Split (2)

train · 33.5k rows

patent_number stringlengths 0 9	section stringclasses 4 values	raw_text stringlengths 0 954k
	summary
	description	The present invention relates to an X-ray imaging apparatus, and more particularly to an X-ray imaging apparatus that selectively uses a plurality of X-ray sources to provide an X-ray fluoroscopic image. International Publication WO/2007/100105 discloses a technique for producing a multi X-ray beam by distributing electron sources two-dimensionally and controlling the electron sources individually. The divergence angle of the multi X-ray beam is determined by the opening conditions of X-ray extraction windows disposed in a vacuum. However, there are cases where it is desirable to adjust the divergence angle of the multi X-ray beam depending on the imaging conditions. To accommodate this, in International Publication WO/2007/100105, a vacuum X-ray shielding plate 23 is added as a first shielding plate, and combined with an atmospheric X-ray shielding plate 41 constituting a second shielding plate. The divergence angle of the multi X-ray beam can be freely selected in accordance with the irradiation conditions of the object, given that this second shielding plate provided in air can be easily replaced. Japanese Patent Laid-Open No. 09-187447 discloses a movement mechanism for moving the distance between two X-ray tubes (foci) or the interfocus distance of one X-ray tube, based on information on an imaging magnification factor or imaging geometry for stereo imaging. Japanese Patent Laid-Open No. 09-187447 further discloses providing another movement mechanism that enables adjustment of an X-ray aperture, such that an appropriate X-ray exposure range can be set in response to driving of the above movement mechanism. Japanese Patent Laid-Open No. 2006-136500 discloses a movement mechanism of a movable aperture device moving aperture blades to a prescribed position based on information on an imaging range and forming a diagnostic imaging region, in a fluoroscopic imaging apparatus. Herein, the state of the aperture blades in the case where a monitoring imaging region is formed, and the state of the aperture blades in the case where a diagnostic imaging region is formed are disclosed. The four aperture blades move at high speed when generating monitoring image data, as a result of an aperture movement control unit receiving arrival signals from a pixel value comparing unit, and form a diagnostic imaging region. Japanese Patent Laid-Open No. 2001-120526 discloses an X-ray fluoroscopic apparatus provided with a cradle for the patient to lie down on, and a first X-ray tube and a semiconductor detector that are respectively attached to first and second ends of a C-arm whose arms are capable facing one another with the cradle therebetween. This apparatus is equipped with a second X-ray tube that is positioned further away than the distance from the semiconductor detector to the first X-ray tube. Further, this apparatus is also equipped with semiconductor detector movable supporting means for movably supporting the semiconductor detector so as to be capable of taking a first position or orientation facing the first X-ray tube and a second position or orientation facing the second X-ray tube. Japanese Patent Laid-Open No. 2001-137221 discloses a CT gantry provided with two angiographic arms in addition to a CT imaging X-ray tube and an X-ray detector. One angiographic arm is a frontal arm provided with an X-ray tube and an X-ray image receiving device for performing vertical angiography of a sample. The other angiographic arm is a lateral arm provided with an X-ray tube and an X-ray image receiving device for performing horizontal angiography of a sample. According to Japanese Patent Laid-Open No. 2001-137221, the CT gantry is removed to a position that does not obstruct the angiography, and the frontal arm and the lateral arm are moved to an angiography position, based on an instruction from an operator. Also, the frontal arm and the lateral arm can be removed to a position that does not obstruct the CT imaging, based on an instruction from an operator. In the operating room, the surgeon moves the C-arm device himself or herself to locate the best angle. The surgeon needs to perform fine positional setting of the entire C-arm device. The present invention is premised on applying an X-ray imaging apparatus having a plurality of X-ray sources (multi X-ray source, MBX), in order to facilitate this positional setting. Specifically, the following three types of changes to the examination region are available, in the case where fluoroscopy is performed after narrowing the examination region with an X-ray aperture in order to reduce radiation exposure to the patient. The first involves scaling the examination area, the second involves shifting the examination region, and the third involves changing the examination direction. A plurality of aperture units need to be changed in conjunction with each of these three types of changes to the examination region. In the case of shifting the examination region, it is considered necessary to maintain the examination direction and also preferably the examination area, and in the case of changing the examination direction, it is considered necessary to maintain the examination center and also preferably the examination area. However, as for conventional apparatuses that use a plurality of X-ray sources, there are only commonly known examples of a stereo imaging apparatus and a double C-arm device, as described above, and there is no known technology of a C-arm device that uses a multi X-ray source. Therefore, there is no recognition of the above problems, and consequently no technique for solving these problems. On the other hand, there are cases where it is desirable to use a plurality of X-ray sources to examine a plurality of examination areas substantially at the same time (or sequentially). In these cases, it is envisioned that it may be desirable to change the selection of one X-ray source in response to a change in the selection of another X-ray source. However, there is currently no technique for meeting such a requirement. The present invention solves at least one of the above problems. An X-ray imaging apparatus according to one aspect of the present invention includes a multi X-ray source having a plurality of X-ray sources arranged two-dimensionally, an X-ray detector having a plurality of detecting elements two-dimensionally arranged facing the multi X-ray source, and a collimator provided between the multi X-ray source and the X-ray detector, for restricting an irradiated area of X-rays from the multi X-ray source. The collimator is configured to form a plurality of slits through which X-rays pass, such that the plurality of slits being two-dimensionally arrayed in correspondence with the plurality of X-ray sources. The collimator is further configured to be capable of adjusting a size and a position of the plurality of slits. Selecting means selects one or more X-ray sources for performing X-ray irradiation, from the plurality of X-ray sources, in order to select an examination region of an object. Control means controls the size and the position of the plurality of slits of the collimator according to the selection by the selecting means. The control means has a first control mode for controlling, when there is a change to a different X-ray source by the selecting means, the size and the position of the plurality of slits to move the examination region in parallel, such that examination directions before and after the change are parallel, and a second control mode for controlling, when there is a change to a different X-ray source by the selecting means, the size and the position of the plurality of slits to rotate the examination direction, such that a center of the examination regions before and after the change is the same. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. Various exemplary embodiments, features, and aspects of the present invention will be described in detail below with reference to the drawings. First Embodiment A preferred embodiment of the present invention will be described in detail with reference to FIG. 1 to FIG. 8. FIG. 1 shows a scene in which an X-ray fluoroscopic image of a body is imaged with a C-arm device serving as an X-ray imaging apparatus according to the present embodiment. A two-dimensional detector 28 and a multi X-ray source 26 are fixed to a C-arm 25. A collimator 27 as an X-ray aperture is fixed to an irradiation side of the multi X-ray source 26. The multi X-ray source 26, which has a plurality of two-dimensionally arranged X-ray sources, or more specifically, N×M X-ray foci, is provided on the underside of the patient, for example. X-rays discharged from a transmission target 13 (X-ray focus) of the multi X-ray source 26 (described below) arrive at the two-dimensional detector 28 after passing through the body. The two-dimensional detector 28 is an X-ray detector having a plurality of detecting elements two-dimensionally arranged facing the multi X-ray source. The intensity distribution of X-rays reaching the two-dimensional detector 28 is displayed as an X-ray fluoroscopic image on a display 31. A control panel 30 is connected to a control unit 29. The control unit 29 is able to select an X-ray focus for performing exposure from out of the N×M X-ray foci, and change the X-ray fluoroscopic image on the display 31 based on an image read out from the two-dimensional detector 28, in accordance with operation of the control panel 30 by a doctor. Also, the irradiation area and the irradiation angle can be changed as a result of an X-ray focus for performing exposure being selected from the N×M X-ray foci and the corresponding collimator 27 changing, in response to a command from the control panel 30. The structure of the multi X-ray source 26 will be described using FIG. 8. Note that FIG. 8 is the same as a figure disclosed in International Publication WO/2007/100105. Electrons are emitted from one of multi-electron emitting elements 15 configured on an element array 16. Emitted electrons hit the transmission target 13 after being shaped by a lens electrode 19 and accelerated by an acceleration electric field. X-rays transmitted from the transmission target 13 are directionally restricted by a vacuum X-ray shielding plate 23. Note that while in FIG. 8, transmitted X-rays are further directionally restricted using an atmospheric X-ray shielding plate 41, whereas in the present embodiment, the portion corresponding to the atmospheric X-ray shielding plate 41 is replaced by the collimator 27. The collimator 27 is provided between the multi X-ray source 26 and the two-dimensional detector 28, and is for restricting the irradiated area of X-rays from the multi X-ray source 26. With this collimator 27, a plurality of slits 42 for X-rays to pass through are formed two-dimensionally in correspondence with the plurality of X-ray sources in the multi X-ray source 26, using a plurality of aperture plates 32, as shown in FIGS. 3A to D. The size and position of the plurality of slits 42 are adjustable by controlling the aperture plates 32. Control of the collimator 27 constituting a main portion of the present embodiment will be described using FIGS. 2A to C. Description is limited to one dimension in FIGS. 2A to C because action is independent between dimensions even if the figures were expanded to two dimensions. The figures can be easily expanded from one dimension to two dimensions. FIG. 2A shows an example in which the aperture plates 32 of the collimator 27 are controlled such that the X-ray sources constituting the multi X-ray source 26 have irradiation regions in the same place on the two-dimensional detector 28. The aperture plates 32 are members for shielding X-rays, and are manufactured from tungsten, lead, copper, iron, or an alloy thereof, for example. In the present embodiment, the aperture plates 32 are constituted by four types of aperture plate denoted by 321, 322, 323 and 324, as shown in FIGS. 3A to D. That is, the collimator 27 is constituted by a set of aperture plates and a drive mechanism (not shown) that drives these aperture plates. Control of the collimator 27 such that a light-receiving region 40 is in the same place on the two-dimensional detector 28, as shown in FIG. 2A, may be clinically inconvenient for the following reasons. For example, assume that when examining an object 34 with X-rays from a target t2 constituting the X-ray source, the physician wants to examine the right side of the object 34. The physician, in order to select an examination region of the object, is able to select one or more X-ray sources for performing X-ray irradiation from the plurality of X-ray sources, using the control panel 30, and further issue a request to switch the X-ray sources. While examination of the right side region of the object 34 does become possible once the target constituting the X-ray source is switched from t2 to t3 in response to this request, the examination direction (examination angle) of the object 34 is changed. This change in the examination direction is not what the doctor wanted. Similarly, assume that when examining the object 34 with X-rays from the target t2, the physician wants to examine the object 34 after rotating the observation direction to the right side. While examination of an image obtained after rotating the observation direction of the object 34 to the right side does become possible once the target constituting the X-ray source is switched from t2 to t3 in response to this request, the examination region 33 and the examination center of the object 34 are changed. This change in the examination region 33 and the examination center is not what the doctor wanted. Control of the collimator 27 in a shifting mode will be described using FIG. 2B. In the shifting mode (first control mode), the aperture plates 32 are controlled such that the examination regions 33 formed by a target ti and another target tj are in a relation where the examination region 33 shifts while maintaining the examination direction (moves horizontally). In other words, when the X-ray source for performing X-ray irradiation is changed to a different X-ray source, the size and position of the plurality of slits 42 are controlled to move the examination region in parallel, such that the examination directions before and after the change are parallel. Because the examination area preferably is also maintained in addition to the examination direction with control in the shifting mode, control for maintaining both the examination direction and the examination area will be described in the present embodiment. With the C-arm device according to the present embodiment, there is a rotational mode in additional the shifting mode. Switching between the shifting mode and the rotational mode can be performed by operation of the control panel 30. In the shifting mode, when the aperture plate 32 facing the target t2 is controlled in order for the physician to scale the examination region 33, in the case where the physician is examining the object 34 with X-rays from the target t2, the aperture plates 32 facing the other targets t1 and t3 are also scaled in conjunction with this control. Similarly, in the shifting mode, when the aperture plate 32 facing the target t3 is controlled in order for the physician to scale the examination region 33, in the case where the physician is examining the object 34 with X-rays from the target t3, the aperture plates 32 facing the other targets t1 and t2 also change in conjunction with this control. Control of the collimator 27 in the rotational mode will be described using FIG. 2C. In the rotational mode (second control mode), the aperture plates 32 are controlled such that the examination regions 33 formed by a target ti and another target tj are in a relation where the examination direction is rotated while maintaining the examination center. In other words, when the X-ray source for performing X-ray irradiation is changed to a different X-ray source, the size and position of the plurality of slits 42 are controlled to rotate the examination direction, such that the center of the examination regions before and after the change is the same. It is additionally desirable to also maintain the examination area so as to be constant. Here, maintaining both the examination center and the examination area will be referred to as “maintaining the examination region 33”. In the rotational mode, when the aperture plate 32 facing the target t2 is controlled in order for the physician to scale the examination region 33, in the case where the physician is examining the object 34 with X-rays from the target t2, the aperture plates 32 facing the other targets t1 and t3 are also scaled in conjunction with this control. Because the interval between the transmission targets 13 is physically fixed, the amount of change in the examination direction can be calculated by hypothetically setting the distance (FCD: Focus Center Distance) from the transmission target in the center of the multi X-ray source 26 to the center of the object 34. In the present embodiment, the FCD can be input from the control panel 30. FIGS. 3A to D show an exemplary structure of the aperture plates 32. FIGS. 3A and B show an example where the irradiation field is scaled down in the shifting mode. With the change from FIGS. 3A to B, only the areas of the slits 42 are scaled down, and the distance relation between the centers of the slits 42 remains unchanged. FIGS. 3C and D show an example in which the irradiation field is scaled down in the rotational mode. With the change from FIGS. 3C to D, the distance relation between the centers of the slits 42 changes at the same time, when only the areas of the slits 42 are scaled down. Control of the collimator 27 in the case where the shifting mode and the rotational mode are combined will be described using FIGS. 4A and B. FIG. 4A shows the case of switching from the shifting mode to the rotational mode. Assume the case of changing to the rotational mode during examination of a portion of the object 34 using the target t1 under control in the shifting mode. In this case, the other targets t2 and t3 are controlled such that the examination direction rotates while maintaining the examination region 33, as shown in FIG. 4A. FIG. 4B shows the case of changing to the shifting mode during examination of a portion of the object 34 using the target t3 under control in the rotational mode. In this case, the other targets t1 and t2 are controlled such that the examination region 33 shifts while maintaining the examination direction, as shown in FIG. 4B. There are some problems to be aware of in FIGS. 4A and B. X-rays that pass through the collimator 27 may extend beyond the surface of the two-dimensional detector 28 when the collimator 27 is set so as to satisfy each mode. In this case the patient is unnecessarily exposed to radiation. In order to inhibit such unnecessary radiation exposure, the collimator 27 is controlled such that X-rays do not extend beyond the two-dimensional detector 28. In other words, the collimator 27 is controlled such that X-rays irradiated from the multi X-ray source 26 are all projected onto the two-dimensional detector 28. The C-arm device according to the present embodiment is able to repeatedly select transmission targets 13 and switch between the shifting mode and the rotational mode indefinitely. The C-arm device according to the present embodiment has the transmission target 13 selected by an operator, the examination region 33 formed by the selected target, and the display 31 for informing the operator of the examination direction. FIG. 5 shows an exemplary display screen structure of the display 31. The display 31 is constituted by a liquid crystal display or the like. An image display portion 35 displays an image imaged with X-rays from the currently selected transmission target 13. A patient information display portion 36 and an image processing information display portion 37 for displaying window information and the like are arranged above the image display portion 35. A target display portion 38 is for displaying the selected target, and displays the position, on the entire multi beam X-ray source, of the transmission target 13 currently selected by the operator. An examination region/direction display portion 39 is for displaying the examination region 33 and examination direction of the object 34, and displays the examination region 33 and the examination direction in the case where a hypothetical object 34 is assumed, as cross-sectional information. The hypothetical object 34 is calculated using the FCD (Focus Center Distance) input from the control panel 30. Next, an operation for resetting the collimator 27 will be described. As described above, the C-arm device in the present embodiment is able to repeatedly select transmission targets 13 and switch between the shifting mode and the rotational mode indefinitely. However, when the examination direction at a peripheral transmission target 13 is set at a large angle, X-rays formed by another target may not form an image on the two-dimensional detector 28. In this case, the operator preferably is able to return the collimator 27 to a reset state. The collimator 27 also needs to be returned to a reset state if the object 34 (patient) is changed. The reset state of the collimator 27 can be set by the operator. Exemplary reset states of the collimator 27 include the states of FIGS. 2B and C. Next, a method of controlling the collimator 27 using the position and size of the slits 42 rather than the movement of the aperture plates 32 shown in FIGS. 4A and B will be described with reference to FIGS. 6A to C. While this will be described in one dimension, calculations can be performed two-dimensionally for each axis independently. FDD (Focus Detector Distance) is the length of a vertical line from the transmission targets 13 of the multi X-ray source 26 down to the two-dimensional detector 28. FCD (Focus Center Distance) is the distance from the transmission target 13 positioned in the center of the multi X-ray source 26 to the center of a hypothetical object. FSD (Focus Slit Distance) is the distance from the transmission targets 13 to the slits 42. Also, the relation of an equation (1) is satisfied, where FW (Focus Width) is the width of the transmission targets 13, SW (Slit Width) is the width of the slits 42, and ROI (Region Of Interest) is the width of the examination region 33. Note that SW z FW is assumed.ROI=(FW+SW)·(FCD/FSD)−FW (1) Because FW of the equation (1) is very small relative to the second term, the equation (1) can be approximated as in an equation (2).ROI≈(FW+SW)·(FCD/FSD) (2) Transforming the equation (2) enables the width SW of the slits 42 when the ROI has been determined by the operator to be calculated by an equation (3).SW=ROI·(FSD/FCD)−FW (3) If the control mode of the collimator 27 is the shifting mode, the width SW(t0) of the slit 42 facing a target t0 being examined by the operator will equal the width SW(tn) of the slit 42 facing a target tn positioned n targets away, as in the equation (4).SW(t0)=SW(tn) (4) If the control mode is the shifting mode, the relation of an equation (5) is satisfied between a position P(SW(t0)) of the slit 42 facing the target t0 being examined by the operator and a position P(SW(tn)) of the slit 42 facing the target tn positioned n targets away. Here, FP (Focus Pitch) is the pitch of transmission targets 13. FIG. 6B represents the relation between the equation (4) and the equation (5).P(SW(tn))=P(SW(t0))+n·FP (5) If the control mode of the collimator 27 is the rotational mode, the width SW(t0) of the slit 42 facing a target t0 being examined by the operator and the width SW(tn) of the slit 42 facing a target tn positioned n targets away will be equal, as in the equation (6).SW(t0)=SW(tn) (6) If the control mode of the collimator 27 is the rotational mode, the relation of an equation (7) is satisfied between a position P(SW(t0)) of the slit 42 facing the target t0 being examined by the operator and the position P(SW(tn)) of the slit 42 facing a target tn positioned n targets away. FIG. 6C represents the relation between the equation (6) and the equation (7).P(SW(tn))=P(SW(t0))+n·FP·((FCD−FSD)/FCD) (7) FCD defines the distance from the transmission target 13 positioned in the center of the multi X-ray source 26 to the center of a hypothetical object. If the placement of the actual object 34 differs from the FCD stored by the C-arm device, the values calculated by the above equations (1) to (7) will not coincide with the operator's expectations. In view of this, the FCD value can be changed from the control panel 30 at any time. Next, a technique for making the examination centers coincide in response to the switching of a plurality of X-ray sources under control in the rotational mode will be described. As described above, the collimator 27 is controlled such that the centers of the examination regions 33 (examination centers) coincide in the rotational mode. The region on the two-dimensional detector 28 in the case where X-rays are projected onto the examination region 33 is a light-receiving region 40 (see FIG. 6A). If the slit 42 is positioned in front of the transmission target 13, the light-receiving region 40 will be rectangular. Here, the slits 42 are rectangular, and “in front of” denotes a vertical line from the center of a transmission target 13 down to the plane of the collimator 27 passing through the center of a slit 42 (see light-receiving region 40 from X-ray source t0 in FIG. 7A). If the slit 42 is not positioned in the front of the transmission target 13 (this is called oblique incidence), the light-receiving region 40 will be a quadrilateral other than a square or rectangle. On the other hand, in the rotational mode, it is appropriate to perform image display such that that the transmission target 13 for discharging X-rays is orthogonal to the light beam that passes through the center of the examination region 33. In view of this, images are affine-transformed (projected) from the two-dimensional detector 28, assuming an affine transform plane 44 such as shown in FIG. 7B. The affine transform plane 44 is orthogonal with a line connecting the X-ray source for discharging X-rays and the center of the examination region 33, and includes the point at which this line intersects the two-dimensional detector 28. There are two methods for clipping the light-receiving region 40 from an image read out from the two-dimensional detector 28. One method involves clipping the light-receiving region 40 using X-ray signal values. The other method involves deriving the light-receiving region 40 on the two-dimensional detector 28 from the position and area of the slits 42 of the collimator 27 by calculations. The light-receiving region 40 clipped with either method is displayed on the display 31 after having an affine transform applied thereto. If the calculation time of the affine transform is short, the light-receiving region 40 can be clipped after the entire image from the two-dimensional detector 28 has been affine-transformed. If the calculation time of the affine transform is long, the affine transform is preformed after clipping a partial image from the two-dimensional detector 28, so as to include the light-receiving region 40. Affine-transformed images obtained by the above processing will have coinciding examination centers. In order to inhibit unnecessary radiation exposure to the patient, the collimator 27 is controlled such that X-rays do not extend beyond the two-dimensional detector 28 (are not vignetted). The position and area of the slits 42 of the collimator 27 are calculated in accordance with each mode of the collimator 27. The light-receiving region 40 on the two-dimensional detector 28 is derived by calculations from the calculated position and area of the slits 42. The width of the light-receiving region IRA (Irradiation Area) in the case of the control mode of the collimator 27 being the shifting mode is calculated by an equation (8).IRA=(FW+SW)·(FDD/FSD) (8) If the control mode of the collimator 27 is the shifting mode, the relation of an equation (9) is satisfied between a position P(IRA(t0)) of the light receiving region 40 formed by a target t0 being examined by the operator and a position P(IRA(tn)) of the light-receiving region 40 formed by a target tn positioned n targets away.P(IRA(tn))=P(IRA(t0))+n·FP (9) The light-receiving region 40 will extend beyond the two-dimensional detector 28 if an equation (10) is satisfied, where DW (Detector Width) is the width of the two-dimensional detector 28, and assuming that P(IRA(t0)) coincides with the center of the two-dimensional detector 28. The aperture plates 32 are controlled such that the equation (10) has equality.IRA(tn)/2+n·FP≧DW/2 (10) The light-receiving region IRA (Irradiation Area) in the case of the control mode of the collimator 27 being the rotational mode is calculated by an equation (11).IRA=(FW+SW)·(FDD/FSD) (11) If the control mode is the rotational mode, the relation of an equation (12) is satisfied between a position P(IRA(t0)) of the light-receiving region 40 formed by a target t0 being examined by the operator and a position P(IRA(tn)) of the light-receiving region 40 formed by a target tn positioned n targets away.P(IRA(tn))=P(IRA(t0))+n·FP·((FDD-FCD)/FCD) (12) The light-receiving region 40 will extend beyond the two-dimensional detector 28 if an equation (13) is satisfied, assuming that P(IRA(t0)) coincides with the center of the two-dimensional detector 28. The aperture plates 32 are controlled such that the equation (13) has equality.IRA(tn)/2+n·FP·(FDD−FCD)/FCD)≧DW/2 (13) The first embodiment of the present invention is as described above. In the related art, there is no technique, such as described above, where in conjunction with the change of one aperture in a multi X-ray source, another aperture is changed. The provision of two modes for changing the apertures in conjunction with one another, the first mode being for shifting the examination region, and the second mode being for rotating the examination direction, is also not disclosed in the related art. In contrast, according to the present embodiment, images in which the center of the examination region (examination center) and the examination area are maintained, in the case where the object 34 is fluoroscopically examined while changing the examination direction, can be provided instantaneously. Also, the patient is not subjected to unnecessary radiation exposure, because the examination center and the examination area are suitably changed prior to changing the examination direction. Further, the examination region is easily changed, and a shortening of the operation time and a reduction of radiation exposure to the patient can be anticipated. Second Embodiment Hereinafter, a second embodiment will be described. The configuration of the C-arm device of the second embodiment is similar to the configuration shown in FIG. 1. Hereinafter, control of a collimator 27 will not be described in detail. The collimator 27 is controlled in two control modes, namely, a shifting mode and a rotational mode, similarly to the abovementioned first embodiment, but the present embodiment is not limited to these two control modes. Features of the present embodiment will be described using FIGS. 9A to C and FIGS. 10A to C. FIG. 9A shows an example in which a body is imaged after selecting five X-ray sources indicated with black circles in a two-dimensional multi X-ray source. The two-dimensional multi X-ray source in FIG. 9A is constituted by a total of 81 X-ray sources arranged in a 9×9 array. The selected X-ray sources, expressed in the format X(m,n), are X(5,4), X(4,5), X(5,5), X(6,5) and X(5,6). Rather than the five selected X-ray sources performing exposure simultaneously, only one X-ray source performs exposure at any one time. Conceivable methods of switching the X-ray source for performing exposure include the X-ray sources being switched periodically using a timer built into in a control unit, or being switched non-periodically by an operator. An X-ray image resulting from exposed X-rays is displayed on a display. Methods of displaying images resulting from a plurality of X-rays include displaying all selected X-ray images or displaying only images resulting from recently exposed X-rays. FIG. 9B illustrates an X-ray source selection change in a mode for substantively maintaining the relation of the angles of incidence of currently selected X-ray sources (relation maintaining mode). Switching between the relation maintaining mode and a mode for substantively proportionally maintaining the relation of the angles of incidence of X-ray sources as illustrated in FIG. 9C is performed by an instruction of an operator from a control panel. A control panel 30 is able to receive, when at least two X-ray sources for performing X-ray irradiation are selected from a plurality of X-ray sources, an instruction to change a first X-ray source out of the at least two X-ray sources to a second X-ray source at another position. In the case of the relation maintaining mode, when the X-ray source X(5,4) selected in FIG. 9A is changed to X(6,6), the other X-ray sources are respectively changed as follows: X(4,5)->X(5,7), X(5,5)->X(6,7), X(6,5)->X(7,7) and X(5,6)->X(6,8). In other words, in the case of the relation maintaining mode, when selection is changed from one currently selected X-ray source X(m1,n1) to X(m1+Δm,n1+Δn), another currently selected X-ray source X(m2,n2) is changed to X(m2+Δm,n2+Δn), such that the relative positional relation of the selected X-ray sources prior to the change is maintained. The change in the X-ray images imaged in the case of the relation maintaining mode is as shown in FIGS. 10A to C. FIGS. 10A to C show the case of a one-dimensional multi X-ray source for simplicity. In FIG. 10A, three X-ray sources are selected. When selection the black X-ray source in the middle of the three selected X-ray sources in FIG. 10A is changed to the X-ray source on the right, selection of the other X-ray sources on either side is changed so as to substantively maintain the angles of incidence (FIG. 10B). Looking at the relation between an X-ray image resulting from the three X-ray sources selected in FIG. 10B and an X-ray image resulting from the three X-ray sources selected in FIG. 10A, the angles of incidence relative to the region of interest are changed. However, the relation of the angles of incidence of the three selected X-ray sources is substantively maintained. Here, “substantively maintained” denotes the following. If the X-ray sources in the multi X-ray source are arranged equidistantly, the relation of the angles of incidence before and after the selection change cannot be made to completely coincide. However, if the X-ray source arrangement pitch of the multi X-ray source is very small compared with the distance from the multi X-ray source to the object, the difference in the relation of the angles of incidence before and after the selection change can be disregarded. This is referred to as being “substantively maintained.” FIG. 9C shows an X-ray source selection change in the mode for substantively proportionately maintaining the relation of the angles of incidence (proportion maintaining mode). In the case of the proportion maintaining mode, when the X-ray source X(6,5) selected in FIG. 9A is changed to X(7,5), the remaining X-ray sources are respectively changed as follows: X(5,4)→X(5,3)→X(4,5)→X(3,5), and X(5,6)→X(5,7). Here, X(5,5) is a fixed reference X-ray source. In other words, in the case of the proportion maintaining mode, when one currently selected X-ray source X1 is changed to X1′, another currently selected X-ray source Xn is changed to Xn′, where the fixed reference X-ray source is X0. That is, the other X-ray source is changed to an X-ray source at a position where the relative positional relation of the at least two X-ray sources before the change is scaled. Here, the displacement from the X-ray source X1 to X1′ is expressed as follows.{right arrow over (X1X1′)} If this is the case, the following equations (14) and (15) are satisfied.  X ⁢ ⁢ 1 ⁢ X ⁢ ⁢ 1 ′ →  =  X ⁢ ⁢ n ⁢ ⁢ X ⁢ ⁢ n ′ →  ( 14 ) X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ 1 → · X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ 1 ′ →  X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ 1 →  *  X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ 1 ′ →  = X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ n → · X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ n ′ →  X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ n →  *  X ⁢ ⁢ 0 ⁢ ⁢ X ⁢ ⁢ n ′ →  ( 15 ) The change in the X-ray images imaged in the case of the proportion maintaining mode is shown in FIGS. 10A to C. FIGS. 10A to C show the case of a one-dimensional multi X-ray source for simplicity. In FIG. 10A, three X-ray sources are selected. When selection of the X-ray source shown by the cross-hatched circle on the far right of the three X-ray sources selected in FIG. 10A is changed to an X-ray source further to the right, the other X-ray source on the far left is changed so as to substantively proportionately maintain the angles of incidence (FIG. 10C). Looking at the relation between the X-ray image resulting from the three X-ray sources selected in FIG. 10C and the X-ray image resulting from the three X-ray sources selected in FIG. 10A, the angles of incidence relative to the region of interest are changed. However, the relation of the differences in the angles of incidence of the three selected X-ray sources is substantively maintained. Here, “substantively maintained” denotes the following. If the X-ray sources in the multi X-ray source are arranged equidistantly, the differences of the angles of incidence before and after the selection change cannot be made to completely coincide. However, if the X-ray source arrangement pitch of the multi X-ray source is very small compared with the distance from the multi X-ray source to the object, any difference in the differences of the angles of incidence before and after the selection change can be disregarded. This is referred to as being “substantively maintained.” Note that the relation maintaining mode and the proportion maintaining mode of the second embodiment respectively correspond to control of the collimator 27 in the shifting mode and the rotational mode of the first embodiment. In particular, implementing the second embodiment with the rotational mode of the first embodiment is effective. The relation maintaining mode and the proportion maintaining mode of the second embodiment are, however, not limited to the shifting mode and the rotational mode of the first embodiment. Hereinabove, the second embodiment was described. Hereinafter, the superiority of the present invention over the related art will be described. Conventionally, there were only techniques for coordinating a plurality of C-arm imaging systems in fixed relation in a device having a plurality of C-arms. Also, the number of X-ray sources of the plurality of imaging systems was commonly two at most, and there was no imaging system capable of having from 10 to 100 X-ray sources, such as the above-mentioned first and second embodiments. Therefore, conventionally, changing the selection of X-ray sources currently selected to X-ray sources at other positions was not necessary in the first place in imaging using a plurality of X-ray sources. Accordingly, the problems solved by the present invention can be said to be new problems that were not conventionally known. According to the present invention, control relating to scaling the examination area, shifting the examination region, and changing the examination direction in the case where fluoroscopy is performed after narrowing the examination region in order to reduce radiation exposure to the patient can be favorably performed in an X-ray imaging apparatus provided with a multi X-ray source. Other Embodiments Aspects of the present invention can also be realized by a computer of a system or apparatus (or apparatuses such as a CPU or MPU) that reads out and executes a program recorded on a memory apparatus to perform the functions of the above-described embodiments, and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory apparatus to perform the functions of the above-described embodiments. For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory apparatus (e.g., computer-readable medium). While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. This application claims the benefit of Japanese Patent Application No. 2008-289173, filed Nov. 11, 2008, which is hereby incorporated by reference herein in its entirety.
	summary
061608653	claims	1. A synchrotron radiation measuring system for measuring synchrotron radiation from a synchrotron radiation ring, the synchrotron radiation having a beam profile with an intensity distribution that is variable in accordance with at least one of an accumulated current value and a vacuum level of the synchrotron radiation ring, said system comprising: an X-ray detector movable in a direction of the intensity distribution of the synchrotron radiation in order to follow a shift of the synchrotron radiation, said X-ray detector detecting the synchrotron radiation and outputting a signal based on the detected synchrotron radiation; and computing means for computing an intensity of the synchrotron radiation based on the signal of said X-ray detector and for reserving therein, taking into account variations of the intensity distribution of the synchrotron radiation due to a chance in the accumulated current value, one of (i) a relation between the signal of said X-ray detector and the intensity distribution of the synchrotron radiation and (ii) a relation among the signal of said X-ray detector, the vacuum level, and the intensity distribution of the synchrotron radiation. a synchrotron radiation intensity measuring system as recited in any one of claims 1-4; and control means for controlling exposure amount on the basis of measurement by said measuring system. preparing an X-ray exposure apparatus as recited in claim 5; and performing an exposure process by use of the X-ray exposure apparatus. 2. A system according to claim 1, wherein said computing means reserves therein a relation between a signal of said X-ray detector and the intensity distribution of synchrotron radiation, and wherein, when the intensity distribution of synchrotron radiation is I and the output of said X-ray detector is v, the relation satisfies a condition: EQU I(v)=a.sub.0 +a.sub.1 v+a.sub.2 v.sup.2 +a.sub.3 v.sup.3 + . . . 3. A system according to claim 1, wherein said computing means reserves therein a relation among a signal of said X-ray detector, the level of vacuum at the synchrotron ring and the intensity of synchrotron radiation, and wherein, when the intensity of synchrotron radiation is I and the output of said X-ray detector is v, the relation satisfies a condition: EQU I(v)=a.sub.0 (p)+a.sub.1 (p)v+a.sub.2 (p)v.sup.2 +a.sub.3 (p)v.sup.3 + . . . 4. A system according to claim 1, wherein said X-ray detector has two elements which are disposed in array along the direction of intensity distribution of the synchrotron radiation. 5. An X-ray exposure apparatus, comprising: 6. An apparatus according to claim 5, wherein said control means comprises means for controlling exposure time. 7. An apparatus according to claim 6, wherein said exposure time controlling means comprises shutter control means for controlling a driving speed or a driving pattern for a shutter thereby to control the exposure time. 8. A device manufacturing method comprising the steps of:
	abstract	A method and apparatus for producing a scanned beam of penetrating radiation. A beam of particles illuminates a portion of a target, the illuminated portion comprising a focal spot having a centroid. Illumination of the target creates a beam of penetrating radiation such as x-rays. The beam of particles is swept across the target in such a manner that the centroid of the focal spot lies on a line defined by the instantaneous direction of the beam of penetrating radiation as defined, in turn, by a collimating path.
	abstract	Methods and apparatus are provided for managing test procedures for a hardware-in-the-loop (HIL) simulation environment. The apparatus comprises an input interface for receiving input from a user, a first processor coupled to the input interface and in operable communication with the HIL simulation environment. The first processor is configured to generate a test sequence comprising a plurality of test procedure references based on input from the user, wherein each test procedure reference corresponds to a test procedure that comprises instructions for issuing commands to, and receiving data from, the HIL simulation environment, and sequentially execute each referenced test procedure within the generated test sequence in cooperation with the HIL simulation environment, in response to a command from the user.
048428078	abstract	A reactor cavity dosimetry system and method for deploying the system which includes a top access support stand. Having a generally rectangular frame assembly formed by a pair of cross members and a pair of frame tubes, the support stand holds the dosimetry in place as part of a continuous loop. The continuous loop is first fed through a U-shaped tube situated beneath the support stand, and coupled together by a chain support plug which is adapted for insertion within a hole formed in an upper one of the cross members to fix the position of the dosimetry axially with respect to the core of a nuclear power plant within which the system is deployed. Each of the frame tubes has mounted thereon a pivotable arm assembly with a spring-loaded slide. After insertion within the cavity, the arm assemblies are pivoted out from the plane of the frame assembly, and disposed locked in place perpendicularly across the cavity. The spring-loading of the arm assemblies thus maintains the support stand in a substantially upright position.
	summary
	abstract	Systems and methods are used to increase the penetration and reduce the exclusion zone of radiographic systems. An X-ray detection method irradiates an object with X-ray fanlets including vertically moving fan beams, each fanlet having an angular range smaller than the angular coverage of the object. The fanlets are produced by modulating an X-ray beam, synchronizing the X-ray beam and the fanlets, detecting the fanlets irradiating the object, collecting image slices from the detector array corresponding to a complete scan cycle of the fanlets, and processing the image slices collected for combining into a composite image.
	description	This application is based on and claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 62/841,930, filed May 2, 2019, the entire contents of which are incorporated herein by reference. The disclosure relates generally to a modular mobile reactor, which can be embodied in a fission reactor and, in some embodiments, as a graphite-moderated fission reactor. In particular, the disclosure relates to a mobile, modular reactor in which an active core region and at least a portion of the at least one control region is located within an interior volume of a pressure vessel. Flow annulus features located in the flow annulus between an outer surface of the control rod/fuel rod and an inner surface of the cladding of the channel in which the rod is located stabilizes the flow annulus and maintains a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Sections of the reactor can be pre-assembled as modular sections and later assembled into the reactor. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck, for example, by fitting within a standard 40 ft. shipping container. Although this disclosure references and provides examples using a graphite-moderated, thermal fission reactor, the principles, compositions, structures, features, arrangements and processes described herein can apply to and be embodied in reactors using other moderators (such as water and light-elements) and other coolants (such as water, liquid metal, molten salts, and gas). In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention. As an example, a graphite-moderated reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows low-enriched uranium to be used as nuclear fuel. Several types of graphite-moderated nuclear reactors have been used in commercial electricity generation, including gas-cooled reactors, water-cooled reactors, and high-temperature gas-cooled reactors. FIG. 1 is a schematic, cross-sectional view of a conventional gas-cooled graphite reactor 10 and an associated heat exchanger 20. The gas-cooled graphite reactor 10 includes clad fuel 12 surrounded by graphite 14, which functions as the moderator for the nuclear fission reaction that occurs in the clad fuel 12. The clad fuel 12 and graphite 14 are housed in a pressure vessel 30, with suitable penetrations 60 for support features, such as for control rods 16, instrumentation (not shown). A coolant inlet line 40 and coolant outlet line 42 provide a coolant path between the heat exchanger 20 and the gas-cooled graphite reactor 10. Radiation shielding 50 encloses the reactor 10, although certain penetrations 60 may be present, such as for control rod equipment and charging tubes. Coolant circulates (with the assistance of gas circulator 70) within the coolant path, whereby cool gas coolant supplied to the graphite reactor 10 via coolant inlet line 40 is heated by the reactor 10 as the gas traverses the reactor and then exits the gas-cooled graphite reactor 10 via coolant outlet line 42. The hot gas coolant exiting the gas-cooled graphite reactor 10 is supplied to the heat exchanger 20, which transfers the energy from the heated coolant gas to a secondary coolant, such as water, as in the water/steam heat exchanger shown in FIG. 1. The conventional graphite-moderated nuclear reactors are plant size reactors, with large containment buildings and acreage footprints. Examples of graphite reactors include the Magnox reactor in the UK, a 835 MWt, carbon dioxide cooled reactor using magnesium-aluminum alloy clad natural uranium fuel; the UNGG reactor in France, a 540 MWe, carbon dioxide cooled reactor using magnesium-zirconium alloy clad natural uranium fuel, and the advanced gas-cooled reactor (AGR) in the UK, a 1200 MWe, carbon dioxide cooled reactor using stainless steel clad uranium dioxide fuel. In recent years, there has been increasing interest in small, mobile reactors, especially in the arena of emergency response and military forward-base plant power. However, to date it has been difficult to address and balance competing characteristics for a mobile nuclear power plant (MNPP), including reduced (comparatively) manufacturing costs, transportability, safety, simple installation, and sufficient power generation capacity (e.g., 1-10 MWt). In general, the disclosure relates to a modular mobile reactor, which in some embodiments is a graphite-moderated fission reactor, that is transportable and on a mobile platform for as-needed relocation to provide a mobile power source for short-term and long-term purposes, including emergency response purposes. These characteristics are met by a combination of features including, for example, use of tristructural-isotropic (TRISO) fuel and negative thermal reactivity feedback (due to graphite thermal properties) to provide innate reactor safety; leveraging proven TRISO designs, cladding manufacturing, reactivity control rod drive mechanisms, and pressure vessel design to yield an economic design; locating the entire reactor and heat rejection system on a mobile-based platform, such as “sea lands” or shipping containers for ease of use and installation; and basic and simple geometry design of the reactor core for stable reactor neutronics and simplified reactor analytics. Embodiments of a mobile, graphite-moderated fission reactor include a pressure vessel defining an interior volume, an active core region located within the interior volume of the pressure vessel, the active core region including fuel assemblies and a reflector, and at least a portion of the at least one control system is located in a control region within the interior volume of the pressure vessel. The fuel assembly includes a plurality of fuel unit cells and a plurality of control unit cells, each unit cell including a longitudinally extending graphite body with a longitudinally extending channel with a cladding. For the fuel unit cells, a fuel rod is positioned in the channel of each of the plurality of fuel unit cells and forms a flow annulus between an outer surface of the fuel rod and an inner surface of the cladding of the channel of the fuel unit cell; for the control unit cells, a control rod is positioned in the channel of each of the plurality of control unit cells and forms a flow annulus between an outer surface of the control rod and an inner surface of the cladding of the channel of the control unit cell. In some embodiments, a plurality of flow annulus features can be attached to at least one of the outer surface of the fuel rod and the inner surface of the cladding of the channel of the fuel unit cell. In other embodiments, a plurality of flow annulus features can be attached to at least one of the outer surface of the control rod and the inner surface of the cladding of the channel of the control unit cell. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck. In a particular embodiment, the mobile, graphite-moderated fission reactor includes a shipping container, wherein the pressure vessel is contained within the shipping container. In one particular embodiment, the plurality of flow annulus features are located at equidistant, longitudinally separated locations, and, at each longitudinally separated location, there are at least three, circumferentially distributed, flow annulus features. Additionally, the plurality of flow annulus features are circumferentially distributed by equal spacing and are rotated half the radial spacing between adjacent longitudinal locations. These flow annulus features can be utilized in any of the applicable reactor types that may be designed as a modular mobile reactor. Note, for ease of viewing, not all instances of the features shown in the figures are labeled with reference numerals. FIG. 2 is a schematic, longitudinal cross section illustrating the general arrangement of major components of an exemplary mobile graphite reactor 100. The mobile graphite reactor 100 includes an active core region 105, which includes a fuel assembly region 110 within a reflector region 115, typically a reflector annulus. A core former adapts the outer peripheral geometry of the fuel assembly region 110 to the inner diameter geometry of the reflector region 115. The reflector region 115 mates geometrically and structurally with a pressure vessel 120, which encases at least the active core region 105. This mating accommodates thermal growth of the structures due to thermal expansion that occurs at operating temperatures. The mobile graphite reactor 100 also includes at least one control region 125 that includes a control system (the control system including, for example, control rod drive mechanisms (CRDM) 130 and other necessary ancillary equipment). The exemplary embodiment in FIG. 2 includes two control regions 125, but more than one control region 125 is optional. The typically domed pressure vessel 120 sections corresponding to the control region(s) 125 mate to the cylindrically shaped pressure vessel 120 section associated with the active core region 105 with, for example, bolted flanges. The control region 125 can accommodate operation of the control rods drive mechanism 130 of the control system as they are moved (T) into and out of the active core region 105 to control reactivity during operation. The control rods drive mechanism(s) 130 can be located within the pressure vessel 120 or can protrude from the pressure vessel 120 in a location corresponding to the control region 125. If control rod drive mechanisms 130 are located in both control regions 125, the orientation of the control rods in each region are not co-axial or are otherwise offset to prevent interference when inserted into the fuel assembly region 110. The active core 110 and reflector 115 diametric dimensions can be suitably sized for mobile transport and the desired output power level. For example, in one embodiment, the diameter of the pressure vessel containing the active core and reflector can be 197.5 cm, which would fit in a 40 foot shipping container and which can then be accommodated on a ship, train or truck. Such a sized reactor with TRISO fuel can be designed to produce 1-10 MWe with exit temperatures ranging from 800K-1100K, using a helium coolant configuration. It will be appreciated that the power, dimensions, weight and other parameters discussed herein are examples and, more specifically, are examples based on TRISO fuel. Depending on fuel, moderator, and cladding materials, different temperature limits and different energy production ranges may be realized. Further, different TRISO fuel compositions as well as other, non-TRISO fuels are contemplated, such as compositions including UCO TRISO, UO2 TRISO, U-metal, UO2, UN, and other nuclear fuel (hafnium, thorium, plutonium, etc.). FIG. 3 illustrates a perspective view of an exemplary pressure vessel 200 for a mobile graphite reactor configured for one-sided, control rod insertion for reactivity control. The pressure vessel 200 surrounds and restrains the active core and control rod drive mechanisms and is comprised of an upper dome section 210 and lower dome section 215 and a main section 220 located corresponding to the active core region 105. An extension section 225 provides a stand-off distance between the active core region 105 and control region 125 to allow for the CRDM 130 stroke length. Each of these sections is bolted to the other via mating hole patterns, the number and location of which are as prescribed by the ASME Pressure Vessel Code. The pressure vessel 200 has two cold leg ports 230a, 230b that are in fluid connection with a heat exchanger (not shown) and a hot leg port 235 in fluid connection with the heat exchanger (not shown). More or less hot and cold leg parts may be used per design constraints. In the embodiment shown in FIG. 3, the control rods drive mechanism(s) extend past the envelope of the upper dome section 210 and are contained within control rod drive shaft retention tubes 240. Alternatively, the control rod drive shaft retention tubes 240 could be housed within the pressure vessel 200 if the control rod motors meet the necessary design conditions. Each of the hot leg port flange, cold leg port flange, and control rod drive shaft retention tubes are welded to the appropriate section of the pressure vessel 200. The pressure vessel 200 in FIG. 3 is shown in partial see-through view, which allows for observation of triangular struts 250 welded to the main section 220. These triangular struts 250 have bolt holes to affix upper and lower core plates that retain the fuel assemblies (discussed further below). In embodiments in which control rods are inserted from both ends, the lower dome section 215 shown in FIG. 3 can be removed and substituted by an extension section and dome section similar to extension section 225 and upper dome section 210, in which case the final pressure vessel appearance would be substantially symmetrical. FIG. 4 schematically illustrates such a symmetrical pressure vessel 280. FIG. 5 is a schematic, longitudinal cross section illustrating the internal arrangement of major components in an exemplary mobile graphite reactor, such as that shown in FIG. 3. For assembly and safety, various sections and components are preassembled into subassembly units, each of which is subcritical, per neutron fission production. For example, the active core section 305 and control rod drive mechanism sections 310 (including control rods 325 and threaded shaft 330) of the mobile graphite reactor 300 can be assembled separately (with their respective pressure vessel section) and then brought together by joining the main section with the extension section. The overall reactor assembly is designed to confine the fuel assemblies and control rod drives within the pressure vessel, with the fuel assemblies transported separately and installed via pin locators in upper and lower core plates 315, 320. Alternatively, the assembled core can be transported with hard stops placed on the control rods to prevent core insertion. The CRDM equipment is shown outside the active core with the threaded shaft 330 of each CRDM 130 enveloped by control rod drive shaft retention tubes 240. FIG. 6A is a schematic, magnified, cross-sectional view of a simple hexagonal pitch active core. The fuel assembly 400 includes a plurality of fuel unit cells 405 and control unit cells (not shown) in periodic arrangement (in cross-sectional view). The cross-sectional view in FIG. 6A extends to the inner surface of the reflector, such as a graphite reflector, with a core former providing mating for any geometric mismatch. As seen in cross-sectional view in the magnified fuel unit cells in FIG. 6B (corresponding to the four fuel unit cells 405 enclosed by dashed lines in FIG. 6A), each fuel unit cell 405 includes a fissionable fuel composition 410 located within a cladding structure 415 having an inner cladding 420 with an inner surface oriented toward the fissionable fuel composition 410 and an outer cladding 425 with an outer surface oriented toward a graphite moderator 430 of the fuel unit cell 405. The fissionable fuel composition 410 and inner cladding 420 constitute a fuel (or control) rod cross-section. The inner cladding 420 and the fissionable fuel composition 410 are dimensionally offset to form a gap. This gap makes it easier to insert the fuel composition into the cladding during mechanical loading and also provides a fission gas relief void. The space between the inner cladding 420 and outer cladding 425 defines a flow annulus 435 for coolant, such as gas, to flow. The outer cladding 425 and the graphite moderator 430 are intimately affixed, for example by hot isostatic pressing or press fitting. The outer cladding 425 that separates the flow annulus 435 from the graphite moderator 430 acts as an erosion barrier, without which the hot, high-pressure, and fast moving coolant would erode the graphite moderator 430 resulting in decreased life cycle. The flow annulus 435 inner and outer surface are held stable by flow annulus features (addressed further herein). The fissionable fuel composition 410 can be any suitable fissionable fuel composition, including TRISO fuel compositions as well as non-TRISO fuels, such as compositions including UCO TRISO, UO2 TRISO, U-metal, UO2, UN, and other nuclear fuel (hafnium, thorium, plutonium, etc.). FIG. 7 is an electron microscope image of an exemplary TRISO fuel particle 500. The TRISO fuel particle 500 includes a fuel kernel 505 surrounded by a buffer layer 510, an inner pyrocarbon layer 515, a silicon carbide (SiC) layer 520, and an outer pyrocarbon layer 525. Each of the layers performs an accident-tolerant task, including (in order from inner layer to outer layer) stress mitigation, flexibility, strength and containment. The kernel can be a suitable fissionable fuel, examples of which include a 1 mm diameter particle of UO2 or UCO fuel. The TRISO particle is placed into a matrix of carbon and resin and formed into pellet-shaped fuel or compacts-shaped fuel. The arrangement in FIGS. 6A-B represents a simple hexagonal pitch reactor design, where the pitch is the distance between the centerline of the regions containing the fissionable fuel composition in adjacent fuel unit cells. For example, in the FIGS. 6A-B embodiment with a fissionable fuel composition 410 having a 12.45 mm diameter, the pitch (P) can be 3 to 8 cm. The arrangement shown in FIGS. 6A-B is a singular example and the base dimensions can be altered to optimize different reactor properties based on material ratios (e.g. fuel enrichment or U-235 mass minimization). The flow annulus 435 is stabilized with structural features that are either on the outer surface of the inner cladding 420 or on the inner surface of the outer cladding 425. FIGS. 8 and 9 schematically illustrate examples of external features associated with exemplary embodiments of fuel rods (FIG. 8) and control rods (FIG. 9). FIG. 10 schematically shows a cross-section of a portion of the control rod in FIG. 9. Both fuel rods 600 and control rods 700 use the same basic design with pelletized neutronic material (fuel or absorber) clad over a length of the rod, such as an approximate two meter span as in some embodiments. The cladding can be any suitable material, including all types of Zircaloy, stainless steel, or molybdenum. At equally spaced axial intervals along the length of the fuel rod 600 and/or control rod 700, there are flow annulus features distributed at equal intervals/spacing about the circumference of the cladding, whether as tags 605, 705 on the outer surface of the inner cladding 420 (see FIGS. 8-10) and/or as dimples 610 on the inner surface of the outer cladding 425 (see FIG. 11), whether on the inner surface of the outer cladding of the fuel rods 600 or of the control rods 700. In exemplary embodiments, there are at least three flow annulus features at specified longitudinal locations along the length and they are circumferentially distributed at 30±5 to 60±5 degree intervals, although other angular separations can be used where the angular separation satisfies the relationship 360/N, where N≥3. In some embodiments, there are flow annulus features located at equally-spaced, longitudinal locations along the length of the outer surface of the inner cladding/inner surface of the outer cladding and, at each longitudinally separated location, the flow annulus features are circumferentially distributed at a specified interval, such as at 30±5 to 90±5 degree intervals. The locations of flow annulus features at least at two of the successive longitudinal locations (alternatively at each successive longitudinal location) are rotated by half the degree interval (i.e., 180/N) to prevent the flow annulus features from riding in any longitudinally extending guide grooves. For example, if first flow annulus features at longitudinal position A are at 120, 240 and 360 degrees around the circumference (in relation to an arbitrary reference point), then second flow annulus features at longitudinal position B are at 60, 180 and 300 degrees around the circumference (in relation to an arbitrary reference point). In addition, longitudinal locations are spaced such that at least three longitudinal locations are present in the control guide 1020 at any particular time. The flow annulus features are attached to the cladding by suitable means, such as TIG welding, brazing, or resistance welding. The flow annulus features—whether tags 605, 705 or dimples 610—act as a guide during assembly and control insertion, and stabilize the flow annulus 435. Stabilizing the flow annulus is beneficial because, for example, the flow annulus features maintain a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Without a stable flow annulus, there could be consequential hot spots that downgrade the longevity of the reactor. In a secondary effect, the flow annulus features can act as a flow turbulator, increasing convection. Both the fuel rods 600 and control rods 700 include an upper end cap and a lower end cap, which seal the rod and completes the rod pressure barrier. Although both the fuel rods 600 and control rods 700 have such caps, the caps differ between the fuel rods 600 and the control rods 700. For example, the upper end cap 620 on the fuel rod 600 has a groove 625 with a circular ledge 630 to engage an external hold-down spring and a grappling device for reconstitution. The upper end cap 720 on the control rod 700 has a threaded feature 725, such as a threaded post, to engage a drive system of the control rods drive mechanism. Also for example, the lower end cap 640 on the fuel rod 600 has a threaded feature 645, such as a threaded post, to statically engage a bottom fuel assembly or core plate. The lower end cap 740 of the control rod 700 has a tapered head 745 for guiding the control rod 700 as the control rods 700 are moved (T) into and out of the active core region to control reactivity during operation. The fuel rods 600 include fissionable fuel material and control rods 700 can include both fissionable fuel material and absorber material, depending on the design of the reactor. When present, fissionable fuel material in control rods indicate a subcritical static core that becomes critical as control rods are inserted; when present, absorber material in control rods indicate a supercritical static core that is suppressed to a critical/subcritical state when the control rods are inserted. FIG. 10 shows a generalized cross-section of a portion of a control rod. The internal features include fissionable fuel material or absorber material 760 and an internal hold-down spring 765 located in a plenum to minimize pellet vibration and establish a void for fission gas release. The composition of the fissionable fuel material or absorber material 760 can be altered (compositionally and spatially) to mitigate temperature and fission peaking. A generalized cross-section of a portion of a fuel rod would look similar to the control rod cross-section shown in FIG. 10, except that the threaded feature 725 would be replaced with upper end cap 620. FIGS. 12A and 12B are a schematic side view of a fuel assembly (FIG. 12A) and a magnified, perspective view of an end portion of the fuel assembly with associated features (FIG. 12B). The fuel assembly 800 is an assemblage of both fuel unit cells 805 and control unit cells 810 between a top plate 815 and a bottom plate 820. Individual fuel rods 600 and control rods 700 are located in the fuel assembly 800 amongst their associated unit cells, and the fuel assembly 800 is located within the active core region of the reactor, so as to achieve desired neutronics. FIG. 12B is a magnified perspective view of the top end of the fuel assembly 800 and showing the top plate 815. As shown, thirteen fuel unit cells 805 and six control unit cells 810 are included in the fuel assembly 800 (although other numbers of fuel unit cells and control unit cells can be used) and the top plate 815 contributes to holding these unit cells in position. Some rods inserted into the unit cells in the fuel assembly 800 are dynamic (e.g., the control rods 700) and will govern reactivity while other rods inserted into the unit cells in the fuel assembly 800 are static (e.g., the fuels rods 600). The top plate 815 includes openings 825, which correspond with and lead to the flow annulus 435 of the fuel unit cell 805, and control rod insertion holes 830, which correspond with and lead to the control rod channel of the control rod unit cell 700. A counterbore 835 is provided around the control rod insertion holes 830 to allow for a threaded fastener, such as a tightening nut, to have access to threads of a threaded feature on an outer surface of the control rod insertion hole 830. A plurality of asymmetric pins 840 protrude from the surface 845 of the top plate 815 and are aligned with holes in the upper core plate 315. A plurality of asymmetric pins also protrude from the surface of the bottom plate 820 and provide similar alignment function with the lower core plate 320. FIGS. 13A-D are schematic illustrations of the fuel assembly, including features associated with the fuel unit cell and control unit cell. FIG. 13A shows a partial, cross-sectional view of the fuel assembly 900, FIG. 13B shows an example of a static fuel unit cell 905; FIG. 13C shows an example of a top section of a control unit cell 910; and FIG. 13D shows an example of a bottom section of a control unit cell 915. As readily seen, the bodies of the unit cells are hexagonal, long sleeves of graphite 920 that have a channel 925 in which the cladding 930 is located (note the cladding is the observable inner diameter surface in FIG. 13B, but is not visible in FIG. 13C). In some embodiments, the cladding is inserted via a press fit method. The cladding 930 acts as a barrier between the graphite 920 and coolant (when flowing through the cladding). The cladding 930 also guides any static fuel rods inserted into the channel 925 of the static fuel unit cell 905 during assembly. The channel 925 in FIG. 13C corresponds to the control rod insertion hole 830 and guides any control rods present in the channel 925 of the control unit cell 910 during operation. The control unit cells 910 has an upper guide cap 940 and lower guide cap 945. The lower guide cap 945 is a post or other protrusion that fits into a recess in the bottom plate 810. The upper guide cap 940 includes a threaded feature on the outer surface (described above in connection with control rod insertion hole 830) that receives a threaded fastener, such as a nut, to clamp the control unit cell (and the adjacent fuel unit cells) in place between the bottom plate 820 and the top plate 815 in the fuel assembly 800 (see also FIGS. 12A and 12B). As seen in FIG. 13A, the fuel unit cell cladding 930 longitudinally extends to and/or overextends the end of the graphite 920 and joins the top and bottom plates 805, 820 to encapsulate a recess 960. The recess 960 provides a housing and bearing surface for the external hold-down spring 965 that engages with the circular ledge 630 of the groove 625 of the upper end cap 620 on the fuel rod 600. The external hold-down spring 965 bears against the upper end cap 620 on the fuel rod 600 to provide a seating bias to the fuel rod 600 (see FIG. 8). Internal hold-down spring 765 is also visible in FIG. 13A. Note that the static fuel unit cell 905 does not have an upper end cap (and though not shown, also does not have a lower end cap). Rather, the static fuel unit cell 905 is held in place directly by the top and bottom plates 815, 820. FIG. 14 is a magnified, perspective schematic view of control rods 700 inserted into the upper guide cap 940. The threads of the upper guide cap 940 are exposed. Once the control unit cell 810 are assembled into an assembly 800 with the top and bottom plates 815, 820, the threads of the upper guide cap 940 would typically receive a fastener, such as a nut that would be tightened to clamp the upper guide cap 940 (and hence the control unit cell 810) to the top plate 815. The control unit cells 810 (and their position in the active core) provide control of the reactivity of the reactor. This reactivity can be controlled positively or negatively. In positive control, the reactivity is increased as a rod loaded with fissionable fuel is inserted into the core. In negative control, the reactivity is decreased as a rod loaded with absorber (or neutron poison) is inserted into the core. For longevity of duty cycle, one option is to slowly insert fuel loaded control rods to slowly burn the fuel. The fine-tuned movement of the fuel loaded control rods can be controlled by a control rod motor that engages the shaft 330 in the CRDM. The reactivity can be controlled by movement of the control rods 700, either singularly or as a group (also called a control rod bundle). FIG. 15 is a perspective schematic view showing a guide mechanism 1000 for the control rods 700. In the view, control rods 700 are attached to a translatable control rod assembly 1010 (also known as a “spider”) which can collectively translate the plurality of attached controlled rods. The control rods are supported along their length by a guide structure 1020. In a horizontal orientation of the graphite reactor, such a guide structure 1020 can mitigate sagging of the control rods when extended outside of the active core. The guide structure 1020 itself is positioned at an axial location above the active core and affixed by mating it directly or indirectly to the inner surface of the pressure vessel. The control rod assembly 1010 is translatable (M) so that control rods 700 can be fully inserted into the active core. To accommodate full insertion, the guide structure 1020 has openings or slots 1030 to accommodate the arms 1040 of the control rod assembly 1010 and to allow for such full insertion. Here, the previously described tags 705 on the control rods 700 contribute to guide the control rods 700 relative to the guide structure 1020 during insertion. For example, circumferentially separated tags 705 rotationally offset at successive axial locations along the length of the outer surface of the control rod provide that no tag 705 can ride or otherwise be stuck in an opening or slot 1030 and that the tags 705 will provide proper spacing between the outer circumference of the control rod 700 and the inner surface formed by the length of the opening or slot 1030 (as the opening or slot 1030 runs from the top surface 1050 of the guide structure 1020 to the bottom surface 1060 of the guide structure 1020). This arrangement of the tag features 705 will prevent the fuel/control rod claddings from scraping against the guide structure 1020, which could otherwise potentially damage the fuel/control rod. FIGS. 16A and 16B show a perspective view and side, transparent view, respectively, of an exemplary mobile graphite-moderated fission reactor 1100 and associated container 1110 for mobile transportation. In exemplary embodiments, the container 1110 can be a standard ISO shipping container, which is 8 ft (2.43 m) wide, 8.5 ft (2.59 m) high and come in two lengths—20 ft (6.06 m) and 40 ft (12.2 m). Extra tall shipping containers (called high-cube containers) can also be used and are 9.5 ft (2.89 m) high. Other suitable containers can be used that allow for loading onto and transport by equipment such as ships, trains and trucks. In the illustrated example, the container 1110 is a 40 foot long standard ISO shipping container. Although the present invention has been described in connection with embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departure from the spirit and scope of the invention as defined in the appended claims. For example, although described in relation to fissionable fuel materials, nuclear reactors, and associated components, the principles, compositions, structures, features, arrangements and processes described herein can also apply to other materials, other compositions, other structures, other features, other arrangements and other processes as well as to their manufacture and to other reactor types. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. In some instances, one or more components may be referred to herein as “configured to,” “configured by,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Those skilled in the art will recognize that such terms (e.g., “configured to”) can generally encompass active-state components and/or inactive-state components and/or standby-state components, unless context requires otherwise. While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. Those skilled in the art will appreciate that the foregoing specific exemplary processes and/or devices and/or technologies are representative of more general processes and/or devices and/or technologies taught elsewhere herein, such as in the claims filed herewith and/or elsewhere in the present application. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting.
050842323	abstract	In 1974, a well-known research problem in Statistical Mechanics entitled "To determine and define the probability function P.sub.2 of a particle hitting a predesignated area, given all its parameters of generation and ejection." was openly solicited for its solution from research and development organizations in U.S.A. One of many proposed solutions of the problem, initiated at that time, is by means of the TRAJECTORY SOLID ANGLE(TSA). TSA is defined as the integral of the dot product of the unit tangent of the particle's trajectory to the vectorial area divided by the square of the position vector connecting between the point of ejection and that of the surface to be hit. The invention provides:(1) The precise and the unique solution of a previously unsolved P.sub.2 problem:(2) Impacts to the governmental NRC safety standards and DOD weaponary systems and many activities in the Department of Energy;(3) Impacts to update the contents of text books of physics and mathematics of all levels; (4) Impacts to the scientific instrumentations with applications in high technologies. The importance of TRAJECTORY SOLID ANGLE can be quoted from a letter by the late Institute Professor P. M. Morse of MIT who reviewed the DOE proposal P7900450 (reference No. 7) in 1979 and addressed to the inventor." If the TRAJECTORY SOLID ANGLE is correct it will provide a revolutionary concept in physics. . . ".
047215968	abstract	A method for decreasing the amount of hazardous radioactive reactor waste materials by separation from the waste of materials having long-term risk potential and exposing these materials to a thermal neutron flux. The utilization of thermal neutrons enhances the natural decay rates of the hazardous materials while the separation for recycling of the hazardous materials prevents further transmutation of stable and short-lived nuclides.
	summary
	claims	1. A strap member of a grid of a fuel assembly of a nuclear reactor, the nuclear reactor including at least a first fuel rod, the strap member comprising: a first plate; the first plate including a first dimple; a second plate; the second plate including a second dimple; a spring apparatus including a spring member, a first leg, and a second leg, the first and second legs each extending nonlinearly between the first and second plates; the first and second legs being generally coplanar with the first and second plates when the spring apparatus is in a relaxed state; the spring member extending between the first and second legs; and the spring member including a spring plate and a pair of spring ligaments, the spring plate being interposed between the spring ligaments, one of the spring ligaments being connected with the first leg, the other of the spring ligaments being connected with the second leg. 2. The strap member as set forth in claim 1 , in which the spring plate is shaped to include a spring contour, the spring contour being structured to substantially complementarily engage the fuel rod. claim 1 3. The strap member as set forth in claim 2 , in which the spring plate includes a spring embossment and a spring perimeter frame, the spring embossment protruding from the spring perimeter frame, the spring contour extending along the spring embossment, the spring embossment being structured to substantially complementarily engage the fuel rod. claim 2 4. The strap member as set forth in claim 2 , in which the first and second dimples each include a dimple plate and a pair of dimple ligaments, the dimple plates each being shaped to include a dimple contour, the dimple contour being structured to substantially complementarily engage the fuel rod. claim 2 5. The strap member as set forth in claim 4 , in which the spring plate includes a spring embossment and a spring perimeter frame, the spring embossment protruding from the spring perimeter frame, the spring contour extending along the spring embossment, the spring embossment being structured to substantially complementarily engage the fuel rod, and in which each dimple plate includes a dimple embossment and a dimple perimeter frame, the dimple embossments protruding from the dimple perimeter frames, the dimple contours extending along the dimple embossments, the dimple embossments being structured to substantially complementarily engage the fuel rod. claim 4 6. The strap member as set forth in claim 1 , in which the spring plate and the pair of spring ligaments are substantially non-coplanar with the first and second plates when the spring apparatus is in the relaxed state. claim 1 7. The strap member as set forth in claim 1 , in which the strap member includes a central axis extending along the spring apparatus and the first and second plates, and in which the portions of the first and second legs connected with the spring ligaments are spaced farther from the central axis than the portions of the first and second legs connected with the first and second plates. claim 1 8. A fuel assembly for a nuclear reactor, the fuel assembly comprising: at least a first fuel rod; and at least a first grid; the at least first grid including a plurality of first straps aligned with one another and a plurality of second straps aligned with one another, the first and second straps being connected with one another in a lattice to define a plurality of cells; the at least first fuel rod being disposed in one of the cells; at least one of the first and second straps including a strap member including a first plate, a second plate, and a spring apparatus; the first plate including a first dimple; the second plate including a second dimple; the spring apparatus including a spring member, a first leg, and a second leg; the first and second legs each extending nonlinearly between the first and second plates; the first and second legs being generally coplanar with the first and second plates when the spring apparatus is in a relaxed state; the spring member extending between the first and second legs; and the spring member including a spring plate and a pair of spring ligaments, the spring plate being interposed between the spring ligaments, one of the spring ligaments being connected with the first leg, the other of the spring ligaments being connected with the second leg. 9. The fuel assembly as set forth in claim 8 , in which the spring plate is shaped to include a spring contour that substantially complementarily engages the fuel rod. claim 8 10. The fuel assembly as set forth in claim 9 , in which the spring plate includes a spring embossment and a spring perimeter frame, the spring embossment protruding from the spring perimeter frame, the spring contour extending along the spring embossment, the spring embossment substantially complementarily engaging the fuel rod. claim 9 11. The fuel assembly as set forth in claim 9 , in which the first and second dimples each include a dimple plate and a pair of dimple ligaments, the dimple plates each being shaped to include a dimple contour, the dimple contour substantially complementarily engaging the fuel rod. claim 9 12. The fuel assembly as set forth in claim 11 , in which the spring plate includes a spring embossment and a spring perimeter frame, the spring embossment protruding from the spring perimeter frame, the spring contour extending along the spring embossment, the spring embossment substantially complementarily engaging the fuel rod, and in which each dimple plate includes a dimple embossment and a dimple perimeter frame, the dimple embossments protruding from the dimple perimeter frames, the dimple contours extending along the dimple embossments, the dimple embossments substantially complementarily engaging the fuel rod. claim 11 13. The fuel assembly as set forth in claim 8 , in which the spring plate and the pair of spring ligaments are substantially non-coplanar with the first and second plates when the spring apparatus is in the relaxed state. claim 8 14. The fuel assembly as set forth in claim 8 , in which the strap member includes a central axis extending along the spring apparatus and the first and second plates, and in which the portions of the first and second legs connected with the spring ligaments are spaced farther from the central axis than the portions of the first and second legs connected with the first and second plates. claim 8 15. A fuel assembly for a nuclear reactor, the fuel assembly comprising: at least a first fuel rod; and at least a first grid; the at least first grid including a plurality of first straps aligned with one another and a plurality of second straps aligned with one another, the first and second straps being connected with one another in a lattice to define a plurality of cells; the at least first fuel rod being disposed in one of the cells; at least one of the first and second straps including a strap member including a first plate, a second plate, and a spring apparatus; the first plate including a first dimple; the second plate including a second dimple; the spring apparatus including a spring member, a first leg, and a second leg; the first and second legs each extending nonlinearly between the first and second plates; the spring member extending between the first and second legs; the spring member including a spring plate and a pair of spring ligaments, the spring plate being interposed between the spring ligaments, one of the spring ligaments being connected with the first leg, the other of the spring ligaments being connected with the second leg; the spring plate being shaped to include a spring contour that substantially complementarily engages the fuel rod; and in which the spring contour is generally of a spring radius when the spring apparatus is in a relaxed condition, and in which the at least first fuel rod is of a fuel rod radius, the spring radius being greater than the fuel rod radius. 16. A fuel assembly for a nuclear reactor, the fuel assembly comprising: at least a first fuel rod; and at least a first grid; the at least first grid including a plurality of first straps aligned with one another and a plurality of second straps aligned with one another, the first and second straps being connected with one another in a lattice to define a plurality of cells; the at least first fuel rod being disposed in one of the cells; at least one of the first and second straps including a strap member including a first plate, a second plate, and a spring apparatus; the first plate including a first dimple; the second plate including a second dimple; the spring apparatus including a spring member, a first leg, and a second leg; the first and second legs each extending nonlinearly between the first and second plates; the spring member extending between the first and second legs; the spring member including a spring plate and a pair of spring ligaments, the spring plate being interposed between the spring ligaments, one of the spring ligaments being connected with the first leg, the other of the spring ligaments being connected with the second leg; the spring plate being shaped to include a spring contour that substantially complimentarily engages the fuel rod; the first and second dimples each including a dimple plate and a pair of dimple ligaments, the dimple plates each being shaped to include a dimple contour, the dimple contour substantially complementarily engaging the fuel rod; and in which the spring contour is generally of a spring radius and the dimple contour is generally of a dimple radius when the spring apparatus is in a relaxed condition, and in which the at least first fuel rod is of a fuel rod radius, the spring radius and the dimple radius each being greater than the fuel rod radius.
061370282	claims	1. A method for the disposal of oil field wastes contaminated with naturally occurring radioactive materials, comprising the steps of: drilling a first well into a salt formation; drilling a second well so as to intersect said first well within said salt formation; providing a slurry of wastes, contaminated with naturally occurring radioactive materials, and a relatively less-dense carrier liquid; injecting said slurry through said first well into said salt formation wherein said wastes, being more dense than said carrier liquid, settle within said first well; and, removing said carrier liquid from said first well by drawing such through said second well. drilling a first well into a salt formation; drilling a second well so as to intersect said first well within said salt formation; injecting fresh water into said first well and simultaneously withdrawing the resulting brine from said second well thereby dissolving a cavern in said salt formation; providing a slurry of wastes, contaminated with naturally occurring radioactive materials, and a relatively less-dense carrier liquid; injecting said slurry through said first well into said cavern wherein said wastes, being more dense than said carrier liquid, settle within said cavern; and, removing said carrier liquid from said cavern by drawing such through said second well. drilling a third well into a permeable formation remote from said salt formation; and, injecting said liquid carrier removed from said cavern through said third well into said permeable formation. terminating injecting said slurry through said first well; terminating removing said carrier liquid from said cavern by drawing such through said second well; injecting said slurry through said second well into said cavern wherein said wastes, being more dense than said carrier liquid, settle within said cavern; and, removing said carrier liquid from said cavern by drawing such through said first well. drilling a first well into a salt formation; drilling a second well so as to intersect said first well within said salt formation; drilling a third well into a permeable formation remote from said salt formation; injecting fresh water into said first well and simultaneously withdrawing said water through said second well thereby dissolving a cavern in said salt formation; terminating injecting fresh water into said first well and withdrawing said water from said second well; injecting fresh water into said second well and simultaneously withdrawing said fresh water through said first well thereby enlarging said cavern; providing a slurry containing wastes, contaminated with naturally occurring radioactive materials, and a less-dense carrier liquid; injecting said slurry through said first well into said cavern wherein said wastes, being more dense than said carrier liquid, settle within said cavern; removing said carrier liquid from said cavern by drawing such through said second well; and, injecting said carrier liquid removed from said cavern through said third well into said permeable formation. terminating injecting said slurry through said first well; terminating removing said carrier liquid from said cavern by drawing such through said second well; injecting said slurry through said second well into said cavern wherein said wastes, being more dense than said carrier liquid, settle within said cavern; and, removing said carrier liquid from said cavern by drawing such through said first well. 2. The method according to claim 1 wherein said carrier liquid is fresh water. 3. The method according to claim 1 wherein said carrier liquid is salt water. 4. The method according to claim 3 wherein said carrier liquid is saturated with salt. 5. A method for the disposal of oil field wastes contaminated with naturally occurring radioactive materials, comprising the steps of: 6. The method according to claim 5 and further comprising the steps of: 7. The method according to claim 5 and further comprising the steps of: 8. The method according to claim 5 wherein said carrier liquid is fresh water. 9. The method according to claim 5 wherein said carrier liquid is salt water. 10. The method according to claim 9 wherein said carrier liquid is saturated with salt. 11. A method for the disposal of oil field wastes contaminated with naturally occurring radioactive materials, comprising the steps of: 12. The method according to claim 11 and further comprising the steps of: 13. The method according to claim 11 wherein said carrier liquid is fresh water. 14. The method according to claim 11 wherein said carrier liquid is salt water. 15. The method according to claim 11 wherein said carrier liquid is saturated with salt.
053176120	summary	FIELD OF THE INVENTION The invention described herein relates to holddown springs for use in minimizing pellet-to-pellet gaps in nuclear fuel rods. More particularly, the invention relates to the use of shape-memory alloys in fuel pellet holddown springs. BACKGROUND OF THE INVENTION Commercial nuclear reactors used for generating electric power include a core composed of a multitude of fuel assemblies which generate heat used for electric power generation purposes. Each fuel assembly includes an array of fuel rods held in spaced relationship with each other by spacer grids. The fuel rods may be approximately 0.5 inches in diameter and about 12 feet long and typically comprise a hollow zirconium alloy tube, or cladding, which is filled with a stacked column of cylindrical uranium dioxide fuel pellets and provided with zirconium alloy end caps. After multiple cycles of operation, highly localized concentrations of zirconium hydride have been observed in the cladding at locations corresponding to pellet-to-pellet gaps in the uranium dioxide fuel column. The localized concentrations are believed to be due to hydrogen migration. Hydrogen apparently peripherally migrates down the thermal gradients that arise in the cladding from "cool spots" associated with the formation of pellet-to-pellet gaps. The source of the hydrogen is believed to be the water-side corrosion process which liberates hydrogen which is, in turn, absorbed by the cladding. When the concentration of hydrogen in a local region of the cladding exceeds the solubility limit at a given temperature, a phase transformation occurs, resulting in the formation of delta- phase zirconium hydride. Such local concentrations of zirconium hydride at fuel column gaps have been confirmed by Combustion Engineering, Inc., the assignee of the present invention, in fuel rods irradiated for multiple cycles. A high local concentration of zirconium hydride can diminish cladding performance capability. For example, at the ANS Topical meeting on Fuel Performance in April, 1991, results from a failure diagnostic program on 2-cycle fuel rods were presented which suggested a link between local zirconium hydride concentrations at fuel pellet gaps and fuel failure. The cause of approximately 21% of the fuel rod failures experienced by Combustion Engineering, Inc. is not known. Local zirconium hydride concentrations at fuel pellet gaps are suspected as being responsible for a portion of these failures, particularly in those cases where failure occurred during the second or third cycle of operation. Therefore, any method of lessening or eliminating these fuel pellet gaps would be beneficial. One way of decreasing the number and extent of the fuel pellet gaps that are formed during operation is to maintain a force on the fuel pellet stack. Presently, fuel pellet holddown springs are made of stainless steel. Unfortunately, after a cycle of operation, stainless steel springs lose their holddown capability at high temperatures and their effectiveness in reducing fuel pellet gaps is therefore compromised. SUMMARY OF THE INVENTION In view of the foregoing, it is readily apparent that conventional fuel pellet holddown springs do not provide adequate holddown force on the fuel pellet stack after multiple cycles of operation. One advantage of the present invention is the elimination of reduction of the above problems encountered in prior art holddown springs. These and other advantages have been achieved by providing a fuel pellet holddown spring comprising a conventional holddown spring material, such as stainless steel, and a two-way shape-memory alloy, such as a nickel-titanium alloy. Accordingly, when reactor coolant temperature increases, the shape-memory alloy spring expands, while the conventional spring weakens and is compressed. As coolant temperature decreases, the shape-memory alloy spring contracts, while the steel spring strengthens and expands. Upon further study of the specification and appended claims, further advantages of this invention will become apparent to those skilled in the art.
	abstract	An ultraviolet ionizing unit for an air purifying that treats all air passing therethrough. The unit has a housing with an air ingress opening at first end, an air egress opening at a second end, an open end, at least two spaced apart internal retainers formed inside the housing, and a cavity formed in a space between the two spaced apart internal retainers. Two sections of ion generating material are retained in a spaced apart manner by the two spaced apart internal retainers. Spacers are used to hold a U-shaped UV lamp in the cavity, provide cushioning of the UV lamp therein, and providing additional sealing so that all air passing through the ionizing unit will be treated. A housing end cap covers the open end of the housing and retains the UV lamps therein so that the ion generating materials is fully exposed by UV light.
047708425	claims	1. A nuclear power plant including a common bus multinode sensor system for sensors in the nuclear power plant, each sensor producing a sensor signal, said system comprising: a power supply providing power; a communication cable coupled to said power supply; plural remote sensor units coupled between said cable and one or more sensors, and comprising: a receiver connected to said cable and comprising:
	abstract	A technique for improving ion implanter productivity is disclosed. In one particular exemplary embodiment, the technique may be realized as a method for improving productivity of an ion implanter having an ion source chamber. The method may comprise supplying a gaseous substance to the ion source chamber, the gaseous substance comprising one or more reactive species for generating ions for the ion implanter. The method may also comprise stopping the supply of the gaseous substance to the ion source chamber. The method may further comprise supplying a hydrogen containing gas to the ion source chamber for a period of time after stopping the supply of the gaseous substance.
	abstract	A ceramic waste immobilizing material for the encapsulation of high level radioactive waste (HLW), e.g. resulting from the reprocessing of irradiated nuclear fuel. The ceramic waste immobilising material enables waste ions from at least fission products in irradiated nuclear fuel to be dissolved in substantially solid solution form. The ceramic waste immobilising medium has a matrix comprising phases of hollandite, perovskite and zirconolite in which the waste ions are dissolved. The invention also includes a method of immobilizing HLW from reprocessed nuclear fuel assemblies comprising the steps of mixing a liquor containing the HLW with a precursor material comprising oxides or oxide precursors of at least titanium, calcium and barium to form a slurry, drying the slurry, and calcining the dried slurry under a reducing atmosphere to form a powder comprising 30–65 weight % waste.
	abstract	This invention relates to the vitrification of radioactive waste products. According to this invention, a glass composition that is suitable for mixed waste products, which include flammable waste products, such as gloves, working clothes, plastic waste, and rubber, and low-level radioactive waste products, and a method of vitrifying the mixed waste products using the same are provided to significantly reduce the volume of radioactive waste products and to vitrify the mixed waste products using the glass composition, which is suitable for vitrifying the mixed waste products, thereby maximally delaying or completely preventing the leakage of radioactive materials from a glass solidified body.
	abstract	A fuel assembly for a pressurized water nuclear reactor includes a multiplicity of fuel rods which extend in a longitudinal direction and are guided in a plurality of spacers that are spaced apart from one another axially. The spacers of an upper region have a lower flow resistance in a transverse direction perpendicular to the longitudinal direction, than the spacers of a lower region.
	abstract	The invention relates to the confinement of an alloy formed of actinide transuranic radioactive wastes and beryllium metal within a neutron moderating and reflecting apparatus to cause accelerated destruction (burning) of the actinide wastes. Waste actinides, including plutonium, neptunium, americium, and curium, emit alpha particles by radioactive decay. The alpha particles are converted into neutrons by the beryllium through an alpha-neutron (alpha, n) reaction. The neutrons developed by the alpha, n reaction are moderated by a surrounding layer of graphite, which allows the slowed neutrons to cause additional fission or decay events within the waste actinide alloy. This process is passive because the alpha particles that initiate the actinide burning are an intrinsic physical property of the actinides. The burning or decay process is accelerated because neutrons that would ordinarily escape the confinement fixture (a Standard Source capsule) are reflected back into the actinide waste, transmuting them into heavier, less stable isotopes that decay more rapidly. The use of the moderator/reflector material allows the waste actinides to be destroyed in a 10,000-year repository period instead of requiring one million years to attain the same waste reduction by natural radioactive decay alone. Beryllium may also be used as a neutron moderator/reflector, but is not a cost effective choice for large scale use.
