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044329423	abstract	In apparatus for filling a container suitable for storage with radioactive solid wastes arising from atomic power plants or the like, a plasma arc is irradiated toward a portion of the wastes to melt the portion of the wastes; portions of the wastes are successively moved so as to be subjected to irradiation of the plasma arc to continuously melt the wastes; and the melts obtained by melting the wastes are permitted to flow down toward the bottom of the container.
	abstract	A control rod drive mechanism (CRDM) configured to latch onto the lifting rod of a control rod assembly and including separate latch engagement and latch holding mechanisms. A CRDM configured to latch onto the lifting rod of a control rod assembly and including a four-bar linkage closing the latch, wherein the four-bar linkage biases the latch closed under force of gravity.
	description	This application claims the benefit of Japanese Application No. 2004-2358899 filed Aug. 13, 2004. The present invention relates to a collimator control method and an X-ray CT (Computed Tomography) apparatus, and more specifically to a collimator control method for an X-ray CT apparatus, which helically scans a subject with an X-ray beam formed by a collimator, and an X-ray CT apparatus which performs collimator control. When a helical scan is performed, an X-ray tube and an X-ray detector are rotated around a subject to be photographed and a table with the subject placed thereon is linearly moved. A multi-row detector or a plane X-ray detector is used as the X-ray detector and an X-ray beam is formed as a cone beam in association with it, so that the efficiency of acquisition of X-ray data through the helical scan is improved. A collimator for forming the X-ray beam as the cone beam has an aperture width held constant during the helical scan (refer to, for example, the following patent document 1). [Patent Document 1] Japanese Unexamined Patent Publication No. 2003-052684 (Fifth page and FIG. 5) Since X-ray data unused in image reconstruction are also acquired or collected at start and end points of the helical scan in the above X-ray CT apparatus, the irradiation of X rays corresponding thereto results in needless irradiation. Thus, the X-ray irradiation is not preferable in view of exposure of a patient. Therefore, an object of the present invention is to realize a collimator control method which reduces exposure of a patient at the time of a helical scan and realizes an improvement in efficiency of X-ray data acquisition, and an X-ray CT apparatus which performs such collimator control. (1) The invention according to one aspect for resolving the above problem provides a collimator control method for an X-ray CT apparatus wherein a subject is helically scanned in the direction of a body axis thereof using an X-ray beam formed by a collimator and image reconstruction is performed based on projection data obtained through an X-ray detector, comprising changing an opening degree of an aperture of the collimator according to a position on the body axis of the subject in the process of the progress of the helical scan. (2) The invention according to another aspect for resolving the above problem provides an X-ray CT apparatus comprising an X-ray source, a collimator for shaping X-rays emitted from the X-ray source, control means for controlling the collimator, an X-ray detector disposed so as to be opposed to the X-ray source and the collimator with a subject interposed therebetween, and image reconstructing means for helically scanning the subject in the direction of a body axis thereof and reconstructing an image on the basis of projection data obtained through the X-ray detector, wherein the control means changes an opening degree of an aperture of the collimator according to a position of a helical scan on the body axis in the process of the progress of the helical scan. It is preferable to, at a start position of the helical scan, open an aperture of the collimator at a first half of a predetermined collimator aperture width determined from a slice thickness in the direction of the progress of the helical scan and brings the aperture of the collimator into a closed state at its latter half, bring the aperture of the collimator into an opened state at both the first and latter halves in the progress direction of the helical scan halfway through the helical scan, and at an end position of the helical scan, close the aperture of the collimator at the first half in the progress direction of the helical scan and brings the aperture of the collimator into an opened state at its latter half, in that exposure of a patient is reduced to the minimum. It is preferable to allow a change of the aperture of the collimator from the closed state to the opened state at the latter half thereof to be performed continuously and allow a change of the aperture from the opened state to the closed state to be performed continuously, in that they are adapted to a continuous change in data acquisition position. It is preferable to allow a change of the aperture of the collimator from the closed state to the opened state to be performed at the latter half thereof during acceleration of the progress of the helical scan in the body-axis direction, and allow a change of the aperture of the collimator from the opened state to the closed state to be performed at the first half thereof during deceleration of the progress of the helical scan in the body-axis direction, in that exposure of the patient can be reduced similarly even though the collimator aperture is controlled during a constant velocity period. The acceleration and deceleration of the progress of the helical scan in the body-axis direction may preferably be linear in that collimator control is easy. The acceleration and deceleration of the progress of the helical scan in the body-axis direction may preferably be nonlinear in that the acceleration and deceleration are smooth. The X-ray detector may preferably be a multi-row X-ray detector or a plane X-ray detector in that the efficiency of the helical scan is improved. The X-ray CT apparatus may preferably perform image reconstruction by a three-dimensional image reconstructing method in that the quality of an image is improved. In the invention according to each of the respective aspects, the opening degree of an aperture of a collimator is changed according to a position of a helical scan on a body axis in a progress process of the helical scan. It is therefore possible to realize a collimator control method which reduces exposure of a patient at the time of the helical scan and realizes an improvement in efficiency of X-ray data acquisition, and an X-ray CT apparatus which performs such collimator control. Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. Best modes for carrying out the invention will be explained below with reference to the accompanying drawings. Incidentally, the present invention is not limited to the best modes for carrying out the invention. A block diagram of an X-ray CT apparatus is shown in FIG. 1. The present apparatus is one example showing the best mode for carrying out the present invention. One example of the best mode for carrying out the present invention related to the X-ray CT apparatus is shown by the configuration of the present apparatus. One example of the best mode for carrying out the present invention related to a collimator control method is shown by the operation of the present apparatus. The X-ray CT apparatus 100 is equipped with an operation console 1, a photographing table 10 and a scan gantry 20. The operation console 1 is equipped with an input device 2 which accepts an input from an operator, a central processing unit 3 which executes an image reconstructing process or the like, a data acquisition buffer 5 which acquires or collects projection data acquired by the scan gantry 20, a CRT 6 which displays a CT image reconstructed from the projection data, and a storage device 7 which stores programs, data and X-ray CT images therein. The central processing unit 3 is one example of an image reconstructing means according to the present invention. The table device 10 is provided with a cradle 12 which inserts and draws a subject into and from a bore (cavity portion) of the scan gantry 20 with the subject placed thereon. The cradle 12 is elevated and moved linearly along the table by a motor built in the photographing table 10. Coordinates in a Z-axis direction are counted by an encoder. The corresponding z-axis coordinate is calculated by a controller 29. The controller 29 adds a z-axis coordinate Z (view, i) corresponding to a center coordinate in a z direction of a detector to its corresponding projection data (view, j, i) of a DAS through a slip ring 28. Here, a channel number, a detector row or sequence and a view angle are assumed to be i, j and view respectively. The scan gantry 20 is equipped with an X-ray tube 21, an X-ray controller 22, a collimator 23, a multi-row detector 24, the DAS (Data Acquisition System) 25, a rotation controller 26 which rotates the X-ray tube 21 or the like about a body axis of the subject and controls the collimator 23, and the controller 29 which performs the transfer of control signals or the like between the operation console 1 and the photographing table 10. The X-ray tube 21 is one example of an X-ray source according to the present invention. The collimator 23 is one example of a collimator according to the present invention. The rotation controller 26 is one example of a control means according to the present invention. The multi-row detector 24 is one example of an X-ray detector according to the present invention. FIG. 2 is an explanatory view showing the X-ray tube 21 and the multi-row detector 24. The X-ray tube 21 and the multi-row detector 24 rotate about the center of rotation IC. When the vertical direction is assumed to be a y direction, the horizontal direction is assumed to be an x direction and the direction orthogonal to these is assumed to be a z direction, the plane of rotation of each of the X-ray tube 21 and the multi-row detector 24 is an xy plane. The direction of movement of the cradle 12 corresponds to the z direction. An X-ray beam called cone beam CB is generated by the X-ray tube 21 and the collimator 23. When the direction of a center axis of the cone beam CB is parallel to a y direction, the view angle is assumed to be equal to 0°. The multi-row detector 24 has detector rows corresponding to 256 rows, for example. The direction of side-by-side provision of the detector rows corresponds to the z direction. The respective detector rows respectively have channels corresponding to 1024 channels, for example. FIG. 3 is a flow diagram schematically showing the operation of the X-ray CT apparatus 100. In Step S1, a table linear movement position z and projection data D (view, j, i) expressed in the view angle view, detector row number j and channel number i are acquired while the X-ray tube 21 and the multi-row detector 24 are being rotated about a subject to be photographed and the cradle 12 is being linearly moved along the table. That is, the acquisition of data by a helical scan is performed. Incidentally, the coordinate of the photographing table in the z-axis direction at this time results in one obtained by adding z-coordinate information Z (view) of the photographing table at the center position in the z direction, of the data acquisition system comprised of the multi-row detector 24 and the X-ray tube 21 to the corresponding projection data D0 (view, j, i). A data acquisition process in Step S1 will be explained with reference to FIGS. 5 through 21. In Step S2, the projection data D0 (view, j, i) is pre-processed. The details of the pre-processing include an offset correction (Step S21), logarithmic translation (Step S22), an X-ray dosage correction (Step S23) and a sensitivity correction (Step S24) as shown in FIG. 4. In Step S3, a reconstruction function superimposition process is effected on the pre-processed projection data D2 (view, j, i). That is, the projection data is Fourier-transformed and multiplied by a reconstruction function, followed by being inversely Fourier-transformed. In Step S4, a three-dimensional backprojection process is performed on the projection data D0 (view, j, i) subjected to the reconstruction function superimposition process to determine backprojection data D3 (x, y). The three-dimensional backprojection process will be described later with reference to FIG. 22. In Step S5, the backprojection data D3 (x, y) is post-processed to obtain a CT image. FIG. 5 is a flow diagram showing the details of the data acquisition process (Step S1 in FIG. 3). Controlled states of an aperture of the collimator 23 at data acquisition are shown in FIG. 6 and FIGS. 7 through 12. In Step S101, the cradle 12 linearly moves along the table up to table linear movement start positions shown in FIGS. 14 and 16 at low velocity. In Step S102, the collimator is kept open only at a location where z≧0 at the position of the center of rotation IC. This condition is shown in FIG. 6(A) and FIG. 7. Incidentally, the sign of z relates to the center of rotation IC, the direction in which the helical scan proceeds is assumed to be + (front side) and its opposite direction is assumed to be − (rear side). In Step S103, the X-ray tube 21 and the multi-row detector 24 are rotated about the subject to be photographed with IC as the center of rotation. In Step S104, the table linear movement of the cradle 12 is started. In Step S105, the velocity of the table linear movement of the cradle 12 is accelerated on the basis of a predetermined function. A case in which the predetermined function is linear relative to the time, is shown in FIGS. 14 and 15, and a case in which the predetermined function is nonlinear relative to the time, is shown in FIGS. 16 and 17. When the position of center of the X-ray data acquisition system in the z direction reaches z=0, X rays are outputted. With the output thereof, the following control of collimator's aperture is performed. Assuming that the opening/closing states of the collimator at this time are as follows: cw: collimator aperture width (aperture), Zce: z coordinate maximum value of collimator aperture (+ side), and Zcs: z coordinate minimum value of collimator aperture (− side), cw=Zce−Zcs is reached. Also assuming that Zd, Zs and Ze are set as follows: Zd: center z coordinate of data acquisition system, Zs: z coordinate at the start of helical scan (Zs=0), and Ze: z coordinate at the stop of helical scan, Zce is set to a z coordinate equivalent to the first half of a pre-set slice thickness at an X-ray data acquisition start position and controlled so that Zcs=Zs is reached. This condition is illustrated in FIG. 6(A) and FIG. 7. Thus, the first half of the aperture is opened and the latter half thereof is brought into a closed state. The state of opening/closing of the collimator is measured using each of collimator position detection channels (portions indicated by broken lines) shown in FIGS. 7 through 12. When the outputs of the corresponding channel are taken along the z direction (row direction), they are represented as shown in FIG. 13. The states of opening and closing of the collimator can be recognized by determining widths wa, wb and wc with which detector output signals at this time are outputted. At this time, each of the z-direction coordinates counted by the encoder for determining the z-direction coordinates of the photographing table 10 is calculated as a z-axis coordinate by the controller 29, which in turn reach the DAS 25 through the slip ring 28. The DAS 25 is capable of recognizing the present opening/closing state of the collimator from each of the outputs of the collimator position detection channels. The rotation controller 26 issues a command to the collimator 23 in such a manner that the collimator is opened or closed to a collimator opening/closing target value determined from each of the z coordinates. The difference between a collimator opening/closing value determined from each of the outputs of the collimator position detection channels and the collimator opening/closing target value is determined to generate a feedback signal. The rotation controller 29 issues instructions to the collimator 23 in accordance with the feedback signal to thereby perform feedback control which determines whether the collimator 23 has acted on instructions. In Step S106, the collimator is kept open only at a location where when z≧0. That is, the collimator is controlled in such a manner that Zcs=Zs=0 is reached. This condition is represented as shown in FIG. 6(A) and FIG. 7. In Step S107, projection data D0 (view, j, i) in acceleration is acquired. At this time, the latter half of the aperture is opened with the progress of the helical scan. The latter half thereof is opened with an increase in the difference between Zs and Zd as shown in FIG. 6(B). This state is illustrated in FIG. 8. In Step S108, it is determined whether the table linear movement velocity of the cradle 12 reaches a predetermined velocity Vc shown in FIGS. 14 and 16. When the table linear movement velocity reaches the predetermined velocity Vc, the X-ray CT apparatus 100 proceeds to Step S109. When the table linear movement velocity is found not to reach the predetermined velocity Vc, the X-ray CT apparatus 100 is returned to Step S104, where the table linear movement velocity is further accelerated. In Step S109, projection data D0 (view, j, i) at low velocity is acquired in a state in which the table linear movement velocity of the cradle 12 is being maintained at a predetermined velocity. At this time, the latter half of the aperture is completely opened up. Thus, the first and latter halves of the aperture are both placed in an opened-up state. This condition is illustrated in FIG. 6(C) and FIG. 9. In Step S110, it is determined whether the cradle 12 reaches a constant-velocity end position shown in each of FIGS. 14 and 16. When the cradle 12 has reached the constant-velocity end position, the X-ray CT apparatus 100 proceeds to Step 111. When it is determined that the cradle 12 does not reach the constant-velocity end position, the X-ray CT apparatus 100 is returned to Step S109, where the acquisition of projection data at constant velocity is continued. In Step S111, the table linear movement velocity of the cradle 12 is decelerated based on a predetermined function and a tube current is reduced correspondingly. A case in which the predetermined function is linear, is shown in FIGS. 14 and 15. A case in which the predetermined function is non-linear, is shown in FIGS. 16 and 17. When, at this time, the coordinate Zce on the maximum value side in the z direction, of the collimator of the X-ray data acquisition system begins to reach the coordinate Ze at the stop of the helical scan, the X-ray CT apparatus starts controlling the opening/closing of the collimator such that Zce=Ze is reached. That is, the X-ray CT apparatus starts to gradually close the first half of the aperture. This condition is illustrated in FIGS. 6(D) and 6(E) and FIGS. 10 and 11. When the center coordinate of the X-ray data acquisition system reaches Zd=Ze, the output of X rays is stopped. This condition is illustrated in FIG. 6(F) and FIG. 12. Thus, the first half of the aperture is closed and the latter half thereof is brought into a closed state. In Step S112, the collimator is kept open only at a location where Z≦Ze. That is, the collimator is controlled in such a manner that Zce=Ze is reached. This condition is represented as shown in FIG. 6(F) and FIG. 12. In Step S113, projection data D0 (view, j, i) placed under deceleration is acquired. In Step S114, it is determined whether the table linear movement velocity of the cradle 12 reaches a stoppable velocity shown in each of FIGS. 14 and 16. When the stoppable velocity is reached, the X-ray CT apparatus proceeds to Step S115. When the stoppable velocity is not reached, the X-ray CT apparatus returns to Step S11, where the table linear movement velocity is decelerated. In Step S115, the table linear movement of the cradle 12 is stopped. Incidentally, if the constant velocity start position is set to be equal to the constant velocity end position as shown in FIGS. 18 through 21, then the projection data D0 (view, j, i) can be acquired at the shortest table linear movement distance. Even in the case of such a scan, collimator control, which conforms to the above, is performed. Thus, since only the first half of the aperture is kept open and the latter half thereof is closed at the start of the helical scan, the dose of exposure of a patient can be reduced correspondingly. Since only the latter half of the aperture is made open and the first half thereof is closed at the end of the helical scan, the dose of exposure of the patient can be reduced correspondingly. It is thus possible to set the patient's exposure to a required minimum. A change of the aperture at the latter half from the closed state thereof to the opened state thereof is continuously performed, and a change of the aperture at the first half thereof from the opened state thereof to the closed state thereof is continuously performed. This can therefore adapt to a continuous change in data acquisition position. The change of the aperture at the latter half from the closed state thereof to the opened state thereof is made during acceleration of the progress of the helical scan in the body-axis direction, and the change of the aperture at the first half from the opened state thereof to the closed state thereof is made during deceleration of the progress of the helical scan in the body-axis direction. It is therefore possible to improve the efficiency of the helical scan. Making linear the acceleration and deceleration of the progress of the helical scan in the body-axis direction enables the collimator to be easily controlled. Incidentally, the acceleration and deceleration can be smoothed by making nonlinear the acceleration and deceleration of the progress of the helical scan in the body-axis direction. Since the X-ray detector is of a multi-row X-ray detector or a plane X-ray detector, the efficiency of the helical scan can be improved. Even though such collimator control is done, the complete data set from the scan start position Zs to the scan end position Ze is acquired as the projection data. Accordingly, a complete reconstructed image can be obtained with respect to the range from the scan start position Zs to the scan end position Ze on the basis of these projection data. FIG. 22 is a flow diagram showing the details of the three-dimensional backprojection process (Step S4 in FIG. 3). In Step S61, attention is paid to one of all views (i.e., views corresponding to 360° or views corresponding to “180°+fan angles”) necessary for reconstruction of a CT image. Projection data Dr corresponding to respective pixels in a reconstruction area P are extracted. As shown in FIG. 23, a square area of 512×512 pixels, which is parallel to an xy plane, is defined as a reconstruction area P, and a pixel row L0 parallel to an x axis of y=0, a pixel row L63 of y=63, a pixel row L127 of y=127, a pixel row L191 of y=191, a pixel row L255 of y=255, a pixel row L319 of y=319, a pixel row L383 of y=383, a pixel row L447 of y=477, and a pixel row L511 of y=511 are taken as rows respectively. In this case, when projection data on lines T0 through T511 shown in FIG. 24 obtained by projecting these pixel rows L0 through L511 on the plane of the multi-row X-ray detector 24 in an X-ray penetration direction are extracted in such a condition, then they result in projection data Dr for the pixel rows L0 through L511. Although the X-ray penetration direction is determined depending on geometrical positions of an X-ray focal point of the X-ray tube 21, the respective pixels and the multi-row X-ray detector 24. Since, however, the z coordinates of projection data D0 (z, view, j, i) are known, the X-ray penetration direction can be accurately determined even in the case of the projection data (z, view, j, i) placed under acceleration and deceleration. Incidentally, when some of lined are placed out of the plane of the multi-row X-ray detector 24 as in the case of, for example, the line T0 obtained by projecting the pixel row L0 on the plane of the multi-row X-ray detector 24 in the X-ray penetration direction, the corresponding projection data Dr is set to “0”. Thus, as shown in FIG. 25, the projection data Dr (view, x, y) corresponding to the respective pixels of the reconstruction area P can be extracted. Referring back to FIG. 22, in Step S62, the projection data Dr (view, x, y) are multiplied by a cone beam reconstruction weight coefficient to create projection data D2 (view, x, y) shown in FIG. 26. When the distance between the focal point of the X-ray tube 21 and each of a detector row j of the multi-row detector 24, corresponding to the projection data Dr and a channel i thereof is assumed to be r0, and the distance between the focal point of the X-ray tube 21 and each of the pixels on the reconstruction area P corresponding to the projection data Dr is assumed to be r1 here, the cone beam reconstruction weight coefficient becomes (r1/r0)2. In Step S63, as shown in FIG. 27, the projection data D2 (view, x, y) are added to the backprojection data D3 (x, y) cleared in advance, in association with pixels. In Step S64, Steps S61 through S63 are repeatedly effected on all views (i.e., views of 360° or views of “180°+fan angles”) necessary for reconstruction of a CT image to obtain backprojection data D3 (x, y) as shown in FIG. 27. Incidentally, the reconstruction area P may be configured as a circular area as shown in FIG. 28. According to the X-ray CT apparatus 100 described above, projections data are acquired or collected even during not only a period in which a table linear movement velocity is being kept constant but also a period in which a table linear movement is being under acceleration/deceleration. Coordinate information in a body-axis direction (hereinafter called z axis) while the scan is running, is added to each view data or several view data once. The acquired projection data are used for image reconstruction together with z-axis coordinates and information. Therefore, a table linear moving distance for acceleration/deceleration, of the entire table linear moving distance is also available for image reconstruction. Incidentally, the image reconstructing method may be the two-dimensional image reconstructing method known to date or a three-dimensional image reconstructing method based on the FeldKamp method known to date. Further, three-dimensional image reconstructing methods proposed by Japanese Patent Application Nos. 2002-066420, 2002-147061, 2002-147231, 2002-235561, 2002-235662, 2002-267833, 2002-322756 and 2002-338947 may be used. Many widely different embodiments of the invention may be configured without departing from the spirit and the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.
054004993	claims	1. A tool for removing an internal bushing, comprising: a first member having a first arcuate planar contact surface, a first seat and a first circular cylindrical bore; a second member having a second arcuate planar contact surface, a second seat and a second circular cylindrical bore, said first and second members being arranged so that said first and second circular cylindrical bores are coaxial; a swivel pin having a longitudinal axis and arranged to pass through said first and second circular cylindrical bores, each of said first and second members being pivotable relative to said swivel pin and relative to each other about said longitudinal axis of said swivel pin, said first and second members having a first relative angular position in which said first and second arcuate planar contact surfaces are co-planar and a second relative angular position in which said first and second arcuate planar contact surfaces are closer together than in said first relative angular position; means for preventing removal of said swivel pin from said first and second circular cylindrical bores; a third member rigidly connected to said second member, said third member being a solid cylinder having a longitudinal axis perpendicular to said longitudinal axis of said swivel pin; and a first compression spring having one end seated in said first seat and another end seated in said second seat, said first compression spring urging said first and second members apart in said second relative angular position. 2. The tool as defined in claim 1, further comprises a guide pin mounted on said second member and projecting inside said first compression spring to prevent flexing of said first compression spring. 3. The tool as defined in claim 1, wherein said first and second seats are separated from said axis of rotation by a first longitudinal distance and said first and second arcuate planar contact surfaces are separated from said axis of rotation by a second longitudinal distance less than said first longitudinal distance. 4. The tool as defined in claim 1, wherein said first member has a third seat concentric with said first seat and said second member has a fourth seat concentric with said second seat, further comprising a second compression spring having one end seated in said third seat and another end seated in said fourth seat, said second compression spring encircling said first compression spring. 5. The tool as defined in claim 1, wherein said first member has a first straight portion located between said first arcuate planar contact surface and said first circular cylindrical bore and said second member has a second straight portion located between said second arcuate planar contact surface and said second circular cylindrical bore, said first and second straight portions having first and second camming surfaces respectively, said first and second camming surfaces being separated by an acute angle when said first and second members have said first relative angular position.
	claims	1. A charged beam drawing apparatus which draws a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:a main deflector which deflects a charged beam, the main deflector sequentially selecting a plurality of sub-deflection drawing regions obtained by dividing a main deflection drawing region of a sample,a main deflection driving unit which drives the main deflector,a sub deflector which deflects the charged beam in the selected sub deflection region, the sub deflector drawing a pattern in the selected sub deflection region, anda sub deflection driving unit which drives the sub deflector, the sub deflection driving unit including a sub deflection sensitivity correction circuit which corrects deflection sensitivity according to a shot position in the sub deflection region, a sub deflection astigmatic correction circuit which corrects a deflection astigmatic point according to a shot position in the sub deflection region, an adder circuit which superimposes an output of the sub deflection sensitivity correction circuit and an output of the sub deflection astigmatic correction circuit and a deflection amplifier which applies an output of the adder circuit to the sub deflector. 2. The charged beam drawing apparatus according to claim 1, wherein the sub deflection driving unit divides the main deflection drawing region into meshes and has a memory which stores a sub deflection sensitivity correction coefficient and sub deflection astigmatic correction coefficient for each mesh. 3. The charged beam drawing apparatus according to claim 2, wherein the mesh is not smaller than the sub deflection region. 4. The charged beam drawing apparatus according to claim 2, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit respectively read out a sub deflection sensitivity correction coefficient and sub deflection astigmatic correction coefficient corresponding to the position of the selected sub deflection region from the memory and perform correction operations according to a shot position in the selected sub deflection region based on the readout correction coefficients. 5. The charged beam drawing apparatus according to claim 2, wherein the sub deflection driving unit includes a sub deflection astigmatic correction value calculating unit which measures a preset inclination coefficient and a sub deflection astigmatic difference of a charged particle beam by scanning a preset mark in two perpendicularly intersecting directions by using the charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value and calculates an (n+1)-th sub deflection astigmatic correction value in which no sub deflection astigmatic difference occurs based on the measured preset inclination coefficient and sub deflection astigmatic difference to derive the sub deflection astigmatic correction coefficient stored in the memory, and a sub deflection astigmatic correction coefficient calculating unit which repeatedly performs a calculating operation starting from the first correction value by the astigmatic correction value calculating unit until an absolute value of a difference between the n-th and (n+1)-th sub deflection astigmatic correction values becomes smaller than a preset value and calculates a sub deflection astigmatic correction coefficient which is a coefficient of a relational expression defining a sub deflection astigmatic correction amount by use of the (n+1)-th sub deflection astigmatic correction value which is finally obtained. 6. The charged beam drawing apparatus according to claim 1, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit are configured to perform an operation in a pipeline system. 7. The charged beam drawing apparatus according to claim 1, wherein the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit simultaneously and respectively perform a deflection sensitivity correcting process and deflection astigmatic correction process in parallel and the adder circuit adds outputs of the sub deflection sensitivity correction circuit and sub deflection astigmatic correction circuit in adequately adjusted timing. 8. The charged beam drawing apparatus according to claim 1, wherein the sub deflector is an octopole deflector having eight electrodes. 9. A charged beam drawing apparatus which draws a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:a sub deflection astigmatic correction value calculating unit which measures a preset inclination coefficient and a sub deflection astigmatic difference of the charged particle beam by scanning a preset mark in two perpendicularly intersecting directions by use of a charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value and calculates an (n+1)-th sub deflection astigmatic correction value used to eliminate a sub deflection astigmatic difference based on the measured preset inclination coefficient and sub deflection astigmatic difference,a sub deflection astigmatic correction coefficient calculating unit which repeatedly performs an operation of calculating sub deflection astigmatic correction values starting from the first sub deflection astigmatic correction value by use of the astigmatic correction value calculating unit until an absolute value of a difference between the n-th and the (n+1)-th sub deflection astigmatic correction values becomes smaller than a preset value and calculates a sub deflection astigmatic correction coefficient which is a coefficient of a relational expression defining a sub deflection astigmatic correction amount by use of the (n+1)-th sub deflection astigmatic correction value which is finally obtained, anda drawing unit which draws a preset pattern on the sample by use of charged particle beam in which the sub deflection astigmatic point is corrected according to the relational expression containing the calculated sub deflection astigmatic correction coefficient. 10. The charged beam drawing apparatus according to claim 9, wherein the operation of calculating the sub deflection astigmatic correction coefficient is performed in a plurality of positions of the drawing region. 11. The charged beam drawing apparatus according to claim 9, wherein the operations of calculating the sub deflection astigmatic correction value and calculating the sub deflection astigmatic correction coefficient are performed in two perpendicularly intersecting directions different from the above two directions in addition to the above two directions. 12. The charged beam drawing apparatus according to claim 9, wherein the preset inclination coefficient is an inclination value of a variation amount of the sub deflection astigmatic difference when sub deflection astigmatic correction amounts in the two perpendicularly intersecting directions are used as variables. 13. A charged beam drawing method for drawing a desired pattern on a sample by use of a charged beam deflected in main/sub two stages, comprising:measuring sub deflection astigmatic differences in two perpendicularly intersecting directions of a charged particle beam by scanning a preset mark in the two perpendicularly intersecting directions by use of the charged particle beam in which a sub deflection astigmatic point is corrected by use of an n-th sub deflection astigmatic correction value,calculating an (n+1)-th sub deflection astigmatic correction value used to eliminate a sub deflection astigmatic difference based on the n-th sub deflection astigmatic correction value, measured sub deflection astigmatic difference and preset inclination coefficient,determining whether an absolute value of a difference between the (n+1)-th sub deflection astigmatic correction value calculated and the n-th sub deflection astigmatic correction value used for calculation is smaller than a preset value,repeatedly performing operations of measuring the sub deflection astigmatic difference, calculating the sub deflection astigmatic correction value and determining whether the absolute value of the difference is smaller than the preset value starting from the first sub deflection astigmatic correction value and terminating the above operations when the absolute value of the difference between the (n+1)-th and n-th sub deflection astigmatic correction values becomes smaller than the preset value, anddrawing a desired pattern on the sample by use of the charged particle beam subjected to astigmatic correction by use of an (n+1)-th sub deflection astigmatic correction value obtained when the difference becomes smaller than the preset value. 14. The charged particle beam drawing method according to claim 13, wherein (n+1)-th sub deflection astigmatic correction amounts in which the difference becomes smaller than a preset value are respectively calculated in a plurality of positions of the drawing region and a sub deflection astigmatic correction coefficient which is a coefficient of a relational equation defining the sub deflection astigmatic correction amount in each position of the drawing region is calculated by use of the (n+1)-th sub deflection astigmatic correction value calculated in each position. 15. The charged particle beam drawing method according to claim 13, wherein an inclination value of a variation amount of the sub deflection astigmatic difference is used as the preset inclination coefficient when sub deflection astigmatic correction amounts in the two perpendicularly intersecting directions are used as variables. 16. The charged particle beam drawing method according to claim 13, wherein an operation of measuring the sub deflection astigmatic difference in two perpendicularly intersecting directions different from the above two directions, calculating the sub deflection astigmatic correction value and determining whether the absolute value of the difference is smaller than the preset value is repeatedly performed from the first sub deflection astigmatic correction value and terminated when an absolute value of a difference between the (n+1)-th and n-th sub deflection astigmatic correction values becomes smaller than a preset value and the charged particle beam subjected to astigmatic correction by use of the (n+1)-th sub deflection astigmatic correction value obtained when the difference becomes smaller than the preset value is used to draw a pattern on a sample.
	abstract	A nuclear fuel storage cask includes an outer shell having a length extending from a first end to a second end of the outer shell, the outer shell defining an inner cavity circumscribed by the outer shell, an outer perimeter extending around the outer shell, an inner perimeter positioned inward from the outer perimeter, and a cooling circuit extending along the length of the outer shell, the cooling circuit including an inner passage, and an outer passage, a coolant positioned within the cooling circuit, where the coolant is configured to move through the inner passage, absorbing heat from the inner cavity of the outer shell, and the coolant is configured to move through the outer passage, dissipating heat through the outer perimeter of the outer shell, and a lid coupled the outer shell, where the lid covers the inner cavity of the outer shell.
	claims	1. A cask for containing radioactive materials comprising:a cask body comprising an opening forming a passageway into an internal storage cavity of the cask;a closure lid configured to be detachably coupled to the cask body to enclose the opening; anda locking mechanism comprising at least one first locking member and at least one second locking member, the first and second locking members slideable relative to one another to alter the locking mechanism between: (1) a first state in which the closure lid can be removed from the cask body; and (2) a second state in which the first and second locking members engage one another to prevent the closure lid from being removed from the cask body. 2. The cask according to claim 1, wherein the locking mechanism is configured so that upon the locking mechanism be altered from the first state to the second state, the closure lid and the cask body are pulled together to fluidly seal the internal storage cavity. 3. The cask according to claim 2, wherein the first and second locking members translate relative to one another when the locking mechanism is altered from the first state to the second state. 4. The cask according to claim 3, further comprising a gasket located at an interface between the cask body and the closure lid, and wherein the gasket is compressed a greater amount in the second state than in the first state. 5. The cask according to claim 1, wherein one of the first and second locking members is fixed relative to the cask body or the closure lid, and the other one of the first and second locking members is slideable relative to both the cask body and the closure lid. 6. The cask according to claim 1, wherein the locking mechanism does not include threaded fasteners in the second state. 7. The cask according to claim 1, wherein the first locking member comprises a plurality of spaced-apart first locking protrusions and the second locking member comprises a plurality of spaced-apart second locking protrusions which are selectively interlockable with the first locking protrusions to lock the lid to the cask body. 8. The cask according to claim 7, wherein the first locking member with first locking protrusions is disposed on the lid, and the second locking member comprises portions of the cask body in the storage cavity in which the second locking protrusions are fixedly disposed on the cask body. 9. The cask according to claim 8, wherein the first and second locking protrusions are each wedge shaped defining tapered first and second locking surfaces respectively, the first locking surfaces being slideably engageable with the second locking surfaces when the locking mechanism is in the second state. 10. The cask according to claim 9, wherein the first locking surfaces frictionally engage the second locking surfaces to lock the lid to the cask body via a wedging-action which draws the lid towards and against the cask body. 11. The cask according to claim 8, wherein the first locking member comprises an elongated locking bar and the first locking protrusions are disposed thereon, the locking bar being slideably disposed in a corresponding elongated guide channel formed on the lid such that the locking bar is movable relative to the lid. 12. The cask according to claim 8, wherein the first locking protrusions of the lid are insertable between and through the second locking protrusions of the cask body, and vice versa. 13. The cask according to claim 11, wherein the locking bar is movable to interlock the first and second locking protrusions without moving the lid relative to the cask body when the lid is coupled to the cask body. 14. The cask according to claim 11, wherein the locking bar is movable between a locked position in which the first and second protrusions are mutually engaged to prevent removal of the lid from the cask body, and an unlocked position in which the first and second protrusions are disengaged to allow removal of the lid from the cask body. 15. The cask according to claim 14, wherein the first locking protrusions of the lid are positioned below the second locking protrusions of the cask body when the locking bar is in the locked position. 16. The cask according to claim 11, wherein the first locking protrusions are received and slideable within an elongated and inwardly open locking recess formed in the second locking member on the cask body below the second locking protrusions. 17. The cask according to claim 1, further comprising a hydraulic or pneumatic actuator coupled to the first locking member and operable to slide the first locking member to change the locking mechanism between the first and second states. 18. The cask according to claim 17, wherein each actuator includes an extendible and retractable piston rod fixedly coupled to the first locking member. 19. The cask according to claim 5, further comprising a locking handle assembly mounted to the cask body, the locking handle assembly configured and movable to retain the locking mechanism in the second state. 20. The cask according to claim 1, wherein the cask body has an elongated rectangular cuboid configuration and the lid has a rectangular configuration. 21. The cask according to claim 20, wherein the lid comprises a plurality of first locking members and the cask body includes a plurality of second locking members slideably engageable with each other.
