each of the legs 41 is C-shaped, as shown. The canister grapple 29 is connected to the overhead crane system via an eye 44 in an eye hook assembly 44 that extends upwardly from the body 42. Ideally, an extension beam is used to connect the grapple to the overhead crane hoist (so as to keep the crane hook dry), but this depends on whether or not there is sufficient overhead height for the crane arrangement currently installed at the reactor in question. The overhead crane hoist hook should have a rotation device for rotating the crane hook to the required polar location. The canister grapple 29 is lowered such that the legs 41 of the canister grapple 29 enter into the L-shaped slots 48 and 50 on, respectively, the canister 10 or canister closure lid 17. Once lowered into position, the canister grapple 29 will be rotated to engage the dogs on the grapple legs with the corresponding openings on the canister 10 or canister lid 17. Once the canister 10 or canister lid 17 has been relocated to the desired location, the canister grapple 29 is disengaged from either the slots 48 or 50 by first rotating it in the other rotational direction, and then lifted it up and away. FIG. 16 is a perspective view of a basket spider grapple 45 that can be used to lift the basket 30 of FIG. 13. The basket spider grapple 45 has a plurality of arms 47, which total five in number in this example and which extend outwardly from a central body 53. Each of the five arms 47 has an L-shaped, outwardly open hook 49 that is designed to engage a respective lifting bar eye hook 41 so that the basket 30 can be lifted and moved, e.g., so that the basket 30 can be placed in or removed from an overpack 61 (FIG. 9). Furthermore, the spider grapple 45 has a lifting eye assembly 55 that extends upwardly from the central body 53. An eye 57 can be used by an overhead crane (not shown) to move the spider grapple 45 as well as an attached basket 30. FIG. 17 is a perspective view of an overpack 61, without its lid, into which is placed the basket 30 of FIG. 13. The overpack 61 has an elongated cylindrical body 63 extending between a top end 65 and a bottom end 67. There is a planar bottom part welded or bolted to the body 63 at the bottom end 67. An open top at the top end 65 is designed to receive a circular planar lid 69, first and second embodiments of which are shown in FIG. 18A and FIG. 18B and designated by respective reference numerals 69a and 69b. Each of the lids 69a and 69b has a plurality of holes 71 through which air or water passes as wells as a plurality of threaded holes 73 that provide a means for enabling the overhead crane to move the overpack 65 with the contained basket 30 and canisters 10 with, for example, lifting lugs. The lid 69a of FIG. 18A is designed to be welded to the body 63. As an alternative, the lid 69b of FIG. 18B is designed to be bolted to the body 63 via bolt holes 75. Bolts (not shown) are passed through respective holes 75 in the lid 69b and then into respective threaded assemblies 77, as shown in FIG. 17, that are welded or otherwise attached to the interior of the body 63. In some embodiments, an inflatable seal can be positioned around the periphery of the lid 69a or 69b prior to placement on the overpack 61. FIG. 19 is a perspective view of a container 90 having the overpack 61 containing the basket 30 containing the canisters 10. The container 90 is shown with a welded lid 69a (FIG. 18A). The container 90 is also shown with a filter 92, which is used when the container 90 is in a storage configuration. FIG. 20 is a top view of the container 90 of FIG. 11. FIG. 21 is a cross-sectional perspective view of the container 90 of FIG. 11 taken along sectional line A-A of FIG. 20. FIG. 22 is a cross-sectional view of the container 90 of FIG. 11 taken along sectional line A-A of FIG. 20. FIG. 23 is a cross-sectional view of the container 90 of FIG. 11 taken along sectional line B-B of FIG. 22. In this example, the basket 30 is shown with three canisters 10a and two canisters 10b. The container 90 is shown with a cover plate 94, which is used when the container 90 is in a transport configuration. FIG. 24 is a partial enlarged view showing detail C-C of FIG. 21 involving use of the filter 92 with drain line 96 when the container 90 is in a storage configuration. FIG. 25 is a partial enlarged view showing detail C-C of FIG. 21 involving use of the cover plate 94 when the container 90 is in a transport configuration. FIG. 26 is a partial enlarged view showing detail D-D of FIG. 21 involving an inflatable seal 98 associated with the overpack lid 69 of the container 10. Although not limited to this design choice, in the preferred embodiments, all parts associated with the canisters 10, the basket 30, and the overpack 61 are made of metal, such as stainless steel, based upon its long term resistance to corrosion and its reasonable cost. FIG. 27 is a perspective view of an elongated perforated columnizing insert 100 that can be placed within one or more of the canisters 10a of FIG. 1A when the canister 10a receives hazardous debris in the form of finer grade material (as opposed to more coarse material). FIG. 28 is a partial enlarged view of the top part and the bottom part of the insert of FIG. 27. The insert tube structure, which creates debris columns, in combination with tube perforations and screening, exposes more surface area of the debris, thereby enabling easier removal of liquid, primarily water, from the debris. The interior of the canister 10a can be subjected to a vacuum condition, to thereby cause liquid, primarily water, to evaporate from the debris and effectively dry the debris. The perforated columnizing insert 100 is particularly useful when the debris is corium type debris in a finer form (less coarse form). With this type of debris, the drying process is more challenging. Use of the perforated columnizing insert 100 also has the advantage of reducing the risk of nuclear criticality as the fissile content is more organized. More specifically, in terms of structure, the perforated columnizing insert 100 has a plurality of elongated cylindrical tubes 102, seven in this embodiment, that are parallel along their lengths inside of the canister 10a. The tubes 102 can be held together by any suitable mechanism(s). In the preferred embodiment, the tubes 102 are held together with a circular top rim 105 and a circular planar bottom plate 107. At the top, the tubes 102 fit into respective downwardly extending circular sockets 112, which have a diameter slightly larger than that of the tubes 102, and are welded in the sockets 112. At the bottom, the tubes 102 are welded to the bottom plate 107. Debris can be inserted into the tubes 102 via a plurality of circular openings 114 in the top rim 105. Each of the tubes 102 has a side wall 104 extending between a top end and a bottom end and has a plurality of, preferably numerous, perforations 106. Each of the tubes 102 is wrapped with screening 109, part of which is shown in FIG. 27 for illustration purposes (screening 109 not shown in FIG. 28). The screening 109 has a screen mesh size that is smaller than the perforations 106 and that, in the preferred embodiment, is about 100 to about 250 microns. The perforations 106 and screening can take any suitable shape and geometry. In the preferred embodiment, the screening is held on each of the tubes 102 with a wrapping support structure 108. In other embodiments, the wrapping support structure 108 can be eliminated. In these other embodiments, the screening 109 is bonded or mounted to the inside or outside of the tubes 102, or made as an integral part of the tubes 102. Together, the perforations 106 and screening enable gas flow through the side wall to a region between the outside of the insert 100 and the inside surface of the canister 10a, and then out of the canister 10a, to enable evaporation of liquid from the radioactive debris. They also effectively contain the debris so that it does not enter this region. In a sense, the screening 109 delimits the size of the perforations 106 to achieve this containment function. It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible nonlimiting examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention. |
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048881520 | abstract | A grid for the fuel rods of a light water reactor.. It is formed by cylinder portions (11, 13) of polygonal section having cut-out parts (12) in which the projecting portions (15) of those adjacent cylinder portions are overlapped against which the rods (1) bear. The portions are then assembled. |
summary | ||
048184691 | claims | 1. In combination with a value in a nuclear plant, comprising a housing and a valve body, a seal composed of a molded flexible graphite element positioned on said body to seal said valve body against said housing, said element being coated with a thin flexible layer of tantalum. 2. The combination of claim 1 wherein the element is a hollow cone open at both ends, said cone having inner and outer exposed surfaces, said layer coating all of said exposed surfaces. 3. In combination with a valve in a nuclear plant, comprising a housing and valve body, a seal composed of a molded flexible graphite element positioned on said body to seal said valve body against said housing, said element being formed of a hollow cone open at first and second oppositely disposed diametrically different flat annularly shaped end faces, and a thin flexible tantalum layer coating all of the exposed surfaces, said layer including a conically shaped first section coating the outer conical surface of the element, a conically shaped second section coating the inner conical surface of the element, an annularly shaped third section coating the first end face and an annularly shaped fourth section coating the second end face. 4. The combination of claim 3 wherein the third and fourth sections are each welded to the first and second sections. 5. In combination with a valve in a nuclear plant, said valve including a housing with oppositely disposed inlet and outlet ports and a conically shaped valve cone movable in the housing, the cone having a passageway PG,13 which can be moved into alignment with the ports to open the valve and which can be moved out of alignment with the ports to close the valve, a seal composed of conically shaped molded flexible graphite element slid over the cone and having oppositely disposed openings which are aligned with opposite ends of the passageway, and a thin flexible layer of tantalum coating all surfaces of the element, and holding means disposed between the coated element and the valve cone to prevent the coated element from moving relative to the cone when the cone is moved to open and close the valve. 6. The combination of claim 5 wherein the holding means includes first and second holding devices, each device being disposed adjacent and between a corresponding opening in the coated element and the corresponding aligned end of the passageway. 7. The combination of claim 6 wherein the valve cone has a first and second oppositely disposed grooves in its outer surface, each groove being disposed peripherally around the corresponding one of the opposite ends of the passageway, and the coated element has first and second oppositely disposed recesses, each recess being disposed in alignment with the corresponding groove, each device extending between and engaging the corresponding recess and the corresponding groove. |
description | The present invention relates to a method for calculating a PCI margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets. The present invention also relates to an associated electronic calculating system, and a computer program including software instructions which, when executed by a computer, implement such a method. The invention for example applies to light water nuclear reactors, whether using pressurized water or boiling water. A large number of these reactors are currently used around the world. It may be useful, in particular in countries such as France, where more than 50% of electricity is produced using nuclear reactors, for the overall power supplied by these reactors to vary in order to adapt to the needs of the electrical grid that they supply. In particular, it is desirable to be able to operate the nuclear reactors at an intermediate power during a period during which the demand of the grid is low, typically from several days to at least 2 months, before returning to the nominal power. For all that, such an operation of a nuclear reactor, which would make it possible to better use its capacities, must not cause a safety problem, in particular in case of accidental operational transients that may occur for example during, or shortly after, the operation at intermediate power. One aim of the invention is to resolve this problem by providing a method allowing to calculate a PCI margin associated with a loading pattern of a nuclear reactor, making it possible to better exploit the capabilities of the reactor, while retaining a safe operation. To that end, a method is provided for calculating a PCI margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets, the method being implemented by a computer and comprising the following steps: b) calculating a reference principal PCI margin for a reference loading pattern of the fuel assemblies in the core, c) calculating a reference secondary PCI margin for the reference pattern, d) calculating a modified secondary PCI margin for a modified loading pattern of the fuel assemblies in the core, e) calculating a modified principal PCI margin for the modified pattern, depending on a comparison of the modified secondary PCI margin with the reference secondary PCI margin. The calculating method then makes it possible to calculate the value of the PCI margin more precisely, taking account of a variability of the loading patterns of the fuel assemblies in the core of a nuclear reactor for a given radiation cycle, relative to a reference pattern. The reference pattern for example defines a nominal load, also called breakeven load, according to which, from one radiation cycle to another, the fuel assemblies present in the core are similar, in particular in terms of initial enrichment of the nuclear material, and are loaded into the core according to a reproducible loading pattern. The reference pattern then corresponds to an operating cycle of the reactor called breakeven cycle. The modified pattern makes it possible to provide flexibility relative to the reference pattern: it for example defines a transitional load to or from the nominal load, such as a load corresponding to the startup of a first core, a rise to the breakeven point, a change of management of the operation of the reactor, or to an end-of-life cycle of a reactor, or a variation relative to the reference pattern. The modified pattern is also called flexibility pattern. The modified pattern then differs from the reference pattern by at least one fuel assembly 16 loaded into the core, some fuel assemblies 16 for example not being loaded into the core according to the modified loading pattern and being replaced by different fuel assemblies, for example by the nature of the fissile material or its enrichment or the irradiation history of the replacement fuel assemblies. Alternatively, the fuel assemblies 16 loaded into the core 2 are identical between the modified pattern and the reference pattern, the modified pattern then differing from the reference pattern only by the position of at least two fuel assemblies 16 in the core 2. According to advantageous embodiments of the invention, the method comprises one or more of the following features, considered alone or according to any technically possible combinations: when the modified secondary PCI margin is greater than or equal to the reference secondary PCI margin, the modified principal PCI margin is equal to the reference principal PCI margin; and when the modified secondary PCI margin is less than the reference secondary PCI margin, the modified principal PCI margin is less than the reference principal PCI margin; when the modified secondary PCI margin is less than the reference secondary PCI margin, the modified principal PCI margin is equal to the reference principal PCI margin reduced by a corrective factor depending on the deviation between the modified secondary PCI margin and the reference secondary PCI margin; the corrective factor depends on a ratio between the modified secondary PCI margin and the reference secondary PCI margin and is strictly between 0 and 1; step b) comprises the following sub-steps: b1) simulating at least one operating transient of the nuclear reactor, b2) calculating the value reached by at least one physical quantity during the operating transient in at least part of a cladding of a fuel rod, and b3) determining, as reference principal PCI margin, the deviation between the maximum value reached by said value calculated in sub-step b2) during the transient and a technological limit of the fuel rod; the transient simulated in sub-step b1) is a transient chosen from among the group consisting of: an excessive load increase, an uncontrolled withdrawal of at least one group of control clusters, a fall of one of the control clusters, and an uncontrolled dilution of boric acid; the method comprises, before step b), the step of: a) determining a rupture value of the physical quantity characterizing a rupture of the cladding; step a) includes: subjecting previously irradiated fuel rods to experimental nuclear power ramps, calculating the values reached by the physical quantity in at least one cladding broken during a power ramp, and selecting the rupture value as being the minimum value from among the calculated values reached; each of steps c) and d) includes, for each fuel assembly, the following sub-steps: i) simulating an evolution of the operation of the nuclear reactor by applying, to the fuel rods, a nuclear power ramp from the nil power, ii) calculating the values reached by a physical quantity in the claddings of the fuel rods, iii) comparing the values reached to the rupture value, iv) determining a power at break equal to: I) the power associated with the rupture value, if a minimum value from among the values reached calculated in sub-step ii) is equal to the rupture value, or II) infinity, if no value, from among the values reached calculated in sub-step ii), is equal to the rupture value, v) evaluating a power margin by difference between the power at break determined in sub-step iv) and an estimated maximum power in the fuel assembly, the corresponding secondary PCI margin, calculated during each of steps c) and d), is equal to the minimum margin from among the power margins evaluated for the fuel assemblies in sub-step v); neutronic calculations and thermomechanical calculations are done to calculate each PCI margin, and the neutronic calculations and the thermomechanical calculations are coupled to calculate a corresponding principal PCI margin, the thermomechanical calculations being uncoupled from the neutronic calculations to calculate a corresponding secondary PCI margin; the method further comprises the following step: f) determining a limit value to trigger an emergency stop and/or an alarm from the calculated principal PCI margin and for the considered loading pattern of the fuel assemblies in the core; the physical quantity is chosen from among the group consisting of: a constraint or a constraint function in the cladding; and a deformation energy density in the cladding; the method further comprises operating the nuclear reactor by using the calculated principal PCI margin for the considered loading pattern of the fuel assemblies in the core. A computer program is also provided including software instructions which, when executed by a computer, implement a method as defined above. An electronic system for calculating a PCI margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern is also provided, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets, the system comprising: a first calculating module configured to calculate a reference principal PCI margin for a reference loading pattern of the fuel assemblies in the core, a second calculating module configured to calculate, on the one hand, a reference secondary PCI margin for the reference pattern, and on the other hand, a modified secondary PCI margin for a modified loading pattern of the fuel assemblies in the core, a comparison module configured to compare the modified secondary PCI margin with the reference secondary PCI margin, the comparison module further being configured to calculate a modified principal PCI margin for the modified pattern, depending on said comparison of the modified secondary PCI margin with the reference secondary PCI margin. In FIG. 1, a pressurized water nuclear reactor 1 comprises, as is known in itself, a core 2, a steam generator 3, a turbine 4 coupled to an electrical energy generator 5, and a condenser 6. The nuclear reactor 1 comprises a primary circuit 8 equipped with a pump 9 and in which pressurized water circulates, along a path embodied by the arrows in FIG. 1. This water in particular rises through the core 2 to be heated therein while providing the refrigeration of the core 2. The primary circuit 8 further comprises a pressurizer 10 making it possible to pressurize the water circulating in the primary circuit 8. The water of the primary circuit 8 also supplies the steam generator 3, where it is cooled while providing the vaporization of water circulating in a secondary circuit 12. The steam produced by the steam generator 3 is channeled by the secondary circuit 12 toward the turbine 4, then toward the condenser 6, where this steam is condensed by indirect heat exchange with the cooling water circulating in the condenser 6. The secondary circuit 12 comprises, downstream from the condenser 6, a pump 13 and a heater 14. Traditionally, the core 2 comprises fuel assemblies 16 that are loaded in a vessel 18 according to a loading pattern. A single assembly 16 is shown in FIG. 1, but the core 2 for example comprises 157 assemblies 16. The reactor 1 comprises control clusters 20 that are positioned in the vessel 18 above certain fuel assemblies 16. A single control cluster 20 is shown in FIG. 1, but the core 2 for example comprises around sixty control clusters 20. The control clusters 20 are movable by mechanisms 22 to be inserted into the fuel assemblies 16 that they overhang. Traditionally, each control cluster 20 comprises rods, at least some of which include a material absorbing the neutrons. Thus, the vertical movement of each control cluster 20 makes it possible to adjust the reactivity of the reactor 1 and allows variations of the overall power P supplied by the core 2 from the nil power to the nominal power PN, as a function of the pushing of the control clusters 20 into the fuel assemblies 16. Some of said control clusters 20 are intended to regulate the operation of the core 2, for example in terms of power or temperature, and are called regulating clusters. Others are intended to stop the reactor 1 and are called stop clusters. The control clusters 20 are joined into groups based on their nature and intended use. For example, for reactors of type 900 Mwe CPY, these groups are called G1, G2, N1, N2, R, SA, SB, SC, SD. Groups G1, G2, N1 and N2, called power groups, are used overlapping for power regulation, and group R is used for temperature regulation. Groups SA, SB, SC and SD are used for the emergency stopping of the reactor 1. As illustrated by FIG. 2, each fuel assembly 16 traditionally comprises an array of nuclear fuel rods 24 and a support skeleton 26 for the fuel rods 24. The skeleton 26 traditionally comprises a lower end-piece 28, an upper end-piece 30, an array of guide tubes 31 connecting the two end-pieces 28 and 30 and designed to receive the rods of the control clusters 20 and to position spacer-forming grids 32 to position the arrays of fuel rods 24 and guide tubes 31. As illustrated by FIG. 3, each fuel rod 24 traditionally comprises a cladding 33 in the form of a tube closed at its lower end by a lower stopper 34 and at its upper end by an upper stopper 35. The fuel rod 24 comprises a series of pellets 36 stacked in the cladding 33 and bearing against the lower stopper 34. A maintaining spring 38 is positioned in the upper segment of the cladding 33 to bear on the upper stopper 35 and on the upper pellet 36. Traditionally, the pellets 36 have a base of fissile material, for example uranium oxide, and the cladding 33 is made from zirconium alloy. In FIG. 3, which corresponds to a fuel rod 24 derived from manufacturing and before irradiation, radial play J exists between the pellets 36 and the cladding 33. This is illustrated more particularly by the circled enlarged part of FIG. 3. When the reactor 1 is going to operate, for example at its nominal power PN, the fuel rod 24 will be, according to the term used in the art, conditioned. Conditioning is essentially characterized by the closing of the play J between the pellets 36 and the cladding 33, due to the creep of the cladding 33 and the swelling of the pellets 36. More specifically, the following steps are for example distinguished for each fuel rod 24 during irradiation: 1) Under the effect of the pressure difference between the outside (water from the primary circuit 8) and the inside of the fuel rod 24, the cladding 33 gradually deforms by creeping radially toward the inside of the fuel rod 24. All other things being equal, the creep speed of the cladding 33 is one characteristic of its component material. Furthermore, the fission products, the majority of which are retained in the pellet 36, cause swelling of the pellet 36. During this phase, the stress exerted on the cladding 33 in terms of constraints results solely from the pressure differential existing between the outside and the inside of the fuel rod 24. The stresses in the cladding 33 are compression stresses (conventionally negative).2) The contact between the pellet 36 and the cladding 33 begins after a length of time that essentially depends on local irradiation conditions (power, neutron flux, temperature, etc.) and the material of the cladding 33. In reality, the contact is established gradually over a period that begins with gentle contact followed by the establishment of firm contact. The increased contact pressure of the pellet 36 on the inner face of the cladding 33 leads to an inversion of the stresses in the cladding 33, which become positive and tend to exert tensile stress on the cladding 33.3) The swelling of the pellet 36 continues, and the pellet 36 then imposes its deformation on the cladding 33 toward the outside of the fuel rod 24. In the established steady state, this expansion is slow enough for the relaxation of the material of the cladding 33 to allow an equilibrium of the forces in the cladding 33. An analysis shows that under these conditions, the level of the tensile stresses is moderate (several tens of MPa) and does not present any risk with respect to the integrity of the cladding 33. If there is no risk of rupture of the cladding 33 in a steady state due to the thermomechanical equilibrium in the cladding 33 at fairly low stress levels, a risk appears once the power supplied by the fuel rod 24 varies greatly. Indeed, a power increase generates a temperature increase in the fuel rod 24. Given the difference in mechanical characteristics (thermal expansion coefficient, Young's modulus) and the temperature difference between the pellet 36 of fissile material and the cladding 33 made from zirconium alloy, the pellet 36 will expand more than the cladding 33 and impose its deformation on the latter. Furthermore, an operation at intermediate power lasting several days results in deconditioning the fuel rods 24. For the portions of the fuel rods 24 where the contact between the cladding 33 and the pellets 36 is not established, the radial play J becomes greater. Regarding the portions of the fuel rods 24 where the play J was closed, the play J can open again. In case of open play J, the compression creep of the cladding 33 by pressure effect resumes. This results in increased stresses in the cladding 33 when the accidental transient occurs. Furthermore, the presence of corrosive fission products, such as iodine, in the space between the cladding 33 and the pellet 36 creates the conditions for corrosion under stress. Thus, the deformation imposed by the pellet 36 on the cladding 33 during a power transient, or a power variation, can cause a rupture of the cladding 33. Yet such a rupture of the cladding 33 is not acceptable for safety reasons, since it may result in the release of fission products into the primary circuit 8. Power transients may occur during normal operation of the reactor 1, i.e., in so-called category 1 situations. Indeed, power variations may be necessary in particular to adapt to the electrical energy needs of the power grid that the generator 5 supplies. Power transients may also occur in so-called category 2 accidental situations, such as excessive charge increase, uncontrolled withdrawal of power control cluster group(s) 20, boric acid dilution or undetected fall of control clusters 20. Starting from the state of the balance of the margins obtained in normal operation, the acceptable operating duration and intermediate power is determined so as to guarantee the non-rupture by pellet-cladding interaction of the claddings 33 present in the core 2 in case of category 2 power transient, also called class 2 power transient. To guarantee the integrity of the fuel rods 24 with respect to the pallet-cladding interaction, a margin is calculate with respect to the rupture risk of a cladding 33 by pellet-cladding interaction (PCI) for a loading pattern of the reactor 1; this margin is called PCI margin. Each PCI margin is a deviation relative to a characteristic quantity of the nuclear reactor 1 and its core 2, i.e., a delta of said characteristic quantity of the nuclear reactor 1, this deviation coming from taking account of the rupture risk of the claddings 33 by the pellet-cladding interaction. Each PCI margin is for example chosen from among the group consisting of: a power margin, a margin in a thermomechanical quantity associated with the cladding 33, a margin in an operating duration of the reactor 1 at an intermediate power. The characteristic quantity of the nuclear reactor 1, a deviation, or delta, of which is determined to calculate the PCI margin, is then the nuclear power, the thermomechanical quantity associated with the cladding 33, or the operating duration of the reactor 1 at intermediate power. One skilled in the art will understand that the higher the PCI margin is, the lower the likelihood of rupture of a cladding 33 is. To that end, one for example uses an electronic system 40, in particular a computer system, for calculating a PCI margin associated with a loading pattern of the nuclear reactor 1, like that shown in FIG. 4. The calculating system 40 comprises a first calculating module 42 configured to calculate a reference principal PCI margin for a reference loading pattern of the fuel assemblies 16 in the core 2. The calculating system 40 comprises a second calculating module 44 configured to calculate, on the one hand, a reference secondary PCI margin for the reference loading pattern of the nuclear fuel assemblies, and on the other hand, a modified secondary PCI margin for a modified loading pattern of the fuel assemblies 16 in the core 2, modified relative to the reference pattern. Each principal PCI margin and each secondary PCI margin are each a PCI margin of the aforementioned type, for example a power margin, a margin on the thermomechanical quantity, a margin on the operating duration at intermediate power. The principal PCI margin and the secondary PCI margin are for example of the same type Alternatively, the principal PCI margin and the secondary PCI margin are each of different types. The principal PCI margin is for example a margin on the thermomechanical quantity or a margin on the operating duration at intermediate power. The secondary PCI margin is for example a power margin. One skilled in the art will understand that the secondary PCI margin is by definition the PCI margin calculated by the second calculating module 44, and that the name secondary PCI margin is not in particular related to the secondary circuit 12, the reference principal PCI margin also being calculated by the first calculating module 42. The calculating system 40 comprises a comparison module 46 configured to compare said modified secondary PCI margin with a reference secondary PCI margin, the comparison module 46 further being configured to calculate a modified principal PCI margin for the modified pattern, depending on the result of said comparison of the modified secondary PCI margin with the reference secondary PCI margin. When said modified secondary PCI margin is less than the reference secondary PCI margin, the comparison module 46 is configured to calculate a value of the modified principal PCI margin that is less than that of the reference principal PCI margin. Otherwise, when said modified secondary PCI margin is greater than or equal to the reference secondary PCI margin, the modified principal PCI margin is equal to the reference principal PCI margin. This modified principal PCI margin is supplied to the operator of the nuclear reactor 1 having to carry out the modified loading pattern for adaptation, if necessary, of its operating technical specifications, in particular the authorized operating durations at intermediate power. The modified PCI margins, namely the modified principal PCI margin and the modified secondary PCI margin, are also called flexibility PCI margins, said PCI margins being associated with the modified pattern, also called flexibility pattern. As an optional addition, the calculating system 40 comprises a determining module 48 configured to determine, from the value of the calculated principal PCI margin corresponding to the loading pattern of the reactor 1, a limit value to trigger an emergency stop and/or an alarm of the nuclear reactor 1, the limit value to trigger an alarm being reduced relative to or at most equal to the limit value to trigger an emergency stop. In particular, when the loading pattern of the reactor 1 is the modified pattern, also called flexibility pattern, the limit value to trigger an emergency stop and/or an alarm of the nuclear reactor 1 is determined from the value of the calculated modified principal PCI margin, and said triggering limit value for the flexibility pattern is then reduced relative to, or at most equal to, the triggering limit value for the reference pattern. In the example of FIG. 4, the calculating system 40 comprises an information processing unit 50, for example made up of a memory 52 and a processor 54 associated with the memory 52. In this example, it further comprises input/output means 56 and optionally a display screen 58. In the example of FIG. 4, the first computing module 42, the second computing module 44, the comparison module 46 and, as an optional addition, the determining module 48 are each made in the form of software executable by the processor 54. The memory 52 of the information processing unit 50 is then able to store first computing software configured to compute a reference principal PCI margin for a reference loading pattern, second computing software configured to compute a reference secondary PCI margin for the reference loading pattern and a modified secondary PCI margin for the modified loading pattern, comparison software configured to compare the modified secondary PCI margin with the reference secondary PCI margin, and further to compute the modified principal PCI margin based on the comparison between the modified secondary PCI margin and the reference secondary PCI margin. The memory 52 is, optionally and additionally, able to store determining software configured to determine a limit value for triggering an emergency stop and/or an alarm of the nuclear reactor 1 from the calculated principal PCI margin corresponding to the loading pattern, reference or modified depending on whether the reactor 1 is loaded. The processor 54 of the information processing unit 50 is then able to execute the first calculating software, the second calculating software, the comparison software and, optionally and additionally, the determining software. In an alternative that is not shown, the first calculating module 42, the second calculating module 44, the comparison module 46 and, optionally and additionally, the determining module 48 are each made in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or in the form of a dedicated integrated circuit, such as an ASIC (Applications Specific Integrated Circuit). The first calculating module 42 is configured to calculate the reference principal PCI margin for the reference loading pattern, for example according to a first methodology, for example the RPM methodology, for Renovated PCI Methodology. The first calculating module 42 is, according to this example, configured to simulate at least one operating transient of the reactor 1, calculate the value reached by a physical quantity G during the operating transient in at least one portion of a cladding 33 of the fuel rod 24, and determine, as reference principal PCI margin, the deviation between the maximum value reached by said calculated value during the transient and a technological limit of the fuel rod 24. In this methodology, the neutron (simulation of the power transient) and thermomechanical (calculation of a physical quantity in the cladding) calculations are coupled. The physical quantity G is for example the circumferential stress σθ or the radial stress σr in the cladding 33. Alternatively, the physical quantity G is a function of stress(es), for example of the difference for instance between the circumferential stress σθ and the radial stress σr. Also alternatively, the physical quantity G is the deformation energy density DED in the cladding 33. The transient simulated by the first calculating module 42 is preferably a transient chosen from among the group consisting of: an excessive load increase, an uncontrolled withdrawal of at least one group of control clusters 20, a fall of one of the control clusters 20, and an uncontrolled boric acid dilution. The excessive load increase corresponds to a rapid increase in the steam flow rate in the steam generator 3. Such an increase causes an imbalance between the thermal power of the core 2 and the load of the steam generator 3. This imbalance leads to cooling of the primary circuit 8. Due to the moderating and/or regulating effect of the mean temperature in the core 2 by the control clusters 20, the reactivity, and therefore the neutron flux, increase in the core 2. Thus, the overall power P supplied by the core 2 increases quickly. The uncontrolled withdrawal of groups of control clusters 20 while the reactor is operating causes an uncontrolled increase in the reactivity. This results in a rapid increase in the overall nuclear power P and the heat flux in the core 2. Until a discharge valve or pressure release valve of the secondary circuit 12 is opened, the extraction of heat in the steam generator 3 increases less quickly than the power given off in the primary circuit 8. This results in an increase of the temperature and the pressure of the water in the primary circuit 8. To simulate this transient, a withdrawal of the power groups is assumed at the maximum speed of 72 pitches/min until complete removal of the control clusters 20 in question. If one or several control clusters 20 fall into the core, there is an immediate reduction in reactivity and overall power P in the core 2. Without protective action, the imbalance thus caused in the primary circuit 8 and the secondary circuit 12 causes a drop in the entry temperature of the water into the core 2, as well as an increase in the nuclear power by the counter-reactions, for example by Doppler effect, and the temperature regulation, until reaching a new breakeven point between the primary circuit 8 and the secondary circuit 12. The presence in the core 2 of the nuclear reactor 1 of the control cluster(s) 20 having fallen causes a deformation of the radial power distribution, while the removal of the regulating group leads to an axial modification of the power. The uncontrolled boric acid dilution leads to a decrease of the boron concentration of the water in the primary circuit of the reactor due to a failure of a system of the reactor 1. It causes an insertion of reactivity, which leads to a local increase of the linear power in the core 2. The technological limit of a fuel rod 24 is established from values reached by the physical quantity in claddings during experimental power ramps, done in test reactors, on fuel rod segments representative of fuel rods 24 and previously irradiated in a nuclear power reactor and having different combustion rates. The technological limit of the physical quantity corresponds to the minimum value of the physical quantity from among the values reached during experimental tests. Below this limit, no fuel rod 24 rupture by pellet-cladding interaction is considered. Above it, the likelihood of a cladding rupture by pellet-cladding interaction is not nil. The second calculating module 44 is configured to calculate each secondary PCI margin, for example using a second methodology different from the first methodology, for example the methodology called power at break methodology. The second calculating module 44 is, according to this example, for each fuel assembly 16, configured to simulate an evolution of the operation of the nuclear reactor 1 by applying, to each fuel rod 24, a nuclear power ramp from the nil power, in order to calculate the values reached by a physical quantity locally in each cladding 33 of each fuel rod 24 present in the core 2 and to determine, if applicable, a local power at break equal to the power associated with the local power of the physical quantity when this value reaches the technological limit. If the technological limit is not reached, the local power at break at the considered point is infinite. In this methodology, the simulated power ramp is a theoretical ramp, independent of the neutronic studies, and the thermomechanical calculations are then uncoupled from the neutronic calculations. The second calculating module 44 is further configured to evaluate, at each point of the core 2, a power margin by difference between the power at break calculated for a loading pattern and a local maximum power estimated at the same moment of the irradiation cycle for the considered loading pattern, the secondary PCI margin calculated according to the second methodology then depending on the minimum margin from among the power margins thus evaluated. The calculated secondary PCI margin is for example equal to the minimum margin from among said evaluated power margins. The estimated maximum power is for example a power envelope at any point of the core 2 and taking account of all of the limiting transients. This estimated maximum power in particular takes into account power transients that may occur in so-called category 2 accidental situations. One skilled in the art will then understand that, in the example described above, the first calculating module 42 is more generally configured to calculate a principal PCI margin according to the first methodology, called renovated PCI methodology, and that the second calculating module 44 is more generally configured to calculate a secondary PCI margin, reference or modified, according to the second methodology, called power at break methodology. The comparison module 46 is then configured to compare the modified secondary PCI margin with said reference secondary PCI margin, and to deduce the modified principal PCI margin therefrom. When the modified secondary PCI margin is greater than or equal to the reference secondary PCI margin, the comparison module 46 is then configured to validate, as modified principal PCI margin, associated with the modified loading pattern, the value of the reference principal PCI margin. When the modified secondary PCI margin is less than the reference secondary PCI margin, the comparison module 46 is configured to calculate a value of the modified principal PCI margin that is less than that of the reference principal PCI margin. The modified principal PCI margin is, for example, calculated by applying a corrective factor to the reference principal PCI margin. The corrective factor is for example a positive value subtracted from the reference principal PCI margin, or a multiplicative factor strictly between 0 and 1. The corrective factor preferably depends on the deviation between the modified secondary PCI margin and the reference secondary PCI margin. The corrective factor for example depends on a ratio between the modified secondary PCI margin and the reference secondary PCI margin. The modified principal PCI margin is then for example calculated by multiplying the reference principal PCI margin by the modified secondary PCI margin and the reference secondary PCI margin. The modified principal PCI margin is sent to the operator needing to carry out said modified loading pattern in order to adapt, if needed, the protection thresholds of his reactor 1 that are unchanged, the operating duration at intermediate power during the radiation cycle, and therefore to best exploit the capacities of the reactor 1 while reducing the risks of damage to the fuel rods 24. Optionally and additionally, the determining module 48 is configured to determine the limit value for triggering of an emergency stop and/or an alarm from the calculated principal PCI margin and according to the considered loading pattern, the reference principal PCI pattern being used when the loading pattern is the reference loading pattern, and the modified principal PCI pattern being used when the loading pattern is the modified loading pattern. In other words, the determining module 48 is configured to determine emergency stop and/or alarm thresholds as a function of the calculated principal PCI margin, and more generally to use the calculated principal PCI margin in order to control the reactor 1. The method for calculating a PCI margin associated with a loading pattern is illustrated by the flowchart of FIG. 5. During a first step 100, a reference principal PCI margin is calculated by the first calculating module 42 for the reference loading pattern of the fuel assemblies 16 in the core 2. The reference principal PCI margin is preferably calculated using the RPM methodology, as previously described. One skilled in the art will note that document FR 2 846 139 A1, in particular in pages 9 to 19, in light of FIGS. 5 to 11, also relates to the RPM methodology. The pellet-cladding interaction being local by nature, the risk of cladding rupture is determined from the thermomechanical state of the fuel rods 24 in each mesh of the core 2 of the nuclear reactor 1. The thermomechanical state of a fuel rod 24 at a given moment depends on the power histories experienced by said fuel rod 24 from its first insertion in new condition into the core 2 up to the moment of the calculation. To calculate the reference principal PCI margin, the first calculating module 42 begins, for example, by determining a value of a physical quantity G for each axial mesh of each fuel rod 24 present in the core 2 of the reactor 1. The power histories are created by the first calculating module 42 for each fuel rod 24 present in the core 2, for example by finite element modeling of the neutronic behavior of the fuel rods 24. The operating histories relative to each fuel rod 24 are generated for different operating modes of the core 2, namely: the basic operation, where the overall power P of the core 2 is equal to its nominal power PN, the operation at intermediate power with the control clusters 20 inserted into the fuel assemblies 16, the operation at intermediate power with the control clusters 20 removed from the fuel assemblies 16. The histories can be generated taking account of different intermediate power levels, for example 10% PN, 30% PN, 50% PN, etc. The first calculating module 42 next simulates at least one operating transient of the nuclear reactor 1, such as one or several accidental operating transients of the reactor 1 that cause abrupt power variations. The accidental transients are for example simulated from simulated initial conditions corresponding to a so-called category 1 situation, at several moments in each cycle. The simulated transients are the so-called category 2 accidental transients causing the strongest and fastest power variations in the core 2, such as the transients previously described, namely the excessive load increase, the uncontrolled withdrawal of groups of control clusters 20, while the reactor 1 is powered on, and falling cluster(s) 20. The first calculating module 42 then calculates the maximum value reached by the physical quantity G, such as the circumferential stress σθ, during the operating transient in each axial mesh of each fuel rod 24, then compares, for each axial mesh, said maximum value to said technological limit and determines the PCI margin as being the difference between the technological limit and the maximum value of the physical quantity on the core 2. During a second step 110, the reference secondary PCI margin is calculated by the second calculating module 44 for the reference loading pattern of the fuel assemblies 16 in the core 2. The reference secondary PCI margin is preferably calculated using the second methodology, called power at break methodology. The second calculating module 44 then simulates, for each fuel assembly 16, an evolution of the operation of the nuclear reactor 1 by applying, to each axial mesh of each fuel rod 24, after a plateau 112 with substantially constant power, a power ramp 114 from the nil power, as shown in FIG. 6. The second calculating module 44 then calculates the values reached locally in each axial mesh of each fuel rod 24, by a physical quantity and, if the technological limit is exceeded, determines a power at break Plin_rupt equal to the power associated with the physical quantity at break. In the example of FIG. 6, the power ramp 114 is a linear power ramp, and the physical quantity is the deformation energy density DED in the cladding 33, the power at break Plin_rupt then corresponding to the maximum deformation energy density DEDMAX, i.e., to the value of the deformation energy density reached when the cladding 33 ruptures. The second calculating module 44 next evaluates, for reached each axial mesh of each fuel rod 24, a power margin by difference between the power at break and the maximum power over all of the transients, the calculated secondary PCI margin according to the second methodology then depending on the minimum margin from among the power margins evaluated for each axial mesh of each fuel rod 24 of each fuel assembly 16. During the following step 120, the second calculating module 44 calculates the modified secondary PCI margin for the modified loading pattern of the fuel assemblies 16 in the core 2. The modified loading pattern for example differs from the reference loading pattern by at least one fuel assembly loaded into the core. Alternatively, the fuel assemblies 16 loaded into the core are identical between the modified loading pattern and the reference loading pattern, the modified pattern then differing from the reference pattern by the position of at least two fuel assemblies in the core 2. The modified secondary PCI margin is preferably calculated using the second methodology, called power at break methodology, i.e., as indicated previously for step 110, but with the modified loading pattern. During the following step 130, the comparison module 46 then compares said modified secondary PCI margin with said reference secondary PCI margin, and validates, as modified principal PCI margin, the reference principal PCI margin previously calculated, when said modified secondary PCI margin is greater than or equal to said reference secondary PCI margin. When said modified secondary PCI margin is less than said reference secondary PCI margin, the comparison module 46 calculates the modified principal PCI margin, the latter then having a value lower than that of the reference principal PCI margin previously calculated, for example by applying a corrective factor to said reference principal PCI margin. The corrective factor is for example a positive value subtracted from the reference principal PCI margin, or a multiplicative factor strictly between 0 and 1. The corrective factor preferably depends on the deviation between the modified secondary PCI margin and the reference secondary PCI margin. The corrective factor for example depends on a ratio between the modified secondary PCI margin and the reference secondary PCI margin. The modified principal PCI margin is then for example obtained by multiplying the reference principal PCI margin by the modified secondary PCI margin and the reference secondary PCI margin. This principal PCI margin value, in particular the modified principal PCI margin when the reactor 1 is loaded according to the modified pattern, is supplied to the operator of the nuclear reactor 1 having to carry out the modified loading pattern for adaptation, if necessary, of its operating technical specifications. Optionally and additionally, from this value of the modified principal PCI margin, associated with the modified loading pattern, the determining module 48 then establishes emergency stop and/or alarm thresholds, and more generally uses the modified principal PCI margin to reduce, if applicable, the emergency stop and/or alarm thresholds to control the reactor 1. Thus, the calculating method and the calculating system 40 according to the present disclosure make it possible to calculate a PCI margin, taking to account a variability of the loading patterns, considering for example a transitional load to or from the nominal load, such as a load corresponding to the startup of a first core, a rise to the breakeven point, a change of management of the operation of the reactor, or to an end-of-life cycle of a reactor, or a variation relative to the reference pattern. The calculating method and the calculating system 40 according to the present disclosure also make it possible to adjust, if applicable, the settings for certain stoppage or alarm thresholds of the nuclear reactor 1 to lower values if necessary and to convert the deviation corresponding to the PCI margin to an authorized operating duration at intermediate power. It is thus possible to provide safe operation of the nuclear reactor 1, while best exploiting its capacities, in particular in case of prolonged operation at intermediate power (POIP). The calculating method and the calculating system 40 according to the present disclosure thus allow a better match between fuel management and the maneuverability of the reactor 1 for the operator: choice of loading pattern, justification for transition cycles, possibility of extending POIP durations. |
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061608637 | abstract | A nuclear reactor coolant system includes a primary coolant circuit connected to a secondary coolant circuit. A desired amount of coolant is bled from the primary circuit to the secondary circuit for purification and controlling chemical composition of the coolant. Variable speed charging pumps are provided in the secondary circuit to pump coolant back into the primary circuit at variable pressures and flow rates. A pressurizer level control system is also disclosed for controlling pump speeds. |
042773075 | claims | 1. In a method of restoring crystal lattice order in a carbon containing Si monocrystal by annealing this crystal at a minimum temperature, wherein such Si monocrystal is doped by neutron irradiation within a nuclear reactor and is then annealed as a function of irradiation conditions (ratio of thermal to fast neutrons) therein and as a function of the amount of carbon within such irradiated Si monocrystal, the improvement comprising: (a) when the ratio of the thermal to fast neutrons within such nuclear reactor is in the range of 1:1 to less than 10:1 and (b) when the ratio of thermal to fast neutrons within said nuclear reactor is in the range of 10:1 to less than 100:1 and |
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abstract | A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train. |
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056595913 | summary | CROSS-REFERENCE TO RELATED APPLICATION This application is a Continuation of International Application Ser. No. PCT/DE94/01473, filed Dec. 12, 1994. BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a containment spray system for a light-water reactor, having a water trough in a safety tank and having a spray branch, a pump and an outlet-side spray nozzle array, connected to the water trough, for injecting water into the containment in finely dispersed form in the event of an operational incident. One such containment spray system is known from German Patent DE 22 07 870 C3, corresponding to U.S. Pat. No. 3,966,548. In that system, the water trough communicates with a sump cooler disposed in the containment through supply and drainage lines. Accordingly, not only trough water but water from the sump cooler as well is used for the spraying. Such containment spray systems have the task of spraying water being aspirated through a pump, in finely dispersed form in the safety tank, in order to allow both the temperature and the pressure in the safety tank to be reduced and also to allow radioactive aerosols, which form inside the safety tank to be bound, in an incident that cannot reach the outside. Containment spray systems like that referred to above, which aspirate the spray water from the sump of the safety tank, cannot spray with the desired fineness because if the return cooling water and emergency core cooling water fed into the primary loop during the incident is returned to it, the sump can contain contaminants or impurities that can stop up the nozzles. Published Japanese Patent Application 60-31092 describes a spray apparatus for a nuclear reactor with a pressure vessel. The pressure vessel is surrounded by a safety tank in which two water-filled chambers are present below the pressure vessel. The spray apparatus is disposed both on the walls of the safety tank and on a ceiling of the water-filled chamber. The spray apparatus on the safety tank wall is supplied with water from the chamber or from an additional tank located outside the safety tank through a pump, which is disposed in a separate chamber outside the safety tank. German Published, Non-Prosecuted Patent Application DE 33 02 773 A1, corresponding to U.S. Pat. No. 4,587,080, describes an emergency core cooling system for a pressurized water nuclear reactor plant. The emergency core cooling system has a building spray pump that communicates with a fuel exchange and water storage tank. Through the emergency core cooling system, if an elevated pressure occurs in the reactor building, water is sprayed in through a spray apparatus on the ceiling of the reactor building. The water is pumped to the spray apparatus from an emergency water storage tank located inside the reactor building or a water storage tank located outside the reactor building through a pump, in particular a low-pressure pump. The pump is located in a directly attached structure outside the reactor building. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a containment spray system for a light-water reactor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which assures highly effective trapping of fission products, suppression of pressure and heat dissipation over long-term operation in the context of overcoming severe incidents and which excels in having substantially smaller spray droplet sizes than with previously known spray systems. The novel spray system is not intended to share a supply of boron water with the nuclear emergency core cooling and aftercooling systems, in order to make it possible to avoid any competing or rival circuits. Another aspect of the stated object is that the containment spray system according to the invention should be disposed entirely inside the containment, except for energy supply devices. With the foregoing and other objects in view there is provided, in accordance with the invention, in a light-water reactor having a safety tank defining a containment, a containment spray system, comprising a water trough being disposed in the safety tank and having a bottom; and an immersion pump disposed in the vicinity of the bottom of the water trough, a spray branch and an outlet-side spray nozzle array, connected to the water trough for injecting water into the containment in finely dispersed form in the event of an operational incident. It is characteristic for the invention that except for the electrical energy supply for the spray pump, the novel containment spray system is disposed inside the containment. It includes an immersion pump which is disposed inside a water trough near the bottom, a riser line and the distribution system having the spray nozzles. In accordance with another feature of the invention, the water trough is a fuel assembly storage trough that during normal operation is not used and is decoupled from a reactor sump circuit and in particular is filled with borated water. The spray medium is the boron water of the fuel assembly trough which contains fuel assemblies only in the fuel assembly changing phase. The boron water surrounds the spray pump. In accordance with a further feature of the invention, the fuel assembly trough is an inner trough toward the reactor pressure vessel. In accordance with an added feature of the invention, protection against the effects of severe accidents is provided by suitable devices or coverings of the fuel assembly trough, particularly in the region of the surface of the water. Rubble and other contaminants are thus unable to reach the interior of the fuel assembly trough, so that on one hand the spray pump is protected and on the other hand nothing but clear spray medium is available. Accordingly, small bore diameters for the spray nozzles are possible which in turn brings about the desired high effectiveness of the spraying. In accordance with an additional feature of the invention, the spray system of the invention has a bore diameter of the spray nozzles and a feed pressure of the immersion pump ensuring that the maximum droplet diameter of a spray mist being produced is 100 .mu.m. Preferably, droplet diameters in the range below 100 .mu.m are employed. The feed pressure in the lower range must be raised in accordance with the nozzle bore diameters. In accordance with a concomitant feature of the invention, for a bore diameter in the range between 0.5 mm and 1 mm, the feed pressure of the immersion pump is between approximately 3 bar and 80 bar and for a bore diameter in the range between 1 mm and 1.5 mm, the feed pressure of the immersion pump is between approximately 6 bar and 80 bar. The advantages attainable with the invention and/or its features are considered to be above all that: the novel spray system does not or need not have any water supply shared with the nuclear emergency core cooling and aftercooling systems; the spray pump is located in the containment; the spray pump is constructed as an immersion pump; the spray pump is or may be disposed in the inner fuel assembly trough which is filled with boron water, in such a way that it is secure against the effects of a severe accident; the spray pump has optimal inflow conditions; clean boron water is used for the spraying; minimal-sized spray droplets with a diameter of less than 100 .mu.m are possible; and the supply of boron water of the inner fuel assembly trough is pumped for long periods into the sump of the containment. 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 containment spray system for a light-water 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. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. |
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051475995 | abstract | A fuel assembly for a nuclear reactor with a number of parallel fuel rods which are retained by means of spacer lattices and guide tubes (3), which guide tubes (3) are also fixed to the spacer lattices, a top tie plate (4) and a bottom tie plate between which the guide tubes (3) with associated fuel rods are fixed. The top tie plate (4) has been provided with through-holes (10) for connection to a top sleeve (7) joined to the upper end surface of the respective guide tube (3). According to the invention, there is arranged inside the top sleeve (7) a first locking element (9) for cooperation with a second locking element (13). This is arranged on a guide sleeve (11) which is insertable through a hole (10) in the top tie plate (4), which hole corresponds to the respective top sleeve (7). |
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abstract | A support plate for retaining tube array spacing within a heat exchanger tube and shell structure. The support plate having a plurality of individual tube receiving apertures formed therein. Each apertures has at least three inwardly protruding members and bights are formed therebetween when the tube associated therewith is lodged in place to establish secondary fluid flow through the support plate. The inwardly protruding members terminate in flat lands that restrain but do not all contact the outer surface of the respective tube. These flat lands minimize fretting wear and eliminate potential gouging of the outer wall of the tube. The plate wall forming each aperture has an hourglass configuration which, inter alia, reduces pressure drop, turbulence and local deposition of magnetite and other particulates on the support plates. |
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claims | 1. A jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump comprising:a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; anda self vibration damping structure configured such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path. 2. The jet pump according to claim 1, wherein the self vibration clamping structure includes a narrowing clearance flow path configured to gradually narrow the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe toward an upper end of the diffuser pipe. 3. The jet pump according to claim 2, wherein the narrowing clearance flow path is defined by the outer pipe wall of the inlet mixer pipe configured to gradually increase an outer diameter thereof with distance away from a lower end of the inlet mixer pipe, and the inner pipe wall of the diffuser pipe configured such that an inner diameter thereof is uniform. 4. The jet pump according to claim 2, wherein the narrowing clearance flow path is defined by the inner pipe wall of the diffuser pipe configured to gradually increase an inner diameter thereof with distance away from the upper end of the diffuser pipe, and the outer pipe wall of the inlet mixer pipe configured such that an outer diameter thereof is uniform. 5. The jet pump according to claim 2, wherein the narrowing clearance flow path is defined by the outer pipe wall of the inlet mixer pipe configured to gradually increase an outer diameter thereof with distance away from a lower end of the inlet mixer pipe, and the inner pipe wall of the diffuser pipe configured to gradually increase an inner diameter thereof with distance away from the upper end of the diffuser pipe. 6. The jet pump according to claim 2, further comprising a slip joint clamp provided so as to cover an opening edge of the diffuser pipe, and inserted into the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe;wherein the narrowing clearance flow path is defined by an inner wall of the slip joint clamp configured to gradually decrease an inner diameter thereof with distance away from a lower end of the slip joint clamp, and the outer pipe wall of the inlet mixer pipe. 7. The jet pump according to claim 2, further comprising a slip joint clamp provided so as to cover an opening edge of the inlet mixer pipe, and inserted into the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe;wherein the narrowing clearance flow path is defined by an outer wall of the slip joint clamp configured to gradually increase an outer diameter thereof with distance away from a lower end of the slip joint clamp, and the inner pipe wall of the diffuser pipe. 8. The jet pump according to claim 1, wherein the self vibration clamping structure has a configuration in which the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe has a minimum clearance flow path width on a downstream side in a coolant water pumping direction, and a maximum clearance flow path width on an upstream side in the coolant water pumping direction, as well as is configured such that a value of “(the maximum clearance flow path width−the minimum clearance flow path width)÷(the minimum clearance flow path width)” is less than 1. 9. The jet pump according to claim 1, wherein the self vibration damping structure comprises a labyrinth structure provided on any one side of the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe, the labyrinth structure forming a turbulent flow in a clearance flow flowing through the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe. 10. The jet pump according to claim 9, wherein the labyrinth structure is provided on any one of the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe. 11. The jet pump according to claim 1, wherein the self vibration damping structure is provided on any one of the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe, and comprises a ridge structure that projects so as to block a clearance flow flowing through the clearance flow path for pumped coolant water defined by the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe. 12. The jet pump according to claim 11, wherein the ridge structure is provided on any one of the outer pipe wall of the inlet mixer pipe and the inner pipe wall of the diffuser pipe. 13. A jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump comprising:a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; anda self vibration damping structure including a groove portion provided on any one side of an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe, and a convex portion provided on the other side and being fit into the groove portion with a minute clearance left therebetween. 14. A jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump comprising:a non-slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by abutting an opening edge of the inlet mixer pipe against an opening edge of the diffuser pipe. 15. The jet pump according to claim 14, wherein any one side of the opening edge of the inlet mixer pipe and the opening edge of the diffuser pipe is formed into a convex sphere, and the other side is formed into a concave sphere that receives the convex sphere. 16. A method for restraining vibration of a jet pump disposed in a reactor pressure vessel of a boiling water reactor, in which an inlet mixer pipe and a diffuser pipe are connected to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween, to cause a forced circulation of coolant water in the reactor pressure vessel, the method including:controlling a flow of a clearance flow such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path. |
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abstract | Disclosed embodiments include nuclear fission reactors, nuclear fission fuel pins, methods of operating a nuclear fission reactor, methods of fueling a nuclear fission reactor, and methods of fabricating a nuclear fission fuel pin. |
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044877420 | claims | 1. A fast neutron nuclear reactor comprising a vertically axed vessel containing the reactor core and a volume of liquid metal for cooling the same, a horizontal sealing slab sealing the upper part of the vessel, at least one pre-vacuum pump and at least one heat exchanger respectively ensuring in operation the circulation of the liquid metal in the core and its cooling, as well as at least one device for removing the residual power ensuring the cooling of the liquid metal in the case of a stoppage of the pre-vacuum pumps, wherein the residual power removal device comprises an evaporator incorporating a bundle of tubes in glove finger-like form immersed in the liquid metal, so as to pass into the vapour phase a heat transfer fluid initially in the liquid phase, an adiabatic collector of said vapour phase incorporating a pipe traversing the reactor slab and a condenser in which the heat transfer fluid in the vapour phase exchanges its heat with an external cooling fluid and condenses in the liquid phase before dropping again into the evaporator by the adiabatic collector and wherein the wall of the pipe constituting the collector, as well as the wall of each of the tubes of the evaporator internally have a capillary structure piping the heat transfer fluid in the liquid phase. 2. A nuclear reactor according to claim 1, wherein the heat transfer fluid is mercury. 3. A reactor according to claim 1, wherein the condenser comprises a caisson or box in which are located at least one substantially horizontal and rectilinear supply collector connected to the upper end of the pipe constituting the adiabatic collector, two condensate receiving collectors positioned below the supply collector and on either side of the vertical plane passing through the latter and two planar bundles of fin tubes connecting the supply collector to the condensate receiving collector in order to define a dihedron with substantially horizontal edges, the cooling fluid being atmospheric air which then enters the box via the interior of the dihedron and leaves it by a chimney or flue positioned above the bundle of tubes. 4. A nuclear reactor according to claim 1, wherein the upper end of the bundle of tubes is installed on a tube plate constituting the lower end of the adiabatic collector and the upper end of each of the tubes projects over a given height above the tube plate in order to define a buffer reservoir for the heat transfer fluid in the liquid phase. 5. A nuclear reactor according to claim 4, wherein the upper end of each of the tubes projecting above the tube plate has at least one row of slits and/or holes on its periphery. 6. A reactor according to claim 1, wherein the evaporator also has a ferrule surrounding the bundle of tubes, which is open at its lower end and has at least one inlet port at its upper end. 7. A reactor according to claim 1, wherein the condenser is supported by the reactor slab and is located in the reactor enclosure. 8. A reactor according to claim 1, wherein the condenser is positioned externally of the reactor enclosure. 9. A reactor according to claim 1, wherein the condenser comprises a caisson or box in which are located a toroidal supply or feeding collector connected to the upper end of the pipe constituting the adiabatic collector, a toroidal collector for receiving the condensate positioned below the supply collector and an annular bundle of fin tubes connecting the supply and condensate receiving collectors, the external cooling fluid being atmospheric air which enters the box by a lateral pipe and leaves it by a chimney or flue positioned above the supply collector. |
039754715 | summary | The invention is directed to a process for the production of fuel compacts which consist of an isotropic radiation resistant graphite matrix of good heat conductivity with coated fuel and/or fertile (breeder) particles embedded therein, for insertion into a high temperature fuel element by providing the coated particles with an overcoat of molding mixture consisting of graphite powder and a thermoplastic binder. An important form of block shaped fuel elements for high temperature nuclear reactors is prisms of electrographite, preferably hexagonal in cross-section, with numerous axial bores which serve in part to receive the fuel bodies and partially for conducting cooling gas. The fuel and fertile materials are added in the form of coated fuel spheres of about 0.5 to 1 mm size which are coated with pyrolytic carbon, i.e, they are coated particles. The fuel nucleus consists of a mixture of uranium-thorium dioxide or uranium-thorium dicarbide. The thorium and the isotope U 238 serve as fertile materials. As the fissile material today there is inserted exclusively the isotope U 235 which can be enriched up to 90% in the uranium-isotope mixture but U 233 or Pu 239 also can be used. Coating of the fuel particles with carbon which generally is formed on the particles from gaseous hydrocarbons in a fluidized bed at temperatures between 1000.degree. and 2000.degree.C. has the function of retaining the radioactive fission products arising during the operation of the reactor in the interior of the individual fuel particles. These particles are embedded in a good thermally conductive carbon matrix and form with this a dimensionally stable compact. Prerequisite for a good thermal conductivity is a carbon matrix with as high as possible a geometrical density and a good crystalline arrangement. The dimensional stability of the compact during the total residence time in the reactor besides assumes as high as possible good isotropy of the physical properties of this matrix. According to a known process, the fuel particles are overcoated with the total necessary amount of molding mixture, consisting of graphite powder and thermoplastic binder resin and molded with heating of the compacts (Redding, U.S. Pat. No. 3,344,211). Since the hardening process already begins during the plasticization, i.e., before a sufficient compression can occur, a relatively high molding pressure is necessary. At the partially necessary high volume loading of coated particles (over 40%) this often leads to injury of the coating of the fuel particles. Exposed fuel, however, causes an inadmissibly high loading of fission products in the cooling cycle of the reactor. In order to avoid the high molding pressure, it was attempted to plasticize the molding mixture at temperatures which do not lead to hardening, and subsequently to effect the hardening by increase in temperature (HROVAT German Offenlegungsschrift 2 154 622). A disadvantage of this is that the energy requirement for heating and cooling is relatively high. The necessarily existing heat capacity of the tools, the conduits and the heating or cooling agents limits the speed of change of the temperature and therewith the throughput. At the usable temperature levels below the limit of hardening the plasticization is incomplete and the introduction of heat into the material to be pressed is correspondingly slow. For reduction of the molding pressure, it has further been proposed (Sturge, Great Britain Patent 1,286,286) to incorporate a mold release agent with the overcoating material prior to coating on the fuel particles. To substantially reduce friction, however, there must be added a relatively high portion of mold release agent. This high portion after the heat treatment leaves behind considerable porosity and considerably impairs the strength and heat conductivity of the compacts thus produced. In order to attain high bonding of fuel and/or fertile particles without destruction of coated particles, moreover, there are known processes in which the intermediate space of the particle packing is filled with a flowable mass. (Goeddel, German Offenlegungsschrift 1764558.) This mass consists largely of thermoplastic binders to which a small portion of finely ground graphite powder is admixed since the mass cannot otherwise be pressed into the narrow hollow space. From this there results the disadvantage that the compacts before the carbonization is not dimensionally stable in the heated condition. Therefore, it can only be expelled from the mold after cooling and must be trimmed in the later heat treatment. The high binder portions cause a considerable weight loss in the carbonization. The remaining geometric matrix density, therefore, is lower (considerably below 1 g/cm.sup.3). Besides there is present a higher carbon portion with lower crystalline arrangement. According to the later position in the reactor core, it is necessary to accommodate different heavy metal loadings in compacts of the same volume. By heavy metals is meant uranium and thorium. In order to balance the filling of the volume and heavy metal loading one after the other, there must be set up an exactly given amount of material to be pressed as over covering material on the fuel particles. Since the overcoating process does not work without loss, the amount given in advance can only be estimated inexactly and, therefore, requires correction. The present invention avoids the abovementioned disadvantages and permits the production of fuel compacts for high temperature-fuel elements with uniformly high matrix density, high strength and high heat conductivity in tight packaging, as well as extremely low stresses in narrow packing, and also extremely low requirements for the fuel particles, whereby the fuel and/or fissile particles are overcoated with a molding mixture made of graphite powder and thermoplastic binder resin. According to the invention, the overcoated particles are provided with hardener and lubricant only on the surface and subsequently compressed in a die heated to a constant temperature of about 150.degree.C., hardened and expelled therefrom as finished compacts. Preferably, hardeners, as for example, hexamethylene tetramine, formaldehyde (or formaldehyde sources such as paraformaldehyde or trioxane) and lubricants for reducing external and internal friction are supplied in a solvent for example water, petrol, benzene, carbon tetrachloride or trichloroethylene which does not dissolve the binder. As lubricants there can be used any conventional mold lubricant, as for example stearic acid, paraffin, long chain alkanols, e.g., octadecanol or fatty oils, e.g., soybean oil. As the hardenable thermoplastic resin binder there can be used resins such as phenol-aldehyde resins, e.g, phenol-formaldehyde novolaks, cresol-formaldehyde resin, phenol-hexamethylentetramine-resin and furfurylalcohol resin. It is advantageous to supply the hardener and lubricant directly after the overcoating process in the same apparatus. It has been found especially good to supply only a part of the required mixture of graphite and binder resin to be pressed as an overcoating to the fuel and/or fertile particles. The remainder necessary to fill the volume is addes as three dimensional pre-compressed granulates of similar granulate size as the overcoated particles. According to the invention these particles are also provided only on the surface with hardener and lubricant. The three-dimensional precompressed granulates when employed can be 5 to 95 % by volume of the total of (1) mixture of graphite and binder present as overcoating on the particles, and (2) the precompressed granulates. The thermoplastic resin binder is employed in conventional proportions, e.g., 5 to 30 % of the total weight of the thermoplastic resin and the graphite. The amount of hardener is not critical and it is used in customary amounts of 1 to 15 % of the binder portion of the matrix to convert the thermoplastic resin to a thermosetting resin. The amount of lubricant also is not critical and is employed in an amount sufficient to supply lubricity, e.g., it can be 2 to 20 % of the weight of the binder portion of the graphite matrix. The hardening which necessarily occurs to some degree in the heating for plasticization and handicaps the compression, according to the process of the invention is according to desire so delayed that the hardener is not homogeneously distributed in the material to be pressed but is only found on the surface of the particles. The thermoplastic phase of the binder despite the relatively high temperature which is held constant is thereby so increased in length of time that it is sufficient for the thorough heating and compression of the compact and this is moldable at lower pressing pressure. The amount of the hardener addition is advantageously so adjusted that the hardening first occurs after the end of the compression and the article to be pressed already shortly after reaching its final dimensions can be expelled again without deformation. Unless otherwise indicated, all parts and percentages are by weight. |
abstract | A radiation source comprising: a source of radiation; a plate having an aperture formed therein, said aperture facing the source of radiation; and means for moving the source when no radiation is desired on the side of the plate away from the source. |
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abstract | A debris trap catches debris falling through a fuel bundle orifice in a nuclear reactor. The debris trap includes a shaft and a debris capture tray attached to an end of the shaft. The debris capture tray includes a tray cavity sized larger than the fuel bundle orifice. |
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042788900 | description | DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a sectional side view of an apparatus for the practice of the present invention. In FIG. 1, target 10 is an insulating material such as sapphire. Target 10 is placed in a beam 12 of ions that has originated in an ion gun 14 and has been collimated to a desired size by an orifice plate 16. Target 10 is attached by a collar 18 which is placed in threaded engagement with a tube 22. One or more O-rings 24 provide a vacuum seal to help maintain the interior 26 under vacuum conditions provided through line 28 from a vacuum pump. A housing 30 supports tube 22 which is insulated electrically from housing 30 by insulating gasket 32 and insulated bolts 34. Housing 30 will typically be maintained at electrical ground for convenience in operation. Housing 30 is also insulated from ion gun 14 by insulating gasket 36 and is mounted to ion gun 14 by insulated bolts 38. Housing 30 is equipped with a viewing port 40, a glass plate held in a vacuum seal by flange 42 which in turn is secured by bolts 44. A viewing port 40 is not necessary for the operation of the invention but can be of assistance in letting an operator see the progress of ion implantation or sputtering. An additional flanges 46 is attached to housing 30 by bolts 48. Two feedthroughs 50 maintain a vacuum seal and permit the insulated passage through flange 46 of two electrical leads 52. Outside the flange 46 leads 52 are connected to the secondary winding 54 of a transformer 56 of which the primary winding 58 is connected to a current source 60. In the interior 26 the electrical leads 52 are connected through a filament 62 that will be heated by the passage of current to emit electrons. One of the leads 52 is also connected electrically through an ammeter 64 to a positive terminal of a voltage source 66. The positive terminal is also connected through an ammeter 68 to tube 22. The negative termial of the voltage source 66 is connected to a current integrator 69 and thence to electrical ground which is connected to housing 30. A substrate 70 is mounted by support 72 to housing 30 in one version of the present invention. Support 72 provides an electrical connection to housing 30 that maintains substrate 70 at electrical ground as well as providing physical support and a path for conducting heat. Substrate 70 is shown in FIG. 1 as being cooled by whatever conduction occurs along support 72 and by radiation within interior 26. Under some conditions of operation, it might be desirable to provide additional cooling for substrate 70 by means such as connecting external water tubing through support 72. This is a minor design modification that will not normally be necessary but that would be accomplished readily if the need for cooling became apparent. FIG. 2 is a partial sectional view of a portion of the apparatus of FIG. 1 taken along section lines 2--2 of FIG. 1. In FIG. 2, electrical leads 52 are seen to be connected to filament 62 which encloses beam 12. Target 10 is illuminated by beam 12 and is held in place by collar 18. Operation of the apparatus of FIGS. 1 and 2 is initiated by establishing a vacuum of the order of 0.2 microtorr in interior 26 with the vacuum pump. Ion gun 14 is a commercially obtained source such as a duoplasmatron, only the exit portion of which is shown in FIG. 1 as ion gun 14. The ion gun is operated to generate a beam of ions directed at target 10. If target 10 were an electrical conductor, then its surface would be an equipotential surface that would conduct intercepted charge away readily. In such a case, the present invention would not be necessary. However, where target 10 is an insulator such as sapphire, silica, magnesia, or the like, the incidence of a beam of ions results in a local buildup of electrical charge that is not readily dispersed because of the insulating properties of the material of the target 10. While such a charge buildup will leak away in time, it sets up an opposing potential before it leaks. This opposing potential will direct the ion beam away from the spots of buildup and cause the ion beam to appear to wander about the surface of the crystal. In extreme cases, the charge buildup may be sufficient to deflect the beam entirely from the insulating surface of the target 10 until the charge has leaked sufficiently. If the apparatus is being operated to implant ions from the beam 12 into target 10, then the result of such charge buildup will be an uncontrolled and nonuniform implantation of ions. If the objective is to sputter atoms of the target 10 onto the substrate 70, then the result of such a charge buildup will be to produce uneven sputtering that will be difficult to control. These disadvantages are overcome by connecting current source 60 to filament 62 through transformer 56. Varying the a-c current of current source 60 will vary the degree to which filament 62 is heated and hence will vary the electron emissivity of filament 62. In operation, the level of current source 60 is varied, typically by adjusting a variable autotransformer, until ammeter 68 reads zero current. This means that the amount of electron current emitted by filament 62 and captured by the target 10 and the other elements at its potential are equal to the ion current in beam 12. It is to be expected that most of the electron current from filament 62 will be attracted to target 10 which would otherwise exhibit a buildup of positive charge from the ions in beam 12. When the current in ammeter 68 is adjusted to zero, the ammeter 64 reads the magnitude of the electron current from filament 62 which is thus equal to the ion beam current. The application of the current that flows through ammeter 64 to current integrator 69 provides a measure of the cumulative amount of charge and hence of the number of ions incident upon target 10. An apparatus for the practice of the present invention has been built and used at the Argonne National Laboratory for the implantation of ions of hydrogen, deuterium, helium, neon and argon into single-crystal sapphire. The targets were 1/2 inch or 3/4 inch in diameter and were either 0.020 or 0.40 inches in thickness. Other targets were sapphire plates 52 mm.times.20 mm.times.2 mm. Typical conditions of bombardment were by ion currents of the order of 70 microamperes at 15 keV. Voltage source 66 was set at 45 volts to prevent loss of electron current to the grounded housing 30. Filament 62 could have been made of any good electron emitter but was a thoria-coated iridium filament. Under some conditions of operation, it might be desirable to assist the vacuum pump in maintaining a vacuum by cooling a portion of the housing 30 or a corresponding thermally conducting surface in contact with the interior 26 to provide cryopumping. This is not generally necessary and has been omitted in FIG. 1 for clarity. In operation, the neutralization of current that was provided by the combination of current from filament 62 and the current in beam 12 resulted in a visibly uniform implantation of ions into the insulating target of sapphire and also resulted in an improved control of ion bombardment of the target for sputtering onto a substrate 70. |