047924292	description	PREFERRED EMBODIMENT OF THE INVENTION The numeral 10 generally designates a nuclear fuel assembly upper end fitting which includes a pair of spring retention caps, generally designated 12, according to the principles of the invention. The spring retention caps 12 are diagonally opposite each other on the upper surface of an upper end fitting or top nozzle 14. The top nozzle 14, as seen in plan view in FIG. 1, has a plurality of coolant flow ports 16 and openings 18 through which control rods pass in a manner known to those skilled in the art. On the top of the nuclear fuel assembly upper end fitting, along each of its four sides, is a leaf spring pack 20 made up of upper springs 22 and a plurality of lower springs 24. The spring packs 20 have tangs 26 which insert into the top nozzle body through access holes 28 after the lower springs 24 have first had the upper spring tangs 26 inserted through the opening 30 at the upper end thereof. Each of the springs 22 and 24 have an opening 32 for receipt of a spring retention screw 34 which is tightened in a threaded bore 36 in the upper end fitting 14. The spring retention screws 34 are typically driven by hex keys and have a hexagonal opening in their head for this purpose. Once all of the spring packs 20 are assembled in this manner, the upper end fitting is ready to receive the novel spring retention cap of the invention. The spring retention cap 12 is generally shaped in the same shape as upper end fitting posts 40 at the diagonal corners opposite therefrom. Cap 12 has two plane exterior surfaces 42 and 44 which form an angled corner 46, slightly bevelled for convenience, which corresponds to a corner formed by the side walls of the upper end fitting 14 as they converge at the upper end fitting corner below where the retention cap 12 is to be mounted. The cap 12 has a base 50,52 for engaging the end fitting 14 and a slot 54 in the base 50,52 spaced from and extending substantially parallel to the two plain exterior surfaces 42 and 44. Thus, the slot 54 is basically an L-shaped slot. An inwardly directed flanged base portion 50 defines a connecting hook-like structure which engages a slot 56 in the corner of the upper end fitting 14 where the exterior surfaces corresponding to the two exterior plane surfaces 42 and 44 of the cap converge. The base has a portion 52 on the opposite side of the slot 54 from the flange portion 50 of the base which is inward of the hook-like structure defined by flange 50. Between the spring retention screws 34 and of slightly smaller diameter, but also with a head having a hexagonal opening, is a third screw 60 countersunk in a bore, directly opposite corner 46, running vertically through cap 12. Screw 60 secures the retention cap 12 in position with ends of the leaf spring and the spring retention screws 34 covered thereby. The spring retention screws and spring ends are thus protected from being impacted during fuel handling operations. The distance from the two plane exterior surfaces 42,44 of the body to the slot 54, and the cross-section of screw 60, are sufficient to provide strength to accommodate a jacking force which would be created by the leaf spring assembly or assemblies 20 in the event of failure of one or both of the two leaf spring assembly retention screws 34 positioned under the cap 12 in partial register with access openings 58 in the top of the cap. All of the screws 34 and 60 are provided with a crimp to prevent rotation. This eliminates the necessity of wire rotation preventing and retaining members previously used, which require welds and which can become debris in the circulating coolant of the reactor. Crimps in the heads of screws 34 are made after installing cap 12 by means of a tool inserted through access holes 62 in cap 12. Note that the positioning of the cap 12 requires two separate motions, one to drop it vertically over the springs and screws 34, and the other slightly horizontally to move the cap hooks into the top nozzle body slots 56. The various cutaway sections of the cap 12 and nozzle body 14 are designed such that these motions are permitted with clearance between the cap and the spring packs. Thus, the distance between the base portion defined by flange 50 and that defined by the inward portion 52, on the opposite side of slot 54, is slightly larger than the width of the spring packs 20. The wall thicknesses 42, 44, the flange 50, and the screw 60, as previously stated, are of sufficient strength and stiffness to accommodate the jacking forces, if one or both of the spring retention screws 34 should break. It is important to notice that there is normally no contact between the cap 12 and the spring packs 20 in order that this not be a source of friction that reduces the holddown force or interferes with installation. The absence of contact also eliminates differential thermal expansion, since the springs of the spring packs 20 and the spring retention screws 34 are typically made of high strength Inconel alloys and the cap 12 and the cap retention screws 60 are made from less expensive stainless steel. The spring retention screws 34 contact the cap 12 only at the crimp region as an anti-rotation measure. The cap retention screw 60 serves normally only to hold the cap 12 in position. If one of the spring retention screws 34 should fracture, the following sequence would occur: The spring ends of the spring pack 20 would become free to raise off the top nozzle's 14 seating surface, until the springs would contact the underside of the cap 12. The design is such that this is a very short distance. Once that contact is made, the cap "rocks" slightly until the cap 12 hooks, i.e. flanges 50 engage the edge of the slots 56 in the top nozzle or upper end fitting 14. At this point, further lifting of the spring ends is prevented by the combined action of the cap hook formed by flange 50 and the cap retention screw 60. At the same time, the head of the spring retention screw 34 is lifted by the spring pack 20. However, the vertical clearance between the underside of the cap 12 and the screw head of broken screw 34 is greater than that at the end of the spring. Therefore, the screw head is captured vertically by the cap 12, but not under a load, since this would tend to crush the portion of the screw head utilized for crimping. The cap 12 also provides lateral restraint on the screw head 34 so that the springs remain aligned both vertically and horizontally by the two pieces of the broken screw 34. Rotationally, the screw pieces act with the upper spring tang 26 and the cap edge to preclude rotation of the spring pack 20 into the path of control rods 18. None of these actions results in any loading on the other spring pack or retention screw covered by the cap. The small movement of the spring ends relieves a portion of the spring compression in the pack in the event of the screw 34 breaking. However, most of the spring compression is retained, and based on the experience of other fuel suppliers, it is likely that only one spring pack 20 of the four in each assembly would be affected. There should normally be sufficient margin to accommodate the small loss in holddown force because the design includes added holddown force to accommodate transient conditions in reactor coolant flow. The mechanical arrangement retaining the spring pack 20 remains in effect, even if the screw 34 should break, until the reactor shuts down for refueling. At this time, the upper core plate (not shown) over the end fitting assembly 14 and spring retention caps 12 is removed and the spring compression of the spring pack 20 is relieved. The fuel assembly can be handled normally, since the cap 12, spring screw 34 pieces, and upper spring tang 26 continue to restrain the spring pack 20 from movement out of position. The fuel assembly could be operated for additional periods since there should be no long term degradation of the components. However, if reconstitution of the broken screw 34 is desirable, the designs of the various components lend themselves to remote underwater disassembly and assembly operations. First, the cap retention screw 60 is unscrewed and removed. Its crimp is designed to be overridden with modest torque by use of a hex key and its threaded length is such that the act of unscrewing it from the top nozzle 14 raises its head above the upper surface of the cap 12. In this position, it can easily be gripped and retained by conventional tools for use in reconstitution of fuel assemblies under water. The cap 2 is moved horizontally on a 45.degree. angle with respect to the sides of the top nozzle 14, until the cap hooks or flange 50 are disengaged from the nozzle 14. Because of the orientations of the crimps on the spring retention screws 34, they do not interfere with this movement. The cap 12 is lifted off vertically, exposing the broken screw 34 for removal and replacement. The head of the screw 34 is lifted off and then the springs can be lifted off the remaining section of the screw to expose it for removal by a gripping tool. All components are reuseable except for the broken screw 34. The reassembly procedure would be the reverse of that just described, except that at the end, the cap retention screw 60 would be recrimped and the new spring retention screw 34 would require a crimp through access hole 62. The unbroken retention screw on the other spring pack has its crimped region returned to the original alignment with the cap and requires no new operation. All of the above description referred to a case where one spring retention screw 34 was fractured. If both screws 34 should fracture, the same sequence of events would follow, except the reconstitution would involve both spring packs. The strengths of cap 12 and screw 60 are sufficient to accommodate the combined jacking force from both spring packs 20. Thus, it will be seen that the components are designed to minimize the effects of broken holddown spring retention screws, which have created problems in operating fuel. The specific problems which are addressed are a loss of holddown force, creation of loose parts, the failure of one screw leading to the failure of a second, interference with control rod operation, and the expense for reconstitution.
	claims	1. A one body piece molded hunting blind comprising:a one piece molded body having walls and a roof and a base flange defining an open bottom and adapted for use on an outdoor ground surface, said one piece molded body comprising an inside surface and an outside surface:wherein said outside surface of said one piece molded body comprises a light color and said inside surface of said one piece molded body comprises a dark color for use in warm or hot temperature applications, orwherein said outside surface of said one piece molded body comprises a dark color and said inside surface of said one piece molded body comprises a dark color for use in cool or cold temperature applications;a molded door and a plurality of windows disposed in said walls of said one piece molded body;at least one archery door with a taper configured to limit movement, or at least one gun door with a gun rest and an arm rest, disposed in said walls of said one piece hunting blind molded body;at least one archery window having a tapered opening framed by non-rectangular side lines to form a vertical tapering wider at the top to provide archer shooting room and narrow at the bottom to limit visibility from the archer being spotted;a molded shelf;wherein two or more of said one piece molded bodies are configured to be nestably stackable;wherein expanded protruding sections of each of said one piece molded body enhances a stability of a nestably stacked structure; andwherein said archery door and said gun door are configured to open inwardly to minimize detection by wildlife. 2. The molded hunting blind of claim 1, wherein said one piece molded body comprises walls which slant inward towards a roof. 3. The molded hunting blind of claim 2, wherein said walls slant inward towards said roof at an angle of between about 1 degree and about 18 degrees. 4. The molded hunting blind of claim 1, wherein said archery door and said gun door are recessed in a wall of said molded hunting blind. 5. The molded hunting blind of claim 1, wherein said archery door comprises a vertical taper of between about 1 degree and 8 degrees off vertical. 6. The molded hunting blind of claim 1, wherein said one piece body further comprises a plurality of outwardly protruding molded sections configured to house an inwardly open window or door. 7. The molded hunting blind of claim 1, wherein said one piece body further comprises a plurality of outwardly protruding molded sections configured to mechanically strengthen said molded hunting blind. 8. The molded hunting blind of claim 1, wherein said one piece molded body comprises molded brackets configured to accept said arm rest. 9. The molded hunting blind of claim 1, wherein said arm rest is configurable to a right hand or left hand shooter. 10. The molded hunting blind of claim 1, further comprising a molded gun rack. 11. The molded hunting blind of claim 1, wherein a color is died into a plastic of said one piece molded body. 12. The molded hunting blind of claim 1, further comprising handles configured for carrying and positioning said hunting blind. 13. The molded hunting blind of claim 1, further comprising holes in said base flange configured for anchoring said hunting blind. 14. The molded hunting blind of claim 1, wherein said one piece molded body is seamless. 15. The molded hunting blind of claim 1, wherein two or more of said one piece molded bodies are configured to be nestably stackable such that the added height for each additional nestably stacked hunting blind body is less than about 10% of the height of a single one piece hunting blind body. 16. A process for molding a one piece molded hunting blind comprising the steps of:providing a mold of said one piece molded hunting blind to make a one body piece molded hunting blind comprising: a one piece molded body having walls and a roof and a base flange defining an open bottom and adapted for use on an outdoor ground surface, said one piece molded body comprising an inside surface and an outside surface: wherein said outside surface of said one piece molded body comprises a light color and said inside surface of said one piece molded body comprises a dark color for use in warm or hot temperature applications, or wherein said outside surface of said one piece molded body comprises a dark color and said inside surface of said one piece molded body comprises a dark color for use in cool or cold temperature applications,a molded door and a plurality of windows disposed in said walls of said one piece molded body, at least one archery door with a taper configured to limit movement, or at least one gun door with a gun rest and an arm rest, disposed in said walls of said one piece hunting blind molded body, at least one archery window having a tapered opening framed by non-rectangular side lines to form a vertical tapering wider at the top to provide archer shooting room and narrow at the bottom to limit visibility from the archer being spotted, wherein two or more of said one piece molded bodies are configured to be nestably stackable, a molded shelf, wherein expanded protruding sections of each of said one piece molded body enhances a stability of a nestably stacked structure, andwherein said archery door and said gun door are configured to open inwardly to minimize detection by wildlife;providing a molding material; andmolding a one piece molded body. 17. The process of claim 16, wherein said step of molding comprises molding simultaneously a plurality of hunting blind components using a common mold. 18. The process of claim 16, wherein said step of providing a molding material comprises providing a molding material having a color dyed into at least one side of said molding material. 19. The process of claim 18, wherein said step of providing a molding material comprises providing a molding material comprising a first molding material having a first color for forming an outer surface of said molded hunting blind and a second molding material having a second color for forming an inner surface of said molded hunting blind.
	description	This application is a division of co-pending U.S. patent application Ser. No. 10/969,722 filed Oct. 20, 2004, entitled “Stable and Passive Decay Heat Removal System for Liquid Metal Reactor”, which is incorporated by reference herein in its entirety. 1. Field of the Invention The present invention relates to a decay heat removal system of a liquid metal reactor, and introduces a new heat exchange system which integrates a decay heat removal heat exchanger or decay heat exchanger (DHX) and an intermediate heat exchanger (IHX). The new heat exchange system makes it possible for effective decay heat removal to start immediately after an occurrence of an accident while maintaining the complete passivity of the decay heat removal operation. By this invention, passive, proper and stable cooling of the nuclear core can be achieved from the initial stage of an accident. 2. Description of Related Art Liquid Metal Reactor A liquid metal reactor (LMR) generates heat using fast neutrons from nuclear fission, and simultaneously converts a non-fissile material U238 into a fissile material Pu239, thereby serving as a breeding reactor by producing more fissile material than the fuel it consumes. Further, the liquid metal reactor is a reactor which can burn radioactive nuclides produced from other type reactors such as water-cooled reactors, and thus can reduce substantially the storage load of high level radioactive wastes generated from other type reactors. The above liquid metal reactors are divided into loop type reactors and pool type reactors. The loop type reactor has a structure such that heat transfer devices of its primary heat transport system are installed outside a reactor vessel, and is advantageous in that the heat transfer devices are easily maintained and repaired and the reactor vessel has a simple structure. On the other hand, the pool type reactor has a structure such that its primary heat transport system including the equipment such as intermediate heat exchangers (IHXs) and pumps are installed in a reactor vessel, and is advantageous in that the leakage of the coolant due to the breakage of a pipeline of the primary system is prevented and a large amount of the coolant is contained in the primary system, thus having a high thermal inertia that makes the system transient speed slow and provides a long grace time in an accident. The liquid metal reactor uses liquid metal as coolant, and preferably uses sodium (Na) having an excellent heat removal capacity as coolant. Decay Heat Removal Type Conventional liquid metal reactors use various types of decay heat removal systems for removing decay heat from the nuclear core in an accident. Hereinafter, a pool type reactor will be exemplarily described. FIG. 1 is a longitudinal-sectional view of a conventional active decay heat removal system. In FIG. 1, a nuclear core 11 installed in a reactor 10 heats sodium (Na) 17 and feeds the heated sodium 17 into a hot pool 18, which is positioned in the upper part of the reactor 10. The reactor includes conventional pumps 12 for circulating the liquid sodium. The sodium 17 in the hot pool 18 transfers its heat to intermediate heat exchangers (IHXs) 13, thus being cooled. The cooled sodium 17 is fed into the cold pool 19, which is positioned in the lower part of the reactor 10, and again enters the core 11. The IHXs 13 transfer heat thereof to a steam generation system (not shown), and the steam generation system generates steam, and then generates electricity. A decay heat exchanger 14 is installed separately from the IHXs 13 in the hot pool 18 of the reactor 10, and a valve 15 is installed in the pipeline connected to the decay heat exchanger 14. The valve 15 serves to prevent heat loss to the outside through the decay heat exchanger 14 when the reactor 10 operates normally. That is, the valve 15 is closed when the reactor 10 operates normally, and is opened in an accident. In the active decay heat removal system shown in FIG. 1, the switch valve 15 installed in the pipeline connected to the decay heat exchanger 14 needs to be opened in an accident in order to activate heat exchange with the external atmosphere. It means that an active decay heat removal system has weak safety features of requiring the operation of active devices such as a motor and valve 15 and also the supply of electric power from the outside for the operation of the valve 15. Accordingly, instead of the above active decay heat removal system, there is required a passive decay heat removal system, in which removal of decay heat is automatically activated without relying on active devices. FIG. 2 illustrates a conventional passive decay heat removal system. The structure of the passive decay heat removal system of FIG. 2 is the same as that of the active decay heat removal system of FIG. 1 in that a nuclear core 21, which is installed in a reactor 20, heats sodium (Na) 27 and feeds via pumps 22 the heated sodium 27 into a hot pool 28, which is positioned in the upper part of the reactor 20, and the sodium (Na) is cooled by exchanging heat in IHXs 23. In an accident, the normal heat transfer path of the core-IHX-steam generation system is not credited and the sodium in the reactor is heated since the normal heat transfer path is no longer available, and the sodium expands. Consequently, the sodium level X1 in the hot pool 28 rises, and the sodium in the reactor 20 flows over the overflow slot 30. The overflowed sodium 27 directly contacts the wall 31 of a reactor vessel 30, thus transferring its heat to the wall 31 of the reactor vessel 30. The heat transferred to the wall 31 of the reactor vessel 30 is transferred to the air route 26 outside the reactor vessel 30 by radiation and convection heat transfer, and is then transferred to the air flowing in the air route 26 divided by an air separator 24. The air, to which the heat is transferred, continuously flows out to the atmosphere by virtue of the difference in its density along its path, that is, by natural convection. Cold external air is introduced into the reactor vessel 30 through the air path 26. The arrow 25 in the air path 26 represents the flow path of the air. The above-described passive decay heat removal system is operated completely by the natural phenomena without relying on any operator action or any active device operation at an accident, thus being advantageous in that the reliability of the system operation is very high. However, it takes several hours for the sodium to overflow, that is, it takes several hours for the decay heat removal system to become fully functional and be able to remove the decay heat properly. During this period of time before the system becomes functional, proper heat removal from the reactor pool is not made and it is difficult for the natural circulation flow head to be built up. The flow head is the driving force of the natural circulation in the pool which cools the core. Consequently, the core cooling capability becomes low and the temperature of the nuclear fuel in the core can rise excessively high. Summarizing the description, in a conventional passive decay heat removal system, the volume of the fluid in the reactor needs to be expanded substantially for the system to be able to remove decay heat properly, and the expansion of the fluid volume requires time and a rise of the pool temperature, and this feature results in weak safety features that the core cooling capability is not certain during the time period of the volume expansion and the temperature in the reactor may become unnecessarily high. Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a decay heat removal system which can passively and effectively remove the decay heat immediately after the initiation of an accident without relying on any external support such as an operator action or power supply. To achieve the object, the system is designed so that the natural circulation flow head can be properly built and maintained during an accident from the moment immediately after an accident. According to an aspect of the present invention, the above and other objects of the present invention can be accomplished by the provision of a decay heat removal system for a liquid metal reactor comprising: a reactor vessel including a hot pool for containing a high-temperature fluid discharged from a reactor core and a cold pool which is separated from the hot pool by a partition and contains a low-temperature fluid; an intermediate heat exchanger (IHX) transferring heat from the hot pool to an external steam generation system and positioned in the hot pool, the IHX having a bottom portion connected to the cold pool and discharging the fluid from the hot pool into the cold pool; a decay heat exchanger (DHX) separated form the IHX by a designated distance for transferring reactor core decay heat to the external air; a cylinder surrounding the IHX and the DHX, and having an opened top portion protruding out of the level of the fluid in the hot pool, a bottom portion connected to the cold pool and a guide pipe for allowing the passage of the fluid from the hot pool into the IHX; and a pump for pumping the fluid from the cold pool to the reactor core, whereby the level of the fluid in the cylinder is maintained lower than the level of the fluid in the hot pool during its operation. According to another aspect of the present invention, there is provided a modified decay heat removal system for a liquid metal reactor comprising: a reactor vessel including a hot pool for containing a high-temperature fluid discharged from a reactor core and a cold pool which is separated from the hot pool by a partition and contains a low-temperature fluid; an intermediate heat exchanger (IHX) transferring heat from the hot pool to an external steam generation system and positioned in the hot pool, the IHX having a bottom portion connected to the cold pool and discharging the fluid from the hot pool into the cold pool; a decay heat exchanger (DHX) separated from the IHX by a designated distance for transferring reactor core decay heat to the external air; a cylinder surrounding the IHX and the DHX, and having an opened top portion protruding out of the level of the fluid in the hot pool, a bottom portion connected to the cold pool and a guide pipe for allowing the passage of the fluid from the hot pool into the IHX; a switch valve installed on the outer wall of the guide pipe in the cylinder and having a buoy floatable on the fluid by buoyancy to switch the flow path from the guide pipe into the cylinder; and a pump for pumping the fluid from the cold pool to the reactor core, whereby the level of the fluid in the cylinder is maintained lower than the level of the fluid in the hot pool during its operation. Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. Hereinafter, although the following discussion will present a decay heat removal system for a pool type reactor, this may be also applied to a loop type reactor (through modification more or less or even omission of an element). Structure of Decay Heat Removal System FIG. 3 is a longitudinal-sectional view of a decay heat removal system for a pool type reactor in accordance with the first embodiment of the present invention; FIG. 4 is a perspective view illustrating the installation of an intermediate heat exchanger (IHX), a decay heat exchanger (DHX) and a cylinder; FIG. 5 is a cross-sectional view taken along the line A-A of FIG. 4; and FIG. 6 is a cross-sectional view taken along the line B-B of FIG. 4. A pool type reactor 50 has intermediate heat exchangers (IHXs) 70 and pumps 53 installed in a reactor vessel 51, which is filled with coolant. As shown in FIG. 3, a hot pool 56 is formed in the reactor vessel 51 of the pool type reactor 50 to contain a hot fluid discharged from a reactor core 52. Further, a cold pool 55 is divided from the hot pool 55 by a partition 54 to contain cooled fluid formed from the hot fluid in the hot pool 55 by heat transfer. When the heat generated by nuclear fission in the reactor core 52 is transferred to the fluid in the reactor core 52, the heated fluid moves to the hot pool 56 and into the IHXs 70 positioned in the hot pool 56 transferring heat to operating fluid in the IHXs 70. The IHXs 70 serve to transfer the heat of the hot pool fluid to the intermediate heat transport system (IHTS) (not shown). It means that each of the IHXs 70 is also a part of an intermediate heat transport system (IHTS) that includes a steam generator, a pipeline and a pump, which are positioned outside the reactor vessel 51. The coolant filling the hot pool 56 and the cold pool 55 of the reactor vessel 51 is made of sodium (Na) having an excellent heat removing capacity. The IHX 70 has an opening at the bottom communicating with the cold pool 55 so that the IHX 70 discharges the fluid from the hot pool 56 into the cold pool 55 while exchanging heat with the fluid flowing inside the heat transfer tubes 71. That is, as shown in FIG. 4, the fluid from the hot pool 56 is flown along outer surfaces of heat transfer tubes 71 of the IHX 70 to perform heat transfer through convection. Then, the fluid cooled by the heat transfer is discharged into the cold pool through the bottom opening of the IHX 70. As shown in FIGS. 3 and 4, the decay heat exchanger (DHX) 80 is installed around the IHX 70. That is, as shown in FIGS. 3 and 4, the DHX 80 has heat transfer tubes that are coiled around the IHX 70, spaced at a designated distance from the IHX 70. The DHX 80 consists of the cylinder, heat transfer tubes and the outer wall of the IHX 70 and comes to have the shape of an annular cylinder. The decay heat removal system includes the DHX 80, an external heat exchanger, piping connecting the DHX to the external heat exchanger, in which only the decay heat removal exchanger 80 is installed inside the reactor vessel 51. The external heat exchanger finally discharges the transferred core decay heat to the atmosphere. As in the reactor 50, sodium (Na) is used as operating fluid contained within flow channels of the external heat exchanger and the DHX since it has an excellent heat conductivity. The external heat exchanger installed outside the reactor is located at a higher level than the DHX in order to generate natural convection and can be operated without using a pump. The heat transfer tubes of the DHX 80 are arranged adjacent to the IHX 70. The IHX 70 and the heat transfer tubes of the DHX 80 are primarily separated from the fluid in the hot pool 56 by the cylinder 61. The cylinder 61 surrounds the IHX 70 and the DHX 80. The top portion of the cylinder 61 is open and protrudes from the upper surface of the level X1 of the fluid in the hot pool 56. Further, the bottom portion of the cylinder 61 extends to the cold pool 55. As shown in FIG. 4, the cylinder 61 has an overall cylindrical shape. The IHX 70 and the heat transfer tubes of the DHX 80 are arranged inside the cylinder 61, and a guide pipe 63 is connected to the IHX 70 so that the fluid can flow from the hot pool 56 into the IHX 70. As shown in FIG. 4, the guide pipe 63 has a cylindrical tubular shape, and is so designed that the fluid flows only into the IHX 70 through the pipe 63. The bottom portion of the cylinder 61 is connected to the cold pool 55 through the peripheral holes 62 so that the fluid can flow between the cylinder 61 and the cold pool 55. That is, the bottom portion of the cylinder 61 has a central through hole 72 formed in the center thereof, to which the lower end of the IHX 70 is installed. The IHX, the heat transfer tubes of the DHX and the cylinder are constituted into one unit of the heat exchanger system, and a plurality of such heat exchanger systems are arranged in the reactor vessel. Pumps 53 are installed in the cold pool 55 of the reactor vessel 51 to circulate the fluid from the cold pool 55 into the reactor core 52. While the pumps 53 pump the fluid from the cold pool 55 into the reactor core 52 during normal operation, the fluid flow automatically maintains the level X2 of the fluid in the cylinders 61 lower than the level X1 of the fluid in the hot pool 56 and prevents undesirable heat loss through DHX during normal reactor operation. This feature will be explained later in detail. FIG. 11 is a schematic view illustrating the principle of forming different levels of the fluid in the cylinder 61 and the hot pool 55 of the present invention during the operation of the pump. The following discussion explains the vertical pressure distribution between a point □ and a free surface, in which the point □ is positioned at the bottom portion of the annular space in which the heat transfer tubes of the DHX 80 are arranged, as well as the bottom portion of the IHX 70. The pressure at the point □ can be described by Equations 1 and 2 below:P2a=P1+ρgΔHa−(ρva2)/2 Equation 1, andP2b=P3+ρgΔHb−(ρvb2)/2 Equation 2, wherein P2a is obtained by the integral path from the point □ on the hot pool free surface to the point □ along the IHX path, and P2b is obtained by an integral path from the point □ on the free surface to the point □ along the annular space path, in which the heat transfer tubes of the DHX 80 therein are arranged. When the pump 53 is operated, the velocity va of the fluid flowing in the IHX is considerably high, but the velocity vb of the fluid flowing in the space, in which the heat transfer tube of the DHX 80 therein is arranged, is practically zero. Accordingly, Equation 2 above is expressed as Equation 3 below:P2b=P3+ρgΔHb Equation 3. Since P2a and P2b denote the pressure at the same point, they need to be the same, and thus are expressed as Equation 4 below:P1+ρgΔHa−(ρva2)/2=P3+ρgΔHb Equation 4. Since the pressures at the point □ and the point □ are pressures on the free surface exposed to the gas inside the reactor, P1=P3 and thus Equation 5 below is obtained:ΔHb=ΔHa−(va2)/2g Equation 5. When the pump 53 is operated, the relation of ΔHa □ ΔHb is obtained due to the velocity of the fluid. Accordingly, the fluid level X2 in the cylinder becomes much lower than the fluid level X1 in the hot pool. However, when the pumps 53 are not operated such as during an accident, the velocity of the fluid flowing in the IHX 70 reaches approximately zero, and thus ΔHa and ΔHb become nearly the same (ΔHb □ ΔHa). This means that the fluid in the cylinder 61 rises to the level X1 of the fluid in the hot pool when the pump 53 is stopped. Accordingly, when the pump 53 is operated, during normal reactor operation, the level X2 of the fluid in the cylinder 61 is maintained much lower than the level X1 of the fluid in the hot pool 56 so that the heat transfer tubes of the DHX 80 do not contact the fluid in the reactor 50. When the pump 53 is stopped, the level X2 of the fluid in the cylinder 61 rises to the level X1 of the fluid in the hot pool 56 so that the heat transfer tubes of the DHX 80 contact the fluid in the reactor 50. Operation of Decay Heat Removal System As described above, the decay heat removal system of the present invention comprises the IHXs installed in the reactor vessel and the DHXs surrounding the IHXs. Both of the IHXs and DHXs are arranged within the same cylinders. Here, the operation of the decay heat removal system of the present invention will be described in detail with reference to FIGS. 7a and 7b. FIGS. 7a and 7b illustrate the operation of the decay heat removal system of FIG. 3, and more particularly, FIG. 7a illustrates the decay heat removal system during normal operation in a pool type reactor, and FIG. 7b illustrates the decay heat removal system during an accident in a pool type reactor. It is necessary to design the DHX 80 so that the heat transfer rate by the DHX during normal reactor operation, that is, the heat loss during normal operation is minimal but is sufficiently large to achieve sufficient reactor core cooling during an accident. For this purpose, the DHX 80 is placed within the cylinder 61 isolating its heat transfer tubes from the fluid in the hot pool 56 and also its heat transfer tubes are separated from the IHX 70 by a designated distance in a radial direction in order to avoid direct contact with the IHX 70. In a vertical direction, the DHX 80 is isolated from the fluid in the reactor 50 based upon the different fluid levels formed by the operation of the pump 53 as above. That is, as shown in FIG. 7a, the level X2 of the fluid in the cylinder 61 from the cold pool 55 is lower than the level X1 of the fluid in the hot pool 56 during normal reactor operation. Accordingly, the heat transfer tubes of the DHX 80 are placed in gas filled in the reactor 50 without contacting the fluid in the cold pool. In this case, the cylinder 61 is filled with inert gas such as helium, nitrogen, argon and etc. The inert gas prevents direct contact of the fluid in the pool such as sodium with air to avoid chemical reaction. Also, the inert gas can achieve thermal shielding since it has poor heat transfer characteristics. In normal operation of the reactor 50, the fluid is fed from the hot pool 56 into the IHX 70 through the guide pipe 63, discharges its heat in the IHX 70, and is then fed to the cold pool 55. Because the DHX 80 does not contact the fluid in the hot pool 56 or in the cold pool 55 as shown in FIG. 7a, the heat transfer in the DHX 80 is made only by the very inefficient gas convection or radiation. As a consequence, the entire quantity of the heat transfer made in the DHX 80, that is, the heat loss during normal operation of the reactor 50, becomes negligibly small. In an abnormal state, i.e., in an accident of the reactor 50, the pumps 53 are stopped by a reactor protection system (not shown), and the level X2 of the fluid in the cylinder 61 becomes approximately the same as the level X1 of the fluid in the hot pool 56. It means the cylinder 61 is filled with the fluid from the cold pool 55 and the heat transfer tubes of the DHX 80 come to have direct contact with the fluid of the cold pool 55 so that heat transfer can be effectively made. The fluid level elevation in the cylinder 61 as above is immediately formed when the pump 53 is stopped in an accident. Since the normal heat transfer path of a plant, that is, reactor core—IHX—IHTS—steam generator—condenser—atmosphere is for normal reactor operation, its design is made with much emphasis on plant economics while less emphasis is given to safety. Consequently, the normal heat transfer path is not formally credited for assessing the plant safety at an accident, and a nuclear plant should be able to remove the core decay heat only by the system dedicated for the decay heat removal, such as the decay heat removal system of this invention, without using the normal heat transfer path. That is, it is preferable not to consider decay heat removal through the IHX during the accident, though some of the reactor core decay heat would be extracted by the IHX. In an accident, the decay heat will be removed as follows. When the reactor has an accident, the pumps 53 are stopped by a reactor protection system (not shown). Then, the level of fluid in the annular space of the DHX 80 is raised so that the heat transfer tube of the DHX 80 is submerged into the fluid in the reactor 50. The hot fluid in the hot pool 56 from the reactor core 52 flows into the IHX 70 via natural. Heat of the fluid entered in the IHX 70 is transferred to the fluid filled in the cylinder 61 through the wall of the IHX 70, and then to the heat transfer tubes of the DHX 80. Here, since the fluid is made of liquid metal such as sodium having a high heat transfer coefficient, it can efficiently transfer heat to the DHX 80. The heated fluid inside the heat transfer tubes of the DHX 80 flows to an external heat exchanger (not shown) placed outside the reactor 50, and after being cooled by the air of the external heat exchanger, is circulated again into the DHX 80 inside the reactor 50 by the natural circulation, thereby forming a natural and continuous heat transfer cycle. Also explaining the fluid in the reactor side, after being cooled through the heat exchange with the DHX 80, the fluid flows from the IHX 70 into the cold pool 55, and into the reactor core 52 and then is heated by the decay heat, and then is circulated into the hot pool 56 and the IHX 70. The above fluid circulation has two flow segments, i.e., a high-temperature segment from the reactor core 52 through the hot pool 56 to the DHX 70 and a low-temperature segment from the DHX 70 through the cold pool 55 to the reactor core 52. At the two segments there are definite and stable heating and cooling, respectively, and thereby stable and passive natural convection cooling of the core can be achieved. Also, the initiation of the decay heat removal by the DHX 80 of the present invention is made purely passively without relying on any operator action or external power supply. Further, the decay heat removal system of the present invention performs the decay heat removal function immediately after the reactor has an accident. In the conventional decay heat removal system shown in FIG. 2, the heat transfer for removing decay heat is performed only after the temperature rises to the extent that the fluid in the hot pool 28 expands and floods into the cold pool 29 to form a decay heat removal circuit. This requires a long time before initializing the decay heat removal system, and thus has difficulty in immediately coping with an accident. However, in the decay heat removal system of the present invention, the level of the fluid in the cylinder rises immediately after the stoppage of the pumps, and contacts the DHX, thereby forming an efficient decay heat removal circuit. Accordingly, the decay heat removal system of the present invention immediately copes with an accident of the reactor. In addition to the immediate removal of the decay heat in the reactor, the decay heat removal system of the present invention further has several advantages, as follows. 1) Stable Cooling of Reactor Core In the conventional system as described above, the decay heat removal is not effectively made until the fluid temperature increases to the extent of expansion so that the flow over the overflow slot is formed. Accordingly, a cooling source is not clear during that period of the expansion, and the formation of the natural convection head required for cooling the reactor core is unreliable. Thereby, the local temperature in the reactor core can exceed a limit value even though the mean temperature of the fluid in the reactor remains under the limit value. However, the decay heat removal system of the present invention performs decay heat removal immediately after the accident of the reactor and presents a cooling source clear, thereby reliably forming a route for natural convection through the reactor core. Accordingly, the decay heat removal system of the present invention overcomes the unreliability of the convention system in order to stably cool the reactor core. 2) Prevention of Exposure of Internal Structure of Reactor to High Temperature In the conventional system, the decay heat removal is performed only after the fluid in the reactor is heated to a designated temperature or more. However, the decay heat removal system of the present invention operates immediately after the occurrence of an accident without waiting for the fluid temperature increase to a designated value or more. This can limit the maximum temperature of an internal structure of the reactor remarkably below a limit temperature as well as remarkably shorten the exposure time of the internal structure to high temperature and reduce heat load to the internal structure, thereby improving the mechanical integrity of the internal structure. In an accident, the fluid passing through the IHX in the conventional system does not remove the decay heat from the reactor, but merely connects the hot pool with the cold pool. This reduces the temperature difference between a high-temperature region and a low-temperature region in the reactor, making it difficult to build up a fluid head for natural convection required to cool the reactor core in an accident and deteriorating a cooling capacity. However, the present invention allows the fluid passing through the IHX to be cooled also via the heat transfer to the DHX. The reactor protection system is designed to automatically trip the pumps when there is an accident to prevent the heat input from the pumps to the system. In the case of an extremely unlikely event of multiple failures, in which the reactor protection system is not enabled either, the decay heat removal system of the present invention operates similar to the conventional decay heat removal system. That is, when the fluid in the hot pool 56 of the reactor 50 expands according to temperature growth to the extent of flowing over the top of the cylinder 61, the hot fluid from the hot pool 56 directly contacts the heat transfer tube of the DHX 80, thereby to efficiently remove decay heat. In this case, since the pumps 53 are operated, the fluid is fed at a sufficient flow rate to the reactor core 52, thereby to prevent the above-described problem in that the reactor core is of locally overheated. That is, the decay heat removal system of the present invention stably cools the reactor core 52 in any type of accidents including the exceptional multiple failures. The decay heat removal system in accordance with the first embodiment of the present invention has been described. Hereinafter, a decay heat removal system in accordance with a second embodiment of the present invention will be described in detail. In addition to the structure of the decay heat removal system of the first embodiment, the decay heat removal system of the second embodiment further comprises a switch valve, which is operated based on the action of the pumps, in order to enhance the cooling function. Operation of Switch Valve of Decay Heat Removal System FIG. 8 is a perspective view of a decay heat removal system for a pool type reactor in accordance with the second embodiment of the present invention, FIG. 9 is a cross-sectional view of the switch valve of FIG. 8 during normal operation, and FIG. 10 is a cross-sectional view of the switch valve of FIG. 8 in an accident. The decay heat removal system of the second embodiment of the present invention comprises a switch valve for allowing the fluid in the hot pool to circulate directly into the cylinder. The reactor vessel, the IHX 70, the DHX 80 and the pump of the decay heat removal system in this embodiment have the same structures as those in the first embodiment. The components in this embodiment shown in FIG. 8, which are substantially the same as those in the first embodiment, are denoted by the same reference numerals even though they are depicted in different drawings. A switch valve 91 is installed on the outer wall of the guide pipe 64 in the cylinder 61. A through hole 94 is formed through the guide pipe 64 of the cylinder 61 so that the fluid flowing from the hot pool to the IHX 70 is introduced into the cylinder 61 therethrough. When the switch valve 91 is opened from the through hole 94, the fluid in the hot pool flows through the through hole 94 into the cylinder 61, in which the DHX 80 is installed, thereby forming a flow path from the hot pool to the cylinder 61. Here, the through hole 94 is formed in an inclined surface of an inlet 92 protruded from the outer circumference of the cylinder 61. The inlet 92 protrudes from the guide pipe 64 such that the lower surface of the inlet 92 has the longest length and the upper surface of the inlet 92 has the shortest length, thereby obtaining the inclined surface, which is closed by the switch valve 91. The above inclination of the inclined surface of the inlet 92 allows the switch valve 91 to steadily close the inlet 92 by means of the weight load of the valve and the buoy 93 which is described below. The switch valve 91 is hinged to the upper part of the inlet 92. A buoy 93 is attached to the switch valve 91 to be floated on the fluid by buoyancy. The buoy 93 is designed heavy enough to withstand the pressure of the fluid in the guide pipe 64 so that the inlet 92 is closed by the switch valve 91 during normal operation. That is, as shown in FIG. 9, the force for closing the switch valve 91 by means of a moment of the buoy 93 is larger than the force for opening the switch valve 91 by means of the pressure of the fluid acting inside the switch valve 91. This prevents the fluid from flowing into the decay heat removal system in normal operation. Also, the switch valve 91 is designed to be automatically opened by the buoyancy acting on the buoy 93 as shown in FIG. 10 when the cylinder 61 is filled with the fluid in an accident of the reactor. The buoy 93 has a volume sufficient to automatically open the switch valve 91 by the buoyancy. That is, the buoy 93 has a structure of a balloon containing a weight, with a weight sufficient to maintain the closed position of the switch valve 91 against the pressure of the fluid in the guide pipe 64 if surrounded by gas, and a volume sufficient to completely open the switch valve 91 by means of the buoyancy if floated on the fluid in the cylinder 61. Here, the volume of the buoy 93 sufficient to completely open the switch valve 91 means that the mean density of the buoy 93 is much lower than the density of the fluid. Operation of Switch Valve of Decay Heat Removal System In the decay heat removal system of this embodiment of the present invention, the switch valve 91 is closed when the reactor operates normally. When the reactor operates normally, the level X2 of the fluid in the cylinder 61 is much lower than the level X1 of the fluid in the hot pool 56 as shown in FIG. 7a, and the heat transfer tubes of the DHX 80 lose contact with the fluid of the pool but are exposed to gas. Accordingly, as described above, the efficient heat transfer in the DHX cannot be made and the heat loss during normal operation becomes negligible. This means that the switch valve 91 is closed as shown in FIG. 9. In gas, the weight of the buoy 93 generates a clockwise moment which closes the switch valve 91 larger than the counterclockwise moment from the pressure of the fluid in the guide pipe 64 which opens the switch valve 91, in order to maintain the closed position of the switch valve 91. When the reactor has an accident, the level X2 of the fluid in the cylinder 61 rises up to the level X1 of the fluid in the hot pool as shown in FIG. 7b. This means that the inside of the cylinder 61 is filled with the fluid and the switch valve 91 is affected by the fluid. When the buoy 93 of the switch valve 91 rises by the buoyancy of the fluid, the switch valve 91 is opened as shown in FIG. 10 so that the fluid flows from the hot pool into the cylinder 61. When the fluid in the hot pool flows into the cylinder 61 through the switch valve 91, a flow path from the hot pool into the cold pool is formed, and the fluid from the hot pool directly contacts the heat transfer tubes of the DHX 80, thereby forming an efficient heat transfer path for removing decay heat. Such a heat transfer path is used together in parallel with the heat transfer path between the fluid passing through the IHX and the heat transfer tubes of the DHX as described in the above first embodiment. Accordingly, the decay heat removal system of the second embodiment can have enhanced decay heat removal capability while maintaining those advantages of the decay heat removal system of the first embodiment. As is apparent from the above description, the present invention provides a decay heat removal system which works on the natural convection and completely passively without relying on any operator action or external support in an accident. Further, the decay heat removal system of the present invention is designed to operate immediately after an accident without losing the complete passivity by utilizing the natural level rise at the trip of the pump. Accordingly, the decay heat removal system of the present invention eliminates the uncertainty in cooling the reactor core at an early stage of an accident, thus improving the plant safety, and shortens the time of an internal structure of the reactor exposed to high temperature and lowers the maximum temperature of the internal structure, thus improving the mechanical integrity of the internal structure. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
044434022	claims	1. Method of detecting defective fuel elements in a nuclear reactor fuel assembly constituted by a bundle of elongate fuel rods disposed parallel to each other in the longitudinal direction of said assembly, said method comprising the steps of: (a) keeping said assembly entirely immersed in a protective liquid such as water; (b) emitting ultrasonic waves at one of the ends of each of said fuel rods successively and propagating said waves over the entire length of said fuel rod; (c) moving an ultrasonic sensor near the fuel rod in which said ultrasonic waves are propagated in its longitudinal direction, during propagation of the waves in said rod; (d) determining the presence of a defect in said rod by picking up, by means of said sensor, the ultrasonic waves eventually scattered by the defect in said rod into said protective liquid; (e) determining, when a defect is present, the variations of the amplitude of the signal picked up according to the position of said sensor in the longitudinal direction of said rod; and (f) determining the position of said sensor for which the amplitude of said signal is maximum corresponding to the position of the defect along the length of said rod. (a) at least one ultrasonic emitter connected to a generator and to an addressing means allowing ultrasonic waves to be sent successively into each of said rods and allowing each rod subjected to said ultrasonic waves to be determined; (b) an ultrasonic sensor associated with means for its displacement in the longitudinal direction of said assembly; (c) means for measuring the longitudinal position of said sensor; (d) means for measuring the maximum amplitude of the signal corresponding to the waves scattered and detected by said sensor; and (e) means for determining the variations in said maximum amplitude as a function of the position of said sensor in the longitudinal direction of said assembly and for determining the position of said sensor corresponding to the maximum of the curve representing said variations. 2. Detection method according to claim 1, wherein said ultrasonic sensor (25) is moved outside said assembly (20). 3. Detection method according to claim 1, wherein said ultrasonic sensor (25) is moved inside said assembly in a guide tube thereof. 4. Detection method according to any one of claims 1, 2 or 3, comprising the step of filtering said signal as a function of the position of said sensor in the longitudinal direction to discriminate the waves eventually scattered by the defect from an interference signal due to interference waves propagated in said protective liquid and different from scattered waves, the time of propagation of said interference waves to said sensor being longer than the time of propagation of scattered waves. 5. Apparatus for detecting defective fuel elements in a nuclear reactor fuel assembly having fuel rods, comprising: 6. Apparatus according to claim 5, comprising means for discriminating the signal corresponding to the scattered waves constituted by a filter (30) which takes into account the displacement in the time scale of the signal from the scattered waves as a function of the position of said sensor (25) by taking account of the effect of the position of said sensor (25) on the displacement in time of the signal corresponding to the scattered waves. 7. Apparatus according to claim 5 or 6, wherein said sensor (25) is movable in a direction perpendicular to the longitudinal direction of said assembly (20). 8. Apparatus according to claim 5 or 6, wherein said sensor (25) comprises unit detection elements assembled in a group constituting a bar arranged in a direction perpendicular to the longitudinal direction of said assembly (20) and having a length approaching that of the transverse section of said assembly (20).
043081002	abstract	Apparatus for charging a nuclear reactor disposed at the bottom of a pool. The reactor is constituted by a plurality of tiers of combustible assemblies having different stages of enrichment, each assembly having combustible rods and an auxiliary cluster associated with the particular tier of the assembly. The apparatus comprises a rolling bridge supported for movement in a plane above the pool, and carrying a turnable platform which supports a plurality of vertical telescopic manipulation arms arranged in angular spaced relation thereon. Each arm carries a respective grappling unit for respectively engaging a complete combustible assembly or at least one type of auxiliary cluster. The auxiliary clusters may include control clusters, sealing clusters and poison consumable clusters. In a particular embodiment three manipulation arms are provided one with a grappling unit to engage a complete combustible assembly a second with a grappling unit to engage a control cluster, and a third with a unit to engage a sealing cluster or a poison consumable cluster. The turnable platform has as many angular stop positions as there are telescopic arms and it has an active position at which each telescopic arm is selectively fixed in operative position. At the other angular positions, the arms are inactive. At the active position, each of the telescopic arms can be extended and retracted.
	summary
	claims	1. A scintillator panel comprising:a substrate made of an organic material;a barrier layer formed on the substrate and including thallium iodide as a main component; anda scintillator layer formed on the barrier layer and constituted of a plurality of columnar crystals including cesium iodide with thallium added thereto as a main component. 2. The scintillator panel according to claim 1,wherein the organic material is polyethylene terephthalate. 3. The scintillator panel according to claim 1wherein the organic material is one selected from polyethylene naphthalate, polyimide, and polyetheretherketone. 4. A radiation detector comprising:a scintillator panel having a substrate made of an organic material, a barrier layer formed on the substrate and including thallium iodide as a main component, and a scintillator layer formed on the barrier layer and constituted of a plurality of columnar crystals including cesium iodide with thallium added thereto as a main component; anda sensor substrate including a photo-detection surface provided with a photoelectric conversion element receiving light generated in the scintillator panel,wherein the photo-detection surface of the sensor substrate faces the scintillator layer. 5. A radiation detector comprising:a substrate made of an organic material;a barrier layer formed on the substrate and including thallium iodide as a main component; anda scintillator layer formed on the barrier layer and constituted of a plurality of columnar crystals including cesium iodide with thallium added thereto as a main component,wherein the substrate has a photo-detection surface provided with a photoelectric conversion element receiving light generated in the scintillator layer.
063058421	abstract	The invention relates to an X-ray examination apparatus which includes an X-ray source and a diaphragm unit which is connected to the X-ray source and is provided with shutters for limiting a radiation cone beam emanating from the focal spot of the X-ray source, and also includes a light source for generating a light cone beam which traverses the shutters via a mirror. When the dimensions of the light-emitting parts of the light source are significantly larger than the focal spot, the irradiation field irradiated by the radiation cone beam is smaller than the illuminated field illuminated by the light cone beam. In order to match the irradiation field with the illuminated field, the shutters are provided with correction shutters which are transparent to X-rays but impervious to light and limit the light cone beam.
051715163	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, the reactor core monitoring system according to the invention is shown which includes core 30 made up of a plurality of fuel cells, each fuel cell containing a plurality of fuel rods. FIG. 2 shows nine adjacent fuel segments A.sub.O -A.sub.g. The monitoring system also includes a monitoring and control means 31 which controls the operation of the reactor core 30 and monitors core state parameters such as the core flux and positions of the control rods, etc., of the reactor core 30. Monitor and control means 31 also includes a controller, which may include a microprocessor, and apparatus for moving the control rods 25 to required positions in the core. A detailed description of the controller and moving apparatus is omitted for brevity as they are believed to be well understood by those skilled in the art. In FIG. 3, a fuel segment 21 is shown having fuel rods 23 made of boiling water reactor fuel and arranged in 8 rows and 8 columns in a channel box 22 which is provided with two water rods 24 at its center. A control rod 25 is located at one corner of fuel segment A.sub.O. A typical fuel assembly (not shown) is made up of a number of fuel segments, for example 24, arranged one on top of the other. A fuel assembly is typically 5-6 meters long. The reactor contains a plurality of the fuel assemblies, for example 64, as will be understood by one skilled in the art. FIG. 4 illustrates a section of the reactor 30 with a plurality of fuel segments 21, each group of four having a control rod 25 disposed at a central position of the group, as is conventional in the art. Also shown in FIG. 4 is monitor 26, which is typically in the form of a rod. Monitor 26 provides information of the operation of the reactor core 30 to monitoring means 31. It is be understood that FIG. 4 is provided for illustration purposes only, and the dimensions and positions of the fuel segments 21, control rods 25, and monitor 26 do not necessarily reflect the actual dimensions positions, and arrangement in a reactor core. A memory device 33 stores the nuclear constants in an infinite lattice, the local power distribution in an infinite lattice, and the R factor in an infinite lattice, etc., which were previously found by solving the heterogeneous neutron diffusion equation in an infinite lattice consisting only of the fuel segment in question, of the fuel segments arranged in the core 30 of the atomic reactor. This heterogeneous neutron diffusion equation in an infinite lattice is that typically used in the design calculations of a fuel assembly. Several memory devices are capable of storing the various required data, as will be apparent to one skilled in the art. In this embodiment, a single memory such as a read-only memory is used, but a separate memory may be used for each of the nuclear constants, local power distribution and R factor. The nuclear constants in the infinite lattice are stored in nuclear constant storage area 33A of memory device 33. The local power distribution in the infinite lattice is stored in local power distribution storage area 33B of memory device 33. The R factor in the infinite lattice is stored in R factor storage area 33C of memory device 33. The nuclear constants in infinite lattice stored in nuclear constant storage area 33A include the average spectral index F of a fuel segment in infinite lattice, the average macroscopic removal area S of thermal neutrons in a fuel segment, and the average diffusion coefficient D in a fuel segment. The local power distribution obtained by solving the heterogeneous neutron diffusion equation of a fuel segment in infinite lattice and the R factor for critical quality calculated from this are stored in storage areas 33B and 33C, respectively, as functions of the void fraction and exposure in tabular form or by fitting. In some cases, the local power distribution in infinite lattice which is stored in storage area 33B may be the local power of all the fuel rods in each of the fuel segments. Usually, however, the position, exposure, and void fraction points, etc., of several representative fuel rods or large local power in infinite lattice found by the fuel assembly design calculation are stored and the largest values of these are taken as the thermally most limiting local power of fuel rods of each of the fuel segments. The various parameters from reactor core monitoring means 31 are input to a core performance determining means 32 which determines the global power distribution of the core 30. The global power distribution, and consequently the channel power distribution, in a BWR core are determined by solving coupled nuclear thermal-hydraulics equations. Next, a core neutron diffusion determining means 34 determines the difference of thermal neutron flux between the thermal neutron flux at the position of a fuel rod and the thermal neutron flux in infinite lattice in a fuel segment under consideration, of the various fuel segments in reactor core 30. This core neutron from nuclear constant storage area 33A and the global power distribution from core performance determining means 32 Of all the fuel segments whose global power distribution obtained by core performance determining means 32 is indicated, a particular fuel segment is selected for consideration. The diffusion equation for thermal neutron flux of a system wherein each of the fuel segments is homogenized is then solved in a two-dimensional region defined in the core and constituted of the fuel segment under consideration and the neighboring fuel segments surrounding it. This diffusion equation is expressed by the following equation (4) by a two-group neutron diffusion model, where the first group is the fast group and the second group is the thermal group. EQU -v.sup.2 .PSI.+K.sup.2 .PSI.=K.sup.2 F.PHI. . . . (4) where .PSI. is the thermal neutron flux PA1 .gradient..sup.2 is the Laplace operator, and EQU K.sup.2 =S/D; . . . (5) PA1 F is the average spectral index of the fuel segment in infinite lattice, PA1 .PHI. is the average fast neutron flux of the fuel segment, PA1 S is the average macroscopic removal area, and PA1 D is the average diffusion coefficient of the fuel segment for thermal neutrons. PA1 .delta.P(x,y)=the change in local power distribution and PA1 .delta.P.sub.av =the average change in local power distribution. and where The spectral index F is defined as the ratio of the thermal neutron flux to the fast neutron flux. In equations (4) and (5), the composition in a fuel segment is assumed to be homogeneous. For the nuclear constants, the fuel segment average values obtained by the design calculation of the fuel assembly in infinite lattice are used. Also, the fast neutron flux .PHI. is assumed to be spatially flat within a fuel segment. F.PHI. on the right-hand side in equation (4) expresses the thermal neutron flux when there is no gradient of the thermal neutrons, i.e., in the case of a homogenized infinite lattice. This is provisionally called the asymptotic thermal neutron flux. Diffusion equation (4) is a partial differential equation and can usually be solved numerically by a finite difference method. An example of such a method is given in: L. A. Hageman; "Numerical Methods and Techniques used in the Two-Dimensional Neutron-Diffusion Program PDQ-5", WAPD-TM-364 (1963). The boundary conditions used are the conditions of outer boundary mirror symmetry of the regions defined within the core and the four-side periodic boundary condition, etc. These boundary conditions do not strictly hold, but, in a narrow region such as is in question, it is justifiable to regard the fast neutron flux as practically uniform and the thermal neutron flux as becoming an asymptotic value at a distance of about 1/2 of one side of a fuel segment, so the neutron flux distribution can be obtained with sufficient accuracy for this purpose by these boundary conditions. In order to shorten the calculation time, diffusion equation (4) can be solved analytically under the approximation of fixed boundary conditions. An example of such a method of solution is disclosed in Early Japanese Patent Publication Sho. 62-106396 "Device for Monitoring Local Power Peaking Coefficient". In this method of solution, in ordinary light water reactor fuel, the effect of adjacent fuel segments on the value of the thermal neutron flux decreases with the distance r from the boundary with the adjacent fuel segment practically in the form exp(-Kr) and becomes a practically negligible magnitude at about 1/2 of the fuel segment width. Using this to specify an approximate boundary condition, the difference between the thermal neutron flux at fuel rod position (x,y) in a fuel segment and the asymptotic thermal neutron flux F.PHI. is given by equation (6). ##EQU1## where, as shown in FIG. 2, A.sub.O indicates the fuel segment under consideration and A.sub.1 to A.sub.4 indicate the four fuel segments adjacently facing this fuel segment A.sub.O in the radial direction. Also in equation (6), ##EQU2## indicates the sum of the variables F.sub.n and r.sub.n (n=1 to 4) for these fuel segments A.sub.1 to A.sub.4, and r.sub.n is the length of a perpendicular dropped from a fuel rod at a position (x,y) in fuel segment A.sub.O under consideration onto the boundary line with the adjacent fuel segment A.sub.n (n=1 to 4). F.sub.O is the average spectral index of the fuel segment under consideration, and F.sub.n is the average spectral index of the respective adjacent fuel segments A.sub.n (n=1 to 4). In equation (6) the effect of the fuel segments A.sub.5 to A.sub.8 that are diagonally adjacent to the fuel segment in question is neglected, but, if greater accuracy is required, an analytic solution can be obtained by the following equation using boundary conditions taking into account the effects of these fuel segments A.sub.5 to A.sub.8. ##EQU3## Here, the subscript m indicates the two respective facing adjacent fuel segments A.sub.m on both sides of fuel segments A.sub.5 to A.sub.8 that are diagonally adjacent fuel segment A.sub.O under consideration. For example, in the case of fuel segment A.sub.5 that is diagonally adjacent fuel segment A.sub.O, the two fuel segments A.sub.1 and A.sub.4 correspond to A.sub.m. .delta.F.sub.n (n=1 to 8) indicates the values of the change from the asymptotic spectrum of the spectrum at points (indicated by solid black circles) on the boundary of fuel segment A.sub.O of FIG. 2. Equation (7) is one type of approximate analytical solution of equation (4), and has the following desirable features. (1) At the center of the fuel segment the thermal neutron flux approaches the asymptotic value. That is, .delta. .PSI. approaches O. (2) At the mid-point of the side of the fuel segment and at the apex, equation (7) satisfies the asymptotic boundary values given by equations (8) and (9). (3) On the line linking the centers of the two fuel segments that are facing and adjacent each other (indicated by a broken line in FIG. 2), the thermal neutron flux approaches the solution of the one-dimensional diffusion equation on this line. It has been confirmed by numerical experiment that the deviation .delta..PSI.(x,y) of the thermal neutron flux at a fuel rod position (x,y) in a fuel segment and the asymptotic thermal neutron flux F.PHI. shows good agreement with the change of the thermal neutron flux distribution from infinite lattice obtained by heterogeneous calculation. Thus the neutron flux deviation .delta..PSI.(x,y) determined by core neutron diffusion determining means 34 is input to a local power distribution determining means 35 that finds the local power distribution within the fuel segment in question. Local power distribution determining means 35 determines the local power distribution within fuel segment A.sub.O in question, using the neutron flux deviation .delta..PSI.(x,y) and local power distribution P.sub..infin. (x,y) in infinite lattice stored in local power distribution storage area 33B. The local power distribution P.sub..infin. in infinite lattice is indicated by the following equation. EQU P.sub..infin. (x,y)=S.sub.fl .PHI..sub..infin. +S.sub.f2 .PSI..sub..infin.. . . (10) where p is normalized such that its average is 1.0. The subscript .infin. indicates the value in infinite lattice. S.sub.fl indicates the first group fission cross-section and S.sub.f2 indicates the second group fission cross-section. The local power distribution in a system that is subject to the effects of adjacent fuel segments is indicated by the following equation: EQU [P.sub.28 (x,y)+P(x,y)]/(1+.delta.P.sub.av) . . . (11) where Since practically all the contributions to the power distribution are produced by the thermal group, from equation (10): EQU .delta.P(x,y)=S.sub.fz .delta..PSI.(x,y)=[P.sub.28 (x,y)/.PSI..sub.28 (x,y) . . . (12) If this is substituted in equation (11) and second-order terms in .delta. are neglected, ##EQU4## Thus, within the two-dimensional region defined within the core and constituted by fuel segment A.sub.O under consideration and the neighboring fuel segments surrounding it, the local power distribution taking into account the effect of adjacent fuel segments is obtained using the thermal neutron flux deviation .delta..PSI.(x,y) and local power distribution P.sub.28 (x,y) in infinite lattice found by a neutron diffusion calculation in a system obtained by homogenizing these respective fuel segments. The local power distribution within the fuel segment A.sub.O under consideration obtained by local power distribution determining means 35 is input to an R factor correction means 36. R factor correction means 36 finds a corrected R factor from the R factor in infinite lattice and the local power distribution in segment A.sub.O under consideration obtained by local power distribution determining means 35. When the local power in infinite lattice for all the fuel rods of fuel sequent A.sub.O under consideration have been stored in local power distribution storage area 33B in infinite lattice, calculation is made, using equation (2), directly from the local power distribution obtained by local power distribution determining means 35. In contrast, if only the local power in infinite lattice of the several most thermally limiting fuel rods in fuel segment A.sub.O is stored, the solution is found approximately using the following equation, using the value R.sub.O of the R factor in infinite lattice that is stored in R factor storage area 33C and the change of local power of the most thermally limiting fuel rods. EQU R=R.sub.O +A(.differential.R/.differential.P.sub.max).delta.P.sub.max . . . (14) P.sub.max is the local power of the fuel rod that is most thermally limiting. The maximum local power peak of fuel segment A.sub.O can also be substituted for P.sub.max. The maximum local power peak is given as the maximum value of the corrected values determined by local power distribution determining means 35, of the local power in infinite lattice of the several most thermally limiting fuel rods that are stored. Also, the coefficient A in equation (14) is a correction coefficient that depends on the position of generation of P.sub.max in the assembly. The thus-obtained corrected R factor is input to a critical power ratio determining means 37. Critical power ratio determining means 37 determines the critical power ratio based on the corrected R factor obtained from R factor correction means 36. The critical power ratio is output to a reactor core status indicator 38 which produces a representation of the status of each of the fuel segments 21 of the reactor core 30. FIG. 5 shows a display of the reactor core status indicator according to the invention in which the various fuel segments may be represented by a group of pixels, and various critical power ratios can be assigned a corresponding color. The display includes a core map of the reactor core on the left hand portion where the channels, i.e. the fuel assemblies are displayed according to the calculated CPR value. In the lower right corner, ranges of CPR are assigned a particular color (shown by shading in FIG. 5). The ten most limiting channels are listed in the upper right portion of the screen along with their corresponding positions in the core map. In the case where the CPR has fallen below a particular range, control rods (shown by a cross symbol) have been inserted to avoid possible burn-out of the fuel rods. Thus, the status of the reactor core can be instantly and continuously provided to an operator, thereby giving warning of any undesirable conditions of any danger of burn-out of the fuel rods. As shown in FIG. 1, the critical power ratio determining means 37 provides data which is fed back to reactor core monitor and control means 31. In the event that the determined CPR falls below a predetermined value, the power of the reactor core must be reduced to avoid a boiling transition. Upon receipt of a signal indicating that the CPR has fallen below a predetermined threshold, the reactor core monitor and control means 31 then carries out insertion of control rods 25 to reduce the power and thereby avoid a boiling transition. The controller of the monitor and control means 31 activates the moving apparatus to position the appropriate control rods 25 at the required positions. The reactor core monitoring method according to the invention will be described in relation to FIG. 6. In step 60, nuclear constants in infinite lattice, a local power distribution in infinite lattice and R factor in infinite lattice are stored. In step 61, the core state parameters of the reactor core are monitored which are used to determine a global power distribution (step 62). Using the global power distribution and the stored nuclear constants, a deviation between the thermal neutron flux in a fuel rod position in the selected fuel segment and a thermal neutron flux in infinite lattice for the selected fuel segment is determined in step 63. In step 64, a local power distribution of the selected fuel segment is determined based on the thermal neutron flux deviation and the stored local power distribution in infinite lattice. A corrected R factor is determined in step 65 based on the stored R factor in infinite lattice and the local power distribution in the selected fuel segment. In step 66, the CPR is determined based upon the corrected R factor. It is determined in step 67 whether the CPR falls below a predetermined threshold. If the CPR falls below the threshold, the positions of the control rods of the reactor core are adjusted to the appropriate positions to avoid a boiling transition (step 67). Next, as an example, the R factors found by the invention will be compared with the R factors found by a monitoring apparatus which uses an infinite lattice and a monitoring apparatus which finds R factors using a two-dimensional diffusion calculation in four fuel segments. FIG. 7 shows a fuel segment arrangement used in two-dimensional calculation in four fuel segments. The fuel segments are numbered A.sub.1, A.sub.2, . . . A.sub.16, beginning from the bottom leftmost segment. The four fuel segments which will now be considered are fuel segments A.sub.6, A.sub.7, A.sub.10 and A.sub.11 disposed in the middle region. The other fuel segments constitute a boundary layer. FIG. 8 shows the arrangement of fuel types of the respective fuel segments in the fuel segment arrangement shown in FIG. 7. It is assumed that fuel type I is a low enriched fuel of average enrichment 1.3 w/o, fuel type II is a medium enriched fuel of average enrichment 2.4 w/o, and fuel type III is a high enriched fuel of average enrichment 3.3 w/o. All the fuel types have a fuel rod enrichment distribution. It will also be assumed that fuel type II and fuel type III include gadolinia-containing fuel rods. It will further be assumed that the control rod is not inserted. FIG. 9 is a plot showing a comparison of the results of an R-factor determination according to this invention, a two-dimensional diffusion calculation in four fuel segments, and a calculation in infinite lattice, for low enrichment fuel type I, medium enrichment fuel type II, and high enrichment fuel type III. The void fraction is 40% for fuel type I, II, and III. FIG. 10 shows a case where the void fraction of fuel type I is 40%, and the void fraction of fuel types II and III is 70%. In FIG. 9 and FIG. 10, the calculations in infinite lattice are indicated by a triangle symbol, while the two-dimensional diffusion calculation in four fuel segments is indicated by a solid black circle. The R factor of the system according to this invention in which the local power of all the fuel rods is stored is indicated by an open circle, and that when equation (14) is used, in which only the local power in infinite lattice of the several most thermally limiting fuel rods is stored, is indicated by X, respectively. However, in the local power distribution determination according to the invention, the method of equation (7) is employed, in which the power distribution is found analytically for the sight fuel segments adjacent to the fuel segment under consideration. Usually, if the R factor is increased by 0.1, the CPR drops by about 0.25 and the thermal margin is decreased. However, from FIG. 9 and FIG. 10, it can be seen that, due to enrichment mismatch, resulting in spectral mismatch, between the fuel segments, the R factor in the medium enrichment fuel and high enrichment fuel is increased by an amount in the range about 0.02-0.05 from the value in infinite lattice. In contrast, in the system according to the invention, in which the local power of all fuel rods is stored, it can be seen that the R factor can be determined with an error of better than 1%, irrespective of fuel type. Also, even in the case of a system wherein only the local power in infinite lattice of the several most thermally limiting fuel rods is stored, notwithstanding that the error is somewhat larger in the case of the medium enrichment fuel, it can be seen that the R factor can be calculated with an average error of better than 1%. As an example, calculated CPR for a representative BWR core is shown in FIG. 11. FIG. 11 illustrates one quarter of the BWR core where the operating limiting CPR threshold is 1.20. The fuel assemblies here are shown arranged in 15 columns and 15 rows for a BWR core having fuel assemblies arranged in a matrix having 30 columns and 30 rows (and correspond to the core map which is displayed in FIG. 5). As described above, with the reactor core monitoring system according to the invention, the benefit is obtained that the critical power can be determined with high accuracy solely from the results of a single fuel segment nuclear calculation, even when there is a large degree of spectral mismatch between fuel segments. Thus, control of the reactor core 30 is enhanced and an undesirable boiling transition can be avoided by inserting control rods 25 when the CPR falls below a predetermined threshold. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
044514280	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention has been developed based on the results of detailed study of the performances of control rods of the prior art. The results of the detailed study will be described hereinafter. Generally, the service life of a control rod is evaluated in terms of a nuclear lifetime of boron (i.e. the time until which boron loses its neutron absorbing capacity) and a mechanical life. The nuclear lifetime is determined by the neutron absorbing capcacity or the amount of boron-10 (hereinafter B.sup.10) in the powder of B.sub.4 C charged in the poison tubes. The mechanical life may vary depending on the material strength of the poison tubes and evaluation of the stress. In desiging a control rod, it is required that the control rod has a longer mechanical life than a nuclear lifetime. Meanwhile the B.sup.10 in the B.sub.4 C having a neutron absorbing capacity under goes an (n, .alpha.) reaction and absorbs neutron, thereby producing helium. This causes swelling of the B.sub.4 C powder, tending to cause the poison tubes to expand outwardly. The phenomenon of swelling of the B.sub.4 C power is most markedly observed in a forward end portion of the control rod at which the rod is inserted into the core and which has the highest degree of burn-up. There are possibilities that the sheaths of the poison tubes are expanded outwardly and suffer damage. Thus the mechanical life of the poison tubes determined by evaluation of the stress at the forward end portion of the control rod at which the rod is inserted in the core determines the service life of the control rod because it is about one-half the nuclear life. When a control rod is inserted in the core, the neutron flux distribution shows a sudden change in the vicinity of the forward end portion of the control rod at which the rod is inserted. Being proportional to the neutron flux distribution, the reactor power distribution also shows a sudden change in the vicinity of the forward end portion of the control rod at which the rod is inserted. This gives rise to the possibilities that the fuel rods disposed in the nuclear core might suffer damage. Heretofore, various proposals have been made to obviate the aforesaid problems. As a means for prolonging the mechanical life, it has been proposed to fill the forward end portions of the poison tubes at which the control rod is inserted with Ag-Cd-In powder which mainly causes an (n, .UPSILON.) reaction to take place. This proposal has not been put to practical use because of complex production steps involved. On the other hand, a proposal has been made to use a control rod in which the neutron absorbing capacity is gradually reduced in going toward the forward end portion at which the rod is inserted, to obtain flattening of the neutron flux distribution in the vicinity of the forward end portion of the control rod at which the rod is inserted. In this proposal, there are several problems that should be solved before the proposal is carried into practice. One of such problems is how to adjust the neutron absorbing capacity in the connection between the forward end portion (gray nose portion) at which the neutron absorbing capacity is reduced and the control rod main body having uniform neutron absorbing capacity. Another problem is how to successively change the neutron absorbing capacity in the gray nose portion extending from the connection to the forward end. However, a process is known whereby the neutron absorbing capacity of a control rod is successively changed in going toward the forward end of the control rod by forming the control rod from a material having uniform neutron absorbing capacity and reducing the thickness of the rod in going toward the forward end. Macroscopically speaking, this process causes the neutron absorbing capacity to be successively reduced. However, the neutron absorbing capacity undergoes a sudden change in the forward end portion of the control rod when this process is used, when considered from a microscopic standpoint. One embodiment of the present invention which is based on the results of the study described hereinabove will now be described by referring to FIGS. 1, 2A and 2B. A control rod 1 used for a boiling-water reactor has blades 2 in the form of a cross in transverse cross section. The blades 2 each have a sheath 4 (formed of SUS 304) attached to one of four sides of a tie rod 3 in the form of a cross disposed in the center of the control rod 1. A support member 5 is connected to an end of the control rod 1 at which the rod is inserted and attached to an upper end of the tie rod 3. A handle 6 is connected to the support member 5. Another support member, not shown, of the same shape as the support member 5 is connected to the lower end of the tie rod 3. A plurality of poison tubes 7 having a charge of B.sub.4 C powder filled therein are arranged in each sheath 4 and supported by the lower support member. A neutron absorbing plate 8 is arranged in each sheath 4 in a portion of the control rod 1 disposed nearer to its forward end of entry into the core than the poison tubes 7, and maintained at its lower end in contact with the upper ends of the poison tubes 7. The neutron absorbing plates 8 are neutron absorbers formed of an alloy of a material of large neutron absorption cross section and a material of small neutron absorption cross section. Table 1 shows the thermal neutron absorption cross sections of principal materials. TABLE 1 ______________________________________ Thermal Neutron Absorption Cross Section of Principal Materials Thermal Neutron Absorp- Type Material tion Cross Section (Barn) ______________________________________ 1 Zirconium 0.18 Aluminum 0.22 Zinc 1.1 Niobium 1.1 Iron 2.4 Chromium 2.9 Steel 3.6 Nickel 4.5 2 Hafnium 115 Boron 750 Cadmium 2400 Samarium 6500 Gadolinium 44000 ______________________________________ In this specification, materials having a thermal neutron absorption cross section of over 100 barns are defined as materials of large neutron absorption cross section and materials having a thermal neutron absorption cross section of below 100 barns are defined as materials of small neutron absorption cross section, from the point of view of controlling the chain reaction of neutrons. In the materials shown in Table 1, type 1 materials are of small neutron absorption cross section and type 2 materials are of large neutron absorption cross section. The neutron absorbing plates 8 are formed of an alloy of the materials of type 1 and type 2 shown in Table 1. The control rod 1 is connected at its lower end portion to a control rod driving apparatus mounted in a pressure vessel of a nuclear reactor and inserted between fuel assemblies arranged in an array in the core in the pressure vessel. When inserted in the core, the control rod 1 is inserted at its upper end or the end at which the handle 6 is connected. That is, the handle 6 is at the end of the control rod 1 at which the rod 1 is inserted. The embodiment will be described as using a Hf-Zr alloy for forming the neutron absorbing plates 8. In a Hf-Zr alloy, hafnium is the material of large neutron absorption cross section and zirconium is the material of small neutron absorption cross section. The reasons why the Hf-Zr alloy is arranged in the forward end portion only of the control rod 1 are that the portion of a control rod that has determined the control rod life in the prior art is the forward end portion that has a high degree of burn-up, and that it is necessary to reduce the weight of the absorbers because hafnium is expensive. When neutron absorbers formed of hafnium are located in every part of the control rod 1, the control rod would have a weight about three times as large as the weight of control rods of the prior art. This would make it necessary to improve the conventional control rod driving apparatus, as well as to increase the cost of the control rods. One of the reaons why an alloy, such as a Hf-Zr alloy, is used for forming the neutron absorbing plates 8 is that the strength of the material of high neutron absorption cross section can be increased by using the material of low neutron absorption cross section as reinforcing material because the former has low strength as material. The concentration of hafnium in each of the neutron absorbing plates 8 of Hf-Zr alloy is 100% in an end thereof at which it is in contact with the poison tubes 7 and gradually reduced in going toward the forward end of the control rod 1 until the concentration becomes zero at the forward end of the control rod 1. The neutron absorbing plates 8 of Hf-Zr alloy each have a length which is over 1/24 the total length of the control rod 1 (from the upper support member 5 to the lower support member) from the forward end of the control rod 1. This is because there is the possibility that a portion of the control rod 1 occupying about 1/24 its total length from its forward end is most liable to suffer damage. In case the length of the neutron absorbing plates 8 of Hf-Zr alloy is over 1/4 the total length of the control rod 1, the control rod 1 would not have sufficient neutron absorbing capacity. Thus the length of the neutron absorbing plates 8 of Hf-Zr alloy is advantageously 1/24 to 1/4 the total length of the control rod 1. It is essential that the two neutron absorbing materials have substantially the same neutron absorbing capacity in the boundary between the poison tubes 7 and each neutron absorbing plate 8 of Hf-Zr alloy, in order to minimize thermal strain produced in the cladding of each fuel rod. Control material of 100% Hf matches control material of B.sub.4 C. This has been ascertained by the following method. It is known that the control material of Hf has substantially the same neutron absorbing capacity as control material of 3 wt% B.sup.10 stainless steel (See Nuclear Reactor Material Handbook, published by Nikkan Kogyo Shimbunsha, page 415). Instead of comparing the neutron absorbing capacity of the control material of Hf with that of the control material of B.sub.4 C, the neutron absorbing capacity of the control material of Hf was compared with that of the control material of 3 wt% B.sup.10 stainless steel. A comparison of the two control materials with each other with regard to the amount of B.sup.10 that determines the neutron absorbing capacity of the two control materials carried out under the condition of charging rate of 70% of B.sub.4 C powder and the abundance ratio of 18.8% of B.sup.10 in B.sub.4 C has shown that the amount of B.sup.10 is 1.43.times.10.sup.22 in the control material of B.sub.4 C and 1.40.times.10.sup.22 in the control material of 3 wt% B.sup.10 stainless steel per 1 cc. It will be seen that the two control materials have substantially the same amount of B.sup.10 and hence the same neutron absorbing capacity. From this observation, it can be surmised that the control material of Hf has substantially the same neutron absorbing capacity as the control material of B.sub.4 C. Thus by using the neutron absorbing plates 8 of Hf-Zr alloy as aforesaid, a neutron absorbing capacity distribution of the forward end portion of the control rod 1 as shown in FIG. 2B has been obtained. FIG. 3 shows a neutron flux distribution obtained when the control rod 1 having the neutron absorbing capacity distribution shown in FIG. 2B was inserted in an array of fuel rods in the reactor core. The symbol E designates the range of insertion of the control rod 1. In FIG. 3, a curve of dotted line represents a neutron absorbing capacity distribution of a control rod of the prior art used as a control. In FIG. 3, it will be seen that flattening of the neutron flux distribution can be obtained in the vicinity of the forward end portion of the control rod 1. This minimizes the risk that the control rod 1 might suffer damage due to the movement thereof in the reactor core when the control rod 1 is withdrawn from the core. FIGS. 4 and 5 are views in explanation of the principle of producing the neutron absorbing plates 8 of Hf-Zr alloy that have the neutron absorbing capacity distribution shown in FIG. 2B, by a zone melting process. FIG. 4 is a phase diagram of a Hf-Zr alloy. As shown in the figure, the Hf-Zr alloy is an all solid solution type alloy in which Hf has a higher melting point than Zr. FIG. 5 shows a zone melting process in which 9 designates a movable heater adapted to move in the direction of an arrow 10. The numeral 8 designates a plate of Hf-Zr alloy. Assume that the movable heater 9 is disposed in the position shown in FIG. 5 after being moved from the left end of the Hf-Zr alloy plate 8. A hatched zone A is already melted by the heat of the movable heater 9. As the movable heater 9 moves slowly in the direction of the arrow 10, the molten metal of the zone A solidifies in a zone B. Assume that the composition of the liquid metal in zone A has a concentration of C1 shown in FIG. 4. It will be seen that the composition of the alloy that solidifies in zone B has a concentration of C2 as shown in FIG. 4. Stated differently, the Zr originally located in zone B is forced to move to zone A which is a molten section disposed rightwardly of zone B. In this way, the concentration of Hf in the plate 8 of Hf-Zr alloy becomes higher in going from the right end toward the left end of the plate 8 in FIG. 5. By repeating the aforesaid process, the zone originally having the concentration of C1 can be made to have increasingly higher concentrations C2, C3, . . . , and the left end portion of the plate 8 shown in FIG. 5 can be made progressively to have a 100% concentration of Hf. A suitable Hf concentration distribution can be obtained in the plate 8 of the Hf-Zr alloy by controlling the speed of movement of the movable heater 9, varying the number of movements of the movable heater 9 in different portions of the plate 8, and varying the temperature at which heating is effected by the movable heater 9 in different portions of the plate 8. Thus when a zone melting process is used, a concentration gradient of one element of an alloy can be readily imparted to the alloy when it is of the Hf-Zr alloy (all solid solution type alloy). The sheaths 4 are each attached to one of four sides of the tie rod 3 and thelower support member of thecross shape is connected to the lower end of the sheaths 4. A plurality of poison tubes 7 are inserted in each of the sheaths 4, and then the neutron absorbing plates 8 of the Hf-Zr alloy having a Hf concentration gradient imparted thereto by the zone melting process are each inserted in one of the sheaths 4, so that the plates 8 are located in the upper portion of the control rod 1 above the poison tubes 7. Thereafter the support member 5 having the handle 6 is connected to the upper ends of the sheaths 4. The embodiment of the invention shown and described hereinabove can achieve the effects described hereinafter. Hf causes an (n, .UPSILON.) reaction to take place and produces no gas when it absorbs neutrons. The arrangement whereby the neutron absorbing plates 8 of Hf-Zr alloy are located in the forward end portion of the control rod 1 having a high neutron absorption rate at which the control rod 1 is inserted in the core minimizes swelling of the B.sub.4 C powder in the poison tubes 7, thereby markedly reducing the risk of the control rod 1 suffering damage and improving the safety thereof. In the forward end portion of the control rod 1, the concentration of Hf is reduced successively in going toward the forward end of the rod 1, thereby enabling changes in the reactor power occurring axially of the core or those occurring in the vicinity of the forward end portion of the control rod 1 in particularly to take place smoothly as the control rod 1 is inserted in the nuclear core. This minimizes changes in reactor power occurring when the control rod 1 is withdrawn, thereby minimizing damage suffered by the control rod 1. The progressive reduction of the Hf concentration in the Hf-Zr alloy can be readily achieved, so that the neutron absorbing plates 8 can have a suitable Hf concentration gradient. FIGS. 6 and 7 show other embodiments of the invention. In the embodiments shown in FIGS. 6 and 7, parts similar to those of the embodiments shown in FIGS. 1, 2A and 2B are designated by like reference characters. In the embodiment shown in FIG. 6, the control rod 11 has the neutron absorbing plates 8A of Hf-Zr alloy each arranged at an outer peripheral edge of one of the blades 2 which shows the highest degree of burn-up. In control rods of the prior art, swelling has tended to occur in the portion of each blade 2 at which the neutron absorbing plate 8A of Hf-Zr alloy is arranged. In the embodiment shown in FIG. 7, the control rod 12 has the neutron absorbing plates 8B formed of an alloy of high physical and chemical stability and high strength serving as blades directly exposed to cooling water without being converted with sheaths. The present invention enables the risk of the control rod suffering damage to be minimized and permits changes in reactor power to take place smoothly when the control rod is inserted in or withdrawn from the reactor core. The forward end portion of the control rod at which the control rod is inserted in the reactor core can be readily imparted with a suitable neutron absorbing material concentration gradient.
	abstract	A reflective optical element for a microlithographic projection exposure apparatus, a mask inspection apparatus or the like. The reflective optical element has an optically effective surface, an element substrate (12, 32, 42, 52), a reflection layer system (14, 34, 44, 54) and at least one deformation reduction layer (15, 35, 45, 55, 58). When the optically effective surface (11, 31, 41, 51) is irradiated with electromagnetic radiation, a maximum deformation level of the reflection layer system is reduced in comparison with a deformation level of an analogously constructed reflective optical element without the deformation reduction layer.
	abstract	The present embodiments relate to a beam head including a vacuum housing, in which an electron source is arranged. The beam head also includes a beam finger that is connected to the vacuum housing and has an outlet window at a distal end. The beam head includes a transformer housing, in which a transformer connected to the electron source is arranged. The transformer housing is arranged directly on the vacuum housing.
039986926	abstract	A light-water-cooled nuclear reactor capable of breeding U.sup.233 for use in a light-water breeder reactor includes physically separated regions containing U.sup.235 fissile material and U.sup.238 fertile material and Th.sup.232 fertile material and Pu.sup.239 fissile material, if available. Preferably the U.sup.235 fissile material and U.sup.238 fertile material are contained in longitudinally movable seed regions and the Pu.sup.239 fissile material and Th.sup.232 fertile material are contained in blanket regions surrounding the seed regions.
053596340	abstract	A reactor core for a boiling water nuclear reactor comprises a plurality of vertical fuel assemblies (40), each one containing a plurality of fuel rods (10, 10a, 10b) with enriched nuclear fuel material, which are arranged between a bottom tie plate (11) and a top tie plate (12) in a surrounding vertical fuel channel (1). Each fuel assembly is designed with an inlet (3) for water for conducting water in through the bottom tie plate, through the vertical fuel channel, and out through the top tie plate. Further, each fuel assembly is arranged with intermediate gaps (37a, 37b) with respect to adjacent fuel assemblies and possibly with a channel (32, 50) arranged internally in the fuel assembly for conducting water through the gaps and through the internal channel (if any) in a vertical direction from below and upwards through the core. Each one of at least the main part of those fuel rods, central rods (10a), which in a fuel assembly are surrounded by fuel rods, edge rods (10b), which are located close to a water gap or close to an internal water channel, is arranged with a ratio of the enrichment in the central rod in question to the medium enrichment for the central rods and the edge rods, in a horizontal section, which is lower for an upper part than for a lower part of the central rod.