	summary
	claims	1. Method of welding a nuclear fuel rod including two end plugs, a cladding tube and a pile of fuel pellets in the interior of the cladding tube, the method comprising the steps of:bringing one of the end plugs and the cladding tube together to abut each other at an interface; andwelding the end plug and the cladding tube by means of a welding equipment by applying a laser beam of a laser source of the welding equipment, the laser beam having a wavelength and being directed along an optical path of the welding equipment to a welding zone at the interface to melt material of the end plug and the cladding tube at the interface;wherein the welding takes place in a closed enclosure containing an atmosphere of helium at a pressure above the atmospheric pressure, wherein the closed enclosure encloses the end plug and end section of the cladding tube, andwherein the method comprises the steps of:evacuating the interior of the cladding tube and the closed enclosure to a certain vacuum level during a predetermined time period,then filling the closed enclosure and the interior of the cladding tube with helium to a predetermined pressure,pre-positioning the end plug on the cladding tube at a determined distance from the cladding tube before the evacuating step, thereby permitting a free flow of gas from and to the interior of the cladding tube, andfinal positioning of the end plug on the cladding tube after the filling step and before the welding step, andwherein the method comprises the further steps of:sensing the welding by sensing radiation from the welding zone comprising:sensing radiation within a first wavelength range, which includes the wavelength of the laser beam coming from reflections from the welding zone;sensing radiation within a second wavelength range different from the first wavelength range, which includes infrared radiation from melted material in the welding zone;sensing radiation within a third wavelength range different from the first wavelength range and the second wavelength range, which includes radiation from plasma in the welding zone; andmonitoring the welding and melting of material by monitoring the sensed radiations. 2. The method according to claim 1, wherein said reflections also includes reflections of the laser beam in the optical path, including protective lenses through which the optical beam passes. 3. The method according to claim 1, wherein the radiation of at least one of the first wavelength range, the second wavelength range and the third wavelength range is sensed along a direction being coaxial with the optical path at least in the proximity of the welding zone. 4. The method according to claim 1, further comprising viewing of the welding zone before and during the welding and melting of material by means of a video camera. 5. The method according to claim 4, further comprising controlling the laser beam position relative the interface by means of the viewed interface. 6. The method according to claim 4, wherein the viewing of the welding zone takes place along a viewing direction being coaxial with the optical path at least in the proximity of the welding zone. 7. The method according to claim 1, further comprising the step of controlling the power of the laser beam in response to the sensed radiations. 8. The method according to claim 1, wherein the monitoring step comprises:monitoring the intensity of the radiation of the first wavelength range as a first signal level over time to form a first signal curve;monitoring the intensity of the radiation of the second wavelength range, as a second signal level over time to form a second signal curve; andmonitoring the intensity of the radiation of the third wavelength range as a third signal level over time to form a third signal curve. 9. The method according to claim 8, further comprising the step of verifying the setup of the welding equipment including the power level of the laser beam and the optical path with the signal level of the first wavelength range that includes the radiation of the reflection of the laser beam. 10. The method according to claim 8, further comprising the step of controlling the focus position of the laser beam by the signal level of the second wavelength range that includes the infrared radiation from the melted material. 11. The method according to claim 8 further comprising the step of controlling the effectiveness and the penetration of the welding by the signal level of the third wavelength range that includes the radiation from the plasma. 12. The method according to claim 8, wherein the method comprises the step of monitoring any anomalies any of the signal curves from the three different wavelength ranges compared to a reference signal curve to indicate uneven interface or wobble or dirt in the welding zone and/or possible occurrence of pores or uneven welding quality. 13. The method according to claim 1, wherein the laser beam is a continuous laser beam. 14. The method according to claim 1, wherein the wavelength of the laser beam lies in a range of 1050-1090 nm. 15. The method according to claim 14, wherein the wavelength of the laser lies in a range of 1060-1080 nm. 16. The method according to claim 15, wherein the wavelength is 1070 nm. 17. The method according to claim 1, wherein the second wavelength range is 1100-1800 nm. 18. The method according to claim 1, wherein the third wavelength is less than 600 nm. 19. The method according to claim 18, wherein the third wavelength range is 390-600 nm.
	summary
	description	The present invention relates, in general, to the vitrification of radioactive waste products and, more particularly, to a glass composition, which is suitable for flammable waste products, such as gloves, working clothes, plastic waste, and rubber, discharged from a nuclear power plant, and a method of vitrifying the flammable waste products using the same. Flammable waste products, such as gloves, working clothes, plastic waste, and rubber, which are radioactive waste products discharged from a nuclear power plant, are treated by being encased in cement or contained in a waste drum. There is demand for a technology of manufacturing a solidified body, from which radioactive materials do not leak, or leak into underground water at a much slower speed compared to a cement-solidified body, when the solidified body comes into contact with underground water, and another technology of significantly reducing the number of radioactive waste drums so that a waste disposal site may be used over a long period of time, in consideration of the fact that it is becoming difficult to build waste disposal sites. Recently, various countries have actively made research into technologies for vitrifying radioactive waste products using glass media to meet this demand. Meanwhile, examples of the related art regarding a process of vitrifying radioactive waste products include Korean Patent No. 10-0768093 (a method of vitrifying middle- and low-level radioactive waste products using iron/phosphate glass) and Korean Patent No. 10-0432450 (a system for treating middle- and low-level radioactive waste products). However, since the middle- and low-level radioactive waste products are different from high-level waste products in terms of the type, production amount, and chemical composition thereof, the technology for vitrifying high-level waste products is not capable of being applied to middle- and low-level radioactive waste products without any modification, and, regardless, a glass composition for vitrifying flammable waste products, such as gloves, working clothes, plastic waste, and rubber, is not disclosed in the patents. Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a glass composition which is most suitable for vitrifying flammable waste products. Another object of the present invention is to provide a method of vitrifying flammable waste products using a glass composition for use in the flammable waste products. In order to accomplish the above objects, the present invention provides a glass composition for vitrifying a flammable waste product, the glass composition including SiO2, Al2O3, B2O3, CaO, K2O, Li2O, MgO, Na2O, and TiO2. The glass composition may further include CeO2, CoO, VO2, ZnO, and ZrO2. The glass composition includes 30 to 60 wt % of SiO2, 6.5 to 8.5 wt % of Al2O3, 10 to 16 wt % of B2O3, 8 to 15 wt % of CaO, 1 to 6 wt % of K2O, 2 to 10 wt % of Li2O, 0.5 to 6 wt % of MgO, 8 to 28 wt % of Na2O, and 2 to 5 wt % of TiO2. When the glass composition further includes CeO2, CoO, VO2, ZnO, and ZrO2, the glass composition includes 30 to 60 wt % of SiO2, 6.5 to 8.5 wt % of Al2O3, 10 to 16 wt % of B2O3, 8 to 15 wt % of CaO, 1 to 6 wt % of K2O, 2 to 10 wt % of Li2O, 0.5 to 6 wt % of MgO, 8 to 28 wt % of Na2O, 2 to 5 wt % of TiO2, 0.1 to 5 wt % of CeO2, 0.1 to 2 wt % of CoO, 0.1 to 5 wt % of VO2, 1 to 5 wt % of ZnO, and 0.5 to 3 wt % of ZrO2. In order to accomplish the above objects, the present invention also provides a method of vitrifying a flammable waste product, the method including adding the flammable waste product and a glass composition including SiO2, Al2O3, B2O3, CaO, K2O, Li2O, MgO, Na2O, and TiO2, together to a melting furnace. The glass composition may further include CeO2, CoO, VO2, ZnO, and ZrO2. The glass composition includes 30 to 60 wt % of SiO2, 6.5 to 8.5 wt % of Al2O3, 10 to 16 wt % of B2O3, 8 to 15 wt % of CaO, 1 to 6 wt % of K2O, 2 to 10 wt % of Li2O, 0.5 to 6 wt % of MgO, 8 to 28 wt % of Na2O, and 2 to 5 wt % of TiO2. When the glass composition further includes CeO2, CoO, VO2, ZnO, and ZrO2, the glass composition includes 30 to 60 wt % of SiO2, 6.5 to 8.5 wt % of Al2O3, 10 to 16 wt % of B2O3, 8 to 15 wt % of CaO, 1 to 6 wt % of K2O, 2 to 10 wt % of Li2O, 0.5 to 6 wt % of MgO, 8 to 28 wt % of Na2O, 2 to 5 wt % of TiO2, 0.1 to 5 wt % of CeO2, 0.1 to 2 wt % of CoO, 0.1 to 5 wt % of VO2, 1 to 5 wt % of ZnO, and 0.5 to 3 wt % of ZrO2. According to the present invention, a glass composition, which is suitable for flammable waste products, such as gloves, working clothes, plastic waste, and rubber, and a method of vitrifying the flammable waste products using the same are provided to significantly reduce the volume of radioactive waste products and to vitrify the flammable waste products using the glass composition, which is suitable for vitrifying the flammable waste products, thereby maximally delaying or completely preventing the leakage of radioactive materials from a molten solidified body. A better understanding of the present invention may be obtained through the following Examples. It will be obvious to those skilled in the art that the Examples are set forth to illustrate the present invention but are not to be construed to limit the scope of the present invention. In order to vitrify target waste products for vitrification, discharged from the Uljin nuclear power plant, the type and the concentration of inorganic substances contained in each waste product were evaluated, and a suitable additive was added to the inorganic substances that were generated in the waste products to thus select glass compositions that were excellent in terms of process variables of a melting furnace, the quality of a molten solidified body, and the volume reduction effect. As shown in the flowchart of glass composition selection of FIG. 1, a process of selecting the candidate glass for each target waste product for vitrification included steps of selection of the additive (base glass frit), selection of the candidate glass, laboratory evaluation, and a pilot test. The inorganic substances in the target waste products for vitrification should be mixed with the additive to form the glass composition meeting the vitrification process and the quality of the molten solidified body. First, the suitable additive, that is, the base glass frit, was selected based on the analyzed concentration of the inorganic substance in the waste product. The properties of the candidate glass depend on the amount of the inorganic substance that is added to constitutional components of the base glass frit (the waste loading amount). As for main items which are evaluated by executing computer code, it is evaluated whether viscosity and electric conductivity values, which are important in views of the vitrification process, are in the range of 10 to 100 poise and 0.1 to 1.0 S/cm at an operating temperature of 1,150° C., and it is evaluated whether the 7-day PCT leaching rate, which is a factor for evaluating chemical robustness in view of the quality of the molten solidified body, is 2 g/m2 or less with respect to the elements B, Na, Li, and Si. When the aforementioned two aspects are satisfied, the volume reduction effects of the waste products are very different from each other, but the volume reduction ratio of each waste product, which is evaluated to be at a suitable level, is calculated in order to select the candidate glass. Whether the candidate glass that was selected using the computer code operation satisfied the properties required in views of the vitrification process and the quality of the molten solidified body was evaluated during the laboratory operation, and was finally verified using the pilot test. In order to vitrify the target waste products for vitrification, AG8W1 was selected as the candidate glass of the mixed waste product (hereinafter, referred to as ‘W1 waste product’), DG-2 was selected as the candidate glass of the flammable waste product (hereinafter, referred to as ‘dry active waste’), and SG was selected as the waste resin using GlassForm 1.1 computation code. The components and main properties are described in Table 1. TABLE 1Properties of base glass frit and candidate glass (values at 1,150° C.)W1 waste Dry active wasteproductBase/candidateWaste resinBase/candidateglassBase/candidateglassDG-glassAG8AG8W12BaseDG-2SG-BSGAl2O314.4212.308.007.077.57.36As2O51.040.62————B2O38.579.9715.0011.2915.0010.59BaO———0.04——CaO—4.82—9.77—18.1CeO21.040.62————CoO0.520.31—0.01——Cr2O3——————Cs2O——————CuO———0.01—2.86Fe2O3—1.78—0.35—2.86K2O—1.632.004.47—7.3Li2O2.071.247.005.257.505.13MgO—2.120.504.63—2.22MnO2—0.05—0.17—0.32Na2O24.1717.5711.0010.067.504.5NiO———0.11——P2O5—0.40—0.82——PbO———0.02——SiO244.5243.1455.0041.2562.5037.5SrO———0.14——TiO2—1.24—3.09——VO22.101.26—0.08——ZnO———0.22—1.26ZrO21.550.931.501.13——Loading 040025040amount of inorganicsubstance (wt %)Density 2.592.672.402.652.622.65(g/cm3)Viscosity 62673310864(poise)+Electric0.620.310.570.460.350.40conductivity(S/cm)+7-day PCT —Si, B, —Si, B, —Si, B, (g/m2)Li,Li,Li,Na < 2Na < 2Na < 2 The viscosity, electric conductivity, phase homogeneity, liquidus temperature, transition temperature, softening point, thermal expansion coefficient, and compressive strength of the AG8W1 candidate glass of the W1 waste product, the DG-2 candidate glass of the dry active waste, and the SG candidate glass of the waste resin, which were selected in Example 2, were tested as follows. (1) Viscosity and Electric Conductivity From FIGS. 2 and 3, it was confirmed that the viscosity of the DG-2, AG8W1, and SG candidate glass was in the required range of 10 to 100 poise at the operating temperature of 1,150° C. when measured. Further, from FIGS. 4 and 5, showing the result of measurement of electric conductivity, it could be seen that all of the DG-2, AG8W1, and SG candidate glass satisfied the required value of electric conductivity at 1000° C. or higher. (2) Phase Homogeneity and Liquidus Temperature When the glass is melted over a long period of time, it is very important to maintain the glass at the liquidus temperature or higher in order to prevent crystals from being formed. When the homogeneous molten glass is formed at the melting temperature, normal production of the glass and long-term operation are feasible. On the other hand, when a crystal phase is formed, precipitation may occur, eventually clogging a glass outlet and possibly affecting the chemical robustness of the glass, that is, leachability. It is empirically known that the difference between the temperature of a melting state and the liquidus temperature of glass is preferably more than 100° C. The three kinds of candidate glass (AG8W1, DG-2, and SG) were subjected to a heat-treatment test at 950° C. for 20 hr, and analyzed using SEM/EDS. As a result, crystals were not formed at a meniscus and not at the boundary of a crucible. The minimum temperature, at which the crystals were not formed, determined from the result of the heat-treatment test for 20 hr, was defined as the liquidus temperature of the glass. From the result of the test, the liquidus temperature of the candidate glass was estimated to be 950° C. or less. Therefore, it could be seen that there was no possibility of the molten glass being converted into crystals during the long-term vitrification process. (3) Transition Temperature and Softening Point Glass has a transition region, making it unlike crystals in physical and chemical aspects. In other words, it can be seen that, with respect to a change in volume as a function of temperature when the molten liquid is supercooled, the volume of a crystal is rapidly changed at the melting temperature, but the volume of the molten glass body is slowly changed, reaching an equilibrium state when the molten glass body is supercooled. The volume of glass changes depending on the temperature. The temperature at which the slope is changed is called a glass deformation temperature or a glass transition temperature Tg, and refers to a thermodynamically meta-stable equilibrium state. The transition temperatures of the AG8W1 and SG candidate glass were evaluated to be about 498° C. and 466.7 to 498.1° C., respectively, when measured using analysis equipment. The softening points of the AG8W1 and SG candidate glass were measured to be 551° C. and 547° C., respectively. (4) Thermal Expansion Coefficient All existing constitutional elements of materials are vibrated by heat energy. Heat energy increases as the temperature is increased. Accordingly, a vibration width is increased, to thus increase the distance between two atoms connected by bonding force. In other words, expansion occurs as the temperature is increased. Vibration attributable to heat energy is limited by strong bonding in a solid state, but is not significantly limited in a liquid state, and accordingly, the expansion coefficient of liquid is large. The respective thermal expansion coefficients of the AG8W1 and SG candidate glass were 107×10−7 K−1 and 98×10−7 K−1 when measured. It can be seen that these values are similar to the thermal expansion coefficient of typical soda lime glass. (5) Compressive Strength The compressive strength of glass in use has been considered as an important property, and an effort has been made for a long time into investigating the cause of breakage to thus produce stronger glass. A breaking process is directly connected to a fatigue phenomenon, and influences attributable to hysteresis and the characteristic condition thereof need to be well understood. Surface bonding is a very important factor and needs to be sufficiently considered in order to increase strength. The strength of glass corresponds to a value until a breakage line is formed through an entire piece of glass. The AG8W1 and SG candidate glass was cooled from the transition temperature at a rate of about 2.7° C. per min to measure compressive strength, and the measured values were 2,146 psi and 7,985 psi. It is required that compressive strength be 500 psi or more based on US NRC requirements for cement, which is used to treat radioactive waste products. The aforementioned requirement may be applied to the molten solidified body, and accordingly, the compressive strength of the candidate glass may be evaluated as favorable. The molten solidified body, which is formed during the vitrification process, must be chemically stable in intermediate storage and final waste disposal environments. The most main reason why glass is selected as a treatment medium of radioactive waste products among many other materials is that glass prevents radioactive materials from leaking into the environment and is capable of storing the radioactive materials for a long period of time due to the excellent chemical robustness thereof. Accordingly, the selected candidate glass compositions were tested and analyzed using the internationally certified leaching test methods in order to compare and evaluate the chemical stabilities of the molten solidified bodies. In order to perform a robustness comparison with the glass selected by the Nuclear Environment Technology Institute, the high-level R7T7 candidate glass of France and the SRL-EA benchmark glass of the USA were tested together. (1) TCLP (Toxicity Characteristic Leaching Procedure) The US EPA TCLP (Toxicity characteristic leaching procedure) test is the most important index indicating the stability of the solidified body against various accidents after final disposal of the molten solidified body. The risk that the molten solidified body may face in the final waste disposal site is leakage of radioactivity and harmful materials into water when the solidified body comes into contact with water, and the TCLP test may be considered as a simulation of this situation. The molten solidified bodies (AG8W1, DG-2, and SG), which are obtained from research on selection of the glass composition, particularly contain vanadium (V), which is a strong oxidant, and chromium (Cr) and nickel (Ni), which are harmful materials, in small amounts in order to prevent the precipitation of reducing materials during the vitrification process. Accordingly, the TCLP test was performed using the three candidate glass compositions. In the TCLP test, the degree of elution of elements, which were regulated based on the Resources Conservation and Recovery Act (RCRA) (a total of 14 elements: Ag, As, Ba, Be, Cd, Cr, Hg, Ni, Pb, Sb, Se, Th, V, and Zn), into a leaching solution was analyzed. The concentrations of all target elements were analyzed to be the same as or lower than the detection limit of the analyzer, thereby satisfying all US EPA standards. (2) ANSI/ANS 16.1 (American National Standards Institute/American Nuclear Society 16.1) The ANSI/ANS 16.1 (American National Standards Institute/American Nuclear Society 16.1) leaching test, which was accomplished in a short period of time (three months), was performed as a leaching test for evaluating the chemical durability of the glass. The concentrations of main elements and simulated radionuclides, such as Co and Cs, which were leached from the molten solidified bodies, were analyzed to calculate effective diffusivity, and the average value of ten leaching indexes of each radionuclide, which were determined in ten leaching sections, was evaluated as the leachability index (Li) of the radionuclide. As seen in FIG. 6, showing the result of the ANSI/ANS 16.1 leaching test, Co and Cs did not leak into a leachate during a test period of three months, and the leaching indexes of all elements were 6 or more, which was the US NRC requirement. After pollutants were rapidly separated from the surface of the sample in an early stage of the test, initially observed leaching from the waste product solidified body was considered to be mainly attributable to diffusion. The leaching index of the radionuclides depends on the magnitude of the mobility of chemical elements in the single solidified substance. Therefore, the leaching indexes of all elements of the candidate glass satisfied the US NRC requirement, namely 6.0 or more, and cobalt, which was contained in the glass, and cesium, which was added in a small amount to the AG8W1 glass in order to perform the present test, were not detected. (3) PCT (Product Consistency Test) The US DOE PCT (product consistency test) as a robustness test for measuring the stability, the homogeneity, and the reproducible component ratio of a solidified body is a test for comparing leaching behavior of the elements in the molten solidified body for at least 7 days or over a long period of time (hundreds of days) to leaching behavior of the benchmark glass. DG-2, AG8W1, and SG, and R7T7 of France were used as the candidate glass, and the SRL-EA (environmental assessment) glass, which was manufactured by the Savannah River National Laboratory in the USA, was used as the benchmark glass. A PCT was performed on the DG-2, AG8W1, and SG candidate glass, the R7T7 candidate glass of France, and the SRL-EA benchmark glass for 7 days. As a result, the DG-2, AG8W1, and SG candidate glass exhibited relatively better leaching resistance than the R7T7 candidate glass and the benchmark glass, as shown in FIGS. 7 and 8. It is shown that the leaching rate of boron and sodium is higher than that of other elements. This is considered to be because a silicate compound is formed at a leaching boundary surface to thus reduce the concentration of the silicic acid in the leaching solution, but the leaching of other elements is increased. It is shown that the leaching resistance of four elements of the AG8W1 glass is relatively good compared to the DG-2 glass. The SG glass satisfied the US Hanford high/low-level vitrification limit, namely 2 g/m2 or less. The candidate glass and the SRL-EA benchmark glass were subjected to a long-term leaching test for 120 days, and the result is shown in FIG. 9. It could be seen that the leaching rate of each element in the candidate glass was better than that of SRL-EA and was lower than the US Hanford high/low-level vitrification limit, namely 2 g/m2 or less. (4) ISO (International Standards Organization) In order to evaluate the leaching mechanism of the elements constituting the molten solidified body and chemical integrity over a long period of time, a leaching test was performed using the ISO (International Standards Organization) standard test, which is a long-term leaching test. AG8W1 was subjected to the leaching test over a long period of time to thus evaluate the leaching behavior of the main elements, which leaked from the glass structure into the leaching solution. FIG. 10 shows the development of the leaching rate change of B, Na, and Si for 602 days. The three elements in AG8W1 exhibited a relatively stable leaching rate. FIG. 11 shows the cumulative fraction leached of the main elements. It could be seen that the curve of the cumulative fraction leached of B and Na rose with a very gentle slope but that Si, which constituted the main frame of the glass structure, was saturated. It is considered that the concentration of silicic acid in the leaching solution was reduced but that other elements were continuously diffused. In the result of the ISO leaching test for 602 days, cesium, which was added in a small amount to AG8W1 in order to check the leaching behavior of cesium, was not detected, but cobalt was intermittently detected in the leachate, thus exhibiting a very small cumulative fraction leached compared to other elements. Three types of candidate glass, which were selected in Example 2, were subjected to a pilot test using a pilot test device in order to check the ease of the vitrification process of the glass and the quality of the molten solidified body formed during the vitrification process. The pilot test was successfully repeated five times in order to analyze the pilot test characteristic of the AG8W1 candidate glass, the pilot test was repeated twice in order to check the pilot test characteristic of the DG-2 candidate glass composition, and the pilot test of the SG candidate glass composition was performed once. The main pilot test results of the waste products are arranged in the following Table 2. TABLE 2Summary of pilot test resultsOperation variablesSupply ratioSupplyExpectedNo.Integrity ratioappropriateofofduring supply WastepilotInitialmoltentestratioproducttestsignitionglass(kg/h)(kg/h)Supply typeW15Favor-Favor-1818Grain (wastewasteableableresin)/cuttingproduct(dry activewaste)Dry2Favor-Favor-2020CuttingactiveableablewasteWaste1Favor-Favor-77Grain (wasteresinableableresin) The pilot test of the W1 waste product was continuously performed for a maximum of about 10 days, based on a single operation cycle, during which 70 kg of the AG8W1 candidate glass was used to prepare the initial molten glass, the waste product and the base glass frit AG8 were continuously supplied for 6 hours, residues were combusted for 1 hr, mixing was performed, and the glass was discharged in an increased amount. It was very easy to initially ignite the AG8W1 candidate glass used during the test and to control the molten glass when the waste product was not supplied. From the result of analysis of the discharged molten solidified body, it could be seen that a homogeneous molten solidified body was produced. It was evaluated that the dry active waste did not particularly affect the control of process variables and the quality of a molten solidified body even when the dry active waste was supplied in amounts of 20 kg and 25 kg per hour. When the dry active waste was supplied in an amount of 20 kg per hour, the dry active waste was capable of being continuously supplied together with the DG-2 base glass frit for 8 hrs, and an operation mode was capable of being successfully performed based on a single cycle for a total of 9 hrs by combusting residue for 1 hr, performing mixing, and discharging the glass in an increased amount. Even though PVC, rubber, lancing filters, and wood were supplied into the dry active waste at content levels (5, 15, and 1 wt %) that were higher than target values (0, 11.62, 03, and 0.5 wt %) for supply to a nuclear power plant, the concentration of generated harmful gas, the dust generation amount, and the color of the dry active waste were very favorable. Therefore, it was evaluated that there is no particular problem occurring in the case where a predetermined amount of waste product is mixed and supplied due to human error while the dry active waste is classified during a commercial operation. From the result of evaluation of the chemical robustness of the molten solidified body, which was discharged at early, middle, and final stages of the pilot test, it could be seen that the glass, which was discharged during the present pilot test, exhibited better robustness than that of the SRL-EA glass, which was the benchmark glass of the high-level molten solidified body of the USA. From the pilot test, it could be seen that it was very easy to control the operation variables of vitrification of the dry active waste and that it was possible to produce a high-quality molten solidified body compared to other flammable waste products (waste resin and the like). Accordingly, the simple volume reduction ratio that is expected when the used glass composition and operation mode for the vitrification process are applied to a commercialization process is evaluated to be high, namely about 175. However, in consideration of the occurrence of secondary waste products, such as the amount of discharged waste washing solution and high-temperature filters that are no longer of any use, it was judged that the overall volume reduction ratio was slightly reduced but, nonetheless, a very high volume reduction ratio of 100 or more was capable of being ensured. The pilot test of the waste resin was continuously performed, based on a single operation cycle, during which 70 kg of the SG candidate glass was used to prepare the initial molten glass, the waste product and the base glass frit SG-F were continuously supplied for 20 hours, residues were combusted for 1 hr, mixing was performed, and the glass was discharged in an increased amount. It was very easy to initially ignite the SG candidate glass used during the test and to control the molten glass when the waste product was not supplied. The simple volume reduction ratio, which is expected when the operation mode for the waste resin vitrification process is applied to a commercialization process, is evaluated to be about 50. Even in consideration of the occurrence of secondary waste products, it is judged that a volume reduction ratio of 30 or more was capable of being ensured. 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.
	abstract	A method and device is claimed for preventing reverse coolant flow in a BWR Power Reactor. The device comprises a screen that is free to move between a top plate and a bottom plate in a fuel assembly lower tie plate box. Flow holes are formed and aligned in the top plate and in the bottom plate, creating a path for reactor coolant. Disks at a bottom of the screen are aligned with the flow holes in the bottom plate, and are shaped and formed to cover flow holes in the bottom plate. When flow stagnates or reverses, the screen drops causing the disks to rest on the bottom plate blocking downward flow. Upstanding tabs at the top surface of the screen contact the top plate when normal coolant flow is in the upward direction, allowing flow through the flow holes in the top plate.
	claims	1. A scintillator panel comprising:a deposition substrate; anda scintillator layer formed by deposition on a scintillator layer formation scheduled surface of the deposition substrate,wherein the deposition substrate comprises a support and a reflective layer disposed on the support,the reflective layer includes light-scattering particles and a binder resin with a glass transition temperature of −100° C. to 60° C., andthe thickness of the reflective layer is 5 to 300 μm. 2. The scintillator panel according to claim 1, wherein the light-scattering particles include at least one selected from alumina, yttrium oxide, zirconium oxide, titanium dioxide, barium sulfate, silica, zinc oxide, calcium carbonate, glasses and resins. 3. The scintillator panel according to claim 1, wherein the light-scattering particles include at least one type of particles selected from hollow particles having a hollow portion within the particle, multi-hollow particles having a number of hollow portions within the particle, and porous particles. 4. The scintillator panel according to claim 1, wherein the light-scattering particles include at least titanium dioxide. 5. The scintillator panel according to claim 1, wherein the support includes a resin as a main component and the reflective layer is disposed on the support. 6. The scintillator panel according to claim 5, wherein the resin is polyimide. 7. The scintillator panel according to claim 1, further comprising a light-absorbing layer on the side opposite to the surface of the reflective layer on which the scintillator layer is disposed. 8. The scintillator panel according to claim 1, wherein the scintillator layer has a columnar crystal structure formed by depositing raw materials including cesium iodide and one or more activators including at least thallium. 9. The scintillator panel according to claim 1, wherein the surface of the scintillator layer is covered with a protective film. 10. The scintillator panel according to claim 9, wherein the protective film is a polyparaxylylene film. 11. The scintillator panel according to claim 1, wherein the scintillator layer includes columnar crystals grown from an interface between the reflective layer and the scintillator layer. 12. The scintillator panel according to claim 1, wherein the scintillator panel is supported on a support plate having higher rigidity than the deposition substrate.
045086788	abstract	The invention relates to a fast neutron nuclear reactor in which the primary pumps and exchangers are suspended on the rigid slab sealing the vessel containing the reactor core.. The slab has in its thickness housings of reduced dimensions in which are confined the heads of the exchangers and the primary pumps. The flywheels of the pumps and part of the pipes of the secondary circuits are also contained in the housings. Other housings can be provided in the slab, particularly for the handling of fuels.. Application to the improvement of the safety and reliability of fast neutron reactors is taught.