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050193279 | summary | FIELD OF THE INVENTION This invention relates to fuel assembly transfer baskets for pool type nuclear reactors. The invention is specifically directed to an improved assembly transfer basket for transferring fuel assemblies within the vessel of a pool type, liquid metal cooled nuclear reactor. BACKGROUND OF THE INVENTION Pool type, liquid metal cooled nuclear fission reactors typically comprise a vertically positioned tank or vessel having an open upper end provided with a cover member closing off the opening in the upper end. The reactor vessel, which has no components penetrating through its wall structure, contains a core of fissionable nuclear fuel conventionally positioned centrally and adjacent to the lower end of the reactor vessel or tank. The fuel core of fissionable material is submerged within a pool of liquid metal coolant, such as sodium, which substantially fills the reactor vessel to a level sufficient to submerge the fuel units both within the core and handled at a level above the fuel core. Liquid metal coolant is circulated through the fuel core to remove fission produced heat from the core and transfer the heat removed from the core to a heat exchanger for conveyance and use outside of the reactor vessel by means of a fluid pumping system. Operating means comprising fission control rods are suspended down from the reactor vessel top member for reciprocal movement into and out from the fuel core. Typically the area or plenum within the reactor vessel above the surface of the pool of liquid metal is filled with an inert gas such as nitrogen or argon to preclude reactive material from contacting the coolant. Heat generating, fissionable fuel comprising uranium, plutonium and/or thorium metal, or alloys thereof, in the form of small pellets or slugs, is sealed within metal, such as stainless steel, tubes or elongated containers. A plurality of such fuel containing tubes are combined into a single unit or assembly. Typically these reactor fuel core assemblies are of hexagonal or similar angular cross sections, and their lower end is provided with a conical end member to facilitate seating in a bottom support structure. The upper end of the reactor fuel core assembles is provided with a top member having a cylindrical portion of substantially smaller diameter than the assembled body of joined fuel tubes which projects axially upward from the assembly, and an end cap thereon comprising a transverse annular flange of hexagonal or similar multi angular cross section. This configuration of the top member, which resembles the head end of a lag bolt, provides for vertical aligning of the fuel assembly in both core and storage mounting brackets or supports. An in-vessel transfer device extends down from a circular revolving section of the reactor vessel cover member whereby it can move over a substantial cross-sectional area of the central portion of the reactor vessel including the fuel core. The in-vessel transfer device serves to introduce and remove fissionable fuel in the form of the typical assembled bodies into and out from the reactor vessel, and within and about the reactor vessel including to and from the fuel core and internal reactor vessel storage means such as racks. In-vessel transfer devices conventionally comprise a vertical support structure which extends through the sealing reactor vessel top member whereby it can be manipulated by an operator from above the reactor vessel. The vertical support structure is provided with a gripping mechanism for securely attaching to and holding assembled fuel bodies whereby they can be safely and effectively moved about within the reactor vessel remotely by an operator located a distance above the reactor vessel. A conventional type of gripping mechanism mounted on the vertical support structure as a means for extending the operating scope or reach and maneuverability is a device having a panographic action or system. Such a means reciprocally mounted on the vertical support structure provides significantly extended vertical and lateral maneuverability and grasping action for fuel assemblies within the reactor vessel by an externally located operator from a distance above the reactor vessel. Although various grasping systems can be employed for attaching to the fuel assemblies, a preferred means comprises a socket type of union which minimizes the potential for causing damage to the fuel assemblies. A common and suitable socket union for securing fuel assemblies consists of a socket cavity in the uppermost end of the fuel assembly units and a counterpart mating socket extension having retractable lateral projections affixed to the gripping mechanism. Thus, the socket extension can vertically enter down into a mating socket cavity of a fuel assembly with the lateral projections retracted, and upon extension of the lateral projections of the socket while mated within the socket cavity into lateral counterpart receiving recesses, the gripping mechanism will be effectively locked to the fuel assembly for secure transfer within the vessel. A transfer basket or receptacle is conventionally employed with the in-vessel transfer device for the conveyance of fuel core assemblies into and out from the reactor vessel of such pool type, liquid metal cooled nuclear reactors. The typical transfer basket comprises an open top container or receptacle suspended from a support member extending down through the reactor vessel top member and into the vessel interior. The basket member generally consists of an elongated container or receptacle of a size adequate to accept at least one fuel core assembly through an open upper end or top and essentially enclose the assembly within its internal cavity whereby the fuel core assemblies can be effectively retained and securely moved or transferred into and out from the reactor vessel without the possibility of accidental disgorgement. However, the conventional transfer baskets being top loading, the in-vessel transfer device in handling the elongated fuel core assemblies between the fuel core or in-vessel storage racks, must exercise extensive vertical movement in raising the fuel assemblies up above the transfer basket for their introduction or withdrawal through top openings of the transfer baskets. SUMMARY OF THE INVENTION This invention comprises an improved fuel assembly transfer basket for fuel assembly conveyance into and out from the reactor vessel of a pool type of a nuclear reactor. The improved fuel assembly transfer basket of this invention comprises a novel construction enabling lateral loading and unloading of the basket with fuel assemblies through a side access port. OBJECTS OF THE INVENTION It is a primary object of this invention to provide an improved transfer basket for nuclear reactor fuel assemblies. It is an additional object of this invention to provide a side loading and unloading nuclear reactor fuel assembly transfer basket for fuel transfer within a pool type nuclear reactor system. It is a further object of this invention to provide an improved fuel assembly transfer basket for nuclear reactor service that securely supports and grasps fuel assembly units with both vertical and horizontal support means. It is a still further object of this invention to provide an improved fuel assembly transfer basket that enables a reduction in the vertical movement or length of travel of an in-vessel transfer device for loading or unloading fuel assemblies into or out from the transfer basket. It is also an object of this invention to provide an improved fuel assembly transfer basket for conveying fuel assemblies into and out from the reactor vessel of pool type, liquid metal cooled nuclear rectors having a side opening for lateral loading or unloading. |
046438661 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a test device for testing the physical reactions of nuclear fuel pellets and the interaction of nuclear fuel pellets with nuclear fuel rod cladding. More particularly, the present invention is directed to a test device which models the thermal conditions existing within an operating nuclear fuel reactor. 2. The Prior Art In commercial water-cooled nuclear reactors used for central station electric power production, the fuel is based on urania which is sheathed or clad with zirconium alloys such as Zircaloy. Experience in the nuclear industry with fuel rod of Zircaloy-clad urania has indicated several causes for fuel rod failure. Most of these causes have been corrected by improvements in fuel design specifications and improvements in the manufacturing processes. There persists one class of fuel rod failures which has yet to be eliminated and which appears to be of a fundamental nature. These failures are caused by the direct interaction between the irradiated urania fuel, including its inventory of fission products, and the Zircaloy fuel sheath, or cladding. This phenomenon has been called "fuel/cladding interaction" or fuel "pellet-cladding interaction" (PCI). The incidence of such failures is closely linked to the power history of the fuel rod and to the severity and duration of power changes. Pellet-cladding interaction fuel rod failures have occurred in both Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR) as well as in Canadian Deuterium Moderated Reactors (CANDU) and Steam Generating Heavy Water Reactors (SGHWR). To ameliorate this situation, reactor operational procedures have been established which minimize the incidence of fuel rod failures by PCI. While the operational procedures have been successful in reducing the incidence of fuel failures, the procedures are inconvenient to reactor operators and are costly in terms of reduced capacity factor for plant operation and thus in reduced electrical output. There is a strong incentive to provide a remedy that would eliminate the need for these operational procedures. As part of this remedy, it is desirable therefore to test nuclear fuel pellets and the interaction of nuclear fuel pellets with the fuel rod cladding to improve the performance of the fuel, increase the life of the fuel rod, to determine the effects of severe temperature transients on fuel pellets and cladding and so forth. Many such tests cannot be desirably conducted in an operating reactor because variables cannot be satisfactorily controlled, test conditions are too severe, or adequate instrumentation cannot survive. Therefore, it is desirable to have a test device that can model conditions in the core of an operating nuclear reactor. During operation of a nuclear reactor, the fuel pellets, typically uranium dioxide, and the fuel rod cladding interact in three ways which effect the performance of the fuel and the life of the fuel rod: thermal interaction; chemical interaction, including reaction of decay products with cladding; and radioactive reactions, i.e., radiation damage to fuel pellets and cladding. The prior art discloses two approaches to the problem of testing and assessing fuel pellet-cladding interaction. First, destructive testing of nuclear fuel rods after they have been in service is known in the art. Such testing cannot, however, be truly experimental since control and independent manipulation of variables is not possible in an operating nuclear reactor. In addition, reaction of fuel rods to extreme conditions that might damage the reactor cannot be tested, since the most important such tests involve the effects of repeated rapid heating, and wide temperature excursions. Additionally, the long term hostile conditions within an operating nuclear reactor do not permit effective instrumentation of such tests. Second, tests have been conducted on a laboratory basis by using a test section of fuel rod having an electrical heating element embedded along the longitudinal axis of the fuel rod test section. Such a device clearly must heat the test sample from the inside to the outside, so that the hotest portion of the test sample is along the axis of the fuel pellet and the coolest portion is the exterior side wall of the fuel rod cladding. This "inside-out" temperature profile is quite different from the more nearly uniform temperature profile produced in fuel rods of an operating nuclear reactor. Test results from this apparatus are not as reliable as desired because the test apparatus cannot model actual reactor conditions closely, particularly when examining the effects of temperature transients involving wide temperature excursions. Currently, the prior art has no ability to model the in-core temperature profile. This failing has been identified as a major problem in fuel performance testing (see, e.g., "Simulation of Nuclear Fuel Rods by Electrically Heated Rods", S. Malang, K. Rust, Nuclear Technology, Vol. 58, July 1982, pages 53-62). Therefore, a need exists for a method and apparatus for testing pellet-cladding interactions on a small scale in a laboratory before a particular combination of fuel pellets and fuel rods is placed into service. SUMMARY OF THE INVENTION Accordingly, it is a primary object of the invention to provide a test apparatus overcoming these and other deficiencies of the prior art. More particularly, it is an object of the present invention to provide a test apparatus wherein thermal interactions of nuclear fuel pellets and nuclear fuel rod cladding can be observed under realistic conditions without the necessity of actually operating a nuclear reactor. It is a further object of the present invention to provide a test device in which the temperature profile of fuel pellets and fuel rod cladding is very similar to that found inside of the fuel rods of an operating nuclear reactor. It is a further object of the present invention to provide a novel method of testing pellet and cladding interaction. It is a further object of the invention to provide a test apparatus that permits accurate testing of the effects of thermal transients and repeated thermal transients on fuel pellets, fuel rod cladding and their interactions in their actual in service configuration. Accordingly, the present invention provides a method of testing pellet-cladding interaction comprising: inserting a plurality of fuel pellets into a length of fuel rod cladding, connecting a source of microwave radiation to the fuel rod cladding, generating microwave radiation in the microwave source, guiding the microwave radiation through a waveguide into the fuel pellets to heat the fuel pellets with a temperature profile analogous to that occurring in a nuclear reactor, and monitoring the resulting pellet-cladding interactions. Furthermore, the invention includes an apparatus for testing pellet-cladding interaction comprising: a length of fuel rod cladding, a plurality of nuclear fuel pellets inserted into the cladding, means for cooling the fuel rod cladding attached to the fuel rod cladding, means for guiding microwave radiation into one end of the fuel rod cladding, connected to the fuel rod cladding, means for generating microwaves attached to the guiding means, and a reflector attached to the other end of the fuel rod cladding. Another embodiment of the present invention provides an apparatus for testing pellet-cladding interaction comprising: a length of fuel rod cladding on the order 3.5 inches to 12 inches long having an inside diameter on the order from about 0.25 inches to about 0.55 inches, a plurality of fuel pellets forming a fuel column inserted into the fuel rod cladding, means for cooling the fuel rod cladding attached to the fuel rod cladding, means for guiding microwave radiation into each end of the fuel rod cladding, connected to each end, separate means for generating microwaves comprising gyrotons each producing microwaves having a frequency greater than about 16 GHz with an output power greater than about 18 KW, attached to the respective waveguides. |
abstract | A hold-down spring unit for a top nozzle of a nuclear fuel assembly. The hold-down spring unit is coupled to the upper end of the top nozzle of the nuclear fuel assembly. The hold-down spring unit includes a first spring which provides a hold-down force upon the nuclear fuel assembly under start-up conditions and hot full power conditions of a nuclear reactor, and a second spring which provides an additional hold-down force upon the nuclear fuel assembly under start-up conditions of the nuclear reactor. The hold-down margin under start-up conditions and hot full power conditions is reduced, thus enhancing the mechanical and structural stability of the nuclear fuel assembly. |
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description | This is a Continuation Application of International Application No. PCT/JP2008/051119, filed Jan. 25, 2008, which claims priority to Japanese Patent Application No. 2007-014920, filed Jan. 25, 2007. The contents of the aforementioned applications are incorporated herein by reference. 1. Field of the Invention The present invention relates to an optical element used for extreme ultraviolet radiation, an exposure apparatus using this, and a device manufacturing method. 2. Description of Related Art In conjunction with the miniaturization of semiconductor integrated circuits in recent years, exposure technology has been developed which, instead of conventional ultraviolet radiation, uses extreme ultraviolet radiation composed of wavelengths (11-14 nm) that are shorter than this conventional radiation in order to enhance optical system resolution that is attained according to the diffraction limits of light. By this means, it is anticipated that exposure light with a pattern size of approximately 5-70 nm will be feasible, and as the refractive index of materials of this region approaches 1, transmission-refractive type optical elements cannot be used as heretofore, and reflective optical elements are used. For reasons also of transmissivity assurance and the like, the mask used in the exposure apparatus is that of an ordinary reflective optical element. In this regard, in order to attain a high reflectance in each optical element, it is common to alternately laminate atop a substrate a material with a high refractive index and a material with a low refractive index in the employed wavelength region (see, e.g., Japanese Unexamined Patent Application, First Publication No. 2003-14893). In the case where oxygen, moisture or the like remains inside the aforementioned type of exposure apparatus, an oxidation reaction is produced when the surface of the optical element is irradiated with extreme ultraviolet radiation. Due to this, the problem arises that reaction properties of the optical element are degraded, and that life is shortened. Moreover, the light source that is employed by the exposure apparatus not only emits the extreme ultraviolet radiation required for exposure, but also non-exposure light that is unnecessary for exposure. When non-exposure light is included in the source light, it engenders the problems of: (1) degradation of imaging properties of the projection optical system; (2) reduction in resolution of the pattern; and (3) generation of distortions in the alignment accuracy of the sensitive substrate. A purpose of some aspects of the present invention is to offer an optical element which improves optical properties by incorporating the two qualities of oxidation resistance and absorptivity of non-exposure light in a balanced manner. Other purposes are to offer an exposure apparatus which incorporates the aforementioned type of optical element as a projection optical system or the like that uses extreme ultraviolet radiation and to offer a device manufacturing method. An aspect of the present invention provides an optical element including: (a) a substrate used for support; (b) a multilayer film which is supported on the substrate, and which reflects exposure light containing at least one of ultraviolet radiation and soft X-radiation from source light in a prescribed wavelength region; and (c) a protective layer which is provided on the multilayer film, which prevents oxidation of the pertinent multilayer film, and which has an absorption index relative to non-exposure light (other than exposure light) that is larger than the absorption index relative to exposure light. In the aforementioned optical element, with respect to, for example, the protective layer, a single layer may be given the two properties of oxidation resistance and absorptivity of non-exposure light by, for example, changing composition in the depthwise direction. Consequently, it is possible to inhibit oxidation of the optical element, and prevent reduction in the reflectance of the optical element by, for example, the oxidation-resistant portion of a protective layer that is endowed with oxidation resistance. In addition, it is possible to relatively absorb non-exposure light compared to exposure light, and reduce the non-exposure light that is projected onto a sensitive substrate such as a wafer by, for example, the non-exposure-light-absorptive portion of a protective layer that is endowed with the capability of absorbing non-exposure light. Another aspect of the present invention provides an optical element including: (a) a substrate used for support; (b) a multilayer film which is supported on the substrate, and which reflects exposure light comprising at least one of extreme ultraviolet radiation and soft X-radiation from source light in a prescribed wavelength region; (c) and a protective layer which is provided on the multilayer film, which has a surface-side layer on its outermost. As with the aforementioned optical element, this optical element also has oxidation-resistant properties due to the fact that, in a state of saturated oxidation; oxidation does not occur beyond that point. Moreover, it also has absorptivity to non-exposure light, because absorption of non-exposure light occurs more in a state of unsaturated oxidation than in a state of saturated oxidation. In short, it is possible to inhibit oxidation of the optical element, and prevent a reduction in the reflectance of the optical element by means of an oxidation-resistant portion of the protective layer that is saturated by oxidation. In addition, it is possible to relatively absorb non-exposure light compared to exposure light, and reduce the non-exposure light that is projected onto a sensitive substrate such as a wafer by means of a non-exposure-light-absorptive portion of the protective layer that is unsaturated by oxidation. Still another aspect of the present invention provides an exposure apparatus including: (a) a light source which generates extreme ultraviolet radiation; (b) an illumination optical system which guides the extreme ultraviolet radiation from the light source to a mask used for transference; (c) and a projection optical system which forms a pattern image of the mask on a sensitive substrate. In this exposure apparatus, at least any one of the mask, the illumination optical system, and the projection optical system contains the aforementioned optical element. By using at least one of the aforementioned optical elements in the aforementioned exposure apparatus, it is possible to inhibit oxidation of the surface of the pertinent optical element inside the apparatus, thereby enabling maintenance of the reflective properties of the optical element over a long period. This means that the throughput of the exposure apparatus can be maintained over a long period, and that the exposure apparatus can be given a long life. By using the aforementioned optical elements, it is also possible to reduce non-exposure light, from the light source, that is unnecessary for exposure, and to suppress the non-exposure light that is received by the sensitive substrate or the like, thereby enabling achievement of a high-precision exposure apparatus. Still another aspect of the present invention provides a device manufacturing method. In the method, it is possible to manufacture high-performance devices by using the aforementioned exposure apparatus in a manufacturing process. FIG. 1 is a cross-sectional view which shows the structure of the optical element pertaining to a first embodiment. The optical element 100 of the present embodiment is, for example, a flat mirror and has a substrate 10 that supports a multilayer film structure, a multilayer film 20 for reflection, and a protective layer 30 that constitutes the surface layer. The underlying substrate 10 is formed, for example, by machining synthetic quartz glass or low-expansion glass, and its top face 10a is polished to a mirror surface of prescribed accuracy. The top face 10a may be made into a plane as illustrated in the drawing, or it may be made concave, convex, multifaceted or some other shape (not illustrated in the drawing) according to the application of the optical element 100. The multilayer film 20 that is above is a thin film of from several layers to several hundred layers, and is formed by alternately laminating two types of materials having different refractive indices. In order to raise the reflectance of the optical element 100 which is a mirror, this multilayer film 20 is provided with numerous lamination layers of low-absorption material, and the film thickness of each layer is adjusted based on optical interferometry so that the phases of the respective reflected waves are balanced. In short, the multilayer film 20 is formed by alternately laminating in prescribed film thicknesses a thin-film layer L1, which has a comparatively small refractive index relative to the wavelength region of the extreme ultraviolet radiation that is used in the exposure apparatus, and a thin-film layer L2, which has a comparatively high refractive index relative thereto, so that the phases of the reflected waves are balanced. By this means, it is possible to efficiently raise the reflectance of extreme ultraviolet radiation and the like in the target wavelength. In order to simplify the description, the actual number of lamination layers of the multilayer film 20 is illustrated in the drawing with omissions (dashed lines). The two types of thin-film layers L1 and L2 which configure this multilayer film 20 can be composed respectively of a silicon (Si) layer and a molybdenum (Mo) layer. Conditions such as the lamination sequence of the thin-film layers L1 and L2 and which of the thin-film layers is to constitute the outermost layer can be suitably varied according to the application of the optical element 100. The materials of the thin-film layers L1 and L2 are not limited to a combination of Si and Mo. For example, the multilayer film 20 may be fabricated by suitably combining materials such as Si, beryllium (Be), and carbon tetraboride (B4C) with materials such as Mo, ruthenium (Ru), and rhodium (Rh). In the multilayer film 20, it is also possible to provide a further boundary layer (not illustrated in the drawing) between the thin-film layer L1 and the thin-film layer L2. Particularly in the case where metal or Si or the like is used as the thin-film layers L1 and L2 that form the multilayer film 20, there is a tendency for the mated materials that respectively form the thin-film layer L1 and thin-film layer L2 to intermingle at their boundary area, and for the interface to be ill-defined. In consequence, reflective properties may be affected, and the reflectance of the optical element 100 may decline. Thus, in order to render the interface more distinct, a further boundary layer is provided between the thin-film layer L1 and thin-film layer L2 when forming the multilayer film 20. As the material of this boundary layer, one may use, for example, B4C, carbon (C), molybdenum carbide (MoC), molybdenum oxide (MoO2), etc. By rendering the interface more distinct in this manner, the reflective properties of the optical element 100 are enhanced. FIG. 2 is a cross-sectional view that serves to describe the top layer of the multilayer film 20 and the protective layer 30. The protective layer 30 protects the multilayer film 20 from the ambient environment (generally, a reduced-pressure or vacuum environment that provides efficient transmission of extreme ultraviolet radiation) by covering the entire surface of the multilayer film 20. Moreover, in relative terms, the protective layer 30 absorbs more of the non-exposure light than of the exposure light of the incoming source light. The protective layer 30 is formed so that its composition changes in the depthwise direction, and has an interfacial-side layer 31 which is provided on top of the thin-film layer L1 that is the outermost layer of the multilayer film 20, a surface-side layer 32 which is provided above the interfacial-side layer 31 and which constitutes the outermost surface of the optical element 100, and an intermediate layer 33 which is provided between the two layers 31 and 32. For purposes of convenience of description, the protective layer 30 is divided into the three layers 31, 32, and 33, but these layers 31, 32, and 33 are integrally formed by a continuous change of composition, and no clear boundaries exist among them. The protective layer 30 is formed in its entirety by increasing the partial pressure of oxygen during sputtering. The respective thicknesses of the interfacial-side layer 31, surface-side layer 32, and intermediate layer 33 can be controlled by adjusting the timing in which the partial pressure of oxygen is varied during sputtering. These thicknesses are appropriately adjusted in consideration of the reflective properties of the optical element 100. In the protective layer 30, the interfacial-side layer 31 is formed of a compound which is in a state of unsaturated oxidation. Specifically, silicon monoxide (SiO) may be used as the material of the interfacial-side layer 31, and titanium monoxide (TiO), zirconium monoxide (ZrO), etc., may also be used as other materials that have similar properties. The interfacial-side layer 31 has the property of relatively absorbing non-exposure light from the source light. In the case where Si is used as the target material for forming the interfacial-side layer 31, X of SiOx of the interfacial-side layer can be within 0 to 2. The same also applies to the case of Ti and the case of Zr. The surface-side layer 32 is formed of a compound which is in a state of saturated oxidation. Specifically, silicon dioxide (SiO2) may be used as the material of the surface-side layer 32, and titanium dioxide (TiO2), zirconium dioxide (ZrO2), etc., may also be used as other materials that have similar properties. As the surface-side layer 32 does not oxidize beyond the oxidation state of its constituent material, its structure is stable. The surface-side layer 32 has oxidation resistance which is superior to that of the interfacial-side layer 31 that is unsaturated by oxidation. That is, the layer 32 has stable oxidation resistance. FIG. 3 was drawn in order to describe the role of the interfacial-side layer 31 and the surface-side layer 32 of FIG. 2, and is a graph that shows the relation of the transmittance of Si and SiO2 of 10 nm thickness relative to prescribed wavelengths included in the source light. The non-exposure light other than exposure light in the source light includes at least any one of ultraviolet radiation, visible light, and infrared light, and it is the ultraviolet radiation region of approximately 150-400 nm in wavelength in particular that adversely affects the exposure light, that is, the light to which the resist is sensitive. From the drawing, it is clear that the transmittance of SiO2 in the ultraviolet radiation region of 150-400 nm wavelength is high, and that the transmittance of SiO is low. In short, SiO2 which is saturated by oxidation is transparent with respect to ultraviolet radiation of this region, and has the property of transmitting non-exposure light. On the other hand, SiO which is unsaturated by oxidation has the property of absorbing non-exposure light from the source light. The foregoing is a description concerning silicon oxide material, but the same properties are obtained in the cases of titanium oxide and zirconium oxide. Returning to FIG. 2, the intermediate layer 33 is in a transitional state between a state that is saturated by oxidation and a state that is unsaturated by oxidation, and has both properties of the interfacial-side layer 31 and the surface-side layer 32. For example, in the case of a protective layer 30 that contains SiO and SiO2, the composition of the intermediate layer 33 is SiOx (X=1 to 2), which is a state where the composition continuously changes from the X=1 of SiO to the X=2 of SiO2. The same also applies to the cases of titanium oxide and zirconium oxide, where the composition of the intermediate layer 33 is respectively TiOx (X=1 to 2) and ZrOx (X=1 to 2), which is a state where the composition continuously changes from X=1 to X=2. The transitional state is not limited to a state in which the composition evenly and gradually changes. Alternatively, for example, SiOx can unevenly change in X=0 to 2 for forming the intermediate layer. The same also applies to the case of Ti and the case of Zr. In the case where organic matter remains inside the exposure apparatus, carbon is deposited on the surface of the optical element 100, and a phenomenon occurs where the reflective properties of the optical element 100 are degraded. The carbon that is deposited on the surface of the optical element 100 is removed when oxidation occurs. Consequently, in order to inhibit the deposition of carbon while protecting the multilayer film 20 of the optical element 100, it is sufficient if the surface of the optical element 100 has oxidation resistance. According to the present embodiment, the surface-side layer 32 is not only able to prevent oxidation of the surface of the multilayer film 20, but it is also able to prevent carbon deposition on the surface of the multilayer film 20 by oxidizing the carbon that is deposited on the surface thereof in the case where use is conducted in an oxidizing atmosphere. As a result of the aforementioned oxidation prevention and carbon deposition prevention, it is possible to inhibit lowering of the reflectance of the multilayer film 20 over a long period. In addition, according to the present embodiment, the interfacial-side layer 31 plays the role of inhibiting projection of non-exposure light from the projection optical system to the wafer, and enables inhibition of sensitization of the wafer by non-exposure light. As a method of reducing the non-exposure light, one may also conceive of a method wherein a non-exposure light separation filter is inserted into the optical system, but such non-exposure light separation filters have the drawbacks that they are very breakable, that providing them with a large diameter is difficult, that transmittance of exposure light is approximately 50% lower, etc. On the other hand, the optical element 100 of the present embodiment eliminates the necessity of independently providing a non-exposure light separation filter, and absorbs non-exposure light while efficiently reflecting exposure light, thereby enabling mitigation of the loss of the reflected light volume of the exposure light. Below, a description is given of a specific working example of the optical element 100 pertaining to the first embodiment. “ULE”® (Ultra-Low Expansion), which is a low thermal expansion glass manufactured by Corning International Co., was used as the material of the substrate 10. One may also use other low thermal expansion glass instead of ULE, such as “Zerodur” ® manufactured by Schott Co., and “CLEARCERAM-Z”® manufactured by Ohara Co. In order to prevent a reduction in reflectance due to surface roughness of the substrate 10, the surface of the substrate 10 is polished to a surface roughness of 0.3 nm RMS or less. A multilayer film 20 of Mo/Si type was then formed by the sputtering method on the aforementioned substrate 10. In this case, the thin-film layer L1 was a Si layer with a small difference relative to a refractive index of 1, and its thickness was set to 4.6 nm. The thin-film layer L2 was a Mo layer with a large difference relative to a refractive index of 1, and its thickness was set to 2.3 nm. Accordingly, the thickness of one cycle (cycle length) of the multilayer film 20 was 4.6+2.3=6.9 nm. Formation of the multilayer film 20 was started from the thin-film layer L2 of Mo, on which a thin-film layer L1 of Si and a thin-film layer L2 of Mo were alternately laminated. A total of 45 layers of the thin-film layer L1 of Si and a total of 45 layers of the thin-film layer L2 of Mo were laminated to complete the multilayer film 20. The protective layer 30 was then formed by the sputtering method on top of the uppermost layer of the multilayer film 20, that is, on the 45th layer of the thin-film layer L1 of Si. The thickness of the thin film serving as the protective layer 30 was set to the same 2.3 nm as the thin-film layer L2 of Mo. As the thickness of the protective layer 30 of this case was determined with a view to contributing to reflection in the 13.5 nm wavelength of extreme ultraviolet radiation, the thickness changes according to the substance of the layer. Moreover, Mo tends to absorb extreme ultraviolet radiation, while Si, in contrast, tends to transmit it. Consequently, in order to improve the reflective properties pertaining to extreme ultraviolet radiation, it is desirable that the sequence of lamination on top of the multilayer film 20 alternate from the material that is absorptive to the material that is transmissive relative to extreme ultraviolet radiation. Here, the interfacial-side layer 31 of the protective layer 30 is absorptive relative to extreme ultraviolet radiation, while the surface-side layer 32 is transmissive. Accordingly, as the configuration of the protective layer is such that the surface-side layer 32 is provided on top of the interfacial-side layer 31, the protective layer 30 is formed on top of the thin-film layer L1 of Si. In the present embodiment, in the case where the interfacial-side layer 31 is SiO and the surface-side layer 32 is SiO2, the protective layer 30 containing SiO and SiO2 is formed by a reactive sputtering method that intermingles oxygen with an inert gas such as argon and that uses Si as the target material. By changing the partial pressure of oxygen during film formation, it is possible to change the composition of the protective layer 30 in the depthwise direction from SiO to SiO2. Specifically, in this example, the partial pressure of oxygen is changed from 1×10−2 to 5×10−2 Pa. As described above, the multilayer film 20 of Mo/Si type and the protective layer 30 are continuously formed inside the same film-formation apparatus without breaking the vacuum. During film formation, the substrate 10 is water-cooled, and maintained at room temperature. In the present embodiment, an example was described where the interfacial-side layer 31 is SiO, and the surface-side layer 32 is SiO2. Alternatively, as mentioned above, it is also acceptable if the interfacial-side layer 31 is TiO, and the surface-side layer 32 is TiO2. In this case, film formation is conducted while continuously adjusting the partial pressure of oxygen in the same manner described above, using Ti as the target material. Moreover, it is also acceptable if the interfacial-side layer 31 is ZrO and the surface-side layer 32 is ZrO2. In this case, film formation is conducted while continuously adjusting the partial pressure of oxygen in the same manner described above, using Zr as the target material. Below, a description is given of a specific second example of the optical element 100 pertaining to the first embodiment. It should be noted that the optical element 100 in the second example is a modified example of the first example. Substantial descriptions of elements that are identical to the elements of the first example are omitted. In the second example, the protective layer 30 is provided on top of the Si layer (i.e., the topmost Si thin film layer L1) that is the topmost layer of the Mo/Si multilayer film 20 and that has a thickness of 3.2 nm. In the protective layer 30, the interfacial-side layer 31 consisting of SiO and having a thickness of 3.2 nm is formed, the intermediate layer 33 consisting of SiO1.5 and having a thickness of 3.2 nm is formed, and the surface-side layer 32 consisting of SiO2 and having a thickness of 3.2 nm is formed. FIGS. 4A and 4B show reflection characteristics of the optical element 100 in the second example. In FIG. 4A, the solid line represents a reflectance for the light in a vicinity of a region from a wavelength of 13 nm to a wavelength of 14 nm. In FIG. 4B, the solid line represents a reflectance for the light in a vicinity of a region from a wavelength of 190 nm to a wavelength of 400 nm. In FIGS. 4A and 4B, as a comparative example, the alternate long and short dash line shows the reflection characteristic of an optical element in which the protective layer 30 is provided on the Mo/Si multilayer film 20, specifically, Si3N4 with non-exposure light absorptivity and a thickness of 10 nm is provided on the Mo/Si multilayer film 20, and Ru with oxidation-resistant properties and a thickness of 1.5 nm is provided thereon. Furthermore, in FIG. 4B, the dashed line shows the reflection characteristic of an optical element in which no protective layer 30 is provided on the Mo/Si multilayer film 20. As is shown from FIGS. 4A and 4B, in the present example, by using SiO, SiO1.5, and SiO2 as the protective layer 30, the optical element 100 can have a characteristic that it absorbs non-exposure light while efficiently reflecting exposure light. Below, a description is given of a specific third example of the optical element 100 pertaining to the first embodiment. It should be noted that the optical element 100 in the third example is a modified example of the first example. Substantial descriptions of elements that are identical to the elements of the first example are omitted. In the third example, the protective layer 30 is provided on top of the Si layer (i.e., the topmost Si thin film layer L1) that is the topmost layer of the Mo/Si multilayer film 20 and that has a thickness of 1.3 nm. In the protective layer 30, the interfacial-side layer 31 consisting of SiO and having a thickness of 1.3 nm is formed, the intermediate layers 33 consisting of SiO1.5, SiO2, SiO1.5, SiO, Si, SiO, and SiO1.5, respectively, in series and each having a thickness of 1.3 nm are formed, and the surface-side layer 32 consisting of SiO2 and having a thickness of 1.3 nm is formed. FIGS. 5A and 5B show reflection characteristics of the optical element 100 in the third example. The solid line, the alternate long and short line, and the dashed line show the same representations as that of the second example. As is shown from FIGS. 5A and 5B, in the present example, by using Si, SiO, SiO1.5, and SiO2 as the protective layer 30, the optical element 100 can have a characteristic that it absorbs non-exposure light while efficiently reflecting exposure light. Below, a description is given of a specific fourth example of the optical element 100 pertaining to the first embodiment. It should be noted that the optical element 100 in the fourth example is a modified example of the first example. Substantial descriptions of elements that are identical to the elements of the first example are omitted. In the fourth example, the protective layer 30 is provided on top of the Si layer (i.e., the topmost Si thin film layer L1) that is the topmost layer of the Mo/Si multilayer film 20 and that has a thickness of 2.9 nm. In the protective layer 30, the interfacial-side layer 31 consisting of SiO and having a thickness of 15.1 nm is formed, and the surface-side layer 32 consisting of SiO2 and having a thickness of 1.5 nm is formed. FIGS. 6A and 6B show reflection characteristics of the optical element 100 in the fourth example. The solid line, the alternate long and short line, and the dashed line show the same representations as that of the second example. As is shown from FIGS. 6A and 6B, in the present example, by using SiO and SiO2 as the protective layer 30, the optical element 100 can have a characteristic that it absorbs non-exposure light while efficiently reflecting exposure light. The present embodiment is a variation of the manufacturing method of the optical element 100 of the above-described first embodiment; identical components are assigned identical reference symbols, and description thereof is omitted. In addition, parts which are given no particular description are the same as those of the first embodiment. The optical element of the second embodiment has a structure which is almost identical to that of the optical element 100 shown in FIG. 1. However, while the description of the first embodiment concerned the case where the sputtering method was used with variation of the partial pressure of oxygen as the film formation method of the protective layer 30, in the second embodiment, the protective layer 30 is formed by a method that oxidizes the surface into SiO2 after SiO film formation without variation of the partial pressure of oxygen. Specifically, in the case where the interfacial-side layer 31 is SiO and the surface-side layer 32 is SiO2, the multilayer film 20 is formed on top of the substrate 10, and film formation of a SiO layer of, for example, 2.3 nm is conducted on top of this multilayer film 20 using SiO as the target material. Subsequently, the substrate is placed in the atmosphere, whereby the surface-side layer of the SiO layer is oxidized, and SiO2 is formed. By this means, it is possible to form a protective layer 30 having SiO in the interfacial-side layer 31 and SiO2 in the surface-side layer 32. In the cases where the interfacial-side layer 31 is TiO and the surface-side layer 32 is TiO2, and where the interfacial side layer 31 is ZrO and the surface-side layer 32 is ZrO2, the protective layer 30 may be formed by the same method by respectively using TiO and ZrO as the target material. FIG. 7 is a drawing that serves to describe the structure of an exposure apparatus 200 pertaining to a third embodiment, which incorporates the optical element 100 of the first and second embodiments as an optical part. As shown in FIG. 7, as its optical system, this exposure apparatus 200 is provided with a light source apparatus 50 that generates extreme ultraviolet radiation, an illumination optical system 60 that illuminates a mask MA by illuminating light of extreme ultraviolet radiation, and a projection optical system 70 that transfers a pattern image of the mask MA onto a wafer WA, and as its mechanical mechanism, it is provided with a mask stage 81 that supports the mask MA, and a wafer stage 82 that supports the wafer WA. Here, the wafer WA embodies a sensitive substrate, and the photosensitive layer of a resist or the like is surface coated. The light source apparatus 50 is provided with a laser light source 51 which generates laser light used for plasma excitation, and a tube 52 which supplies a gas such as xenon that is the target material into a casing SC. In addition, a capacitor 54 and a collimator mirror 55 are attached as accessories to this light source apparatus 50. By focusing the laser light from the laser light source 51 on the xenon emitted from the tip of the tube 52, the target material of this portion is turned into plasma, and generates extreme ultraviolet radiation. The capacitor 54 collects the extreme ultraviolet radiation that is generated at the tip S of the tube 52. The extreme ultraviolet radiation that transits the capacitor 54 is emitted to the exterior of the casing SC while converging, and is received by the collimator mirror 55. Instead of source light from the foregoing laser plasma type of light source apparatus 50, one may also use emitted light or the like from a discharge plasma radiation source or a synchrotron radiation source. The illumination optical system 60 is configured from reflective optical integrators 61 and 62, a condenser mirror 63, a bent mirror 64, etc. The source light from the light source apparatus 50 is homogenized as illuminating light by the optical integrators 61 and 62, is focused by the condenser mirror 63, and is received in the prescribed wavelength region (e.g., a band region) onto the mask MA via the bent mirror 64. By this means, it is possible to uniformly illuminate a prescribed region on the mask MA by extreme ultraviolet radiation of appropriate wavelength. There does not exist a substance that has adequate transmittance in the wavelength region of extreme ultraviolet radiation, and a reflective mask is used for the mask MA, rather than a transmissive mask. The projection optical system 70 is a reduced projection system configured by numerous mirrors 71, 72, 73, and 74. A circuit pattern, which is the pattern image formed on the mask MA, is imaged by the projection optical system 70 onto the wafer WA to which a resist is applied, and is transferred to this resist. In this case, the region onto which the circuit pattern is instantly projected is a rectilinear or arc-shaped slit region, and it is possible to efficiently transfer, for example, the circuit pattern of a rectangular region that is formed on top of the mask MA to a rectangular region on top of the wafer WA by scanning exposure that synchronously moves the mask MA and the wafer WA. The portions in the aforementioned light source apparatus 50 that are disposed on the optical path of extreme ultraviolet radiation, the illumination optical system 60, and the projection optical system 70 are disposed within a vacuum container 84 to prevent attenuation of the exposure light. In short, extreme ultraviolet radiation is absorbed and attenuated in the atmosphere, but an attenuation of extreme ultraviolet radiation, that is, a reduction in luminance and a reduction in contrast of the transfer image are prevented by shielding the entire apparatus from the exterior by the vacuum container 84, and by maintaining the optical path of extreme ultraviolet radiation at a prescribed degree of vacuum (for example, 1.3×10−3 Pa or less). In the foregoing exposure apparatus 200, the optical element 100 illustrated in FIG. 1 is used as the optical element 54, 55, 61, 62, 63, 64, 71, 72, 73, 74, and the mask MA that are disposed on the optical path of extreme ultraviolet radiation. In this case, the shape of the optical surface of the optical element 100 is not limited to a plane, and may be suitably adjusted by sites that incorporate concavities, convexities, multiple facets, etc. With respect to the exposure apparatus 200, in order to remove the carbon that is deposited on the surface of the optical element 100, it is possible to create the conditions of an oxidizing atmosphere by conducting gas control inside the exposure apparatus 200. These oxidizing atmosphere conditions are adjusted by appropriately conducting introduction and discharge of oxidative gas based on the illuminance of the exposure light. Below, a description is given concerning the operation of the exposure apparatus 200 that is shown in FIG. 7. In this exposure apparatus 200, the mask MA is irradiated by illuminating light from the illumination optical system 60, and the pattern image on the mask MA is projected onto the wafer WA by the projection optical system 70. By this means, the pattern image of the mask MA is transferred to the wafer WA. In the above-described exposure apparatus 200, an optical element 54, 55, 61, 62, 63, 64, 71, 72, 73, 74 and a mask MA are used that are controlled with a high degree of accuracy at high reflectance; there is high resolution, and highly accurate exposure is possible. Furthermore, the optical properties of the optical element 54, 55, 61, 62, 63, 64, 71, 72, 73, 74, and the mask MA can be maintained over a long period by inhibiting the oxidation and carbon deposition of the optical element. As a result, the resolution of the exposure apparatus 200 can be maintained, and, by extension, the life of the exposure apparatus 200 can be prolonged. Moreover, the exposure apparatus can be made highly accurate by decreasing non-exposure light from the source light by inhibiting the reflection of non-exposure light by the optical element. The foregoing was a description of the exposure apparatus 200 and an exposure method using this, and it is possible to offer a device manufacturing method for manufacturing semiconductor devices and other micro-devices with a high degree of integration by using this exposure apparatus 200. When a specific description is given, as shown FIG. 8, the micro-device is manufactured via a process (S101) wherein design and the like of the functions and performance of the micro-device are conducted, a process (S102) wherein the mask MA is fabricated based on this design process, a process (S103) wherein the substrate—i.e., the wafer WA—which is the base material of the device is prepared, an exposure treatment process (S104) wherein the pattern of the mask MA is exposed on the wafer WA by the exposure apparatus 200 of the above-described embodiment, a device assembly process (S105) wherein the element is completed while repeating a series of exposures or etchings, etc., and a device inspection process (S106) following assembly. It should be noted that the device assembly process (S105) ordinarily includes a dicing process, a bonding process, a packaging process, etc. The foregoing was a description of the present invention in conformity with embodiments, but the present invention is not limited to the aforementioned embodiments. For example, with respect to the film formation method of the protective layer 30, a film formation method other than the sputtering method may be used so long as it does not worsen surface roughness, and enables formation of fine film. Moreover, another material may be formed as a film between the multilayer film 20 and protective layer 30 in order to aid in curbing surface roughness and forming fine film, and in order to define the interface of the multilayer film 20 and protective film 30. As the protective layer 30 that is provided on top of the multilayer film 20, it is also possible to create a two-layer structure by providing an oxidation-resistant protective layer which is formed on top of the non-exposure-light absorbing layer with material that is different from that of the non-exposure-light absorbing layer. However, as the material that is used as the oxidation-resistant protective layer generally has the property of reflecting non-exposure light, it is not easy to efficiently decrease the non-exposure light from the source light. Here, the aforementioned problem is resolved if one uses oxides of different material in the two layers (for example, a combination of SiO in the interfacial-side layer 31 and TiO2 in the surface-side layer 32). However, the film formation process will be complicated compared to the case where the same oxide material is used. In the foregoing embodiment, a description was given of an exposure apparatus 200 which uses extreme ultraviolet radiation as the exposure light, but even with an exposure apparatus which uses soft X-radiation or the like instead of extreme ultraviolet radiation as the source light, it is possible to incorporate an optical element identical to the optical element 100 that is illustrated in FIG. 1. One may similarly incorporate the optical element 100 that is illustrated in FIG. 1 in a variety of optical equipment other than exposure apparatuses, including soft X-ray optical equipment such as soft X-ray microscopes and soft X-ray analyzers. The optical element 100 that is incorporated so as to be compatible with such soft X-ray optical equipment also inhibits the degradation of optical properties over long periods as in the case of the aforementioned embodiments, and mitigates unnecessary non-exposure light from the exposure light (in this case, simple illuminating light is also included in the exposure light) which is the light that is utilized from the source light. |
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043449115 | abstract | Apparatus for protecting the inner wall of a fusion chamber from microexplosion debris, x-rays, neutrons, etc. produced by deuterium-tritium (DT) targets imploded within the fusion chamber. The apparatus utilizes a fluidized wall similar to a waterfall comprising liquid lithium or solid pellets of lithium-ceramic, the waterfall forming a blanket to prevent damage of the structural materials of the chamber. |
abstract | An underground ventilated system for storing nuclear waste materials. The system includes a storage module having an outer shell defining an internal cavity and an inner shell. A majority of the height of the outer shell may be disposed below grade. The outer shell may include a hermetically sealed bottom. First and second canisters are positioned in lower and upper portions within the cavity respectively in vertically stacked relationship. A centering and spacing ring assembly is interspersed between the first and second canisters to transfer the weight of the upper second canister to the lower first canister. The assembly may include centering lugs which laterally restrain the first and second canisters in case of a seismic event. A natural convection driven ventilated air system cools the canisters to remove residual decay heat to the atmosphere. In one non-limiting embodiment, the shells are made of steel. |
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claims | 1. A method for in situ passivation of steel surfaces of a nuclear reactor, comprising the steps of:forming a protective film on a surface of the nuclear reactor primary circuit elements by introduction of a substance interacting with a material of the primary circuit elements into a primary circuit coolant, thus forming the protective film;wherein, during installation of the nuclear reactor prior to its filling with a reactor coolant, a core simulator is installed in place of a core, the nuclear reactor is filled with a reactor coolant that is heated to temperatures ensuring passivation conditions and then the core simulator is removed and replaced with a standard core. 2. The method according to claim 1, wherein a liquid metal coolant is used as the primary circuit coolant. 3. The method according to claim 2, wherein the in situ passivation is carried out in two stages, wherein the first stage is carried out under isothermal passivation conditions where oxygen is introduced into the liquid metal coolant, and the second stage is conducted under non-isothermal passivation conditions. 4. The method according to claim 3, wherein the isothermal passivation is carried out at T=300° C.-330° C. 5. The method according to claim 4, wherein oxygen is introduced in the liquid metal coolant with a thermodynamic activity a=10−1÷10−3. 6. The method according to claim 5, wherein the oxygen thermodynamic is maintained fort=220 (±20) hours. 7. The method according to claim 3, wherein the non-isothermal passivation is performed with at least one pump on. 8. The method according to claim 7, wherein a power of the pump amounts to at least 30 percent of a rated value. 9. The method according to claim 7, wherein an oxygen concentration is maintained at a level of Co2=(1-4)*10−6 wt %. 10. The method according to claim 7, wherein the oxygen thermodynamic activity a is increased to a=10−2÷ 10−4. 11. The method according to claim 7, wherein the power of the pump is at least 30 percent of the rated value, the oxygen concentration Co2=(1-4)*10−6 wt % and the oxygen thermodynamic activity a=10−2÷10−4 are maintained for t=550 (±50) hours. 12. The method according to claim 1, wherein the core simulator is a core model simulating its shape, relative position of core elements, and their masses and dimensions. |
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041683943 | abstract | An electric penetration assembly for passing electrical conductors through the wall of a pressure vessel has at least one hermetically sealed electric feed-through conductor surrounded by an insulator. The insulator is symmetrical about an axis parallel with the conductors and is impervious with a pervious means disposed between the ends. The insulator is shaped wherein an external conical section is disposed between two external cylindrical sections and wherein the pervious means communicates with the conical section. The assembly is inserted into a header plate having at least one transverse aperture formed with a female conical section disposed between two female cylindrical sections. In the female conical sections are formed two axially spaced grooves for accepting O-ring type gaskets and the plate has at least one capillary bore formed therein which communicates with the conical section and with one face of the plate. This one face seals against a flange of a penetration nozzle of the vessel, with therebetween a gasket having interconnected double circumferential indentations or grooves. The bores in the plate communicate with these double indentations and with a pressure gauge so that any pressure therein can be monitored. A suitable clamping ring secures to the exterior surface of the plate to urge the assembly into the respective aperture and against the O-rings. |
052971872 | summary | BACKGROUND AND SUMMARY OF THE INVENTION The present invention pertains to nuclear steam supply systems (NSSS) and, more particularly, to a device for sealing a penetration in a pressurizer for such a system. In a nuclear steam supply system, the pressurizer maintains reactor coolant system operating pressure and, in conjunction with the chemical and volume control system, compensates for changes in reactor coolant volume during load changes, heatup, and cooldown. During full-power operation, the pressurizer is about one-half full of saturated steam. Reactor coolant system pressure may be controlled automatically or manually by maintaining the temperature of the pressurizer fluid at the saturation temperature corresponding to the desired system pressure. Typically, the pressurizer is a cylindrical pressure vessel, vertically mounted and bottom supported. A small continuous spray flow is maintained in the pressurizer to avoid stratification of the pressurizer boron concentration and to maintain the temperature in the surge and spray lines. Energy is supplied to the water by replaceable, direct-immersion, electric heaters which are inserted from the bottom head of the pressurizer. A number of the heaters are connected to proportional controllers which adjust the heat input to account for steady-state losses and to maintain the desired steam pressure in the pressurizer. The individual heaters are carried in tubular heater sleeves which are sealingly attached to the pressurizer pressure vessel. In the event that a leak develops in one of the heater sleeves, means must be available to quickly and effectively seal the leak, to prevent the escape of radioactive water, while the system remains in operation. It is, therefore, a primary object of the present invention to provide a device for sealing a penetration in a pressurizer for a nuclear steam supply system and, more particularly, a leak associated with a pressurizer heater sleeve. It is a further object to provide such a sealing device which may be quickly and effectively utilized to seal such a leak while the system remains in operation. These and other objects and advantages of the invention as may hereinafter appear are achieved by a sealing device including a hollow cylinder adapted to be inserted into the tubular heater sleeve, in place of the heater. The cylinder includes a nose portion formed with a plurality of axially extending slots defining therein a number of radially displaceable segments, each of which has an outwardly extending flange, proximate its distal end, which is engageable with the heater sleeve to resist blowout. A rod, inserted into the cylinder, seals the passage therethrough while locking the displaceable nose portion segments in their sleeve-engaging position. Advantageously, the cylinder is formed of a nickel alloy and includes an annular band of soft nickel on its external surface which engages the inner surface of the heater sleeve to provide an effective seal therebetween. |
abstract | There is provided a radiographic imaging apparatus including: a control unit housing a control section and a power source section; a panel unit housing a radiation detection panel; a connection member that rotatably connects one edge portion of each of the control unit and the panel unit so as to adopt two states: a closed state in which one face of the control unit faces one face of the panel unit, and an open state in which the one face of the control unit and the one face of the panel unit are side-by-side facing in substantially the same direction, wherein in the open state the other face of the panel unit is positioned higher than the other face of the control unit; and a support member positioned below the other face of the panel unit and supporting the panel unit when in the open state. |
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abstract | A scanned ultraviolet-light emitting diode (UV-LED) exposure device, exposing a large area by using a periodic UV-LED exposure light source with a fixed rate in an exposure task without a need of stopping movement of the device, so as to periodically repeat a use of an exposure light source to increase a use efficiency of the energy source, resulting in an improved uniformity of exposure, with the LEDs alternatively arranged policy, which further results in an improved yield. In addition, the overall design of the upper and lower exposure stations and the periodic moving ring assembly sufficiently employs the available space, and results in a reduced volume, a corresponding production space, energy consumption and production cost. |
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046817280 | abstract | A nuclear reactor including, in the upper internals, a guide structure capable of effectively accommodating and guiding without binding the large number of neutron-absorber rods included in modern reactors of improved efficiency. The neutron-absorber rods include control rods, gray rods, and water-displacement rods. All rods are suspended in clusters from spiders or vanes. The upper internals of the reactor includes cruciform guides for the control-rod and gray-rod clusters. Each of these guides is composed of a plurality of vertical guide sections of transverse cruciform cross section. Plates extending throughout the cross-section of the reactor are supported between each pair of successive guide sections. The plates are perforated, the perforations in each plate being patterned to pass the water-displacement rod clusters. The plates are oriented so that the patterned perforations are aligned to serve as guides for the water-displacement rod clusters. The plates are of very large diameter and, as perforated, would not be self-supporting unless they were very thick. To overcome this drawback, each plate is formed of separate plate sections which are, when assembled nested together, like the parts of a "jig-saw puzzle". |
051695960 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings wherein like reference numerals refer to like elements, FIG. 1 depicts a shield building 1 which encloses a containment vessel 3, yet spaced outwardly thereof with the space formed between the two referred to herein as the annulus 4. The containment vessel 3 is desirably made of steel and has a generally cylindrical side 5 and a generally hemispherical or ellipsoidal top 6a and bottom 6b. Illustrated by way of example inside the containment vessel 3 is a portion of the primary system of a pressurized water reactor including a reactor vessel 2 and two steam generators 8, both well known in the art. The shield building includes a generally cylindrical side wall 7 which terminates at its lower end with a floor 9, and at its upper end by a frustoconical roof 11. The wall 7, made of, for example, reinforced concrete, includes a plurality of openings 15 spaced circumferentially about the upper end of the wall 7 for allowing air to enter the shield building 1. Each opening 15 in this embodiment has a wire mesh screen positioned in it to prevent debris and the like from entering through the opening 15. The frustoconical roof 11 is desirably made of a structural material, such as reinforced concrete and includes an angled roof portion 17 which closes the upper end of the wall 7 and includes a skirt 16 extending from its lower edge and extending concentrically with a portion of wall 7 thereby providing additional protection from external conditions. The frustoconical roof 11 includes a circular opening 19 in the center of the roof 11 with a cupola-like structure 22 extending upwardly over the roof 11 and surrounding the opening 19. A circular platform 21 is located directly above the center of the containment vessel 3 and below the opening 19 in the roof 11. The platform 21 is supported from the roof 11 by beams 23 attached to the periphery of the circular opening 19. A wire mesh screen 25 is positioned surrounding the beams 23 forming a cylinder like apparatus between the platform 21 and the opening 19. This prevents larger objects such as birds and the like from entering the shield building 1. The cupola structure 22 includes a water storage tank 27 of a toroidal-like configuration. The water storage tank 27 provides a source of water for the inside the shield building 1 for cooling when ambient air passing over the containment vessel may be insufficient, for example, in the unlikely event of an accident in which large quantities of heat are generated inside vessel 3. One means of access inside the shield building 1 is through a door 29 located in the lower end of the wall 7. Another means of access is through one of the openings 15. An elevator (not shown) positioned outside of the shield building 1 is used to access the opening 15 at the top of the shield building wall 7. The opening 15 adjacent the elevator has hinges or the like (not shown) allowing it to be opened or removed. A partially fixed, partially movable air baffle means 30 is disposed within the shield building 1 and comprises three major components, i.e., a sectional movable baffle means 31, a fixed baffle means 33 and a combined fixed and movable baffle means 35. Referring to FIGS. 1 and 2, the fixed baffle 33 is shown as a unitary structure while the movable baffle 31, and combined fixed and movable baffle 35 are divided into defined sections respectively herein referred to as movable sections 31a, and combined fixed and movable sections 35a. The fixed baffle 33 is supported and attached from the shield building roof 11. Each movable sections 31a is supported by at least two vertical columns 38, made of for example concrete, positioned beneath each movable section 31a and each vertical column 38 extends to the floor 9. A plurality of support means 42 are for additional support of the movable sections 31a and are attached and positioned at one end to each movable section 31a. Each support means 42 on the other end is attached to the shield building wall 7. The air baffle 30 is positioned in the annulus 4 dividing the annulus 4 into an inner annulus 37 and outer annulus 39 surrounding the inner annulus 37. The air baffle 30 generally has a shape that conforms to the shape of the containment vessel 3. The movable baffle means 31 is the lower part of the air baffle means 30, the fixed baffle means 33 is the upper part thereof, with the combined fixed and movable baffle means 35 positioned between the fixed baffle means 33 and the movable baffle means 31. The movable baffle means 31 is positioned surrounding a major portion of the cylindrical side 5 portion of the containment vessel 3. The fixed baffle means 33 is positioned surrounding the top hemispherical or ellipsoidal portion 6a of the containment vessel 3. The fixed baffle means 33 has a frustoconical shape with both ends open allowing air passage. Referring to FIGS. 1 and 3, the combined fixed and movable baffle means 35 is divided into sections and each section 35a is comprised of two metal plates 40a and b. Each outer plate 40a is attached to the outer surface of the adjacent movable sections 31a. The inner plate 40b is attached to the fixed baffle 33 adjacent the inner wall thereof and extends into engagement with the adjacent movable section 31a. Each outer plate 40a, at its upper portion, is contiguous to and overlapping with the fixed baffle 33 and the lower end of each plate 40a is secured by suitable means, such as by bolts (not shown), to the adjacent movable section 31a. Each inner plate 40b is attached, at its top, to the lower end of the fixed baffle 33 by a suitable securing means such as by bolts (not shown), an elastomer material 41 may be positioned between the bolts and the inner plate 40b. The elastomer material 41 may comprise a long, thin, belt like configuration extending the entire width of the lower surface of fixed baffle 33. The elastomer material 41 functions as a supplemental biasing means spring means with each inner plate 40b to result in a slight horizontal outward movement of the inner plate 40b which may be designed to be biased outwardly a small but fixed amount when the bottom portion thereof is disengaged from adjacent baffle segment 31a. Inner plate 40b, at its lower end, is contiguous to and overlapping with each adjacent baffle section 31a. A plurality of long, thin, belt-like elastomer pads 55 are also attached at the top and extend the entire width of each respective movable section 31a and is positioned to be between each inner plate 40b and movable section 31a when the movable sections 31a are in the normal position. Elastomer pad 55 functions to cushion and form a general seal between the movable section 31a and inner plate 40b. When the movable section 31a is moved up and away from the containment vessel 3 (as illustrated in phantom in FIGS. 3 and 4) the inner plate 40b is biased to move slightly in an outwardly direction. The outer plate 40a moves generally with the movable sections 31a as it is moved up and away from the containment vessel 3. When the movable section 31a are returned to the normal position the elastomer pad 55 on each movable section 31a pushes slightly against the bottom portion of each inner plate 40b and forces it into the normal position thus effecting a seal between elastomer 55 and plate 40 b. Concurrently, the outer plate 40a moves with the movable sections 31a when each movable section 31a is returned to the normal position, as shown in FIG. 3, so that the upper edges of sections 31a engage fixed baffle 33. Referring to FIG. 1, the shield building 1 and air baffle 30 cooperate to form a passive containment cooling system which functions to provide a pathway for natural circulation to occur thereby removing ambient heat dissipated by the containment vessel 3. The passive containment cooling system is designed to function in the unlikely event of an accident where a large energy release occurs or when normal cooling fans are not available or the like. Heat removal is accomplished by allowing air to flow into the opening 15 of the shield building 1 and down the outer annulus 39. The air then flows around the bottom of the movable shield baffle means 31 and upward in the inner annulus 37 thereby cooling the containment vessel 3. The air is directed along the inner boundary of the fixed baffle means 33 then through the opening 19 containing the wire mesh 25 at the top of the shield building 1. Referring to FIG. 5, in this embodiment of the invention, the defined sections 31a of the movable baffle 31 are comprised of flat planar surfaces 44 at angle increments of approximately six degrees. As shown in FIG. 6, the movable baffle means 31 is divided into several defined sections 31a. A sealing means 45 is positioned between adjacent movable baffle sections 31a to prevent significant air leakage across the air baffle boundary providing an essentially continuous inner surface. The sealing means 45 in this embodiment may comprise, for example, a dichotomous seal creating a seam 45a at the center of the seal 45. One segment of seal 45 is rigidly attached to each respective movable baffle section 31a. The splitting of the sealing means 45 enables the seal to follow the movable shield baffle sections 31a to which the seal is attached when the movable baffle 31 is moved up and away. The two portions of the seal 45 are compressed together as the movable baffle 31a is moved into its operating position. As shown in FIGS. 4 and 7, a plurality of support means 42 are rigidly and pivotally attached to the wall 7 of the shield building 1 and to the movable baffle section 31a respectively. FIG. 3 illustrates an example of an appropriate vertically aligned configurations for support means 42 and includes outer support means 42a, inner support means 42b, and cross brace 43. Each of the plurality of movable baffle sections 31a is supported in an adequate manner, for example by outer support means 42a at the outer edges and inner support means 42b in conjunction with cross brace 43 at the midsection of the movable baffle section 31a. This configuration of outer support means 42a, inner support means 42b, and cross brace 43 is repeated in this example at seven vertical locations along each plurality of baffle sections 31a. Referring to FIG. 5, each inner support means 42b at the midsection of each movable baffle section 31a is further supported by a cross brace 43. Regulations require that equipment or systems essential to the operation of nuclear facilities be capable of withstanding seismic events. The cross braces 43 are an example of support means which will provide the required additional support that may be required during seismic events. The support means 42 are all parallel to each other on each movable baffle section 31a and include a pivotal clevis mount 41 at each end which allows movement in a vertical plane. Referring to FIG. 4, a lifting means 47 positioned inside the shield building 1 at the intersection of the roof 11 and the wall 7 comprises a cable with a hook on the end and a means for lowering and raising the cable. The lifting means 47 may be moved circumferentially around the shield building by a monorail 49 to allow each movable baffle sections 31a to be lifted. At least two eyebolt devices 51 are attached to the movable baffle section 31a. The cable is lowered with a lifting bridle (not shown) attached to the hook. A lifting bridle comprises at least two or more cables connected or bonded together at one of the cable ends and a device for latching, such as metal rings, attached at the bonded point of the cables and at the unconnected ends of each cable. The lifting bridle attaches to one or more eyebolts 51 and the cable is lifted thereby lifting the movable baffle section 31a. A personnel basket 57 may be used in this embodiment and is positioned at the intersection of the wall 7 and roof 11 with the capability to support maintenance workers inside the personnel basket 57. The personnel basket 57 includes a basket-like structure attached by cable to a monorail 59 allowing it to move circumferentially around the containment vessel 3. Maintenance personnel inside the basket can attach the lifting bridle to the eyebolts 51 and perform disengagement, adjustment, and like activities. Referring to FIG. 8, each section 31a of the movable baffle 31 is retained in the up and away position by at least two hinged support devices 53 located on the wall 7. These supports are positioned and hinged so that they fold out of the way as the movable section 31a is raised and may be rotated into position to support the movable section 31a after it is raised. Hinged support devices 53 swing generally horizontally outwardly to support the adjacent baffle segment 31a in a manner similar to a door and are positioned up against the wall 7 when movable sections 31a are being lifted up and away from the containment vessel 3. Each support device 53 is rotated perpendicular to the shield building wall 7 after the movable section 31a is lifted slightly above support devices 53. Movable sections 31a are then slightly lowered onto support devices 53. Support devices 53 may be accessed from the floor 9, as shown in FIG. 1, to rotate the hinged platform devices 53. As best seen in FIG. 9, when the support device 53 is not in use support device 53 is positioned against wall 7 (as illustrated in phantom). To support the movable baffle 31 in the position up and away from the containment vessel 3 (FIG. 1), support device 53 is rotated perpendicular to wall 7. An alternative method of retaining each movable baffle sections 31a up and away from the containment vessel 3 is for the hoisting means 47 (FIG. 4) to maintain the movable baffle means 31 in the up and away position from the containment vessel 3. The method by which the movable baffle sections 31a are moved up and away from the containment vessel 3 allowing access to the outer surface of the containment vessel as desired, is as follows. Referring to FIG. 4, first the personnel basket 57 is lowered to a position adjacent a movable section 31a. A lifting bridle (not shown) is attached to the hoisting means 47 cable. The lifting bridle is lowered to a position near the personnel basket 57 to allow a person inside the personnel basket 57 to grasp the lifting bridle. The lifting bridle is attached to eyebolts 51 on one movable section 31a. The personnel basket 57 is raised to a position so as not to interfere with the lifting of the movable sections 31a. Next, the hoisting means 47 lifts the movable section 31a with the removable section inner plate 40b remaining stationary and the outer plate 40a moving with the movable section 31a. The movable section 31a is maintained in the up and away position by the hoisting means 49. An alternate means of maintaining the baffle sections 31a in the up and away position is by hinged support devices 53 located on the wall 7 of the shield building 1. The hinged support devices 53 are hinged out of the way so that platform devices 53 fold out of the way as the movable section 31a is raised and may be rotated into position to support the movable section 31a after it is raised. The lifting of each movable section 31a is repeated until all sections 31a have been moved and the entire outer surface of containment 3 is accessible. The procedure is reversed to return the movable sections 31a to the normal position. |
042776880 | summary | The present invention relates to a device comprising a bag for covering a cask for transporting radioactive fissionable materials such as a used nuclear fuel to prevent the outer surface of the cask from contamination with the contaminated water of a fuel storage pool. The nuclear fuel used in a nuclear reactor (hereinafter referred to simply as "fuel"), for example, is transported to a fuel reprocessing plant as accommodated in a special container to prevent the radioactive contamination of the environment during the transport. The fuel transport container is usually called a "cask." To assure safety against the radioactivity, the fuel is placed into the cask as submerged in the pool in which the fuel is stored. The water of the fuel pool, which is in direct contact with the fuel, usually has a considerably high level of radioactivity, which invariably contaminates the outer surface of the cask. Consequently there arises the necessity of removing the contaminant from the cask outer surface after the cask has been withdrawn from the pool with the fuel contained therein. This procedure, however, is difficult and requires much labor and time since the cask has a large number of cooling fins on its outer surface as is well known. To simplify the removal of the contaminant to the greatest possible extent, it is known to render the cask free from contaminant before immersion into the fuel pool, for example, by covering the cask with a bag of impermeable flexible sheet. As such a bagging method, it has heretofore been proposed to bag a cask and fasten the edge of the bag opening with a stainless steel band into pressing contact with the outer surface of the cask to seal off the interior of the bag. The proposed method nevertheless involves the problem of failing to provide perfect liquid tightness and being inefficient to practice. It has also been proposed to inject clean water into the bag under pressure to prevent the contaminated water from penetrating into the bag, but this method still has the drawback that after the cask has been withdrawn from the pool, the water within the bag must be disposed of by a cumbersome procedure which leads to a reduced efficiency. The main object of this invention is to provide a cask bagging device which affords a reliable seal between the opening edge of the bag and the outer surface of a cask and which ensures an efficient operation. To fulfil this object, the present invention provides a cask bagging device comprising a bag and a flexible annular tube disposed at the opening end of the bag. A pressure gas is fed to the annular tube to cause the pressure to hold the opening end in pressing contact with the outer periphery of the cask to seal off the bag. According to a preferred embodiment of the invention, the annular tube is adapted to fit into the space between a pair of adjacent fins among a large number of annular fins on the outer surface of the cask, and/or a member of high rigidity is held in contact with at least part of the outer surface of the annular tube except where the tube is in contact with the cask outer surface, the annular tube thus providing a reliable seal. When the cask bagged in the device is immersed into the fuel pool with the pressure gas fed to the annular tube to seal off the bag, the pressure of the water will act on the tube in accordance with the submerged position of the cask, thus reducing the sealing function of the tube. While it appears useful to give the tube such initial pressure that the liquid tightness will not be impaired when subjected to the water pressure, a problem will then arise in respect of the strength of the fins because the thinner the fins, the higher are the characteristics thereof so that it is not desirable to increase the thickness of the fins for reinforcement. Furthermore the bag will be subjected to the external water pressure in corresponding relation to the submerged position. The bag will not be liable to damage despite the water pressure if made from a material of high strength, but this is in conflict with the requirement that the bag be made of thin combustible material so as to be disposable with ease after use. According to another preferred embodiment of the present invention, the device is provided with means disposed close to the annular tube for detecting the external water pressure and a system for controlling the pressure of gas to be supplied to the tube in accordance with the external water pressure detected, whereby a constant pressure difference is maintained at all times between the inside and outside of the annular tube to assure liquid tightness with stability without any adverse effect on the strength of the fins. Additionally the pressure gas is also fed to the interior of the bag under similar control so that the external pressure on the bag is limited to a specified range, rendering the bag serviceable free of any damage notwithstanding that it is made of combustible lightweight material. Preferably the interior of the bag is maintained at a specified negative pressure to keep the bag in intimate contact with the cask before the cask is immersed into the pool so that the bag will not be damaged by engagement with part of some other article or apparatus during handling. When the cask has been placed into the body of water, the interior of the bag is usually adjusted by the control system to a predetermined negative pressure relative to the external pressure of water, whereby the bag can be held in its initial state as fitted to the cask throughout the whole process of immersion into the fuel pool and withdrawal therefrom. On the other hand, the interior of the bag, which is at the specified negative pressure before immersion into the pool, may be controlled to a slightly positive pressure relative to the external water pressure on immersion into the pool to preclude the penetration of contaminated water into the bag more effectively. In this case, however, the positive pressure in the bag will inflate the bag when the cask is withdrawn from the pool. Further in this case, the pressure line for feeding the pressure gas to the bag must be provided with an intermediate start valve which opens the line on detecting the immersion of the cask into the water. |