062663933	claims	1. A multileaf collimator for use in a radiation system providing a radiation beam in a given beam direction, comprising: a first layer of a plurality of radiation blocking leaves, said leaves being arranged adjacent one another so as to form two opposed rows of adjacently positioned leaves and being movable in a longitudinal direction which is generally traverse to the beam direction so as to define a radiation beam shaping field between the opposed ends of the leaves; a second layer of a plurality of radiation blocking leaves, said leaves of said second layer being arranged adjacent one another so as to form two opposed rows of adjacently positioned leaves and being movable in a cross-over direction which is generally traverse to the beam direction and angled with respect to said longitudinal direction so as to define a radiation beam shaping field between the opposed ends of the leaves of said second layer; and actuator apparatus for moving said leaves of said first layer in the longitudinal direction and said leaves of said second layer in the cross-over direction, wherein said first and second layers are arranged one above another in an overlapping manner in the beam direction, wherein said first layer has a first longitudinal axis and said second layer has a second longitudinal axis, and wherein said longitudinal axes at said leaves in said layers are mutually perpendicular, the layers lying in mutually parallel planes. 2. The multileaf collimator (12) according to claim 1 and wherein gaps (52) are formed generally traverse to the beam direction and generally in a plane of the X and Y directions (34, 44), each of said gaps (52) only allowing an amount of radiation to pass therethrough below a predetermined threshold. 3. The multileaf collimator (12) according to claim 1 and wherein said cross-over direction (44) is generally orthogonal to said longitudinal direction. 4. The multileaf collimator (12) according to claim 1 and wherein said leaves (32) of said first layer (30) and said leaves (42) of said second layer (40) are housed in a frame (50). 5. The multileaf collimator (12) according to claim 1 and comprising a source of radiation (19) for providing a radiation beam (20) in said given beam direction. 6. The multileaf collimator (12) according to claim 1 and comprising imaging apparatus (25) for imaging a target (37) irradiated by said radiation beam (20). 7. The multileaf collimator (12) according to claim 1 and comprising an optical control device (54) that monitors travel of any of the leaves (32, 42) and signals said actuator apparatus (38, 48) to stop moving said leaves (32, 42). 8. The multileaf collimator (12) according to claim 1 and comprising a plurality of said first layers (30) of radiation blocking leaves (32). 9. The multileaf collimator (12) according to claim 1 and comprising a plurality of said second layers (40) of radiation blocking leaves (42).
	claims	1. A computer implemented method for analyzing load run test results of a computer system, the method performed by the computer comprising the steps of:providing a plurality of performance measure sets derived from a first series of load run tests of a computer system performed over a same time period under a constant load, each said set comprising a plurality of records, each record having a timestamp and a value;sorting performance measure records by value in ascending order, for each performance measure set;determining whether said computer system has equilibrated under said load run tests by identifying plateau regions in said sorted performance measure sets, for each performance measure;sorting performance measure records within each plateau region by time stamp in ascending order, for each performance measure;identifying a single overlapping time interval covered by each plateau region for the plurality of performance measure sets, wherein said computer system has equilibrated if said performance measures have plateau regions in common; andcomputing averages of performance measures over the overlapping time intervals. 2. The method of claim 1, wherein identifying a plateau region in a sorted performance measure set comprises looking for an unbroken sequence of measurement values wherein estimates of a first derivative and a second derivative for each value in said sequence are close to zero in absolute value. 3. The method of claim 2, wherein a difference between a smallest value and a largest value of said measurement values in said unbroken sequence is small. 4. The method of claim 2, wherein said first derivative {circumflex over (ƒ)}′(xn) at a measurement value ƒ(xn) is estimated by the formula f ^ ′ ⁡ ( x n ) = 1 12 ⁡ [ f ⁡ ( x n - 2 ) - 8 ⁢ f ⁡ ( x n - 1 ) + 8 ⁢ f ⁡ ( x n + 1 ) - f ⁡ ( x n + 2 ) ] , n ≥ 2. 5. The method of claim 2, wherein said second derivative {circumflex over (ƒ)}″(xn) at a measurement value ƒ(xn) is estimated by the formula{circumflex over (ƒ)}″(xn)=[ƒ(xn−1)−2ƒ(xn)+ƒ(xn+1)]. 6. The method of claim 2, wherein a measurement value for a first point xn+1 in the plateau satisfies \|{circumflex over (ƒ)}′(x0)\|<ε1 and \|{circumflex over (ƒ)}″(x0)\|<ε2, wherein {circumflex over (ƒ)}′, {circumflex over (ƒ)}″ are first and second derivatives of the measurement values, respectively, and ε1, ε2>0. 7. The method of claim 6, wherein a measurement value for a subsequent point xn+1 in the plateau satisfies \|{circumflex over (ƒ)}′(xn+1)\|<ε1, \|{circumflex over (ƒ)}″(xn+1)\|<ε2, and \|ƒ(xn+1)−ƒ(xn)\|<ε3, for εi>0, i=1, 2, 3. 8. The method of claim 7, further comprising excluding a point from said plateau, if a first derivative evaluated for said point is negative. 9. The method of claim 1, wherein identifying overlapping time intervals covered by said plateau regions comprises, if a measurement value for an interval is missing for one performance measure,discarding corresponding measurement values for other performance measures,computing averages of performance measures over a largest set for which all measurement values are present and sufficiently close together,wherein chronologically successive measurement values within the plateau sets of the different performance measures are deemed to be sufficiently close together if said measurement values are no more than kδ apart, where k is a small positive integer and δ is a length of measurement intervals. 10. The method of claim 1, wherein said performance measures are based on rates, sample statistics, and time-averaged quantities. 11. The method of claim 10, wherein said performance measures include processor utilization, bandwidth utilization, memory occupancy, throughput and transaction response time. 12. The method of claim 1, further comprising:providing one or more performance measure sets derived from a second series of load run tests performed after modifying said computer system, said second series of load run tests being performed over the same time period duration and under the same load conditions as said first series of load run tests;for each performance measure in said second series of load run tests, sorting measurement values of each said performance measure from said first series load run test and from said second series load run test by value;computing a first and second empirical distribution function for said first and second set of sorted data;comparing the first and second empirical distribution functions using a Kolmogorov-Smirnov test; andidentifying those pairs of runs that are different according to the Kolmogorov-Smirnov test as needing further investigation. 13. The method of claim 2, wherein said empirical distribution function is defined by F(x)=i/n if x(i)≦x, x(i+1)>x and i=1, 2, . . . , n−1, and ƒ(x)=1 if x≧x(n), wherein n is a number of measurement values. 14. The method of claim 1, wherein identifying overlapping time intervals covered by said plateau regions comprises constructing a tree ordered by timestamps at intervals corresponding to those at which the performance measures were collected, wherein each leaf node of said tree contains the time stamp and a list of records including names of those performance measures whose values lie on respective plateaus and the corresponding values themselves, internal nodes contain time stamps within the equilibrium intervals at the leaf nodes, and wherein the set of values belonging to each time stamp are treated as belonging to the equilibrium interval if the associated list of records contains all performance measures of interest, and if the list of records at the neighboring leaves also contain all performance measures of interest. 15. A non-transitory program storage device readable by a computer, tangibly embodying a program of instructions executable by the computer to perform the method steps for analyzing load run test results of a computer system, the method comprising the steps of:providing a plurality of performance measure sets derived from a first series of load run tests of a computer system performed over a same time period under a constant load, each said set comprising a plurality of records, each record having a timestamp and a value;sorting performance measure records by value in ascending order, for each performance measure set;determining whether said computer system has equilibrated under said load run tests by identifying plateau regions in said sorted performance measure sets, for each performance measure;sorting performance measure records within each plateau region by time stamp in ascending order, for each performance measure;identifying a single overlapping time interval covered by each plateau region for the plurality of performance measure sets, wherein said computer system has equilibrated if said performance measures have plateau regions in common;and computing averages of performance measures over the overlapping time intervals. 16. The computer readable program storage device of claim 15, wherein identifying a plateau region in a sorted performance measure set comprises looking for an unbroken sequence of measurement values wherein estimates of a first derivative and a second derivative for each value in said sequence are close to zero in absolute value. 17. The computer readable program storage device of claim 16, wherein a difference between a smallest value and a largest value of said measurement values in said unbroken sequence is small. 18. The computer readable program storage device of claim 16, wherein said first derivative {circumflex over (ƒ)}′(xn) at a measurement value ƒ(xn) is estimated by the formula f ^ ′ ⁡ ( x n ) = 1 12 ⁡ [ f ⁡ ( x n - 2 ) - 8 ⁢ f ⁡ ( x n - 1 ) + 8 ⁢ f ⁡ ( x n + 1 ) - f ⁡ ( x n + 2 ) ] , n ≥ 2. 19. The computer readable program storage device of claim 16, wherein said second derivative {circumflex over (ƒ)}″(xn) at a measurement value ƒ(xn) is estimated by the formula{circumflex over (ƒ)}″(xn)=[ƒ(xn−1)−2ƒ(xn)+ƒ(xn+1)]. 20. The computer readable program storage device of claim 16, wherein a measurement value for a first point x0 in the plateau satisfies \|{circumflex over (ƒ)}′(x0)\|<ε1 and \|{circumflex over (ƒ)}″(x0)\|<ε2, wherein {circumflex over (ƒ)}′, {circumflex over (ƒ)}″ are first and second derivatives of the measurement values, respectively, and ε1, ε2>0. 21. The computer readable program storage device of claim 20, wherein a measurement value for a subsequent point xn+1 in the plateau satisfies \|{circumflex over (ƒ)}′(xn+1)\|<ε1, \|{circumflex over (ƒ)}″(xn+1)\|<ε2, and \|ƒ(xn+1)−ƒ(xn)\|<ε3, for εi>0, i=1, 2, 3. 22. The computer readable program storage device of claim 21, the method further comprising excluding a point from said plateau, if a first derivative evaluated for said point is negative. 23. The computer readable program storage device of claim 15, wherein identifying overlapping time intervals covered by said plateau regions comprises, if a measurement value for an interval is missing for one performance measure,discarding corresponding measurement values for other performance measures,computing averages of performance measures over a largest set for which all measurement values are present and sufficiently close together,wherein chronologically successive measurement values within the plateau sets of the different performance measures are deemed to be sufficiently close together if said measurement values are no more than kδ apart, where k is a small positive integer and δ is a length of measurement intervals. 24. The computer readable program storage device of claim 15, wherein said performance measures are based on rates, sample statistics, and time-averaged quantities. 25. The computer readable program storage device of claim 24, wherein said performance measures include processor utilization, bandwidth utilization, memory occupancy, throughput and transaction response time. 26. The computer readable program storage device of claim 15, the method further comprising:providing one or more performance measure sets derived from a second series of load run tests performed after modifying said computer system, said second series of load run tests being performed over the same time period duration and under the same load conditions as said first series of load run tests;for each performance measure in said second series of load run tests, sorting measurement values of each said performance measure from said first series load run test and from said second series load run test by value;computing a first and second empirical distribution function for said first and second set of sorted data;comparing the first and second empirical distribution functions using a Kolmogorov-Smirnov test; andidentifying those pairs of runs that are different according to the Kolmogorov-Smirnov test as needing further investigation. 27. The computer readable program storage device of claim 26, wherein said empirical distribution function is defined by F(x)=i/n if x(i)≦x, x(i+1)>x and i=1, 2, . . . , n−1, and ƒ(x)=1 if x≧x(n), wherein n is a number of measurement values. 28. The computer readable program storage device of claim 15, wherein identifying overlapping time intervals covered by said plateau regions comprises constructing a tree ordered by timestamps at intervals corresponding to those at which the performance measures were collected, wherein each leaf node of said tree contains the time stamp and a list of records including names of those performance measures whose values lie on respective plateaus and the corresponding values themselves, internal nodes contain time stamps within the equilibrium intervals at the leaf nodes, and wherein the set of values belonging to each time stamp are treated as belonging to the equilibrium interval if the associated list of records contains all performance measures of interest, and if the list of records at the neighboring leaves also contain all performance measures of interest.
	summary
055240321	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS I. THE CLADDING TUBE STRUCTURE As used herein, the term "tubing" refers to a metal tube having various uses, and the term "fuel rod container" or simply "container" refers to tubing used in fuel rods to enclose fuel pellets. Sometimes the fuel rod container is referred to as "cladding" or "cladding tube". Referring to FIG. 1, a fuel element 14 (commonly referred to as a fuel rod) includes a fuel rod container 17 surrounding a fuel material core 16. The fuel element 14 is designed to provide excellent thermal contact between the fuel rod container 17 and the fuel material core 16, a minimum of parasitic neutron absorption, and resistance to bowing and vibration which is occasionally caused by flow of coolant at high velocity. The fuel material core is typically a plurality of fuel pellets of fissionable and/or fertile material. The fuel core may have various shapes, such as cylindrical pellets, spheres, or small particles. Various nuclear fuels may be used, including uranium compounds, thorium compounds and mixtures thereof. A preferred fuel is uranium dioxide or a mixture comprising uranium dioxide and plutonium dioxide. The container 17 is a composite cladding having a structure including a substrate 21, a zirconium barrier 22, and an inner layer or liner 23. The substrate forms the outer circumferential region of a cladding tube, the inner liner forms an inner circumferential region, and the zirconium barrier is located between the substrate and inner liner. In alternative preferred embodiments, the composite cladding has no well-defined inner liner. Rather, the inner regions of zirconium barrier (closer to the fuel) contain a high concentration of alloying elements while the interior regions of the barrier layer (between the barrier layer inner and outer surfaces) contain lower concentrations of alloying elements. The substrate may be made from a conventional cladding material such as a stainless steel or, preferably, a zirconium alloy. Suitable zirconium alloys for the substrate preferably include at least about 98% zirconium, up to about 0.25% iron, up to about 0.1% nickel, up to about 0.25% chromium, and up to about 1.7% tin (all percents by weight). Other alloying elements may include niobium, bismuth, molybdenum, as well as various other elements used in the art. Most generally, any zirconium alloy with suitable corrosive resistance to BWR water and with sufficient strength and ductility may be employed. In a preferred embodiment of this invention, the substrate is Zircaloy-2 or Zircaloy-4. In other preferred embodiments, "Zirlo"--a zirconium based alloy containing about 1% tin, about 1% niobium, and less than about 0.2% iron--is employed. Other exemplary substrate alloys include zirconium/2.5% niobium, "NSF" alloys (about 1% tin, about 0.2-0.5% iron, about 0.05% nickel, about 0.6-1% niobium, and the balance zirconium), "Valloy" (about 0.1% iron, about 1.2% chromium, and the balance zirconium), other high chromium content alloys, and "Excel" or "Excellite" (about 0.3% niobium, about 0.3 molybdenum, about 1.2 to 1.5% tin, and the balance zirconium). Still other exemplary alloys include various bismuth-containing zirconium alloys such as those described in U.S. Pat. No. 4,876,064 issued to Taylor on Oct. 24, 1989. These alloys include, for example, (1) about 0.5 to 2.5 weight percent bismuth, (2) about 0.5 to 2.3 weight percent of a mixture of bismuth and tin plus about 0.5 to 1.0 weight percent of solute which may be niobium, molybdenum, tellurium, or mixtures thereof, or (3) about 0.5 to 2.5 weight percent of a mixture of tin and bismuth plus about 0.3 to 1.0 weight percent tellurium. In some preferred embodiments, the substrate will have a microstructure (i.e. precipitate size distribution) that resists corrosion and/or crack propagation. It is known that the microstructure of Zircaloys and other alloys can be controlled by the anneal temperature and time as well as other fabrication parameters. It is also known that in boiling water reactors (BWRs), smaller precipitates generally provide superior resistance to corrosion while in pressurized water reactors (PWRs), larger precipitates generally provide superior resistance to corrosion. In either environment, coarse precipitates provide improved resistance to axial crack propagation. In a preferred embodiment, the substrate will have a dense distribution of fine precipitate (e.g., between about 0.01 and 0.1 micrometers in diameter) in the outer regions (radially) of the substrate and a less dense distribution of coarse precipitates (e.g., between about 0.1 and 1 micrometers in diameter) in the inner regions of the substrate. Detailed discussions of Zircaloy microstructure and methods of fabricating cladding having a desired microstructure are found in U.S. patent application Ser. No. 08/052,793 entitled ZIRCALOY TUBING HAVING HIGH RESISTANCE TO CRACK PROPAGATION and U.S. patent application Ser. No. 08/052,791 entitled METHOD OF FABRICATING ZIRCALOY TUBING HAVING HIGH RESISTANCE TO CRACK PROPAGATION, both of which were filed on Apr. 23, 1993, assigned to the assignee hereof, and are incorporated herein by reference for all purposes. Metallurgically bonded on the inside surface of substrate 21 is the zirconium barrier 22. See the above-mentioned U.S. Pat. Nos. 4,200,492 and 4,372,817 to Armijo and Coffin, U.S. Pat. No. 4,610,842 to Vannesjo, and U.S. Pat. No. 4,894,203 to Adamson. Because the zirconium barrier is at least partially alloyed in the present invention, it resists accelerated corrosion in the event of a cladding breach and the subsequent ingress of steam. In the present invention, such protection is provided by imparting a significant alloying element concentration to the barrier layer through a diffusion anneal step. This will drive some of the elements from the substrate and inner liner into the zirconium barrier layer. As is well-known in the art, the presence of alloying elements such as iron and nickel in zirconium can provide resistance to accelerated corrosion. In preferred embodiments, the thickness of the barrier layer is between about 50 and 200 micrometers (approximately 2 to 8 mils) and more preferably between about 75 and 115 micrometers (approximately 3.2 to 4.7 mils). In a typical cladding, the zirconium barrier forms between about 5% to about 30% of the thickness or cross-section of the cladding. Generally, the zirconium barrier layer is initially in an "unalloyed" form. Suitable barrier layers are made from "low oxygen sponge" grade zirconium, "reactor grade sponge" zirconium, and higher purity "crystal bar zirconium". Generally, there are at least 1,000 parts per million (ppm) by weight and less than about 5,000 ppm impurities in sponge zirconium and preferably less than 4,200 ppm. Sponge zirconium is typically prepared by reduction with elemental magnesium at elevated temperatures at atmospheric pressure. The reaction takes place in an inert atmosphere such as helium or argon. Crystal bar zirconium is produced from sponge zirconium by converting the zirconium metal in sponge zirconium to zirconium tetraiodide vapor and then decomposing the iodide on an incandescent wire. Crystal bar zirconium is more expensive than sponge zirconium, but has few impurities and has greater resistance to radiation damage. As noted, the zirconium barrier in conventional barrier layer cladding serves to provide the compliance necessary to counteract the detrimental effects of pellet-cladding interaction. However, it is also important that the barrier layer resist accelerated corrosion that can result if steam enters cladding interior through a defect. The inner liner provides some protection against accelerated corrosion, but in case the liner has tears or other defects, the barrier layer should have some additional corrosion protection. In the present invention, such protection is provided by imparting a significant alloying element concentration to the barrier layer through, for example, a diffusion anneal step. This will drive some of the elements from the substrate and inner liner into the zirconium barrier layer. As is well-known in the art, the presence of alloying elements such as iron and nickel in zirconium can provide resistance to accelerated corrosion. Throughout the present specification, various references are made to "alloying elements" in the zirconium barrier layer or to an "alloyed" zirconium barrier layer. Such references are intended to include cladding tubes in which the concentration of alloying elements (e.g., iron and nickel) purposely added is in excess of the concentration of those elements in a conventional "unalloyed" zirconium barrier layer. As explained above, conventional barrier layers made to specification are of only finite purity (i.e., they typically contain some low concentration of elements). Thus, all values provided herein for alloying element concentrations refer to concentrations beyond those conventionally found in zirconium barrier layers. For example, if ziconium used in "unalloyed" barrier layers is made to a specification of 500 ppm iron, an alloyed zirconium barrier layer having 0.1 weight percent iron, will contain that weight percent plus the 500 ppm of conventional zirconium. The alloyed barrier layers of this invention may have alloying elements in a concentration sufficient to cause precipitation. However, this is not critical to present invention. The alloying elements should simply be present in concentrations sufficient to provide some measure of protection against accelerated corrosion without significantly compromising the compliance of the zirconium. It is especially important that the alloying elements be present at the inner surface of the zirconium barrier layer (adjacent to the inner liner). This ensures that if the barrier layer becomes exposed to a corrosive environment as a result of a defect in the inner liner, the barrier layer's inner surface will have some measure of corrosion protection. Suitable concentrations of alloying elements at the zirconium barrier inner surface are (on a per weight basis) at least about 0.03 percent iron, at least about 0.01 percent chromium, and at least about 0.01 percent nickel (all concentrations beyond the "unalloyed" levels for the alloying elements). More preferably, these concentrations should be between about 0.03-0.40 percent iron, between about 0.01-0.20 percent chromium, and between about 0.01-0.20 percent nickel (again, beyond the unalloyed levels). The barrier layer will have a diffusion layer extending from the barrier layer's inner surface (facing the fuel) to the barrier layer's interior (the interior being defined between the barrier layer's inner and outer surfaces). At the interior edge of the diffusion layer, there will be substantially no alloying elements beyond those normally present in unalloyed sponge or crystal bar zirconium (e.g., chromium--70 ppm or less; iron--500 ppm or less; and nickel--70 ppm or less). This will be the concentration at the interior edge of the diffusion layer. At the barrier layer's outer edge of the diffusion layer (the barrier layer's inner surface), the maximum concentration of alloying elements will occur. Preferably, the diffusion layer extends from the barrier layer's interface with the inner liner toward the interior covering at most about 10% of barrier layer's total width. This corresponds to about 8 micrometers of a conventional 75 micrometer barrier layer's total radial thickness. In more preferred embodiments, the diffusion layer has a thickness of at most about 5% of the barriers layer's total width. As will be discussed below, the diffusion layer is typically formed by a diffusion anneal which drives some of the alloying elements from the inner liner into the barrier layer. During this anneal step, some of the alloying elements in the outer circumferential substrate will also diffuse into the barrier layer, albeit at the substrate/barrier layer interface. This will result in the formation of two diffusion layers across the barrier layer in the radial direction. The alloying elements at the zirconium barrier layer's interface with the outer circumferential substrate are preferably present in concentrations of between about 0.03-0.40 percent iron, between about 0.01-0.20 percent chromium, and between about 0.01-0.20 percent nickel (all concentrations beyond the unalloyed levels). Because alloying elements can harden pure zirconium, it is important that the interior regions of the barrier layer (those interior to the diffusion layers) remain substantially unalloyed. This allows the barrier layer to remain sufficiently compliant to resist damage caused by the pellet-cladding interaction. Metallurgically bonded to the inside surface of the zirconium barrier 22 is the inner liner 23. As shown, the inner liner is the portion of the composite cladding closest to the nuclear fuel material 16. This layer provides some protection of the zirconium barrier from rapid oxidation should the fuel element interior come in contact with steam. Thus, the inner liner should be a relatively corrosion resistant material such as Zircaloy. However, modified Zircaloys and other corrosion resistant materials may also be employed. For example, the inner liner may be softer than conventional Zircaloy so that crack initiation and propagation on the inner surface of the cladding tube are minimized. See U.S. patent application Ser. No. 08/092,188, previously incorporated herein by reference. In an alternative embodiment, the inner liner may be made from an alloy designed to have strongly hydrogen absorbing properties. One such material is a zirconium alloy having a high concentration of nickel (e.g., up to 15% nickel). In some embodiments, the inner liner is so thin that it is completely consumed by interdiffusion with the barrier layer in a diffusion anneal. The resulting cladding contains a barrier layer having significant resistance to accelerated corrosion because of the increased alloying element concentration at the barrier layer inner region (where it is most susceptible to corrosion). The diffusion anneal also homogenizes the concentration distribution over the barrier layer's inner surface. (This advantage of the diffusion anneal also results when the inner liner is retained in the final cladding.) Thus, if there were any tears or other defects in the inner liner (that could provide a site for accelerated corrosion), the diffusion anneal causes the alloying elements to move into the barrier layer at these defects sites to protect against accelerated corrosion. Aside from the inner liner being completely consumed in a diffusion anneal, the product cladding tube is structurally similar to the three-layer cladding tube described above (i.e., the barrier layer will have diffusion layers at both of its edges). If the cladding tube contains an inner liner, that liner may be made from many different materials. For example, preferred low-tin inner liner compositions of this invention will be zirconium alloys (e.g., modified Zircaloys) having less than about 1.2% tin by weight. One class of suitable alloys include at least about 98% zirconium, up to about 0.24% iron and less than about 1.2% tin (all percents by weight). Some liner alloys will also contain between about 0.05 and 0.15 chromium and/or between about 0.03 and 0.08 nickel. Other additives may include niobium, bismuth, and molybdenum, as well as various other elements used in the art. Other preferred zirconium alloys have reduced oxygen concentrations. Generally, lower oxygen contents in the liner alloy translates to greater resistance to cracking. In commercially available Zircaloy, the oxygen concentration is made purposely high, about 1000 ppm by weight, so that the Zircaloy is sufficiently strong to withstand the stresses encountered by a cladding tube. Because the inner liners of the structures of this invention need not be particularly strong, the oxygen content of these liner can be reduced to values substantially below that of conventional structural alloys. Zircaloy inner liners of the present invention therefore preferably contain less than about 1000 ppm, more preferably less than about 800 ppm, and most preferably less than about 600 ppm oxygen by weight. Of course, the hardness of other, non-Zircaloy, zirconium alloys can be reduced by decreasing the oxygen and tin concentrations. In addition to the modified Zircaloys described above, relatively soft and corrosion resistant zirconium alloys suitable for the inner liners of this invention include the dilute iron-chrome alloys, the Zirlos (as described above), and modified versions of these alloys having reduced tin and oxygen contents. Dilute iron-chromium zirconium alloy liners preferably contain about 0.07 to 0.24% iron and about 0.05 to 0.15% chromium by weight. Such alloys are described in U.S. patent application Ser. No. 08/011,559 (attorney docket No. 24-NT-05309, filed on Feb. 1, 1993, naming Rosenbaum, Adamson, and Cheng as inventors, and assigned to the assignee of this application). Still other suitable alloys are the bismuth containing zirconium alloys disclosed in U.S. Pat. No. 4,876,064 (containing between about 0.5 and 2.5 weight bismuth as discussed above in connection with the substrate). Non-zirconium based alloys containing nickel (and iron) such as stainless steel and Inconel may also be employed. The inner liner should be sufficiently thin that microcracks are prevented from reaching critical depth. If a crack in the inner liner exceeds the critical depth, it could propagate beyond the inner liner and into the barrier and even the substrate. Preferably, the inner liner average thickness is between about 10 and 50 micrometers thick. It should be recognized, however, that thinner layers can be produced with slightly modified fabrication methods such as those employing vapor deposition techniques. In a particularly preferred embodiment, the inner liner is, on average, about 25 micrometers thick. In one example, the cladding tube total thickness is about 700 micrometers (approximately 28 mils), of which the inner liner or layer occupies less than 15 micrometers (approximately 0.6 mils) and the zirconium barrier occupies about 75 to 115 micrometers (approximately 3.2 to 4.7 mils). Referring now to FIG. 2, a cutaway sectional view of a nuclear fuel bundle or assembly 10 is shown. The fuel bundle is a discrete unit of fuel containing many individual sealed fuel elements or rods R each containing a cladding tube of this invention. In addition, the fuel bundle consists of a flow channel C provided at its upper end with an upper lifting bale 12 and at its lower end with a nose piece L and lower lifting bale 11. The upper end of channel C is open at 13 and the lower end of the nose piece is provided with coolant flow openings. The array of fuel elements or rods R is enclosed in channel C and supported therein by means of upper tie plate U and lower tie plate (not shown). Certain of the fuel rods serving to "tie" the tie plates together--thus frequently being called "tie rods" (not shown). In addition, one or more spacers S may be disposed within the flow channel to hold the fuel elements in alignment with one another and the flow channel. During the in service life of the fuel bundle, the liquid coolant ordinarily enters through the openings in the lower end of the nose piece, passes upwardly around fuel elements R, and discharges at upper outlet 13 in partially vaporized condition. Referring now to FIG. 3, the fuel elements or rods R are sealed at their ends by end plugs 18 welded to the fuel rod container 17, which may include studs 19 to facilitate the mounting of the fuel element in the fuel assembly. A void space or plenum 20 is provided at one end of the element to permit longitudinal expansion of the fuel material 16 and accumulation of gases released by the fuel material. A getter (not shown) is typically employed to remove various deleterious gases and other products of the fission reaction. A nuclear fuel material retainer 24 in the form of a helical member is positioned within space 20 to provide restraint against axial movement of the pellet column during handling and transportation of the fuel element. II. MANUFACTURE OF THE TUBING Various methods can be used to fabricate the cladding tubes of this invention. Suitable methods should produce a metallurgical bond between the substrate and the metal barrier and between the metal barrier and the inner liner. Typically, the barrier and inner liner are provided as cylindrical tubes or sleeves that are bonded to the inside surface of a hollow zirconium alloy billet (which forms the substrate in the final cladding). Preferably, the components are bound to one another by coextrusion, but other methods may be employed. For example, the components can also be bonded to the billet by hot isostatic pressing or explosive bonding. In another method, the barrier and inner liner sleeves are bonded to the billet inner surface by heating (such as at 750.degree. C. for 8 hours) to give diffusion bonding between the tubes and the billet. Prior to bonding (by, for example, extrusion), the barrier and inner liner sleeves preferably are joined to the billet at their ends by a bonding process such as electron beam welding in a high vacuum. Electron beam welding is a conventional process in which an electron beam is used to heat the ends of the cylindrical tubes until they fuse. Extrusion is accomplished by putting the tube through a set of tapered dies under high pressure at about 1000.degree. to 1400.degree. F. (about 538.degree. to 760.degree. C.). Suitable extruders are available from Mannessmann Demang, Coreobolis, Pa. After extrusion, the composite is subjected to a conventional annealing and tube reduction processes to produce a product known as a "tubeshell" which is available in specified dimensions and compositions from various vendors such as Teledyne Wahchang (Albany, Oreg. USA), Western Zirconium (A Westinghouse company of Ogden, Utah), and Cezus (France). To obtain the final tubing of the necessary dimensions, various manufacturing steps such as cold-working, heat treating, and annealing may be employed. One suitable method of tube reduction involves three passes of about 65 to 80% cold work (conducted with a Pilger mill) followed in each case by a stress relief or recrystallization anneal. The equipment and operating conditions necessary to carry out the various steps will be readily apparent to those of skill in the art, and are described in the following patent applications: (1) U.S. patent application Ser. No. 08/091,672, (2) U.S. patent application Ser. No. 08/215,456, entitled METHOD OF PREPARING FUEL CLADDING HAVING AN ALLOYED ZIRCONIUM BARRIER LAYER, fried concurrently herewith and naming Adamson et al. as inventors, and (3) U.S. patent application Ser. No. 08/215,457, entitled METHOD OF PREPARING FUEL CLADDING HAVING AN ALLOYED ZIRCONIUM BARRIER LAYER filed concurrently herewith and naming Marlowe et al. as inventors. Each of these applications is assigned to the assignee hereof and is incorporated herein by reference for all purposes. To form the alloyed barrier of this invention, a diffusion anneal is performed whereby some alloying elements from the substrate and inner liner are transported to the zirconium barrier layer to form a partially alloyed barrier layer. As will be apparent to those of skill in the art, the diffusion anneal can be performed with various commercially available pieces of equipment such as a vacuum furnace, an inert gas furnace, or an induction coil. Suitable vacuum annealing furnaces are available from Centorr Vacuum Industries of Nashua, N.H. The details of the processes having suitable diffusion anneals are provided in the above-mentioned U.S. patent application Ser. No. 08/215,456. However, it should be noted that the diffusion anneal should be conducted for a time and at a temperature that is appropriate for thickness of the barrier layer. In other words, the diffusion should be sufficiently controlled that the alloying elements do not diffuse across the entire barrier layer. Rather, the diffusion anneal should provide a diffusion layer as described above. The diffusion anneal can be performed at any stage in the process including at the tubeshell stage or after any cold work step. Usually, the anneal temperature will be between about 650.degree. and 1000.degree. C. and last for between about 5 minutes and 20 hours depending upon the barrier layer thickness. The composite tubing of this invention can be used to make nuclear fuel elements by first affixing a closure to one end of the cladding tube so that only one open end remains. The completed fuel element is then prepared by filling the cladding container with nuclear fuel material, inserting a nuclear fuel material retaining means into the cavity, evacuating the cladding tube interior, pressurizing the interior with helium, applying a closure to the open end of the container, and bonding the end of the cladding container to the closure to form a tight seal there between. Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. For instance, although the specification has described preferred zirconium alloy tubes, other shapes may be used as well. For example, plates and metal sections of other shapes may also be used. In addition, the Zircaloy-2 described above is an example of an alloy that can advantageously be used in the present invention. Some other zirconium-based alloys as well as other metal alloys having similar structures can in many instances also be used in the methods of this invention.
039309428	abstract	An illustrative embodiment of the invention provides for a space between the two barriers that ordinarily form the emergency containment system for a nuclear reactor. Tracks set within this space, and a television camera bearing trolley adapted to move on these tracks enables the surface of the inner containment structure to be thoroughly inspected at low cost.
	claims	1. A method for performance monitoring in a multiprocessing system, the method comprising:counting occurrences of a first hardware event in a first hardware event counter of a processor;counting occurrences of a second hardware event in a second hardware event counter of the processor;sampling the second hardware event counter after a specified number of occurrences of the first hardware event have been counted, and resetting the first and second hardware event counters, wherein a value corresponding to the sampled second hardware event is to be stored in a storage device, wherein both the first hardware event counter and the second hardware event counter of the processor are to be utilized for a particular process and/or thread without including contamination from events captured from other processes and/or threads. 2. The method of claim 1 wherein said first hardware event is a descriptor table load event. 3. The method of claim 2 wherein said first hardware event is a local descriptor table load event. 4. The method of claim 1 wherein said first hardware event is a segment register load event. 5. The method of claim 1 wherein said first hardware event is a memory load event from an address predetermined to trigger the sampling of the second hardware event counter. 6. The method of claim 1 wherein said first hardware event is a process identifier change event. 7. The method of claim 1 further comprising:recording the sampled second hardware event counter value with a process identifier value. 8. The method of claim 1 wherein said first hardware event is a thread identifier change event. 9. The method of claim 1 further comprising:recording the sampled second hardware event counter value with a thread identifier value. 10. A method for performance monitoring in a multiprocessing system, the method comprising:counting occurrences of a segment register load event in a first hardware event counter of a processor;counting occurrences of a second hardware event in a second hardware event counter of the processor;sampling the second hardware event counter after a specified number of occurrences of the segment register load event have been counted, and resetting the first and second hardware event counters, wherein a value corresponding to the sampled second hardware event is to be stored in a storage device, wherein both the first hardware event counter and the second hardware event counter of the processor are to be utilized for a particular process and/or thread without including contamination from events captured from other processes and/or threads. 11. The method of claim 10 further comprising:recording the sampled second hardware event counter value with a process identifier value. 12. The method of claim 11 further comprising:recording the sampled second hardware event counter value and the process identifier value with a thread identifier value. 13. An article of manufacture for performance monitoring in a multiprocessing system, the article comprising:a machine-accessible medium including data and instructions for performing context switch sampling such that, when accessed by a machine, cause the machine to:count occurrences of a first hardware event in a first hardware event counter;count occurrences of a second hardware event in a second hardware event counter;sample the second hardware event counter after a specified number of occurrences of the first hardware event have been counted, and reset the first and second hardware event counters, wherein both the first hardware event counter and the second hardware event counter of the processor are to be utilized for a particular process and/or thread without including contamination from events captured from other processes and/or threads. 14. The article of claim 13 wherein said first hardware event is a descriptor table load event. 15. The article of claim 14 wherein said first hardware event is a local descriptor table load event. 16. The article of claim 13 wherein said first hardware event is a segment register load event. 17. The article of claim 13 wherein said first hardware event is a memory load event from an address predetermined to trigger the sampling of the second hardware event counter. 18. The article of claim 13 wherein said first hardware event is a process identifier change event. 19. The article of claim 13, said machine-accessible medium including data and instructions such that, when accessed by the machine, causes the machine to:recording the sampled second hardware event counter value with a process identifier value. 20. The article of claim 13 wherein said first hardware event is a thread identifier change event. 21. The article of claim 13, said machine-accessible medium including data and instructions such that, when accessed by the machine, causes the machine to:recording the sampled second hardware event counter value with a thread identifier value. 22. A computing system comprising:an addressable memory to store data and machine executable instructions for performing context switch sampling;a processor including a first hardware event counter and a second hardware event counter, and being coupled with the addressable memory to access said machine executable instructions, wherein responsive to said machine executable instructions, said processor is to:count occurrences of a segment register load event in the first hardware event counter;count occurrences of a second hardware event in the second hardware event counter;sample the second hardware event counter after a specified number of occurrences of the first hardware event have been counted, and reset the first and second hardware event counters, wherein both the first hardware event counter and the second hardware event counter of the processor are to be utilized for a particular process and/or thread without including contamination from events captured from other processes and/or threads. 23. The computing system of claim 22 wherein responsive to said machine executable instructions, said processor is to:record the sampled second hardware event counter value with a process identifier value. 24. The method of claim 23 wherein responsive to said machine executable instructions, said processor is to:record the sampled second hardware event counter value and the process identifier value with a thread identifier value. 25. A computing system comprising:an addressable memory to store data and machine executable instructions for performing context switch sampling;a processor including a first hardware event counter and a second hardware event counter, and being coupled with the addressable memory to access said machine executable instructions, wherein responsive to said machine executable instructions, said processor is to:count occurrences of a first hardware event in the first hardware event counter;count occurrences of a second hardware event in the second hardware event counter;sample the second hardware event counter after a specified number of occurrences of the first hardware event have been counted, and reset the first and second hardware event counters, wherein both the first hardware event counter and the second hardware event counter of the processor are to be utilized for a particular process and/or thread without including contamination from events captured from other processes and/or threads. 26. The computing system of claim 25 wherein responsive to said machine executable instructions, said processor is to:record the sampled second hardware event counter value with a process identifier value. 27. The computing system of claim 25 wherein responsive to said machine executable instructions, said processor is to:record the sampled second hardware event counter value with a thread identifier value. 28. The computing system of claim 25 wherein said first hardware event is a descriptor table load event. 29. The computing system of claim 28 wherein said first hardware event is a local descriptor table load event. 30. The computing system of claim 25 wherein said first hardware event is a segment register load event. 31. The computing system of claim 25 wherein said first hardware event is a memory load event from an address predetermined to trigger the sampling of the second hardware event counter. 32. The computing system of claim 25 wherein said first hardware event is a process identifier change event. 33. The computing system of claim 25 wherein said first hardware event is a thread identifier change event.
061809519	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for irradiating a target material, and in particular, to a process for irradiation producing a constant dose of radiation at various depths within the irradiated material. 2. Description of the Related Art Controlled irradiation of target materials is a mature technology having many industrial applications. Important uses for irradiation include lithography in the fabrication of semiconductor devices, high-power magnification and imaging in the form of electron microscopy, cross-linking of polymeric materials, and sterilization of medical devices and foodstuffs. Each of these applications involve the generation of radiation from a source, followed by direction of this radiation to a target material. Emission of a variety of forms of radiation is commonly utilized, including electron beam, x-ray, and gamma radiation. Conventional irradiation processes suffer from an important disadvantage in that the dose of radiation delivered to an irradiated object varies over the thickness of the target material. FIG. 1 shows a typical depth/dose profile resulting from exposing a target material to conventional electron beam irradiation. FIG. 1 shows that the relationship between radiation dose and material depth is nonlinear. For example, the radiation dose is lower at the surface of the target material than at a depth X into the target material. In a conventional method of electron beam irradiation, the peak subsurface irradiation dose can be as much as 30-50% greater than the surface dose. While FIG. 1 depicts the depth/dose profile for electron beam irradiation, both x-ray and gamma radiation also exhibit a profile similar to that shown in FIG. 1. For electron beam irradiation, the non-linear character of the curve shown in FIG. 1 is attributable to the impact of high energy radiated electrons with low energy local electrons present in target surface regions. The initial impact of these high energy electrons with local surface electrons imparts energy to the local electrons, which then penetrate more deeply. The penetrating electrons in turn collide with local electrons positioned even more deeply within the target, displacing them further into the target material. As a result of this chain reaction, the impact of high energy electrons at the surface results in the shifting of maximum radiation concentrations to subsurface regions. However, below a depth X' in the target material, energy imparted to the target material becomes sufficiently diffused that local electrons no longer possess sufficient energy to penetrate further, and the radiation dose tails off. This nonlinear relationship between radiation dose and target material depth creates a number of problems. One problem is lack of predictability. Because of the nonlinear depth/dose relationship, in order to anticipate the expected radiation dosage engineers must resort to statistical computer programs utilizing Monte Carlo approximations. These approximations are complex, time consuming, and costly. Therefore, there is a need in the art for a method of irradiation that provides a linear relationship between electron dose and the thickness of the irradiated material. An even more important problem with conventional irradiation techniques is that subsurface regions can be expected to receive heavier doses of radiation than surface regions. For example, where electron beams are applied to trigger polymerization and cross-linking, the dose profile shown in FIG. 1 can lead to an uneven degree of polymerization and hardness at different depths within the material. This non-uniformity of cross-linking can create quality control and other problems. Similarly, where electron beams are applied to sterilize a material, variation of dose with depth can lead to nonuniform sterilization and the possibility of infection and other problems. In theory, the problem of variation in radiation dosing can be overcome by applying such intense radiation that even surface material regions receive sufficiently high doses. In practice however, this approach can cause a host of problems associated with over-irradiation of the subsurface regions. Perhaps most significantly, subsurface regions receiving heavier doses of radiation can begin to degrade. Moreover, accumulated heat from the over-irradiation can also affect temperature-sensitive target materials such as plastics or foodstuffs. In addition to problems with degradation and heat, excess electron beam irradiation needlessly consumes large amounts of power and imposes strain on expensive and difficult-to-maintain irradiation equipment. Therefore, there also is a need in the art for a method of electron beam irradiation that produces a relatively constant dose of electrons from target surface regions to subsurface target regions. SUMMARY OF THE INVENTION The present invention relates to a process for irradiation which results in a linear and substantially constant relationship between radiation dose and irradiated target material depth. Specifically, where a target material is disposed on a reel rotated about an axis perpendicular to the direction of sweep of a beam of radiation, the relationship between dose and material depth becomes linear. Moreover, by making the core of the rotating reel substantially transparent to the radiation, portions of the target material on the backside of the reel are also irradiated, producing a constant depth/dose profile. By varying certain irradiation parameters, a constant relationship between radiation dose and material depth can be achieved. A process for irradiating a target material in accordance with one embodiment of the present invention comprises the steps of providing a beam of radiation having an energy and a direction of scan sweep, and providing a reel having a center axis, the reel including a core substantially transparent to the beam of radiation. A target material having a thickness is disposed around the reel. The reel is rotated around the center axis, and the beam is directed at the target material such that the direction of scan sweep is substantially perpendicular to the center axis, whereby the beam of radiation encounters the target material on a frontside of the reel, passes through the core, and reencounters target material on a backside of the reel, such that the target material receives a substantially constant dose of radiation throughout its thickness. A method of optimizing an irradiation process in which a target material is rotated on a core substantially transparent to a beam of radiation in accordance with one embodiment of the present invention, comprises the steps of maintaining constant an energy of the radiation beam, a density of the target material, and a diameter of the core, and then varying a thickness of the target material to produce a substantially constant dose of radiation throughout the thickness of the target material. The features and advantages of the present invention will be understood upon consideration of the following detailed description of the invention and the accompanying drawings.
	summary
043572979	description	For the purposes of explanation, the preferred embodiment is described herein as it is incorporated into a pool-type liquid metal cooled fast breeder reactor. A side elevational view of such a reactor is illustrated in section in FIG. 1. It should be understood, however, that the present invention has application in both loop and pool-type nuclear reactors as well as reactors which are cooled by water, gas and liquid metal (sodium). The nuclear reactor illustrated in FIG. 1 includes a reactor core 4, a primary tank 6, a coolant circulating pump 8, and an intermediate heat exchanger 11. In the actual plant there are a plurality of circulating pumps and intermediate heat exchangers but only one of each is illustrated in FIG. 1. The sodium coolant is contained in the reactor in a cold pool 9 and in a hot pool 10. The hot and cold pools are separated by a horizontal structure 12 which is a structural and thermal barrier that extends horizontally across the reactor and contains a plurality of cylindrical pump wells 16. These pump wells shroud each pump from the heat of the hot pool. The free surface of the sodium in the hot pool is indicated by numeral 13 and the free surface of the sodium in the cold pool 17, FIG. 2 is located within the pump wells 16. Referring to FIG. 2, the primary containment for the sodium coolant and the cover gas is the primary tank 6. Since the reactor is a pool-type reactor, the primary tank is generally cup-shaped and has no penetrations through its side and bottom walls. The fission products are thereby contained within the boundaries of the primary tank at all times. The upper portion of the primary tank terminates in an upper cylindrical support skirt 20. The support skirt and in turn the entire reactor are supported at point 7 from the ledge in the reactor cavity wall. The cavity wall is fabricated from concrete and the reactor cooling system is designed so that the point of support 7 never exceeds 150.degree. F. The thermal insulating apparatus of the present invention includes a cylindrical metal liner 22, FIG. 2 located vertically along the inner side wall of the primary tank. The liner is the first thermal barrier to the hot sodium and is in direct fluid contact with the sodium in the hot pool. The purpose of the liner is to form, in combination with the reactor vessel wall, an impermeable boundary to the gas-filled annular space and thus provide a satisfactory gaseous environment for the reflective insulation. The liner also forms the side wall of a trapped gas space as described below. The liner is supported from the upper support skirt 20 by a cylindrically shaped member 23 having an L-shaped cross section as illustrated in FIGS. 2 and 5. The liner extends from the bottom of the L-shaped member 23 down to the supporting structure 26, FIG. 2, located below the horizontal structure 12. The configuration of the L-shaped member is determined by fabrication and assembly considerations. Referring to FIG. 2, between the liner 22 and the primary tank side wall 6 and a plurality of vertically oriented, reflective metal plates 28. These plates are radially spaced apart around the outside of the core of the reactor and each has an arcuate cross-section. These plates are illustrated in detail in FIGS. 5 and 9. The purpose of these reflective metal plates is to thermally insulate the side walls of the primary tank from the temperatures generated by the reactor. Referring to FIG. 9, the plates are vertically segmented into arcuate sections to permit the lateral thermal expansion. In addition, the plates each contain a plurality of indentations 29, FIG. 5 which preserve the stand-off spacing between adjacent plates. The indentations also reduce convective heat transfer between the plates by minimizing the circulation of inert gas and sodium vapor in the trapped gas space which is described in detail below. The vertically segmented cylindrical plates are circumferentially staggered as illustrated in FIG. 9 in order to prevent direct radiative heat transfer from the liner 22 to the primary tank through the vertical slots between the arcuate sections. The metal plates 28, FIG. 2 reduce the radiation heat transfer from the hot pool in the radial direction by presenting a large vertical surface area. The plates are dimensioned to minimize their thickness and to incorporate as many plates as possible into the space between the liner 22 and the wall of the primary tank 6. In one embodiment there are twenty-three reflective plates each 0.1" thick, and spaced apart 0.5". The plates have a 0.06" cold clearance and each arcuate section has a 4' vertical length. The resulting arrangement gives an effective thermal conductivity of between 0.3 to 0.6 BTU/H-ft-.degree.F. Referring to FIGS. 5 and 6, each reflective plate 28 has a rigid supporting member attached along its upper margin. The supporting members engage two T-shaped brackets 33. The T-shaped brackets are radially spaced around the reactor and are welded to the bottom of the L-shaped member 23. The supporting members along with the reflective plates hang from the T-shaped brackets and the spacing between the reflective plates is maintained by the thickness of the supporting members 31 and the indentations 29. Referring to FIG. 2, the primary tank 6, the upper support skirt 20, the L-shaped member 23, and the liner 22 together form a trapped gas annulus. The trapped gas annulus is open at the bottom, hermetically sealed at the top, and has an inverted U-shaped cross section. When the primary tank is filled with sodium, the trapped gas annulus contains within its boundary a bubble of inert gas which is supplemented during filling via the makeup line 35 described below. The bubble prevents the reflective plates 28 which are located within this annulus from coming into fluid contact with the liquid sodium. The purpose of this construction is to eliminate the conductive heat transfer between the reflective plates and the primary tank which would occur if the plates were submerged in sodium. The gas annulus is open at the bottom so that in the event that in-leakage of liquid coolant occurs, it will readily drain. The level of sodium within the trapped gas annulus varies with power level. The level is illustrated in FIG. 2 at 40% power 38 and at 100% power 38'. The free surface 17 of the sodium in the cold pool 10 is located within the pump well 16, FIG. 2 and a hydrostatic head is developed between the cold pool free surface 17 and the level of sodium in the bottom of the trapped gas annulus. The level of sodium in the annulus falls as the reactor power level increases because as the power level increases, the level of the free surface in the pump well decreases. The top of the reactor is sealed by a cover 14, FIGS. 1 and 2. The cover includes both insulation and radiation shielding and forms no part of the present invention. The open space between the bottom of the cover and the hot pool operating level 13 is the cover gas space which is filled with helium. Located along the side wall of the primary tank in the cover gas space is a series of vertically oriented, reflective metal plates 40. These plates are arranged in a triangular shaped array which is shown in detail in FIG. 7. These reflective plates are fabricated and operate in the same manner as the reflective plates 28, FIG. 5 described above. The reflective plates 40 are suspended by a series of T-shaped brackets 33', 33" which are welded to the bottom of the cover 14 as illustrated in FIG. 8. The primary purpose of these plates is to control the axial temperature gradient in the liner 22. The reflective plates 40 also supplement the larger reflective plates 28 in passively insulating the primary tank side wall from the temperatures generated by the reactor. These plates are positioned to insure that the temperature gradient from the operating level 13 to the point of support 7 is smooth and without excessive thermal stresses. The reflective plates 28, 40 in combination with the cover insulation establish the temperature profile illustrated in FIG. 3. There is an additional triangular array of metal plates 44 located adjacent to the liner 22 between the hot pool 10 and the cool pool 9. These metal plates, which are vertically oriented and extend around the circumference of the reactor, provide a variable resistance to thermal conduction and so reduce the temperature gradient between the hot pool and the cold pool. The plates in this set are fully immersed in the sodium in the cold pool and are therefore considerably less efficient thermal barriers than the reflective plates. Referring to FIGS. 1 and 2, the primary tank 6 is positioned within a guard tank 42. The guard tank is an emergency boundary to protect against any sodium leakage from the primary tank. The annular space between the primary tank and the guard tank is filled with an inert gas and is used for in-vessel inspection of the primary tank. The outside of the guard tank is insulated with conventional ceramic fibrous insulation and is cooled by a cavity heat-removing system (not shown). The trapped gas annulus formed by the side walls of primary tank 6, the bottom of the L-shaped member 23 and the liner 28 is placed into operation by purging the oxygen from the primary tank and filling the primary tank with an inert gas such as helium. Thereafter, sodium is added to the primary tank and it is filled to the operational level 13. During the process of filling the primary tank, the sodium traps a bubble of helium in the annulus. After filling the primary tank, the level of sodium in the annulus is adjusted by adding helium through a make-up line 35, FIGS. 2, 4. During operation, the level of sodium in the annulus is monitored by measuring its pressure through the line 36. To minimize the number of penetrations through the reactor cover 14, the monitoring line 36 is located inside of and coaxial with the make-up line 35. If the level of sodium in the trapped gas annulus falls excessively, the helium in the annulus is vented through a vent line 37. The vent line directs the helium up the side wall of the primary tank to a point located just below the hot pool operating level 13. The vent line prevents bubbles of helium from being drawn into the circulating pump 8, FIG. 1, and thereafter flowing through the reactor and causing reactivity perturbations. It should be understood that the apparatus described above constitutes a passive thermal insulating system. The apparatus does not require any energy input from the reactor and does not degrade the efficiency and performance of the reactor. It should further be understood that this apparatus is used in combination with the insulation on the outside side walls of guard tank 42, FIG. 1 and a reactor cavity heat removing system (not shown). The temperature gradient from the sodium hot pool 10 to the guard tank 42 can be altered by adjusting both the amount of insulation used inside of the primary tank and on the outside of the guard tank. By proportioning this insulation any primary tank temperature or temperature gradient along the side wall of the primary tank can be attained. Thus, although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.
	summary
	description	The present invention relates to a control device used in various plants, such as a nuclear plant, a chemical plant and the like. Some control devices such as a safety interlock or the like are installed in a nuclear plant. The safety interlock carries out emergency shut down of the nuclear reactor at the time of abnormalities, or starts automatically engineered safety systems such as an emergency core cooling system or the like. For example, the emergency core cooling system in a boiling water reactor of the electric power plant can be started automatically, or can also be started by the manual operation of a plant operator, if the water level of a nuclear reactor falls abnormally or the pressure of a containment vessel rises abnormally. Boolean value such as TRUE or FALSE are made to correspond to arbitrary process signals to perform logical judgment for the pump starting of the emergency core cooling system. Conventionally such logic realized by hardware such as comparator, relay and timer. Recently such logic realized by programmable controller (PLC; Programmable Logic Device) using CPU with development of computer technology. It is known Operating System (OS) designed for such PLC used for the safety interlock of a nuclear power generation plant, having a function of input/output of a process signal, periodic execution of program, execution mode of communicative management, and a self-diagnosis of under initialization and execution (for example, non-patent literature 1). On the other hand, some trial also conducted to realize such logic by semiconductor device such as FPGA (Field Programmable Gate Array) (for example, patent documents 1-4). According to the FPGA, vendor of the safety interlock can be constructed logic in their discretion, without depending on the vendor of a semiconductor. Further, logic change is comparatively easy if the FPGA is used SRAM type or flash type. FPGA can perform operation of the Boolean value on the hardware gate directly. That FPGA is unnecessary loading of an operation command and decoding like in PLC, and also unnecessary an OS. Further, the directly wiring among the FPGA realizes high efficiency in accessing the Boolean value as an operating object, compare with PLC loading the Boolean value from RAM or storing them to RAM. Thus the FPGA performs processing by the assigned dedicated circuit, and then processing of the Boolean value can be efficiently performed rather than CPU. [Patent documents 1] JP2005-249609A [Patent documents 2] JP2006-236214A [Patent documents 3] JP2009-522644A [Patent documents 4] JP2003-177806A [Non-patent literature 1] EPRI, TR-107330, “Generic Requirements Specification for Qualifying a Commercially Available PLC for Safety-Related Applications in Nuclear Power Plants” As mentioned above, FPGA can operate logical processing such as the Boolean value efficiently rather than CPU. But FPGA cannot operate numerical processing efficiently enough. Indeed FPGA is theoretically possible to execute the numerical operation for numerical comparison. But in this case tens times or more gate is needed compared with the case of logical operation. For this reason, if it is going to perform all the numerical operations in the safety interlock by FPGA, a hardware scale becomes large with assignment of a dedicated circuit, and it is not economical. FPGA have several kind of mounting method on semiconductor such as SRAM type, flash type, and anti-fuse type. Anyone of these mounting methods of FPGA, working speed of the circuit itself is very lower comparing with the speed of CPU. The above mentioned content derives from the ability of FPGA to compose logical construction after manufacturing semiconductor. Although OS of PLC is simplified in comparison with general-purpose OS, it has a certain amount of complexity by mounting the self-diagnostic function, the communication function, and the maintenance function. For this reason, burden of the activity become increase for guaranteeing quality of OS of PLC such as accumulation of sufficient operation track record, and the verification and a validity check (V&V). For example, if OS of PLC operates the program code of a diagnostic function accidentally during the operation in execution mode, it may change a program or a constant and will cause malfunction. In general-purpose OS, in order to prevent referring incorrect memory, mounted memory protection function performs error handling by interruption when the memory is referred incorrectly. However, mounting such a memory protection function makes OS complicate, and brings risk of new malfunction, and increases the burden of V&V. The present invention has been made in view of the circumstances, and an object of the present invention is to provide the control device having simple configuration, excellent in the whole processing efficiency, and excellent in stability of operation. The embodiment of present invention provides a control device includes: an input portion for inputting a process signal transmitted from a plant; a numerical processing part for outputting a Boolean value evaluating normal/abnormal of the process signal by an numerical processing based on a program; and a logical processing part for a logical processing of the Boolean value based on a logic circuit and then outputting a control signal of the plant for a safety protection operation. According to the control device concerning the embodiment of present invention, a control device having simple configuration, excellent in the whole processing efficiency, and excellent in stability of operation is provided. (The First Embodiment) Hereafter, the embodiment of the present invention is described with reference to the attached drawings. As shown in FIG. 1 first embodiment of the control device 10 (henceforth “safety interlock 10”) relating safe protection of the plant includes: a numerical processing part 11 provided with the function of CPU, ROM and RAM; a manual operation part 12 for a plant operator to handle; an input portion 13 inputs the process signal T transmitted from a plant and then memorize temporarily; an output portion 14 memorizes the operation result of the CPU temporarily and then output to a logical processing part 20; and a watch dog timer 15. Among the components of the safety interlock 10 such as ROM, RAM, the manual operation part 12, the input portion 13 and the output portion 14 are arranged on the address space of CPU via bus 19. Therefore, CPU can uniquely access the data on RAM, the input portion 13, and the output portion 14 by specifying the address on an address space. The input portion 13 inputs the process signal T transmitted from various sensors installed in the plant and then holds it temporarily. If the process signal T is originally an analog signal, the process signal T is inputted into input portion 13 after being digitized by the A/D converter (not shown). The process signal T includes the numerical signal expressing physical quantity such as temperature, pressure, flow, flow velocity, voltage, current, the degree of valve-opening, and dose of radiation, etc. and Boolean value expressing ON/OFF of a pump, opening/closing of a valve, ON/OFF of a pressure switch, ON/OFF of a manual operation signal, etc. concretely. The control signal from other process control equipments is also included. The output portion 14 holds temporarily the Boolean value which is the operation result of the numerical processing part 11 mentioned later, and transmits it to the logical processing part 20. The input portion 13 and the output portion 14 having a buffer function, by using a dual port memory for example, inputting the process signal T from the exterior without applying excessive load to CPU, and the operation result data from CPU is transmitted to the logical processing part 20. The input portion 13 has a bit showing whether the logical processing part 20 is a processing state or a non-processing state, and CPU scans this bit to check the logical processing part 20 is a non-processing state (FALSE), and then starts the numerical processing in the part 11. The output portion 14 has a bit showing whether the numerical processing part 11 is a processing state or a non-processing state, if in the non-processing state, CPU changes the setting of this bit into FALSE from TRUE to transmit the temporarily held Boolean value for the logical processing part 20 and then start logical processing. The numerical processing part 11 outputs the Boolean value evaluating normal/abnormal of the process signal T by the numerical processing based on a program. Then the Boolean value is transmitted to the logical processing part 20 after temporarily memorized in the output portion 14 via the bus 19. The numerical processing part 11 starts the numerical processing of the next inputted various process signals T after the logical processing of the Boolean value was completed in logical processing part 20. The numerical processing part 11 performs the numerical processing of the various process signals T sequentially, and then finally outputs an operation complete signal. ROM (Read Only Memory) is a nonvolatile memory storing the program and the constant to perform a numerical operation. Then the program and the constant stored in ROM will read into RAM when the safety interlock 10 boot-up. The constant includes the threshold value for judging whether which Boolean value of TRUE or FALSE is made to apply for the inputted process signal T. The program contrasts the inputted process signal T and its corresponding threshold value, and then output either a TRUE signal (1) or a FALSE signal (0). RAM (Random Access Memory) is a volatile memory reading and writing data freely to make CPU perform numerical processing according to the resident program and constant read from ROM, and then memorizes the operation result in CPU temporarily. CPU performs next numerical processing to the process signal T memorized temporarily in the input portion 13 according to the RAM-resident program and then makes the operation result hold in the output portion 14. CPU performs these series processing with the cycle of several 10 milliseconds in consideration of the response time required in the safety protection operation. Next, the numerical processing in CPU is explained concretely. CPU starts the processing with defined cycle according to an internal clock. Here, nuclear reactor water level signal T1 is taken up as process signal T, and applying the threshold value L for normal/abnormal judgment of the water level. Then suppose that each data is assigned to the following address. water level signal Taddress 500 to 501stthreshold value Laddress 3000 to 3001stdecision result5th-bit at number 2001st The numerical processing for deriving the decision result is performed by the next program. Here, R0 and R1 are the registers of CPU and X register is a register for bit processing in CPU. A1: LD R0, 500;500-501st data is loaded to R0.A2: LD R1, 3000;3000-3001st data is loaded to R1.A3: SUB R0, R1;R0-R1 (nuclear reactor water level - L)A4: BGE A7;If results are positive and the water level ≧L, branch to A7.A5: LDX #1;‘1’ is put into X register.A6: BRA A8;branch to A8.A7: LDX #0;‘0’ is put into X register.A8: STX 2001:5;value in X register is stored in the 5th-bitat 2001st. This program has a simple structure with start processing from command (A1) and end processing to command (A8) certainly without repetition on the way, though the branching is included in the command (A4, A6) setting up an output address from the decision result of the size relation. When performing comparison numerical processing to the plurality of input signal such 500 process signals T, placing the 500 above-mentioned program with exchanging the address of the input signal (operand of A1), the address of the threshold value (operand of A2), the size relation between the input signal and the threshold value (operator of A4), and the address of the output place of an operation result (operand of A8) and then processes sequentially. For this reason, in order to operate the plurality of process signals T, the program of the length is arranged proportional to the number of these process signals T, nevertheless complexity does not increase and prediction of processing time is also attained. When the numerical processing part 11 completes a numerical processing, CPU makes the processing result memorize in the output portion 14 temporarily. Then the CPU sets the bit on the output portion 14 FALSE (non-processing state), the bit shows whether the CPU is a processing state or a non-processing state. This sequence is realized to mount a writing program for the output portion 14, on the tail end of the above-mentioned plural arranged programs. CPU also has the diagnostic function like PLC explained in the “Background Art” in addition to the above-mentioned program. As mentioned above the numerical processing has simple sequential processing that it is easily verifiable existence of an access error of the memory under execution by the diagnostic function. It is easy to design exclusive-purpose CPU applied with the safety interlock 10 in this embodiment, because a little function is demanded compared with general-purpose CPU. The watch dog timer 15 is constituted independently from the numerical processing part 11 and the logical processing part 20. The watch dog timer 15 reports the timeout information a period to end from a start of the logical processing part 20 or a period to end of the logical processing part 20 from a start of the numerical processing part 11 exceeds a setting time. Accordingly the operation state of CPU and the logical processing part 20 can be diagnosed with high reliability, and contributing an improvement of the plant safety. The watch dog timer 15 is realized by one shot multi-vibrator, for example. The watch dog timer 15 is initialized synchronizing with the start or finish of the numerical processing part 11 or the logical processing part 20. Then the watch dog timer 15 is set up to time out somewhat long period rather than the processing cycle of logical processing part 20 or combining the processing cycle of the logical processing part 20 and the numerical processing part 11. For example, it will be set up to time out in 30 ms, if a processing cycle is 25 ms. Thereby the watch dog timer 15 is time-out to notify the abnormalities of the safety interlock 10 when the periodic processing of the numerical processing part 11 or the logical processing part 20 is stopping or delaying abnormally. The numerical processing part 11 and the logical processing part 20 starts their own processing by checking other's processing state mutually that one side stops will also stop another side. Therefore, even if processing of either one of CPU and the logical processing part 20 stops, abnormalities are notified by the watch dog timer 15. As shown in FIG. 2A, the logical processing part 20 contains some logic element such as 1st-OR gate 21, 2nd-OR gate 22, NOT gate 23, and AND gate 24. The logical processing part 20 is realized by FPGA (Field Programmable Gate Array) to perform operation of the Boolean value and time delay of the Boolean value. The logic element of the FPGA is wired by programming. The logical processing part 20 inputs the Boolean value currently held at the output portion 14 (FIG. 1), processes it based on the logic circuit and then outputs the control signal related the safety protection operation of the plant. Here the logical processing part 20 is illustrated the logic for outputting the control signal which starts the pump P of the reactor core emergency cooling system (not shown). The manual starter 12b starts the safety protection operation by the manual operation of a plant operator, even if a case the process signal T from the plant shows normalcy. The manual stopper 12a stops the started safety protection operation by the manual operation of the plant operator. The function of the manual starter 12b and the manual stopper 12a are included in the manual operation part 12 (FIG. 1), FALSE is normally outputted, and the output changes to TRUE by the manual operation of the plant operator. However, the manual starter 12b and the manual stopper 12a have a switch structure which is not simultaneously set to TRUE. The judging means 11a and 11b are shown as functional elements in the numerical processing part 11, expressing each program (above-mentioned A1-A8 command) which judges normal/abnormal of each process signal T. The judging means 11a performs judgment of the process signal T1 from the water level sensor which detects the nuclear reactor water level. If the nuclear reactor water level detected by the water level sensor is lower than preset value L, abnormal judgment will be done to output TRUE, and incase another detecting result, normal judgment will be done to output FALSE. The judging means 11b performs the judgment of the process signal T2 from the pressure sensor which detects the pressure of a containment vessel. If the pressure detected by the pressure sensor is higher than preset value P, abnormal judgment will be done to output TRUE, and incase another detecting result, normal judgment will be done to output FALSE. It assumes detecting the internal pressure of the containment vessel when leakage of the reactor pressure vessel occurs to raise the internal pressure of the containment vessel. As mentioned above, if the output portion 14a sets a bit FALSE showing the part 11 completed the numerical processing, transmits the currently held Boolean value to the logical processing part 20 for performing the logical operation. Simultaneously the input portion 13 sets the bit TRUE showing the logical processing part 20 is currently performing. Here, it is usual to make TRUE and FALSE of the Boolean value correspond to the high potential and low potential of electric signal, respectively. However, this correspondence may be made reverse from a viewpoint of fail-safe. Several or tens of valves are provided in addition to the pump P shown in FIG. 2A in the reactor core emergency cooling system (not shown) which works when the safety interlock 10 (FIG. 1) perceived abnormalities. The logic shown in FIG. 2A is a part of the logic scale of the whole safety interlock 10. Since the reactor core emergency cooling system is multiplexed so that the real logic scale is several hundred times of the logic shown in FIG. 2A. When using flash type FPGA, in order to change the logic design of FPGA, the high voltage is needed rather than the usual operating voltage. In order to the logic design changeable, the logical processing part 20 considered as the removable, after removing the part 20 the logic design is changed using a exclusive tool. By considering such a structure, the risk of exchanging the logic design of FPGA by malfunction can be eliminated. Otherwise instead of considering above removable design, a logic change function is provided in the safety interlock 10 and then the logical processing part 20 make the logic change by high voltage supply from the outside. While, the logical processing part 20 can also be realized using the anti-fuse type which cannot change logic, SRAM type FPGA and ASIC. A delay circuit (not shown) is provided after the judging means 11a and 11b. The delay circuit acts, for example, input TRUE into a logic gate (here 1st-OR gate 21) when the TRUE continues for a definite period of time (e.g. 30 seconds), even if the Boolean value changes from FALSE to TRUE by the water level sensor T1 shows the water level falls below L. This delay circuit is easily realizable by mounting a counter circuit with a reset function and counting up a clock after the input signal is set to TRUE. But it is little use in frequency of the time delay of the Boolean value, though a circuit becomes complicated and many logic elements are used. The logical processing time of the Boolean value is decided by the logic gate delay time and the wiring delay time in FPGA. In the case of flash type FPGA, the OR gate delay time for two signals calculation is 1 or less nanosecond, and the wiring delay time is smaller than that. The logical processing part 20 configured with FPGA having synchronous design, and can process the logic gates circuit shown in FIG. 2A combined about 100 steps with one clock under the operation condition of about 10 MHz clocks. However, the clock frequency of FPGA is considered that the malfunction with the signal delay does not cause, that it is not necessarily to perform all of binary operation and delay processing of the Boolean value with one clock. After ending all binary operation and delay processing of the Boolean value, the logical processing part 20 outputs the control signal to the reactor core emergency cooling system (not shown), and then the input portion 13 set the bit (FALSE) showing the logical processing part 20 completes the job. The 1st-OR gate 21 inputs the Boolean value originated in the various process signals T1 T2 and the Boolean value originated in a manual starter 12b of the safety protection operation. Besides 1st-OR gate 21 outputs FALSE if all the inputted Boolean values are FALSE, while outputs TRUE if at least one of the inputted Boolean values is TRUE. Although FIG. 2A is illustrated three Boolean values are inputted in 1st-OR gate 21 as an example. As shown in FIG. 4, in practice, 1st-OR gate 21 can also inputs and processes the Boolean value K1 K2 originated in the control information of other devices (not shown) and another Boolean value T1 T2 - - - TN originated in the tens to hundreds of process signals. As shown in FIG. 4, 1st-OR gate 21 composed plural steps of OR elements, according to the number of Boolean values to input. The processing time of these plural steps of OR elements also becomes longer according to this number of steps, but usually taken several nanoseconds to tens of nanoseconds. 2nd-OR gate 22 inputs the Boolean value outputted from 1st-OR gate 21 and a feedback signal from AND gate 24, and then outputs a signal to AND gate 24. Then 2nd-OR gate 22 will continue outputting TRUE if once inputted FALSE from 1st-OR gate 21, even if TRUE is inputted later from 1st-OR gate 21. NOT gate 23 reverses the Boolean value outputted from the manual stopper 12a. NOT gate 23 normally outputs TRUE to AND gate 24 since the manual stopper 12a is normally outputting FALSE and then FALSE will be outputted to AND gate 24 if the manual stopper 12a operates. AND gate 24 outputs TRUE if all the inputted Boolean values set to TRUE, and outputs FALSE if at least one of the inputted Boolean values set to FALSE. Thereby, AND gate 24 normally outputs FALSE, because normally inputs TRUE from NOT gate 23 and normally input FALSE from 2nd-OR gate 22. Then the input signal from 2nd-OR gate 22 changes to TRUE, and AND gate 24 outputs TRUE to output the control signal for starting the pump P. Then TRUE outputted from AND gate 24 may return to 2nd-OR gate 22 as mentioned above, AND gate 24 will continue inputting TRUE from 2nd-OR gate 22. If the manual stopper 12a goes into function, AND gate 24 inputs FALSE from the NOT gate 23 and then outputs FALSE to output control signal for stopping the pump P. Based on FIG. 5 (suitably refer to FIG. 1) the first embodiment of the operation of the safety interlock 10 is explained. First, when the safety interlock 10 is turned on, the program and constant (threshold value) stored in ROM will be read into RAM to boot up (S11). Then setting the bit TRUE on the input portion 13 showing the numerical processing part 11 is performing (S12), and then the numerical processing mentioned later is operated (S13). The numerical processing (S13) is started after checking of logical processing is set to FALSE (S17). After complete of the numerical processing in the part 11, setting the bit will exchange from TRUE to FALSE on the input portion 13 (S14). Then setting the bit TRUE on the output portion 14 showing the logical processing part 20 is performing (S15), and then the logical processing mentioned later is operated (S16). The logical processing (S16) is started after checking of numerical processing is set as FALSE (S14). After complete of the logical processing in the part 20, outputting the control signal concerning the safety protection operation of a plant and then setting the bit will exchange from TRUE to FALSE on the output portion 14 (S17). When passing the time set up with the watch dog timer 15 (S18 No), setting the bit TRUE on the input portion 13 (S12), and then the numerical processing by the part 11 is operated (S13). Thereby, the loop of (S12)-(S17) is repeated with the cycle related with the setting period of the watch dog timer 15. The reset timing of the watch dog timer 15 may be sufficient any one point of the start point (TRUE setup point) and the end point (FALSE setup point) of the numerical processing operation (S13) and the logical processing operation (S16). On the other hand, if FALSE of logical processing is not set up within the setting period of the watch dog timer 15, it is regarded as timeout (S18 Yes) and the processing error signal will be outputted (S19). Thus, it is hardly the processing error signal outputted because the numerical processing operation (S13) and the logic operation process (S15) are not operated simultaneously. In case such the processing error is needless to consider, the numerical processing operation (S13) and the logical processing operation (S16) may be operated without checking FALSE setup with the logical processing (S17) and a FALSE setup with the numerical processing (S14). Based on FIG. 6, operation of the numerical processing part 11 is explained. In a series of flows of operation shown in FIG. 5, when the operating in the numerical processing part 11 is started (S13), the process signal T from the plural various sensors (N pieces) is inputted into the input portion 13, and then each loaded to CPU in turn (S21). Then CPU executes the command mentioned above A1-A8, compare with the loaded process signal T and the corresponded threshold value L (S22, S23), and then the normal/abnormal judged Boolean value (FALSE/TRUE) is set to the output portion 14 (S24, S25). The exemplified command above A1-A8 is executed in order from n=1 to N toward to N process signals Tn (T1-TN) (S26 No), and then complete the numerical processing operation (S26 Yes). Although FIG. 6 the repeated loop exists in S26, but an actual operation program can constitute sequentially the N operation programs correspond to the N process signals T, and can also exclude the repetition processing on a program. Based on FIG. 2A, FIG. 2B, FIG. 3A, and FIG. 3B explain the operation of the logical processing part 20 (operational flow of S16 in the whole flow of FIG. 5). First, as shown in FIG. 2A, all the Boolean values of each means 12a, 12b, 11a, and 11b stored in the output portion 14 are FALSE under the normal operating state there is no abnormalities in the plant. Then the logical processing part 20 output FALSE to output the control signal for stopping the pump P. As shown in FIG. 2B, suppose that abnormalities occurred in the plant, the plant signal T2 of the pressure sensor is judged abnormal, and the judging means 11b set Boolean value to TRUE, for example. Then, 1st-OR gate 21 inputs TRUE to output TRUE, and 2nd-OR gate 22 inputs TRUE to output TRUE as well. Since NOT gate 23 normally output TRUE, if TRUE is outputted from 2nd-OR gate 22, AND gate 24 inputs these two TRUE and output TRUE to output the control signal for starting the pump P. FIG. 3A shows the states that the plant signal T2 of the pressure sensor is recovered normally and the judging means 11b came to output FALSE. However, TRUE currently outputted from AND gate 24 returned to the input side of 2nd-OR gate 22, AND gate 24 continues outputting TRUE to output the control signal for starting the pump P. FIG. 3B shows the condition that the manual stopper 12a outputs TRUE to stop the pump P by manual operation of the plant operator. Accordingly the Boolean value outputted from the NOT gate 23 will change to FALSE, and AND gate 24 will output FALSE to output the control signal for stopping the pump P. In this embodiment mentioned above, the numerical processing part 11 which operates the numerical process efficiently, and the logical processing part 20 which operates the logical process efficiently are combined. Therefore the whole operation is performed efficiently, compared with the case where the logical operation is made also with CPU alone or where the numerical operation is incorporated also in FPGA As a result, the safety interlock 10 is configured with cheap parts and the reliability thereof is improved because there is no necessity of using high performance CPU with high fever. Besides simplifying CPU processing and simplifying the composition of the software including the diagnostic function. (The Second Embodiment) FIG. 7(A) shows the block diagram of the safety interlock 10 according to a second embodiment. Here, among the components described in FIG. 7(A), same reference numerals will be given to components common to those described in FIG. 1, and description thereof will be omitted by citation of the above-mentioned description. The safety interlock 10 according to this second embodiment further having some functions contrasted with the first embodiment; a function for calculating the hash value of the program and the constant at the numerical processing part 11; a function for the output portion 14 outputting the calculated hash value with the Boolean value to the logical processing part 20; a storing means 16 for storing the outputted hash value; a function for the logical processing part 20 evaluating the identity of the stored hash value and the next outputted hash value and sending an error signal together with an alarm in case inharmonious; and means 17 for alarm resetting to stop the alarm manually. The hash value storing means 16 is realized as external RAM of the logical processing part 20, and also be realized as an internal circuit of the logical processing part 20. The alarm resetting means 17 is realized also as a push button provided in the manual operation part 12 for example. A hash value calculation program calculates the hash value of the program and the constant resided in RAM, and sets the result to the output portion 14. These program and constant will not change after initialization of the safety interlock 10 and start processing of the execution mode. Therefore, exchanging the hash value means a memory error, a program error, or an intentional change with malicious, and the abnormal condition occurred anyway. As a calculation method of a hash value, SHA (hash function which U.S. National Institute of Standards and Technology published), and MD5 (hash function released to IETF RFC1321) can be used. Otherwise a cyclic redundancy code (CRC) inspection etc. can be used. In a viewpoint of cyber security, it is desirable a cryptography hash function such as SHA or MD5. Logic processing part 20 reads a new hash value from the output portion 14 for every cycle of starting logical processing to compare with a last hash value recorded on the storing means 16, and replaces the last hash value by the new hash value. Then alarm is generated if the result of comparison of the hash value is not in agreement. At the time of starting of the safety interlock 10, the alarm is generated because the last hash value in the storing means 16 and the new hash value calculated in the numerical processing part 11 are not in agreement. The plant operator resets the alarm by the resetting means 17 at the time of starting of the safety interlock 10. Thereby, the plant operator can be checked about whether the hash value comparison function operates normally. When the alarm generated during the execution mode, the operator can recognize that the program or the constant memorized in RAM is changed. The means for setting or resetting the alarm is easily realized by the flip-flop. FIG. 7B shows the reset circuit diagram of the alarm which can also prevent first-time alarm generating. The reset circuit diagram includes; the flip-flop 25 to be reset when the new hash value read from the output portion 14 corresponds with the last hash value recorded on the storing means 16; and AND gate 26 executing AND calculation of the reversal output of the flip-flop 25 with the reversal of the hash value corresponding signal. The first-time alarm does not generate because the reversal output of flip-flop 25 is not set to TRUE unless the hash value corresponds at least once. Based on FIG. 8 the second embodiment of the operation of the safety interlock of the plant is explained. Here the flow (S11) to (S19) of FIG. 8 in the second embodiment is the same as the flow (S11) to (S19) of FIG. 5 in the first embodiment, the explanation thereof is omitted. According to a second embodiment, calculation of the hash value of the program and the constant are performed in parallel (S31) with the logic operation process (S16). Then the calculated hash value is stored in the output portion 14 together with the numerical processing operation result carried out in the next cycle. If TRUE declared starting logical processing is set to the output portion 14, the new hash value is called (S32), and compare with the last hash value, and will be overwritten save at the storing means 16. If the new hash value agree with the last hash value (S33 Yes), it is judged with having no abnormalities, and then the operation flow (S16)-(S18 No) is repeated. On the other hand, if the new hash value do not agree with the last hash value (S33 No), it is judged with occurring abnormalities, and then error is outputted (S19). As a modification, calculation of the hash value (S31) may not be performed in parallel with the logic operation process (S16), but may be performed in series before or after of the numerical processing operation (S13). The calculation of the hash value (S31) may also be performed by hash value calculating means 18, as shown in FIG. 7A, provided for exclusive use besides performed by CPU. The program and the constant resided in RAM may be contrasted the same stored in ROM directly, without performing calculation of the hash value (S31). According to the second embodiment, it is possible to detect an error occurred in the program and the constant which are indispensable to CPU processing. Moreover malicious change is certainly detectable. (The Third Embodiment) FIG. 9A shows the block diagram of the safety interlock 10 according to the third embodiment. FIG. 9B shows the packet structure of the plant signal T. Here, among the components described in FIG. 9A, same reference numerals will be given to components common to those described in FIG. 1, and description thereof will be omitted by citation of the above-mentioned description. In the third embodiment, the various process signals T (T1-TN) are multiplexed with a cyclic code; and further comprising: a receiver 41 for receiving the multiplexed process signal T and then checking an error from the cyclic code; and a timer 42 for holding the checked process signal in the input portion 13 for a predetermined time interval. The receiver 41 is realizable by the hardware which used FPGA or ASIC. The receiver 41 receives the process signal T of the packet multiplexed at the remote I/O station (not shown). The packet form as shown in FIG. 9B, at the header of the packet contains the cyclic code for detecting the error of the signal. Behind the header, various process signals T1-TN are stored as 16 bits data each, and EOD code is formed in the termination. The receiver 41 saves the various process signal T1-TN at the same number of register provided inside. Then the receiver 41 calculates the cyclic code from the signal saved at the register, compared with the cyclic code contained in the header, and then notifies an error if not in agreement. The timer 42 sends a signal to receiver 41 every 25 ms, if the error is not detected in comparison with a cyclic code, the various process signals T1-TN saved at the register of the receiver 41 will be written in the input portion 13 in order after the address set beforehand. Then the various process signal T1-TN written in the input portion 13 will be performed the numerical processing in the part 11, after that will be performed the logical processing in the part 20. According to the third embodiment, also in the safety interlock composed using a remote I/O station for cable reduction, CPU can concentrate on numerical processing operation without applying a new load. Even when abnormalities are occurred in the remote I/O station, the influence can be made into the minimum. (The Fourth Embodiment) FIG. 10 shows the block diagram of safety interlock 10 according to the fourth embodiment. Here, among the components described in FIG. 10, same reference numerals will be given to components common to those described in FIG. 1, and description thereof will be omitted by citation of the above-mentioned description. Back plane 50 has plural connectors (not shown) in which plural extended boards 51, 52, 53, and 54 are inserted, respectively, and these connectors are formed on the bus data exchangeable mutually. The manual operation part 12 is mounted on the first extended board 51. The input portion 13 and the controller (not shown) for transmitting data to back plane 50 are mounted on the second extension board 52. The numerical processing part 11 and the first transmission-reception means 55 are mounted on the third extension board 53. The second transmission-reception means 56, the logical processing part 20, and the watch dog timer 15 are mounted on the fourth extension board 54. The input portion 13 transmits the inputted process signal T to the first transmission-reception means 55 on the third extension board 53 via the bus of the back plane 50. Then the transmitted process signal T is recorded on the address in RAM defined beforehand, the decision of normal/abnormal is made in the numerical processing part 11, and the Boolean value corresponding to the decision result is outputted. The first transmission-reception means 55 and the second transmission-reception means 56 exchange data to the parts mounted on other extended boards mutually via the bus on the back plane 50. The Boolean value outputted from the numerical processing part 11 is transmitted to the second transmission-reception means 56 on the fourth extension board 54 via the first transmission-reception means 55 and the bus on the back plane 50. The Boolean value transmitted to the fourth extension board 54 is operated in the logical processing part 20, and outputs the control signal concerning the safety protection operation of a plant. The second transmission-reception means 56 transmits the end signal to the numerical processing part 11 via the first transmission-reception means 55 and the bus on the back plane 50. The end signal indicates that the processing in the logical processing part 20 was completed. The end signal is recorded on the determined address on RAM, and is used as conditions of the numerical processing in the part 11. Further not only the end signal but also the processing result of the logical processing part 20 can be used as conditions of the numerical processing by feed back to the numerical processing part 11 via the transmission-reception means 55, 56. 10 safety interlock (control device) 11 numerical processing part 11a, 11b judging means 12 manual operation part 12a manual stopper 12b manual starter 13 input portion 14 output portion 15 watch dog timer 16 hash value storing means 17 alarm resetting means 20 logical processing part 21 1st-OR gate 22 2nd-OR gate 23 NOT gate 24 AND gate 25 flip-flop 41 receiver 42 timer 50 back plane 51, 52, 53, 54 extended board 55 first transmission-reception means 56 second transmission-reception means T (T1-TN) process signal
	claims	1. A method for transferring a plurality of containers for storage of substances for medical, pharmaceutical or cosmetic purposes and/or closure elements of such containers from a transport and packaging container into a clean room, wherein the transport and packaging container has a side wall having an access opening, which is sterile sealed by a gas-permeable protective sheet or gas-permeable cover, the method comprising the steps of:placing the transport and packaging container together with the plurality of containers and/or closure elements accommodated therein, so that the side wall of the transport and packaging container is disposed directly at a side wall of the clean room and in close proximity to a transfer port door of the clean room;opening the transfer port door, wherein by coupling the gas-permeable protective sheet or gas-permeable cover with the transfer port door the gas-permeable protective sheet or gas-permeable cover is separated from the side wall of the transport and packaging container at the same time so that the access opening of the transport and packaging container is in communication with an inside space of the clean room;transferring the plurality of containers and/or the closure elements from the transport and packaging container into the inside space of the clean room; andclosing the transfer port door. 2. The method as claimed in claim 1, wherein the side wall of the transport and packaging container is placed so close to the side wall of the clean room that a gap between the side wall of the transport and packaging container and the side wall of the clean room is sealed by a sealing element. 3. The method as claimed in claim 2, wherein the sealing element is an elastic sealing element, which is disposed on the side wall of the transport and packaging container and/or on the side wall of the clean room. 4. The method as claimed in claim 1, wherein the coupling of the gas-permeable protective sheet or gas-permeable cover with the transfer port door is performed by latching, by temporarily fixing the gas-permeable protective sheet or gas-permeable cover on an outside of the transfer port door by adjustable grippers or by sucking the gas-permeable protective sheet or gas-permeable cover against the outside of the transfer port door by suction devices. 5. The method as claimed in claim 1, wherein the gas-permeable protective sheet is a gas-permeable plastic film consisting of a mesh of plastics fibers that is bonded to the side wall of the transport and packaging container. 6. The method as claimed in claim 1, wherein the cover, when present, has a gas-impermeable frame having an opening, which is sterile sealed by a gas-permeable plastic film, or wherein the gas-permeable protective sheet, when present, is a gas-permeable plastic film consisting of a mesh of plastics fibers that is bonded to the side wall of the transport and packaging container. 7. The method as claimed in claim 5, comprising the further step of sterilizing an inside space of the transport and packaging container and/or the containers accommodated therein and/or the closure elements by a flow of a gas or vapor through the gas-permeable protective sheet. 8. The method as claimed in claim 6, comprising the further step of sterilizing an inside space of the transport and packaging container and/or the containers accommodated therein and/or the closure elements by a flow of a gas or vapor through the gas-permeable protective sheet. 9. The method as claimed in claim 5, wherein a heating device is disposed at the transfer port door in correspondence with an adhesive rim along which the gas-permeable plastic film is bonded to an edge of the side wall of the transport and packaging container, wherein:the adhesive rim is heated and softened by activating the heating device, andthe gas-permeable plastic film is coupled with the transfer port door in such a manner that the gas-permeable plastic film is pulled off from the side wall of the transport and packaging container by opening the transfer port door after the softening of the adhesive rim. 10. The method as claimed in claim 6, wherein a heating device is disposed at the transfer port door in correspondence with an adhesive rim along which the gas-permeable plastic film is bonded to the frame, whereinthe adhesive rim is heated and softened by activating the heating device, andthe gas-permeable plastic film is coupled with the transfer port door in such a manner that the gas-permeable plastic film is pulled off from the frame by opening the transfer port door after the softening of the adhesive rim. 11. The method as claimed in claim 5, wherein:the gas-permeable protective sheet is disposed on the side wall of the transport and packaging container,a plurality of recesses or depressions is formed in the side wall of the transport and packaging container,adjustable gripping devices corresponding to the recesses or depressions are disposed on an outside of the transfer port door,the gripping devices are adjusted such that, in a first position of the gripping devices, the transport and packaging container is brought freely to a vicinity of the transfer port door of the clean room,the gripping devices are then adjusted to a second position, in which the gripping devices engage with the corresponding recesses or depressions in the side wall of the transport and packaging container behind the gas-permeable protective sheet for temporarily fixing the gas-permeable protective sheet to the transfer port door,the transfer port door is opened in the second position of the gripping devices, andthe gripping devices are adjusted back to the first position after closing the transfer port door. 12. The method as claimed in claim 6, wherein:the gas-permeable protective sheet is disposed on a frame-like projection formed on the side wall of the transport and packaging container,a plurality of recesses or depressions is formed in the frame-like projection,adjustable gripping devices corresponding to the recesses or depressions are disposed on an outside of the transfer port door,the gripping devices are adjusted such that, in a first position of the gripping devices, the transport and packaging container is brought freely to a vicinity of the transfer port door of the clean room,the gripping devices are then adjusted to a second position, in which the gripping devices engage with the corresponding recesses or depressions in the frame-like projection behind the gas-permeable protective sheet for temporarily fixing the gas-permeable protective sheet to the transfer port door,the transfer port door is opened in the second position of the gripping devices, andthe gripping devices are adjusted back to the first position after closing the transfer port door. 13. The method as claimed in claim 1, wherein all the containers and/or the closure elements are supported in a supporting structure which is accommodated in said transport and packaging container and wherein the supporting structure together with the containers and/or the closure elements supported by it are transferred from the transport and packaging container into the inside space of the clean room by shifting. 14. The method as claimed in claim 13, wherein the supporting structure comprises a box-shaped bottom part having a bottom, on which the containers are directly supported, and wherein the box-shaped bottom part is shifted directly on a bottom of the transport and packaging container and transferred to the clean room. 15. The method as claimed in claim 13, wherein the supporting structure comprises a box-shaped upper part, which rests directly, or indirectly with interposition of an intermediate part, on upper ends of the containers. 16. The method as claimed in claim 1, wherein the transport and packaging container is provided sterile packaged inside a sterile packaging bag and wherein a first space is disposed upstream of the clean room, said first space having a higher concentration of particles, said method further comprising the steps of:sterilizing an outside of the packaging bag in the first space; andremoving the transport and packaging container from the sterile packaging bag after the step of sterilizing. 17. The method as claimed in claim 16, wherein the plurality of containers is transferred back into the transport and packaging container after a further processing in the clean room by the following steps:placing the transport and packaging container in the first space having the higher concentration of particles, so that the side wall of the transport and packaging container with the access opening is arranged directly at the side wall of the clean room and in close proximity to the transfer port door of the clean room;opening the side wall of the transport and packaging container and the transfer port door so that the access opening of the transport and packaging container communicates with the inside space of the clean room;transferring the plurality of containers from the inside space of the clean room into the transport and packaging container;closing the transfer port door; andclosing the transport and packaging container by the cover. 18. The method as claimed in claim 16, wherein the first space is a first clean room having a higher concentration of particles than the clean room. 19. The method as claimed in claim 17, wherein closing the transport and packaging container by the cover is caused by a simultaneous closing of the transfer port door. 20. The method as claimed in claim 17, further comprising:sterilizing an outside of the transport and packaging container in the first space having the higher concentration of particles after transferring the plurality of containers into the transport and packaging container;inserting the transport and packaging container into the sterile packaging bag after the step of sterilizing the outside; andsealing the sterile packaging bag. 21. The method as claimed in claim 20, wherein the first space is a first clean room having a higher concentration of particles than the clean room.