060884274	abstract	An apparatus for radiological examination is provided with the grid 16 that is driven in reciprocating motion in order to reduce the effect of radiation scattered by the body of the patient being irradiated. The grid 16 is connected to a counterweight 23, and is moved through a motion transmission mechanism that is of the crank and connecting-rod type so as to ensure a dynamic balancing of the oscillating masses. With this simple and accurate type of driving system, better quality radiographic images can be obtained under different adjustment and set-up conditions of the apparatus.
	claims	1. A method for detecting overlay errors, comprising:directing a primary electron beam to interact with an inspected object, wherein (i) the inspected object has a first feature formed on a first layer, a second feature formed on a second layer, and an intermediate layer positioned between the first layer and the second layer, (ii) the second feature is buried under the first layer, affects a shape of an area of the first layer, and does not overlap with the first feature, and (iii) the area includes a protuberance positioned above the second feature and that is smaller than the first feature, said directing comprising propagating the primary electron beam along an optical axis, diverting the primary electrical beam to propagate along a secondary optical axis that is parallel to but spaced apart from the optical axis, and subsequently diverting the primary electron beam so as to again propagate along the optical axis;detecting electrons reflected or scattered from the protuberance of the area of the first layer, wherein said electrons are scattered or reflected at angles less than eighty degrees with respect to a surface of the inspected object;receiving detection signals from a first in-lens detector and a second in-lens detector, the second in-lens detector positioned to detect those of the electrons that pass through an aperture in the first in-lens detector; anddetermining the overlay errors according to the detection signals. 2. The method of claim 1 wherein the step of directing further comprises directing electrons of the primary electron beam to interact with the second feature. 3. The method of claim 2 wherein the step of detecting comprises detecting electrons reflected or scattered from the second feature. 4. The method of claim I further comprising a preliminary step of charging the second feature. 5. A method for detecting overlay errors, comprising:directing a primary electron beam to interact with first and second features of an inspected object, wherein (i) said inspected object comprises an intermediate layer positioned between first and second layers, (ii) the first and second features are formed on the first and second layers, respectively, (iii) the second feature is buried under the first layer, and does not overlap with the first feature, and (iv) the first layer includes a protuberance positioned above the second feature and that is smaller than the first feature, said directing comprising propagating the primary electron beam along an optical axis, diverting the primary electrical beam to propagate along a secondary optical axis that is parallel to but spaced apart from the optical axis, and subsequently diverting the primary electron beam so as to again propagate along the optical axis;detecting electrons reflected or scattered from the protuberance, wherein said electrons are scattered or reflected at angles less than eighty degrees with respect to a surface of the inspected object;receiving detection signals from a first in-lens detector and a second in-lens detector, the second in-lens detector positioned to detect those of the electrons that pass through an aperture in the first in-lens detector; anddetermining the overlay errors according to the detection signals. 6. The method of claim 5 wherein the second feature affects a shape of an area of the first layer. 7. The method of claim 6 wherein the detecting comprises detecting electrons reflected or scattered from the area of the first layer. 8. The method of claim 5 further comprising a preliminary step of charging the second feature.
	claims	1. An apparatus for controlling intensity of charged particles extracted from a circulating charged particle beam path in a synchrotron, said apparatus comprising:a radio-frequency field generator, wherein during use said radio-frequency generator applies a radio-frequency field to the circulating charged particles yielding betatron oscillating charged particles;an extraction material, wherein during use at least a portion of the betatron oscillating charged particles pass through said extraction material resulting in a secondary emission electron flow using electrons originating from the extraction material and without loss of electrons from the betatron oscillating charged particles;an intensity sensor, said intensity sensor configured to determine a measure of the electron flow; anda feedback control loop comprising an intensity controller, said intensity controller configured to provide the measure of electron flow as a feedback to said radio-frequency generator,said feedback control loop configured to control intensity of charged particles extracted from said synchrotron via control of said radio-frequency generator,wherein intensity comprises a number of the charged particles extracted as a function of time. 2. The apparatus of claim 1, further comprising:a target signal, wherein said intensity controller calculates a difference between said measure of said electron flow and said target signal, wherein said intensity controller alters amplitude of said radio-frequency field based upon said difference. 3. The apparatus of claim 1, wherein said extraction material consists essentially of atoms having six or fewer protons. 4. The apparatus of claim 1, wherein said extraction material comprises a foil of about thirty to one hundred micrometers thickness, said foil comprising any of:beryllium;lithium hydride; andcarbon. 5. The apparatus of claim 1, further comprising:at least a one kilovolt direct current field applied across a pair of extraction blades; anda deflector,wherein said at least a portion of the betatron oscillating charged particles passing through said extraction material yield reduced energy charged particles,wherein the reduced energy charged particles pass between said pair of extraction blades, andwherein said direct current field redirects the reduced energy charged particles through said deflector yielding intensity controlled extracted charged particles. 6. The apparatus of claim 1, further comprising at least one turning magnet, wherein said turning magnet comprises a magnetic field concentrating first magnet, wherein said first magnet comprises:a gap circumferentially encompassing the circulating charged particle beam path;a first cross-section diameter not in contact with said gap; anda second cross-sectional diameter proximate said gap, wherein said second cross-section diameter is less than seventy percent of said first cross-sectional diameter,wherein a magnetic field passing through said first cross-sectional diameter concentrates in said second cross-sectional diameter before crossing said gap. 7. A method for controlling intensity of charged particles extracted from a circulating charged particle beam path in a synchrotron, said method comprising the steps of:generating a radio-frequency field using a radio-frequency field generator, wherein said radio-frequency generator applies the radio-frequency field across the circulating charged particle beam path yielding oscillating charged particles;traversing at least a portion of the oscillating charged particles through an extraction material yielding a secondary emission electron flow, the secondary emission electron flow using electrons originating from the extraction material without substantial loss of electrons from the betatron oscillating charged particles;determining a measure of the electron flow using an intensity sensor; andproviding the measure of the electron flow to an intensity controller via a feedback control loop,wherein said intensity controller controls intensity of charged particles extracted from said synchrotron via control of said radio-frequency generator,wherein intensity comprises a number of the charged particles extracted as a function of time. 8. The method of claim 7, further comprising the step of:determining a difference between a target signal and said measure of electron flow, wherein said intensity controller alters amplitude of said radio-frequency field based upon said difference.
	description	The present invention relates generally to an apparatus for the irradiation of objects and the like, and more particularly to a device for forming a chamber that focuses an electron beam for irradiating a product. It is known that the physical properties of a material may be altered by exposing the material to electron (e-beam) radiation. In this respect, manufacturers treat certain products, such as plastic articles or animal feed, to produce a desired alteration in the products. In a conventional product irradiation process, a product is moved along a conveyor through an e-beam that scans across, i.e. traverses, the path of the conveyor. The e-beam is scanned across the conveyor by means of a scan horn that is a fixed distance from the surface of the conveyor. Depending upon the size of the product to be irradiated, the distance between the scan horn and the product may vary. As the e-beam travels through air from the scan horn to the product, instabilities occur in the e-beam. These instabilities in the e-beam are the result of uncontrolled air plasma that is formed by the e-beam as a result of ionization of gases molecules, such as oxygen and nitrogen molecules in the air. Once the electron beams exit the accelerator through a foil window in the scan horn, the beam tends to increase in cross section, and the beam current density decreases. These events lead to two (2) negative effects in the irradiation process. First, there is a decrease in the value of absorbed dose in the irradiated product. Second, the angle of incidence of the scanning electron beam on the product decreases the penetration of the e-beam into the product. A 20% variation of absorbed dose may occur. A still further problem with irradiating products in air is that certain products give off gases that accumulate at the surface of the product during irradiation. This accumulation of gases leads to uncontrolled variation of the parameters of the air plasma. The accumulation of gases may also lead to chemical reactions on the surface of a product being irradiated. It is also known to use a high current e-beam from a pulsed electron accelerator to irradiate product(s). A high current beam from a pulsed electron accelerator (without a scanning system) exhibits the effects of the space charge in vacuum or air because of the high current and the high charge of the e-beam. For example, the diameter of an e-beam in vacuum for a beam current of 1 kA and a kinetic energy of 500 keV may increase 10 times over a distance of 12 cm. The propagation of this type of e-beam in air has the same problems with non-stability as described above. An additional problem is that the variation of current density tends to lead to a variation of dose distribution in an irradiated product. The present invention overcomes these and other problems and provides a method and apparatus for the transport of an electron beam from the accelerator to a product to be irradiated. In accordance with a preferred embodiment of the present invention, there is provided a system for irradiating objects. The system comprises a conveyor for conveying objects along a predetermined path. An e-beam scanning device is disposed a predetermined distance from the path. The e-beam scanning device is operable to scan an e-beam across the path at a specific location along the path. A chamber is disposed between the scanning device and the specific location along the path. The chamber is dimensioned to maintain the scanning e-beam within the confines of the chamber and to occupy a majority of the distance between the e-beam scanning device and an object at the specific location. There is provided a means for creating vacuum conditions in the chamber that is suitable for the creation of a plasma within the chamber when the e-beam is scanned through the chamber. In accordance with another aspect of the present invention, there is provided a method of irradiating an object, comprising the steps of: providing a chamber between a source of an electron beam (e-beam) and an object to be irradiated by the electron beam, the chamber being dimensioned to occupy a majority of the space between the source and the object; and maintaining a vacuum within the chamber while directing an e-beam through the chamber into the object, the vacuum in the chamber being at a level to create conditions within the chamber suitable for forming a plasma within the chamber. In accordance with another aspect of the present invention, there is provided an e-beam transport device. The device is comprised of a housing that defines a chamber. The housing is dimensioned to withstand a vacuum of less than 2 Torr within the chamber. A window for inputting an electron beam and a window for outputting an electron beam forming a part of the housing. The foil is oriented in the housing to be aligned with the path of an e-beam through the housing, wherein the e-beam enters the chamber through the window for inputting an electron beam and exits the chamber through the window for outputting an electron beam. A vacuum-generating device is connected to the chamber. The vacuum-generating device is capable of creating a vacuum between 2 Torr and 0.1 Torr within the chamber. In accordance with still another aspect of the present invention, there is provided a method of irradiating an object, comprising the steps of: positioning a chamber between a source of an electron beam (e-beam) and an object to be irradiated; creating a vacuum within the chamber, the vacuum being at a level of 0.2 Torr or less; and scanning an e-beam through the chamber toward the object. An advantage of the present invention is a method and apparatus for the transport of an e-beam for irradiating articles. Another advantage of the present invention is a method and apparatus as described above that increases the efficiency of the irradiation process. Another advantage of the present invention is a method and apparatus as described above that facilitates using lower-energy e-beams to irradiate the articles. A still further advantage of the present invention is a method and apparatus as described above that facilitates a more homogeneous distribution of absorbed doses in the irradiated article. A still further advantage of the present invention is a method and apparatus as described above that is adjustable to irradiate objects of different dimensions. These and other objects will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings and the appended claims. Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purposes of limiting the same, FIG. 1 shows a process 10 for irradiating products or objects 12. The object 12 to be irradiated is shown moving along a conveyor system 20. Conveyor system 20 includes a generally endless conveyor belt 22 that is movable over a pair of rollers 24. (Only one roller is illustrated in the drawing.) One roller 24 is driven by a motor 26 that is schematically illustrated in FIG. 1. An electron accelerator 30, schematically illustrated in FIG. 1, generates an electron beam 32 (best seen in FIG. 2) that is conveyed through a scan horn 34 that scans beam 32 back and forth, in a conventionally known manner. Conveyor system 20 is disposed relative to scan horn 34 such that e-beam 32 from scan horn 34 traverses back and forth across conveyor belt 22. In this respect, any product or object 12 moving along conveyor system 20 will intersect and pass through the scanned e-beam 32. In the embodiment shown, an electron-absorbing device 38 is disposed below the upper run of conveyor belt 22. A beam transport device 40 is associated with scan horn 34 to maintain the focus of e-beam 32, as shall be described in greater detail below. Beam-focusing device 40 is generally comprised of a housing 42 having a first end member 44, a second end member 46, and an intermediate, expandable and collapsible wall member 48. In the embodiment shown, first and second end members 44, 46 are generally comprised of elongated, rectangular plates having a longitudinal length approximately equal to the width of conveyor belt 22. First end member 44 is dimensioned to be mounted below an opening 34a in scan horn 34. In this respect, first end member 44 may be fixedly mounted to scan horn 34, or may be mounted to a structure (not shown) supporting scan horn 34. In this respect, first end member 44 is stationary relative to scan horn 34. An opening 52 is formed in first end member 44. In the embodiment shown, opening 52 is rectangular in shape. Opening 52 is disposed below scan horn 34 to be in registry with opening 34a in scan horn 34, as best seen in FIGS. 2 and 4. A foil window 54 is disposed across opening 52. Foil window 54 is preferably formed of a metallic material, and more preferably, is a metal foil, such as by way of example and not limitation, Ti, A1 Be with thickness 20–200 microns on dependence. Foil window 54 is disposed within a rectangular recess 56 formed around opening 52 in the surface of first end member 44. A frame-shaped retainer 58 maintains panel 54 within recess 56, as illustrated in FIGS. 2 and 4. Second end member 46 is adapted to be movable relative to scan horn 34 and first end member 44. In the embodiment shown, cylinders 62 are attached to the corners of first and second end members 44, 46. Each cylinder 62 has a housing portion 64 that is attached to first end member 44, and a movable rod portion 66 that is attached to second end member 46. More specifically, housing portion 64 of each cylinder 62 has a threaded extension 64a that is matingly received in a threaded opening 74 in first end member 44. Each rod portion 66 of cylinder 62 includes a threaded shank 66a that extends through a hole 76 in second end member 46. A conventional threaded nut 78 secures rod portion 66 of cylinder 62 to second end member 46. Cylinders 62 may be hydraulic or pneumatic, and preferably are controlled simultaneously so as to allow second member 46 to be automatically moved relative to first end member 44. As will be appreciated by those skilled in the art, other mechanical arrangements are contemplated for connecting second end member 46 to first end member 44 so as to allow adjustable movement of second end member 46 relative to first end member 44. By way of example and not limitation, such means may include a drive screw, or guide shafts with mechanical-locking devices. An elongated rectangular opening 82, best seen in FIG. 6, is formed in second end member 46. Opening 82 is oriented to be transverse to the path of conveyor belt 22. A foil window 84 is disposed within opening 82 in second end member 46. Foil window 84 is disposed in a rectangular recess 86 formed in second end member 46 around opening 82. A frame-shaped retainer 88 is mounted to second end member 46 by conventional fasteners to secure foil window 84 to second end member 46 in an airtight fashion. Wall member 48 is disposed between, and is attached to, first end member 44 and second end member 46. In the embodiment shown, wall member 48 is comprised of an expandable and collapsible, accordion-like structure. Wall member 48 has an obround shape and is dimensioned to be larger, i.e., longer and wider, than elongated opening 82 in second end member 46. Wall member 48 has an outwardly extending flange 48a formed at each end thereof, as best seen in FIG. 3. In one preferred embodiment, wall member 48 is comprised of layers of a flexible metal cloth or screen 92 having a flexible, resilient polymeric material 94 covering the same, as illustrated in FIG. 3. A plurality of conventional fasteners 96 extends through flange 48a of wall member 48 to secure wall member 48 to first and second end members 44, 46. An airtight chamber 100 is defined within housing 42 of beam-transport device 40. A conduit 112 communicates with chamber 100. Conduit 112 is connected to a vacuum-generating system 114. Vacuum-generating system 114 is comprised of a vacuum pump driven by a motor (not shown). Vacuum-generating system 114 is capable of creating a predetermined vacuum within chamber 100. Vacuum-generating system 114 is preferably capable of generating a vacuum down to 0.01 Torr (1.3×10−5 atmospheres, 1.22 Pascals). A secondary conduit 116 branches off of conduit 112, as illustrated in FIG. 1. Secondary conduit 116 communicates with the atmosphere. A valve 118 is disposed in secondary conduit 116 to control flow therethrough. A sensor 122 is attached to conduit 112 to monitor the pressure levels within chamber 100. Process 10 shall now be further described by discussing the operation thereof. Conveyor system 20 is dimensioned to convey objects or products 12 to be irradiated along a path “P” that intersects the path of scanned e-beam 32. Scan horn 34 is disposed relative to conveyor system 20 to scan across the width of conveyor belt 22. In the embodiment shown, the path of scanned e-beam 32 is perpendicular to the path of conveyor belt 22. Beam-transport device 40 is disposed between scan horn 34 and the surface of conveyor belt 22. Second end member 46 of beam-transport device 40 is adjustable relative to the surface of conveyor belt 22, such that objects or products 12 can pass thereunder. In this respect, beam-transport device 40 is adjusted such that chamber 100 occupies the space between scan horn 34 and the surface of object 12. Preferably, chamber 100 occupies the maximum allowable space between scan horn 34 and the surface of object 12. FIG. 1 shows an object 12 being conveyed along conveyor belt 22 beneath scan horn 34 and beam-transport device 40. As best seen in FIG. 2, second end member 46 of beam-transport device 40 is adjusted such that the lowermost surface of second end member 46 is slightly above object or product 12 on conveyor belt 22. In other words, only a slight gap or space exists between the upper surface of product 12 and the lowermost surface of second end member 46 of beam-transport device 40. A second product or object, different in dimensions from the first product, is shown in phantom in FIG. 2. Also shown in phantom is how beam-transport device 40 may be adjusted with respect to the second package. Once the position of beam-transport device 40 is adjusted relative to product or object 12 to be irradiated, a vacuum is drawn within the chamber. A vacuum between about 0.1 Torr (1.3×10−4 atmospheres, 13.33 Pascals) and 0.01 Torr (1.3×10−5 atmospheres, 1.33 Pascals) is preferably established within chamber 100. When e-beam 32 is created by electron accelerator 30, scan horn 34 causes e-beam 32 to move back and forth, forming a fan-like pattern 132, as schematically illustrated in phantom in FIG. 2. As e-beam 32 exits scan horn 34, it passes through panel 54 disposed within opening 52 in first end member 44 and enters chamber 100 within housing 42 of beam-transport device 40. E-beam 32 travels through chamber 100 and exits housing 42 through Change-panel 84 disposed within opening 82 in second end member 46. E-beam 32 exiting beam-transport device 40 irradiates product 12 passing under scan horn 34 and beam-transport device 40. As e-beam 32 passes through chamber 100, a plasma is formed within chamber 100. The plasma is created by gas molecules in chamber 100 being ionized by e-beam 32. The scanning mode of e-beam 32 increases the number of gas molecules being ionized. As a result, a plasma is formed with concentrations of ions, electrons and neutral atoms that can be used for neutralization of the space charge of electron beam from accelerator. The plasma formed in chamber 100 has ions of oxygen and nitrogen, because of the air molecules within chamber 100. The vacuum within chamber 100 reduces the number of oxygen and nitrogen molecules within chamber 100. Under the vacuum condition, a rarified gas (air) is within chamber 100. According to the present invention, the propagation of e-beam 32 in chamber 100 of beam transport device 40 preferably occurs under certain conditions within chamber 100 that result in the neutralization of the space charge within chamber 100, such that e-beam 32 is maintained as a tight, focused beam. According to the present invention, a plasma with a desired, predetermined concentration of ions is created within chamber 100. Establishing the desired concentration of ions in chamber 100 is based upon the concentration of gas molecules in chamber 100 and the parameters of e-beam 32, namely the kinetic energy of e-beam 32 and the diameter of e-beam 32. In this respect, the concentration of molecules in chamber 100 and the energy and diameter of e-beam 32 as it scans through chamber 100, will determine the number of molecules of gas ionized by e-beam 32. The number, i.e., the density, of gas molecules within chamber 100 is a function of the pressure of the gas within chamber 100. Vacuum generating system 114 reduces the pressure in chamber 100. Adjustments to the pressure level in chamber 100 may be performed using valve 118, which allows vacuum in chamber 100 to be “bled-off” to establish an optimum pressure level in chamber 100. The concentration of ions in chamber 100 is a function of the concentration of molecules in chamber 100. As indicated above, the pressure level in chamber 100 is preferably established to create conditions suitable for neutralization of the space charge around e-beam 32. A neutral space charge indicates there is no excess of ions or electrons in a given volume. The ideal conditions, i.e., a neutral space charge, for obtaining the desired beam containment occurs when: n i n eb ≤ 1where, ni is concentration of plasma ions, and neb is concentration of electrons in e-beam 32.The foregoing condition, i.e., n i n eb ≤ 1 ,can also be expressed as a factor of space charge neutralization, fe. f e = n i n eb The space charge neutralization factor, fe, may also be expressed as: 1 ≥ f e ≥ 1 γ 2 where, γ = 1 + E ⁢ [ MeV ] 0.511 ⁢ [ MeV ] FIG. 8 is a pictorial illustration showing electrons 162 from e-beam 32 and positive plasma ions 162 in chamber 100. The e-beam 32 propagates across the plasma in chamber 100. In relation to the electrons in e-beam 32, the ions of oxygen and nitrogen within the plasma are large and heavy, and their velocity is relatively small. In this respect, the oxygen and nitrogen ions can be considered as stationary, i.e., non-moving, relative to the electrons in e-beam 32. The total charge in cross-section of e-beam 32 from accelerator is close to zero, and thus, a neutralization of the space charge of e-beam 32 exists. As a result, the diameter of e-beam 32 does not change within beam transport device 40. As indicated above, the formation of plasma in chamber 100 by e-beam 32 depends on pressure of gas in chamber 100. The typical pressure in chamber 100 for a high current electron beam having a kinetic energy of 100–500 KeV and a current up to 2 kA is about 10−2–10−1 Torr. The mechanism of ionization of the gas molecules in chamber 100 is determined by a collision of electrons of e-beam 32 with the gas molecules in chamber 100 (plasma-beam discharge). The neutralization of the space charge of e-beam 32 results in the dimensions of electron beams in cross-section being maintained. The plasma formed by the ionization of gas molecules in chamber 100 can be considered as a medium for the transport or propagation of e-beam 32 without a change in the dimensions of e-beam 32 in cross section, as a result of the neutralization of the space charge around e-beam 32. Beam-transport device 40 thus maintains the focus of e-beam 32 from scan horn 34 to object 12. As a result of the more stable e-beam 32, the energy levels required to irradiate a product may be lower because of the greater efficiency and less energy loss as compared to the same beam traveling through air from scan horn 34 to product 12. Referring now to FIG. 7, beam transport device 40 is shown with an electron accelerator 30 and a conventionally known, parallel scanning device 210. Parallel scanning device 210 is operable to move e-beam 32 back and forth through beam transport device 40 while maintaining e-beam 32 in a vertical position. FIG. 7 thus illustrates that beam transport device 40 finds advantageous application with a conventional scanning horn 30 or a parallel scanning device 210. The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purposes of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.
	abstract	An anti-scatter grid for medical x-ray devices is provided. The anti-scatter grid comprising a number of first elements from a first material with second elements made from a second material integrated therein. In this case the first material is more transparent to radiation than the second material. The second elements are arranged in the first elements such that for stacking of the first elements a grid absorbing scattered radiation is formed by means of second elements for radiation arriving perpendicular to the direction of the stacking of the first elements. The advantage of this is that this anti-scatter grid is able to be produced simply and reliably with a large aspect ratio.
044316038	summary	BACKGROUND OF THE INVENTION This invention is a self-actuated, automatic device, especially a valve for control of fluid flow for application within a radiation field in a nuclear reactor. Some applications exist in which it would be of benefit if a specific future operation of a valve could be planned in advance and designed as an inherent characteristic of the valve. The following is illustrative. Fuel assemblies in nuclear reactors generally have nuclear and thermodynamic properties which change over the course of exposure to neutrons in the reactor. The content of fissile uranium 235 decreases in a fuel assembly during exposure to a neutron flux while the plutonium 239 content of a blanket assembly may increase. In the case of a fuel assembly, it may be desired to gradually decrease coolant flow through the assembly to match a gradual decrease in the assembly fission rate. In the case of the blanket assembly, it may be desired to gradually increase coolant flow through the blanket assembly to match a gradual increase in fission reactions. Coolant flow through an individual fuel or blanket assembly can be controlled by inlet or outlet valves (or variable-size orifices) attached to the individual assemblies in the reactor. A problem lies in access to the vlave in the nuclear reactor. Fuel and blanket assemblies in a reactor are numerous such that any system for control of many valves from outside of the reactor would be extremely complex. Several schemes have been attempted to provide assemblies with variable-size orifices, but as yet no economically viable or practical system for true variability in orifice size has been discovered. Consequently, it is desired to provide an automatic, self-actuated valve, which is of particular use as an orificing valve for use with nuclear fuel and blanket assemblies. SUMMARY OF THE INVENTION The self-actuating valve of this invention has an actuating shaft connected to an expandable bellows. The bellows is so arranged that expansion of the bellows moves the valve shaft thus opening or closing the valve as appropriate to the application. The bellows has a "reaction material" located inside. A "reaction material" is defined herein as a material containing elemental nuclei which absorb nuclear radiation, enter into a nuclear reaction or transformation, and emit as a byproduct new nuclei which are or become a species of gas. Compounds of boron are likely reaction materials, since boron reacts with neutrons to emit helium. Lithium and beryllium are also likely candidates. As the neutron flux at the valve site exposes the reaction material, byproduct gas pressure builds up which expands the bellows. The generation of a pressure of several thousand pounds per square inch in the bellows is considered feasible. The identity and mass content of this reaction material can be planned to generate sufficient gas to properly open or close the valve as desired. This valve can open or close according to a preplanned scheme developed prior to closure and operation of the reactor, varying the orifice size to an assembly without operator access or control.
056446071	abstract	An automatic refueling apparatus has a travel carriage, a traverse carriage and a fuel assembly grappling apparatus composed of a grapple, an extension pipe and a hoist. The automatic refueling apparatus also includes a system for controlling automatic fuel transferring operations, in which a calculation unit and a control unit are provided. After the positions of a start point and a target terminal point of a fuel assembly transfer are input through an input device, the calculation unit determines the shortest route from the start point to the terminal point in a preset fuel transferring permitted region, and the control unit generates driving command signals for moving the fuel assembly grappling apparatus along the obtained shortest route through a simultaneous control along X, Y, Z (Z: an elevation direction vertical to a X-Y horizontal plane of the grapple) and .theta. (a rotation direction in a X-Y horizontal plane of the grapple) axes.
047553510	abstract	The leaf springs mounted in the upper nozzle of a prior art fuel assembly, which are compressed by the upper core plate to restrain the upward movement of the fuel assembly under the pressure of upwardly-flowing coolant, as dispensed with. Instead the fuel assembly is permitted to rise in a controlled manner into engagement with the upper core-support plate. The lower nozzle is provided with snubbers which engage, and exert low pressure, as required by the specifications governing a reactor, on the lower core plates when the fuel assembly is raised into engagement with the upper core plate by the force of the flowing coolant. In addition springs are provided between the pins extending from the upper and lower core plates and the walls of the holes in the upper and lower nozzles to suppress vibration under the transverse forces impressed by the flowing coolant.
	description	This application is the national phase of PCT application PCT/KR2014/012995 having an international filing date of 29 Dec. 2014, which claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2014-0001461, filed on 6 Jan. 2014, the contents of which are incorporated by reference herein in their entirety. The present disclosure relates to a passive residual heat removal system to which a plate type heat exchanger is applied and a nuclear power plant including the same. Reactors are divided into active reactors using active power such as a pump, and passive reactors using passive power such as a gravity force, a gas pressure or the like according to the configuration method of a safety system. Furthermore, reactors are divided into loop type reactors (for example, Korean pressurized water reactor) in which main components (a steam generator, a pressurizer, a pump impeller, etc.) are installed at an outside of the reactor vessel, and integrated type reactors (for example, SMART reactor) in which the main components are installed at an inside of the reactor vessel according to the installation location of the main component. A passive residual heat removal system has been employed as a system for removing heat in a reactor coolant system (sensible heat in the reactor coolant system and residual heat in the core) when an accident occurs in various nuclear power plants including an integral reactor. For a coolant circulation method of the passive residual heat removal system, two methods such as a method of directly circulating reactor primary coolant to cool a reactor (AP1000: U.S. Westinghouse) and a method of circulating secondary coolant using a steam generator to cool a reactor (SMART reactor: Korea) are mostly used, and a method of injecting primary coolant to a tank to directly condense it (CAREM: Argentina) is partially used. Furthermore, for a method of cooling an outside of a heat exchanger (condensation heat exchanger), a water-cooled method (AP1000), a partially air-cooled method (WWER 1000: Russia), and a water-air hybrid cooled method (IMR: Japan) have been used. A heat exchanger of the passive residual heat removal system performs a function of transferring heat received from a reactor to an outside (ultimate heat sink) through an emergency cooling tank or the like, and condensation heat exchangers using a steam condensation phenomenon with an excellent heat transfer efficiency have been mostly employed for a heat exchanger method. However, in general, a passive residual heat removal system may use primary coolant (reactor coolant system) or secondary coolant (steam generator) to perform the role of a pressure boundary to a primary system or secondary system, and a heat exchanger of the passive residual heat removal system may typically form a boundary to atmospheric environment outside the containment building, and when a pressure boundary is damaged, primary coolant or secondary coolant may be discharged to atmospheric environment, and therefore, maintaining a pressure boundary during an accident is a very important role. Accordingly, a method of enhancing the performance of a passive residual heat removal system may be taken into consideration to enhance the performance of a reactor. An object of the present disclosure is to provide a passive residual heat removal system for overcoming the coverage limit of a plate type heat exchanger and solving a problem such as flow instability or the like occurring in applying the plate type heat exchanger, and a nuclear power plant including the same. Another object of the present disclosure is to propose a passive residual heat removal system for effectively removing sensible heat in a reactor coolant system and residual heat in a core through a high heat exchange efficiency while maintaining a pressure boundary between heat exchange fluids in a passive manner, and a nuclear power plant including the same. In order to accomplish the foregoing object of the present disclosure, a passive residual heat removal system according to an embodiment of the present disclosure may include a plate type heat exchanger configured to exchange heat between primary system fluid or secondary system fluid that has received sensible heat in a reactor coolant system and residual heat in a core and cooling fluid introduced from an inside or outside of a containment to remove the sensible heat and residual heat, and a circulation line configured to connect the reactor coolant system to the plate type heat exchanger to form a circulation flow path of the primary system fluid or connect a steam generator disposed at a boundary between a primary system and a secondary system to the plate type heat exchanger to form a circulation flow path of the secondary system fluid. According to the present disclosure having the foregoing configuration, a plate type heat exchanger having high-density heat transfer performance and durability to high temperature and high pressure may be applicable to a passive residual heat removal system. According to the present disclosure, a closed flow path and an open flow path or partially open flow path may be selectively introduced to a plate type heat exchanger of a passive residual heat removal system to efficiently circulate and discharge cooling fluid or atmosphere, and a water cooling, air cooling or hybrid cooling method may be all applicable thereto. Furthermore, according to the present disclosure, a passive residual heat removal system having a collection of heat exchangers configured with a plurality of plate type heat exchangers may be provided by freely choosing a width and a height of the plate and freely selecting a number of plates. Accordingly, it may be possible to provide a passive residual heat removal system for mitigating a bottleneck phenomenon at an inlet of the plate type heat exchanger. In addition, the present disclosure may maintain a safety function of a passive residual heat removal system for a long period of time (in a semi-permanent manner) through the employment of an air cooling or hybrid cooling method. Hereinafter, a passive residual heat removal system associated with the present disclosure will be described in more detail with reference to the accompanying drawings. Even in different embodiments according to the present disclosure, the same or similar reference numerals are designated to the same or similar configurations, and the description thereof will be substituted by the earlier description. Unless clearly used otherwise, expressions in the singular number used in the present disclosure may include a plural meaning. A plate type heat exchanger in the present disclosure may refer to all plate type heat exchangers as far as there is any difference in the processing method or bonding method of a plate thereof as well as a typical plate type heat exchanger and a printed circuit type heat exchanger, unless otherwise specified in particular. FIG. 1 is a conceptual view illustrating a passive residual heat removal system 100 and a nuclear power plant 10 including the same associated with an embodiment of the present disclosure. The nuclear power plant 10 illustrated in FIG. 1 is illustrated as an integral reactor, but the present disclosure may not only be applicable to an integral reactor, but also be applicable to a loop type reactor. Referring to FIG. 1, for the sake of convenience of explanation, the passive residual heat removal system 100 and the nuclear power plant 10 including the same disclosed in the present disclosure are symmetrically illustrated around a reactor coolant system 12. Furthermore, a normal operation of the nuclear power plant 10 is illustrated on the right of FIG. 1, and the occurrence of an accident at the nuclear power plant 10 is illustrated on the left. It is likewise in the other drawings illustrated below to be symmetrical to each other. The nuclear power plant 10 may include various systems maintaining the integrity of the nuclear power plant 10 in preparation for a normal operation and the occurrence of an accident, and further include structures such as the containment 11, and the like. The containment 11 is formed to surround the reactor coolant system 12 at an outside of the reactor coolant system 12 to prevent the leakage of radioactive materials. The containment 11 performs the role of a final barrier for preventing the leakage of radioactive materials from the reactor coolant system 12 to external environment. The containment 11 is divided into a containment building (or referred to as a reactor building) configured with reinforced concrete, and a containment vessel and a safeguard vessel configured with steel containment. The containment vessel is a large sized vessel designed at a low pressure such as a containment building, and the safeguard vessel is a small-sized vessel designed with a small size by increasing a design pressure. According to the present disclosure, the containment 11 may collectively refer to a containment building, a reactor building, a containment vessel, a safeguard vessel, and the like, unless otherwise specified in particular. During a normal operation of the nuclear power plant 10, when feedwater is supplied from a feedwater system 13 to a steam generator 12b through a main feedwater line 13a, steam is generated by the steam generator 12b using heat transferred from a reactor core 12a. The steam is supplied to a turbine system 14 through a main steam line 14a, and the turbine system 14 produces electricity using the supplied steam. Isolation valves 13b, 14b installed at the main feedwater line 13a and main steam line 14a are open during a normal operation of the nuclear power plant 10, but closed by an actuation signal during the occurrence of an accident. Primary system fluid is filled into the reactor coolant system 12, and heat transferred from the reactor core 12a to the primary system fluid is transferred to secondary system fluid in the steam generator 12b. A primary system of the nuclear power plant 10 is a system for directly receiving heat from the reactor core 12a to cool the reactor core 12a, and a secondary system is a system for receiving heat from the primary system while maintaining a pressure boundary to the primary system to produce electricity using the received heat. In particular, a pressure boundary should be necessarily maintained between the primary system and the secondary system to ensure the integrity of a pressurized water nuclear power plant. A reactor coolant pump 12c for circulating primary system fluid, and a pressurizer 12d for suppressing the boiling of coolant and controlling an operating pressure are installed at the reactor coolant system 12. The steam generator 12b is disposed at a boundary between the primary system and the secondary system to transfer heat between the primary system fluid and the secondary system fluid. The passive residual heat removal system 100, as one of major systems for securing the safety of the nuclear power plant 10 when an accident occurs, is a system for removing sensible heat in the reactor coolant system 12 and residual heat in the reactor core 12a to discharge them to an outside. Hereinafter, first, the