claims | 1. Apparatus for irradiating articles in sequence to sterilize the articles, including an accelerator for providing radiation in a particular direction, a first conveyor system for moving the articles in sequence past the accelerator for irradiating the articles with the radiation from the accelerator, a second conveyor system for receiving the articles in sequence from the first conveyor system after the irradiation of the articles with the radiation from the accelerator and for moving the articles in sequence past the accelerator and for irradiating the articles with the radiation passing from the accelerator, during the movement of the articles on the second conveyor system, through the articles on the first conveyor system to obtain further radiation of the articles. 2. Apparatus as set forth in claim 1 wherein claim 1 the accelerator provides x-ray radiation to the articles on the first and second conveyor systems. 3. Apparatus as set forth in claim 1 wherein claim 1 the first and second conveyor systems are operative to produce a movement of the articles on the second conveyor system past the radiation passing through the articles on the first conveyor system from the accelerator in synchronism with the movement of the articles on the first conveyor system past the radiation from the accelerator. 4. Apparatus as set forth in claim 1 , including claim 1 a loading area disposed in displaced relationship to the first and second conveyor systems and constructed to hold the articles and transfer the articles in sequence from the loading area to the first conveyor system, and an unloading area disposed in displaced relationship to the first and second conveyor systems and constructed to hold the articles and transfer the articles in sequence from the second conveyor system to the unloading area. 5. Apparatus as set forth in claim 1 wherein claim 1 each of the articles has first and second opposite sides and wherein the first conveyor system is constructed to move each of the articles first and second times past the radiation from the accelerator and to obtain an irradiation of the first side of the article in the first movement of the article past the radiation from the accelerator and to obtain an irradiation of the second side of the article in the second movement of the article past the radiation from the accelerator and wherein the second conveyor system is constructed to move each of the articles first and second times past the radiation from the accelerator and to obtain an irradiation or the first side of the article in the first movement of the article past the radiation from the accelerator and to obtain an irradiation of the second side of the article in the second movement of the article past the radiation from the accelerator. 6. Apparatus as set forth in claim 3 wherein claim 3 a loading area is disposed in displaced relationship to the first and second conveyor systems and is constructed to hold the articles and transfer the articles in sequence from the loading area to the first conveyor system and wherein an unloading area is disposed in displaced relationship to the first and second conveyor systems and is constructed to hold the articles and transfer the articles in sequence from the second conveyor system to the unloading area and wherein each of the articles has first and second opposite sides and wherein the first conveyor system is constructed to move each of the articles first and second times past the radiation from the accelerator and to obtain an irradiation of the first side of the article in the first movement of the article past the radiation from the accelerator and to obtain an irradiation of the second side of the article in the second movement of the article past the radiation from the accelerator and wherein the second conveyor system is constructed to move each of the articles first and second times past the radiation from the accelerator and to obtain an irradiation or the first side of the article in the first movement of the article past the radiation from the accelerator and to obtain an irradiation of the second side of the article in the second movement of the article past the radiation from the accelerator. 7. Apparatus as set forth in 6 wherein the accelerator provides x-ray radiation to the articles on the first and second conveyor systems. 8. Apparatus for irradiating articles in sequence to sterilize the articles, including an accelerator for providing a radiation beam in a particular direction, first support structure for disposing articles relative to the accelerator in the particular direction to obtain an irradiation of the articles by the accelerator, second support structure for disposing articles in the particular direction relative to the accelerator and the articles on the first support structure to obtain an irradiation of the articles by radiation passing in the particular direction from the accelerator through the articles on the first structure, and a transfer mechanism for transferring the articles on the first structure to the second structure after the irradiation of the articles on the first structure by radiation in the particular direction from the accelerator to obtain the irradiation of the articles on the second structure by the radiation passing in the particular direction from the accelerator through the articles on the first support structure. 9. Apparatus as set forth in claim 8 , including claim 8 a loading area for transferring articles to the first support structure to obtain an irradiation of the articles in the particular direction by the radiation from the accelerator, and an unloading area for providing for a transfer of articles from the second support structure after the irradiation of the articles in the particular direction on the second support structure. 10. Apparatus as set forth in claim 8 wherein claim 8 the radiation in the particular direction to the articles on from the first support structure is in the form of a beam and wherein the first support structure positions the articles in the first support structure to receive the radiation beam in the particular direction from the accelerator and wherein the second support structure positions the articles on the second support structure to receive the radiation beam passing in the particular direction through the articles on the first support structure from the accelerator. 11. Apparatus as set forth in claim 8 wherein claim 8 each of the articles has first and second opposite sides and wherein the first support structure provides for the passage of the radiation in the particular direction from the accelerator through the first and second opposite sides of the articles on the first support structure and wherein the second support structure provides for the passage, in the particular direction through the first and second opposite sides of each of the articles on the second support structure, of the radiation passing in the particular direction through the accelerator and the articles on the first support structure. 12. Apparatus as set forth in claim 9 wherein claim 9 the radiation from the first support structure is in the form of a beam and wherein the first support structure positions the articles in the first support structure to receive the radiation beam in the particular direction from the accelerator and wherein the second support structure positions the articles on the second support structure to receive the radiation beam passing in the particular direction through the articles on the first structure from the accelerator and wherein each of the articles has first and second opposite sides and wherein the first support structure provides for the passage of the radiation in the particular direction from the accelerator through the first and second opposite sides of the articles on the first support structure and wherein the second support structure provides for the passage, in the particular direction through the first and second opposite sides of the articles on the second support structure, of the radiation passing in the particular direction through the accelerator and the articles on the first support structure. 13. Apparatus as set forth in claim 12 wherein claim 12 the radiation is in the form of a beam of x-rays. 14. Apparatus as set forth in claim 8 wherein claim 8 each of the articles has first and second opposite sides and wherein the first support structure provides for an irradiation of each of the articles on the first support structure in the particular direction from the accelerator initially through the side of the article and subsequently through the second side of the and wherein the second support structure provides for an irradiation of each of the articles in the particular direction on the second support structure initially through the first side of the article, and subsequently through the second side of the article on the first support structure. 15. Apparatus as set forth in claim 14 wherein claim 14 the first and second support structures provide for the radiation from the accelerator to pass in the particular direction initially through the first sides of the articles respectively on the first and second support structures and subsequently through the second sides of the articles respectively on the first and second support structures and wherein the transfer mechanism provides for the transfer of the articles from the second support structure, and from the first support structure to the second support structure after the irradiation of the second sides of the articles on the first and second support structures. 16. Apparatus as set forth in claim 15 , including, claim 15 a loading area for transferring articles to the first support structure to obtain an irradiation of the articles in the particular direction by the radiation from the accelerator, and an unloading area for providing for a transfer of articles from the second structure after the irradiation of the first and second sides of the articles in the particular direction on the second support structure. 17. Apparatus as set forth in claim 16 wherein claim 16 the radiation of the beam from the accelerator is in the form of x-rays. 18. A method of irradiating articles to sterilize the articles, including the steps of: providing a beam of radiation, disposing first articles to become irradiated by the radiation beam, disposing second articles to become irradiated by the radiation beam after the passage of the radiation from the beam through the first articles, and providing for the first articles to become the second articles after the irradiation of the first articles with the beam of radiation. 19. A method as set forth in claim 18 , including the steps of: claim 18 providing for additional articles to become the first articles in substitution for the first articles becoming the second articles. 20. A method as set forth in claim 18 , including the step of: claim 18 providing for the second articles to become transferred from the position of irradiation by the passing of the beam of radiation through the first articles, and to be replaced by the first articles after the irradiation of the second articles with the beam of radiation passing through the first articles. 21. A method as set forth in claim 18 wherein claim 18 the radiation from the beam constitutes x-rays. 22. A method as set forth in claim 18 wherein claim 18 articles are transferred in sequence from a loading area to become the first articles and wherein the first articles are transferred in sequence to become the second articles after the first articles have been irradiated with the beam of radiation and wherein the second articles are transferred in sequence to an unloading area after they have been irradiated with the beam of radiation passing through the first articles. 23. A method as set forth in claim 22 wherein claim 22 the transfer of articles in sequence from the loading area to become the first articles, the transfer of the first articles in sequence to become the second articles and the transfer of the second articles in sequence to the unloading area are synchronized. 24. A method as set forth in claim 23 wherein claim 23 the synchronization provides for the first articles and the second articles to be aligned with the beam of radiation to obtain an irradiation of the first articles with the radiation of the beam and simultaneously to obtain the irradiation of the second articles with the radiation of the beam passing through the first articles. 25. A method of irradiating articles in sequence to sterilize the articles, including the steps of: providing an accelerator for producing radiation, providing a first conveyor system for moving the articles in a first loop past the accelerator to obtain an irradiation of the articles with the radiation from the accelerator, providing a second conveyor system for moving the articles in a second loop past the accelerator to obtain an irradiation of the articles with the radiation from the accelerator, providing a disposition of the first and second conveyor systems relative to the accelerator to provide for the passage of the radiation from the accelerator through the articles on the first conveyor system and the articles on the second conveyor system, and transferring successive ones of the articles on the first conveyor system at each instant to the second conveyor system for the irradiation at that instant of the successive ones of the articles on the second conveyor system, after the previous irradiation of such successive ones of the articles on the first conveyor system, with the radiation passing from the accelerator at that instant through the articles on the first conveyor system. 26. A method as set forth in claim 25 , including the steps of claim 25 transferring successive ones of the articles in a loading area to the first conveyor system for the irradiation of the articles by the radiation from the accelerator, and transferring successive ones of the articles on the second conveyor system to an unloading area after the irradiation of the articles by the radiation passing through the articles on the first conveyor system from the accelerator. 27. A method as set forth in claim 25 , including the step of: claim 25 synchronizing the movements of the articles on the first conveyor system past the radiation from the accelerator with the movement of the articles on the second conveyor system past the radiation passing through the articles on the first conveyor system from the accelerator. 28. A method as set forth in claim 27 , including the step of: claim 27 synchronizing the transfer of the successive ones of the articles in the loading area to the first conveyor system and the transfer of the successive ones of the articles on the successive conveyor to the unloading area. 29. A method as set forth in claim 25 wherein claim 25 the first conveyor system defines a first closed loop and wherein the first conveyor system provides first and second movements of the articles on the first conveyor system in the first closed loop past the radiation from the accelerator and provides for a rotation of the articles on the first conveyor system through an angle of substantially 180xc2x0 between the first and second movements of the articles on the first conveyor system past the radiation from the accelerator and wherein the second conveyor system provides first and second movements of the articles in the first conveyor system past the radiation passing through the articles on the first conveyor system from the accelerator and provides for a rotation of the articles on the second conveyor system through an angle of substantially 180xc2x0 between the first and second movements of the articles on the second conveyor system past the radiation from the source. 30. A method as set forth in claim 29 wherein claim 29 successive ones of the articles in a loading area are transferred to the first conveyor system when the successive ones of the articles on the first conveyor system are transferred to the second conveyor system and wherein successive ones of the articles on the second conveyor system are transferred to an unloading area when successive ones of the articles on the first conveyor system are transferred to the second conveyor system. 31. A method as set forth in claim 30 wherein claim 30 the first movement of the articles on the first conveyor system past the radiation from the accelerator is synchronized with the first movement of the articles on the second conveyor system past the radiation passing through the articles on the first conveyor system from the accelerator and wherein the second movement of the articles on the first conveyor system past the radiation from the accelerator is synchronized with the second movement of the articles on the second conveyor system past the radiation passing through the articles on the first conveyor system past the accelerator. 32. A method as set forth in claim 31 wherein claim 31 the first sides of the articles are irradiated during the first movement of the articles past the radiation from the source and wherein the second sides of the articles are irradiated during the second movements of the articles past the radiation from the source. 33. A method of irradiating articles with an x-ray beam providing a first path for the irradiation of articles, disposing a second path for the irradiation of the article, providing x-rays for the irradiation of the articles in the first and second path, disposing the first and second paths relative to the x-rays to provide for the passages of the x-rays through the articles in the first and second paths, and providing a transfer of the articles in the first path to the second path after the irradiation of the articles in the first path. 34. A method as set forth in claim 33 wherein claim 33 the movement of the articles in the first path to the position for irradiation by the x-rays of the articles in the first path is synchronized with the movement of the articles in the sum path to the position for irradiation of the articles in the second path. 35. A method as set forth in claim 33 wherein claim 33 each of the articles in the first path is irradiated twice by the x-rays, once on a first side of the articles and the other time on a second side of the articles, and wherein each of the articles in the second path is irradiated twice by the x-rays, once on a first side of the articles and the other time on a second side of the articles. 36. A method as set forth in claim 35 wherein claim 35 the irradiation of the first sides of the articles in the first and second paths by the x-rays and synchronized and wherein the irradiation of the second sides of the articles in the first and second paths is synchronized. 37. A method as set forth in claim 36 wherein claim 36 the x-rays are disposed relative to the articles in the first and second paths to pass initially through the articles in the first path and then through the articles in the second paths. 38. A method as set forth in claim 36 wherein claim 36 the articles in the first path are rotated through an angle of 180xc2x0 between the first and second irradiations of the articles in the first path, the articles in the first path are transferred to the second path after the second irradiation of the articles in the first path and wherein the articles in the second path are related through an angle of 180xc2x0 between the first and second irradiations of the articles in the second path. |
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claims | 1. An apparatus for imaging a tumor of a patient with positively charged particles, comprising:a beam transport system configured to transport the positively charged particles from a synchrotron to at least the tumor of the patient along a treatment beam path;a first imaging system comprising a first imaging beam path from a gantry to the tumor; anda second imaging system comprising a second imaging beam path from said gantry to the tumor, said first imaging beam path, a rotation point about which the gantry rotates, and the second imaging beam path forming an angle of greater than fifty degrees,said gantry configured to physically support a set of elements comprising: (1) at least a portion of said beam transport system, (2) at least a portion of said first imaging system, and (3) at least a portion of said second imaging system. 2. The apparatus of claim 1, said first imaging system comprising a first X-ray imaging system, said second imaging system comprising a second X-ray system. 3. The apparatus of claim 2, said gantry further comprising:an arc, said gantry configured to co-move said set of elements along said arc. 4. The apparatus of claim 3, said first X-ray imaging system comprising a first cone beam X-ray element, said second X-ray imaging system comprising a second cone beam X-ray element. 5. The apparatus of claim 4, said first X-ray imaging system and said second X-ray imaging system combining to form at least one cone beam computed tomography X-ray system. 6. The apparatus of claim 4, said first imaging system further comprising:a first two-dimensional detection surface mounted opposite the rotation point from a center of a connection point of said at least a portion of said first imaging system to said gantry. 7. The apparatus of claim 1, said first imaging system comprising an element of a two-dimensional cone beam computed tomography X-ray system. 8. The apparatus of claim 7, said second imaging system comprising a fluoroscopy system. 9. A method for imaging a tumor of a patient with positively charged particles, comprising the steps of:transporting the positively charged particles, using a beam transport system, from a synchrotron to at least the tumor of the patient along a treatment beam path;functioning a first imaging system along a first imaging beam path from a gantry to the tumor; andoperating a second imaging system along a second imaging beam path from said gantry to the tumor, said first imaging beam path, the tumor, and said second imaging beam path forming an angle of greater than sixty degrees,wherein said gantry physically supports a set of elements comprising: (1) at least a portion of said beam transport system, (2) at least a portion of said first imaging system, and (3) at least a portion of said second imaging system. 10. The method of claim 9, further comprising the step of:rotating said gantry about a rotation point, said step of rotating further comprising the step of:moving said set of elements along a first arc. 11. The method of claim 10, further comprising the steps of:imaging the tumor using both said first imaging system and said second imaging system to form an image; andtreating the tumor with the positively charged particles using the image. 12. The method of claim 11, further comprising the step of:controlling both said step of imaging and said step of treating with a portable control pendant positioned in view of said gantry and outside of a treatment room housing said gantry. 13. The method of claim 11, further comprising the step of:generating a tomographic image from a detected signal resultant from the positively charged particles after the positively charged particles transit through said tumor; andsaid step of treating the tumor further comprising the step of using the tomographic image in targeting the tumor. 14. The method of claim 13, further comprising the steps of:positioning a first light emitting material in a plane across the treatment beam path between an exit nozzle of said beam transport system and the tumor;detecting photons emitted from said light emitting material upon transmission of the positively charged particles through said first light emitting material; anddetermining a path of the positively charged particles using both the photons and said tomographic image. 15. The method of claim 9, said first imaging system further comprising a cone beam computed tomography X-ray based imaging system. 16. The method of claim 15, further comprising the step of:co-rotating: (1) a first source element and a first detector of said first imaging system and (2) a second source element and a second detector of said second imaging system. 17. The method of claim 16, further comprising the step of:tomographically imaging the tumor to form a tomographic image using the positively charged particles. 18. The method of claim 17, further comprising the step of:implementing a cancer treatment therapy plan using both a first image generated using said cone beam computed tomography X-ray based imaging system and said tomographic image. 19. The method of claim 18, further comprising the steps of:said gantry physically supporting a third imaging system, said third imaging system not using X-rays or the positively charged particles; andgenerating a tumor image using said third imaging system. 20. The method of claim 9 further comprising the steps of:rotating the patient with a patient positioning system;generating a cone beam computed tomography image of the tumor without rotation of the gantry; andtreating the tumor of the patient, using the cone beam computed tomography image, with the positively charged particles. |
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claims | 1. A method for producing an actinide metal halide, the method comprising:a) establishing a molten salt bath;b) generating a liquid alloy containing an actinide metal of the metal halide in a crucible;c) submerging the crucible containing the liquid alloy in the molten salt bath;d) contacting the liquid alloy with halogen in a first reaction to form a first metal halide that dissolves in the molten salt bath, wherein the metal is more electropositive than the halogen;e) removing unreacted liquid alloy from the molten salt bath by removing the crucible from the molten salt bath; andf) contacting the first metal halide with halogen in the molten salt bath to initiate a second reaction between the halogen and the metal halide to form a second metal halide. 2. The method of claim 1 wherein the molten salt bath generated in the establishing step is comprised of alkali and alkaline earth salts comprising alkali and alkaline earth fluorides, chlorides, bromides, iodides or combinations thereof. 3. The method of claim 1 wherein after the contacting the alloy with halogen step the molten salt bath contains halide of actinide elements selected from the group consisting of Th, U, Np, Pu, Am, Cm, and combinations thereof. 4. The method of claim 1 wherein the liquid alloy contains actinide metals selected from the group consisting of Th, U, Np, Pu, Am, Cm, and combinations thereof. 5. The method of claim 1, wherein the liquid alloy further comprises an element selected from group consisting of cobalt, iron, nickel, bismuth, gallium, aluminum, cadmium and combinations thereof. 6. The method of claim 1, wherein a surface of liquid alloy is formed beneath a surface of the molten salt bath and the halogen gas is injected under the surface of the surface of the liquid alloy. 7. The method of claim 1, wherein the second metal halide is part of a eutectic mixture and the second metal halide is removed from the molten salt bath. 8. The method of claim 1 wherein the alloy containing the actinide metal of the metal halide is generated before the crucible is submerged into the molten salt bath. 9. The method of claim 1 wherein the first reaction is a direct reaction between the liquid alloy and halogen. 10. The method of claim 1 wherein the contacting the alloy with halogen in a first reaction step further comprises providing additional metal to the crucible to allow for continuous operation. |
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summary | ||
description | This is a Continuation-In-Part Application of application Ser. No. 15/807,182 filed Nov. 8, 2017, entitled FLOATING NUCLEAR REACTOR PROTECTION SYSTEM. This invention relates to a floating nuclear power reactor. More particularly this invention relates to a floating nuclear power reactor including a barge which is floatably positioned in the interior of a large water-filled tank and wherein the nuclear power reactor is positioned on the barge. Even more particularly, the invention relates to a counter weight system which creates a lifting force to the barge to increase the buoyancy thereof. Even more particularly, the invention relates to a counter weight system which maintains the barge in a level condition with respect to the water-filled tank. Even more particularly, the invention relates to structure which permits normal vertical movement of the counter weights while preventing horizontal movement of the counter weights in the event of an earthquake. Applicant has received U.S. Pat. Nos. 9,378,855; 9,396,823; and 9,502,143 relating to nuclear reactors positioned in a body of water or tank to be able to flood and cool the nuclear reactor in the event of overheating or over pressurization of the nuclear reactor. In Applicant's latest invention shown and described in the co-pending application Ser. No. 15/807,182 filed Nov. 8, 2017, a suspension system is described for suspending and stabilizing a barge which is floating in a large water tank. The barges of Applicant's prior patents and patent applications, due to engineering requirements, may become too heavy to float in the water tank. Further, one side of the barge may be heavier than the other side of the barge which makes it difficult to maintain the barge in a level condition. Additionally, one end of the barge may be heavier than the other end of the barge which also makes it difficult to maintain the barge in a level condition. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. A floating nuclear reactor is disclosed. The floating nuclear reactor of this invention includes a tank, which may be rectangular, having a bottom wall, an upstanding first end wall, an upstanding second end wall, an upstanding first side wall and an upstanding second side wall. Each of the first end wall, the second end wall, the first side wall and the second side wall of the tank have an outer side, an inner side, a lower end and an upper end. The tank may be partially or fully buried in the ground with the tank having water therein. A barge is floatably positioned in the tank with the barge having a bottom wall, a first end wall, a second end wall, a first side wall and a second side wall. A nuclear reactor is positioned on the barge. At least one, and preferably a plurality of counter weight assemblies are secured to each of the first end wall, the second end wall, the first side wall and the second side wall of the barge. Each of the counter weight assemblies includes an elongated cable, having first and second ends, with the first end of the cable being secured to the barge. The cable extends from the barge and passes over a pulley mounted on the tank. The second end of the cable has a counter weight secured thereto. The counter weight assemblies create a lifting force to the barge to increase the buoyancy thereof and to maintain the barge in a level condition. If one side of the barge is heavier than the other side of the barge, the weights of the counter weights at the heavy side may be increased. If one end of the barge is heavier than the other end of the barge, the weights of the counter weights at the heavy end of the barge may be increased. The increased weights of the counter weights will maintain the barge in a level condition. In the alternative, an additional counter weight assembly may be positioned at the heavier side or end of the barge. The counter weights are vertically movable in channels which prevent other movement of the counter weights during an earthquake. It is therefore a principal object of the invention to provide a floating nuclear reactor which is positioned on a barge which floats in a water filled tank. A further object of this invention is to provide counter weight assemblies which are attached to the barge to provide a lifting force to the barge to increase the buoyancy of the barge. A further object of this invention is to provide counter weight assemblies which are attached to the barge to maintain the barge in a level position. Yet another objective of the invention is to provide a counterweight that moves only vertically during an earthquake. These and other objects will be apparent to those skilled in the art. Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense in that the scope of the present invention is defined only by the appended claims. Applicant has previously received U.S. Pat. Nos. 9,378,855; 9,396,823; and 9,502,143 relating to floating nuclear power reactors. Applicant incorporates the disclosure of the above identified patents in their entirety by reference thereto to complete this disclosure if necessary. The floating nuclear reactor of this invention is referred to generally by the reference numeral 10. The nuclear reactor 10 floats in a concrete tank 12 having a bottom wall 14, a first end wall 16, a second end wall 18, a first side wall 20, a second side wall 22 and an open upper end 24. Tank 12 is buried in the ground 26 as seen in FIG. 1 so that the open upper end 24 of tank 12 is at or above ground level 28. The tank 12 is partially filled with water 30 from a source of water. Preferably the water 30 is gravity fed to the tank 12. The tank 12 may be completely buried in the ground. The numeral 32 refers to a barge-like vessel which floats in the tank 12. Barge 32 includes a bottom wall 34, a first side wall 36, a second side wall 38, a semi-circular end wall 40 and an open end 41 at the ends 42 and 43 of side walls 36 and 38 respectively. Barge 32 is comprised of a metal material such as stainless steel, steel, iron, aluminum or other suitable material. Barge 32 is supported in tank 12 by a plurality of upper suspension assemblies 44, 46, 48, 50, 52, 54, 56 and 58 which extend between the barge 32 and the tank 12 as will be described in detail hereinafter. Barge 32 is also supported in tank 12 by eight lower suspension assemblies, identical to suspension assemblies 44, 46, 48, 50, 52, 54, 56 and 58, which are positioned below suspension assemblies 44, 46, 48, 50, 52, 54, 56 and 58. The numeral 59 refers to a nuclear reactor which is positioned in barge 32 so as to close the open end 41 of barge 32 as will be explained in detail hereinafter. Reactor 59 includes an upstanding containment member 60 which has a cylindrical body portion 62, a hemi-spherical upper end 64 and a hemi-spherical lower end 66. Containment member 60 is comprised of stainless steel or other suitable material. Containment member 60 is positioned at the open end 41 of barge 32 with the sides of containment member 60 being in engagement with the ends 42 and 43 of side walls 36 and 38 respectively of barge 32 and being secured thereto by welding or the like to close the open end 41 of barge 32. The positioning of the containment member 60 as just described causes the outer side of containment member 60 to be in contact with the water 30 in tank 12. Containment member 60 defines a sealed interior compartment 68. Containment member 60 has a hatch 70 mounted therein as seen in FIG. 3. Containment member 60 also has a pipe 72 extending from the lower end thereof which is in fluid communication with the interior compartment 68. A normally closed one-way valve 74 is imposed in pipe 72. A reactor vessel 75 is positioned in compartment 68 and has an interior compartment 76. Vessel 75 is supported in compartment 68 by braces 77 which extend between the exterior of reactor vessel 75 and the interior side of containment member 60 as seen in FIG. 3. The numeral 80 refers to an upstanding heat exchanger which is positioned adjacent containment member 60 as seen in the drawings. Heat exchanger 80 includes a body section 82, an upper section 84 and a lower section 86. Heat exchanger 80 is comprised of a metal material such as stainless steel or other suitable material. A vessel 88 is positioned within heat exchanger 80 and is supported therein by braces 90 extending therebetween. Vessel 88 defines an interior compartment 92. A tube 94 interconnects the reactor vessel 75 and the vessel 88 of heat exchanger 80 as seen in the drawings. The heat exchanger 80 is connected to a turbine 96 or other device which is connected to a generator 98 or other structure. A hollow metal cone 100 is mounted on the hemi-spherical upper end 64 of containment member 60. Cone 100 is comprised of stainless steel, steel or other suitable material. Cone 100 has an interior compartment 102 which is preferably filled with a filter material 104 which not only may serve as a filtration bed but serves as an impact absorber should the cone 100 be struck by an aircraft or a missile. The cone 100, if struck by an aircraft or missile, will disintegrate or tear apart the aircraft or missile and deflect the aircraft or missile away from the cone 100. An outlet pipe 106 may be provided in the upper end of containment member 60 to permit steam or the like to pass upwardly therethrough onto the filtration material 104. The cone 100 may also have a discharge tube assembly 108 extending upwardly from pipe 106 and which has discharge tubes 110 extending downwardly and outwardly from the upper end of tube 108. A metal cone 112 extends upwardly from the upper end of heat exchanger 80 and is filled with an impact absorbing material 114. Cone 112, if struck by an aircraft or missile, will disintegrate the aircraft or missile in the same manner as the cone 100. A roof 116 extends over the cones 100, 112 and the barge 32 to hide the reactor 59 and the heat exchanger 80 from view. Thus, if an aircraft is attempting to strike the reactor 59, the pilot of the aircraft will not be able to determine the exact location of the reactor 59. A pair of vertically disposed guide tracks or channels 120 and 122 are secured to the inner side of end wall 18. A pair of vertically disposed guide tracks or channels 124 and 126 are secured to the inner side of side wall 20. A pair of vertically disposed guide tracks or channels 128 and 130 are secured to the inner side of end wall 16. A pair of vertically disposed guide tracks or channels 132 and 134 are secured to the inner side of side wall 22. Each of the guide tracks 120, 122, 124, 126, 128, 130, 132 and 134 have an upper wheel and a lower wheel vertically movable therein. The guide tracks 134, 120, 122, 124, 126, 128, 130 and 132 form a part of the suspension assemblies 44, 46, 48, 50, 52, 54, 56 and 58 respectively. Inasmuch as the suspension assemblies 44, 46, 48, 50, 52, 54, 56 and 58 of FIGS. 1-6 are identical except for length, only suspension assembly 48 will be described in detail. Suspension assembly 48 includes an upper chain member 136, a lower chain member 138 and an intermediate chain member 140. The outer ends of chain members 136, 138 and 140 are secured to the upper wheel in guide track 122. The inner ends of chain members 136, 138 and 140 are secured to the barge 32. As seen, upper chain member 136 extends upwardly and inwardly from guide track 122 to barge 32. As also seen, lower chain member 138 extends downwardly and inwardly from guide track 122 to barge 32. Further, as seen, intermediate chain member 140 extends horizontally inwardly from guide track 122 to barge 32. The suspension assembly below suspension assembly 46 would be similarly attached to the lower wheel in guide track 122 and the barge 32. The other suspension assemblies would be attached to the guide tracks 124, 126, 128, 130, 132 and 134 and the barge 32. The suspension assemblies 44, 50, 56 and 58 of FIGS. 1-6 are identical. The suspension assemblies 46, 48, 54 and 56 of FIGS. 1-6 are identical. The only difference between the suspension assemblies 44, 50, 56, 58 and the suspension assemblies 46, 48, 54 and 56 is that the suspension assemblies 46, 48, 54 and 56 are somewhat longer than the suspension assemblies 44, 50, 56 and 58. FIGS. 7 and 8 illustrate a portion of the subject matter of this application. As stated hereinabove, some of the barges having nuclear reactors therein which are very heavy and will not float in the tank 12. Thus, a plurality of counter weight assemblies 142 are provided which interconnect the barge 32 with the tank 12 to provide a lifting force to the barge 32 thereby increasing the buoyancy of the barge 32. Each of the counter weight assemblies 142 of FIG. 7 includes a pulley 144 which is rotatably secured, about a horizontal axis, to the respective side wall of the tank 12. As seen in FIG. 7, the pulley 144 at the right side of FIG. 7 is mounted on wall 20 of tank 12 and the pulley 144 at the left side of FIG. 7 is mounted on wall 22 of tank 12. Each of the counter weight assemblies 142 of FIG. 7 includes a cable 146 having end 147 thereof secured to the barge 32. Cable 146 extends upwardly from barge 32 and passes over pulley 144 and thence downwardly therefrom. A counter weight 148 is connected to end 150 of cable 146. In FIG. 7, the counter weights 148 have the same weights. Although FIG. 7 illustrates that the counter weight assemblies are attached to opposite sides of the tank 12, there normally will be a pair of counter weight assemblies attached to each of the ends of the barge 32. Further, there may be a plurality of counter weight assemblies attached to each side of the barge 32 and to each end of the barge 32. FIG. 8 illustrates the situation wherein the right side of barge 32 is heavier than the left side of barge 32. In that case, the counter weight 148A will be larger and heavier than the counter weight 148 at the left side of the barge 32 to maintain the barge 32 in a level position. Further, if one end of the barge 32 is heavier than the other end of the barge 32, a heavier counter weight will be used at the heavy end of the barge 32 to maintain the barge 32 in a level position. Referring now to FIG. 9, structure is provided to prevent horizontal movement of the counter weight assemblies in the event of an earthquake. Referring to the left hand counter weight assembly 142, a pair of elongated and vertically disposed brackets 150 and 152 are secured to the wall 20 of tank 12. An elongated and vertically disposed channel 154 is secured to bracket 150. An elongated and vertically disposed channel 156 is secured to bracket 152. The channels 154 and 156 embrace the ends of the counter weight 148. The channels 154 and 156 permit counter weight 148 to vertically move therein. The channels 154 and 156 prevent horizontal movement of the counter weight 148 in the event of an earthquake. The structure at the right side of FIG. 9 is identical to the structure at the left side of FIG. 9 and will not be described in detail. FIG. 10 is a partial sectional view illustrating the barge 32 and which is supported by the structure of FIG. 9. Thus it can be seen that the invention accomplishes at least all of its stated objectives. Although the invention has been described in language that is specific to certain structures and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. |
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abstract | A nuclear fuel and a method to produce a nuclear fuel wherein a porous uranium dioxide arrangement is provided, the arrangement is infiltrated with a precursor liquid and the arrangement is thermally treated such the porous uranium dioxide arrangement is infiltrated with a precursor liquid, followed by a thermal treating of the porous uranium dioxide arrangement with the infiltrated precursor liquid such that the precursor liquid is converted to a second phase. |
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abstract | At least one pair of hodoscope radiation monitors arranged to simultaneously monitor a target region that contains a source of radiation. The hodoscopes are preferably arranged so that their fields of view of the region are approximately orthogonal. The fields of view of the two detectors will overlap in a region that contains the source of radiation. Each of the two detectors will record radiation from the overlap region and, in addition, will record background radiation emanating from other regions within detector fields of view. The present invention provides statistical correlation techniques to estimate the extent to which unusually high radiation originates in the overlap region, irrespective of background in the field-of-view of individual hodoscope detectors. The source of radiation might be spontaneous, might be from an activation process, or might be scattered in from an external beam. |
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description | This application claims the benefit of Provisional Application Ser. No. 60/707,272, filed Aug. 11, 2005, entitled In-The-Loop Novelty Detection Systems, Methods and Computer Program Products For Real-Time Diagnostics And Prognostics In Complex Physical Systems, assigned to the assignee of the present application, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. This invention relates to computer systems, methods and/or computer program products, and more particularly to systems, methods and/or computer program products that are capable of performing real-time diagnostics/prognostics on complex physical systems. Diagnostic and prognostic systems, methods and computer program products are widely used to monitor, interpret and/or predict the health of a physical system. As is well known to those having skill in the art, diagnostics refers to determining the state of a part, component, subsystem or system with respect to its ability to perform its function according to design-intended parameters, whereas prognostics refers to predictive diagnostics which includes determining the remaining life, anticipated operational time-to-failure, and/or failure trajectory of a part, component, subsystem or system. In general, conventional diagnostic systems may use physical models of the physical system and/or predetermined nominal limits of sensor values to determine the health of the physical system. A typical scenario in the automotive industry may involve the on-board retention of diagnostic data, such as misfire flops in automotive engine control applications, followed by batch downloads of diagnostic information to base stations for further analysis and logistics decision support. Conventional techniques that use predetermined normal limits of sensor values may use electronic lookup tables. Thus, current observations of sensor values may be compared against a lookup table of case-based histories of known behaviors. During field operations, baseline states of the system may be recorded as either normal or abnormal. Observed states are then compared with the historical states to determine whether they have been seen before and whether they are normal or not. While this approach can be performed quickly enough for relatively well behaved operations, it may not be suitable to complex behaviors, especially in changing environments when new behavior may be observed that is not in the library of observed states. Moreover, lookup table-based analysis may become exceedingly complex as the complexity of the physical system increases. The experimental baseline determination for vehicles, for example, may assume that all possible states encountered in the field can be predicted and captured in lookup tables for real-time diagnostics and prognostics. Moreover, pre-established lookup tables also may be based on vehicle platform averages, and may not provide granularity for individual vehicles. Finally, cross-sensor associations may be difficult to capture in conventional lookup tables. Many other diagnostics and primitive prognostics techniques may be based on physical models that describe normal behavior under a range of different input parameters. For example, engine management might be based on physical modeling in the form of a set of equations, which may involve, for example, pressure, temperature and other variables. Such physical models, using a “reductionist” approach, may often be constrained to small parameter sets for mathematical tractability. As a result, comprehensive physical modeling for diagnostics of complex systems may be difficult, if not impossible. As an alternative to physical models, statistical approaches like neural computing may be used in some applications for pattern recognition. In these approaches, large data sets of attributes are obtained through observation of the system, usually during a test-and-validation stage. This data may then be used to fit statistical models that can be used to determine whether an observed state is “normal”. These techniques may require large data sets for model fitting, may not be adaptable over time and may be computationally prohibitive in a real-time environment. Several potential difficulties may be associated with the use of the above approaches for complex systems and/or for real-time diagnostics. In particular, comprehensive physical modeling of complex systems for real-time applications may be difficult if not impossible, and the computational requirements may well be prohibitive. Moreover, the experimental baseline determination on sample physical systems may assume all possible states encountered in the field can be predicted and captured in lookup tables for real-time diagnostics and/or prognostics, and that the results are representative of an entire fleet of systems. Aging phenomena during real world operation also may be difficult to anticipate, since aging patterns are biased by history of individual use, and may not be easily extrapolated. Moreover, batch downloads from a complex system can add response delay and make real-time diagnostics difficult. In summary, real-time diagnostics/prognostics during field operation may use continuous comparison and interpretation of the current system states with respect to design-intended performance baselines. Practical development of such onboard diagnostics may be hampered by the lack of analytical tools that are fast enough to keep up with the physical process in real-time, especially in the case of large, complex systems, where physical models may not be practically possible. Some embodiments of the present invention provide diagnostic/prognostic systems for a physical system, wherein a plurality of sensors is configured to repeatedly monitor variables of the physical system during operation. In some embodiments, the monitoring may be continuous and/or periodic. A first associative memory is provided that is configured to learn associations of sensor values. A novelty detection system also is provided, that is responsive to the plurality of sensors and that is configured to repeatedly observe into the first associative memory, states of associations among the variables that are repeatedly monitored, during a learning phase. The novelty detection system is further configured to thereafter imagine at least one state of associations among the variables that are monitored relative to the states of associations that are observed in the first associative memory, to identify a novel state of associations among the variables. Accordingly, the novelty detection system may be configured to track the outputs of the plurality of sensor values and their associations, comparing them to previously learned associations in the first associative memory, and identifying novel (i.e., not previously learned) associations. In some embodiments, the novelty detection system is further configured to determine whether the novel state is indicative of normal operation or of a potential abnormal operation. In still other embodiments, the novelty detection system may be further configured to observe the novel state that is indicative of normal operation into the associative memory. In some embodiments, the variables that are repeatedly monitored may be assigned to simple or “fuzzified” bins, and the novelty system may be configured to repeatedly observe into the associative memory, states of associations among the binned variable values, during the learning phase. Binning and/or fuzzification may be applied to continuous and/or discrete variables. Other embodiments of the present invention may provide sensor output pattern completion in case of sensor failure. Such pattern completion may provide limp-home capability by feeding to controllers sensor values for proper operation. In still other embodiments of the invention, a second associative memory also is provided that includes therein associations of attributes of failure modes of the physical system. A failure mode learning system is also provided that is responsive to the novelty detection system and to the second associative memory. The failure mode learning system is configured to imagine attributes of the novel state relative to the associations of attributes of failure modes of the physical system, to identify and/or predict a potential failure mode for the physical system. In other embodiments, the failure mode learning system may be further configured to identify and/or learn a new failure mode for subsequent associations. In still other embodiments of the invention, a trend learning-enabled prognostic system is provided that is configured to imagine time-line-based associations based on previously learned time-stamped patterns. In these embodiments, the time-stamped associations may also be observed into the second associative memory of attributes of failure modes to enable prognostics. In yet other embodiments of the present invention, a third associative memory is also provided that includes therein associations of attributes of previous corrective actions and/or responses to failure modes of the physical system. An intervention learning system also is provided, that is responsive to the failure mode learning system and to the third associative memory. The intervention learning system is configured to observe the attributes of the potential failure mode relative to the responses in the third associative memory, to identify a potential corrective action and/or response to the potential failure mode. In some embodiments, the intervention learning system is further configured to apply the potential response to the physical system in real-time. In other embodiments, the novelty detection system, the failure mode learning system, the intervention learning system and the first, second and third associative memories operate on the physical system in real-time. Still other embodiments of the present invention provide a diagnostic/prognostic system for a physical system that includes a plurality of sensors that are configured to repeatedly monitor physical system variables during operation. The diagnostic/prognostic system includes a novelty detection system, a failure mode learning system and an intervention system. The novelty detection system is responsive to the plurality of sensors and is configured to identify a novel state among the sensor values that is indicative of a potential abnormal operation. The failure mode learning system is responsive to the novelty detection system, and is configured to identify potential failure modes for the physical system in response to the novel state. The failure mode learning system may include a trend learning system that is responsive to the novelty detection system and is configured to identify and learn failure trends for prognostics. The intervention system is responsive to the failure mode system and is configured to identify a potential response and/or corrective action to the potential failure mode. Embodiments of the invention have been described above in connection with diagnostic/prognostic systems for a physical system. However, analogous diagnostic/prognostic methods and computer program products may also be provided according to other embodiments of the present invention. Moreover, embodiments of the invention that are described herein may be used in various combinations and subcombinations. The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will filly convey the scope of the invention to those skilled in the art. It will be understood that when an element is referred to as being “coupled”, “connected” or “responsive” to another element, it can be directly coupled, connected or responsive to the other element, or intervening elements may also be present. In contrast, when an element is referred to as being “directly coupled”, “directly connected” or “directly responsive” to another element, there are no intervening elements present. Like numbers refer to like elements throughout. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items and may be abbreviated by “/”. It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The present invention is described in part below with reference to block diagrams and flowcharts of methods, systems and computer program products according to embodiments of the invention. It will be understood that a block of the block diagrams or flowcharts, and combinations of blocks in the block diagrams or flowcharts, may be implemented at least in part by computer program instructions. These computer program instructions may be provided to one or more enterprise, application, personal, pervasive and/or embedded computer systems, such that the instructions, which execute via the computer system(s) create means, modules, devices or methods for implementing the functions/acts specified in the block diagram block or blocks. Combinations of general purpose computer systems and/or special purpose hardware also may be used in other embodiments. These computer program instructions may also be stored in memory of the computer system(s) that can direct the computer system(s) to function in a particular manner, such that the instructions stored in the memory produce an article of manufacture including computer-readable program code which implements the functions/acts specified in block or blocks. The computer program instructions may also be loaded into the computer system(s) to cause a series of operational steps to be performed by the computer system(s) to produce a computer implemented process such that the instructions which execute on the processor provide steps for implementing the functions/acts specified in the block or blocks. Accordingly, a given block or blocks of the block diagrams and/or flowcharts provides support for methods, computer program products and/or systems (structural and/or means-plus-function). It should also be noted that in some alternate implementations, the functions/acts noted in the flowcharts may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Finally, the functionality of one or more blocks may be separated and/or combined with that of other blocks. It will also be understood that, in many systems that are already equipped with some form of microprocessor-based computational capability, the blocks of the block diagram may be embedded within operating and/or application programs that execute on the microprocessor. FIG. 1 is a block diagram of diagnostic/prognostic systems, methods and/or computer program products according to various embodiments of the present invention. These diagnostic/prognostic systems, methods and/or computer program products 100 may be used to monitor and/or predict the health of a physical system 110. As used herein, a physical system may include an individual physical component, such as a motor or engine, or a more complex and dynamic physical system, such as an entire manufacturing system, power system, transportation system, supply chain and/or other complex systems that are characterized by interrelated subsystems with large numbers of operating parameters and multiple modes of operation that depend dynamically on the physical operating environment. Such real-time system health and trend characterization not only can enable condition-based maintenance and repair, but can also provide real-time decision support to a supply chain, command and control, engineering, research and development, and/or other operations. A plurality of sensors 120 may be configured to repeatedly monitor variables 122 of the physical system 110 in operation. In some embodiments, monitoring may take place continuously and/or periodically. The design and operation of sensors 120 can vary widely, depending on the physical system and/or the variables being monitored, as is well known to those having skill in the art. Signal conditioning, aggregating, pre-processing, post-processing and/or other operations also may be performed using techniques well known to those having skill in the art. Moreover, as will be described in detail below, the variable values 122 may be “fuzzified”, for example by assigning values to bins, and embodiments of the invention may operate on the binned or otherwise fuzzified values. As illustrated in FIG. 1, in some embodiments of the present invention, a first layer 191 may include a first associative memory 140 and a novelty detection Block 130. An optional second layer 192 may include a second associative memory 160 and a failure mode learning Block 150. Finally, an optional third layer 193 may include a third associative memory 180 and an intervention learning Block 170. Each of these layers 191-193 will now be described in general, followed by more detailed description. In general, the novelty detection Block 130 is responsive to the plurality of sensors 120, and is configured to repeatedly observe into the first associative memory 140 states of associations among the variables 122 that are repeatedly monitored, during a learning phase. The novelty detection Block 130 is further configured to thereafter imagine at least one state of associations among the variables 122 that are monitored relative to the states of associations that are observed in the first associative memory 140, to identify a novel state 132 of associations among the variables 122. In some embodiments, the novelty detection Block 130 is further configured to determine whether the novel state 132 is indicative of normal operation or of a potential abnormal operation. Moreover, if the novel state is indicative of normal operation, the novelty detection Block 130 may be further configured to observe the novel state into the first associative memory 140. As was also described above, the novelty detection Block 130 may be further configured to assign the variables that are repeatedly sensed into bins and/or to otherwise fuzzify the variable values, and to repeatedly observe into the first associative memory 140 states of associations among the binned or otherwise fuzzified values during the learning phase. Continuing with the description of FIG. 1, in the optional second layer 192, the second associative memory 160 includes therein associations of attributes of failure modes of the physical system 110. A failure mode learning Block 150 is responsive to the novelty detection Block 130 and to the second associative memory 160, and is configured to imagine attributes of the novel state 132 relative to the associations of attributes of failure modes of the physical system that are observed in the second associative memory 160, to identify a potential failure mode 152 for the physical system 110, and thereby provide failure diagnostics and/or prognostics. More specifically, in some embodiments of the invention, the failure mode learning Block 150 can include a failure mode identification and diagnostics Block 154 and a trend learning and prognostics Block 156. The second associative memory 160 contains attributes of previously experienced failure modes that are observed during “strife” (stress-life) testing, are observed during training and validation, and/or are observed during operation and identified as failure modes by experts, as well as contextual attributes. When a novel state is observed by the novelty detection system 130 this state is observed into the second associative memory 160 by the failure mode identification and diagnostics Block 154, to identify the potential failure mode based on previously learned failure modes. When the second associative memory 160 contains time-stamped attributes of previously observed failure modes, the trend learning and prognostics Block 156 is able to predict time to-failure and other prognostics. In other embodiments, the failure mode learning Block 150 may be further configured to identify a potential new failure mode for the physical system 110 when the failure learning mode is not able to correlate attributes of the current potential failure trajectory with failure modes contained in the second associative memory 160. The difference between degradation and failure modes on one hand and benign operational changes (e.g., aging) may be based on an interpretation process that may rely both on associative memory learning of patterns of previously experienced failure modes and expert experience. Based on the imaginings of the failure mode learning system and expert experience, the state space of normal operations can be updated in the novelty detection Block 130 for future state tracking. Still referring to FIG. 1, the optional third layer 193 may include the third associative memory 180 that includes therein associations of attributes of corrective actions and/or responses to failure modes of the physical system 110. An intervention learning Block 170 is responsive to the failure mode learning system 150 and to the third associative memory 180, and is configured to imagine attributes of the potential failure mode 152 relative to the responses in the third associative memory, to identify a potential corrective action and/or response 172 to the potential failure mode. More specifically, in some embodiments of the invention, the third associative memory 180 contains attributes of experienced failure modes, successful corrective actions or responses, associated mean-times-to-failure and contextual attributes and is configured to make correlations between failure mode attributes and corrective responses that can be implemented to return the physical system 110 to the normal operating regime. In the event of a potential failure, the intervention learning system 170 observes into the third associative memory 180 the attributes of the current potential failure mode to imagine a recommendation of a corrective action or response 172 that can return the physical system 110 to design-intended operating conditions. In some embodiments, the intervention learning Block 170 is further configured to apply the potential response 172 to the physical system 110 in real-time, as shown by dashed arrow 174. In other embodiments, the novelty detection system 130, the failure mode learning system 150, the intervention learning system 170 and the first, second and third associative memories 140, 160 and 180 all operate on the physical system 110 in real-time, to thereby provide real-time diagnostics, which may include real-time prognostics. Additional detailed description of the various blocks of FIG. 1 will now be provided in connection with FIGS. 2-11. In particular, some embodiments of the invention can extend the operational capabilities of current diagnostics and prognostics for monitoring, interpreting and predicting the health of complex physical systems. By implementing novelty detection, some embodiments of the invention are capable of real-time state learning for the purpose of identifying system states that are novel (outside the “normal” baseline, and potential performance degradation indicators) as well as identifying system states associated with previously learned failure modes. During a validation, learning or training mode, novelty detection learns normal (baseline) system behavior over a range of design-intended operational regimes using a non-symbolic, associative memory. During an operational mode, these patterns of system-specific, normal behavior are used as a reference for identification of novel and potential failure states that may warrant attention and/or corrective action. Corrective action can be autonomous and/or human-implemented. As was described in FIG. 1, the novelty detection and prognostics/diagnostics capability may be implemented in a layered learning framework. Thus, some embodiments of the invention can recognize previously unobserved or “novel” system behavior that may be associated with a potential failure state before failure occurs. In some embodiments, the novelty detection Block 130, also referred to as a novelty detection engine, learns normal system behavior that is consistent with design-intended performance specifications during training. As used herein, any system behavior that is consistent with the design-intended performance specifications may be considered to be normal behavior. A normal baseline may be established during standard product test and validation. During use, newly observed system states are compared with (imagined) a learned associative memory of normal states in order to identify behavior that is “novel” and possibly associated with a failure state or performance degradation trend potentially leading to future failure (prognostics). Novelty detection can incorporate a non-symbolic and memory efficient associative memory technology that is capable of very fast real-time state learning. Embodiments of the invention need not use physical models or pre-determined normal limits to sensor values. Further, embodiments of the invention can be real-time capable and, thus, adaptable to dynamic system behaviors. Other conventional techniques often compare the observed values of the current system state with known failure modes or with previously experienced failure states of similar systems obtained by “strife” (stress-life) testing during product development. In contrast, embodiments of the invention need not rely on a prior knowledge of known failure modes, but rather can assess the “novelty” of a current state by comparing it to an associative memory of learned normal behavior that may include not only system variables but also may include contextual information related to the operating environment. By comparing current in-use performance with learned normal performance as captured in a design-intended performance envelope and/or learned trends to failure, it is possible to discern and anticipate potentially fatal trajectories during system operations that may be obtained during strife (stress-life) testing and/or physical system operations and training. In human cognition, an observed system state is new or “novel” if it has not been observed in the past or has not been installed in human memory. Similarly, in exemplary embodiments of the invention, the novelty of an observed state may be assessed against the backdrop of previously observed and learned system states that have been accumulated (observed) in an associative memory, such as associative memories 140, 160 and/or 180 of FIG. 1. As with human learning, this associative memory is built through “experiential” leaning in which a newly observed state is accumulated in the associative memory as a basis for interpreting future events. For the purposes of the discussion below, the health of a physical system may be characterized by the simultaneous and time-stamped combination of significant outputs 122 of sensors 120 of the physical system 110 and their relationships, plus any sensored contextual variables related to the physical environment that might affect system performance. Over a period of time, the accumulation of these multi-parameter sensor outputs, any derived variables, and/or contextual variables can determine an n-dimensional state space in the first associative memory 140 that represents the behavior of the physical system. Embodiments of the invention, thus, are able to learn through experience, one time-stamped observation of simultaneous sensor readings at a time. These observations may then be filtered through a significance filter that may be included in the novelty detection Block 130, as being consistent with design-intended expectations, or inconsistent with design-intended expectations, and thus subject to further interpretation and response. In some embodiments, the resulting state space that is observed in the first associative memory 140 can serve as a basis for evaluating future states. Newly observed states that do not belong to this state space are considered to be novel states 132 and may (or may not be) associated with a failure mode or a trend towards failure. For example, the direction and rate at which a sequence of observed states moves away from the state space can be used to help predict failure patterns and time-to-failure. The state space that is observed in the first associative memory 140 can provide a useful tool for capturing observed relationships, or associations, between state space variables. In conventional single or multi-sensor systems, individual sensor values are tracked to assure that they stay within pre-determined limits. However, system-level malfunctioning may occur even if all individual sensor outputs are within limits, due to inconsistent correlation of sensor outputs. By defining the time-dynamic state of a system as the complete time-stamped set of sensor outputs according to some embodiments of the invention, one can compute the correlated behavior of individual sensor values in defining the acceptable state space. Moreover, in some embodiments, pattern completion may also be used, for example, in the case of a sensor failure. Further, novelty detection according to some embodiments of the invention can reflect system-specific behavior on the premise that more efficient and reliable prognostics can be achieved by comparing system-specific multi-sensor states to a system-specific learned normal baseline, rather than a platform-based generic performance baseline. Novelty generally has limited meaning for specific system diagnostics and prognostics when based on averages over multiple system performance histories, because a novel state for one system may not be novel for another system under the same or different operating conditions. In some embodiments of the invention, the ability to implement novelty detection may be enabled by a type of machine learning called associative memory 140, for example associative memory technology developed by Saffron Technology, Inc., Morrisville, N.C. This associative memory technology is described in U.S. Pat. No. 6,581,049 entitled “Artificial Neurons Including Power Series of Weights and Counts That Represent Prior and Next Association”, U.S. Pat. No. 7,016,886 entitled “Artificial Neurons Including Weights That Include Maximal Projections”, U.S. Patent Application Publication No. 2005/0163347 A1, published Jul. 28, 2005, entitled “Distance-Based Spatial Representation and Prediction Systems, Methods and Computer Program Products for Associative Memories”, U.S. Application Publication No. 2006/0095653 A1, published May 4, 2006, entitled “Network of Networks of Associative Memory Networks for Knowledge Management”, U.S. application Ser. No. 11/035,472, filed Jan. 14, 2005, entitled “Methods, Systems And Computer Program Products For Analogy Detection Among Entities Using Reciprocal Similarity Measures”, application Ser. No. 11/196,871, filed Aug. 4, 2005, entitled “Associative Matrix Methods, Systems and Computer Program Products Using Bit Plane Representations of Selected Segments” and/or application Ser. No. 11/426,520, filed Jun. 26, 2006, entitled Nonlinear Associative Memories Using Linear Arrays of Associative Memory Cells, and Methods of Operating Same, the disclosures of which are hereby incorporated herein by reference in their entireties as if set forth fully herein. These patents and applications may be referred to collectively herein as the Saffron Technology. Associative memories 140, 160 and/or 180 may include the Saffron Technology and/or other conventional associative memory technology. An associative memory can allow storage, discovery, and retrieval of learned associations between extremely large numbers of attributes in real-time. At a most basic level, an associative memory stores (observes) information about how attributes and their respective features occur together. The predictive power of the associative memory technology comes from its potential ability to efficiently interpret and analyze the frequency of these co-occurrences and to produce various metrics in real-time. In some embodiments of the invention, a first associative memory 140 can contain stored information about previously observed system states (such as sensor outputs within a context) as “counts” between co-occurring sensor value pairs, or attribute combinations, across all observations. As new system states are observed, this co-occurrence matrix is incremented and the “strength” of correlations across the sensor variables is reflected in the increasing number of counts of observed co-occurring value combinations. As in human learning, this memory of learned associations and experience can be queried (imagined) as a basis for interpreting the significance of new system states and identifying recommended responses as described above. In the case of large complex systems involving up to hundreds, thousands or more of sensors transmitting at small time-steps, the size of the co-occurrence matrix may quickly become intractable and unsuitable for real-time applications using classical data mining and model-fitting approaches. Other approaches may compress the memory to reduce storage requirements, but may require that the memory be uncompressed to add new observations or to respond to queries. By allowing learning in a compressed state, however, the associative memory is able to learn extremely quickly-enabling fast state learning for real-time prognostics and diagnostics. By virtue of the above-cited Saffron Technology, Saffron's implementation of associative memory has been demonstrated to be able to handle up to one million or more attributes. The ability of associative memory to handle extremely large and complex datasets makes it well suited for real-time prognostics applications as well as for large-scale diagnostics tasks. For example, using associative memory it is possible to simultaneously monitor the operational performance of a fleet of vehicles in order to observe broad trends in system-wide behavior. Conventional techniques may not be able to interpret hundreds of thousands of attribute values in real-time (along with contextual variables) such as would be used to monitor a fleet of vehicles operating in different regimes and environments. The state space of accumulated sensor and contextual values that is accumulated in the first associative memory 140 by the novelty detection Block 130 obtained during training, under both normal and in-use operations, may be represented in a construct referred to as the design-intended performance envelope. The disposition of a new observation with respect to both novelty and normality is a function of its “closeness” to the design-intended performance envelope. A new observation is novel if it falls sufficiently outside the envelope. Similarly, a new observation is normal if it falls within the envelope or “close enough” to it. The design-intended envelope is typically established based on exercising the system 110 within the intended design envelope, e.g., during a test and validation phase. There are a number of ways to assess the “closeness” of a new observation. One direct approach would be to compute the n-dimensional vector distance between the most recent observation and the closest point on the state space frontier, as illustrated in FIG. 2A for a simple two-attribute problem and 20 observations. Computing this metric may be computationally time-consuming when the state space is defined by an extremely large number of observations and attributes. According to other embodiments of the invention, an alternative approach may be used that may be better aligned with the machine representation of associative memory 140 as a matrix of co-occurrences of attribute values. In particular, some embodiments of the invention may approach the building of the design-intended performance envelope as a “covering” problem. The fullest possible range of attributes is mapped into bands, in essence creating fuzzy sets of attribute values. Enumerating all possible combinations of bands produces a set of “bins” that can fully cover the potential normal performance envelope. The use of fuzzy values instead of scalar data to represent system states can be consistent with the particular way associative memory understands and represents data. An associative memory may not understand the semantics of the values that it stores. Rather, it may understand them as symbols, and the matching it does may be based on matching of symbols. For example, suppose a set of values is observed as (23.4, 10.8, 2.5). An associative memory may not determine that (20.6, 12.5, 1) is nearer than (29.23 16, −8). Both vectors are new values that haven't been seen before. Similarly, the vectors (20.6, 12.5, 1.44) and (20.6, 12.5, and 1.42) may not be recognized as the “same” value to one significant digit. The use of fuzzy sets can avoid the potential problem of requiring an associative memory to recognize both scalar values and ordinal relationships. The covering approach can provide an elegant way for the memory to store observed system states as “counts” between co-occurring sensor values or attributes. An example is shown in FIG. 2B. This figure shows the same simple two-attribute problem as FIG. 2A. Before the data are fed to the associative memory, they are preprocessed into bands or bins as described above. Collectively, the adjoining bins define the normal design-intended performance envelope. The size of the bands may be determined such that, during training, one might expect the 2-dimensional space of normal behavior to be well covered by observed values. The bins need not be of the same size. More than one observation may fall into one bin. The dimensions of the bins and the length of training may be determined a priori by an analyst and/or may be dynamically determined. Typically, with longer training periods, smaller bin sizes will fully cover the normal envelope, but this may depend on the specific dynamics on the physical system. With adequate training, it is possible to increase or maximize the possibility that all normal states are observed by adjusting the granularity of the bin size. An accurate map of system-operating-within-the-design-intended-performance-envelope and the observed sensor states may be desirable for the integrity of the system. In some cases, independent performance indicators may be used. For example, during training, the system can be instrumented with performance tracking capabilities, for example using a dynamometer, noise and vibration tracking equipment, etc. These instruments would confirm that the observed states represent normal states. Further, during training, the physical systems should be operated in all operating regimes that might be expected. For example, in the case of a car engine one might include start-up mode, as well as acceleration, deceleration and so forth. During training, the behavior of the physical system is assumed to be normal, subject to the discussion above, and all observed values are added (observed) to memory unless it is determined that there is a likelihood of aberrant system behavior. During use, newly observed novel states may or may not be normal. Novel states that indicate possible future failure (a “potential failure”) can be characterized by variables such as the speed of a shift away from the normal performance envelope, the magnitude of shift, and/or the persistence of the shift. The determination of these variables may be made based on a priori assessment of the dynamic behavior of the system and/or may be determined dynamically. Appropriate policies (such as alerts to operators) may be implemented as rules within the novelty detection Block 130. Those novel states identified as not normal or indeterminate may be passed for further analysis as described below. In some embodiments, observed states may be grouped by the novelty detection Block 130 into three types: 1) novel and normal; 2) novel and not normal; and 3) novel and indeterminate. These three types are discussed below. Type 1: Novel and Normal. As shown in FIG. 3A, a novel state may indicate an external shock which momentarily throws the system into a new behavioral regime, but which returns to normal behavior quickly. This transient shock dissipates with no lingering effect on system behavior. Alerts might not be necessary in these situations. Alternatively, as shown in FIG. 3B, the newly observed state is clearly inside the normal performance envelope but is novel simply because the system has not “hit” that bin during training. If such an observation is followed by one or more states that also fall within the normal performance envelope, it is likely that the system is behaving normally. Type 2: Novel and Not Normal. Novel states that are not normal may be indicated by a number of different behaviors. Non-normal behavior might be manifested by the rapid divergence of observed states from the normal performance envelope. As shown in FIG. 3C, repeated observation of novel states with sudden and sustained movement away from normal performance envelope might represent a shift to a new and persistent abnormal operating regime. Type 3: Novel and Indeterminate. Indeterminate behaviors, as shown in FIG. 3D, manifest themselves as random sequences of novel and not novel states that result in the migration of the performance envelope. Depending on the nature of the sequence, this might indicate a new environmental regime which quickly stabilizes, or might indicate normal aging of the system which was not captured during training. These behaviors and rule sets may be worked out in advance by an expert who is extremely familiar with the operating characteristics of the physical system and/or may be derived dynamically. Novelty detection Block 130 according to exemplary embodiments of the invention can consider the context of a system's behavior in the assessment of its performance. These contextual attributes may assist in assessing whether a novel state is normal or not normal, and also the root cause of failure. The learning process can also observe clustering of states within a state envelope. Such clusters may provide valuable information in at least two ways: (1) a shift of such clusters may indicate an environmentally induced change in system behavior (desert heat or high altitudes), or (2) a degradation trend towards failure. Some embodiments of the invention can use the novelty detection engine 130 for real-time diagnostics/prognostics. Adaptive real-time control also may be provided, as illustrated by dashed arrow 174 of FIG. 1, to the extent that may not be possible in previous approaches. FIG. 4 illustrates a novelty detection Block 130 embedded in a feedback loop comprised of four functionalities: sensing 120, transmission 420, processing 430 and response 440. Each of these four functionalities will now be described. Sensing Block 120 was described earlier in connection with FIG. 1. As discussed earlier, the state-space approach assumes that the state (i.e., health) of a physical system can be characterized by the simultaneous and, in some embodiments, time-stamped combination of significant sensor outputs 120 of a physical system 110. In a noise-rich environment, preprocessing 410 may be used to extract meaningful data from sensored data and signals. The preprocessor 410 can translate sensored data into meaningful attributes that can be interpreted by the associative memory 140, and can build a context for these attributes. For example, vibrational signatures may be best dealt with through some form of spectral analysis such as a Fast Fourier Transform. Some data may be represented as fuzzy values or sets that can be expressed as linguistic variables. Contextual attributes might include operating conditions such as temperature, pressure or altitude. Sensed (and, in some embodiments, pre-processed) data is transmitted by the transmission Block 420 to the processing Block 430 for interpretation. In many modern systems, a data bus protocol such as CAN (Controller Area Network) or one of its derivatives may be used for sensor information transmission 420 to process modules in real-time, i.e., fast enough to keep up with control cycles. In principle, embodiments of the invention can pull sensor data from a central processor, distributed modules, and/or plug directly into a data bus. The processing Block 430 represents the intelligence of any system controller or logistics support function. It comprehends monitoring the system controller, data processing, and analysis, if a closed-loop feedback controller is used, as well as actuation outputs. In some embodiments of the invention, the processing function 430 can be enhanced by the real-time implementation of learning and novelty detection. The response Block 440 can respond to outputs of the novelty detection engine 130, in some embodiments of the invention. Some embodiments of the invention can provide a real-time response. In particular, while the execution time of an action called for by a control function may not be reduced beyond that dictated by physical limits (e.g., milliseconds to inject fuel into the intake manifold of an automobile engine or hours to deliver spare parts from a warehouse to a maintenance location), the time taken to compute actions based on sensor inputs may be a function of the computational speed of the controller. Accordingly, real-time in this context can mean fast enough to keep up with the physical system, which might be quite slow in a chemical factory, but much faster in electronic fuel injection. Alternatively, in a real-time control application where the observed states might be used for real-time adaptive control (e.g., parametric adjustments for altitude and such), the real-time computation should be fast enough to keep up with the parametric correction, which might be much slower than the actual feedback control loop update interval itself. Finally, for corrective action to diagnostics and prognostics indicators, the alert to all stake holders (operator, maintenance, spare parts, engineering, R&D, etc.) may be in near real-time and near simultaneous, but the time required for execution may be orders of magnitude higher. For example, a real-time alert may be issued to make a part available at a specific location to repair an aircraft engine after landing. However, actually transporting the part will take time. The triggering action, however, may take place in real-time. By recognizing potential performance degradation and associated trends in real-time, a control system according to some embodiments of the invention, be it a logistics support function or an internal combustion engine, can drive corrective response almost immediately. Appropriate correction can thus be accomplished in near real-time in some embodiments of the invention, and can be compared with classical techniques where data downloads and off-line data processing may need to be performed before corrective action can be taken. Continuing with the description of FIG. 4, the novelty detection engine 130 builds (i.e., learns) a normal (i.e., performance-as-intended) state-space baseline that can serve as a reference for recognition of novel (i.e., previously unobserved) system states. Moreover, subsequent interpretation (Block 460) of these new states may be provide indicators of either impeding failure or parametric shifts due to aging and/or external factors for which human attention and/or parametric updates may be desired. Data presentation Block 450 may be used to format the data in a manner that can be used by the novelty detection engine 130. FIG. 5 is a flowchart of operations that may be performed by a novelty detection Block 130 of FIGS. 1 and/or 4, according to various embodiments of the present invention. As shown in FIG. 5, an initial system state is observed at Block 510 to initiate learning and building of the first associative memory 140. Two phases of state learning may be defined: training and in-use operation. An associative memory 140 of normal behavior is built during a training (i.e., test and validation) period during which the system learns what is normal for that particular system and environment with independent verification of normal performance. Memory building and learning may also continue to occur during in-use operation. It is assumed that the system 110 is operating normally during training as verified through independent observation (e.g., user assessment and/or independent performance testing). The length of the training phase may depend on the dynamics of the system 110 under consideration, and may be comparable to the testing that an automobile engine might undergo in an assembly plant prior to being released for sale. While the system 110 is training it will generally encounter many novel states. The learning phase may continue sufficiently long to learn almost all normal behaviors. If a system failure occurs during learning, the process may need to be restarted for validity. During in-use operations, novelty is assessed (as described earlier) depending on how “close” the currently observed observation is from normal learned behavior. A state is determined to be new if it is sufficiently “far away” from the design-intended performance envelope accumulating in associative memory. Again, not all novel states encountered during use are non-normal and associated with failure modes. When a novel state is detected, it is first interpreted. Based on an accumulated history of experienced system-specific failures accumulated during operation, the novel states are characterized as either (1) normal behavior (i.e., no history of associated failure) or performance shifts due external influences that, while not normal, stabilize or return to normal; (2) non-normal behavior (based on previously experienced failure histories) for which parametric updates and/or corrective action may be desired; or (3) possible states of performance degradation that may nor may not lead to failure. Interpretation may be accomplished by the failure mode learning Block 150 and may be aided by the interpretation of human experts as was already described. The granularity of the filter for acceptable novel states may be set by a human analyst and/or automatically depending on, for example, the nature and application of the physical system, and/or the cost of not recognizing non-normal behaviors that lead to system failure. In other embodiments, the granularity of the filter may be adaptively set by a human analyst and/or by a data processing system. Referring to the flowchart of the novelty detection Block 130 shown in FIG. 5, an initial state of the physical system is observed at Block 510. Since no states have been previously observed, this state is a novel state and becomes the first state in associative memory 140 at Block 520. A second observation is made and checked for novelty at Block 530. If this state is identical to the previous state (i.e., not novel) at Block 540, then the associative memory is reinforced (i.e., the “counts” of co-occurring attributes are increased). If the state is novel at Block 540, then it is determined at Block 550 whether the novelty detection engine is operating in training mode or is in operational use. If the novelty detection engine is in training mode at Block 550, the observed novel state is added to the memory to build the normal performance envelope. If the system is in use at Block 550, the observed novel state is determined to be normal or non-normal at Block 560 based on a previously developed rule set described earlier. If the state can be identified at Block 560 as normal, then the associative memory is reinforced. If the state is not normal according to the previously developed rule set, or if it is indeterminate, the state is passed to the diagnostics/prognostics engine at Block 570 for further analysis. FIG. 6 is a flowchart of operations that may be performed by failure mode learning Block 150 and/or intervention learning Block 170, according to various embodiments of the present invention. The failure mode learning/intervention learning Blocks 150/170 may also be referred to collectively as a diagnostics/prognostics engine 570. In general, when non-normal or indeterminate states are observed, the novelty detection Block 130 passes information about the novel state to the diagnostics/prognostics engine 570 that can provide alerts to system operators who are dependent on timely awareness of current or anticipated problems, and associated needs for maintenance, network reconfiguration, and/or mission modifications. Information about the observed state may also be passed to the intervention learning Block 170 for further analysis. The intervention learning Block 170 can assist an analyst (or operator) in determining whether this is a common failure mode or one which has never been seen before-and what kind of response is appropriate. While failure mode analysis and the identification of underlying causes is often as much an art as a science, some embodiments of the invention can aid analysts by pattern completing currently observed symptoms to related failure and failure correction history for similar systems and environmental contexts. Previously experienced failure states and contextual attributes may be contained in a library of failure modes and failure trajectories that can then be associated in a second associative memory 160 with information such as likelihood of associated failure, mean-time-to-failure, and corrective measures (as appropriate). As the history of failures is accumulated in the second associative memory 160, it is possible to correlate observed performance problems to previously captured failure mechanisms and their resolution as the basis for near-real-time likelihood estimation of root cause and/or recommendation for corrective actions. In the event that the failure mode is known, appropriate corrective response can be taken. Corrective actions, mean times-to-failure, and appropriate responses can be included in the third associative memory 180, so that appropriate and previously successful remedial actions can be recommended, when similar states are observed in the future. Moreover, in the event that the observed non-normal state is not a known failure mode, or is not on a known trajectory to failure, then the operator may need to decide how to respond. The most likely choice may be to continue to observe the system, to assess the subsequent behavior until a decision can be made about possible corrective action. Referring specifically to the flowchart of the diagnostics/prognostics engine in FIG. 6, an observed novel state 132 that is either not normal or indeterminate is passed to the diagnostics/prognostics engine 570 for further review and assessment. The state is first recorded at Block 610 in the second associative memory 160 of previously observed non-normal and indeterminate states along with any time-stamped attributes of previously observed failure trajectories. The second associative memory 160 is queried to determine whether the state is associated with a known failure mode at Block 620. If the state does not match a known failure mode, then additional states may be observed to better understand the system dynamics. If the state matches a known failure mode, then the third associative memory 180, that may also contain past responses, outcomes and/or analyst notes, may be queried for information such as estimated time-to-failure, number of previously observed similar states, operating context, previous responses, and/or outcomes, at Block 630. Depending on the results of the query, real-time alerts may be provided to the operators and response recommendations at Block 640. The real-time alerts of Block 640 may correspond to the potential response 172 of FIG. 1. At Block 650, response and/or correction action, which may correspond to the dashed arrow 174 of FIG. 1, also may be provided. FIG. 7 is a block diagram of systems, methods and/or computer program products according to other embodiments of the present invention, and illustrates additional detail of the functional processing by the first, second and third layers 191-193 of FIG. 1. Thus, in FIG. 7, the systems, methods and/or computer program products 700 include a first layer 191 for state space learning 130, a second layer 192 for failure mode learning 150, and a third layer 193 for intervention learning 170. From a functional standpoint, each of the layers 191-193 can provide observe→learn→interpret→respond functionality at the given layer, to provide what may be referred to as a “Learn-and-Respond Loop” 740. Thus, to implement real-time prognostics/diagnostics capability for both dynamic and static systems, the Learn-and-Respond Loop 740 may be embedded within a set of nested tasks. “Layered” learning describes the paradigm in which learning occurs at different levels in a prognostics/diagnostics system, according to some embodiments of the present invention. The layers 191-193 represent a hierarchy of tasks for prognostics/diagnostics determination that transform inputs into outputs, or attributes into predictions, in the Learn-and-Respond Loop 740. Further, this “layered” learning can seamlessly integrate the learning tasks at each layer. Embodiments of FIGS. 1 and 7 can provide three layers of learning: pattern matching for state-space learning 130 to determine novelty 132; failure mode learning 150 to determine failure trends 152; and intervention learning 170 to recommend actions 172 to prevent failures. The elements of and interactions among the learning layers, according to some embodiments of the invention, are illustrated in FIG. 7 and will now be described in detail. In some embodiments, the foundation of the layered learning is a Learn-and-Respond Loop 740 by which the design-specific performance envelope is determined, as was described earlier. For the state space learning 130, ongoing monitoring and state tracking is performed at Block 710. The accumulated sensor 120 attribute (parameter) values 122 determine a state-space in first associative memory 140 against which new states are assessed at Block 712 to determine novelty at Block 714. If the state is determined not to be novel, the design-specified performance envelope is reinforced. For an in-use operational system, most states are expected to fall within the design-specified performance envelope which is assumed to represent normal behavior. If the state is determined to be novel and normal, the normal performance envelope is extended as appropriate at Block 716. For example, the observation represented by State 2 in FIG. 3B would be added to the envelope. It is novel but clearly falls within the envelope. Thus, determination of normality can depend on the localized behavior of the system and can be assessed using a layered learning approach for failure mode tracking that observes the patterns in sequences of novel and not-novel observed states to determine whether a particular pattern can be correlated with a previously observed failure mode. In the example above, all observed states prior to and after are normal, so a rule could be learned that patterns which isolated novel states within a sequence of normal states should be interpreted as normal. During Failure Mode and Trend Learning 150, as illustrated in FIG. 7, ongoing monitoring and state tracking also takes place at Block 720. The novel states 132 are passed to another Learn-and-Respond Loop that learns possible failure trends by matching pattern sequences of novel states with previously experienced failure modes at Block 722. An assessment is made as to potential failure 152 at Block 724 and alerts may be provided at Block 726. During Intervention Learning 170, also shown in FIG. 7, the novel states (Block 730), learned failure modes, and successful interventions (Block 732) are passed to another Learn-and-Respond Loop that classifies failure states (Block 734) and recommends human and/or machine response (Block 736). For example, interventions might include computer-controlled adaptive parametric updates, or human maintenance interventions. During learning, correlations are made between successful interventions and failure modes. The output of the Learn-and-Respond Loop may be a recommendation for an action (e.g., ordering a repair part) or parameter adjustment (e.g., adaptive parameter adjustment in an engine controller) that has the highest likelihood of successfully returning the system to design-specified behavior. Embodiments of the invention may have application over a range of physical systems 110 that can be distinguished in practice by the “cycle time”, where cycle time refers broadly to the elapsed time to close the loop between sampling by sensors 120, transmission of sensor outputs 122, processing by the three layers 191-193, and response 172. At one end of the spectrum, one can think of fast cycle applications such as control systems for optimizing engine performance. In