	description	This application is a national phase application filed under 35 USC § 371 of PCT Application No. PCT/GB2015/050261 with an International filing date of Feb. 2, 2015 which claims priority of GB Patent Application 1410447.5 filed Jun. 12, 2014 and EP Patent Application 14275136.1 filed Jun. 12, 2014. Each of these applications is herein incorporated by reference in its entirety for all purposes. This invention relates to electro-optic (EO) windows which pass radiation in the infra-red waveband and/or optical and/or UV bands but which either absorb or reflect RF/microwave radiation and to methods of their production. There are many applications where an infra-red transparent window is positioned in the optical path of EO equipment to protect the equipment during use. Where such windows are used on military vehicles, they can give unwanted radar returns if they pass a substantial proportion of any incident RF transmission, and particularly in the microwave band, which is understood to refer to radiation in the waveband of from a few MHz—300 GHz. This places stringent design criteria on the window so that it transmits in the infra-red and preferably also the visible spectral bands but does not transmit microwaves. The term ‘window’ is used broadly herein to mean an element capable of transmitting radiation in the optical and/or infra-red wavebands, said window being with or without optical power, and so includes lenses as well as refractive and diffractive elements generally. The term ‘transparent’ is used to mean that the window transmits a usable amount of radiation at the mid value of the infra-red and/or optical wavebands. In order to provide low RF/MICROWAVE transmission infra-red windows it is known to apply a metal mesh or grid to the surface of the window. However, the metal mesh may have the drawback that, where the window is exposed to the environment, to air, water or sand abrasion, the thickness of the metal mesh can deflect water droplets or sand particles so as to accelerate abrasion of the window. In some current applications, zinc sulphide windows that exhibit low RF/MICROWAVE transmission are used in EO sensors. Current designs incorporate fine metal grids close to the surfaces of the zinc sulphide windows in order to reflect microwave radiation. The bulk zinc sulphide windows are manufactured by chemical vapour deposition and the grid is then produced by sputtering/chemical vapour deposition onto the surface of the window, so producing large areas is a problem. Such designs are not cost effective; it is difficult to ensure uniformity of the metal grids, and there is a high risk of environmental damage to the metal grids. Encapsulation of the grids by overgrowing with ZnS may circumvent the problems of environmental degradation, but this also suffers from scale-up difficulties and from induced defects in the surface topography caused by the grid sitting proud of the window surface and delamination or weaknesses at the interfaces. This problem can therefore create the need for additional post-fabrication machining or polishing in order to flatten the outer surface of the grown on ZnS. Accordingly, it is an object of the present invention to overcome or reduce some of the above mentioned drawbacks. According to one aspect of the invention there is provided an EO window made of a material substantially transparent to at least one of infra-red, visible and UV radiation and treated to have reduced RF/MICROWAVE transmission characteristics by the provision of a grid pattern set into a surface thereof the grid being formed of a material selected to be one of reflective and absorptive to RF/MICROWAVE radiation. It is to be understood that the use of the term “grid” herein is to be interpreted to include a frequency selective pattern. In another aspect, this invention provides a method of making an electro-optic window formed from a material substantially transparent to at least one of infra-red, visible and UV radiation whereby to render the window capable of reduced RF/MICROWAVE transmission characteristics, the method including the steps of forming on a surface of the window a grid of channels, creating a corresponding grid pattern of a material having one of electrically conductive and dielectric properties within the channels whereby to render the window non transmissive to RF/MICROWAVE radiation and treating the material as required to render the grid usable to reduce the RF/MICROWAVE transmission characteristics of the window. It will be appreciated that more than one window may be used, to form a “stack” of windows attached to one another. More than one window may include a said grid and each window may have a grid set into more than one surface thereof, for example into opposed surfaces thereof. The grid may be set into channels in the window whereby to fill the channels no more than substantially flush with the said surface of the window. If the grid is flush with the surface of the window, then a smooth surface will be offered to any cover layer or to the atmosphere, if the window is to be used without a cover. The effect of the channels not being entirely filled with the grid material may be advantageous in that the grid may then effectively form a micro-structured surface having an anti-reflection effect. The electro-optic window may include a capping layer covering the grid and attached to the said window surface. Such a capping layer will offer protection from weather erosion. The capping layer may be fusion bonded or adhered to the surface of the window, may be formed on the surface of the window or may be spun coated or spray coated onto the surface of the window. The grid may be at least partly formed of a liquid and the grid may include a closable port adapted to allow passage of liquid, when open, into and out of the grid during the operational life of the window. The grid may be formed of both liquid and solid, thus a metal or other solid may be deposited so that it is disconnected then connected electrically by flowing liquid through it. Thus, an adaptive window may be created, using this method, having RF/MICROWAVE reflective/absorptive characteristics which are variable according to the liquid forming, or partly forming, the grid at any one time. The step of treating the material as required to render the grid usable to reduce the RF/MICROWAVE transmission characteristics of the window may comprise solidifying the liquid. The liquid may be colloidal having particles therein to render the window non transmissive to RF/MICROWAVE radiation and the step of treating the material as required to render the grid usable to reduce the RF/MICROWAVE transmission characteristics of the window may include evaporating off the liquid to leave the said particles within the channels. The step of evaporating off the liquid may include sealing the colloidal liquid within the channels of the grid, forming a port for evaporation having a size less than the particulate size of the said particles and then evaporating off the liquid through the port. The step of treating the material as required to render the grid usable to reduce the RF/MICROWAVE transmission characteristics of the window may include covering the channels of the grid and confining the liquid within the covered channels and the step of confining the liquid within the channels may comprise confining an electroless plating solution within the channels and may include the step of electrolessly plating the channels with a metal contained in the solution. The step of covering the channels of the grid may include growing a layer of protective material over the grid or attaching a protective layer to the surface of the window. The step of causing a liquid having one of electrically conductive and dielectric properties to RF/MICROWAVE radiation substantially to fill the channels may be carried out after the channels of the grid have been covered and the step of causing the liquid to substantially fill the channels of the grid may thus include introducing the liquid to the grid and continuously making the liquid available to the grid while capillary action draws the liquid throughout the grid. Alternatively or in addition, suction and/or pressure may be applied to the grid to urge or draw the liquid therethrough. The step of causing a material having one of electrically conductive and dielectric properties to RF/MICROWAVE radiation substantially to fill the channels may include the steps of covering the surface of the window defining the grid with a layer of the liquid to substantially fill the channels of the grid and then wiping the surface of the window whereby to remove the liquid from the surface while leaving the channels of the grid substantially filled with the liquid. The step of causing a material having one of electrically conductive and dielectric properties to RF/MICROWAVE radiation substantially to fill the channels may include the steps of covering the surface of the window defining the grid with a layer of liquid metal to substantially fill the channels of the grid, allowing the liquid metal to solidify and polishing the surface of the window whereby to remove the metal from the surface while leaving the channels of the grid substantially filled with the metal. The step of causing a material having one of electrically conductive and dielectric properties to RF/MICROWAVE radiation substantially to fill the channels may include the steps of sputtering over the surface of the window defining the grid a layer of metal to substantially fill the channels of the grid and selectively etching the surface of the window whereby to remove the sputtered metal from the surface while leaving the channels of the grid substantially filled with the metal. The step of forming on a surface of the window a grid of channels may include forming the grid of channels by laser etching or chemically etching the window material. The step of forming on a surface of the window a grid of channels may include the following steps: forming a mould in the shape of an EO window, the mould defining a positive grid formation whereby to impart to a moulded window a negative grid formation on one surface of the window, forming a sol of a material suitable for sintering and pouring the sol into the mould, converting the sol to a gel by the application of heat, drying the gel whereby to impart to the gel a permanent shape corresponding to that of the mould, and vitrifying the gel by sintering whereby to form a sintered EO window having the grid of channels formed on one surface thereof. The step of forming a capping layer for the window may include the following steps: forming a mould in the shape of the layer, forming a sol and pouring the sol into the mould, converting the sol to a gel by the application of heat, drying the gel whereby to impart to the gel a permanent shape reflecting that of the mould, and vitrifying the gel by sintering whereby to form a said capping layer. Optically suitable materials for an EO window according to the invention are well-known. Work has been done by the inventors on sapphire (aluminium oxide, Al2O3) and spinel (magnesium aluminium oxide, MgAl2O4). Synthetic sapphire can be grown in several of its crystal orientations including the “A”, “C”, “R” and “M” plane. For EO window applications the ‘C’ or ‘A’ plane axes may be used. Sapphire crystals are grown using a variety of crystal growth techniques and then machined and polished into the finished window geometry. Sapphire can be processed to a very high optical specification of flatness and surface quality. For example, scratch/dig (S/D) of 20/10 can be achieved for flatness of λ/4, which is suitable for almost all optical applications. Magnesium aluminate or magnesium aluminium oxide, or spinel, is a durable polycrystalline transparent ceramic. Spinel blanks may be made using conventional ceramic processing techniques. A powder of the raw constituent materials is prepared (usually to a proprietary formulation), compacted and can be dry-isostatically pressed, slip cast or injection moulded into the required shape. This is followed by a heat treatment to densify the material. The blanks may then be ground and polished to specification. Spinel can also be produced by crystal growth methods, chemical vapour deposition and chemical synthesis routes, including sol gel synthesis, as described below. Sapphire is currently available as follows:— Max. planar dimension: 300 mm×500 mm or 225 mm×660 mm; Ratio of thickness to planar length required for polishing: 1:70; Min. thickness required for optical polishing & processing: 7 mm; Max. thickness available: 7.7 mm. Spinel is currently available as follows: — Max. planar dimension: 300 mm×460 mm; Ratio of thickness to planar length required for polishing: 1:35-1:10; Min. thickness required for optical polishing & processing: 13-40 mm; Max. thickness available: 25 mm. For reasons of commercial availability only, the EO window was made of sapphire or spinel, between 5-20 mm thick, with a planar edge of 300-500 mm. Because a grid that is on the surface of the window will be exposed to abrasion and erosion, it will need protection. Protection may be imparted by adding protective coatings. Referring to FIG. 1, an embodiment of the invention is shown. Here, a sub-surface grid 1 is shown flush with a surface 2 of a window 3; the grid 1 is positioned within the window 3 rather than on it. This reduces the exposure of the grid to impacts and abrasion and still renders electrical connection to the grid very accessible. FIG. 2 shows a further embodiment with a grid 1 completely protected from the elements. The grid 1 is located, as in FIG. 1, within the window 3. In addition, both the grid 1 and the upper surface 2 of the window are covered with a capping layer 4. This design will completely protect the grid from a harsh aerospace environment. It will be noted that electrical connection to the grid 1, in this embodiment, is through the exposed cross-section of the embedded grid. However, electrical connection can be made through vias from the back of the window or from top or edge surfaces, with bus bars or electrical connections surrounding the edge. For use on aircraft, it may be also be important to connect electrically to airframe window surrounds, for metal grids at least. The flow diagram of FIG. 3 shows the manufacturing steps required to make a window according to the invention, by two alternative routes. On the left side of the diagram, is shown one route, on the right, another. Looking at the left side, channels 5 of a grid are etched into a surface 2 of a sapphire or spinel window 3 by any suitable etching process. The channels 5 are then metallized, again, by any suitable process. Following this step, capping layer 4 which may also be of spinel or of another suitably hard material having transparent properties, is attached to the upper surface 2 of the window 3 by one of several methods described below. Following the right side of the diagram, an alternative method is shown where, following etching of the channels 5, the capping layer 4 is immediately attached to the window, followed by metallisation, again, as further described below. In an example, according to the invention, a grid has been etched in a window using a laser system suitable for both glass and sapphire substrates. The laser etching system uses a 200 KHz pulsed excimer laser with a 193 nm lens and a chrome on quartz mask of the required grid. A glass wafer etched by this method is shown in FIG. 4. This technique is also applicable to etching spinel. This method of etching has potential to be scaled up, but this may be at significant cost. The throughput of such a process may be of the order of ˜10 mm/s. Vacuum processing techniques have been developed for achieving mirror finishes on laser etched arrays. Chemical etching has also been used to etch glass wafers, see FIGS. 5a, b and c, and may be used according to the invention to etch sapphire. The channels 5 are 3 μm deep, 7 μm wide and with a 100 μm separation. Work has been carried out to research the deposition of metal into surface channels. Many materials are suitable for use as RF/MICROWAVE reflector fillers for the grid channels. Most metals and many alloys are suitable. Gold, silver, aluminium, platinum and the refractory metals are suitable, as are iron, cobalt, nickel and many fluids. In an example, aluminium was sputtered over a gridded sample 6 and then selectively etched to leave metal 7 within the channels 5 of the grid 1, see FIGS. 6a and 6b. Cross sectional image analysis of this sample was used to evaluate the channel metallisation, see FIG. 6c. A channel 5 in the glass 8 is filled with aluminium 9. The initial channel 5 was 7 μm wide and 3 μm in depth. Variability across the grid can lead to over etched patches of metal. To mitigate this, the grid channels 5 were deepened to ensure the grid could be etched back from the surface 10 without affecting the continuity of the grid. The microwave reflectivity of the samples were characterised and the results are shown in FIG. 7. The results indicate that sputtered layers of metal just a few microns thick and electrolessly plated metal layers of the order of a micron thick have a high enough conductivity to provide significant radar reflection. The use of electroless plating to generate a grid is described in the following section. An electroless gold plating process occurs in the liquid phase at elevated temperatures (˜50 C). Therefore it is important that the electroless solution is contained, to avoid evaporation during heating. In order to achieve this, a section of pre-cavitated glass wafer was placed face down (cavities side down) on a glass slide. The electroless gold plating solution was introduced to the edge of the wafer section by pipette and was observed to be drawn into the channels by capillary action. Once the sample was fully wetted with plating solution it was placed in an oven at 50 C for ˜15 minutes to activate the plating process. The wafer section was removed from the carrier slide and examined. A thin layer of gold was seen to be plated across the entire top surface of the wafer (visible as a transparent purple film) in addition to the metal filling the trenches. The surface gold film was wiped off leaving the metal in the trenches intact. The present invention is partly concerned with methods of forming metal coatings within channels embedded within window structures. Optically transparent spinel is manufactured using ceramic processing techniques. A metallic mesh or conductive grid may be embedded within the window during manufacture by embedding a mesh of a sacrificial material in any suitable window bulk material. Examples of suitable sacrificial materials are: polymers, some low melting-point metals, eutectics, carbon nanotubes, and wax. The mesh or grid is then removed by, for example, melting the sacrificial material to leave a grid of channels in the manufactured window for receiving a conductive or dielectric grid, as desired, for use in operation. As illustrated on an opaque ceramic 14 in FIGS. 8a and 8b, it is also possible to use free standing meshes to create a grid image 13 within the pre-sintered compressed ceramic 14 and to fire the ceramic to form a grid 13 in the surface of the fired ceramic 14 that may then be filled with conductive or resistive materials. In principle, this is applicable to spinel using a similar process. It is also possible to use this technique to form a resistive or absorbing grid from carbon based materials such as carbon powders or nanotubes. FIGS. 9a and 9b illustrate forming, with an expanded metal foil, see FIG. 9a, subsurface carbon grids in a pre-sintered ceramic compact. Carbon particles or nanotubes can then be distributed in the grid channels as required and the ceramic sintered. FIG. 9b illustrates the result, with carbon residing in the channels. Examples of absorptive materials include ferrites such as nickel zinc, manganese zinc and cobalt ferrites; magnetites; ceramics, and carbon based materials as above. Fluids may also be used to form the grid material, in use. Examples are: electrolyte solutions, such as potassium ferrocyanate; ethylene glycol; methanol, and acids. Colloids such as magnetic colloids like ferro-fluids are also suitable to act as the grid material. Spinel can be made using sol gel techniques, allowing for optically transparent thin films to be synthesized. These may be used to protect surface or sub-surface grids. Conventionally, spinel films are deposited using chemical vapour deposition methods but that method is presently limited to relatively small areas (a few cm2). According to the present invention, the use of sol gel methods for manufacturing large area capping layers of spinel is proposed. It is known that mixtures of salts of magnesium and aluminium in the appropriate ratio decompose at high temperatures to produce spinel and the method is often used to manufacture powders of spinel.Mg(NO3)2+2Al(NO3)3→MgAl2O4 Studies were initially undertaken using silica, rather than spinel because of the simpler chemistry involved. A thin film of a silica gel was cast onto a perforated copper foil, see FIG. 10a. When the gel was partially dry, and shrinkage was minimal, the film was removed from the foil and then dried and sintered. The final body, although dimensionally smaller, showed the features of the original green body, see FIG. 10b. Thus, this technique may be adopted for the manufacture of EO windows with grid channels set into one surface thereof. For spin coating of spinel, methanolic solutions of the mixed metal nitrates were spun onto substrates (glass slides, silicon wafer and sapphire windows). It was found that the addition of a very small amount of a suitable polymer led to excellent film formation after spin coating, and the films remained intact and continuous after low temperature drying to remove solvent and subsequent high temperature thermal treatment. The choice of polymer was found to be very important and certain polymers were more suitable than others for ensuring good quality film formation. FIGS. 11a and 11b show examples of good continuous solvent free films of mixed metal nitrates on silicon wafer substrates produced by spin coating. In FIG. 11a, an uncoated Si wafer 18 is shown on the left and a spin coated and dried wafer 19, on the right. FIG. 11b shows a coated wafer 20, after high temperature processing. FIG. 12 shows sapphire windows before and after coating and subsequent heat treatment, with 21 being an uncoated sapphire window and 22 being a sapphire window having a spin coating of mixed Mg and Al nitrates, with polymer. FIGS. 13a, b and c show the importance of the choice of polymer for aiding film formation. Here, FIGS. 13a and 13b show films prepared from a precursor with a good choice of polymer and FIG. 13c shows film prepared from a poor choice of polymer where the nitrates have crystallised from solution. XPS (x-ray photoelectron spectroscopy) analysis of coatings deposited on silicon wafers and sapphire windows confirms the presence of magnesium oxide and aluminium oxide, see FIG. 14a and FIG. 14b. TABLE 1eVAssignmentOn waferOn sapphire discCarbon284.9Hydrocarbon22.9%16.8%Oxygen531.2Inorganic oxide47.3%51.57%Aluminium74.6Al oxide20.2%22.9%Magnesium50.5Mg oxide9.7%8.7% Quantitative analysis of the composition of the coating on silicon shows that the ratio of magnesium to aluminium (as oxide) is the expected 1:2, see Table 1, above. The ratio of the coating on the sapphire window shows a higher amount of aluminium but this is to be expected because of contributions from the aluminium oxide present in the structure of the sapphire substrate, see FIG. 15. Comparison of an uncoated sapphire window and sapphire window that has been spin coated with the precursor mixture followed by thermal treatment reveals only small differences in the transmission window. The uncoated window transmits ˜85% of light from 1100 nm to ˜270 nm at which point the transmission falls rapidly to ˜55% at 190 nm. Transmission through a spinel coated sample has similar transmission from 100 nm to ˜270 nm but thereafter the fall in transmission is faster than in the control sample and the final transmission is ˜35% at 190 nm, see also FIG. 15. FIG. 16 shows the IR transmission spectra of an uncoated sapphire window, a sapphire window coated with the dried precursor and the same window after full thermal treatment. The transmission window for all samples is ˜3 μm to 5 μm and at 5 μm and higher the transmission is essentially zero. The OH stretch arising from the presence of a polymer can clearly be seen. This absorption band disappears following thermal treatment. The presence of the final coating does not significantly attenuate transmission in the 3 to 5 μm band. In all samples transmission falls below ˜50% at ˜4 μm. Thus, there is little degradation in the optical and IR transmission spectra of a capped window. For large substrates spin coating may not be appropriate, thus deposition of magnesium aluminate films using spray techniques was investigated. Modification of the spin coating precursor for spinel, used above, produced a mixture that could be sprayed onto substrates (glass, and silicon wafers). Visual inspection by eye and under an optical microscope showed the wet, (as deposited) film and the dried film to be fairly uniform. FIG. 17a shows an example of a coated Si wafer 23, a portion 24 of which was masked off prior to spray coating and FIG. 17b shows a sample having a masked portion 25 and an unmasked portion 26 that has subsequently undergone full thermal treatment. Fusion bonding is a method of joining materials including ceramics to each other through the application of pressure and heat without the use of adhesives. It has been successfully used by the inventors on several materials such as silicon and glass to form strong bonds. If fusion bonding is possible with gridded windows, then grids could potentially be protected by a layer of the substrate material without a glue line. Such glue lines can severely compromise the optical and mechanical properties of the structure. Fusion bonding can create optically transparent bonds under the right conditions. Fusion bonding requires flat, clean surfaces. The surfaces are mated under pressure and at elevated temperatures. The surfaces of the material are prepared using a proprietary process to degrease, clean and chemically activate the surface of a wafer. The surfaces are then bonded using wafer bonding equipment and post treated in a vacuum oven. The bonding process has been demonstrated on a pair of sapphire windows, as shown in FIG. 18. Interferences fringes 27 (known as Newton's rings) indicate there is a bond gap; the gap can be estimated using the separation between the interference fringes, as indicated by the tips of the arrows. Analysis of the fringes indicated a gradual separation between the windows from a successful fusion bond at a clear part 28 of the sample to ˜1 μm separation between the windows at the edge 29 of the sample. The specification of these windows has a flatness of 2λ over the 20 mm window. Generally, for fusion bonding, a flatness of λ/10 over 50 mm would be necessary for a good fusion bond. The defect in the bond is probably due to a variation in flatness across the window samples. From the above it is concluded that fusion bonding techniques may be used to create a window according to the invention with an embedded grid by fusion bonding a capping layer onto the gridded window. A gridded pattern was etched into a glass wafer and a second glass wafer was fusion bonded onto the surface. An image of the resulting structure is shown in FIG. 19. The interference fringes 30 indicate the central area has not properly bonded. The optical transmission through this sample, see FIG. 20a, is compared to an adhesively bonded wafer, see FIG. 20b, and the IR transmission of the samples is compared to an untreated glass wafer in FIG. 21.
052689395	description	DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Illustrated schematically in FIG. 1 is a nuclear reactor 10 in the exemplary form of a boiling water reactor (BWR), and a control system 12 therefor. The reactor 10 includes a pressure vessel 14 having a reactor core 16 submerged under reactor water 18 therein. During operation, the core 16 heats the water 18 for generating main steam 20 under pressure for discharge through a main steamline 22 to a conventional steam turbine 24 disposed in flow communication with the reactor 10. The main steam 20 provided to the turbine 24 rotates an output shaft of the turbine 24 for powering a conventional electrical generator 26 which provides electrical power to a conventional utility grid. One manner of regulating power of the reactor 10 is a conventional recirculation flow control system (RFCS) 28 which selectively varies the recirculation flow of the water 18 through the core 16 in the vessel 14. The RFCS 28 includes a conventional recirculation pump 30 joined in flow communication with the vessel 14 for receiving therefrom a portion of the water 18 and discharging the water 18 under pressure through a conventional control valve 32 which is conventionally disposed in flow communication with the vessel 14 for returning thereto the water 18 for powering a conventional jet pump (not shown), for example, for circulating the water 18 through the core 16. A conventional closed-loop feedback control includes a flow sensor 34 which provides a flow signal to a conventional comparator 36, which also receives a recirculation flow demand signal from a conventional master controller 38. The difference, or error, between these two signals is provided by the comparator 36 to a conventional flow controller 40 which controls a conventional valve positioner or servomotor 42 which mechanically opens and closes the control valve 32 as desired in response to the error signal. In this way, the flow through the control valve 32, and therefore the recirculation flow through the core 16, is controlled in a conventional feedback loop in response to a demand signal from the master controller 38 and the feedback flow signal from the sensor 34. The master controller 38 is provided with conventional inputs 38a such as a signal indicative of the desired reactor power. By increasing recirculation flow of the water 18 through the core 16, power of the reactor 10 may be increased for increasing the volume, or flowrate, of the main steam 20 channeled through the main steamline 22. Conventionally disposed in parallel flow communication in the steamline 22 are a plurality of conventional flow control or modulating valves 44, three being shown for example, for controlling flow of the main steam 20 from the reactor 10 to the turbine 24. At least one conventional bypass valve 46 is disposed in flow communication with the steamline 22 upstream of the control valves 44 and with a conventional main condenser 48 of the turbine 24 for selectively bypassing a portion of the main steam 20 as bypass steam 20a around the control valves 44 and the turbine 24 for direct flow to the condenser 48 without passage firstly through the turbine 24. The bypass valve 46 is conventionally provided to bypass, or dump the bypass steam 20a into the condenser 48 whenever more steam is available than required by the turbine 24 during operation, for example. In a conventional BWR, pressure of the main steam 20 is controlled by a conventional pressure control system including a conventional pressure regulator or controller 50 operatively joined to the control valves 44 and the bypass valve 46 for controlling flow of the main steam 20 to the turbine 24, and for controlling the amount of bypass steam 20a bypassed directly to the condenser 48. A conventional pressure sensor 52 provides a pressure signal to the regulator 50 which may conventionally be either the pressure of the main steam 20 in the reactor pressure vessel 14 or the pressure of the main steam 20 at the inlet to the turbine 24. The pressure of the main steam 20 is, therefore, conventionally regulated using the sensed pressure thereof and conventionally modulating the control valves 44. A conventional turbine control system including a conventional turbine controller 54 is also operatively joined to the control valves 44 and the bypass valve 46 in conjunction with the pressure regulator 50 for controlling flow of the main steam 20 to the turbine 24, as is conventionally known. More specifically, the pressure regulator 50 receives conventional inputs 50a, such as pressure setpoint, and dynamically generates or computes a total steamflow (TF) demand in the form of an electrical signal which is indicative of the required total steamflow through the several control valves 44. A conventional first low valve selector or gate 56 is operatively joined between the pressure regulator 50 and the turbine controller 54 for receiving the TF demand from the pressure regulator 50 and a conventional speed-load, or simply load, demand from the turbine controller 54. The turbine controller 54 receives conventional inputs 54a such as the desired load demand for the turbine-generator 24, 26, for example, and conventionally also receives a feedback speed signal from a conventional speed sensor 58 which monitors the rotational speed of the turbine-generator 24, 26. During normal operation with the generator 26 locked on to the utility grid and the turbine 24 operating at its synchronous speed, the load demand from the turbine controller 54 is predeterminedly higher than the TF demand from the regulator 50, and the low value selector 56 will, therefore, select the lesser thereof, e.g. TF demand, as a control valve (CV) flow demand, in the form of an electrical signal for controlling flowrate of the several control valves 44. During an overspeed condition of the turbine 24, for example, the turbine controller 54 provides override capability of the pressure regulator 50 and, therefore, the load demand will be selected in such instance by the first selector 56. Accordingly, during normal operation of the reactor 10 the pressure regulator 50 controls flow through the control valves 44, and the CV demand has the value of the TF demand. The CV demand is conventionally used in feedback operation in redundant closed-loops for the several control valves 44 including for each control valve loop, for example, a conventional comparator 60 which receives the CV demand from the first selector 56 and subtracts therefrom an actual position signal for the respective control valve 44 provided by an conventional position sensor 62 operatively joined to a conventional valve positioner or servomotor 64 which selectively opens and closes the control valve 44. A conventional control valve (CV) controller 66 is operatively joined to the first selector 56 through the comparator 60 for receiving from the selector 56 the CV demand from which is subtracted in the comparator 60 the actual position signal from the position sensor 62 for generating a difference or error signal used by the CV controller 66 to position the control valve 54 at the desired position. The control of each control valve 44 is conventional and is typically provided with redundant control circuits to ensure proper operation of the control valves 44. Accordingly, the control valves 44 are selectively opened and closed as required in response to desired power levels of the reactor 10 and for maintaining a substantially constant pressure of the main steam 20 as regulated by the pressure regulator 50. During a mode of operation of the turbine 24 requiring a substantial reduction in flow of the main steam 20 thereto, the bypass valve 46 is conventionally operated to bypass the undesired, excess portion of the main steam 20 as the bypass flow 20a directly to the condenser 48. More specifically, the steam bypass system including the bypass valve 46 also includes a conventional bypass comparator 68 which is operatively joined to both the pressure regulator 50 and the first selector 56 for receiving from the former the TF demand, and receiving from the latter the CV demand, which two signals are compared by the comparator 68 to determine the magnitude of steamflow that must be bypassed directly to the maim turbine condenser 48 in order to maintain adequate pressure control. The difference of the two signals obtained by the comparator 68 is the bypass demand, in the form of an electrical signal, which is conventionally provided to a conventional closed-loop feedback control system for the bypass valve 46. The bypass feedback control system includes a conventional comparator 70 which receives the bypass demand and also receives an actual position signal from a conventional position sensor 72 operatively connected to a conventional valve positioner or servomotor 74 which conventionally selectively opens or closes the bypass valve 46. The comparator 70 provides a difference or error signal to a conventional bypass valve (BV) controller 76 which controls operation of the servomotor 74 to selectively control operation of the bypass valve 46 in a conventional fashion. The control system 12 described above is conventional in structure and function and is implemented in conventional control system components or computers in redundant circuits as desired. The control system 12 further conventionally includes conventional first and second limiters 78 and 80 to ensure that the respective signals from the pressure regulator 50 and the turbine controller 54 do not exceed predetermined ranges including predetermined maximum values for ensuring safe operation of the reactor 10. More specifically, the first limiter 78 is operatively joined between the pressure regulator 50 and the first selector 56 and provides a predetermined limit to the total steamflow (TF) demand which limits the total flow through all of the control valves 44 and bypass valve 46 in the event that they are all opened simultaneously. This is done to prevent, for example, a condition known as blowdown wherein a failure in the control system causes excessive steamflow from the reactor 10 through the main steamline 22 which would drop the water level within the vessel 14 and depressurize the vessel 14. This could then lead to conventional transition boiling of the water adjacent the fuel bundles within the core 16 which could damage the fuel by overheating. By suitably limiting the opening of the control valves 44 and the bypass valve 46, the total steamflow therethrough is limited in response to the TF demand limit provided by the first limiter 78. The second limiter 80 is conventionally operatively joined between the first selector 56 and the comparator 60 to conventionally limit the value of the load demand to a preferred range with a predetermined maximum value. By limiting the load demand, steamflow through the control valves 44 is thereby limited which in turn limits the total flow to the turbine 24. The second limiter 80 therefore prevents excessive flow to the turbine 24 which could possibly damage the turbine 24. The first and second limiters 78 and 80 in the control system 12 conventionally prevent excessive blowdown in the reactor 10 and excessive flow to the turbine 24 but, prevent both the control valves 44 and the bypass valve 46 from opening past the predetermined limits which assumes that all the control valves 44 are fully operable. However, in the event of failure of one or more of the control valve 44 which prevents them from opening upon demand or causes them to fully or partially close below demand, the pressure in the reactor 10 will undesirably increase since full demanded flow through the collective control valves 44 to the turbine 24 is therefore prevented. In such an occurrence, the pressure regulator 50 will automatically increase the TF demand for increasing flow through the control valves 44 to decrease the rising pressure in the reactor 10. The non-failed control valves 44 will therefore be further opened for increasing the steam flowrate therethrough in an attempt to decrease the increasing pressure within the reactor 10. However, the TF demand from the pressure regulator 50 will increase only up to the preset limit provided by the first limiter 78 which is based upon the operability of all the control valves 44 including the failed valve. If the reactor 10 is operating at a sufficiently high power level, the steamflow through the operable control valves 44 will reach the limit set by the first limiter 78, and the bypass valve 46 will conventionally be opened to dump a portion of the excessive steamflow to the condenser 48. Furthermore, for high power operation of the reactor 10, the bypass valve 46 can also reach its limiting open value due to the first limiter 78 and therefore, the maximum opening of the non-failed control valves 44 and the bypass valve 46 as limited by the first limiter 78 will be insufficient to avoid excessive reactor pressure increase which will then actuate the conventional reactor protection system (not shown) which will effect a reactor shutdown or scram. Reactor shutdown is undesirable since electrical generating capability will be lost, and since the transition boiling margin will be approached possibly leading to fuel damage from overheating. The normal capacity of the non-failed operable control valves 44 and of the bypass valve 46 is typically sufficient in a conventional power plant to accommodate failure of a single control valve 44 without requiring reactor shutdown but for the first limiter 78. The first limiter 78 is required as above described to provide safe operation to minimize blowdown, but includes no provision in the event of a failed-closed control valve 44 as above described wherein blowdown is not a concern. In accordance with the present invention, an improved method of operating the reactor 10 includes automatically detecting failure of a failed one of the control valves 44 which passes steamflow therethrough at a flowrate below the demand flowrate therefor, i.e. below CV demand, provided by one of the pressure regulator 50 and the turbine controller 54, and automatically opening the bypass valve 46 upon detecting the failed control valve 44 to a level which can exceed that provided by the first limiter 78. The bypass valve 46 will then channel the excessive steamflow to the condenser 48 wherein it is wasted. In order to prevent such wasted energy, the method further includes the step of automatically reducing power of the reactor 10, for example by reducing the recirculation flow of the water 18 in the reactor 10 to reduce the power level thereof, and therefore reduce the main steamflow 20, which will then allow the open bypass valve 46 to normally close, with required total steamflow being instead channeled solely through the non-failed operable control valves 44. This is all done while still maintaining the safely features of both the first and second limiters 78 and 80. The method is practiced in accordance with one embodiment of the present invention by providing in the conventional control system 12 means 82 for detecting failure of a failed one of the control valves 44 which passes steamflow therethrough at a flowrate below the CV demand therefor provided by the pressure regulator 50 or the turbine controller 54. The detecting means, or simply valve failure detector 82, may be conventionally implemented in the conventional computer in which the control system 12 is implemented and is effective for detecting a decrease in the steamflow through the turbine 24 when one of the control valves 44 fails to channel its required portion of the total steamflow from the reactor 10. The valve failure detector 82 is operatively joined to the bypass valve 46 and is effective for opening the bypass valve 46 upon detecting the failed control valve 44. In this way the reduction in transition boiling margin leading to fuel bundle overheating may be reduced or eliminated by detecting failure of the failed control valve 44 and suitably opening the bypass valve 46 to dump the excess steamflow to prevent undesirable reactor pressure rise. The valve failure detector 82 is joined to the conventional control system 12 through a conventional second low value selector or gate 84 operatively joined between the first selector 56 and the bypass comparator 68. The second selector 84 receives the CV demand from the first selector 56 and receives from the valve failure detector 82 an actual turbine flow signal, and is effective for selecting the lesser thereof as a bypass reference signal provided to the comparator 68. During normal operation, the CV demand is provided to the comparator 68 by the second low value selector 84 for normal operation of the control system 12, since the actual turbine flow signal will be substantially equal to the CV demand that it follows. Upon failure of one of the control valves 44, wherein steamflow to the turbine 24 is reduced below CV demand, the actual turbine flow signal indicative of such reduced steamflow is instead provided by the second selector 84 to the comparator 68 which will provide a suitable value of the bypass demand to the bypass valve controller 76 to open the bypass valve 46 without regard for the predetermined limit normally effected by the first limiter 78. However, the first limiter 78 is still effective, nevertheless, to prevent excessive opening of the control valves 44, and of the bypass valve 46 wherein a failure of one of the control valves 44 does not occur. In the failure of one of the control valves 44 which causes it to fully or partially close below that required for normal operation, steamflow to the turbine 24 will correspondingly decrease and may be suitably observed for providing suitable inputs 86 to the valve failure detector 82 for processing therein. Conventional parameters indicative of steamflow to the turbine 24 include the actual positions of the control valves 44, the collective flowrate through the several control valves 44, the pressure within the first stage shell of the turbine 24 which receives the steamflow from the control valves 44, and the electrical power output from the generator 26, for example. Any one of these inputs 86 may be used to generate the actual turbine flow signal provided by the detector 82 to the second selector 84. Illustrated schematically in FIG. 2 is one embodiment of the failure detecting means 82 configured for determining actual steamflow provided to the turbine 24 by monitoring the actual positions of the several control valves 44. More specifically, the detector 82 is operatively joined to the first low value selector 56 for receiving therefrom the respective CV demands designated 86a, b, c which are also provided directly to the respective controller 66 for each of the control valves 44. The detector 82 is also operatively joined to the respective position sensors 62 for each of the control valves 44 for receiving therefrom a control valve (CV) actual position signal designated 86d, e, f which are also provided to the respective comparators 60 for each feedback loop of the respective control valves 44. The detector 82 may include a conventional comparator therein for comparing the respective CV demand and the CV actual position signal for each of the control valves 44 to detect a failure of a control valve 44 based on a predetermined difference therebetween including any appropriate time delay. During normal operation of the control valves 44, the CV demand and the CV actual position signal will be substantially equal to each other except during transient operation wherein the control valves 44 are either being opened or closed. The typical differential between the CV demand and actual position signal including conventional response time may be conventionally provided in the detector 82 so that for differences between the two signals which exceed a predetermined limit, failure of the corresponding control valve 44 will be indicated. For example, if one of the control valves 44 fails fully closed, the CV actual position signal, e.g. 86d, will indicate such closure and will continuously be substantially lower than the respective CV demand, e.g. 86a, which will, therefore, indicate a failure of that control valve 44. Since each of the control valves 44 has a conventionally determined performance definition with flowrate therethrough being proportional to opening of the control valve 44, then the CV actual position signals from the valves 44 may be used to conventionally determine or calculate the collective actual steamflow through all three control valves 44 to generate the actual turbine flow signal provided to the second selector 84. Accordingly, the detector 82 may include a conventional signal processor therein to generate the actual turbine flow signal based on the CV actual position signal inputs provided thereto. During the occurrence of a failed control valve 44 having no flow therethrough, for example, the actual turbine flow signal illustrated in FIG. 1 sent to the second low value 84 will be selected over the CV demand which will be higher compared thereto which, in turn, will generate a suitable bypass demand for opening the bypass valve 46 to bypass the excess flowrate from the failed control valve 44 directly to the condenser 48. The non-failed control valves 44 will also be conventionally opened during such failure by the pressure regulator 50 in conventional fashion but their opening values will be limited by the first limiter 78. As shown in both FIGS. 1 and 2, the failure detecting means 82 are preferably also operatively joined to the RFCS 28 and are effective for reducing the reactor recirculation flow for reducing the main steamflow 20 through the steamline 22 upon detecting the control valve failure. The detector 82 conventionally provides a suitable reduction demand signal to the master controller 38 which in turn is used by the flow controller 40 for suitably closing the control valve 32 to decrease recirculation flow through the core 16 for reducing power output from the reactor 10. Alternatively, the speed of the recirculation pump 30 may instead be regulated to control the recirculation flow in a conventional manner. As power from the reactor 10 is reduced, the steamflow 20 is reduced in turn, and the control system 12 will enter a new equilibrium condition allowing the bypass valve 46 to automatically close, with the required lower total steam flowrate then being channeled through the non-failed operable control valves 44 to the turbine 24 for operation at reduced power. In this way, the bypass valve 46 may be initially opened upon failure of one of the control valves 44 to bypass the excessive steamflow to the condenser 48 and prevent undesirable reactor pressure rise which would otherwise effect a reactor scram. The opening of the bypass valve 46 is not limited by the first limiter 78 in this situation. The bypass valve 46 then automatically closes and prevents the wasting of the steamflow directly in the condenser 48. A suitable failure message may be conventionally sent to the plant control room so that appropriate corrective action for the failed control valve 44 may be taken. The invention, therefore, prevents reactor scram which would otherwise occur, and places the plant in a reduced power output mode of operation and allows the failed control valve to be repaired without reactor shutdown. Illustrated schematically in FIG. 3 is a second embodiment of the failure detecting means 82 which alternatively include a conventional pressure sensor 88 joined to the turbine 24 for conventionally providing a pressure signal for the main steam inside the first stage shell of the turbine 24 which is indicative of the total steam flowrate thereto. The detector 82 is operatively joined to the pressure sensor 88 for receiving therefrom the pressure signal as an input 86g, and is effective for comparing the pressure signal with a predetermined reference value thereof stored therein to detect the control valve failure based on a predetermined difference therebetween. Upon detecting a control valve failure which fails to provide the required steam flowrate to the turbine 24 in response to the CV demand, the signal processor of the detector 82 will conventionally generate the actual turbine flow signal provided to the second selector 84 based on the monitored pressure signal from the sensor 88. A suitable reduction demand signal will also be sent to the master controller 38 for reducing the power of the reactor 10 to allow the bypass valve 46 to close after it is initially opened to prevent undesirable reactor pressure rise. Also illustrated in FIG. 3 is a third embodiment of the present invention which alternatively includes a conventional electrical power sensor 90 operatively joined to the generator 26 for providing an electrical power signal indicative of generator output power as an input 86h to the detector 82. The output power of the generator 26 is also related to the steamflow to the turbine 24 and a decrease in the power of the generator 26 may be used to indicate failure of one of the control valves 44. The detector 82 compares the electrical power signal from the sensor 90 to a predetermined reference electrical power value thereof to detect the control valve failure based on a predetermined difference therebetween. Again, upon detecting the control valve failure, the signal processor of the detector 82 will provide a suitable actual turbine flow signal to the second selector 84 based on the monitored electrical power signal from the sensor 90 for opening the bypass valve 46, and, a suitable reduction demand signal is also sent to the master controller 38 for reducing power of the reactor 10 to allow the bypass valve 46 to close after preventing undesirable reactor pressure increase. Illustrated schematically in FIG. 4 is yet another, fourth embodiment of the present invention which alternatively includes a plurality of conventional flow sensors 92 each joined in serial flow communication between a respective one of the control valves 44 and the turbine 24 for providing an actual flow signal indicative of the main steamflow through each of the control valves 44, i.e. 86i, j, k. The detector 82 is again effective for comparing each of the flow signals 86i, j, k from the respective sensors 92 with predetermined reference values thereof to detect a control valve failure based on a predetermined difference therebetween. Upon detecting the failure, the signal processor of the detector 82 will provide a suitable actual turbine flow signal to the second selector 84 for again opening the bypass valve 46 to prevent undesirable pressure rise in the pressure vessel 14. Similarly, the signal processor of the detector 82 provides a suitable reduction demand signal through the master controller 38 to the RFCS 28 for reducing the main steamflow from the reactor 10 to allow the bypass valve 46 to close after initially preventing undesirable pressure rise within the pressure vessel 14. The flow sensors 92 may be any conventional sensor including conventional flow venturis which are effective for accurately indicating flowrate, or could be acoustic noise monitors which less accurately indicate flowrate as being either normal or abnormal depending on noise generation. The reduction demand signal provided by the detector 82 to the master controller 38 in all the above examples could be either proportionately related to the decreased ability of the failed control valve 44 to channel its required flowrate, or, in the preferred embodiment, reduces the main steamflow through the steamline 28 in a value attributed to a maximum, normal contribution of a single one of the control valves 44. Since each control valve 44 is predeterminedly sized and limited in flowrate by the first limiter 78, the reduction demand signal from the detector 82 may simply effect a decrease in total steam flowrate through the steamline 22 attributed to the maximum normal contribution of the failed control valve 44. For example, each of the three control valves 44 may be identical for each providing one third of the total required flowrate to the turbine 24. Upon failure of one of the control valves 44, the reduction demand signal provided to the master controller 38 may simply reduce the total flowrate by one third. In another embodiment of the invention as shown in FIG. 1, the reduction demand signal may also be provided to a conventional rod control and information system (RCIS) 94 which controls insertion and withdrawal of conventional control rods 96 by a conventional control rod drive 98 (only one of several being shown). In accordance with the method, power may be reduced in the reactor 10 by suitably inserting the control rods 96 to reduce the main steamflow 20 upon detection of a failure of one of the control valves 44. This will allow the bypass valve 46 to normally close while the non-failed control valves 44 are additionally opened in accordance with the invention described above. The reduction demand signal may be provided by the detector 82 to either or both the RFCS 28 and the RCIS 94 for reducing reactor power in a conventional manner. In yet another embodiment wherein the reactor 10 is in the form of a natural circulation BWR without the RFCS 28, power reduction can be effected by providing the reduction demand signal from the detector 82 solely to the RCIS 94. Accordingly, the control system 12 described above is otherwise conventional except for providing the valve failure detector 82, the second low value selector 84, and related components therein so that conventional normal operation of the control system 12 may occur including the limits provided by the first and second limiters 78 and 80. However, during a failure of one of the control valves 44, the second low value selector 84 provides the actual turbine flow signal as the bypass reference signal to the bypass comparator 68 instead of the normal CV demand ordinarily provided thereto. The lower bypass reference signal will cause the bypass valve 46 to open to prevent undesirable reactor pressure rise, and then reactor power level may be decreased for allowing the bypass valve 46 to close to prevent wasting of the steamflow in the condenser 48 and allowing operation of the reactor 10 at reduced power consistent with the steamflow capability of the non-failed, operable control valves 44. The logic within the detector 82, therefore, effects automatic bypass operation as well as automatic power decrease of the reactor 10 to a level where the bypass valve 46 may be fully closed and the reactor steamflow is within the capability of the unfailed control valves 44. The invention may be implemented in any conventional fashion, for example in the conventional control system components or computer provided for implementing the pressure control system, the turbine control system, the bypass control system, the RFCS 28, and the RCIS 94. And, the various levels of conventional redundancy in the control system may also be provided. For example, the pressure control system including the pressure regulator 50 is typically provided with double redundancy, and the control valve feedback loops are typically provided with triple redundancy for each control valve 44. And, the valve failure detector 82 and its associated components may also be provided in double or triple redundancy as desired. While there have been described herein what are considered to be preferred embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims:
	claims	1. A reactor vessel comprising:a neutron reflector;a lower core plate;a core vessel, the core vessel including a flange portion extending in a direction towards the neutron reflector; anda neutron reflector bolt fastening structure, the neutron reflector bolt fastening structure including:a plurality of divided stage portions composing said neutron reflector which is situated in said core vessel in said reactor vessel;a plurality of tie rods that fix said neutron reflector to said core vessel; anda plurality of bolts that fasten solely a lowermost stage portion of said plurality of stage portions of said neutron reflector to said core vessel,wherein said lowermost stage portion of said neutron reflector includes a plurality of flange portions extending in a direction towards the core vessel and positioned above the lower core plate, andwherein the plurality of bolts are configured to extend through each of the plurality of flange portions of the lowermost stage portion and the lower core plate, and the plurality of bolts extend partially into the flange portion of the core vessel positioned below the lower core plate, to secure the lowermost stage portion of the neutron reflector to the core vessel. 2. The reactor vessel according to claim 1, wherein said plurality of flange portions of the lowermost stage portion are arranged at opposing positions in the outer periphery of said lowermost stage portion of said neutron reflector. 3. The reactor vessel according to claim 1, wherein four of said flange portions of the lowermost stage portion are arranged at equal intervals in the outer periphery of said lowermost stage portion of said neutron reflector. 4. A method for fastening a neutron reflector comprising:fixing a neutron reflector composed of a plurality of divided stage portions and situated in a core vessel in a reactor vessel to said core vessel by means of a plurality of tie rods; andfastening solely a lowermost stage portion of said plurality of stage portions of said neutron reflector to a flange of said core vessel by means of a plurality of bolts, in which said plurality of bolts extend through each of a plurality of flanges of the lowermost stage portion and a lower core plate located below the plurality of flanges of the lowermost stage portion, and the plurality of bolts extend partially into a portion of the flange of the core vessel that extends in a direction of the neutron reflector and is located below the lower core plate, such that the lowermost stage portion is fastened to said flange of the core vessel.
059463660	claims	1. A nuclear reactor, comprising: a core melt collection chamber having at least one wall with structural concrete and a multilevel protective layer; said protective layer having one layer made of refractory concrete and another layer made of ceramic bricks, said protective layer anchored to said structural concrete; said layer made of refractory concrete constructed as prefabricated blocks jointed together and fastened to said structural concrete; and said layer made of ceramic bricks braced to said blocks of said layer made of refractory concrete. a core melt collection chamber including a concrete structure having at least one wall, and a multilevel protective layer; said multilevel protective layer having: a plurality of ceramic bricks forming a second layer, some of said plurality of ceramic bricks fastened to said first layer, others of said plurality of ceramic bricks not fastened to said first layer. 2. The nuclear reactor according to claim 1, wherein said at least one wall is a bottom. 3. The nuclear reactor according to claim 1, wherein said ceramic bricks are jointed together and braced only at individual locations. 4. The nuclear reactor according to claim 1, including tensioning elements concreted into said structural concrete and engaging through holes in said blocks made of refractory concrete for holding said blocks. 5. The nuclear reactor according to claim 1, including ceramic anchors bracing said ceramic bricks. 6. The nuclear reactor according to claim 5, wherein said ceramic anchors contain threaded sleeves. 7. The nuclear reactor according to claim 1, including C-rails, and T-anchors seated in said C-rails for fastening said ceramic bricks. 8. The nuclear reactor according to claim 1, wherein said ceramic bricks have joints therebetween, and zircon felt fills said joints. 9. A nuclear reactor comprising: 10. The nuclear reactor according to claim 9, wherein said second layer includes joints securing adjacent said ceramic bricks together.
	summary
051695944	description	DETAILED DESCRIPTION OF THE INVENTION The numeral 10 generally designates the nozzle dam or subassembly thereof, for which the method of assembly and tool set used therein comprise the invention. As seen in FIG. 1, a portion of the lower head 12 of a nuclear steam generator has a substantially circular manway 14 penetration having a first diameter and a circular or tapered nozzle 16 penetration having a second, larger diameter. The nozzle is connected to a hot or cold leg pipe 18, which contains, during normal operation, a flow of primary coolant from the nuclear reactor vessel into the steam generator. The upper portion of the lower head is defined by a tube sheet 20 which in FIG. 1 is schematically shown, and which is further shown supporting a manipulator 22 for maintenance purposes. The manipulator, typically, may be a Titan 7F available from Schilling Development Inc. of Davis, Cal. and is typically used as fully disclosed and described in U.S. Pat. No. 5,032,350 to install and remove a nozzle dam 10 in nozzle 16. It is immaterial to the instant novel method whether the manipulator 22 is mounted within head 12, for example on tube sheet 20, or outside of head 12. The important requirement is that the manipulator 22 have, for use in head 12, a free end which includes a clamp mechanism 24 for holding an inner nozzle dam segment 30, by means of handle 31 with transverse projection 31a, while outer dam segments 32 are secured thereto or detached therefrom. The dam segments 30 and 32 are sized to pass through the manway 14 and each has means on its edge surface or surfaces facing adjacent segments for engaging its adjacent segments 30 or 32 for assembly and securement by means of the spring loaded camlock component generally designated 36 in FIG. 13. The manipulator 22 is mounted and arranged such that its free end with clamp mechanism 24 can translate the dam subassembly or assembly 10 within the head until the dam subassembly seats within the nozzle 14 to be locked and radially secured therein or released therefrom, by remotely pneumatically actuated radial pins 38 mounted on the dam subassembly or assembly as shown in FIGS. 2 and 14. The means on the edge surface or surfaces of the segments 30 and 32 facing adjacent segments for engaging them for assembly and securement or detachment and disassembly are called sliding brackets and cooperating support bars. In the embodiment illustrated in FIGS. 2 to 5, a sliding bracket 40 is attached by screws 42 to the outer nozzle dam segments 32 and a support bar 44 is attached by screws 42 to either side of center nozzle dam segment 30 for sliding cooperation with the sliding brackets 40. A stop block 46 is fixedly mounted on the end of the support bars 44 to engage stop surfaces 48 on sliding brackets 40 with the completion of the proper amount of sliding action to create the dam subassembly of center segment 30 and adjacent outer segments 32 is accomplished. FIGS. 6 to 8B illustrate alternative sliding bracket, support bar and stop block combinations to those shown in FIGS. 2 to 5. The primed and double primed numbers used in FIGS. 6 to 8B, respectively, correspond to numbers and parts in FIGS. 2 to 5. The major differences between the embodiment of FIGS. 2 to 5 and the alterantives of FIGS. 6, 6A; 7, 7A; and, 8, 8A, 8B are in the shapes and in the amount of "capture" of the support bars 44, 44' and 44'' by the corresponding sliding brackets 40, 40' and 40''. Also, the holes for screws 42 are oriented at 90.degree. in the alternative embodiment of FIGS. 8 to 8B, relative to the embodiments of FIGS. 2 to 7A. Notice that there can be no edgewise assembly or disassembly in FIGS. 6 to 8B, as opposed to FIGS. 2 to 5. The sliding action between segments 30 and 32 is facilitated by orienting the center segment 30 with support bars 40 attached thereto in a generally horizontal position adjacent manway 14 by means of clamp mechanism 24, as opposed to the position of orientation schematically shown in FIG. 1. Then as a sliding bracket 40 on segment 32 moves forward toward stop block 46 for assembly, and away from block 46 for disassembly, the segments 30 and 32 are aligned relative to each other (See FIG. 5) by the application of torque, for example, in the direction of arrow "T" to move segment 32 relative to the manipulator held segment 30. The torquing in the direction of arrow "T", will align the segments 30 and 32 such that their faces 30a and 32a in FIG. 5 are substantially slightly out of contact. This will minimize sliding physical contact between surface 30a and 32a and facilitate relative sliding between the sliding bracket 40 and the support bar 44. In order to facilitate torquing in the direction of arrow "T", for example, and for other assembly and disassembly operations to be described, a tool set is provided and used having a plurality of elongated tools as shown in FIGS. 15-21 for engagement and disengagement with said dam segments 30 and 32; spring loaded camlock components 36; and pneumatically remotely actuated radial pins 38 and fluid lines 50 with quick-connects 52 therefor. The method includes the step of providing and using the tool set of elongated tools of FIGS. 15-21, and within this step are component or subsidiary procedural steps of physical manipulation of the elongated tools of the set from outside the head 12 through the manway 14 to minimize exposure of the tool operator to radiation from within the head 12 and to avoid the necessity of the operator to enter the head. In the case of the torquing operation functionally described above, the tool 60 of FIGS. 15 and 16 is used. Tool 60 is an elongated nozzle dam segment torquing or lifting tool. It is bifurcated and has spaced opposing members 62 and 64 which can engage the peripheral margin or rim 32c of segments 32 from outside the head 12. Torque in the direction of arrow "T" in FIG. 5 is created on segment 32 as the torquing handle 66 on the opposite end from the bifurcation formed by members 62 and 64 to separate surfaces 32a and 30a to reduce sliding friction contact therebetween. At the same time as torquing, or "lifting" as it can be termed when segments 30 and 32 are oriented generally horizontally by the manipulator 22, a pushing action for assembly toward stop block 46 can be accomplished by the tool material joining members 62 and 64. Because this portion of tool 60 is transversely extending it could also engage transverse stiffening ribs 70 of the dam subassembly 10 or the peripheral rim 32c of segments 32 for pulling to slidingly disassembly the segments 30 and 32. The method of the invention includes providing and using an elongated nozzle dam camlock operating tool 80, as shown in FIGS. 17 and 18, as part of the tool set for operation of the components 36 used in the dam subassembly for securing or detaching the aligned dam segments 30, 32 in assembled relation. The camlock operating tool 80 is used on the initially provided camlocks 36 which are mounted in openings 72 through ribs formed by the sliding face to face surfaces 30a and 32a. The tool 80 operates camlocks 36 by means of the levers 36a thereon which are oriented generally parallel to and spaced from the ribbed concave segment surface to face the inside of the head. Some of the ribs create the segment interface surfaces 32a and 32b and some of the ribs 70 are transverse thereto for stiffening the subassembly 10. The elongated tool 80 for operation of the components 36 is manipulated during use over and between the ribs to engage the levers 36a to operate the rib mounted spring loaded camlock components 36 for use in securement or detachment of the segments 30 and 32 into or from a dam subassembly 10. Tool 80 as provided and used has an elongated shaft portion 82 with a handle end 82a and an opposite lever 36a engaging generally T-shaped end with the stem 84 and cross-member 86 of the T-shaped end offset by arm 88 from the axis of shaft 82 to permit operation of the rib mounted spring loaded camlock components 36 of the T-shaped end for securement of the segments 30 and 32 into, or detachment from, a dam subassembly 10 by engagement and manipulation of the T-shaped end 84, 86 against the lever 36a despite the lever 36a being somewhat behind the ribs 70 and 30a, 32a from the manway 14. The method of the invention also includes the providing and using of an elongated nozzle dam quick-connect operating tool or wrench 90 for disconnection of subassembly 10 mounted remotely actuated radial pins 38 including fluid lines 50 which include quick-connects having push-pull operation for stem 50a and body portion 50b connection and disconnection by means of a spring biased body sleeve 50c, in known manner as mentioned above as a "QC" Model. The tool 90 of FIGS. 19 and 20 includes at one end of a shaft portion 92 an offset 94 and a transverse quick-connect body-straddling bifurcated end 96 for engaging the end of spring biased sleeve 50c. A handle end 98 for manipulation outside of head 12 is provided at the opposite end of the shaft portion 92. The offset 94 provides a portion with an axis substantially parallel to the stem 50a and body 50b such that by engagement and physical manipulation of the bifurcated end 96 against the end of the sleeve 50c, from the handle end, the quick-connect "pull" operation to disconnect stem 50a and body 50b can be accomplished to disconnect the subassembly 10 mounted remotely actuated radial pins 38 fluid lines 50. The method of the invention also includes the providing and using an elongated nozzle dam subassembly sealing diaphragm 100 removing and installing tool 102 as shown in FIG. 21. The sealing diaphragm, as seen in FIGS. 2, and 12 have peripheral tabs 104 tensionable, by means of openings 106 in the tabs, into hooked engagement with other tab openings 108 with projections 110 spaced on the subassembly 10 peripheral margin to face the inside of the head 12. The tabs 104 are tensioned for hooking and unhooking operations by providing and using the elongated nozzle dam seal tab tensioning or locking tool 102, for removing and installing the diaphragm 100 on subassembly 10. The elongated tool 102 of the tool set of the method of the invention has an elongated shaft portion 110 with a transversely extending hook end 112 and an opposite handle end 114 for manipulation from outside the head 12. The tensioning of the tab includes the step of inserting the hook end 112 in a tab 104 opening 106 to provide hooking or unhooking clearance within a tab opening 108 for movement of tab 104 into or out of hooked engagement with the projection 110. A tapped hole 109 is used with a screw to provide the projection 110. The tab opening 106 is closer to the tab end than the opening 108 to facilitate use of the tool 102 in the operation. It should be clear that a single larger hole 108 could be used, however, if there were enough clearance provided for both the tool end 112 and the projection or screw 110. Thus, it will be seen that an improved method of remotely installing or removing a nozzle dam in a nuclear steam generator without entering the generator head and by use of a set of elongated tools is provided.
060524359	abstract	A system and method for radiation therapy delivery. Prior to the delivery of the actual treatment, a run up is executed in order to stabilize the RF system. The run up is accomplished by initiating the triggers with the injector and RF pulses out of phase so that the electrons, for example, in the accelerating waveguide do not get accelerated even though the RF system is being pulsed. The RF warm up period during which the injector and RF pulses are out of phase, ends at RAD ON (Radiation On) with the injector pulse being phase-shifted to coincide in time with the RF pulse thereby resulting in the production of electron beam pulses. Following the application of this run up period, precise and rapid disabling and enabling of the treatment beam between IMRT fields can be accomplished. The electron injection is phase-shifted in and out without affecting either the injector or the RF pulse amplitudes, thereby allowing transitions between a stable RAD ON beam and no beam between one pulse and the next.
040242099	description	Very generally, the invention pertains to the manufacture of a nuclear fuel rod in which a mold cavity is partially filled with a bed of nuclear fuel particles and is then closed. The cavity volume is made reducible and is reduced such that fuel particles substantially fill the mold cavity. A fluid solidifiable binder is then injected into the mold cavity to fill the interstices between the fuel particles. The continuing adjustability of the volume of the mold cavity enables compensation for bed contraction resulting from binder injection under pressure and also avoids formation of the voids and/or end caps when the binder material cools and solidifies. Finally, a piston or adjustable column mechanism which is provided to effect adjustment of mold cavity volume is also used to eject the fuel rod from the cavity after solidification. Referring now more particularly to FIG. 1, a cast housing 11 is shown which contains several mold cavities 12 in the form of cylindrical cavities of circular cross section. The cavities may be machined to provide an interior smooth surface, and the housing is also provided with passages 13 and 14 through which a suitable heating fluid or coolant is circulated in order to heat or cool the mold as required during the molding process. The cavities 12 are each of identical construction. A horizontal bore 16 is provided in the housing 11 in a location where it intersects all of the cavities 12 near the lower ends thereof. The bore 16 terminates on the exterior of the housing 11 at a raised boss 18 in which a socket 21 is provided for purposes explained below. The lower ends of each of the cavities 12 are closed by a piston 23 attached to the upper end of a piston rod 25 which passes through a suitable opening 27 formed in a lower closure plate 29. The closure plate 29 is suitably secured to the underside of the housing 11 by means not shown. The employment of the movable piston 23 enables the interior volume of the mold cavity 12 to be adjusted as desired. Referring to FIG. 6, the detailed construction of the piston 23 may be clearly seen, along with the upper end of the piston rod 25 which has an axial bore 31. The lower end of the piston has a cylindrical projection 33 which extends downwardly into the axial bore 31 and is held therein by a transverse pin 35 that is received in aligned openings in the upper end of the piston rod 25 and in the cylindrical extension 33. A land 37 is provided on the piston 23 which provides a close, sliding fit with the inner wall of the mold cavity 12. A second land 39 is spaced above the land 37 and also provides a close sliding fit with the cavity wall. The lands 37, 39 assure the piston slides smoothly up and down within the cylindrical mold cavity. An O-ring 41 is held between the lands 37 and 39 to provide a positive fluid seal between the piston and walls of the cavity 12. The piston 23 is formed with an uppermost head 43 which is dimensioned so there is some clearance between its periphery and the inner surface of the cavity 12. In the region between the head 43 and the land 39, the piston 23 is necked down to a stem portion 45 to provide an annular space 47 between the piston and the walls of the cavity 12. Prior to molding fuel rods, the mold 11 is primed. An injection device 61 having a nozzle 63 is brought in mating engagement with the recess 21 in the boss 18 of the mold housing. At the same time, a suitable heated liquid is circulated through the passageways 13 and 14 in the mold to bring it up to the desired temperature. When the appropriate temperature is reached, a suitable fluid binder is injected into the horizontal bore 16 with the pistons located at the vertical levels shown in FIGS. 3 and 4. The illustrated fuel rods are designed for use in a graphite-moderated reactor, and a binder is used which can be subsequently carbonized to produce a substantially carbon matrix wherein the nuclear fuel particles will be individually supported. The binder is usually a pitch material, such as coal tar pitch, and may contain additional fillers, such as graphite flour or the like, as is known in this art. In general, the binder may be any type of plastic material which can be rendered fluid by the application of heat and which can be solidified by cooling to about room temperature. Because the molding process contemplates heating, cooling and reheating of the binder, it should have thermoplastic properties, as opposed to being based upon a resin which will cross-link or otherwise rigidify upon initial application of heat and thereafter resist softening. The binder injected into the main bore 16 flows about each of the stems 45 of the pistons through each annular space 47 and into the next continuation section of the horizontal bore 16. The binder also flows upward through the clearance provided about the head 43 of each piston to fill the mold cavity 12. After the cavities are all filled with binder, which will mean that the annular spaces 47 about the piston stems 45 are likewise filled, injection of binder is halted, as is heating of the mold 11. Coolant is then circulated through passageways 13 and 14 to cause solidification of the binder in the mold cavities. Thereafter, the top of the mold cavities is removed, and the piston rods 25 are driven upward, as by the application of hydraulic pressure, to eject the cylindrical slugs of solidified binder from the mold cavities 12. Because of its thermoplastic character, the binder material can be salvaged and reused if desired. After ejection, the pistons 23 are retracted to their lowermost position depicted in FIG. 1, and molding of fuel rods is ready to begin. With the mold suitably primed and the pistons 23 lowered, nuclear fuel particles 51 are metered into the cavities from a suitable hopper 53 to only partially fill each cavity. As can be seen in FIG. 2, after filling with the metered charge of fuel particles, a temporary excess space 54 is left at the top of each mold cavity. Because the mold was primed with binder, the binder occupies the clearance between the piston head 43 and the inner wall of the cavity 12, as well as all of the sections of the horizontal bore 16 and thus confines the fuel particles to the cylindrical cavities. After the mold cavities have each received their metered charges of fuel particles, a mold cover plate 55 is attached to the top of the housing 11 and suitably secured thereto by means not shown. The pistons 23 are then raised to an intermediate position by moving the piston rods 25 upward, by the application of hydraulic pressure or the like, in order to substantially eliminate the temporary excess space 54 within each mold cavity so that the particles 51 substantially completely fill the space in the mold cavity between the piston 23 and the mold cover plate 55. Preferably, the piston is moved upwardly with sufficient force to slightly compact the bed of fuel particles therewithin, as depicted in FIG. 3. However, the fuel particles preferably have individual fission-product-retentive coatings, as for example pyrolytic carbon coatings, and care is taken not to fracture the coatings. Generally, coated fuel particles between about 500 and 1200 microns in size are used. Usually, the piston 23 will not be driven to exert a pressure of more than about 600 p.s.i. upon the particles at this time. The cover plate 55 is provided with a plurality of apertures 57 therein which are not aligned with the mold cavities but which communicate with large circular recesses 59 on the underside of the mold cover plate, that are positioned in the areas between the mold cavities, the purposes of which are explained below. Referring now to FIG. 4, the mold cavities 12 are ready for the injection of the solidifiable binder, and the mold is heated by circulating a hot liquid therethrough to soften the binder with which the mold was earlier primed. With the mold at the desired temperature, binder is supplied from an injection device 61 through the nozzle 63 and flows through the bore, through the annular space 47 around each of the piston stems 45, upward past the piston head 43 and into the mold cavity 12. The annular space around each piston registers with the next section of the bore 16 and thus serves as a feeder connection to the next adjacent mold cavity 12. The clearance between the head 43 on each piston 23 and the wall surface of the cavity 12 is dimensioned to prevent the passage of fuel particles therepast, and it acts as a gate through which the fluid binder material enters the mold cavity where the particle bed is located. As the binder enters the particle bed, its lubricity allows the coated fuel particles to readjust their positions and settle still further. This settling is accompanied by upward incremental movements of the piston which, due to the continued upward hydraulic biasing, applies a constant pressure, preferably at least about 600 p.s.i. on the particle bed, keeping it compacted. The piston is also free to move to accommodate any minor shifts in the particle bed due to differential thermal expansion. Because the gate which is formed between the piston head 43 and the inner surface of the mold cavity also travels with any movement in the bed, the effect is one of a moving gate in the molding process, which is possible even though the horizontal bore 16 is stationary, because the axial length of the annular recess 47 is sufficient to remain in registration with the sections of the bore 16. At the beginning of the injection of the fluid binder material, air is expelled from the cavity via an air vent 64 in the form of a shallow groove provided at the top edge of the mold cavity. The circular recess 59 in the underside of the cover plate 55 overlaps the air vent 64, and the aperture 57 leads upward from this recess and out through the plate. Typically, one recess 59 and one aperture 57 serve each pair of cavities, and the groove is dimensioned, e.g., about one-eighth inch long by 0.005 inch deep to prevent the entry of fuel particles thereinto. Air is expelled from the cavity during injection of the fluid binder via the air vent 64, the recess 59 and the aperture 57 to the atmosphere. Once the cavity 12 is completely filled, excess binder material can flow into the recess 59 through the vent passage 64 and up into the aperture 57, as shown in FIG. 4. However, the vent passage 64 is sized so that the coated fuel particles cannot pass therethrough so that there can be no loss of fuel from the metered charge. Once the fluid material reaches the vent passage 64, the back pressure in the mold cavity rises, which in turn restricts the flow of fluid material into that particular cavity, routing it instead through the bore 16. Thus, the vents 64 are used as a control device to ensure the complete filling of all cavities. Upon completion of the injection process, cooling and consequent solidification of the binder material is effected. The cover plate 55 is then raised, and the piston rods 25 are driven further upward in the cavities to eject the fuel rods, indicated at 67 in FIG. 5. At the same time, the excess binder material which has escaped into the recess 59 and the bore 57 is ejected by bringing the plate 55 up sufficiently to cause an ejector pin 69 to contact the machine frame, indicated at 71. The solidified excess binder material, indicated at 73, then falls for suitable collection and possible reuse, as the binder will preferably become sufficiently fluid for molding purposes when heated to a temperature of about 150.degree. to 190.degree. C. At relatively low shear rates, i.e., about 20 to 40 sec..sup.-.sup.1, binders having a viscosity between about 300 and 1000 poise, at 175.degree. C., may be used with coated fuel particles having a minimum size of about 300 microns. However, if higher shear rates are to be employed in the injection, binders having lower viscosities, e.g., 40 to 90 poise may be selected. Referring to FIG. 7, an alternative piston-piston rod combination construction is shown wherein a piston 123 is provided with a pair of lower lands 137 and 139 axially spaced and affixed to the upper end of a piston rod 125. An O-ring 141 is disposed between the lands 137, 139 and a head 143 is provided atop the piston. The head 143 is dimensioned about the same as the lands 137, 139 and forms a close sliding fit with the interior wall of the cavity, not shown. As was the case in the previous embodiment, the piston 123 has a recessed stem 145 that creates an annular space which, when so aligned, interconnects the sections of the bore 16 in the mold cavity. A transverse bore 171 across the piston 123 in the stem 145 provides a passage communicating with the annular space that will be filled with binder, and an axial bore 173 extends to the top of the piston from the passage 171 and acts as the gate which allows fluid binder to enter the mold cavity. Thus, the fluid binder is gated axially through the piston head 143 rather than around the piston head. The invention thus provides an improved method for manufacturing nuclear fuel rods of the type which employs a plurality of nuclear fuel particles embedded within a solid binder matrix. Accidental spillage of nuclear fuel particles from the mold cavities during and after filling due to vibration and shock is alleviated, due to the fact that the mold cavities are only partially filled. The ability of the mold cavity volume to be adjusted as desired avoids the creation of particle voids caused by the need to apply a negative filling tolerance and caused by bed shrinkage under certain circumstances. These are accomplished by providing a mold of variable geometry such that temporary excess space is initially provided for the easy containment of a metered, full charge of particles but which is capable of subsequent adjustment of the cavity volume during injection of binder material. Moreover, voids which could occur as a result of additional compaction during injection of binder are eliminated by maintaining pressure loading on the bed of particles. Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appended claims.
039752330	summary	The present invention relates to neutronic reactors, and to neutron absorbing control elements for neutronic reactors. Structures capable of neutronic reactions produce either converging or diverging reactions, that is, the neutron flux density within the structures either increases or decreases with the passage of time. Structures which converge will not sustain a neutronic chain reaction, the reaction merely dying out as a result of the absorption of neutrons in the structure and leakage from the structure. However, a diverging neutronic chain reaction is self-sustaining and will increase exponentially as long as the structure remains physically unchanged. One of the methods used in the art to control diverging neutronic chain reactions is to insert an adjustable neutron absorbing element into the structure. Fermi et al. U.S. Patent No. 2,708,656, dated May 17, 1955, discloses neutronic reactors controlled by means of neutron absorbing elements positionable within the mass of the reactor structure. Neutronic reactors are generally provided with a radiation and particle shield disposed thereabout in order to protect operating personnel from injurious radiations emanating from the reactor. If a control element is to be positionable within the structure of the reactor, it is generally necessary that the control element pierce the shield surrounding the active portion of the reactor. However, apertures in the shield provide a pathway of escape for neutrons and other radiations and often necessitate additional shielding for the reactor. Hence, it is an object of the present invention to provide a neutronic reactor with neutron absorbing elements for controlling the reaction which pierce the shield of the reactor and minimize the amount of neutrons and other radiations escaping from the apertures in the shield. Most neutronic reactors which are controlled by neutron absorbing elements, are provided with at least two types of neutron absorbing elements. The neutron absorbing elements are often in rod form and are designated "safety rods" and "control rods". Both types of control elements are constructed of neutron absorbing materials and are intended to retard the neutronic chain reaction, but the "control rods" are positionable to provide control for small variations in neutron flux density within the reactor, and the "safety rods" are positionable to control large changes in the neutron flux density within the reactor, or solely for the purpose of starting and stopping the reactor. The present invention is also directed to providing "safety rods" which minimize the escape of radiations through the apertures in the radiation shield, although it may be utilized with "control rods" also.
	description	In a nuclear reactor, a core of nuclear material is confined to a small volume internal to the reactor so that a reaction may occur. In many instances, a controlled nuclear reaction may persist for an extended period of time, such as several years, before refueling of the reactor core is required. Accordingly, when used as a source of heat for converting water into steam, a properly designed nuclear reactor may provide a carbon-free, stable, and highly reliable source of energy. A nuclear reactor may make use of a working fluid, such as water, which may be converted to steam at a pressure significantly above atmospheric pressure. The pressurized steam may then be used to drive a turbine for converting mechanical energy to electric current. The steam may then be condensed back into water, and returned to the reactor. In many nuclear reactors, the cycle of vaporization, condensation, and vaporization of the working fluid may continue day after day and year after year. Thus, a significant feature of a nuclear reactor may be a steam generator that receives liquid coolant at an input side, vaporizes the coolant by way of exposure to the heat source of the nuclear reactor, and provides the vaporized coolant to the input of a turbine. Accordingly, the efficiency, ease of manufacture, performance, and the safety features of the steam generator represent areas of continued investigation, analysis, and evaluation. In some embodiments, a steam generator for a nuclear reactor comprises three or more plenums proximate with a first plane, wherein the first plane intersects a bottom portion of a column of a reactor vessel. The steam generator may further comprise three or more plenums proximate with a second plane, approximately parallel with the first plane, wherein the second plane intersects a top portion of the column. The steam generator may further include a plurality of steam-generating tubes from a flowpath that conveys coolant from one of the three or more plenums located proximate with the first plane to at least one of the three or more plenums proximate with the second plane. In other embodiments, a top portion of a steam generator includes three or more plenums disposed in a plane at approximately 90-degree intervals around a riser column, wherein at least one plenum of the three or more plenums includes an approximately flat tubesheet that faces a bottom portion of the steam generator, and wherein the approximately flat tubesheet of the at least one plenum includes a plurality of perforations, wherein the plurality of perforations changes in density between an area near an inner edge of the at least one plenum and an area near an outer edge of the at least one plenum. In other embodiments, a method of operating a nuclear reactor includes conveying a working fluid from a first group of three or more plenums to a plurality of flowpaths, vaporizing the working fluid in at least some of the plurality of flowpaths, wherein the vaporizing results, at least in part, from coupling thermal energy from a reactor coolant to the at least some of the plurality of flowpaths. The method may further include transferring the vaporized coolant to a second group of three or more plenums. Various systems and arrangements of a steam generator used in a nuclear reactor are described. In implementations, a group of plenums, wherein the group may include four plenums, may be arranged in a first plane at 90-degree increments around a bottom portion of an approximately cylindrical riser column of a nuclear reactor. A second group of plenums, wherein the second group may include four plenums, may be arranged in a second plane at 90-degree increments around a top portion of a cylindrical column of a nuclear reactor. Plenums located at both the top and bottom portions of the cylindrical riser column may include a substantially or approximately flat tubesheet having perforations that permit coupling to one of the plurality of steam generator tubes. In some embodiments, an orifice may be disposed within with at least some perforations of the plenums located proximate with the bottom portion of the cylindrical riser column. The presence of an orifice may result, at least in part, in a decrease in pressure as fluid flows upward from the plenum at the bottom portion of the riser. In certain other embodiments, three plenums may be arranged in a first plane at 120-degree around a bottom portion of an approximately cylindrical riser column of a nuclear reactor. A second group of plenums, wherein the second group may include three plenums, may be arranged in a second plane at 120-degrees around a top portion of a cylindrical riser column of a nuclear reactor. Plenums located at both the top and bottom portions of the cylindrical riser column may include substantially or approximately flat tubesheets having perforations that permit coupling to one or more of the plurality of steam generator tubes that form a flowpath between plenums located at the bottom and top portions of the cylindrical riser column. In some embodiments, an orifice may be disposed within at least some perforations of the plenums located proximate with the bottom portion of the cylindrical riser column. The presence of an orifice may result, at least in part, in a decrease in pressure as fluid flows upward from the plenum at the bottom portion of the riser. In certain embodiments, perforations in one or more of the approximately flat tubesheets of the plenums may be lower in density (for example, fewer in number per unit of area of the tubesheet) near an edge of the plenums closer to the cylindrical riser column and be of higher density (for example, greater in number per unit of area) nearby an outer wall of the reactor vessel enclosing the steam generator. Such a change in density of the perforations in the approximately flat tubesheet may result in an approximately uniform coupling of heat from a primary fluid within the reactor vessel to a secondary, working fluid within the steam generator tubes. As used herein and as described in greater detail in subsequent sections, embodiments of the invention may include various nuclear reactor technologies. Thus, some implementations may include nuclear reactors that employ uranium oxides, uranium hydrides, uranium nitrides, uranium carbides, mixed oxides, and/or other types of radioactive fuel. It should be noted that embodiments are not limited to any particular type of reactor cooling mechanism, nor to any particular type of fuel employed to produce heat within or associated with a nuclear reaction. FIG. 1 is a diagram of a nuclear reactor module employing a steam generator according to an example embodiment. In FIG. 1, reactor core 5 is positioned at a bottom portion of a cylinder-shaped or capsule-shaped reactor vessel 20. Reactor core 5 comprises a quantity of fissile material that generates a controlled reaction that may occur over a period of, for example, several years. Although not shown explicitly in FIG. 1, control rods may be employed to control the rate of fission within reactor core 5. Control rods may comprise silver, indium, cadmium, boron, cobalt, hafnium, dysprosium, gadolinium, samarium, erbium, and europium, or their alloys and compounds. However, these are merely a few of many possible control rod materials. In implementations, a cylinder-shaped or capsule-shaped containment vessel 10 surrounds reactor vessel 20 with the containment vessel being partially or completely submerged within a pool of water or other fluid coolant. The volume between reactor vessel 20 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from reactor vessel 20 to the external environment. However, in other embodiments, the volume between reactor vessel 20 and containment vessel 10 may be at least partially filled with a gas and/or a fluid that increases heat transfer between the reactor vessel and the containment vessel. In a particular implementation, reactor core 5 may be partially or completely submerged within a fluid, such as water, for example, which may include boron or other additive, which rises after making contact with a surface of the reactor core. In FIG. 1, the upward motion of heated coolant is represented by arrow 15 above reactor core 5. The coolant travels upward through riser column 30, which may be at least partially or approximately cylinder shaped, and over the top of steam generators 40 and 42 and is pulled downward by way of convection along the inner walls of reactor vessel 20, thus allowing the coolant to impart heat to steam generators 40 and 42. After reaching a bottom portion of the reactor vessel, contact with reactor core 5 results in heating the coolant as symbolized by arrow 15. Although steam generators are 40 and 42 are shown as comprising distinct elements in FIG. 1, steam generators 40 and 42 may represent a number of helical coils that wrap around riser column 30, which may comprise a cylindrical shape. In another implementation, another number of helical coils may wrap around an upper portion of riser column 30 in an opposite direction, in which, for example, a first helical coil wraps in a counterclockwise direction, while a second helical coil wraps in a clockwise direction. However, nothing prevents the use of differently configured and/or differently oriented heat exchangers and embodiments are not limited in this regard. Further, although fluid line 70 is shown as being positioned just above upper portions of steam generators 40 and 42, in other implementations, reactor vessel 20 may include a lesser or a greater amount of coolant. In FIG. 1, normal operation of the nuclear reactor proceeds in a manner wherein heated coolant rises through a channel defined by riser column 30 and makes contact with steam generators 40 and 42. After contacting steam generators 40 and 42, the coolant sinks towards the bottom of reactor vessel 20 in a manner that induces a thermal siphoning process as shown by arrows 25. In the example of FIG. 1, coolant within reactor vessel 20 remains at a pressure above atmospheric pressure, thus allowing the coolant to maintain a high temperature without vaporizing (i.e. boiling). As coolant within steam generators 40 and 42 increases in temperature, the coolant may begin to boil. As boiling commences, vaporized coolant is routed from a top portion of heat exchangers 40 and 42 to drive one or more of turbines 80 and 82 that convert the thermal potential energy of steam into electrical energy. After condensing, coolant is returned to a bottom portion of heat exchangers 40 and 42. Plenums 85 are located at input ports of steam generators 40 and 42 of FIG. 1. In some embodiments, plenums 85 include an approximately flat tubesheet that couples coolant from turbines 80/82 to steam generators 40/42. At least one of plenums 85, which may be located proximate with a first horizontal plane that intersects a lower portion of riser column 30, comprises an approximately flat tubesheet wherein the flat tubesheet faces upward in the direction of a plane intersecting an upper portion of riser column 30. At least one of plenums 87, which may be located proximate with a second horizontal plane intersecting an upper portion of riser column 30, comprises an approximately flat tubesheet wherein the flat tubesheet faces in the direction of a lower portion of the plane intersecting riser column 30. FIG. 2 shows a dimetric view of a steam generator around an approximately cylindrical riser column according to an example embodiment. In FIG. 2, a flowpath comprising several layers of closely spaced tubes can be seen as extending helically between plenums 100 and plenums 120. In some embodiments, plenums 100 are spaced at 90-degree intervals in a first plane, such as plane 105, around an approximately cylindrical shape that surrounds a riser column. Both plenums 100 and plenums 120 include an approximately flat tubesheet that faces in the direction of plane 115, which intersects a midsection of steam generator 110. In FIG. 2, the tubes extending between plenums 100 and 120 may comprise lengths of approximately 24.0 to 30.0 meters. In certain implementations, the use of three or more plenums proximate with plane 105 and three or more plenums proximate with plane 125 may result, at least in part, in reducing variation in length to a predetermined threshold of each of the steam generator tubes that forms a flowpath between one of plenums 120 with one or more of plenums 100, for example. However, it should be noted that in other implementations, steam-generator tubes forming one more flowpaths between plenums 100 and 120 might comprise lengths of less than 24.0 meters, such as 22.0 meters, 20.0 meters, 18.0 meters, and other example lengths. In still other implementations, the tubes extending between plenums 100 and 120 comprise lengths greater than 30.0 meters, such as 32.0 meters, 35.0 meters, 40.0 meters, and other example lengths. Further, it should be understood that implementations and embodiments of the invention are not limited in this respect. Plenums 120, which may be approximately located in plane 125 near a bottom portion of a riser column, may also be spaced at 90-degree intervals. In FIG. 2, both plenums 100 and 120 comprise approximately flat tubesheets, wherein each tubesheet comprises perforations for coupling coolant from a plenum to the tubes of steam generator 110. In the embodiment of FIG. 2, each of plenums 100, which may be proximate with plane 105, is shown as being approximately or directly above a corresponding plenum of plenums 120 proximate with plane 125. However, nothing prevents one or more of plenums 100 from being rotated in plane 105 with respect to plenums 120. In some embodiments, tubesheets include perforations having a diameter of between 15.0 and 20.0 mm for coupling to the tubes of steam generator 110. However, other embodiments may make use of a tubesheet having perforations of less than 15.0 mm, such as 12.0 mm, 10.0 mm in diameter or smaller. Additionally, certain other embodiments may make use of a tubesheet having perforations greater than 20.0 mm in diameter, such as 25.0 mm, 30.0 mm, 35.0 mm, and other example diameters. FIG. 3 shows a bottom view of a steam generator around an approximately cylindrical riser column according to an example embodiment. In FIG. 3, plenums 220 may be spaced at approximately 90-degree intervals, for example, around an approximately circular shape, which may represent, for example, riser column 30 of FIG. 1. FIG. 3 also shows various concentric layers of steam generator tubes, which may surround a riser column. FIG. 4 shows a top view of a plenum used in a steam generator for a nuclear reactor according to an example embodiment. In FIG. 4, an approximately flat tubesheet having perforations suitable for coupling to individual tubes of a steam generator is shown. The perforations of FIG. 4 may be arranged in concentric arcs in which a larger number of perforations per unit area (e.g., higher density) may be present towards an outer edge, such as outer edge 260, than at inner edge 250 (e.g., lower density). In FIG. 5, edge 250 may correspond to a portion of the plenum closer to a cylindrical riser column, and outer edge 260 may correspond to a portion of the plenum closer to a wall of a reactor vessel, such as reactor vessel 20 of FIG. 1. FIG. 5 shows details of a plenum used in a steam generator for a nuclear reactor according to an example embodiment. In FIG. 5, tubesheet 330 is shown as being approximately flat and comprising an increasing density of perforations as the distance from riser column edge 335 increases. At a portion of plenum 320 closer to reactor vessel wall edge 340, a much larger density of perforations may be present than at a portion of the tubesheet closer to riser column edge 335. FIG. 6 shows an orifice used in a tubesheet perforation of a plenum used in a steam generator of a nuclear reactor according to an example embodiment. In some embodiments, an orifice may be used to reduce pressure of coolant 350, for example, perhaps by an amount of at least 15.0% of an overall pressure drop brought about by the length of a steam generator tube. In some embodiments, by reducing the pressure of coolant 350, pressure stability, which may be of particular concern during startup conditions, for example, may be enhanced. By stabilizing pressure, such as by way of an orifice of FIG. 6 placed within at least some of the perforations of tubesheet 330 of FIG. 5, for example, momentary oscillations between wet steam and dry steam, which may be particularly prevalent during low power operation of the nuclear reactor module of FIG. 1 may be reduced or eliminated. In turn, this may reduce the possibility of wet steam being coupled into turbines 80 and 82 of FIG. 1, for example, which may degrade the performance of one or more of turbines 80 and 82. In some embodiments, a method of operating a nuclear reactor may include conveying a working fluid from a first group of three or more plenums perhaps proximately located, for example, in a first plane of a reactor vessel, to a plurality of flowpaths. The conveying may include reducing pressure of the working fluid by an amount sufficient to preclude flow instability. In an embodiment, the percentage of pressure drop may comprise at least 15.0% of an overall pressure drop brought about by a length of steam generator tubing that may extend between a first plenum located at a first plane and a second plenum located at a second plane. The conveying may include coupling the working fluid to flowpaths through an approximately flat tubesheet of at least one plenum of the first group of three or more plenums. The method may further include vaporizing the working fluid in at least some of the plurality of flowpaths, wherein the vaporizing results, at least in part, from coupling thermal energy from a reactor coolant to at least some of the flowpaths. The method may further include transferring the vaporizing coolant to a second group of three or more plenums perhaps through an approximately flat tubesheet of at least one of the plenums. While several examples have been illustrated and described, it will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from the scope of the following claims.