composition of the passive residual heat removal system 100 will be described, and then the operation of the passive residual heat removal system 100 when an accident occurs at the nuclear power plant 10 will be described. The passive residual heat removal system 100 may include a plate type heat exchanger 110, and a circulation line 120, and further include an emergency cooling water storage section 130. The plate type heat exchanger 110 is surrounded by a casing 113. The plate type heat exchanger 110 may be installed at least one place of an inside and an outside of the containment 11. The plate type heat exchanger 110 exchanges heat between primary system fluid or secondary system fluid that have received the sensible heat and residual heat and cooling fluid introduced from an outside of the containment 11 to remove sensible heat in the reactor coolant system 12 and residual heat in the reactor core 12 a. The plate type heat exchanger 110 illustrated in FIG. 1 is installed at an outside of the containment 11, and configured to exchange heat between secondary system fluid and cooling fluid outside the containment 11. The circulation line 120 connects the reactor coolant system 12 to the plate type heat exchanger 110 or connects the steam generator 12 b between the primary system and the secondary system to the plate type heat exchanger 110 to form a circulation flow path of the primary system fluid or secondary system fluid. The circulation line 120 connected between the steam generator 12 b and the plate type heat exchanger 110 to form a circulation flow path of the secondary system fluid is illustrated in FIG. 1. The plate type heat exchanger 110 is arranged on a plate to be distinguished from each other to exchange heat between primary system fluid or secondary system fluid supplied through the circulation line 120 and cooling fluid while maintaining a pressure boundary, and may include a plurality of channels (not shown) for allowing the fluids to alternately pass therethrough. The plate type heat exchanger 110 may include at least one of a printed circuit type heat exchanger and a plate type heat exchanger. The printed circuit type heat exchanger is provided with channels formed by diffusion bonding and densely formed by a photochemical etching technique. On the contrary, the plate type heat exchanger extrudes a plate to form channels, and is formed to couple (or join) the plates using at least one of a gasket, a welding, and a brazing welding methods. The channels may include first flow paths (not shown) and second flow paths (not shown) for allowing different fluids to pass therethrough. The first flow paths are arranged to be separated from one another to allow cooling fluid for cooling primary system fluid or secondary system fluid to pass therethrough. A plurality of second flow paths are formed to allow the primary system fluid or the secondary system fluid to pass therethrough, and alternately arranged with the first flow paths to exchange heat while maintaining a pressure boundary to the cooling fluid. The plate type heat exchanger 110 of FIG. 1 uses the circulation of secondary system fluid, and thus the secondary system fluid flows through the second flow path, and cooling fluid flowing through the first flow path cools the secondary system fluid. An inlet header 111 a, 112a and an outlet header 111 b, 112 b are formed at each inlet and outlet of the plate type heat exchanger 110. The inlet header 111 a, 112a is formed at an inlet of the first flow path and the second flow path to distribute fluids supplied to the plate type heat exchanger to each channel. The outlet header 111b, 112b is formed at an outlet of the first flow path and the second flow path to collect the fluids that have passed the each channel. The fluids supplied to the plate type heat exchanger 110 may include cooling fluid passing through the first flow path, primary system fluid or secondary system fluid passing through the second flow path. In particular, in the passive residual heat removal system 100 illustrated in FIG. 1, the fluids supplied to the plate type heat exchanger 110 are cooling fluid and secondary system fluid. In FIG. 1, the inlet header 111a and outlet header 111b of the second flow path are necessarily provided to maintain a pressure boundary. However, since the first flow path has a configuration in which the inlet and outlet thereof are open to the fluid of the emergency cooling water storage section, it is a configuration in which the inlet header 112 a and outlet header 112 b are selectively provided to efficiently perform inlet and outlet flow. Accordingly, the inlet header 112 a and outlet header 112 b may not be provided at the first flow path, and replaced by an inlet guide structure, an outlet guide structure, and the like in the form of being extended from the first flow path to an outside. The cooling fluid and secondary system fluid exchange heat while flowing in different directions, and thus the inlet of the first flow path is disposed adjacent to the outlet of the second flow path, and the outlet of the first flow path is disposed adjacent to the inlet of the second flow path. Furthermore, the inlet header 112 a of the first flow path is disposed adjacent to the outlet header 111 b of the second flow path, and the outlet header 112 b of the first flow path is disposed adjacent to the inlet header 111 a of the second flow path. The circulation line 120 may include a steam line 121 for supplying secondary system fluid to the plate type heat exchanger 110 and a feedwater line 122 for receiving secondary system fluid from the plate type heat exchanger 110. The steam line 121 is branched from a main steam line 14 a and connected to the inlet of the second flow path to receive the secondary system fluid from the main steam line 14 a extended from an outlet of the steam generator 12 b. The feedwater line 122 is branched from a main feedwater line 13 a extended to the inlet of the steam generator 12 b and connected to the outlet of the second flow path to transfer heat to the cooling fluid and recirculate the cooled secondary system fluid into the steam generator 12 b. The passive residual heat removal system 100 may include the emergency cooling water storage section 130. The emergency cooling water storage section 130 is formed to store cooling fluid therewithin and installed at an outside of the containment 11. The emergency cooling water storage section 130 is provided with an opening portion 131 at an upper portion thereof to dissipate heat transferred by evaporating the cooling fluid stored therewithin during a temperature increase due to heat transferred from the primary system fluid or the secondary system fluid to cooling fluid. At least part of the plate type heat exchanger 110 may be installed within the emergency cooling water storage section 130 to allow at least part thereof to be immersed into the cooling fluid. In this case, the steam line 121 and the feedwater line 122 may be connected to the main steam line 14a and the main feedwater line 13a, respectively, from an outside of the containment 11 through the emergency cooling water storage section 130. As illustrated in FIG. 1, when the plate type heat exchanger 110 is completely immersed into the cooling fluid of the emergency cooling water storage section 130, the plate type heat exchanger 110 cools secondary system fluid using the cooling fluid (coolant) of the emergency cooling water storage section 130 with a water cooling method. Next, the operation of the passive residual heat removal system 100 during the occurrence of an accident will be described. The left side of the drawing illustrated to be symmetric to each other in FIG. 1 illustrates a state of the passive residual heat removal system 100 during the occurrence of an accident. When a loss of coolant accident or non-loss of coolant accident (steam line break or the like) occurs at the nuclear power plant 10, isolation valves 13 b, 14 b installed at the main feedwater line 13 a and the main steam line 14 a are closed by related signals. Furthermore, an isolation valve 122 a installed at the feedwater line 122 of the passive residual heat removal system 100 is open by related signals, and a check valve 122 b installed at the steam line 121 is open by the flow of the secondary system fluid formed by opening the isolation valve 122 a. Accordingly, the supply of feedwater from the feedwater system 13 to the steam generator 12 b is suspended, and secondary system fluid is circulated within the passive residual heat removal system 100. The secondary system fluid sequentially passes through the feedwater line 122 and the main feedwater line 13 a to be introduced to an inlet of the steam generator 12 b. The secondary system fluid supplied to the steam generator 12 b receives sensible heat from primary system fluid within the reactor coolant system 12 and residual heat in the reactor core 12 a at the steam generator 12 b, and the temperature of the secondary system fluid increases to evaporate at least part thereof. The secondary system fluid discharged through the outlet of the steam generator 12 b flows upward along the main steam line 14 a and the steam line 121 of the passive residual heat removal system 100 and is introduced to the second flow path of the plate type heat exchanger 110. The cooling fluid within the emergency cooling water storage section 130 is introduced to the first flow path of the plate type heat exchanger 110, and heat is transferred from the secondary system fluid to the cooling fluid in the plate type heat exchanger 110. The secondary system fluid that has transferred heat to the cooling fluid is cooled and condensed and flows downward, and moves again along the feedwater line 122 to circulate through the steam generator 12 b. The circulation of the secondary system fluid is generated by natural phenomenon due to a density difference, and thus the circulation of the secondary system fluid continues until sensible heat in the reactor coolant system 12 and residual heat in the reactor core 12 a are almost removed and a density difference required for the circulation of the secondary system fluid almost disappears. When heat is transferred from the secondary system fluid to the cooling fluid, the temperature within the emergency cooling water storage section 130 gradually increases. At least part of the cooling fluid is evaporated and discharged to an outside through the opening portion 131, and heat transferred to the cooling fluid is also discharged to the outside. In this manner, the passive residual heat removal system 100 may circulate secondary system fluid in a passive method due to a natural force to remove sensible heat in the reactor coolant system 12 and residual heat in the reactor core 12 a. Furthermore, the plate type heat exchanger 110 may be configured to allow the secondary system fluid and the cooling fluid to pass through different channels to exchange heat, thereby preventing damage at a pressure boundary and inducing sufficient heat exchange through small flow paths. Hereinafter, another embodiment of the passive residual heat removal system will be described. FIG. 2 is a conceptual view illustrating a passive residual heat removal system 200 and a nuclear power plant 20 including the same associated with another embodiment of the present disclosure. At least part of a plate type heat exchanger 210 is immersed into the cooling fluid of an emergency cooling water storage section 230 to allow cooling fluid within the emergency cooling water storage section 230 and atmosphere outside a containment 21 to pass therethrough to a first flow path. The emergency cooling water storage section 230 is provided with an opening portion 231 at an upper portion thereof. An upper end portion of the plate type heat exchanger 210 may be formed in a protruding manner to an upper side of the emergency cooling water storage section 230 through the emergency cooling water storage section 230 to discharge cooling fluid evaporated by heat transfer with secondary system fluid and/or atmosphere to the outside. The other configuration is similar to the description of FIG. 1. The plate type heat exchanger 210 is formed in a relatively lengthy manner compared to the plate type heat exchanger 210 illustrated in FIG. 1 to provide two heat exchange conditions of water cooling and air cooling methods to fluids that exchange heat in the plate type heat exchanger 210. The left and the right of nuclear power plant 20 of FIG. 2 are symmetrically illustrated, wherein the right side thereof illustrates a normal operation state, and the left side thereof illustrates an early stage of the occurrence of an accident. When an accident occurs such as a loss of coolant accident or the like, secondary system fluid discharged from an outlet of the steam generator 22b is introduced into an inlet of the second flow path of the plate type heat exchanger 210 through a main steam line 24a and a steam pipe 221. During an early stage of the occurrence of an accident, cooling fluid is sufficiently stored within the emergency cooling water storage section 230, and at least part of the plate type heat exchanger 210 is immersed into the cooling fluid, and the heat exchange performance of a water cooling method is significantly higher than that of an air cooling method, and thus the secondary system fluid is cooled by the water cooling method. The secondary system fluid cooled in the plate type heat exchanger 210 and discharged from an outlet of the second flow path is circulated again into the steam generator 22b through a feedwater pipe 222 and a main feedwater line 23a to remove sensible heat in the reactor coolant system 22 and residual heat in the reactor core 22a through a continuous circulation. FIG. 3 is a conceptual view illustrating an intermediate stage and a late stage of the accident in which time has passed after the occurrence of the accident in a passive residual heat removal system 200 and a nuclear power plant 20 including the same illustrated in FIG. 2. In FIG. 3, the left side thereof illustrates an intermediate stage of the accident and the right side thereof illustrates a late stage of the accident around a symmetric drawing. First, referring to the drawing illustrating an intermediate stage of the accident, it is seen that a water level is decreased due to the evaporation of the cooling fluid of the emergency cooling water storage section 230 compared to an early stage of the accident. The emergency cooling water storage section 230 is provided with an opening portion 231 at an upper portion thereof. As a water level of the cooling fluid of the emergency cooling water storage section 230 is reduced, the cooling fluid of the emergency cooling water storage section 230 and atmosphere outside the containment 21 are introduced to the first flow path of the plate type heat exchanger 210 to cool the secondary system fluid with a water-air hybrid cooled method. Next, referring to a drawing illustrating a late stage of the accident on the right, it is seen that the water level is further decreased due to the evaporation of most cooling fluid of the emergency cooling water storage section 230 compared to an intermediate stage of the accident. Accordingly, atmosphere outside of the containment 21 is introduced to the first flow path of the plate type heat exchanger 210 to cool the secondary system fluid with an air cooled method. The cooling method of the plate type heat exchanger 210 formed as described above may vary according to the water level of the cooling fluid stored in the emergency cooling water storage section 230 and the passage of time subsequent to the occurrence of an accident. It uses a characteristic in which residual heat in the reactor core 22a is gradually reduced as time has passed subsequent to the occurrence of an accident. A water cooling method, a hybrid method mixed with a water cooling method and an air cooling method may be sequentially employed and configured to be switched to an appropriate cooling method according to residual heat reduction to enhance cooling efficiency and maintain cooling durability. Accordingly, the passive residual heat removal system 200 may continuously remove sensible heat in the reactor coolant system 22 and residual heat in the reactor core 22a. FIGS. 2 and 3 also illustrate a circulation line 220, an isolation valve 222a, a check valve 222b, a reactor coolant pump 22c, a pressurizer 22d, isolation valves 23b, isolation valves 24b, an outlet header 212b, an inlet header 211a, a casing 213, an outlet header 211b, an inlet header 212a. FIG. 4 is a conceptual view illustrating a passive residual heat removal system 300 and a nuclear power plant 30 including the same associated with yet still another embodiment of the present disclosure. The right side of a drawing symmetrically illustrated in FIG. 4 illustrates a normal operation of the nuclear power plant 30, and the left side thereof illustrates the occurrence of an accident at the nuclear power plant 30. The passive residual heat removal system 300 cools secondary system fluid only with an air cooling method without any emergency cooling water storage section contrary to the passive residual heat removal system 100, 200 illustrated in FIGS. 1 through 3. Atmosphere outside a containment 31 is introduced to a first flow path of a plate type heat exchanger 310, and secondary system fluid supplied from a steam generator 32b is introduced to a second flow path thereof. Heat is transferred to atmosphere from secondary system fluid passing through each flow path, and the atmosphere is discharged to an outside of the plate type heat exchanger 310. Accordingly, sensible heat and residual heat transferred from a reactor coolant system 32 and a reactor core 32a may be discharged to external atmosphere. FIG. 4 also illustrates a circulation line 320, a steam line 321, a feedwater pipe 322, an isolation valve 322a, a check valve 322b, a reactor coolant pump 32c, a pressurizer 32d, a feedwater system 33, a main feedwater line 33a, isolation valves 33b, a turbine system 34, a main steam line 34a, isolation valves 34b, an outlet header 312b, an inlet header 311a, a casing 313a, an outlet header 311b, and an inlet header 312a. FIG. 5 is a conceptual view illustrating a passive residual heat removal system 400 and a nuclear power plant 40 including the same associated with still yet another embodiment of the present disclosure. A plate type heat exchanger 410 is installed in an inner space of a containment 41, and an emergency cooling water storage section 430 is installed at an outside of the containment 41. The plate type heat exchanger 410 is connected to the cooling water storage section 430 by connection lines 441, 442 on which an inlet and an outlet of the first flow path pass through the containment 41, respectively, to allow cooling fluid within the cooling water storage section 430 through the first flow path. Secondary system fluid is supplied to a second flow path of the plate type heat exchanger 410 through a main steam line 44a and a steam pipe 421 to exchange heat with cooling fluid supplied to the first flow path of the plate type heat exchanger 410 from the cooling water storage section 430. Accordingly, the secondary system fluid is cooled by a water cooling method. Both the secondary system fluid and cooling fluid continuously circulate through the plate type heat exchanger 410. The cooling fluid of the cooling water storage section 430 is supplied to the plate type heat exchanger 410 through the connection line 441, but flows through a flow path distinguished from the secondary system fluid, and thus a pressure boundary is not damaged at the plate type heat exchanger 410. The cooling fluid of the cooling water storage section 430 receives heat from the secondary system fluid while circulating through the plate type heat exchanger 410 to increase the temperature thereof, and is introduced again to the cooling water storage section 430 through the connection line 442. When the temperature increases, the cooling fluid of the cooling water storage section 430 is evaporated to discharge the received heat to an outside. Isolation valves 441a, 442a and a check valve 441b installed at the connection lines 441, 442 are normally open, but closed only when required for maintenance. FIG. 5 also illustrates an opening portion 431, a circulation line 420, a feedwater pipe 422, an isolation valve 422a, a check valve 422b, a casing 413, an inlet header 412a, an outlet header 412b, an inlet header 411a, an outlet header 411 b, a reactor core 42a, a steam generator 42b, a reactor coolant pump 42c, a pressurizer 42d, a feedwater system 43, a main feedwater line 43a, isolation valves 43b, an isolation valve 442b, a turbine system 44. FIG. 6 is a conceptual view illustrating a passive residual heat removal system 500 and a nuclear power plant 50 including the same associated with yet still another embodiment of the present disclosure. A plate type heat exchanger 510 is installed in an inner space of a containment 51, but an emergency cooling water storage section is not installed. The plate type heat exchanger 510 is formed such that an inlet and an outlet of the first flow path communicate with an outside of the containment 51 by connection lines 541, 542 passing through the containment 51. External atmosphere is introduced into the plate type heat exchanger 510 through the connection lines 541, 542 by natural circulation and flows along the first flow path. Accordingly, secondary system fluid flowing along the second flow path is cooled with an air cooling method. Atmosphere introduced from an outside of the containment 51 is supplied to the plate type heat exchanger 510 through the connection lines 541, 542, but flows through a flow path distinguished from the secondary system fluid, and thus a pressure boundary is not damaged at the plate type heat exchanger 510. FIG. 6 also illustrates a casing 513, a circulation line 520, a steam line 521, a feedwater pipe 522, a reactor core 52a, a steam generator 52b, a reactor coolant pump 52c, a pressurizer 52d, a feedwater system 53, a main feedwater line 53a, isolation valves 53b, a turbine system 54, a main steam line 54a, isolation valves 54b, an isolation valve 542a, an outlet header 512b, an inlet header 511a, an outlet header 511b, an inlet header 512a, an isolation valve 541a, a check valve 522a. FIG. 7 is a conceptual view illustrating a passive residual heat removal system 600 and a nuclear power plant 60 including the same associated with still yet another embodiment of the present disclosure. The passive residual heat removal system 600 is configured to remove sensible heat in a reactor coolant system 62 and residual heat in a reactor core 62a using primary system fluid contrary to the passive residual heat removal system illustrated in FIGS. 1 through 6. An emergency cooling water storage section 630 is installed at an outside of a containment 61, and a plate type heat exchanger 610 is immersed into the cooling fluid of the emergency cooling water storage section 630. A circulation line 620 may include a steam line 621 and an injection line 622. The steam line 621 is connected to the reactor coolant system 62 and an inlet of the second flow path through the containment 61 to receive primary system fluid from the reactor coolant system 62 and transfer it to the plate type heat exchanger 610. The injection line 622 is an outlet of the second flow path and the reactor coolant system 62 through the containment 61 to transfer heat to the cooling fluid and reinject the cooled primary system fluid to the reactor coolant system 62. The cooling fluid of the emergency cooling water storage section 630 flows into the first flow path of the plate type heat exchanger 610, and primary system fluid flows into the second flow path to carry out cooling with a water cooling method, and the passive residual heat removal system 600 circulates primary system fluid to remove sensible heat in the reactor coolant system 62 and residual heat in the reactor core 62a. FIG. 7 also illustrates a casing 613, a steam generator 62b, a reactor coolant pump 62c, a pressurizer 62d, a feedwater system 63, a main feedwater line 63a, isolation valves 63b, a turbine system 64, a main steam line 64a, isolation valves 64b, opening portion 631, an outlet header 612b, an inlet header 611a, an outlet header 611 b, and an inlet header 612a. The primary system fluid and the cooling fluid flow through flow paths distinguished from each other, and thus the passive residual heat removal system 600 may exchange heat without damaging a pressure boundary. Unless the pressure boundary is damaged, the plate type heat exchanger 610 may be installed within the containment 61 contrary to the illustration. Furthermore, it may employ a circulation composition of the primary system fluid instead of the secondary system fluid in FIGS. 1 through 6. In the above, a composition of the passive residual heat removal system and the operation of the passive residual heat removal system due to natural circulation have been described, but in actuality when the plate type heat exchanger is applied to the passive residual heat removal system, problems such as flow instability in a two phase flow region, bottleneck phenomenon at a heat exchanger inlet, and the like may occur, and thus it is required to resolve them. Hereinafter, a structure of the plate type heat exchanger proposed by the present disclosure to enhance the problems will be described. The following description will be described without distinguishing a first flow path from a second flow path, and unless the description thereof is only limited to either one of the first flow path and the second flow path, the description of the first flow path will be also applicable to that of the second flow path, and the description of the second flow path will be also applicable to that of the first flow path. Hereinafter, the detailed structure of a plate type heat exchanger 710 applicable to a passive residual heat removal system 100, 200, 300, 400, 500, 600 illustrated in FIGS. 1 through 7 will be described. FIGS. 8 through 14 are flow path conceptual views illustrating a plate type heat exchanger 710 selectively applicable to the passive residual heat removal system 100, 200, 300, 400, 500, 600 illustrated in FIGS. 1 through 7. When a fabrication technique of a printed circuit type heat exchanger is applied to the plate type heat exchanger 710, it has a structure capable of allowing a dense flow path arrangement by a photochemical etching technology and removing a welding between the plates of the heat exchanger using a diffusion bonding technology, and allows a typical plate type heat exchanger to have a dense flow path arrangement. The plate type heat exchanger 710 may include channels 715, 716 distinguished from each other on a plate to exchange heat between the atmosphere of the containment 11, 21, 31, 41, 51, 61 (refer to FIGS. 1 through 7) and the cooling fluid of the emergency cooling water storage section 130, 230, 430, 630 (refer to FIGS. 1 through 3, 5, and 7) and exchange heat between fluids while maintaining a pressure boundary. The channels 715, 716 may include a first flow path 715 for allowing cooling fluid to pass therethrough, and a second flow path 716 for allowing primary system fluid or secondary system fluid to pass therethrough, and each channel 715, 716 corresponds to either one of the first flow path 715 and the second flow path 716. The shape of the first flow path 715 and second flow path 716 may be a closed flow path in the shape of allowing cooling fluid or atmosphere to pass therethrough only in one direction and allowing primary system fluid or secondary system fluid to pass therethrough only in a direction opposite to the one direction. Furthermore, contrary to the second flow path 716, the shape of the first flow path 715 may be also an open flow path or partially open flow path in the shape of allowing cooling fluid or atmosphere to pass therethrough even in a direction crossing the one direction. The first flow path for allowing cooling fluid or atmosphere to pass therethrough may selectively employ an open flow path or partially open flow path for cooling with an air cooling method or with an air cooling method and a hybrid cooling method in the plate type heat exchanger 710 in a relatively long length. However, when the open flow path is employed in case of the second flow path 716, a pressure boundary may be damaged, and thus the open flow path cannot be applied thereto. First, referring to FIG. 8, the plate type heat exchanger 710 illustrated in the drawing shows a cross-section of the first flow path 715 through which cooling fluid flows. The plate type heat exchanger 710 may include an inlet region 710a, a main heat transfer region 710b, and an outlet region 710c. The inlet region 710a is a region for distributing cooling fluid supplied to the plate type heat exchanger 710 to each first flow path 715, and the main heat transfer region 710b is a region for carrying out substantial heat exchange between cooling fluid and primary system fluid, cooling fluid and secondary system fluid, and the outlet region 710c is a region for collecting and discharging fluids that have completed heat exchange from the first flow path 715. The main heat transfer region 710b is connected between the inlet region 710a and the outlet region 710c, and formed between the inlet region 710a and the outlet region 710c. The temperature of the cooling fluid is lower than that of the primary system fluid or secondary system fluid, and thus the cooling fluid receives heat from the primary system fluid or secondary system fluid while passing through the plate type heat exchanger 710 to increase the temperature. When the temperature of the cooling fluid increases, the density thereof decreases, and thus the cooling fluid flows upward within the plate type heat exchanger 710. Next, referring to FIG. 9, the flow paths may be formed in such a manner that a flow resistance of the inlet region 710a is relatively larger than that of the main heat transfer region 710b connected between the inlet region 710a and the outlet region 710c to mitigate flow instability due to two phase flow. There may be various methods of forming a relatively large flow resistance, but the plate type heat exchanger 710 illustrated in FIG. 9 employs a method in which a flow path in the inlet region 710a is formed with a smaller width than that of the main heat transfer region 710b and extended in a lengthy manner. A flow path 715a of the inlet region 710a is formed in a zigzag shape to have a relatively larger flow resistance than that of a straight flow path and connected to the main heat transfer region 710b. Specifically, it is formed in a shape in which the flow path of the inlet region 710a is alternatively and repetitively connected in a length direction and a width direction of the plate type heat exchanger 710, and extended to the main heat transfer region 710b. As a flow resistance of the inlet region 710a is formed to be larger than that of the main heat transfer region 710b, it may be possible to reduce a flow instability occurrence probability in two phase flow. A flow expansion section 715b is formed between the inlet region 710a and the main heat transfer region 710b, and formed in such a manner that a width of the flow path gradually increases toward an extension direction from a flow path size of the inlet region 710a to a flow path size of the main heat transfer region 710b. The flow resistance relatively decreases while passing the flow expansion section 715b, and the relatively small flow resistance is maintained on the flow path of the subsequent main heat transfer region 710b and outlet region 710c. FIGS. 10 through 12B are conceptual views illustrating the plate type heat exchanger 710 having a header at an inlet and an outlet, respectively. First, referring to FIG. 10, an inlet header 712a for distributing a fluid to each flow path and an outlet header 712b for collecting a fluid from each flow path may be installed at the plate type heat exchanger 710. The inlet header 712a and outlet header 712b are structures that should be necessarily installed to prevent a pressure boundary damage when the plate type heat exchanger is installed at an inside of the containment 11, 21, 31, 41, 51, 61 (refer to FIGS. 1 through 7), but they are not structures that should be necessarily installed when installed at an outside of the containment, and may not be installed or replaced with a flow path guide structure for efficiently carrying out the flow of the inlet and outlet. The inlet header 712a is installed at an inlet of the flow path to distribute cooling fluid supplied from the emergency cooling water storage section 130, 230, 430, 630 (refer to FIGS. 1 through 3, 5, and 7) or atmosphere supplied from an outside of the containment to each first flow path 715. Furthermore, the outlet header 712b is installed at an outlet of the first flow path 715 to collect cooling fluid that has passed the first flow path 715 and return it to the emergency cooling water storage section or discharge it to an outside. The installation location of the inlet header 712a and outlet header 712b may vary according to the design of the plate type heat exchanger 710. In particular, when a fabrication technique of a printed circuit type heat exchanger is applied to the plate type heat exchanger 710, it may be fabricated by a photochemical etching technology to freely select the structure of channels 715, 716, and a typical plate type heat exchanger may have a very free flow path structure, and thus the location of the inlet header 712a and outlet header 712b may also vary. Referring to FIGS. 11 through 12B, the inlet header 711a, 712a and outlet header 711b, 712b are installed at a lateral surface of the plate type heat exchanger 710, respectively, and each flow path 715, 716 is bent in the inlet region 710a and outlet region 710b or formed to have a curved flow path and extended to the inlet header 711a, 712a or outlet header 711b, 712b. An extension direction of the flow path 715, 716 in the inlet region 710a and an extension direction of the flow path 715, 716 in the outlet region 710c may be the same direction as illustrated in FIG. 11, or may be opposite directions to each other as illustrated in FIGS. 12A and 12B, and vary according to the design of the passive residual heat removal system. FIGS. 12A and 12B illustrate the first flow path 715 and second flow path 716 of the plate type heat exchanger 710, respectively. The first flow path 715 receives heat while cooling fluid or external atmosphere passes therethrough to increase the temperature or evaporates to decrease the density, and the second flow path 716 transfers heat to the cooling fluid or atmosphere while primary system fluid or secondary system fluid passes therethrough to decrease the temperature or condenses to increase the density. FIGS. 13 and 14 are flow path conceptual views illustrating the plate type heat exchanger 710 having an open flow path or partially open flow path, respectively. Referring to FIG. 13, the plate type heat exchanger 710 may include an open flow path formed to introduce cooling fluid or atmosphere from a lateral surface to join cooling fluid and atmosphere passing through the first flow path so as to mitigate a bottleneck phenomenon at the inlet while maintaining a pressure boundary between fluids. Furthermore, referring to FIG. 14, the plate type heat exchanger 710 may include a partially open flow path in which a flow path is formed in an open shape only at part of the main heat transfer region 710b. The plate type heat exchanger 710 having an open flow path or partially open flow path may include a longitudinal flow path 715 and a transverse flow path 717 forming the open flow path or partially open flow path. The longitudinal flow path 715 is connected between the inlet region 710a at an upper end portion of the plate type heat exchanger 710 and the outlet region 710c at a lower end portion thereof. The transverse flow path 717 is formed to flow the cooling fluid or atmosphere in or out through an inlet and an outlet formed at both side sections of the plate type heat exchanger 710 and cross the longitudinal flow path 715 so as to mitigate a bottleneck phenomenon of the inlet. In particular, the plate type heat exchanger 710 formed with an open flow path may form a passive residual heat removal system with only an air cooling method for cooling primary system fluid or secondary system fluid with only atmosphere. Furthermore, the plate type heat exchanger 710 may form a passive residual heat removal system with a hybrid method (water-air hybrid) for cooling primary system fluid or secondary system fluid with atmosphere and cooling fluid. The plate type heat exchanger 710 for cooling primary system fluid or secondary system fluid with an air cooling or hybrid method may be preferably formed in a relatively long length. The plate type heat exchanger 710 formed with a partially open flow path is to alleviate the overcooling problem of the reactor coolant system 12, 22, 32, 42, 52, 62 (refer to FIGS. 1 through 7), and the partially open flow path is configured to operate in a water cooling method at an early stage of the accident so as to facilitate the circulation of cooling fluid, and suppress an additional cooling rate increase due to the introduction of atmosphere. In the plate type heat exchanger 710 of the present disclosure, the open flow path or partially open flow path may be formed only on the first flow path 715 for allowing cooling fluid or atmosphere to pass therethrough. It is because the second flow path 716 circulates a closed circuit to prevent a pressure boundary from being damaged. FIG. 15 is a conceptual view illustrating a plurality of plate type heat exchangers 810 selectively applicable to the passive residual heat removal system 100, 200, 300, 400, 500, 600 (refer to FIGS. 1 through 7) in FIGS. 1 through 7. FIG. 15 includes four views (a), (b), (c) and (d) for showing a plan view, a left side view, a front view, and a right side view of the plurality of plate type heat exchangers 810, respectively. Each plate type heat exchanger 810 of plurality of plate type heat exchangers is surrounded by a casing 813, and a cooling fin 818 for expanding a heat transfer area is installed at the casing 813. The primary system fluid or secondary system fluid is distributed to each plate type heat exchanger 810 through a steam line 821, and distributed to each second flow path (not shown) by an inlet header 811a within the each plate type heat exchanger 810. The primary system fluid or secondary system fluid that has passed through the second flow path is collected by an outlet header 811b and joins again an injection line (primary system fluid circulation method) or feedwater line 822 (secondary system fluid circulation method). The cooling fluid or atmosphere is also distributed to each first flow path (not shown) by an inlet header 812a, and the cooling fluid or atmosphere that has passed through the first flow path is collected by an outlet header 812b. However, as described above, when the heat exchanger is installed at an outside of the containment, the inlet and outlet header 812a, 812b are not essential structures. FIG. 16 is a layout conceptual view illustrating a plurality of plate type heat exchangers 910 illustrated in FIG. 15. Referring to FIG. 16A, the plurality of plate type heat exchangers 910 may be transversely arranged to form a collection of heat exchangers, and disposed within an emergency cooling water storage section 930. Referring to FIG. 16B, the plurality of plate type heat exchangers 910 may be arranged in a lattice shape to form a collection of heat exchangers, and disposed within an emergency cooling water storage section 930. The configurations and methods according to the above-described embodiments will not be applicable in a limited way to the foregoing passive residual heat removal system and a nuclear power plant including the same, and all or part of each embodiment may be selectively combined and configured to make various modifications thereto. The present disclosure may be used to enhance the performance of a passive residual heat removal system in the nuclear power plant industry.
043158315	description	A number of examples illustrating the process of the invention are given hereinafter in a non-limitative manner. EXAMPLE 1 About 60 liters of solid radioactive waste are to be dry-encased. The following are introduced into a cylindrical mould: 130 kg of a glycol-maleophthalate-based polyester resin dissolved in styrene, marketed under the trade name "NS 574" by the CDF Chimie Company; PA1 150 kg of silica sand of grain size ranging between 0.1 and 1.2 mm; PA1 70 kg of borax (Na.sub.2 B.sub.4 O.sub.7, 10 H.sub.2 O); PA1 2.5 kg of silica gel; PA1 1.95 kg or 1.5% by weight based on the resin of methyl-ethyl-ketone peroxide. PA1 130 kg of polyester resin "NS 574"; PA1 150 kg of silica sand, grain size 0.1 to 1.2 mm; PA1 23 kg of polystyrene in the form of balls; PA1 700 g of silica gel; PA1 1.95 kg of methyl-ethyl-ketone peroxide; PA1 350 g of a retarding agent marketed under the trade name "NLC 10" by the Akzo France Company. PA1 10 kg of polyester resin "NS 574"; PA1 6 kg of polyethylene in the form of balls; PA1 14 kg of silica sand, grain size 0.1 to 1.25 mm; PA1 150 g of methyl-ethyl-ketone. PA1 40 kg of epoxy resin "LOPOX 200" (marketed by the CDF Chimie Company); PA1 11 kg of hardening agent "D 544" (marketed by the CDF Chimie Company); PA1 1.2 kg of accelerator "A 101"; PA1 75 kg of silica sand of grain size 0.1 to 1 mm; PA1 1 kg of silica gel. The complete mixture is mixed homogeneously for 20 minutes, followed by the addition of 120 g or 0.8% by weight based on the resin of cobalt naphthenate. The basket containing 60 liters of solid radioactive waste is then introduced and cross-linking takes place. A homogeneous block is obtained without cracks whose diameter is 60 cm, height 77 cm and volume 220 liters. Polymerisation shrinkage is small and no cracks are encountered. EXAMPLE 2 60 Liters of solid radioactive waste contained in a basket are encased under water, said basket being placed at the bottom of a conditioning pond. The following are introduced into a mould: The whole mixture is mixed for 30 minutes, followed by the addition of 130 g of cobalt naphthenate. Mixing is then continued for a further 15 minutes. The mould containing this mixture is then introduced into the pond vessel at a depth of about three meters. The basket containing the solid waste is then introduced into the mould. 50 minutes after the introduction of the accelerator (cobalt naphthenate) the start of solid setting is observed. The maximum temperature reached in the centre of the block is 95.degree. C. after about five hours, and this is followed by slow cooling. After 22 hours the temperature is 50.degree. C. Gas is given off at the time of the temperature maximum. In this way a solid cylindrical block is obtained of volume 230 liters containing 60 liters of radioactive waste. The weight of this block is 450 kg and the weight of the waste 120 kg. It is found that cross-linking has taken place correctly under a depth of three meters of water without any release of solid material. There is merely an evolution of gas at the time of solid setting. The block has a homogeneous appearance without cracks. It is pointed out that the solid polystyrene used as the plasticizer has a resistance to ionising radiation which is close to that of the polyester resin used. EXAMPLE 3 15 kg of solid radioactive waste placed in a basket at the bottom of a pond are encased under water. The following are introduced into a mould of volume 30 liters: The complete mixture is mixed for 15 minutes, followed by the addition of 15 g of cobalt naphthenate, followed by further mixing for 10 minutes. The mould containing this mixture is then placed in the pond vessel. The basket containing the solid radioactive waste is then introduced into the mould. Polymerisation starts 15 minutes after incorporating the accelerator. A homogeneous compact block is obtained. EXAMPLE 4 100 kg of solid radioactive waste placed in a basket are encased. The following are introduced into a container with a volume of 100 liters: The complete mixture is mixed for 15 minutes and then the basket containing the solid radioactive waste is introduced into the container. After a few hours a compact block is obtained. The block obtained has the same characteristics as that of Example 3.
	summary
	abstract	According to the present invention there is provided a container for the storage and transport of nuclear fuel elements comprising a plurality of elongate compartments for receiving the nuclear fuel elements, the compartments being defined by a first set of plates intersecting with a second set of plates, the first set of plates extending perpendicularly with respect to the second set of plates to define compartments having a rectangular cross section, wherein the plates include an interlocking joint, the interlocking joint comprising at least one projection provided on one plate and a recess formed in the other plate, and wherein a retaining portion is provided in the recess for engagement by the projection so as to interlock the plates.
	abstract	A scintillator plate includes a substrate, a buffer layer, a scintillator layer arranged on the buffer layer, and a protective layer. The buffer layer and/or the protective layer is colored. A method for the production of the scintillator plate is also described.