the event of fast cycle times, learned parameter adjustments can be made in real-time (e.g., on the order of seconds or milliseconds) to keep the system operating within normal boundaries. If real-time fixes should be made, control parameters can be tuned to performance criteria in real-time and parametric changes can be initiated and electronically downloaded within the cycle time of the physical process. At the other end of the spectrum one can think of examples like repair parts logistics in which the cycle time may be as long as hours or days, and the response time for providing the remedial action (e.g., get a spare part) of similar order. Mean-time-to-failure predictions determined from learned history of previous failures can trigger a re-supply decision for spare and repair parts that can avoid costly delays. Alerts can be provided in real-time to the various support personnel such as maintenance and logistics, as well as command and control personnel in charge of system operations. Embodiments of the invention described herein may also have significant application over a range of physical systems that can be distinguished in practice by the whether they are dynamic or static, and the degree of computer control, as described, for example, in the following four categories: static (and quasi-static) systems, dynamic systems, computer-controlled closed loop systems and multiple complex systems. Each of these categories of systems will now be described generally. Static and quasi-static systems, in contrast to dynamic systems, do not have interrelated moveable parts whose behavior affects the operation of other system parts. Nonetheless, the behavior of these static systems can be learned during operational use and failures can be predicted. An example of the behavior of a static system might be the fluctuations of gas pressure or oil pressure in a system. Quasi-static systems might include drive shafts in automobiles. Driveshaft failures can be attributed to one or a combination of factors. These factors can include maintenance, driver abuse, external damage, improper installation, poor driveline geometry, and the quality and strength of the components. Indicators such as increased vibrations and grinding can be monitored to predict a future failure state. A dynamic system refers to a system whose parts are interrelated in such a way that a change in one part necessarily affects other parts of the system. Dynamic systems can be well described through the state space framework. Dynamic systems represent rapidly changing operational variables, possibly including transient phenomena. While dynamic systems, including transient behavior, can theoretically be modeled with appropriate sets of state equations, in highly complex nonlinear systems such modeling may require a reductionist approach. For such highly complex systems, some embodiments of the present invention may provide an alternative based on a learn-and-respond approach to system diagnostics and prognostics. Computer-controlled closed-loop systems have the ability to make observations about their current state, including the environmental context, and to control some aspects of their behavior with the goal of achieving some “good” or optimal level of performance. Control is achieved by feedback within the system, i.e., by measuring the degree to which actual system response conforms to desired system response and utilizing the difference to drive the system into conformance. In response to environmental changes and/or aging, such control systems may require an adaptive feature. Some embodiments of the invention may be applied for parametric adaptation in computer-controlled closed-loop systems in response to changes in environment and/or aging. Finally, in addition to observing the performance of a single system, some embodiments of the invention are able to simultaneously analyze the performance of multiple systems. One example might be a fleet of aircraft or automobiles with common parts and components where information about the behavior of the same part across multiple systems can enhance the failure prediction. This may be especially critical when failure events are rare and traditional statistical approaches for predicting failure may be unreliable. In addition, by including environmental attributes, it is possible to identify operating regimes that may hasten failure or wear-and-tear. In the case of a fleet of aircraft, for example, it may be possible to predict more frequent failures for aircraft flying under more stressful operating conditions. In doing so, the associative memory can assess associations between normal operating regimes in particular contexts or environments and, by extension, adjustments to mean-time-to-failure predictions based on site-specific contexts. Moreover, large-scale patterns in the failure behavior of multiple systems also may be assessed. For example, the failure history captured in the associative memory of one physical system can be used to help predict the failure potential of another system in similar environments. The following Example shall be regarded as merely illustrative and shall not be construed as limiting the invention. It is intentionally simple for didactic purposes. An embodiment of the present invention is described in the context of a real-time diagnostic applied to a Direct Current (DC) motor and fan as shown in FIG. 8A. The system includes a simple fan, which draws current from a battery-powered direct current motor. Four independent variables are sensored at regular intervals: temperature (T), speed (S), battery voltage (V) and battery current (Ib). As is well known, the governing equation for steady state DC operation relating armature current Ia to speed S is Ia=A+BS, which defines an offset negative ramp function where the offset coefficient A represents the stall current and the slope parameter B represents the negative slope of the Ia(S) curve, as shown in FIG. 8B. Referring now to FIG. 9, ten “bands” were created for each attribute to yield a total of 10,000 possible states of behavior. The system was calibrated so that between one and three of the ten bands for each attribute can be expected to cover the normal design-intended performance envelope, as shown in FIG. 9. An additional two of the 10 bins represent normal behavior at the “fringe”. The remaining four to six bins represent non-normal operations. These guidelines were intended only to assure that the processing system can accommodate the full range of experimental data. The guidelines were not intended to pre-define or limit novel or normal behavior. It will also be understood that any other banding/fuzzification scheme may be used. Sensored data from the fan may be assessed by a novelty detection engine as described herein. During training, the system rapidly converges on a normal performance envelope over the design-intended range of fan speed and associated torque loads. During operation under stable conditions, the system can be expected to perform as intended, wherein observed states fall within the normal performance envelope. Deviations from the normal performance envelope can be induced for demonstration purposes, for example by increasing operating temperature, increasing bearing-related loss torque or introducing a partial short shunt current added to the battery current. When the stress to the system is relieved, operations quickly return to normal. Referring again to FIG. 8A, it will be understood that a demonstration that can be modeled was used for verification and didactic purposes. Embodiments of the invention need not use mathematical models. During the learning phase the observed Ib (S) points will scatter narrowly (within instrumentation variability) along the shown ramp function of FIG. 8B representing the normal state space. It for example, a shunt (fault) current Ish (S) is introduced, the Ib (S) points will fall above the ramp indicating novelty and a potential degradation as shown by non-contiguous scatter above the normal state space. FIG. 10 is a block/flow diagram representing generic hardware and software structure and interfaces for the Example. This structure provides a high-level guide to implementing some embodiments of the invention in a physical system. The structure of FIG. 10 includes hardware 1010 for sensing and data acquisition; software 1020 for pre-processing and attribute development; and associative memory, such as Saffron Technology 1030 for associative memory-based learning and decision support. The hardware 1010 can include sensing and data acquisition technology 1012 for the physical system, off-the-shelf components that perform the analog-to-digital conversion 1014 of the sensored data so that it can be interpreted by a personal computer (PC), and a PC interface 1016 that moves the data into the PC so that it can be manipulated by the Saffron Technology 1030. Once the data has been loaded into the PC as a data file 1022, it can be pre-processed 1024 as was described earlier. This may entail transforming or filtering the data so that is may be interpreted by the associative memory 1030. As part of pre-processing, data may be placed in “bins” and/or fuzzy sets at Block 1024, as was described earlier. These bins can define a system-specific associative memory 1026, including contextual data, which is ready for training and in-use operation. Finally, novelty detection and decision support functions operate to provide decision support to the analysts and operators. Normal states are learned during training at Block 1032. Novel states that cannot be identified as normal during use at Block 1034 are passed to the diagnostics/prognostics engine at Block 1036. Novelty detection according to exemplary embodiments of the invention can offer an approach to prognostics which can identify previously unobserved or novel system states, distinguish between normal and non-normal modes of operation and/or provide alerts and recommendations for remedial action, as appropriate. Current initiatives in prognostics may assume that known baseline profiles or failure modes are available as the basis for ongoing in-use comparison. They may focus on look-up tables, and use batch downloads from the physical system to analyze system behavior. In contrast, some embodiments of the invention can use learning and novelty detection in real-time, a learned baseline represented by a design-intended normal performance envelope. While in-use, novelty detection can compare observed system behavior with the normal performance envelope. Also, the associative memory can be expandable. Information about new behavior can be added dynamically while the physical system is in-use, which can make the novelty detection smarter as time goes by. Moreover, in some embodiments, novelty detection is implemented by the Learn-and-Respond Loop using an associative memory technology for fast state learning, While a number of technologies can be considered to “learn”, including neural nets, these approaches to machine learning may suffer from computational burdens and/or modeling difficulties that may result from the need to analyze very large data sets in real-time. These potential deficiencies may limit their extensibility to real-time, prognostics and intervention applications. Associative memory technology is able to surmount these barriers through a compression technology, which enables learning in a compressed state. Associative memory technology is not only able to meet real-time speed requirements, but also can provide a transparent view of the associations between variables used for prognostics interpretation and failure learning. Further, because the technology is able to “learn” incrementally as information is encountered, it is possible to recognize temporal shifts in system performance and health. Since learning occurs in real-time, in some embodiments, monitoring of (and, if possible, automated corrections to) performance degradation can be handled in-step with the cycle time of the process. In the case of slow-cycle applications such as logistics support with time constants on the order of minutes or hours, anticipation of failure may enable systems operators to provision spare parts where and when needed. In the case of fast cycle applications such as engine management with cycle times in the order of microseconds, real-time fault mode tracking may enable an overlay of adaptive tuning of control parameters and/or timely downloads of parametric changes. Further, as a history of failures is accumulated, some embodiments of the invention can, in real-time, correlate observed performance problems to previously captured failure mechanisms and their resolution as the basis for near-real-time likelihood estimation of root cause and/or recommendation for corrective actions. Novelty detection according to some embodiments of the invention can be based on learned behavior for a specific physical system. Thus, it is possible to monitor and assess the unique behavior of that system without relying on average behaviors. Reliance on average behaviors can make it difficult, for example, to recognize and anticipate normal aging since aging patterns may be biased by history of individual use and may not be easily extrapolated. Consider a fleet of vehicles. A particular automobile may exhibit a particular aging profile that does not fit the expected model because the owner consistently rode the clutch. On the other hand, shared knowledge about behaviors across an entire fleet can provide useful information at the vehicle level. For example, it is not always possible able to assess whether a novel state for a particular vehicle is a potential failure mode. However, if that novel state has been associated with failure on a similar vehicle in similar operating environments, this information can be passed to an analyst for consideration. Typically, in single or multi-sensor systems, individual sensor values are tracked to assure that they stay within pre-determined limits. In complex systems, however, system-level malfunctioning may occur even if all individual sensor outputs are within limits. This point is illustrated in FIG. 11. The values for Sensor 1 and Sensor 2 are both within normal limits. However, using associative memory, some embodiments of the invention can recognize that the co-occurrence of sensor values that are “normal” when considered in isolation has been associated with system failure in the past. Note that no impending failure would be indicated if the sensors were being tracked individually since each is within normal limits. Using the notion of layered learning, the prognostics/diagnostics process may be organized into a hierarchy of three tasks that utilizes associative memory technology to perform learning tasks. Three layers may be used: pattern matching for state-space learning to determine novelty (layer 191); failure mode learning to identify failure modes and predict trends (layer 192); and intervention learning to recommend actions to prevent failures (layer 193). Further, this layered learning can seamlessly integrate the learning tasks at each layer, and can allow the prognostics/diagnostics process embodied herein to operate in a semi-autonomous mode and support operators of complex physical systems who may be tasked with assuring continuous operation of these systems with design-intended parameters. Accordingly, exemplary embodiments of the invention can offer an innovative approach to diagnostics for large, complex systems with significant practical benefits. Cost savings, performance improvements, more reliable product performance and/or less system downtime may be provided. In addition, better predictions of system-specific impending failure can lead to lower maintenance and operational costs, plus extended product lifecycles. These benefits may be attributed to the ability of some embodiments of the invention to provide earlier warning of failure, adaptive monitoring and/or fewer prediction failures as a result of the simultaneous monitoring of not only a small subset of variables related to a subsystem, but rather a large number (hundreds or thousands) of variables including contextual attributes that reflect the environment of use. In the drawings and specification, there have been disclosed embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims. |
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abstract | The invention relates to rod thermometer device for detecting a temperature, including a plurality of temperature-sensitive elements and a protective sheath having an axis X in which the sensitive elements are partially inserted. The sheath is made of a metal constituting one of the two metals of a thermocouple, and the sensitive elements of a plurality of wires made of a metal other than that of the sheath and constituting the other one of the two metals of a thermocouple, one of the ends of each one of the wires being welded inside the sheath forming a junction for measuring a given thermocouple, the welded ends of the wires being distributed along a plurality of axial and azimuth positions relative to the axis X inside the sheath, each one of the wires extending out of the sheath by at least one of the ends thereof. |
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description | The present disclosure relates to generation of low-energy secondary electrons. More specifically, the present disclosure relates to a method and a system for generating low-energy electrons in a biological material. Secondary electrons are electrons generated as ionization products. They are called “secondary” because they are generated by other radiation, called primary radiation. This primary radiation may be in the form of ions, electrons, or photons with sufficiently high energy to exceed an ionization potential. Photoelectrons are an example of secondary electrons where the primary radiation consists of photons. Low-energy secondary electrons play a crucial role in the degradation of high-energy ionizing radiation such as X-rays, γ-photons or charged particles. Low-energy secondary electrons are a means to define the geometry of the radiation track. The present disclosure broadly relates to generation and applications of low-energy secondary electrons. Therefore, according to the present disclosure, there is provided a method for generating low-energy electrons in a biological material. The method comprises a step of supporting the biological material. Laser beam pulses are generated. The laser beam pulses are focused pulses toward a region of interest within the biological material to generate filaments of low-energy electrons. According to the present disclosure, there is also provided a system for generating low-energy electrons in a biological material. The system comprises a support for the biological material, a pulsed laser and a focusing mechanism. The focusing mechanism directs laser beam pulses toward a region of interest within the biological material to generate filaments of low-energy electrons. The foregoing and other features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings. Generally stated, the non-limitative illustrative embodiment of the present disclosure provides a method and a system for generating low-energy secondary electrons for applications in biological sciences, medical applications, radiochemistry, and chemistry of polymers and physics of radiotherapy. More specifically, the low-energy secondary electrons are produced using femtosecond (fs) laser filamentation. Although femtosecond laser filamentation (FLF) is a well-known process, it has seldom been used for radiolysis of water [7]. It has been discovered that low-energy electrons (LEE) in FLF and ionization radiation are radiochemically equivalent for applications in biological sciences, radiochemistry, and chemistry of polymers and physics of radiotherapy. The LEE are generated by laser pulses and are then directly recombined or solvated in liquid, in about 300 to 500 fs in water. In the degradation of high-energy ionizing radiation like X-rays, γ photons or charged particles such as, for example, accelerated electrons or heavier charged particles, low-energy secondary electrons serve to define a geometry of a radiation track. They consist of highly anisotropic ionization energy deposition of secondary electrons with energy between about 1 and 20 eV, for example about 5×104 electrons/MeV [1]. In this energy range, an electron penetration range in water is in the order of 10 nanometers (nm) [2]. Demonstration of genotoxic action of low-energy electrons on fundamental biological molecules, such as for example deoxyribonucleic acid (DNA), film of biological molecules, and similar compounds, may be achieved in ultrahigh vacuum conditions [5]. To extend this demonstration, an anisotropic concentration of low-energy electrons in a macroscopic volume of water, in the order of a cubic centimeter (cm3) of water, is generated using intense, ultra-short laser pulses, which lead to self-focusing and filamentation. The physical origin of the formation of filaments is well understood. Briefly, self-focusing is an induced lens effect, resulting from wavefront distortion self-inflicted on a beam while traversing a nonlinear medium. Consequently, as the beam travels in the nonlinear medium, an original plane wavefront of the beam gets progressively more distorted. The distortion is similar to that imposed on the beam by a positive lens. Since the optical ray propagation is in the direction perpendicular to the wavefront, the beam appears to focus by itself. This degenerative process, in which the positive lens effect increases with intensity, is stabilized in the femtosecond regime by the generation of electrons forming a filament. Electrons are produced by multiphoton or tunnel ionization and are further accelerated by an electric field of the pulse in an inverse Bremstrahlung effect. When they acquire enough kinetic energy, for example 6.5 eV in the case of water, the electrons give rise to a second generation of electrons by impact ionization of other molecules in an avalanche-like process. This linear distribution of electrons formed in the filament, in the range of 1016-1018 electrons per cm3, transfers their excess energy to surrounding water molecules, which leads to the generation in a self-focusing region of chemically reactive species such as eaq, H*, O*, and *OH, and recombination products H2, O2, H2O, and O2*— (or HO2*, pKa=4.8). There does not exist in the literature any mention of real time measurements of the presence of LEE in a filament. However, as LEE are generated in filamentation, solvated electrons become measureable along the filament. Pump-probe measurements may be used for this purpose. Solvated electrons have an optical spectrum measurable by a femtosecond pump-probe technique. The presence of solvated electrons along the filament may be measured using a delay of 50 picoseconds (ps) between an 800 nm pump pulse having a 100 fs pulse duration, which generates the filament, and an optical probe of a 125 fs pulse duration at 720 nm from an optical parametric amplifier (OPA). Scanning a position of a pump lens changes the position of the filament in a linear direction. A characteristic intensity evolution of the length of the filament in FLF has been observed from the pump-probe scan measurement in function of the pump pulse intensity [6]. Referring to FIG. 1, which is schematic view of a laboratory system for generating femtosecond laser filamentation in accordance with an illustrative embodiment, a system 10 comprises a laser 12 producing a beam 20 aimed at a region of interest (ROI) in an optical path cuvette 16 through a focusing mechanism 14. Concurrently, FIG. 6 shows steps of an exemplary method for generating low-energy electrons in a biological material. A sequence 60 of steps, as shown on FIG. 6, will be described concurrently with details of FIG. 1 and with details of the following Figures. Some of the steps of sequence 60 may be present in some embodiments and not in other embodiments. Some of the steps may be executed in a different order compared to that shown on FIG. 6. The optical path cuvette 16 supports a biological material (step 62), used as a laboratory sample, contained in an aqueous solution 22. The cuvette 16 is positioned on a magnetic steering device 18 in order to homogenize the solution 22 between pulses. The laser generates laser beam pulses (step 64), which are focused by the focusing mechanism 14 towards the ROI to generate filaments of low-energy electrons (not shown) within the ROI (step 66). The filaments have a length of about one (1) cm, producing low-energy electrons 24 in the solution 22. A detector 26, for example a streak camera, detects an image of the beam 20 diffracted within the solution 22. A resulting image may be used for time-resolved spectroscopy or for resonance imaging (MRI) analysis. The laser 12 may be, for example, a Spectra-Physics® 300-750 mW femtosecond Regenerative Ti-Sapphire laser having an optical parametric amplifier (OPA) and harmonic generator (HG), used at 300 μJ/pulse, 100 fs pulses at 800 nm and at 1 kHz repetition rate. The focusing mechanism 14 may have a focal lens of f=30 cm. This setup results in the production of filaments of about one (1) cm in a one (1) cm optical path cuvette 16. In another embodiment, a High Power Spitfire PRO—35F-1KXP, 35 fs Ti:Sapphire regenerative laser, 4 watts at 1 kHz and at 800 nm, may be used, along with a AXIS-PV Streak Camera from Axis Photonique Inc. Details of a laser source used in the context of the present disclosure may vary; characteristics of the laser 12 as presented hereinabove are exemplary and not intended to limit the scope of the present disclosure. Examples of applications of LEE in FLF include the following applications. These applications are generally illustrated on FIG. 6, step 67. Radiotherapy One of the applications of the control of the distribution of the LEE is a better dose distribution of radiation interaction in radiotherapy. FIG. 2 is a graph of a relative dose distribution using X-rays, proton Bragg peak and an effective spread-out proton peak for radiotherapy treatment. The present disclosure proposes to replace the use of X-ray therapy or proton therapy with an LEE-based approach. On FIG. 2, a tumor 30 may be treated using X-rays having a distribution curve 34, or using protons having a Bragg peak 36 and being further spread along curve 38. Using instead the LEE-based approach allows to obtain a near ideal dose distribution 32 around the tumor 30. For this purpose, a local distribution of LEE in a macroscopic volume (˜cm3) of water needs to be controlled. LEE cannot be injected deeply in a large volume of water. Anisotropic LEE is therefore locally generated with a control of the energy of these LEE and of the geometry of the distribution. The laser 12 producing the beam 20 and the focusing mechanism 14—or an equivalent focusing mechanism—from FIG. 1 are used to direct laser pulses toward a properly supported and immobilized region of interest (ROI), which replaces the laboratory sample of FIG. 1. This modified system is thus a radiation dose delivery system. The ROI, for example bodily tissues or other biological material, comprises aqueous components and may further comprise a tumor or like aspect that requires treatment. It is through parameter adjustment of the laser 12 and/or of the focusing mechanism 14 that the filaments of anisotropic LEE are generated in proper location, with desired energy and distribution geometry. Filaments are analogue of tracks with an important difference. Diameters of filaments in condensed matter are around 10 to 100 μm. Demonstration of the presence of H2 and H2O2 is well-known. Although stabilization of the filament is due to the presence of electrons, no time-resolved measurement of this presence has earlier been publicly made. The present disclosure therefore suggests to measure femtosecond time-resolved presence of the eaq along the filament. A Fricke dosimeter (not shown), also called a ferrous sulphate dosimeter, measures oxidation conversion of ferrous ions (Fe2+) to ferric ions (Fe3+) by ionizing radiation having produced eaq, *OH, HO2*, H2O2, and the like, in water. Increase of ferric ions concentration in filaments may be measured spectrophotometrically (FIG. 6, step 68) at an optical absorption maximum at 303 nm. 6.5 eV electrons, which correspond to a maximum energy of the LEE in water, have linear energy transfer (LET) of 1 keV/μm [2] and G(Fe3+) of 15.3 molecules/100 eV (G(Fe3+)) for 1 keV/μm radiation [3]. Those values correspond to radiation from a Cesium 137 (137Cs) Gammacell® Elan 3000 irradiator from Best Theratronics Ltd. In view of those characteristics, the Fricke dosimeter is an appropriate tool to compare radiation equivalent of FLF and Gamma irradiation, also called “Gammaknife”. Referring now to FIG. 3, there is shown a graph of an irradiation dose deposition equivalent of intense femtosecond laser filamentation and Gamma irradiation as a function of time. A 1 kHz repetition rate is used for the laser 12 of FIG. 1. FIG. 3 shows a curve 40 for the laser irradiation and a curve 32 for the Gamma irradiation. At a 60-second time point 44, a dose rate of 168 Gy/min is obtained using FLF, compared to 12 Gy/min using the 137Cs irradiator. Comparison of measurements obtained with the Fricke dosimeter with those obtained from Gamma irradiation thus provides a dose rate for the filaments. It may be observed that the irradiation dose deposition equivalent of intense femtosecond laser filamentation could also be compared with results obtained from Cobalt 60 (60Co) irradiation. Polyacrylamine gel (PAG) dosimetry is used in three-dimensional (3D) magnetic MRI of radiation. PAG is composed of 2 monomers (3% of acrylamide, 3% of bisacrylamine) in 5% gelatin and 89% of water. LEE may also be generated in PAG and in like polymers. Because radiologic properties of gel dosimeter are equivalent to properties of tissues, radiation-induced polymerization of the comonomers generates a fast-relaxing insoluble polymer. Filament diameters may be estimated in PAG imaged by MRI, whereby PAG effectively becomes a 3D dosimeter. In laboratory tests, optical and MRI imaging of energy deposition in the PAG is obtainable and an image of the LEE filamentation in a polymer volume has been observed. Production, analysis and control of a dose deposition of LEE in FLF in PAG media, in function of optical irradiation conditions involving control of optical parameters and pulse duration, allow analysis of related fundamental physical and chemical processes and a determination of an ideal dose deposition for radiotherapy treatment. The use of PAG dosimeter is useful in obtaining 3D imaging of energy deposition, for MRI imaging and for optical imaging. PAG material is a radiological equivalent of tissues, especially for MRI imaging. PAG is a good prototype material to test the physics of radiotherapy without using actual tissues and may be put to use for demonstrating the capability of FLF to produce an ideal radiation beam for dose deposition in radiotherapy treatment. For a specific optical setting, using a fixed focal lens, the length of a produced filament depends of the instantaneous laser intensity. The local intensity dependence may be controlled by pulse duration. Adjusting the pulse duration so that an image does not start in the front of a cuvette containing the PAG allows adjusting the beginning of the filamentation and thus the dose deposition. Modifying the optical setting allows changing the end of the filamentation. In an approximation, it is estimated that a multifilament diameter in PAG material is at a maximum of 625 μm diameter, an accuracy of this measure being limited by imaging resolution of MRI techniques, which in turn are controlled by a magnetic field of seven (7) tesla and by the size of the cuvette. In gas phase, the diameter of a monofilament is evaluated at 10 μm [6]. The diameter of a monofilament may also be limited by the chemistry of polymerization and by set-up of the optical system, including parameterization of filtering and of pulse duration. This polymerization is controlled by a chain reaction and by a distribution of a radical produced by ionization. In an embodiment, MRI analysis of energy deposition using monofilament and deposition of energy using Gammaknife in PAG may be compared. In another embodiment, time-resolved spectroscopy and optical imaging, for example using a streak camera, may be used to measure a time-resolved fluorescence spectroscopy during monofilament formation. Analysis may be made in function of oxygen concentration and in function of laser pulse duration, whereby conditions for controlling energy deposition in PAG may be optimized. In yet another embodiment, simultaneous control of pulse duration and focalization, for example using a deformable mirror, in monofilament and multifilament conditions, while using a Gammaknife reference, allows optimal calibration of a dose deposition using MRI. Radiochemistry Another application of the control of the distribution of the LEE is radiochemistry. This is illustrated using a thymidine solution [4]. It is well established that LEE, in a range of 3-100 eV, cleave thymidine in a molecule of thymine and a 2-deoxy-D-ribose. Referring to FIG. 4, which is a graph of a comparative concentration of thymine production as a function of an irradiation dose, the concentration of thymine may be obtained using a chromatograph (not shown) by measuring (FIG. 6, step 69) the thymine concentration production using high performance liquid chromatography (HPLC) in the ultraviolet range [4]. A chemical equivalence action of LEE in FLF and Gamma irradiation is thus obtained. Curves on FIG. 4 show very similar results obtained in the presence of oxygen (O2 condition) with Gamma irradiation (curve 46) and with FLF (curve 47). Likewise, FIG. 4 shows very similar results obtained in the absence of oxygen (N2 condition) with Gamma irradiation (curve 48) and with FLF (curve 49). Sterilization Yet another application of the control of the distribution of the LEE is radiation-induced damage in tissue for sterilization purposes. This is illustrated using E. Coli cells in water. FIG. 5 is a graph of agarose gel electrophoresis, using (a) Gamma irradiation and (b) femtosecond laser filamentation irradiation, of pGEM-3Zf(−) plasmid DNA. The plasmid DNA (3197 bp, Promega) was extracted form E. coli DH5α and purified with the QIAfilter Plasmid Giga Kit (Qiagen). Agarose gel electropholysis was used to show that 95% of DNA was initially in the supercoil form, 4% was in the concatemeric form and 1% was in the circular form. The DNA was dissolved in de-ionized water. The concentration of DNA was measured by its UV absorption at 260 nm, assuming a molar extinction of 7120 mol−1/cm−1 at pH7.0. The amount of DNA in each sample that was used for irradiations was 200 ng/ml. After Gamma irradiation (12 Gy/min) and filamentary laser irradiation (168 Gy/min), plasmid DNA was extracted [5] and analyzed by agarose gel electrophoresis and quantified as supercoil (undamaged) DNA, single strand break (SSB) and double strand break (DSB), which results are shown in FIG. 5 (a). FIG. 5 (b) shows the results obtained by LEE in FLF (462 Gy/min), using a Ce dosimeter adapted for high dose irradiation. Comparing results obtained in FIG. 5 for Gamma irradiation (a) and for LEE in FLF (b) demonstrates that LEE in FLF produces a radiochemical equivalent action to that obtained using ionization radiation in certain type of living cells. This confirms that LEE in FLF and ionization radiation are radiochemically equivalent for application in biological sciences, radiochemistry, and chemistry of polymers and physics or radiotherapy. LEE in FLF may be used, for example, for the sterilization of injectable drugs and the decontamination of hospital waste water. Polymerization A further application of the control of the distribution of the LEE is radiation-induced polymerization of the co-monomers generates a fast-relaxing insoluble polymer. Nanoparticle Coating The polymerization may be used for coating nanoparticles in solution. Nanoparticle Generation FLF may be used to generate gold nanoparticles in solution. Those of ordinary skill in the art will readily appreciate that the above mentioned fields of application of LEE in FLF are exemplary and are not intended to limit the scope of the present disclosure. Generating low-energy secondary electrons as taught herein may be advantageously applied in other fields of endeavor. Although the present disclosure has been described hereinabove by way of non-restrictive, illustrative embodiments thereof, these embodiments may be modified at will within the scope of the appended claims without departing from the spirit and nature of the present disclosure. [1] Simon M. Pimblott, Jay A. LaVeme, Production of low-energy electrons by ionizing radiation, Rad. Phys. and Chemistry, 76, 1244-1247 (2007). [2] J. Meesungnoen, J.-P. Jay-Gerin, A. Filali-Mouhim, S. Mankhetkom, Low-energy penetration range in liquid Water, Rad. Res 158, 657-660 (2002). [3] N. Austsavapromprom, J. Meesungnoen, 1. Plante, J.-P. Jay-Gerin, Monte-Carlo study of the effects of acidity and LET on primary free-radical and molecular yields of water radiolysis—Application to the Fricke dosimeter, Can. J. Chem. 85,214-229 (2007). [4] Y. Zheng, P. Cloutier, D. J. Hunting, J. R. Wagner, L. Sanche, Glycosidic Bond Cliveage of Thymidine by Low-Energy Electrons, JA.C.S. 126, 1002-1003 (2004). [5] B. Boudaiffa, P. Cloutier, D. Hunting, M. A. Huels, L. Sanche, Resonant formation of DNA Strand breaks by low-energy (3 to 20 eV) electrons, Science, 287,1658-1660 (2000). [6] S. Chin, et al., The propagation of powerful femtosecond laser pulses in optical media: physics applications, and new challenges. Can, J. Phys 83, 863-905 (2005). Review article with extensive reference. [7] S L. Chin, S. Lagaće, Generation of H2O, O2 and H2O2 from water by the use of femtosecond laser pulses and the possibility of laser sterilization. Appl. Opt. 36, 907-911 (1996). |
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abstract | A method of diagnosing an adaptive process control loop includes measuring process control loop signal data, generating a plurality of process control loop parameters from the process loop signal data and evaluating a condition of the adaptive process control loop from one or more of the plurality of process control loop parameters. The process control loop data is generated as a result of a normal operation of one or more process control devices within the adaptive process control loop when the adaptive process control loop is connected on-line within a process control environment. A self-diagnostic process control loop includes a diagnostic tool adapted to receive a diagnostic index pertaining to a process control loop parameter for each component of the process control loop and for the complete process control loop. Each diagnostic index is generated from signal data by a corresponding index computation tool. The diagnostic tool is further adapted to evaluate a condition of the process control loop from one or more of the diagnostic indices. |
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claims | 1. A phase-contrast x-ray imaging device, comprising:an x-ray source for generating an x-radiation field;an x-ray detector having a one-dimensional or two-dimensional arrangement of pixels; anda phase-contrast differential amplifier disposed between said x-ray source and said x-ray detector and configured to amplify spatial phase differences in the x-radiation field during operation;said phase-contrast differential amplifier having two diffraction gratings which, when viewed in a radiation incidence direction, are arranged one behind another; and wherein each said diffraction grating includes:a transverse surface to be aligned substantially at right angles to the radiation incidence direction and being spanned by an x-axis and a y-axis perpendicular thereto; anda plurality of diffraction ridges made of an optically comparatively thin base material arranged in alternation with optically denser interspaces;said diffraction ridges being formed to subdivide the transverse surface into elongate diffraction strips that extend in each case in a y-direction and that are arranged next to one another in parallel rows in an x-direction, wherein adjacent diffraction strips are different from one another in that they are always aligned to different focuses in terms of the diffraction properties of a grating material arranged in each case in a vicinity of said diffraction strip or diffract in different directions. 2. The phase-contrast x-ray imaging device according to claim 1, wherein said phase-contrast differential amplifier is configured such that unaffected x-radiation experiences a uniform phase shift due to said phase-contrast differential amplifier irrespective of an entry position of the unaffected x-radiation at said phase-contrast differential amplifier. 3. The phase-contrast x-ray imaging device according to claim 1, wherein said two diffraction gratings of said phase-contrast differential amplifier are two identical diffraction gratings. 4. The phase-contrast x-ray imaging device according to claim 1, wherein said diffraction ridges are formed to extend diagonally at least in sections within the transverse surface, wherein lateral faces of at least one said diffraction ridge which delimit said diffraction ridge in the x-direction in each case extend across a plurality of said diffraction strips. 5. The phase-contrast x-ray imaging device according to claim 1, wherein said diffraction ridges are formed as oblique prisms inclined in the y-direction, and having a base surface and a top surface that lie in the end faces of said diffraction grating that are parallel to the transverse surface. 6. The phase-contrast x-ray imaging device according to claim 5, wherein:said diffraction ridges are arranged such that in each diffraction strip there results a material structure repeating itself with a y-period length in the y-direction; andsaid diffraction ridges are inclined in the y-direction such that a top surface of each diffraction ridge opposite the base surface is offset with respect to the base surface by a whole number of period lengths. 7. The phase-contrast x-ray imaging device according to claim 6, wherein the top surface of each diffraction ridge opposite the base surface is offset with respect to the base surface by precisely one period length. 8. The phase-contrast x-ray imaging device according to claim 1, wherein each said diffraction ridge adjoins the interspaces arranged between said diffraction ridges with two lateral faces in each case, wherein said lateral faces are composed of active subareas having a comparatively strong diffraction effect in the x-direction alternating with passive subareas having a small or neglectable diffraction effect in the x-direction. 9. The phase-contrast x-ray imaging device according to claim 8, wherein each active or passive subarea extends across a whole number of diffraction strips in the x-direction. 10. The phase-contrast x-ray imaging device according to claim 1, which comprises an object support for accommodating an examination object disposed between said x-ray source and said phase-contrast differential amplifier. 11. The phase-contrast x-ray imaging device according to claim 1, which further comprises an analysis grating arranged between said phase-contrast differential amplifier and said x-ray detector. 12. The phase-contrast x-ray imaging device according to claim 1, which further comprises a coherence grating arranged between said x-ray source and said phase-contrast differential amplifier. 13. The phase-contrast x-ray imaging device according to claim 1, which further comprises an additional diffraction grating arranged between said phase-contrast differential amplifier and said x-ray detector. |
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054992788 | summary | FIELD OF THE INVENTION This invention relates generally to protection systems for shutting down a boiling water reactor (BWR) and maintaining it in a safe condition in the event of a system transient or malfunction that might cause damage to the nuclear fuel core, most likely from overheating. In particular, the invention relates to passive systems applied to BWRs for suppressing the pressure inside the containment following a postulated accident. BACKGROUND OF THE INVENTION BWRs have conventionally utilized active safety systems to control and mitigate accident events. Those events varied from small break to design basis accidents. Passive safety systems have been studied for use in simplified BWRs (SBWRs) because of their merits in reducing specialized maintenance and surveillance testing of the safety-related equipment, and in eliminating the need for AC power, thereby improving the reliability of essential safety system responses necessary for the control and mitigation of adverse effects produced by accidents. SBWRs can additionally be designed with certain passive safety features that provide more resistance to human error in accident control and mitigation. The current SBWR designs utilize passive operational principles for the key safety systems employed to (a) provide emergency coolant injection, for assured core cooling over the design basis post-LOCA lifetime (specifically, 72 hr for these designs), and (b) provide assured containment heat removal over this same design basis accident duration. The decay heat removal accomplishes, by essentially passive means, the transfer of core decay heat (which manifests itself ultimately as hot steam inside the containment drywell) to the reactor building environs through the use of passive containment cooling (PCC) heat exchangers, as disclosed, for example, in U.S. Pat. No. 5,295,168. The term "passive" as used to describe the actions of such safety systems, is defined to include systems which operate exclusively on stored energy, such as batteries, or pressurized gases, or chemical charges, or appropriately positioned tanks of water which can drain by gravity, to accomplish the essential safety function. The term "passive" further implies that no rotating or reciprocating machinery is used; valves, where used, are one-time change-of-position valves such as squib valves, or, in the case of check valves, are altogether unpowered insofar as their open/close state is concerned. Where water is used in such passive systems for flooding, quantities must be sufficient to accomplish all design goals over the prescribed accident period, i.e., 72 hr. Where water is used for decay heat rejection via the process of evaporation, quantities again must be sufficient to allow for boiloff of such pools without the pool drawdown uncovering the critical heat exchanger heat transfer surfaces (tubes) through which the heat is transferred via condensation of steam inside the tubes, and evaporation of a secondary water quantity (pool) external to these tubes, which secondary pool communicates via piping/ducting to the environs. A typical SBWR reactor building arrangement has a plurality of PCC heat exchangers positioned in an interconnected series of pool chambers collectively referred to herein as the condenser pool. This pool requires a certain critical water inventory, i.e., the inventory for which the integrated design (pool plus positioned heat exchanger) is reckoned as boiloff volume. Before focusing on this aspect of water inventory management, a brief summary of the overall structure and operation of the current SBWR design is given below. Referring to FIG. 1, the SBWR includes a reactor pressure vessel 10 containing a nuclear reactor fuel core 12 submerged in water 14. The fuel core heats the water to generate steam 14a which is discharged from the reactor pressure vessel through a main steam line 16 and used to power a steam turbine-generator for producing electrical power. The reactor pressure vessel is surrounded by a containment vessel 18. The volume inside containment vessel 18 and outside reactor pressure vessel 10 is called the drywell 20. The containment vessel is a concrete structure having a steel liner and is designed to withstand elevated pressure inside the drywell. The drywell typically contains a noncondensable gas such as nitrogen. In accordance with the conventional SBWR containment design, an annular suppression or wetwell pool 22 surrounds the reactor pressure vessel within the containment vessel. The suppression pool is partially filled with water 24 to define a wetwell airspace or plenum 26 thereabove. The suppression pool 22 serves various functions including being a heat sink in the event of certain accidents. For example, one type of accident designed for is a loss-of-coolant accident (LOCA) in which steam from the reactor pressure vessel 10 leaks into the drywell 20. Following the LOCA, the reactor is shut down but pressurized steam and residual decay heat continue to be generated for a certain time following the shutdown. Steam escaping into the drywell 20 is channeled into the suppression pool 22 through a multiplicity of (e.g., eight) vertical flow channels, each flow channel 27 having plurality of (e.g., three) horizontal vents 28. Steam channeled into the suppression pool 22 through the vents 28 carries with it portions of the drywell noncondensable gas 30. The steam is condensed and the noncondensable gas 30 is buoyed upwardly to the wetwell plenum 26, where it accumulates. When the pressure in wetwell plenum 26 exceeds that in drywell 20, one or more vacuum breakers 36, which penetrate the wetwell wall, are opened to allow non-condensable gas 30 in the wetwell plenum 26 to vent to the drywell 20. The vacuum breakers 36 remain closed when the pressure in drywell 20 is equal to or greater than the pressure in the wetwell plenum 26. The system further includes one or more gravity-driven cooling system (GDCS) pools 38 located above the suppression pool 22 within the containment vessel 18. The GDCS pool 38 is partially filled with water 42 to define a GDCS plenum 44 thereabove. The GDCS pool 38 is connected to an outlet line 46 having a valve 48 which is controlled by controller 40. The valve 48 is opened to allow GDCS water 42 to drain by gravity into pressure vessel 10 for cooling the core following a LOCA. Steam and noncondensable gas can be channeled directly into the GDCS plenum 44 from the drywell 20 via an inlet 50. An optional condenser or heat exchanger 72 may be provided for condensing steam channeled through inlet 50 following draining of the GDCS water 42 for drawing in additional steam and noncondensable gas. The suppression pool 22 is disposed at an elevation which is above the core 12 and is connected to an outlet line 32 having a valve 34 which is controlled by a controller 40. The valve 34 is opened after an appropriate time delay from the opening of valve 48 to allow wetwell water 24 to also drain by gravity into the pressure vessel 10 for cooling the core following a LOCA. In the SBWR design, a passive containment cooling system (PCCS) is provided for removing heat from the containment vessel 18 during a LOCA. A condenser pool 52, configured as a collection of subpools (not shown) interconnected so as to act as a single common large pool, is disposed above the containment vessel 18 and above the GDCS pool 38. The condenser pool 52 contains a plurality of PCC heat exchangers 54 (only one of which is shown in FIG. 1), also commonly referred to as PCC condensers, submerged in isolation water 56. The condenser pool 52 includes one or more vents 58 to atmosphere outside the containment for venting the airspace above the condenser pool water 56 for discharging heat therefrom upon use of the PCC heat exchanger 54. The PCC heat exchanger 54 has an inlet line 60 in flow communication with the drywell 20 and an outlet line 62 joined to a collector chamber 64 from which a vent pipe 66 extends into the suppression pool 22 and a condensate return conduit 68 extends into the GDCS pool 38. The PCC heat exchanger 54 provides passive heat removal from the drywell 20 following the LOCA, with steam released into the drywell flowing through inlet 60 into the PCC heat exchanger wherein it is condensed. The noncondensable gas (e.g., nitrogen) within the drywell is carried by the steam into the PCC heat exchanger and must be separated from the steam to provide effective operation of the PCC heat exchanger. The collector chamber 64 separates the noncondensable gas from the condensate, with the separated noncondensable gas being vented into the suppression pool 22, and the condensate being channeled into the GDCS pool 38. A water trap or loop seal 70 is provided at the end of the condensate return conduit 68 in the GDCS pool 38 to restrict backflow of heated fluids from the GDCS pool 38 to the suppression pool 22 via the condensate return conduit 68, which would bypass PCC heat exchanger 54. Accordingly, this system is configured to transport the noncondensable gas from the drywell 20 to the wet-well plenum 26 and then condense steam from the drywell in the PCC heat exchanger 54. The noncondensable gas will remain in the enclosed wetwell until the PCC heat exchanger 54 condenses steam faster than it is released from the reactor pressure vessel. When this occurs, the PCC heat exchanger lowers the drywell pressure below that of the wetwell, which causes the vacuum breakers 36 to open, thereby allowing noncondensable gas stored in the wetwell to return to the drywell. As shown in greater detail in FIG. 2, the PCC heat exchanger 54 is a drum and tube heat exchanger comprising an upper drum 74 and a lower drum 76 connected via a multiplicity of vertical tubes 78. The PCC heat exchanger 54 is positioned within reactor building 80 in a chamber 52a of condenser pool 52. Pool chamber 52a is bounded by vertical walls 82 and 84, floor 86 and ceiling 88. The upper surface 90 of ceiling 88 is commonly the refueling floor of reactor building 80. A hatch 92 standing above the PCC heat exchanger 54 has a cover (not shown) which is removable to allow access to PCC heat exchanger 54 for servicing. During operation following a LOCA, as heat is conducted out of PCC heat exchanger 54, secondary steam formed in pool chamber 52a flows through airspace 94 and passes through moisture separator/dryer unit 96 and then through outlet piping 98 to reach the environs outside reactor building 80. The allowable drawdown (i.e., boiloff) volume for pool chamber 52a has conventionally been taken to be that volume represented by all initial pool inventory located above the lower horizontal tangent to upper drum 74 of PCC heat exchanger 54 (diagrammed as "ELEV. A" in FIG. 2) up to the initial pool surface level. The effective pool inventory is amplified, in this ESBWR design, by providing a multiplicity of interconnected auxiliary pool chambers, where the interconnections are accommodated via piping and open-positioned valves. Auxiliary pool chamber 52b, shown in FIG. 2, is bounded by vertical walls 81 and 84, floor 86 and ceiling 88 and is connected to pool chamber 52a via piping 100 and valve 102. As is evident from FIG. 2, any preferential boiloff occurring to the water inventory in pool chamber 52a is passively replaced by drawdowns via gravity action in all interconnected pool chambers 52b, so that level remains essentially uniform throughout the entire interconnected pool chamber system, namely, condenser pool 52. As is apparent from the foregoing description, a sizeable portion of condenser pool 52 is "underutilized", i.e., not given credit for boiloff The underutilized portion is the entire portion of condenser pool 52 standing below ELEV. A in FIG. 2. No other constructive use has yet been identified for this portion of the condenser pool 52, although it is recognized that some very modest credit may associate with a warmup of this water to boiling temperatures. It would be desirable to minimize the required amounts of water in the condenser pool 52. This is because, among other reasons, such water represents a large mass which is located high in the reactor building 80, and which therefore represents a considerable design challenge to the reactor building structural designer in accommodating the resultant seismic loadings. Even more important, the requirements for adequate boiloff quantity in the condenser pool 52 means that quite some number of "auxiliary" pool chambers 52b must be provided, and this translates into considerable expanse of pool area, which in many cases sets the allowable minimum width and length of the reactor building. Furthermore, any approach which attempts to meet the water inventory need by increasing the depth of the condenser pool results in even greater overall plant costs. Thus, there is a need for an economically advantageous passive means for constructively employing some selected amount of the heretofore "underutilized" water inventories in auxiliary pool chambers to increase the "credited" amount of heat removal during a LOCA via the PCC heat exchangers. SUMMARY OF THE INVENTION The present invention is an improved system for managing the water inventory in the condenser pool of a boiling water reactor. In particular, the invention comprises a means for raising the level of the upper surface of the condenser pool water without adding water to the condenser pool. This is accomplished by displacing a volume of condenser pool water to a higher level. In accordance with one preferred embodiment, a tank filled with water is installed in a chamber of the isolation pool. The water-filled tank contains one or more holes or openings at its lowermost periphery and is connected via piping and a passive-type valve (e.g., squib valve) to a high-pressure gas-charged pneumatic tank of appropriate volume. The valve is normally closed, but can be opened at an appropriate time following a LOCA. When the valve opens, high-pressure gas, such as nitrogen, inside the pneumatic tank is released to flow passively through the piping to pressurize the interior of the water-filled tank. In so doing, the initial water contents of the tank are expelled through the openings, causing the water level in the condenser pool to rise. This increases the volume of water available to be boiled off by heat conducted from the passive containment cooling heat exchangers. The nitrogen is supplied to the pneumatic tank by high-pressure nitrogen gas supply. In accordance with the preferred embodiment, the accumulator tank of a standby liquid control system for injecting poison solution into the fuel core of a BWR can serve the dual function of providing high-pressure gas to the pneumatic tank of the present invention. Alternatively, the means for displacing condenser pool water to a higher level can be an inflatable bladder anchored in the condenser pool or a movable wall forming part of an auxiliary chamber of the condenser pool. |
description | This application claims the benefit under 35 USC 119(e) of U.S. Provisional Application No. 61/096,502, filed on Sep. 12, 2008, which is incorporated herein by reference in its entirety. Microscopy has played an important role in science and technology. One area where light and electron microscopy techniques have been indispensable is biological sciences. Light microscopy has allowed observation at 200 nanometer (nm) scale resolution, while electron microscopy has demonstrated atomic scale resolution with thin-sectioned specimens. Recent developments in x-ray microscopy have allowed thick hydrated samples with tens of nanometer resolution. For most effective observations, cells and biological tissues must be imaged in a hydrated state in order to have the highest fidelity representation of the living state. But when imaging hydrated organic specimens using ionizing radiation, radiation damage often limits the quality and resolution of the images that can be obtained. The solution is to work with hydrated specimens that have been rapidly frozen so as to minimize the formation of crystalline ice in the specimens. Cryogenic specimen handling methods were first developed in electron microscopy in 1974 by K. Taylor and R. Glaeser, see Electron diffraction of frozen, hydrated protein crystals. Science, 106:1036-1037, 1974, and by the late 1980s there was a considerable knowledge base in place regarding rapid freezing and cryo electron microscopy. Cryomicroscopy is also expected to be important in trace element mapping in fluorescence microprobes, since specimen drying is likely to affect the distribution of the diffusible ions that can play such important physiological roles. Cryogenic methods have also found wide spread use in protein crystallography, where the usual practice involves a cryogenic gas stream directed onto a specimen to cool it within an atmospheric pressure, room temperature environment. Aspects of the present invention concern cryogenic sample handling systems for high-resolution microscopy applications, such as x-ray, optical, and/or electron microscopy. By using a cartridge sample mount and robotic sample handling system, highly automated sample transfer and loading can be achieved. These are essential components of a high-throughput automated cryogenic microscopy that maintains the temperature of the specimen at between 80 and 170 degrees Kelvin, for example, or lower. This system uses a kinematic mount and cold interface system that provide 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. In general, according to one aspect, the invention features a cryogenic imaging system, comprising a kinematic base that receives cartridges on a cryogenic base, with each cartridge carrying a specimen. The system further includes a positioning stage and a warm-cold interface between the positioning stage and the cryogenic base. A flexible thermal linkage is included between the cryogenic base and a refrigeration source to provide conductive cooling. A robotic loading and transfer system accepts one or more cartridges and loads the cartridges onto the cryogenic base, and a microscopy system images specimens in the cartridges. In one example, this microscopy system comprises an x-ray source for generating an x-ray beam that irradiates the cartridges on the cryogenic base and a detector for detecting the x-ray beam from the cartridges. In embodiments, the positioning stage positions the cryogenic base along three axes and also rotates the cryogenic base. The warm-cold interface comprises a ball and groove configuration for low thermal conductivity. The flexible thermal linkage includes one or more metal wires. In general, according to another aspect, the invention features, a cryogenic x-ray imaging method, comprising generating an x-ray beam that irradiates specimens, detecting the x-ray beam from the specimens, holding the specimens on a cryogenic base in the x-ray beam, positioning the specimens in the beam by moving the cryogenic base, and cooling the cryogenic base via a flexible thermal linkage between the cryogenic base and a refrigeration source. The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. The radiation biology literature uses the International System (SI) unit of the Gray (equal to one Joule of absorbed energy per kilogram of mass) as its unit of radiation dose. At 100 keV in transmission electron microscopes (TEM), an electron exposure of 1 e−/nm2 corresponds to a radiation dose of about 3×104 Gray. From both protein crystallography and electron microscopy or crystallography data, diffraction spots corresponding to atom resolution information begin to fade at radiation doses in the 107-108 Gray range, with diffraction spots corresponding to 2-10 nm structural information fading at 108-109 Gray. In electron microscopy, radiation doses of about 1000 e−/nm2 or about 3×107 Gray lead to the onset of “bubbling” in the specimen, where water is broken down into OH− and H+ and the hydrogen gas will form voids in the ice matrix when it is unable to diffuse through the ice; enhanced diffusion may explain the observation that in some cases liquid nitrogen temperatures are preferred to liquid helium temperatures. In cryogenic x-ray microscopy, excellent structural preservation has been observed at radiation doses as high as 1010 Gray, without “bubbling”. The absence of “bubbling” is presumably due to some combination of the lower dose rate relative to cryogenic electron microscopy (giving more time for diffusive release of H+ through the ice matrix) and the lower ratio of absorption in water versus organic materials at the 520 eV “water window” photon energies used in these experiments. These energies are just below the energy of the oxygen absorption edge. Sensitive coherence-based “speckle” measurements have shown that there is no measurable shrinkage of frozen hydrated cryo specimens, at least at doses up to 1010 Gray. These studies emphasize the essential nature of cryogenic approaches for x-ray microscopy of hydrated organic specimens such as cells and tissues. For tomography, the specimen must remain constant as projections from different viewing angles are acquired so that all the individual views provide true representations of the object that is to be reconstructed. For spectrum imaging/spectromicroscopy image sequences, the specimen must not shrink or otherwise change its morphology so that all images can be registered to each other to yield a spectrum per pixel for subsequent analysis. For trace element mapping, it is important to not lose side groups that might be bound to the very elements one is hoping to measure and quantify. Cryogenics is essential to realize these important x-ray microscopy techniques. FIG. 1 shows a cyrogenic x-ray imaging system 100 that has been constructed according to the principles of the present invention. In more detail, the system has an x-ray source 110 that generates an x-ray beam 112. In the one embodiment, the source 110 is a beamline of a synchrotron x-ray generation facility. In other embodiments, smaller sources are used, such as laboratory sources. For example, laboratory sources that generate x-rays by bombarding a solid target anode with energetic electrons are one possible source that could be used, including microfocus and rotating anode type sources. In still other embodiments, the imaging modality is other than x-rays. In one such embodiment, the source generates an electron beam or an optical beam. The condenser 114 collects and focuses the x-ray beam 112 from the source 110. For the full field imaging setup, a suitable illumination of the sample 10 is required. This is most conveniently achieved by the use of a zone plate condenser, capillary, or Wolter optic. When the imaging modality is an electron beam or an optical beam, other condenser systems are used such as focusing magnets or refractive/reflective optics, respectively. A chamber or housing 116 is used to create a controlled environment for the specimens. The x-ray beam 112 enters the housing 116 through a housing input window 118. In some examples, the inside of the housing 116 is cooled to cryogenic temperatures such as less than 274 Kelvin (K) and usually about 77K, the temperature of liquid nitrogen, or colder. It is therefore insulated from the surrounding atmosphere. In other examples, the housing 116 is capable of holding a vacuum. In such cases, a vacuum pump system 144, such as a system including a turbomolecular pump, is in communication with the housing 116 via a pipe 152 in order to pull a vacuum within the housing 116. The x-ray or other beam 112 is projected onto the specimen that is contained within a cartridge 10. The cartridge 10 is held on a horizontally extending base 150. This base 150 is a kinematic unit that positions the sample cartridge 10 along both the x, y, and z. axes. The kinematic base 150 further has the capability of rotating the specimen/cartridge 10 around the y axis to enable the acquisition of tomographic projections at different angles to the axis 115 of the x-ray beam 112. The kinematic base 150 is held on a mounting plate 122. Then, on top of the kinematic base 150 and mounting plate 122, a cryogenic shield 140 surrounds the cartridge 10. This cryogenic shield 140 includes a shield input beam port 142 through which the beam 112 passes to the sample cartridge 10. A shield output beam port 144 of the cryogenic shield 140 allows the beam to exit after passing through the specimen/cartridge 10. A refrigeration source 124 is preferably located within the housing 116. It is connected via a heat transfer element 125 to the cryogenic shield 140. In one example, this refrigeration source 124 is a refrigeration unit. In other examples, the refrigeration source 124 is a dewar or other container containing liquid nitrogen. The heat transfer element 125 is constructed from a high thermal transfer material such as braided copper cable. The beam 112 from the sample cartridge 10 exits the cryogenic housing 116 through a housing output port 126. An x-ray objective 128 collects x-rays 112 from the specimen and images the x-ray beam 112 onto a detector system 130. In a current embodiment, the objective 128 is a Fresnel zone plate. In examples where the beam 112 is an optical beam, the image is formed with refractive or reflective optics. The detector system 130 is preferably a high-resolution, high-efficiency scintillator-coupled CCD (charge coupled device) camera system for detecting x-rays from the specimen. In one example, a camera system 130 as described in U.S. Pat. No. 7,057,187, which is incorporated herein by this reference in its entirety, is used. A robotic loading and unloading system is provided in the preferred embodiment. Microscopy specimens are delicate and have a poor chance of surviving repeated handling. For this reason it is good practice to mount them once in a cartridge, and then handle that cartridge in subsequent operations. Cartridges 10 are loaded into the system 100 on a shuttle 176. A robot system 170 then individually loads and unloads the cartridges 10 onto kinematic base 150. Cartridge covers are preferably used to prevent contamination buildup on the specimen during the various handling steps. Further the cartridges 10 preferably all share a common design in the top that is grabbed by the robot system's gripper 174 and for the end that is inserted into the kinematic base 150. Preferably, a unified base can support a variety of specimen mounting schemes. For example, one type of cartridge might use clamping rings for standard 3 mm TEM grids, another might use a micro-fabricated silicon stalk to minimize x-ray fluorescence background while maintaining good dimensional stability and thermal conductivity, while yet another might use a thin-walled capillary for the mounting of tomography specimens. A horizontal linear travel stage 175 is used to move the shuttle base 176 from a position well out of the way of the kinematic base 150, to a series of locations that put each of the cartridges 10 or cartridges slots in the shuttle 176 directly above the center of the kinematic base 150 and the loading port 146 formed in the cryo shield 140. A robot arm 172 the picks the cartridges with the gripper 174 and transfers the cartridges 10 between the kinematic base 150 and the cartridge slots of the shuttle 176, accessing the kinematic base 150 via the loading port 146. The robot system 170 preferably has a vertical linear travel stage 172 upon which the gripper 174 is mounted. A fiberglass insert provides thermal isolation for the gripper end 174 which is in turn conductively cooled using a copper braid to a dewar, in one example. This requires access to the specimen from above, and either enough “headroom” in the chamber 116 to hold the vertical linear travel stage upon which the robot grabber is mounted, or a port with a linear feedthrough. FIG. 2 shows the details of the kinematic base 150 and shield 140. A small, low-mass cryo base 152 is mounted on a high-temperature rotation and/or nanopositioning stage 154 that is supported on the mounting plate 122. The nanopositioning stage 154 positions and moves the cryo base 152 and thus the specimen in the cartridge 10 along the x, y and z axes to position the region of interest of the specimen within the x-ray beam 115, and also preferably rotates the specimen about the y axis. A warm-cold interface 156 separates the nanopositioning stage 154 from the cryo base 152. It is constructed from an interface material and has a geometry with low mechanical creep and low thermal conductance. The cold cryo base 152 mainly “sees” the area of the cryo shield 140, radiative heat transfer into the specimen 10 is thus greatly reduced. The dominant heat transfer path becomes that of the warm-cold interface 156, which has both high mechanical stiffness and low thermal conductivity. In this way only modest cooling power (well below 100 milliWatts (mW)) must be supplied to the cryo base 152. This is preferably supplied by “weak” heat conductors 158 which involve very low mechanical coupling force between the cryo base 152 and the cryo shield 140 for rotations up to ±90 of the cryo base by the movement of the nanopositioning stage 154 or translations of several millimeters. (Initial cool-down involves moving a raised surface on the cryo base into strong contact with a cold “finger” from the cryo shield). This cryo base 152 is normally kept cold in the microscope 100 at all times. Key thermal design considerations for this approach include the following: Gas conductivity becomes negligible at pressures of below about 10−4 torr, and pressures well below this are needed to minimize ice buildup on cryo specimens. Because the thermal conductivity of high-purity copper increases at lower temperatures, weak heat conductors 158 comprise a number of copper wires that can provide good thermal cooling power, such as less than 500 wires. As an example, 150 wires in parallel, each 100 micrometers (μm) in diameter and 50 millimeters (mm) long, can provide 120 mW of cooling power over a temperature difference of 10 K between the cryo shield 140 that is cooled by the heat conduction through heat transfer element 125 to the refrigeration source 124. The wire conductors 158 are much longer than the distance (D) between the outer wall of the base 152 and the shield 140 so that the base 152 is moved and rotated freely by the nanopositioning stage 154. In one example, the length of the wire conductors 158 are more than 5 times distance D. FIG. 3 shows an embodiment of the warm-cold interface 156. In more detail, the warm-cold interface 156 comprises an upper member 312 on which the cryogenic base 152 is placed and lower member 310 that is secured to the nanopositioning stage 154. Both the upper member 312 and lower member 310 have low emissivity coatings, especially on the two surfaces that face each other. For example, using a conservative estimate for the emissivity (ε) of highly polished gold of ε=0.05 (as opposed to the ε=0.018-0.035 values given in published tables), the radiative heat transfer between two 25 mm disks when one is at 100 K and the other at 300 K is only about 11 mW. Thermal conductivity then becomes the dominant path. This is controlled by using a ball-on-flat mounting approach and with both low conductivity materials. Preferably, both the upper member 312 and lower member 310 are constructed from fused silica or an infrared glass. AMTIR-1, from Amorphous Materials Inc, for example, has 5× lower conductivity and nearly equal stiffness. The current ball-on flat approach to thermal isolation uses three recesses 316A, 316B, 316C are formed in the lower member 310. In the preferred embodiment, each of these three recesses 316A, 316B, 316C comprises three planar surfaces in the general form of a pyramid. In an alternative design, the three recesses 316A, 316B, 316C are in the form of a cone. Low thermal conductivity balls or spheres 314A, 314B, 314C are each placed in a corresponding one of the three recesses 316A, 316B, 316C. The upper member 312 has a corresponding, mirrored series of recesses that receive the balls 314A, 314B, 314C. This creates rigid yet low thermal conductivity interface. Depending on the choice of materials and the force applied, a thermal conduction power of no more than 20-50 mW can be obtained between the cryo base 152 and the warm nanopositioning stage 154. This ball-on-flat system implemented in the upper member, 312, lower member 310 and balls or spheres 314A, 314B, 314C also has the advantage of being naturally suited to a kinematic mounting system, where no mechanical stress is induced that would otherwise lead to mechanical drift. Other design configurations can include the commonly used ball-groove-flat kinematic mounting system. While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. |
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abstract | Example embodiments and methods are directed to irradiation target positioning devices and systems that are configurable to permit accurate irradiation of irradiation targets and accurate production of daughter products, including isotopes and radioisotopes, therefrom. These include irradiation target plates having precise loading positions for irradiation targets, where the targets may be maintained in a radiation field. These further include a target plate holder for retaining and positioning the target plates and irradiation targets therein in the radiation field. Example embodiments include materials with known absorption cross-sections for the radiation field to further permit precise, desired levels of exposure in the irradiation targets. Example methods configure irradiation target retention systems to provide for desired amounts of irradiation and daughter product production. |
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abstract | Various embodiments include systems and methods to provide a pulsed chemical neutron source. The pulsed chemical neutron source can be used in well logging applications. Apparatus can be arranged to generate neutrons from a chemical neutron emitter and to pass the neutrons through an aperture of a neutron shield when the chemical neutron emitter aligns with the aperture such that the neutrons are substantially blocked by the neutron shield when the chemical neutron emitter is unaligned with the aperture. In various embodiments, movement of one or more of the chemical neutron emitter or the neutron shield can be controlled such that the aperture and the chemical neutron emitter operatively align with each other during a selected portion of the movement, generating pulses of neutrons output from the neutron shield. Additional apparatus, systems, and methods are disclosed. |
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description | This application is a 371 of PCT/NO2005/000245 filed on Jun. 30, 2005, published on Jan. 12, 2006 under publication number WO 2006/004426 A1 which claims priority benefits from Norwegian Patent Application Number 2004 2763 filed Jun. 30, 2004. The present invention relates to a specific tracer delivery system composed of a melamine formaldehyde resin (MFR) doped with various tracer materials. The MFR/tracer mixture is used as part of a monitoring system where tracer is delivered from the MFR/tracer mixture at a specific location upstream and detected at some location downstream, thereby verifying fluid flow from that specific location upstream. The system is intended for long-term monitoring of fluid inflow in production wells in oil reservoirs. Tracers are used to follow fluid flow in various systems such as oil reservoirs, process flow lines, ground water is leakage studies etc. Tracers are released up-stream and detected downstream. Analysing tracer concentration downstream may give information about flow rates, dilution volumes, communication, fluid mixing, mass residence time distribution etc. Tracers may be injected into the system by a variety of methods, however the most common being either as a sharp pulse (Dirac pulse) or at a constant concentration rate. In several types of well operation there is a need for tracer delivery systems, which are able to release tracers at places where it will, due to practical constrains, be difficult to position or install more conventional mechanical injection equipment. There is also a need for delivery systems that are able to reflect changes in the well conditions such as temperature, single-phase fluid chemical composition or fluid phase types. Examples of suitable non-radioactive tracers are salts of naphthalenesulfonic acids, salts of amino naphthalenesulfonic acids, fluorescein and fluorinated benzoic acids. 3H-labelled or 14C-labelled tracers of the same kind of components may also be applied. Application of such release methods has been proposed in several patents with the specific aim to measure fluid inflow in oil production wells (patent US06645769, patent US0582147). Due to the complexity of most oil reservoirs and the modern horizontal, undulating, multilateral or multi-branched production wells it may be difficult to know from which well or zones in the well the fluids are produced. The water production rates in oilfields may in some wells be at a level of 10.000-20.000 m3/d for many years. The tracer release system has to be able to deliver tracer amounts giving a tracer concentration above the detection limit at the downstream detection position. In many situations the available and accessible volume for the delivery system is limited. The system should therefore be able to deliver tracers that are detectable in sub ppb concentrations. This is easily achieved with radioactive tracers (mainly pure beta-emitters). In many systems, however, this should be avoided and the radioactive tracers should be replaced with non-radioactive chemical species. Optimal oil production from the reservoir depends upon reliable knowledge of the reservoir characteristics. Traditional methods for reservoir monitoring include seismic log interpretation, well pressure testing, production fluid analysis, production history matching and interwell tracer techniques. Due to the complexity of the reservoir all information available is valuable in order to give the operator the best possible knowledge about the dynamics in the reservoir. One common secondary oil recovery process is water injection in dedicated injection wells. The water may travel in different layers and sweep different area in the reservoir. Monitoring of the production of this water in different zones in the well is important to design a production program that improves the sweep efficiency and thereby increased the oil recovery. Mixing of injection water and formation water originally present in the reservoir may cause supersaturated solutions leading to precipitation of particles (scale) in either the reservoir near-well zone or in the production tubing. By knowing which zones contribute to water production, action can be taken to reduce the effect of scaling and thereby maintain productivity. The present application proposes a specific tracer delivery system that has been tested. The claimed system is composed of melamine formaldehyde resin (MFR) doped with various tracer materials. The MFR is used to slowly release tracer compounds into a liquid system. The MFR/tracer mixture is applied as part of a monitoring system where tracer is delivered from the MFR/tracer mixture at a specific location up-stream and detected at some location downstream, thereby verifying fluid flow from that specific location up-stream. The MFR can be doped with different types of tracers, thereby allowing placement of different tracers at several different positions upstream. Production from the various labelled zones can be verified through the analysis of one sample downstream. In other systems, tracers may be added either as a pulse or at a constant delivery rate. The MFR system is developed to work as a stable delivery system at remote sites. The system will in many situations be a cost efficient method for tracer delivery. Once installed, no further maintenance or work is needed to deliver the tracer. The MFR system may work as a delivery system for many years. The MFR tracer delivery system has been developed to enhance the possibilities for using tracers as a tool to measure fluid flow parameters in a large variety of mass transfer systems. The MFR works as a release system for the tracer compound under high temperature and high pressure conditions. The MFR can be doped with different types of tracers in different concentrations. The application of MFR includes, but is not limited to, the delivery of water or oil tracers in oil production wells. The MFR system can be placed in a production well in the oil reservoir. The MFR can be placed in the toe, along the production line or in the heel of the production well. Different tracers can be applied at different locations. The system may be placed together with production liner, during workover. The MFR can be an integrated part of production tubing or placed as separate objects. The MFR can be placed in the gravel pack or in a rat hole. The tracer is mixed into a MFR condensate solution before hardening with a suitable hardener. The condensate solution is commercially available from suppliers such as Dynea ASA, Norway, and is a reaction mixture of melamine, formaldehyde, methanol and water. It may also contain additives such as stabilizers, fillers, plasticizers and/or colorants. The original content before condensation is 25-40% melamine, 25-35% formaldehyde and 1-10% methanol. The hardener can be formic acid or other products from the supplier. One possible product is Prefere 4720 with addition of 10% (w/w) of the hardener Prefere 5020 from Dynea ASA. The condensate solution can also be prepared by mixing dried powder of the condensate with water. The dried powder is available from Dynea ASA or other suppliers and is made by spray drying of a condensate solution with the same original composition of ingredients as listed above. One possible resin powder product is Dynomel M-765 from Dynea ASA. The tracer is mixed into the condensate solution using a mechanical blender before the hardener is mixed in. Some tracers such as amino naphthalene sulfonic acids and fluorescein will react with formaldehyde and melamine in the condensate solution. The chemical reaction may be enhanced by applying heat. These tracers will be incorporated into the polymer structure after hardening. Tracers may be mechanically distributed as salt crystals in the polymer matrix, be chemically incorporated or a combination of both cases may be possible. The chemically bound tracers may be released through hydrolyses either as the tracer itself or as derivatives of the tracer when the polymer is exposed to water at high temperature. Tracers that are chemically bound will be released at a slower rate than when the tracer is present as salt particles only, something which will extend the lifetime of the tracer source. In cases where a long release period is desirable, this type of chemically bound tracer matrixes may be preferable to others. Urea formaldehyde resin was also tested as carrier for the water tracers. This resin type was discarded because it was much less stable to water at elevated temperatures. It is an advantage to make use of water based resins for the water soluble tracers. One reason for this is that the tracers are more easily distributed into a hydrophilic resin than a hydrophobic resin. A more hydrophobic resin like polymethylmethacrylate was also tested as carrier, but it was more difficult to disperse the tracer particles evenly in the resin. The tracers applied can be radioactive or non radioactive. The tracer release rate from this MFR/tracer system will depend on the surface and geometry of the MFR exposed to the fluid. The release rate of tracer will further be influenced by parameters such as temperature, fluid composition and pressure. The MFR will tolerate a large fraction (in %) of tracer compound and still maintain acceptable mechanical properties. Typical tracer loading will be 5-20 weight %. A standard temperature/pressure range where the MFR system according to the present invention may be used will be up to 120° C. and 600 bar. The MFR release system may be shaped to adapt into different geometries suitable for the actual application. This may be rods, cubes, surfaces or direct adaptation to a predefined form. To reinforce the polymer different armouring techniques can be applied. Leaching experiments using naphthalenesulfonic acids have been performed. These compounds constitute a class of chemicals with excellent tracer properties. In the example reported here a MFR cube with a side length of 4 cm has been prepared containing 10% by weight of chemical tracer compound. This experiment has been carried out at a temperature of 90° C. The MFR in this experiment was made from Dynomel M-765. The cube was placed in a pressure container as shown in FIG. 1. In the example saline water, comparable to what can be expected in an oil reservoir, has been used as the flowing phase. The system allows testing at different temperatures, pressure and flow rates. FIG. 2 provides an example of the measured release rates. The release rate measured was about 0.3%/day of the total tracer amount in the actual cube. The release rate will depend upon the geometry and accessible surface of the MFR system. The obtained release rate shows that the polymer can last for about one year releasing tracer at rates suitable for detection downstream using state-of-the-art analytical methods. The set-up for Example 2 is shown in FIG. 3. A hole of 3 mm diameter was drilled through a cube of MFR made from Dynomel M-765 with size 20×20×7 mm containing 10% chemical tracer. One length of stainless steel tubing was inserted into the hole from each side of the cube so that only a length of 5 mm of the hole in the resin was exposed to the formation water that was flowing through. The tracer source was placed in a heating oven at 90° C. and the flow rate of formation water was set at 0.5 ml per minute. The measured release rate is shown in FIG. 4. Both examples show that it is possible to construct tracer sources from MFR doped with chemical tracer that will provide a fairly constant release of tracer over time. |
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056419686 | claims | 1. A radiation image storage panel having a phosphor layer comprising a stimulable phosphor and a binder, wherein the binder comprises a thermoplastic elastomer having a softening or melting point of 30.degree. to 150.degree. C. and a modulus of elasticity of not more than 0.3 kgf/mm.sup.2. 2. The radiation image storage panel of claim 1, wherein the modulus of elasticity of the thermoplastic elastomer is in the range of 0.001 to 0.1 kgf/mm.sup.2. 3. The radiation image storage panel of claim 1, wherein the thermoplastic elastomer has a tensile strength in the range of 0.1 to 20 kgf/mm.sup.2. 4. The radiation image storage panel of claim 1, wherein the thermoplastic elastomer has a tensile elongation in the range of 10 to 2,000%. 5. The radiation image storage panel of claim 1, wherein the thermoplastic elastomer is selected from the group consisting of polystyrene, polyolefin, polyurethane, polyester, polybutadiene, ethylene-vinyl acetate copolymer, poly(vinyl chloride), natural rubber, fluorinated rubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber, and silicon rubber. 6. The radiation image storage panel of claim 1, wherein the thermoplastic elastomer is polyurethane elastomer. |