	description	This application claims the benefit of and priority to Indian Patent Application No. 2751/DEL/2015, filed on Sep. 2, 2015, the entire content of which is incorporated herein by reference in its entirety for all purposes. The present invention relates to functionalized brine sludge material useful for multifarious applications. The invention further relates to a process for the preparation of the said brine sludge functionalized material, which involves in-situ synthesis of multi elemental, micron to nano-sized, non-toxic, functional materials, utilizing unique characteristics of chemical compounds inherently present in the brine sludge. The developed materials find application in areas such as radiation shielding materials, geopolymeric materials and chemically designed composites. The development of nano and non-toxic materials have attracted great attention of material scientists due to their fascinating characteristics, enabling synthesis of multifunctional materials and addressing the challenges of solving problem of utilization of toxic and non-toxic industrial wastes for making value added materials useful for broad application spectrum. Brine sludge is an industrial waste generated in the chloralkali industry. The chloralkali process is the main process for manufacturing of caustic soda and chlorine production all over the world. In India a total of almost 36 chloralkali plants are in operational form. Brine mud generation is around 30 kg per ton caustic soda in India, which is more than double the international average. To achieve total utilization of this brine sludge, no processes have been developed to date. In the chloralkali industry, the production of NaOH and chlorine is carried out by the electrolysis of purified brine solution, i.e. 30% sodium chloride solution, and the process of purification of impure brine solution involves removal of sulphate and chloride salts of magnesium and potassium. Removal of sulphate species is carried out by adding barium carbonate, which is expensive and leads to the generation of toxic brine sludge waste containing barium sulphate. Further removal of chloride species is carried out by adding sodium carbonate leading to the generation of brine sludge containing calcium carbonate and magnesium hydroxide. The generated brine sludge waste is dumped into landfills, which contains barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, clay and toxic elements like chromium, zinc, copper and vanadium, therefore posing environmental threat. Therefore, there is an urgent need to provide a process which converts toxic brine sludge waste into non-toxic form. Reference may be made to the article Utilization of Brine Sludge in Nonstructural Building components: A Sustainable Approach, by Mridul Garg and Aakanksha Pundir in Journal of Waste Management, vol.2014, Article ID 389316, 7 pages, wherein brine sludge has been utilized for making low value items like bricks and paver blocks using conventional cement and fly ash. However, the drawbacks of the cited process are that the brine sludge has been used in conjunction with cement and fly ash for making only paver blocks and bricks with only 35%, i.e. minimal utilization, of brine sludge. Thus, the problem of utilization of 65% brine sludge still remains. Further, the toxic elements present in the brine sludge have only been stabilized in cement matrix without forming any chemical linkages with the toxic elements. Hence, there is no assurance of non-leaching of the toxic elements in the environment from the prepared bricks and paver blocks. Since the brine sludge has not been converted into nano size and in functionalized form, it poses limited application in making paver blocks and brick materials only. Additionally, the developed process is based on the age old concept of stabilization of industrial waste into low value added materials to somehow address the problem of disposal and utilization of waste. The process does not teach the use of any advance synthesis technology for making value added materials so as to meet the challenges and stringent rules and regulations of environmental protection acts to address the problem of utilization of industrial toxic wastes. Reference may be made to the patent publication No. CN101823738A, wherein a method for co-production of fine calcium carbonate and sodium silicate during preparation of light magnesium carbonate by chloralkali brine sludge has been reported. However, the drawbacks of the process are that it involves multiple steps, is energy intensive, and does not utilize the brine sludge in totality, thereby posing threat to the environment. Reference may be made to the patent publication No. CN101823822A, wherein hydrochloric acid is used for purifying precipitates of calcium carbonate and calcium sulphate left after the production of light magnesium carbonate. However, the drawbacks of the process reside in the fact that it involves multiple steps, is energy and equipment intensive, and does not utilize the brine sludge in totality, thereby posing threat to the environment. Further, from the reported prior art it is evident that total utilization of brine sludge for making highly value added advance materials has not been pursued seriously. From the hitherto reported prior art and based on the drawbacks of the known processes, the various issues that need to be addressed and problems to be solved for utilization of toxic brine sludge are summarized here as follows: The brine sludge is toxic and therefore, it creates threat to the environment by remaining unutilized. Since the brine sludge contains very useful and expensive chemical compounds such as barium sulphate, magnesium hydroxide and calcium carbonate, it can find application in making highly value added and functionalized materials such as radiation shielding materials, geo polymeric materials, and advanced chemically designed composite (ACDC) materials by utilizing unique characteristics of chemical compounds inherently present therein. Brine sludge waste is available in micron size particles, thus restricting its functionality and thereby leading to limited applications thereof in making low value items such as paver blocks and brick materials only. The main object of the present invention is therefore to provide functionalized brine sludge composites useful for multifarious applications. Another object of the present invention is to provide a process for the preparation of functionalized brine sludge composites by simultaneous in-situ synthesis of materials inherently present in brine sludge. Yet another object of the present invention is to provide a process which converts micron sized brine sludge to nano sized brine sludge based materials. Still another object of the present invention is to provide a process for the preparation of non-toxic functionalized brine sludge based composite materials which have increased homogeneity among the various constituents present therein. Yet another object of the present invention is to provide a process which utilizes irradiation capability of microwave so as to enable simultaneous and synergistic chemical reactions among the various ions of the reactants, namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water leading to multifunctional ability of the developed materials. Still another object of the present invention is to provide a process which ensures total utilization of toxic brine sludge thereby solving the problem associated with disposal thereof. Yet another object of the present invention is to provide a process which exhibits marked reduction in steps, duration and temperature of synthesis thereby leading to increased productivity. The present invention provides a functionalized brine sludge material and a novel process for making such functionalized brine sludge material useful for a broad application spectrum. The novel process enables simultaneous in-situ synthesis of multi elemental nano-sized, non-toxic, and functionalized brine sludge material, conversion of toxic brine sludge into non-toxic form by forming chemical linkages of toxic elements with silicon and aluminum in fly ash based geopolymeric matrix, conversion of chemical compounds present in brine sludge from micron to nanosize, and increased chemical homogeneity among the various constituents present in the brine sludge imparting functionality to the developed materials. Further, in said process, instead of conventional heating alone, the synchronizing irradiation capability of microwaves can also be utilized so as to enable simultaneous and synergistic chemical reactions among the various ions of the reactants, namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water, which leads to the development of novel materials useful for miscellaneous applications. The developed functionalized brine sludge material has a broad application spectrum (e.g., for making a) radiation shielding materials, b) geopolymeric materials, and c) chemically designed composite materials). The process consist of only two steps, namely 1) Refluxing 2) Filtration and drying. Refluxing—a) Mixture of 10 g-50 g of brine sludge, 50 g-100 g of fly ash, 6 g-13 g of sodium hydroxide, 250 ml-500 ml of ethylene glycol, 1 g-10 g of Cetyl trimethyl ammonium bromide and 12 ml-26 ml of water is refluxed in a round bottom flask in the temperature range of 190 to 250 degree C. for the period of 2-6 hours, OR b) the above mixture is refluxed using microwave synthesizer in the temperature range of 40-45 degree C. for a duration of 15-20 minutes. Filtration and Drying—The above solution was filtered and further dried in an air oven at temperature of 100 degree C.-110 degree C. for a period of 1-2 hours resulting in the simultaneous in-situ synthesis of multi elemental, nano-sized, non-toxic, functionalized brine sludge material. In an embodiment, the present invention provides a process which encompasses the following: Simultaneous in-situ synthesis of materials utilizing brine sludge. Making of nano-sized brine sludge materials from micron size. Creation of non-toxic functionalized brine sludge materials. To have increased homogeneity among the various constituents present in the developed multi-elemental, nano-sized, non-toxic, and functionalized brine sludge material, which is useful for imparting desired functionality thereto. Apart from the conventional heating, the heating done using microwave enables simultaneous and synergistic chemical reactions among the various ions of the reactants, namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water, leading to the development of desired characteristics in the material. Reduction in the duration of synthesis of materials from hours to 15-20 minutes, thereby achieving increased productivity. Solving the problem associated with the disposal of toxic brine sludge waste so as to address the concern of choralkali industry all over the world. To ensure complete utilization of toxic brine sludge in making highly value added and advanced functional materials. To save upon the cost of costly chemicals required for the synthesis of claimed functionalized brine sludge materials, as the process involves the use of chemical entities inherently present in the brine sludge. The prepared functionalized materials have applications in the areas like, e.g., a) radiation shielding materials, b) geopolymeric materials, and c) chemically designed composite (ACDC) materials. The process involves only two steps for the synthesis. In the present process, the synthesis is carried out at relatively low temperature of 40 to 45 degrees C. using microwave synthesizer as compared to a temperature of 190 to 250 degrees C. using conventional heating. In another embodiment of the present invention, the process comprises together refluxing of homogenized mixture of brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water in a round bottom flask. In still another embodiment, the present invention provides a process wherein the solution so obtained after mixing the brine sludge with other ingredients is either heated at a temperature ranging from 190 to 250 degrees C. for a period of 2 to 6 hours or using microwave synthesizer at a temperature ranging from 40 to 45 degrees C. for a period of 15 to 20 minutes. In yet another embodiment, the present invention provides a process wherein the material so obtained is filtered. In still another embodiment, the present invention provides a process wherein the material obtained after filtration is dried in an air oven at a temperature of 100 to 110 degrees C. for a period of 1 to 2 hours, resulting in the simultaneous in-situ synthesis of multi elemental, nano-sized, non-toxic, functionalized brine sludge material. In yet another embodiment, the present invention provides a process wherein the synthesized functionalized brine sludge composite material is useful for making radiation shielding materials, geopolymeric materials, and chemically designed composite materials ensuring total utilization of brine sludge. In still another embodiment, the present invention provides a process which enables a) conversion of toxic brine sludge into non-toxic form by forming chemical linkages of toxic elements with silicon and aluminum present in fly ash-based geopolymeric matrix, b) conversion of chemical compounds present in brine sludge from micron to nano size, and c) increased chemical homogeneity among the various constituents present in brine sludge waste and other reactants. In yet another embodiment, the present invention provides a process wherein the simultaneous and synergistic chemical reactions among the various ions of the reactants, namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water leads to the designing of molecular moieties resulting in multifunctional ability of the developed materials for broad application spectrum. In still another embodiment, the present invention provides a process which obviates the cost of costly chemicals such as barium sulphate, magnesium hydroxide, and calcium carbonate required to be added externally for the synthesis as the chemicals inherently present in brine sludge are utilized. In yet another embodiment, the present invention provides a process wherein cetyl trimetyl ammonium bromide (CTAB) acts as an effective capping agent necessary for the conversion of materials to nano-size. In still another embodiment, the present invention provides a process which involves only two steps for the synthesis of functionalized brine sludge composite material. In yet another embodiment, the present invention provides a process wherein the synthesis temperature is reduced from 190 to 250 degrees C. to 40 to 45 degrees C. because of the use of microwave synthesizer. The brine sludge contains a number of chemical compounds, namely barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, toxic elements like chromium, zinc, copper, and vanadium, and clay-like materials. The presence of all these materials makes the matrix of brine sludge most non-uniform, non-homogeneous, and in segregated form. Therefore, a novel process has been developed to provide uniform, homogeneous brine sludge in non-segregated form. Homogenization of the materials is done automatically during the reaction due to simultaneous and synergistic chemical reactions among the various ions of the reactants namely brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethylammonium bromide, and water. Conversion of brine sludge from micron size to nano-size is done on its own during synthesis due to the presence of cetyl trimethyl ammonium bromide (CTAB), which acts as a powerful capping agent by converting the size of particles into nano range and also acting as a stabilizing agent. The present invention thus provides functionalized brine sludge material prepared from brine sludge waste having multiple elements which are toxic and micron sized. The in-situ synthesis process of the present invention enables the conversion of the brine sludge waste into multi-elemental, nano-sized, non-toxic, and functionalized brine sludge material after adding a few ingredients such as fly ash, CTAB, ethylene glycol, and NaOH. The developed functionalized material is useful for multifarious applications. Accordingly, the present invention provides functionalized brine sludge composite material comprising 10 g-50 g of brine sludge, 50 g-100 g of fly ash, 6 g-13 g of sodium hydroxide, 250 ml-500 ml of ethylene glycol, 1 g-10 g of cetyl trimethyl ammonium bromide, and 12 ml-26 ml of water. The physico-chemical characteristics of the developed functionalized materials are as follows. Field Emission Scanning Electron Microscope (FESEM) imaging of the material shows the size of particles up to 15 nm, which confirms the development of nano-sized functionalized brine sludge material so synthesized. Energy-Dispersive X-Ray Spectroscopy (EDXA) shows the presence of elements like Ba, C, O, Na, Mg, Al, Si, S, Cl, and Ca, which confirms the development of multi-elemental functionalized brine sludge material so synthesized. Fourier Transform Infrared Spectroscopy (FTIR) shows the presence of varying functional group like sulphate, carbonate, hydroxide, etc. in the synthesized functionalized brine sludge. X-Ray Power Diffraction (XRD) confirms the crystalline nature and presence of different phases like barium sulphate, sodium chloride, magnesium hydroxide, silica, calcium carbonate, etc. in the synthesized functionalized brine sludge material. The process for the preparation of the aforesaid functionalized material comprises together refluxing of a homogenized mixture of 10-50 g of brine sludge, 50 g-100 g of fly ash, 6 g-13 g of sodium hydroxide, 250 ml-500 ml of ethylene glycol, 1 g-10 g of Cetyl trimethyl ammonium bromide, and 12 ml-26 ml of water in a round bottom flask at a temperature ranging from 190 to 250 degrees C. for a period of 2 to 6 hours or using a microwave synthesizer at a temperature ranging from 40 to 45 degrees C. for a period of 15 to 20 minutes, thereby enabling simultaneous and synergistic chemical reactions among the various constituents of the brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water. The material thus obtained was filtered and dried in an air oven at a temperature of 100 to 110 degrees C. for a period of 1 to 2 hours resulting in multi-elemental, nano-sized, non-toxic, functionalized brine sludge material. The developed process involves total utilization of toxic brine sludge possessing required complementary constituents for making desired composite materials. It is an energy efficient process requiring low temperature for the synthesis of materials. The use of microwave heating instead of conventional heating in the present process leads to reduction in the synthesis temperature as well as time. The process obviates the need of costly chemicals as it utilizes the chemicals inherently present in brine sludge, thereby making it cost effective and economic. The invented process involves only two steps for the synthesis of functionalized brine sludge composite material. The developed functionalized brine sludge material has a broad application spectrum, e.g., for making a) radiation shielding materials, b) geopolymeric materials, and c) chemically designed composite materials. The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention in any manner. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge material, refluxing of a homogenized mixture of 10 g of brine sludge, 50 g of fly ash, 6 g of sodium hydroxide, 250 ml of ethylene glycol, 1 g of cetyl trimethylammonium bromide, and 12 ml of water was done in a round bottom flask that was heated at temperature of 190 degrees C. for a period of 2 hours, and the material so obtained was further filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge composite material, refluxing of a homogenized mixture of 20 g of brine sludge, 70 g of fly ash, 10 g of sodium hydroxide, 400 ml of ethylene glycol, 5 g of cetyl trimethyl ammonium bromide, and 20 ml of water was done in a round bottom flask and heated at a temperature of 200 degrees C. for a period of 2 hours, and the material so obtained was filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge composite material, refluxing of a homogenized mixture of 40 g of brine sludge, 100 g of fly ash, 13 g of sodium hydroxide, 500 ml of ethylene glycol, 10 g of Cetyl trimethyl ammonium bromide, and 26 ml of water was done in a round bottom flask and heated at a temperature of 210 degrees C. for the period of 6 hours. The material so obtained was filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge composite material, refluxing of a homogenized mixture of 30 g of brine sludge, 90 g of fly ash, 10 g of sodium hydroxide, 300 ml of ethylene glycol, 3 g of cetyl trimethyl ammonium bromide, and 20 ml of water was done in a round bottom flask and heated at a temperature of 200 degrees C. for a period of 2 hours. The material so obtained was filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge composite material, refluxing of a homogenized mixture of 50 g of brine sludge, 50 g of fly ash, 6 g of sodium hydroxide, 250 ml of ethylene glycol, 1 g of Cetyl trimethyl ammonium bromide, and 12 ml of water was done in a round bottom flask at temperature of 220 degrees C. for a period of 2 hours, and the material so obtained was filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. For making multi-elemental, nano-sized, non-toxic, and functionalized brine sludge composite material, refluxing of a homogenized mixture of 45 g of brine sludge, 45 g of fly ash, 6 g of sodium hydroxide, 300 ml of ethylene glycol, 10 g of cetyl trimethyl ammonium bromide, and 12 ml of water was done in a round bottom flask using a microwave synthesizer at a temperature of 45 degrees C. for a duration of 15 minutes. The material so obtained was filtered and dried in an air oven at 110 degrees C. for a period of 1 hour so as to obtain the desired functionalized brine sludge material. Table 1 below recites the properties/characteristics of the composite material obtained in Examples 1 to 6 and demonstrates the effect of various concentrations of raw materials and process parameters on the quality of the product obtained. The product obtained in Example 6 is most desirable. TABLE 1Properties/Characteristics of the prepared functionalized brine sludge materialSlTechniquesProperties/No.usedCharacteristicsExample 1Example 2Example 3Example 4Example 5Example 61Field EmissionIt provides theSize ofSize ofSize ofSize ofSize ofSize ofScanningTopographical ofparticlesparticlesparticlesparticlesparticlesparticlesElectronthe material i.ewere Upwere Upwere Upwere Upwere Upwere UpMicroscopesize of particlesto 20 nmto 17 nmto 16 nmto 18 nmto 20 nmto 15 nm(FESEM)so synthesized.2Energy-It identifies theConfirms theConfirms theConfirms theConfirms theConfirms theConfirms thedispersiveelementalpresence ofpresence ofpresence ofpresence ofpresence ofpresence ofX-raycomposition ofBa, C, O, Na,Ba, C, O, Na,Ba, C, O, Na,Ba, C, O, Na,Ba, C, O, Na,Ba, C, O, Na,spectroscopymaterial.Mg, Al, Si, S,Mg, Al, Si, S,Mg, Al, Si, S,Mg, Al, Si, S,Mg, Al, Si, S,Mg, Al, Si, S,(EDXA)Cl, CaCl, CaCl, CaCl, CaCl, CaCl, Ca3X-rayIt is used forConfirms theConfirms theConfirms theConfirms theConfirms theConfirms thepowderphase identi-presence ofpresence ofpresence ofpresence ofpresence ofpresence ofdiffractionfication ofcrystallinecrystallinecrystallinecrystallinecrystallinecrystalline(XRD)a crystallinenature andnature andnature andnature andnature andnature andmaterial anddifferentdifferentdifferentdifferentdifferentdifferentcan providephases likephases likephases likephases ofphases ofphases ofinformationBaSO4,BaSO4,BaSO4,elementelementelementon unit cellNaCl,NaCl,NaCl,present likepresent. likepresent. likedimensions.Mg(OH)2,Mg(OH)2,Mg(OH)2,BaSO4,BaSO4,BaSO4,SiO2SiO2SiO2NaCl,NaCl,NaCl,CaCO3,CaCO3,CaCO3,Mg(OH)2,Mg(OH)2,Mg(OH)2,Al2O3,Al2O3.Al2O3.SiO2SiO2SiO2CaCO3,CaCO3,CaCO3,Al2O3.Al2O3.Al2O3.4FourierIt identifiesIt confirms theIt confirms theIt confirms theIt confirms theIt confirms theIt confirms theTransformstructures bypresence ofpresence ofpresence ofpresence ofpresence ofpresence ofInfra Redgiving infor-varying func-varying func-varying func-varying func-varying func-varying func-Spectrometermation abouttional grouptional grouptional grouptional grouptional grouptional group(FTIR)functionallike sulphate,like sulphate,like sulphate,like sulphate,like sulphate,like sulphate,groups present.carbonate,carbonate,carbonate,carbonate,carbonate,carbonate,hydroxide etc.hydroxide etc.hydroxide etc.hydroxide etc.hydroxide etc.hydroxide etc. The process enables the conversion of toxic brine sludge into non-toxic form by forming chemical linkages of toxic elements with silicon and aluminum present in fly ash. Due to the use of microwave heating the number of steps in the process, temperature of synthesis and duration are minimized. It enables the conversion of chemical compounds present in brine sludge from micron size to nano size. It enables increased chemical homogeneity among the various constituents present in brine sludge waste and other reactants. The use of cetyl trimethyl ammonium bromide (CTAB) results in effective capping necessary for the synthesis of materials in nanosizes. The process saves the cost of costly chemicals such as barium sulphate, magnesium hydroxide and calcium carbonate as the chemicals inherently present in brine sludge are utilized for the reaction. It involves only two steps for the synthesis of functionalized brine sludge material.
056065892	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to the field of medical radiography, and more particularly to a method of making an X-ray scatter reducing air cross grid for use in mammographic procedures, a movable or Bucky air cross grid produced by the method and a method for using the air cross grid in a mammographic procedure. 2. Description of the Prior Art Scattered X-ray radiation (sometimes referred to as secondary or off-axis radiation) is generally a serious problem in the field of radiography. Scattered X-ray radiation is a particularly serious problem in the field of mammography where high contrast mammogram images are required to detect subtle changes in breast tissue. Prior to the present invention, scattered X-ray radiation in mammography has been reduced through the use of a conventional linear focused scatter-reducing grid. The grid is interposed between the breast and the film-screen and tends to allow only the primary, information-containing radiation to pass to the film-screen while absorbing secondary or scattered radiation which contains no useful information about the breast being irradiated to produce an X-ray image. Conventional focused grids used in mammography generally comprise a plurality of X-ray opaque lead foil slats spaced apart and held in place by aluminum or fiber interspace filler. In focused grids, each of the lead foil slats, sometimes referred to as lamellae, are inclined relative to the plane of the film so as to be aimed edgewise towards the focal spot of the X-rays emanating from the mammographic X-ray source. Usually, during a mammographic exposure, the standard practice is to move the focused grid in a lateral direction, perpendicular to the lamellae, so as to prevent the formation of a shadow pattern of grid lines on the X-ray image, which would appear if the grid were allowed to remain stationary. Such moving grids are known as Bucky grids. One problem with conventional mammographic grids of the type described above is that the aluminum or fiber interspace filler material absorbs some of the primary, relatively low energy, information-containing X-ray radiation. Because some of the primary radiation is absorbed by the interspace material, the patient must be exposed (theoretically) to a higher dose of radiation than would be necessary if no grid were in place in order to compensate for the absorption losses imposed by the grid. It is an obvious goal in all radiography applications to expose the patient to the smallest amount of radiation needed to obtain an image having the highest image quality in terms of film blackening and contrast. Another problem with such conventional focused mammographic grids of the parallel lamellae type described above is that they do not block scattered radiation components moving in a direction substantially parallel to the plane of the lamellae. The resulting images using these grids have less than optimal darkness and contrast. These and other disadvantages, such as structural weaknesses, with the conventional focused scatter reducing grids of the type described above are set forth in U.S. Pat. Nos. 1,476,048; 2,133,385; and 2,605,427. Several prior art patents, such as U.S. Pat. Nos. 4,288,697; 4,465,540; 4,951,305 have suggested focused crossed-pattern type grid structures to overcome some of the above noted disadvantages with the conventional parallel-lamellae scatter reducing grids described above. For example, U.S. Pat. No. 2,605,427 suggests forming a cross-patterned grid comprising a plate of a substance permeable to X-rays formed, in two preferably perpendicular directions with narrow closely-spaced grooves filled with a substance impermeable to X-rays. The basic problem with the cross-patterned grid described in this U.S. Pat. No. 2,605,427 is that the X-ray permeable materials, similar to the fiber and aluminum interspace materials in conventional mammographic grids currently used, are not totally X-ray permeable, that is, the material still absorbs some of the primary X-rays, resulting in a lower transmission rate of primary X-rays to the X-ray film and leading to higher X-ray dosages to the patient. U.S. Pat. No. 4,465,540 describes a collimator for a Gamma camera system. The collimator described therein is constructed by assembling a plurality of X-ray collimating layers comprising radiation-absorbent materials having openings etched therein. The collimating layers are assembled in a spaced apart relationship with a plurality of radiation transmissive spacer layers between each collimating layer. The assembly is held together at the periphery by bolts. Several problems arise when attempting to apply this particular construction to make a focused, moving mammographic scatter reducing grid. First, like other grids previously mentioned, there are several layers of X-ray transmissive spacer layers within each focused passage or opening. Although characterized as X-ray transmissive, these layers within the X-ray transmissive openings still absorb more radiation than if the openings were straight through and only filled with air. These layers also present the potential to cause some scatter of X-rays leaving the collimator. Another problem with this construction is that the X-ray absorbing layers in the middle of the collimator are not physically bound together. Although not apparently a problem in Gamma camera systems, this can present a problem in mammography because the common practice is to move the grid during an exposure to blur grid lines, and there is a risk that the unbonded layers could physically separate from one another and distort the resulting image. Two additional patents, U.S. Pat. Nos. 5,231,654 and 5,231,655, describe computerized tomography (CT) X-ray collimators formed of one or more layers of Corning Fotoform.TM. photosensitive glass, with focused passages etched away to form cross grids with thick glass partitions between the air passages. The effective primary radiation-transmission area of these cross grids is drastically reduced by the radiation absorbing cross-sectional area of the thick glass partitions. Only about 20% to 25% of the grid transmits primary radiation and the X-ray dose absorbed by the patient is correspondingly increased. Therefore, such thick-partition glass grids are totally unsuitable for low energy mammography X-rays requiring maximum image contrast with minimum radiation dosage. SUMMARY OF THE INVENTION Accordingly, a principal object of the present invention is to produce sturdy cellular air cross grids having focused air passages extending through them offering maximum radiation transmissivity area and minimum structural area necessarily blocking primary radiation while maintaining adequate structural integrity for the cross grid during use. Another object of the invention is to provide such air cross grids maximizing contrast and accuracy of the resulting mammograms produced with the same or comparable radiation dosages. A further object of the invention is to provide such cross grids sturdily formed of laminated layers of metal selectively etched by chemical milling or photo-etching techniques to provide open focused passages through the laminated stack of etched metal layers. Still another object of the invention is to provide methods of fabricating laminated focused metal cross grids of this character, employing adhesive or diffusion bonding joining the abutting edges of thin partition portions of the laminated abutting layers with minimum intrusion of bonding material into the open focused passages. Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.
051981831	summary	FIELD OF THE INVENTION The present invention relates generally to an apparatus and method for close packing of nuclear fuel assemblies. More specifically, the present invention relates to placement of at least one neutron absorbing plate between columns of nuclear fuel rods within a nuclear fuel assembly. BACKGROUND OF THE INVENTION In the nuclear power industry, storage and transportation of nuclear fuel assemblies is complicated by having to "nuclearly" isolate portions of nuclear fuel from other portions in order to avoid conditions of criticality which could lead to an uncontrolled nuclear chain reaction. Nuclear fuel assemblies are made up of fuel rods supported in a rack structure and separated with grid spacers. Interspersed within the fuel rod matrix are control rod guide tubes. Nuclear isolation in storage and transportation is presently done in three ways; (1) placing neutron absorbing material between nuclear fuel assemblies, or by placing nuclear fuel assemblies into neutron absorbing baskets, (2) dismantling the nuclear fuel assembly and consolidating fuel rods into close packed arrays, and (3) relying on "burnup" or depletion of fuel to allow close packing of nuclear fuel assemblies without interposing neutron absorbing material. Each method has inherent disadvantages. Placement of neutron absorbing material between nuclear fuel assemblies or placement of nuclear fuel assemblies into baskets increases the volume required for storage or transportation of multiple nuclear fuel assemblies. Moreover, use of a basket imposes a fixed amount of neutron absorbing material whether the assembly is fresh or spent. Consolidation of nuclear fuel assemblies is limited because the operation must be done under water such as in a spent fuel pool. Relying on burnup precludes close storage or transportation of new or partially spent nuclear fuel assemblies. In addition, there is a risk that a spent nuclear fuel assembly is not as "spent" as expected. It would be advantageous to closely pack nuclear fuel assemblies by eliminating neutron absorbing material placed between nuclear fuel assemblies, without having to consolidate them and using only enough neutron absorbing material appropriate for the status of a particular nuclear fuel assembly. The present invention offers just such a solution. SUMMARY OF THE INVENTION The present invention relates generally to an apparatus and method for close packing of nuclear fuel assemblies. More specifically, the present invention relates to placement of at least one neutron absorbing plate between columns of nuclear fuel rods within a nuclear fuel assembly. The apparatus of the present invention is a plate of neutron absorbing material. The plate may have a releasable locking feature permitting the plate to be secured within a nuclear fuel assembly between nuclear fuel rods during storage or transportation, then removed for further use or destruction of the nuclear fuel assembly. The method of the present invention has the step of placing a plate of neutron absorbing material between nuclear fuel rods within a nuclear fuel assembly, preferably between the two outermost columns of nuclear fuel rods. Additionally, the plate may be releasably locked in place. The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.
051951134	claims	1. An X-ray exposure apparatus comprising: an X-ray beam generating source; an exposure apparatus body disposed independently from the X-ray beam generating source, said exposure apparatus body including an outer casing defining an exposure chamber; an alignment optical system accommodated in the exposure chamber; supporting means disposed on a base for supporting the exposure apparatus body to be swingable thereto; raising means mounted on the supporting means for raising the exposure apparatus body in a floating manner and adjusting a height position and an inclination thereof so that an optical axis of the alignment optical system substantially coincides with an axis of an irradiated X-ray beam; and securing means for securing the exposure apparatus body after adjusting the height position and the inclination thereof. said supporting means comprises an oscillation removing member and an elastic member disposed between the base and the oscillation removing member and wherein said raising means comprises an air cushion means secured to the oscillation removing member and expandable vertically so as to raise the exposure apparatus body in a floating manner. said air cushion means comprises a plurality of air cushions disposed at predetermined portions on the oscillation removing member, each air cushion being adjustable in a desirable expanded height individually by adjusting an amount of air to be supplied the air cushion. said securing means comprises a plurality of adjusting bolts each having one end secured to the oscillation removing member and another end formed in spherical shape so as to be capable of carrying the bottom of the exposure apparatus body on the spherical shape, a bracket arranged on the oscillation removing member and a plurality of clamping bolts screw engaged with the bracket for clamping side peripheral portions of the exposure apparatus body in a clamped manner so as to prevent the exposure apparatus body from moving in a horizontal plane. said adjusting bolts are disposed at more than three portions on the oscillation removing member. said adjusting bolts are adjustable in height positions. said X-ray beam generating source is a synchrotron. said apparatus further comprises a controller for calculating a front height and a rear height of the exposure apparatus body on the basis of at least two heights of the X-ray beam so that the optical axis of the alignment optical system substantially coincides with the axis of the irradiated X-ray beam; and height sensors provided on the supporting means for measuring an actual front height and an actual rear height of the exposure apparatus and for outputting signals to the controller, wherein the raising means has a plurality of air cushions connected to air pipes supplying the air thereto, each pipe having an adjusting valve, and wherein the adjusting valves are controlled by the controller on the basis of the calculated values and the measured actual values of the front height and the rear height of the exposure apparatus body. raising the exposure apparatus body in a floating manner by raising means on the supporting means; adjusting a height position and an inclination of the exposure apparatus body by controlling the raising means so that an axis of an X-ray beam generated from the X-ray beam generating source substantially coincides with an optical axis, as a measurement reference, of the alignment optical system, and wherein said adjusting step further comprises, calculating a front height and a rear height of the exposure apparatus body on the basis of at least two heights of the X-ray beam so that the axis of the X-ray beam coincides with the optical axis of the alignment optical system, measuring an actual front height and an actual rear height of the exposure apparatus body, and controlling the raising means on the basis of the calculated values and the measured actual values of the front height and the rear height of the exposure apparatus body; and securing the exposure apparatus body to the height position and the inclination adjusted in the aforementioned step by securing means. 2. The X-ray exposure apparatus according to claim 1, wherein 3. The X-ray exposure apparatus according to claim 2, wherein 4. The X-ray exposure apparatus according to claim 1, wherein 5. The X-ray exposure apparatus according to claim 4, wherein 6. The X-ray exposure apparatus according to claim 5, wherein 7. The X-ray exposure apparatus according to claim 1, wherein 8. The X-ray exposure apparatus according to claim 1, wherein 9. A method of positioning an X-ray exposure apparatus comprising and X-ray beam generating source, supporting means and an exposure apparatus body supported on the supporting means and including an alignment optical system, the method comprising the steps of:
	description	This application is a continuation-in-part of U.S. patent application Ser. No. 11/297,641 filed Dec. 9, 2005, the entire contents of which is hereby incorporated by reference. The present invention relates to lithographic projection apparatus and methods. The term “programmable patterning structure” as here employed should be broadly interpreted as referring to any configurable or programmable structure or field that may be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of a substrate; the terms “light valve” and “spatial light modulator” (SLM) can also be used in this context. Generally, such a pattern will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit or other device (see below). Examples of such patterning structure include: A programmable mirror array. One example of such a device is a matrix-addressable surface having a viscoelastic control layer and a reflective surface. The basic principle behind such an apparatus is that (for example) addressed areas of the reflective surface reflect incident radiation as diffracted radiation, whereas unaddressed areas reflect incident radiation as undiffracted radiation. Using an appropriate filter, the undiffracted radiation can be filtered out of the reflected beam, leaving only the diffracted radiation behind; in this manner, the beam becomes patterned according to the addressing pattern of the matrix-addressable surface. An array of grating light valves (GLVs) may also be used in a corresponding manner, where each GLV may include a plurality of reflective ribbons that can be deformed relative to one another (e.g., by application of an electric potential) to form a grating that reflects incident radiation as diffracted radiation. A further alternative embodiment of a programmable mirror array employs a matrix arrangement of very small (possibly microscopic) mirrors, each of which can be individually tilted about an axis by applying a suitable localized electric field, or by employing piezoelectric actuation means. For example, the mirrors may be matrix-addressable, such that addressed mirrors will reflect an incoming radiation beam in a different direction to unaddressed mirrors; in this manner, the reflected beam is patterned according to the addressing pattern of the matrix-addressable mirrors. The required matrix addressing can be performed using suitable electronic means. In both of the situations described hereabove, the patterning structure can comprise one or more programmable mirror arrays. More information on mirror arrays as here referred to can be gleaned, for example, from U.S. Pat. Nos. 5,296,891 and 5,523,193 and PCT Patent Application Nos. WO 98/38597 and WO 98/33096, which documents are incorporated herein by reference. In the case of a programmable mirror array, the support structure may be embodied as a frame or table, for example, which may be fixed or movable as required. A programmable LCD array. An example of such a construction is given in U.S. Pat. No. 5,229,872, which is incorporated herein by reference. As above, the support structure in this case may be embodied as a frame or table, for example, which may be fixed or movable as required. It should be appreciated that where pre-biasing of features, optical proximity correction features, phase variation techniques, and/or multiple exposure techniques are used, the pattern “displayed” on the programmable patterning structure may differ substantially from the pattern eventually transferred to the substrate or layer thereof. Lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays, and other devices involving fine structures. In such a case, the programmable patterning structure may generate a circuit pattern corresponding to an individual layer of, for example, the IC, and this pattern can be imaged onto a target portion (e.g., comprising one or more dies and/or portion(s) thereof) on a substrate (e.g., a glass plate or a wafer of silicon or other semiconductor material) that has been coated with a layer of radiation-sensitive material (e.g., resist). In general, a single substrate will contain a whole matrix or network of adjacent target portions that are successively irradiated via the projection system (e.g., one at a time). The lithographic projection apparatus may be of a type commonly referred to as a step-and-scan apparatus. In such an apparatus, each target portion may be irradiated by progressively scanning the mask pattern under the beam in a given reference direction (the “scanning” direction) while substantially synchronously scanning the substrate table parallel or anti-parallel to this direction. Since, in general, the projection system will have a magnification factor M (generally<1), the speed V at which the substrate table is scanned will be a factor M times that at which the mask table is scanned. A beam in a scanning type of apparatus may have the form of a slit with a slit width in the scanning direction. More information with regard to lithographic devices as here described can be gleaned, for example, from U.S. Pat. No. 6,046,792, which is incorporated herein by reference. In a manufacturing process using a lithographic projection apparatus, a pattern (e.g., in a mask) is imaged onto a substrate that is at least partially covered by a layer of radiation-sensitive material (e.g., resist). Prior to this imaging procedure, the substrate may undergo various other procedures such as priming, resist coating, and/or a soft bake. After exposure, the substrate may be subjected to other procedures such as a post-exposure bake (PEB), development, a hard bake, and/or measurement/inspection of the imaged features. This set of procedures may be used as a basis to pattern an individual layer of a device (e.g., an IC). For example, these transfer procedures may result in a patterned layer of resist on the substrate. One or more pattern processes may follow, such as deposition, etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., each of which may be intended to create, modify, or finish an individual layer. If several layers are required, then the whole procedure, or a variant thereof, may be repeated for each new layer. Eventually, an array of devices will be present on the substrate (wafer). These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc. Further information regarding such processes can be obtained, for example, from the book “Microchip Fabrication: A Practical Guide to Semiconductor Processing,” Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN 0-07-067250-4. The term “projection system” should be broadly interpreted as encompassing various types of projection system, including refractive optics, reflective optics, catadioptric systems, and micro lens arrays, for example. It is to be understood that the term “projection system” as used in this application simply refers to any system for transferring the patterned beam from the programmable patterning structure to the substrate. For the sake of simplicity, the projection system may hereinafter be referred to as the “projection lens.” The radiation system may also include components operating according to any of these design types for directing, shaping, reducing, enlarging, patterning, and/or otherwise controlling the beam of radiation, and such components may also be referred to below, collectively or singularly, as a “lens.” Further, the lithographic apparatus may be of a type having two or more substrate tables (and/or two or more mask tables). In such “multiple stage” devices the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposures. Dual stage lithographic apparatus are described, for example, in U.S. Pat. No. 5,969,441 and PCT Application No. WO 98/40791, which documents are incorporated herein by reference. The lithographic apparatus may also be of a type wherein the substrate is immersed in a liquid having a relatively high refractive index (e.g., water) so as to fill a space between the final element of the projection system and the substrate. Immersion liquids may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the first element of the projection system. The use of immersion techniques to increase the effective numerical aperture of projection systems is known in the art. In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g., having a wavelength in the range 5-20 nm), as well as particle beams (such as ion beams or electron beams). In presently known lithographic projection apparatus using programmable patterning structure, the substrate table is scanned in the path of the patterned radiation beam (e.g., below the programmable patterning structure). A pattern is set on the programmable patterning structure and is then exposed on the substrate during a pulse of the radiation system. In the interval before the next pulse of the radiation system, the substrate table moves the substrate to a position as required to expose the next target portion of the substrate (which may include all or part of the previous target portion), and the pattern on the programmable patterning structure is updated if necessary. This process may be repeated until a complete line (e.g., row of target portions) on the substrate has been scanned, whereupon a new line is started. During the small but finite time that the pulse of the radiation system lasts, the substrate table may consequently have moved a small but finite distance. Previously, such movement has not been a problem for lithographic projection apparatus using programmable patterning structure, e.g., because the size of the substrate movement during the pulse has been small relative to the size of the feature being exposed on the substrate. Therefore the error produced was not significant. However, as the features being produced on substrates become smaller, such error becomes more significant. U.S. Publication Application No. 2004/0141166 proposes one solution to this problem. Although specific reference may be made in this text to the use of the apparatus according to an embodiment of the invention in the manufacture of ICs, it should be explicitly understood that such an apparatus has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display (LCD) panels, thin-film magnetic heads, thin-film-transistor (TFT) LCD panels, printed circuit boards (PCBs), DNA analysis devices, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” in this text should be considered as being replaced by the more general terms “substrate” and “target portion”, respectively. According to an embodiment of the invention, there is provided a lithographic projection apparatus, comprising a projection system configured to project a patterned radiation beam onto a target portion of a substrate; a positioning structure configured to move the substrate relative to the projection system during exposure by the patterned radiation beam; a pivotable mirror configured to move the patterned radiation beam relative to the projection system during at least one pulse of the patterned radiation beam; and an actuator configured to oscillatingly pivot the mirror according to an oscillation timing that substantially corresponds to a pulse frequency of a radiation system and such that the patterned radiation beam is scanned in substantial synchronism with the movement of the substrate during the at least one pulse. According to an embodiment of the invention, there is provided a device manufacturing method, comprising: providing a pulsed beam of radiation; patterning the pulsed beam of radiation according to a desired pattern; projecting the patterned radiation beam onto a target portion of a layer of radiation-sensitive material that at least partially covers a substrate; moving the substrate relative to a projection system that projects the patterned radiation beam onto the substrate during exposure; and oscillatingly pivoting a pivotable mirror according to an oscillation timing that substantially corresponds to a pulse frequency of the patterned radiation beam, so as to alter a path of the patterned radiation beam relative to the projection system during at least one pulse of the patterned radiation beam, wherein the path is altered in substantial synchronism with the movement of the substrate during the at least one pulse and wherein a cross-section of the patterned radiation beam is projected onto a plane substantially parallel to a surface of the target portion of the substrate. According to an embodiment of the invention, there is provided a device manufacturing method, comprising: moving a substrate relative to a projection system that projects a patterned radiation beam onto a substrate during exposure; oscillatingly pivoting a pivotable mirror according to an oscillation timing that substantially corresponds to a pulse frequency of the patterned radiation beam so as to alter a path of the patterned radiation beam in substantial synchronism with movement of the substrate; and projecting the patterned radiation beam onto the substrate. In the Figures, corresponding reference symbols indicate corresponding parts. Embodiments of the invention include, for example, methods and apparatus that may be used to reduce errors caused by movement of the substrate during a pulse of the radiation system. FIG. 1 schematically depicts a lithographic projection apparatus 1 according to a particular embodiment of the invention. The apparatus comprises: A radiation system configured to supply (e.g., having structure capable of supplying) a beam of radiation. In this particular example, the radiation system Ex, IL, for supplying a beam PB of radiation (e.g., UV or EUV radiation) also comprises a radiation source LA; A programmable patterning structure PPM (e.g., a programmable mirror array) configured to apply a pattern to the beam. In general, the position of the programmable patterning structure will be fixed relative to projection system PL. However, it may instead be connected to a positioning structure configured to accurately position it with respect to projection system PL; An object table (substrate table) WT configured to hold a substrate. In this example, substrate table WT is provided with a substrate holder for holding a substrate W (e.g., a resist-coated semiconductor wafer) and is connected to a positioning structure PW for accurately positioning the substrate with respect to projection system PL and (e.g., interferometric) measurement structure IF, which is configured to accurately indicate the position of the substrate and/or substrate table with respect to projection system PL; and A projection system (“projection lens”) PL (e.g., a quartz and/or CaF2 projection lens system, a catadioptric system comprising lens elements made from such materials, and/or a mirror system) configured to project the patterned beam onto a target portion C (e.g., comprising one or more dies and/or portion(s) thereof) of the substrate W. The projection system may project an image of the programmable patterning structure onto the substrate. As here depicted, the apparatus is of a reflective type (e.g., has a reflective programmable patterning structure). However, in general, it may also be of a transmissive type (e.g., with a transmissive programmable patterning structure) or have aspects of both types. The source LA (e.g., a mercury lamp, an excimer laser, an electron gun, a laser-produced plasma source or discharge plasma source, or an undulator provided around the path of an electron beam in a storage ring or synchrotron) produces a beam of radiation. This beam is fed into an illumination system (illuminator) IL, either directly or after having traversed a conditioning structure or field, such as a beam expander Ex, for example. The illuminator IL may comprise an adjusting structure or field AM for setting the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the beam, which may affect the angular distribution of the radiation energy delivered by the beam at, for example, the substrate. In addition, the apparatus will generally comprise various other components, such as an integrator IN and a condenser CO. In this way, the beam PB impinging on the programmable patterning structure PPM has a desired uniformity and intensity distribution in its cross-section. It should be noted with regard to FIG. 1 that the source LA may be within the housing of the lithographic projection apparatus (as is often the case when the source LA is a mercury lamp, for example), but that it may also be remote from the lithographic projection apparatus, the radiation beam which it produces being led into the apparatus (e.g., with the aid of suitable direction mirrors); this latter scenario is often the case when the source LA is an excimer laser. The one or more embodiments of the invention and the claims encompass both of these scenarios. In a typical source LA, there are a number of effects that can result in imaging errors in lithographic imaging processes. In an embodiment wherein the source LA provides pulsed radiation, for instance, these may include pulse amplitude variation, pulse-width variation, and pulse-to-pulse variation, also known as jitter. The beam PB subsequently intercepts the programmable patterning structure PPM, which may be held on a mask table (not shown). Having been selectively reflected by (alternatively, having traversed) the programmable patterning structure PPM, the beam PB passes through the projection system PL, which focuses the beam PB onto a target portion C of the substrate W. In the embodiment of FIG. 1, a beam splitter BS serves to direct the beam to the patterning structure PPM, while also allowing it to pass through to the projection system PL, however alternate geometries are within the scope of one or more embodiments of the present invention. It should be appreciated that although an embodiment of the present invention is described herein in relation to a lithographic apparatus incorporating a programmable patterning structure to impart a pattern to a beam of radiation, the invention is not limited to such an arrangement. In particular, an embodiment of the invention may be used in conjunction with a lithographic apparatus in which a mask, for example held on a mask table, is used to impart a pattern to the beam of radiation. With the aid of the positioning structure (and interferometric measuring structure IF), the substrate table WT can be moved accurately, e.g., so as to position different target portions C in the path of the beam PB. Where used, a positioning structure for the programmable patterning structure PPM can be used to accurately position the programmable patterning structure PPM with respect to the path of the beam PB (e.g., after a placement of the programmable patterning structure PPM, between scans, and/or during a scan). In general, movement of the object table WT may be realized with the aid of a long-stroke module (e.g., for coarse positioning) and a short-stroke module (e.g., for fine positioning), which are not explicitly depicted in FIG. 1. A similar system may be used to position the programmable patterning structure PPM. It will be appreciated that, to provide the required relative movement, the beam may alternatively or additionally be movable, while the object table and/or the programmable patterning structure PPM may have a fixed position. Programmable patterning structure PPM and substrate W may be aligned using substrate alignment marks P1, P2 (possibly in conjunction with alignment marks of the programmable patterning structure PPM). The depicted apparatus can be used in several different modes. In one scan mode, the mask table is movable in a given direction (the so-called “scan direction,” e.g., the y direction) with a speed v, so that the beam PB is caused to scan over a mask image. Concurrently, the substrate table WT is simultaneously moved in the same or opposite direction at a speed V=Mv, in which M is the magnification of the projection system PL (typically, M=¼ or ⅕). In some embodiments, the demagnification is significantly smaller than 1, for example smaller than 0.3, smaller than 0.1, smaller than 0.05, smaller than 0.01, smaller than 0.005, or smaller than 0.0035. Likewise, it is contemplated that M may be larger than 0.001, or may be within a range between 0.001 and the foregoing upper limits. In this manner, a relatively large target portion C can be exposed, without having to compromise on resolution. In another mode, the mask table is kept essentially stationary holding a programmable patterning structure, and the substrate table WT is moved or scanned while a pattern imparted to the beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning structure is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to lithography that utilizes programmable patterning structure, such as a programmable mirror array as referred to above. Combinations and/or variations on the above-described modes of use or entirely different modes of use may also be employed. An apparatus as depicted in FIG. 1 may be used, for example, in the following manner. In pulse mode, the programmable patterning structure PPM is kept essentially stationary, and the entire pattern is projected onto a target portion C of the substrate using a pulsed radiation source. The substrate table WT is moved with an essentially constant speed such that the beam PB is caused to scan a line across the substrate W. The pattern on the programmable patterning structure PPM is updated as required between pulses of the radiation system, and the pulses are timed such that successive target portions C are exposed at the required locations on the substrate W. Consequently, the beam PB can scan across the substrate W to expose the complete pattern for a strip of the substrate. Such a process may be repeated until the complete substrate W has been exposed line by line. Different modes may also be used. Because of the relative motion of the substrate table during imaging, changes in the time domain at the radiation source LA map to changes in the spatial domain at the substrate table WT. This results in two main effects. First, when there is a change in the pulse interval, there is a change in imaged position on the substrate. For example, a pulse interval that is slightly longer than average results in a greater distance between imaged portions of the substrate. Second, a change in pulse duration results in a blurring effect, as a longer or shorter portion of the substrate traverses the image field during the pulse. In order to account for the movement of the substrate table WT, a device in accordance with an embodiment of the present invention may include a mirror 10 forming a part of the projection system PL, as shown in FIG. 2. In particular, the mirror 10 is beneficially located proximate a pupil of the projection system PL or at a conjugate plane thereof. Though FIG. 2 shows the projection system PL as a two-part device, with the mirror 10 bisecting the projection system PL, that is not, in general, a requirement of one or more embodiments of the present invention. To the contrary, the specific arrangement of the projection system PL may be varied as required according to other desired imaging characteristics. As will be appreciated, the mirror 10 should be substantially planar, though in practice it may be possible to allow for some curvature, whereby a portion of the optical power of the projection system resides in the mirror. An actuator, or group of actuators, 12 is positioned to move the mirror 10 during an imaging operation. In a particular embodiment, the actuator 12 is arranged to rotate the mirror 10 about a small angle at a relatively high frequency, and with a small displacement. The pivotable mirror 10 is supported by a support assembly 22. A frequency of oscillation timing of the mirror 10 substantially corresponds to a resonance frequency of the mirror 10 and support assembly 22. Support assembly 22 includes counter-mass 25, constructed and arranged to isolate forces produced by the actuator 12 from a remaining part of the apparatus. Actuator 12 includes multiple motors 29, and is constructed and arranged to impart rotational forces on the mirror 10. The system of FIG. 2 is shown as having a 1:1 magnification ratio, and a relatively large rotation of the mirror 10. As a result, the focal point 14 at the image plane 16 is displaced from the optical axis 18 by a relatively large amount d. In practice, there may be a significant de-magnification, and the tilt of the mirror 10 will be quite small, so that the displacement may then be quite small. In particular, the displacement of the image should correspond substantially to a distance traversed by the substrate table over the duration of a single pulse of the radiation source. By way of example, a displacement at the mirror 10 of 1 nm at the position of a marginal ray maps to a displacement at the image plane 16 of 1/NA, where NA is the numerical aperture of the projection system PL. Likewise, the rotational change of the mirror a′ [in rad/s] that translates over the diameter of the beam at the pupil D [in m] equals to a velocity v at substrate level [in m/s] as follows: v=a′ D/(2 NA). FIGS. 3 and 4 illustrate schematically later times in a single scan, as successive pulses are imaged onto the focal plane. In FIG. 3, the mirror 10 has rotated through to its zero-crossing, and the focal point 14 is aligned with the optical axis 18. FIG. 4 continues the motion and the focal point 14 is once more displaced from the optical axis 18, in a direction opposite to its initial displacement of FIG. 2. In a typical lithographic apparatus, the source LA may have a pulse repetition rate on the order of 1-10 kHz. As a result, it is useful to ensure that the mirror 10 can be adequately vibrated in phase with that frequency, meaning that the actuator or actuators 12 should be adapted for high frequency operation. Furthermore, if the mirror 10 is designed so that, along with its associated mounting structure, it has a resonant frequency that is substantially equal to the pulse frequency of the source LA, energy required to move the mirror should be minimized. This has the additional effect that the load on the actuators and consequently the deformation load on the mirror 10 should be minimized. In furtherance of the goal of matching the frequency of the vibration of the mirror 10 with the pulse frequency of the source LA, it is possible to include a sensor 30 that is connected in a control loop with the mirror 10, its actuator(s) 12 and, if required, the substrate table. For synchronization of the movement of the mirror to the source pulse frequency, different methods may be used. By way of example, a signal from the sensor 30 on the vibrating mirror may be used to trigger the source pulse, or a phase locked loop system may be used where the source frequency is fixed to the average resonant frequency of the mirror while the controller adjusts the mirror frequency and phase to the fixed source frequency. As a further example, an external timing source may be provided that both triggers the source pulse and is used to control both the phase and amplitude of the mirror motion. In addition to ensuring that the frequency of vibration of the mirror 10 is substantially synchronized with the frequency of the source LA, it may be beneficial to ensure that the amplitude A of the rotational velocity of the mirror 10 corresponds to a scan speed of the substrate table. Further by way of example, in a typical system, the actual values may be as follows. The scan speed may be on the order of 10 mm/s, NA=1, and D=20 mm. This leads to a′=1 rad/s at the zero-crossing of a sinusoidal rotational movement of the mirror 10. Given that for a sinusoidal movement a=A sin(2π t υ) where A is the amplitude in rad, so the time derivative equals: a′=A 2 π υ cos(2 π t υ). At t=0 this becomes: a′=A 2 π υ so that for a 1 kHz vibration, the amplitude of the movement of the mirror becomes: A=0.16 mrad. The choice of a sinusoidal rotational motion of the mirror may allow for some useful effects. In particular, by choosing a portion of the motion close to the zero crossing to coincide with the imaging pulse, and a small amplitude, the sinusoidal motion is substantially linear. Furthermore, the gradual deceleration and acceleration at the end points of the motion reduce stresses on the mirror, which, if unchecked, could lead to deformations of the mirror over time. It should be appreciated, however, that one or more embodiments of the invention are not limited to the use of a sinusoidal rotation motion. The mirror may also be coupled to one or more balance masses. The one or more balance masses are configured to take up and isolate forces produced by the actuator in vibrating the mirror. In particular, the one or more balance masses are configured to be freely movable in a direction opposite to the forces generated by the actuator, conserving momentum of the balance mass-mirror system and thereby reducing forces introduced into other portions of the lithographic apparatus. Embodiments of the present invention can provide the ability to increase pulse time as a result of decreasing blur associated with movement of the substrate table. One useful result of increased pulse time is the ability to reduce peak intensity, without reducing a total energy per pulse, thereby reducing potential damage to optical components. Another useful result is that the number of temporal modes may increase, thereby reducing speckle in the optical system. Finally, longer pulse times may allow for the ability to truncate individual pulses, thereby allowing for pulse-to-pulse dose control adjustments. Errors caused by the movement of the substrate relative to the projection system during a pulse of radiation may be reduced by providing one or more apparatus to shift the patterned radiation beam in substantial synchronism with the movement of the substrate during a pulse of radiation, which may allow the radiation beam to remain more accurately aligned on the substrate. Alternative structures that may be applied to shift the patterned radiation beam are also within the scope of one or more embodiments of the invention. In particular, it is possible to compensate for an error of movement of the substrate relative to the projection system during a pulse of radiation. Such an error is a deviation, for example, from an intended motion of the substrate relative to the projection system, for example the substrate scanning relative to the projection system at a substantially constant speed. This deviation from the intended movement may be caused by an imperfection in the system used to control the movement of the substrate, for example cogging or a motor force factor variation within an actuator used to control the position of the substrate and/or a vibration that may be transferred to the substrate from other components within the lithographic apparatus. The deviation of the movement of the substrate relative to the projection system from the intended movement of the substrate may be derived from the output of a sensor configured to measure the position or displacement of the substrate or a support on which the substrate is held. The difference between the intended position of the substrate and the actual position of the substrate corresponds to a required change of position of the mirror 10. Accordingly, the actuator(s) 12 may be configured to control the movement of the mirror 10 by a combination of the movement required to oscillate the mirror in substantial synchronism with the pulse rate of the source LA such that the patterned radiation beam scans in substantial synchronism with the intended position of the substrate plus a correction in order to compensate for the deviation of the movement of the substrate relative to its intended movement. The correction of the movement of the mirror 12 to compensate for a deviation from the intended movement of the substrate may be effected by adjusting the mid-point of the oscillation of the mirror 10. Alternatively or additionally, the adjustment may be effected by controlling a phase difference between the oscillation of the mirror 10 and the pulsing of the radiation source LA. Alternatively or additionally, as depicted in FIG. 6, one or more second actuators 20 may be provided that provides the adjustment of the position of the mirror 10, corresponding to the correction required to compensate for the deviation of the movement of the substrate from its intended movement, by adjusting the position of the actuator(s) 12. For example, the actuator(s) 12 may control the position of the mirror 10 relative to a base 12a of the actuator(s) 12. The second actuator(s) 20 may therefore be configured to control the position of the base 12a of the actuator(s) 12 relative to a reference within the lithographic apparatus. Accordingly, the actuator(s) 12 is used to control the oscillation of the mirror 10 such that the patterned radiation beam is scanned in substantial synchronism with the intended motion of the substrate and the second actuator(s) 20 is used in order to provide any necessary correction for deviation of the substrate from its intended movement. Regardless of how the corrections are applied to the motion of the mirror 10, it should be appreciated that the corrections may be applied in order to rotate the mirror about the same axis as the axis about which the mirror oscillates. Alternatively or additionally, the corrections may be applied to rotate the mirror about an axis lying within a plane substantially parallel to the surface of the mirror at the location on which the patterned radiation beam is incident on the mirror, but perpendicular to the axis about which the mirror oscillates. Accordingly, the corrections may adjust for deviations from the intended movement of the substrate in a direction parallel and/or perpendicular to, respectively, the scanning motion of the substrate. One or both of the actuator(s) 12 and the second actuators 20 may be formed from any suitable actuator or a combination thereof. In particular, one or more piezo-electric elements may be used as the actuator(s) 12,20. As an alternative, one or both of the actuator(s) may be a Lorentz actuator. An advantage of such an arrangement is that it may be arranged to minimize the transfer of vibration from one component to the other. Accordingly, the second actuator(s) 20 may, in particular, be a Lorentz actuator and configured to minimize the transfer of vibrations from the actuator(s) 12, that oscillates the mirror 10, to the remainder of the apparatus. In general, it should be appreciated that one or both of the actuator(s) 12,20 may be able to adjust the position of the mirror in up to six degrees of freedom. It may be desirable to move the substrate at a substantially constant velocity relative to the projection system during a series of pulses of the radiation system and the intervals in between the pulses. An apparatus as described herein may then be used to move the patterned radiation beam in substantial synchronism with the movement of the substrate for the duration of at least one pulse of the radiation system. Having the substrate moving at a substantially constant velocity may reduce the complexity of the substrate table and the positional drivers associated with it, and moving the patterned radiation beam in substantial synchronism with the movement of the substrate may reduce consequent errors. The patterned radiation beam may be moved in substantial synchronism with the movement of the substrate during a plurality of pulses. Such an arrangement may enable the images of the programmable patterning structure to be projected onto the same part of the substrate a plurality of times. This technique may be done, for example, if the intensity of the pulse of the patterned radiation beam is not sufficient to produce a complete exposure on the substrate. Moving the patterned radiation beam in substantial synchronism with the substrate may reduce the occurrence of overlay errors between subsequent exposures of the pattern on the substrate. Successive patterns on the programmable patterning structure that are exposed on the substrate by each pulse may be different. For example, one or more corrections may be made in one or more subsequent pulses to offset an error in a first pulse. Alternatively, a change in the pattern may be used to produce a gray scale image for one or more of the features (for example, by only exposing those features for a proportion of the total number of pulses imaged onto a given part of the substrate). Additionally or alternatively, the intensity of the patterned radiation beam, the illumination of the programmable patterning structure, and/or the pupil filtering may be changed for one or more of the pulses of the radiation system that are projected onto the same part of the substrate. This technique may be used, for example, to increase the number of gray scales that may be generated using the technique described in the preceding paragraph or may be used to optimize different exposures for features oriented in different directions. While specific embodiments of the invention have been described above, it will be appreciated that the invention as claimed may be practiced otherwise than as described. For example, although use of a lithography apparatus to expose a resist on a substrate is herein described, it will be appreciated that the invention is not limited to this use, and an apparatus according to an embodiment of the invention may be used to project a patterned radiation beam for use in resistless lithography. Thus, it is explicitly noted that the description of these embodiments is not intended to limit the invention as claimed.
052873919	claims	1. A system for metering the feed of portions of nuclear fuel assemblies, the system comprising a declivitous screen for receiving the portions and for separating the portions into larger and smaller components thereof, a first receptacle for collecting the larger components falling from the screen and for discharging the larger components into a collecting receptacle, the collecting receptacle being controllable so as to discharge the larger components therein on to means for directing the larger components into a container, means for sensing the level of the portions in the container, a buffer chamber for receiving the smaller components passing through the screen, a discharge port of the buffer chamber for discharging the smaller components from the buffer chamber into an oscillatable trough adapted to oscillate around the longitudinal axis thereof to discharge a metered quantity of the smaller components therefrom, and means for receiving the smaller components discharged from the trough and for feeding said smaller components to the container. 2. A system as claimed in claim 1 and wherein the means for sensing the level of the portions in the container comprise ultrasonic probes. 3. A system as claimed in claim 1 and wherein means are provided for monitoring overfilling of the container and the said means comprise capacitance probes. 4. A system as claimed in claim 1 and wherein the system is of modular form so as to assist maintenance and replacement of defective elements. 5. A system as claimed in claim 1 and wherein the system is manually initiated. 6. A system as claimed in claim 1 wherein the elements of the system are interrelated through a control system so as to automate the operation of the system.
046648755	summary	CROSS REFERENCE TO RELATED APPLICATIONS Reference is hereby made to the following copending applications dealing with related subject matter and assigned to the assignee of the present invention: 1. "Nuclear Reactor Fuel Assembly with a Removable Top Nozzle" by John M. Shallenberger et al, assigned U.S. Ser. No. 644,758 and filed Aug. 27, 1984. 2. "Locking Tube Removal and Replacement Tool and Method in a Reconstitutable Fuel Assembly" by John M. Shallenberger et al, assigned U.S. Ser. No. 670,418 and filed Nov. 9, 1984. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fuel assemblies for nuclear reactors and, more particularly, is concerned with a fixture and method for removing a top nozzle from and replacing it on the upper ends of a plurality of guide thimbles of a reconstitutable fuel assembly. 2. Description of the Prior Art In most nuclear reactors, the reactor core is comprised of a large number of elongated fuel assemblies. Conventional designs of these fuel assemblies include a plurality of fuel rods and control rod guide thimbles held in an organized array of grids spaced along the fuel assembly length and attached to the control rod guide thimbles. Top and bottom nozzles on opposite ends of the fuel assembly are secured to the guide thimbles which extend slightly above and below the ends of the fuel rods. At the top end of the fuel assembly, the guide thimbles are attached in passageways provided in the adapter plate of the top nozzle. The guide thimbles may each include an upper sleeve for attachment to the top nozzle. During operation of such fuel assembly in a nuclear reactor, a few of the fuel rods may occasionally develop cracks along their lengths resulting primarily from internal stresses, thus establishing the possibility that fission products having radioactive characteristics may seep or otherwise pass into the primary coolant of the reactor. Such products may also be released into a flooded reactor cavity during refueling operations or into the coolant circulated through pools where the spent fuel assemblies are stored. Since the fuel rods are part of the integral assembly of guide thimbles welded to the top and bottom nozzles, it is difficult to detect and remove the failed rods. Until recently, to gain acess to these rods it was necessary to remove the affected assembly from the nuclear reactor core and then break the welds which secure the nozzles to the guide thimbles. In so doing, the destructive action often renders the fuel assembly unfit for further use in the reactor because of the damage done to both the guide thimbles and the nozzle which prohibits rewelding. In view of the high costs associated with replacing fuel assemblies, considerable interest has arisen in reconstitutable fuel assemblies in order to minimize operating and maintenance expenses. The general approach to making a fuel assembly reconstitutable is to provide it with a removable top nozzle. One reconstitutable fuel assembly construction, devised recently, is illustrated and described in the first U.S. Pat. application cross-referenced above. It incorporates an attaching structure for removably mounting the top nozzle on the upper ends of the control rod guide thimbles. The attaching structure includes a plurality of outer sockets defined in an adapter plate of the top nozzle, a plurality of inner sockets with each formed on the upper end of one of the guide thimbles, and a plurality of removable locking tubes inserted in the inner sockets to maintain them in locking engagement with the outer sockets. Each outer socket is in the form of a passageway through the adapter plate which has an annular groove. Each inner socket is in the form of a hollow upper end portion of the guide thimble having an annular bulge which seats in the annular groove when the guide thimble end portion is inserted in the adapter plate passageway. A plurality of elongated axial slots are provided in the guide thimble upper end portion to permit inward elastic collapse of the slotted portion so as to allow the larger bulge diameter to be inserted within and removed from the annular circumferential groove in the passageway of the adapter plate. In such manner, the inner socket of the guide thimble is inserted into and withdrawn from locking engagement with the outer socket. The locking tube is inserted from above the top nozzle into a locking position in the hollow upper end portion of the guide thimble forming the inner socket. When inserted in its locking position, the locking tube retains the bulge of the inner socket in its expanded locking engagement with the annular groove and prevents the inner socket from being moved to a compressed releasing position in which it could be withdrawn from the outer socket. In such manner, the locking tubes maintain the inner sockets in locking engagement with the outer sockets, and thereby the attachment of the top nozzle on the upper ends of the guide thimbles. Furthermore, due to vibration forces and the like, it is desirable to secure the locking tubes in their locking positions. For such purpose, suitable means, such as a pair of bulges, are formed in the upper portion of each locking tube after insertion in its locking position which bulges fit into the circumferential bulge in the upper end portion of the guide thimble. While the reconstitutable fuel assembly construction briefly described above has demonstrated considerable promise as to measure by which domestic and foreign utilities can minimize both operating and maintenance expenses, a need exists for means to effectively and efficiently carry out removal and replacement of the locking tubes and top nozzle of the reconstitutable fuel assembly so as to enhance commercial acceptance thereof. SUMMARY OF THE INVENTION The present invention together with other components, some of which comprise the invention disclosed and claimed in the second U.S. patent application cross-referenced above, provide a system of remotely-operated, submersible equipment designed to satisfy the aforementioned needs. The equipment is operable to remove and subsequently remount or replace the locking tubes and top nozzle of a reconstitutable fuel assembly, such as the one disclosed in the first U. S. patent application cross-referenced above, at a reactor plant. After the locking tubes and top nozzle have been removed, the upper ends of the fuel rods are exposed from the top of the reconstitutable fuel assembly. Thus, access to the fuel rods is gained for any of a variety of purposes: inspecting them for failure, removing and replacing failed rods, transferring partially spent fuel rods from one assembly to another, and/or rearrangement of fuel rods to attain better uranium utilization in the reactor core. Once inspection, removal, replacement and/or rearrangement of the fuel rods is completed, the top nozzle is placed back on the upper ends of the guide thimbles and the locking tubes replaced in their locking positions. The present invention provides a fixture and method for removing the top nozzle from and replacing it on the guide thimbles in a reconstitutable fuel assembly once the locking tubes have been removed. In particular, the fixture provides for safe, positively controlled removal and replacement of the top nozzle from and onto the slotted upper end portions of the guide thimbles comprising the inner sockets of the top nozzle attaching structure. Not only does the fixture include a gear driven mechanism operable to generate sufficient force to cause the collapse of the slotted upper end portions of the guide thimbles for removal and replacement of the top nozzle thereon, in addition thereto the fixture incorporates stop devices for ensuring that the remounted top nozzle is in precisely the same axial position on the fuel assembly as it was prior to removal. This is an important feature of the fixture because of the potential for fuel assembly damage should the remounted top nozzle be driven down an excessive distance over the upper end portions of the guide thimbles. Because the split or slotted guide thimble upper end portions must be collapsed to a smaller diameter while passing through the passageways in the top nozzle adapter plate (i.e. outer sockets of the top nozzle attaching structure), the fixture must be capable of exerting a force in excess of 100 pounds to remove or replace a top nozzle. Accordingly, the present invention sets forth for use with a reconstitutable fuel assembly being held in a fixed position within a work station wherein the fuel assembly includes a top nozzle with an adapter plate having at least one passageway, at least one guide thimble with an upper end portion and an attaching structure releasably mating the upper end portion of the guide thimble within the passageway of the top nozzle adapter plate, a fixture and method for removing the top nozzle from and replacing it back onto the guide thimble of the reconstitutable fuel assembly. The fixture for removing the top nozzle includes: (a) a base; (b) means for movably mounting the base on the work station in alignment with the top nozzle of the fuel assembly; (c) means for locking the top nozzle to the base when the base is movably mounted on the work station; and (d) means for moving the base, and the top nozzle therewith when locked thereto, relative to the work station so as to lift the top nozzle away from the guide thimble and thereby cause release of the attaching structure and removal of the top nozzle from the guide thimble. In addition, the fixture also includes means operable for establishing a reference representing the displacement between the base and the work station when the top nozzle is locked to the base but before the base and top nozzle have been lifted away from the work station for facilitating replacement of the top nozzle back onto the guide thimble at the same axial position on the fuel assembly as it was prior to removal. The method for removing the top nozzle from the guide thimble includes the operative steps of: (a) movably mounting a fixture on the work station in alignment with the top nozzle of the fuel assembly; (b) locking the top nozzle to a base of the fixture; and (c) moving the base, and the top nozzle therewith when locked thereto, away from the work station so as to lift the top nozzle off the guide thimble and thereby cause release of the attaching structure and removal of the top nozzle from the fuel assmebly. Furthermore, the method also includes the step of establishing a reference representing the displacement between the base of the fixture and the work station when the top nozzle is locked to the base but before the base and top nozzle have been lifted away from the work station for facilitating replacement of the top nozzle back onto the guide thimble at the same axial position on the fuel assembly as it was prior to removal. These and other advantages and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
	abstract	A scanning device for providing a radiation scan to an article is disclosed. The scanning device includes a housing, a transport system and a radiation attenuation system. The housing has a entrance port and an exit port and encloses a radiation analysis unit. The transport system is configured to move the article from the entrance port, through the housing and to the exit port. The radiation attenuation system is supported at one of the entrance port and the exit port. The radiation attenuation system includes at least one substantially rigid panel rotatable relative to the housing and a counter balance coupled to the panel to at least partially offset the weight of the panel.
049869523	description	As shown in FIG. 1, a prior art pressurized water nuclear reactor comprises a core 2 having a vertical axis A. The plan of this core is in the form of a square grid whose edges constitute, in part, the above-mentioned circumscribing square. The corners of the square are omitted since they do not form parts of the core. That is why they are not shown. Only the middle portions such as 4 of the sides of the square are shown since they constitute parts of the edge of the core. The core has two median axes parallel to pairs of its sides, and two diagonal axes parallel to its diagonals. Four neutron flux detectors D1, D2, D3, and D4 are disposed on the diagonal axes of the core, outside and close to the core. I.e., they are disposed around the vertical axis A at the following angular positions 45.degree., 135.degree., 225.degree., and 315.degree. measured from an angular origin extending upwardly in the figure. Each of the four identical protection chains includes one of the detectors, for example the detector D1, together with a primary treatment circuit operating as a differentiator R1, followed by a threshold member S1. This circuit provides the above-mentioned primary fall signal, in the event that an accidental fall of a cluster of control rods has occurred in the vicinity of the detector, or even at a distance from the detector if the previously established neutron flux distribution makes that possible. A secondary treatment circuit 6 receives the fall signals provided at the outputs from the four protection chains. These signals are said primary fall signals. The secondary circuit provides the above-mentioned secondary fall signal if it receives two signals at the outputs from said chains. This secondary fall signal controls measures for protecting the reactor by means not shown which cause all of the control rods to fall almost immediately. Starting from this prior system, a characteristic of the invention lies in using four additional detectors and in coupling them with the four conventional detectors within the protection chains. These additional detectors are not necessarily identical to the four conventional detectors. They are situated on the median axes, and outside the core. It is preferable for the detectors to be uniformly distributed, although an angular pitch of 45.degree. is not absolutely necessary. The two systems shown in FIGS. 2 and 3 ensure that in the event of an accidental cluster fall, a minimum of three detectors belonging to three different protection chains will be in the proximity of the cluster(s), thus giving rise to a large fall signal. The system thus ensures 2/4 logic protection even in the event of one of the chains being faulty. The two systems differ as follows: The first system shown in FIG. 2 has the advantage of its chains being symmetrical: each chain has one diagonal detector and one median detector. The second system shown in FIG. 3 is optimized with respect to the probability of detecting an accidental fall: four adjacent detectors always belong to four different chains. However, the chains are not symmetrical with respect to the detectors: two of the chains are fitted solely with diagonal position detectors, while the other two chains use median position detectors only. One or other of these two solutions is selected depending on the characteristics of the detectors, which characteristics may depend on their median or diagonal position, and taking account of the fact that the treatment circuits used in accordance with the invention are typically incorporated in treatment units which provide protection functions other than those described above. More specifically, and as shown in FIG. 2, the first system in accordance with the invention comprises eight detectors: D1A, D4B, D3A, D1B, D2A, D4A, and D2B at angular positions of 45.degree., 90.degree., 135.degree., 180.degree., 225.degree., 270.degree., 315.degree., and 360.degree. respectively, with a single chain, e.g. the first, including two detectors D1A and D1B whose references include the same digit. In addition, each chain includes two primary treatment circuits RIA, SIA and RIB, S1B associated with respective ones of its two detectors, together with an intermediate treatment circuit P1 constituted by an OR gate. In the second system in accordance with the invention as shown in FIG. 3, the detectors are in the same positions as in the first system but in the following order: D1C, D2C, D3C, D4C, DID, D2D, D3D, and D4D, with the digit likewise specifying the number of the chain to which the detector belongs. For example, the first chain comprises primary treatment circuits R1C, SIC and R1D, S1D associated with the detectors D1C and D1D respectively, together with the intermediate treatment circuit P1. In other respects, this system is identical to the first.
	description	This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0057352, filed on May 13, 2020, the disclosure of which is incorporated herein by reference in its entirety. The present invention relates to a nuclear fuel pellet laminate structure having enhanced thermal conductivity, and a method for manufacturing the same. Uranium dioxide (UO2), which is a nuclear fuel pellet material of a light water reactor, has good compatibility with water used as a coolant for a light water reactor, has a high melting point of about 2,850° C., and exhibits excellent furnace stability such as no phase transformation even at high temperatures and the like. Therefore, although it has disadvantages in terms of thermal conductivity, uranium density, and the like compared to other uranium compounds (e.g., UC, UN, etc.), it is widely used as a nuclear fuel pellet material of a light water reactor. However, the characteristics of low thermal conductivity of UO2 form a rapid temperature gradient (about 500° C. to 700° C. in normal operations) inside UO2 nuclear fuel pellets (radius of about 4.1 mm), which causes thermal and mechanical problems such as a high core temperature of nuclear fuel, a steep thermal stress gradient, and the like. These characteristics act as adverse factors in normal operations, and excessive and accident conditions. Therefore, the technology to enhance the thermal conductivity of UO2 nuclear fuel pellets has been emphasized as the most important factor in terms of nuclear fuel performance and safety. Korean Registered Patent Publication No. 10-2084466 (Feb. 27, 2020) The present invention is for maximizing the effect of thermal conductivity enhancement by suppressing the formation of impurity without restriction on the selection of thermally conductive metal materials, and the present invention is directed to providing a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet, and the like However, the technical problems to be achieved by the present invention are not limited to the above-mentioned problem, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description. The present invention provides a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet. In another embodiment of the present invention, provided herein is a method for manufacturing a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including (a) a step of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet; and (b) a step of disposing a thermally conductive metal layer above or below the nuclear fuel pellet manufactured in step (a). The present invention relates to a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet, and the present invention is characterized in that the thermally conductive metal layer is disposed separately in a post-processing process so as not to cause a chemical reaction under thermal treatment conditions. Thus, it is possible to enhance thermal conductivity by suppressing the formation of impurity. In particular, by optimizing the ratio of the diameter to the height of the nuclear fuel pellet, the effect of thermal conductivity enhancement can be maximized by spacing apart the thermally conductive metal layer at a regular interval. Therefore, the nuclear fuel pellet laminate structure according to the present invention can be easily applied to existing commercial nuclear fuel manufacturing facilities, and it can greatly improve nuclear fuel safety and performance in normal operations, and excessive and accident conditions. Conventionally, to enhance thermal conductivity of a nuclear fuel pellet, thermally conductive metal powder was used and mixed as an additive to nuclear fuel powder, followed by molding and thermally treating to manufacture a nuclear fuel pellet, and in this case, there were some limitations. First, in the selection of thermally conductive metal powder, considering various requirements such as high thermal conductivity, a melting point, a volatility point, a neutron absorption cross-sectional area, a coefficient of thermal expansion, UO2 and Zr chemical reactivities, cooling water reactivity, and the like, the effect on the function as nuclear fuel should be minimized. Second, as the thermally conductive metal powder is added, the ratio of the nuclear fuel powder decreases. In order to minimize this, the thermally conductive metal powder must be efficiently disposed to minimize the addition amount. Third, there should be no problem in maintaining the chemical properties of thermally conductive metal powder under thermal treatment conditions (hydrogen atmosphere and 1,300° C. to 1,800° C.) during the manufacturing process of a nuclear fuel pellet, and it must be controlled such that it does not combine with hydrogen to form a hydride under high temperature thermal treatment conditions, or does not react with nuclear fuel powder to form a second phase. As such, the present inventors manufactured a nuclear fuel pellet laminate structure, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet, and accordingly, the present invention was completed by confirming that the effect of thermal conductivity enhancement be maximized by suppressing the formation of impurity, without restriction on the selection of thermally conductive metal materials. Hereinafter, the present invention will be described in detail. Nuclear Fuel Pellet Laminate Structure Having Enhanced Thermal Conductivity The present invention provides a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet. The nuclear fuel pellet laminate structure having enhanced thermal conductivity according to the present invention includes a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet. The nuclear fuel pellet laminate structure has an advantage of being able to enhance thermal conductivity in a radial direction (horizontal direction) while suppressing the formation of impurity. The nuclear fuel pellet is a nuclear fuel matrix, and may be in a state in which thermally conductive metal powder is not added. Specifically, the nuclear fuel pellet may include one or more oxide nuclear fuel powders selected from the group consisting of uranium oxide (UO2), plutonium oxide (PuO2), and thorium oxide (ThO2), and other than the above, it may include one or more uranium or alloy compounds thereof selected from the group consisting of a uranium compound (U compound), a uranium-silicon compound (U—Si compound), a uranium-gadolinium compound (U—Gd compound), a uranium-thorium compound (U—Th compound), and a uranium-plutonium compound (U—Pu compound). in this case, the nuclear fuel pellet may be formed by molding and thermally treating nuclear fuel powder, and the nuclear fuel powder and the process thereof will be described below. In this case, the height of the nuclear fuel pellet may be 3 mm to 10 mm, preferably, 3 mm to 6 mm, but is not limited thereto. Accordingly, the effect of thermal conductivity enhancement may be maximized by spacing apart the thermally conductive metal layer at a regular interval. When the height of the nuclear fuel pellet is too low, not only there is a difficulty in manufacturing, but also it is difficult to insert into a nuclear fuel cladding tube. On the other hand, when the height of the nuclear fuel pellet is too high, there is a problem in that the temperature reduction effect is lowered, and accordingly, the significant effect of thermal conductivity enhancement is reduced. In other words, it can be seen that the ratio of the diameter to the height of the nuclear fuel pellet is 1.6 or more, preferably, 1.6 to 2.0. When the ratio of the diameter to the height of the nuclear fuel pellet is too large, not only there is a difficulty in manufacturing, but also it is difficult to insert into a nuclear fuel cladding tube. On the other hand, when the ratio of the diameter to the height of the nuclear fuel pellet is too small, there is a problem in that the temperature reduction effect is lowered, and accordingly, the significant effect of thermal conductivity enhancement is reduced. The thermally conductive metal layer is disposed above or below the nuclear fuel pellet, and may promote heat transfer from the center to a peripheral portion in contact with a nuclear fuel cladding tube in a radial direction (horizontal direction). Meanwhile, the thermally conductive metal layer should only be physically attached and bonded to the nuclear fuel pellet, and should not react chemically. In other words, it is preferable that impurity is not formed due to a chemical reaction of the thermally conductive metal layer, and the impurity may interfere with heat transfer. Specifically, the impurity may be a hydride formed by bonding of the thermally conductive metal with hydrogen under a high-temperature thermal treatment condition, or a secondary phase formed by reacting with nuclear fuel powder. More specifically, the impurity may include one or more selected from the group consisting of a thermally conductive metal hydride, a thermally conductive metal oxide, a thermally conductive metal nitride, a thermally conductive metal-uranium compound, a thermally conductive metal-plutonium compound, and a thermally conductive metal-thorium compound. Specifically, the thermally conductive metal layer may include one or more selected from the group consisting of molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf), tantalum (Ta), rhodium (Rh), zirconium (Zr), beryllium (Be), and aluminum (Al). Based on the total weight of the nuclear fuel pellet, the content of the thermally conductive metal layer may be 1 wt. % to 10 wt. %, and the content of the thermally conductive metal layer is preferably 1 wt. % to 5 wt. %, but is not limited thereto. This corresponds to a small amount compared to the case of using thermally conductive metal powder as an additive to the nuclear fuel powder. Therefore, a significant effect of thermal conductivity enhancement may be derived even with a small amount. The thermally conductive metal layer may be manufactured in various forms, and may be a plate shape entirely formed above or below the nuclear fuel pellet, and it may be a cross shape or radial shape partially formed above or below the nuclear fuel pellet, in order to connect a peripheral portion in contact with a nuclear fuel cladding tube in a radial direction from the center. As such, the temperature reduction effect is effective, and accordingly, a significant effect of thermal conductivity enhancement may be derived. The shapes (plate shape, cross shape, and radial shape) of the thermally conductive metal layer according to various embodiments of the present invention are as shown in FIG. 1. Meanwhile, the nuclear fuel pellet laminate structure having enhanced thermal conductivity according to the present invention may be manufactured by including (a) a step of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet; and (b) a step of disposing a thermally conductive metal layer above or below the nuclear fuel pellet manufactured in step (a), and each step will be described below. Method for Manufacturing a Nuclear Fuel Pellet Laminate Structure Having Enhanced Thermal Conductivity The present invention provides a method for manufacturing a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including (a) a step of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet; and (b) a step of disposing a thermally conductive metal layer above or below the nuclear fuel pellet manufactured in step (a). In addition, the present invention may provide a method for enhancing thermal conductivity of a nuclear fuel pellet laminate structure, including (a) a step of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet; and (b) a step of disposing a thermally conductive metal layer above or below the nuclear fuel pellet manufactured in step (a). First, the method for manufacturing a nuclear fuel pellet laminate structure having enhanced thermal conductivity according to the present invention includes a step [step (a)] of molding and thermally treating nuclear fuel powder to manufacture a nuclear fuel pellet. The nuclear fuel powder is formed from a nuclear fuel precursor, and it refers to a state before performing a granulation process, which is a distinct concept. Specifically, the nuclear fuel powder may include one or more oxide nuclear fuel powders selected from the group consisting of uranium oxide (UO2), plutonium oxide (PuO2), and thorium oxide (ThO2), and other than the above, it may include one or more uranium or alloy compounds thereof selected from the group consisting of a uranium compound (U compound), a uranium-silicon compound (U—Si compound), a uranium-gadolinium compound (U—Gd compound), a uranium-thorium compound (U—Th compound), and a uranium-plutonium compound (U—Pu compound). In this case, the average particle size of the nuclear fuel powder may be 0.1 μm to 50 μm, preferably, 0.1 μm to 30 μm, but is not limited thereto. In addition, the molding may be performed through a pressing method, and is preferably performed through a uniaxial pressing method, but is not limited thereto. In this case, the molding may be performed for 30 seconds to 10 hours under a pressure of 100 MPa to 500 MPa. In addition, the thermal treatment is for the manufacture of a nuclear fuel pellet, and may be performed at a temperature of 1,300° C. to 1,800° C. for 1 hour to 20 hours, and is preferably performed at a temperature of 1,500° C. to 1,800° C. for 1 hour to 20 hours, but is not limited thereto. Since it is a state in which thermally conductive metal powder is not added to a nuclear fuel molded body to be subjected to the thermal treatment, it is not necessary to consider suppressing impurities formed by the thermally conductive metal powder when setting the thermal treatment conditions. Since the nuclear fuel pellet manufactured according to the above molding and thermally treating processes has been described above, duplicate description will be omitted. In particular, by maintaining the ratio of the diameter to the height of the nuclear fuel pellet at 1.6 or more, preferably, 1.6 to 2.0, the effect of thermal conductivity enhancement may be maximized by spacing apart the thermally conductive metal layer at a regular interval. Next, the method for manufacturing a nuclear fuel pellet laminate structure having enhanced thermal conductivity according to the present invention includes a step [step (b)] of disposing a thermally conductive metal layer above or below the manufactured nuclear fuel pellet. Since the thermally conductive metal layer has been described above, duplicate description will be omitted. Meanwhile, the thermally conductive metal layer is characterized in that it is separately disposed in a post-processing process after the thermal treatment, and it is preferable that impurity is not formed due to a chemical reaction of the thermally conductive metal layer, and the impurity may interfere with heat transfer. Specifically, the impurity may be a hydride formed by bonding of the thermally conductive metal with hydrogen under a high-temperature thermal treatment condition, or a secondary phase formed by reacting with nuclear fuel powder. More specifically, the impurity may include one or more selected from the group consisting of a thermally conductive metal hydride, a thermally conductive metal oxide, a thermally conductive metal nitride, a thermally conductive metal-uranium compound, a thermally conductive metal-plutonium compound, and a thermally conductive metal-thorium compound. That is, the thermally conductive metal layer should only be physically attached and bonded to the nuclear fuel pellet, and should not react chemically. In addition, the disposing of the thermally conductive metal layer may be performed through a known method, and may be performed through a coating method, a vapor deposition method, and a 3D printing method. In particular, when the 3D printing method is used, it has an advantage of being able to manufacture the shape of the thermally conductive metal layer in various ways, and in particular, it may be preferably used for manufacturing in a cross shape or radial shape. In addition, the present invention may provide nuclear fuel including a nuclear fuel pellet laminate structure having enhanced thermal conductivity; and a nuclear fuel cladding tube in which a plurality of the nuclear fuel pellet laminate structures are inserted therein. Cooling water of about 320° C. flows in a vertical direction (height direction) on the outer surface of the nuclear fuel such that the main direction of heat generated from the nuclear fuel pellet is a radial direction (horizontal direction). In this case, the temperature of the center of the nuclear fuel pellet reaches about 1,000° C. to 1,200° C. even under normal operating conditions. Therefore, it is important to control heat transfer characteristics in a radial direction (horizontal direction), and the nuclear fuel pellet laminate structure having enhanced thermal conductivity has an advantage of being able to enhance thermal conductivity in a radial direction (horizontal direction) while suppressing the formation of impurity. As described above, the present invention relates to a nuclear fuel pellet laminate structure having enhanced thermal conductivity, including a nuclear fuel pellet; and a thermally conductive metal layer disposed above or below the nuclear fuel pellet, and it is characterized in that the thermally conductive metal layer is separately disposed in a post-processing process such that a chemical reaction does not occur under a thermal treatment condition, thereby being able to enhance thermal conductivity by suppressing the formation of impurity. In particular, by optimizing the ratio of the diameter to the height of the nuclear fuel pellet, the effect of thermal conductivity enhancement may be maximized by spacing apart the thermally conductive metal layer at a regular interval. Therefore, the nuclear fuel pellet laminate structure according to the present invention may be easily applied to existing commercial nuclear fuel manufacturing facilities, and may greatly improve nuclear fuel safety and performance under normal operations, and transient and accident conditions. Hereinafter, preferred exemplary embodiments are presented to aid in understanding the present invention. However, the following exemplary embodiments are only provided to understand the present invention more easily, and the contents of the present invention are not limited by the following exemplary embodiments. As nuclear fuel powder, UO2 powder having an average particle size of about 0.3 μm was prepared. It was placed into a powder molding mold, then uniaxially pressurized for about 1 minute under a pressure of about 300 MPa, and then, it was thermally treated for about 4 hours at a temperature of about 1,700° C. under a hydrogen reducing atmosphere with a slight oxygen partial pressure (2% CO2 equivalent) to manufacture a nuclear fuel pellet (about 96% TD). in this case, the diameter of the nuclear fuel pellet was about 8.2 mm, and the height was about 4.5 mm. A plate-shaped Mo layer was deposited on the upper and lower portions thereof under a pressurizing condition of 1,700° C. to manufacture a nuclear fuel pellet laminate structure. In this case, based on the total weight of the nuclear fuel pellet, the content of the plate-shaped Mo layer was about 5 wt. % (refer to FIG. 2(a)). A nuclear fuel pellet laminate structure was manufactured in the same manner as in Example 1, except that the height of the nuclear fuel pellet was adjusted to about 5 mm (refer to FIG. 2(a)). Nuclear fuel pellet laminate structures were manufactured in the same manner as in Example 1, except that the heights of the nuclear fuel pellets were adjusted to about 7 mm and 9 mm, respectively (refer to FIG. 2(b)). As nuclear fuel powder, UO2 powder having an average particle size of about 0.3 μm was prepared. It was placed into a powder molding mold, then uniaxially pressurized for about 1 minute under a pressure of about 300 MPa, and then, it was thermally treated for about 4 hours at a temperature of about 1,700° C. under a hydrogen reducing atmosphere with a slight oxygen partial pressure (2% CO2 equivalent) to manufacture a nuclear fuel pellet (about 96% TD). In this case, the diameter of the nuclear fuel pellet was about 8.2 mm, and the height was the same as Table 1 below. As nuclear fuel powder, UO2 powder having an average particle size of about 0.3 μm was prepared. Afterwards, based on the total weight of the UO2 powder, a mixture was prepared by mixing Mo powder having an average particle size of about 0.3 μm at 5 wt. %. It was placed into a powder molding mold, then uniaxially pressurized for about 1 minute under a pressure of about 300 MPa, and then, it was thermally treated for about 4 hours at a temperature of about 1,700° C. under a hydrogen reducing atmosphere with a slight oxygen partial pressure (2% CO2 equivalent) to manufacture a nuclear fuel pellet (about 96% TD). In this case, the diameter of the nuclear fuel pellet was about 8.2 mm, and the height was the same as Table 1 below (refer to FIG. 2(d)). TABLE 1DiameterHeightDiameter/Height (AR)Example 1About 8.2 mmAbout 4.5 mmAbout 1.82Example 2About 8.2 mmAbout 5 mmAbout 1.64Example 3About 8.2 mmAbout 7 mmAbout 1.17Example 4About 8.2 mmAbout 9 mmAbout 0.91ComparativeAbout 8.2 mmAbout 4.5 mmAbout 1.82Example 1ComparativeAbout 8.2 mmAbout 5 mmAbout 1.64Example 2ComparativeAbout 8.2 mmAbout 7 mmAbout 1.17Example 3ComparativeAbout 8.2 mmAbout 9 mmAbout 0.91Example 4ComparativeAbout 8.2 mmAbout 4.5 mmAbout 1.82Example 5ComparativeAbout 8.2 mmAbout 5 mmAbout 1.64Example 6ComparativeAbout 8.2 mmAbout 7 mmAbout 1.17Example 7ComparativeAbout 8.2 mmAbout 9 mmAbout 0.91Example 8 FIG. 3 is a calculation and evaluation of thermal conductivity according to the temperature of the nuclear fuel pellet laminate structures manufactured in Examples 1 to 4 by FEM (Finite Element Method) computing simulation, and it is a graph comparing whether the thermal conductivity is enhanced under a temperature condition of 1,200° C., as a result of actually measuring the thermal conductivities of the nuclear fuel pellets manufactured in Comparative Examples 1 to 8. As shown in FIG. 3, it was confirmed that the nuclear fuel pellet laminate structures manufactured in Examples 1 to 4 had significantly enhanced thermal conductivity compared to the nuclear fuel pellets manufactured in Comparative Examples 1 to 8. This can be seen as a result of the plate-shaped Mo layer being disposed in a horizontal direction at a regular interval without forming impurities as a thermally conductive metal layer. Compared to the nuclear fuel pellets manufactured in Comparative Examples 1 to 4, it was confirmed that the nuclear fuel pellets manufactured in Comparative Examples 5 to 8 had slightly enhanced thermal conductivity, but it was confirmed that there was no significant difference. In particular, the nuclear fuel pellet laminate structures manufactured in Examples 1 to 4 were confirmed to have a maximized effect of thermal conductivity enhancement as the value of the diameter/height (AR) increased, and thus, the optimized value of diameter/height (AR) can be seen as about 1.6 or more. The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the exemplary embodiments described above are illustrative and non-limiting in all respects.
	abstract	An injection and solidification operation as well as a kneading and solidification operation can be performed by a single facility. A decreased amount of radioactive secondary waste is generated. A solidifying agent paste is prepared by kneading a solidifying agent and additive water. The solidifying agent paste is injected into a solidifying container. The radioactive waste is charged into the solidifying container and kneaded.