059603682	description	DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS In one embodiment of the present invention, shown in FIG. 1, radioactive, hazardous, or mixed waste feedstocks 1 containing organic carbon compounds are fed to oxidation vessel 2. Nitric acid 3 and phosphoric acid 4 are added to the oxidation vessel 2. Air 5 is not necessary for the operation of the process, but may be optionally pumped in to aid in the oxidation process (in particular, to aid in the recycling of nitric acid) if desired. Heat 6 is added and/or removed as needed to maintain an appropriate oxidation reaction rate. As oxidation of the organic materials occurs in the oxidation vessel, off gases 7 such as carbon monoxide, carbon dioxide, water, HCl, and nitrogen oxides are generated. The nitrogen oxides are optionally converted into nitric acid in nitric acid recovery unit 8. The residual concentrated waste product 9 comprising substantially all of said radioactive or hazardous metal components of the waste feedstock can then be removed from the oxidation vessel and vitrified or ceramified (e.g., by combining with a vitrifying or ceramifying substance or other solidification feed 10) in a melter or other vessel 11 and processed into a final, stable form 12 suitable for disposal in a repository. The present invention is applicable to a wide variety of radioactive, hazardous, and mixed waste starting materials, but is particularly suitable for treatment of low level radioactive and mixed waste containing organic carbon components. Radioactive waste contains at least one radioactive element, such as U, Th, Cs, Sr, Am, Co, Pu, or any other element that is defined in the waste storage or waste disposal art as radioactive. Hazardous waste contains at least one Resource Conservation and Recovery Act (RCRA) listed hazardous material, such as the metals As, Cd, Cr, Hg, Pb, Se, Ag, Zn, and Ni, or a hazardous organic compound. Mixed waste contains both radioactive and hazardous waste components. These radioactive or hazardous materials may contain these elements in the form of metals, ions, oxides, or other compounds, such as organic compounds. Low level waste generally involves a large quantity of waste material and a small amount of radioactive components contaminating the waste material. The non-radioactive, non-hazardous components of the waste are generally organic carbon-containing compounds, and make up the predominant proportion of the waste. The organic carbon components which are oxidized by the process of the present invention are present in the waste as any of a variety of organic compounds. Nonlimiting examples include neoprene, cellulose, EDTA, tributylphosphate, polyethylene, polypropylene, polyvinylchloride, polystyrene, oils, resins, particularly ion exchange resins, and mixtures thereof. The radioactive, hazardous, and mixed waste materials to which the process of the present invention is applied arise from a variety of sources. One source of such waste is job control waste from, e.g., fuel fabrication operations, nuclear power plant maintenance and operations, and hospital, medical, and research operations. This job control waste includes items such as used rubber gloves, paper, rags, glassware, brushes, and various plastics. These items often come into contact with radioactive and/or hazardous material. Although only small quantities of radioactive and/or hazardous material may adhere thereto, large volumes of this material must be disposed of as radioactive or hazardous waste. Another source of radioactive, hazardous, or mixed organic carbon-containing waste is spent organic ion exchange resins used to purify water in fuel fabrication plants, nuclear reactors, and reprocessing plants. These resins are used for the continuous cleaning of water in cooling circuits, as well as the water in nuclear fuel storage basins, where the resins remove ionic corrosion products which have become radioactive when they pass near the reactor core, and fission products of reactor fuel, such as cesium and strontium ions, that have leaked out of the fuel and into the storage basin water. The resins are typically granulated or sulfonated crosslinked divinylbenzenes. Yet another source of radioactive, hazardous, or mixed organic carbon-containing waste suitable for the process of the present invention is the aqueous streams used to clean cooling systems in nuclear power plants. These cleaning streams typically contain EDTA and other organic chelating agents to help remove corrosion from the interior surfaces of piping and other process equipment used to provide reactor cooling water in secondary reactor cooling systems. These cleaning streams typically contain iron, cesium, nickel, chromium, and other stainless steel corrosion and erosion products, some of which have become radioactive due to proximity to the reactor core. Cleaning streams containing EDTA typically exit the cooling system containing iron as the primary metal component. In a nonlimiting example, a suitable waste feedstock material would include solid Pu-contaminated waste of which 60% is combustible, and including, e.g., a mixture of 14% cellulose, 3% rubber, 64% plastic, 9% absorbed oil, 4% resins and sludges, and 6% miscellaneous organics. In one embodiment of the invention, the nitric acid and phosphoric acid are combined together in varying concentrations prior to introduction to the oxidation vessel. In this case, nitric acid, usually added in a concentration of about 0.25 to 1.5 M, is used in a concentrated phosphoric acid media as the main oxidant. In the resulting mixture, nitric acid is generally present in amounts of about 3% to about 7% by weight, phosphoric acid is present in amounts of about 90% by weight, and the balance (typically a few % by weight) is water. Molar quantities of nitric acid may generally be in the range of about 0.03 to about 2.0, and molar quantities of phosphoric acid may generally be in the range of about 12.8 to about 14.77 moles. The large quantity of phosphoric acid retains the nitric acid in the solution well above its boiling point (i.e., the boiling point of concentrated nitric acid), thereby allowing temperatures of up to 200.degree. C. to be used for the oxidation reaction, and is relatively noncorrosive to most types of stainless steel process equipment at room temperature. The temperature of the oxidation reaction may be varied depending on the particular composition of the waste feedstock material. In general, the oxidation reaction is carried out at a temperature of from about 140.degree. C. to about 210.degree. C., more particularly about 160.degree. C. to about 180.degree. C. Most organic compounds can be quantitatively oxidized at temperatures below about 175.degree. C. and pressures below about 5 psig. However, some long chain, saturated hydrocarbyl or halohydrocarbyl compounds like polyethylene, polypropylene, and/or polyvinylchloride, require a contacting temperature in the range of about 185.degree. C. to about 190.degree. C., and a pressure in the range of about 10 to about 15 psig. Organic compounds such as neoprene, cellulose, EDTA, tributylphosphate, and nitromethane have been quantitatively oxidized at temperatures below 180.degree. C. at atmospheric pressure. The concentration of acids and the temperature of oxidation can be varied to obtain reaction rates wherein most organic materials are completely oxidized in under about 1 hour. In general, oxygenated organic materials in the waste feedstock are more easily oxidized than hydrocarbons. While not wishing to be bound be any theory, it is believed that the decomposition of the organic components of the waste material feedstock proceeds by direct oxidation by nitric acid, which is energetically favorable, but very slow due to the difficulties in breaking the carbon-hydrogen bond. It is believed that the oxidation of the organic compounds in the waste feedstock is initiated by dissolved NO.sub.2 and NO radicals in solution. For many types of oxygenated organic compounds, the attack by NO.sub.2 radical can be first order, as shown below. ##STR1## For aliphatic compounds, higher concentrations of NO.sub.2 and NO radicals are needed to obtain comparable oxidation rates. ##STR2## The organic radicals generated are oxidized or nitrated by the various species in solution, according to the following reactions. ##STR3## In some of the reactions, the oxidants and/or catalysts NO.sub.2 .cndot. and NO .cndot. are regenerated. Nitration is a major source of oxidation because radical-radical reactions are relatively fast. In water where strong mineral acids are still abundant, such as 14.8 M (85%) H.sub.3 PO.sub.4, hydrolysis occurs producing an organic carboxylic acid from the nitration products according to the reaction below. EQU RCH.sub.2 NO.sub.2 +H.sub.2 O+H.sub.3 PO.sub.4 .fwdarw.RCO.sub.2 H+H.sub.2 NOH.cndot.H.sub.3 PO.sub.4 .DELTA.H .congruent.-44 In process for producing nitrated organic explosive materials, it is known that water can interfere with nitration of the organic species by nitric acid. In such processes, sulfuric acid is often added to the system to tie up water and keep it from interfering in the nitration reaction. Conversely, in the present process, if the reaction solution is allowed to become sufficiently depleted of water, the phosphoric acid might possibly mimic the activity of sulfuric acid, and prevent the remaining water from denitrating the explosive organic species. If this were to occur, nitrated organic species concentration may build up and possibly cause an explosion hazard. This hazard can be reduced by maintaining sufficient water in the system to denitrate any nitrated organic species. Based upon what is known about sulfuric acid and nitric acid, and based upon past experience with the phosphoric acid and nitric acid system of the present invention, it is believed that any explosion hazard can be minimized by maintaining a maximum temperature of 185 to 190.degree. C. Nitromethane was found to be completely oxidized (101.+-.2%) in a 0.1 M HNO.sub.3 /14.8 M H.sub.3 PO.sub.4 solution, when the water content was maintained during the oxidation. Above 130-150.degree. C., any formed organic hydroperoxides should decompose. In fact, complete oxidation of the organic material usually does not occur until these temperatures are reached possibly due to the formation of the relatively stable organic hydroperoxides. Once carbon chain substitutions begin, hydrogen-carbon bonds on carbon atoms which are also bonded to oxygen are also weakened. As the organic molecules gain more oxygen atoms, they become increasingly soluble in the nitric-phosphoric acid solution. Once in solution, these molecules are quickly oxidized to CO.sub.2, CO, and water. If the original organic compound contains chlorine, hydrochloric acid will also be formed. Relative oxidation rates for various organic compounds in the waste starting material are given below in Table 1. "Fast" oxidation rates denote complete oxidation in less than one hour. "Moderate" oxidation rates denote complete oxidation in 1-3 hours. "Slow" oxidation rates denote complete oxidation in over three hours. TABLE 1 ______________________________________ PRESSURE COMPOUND RELATIVE RATE TEMP. (.degree. C.) (psig) ______________________________________ Neoprene Moderate 165 0 Cellulose Fast 148 0 EDTA Fast 140 0 Tributylphosphate Fast 161 0 Resins Slow 140 0 PE/PP/PVC Slow 161-170 0 PE Moderate 185-190 0 PE Fast 200-205 10-15 PVC Moderate 200-205 10-15 Benzoic Acid Fast 190 0 Nitromethane Fast 155 0 ______________________________________ Typical throughputs for various waste starting materials (at the specified temperature and pressure conditions) are: EDTA (140.degree. C., 0-5 psig) 142 g/L-hr; Cellulose (150.degree. C., 0-5 psig) 90 g/L-hr; Polystyrene resin (175.degree. C., 5-10 psig) 65 g/L-hr; Neoprene (165.degree. C., 0-5 psig) 50 g/L-hr; and Polyethylene (200.degree. C., 10-15 psig) 35 g/L-hr. Since oxidation of plastics is typically slower than the oxidation of other organic materials in a waste feedstock stream, and since plastics often form the predominant component of the waste feedstock stream, plastics oxidation is often the rate limiting step in the processing of waste feedstock streams. In one embodiment of the invention, a catalytically effective amount (e.g., 0.001 M) of Pd(II) or other catalyst is added to the oxidation mixture to reduce the proportion of carbon based off gases that is carbon monoxide. This procedure can result in reduction of CO generation to near 1% of released carbon gases. It is often desirable to recapture nitrogen oxides and convert them back into nitric acid for recycle to the oxidation process, both from a reagent cost standpoint and a pollution reduction standpoint. This can be done using commercially available acid recovery units, and recovery can be improved by introducing air into the oxidation reaction vessel. Air is typically added in amounts that will provide 1-2 moles of O.sub.2 per mole of NO gas produced by the process. Once oxidation is complete and off gases have been removed, the remaining radioactive or hazardous metal components are concentrated in a residual concentrated waste product, which is then removed from the oxidation vessel and placed into a final form where it is immobilized and suitable for long term storage in a suitable repository. Several processes for immobilizing the residual concentrated waste product may be used, including vitrification and ceramification. When vitrification is used, the residual concentrated waste product is introduced into a melter, which may be heated by induction or other methods. The residual concentrated waste may optionally be combined with an additive (such as ferric oxide). The composition of the glass may be varied depending on the composition of the residual concentrated waste product, but typically will involve adding ferric oxide to form an iron phosphate glass. Typically, iron phosphate glasses are processed using ceramic (e.g., silica, alumina, or mullite) or platinum group metal containers. Glasses produced according to the present invention should contain no less than about 20% Fe.sub.2 O.sub.3 by weight. Fabrication is difficult if the iron content exceeds 45% (by weight as Fe.sub.2 O.sub.3). Approximately 4-8% by weight of alkali oxide and about 2-4% by weight of alkaline earth metal oxide is desirably used to help ensure waste solubility. The balance of the system is phosphorus pentoxide P.sub.2 O.sub.5), and the total P.sub.2 O.sub.5 content should not be less than about 50% by weight. All percentages are based upon the final glass composition. The phosphate glasses are typically melted at temperatures between about 1050.degree. C. and about 1300.degree. C., more particularly between about 1080.degree. C. and 1200.degree. C. If the melt is stirred, a typical residence time of less than about 1 hour is used. A static melt typically remains in the melter for a residence time of between about 1 and 4 hours. For example, spent cationic and anionic exchange resins (e.g., sulfonated divinylbenzene polymer, quaternary amine divinylbenzene polymer, or resorcinol resins) suitable for use in purifying water in nuclear facilities can be oxidized according to the present invention by dissolving the resin in the mixed acid oxidizing solution, and the resulting reduced volume product immobilized as a homogeneous glass by adding glass forming additives including 25% by weight of Fe.sub.2 O.sub.3, 15% by weight Na.sub.2 HPO.sub.4 .cndot.7H.sub.2 O, and 3% by weight of BaCl.sub.2 .cndot.2H.sub.2 O at a melt temperature of 1150.degree. C., to yield a glass which provides a two fold volume reduction. The residual concentrated waste product may also be immobilized in the form of a ceramic, such as magnesium phosphate or ferric phosphate ceramic. These ceramics are formed by acid-base reactions between inorganic oxides and the phosphoric acid solution exiting the oxidation vessel. Phosphate ceramics have low temperature setting characteristics, good strength, and low porosity, and can be produced from readily available starting materials. For instance, a magnesium phosphate ceramic can be made by combining calcined MgO with the phosphoric acid residual waste solution from the oxidation vessel with thorough mixing. The reaction between the acid mixture and the MgO is slightly exothermic, but cooling of the reaction vessel is generally not required. The resulting slurry is poured into a mold and allowed to set. Magnesium phosphate ceramics allow for a relatively high waste loading and a chemically stable, high strength final form. As a nonlimiting example, a magnesium phosphate ceramic may be formed from a mixture of about 33.5 wt % H.sub.3 PO.sub.4, about 16.5 wt % H.sub.2 O, about 42.5 wt % MgO, and about 7.5 wt % H.sub.3 BO.sub.3, where the percentages are based upon the final magnesium phosphate ceramic composition. Since the residual waste solution typically may contain 50-70 wt % H.sub.3 PO.sub.4 (based upon the residual waste solution), the amounts of water, magnesium oxide, and boric acid may be suitably adjusted to approximate the above composition. It should be understood that the particular composition of the magnesium phosphate ceramic is not critical to the invention, and variations from the above composition are within the scope of the invention. EXAMPLES The following Examples 1 through 7 were conducted using the following procedures: A glass reaction vessel was charged with a mixture of nitric acid and phosphoric acid. Palladium catalyst was also added to help convert CO to CO.sub.2. TEFLON fittings and VITON o-rings were used to help create gas seals. The system temperature and pressure were measured using standard methods. Example 1 2.15 grams of disodium EDTA was added to 34 mL of mixed nitric and phosphoric acid containing 1.5 molar HNO.sub.3 and 13.3 molar H.sub.3 PO.sub.4 at 140.degree. C. and atmospheric pressure. Completion of oxidation was measured by converting any carbon monoxide produced to carbon dioxide and monitoring the total amount of carbon dioxide produced and comparing this amount to the theoretical yield of carbon dioxide based upon the amount of EDTA added to the reaction mixture. Complete oxidation of the organic materials occurred in less than one hour. Example 2 A solution of 480 mL of disodium EDTA (16.6% by weight) and Fe.sub.2 O.sub.3 (4.1% by weight) in water (79.3% by weight) was gradually added to 100 mL of mixed nitric and phosphoric acid, the nitric acid concentration of which varied between 0.25 molar and 1 molar, and phosphoric acid concentration of which varied between 14.55 molar and 13.8 molar, at 165.degree. C. and atmospheric pressure. After 8 hours, the resulting residual concentrated waste solution was heated at 200.degree. C. to form 60 mL of iron phosphate ceramic. Example 3 1.01 grams of cellulose was added to 32 mL of mixed nitric and phosphoric acid having a concentration of 1.5 molar HNO.sub.3 and 13.3 molar H.sub.3 PO.sub.4 at 155.degree. C. and 0-2 psig. Complete oxidation of the organic components occurred in less than one hour. Example 4 0.12 grams of polyethylene was added to 25 mL of mixed nitric and phosphoric acid having a concentration of 0.25 molar HNO.sub.3 and 14.55 molar H.sub.3 PO.sub.4 at 200.degree. C. and 10-15 psig. Complete oxidation of the organic components occurred in less than two hours. Example 5 0.15 grams of polyvinylchloride was added to 25 mL of mixed nitric and phosphoric acid having a concentration of 0.25 molar HNO.sub.3 and 14.55 H.sub.3 PO.sub.4 at 190.degree. C. and 10-15 psig. Complete oxidation of the organic components occurred in approximately two hours. Example 6 4.01 grams of divinylbenzene ion exchange resin was added to 200 mL of mixed nitric and phosphoric acid having a concentration of 1 molar HNO.sub.3 and 13.8 molar H.sub.3 PO.sub.4 at 175.degree. C. and 5-10 psig. Complete oxidation of the organic components occurred in less than two hours. Example 7 360 mL of radioactively contaminated ion exchange resin was gradually added to 100 mL of mixed nitric and phosphoric acid whose concentration varied between 0.25 molar and 1.0 molar HNO.sub.3 and 14.55 molar and 13.8 molar H.sub.3 PO.sub.4. The resulting residual concentrated waste solution was then combined with ferric oxide (30% by weight), NaCO.sub.3 (5% by weight), Na.sub.2 O (5% by weight), BaO (2% by weight) and P.sub.2 O.sub.5 (balance) and heated to 1150.degree. C. for about 1.5 hours to form 60 mL of iron phosphate glass. Example 8 Approximately 120 mL of spent resin used in the cleaning basin water from the reactor facilities at Savannah River Site were dissolved in 100 mL of the mixed acid solution of Example 7. Analyses of the resin solution indicated that it contained the species shown below in Table 2 TABLE 2 ______________________________________ SPECIES CONTENT ______________________________________ Al 130 ppm B 11.1 ppm Ca 451 ppm Cd 2.7 ppm Cr 9.3 ppm Cu 6.7 ppm Fe 191 ppm Mg 31 ppm Na 6582 ppm Ni 22.4 ppm P 174,260 ppm Si <2.7 ppm Zn 16.5 ppm Cl.sup.- 1776 ppm F.sup.- 274 ppm NO.sub.3.sup.- 27,236 ppm PO.sub.4.sup.3- <1000 ppm SO.sub.4.sup.2- 15,865 ppm alpha 9.4 * 10.sup.4 dpm/mL Beta/Tritium 3.1 * 10.sup.5 dpm/mL Cs-137 6.29 * 10.sup.-2 .mu.Ci/mL Tritium 2.31 * 10.sup.-2 .mu.Ci/mL ______________________________________ The resulting oxidation solution was mixed with glass forming additives BaCl.sub.2 .cndot.2H.sub.2 O, Fe.sub.2 O.sub.3, and Na.sub.2 BPO.sub.4 .cndot.H.sub.2 O and heated to 1150.degree. C. at a rate of approximately 5.degree. C./minute, and melted at 1150.degree. C. for 4 hours to form a homogeneous black glass having the composition set forth below in Table 3. TABLE 3 ______________________________________ OXIDE AMOUNT (WT %) ______________________________________ Al.sub.2 O.sub.3 2.649 B.sub.2 O.sub.3 0.013 BaO 2.796 CaO 0.262 Cr.sub.2 O.sub.3 0.162 Fe.sub.2 O.sub.3 34.007 La.sub.2 O.sub.3 0.023 Na.sub.2 O 0.233 Nd.sub.2 O.sub.3 0.142 NiO 0.066 P.sub.2 O.sub.5 58.383 PbO 0.173 SiO.sub.2 0.199 SrO 0.007 Total 99.116 ______________________________________ A gamma PHA of this glass indicated a Cs-137 content of 4.2210.sup.-2 .mu.Ci/g, or a total of 1.181 .mu.Ci. Based on the analyses of the spent resin, indicating that 6.2910.sup.-2 .mu.Ci/mL or a total of 1.037 .mu.tCi of Cs-137 were present in the solution stabilized in the glass, Cs-137 was retained in the glass. Standard PCT leaching tests were performed on the glass, resulting in an average measured release of 0.031 g/L P, 0.002 g/L Ba, 3.104 g/L Na, and 0.000 g/L Fe, at a measured leachate pH of 6.00. These values are much lower than the EA accepted value for HLW borosilicate glass. A TCLP extraction using a modified EPA protocol was performed to determine the amount of RCRA metal leaching. The modification consisted of using ground glass, approximately 150 .mu.m, instead of the specified <1 cm glass specimen size, and was made due to the small amount of glass produced and the conservative results that would be obtained by using a large leaching surface area. Results indicated that Ba was the only metal to leach in an amount (1.049 ppm) above the analytical detection limits. This amount is much lower than any of the EPA allowable limits. It will be apparent to those skilled in the art that many changes and substitutions can be made to the specific embodiments disclosed herein without departing from the spirit and scope of the present invention as set forth in the claims.
062698737	claims	1. A method for controlling heat exchange in a nuclear reactor comprising the steps of: circulating a heated liquid through a conduit forming a closed loop extending from a heat exchanger in the nuclear reactor to at least one other heat exchanger immersed in a pool of relatively cold liquid located external of the nuclear reactor; confining said at least one other heat exchanger within a container immersed in said pool of liquid, said container having an upper part forming an area surrounding said at least one other heat exchanger and an open lower part through which the liquid of said pool may freely pass; forming a passageway in said upper part of said container to permit communication through said passageway from said area surrounding said at least one other heat exchanger and said pool; and controlling the opening and closing of said passageway such that when the passageway is closed a vapor is formed in said area inhibiting further heat exchange with the heated liquid in the conduit and when the passageway is open heat exchange is maximized. 2. The method of claim 1, wherein said passageway forms an outlet located in the upper part of the container and controlling the opening and closing of the outlet using a thermal valve. 3. The method of claim 2 wherein at least two valves arranged in a parallel manner are located at said outlet. 4. The method of claim 2 wherein said open lower part of the container comprises one or more openings in said container for communicating with said pool. 5. The method of claim 1 wherein the heat exchanger contains a fluid entrance pipe and a fluid outlet pipe, said entrance and outlet pipes penetrating the lower part of the container. 6. The method of claim 5 wherein the fluid entrance pipe and the fluid outlet pipe are thermally insulated. 7. The method of claim 5 comprising using said loop for carrying a fluid, said loop being connected to: (a) the fluid entrance pipe through which a fluid is passed into the heat exchanger and (b) the fluid outlet pipe through which the fluid exits from the heat exchanger. 8. The method of claim 7 comprising using a pump in communication with the loop. 9. The method of claim 7 comprising using an expansion tank in communication with the loop, thereby causing any fluid present in the loop to be maintained under pressure. 10. The method of claim 1 wherein the heat exchanger contains a fluid entrance pipe and a fluid outlet pipe located such that the fluid entrance pipe and/or the fluid outlet pipe penetrate through a side or the top of the container. 11. The method of claim 10 wherein the fluid entrance pipe and the fluid outlet pipe are thermally insulated. 12. The method of claim 10 comprising using said loop for carrying a fluid, said loop being connected to: (a) the fluid entrance pipe through which a fluid is passed into the heat exchanger and (b) the fluid outlet pipe through which the fluid exits from the heat exchanger. 13. The method of claim 12 comprising using a pump in communication with the loop. 14. The method of claim 12 comprising using an expansion tank in communication with the loop, thereby causing any fluid present in the loop to be maintained under pressure.
	abstract	Systems and methods determine locations of moving equipment in an area holding components to be moved. Moving equipment can relocate relative to the holding area to pick up components in the holding area from an origin and deliver them to a desired location or orientation. The moving equipment includes a device emitting a signal that is detectable where it hits components or other structures in a straight line or known path from the moving equipment. A human or computer can determine a position the moving equipment in the holding area from such signals. Devices can operate with visible light generators including LEDs, incandescent or fluorescent bulbs, and lasers and including lenses or reflectors to shape the light into detectable and high fidelity configurations. Automation components including a hardware processor, controller, and detector can operate moving equipment based on detected light, without human interaction or as a verification in human operations.
048719110	description	A scanning electron microscope as shown in FIG. 1, comprises an electron source 2, an anode 4, a control electrode 6, a condensor lens system 8, a beam scanning coil system 10, an objective lens system 12, and a specimen table 14. An electron beam 16 generated in the electron source is incident on a specimen 18 arranged on the specimen table. Detectors 20, 22 and 24 are capable of detecting different types of radiation as products of the interaction between the electron beam and the specimen. By a signal selector 25 and a signal processing device 26, the signals are applied to a monitor 28. The monitor in a scanning electron microscope is synchronized by signals from the beam scanning system 10 and is also connected, for example to a control device 30 for beam blanking. Even though the invention is described herein with reference to the scanning electron microscope shown it will be apparent that the invention is by no means restricted thereto; and the invention can also be very well used, for example in electron beam writers, (scanning) transmission electron microscopes and similar apparatus. A column of a scanning electron microscope in adapted form can serve, for example as a column for a beam writer as described, for example, in U.S. Pat No. 3,491,236. An electron source as shown in FIG. 2 comprises a semiconductor element 40 which is accomdated in a housing 42 with a carrier table 44 and a diaphragm aperture 46 for the passage of the electron beam 16. The base plate or carrier table 44 comprises passages 48 for supply leads 50 of the electron emitter. The semiconductor element 40 contains a crystal semiconductor material 52 which consists, for example of Si, GaAs, SiC etc. At a small distance from a free surface 54 a p-n junction 56 is provide in the crystal, with transverse dimensions of the junction, that is to say the dimensions in its plane, being well defined. As is customary, a part of the crystal is covered with, for example, an oxide layer 58 on which there may be provided a conductive layer 60. The conductor 60 can act as a gate electrode. For a more detailed description of the geometry and the construction of such an element reference is made to U.S. Pat. No. 4,303,930. Because the p-n junction is connected in the reverse direction, electrons will be emitted from and emissive surface 62 which is situated opposite the p-n junction, with the electrons reaching the electron-optical system under the influence of a positive potential which acts through the aperture 46. On the free surface 54 of the semiconductor element there may be provided a preferably approximately monomolecular layer of a material which reduces the electron exit potential, such as for example, Cs or Ba, so that the efficiency of the source can be increased, if necessary. Such a layer can be provided, for example, by depositing the desired material in a space 66 within the housing 42 from the gaseous phase. FIG. 3 diagrammatically shows some preferred embodiments of emissive surfaces. For the sake of clarity it is to be again noted that the geometry of the emissive surface is in this case determined by the geometry of the p-n junction. All surfaces are chosen so that optimum adaptation to the electron-optical properties of the apparatus is obtained. Depending on the relevant application, a round emissive surface 70 has a diameter of, for example from approximately 0.5 to 5 .mu.m and thus has optimum dimensions as an object for further imaging in the apparatus. Due to this choice of the dimensions, the electrons which escape in the transverse direction, i.e. electrons which are not deliberately emitted, do not cause a disturbing field or distrubing heating of the semiconductor element at this area. A round emissive surface is suitable, for example for imaging apparatus such as an electron microscope. For applications requiring an electron spot which is sharply defined mainly in one direction, use can be made of an emissive surface 72. The advantages of such a geometry are described in U.S. Pat No. 3,881,136; it can be used extremely well, for example, for the formation of images in which a high resolution is desired mainly in one direction. The dimensions may then be, for example 1.times.5 .mu.m.sup.2. Notably for use in electron beam writers in which an electron spot is required which is sharply defined on two sides there is a square emissive surface 74 with sides of, for example from 0.5 to 5 .mu.m. Such a geometry is also very suitable for beam shaping as well as for splitting the electron spot into geometrically defined parts. As has already been stated, use can also be made of a regular polygon. The emissive surfaces 76 and 78 are composite emissive surfaces. The emissive surface 76 comprises a linear array of, for example 10 emissive sub-surfaces which are identical in this case. An apparatus can then operate with a multiple beam as described in U.S. Pat. Nos. 4,524,278 and 4,568,833, it being possible to control each of the sub-beams individually. The same consideration hold good for the emissive surface 78 in the form of a matrix of emissive sub-surfaces. Composite emissive surfaces are particularly suitable for electron beam writers, notably when such apparatus are used for the direct manufacture of integrated circuits, i.e. without the assistance of masks. A composite emissive surface 78 comprises a central sub-surface 80 and an annular sub-surface 82 as the emissive surfaces and a ring 84 as a non-emissive surface. Such a surface is useful, for example for measurement methods related to dark-field illumination ect. Such a composite surface may alternatively have a rectangular, square or other shape. The references U.S. Pat. Nos. 4,524,278 and 4,568,833 cited in this specification have been published as EP pat. appln. No. 87196 and EP pat. appln. No. 92873 respectively. The article "An efficient silicon cold cathode for high current densities" is published by two of the inventors in Philips J. Res. 39, October 1984, pp 51-60 , describes some properties of the semi-conductor device per se
054815762	abstract	A vibrating assembly for vibrating an ice basket of a pressurized water reactor comprises first and second vibrators and a bracket operatively connected to the vibrators. The bracket includes a horizontally extending first armature portion and a horizontally extending second armature portion pivotably attached to the second armature portion. The first and second armature portions have clamps extending downwardly from each of their ends, and each of the clamps includes an arcuate groove extending vertically upwardly from its bottom surface to engage the rim of the ice basket. An attachment portion extends vertically upwardly from and is formed unitarily with the first armature portion, the vibrators being attached to the sides of the attachment portion. The clamps extending from the second armature portion are pivotably connected to and are also laterally adjustable with respect to the first and second ends of the second armature portion. In use the vibrator assembly is attached to the rim of the ice basket by adjusting the positions of the clamps to fit the rim and then securing the rim in the clamps. The vibrators are then activated to free the ice in the ice basket. While the vibrators are activated, the ice basket is pulled from above by exerting an upward force on the bracket and is pushed from below.
051903334	abstract	An end effector deploying and inverting linkage. The linkage comprises an air cylinder mounted in a frame or tube, a sliding bracket next to the air cylinder, a stopping bracket depending from the frame and three, pivotally-attached links that are attached to the end effector and to each other in such a way as to be capable of inverting the end effector and translating it laterally. The first of the three links is a straight element that is moved up and down by the shaft of the air cylinder. The second link is attached at one end to the stopping bracket and to the side of the end effector at the other end. The first link is attached near the middle of the second, sharply angled link so that, as the shaft of the air cylinder moves up and down, the second link rotates about an axis perpendicular to the frame and inverts and translates the end effector. The rotation of the second link is stopped at both ends when the link engages stops on the stopping bracket. The third link, slightly angled, is attached to the sliding bracket at one end and to the end of the end effector at the other. The third helps to control the end effector in its motion.
	abstract	A system and method for the extraction of americium from radioactive waste solutions. The method includes the transfer of highly oxidized americium from an acidic aqueous feed solution through an immobilized liquid membrane to an organic receiving solvent, for example tributyl phosphate. The immobilized liquid membrane includes porous support and separating layers loaded with tributyl phosphate. The extracted solution is subsequently stripped of americium and recycled at the immobilized liquid membrane as neat tributyl phosphate for the continuous extraction of americium. The sequestered americium can be used as a nuclear fuel, a nuclear fuel component or a radiation source, and the remaining constituent elements in the aqueous feed solution can be stored in glassified waste forms substantially free of americium.
	claims	1. A water jet peening method comprising the steps of:preparing a water jet peening apparatus having a supporting member, a first divider plate mounted on one end of the supporting member, a nozzle support body formed by disposing a jet nozzle around the supporting member, and a second divider plate mounted on the supporting member, the jet nozzle being disposed between the first divider plate and the second divider plate;inserting the water jet peening apparatus into a piping in which a structure or electronic device is mounted that is susceptible to damage by a jet of water discharged from the jet nozzle or by shock waves;disposing either the first divider plate or the second divider plate between the jet nozzle and the structure or electronic device;filling water into an internal area formed in the piping between the first divider plate and the second divider plate;subjecting the inner surface of the piping to water jet peening by allowing the jet nozzle to discharge a jet of water into the water in the internal area;discharging uncollapsed cavitations outside the internal area through a scoop formed in the first divider plate, on its surface facing the second divider plate and connected to an air emission route formed in the supporting member, the uncollapsed cavitations being included in the jet of water discharged from the jet nozzle into the water; anddischarging the water in the internal area through the water discharge route formed in the second divider plate, whereinthe uncollapsed cavitations and the water in the internal area are discharged simultaneously. 2. The water jet peening method according to claim 1, further comprising the steps of:before filling the water into the internal area, expanding a first hollow seal member and a second hollow seal member by supplying air to the internal space of the first hollow seal member and of the second hollow seal member, the first hollow seal member being disposed on the outer circumference of the first divider plate to surround the first divider plate, the second hollow seal member being disposed on the outer circumference of the second divider plate to surround the second divider plate;sealing a gap between the inner surface of the piping and the first divider plate with the expanded first hollow seal member; andsealing a gap between the inner surface of the piping and the second divider plate with the expanded second hollow seal member. 3. The water jet peening method according to claim 1, further comprising the step of rotating the jet nozzle, which is discharging a jet of water, around the supporting member and moving the jet nozzle in the axial direction of the supporting member. 4. The water jet peening method according to claim 3, further comprising the step of:before filling the water into the internal area, expanding a first hollow seal member and a second hollow seal member by supplying air to the internal space of the first hollow seal member and of the second hollow seal member, the first hollow seal member being disposed on the outer circumference of the first divider plate to surround the first divider plate, the second hollow seal member being disposed on the outer circumference of the second divider plate to surround the second divider plate;sealing a gap between the inner surface of the piping and the first divider plate with the expanded first hollow seal member; andsealing a gap between the inner surface of the piping and the second divider plate with the expanded second hollow seal member. 5. The water jet peening method according to claim 1, further comprising the step of:before filling the water into the internal area, expanding a first hollow seal member and a second hollow seal member by supplying air to the internal space of the first hollow seal member and of the second hollow seal member, the first hollow seal member being disposed on the outer circumference of the first divider plate to surround the first divider plate, the second hollow seal member being disposed on the outer circumference of the second divider plate to surround the second divider plate;sealing a gap between the inner surface of the piping and the first divider plate with the expanded first hollow seal member; andsealing a gap between the inner surface of the piping and the second divider plate with the expanded second hollow seal member. 6. The water jet peening method according to claim 1,further comprising the step of rotating the jet nozzle, which is discharging a jet of water, around the supporting member and moving the jet nozzle in the axial direction of the supporting member. 7. The water jet peening method according to claim 5, further comprising the step of rotating the jet nozzle, which is discharging a jet of water, around the supporting member and moving the jet nozzle in the axial direction of the supporting member.