041397770 | claims | 1. A light, compact cyclotron suitable for use in neutron therapy, and capable of being moved to change the direction of an exiting neutron beam comprising: (a) a pair of opposed, spaced pole shoes having their adjacent inner surfaces defining an accelerator zone, the surfaces being adapted to constitute magnetic equipotential surfaces which establish a magnetic field configuration for the cyclotron during use, (b) an electromagnetic coil system around the pole shoes and adapted for connection to an electrical power source for generating the cyclotron magnetic field between the pole shoe surfaces, (c) a magnet yoke to provide a magnetic flux return path for the pole shoes, the magnet yoke together with the pole shoes providing a low magnetic resistance relatively to that of the accelerator zone, and the magnet yoke being shaped to substantially enclose the accelerator zone to constitute, together with the pole shoes, a neutron attenuation shield for neutrons produced in the cyclotron, (d) at least one hollow accelerating dee electrode positioned in the accelerator zone, and having a radio frequency resonator associated therewith, (e) a vacuum chamber enclosing the acclerator zone and each dee electrode, (f) means for providing charged particles for acceleration within the accelerator zone, (g) a target zone for a target device, and (h) a neutron beam outlet in the magnet yoke for emission of a neutron beam produced in the cyclotron. (a) a pair of opposed, spaced pole shoes having their adjacent inner surfaces defining an accelerator zone, the surfaces being adapted to constitute magnetic equipotential surfaces which establish a magnetic field configuration for the cyclotron during use, (b) an electromagnetic coil system around the pole shoes and adapted for connection to an electrical power source for generating the cyclotron magnetic field between the pole shoe surfaces, (c) a magnet yoke to provide a magnetic flux return path for the pole shoes, the magnet yoke together with the pole shoes providing a low magnetic resistance relatively to that of the accelerator zone, and the magnet yoke being shaped to substantially enclose the accelerator zone to constitute, together with the pole shoes, a neutron attentuation shield for neutrons produced in the cyclotron, (d) at least one hollow accelerating dee electrode positioned in the accelerator zone, and having a radio frequency resonator associated therewith, (e) a vacuum chamber enclosing the accelerator zone and each dee electrode, (f) means for providing charged particles for acceleration within the accelerator zone, (g) a target zone for a target device, and (h) a neutron beam outlet in the magnet yoke for emission of a neutron beam produced in the cyclotron. 2. A cyclotron according to claim 1, in which the adjacent inner surfaces of the pole shoes are shaped to define at least three hills and valleys to establish an isochronous magnetic field configuration during use. 3. A cyclotron according to claim 2, in which the hills and valleys are radial. 4. A cyclotron according to claim 2, having a dee electrode positioned in each valley, with each dee electrode having a radio frequency resonator associated therewith. 5. A cyclotron according to claim 4, in which the dee electrodes are connected to each other at the centre of the accelerator zone. 6. A cyclotron according to claim 5, having a transmission bore extending along the polar axis of one of the pole shoes, having a radio-frequency transmission line located in the transmission bore and connected to the dee electrodes at the centre of the accelerator zone, and having coupling means for coupling the transmission line to a radio-frequency power source. 7. A cyclotron according to claim 1, having auxiliary neutron shield means in the forward neutron peak zone of a neutron beam produced in the cyclotron to attenuate neutron and gamma radiation in the forward peak zone to provide a combined neutron and gamma radiation dose rate of less than about 3% of that in a neutron beam emitted from the neutron beam outlet during use. 8. A cyclotron according to claim 7, in which the auxiliary neutron shield means comprises a neutron attenuation shield and a neutron moderating shield. 9. A cyclotron according to claim 8, in which the neutron attenuation shield is provided within the magnet yoke and the neutron moderating shield is provided in the magnet yoke. 10. A cyclotron according to claim 2, in which the neutron beam outlet is shaped to removably receive a collimator to control the radiation field size of a neutron beam emitted from the neutron beam outlet. 11. A cyclotron according to claim 2, in which the vacuum chamber is defined by the adjacent inner surfaces of the pole shoes and by an annular channel member surrounding the accelerator zone and having its free edges sealingly secured to the opposed pole shoes. 12. A cyclotron according to claim 2, in which the magnet yoke comprises a plurality of separate yoke sections which together constitute the magnet yoke. 13. A cyclotron according to claim 1, in which each radio-frequency resonator extends radially and is enclosed within the magnet yoke. 14. A cyclotron according to claim 13, in which each radio-frequency resonator comprises a flat, narrow inner conductor plate mounted on the dee, and two flat, wider outer conductor plates on opposed sides of and laterally spaced from the inner conductor plate, with the outer conductor plates connected to the inner conductor plate by means of short circuit plates. 15. A cyclotron according to claim 14, in which each outer conductor plate includes a flexible hinge, in which each short circuit plate is flexible, and in which frequency adjustment means extends from each outer conductor plate to allow for adjustment of the characteristic impedance of each radio frequency resonator. 16. A cyclotron according to claim 1, having pivot means for pivotally mounting the cyclotron to allow variation of the direction of a neutron beam emitted from the neutron beam outlet during use. 17. A cyclotron according to claim 16, in which the pivot means comprises pivot bores in opposed sides of the cyclotron, for receiving pivot shafts to pivotally support the cyclotron. 18. A cyclotron according to claim 16, in which the pivot means comprises two pivot shafts extending outwardly from opposed sides of the cyclotron, each pivot shaft having a support gear wheel mounted thereon for pivotally supporting the cyclotron on suitable support rails in the form of linear gear rails having teeth to mesh with the gear wheel teeth. 19. A cyclotron according to claim 16, in which the polar axis of the pivot means extends normally to the plane of the accelerator zone along the polar axis of the cyclotron. 20. A cyclotron according to claim 16, in which the pivot means comprises a pivot frame in which the cyclotron is mounted, the pivot frame having a pair of opposed supporting legs, with each supporting leg having a pivot bore for pivotally mounting the frame on a pair of support axles, and the pivot frame having a pivot beam mounted thereon, with the pivot beam having guide gear wheels mounted at its opposed ends to co-operate with a pair of curved, complementarily toothed guide rails positioned concentrically with the pivot bores to guide pivotal displacement of the cyclotron about the pivot bores, the pivot bores being positioned so that their axes will intersect the core of a neutron beam emitted from the neutron beam outlet during use, in the treatment zone of such a beam where the centre of an affected area of a patient to be treated would be positioned during treatment, thereby providing an isocentric therapy system. 21. A cyclotron according to claim 20, in which the cyclotron is pivotally mounted in the pivot frame. 22. A cyclotron according to claim 16, in which the pivot means comprises a turntable to support the cyclotron on a surface for pivotal displacement about a vertical axis. 23. A neutron therapy installation comprising biological shielding means to define the installation, and having a light, compact cyclotron for use in neutron therapy, mounted therein, and capable of being moved to change the direction of an exiting neutron beam,. the cyclotron comprising: 24. A neutron therapy installation according to claim 23, in which the cyclotron has pivot means for pivotally mounting the cyclotron to allow variation of the direction of a neutron beam emitted from the neutron beam outlet during use, and in which the installation has pivot support means for engaging with the pivot means. 25. A neutron therapy installation according to claim 24, in which the cyclotron has pivot means in the form of pivot bores in opposed sides thereof, and the pivot support means comprises opposed pivot shafts which extend into the pivot bores and have bearings mounted thereon which engage with the pivot bores. 26. A neutron therapy installation according to claim 24, in which the cyclotron has pivot means in the form of two pivot shafts extending outwardly from opposed sides thereof, with each pivot shaft having a support gear wheel mounted thereon, and the installation includes two linear gear support rails having teeth to mesh with the teeth of the gear wheels. 27. A neutron therapy installation according to claim 24, in which the pivot means comprises a pivot frame in which the cyclotron is mounted, the pivot frame having a pair of opposed supporting legs, with each supporting leg having a pivot bore, and the pivot frame having a pivot beam mounted thereon, with the pivot beam having guide gear wheels mounted at its opposed ends, and in which the pivot support means comprises two opposed support axles on which the pivot bores are mounted, and two opposed curved, toothed guide rails which are concentric with the support axles to co-operate with the guide gear wheels of the pivot beam and guide pivotal displacement of the cyclotron about the pivot bores, the pivot bores being positioned so that their axes will intersect the core of a neutron beam emitted from the neutron beam outlet during use, in the treatment zone of such a beam where the centre of an affected area of a patient to be treated would be positioned during treatment, thereby providing an isocentric therapy system. 28. A neutron therapy installation according to claim 23, in which the cyclotron has pivot means in the form of a turntable to support the cyclotron on the floor of the installation for pivotal displacement about a vertical axis, and in which the installation has a plurality of separate treatment rooms circumferentially spaced about the cyclotron, with each room having an access opening to register with the neutron beam outlet of the cyclotron. |
051075296 | summary | FIELD OF THE INVENTION The present invention relates generally to the area of x-ray radiography. More particularly, the present invention relates to an equalization system for fluoroscopic and radiographic diagnostic x-ray systems. BACKGROUND OF THE INVENTION Equalization is a common term in the x-ray radiography field which refers to the process of selectively attenuating portions of the x-ray beam that are too intense for the density of a corresponding portion of the patient or object ("subject") exposed to the x-ray. Without equalization, the resulting x-ray image (appearing on either film or a monitor) may have inconsistent overall exposure, manifested as light and dark areas in the image, as a result of corresponding variations in density in the exposed portions of the subject. The effect of equalization is to reduce the intrinsically large dynamic range of the x-ray beam intensities in order to accommodate the dynamic range limitations of the x-ray detector system. The most common detector systems employed in diagnostic x-ray radiography are film and image intensifier-TV systems, both of which have severely limited dynamic range. Equalization is also useful in digital subtraction angiography (DSA). DSA is a known imaging technique where digital radiographic images are obtained both before and after injection of an iodine based dye into the vasculature, and then the two images are subtracted. DSA employs an x-ray image intensifier (fluoroscope) that is optically coupled to a high quality television chain and to a video digitizer. Although the image intensifier has a relatively large dynamic range (i.e., the ratio of the highest allowable signal intensities to the lowest is large), the TV camera presents substantial dynamic range limitations and thus limits the dynamic range of the entire imaging system. It is known to equalize an x-ray radiographic image by selectively attenuating only those areas of the image that are determined to have been overexposed. One such method involves arranging a plurality of filters between the x-ray emitter and the image receptor. The filters are selected and arranged so that only the areas of over-exposure are attenuated. Practice of this method provides acceptable results once the correct combination of filters has been found. However, a serious drawback of this method is that it is cumbersome since filter selection and juxtaposition is a manual process, and can require time consuming trial and error for the correct combination to be found. It is therefore desirable to provide an apparatus and method for performing selective equalization of x-ray radiographic images that is automated and rapid, but yet is simple and relatively inexpensive to implement. The present invention achieves these goals. SUMMARY OF THE INVENTION According to one embodiment of the invention, a plurality of juxtaposed members, such as disks, is provided wherein each disk has an annulus defining a filter region for attenuating electromagnetic radiation such as x-rays. The attenuation provided by the annular filter region of each disk varies throughout at least selected angular portions of the annulus. At least a portion of the annular filter region of each disk overlaps a portion of the annular filter region of all other disks. The members may be embodied as strips or belts. In such case, the surface of the member defines the filter and varies throughout its length. Motive means are operatively coupled to the disks for selectively and independently rotating each disk relative to the other disks and relative to an electromagnetic radiation emitter, such as an x-ray emitter. The emitter is disposed to emit radiation along a path intersected by the overlapping portions of the filter regions. Rotation of a disk thereby alters attenuation of the radiation along the path and received by the image receptor. A control means is operatively coupled to the motive means for controlling the operation of the motive means to alter the attenuation provided by the overlapping filters. According to a preferred embodiment of the invention, the filter of each disk is comprised of a plurality of adjacent and unique preselected attenuation or filtration patterns. Thus, rotation of a disk results in a selected, unique combination of attenuation or filtration patterns along the path, wherein the attenuated radiation has a pattern that corresponds to the selected combination of attenuation patterns. According to yet a further embodiment of the invention, the control means is operative to rotate the disks to a selected position for irradiating a subject to obtain a preliminary non-attenuated image. The control means is operatively coupled to the image receptor to receive and process the preliminary image. The control means determines locations and magnitudes of unsuitable exposures (i.e., overexposures) in the preliminary image and rotates the disks to select one of the unique combinations of attenuation patterns to compensate for the regions of unsuitable exposures. According to yet a further embodiment of the invention, each disk has an area in the annular region that provides substantially constant attenuation to electromagnetic radiation and defines a parked position of the disk. The disks are rotatable to substantially align the parked positions with the path when it is desired to obtain the preliminary image . |
summary | ||
043426204 | abstract | A box insert for receiving nuclear fuel is formed from a plurality of vertically extending plates arranged as an open-ended polygonal container having a smaller cross-sectional area than the opening where the box is to be located in the fuel storage rack. 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 plate. The adjacent tabs of each plate are connected, thereby giving the container rigidity and providing the container with a plurality of outwardly projecting ribs. When the boxes are located in the rack, the ribs fit into the corners of openings and maintain the container in proper spaced relation relative to the side walls of the opening. |
055920276 | abstract | A method of compacting, without danger of ignition and/or explosion, metal waste that is liable to ignite and/or explode while being compacted. The method comprises in compacting a container that contains said waste and that is saturated in inert gas. |
abstract | A radiation attenuation system for shielding from scatter radiation one or more portions of a patient that are not of primary interest to a particular radiological procedure (i.e., non-target areas, etc.). The radiation attenuation system may be configured to shield the head of a patient (such as the head of a pediatric patient), and/or any other portion of the patient that may benefit from being shielded from scatter radiation. The radiation attenuation system is preferably configured to conform to the contours of the patient. The radiation attenuation system may be a flexible member that can be reconfigured to accommodate patients of varying size. |
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description | This is a continuation application, under 35 U.S.C. § 120, of copending international application No. PCT/EP2016/050255, filed Jan. 8, 2016, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. DE 10 2015 200 679.4, filed Jan. 16, 2015; the prior applications are herewith incorporated by reference in their entirety. In a nuclear power plant, a possibly significant release of radioactive fission products, in particular iodine, aerosols and inert gases, should be anticipated in accident or incident situations, depending on the accident in question and any counter measures that may have been introduced. In this case, before release into the surroundings of the power plant occurs, it should be assumed that there will also be a release and spread of activity in the power plant buildings (e.g. auxiliary installation building, switching facility, control room, etc.) on account of leakage of the containment. In this case, in addition to the release of aerosol-bound activity, in particular the release of inert gases is problematic for the power plant staff. A huge release of inert gas may also occur when filtered pressure release is introduced and an inert gas cloud is formed over the power plant site. Depending on the weather conditions, longer-term pollution cannot be entirely excluded. In order to introduce what are known as accident management measures, it is essential that the conditions in the control room, which is also referred to as the control station, allows operators to be present without the operators suffering unacceptable radiation exposure and contamination. In the case of beyond-design-basis accidents involving a station blackout (SBO), the intended or normally operational ventilation systems and filter systems are no longer available for ensuring the essential ventilation-related parameters for maintaining the accessibility of the control room. Previous designs provide isolation of the control room in order to overcome scenarios of this kind. The supply is achieved for example using mobile ventilation systems that are equipped with different filters. It is not possible to satisfactorily retain inert gas using these systems. Other designs provide the control room with stored compressed air. However, storage in pressure vessels for a long period of time requires significant outlay and therefore limited. A more modular and mobile system design is practically impossible. Pressure accumulator designs additionally require significant outlay in the event of retrofitting in running installations. The object of the invention is to specify a ventilation system for a control station of a nuclear installation or for a similar space accessible to operators that is as simple and compact as possible and that allows a supply of decontaminated fresh air at least for a period of a few hours in the event of serious accidents involving the release of radioactive activity, such that operators present in the control station are exposed as little as possible to radiation. In particular, the component of radioactive inert gases in the fresh air supplied to the control station should be as small as possible. Furthermore, the ventilation system should be as passive as possible and consume only a small amount of electrical power. In addition, a particularly advantageous method for operating a ventilation system of this kind should be specified. The ventilation system according to the invention advantageously contains, inter alia, an aerosol and iodine filter module. In this case, the intake air into the supply air line is sucked in by a fan and guided over high-efficiency particulate air (HEPA) filters in order to separate the aerosols. After the particulate matter has been separated, radioactive iodine compounds are advantageously separated in an activated carbon filter bed. Impregnated activated carbon can be used to separate the radioactive methyl iodide by isotope exchange or salification. A particle filter is advantageously connected downstream of the activated carbon bed in order to retain abraded particles. The air that is thus filtered is then fed to an inert gas module in a second process step. The inert gas module substantially contains two adsorber columns in a twin column configuration that are filled with adsorbent(s), preferably activated carbon. The adsorbent of the columns can also be composed of a plurality of layers of activated carbon and/or zeolite and/or molecular sieves. The supply air enters the first adsorber column, the inert gases such as xenon and krypton being slowed by dynamic adsorption as they pass through the column. A filter for retaining adsorber particles is expediently arranged after the column. The exhaust air from the spatial region to be supplied is at the same time guided over the second adsorber column where it causes backwashing of the previously accumulated inert gas activity, such that this column is again ready for loading after switching. The switching is carried out at the latest shortly before the activity breaks through into the first adsorber column, the column then being backwashed by the exhaust air. The switching is preferably triggered passively by a timer or an activity measurement. The backwashing is advantageously assisted by a fan in the exhaust air line, the increase in volume of the exhaust air stream intensifying the backwash process of the inert gases on account of the negative pressure. A throttle is advantageously provided in the exhaust air line of the control room, which throttle results in passive superheating of the exhaust air and thus in a reduction in the moisture present in the exhaust air (expansion drying). This is favorable for the speed of desorption of the inert gases in the adsorber column to be rinsed that is connected downstream. A throttle and/or an air dryer are advantageously provided in the supply air line into the inert gas module in order to prevent too much moisture from being conveyed to the inert gas columns. The inert gas module can additionally be equipped with a passive cold accumulator for increasing the k-values. In this connection, the k-value describes the adsorption capacity of the adsorber material for inert gas, for example in the unit cm3 inert gas/g adsorbent. The k-value is dependent on the temperature, the pressure and the moisture content of the gas. The value is generally determined empirically. The adsorber columns are preferably operated according to the pressure-swing method, i.e. negative pressure in the column to be rinsed and excess pressure in the column to be loaded (in each case in relation to atmospheric pressure), in order to improve the k-values of the columns and reduce the dimensions thereof. The excess pressure in the adsorber column through which the supply air flows is regulated by an adjustment valve in the supply air line. The exhaust air, together with the backwashed inert gases, is emitted into the surroundings of the power plant at a sufficient distance from the supply air intake. The ventilation system expediently contains a controller and corresponding adjustment members for through-flow and pressures. The advantages achieved by the invention are in particular that, in addition to the air-borne activities in the form of aerosols and iodine/iodine compounds (in particular organoiodine), at the same time the radioactive inert gases are kept out of the supply air of the control room. Using the pressure swing and rinsing method for the twin columns, even long-lived inert gas isotopes such as krypton-85 can be reliably separated out of the supply air stream. The conditions required for removing the inert gases from the sorbent/adsorbent are passively assisted by expansion superheating. Electrical operating current is substantially required only for the fans in the supply air line and the exhaust air line and, to a limited extent, for the associated control unit and for the switching means for switching between operating cycles. This requirement can be met without difficulty for at least 72 hours using a stand-alone power supply module (e.g. by means of batteries and/or a diesel generator set). In summary, in order to guarantee the accessibility of the control room, the following functions are ensured: a) isolation of the control room ventilation from the remaining parts of the building; b) excess pressure compared with the adjacent building spaces (e.g. <1 mbar); c) maintenance of the admissible carbon monoxide and carbon dioxide concentration; d) iodine retention; e) aerosol retention; f) retention of the inert gases (e.g. Kr, Xe); g) limitation of the dose (e.g. <100 mSv/7 d); h) limitation of the temperature in order to comply with the I&C temperature conditions; and i) guarantee of the above-mentioned functions for at least 72 hours In a bulleted summary, further advantages are: a) more modular and mobile system design; b) less outlay and significant flexibility when being integrated into running installations; c) less maintenance outlay; d) storage of breathable air, requiring significant outlay, is omitted; and e) it is possible to cover larger air volumes (change of air) and spatial regions. 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 ventilation system and associated operating method for use during a serious accident in a nuclear installation, 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. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown an accident ventilation system, referred to for short as ventilation system 2. The ventilation system 2 is used to supply fresh air to a control station 4 (also referred to as a control room or main control room (MCR)) of a nuclear power plant 6 in accident or incident situations, in particular in the initial phase of a serious accident involving the release of nuclear fission products inside the power plant building and possibly also into the surroundings. In scenarios of this kind, which are usually associated with failure of the autonomous power supply of the nuclear power plant 6 and thus also the failure of the normally operational ventilation system (not shown) for the control station 4, it is particularly important to be able to continue to keep the control station 4 manned for a certain amount of time—approximately up to 72 hours after the onset of the accident—without endangering the operators, in order to introduce and monitor initial countermeasures. The operators may also have to stay in the control station 4 until safe evacuation is possible following the decay of an initial activity maximum in the surroundings. For this purpose, the ventilation system 2 for the control station 4 is configured to supply decontaminated and oxygen-rich fresh air (also referred to as supply air) from the surroundings of the control station 4 or of the power plant building and is equipped with corresponding filter and purification stages. In addition, the ventilation system 2 brings about the removal of spent and carbon dioxide-rich air (also referred to as exhaust air) from the control station 4 into the surroundings. In contrast with other designs that have been conventional up to now, neither a supply of fresh air from an associated compressed air storage system, nor any significant recirculation and reprocessing of the air in the interior of the control station 4 is provided here. Specifically, a supply air line 10, also referred to as a fresh air supply line or fresh air line for short, is connected to an interior 8 of the control station 4 which is at least approximately hermetically encapsulated with respect to the external surroundings, via which line fresh air is sucked from the surroundings and conveyed into the interior 8 by a fan 12 during operation of the ventilation system 2. The suction inlet, or inlet 14 for short, of the supply air line 10 can be located at some distance from the control station 4, in particular outside the power plant building. Depending on the progression of the accident, the fresh air sucked in through the inlet 14 may nonetheless be significantly contaminated with radioactive fission products, in particular in the form of aerosols, iodine and iodine compounds, as well as inert gases. These components need to be removed as completely and reliably as possible from the fresh air stream (also referred to as the supply air stream) before the air steam is introduced into the interior 8 of the control station 4 through a lead-through 16 in the enclosing wall 18 (shown only in portions). For this purpose, a first filter stage in the form of an aerosol filter 20, formed in the example here by two HEPA filters 22 that are connected in parallel in terms of flow, is connected into the supply air line 10 downstream of the inlet 14, viewed in the direction of flow of the supply air. he HEPA filters 22 accordingly bring about highly efficient separation of the aerosol particles (also referred to as floating particles) out of the fresh air stream, in particular with respect to the isotopes Te, Cs, Ba, Ru, Ce, La. Further downstream, a second filter stage containing an iodine filter 24 and a particle filter 26 connected downstream thereof are connected into the supply air line 10. The iodine filter 24 is preferably formed as an activated carbon filter bed having a layer thickness of from 0.1 m to 0.5 m for example. Following the separation of the particulate matter previously carried out in the aerosol filter 20, radioactive iodine compounds and elementary iodine having a k-value of >8 at contact times of from 0.1 to 0.5 seconds for example, are separated in the iodine filter 24. Impregnated activated carbon (e.g. containing potassium iodide as the impregnating agent) can be used in order to separate the radioactive methyl iodide by isotope exchange or salification. The particle filter 26 that is connected downstream of the iodine filter 24 is provided in order to retain abraded particles from the activated carbon bed. A conveyor fan, or fan 12 for short, for transporting the fresh air stream is connected into the supply air line 10 downstream of the second filter stage. The preferably electrically operated fan 12 has a suction capacity in the range of from 100 to 6,000 m3/h for example. In order to provide the necessary operating current, a stand-alone power supply module 28 is provided that is independent of the normally operational autonomous power supply and preferably also of the conventional (installation-wide) emergency power supply, for example on the basis of electrical batteries/accumulators and/or a diesel generator set. The power supply module 28 is activated, if required, preferably independently in the manner of an uninterruptible power supply or, alternatively, is actuated by an associated control unit 30. Further downstream, an air dryer 32, also referred to as a cold trap, is optionally also connected into the supply air line 10, by which dryer condensable components can be separated out of the fresh air stream. This may, for example, be a passive cold trap containing silica gel and/or ice as a desiccant. As a result, the moisture content of the fresh air stream flowing into the functional units (see below) connected downstream is reduced. A throttle 34, which is alternatively or additionally provided and is arranged in the embodiment here downstream of the air dryer 32 in the direction of flow of the fresh air, fulfils the same purpose and acts on the fresh air stream in accordance with the principle of expansion drying. This may in particular be a controllable throttle valve. After being filtered and dried, when associated adjustment members (see below) are adjusted accordingly, the fresh air stream flows through the line portion 36 for example, into which an inert gas adsorber column, or adsorber column 38 for short, is connected. In the process, the inert gases, in particular xenon and krypton, contained in the fresh air stream are bound, within the context of a dynamically occurring equilibrium, by physical and/or chemical adsorption, to the adsorbent present in the adsorber column 38 and the gases are thus slowed in the line portion 36, as long as the adsorption capacity of the adsorber column 38 is not exhausted. In particular, one or more layers of activated carbon and/or zeolite and/or molecular sieves can be provided as the adsorbent. A line portion leading to the control station 4 is connected downstream of the adsorber column 38, into which line portion a particle filter 40 for retaining detached adsorber particles is connected. Finally, the fresh air stream that has been decontaminated in the manner described enters the interior 8 of the control station 4 via the lead-through 16 through the enclosing wall 18 of the control station, such that this unspent, oxygen-rich breathable air is supplied at an activity level that is permissible for the operators. The air exchange is completed by spent, carbon dioxide-rich breathable air being removed from the control station 4 via the exhaust air line 44 that is connected to the interior 8 of the control station and is guided through the lead-through 42 in the enclosing wall 18 and into the surroundings, and into which line a fan 46 is connected in order to assist the gas transport. The fan is preferably an electrically operated fan 46 which, just like the fan 12, is supplied with electrical power by the power supply module 28. Since, at a feasible installation size, the adsorption capacity of the adsorber column 38 acting on the fresh air stream is usually exhausted after just a relatively short operating time, the ventilation system 2 is configured to backwash the adsorbed inert gases into the surroundings during operation. For this purpose, two substantially structurally identical adsorber columns 38 and 48 are provided, to which columns fresh air or exhaust air is applied via corresponding line branches and connections and adjustment members, here in the form of 3-way valves, such that one of the two adsorber columns 38 and 48 acts on the fresh air stream in adsorption mode as already described, while the other column is simultaneously backwashed by the exhaust air stream in desorption mode or rinsing mode, and is thus made ready for the next adsorption cycle. By switching the adjustment members, the role of the adsorber columns 38 and 48 can be interchanged, and it is thus possible to swap in a cyclical manner between adsorption mode and desorption mode with respect to the relevant columns. In the embodiment shown in the drawings, this function is achieved in that one adsorber column 38 is arranged in the line portion 36, and the other adsorber column 48 is arranged in the line portion 50, in an antiparallel connection in terms of flow. The two line portions 36 and 50 come together on one side in the 3-way valve 52 and on the other side in the confluence 54 arranged on the suction side of the fan 46. Furthermore, a cross connection 60 that can be switched by the two 3-way valves 56 and 58 and that is connected by a T-connection 62 to the portion of the supply air line 10 leading to the particle filter 40 is connected between the two line portions 36 and 50 on one side between the 3-way valve 52 and the two adsorber columns 38, 48. A cross connection 68 that can be switched by the two 3-way valves 64 and 66 and that is connected by a T-connection 70 to the portion of the supply air line 10 coming from the throttle 34 is connected, in an analogous manner, on the other side between the adsorber columns 38, 48 and the confluence 54. When the valve settings are selected accordingly, as already described above, the supply air coming from the throttle 34 flows through the T-connection 70, the 3-way valve 66, the lower adsorber column 38 in the drawing, the 3-way valve 58 and the T-connection 62 to the particle filter 40, and from there onwards to the control station 4. In the other line strand, the exhaust air coming from the control station 4 flows through the 3-way valve 52, the 3-way valve 56, the upper adsorber column 48 in the drawing and the 3-way valve 64 to the suction connection of the fan 46, and from there onwards to an exhaust air flue or to another outlet 72 that is expediently located at a distance from the inlet 14 for fresh air. In other words, in this operating mode the inert gases accumulated in the adsorber column 48 by adsorption during the previous cycle are desorbed from the adsorbent by the substantially inert gas-free exhaust air from the interior 8 of the control station 4, and are washed back into the surroundings together with the exhaust air stream. The backwashing is assisted by the fan 46 that is arranged downstream of the backwashed adsorber column 48, the increase in volume of the exhaust air stream being intensified by the negative pressure of the backwash process for the inert gases. A throttle 74, preferably in the form of an adjustable throttle valve, is arranged in the exhaust air line 44 of the control room, upstream of the 3-way valve 52 and thus upstream of the adsorber column 48 currently in rinsing mode, when viewed in the direction of the exhaust air flow, which throttle causes passive overheating of the exhaust air and thus a reduction in the moisture in the exhaust air (expansion drying). This is favorable for the speed of desorption of the inert gases in the adsorber column 48 connected downstream. After switching, the roles of the adsorber columns 38 and 48 are interchanged. Now, the fresh air flows from the throttle 34, through the 3-way valve 64, the adsorber column 48 and the 3-way valve 56 to the particle filter 40, and from there to the control station 4. The exhaust air from the control station 4, in contrast, flows from the throttle 74, through the 3-way valve 52, the 3-way valve 58, the adsorber column 38 and the 3-way valve 66 to the fan 46, and from there to the outlet 72. The previously loaded adsorber column 38 is now backwashed by the exhaust air, while the adsorber column 48 is available for purifying the fresh air and accordingly for being loaded again. A control unit 30 is provided for controlling the switching processes by the 3-way valves 52, 56, 58, 64, 66, which control unit expediently also actuates the two fans 12 and 46 and, optionally, further adjustment members for through-flow and pressures. It is obvious to a person skilled in the art that the switching function can also be achieved in an equivalent manner using other line topologies and adjustment members. As shown by the dashed boundary lines, the ventilation system 2 is preferably constructed in a modular manner from an inert gas module 76, an iodine and aerosol module 78 and a power supply module 28. The boundaries between the modules can of course also be selected so as to be different in detail, and there may be further modules or sub-modules. The individual modules are for example accommodated in a transportable manner in standard containers, so that the modules can be easily transported to the usage site and easily constructed at the site by means of the associated, standardised line connections being connected. The variant of the ventilation system 2 shown in FIG. 2 contains, in addition to the components known from FIG. 1, a retaining unit for carbon dioxide (CO2), preferably containing a CO2 adsorber column 82 that is based predominantly on chemical adsorption (chemisorption) or adsorption. It is therefore possible to operate the control station 4 for a certain amount of time in circulating-air mode without (filtered) breathable air being fed in from the outside, without the CO2 concentration in the control station 4 exceeding a critical value for the well-being of the operators. This is advantageous in that no activity can penetrate into the control station 4 in circulating-air mode in the event of extreme activity loads outside the containment. The CO2 adsorber column 82 is preferably integrated into the system known from FIG. 1 in that a recirculation line or circulating-air line 80 is provided, which line branches off from the exhaust air line 44 and leads to the supply air line 10 and into which the CO2 adsorber column 82 is connected. Thus, in circulating-air mode, a circulating-air fan 84 connected into the circulating-air line 80 conveys the CO2-rich exhaust air removed from the control station 4 through the CO2 adsorber column 82 and back into the control station 4 at a reduced CO2 content as breathable air. The CO2 adsorption is carried out almost at the pressure prevailing inside the control station 4, i.e. approximately at atmospheric pressure or slightly higher (prevention of inleakage; see below). As a result, the circulating-air fan 84 does not have to carry out any significant compression. Specifically, in the example shown, the inlet side of the circulating-air line 80 is connected by a line branch (e.g. a T-piece) to the line portion of the exhaust air line 44 located between the lead-through 42 to the control station 4 and the throttle 74. The outlet side of the circulating-air line 80 is connected by a line branch to the line portion of the supply air line 10 located between the lead-through 16 and the 3-way valve 58, here in particular upstream of the particle filter 40. Additionally or alternatively, filters 86 can be connected into the circulating-air line 80, here for example downstream of the CO2 adsorber column 82 (the flow direction in circulating-air mode is indicated by a flow arrow beside the column). With regard to the connection of the circulating-air system to the remainder of the ventilation system 2, modifications are of course possible, but the variant shown is advantageous in particular in that just two lead-throughs 16, 42 in total are required through the enclosing wall 18 of the control station 4/through the containment. It is furthermore advantageous that, in circulating-air mode, the part of the ventilation system 2 containing the inert gas adsorber columns 38, 48 and the upstream components can be easily and reliably disconnected and/or isolated from the circulating-air system in terms of flow and media by corresponding shut-off devices or valves. The circulating-air line 80 itself is provided with shut-off valves 88, 90 on the inlet side and the outlet side in order to be able to isolate said line from the remainder of the line system if required. Preferably, the shut-off valves 88, 90 can be controlled with regard to the through-flow (control valves), so that partial flows can also be adjusted. This also applies to the further valves, in particular the shut-off valves 92, 94 described below. It is possible to provide an individual, separate circulating-air fan 84 for the circulating-air line 80. It is particularly advantageous, however, in the variant according to FIG. 1, to exclusively use fans 46 used as exhaust air fans in the exhaust air line 44 within the meaning of a dual use as circulating-air fans 84 during the circulating-air mode. For this purpose, the circulating-air line 80 is connected by suitable line branches or connections to a line portion of the exhaust air line 44 that contains the fan 46. This line portion can be isolated from the outlet 72 and from the part of the ventilation system 2 containing the inert gas adsorber columns 38, 48 by shut-off valves 92, 94, and forms a portion of the circulating-air line 80 in circulating-air mode. As shown, the CO2 adsorber column 82 is preferably arranged downstream of the fan 46 (or, more generally, the circulating-air fan 84) on the pressure side thereof. The shut-off valve 94 is preferably a controllable 3-way valve on the line branch, which valve releases the outlet 72 and shuts off the connected strand of the circulating-air line 80 during desorption (backwashing) of the inert gas adsorber column 38 or 48. This ensures that the activities released from the inert gas adsorber columns 38 or 48 during desorption are blown out into the surroundings and are not transported into the control station 4 via the circulating-air line 80. Inert gas desorption mode (rinsing of the inert gas adsorber column 38 or 48) and CO2 adsorption mode (circulating-air mode) are therefore preferably not operated simultaneously. However, inert gas adsorption mode (loading of the inert gas adsorber column 38 or 48) and CO2 adsorption mode (circulating-air mode) can be operated simultaneously without difficulty. In this case, filtered fresh air is blown into the control station 4 by at least one of the two inert gas adsorber columns 38 or 48 and the supply air line 10. When the shut-off valve 88 is open, the exhaust air from the control station 4 is transported through the circulating-air line 80 by means of the fan 46. Depending on the setting of the shut-off valve 94 that is configured as a 3-way control valve, in the process a larger or smaller partial flow (which can optionally also have the value of zero) is released through the outlet 72 into the surrounding atmosphere, and the remainder of the partial flow is returned to the control station 4 via the CO2 adsorber column 82. In this case, the shut-off valve 92 is closed, and therefore, as mentioned above, the undesired return of activities from the inert gas adsorber columns 38 or 48 into the control station 4 is prevented. A further possible mode of operation contains operating the inert gas adsorber columns 38 or 48 simultaneously in adsorption and desorption mode in a recurrently alternating manner, as already described in conjunction with FIG. 1. In this operating mode, as mentioned above preferably no CO2 adsorption occurs in circulating-air mode. However, it has been found that the physical adsorption in the inert gas adsorber columns 38 or 48 is significantly more effective at a higher pressure (for example 8 bar) than at atmospheric pressure, whereas the desorption preferably takes place at a relatively low pressure, in particular at a slight negative pressure in relation to atmospheric pressure. As a result, following each change-over process (switching) a certain amount of time, for example from 10 to 30 minutes, must be planned in for the required pressure increase using the fan 12 that operates as a compressor. In this pressure increase phase, during which the retaining capacity of the inert gas adsorber columns 38 or 48 is not yet fully developed, the control station 4 is preferably ventilated only by means of CO2 adsorption in circulating-air mode. In the process, although the oxygen content of the air in the control station 4 occupied by operators gradually reduces due to being consumed, the CO2 content is reliably kept below a critical value. Later, once the operating pressure required for effective inert gas retention has been reached, a switch is preferably made to the filtered air supply via the inert gas adsorber columns 38 or 48 (simultaneous operation of inert gas adsorption and CO2 adsorption, as described above). As a result, the oxygen content of the air in the control station 4 which had previously dropped is renewed. Later, regeneration phases (desorption) can be carried out when the circulating air is cut off, and the adsorber columns 38 and 40 can be interchanged. In other words, a preferred mode of operation of the ventilation system 2 according to FIG. 2 contains supplying the control station 4 preferably exclusively in circulating-air mode during the time period required for increasing the pressure in the adsorber columns 38, 48. After the pressure increase, fresh air is fed in via the inert gas hold-up line by the adsorber columns 38, 48, preferably during/together with the chemical CO2 adsorption. The increased volumetric flow is preferably used for maintaining the oxygen concentration and for increasing the pressure in the control station 4. As a result, a directed flow is generated that has an overpressure in the control station 4 compared with the external surroundings, which flow reliably prevents activity from penetrating into the control station 4 from the outside (inleakage). Simple systems that operate only by CO2 separation cannot ensure this function in a sufficiently reliable manner. The adsorbent used for CO2 adsorption in the adsorber column 82 can be soda lime, zeolite/a molecular sieve or a regeneratable adsorbent for example. In particular, oxides, peroxides and superoxides (e.g. potassium superoxide) can be used as further examples of possible adsorbents. Regeneratable adsorbents can also consist of metal oxides or mixtures thereof. Thus, for example, silver oxide reacts with CO2 to form silver carbonate. In principle, mixtures of the mentioned adsorbents can also be used, or multi-stage adsorber columns having the same or different adsorbents in the different stages can be implemented. When the adsorbent is correspondingly suitable, the chemisorption occurring in the adsorber column 82 can be carried out so as to be reversible at high temperatures, and the adsorbent can in principle be regenerated. Simple modifications in the line arrangement of the circulating-air system may be expedient for this purpose in order to be able to carry out regeneration phases of this kind outside the above-described circulating-air mode without polluting the control station 4. In summary, the systems according to FIG. 1 and FIG. 2 ensure that, in addition to the air-borne activity of the aerosols and organoiodine, the inert gases are also kept out of the breathable air of the control room. In the extended system according to FIG. 2, the CO2 is additionally removed from the breathable air by means of chemical adsorption/absorption. Integrating the direct CO2 adsorption makes it possible for the control station 4 to be operated in circulating-air mode, in extreme accident situations, until the oxygen concentration of the control room air drops to a lower threshold (approximately 17-19 vol. %) and therefore a fresh air supply from the outside is required. The inert gas retaining module containing the adsorber columns 38, 48 is then operated in particular in order to meet and raise the oxygen content. As a result, the required capacity of the module can be significantly reduced with regard to the driving energy and the amount of activated carbon. The required compression energy for producing the pressure-swing adsorption can be minimised. As a result, the units required for autonomously generating power can be made smaller. Even though the description has so far been directed to the ventilation of the (central) control station of a nuclear power plant, it is nonetheless clear that the ventilation system 2 can also be used for ventilation, in the event of accidents, of other spatial regions within a nuclear power plant or, more generally, a nuclear installation, such as also fuel element stores, reprocessing plants, fuel-processing facilities, etc., for example of auxiliary installation buildings, switching facility spaces, control rooms or other operating and monitoring spaces. The term “operating space” is also used for spaces of this kind, in the manner of a summary and a key word. The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: 2 ventilation system 4 control station 6 nuclear power plant 8 interior 10 supply air line 12 fan 14 inlet 16 lead-through 18 enclosing wall 20 aerosol filter 22 HEPA filter 24 iodine filter 26 particle filter 28 power supply module 30 control unit 32 air dryer 34 throttle 36 line portion 38 adsorber column 40 particle filter 42 lead-through 44 exhaust air line 46 fan 48 adsorber column 50 line portion 52 3-way valve 54 confluence 56 3-way valve 58 3-way valve 60 cross connection 62 T-connection 64 3-way valve 66 3-way valve 68 cross connection 70 T-connection 72 outlet 74 throttle 76 inert gas module 78 iodine and aerosol module 80 circulating-air line 82 CO2 adsorber column 84 circulating-air fan 86 filter 88 shut-off valve 90 shut-off valve 92 shut-off valve 94 shut-off valve |
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claims | 1. A charged particle multi-beamlet system for exposing a target using a plurality of beamlets, the system comprising:a charged particle source for generating a charged particle beam;a sub-beam aperture array for defining sub-beams from the generated beam,a beamlet aperture array for defining groups of beamlets from the sub-beams;a beamlet blanker array comprising an array of blankers for controllably blanking the beamlets;a beam stop array for blanking beamlets deflected by the blankers, the beam stop array comprising an array of apertures, each beam stop aperture corresponding to one or more of the blankers; andan array of projection lens systems for projecting beamlets on to the surface of the target,wherein the system images the source onto a plane at the beam stop array, at the effective lens plane of the projection lens systems, or between the beam stop array and the effective lens plane of the projection lens systems, and the system images the beamlet aperture array onto the target. 2. The system of claim 1, wherein the source is imaged onto a plane at or between the beam stop array and the effective lens plane of the projection lens systems by a condenser lens array. 3. The system of claim 2, wherein the condenser lens array is positioned upstream of the beamlet aperture array. 4. The system of claim 1, wherein the sub-beams are focused onto a plane at or between the beam stop array and the effective lens plane of the projection lens systems by a condenser lens array. 5. The system of claim 4, wherein the condenser lens array is positioned between the sub-beam aperture array and the beamlet aperture array. 6. The system of claim 1, wherein the beamlet aperture array and the beamlet blanker array are integrated. 7. The system of claim 1, wherein the apertures of the beam stop array are limiting the cross-section of beamlets passing therethrough. 8. A charged particle multi-beamlet system for exposing a target using a plurality of beamlets, the system comprising:at least one charged particle source for generating a charged particle beam;a first aperture array for creating sub-beams from the generated beam;a condenser lens array for focusing the sub-beams;a second aperture array for creating a group of beamlets from each focused sub-beam;a beamlet blanker for controllably blanking beamlets in the groups of beamlets; andan array of projection lens systems for projecting beamlets on to the surface of the target, wherein the condenser lens array is adapted for focusing each sub-beam at a point corresponding to one of the projection lens systems. 9. The system of claim 8, wherein the second aperture array is combined with the beamlet blanker array. |
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description | This application claims the benefit of U.S. Provisional Application 60/891,859, filed Feb. 27, 2007, and PCT Application PCT/US2008/055083, filed Feb. 27, 2008, the disclosures of which are incorporated herein by reference. This invention was made with United States government support awarded by the following agency: NIH CA088960. The United States government has certain rights in this invention. The present invention relates to radiotherapy systems, such as those using ions like protons, for the treatment of cancer and, in particular, to a system providing improved treatment speed and accuracy. In external beam radiation therapy, tumors within a patient are treated by directing high-energy radiation in one or more beams toward the tumor. Highly sophisticated external beam radiation systems, for example, as manufactured by TomoTherapy Inc., employ intensity modulation techniques to improve the conformity of high dose regions to the tumor volume. With TomoTherapy, a tumor is treated with multiple x-ray fan beams directed at the patient over an angular range of 360°. Each of the beams is comprised of individually modulated rays whose intensities can be controlled so that the combined effect of the rays over the range of angles, is the delivery of highly conformal dose distributions to arbitrarily complex target volumes within the patient. One of the drawbacks of external beam x-ray therapy is that x-rays irradiate tissue along the entire path of each ray, including healthy tissues both proximal and distal to the tumor volume. While judicious selection of the angles and intensities of the x-ray beams can minimize radiation applied to healthy tissue outside of the tumor, the inevitability with x-rays of irradiating healthy tissue along the path leading to and exiting from the tumor has led to a renewed interest in the use of ions, such as protons, as a substitute for x-rays in radiotherapy. Unlike x-rays, protons and other charged particles can be range modulated and made to stop within the target volume; thereby eliminating exit dose to healthy tissue on the far side of the tumor. In addition, the dose deposited by a proton beam is not uniform along the path of the beam, but rather rises substantially near the protons end of range in a region known as the “Bragg peak”. These two features allow improved concentration of dose within the tumor. Because the size of the proton beam extracted from a typical proton accelerator is generally too small for the treatment of most disease sites, current proton therapy systems adopt one of two general approaches to treat clinically observed target volumes. In the first approach, termed the “spread out Bragg peak” (SOBP) approach, the range of the distal end of a narrow proton pencil beam (the Bragg peak) is modulated using a spinning propeller of low atomic-number material with blades of varying thickness; allowing for a uniform dose to be delivered to a spread out region in depth. This beam is then broadened laterally using a series of lead scattering foils and shaped using field specific brass collimators. At this point, the depth of penetration of the broadened beam is shaped to conform to the distal side of the target volume from each beam angle using custom-built, 2-D range compensators before finally being delivered to the patient for treatment. This technique can treat the entire tumor at once and therefore is fast. However, the use of the range modulating wheel makes it difficult to conform the dose to the tumor in regions proximal to the target volume, and the construction of special collimators and compensators are required for each treatment field. In addition, the use of high atomic number scattering foils and collimators result in neutron production—which can contribute unwanted dose to the patient during treatment. In a second approach, termed the “magnetic spot scanning” (MSS) approach, the narrowly collimated proton “pencil beam” extracted from the proton accelerator is modulated in range and magnetically steered in angle to deposit the dose as a series of small spots within the target volume. The spots are positioned in successive exposures until an arbitrary tumor volume has been irradiated. This approach is potentially very accurate, but because the tumor is treated in many successive exposures, this approach is much slower than the SOBP approach. Furthermore, the use of many small, precisely overlapping beam spots creates the risk of “hot and cold spots” appearing in the target volume due to errors in spot placement. This risk is greatly exacerbated if there is any patient movement between spot exposures. The present invention provides a treatment system that employs a fan beam of ions composed of “beamlets”, each of which may be separately modulated in both range and intensity. In this way, the present invention combines the benefits of simultaneously treating different portions of the tumor (as with SOBP) with the benefit of having precise control over each individual beamlet (as with MSS). The invention described in this application concerns a method of converting a pencil beam into a fan beam relying entirely on magnetic deflection and does not require scattering foils or the like. Using this method, the production of neutrons—which result in unwanted dose to the patient—is greatly reduced. Specifically then, the present invention provides an ion therapy machine for the treatment of a patient, with the machine having a treatment head positionable about a patient support (i.e. a treatment couch) for directing a beam of protons or other ions toward the patient over a range of angles. A magnet system within the treatment head receives a pencil beam of ions and spreads them into a fan beam by magnetic deflection. It is thus one object of one embodiment of the invention to provide for a fan beam of protons or other ions with greatly reduced neutron contamination compared to that obtained using a spreading foil or other conventional scattering materials. The fan beam may have a cross-sectional width greater than five times that of its cross-sectional thickness. It is thus an object of one embodiment of the invention to create a fan beam with a aspect ratio that can subtend a large tumor and yet provide high-resolution treatment along the direction normal to the broad face of the fan beam. The ion therapy machine includes a modulator receiving the fan beam to separately modulate individual beamlets, with beamlets being defined as adjacent sectors of the fan beam. It is thus an object of one embodiment of the invention to provide a beam shape and size that may be readily modulated to allow sophisticated, simultaneous treatment of different regions of the tumor. The magnet system may comprise one or more quadrupole magnets positioned successively along an axis of the pencil beam of ions with any successive quadrupole magnets (if any) aligned in the same orientation as the first. The quadrupole magnet(s) may each include two pairs of magnets, magnets of each pair opposed along a magnet axis perpendicular to the axis of the pencil beam of ions, with the two magnet axes perpendicular to each other and with one pair of magnets having opposed north poles and the other pair having opposed south poles. It is thus an object of one embodiment of the invention to make use of a well-characterized quadrupole magnet structure for the purpose of creating a fan beam. The invention may further include a means for adjusting the separation of the quadrupole magnets along the axis to change the cross-sectional dimension of the fan beam. It is thus another object of one embodiment of the invention to permit the size of the fan beam to be adjusted either to conform to a predetermined size with changes in the proton beam characteristic or to allow dynamic changes of the fan beam size as part of the treatment process. These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. Referring now to FIG. 1, a conventional ion radiation therapy system 10 employing the SOBP approach described above provides an ion source 12 producing a pencil beam 14 of ions traveling along an axis 20. The pencil beam 14 may be received by a foil 17 scattering the pencil beam into a cone beam 18 having a circular cross-section 21. The energy of the ions in the cone beam 18 is then received by a rotating wedge propeller placing a material of varying thickness in the cone beam 18 and acting as a range shifter 16 continuously changing the energy and thus range of penetration of the ions into tissue. The cone beam 18 then passes through a collimator 24 approximating the outline of the tumor and a compensator 22 tailor-made for the particular tumor being treated after which the cone beam 18 is received by the patient 26 to produce a treatment pattern 28. As noted, this treatment approach simultaneously treats the entire volume of the tumor and is therefore relatively quick, but requires custom built collimators 24 and compensators 22 and also produces a treatment pattern 28 with imperfect conformance to an arbitrary tumor volume. Referring to FIG. 2, a radiation therapy system 10′ for implementing the MSS approach, described above, receives a pencil beam 14 from an ion source 12 and passes it through a range shifter 16, for example, a set of movable plastic blocks of different thicknesses. The range shifted pencil beam 14 passes next to a magnetic steering yoke 19 which steers the pencil beam 14 to different spots 30 within the patient 26. Multiple spots 30 together create the treatment pattern 28. This system produces good conformance of the treatment pattern 28 to an arbitrary tumor, but the sequential process is slow. Referring now to FIG. 3, the radiation therapy system 10″ of the present invention employs an ion source 12 producing a pencil beam 14. In a preferred embodiment, the pencil beam 14 is received by a magnetic beam former 32 converting the pencil beam 14 into a fan beam 34 by magnetic deflection rather than scattering and thus minimizing the generation of neutrons. The fan beam 34 is next received by a binary shutter system 36 which individually modulates the range and the intensity of the individual beamlets 38 of the fan beam 34, the beamlets 38 being adjacent sectors of that fan beam 34. The modulated fan beam 34 may be moved in a partial arc 40 with respect to the patient 26 to provide for more complex treatment patterns 28 taking advantage both of multiple angles of treatment and the ability to individually control the intensity and range of the beamlets 38. Referring now to FIG. 4, the structure of the radiation therapy system 10″ may provide, for example, an axial proton beam conduit 42 receiving the pencil beam 14 of protons, for example, from a remote cyclotron or synchrotron (not shown). Beam steering magnets of a type well known in the art (not shown) may bend to the pencil beam 14 to follow a “crank arm” path of a gantry 44 having a radially extending segment 47 passing on a line of radius from an axis 46 of the entering pencil beam 14 and an axial segment 48 parallel to the axis 46 but spaced from the axis 46 as attached to the end of the radially extending segment 47. The distal end of the axial segment 48 holds a gantry head 50 (whose elements are shown generally in FIG. 3) and which directs a fan beam 34 toward a patient support 52, the latter generally aligned with the axis 46. The fan beam 34 lies generally within a plane of rotation 54 of the gantry head 50 as the gantry head 50 moves about the patient support 52. By aligning the axis of rotation of the gantry head 50 with the axis 46 of the entering pencil beam 14, constant field bending magnets within the gantry 44 may channel the pencil beam 14 to the gantry head 50 at any of its angular positions. Referring momentarily to FIG. 5, the gantry head 50 may rotate in an arc 56 about the axis 46 by an amount substantially less than 180° and in the preferred embodiment approximately 150°. As will be described further below, the present inventors have determined that this limited rotation, un-intuitively, can provide a superior dose pattern 28 when compared to a more complete 360° rotational of the gantry head 50, such as would be preferred for intensity modulated radiation therapy using photons. The limited range of arc 56 allows a massive stationary neutron stop 58 to be placed under the patient support 52 to receive neutrons generated by interaction of the ions with the patient 26 over the full range of arc 56. The ability to use a stationary neutron stop 58, allows the neutron stop 58 to be larger and closer to the patient 26, allowing, for example, a form in-place concrete neutron shield. Referring now to FIG. 3, optionally, the stationary neutron stop 58 may be supplemented with a movable neutron stop 23 mounted to an extension on the gantry 44 (not shown) to move therewith in opposition to the ion source 12. This movable neutron stop 23 may provide a counterweight for the gantry 44 and may reduce the size of the stationary neutron stop 58. Referring now to FIGS. 4 and 6, an x-ray tomography ring 60 may be placed adjacent to the neutron stop 58 along the axis 46 so as to provide for planning tomographic images of the patient 26 contemporaneous with the radiation treatment. The displacement of the x-ray tomography ring 60 from the plane of rotation 54 allows a full 360° of access to the patient (generally required of an x-ray tomography machine) for supporting both the detector and opposed x-ray source on opposite sides of the patient. Referring now to FIGS. 7a and 7b, a simplified treatment plan may be developed to treat a tumor 62 in the patient 26 having circular cross-section. Such a plan implemented with ion beam exposure over 360° provides a central region 64 of a dose pattern 28 having a high dose value resulting from aligned Bragg peaks 67 of ion beams entering the patient 26 over a range of angles of 360° about the patient. This central region 64 is surrounded by a fringe 68 resulting from a reduced but measurable entrance dose of these proton beams. This fringe 68 can be problematic if there is radiation sensitive tissue 70, as is often the case, directly adjacent to the tumor 62. As shown in FIG. 7b, a constrained rotation of the gantry head 50 and hence the fan beam 34 can substantially limit the fringe 68 while preserving good conformity between the central region 64 and the tumor 62. The ability to stop the ions within the target volume at the Bragg peak 67 can wholly spare the radiation sensitive tissue 70. The present inventors have determined that the limitation of the arc 56 to as little as 150° still provides close conformance of the shape of the central region 64 to the tumor 62 with minimization of hot/cold spots. Referring now to FIG. 8, the limited width of the fan beam along axes 46 makes it desirable to translate the patient support 52 along axes 46 with respect to the gantry head 50 in order to obtain treatment volumes matching the longitudinal extent of the tumor while still preserving good spatial resolution determined by the thickness of the fan beam. The table may be translated by a table translation mechanism 61 such as a motorized carriage moving the patient support 52 or the gantry head 50 or both. In one embodiment of the present invention, the translation of the patient support 52 may be continuous as the gantry head 50 rocks back and forth over the treatment arc 56 in a so-called “semi-helical” scan pattern, tracing a sawtooth raster 66 along axes 46 on an imaginary cylinder 69 surrounding the axis 46. Referring now to FIG. 9, a sweeping of the cross-sectional area 71 of the fan beam 34 in this semi-helical scan pattern may be given a “pitch” by changing the relative speed of movement of the patient support 52 with respect to the speed of movement of the gantry head 50 in each cycle of reciprocation. The pitch determines a degree of overlap between successive sweep paths 72 of the sawtooth raster 66 moving cross-sectional area 71; such overlap serving to reduce hotspots. The pitch shown here is greatly exaggerated and, in practice, would be reduced to a fraction of the width of the cross-sectional area 71 along axes 46. The scanning of the cross-sectional area 71 serves also to eliminate inhomogeneities in the treatment caused by gaps between shutters used to modulate the beamlets 38 as will be described below. Referring now to FIG. 10, alternatively a rectilinear raster 66′ may be adopted where the gantry head 50 is allowed to complete one half of a cycle of its reciprocation about axis 46 and then is stopped at the limits of the arc 56 to allow translation of the patient 26 along axes 46. When movement of the patient 26 is complete the next cycle of reciprocation along arc 56 is performed. Referring now to FIG. 11 and FIG. 5, motion gating may be incorporated into the radiation therapy system 10″ of the present invention in which a sensor system 73 senses movement of the patient 26 or internal organs of the patient 26 (for example, using ECG or respiration signals) to turn the fan beam 34 from the gantry head 50 on and off to treat the patient 26 at a constant phase of periodic motion. This gating process may be improved with a rectilinear raster 66″ shown in FIG. 11, essentially rotating the rectilinear scanning pattern of FIG. 10 so that a full range of translation of the patient support 52 is completed before moving the gantry head 50 incrementally along arc 56. Referring now to FIG. 12, the magnetic beam former 32 (shown in FIG. 1) in a preferred embodiment may comprise two quadrupole magnet assemblies 74 and 76 receiving the pencil beam 14 (as delivered to the gantry head 50 along gantry 44). The pencil beam 14 is first received by a first quadrupole magnet assembly 74 and then received by the second quadrupole magnet assembly 76 downstream from the first quadrupole magnet assembly 74. Both quadrupole magnet assemblies 74 and 76 include apertures 78 coaxially aligned along a center axis 20 of the pencil beam 14 and the fan beam 34. Referring momentarily to FIGS. 13 and 14, quadrupole magnets of the type used in quadrupole magnet assemblies 74 and 76 are well known in the fields of high-energy accelerator physics and electron microscopy where quadrupole magnets with relative rotations of 90° about the axis of the beam are used to help refocus a pencil beam 14 to maintain its narrow cross-section. Each quadrupole magnet assembly 74 and 76 comprises two pairs of magnets: a first pair 82a and 82b opposed across the aperture 78 along axes 79 with facing north poles, and a second pair 84a and 84b opposed across the aperture 78 along axes 79′ perpendicular to axes 79. The magnets may be permanent magnets or preferably electromagnets so that the field strengths may be varied to allow the width and intensity profiles of the resultant fan beam 34 to be varied in both the convergent and divergent planes. Referring again to FIG. 12, two quadrupole magnet assemblies 74 and 76 are aligned with respect to each other so that axes 79′ of quadrupole magnet assembly 74 shares the same orientation as axes 79′ of quadrupole magnet assembly 76. Referring to FIGS. 6, 14 and 15, the quadrupole magnet assemblies 74 and 76 produce a magnetic field 86 that tends to widen a cross-section 35 of the fan beam 34 along the plane of rotation 54 and compress it in a z-direction normal to the plane of rotation 54. As shown in FIG. 15, quadrupole magnet assemblies 74 and 76 act like diverging lenses when viewed in the plane of rotation 54 and converging lenses when viewed across the plane of rotation 54. Because the forming of the pencil beam 14 into a fan beam 34 is done without scattering in a solid material, the production of neutrons is greatly reduced. Note the quadrupole system will work for heavy ions of either polarity with a simple reversal of dimensions. Referring again to FIG. 12, the quadrupole magnet assemblies 74 and 76 may be connected by controllable actuator mechanism 88 (such as a motor and rack and pinion mechanism) that may separate each of the quadrupole magnet assemblies 74 and 76 along the axis 20 according to an electrical signal and/or by mechanical adjustment. This controllable separation allows adjustment of the cross-sectional dimensions of the fan beam 34 to reduce collimation that also produces neutrons. The adjustment of the fan beam size may also be used for dynamic change of the beamlets 38 during treatment. Referring now to FIG. 16, the pencil beam 14, ultimately received by the magnetic beam former 32 (composed of quadrupole magnet assemblies 74 and 76) may first pass through an emergency beam stop 80 and an entrance dose monitor 81 of conventional design, the latter measuring the energy of the beam 14. A pencil beam aperture collimator 83 may then shape the pencil beam 14 into a predictable cross-section for receipt by quadrupole magnet assembly 74. After exiting from quadrupole magnet assembly 76 the fan beam 34 may pass through a segmented monitor measuring an energy or intensity profile of the beam 34 that may be used to further correct the energy profile of the fan beam 34 (by compensation using the binary shutter system 36 as will be described) or to correct a cross-section of the fan beam 34, for example by controlling the field strengths of electromagnets of the quadrupole magnet assemblies 74 and 76. The fan beam 34 is then received by a set of collimator blocks 87 sharpening the edges of the fan beam to conform with a binary shutter system 36 as will be described below. Simulations have been performed modeling a 235 MeV proton beam traversing two quadrupole magnet assemblies 74 and 76 having effective lengths of 20 cm and 40 cm with transverse gradients of 22 T/m and 44 T/m respectively and a center-to-center quadrupole separation of 50 cm. The results of these simulations indicate that a proton fan beam of suitable cross-section (40×2 cm2) can be generated from an entrant Gaussian beam of protons (1.5 cm FWHM) over a distance of 1.5 m. Referring now to FIGS. 16 and 17, the binary shutter system 36 may provide a set of attenuating arrays 90 each aligned with a separate beamlet 38 of the fan beam 34. Each attenuating array 90 may be composed of a set of attenuating elements 92 (blade) each attenuating element 92 of a single array 90 being aligned with a particular beamlet 38. Multiple arrays 90 are placed side by side to span the width of the fan beam 34 so that each beamlet 38 may be controlled independently by a different array 90. Referring now to FIG. 18, each attenuating element 92 comprises a blade 94 of an energy absorbing material having a thickness 93 approximating the angular width of a beamlet within the plane of rotation 54 and a variable length 95 that will differ for different blades 94 as will be described. The blade 94 is attached to an actuator 96 that may move the blade 94 up and down along the y-axis generally perpendicular to the central axis 20 of the fan beam 34. In a preferred embodiment, the blade 94 may be moved between two positions, one within the path of the fan beam 34 and the other completely removed from the path of the fan beam 34. With this “binary” motion the actuator 96 may be extremely simple, for example, a pneumatic piston and cylinder (controlled by fluid pressure controlled in turn by a valve mechanism not shown) or electrical solenoid directly controlled by an electrical circuit. Referring now to FIG. 19, a single array 90 may, for example, contain eight attenuating elements 92 having blades 94a-94h. In a first embodiment, the length 95 of each blade 94a-94h along axis 20 may be according to a binary power series so, for example, blade 94a through 94h will have relative lengths 95 corresponding to successive terms in a binary power sequence (e.g.: 1, 2, 4, 8, 16 etc.). Thus, for example, blade 94d may be eight times as thick as the thinnest blade 94a. In this way, as shown in FIG. 20, any one of 256 equal increments of attenuation may be obtained by drawing some of the blades 94 out of the beam 34 and placing some of the blades 94 into the beam. In the example of FIG. 20, a relative attenuation of 43 may be obtained consisting of the combined blades 94d, 94a, 94b, and 94f (having attenuation's 8, 1, 2, and 32 respectively where 1 is the attenuation provided by the thinnest blade 94a). This “binary” sequence must be distinguished from the “binary” action of the shutters and a binary sequence need not be used for the binary shutter system 36 as will be described below. This binary power series provides the simplest blade structure and actuation mechanisms but it will be understood that other power series can also be used and in fact the variations in attenuations among blades 94 need not conform to a power series but, for example, may conform to other series and may include duplicate blades 94 of a single attenuation, for example to operate at higher speed or distribute wear. For example, the blades 94 may have the relative lengths 95 of 1, 1, 3, 6, 9, 18, etc. Alternatively blades 94 positionable in any of three (or more) positions with respect to the fan beam 34 (and hence capable of providing three effective attenuation levels per attenuating element 92) could be used providing attenuations in the series (0, 1, 2), (0, 3, 9), (0, 9, 18), (0, 27, 54) . . . . It will be further understood that attenuating elements 92 need not be constructed of a uniform material in which their length 95 corresponds to attenuation, but may be constructed of different materials having different densities to minimize their differences in length 95 for mechanical or structural reasons. The order of the blades 94 in the fan beam 34 need not conform to their relative ranking in attenuation, and in fact in the preferred embodiment this order is buried so as to provide for suitable clearance for the attached actuators 96. In a preferred embodiment the combination of all attenuating elements 92 completely stops the fan beam 34, and thus a proper selection of different attenuating elements 92 (short of blocking the fan beam 34) may be used to control range shifting of ions of the fan beam 34, while a selection of all attenuating elements 92 (fully blocking the fan beam 34) may be used to control the intensity of the beam through duty-cycle modulation so that both range and intensity may be controlled with the modulator 36. Alternatively a separate blocking element (not shown) for each beamlet 38 may be used to provide this intensity modulation. The intensity modulation or range shifting effected by the binary shutter system 36 may be augmented by other mechanisms applied to some or all of the beamlets 38, for example those correcting the profile of the fan beam 34 or serving to offset the range shifting of all the beamlets 38 based on patient size. The control of the individual blades 94 may be performed, for example, so that all of the attenuating blades 94 do not move simultaneously but are rather staggered to ensure the minimum deviation in range shifting during the transition of the blades 94. Thus, for example, the movement of blades 94 providing greater attenuation may be alternated with movement of blades 94 providing less attenuation to reduce variations in range shifting. Referring now to FIG. 21, two binary shutter system 36 and 36′ may be opposed about the fan beam 34 effectively dividing the fan beam 34 along an x-y plane (parallel to the plane of rotation 54) into two separately modulated fan beams 34 and 34′ effectively allowing multi-slice treatment of the patient improving the speed/resolution trade-off of the treatment system. In this case the geometry of the actuators 96 and blades 94 allows all of the actuators 96 to be fully displaced out of the area of the beam 34. The binary shutter system 36 may also be used for photon modulation; the term “radiation” as used herein will include generally both photons and particles serving for treatment of tissue. Referring again to FIG. 4, an electronic computer 100 executing a stored program may be associated with the radiation therapy system 10″ executing a radiation treatment plan that coordinates and controls all of the electrically controllable elements described above including but not limited to the binary shutter system 36, the magnetic beam former 32 (including magnetic field strength of the magnets and their separation) and the movement of the gantry 44 and patient support 52 as well as receipt and control of the x-ray tomography ring 60. This control may be done according to a stored radiation treatment plan, and in light of signals obtained from monitors 81 and 85. Data collected by the computer 100 then provides images, and assessment of the treatment plan, as well as implements feedback loops confirming the proper operation of the system according to techniques known in the art of intensity modulated radiation therapy. During the movement of the gantry head 50 with respect to the patient support 52, the range and intensity of individual beamlets 38 will be modulated according to a treatment plan stored in the computer 100 and typically determined by a health care professional using an image of the tumor using the tomography ring 60. Determination of the proper modulation of the beamlets 38 may be done by techniques analogous to those used with prior art intensity modulated radiation therapy adapted to the unique properties of ion beams. These techniques include for example Simulated Annealing and gradient based optimization techniques. The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims. |
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abstract | A collimator includes a pair of first plate members which define an X-ray passing aperture by a spacing between their opposed end faces, a second plate member which is movable in a direction parallel to a moving direction of the first plate members, a pair of third plate members which are movable symmetrically with each other in a direction perpendicular to the moving direction of the first plate member and which define an X-ray passing aperture by a spacing between their opposed end faces, and a fourth plate member which is movable in a direction parallel to the moving direction of the third plate members. |
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052746844 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling a nuclear fuel assembly, and an apparatus for performing such a task. 2. Background Art Fuel assemblies such as the one disclosed in U.S. Pat. NO. 5,068,081 shown in FIG. 7 have been known. In this figure, the numerals 1 and 2 refer to a top and a bottom nozzles, respectively, which are disposed vertically and oppositely spaced apart, and between the top nozzle 1 and the bottom nozzle 2 are a plurality of rigidly fixed control-rod guide pipes 3 (hereinbelow referred to as guide pipes 3), and in the midway section of the control-rod guide pipes 3 are a plurality of grids 4 disposed vertically and spaced apart from each other. The grids 4 are, as shown in FIGS. 8, 9 and 10, constructed of a plurality of straps 7 made of thin metal strips which have slits 8 provided at regular intervals in the longitudinal direction. By inserting the straps 7 into the slits 8 in each other's slits, a plurality of grid cell spaces 5 (hereinbelow referred to as grid cells 5) are formed. The fuel rod 6 is held firmly in the grid 5, by means of a pair of holding means consisting of a dimple 9 and a spring 10 disposed on opposing walls. The fuel rod 6 inserted into a grid cell 5 is pressed against the dimples 9 by the springs 10 as illustrated in FIG. 10, thereby supporting the fuel rod 6 firmly by the springs 10. The conventional method of assembling such a fuel assembly will be described with reference to FIG. 11. First, the grids 4 are placed apart with a certain distance (positioning of grids). The guide pipes 3 are inserted into the predetermined and corresponding grid cells 5 of each of the grids 4, and are then rigidly attached to the grids 4 by bulge forming. Subsequently, the fuel rods 6 are inserted into the predetermined and corresponding grid cells 5 of each of the grids 4, by sliding the rods 6 against the springs 10 and dimples 9. The rods 6 are thereby secured in the grid cells 5 via the pressing force exerted by the springs 10 and dimples 9. When all of the rods 6 are inserted into the grid cells 5, the top and bottom nozzles 1 and 2 are firmly mounted to the opposite ends of the respective guide pipes 3. In the conventional assembling method described above, the rods 6 are inserted, by sliding over the holding device (composed of dimples 9 and springs 10 ), into the spaces of the grid cells 5 after the guide pipes 3 have been rigidly attached to the grids 4. Because of the procedure, the guide pipes 3 are placed under slight non-uniform compressive stresses transmitted from the fuel rods 6 through to the grids 4. Further detailed explanations are provided in the preferred embodiments of the invention, but it suffices to mention that one of the contributions of the present invention is that the completed assembly shows very little distortion, as a result of the invented process of assembling the fuel assembly. SUMMARY OF THE PRESENT INVENTION The present invention was made in consideration of such problems associated with the conventional assembling method of the fuel assembly, and a purpose is to present a method of assembling the fuel assembly so as to prevent the generation of the distortion of the assembly as described above., and to present an apparatus for performing such a task. According to a method of assembling a fuel assembly presented in the present invention, the springs formed on the wall of the grid cell and protruding out into the cell space are deactivated by means of key means for deactivating the holding means and then a fuel rod is inserted into the grid. Then the key means is removed from the grid cell to activate the springs so as to provide a firm holding of the fuel rod in the grid. The next step is to insert control rod guide pipes into the designated grid cells, and rigidly fixing the control rod guide pipe to the grid. By following the procedure described, it becomes possible to avoid introducing non-uniform stresses on the guide pipes, thereby preventing the distortion of the entire fuel assembly. In the following, the explanations on the apparatus for assembling a fuel assembling are based on the fuel rods, shown in FIGS. 1 and 4, travelling from left to right in the illustration. The entry-side (left) is defined as the side from which the fuel rods enter some object, and the exit-side (right) is defined as the side from which the fuel rods exit. The apparatus for assembling the fuel assembly in the present invention comprises: (a) a fuel rod magazine which holds a plurality of parallel fuel rods in a horizontal position before insertion into the grids; PA1 (b) a driving means disposed on the entry-side of the fuel rod magazine for driving the fuel rods from the fuel rod magazine and inserting the fuel rods into the grids; PA1 (c) a plurality of regularly spaced support frames disposed outward of the exit-side of the fuel rod magazine, said frames supporting grids so that the opening of the grid faces the fuel rod magazine; PA1 (d) regularly spaced guiding means disposed on the entry-side of each of the plurality of regularly spaced support frames providing support to the underside of the fuel rods exiting the fuel rod magazine to prevent sagging of the fuel rods; PA1 (e) an expander jig for bulging the control rod guide pipes. According to the assembling apparatus presented above, after the springs which are protruding into the spaces of the grid cell are deactivated manually or automatically with the use of key means, the fuel rods are inserted into the grids, then the springs are reactivated to hold the fuel rods firmly therein. The control rod guide pipes are then inserted into the designated grid cells and are rigidly fixed to the grids. The top and the bottom nozzles are installed to complete the steps of manufacturing a fuel assembly. According to the assembling apparatus presented, guiding means are effective in preventing damages being introduced to the fuel rods, by preventing sagging of the fuel rods while entering the grid cells and causing possible damage to the rod surface or to the grids 4. |
claims | 1. A method of coating a substrate of a component for use in a water cooled nuclear reactor, the method comprising:coating a substrate using a cold spray thermal deposition process comprising:heating a pressurized carrier gas to a temperature greater than 400° C. to 1200° C.;adding particles to the heated carrier gas, the particles being selected from the group consisting of pure chromium, chromium-based alloys, and combinations thereof, and having an average diameter of 20 microns or less; andspraying the carrier gas and entrained particles onto a substrate at a velocity of 800 to 4000 ft./sec. (about 243.84 to 1219.20 meters/sec.) to form a coating on the substrate. 2. The method recited in claim 1 wherein the substrate is a zirconium alloy. 3. The method recited in claim 1 wherein the carrier gas is selected from the group consisting of nitrogen, carbon dioxide, combinations of nitrogen and carbon dioxide, and combinations of nitrogen and helium. 4. The method recited in claim 1 wherein the particles are pure chromium particles. 5. The method recited in claim 1 wherein the carrier gas and entrained particles are sprayed continuously until the desired coating thickness is reached. 6. The method recited in claim 1 wherein the component is a nuclear fuel rod cladding tube. 7. The method recited in claim 1 wherein the substrate is cylindrical in shape. 8. The method recited in claim 1 wherein the substrate is flat. 9. The method recited in claim 1 wherein the coating thickness is between 5 and 100 microns. 10. The method recited in claim 1 wherein the rate of particles deposition is up to 1000 kg/hour. 11. The method recited in claim 1 further comprising, following formation of the coating, increasing the smoothness of the coating. 12. The method recited in claim 1 wherein the chromium-based alloy particles comprise 80 to 99 atom % of chromium. 13. The method recited in claim 12 wherein the Cr-based alloy further comprises at least one element selected from the group consisting of silicon, yttrium, aluminum, titanium, niobium, zirconium, and transition metal elements, at a combined content of 0.1 to 20 atomic %. 14. The method recited in claim 1 wherein the carrier gas is heated at a pressure up to 5.0 MPa. 15. A method of coating a substrate of a component for use in a water cooled nuclear reactor, the method comprising:heating a pressurized carrier gas to a temperature between 200° C. and 1200° C.;adding particles to the heated carrier gas, the particles being selected from the group consisting of pure chromium, chromium-based alloys, and combinations thereof, and having an average diameter of 20 microns or less; andspraying the carrier gas and entrained particles onto a substrate at a velocity of 800 to 4000 ft./sec. (about 243.84 to 1219.20 meters/sec.) to form a coating on the substrate; and, following formation of the coating, annealing the coating. 16. The method recited in claim 15 wherein the particles are pure chromium particles. 17. The method recited in claim 15 wherein the coating thickness is between 5 and 100 microns. 18. The method recited in claim 15 wherein the rate of particles deposition is up to 1000 kg/hour. 19. The method recited in claim 15 wherein the chromium-based alloy particles comprise 80 to 99 atom % of chromium. 20. The method recited in claim 15 wherein the Cr-based alloy further comprises at least one element selected from the group consisting of silicon, yttrium, aluminum, titanium, niobium, zirconium, and transition metal elements, at a combined content of 0.1 to 20 atomic %. 21. The method recited in claim 15 wherein the carrier gas is heated at a pressure up to 5.0 MPa. 22. The method recited in claim 15 wherein the carrier gas is selected from the group consisting of nitrogen, hydrogen, argon, carbon dioxide, helium, and combinations thereof. 23. The method recited in claim 15 wherein the substrate is a zirconium alloy. |
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047524324 | abstract | A system and process for the production of nitrogen-13 atoms from carbon-13/fluid slurry is provided. The system (10) includes a device (14) for producing a proton beam (15) which travels along a preselected path and strikes a target in slurry. This target is positioned in the path of the proton beam (15) such that subjection of the target to such beam produces nitrogen-13 atoms in a predetermined form. The nitrogen-13 atoms are conducted from the target area and carried to a purification device for collecting a purified product containing such atoms. The cooling system serves to dissipate heat generated during the production of such nitrogen-13 atoms. |
abstract | A radiation scatter protection system designed to attach to an X-ray table to limit exposure to radiation for both medical staff and patient. The radiation scatter protection system includes an arm board adapted to be disposed around an arm of the patient; an arm board shielding including one large sheet of shielding extending downward from the X-ray table and a plurality of additional sheets of shielding, removably mounted to the arm board; a sand bag shield including a plurality of sheets of top shielding and a plurality of sheets of bottom shielding which connect to an elongated, cylindrical sandbag; a side curtain shield hanging from the X-ray table; and a throw shield. |