062947915	description	DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, a preferred embodiment of an irradiation system according to the present invention includes a radiation source 10, a conveyor system 12, radiation shielding material 14 defining a chamber 15 and an intermediate wall 16 of radiation shielding material. Articles carried by article carriers 17 are transported by the convey system 12 in a direction indicated by the arrows from a loading area 18 through a target region 20 to an unloading area 22. The conveyor system 12 includes a process conveyor 24 for transporting articles carried by the article carriers 17 in a given direction through the target region 20. The radiation source 10 preferably is a 10-million-electron-volt linear accelerator having an electron accelerating wave guide that provides an electron beam for irradiating articles transported through the target region 20 by the conveyor system 12. The radiation source 10 is disposed along an approximately horizontal axis 25 inside a loop 26 defined by a portion of the conveyor system 12 and is adapted for scanning the articles being transported through the target region 20 with an electron beam at a given rate in a plane perpendicular to the given direction of transport by the conveyor system 12. The scanning height and the current of the electron beam are adjusted in accordance with the height and radiation absorption characteristics of the articles being scanned. The scanning of the articles by the electron beam is further controlled as described in the above-referenced U.S. Pat. No. 5,396,074. The accelerator is located inside a removable shield and protected from ionizing radiation and ozone by interior walls. In alternative embodiments, the radiation source scans the articles with a type of radiation other than an electron beam, such as X-rays. The conveyor system 12 includes a power-and-free conveyor throughout and, in addition to the process conveyor 24, further includes a load conveyor 28, all three of which are independently powered. The power-and-free-conveyor functions as a transport conveyor for transporting the article carriers 17 at a first given speed from the process conveyor 24 through the unloading area 22 and the loading area 18 to the load conveyor 28. The process conveyor 24 transports the articles carriers 17 through the target region 20 at a second given speed that is different than the first given speed at which the article carriers 17 are transported by the transport conveyor. The load conveyor 28 transports the article carriers 17 from the transport conveyor to the process conveyor 24 at a speed that is varied during such transport in such a manner that when the article carriers 17 are positioned on the process conveyor 24 there is a predetermined separation distance between adjacent positioned articles carriers 17. When an article carriers 17 is positioned on the process conveyor 24, the load conveyor 28 is transporting the article carriers 17 at the speed of the processor conveyor 24. Such a conveyor system 12 and the operation thereof is described in detail in the above-referenced U.S. Pat. No. 5,396,074. In order to reorient articles for retransportation through the target region 20 so that such articles can be irradiated from opposite sides, upon it being detected that an article carrier 17 carrying such articles is so oriented as to have been transported trough the target 20 only once, such article carrier 17 is diverted onto a reroute conveyor section 30 and then transported by the transport conveyor past a mechanism 32 that reorients the so-oriented article carrier 17 by 180 degrees for said retransportation through the target region 20. Such a reorienting mechanism 32 and means for detecting the orientation of an article carrier 17 are also described in U.S. Pat. No. 5,396,074 to Peck et al. The radiation shielding material 14 includes walls 14A, 14B, 14C, a floor 14D and a ceiling 14E defining the chamber 15 that contains the radiation source 10, the target region 20 and at least the portion of the conveyor system 12 that includes the process conveyor 24, the load conveyor 28 and the adjacent portions of the transport convey. Additional walls 14F of radiation shielding material define an angled passageway 36 into the chamber 15 for the conveyor system 12 and shield the loading area 18 and the unloading area 22, which are located outside of the chamber 15, from radiation derived from the radiation source 10. The intermediate wall 16 is position within the loop 26 and transverse to the approximately horizontal axis 25 of the radiation source 10. The intermediate wall 16 has an aperture 38 through which the radiation source 10 is disposed. The ceiling section 14E of the radiation shielding material is supported in part by the intermediate wall 16; whereby the underlying chamber 15 may be of a greater area and/or the ceiling section 14E may be of a greater span and/or of a greater weight than would be permitted in the absence of such support. Preferably, the radiation shielding material 14A, 14B, 14C, 14D, 14E, 14F (collectively referred to as 14), 16 is primarily concrete because of cost considerations. However, other types of radiation shielding material may be used when spaced is limited or in view of other requirements, such as steel. In alternative embodiments, some of the radiation shielding material may be concrete and some not. For example, in one alternative embodiment shielding material other than concrete, such as steel, selected in accordance with limited space requirements, while the remainder of the radiation shielding material 14 is concrete. A beam stop 40 is disposed in a recess 42 in the wall 14A of radiation shielding material that is on the opposite side of the target region 20 from the electron beam radiation source 10. The beam stop 40 is made of a material, such as aluminum, that absorbs electrons and converts the energy of the absorbed electrons into photons that are emitted from the beam stop 40. The beam stop 40 is so disposed in the recess 42 that some of the photons emitted from the beam stop 40 toward the radiation source 10 but obliquely thereto are inhibited from entering the chamber 15 by the portion of the radiation shielding material in the wall 14A that defines the recess 42. The recessing of the beam stop 40 reduces the intensity of back scattered photons, thereby decreasing the thickness required for the side walls 14B, the back wall 14C and the ceiling section 14E. This reduces construction costs and shortens the construction schedule. Sections 44 of the transport conveyor portion of the conveyor system 13 are positioned for transporting the article carries 17 in directions that are transverse to the given direction of transport by the process conveyor 24. The lateral walls 14B of the chamber-defining radiation shielding material are disposed outside the loop 26 adjacent these transversely positioned sections 44 of the conveyor system 12 and portions of the intermediate wall 16 are positioned adjacent these transversely positioned sections 44 of the conveyor system 12 and across from substantial portions of the lateral walls 14A. The intermediate wall 16 is thereby positioned between the beam stop 40 and the lateral walls 14B so that photons emitted into the chamber 15 from the beam stop 40 are inhibited from impinging upon the lateral walls 14B. The intermediate wall 16 is also positioned between the beam stop 40 and the wall 14C on the opposite side of the chamber 15 from the wall 14A in which the beam stop 40 is recessed so that photon emitted from the chamber 15 from the beam stop are inhibited from impinging upon the opposite wall 14C. As a result, the lateral walls 14B and the opposite wall 14C may be of a lesser thickness of radiation shielding material than would be required in the absence of the intermediate wall 16. The intermediate wall 16 also is positioned for restricting flow throughout the chamber 15 of ozone derived in the target region 20 from the radiation source 10. Accordingly, most of such ozone can be removed from the chamber 15 b exhaust ducts 46 in the chamber 15 disposed above the target region 20. The dimensions of the various components of the radiation shielding material 14 and of the intermediate wall of radiation shielding material 16 are determined by computer-aided modeling in accordance with a technique described in a manual entitled "MCNP--A General Monte Carlo Code for Neutron and Photo Transport" published by the Radiation Shielding Information Center, P.O. Box 2008, Oak Ridge, Tenn. 37831. A plurality of queues respectively indicated generally at 100,102 and 104 are included in the embodiment shown in FIG. 1. Each of the queues may be defined by a plurality of the article carriers 17. The queue 100 is disposed at a position preferably just outside the loop 26 for a transfer into the loop of the articles in the queue. The queue 102 is disposed within the loop at a position for each of the article carriers 17 to be released from the queue and to be moved past the radiation source 10 for an irradiation of the article in the article carrier. The queue 104 is disposed within the loop 26 at a position just inside the loop for a transfer of each of the article carriers 17 out of the loop. The operations of the queues 100, 102 and 104 are synchronized. In this way, the first one of the article carriers 17 in the queue 100 is transferred into the loop 26 at the same time that the first one of the article carriers in the queue 102 is moved past the radiation source 10. In like manner, the first one of the article carriers 17 in the queue 100 is transferred into the loop 26 at the same time that the first one of the article carriers in the queue 104 is transferred out of the loop. A synchronizer for providing this function is indicated by broken lines 108 extending between the queues 100, 102 and 104. The intermediate wall 16 is disposed relative to each of the queues 100, 102 and 104 so that it shields the article carriers in the queue from radiation from the source 10. In this way, the articles in the article carriers 17 are not exposed to radiation from the source 10 during the time that the article carriers are disposed in the queues 100, 102 and 104. In an alternative embodiment, the loop within which the intermediate wall 14B is positioned is not a closed loop, such as shown in FIG. 1, but instead is an open loop, such as would be formed by elimination of the reroute conveyor section 30. An article irradiation system in accordance with the present invention provides the advantages of: (a) reducing the volume of concrete required in the ceiling section 14E, thereby reducing the cost and complexity of the structure; (b) reducing radiation levels incident on sensitive electrical and mechanical equipment, such as the radiation source 10 and the reorienting mechanism 32, thereby prolonging the life of such equipment; and (c) constraining ozone production to the vicinity of the process conveyor 24, thereby reducing the quantity of ozone produced and its dispersal throughout the chamber 15 so to prolong the life of the equipment and reduce the environmental impact of ozone vented to the atmosphere. The advantages specifically stated herein do not necessarily apply to every conceivable embodiment of the present invention. Further, such stated advantages of the present invention are only examples and should not be construed as the only advantages of the present invention. While the above description contains many specificities, these should not be construed as limitations on the scope of the present invention, but rather as examples of the preferred embodiments described herein. Other variations are possible and the scope of the present invention should be determined not by the embodiments described herein but rather by the claims and their legal equivalents.
	summary
	description	This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/602,711, filed May 4, 2017. The use of vision for localizing underwater robots has been studied both in research experiments and in deployed field robots. Submersible robots, for example, remotely-operated vehicles (ROVs), typically utilize a range of sensor modalities, but the choice of sensor modalities may be restricted in environments with challenging conditions. As an example, walls of nuclear reactor containment vessels must be periodically inspected to ensure integrity. However, the existence of radiation in this environment may constrain the use of other sensors that could otherwise provide accurate localization, for example, inertial measurement units, gyroscopes, or depth sensors. Radiation-sensitive electronics can degrade and fail with exposure of a few kRad, which is often below the expected exposure dosage in this setting. The underwater setting and the radiation shielding provided by the vessel may also exclude the use of GPS, and water attenuation excludes sensing depth using projective infrared light without the use of an external light source. However, the underwater setting, in most cases, lacks turbidity, and thus vision-based perception is viable. As such, systems where vision is a primary sensor modality for localization or inspection are preferred. Therefore, it would be desirable to be able to provide state estimation and localization using a visual modality in this very challenging environment. The invention consists of a tightly integrated combination of software and hardware components that form a system to address the problem of robot localization for the ROV-based inspection of nuclear reactor pressure vessels. This is important because ROVs used for this purpose may not be visible to the operator, or may be automatically controlled based on feedback from this system. Underwater cameras exist for nuclear reactor inspection, but they are typically only used for human monitoring by inspection personnel. In contrast, the present invention couples the camera with underlying algorithms to provide an automated capability for localization of ROVs used for vessel inspection. The system consists of computer vision and state estimation algorithms coupled with an underwater pan-tilt-zoom (PTZ) camera. The invention estimates the position and orientation of a remotely operated vehicle, for example, a tethered, submersible robot, that inspects an underwater structure. The system is particularly useful for the inspection of the walls of a nuclear reactor pressure vessel. The present invention solves the sensor constraint issue by utilizing a variable focal length camera. The camera may be positioned above the vessel, away from the radiation-emitting walls, and utilize zoom to compensate for its position. This yields a high optical resolution image suitable for processing with the software algorithms, while mitigating camera exposure to radiation. The invention is able to localize the robot within the highly irradiated environment of a nuclear reactor pressure vessel, particularly when the robot is in close proximity to the vessel wall. Due to extreme radiation emitting from the walls, only the most hardened electronics are viable when in close proximity to the walls, and these electronics are typically prone to image noise or are otherwise difficult to utilize in an automated context. However, operating in close proximity to the vessel walls is imperative for the robot to inspect the structure. The present invention has several advantages over existing camera-based systems and methodologies due to its tightly coupled design between the camera hardware and the software algorithms. The ROV can be automatically tracked through visual serving to keep the robot in view, obviating the need for inspection personnel to manually control the external camera. Additionally, the system is capable of a self-initialization procedure, requiring minimal input from inspection personnel. This removes the need for technical domain experts to start the system. The system is also self-calibrating, using an initial known map of the geometry of the structure. The camera algorithms extract lines and points from the scene, inferring the position and orientation of the camera itself. Lastly, the invention has automated failure detection. The software will detect when ROV tracking is lost, or when the uncertainty in the estimated camera or ROV position and orientation becomes unreasonable. In these cases, the system automatically takes corrective action, such as suspending tracking and attempting to re-acquire the ROV. Additionally, camera maneuvers may be performed to increase the belief state of the camera. Note that, as used herein, the terms, “vehicle”, “remotely-operated vehicle”, “ROV” and “robot” are used interchangeably and refer to the vehicle being localized. Also, as used herein, the terms “pan-tilt-zoom”, “PTZ” and “camera” are used interchangeably, and refer to the external camera used for image capture for purposes of localization of the robot, and not a camera or cameras which may be mounted on the robot and used for capturing images of the structure being inspected. The invention uses a vision-based state estimation and localization framework to enable submersible robots to conduct precision inspection of nuclear reactor pressure vessels and other underwater structures. The framework is formulated as an extended Kalman filter (EKF) that is robust to sensor degradation and image corruption that may occur due to environmental effects, such as radiation and color attenuation. The proposed framework relies on a pan-tilt-zoom (PTZ) camera that is autonomously controlled. To model the structure, a sparse geometric map that concisely represents the geometry of the structure as a series of planes and landmarks is used. The map is assumed as being known in advance with limited uncertainty arising from differences between engineering blueprints and actual construction. The map is added to the state to enable updates based on projections of lines and landmarks on the map by the camera. The computer vision algorithms extract landmarks (i.e., points and lines) from images of the vessel, as well as fiducial markers mounted on the ROV. These observations are then utilized by the state estimation framework to estimate the position and orientation of the camera and ROV with respect to the vessel, which is represented by the system mapping component as a series of intersecting planes and coincident landmarks. Preferably, the camera is mounted in a waterproof housing, designed to be submersible to at least 10 m. A transparent hemisphere is mounted to the bottom of the housing to enable viewing at various camera angles. Preferably, the housing will be submerged under the surface of the water and will be locked in a fixed position. In preferred embodiments, the camera housing is fabricated from aluminum and anodized to prevent corrosion from radiation. The housing uses a high precision transparent acrylic hemisphere to allow for the camera to view the scene at nearly the full range of pan and tilt angles, with minimal optical distortion. The housing further uses a pressurization system which enables the housing to be purged with nitrogen gas and kept at a positive pressure to aid with preventing the ingress of water in the event of a housing structural failure. In this event, bubbles will be produced at the leak site, allowing for visual identification of this failure mode. Preferably, a diopter (i.e., close-up) lens is installed on the PTZ camera to compensate for the adverse optical effects of underwater spherical lenses (i.e., light refraction), which causes a reduction in focal length. The submersible robot that is used to inspect structure may be, in certain embodiments, an underwater ROV having a planar structure. The robot is preferably equipped with at least three fiducial markers that are used for pose estimation. A tether may be used to remotely transmit control signals to the robot. FIGS. 1(A-B) illustrate the system and depict three distinct reference frames 1. the body frame {B}, located at the robot center of mass; 2. the external camera frame {E}, located at the optical center of the camera; and 3. the inertial world frame {W}, which is the reference frame for the structure map. The pose of the robot is estimated via an EKF with a state that also includes the pose and focal length of the PTZ camera. To account for uncertainties in the geometry of the structure, a representation of the structure as a sparse map is included in the framework. The framework is detailed in FIG. 2. External PTZ Camera—The PTZ camera utilized to monitor the robot and vessel during inspection of the structure is mounted to the structure, external to the robot. The camera is controlled via visual serving such that the robot is always in view with reasonable magnification. The PTZ images are used for inference of camera motion and intrinsic change due to zoom, camera-to-robot localization and camera-to-world localization using projections of structural landmarks in the image space. Pinhole projection is assumed as the underlying camera model: K = [ f x 0 c x 0 f y c y 0 0 1 ] ( 1 ) Submersible Robot and Fiducial Markers—The submersible robot is preferably equipped with at least three fiducial markers, as shown in FIG. 4, to enable pose estimation from the marker projections in the camera image space. These projections (mi=[ui,vi]T={1, 2, 3}) provide corrections between the external camera and the robot frames. The markers are detected by color and grouping, such as with the K-means clustering algorithm, and assigned based on the estimated robot pose. The position of the markers with respect to the body frame {B}, (Mib), is static and known from robot measurements. Therefore, the projections of these markers in the external camera image space are related as follows:{tilde over (m)}i˜K[Rwe\|twe]Tbw{tilde over (M)}ib (2) In this model, Tbw is the rigid body transformation matrix that relates points expressed in the body frame to the world frame, calculated from the robot pose estimate (pbw,qbw). Similarly, the extrinsic calibration matrix [Rwe,tbe] is determined from the pose estimate of the external camera (pew,qew). Sparse Map from Structural Elements—In the case where the structure is the pressure vessel of a nuclear reactor, the characteristic geometric appearance of the structure can be described as a series of intersecting planes, with landmarks that exist on these planes. These three-dimensional geometric entities (planes and points) form the two types of landmarks that are used for correction in the image space, namely, lines and points. The vessel geometry is specified in the world frame {W}. Each plane π=[nT,d]T∈4 is described by a unit normal vector. The three-dimensional line that arises from the intersection of two adjacent planes, πi and πj, can therefore be represented in Plücker coordinates ij=πi{circumflex over ( )}πj, where ∈5. The infrastructure contains landmarks, as shown in FIG. 4, which are engineered structural elements such as relief holes, cavities, or bolts that can be represented as a three-dimensional point, P. Repeated point elements such as flow holes on the reactor core floor and bolts are prominent. These landmarks exist on a plane, as represented by the π·{tilde over (P)}=0, where {tilde over (P)}˜[PT,1]T is the three-dimensional point in homogeneous coordinates. Homography-Based Inference of Camera Rotation—To infer the change in the external camera process, a homography-based methodology is used which leverages image registration. The process change is used by the state estimation framework to drive the system. The pixel coordinates of successive images from the external camera are always related by a homography (projective transformation):{tilde over (x)}′=H{tilde over (x)} (3)where {tilde over (x)} is the homogeneous pixel coordinates, (i.e., {tilde over (x)}=[u,v,1]T). This is because the external camera does not experience translation, causing image pixel displacements that do not depend on scene structure. Specifically, this homography H is the infinite homography H∞ induced by the plane of rotation at infinity. Between frames i and j, this homography may have two structures depending on the process:Hstatic=I3×3 (4)Hrot=KRijK−1 (5) The homography, H, is calculated via intensity-based image registration to determine the best similarity matrix, and is utilized to drive the model of the external camera in the state estimation framework. Projections of Structural Elements—The projections of structural elements that compose the map are observable from the external camera image space. Landmarks (points and lines) are used for correcting the state estimate by identifying and associating them in the image space. These projections are utilized for localization between the robot and the world or for localization between the external camera and the world. Landmarks are identified and associated first using feature detection based on geometric shape. Specifically, the Hough transform is used to detect lines and circles (points). Points are also detected using genetic blob detection. After detection, data association is performed by first projecting map elements into the image space, and comparing them against candidate detected landmarks. The closest detected landmark (within a heuristic threshold) to a projected landmark is then associated. Three-dimensional points and their projections in the image space are related by{tilde over (P)}i˜K[Rwe\|twe]{tilde over (P)}iw (6) For lines, the Plücker line ij=πi{circumflex over ( )}πj formed from the intersection of adjacent planes defined in the world coordinate j frame are projected in the external camera image space as a line lij∈2:lij˜Lweijw, (7) The matrix Lwe is the rigid displacement matrix for lines, and is the perspective projection matrix for lines. EKF Methodology—The non-linear state of the system (camera, robot, and map) is estimated using a distinct extended Kalman filter (EKF) with quaternions to obtain a recursive state estimate. This state estimation framework leverages the algorithms described above and requires as priors the position of the fiducial markers on the robot, the vessel geometry as could be obtained from blueprint specifications, and the camera radial and tangential distortion parameters, obtained via a previously known calibration. The external camera images are unwarped following a transformation to reverse any lens distortion. To initialize the filter, the initial position of the external camera and focal length is optimized to minimize the reprojection error between the observed and predicted vessel landmarks. Thereafter, the initial pose of the robot may be estimated from the marker projections from constrained optimization. System Parameterization—The non-linear state of the inspection system X(t) is estimated via an extended Kalman filter with inputs u(t)∈3 and a variable number of measurements z(t), depending on the scene. The system state encompasses the state of the inspection system (robot and external camera) Xs(t) and the map of the vessel XM:X(t)=[Xs(t)T,XMT]T (8) Inspection System State—The state of the system is represented byXS(t)=[pbw(t)T,qbw(t)T,pewT,qe−w(t)T,fe(t)T]T (9)where pbw(t)=[xbw(t),ybw(t),zbw(t)]T is the position of the robot with respect to the world frame (pew=[xew,yew,zew]T), qbw(t) is the orientation of the robot with respect to the world frame; qew(t) is the (static) position and orientation of the external camera with respect to the world frame; andfe(t)=[fx(t), fy(t)]T are the two focal length components. Map State—The world structure is represented by a map in the state estimate XM that encompasses the vessel planes and three-dimensional landmarks that exist on these planes. Each plane π=[nT,d]T is described by the unit normal vector n and distance d. A formal representation for utilizing the sparse map in the EKF framework by extending the geometric representation described above is used. Assuming that the walls of the structure are orthogonal to the floor, then planes are specified by their rotational degree of freedom (θ) about the world z-axis and translational degree of freedom (d). Therefore, the unit normal for each wall is n=[cos θ, sin θ, 0]T. For the floor of the vessel, only the height of the vessel h is needed in the state, for n=[0, 0, 1]T and d=−h. Therefore, if the vessel consists of N walls, 2N+1 parameters are needed for the planar structure of the vessel. Although landmark points are three-dimensional, they all must exist on a plane. To enforce the coplanarity of a landmark with its associated plane, a point is represented by two translational degrees of freedom within in the plane, δ1 and δ2, relative to the point −nd, which is the point on the plane closest to the origin of the world frame {W}. These represent the two-dimensional position of the landmark in the two-dimensional subspace of 3 formed by π. When considering n as one axis of an orthogonal basis of the plane, the other two axes are v1=[−sin θ, cos θ, 0]T and v2=[0, 0, 1]T for walls, and v1=[1, 0, 0]T and v2=[0,1,0]T for the floor. A landmark's three-dimensional position in the world frame {W} can be recovered from its coincident plane and two-dimensional position within this plane:P=−nd+δ1v1+δ2v2 (10) It follows from (10) that the coplanarity constraint of the landmark, π·{tilde over (P)}=0, is always satisfied for any choice of θ, d, δ1 or δ2. With this minimal geometric representation, the map state XM ∈2N+1+2L for N planes and L points is as follows:XM=[θ1,d1, . . . ,θN,dN,h,δ1,1,δ1,2, . . . ,δL,1,δL,2]T (11) Process Models—The system process model characterizes the temporal evolution of the state. The process input, u(t), consists of the frame-referenced angular velocity of the external camera, ωew(t). The entire process model is provided by:{dot over (p)}bw(t)=0 (12){dot over (q)}bw(t)=0 (13){dot over (p)}ew=0 (14){dot over (q)}ew(t)=½Q(ωew(t))qew(t) (15)fe(t)=0 (16){dot over (π)}=0 (17){dot over (P)}=0 (18) The process of the robot is modeled as random by accounting for state evolution in the process noise. For the external camera process, the position of the external camera pew is static. The external camera rotates with an average angular velocity ωew(t) determined, from the output of the homography, described above. Q(ω(t)) is the quaternion kinematic matrix that relates angular velocity in a body-referenced frame and quaternion orientation to quaternion rate. Lastly, the map is static as it is defined in the world frame {W}. Measurement Models—All system measurements z(t) consist of projections into the external camera image space. The measurements can be categorized into two types: 1) zbe(t), relating the robot body frame {B} to the external camera frame {E}; and 2) zee(t), which relates the external camera frame {E} to the world frame {W}:z(t)=[zbe(t)T,zew(t)T]T (19) The body-to-external-camera measurements, zbe(t), are determined through robot fiducial marker detection:zbe(t)=[m1(t)T,m2(t)T,m3(t)T]T (20) Projections of structural elements provide observations for external camera-to-world localization and robot-to-world localization. While the number of marker corrections is fixed while the robot is in view, the number of landmark corrections varies depending on the number of visible landmarks. A measurement noise σ=3 is used for all measurements. The predictions for these measurements, {circumflex over (z)}(t), utilize an ideal projective camera model as detailed above. For points, the correction model is simply the predicted landmark projection in the image space. For lines, the line error formulation as shown in FIG. 3 is adopted, which is based on the distance from each point of the detected line to its nearest point on the predicted line. The process of the invention is shown in schematic form in FIG. 2. Box 202 represents the homography-based inference of camera rotation, as described above. The angular velocity of the camera is calculated from a comparison of two sequential images. A previous and current image are obtained and image registration is performed to determine mathematically how the two images differ. The difference between the images is represented by a 3×3 homography matrix. More specifically, the pixel intensities between two sequential images are compared to determine the 3×3 homography matrix that, when applied to the first image, will produce (as best as possible) the second image. The angular velocity of the camera is then obtained from the terms in the 3×3 homography matrix using equation (6) above. Boxes 204 and 206 produce projections used to estimate the position and orientation of the robot and PTZ camera in the {W} reference frame. A two-dimensional reference frame exists at {E}. {E} represents the environment when viewed in three-dimensions at the camera position and orientation. Capturing an image at {E} collapses the three-dimensional content into two-dimensions, providing a two-dimensional reference frame, which is referred to herein as the “camera image space”. The fiducials and landmarks are detected and compared in this two-dimensional camera image space. The camera image space is shown in FIG. 1A. Box 204 represents the robot and fiducial markers process described above. The fiducial markers on the robot are a distinct color from the rest of the image, and so can be identified and tracked in the camera image by color. The fiducials can be seen in FIG. 1A. The identification of the 3 fiducial markers in the camera image produce pixel coordinates (m1, m2, m3) of these markers, which is the output of this box. Box 206 represents the projections of structural elements described above. In this process, points and lines are detected using various detection algorithms. For points, blob detection is used to find small patches in the image with high image gradient that fit certain geometric properties and the Hough transform is used (a polling based technique that allows for circles to be identified in an image). For lines, the edges of the image are exposed using a Canny image filter, which produces an image where the edges/lines are identified (this is done from inference of the image gradient). Then, the Hough transform is again used, but to detect lines. For each detected point and line, it is determined if the point or line corresponds to an actual three-dimensional point or line on the structure. Within a reactor vessel, points may be, for example, reactor flow holes, bolts, small cavities, etc. (i.e., structural landmarks that are known to exist) and lines may be, for example, the intersection of adjacent reactor planes. The process described allows for robustness as it provides a mechanism for rejecting spurious points or lines that are not associated with any structural element of the reactor. This is determined by using the model of the camera to project known structural elements (that are known to exist in the reactor) into the image, and comparing them in two-dimensions against detected points and lines, so that only detected points and lines that are actually associated with real structural entities are kept. Box 208 uses an extended Kalman filter to generate the prediction of the next state of the system (and its covariance), as represented by equation (9), which includes the position and orientation of the robot, the position and orientation of the camera, and the focal length or the camera. The predicted state is based on the angular velocity of the camera, which is derived as described above with respect to box 202. The EKF is also used to generate a correction to the prediction, the correction being based on the projections of the fiducial markers, obtained as described above with respect to box 204, and the projections of the landmarks, obtained as described above with respect to box 206, and applied the correction to the predicted state to produce a corrected state (and its covariance). The corrected state is used as the previous state for analysis of the next image captured. Box 210 represents the PTZ camera, as described above, housed in a watertight housing. Images may be captured at any rate, however, in preferred embodiments of the invention, a 20-25 Hz capture rate was found to be sufficient. Box 212 represents the sparse map of the structure, used as described above. The invention described herein may be used with any underwater remotely operated vehicle, either controlled by a human operator or automatically controlled. In some instances, a human operator may control the ROV based on feedback from the system described herein, with an output displayed on a monitor showing the opposition and orientation of the ROV with respect to the structure. In other cases, the output of the system may be used directly to automatically operate the ROV. The system may be implemented by executing software by any known means. The invention is not meant to be limited to particular hardware or software implementations. The scope of the invention is captured in the claims which follow.
	description	This application is the U.S. National Phase application under 35 U.S.C. §371 of International Application Serial No. PCT/IB2014/063727, filed on Aug. 6, 2014, which claims the benefit of European Application Serial No. 13180568.1, filed on Aug. 15, 2013. These applications are hereby incorporated by reference herein. The invention relates to a system in the field of X-ray imaging and more specifically to the mechanics for enabling motion of the collimator arrangement, the detector and the x-ray source. Conventional systems for X-ray imaging comprise an X-ray source and an area detector placed behind an object to register an image. The main drawback with this setup is its sensitivity to background noise in form of Compton scattered radiation. As a solution to this, a slot scanning system has been proposed. Such a system is for example known from EP1192479 B1. A slot scanning system described in EP1192479 B1 comprises an X-ray source and a collimator arrangement comprising several collimator structures. Furthermore, the slot scanning system comprises a detector array and compression plates in between for example a breast can be positioned and compressed. The compression plates are transparent to X-rays. One of the collimator structures is positioned on one side of the compression plates, whereas another collimator structure is positioned at the other side of the compression plates. The slots of the collimator structures are matched and in line with the X-ray source so that the X-rays coming straight from the source, without deflections, that will pass one collimator structure, will also pass the other collimator structure and will hit the detector which is positioned in line with the collimator structures and the X-ray source. The collimator structures are positioned on an arm together with the detector. This arm can move the slots relative to the object. The stage of the movement is computer controlled and equipped with an accurate position reading. While the slots are moving, data from the detector arrays are read out together with the present coordinate according to the position reading. From this information the image is reconstructed. The scan trajectory described in EP 1192479 B1 can be a circular movement around the X-ray source. The trajectory can also be arranged to refract the beam in a plane parallel with the compression plates, whereby a linear movement of the collimator and detector will be needed. Moreover, due to the circular radiation, the detectors are arranged in a circular carrier, which in case of a linear movement should be arranged in a flat carrier. It is an object of the invention to obtain better coverage of an object to be scanned, when scanning with an X-ray apparatus comprising a detector and a collimator arrangement which are configured to move along a scan trajectory in order to enable medical X-ray imaging. This object is achieved by an X-ray apparatus, comprising An X-ray source (20) configured for producing an X-ray beam (16) and comprising a focus position (12b); A detector (28b) configured for detecting X-radiation; A collimator arrangement (12a, 18, 28a) comprising at least one collimator structure, positioned between the focus point (12b) and the detector (28b); Mechanics (43) for enabling motion of the collimator arrangement, the detector and the x-ray source along a scan trajectory (30) in an x-z plane (83) A control unit configured for controlling the mechanics for enabling motion of the collimator arrangement (12a, 18, 28a), the detector (28b) and the x-ray source (20, 12b) along the scan trajectory (30)Characterized in that The mechanics (43) for enabling the scan trajectory (30) of the collimator arrangement (12a, 18, 28a), the detector (28b) and the x-ray source (20, 12b) is also configured for enabling motion along a curved scan trajectory (45), which partly extents along a y-axis (35) perpendicular to the x-z plane. It is an insight of the invention that when scanning an object with a curved edge (like a breast) with the conventional slot scanning system (or other X-ray apparatus comprising a detector and a collimator arrangement which are configured to move along a scan trajectory in order to enable medical X-ray imaging), part of the object may not be scanned. For example, during a conventional mammography acquisition, the breast is positioned on a rectangular table or detector housing with a rectangular detector. Also the scan trajectory is limited to one plane (here further called x-z plane). However, the thorax has a curved cross section. Limitation of the scan trajectory to the x-z plane limits the amount of breast tissue that can be imaged. As a result, medial and/or lateral parts of the breast are challenging to image. By allowing a curved scan trajectory, which extents along an axis (here further called y-axis) perpendicular to the x-z plane, better coverage of breast tissue and other objects with curved edges can be obtained when using a slot scanning system. In turn, better coverage of objects may lead to a higher sensitivity in detecting cancer or other pathologies. To fully benefit from the curved scan trajectory that also extents along the y-axis, also the scanner housing in the vicinity of the detector needs to match the curvature in a x-y plane, perpendicular to the x-z plane. In case the slot scanning system is used as a mammography system, also the curvature of compression plates of the system needs to be adjusted. According to one aspect of the invention the curved trajectory can be obtained by mechanics for enabling motion of the X-ray source, the collimator arrangement and the detector, wherein the mechanics comprise a base element, a guiding element and a moving element. The guiding element is connected to the base element and configured for guiding the moving element along the curved scan trajectory relative to the base element and the guiding element. The detector and/or the collimator arrangement and/or the x-ray source are connected to the moving element. The mechanics for enabling motion of the X-ray source, the collimator arrangement and the detector could be separately connected to the each of the said items. In this case separate mechanical structures are required to move the X-ray source, the detector and the collimator arrangement along the curved scan trajectory. Also the mechanics for enabling motion of the collimator arrangement and the detector could be connected to an arm to which in turn the detector and collimator arrangement can be connected. This is advantageous when used for slot scanning, because in this way the detector and collimator arrangement remain aligned during movement. In a breast cancer screening environment two images of the breast are acquired: one from head to toe (cranio caudal (CC) view) and one from the side (medio lateral oblique (MLO) view). The thorax has a different curvature in both directions. Therefore it may be beneficial to enable adjustment of the curvature of the curved scan trajectory to better image the breast in both directions. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. FIG. 1 diagrammatically shows part of a slot scanning system. The slot scanning system comprises an X-ray source (20), which comprises a focus position (12b) and a first rough collimator structure (12a). From the X-ray focus position a conical X-ray beam (16) emerges, which passes onto the collimators and the detector. The slot scanning system further comprises an X-ray shield (22) to shield scattered X-rays for example coming from the collimators 12a and 18 and other components of the surroundings of the system. The slot scanning system comprises a collimator structure (18) above and below (28a) the examination area (32). The combined collimator structures in the slot scanning system are here called the collimator arrangement (12a, 18, 28a). X-rays will travel from the X-ray focus position (12b) via the collimator arrangement (12a, 18, 28a) to a detector (28b). The X-ray source, collimator arrangement and detector are connected to arms (24, 25), which can move relative to a holder (26) within a plane (83, x-z plane). The movement of the detector and collimator arrangement is computer controlled by means of a control unit (101) and equipped with position reading. In a further configuration the arm (25) keeping the detector and the collimator arrangement, is configured to make a circular scan trajectory (14, 30), within the x-z plane (83), partly around the X-ray focus position (12b). The invention proposes to extent the scan trajectory partly along an axis (35, y-axis) perpendicular to the x-z plane (83). This can for example be obtained by making arms (24) and (25) movable relative to each other. One arm (24 or 25) could be configured to enable motion inside the x-z plane, whereas the other arm (25 or 24) could be configured to extent the scan trajectory along the y-axis (35). However, independent motion of arms (24) and (25) is not necessary. For example, also a single arm could be used and configured to enable motion along the curved scan trajectory (45), that partly extents along the y-axis (35). To fully benefit from the invention also the scanner housing close to the detector (28b) and the collimator structures (28a) need to have a similar curvature in the x-y plane (27), as the curved scan trajectory. When used in mammography also compression plates need to have a similar curvature in the x-y plane as the curved scan trajectory. In the configuration shown in FIG. 1, this would imply that the extension of the scan trajectory along the y-axis would be larger close to the detector (28b), than close to the X-ray source (20). The curvature of the scan trajectory can be adjusted by extending the movement of the detector and collimator arrangement more or less along the y-axis. The curved scan trajectory is enabled by mechanics enabling motion of the collimator arrangement (12a, 18, 28a) and the detector (28b), which are preferably located at one of locations (33). FIG. 2 diagrammatically shows an embodiment of the mechanics enabling motion of the collimator arrangement (12a, 18, 28a), the detector (28b) and the x-ray source (20). FIG. 3 diagrammatically shows another embodiment of the mechanics enabling motion of the collimator arrangement (12a, 18, 28a), the detector (28b) and the x-ray source (20). The mechanics (43) enabling motion of the collimator arrangement (12a, 18, 28a), the detector (28b) and the x-ray source (20) comprises a base element (40,40a), which can be connected to a part of the slot scanning system, which is fixed relative to the detector and collimator arrangement, e.g. the holder (26) or arm (24). Also the base element (40,40a) can be connected to any location in an examination room, wherein the slot scanning system is positioned. The mechanics (43) further comprises a guiding element (44, 44a) configured for guiding a moving element (42, 42a) along a curved scan trajectory (45). In one embodiment of the invention the guiding element (44) is rotatable connected to the base element (40), whereas the moving element (42) is rotatable connected to the guiding element (44). Rotation can be performed around connection areas (48). In this way the curved scan trajectory (45) can be established. In FIG. 2A only one guiding element is depicted. Preferably another guiding element is added to the mechanics in order to create a parallelogram structure. An example of such a parallelogram structure is depicted in FIG. 2B. A parallelogram structure increases the stability and robustness of the mechanics. According to another embodiment of the invention, the moving element (42a) is translatable connected to the guiding element (44a), which is for example a curved guide, rail. The guiding element could also be a curved cut, notch, cavity or the like in base element (40a) to which the moving element is translatable connected. In FIG. 3, two guiding elements are depicted. Of course, also one curved guide, rail, cut, notch, or cavity etc could be used. The X-ray source, the detector (28b) and the collimator arrangement (12a, 18, 28a) are connected to the mechanics enabling motion of the collimator arrangement (12a, 18, 28a) and the detector (28b) preferably via an arm (24). The detector (28b) and the collimator arrangement (12a, 18, 28a) as well as the X-ray source could also be connected separately to a fixed part of the slot scanning system or to position in the examination room. In this case more than one mechanical structure (43) is needed for moving the detector and collimator arrangement. The arm (24, 25), or detector (28b) and collimator arrangement (12a, 18, 28a) can be connected to part (50) of the mechanics for enabling motion of the collimator arrangement and the detector. According to another embodiment of the invention, the guiding element is translatable connected to the base (40) and moving element (42), in such a way that the rotation points can be shifted. In this way an effective length (51a, 51b, 51c, 51d) of the guiding and/or moving element can be adjusted. This could result in an extension of the curved scan trajectory in x and/or y direction. FIG. 4 diagrammatically shows an example on how the curved scan trajectory can be extended in the x and/or y direction. The mechanics can be adjusted prior or during scanning in order to change the curvature of the curved scan trajectory. This embodiment is also advantageous for adjusting the curve of the curved scan trajectory depending on the curvature of the object to be scanned (e.g. scan in CC or MLO view). Adjustment of the effective length (51a, 51b, 51c, 51d) could be performed as a result of a user request, but could also be performed automatically when changing from CC to MLO scan orientation or the other way around. Adjustment of the effective length could be obtained for example by sliding the moving and/or the guiding element to a second connection area on the respectively guiding and/or moving element. Also the guiding and/or moving element could comprise two concentric parts, which can shift relative to each other (a telescope like structure) whereby the moving and/or guiding element is connected to one of inner of outer parts. The adjustment could for example be controlled by a stepper motor. Adjustment of the curvature of the housing of the detector and/or compression plates is important to match the curvature in the x-y direction of the curved scan trajectory. The adjustment of the curvature of the housing of the detector and/or compression plates could be established in a manner known per se from the U.S. Pat. No. 6,741,673 B2. Different sides of the housing and/or compression plates could have different curvatures. By turning the housing and/or compression plates, the housing and/or compression their curvature can be adjusted to meet adjustments in the curvature of the curved scan trajectory. Whilst the invention has been illustrated and described in detail in the drawings and foregoing description, such illustrations and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.
	abstract	Method and systems are disclosed for radiating a moving target inside a heart. The method includes acquiring sequential volumetric representations of an area of the heart and defining a target tissue region and/or a radiation sensitive structure region in 3D for a first of the representations. The target tissue region and/or radiation sensitive structure region are identified for another of the representations by an analysis of the area of the heart from the first representation and the other representation. Radiation beams to the target tissue region are fired in response to the identified target tissue region and/or radiation sensitive structure region from the other representation.
047537736	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The steam generator of the present invention is essentially a heat exchanger having a water/steam circuit enveloped in a stagnant barrier/heat transfer system which may be contacted with hot media for transferring the heat from the media to the water for the production of steam. Although the safety and efficiency of the steam generator of the present invention make it particularly suitable for cooling the hot liquid metal coolant from a nuclear reactor, the invention will be useful in many other applications where efficient exchange of heat between incompatible liquid media is desired. In the following detailed description, the steam generator of the present invention will be described as if it were connected to the circulating liquid metal coolant system of a nuclear reactor. For such an application the customary intermediate heat transfer system components including the intermediate heat exchanger, pump, piping, valves, auxiliary equipment, and associated structures are not required. Elimination of these components and structures results in a compact and low cost nuclear reactor system. A nuclear reactor is chosen as the most preferred embodiment and for ease of explanation, however the following description should not be construed as a limitation of the scope of this invention. The principal element of the steam generator is a duplex tube heat exchanger module. Several embodiments of the coil configuration are possible, including helical configuration, serpentine (sinusoidal) tube configuration, or a U-tube configuration. FIGS. 1-10 describe a serpentine coil embodiment. Referring to FIG. 1, the serpentine steam generator configuration of the invention is comprised essentially of a vertical, cylindrical steam generator vessel (1) closed at its lower end, subdivided into two main chambers, an upper plenum (3) and a lower plenum (5). The upper plenum (3) houses a heat exchange module (7) having double tube assemblies (66) in the configuration of a serpentine coil. As illustrated, the upper plenum (3) of the cylindrical vessel (1) houses four such heat exchange modules (see FIG. 5), however the number and relative position of the modules selected in the practice of this invention may of course be varied according to design requirements, available space, etc. In general operation, hot liquid metal introduced into the upper plenum (3) transfers its heat to water circulating through the serpentine coil double tube assemblies (66), then the cooled liquid metal flows to the lower plenum (5), from which it is ultimately discharged. At the top of the steam generator vessel there is a grid of support elements (11) on which the heat exchange modules (7) and a core module (8) are mounted. Optional steel sheets (13) at the top and periphery of the steam generator vessel (1) provide insulation when the vessel is filled with hot liquid metal. The top of the cylindrical steam generator vessel (1) is capped by a welded closure plate (15). The steam generator is supported from the surrounding concrete supporting enclosure (17) by a gusseted, torsion-resistant ring girder (19) welded to a cylindrical skirt (21) having bolting flanges (22). Each heat exchange module (7) is supported by the support grid (11), and at the contact points self-sealing metallic gaskets provide a closure around the module. The dead weight of the module, even when buoyed by the liquid metal coolant filling the steam generator vessel (1) is sufficient to effect a complete seal at the gasket surface. The volume above the coolant level (25) in the upper plenum (3) is filled with an inert cover gas such as argon, and the gaskets (23) prevent leakage of the gas without the need for hold-down bolts. This provides convenience in the removal and replacement of modules. A backup welded omega seal (24) can be provided for additional assurance of leak tightness at the upper contact point of the module at the top of the support grid (11). Alternatively, a boltdown design to secure the modules to the top of the support grid (11) can be provided. Support grid (11) is comprised of vertical plates (27) welded to horizontal plates (28) at their lower extremity, which horizontal plates (28) also form the seat and sealing surface for the modules (7). The square openings are provided for the heat exchange modules (7) and for a core module (8). (See FIG. 5). Welded to the horizontal grid plate members (28) are shroud plates (29) which extend vertically downward to below a horizontal diaphragm (31) which separates the vessel (1) into upper (3) and lower (5) plenums. A square shroud (29) is provided for each square opening within the support grid (11) and surrounds a heat exchanger module (7) that is lowered into the steam generator vessel (1). At the lower end of each shroud, bumper blocks (33) are provided for lateral stability against strong vibrational forces, including earthquakes. The bumper blocks (33) are preferably located at the corners of the square shrouds so that any lateral motion is transmitted to the diaphragm (31). The diaphragm (31) is shaped to allow free vertical passage of the shroud (29). The shrouds (29) form (in the illustrated configuration) a continuous sealed cruciform opening allowing insertion of a central core module (8), for housing equipment such as a pump or monitoring/regulating devices (not shown), and four heat exchange modules (7). (See FIG. 5). The core module (8) of this illustration consists of a cylindrical support housing (35) which has a box-shaped collar (37) providing snug insertion into the center of the support grid (11) and stable seating on the horizontal plates (28). At the height of the horizontal diaphragm (31), the bumper blocks (33) extend from the cylindrical support housing (35) to adjacent shrouds (29). The cylindrical support housing (35) extends beyond the diaphragm (31) and is closed at the lower end. Holes (39) are provided in the lower end of the cylindrical support housing (35) which allow entry into the cylindrical support housing (35). A pump (not shown) may be located within the housing (35), e.g., at an elevation at or above the diaphragm (31), supported from the interior of the cylindrical support housing (35). The pump discharge line (41) exits through the side of the cylindrical support housing (35), below the bottom of the diaphragm (31). Preferably, the discharge line (41) is shaped as a nozzle (42) and an eductor (43), followed by a diffuser assembly (45), may be installed adjacent to the discharge nozzle (42), leading to discharge pipe (47) exiting the steam generator vessel (1) through a lower duct (49). Alternatively, a pipe coupling may be provided which connects the pump discharge line (41) with the discharge pipe (47) that exits the lower plenum (5) through the lower duct (49). The liquid metal coolant entering the upper (3) plenum of the steam generator vessel (1) is separated from the liquid metal coolant in the lower plenum (5) by the horizontal diaphragm (31) and a gas seal (51). The gas seal (51) is continuous around the entire cruciform periphery of the shrouds (29). FIG. 2 illustrates a serpentine coil heat exchange module (7). In general, each heat exchange module comprises a box header (53), inlet (55) and outlet (57) nozzles, double tube coils (59) and a coil support bracket (81). Preferably, each module (7) features a large multiplicity (e.g., 10-1000) double tube coils (59), the inner tubes of which extend from inlet nozzles (55) to outlet nozzles (57) and form a serpentine coil in between. Each of the double tube coils (59) is comprised of a multiplicity of double tube assemblies (66), having an inner tube (63) and an outer tube (65), which structures are best seen in FIG. 3. The outer tubes (65) of the serpentine double tube coil are welded to the lower tube plate (71) of the box header (53). At the top of the box header (53) there is a multiplicity of nozzles for feedwater inlet (55) and steam (57). The inner tubes (63) are welded to tube sheets (75) in the necks of these nozzles. The neck of each of the nozzles (55, 57) leads into the upper plate (70) of the box header (53), and the upper plate (70), side walls and lower tube plate (71) of the box header (53) form a disengaging chamber (77) into which outer tubes (65) open. The disengaging chamber (77) may be further subdivided by partitions (78), forming a separate disengaging chamber for either end of each double tube bundle (67). The heat exchange module (7) includes a coil support bracket (81) for the tube bundles. FIG. 4 provides a perspective view of the coil support bracket (81). Although the exact number of duplex tubes may of course be varied, the embodiment illustrated herein shows several rows of double tube assemblies (66) gathered together to form a descending tube bundle (67) which has about 304 duplex tubes. The tubes of each tube bundle (67) are secured in the bundle configuration at intervals by spacer plates (83) and a vertical support strip (85), which structures serve to maintain the relative position and spacing of each duplex tube in the bundle (67) and along the length of the serpentine coil (59). Primary support for the coil is provided by the vertical support strips (85), which are fastened at their upper end to the coil support bracket (81), which, in turn, is fastened to the underside of the box header (53) of the heat exchange module (7). The spacer plates (83) also serve as a flow baffle, preventing channeling of the liquid metal coolant in the vertical tube bundle area. Additional support for the duplex tube bundle may be provided with bottom spacer supports (84) which stand on a base structure (30) at the foot of the square shroud (29) (see FIG. 1). The bottom spacer supports may be designed to provide an initial (cold) prestress in the vertical tube bundle. The base structure (30) of the square shroud (29) is preferably a series of parallel bars extending across the bottom of the shroud and located directly beneath each row of duplex tubes. This particular configuration for the base structure (30) lends stiffness to the lower end of the shroud (29) and permits transfer of lateral seismic forces to the diaphragm (31), increasing the overall operational safety of the steam generator. The circulating water system within each heat exchange module (7) begins at a feedwater inlet nozzle (55). A large diameter feedwater inlet tube (52, FIG. 3), leading from an outside feedwater source, ends at an inner tube sheet (75) at the bottom of the feedwater inlet nozzle (55). A multiplicity of water-carrying inner tubes (63) are connected to the bottom of the inner tube sheet (75). As best seen in FIG. 3, each of the inner tubes (63) is joined with a co-axial outer tube (65) to form a concentric double tube assembly (66). The mating of the inner tube (63) with an outer tube (65) defines an annular gap (64) which in operation of the steam generator will be filled with liquid metal as a heat transfer agent. Spacing between the co-axial tubes (63 and 65) may be provided by a helically wound spacer wire (not shown), brazed to the outer surface of the inner tube (63), which will separate both tubes and provide an unimpeded flow path for the liquid metal within the annular gap (64). As noted above, welded components of the box header (53) create a closed disengaging chamber (77) into which the outer tubes (65) open. In preferred embodiments, the disengaging chamber (77) for each heat exchange module (7) is further subdivided with vertical partitions (78), which separate the disengaging chamber (77) into discrete compartments, with (most preferably) one such compartment for each feedwater inlet nozzle (55) and each steam outlet nozzle (57). The multiplicity of double tube assemblies (66) of each module (7) are gathered into a tube bundle (67) and extend into the square inner cavity of the upper plenum (3), which inner cavity is formed by the square shroud (29). Preferably, as shown in FIG. 1, the tube bundle (67) will extend from the header box header (53) downward to a point near the end of the shroud (29), then curve upward in a serpentine coil (59). At the end of the serpentine coil, the tube bundles (67) extend upward to meet the lower tube plate (71) at the bottom of the box header (53), where the outer tubes (65) terminate within a disengaging chamber (77), and the inner tubes (63) continue through the disengaging chamber (77) to terminate at the inner tube sheet (75). Steam generated within the inner tubes (63) exits the steam generator through steam outlet nozzle (57), which in turn may be connected to a turbine generator for the production of electricity. The steam generator vessel (1) is provided with at least one liquid metal coolant inlet duct (48) connected to the circulating coolant system around the nuclear reactor core. As noted above, the diaphragm (31) between the upper plenum (3) and the lower plenum (5), and a gas seal (51) between the diaphragm male portion (31a) and the shroud female portion (29a), prevent liquid metal coolant entering the upper plenum (3) through the inlet duct (48) and passing directly to the lower plenum (5). Hot liquid metal coolant entering the upper plenum (3) rises to a level (25) outside the inlet shroud (90) which is connected at its bottom by a perforated distributor sheet (91) to the square shroud (29), as best seen in FIG. 1. This inlet shroud (90) provides the only opening (through the distributor sheet (91)) by which liquid metal may flow between the upper plenum (3) and the lower plenum (5). A vent space (93) is provided at the top of the inlet shroud (90) near the support grid (11) to prevent a gas bubble from forming. The perforations of the distributor sheet (91) are sized to provide uniform flow to each heat exchange module (7). Above the perforated distributor sheet (91), inside the inlet shroud (90) at the elevation of the top of the serpentine coils, a coolant opening (95) is provided in the shroud (29) to allow hot liquid metal coolant to pour evenly over the serpentine coil tube bundles (67). As more easily seen from the plan view sections (FIGS. 5-9), ample space within the cylindrical steam generator vessel (1) around the outside of the square shrouds (29) is provided, so that liquid metal coolant entering the upper plenum (3) via inlet duct (48) will distribute evenly to all of the heat exchange modules (7). Heat from the liquid metal coolant is exchanged through the outer tubes (65) to the inner tubes (63) through a barrier liquid metal contained within the annular gap (64) of the double tube assemblies (66). Water in the inner tubes (63) is converted to superheated steam. Cooled liquid metal coolant proceeds downward past the serpentine coil tube bundles (67), past the end of the square shroud (29) and into the lower plenum (5). In preferred features, a guard vessel (2) is present which, with the closure plate (2a), completely surrounds the steam generator vessel (1) and serves as a containment vessel. Its primary function is to contain any liquid metal coolant or radioactive gas that might leak through the wall of the steam generator vessel (1) or any of its connected structures (i.e., closure plate (15), support grid (11), liquid metal inlet duct (48), liquid metal outlet duct (49)). The free volumes above the liquid metal coolant level (25) within the upper plenum (3) and within the heat exchange and core modules (7, 8) may be interconnected with vent holes (18). The space including the volume enclosed by the guard vessel (2) is filled with an inert cover gas such as argon to prevent oxygen contamination of the liquid metal coolant. The volume between the steam generator vessel (1) and the guard vessel (2) is in communication with the volume under the guard vessel closure plate (2a) by means of bleed holes (14). The feedwater inlet nozzle (55) are preferably combined to a common manifold (not shown). There are preferably four inlet (55) and four outlet nozzles (57) per module. Partition plates may be inserted within the disengaging chamber (77) between the feedwater inlet nozzles and steam outlet nozzles and welded around all edges to make each of the feedwater inlet and steam outlet nozzles completely discrete from the other nozzles. Alternatively, vent and drain holes may be provided in the partition plates between the steam nozzles and between the feedwater nozzles, to form two disengaging chambers, separating the four steam outlet nozzles from the four feedwater inlet nozzles. Although in FIG. 1 only one tube bundle (67) and one row of serpentine coils are detailed it will be understood that multiple rows of double tubes and typically four inlet and four outlet nozzles will be present for the heat exchange module shown. (See FIG. 4). In the preferred arrangement four heat exchange modules (representing a total of about 1,216 double tube serpentine coils) are installed in the steam generator vessel. Referring to FIG. 2, each heat exchange module (7) includes a multiplicity of co-axial double tube assemblies (66). A large number, for example 76 inner tubes (63) will emanate from each feedwater inlet nozzle (55), extend across the disengaging chamber (77) and form co-axial double tube assemblies (66) by mating with outer tubes (65) adjacent a lower tube plate (71). For a module with four feedwater inlet nozzles a total of 304 double tube assemblies are formed. As mentioned above, the double tubes are gathered into a tube bundle (67) which continue, most preferably, to the bottom of the square shroud (29, FIG. 1) where the 304-tube bundle (67) has formed 38 rows of double tubes, with 8 tubes to a row, which all turn upward to from serpentine coils. It is most preferred that all 38 double tube rows be identically wound (in the coil region) to form individual sets of identical serpentine coils having sixteen turns each. Such a design facilitates fabrication and reduces costs, since extensive automation is possible when each coil assembly of each module is identical. The simple square shape of each module in this embodiment also serves to facilitate fabrication, and the compact size of the module makes transportation and installation of the modules easier. Referring to FIG. 3, each of the feedwater inlets (55) consists of an inlet nozzle tube (52) welded to inner tube sheet (75) to which 10-200, preferably about 76, water-carrying inner tubes (63) are connected. The tube sheet (75) is attached to the box header (53) by a connecting tube (54) which opens into disengaging chamber (77). A concentric guard pipe (56) is welded to the inner tube sheet (75). Most preferably, a pipe, e.g., a schedule 120 pipe, is welded to the inlet nozzle tube (52) near its upper extremity, and another pipe, e.g., a schedule 120 pipe, is welded to the outer guard pipe (56). These pipes are also concentric. The purpose of this concentric construction is to contain released fluid from the inner nozzle tube (52), or the inner pipe, in the event of a leak. The penetration through the guard vessel is sealed with a bellows connection (58). Each of the steam outlet nozzles (57) are constructed in an identical manner to the feedwater inlet nozzle (55) described above. Most preferably, there are four feedwater and four steam discharge nozzles for each heat exchange module. Each inner tube (63) is attached to the inner tube sheet (75). Each outer tube (65), ending in a disengaging chamber (77), is mated with an inner tube (63), forming double tube assemblies (66) which pass through the lower tube plate (71). The double tube assemblies (66) continue into one of the square inner cavities created by the shrouds (29) in the upper plenum (3) and eventually forms a serpentine coil. The concentric arrangement of the inner tube (63) with the outer tube (65) defines an annular gap (64) which will be filled for at least part of the length of double tube assembly (66) with a liquid metal. The stagnant liquid metal in annular gap (64) may be the same as or different from the liquid metal coolant which circulates through the upper and lower plenums (3, 5) of the steam generator vessel (1). A sodium-potassium alloy, NaK, or sodium are the preferred liquid metals. Other liquid metals and fluids may be utilized, as long as they are compatible with the liquid metal coolant introduced into the steam generator vessel (1). As used herein, "compatible" signifies that the liquid metal in the annular gap efficiently transfers heat between the liquid metal coolant and the water in the inner tubes (63) and which, in the event of a leak in an outer tube (65), will not react violently with the liquid metal coolant and will not form byproducts which could be harmful to the nuclear reactor core. Preferably, the heat transfer liquid metal in the annular gap and the liquid metal coolant are the same. Most preferably the liquid metal coolant will be sodium and the heat transfer liquid metal will be sodium, or a sodium-potassium mixture. Use of such a liquid metal in the annular gap will serve to prevent the occurance of "hot spots" in the inner tubes (63). Although the precise dimensions of the aforementioned tubing are not critical, it is preferred to use a large number of double tube assemblies (66), each having a relatively small diameter. By way of illustration, an inlet nozzle tube (52) can be 10-inch schedule pipe expanding to 22 7/16-inch internal diameter inner at the tube sheet. The guard pipe (56) can be 14-inch schedule 100 pipe expanding to 267/8-inch internal diameter at the tubesheet (75). The inner tube sheet (77), has 76 inner tubes (63) having a 1.25 inch outside diameter. The inner tubes (63), 1.25 inch outside diameter by 0.17 inch thickness, join outer tubes (65) having inside diameter 1.50 inch and outside diameter 1.75 inch. In the annular gap (64), the inner tube may be preferably provided with a 0.125 inch diameter rod, helically wound at a 1.25 inch pitch, brazed to its outer surface to form a spacer across the annular gap (64). The spacer design within the annular gap (64) permits free expansion of the liquid metal. A range of tube sizes is possible, encompassing an outside diameter of 0.5 inch to over 2.0 inches for the inner tube and 0.6 inch to over 2.5 inches for the inside diameter of the outer tube. The annular liquid metal functions as a barrier between the water flowing through the inner tubes (63) and the liquid metal coolant flowing over the outer tubes (65). A detection system monitors the level of liquid metal in the annular gap to detect any breach of the integrity of an outer tube. In addition, a detection system, such as a hydrogen monitor, monitors the inert gas space in the disengaging chamber (77) above the stagnant liquid metal to detect any leakage of water/steam into the annular gap (64) or into the disengaging chamber (77). Referring again to FIG. 1, the core module (8) may house a discharge pump (not shown), which is supported within the cylindrical support housing (35). The support housing (35) terminates inside the lower plenum (5) with a rounded end having numerous perforations (39) through which liquid metal coolant entering the lower plenum (5) may pass. A discharge pump inducts cooled liquid metal coolant from the lower plenum (5) through the perforations (39). The liquid metal is inducted through the intake of the pump and discharged under pressure through discharge line (41) and nozzle (42), then to a jet eductor (43) followed by an outlet diffuser assembly (45), directing cooled liquid metal coolant back to the nuclear reactor. The circulating pump may be of a mechanical centrifugal type or a electromagnetic type of pump. For an electromagnetic type, electrical leads (12) would be provided at the top plate of the core module (8). For a mechanical pump, the pump may be supported at the support grid (11) at the top of the vessel (1). In this case a cylindrical support housing (35) would not be required. FIG. 4 shows an enlarged perspective detail of the coil support bracket (81) of FIG. 1. The coil support bracket (81) will be attached at its upper end to the box header (53 in FIG. 1). The vertical support strips (85) are attached to the lower end and are supported by the coil support bracket (81). The double tube serpentine coil (59), comprised of individual double tube assemblies (66), is supported by the vertical support strips (85), with each double tube assembly (66) passing back and forth through individual circular openings formed by the vertical support strips (85). Sectional views of the double tube assemblies (66) in FIG. 4 and FIGS. 6-8 omit representation of the inner tube of the duplex tube for clarity, and it will be understood that concentric double tubes (best seen in FIG. 3) are intended by references to the double tube assemblies (66) in these Figures. FIGS. 5 through 9 provide cross-sectional views of the modular steam generator illustrated in FIG. 1 and show the cruciform construction of this embodiment of the steam generator. The drawings show that the steam generator vessel is completely surrounded by the surrounding enclosure (17). A partial representation of an insulation shroud (20) and fins (24), which may be used for decay heat removal and are more fully discussed below, are supported on the outside of the guard vessel (2). The guard vessel (2) encloses the steam generator vessel (1). Immediately inside the steam generator vessel (1) is the upper plenum (3). FIG. 5 shows a cross-section of the entire steam generator emplacement, taken at line V-V in FIG. 1, just outside the welded closure plate (2a). This Figure shows the cruciform arrangement of the support grid (11), forming five square cavities which are occupied by the four heat exchange modules (7) and a central core module (8). For each heat exchange module (7) the Figure shows a multiplicity of inner tubes (63) encircled by the necks of four inlet nozzles (55) and four outlet nozzles (57). The necks of the nozzles (55, 57) end at the upper plate (70) of the box header (53), which is seated securely in the support grid (11). FIG. 6 shows an enlarged section of the steam generator taken at line VI--VI in FIG. 1. Bundles of double tubes (66) are shown enclosed within the box header (53), which is subdivided with partitions (78) into eight separate disengaging chambers (77). FIG. 7 shows an enlarged quarter section of the steam generator taken at line VII--VII in FIG. 1. The approximately 304 double tube assemblies (66) associated with the four inlet nozzles (FIG. 5) are shown aligned in thirty-eight rows along the inside of the square shroud (29). Double tubes in the serpentine coil portion (59) are shown in a section taken mid-way through an outside half curve in the serpentine coil, accordingly straight tubing sections are shown extending across the width of the cavity bounded by the square shroud (29) and, along the outside of the cavity, cross-sections of upwardly curving double tubes are seen. Representation of the vertical supporting strip (85 in FIG. 1) is omitted from this Figure. The flow distributor sheet (91) around the outside of the square shroud (29) provides uniform flow around the periphery of the square shrouds (29) to all of the heat exchange modules. Cross-hatching is used to represent the perforations of the flow distributor sheet (91) in order to avoid confusion with the representation of double tube assemblies (66). The perforations of the flow distributor sheet (91) are sized to provide uniform distribution of the liquid metal coolant to all sides of all of the heat exchange modules in the steam generator vessel. It will be understood that the number of nozzles, the number of double tube assemblies, the configuration or alingment of the tube rows, and other physical features may be varied in accordance with engineering constraints or the needs of the practitioner. An example of one such variation in the configuration of the tubes is illustrated by FIG. 7A. This feature shows a square shroud (29) into which descend three tube bundles (67) corresponding to three inlet nozzles, instead of four inlet nozzles illustrated in the other drawings. The bundled configuration of the tubes, in the same pattern as the tube sheet of the inlet nozzle where the inner tubes originated, is retained along the entire length of the shroud (29) and throughout the upward coil to the oulet nozzles. By retaining the bundled pattern, the fabrication of custom-made, curved segments to align all of the descending double tube assemblies into a closely packed, rectangular area as seen in FIG. 7 is avoided. Instead, the tubes descend in straight sections from the nozzles. The gaps between the tube bundles necessitates the inclusion of additional baffles (83a), to ensure contact of the liquid metal coolant with the coils and to avoid channeling of the liquid metal coolant flow. FIG. 8 shows another quarter section, taken at line VIII--VIII of FIG. 1. This Figure is substantially similar to FIG. 7, however it is taken below the level of the distributor sheet (91, FIGS. 1, 7), therefore along the outside of the square shroud (29) is seen the diaphragm male portion (31a) and bumper blocks (33), which are also seen on the inside of the module between the square shroud (29) and the core module cylindrical support housing (35). FIG. 9 is taken at line IX--IX in FIG. 1. This section is taken below the level of the serpentine coil (See FIG. 1), therefore within the boundary of the square shroud (29) is seen the base structure (30), through which cooled liquid metal coolant passes into the lower plenum (5) after flowing over the serpentine coils. Preferred materials for the serpentine coil module assembly are 9 Cr - 1 Mo or 21/4 Cr - 1 Mo for the serpentine coils, the disengaging chamber and the associated structures which are welded to such assemblies. The material for the steam generator vessel is preferably 316 SS. The guard vessel is preferably 304 SS or 316 SS. Temperature transients originating in the reactor vessel are mitigated in the steam generator module by means of the hot liquid metal coolant plenum (upper plenum (3)), in which the liquid metal coolant mixes prior to entering the inlet shrouds (90) around the outside of the square shrouds (29) enclosing the heat exchange modules (7). Temperature transients caused by malfunction of the steam generator are mitigated by the cold liquid metal coolant plenum (lower plenum (5)) of the module. The mitigating effect of the upper and lower plenums results in less severe thermal transients for the primary reactor circulation pump and for the liquid metal coolant returning to the reactor core. Decay heat removal is accomplished by utilizing one or more of the feedwater steam connections to a serpentine coil module for this purpose. A separate reliable source of water may be provided to the feedwater inlet. The outlet from these coils is connected to a local natural draft cooling tower where steam is condensed and returned as cooled condensate to the coils. On scram, the steam generators may be removed from the operating feedwater/steam circuit and connected to a naturally circulated water system, dedicated to core decay heat removal. Water enters the feedwater inlets of the steam generators and leaves the steam outlets as superheated steam. The steam flows to a natural draft cooling tower where it is condensed and cooled. The cooling tower height is sufficient to create the driving force required to cause the cooled water to circulate naturally through the coils within the steam generators by virtue of the density differential between the steam condensate and the cooled water. An alternate or backup means of decay heat removal is provided by attachment of fins to the exterior of the guard vessel and utilizing air cooling for heat removal. As an illustration, the outside surface of the guard vessel (7) is covered with vertical fins or vanes (24, FIG. 7) which are, for example, 8 inches deep and 1/4 inch wide, and are welded to the surface of the guard vessel (2). A 1/4 inch thick cylindrical insulation shroud (6) is attached to the outer boundary of the fins (24), to support a 3 inch thick layer of fiberglass thermal insulation (20). A steel clad fiberglass blanket (not shown) that insulates the bottom of the well in the concrete cavity in which the steam generator is mounted may also be provided. Outside ambient air is piped to the lower end of the shroud from an air shaft and flows upward by chimney effect through the passages formed by the fins and exhausts to a stack. In the event that the main coolant circulating pump is not available, provision can been made for assuring a direct and low pressure drop pathway for natural circulation of the liquid metal coolant when the air cooling system is employed for decay heat removal. For this eventuality, the gas seals (51) separating the upper and lower plenums (3, 5) at the bottom area of the serpentine coil modules (7) are purged, thereby allowing a free flow of coolant from the hot plenum area (3), down through the cruciform opening and into the lower plenum (5) where it returns to the reactor via the jet eductor outlet (43, 45, 47). In the event an eductor is not utilized in the design, the flow would enter the pump suction through the perforations (39), pass through the pump and return to the reactor via the pump discharge line (41). To illustrate operation of an embodiment utilizing sodium as coolant, with reference to FIG. 1, sodium at approximately 985.degree. F. enters the steam generator vessel (1) via a sodium inlet line (48). The hot sodium mixes in the upper plenum (3) of the steam generator vessel (1) and flows into the orificed opening (91) of the inlet shrouds (90) associated with each serpentine coil module. The sodium enters the heat exchange area through openings (95) in the serpentine coil square shroud (29) and then passes over the serpentine coil bundles (59). Sodium flows downward over the coils (59), exchanging its heat across the double tube annular gap to the water/steam flowing within the inner tube (63) of the double tube assemblies (66). The flow path of the sodium is such that a low pressure drop occurs for the cooled sodium flow (less than 3 psi). The cooled sodium exits the bottom of the coil bundle (59) through base structure (30) at the bottom of the square shrouds (29) and mixes within the lower plenum (5) at the bottom of the steam generator vessel (1). A small portion of this sodium is entrained in the jet eductor (43) and returns to the reactor via the pump discharge pipe (47). The balance of the sodium flow enters the pump intake suction through perforations (39) at the bottom portion of the core module (8). Perforated openings (39) provide a uniform and well mixed sodium flow pattern within the lower plenum (5). The discharge pump raises the pressure of the liquid sodium and discharges it to the reactor via the eductor and discharge line. To illustrate the water/steam circuit, with reference to FIG. 1, water enters the top of the steam generator vessel (1) at four separate nozzles (55). The water enters the inner tube (63) of the double tube assemblies (66) and flows through the inner tubes (63) of the serpentine coils (59), picking up heat through the sodium in the annular gap (64) from the hot sodium coolant cascading downward over the coils. Sufficient heat transfer area is provided by the heat exchange modules (7) to boil the water and superheat the resulting steam within the coils. Superheated steam then exits from four steam nozzles (57) at the top of each heat exchange module (7). Primary coolant flow past the steam generator coils can be terminated by closing a plate (not shown) which blocks the orifices (91) of the inlet shroud (90). Alternatively, a closure plate may be utilized for the opening (95) to the serpentine coil square shroud (29). The serpentine coil module design has important advantages regarding possible breaks in either the inner tube or the outer tube of the double tube assembly. If the outer tube fails, the consequences are benign since the fluid in the annular gap of the duplex tube is chemically compatible with the primary coolant filling the steam generator vessel. In operation, the primary concern with the failure of an outer tube is having the ability to monitor outer tube ruptures in case of a corresponding rupture in the inner tube. Detection of an outer tube failure can be accomplished by sensors monitoring the sodium (or NaK) level in the annulus of each tube. If the unit is operated with the annulus level above the normal operating level of the primary coolant (25 in FIG. 1) then failure of the outer tube would cause the annulus level to either fall, if the disengaging chamber (77) is at the same or higher pressure than the cover gas in the vessel (1). Alternatively the disengaging chamber and annulus area above the liquid level in the annular gap can be maintained at a lower level than in the cover gas of the vessel. A leak in the outer tube would cause the level in the annular gap to rise. This can be detected by level or temperature sensors. In addition, pressure sensors in the disengaging chamber can be utilized. Pressure sensors would also immediately detect any leakage of water or steam within the disengaging chamber. Failure of the inner tube is accommodated by having the outer tube of sufficient strength to withstand pressure pulses which could result from such a failure. In addition, the spacer within the annulus region serves to hold the inner tube and prevents it from separating at the failed point, thereby controlling the amount of water or steam released. Also, as discussed above the amount of sodium (or NaK) in the annular gap is small thereby limiting the sodium-water (NaK-water) reaction that would occur after a water tube break. The spiral pattern of the spacer rod within the annular gap provides a tortuous path through which escaping water/steam must flow. This further inhibits the effects of the sodium/water (NaK-water) reaction and, together with the limited amount of sodium (NaK) available, resulting in a slow reaction which can be easily accommodated by the disengaging chambers. Finally, a rupture disc in the disengaging chamber will serve to limit the peak pressure within this chamber. In the event of a rupture of one of the inner tubes the escaping steam and feedwater, and the hydrogen and sodium hydroxide from the resulting reaction with the small amount of sodium in the annular gap, all flow to the disengaging chamber at either end of the double tube assembly in which the rupture occurred. Each disengaging chamber preferably has connections to a rupture disc which exhausts to a steam and hydrogen disposal system, and separate connections (not shown) for a sodium (or NaK) disposal system. Each pipe to the steam and hydrogen disposal system is sealed with a rupture disc, e.g., 45 psia. Each pipe to the sodium disposal and fill system has a closure valve which is closed while the steam generator is operating. As pressure within a disengaging chamber rises to the tolerance set point of the rupture disc, the blowout of the rupture disc allows the escaping steam and hydrogen to vent to a disposal system. Only a low pressure buildup occurs: Since the quantity of sodium in the annular gap is small, only a small fraction of this sodium initially is exposed to the water/steam released from the breach in the inner tube and the rupture disc limits the peak pressure in the disengaging chamber. An important feature of this invention is that through utilization of a multiplicity of duplex tube assemblies, the flash discharge from a water tube rupture is very small compared with prior art systems, and shut-down procedures in the event of such a rupture may be instituted before an emergency situation develops. The duplex tube construction is such that the spacer within the annulus of the duplex tube inhibits gross movement of an inner tube in the event of an inner tube break. Thus, the flow area for water or steam to emerge from the break is small and the resulting pressure transient within the annulus is significantly reduced. The small volume of sodium in the annular gap is beneficial from a sodium-water reaction standpoint because even if water/steam flow to the failed inner tube is not stopped, the small amount of sodium in the annular gap will limit the water-sodium reaction to a level that can be readily accommodated by the serpentine coil module. Because the sodium/water reaction is slowed and controlled by the design of the heat exchange module, fast-acting (i.e., less than 5 seconds closure time) valves to isolate a failed tube are not required. Closure of the valves in steam and feedwater pipes associated with the module containing the failed tube terminates the source of water/steam flowing through a failed inner tube. Consequently, immediate closure of all water/steam flow paths to and from the unaffected heat exchange modules is not required for a single water tube rupture, and the steam generator/reactor system may continue limited operation or may be shut down without experiencing a severe temperature transient. After the feedwater line and the steam line leading to the double tube assembly in which a rupture occurs are valved off and the pressure within the disengaging chamber has been reduced to atmospheric, any sodium remaining in the disengaging chamber is drained to a sodium disposal system. All sodium piping is heat traced. This is accomplished either in situ by connecting a drainage system to the module and flushing the disengaging chamber and annular gaps of the double tube assemblies or by removing the serpentine coil module from the vessel and cleaning the disengaging chamber at a maintenance area. For operations in which the module is not removed, after the disengaging chamber has been drained, the blowout rupture discs are replaced and all sodium remaining in the annular gap of the double tube assemblies is sent to the sodium disposal unit by pressuring one side of the disengaging chamber with hot argon gas. Following this, the failed tube is plugged and the tube cluster is flushed with hot sodium to the sodium disposal unit to remove the remaining sodium hydroxide resulting from the sodium-water reaction. The annular gap is then refilled with hot sodium (or NaK) to the operating level and the module is returned to service. Alternatively, the module may be removed from the steam generator vessel and replaced with a spare module, or the shroud opening for the removed module may be sealed and operation continued until a replacement module is available. The double tube serpentine coil steam generator of this invention may also be directly used in the pool or integrated type of liquid metal cooled reactor. This type of reactor features a multiplicity of low pressure drop (less than 3 psi) heat exchangers, which are immersed a pool of liquid metal coolant within the reactor vessel. This application of the serpentine coil design is effective because the compact serpentine coil assembly may be readily integrated into conventional pool-type reactor vessels, and the unit has approximately the same pressure drop as an intermediate heat exchanger. Such an embodiment is diagrammed in FIG. 10. For this application, the serpentine coil steam generator assembly is not enclosed in a steam generator vessel and guard vessel, as in the modular steam generator illustrated in FIG. 1. Rather, the apparatus is enclosed by the main reactor vessel (101). A circulating pump (not shown) is located at a separate area of the reactor vessel. In this type of embodiment, a multiplicity of serpentine coil modules (7) are provided. The serpentine coil modules (7) may be square in the plan view, rectangular or another shape. The central support for the coil modules (7) is provided by a grid (11). The serpentine coil module, complete with coils, coil supports, disengaging chamber, feedwater nozzles, and steam nozzles is supported from the grid structure in the same manner as in FIG. 1. For this application a greater number of tubes (and thus larger modules) may be employed in order to limit the total number of modules within the single vessel. The supporting grid structure is composed, for example, of 3 inch thick vertical plates approximately 90 inches high welded to both sides of a 10 inch wide.times.6 inch thick horizontal plate. The shrouds for the serpentine module extend from the bottom of the 3 inch thick vertical plate. Referring to FIG. 10, a single pool type vessel (101) contains a reactor core (102), serpentine coil modules (7), a pump module of which the circulating discharge line (108) is shown, structure for housing control rods and core monitoring equipment (103), a ring girder (19) and skirt (21), a closure plate (15), a diaphragm (31), and gas seals (51) separating the vessel into a hot and cold plenum. Refueling equipment and the guard vessel are not shown. The grid structure is arranged such that box-like compartments are formed for insertion of the serpentine coil modules (7). Flow exiting the control rod drive housing structure (103) and flow exiting the core area is mixed in the upper plenum area (3) before entering the inlet shrouds (90) of each module. Sodium then enters the coil bundle area through shroud opening (95) and flows by gravity past the duplex tubes. Flow exiting the serpentine coil bundle then mixes in the cold plenum area (5). Flow then enters the pump module and is discharged to the inlet of the core via the pump discharge line (108). FIG. 10 illustrates a gas seal (51) only on one side of of the modules. Free flow of hot sodium may be allowed past the module shrouds so that flow enters the modules from both the upper plenum region (3) and the region adjacent to the vessel walls. In this case the gas seal would be extended to ensure that hot sodium does not bypass the serpentine coil modules in the diaphragm area. The inlet flow shroud (90) may be separately provided for each serpentine coil module shroud (29) or may be an integral unit for all serpentine coil module shrouds. For the integral unit design, flow past the orifices (91) would collect in an annular header which is common to all inlet openings for the serpentine coil shrouds. For separately provided inlet shrouds, flow past the orifices would collect in an annulus that feeds the sodium to only one shroud opening. To stop circulation to a specific serpentine coil assembly of the separate inlet shroud design, either a plate would be placed over the orifice openings or a closure plate would be inserted in the area of the shroud inlet opening. For the integral inlet flow shroud design, a closure plate for the shroud opening would be used. Such a closure would be needed in the event a serpentine coil module was removed from the vessel. In such a case once the module was removed, a cover plate would be placed over the shroud opening. Such a plate may be inserted at the time of maintenance operations or may be located within the shroud and unlatched for closure of the opening once the serpentine coil module has been removed. The operation of the double tube serpentine coil steam generator in the pool reactor is similar to that described above for the modular steam generator vessel system. Liquid metal coolant exiting the reactor core (102) enters under the inlet shroud (90) region for each module. Sodium then flows into the opening of the serpentine coil shroud, and is distributed evenly over the serpentine coils. The liquid metal coolant then flows by gravity downward past the serpentine coils into the bottom pump plenum (5). The pump (not shown) circulates the liquid metal coolant through the reactor core (102) via pump discharge line (41) to complete the coolant flow circuit. All of the patents mentioned above are incorporated herein by reference. From the foregoing diclosure, variations and modifications will be readily apparent to persons skilled in this art. However, all such obvious variations are intended to be within the scope of the invention as defined by the appended claims.
	claims	1. A method for preparing a sample for TEM/STEM imaging, comprising:providing a substrate inside a dual beam FIB/electron beam system, and said system comprising a vertical electron beam column and a FIB column oriented at an angle relative to the electron beam column;providing a sample holder for holding an extracted TEM/STEM sample, the sample holder mounted on a sample stage inside the FIB/electron beam system, said sample stage having a sample stage plane and comprising a rotating and tilting stage with a maximum tilt of less than 90 degrees, and said sample holder having a sample holder plane perpendicular to the sample stage plane;freeing a sample from the substrate using an ion beam, said freed sample having a top surface;tilting the sample holder to a first angle by tilting the sample stage;mounting the sample onto the tilted sample holder so that the top surface of the sample is oriented at said first angle relative to the sample holder plane;tilting the sample stage so that the sample stage plane is at a 0 degree tilt;rotating the sample holder by 180 degrees;tilting the rotated sample holder to a second angle such that the combination of the first angle and the second angle results in the top surface of the mounted sample being oriented perpendicular to the orientation of the FIB column;thinning the sample using the ion beam by milling the sample, said milling producing a sample face parallel to the orientation of the FIB column;tilting the sample holder to third angle, such that the combination of the first angle and the third angle equals approximately 90 degrees and the sample face is oriented substantially perpendicular to the vertical electron beam column; andviewing the mounted sample with the TEM/STEM. 2. The method of claim 1 where said first angle is chosen from the range of angles between the maximum tilt angle of the stage and the difference between the maximum tilt and 90 degrees. 3. The method of claim 1 in which said sample stage has a maximum tilt of 60 degrees and said first angle is greater than 30 degrees. 4. The method of claim 1 where the FIB column is oriented at approximately 52 degrees from the vertical electron beam column. 5. The method of claim 1 in which the sample holder is a TEM finger grid. 6. The method of claim 1 further comprising viewing the mounted sample using a scanning electron microscope. 7. The method of claim 1 further comprising imaging the mounted sample during ion beam milling using SEM or STEM. 8. The method of claim 1 in which tilting the sample holder to a first angle comprises tilting the sample holder to approximately 38 degrees. 9. The method of claim 8 in which tilting the sample holder to a second angle comprises tilting the sample holder to approximately 14 degrees. 10. The method of claim 9 in which tilting the sample holder to a third angle comprises tilting the sample holder to approximately 52 degrees. 11. The method of claim 1 in which tilting the sample holder to a first angle comprises tilting the sample holder to approximately 52 degrees. 12. The method of claim 11 in which tilting the sample holder to a third angle comprises tilting the sample holder to approximately 38 degrees. 13. The method of claim 1 in which thinning the sample using the ion beam further comprises tilting the sample stage during the milling process. 14. The method of claim 1 in which thinning the sample using the ion beam comprises thinning the sample into an electron-transparent thin section.