041467965	claims	1. An apparatus for determining the depth of a radiation source within a body of material and transforming the same into a signal for computer usage comprising: a. radiation source holder transporting the radiation source within the body; b. plurality of switches having contacts which are fixed in relation to the movement of said radiation source transported by said radiation source holder; c. trigger means for indicating the activation of any of said plurality of switches, corresponding to preselected depths of the radiation source within the body; and d. means for indicating the activation of any of said plurality of switches, said indicating means producing a characteristic signal determinative of the activation of any of said plurality of switches which corresponds to the depth of the radiation source within a body and including detection means for distinguishing said characteristic signals and associating the same with the activation of any of said plurality of switches. 2. The device of claim 1 in which said trigger means produces a magnetic field and said switches are activated by said trigger means magnetic field. 3. The apparatus of claim 2 in which said trigger means is affixed to said radiation source holder and is movable therewith. 4. The apparatus of claim 3 in which said apparatus additionally includes means for guiding said radiation source holder within the body. 5. The device of claim 4 in which said guiding means interposes said trigger means and said plurality of switches. 6. The device of claim 1 in which said indicating means comprises a series of resistors electrically linked to a source of power, said plurality of switches connected to an electrical ground, each of said plurality of switches connected between each of said resistors, and said means for distinguishing said characteristic signals produced by the circuit formed by said ground, any of said plurality of switches, a selected number of said series of resistors and said power source. 7. The device of claim 6 in which said trigger means is affixed to said radiation source holder and is movable therewith. 8. The device of claim 7 in which said apparatus additionally includes means for guiding said radiation source holder within the body. 9. The device of claim 8 in which said guiding means interposes said trigger means and said plurality of switches. 10. The device of claim 9 in which said trigger means produces a magnetic field and said switches are activated by said trigger means magnetic field.
	summary
	claims	1. An apparatus for catching, fragmenting and then uniformly cooling a melt, the apparatus comprising: a coolant supply system containing a pre-pressurized coolant running from said coolant supply system toward the melt for cooling the melt, said coolant supply system having an outlet region; and a porous body formed of composite and/or particle material disposed directly at said outlet region of said coolant supply system for catching the melt, said porous body having a plurality of flow channels formed therein, said porous body having a flow resistance, the pre-pressurized coolant being fed with a feed-flow rate limited by said flow resistance of said porous body. 2. The apparatus according to claim 1 , including a supporting substructure for supporting said porous body. claim 1 3. The apparatus according to claim 1 , wherein said porous body contains a porous composite material. claim 1 4. The apparatus according to claim 3 , wherein said porous composite material is porous concrete, which contains at least one of an aggregate, a binder and a ceramic. claim 3 5. The apparatus according to claim 1 , wherein said porous body is constructed from particles being at least one of regular particles and irregular particle. claim 1 6. The apparatus according to claim 5 , wherein said particles contain at least one of a mineral material, steel, cast iron and a ceramic. claim 5 7. The apparatus according to claim 1 , including a sacrificial layer covering said porous body. claim 1 8. The apparatus according to claim 7 , wherein said porous body has cavities formed therein which are to be completely filled with the pre-pressurized coolant. claim 7 9. The apparatus according to claim 7 , wherein said porous body and said sacrificial layer are cast together in their boundary region. claim 7 10. The apparatus according to claim 7 , including a sealing layer disposed between and separating said porous body and said sacrificial layer. claim 7 11. The apparatus according to claim 10 , wherein said sealing layer is formed from at least one material selected from the group consisting of metals and plastics. claim 10 12. The apparatus according to claim 1 , wherein said porous body is to be disposed directly beneath a reactor pressure vessel. claim 1 13. The apparatus according to claim 12 , including a core-catching device and a channel connected to said core-catching device, said porous body is disposed laterally offset below the reactor pressure vessel and is connected to said core-catching device by said channel. claim 12 14. The apparatus according to claim 1 , wherein said porous body has an underside and side faces and the pre-pressurized coolant can be fed to at least one of said underside and said side faces of said porous body over a large area. claim 1 15. The apparatus according to claim 1 , wherein said porous body has an underside and side faces, and including channels connected to said porous body, the pre-pressurized coolant is fed to at least one of said underside and said side faces of said porous body through at least one of said channels and over a large area. claim 1 16. The apparatus according to claim 1 , wherein said coolant supply system includes: claim 1 a coolant reservoir; coolant lines supplying the pre-pressurized coolant to said porous body; and a cooling channel connecting said coolant reservoir to said coolant lines. 17. An apparatus for catching, fragmenting and then uniformly cooling a core melt in a containment of a nuclear power plant, the apparatus comprising: a coolant supply system containing a pre-pressurized coolant running from said coolant supply system toward the melt for cooling the melt, said coolant supply system having an outlet region; and a porous body formed of composite and/or particle material disposed inside the containment directly at said outlet region of said coolant supply system for catching the melt, said porous body having a plurality of flow channels formed therein, said porous body having a flow resistance, the pre-pressurized coolant being fed with a feed-flow rate limited by said flow resistance of said porous body.
045171548	description	DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The present invention, a self-test subsystem for nuclear system protection systems, rapidly detects hardware failures and thereby facilitates repair of a nuclear reactor protection system (RPS). The self-test system (STS) includes a memory in which sets of input stimuli test patterns and expected output results are stored. After running a test, the actual outputs obtained are compared with the expected outputs and should discrepancies exert such fact is annunciated to plant operators. A unique aspect of the present invention is the fact that RPS tests may be run in real time while the system is in actual operation, without interfering with system operation. This is accomplished by using test pulses of short duration. Such pulses do not cause actual activation of the RPS components other than to check their continuity. Thus, the pulses are transparent to system operations. The self-test system includes four optically coupled, intercommunicating self-test system divisions (FIG. 1), each division capable of operating as a master for the other three divisions and capable of operating as a slave to one of the other three divisions. Each division includes a self-test system (FIG. 2). The self-test system includes a CPU/memory card 12 that contains a Z80 central processing unit 14, a read only memory (ROM) 15 that contains the self-test system operating program, and a random access memory 16. The CPU/memory card also includes an address decoder 17 and a processor clock 18. The processor includes a control bus, data bus, and address bus. The buses are routed through control bus, data bus, and address bus buffer circuits 19-21. The buffers serve as a bus interface between the CPU/memory card and the rest of the STS. The CPU/memory card is interfaced to six universal input/output (I/O) cards 22-27 and one serial input/output (I/O) card 28. FIG. 2 shows universal I/O card 22 in detail and another five universal I/O cards 23-27 in block form. FIG. 3 is an overview of the STS hardware rack architecture. FIGS. 4 and 5 show specific wiring interconnects between the self-test system rack and the rest of the self-test system. FIG. 6 is an overview of the STS system architecture. Serial I/O card 28 is buffered to the control, data, and address buses by control bus, data bus, and address bus buffers 30-32. The serial I/O card includes 32K of ROM 34 containing the data base for this particular one of the four divisions. ROM 34 is associated with an address decoder 35. Serial I/O card 28 also contains a data flow control network 36 and includes two parallel-to-serial I/O chips 37 that provide two output channels each. The chip output channels are interfaced to the self-test system motherboard I/O via a differential driver and receiver 38. Parallel-to-serial I/O 37 is driven by an on-board clock 39. The serial I/O board provides four I/O channels. Three of the serial I/O board channels are connected, via optical isolators 42, to the other three divisions of the four division system. A fourth channel is a diagnostic function channel. The four divisions communicate with each other through each division's serial I/O board. The four divisions are optically coupled such that electrical failure of one division does not interfere with the operation of the other divisions. The serial I/O board's fourth I/O channel provides diagnostic and functional information to system process computers 44 (FIG. 1). In this way, a particular error code may be routed to the process computer and then to an operator diagnostic terminal 45 wherein the error code is translated to English or other operator understandable messages to alert maintenance personnel. During operation, when an annunciator 43 is activated, the operator can go to the process computer to locate the error by transferring commands through the serial I/O board to the self-test system to retrieve the failure information or to run the self-test system through particular tests, which tests then provide data back to the process computer indicating test results. In this way, a failure may be localized and more readily corrected. The six universal I/O cards are interfaces between the self-test system rack and the self-test circuitry located on protection function cards (FIGS. 8 and 9). Each universal I/O card 22-27 has an interface to the control, data, and address busses consisting of control bus buffer 46, data bus buffer 47, and address bus buffer 48. Addresses are decoded by universal I/O card decoder 50 to operate either a 24-line input port 52, in which case the universal I/O is an input device; or to operate a 24-line output port 53, in which case the universal I/O is an output device. Selection of input or output ports is under CPU control. Timing and signals on the universal I/O card may be controlled by an on-board clock timer chip (CTC) 51. The universal I/O card provides a first level of decoding to access the protection function cards, test circuitry. The second level of decoding is provided by the card select monitors 54 (FIG. 7, discussed below). In general, to communicate with a protection function card, its card select monitor 54 must first be selected. Address data is then shifted through the universal I/O cards to the card select monitor to select a particular protection function card located in a particular slot of the card file under control of the selected card select monitor. Once the protection function card is selected, the data necessary to configure it to test the RPS is provided via the data bus. The data is routed across the bus from the universal I/O card directly to the selected functional card and does not pass through a card select monitor. The card select monitor is an interface between the universal I/O cards and the protection function cards and provides a second level of address decoding. The universal I/O card can select one of up to 24 card select monitors. Generally, 24 card select monitors per universal I/O card are not required, but the capacity is available for certain embodiments of the invention. The card select monitor is "selected" by the universal I/O when it receives a system select signal from the universal I/O card (FIGS. 10a-c). The universal I/O sends a particular test address vector (input data) to the card select monitor after the card select monitor is selected. The test vector selects the particular card in the card file to receive test data from the CPU. A 27-bit word is received from the universal I/O at the card select monitor as serial data. The serial data is shifted into an address register 55 by means of an address clock. Each bit of data shifted in refers to a particular protection function card that may be selected. Thus, if a `1` is shifted in at bit position 7, then the seventh protection functional card in that card file is selected. A select strobe signal is sent to the card select monitor causing serial data that has been shifted into the card select monitor address register 55 to be latched in the card select monitor output register 56. This output register now actuates the card select line for the desired protection function card in the card file. One of the important features of the present invention is that of verification and acknowledgement. Thus, when a select strobe signal is sent to latch data into the output register, a strobe echo is returned to the universal I/O, verifying that the card select monitor indeed received the select strobe signal. Likewise, when a system select signal is provided to the card select monitor, a system acknowledge signal is routed back to the universal I/O to confirm that the system select signal reached the card select monitor. The card select monitor can be used to inventory the functional cards in a given card file to determine if there are any missing or added cards in the file. In order to do this, patterns are latched into the output register to select every functional card in the card file. An echo from each functional card is returned to the card select monitor and latched into monitor register 57. Upon receiving a compare clock signal from a universal I/O, the parallel data in the monitor register indicating echos from the selected functional cards is latched and then serially shifted out of the monitor register and back to a universal I/O. The pattern received by the universal I/O is checked by the CPU to be certain that echos from all cards are received and that no cards are out of file. In addition to performing a functional card inventory, this procedure is used during actual testing to verify that the correct functional cards for a particular test pattern have been selected. Due to the complexity of a nuclear reactor, many component portions of the nuclear reactor protection system must be tested in separate, overlapping system tests. In this particular embodiment of the invention seven different protection systems are tested in this manner. FIG. 8 shows a typical functional or logic test card used in the present invention. From a self-testing point of view, the card shown is substantially similar to all other protection function cards, although certain modifications may be necessary for particular applications. The protection function card is selected when a test vector specifying that particular card is decoded by the card select monitor which, in turn, selects the appropriate protection function card in its associated card file. Some protection function cards may have more input or output registers but most are configured similarly. Typically, signals present at all protection function cards are those of the self-test bus which include data-in, clock, test pulse, test pulse echo, card select, card select acknowledge, and compare clock. When a functional card is selected by the card select monitor, a card select signal is routed to the card to set one-half of `AND` gate 62. An echo or card select acknowledge is provided to the card select monitor to verify that the card select signal has reached the functional card. Whenever, the card select signal and the clock signal are present at `AND` gate 62, the serial, "data-in" may be shifted into data input register 63 via the data bus (FIG. 11a). Thus, a test vector is shifted into the data input registers bit-by-bit to set up various test patterns. After the functional card is selected by the card select monitor and the test vector is shifted into the data input register, a one millisecond test pulse is provided (FIG. 11b). A test pulse echo is sent back to the universal I/O to verify that the test pulse reached the selected functional card. Approximately 800 microseconds after the test pulse first issues, a compare clock signal is provided to the functional card. The compare clock signal latches parallel data output from the tested reactor protection system (RPS) into received pattern register 64. The parallel data latched into the received pattern register are serially clocked out (FIG. 12) bit-by-bit by the clock signal. This returns serial data to a universal I/O. The data input to the functional card are typically dependent on the actual number of functional inputs the card has and the results data are dependent on the number of outputs. In addition to the test result data, the protection function card data provides two additional types of information: card type data and card address data. The card type data identify a protection function card as to its particular performance characteristics. Thus, in the example shown, five of the inputs of shift register 65 are uniquely connected to indicate the protection function card's type. To insure that the card selected is located in its proper slot, a card address portion is also provided with the serial data output from the functional card. Thus, two inputs of shift register 65 and four inputs of shift register 66 are connected to a jumper arrangement. As shown in FIG. 4, each bit of the card address (A0-A5) may be jumpered high or left low. Thus, for card A125 (60) in FIG. 4, bits A0, A3 and A4 are jumpered to high to provide a unique binary number indicative of the particular slot which the functional card is occupying. The Z80 CPU receives the protection function card output data, card type information, and card address information from the universal I/O. The values obtained for the test are compared with expected values for the test stored in the data base. If the test results match the expected results, the test program goes to the next test. If the results do not match, an indication of inconsistency is annunicated to plant operating personnel. The accuracy of the test is maintained by verifying that the card address and card type are proper prior to verifying that the received data matches the expected data. If an improper card type or card address is detected, an alarm is annunciated to the operating personnel so that corrective measures may be taken. The particular functional card selected depends on which RPS test is performed. During certain tests it is desirable that a protection function card remain unselected but continue to provide an output monitor function. Such a situation might arise when a card is not directly loaded with test data from the STS but rather is indirectly loaded from cards undergoing direct testing at different points in the reactor protection system. For example, this may happen in end-to-end testing where a certain condition is input to one of a set of cards performing a given system function and the outprint from a second card is monitored. For example, in a system test that requires performance from ten protection function cards, five protection function cards might be configured as monitor cards; while the other five might be configured for data injection. In such test configuration, the card select monitors select each protection function card to be injected one at a time. Test vector data for the particular test are then shifted into each card's data input register. Once the protection function cards are conditioned for the test, the system goes back and selects the five protection function cards that are to inject a test signal into the RPS. During the actual test each selected protection function card simultaneously receives the one millisecond test pulse. The one millisecond test pulse period is quite significant for test purposes because it provides sufficient time to check the integrity of the RPS control loops, but it does not seize the RPS control loops long enough to actually affect protection system operation. In this way, the self-test system appears transparent to the nuclear reactor protection system and the protection system may be continually tested in real time while it is operating, without interfering with reactor operation. To avoid a cumulative test effect on nuclear system operation, the one millisecond test pulse does not generally occur more often than once in every 33 milliseconds. Hardware and software timers are provided to prevent this occurrence. Additionally, protection function card circuitry is provided with a time constant such as time-out circuit 61 to further prevent test interference with nuclear system operation. The protection function cards may be characterized as having test circuitry, as shown in FIG. 8, and as having functional or "essential" circuitry, as shown in FIG. 9. Essential circuitry is that which is connected to the actual RPS system and, as such, classified by various government standards as essential to the safe operation of the nuclear reactor. Thus, if there is a failure in essential circuitry the potential exists for interference with normal plant operation and the reactor is then put in a shut down or reduced power condition until the error is corrected. Most circuitry in the present invention is of the nonessential type. Thus, a failure of the present invention would not necessarily be cause for shutting down a reactor. The circuitry shown in FIG. 9 is essential circuitry in that it is an actual part of the reactor protection system. Referring now to FIG. 9, a card select and deselect are provided through AND/OR gate 70. The select function is under the control of the circuitry shown for the protection functional card in FIG. 8. The circuitry in FIG. 8 is in turn under the control of the card select bus. The one millisecond test pulse is provided to the essential circuitry through buffer 71. It should be noted that FIG. 9 discloses two identical essential circuitry test circuits, 68 and 69. These particular circuits are "load driver" circuits such as are connected to remotely located devices and actuators, e.g., scram solenoids. For the particular test performed in this illustrative example the data is provided in the form of an oscillating signal (OSC). At `AND` gate 73 the data input is `ANDed` with the functional signal to operate field effect transistor (FET) switch 74. A timer 75 having a time constant controlled by capacitor 23 maintains a proper select/deselect interval during the actual test. In this particular test circuit, the test pulse provides a current source that senses loop current present in transformer T7. Current sensed is compared with a preset current level at comparator 76 and provided as output data on the data bus. Testing of the nuclear reactor protection system is accomplished by a series of short duration pulses, on the order of one millisecond, injected into the protection system logic such that no single test pulse is of significant duration with respect to the response time of the functional system and so that combinations of test pulses do not alter system performance. The chief method of testing is to control all RPS control cabinet inputs for a particular functional safety system and to observe all cabinet outputs. These outputs are compared to the known transfer function of the particular system for all significant combinations of the input condition in order to establish that the circuit is operable. To minimize test time, each of the functional safety systems--in this embodiment of the invention, seven safety systems--is subdivided into circuits having independent inputs and outputs so that they can be tested separately. Overlap testing is employed to minimize test time and facilitate localization of fault to a replacable module (circuit card). Faults are located to the module level which is a preferred increment of field replacement. Replacement modules are separately verified as operable to a high confidence level. Testing with the self-test system is automatic, once it has been initiated, to assure a consistent and minimized test interval. Manual testing is performed to check a newly replaced module. The self-test system is microprocessor controlled, the microprocessor operating from a series of software modules. For purposes of better understanding, a microfilmed copy of the self-test system computer program is included as a Microfiche Appendix to this document. Program organization is shown in FIG. 13. The main software module is the executive module, the main program loop in each of the four redundant divisions. The executive checks for messages from the plant process computer, other divisions, and the analog trip module (ATM) control card via communicating links, and during certain periods of operation. When a given division's self-test system reaches its turn to exercise control over all divisions, i.e., becomes the master, its executive directs those tests assigned to it. The tests to be run are found using a counter as an index into a test table. The test located at that index is then called. The test run then returns a code describing the test results. On a test failure, the self-test system division is taken off line. When all the major tests have been run, the race flag is set, and the race for master routine is called to hand off the master status to another self-test controller (STC). The watch-dog routine is called when the watch-dog timer is timing the initialization of a new master. The watch-dog timer checks that the allotted time for this initialization has not been exceeded; if it has, the watch-dog routine enters the proper message in the error log and jumps to a routine that annunciates the error and stops the testing. Operation of the executive loop is shown on the flow chart of FIG. 14. When the system is brought up, a power up initialization (100) is performed and an on-line and race flag is set (101). The program then looks for messages from other divisions (102), decodes them and executes the necessary responses (103) if such messages are present. The division also looks for messages from the process computer (104), decodes them, and executes the necessary responses, if they are present (105). If no messages are encountered or when all the messages have been answered, a dead man timer is reset (106) and the executive program checks to see if any division is currently a master (107). If the division is not on-line, it remains in the executive loop watching for messages from other divisions (102). If the division is on line, then a race for master flag must be checked (108). If the race for master flag is set, the race for master routine is called (109) and the race for master is executed to determine which of the four divisions will be master and, by default, which will be slaves. If the race for master flag has not been set, there is already a master and the executive checks to see if its division is a master (110). If its division is not a master, the watch-dog timer flag is checked (111) and is set at that point (112). If the division is a master, the executive goes to the program tables, gets the major and minor test numbers (113), and calls the major tests first (114) (discussed below). If the major tests are passed (115), the minor test numbers are incremented (116). If the tests are not passed, or if there is a watch-dog timer time out interrupt (indicating that a division is hung up), a record of the error is made in the error log (123), an annunciator is turned on, the on-line flag is reset (122), and a race for master flag is reset (121). If the minor tests are successfully finished, the minor test number is reset, the major test number is bumped (117), and the interdivisional tests are then performed (118). If the interdivisional tests are passed, the executive checks to see if all major tests are finished (120) and, if so, sets the race for master flag (121). If not, the executive returns to the beginning of the loop. If the interdivisional tests are to be performed (118), the executive checks for an interdivisional configuration (more than one division) (119). If the system is configured for several divisions, a test is made to see if all major tests are finished (120) and, if so, the race for master flag is set (121). If there is not an interdivisional configuration (119) the system loop goes directly to the race for master routine (121) and then, to the beginning of the loop (102). The following is a discussion of the major tests and routines peformed by the system software under control of the executive loop. The first test is the self-checking routine. The self-checking routine does a self check of the self-test controller's CPU which includes a test of the Z80 microprocessor, ROM memory, RAM memory, and the counter/timer circuit. These tests are executed sequentially and, should a failure be detected, the processor is halted. If all tests are successful, a normal return occurs. During the self checking routine a Z80 microprocessor check is performed. The microprocessor check has two major components: program control test and pattern manipulation tests. Interrupts to the microprocessor are disabled for this test. If any failures occur in the process of the test, a halt occurs. The program control test exercises the program instructions of the Z80 instruction set. The pattern manipulation tests provide various parity checking procedures. The RAM test routine tests the top part of the RAM for operation and then moves the portion of RAM data that must be saved up to the top portion just tested. The routine then tests the bottom portion of the RAM. When the test is completed, the portion of RAM data saved is moved back to its original location. The next routine is the self-test routine. The self-test routine contains a series of subtests, each of which tests a part of the self-test controller hardware. These subtests are executed in the order that follows below, the results of a subtest are not valid until all the proceeding subtests have passed. During the self checking and self testing procedures a watch-dog timer routine is executed in each division. Typically, the watch-dog timer is used when a given division has finished its testing and is about to pass off its master status to another division. The retiring division sends an inquiry to the master-to-be. The master-to-be begins its self-testing and self-checking procedures. The retiring master times these procedures with its watch-dog timer and, if the tests are concluded within the allocated time, the retiring division passes master status to the master-to-be. The latter then proceeds with system testing. Additionally, each division maintains a dead man timer for the master division. Should the master not complete the its RPS testing in its allotted amount of time, an error flag is set and the fault is annunciated. Such annunciation indicates that the master division is hung up at some point but has not yet annunciated the fact itself. If a failure is detected in any of the following subtests of the self-test routine, the error is logged with the executive. The following tests are part of the self-test: (1) Counter timer circuit test; PA1 (2) Universal input/output test; PA1 (3) Power monitor test; PA1 (4) Card selector/monitor test; PA1 (5) Card out of file test; PA1 (6) Card address test; PA1 (7) Bus fuse test; and PA1 (8) Time delay card test. The test sequence incorporating the above routines and the individual functional watch test routines are as follows. When a self-test controller becomes a master, it first tests itself before testing the protection circuitry. It does this in two phases: a self-check phase, which tests the CPU function, ROM and RAM, and the hardware counter/timer circuit; and a self-test phase, which tests the universal I/O ports and all other self-test control or interface circuitry. If a problem is enountered during the self-check phase, the CPU is halted and no further test activities are undertaken by that division. However, during this period a watch dog timer in the division that has just previously served as a master is timing out. If the new master doesn't make it through self-check, the retiring master logs that fact in its error log and activates the self-test controller fault annunciator. Thus, during this critical phase of tester self-check, another self-test controller--in particular, a self-test controller which has just validated its operability by having successfully tested its own division--is watch dogging the process. If a problem is encountered during the self-test phase, card type and location are reported in the division error log and a self-test controller fault annunciator is activated. In more detail, self-testing begins with a test of the counter timer circuits found on the universal I/O cards. These timer circuits are used to do timing functions, such as the watch-dog timer function and the slave keep-alive function. The timers are also used to time test pulse intervals and duty cycles; when a division communicates with another division, a counter is started and a timer is started if that other division does not respond. Once the timers are all exercised and verified to be operating properly, the universal I/O test is performed. In this particular embodiment six universal I/O cards are tested. There are basically three types of I/O card tests: the quiescent state test, in which all output points are disabled to make sure that the input ports are at an appropriate logic level; the tri-state isolation test, in which it is verified that the output circuitry of the card is turned off when the command to turn it off is given; and the wraparound test, in which all `0s` are written into the input ports of the universal I/O cards, and the system checks to make sure that all `0s` are returned by the output ports. The wraparound test is then run with all `1s` and the system checks for all `1s` being written back; the test is also run with alternate `1s` and `0s` to make sure that the same alternation is written back. The wraparound test verifies that there are no shorts or broken input or output ports. The next test is the power monitor test which retrieves the data in the register on the power monitor cards (not shown). This test verifies that the power monitor cards are reporting the status of each of the power supplies in proper format. The card select monitor test does an inventory of card select monitor cards as discussed above. Following this test is the card out-of-file test that assures that a proper echo is returned from each card select monitor. The next test is the card address test which verifies that the card select monitor cards are in their proper card files and in the proper slots of these card files. Additionally, this test checks the address of the card select monitor. The bus fuse test checks the bus fuses in every system to make sure that when the card uses all the voltages necessary to observe the STS a proper reading is made. If an inconsistent result is obtained, a fuse failure is to be suspected. The last test is the time delay card test. This test verifies that each time delay in the self-test system is within specifications. Following the self-check and self-test phases, the self-test controller is ready to perform tests on the actual protection circuitry. These tests take two general forms: system tests (FIGS. 15 and 16) and interdivisional tests. In system testing, each major RPS system is broken down into a number of subsystems and tested separately with due regard for overlap so that there are no untested "islands" within the division. Any failure that is detected causes the test sequence to stop and a fault isolation routine to be automatically initiated. The fault isolation routine has as its objective the finding of an individual card fault or card with an associated input signal path fault. The routine can distinguish which is which. Once found, localization faults are logged in the error log, the safety system in the division in which the fault occurred is annunciated, and a fault annunciator is activated. At the start of a systems test (200) (FIG. 15) the system pointer is initialized to a system card table system and pattern table to a `1`. An entry in the system card table is read (202) and the test is made to determine if the end of the system card cable has been reached (203). If the end of the system card table has not been reached the system test determines if the card is an injection card or a monitor card (204). A monitor card does not inject data into the RPS system. The pointer in the system card table is incremented (210) and the routine loops back to reading the card table (202). If the end of the card table is reached (203), then all inject cards loaded with injection patterns are called (205). The injection pattern is obtained from the individual card tables (207) and the injection bits are obtained from the system pattern table and increment pointer (208). The routine then calls a routine that loads the injection bits into the cards (209). The pointer and the system card table are then incremented (210). Because the test sequence has reached the end of the system card table (203), the system returns to the next major routine (206) when the present test is finished. When the end of the system card table is not yet reached (203), and the card is an injection card (204), the routine for obtaining the injection patterns and bits and for performing the injection (207 through 208) is called. The interdivisional tests are performed in a very similar way except that they involve sending test signals across divisional boundaries in order to check the interdivisional electrical optical isolators and associated circuitry. Timing is critical in this operation, so a suitable handshake signal between divisions is included to minimize the problem. All information pertaining to which cards are to be injected and what test patterns are to be used is derived from the data base of the division that initiated the inter-divisional test. Communication is via the division's serial I/O cards. It should be noted at this point that many of the RPS system tests are redundant. A critical test might involve the functional cards of all four divisions. To perform such a test the cards in the master division are configured as discussed above. The cards in the slave division are configured according to data sent from the master division's serial I/O to each selected slave division. All slave divisions cooperating with the master division during a particular test use the master's data and, therefore, cannot introduce any errors based on faulty or inconsistent data they themselves may have generated. An RPS fault check routine is shown in the flow chart of FIG. 16. At the start of the routine (300) the pointers to system card table and system pattern table are initialized (301). An entry in the system card table is read (302) and, if the end of the table is encountered (303), the routine returns to the main routine indicating no system fault (304). If the end of the table is not encounted (303) the system determines if the card is a system fault card (305). If the card is not a system fault card, the pointer in the system card table is incremented (306) and the loop continues (302). If the card is a system fault card, the length of the monitor bit pattern is obtained from the individual card table (307). The monitor data obtained from the functional card hardware (308); the monitor bits are obtained from the system pattern table (309). The pointer is incremented at this point. Data obtained from a test are compared with data in the tables (310). If the test is successful, the pointer is incremented (306) and the loop continues. If the data comparison indicates a failure or system error, the test routine returns to the main routine and indicates a system fault (311). In interdivisional testing, fault reporting and error logging are handled similarly to the system tests, except that an inherent ambiguity exists. Typically, interdivisional faults are caused by optically coupled isolators, in which case the self-test system is not able to distinguish whether it is the input or output isolator that is at fault. Both possibilities are reported to the test technician via the diagnostic terminal. If no faults are encountered in either the systems or interdivisional tests, the retiring master initiates a race for master with the other three divisions. Under normal conditions, the next division in numerical sequence wins the race and becomes the next master, thereby setting the other divisions to slave status. The self-test controller firmware is composed of software modules, each having a distinct functional purpose. Data is passed between the modules in the form of direct parameters and system flags and tables. All information relating to specific tests is contained in a table oriented data base. The self-test systems test and interdivisional test handlers are essentially parsing interpreters which read the data base and determine what tests to perform and how to perform them. The purpose of the system test is to provide diagnostic testing of all cards which contain safety circuitry. The basic philosophy behind the system test is to perform end-to-end testing for each signal entering and leaving the division. For example, to produce a particular output signal, all input stimuli effecting the signal are injected and the response monitored. The procedure is repeated with different test vectors as many times as necessary to ascertain correct circuit performance. If a failure is detected, the program isolates the failed card or signal path. This is accomplished by individually testing all the cards in the system. If this test passes, the fault lies not in a card but in a signal path between cards. To determine just where, all predecessor cards to the system output card indicating a fault are checked in order of sequence. Because of the importance of the safety functions performed by the nuclear system protection system any effects on it by the self-test system, either under normal operation or under hardware failure conditions, must be miminized. In order to insure maximum possible separation of the self-test system from the nuclear system protection system (essential circuitry), the following steps have been taken: (1) The self-test computers run on their own power supply and power sources. They are housed separately from functional circuits and a minimum of one-inch separation between functional and computer wiring is maintained; (2) Communication between divisional panels is through optically coupled isolators with one-inch quartz rods providing mechanical separation; and (3) Injected pulses are capacitively coupled to minimize changes in static voltage levels. Impedances between self-test circuits and functional circuits and are kept high so that fault in the former cannot effect the latter. Although one embodiment of the invention has been described, it will be apparent that many variations may be made to the invention without departing from the scope of the appended claims, which are intended to more fully characterize the invention. Therefore, the scope of the invention should be limited only by the breadth of the following claims.
056231091	abstract	Plant operating conditions 1, apparatus operating conditions 2 and environment conditions 3 are accumulated, combined and put together as a set of plant status variables 8 -through a monitor 6, while water chemistry information 4 is accumulated as another set of plant status variables 9. The set of status variables 8 is updated and the past data are accumulated in the set of status variables 9. Periodical inspection data 5 are also accumulated in the set of status variables 9 along with the water chemistry information 4. The set 9 is compressed and stored as a plant chart 11 such as a personal clinical chart. A status variable prediction 12 is performed in consideration of the personality of a plant. Both data of the sets 8 and 10 are compared with each other by comparison means 13. If both the data nearly coincide with each other, the plant is diagnosed to be normal and, if not, it is diagnosed to be abnormal. When the plant is diagnosed to be abnormal, an abnormal apparatus and an abnormal factor are identified.
	claims	1. A system for diagnosing a process device, the system comprisingat least one control computer (6, 23) collecting diagnostics data relating to the process device (2, 14, 15, 16);a field bus (27, 45);field devices (14A, 15A, 16A, 18A, 28A, 28B, 29A, 29B) which comprise a control unit (430) and a field bus interface (44) for interfacing with the field bus (45) and for communicating with said at least one control computer over the field bus, characterized in that the system further comprisesa remote diagnostics device (1) which is placed in connection with the process device (2) separate from the field devices and which comprises diagnostics electronics (31) collecting diagnostics data relating to the process device, and a transmitter part (33) for wireless (17) transmission of the diagnostics data to one of said field devices, and thatsaid one field device comprises a receiver part (41) for wireless (17) reception of the diagnostics data from said remote diagnostics device (1), said control unit (430) being arranged to process the received diagnostics data and to transmit a diagnostics report over said field bus interface (44) and field bus to said control computer (6, 27). 2. A system according to claim 1, characterized in that the diagnostics data sent by the remote diagnostics device (1) substantially consists of raw data, and that the field device is arranged to store and analyse the received diagnostics data to produce a processed diagnostics report. 3. A system according to claim 1 or 2, characterized in that the field device sends the diagnostics data at predetermined intervals, in response to a request from the control computer and/or when the diagnostics data show that the process device requires servicing or that it functions abnormally. 4. A system according to any one of the preceding claims, characterized in that the field device forwards the diagnostics data in a substantially non-analysed form. 5. A system according to any one of the preceding claims, charactrized in that the field device can be configured to perform wireless reception of diagnostics data from two or more remote diagnostics devices (1), and to process the received data. 6. A system according to any one of the preceding claims, characterized in that the wireless transmission between the remote diagnostics device (1) and the field device is based on Bluetooth technology or a similar short-range wireless transmission technology. 7. A field device in a process automation system, the device comprising a control unit (430) and a field bus interface (44) for interfacing with a field bus (27, 45) of the process automation system and for communicating with at least one control computer (6, 23) over the field bus, characterized in that the field device (14A, 15A, 16A, 18A, 28A, 28B, 29A, 29B) comprises a receiver part (41) for wireless (17) reception of diagnostics data from a remote diagnostics device (1) placed separate from the field device for collecting diagnostics data of relating to a second process device (2), and that the control unit (430) is arranged to process the received diagnostics data and to transmit a diagnostics report over said field bus interface (44) and field bus (27, 45) to said control computer. 8. A field device according to claim 7, characterized in that the diagnostics data received from the remote diagnostics device (1) substantially consists of raw data, and that the field device is arranged to store and analyse the received diagnostics data to allow a processed diagnostics report to be produced. 9. A field device according to claim 6 or 7, characterized in that the field device sends the diagnostics report at predetermined intervals, in response to a request from the control computer and/or when the diagnostics data show that the process device (2) requires servicing or that it functions abnormally. 10. A field device according to any one of claims 7 to 9, characterized in that the field device forwards the diagnostics data in a substantially non-analysed form. 11. A field device according to any one of claims 7 to 10, characterized in that the field device can be configured to perform wireless reception of diagnostics data from two or more remote diagnostics devices (1), and to process the data. 12. A field device according to any one of claims 7 to 11, characterized in that the wireless transmission (17) between the remote diagnostics device and the field device is based on Bluetooth technology or a similar short-range wireless transmission technology. 13. A diagnostics device for a process device in a process automation system in which field devices (14A, 15A, 16A, 18A, 28A, 28B, 29A, 29B) communicate over a field bus (27, 45), characterized in that the diagnostics device (1) is a remote diagnostics device meant to be placed separate from the field bus (27, 45) in connection with the process device (2), the remote diagnostics device comprisingdiagnostics electronics (31) collecting diagnostics data relating to the process device (2),a transmitter part (33) for wireless transmission of the diagnostics data to one of said field devices connected to the field bus (27, 45). 14. A diagnostics device according to claim 13, characterized in that the diagnostics data sent by the diagnostics device (1) substantially consists of raw data which is analysed in the field device or elsewhere in the process automation system. 15. A diagnostics device according to claim 13 or 14, characterized in that the power source (34) of the diagnostics device (1) comprises an energy converter which converts the mechanic energy, such as kinetic energy or noise, of the process device, or the energy of hydraulic pressure or compressed air supplied to the process device, into electric energy to be used for generating operating voltage for the diagnostics electronics (31) and the transmitter part (33).