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description | The present application claims priority under 35 U.S.C. §119(e)(1) of U.S. Ser. No. 61/368,718, filed on Jul. 29, 2011 in the United States of America, entitled “CHARGED PARTICLE BEAM SYSTEM”. The present application also claims priority under 35 U.S.C. §119 of German patent application serial number 10 007 939.1, filed on Jul. 29, 2011 in Europe, entitled “CHARGED PARTICLE BEAM SYSTEM”. The contents of these applications are hereby incorporated by reference. The present disclosure relates to a charged particle beam system which can be used to measure diffraction patterns and in which a charged particle beam incident on a sample can be tilted. X-ray diffraction, neutron diffraction and electron diffraction are commonly used to determine crystal structures of samples. Herein, x-ray diffraction is useful in analyzing single crystals of sizes down to some μm, whereas electron beam diffraction can be applied to even smaller crystal sizes since an electron beam probe may have a very low diameter and due to a higher scattering cross section of electrons. The higher scattering cross section of electrons also results in multiple scattering of the electrons in the sample such that both desired single scattering events and undesired multiple scattering events are recorded in a scattering image. A method known as precession diffraction can be used to reduce the amount of multiple scattering events relative to single scattering events in a recorded scattering image such that a crystal structure of a measured sample can be derived from such image with a higher accuracy. In precession diffraction, a deflection system upstream of a sample in a transmission electron microscope is used to tilt an incident beam such that it rotates about its location of incidence on the sample. A second deflection system downstream of the sample and upstream of a detector compensates the rotating tilt of the incident beam such that a stable diffraction pattern can be recorded on the detector. This recorded diffraction pattern is better suited to derive a crystal structure of the sample than a corresponding pattern recorded without the rotating tilt of the incident beam. It is desirable to improve a quality of diffraction patterns obtained with precession diffraction. The disclosure has been accomplished taking the above problems into consideration. The disclosure provides a charged particle beam system that allows for recording diffraction patterns at a high accuracy and using a tilted particle beam incident on a sample. According to embodiments of a charged particle beam system, a charged particle beam system includes a charged particle beam generator, a first lens configured to focus a beam generated by the charged particle beam generator in an object plane, a second lens located downstream of the object plane, a first deflection system upstream of the first lens and configured to tilt the beam about the object plane such that an angle of incidence of the charged particle beam on the object plane is changed, a second deflection system located downstream of the second lens and configured to tilt the beam such that a change of the angle of incidence of the charged particle beam on the object plane generated by the first deflection system is compensated, and a corrector located downstream of the second lens and configured to compensate for imaging errors introduced by the second lens. According to further embodiments of a charged particle beam system, a charged particle beam system includes a charged particle beam generator, a first lens configured to focus a beam generated by the charged particle beam generator in an object plane, a second lens located downstream of the object plane, a first deflection system upstream of the first lens and configured to tilt the beam about the object plane such that the charged particle beam is obliquely incident on the object plane, a second deflection system located downstream of the second lens and configured to tilt the beam such that a tilt of the charged particle beam generated by the first deflection system is compensated, and a corrector located downstream of the second lens and configured to compensate for imaging errors introduced by the second lens. Herein, the first deflection system can be configured such that the charged particle beam is obliquely incident on the object plane having an angle of incidence significantly deviating from normal incidence. For example, an angle between a surface normal of the object plane and a direction of a central axis of the charged particle beam incident on the object plane can be greater than 1 mrad, greater than 3 mrad or greater than 10 mrad. According to embodiments, the corrector includes a first lens doublet located downstream of the second lens, a first multipole located downstream of the first lens doublet, a second lens doublet located downstream of the first multipole and a second multipole located downstream of the second lens doublet. Herein, a multipole is a particle optical component generating a magnetic field and/or an electric field having multipole symmetry about an optical axis of the corrector, wherein the multipole symmetry is higher than dipole symmetry. Examples of such multipole symmetry are a quadrupole symmetry, a hexapole symmetry and an octupole symmetry, and the corresponding particle optical components are a quadrupole, a hexapole and an octupole, respectively. According to embodiments, the second deflection system and the corrector are integrated in that components of the second deflection system and the corrector overlap along an optical axis of the charged particle beam system. According to particular embodiments herein, at least one deflector of the second deflection system is located between two lenses of the first lens doublet. According to further embodiments herein, the second deflection system is configured to tilt the beam about a location within a plane located downstream of the second lens and upstream of the first multipole. According to exemplary embodiments herein, the second deflection system is configured to tilt the beam about a location within an intermediate image plane into which the object plane is imaged by the second and third lenses. According to further exemplary embodiments herein, the second deflection system includes a first deflector located at the intermediate image plane, wherein, in some embodiments, the second deflection system is free of additional deflectors located outside of the intermediate image plane. According to an exemplary embodiment, a charged particle beam system includes a charged particle beam generator; a first lens configured to focus a beam generated by the charged particle beam generator in an object plane; a second lens located downstream of the object plane and having a diffraction plane; a first lens doublet located downstream of the second lens and including a third lens and a fourth lens and configured to image the diffraction plane into a first intermediate diffraction plane; a first multipole located at the first intermediate diffraction plane; a second lens doublet located downstream of the first multipole and including a fifth lens and a sixth lens and configured to image the first intermediate diffraction plane into a second intermediate diffraction plane; a second multipole located at the second intermediate diffraction plane; a first deflection system upstream of the first lens and configured to tilt the beam about the object plane such that an angle of incidence of the charged particle beam on the object plane is changed; and a second deflection system located downstream of the third lens and upstream of the fourth lens and configured to tilt the beam such that a change of the angle of incidence of the charged particle beam on the object plane generated by the first deflection system is compensated. According to exemplary embodiments herein, the second deflection system includes a first deflector located at an intermediate image plane into which the object plane is imaged by the second and third lenses, wherein it is possible that the second deflection system does not include any other deflectors apart from the deflector located at the intermediate image plane. According to other embodiments herein, the second deflection system includes two or more deflectors which are controlled such that the beam appears to be tilted about a virtual location in the intermediate image plane. According to some embodiments, the fourth lens and the fifth lens are configured to image the first intermediate image plane into a second intermediate image plane located downstream of the fifth lens and upstream of the sixth lens. According to further embodiments, the system includes a tilt controller configured to control an amount of beam tilt generated by the first deflection system in synchronism with an amount of beam tilt generated by the second deflection system. With such controller it is possible to generate a tilt of the beam incident on the object plane such that it rotates about an optical axis of the first lens along a cone shaped surface. Downstream of the object plane, this beam tilt is compensated by the second deflection system such that the beam propergates parallel to the optical axis downstream of the second deflection system. This allows recording of diffraction patterns when precession diffraction methods are applied. According to exemplary embodiments herein, the tilt controller is configured to control the first and second deflection systems such that the amounts of beam tilt generated by the first and second deflection systems change at frequencies greater than 50 Hz or greater than 100 Hz. According to exemplary embodiments, the charged particle beam system includes a corrector controller configured to control components of the corrector. According to exemplary embodiments herein, the corrector controller is configured to control one or more of the third, fourth, fifth and sixth lenses and the first and second multipoles. According to particular embodiments herein, the charged particle beam system includes a switch for switching an operation mode of the system from a first mode to a second mode. In the first mode of operation, the second deflection system is controlled by the tilt controller, whereas the second deflection system is controlled by the corrector controller in the second mode of operation. Precession diffraction can be performed in the first mode of operation. If this is not desired, the system can be switched to the second mode in which the second deflection system can be used, under the control of the corrector controller, to adjust the beam relative to an optical axis of the corrector and to improve a performance of the corrector. According to particular embodiments herein, the corrector controller includes a low-pass filter configured such that control signals supplied to deflectors of the second deflection system are substantially free of signal components having frequencies greater than 30 Hz. According to exemplary embodiments, the charged particle beam system includes a seventh lens located downstream of the second multipole, wherein the sixth lens and the seventh lens are configured to image the second intermediate image into a third intermediate image. According to an exemplary embodiment herein, the sixth lens and the seventh lens are further configured to generate a virtual image of the diffraction plane. According to exemplary embodiments, the charged particle system includes an energy filter having an entrance pupil plane and an entrance image plane, wherein the energy filter is located downstream of the corrector. The energy filter provides a dispersion to charged particles traversing the energy filter and is configured such that the entrance image plane of the energy filter is achromatically imaged by the energy filter into an exit image plane of the energy filter located at an exit side of the energy filter or downstream of the energy filter. The entrance pupil plane of the energy filter is dispersively imaged by the energy filter into an exit pupil plane of the energy filter located at the exit side of the energy filter or downstream of the energy filter. With such configuration it is possible to use a slit shaped aperture located in the exit pupil plane of the energy filter to restrict an energy spread of the charged particles contributing to the imaging downstream of the energy filter without disturbing the imaging of a plane imaged into the entrance image plane of the energy filter. According to embodiments herein, an eight lens is located upstream of the energy filter and configured such that an image or intermediate image of the object plane is generated at the entrance pupil plane of the energy filter and/or such that an image or intermediate image of the diffraction plane of the second lens is imaged into the entrance image plane of the energy filter. According to exemplary embodiments, a slit shaped aperture is arranged in the exit pupil plane of the energy filter such that only so called “zero loss charged particles” can traverse the energy filter. In such configuration only charged particles which have been elastically scattered at the object can traverse the energy filter, whereas charged particles which have been inelastically scattered at the object and have experienced a loss of kinetic energy are prevented from traversing the energy filter. This may have an advantage in that an image blurring of the recorded diffraction image is significantly reduced, such that a contrast in the recorded diffraction image is increased. This provides advantages to ensure that also diffraction maxima of low intensities can contribute an analysis of the diffraction patterns contained in a recorded image. According to some embodiments, the first deflection system is further configured to displace the beam in the object plane such that a location of incidence of the beam on the object plane is changed. Thus, the first deflection system is configured to change both the angle of incidence of the beam on the object plane and the location of incidence of the beam in the object plane. The beam can be selectively directed to plural locations of interest within the sample, and precession diffraction can be performed at each such location of interest. In exemplary embodiments herein, the charged particle beam system includes a third deflection system located downstream of the corrector and configured to tilt the beam such that a change of the locations of incidence of the charged particle beam on the object plane generated by the first deflection system is compensated. In embodiments using the energy filter, the third deflection system may be configured to tilt the beam about the entrance image plane of the energy filter into which the diffraction plane of the objective lens is imaged. According to embodiments herein, the third deflection system may include a single deflector located in the entrance image plane of the energy filter or two or more deflectors located upstream of the entrance image plane of the energy filter and controlled such that the beam is tilted about a virtual location positioned in the entrance image plane of the energy filter, such that the off-axis beam is shifted back to the optical axis. According to embodiments, the charged particle beam system includes a displacement controller configured to control an amount of beam displacement generated by the first deflection system in synchronism with an amount of beam tilt generated by the third deflection system. According to embodiments, one or more or all of the deflection systems mentioned above are configured to deflect the charged particle beam in two independent directions, such as orthogonal x- and y-directions. For this purpose, the deflector or the two deflectors of the deflection system may include two pairs of deflection elements distributed about the optical axis of the charged particle system. For example, the pairs of deflection elements may include pairs of electrodes for providing deflecting electrical fields and/or pairs of coils providing deflecting magnetic fields. The pairs of deflection elements may be energised such that one pair is energised according a signal having a temporal shape following a cosine function while the other pair is energised according a signal having a temporal shape following a sine function. If the first deflection system is energised according to such pattern, the charged particle beam obliquely incident on the object plane will perform a precession about the optical axis of the charged particle system. In the exemplary embodiments described below, components that are alike in function and structure are designated as far as possible by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the descriptions of other embodiments and of the summary of the disclosure should be referred to. FIG. 1 is a schematic illustration of a charged particle beam system 1 having a configuration of a transmission electron microscope. The charged particle beam system 1 includes a charged particle beam generator 3 configured to generate a charged particle beam 5. In the illustrated embodiment, the charged particle beam generator is an electron source, such that the charged particle beam 5 is an electron beam. However, other sources of charged particles, such as ions, are envisaged within the scope of the present disclosure. The charged particle beam 5 is collimated by one or more lenses 7 to shape the beam 5 such that it has a small cross section and a low convergence in a plane 8. For example, the cross section of the beam 5 can be smaller than 50 μm and the convergence of the beam 5 can be smaller than 1.5 mrad in the plane 8. The plane 8 is imaged into an object plane 9 by a lens 11. A sample to be inspected can be positioned in the object plane 9. A second lens 13 is located downstream of the object plane 9 and forms the objective lens of the transmission electron microscope. In the illustration of FIG. 1, the lenses 11 and 13 are represented as two individual lenses for illustrative purposes. It is also possible to provide the functions of the two lenses 11 and 13 by one single lens configuration which is referred to as condenser-objective-single-field-lens according to Riecke-Ruska. Similarly, some groups of other individual lenses shown in the illustration of FIG. 1 can be embodied in practice by one single lens structure while it is also possible that some of the individual single lenses shown in the illustration in FIG. 1 are embodied in practice by groups of plural lens structures. A first deflection system 15 is provided upstream of the first lens in the beam path of the charged particle beam 5. The first deflection system 15 includes two deflectors 17 and 19 spaced apart along an optical axis 2 of the first lens 11. In the illustrated example, the deflector 17 is located in the plane 8 where the beam spot is formed by the lens 7. The deflectors 17 and 19 are controlled by a deflector controller 21 which is configured to independently perform two functions of tilting the beam about the object plane 9 and displacing the beam in the object plane 9. Reference numerals 18 in FIG. 1 illustrate beams which are deflected by the deflection system 15 such that a location of incidence on the object plane of the beam 5 is on the optical axis 2, while the beam 5 is tilted relative to the optical axis 2 by angles +α and −α, respectively, wherein α is greater than 0. In exemplary embodiments, α may have values from 3 mrad to 100 mrad, for example. Moreover, the controller 21 is configured such that the direction of incidence of the beam can be rotated about the optical axis 2 while maintaining the angle α constant as illustrated by an arrow 23 in FIG. 1. Reference numeral 20 in FIG. 1 illustrates a beam which is deflected by the deflection system 15 such that the location of incidence of the beam is displaced within the object plane 9, wherein the tilt angle α is 0. The controller is configured to energize the deflection system 15 such that both a location of incidence of the beam 5 in the object plane 9 and a tilt angle α relative to the optical axis 2 can be independently adjusted. The second lens 13 has a focal plane 27 located downstream of the object plane 9. Reference numeral 29 in FIG. 1 illustrates a charged particle ray which was tilted relative to the optical axis 2 by an angle α, which traversed the object plane on the optical axis 2 (axial ray) and which has not been scattered by the object. Reference numerals 30 in FIG. 1 illustrate charged particle rays which were tilted relative to the optical axis 2 by the angle α and which have been scattered by the object by a scattering angle towards the optical axis and away from the optical axis, respectively. An intermediate image of the object plane 9 is generated in an intermediate image plane 33 located downstream of the lens 13. In the illustrated example, the intermediate image in the intermediate image plane 33 is generated by the second lens 13 and an additional lens 35. According to other examples, it is possible that the additional lens 35 is omitted and that the intermediate image is generated directly by the lens 13. Lines 32 in FIG. 1 connect, for illustrative purposes, planes which are conjugate to each other and conjugate to the object plane 9, while lines 34 connect planes which are conjugate to each other and conjugate to the focal plane 27 of objective lens 13. A second deflection system 37 is located downstream of the lens 13 and configured to tilt the beam about a location in the intermediate image plane 33. In the illustrated example, the second deflection system 37 includes one single deflector 39 positioned in the intermediate image plane 33. According to other examples, the second deflection system 37 may include plural deflectors configured such that the beam can be tilted about a (virtual) location in the intermediate image plane 33. The second deflection system 37 is controlled by a controller 41 configured to adjust a deflection angle or tilt generated by the second deflection system 37. The controller 41 of the second deflection system 37 and the controller 21 of the first deflection system 15 are controlled by a main controller 43 such that a beam tilt generated by the first deflection system 15 upstream of the object plane 9 is compensated by a tilt generated by the second deflection system 37 downstream of the object plane 9. This has an effect that the tilted rotating beam upstream of the second deflection system 37 which is illustrated by a ray 29, and a bundle of scattered rays 30 are deflected by the second deflection system 37 such that they travel symmetrically to the optical axis 2 downstream of the second deflection system 37 as indicated by reference numerals 29′ and 30′ in FIG. 1. A stationary diffraction pattern is formed by these rays in the intermediate diffraction plane 69 as illustrated in more detail below. The beam traversing the sample positioned in the object plane 9 is diffracted by the sample, and a corresponding diffraction pattern can be recorded by a detector 45 positioned downstream of the object plane 9. FIG. 2a shows an exemplary diffraction pattern recorded with a non-tilted beam from a sample including an uvarovite crystal. FIG. 2b shows a diffraction pattern obtained when the incident beam is tilted and rotated about the optical axis by the first deflection system 15 while the second deflection system 37 is not operated to compensate for the tilt and rotation. FIG. 2c is an illustration of a diffraction pattern recorded from a tilted rotating beam wherein the second deflection system 37 is operated as illustrated above to compensate the beam tilt and rotation. It is evident that the diffraction pattern of FIG. 2c shows less dynamical scattering than the diffraction pattern of FIG. 2a which makes it better suitable for deriving a crystal structure of the sample. FIG. 2d shows a diffraction pattern derived from the uvarovite crystal structure by calculation and simulation. The diffraction pattern of FIG. 2c has a higher similarity with the expected pattern of FIG. 2d than the pattern of FIG. 2a which is obtained without precession diffraction. It is apparent that precession diffraction is helpful in obtaining diffraction patterns allowing to derive complicated crystal structures of measured samples. The charged particle beam system 1 illustrated in FIG. 1 includes a corrector 51 located downstream of the objective lens 13 and upstream of the detector 45 and configured to compensate aberrations generated by the objective lens 13. In the illustrated example, the corrector 51 includes a lens 53, a hexapole 55, a lens 57 and a hexapole 59 arranged in that order along the optical axis 2. As illustrated in FIG. 1, the lens 53 can be formed by a lens doublet of lenses 35 and 63, and also the lens 57 can be formed of a lens doublet of lenses 65 and 67. While the corrector of the illustrated example includes hexapoles as multipole elements, other examples of correctors include other types of multipoles, such as quadrupoles and octupoles. Background information relating to correctors of various types can be obtained from U.S. Pat. No. 7,223,983 B2, EP 0 451 370 A1 and U.S. Pat. No. 7,321,124 B2, wherein the full disclosure of these documents is incorporated herein by reference. The components of the corrector 51 are controlled by a corrector controller 61 such that the diffraction plane 27 of lens 13 is imaged into an intermediate diffraction plane 69 at which the first hexapole 55 is located. Further, the lens 57 images the intermediate diffraction plane 69 into a further intermediate diffraction plane 71 at which the second hexapole 59 is located. Still further, the intermediate image plane 33 may be imaged into a further intermediate image plane 73 located between the hexapole 55 and the hexapole 59. In the illustrated example, the further intermediate image plane 73 is located in between lenses 65 and 67 of the lens doublet 57. The corrector 51 is controlled by the controller 61 such that lens aberrations, such as a spherical aberration of the objective lens 13 and possibly other aberrations are reduced or compensated. In the illustrated example, the two hexapoles 55 and 59 provide, in cooperation, an effect of a negative aberration coefficient which is suitable to compensate spherical aberrations of the objective lens 13. The present disclosure is, however, not limited to this type of corrector. Other types of correctors are envisaged within the scope of the present disclosure, wherein a deflection system generates a beam tilt at an intermediate image plane located between components of the corrector. In the illustrated example, it is the intermediate image plane 33 about which the second deflection system 37 is capable to tilt the beam for compensating a beam tilt introduced by the first deflection system 15, and wherein the intermediate image plane 33 is located between lenses 35 and 63 of the corrector 51. A third deflection system 74 is located downstream of the corrector 51 and configured to deflect the beam such that a change of the location of incidence of the charged particle beam 5 on the object plane 9 generated by the first deflection system 15 is compensated. In the illustrated example, the third deflection system 74 includes two deflectors 75, 77 spaced apart along the optical axis 2 and controlled by a controller 79. As illustrated in the example shown in FIG. 1, the corrector 51 may include an adaptation lens 93, and the charged particle system may further include a projection lens 95. In the illustrated example, the adaptation lens 93 is configured to generate an image of the object plane 9 in an entrance image plane 81 of the projection lens 95. At the same time, the adaptation lens 93 produces a virtual image of the intermediate image 71 of the focal plane 27 at a plane 94. The virtual image plane 94 is located upstream of the lens 95. The virtual image plane 94 can be located upstream of the hexapole 59 as illustrated in the example shown in FIG. 1. Still further, the deflectors 75, 77 of the third deflection system 74 are located in between the adaptation lens 93 and the projection lens 95. The controller 79 is configured to control the deflectors 75, 77 of the third deflection system 74 such that the beam is tilted about a location in the virtual image plane 94. In the illustrated example, the deflectors 75 and 77 deflect the beam in opposite directions by angles γ1 and γ2, respectively, and such that the field ray 20 displaced by the first deflection system 15 and traversing the sample in the object plane 9 coincides with the optical axis 2 downstream of the deflection system 74, and such that the beam appears to be tilted about location 94 on the optical axis 2. According to other examples, the third deflection system 73 may include one single deflector which is positioned in any one of the intermediate image planes of the focal plane 27. The controller 79 of the third deflection system 74 is controlled by the main controller 43 in synchronism with the controller 21 of the first deflection system 15 such that the change of location of incidence of the charged particle beam on the object plane 9 generated by the first deflection system 15 is compensated. The charged particle system 1 further includes an energy filter 87 located downstream of the corrector 51. As shown in the example illustrated in FIG. 1, the energy filter is located downstream of the projection lens 95. The energy filter 87 has an entrance pupil plane (not shown in FIG. 1) and an entrance image plane (not shown in FIG. 1), and projection lens 95 is configured such that an intermediate image of the object plane 9 is generated in the entrance pupil plane of the energy filter, and that an image of the focal plane 27 of the objective lens 13 is generated in the entrance image plane of the energy filter 87. The lens 95 includes plural individual lenses which are represented in FIG. 1 as one single lens 95. Lens 93 is configured such that an intermediate image of the object plane 9 is generated in the plane 81 located between lenses 93 and 95 by imaging intermediate image plane 73 into intermediate image plane 81. The adaptation lens 93 also generates the virtual image of the focal plane 27 of the second lens 13 in the intermediate image plane 94 as indicated by a broken line 31′ in FIG. 1. The charged particle beam system 1 shown in FIG. 1 can be operated in two modes. In a first mode of operation, the controller 41 of the second deflection system 37 is controlled by the main controller 43 which has a tilt control function for controlling the second deflection system 37 in synchronism with the first deflection system 15 such that a beam tilt and rotation generated by the first deflection system 15 is compensated by the second deflection system 37. In a second mode of operation, the second deflection system 37 is under the control of the corrector controller 61 such that the second deflection system 37 can be used to adjust the corrector 51 and improve its performance. FIG. 1 shows a switch 99 which can be used to change the operation modes of the charged particle beam system 1 by connecting the second deflection system 37 to one of the deflection controller 41 to perform the tilt control function and the corrector controller 61 controlling the corrector 51. The corrector controller 61 includes a low-pass filter in the control path towards the second deflection system 37 such that control signals supplied to the deflectors of the second deflection system 37 are substantially free of signal components having frequencies greater than 30 Hz. This allows for a stable operation of the corrector 51. On the other hand, the deflection controller 41 performing the tilt compensation function is configured to control the controller 41 of the second deflection system 37 such that it can generate beam deflections at frequencies greater than 50 Hz. In both the first and second operation modes of the charged particle beam system 1, the main controller 43 can perform its deflection control function to control the controller 79 of the third deflection system 74 such that a deflection of the location of incidence of the beam in the object plane 9 generated by the first deflection system 15 is compensated. FIG. 3 shows a portion of a further example of a charged particle beam system which is a variation of the system illustrated with reference to FIG. 1 above. The charged particle beam system 1a shown in FIG. 3 has a charged particle beam generator, lenses, first and second deflection systems for performing precession diffraction similar to the system illustrated with reference to FIG. 1 and not shown in FIG. 3. The system 1a also includes a corrector having two hexapoles and lenses similar to the corrector of the system illustrated with reference to FIG. 1, wherein only a hexapole 59a and a lens 93a of the corrector 51a are shown in FIG. 3. The system 1a differs from the one illustrated with reference to FIG. 1 above in that a projection lens 95a is located downstream of the lens 93a of the corrector 51a and upstream of a third deflection system 74a, wherein the third deflection system 74a is located upstream of an energy filter 87a. The third deflection system 74a is configured to deflect the beam such that a change of the location of incidence of the charged particle beam on an object plane of the system generated by the first deflection system is compensated. In the illustrated example, the third deflection system 74a includes two deflectors 75a, 77a spaced apart along an optical axis 2a. The deflectors 75a, 77a of the third deflection system 74a are controlled by a controller 79a to tilt the beam about a location in a plane 91a at which an intermediate image of a focal plane of an objective lens of the system is formed. In the illustrated example, the deflectors 75a and 77a deflect the beam in opposite directions by angles γ1 and γ2, respectively and such that a field ray 31a originating from the object plane coincides with the optical axis 2a and such that the beam appears to be tilted about location 83a on the optical axis 2a and in the intermediate image plane 81a as indicated by a broken line 84. According to other examples, the third deflection system 73a may include one single deflector which is positioned in the intermediate image plane 81a. The controller 79a of the third deflection system 73 is controlled by a main controller (not shown in FIG. 1) of the system in synchronism with the first deflection system such that the change of location of incidence of the charged particle beam on the object plane generated by the first deflection system is compensated. The energy filter 87a is located downstream of the corrector 51a. The energy filter 87a has an entrance pupil plane 89a and an entrance image plane 91. Lenses 93a and 95a are located between the corrector 51a and the entrance pupil plane 89 and entrance image plane 91 of the energy filter 87 and configured such that an intermediate image of the object plane is generated in the entrance pupil plane 89a of the energy filter, and such that an image of the focal plane of the objective lens is generated in the entrance image plane 91 of the energy filter 87. The lens 95a includes plural individual lenses as represented in FIG. 1. The lens 93a is configured such that an intermediate image of the object plane is generated in an intermediate image plane 97a located between the lenses 93a and 95a. The lens 93a also generates a virtual image of the focal plane of the objective lens upstream of the lens 93a. The present disclosure illustrates certain exemplary embodiments wherein it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Therefore, the exemplary embodiments illustrated in this disclosure are intended to be illustrative and not limiting in any way. Various changes may be made without departing from the spirit and scope of the present disclosure as defined in the following claims. |
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abstract | A cooling system for spent nuclear fuel may include a device configured to generate electricity using energy emitted from the spent nuclear fuel. The cooling system may be configured to use the electricity when cooling the spent nuclear fuel. A cask for storage, transport, or storage and transport of spent nuclear fuel may include the cooling system and a container configured to hold the spent nuclear fuel. A method for cooling spent nuclear fuel may include generating electricity using energy emitted from the spent nuclear fuel, and using the electricity in a cooling system for the spent nuclear fuel when cooling the spent nuclear fuel. |
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claims | 1. A passage selector of a reactor in-core nuclear-measuring apparatus, comprising:a passage selecting guide tube;a plurality of detector passages;a drive motor;an index device that is driven by said drive motor, the index device including an output shaft that makes a rotary output of a fixed predetermined index number;a central rotating shaft that is rotated so as to cause the passage selecting guide tube to be aligned to a detector passage; anda speed-increasing and decreasing device that comprises a first gear directly connected to the output shaft of the index device and a second gear that is meshed with said first gear and directly connected to said central rotating shaft; andwherein when a stop number (index number) of the index device is Y where a teeth number of the first gear is Z1, and a teeth number of the second gear is Z2, the stop number (index number) of the central rotating shaft is Y×Z2/Z1. 2. A passage selector of a reactor in-core nuclear-measuring apparatus, comprising:a passage selecting guide tube;a plurality of detector passages;a drive motor;an index device that is driven by said drive motor, the index device including an output shaft that makes a rotary output of a fixed predetermined index number;a central rotating shaft that is rotated so as to cause the passage selecting guide tube to be aligned to a detector passage; anda speed-increasing and decreasing device that comprises a first gear directly connected to the output shaft of the index device and a second gear that is meshed with said first gear and directly connected to said central rotating shaft; andwherein when an input shaft of the index device makes one revolution by the drive motor, an output shaft of the index device makes 1/Y revolution in accordance with an index number Y that is specific to the index device, where a teeth number of the first gear is Z1, and a teeth number of the second gear is Z2, the revolutions of the central rotating shaft is set to be 1/Y×Z1/Z2. |
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039754715 | abstract | There is provided a process for the production of fuel compacts consisting of an isotropic, radiation resistant graphite matrix of good heat conductivity having embedded therein coated fuel and/or fertile particles for insertion into high temperature fuel elements by providing the coated fuel and/or fertile particles with an overcoat of molding mixture consisting of graphite powder and a thermoplastic resin binder. The particles after the overcoating are provided with hardener and lubricant only on the surface and subsequently are compressed in a die heated to a constant temperature of about 150.degree.C., hardened and discharged therefrom as finished compacts. |
claims | 1. A method of fabricating an X-ray mask comprising:etching an X-ray transmitter at a surface of said X-ray transmitter to form a plurality of recesses extending from the surface and into said X-ray transmitter, leaving portions of the surface between respective parts of recesses; andforming a laminated X-ray absorber on said surface of said X-ray transmitter, but not in said recesses, wherein said laminated X-ray absorber includes at least two layers having different compositions, wherein phase shift of X-rays transmitted through said X-ray absorber is in a range of 0.3π to 0.6π and transmittance of the X-rays transmitted through said X-ray absorber is in a range of 30% to 60% for X-rays having an average exposure wavelength longer than 0.3 nm and shorter than 0.7 nm. 2. The method of fabricating an X-ray mask according to claim 1, whereinsaid laminated X-ray absorber includes a first X-ray absorber opposite said X-ray transmitter and a second X-ray absorber in contact with said first X-ray absorber,tungsten is employed as one of said first X-ray absorber and said second X-ray absorber, anddiamond is employed as the other of said first X-ray absorber and said second X-ray absorber. 3. The method of fabricating an X-ray mask according to claim 1, whereinsaid laminated X-ray absorber includes a first X-ray absorber on said X-ray transmitter and a second X-ray absorber on said first X-ray absorber, andthe method of fabricating an X-ray mask further comprises:forming an etching stopper film, stopping etching when etching said first X-ray absorber on said X-ray transmitter, andforming said second X-ray absorber on said etching stopper film. 4. The method of fabricating an X-ray mask according to claim 1, whereinsaid laminated X-ray absorber includes a first X-ray absorber opposite said X-ray transmitter and a second X-ray absorber on said first X-ray absorber, andthe method of fabricating an X-ray mask further comprises:forming an interlayer film as an etching stopper or a hard mask on said first X-ray absorber, andforming said second X-ray absorber on said interlayer film. 5. The method of fabricating an X-ray mask according to claim 1, wherein said laminated X-ray absorber has a layer containing at least one substance selected from the group consisting of lithium, beryllium, boron, carbon, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, palladium, silver, cadmium, indium, tin, antimony, tellurium, cesium, barium, mixtures of these elements, a carbide including silicon carbide and tungsten carbide, a nitride including silicon nitride, aluminum nitride, and chromium nitride, an oxide including silicon oxide and chromium oxide, a fluoride, and an iodide. 6. The method of fabricating an X-ray mask according to claim 1, wherein said laminated X-ray absorber has a layer containing a substance selected from the group consisting of carbon, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, gallium, germanium, arsenic, selenium, palladium, silver, cadmium, indium, tin, antimony, and tellurium. 7. The method of fabricating an X-ray mask according to claim 1, further comprising selectively implanting ions into regions of said X-ray transmitter where portions of said X-ray transmitter are to be removed in forming said recesses, before forming said recesses. 8. The method of fabricating an X-ray mask according to claim 1, including forming said laminated X-ray absorber in a periodic pattern. 9. A method of fabricating an X-ray mask comprising:forming an X-ray transmitter;forming a first X-ray absorber opposite said X-ray transmitter, said first X-ray absorber including a plurality of spaced apart first X-ray absorber portions, each first X-ray absorber portion having side surfaces substantially transverse to said X-ray transmitter and a first width measured between the side surfaces of said first X-ray absorber portions; andforming a second X-ray absorber on said first X-ray absorber, said second X-ray absorber comprising a plurality of second X-ray absorber portions spaced from each other, each second X-ray absorber portion being disposed on a corresponding one of the first X-ray absorber portions, each second X-ray absorber portion having side surfaces substantially transverse to said X-ray transmitter and a second width measured between the side surfaces of the second X-ray absorber portions, the second width being larger than the first width and none of the side surfaces of the second X-ray absorber portions being contiguous with the side surfaces of the first X-ray absorber portions. 10. The method of fabricating an X-ray mask according to claim 9, wherein at least one of said first and second X-ray absorbers is selected from the group consisting of lithium, beryllium, boron, carbon, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, palladium, silver, cadmium, indium, tin, antimony, tellurium, cesium, barium, mixtures of these elements, a carbide including silicon carbide and tungsten carbide, a nitride including silicon nitride, aluminum nitride, and chromium nitride, an oxide including silicon oxide and chromium oxide, a fluoride, and an iodide. 11. The method of fabricating an X-ray mask according to claim 9, wherein at least one of said first and second X-ray absorbers is selected from the group consisting of carbon, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, gallium, germanium, arsenic, selenium, palladium, silver, cadmium, indium, tin, antimony, and tellurium. 12. A method of fabricating a semiconductor device including carrying out an exposure with an X-ray mask having a geometric X-ray phase difference between the phase of X-rays transmitted through an X-ray transmission part of said X-ray mask and the phase of X-rays transmitted through an X-ray absorber of said X-ray mask in a range including 0.5π and proximity to 0.5π, between a resist film located at a position for forming an optical image with said X-rays and said X-ray mask, whereinsaid X-ray mask comprises an X-ray transmitter and said X-ray absorber includes a laminated structure having at least two layers on said X-ray transmitter,said laminated structure includes at least two layers having different compositions, andeither the phase shift of the X-rays transmitted through said X-ray absorber is in a range of 0.3π to 0.6π or the transmittance of the X-rays transmitted through said X-ray absorber is in a range of 30% to 60%. 13. The method of fabricating a semiconductor device according to claim 12, including carrying out the exposure with an average exposure wavelength of the X-rays longer than 0.3 nm and shorter than 0.7 nm. 14. The method of fabricating a semiconductor device according to claim 12, wherein absolute value of difference between the geometric phase difference and the phase shift quantity is in a range including π and proximity to π. 15. A method of fabricating an X-ray mask comprising:forming an X-ray transmitter;forming a first X-ray absorber opposite said X-ray transmitter, said first X-ray absorber including a plurality of spaced apart first X-ray absorber portions, each first X-ray absorber portion having a first width; andforming a second X-ray absorber on said first X-ray absorber, said second X-ray absorber comprising a plurality of second X-ray absorber portions spaced from each other, each second X-ray absorber portion being disposed on a corresponding one of the first X-ray absorber portions, each second X-ray absorber portion having a second width, larger than the first width, whereintungsten is employed as one of said first and second X-ray absorbers, anddiamond is employed as the other of said first and second X-ray absorbers. 16. A method of fabricating an X-ray mask comprising:forming an X-ray transmitter;forming a first X-ray absorber opposite said X-ray transmitter;forming an etching stopper film, stopping etching when etching said first X-ray absorber on said X-ray transmitter, said first X-ray absorber including a plurality of spaced apart first X-ray absorber portions, each first X-ray absorber portion having a first width; andforming a second X-ray absorber on said etching stopper film on said first X-ray absorber, said second X-ray absorber comprising a plurality of second X-ray absorber portions spaced from each other, each second X-ray absorber portion being disposed on a corresponding one of the first X-ray absorber portions, each second X-ray absorber portion having a second width, larger than the first width. 17. A method of fabricating an X-ray mask comprising:forming an X-ray transmitter;forming a first X-ray absorber opposite said X-ray transmitter;forming an interlayer film as an etching stopper or a hard mask on said first X-ray absorber, said first X-ray absorber including a plurality of spaced apart first X-ray absorber portions, each first X-ray absorber portion having a first width; andforming a second X-ray absorber on said interlayer film on said first X-ray absorber, said second X-ray absorber comprising a plurality of second X-ray absorber portions spaced from each other, each second X-ray absorber portion being disposed on a corresponding one of the first X-ray absorber portions, each second X-ray absorber portion having a second width, larger than the first width. 18. A method of fabricating an X-ray mask comprising:forming an X-ray transmitter;forming a first X-ray absorber of a first X-ray absorbing material opposite said X-ray transmitter, said first X-ray absorber including a plurality of spaced apart first X-ray absorber portions, each first X-ray absorber portion having a first width; andforming a second X-ray absorber of a second X-ray absorbing material, different from said first X-ray absorbing material, on said first X-ray absorber, said second X-ray absorber comprising a plurality of second X-ray absorber portions spaced from each other, each second X-ray absorber portion being disposed on a corresponding one of the first X-ray absorber portions, each second X-ray absorber portion having a second width, larger than the first width. |
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039882586 | abstract | A process of safe disposal, handling or storage of radwaste associated with nuclear power production is described. A feature of the invention is to incorporate the radwaste in a hardenable, matrix-forming mass employing a cement-type binding agent to which alkali or alkaline-earth silicate is added, among other things, to increase liquid absorption. |
059490837 | abstract | A container for nuclear fuel assemblies comprises a thick cylindrical body of forged steel which delimits an inner cavity for housing said assemblies, said cavity being able to be hermetically sealed at its two ends by plugs which are also formed of metal, characterized in that the cross section of the cylindrical body is non-circular. The outer wall usually comprising flat surfaces which are parallel to the flat face of crescent-shaped sections fixed to its inner wall, providing the cross section with the shape of a square or rectangle with rounded corners. |
abstract | A method of preparing two dimension bent X-ray crystal analyzers in strips feature is provided. A crystal wafer in strips is bonded to a curved substrate which offers the desired focus length. A crystal wafer in strips is pressed against the surface of the substrate forming curved shape by anodic bonding or glue bonding. The bonding is permanently formed between crystal wafer and its substrate surface, which makes crystal wafer has same curvature as previously prepared substrate. |
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claims | 1. An X-ray diffraction apparatus comprising:an X-ray generator for generating an X-ray beam that propagates in a beam direction to illuminate a sample in order to make an X-ray diffraction measurement;a movable component having a plurality of apertures with identical sizes and shapes, but located at different positions along a first direction perpedicular to the beam direction, the component being positioned between the generator and the sample so that the X-ray beam illuminates the sample through a single first aperture; anda mechanism for moving the component in a second direction different from the first direction to cause the X-ray beam to illuminate the sample through another single aperture with a position that is shifted in the first and second directions from the position of the first aperture. 2. An apparatus according to claim 1 wherein the movable component comprises an aperture medium that is substantially opaque to the X-ray beam and within which a plurality of holes are located. 3. An apparatus according to claim 2 wherein the aperture medium comprises a disk that is moved rotationally. 4. An apparatus according to claim 3 wherein rotation of the disk by a predetermined angular distance moves a first one of the holes out of alignment with the beam and a second one of the holes into alignment with the X-ray beam. 5. An apparatus according to claim 4 wherein the second hole has a different radial position than the first hole relative to an axis about which the disk is rotated. 6. An apparatus according to claim 5 wherein at least some of the holes in the disk are aligned in a row that, from one end of the row to an opposite end, is characterized by the incremental increase in radial position of the holes in the row relative to an axis about which the disk is rotated. 7. An apparatus according to claim 6 wherein all of the holes of the row have the same cross-sectional size and shape. 8. An apparatus according to claim 6 wherein the row is a first row and wherein the holes of the disk are organized into a plurality of rows located in different radial segments around the disk. 9. An apparatus according to claim 8 wherein the holes of a given row all have the same cross-sectional size as each other, and a cross-sectional size different from that of the holes in the other rows. 10. An apparatus according to claim 4 wherein the disk rotation is driven by a motor. 11. An apparatus according to claim 10 further comprising a position sensor that detects indicia of the disk to determine the rotational position of the disk. 12. An apparatus according to claim 11 wherein the indicia comprise the holes of the disk. 13. An apparatus according to claim 11 further comprising a controller that controls the position of the disk so as to align a chosen one of the holes with the beam. 14. An apparatus according to claim 2 wherein the aperture medium comprises a tape that is moved in a linear direction in the vicinity of the beam. 15. An apparatus according to claim 14 wherein movement of the tape by a predetermined distance moves a first one of the holes out of alignment with the beam and a second one of the holes into alignment with the beam. 16. An apparatus according to claim 15 wherein the second hole has a different lateral position than the first hole relative to a direction perpendicular to the direction along which the tape is moved in the vicinity of the beam. 17. An apparatus according to claim 16 wherein at least some of the holes in the tape are aligned in a row that, from one end of the row to an opposite end, is characterized by the incremental increase in lateral position of the holes in the row relative to a direction perpendicular to the direction along which the tape is moved in the vicinity of the X-ray beam. 18. An apparatus according to claim 17 wherein all of the holes of the row have the same cross-sectional size and shape. 19. An apparatus according to claim 17 wherein the row is a first row and wherein the holes of the tape are organized into a plurality of rows located in different linear segments along the length of the tape. 20. An apparatus according to claim 19 wherein the holes of a given row all have the same cross-sectional size as each other, and a cross-sectional size different from that of the holes in the other rows. 21. An apparatus according to claim 15 wherein the tape movement is driven by a motor. 22. An apparatus according to claim 15 wherein the tape is wound onto take-up reels that are rotated to move the holes on the tape relative to the X-ray beam. 23. An apparatus according to claim 22 further comprising a position sensor that detects indicia of the tape to determine the position of the tape relative to the X-ray beam. 24. An apparatus according to claim 23 wherein the indicia comprise the holes of the tape. 25. An apparatus according to claim 23 further comprising a motor that drives one of the take-up reels and a controller that controls the motor to position the tape so as to align a chosen one of the holes with the X-ray beam. 26. An apparatus according to claim 22 further comprising a cassette within which the tape and take-up reels are housed, the cassette having apertures that allow the X-ray beam to enter a first side of the cassette, encounter the tape, and exit a second side of the cassette. 27. An apparatus according to claim 15 wherein the tape forms a closed loop. 28. An apparatus according to claim 27 wherein the tape forms a Möbius loop. 29. An apparatus according to claim 2 wherein the aperture medium has a minimum of thirty-six holes. 30. An apparatus according to claim 1 further comprising at least one fixed aperture positioned between the generator and the sample along with the movable component. 31. A method for operating an X-ray diffraction apparatus, the method comprising:generating an X-ray beam that propagates in a beam direction to illuminate a sample in order to make an X-ray diffraction measurement;positioning a movable component between the generator and the sample, the movable component having a plurality of apertures with identical sizes and shapes, but located at different positions along a first direction perpendicular to the beam direction, so that the X-ray beam illuminates the sample through a single first aperture; andmoving the component in a second direction different from the first direction to cause the X-ray beam to illuminate the sample through another single aperture with a position that is shifted in the first and second directions from the position of the first aperture. |
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claims | 1. A method of producing a nuclear fusion reaction, comprising:starting and completing a single cycle of a nuclear fusion reaction, the single cycle includingevacuating a reaction chamber to a pressure that is lower than about 10−3 torr;inducing a pulse of (i) a first reactant into the evacuated reaction chamber through a first reactant port and a pulse of (ii) a second reactant into the evacuated reaction chamber through a second reactant port, wherein the first reactant and the second reactant are independently selected as comprising deuterium or tritium;converging the first reactant with the second reactant at a target cathode for colliding and fusing the first reactant with the second reactant to create a heat energy, the converging creating a higher reaction density at the target cathode rather than relying on random collisions, and includingcreating an electrical field in the reaction chamber by applying a voltage that is selected from the group consisting of about 10 kV, about 11 kV, about 12 kV, about 13 kV, about 14 kV, about 15 kV, about 20 kV, about 25 kV, about 30 kV, about 35 kV, about 40 kV, about 45 kV, about 50 kV, about 60 kV, about 70 kV, about 80 kV, about 90 kV, about 100 kV, about 200 kV, about 300 kV, about 400 kV, about 500 kV, about 600 kV, about 700 kV, about 800 kV, about 900 kV, about 1 MV, about 2 MV, about 3 MV, about 4 MV, about 5 MV, about 10 MV, or any voltage therein, or range of voltages therein, in increments of 1 kV across an anode surface positioned in the interior of the reaction chamber and a surface of the target cathode positioned in the interior of the reaction chamber, the surface area of the target cathode ranging from about from about 1.00×10−10 m2 to about 1.00×10−6 m2, the electric field ionizing the first reactant to generate a cationic first reactant and ionizing the second reactant to generate a cationic second reactant; and,establishing a negative charge on the target cathode for attracting and converging the cationic first reactant and the cationic second reactant at the target cathode for colliding and fusing the cationic first reactant with the cationic second reactant to create the heat energy. 2. The method of claim 1, wherein the first reactant is deuterium and the second reactant is tritium. 3. The method of claim 1, wherein deuterium is both the first reactant and the second reactant. 4. The method of claim 1, wherein tritium is the first reactant and tritium is the second reactant. 5. The method of claim 1, further comprising adjusting the pressure in the evacuated reaction chamber to range from about 10−4 torr to about 10−9 torr. 6. The method of claim 1, further comprising adjusting the pressure in the evacuated reaction chamber to range from about 10−6 torr to about 10−9 torr. 7. The method of claim 1, further comprising:replacing the target cathode with a replacement target cathode to complete a first cycle of the nuclear fusion method and provide the replacement target cathode for a second reaction cycle. |
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description | The present invention claims priority from Japanese application JP 2007-113358 filed on Apr. 23, 2007 and JP 2007-161691 filed on Jun. 19, 2007, the contents of which are hereby incorporated by reference into this application. The present invention relates to an inspection and analysis technique for use in an electronic component such as semiconductor devices including a semiconductor memory, a microprocessor, a semiconductor laser, etc., and as a magnetic head; and, more particularly, to a technique of machining (or processing) and observation of the cross section of a sample by an ion beam. High manufacturing yield is an important requisite for the manufacture of electronic components, such as semiconductor devices, e.g., semiconductor memories typically represented as dynamic random access memories (DRAMs), microprocessors and semiconductor lasers, and magnetic heads. This is because a fall of the product yield is directly linked to lower corporate profits. Therefore, early detection of and countermeasures to deal with defects, foreign matter and poor machining are indeed major issues to be resolved. For example, electronic component manufacturing plants have put much effort on discovery of defects by careful inspection, and analysis of their causes. In actual electronic component manufacturing processes using wafers, the wafers in the course of machining are examined, the cause of abnormalities such as defects and foreign matter in circuit patterns is investigated, and methods to deal with them are considered. Typically, high resolution scanning electron microscope (hereinafter abbreviated as SEM) is used to observe an abnormal spot on a sample. A composite FIB (Focused Ion Beam)-SEM is also currently used. The FIB-SEM machine irradiates FIB to form a square hole into a desired spot, and allows one to observe its cross section by SEM. For instance, Japanese Patent Application Laid-Open No. 2002-150990 discloses a square hole for the observation and analysis of a defect or a foreign matter, in which an aperture is formed by using an FIB in the vicinity of an abnormal spot in a sample and cross section of the square hole is observed by SEM. Moreover, International Patent Application Publication No. WO99/05506 discloses a technique for extracting a micro sample for TEM observation from a bulk sample by using an FIB and a probe. Also, one example of ion beam processor related techniques in Japanese Patent Application Laid-Open No. 2-062039 discloses that reactive gas cylinders of plural kinds of gases are connected to an ionization chamber through valves, such that a reactive gas corresponding to the material of a layer to be processed of a sample is switched and supplied when a reactive etching process is executed locally in an ion beam irradiation unit. In addition, Japanese Patent Application Laid-Open No. 2004-40129 discloses a technique for filling up a processed hole of a wafer from which a micro sample is extracted and returning the wafer to the production line. However, the technique for machining a sample by using an ion beam to form a cross section and observing the cross section by SEM (or TEM) necessarily uses both the FIB irradiation system and the SEM irradiation system (or the TEM irradiation system). Therefore, a device thereof has a complicated structure and is difficult to control. This consequently causes device prices to increase. Spatial interference between nearby lenses is another problem as they are positioned to let ion beam and electron beam irradiate the same spot on a sample. This problem cannot be resolved without suffering from performance degradation of each beam. It is certainly possible to use only one of them for sample observation. For example, the ion beam, not the electron beam, may irradiate the sample to be observed. However, if the same kind of ion used for machining is used for observation again, the sample surface is cut away, making it difficult to observe a desired cross section of the sample. Unfortunately, a new technique for sample machining and observation by ion beam has not been developed yet. In addition, flatness level at a filled processed hole needs to be suppressed to at least a submicron level. Meanwhile, because the hole fill volume is a large value at an equivalent level to the processed hole volume, it takes a long period of time (from several minutes to several tens of minutes) to fill up the hole, and the amount of time it takes to return the wafer to a production line occupies a large portion of a series of processes. In view of the foregoing problems, it is, therefore, an object of the present invention to provide an ion beam machining and observation method relevant to a technique of cross sectional observation of an electronic component, through which a sample is machined by using an ion beam withdrawn from the same ion source and one can observe a machined portion of the sample. Another object of the present invention is to provide a charged particle beam processor capable of reducing the time it takes to fill up a processed hole yet ensuring a high degree of flatness at a filled hole area. To achieve the above objects, there is provided a cross sectional observation device, which does not use an electron beam for the observation but irradiates at least two kinds of gas ions with different mass numbers onto a sample and which is capable of switching the kind of a gas ion beam used for machining a sample with the kind of a gas ion beam used for observing the sample. An ion source for realizing the switch between the kind of a gas ion beam used for sample machining and the kind of a gas ion beam used for sample observation includes at least two gas introduction systems, each system having a gas cylinder, a gas tube, a gas volume control valve, and a stop valve. The gas volume control valve of each system can set up gas pressure conditions for a vacuum chamber, and the stop valve of each system serves to switch the kind of gas being introduced into the vacuum chamber. Particularly, when the ion beam machining and observation device of the present invention irradiates a gas ion beam to process a sample, it projects a hole shape of an aperture mask inside an ion beam irradiation column into a sample shape, such that a high-speed machining can be possible. Moreover, to reduce the amount of a sample being cut out at the time of cross sectional observation, the ion beam machining and observation device of the present invention includes a mechanism for mass-separating a gas ion beam emitted from an ion source, and executes a control operation to prevent an ion having a relatively large mass number from reaching the sample when it irradiates an ion having a relatively small mass number. A method of machining and observing cross section of a sample includes the steps of: irradiating an ion having a relatively large mass number to form a roughly vertical cross section to the surface of a sample; and irradiating an ion having a relatively small mass number onto the cross section for observation thereof. Therefore, the present invention addresses the deficiencies of the related art by providing a device suitable for cross sectional observation, which does not use an electron beam as in the art but uses an ion beam with a mass number smaller than that of an ion beam irradiated for cross sectional machining. The following will now go through the list of characteristic embodiments of the present invention. (1) An ion source of the present invention includes a vacuum chamber and a gas supply mechanism to introduce gas into the vacuum chamber, wherein gas ions are produced in the vacuum chamber, and the gas supply mechanism includes at least two gas introduction systems, each system having a gas cylinder, a gas tube, a gas volume control valve, and a stop valve, the gas volume control valve of each system being capable of setting up gas pressure conditions for a vacuum chamber, and the stop valve of each system being capable of switching the kind of gas being introduced into the vacuum chamber. Preferably, the ion source with the above structure generates gas ions by gas discharge, and includes a control device having a function to memorize two or more gas discharge voltages and capable of switching the gas discharge voltages. Here, the kind of gas is switched with the help of the stop valve and a switching operation of the discharge voltages. In the ion source with the above structure, one of the gas introduction systems supplies any one of argon gas, xenon, krypton gas, neon gas, oxygen gas, and nitrogen gas, while the other gas introduction system supplies either hydrogen gas or helium gas. (2) An ion beam machining and observation device of the present invention includes an ion source including a vacuum chamber and a gas supply mechanism to introduce gas into the vacuum chamber and generating gas ions in the vacuum chamber; a sample chamber for keeping a sample; and an ion beam irradiation column connected to the vacuum chamber to extract an ion beam from the ion source, and irradiate the ion beam onto the sample, wherein the gas supply mechanism includes at least two gas introduction systems, each system having a gas cylinder, a gas tube, a gas volume control valve, and a stop valve, the gas volume control valve of each system being capable of setting up gas pressure conditions for a vacuum chamber, and the stop valve of each system being capable of switching the kind of gas being introduced into the vacuum chamber and switching between the kind of a gas ion beam used for machining the sample and the kind of a gas ion beam used for observing the sample. In the ion beam machining and observation device with the above structure, the ion source generates gas ions by gas discharge, and has a control device having a function to memorize at least two or more gas discharge voltages and capable of switching the gas discharge voltages. Here, the kind of the gas ion beam is switched with the help of the stop valve and a switching operation of the discharge voltages. Preferably, when the ion beam machining and observation device with the above structure irradiates a gas ion beam to process a sample, it projects a hole shape of a mask installed in the ion beam irradiation column into a sample. Preferably, when the ion beam machining and observation device with the above structure irradiates a gas ion beam to observe the sample, it converges an ion beam emitted from the ion source onto a sample in a dot-like pattern. (3) Another ion beam machining and observation device of the present invention includes an ion source capable of generating at least two kinds of gas ions having different mass numbers, and an ion beam irradiation column for emitting a gas ion beam from the ion source and irradiating the gas ion beam onto a sample, wherein the ion beam irradiation column includes a mechanism for mass-separating the gas ion beam emitted from the ion source so that, among the mass separated gas ions, an ion with a relatively large mass number is used for machining a sample cross section while an ion with a relatively small mass number is used for observing the cross section of the sample, and the ion with a relatively large mass number is controlled not to reach the sample when the ion with a relatively small mass number is irradiated onto the sample. In the ion beam machining and observation device with the above structure, the ion source can introduce two or more kinds of gas at the same time. In the ion beam machining and observation device with the above structure, the ion beam irradiation column includes at least two kinds of masks having an aperture to define the shape of the gas ion beam, and a plate having the aperture used for irradiating the gas with the relatively large mass number is thicker than a plate having the aperture used for irradiating the gas with the relatively small mass number. In the ion beam machining and observation device with the above structure, the ion having a relatively large mass number is a gas ion containing at least one kind among argon, xenon, krypton, neon, oxygen, and nitrogen, while the ion having a relatively small mass number is either a hydrogen gas ion or a helium gas ion, or a mixed gas ion. (4) Still another ion beam machining and observation device of the present invention includes an ion source including a vacuum chamber and a gas supply mechanism to introduce gas into the vacuum chamber and generating gas ions in the vacuum chamber by gas discharge; and an ion beam irradiation column extracting a gas ion beam from the ion source, and irradiating the gas ion beam onto a sample, wherein the gas supply mechanism includes at least two gas introduction systems, one gas introduction system for supplying a first gas and the other gas introduction system for supplying a second gas, and each gas introduction system including a switching means for switching the kind of gas to be supplied from the gas introduction system to the vacuum chamber according to whether the gas ion beam is used for sample machining or sample observation. In the ion beam machining and observation device with the above structure, the switching means includes a control device having a function to memorize at least two or more gas discharge voltages and capable of switching the gas discharge voltages. As such, the kind of the gas is switched based on a switching operation of the discharge voltages. In the ion beam machining and observation device with the above structure, the first gas contains at least any one of argon, xenon, krypton, neon, oxygen, and nitrogen, while the second gas is either hydrogen gas or helium gas, or mixed gas. (5) A sample cross section observation method of the present invention, where a gas ion beam emitted from an ion source capable of generating at least two or more kinds of gas ions with different mass numbers is irradiated onto a sample, includes the steps of: irradiating a gas ion having a relatively large mass number among at least the two or more kinds of gas ions, so as to form a roughly vertical cross section to the surface of a sample; and irradiating a gas ion having a relatively small mass number onto the cross section to be observed. In the sample cross section observation method demonstrated above, for cross sectional observation the ion with a relatively small mass number is irradiated at a lower current than a maximum current used for irradiating the ion with a relatively large mass number. The sample cross section observation method demonstrated above includes the steps of: simultaneously generating at least two kinds of gas ions by the ion source; mass-separating at least the two kinds of gas ions with different mass number from each other and irradiating a gas ion beam having a relatively large mass number onto a sample to process a roughly vertical cross section to the sample surface; and changing mass-separating conditions to irradiate a gas ion beam having a relatively small mass number onto the cross section to be observed. In the sample cross section observation method demonstrated above, the ion having a relatively large mass number is a gas ion containing at least any one of argon, xenon, krypton, neon, oxygen, and nitrogen, while the ion having a relatively small mass number is either a hydrogen gas ion or a helium gas ion, or a mixed gas ion. Another aspect of the present invention provides a charged particle beam device including: a charged particle beam generating source; a charged particle beam optical system for focusing and irradiating a charged particle beam onto a sample; a holder for keeping the sample; and a gas gun, wherein a material gas of a charged particle beam used for extracting a micro-sample piece is switched with a material gas used for a volume layer including a hole fill processing following the extraction of a micro-sample piece. Therefore, the ion beam machining and observation technique according to the present invention can be advantageously used for observing a cross section of an electronic component such as semiconductor devices including a semiconductor memory, a microprocessor, a semiconductor laser, etc., and a magnetic head, by using ion beams extracted from the same ion source to process a sample and to observe a machined portion of the sample. Moreover, the present invention technique is capable of reducing the amount of time it takes to fill up a processed hole, while ensuring a high degree of flatness at a filled hole area. Hereinafter, preferred embodiments of the present invention will be set forth in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the invention. FIG. 1 illustrates an ion beam machining and observation device according to one embodiment of the present invention. Particularly, the device of this embodiment is capable of irradiating two kinds of gas ions onto a sample by using a duoplasmatron 1 as a plasma ion source. In general, brightness of the plasma ion source is lower than brightness of a liquid metal ion source such as Ga by at least 2 to 3 orders of magnitude. Therefore, in case of this embodiment a stencil mask 5 having a predetermined shape aperture is inserted into the mid course of an ion beam irradiation system inside an ion beam column 21, and the aperture shape is projected onto a sample to obtain a projected beam for use. Preferably, inert gases or the kind of an element like oxygen and nitrogen may be chosen as the kind of the ion for the ion source such that electrical properties of a device are not affected thereby, and defects are much less likely to occur even when a completely machined wafer by using an ion beam is returned to the production line. A vacuum sample chamber 23 is disposed in the lower part of the ion beam column 21, and a first sample stage 13 on which a sample 11 is placed, a secondary particle detector 12, and a precursor gas dispenser 18 are housed in the vacuum sample chamber 23. The device of this embodiment also includes a probe 15 for delivering a sample piece extracted from the sample 11 on the first sample stage 13 by using ion beam machining, a manipulator 16 for driving the probe 15, and a second sample stage 24 on which a micro sample 303 is placed. Needless to say, inside the ion beam column 21 is maintained under vacuum. A control section for the ion beam machining and observation device is constituted by a duoplasmatron controller 91, a lens controller 94, a stencil mask controller 95, a first sample stage controller 14, a manipulator controller 17, a controller for precursor gas dispenser 19, secondary particle detector controllers 27 and 28, and a central processing unit 98. Among them, the central processing unit 98 has a display to provide an image generated based on a detection signal provided from the secondary particle detector 12, or information inputted by information input means. Here, the first sample stage 13 is provided with a linear transposition mechanism which transposes it in two orthogonal directions in a sample mounting plane, a linear transposition mechanism which transposes it in a vertical direction to the sample mounting plane, a rotation mechanism which rotates it in the sample mounting plane, and an inclination function of varying an irradiation angle of an ion beam onto a sample by rotating around an inclined axis, and these controls are all performed by the first sample stage controller 14, under a command from the central processing unit 98. Because the second sample stage 24 is positioned on the first sample stage 13, the linear movement in two orthogonal directions in the sample mounting plane, the linear movement in a vertical direction to the sample mounting plane, the rotation in the sample mounting plane, and the inclination resulted from the rotation around the inclination axis are made possible by moving, rotating, and inclining the first sample stage 13. FIG. 2 is a detailed view of an ion source having a gas supply mechanism according to the present invention. The gas supply mechanism includes two systems, each system being constituted by a gas cylinder 53 or 54 having a cylinder valve 51 or 52, a pressure regulator valve 55 or 56, a stop valve 57 or 58, and a needle valve 59 or 60 to regulate a small amount of gas volume. The first gas cylinder 53 in one system is filled up at high pressure with any one of argon, xenon, krypton, neon, oxygen, and nitrogen. The second gas cylinder 54 on the other side is filled up with helium or hydrogen at high pressure. The duoplasmatron is composed of a cathode 71, an intermediate electrode 72, an anode 73, a magnet 74, etc. In this embodiment it is assumed that the first gas cylinder is filled up with xenon, and the second gas cylinder is filled up with hydrogen. The operation of the ion source will now be described. An operator opens the cylinder valve 51 of the xenon cylinder, and adjusts an internal pressure of the gas tube using the pressure regulator valve 55. Next, the operator opens the stop valve 57 functioning as a gas supply opening/closing valve for sake of the ion source. Lastly, the operator adjusts the gas volume flow rate to the ion source by using the needle valve 59. For instance, the adjustment is made to let the vacuum level of the ion source be several Pa, so that a gas discharge is generated when a voltage of approximately 1 kV is impressed between the cathode 71 and the anode 73. Xenon ions are then extracted from this discharge plasma through an anode hole. That is to say, an ion beam 75 is emitted in a direction of an extractor electrode 76 having earth potential by applying a high voltage of 20 kV to the ion source. In addition, a voltage of 20 kV (the ion source voltage) is applied to the block surrounded by the dotted line 85 in FIG. 2. To maximize the amount of a xenon ion beam, the operator adjusts the gas volume flow rate with the needle valve 59, and adjusts the discharge voltage as well. With a needle valve adjustment knob 61 being fixed, the discharge voltage is memorized in the (duoplasmatron) controller 91. Next, the operator closes the stop valve and releases the application of the discharge voltage to stop the xenon discharge. Next, the operator opens a bypass valve 81 to exhaust xenon in the ion source by a vacuum pump 82. The ion source column is also exhausted by a vacuum pump 83. Similarly, for hydrogen gas, the operator opens a hydrogen cylinder valve 52, adjusts the internal pressure of the gas tube with the pressure regulator valve 56, and opens the stop valve 58. Lastly, the operator manipulates the needle valve 60 to adjust the gas volume flow rate in the ion source and cause a gas discharge. As in done in the case of xenon, the operator maximizes the amount of a hydrogen ion beam by adjusting the gas volume flow rate with the needle valve 60, and adjusting the discharge voltage as well. With a needle valve adjustment knob 62 being fixed, the discharge voltage is memorized in the controller 91 for duoplasmatron. Likewise, to switch the hydrogen beam to the xenon beam, the operator closes the stop valve 58 and releases the application of the discharge voltage to stop the hydrogen discharge. Then the operator opens the bypass valve 81 to exhaust hydrogen in the ion source. In order to generate xenon ions, the operator opens the stop valve 57 of xenon and switches to the discharge voltage being memorized. Therefore, switching of gas is accomplished by operating the stop valve and switching of the discharge, while leaving the respective needle valves in their positions. In general, xenon and hydrogen are different in terms of the amount of gas that should be present in the ion source in order to maximize the emission amount of ion beams. Also, it is known that the needle valve for use in adjustment of a very low gas volume flow rate is poor in reproducibility. Thus, in case that only one needle value is available to switch the kind of gas, the operator must adjust the needle valve for every switching operation and it is not easy either to do the gas switching speedily. However, this embodiment realizes a speedy gas switching by installing two kinds of independent, discrete gas supply systems under optimum conditions in advance. In addition, these gas switching operations can be manipulated mainly by the central processing unit 98. In detail, the central processing unit 98 shows on its display kinds of gases, an image of gas switch, button(s), etc. Therefore, when the operator selects the kind of a desired gas or the switch shown on the display, and the gas switching operation is executed automatically. The following will now explain the operation of the ion beam irradiation system. The operation of the ion beam irradiation system is controlled by commands from the central processing unit 98. First, a condenser lens 2 converges a xenon ion beam emitted from the duoplasmatron 1 (i.e. an ion source) to near the center of an objective lens 3. That is, a voltage being applied to an electrode of the condenser lens 2 is set to a precalculated value provided by the central processing unit 98 in advance to satisfy the condition. The xenon ion beam passes through a stencil mask 5 having a rectangular hole. The objective lens 3 is controlled such that the stencil mask 5 can be projected onto a sample. Again, a voltage being applied to the electrode of the objective lens 3 is set to a precalculated value provided by the central processing unit 98 in advance to satisfy the condition. In result, a rectangular shaped ion beam is irradiated onto the sample. Since the shaped beam is utilized, it is possible to irradiate a high current beam of approximately 100 nA onto the sample. The shaped ion beam is continuously irradiated to form a rectangular hole at the sample. Formation of the rectangular hole is finished such that the hole has a sufficient depth, i.e. deeper than the depth designated for observation, and is roughly perpendicular to the sample surface. Next, the sample stage controller inclines the first sample stage 13 as shown in FIG. 3, allowing the operator to observe the sample cross section formed by using an ion beam from the ion beam irradiation system. Also, the ion source is operated in order of the above-described procedure to switch xenon to hydrogen. Voltage conditions for the condenser lens 2 and the objective lens 3 are also changed, and an anode hole of the ion source is used as a light source. In this way, an ion beam of a smaller size is projected onto the sample. Accordingly, a micro dot-shaped beam as small as a several millionth of the anode hole diameter can be obtained on the sample. Even though a current used in this case is as small as several pA, the beam diameter can be decreased down to several tens of nanometers. This micro ion beam scanned on the sample surface enables to obtain a detailed observation image. In other words, the sample can be observed with higher resolution by using a smaller converged ion beam current than the shaped ion beam current used for machining. Traditionally, when a xenon ion beam, which had been already used for machining, is used again for observation, the surface of a sample is likely to be cut out and this consequently makes it harder to have a detailed observation of the sample. On the contrary, the present invention uses a hydrogen ion beam to reduce the amount of a sample being cut out, allowing a detailed observation for the operator. Further, the observation in use of a hydrogen ion beam helps the operator to observe not only the cross section of a sample, but also the structure of the sample surface, foreign matter, and defects. To obtain a sample image, this embodiment suggests that an ion source should be projected onto a sample to form a dot-like hydrogen ion beam of a smaller size and the ion beam should be scanned on the sample. But it is also possible to adopt a mechanism for limiting a mask hole size on the stencil mask and scanning the shaped (or projected) beam, which has been projected through the hole, over the sample. In this case, the lens voltage does not need to change for machining and observation, a beam irradiation axis does not get dislocated, and the control operation on the device becomes quite stable. The mechanism for limiting the size of the mask hole may have a stencil mask structure having a built-in small diameter hole, or a structure which superimposes a fine aperture on a stencil mask. When the stencil mask is irradiated by an ion beam, a mask hole may for example be enlarged or a plate thickness of the mask can be reduced by sputtering, eventually deforming the hole shape. Therefore, it is preferable to use a stencil mask with a thick plate. Meanwhile, it is usually difficult to bore a micro hole in a thick plate. As such, when an ion with a relatively large mass number, e.g., xenon, is used for machining, a mask having a relatively thick plate is used, while an aperture having a small plate thickness is used for hydrogen with a small sputtering rate compared with xenon. Accordingly, it becomes possible to form an even smaller hole at the aperture, and a micro beam thusly obtained allows a high-resolution observation. This embodiment employed the duoplasmatron as an ion source, but the same effects are obtained by using a plasma ion source using microwaves, an inductively coupled plasma ion source, a multi-cusp type ion source, a gas field ion source, and so on. The secondary electron detector may detect not only secondary electrons but also reflection electrons or secondary ions. The secondary electron detector controllers are configured with two systems 27 and 28. The secondary electron detector controller 27 on one side amplifies a signal from the detector by direct current amplification. The secondary electron detector controller 28 on the other side counts pulses of a signal from the detector to measure strength of the signal. In the latter case, since detected particles are counted directly, it is possible to remove noises of the detector and increase the detection sensitivity. Traditionally, a sufficient amount of ion beams or electron beams was irradiated onto a sample, so there was no need to count signal pulses. However, in case of irradiating a fine (or micro)-hydrogen ion beam, lower ion current is used, so the detector controller 28 which measures signal strength by counting pulses becomes effective in such case. Accordingly, the operator is able to observe the sample with higher resolution than that of the traditional method. Meanwhile, there is a counting limit of 1 million pulses per second, and pulse counting is not possible in high current conditions above picoampere current levels. Thus, two controllers may be switched according to current magnitude of an ion beam being irradiated. It is another option to monitor current of charged particles being irradiated onto a sample, thereby automatically switching the two controllers by the central processing unit 98. Moreover, machining by an ion beam, the probe 15 at a front end of the manipulator 16, and an ion beam assisted deposition layer may be used to extract a micro sample 303 from a sample 11 and place it at the second stage 24. The micro sample can be prepared to a membrane suitably for TEM samples. A procedure associated with this will be explained later in sequential order in Embodiment 2. As explained so far, the ion beam machining and observation device and the machining/observation method of this embodiment made it possible to process a sample cross section by using a xenon projected ion beam and observe the cross section by using a micro-hydrogen ion beam. That is, once an abnormal spot such as a defect or foreign matter in a semiconductor circuit pattern is prepared to a cross section sample, one can observe the cross section of the defect or foreign matter and analyze their causes. Especially this embodiment performs a highly accurate machining by using a projected ion beam. Even if an ion source may have low brightness, the cross section machining can be done within a short period of time by increasing the beam current and improving the machining precision. This means that an ion beam of gaseous elements such as an inert gas, oxygen or nitrogen, which do not much affect the sample properties, may be used in replacement of Ga, which is very likely to cause defects in the manufacturing process of a semiconductor device. Therefore, for improving the semiconductor device manufacturing yield, there is provided a novel inspection and analysis method, which can form a cross section by an ion beam without contaminating a wafer with metals such as Ga, yet allowing an operator to observe the cross section without splitting a wafer. With this method, wafers do not need to be discarded due to testing, and defects are not generated even if wafers from which samples for inspection are removed are returned to the process. Also, wafers can be tested without being split, new defects are not created and expensive wafers are not going to be wasted. Consequently, the manufacturing yield of semiconductor devices can be improved. Unlike the ion beam machining and observation device discussed in Embodiment 1 where ion beam irradiation systems are arranged in a perpendicular direction, an ion beam machining and observation device of this embodiment has ion beam irradiation systems arranged in a direction inclined from the perpendicular direction, and a stage plane is fixed in a horizontal direction. Moreover, the device of this embodiment includes a mass divider installed midway in the ion beam path to get rid of ions of large mass numbers when ions of relatively small mass numbers are irradiated. This embodiment will also explain a means for preparing a TEM (Transmission Electron Microscope) sample by extracting a micro sample from a sample. This embodiment also uses a mask aperture shaped ion beam projected on a sample. FIG. 4 illustrates an ion beam machining and observation device of this embodiment. The ion beam machining and observation device includes a duoplasmatron 1, which is an ion source, emitting gas ions such as argon, neon, xenon, krypton, oxygen, nitrogen, helium, hydrogen, a mass spectrometry 300, an ion source limiting aperture 26, a condenser lens 2, an objective lens 3, an ion beam scanning deflector 4, a stencil mask 5, and an electron beam column 21 for housing these elements. The mass spectrometry 300 in this embodiment is a so-called ExB mass separator which provides an electric field and a magnetic field respectively being perpendicular to an ion beam, the electric field and the magnetic field being in a mutually perpendicular relationship. Although this embodiment used a permanent magnet, it may also use an electro-magnet. Only the magnetic field may be associated with mass separation. The device is provided with an electron beam irradiation system constituted by an electron gun 7, an electron lens 9 for converging an electron beam 8 emitted from the electron gun 7, an electron beam scanning deflector 10, and an electron beam column (SEM column) 22 for housing these elements. A vacuum sample chamber 23 is disposed in the lower part of the ion beam column 21 and the SEM column 22, and a first sample stage 13 on which a sample 11 is placed, a secondary particle detector 12, and a precursor gas dispenser 18 are housed in the vacuum sample chamber 23. Moreover, the device includes a probe 15 for delivering a sample piece extracted from the sample on the first sample stage by using ion beam machining, a manipulator 16 for driving the probe 15, and a second sample stage 24 on which a micro sample 303 is placed. Needless to say, inside the ion beam column 21 is maintained under vacuum. Here, both the node (irradiation spot) of an ion beam on the sample and the node of an electron beam on the sample are aberrant from the center of the sample mounting surface, and are located at different positions. That is, an ion beam irradiation axis 301 and an electron beam irradiation axis 302 do not cross with each other. A control section for this device the ion beam machining and observation device is constituted by a duoplasmatron controller 91, a mass separator controller 62, an ion source aperture controller 93, a lens controller 94, a stencil mask controller 95, an ion beam scanning deflector controller 96, a first sample stage controller 14, a second sample stage controller 25, a manipulator controller 17, a