	summary
	summary
061371149	abstract	An irradiation apparatus has at least one exchangeable radiation source that may be moved by means of a transport cable between at least one rest position and at least one irradiation position and a long-distance transport container for radiation sources to be exchanged. In order to reduce the danger of control errors, the rest position is located inside the long-distance transport container and the transport container forms or may form an integral part of the irradiation apparatus. For that purpose, interface elements are provided on the transport container and other parts of the irradiation apparatus. By winding and unwinding the transport cable on and from a feeding drum with a cable-receiving groove at least partially covered by a pressing strip, particularly thin transport cables may be used, so that the width of the pressing strip substantially corresponds to the width of the cable-receiving groove. The pressing strip is helically wound in the cable-receiving groove around the feeding drum, in the axial or radial direction with respect to the feeding drum, and the cable-receiving groove is thus covered in a substantially uninterrupted manner. Means for lifting, preferably also for deflecting and lowering again the pressing strip, may be moved along the transport cable in relation to the feeding drum in order to let free an output joint for the transport cable from the feeding drum.
	claims	1. An electro-technical device, comprising:a point source supplied with an input signal;a first portion electrically isolated from a second portion, the point source including an elongated element extending through and disposed within the first portion, the elongated element extending away from the first portion and toward the second portion; anda movable metallic film conductor fixedly connected to the first portion and being responsive to an electric field generated by the point source to move away from the point source and contact the second portion to complete a circuit and send out a control signal. 2. The electro-technical device according to claim 1, wherein the input signal is representative of one of a signal from a temperature sensor, a pressure sensor or a flow sensor. 3. A method of making an electro-technical device, comprising:forming a first housing portion;fixedly connecting a movable metallic film conductor to the first housing portion;inserting a point source including an elongated element extending through and into the first housing portion at a fixed location and spaced from the movable conductor, the elongated element extending away from the first portion, the point source being supplied with an input signal;providing a second housing portion opposite to and electrically isolated from the first housing portion, wherein the movable conductor is responsive to an electric field generated by the point source to move away from the point source and contact the second portion to complete a circuit and send out a control signal. 4. The method according to claim 3, wherein the input signal is representative of one of a signal from a temperature sensor, a pressure sensor or a flow sensor. 5. The method according to claim 3, wherein the first housing portion, the second housing portion and the movable conductor are made from metal by 3-D digital printing.
	claims	1. A method of shielding gamma radiation comprising:producing a region of heavy electrons; andreceiving incident gamma radiation in said region,said heavy electrons absorbing energy from said gamma radiation and re-radiating it as photons at a lower energy and frequency. 2. The method of claim 1 including providing surface plasmon polaritons and producing said heavy electrons in said surface plasmons polaritons. 3. The method of claim 1 including providing multiple regions of collectively oscillating protons or deuterons with associated heavy electrons. 4. The method of claim 1 including providing a plurality of nanoparticles of a target material on a metallic surface capable of supporting surface plasmons, said region of heavy electrons being associated with said metallic surface. 5. The method of claim 1 including inducing a breakdown in a Born-Oppenheimer approximation. 6. The method of claim 1 including providing low energy nuclear reactions catalyzed by ultra low momentum neutrons within said region of heavy electrons. 7. The method of claim 1 wherein said step of providing a region of heavy electrons includes: providing a metallic working surface capable of supporting surface plasmons and of forming a hydride or deuteride; fully loading said metallic surface with H or D thereby to provide a surface layer of protons or deuterons capable of forming coherently oscillating patches; and developing at least one patch of coherently or collectively oscillating protons or deuterons on said surface layer. 8. The method of claim 7 including breaking down the Born-Oppenheimer approximation on said upper working surface. 9. The method of claim 7 wherein said surface material comprises palladium or a similar metal and/or alloy capable of forming a hydride or deuteride; and providing a plurality of target nanoparticles on said metallic working surface. 10. The method of claim 9 wherein said target nanoparticles comprise a palladium-lithium alloy. 11. The method of claim 7 further comprising directing laser radiation to said working surface to stimulate and transfer energy into said surface plasmons. 12. The method of claim 7 wherein said H or D surface layer is fully loaded by one or more of an enforced chemical potential difference, an electrical current, or a pressure gradient. 13. The method of claim 1 including forming ultra-low momentum neutrons. 14. The method of claim 1 wherein said gamma radiation comprises gamma photons having energies in the range of about 0.5 MeV to about 10.0 MeV. 15. The method of claim 14 wherein said gamma photons result from neutron capture. 16. The method of claim 14 wherein said gamma photons result from an external source. 17. A gamma radiation shield comprising: a substrate; a metallic working surface capable of supporting surface plasmons and of forming a hydride or deuteride, located above said substrate; above said metallic surface, a surface layer of protons or deuterons comprising fully loaded H or D; at least one patch of collectively oscillating protons or deuterons associated with said surface layer; a region of surface plasmon polaritons located above the surface layer and said at least one patch; and a flux of protons or deuterons incident on said surface plasmon polaritons, surface layer, and working surface. 18. The shield of claim 17 wherein said surface material comprises palladium or a similar metal and/or alloy capable of forming a hydride or deuteride. 19. The shield of claim 17 further comprising laser radiation incident on said working surface to stimulate and transfer energy into said surface plasmon polaritons. 20. The shield of claim 17 further comprising a plurality of target nanoparticles on said metallic working surface. 21. The shield of claim 20 wherein said target nanoparticles comprise a palladium-lithium alloy. 22. The shield of claim 17 wherein said H or D surface layer is fully loaded by one or more of an enforced chemical potential difference, an electrical current, or a pressure gradient. 23. The shield of claim 17 wherein said at least one patch produces heavy electrons;and wherein said heavy electrons absorb gamma radiation.
	claims	1. A process for dissolving aluminum during the recovery of a nuclear fuel comprising:contacting a material containing aluminum and a nuclear fuel with an acid in the presence of a metal catalyst and an iron source, the acid and metal catalyst dissolving the aluminum, the iron source being present in an amount sufficient to decrease an off-gas stream rate during the dissolving process. 2. A process as defined in claim 1, wherein the iron source is present in an amount sufficient to decrease hydrogen off-gas rate during the dissolving process. 3. A process as defined in claim 1, wherein the acid comprises nitric acid. 4. A process as defined in claim 3, wherein the material is initially contacted with nitric acid at a concentration of from about 4 molar to about 15 molar. 5. A process as defined in claim 3, wherein the material is initially contacted with nitric acid at a concentration of from about 5 molar to about 8 molar. 6. A process as defined in claim 1, wherein the iron source is present such that the molar ratio between iron and the catalyst is from about 3:1 to about 40:1. 7. A process as defined in claim 1, wherein the iron source is present such that the molar ratio between iron and the catalyst is from about 11:1 to about 20:1. 8. A process as defined in claim 3, wherein the nitric acid concentration after 95 wt % of the aluminum has dissolved is no less than 0.5 molar. 9. A process as defined in claim 2, wherein the iron source is present in an amount sufficient to decrease the rate of hydrogen off-gas production by more than 10% by volume of the total off-gas produced. 10. A process as defined in claim 2, wherein the iron source is present in an amount sufficient to decrease the rate of hydrogen off-gas production by more than 20% by volume of the total off-gas produced. 11. A process as defined in claim 1, wherein the metal catalyst comprises mercury. 12. A process as defined in claim 1, wherein the acid, the metal catalyst, and the iron source form a dissolution solution and wherein the metal catalyst comprises mercury and wherein mercury is present in the dissolution solution in an amount from about 0.001 molar to about 0.02 molar. 13. A process as defined in claim 1, wherein the iron source comprises a ferrous metal, a ferrous salt, a ferric metal, a ferric salt, or mixtures thereof. 14. A process as defined in claim 1, wherein the iron source comprises either ferrous sulfamate or ferrous nitrate. 15. A process as defined in claim 1, wherein the material containing aluminum and a nuclear fuel comprises used nuclear fuel. 16. A process as defined in claim 1, wherein the material containing aluminum and a nuclear fuel comprises an aluminum-uranium alloy or uranium aluminide dispersed in a continuous aluminum phase with an aluminum cladding. 17. A process as defined in claim 1, wherein the nuclear fuel comprises uranium, plutonium, or mixtures thereof. 18. A process as defined in claim 1, wherein the acid comprises nitric acid and the metal catalyst comprises mercury, the acid, metal catalyst and the iron source comprise a dissolution solution, the initial concentration of nitric acid in the dissolution solution being from about 5 molar to about 8 molar, the concentration of mercury being from about 0.001 molar to about 0.02 molar. 19. A process as defined in claim 1, wherein the iron source is present during the process so that hydrogen off-gas production is maintained below 4% by volume in the off-gas stream. 20. A process as defined in claim 1, wherein the acid, the metal catalyst and the iron source comprise a dissolution solution and wherein iron is present in the dissolution solution in an amount from about 2.5 g/L to about 20 g/L. 21. A process as defined in claim 1, wherein the iron source comprises iron nitrate, iron fluoride, iron sulfate, iron phosphate, iron chloride, iron bromide, iron perchlorate, iron acetate, iron hydroxide, iron carbonate, or mixtures thereof.
	description	This application takes priority from U.S. Provisional Patent Application Ser. No. 60/613,734, filed Sep. 28, 2004. This invention relates generally to the field of x-ray diffraction analysis and, more particularly, to the imaging of an x-ray beam with a structure that provides both focusing and monochromating of the beam. In an x-ray diffraction system the function of x-ray optics is to condition the primary x-ray beam into the required wavelength, beam focus size, beam profile and divergence. One type of x-ray optics device is the total external reflection mirror. Total external reflection happens when x-rays strike on a polished surface at a small grazing incident angle. The reflected x-rays from the surface take off at the same angle as the incident angle. The polished surface behaves similarly to a mirror reflecting visible light. Therefore such a mirror is referred as an x-ray mirror. The reflecting mirror is made of materials with refractive index less than unity. The total external reflection can only be observed at an incident angle less than the critical incident angle θC. The value of the critical angle is dependent on the wavelength of the x-ray radiation and the reflecting materials. For a typical laboratory x-ray source, the wavelength is in the range of a fraction of nanometer, and the critical angle is in the range of a fraction of a degree to several degrees. Another type of x-ray optics device is the multilayer mirror. A multilayer mirror consists of alternating layers of heavy materials as reflection layers and light materials as spacer layers. A multilayer mirror works on the same principle as Bragg diffraction from a natural crystal, selectively reflecting certain wavelengths based on the spacing between the mirror layers. In this way, multilayer mirrors can be used as monochromators. In contrast to a natural crystal, a multilayer mirror typically has larger d-spacing so that the incident angle and the diffracted angle are typically only a few degrees. In these mirrors, the number of layers, the d-spacing of the layers, and the distribution of the layer thickness can be varied to modify the mirror performance. In accordance with the present invention, a hybrid mirror for x-ray diffraction systems is provided that provides monochromatization, but maintains a higher overall reflectivity than conventional multilayer mirrors. The hybrid mirror can take a number of different forms, but in each case includes a multilayer mirror portion and a total external reflection mirror portion. The multilayer mirror portion provides the desired monochromatization and, together, the multilayer mirror portion and the total external reflection mirror portion provide the desired focusing of the x-ray energy, which may originate at substantially a point source, toward a focal point. In one embodiment, the mirror uses two mirror surfaces side-by-side, one surface being a multilayer material and the other being a total external reflection material. In another embodiment, the multilayer mirror portion and the total reflection mirror portion are arranged in a Kirkpatrick-Baez configuration. In still another embodiment, a side-by-side single bounce mirror component is coupled with a double side reflection mirror component, where one of the components comprises a multilayer, while the other comprises a total reflection material. In a different embodiment, the multilayer mirror portion and the total external reflection portion are located on two partially cylindrical surfaces that lie opposite each other. One partially cylindrical portion has its reflective surface on an inner surface that faces a reflective outer surface of the other partially cylindrical portion, which lies adjacent to it. Still another embodiment uses double cross-coupled hybrid mirror sections, that is, two side-by-side mirror sections, one a multilayer and the other a total reflection material. Yet another embodiment of the invention is configured so that one mirror surface completely encompasses another mirror surface circumferentially. On the outer portion is an inner surface that faces an outer surface of the inner portion. One of these surfaces comprises a multilayer while the other comprises a total reflection surface. Shown in FIG. 1 is a hybrid mirror 10 according to a first embodiment of the invention. The mirror 10 includes a total reflection portion 12 and a multilayer portion 14. The x-ray radiation energy from x-ray source 16 diverges toward both portions of the mirror. Part of the x-ray energy is first reflected by the total external reflection portion 12 and then reflected by the multilayer mirror portion before reaching a focus point 18. Similarly, another part of the x-ray radiation energy from the same x-ray source 16 is first reflected by the multilayer portion 12 and then reflected by the total external reflection portion en route to the same focus point 18. Thus, all of the x-ray energy from the source is reflected by the total external reflection mirror once and by the multilayer portion once. All of the initial x-ray beam is therefore monochromatized by the multilayer portion prior to reaching focus point 18. However, compared to conventional side-by-side multilayer mirrors, the output x-ray beam from this device has a higher intensity, since the high reflectively portion is relatively low loss. In this embodiment, both mirror portions in the hybrid mirror may be either flat or curved depending on the desired performance. Various curved shapes and multilayer features available to the existing multilayer mirrors and total reflection mirrors are applicable to this hybrid mirror. FIG. 2 is an illustration showing the relation between reflectivity and 2θ angles for the total external reflection portion and the multilayer portion of the hybrid mirror 10. The use of 2θ as a measurement is commonplace in x-ray diffraction analysis, where the resulting direction of a reflected or refracted x-ray beam is twice the angle of incidence θ. In FIG. 2, θC is the critical angle for total external reflection, that is, the maximum incident angle that allows total external reflection. It depends on the reflection material and the energy (or wavelength) of the radiation. θB is the Bragg angle of the multilayer mirror which depends on the d-spacing of the multilayer. The reflectivity of a typical total reflection surface is better than 90%, while the reflectivity of a multilayer surface is typically lower, 70% for instance. The graph in FIG. 2 also indicates the wavelength selectivity of the multilayer surface as compared to the total reflection surface. In a double bounce mirror, the overall reflectivity is a multiple of the first bounce and the second bounce. For the hybrid mirror shown in FIG. 1, in which x-rays encounter the multilayer portion and the total reflection portion, the overall reflectivity ROH can be given as:ROH=RT·RM where RT is the reflectivity of the total reflection portion and RM is the reflectivity of the multilayer portion. For a conventional side-by-side multilayer mirrors, x-rays are bounced twice by multilayer mirrors, so the overall reflectivity ROC can be given as:ROC=RM·RM Because of the relative higher reflectivity from a total reflection mirror:RT>RM, orROH>ROC The intensity gain with the hybrid mirror relative to a side-by-side multilayer mirror is therefore RT/RM. FIG. 3 shows another embodiment of a hybrid mirror 20 according to the present invention. In this embodiment, two mirror portions are arranged in a so-called “Kirpatrick-Baez” configuration. x-rays from a source 16 are bounced by a multilayer portion 22 and then bounced by a total reflection portion 24 further down in the beam path. The surface of the total reflection portion 24 is rotated 90 degrees relative to the multilayer portion 22. This arrangement may also use the two mirror portions in a reverse configuration, where the total reflection portion is upstream from the multilayer portion in the beam path. The reflectivity of the mirror group in a Kirpatrick-Baez configuration can also be calculated in the manner described above. FIG. 4 is an experimental result comparing hybrid mirrors according to the present invention (for which the peaks are shown in broken lines) and conventional multilayer mirrors (for which the peaks are shown in solid lines), each in a Kirpatrick-Baez configuration. The diffraction peaks with multilayer mirrors are shifted to the right for easy comparison. As shown in FIG. 4, the hybrid mirrors have intensity gains of 38% to 42% relative to multilayer mirrors in a Kirpatrick-Baez configuration. The side-by-side hybrid mirrors should have about the same intensity gain advantage. FIG. 5 shows another embodiment of the present invention, in which a side-by-side single bounce mirror 26 is coupled with a double side reflection mirror 28. The two adjacent sides of the mirror 26 are multilayer surfaces. The two adjacent sides of the mirror 28, however, are total external reflection surfaces. A part of the x-ray radiation energy from the x-ray source 16 is first reflected by side-by-side mirror 26, and then reflected by the double side reflection mirror 28 to reach the focus 18. The mirrors 26 and 28 face each other. Another part of the x-ray radiation energy from the same x-ray source 16 is first reflected by the double side reflection mirror 28, and then reflected by the side-by-side mirror 26 to reach the same focus 18. Both parts of the x-rays are reflected by both multilayer surfaces and by total external reflection surfaces. In the embodiment of FIG. 5, the position of the block 28 with the two side reflection mirrors can be adjusted to change the focus distance between the hybrid mirrors and the focus spot 18. The block can also function as a beamstop to prevent the unconditioned x-rays from the source 16 from reaching the focus 18. Those skilled in the art will also recognize that, as with the aforementioned embodiments, the relative position of the multilayer surfaces and the total reflection surfaces may be reversed. FIG. 6 shows still another embodiment of the present invention, in which a configuration of partially cylindrical surfaces is used. This configuration is a variation from the face-by-face surfaces discussed above. Instead of two side-by-side surfaces for each mirror section, a single curved surface is used for each. In the configuration shown in FIG. 6, an outer partially cylindrical mirror portion 30 may have a concave multilayer mirror surface. An adjacent, inner partially cylindrical mirror portion 32 may have a convex total external reflection surface facing the mirror portion 30. The x-ray radiation energy from the x-ray source 16 is first reflected by the multilayer mirror portion 30, and then reflected by the total external reflection mirror portion 32 to reach the focus 18. The convex mirror portion 30 may be tilted to allow for a variable focus distance. Meanwhile, the convex mirror 32 may act as a beam stop, blocking the direct x-ray energy from reaching the focus 18. FIG. 7 shows an embodiment that uses a configuration of double cross-coupled hybrid mirror portions. This configuration is a variation of the aforementioned hybrid mirrors that use a Kirpatrick-Baez arrangement. Instead of using a single surface for each mirror surface of a given section, a side-by-side multilayer mirror portion 34 is coupled with a side-by-side total external reflection mirror portion 36. The x-ray radiation energy from the x-ray source 16 is first reflected by the multilayer mirror portion and then reflected by the total external reflection mirror portion to reach the focus 18. The total external reflection mirror portion 36 may be tilted relative to the multilayer mirror portion 34 to allow the focus distance to be varied. FIG. 8 shows yet another embodiment of the present invention. In this configuration, two mirror portions are used that are arranged with one encompassing the other. This configuration is a variation of the aforementioned coupled partial cylinder hybrid mirrors, but instead of a partially cylindrical surface for each mirror portion, fully circumferential surfaces are used. An outer mirror portion 38 has an inner surface that is a multilayer mirror surface. Although this mirror portion 38 is shown in cross-section in the figure, those skilled in the art will recognize that it fully encompasses the inner portion 40. The inner mirror portion 40 has an outer surface that is a total external reflection mirror surface. The outer mirror portion 38 and the inner mirror portion 40 have a common longitudinal axis. The x-ray radiation energy from x-ray source 16 is first reflected by the multilayer mirror surface of the outer portion 38, and then reflected by the total external reflection mirror surface of the inner mirror portion 40, so as to reach the focus 18. The total external reflection mirror surface of the inner portion reduces the divergence of the x-rays by reflecting them to a longer focus distance. The inner portion 38 may also be moved along the common longitudinal axis relative to the outer portion so as to vary the focus distance. As with each of the embodiments herein, the relative position of the multilayer mirror surface and the total external reflection surface may be reversed. While the invention has been shown and described with reference to a preferred embodiment thereof, it will be recognized by those skilled in the art that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
	summary
	description	The present application is a continuation of, and claims benefit under 35 USC 120 to, international application PCT/EP2016/052168, filed Feb. 2, 2016, which claims benefit under 35 USC 119 of German Application Nos. 10 2015 202 411.3, filed Feb. 11, 2015 and 10 2015 208 571.6, filed May 8, 2015. The entire disclosure of these applications are incorporated by reference herein. The disclosure relates to an illumination optical unit for EUV projection lithography for illuminating an object field, in which an object to be imaged is arrangeable, with illumination light. Furthermore, the disclosure relates to an illumination system including such an illumination optical unit, an optical system including such an illumination optical unit, and a projection exposure apparatus including such an optical system. Furthermore, the disclosure relates to a method for prescribing an intended distribution of an illumination light intensity over a field height of an object field of a projection exposure apparatus. Furthermore, the disclosure relates to a method for prescribing a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of an illumination optical unit for projection lithography. Furthermore, the disclosure relates to a method for producing a microstructured or nanostructured component using such a projection exposure apparatus, and a microstructured or nanostructured component produced using such a method. An illumination optical unit of the type set forth at the outset is known from DE 10 2008 001 511 A1, DE 10 2007 047 446 A1, US 2011/0001947 A1, WO 2009/132 756 A1, WO 2009/100 856 A1, and also U.S. Pat. Nos. 6,438,199 B1 and 6,658,084 B2. The disclosure seeks to develop an illumination optical unit so that a flexible field-dependent correction of illumination parameters is ensured. In one aspect, the disclosure provides an illumination optical unit for EUV projection lithography for illuminating an object field, in which an object to be imaged is arrangeable. The unit includes a field facet mirror with a plurality of field facets, arranged in the region of a field plane of the illumination optical unit. The unit also includes a pupil facet mirror with a plurality of pupil facets, arranged in the region of a pupil plane of the illumination optical unit. Each of the field facets serves to transfer used illumination light from a light source to respectively one of the pupil facets. Via respectively one illumination channel, a respective used illumination light partial beam is guided between the light source and the object field via exactly one field facet and exactly one pupil facet. A transfer optical unit that is disposed downstream of the field facet in the respective illumination channel is embodied for superposed imaging of the field facets into the object field. For each illumination channel, the transfer optical unit respectively includes one of the pupil facets for transferring the illumination light partial beam from the field facet toward the object field. At least some pupil facets, which are usable as correction pupil facets, are arranged in the beam path of the illumination light partial beam impinging thereon in such a way that an image of the light source arises at an image location which lies at a distance from the pupil facet along the illumination channel. The unit further includes a correction control device for the controlled displacement of at least some of the field facets, which are assigned to the correction pupil facets via the respective illumination channels and which are usable as correction field facets, via correction actuators that are connected to the correction field facets. The correction control device and the correction actuators are embodied in such a way that a correction displacement travel of the correction field facets in a correction displacement range is so large that a respective correction illumination channel is cut off by an edge of the correction pupil facet in such a way that the illumination light partial beam is not transferred in the entirety thereof from the correction pupil facet into the object field. According to the disclosure, it was recognized that introducing a targeted distance between a light source image and the pupil facets that are impinged upon by the illumination light leads to a field-dependent spatial distribution of an illumination light impingement on the pupil facets which can be used for illumination parameter correction purposes. The distance between the correction pupil facets and the light source image leads to a light spot of the illumination light partial beam that impinges on the correction pupil facets arising on the correction pupil facets, the light spot representing a convolution of a field facet edge or marginal contour with a source marginal contour of the light source. Trimming the illumination light partial beam within the scope of the correction leads to illumination light being transferred from this correction pupil facet toward the object field with different intensities, depending on the location on the object field. A field-dependent correction of an illumination angle distribution over the object field can be obtained by a controlled displacement of the correction field facets. All field facets of the field facet mirror can represent correction field facets. All pupil facets of the pupil facet mirror can represent correction pupil facets. The controlled displacement, which may be caused by way of the correction control device, may be a controlled tilt. Accordingly, the correction actuators can be correction tilt actuators. The correction displacement travel can be a correction tilt angle of the correction field facets, which is so large in a correction tilt angle range that a respective correction illumination channel is trimmed by an edge or margin of the correction pupil facet in such a way that the illumination light partial beam is not transferred in the entirety thereof from the correction pupil facet into the object field. In addition to a tilt, the displacement can also be a translation or else the targeted establishment of a defocus. For the purposes of flexibly prescribing illumination settings, the number of pupil facets may be greater than the number of field facets, wherein there may be a change between different pupil facets that are impinged upon by the field facets by way of an actuation of appropriate tilt actuators and a corresponding tilt of these field facets. Despite this possibility for change, each of the field facets transfers illumination light from the light source to, in each case, exactly one of the pupil facets in a specific, set illumination geometry. Accordingly, via respectively one illumination channel, a respective illumination light partial beam is guided in this illumination situation between the light source and the object field via exactly one field facet and exactly one pupil facet. The change-tilt actuators that bring about the change between various pupil facets that can be impinged upon via a respective field facet can be actuators that are independent of the correction actuators. Alternatively, it is possible for the change-tilt actuators to be designed in such a way that they meet both functions of “changing illumination setting” and “correcting illumination parameters”. The field facet mirror need not be arranged precisely in the field plane. It is sufficient for the field facet mirror to be arranged in a near-field manner. The pupil facet mirror need not be arranged precisely in a pupil plane. It is sufficient for the pupil facet mirror to be arranged in a near-pupil manner. For the purposes of characterizing these terms of “near-field” and “near-pupil”, use can be made of the following parameter P, which is likewise explained in WO 2009/024 164 A:P(M)=D(SA)/(D(SA)+D(CR)) Here: D(SA) is the diameter of a sub-aperture, i.e. a partial beam, of the used illumination light, which emanates from exactly one field point, on a beam-forming surface of the component M, i.e., for example, of the field facet mirror or of the pupil facet mirror; D(CR) is the maximum spacing of chief rays of an effective object field that is imaged by the lens, measured in a reference plane (e.g. in a plane of symmetry or a meridional plane), on the beam forming surface of M; in a field plane, the following applies: P=0, since D(CR) is unequal to 0 and D(SA)=0; in a pupil plane, the following applies: P=1, since D(CR)=0 and D(SA) is unequal to 0. “Near-pupil” means: P is at least 0.7, e.g. 0.75, at least 0.8, e.g. 0.85, or at least 0.9, e.g. 0.95. “Near-field” means: P is at most 0.3, e.g. 0.25, at most 0.2, e.g. 0.15, or at most 0.1, e.g. 0.05. The parameter P can also be used to characterize the distance between the image location of the image of the light source and the respective correction pupil facet along the illumination channel. For the purposes of this characterization, the image location of the light source image is defined as prescribing the positioning of the pupil plane. Then, the respective correction pupil facet lies in a near-pupil manner in relation to this image location, but not exactly in the pupil plane. Thus, 0.5<P<1 applies. Here, in particular, P is at least 0.7, e.g. 0.75, at least 0.8, e.g. 0.85, or at least 0.9, e.g. 0.95. P can be less than 0.995, less than 0.99 or else less than 0.98. In the case of specific illumination geometries, illumination light may also be transferred to a plurality of pupil facets at the same time via exactly one field facet. However, used illumination light is transferred exactly to one pupil facet in the process. The illumination light possibly still impinging on other pupil facets is not used illumination light and not transferred toward the illumination field by these other pupil facets; instead, it is either used for other purposes or disposed of in a controlled manner. Some or all of the field facets and/or of the pupil facets may, in turn, be constructed from a plurality of individual small mirrors. In particular, the field facet mirror and/or the pupil facet mirror can be constructed as a MEMS (micro-electromechanical mirror) array, wherein each of the field facets and each of the pupil facets may then be constructed from a multiplicity of small MEMS mirrors. An example of such a MEMS structure is supplied by WO 2009/100 856 A1. In the case of such a MEMS embodiment, a targeted defocus may be brought about as an option for the correction displacement, which is to be produced, by prescribing a change in a curvature angle of the respective field facet. The transfer optical unit that is disposed downstream in the respective illumination channel of the field facets can be formed exclusively by the respective downstream pupil facet lying within the illumination channel. Alternatively, the transfer optical unit may also still include further components, in particular further mirrors, which are still disposed downstream of the pupil facet of a respective illumination channel and disposed upstream of the object field. The correction actuators can be embodied for the continuous dis-placement of the correction field facets. Such displacement actuators facilitate fine influencing of illumination parameters to be corrected. Alternatively, it is possible to design the displacement actuators in such a way that a plurality of discrete tilt states of the correction field facets can be achieved. By way of example, such a design of the displacement actuators can ensure reliably reproducible displacement positions. A continuous displacement of the correction field facets leads to a continuous prescription of a displacement path. The correction actuators can be embodied to displace the correction field facets about two mutually perpendicular axes. Such correction actuators facilitate particularly flexible correction displacements of the correction field facets. The object can be displaceable along an object displacement direction, wherein an arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour in such a way that, over a variable of the correction displacement path, it is possible to prescribe a marginal trimming or cut off of the cross section in a direction (+/−x) perpendicular to the object displacement direction. Such a configuration of the illumination optical unit facilitates a flexible illumination correction, via which it is possible to influence different field dependencies and/or influence different, field-dependent illumination parameters. The object can be displaceable along an object displacement direction, wherein an arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour in such a way that, over a variable of the correction displacement path, it is possible to prescribe a marginal trimming or cut off of the cross section in a direction parallel to the object displacement direction. Such a configuration of the illumination optical unit facilitates a flexible illumination correction, via which it is possible to influence different field dependencies and/or influence different, field-dependent illumination parameters. By way of a direction of the correction displacement path, it is possible to prescribe whether trimming of the cross section of the illumination channel is carried out centrally or marginally when seen in a dimension perpendicular to a trimmed or cut off edge or margin. Such a configuration of the illumination optical unit facilitates a flexible illumination correction, via which it is possible to influence different field dependencies and/or influence different, field-dependent illumination parameters. By using arcuate field facets, it is possible to obtain a corresponding arcuate light spot of the illumination light partial beam, which arises by way of the convolution with the source structure, on the correction pupil facets, the edge or marginal contour of which is particularly suitable for a trim correction since, depending on the displacement direction of the light spot, this results in trimming at the edge or margin of the correction pupil facet which leads to a different field-dependent illumination parameter correction effect. Alternatively, the field facets may also have a straight, i.e. not arcuate, and e.g. rectangular embodiment. The advantages of an illumination system including such an illumination optical unit and a light source for producing the illumination light, of an optical system including such an illumination optical unit and a projection optical unit for imaging the object field into an image field, of a projection exposure apparatus including such an illumination optical unit, of an illumination light intensity prescription method using such an illumination optical unit, of a production method using such an illumination optical unit, and of a microstructured or nanostructured component made by such a method correspond to those which have already been explained above with reference to the illumination optical unit according to the disclosure. The disclosure also seeks to specify a method for prescribing a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of an illumination optical unit for projection lithography, which can be used for increasing the illumination light throughput during the projection exposure. In one aspect, the disclosure provides a method for prescribing a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of an illumination optical unit for projection lithography, wherein an object to be imaged is arrangeable in the object field, wherein the transverse field coordinate extends transversely to an object displacement direction, along which the object is displaceable, wherein the illumination optical unit includes two facet mirrors that are arranged in succession in the beam path of the illumination light in such a way that, via respectively one illumination channel, a respective used illumination light partial beam is guided between a light source and the object field via exactly one facet of the first facet mirror and exactly one facet of the second facet mirror. The method includes: identifying a minimum intensity transverse field coordinate, at which the overall illumination intensity of the illumination light partial beams that are guided via all illumination channels is minimal; identifying at least one illumination channel, in which a variation of a marginal trimming or cut off of the illumination light partial beam, which is guided thereover, at the second facet leads to an increase in an illumination intensity of this illumination light partial beam at the minimum intensity transverse field coordinate; aligning the first facet of this illumination channel for increasing the inllumination intensity thereof at the minimum intensity transverse field coordinate. According to the disclosure, it was recognized that by increasing the illumination intensity of the illumination channel, which is respectively identified in this case, at the minimum intensity transverse field coordinate, it is possible to raise the minimum overall illumination intensity which is present at the minimum intensity transverse field coordinate. This results in less illumination light remaining unused by shadowing, for example by using a field intensity prescription device in the style of a UNICOM, if the same illumination intensity should be present over all transverse field coordinates. This results in a higher illumination light throughput. The prescription method starts at the global intensity minimum, which emerges from the superposition of the illumination intensities of all illumination light partial beams over the transverse field coordinate. The two facets mirrors can be a field facet mirror and a pupil facet mirror. The illumination channels, which can be used for alignment when the prescription method is used, may be illumination channels with correction facets of the illumination optical unit according to the disclosure. During the prescription method according to the disclosure, it is possible to identify a plurality of illumination channels and the first facets thereof may be aligned accordingly. It is also possible to accordingly identify and align all illumination channels. To the extent that individual illumination channels are identifeed by a measurement, the individual illumination channels can be identified e.g. by shadowing all other illumination channels and measuring, across the transverse field coordinate, the intensity of an illumination light intensity which is guided to the object field via the remaining illumination channel. This can be carried out using a spatially resolved sensor. The method can further include: identifying at least one illumination channel, in which a variation of a marginal trimming or cut off of the illumination light partial beam, which is guided thereover, at the second facet leads to an increase in a minimum illumination intensity of this illumination light partial beam over the trans-verse field coordinate; and aligning the first facet of this illumination channel for increasing this minimum illumination intensity. In such a case, a minimum illumination intensity in each individual illumination channel can be increased across the transverse field coordinate where this is possible by way of an appropriate trimming variation. The transverse field coordinate of an appropriate individual illumination channel minimum need not be the minimum intensity transverse field coordinate. It is also possible to identify and align a plurality of illumination channels. In the extreme case, it is possible to identify and align all illumination channels. When prescribing the minimum illumination intensity of the illumination light over the object field transverse field coordinate, it is possible to dynamically tilt the first facet for alignment purposes. In this method, use can be made of an actuator that displaces the facet, in particular the correction actuator. Alternatively, the first facet can also be aligned statically in the basic set-up of the field facet mirror. When adjusting the actual illumination setting within the scope of the production method, use can be made of a field-dependent individual channel intensity correction. The field-dependent individual channel intensity correction may contain the following sequence of method steps: 1. Determining an illumination light partial beam of at least one illumination channel selected for correction purposes, by measurement and/or by calculation. During the measurement, the illumination light partial beam can be measured in a prescribed correction plane, for example by the use of a spatially resolved intensity detector. A calculation of the illumination light partial beam can be effectuated by computational determination of a point spread function, for example with the aid of an optical design program. This calculation can be carried out analytically or numerically, or else by way of a simulation. 2. Determining a correction information item, in particular a set of actuator positions of the correction actuators of the correction field facets. In particular, the correction information item can be a set of tilt angles of the correction field facets. Determining this correction information item can be effectuated by a numerical computational method and/or by an analytical computational method. 3. Using the correction information item for the correction displacement of the correction field facets. This can be carried out by actuating the correction actuators. 4. Verifying the effect of the correction information item as an optional step. This verification can be effectuated by a measurement and/or by a simulation. Within the scope of the field-dependent individual channel intensity correction, the method mentioned above can be used for prescribing an intended distribution of an illumination light intensity over the field height of the object field of the projection exposure apparatus. The component can be produced with an extremely high structural resolution. In this way it is possible, for example, to produce a semiconductor chip having an extremely high integration or storage density. FIG. 1 schematically shows a microlithographic projection exposure apparatus 1 in a meridional section. The projection exposure apparatus 1 includes a light or radiation source 2. An illumination system 3 of the projection exposure apparatus 1 has an illumination optical unit 4 for exposing an illumination field coinciding with an object field 5 in an object plane 6. The illumination field may also be larger than the object field 5. In this case, an object in the form of a reticle 7 arranged in the object field 5, the reticle being held by an object or reticle holder 8, is exposed. The reticle 7 is also referred to as lithography mask. The object holder 8 is displaceable along an object displacement direction via an object displacement drive 9. A projection optical unit 10 serves for imaging the object field 5 into an image field 11 in an image plane 12. A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. By way of a wafer displacement drive 15, the wafer holder 14 is displaceable parallel to the object displacement direction in a manner synchronized with the object holder 8. The radiation source 2 is an EUV radiation source having an emitted used radiation in the range of between 5 nm and 30 nm. This may be a plasma source, for example a GDPP (gas discharge-produced plasma) source or an LPP (laser-produced plasma) source. A radiation source based on a synchrotron or on a free electron laser (FEL) may also be used for the radiation source 2. Information about such a radiation source is able to be found by the person skilled in the art for example from U.S. Pat. No. 6,859,515 B2. EUV radiation 16, which emanates from the radiation source 2, in particular the used illumination light that illuminates the object field 5, is focused by a collector 17. A corresponding collector is known from EP 1 225 481 A. Downstream of the collector 17, the EUV radiation 16 propagates through an intermediate focal plane 18 before being incident on a field facet mirror 19. The field facet mirror 19 is a first facet mirror of the illumination optical unit 4. The field facet mirror 19 includes a plurality of reflecting field facets which are not depicted in FIG. 1. The field facet mirror 19 is arranged in a field plane of the illumination optical unit 4 which is optically conjugate with respect to the object plane 6. The EUV radiation 16 is also referred to hereinafter as illumination light or as imaging light. Downstream of the field facet mirror 19, the EUV radiation 16 is reflected by a pupil facet mirror 20. The pupil facet mirror 20 is a second facet mirror of the illumination optical unit 4. The pupil facet mirror 20 is arranged in a pupil plane of the illumination optical unit 4, which is optically conjugate with respect to the intermediate focal plane 18 and with respect to a pupil plane of the illumination optical unit 4 and to the projection optical unit 10 or coincides with the pupil plane. The pupil facet mirror 20 has a plurality of reflecting pupil facets which are not depicted in FIG. 1. The field facets of the field facet mirror 19 are imaged superposed on one another into the object field 5 with the aid of the pupil facets of the pupil facet mirror 20 and an imaging optical assembly, downstream thereof, in the form of a transfer optical unit 21 with mirrors denoted by 22, 23 and 24 in the order of the beam path. The last mirror 24 of the transfer optical unit 21 is a grazing incidence mirror. In order to simplify the description of positional relationships, FIG. 1 plots a Cartesian xyz-coordinate system as a global coordinate system for the description of the positional relationships of components of the projection exposure apparatus 1 between the object plane 6 and the image plane 12. The x-axis extends perpendicularly to the plane of the drawing into the latter in FIG. 1. In FIG. 1, the y-axis extends to the right and parallel to the displacement direction of the object holder 8 and of the wafer holder 14. The z-axis extends downward in FIG. 1, i.e. perpendicular to the object plane 6 and to the image plane 12. The x-dimension over the object field 5 or the image field 11 is also referred to as field height. The object displacement direction extends parallel to the y-axis. Local Cartesian xyz-coordinate systems are plotted in the further figures. The x-axes of the local coordinate systems extend parallel to the x-axis of the global coordinate system according to FIG. 1. The xy-planes of the local coordinate systems represent arrangement planes of the components respectively presented in the figure. The y- and z-axes of the local coordinate systems are accordingly tilted about the respective x-axis through a certain angle. FIGS. 2 and 3 show examples of different facet arrangements for the field facet mirror 19. Each of the field facets 25 presented therein can be constructed as an individual mirror group from a plurality of individual mirrors, as is known from e.g. WO 2009/100 856 A1. Respectively one of the individual-mirror groups then has the function of a facet of a field facet mirror such as is disclosed for example in U.S. Pat. Nos. 6,438,199 B1 or 6,658,084 B2. The field facet mirror 19 according to FIG. 2 includes a multiplicity of field facets 25 with an arcuate embodiment. These are arranged, in groups, in field facet blocks 26 on a field facet carrier 27. Overall, the field facet mirror 19 according to FIG. 2 includes twenty-six field facet blocks 26, in which three, five or ten of the field facets 25 are combined in groups. Interstices 28 are present between the field facet blocks 26. The field facet mirror 19 according to FIG. 3 includes rectangular field facets 25, which, once again, are arranged in groups to form field facet blocks 26, between which interstices 28 are present. FIG. 4 schematically shows a plan view of the pupil facet mirror 20. Pupil facets 29 of the pupil facet mirror 20 are arranged in the region of an illumination pupil of the illumination optical unit 4. In reality, the number of pupil facets 29 is much greater than what is presented in FIG. 4. The pupil facets 29 are arranged on a pupil facet carrier of the pupil facet mirror 20. A distribution of pupil facets 29, which are impinged with the illumination light 16 via the field facets 25, within the illumination pupil prescribes an actual illumination angle distribution in the object field 5. Each of the field facets 25 serves to transfer a part of the illumination light 16, i.e. an illumination light partial beam 16i, from the light source 2 toward one of the pupil facets 29. Thus, the field facets 25 in each case are first facets of the illumination optical unit 4 in the beam path of the illumination light 16. Accordingly, the pupil facets 29 are second facets of the illumination optical unit 4 in the beam path of the illumination light 16. Below, in a description of the illumination light partial beams 16i, the assumption is made that the associated field facet 25 is in each case illuminated to the maximum extent, i.e. over its entire reflection surface. In this case, an edge or marginal contour of the illumination light partial beam 16i coincides with an edge or marginal contour of the illumination channel, which is why the illumination channels are also denoted by 16i below. The respective illumination channel 16i represents a possible light path of an illumination light partial beam 16i that illuminates the associated field facet 25 to the maximum extent, via the further components of the illumination optical unit 4. For each illumination channel 16i, the transfer optical unit 21 respectively includes one of the pupil facets 29 for transferring the illumination light partial beam 16i from the field facet 25 toward the object field 5. Respectively one illumination light partial beam 16i, of which two illumination light partial beams 16i (i=1, . . . , N; N: number of field facets) are schematically presented in FIG. 1, is guided between the light source 2 and the object field 5 via exactly one of the field facets 25 and via exactly one of the pupil facets 29 via respectively one illumination channel. At least some of the pupil facets 29, all of the pupil facets 29 of the pupil facet mirror 20 in the considered exemplary embodiment, are usable as correction pupil facets. These correction pupil facets are arranged in the beam path of the illumination light partial beam 16i impinging thereon in such a way that an image 2′ of the light source 2 arises at an image location which lies at a distance from the pupil facet 29 along the illumination channel 16i. In FIG. 1, a denotes a distance between the respective image 2′ and the assigned pupil facet. Below, this distance a is also referred to as a defocusing distance. FIG. 1 schematically presents two variants of such an arrangement of the light source images 2′. A first light source image 2′1 is arranged at an image location which is situated in the beam path of the associated illumination light partial beam 16i before the reflection at the pupil facet 29 of the pupil facet mirror 20. In FIG. 1, a1 denotes the distance between the light source image 2′1 and the associated pupil facet 29. A second light source image 2′2 is arranged in the beam path of a further illumination light partial beam 16i at an image location after the reflection at the pupil facet of the pupil facet mirror 20. In FIG. 1, a2 denotes the distance between the light source image 2′2 and the associated pupil facet 29. Moreover, in FIG. 1, BIF denotes a typical size, namely the typical diameter, of a light source image IF, i.e. of an intermediate focus, in the intermediate focus plane 18. In FIG. 1, Bif denotes a typical size of an image of the intermediate focus IF on the respective pupil facet 29. Additionally, Bf denotes an x-extent of the respective field facet 25, i.e. a typical size of the field facet 25, in FIGS. 2 and 3. At least some of the field facets 25, all field facets 25 in the presented exemplary embodiment, are usable as correction field facets, which are each assigned to a respective correction pupil facet 29 via one of the illumination channels 16i. The correction field facets 25 are connected to correction or displacement actuators in the form of tilt actuators 31, of which only a few displacement actuators 31 are presented schematically in FIG. 2. The displacement actuators 31 are embodied for the continuous displacement, namely for the continuous tilt, of the correction field facets 25. The displacement actuators 31 are embodied for tilting the correction field facets 25 about two mutually perpendicular axes, which extend parallel to the x-axis and to the y-axis, for example through a respective center or through a respective centroid of a reflection surface of the correction field facet 25. The displacement actuators 31 are signal connected (cf. FIG. 1) via a signal connection not presented here to a correction control device 32 of the projection exposure apparatus 1. The correction control device 32 serves for the controlled tilt of the correction field facets 25. The correction control device 32 and the displacement actuators 31 are embodied in such a way that a correction displacement travel—namely a correction tilt angle—of the correction field facets 25 in a correction displacement range—namely in a correction tilt angle range—is so large that a respective correction illumination channel 16i is trimmed by an edge or margin of the associated correction pupil facet 29 in such a way that the illumination light partial beam 16i is not transferred in the entirety thereof from the correction pupil facet 29 into the object field 5. This is explained in greater detail below with reference to FIG. 5 ff. FIG. 5 shows one of the pupil facets 29 that can be used in the pupil facet mirror 20. The pupil facet 29 according to FIG. 5 does not have a circular edge or marginal contour, as presented in FIG. 4, but instead an almost square edge or marginal contour with rounded-off corners. Such an edge or marginal contour, which may also be designed without rounded-off corners, i.e. in a square or rectangular manner, allows the pupil facet carrier 30 to be occupied relatively densely with the pupil facets 29. The pupil facet 29 according to FIG. 5 is impinged upon with the illumination light partial beam 16i from an arcuate field facet 25 of the field facet mirror 19 according to FIG. 2. FIG. 5 shows a location of the illumination light partial beam 16i that is reflected by the pupil facet 29, in a tilt angle position of the field facet 25 that is assigned to this pupil facet 29 in which no illumination correction occurs. In this arrangement presented in FIG. 5, an entire cross section of the illumination light partial beam 16i lies on the pupil facet 29, and so the edge or margin of the illumination light partial beam 16i is not cut off or trimmed by the edge or margin of the pupil facet 29. An edge or marginal contour of the cross section of the illumination light partial beam 16i on the pupil facet 29 has an approximately arcuate, bean-shaped or kidney-shaped form and can be understood to be the convolution of an image of the arcuate field facets 25 (cf. solid line “25B” in FIG. 5) according to FIG. 2 with a round source area of the light source 2. This convolution arises on account of the fact that, as already explained above, the image 2′ of the light source 2 arises at an image location which lies along the illumination channel 16i at a distance from the pupil facet 29, i.e. upstream or downstream of the pupil facet 29 in the beam path. The arcuate edge or marginal contour of the illumination light partial beam 16i on the pupil facet 29 represents a light spot of the illumination light partial beam 16i. Three sub-beams 16i1, 16i2 and 16i3 are plotted using dashed lines in the edge or marginal contour of the illumination light partial beam 16i on the pupil facet 29. The illumination light partial beam 16i is composed of a multiplicity of such sub-beams 16ij. To the extent that the optical parameters of the illumination are known, the illumination light partial beam 16i can be calculated, for example with the aid of an optical design program, and it is also referred to as “point spread function” in this context. The illumination light 16 of these sub-beams 16i1 to 16i3 proceeds from a left edge or marginal point 251, from a central point 252 and from a right edge or marginal point 253 of the associated field facet 25. In FIG. 2, these initial points 251 to 253 are plotted in an exemplary manner on one of the field facets 25. In FIG. 5, r denotes the radius (half the diameter) of the sub-beams 16ij. In FIG. 5, xf denotes the x-dimension of the field facet image 25B on the pupil facet 29, i.e. the x-extent of a residual field component on the pupil facet 29. By carrying out a correction tilt of the field facet 25, which impinges the pupil facet 29 according to FIG. 5, it is possible to achieve a field-dependent correction of an illumination angle distribution over the object field 5. To render such a field-dependent correction possible, the following condition is satisfied for the defocus distance a:a=k Bifff/Bf Here, k characterizes the ratio between the sizes xf and r, i.e. between the typical extent xf of the residual field component 25B and the radius r of the sub-beams 16ij. Bif is the typical size of the image of the intermediate focus IF on the respective pupil facet 29. ff is the focal length of the associated field facet 25, i.e. the focal length with which the respective illumination light partial beam 16i is imaged by the associated field facet 25. Bf is the typical extent of the field facet 25. Thus, the ratio K=xf/r, i.e. the ratio of the size of the residual field component xf on the pupil facet 29 to the typical dimension r of the sub-beams 16ij, inter alia, is decisive for the defocus value a. The following holds true: 2r=Bif. So that the field-dependent correction is possible, the following additionally applies:k≥0.5 In particular, k≥1 may apply, i.e. that residual field component xf has a typical size that is greater than the radius of the sub-beams 16ij. The field dependence of the correction described above improves with increasing k. k may be greater than 1.5, may be greater than 2, may be greater than 3, may be greater than 4, may be greater than 5 and may also be even greater. As soon as the typical diameter Bif of the sub-beam 16ij is very much larger than the typical dimension xf of the field component, there is no usable field dependence via a correction tilt of the field facet 25, which impinges the pupil facet 29 according to FIG. 5. All that emerges then is a field-independent reduction in the intensity of the illumination light partial beam 16i. Thus, as Bif increases, the defocus distance a increases so that the field dependence for the correction is maintained during the correction tilt of the field facet 25. FIG. 6 shows a dependence of a scan-integrated intensity IK, which one of the illumination channels 16i contributes for illuminating the object field 5, on the field height x. A scan integration means an integration of the illumination intensity along the y-coordinate of the object field 5. A nominal field profile, which emerges if the entire illumination light partial beam 16i is reflected from the pupil facet 29 toward the object field 5, is plotted using a dashed line. The solid line in FIG. 6 represents a field profile of the channel intensity IK which arises when the illumination light partial beam 16i is displaced on the pupil facet 29 by tilting the correction actuator 31 of the associated correction field facet 25 in the −x-direction such that the associated correction illumination channel 16i—and hence also the illumination light partial beam 16i—is cut off or trimmed by the edge or margin of the correction pupil facet 29. This edge, the left edge in FIGS. 5 and 6, of the illumination light partial beam 16i now no longer contributes to illuminating the object field 5, and so the field profile plotted with a solid line in FIG. 6 emerges, in which the channel intensity IK in the case of small field height values x drops faster to a value of 0 than the dashed, nominal field profile. As a result, there is a field-dependent curve of an illumination over this pupil facet 29 via this illumination channel, i.e. a field-dependent curve of the intensity of the associated illumination angle. In the correction tilt position according to FIG. 6, an object field point at the x-value xmin practically does not “see” illumination light 16 from the direction of the pupil facet 29 because illumination light 16, which emanates from an original image corresponding to this field height xmin from the associated field facet of the illumination channel 16i is not reflected by the pupil facet 29. Above a limit field height xG, the correction field profile of the channel intensity IK merges back into the nominal field profile. FIG. 7 correspondingly shows a corrective effect when the tilt actuator 31 tilts the correction field facet 25 in such a way that the illumination light partial beam 16i is displaced in the positive x-direction on the correction pupil facet 29 and cut off or trimmed by the edge or margin of the correction pupil facet 29. Presented once again by a solid line is the curve of the channel intensity IK over the field height x after the displacement has taken place, in comparison with the nominal field profile that is presented using a dashed line. Then, the object field points see practically no illumination light emerging from the associated correction pupil facet 29 in the region of a maximum field height xmax. Below a limit field height xG, the correction field profile, which is depicted using a solid line, according to FIG. 7 merges back into the nominal field profile, which is depicted using a dashed line. For the purposes of displacing the illumination light partial beam 16i in the +/−x-direction, the associated correction field facet 25 is tilted by the associated tilt actuator about an axis that is parallel to the y-axis in FIG. 2. Thus, an geometry of the arrangement of guiding the illumination light 16 via the illumination channels 16i is such that a cross section of the illumination channel 16i on the correction pupil facets 29 has such an edge or marginal contour that, by way of a size of the correction tilt angle, it is possible to set or prescribe marginal cutting off or trimming of the cross section in a direction +/−x perpendicular to the object displacement direction y. FIG. 8 shows the result of a correction displacement of the illumination light partial beam 16i on the correction pupil facet 29 according to FIG. 5 in the positive y-direction, caused by a corresponding correction tilt of the associated correction field facet 25 about an axis that is parallel to the x-axis. On account of the arcuate form of the illumination light partial beam 16i on the correction pupil facet 29, the edge of the illumination light partial beam 16i that is leading in the +y-direction is trimmed first in the region of the sub-beam 16i2 by the edge or margin of the correction pupil facet 29 on account of this +y-displacement. This results in a reduction or a dip in the channel intensity IK in the region of a central field height x0. Above a field height x0+xA2 and below a field height x0−xA1, the correction field profile of the channel intensity IK, which is depicted in FIG. 8 using a solid line, merges back into the nominal field profile, which is depicted using a dashed line. FIG. 9 shows the effects of a correction by a displacement of the illumination light partial beam 16i in accordance with FIG. 5 in the negative y-direction, caused by a tilt of the associated correction field facet 25 about an axis that is parallel to the x-axis. On account of the trimming of both ends of the arcuate form of the illumination light partial beam 16i in the region of the sub-beams 16i1 and 16i3, this results in a drop in the channel intensity IK at both field height edges or margins, i.e. simultaneously in the region of the field height xmin and xmax. In the region of the central field height x0, the corrected field profile, which is depicted in FIG. 9 using the solid line, merges back into the nominal field profile of the channel intensity IK, which is depicted using a dashed line. Thus, an geometry of the arrangement of guiding the illumination light 16 via the illumination channels 16i is such that a cross section of the illumination channel 16i on the correction pupil facets 29 has such an edge or marginal contour that, by way of a size of the correction tilt angle, it is possible to prescribe marginal trimming or cutting off of the cross section in a direction +/−y along or parallel to the object displacement direction y. Thus, by way of a direction +/−y of the correction tilt angle, it is possible to prescribe whether the cross section of the illumination channel 16i is trimmed centrally (i.e. in the region x0) or marginally (i.e. in the regions xmin and xmax), as seen in a dimension x perpendicular to a trimmed or cut off edge or margin +/−y. Trimming or cutting off the illumination light partial beam 16i thus leads to illumination light 16 being transferred from this correction pupil facet 29 toward the object field 5 with different intensities, depending on the location on the object field 5. Thus, field-dependent correction of an illumination intensity distribution over the object field 5 can be obtained by a controlled tilting of the correction field facets 25. A correspondingly trimmed illumination channel 16i represents a correction illumination channel. The correction displacements of the illumination light partial beam 16i in the positive or negative x-direction can be combined with the correction displacements in the negative or positive y-direction. This can be effectuated by the simultaneous tilt of the correction field facets 25, which is assigned to the considered correction pupil facet 29, about the y-axis and about the x-axis through a corresponding correction tilt angle. The arising correction field profiles of the channel intensity IK emerge as superpositions of e.g. the correction field profiles according to FIGS. 6 and 8, according to FIGS. 6 and 9, according to FIGS. 7 and 8, or according to FIGS. 7 and 9. In this way, it is also possible to produce relatively complex correction field profiles. A specific correction application of the illumination optical unit 4 described above is explained by way of example below on the basis of FIGS. 10 and 11. FIG. 10 shows a field profile, to be corrected, of an x-telecentricity Tx. The following holds true: T x ⁡ ( x ) = K · ∑ c ⁢ I c ⁡ ( x , ρ x , ρ y ) · ρ x ∑ c ⁢ I c ⁡ ( x , ρ x , ρ y ) ,where x describes the field point, K is a normalization factor and IC (x, ρx, ρy) denotes the intensity of the pupil of the c-th channel at the location ρx, ρy at the field point x. The telecentricity value Tx rises monotonically over the field height x, from a minimum value Tx,min at the field height xmin to a value Tx,max at the maximum field height xmax. A curve of the x-telecentricity Tx is depicted with a solid line at 33 in FIG. 10. FIG. 11 shows an illumination pupil of the illumination optical unit 4, which is seen by points of the object field 5 at the maximum field height xmax. An x-dipole setting is presented schematically and not true to scale. A left-hand pole 34 of this dipole illumination setting is formed by intensity contributions or pupil spots 35, which are produced by impinging this field height xmax with corresponding pupil facets 29. The intensity contributions 35 are relatively weak, which is elucidated in FIG. 11 by the small radii of these intensity contributions 35. A right-hand pole 36 of the dipole illumination setting according to FIG. 11 contains intensity contributions or pupil spots 37, proceeding from corresponding pupil facets 29 of the pupil facet mirror 20. The intensity contributions 37 are stronger than the intensity contributions 35, which is clarified in FIG. 11 by the correspondingly larger radii of these intensity contributions 37. On account of the stronger intensity contributions 37, the integrated illumination intensity over the pole 36 is greater than the integrated illumination intensity over the pole 34, leading to the positive x-telecentricity value Tx,max at the location xmax. Thus, the intensity contributions 37 that are highlighted in FIG. 11 by way of a dashed boundary can now be corrected by selecting the associated pupil facets 29 as correction pupil facets, i.e. they can now be reduced in respect of their intensities. In these associated pupil facets 29, there then is a displacement of the illumination light partial beams 16i, in the positive x-direction such that a field correction in accordance with FIG. 7 results. An integral intensity over the illumination pole 36, and hence the value Tx,max, can therefore be reduced. FIG. 11 shows this scan-integrated illumination pupil of the field coordinate x, plotted over pupil coordinates σx, σy. During the projection exposure with the aid of the projection exposure apparatus 1, a prescribed illumination setting is initially set and measured in respect of its illumination parameters. Subsequently, there is a selection of correction pupil facets and, by way of the controlled prescription of corresponding correction tilt angles of the assigned correction field facets, there is a correction of prescribed values of illumination parameters that cannot be maintained, until these lie within prescribed tolerance limits around prescribed intended values of the illumination parameters. Furthermore, the illumination optical unit 4 includes a sensor unit 40 (cf. FIGS. 1 and 12) for capturing an intensity of the illumination light 16 depending on the field height x, i.e. depending on a transverse field coordinate x of the object field 5. The sensor unit 40 includes an upstream optical unit 41 and a sensor 42 that measures in a spatially resolved manner. The upstream optical unit 41, which is schematically presented in FIG. 12, includes a capturing region 43 which covers the entire object field 5. The upstream optical unit 41 images the object field 5 on the sensor 42. The sensor 42 can be a line array or a line and column array made of individual illumination-light-sensitive sensor pixels. In particular, the sensor 42 is a CCD array. With the aid of appropriate wavelength conversion devices, for example with the aid of a scintillation coating, the EUV wavelength is converted in a detection wavelength, to which the sensor 42 is sensitive, for the purposes of measuring the illumination light intensity dependence on the field height x. Alternatively, it is possible to simulate the EUV light source 2 by a measurement light source for the purposes of measuring the dependence of the illumination light intensity on the field height x, the emission characteristic of the measurement light source corresponding to that of the EUV light source, but the measurement light source emitting a measurement wavelength for which the sensor 42 is sensitive. With the aid of the sensor unit 40, the central control device 32 and the tilt actuators 31, it is possible to carry out a method, described below, for prescribing a minimum illumination intensity Imin (cf. FIGS. 14 and 15) over the field height x, which will still be described in more detail below, in particular on the basis of FIG. 13. To this end, a minimum intensity transverse field coordinate xmin, at which an overall illumination intensity IGes,0 of the illumination light partial beams 16i that are guided via all illumination channels 16i is minimal, is initially identified in an identification step 44. This identification is carried out by measuring the overall illumination intensity IGes over the field height x with the aid of the sensor unit 40 in the case of a first set of tilt positions of the tilt actuators 31 of the field facet mirror 19. An exemplary result of this measurement is presented in FIG. 14. The minimum intensity transverse field coordinate xmin at the right field edge or margin of the object field 5 emerges. The associated intensity I(xmin) is Imin. Subsequently, in an illumination channel identification step 45, at least one illumination channel 16i is identified, in which a variation of a marginal trimming or cut off of the illumination light partial beam 16i, which is guided thereover, at the respective pupil facet 29 leads to an increase in an illumination intensity I(xmin) at the minimum intensity transverse field coordinate xmin. This illumination channel identification can be carried out by measuring the respective I(x) variation of the respective illumination channel 16i when actuating the tilt actuator 31 of the field facet 25 that belongs to this illumination channel 16i, which, in principle, can be carried out for all illumination channels 16i from a metro-logical point of view. In so doing, it is possible to measure individual illumination channels 16i, with all other illumination channels 16i then being shadowed. Alternatively, a corresponding I(x) variation may also be effectuated by simulating the light guiding conditions of the respective illumination light partial beam 16i over the illumination channel 16i. For the illumination channels 16i, for which the illumination channel identification step 45 was successful, there subsequently is, in an alignment step 46, an alignment of the respective field facet 25 of the identified illumination channel 16i for the purposes of increasing the illumination intensity of the associated illumination light partial beam 16i, at the minimum intensity transverse field coordinate xmin. Aligning is carried out by way of an appropriate actuation of the tilt actuator 31 of the at least one identified illumination channel 16i. The result of this prescription method with steps 44 to 46 is shown by FIG. 15 in an exemplary manner. As a result, the minimum illumination intensity Imin,k is raised when compared with the initial minimum illumination intensity Imin (cf. FIG. 14). Imin,k can be greater than Imin by 1 percent, 2 percent, 3 percent, 5 percent, 10 percent or a higher percentage. On account of the new alignment of the field facets 25 in alignment step 46, a dependence of an illumination intensity IGes,k of the entire illumination light 16 over the field height x has changed in comparison with the original intensity distribution IGes,0 such that, in the example of FIG. 15, the prescribed minimum illumination intensity Imin,k now is present not only at the right field edge or margin, i.e. at the minimum intensity transverse field coordinate xmin, but also at the left field edge or margin. In the method described above, the start is at the global intensity minimum over the field height x, which emerges from the superposition of the illumination intensities of all illumination light partial beams 16i over the field height x, i.e. over the transverse field coordinate. In the prescription method, it is possible to identify exactly one illumination channel 16i or it is possible to identify a plurality of illumination channels 16i. It is possible to identify all illumination channels 16i in which the desired illumination light intensity increase at the minimum intensity transverse field coordinate xmin emerges by varying the marginal trimming or cutting off of the illumination light partial beam 16i, guided thereover, at the pupil facet 29. Additionally, it is also possible to carry out a further illumination channel identification step and a further facet alignment step during the prescription method explained above. These further identification and alignment steps can be carried out parallel to or sequentially with the identification and alignment steps explained above. In the further illumination channel identification step, at least one illumination channel 16i is identified, in which a variation of a marginal trimming or cut off of the illumination light partial beam 16i, which is guided thereover, at the pupil facet 29 leads to an increase in a minimum illumination intensity Imin,i of this illumination light partial beam 16i over the transverse field coordinate, i.e. over the field height x. In FIG. 14 and using a dashed line, a dependence of an intensity curve Ii of an illumination intensity of an illumination channel 16i identified thus is plotted in relative intensity units. This identification is once again carried out by way of a measurement with the aid of the sensor unit 40, within the scope of which all other illumination channels 16i are shadowed. In the case of this intensity curve Ii over the field height x, the illumination channel intensity Ii is not minimal at the minimum intensity transverse field coordinate xmin, but at the other, left field edge or margin, i.e. at the coordinate xmin,i. The minimum intensity of this illumination channel 16i at the individual minimal coordinate xmin,i is denoted by Imin,i in FIG. 14. In reality, Imin,i is naturally many orders of magnitude smaller than Imin. However, as already mentioned above, the curve Ii is plotted in relative intensity units in FIG. 14 for elucidation purposes. After this further illumination channel identification step, there is an alignment of the field facet 25 associated with this illumination channel 16i in the further facet alignment step for the purposes of increasing the minimum illumination intensity Imin,i of this illumination channel 16i by virtue of the corresponding trimming variations being set at the associated pupil facet 29 of the illumination channel 16i. The alignment in the alignment steps is carried out by way of the tilt or correction actuators 31 in accordance with the exemplary embodiments described above. Thus, the field facets 25 can be tilted dynamically for alignment purposes. Alternatively, such an alignment can also already be effectuated statically in the basic design of the field facet mirror 19 such that field facets 25 that are tiltable via tilt actuators are not mandatory for carrying out the methods described above. The result of the further illumination channel identification step and also of the further alignment step is an increase in the illumination intensity, not only in the region of the minimum intensity transverse field coordinate xmin but also in the region of other field coordinates that may be important in respect of their possibly low illumination intensity; i.e., in the region of the left field coordinate xmin,i that lies opposite to the minimum intensity transverse field coordinate xmin in the example presented in FIGS. 14 and 15. Accordingly, carrying out the further illumination channel identification and facet alignment steps ensures that, when lifting the illumination intensity to the intensity Imin,k at the minimum intensity transverse field coordinate xmin with the aid of steps 44 to 46 explained above, the illumination intensity is not undesirably lower than Imin,k at another field coordinate. During the projection exposure with the aid of the projection exposure apparatus 1, an illumination geometry is initially set with the aid of the setting method explained above. Then, at least one part of the reticle 7 in the object field 5 is imaged onto a region of the light-sensitive layer onto the wafer 13 in the image field 11 for the lithographic production of a microstructured or nanostructured component, in particular of a semiconductor component, for example of a microchip. In this case, the reticle 7 and the wafer 13 are moved in a temporally synchronized manner in the y-direction continuously in scanner operation.
	claims	1. A system comprising:a plurality of moulding sections located in a physical space, wherein the plurality of moulding sections comprise a plurality of sensors configured to obtain first sensor data, wherein the first sensor data corresponds to a location of an object;at least one electrical conductor affixed at least partially within one or more of the plurality of moulding sections;one or more joints between various ones of the plurality of moulding sections, at least some of the one or more joints arranged to preserve electrical conductivity, via the at least one electrical conductor between the various ones of the plurality of moulding sections; andat least one smart floor tile located in the physical space, wherein:the at least one electrical conductor is communicably connected to the at least one smart floor tile,the at least one smart floor tile comprises a sensor configured to obtain second sensor data,the second sensor data corresponds to the location of the object,the first sensor data and the second sensor data are used to perform smart building control,a determination is made whether the first sensor data and the second sensor data align, anda control action is performed in response to determining the first sensor data and second sensor data differ. 2. The system of claim 1, wherein at least one of the at least one electrical conductors is positioned in electrical communication with a power supply. 3. The system of claim 1, wherein at least one of the at least one electrical conductors is configured for wired data transmission. 4. The system of claim 1, wherein at least one of the at least one electrical conductors is substantially enclosed within one or more of the plurality of moulding sections. 5. The system of claim 1, wherein at least one of the at least one electrical conductors comprises an insulated electrical wiring assembly. 6. The system of claim 1, wherein at least one of the at least one electrical conductors comprises a communications cable assembly. 7. The system of claim 1, further comprising a fire-retardant backing layer positioned between at least one of the plurality of moulding sections and a wall. 8. The system of claim 1, wherein various ones of the plurality of moulding sections are constructed using one or more materials selected from: solid wood, vinyl, rubber, fiberboard, and wood composite materials. 9. The system of claim 1, wherein at least one of the plurality of moulding sections comprises one or more of: a baseboard, a shoe moulding, a crown moulding, a door casing, and a window casing. 10. The system of claim 1, further comprising one or more electrical conductors affixed at least partially within one or more of the plurality of moulding sections. 11. A system comprising:a plurality of moulding sections located in a physical space, wherein the plurality of moulding sections comprise a plurality of sensors configured to obtain first sensor data, wherein the first sensor data corresponds to a location of an object;at least one communication cable affixed at least partially within one or more of the plurality of moulding sections;one or more joints between various ones of the plurality of moulding sections, at least some of the one or more joints arranged to preserve communications connectivity, via the at least one electrical conductor between the various ones of the plurality of moulding sections; andat least one smart floor tile located in the physical space, wherein:the at least one electrical conductor is communicably connected to the at least one smart floor tile,the at least one smart floor tile comprises a sensor configured to obtain second sensor data,the second sensor data corresponds to the location of the object,the first sensor data and the second sensor data are used to perform smart building control using directional occupancy sensing,a determination is made whether the first sensor data and the second sensor data align, anda control action is performed in response to determining the first sensor data and second sensor data differ. 12. The system of claim 11, wherein at least one of the at least one communication cables comprises a fiber optic cable. 13. The system of claim 12, wherein at least one of the one or more joints comprises a fiber optic relay. 14. The system of claim 11, wherein at least one of the at least one communication cables is configured for wired data transmission. 15. The system of claim 11, wherein at least one of the at least one communication cables is substantially enclosed within one or more of the plurality of moulding sections. 16. The system of claim 11, further comprising a fire-retardant backing layer positioned between at least one of the plurality of moulding sections and a wall. 17. The system of claim 11, wherein various ones of the plurality of moulding sections comprise a fire-retardant material.
050330748	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT It has recently been discovered, in the course of development of the present invention, that there is a source of significant secondary radiation found in known microfocus projection radiography apparatus which is sufficient to account for the observed shadow anomaly. The source of this secondary radiation is shown in FIG. 3, in which like features to those in FIGS. 1 and 2 are designated by the same reference numerals. In FIG. 3, article 10 is disposed between focal point 1 and film 6 at a position relative to each selected to produce the desired degree of magnification. Primary radiation 2 directed toward article 10 produces a magnified image on film 6, shown as two regions, 34 and 36. Secondary radiation, as 30a and 30b, is produced when primary radiation 2 from x-ray focal spot 1 penetrates the tube head housing (typically fabricated of brass), not shown, and the window housing (typically of aluminum), not shown, and is re-radiated (as fluorescent radiation) and/or scattered, generating the secondary radiation. Some of the secondary radiation is directed toward object 10 from points, as 32, separated from primary focal spot 1. Some of the secondary radiation, as 30b, reaches film 6, independently of the primary radiation causing darkening of the film (out of focus fog), except where article 10 prevents the secondary radiation from reaching the film. This is analogous to a shadow cast by the object. The secondary source darkening at region 34 overlaps the image from primary radiation 2 and causes a shadow to appear at the edge of the image similar to that shown as shadow 7 in FIG. 1. The secondary source darkening is readily observed only where it is superimposed on the intended projection image of article 10 produced by the primary beam. Elsewhere on film 6 the darkening from primary radiation 2 is too intense for the additional darkening from the secondary radiation to be noticeable. Secondary radiation 2 is blocked by article 10 from reaching film 6 at region 36 of the image. Thus, the image in region 36 exhibits no shadow. Several factors contribute to the observation of the shadow anomaly, including the imaging geometry of the microfocus projection radiography system, the degree of magnification, the size and material composition of the object, the size and intensity of the secondary source, and operation of the apparatus at low accelerating potentials where the second source has a significant contribution. However, it is important to realize that the secondary radiation is always present, even when the shadow anomaly is not readily observable, and can significantly degrade the signal-to-noise ratio, which is the major limiting factor in flaw detection sensitivity (the ability to distinguish local inhomogeneities from the background image). For example, placing the object to be imaged on the centerline between the x-ray source and the film will minimize the shadow observed, but the secondary radiation still causes darkening of the film and reduces image contrast. Similarly, the shadow anomaly is not apparent in the imaging of large complex-shaped objects, but the secondary radiation still compromises the signal-to-noise ratio, reducing image contrast. Thus, it was determined tat suppression of the source of secondary radiation was essential to achieving the required flaw detection sensitivity for nondestructive evaluation using microfocus projection radiography. Such suppression has been achieved by the use of a collimating device according to the invention, for example by its addition to known microfocus projection radiography apparatus. The steps leading to the discovery of the cause of the shadow anomaly, and to the solution to the problem, are described in further detail below. Shown in FIG. 4 is a cross sectional view of anode assembly 40 of a typical microfocus x-ray system, for example model HOMX 161A, manufactured by IRT Corporation, San Diego, Calif. Anode assembly 40 includes tube head or anode body 42 with anode target 44 container therein. Entire assembly 40 is enclosed by means not shown and a vacuum environment, typically about 1.2.times.10.sup.-6 Torr, is maintained therein. Aluminum bushing 46 is positioned within opening 48 in anode body 42 to hold window O-ring 50 in place. Beryllium window 52 is disposed against window O-ring 50 and aluminum bushing 46, and is held in place by a window cap (not shown) and by the external pressure exerted against beryllium window 52 due to the internal vacuum environment. X-rays which are emitted from anode target 44 upon bombardment from a directed electron beam and which enter opening 48 of anode body 42 define a radiation path through the opening and toward the sample and the film. The x-rays are directed, in typical prior art apparatus, both toward aluminum bushing 46 and through beryllium window 52. The term "path" or "radiation path", as used herein and in the accompanying claims, is intended to mean the region in space through which the primary radiation from focal point 1 passes through opening 48 toward the sample and toward the imaging means. In such prior art apparatus an external collimator, as external collimator 54 in FIG. 4, typically is provided to attenuate extraneous radiation outside of a diameter slightly less than that of the window opening. Thus, only radiation passing through aperture 56 of external collimator 54 reaches the sample. A portion of the rays passing through aperture 56 are then absorbed by the sample, shown as article 10 in FIGS. 2 and 3, the remaining transmitted portion exposing the x-ray film, shown as film 6 in FIGS. 1-3. In such prior art apparatus, x-rays striking aluminum bushing 46 are re-radiated and/or scattered, forming secondary sources of radiation, shown as secondary radiation 30a and 30b in FIG. 3. External collimator 54, as described in more detail below, is not sufficient to eliminate all of the secondary radiation. Thus some secondary radiation passes through aperture 56, causing the shadow anomaly, as illustrated in FIGS. 1 and 3. Also shown in FIG. 4 is internal collimator 60 installed within aluminum bushing 46 between anode target 44 and beryllium window 52. As used herein and in the accompanying claims, the term "internal collimator" is intended to mean a collimator positioned within the anode body, as body 40, between the focal point, as focal point 1, and the window, as beryllium window 52. The geometry and positioning of collimator 60 is selected to preclude any of the x-rays emitting from anode target 44 from striking aluminum bushing 46, or any other material within opening 48 which could generate secondary sources of radiation, which would then pass through beryllium window 52 and aperture 56, causing shadow anomalies on the x-ray film image. Collimator 60, shown also in FIGS. 5 and 6, is preferably formed from tungsten, but can be formed from any material having an atomic number, according to the periodic table of the elements, higher than the atomic number of the elements in the housing which are exposed to the radiation emitted by anode target 44. For example, bushing 46 is typically formed from aluminum, anode body 42 is typically formed from brass. Thus, the collimator is preferably formed from a material having a higher atomic number than those of aluminum and the elements included in the brass. The term "a material having an atomic number", as used herein with reference to the internal collimator, is intended to include elemental materials, alloys, composites, etc. wherein all of the component elements have the required high atomic numbers as described above or are present in amounts resulting in negligible contribution of secondary radiation on exposure to primary radiation in the above-described system. Although it is intended that the invention disclosed herein include a collimator having a non-tapered aperture, it is much preferred that the aperture be tapered, the maximum angle of taper (from the collimator axis) following closely the maximum angle at which primary radiation will directly strike the x-ray window. Collimator 60, as shown in FIGS. 4-6, includes tapered aperture 62 such that primary x-ray beam 2 passing through aperture 62 of collimator 60 will not strike any material within opening 48 except beryllium window 52 (FIG. 4), and such that x-ray beam 2 passes through the maximum area of beryllium window 52 to provide the maximum "field of view" for exposure of the sample to primary radiation. Taper 64 of aperture 62, as illustrated in FIG. 6, is 15.degree. but can be any taper such that primary x-ray beam 2 passing through collimator 60 will not generate secondary sources of x-rays and yet be sufficient to expose the sample to primary radiation, permitting detection of defects within the sample on x-ray film 6. Various taper configurations are also within the scope of the invention, for example a collimator having a different degree or direction of taper at each end. Collimator 60, as shown in FIGS. 4-6, typically extends only a short distance into opening 48, and is conveniently a separate component from bushing 46 and is concentric therewith. Alternative arrangements, however, are possible within the scope of the invention. In one alternate embodiment, for example, the internal collimator extends the full length of the bushing; in another, the bushing incorporates the internal collimator; in yet another, the bushing is replaced by an untapered or tapered internal collimator which extends the entire or a partial length of opening 48; and in still another, the collimator may be positioned between the focal point and the bushing, and not necessarily in contact with it. The collimator aperture, and consequently the path of the primary radiation passing through the aperture, is typically circular in cross-section, but other configurations are within the scope of the invention. Further, the invention is not limited to use with x-ray film, but is effective for improving imaging with any detection system which can be used with the microfocus x-ray system. The shadow anomaly cannot be explained by the imaging situation alone. In fact, an attempt to explain the shadow by modeling the phenomenon using x-ray attenuation data and a representative imaging geometry led to the discovery of its source. A brief description of that attempt follows. A representative imaging situation was modeled using x-ray attenuation data for ceramic bars radiographed at a 10.times. magnification in the above-described IRT Corporation model HOMX 161A microfocus x-ray system. In the imaging geometry shown in FIG. 2, the outer edge of bar 11 presents a shorter x-ray path length than does the main body of the bar. A small change in x-ray path length through the body has a large effect on attenuation for the first few half-value layers, and then attenuation becomes nearly constant in the main body. The term "half value layers", as used herein, is intended to mean that thickness of material which reduces the transmitted x-ray intensity by a factor of 2. The modeled data based on this geometric effect, however, conflicted with the results observed on radiographs obtained using the above-described microfocus x-ray system (without the internal collimator). The width of the principal shadow anomaly was dimensionally greater, by a factor of 3, than that which could be expected based on geometry and x-ray attenuation effects alone. Since the observed experimental results could not be explained considering the imaging physics of the primary x-ray source, it was realized that the most likely cause of the shadow anomaly was extraneous radiation from another source. In the past, the possibility of a second source of radiation had been considered; however, it was concluded that scattered x-rays, as a second source from the tube head, were not sufficiently intense to produce the observed shadow anomaly. Recent data on attenuation for certain materials being imaged (silicon nitride ceramics) revealed that, for typical film imaging conditions, only 0.3 percent of the primary radiation exposed the film. Therefore, even a weak second source of radiation could contribute a significant amount of exposure to the image, resulting in excess darkening. An experiment was conducted in which a thin lead sheet (0.005 inches) was placed against the bars (0.125 inches thick) between the bars and the x-ray source. The sheet contour matched that of the bars. Thus, the transmitted primary radiation directed toward the bars was heavily attenuated, but the imaging geometry was not significantly changed. The shadow anomaly remained, confirming the existence of another source of radiation. Contact exposures (images of the tube head made by placing the film directly in front of the tube head) were made of the tube head and x-ray window assembly with high speed instant photography film. The first image revealed that the x-ray window port appeared to be about twice its actual size, indicating that primary radiation from the x-ray focal spot was penetrating the brass tube head housing and aluminum window assembly and producing secondary radiation in the form of re-radiation and/or scatter, effectively producing a second source. The imaging geometry and nominal size of the second source is consistent with the observed shadow anomaly. Having discovered the cause of the shadow anomaly and defined the origin of the second source of radiation, the solution to the problem could now be addressed. Study of the x-ray tube head revealed that the collimation of the beam in the design of the apparatus was not adequate to suppress extraneous radiation. A series of experiments were conducted by placing collimators made from 1/8 inch thick lead sheet with holes of decreasing diameter outside the window assembly of the above mentioned IRT model HOMX 161, replacing the external collimator provided with the apparatus. A collimator with a 3/16 inch diameter aperture was found to eliminate the shadow anomaly. The compromise was that the field of view (projection) was reduced. The standard lead collimator, as external collimator 54, that was supplied with the x-ray system is located outside the window assembly, but is ineffective in eliminating secondary radiation because its aperture is too large. For a collimator to be effective in suppressing the shadow anomaly it must limit radiation emanating from the x-ray target toward the sample to only that part of the primary beam directly striking the beryllium window. It was determined that the discovered second source of radiation may be effectively eliminated by positioning a collimator within opening 48 in tube head 42, for example within bushing 46 as shown in FIG. 4, and as close to the x-ray source, as anode target 44, as practicable. Also, by placing the collimator inside the opening and closer to the x-ray focal spot, the radiation from the second source can be minimized without loss of field of view (projection). A cross-sectional illustration of internal collimator device 60 is shown in FIGS. 4, 5, and 6. Its tapered aperture is designed to limit the primary radiation directed toward the sample to that portion of the beam directly striking x-ray window 52. Since primary rays do not reach the brass tube head and aluminum bushing assembly, these elements are prevented from becoming sources of secondary radiation. Brass and aluminum have low atomic numbers, and low atomic number elements are known to cause re-radiation and scattering. Tungsten is therefore a preferred internal collimator material because its high atomic number makes it a superior attenuator, and because it has a low vapor-pressure at the temperatures and vacuum environment (1.2.times.10.sup.-6 Torr) experienced within the system. External collimator 54 is typically fabricated from lead, which also has a high atomic number. Thus external collimator 54 will not significantly scatter the primary radiation, and may be removed or may remain in place. The x-ray window used is typically beryllium. This low atomic number element could be a second source of radiation, but its extreme thinness (0.003 inches thick) generates negligible secondary radiation. Experiments comparing beryllium (atomic number 4) and aluminum (atomic number 13) x-ray windows showed that neither material had a discernible effect on the observed shadow anomaly. Alternate materials, i.e. those made with high atomic number elements consistent with the tube head environment, may be used to fashion the collimator. Also, as described above, the size and shape of the collimator may be changed without significantly varying from the concept. The x-ray collimating device described herein suppresses second source radiation in microfocus projection radiography systems, effectively eliminating shadow anomalies observed in microfocus projection radiographs. The device significantly improves flaw detection sensitivity in nondestructive evaluation of materials and components by reducing the contribution of unwanted image noise. Thus, the device significantly increases the signal to noise ratio of the image-forming radiation and permits unambiguous interpretation of microfocus projection radiographs cf the materials and components. While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined by the appended claims.
	summary
	claims	1. An X-ray detector, comprisinga scattered radiation grid; anda planar converter element including a first surface and a second surface, the scattered radiation grid and the planar converter element being arranged in a stack arrangement,the planar converter element includinga first electrode embodied on the first surface,a pixelated second electrode including two adjacent first electrode elements, wherein the two adjacent first electrode elements include a first width and a first length and wherein the two adjacent first electrode elements are embodied on the second surface opposite the first surface, andthe scattered radiation grid includinga grid wall with a wall thickness along a boundary between the two adjacent first electrode elements, the grid wall being arranged substantially perpendicular on the first surface and, in a projection, substantially parallel to a direction of incidence of radiation and to a surface normal of the first surface, the grid wall at least partially overlapping the two adjacent first electrode elements, wherein a second electrode element with a second width and a second length is embodied on the second surface, outside the projection. 2. The X-ray detector of claim 1, wherein a first planar extension of one of the two adjacent first electrode elements is relatively greater than a second planar extension of the second electrode element. 3. The X-ray detector of claim 2, wherein at least one ofthe first width is relatively greater than the second width andthe first length is relatively greater than the second length. 4. A medical device comprising:the X-ray detector of claim 2. 5. The X-ray detector of claim 1, wherein at least one ofthe first width is relatively greater than the second width andthe first length is relatively greater than the second length. 6. The X-ray detector of claim 1, wherein one of the two adjacent first electrode elements comprises a first effective pixel area, defined by gradients of field lines in regions bounding at least one of an adjacent first electrode element and an adjacent second electrode element. 7. The X-ray detector of claim 6, wherein the second electrode element comprises a second effective pixel area, defined by gradients of field lines in regions bounding at least one of the adjacent first electrode element and the adjacent second electrode element. 8. The X-ray detector of claim 7, wherein the first effective pixel area and the second effective pixel area are of equal size. 9. The X-ray detector of claim 7, wherein the first effective pixel area and the second effective pixel area are of different sizes. 10. The X-ray detector of claim 9, wherein a surface area of the first effective pixel area and a surface area of the second effective pixel area differ by a maximum of 30 percent. 11. The X-ray detector of claim 7, wherein an extension of the first effective pixel area, at least one of along the first width and along the first length, minus an overlapping region of the first electrode element with the grid wall in a substantially perpendicular projection and an extension of an adjacent second effective pixel area along a second width or along a second length, are of equal size. 12. The X-ray detector of claim 7, wherein a first effective pixel area is defined by shading of incident radiation by the scattered radiation grid. 13. The X-ray detector of claim 12, wherein a first effective pixel area and a second effective pixel area are of equal size. 14. The X-ray detector of claim 13, wherein the first effective pixel area and the second effective pixel area are of different sizes. 15. The X-ray detector of claim 6, wherein the first effective pixel area is defined by shading of incident radiation by the scattered radiation grid. 16. The X-ray detector of claim 15, wherein the first effective pixel area and a second effective pixel area are of equal size. 17. The X-ray detector of claim 15, wherein the first effective pixel area and a second effective pixel area are of different sizes. 18. The X-ray detector of claim 6, wherein an extension of at least one of a first effective pixel area and a second effective pixel area is based on a relationship of an extension a grid opening of the scattered radiation grid and a joint number of the two adjacent first electrode elements and the second electrode elements, along the extension of the grid opening of the scattered radiation grid. 19. The X-ray detector of claim 1, wherein an extension of one of the two adjacent first electrode elements is based on a sum of the first width or the first length and an extension between two adjacent first electrode elements or between the one of the two adjacent first electrode elements and an adjacent second electrode element. 20. The X-ray detector of claim 1, wherein a shade-capture structure is arranged between the scattered radiation grid and the planar converter element. 21. The X-ray detector of claim 20, further comprising a lighting unit arranged between the scattered radiation grid and the first electrode. 22. A medical device comprising:the X-ray detector of claim 21. 23. A medical device comprising:the X-ray detector of claim 1. 24. The X-ray detector of claim 1, wherein the second electrode element comprises a second effective pixel area, defined by gradients of field lines in regions bounding at least one of the two adjacent first electrode elements and an adjacent second electrode element.
	abstract	A collimator for adjusting an X-ray beam includes: an up-and-down adjustment mechanism; a left-and-right adjustment mechanism, a supporting member; and an adjusting plate connected with the supporting member. The up-and-down adjustment mechanism comprises first rotating nuts, up-and-down moving leading screws threadedly connected with the first rotating nuts, and upper and lower sliding stops located in the supporting member. Each of the leading screws is connected with the upper and lower sliding stops to drive the upper and lower sliding stops, respectively, to vertically move. The left-and-right adjustment mechanism comprises second rotating nuts, horizontally moving leading screws connected with second rotating nuts, and left and right sliding stops located in the supporting member. Each of the horizontally moving leading screws are connected with the left and right sliding stops to drive the left and right sliding stops, respectively, to horizontally move.
	abstract	In a specimen analyzing apparatus such as a transmission electron microscope for analyzing the structure, composition and electron state of an observing specimen in operation by applying external voltage to the specimen to be observed, a specimen support (mesh) including a mesh electrode connectable to external voltage applying portions of the specimen and a specimen holder including a specimen holder electrode connectable to the mesh electrode and current inlet terminals as well are provided. Voltage is applied externally of the specimen analyzing apparatus to the external voltage applying portions of the specimen through the medium of the specimen holder electrode and mesh electrode.