046845038	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fuel assemblies for nuclear reactors and, more particularly, is directed to an improved attaching structure for removably mounting the top nozzle as a unitary subassembly on the guide thimbles of a reconstitutable fuel assembly. 2. Description of the Prior Art Conventional designs of fuel assemblies include a multiplicity of fuel rods and control rod guide thimbles held in an organized array by grids spaced along the fuel assembly length. The grids are attached to the control rod guide thimbles. Top and bottom nozzles on opposite ends thereof are secured to the control rod guide thimbles which extend above and below the ends of the fuel rods. At the top end of the assembly, the guide thimbles are attached in openings provided in the top nozzle. Conventional fuel assemblies also have employed a fuel assembly hold-down device to prevent the force of the upward coolant flow from lifting a fuel assembly into damaging contact with the upper core support plate of the reactor, while allowing for changes in fuel assembly length due to core induced thermal expansion and the like. Such hold-down devices have included the use of springs surrounding the guide thimbles, such as seen in the Klumb et al patents (U.S. Pat. Nos. 3,770,583 or 3,814,667). During operation of such assembly in a nuclear reactor, the fuel rods may occasionally develop cracks along their length 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 an integral assembly of guide thimbles welded to the top and bottom nozzles, it is difficult to detect and remove the failed rods. To gain access to these rods, it is necessary to remove the affected assembly from the nuclear reactor core and then break the welds which secure the nozzles to the control rod guide thimbles. In so doing, the destructive action often renders the fuel assembly unfit for further use in a reactor because of the damage done to both the guide thimbles and the nozzles which prohibit rewelding. In view of the high costs associated with replacing fuel assemblies, both domestic and foreign utilities have indicated an interest in reconstitutable fuel assemblies in order to minimize their operating and maintenance expenses. Conventional reconstitutable fuel assemblies incorporate design features arranged to permit the removal of individual failed fuel rods, the option to replace rods, followed by the additional use in the reactor and/or normal handling and storage of the affected fuel assembly. Reconstitution has been made possible by providing a fuel assembly with a removable top nozzle. The top nozzle is mechanically fastened usually by a threaded arrangement to the upper end of each control rod guide thimble assembly, and the top nozzle can be removed remotely from an irradiated fuel assembly while it is still submerged in neutron-absorbing liquid. With rod removal/replacement and after the top nozzle has been remounted on the control rod guide thimbles, the reconstituted assembly can then be reinserted into the reactor and used until the end of its useful life, and/or stored in spent fuel pools or other places in a safe, normal manner. One type of such reconstitutable fuel assembly can be seen in the aforementioned Klumb et al patents. The fuel assembly of Klumb et al includes a top nozzle which incorporates a hold-down plate and also coil springs coaxially disposed about upwardly extending alignment posts. The alignment posts extend through an upper end plate, spaced below the hold-down plate, and are joined thereto and to the upper ends of the guide thimbles with fastener nuts located on the underside of the upper plate. The upper hold-down plate is slidably mounted on the alignment posts and the coil springs are interposed, in compression, between the hold-down plate and the end plate. A radially enlarged shoulder on the upper end of each of the alignment posts retains the hold-down plate on the posts. In an attempt to improve upon the Klumb et al device, Anthony et al set forth another threaded joint arrangement as seen in U.S. Pat. No. 3,992,259. Yet another type of threaded arrangement used for removably attaching the top nozzle on the control rod guide thimbles can be seen in U.S. Pat. No. 3,828,868 to Jabsen. These prior art reconstitutable fuel assemblies involve top nozzle arrangements which are difficult to remove and reattach both due to the locations of the fasteners and because removal appears to cause the hold-down device of the nozzle to come apart, requiring added steps and apparatus to prevent this or to later reassemble the hold-down device. Therefore, what has been lacking and is urgently needed is a reconstitutable fuel assembly employing a simple joining or coupling arrangement which allows for easy, remote removal and reattachment of the top nozzle without the possibility of the hold-down device coming apart. SUMMARY OF THE INVENTION The present invention provides a reconstitutable fuel assembly having features which establish its top nozzle as a unitary subassembly designed to overcome the problems and shortcomings of, and satisfy the needs left unfulfilled by, the prior art reconstitutable fuel assemblies employing threaded arrangements for the attachment of the top nozzle. Unlike the prior arrangements, the present invention provides attaching structure which adapts the top nozzle to be removable and then replaceable as a unitary subassembly on the guide thimbles. Instrumental in maintaining the subassembly as a unit is the use of at least one and preferably a plurality of coupling members in cooperation with the springs of the hold-down device of the top nozzle to capture and retain the hold-down plate and adapter plate together with the coupling members and springs in a subassembly form. Furthermore, the items--caps--which are used to lock the top nozzle subassembly on the guide thimbles and then first removed to initiate the removal of the top nozzle subassembly are relatively simple, inexpensive components. Thus, new ones can be used at each reconstitution when the top nozzle is removed and reattached. The removable caps are also more accessible for remote manipulation than the fasteners used in prior art arrangements and thus provide an easier and faster means for initiating the removal process. Accordingly, the present invention sets forth in a reconstitutable fuel assembly having at least one control rod guide thimble and a top nozzle, an improved attaching structure for removably mounting the top nozzle as a unitary subassembly on the guide thimble of the fuel assembly. The guide thimble includes an upper end portion, while the top nozzle includes at least one hold-down spring, an upper hold-down plate and a lower adapter plate. The improved attaching structure comprises: (a) a coupling member interfitting the lower adapter plate, the upper hold-down plate and the hold-down spring disposed between the plates so as to capture and retain the plates and spring together as a unitary subassembly in which the upper plate is slidably movable along the coupling member relative to the lower plate with the spring biasing the upper plate away from the lower plate, the coupling member having spaced apart upper and lower portions with a central passageway extending therebetween for receiving the upper end portion of the guide thimble therein to removably mount the coupling member on the same; (b) means on the upper end portion of the guide thimble supporting the coupling member at its lower portion; and (c) a detachable member releasably applied to the upper portion of the coupling member and disengagably engaged with the upper end portion of the guide thimble so as to removably lock the coupling member to the guide thimble upper end portion, whereby upon removal of the detachable member, the coupling member and the upper hold-down plate, the hold-down spring and the lower adapter plate retained thereon can be removed therewith as a unitary subassembly from the upper end portion of the guide thimble. More particularly, the supporting means on the upper end portion of the guide thimble is in the form of an outwardly projecting ledge. Further, the upper portion of the coupling member and the upper hold-down plate include respective first and second overlapping means which limit movement of the upper hold-down plate away from the lower adapter plate. Two alternative forms of the first and second overlapping means are disclosed. In the first form, the first and second overlapping means are respectively a recessed slot formed in the coupling member and a pin connected to the hold-down plate which projects into the slot. In the second form, the first and second overlapping means are respectively an outwardly projecting shoulder formed on the coupling member and an upper marginal edge of the hold-down plate which underlies the shoulder. Still further, the detachable member and the upper end portion of the guide thimble include first and second matable means for disengagably engaging the detachable member with the upper end portion, whereas the detachable member and the upper portion of the coupling member include first and second interfering means for releasably attaching the detachable member to the coupling member. 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.
	description	This invention relates to a semiconductor exposure apparatus and, more particularly, to a chamber structure to be used with an X-ray, EUV (extreme ultraviolet) or EB (electron beam) exposure apparatus for performing exposure in a vacuum ambience, the chamber structure being specifically arranged for facilitating stage maintenance. In exposure apparatuses arranged to perform exposure in a vacuum environment, such as X-ray exposure apparatus, EUV exposure apparatus and EB exposure apparatus, hydrostatic or static-pressure bearing assemblies are used as guide means for a moving stage as disclosed in Japanese Laid-Open Patent Application No. 03-211816, for example. Generally, a static-pressure bearing assembly to be used in a vacuum ambience is equipped with a supplying-system piping for supplying a gas to a static-pressure pad and an exhausting-system piping for collecting the gases to prevent gas leakage toward the outside of the static-pressure bearing. Additionally, the structure disclosed in the aforementioned Japanese patent document took a safety precaution that the discharging system piping of the static-pressure bearing was opened to the atmosphere when an electric power was interrupted, this being for protection of the static-pressure bearing, for example. However, generally in vacuum chambers, there is a possibility that, when the static-pressure bearing is operated in a state that a leak valve for communicating the vacuum chamber with the atmosphere is closed (that is, in a state that the vacuum-chamber inside is not opened to the atmosphere) and if a gas to be supplied to the static-pressure pad leaks into the vacuum chamber due to some failure of the apparatus or to operator's mistake, the pressure inside the vacuum chamber becomes positive (higher) with reference to the atmospheric pressure. Although vacuum chambers are generally designed so that it can stand the pressure of atmosphere in the sense that the inside pressure thereof is reduced (negative) relative to the outside atmospheric pressure, the design is not effective where the inside pressure of the chamber becomes positive relative with reference to the atmospheric pressure, to the contrary. Thus, because of weak strength of the chamber, there is a possibility of local breakage of the chamber. The present invention has been made in consideration of these inconveniences, and it is an object of the present invention provide a safety mechanism that can cope with a situation that the inside pressure of a vacuum chamber becomes a positive pressure with reference to the atmospheric pressure due to some failure of the apparatus or to operator's mistake. In accordance with an aspect of the present invention, to achieve the above-described object, there is provided a chamber having a static-pressure bearing disposed therein, said chamber comprising: an inside pressure gauge for detecting an inside pressure of said chamber; and a pressure controller for decreasing the inside pressure of said chamber on the basis of the detection made through said inside pressure gauge. In accordance with another aspect of the present invention, there is provided a chamber having a static-pressure bearing disposed therein, said chamber comprising: a differential pressure gauge for detecting a differential pressure between an inside and an outside of said chamber; and a pressure controller for decreasing the inside pressure of said chamber on the basis of the detection made through said differential pressure gauge. In accordance with a further aspect of the present invention, there is provided a chamber having a static-pressure bearing disposed therein, said chamber comprising: an inside pressure gauge for detecting an inside pressure of said chamber; an outside pressure gauge for detecting an outside pressure of said chamber; and a pressure controller for decreasing the inside pressure of said chamber on the basis of the detections made through said inside pressure gauge and said outside pressure gauge. In one preferred form of this aspect of the present invention, the pressure controller decreases the inside pressure of said chamber when the inside pressure of said chamber is higher than the outside pressure of said chamber. Also, in this aspect of the present invention, the pressure controller may decrease the inside pressure of said chamber when the inside pressure of said chamber is higher than the outside pressure of said chamber, by a predetermined amount. The pressure controller may include a piping for communicating the inside of said chamber with the outside of said chamber, and an adjusting device for adjusting a degree of opening of said piping on the basis of the detections made through said inside pressure gauge and said outside pressure gauge. The pressure controller may include a piping for communicating the inside of said chamber with the outside of said chamber, and a check valve for enabling flow of a gas from the inside of said chamber to the outside of said chamber and also for restricting a flow of a gas from the outside of said chamber to the inside of said chamber. In accordance with a yet further aspect of the present invention, there is provided an exposure apparatus, comprising: an exposure processing system for performing an exposure process to a substrate, said exposure processing system having a static-pressure bearing; and a chamber having said exposure processing system accommodated therein, said chamber including (i) an inside pressure gauge for detecting an inside pressure of said chamber, (ii) an outside pressure gauge for detecting an outside pressure of said chamber, and (iii) a pressure controller for decreasing the inside pressure of said chamber on the basis of the detections made through said inside pressure gauge and said outside pressure gauge. In one preferred form of this aspect of the present invention, the exposure processing system performs an exposure process to the substrate by use of one of X-ray beam, EUV light and electron beam, wherein the inside of the chamber is controlled to provide a vacuum ambience there. In accordance with a still further aspect of the present invention, there is provided an exposure apparatus, comprising: an irradiating system for projecting one of X-ray beam, EUV light and electron beam onto a substrate; a stage for moving the substrate, said stage having a static-pressure bearing including a stationary portion and a movable portion, a predetermined gas being supplied to between the stationary portion and the movable portion of said bearing; and a chamber having said irradiating system and said stage accommodated therein, said chamber being controlled to provide a vacuum ambience inside said chamber, and said chamber having a pressure controller for controlling an inside pressure of said chamber to prevent the inside pressure from exceeding a predetermined value as a result of the predetermined gas supplied to the static-pressure bearing. In one preferred form of this aspect of the present invention, the predetermined gas is nitrogen, helium or inactive gas. Further, in this aspect of the present invention, the pressure controller may include a piping for communicating the inside of said chamber with the outside of said chamber, and an adjusting device for adjusting a degree of opening of said piping on the basis of the detections made through said inside pressure gauge and said outside pressure gauge. In accordance with a yet further aspect of the present invention, there is provided a device manufacturing method, comprising the steps of: performing an exposure process to a substrate by use of an exposure apparatus as recited above; and developing the exposed substrate. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. Preferred embodiments of the present invention will now be described with reference to the attached drawings. FIG. 1 illustrates the structure of a vacuum chamber according to a first embodiment of the present invention. Denoted at 1 is a vacuum chamber, and denoted at 2 is a vacuum pump. Denoted at 3 is a valve for separating the vacuum chamber and the vacuum pump from each other. Denoted at 4 is a leak valve for introducing atmosphere into the vacuum chamber. A static-pressure bearing comprises a housing 5, a bearing pad 6 and a guide bar 7, and this bearing is used as guide means for a moving stage (not shown) such as reticle stage or wafer stage. In this static-pressure bearing assembly, a gas-supply system piping 8 supplies a gas to the bearing pad, from the outside of the vacuum chamber. With this gas supply, a thin gas layer is formed between the bearing pad and the guide bar, such that the friction between them can be made small and the moving stage can be moved smoothly at a high speed. As regards the gas to be supplied to between the bearing pad and the guide bar, it may be any gas such as air, nitrogen, or helium, for example, but preferably it is an inactive gas. The gas to be used is in accordance with an exposure method used or a system design, for example. If the supplied gas leaks from the bearing into the vacuum chamber, the vacuum degree inside the chamber is degraded. In order to prevent this, the bearing assembly is provided with exhaust grooves 9 and 10 for collecting the supplied gas and exhaust-system pipes 11 and 12 for discharging the collected gas outwardly of the vacuum chamber. In this embodiment, as described, double exhaust-groove systems (exhaust groove 9 and exhaust groove 10) are used to reduce gas leakage into the vacuum chamber. However, triple or more exhaust-groove systems may be used. Denoted at 13 is a pressure gauge for detecting the pressure inside the vacuum chamber, and denoted at 14 is a pressure gauge for detecting the atmospheric pressure. With these pressure gauges, a differential pressure between the atmosphere and the inside of the vacuum chamber can be detected. Also, a single differential pressure gauge having the function of both of the pressure gauges 13 and 14 may be used. Furthermore, only the pressure gauge 13 for detecting the inside pressure of the vacuum chamber may be used to detect the differential pressure, while taking the atmospheric pressure as being already known. Denoted at 15 is a valve controller for controlling the degree of opening of an atmosphere open valve 16 mounted on the vacuum chamber, in response to detection of the differential pressure described above. For example, if the inside pressure of the vacuum chamber becomes higher than the outside pressure, there occurs a possibility of breakage of the chamber. For this reason, when the pressure inside the chamber becomes higher than the pressure outside the chamber by a predetermined value, the valve controller 15 opens the atmosphere open valve 16 (more exactly, to increase the degree or opening thereof, or to open more), thereby to decrease the inside pressure of the chamber. Thus, the differential pressure between inside and outside the chamber can be made smaller. As a matter of course, where a vacuum is going to be created inside the chamber, the atmosphere open valve should be kept closed. The atmosphere open valve may be provided anywhere, if pressure communication is assured, and similar effects will be attainable. For example, it may be provided in a portion of the pipe connected to the vacuum chamber, and this is within the scope of the present invention. Where the inside of the vacuum chamber should be kept at atmosphere for maintenance of the moving stage, if the gas supply to the static-pressure bearing is interrupted, the static-pressure pad may contact the guide bar to cause damage of the static-pressure bearing. Thus, in order to avoid damage of the static-pressure bearing, the gas supply from the gas-supply system piping 8 is kept, while on the other hand, the gas collecting function of the exhaust-system pipes 11 and 12 is discontinued. Then, the gas discharged from the static-pressure bearing collects inside the vacuum chamber so that the pressure inside the vacuum chamber increases gradually. Then, the leak valve of the vacuum chamber is opened, and the atmosphere outside the vacuum chamber is introduced into the chamber. As a result, the maintenance operation can be done under the condition that there is substantially no difference between the chamber inside pressure and the chamber outside pressure. The leak valve of the vacuum chamber is kept closed when a vacuum should be created inside the chamber. In consideration of this, in many cases, a normally closed type valve is used therefor. This leads to a possibility that the leak valve is held closed during the maintenance operation because of some failure in the apparatus or of operator's mistake. If the static-pressure bearing operates in this state, the gas supplied into the vacuum chamber collects inside the chamber and it is not discharged out of the chamber. Therefore, the pressure inside the vacuum chamber increases gradually. If the inside pressure of the chamber becomes higher than the outside pressure of the chamber by a predetermined amount, the vacuum chamber may be broken. In consideration of this, in the vacuum chamber of this embodiment, the pressure gauges 13 and 14 are used to continuously monitor the differential pressure between the chamber inside pressure and the atmospheric pressure. If it is detected, by the detection, that the inside pressure of the chamber becomes higher than the outside pressure of the chamber by a predetermined amount, the valve controller 15 operates to open the atmosphere open valve 16 so that the inside pressure of the vacuum chamber approximates to the chamber outside pressure. Thus, in accordance with the detected differential pressure (or detected pressure), the valve controller controls the degree of opening of the atmosphere open valve (the degree of opening may be changed successively or it may be changed stepwise and discontinuously), such that the pressure inside the vacuum chamber can be held with a pressure difference in a preset range, with reference to the atmospheric pressure. FIG. 2 illustrates the structure according to a second embodiment of the present invention. In this embodiment, as a safety system for the vacuum chamber, in place of the combination of a pressure gauge, a valve controller and an atmosphere open valve proposed in the first embodiment, a mechanical check valve 17 is used. The check valve is a valve having a function for enabling flow of a gas only in one direction and prohibiting the gas flow in an opposite direction. In this embodiment, regardless of a command from a pressure gauge 18, if the pressure inside the vacuum chamber becomes equal to or larger than the atmospheric pressure, the flow of a gas from inside the vacuum chamber to the atmosphere side is enabled. As a mater of course, the system may be arranged so that the check valve enables flow of a gas from the inside of the chamber to the outside of the chamber when the chamber inside pressure becomes higher than the chamber outside pressure by a predetermined amount. As a further alternative, in place of using a check valve, a pipe having a large resistance (for example, a pipe having a very small gas flow rate, a narrow and long pipe, or a pipe having an S-shaped curve) may be used to provide communication between the inside and the outside of the chamber, and the large-resistance pipe may be kept opened from the start of maintenance till the end of the maintenance. Anyway, with the structure described above, the vacuum chamber is equipped with a mechanical safety system, the safety and reliability of the apparatus can be improved at a relatively low cost. In accordance with the embodiments of the present invention described hereinbefore, the pressure inside the vacuum chamber can be held at a level not greater than the atmospheric pressure (or alternatively, the inside pressure of the chamber can be held at a level not higher than the chamber outside pressure by a predetermined amount, that is, in other words, the difference between the chamber inside pressure and the chamber outside pressure can be held at a level not greater than a predetermined). As a result, where a static-pressure bearing is used in a vacuum chamber as a guide, breakage of the vacuum chamber which may occur as the chamber is opened to the atmosphere in the maintenance operation or the like, can be prevented. Furthermore, the invention applies not only during the maintenance operation but also during normal operation, and an unexpected increase of the inside pressure of the vacuum chamber beyond the atmospheric pressure due to some failure in the gas-supply system piping or in the static-pressure bearing, not caused by an operator, can be prevented. In an embodiment of the present invention, a valve controller opens an atmosphere open valve in accordance with the differential pressure between the inside pressure of the vacuum chamber and the atmospheric pressure. Since the atmosphere open valve can be opened or closed in response to a smaller change of the pressure, the system can be operated flexibly. In an embodiment of the present invention, the vacuum chamber is equipped with a mechanical safety system based on a check valve. As a result, the safety and reliability of the apparatus can be improved with a relatively low cost. A vacuum chamber such as described above may be used in an exposure apparatus, for example. Particularly, it may be suitably used as a vacuum chamber in an exposure apparatus for performing exposure on the basis of X-rays, an exposure apparatus for performing exposure on the basis of EUV light (wavelength of 13–14 nm), or an exposure apparatus for performing exposure by use of electron beam, for example. In such exposure apparatuses, where a vacuum space that surrounds a reticle state or a wafer stage is defined by a vacuum chamber such as described above, an exposure apparatus having a high safety and good reliability is accomplished. As a matter of course, an exposure light source (light source device), an illumination optical system for illuminating a reticle with light from a light source, a projection optical system for directing light from the reticle to a wafer (substrate to be exposed), and so on, may be accommodated in the above-described vacuum chamber. Here, while the term “vacuum chamber” has been used, the word “vacuum” refers to a state in which the pressure is lower then the atmospheric pressure. Preferably, it may be not greater than 10e-6 Pa. A vacuum chamber having a static-pressure bearing accommodated therein, may be provided with a structure for communicating the inside of the vacuum chamber with the atmosphere when the inside pressure of the vacuum chamber becomes equal to or higher than the atmospheric pressure and, in that occasion, breakage of the chamber can be prevented effectively. To this end, it may have a structure that an atmosphere open valve may be opened or closed in response to an output of a pressure gauge that measures the pressure inside the vacuum chamber. Alternatively, the vacuum chamber may be equipped with a check valve to enable gas communication between the inside of the vacuum chamber and the atmosphere. This accomplishes a simpler structure. If such vacuum chamber is used in an X-ray, EUV or EB exposure apparatus, an apparatus having high safety is provided. Alternatively, a vacuum chamber such as described above may be incorporated into an instrument having a static-pressure bearing, other than the exposure apparatus. Next, referring to FIGS. 3 and 4, an embodiment of a device manufacturing method which uses an exposure apparatus such as described above (an exposure apparatus having a vacuum chamber according to the first embodiment or second embodiment), will be explained. FIG. 3 is a flow chart for explaining the procedure of manufacturing various microdevices such as semiconductor chips (e.g., ICs or LSIs), liquid crystal panels, or CCDs, for example. In this embodiment, description will be made to an example of semiconductor chip production. Step S1 is a design process for designing a circuit of a semiconductor device. Step S2 is a process for making a mask on the basis of the circuit pattern design. Step S3 is a process for preparing a wafer by using a material such as silicon. Step S4 is a wafer process which is called a pre-process wherein, by using the thus prepared mask and wafer, a circuit is formed on the wafer in practice, in accordance with lithography. Step S5 subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed at step S4 is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step S6 is an inspection step wherein an operation check, a durability check an so on, for the semiconductor devices produced by step S5, are carried out. With these processes, semiconductor devices are produced, and they are shipped (step S7). FIG. 4 is a flow chart for explaining details of the wafer process at step S4. Step S11 is an oxidation process for oxidizing the surface of a wafer. Step S12 is a CVD process for forming an insulating film on the wafer surface. Step S13 is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step S14 is an ion implanting process for implanting ions to the wafer. Step S15 is a resist process for applying a resist (photosensitive material) to the wafer. Step S16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step S17 is a developing process for developing the exposed wafer. Step S18 is an etching process for removing portions other than the developed resist image. Step S19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. With these processes, high density microdevices can be manufactured. As described, a device manufacturing method that uses an exposure apparatus as well as a device as a product thereof, are also within the scope of the present invention. In accordance with the present invention as described hereinbefore, even where a static-pressure bearing is used as a guide in a vacuum chamber, breakage of the chamber which may occur during the maintenance as a result of opening to the atmosphere, can be prevented effectively. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.