controller for precursor gas dispenser 18, secondary electron detector controllers 27 and 28, an electron beam irradiation controller 97, and a central processing unit 98. Among them, the central processing unit 98 has a display to provide an image generated based on a detection signal provided from the secondary particle detector 12, or information inputted by information input means. Reference numeral 30 in the drawing designates a sample height sensor controller 30 to control a sample height sensor 29. FIG. 5 shows an ion source having a gas supply mechanism used for this embodiment. The gas supply mechanism includes two kinds of gas cylinders 53 and 54, each having a cylinder valve 51 or 52, pressure regulator valves 55 and 56 for the respective cylinders, stop valves 57 and 58 for respective gas systems, and a needle valve 59 to regulate a small amount of gas volume. The first gas cylinder 53 is filled up at high pressure with any one of argon, xenon, krypton, neon, oxygen, and nitrogen. The second gas cylinder 54 on the other side is filled up with helium or hydrogen at high pressure. In this embodiment it is assumed that the first gas cylinder is filled up with argon, and the second gas cylinder is filled up with helium. The operation of the ion source will now be described. An operator opens the cylinder valve 51 of the argon cylinder 53, and adjusts an internal pressure of the gas tube using the pressure regulator valve 55. Next, the operator opens the stop valve 57 functioning as a gas supply opening/closing valve for sake of the ion source. Lastly, the operator adjusts the gas volume flow rate to the ion source by using the needle valve 59. For instance, the adjustment is made to let the vacuum level of the ion source be several Pa, so that a gas discharge is generated when a voltage of approximately 1 kV is impressed between a cathode 71 and an anode 73. Argon ions are then extracted from this discharge plasma through an anode hole. In addition, a voltage of 20 kV (the ion source voltage) is applied to the block surrounded by the dotted line 85 in FIG. 5. To maximize the amount of an ion beam 75, the operator adjusts the gas volume flow rate with the needle valve 59, and adjusts the discharge voltage as well. With a needle valve adjustment knob 61 being fixed, the discharge voltage is memorized in the controller 91 for duoplasmatron. Next, the operator closes the stop valve 57 and releases the application of the discharge voltage to stop the argon discharge. Next, the operator opens a bypass valve 81 to exhaust argon in the ion source by a vacuum pump 82. The ion source column is also exhausted by a vacuum pump 83. Similarly, for helium gas, the operator opens a helium cylinder valve 52, adjusts the internal pressure of the gas tube with the pressure regulator valve 56, and opens the stop valve 58. Meanwhile, the needle valve 59 should remain fixed. The gas volume flow into the ion source is adjusted by a secondary pressure of the pressure regulator valve 56 to thereby generate a gas discharge. Again for the helium, the operator maximizes the amount of a helium ion beam by adjusting the gas volume flow rate, and adjusting the discharge voltage as well. The discharge voltage is memorized in the (duoplasmatron) controller 91. Next, to switch from a helium beam to an argon beam, the operator closes the stop valve 58 and releases the application of the discharge voltage to stop the helium discharge. Then the operator opens the bypass valve 81 to exhaust helium in the ion source. In order to generate argon ions, the operator opens the stop valve 57 of argon and switches to the discharge voltage being memorized. Therefore, switching of gas is accomplished by operating the stop valve and switching of the discharge, while leaving the needle valve 59 in its set position. In general, argon and helium are different in terms of the amount of gas that should be present in the ion source in order to maximize the emission amount of ion beams. Although this embodiment using one needle valve for gas switching may not have a high precision for regulating the gas volume flow rate compared with the device of Embodiment 1 having a dual-system gas supply mechanism, since it uses only one needle valve, its overall structure becomes simple. The following will now explain the operation of the ion beam irradiation system. First, an argon ion beam is extracted from the duoplasmatron 1. The mass separator 300 is actuated to make the argon ion beam pass through it. The function of the mass separator is performed when the mass separator controller operates on a command from the central processing unit. The argon ion beam having passed through the mass separator (or mass analyzer) 300 is converged near the center of the objective lens 3 by the condenser lens 2. That is, a voltage being applied to an electrode of the condenser lens 2 is set to a precalculated value provided by the central processing unit 98 in advance to satisfy the condition. The argon ion beam passes through the stencil mask 5 having a rectangular hole. The objective lens 3 is controlled such that the stencil mask 5 can be projected onto a sample. Again, a voltage being applied to the objective lens 3 is set to a precalculated value provided by the central processing unit 98 in advance to satisfy the condition. In result, a rectangular shaped ion beam is irradiated onto the sample. Since the shaped beam is utilized, it is possible to irradiate a high current beam of approximately 100 nA onto the sample. The shaped ion beam is continuously irradiated to form a rectangular hole at the sample. Formation of the rectangular hole is finished such that the hole has a sufficient depth, i.e. deeper than the depth designated for observation, and is roughly perpendicular to the sample surface. Next, the sample stage controller rotates the first sample stage 13 by 90 degrees as shown in FIG. 6, allowing the operator to observe the sample cross section formed by using an ion beam from the ion beam irradiation system. FIG. 6 respectively shows a side view and top view of the cross section of a sample that is machined and observed by using an ion beam. In detail, the left side of FIG. 6 shows that a rectangular hole 202 is formed by irradiating an argon ion beam 201 onto a sample 11 from an inclined direction, and the right side of FIG. 6 shows a sample cross section rotated by 90 degrees. The ion source is operated in order of the above-described procedure to switch from argon to helium, and the mass analyzer (or mass separator) 300 is actuated to make a helium ion beam pass through it. Voltage conditions for the condenser lens 2 and the objective lens 3 of the ion beam are also changed, and an anode hole of the ion source is used as a light source. In this way, an ion beam of a smaller size is projected onto the sample by the condenser lens and the objective lens. Accordingly, a micro dot-shaped beam as small as a several millionth of the anode hole diameter can be obtained on the sample. Even though a current used in this case is as small as several pA, the beam diameter can be decreased down to several tens of nanometers. By irradiating and scanning this micro helium ion beam 203 onto a vertical cross section of the sample as shown in the right side of FIG. 6, a detailed observation image of the cross section can be obtained. In other words, the sample can be observed with higher resolution by using a smaller converged ion beam current during observation than the shaped (projected) ion beam current used during processing. When the mass analyzer is not used, sometimes remaining argon in the ion source is ionized and irradiated onto the sample. These argon ions cut out the sample surface, making it harder to observe the sample. On the contrary, the present invention uses only helium ions for observation by the mass analyzer to reduce the amount of the sample being cut out, so that the operator may have a detailed observation of the sample. The observation function in use of a helium ion beam helps the operator to observe not only the cross section of a sample, but also the structure of the sample surface, foreign matter, and defects. Needless to say, the ion source with the dual-system gas supply mechanism depicted in FIG. 2 exerts the same effects when incorporated into the device of this embodiment. Moreover, argon and helium gases may be introduced simultaneously into the ion source, or mixed gas of argon with helium prepared in advance may be introduced to generate argon and helium ions at the same time. Even in this case, an argon ion beam is not irradiated onto the sample, while a helium ion beam is being irradiated. It is not necessarily easy to increase the ion current to a maximum for each of those two kinds of ions, but the mass analyzer takes exclusive responsibility of switching the kind of ions. The operation of the electron beam irradiation system will now be explained. An electron beam 8 emitted from the electron gun 7 is converged by the electron lens 9, and irradiated onto the sample 11. At this time, the electron beam scanning deflector 10 irradiates the electron beam 8 over the sample surface while scanning it, and the secondary particle detector 12 detects secondary electrons emitted from the sample surface, and changes the intensity of them to image brightness to help the operator to observe the sample. According to this sample observation function by electron beam, the operator can observe abnormal spots such as defects and foreign matter in circuit patterns formed on the sample. Especially, the structural feature of this device having an electron beam irradiated in a direction perpendicular to the sample is advantageous for getting information on abnormalities of a large hole with a high ratio of depth to diameter. Although the observation function by electron beam of this device is originally for observing a cross section of defects or foreign matter of a sample, it can also be used for discovering a machining endpoint by observing the cross section of an electron microscope membrane sample. That is, this device is built to enable the operator to observe the sample cross section by using an ion beam as well as an electron beam. In general, an observation image by an ion beam is characterized or advantageous by its high element contrast, while an observation image by an electron beam is characterized or advantageous by its high spatial resolution. Therefore, the sample observation through the device of this embodiment can benefit from both sides. As aforementioned, both the node (irradiation spot) of an ion beam on the sample and the node of an electron beam on the sample are aberrant from the center of the sample mounting surface, and are located at different positions. This gives an enough space to place the objective lenses near the sample, without getting interfered spatially with each other, so that work distance of each objective lens can be shortened. In other words, the ion beam and the electron beam are excellent in micromachining or high current performance. FIG. 7A and FIG. 7B respectively illustrate a sequential procedure for extracting a micro sample from a sample on the first stage by using a projected ion beam. Drawings on the left hand side in FIGS. 7A and 7B are top views of a sample, and drawings on the right hand side in FIGS. 7A and 7B are side views of a sample. Since the device for this procedure uses a projected ion beam of micron-size, it is not necessarily recommended to mark a machining position by using an ion beam. For this reason, the device uses an electron beam of nano-size. First of all, the first sample stage 13 is transposed so that an electron beam can be irradiated onto a sample region from which a micro sample is extracted. Referring (a) in FIG. 7A, a deposition gas is fed from the precursor gas dispenser 18 and an electron beam 8 is irradiated. A deposition layer is thereby formed on the surface of a sample 11 in preparation of two end marks 130 that pinpoints an observation cross section. That is, the operator specifies the observation positions with marks while watching the image of the same on the screen of the display of the central processing unit 85. As the processor uses a micro-size projected ion beam in cooperation with an electron beam, nano-order marking became possible. Next, the first sample stage 13 is transposed so that a first projected ion beam 131 of argon can be irradiated near the marks. Here, a stencil mask is transformed into a hole shape illustrated in FIG. 8(a). In doing so, a current of approximately 200 nA is obtained. Therefore, as shown at (b) of FIG. 7A, the first projected ion beam 131 of argon is irradiated until two marks are enclosed inside, and a first projected hole 132 (a projected hole A) of about 15 μm in depth is formed. Next, the kind of ion beam is switched from argon to helium, and the stencil mask is transformed into a circular hole as shown in FIG. 8(b). At this time, the cross section of the beam becomes roughly circular. However, the cross section of the beam on the sample is elliptical because the ion beam is inclined against the sample, but when the ion beam is scanned across the sample, the operator can observe the sample. The switching operation is executed on a switching command the device operator has inputted through an information input means, or in response to a switching control signal transmitted from the central machining device to the mask control mechanism. Referring to (c) of FIG. 7A, the sample stage controller rotates the sample by about 180 degrees using the vertical axis to the sample surface as a rotation axis. When an elliptical helium ion beam is irradiated onto the sample, secondary electrons are generated from the sample and a secondary electron image is thereby formed. This secondary electron image goes through image processing to thereby recognize an initially formed hole. Referring to (d) of FIG. 7A, while watching the secondary electron image obtained by the irradiation of an helium ion beam 133, the device operator transposes a probe 15 by operating the probe controller so that the end of the sample to be extracted comes in contact with a probe at the tip of a transport means. Using the helium ion beam instead of the argon ion beam, the damage level of the probe due to the ion irradiation is very low. To fix the probe to the sample to be extracted, the ion beam is scanned while a deposition gas is led to flow out into an area including the tip of the probe. In so doing, a deposition layer 134 is formed in the ion beam irradiation area, and the probe and the sample to be extracted are connected. Next, the kind of ion beam is switched from helium to argon, and the stencil mask is also adjusted in advance to let the sample irradiation position of a projected beam 135 having the shape shown in FIG. 8(c) be set by a circular beam. At (e) of FIG. 7B, the ion beam controller is operated to control the ion beam irradiation position based on the sample shape information obtained by irradiating an elliptical beam, and a second projected ion beam 135 is irradiated until two marks together with the first projected beam are enclosed inside, and a second projected hole 136 (a projected hole B) of about 15 μm in depth is formed. This projected hole B intersects with the first projected hole A formed by the first projected ion beam. Through the steps (a) of FIG. 7A through (e) of FIG. 7B, a wedge-shaped micro sample 137 having a triangular cross section, including the marks, is held in the probe. Next, the kind of ion beam is switched from argon to helium, and the stencil mask is transformed into a circular hole as shown in FIG. 8(b). As shown in (f) of FIG. 7B, while watching a secondary electron image obtained by irradiating an ion beam, the device operator manipulates the probe controller to move the probe position, and the extracted micro sample 137, being in contact with the tip of the probe, is transposed to a sample holder 140 on the second stage. At (g) of FIG. 7B, a helium ion beam is then irradiated onto a contact area between the micro sample 137 and the sample holder 140, in the presence of a deposition gas being introduced. A deposition layer 138 is thereby formed in the ion beam irradiation area, and the micro sample 137 is connected to the sample holder 140. Next, referring to (h) of FIG. 7B, the kind of ion beam is switched from helium to argon, and the argon ion beam irradiation and sputtering are carried out to remove the deposition layer which bridges the probe and the micro sample. In result, the probe 15 is separated from the micro sample 137. One of structural features of the ion beam device of this embodiment is that the ion beam column is inclined against the sample. Thanks to this structure, the sample stage does not need to be inclined but be rotated only to extract a micro sample by using an ion beam. In addition, the device includes the probe 15 to transport the micro sample 137 which has been extracted from the sample 11 on the first sample stage 13 by ion beam machining, and the second sample stage 24 on which the micro sample is placed, and has an inclination function such that the device operator is able to vary the irradiation angle of an ion beam onto the micro sample when the second sample stage rotates around an inclination axis. Using the inclination nature of the second sample stage, the operator may arrange the cross section of a sample to face the perpendicular direction against a helium ion beam. In so doing, the operator may have a detailed cross sectional observation from the vertical direction. That is, the device is operated to enable the cross section cutting work by an argon ion beam and the observation by a helium ion beam, and the device operator can obtain three-dimensional information from the sample by repeating cross section cutting work and the observation. Further, a three-dimensional image can be built based on a number of two-dimensional observed images. Next, for the production of an electron microscope sample, three kinds of stencil mask holes prepared to decrease the beam current in the order roughing, intermediate machining and finishing are switched one after another to reduce the sample thickness. Finally, a thin finish is done to produce a wall with an observation area having a thickness of about 100 nm or less to give an electron microscope sample. As a result of the aforesaid machining, a TEM observation area is created. So far, an example has been described where the operator controls the device using the input unit of the central processing unit, but it is also possible to provide a storage means such as a memory in the central processing unit, and store all the process control conditions as a control sequence such that sampling can be fully automated. After membrane machining is performed as described above, the micro sample is introduced into the TEM sample chamber. In TEM observation, one can observe cross sections of defects or foreign matter with higher resolution than in SEM observation, and analyze the cause of those defects in more detail from the observation results. Although this embodiment used an argon ion beam for machining, it is evident that the same effects can be obtained by using nitrogen, oxygen, neon, xenon, krypton, etc. Especially in case of the argon beam, the ratio of its isotopes with mass number 40 is as high as 99.6%, so there is a small decrease in current even after mass separation. Moreover, this embodiment used a helium ion beam for observation, but it is evident that the same effects can be obtained by using hydrogen. Especially in case of the helium beam, its molecular ion is small and the ratio of ion with mass number 4 (4He) is high, so there is a small decrease in current even after mass separation. In this embodiment, the duoplasmatron was used as an ion source, but the same effects are obtained by using a plasma ion source using microwaves, an inductively coupled plasma ion source, a multi-cusp type ion source, a gas field ion source, and so on. The device of this embodiment has a transmitted-ion detector 1201 to detect hydrogen ions having transmitted the sample, and allows the operator to obtain a so-called scanning transmission ion microscopy image and to observe a sample with high spatial resolution. In addition to the effects and benefits of Embodiment 1, the ion beam machining and observation device and method, and a micro sample production method of this embodiment have other effects and benefits. Namely, the irradiation of an ion with relatively large mass number can be avoided at the time of irradiating a helium ion beam, and since the argon ion can be exhausted and substituted to the helium ion beam within a shorter period of time, the total amount of time it takes for ion beam switching can be reduced. Moreover, ions of impurities such as metal ions which are generated by the ion source are removed from the mass separator, and do not reach the sample. In this manner, the sample is not contaminated with impurities, and the device manufacturing yield is not decreased. FIG. 9 illustrates an embodiment of using a gas field ion source as an ion source. The configuration of the gas supply mechanism of this embodiment is identical to that of the system explained in Embodiment 1. Therefore, the description on its operation will be omitted in this embodiment. In this ion source, the apex of an ion emitter tip 402 made of tungsten is machined sharply and cooled to several tens of K by a freezer 401. A gas is also cooled and a strong electric field is applied to the ion emitter tip 402, to thereby extract an ion beam from near the emitter tip. In case of extracting helium ions or hydrogen ions, as shown in FIG. 10, a nano-pyramid structure 404 of an atom is formed at an ion emitter tip apex 403. Since ions are produced only near one through three atoms, an ion source with a very high brightness is realized. That is, an ion beam 405 of 1 nm or less in diameter is obtained on a sample, the sample can be observed at very high spatial resolution. However, this is not suitable for machining because both helium and hydrogen ions have small mass and small ion beam current. For machining, the kind of gas to be fed to the ion source is thus switched from helium to argon, and the nano-pyramid structure at the ion emitter tip apex should be removed by electrolytic evaporation. In so doing, ions are produced from a comparatively broad area near the ion emitter tip apex, and an argon ion beam 406 of the order of nano-amperes is obtained to enable machining. Next, the nano-pyramid structure of an atom is formed again to extract a micro helium ion beam. The nano-pyramid structure may be formed by depositing palladium or platinum on tungsten and then annealing at high temperature. In addition to the effects and benefits of Embodiment 1, the ion beam machining and observation device and method, and a micro sample production method of this embodiment have other effects and benefits. That is, an ultra-fine micro helium or hydrogen ion beam, and high-current argon or xenon ion beam obtained from machining make it possible to perform ultra-fine machining or ultra-high-resolution observation. As has been explained in detail, the present invention provides a device for observing an electronic component cross section, which can be manufactured at lower prices than in the related art. Moreover, the present invention sample cross section observation method can be implemented at lower price than in the related art. Also, the ion beam machining and observation device of the present invention is capable of shortening a cross section forming time by an ion beam. In addition, the present invention provides a novel inspection and analysis method, through which wafers do not need to be discarded due to testing by using an inert gases, oxygen, or nitrogen ions for the ion beam, and defects are not generated even if wafers from which samples for inspection are taken are returned to the process. By using the electronic component manufacturing method of the present invention, wafers can be tested without being split, new defects are not created and expensive wafers are not going to be wasted. As a result, the manufacturing yield of electronic components is improved. The ion beam machining and observation device and the sample cross section observation method according to the present invention include the following configuration examples. (1) An ion beam machining and observation device, including: a sample stage for holding a sample; an ion source for generating ion beams of at least two different kinds of gases; and an irradiation optical system for irradiating an ion beam onto the sample held on the sample stage, wherein the ion beam irradiating optical system is a transmission ion beam irradiation system which irradiates an ion beam onto the sample through a mask having a desired shape aperture and which includes two or more ion beam lenses, and a mask driving mechanism with a variable aperture or an aperture driving mechanism. (2) An ion beam machining and observation device, including: a sample stage for holding a sample; a gas field ion source for generating ion beams of at least two different kinds of gases; and an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, wherein the ion beam machining is performed by using any one of neon ion beam, argon ion beam, krypton ion beam, and xenon ion beam, and the observation is performed by using either helium ion or hydrogen ion. (3) An ion beam machining and observation device, including: a first sample stage for holding a sample; an ion source for generating ion beams of at least two different kinds of gases; an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, a probe for transporting a micro sample that is extracted from the sample by using a first kind gaseous ion beam machining process, and a second sample stage for holding a sample piece, wherein the probe and the micro sample are observed by a second kind of gaseous ion beam. (4) A sample cross sectional observation method using an ion beam machining and observation device provided with a sample stage for holding a sample roughly in a horizontal direction; an ion source for generating at least two kinds of gaseous ions with different mass numbers; and an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, the method including the steps of: irradiating the sample with ions having a relatively large mass number to form a cross section roughly perpendicular to the sample surface; inclining the sample stage around a horizontal axial center; and irradiating gaseous ions with a relatively small mass number onto the cross section and observing the same. (5) A sample cross sectional observation method using an ion beam machining and observation device provided with a sample stage for holding a sample roughly in a horizontal direction; an ion source for generating at least two kinds of gaseous ions with different mass numbers; and an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, while being inclined against a vertical axis, the method including the steps of: irradiating the sample with ions having a relatively large mass number to form a cross section roughly perpendicular to the sample surface; rotating the sample stage around a horizontal axial center; and irradiating gaseous ions with a relatively small mass number onto the cross section and observing the same. (6) An ion beam machining and observation method for sample observation by using an ion beam machining device which includes a sample stage for holding a sample; a gas field ion source for generating at least two kinds of gaseous ions with different mass numbers; and an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, the method including the steps of: performing a machining process by using any one of neon ion beam, argon ion beam, krypton ion beam, and xenon ion beam; and observing the sample by either helium ion or hydrogen ion. (7) An ion beam machining and observation method for sample observation by using an ion beam machining and observation device which includes a sample stage for holding a sample; a gas field ion source for generating at least two kinds of gaseous ions with different mass numbers; and an irradiating optical system for irradiating an ion beam onto the sample held on the sample stage, the method including the steps of: performing a machining process by using any one of neon ion beam, argon ion beam, krypton ion beam, and xenon ion beam; forming a nano-pyramid structure of an atom at an ion emitter tip apex; observing the sample by either helium ion or hydrogen ion; and removing the nano-pyramid structure of the atom. FIG. 11 is a brief schematic view of a charged particle beam processor according to one embodiment of the present invention. The charged particle beam processor shown in FIG. 11 is constituted by a holder 504 where a sample 13 is mounted and held; an ion source (charged particle beam generating source) 501 for generating an ion beam (charged particle beam) 502; an ion beam column 503 having a machining optical system (charged particle beam optical system) for guiding an ion beam 502 emitted from the ion source 501 to a processed spot; a stage 505 for driving the holder 504 in five-axis directions; a sample chamber 506; an exhaust system (not shown) for exhausting a FOUP (Front Opening Unified Pod), a atmosphere transport unit (not shown), a transport chamber (not shown), the sample chamber 506, etc.; a gas supply system 507 for supplying gas for an ion source (material gas for the charged particle beam, to be described) to the ion beam column 503; a secondary electron detector (SED) 508 for detecting secondary electrons generated from the surface of a sample 513 irradiated with the ion beam 502; a micro sampling unit 509 for extracting a micro sample (micro sample piece) from the sample 513; plural control systems (not shown) for controlling each of the constitutional elements mounted in the charged particle beam processor; a central control unit 510 for controlling the entire charged particle beam processor; a console 514 having a screen such as a GUI (Graphical User Interface); and a gas gun 511 for providing GAD (Gas Assisted Deposition) gas to a beam spot (processed spot) of the ion beam 501 and nearby areas. A GAE (Gas Assisted Etching) gas gun may also be added to perform high-speed hole machining. The sample 513 mentioned here is typically a wafer, but a magnetic head or liquid crystal can be a target sample as well. The following will now explain each unit one after another. The sample chamber 506 is connected to the exhaust system (not shown) composed of a turbomolecular pump, a dry pump, and an exhaust valve (none of them is shown), and a high vacuum level of 10 to 5 Pa can be obtained with no gas provided thereto. The sample chamber 506 may include a load lock chamber, a atmosphere transport robot (not shown), etc., such that the sample 513 may be taken into or taken out of it. The stage 505 is designed to be transposed in X and Y-axis directions (horizontal direction) and Z-axis direction (vertical direction), and can also rotate in R direction (rotation direction) or tilt in T direction (tilting direction). The stage 505 is usually tilted when the operator observes a cross section of the sample 513 after sputtering machining by the ion beam 502 is performed, or when a micro sample is extracted from the sample 513. Misalignment due to tilt is calibrated to suppress mismatching of the field of view. The stage 505 can be driven in X and Y-axis directions by means of ball screws/nuts, a DC motor, or an encoder. For instance, in case a φ300 wafer is used as the sample 513, it transposes in the X and Y-axis directions by a certain distance (about 320 mm) for several seconds. The sample 513 is positioned by using laser at a precision on the submicrometer order for example. Meanwhile, a wedge structure is employed to drive the stage 505 in the Z-axis direction, and this positioning also has a precision on the submicrometer order. The console 514 is composed of a display unit providing a GUI screen, an SEM image, an SIM image, etc., and an input unit such as a keyboard or a mouse. The secondary electron detector 508 has a built-in scintillator (not shown) to which positive-potential is applied. Reflected electrons or secondary electrons emitted from the surface of the sample 513 when the ion beam 502 is irradiated thereto are pulled by the electric field of the scintillator and accelerated to illuminate the scintillator. Light produced from the scintillator is then guided by a light guide (not shown) to enter a photomultiplier (not shown) and converted to an electric signal therein. The detected electric signal is synchronized with scanning of the ion beam 502 by the machining optical system, and a secondary electron image is thereby generated at the processed spot. The micro sampling unit 509 has a structure that can be transposed in three (X, Y, and Z-axis) directions. Each axis has a driving transposition distance within a several millimeter range to extract a defect region from the sample 513 and load it onto a mesh 589 (to be described in reference to FIG. 19). The micro sampling unit 509 may be driven by a linear actuator, or a piezoelectric element, and it can manipulate the probe 515 at a positioning precision of submicrometer order. The probe 515 is made out of tungsten for instance, and has a pointed apex portion with a curvature radius of 1 μm or less. If metal contamination due to tungsten is going to be a problem, the probe 515 may be made out of silicon, carbon, or germanium instead. The gas gun 511 has a gas nozzle 512. At the time of GAD, the gas nozzle 512 moves from its retreated position to near the processed spot of the sample 513 (several hundreds of μm above the processed spot). It takes only several seconds for the gas nozzle 512 to move from its retreated position to near the processed spot. Tungsten carbonyl (W(CO)6) is preferably used as a deposition gas ejected from the gas nozzle 512. Tungsten carbonyl is heated above the temperature of sublimation of a solid to a vapor, and decomposed under the irradiation of a focused ion beam (hereinafter abbreviated to FIB) to form a tungsten layer. If metal contamination due to tungsten is going to be a problem, a carbon based gas such as phenanthrene, or ortho-tetraethyl silicate producing a silicon oxide layer can be another option. The gas supply system 507 is constituted by plural (e.g., two in this example) gas cylinders 522A and 522B filled with charged particle material gases (X) (charged particle beam material gas) of different kinds from each other to be supplied to the ion source 501; a gas inlet tube 530, via which the charged particle beam material gases from the gas cylinders 522A and 522B are introduced to the ion source 501; stop valves 523A and 523B for circulating/blocking the charged particle beam material gases from the gas cylinders 522A and 522B, respectively; flow control valves 524A and 524B for controlling the flow volume rate of the charged particle beam material gases from the gas cylinders 522A and 522B, respectively; and a valve controller 525 that controls opening/closing of the stop valves 523A and 523B and openness of the flow control valves 524A and 524B. In case of this embodiment, the gas cylinders 522A and 522B are filled up with oxygen gas and argon gas, respectively. Here, the gas supply system 507 supplies two kinds of charged particle beam material gases to the ion source 501, but three or more kinds of charged particle beam material gases may be supplied to the ion source 501. Besides oxygen gas or argon gas, nitrogen gas, krypton gas, xenon gas, and neon gas can also be utilized. The stop valves 523A and 523B are used provisionally when the flow volume rate cannot be set to 0 by the flow control valves 524A and 524B only. However, if the flow volume rate can be set to 0 by the flow control valves 524A and 524B, the stop valves may be excluded. Although not shown, the charged particle beam processor has a Z sensor to measure height of the sample 513. With this Z sensor, one can measure the height of the sample 513 at a precision on submicrometer order, and fix the distance between the sample 513 and the ion beam column 503 to a constant value by using the sensing result and by driving the stage 505 in Z direction. Further, the charged particle beam processor includes an optical microscope (not shown) which is used to align the sample 513. The FIG. 12 shows an internal structure of an ion source cover 519 shown in FIG. 11. Referring to FIG. 12, since an accelerating voltage of about 30 kV is applied to the ion source 501 with respect to the ion source cover 519 having earth potential, at least 40 mm space is interposed between the ion source cover 519 and the ion source 501 for air insulation. The gas supply system 507 is connected to the ion source 501, and a charged particle beam material gas that flows in the gas inlet tube 503 is supplied to the ion source 501. Since the gas supply system 507 is maintained at earth potential, an insulator 517A is interposed between the system and the ion source 501 for insulation from the ion source 501. Likewise, an insulator 517B is interposed between the system and the ion beam column 503 for insulation from the ion beam column 503. A duoplasmatron is preferably used as the ion source 501. Besides the duoplasmatron, a gas field ion source such as helium or argon gas, an inductively coupled plasma ion source, an electron cyclotron resonance plasma ion source, etc., may also be utilized. When an operator controls the valves 523A, 523B, 524A, and 524B to let the charged particle beam material gases from the gas supply system 507 flow to the ion source 501, and applies a DC voltage between a hollow cathode 531 and an anode 532 while setting the gas pressure inside the ion source 501 to several Torr, a glow charge occurs between the hollow cathode 531 and the anode 532. Then ions are accelerated toward the hallow cathode 531, while the electrons are accelerated toward the anode 532 and collide with the electrode to generate secondary electrons. Prior to the collision with the anode 532, the electrons are ionized as the charged particle beam material gases are electrolytically dissociated. The electrons and the ions are entrapped by an electric field produced by a magnet 535 and generate high density plasma. An ion beam 502 is extracted from this plasma by an electric field around an extractor electrode 533 that is maintained at earth potential. An intermediate electrode 534 is connected to an accelerating power supply (not shown) through a megaohm resistor, and a current value of the ion beam is adjusted mainly by changing bias voltage (voltage that negative potential is added to accelerating voltage) of the bias electrode 529. A hole in the anode 532 to transmit the ion beam 502 is as small as several hundreds of micrometers and has a small conductance. Because of this, it takes a long period of time to take out the charged particle beam material gas in the ion source 501 toward the ion beam column 503 through the hole in the anode 532. Thus, a bypass flow path having a greater conductance than the anode hole is installed from the ion source 501 to the ion beam column 503 (lower side than the extractor electrode 533), and a bypass valve 518 for opening and closing the bypass flow path is provided midway the bypass flow path. Accordingly, in case of switching a gas supplied from the gas supply system 507 from the charged particle beam material gas of the gas cylinder 522A to the charged particle beam material gas of the gas cylinder 522B (or vice versa), the operator opens the bypass valve 518 having been in closed state and discharges the charged particle beam material gas in the ion source 501 to the ion beam column 503, so that the kind of the charged particle beam material gas in the ion source 501 can be substituted within a short period of time. Vacuum level of the ion source 501 with or without gas being introduced thereto is measured by a vacuum gauge 536. The vacuum gauge 536 is, by its nature, highly resistant against the charged particle beam material gas that is introduced to the ion source 501. FIG. 13 shows an internal structure of the ion beam column 503. The ion beam column 503 includes a machining optical system constituted by a mass separator 540, a deflector 541, an iris 542, an irradiation lens 543, a projection mask 544, an aberration corrector 545, a projection lens 547, an alignment coil (not shown), a Blanker (not shown), and a Faraday cup (not shown). The ion beam column 503 is bent by a few degrees in inclined form as shown in FIG. 13, such that neutral particles of metal sputtered materials in the ion source 501 may not directly reach the sample 513. The neutral particles are irradiated onto a damper (not shown). This damper is made of silicon, carbon, or the like to prevent metal contamination due to sputtered particles. The mass separator takes out only a necessary ion beam out of the ion beams 502 that are extracted from the ion source 501, and the deflector 541 curves the ion beam by a few degrees. Moreover, a gun valve (not shown) is installed to separate the sample chamber 506 where the sample 513 is mounted and part of the ion beam column 531. This gun valve is used, for example, when only the sample chamber 506 leaks during maintenance of the sample chamber 506. A preferable example of the deflector 546 is an eight-pole deflector to scan the sample 513 with an ion beam that passed through the projection mask 544 and has a circular cross section for observation. FIG. 14 is a diagram showing diverse apertures formed in the projection mask 544. As shown in FIG. 14, the projection mask 544 has an angled U-shape aperture 550A for extracting a micro sample, a linear aperture 550B, a rectangular aperture 550C mainly for use in deposition, a relatively large circular aperture 550D mainly for use in probe adhesion, a relatively small aperture 550E mainly for use in observation, and an aperture (not shown) with a comparatively large aspect ratio of height/width for use in membrane machining, and only a beam that has passed through this aperture is converted by the projection lens 547 and irradiated onto the sample 513. The projection mask 544 is made out of silicon to prevent metal contamination. Hereinafter, ion beams that passed through the apertures 550A through 550E will be called O-700, O-500, O-200, O-100, and O-20, respectively. FIG. 15 shows the profile of an ion beam 502 irradiated onto the projection mask 544. In case of forming a cross section of the ion beam 502 by using the projection mask 544, it is important to increase a beam current having passed the projection mask 544 to a maximum in order to prevent a beam omission. To this end, size and position of the ion beam 502 are modified to be circumscribed to a target aperture of the projection mask 544. FIG. 15 illustrated a case where the projection mask 544 has one of each kind for the apertures, but a number of apertures of the same shape can also be formed to get a super life span of the projection mask 544. FIG. 16 schematically shows two kinds of beam modes available by the machining optical system. FIG. 16(a) shows an ion beam in projection mode, and FIG. 16(b) shows an ion beam in observation mode. In the projection mode of FIG. 16(a), an irradiation lens 543 is adjusted to obtain a sharp machining shape by decreasing aberration, so that an aperture image of an anode 532 can be formed on a projection lens 547. The irradiation lens 543 and the projection lens 547 are respectively composed of three sets of Butler lenses for example, and an image of the projection mask 544 is being formed at a sample 513 by the projection lens 547. Here, voltages of about 9 kV and about 20 kV are applied to the irradiation lens 543 and the projection lens 547, respectively, and the magnification rate is approximately 1/16 for instance. In the observation mode of FIG. 16(b), image formation is carried out on the side of the ion source 501 of the projection mask 544, and this image is formed again at the sample 513 by the projection lens 547. Therefore, the magnification rate of the image in the projection mode can be reduced to, say, 1/30, and the diameter of a beam spot can be minimized as small as several tens of nanometers for example. When this beam is scanned by the deflection coil 546, a secondary electron image of high resolution compared with an image in the projection mode, is obtained. In the observation mode, voltages of about 23 kV and about 20 kV are applied to the irradiation lens 543 and the projection lens 547, respectively. The present invention is not limited to the FIB device as shown in FIG. 11, but can be applied to the FIB-SEM device as shown in FIG. 17 or FIG. 18 as well. The charged particle beam processor of the present invention can be configured by installing the gas supply system 507 at the FIB-SEM device shown in FIG. 17 or FIG. 18. The gas supply system 507 is not shown in FIGS. 17 and 18, but all like elements or elements having the same functions to those of FIG. 11 and others are given like reference numerals, and descriptions of them are omitted. The FIB-SEM device shown in FIG. 17 is substantially identical with the charged particle beam processor shown in FIG. 11, except that a SEM (scanning electron microscope) 553 using a processed spot by the ion beam column 503 as an observation spot is added. In this case, there is a merit that a device operator can machine the sample 513 with an ion beam and clearly observe a machined plane of the sample 513 in real time. On the other hand, in case of the FIB-SEM device shown in FIG. 18, an observation spot of the SEM 553 and a processed spot by the ion beam column 503 are separated, and the stage 505 moves between the observation spot of the SEM 553 and the processed spot by the ion beam column 503. In this case, since installation spaces for both sides are secured without having to worry about the interference between the SEM 553 and the ion beam column 503, the SEM 553 or the ion beam column 503 can approach the sample 513 more easily than in the configuration example of FIG. 17, and a high-resolution observation image is obtained. FIGS. 19A and 19B respectively illustrate a flow chart describing a sequence of procedure starting from extracting a defect in a sample by using the charged particle beam processor depicted in FIG. 18 to returning the sample with the defect extracted to the line. In particular, FIGS. 19A and 19B explain a procedure, wherein a defect such as a contact failure in a plug of a chip is discovered by the SEM, a micro sample including the defect is machined and extracted by an ion beam, and a processed hole of the sample after sampling is filled up to be returned to the production line. The following will now explain in detail about principal processes shown in FIG. 19A and FIG. 19B. (1) Coordinate Linkage with the Detection Device Before coming to this process, defects of the sample 513 are inspected by an electronic inspection device, a BF (Bright Field) inspection device, a DF (Dark Field) inspection device, or the like, and are classified by the review SEM. At this time, the review SEM first performs ADR (Automatic Defect Review) through low-resolution observation (review mode), and then performs ACD (Automatic Defect Classification). The review SEM classifies the defects into different kinds, i.e. separation, foreign matter, flaw, and dust, and further classified them into short, open, convex defect, concave defect, and VC (voltage contrast) defect. Defect information includes coordinate values where a defect lies, kind of a defect, SEM image of a defect, and so on. Based on the inspection information obtained by the review SEM, the charged particle beam processor of FIG. 18 conducts microsampling of a defect region, observes and analyzes the defect. Therefore, in step S101, the defect region of the sample 513 should be matched precisely with the machined spot of the ion beam 502, and another device (review SEM) that obtained the defect information should be matched with an origin of the coordinates. Here, an operation called coordinate linkage is performed and as a result, coordinate position-matching within an error of several micrometers can be possible. (2) Sample, Cartridge Carrying φ300 silicon is used as the sample 513, and the cartridge is for carrying out a micro sample extracted from the sample 513 outside the charged particle beam processor. FIG. 20 is a perspective view of the holder 504. Referring to FIG. 20, a cartridge holder 555 is attached to the holder 504, and the cartridge 554 is detachable from the cartridge holder 555. The cartridge holder 555 is designed to be able to rotate around the axial direction by a rotation mechanism (not shown). The sample 513 and the cartridge 554 are loaded onto the holder 504 disposed at a load lock chamber by a sample mounting unit (not shown) and a cartridge mounting unit (not shown). The load lock chamber is exhausted by an exhausting system (not shown) to a vacuum. After the sample 513 and the cartridge 554 are mounted, the holder 504 standing by in the load lock chamber is transposed by the stage 505 to an observation spot by the SEM 553 inside the sample chamber 506 (S102). (3) Defect Searching by SEM In step S103, the defect region is transposed into the field of view of the SEM 553 within a position error of several micrometers by coordinate linkage with the review SEM. Accurate position matching can be done by finding, by the naked eye, a feature point indicating the location of the defect region. (4) Deposition by Electron Beam FIG. 21 shows an SEM image 557 of the defect region. Like the SEM image 557 illustrated in FIG. 21, the defect region such as the plug 558 looks relatively dark compared with a normal region when observed by VC (Voltage Contrast) (defect region 559). In general, brightness of a plasma source of the gas ion beam is considerably low compared with a gallium ion source which is a liquid metal ion source being widely used in FIB devices. Meanwhile, because a sufficient amount of secondary electrons is required to get a clear image with a large S/N ratio, it is necessary to set a minimum beam diameter for the gas ion beam to be relatively large, and therefore a low-resolution image is obtained. Normally, a gas ion beam is at least several tens of nanometers in diameter, so it is very difficult to obtain a clear, high-magnification image of the plug 558 having a diameter of several nanometers at the most. Therefore, in step S104, after identifying the defect region by the SEM 553, a mark 560 of several micrometers in size is formed nearby the defect region by electron beam deposition, so that the position of the defect region can easily be detected also by a gas ion beam. FIG. 21 shows a state where the mark 560 is formed on both sides of the defect region 559. To increase the deposition speed to a maximum, an electron beam accelerating voltage is set to a relatively low accelerating voltage (about 1 kV), and an electron beam of several tens of pA is irradiated for several minutes to form a rectangular mark with a side being several micrometers long. When this step is over, the operator drives the stage 505 and moves the holder 504 to an ion beam machined spot (S105). (5) Introduction of Gas A In step S106, a charged particle beam material gas A (oxygen gas) in the gas cylinder 522A is introduced to the ion source 501. At this time, openness of the flow control valve 524A is adjusted in advance to be able to take out the oxygen ion beam with a high current stably. When the operator opens the stop valve 523 from its closed state, oxygen gas flows into the ion source 501 through the gas inlet tube 530. Following the introduction of gas A, an accelerating voltage of 30 kV is applied, and a predetermined voltage is applied to the hallow cathode 531 as well as the bias electrode 529. Here, voltage of the anode 532 equals to the accelerating voltage. The extractor electrode 533 is maintained at earth potential, and an ion beam 502 is extracted by an electric field with the accelerating voltage. And the projection mask 544 is position matched to let the aperture 550E fit into the beam size (diameter) of the ion beam 502 (S107). The ion beam 502 on the surface of the sample 513 has a diameter of about 100 nm. The deflection coil 546 scans this beam onto the sample to obtain an SIM observation image. (6) Formation of Protective Layer In step S108, a protective layer is formed on the upper surface of each defect region 559 of the sample 513 to prevent the defect region(s) from being cut out by sputtering during the observation of the SIM image. FIG. 22 shows a display screen of the console 514. The display screen 536 in FIG. 22 presents an alarm display section 564, a beam parameter display screen section 565 which displays current of a beam of which beam focus contrast brightness is being machined, machining time and the like, a navigation screen section 566 which allows the operator to select an operation such as a job system recipe dialogue, and a machining manipulation screen section 567 for designating a machining process. FIG. 23 shows the machining manipulation screen section 567 used for designating a protective layer forming area. As shown in FIG. 23, the machining manipulation screen section 567 displays a machining start button 570, a gas kind display lamp 571 for informing the kind of a charged particle beam material gas being currently used, a process selection area 561 for selecting a process, a monitor screen 568 for displaying a sample observation image, a button 569 for designating the kind of a beam, a display selection area 562 for switching the display of the monitor screen 568, and a machining condition input unit 573 through which the operator inputs desired machining conditions. The process selection area 561 displays a hole machining button 561a used for commanding hole machining, a protective layer/adhesive button 561b used for commanding the projective layer formation/adhesion jobs, and a hole filling button 561c used for commanding a hole filling operation. The display selection area 562 displays an optical microscope button 562a used for switching the display of the monitor screen 568 to an optical microscopy image, an SEM button 562b used for switching the display to an SEM image, an SIM button 562c used for switching the display to a SIM image, and an edit button 562d. The machining condition input unit 573 displays a hole machining beam scan width designation blank portion 573a, a scan direction designation blank portion 573b, and a machining time designation blank portion 573c. As such, the operator may input numbers required for the hole machining process for example to those designation blank portions 73a through 73c. FIG. 23 illustrates a case where the operator selected A (oxygen gas) as the kind of a charged particle beam material gas, “Protective layer/adhesion” for the process, and switched the display of the monitor screen 568 to the edit screen. The monitor screen 568 displays a rectangle that indicates a perspective protective layer forming area 572. This protective layer film forming area 572 appears on the monitor screen 568 when the operator presses the protective layer/adhesion button 561b in the process. In result, the operator can form a protective layer, while adjusting the position of the displayed protective layer forming area 572. At this time, to make the protective layer forming area 572 of the monitor screen 568 coincide with an actual deposition area, positions of an ion beam by the aperture 550E and the aperture 550C of the projection mask 44 are adjusted in advance by the deflection coil 546. In like manner, ion beam positions by other apertures are all adjusted in advance with respect to the position of the ion beam 502 by the aperture 550E in advance. Tungsten carbonyl (W(CO)6) is preferably used as GAD gas for forming a protective layer. To prevent metal contamination, TEOS producing a silicon oxide layer, or a carbon based gas such as phenanthrene can be used as another option. When the operator presses the button 570, the gas nozzle 512 of the gas gun 511 approaches the processed spot from its retreated position, and GAD gas is sprayed from the nozzle 512. Next, the projection mask 544 is switched from the aperture 550E to the aperture 550C, the ion beam (projection beam) 502 passed the aperture 550C is projected onto the sample 513, and a deposition layer is accumulated at the projective layer forming area 572 by a reaction with the GAD gas. The ion beam 502 is not scanned but halts at the same position all the time during the deposition. For instance, a 1 μm thick deposition layer is formed every 1 minute. FIG. 24 shows an SIM image after the deposition layer is formed. Reference numeral 575 in FIG. 24 indicates the protective layer. Apart from the sample machining (processing) by a projection beam having a cross section formed by the projection mask 504, it is possible to scan the ion beam 502 onto the protective layer forming area 572 to accumulate the projective layer. (7) Hole Machining 1 by Beam A When the operator manipulates the hole machining button 561a of the process selection area 561, an angled U-shape machining area 576 as shown in FIG. 24 appears. Then the operator determines a machining position (S109) by transposing the machining area 576 to a predetermined position in the monitor screen 568, and executes an angled U-shape hole machining (S110) by the ion beam 502 (beam A) by a charged particle beam material gas A. During the angled U-shape hole machining, the projection mask 544 is position matched to make the aperture 550A fit into the beam diameter of the ion beam 502. FIG. 25 shows a state where an angled U-shape projection beam is extracted by matching the projection mask 544 with the aperture 550A, and the sample 513 is being machined. FIG. 25 shows part of the machining optical system shown in FIG. 13. For example, the angled U-shape hole machining is performed for several minutes at the beam current of 100 nA and at the machining speed of 1 μm/min. The ion beam 502 is converged by the irradiation lens 543 and irradiated to the projection mask 544. Only the ion beam passed through the aperture 550A of the projection mask 544 forms an image on the sample 513 by the projection lens 547. At this time, the ion beam 502 is inclined at about 45 degrees with respect to the horizontal direction (the stage 505 is tilted around the T axis to make the sample 513 tilted by 45 degrees with respect to the ion beam column 503). Following the machining process, the projection mask 544 is position matched (S111) to cause the aperture 550E to fit within the beam diameter of the ion beam 502, and the sample 513 is rotated by 180 degrees (S112). FIG. 26 shows an observation image of the monitor screen 568 after the angled U-shape hole is machined. In particular, FIG. 26 is a screen that appears after the operator manipulates the edit button 562d in the display selection area 562. After the angled U-shape hole machining is completed and the stage 505 is rotated, the operator, while watching the screen of FIG. 26, moves the probe 515 into the field of view to bring it into contact with the inner area (micro sample 581) of the angled U-shape processed hole 579 of the sample 513 (S113), and defines a contact region as a deposition area by beam A (S114). In other words, the operator brings the probe 515 into contact with a suitable position in the deposition area. While the gas gun 511 is ejecting the GAD gas near the contact region between the probe 515 and the sample 513, the ion beam 502 (beam A) is irradiated to form a deposition layer 578 (S115) and the probe 515 and the micro sample 581 are adhered by the deposition layer 578 (S116). The ion beam 502 having passed through the aperture 550D of the projection mask 544 was used to form the deposition layer 578. In this example, the probe 515 is made out of silicon materials to prevent metal contamination. After the adhering step of the probe 515, the operator carries out position-matching (S117) of the projection mask 544 to cause the aperture 550E to fit within the beam diameter of the ion beam 502. Next, the operator manipulates the hole machining button 561a of the process selection area 561 to display a linear shaped machining area 576 on the monitor screen 568. While watching an SIM image by the ion beam 502 having passed the aperture 550E, the operator transposes, within the monitor screen 568, the machining area 576 to a position surrounding the angled U-shape processed hole 579 together with the adhesion portion of the probe 515, so as to determine a machining position (S118). Later, the projection mask 544 is position matched to cause the aperture 550B to fit within the beam diameter of the ion beam 502. (8) Hole Machining 2 by Beam A FIG. 27 shows a state where a linear projection beam is extracted by matching the projection mask 544 with the aperture 550B, and the sample 513 is being machined. FIG. 27 shows part of the machining optical system shown in FIG. 13. In this process, a micro sample 581 is cut out and extracted (S102) by machining a hole with the linear ion beam 502 (beam A) (S119). The linear hole machining lasted several minutes at the beam current of about 60 nA. FIG. 28 shows a state where the micro sample of this embodiment is extracted and machined. In particular, FIG. 28(a) shows projected images 577 and 584 of the ion beam 502 that has passed through the apertures 550A and 550B, respectively, and FIG. 28(b) shows an A-A cross section in FIG. 28(a). In fact, the processed hole by the projection beam that passed through the apertures 550A and 550B becomes gradually narrower in a hole depth direction by reattachment at the hole portion. Thus, as shown in FIG. 18(b), the processed trenches 585 and 586 have a triangular shape. For instance, the micro sample 581 to be extracted becomes approximately 10×10×11 (size in micrometers) for width×length×height. In the course of hole machining by the projection beam that passed the apertures 550A and 550B, contrast of the micro sample 581 is degraded. Because of this phenomenon, separation of the micro sample 581 from the sample 513 can be recognized. This change in contrast occurs because the micro sample 581 being separated from the sample 513 has a floating potential, and the amount of secondary electrons generated from the micro sample 581 during the ion beam irradiation is reduced. If it is difficult to judge on the observation image by the naked eye, a contact sensor may be used for separate detection. (9) Loading into Mesh FIG. 29 shows a state where the micro sample 581 is loaded to the cartridge 554. When the micro sample 581 is separated from the sample 513, the operator drives the stage 505 and creates a mesh position so that a mesh 589 of the cartridge 554 becomes near the ion beam processed spot (S121). Then the operator drives the probe 515 to bring the micro sample 581 into contact with the mesh 589 (S122), and determines a deposition area (S123) where a deposition layer used to adhere the mash 589 and the micro sample 581 is formed. While the gas gun 511 is ejecting GAD gas, the ion beam 502 is irradiated to form a deposition layer, and the micro sample 581 is adhered and loaded to the mesh 589 (S124). Next, the tip of the probe 515 is cut by the ion beam 502 (S125). The ion beam 502 that passed through the aperture 550D is used for cutting the probe 515. After the probe 515 is cut, it is decided whether the extracted micro sample 581 is a final sample of the present current sample 513, based on the inspection information obtained in advance by the review SEM (S126). That is, it is decided whether there are more defect regions to be extracted from the sample 513 being currently microsampled. If there is still a defect region to be sampled, the operator drives the stage 505, transposes a next sampling spot to an ion beam processed spot, and repeats the step (S109) in “Hole machining 1 by beam A”. Meanwhile, if there is no more defect region to be sampled, the sample extraction sequence of FIG. 19A ends, and the processed hole filling step (S201) of FIG. 19B is executed. FIG. 30 illustrates a sample 513 having five processed holes 592 formed in result of extracting a micro sample. The sample extraction sequence of FIG. 19A was done by sampling a defect region for inspection and analysis of the defect, but the same sequence of FIG. 19A can be applied equally to a method called ‘Fixed point observation’ that carries out microsampling of a predetermined inspection spot on the sample 513 and inspects quality of the sample 513. The extracted micro sample 581 is then taken out to the outside of this charged particle beam processor, and observed/analyzed by an STEM (Scanning Transmission Electron Microscope) with higher resolution or a TEM (Transmission Electron Microscope). In this way, the cause of defects can be discovered more accurately at high speed, and measures can be taken immediately to deal with the defects. In case of observing a sample by a TEM or an STEM, both being a transmission type, the micro sample 581 should be made into a membrane. Although not shown particularly, the charged particle beam processor can make the micro sample 581 into a membrane. This membrane machining (or processing) of the micro sample 581 is carried out without scanning a beam but in the projection mode shown in FIG. 16(a). To obtain a sharp processed plane out of a cross section to be formed into a membrane, the projection mask 544 needs to be arranged in such a manner that the major axis direction of a membrane machining slit and the membrane machining direction of the micro sample 581 are at right angles (about 90 degrees) with each other. This is because aberration such as spherical aberration decrease as it gets nearer the beam center, and as a result, the machined plane becomes sharper. In projection mode, however, the resolution is not high enough to designate an area to perform the membrane machining as described in FIG. 16. Thus, the membrane machining position is determined in observation mode of FIG. 16(b) where a sufficiently high resolution is provided. Optical conditions are different for the beam in observation mode and for the beam in projection mode, and position misalignment of beam due to axial misalignment occurs. Therefore, when a machining position needs to be designated in observation mode, its misalignment amount should be observed in advance and the offset is calibrated to designate a machining area. Here, a gear 590 is installed at the cartridge holder 555. Since the cartridge holder 555 can be rotated by driving a motor engaged with the gear 590, the operator can randomly change the observation direction of the micro sample 581 or the membrane machining direction. The micro sample extraction procedure ends here. Proceeding to FIG. 19B, the following will now explain the work flow on processed hole-filling. (10) Introduction of Gas B by Closing the Bypass Valve from its Open Position FIG. 31 is a timing chart of principal steps in the work flow shown in FIGS. 19A and 19B. As shown in FIG. 31, in the sample extraction procedure of FIG. 19A, the charged particle beam material gas A (oxygen gas) was introduced to the ion source 501 to extract an oxygen ion beam, and the steps of hole machining at a defect region, micro sampling, and mesh loading were then performed in sequence. Next, the operator opens the bypass valve 518 (S201) to discharge the charged particle beam material gas A (oxygen gas) from the ion source 501 at high speed, and makes it close at a certain vacuum level (if the vacuum level falls below a set threshold) (S202), thereby introducing a charged particle beam material gas B (argon gas) (S203). Thus, the hole filling work is done by using the argon ion beam. To execute the hole filling work, the kind of a charged particle beam material gas to be introduced to the ion source 501 is switched to a gas kind B (argon gas). Before switching to the charged particle beam material gas kind B (argon gas), any remaining charged particle beam material gas A (oxygen gas) in the ion source 501 has to be removed. To this end, the operator opens the bypass valve 519 connected to the ion source 501 that was in its closed position, and allows the charged particle beam material gas A to be discharged from the ion source 501 at high speed. In detail, to stop the introduction of the charged particle beam material gas A (oxygen gas), the operator manipulates the valve controller 525 to close the stop valve 523A that was in its open position and, at the same time, opens the bypass valve 518 that was in its closed position. In result, the vacuum level of the ion source 501 that was around several hundreds of Pa under the introduction of beam A (oxygen gas) gradually decreases until it reaches a previously set threshold (e.g., around 1 E-3 Pa) or less, the operator closes the bypass valve 518 that was in its open position. Next, the operator opens the stop valve 523B that was in its closed position and introduces the charged particle beam material gas B (argon gas) to the ion source 501. Meanwhile, the flow control valve 524B is adjusted in advance to be able to get an ion beam current and stability required to realize the high-speed hole machining. (11) Deposition by Beam B Following the introduction of the charged particle beam material gas B (argon gas) to the ion source 501 by using the same method in the introduction of the charged particle beam material gas A (oxygen gas), plasma was ignited (S204), an acceleration voltage was applied, and an argon ion beam (beam B) 502 was extracted. Since the kind of a charged particle beam material gas and the ion beam current required for hole machining are different from those for hole filling, conditions for generating an ion beam, such as, accelerating voltage, cathode application voltage, bias voltage, and gas volume flow rate, are different from each other. However, the central processing unit 510 may automatically change the ion beam generating conditions to previously set conditions according to the kind of a charged particle beam material gas. And the projection mask 544 is position matched to cause the aperture 550E to fit within the beam diameter of the ion beam 502 (S205). FIG. 32 shows the machining manipulation screen section 567 used for designating a hole filling process area. FIG. 32 illustrates a hole filling process where gas B (argon gas) is used as the charged particle beam material gas and the O-500 is selected as the kind of the beam. When the processed hole 592 of the sample 513 is formed as deep as the lower portion of the monitor screen 568, a formed image is dark as much as the lower portion. The operator designates scan direction and scan width by inputting corresponding information to the designation blank portions 573a and 573b in a manner that the O-500 ion beam 93 passed through the aperture 550B of the projection mask 544 is scanned onto the entire area of the processed hole 592. For example, the scan direction is set to be a vertical direction seen on the drawing, and the scan width is set to several tens of micrometers. While watching the SIM image by the ion beam that passed through the aperture 550E, the operator transposes the stage 505 (S206) to bring the processed hole 592 to the ion beam processed spot, and determines a deposition area (S207). Later, the projection mask 544 is position matched (S208) to make the linear aperture 550B fit into the beam diameter of the ion beam 502. FIG. 33 is a schematic diagram of a projection beam being used for the hole filling process. In FIG. 33, the projection mask 544 is position matched to let the linear aperture 550B fit into the beam diameter of the ion beam 502, and the ion beam 502 having a rectangular cross section is irradiated onto the sample 513. The ion beam 502 then reacts with GAD gas 595 from the gas nozzle 512, and a deposition layer is accumulated at the processed hole 592 as the ion beam 502 is scanned thereon (S209). Deposition speed and ion beam current are predetermined to proper values, according to acceleration voltage. FIG. 34 shows a state where the O-500 beam 599 is irradiated at scan intervals 604 onto the processed hole 592 after the micro sample shown in FIG. 28(b) has been extracted. FIG. 35 shows another example of irradiation method of the ion beam 502 in course of hole fill processing. The example shown in FIG. 35(a) illustrates a method of sequentially forming a deposition layer one after another by retaining the ion beam 599 for a certain period of time, transposing it as much as the beam width, and repeating them. This method is called a beam retainment method. Meanwhile, the example shown in FIG. 35(b) illustrates a method of accumulating a deposition layer evenly at the processed hole 592 by scanning the ion beam 599. This method is called a scan method. FIG. 36 shows the deposition progress time-variantly, and the accumulation of deposition layers progresses in order of FIG. 36(a)→FIG. 36(b)→FIG. 36(c). FIG. 36(a) shows a state where the O-500 beam having passed through the aperture 550B via the step S209 is scanned (Deposition 1 by beam B), and a deposition layer 601 is formed at the processed hole 592. At this point, the center of the processed hole 592 is recessed. FIG. 36(b) shows a state where the ion beam having passed through the aperture 550C via the steps S210 through S213 is retained for several minutes (Deposition 2 by beam B) to superimpose the deposition layer 602 at the recessed part. Although a deeply recessed part was filled, a shallow part still remained. FIG. 36(c) shows a state where the circular ion beam having passed through the aperture 550D via the steps of S214 through S217 is scanned onto the recessed area (Deposition 3 by beam B), and a deposition layer 603 is superimposed at the recessed part. Therefore, according to this embodiment, the apertures of the projection mask 544 are switched so as to change the shape of an ion beam into a proper one as accumulation of the deposition layer proceeds. The deposition layer 603 has high flatness on the subnanometer order. Before the depositions 1, 2, and 3 by beam B, the projection mask 544 is position matched (S205, S210, and S214) to make the aperture 550E to fit within the beam diameter of the ion beam 502, respectively. While watching the SIM image by the ion beam 502 having passed through the aperture 550E, the operator determines the deposition area in the monitor screen 568 (S207, S211, and S215). (12) Measurement of Flatness of Deposition Layer FIG. 37 shows one example of techniques for measuring height of surface roughness of the filled deposition layer of the processed hole 592, which is executed in the step S218. In detail, FIG. 37(a) is a top plan view of a state after the processed hole 592 is filled by deposition. FIG. 37(b) shows a state where a circular beam 502 that is sufficiently thin with respect to the processed hole 592 is irradiated from the left hand side of the drawing onto the processed hole 592 at an incidence angle of about 45 degrees with respect to the surface of the sample 513, and scanned in the direction of an arrow 591. FIG. 37(c) shows a state that a scan line 596 of the ion beam 502 is matched with FIG. 37(a) and superimposed on the plan view of the processed hole 592. FIG. 37(d) shows a state where a machining (or processing) line 597 is further superimposed on the plan view of the processed hole 592 after the hole fill processing. As can be seen from FIG. 37(a), the center of the processed hole 592 with a membrane being deposited thereon is swollen, and a minute step height is formed on the deposition layer. For instance, as shown in FIG. 37(b), suppose that there is a bump with a height (H) on the deposition layer. In this case, if the ion beam 502 is irradiated at an incidence angle of 45 degrees, a misalignment (h) of an approximately equivalent amount to the height (H) of the bump is created at the processing line 597 with respect to the bump. In other words, when a misalignment amount (h) is detected between the processing line 597 and the scan line 596, the amount of the step height (H) of the deposition layer can be calculated from the incidence angle of the ion beam 502 onto the sample surface. Meanwhile, the misalignment amount (h) is given automatically by image processing at an image recognition apparatus. Through the recognition of the misalignment amount (h), it becomes possible to detect the recessed area, recessed location, and recessed depth of the deposition layer. Using this detection information, the operator decides proper deposition conditions from a prestored database in the central processing unit 510, and carries out deposition. Deposition conditions mentioned here include the kind of a beam used, shape or size of an ion beam (kind of aperture in the mask 544), ion beam current value (accelerating voltage, bias voltage, etc.), scan direction, scan area, machining time, beam residence time, scan interval, and so on. Besides the above, one may consider installing a measuring instrument to measure surface roughness of the deposition layer. Examples of such measuring instrument include a laser microscope with submicrometer resolution, an atomic force microscope with resolution of several nanometers, and so forth. These microscopes scan a laser beam and a cantilever, respectively, to give a three-dimensional measurement on the surface roughness of the deposition layer. Following the flatness measurement of the deposition layer, it is decided whether the flatness being measured is below a predetermined threshold range (S219). If it is within the range, the step S214 is repeated to execute “Deposition 3 by beam B” (the flow B in FIG. 19B). However, if it is below the threshold range, it is decided from the sample extraction work history whether this is going to be the last hole fill processing (S220). That is, it is decided whether the sample 513 currently being in course of the hole fill processing has any additional holes to be filled up. If there are more holes to be filled up, the step of hole fill processing is repeated (the flow C in FIG. 19B). In this case, the procedure starts from the step S205 to execute “Deposition 1 by beam B”. On the contrary, if there are no more holes to be filled up, the hole fill processing procedure of FIG. 19B ends. The following will now explain the application effects of this embodiment. FIG. 38 is a schematic view of a processed hole being filled up by an oxygen ion beam (beam A). In detail, FIG. 38(a) shows a processed hole 592 prior to the hole fill processing, FIG. 38(b) shows the mark of a filled hole that is deposited by ion beam retainment, and FIG. 38(c) shows the mark of a filled hole that is deposited by scanning. The ion beam retainment produces a lump deposition 606 of several micrometers on the sample surface (FIG. 38(b)), while the scanning produces a globular deposition 607 of several micrometers on the sample surface (FIG. 38(c)). Neither method failed to achieve submicrometer flatness. From this result, the inventors of this patent application assumed that flatness of the deposition layer is attributed to the kind of a beam, rather than to a deposition method (ion beam retainment method or scanning method), so they formed a deposition layer by using a different kind of a beam and conducted a composition analysis on the deposition layer by Auger electron spectroscopy. FIG. 39 graphically compares Auger electron spectroscopy analysis results between a deposition layer by an oxygen ion beam and a deposition layer by an argon ion beam. For a test, ortho-tetraethyl silicate (TEOS) was commonly used as GAD gas, and an oxygen ion beam and an argon ion beam were selected as beam kinds to be compared. It turned out that the deposition layer formed by using the oxygen ion beam has a flatness on the order of several micrometers, which is not good. Meanwhile, the deposition layer formed by using the argon ion beam achieved an improved flatness of a satisfactory level. As shown in FIG. 39, two disposition layers had a similar composition, but carbon was detected only from the deposition layer with an excellent flatness formed by using an argon ion beam. From this result, the inventors of this patent application discovered that there is a certain relationship between composition and shape of a deposition layer, and that a deposition layer with a desired flatness level can be obtained by forming the deposition layer with a properly selected kind of an ion beam. However, the aforesaid composition analysis test also revealed that the processing on the deposition layer formed by using the oxygen ion beam was done at high speed although the deposition layer did not achieve a sufficient flatness level. On the other hand, in case of forming a deposition layer by using the argon ion beam, a beam current value was lowered and thereby the processing speed was reduced compared with the oxygen ion beam. From this, comparing the oxygen ion beam with the argon ion beam, the inventors believed that the argon ion beam is suitable for the hole fill processing where the flatness of a deposition layer is appreciated, while the oxygen ion beam featuring a high processing speed is suitable for the hole machining where the processing speed is valued over the flatness level. Based on this discovery, the inventors thought of installing a gas supply system 507, and stop valves 523A and 523B as switching means of charged particle beam material gases from the gas supply system 507, whereby the kind of a charged particle beam material gas to be introduced to an ion source 501 for the hole machining operation on a sample 513, the operation including the extraction of a micro sample 581, can be switched with the kind of a charged particle beam material gas to be introduced to the ion source 501 for the layer deposition operation including the hole fill processing. Therefore, according to this embodiment, in a sequential procedure of extracting a defect region of a sample and returning the sample from which the defect region has been extracted to the (production) line, since the high-speed hole processing is compatible with the high flatness of the surface of a deposition layer in the hole fill processing is done, the manufacturing yield can be improved. Moreover, the bypass valve 518 facilitates gas discharge from the ion source 501, so the kind of a charged particle beam material gas as the ion beam generating source can be switched within short time. Also, by installing the vacuum gauge 536 measuring pressure inside the ion source 501, the operator can see that the measurement result is below the predetermined threshold and verifies the end of gas discharge from the ion source 501. Thus, as the charged particle beam material gas to be used next is introduced to the ion source 501, the influence of the remaining, previously used charged particle beam material gas on the processing (or machining) performance can be suppressed. Suitable plasma generating conditions (e.g., accelerating voltage, discharge voltage, bias voltage, vacuum level, etc.) according to the kind of charged particle beam material gas, or suitable processing optical conditions (e.g., applied voltage to each lens, etc.) are prestored in the database, and the central processing unit 510 changes them automatically based on the database whenever the gas kind is to be switched. Accordingly, even if the kind of the charged particle beam material gas is set to change depending on work, since it takes no time to set the plasma generating conditions or the processing optical conditions, high work efficiency can be ensured. By installing the means for measuring surface roughness (height) of the deposition layer while the processed hole is being filled, it becomes possible to measure the surface roughness of the deposition layer in the course of the hole fill processing, and recognize whether there is any area (insufficient portion) short of a predetermined deposition height. If so, its height is measured, and, based on the height measurement result, the central processing unit 510 selects proper deposition conditions (for example, beam shape, scan method, beam irradiation condition, etc.) from the prestored database, to cause a deposition layer to be superimposed at the insufficient portion under the proper deposition conditions. As such, compared to the case where the operator decides to superimpose the deposition layer after he watches an observation image by the naked eye, good flatness of the deposition layer is ensured, irrespective of the operator's ability. In particular, this embodiment uses the projection mask 544 to perform the machining by the ion beam 502, high-speed hole machining or high-speed hole fill processing can be achieved. Traditionally, when a sample cross section was machined by using the FIB device, an ion beam being converged on the submicron order was electrostatically deflected and scanned onto a target position of the sample. Meanwhile, according to this embodiment, a projection ion beam that passed through a mask aperture of a suitable shape corresponding to the machining purpose is irradiated to process a sample. The machining (or processing) speed by an ion beam is roughly determined by beam charges irradiated onto a target processing area. That is to say, although the target processing area may be large, PJIB, compared to FIB, can be machined within a short period of time. In general, the processed hole is several micrometers in size, so if the ion beam used for PJIB has brightness below a certain, fixed value, PJIB can be machined or processed at high speed. However, it is also possible to scan FIB and perform the hole machining and the hole fill processing while the projection mask 544 is being retreated. Another embodiment of the present invention will be described below. FIG. 40 is a schematic view of a charged particle beam processor according to another embodiment of the present invention. In FIG. 40, like components or the components with the same roles as those of the previous drawing are designated by the same reference numerals, and therefore the explanation of those components will be omitted hereafter. In this embodiment, the kind of a charged particle beam material gas is not switched by work, but charged particle beam material gases of different kinds according to work nature are introduced to an ion source 501 at the same time. To be more specific, a charged particle beam material gas kind (e.g., oxygen gas) suitable for hole machining of a sample 513 including the extraction of a micro sample 581, and a charged particle beam material gas kind (e.g., argon gas) suitable for layer deposition including sample 513 hole fill processing are introduced to the ion source 501 through a gas inlet tube 530 at the time of hole machining and layer deposition, so ion beams 502 are generated based on the plural kinds of charged particle beam material gases. That is, for example, oxygen gas and argon gas are introduced simultaneously to the ion source 501, and a mixed gas of both is used as an ion beam generating source. Consequently, an ion beam with intermediate natures of both oxygen ion beam and argon ion beam is produced. Here, plural gas cylinders filled with different kinds of charged particle beam material gases respectively may be prepared to introduce the plural kinds of charged particle beam material gases to the ion source 501 at the same time, or a gas cylinder filed with a mixed gas prepared in advance by mixing different kinds of charged particle beam material gases may be prepared to introduce the mixed gas to the ion source 501. FIG. 40 illustrates a case where the ion source 501 receives a mixed gas from a gas cylinder 522C that is filled with a gas for high-speed machining (e.g., oxygen gas, etc.) and a homogeneous gas for the deposition layer (e.g., argon gas, etc.) mixed at a certain ratio. The mixed gas from the gas cylinder 522C is either cut off or circulated by a stop valve 523C, and its flow volume rate is controlled by a flow control valve 524C. Here, the stop valve 523C or the flow control valve 524C have the same roles or control functions as the stop valves 523A and 523B and the flow control valves 524A and 524B of the previous embodiments. Also, the mixture ratio of different kinds of charged particle beam material gases is given by previous experiments to a condition for optimizing (proper balance) the ion beam stability, hole machining performance, hole fill performance, and the like. In the previous embodiments, when the job is switched from hole machining to hole fill processing for example, the charged particle beam material gas in the ion source 501 had to be substituted and replaced. In this embodiment, however, a mixed gas of the charged particle beam material gas used for hole machining and the charged particle beam material gas used for hole fill processing is used for both hole machining and hole fill processing, so there is no need to substitute the charged particle beam material gas. Therefore, the amount of time it takes to fulfill the work can be shortened as much as the amount of time it takes to substitute the charged particle beam material gas. FIG. 41 is a schematic view showing one example of the in-line defect analysis flow by using a charged particle beam processor of the present invention explained so far. In FIG. 41, reference numeral 613 designates a charged particle beam processor of the present invention, and the processing 110A, 110B, and 110C are part of the semiconductor production line. For instance, starting from the processing 110A, part of the sample 513 is taken out, and an optical or electron beam type inspection device (review SEM) 611 inspects defects and classify extracted defects. Next, the sample 612 including a defect region is brought into the charged particle beam processor 613. As aforementioned, the SEM built in the charged particle beam processor 613 locates the defect region through coordinate linkage with the inspection device 611, and a micro sample 581 having the defect region is extracted by the probe 515. The micro sample 581 is processed to a membrane by FIB, and taken out of the charged particle beam processor in form of cartridge. This micro sample 581 is then observed and analyzed by another inspection device (STEM or TEM) 614, and the analysis result (i.e. estimation of the causes of defects) is fed backed to the semiconductor production line (refer to an arrow 616). Meanwhile, a sample 620 having a processed hole through which the micro sample 518 has been extracted undergoes the hole fill processing, and a hole-filled sample 617 is returned to the processing 110B after the sample 513 extraction processing 110A. Therefore, by returning the sample after the hole fill processing back to the production line, waste in resources can be reduced. While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. |
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claims | 1. A charged particle beam writing method comprising:writing a pattern on a first target object by using a charged particle beam in a writing apparatus;conveying a second target object after having written the pattern on the first target object, wherein even though the second target object is arranged on any one of conveying paths including a carry-out port and a carry-in port of the writing apparatus, a conveying operation for the second target object is not performed during writing the pattern on the first target object;determining the presence/absence of a request of a conveying operation of the second target object, wherein a pattern writing operation for the first target object is stopped by the request; anddetermining whether a stop time of the pattern writing operation of the first target object occurred by performing the conveying operation of the second target object is included in a pattern writing prediction time of the first target object,wherein when the stop time of the pattern writing operation is not included in the pattern writing prediction time, the conveying operation of the second target object is not performed, and the pattern is written on the first target object. 2. The method according to claim 1, whereinthe conveying operation includes at least one of an operation of a conveying robot, opening/closing operations of a gate valve, and an actuating operation of a vacuum pump. 3. The method according to claim 1, wherein when the stop time of the pattern writing operation of the first target object is included in the pattern writing prediction time, the pattern writing operation of the first target object is stopped while the conveying operation of the second target object is performed. 4. The method according to claim 1, whereinthe pattern writing prediction time has a predetermined margin, andwhen the stop time of the pattern writing operation of the first target object falls within the predetermined margin, the pattern writing operation of the first target object is stopped while the conveying operation of the second target object is performed. 5. A charged particle beam writing method comprising:writing, by using a charged particle beam, a pattern on a target object to which a chemical amplification type resist is coated;determining the presence/absence of a request of an item which stops a pattern writing operation for the target object; anddetermining whether a stop time of the pattern writing operation occurred by performing the item is included in a pattern writing prediction time of the target object, whereinwhen the stop time of the pattern writing operation is not included in the pattern writing prediction time, the pattern writing operation for the target object is continued without performing the item regardless of the request of the item. 6. The method according to claim 5, whereinwhen the stop time of the pattern wiring operation is included in the pattern writing prediction time, the pattern writing operation of the target object is stopped while the item is executed. 7. The method according to claim 5, whereinthe pattern writing prediction time has a predetermined margin, andwhen the stop time of the pattern writing operation falls within the predetermined margin, the pattern writing operation of the target object is stopped while the item is executed. 8. The method according to claim 5, whereinwhen the target object on which the pattern writing operation is performed is used as a first target object, the item includes a conveying operation of a second target object. 9. The method according to claim 8, whereinthe conveying operation includes at least one of an operation of a conveying robot, opening/closing operations of a gate valve, and an actuating operation of a vacuum pump. |