058728244	abstract	A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis.. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.
	description	This application claims the benefit of U.S. Provisional Application No. 61/023,914, filed Jan. 28, 2008, which is incorporated herein by reference in its entirety. The present invention relates to a method of installing reactors, and the tools used to perform the same, and in particular, to a method of installing a reactor unit suitable for use in a reactor tube, and the tools used to perform the same. Reactors, such as those used in the field of surface catalytic reactions and heat exchange, can fit within a reactor tube, which can transfer heat from the reactor tube to the interior of the tube or the reactor unit contained therein, or from the interior of the tube or reactor unit to the reactor tube. One example of a reactor unit is a stackable structural reactor, or SSR. One type of SSR is described in U.S. Pat. App. Pub. No. 2008/0145284. Other examples of reactor units include the disclosures in U.S. Pat. App. Pub. Nos. 2007/0025893, 2006/0263278, 2006/0245982, 2006/0245981, 2006/0230613, 2006/0228598, 2006/0019827 and 2006/0008414 and U.S. Pat. Nos. 7,150,099 and 6,920,920. The reactor installation tools described herein can be used with any style of reactor, such as a cylindrical-shaped tube reactor as shown in the above-cited applications and patents. The reactors shown in the above-cited applications and patents, and others reactors of the prior art, can occupy substantially all of the space within a reactor tube and/or press firmly against the interior wall of the reactor tube. Installation of reactors can cause damage, such as denting portions of the reactors, for example, the fins of a reactor. Other damage can be caused, for example, scratching or bending the reactors, which can negatively affect performance, such as the heat transfer or reaction rate. Thus, there is a need to install a reactor or reactor unit in a reactor tube without damaging the reactor. The present inventors have found that the use of the reactor tools described herein can avoid damage to a reactor. A reactor installation tool including a movable assembly having an exterior post unit, an upper manifold and a reactor sleeve attachment means. The upper manifold can be attached to the exterior post unit. The reactor installation tool can further include a fixed assembly having a center post, a lower manifold and an expandable clamping unit. The lower manifold and expandable clamping unit can be attached to the center post. A reactor installation tool including a fixed assembly having an expandable clamping unit. The expandable clamping unit can include a clamp shoe for engaging a portion of the inner surface face of a hollow reactor tube, such that when the clamp shoe engages the inner surface face of the hollow reactor tube, the expandable clamping unit releasably secures the fixed assembly to the hollow reactor tube. The reactor installation tool can further include a movable assembly slidably attached to the fixed assembly, wherein the movable assembly can include a reactor sleeve attachment means for releasably securing the movable assembly to a hollow reactor sleeve, the reactor sleeve having an outer diameter that is less than the inner diameter of the hollow reactor tube, such that the reactor sleeve can slide within the hollow reactor tube. A reactor installation tool including an expandable clamping unit for releasably securing the reactor installation tool to a reactor tube, wherein the reactor tube has an inner diameter and an inner surface face. The reactor installation tool can further include a reactor sleeve attachment means for releasably securing the reactor installation tool to a reactor sleeve, wherein the reactor sleeve has an outer diameter, and the outer diameter of the reactor sleeve is less than the inner diameter of the reactor tube. A method of installing a reactor unit including the steps of providing a reactor installation tool, wherein the reactor installation tool can include an expandable clamping unit and a reactor sleeve attachment means; releasably attaching the reactor installation tool to a reactor sleeve using the reactor sleeve attachment means; lowering the reactor sleeve into a reactor tube; engaging the expandable clamping unit to releasably secure the reactor installation tool to the reactor tube; raising the reactor sleeve attachment means to raise up the reactor sleeve in the reactor tube; releasing the expandable clamping unit from the reactor tube, and removing the reactor installation tool from the reactor tube. A method of installing a reactor unit including the steps of providing a reactor installation tool, wherein the reactor installation tool can include a fixed assembly and a movable assembly slidably attached to the fixed assembly, the fixed assembly having an expandable clamping unit; releasably attaching the movable assembly of the reactor installation tool to a reactor sleeve, the reactor sleeve being loaded with a reactor unit; positioning the reactor sleeve in a reactor tube; engaging the expandable clamping unit to releasably secure the fixed assembly to the reactor tube; extracting the reactor sleeve from enclosing the reactor unit by adjusting the movable assembly relative to the fixed assembly, wherein the extracted reactor sleeve is unloaded and the reactor unit is positioned in the reactor tube, and removing the reactor installation tool from the reactor tube. As used herein, when a range such as 5-25 is given, this means at least 5 and, separately and independently not more than 25. Materials of construction for the reactor installation tool 1, or any component or part thereof, can include any suitable material, for example, metal, non-ferrous metal, metal foil, steel, stainless steel, alloys, non-metals such as plastics or glass, ceramic, or combinations thereof. FIG. 1 shows a reactor installation tool 1. The reactor installation tool 1 includes a fixed assembly 10 and a movable assembly 50. The fixed assembly 10 can be attached to the movable assembly 50 such that the movable assembly 50 can be adjusted relative to the fixed assembly, for example, the movable assembly 50 can slidably move up and down the vertical axis of the fixed assembly 10. The fixed assembly 10 can include a lower manifold 11, a center post 20 and an expandable clamping unit 30. The movable assembly 50 can include an upper manifold 51, an exterior post unit 60 and a reactor sleeve attachment means 70. The fixed assembly 10 and movable assembly 50 are described in more detail below. The reactor installation tool 1 can be used to install one or more reactor units 3 in a reactor tube 4. As shown in FIG. 1, the reactor installation tool 1 is attached to a reactor sleeve 2 loaded with multiple reactor units 3 positioned in a stacked arrangement. The reactor sleeve 2 can be a tube, such as a hollow cylinder, of any diameter or length for accommodating one or more reactor units 3, which can be strung together or arranged in a stacked series in the reactor sleeve 2. The reactor sleeve 2 is described in more detail below with respect to FIGS. 15 and 16. In one example, the reactor sleeve 2 can be loaded with one reactor unit 3, wherein one or more reactor units 3 can be attached to the reactor unit 3 loaded in the reactor sleeve 2. The additional reactor units 3 attached to the loaded reactor unit 3 can hang freely outside of the interior portion of the reactor sleeve 2. As will be described below, such an arrangement of reactor units 3 can be installed in a reactor tube 4 such that the freely hanging reactor units 3 are positioned in the reactor tube 4 below the loaded reactor unit 3 being held in the reactor sleeve 2. The reactor sleeve 2 can be removed or extracted from the reactor tube 4 to leave a stacked arrangement of reactor units 3 and an unloaded reactor sleeve 2, As shown in FIG. 1, the reactor sleeve 2 loaded with one reactor unit 3 has been lowered in a reactor tube 4 such that the bottom reactor unit 3 of the stack of reactor units 3 rests on the bottom of the reactor tube 4, such as the pedestal. The top reactor unit 3 loaded in the reactor sleeve 2 is positioned near the top portion of the reactor tube 4. In this position, the reactor installation tool 1 is directly above the reactor tube 4 in line with the vertical axis of the reactor tube 4. The movable assembly 50 of the reactor installation tool 1 can be raised and lowered with the use of a hoist or other similar device as known in the art. A hoist can also be used for lowering and raising the tool 1 and/or reactor sleeve 2 in and out of a reactor tube 4. As shown in FIG. 1, the reactor installation tool 1 is in the seated or lowered position wherein the reactor sleeve 2 positioned in a reactor tube 4, encloses at least one reactor unit 3 or portion thereof. As shown in FIG. 2, the reactor installation tool 1 is in the raised or unloaded position wherein the one or more reactor units 3 loaded into the reactor sleeve 2 have been removed and are positioned in the reaction tube 4. Transitioning from the seated position to the unloaded position can be achieved by lifting up on the movable assembly 50 of the reactor installation tool 1, which allows the movable assembly 50 to be adjusted relative to the fixed assembly 10. Lifting up on the movable assembly 50 can raise the reactor sleeve 2 within the reactor tube 4 or extract the reactor sleeve 2 from the reactor tube 4. Preferably, lifting up of the movable assembly 50 extracts or removes the one or more reactor units 3 contained within the reactor sleeve 2 such that the one or more reactor units 3 remain within the reactor tube 4. The method of installing a reactor unit 3 is described in more detail below. FIG. 3 shows another cross-section view of a reactor installation tool 1 attached to a reactor sleeve 2 in an unloaded state, no reactor units 3 contained therein. As shown, the fixed assembly 10 and movable assembly 50 of the reactor installation tool 1 are slidably attached to one another such that the movable assembly 50 can travel or be adjusted a set distance (d3), such as a stroke length, relative to the fixed assembly 10. For example, distance (d3) can be measured from the bottom of the expandable clamping unit 30 to the top of the locking hub 72 of the reactor sleeve attachment means 70. Distance (d3) can be set at any length as desired, for example, distance (d3) can be matched to the reactor sleeve 2 length (CO, or a distance greater than the reactor sleeve 2 length to ensure lifting the movable assembly 50 the entire distance (d3) will extract the reactor sleeve 2 from enclosing one or more reactor units 3 secured therein. Extracting the reactor sleeve 2 from the one or more reactor units 3 contained therein allows a user to install a desired number of reactor units 3 in a reactor tube 4. Thus, as described below, the dimensions of the reactor sleeve 2 can be selected according to the size and number of reactor units 3 to be contained therein, or the size and dimensions of the reactor tube 4 being used, which may vary depending on the application, for example heat exchange and/or a catalytic reaction. Turning to FIG. 4, an exploded cross-section view of the upper manifold 51 of a reactor installation tool 1 is shown. The upper manifold 51 can include a lifting means 52, such as an eye bolt or a hook. The lifting means 52 can be used to attach the upper manifold and/or reactor installation tool 1 to a device for raising and lowering, such as a hoist or similar mechanical machine. The lifting means 52 can be secured to the upper manifold 51 or portion thereof by any convention means, such as by welding or a male-female threaded attachment. The upper manifold 51 can include a base member 53. The base member 53 can be in the form of a circular disc having any desirable diameter or length, wherein the base member 53 has an outer surface face 53a. The base member 53 can have recesses or cavities 54, having any size or shape, for receiving one or more posts of the exterior post unit 60, the lifting means 52 and stop block 56. The one or more posts of the exterior post unit 60 can be attached to the base member 53, for example, fixedly attached by welding, or relesably attached with a male-female threaded arrangement. Thus, the recesses or cavities of the base member 53 can be used to rigidly mount the exterior post unit 60. The upper manifold 51 can further include an upper manifold guard 55. The upper manifold guard 55 can be attached to the outer surface face 53a of the base member 53, for example, by welding. The upper manifold guard 55 can be a hollow cylinder for enclosing and protecting the stop block 56 and/or any electrical, pneumatic or hydraulic components, such as pressurized air supply lines or hose coils 57. The upper manifold guard 55 can have any suitable diameter and/or length depending on the size and shape of the stop block 56 and/or other components to be contained therein. As shown in FIG. 4, the upper manifold 51 can further include a stop block 56, such as an elongated shaft with one or more washers located along the length of the shaft, such at both the distal and proximal ends of the shaft. The stop block 56 can be used to rest the upper manifold 51 on the top face of the fixed assembly 10, for example the top face of the primary member 12. The stop block 56 can have a washer 58 at its proximal end for resting on the top face of the fixed assembly 10, thereby preventing the movable assembly 50 from moving downward. Turning to FIG. 5, a cross-section view of a 4-post exterior post unit 60 of a reactor installation tool 1 is shown. The exterior post unit 60 can include one or more posts, such as the 4-post arrangement as shown in FIG. 5, which can be spaced around a center post 20 of the fixed assembly 10 (not shown). The exterior post unit 60 can provide structural integrity and stability to the movable assembly 50. For example, the exterior post unit 60 can prevent or reduce the stress and/or force generated during installation of a reactor unit 3 from damaging the movably assembly 50. As shown, a 4-post arrangement stabilizes the movable assembly 50 during twisting, such as the twisting encountered by securing the reactor sleeve attachment means 70 to the reactor sleeve 2 as described below. The exterior post unit 60 can also act as a guide for raising and lowering the movable assembly 50 during installation of a reactor unit 3 in a reactor tube 4. The movable assembly 50 can be slidably attached to the fixed assembly 10, and thus the movable assembly 50 can move in the vertical direction along the vertical axis of the fixed assembly 10. For example, the posts of the exterior post unit 60 can pass though openings in the lower manifold of the fixed assembly 10 that guide the movable assembly 50 in a linear path as it is adjusted relative to the fixed assembly 10. The posts of the exterior post unit 60, fixed in position through the openings in the lower manifold 11 of the fixed assembly 10, ensure the movable assembly 50 does not bend or twist during movement. One end of the posts of the exterior post unit 60 can be attached to the base member 53 of the upper manifold 51 by any conventional method, such as a male-female threaded attachment or by welding. Although not shown in FIG. 5, the distal ends of the posts can be attached to the base member 53, for example the distal ends can mate with the through holes 54 in the base member 53. The proximal end of the posts can be attached to the reactor sleeve attachment means 70. The reactor sleeve attachment means 70 can include a centering spider plate 71 and a locking hub 72. The centering spider plate 71 can be a circular disc having cavities or through holes 74 for securing or receiving the one or more posts of the exterior post unit 60. The centering spider plate 71 can be fixedly attached to the one or more posts of the exterior post unit by welding, or with releasably attached by a threaded fitting as shown. FIG. 6 shows a top view of the centering spider plate 71 having ring 73 mounted on the top face of the centering spider plate. Radial cogs 75 can extend from the outer surface face 71a of the centering spider plate 71 and have a radiused design, for example, a radius similar to the outer circumference of the centering spider plate 71. The radial cogs 75 can be spaced about the outer surface face 71a, such as equally spaced along the centering spider plate 71 outer circumference. Preferably, the radial cogs 75 have a thickness equal to that of the centering spider plate 71. The radial cogs 75 can be an integral part of the centering spider plate 71, or alternatively, be secured to the outer surface face 71a by any conventional means, such as by welding. One or more radial cogs 75 can be arranged and/or sized to engage the radial cogs 6 of the reactor sleeve 2. In this regard, the exterior post unit 60 of the movable assembly 50 can be releasably secured or attached to the reactor sleeve 2 by the centering spider plate 71, as described below. The radial cogs 75 of the centering spider plate 71 can slide through the openings between the radial cogs 6 of the reactor sleeve 2 such that the reactor sleeve 2 can be moved upward along the vertical axis line of the movable assembly 50. Once the radial cogs 6 of the reactor sleeve 2 clear the top surface of the radial cogs 75 of the centering spider plate 71, and are positioned freely above the cogs 75, the reactor sleeve 2 can be twisted to adjust the radial cogs 6 of the reactor sleeve 2 to be directly above the radial cogs 75 of the centering spider plate 71. In this position the reactor sleeve 2 can rest on the centering spider plate 71 because the radial cogs 6 of the reactor sleeve 2 can rest directly on and be in contact with the radial cogs 75 of the centering spider plate 71, which also aligns the openings between both sets of radial cogs 6, 75. The method of twisting the reactor sleeve 2 can also be reversed in that the reactor installation tool 1 can be twisted to rotate the centering spider plate 71 to align the set of radial cogs 6, 75, which does not require the reactor sleeve 2 to be twisted. With both sets of radial cogs 6, 75 being in register, to ensure that inadvertent twisting or movement that may occur during installation does not dislodge the cogs from the stacked position, a locking hub 72 can be used to fix the cogs 6, 75 position during installation of a reactor unit 3. The locking hub 72, as shown in FIG. 5, can be a circular plate having locking cogs 77 that can be aligned with the open spaces between the radial cogs 75 of the centering spider plate 71. The locking hub 72 can be slidable along the posts of the exterior post unit 60 such that the locking hub 72 can be moved downward to position the locking cogs 77 between the radial cogs 75 of the centering spider plate 71. In the case the radial cogs 75 of the centering spider plate 71 are aligned with the radial cogs 6 of the reactor sleeve 2, the locking cogs 77 preferably are positioned further downward between the cogs 6 of the reactor sleeve 2. The locking hub 72 can be twisted to lock the reactor sleeve 2 and movable assembly 50 together to prevent rotation with respect to one another during installation. A pin can be inserted through a portion of the locking hub 72 and centering spider plate 71 to ensure the two components do not twist, rotate or disengage during installation. In this arrangement, the locking cogs 77 and pin prevent the reactor sleeve 2 and reactor installation tool 1 from twisting and thus the reactor sleeve 2 is releasably locked to the movable assembly 50 of the reactor installation tool 1. To separate the units, the locking hub 72 can be twisted and moved upward to slide the locking cogs 77 from the openings between the sets of radial cogs 6, 75. Twisting can detach the reactor sleeve 2 from the reactor sleeve attachment means 70. Turning to FIG. 8, an exploded cross-section view of a lower manifold 11 of a reactor installation tool 1 is shown. The lower manifold 11 can include a primary member 12. The primary member 12 can be a circular disc having any desirable diameter or length, wherein the primary member 12 has an outer surface face 12a. The primary member 12 can have through holes or openings for receiving one or more posts of the exterior post unit 60. Preferably, the through holes in the primary member 12 have a suitable diameter for allowing the posts to freely slide therethrough as the movable assembly 50 is adjusted relative to the fixed assembly 10. The primary member 12 can have a protrusion 13 extending from the bottom face. The protrusion 13 can mate with the center post 20 of the fixed assembly 10, for example, via a threaded attachment or the like. The center post 20 can be securely attached to the primary member 12 to create a rigid structure for mounting the expandable clamping unit 30. The primary member 12 can further include a lower manifold guard 14. The lower manifold guard 14 can be attached to the outer surface face 12a of the primary member 12, for example, by welding. The lower manifold guard 14 can be a hollow cylinder for enclosing and protecting the expandable clamping unit 30. The lower manifold guard 14 can have any suitable diameter and/or length depending on the size and shape of the expandable clamping unit 30 and/or other components to be contained therein. Preferably, the lower manifold guard 14 does not extend past the intermediate mounting bracket 32, nor cover the movable clamp shoes 34 of the expandable clamping unit 30. During use, the clamp shoes 34 are expanded outward beyond the exterior of the lower manifold guard 14 to contact the inner surface face of a reactor tube 4. Thus, it is desirable that the lower manifold guard 14 does not impede the clamp shoe 34 movement or prevent the clamp shoe 34 from being firmly pressed on the reactor tube 4. FIG. 9 shows an expandable clamping unit 30. The expandable clamping unit 30 can have a mounting sleeve 36 for fitting with the center post 20. The mounting sleeve 36 is an elongated body having a hollow through hole for receiving the center post 20. The through hole of the mounting sleeve 36 extends from the distal to proximal end of the sleeve 36. The mounting sleeve 36 can be secured at any position on the center post 20, for example, with a locking pin 38. A locking pin hole 39 can be drilled in the mounting sleeve 36, and when aligned with a hole in the center post 20, the locking pin 38 can secure the expandable clamping unit 30 on the center post 20 and prevent the two components from sliding with respect to one another during operation. Although not shown, multiple locking pins 38 can be used to secure the expandable clamping unit 30 on the center post 20. The mounting sleeve 36 can have one or more mounting brackets for securing the components of the expandable clamping unit 30. As shown in FIG. 9, the mounting sleeve 36 can have an upper mounting bracket 31, an intermediate mounting bracket 32 and a lower mounting bracket 33. The upper mounting bracket 31 is rigidly secured to the mounting sleeve 36, preferably near the top of the sleeve. The upper mounting bracket 31 connects to the distal end of a pneumatic cylinder 35 having a mounting hole 42 that can align and be in register with the mounting hole 41 in the upper mounting bracket 31. A pin or similar device can be used to secure the pneumatic cylinder 35 to the upper mounting bracket 31. The proximal end of the pneumatic cylinder 35 is secured to the intermediate mounting bracket 32. The proximal end of the pneumatic cylinder 35 can have a slotted member 37 for mating with the mounting pin passing through hole 43 in the intermediate mounting bracket 32. The position of the slotted member 37 on the proximal end of the intermediate mounting bracket 32 can be adjusted by twisting the slotted member 37 on the threaded attachment. The intermediate mounting bracket 32 can have another through hole for attaching a clamp shoe 34. Adjustable connector 45 can link clamp shoe 34 to the intermediate mounting bracket 32, and fixed connector 46 can link the clamp shoe 34 to the lower mounting bracket 33, which is rigidly secured to the mounting sleeve 36, preferably near the bottom of the sleeve. In this arrangement, the clamp shoe 34 is movably attached to the mounting sleeve 36 such that the clamp shoe 34 can extend away from and retract towards the sleeve 36. As shown, the clamp shoe 34 is movably attached to the mounting sleeve 36 by, in part, the fixed connector 46 and pneumatic cylinder 35. FIG. 11 shows a top view of the upper mounting bracket 31, without being attached to a pneumatic cylinder 35. As shown, the upper mounting bracket 31 has four mounting sites, each equally spaced around the mounting sleeve 36, 90° apart. Although not shown, the mounting sleeve 36 can have 2, 3 or more sets of mounting brackets (upper, lower and intermediate), and corresponding components, spaced around the sleeve 36. Each mounting site has a mounting hole 41 for connecting one pneumatic cylinder 35 as described above. The upper mounting bracket 31 can have one or more through holes 47 for receiving posts of the exterior post unit 60. The through holes 47 allow the posts of the exterior post unit 60 to freely slide up and down during operation. FIG. 10 shows a top view of the upper mounting bracket 31 secured to four pneumatic cylinders 35 positioned inside a reactor tube 4. The distal ends of the pneumatic cylinders 35 are attached to the mounting sites of the upper mounting bracket 31 with pins passing through the mounting hole 41 in the bracket 31 and the mounting hole 42 in the cylinder 35, shown in FIG. 9. Pressurized air supply lines or hoses can be run to the pneumatic cylinders 35 of the expandable clamping unit 30 for expanding and contracting the clamp shoes 34 of the unit. As described above, components of the upper manifold 51 and lower manifold 11, such as the base member 53 and primary member 12, can be designed to function as multi-port air manifolds to simplify pneumatic plumbing. For example, one or multiple through holes can be utilized in the various components of the upper manifold 51 and/or lower manifold 11. Complex plumbing, such as multiple tubes, can be guided through one through hole or be combined into one hose for passing through the length of the reactor installation tool 1 to the source to be energized, such as the pneumatic cylinder 35. Electrical, hydraulic, or air supply lines can be run to various components with ease, and with less risk of tangling. For example, to operate the pneumatic cylinders 35, air supply lines can be joined together and plumbed from the top of the reactor installation tool 1 to the site of the expandable clamping unit 30. Energizing the pneumatic cylinders 35 with air pressure can force the cylinders 35 to expand in length, which moves the clamp shoes 34 of the expandable clamping unit 30 outward. The clamp shoes 34 can be forced away from the center post 20 and into contact with the inner surface face of a reactor tube 4 when the pneumatic cylinders 35 are energized with air. A pressurized air supply can be used to firmly press the clamp shoes 34 against a reactor tube 4. Depending on the pressure of air used, the amount of force pressing the clamp shoe 34 on the reactor tube 4 can be controlled. Preferably, a sufficient air pressure is used to press the clamp shoes 34 against a reactor tube 4 to prevent slip between the reactor tube 4 and clamp shoe 34. For example, an electrically operated air valve can be used to supply air at a pressure of 85 psig to the pneumatic cylinders 35. Slippage between the clamp shoe 34 and reactor tube 4 can be caused by many factors, such as available air pressure, reactor tube 4 size (diameter), and the type and cleanliness of the surfaces being used. For example, if the inner surface face of a reactor tube 4 is dirty or covered in grease or residual oils, slippage can occur more easily. To reduce risk of slippage, all surfaces of the reactor tube 4 and clamp shoe 34 should be cleaned before operation. An example clamp shoe 34 is shown in FIG. 12. The clamp shoe 34 can have two faces, one face being in contact with a mounting base 49 and the other face being suitable for pressing against a reactor tube 4 wall. As shown, the clamp shoe 34 can include a mounting base 49 for attaching the clamp shoe 34 to the adjustable connector 45 and fixed connector 46, which can be further attached to the intermediate mounting bracket 32 and lower mounting bracket 33. The mounting base 49 can have a pin hole for receiving a locking pin for securing the adjustable connector 45 and fixed connector 46 to the clamp shoe 34. The clamp shoe 34 can have a pressing pad 48. The pressing pad 48 contacts the surface to which the reactor installation tool 1 is to be attached. Thus, depending on the dimensions of the surface to be contacted, the pressing pad 48 can be designed to have any suitable shape and size. For example, the pressing pad 48 can have a radiused face that corresponds to the curvature of the surface the pad 48 is to be pressed against, such as the inner surface face of a reactor tube 4 or reactor sleeve 2. As shown, the pressing pad 48 has a curved face for contacting the inner surface face of a reactor tube. The pressing pad 48 can be made of any suitable material, such as rubber (natural or synthetic), polymers, rigid foam, or metal. Optionally, the pressing pad 48 can further include contacting layer 48a overlying its face. The contacting layer 48a can be secured to the pressing pad 48 with an adhesive. The contacting layer 48a can provide a protecting interface during operation. The contacting layer 48a can be made of a pliable or softer material than that of the underlying pressing pad 48, for example, foam, rubber (natural or synthetic), polymer and the like, or combinations thereof. The pressing pad 48 without the contacting layer 48a, or the contacting layer 48a, if present, can have various surface textures to accommodate the surface conditions encountered. The surface texture of the pressing pad 48 and contacting layer 48a can also reduce slippage during operation. Turning to FIG. 13, there is shown a center post 20 connected to a stationary end stop 22. The stationary end stop 22 can function as a stop for a reactor unit 3, or multiple reactor units 3 if stacked. As described herein, as the movable assembly 50 is adjusted upward relative to the fixed assembly 10, the reactor sleeve 2 is also lifted equi-distance with the movable assembly 50. To ensure that the reactor unit 3, or series of stacked reactor units 3, is not lifted with the reactor sleeve 2, the stationary end stop 22 prevents the one or more reactor units 3 from moving with the movable assembly 50. Thus, the reactor sleeve 2 is extracted and the reactor units 3 are positioned in the reactor tube 4. The stationary end stop 22 can be a plate, or as shown, include an anvil 23 and an anvil disc 24. The anvil 23 can have any suitable diameter, for example, a diameter less than that of the reactor sleeve 2 and/or reactor tube 4 such that the anvil 23 can be inserted into the interior space of the sleeve 2 or tube 4 during operation, as shown in FIGS. 1 and 2. The anvil 23 can be attached to one end of the center post 20 by conventional means, such as with a threaded screw as shown. The anvil 23 can have attached to the bottom surface an anvil disc 24. The anvil disc 24 can be a circular ring having an empty center. Preferably, the circular ring is dimensioned to fit against the bottom face of the anvil 23 such that substantially the entire bottom face surface of the anvil 23 is covered by the anvil disc 24. As shown in FIG. 14, the anvil disc 24 can have radial cogs 25 extending from the outer face 24a, wherein the radial cogs 25 can have a radiused design, for example, a radius similar to the outer circumference of the anvil disc 24. The radial cogs 25 can be spaced about the outer surface face 24a, such as equally spaced along the anvil disc 24 outer circumference. The radial cogs 25 can be an integral part of the anvil disc 24, or alternatively, secured to the outer surface face 24a by any conventional means, such as by welding. One or more radial cogs 25 can be arranged and/or sized to engage the radial cogs 6 of the reactor sleeve 2. In this regard, the center post 20 of the fixed assembly 10 can be releasably secured or attached to the reactor sleeve 2 by the stationary end stop 22. That is, the radial cogs 25 of the anvil disc 24 can slide through the openings between the radial cogs 6 of the reactor sleeve 2 such that the reactor sleeve 2 can be moved upward along the vertical axis line of the fixed assembly 10. Once the radial cogs 6 of the reactor sleeve 2 clear the top surface of the radial cogs 25 of the anvil disc 24, and are positioned freely above the cogs 25, the reactor sleeve 2 can be twisted to adjust the radial cogs 6 of the reactor sleeve 2 to be directly above the radial cogs 25 of the anvil disc 24, as similarly described above with regard to the centering spider plate 71. As described above, the inner surface face 2a of the reactor sleeve 2 can have one or more radial cogs 6, see FIG. 16. A radial cog 6 can extend from the inner surface face 2a towards the interior of the reactor sleeve 2 and have a radiused design, for example a radius similar to the inner circumference of the reactor sleeve 2. The radial cogs 6 can be spaced about the inner surface face 2a, such as equally spaced along the reactor sleeve 2 inner circumference. The radial cogs 6 can be secured to the inner surface face 2a of the reactor sleeve 2 by any conventional means, such as by welding. The one or more radial cogs 6 can be positioned at any point along the length (l1) of the reactor sleeve 2. For example, the radial cogs 6 can be positioned near the top portion of the inner surface face 2a of the reactor sleeve 2. The radial cogs 6 can be arranged and/or sized to engage radial cogs of other components of the reactor installation tool 1, for example, a radial cog 75 of the reactor sleeve attachment means 70. In other words, the reactor installation tool 1 can be releasably secured or attached to a reactor sleeve 2 by the reactor sleeve attachment means 70 of the movable assembly 50. Attaching the reactor sleeve 2 to the movable assembly 50 is described above. As shown in FIG. 15, a reactor sleeve 2 can have any length (f1), for example, but not limited to, in the range of 1 to 100, 1 to 50, 1 to 25, 1 to 20, 1 to 15, 1 to 10, or 1 to 5 inches. A reactor sleeve 2 can have any inner diameter (d1), for example, but not limited to, in the range of 1 to 50, 1 to 25, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3 inches. A reactor sleeve 2 can have any outer diameter (d2), for example, but not limited to, in the range of 1 to 50, 1 to 25, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3 inches. In the case the reactor sleeve 2 is a tube, such as a hollow cylinder, the reactor sleeve 2 can have an inner diameter (d1), an outer diameter (d2), an inner surface face 2a, an outer surface face 2b and a length (l1). The inner surface face 2a of the reactor sleeve 2 faces the interior of the tube, which can hold a reactor unit 3, whereas the outer surface face 2b of the reactor sleeve 2 faces the exterior of the tube, for example, towards a reactor tube 4 surrounding or enclosing the reactor sleeve 2. The inner surface face 2a of the reactor sleeve 2 can be in direct contact with a reactor unit 3 or a portion thereof. The outer surface face 2b of the reactor sleeve 2 can be in direct contact with a reactor tube 4 or portion thereof. For ease of inserting the reactor sleeve 2 into the reactor tube 4, some clearance between the outer surface face 2b and reactor tube 4 is preferable. The reactor sleeve 2 can have a sufficient diameter to fit within the reactor tube 4 and hold one or more reactor units 3. The reactor units 3 can be compressed to fit in the reactor sleeve 2 such that when the reactor sleeve 2 is removed, the reactor unit 3 expands outward from its center, or uncompresses, and presses against the reactor tube 4 wall. Preferably, the reactor unit 3 presses against the reactor tube 4 wall with enough force that the reactor unit 3 remains in its installed position during operation. As noted above with regard to FIGS. 1 and 2, the reactor unit 3 loaded inside the reactor sleeve 2 can have multiple reactor units 3 hanging below the loaded reactor sleeve 2. The hanging reactor units 3 can be in a compressed form, for example, having tension bands positioned around the exterior of each hanging reactor unit 3. The tension bands can be temperature sensitive such that during operation the tension bands break or melt when exposed to elevated temperatures. In this arrangement, the reactor unit 3 loaded inside the reactor sleeve 2 is installed near the top of the reactor tube 4, and when the reactor sleeve 2 is removed and the reactor unit 3 releases and presses against the reactor tube 4 wall, the top reactor unit 3 can support the remaining hanging reactor units 3. During operation the hanging reactor units 3 can break the tension bands and expand to press against the reactor tube 4 wall, wherein the top reactor unit 3 that was unloaded from the reactor sleeve 2 no longer needs to support the reactor units positioned below it. A method of installing a reactor unit 3 with a reactor installation tool 1 will now be described. A reactor installation tool 1 including a fixed assembly 10 with an expandable clamping unit 30 and a movable assembly 50 with a reactor sleeve attachment means 70 can be releasably attached to a reactor sleeve 2. The fixed assembly 10 is preferably slidably attached to the movable assembly 50. The reactor sleeve attachment means 70 can include a centering spider plate 71 having radial cogs 75 and a locking hub 72. The centering spider plate 71 can be inserted into the interior space of the reactor sleeve 2 by aligning the radial cogs 75 with the open space between the radial cogs 6 of the reactor sleeve 2. Twisting the reactor sleeve 2 or centering spider plate 71 can align the cogs 75, 6 and then the locking hub 72 can be lowered, twisted, and locked with pin to prevent the reactor installation tool 1 and reactor sleeve 2 from twisting with respect to one another. In this arrangement, the movable assembly 50 of the reactor installation tool 1 is releasably attached to the reactor sleeve 2. The reactor sleeve 2, preferably loaded with one or more reactor units 3, can be lowered or positioned into a reactor tube 4 by using a hoist or similar device connected to the reactor installation tool 1. The reactor tube 4 preferably has a diameter greater than the reactor sleeve 2 diameter, and the largest diameter point of the portion of the reactor installation tool 1 to be lowered into the reactor tube 4. Once lowered into the reactor tube 4, the reactor sleeve 2 is preferably positioned below the top surface of the reactor tube 4 such that sufficient space near the top of the reactor tube 4 is left uncontacted by the reactor sleeve 2. In this arrangement, the reactor units 3 can be installed in the reactor tube 4 below the location of the expandable clamping unit 30. The uncontacted portion of the inner surface face of the reactor tube 4 is available for contact with the clamp shoes 34 of the expandable clamping unit 30, for example, the clamp shoes 34 of an expandable jaw unit including a mounting sleeve, wherein the mounting sleeve can be movably attached to one or more clamp shoes 34. The clamp shoes 34 can have a pressing pad for contacting or engaging the inner surface face of the reactor tube 4. The expandable clamping unit 30 can be engaged by energizing the unit 30 with a pressurized air source. A pressurized air source can expand and contract the clamp shoes 34 of the expandable clamping unit 30, the movement of the clamp shoes 34 being relative to the center axis of the reactor installation tool 1 and/or mounting sleeve 36 of the expandable clamping unit 30. The clamp shoes 34 can be expanded outward from the mounting sleeve 36 to contact the inner surface face of the reactor tube 4, and thus releasably securing the reactor installation tool 1, and in particular the fixed assembly 10, to the reactor tube 4. The reactor installation tool 1 is releasable secured because the expandable clamping unit 30 can be de-energized by the user when it is desirable to release the clamp shoes 34. The movable assembly 50 of the reactor installation tool 1 can then be raised relative to the fixed assembly 10 to lift the reactor sleeve 2 in the reactor tube 4. The reactor sleeve attachment means 70 moves upward with the reactor sleeve 2 to extract the sleeve 2 from the one or more reactor units 3 enclosed therein. The expandable clamping unit 30 can be de-energized with the pressurized air source to retract the clamp shoes 34 from the inner surface face of the reactor tube 4, thereby releasing the fixed assembly 10 of the reactor installation tool 1 from the reactor tube 4. The reactor installation tool 1, and empty or unloaded reactor sleeve 2 attached thereto, can be removed from the interior space of the reactor tube 4. The reactor tube 4 is now loaded with the one or more reactor units 3 that were held by the reactor sleeve 2. While various embodiments in accordance with the present invention have been shown and described, it is understood the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modification as encompassed by the scope of the appended claims.
	description	Embodiments of an incore piping section maintenance system according to the present invention will be described hereunder. FIG. 1 is a longitudinal sectional view showing a first embodiment of an incore piping section maintenance system according to the present invention, and FIG. 2 is a plain view showing the same. The incore piping section maintenance system is applied to an incore piping section of a light water reactor such as a boiling water reactor or the like, and performs a surface de-sensitization of metallographic structure of the incore piping section, a preventive maintenance of weld zones (welded or to be welded portion) or the like, and a preventive maintenance work. FIG. 1 and FIG. 2 each shows an example in which an incore piping section maintenance system according to the present invention is applied to an incore piping section 26 in a reactor pressure vessel 1 of a boiling water reactor. The reactor pressure vessel 1 has, as a whole, the same structure as the conventional reactor pressure vessel shown in FIG. 5 to FIG. 7, and therefore, like reference numerals are used to designate the identical components used in these figures, and the detailed explanation thereof is omitted herein. The incore piping section maintenance system 25 shown in FIG. 1 and FIG. 2 is installed and fixed to a maintenance target portion of the reactor pressure vessel 1 or in the vicinity thereof. The maintenance target portion includes an incore piping section 26, for example, an inner weld zone 27a of a core spray pipe 27 of a core spray system 15, or the like, and is a place suitable for preventive repair and preventive maintenance of the incore piping section 26 of the reactor pressure vessel 1. The incore piping section maintenance system 25 includes: a maintenance system main body 30 which is located at a maintenance target portion or in the vicinity of the target portion between the core shroud 4 and the inner wall of the reactor pressure vessel 1; a support means 31 which is located on the maintenance system main body 30 so as to reciprocate towards or apart from the maintenance target portion; a laser de-sensitization treatment means 32 which is rotatably supported around an axis of the support means 31 and carries out a laser beam irradiation with respect to the maintenance target portion; and an optical transmission means 33 which guides a laser beam oscillated from a laser generation device or equipment L, such as shown in FIG. 3, to the laser de-sensitization treatment means 32. Further, the incore piping section maintenance system 25 is supported on an overhead traveling crane (not shown) which is located above the reactor pressure vessel 1 and including a fuel exchanger or the like and is freely movable up and down by means of cable. A reference numeral 35 denotes a hang sling or hang hook of the incore piping section maintenance system 25. The maintenance system main body 30 is a main frame assembly which is constructed in a manner of integrally assembling a support plate 36 and a rectangular base frame 37 which functions as a traveling cradle. The support roller 38 supported on the support plate 36 is removably mounted from the outside to a shroud head bolt bracket 39 which projects from an outer peripheral wall of the core shroud 4 and functions as a support bracket. On the other hand, a pair of fixed cylinders 40 are located on a lower portion of the base frame 37 facing an inner peripheral wall of the reactor pressure vessel 1. The fixed cylinders 40 are arranged in parallel to each other and are provided with an actuating rod 42 which has a mounting head or mounting pad 41 so as to freely reciprocate. The actuating rod 42 constitutes a piston rod, and reciprocates between a non-actuation position retracting by an actuation of the fixed cylinder 40 and an actuation position projecting by the same. When the fixed cylinder 40 is situated on the actuation position, the mounting head 41 presses the inner peripheral wall of the reactor pressure vessel 1 so as to be frictionally held thereto. The maintenance system main body 30 constituting the main frame assembly are pressed against the shroud head bolt bracket 39 at its one side and is pressed against the inner peripheral wall of the reactor pressure vessel 1 at the other side, and thus, is stably fixed and supported. In the maintenance system main body 30, a screw shaft 44 is rotatably supported on the base frame 37. The screw shafts 44 are located in a state of mutually facing at opposite sides of the base frame 37 and are provided with a linear guide 45 which is freely reciprocated. The linear guide 45 is supported so as to be radially movable. Further, the screw shaft 44 is connected with a reversible driving motor 46 which is installed on the support plate 36 through a gear mechanism 47. When the driving motor 46 is driven, the linear guide 45 is reciprocated along the screw shaft 44. On the other hand, the screw shafts 44 located on the opposite sides of the base frame 37 may be driven so as to be synchronous with each other, or one of the screw shafts 44 may be replaced with a guide shaft for a slide guide. Moreover, the linear guide 45 is provided with a bridge-like guide shaft 48 which extends in a direction perpendicular to the screw shaft 44, and the fixed support means 31 is movably supported on the guide shaft 48. The support means 31 is moved while being supported to a frame or plate-like bridge guide member 50 of the linear guide 45 and is supported in a state of projecting downward from the linear guide 45. The guide shaft 48 for moving the support means 31 may be a screw shaft driven by a motor or an actuating rod driven by a cylinder. The support means 31 supported on the linear guide 45 is supported so as to be adjustable and movable in an XY direction on one plane formed by the maintenance system main body 30. Further, the support means 31 includes a cylindrical motor case 53 having a built-in revolving motor 52 as a support cylinder and has a support body (assembly) 54 which extends sideward from a lower end of the motor case 53 so as to be attached integrally therewith and is supported in form of a cantilever beam. The support body 54 of the support means 31 is provided with seal means 56 at its both sides. The seal means 56 is a ring or truss-like seal member 57 which is mounted at both sides of the support body 54 in a state of being arranged in parallel in a multi-stage, for example, two stages. Each seal member 57 has a hollow structure and is freely expandable and shrinkable by freely injecting or removing a compressive fluid, for example, a compressed air, into and from its interior. Moreover, the support body 54 of the fixed support means 31 is provided with a laser de-sensitization treatment means 32. The laser de-sensitization treatment means 32 is rotatably supported on the central portion of the support body 54 by means of bearing 59 while being connected to a revolving motor 52 through a gear mechanism 60. When the revolving motor 52 is driven, the laser de-sensitization treatment means 32 is rotatable around a shaft of the bearing 59. The laser de-sensitization treatment means 32 has a laser scanning optical system 61 and a laser irradiating section 62. The laser irradiating section 62 irradiates with a laser beam the incore piping section 26 which is the maintenance target portion so as to perform a surface de-sensitization of a metallographic structure of the incore piping section 26, a preventive repair of weld zones or the like and a preventive maintenance. In the laser de-sensitization treatment means 32, the laser scanning optical system 61 guides a laser beam incident upon a laser supply port 63 to the laser irradiating section, and therefore, a laser transmission path is formed by the laser scanning optical system 61 in the laser de-sensitization treatment means 32. The laser scanning optical system 61 is constructed in the combination with a condenser (converging) lens, a mirror or the like. A laser beam oscillated from the laser generation device or equipment is guided to the laser supply port 63 of the laser de-sensitization treatment means 32 via a flexible optical transmission means 33 such as an optical fiber cable or the like. The optical transmission means 33 is included in a transmission tube 65. The laser generation equipment may be located on an operation floor (not shown) above the reactor pressure vessel 1, or may be located on a fuel exchanger or the maintenance system main body 30. In the case of locating the laser generation equipment on the maintenance system main body 30, a waterproof treatment is required. On the other hand, in addition to the optical transmission means 33 for transmitting a laser beam, the transmission tube 65 includes power, as a driving source, and control signal cables, various flexible pipes for feeding and discharging an atmosphere (purge) gas filled in the laser de-sensitization treatment means or a pressurized fluid, for example, a pressurized air filled in the seal member 57, and further, sucking and recovering a bubble generated in the laser irradiating section 62. Meanwhile, the laser de-sensitization treatment means 32 is provided with an inspection monitoring camera means, not shown, and a lighting means, not shown, as a maintenance target portion (weld zone) detector at the laser irradiating section 62 or in the vicinity of the laser irradiating section. The lighting means is a underwater light, for example. The inspection monitoring camera is an underwater TV camera, for example, and the underwater TV camera is provided integrally with the underwater light. In the incore piping section maintenance system 25, it is possible to monitor a maintenance work by means of the inspection monitoring camera means from the outside of the reactor pressure vessel 1 and to perform the maintenance work in a water by remote control. Therefore, it is possible to smoothly perform a maintenance work in a state that a reactor well is filled with a water. Moreover, in order to confirm and specify a laser execution position, the laser de-sensitization treatment means 32 is provided with an ultrasonic testing equipment (UT equipment) UT as a weld zone detector, the UT equipment being located to a portion shown in FIG. 1, for example. The UT equipment detects the laser execution position and a degree of damage in the incore piping section 26. After the executing position of the incore piping section 26 is confirmed by the UT equipment, a laser de-sensitization treatment is carried out by the laser de-sensitization treatment means 32. Further, the laser de-sensitization treatment means 32 is provided with a ferrite indicator (FT) in place of the UT equipment or together with the UT equipment. The ferrite indicator FT distinguishes a difference in ferrite quantity between the weld zone and a base material of the incore piping section 26, and then, detects it, and thus, confirms the laser execution position, the ferrite indicator FT being located to a portion on the side or in the vicinity of the de-sensitization treatment means 32 as shown in FIG. 2, for example. After the laser execution position is confirmed, a laser beam is irradiated by the laser de-sensitization treatment means 32, and then, the incore piping section 26 is subjected to a laser de-sensitization treatment. Furthermore, a polishing means PL is incorporated in place of the laser de-sensitization treatment means 32 or together with the laser de-sensitization treatment means 32, the polishing means PL being located to a portion shown in FIG. 1, for example. The polishing means PL is located at an angular position of a predetermined angle, for example, 180xc2x0 to the laser irradiating section 62 of the laser de-sensitization treatment means 32, so as to freely reciprocate and carry out polishing with respect to a laser executed position. The incore piping section maintenance system 25 is hung in the reactor pressure vessel 1 from a fuel exchanger (not shown) or the like by an operation of a worker, and then, is hoisted down above the downcomer portion 8 between the reactor pressure vessel 1 and the core shroud 4. In the upper portion of the downcomer portion 8, the incore piping section maintenance system 25 is placed on the shroud head bolt bracket 39 functioning as the support bracket, and then, an inner side of the maintenance system main body 30 is supported. On the other hand, an outer side thereof is pressed against the inner peripheral wall of the reactor pressure vessel by means of the fixed cylinder 40 and is frictionally supported. In this manner, the core pipe maintenance system 25 is stably fixed and supported on the incore piping section 26 which is a maintenance target portion or at the vicinity of the core pipe. The above-mentioned maintenance target portion is a weld zone between a pipe 66 and a header 67 of the core spray pipe 27, and the weld zone is a detection target portion of the incore piping section 26. The support means 31 of the core pipe maintenance system 25 is previously adjusted so as to be movable in an X-Y direction, so that the support means 31 faces the outside of the maintenance target portion in a state that the core pipe maintenance system 25 is fixed. Therefore, in a state that the incore piping section maintenance system 25 is fixed, when the driving motor 46 is driven, the support means 31 supported on the linear guide 45 is inserted into the pipe 66 of the core spray pipe 27 which is a maintenance target portion. When the support means 31 is inserted by a predetermined position in the pipe 66, a pressurized fluid, for example, a compressed air is supplied into the seal member paring with the seal means 56 so as to expand the seal member 57, and thus, watertight sealing is performed. The support means 31 is inserted into the pipe 66 and is sealed by the seal means 56, and thereafter, a coolant between seal members 57 is discharged with the use of a drain pipe of the transmission tube 65. Then, a purge gas in place of the coolant is supplied from a gas supply pipe, and is filled in the seal member, and thus, an atmospheric environment is formed. The coolant between seal members 57 is discharged, and the interior of the seal member is filled with a purge gas so as to be water-tightly separated from the outside, and thereafter, a maintenance work of the laser de-sensitization treatment portions is carried out by remote control. The laser de-sensitization treatment means 32 is rotatably supported on the fixed support means 31 via the bearing 59 and is provided with inspection monitoring camera means, an underwater light, an ultrasonic flaw detector and a ferrite indicator, which function or operate as the weld zone (maintenance target portion) detector in the laser de-sensitization treatment means 32. Thus, a position of the weld zone 27a, which is a maintenance target portion, is confirmed and detected. Thereafter, a laser beam is irradiated to the weld zone 27a within the core spray pipe 27 which is a maintenance target portion, from the laser irradiating section 62 of the laser de-sensitization treatment means 32, and a maintenance work of the incore piping section 26 is performed. The maintenance work by the laser de-sensitization treatment means 32 is performed by irradiating with a laser beam the weld zone 27a of the incore piping section 26 from the laser irradiating section 62. In this case, the laser irradiating section 62 is rotated along the inner periphery of the pipe 66 by a drive of the revolving motor 52, and then, a laser beam is irradiated over the entire periphery of weld zone of the incore piping section 26. The laser beam is irradiated over the entire periphery, and thereby, a surface de-sensitization of the incore piping section 26 is performed, and thus, a laser de-sensitization treatment for replacing a compressive stress of the weld zone 27a with a tensile stress is performed. By the laser de-sensitization treatment, a surface de-sensitization of the incore piping section 26 is performed, and thus, a preventive repair and preventive maintenance of the incore piping section 26 are performed. Therefore, it is possible to improve a normalization (soundness) and reliability of the incore piping section 26. In a preferred example, the laser de-sensitization treatment will be performed by using YAG laser generator generating a continuous laser beam (continuous wave CW) of the type of Nd-YAG laser (wavelength: 1.06 xcexcm) under an atmospheric environment. Next, the following is a description on an incore piping section maintenance system 70 of a second embodiment of the present invention. The incore piping section maintenance system 70 shown in FIG. 3 and FIG. 4 is an system for carrying out a laser de-sensitization treatment with respect to an outer peripheral surface of the incore piping section 26. The incore piping section maintenance system 70 is removably fixed on the incore piping section 26 which is a maintenance target portion or in the vicinity of the incore piping section 26. The incore piping section maintenance system 70 of a reactor is supported above the reactor pressure vessel 1 so as to be freely moved up and down by means of hang cable (not shown) extending from a fuel exchanger or the like. Further, the incore piping section maintenance system 70 of a reactor includes a maintenance system main body 71 which is inserted and supported in the pipe 66 of the core spray pipe 27 which is the incore piping section 26. The maintenance system main body 71 comprises a cylindrical body 72, and in the cylindrical body 72, a plurality of, for example, at least three main body supporting mechanisms 73 are radially housed therein so as to freely come in and out. The main body supporting mechanism 73 is constructed in combination with a link mechanism 74 such as a pantograph and a cylinder apparatus 75. When the cylinder apparatus 75 is activated, an inner guide 76, which is a guide member located at the distal end of the link mechanism 74, is projected outside the cylindrical body 72 so as to abut against an inner peripheral wall of the pipe 66, and thus, is fixed onto the inner peripheral wall of the pipe 66. The maintenance system main body 71 is provided with a revolving means 80 at its cylindrical end portion. In the revolving means 80, a revolving arm 82 is rotatably supported around its boss by means of revolving motor 81. The revolving arm 82 is freely rotatable around a shaft of the maintenance system main body 71 by a drive of the revolving motor 81. A free end portion of the revolving arm 82 is provided with a support means 84 such as a support beam which is slidable and swingable in a direction perpendicular to the arm. The support means 84 is slidably and swingably moved by means of a head driving unit 85, and thus, constitutes an axial direction moving means 86, which is axially movable with respect to the header 67. The support means 84 is provided with a laser de-sensitization treatment means 88, which is substantially the same as the laser de-sensitization treatment means shown in FIG. 1 and FIG. 2. The laser de-sensitization treatment means 88 irradiates with a laser beam from a laser irradiating section an outer peripheral wall of the core spray pipe 27 which is an incore piping section 26 and carries out a laser de sensitization treatment with respect to the outer peripheral surface of pipe, and thus, a work for preventive maintenance and preventive repair is performed. A laser beam oscillated from the laser generation device or equipment is guide to the laser de-sensitization treatment means 88 via a flexible optical transmission means 33. The optical transmission means 33 is formed of an optical fiber cable or the like. Further, the optical transmission means 33 is included in the transmission tube 65 together with a cable for power and control signal of drive source. The incore piping section maintenance system 70 of a reactor is supported in its load with the use of an inner surface of the pipe 66 of the incore piping section 26 and is fixed on a maintenance target portion or in the vicinity thereof. More specifically, the maintenance system main body 71 of the incore piping section maintenance system 70 is fixed and supported on the inner peripheral surface of the pipe 66 by means of a plurality of, for example, three or more main body supporting mechanisms 73. The incore piping section maintenance system 70 is stably and securely supported in the pipe 66 by means of these three or more main body supporting mechanisms 73. The incore piping section maintenance system 70 is fixed in the pipe 66 of the incore piping section 26 by opening and closing an inner guide 76 which functions as a guide member of the link mechanism 74. The maintenance system main body 71 is fixed on a predetermined position in the pipe 66 of the incore piping section 26, and it is therefore possible to position and set the laser de-sensitization treatment means 88 on the outer peripheral surface of the pipe 66. After the incore piping section maintenance system 70 is fixed with the use of the pipe 66, the revolving motor 81 and the head driving unit 85 are operated. When the revolving motor 81 is driven, the laser de-sensitization treatment means 88 turns along an outer periphery of the pipe 66 so as to draw a circular orbit. Moreover, when the head drive unit 85 is operated, the support means 84 is moved in parallel with an axial direction of the pipe 66 and makes a swing motion as occasion demands. Thus, the laser de-sensitization treatment means 88 can effectively carry out a laser de-sensitization treatment with respect to the outer peripheral surface of the pipe 66 by a revolving (turning) motion by the revolving motor 81 and an axial movement by the head driving unit 85. As described above, the laser de-sensitization treatment means 88 carries out a predetermined laser irradiation with respect to the pipe outer peripheral surface of the incore piping section 26 of the reactor pressure vessel 1, and thereby, a surface de-sensitization of the pipe outer surface is performed, thus, making it possible to securely perform a work for preventive repair and preventive maintenance of the pipe outer surface for a short time, whereby the core spray pipe 27 can be normally restored, and it becomes possible to improve normalization and reliability of the incore piping section 26. It is to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims. For example, the above embodiments of the present invention have made an explanation about the incore piping section maintenance system which is suitable for preventive maintenance and preventive repair of the incore piping section of the reactor pressure vessel. The incore piping section maintenance system may be applicable not only to a boiling water reactor, but also to a pressurized water reactor. Therefore, the incore piping section maintenance system may be applicable to an incore piping section of a reactor pressure vessel of the pressurized water reactor. It is to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.
054917301	claims	1. In a cooling water system for a primary containment vessel in a nuclear power plant which system includes a gas vent which extends from a heat exchanger of a condenser-type heat removal system into a suppression pool to be communicated with the water in the suppression pool; the improvement wherein means for restraining upward movement of a vent fluid is provided on a portion of said gas vent disposed in the suppression pool to extend horizontally to an extent greater than a flow area of said gas vent, said restraining means including communication holes communicated with the water of the suppression pool and disposed below a level where a maximum gas-to-liquid contact area is formed, and said communication holes being distributed over a range larger than the flow area of said gas vent, and in which said restraining means comprises horizontal pipes connected to and communicated with said gas vent in a plurality of directions, each of said pipes having a closed distal end, and each of said pipes having openings which are in free communication with the water of the suppression pool and are disposed only below a horizontal plane in which axes of said pipes lie. the improvement wherein a plurality of horizontal pipes are connected to and communicated with a portion of said gas vent, which is disposed in the suppression pool, in a plurality of different directions, each of said pipes having a plurality of openings which are in communication with the water in the suppression pool to be arranged in a dispersed manner below a horizontal plane in which axes of said pipes lie, and an entire portion of each of said pipes disposed above said horizontal plane being closed. 2. In a cooling system for a primary containment vessel in a nuclear power plant which system includes a gas vent which extends from a heat exchanger of a condensation-type heat removal system into a suppression pool to be communicated with the water in the suppression pool; 3. A cooling system according to claim 2, in which said gas vent includes a main pipe portion and said plurality of horizontal pipes are provided on a lower end portion or a portion near said lower end portion of said main pipe portion in communication therewith in different directions.
	description	1. Field The disclosure relates to devices for maintaining a desired position of a jet pump assembly within a nuclear reactor pressure vessel. 2. Description of Related Art A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically shaped shroud. In a BWR, hollow tubular jet pumps positioned within the shroud annulus provide the required reactor core water flow. The upper portion of the jet pump, known as the inlet mixer, is laterally positioned and supported against two opposing rigid contacts within restrainer brackets by a gravity actuated wedge. The inlet mixers are each held in place at the top end by a preloaded beam. To secure the assembly, the jet pump beam is assembled with a high preload, applied by installing the jet pump beam bolt with a hydraulic tensioner. High static and dynamic jet pump flow loads on the inlet mixer can, under some conditions, such as insufficient beam preload, cause oscillating motion and detrimental vibration excitation in the jet pump. The resultant increased vibration levels and corresponding vibration loads on the piping and supports can cause jet pump component degradation from wear and fatigue. Extreme component degradation can require plant shutdown. To assure the required preload is maintained, the beam bolt is securely locked to prevent loosening after tensioning is completed. Devices for performing tensioning and securing the beam bolt after tensioning are discussed in U.S. Pat. Nos. 6,434,208 and 7,764,760, the entire contents of each of which are incorporated herein by reference. According to at least one example embodiment, a lock plate for a locking device of a jet pump beam, the locking device including a locking sleeve including a bore extending from a first end to a second end of said locking sleeve, and a lower portion having a plurality of locking sleeve ratchet teeth around the periphery of the locking sleeve, may include a beam bolt opening sized to receive the locking sleeve; and an integral beam spring arm including, a plurality of spring arm ratchet teeth, the plurality of spring arm ratchet teeth extending from at least a portion of a side of the spring arm facing the center of the beam bolt opening and sized to mesh with the locking sleeve ratchet teeth, and a capture feature extending from at least a portion of a side of the spring arm toward the center of the beam bolt opening, the integral beam spring arm being structured such that the spring arm has both i) an engaged position where the locking sleeve is in the beam bolt opening and at least a portion of the capture feature overlaps vertically with an upper surface of the lower portion of the locking sleeve, and ii) a disengaged position where the locking sleeve is in the beam bolt opening and the capture feature does not overlap vertically with the upper surface. The engaged position of the spring arm may be a position where the spring arm ratchet teeth are engaged with the locking sleeve ratchet teeth, and the disengaged position of the spring arm may be a position where the spring arm ratchet teeth are not engaged with the locking sleeve ratchet teeth. At least a portion of the capture feature may be located at a position on the spring arm in between a location of the spring arm ratchet teeth on the spring arm and an extreme end of the spring arm opposite an end of the spring arm where the spring arm joins the rest of the lock plate. According to at least one example embodiment, a locking device for a jet pump beam, the jet pump beam including a beam bolt having a head, may include a locking sleeve including a bore extending from a first end to a second end of said locking sleeve; and a lower portion having a plurality of locking sleeve ratchet teeth around the periphery of the locking sleeve, the lock plate including a beam bolt opening sized to receive the locking sleeve, and an integral beam spring arm including, a plurality of spring arm ratchet teeth, the plurality of spring arm ratchet teeth extending from at least a portion of a side of the spring arm facing the center of the beam bolt opening and sized to mesh with the locking sleeve ratchet teeth, and a capture feature extending from at least a portion of a side of the spring arm toward the center of the beam bolt opening, the integral beam spring arm being structured such that the spring arm has both i) an engaged position where the locking sleeve is in the beam bolt opening and at least a portion of the capture feature overlaps vertically with an upper surface of the lower portion of the locking sleeve, and ii) a disengaged position where the locking sleeve is in the beam bolt opening and the capture feature does not overlap vertically with the upper surface. According to at least one example embodiment, a jet pump assembly may include a riser pipe; at least one inlet mixer; at least one diffuser coupled to said at least one inlet mixer; a transition assembly including at least two support arms, the riser pipe being coupled to the at least one inlet mixer by the transition assembly; a jet pump beam extending between two of said at least two support arm, the jet pump beam including a threaded bolt opening; a beam bolt extending through and threadedly engaging the beam bolt opening; and a locking device, the locking device including, a locking sleeve including a bore extending from a first end to a second end of said locking sleeve; and a lower portion having a plurality of locking sleeve ratchet teeth around the periphery of the locking sleeve, the lock plate including a beam bolt opening sized to receive the locking sleeve, and an integral beam spring arm including, a plurality of spring arm ratchet teeth, the plurality of spring arm ratchet teeth extending from at least a portion of a side of the spring arm facing the center of the beam bolt opening and sized to mesh with the locking sleeve ratchet teeth, and a capture feature extending from at least a portion of a side of the spring arm toward the center of the beam bolt opening, the integral beam spring arm being structured such that the spring has both i) an engaged position where the locking sleeve is in the beam bolt opening and at least a portion of the capture feature overlaps vertically with an upper surface of the lower portion of the locking sleeve, and ii) a disengaged position where the locking sleeve is in the beam bolt opening and the capture feature does not overlap vertically with the upper surface. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. 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 “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, 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. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 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 example embodiments belong. It will be further understood that terms, including 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. Jet Pump Assembly FIG. 1 is a sectional view, with parts cut away, of a boiling water nuclear reactor pressure vessel in accordance with an example embodiment of the present invention. As shown in FIG. 1, a boiling water nuclear reactor pressure vessel (RPV) 10 is disclosed. The RPV 10 may have a generally cylindrical shape and is closed at one end by a bottom head 12 and at its other end by a removable top head 14. A side wall 16 extends from bottom head 12 to top head 14. Side wall 16 includes a top flange 18. Top head 14 may be attached to the top flange 18. A cylindrically shaped core shroud 20 surrounds a reactor core 22. Shroud 20 may be supported at one end by a shroud support 24 and may include a removable shroud head 26 at the other end. An annulus 28 is formed between shroud 20 and side wall 16. A pump deck 30, which may have a ring shape, extends between shroud support 24 and RPV side wall 16. Pump deck 30 includes a plurality of circular openings 32, with each opening housing a jet pump 34. Jet pumps 34 are circumferentially distributed around core shroud 20. An inlet riser pipe 36 is coupled to two jet pumps 34 by a transition assembly 38. Each jet pump 34 may include an inlet mixer 40, and a diffuser 42. Inlet riser pipe 36 and the two connected jet pumps 34 may faun a jet pump assembly 44. FIG. 2 is an enlarged perspective view of a portion of the jet pump assembly 44 illustrated in FIG. 1, in accordance with an example embodiment of the present invention. As shown in FIGS. 1 and 2, the jet pump assembly 44 may include a riser pipe 36 coupled to a pair of jet pumps 34 by transition assembly 38. Referring to FIGS. 1 and 2 each jet pump 34 includes a jet pump nozzle 64, a suction inlet 66, an inlet mixer 40, and a diffuser 42 (shown in FIG. 1). The jet pump nozzle 64 may be positioned in the suction inlet 66 which may be located at a first end of inlet mixer 40. The transition assembly 38 may include a base piece 70 and two elbows 71. Each elbow 71 is coupled to a jet pump nozzle 64. Locking arms 72, 74, 76, and 78 extend from the transition assembly base piece 70. Connected between the locking arms 72, 74, 76, and 78 is a jet pump beam 86. In an example embodiment, the jet pump beam 86 engages between support arms 72 and 76, and a substantially identical jet pump beam 86 engages between support arms 74 and 78. The jet pump beam 86 includes a tongue member 81 at the end which engages notches 92 in the locking arms 72, 74, 76, and 78 for preventing and/or reducing movement (e.g., rotational movement) of the beam bolt 94. The beam 86 may engage the locking arms 72, 74, 76, and 78 by sliding the tongue member 81 into the notches 92. Referring to FIG. 3, jet pump beam 86 includes a raised central portion 88. The ends of jet pump beam 86 are supported in the notches 92 located in locking arms 72, 74, 76, and 78. A beam bolt 94 may include a multisided head 96, a threaded portion 98, and a butt end 100 including a lower bearing surface 102 which bears against a disc 104 seated in a counter bore 105 of elbow 71. Beam bolt 94 threadedly engages a threaded bolt opening 106 in jet pump beam 86. A locking assembly 110 prevents beam bolt 94 from loosening. Locking assembly 110 may include a locking sleeve 112 and a lock plate 114. The locking sleeve 112 may include a base portion 116 at a first end 118 and a bore 120 extending from first end 118 to a second end 122. A bore 120 may be sized and shaped to matingly receive beam bolt head 96. Examples structures of the lock plate 114 will now be discussed in greater detail below Lock Plate FIG. 4 is a top view of a first lock plate 400; FIG. 5 is a top view of jet pump beam 86 with locking sleeve 112 and the first lock plate 400 disengaged; and FIG. 6 is a top view of jet pump beam 86 with locking sleeve 112 and the first lock plate 400 engaged. The first lock plate 400 is an example structure for the lock plate 114 discussed above with reference to FIG. 3. Referring to FIGS. 4, 5, and 6, the first lock plate 400 includes a beam bolt opening 126, an integral beam spring arm 128, and a first capture feature 150. The first capture feature 150 is a lip. Beam bolt opening 126 is sized to receive locking sleeve 112. The first capture feature 150 is configured to capture the locking sleeve 112 by engaging an upper portion of the locking sleeve 112 as will be discussed in greater detail below with reference to FIG. 7. Spring arm 128 includes a start portion 130 extending from the first lock plate 400 adjacent beam bolt opening 126, a middle portion 132 extending from start portion 130 and extending around a periphery of beam bolt opening 126, and a first end portion 134 extending from middle portion 132. First end portion 134 includes a plurality of ratchet teeth 136 extending from a side 138 of first end portion 134 facing the center of beam bolt opening 126. First end portion 134 of spring arm 128 also includes a notch 140 located adjacent ratchet teeth 136. Notch 140 is sized to receive a detent 142 extending from the first lock plate 400 into beam bolt opening 126. Locking sleeve 112 includes a plurality of ratchet teeth 144 located circumferentially around base portion 116 and which are sized to engage and mesh with ratchet teeth 136 of spring arm 128. A tab 146 extends from first end portion 134. Tab 146 is used, in conjunction with a simple release cam tool and a cam tool opening 148 in the first lock plate 400, to deflect spring arm 128 to an engaged or disengaged position. Spring arm 128 is movable between a first, or engaged, position (shown in FIG. 6) where detent 142 is positioned in notch 140 and spring arm ratchet teeth 136 are engaged with locking sleeve ratchet teeth 144, and a second, or disengaged, position (shown in FIG. 5) where side 138 of first end portion 134 of spring arm 128 facing contact with detent 142 and spring arm ratchet teeth 136 are disengaged from locking sleeve ratchet teeth 144. Spring arm 128 is initially machined with end portion displaced radially inboard of the first position so that installation deflects spring arm 128 and produces a radial preload force. Also, in another embodiment, spring arm 128 is machined with a thickness tapering from a maximum at start portion 130 so that the available preload displacement is maximized for a given bending stress induced in spring arm 128. It should be noted that machining of the somewhat complex geometry of locking assembly 110 is made practical by the availability of precision controlled wire electrical discharge machining. Any suitable material can be used for locking assembly 110, for example, Ni—Cr—Fe alloy X-750. The X-750 alloy provides high strength, permitting minimum size and weight of locking assembly 110, and provides corrosion resistance in the environment of a boiling water nuclear reactor. FIG. 7 is a cross sectional view of the locking sleeve 112 and the first lock plate 400 with respect to the D-D axis illustrated in FIG. 6. Referring also to FIG. 7, the first capture feature 150 of the first lock plate 400 extends at least partially around beam bolt opening 126. The first capture feature 150 is sized to engage an upper surface 152 of locking sleeve base portion 116. Further, the first lock plate 400 includes at least one guide pin opening 154 sized to receive a jet pump beam guide pin 156 and at least one screw opening 158 sized to receive attachment screws 160. Locking assembly 110 securely locks beam bolt 94 in place and is easily installed by slipping locking sleeve 112 over mating multisided beam bolt head 96 and mounting the first lock plate 400 to beam 86. Particularly, guide pin openings 154 are positioned over guide pins 156, and attachment screws 160 are inserted through screw openings 158 and tightened. To ensure that attachment screws 160 do not loosen, screws 160 can be tack welded to the first lock plate 400 or drilled for insertion of a lock pin. First capture feature 150 captures locking sleeve 112, and the preload force of spring arm 128 holds locking sleeve 112 securely against vibration. The shape of meshing ratchet teeth 136 and 144 permit tightening of beam bolt 94 with a tensioner to a predetermined torque, but subsequent rotation in the loosening direction is limited by meshed ratchet teeth 136 and 144 to less than one tooth space. Use of close tooth spacing minimizes the corresponding possible variation in bolt position after torqueing. The inclined contact surface between notch 140 and detent 142 wedges the meshing ratchet teeth 136 and 144 more tightly against loosening rotation, providing a self-energized lock. To loosen beam bolt 94, a simple release cam tool, not shown, having a screw driver shaped end, is used to deflect spring arm 128 to the second position where detent 142 is in contact with side 138 of first end portion 134 of spring arm 128 so that spring arm ratchet teeth 136 are disengaged from locking sleeve ratchet teeth 144. FIG. 8 is a perspective view of a second lock plate 800. The second lock plate 800 is an example structure for the lock plate 114 discussed above with reference to FIG. 3. The second lock plate 800 may operate in a manner similar to that discussed above with respect to the first lock plate 400 illustrated in FIGS. 4-7. The spring arm 128 of the second lock plate 800 includes the start portion 130, the middle portion 132 and a second end portion 834. The second end portion 834 illustrated in FIG. 8 may include a tool opening 839 in order to facilitate contact between the spring am 128 and a cam tool used to vary the position of the spring arm 128 from an engaged position, where the spring arm ratchet teeth 136 are engaged with the locking sleeve ratchet teeth 144, to a disengaged position, where the spring arm ratchet teeth 136 are disengaged from the locking sleeve ratchet teeth 144, and vice versa. Like the first lock plate 400, the second lock plate 800 includes a capture feature sized to engage an upper surface 152 of locking sleeve base portion 116. For example, the second lock plate 800 includes a second capture feature 850. The second capture feature 850 includes second and third lips 850A and 850B. In the same manner illustrated in FIG. 7 with respect to the first capture feature 150 of the first lock plate 400, each of the second and third lips 850A and 850B of the second capture feature 850 is sized to engage an upper surface 152 of locking sleeve base portion 116. Accordingly, a locking plate 114 having the structure of either the first lock plate 400 or the second lock plate 800 allows the beam bolt 94 to be detensioned and tensioned repeatedly while significantly reducing the need to replace or substantially modify the locking assembly 110. However, sometimes, during detensioning of the beam bolt 94, the locking sleeve 112 may move vertically with respect to the locking plate 114. As is discussed above with reference to FIG. 7, capture features structured like the lip 150 of the first lock plate 400, or the lips 850A and 850B of the second lock plate 800 overlap with the base portion 116 of the locking sleeve 112. In a case where the locking sleeve 112 rises with respect the first lock plate 400, the locking sleeve ratchet teeth a 144 included in the base portion 116 may contact the capture feature of the first lock plate 400, the first capture feature 150. Likewise, in a case where the locking sleeve 112 rises with respect the second lock plate 800, the locking sleeve ratchet teeth 144 may contact the capture feature 850 of the second lock plate 800, second and third lips 850A and 850B. Contact with the first capture feature 150, or either of the second and third lips 850A and 850B, may cause at least some of the locking sleeve ratchet teeth 144 to be sheared off or otherwise damaged. This damage may require the locking sleeve 112 to be replaced in order to ensure proper operation of the locking assembly 110, which is needed to ensure proper operation of the jet pump assembly 44. Replacing the locking sleeve 112 may be costly and time consuming. Accordingly, it may desirable to reduce the chances of damaging the locking sleeve ratchet teeth 144 by using a lock plate which prevents contact between a capture feature and the locking sleeve ratchet teeth 144. A lock plate according to example embodiments will now be discussed with reference to FIGS. 9A-11 below. FIGS. 9A-9I illustrate various views of a third lock plate 900 according to at least one example embodiment. The third lock plate 900 is an example structure for the lock plate 114 illustrated in FIG. 3. FIGS. 9A and 9F-9I illustrate the third lock plate 900 from various perspective views. FIG. 9B illustrates a top view of the third lock plate 900. FIG. 9C illustrates a bottom view of the third lock plate 900. FIG. 9D illustrates a side view which is the top view illustrated in FIG. 9B rotated 90° about the C-C axis illustrated in FIG. 9B. FIG. 9E illustrates a side view which is the top view illustrated in FIG. 9B rotated 90° about the B-B axis illustrated in FIG. 9B. In FIGS. 9A-9I the third lock plate 900 is illustrated in an engaged position. FIG. 10 illustrates a portion of the locking assembly 110 including, as the lock plate 114, the third lock plate 900 according to at least one example embodiment. In FIG. 10, the third lock plate 900 is illustrated in a disengaged position. FIG. 11 is a cross sectional view of the locking sleeve 112 and the spring arm 128 of the third lock plate 900 according to at least one example embodiment. With the exceptions discussed below, the third lock plate 900 may have the same interaction with the locking sleeve 112, structure, and operation as that discussed above with respect to the first lock plate 400 illustrated in FIGS. 4-7. The spring arm 128 of the third lock plate 900 includes the start portion 130, the middle portion 132 and a third end portion 934. According to at least one example embodiment, the third end portion 934 may include a tool opening 839 in order to facilitate contact between the spring am 128 and a cam tool used to vary the position of the spring arm 128 from an engaged position to a disengaged position, and vice versa. Optionally, according to at least one example embodiment, the lock plate 900 may not include the notch 140 or the cam tool opening 148. Further, according to at least one example embodiment, instead of the first capture feature 150, the third lock plate 900 may include a third capture feature 950. The third capture feature 950 may be, for example, a lip or protrusion that extends from the end portion 934 of the spring arm 112 inwards towards a center of the third lock plate 900. According to at least one example embodiment, at least a portion of the third capture feature 950 may be in between the spring arm ratchet teeth 136 and an outermost region 955 of the spring arm 128, the outermost region 955 being a most extreme portion of the spring arm 128 with respect to a point in the start region 130 where the spring arm 128 joins the remaining portion of the third lock plate 900. As is illustrated in FIG. 9D, according to at least one example embodiment, an upper surface of the third capture feature 950 may be positioned at a height D3 above a base 960 of the third lock plate 900. Further, a remaining portion of the spring arm 128 (for example, a portion of the spring arm 128 not including the third capture feature 950) may have a upper surface with a height D2 above the base 960 of the third lock plate 900. As is illustrated in FIG. 9D, the height D2 may be less than the height D1 of an upper surface of the third capture feature 950 as well as a lower surface of the third capture feature 950. Further, a remaining portion of the third lock plate 900 (for example, a portion of the third lock plate 900 not including the spring arm 128) may have an upper surface with a height D1 above the base 960 of the third lock plate 900. According to at least one example embodiment, D3>D2>D1. Accordingly, as is illustrated in FIG. 9D, the third capture feature 950 may be positioned above both an upper surface of a remaining portion of the spring arm 128, and an upper surface of a remaining portion of the third lock plate 900. According to at least one example embodiment, the third capture feature 950 is structured such that when the locking sleeve 112 is in the beam bolt opening 126, and the spring arm 128 is in an engaged position, at least a portion of the third capture feature 950 vertically overlaps at least a portion of the base region 116 of the locking sleeve 112; and when the locking sleeve 112 is in the beam bolt opening 126, and the spring arm 128 is in the disengaged position, there is no overlap between the third capture feature 950 and the base region 116 of the locking sleeve 112 in the vertical direction. The engaged position of the spring arm 128 refers to, for example, a position where the spring arm ratchet teeth 136 of the spring arm 128 are engaged or meshed with the locking sleeve ratchet teeth 144 of the locking sleeve 112. The disengaged position of the spring arm 128 refers to, for example, a position where the spring arm 128 is deflected such that the ratchet teeth 136 are not engaged or meshed with the locking sleeve ratchet teeth 144 of the locking sleeve 112. Thus, according to at least one example embodiment, the third capture feature 950 is sized and positioned on spring arm 128 such that the following conditions are met: 1) when the spring arm 128 of the third lock plate 900 is in the engaged position, the third capture feature 950 engages an upper surface 152 of locking sleeve base portion 116 in the same manner illustrated in FIG. 7 with respect to the first capture feature 150 of the first lock plate 400; and 2) when the spring arm 128 of the third lock plate 900 is in the disengaged position, the third capture feature 950 does not engage, or overlap in the vertical direction, the upper surface 152 of the locking sleeve base portion 116, and a horizontal gap 970 exists between the upper surface 152 and the capture feature 950, as is shown in FIGS. 10 and 11. The positioning on spring arm 128 and sizing of the third capture feature 950 illustrated in FIGS. 9A-11 are provided only as an example. According to at least one example embodiment, the capture feature 950 may have any combination of positioning on the spring arm 128 and sizing which allow the capture feature 950 to move with the end portion 936 of the spring arm 128 such that, if the locking sleeve 112 is in the beam bolt opening 126 of the third lock plate 900, the third capture feature 950 overlaps the base portion 116 of the locking sleeve 112 when the spring arm 128 is in the engaged position, and the capture feature 950 does not overlap the base portion 116 of the locking sleeve 112 when the spring arm 128 is in the disengaged position. Accordingly, using the third lock plate 900, during a detensioning operation where the spring arm 128 is deflected to the disengaged position, no overlap exists in the vertical direction between the third capture feature 950 and the base portion 116 of the locking sleeve 112, as is illustrated in FIGS. 10 and 11. Consequently, in the event the locking sleeve 112 shifts vertically during the detensioning operation, the chances of the third lock plate 900 shearing off or otherwise damaging the sleeve ratchet teeth 144, or any other part of the base portion 116 of the locking sleeve 112, may be significantly reduced. Accordingly, the lost time and expense associated with repairing or replacing the damaged locking sleeve 112 may be avoided by using the third lock plate 900 according to example embodiments. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, 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.
	abstract	The present invention discloses systems and methods for generating low energy, high current ion beams by scaling beamline dimensions and employing multiple beamlines. An array of beamlets is generated by an ion source. The beamlets then pass through a mass analysis module that permits selected ions to pass while blocking other ions and/or particles. The selected ions can then be accelerated to a desired energy level. Subsequently, the beamlets are diverged in horizontal and vertical directions to form a single low energy, high current ion beam.
	abstract	A packaging device for the transport and/or storage of a radioactive medium generating flammable gases and/or explosives via radiolysis, comprising a plurality of canisters intended to contain the radioactive medium, each canister defining an inner storage space accessible via an opening for filling the medium, on which plug-forming means are mounted. According to the invention, the device also comprises a structure forming a chamber, and means for placing in communication allowing a fluid communication to be set up between the inner storage space and the chamber.
	claims	1. A method of inspecting a defect in or on a semiconductor wafer, comprising:directing a beam towards the surface of the semiconductor wafer wherein/whereon the defect resides to thereby emit X-rays;detecting the emitted X-rays with plurality of detectors positioned at a plurality of angles with respect to the wafer surface;collecting X-ray data from the detectors; andbased on the X-ray data collected from the detectors at the plurality of angles, determining a location of the defect in three dimensions in relation to a plurality of different process layers of the wafer. 2. A method as recited in claim 1, wherein the detectors detect the emitted X-rays simultaneously. 3. A method as recited in claim 1, wherein an image is generated by combining the X-ray data from at least two X-ray emission energy spectra. 4. A method as recited in claim 1, wherein the defect resides fully within a sample volume. 5. A method as recited in claim 1, wherein the beam is stepped over an area where the defect resides. 6. A method as recited in claim 5, wherein the beam is stepped in a grid configuration. 7. A method as recited in claim 1, wherein the beam is rastered over an area where the defect resides. 8. A method as recited in claim 1, wherein the directed beam is an electron beam. 9. A method as recited in claim 1, wherein the directed beam is a focused ion beam. 10. A method as recited in claim 1, further comprising determining the elemental composition of the defect based on the collected X-ray data. 11. A method as recited in claim 1, wherein the semiconductor wafer comprises copper surrounded by dielectric material. 12. A method as recited in claim 11, wherein the detected X-rays are at least copper Kα and copper Lα X-rays. 13. A method as recited in claim 11, wherein the detected X-rays are at least copper Kα, copper Lα and silicon Kα X-rays. 14. A method of inspecting a defect in or on a semiconductor wafer, comprising:directing a beam towards the surface of the semiconductor wafer wherein/whereon the defect resides to thereby emit X-rays;detecting the emitted X-rays with a detector at a first angle with respect to the wafer surface;collecting X-ray data from the detector;directing a beam towards the surface of the semiconductor wafer wherein/whereon the defect resides to thereby emit X-rays;detecting the emitted X-rays with the detector at a second angle with respect to the wafer surface;collecting X-ray data from the detector; andbased on the X-ray data collected at the first and second angles, determining a location of the defect in three dimensions in relation to a plurality of different process layers of the wafer,wherein the second angle of the detector with respect to the wafer surface is achieved by (i) moving the position of the detector to the second angle after collecting the X-ray data from the detector at the first angle or (ii) tilting the wafer to achieve the second angle after collecting the X-ray data from the first angle. 15. A method as recited in claim 14, wherein the detector detects the emitted X-rays at the first and second angles at different sampling times. 16. A method as recited in claim 14, wherein the detector detects emitted X-rays at a plurality of angles with respect to the wafer surface. 17. A method as recited in claim 14, wherein the second angle of the detector with respect to the wafer surface is achieved by moving the position of the detector after collecting the X-ray data from the first angle. 18. A method as recited in claim 14, wherein the second angle of the detector with respect to the wafer surface is achieved by tilting the wafer after collecting the X-ray data from the first angle. 19. A method as recited in claim 14, wherein using the X-ray data to spatially resolve the location of the defect is accomplished by generating an image based on the X-ray data. 20. A method as recited in claim 19, wherein the image is generated by combining the X-ray data from at least two X-ray emission energy spectra. 21. A method as recited in claim 14, wherein the defect resides fully within a sample volume. 22. A method as recited in claim 14, wherein the beam is stepped over an area where the defect resides. 23. A method as recited in claim 22, wherein the beam is stepped in a grid configuration. 24. A method as recited in claim 14, wherein the beam is rastered over an area where the defect resides. 25. A method as recited in claim 14, wherein the directed beam is an electron beam. 26. A method as recited in claim 14, wherein the directed beam is a focused ion beam. 27. A method as recited in claim 14, further comprising determing the elemental composition of the defect from the X-ray data collected at the first and second angles. 28. A method as recited in claim 14, wherein the semiconductor wafer comprises copper surrounded by dielectric material. 29. A method as recited in claim 28, wherein the detected X-rays are at least copper Kα and copper Lα X-rays. 30. A method as recited in claim 29, wherein the directed beam is a focused ion beam. 31. A method as recited in claim 29, further comprising determining the elemental composition of the defect from the collected X-ray data. 32. A method as recited in claim 29, wherein the semiconductor wafer comprises copper surrounded by dielectric material. 33. A method as recited in claim 32, wherein the detected X-rays are at least copper Kα and copper Lα X-rays. 34. A method as recited in claim 32, wherein the detected X-rays are at least copper Kα, copper Lα and silicon Kα X-rays. 35. A method as recited in claim 28, wherein the detected X-rays are at least copper Kα, copper Lα and silicon Kα X-rays. 36. A method of inspecting a defect in or on a semiconductor wafer, comprising:directing a beam towards the surface of the semiconductor wafer wherein/whereon the defect resides to thereby emit X-rays;detecting the emitted X-rays substantially, simultaneously at a plurality of angles with respect to the wafer surface with a single detector;collecting X-ray data from the detector; andbased on the collected X-ray data that is detected at the plurality of angles, determining a location of the defect in three dimensions in relation to a plurality of different process layers of the wafer. 37. A method as recited in claim 32, wherein an image is generated by combining the X-ray data from at least two X-ray emission energy spectra. 38. A method as recited in claim 36, wherein the defect resides fully within a sample volume. 39. A method as recited in claim 36, wherein the beam is stepped over an area where the defect resides. 40. A method as recited in claim 39, wherein the beam is stepped in a grid configuration. 41. A method as recited in claim 36, wherein the beam is rastered over an area where the defect resides. 42. A method as recited in claim 36, wherein the directed beam is an electron beam. 43. An apparatus for inspecting a defect in or on a semiconductor wafer, comprising:a beam generator operable to direct a charged particle beam towards a structure;a plurality of detectors positioned at different angles with respect to the surface of the semiconductor wafer to detect X-rays from the structure in response to the charged particle beam; anda processor operable to:cause the beam generator to direct a beam towards the structure; andcharacterize one or more defects based on the detected X-rays from the plurality of detectors so as to spatially resolve a location of the one or more defects in three dimensions and in relation to a plurality of different process layers of the wafer. 44. An apparatus as recited in claim 43, wherein the characterizing operation is based on a ratio of a first X-ray intensity for a first material over a second X-ray intensity for a second material, wherein the first and second X-ray intensities are obtained from the detected X-rays from the scanned structure. 45. An apparatus as recited in claim 43, wherein the scanned structure is a portion of a interconnect structure in an integrated circuit device. 46. An apparatus as recited in claim 43, wherein the directed beam is an electron beam. 47. An apparatus as recited in claim 43, wherein the electron beam is stepped over an area of the sample surface. 48. An apparatus as recited in claim 43, wherein the electron beam is rastered over an area of the sample surface. 49. An apparatus as recited in claim 43, wherein the directed beam is a focused ion beam.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.