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053944488 | description | DETAILED DESCRIPTION FIG. 1 shows the entire installation 1 making it possible to carry out the separate grinding and disposal of the constituents of fuel element jackets of a graphite/gas nuclear reactor. The installation 1 comprises a feed hopper 2 whose output end is placed above an inclined conveyor 3. Fuel element jackets 4 made of graphite containing stainless steel wires are discharged into the hopper 2 which feeds them to the input end of the conveyor 3, the output end of which communicates with a chute for feeding an impeller-disk mill 6. The fuel elements 4 enter the chute 5 which ensures regular feeding of the impeller-disk mill 6 which includes two rollers 7 turning in opposite directions and fitted with grinding cutters. The grinding mill 6 separates the jackets 4 into fragments which consist either of pieces of graphite with a size of a few tens of millimeters, or shredded fragments of the stainless steel wires. At the output of the grinding mill 6, a reception chute 8 receives a heterogeneous mixture of fragments consisting either of pieces of ground graphite or of segments of stainless steel wires. The chute 8 removes the mixture of heterogeneous fragments onto a conveyer 10, of the same type as 3, whose output is situated above the input opening of a two-stage magnetic separator 12. The separator 12 comprises an upper stage 12a and a lower stage 12b, which are equipped with magnetic separation means consisting of assemblies with belts and magnetic rollers, 13a and 13b respectively, of high intensity, of the type comprising rare-earth permanent magnets and which will be referred to below as magnetic rollers 13a and 13b. Each of the separator stages 12a and 12b comprises two outputs, respectively 15a and 16a and 15b and 16b. The outputs 15a and 15b, termed the first outputs, are intended mainly to receive the first constituent which is the magnetic constituent, i.e., in the case of fuel element jackets, the stainless steel wire. The second outputs 16a and 16b are intended mainly to receive the second non-magnetic constituent, i.e., in the case of jackets for fuel elements. Each of the outputs 15a, 16a, 15b, 16b can be equipped with remotely controlled closure means. When the heterogeneous mixture discharged by the conveyer 10 into the input opening of the separator 12 arrives in contact with the magnetic roller 13a, the first magnetic constituent, i.e., the stainless steel wires are retained and carried by the roller 13a which discharges them into the hopper of the output 15a of the separation stage 12a. The fragments consisting mainly of graphite are discharged, without being diverted by the roller 13a, into the second output 16a. The stainless steel wires discharged into the hopper of the output 15a pass into the stage 12b of the separator to be discharged directly into the first output 15b of the stage 12b. The mixture consisting mainly of graphite which is discharged onto the second magnetic roller 13b undergoes a separation, the stainless steel wires which may remain mixed with the pieces of graphite being retained and transported by the magnetic roller 13b to be discharged into the first output 15b of the stage 12b. The fragments reaching the first output 15b of the stage 12b, which mainly consist of stainless steel, are discharged into a hopper 18 comprising a closure hatch 19. Below the hatch 19 is arranged a chute or a storage container 20, as will be explained below with reference to FIGS. 2A, 2B and 2C. It is unimportant that a few fragments of graphite are still present mixed with the segments of stainless steel wires reaching the first output 15b of the separator, since these graphite fragments have much lower activity than that of the stainless steel. The conditions of packaging or disposing of the stainless steel wire may make it possible to process a few residual fragments of graphite. On the other hand, the object of the separation is to obtain, at the second output 16b of the second stage 12b of the separator, only pieces of graphite which constitute the majority of the bulk of the elements processed with a view to their disposal and which have low or moderate activity. The second output 16b of the separator stage 12b is arranged above the input end of a continuous handling means 21 which may consist for example of a belt conveyor. The belt conveyor 21 has drive means which make it possible to run it in either direction, as schematically represented by the double arrows 22. The input end of the conveyor 21 is situated above the hopper 18 for receiving the stainless steel wire. The output end of the conveyor 21 is placed inside a hopper 24 comprising a closure hatch 25 at its lower part, making it possible to isolate the hopper 24 or make it communicate with an output chute or a packaging container 26 as will be explained with reference to FIGS. 2A, 2B and 2C. A radioactivity detector 27, such as a scintillation detector, is arranged above the belt of the conveyor 21. The detector 27 is adjusted to a sensitivity level such that it makes it possible to detect any segment of stainless steel wire inside the graphite fragments supported by the conveyor 21 in the first direction of motion of the conveyor going from the input end, below the output 16b of the separator, to its output end, inside the hopper 24. The detector 27 is connected to a unit 28 for controlling the motorization of the continuous conveyor 21 and of the input carrier 3. In the event that the detector 27 detects the presence of at least one stainless steel wire in the graphite fragments transported by the conveyor 21, the control unit 28 stops the conveyor 21, closes the output 16b of the separator, then operates the continuous conveyor 21 in its second direction of motion, going from the hopper 24 to the hopper 18. The fragments of graphite containing one or more segments of stainless steel wire are then discarded into the hopper 18 intended to receive the segments of stainless steel wires. When the detector 27 no longer detects a high level of radioactivity corresponding to the presence of stainless steel wires on the continuous handling means 21, the latter is operated in its first direction of motion, going from the output 16b of the separator to the hopper 24, the element for blocking the output 16b of the separator being placed in the open position. In the event that the detector 27 detects a very high level of radioactivity corresponding to a large proportion of stainless steel wires in the graphite particles transported by the conveyor 21, the control unit 28 stops the conveyor 3 feeding the grinding mill. In effect, in the event that the proportion of stainless steel wires is high, it can be concluded that the separator 12 is malfunctioning and it is then preferable to shut down the entire grinding and separation installation. The method and the device according to the invention, as described above, therefore make it possible to carry out efficient and very reliable separation of a first constituent and a second constituent having different magnetic properties and activation levels, in activated elements. The operation of the device according to the invention is completely automatic and does not require the presence of operators near the installation. Furthermore, the discharge devices for the materials at the output of the installation, which will be described with reference to FIGS. 2A, 2B and 2C, make it possible to discharge, package and dispose of the fragments separated by the separation, without contaminating the environment and under conditions which ensure effective biological protection. These means are particularly useful as regards removing materials containing mainly stainless steel wire through the first output of the installation comprising the hopper 18, the leaktight closure hatch 19 and the chute or the container 20. The description of the emptying device represented in FIGS. 2A, 2B and 2C will be given with reference to the elements 18, 19 and 20 of the first output of the installation 1 represented in FIG. 1. However, it is clear that the second output comprising the hopper 24, the hatch 25 and the chute or container 26 can also be produced in the manner described in FIGS. 2A, 2B and 2C. As can be seen in FIGS. 2A, 2B and 2C, the output hopper 18 of the installation comprises at its lower part a hatch 19 comprising a hatch body 30 and a sliding closure element 31. The lower part of the hatch body 30 has an opening 30a, at which a container 20 can be placed, this container being closed by a leaktight closure element 32, as represented in FIG. 2A. The container 20 intended to collect the highly radioactive fragments contained in the hopper 18 and consisting mainly of segments of stainless steel wires is a high-integrity container having a large wall thickness. The container 20 can be placed in the position represented in FIG. 2A using a carriage (now shown) which moves it over the floor 33, as schematically represented by the arrow 36. As can be seen in FIG. 2B, a lifting means combined with the carriage for supporting the container 20 makes it possible to lift the container 20, so as to insert its upper part and the leaktight closure element 32 into the opening 30a of the hatch body 30, as represented by the arrow 34. At the end of the upwards movement of the container 20, the elements 31 and 32 are in contact with each other. As represented in FIG. 2C, and represented by the arrow 35, it is then possible to move the two closure elements 31 and 32 simultaneously, so as to place the hopper 18 into communication with the container 20. The radioactive fragments contained in the hopper 18 are then discharged into the container 20 which is filled. The closure elements 31 and 32 are then moved in the direction opposite to the arrow 35 in order to return them into the position of closing the hopper 18 and the container 20. The container 20 can then be lowered into the transport position, for removal to a storage site or a processing plant. It is clear that the removal of the particles of graphite received in the hopper 24 can be carried out by using a container, as in the case of the fragments of stainless steel wires. However, because of the low radioactivity of the graphite particles, it is also possible to discharge the graphite particles via a chute into a continuous transport means feeding a graphite disposal unit, such as an incineration unit. The entire installation 1 represented in FIG. 1 can be placed in a containment unit held under reduced pressure using a conventional ventilation system, which need not be described. In order to operate continuously and entirely automatically, the installation may comprise various detection and control means. In particular, the grinding mill 6 may comprise level detection means. These detection means may be arranged at the grinding mill itself, in order to monitor the feeding of the grinding mill by the carrier 3, or in the outward chute, in order to make it possible to regulate the feed rate of the magnetic separator. It is possible to use a grinding mill other than an impeller-disk mill and a magnetic separator of a type other than a high-intensity roller separator with permanent magnets based on rare earths. It is possible to use any type of radioactivity detector for detecting stainless steel wires, or more generally a constituent with strong radioactivity on the continuous handling means. Finally, the method and the device of the invention can be used for processing activated elements other than jackets of fuel elements of a reactor of the graphite/gas type. The method and the device according to the invention can be used for processing, before disposal, any radioactive element comprising at least two constituents having substantially different magnetic characteristics and activity levels. |
description | Nuclear fuel rods are removed from nuclear power plants when their temperature is not high enough to generate vapor needed to produce electricity. The problem of what to do with used nuclear fuel has plagued the industry since commercialization of nuclear reactors started with the Atomic Energy Act of 1954. The inability of the United States to fully implement the Nuclear Waste Policy Act of 1982 and the utilities inability to use the Private Fuel Storage facility indicate that the problem has not been solved. The report from the Blue Ribbon Commission on America's Nuclear Future recommends storing the used radioactive decay material in an interim storage unit. Interim storage, however, produces no revenue and does not put the radioactive heat to any use. Example embodiments include a vapor forming apparatus, system and/or method for producing vapor from radioactive decay material. The vapor forming apparatus including an insulated container configured to enclose a nuclear waste container. The nuclear waste container includes radioactive decay material. The insulated container includes an inlet valve configured to receive vapor forming liquid. The radioactive decay material transfers heat to the vapor forming liquid. The insulated container also includes an outlet valve configured to output the vapor forming liquid heated by the radioactive decay material. In one embodiment, the vapor forming liquid includes a mixture of one of (1) water and acetone and (2) water and alcohol. The vapor forming apparatus may include at least one thermocouple configured to monitor the heat transferred to the vapor forming liquid. The insulated container may include a removable closure to insert the nuclear waste container into the insulated container. The vapor forming system includes a storage unit configured to hold vapor forming liquid, and a plurality of vapor forming apparatuses that are connected to each other in series. Each of the plurality of vapor forming apparatuses includes an insulated container configured to enclose a nuclear waste container. The nuclear waste container includes radioactive decay material. The vapor forming system also includes a pumping unit configured to pump the vapor forming liquid from the storage unit and transfer the vapor forming liquid through each insulated container of the plurality of vapor forming apparatuses where the radioactive decay material transfers heat to the vapor forming liquid in each stage, a switching valve unit configured to receive the vapor forming liquid from a last vapor forming apparatus of the plurality of vapor forming apparatus, and a control unit configured to control the switching valve unit to output vapor of the vapor forming liquid if at least one property of the vapor forming liquid is above a threshold. The control unit is configured to control the switching valve unit to output the vapor forming liquid via a bypass line to the storage unit if the at least one property of the vapor forming liquid is equal to or below the threshold. In one embodiment, the vapor forming liquid includes a mixture of one of (1) water and acetone and (2) water and alcohol. The at least one property of the vapor forming liquid may include temperature and pressure. The vapor forming system also includes a pressure monitoring unit configured to monitor the pressure of the vapor forming liquid, and a temperature monitoring unit configured to monitor the temperature of the vapor forming liquid. The control unit is configured to receive temperature information and pressure information from the temperature monitoring unit and the pressure monitoring unit, respectively, and configured to control the switching valve unit based on the temperature information and the pressure information. In one embodiment, the pressure monitoring unit and the temperature monitoring unit are connected between an outlet valve of the plurality of vapor forming apparatuses and the switching valve unit. The control unit controls the switching valve unit to output the vapor of the vapor forming liquid if the pressure and temperature are high enough for energy conversion to occur, and the control unit controls the switching valve unit to output the vapor forming liquid via a bypass line to the storage unit if the pressure and temperature are not high enough for energy conversion to occur. The insulated container for each vapor forming apparatus includes a removable closure to insert the nuclear waste container into the insulated container. The vapor forming system may include a power module generator configured to receive the vapor from the switching valve unit and generate electrical energy based on the vapor. The method includes transferring vapor forming liquid through a plurality of vapor forming apparatuses that are connected to each other in series. Each of the plurality of vapor forming apparatuses includes an insulated container configured to enclose a nuclear waste container. The nuclear waste container includes radioactive decay material. The radioactive decay material transfers heat to the vapor forming liquid. The method further includes outputting vapor of the vapor forming liquid from a last vapor forming apparatus of the plurality of vapor forming apparatuses if at least one property of the vapor forming liquid is above a threshold. The method may further include outputting the vapor forming liquid via a bypass line to a storage unit if the at least one property of the vapor forming liquid is equal to or below the threshold. The storage unit holds the vapor forming liquid to be supplied to a first vapor forming apparatus of the plurality of vapor forming apparatuses. In one embodiment, the vapor forming liquid includes a mixture of one of (1) water and acetone and (2) water and alcohol. The at least one property of the vapor forming liquid may include temperature and pressure. The method may further include monitoring the temperature and pressure of the vapor forming liquid. The outputting step outputs the vapor of the vapor forming liquid if the pressure and temperature are high enough for energy conversion to occur. The outputting step outputs the vapor forming liquid via a bypass line to a storage unit if the pressure and temperature are not high enough for energy conversion to occur. Hereinafter, example embodiments will be described in detail with reference to the attached drawings. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the language explicitly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures or described in the specification. For example, two figures or steps shown in succession may in fact be executed in series and concurrently or may sometimes be executed in the reverse order or repetitively, depending upon the functionality/acts involved. Example embodiments include a vapor forming apparatus that utilizes radioactive decay material to generate vapor from vapor forming liquid. The radioactive decay material may include concentrated fission products. The concentrated fission product may be a certain percentage of the mass of used fuel. The radioactive decay material is placed into nuclear waste containers. An insulated container is used to enclose each nuclear waste container. Example embodiments provide a system and method that transfers the vapor forming liquid through each insulated container, where the radioactive decay material transfers heat to the vapor forming liquid. If the properties of the vapor forming liquid are above a threshold level (e.g., the pressure and temperature are above a certain level), vapor is output to a subsequent process or system such as a coolant and vapor circuit that generates electrical energy based on the generated vapor. These features are further explained with reference to FIGS. 1-6. FIG. 1 illustrates a coolant and vapor circuit that generates electrical energy from a heat source according to an example embodiment. The coolant and vapor circuit includes a heat source 100, an integrated power module generator 200, an evaporative condenser 201, a first pump 202, and a second pump 203. The coolant and vapor circuit may include other components that are well known to one of ordinary skill in the art for producing electrical energy from a heat source. The heat source 100 generates pressurized vapor. The details of the heat source 100 are further explained with reference to FIGS. 2-3. The integrated power module generator 200 generates electrical energy based on the heated pressurized vapor received from the heat source 100. The generation of electrical energy utilizing heated pressurized vapor may be performed according to methods that are well known to one of ordinary skill in the art. The integrated power module 200 outputs low pressure vapor to the evaporative condenser 201. The evaporative condenser 201 may be any type of device or unit that condenses vapor into liquid. The evaporative condenser 201 generates low pressure liquid by condensing the low pressure vapor into liquid. The first pump 202 transfers the vapor-liquid mixture back to the evaporative condenser 201 until the vapor liquid mixture has been converted to the low pressure liquid. The evaporative condenser 201 outputs low pressure liquid, which is converted to high pressure liquid via the second pump 203. The high pressure liquid is fed back into the heat source 100. FIG. 2 illustrates a vapor forming apparatus 150 according to an example embodiment. The vapor forming apparatus 150 includes an insulated container 102 enclosing a nuclear waste container 101, an inlet 103, an inlet valve 104, an outlet 105, an outlet valve 106, thermocouples 107, and a removable closure 108. The vapor forming apparatus 150 or the plurality of vapor forming apparatuses 150 (shown in FIG. 3) may operate as the heat source 100 of FIG. 1. The nuclear waste container 101 includes radioactive decay material. According to an embodiment, the radioactive decay material may be concentrated fission products. The concentrated fission products may be a certain percentage of the mass of used nuclear fuel. In one embodiment, the concentrated fission products are four percent of the used fuel. Further, the concentrated fission products are placed in a robust material form, which can be placed into a coolant that can be vaporized under environmentally controlled conditions, as further described below. The forms are robust if after the coolant is removed, the concentrated fission products still maintain their form under passive heat removal conditions. In one embodiment, the concentrated fission products may be metallic or ceramic or both. The nuclear waste container 101 may be a thick walled metal container that is leak tight, similar to that which has been used previously for storing nuclear waste. Referring to FIG. 2, the nuclear waste container 101 is lowered though the removable closure 108 for location inside the insulated container 102. For example, the removable closure 108 is configured to insert the nuclear waste container 101 into the insulated container 102. The insulated container 102 and the removable closure 108 may be insulated such that all or substantially all the heat generated in the waste package is absorbed by the fluid rather than lost to the environment. The inlet valve 104 is configured to receive vapor forming liquid, where the vapor forming liquid is transferred inside the insulated container via the inlet 103. In order to regulate the vapor formation both in amount and quality, example embodiments may use a mixture of two fluids such as water and acetone or water and alcohol such that for startup there is more water in the system for passive heat removal. However, the vapor forming liquid of the example embodiments may be any type of solution or mixture that undergoes a phase change from a liquid to a vapor with heat input. Also, it is noted that when vapor formation is desired for electrical production, the use of the radioactive heat is used to shift the mixture to higher concentration of the more volatile organic liquid thus increasing the vapor content of the fluid. The vapor formation is controlled by the coolant flow rate and system pressure. The inventors have recognized that the shifting of the fluid vapor point by controlling the composition of the coolant uses standard chemical distillation techniques. The vapor forming liquid flows around the nuclear waste container 101, and the radioactive decay material contained inside the nuclear waste container 101 transfers heat to the vapor forming liquid. The radioactive decay material transfers heat to the vapor forming liquid according to the following equations:A(t)=A0·e−λt Eq. (1)Q′=w·h·ΔT Eq. (2) Eq. (1) represents a time-dependent activity A. The time-dependent activity A may be replaced by any number of quantities including the gamma production rate or the heat rate. The parameter A0 represents the initial value such as the initial gamma production rate or the initial heat rate. The parameter λ is the nominal aggregated decay constant. The nominal aggregated decay constant is further explained below. The parameter t is the cooling time. Eq. (2) is the linear heat generation rate in power per channel length. The parameter w is the mass flow rate, the parameter h is the linear heat transfer coefficient and the parameter ΔT is the change in temperature for the vapor forming liquid. Based on Eqs. (1) and (2), it can be seen that the maximum heat of the system is determined by the mass of fission products and the nominal decay constant of the fission products. The unique fission products from a typical light water reactor (LWR) system number over 700, all with different decay constants and concentrations. As such, the example embodiments utilizes an aggregated decay constant. The aggregated decay constant may be approximated from time-dependent specific heat generation data that is provided by NRC Regulatory Guide 3.54 Rev 1. This data provides sample values for which to fit a decay curve. In one embodiment, the nuclear waste container 101 includes discharged nuclear fuel material after the discharged nuclear fuel material has cooled for ten years, for example. However, the example embodiments encompass discharged nuclear fuel material that has been cooled for any number of years. The decay heat rate of the fission products in the used fuel level off such that for an additional ten years, a relatively constant heat rate may be achieved. Furthermore, if the fission products are in use for thirty years, the heat rate decays to approximately 50%. These features are further explained with reference to FIGS. 4-6. The thermocouples 107 are configured to monitor the heat transferred to the vapor forming liquid. In one embodiment, one thermocouple 107 may be placed toward the top portion of the insulated container 102 and another thermocouple 170 may be placed toward the bottom portion of the insulated container 102. However, the example embodiment encompass any number of thermocouples and encompass the placement of such thermocouples in any location of the insulated container 102. The outlet valve 106 is configured to output the vapor forming liquid from the outlet 105 that has been heated by the radioactive decay material. In other words, hot fluid leaves the insulated container 102 flowing out the outlet 105 through the outlet valve 106. FIG. 3 illustrates a vapor forming system that includes a plurality of vapor forming apparatuses 150 according to an example embodiment. The vapor forming system includes a plurality of vapor forming apparatuses 150 (e.g., each vapor forming apparatus of FIG. 3 is the vapor forming apparatus 150 of FIG. 2), a storage unit 112 configured to hold the vapor forming liquid, a pumping unit 109, a first pressure monitoring unit 110, a first temperature monitoring unit 111, a switching valve unit 116, a second pressure monitoring unit 114, a second temperature monitoring unit 115, and a control unit 117 for controlling the switching valve unit 116 and/or the pumping unit 109. Although FIG. 3 only illustrates four vapor forming apparatuses 150, the example embodiments encompass any number of vapor forming apparatuses 150. The plurality of vapor forming apparatuses 150 may be referred to as a train of vapor forming apparatuses or a train of heat sources. As previously explained with reference to FIG. 2, each vapor forming apparatus 150 includes an insulated container 102 that is configured to enclose a nuclear waste container 101. The nuclear waste container 101 includes the radioactive decay material. However, the vapor forming apparatuses 150 of FIG. 3 are connected in series with each other. For example, the outlet valve 106 of the first vapor forming apparatus 150 is connected to the inlet valve 104 of the second vapor forming apparatus via any connection member that supports the transfer of fluid. The other vapor forming apparatuses 150 are connected in the same manner. However, the outlet valve 106 of the last vapor forming apparatus 150 in the train of heat sources is connected to the switching valve unit 116. The pumping unit 109 is configured to pump the vapor forming liquid from the storage unit 112 and transfer the vapor forming liquid through each insulated container 102 of the plurality of vapor forming apparatuses 150, where the radioactive decay material transfers heat to the vapor forming liquid in each stage. For example, the pumping unit 109 pumps the vapor forming liquid from the storage unit 112 and transfers the vapor forming liquid to the insulated container 102 of the vapor forming apparatus 150 via the inlet valve 104. The first pressure monitoring unit 110 is configured to monitor the pressure of the vapor forming liquid that is transferred from the storage unit 112 to the first vapor forming apparatus 150. The first pressure monitoring unit 110 may be located between the storage unit 112 and the first vapor forming apparatus 150. The first temperature monitoring unit 111 is configured to monitor the temperature of the vapor forming liquid that is transferred from the storage unit 112 to the first vapor forming apparatus 150. The first temperature monitoring unit 111 may be located between the storage unit 112 and the first vapor forming apparatus 150. Also, the first temperature monitoring unit 111 and the first pressure monitoring unit 110 may not be two separate units. For example, the example embodiments encompass the situation where the first temperature monitoring unit 111 and the first pressure monitoring unit 110 are implemented in one unit. The first temperature monitoring unit 111 and the first pressure monitoring unit 110 may be any type of device(s) capable of monitoring temperature and/or pressure that is well known to one of ordinary skill in the art. In the first stage, the radioactive decay material transfers heat (Qa) to the vapor forming liquid. In the subsequent stage, the pumping unit 109 operates to transfer the heated vapor forming liquid from the first vapor forming apparatus 150 via the outlet valve 106 to the insulated container 102 of the second vapor forming apparatus 150 via the inlet valve 104. In this stage, the radioactive decay material transfers heat (QB) to the vapor forming liquid. The other vapor forming apparatuses 150 operate in the same manner. As a result, the vapor forming apparatuses 150 transfer heat to the vapor forming liquid based on the following equation:Qtotal=QA+QB+QC+QD Eq. (3) Qtotal is the total amount of heat transferred to the vapor forming liquid in the vapor forming system of FIG. 3. The parameters QA, QB, QC and QD represent the heat transferred in the stages of the vapor forming system. For example, the parameter QA is the heat transfer for the first vapor forming apparatus 150, the parameter QB is the heat transfer for the second vapor forming apparatus 150, the parameter QC is the heat transfer for the third vapor forming apparatus 150, and the parameter QD is the heat transfer for the fourth vapor forming apparatus 150. Each of the parameters QA, QB, QC, QD is defined by Eq. (2). In other word, the pumped vapor forming liquid flowing through the inlet valve 104 of the first vapor forming apparatus 150 continues to flow through each insulated container 102 gaining thermal energy as shown in Eq. (3). The second pressure monitoring unit 114 is configured to monitor the pressure of the vapor forming liquid that is transferred from the outlet valve 106 of the last vapor forming apparatus 150. The second pressure monitoring unit 114 may be located between the outlet valve 106 of the last vapor forming apparatus 150 and the switching valve unit 116. The second temperature monitoring unit 115 is configured to monitor the temperature of the vapor forming liquid that is transferred from outlet valve 106 of the last vapor forming apparatus 150. The second temperature monitoring unit 115 may be located between the outlet valve 106 of the last vapor forming apparatus 150 and the switching valve unit 116. Also, the second temperature monitoring unit 115 and the second pressure monitoring unit 114 may not be two separate units. For example, the example embodiments encompass the situation where the second temperature monitoring unit 115 and the second pressure monitoring unit 114 are implemented in one unit. The second temperature monitoring unit 115 and the second pressure monitoring unit 114 may be any type of device(s) capable of monitoring temperature and/or pressure that is well known to one of ordinary skill in the art. The pressure monitoring unit 114 and the temperature monitoring unit 115 at the exit of the train provide an indication of the thermodynamic properties of the vapor forming liquid. The switching valve unit 116 is configured to receive the vapor forming liquid from the last vapor forming apparatus 150 and output vapor of the vapor forming liquid if at least one of the pressure and temperature is above a respective threshold. The threshold may be the point where energy conversion occurs (e.g., liquid to gas). However, if at least one of the pressure and temperature is equal to or below the respective threshold level, the switching valve unit 116 is configured to output the vapor forming liquid via a bypass line 113 to the storage unit 112. In other words, if the thermodynamic properties are too low for energy conversion to occur, the vapor forming liquid is returned to the storage unit 112 via the bypass line 113 during startup or source reload. The control unit 117 is configured to control the operation of the switching valve unit 116 based on information received from the second pressure monitoring unit 114 and/or second temperature monitoring unit 115. For example, the control unit 117 is configured to receive temperature information and pressure information from the second temperature monitoring unit 115 and the second pressure monitoring unit 114, respectively, and control the switching valve unit 116 based on the temperature information and the pressure information. The control unit 117 controls the switching valve unit 116 to output the vapor of the vapor forming liquid if the pressure and temperature are high enough for energy conversion to occur by transmitting control information to the switching valve unit 116. Also, the control unit 117 controls the switching valve unit 116 to output the vapor forming liquid via the bypass line 113 if the pressure and temperature are not high enough for energy conversion to occur by transmitting control information to the switching valve unit 116. The control information includes information indicating whether to direct the flow of the vapor to a next stage circuit (e.g., the circuit of FIG. 1) or direct the flow of the vapor forming liquid back to the storage unit 112 via the bypass line 113. In addition, the control unit 117 may use temperature information from the first temperature monitoring unit 111 and the pressure information from the first pressure monitoring unit 110, in conjunction with the pressure and temperature information from the second pressure monitoring unit 114 and the second temperature monitoring unit 115 for controlling the switching valve unit 116. Further, the control unit 117 may be configured to control the pumping unit 109 based on the information from the first pressure monitoring unit 110, the first temperature monitoring unit 111, the second pressure monitoring unit 114, the second temperature monitoring unit 115, and/or the thermocouples 107. For example, the control unit 117 may control the flow rate of the vapor forming liquid that is transferred throughout the from the storage unit 112 throughout the vapor forming apparatuses 150. FIG. 4 illustrates power generation for a different number of vapor forming apparatuses according to an example embodiment. It is noted that the fission products within the nuclear waste container 101 are concentrated to 20 times than in current used nuclear fuel. FIG. 4 shows the heat generation rate for a 4-, 15- and 40-container train. The band in each curve, due to the waste power, is dependent on the used nuclear fuel burnup. Higher used nuclear fuel burnup will give the highest heat generation rate. The curve also shows that the relative heat generation rate from the 10th year to 40th year only varies by about 50%. This is a relatively significant and steady output of heat energy. The expected electrical output is based on 13% thermal efficiency, which is an average industry standard for generating electricity from low temperature heat sources. Example embodiments provide an apparatus, system and method of operating a vapor forming coolant in which vapor is produced directly from a radioactive heat section. The system provides a constant power source or produces a constant heat source. This system has no regulation requirements and utilizes the inherent physical property of radioactive decay for heat production and bubble formation. Example embodiments thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied through routine experimentation and without further inventive activity. For example, although electrical contacts are illustrated in example embodiments at one side of an example reducing system, it is of course understood that other numbers and configurations of electrical contacts may be used based on expected cathode and anode assembly placement, power level, necessary anodizing potential, etc. Variations are not to be regarded as departure from the spirit and scope of the example 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. |
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039473228 | abstract | A reactor pressure vessel is supported at its bottom end by an inverted frusto-conical surface concentric with the axis of the vessel and fixed to its bottom, this surface slidably resting on an upright frusto-conical surface which is also concentric with the vessel's axis. Radial thermal movements of the reactor's bottom results in diameter changes in the conical surface fixed to its bottom so that this surface by cam action moves up and down on the other surface, and with a properly defined angularity, compensates for the vertical thermal expansion of the vessel which occurs simultaneously with its radial expansion. |
summary | ||
abstract | A radiation shielding device for meteorological observation with internal air circulation including: a body for allowing meteorological sensors to be mounted therein; a cover for covering the body by engaging with the body; and a modified Venturi tube which is physically formed while the body and the cover are engaged with each other; wherein, the modified Venturi tube is configured as a first opening for receiving external air from an exterior of the body, a second opening for receiving internal air from an interior of the body, and a third opening for releasing the received external air and the received internal air, and wherein, the external air gets into the modified Venturi tube through the first opening, the internal air gets into the modified Venturi tube through the second opening, and the external air and the internal air are released from the modified Venturi tube through the third opening. |
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abstract | An apparatus, suited, for example, for extreme ultraviolet lithography, includes a radiation source and a processing organ for processing the radiation from the radiation source. Between the radiation source and the processing organ a filter is placed which, in the radial direction from the radiation source, comprises a plurality of foils or plates. |
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052951677 | claims | 1. A service pole caddy system for servicing a nuclear reactor using a plurality of service poles which can be coupled in series to form a multi-pole assembly having an end adapted for carrying a tool, comprising: track support means mounted on said nuclear reactor; track means supported by said track support means, said track means extending over said nuclear reactor in a generally horizontal plane; rolling means arranged to roll along said track means between first and second positions; pole storage means for supporting a plurality of service poles in a generally upright position; pole assembly means for hanging a multipole assembly thereon; and rigid frame means for rigidly coupling said pole support means and said pole assembly means, said rigid frame means riding on said rolling means. track support means mounted on said nuclear reactor; track means supported by said track support means, said track means extending over said nuclear reactor in a generally horizontal plane; rolling means arranged to roll along said track means between first and second positions; pole storage means for supporting a plurality of service poles in a generally upright position; pole assembly means for hanging a multipole assembly thereon; a horizontal platform for supporting work personnel thereon; and rigid frame means for rigidly coupling said pole support means, said pole assembly means and said horizontal platform to each other, said rigid frame means riding on said rolling means. pole assembly means for holding a first service pole generally upright at an assembly position during connection of a bottom end of a second service pole to a top end of said first service pole; and rigid support means for supporting said pole assembly means in a position over said nuclear reactor, wherein said pole assembly means comprises a keyway plate having a slot with a pole seat at said assembly position for receiving said neck portion and supporting said seating portion of said first service pole, each of said service poles comprises first and second solid-body end connectors joined to respective first and second ends of a tube having a third diameter which is greater than said first diameter of said neck portion, said neck portion being formed in said first end connector, and said slot further comprises guide means for blocking substantial lateral displacement of a portion of said tube of said service pole when inserted within said guide means, with sufficient play therebetween to allow said first service pole to be vertically displaced without impediment, said guide means communicating with said pole seat by way of a throat having a width greater than said first diameter of said neck portion and less than said third diameter of said tube. pole assembly means for holding a first service pole generally upright at an assembly position during connection of a bottom end of a second service pole to a top end of said first service pole; and rigid support means for supporting said pole assembly means in a position over said nuclear reactor, wherein said pole assembly means comprises a keyway plate having a slot with a pole seat at said assembly position for receiving said neck portion and supporting said seating portion of said first service pole, said pole seat comprising an arc-shaped chamfered surface having a radius greater than the radius of said neck portion of said first service pole, and said seating portion on said first service pole comprising a circular chamfered surface which abuts said arc-shaped chamfered surface in a form-fitting relationship when said first service pole is supported by said keyway plate at said assembly position. 2. The service pole caddy system as defined in claim 1, wherein said pole support means comprises first and second racks which are substantially vertically aligned at first and second elevations respectively, each of said first and second racks comprising a plurality of cells arrayed such that each cell of said first rack overlies a corresponding cell of said second rack, each cell of said first rack having means for blocking lateral displacement of a first portion of a corresponding service pole placed therein and each corresponding cell of said second rack having means for blocking lateral displacement relative thereto of a second portion of said corresponding service pole, and further comprises means for blocking downward displacement of a bottom end of said service pole when inserted in said racks in a generally upright position. 3. The service pole caddy system as defined in claim 2, wherein said downward displacement blocking means comprises a perforated plate. 4. The service pole caddy system as defined in claim 1, wherein said track support means comprises a refueling bridge spanning said nuclear reactor. 5. The service pole caddy system as defined in claim 1, wherein each of said service poles comprises a neck portion and a seating portion, said seating portion being joined to said neck portion and having a diameter greater than a diameter of said neck portion, and said pole assembly means comprises a keyway plate having a slot with a pole seat for receiving said neck portion and supporting said seating portion of said service pole, said pole seat being shaped to form-fit with said seating portion to prevent lateral displacement of said seating portion of said service pole seated thereon. 6. The service pole caddy system as defined in claim 5, wherein each of said service poles comprises first and second solid-body end connectors joined to respective first and second ends of a tube having a diameter which is greater than said diameter of said neck portion, said neck portion being formed in said first end connector, and said slot further comprises guide means for blocking substantial lateral displacement of a portion of said tube of said service pole when inserted within said guide means, with sufficient play therebetween to allow said service pole to be vertically displaced without impediment. 7. The service pole caddy system as defined in claim 6, wherein said guide means communicates with said pole seat by way of throat means having a width greater than said diameter of said neck portion and less than said tube diameter. 8. The service pole caddy system as defined in claim 1, wherein each of said service poles comprises first and second solid-body end connectors joined to respective first and second ends of a tube having a predetermined diameter, and said pole assembly means comprises guide means for blocking substantial lateral displacement of a portion of said tube when inserted within said guide means, with sufficient play therebetween to allow said service pole to be vertically displaced without impediment. 9. The service pole caddy system as defined in claim 1, further comprising a horizontal platform attached to said rigid frame means for supporting work personnel thereon. 10. The service pole caddy system as defined in claim 5, wherein said keyway plate is rotatably coupled to said rigid frame means. 11. A service pole caddy system for servicing a nuclear reactor using a plurality of service poles which can be coupled in series to form a multi-pole assembly having an end adapted for carrying a tool, comprising: 12. The service pole caddy system as defined in claim 11, wherein said pole support means comprises first and second racks which are substantially vertically aligned at first and second elevations respectively, each of said first and second racks comprising a plurality of cells arrayed such that each cell of said first rack overlies a corresponding cell of said second rack, each cell of said first rack having means for blocking lateral displacement of a first portion of a corresponding service pole placed therein and each corresponding cell of said second rack having means for blocking lateral displacement relative thereto of a second portion of said corresponding service pole, and further comprises means for blocking downward displacement of a bottom end of said service pole when inserted in said racks in a generally upright position. 13. The service pole caddy system as defined in claim 11, wherein said downward displacement blocking means comprises a perforated plate. 14. The service pole caddy system as defined in claim 11, wherein said track support means comprises a refueling bridge spanning said nuclear reactor. 15. The service pole caddy system as defined in claim 11, wherein each of said service poles comprises a neck portion and a seating portion, said seating portion being joined to said neck portion and having a diameter greater than a diameter of said neck portion, and said pole assembly means comprises a keyway plate having a slot with a pole seat for receiving said neck portion and supporting said seating portion of said service pole, said pole seat being shaped to form-fit with said seating portion to prevent lateral displacement of said seating portion of said service pole seated thereon. 16. The service pole caddy system as defined in claim 15, wherein each of said service poles comprises first and second solid-body end connectors joined to respective first and second ends of a tube having a diameter which is greater than said diameter of said neck portion, said neck portion being formed in said first end connector, and said slot further comprises guide means for blocking substantial lateral displacement of a portion of said tube of said service pole when inserted within said guide means, with sufficient play therebetween to allow said service pole to be vertically displaced without impediment. 17. The service pole caddy system as defined in claim 16, wherein said guide means communicates with said pole seat by way of throat means having a width greater than said diameter of said neck portion and less than said tube diameter. 18. A service pole caddy system for servicing a nuclear reactor using a plurality of service poles which can be coupled in series to form a multi-pole assembly having a lower end adapted for carrying a tool, each of said service poles having a neck portion of first diameter and a seating portion of second diameter greater than said first diameter, said seating portion being joined to said neck portion, comprising: 19. A service pole caddy system for servicing a nuclear reactor using a plurality of service poles which can be coupled in series to form a multi-pole assembly having a lower end adapted for carrying a tool, each of said service poles having a neck portion of first diameter and a seating portion of second diameter greater than said first diameter, said seating portion being joined to said neck portion, comprising: |
abstract | A rotation detector includes a semiconductor chip, a nonmagnetic case body, a biasing permanent magnet and a nonmagnetic cap fixed to the case body, wherein the case body has a joint surface, and the cap has an inside surface in contact with the joint surface. A method of manufacturing the rotation detector includes the following steps: assembling the semiconductor chip, the case body and the biasing permanent magnet into a unit; forming at least one groove adjacent to the joint surface so as to form a space between the joint surface and the inside surface when the cap is fixed to the case body; fixing the cap to the case body so that the inside surface of the cap can be in contact with the joint surface; irradiating a laser beam at portions behind the inside surface of the cap under a prescribed pressure to melt materials of the case body and the cap and to make melted materials flow to the space; and cooling the melted materials to re-crystallize. |
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description | This application is a U.S. National Stage application of PCT Application No. PCT AT06/000060, filed Feb. 16, 2006, which claims priority from Austrian Patent Application No. A 273/2005, filed on Feb. 18, 2005. The invention relates to improvements on particle-beam projection processing apparatus for irradiating a target by means of a beam of energetic electrically charged particles, comprising an illumination system, a pattern definition (PD) means and a projection system in order to project the beam patterned by the PD means onto a target positioned after the projection system. The illumination system serves to generate and form the energetic particles into a wide-area illuminating beam which is substantially tele/homocentric at the location of the PD means and whose diameter is greater by at least one order of magnitude than the length of the tele/homocentricity region of the illuminating beam; the PD means, located after the illumination system as seen along the direction of the beam, positions an aperture pattern composed of apertures transparent to the energetic particles in the path of the illuminating beam, thus forming a patterned beam emerging from the aperture pattern; and the projection system, positioned after the pattern definition means, projects the patterned beam as mentioned. One important application of processing apparatus of this kind is in the field of particle-beam lithography used in semiconductor technology, as a lithography apparatus, wherein, in order to define a desired pattern on a substrate surface, the wafer is covered with a layer of a radiation-sensitive photoresist, a desired structure is imaged onto the photoresist by means of a lithography apparatus which is then patterned by partial removal according to the pattern defined by the previous exposure step and then used as a mask for further structuring processes such as etching. Another important application of processing apparatus of this kind is in the field of nano-scale patterning, by direct ion beam material modification or ion beam induced etching and/or deposition, used for the fabrication or functionalization of nano-scale devices, particularly having sub-100 nm feature sizes. The IMS-concept PLM2 (short for “Projection Mask-Less Lithography”) as described in the U.S. Pat. No. 6,768,125 realizes a multi-beam direct write concept uses a programmable aperture plate system (APS) as PD device for structuring an electron beam, which is extracted from a single electron source. At the APS the kinetic energy of the electrons is 5 keV. After the APS the electrons are accelerated to 100 keV and the image of the APS is reduced 200 times and projected onto the substrate. In an electron optical system, scattered electrons from the lenses and the APS produce low energetic electrons or ions. Also residual gas atoms ionized either due to the beam or due to large electrostatic fields can be produced. These particles may irradiate the wafer and form a background dose which reduces the contrast of the image. Also components of the electron-optical systems (e.g. lenses and APS) are likely to be contaminated by these particles or, what is unavoidable in lithographical use, by organical resist outgassing from the wafer. The particles may be accelerated into the column, whereas mainly the PD system is sensitive to contamination and, as a consequence, might be affected by local charging effects. The APS can be practically used under high or ultra high vacuum conditions only, otherwise the apertures would accrete due to beam induced deposition of organical material. However, the required high vacuum stage is a major technical issue and cost factor of an overall lithography system like the PML2. It would be an enormous advantage for the PML2 concept to keep the APS under high or ultra high vacuum conditions and apply a conventional air bearing stage (e.g. from manufacturer AeroLas) in a pressure range above 1 mbar at the substrate. Additionally, an important concern for the use of an PML2 apparatus in the semiconductor fabrication environment is connected with the danger of system failure, which could be due to a break down of parts of the aperture plates or electron source. Such an event could lead to severe contamination of the wafer, wafer stage and wafer handling systems. The acceptability of an apparatus for a semiconductor fabrication line is strongly dependent on the reliability of the system with respect to particle purity and the risk of failure during operation. Another aspect of electron-optical systems is the compensation of imaging aberrations for large image fields. As is well-known in prior art, electrostatic lenses formed by a combination of annular electrodes always are focusing lenses (positive refracting power) and, without exception, have significant aberrations of the third order which can only be slightly influenced by the shape of the electrode geometry. By using diverging lenses (negative refractive power) it is possible to achieve a compensation of the aberrations of the combined lens system by cancellation of the contributions to the third-order aberrations of the focusing and diverging lenses, and further making also possible to greatly reduce the other coefficients of aberrations. It is not possible, though, to achieve a lens of negative refractive power by means of annular electrodes alone; on the contrary, it is necessary to use a plate or control grid electrode through which the beam passes. U.S. Pat. No. 6,326,632 of the applicant/assignee proposes to use the mask of a lithography apparatus to form diverging lenses in combination with annular electrodes located in front and after the mask, respectively. However, it is often desirable to have a diverging lens located after the mask or PD device, without involving the latter (particularly if its electrostatic potential cannot be controlled to a satisfactory degree). For such a diverging lens located after the mask or PD device, the plate electrode will cause unwanted effects, most notably absorption and scattering of the beam radiation. For modern structuring purposes, where the minimum feature size is more and more pushed towards lower values, scattering is the most disturbing effect since it leads to blurring of the pattern features. It is a goal of the present invention to provide a particle-beam system using an additional foil, in the following referred to as “transmission foil”, in the region of the beam after the PD system in which overcomes the above-mentioned problems. The provision of a foil is meant to separate spaces containing different gases and/or gas pressures. This enables the use of a mechanical scanning system, which can be run at a residual pressure significantly higher than those that are usually acceptable within an electro-optical device, so existing air bearing stages operated typically at 1-10 mbar can be used. It further allows of a significant improvement of particle purity at the optical columns and APS, and offers a means to avoid a severe contamination and related risks when used in a semiconductor fabrication line. This aim is met by a particle-beam projection processing apparatus of the kind as described above, which further comprises at least one transmission foil located across the path of the patterned beam, said foil(s) being positioned between the pattern definition means and the position of the target at a location close to a respective image of the aperture pattern formed by the projection system. The transmission foil may be made of an electrically conductive material and is held at a well defined electrical potential, so the charged particle beam is neither affected by local charging at the surface or inside the foil, nor by a floating electrical field due to a floating foil potential. It shall be mentioned that the transmission foil may be made as well of an insulating or semiconducting material provided above-mentioned effects (charging, floating potential) are compensated directly or indirectly by either the transmitting beam itself (e.g. by creating electron-hole pairs, etc.), or other supplementary measures which improve charge transport or charge balance along the foil, such as in-situ irradiation with UV light or atomic beams. In this context, the foil is considered to be close to the image when the distance between the foil and the image is not greater than the focal length of the consecutive lens immediately before or after the foil, preferably not greater than ⅕ of that focal length. The basic idea of the invention is to use a thin electrical conducting membrane as transmission foil for filtering particle flows in both directions and/or as electrode close to the position of an image to improve the optical imaging properties. If the image is the final image, its position coincides with the surface of the substrate used as target, so the corresponding foil is positioned close to the target. Due to this choice of the location, deviations in the direction of transmitted beam particles have no or only marginal effect on the imaging properties of the system. Furthermore, the foil can be used as an interlock sensor representing a safeguard device that can rapidly trigger a safety valve in case of mechanical or electrical breakdown that causes a destruction of the foil. The implementation of such a foil is possible since in the type of apparatus considered here, the beam has a wide cross-section. In other systems such as a TEM or a Gaussian beam writer, the imaging optics provide for a beam focused to a narrow, almost point-like, image location. The latter would destroy or contaminate a foil within a comparably short time, not only because of the exposition to radiation, but also due to heating imparting by absorption. In contrast, with the invention the beam is distributed over a comparatively wide area which allows sufficient cooling of the foil, which is done by thermal radiation and conductive cooling over the edge of the foil. Calculations made be the applicants showed that a foil of 0.2 μm will heat up by about 170 K only during continuous exposure to an electron beam in a PML2 apparatus even if only conductive cooling is taken into account. The current density on the foil in the present invention is about 10−07 A/cm2 (assuming here 10 μA current through a 1 mm2 area), which is about 10 million times lower than that in a typical focused beam system. In one realization of the invention such a transmission foil is located in front of the position of the target as seen along the direction of the beam. The distance between the target and the foil is small, so even for those particles which are scattered during their passage through the foil, this will have marginal effect upon the location the particles hit upon the target. The foil may be held at an electrical potential, thus forming a final electrode of the projection system, which is suitable to realize a divergent lens in combination with some other pre-final (annular) electrodes. An image may also be present at other places, in particular an intermediate image which may come about when the projection system comprises at least two consecutive projector stages, namely, at least one non-final projector stage and one final projector stage. In this case a transmission foil according to the invention may be at (or close to) the location of an intermediate image formed from the aperture pattern by a non-final stage of the projection system. Due to the nature of imaging, the radiation is allowed to emerge from the points of an image at any direction (albeit within a certain opening angle), which is why scattering of the beam particles in the foil has only little, if not marginal, effect on the imaging properties of the optical system. In order to deal with beam components which are scattered off by angles that are too high to be processed in the electron-optical system, an aperture diaphragm may be located after the transmission foil as seen along the direction of the beam, said diaphragm having an aperture limiting the lateral extension of the beam. This measure also rules out problems that may occur with regard to higher-order imaging coefficients. Preferably, the transmission foil is sufficiently thin to allow propagation of a fraction of the irradiating beam through the foil at low angles. A typical thickness will be in the order of 100-200 nm. Beside the possibility to use the foil as a plate electrode, the foil is a barrier for gas particles, thus separating the electrooptical column into different sections which may have different vacuum properties (gas filling, pressure) and preventing contamination between sections thus formed. Only fast particles, namely the particles (e.g. electrons) of the particle beam, are able to overcome this mechanical barrier. Thus, the transmission foil may separate two adjacent recipients held at different gas pressures. The transmission foil may, preferably, be continuous across the area of the respective image of the aperture pattern, in order to ensure uniform transparency behavior for each part of the image. The thickness is then chosen suitably (minimum thickness) to allow passage through the foil only for particles having a minimum kinetic energy. Another aspect of the invention concerns the material of the transmission foil. Apart from electrically conducting materials such as metal foils, such as a copper foil with a suitable inert covering if necessary, the foil may be made from a semiconductor material, such as silicon or diamond-like carbon. The foil may also be used as an additional safeguarding device, in conjunction with a sensor means adapted to monitor the integrity of the transmission foil and a mechanical shutter means located near an opening for the patterned beam within the apparatus, such that the shutter means closes the opening upon detection of a damage to said foil by the sensor means. The preferred embodiment of the invention discussed in the following is based on the PML2-type particle-beam exposure apparatus with a pattern definition (PD) system as disclosed in the U.S. Pat. No. 6,768,125 (=GB 2 389 454 A) of the applicant (assignee). In the following, first the technical background of the apparatus is discussed as far as relevant to the invention, then embodiments of the invention are discussed in detail. It should be appreciated that the invention is not restricted to the following embodiments nor the PD system, which merely represent one of the possible implementations of the invention; rather, the invention is suitable for other types of processing systems that employ a particle-beam as well. PML2 System An overview of a maskless particle-beam exposure apparatus PML2 employing a first preferred embodiment of the invention is shown in FIG. 1. In the following, only those details are given as needed to disclose the invention; for the sake of clarity, the components are not shown to size in FIG. 1, particularly the lateral width of the particle beam is exaggerated. As already mentioned, an electron beam generated by an illumination system is used in the PML2 system. It illuminates a PD means having a regular array of apertures in order to define a beam pattern to be projected on a target surface. With each aperture, a small beam is defined, and the passage of each beam through an aperture can be controlled so as to allow (‘switch on’) or effectively deactivate (‘switch off’) the passage of particles of the beam through the respective apertures. The beam permeating the aperture array (or more exactly, through the switched-on apertures of the array) forms a patterned particle beam bearing a pattern information as represented by the spatial arrangement of the apertures. The patterned beam is then projected by means of a particle-optical projection system onto the target (for instance, a semiconductor substrate) where an image of the apertures is thus formed to modify the target at the irradiated portions. The image formed by the beam is moved continuously along a straight path over each die field; additional scanning of the beam in a direction perpendicular to the scanning direction is not necessary (except, where needed, to compensate for lateral travel motion errors of the scanning stage). The main components of the apparatus 100 are—corresponding to the direction of the lithography beam lb, pb which in this example runs vertically downward in FIG. 1—an illumination system 101, a PD system 102, a projecting system 103, and a target station 104 with the substrate 41. The particle-optical systems 101, 103 are realized using electrostatic or electromagnetic lenses. The electro-optical parts 101,102,103 of the apparatus 100 are contained in a vacuum housing 105 held at high vacuum to ensure an unimpeded propagation of the beam lb, pb along the optical axis cx of the apparatus. The illumination system 101 comprises, for instance, an electron source 11 and a condenser lens system 13. It should, however, be noted that in place of electrons, in general, other electrically charged particles can be used as well. Apart from electrons (emitted from an electron gun) these can be, for instance, hydrogen ions or heavy ions; in the context of this disclosure heavy ions refer to ions of elements heavier than C, such as O, N, or the noble gases Ne, Ar, Kr, Xe. The electron source 11 (in principle also ions are possible) emits energetic electrons, i.e., having a defined (kinetic) energy of typically several keV (e.g. 5 keV at the PD system 102) with a comparatively small energy spread of, e.g., ΔE=6 eV. By means of an electro-optical condenser lens system 13, the ions emitted from the source 11 are formed into a wide-area, substantially telecentric electron beam serving as lithography beam lb. The lithography beam lb then irradiates a PD device 20 which, together with the devices needed to keep its position, form the PD system 102. The PD device 20 is held at a specific position in the path of the lithography beam lb, which thus irradiates an aperture pattern 21 formed by a plurality of apertures. As already mentioned, some of the apertures are “switched on” or “open” so as to be transparent to the incident beam; the other apertures are “switched off” or “closed”, i.e. non-transparent (opaque) to the beam. The pattern of switched-on apertures is chosen according to the pattern to be exposed on the substrate, as these apertures are the only portions of the PD device transparent to the beam lb, which is thus formed into a patterned beam pb emerging from the apertures (i.e., in FIG. 1, below the device 20). For details about the architecture and operation of the PD device, and in particular the architecture of its blanking plate, the reader is referred to the U.S. Pat. No. 6,768,125. The pattern as represented by the patterned beam pb is then projected by means of an electro-optical projection system 103 onto the substrate 41 where it forms an image of the switched-on mask apertures 21. The projection system 103 implements a demagnification of, for instance, 200×. The substrate 41 is, for instance, a silicon wafer covered with a photo-resist layer. The wafer 41 is held and positioned by a wafer stage 40 of the target station 104. In the embodiment of the invention shown in FIG. 1, the projection system 103 is composed of two consecutive electro-optical projector stages 31, 32 with a crossover c1, c2, respectively. The electrostatic lenses used to realize the projectors 31,32 are shown in FIG. 1 in symbolic form only as technical realizations of electrostatic imaging systems are well known in the prior art, such as, for instance, the U.S. Pat. No. 4,985,634 (=EP 0 344 646) of the applicant. The first projector stage 31 images the plane of the apertures of the device 20 to an intermediate image i1 which in turn is imaged onto the substrate surface by means of the second projector stage 32. Both stages 31,32 employ a demagnifying imaging through crossovers c1,c2; thus, while the intermediate image i1 is inverted, the final image i0 produced on the substrate is upright (non-inverted). The demagnification factor is about 14× for both stages, resulting in an overall demagnification of 200×. A demagnification of this order is in particular suitable with a lithography setup, in order to elevate problems of miniaturization in the PD device. After the first stage 31 the beam width is well reduced—for instance, from an initial width of a PD field of L=60 mm to about 4 mm at the intermediate image. As a consequence, since the dimensions of the electro-optical components of the second stage 32 need not be reduced to the same scale as the beam width, the lens elements can be realized larger with respect to the beam, which allows for an easier treatment of lens defects and imaging aberrations. For example, with a total source-substrate length of about 2 m, the focal length of the final lens after the second stage crossover c2 can be as small as about 20 mm. This allows for high currents that can be treated, for instance of the order of 4 to 10 μA, because space charge correlation have only little influence. In both projector stages the respective lens system is well compensated with respect to chromatic and geometric aberrations; furthermore, a residual chromatic aberration of the first stage 31 can be compensated by suitable fine correction of the electrode potentials in the second stage 32. By virtue of the chromatic compensation, the energy of the ions (or in general, charged particles) emitted from the source 11 are allowed to have a comparatively high energy spread of up to ΔE=6 eV. This allows to use sources with less stringent requirements for quality and, therefore, emitting higher currents. Furthermore, the effect of stochastic errors, which are due to particle interactions mainly in the crossovers c1,c2, is reduced as the stochastic errors of the first stage are demagnified in the second stage, and stochastic errors in the second stage have little influence due to the small distance of the second crossover c2 from the substrate plane. As a means to shift the image laterally, i.e. along a direction perpendicular to the optical axis cx, deflection means (not shown) are provided in one or both of the projector stages. The deflection means can be realized as, for instance, a multipole electrode system; as discussed in the U.S. Pat. No. 6,768,125; additionally, a magnetic coil may be used to generate a rotation of the pattern in the substrate plane where needed. The electrooptical lenses are mainly composed of electrostatic electrodes, but magnetic lenses may also be used. According to the invention a thin foil is positioned as transmission foil in the path of the patterned beam pb close to the location where an image is formed. In the present PML2 system, two images are formed, namely, the intermediate image i1 and the final image i0 (the latter being formed on the target surface). Consequently, there are two possible regions in this case to place a foil according to the invention. In the first embodiment which is shown in FIG. 1, a thin transmission foil 34 is placed between the last lens and the substrate, so as to bring the foil near to the position of the final image. Preferably, the distance between the foil 34 and the target 41 is very small, in the range of 200-500 μm. While elastic and/or inelastic scattering of some part of the electrons in the foil is inevitable, which will rise to an additional contribution to the blur of imaging (scattering blur), by virtue of the small distance between the foil and the substrate the scattering blur contribution is very small. Details of scattering are further discussed below. The inelastically scattered electrons have a reduced kinetic energy, but at the end of the column the field of the lenses is zero and therefore the trajectory of the electrons is not changed (there is not extra chromatic blur). For a gap between the foil and substrate of Δl=200 μm, the allowed extra blur is about 10 nm resulting in an inelastic scattering angle of θi=50 μrad. In order to reduce the extra blur due to elastically scattered electrons the gap has to much smaller, e.g. Δl=0.5 μm, resulting in an allowed extra blur of 10 nm and an elastic scattering angle of θe=19.6 mrad. Therefore it is very important to reduce the intensity of elastically scattered electrons as discussed below. The foil 34 effectively closes the housing 105 against the target 41, and prevents out-gassing products from the resist, or other source of contaminants on the target, to enter the electro-optical system 101-103 of the apparatus. As a consequence, the entire optical column is protected against contamination. On the other hand, due to the small distance between the foil 34 and the substrate 41, it may be likely that the foil will be contaminated by out-gassing products adsorbed to the foil surface. A heating system 107 is provided for cleaning the foil by heating so the contaminants evaporate (desorb) towards the side of the target and can be pumped off there (the pumping system is not shown). The heating system is, however, positioned at the side of the foil opposite the target; it comprises a laser 71 for producing an IR laser beam, for instance, and a movable mirror 72 mounted inside the housing. By means of the mirror 72 the laser beam is scanned over the area of the foil 34. The laser beam heats up the lighted region of the foil which is thus cleaned successively. The foil can be used as a diverging electrostatic lens in cooperation with the last electrostatic electrodes. The use of a diverging electrostatic lens enhances the optical properties of the imaging system 103. For instance, the imaging aberration blur can be reduced about 15%. The foil 34 is made from a silicon disk etched to a thickness of about 100 μm. Processes for producing silicon foils or foils from diamond-like carbon are well-known in prior art. One suitable method to synthesize conductive diamond-like carbon (DLC) films uses plasma chemical vapor deposition (MPCVD). The films are synthesized on silicon substrates from solid carbon by a very low power (60 W) MPCVD reaction of a mixture of 90-70% helium and 10-30% hydrogen, as described e.g. in “Synthesis of HDLC films from solid carbon”, R. L. Mills, J. Sankar, P. Ray, A. Voigt, J. He and B. Dhandapani, Journal of Materials Science (2004), 39, 3309. FIG. 2 illustrates a second embodiment 200 of the invention, in which a part of the apparatus 200 is shown; elements of the apparatus 200 not described below are identical to those of the apparatus 100 of FIG. 1; same reference numbers refer to corresponding elements throughout. As a consequence of the fact that the foil 35 is located at the position of the intermediate image i1, electrons which are scattered off their initial beam path are, nonetheless, focused at the final image plane i0 to the zero loss peak. Electrons which are scattered with a higher angle than 1.1 mrad have an increased spherical aberration, and these electrons are suitably blanked by a blanking diaphragm 37 situated after the foil 35. The foil 35 divides the apparatus 200 into consecutive sections. In the first section S3, comprising the source 11, illuminating system 101, the PD device 102 and the part of the projection system until the intermediate image i1, is a separated low-pressure chamber in which the pressure p3 is in the range of 10−9 mbar, for instance. The high-pressure side of the foil is sectored into two further sections S2, S1 (at pressures p2, p1, respectively) by the diaphragm 37. The diaphragm aperture through which the beam bp can propagate also serves as pumping opening. The sections are pumped differentially with respect to the pressure p0 at the place around the target 41. For instance, p1˜p0/1000, p2˜p1/1000. (The symbol denotes ‘approximately equal’. The pumping arrangements are not shown in the figures.) By virtue of this setup, the pressure at the foil downstream side (facing toward the target) is considerably lower than at the substrate (pressure p0), in this example by a factor of about 106. This layout complies with another requirement, that the gas pressure p1 in the section S1 should by sufficiently low, namely, in the order of 10−2 mbar or lower, in order to ensure a mean free path of the electrons that is sufficiently high so as to allow unimpeded passage through the entire optical system. In contrast, the pressure p0 at the substrate will be in the order of a few ten mbar, for instance 56 mbar. One important aspect of this embodiment is reduction of contamination of the foil, because the contamination is propositional to the current density and to the pressure. The diameter of the intermediate image is in the range of 1.6 mm. The intermediate image is 10 time larger and the current density is 100 times lower than on the image at the substrate. The pressure p2 of the high pressure side of the foil is ˜1000000 times smaller than the pressure of the substrate p0. The electrooptical column between the foil 35 and the substrate can be heated by means of a heater 73 located in sections S1 and/or S2. Furthermore, a heating system 207 for heating the foil is provided, comprising a laser beam, reflected on a moveable mirror as discussed above. In the embodiment shown, the heating system 207 is located after the foil 35 in the section S2; in a variant it may also be situated in front of the foil 35 (like heating system 107 of the first embodiment). Furthermore, the foil can be used as a diverging electrostatic lens and the optical properties can be enhanced. Scattering at a Membrane FIG. 3 shows a detail of the particle beam at a membrane F (corresponding to foils 34, 35 of FIGS. 1 and 2, respectively) and illustrates the scattering of the beam particles. (It should be noted that in FIG. 3 the optical axis cx is turned so as to be horizontal.) Scattering is due to different physical interactions between fast electrons (or particles) during their passage through a solid. As shown in FIG. 3, the electrons irradiated in the form of a primary beam 1 upon a membrane F can be elastically scattered (the flight direction is changed, but the kinetic energy is unchanged) or inelastically scattered (the electrons lose a bit of their kinetic energy and the foil is heated). Both effects cause a changed flight direction of primary electrons. Elastic scattering occurs if the foil has a crystal structure, and a Bragg reflex will be formed at the substrate. Bragg reflexes are denoted in FIG. 3 by Miller symbols [100] and [200]. The elastic scattering angle θe obeys the relation θe=λ/(2d), wherein d is the distance between lattice planes of the foil as defined by the Miller indices, and λ is the wavelength of the electron. All angles are given in radians where not explicitly denoted otherwise. For instance, for the Bragg-reflection of 100 keV electrons (λ100keV=3.7×10−12 m) passing through silicon (lattice constant 5.43×10−10 m) the smallest elastic scattering angel is θe,min=3.4 mrad. Thus, the gap between a Bragg reflex and the direct beam is a linear function of the distance between the foil and the substrate. The scattering angle is in the range of several mrad. Inelastic scattering can take place due to phonon stimulation (energy loss ΔE<1 eV), plasmon stimulation (ΔE=5-30 eV) and ionization of core levels (ΔE˜keV). The inelastic scattering angle relates to the energy loss by θi=ΔE/(2 Ekin). Plasmons are the most important cause of inelastic scattering. For plasmon-related inelastic scattering the energy loss of electrons with a kinetic energy of 100 keV results the scattering angle is in the range of appr. 50 μrad. In general the larger part of the electrons is elastically scattered. Only a few percent of the primary electrons are inelastically scattered. This is a consequence of the fact that for large electron energies, i.e. >1 keV, the inelastic mean free path exceeds the elastic mean free path by an order of magnitude. It is well known that only a part of the electrons (less than a quarter, depending on material and thickness) irradiated to a silicon foil traverse the foil without elastic or inelastic scattering, so as to form the so-called zero-loss peak at the substrate. The other electrons (more than three quarters, depending on material and thickness) are scattered elastically or inelastically. These electrons are able to irradiate the substrate outside the zero loss peak. While the inelastically scattered electrons will produce a blurred spot, the elastically scattered electrons will form Bragg reflexes on the substrate. Since the latter process is dominant and the Bragg angles are large, it is very important to reduce the number of elastically scattered electrons to improve the efficiency of the electron beam when a foil is present in the beam path. The parts of the beam with large scattering angles are blanked by means of a blanking diaphragm D (corresponding to diaphragm 37 of FIG. 2), in order to ensure a reduced spherical aberration, and the electrons with a small scattering angel are focused to one spot at the image plane. The numerical aperture is increased and therefore the space charged at the last cross over reduced. The main part of the beam which undergoes scattering by a small angle only (inelastic scattering, symbolized by a lobe 1b) or remains unscattered (arrow 1u) propagates unimpeded through the aperture A of the diaphragm D. In the apparatus 200 of FIG. 2, the distance between the foil 35 and the diaphragm 37 is appr. 90 mm. The diameter of the diaphragm aperture A is 200 μm, resulting in an opening angle θA (FIG. 3) of 1.1 mrad. (Of course, all values given here are of exemplary nature only and will vary according to the specific implementation.) All electrons that are scattered to an angle higher than the opening angle θA are blanked and all electrons with a smaller scatter angel are focused again at the image plate to one point. The numerical aperture is increased to 100 μrad. As a result, the last cross over is broadened and, in turn, the coulomb interaction, the stochastic blur and space-charge blur are reduced. Beside blanking out beam parts that are scattered to high angles, an other possible way to reduce and homogenize the electron background on the substrate may be suitable varying the thickness of the foil/membrane, in order to minimize the intensity of a Bragg reflex, in particular the first Bragg reflex [100]. Consequently, the dominant Bragg spots can be reduced by suitable choice of the foil thickness. Yet another measure could be to provide an atomic structure of the foil which is not a single crystal. If the crystal orientation has a random orientation then the electrons on the substrate are not focused to Bragg reflex. The electrons density beyond the zero loss peak are rings and the intensity is distributed along the circumference. One plasmon causes an energy loss of appr. 15 eV and therefore a chromatic blur of 10 nm. For large kinetic energies (100 keV) the inelastic mean free path λi in silicon is about 110 nm. In a thin silicon foil (e.g., 200 nm thick) only few electrons will excite more than one plasmon (since the mean free path for inelastic scattering of electrons with large kinetic energies is about 110 nm), so almost all electrons scattered inelastically will have an energy loss in the range of 5-15 eV. On the other hand, elastic scattering is the dominant process and only few percent of the primary electrons will be inelastically scattered. At the intermediate image the numerical aperture is in the range of 49 μrad (without the foil) and the spherical blur in the range of 5 nm. The inelastically scattered electrons have a numerical aperture increased to 98 μrad, and therefore the spherical blur is raised to 10 nm. But only 5% of the electrons are inelastically scattered and these electrons are forming an extra background dose at the wafer. Contamination of the Foil Contamination of the foil occurs basically from two sources: outgassing products from the target and irradiation-induced contamination from the residual gas in the apparatus. The former contribution was already discussed above; in the following, we address the latter. Irradiation-induced contamination is proportional to the current density of the irradiation and pressure. For instance, a TEM uses a single focused electron beam to irradiate the probe in a single 10 nm spot and the current density is in the range of 30 A/cm2. In the PML2 apparatus several hundreds thousand multi beams are used, adding up to a total current through the column of about 8 μA. The image size at the substrate is about 160 μm and the current density is 31 mA/cm2. The current density is 1000 times smaller than for a single focused beam. If the foil is placed at the end of the column (Example 1), the pressure is at the foil equal to the pressure at the substrate. Therefore, the lifetime of the foil in the PML2 apparatus is much longer than in a normal single focused beam setup (e.g. TEM). If the foil is positioned at the intermediate image (Example 2) contamination is further reduced as a consequence of the fact that the pressure is substantially smaller. FIG. 4 shows another embodiment of the invention, namely an apparatus 300 which comprises two foils 34′,35′ both at the intermediate image and in front of the target. Thus, the beneficial features of the foils can be combined. In particular, the foil 35′ at the intermediate image reduces the coulomb interaction at the last cross over and the total current through the coulomb can be increased (the coulomb interaction blur is the dominate blur), while the final foil 34′ prevents contamination of the optical components of the second stage 32 due to resist out gassing since the section S1 is not vacuum separated from the pressure p0 above the target 41. Interlock Sensor and Safety Valve As shown in FIGS. 5a and 5b, the foil may also be used as an interlock sensor to realize a safeguard device in conjunction with a safety valve. The safeguard device is used to rapidly trigger a safety valve in case of mechanical or electrical breakdown that causes a destruction of the foil. Referring to FIG. 5a, radiation 77, such as laser beam like the one used also as heating laser, is directed onto the foil 35 and the reflected light is detected by a sensor 78. The sensor is connected to a safeguard circuit 781 which controls a mechanical safety valve 79 which is placed near a suitable opening such as the blanking diaphragm 37. If the foil is damaged or otherwise impaired (for instance, due to the heat load or particles from a damaged APS) as shown in FIG. 5b, the laser beam 77 is no longer reflected to the sensor and by means of the safeguard circuit the safety valve 79 closes, preferably within 1 ms. The mechanical shutter is a safety equipment to preclude contamination of the wafer with particles that come from the optical column or vice versa. The shutter also protects the ultra high pressure p3 of the APS system and electron source if the foil is destroyed. Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. |
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claims | 1. A method, comprising:combining an amorphous iron-based alloy and at least one element to form a mixture;wherein the at least one element is selected from the group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel, phosphorus, and yttrium; andwherein the at least one element is present in the mixture in an amount ranging from about 5 atomic percent (at %) to about 55 at %; andball milling the mixture at least until an amorphous alloy of the amorphous iron-based alloy and the at least one element is formed; andwherein the amorphous iron-based alloy comprises:between about 10 atomic percent (at %) and about 50 at % iron;between about 0 at % and about 25 at % of a material selected from a group consisting of manganese, carbon, silicon, zirconium, and titanium;between about 15 at % and about 30 at % of the at least one element; andat least one of the following constituents:between about 20 at % and about 55 at % chromium; andbetween about 20 at % and about 55 at % boron. 2. The method of claim 1, wherein the at least one element is molybdenum. 3. The method of claim 1, wherein the at least one constituent is boron. 4. The method of claim 1, wherein the at least one constituent is chromium. 5. A method, comprising:combining an amorphous iron-based alloy and at least one element to form a mixture;wherein the at least one element is selected from the group consisting of: molybdenum, chromium, tungsten, boron, gadolinium, nickel, phosphorus, and yttrium, andwherein the at least one element is present in the mixture in an amount ranging from about 5 atomic percent (at %) to about 55 at %; andball milling the mixture at least until an amorphous alloy of the amorphous iron-based alloy and the at least one element is formed; andwherein the amorphous iron-based alloy comprises:between about 10 atomic percent (at %) and about 50 at % iron;between about 15 at % and about 25 at % molybdenum; andbetween about 0 at % and about 25 at % of a material selected from the groupconsisting of chromium, tungsten, and boron; andwherein the amorphous iron-based alloy is resistant to corrosion. 6. The method of claim 5, wherein the iron is present in the mixture at between about 40 at % and about 50 at %. 7. The method of claim 6, wherein the molybdenum is present in the mixture at between about 12 at % and about 27 at %. 8. The method of claim 5, wherein an x-ray diffraction pattern of the amorphous iron-based alloy shows no sign of a crystalline form of the molybdenum. 9. A method, comprising:combining an amorphous iron-based alloy and at least one element to form a mixture;wherein the at least one element is selected from the group consisting of: molybdenum, chromium, tungsten, boron, gadolinium, nickel, phosphorus, and yttrium, andwherein the at least one element is present in the mixture in an amount ranging from about 5 atomic percent (at %) to about 55 at %; andball milling the mixture at least until an amorphous alloy of the amorphous iron-based alloy and the at least one element is formed; andwherein the amorphous iron-based alloy comprises:between about 10 atomic percent (at %) and about 50 at % iron;between about 10 at % and about 55 at % boron; andbetween about 0 at % and about 25 at % of the at least one element; andwherein the amorphous iron-based alloy is resistant to radiation. 10. The method of claim 9, wherein the boron is present at between about 20 at % and about 53 at %. 11. A method, comprising:combining an amorphous iron-based alloy and at least one material to form a mixture, wherein the at least one material is selected from the group consisting of tungsten, gadolinium, nickel, yttrium, and alloys thereof, and wherein the at least one material is present in the mixture in an amount ranging from about 5 atomic percent (at %) to about 55 at %; andball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one material is formed. 12. The method of claim 11, wherein the iron-based alloy is a product of atomization. 13. The method of claim 11, wherein the alloy of the amorphous iron-based alloy and the at least one material is at least 90 at % amorphous. 14. The method of claim 11, wherein an x-ray diffraction pattern of the alloy of the amorphous iron-based alloy and the at least one material shows no sign of a crystalline form of the at least one material. 15. The method of claim 11, wherein the amorphous iron-based alloy is characterized by a composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6C3.8Si2.4. 16. The method of claim 15, wherein the alloy of the amorphous iron-based alloy and the at least one material comprises molybdenum present at greater than about 9 at %. 17. The method of claim 11, wherein the amorphous iron-based alloy is characterized by a composition Fe49.1Cr14.6Mo13.9B5.9C14.0Si0.3Y1.9Ni0.2. 18. The method of claim 17, wherein the alloy of the amorphous iron-based alloy and the at least one material comprises boron present at greater than about 8 at %. |
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