	description	A schematically depicted fuel assembly 10 mounted in schematically depicted nuclear reactor 4 is shown generally in FIG. 1. The fuel assembly 10 includes a plurality of grids 20 that are depicted, in whole or in part, in FIGS. 2-10. As will be set forth more fully below, the grids 20 are advantageously configured to minimize the unbalanced forces, moments, and torques applied to other components of the fuel assembly 10 as well as to reduce fretting wear between the grids 20 and other components of the fuel assembly 10. A bottom nozzle 12 supports the fuel assembly 10 on a lower core support plate 14 in the core region of the nuclear reactor 4. The nuclear reactor 4 is a pressurized water reactor that includes a plurality of the fuel assemblies 10 disposed on the core support plate 14. In addition to the bottom nozzle 12, the structural skeleton of the fuel assembly 10 also includes a top nozzle 16 at its upper end and a number of elongated guide tubes or thimble tubes 18 which extend longitudinally between the bottom and top nozzles 12 and 16 and at opposite ends are connected therewith. The fuel assembly 10 further includes a plurality of transverse grids 20 axially spaced along and mounted to the thimble tubes 18 and an organized array of elongated fuel rods 22 transversely spaced and supported by the grids 20. Also, the fuel assembly 10 has an instrumentation tube 24 located in the center thereof that extends between the bottom and top nozzles 12 and 16. With such an arrangement of parts, the fuel assembly 10 forms an integral unit capable of being conveniently handled without damaging the assembly parts. As mentioned above, the fuel rods 22 in the array thereof in the fuel assembly 10 are held in spaced relationship with one another by the grids 20 spaced along the length of the fuel assembly 10. Each fuel rod 22 includes a plurality of nuclear fuel pellets and is closed at its opposite ends by upper and lower end plugs 28 and 30. The fuel pellets are composed of fissile material and are responsible for creating the thermal energy of the nuclear reactor 4. A liquid moderator/coolant such as water, or water containing boron, is pumped upwardly through a plurality of flow openings in the lower core plate 14 to the fuel assembly 10. The bottom nozzle 12 of the fuel assembly 10 passes the coolant flow upwardly through the thimble tubes 18 and along the fuel rods 22 of the assembly in order to extract heat generated therein for the production of useful work. To control the fission process, a number of control rods 34 are reciprocally movable in the thimble tubes 18 located at predetermined positions in the fuel assembly 10. Specifically, a rod cluster control mechanism 36 positioned above the top nozzle 16 supports the control rods 34. The control mechanism 36 has an internally threaded cylindrical member 37 with a plurality of radially extending arms 38. Each arm 38 is interconnected with a control rod 34 such that the control mechanism 36 is operable to move the control rods 34 vertically in the thimble tubes 18 to thereby control the fission process in the fuel assembly 10, all in a well-known manner. As can be seen in FIG. 2, each grid 20 includes a plurality of first straps 42 aligned with one another and a plurality of second straps 42xe2x80x2 that are aligned with one another and are arranged substantially perpendicular to the first straps 42. The first and second straps 42 and 42xe2x80x2 are connected with one another in a lattice fashion in a known manner and, as will be set forth more fully below, to define a plurality of cells 46. The cells 46 are configured to each receive a fuel rod 22 therein and to support the fuel rods 22 in the fuel assembly 10. The first and second straps 42 and 42xe2x80x2 are also arranged to define relatively larger cells within which the thimble tubes 18 and the instrumentation tube 24 are disposed. The grid 20 also includes an imaginary first grid axis 58 that extends substantially parallel with the first straps 42 and an imaginary second grid axis 62 that extends substantially parallel with the second straps 42xe2x80x2. The first and second grid axes 58 and 62 cross one another at a point of intersection 66 and are oriented substantially perpendicular with one another, although in other embodiments the first and second grid axes 58 and 62 may be oriented oblique to one another. The first and second grid axes 58 and 62 define first, second, third, and fourth grid quadrants 70A, 70B, 70C, and 70D. In the exemplary grid 20 depicted generally in FIG. 2, the first and third grid quadrants 70A and 70C are disposed diagonal one another, as are the second and fourth grid quadrants 70B and 70D. An imaginary first alignment plane 74 and an imaginary second alignment plane 78 extend through the grid 20 and out of the page of FIG. 2. The first and second alignment planes 74 and 78, in the example depicted in FIG. 2, are oriented perpendicular with one another and extend through the point of intersection 66. The first and second alignment planes 74 and 78 are also oriented substantially perpendicular with an imaginary grid plane that includes both the first and second grid axes 58 and 62 and is generally parallel with the plane of the page of FIG. 2. Stated otherwise, the first and second alignment planes 74 and 78 are oriented generally perpendicular to a plane defined by the grid 20. The first and second alignment planes 74 and 78 extend diagonally across the grid 20, with the first alignment plane 74 extending across the first and third grid quadrants 70A and 70C, and with the second alignment plane 78 extending diagonally across the second and fourth grid quadrants 70B and 70D. It can be seen from FIG. 2 that the first grid axis 58 is in register with one of the first straps 42, meaning that it overlies the aforementioned first strap 42. Similarly, the second grid axis 62 can be seen to be in register with one of the second straps 42xe2x80x2, meaning that it overlies the aforementioned second strap 42xe2x80x2. It is understood that other nuclear reactors may require grids that are of a generally different configuration than the grid 20 due to different configurations of the thimble tubes, instrumentation tube, and fuel rods. As such, in the event that the grid is configured to include an odd number of cells along either or both of the first and second grid axes 58 and 62, either or both or the first and second grid axes 58 and 62 may not be in register with any of the first and second straps 42 and 42xe2x80x2, but nevertheless will be oriented in a direction generally parallel therewith, respectively. FIG. 3 generally depicts an enlarged view of the indicated portion of FIG. 2, and additionally includes a fuel rod 22 disposed in the cell 46 depicted in FIG. 3. The cells 46 are generally each of a cell height 52 measured in direction generally parallel with the first straps 42. Similarly, the cells 46 are generally each of a cell width 54 measured in a direction generally parallel with the second straps 42xe2x80x2. While the dimensions of the cells 46 are indicated herein as being of a xe2x80x9cheightxe2x80x9d and a xe2x80x9cwidthxe2x80x9d, it is understood that when the grid 20 is installed in the nuclear reactor 4 the cell height and width 52 and 54 will be measured in a generally horizontal plane. As such, the terms xe2x80x9cheightxe2x80x9d and xe2x80x9cwidthxe2x80x9d are not intended to be limiting in any fashion. The first and second straps 42 and 42xe2x80x2 are all formed of relatively thin elongated sheets of an appropriate metal such as a zirconium alloy or other appropriate material that is well suited to the environment within the fuel assembly 10. As is best shown in FIG. 4, the first straps 42 are formed with a plurality of parallel slots 80 that extend transversely through approximately one-half of the first strap 42 along one side thereof. Each first strap 42 includes a plurality of strap members 82 that are generally defined by the slots 80 but are more specifically defined by a plurality of imaginary dividing lines 86 that extend transversely along the first straps 42 and overlie the slots 80. Each strap member 82 includes a central axis 90 defined thereon that is parallel with and spaced midway between the dividing lines 86 that define the strap member 82. As is best shown in FIG. 4A, each strap member 82 includes a first plate 94, a second plate 98 and a spring apparatus 100. The spring apparatus 100 is generally interposed between the first and second plates 94 and 98. When the grid 20 is installed in nuclear reactor 4, the first plates 94 will be disposed generally vertically above the second plates 98. It can be seen that the second plates 98 are generally defined by the slots 80, while the first plates 94 are defined generally by the dividing lines 86. As can be seen in FIG. 5, the second straps 42xe2x80x2 are similar to the first straps 42, except that the slots 80xe2x80x2 are formed in the opposite side of the second straps 42xe2x80x2. More specifically, while each second strap 42xe2x80x2 includes a plurality of strap members 82xe2x80x2, the first plates 94xe2x80x2 are defined generally by slots 80xe2x80x2, and the second plates 98xe2x80x2 are defined generally by the dividing lines 86xe2x80x2. In order to assemble the grids 20, the slots 80 of the first straps 42 are received in the slots 80xe2x80x2 of the second straps 42xe2x80x2 such that the first and second straps 42 and 42xe2x80x2 are engaged with one another in a lattice fashion to define the cells 46. The first and second straps 42 and 42xe2x80x2 are held temporarily in such a position by an appropriately configured fixture (not shown.) The first and second straps 42 and 42xe2x80x2 are then fixedly connected with one another by laser welding or by otherwise connecting together a plurality of welding tabs 102 on the first straps 42 with a plurality of correspondingly positioned welding tabs 102xe2x80x2 on the second straps 42xe2x80x2. Since the second straps 42xe2x80x2 are substantially similar to the first straps 42 except for the opposite positioning of the slots 80 and 80xe2x80x2, the specific configuration of the second straps 42xe2x80x2 will be discussed no further herein, it being understood that the following details related to the first straps 42 are equally applicable to the second straps 42xe2x80x2. Most every first plate 94 includes a mixing vane 104 disposed thereon and extending at an oblique angle (FIG. 4B) from a plane defined by the second plates 98. In this regard, it is understood that a number of the first plates 94 adjacent the perimeter straps or adjacent the cells within which the instrumentation tube 24 or the thimble tubes 18 are disposed, as well as some other first plates 94, may not include a mixing vane 104. Each mixing vane 104 includes a connection end 110 connected with the first plate 94 and a free end 106 opposite the connection end 110. Each mixing vane 104 also includes an imaginary longitudinal axis 114 (FIG. 7) extending between the free end 106 and the connection end 110. As can be understood from FIG. 3, each longitudinal axis 114 is advantageously oriented generally parallel with one of the first and second alignment planes 74 and 78. As can be best understood from FIG. 2, each of the first, second, third, and fourth quadrants 70A, 70B, 70C, and 70D includes substantially the same number of mixing vanes 104. As indicated above, in the exemplary grid 20 depicted in FIG. 2, the first grid axis 58 is in register with one of the first straps 42, and the second grid axis 62 is in register with one of the second straps 42xe2x80x2. For the exemplary grid 20 depicted in FIG. 2, therefore, the specific number of mixing vanes 104 within any of the first, second, third, and fourth quadrants 70A, 70B, 70C, and 70D, are considered to be those mixing vanes 104 that are disposed at least one-half the cell width 54 from the first grid axis 58 and at least one-half the cell height 52 from the second grid axis 62. It can therefore be seen that the mixing vanes 104 that are within one of the first, second, third, and fourth quadrants 70A, 70B, 70C, and 70D, as thusly defined immediately above, are oriented generally parallel with whichever of the first and second alignment planes 74 and 78 that extend through the quadrant. For instance, the mixing vanes 104 that are within the first and third quadrants 70A and 70C are aligned in a direction generally parallel with one another and with the first alignment plane 74. The first and third grid quadrants 70A and 70C are also diagonally disposed with respect to one another on the grid 20. Similarly, the mixing vanes 104 within the second and fourth grid quadrants 70B and 70D are all generally aligned parallel with one another and with the second alignment plane 78. Likewise, the second and fourth grid quadrants 70B and 70D are diagonally disposed with respect to one another on the grid 20. Those mixing vanes 104 that are not strictly disposed xe2x80x9cwithinxe2x80x9d one of the first, second, third, and fourth quadrants 70A, 70B, 70C, and 70D, meaning those mixing vanes 104 that are disposed on the first strap 42 and the second strap 42xe2x80x2 that are in register with the first grid axis 58 and the second grid axis 62, respectively, are all aligned generally parallel with one another and with the first alignment plane 74. In other embodiments of the grid 20, such mixing vanes 104 disposed on the aforementioned first and second straps 42 and 42xe2x80x2 may potentially be aligned generally parallel with one another and in a direction generally parallel with the second alignment plane 78. It can be seen that most of the first and second straps 42 and 42xe2x80x2 include a first portion 116 and a second portion 118 (numbered in a limited fashion in FIG. 2) that are defined on opposite sides of the first grid axis 58 or the second grid axis 62, whichever is appropriate depending upon the alignment of the specific strap. It can be seen that the mixing vanes 104 disposed on the first portion 116 of any given first or second strap 42 and 42xe2x80x2 are aligned generally parallel with one another and with one of the first and second alignment planes 74 and 78. Similarly, the mixing vanes 104 disposed along the second portion 118 of the given strap are oriented generally parallel with one another and with the other of the first and second alignment planes 74 and 78. It can be understood from FIGS. 2 and 4 that the mixing vanes 104 of adjacent strap members 82 are opposed to one another or are mirror images of one another. It can be understood from FIG. 2 that, as a general matter, such opposed or mirror-image mixing vanes 104 also extend outwardly in opposite directions from the plane of the first strap 42 defined by the second plates 98. In this regard, it can be seen that the mixing vanes 104 that are disposed on the first portion 116 of any given strap alternately extend outwardly in opposite directions with respect to the second plates 98, and the mixing vanes 104 that are disposed on the second portion 118 of the given strap similarly alternately extend outwardly in opposite directions from the plane of the strap 42 defined by the second plates 98. As is best shown in FIG. 3, each cell 46 includes an imaginary first cell axis 120 and an imaginary second cell axis 122 that are aligned perpendicular with one another and that define first, second, third, and fourth cell quadrants 126A, 126B, 126C, and 126D. In the exemplary grid 20 of FIG. 2 and the exemplary cell 46 depicted in FIG. 3, the first and third cell quadrants 126A and 126C are diagonally disposed with respect to one another in the cell 46, and the second and fourth cell quadrants 126B and 126D are diagonally disposed with respect to one another. As can be seen in FIGS. 2 and 3, all of the cells 46 except those adjacent one of the first and second grid axes 58 and 62 or adjacent the perimeter of the grid 20 include a pair of mixing vanes 104 disposed in diagonally opposed cell quadrants. By configuring the grid 20 in the aforementioned fashion, the hydraulic reaction forces resulting in the mixing vanes 104 by the water impinging thereon during operation of the nuclear reactor 4 do not result in a net torque, moment, or transverse force on the grid 20 that is applied to the thimble tubes 18, the instrumentation tube 24, or the fuel rods 22. Such reaction forces at most provide only a general force applied longitudinally to the thimble tubes 18 and the fuel rods 22. It is understood, however, that all of the aforementioned teachings regarding the interrelationships among the mixing vanes 104 need not always be applied in all circumstances to achieve the beneficial aspects of the present invention. Rather, the beneficial aspects of the present invention whereby no extraneous forces or torques are applied to the thimble tubes 18, the instrumentation tube 24, and the fuel rods 22 potentially can be achieved by employing fewer than all of the aforementioned teachings. Varying combinations of such teachings of such interrelationships among the mixing vanes 104 can vary with the specific configuration of the grids, the layout and numbering of the fuel rods 22, as well as other factors. As is best shown in FIGS. 4A and 6-8, each spring apparatus 100 includes a first leg 130, a second leg 134, and a spring member 138. The first and second legs 130 and 134 each extend nonlinearly between the first and second plates 94 and 98. The spring member 138 is interposed between the first and second leg members 130 and 134 at approximately the midpoint of each. By stating that the first and second legs 130 and 134 extend xe2x80x9cnonlinearlyxe2x80x9d, it is meant to be expressed that in extending between the first and second plates 94 and 98, the first and second legs 130 and 134 extend at least partially in a direction away from the central axis 90 and/or at least partially in a direction toward the central axis 90. Such nonlinearity of the first and second legs 130 and 134 increases the compliance thereof, as will be set forth more fully below. It can also be seen that the first plate 94 includes a first lug 140 disposed between the first and second legs 130 and 134. Similarly, the second plate includes a second lug 142 that is disposed between the first and second legs 130 and 134. Depending upon the specific configuration of the grid 20, the first and second lugs 140 and 142 may be shortened or eliminated depending upon the extent to which it is desired to permit water to flow between the first and second legs 130 and 134. The spring member 138 includes a spring plate 144 that is interposed between a pair of spring ligaments 146. The spring ligaments 146 each are connected with the spring plate 144, with one of the spring ligaments 146 being connected with the first leg 130, and the other of the spring ligaments 146 being connected the second leg 134. The spring plate 144 includes a spring embossment 150 that protrudes outwardly from a spring perimeter frame 154. The spring embossment 150 is advantageously configured to include a spring contour 158 that is defined to extend along the spring embossment 150, whereby the spring embossment 150 can be generally stated to be contoured. The edges of the spring embossment 150 preferably are also beveled or therwise rounded to resist fretting wear on the fuel rods 22. It can be seen that the first plate 94 is formed to include a first dimple 162, and that the second plate 98 is formed to include a second dimple 166. Since the first and second dimples 162 and 166 are substantially identical, the second dimple 166 will be discussed in detail no further, it being understood that the following description is equally applicable to both the first and second dimples 162 and 166. The first dimple 162 includes a dimple plate 172 disposed between a pair of dimple ligaments 176. The dimple plate 172 and the dimple ligaments 176 are generally non-coplanar with the rest of the first plate 94. The dimple plate 172 includes a dimple embossment 180 that protrudes outwardly from a dimple perimeter frame 184. The dimple embossment 180 is advantageously configured to include a dimple contour 188 that extends generally along the dimple embossment 180, whereby the dimple embossment 180 can be generally stated as being contoured. The edges of the dimple embossments 180 are beveled or otherwise curved to reduce fretting wear with the fuel rods 22. When the grid 20 is installed into the reactor 4, the spring ligaments 146 and the dimple ligaments 176 all extend in a direction generally transverse to the longitudinal extent of the fuel rods 22, and as indicated above the spring plates 144 and the dimple plates 172 are contoured. As such, in the event that the fuel rods 22 vibrate during operation of the reactor 4 and experiences an off-normal impact with the spring plates 144 and the dimple plates 172, the spring ligaments 146 and dimple ligaments 176 closest to the off-normal impact will deflect to a greater degree than the spring ligaments 146 and dimple ligaments 176 relatively farther away from the off-normal impact. As such, the transverse orientation of the spring ligaments 146 and the dimple ligaments 176 with respect to the fuel rods 22, along with the contoured nature of the spring plates 144 and the dimple plates 172, causes individual spring ligaments 146 and dimple ligaments 176 to be relatively more compliant that the spring apparatuses 100 and the first and second dimples 162 and 166 as a whole, which reduces wear on the fuel rods 22 in the event of off-normal impacts. Additionally, by configuring the spring plates 144 and the dimple plates 172 to be contoured to conform with the outer surface of the fuel rods 22, repeated off-normal impacts at different locations on the spring apparatuses 100 and the first and second dimples 162 and 166 advantageously result in corresponding impacts and wear at numerous transverse locations on the fuel rods 22, instead of resulting in impacts and wear at a single location on the fuel rods, which likely would be the case if the spring apparatuses 100 and the first and second dimples 162 and 166 were planar in configuration. Such spreading out of the wear on the fuel rods 22 due to off-normal impacts increases the wear-life of the fuel rods 22. As can be understood from FIG. 4B, the first and second dimples 162 and 166 of any given strap member 82 protrude outwardly from a plane defined generally by the first and second plates 94 and 98 in a direction opposite that of the spring apparatus 100. As such, as can be understood from FIG. 3, each cell 46 includes a pair of spring apparatuses 100 and pairs of both first and second dimples 162 and 166. A fuel rod 22 is received against the aforementioned pairs of spring apparatuses 100, first dimple 162, and second dimples 166. In inserting the fuel rods 22 into the cells 46, the spring apparatuses 100 are changed from a relaxed state to a non-relaxed state. As a general matter, the spring apparatuses 100 are more compliant than the first and second dimples 162 and 166. Compliance of the spring apparatuses 100 is enhanced by the nonlinearity of the first and second legs 130 and 134 thereof and can be optimized by specifically configuring the lengths and widths of the first and second legs 130 and 134. It can be seen that the portions of the first and second legs 130 and 134 connected with the spring ligaments 146 are spaced farther from the central axis 90 than the portions of the first and second legs 130 and 134 that are connected with the first and second plates 94 and 98. When the spring apparatuses 100 are in the relaxed state, it can be seen that the first and second legs 130 and 134 are generally coplanar with the first and second plates 94 and 98. In the relaxed condition of the spring apparatuses 100, however, it can be seen that the spring plate 144 and the spring ligaments 146 are generally non-coplanar with the first and second plates 94 and 98. The spring apparatus is depicted generally in the relaxed state in FIG. 10. FIG. 10 also depicts a fuel rod 22 that is spaced from, and thus not in contact with, the spring apparatus 100. It can be seen that the spring contour 158 of the spring embossment 150 in the relaxed condition has a greater radius of curvature than the radius of the fuel rod 22. With such an advantageous configuration, when the fuel rod 22 is disposed in the cell 46 and is thus engaged with the spring embossment 150 such that the spring apparatus 100 is in the non-relaxed condition, the spring contour 158 becomes flexed by the fuel rod 22 such that the radius of curvature of the spring contour 158 matches the radius of the fuel rod 22 whereby the spring embossment 150 complementarily engages the fuel rod 22. By configuring the spring contour 158 to have a greater radius of curvature in the relaxed condition than the radius of the fuel rod 22, the resulting complementary engagement of the spring contour 158 and the fuel rod 122 when the fuel rod 22 is received in the cell 46 maximizes the area of contact between the spring embossment 150 and the fuel rod 22. Such maximization of the contact area between the spring embossment 150 and the fuel rod 22 reduces the stress therebetween and thus the potential for fretting wear. Moreover, to the extent that any fretting wear occurs at a region of reduced contact area between the grid 20 and the fuel rod 22, the conformal shape of the spring contour 158 results in such fretting being rapidly attenuated by resultingly increased surface contact area between the grid 20 and the fuel rod 22 The dimple embossments 180, each being configured with a dimple contour 188, are similarly configured to have a radius of curvature in the relaxed condition that is greater than the radius of the fuel rod 22. When the fuel rod 22 is received in the cell 46, the dimple embossment 180 in the non-relaxed condition complementarily engaged the fuel rod 22 to advantageously maximize the area of surface contact therebetween and minimize stresses therebetween and the potential for fretting wear. It thus can be seen that by configuring the spring embossments 150 and the dimple embossments 180 to be contoured as set forth above, with the radius of curvature thereof in the relaxed condition being greater than the radius of the fuel rod 22, the spring embossments 150 and dimple embossments 180 complementarily engage the fuel rods 22 in the non-relaxed condition to maximize the area surface contact therebetween. By maximizing the area of surface contact therebetween as set forth above, the magnitude of stress therebetween is correspondingly reduced, as is the potential for fretting wear of the fuel rods 22. It is understood, however, that a grid could be configured such that the spring plate 144 does not include the spring embossment 150, with the spring plate 144 being contoured to include the spring contour 158. In such a configuration, the dimple plate 172 would similarly be configured without the dimple embossment 180, whereby the dimple plate 172 would be contoured to include the dimple contour 188 thereon. Such a configuration would not depart from the concept of the present invention. Alternatively, a grid could be configured without any mixing vanes 104 without departing from the concept of the present invention. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
	abstract	A method to solve the problem of a technique generally used to detect a defect of a semiconductor by calculating the differential image based on pattern matching, which requires that a reference image must be picked up to pick up an image of the inspection position in an area with the semiconductor pattern having no periodicity, resulting in a low throughput. The image of the inspection position is divided into local areas, each local area is matched with the local area of the image already stored and the difference between the local areas thus matched is determined to extract a defect area.
	summary
050892150	abstract	A method of securing a cylindrical centering pin for a nuclear fuel assembly in a bore formed in a plate includes introducing an end of the centering pin into the bore until at least part of a coaxial, radially expandable wall portion of the end to be secured protrudes beyond the plate; and generating pressure in a closed hollow space surrounded by the wall portion with a pressure fluid until the wall portion radially expands and anchors the centering pin. According to another method, the end is introduced into the bore until at least part of the end to be secured, which has a periphery and an interior with radial slits formed therein, protrudes beyond the plate; and a mandrel-like tool is partially brought into the slits in the interior of the end of the centering pin and radially expands the end of the centering pin with the tool for anchoring the centering pin.
	abstract	A system and method for controlling atomic particles using projected light are provided. In some aspects, a method includes providing a plurality of atomic particles, and generating light fields using frequencies shifted from at least one atomic resonance. The method also includes forming a two-dimensional (“2D”) optical array using the generated light fields, wherein the 2D optical array comprises linear segments of light, and projecting the 2D optical array on the plurality of atomic particles to control their respective locations in space.
047028815	abstract	A spacer grid for a nuclear fuel assembly having grid springs and opposing dimples which contact a fuel rod passing through a cell of the spacer grid along arcuate surfaces to cradle the fuel rod and cushion any vibration impact between the fuel rods and the grid springs and dimples during reactor operation and during fuel assembly shipping. The increased bearing surface between the fuel rods and grids also serves to reduce fuel rod scratching during fuel rod insertion. The grid springs and dimples may also be provided with ramped edges to further reduce fuel rod scratching. Stiffening ribs may be on the grid springs and/or dimples. The cradling action of the grid springs and dimples reduces deviations in fuel rod position from a centered position in a spacer grid cell.
052415724	summary	This invention relates to apparatus for locating a floatable platform, and more particularly, but not exclusively, concerns a platform for monitoring multi-element bottles (MEB's) as used for storing irradiated nuclear fuel elements under water in a storage pond. According to one aspect of the present invention there is provided apparatus for locating a floatable platform relative to an article submerged in a liquid, the apparatus comprising support members arranged to be adjacent to the article, extendible members depending from the platform, the extendible members being locatable on the support members such that appropriate extension of the extendible members raises the platform from a buoyant to a partially-buoyant state, means for determining the position of the platform relative to the article, inspection means for inspecting the article, and a leg on which the inspection means is mounted, the leg being supported from the platform and being capable of extending below the platform. Preferably, the extendible leg is supported from a carriage, and the carriage locates on and is movable on first guide means which themselves locate on and are movable on second guide means disposed on the platform and aligned in a direction normal to the first guide means, thereby to provide x-y scanning of the inspection means. According to another aspect of the present invention, apparatus for locating a floatable platform relative to an article submerged in a liquid, comprises support members arranged to be adjacent to the article, extendible members depending from the platform, the extendible members being locatable on the support members such that appropriate extension of the extendible members raises the platform from a buoyant to a partially-buoyant state, means for determining the position of the platform relative to the article, the position determining means comprising laser means on the platform arranged to scan stationary coded targets remote from the platform, and a rack in which the support members are incorporated and in which rack the article is locatable. In accordance with a further aspect of the present invention, there is provided apparatus for locating a floatable platform relative to an article submerged in a liquid, comprising support members arranged to be adjacent to the article, extendible members depending from the platform, the extendible members being locatable on the support members such that appropriate extension of the extendible members raises the platform from a buoyant to a partially-buoyant state, means for determining the position of the platform relative to the article, a rack in which the support members are incorporated and in which rack the article is locatable, the article comprising a container for irradiated nuclear fuel.
	description	The present invention relates to luminescence sensors, for example luminescence biosensors or luminescence chemical sensors, and to a method for the detection of luminescence radiation generated by one or more luminophores present in such a luminescence sensor. More particularly, the invention relates to luminescence sensors with a high signal-to-noise ratio. Sensors are widely used for measuring physical attributes or physical events. They output a functional reading of that measurement as an electrical, optical or digital signal. That signal is data that can be transformed by other devices into information. A particular example of a sensor is a biosensor. Biosensors are devices that detect the presence (i.e. qualitative detection) or measure a certain amount (i.e. quantitative detection) of target molecules such as e.g. proteins, viruses, bacteria, cell components, cell membranes, spores, DNA, RNA, etc. in a fluid, such as for example blood, serum, plasma, saliva, . . . . The target molecules also are called the “analyte”. In almost all cases, a biosensor uses a surface that comprises specific recognition elements for capturing the analyte. Therefore, the surface of the sensor device may be modified by attaching specific molecules to it, which are suitable to bind the target molecules which are present in the fluid. For optimal binding efficiency of the analyte to the specific molecules, large surface areas and short diffusion lengths are highly favorable. Therefore, micro- or nano-porous substrates (membranes) have been proposed as biosensor substrates that combine a large area with rapid binding kinetics. Especially, when the analyte concentration is low (e.g. below 1 nM, or below 1 pM) the diffusion kinetics play an important role in the total performance of a biosensor assay. The amount of bound analyte may be detected by luminescence, e.g. fluorescence. In this case the analyte itself may carry a luminescent, e.g. fluorescent, label, or alternatively an additional incubation with a luminescently, e.g. fluorescently, labelled second recognition element may be performed. In prior art luminescent biosensors, there is a problem in separating the excitation and luminescence radiation, e.g. fluorescence radiation, because these types of radiation have a similar wavelength For solving the above problem, a luminescence sensor using sub-wavelength apertures or slits operating inside a fluid with sub-wavelength spatial resolution was proposed. In simple terms, excitation radiation is reflecting on the sub-wavelength apertures or slits, because they are too small to be seen by the radiation. This yields an evanescent field within the apertures or slits, which is used for exciting luminophores present in the apertures or slits. The luminescence that is generated exits the apertures or slits on the side opposed to the one that is irradiated, i.e. the excitation side, in that way separating excitation and luminescence radiation. Background luminescence generated on the excitation side of the apertures or slits is also suppressed by this (reflection) effect. The problem with luminescence sensors using apertures is that the emitted luminescence needs to be able to exit the aperture, and therefore luminescence needs to be emitted close to the exit side of the aperture. This means that a significant amount of excitation radiation has already been suppressed, before it can ever generate luminescence, e.g. fluorescence, that is able to efficiently leave the aperture. In practice this means that the excitation radiation will be somewhat suppressed before it reaches the luminophore, e.g. fluorophore, in the aperture, and the generated luminescence, e.g. fluorescence, will also be somewhat suppressed before reaching the detector. This problem can be solved by using a sensor with slits instead of apertures because one polarization is always able to travel through the slits, and therefore at least 50% of the generated luminescence, e.g. fluorescence, is always able to reach the detector side. The problem, however, with these kind of sensors is that also 50% of the generated background radiation is able to transmit through the slits. It is an object of the present invention to provide a luminescence sensor, such as a luminescence biosensor or a luminescence chemical sensor, with an improved signal-to-noise ratio. It is a further object of the present invention to provide a method for the detection of luminescence radiation generated by one or more luminophores present in such a luminescence sensor. An advantage of the present invention can be that the excitation radiation is efficiently used and luminescence radiation is efficiently detected. The above objectives are accomplished by a device and a method according to the present invention. Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims. The present invention provides a luminescence sensor, for example fluorescence sensor, comprising at least a first wire grid and a second wire grid. The first wire grid comprises slits and wires extending in a first direction and the second wire grid comprises slits and wires extending in a second direction, the first direction and the second direction being substantially perpendicular with respect to each other. According to the invention, when the sensor is irradiated with excitation radiation, e.g. excitation light, from an excitation radiation source, e.g. light source, the excitation radiation, e.g. excitation light, is polarized such that it is substantially suppressed by one of the at least first and second wire grid and is substantially not suppressed by the other of the at least first and second wire grid. According to a preferred embodiment of the invention, the polarization of the excitation radiation, e.g. excitation light, may be such that it is substantially suppressed by the second wire grid which is positioned farthest away from the excitation radiation source, e.g. light source, and substantially not suppressed by the first wire grid which is positioned closest to the excitation radiation source, e.g. light source. The luminescence sensor according to the invention has some advantages over the prior art sensors. For the luminescence sensor according to the invention, the excitation volume, i.e. the volume between the wires where luminescence is generated, is very small, i.e. below the diffraction limit, in at least two dimensions. This is achieved because the combination of the two wire grids forms sub-wavelength apertures. Another advantage is that the luminescence sensor according to the invention, if used in transmission mode, i.e. with the excitation radiation source on one side of the sensor and a detector at the other side, provides automatic separation of excitation radiation, e.g. excitation light, and luminescence, e.g. fluorescence, radiation. Moreover, in that case, background luminescence, e.g. fluorescence, generated at the side of the sensor opposite to the side on which a detector is positioned is unable to transmit through the apertures formed by the position of the first and second wire grid, thus improving the signal-to-background ratio. The luminescence sensor according to the invention is easy to align and to use and luminescence, e.g. fluorescence, radiation can efficiently reach the detector which also means that excitation can be done efficiently. According to embodiments of the invention, the second wire grid may have a top surface and the first wire grid may be positioned on top of the second wire grid. According to embodiments of the invention, a gap may be present between the first wire grid and the second wire grid, causing a distance d between the first and second wire grid. An advantage of these embodiments is that the full distance between the first and second wire grids can be used for excitation. This means that there is an increased excitation volume, which can be tuned by varying the distance between the wire grids. According to an embodiment of the invention, the distance d may have any suitable value and may typically be between 100 nm and 100 μm, and may, according to other embodiments, optionally be variable by mounting wire grid 1 and wire grid 2 independent from each other. According to an embodiment of the invention, the luminescence sensor may furthermore comprise a third wire grid which is aligned such that the wires of the third wire grid are positioned under or above the slits of respectively the first or second wire grid. According to particular embodiments, the third wire grid may be positioned on the top surface of the second wire grid and may be aligned such that the wires of the third wire grid are positioned above the slits of the second wire grid. In other embodiments according the invention, the third wire grid may be positioned at the bottom surface of the first wire grid and may be aligned such that the wires of the third wire grid are positioned under the slits of the first wire grid. According to embodiments of the invention, the luminescence sensor may furthermore comprise a gap between the first wire grid and the third wire grid or between the third wire grid and the second wire grid. The slits may have a smallest dimension and the sensor may be for being immersed in an immersion fluid. According to embodiments of the invention, the smallest dimension of the slits may be smaller than the wavelength of the excitation radiation in the immersion fluid. According to embodiments of the invention, at least one of the at least first and second wire grid may be positioned on top of a bearing substrate. According to the embodiments of the invention, the luminescence sensor may be a fluorescence sensor. In particular embodiments, the luminescence sensor may be a luminescence biosensor, e.g. a fluorescence biosensor. The present invention furthermore provides a method for the detection of luminescence, e.g. fluorescence, radiation generated by at least one luminophore, e.g. fluorophore. The method comprises irradiating a luminescence, e.g. fluorescence, sensor with excitation radiation, e.g. excitation light, the luminescence, e.g. fluorescence, sensor comprising at least a first wire grid having slits and wires extending in a first direction and a second wire grid having slits and wires extending in a second direction, the first and second direction being substantially perpendicular with respect to each other. According to the method of the invention, the excitation radiation, e.g. excitation light, coming from an excitation radiation source is polarized such that it is not substantially suppressed by one of the at least first and second wire grid and is substantially suppressed by the other of the at least first and second wire grid. According to an embodiment of the invention, the polarization of the excitation radiation, e.g. excitation light, not substantially suppressed by the first wire grid which is closest to the excitation radiation source but is substantially only suppressed by the second wire grid which is farthest away from the excitation radiation source. The method according to the invention may, according to embodiments, furthermore comprise detecting generated luminescence, e.g. fluorescence, radiation. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings. In the different figures, the same reference signs refer to the same or analogous elements. The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term “comprising” is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. “a” or “an”, “the”, this includes a plural of that noun unless something else is specifically stated. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein. It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B. The present invention provides a qualitative or quantitative sensor, more particularly a luminescence sensor, which may for example be a luminescence biosensor or luminescence chemical sensor, which shows good signal-to-background ratio, as well as a method for the manufacturing of such a luminescence sensor. A luminescence sensor according to the present invention comprises at least a first wire grid 1 and a second wire grid 2. The wire grids 1, 2 are formed in a substrate as a network of slits 3, the slits 3 preferably being uniformly spaced apart. This may be obtained by applying conventional techniques known by persons skilled in the art, such as, for example, E-beam lithography or laser interference lithography. The remaining parts of the substrate form wires 4. The substrate may, for example, be a metal substrate, e.g. a gold substrate, or a semiconductor substrate, e.g. a silicon substrate. In the description hereinafter, with substrate is meant the material from which the wire grids 1, 2 are formed, also called the wire grid material. According to an aspect of the present invention, in the first wire grid 1 the slits 3 extend in a first direction and in the second wire grid 2 the slits 3 extend in a second direction, the first and second direction being substantially perpendicular with respect to each other. The sensor according to embodiments of the present invention, comprising such crossed first and second wire grids 1, 2 is irradiated with excitation radiation which is polarized such that it is not suppressed by the first wire grid 1, but is suppressed by the second wire grid 2. In a first embodiment of the invention, the luminescence sensor, e.g. fluorescence sensor, comprises a first wire grid 1 formed in a first substrate and a second wire grid 2 formed in a second substrate. The first and second substrates, or in other words, the wire grid materials used to respectively form the first and second wire grids 1, 2, may, for example, both be metal substrates, e.g. gold substrates or materials, or both be semiconductor substrates or materials, e.g. silicon substrates or materials, or the first (or second) substrate or material may be a metal while the second (or first) substrate or material may be a semiconductor material. The first substrate, and thus the first wire grid 1, and the second substrate, and thus the second wire grid 2, may have, according to embodiment of the invention, the same thickness, but may, in other embodiments, also have a different thickness. The thickness of the first and second wire grid 1, 2 may typically be substantially the same as the width of the slits 3, which according to embodiments of the invention, may be smaller than the wavelength of excitation radiation in the medium which fills the slits. However, the performance of the wire grids 1, 2 improves if its thickness is larger than this wavelength. Therefore, the thickness of the wire grids 1, 2 may be between 100 and 1000 nm. The medium which fills the slits may be a liquid or a gas, but may also be vacuum comprising at least one luminescent particle to be detected. In use the sensor may be immersed in the medium, e.g. in a liquid medium, or the slits may be filled with the medium in any other suitable way, e.g. by means of a micropipette in case of a liquid medium, or e.g. by spraying a gas over the sensor and into the slits. The first wire grid 1 alternately comprises slits 3 and wires 4 extending in a first direction which is indicated by arrow 5 in FIG. 1, and a second wire grid 2, alternately comprising slits 3 and wires 4 extending in a second direction which is indicated by arrow 6 in FIG. 1, the first direction 5 and the second direction 6 being substantially perpendicular with respect to each other. The slits 3 may have a smallest dimension which preferably is smaller than the wavelength of the excitation radiation in the medium in which the sensor is immersed or with which the slits are filled. Preferably slits 3 may have a smallest dimension which is smaller than half the wavelength of the excitation radiation in the fluid in which the sensor is immersed or the medium with which the slits are filled. In this first embodiment of the invention, the first wire grid 1 is positioned at a top surface 7 of the second wire grid 2. The sensor is irradiated through the top surface 8 of the first wire grid 1. The configuration of the first and second wire grid 1, 2 according to the first embodiment is illustrated in FIG. 1, FIG. 2 (top view) and FIG. 3 (bottom view). Luminophores, for example fluorophores, may preferably be attached to the second wire grid 2 which is located farthest away from the excitation radiation source (see further) in the slits 3 of the second wire grid 2, at those sides of the wires 4 of the second wire grid 2 indicated by reference number 9 in FIG. 1 to 3. In that way they are closer to a detector for detecting luminescence radiation coming from the luminophores, e.g. fluorescence from fluorophores, and further away from an excitation source, for example a light source, for irradiating the sensor with excitation irradiation, for example excitation light. According to the invention, the irradiation source, for example light source, may preferably be positioned at a first side of the luminescence sensor while the detector may preferably be positioned at a second side of the luminescence sensor, the first and second side being opposite to each other with respect to the luminescence sensor. Luminescence generated at the first wire grid 1 has to transmit through the combination of the first and second wire grid 1, 2 and this means it will be suppressed. Therefore, the luminophores, e.g. fluorophores, should preferably be attached to the second wire grid 2 closest to the detector. The combination of the first wire grid 1 and the second wire grid 2 as in the first embodiment leads to the formation of apertures 10 having a depth being equal to the sum of the thicknesses of the first wire grid 1 and the second wire grid 2. In FIG. 4, the basic principle of the luminescence sensor according to the first embodiment of the invention is illustrated. Excitation radiation 11, for example excitation light, is illuminating the sensor through the top surface 8 of the first wire grid 1. Wire grids 1, 2 have a polarization dependent suppression. Transmission of radiation through a wire grid 1, 2 shows, similar to a single slit 3, a strong polarization dependence: transmission for TE polarization state (E field parallel to the slits) is significantly lower than for TM polarization state. The intensity distribution for TM polarized radiation inside the wire grid 1, 2 is a standing wave pattern which indicates a Fabry-Perot effect; this is also supported by the stronger maximum normalized intensity for a slit height of 600 nm, i.e. the resonant effect. Behind the wire grid 1, 2, the intensity rapidly drops which is attributed (like for TE polarization) to divergence in the free space behind the wire grid 1, 2. The excitation radiation 11, for example excitation light, coming from an excitation radiation source (not shown in the figures), e.g. a light source, may preferably be polarized such that it is not substantially suppressed, or not suppressed at all, by the first wire grid 1, but is substantially only suppressed by the second wire grid 2. For example, for TM polarized excitation radiation, e.g. TM polarized excitation light, with the electrical field E perpendicular to the slits 3 in the first wire grid 1, the excitation radiation will pass through the first wire grid 1. According to the present invention, the two wire grids 1, 2 are perpendicular. This means that one wire grid 1, 2 passes TM and the other wire grid 1, 2 passes TE polarized excitation radiation, e.g. TE polarized excitation light. If the first wire grid 1 is aligned to have little or no suppression for the excitation radiation, e.g. excitation light, then this means that the excitation radiation, e.g. excitation light, has TM polarization in a direction aligned with respect to the slits 3 in wire grid 1. Consequently, the excitation radiation, e.g. excitation light, has TE polarization aligned with the slits 3 in wire grid 2 and therefor wire grid 2 will substantially suppress the excitation radiation, e.g. excitation light. The suppression is achieved either by absorption or by reflection, the latter resulting in a reflected beam 12 as indicated in FIG. 4. The intensity of the excitation radiation 11, e.g. excitation light, only decreases within wire grid 2 in the direction indicated by arrow 13. The excitation radiation 11, for example excitation light, can be in the form of a broad beam, but can also be in the form of a multi-spot light source, in order to illuminate the open areas of the wire grids 1, 2, i.e. in particular the apertures 10, more efficiently. If, on the other hand, the polarization direction of radiation emitted by the excitation radiation source is not perfectly aligned with the slits of the first wire grid 1, then the first wire grid 1 blocks part of the excitation radiation, e.g. excitation light. This is not a problem for the operation of the luminescence sensor, however, a smaller amount of excitation radiation, e.g. excitation light, is in this case available for generation of luminescence, e.g. fluorescence. Hence, this will lead to a lower efficiency of the luminescence sensor, as the detector will only be able to detect less generated luminescence. Luminophores, for example fluorophores, may, as already mentioned above, preferably be attached to the second wire grid 2 at the sides of the wires indicated by reference number 9 in FIGS. 1 to 3. Luminescence, for example fluorescence, that is generated in this area will only encounter the second wire grid 2. This means that, when a random polarization of the excitation radiation is assumed and thus there is 50% TE and 50% TM polarized light, at least 50% of the luminescence, for example fluorescence, passes through the second wire grid 2 and is not suppressed, i.e. the TM polarized light and a portion of the TE polarized light, because the TE polarized light is substantially suppressed, but a small amount may still transmit. This results in two beams of luminescence, for example fluorescence, both having a different polarization direction. These beams are indicated in FIG. 4 by arrows 14 and 15. Beam 15 leaves the sensor at the bottom side 16 of the second wire grid 2 where it is detected by a detector 17, for example a CCD or CMOS detector. Beam 14 leaves the sensor at the top surface 8 of the first wire grid 1. In order to bring the luminophores, e.g. fluorophores to the preferred binding sites 9 at the second wire grid 2 of the luminescence sensor, a fluid comprising the luminophores needs to flow through the slits 3 of the wire grids 1, 2. This can be done in any of two directions as is illustrated in FIG. 5 by the arrows 18 and 19. One possible fluid flow direction is indicated by arrow 18. The fluid is directly sent through the wire grids 1, 2 and flows in a direction perpendicular to the plane of the wire grids 1, 2. The advantage of using this fluid flow direction 18 is that it is simple to implement and that it has a relatively low flow resistance and thus allows more volume to be pumped through the wire grids 1, 2 per second. Another possible fluid flow direction is in the plane of a wire grid, as indicated by arrow 19 in FIG. 5. In this case, the fluid flow goes through the slits 3 of, in the example given, the second wire grid 2. However, the fluid flow may also go through the slits 3 of the first wire grid 1. Thus, the fluid flows parallel to the wire grids 1, 2, in the slits 3 of one of the wire grids 1, 2. Preferably, the fluid flows parallel to and in the slits 3 of the second wire grid 2, if the second wire grid 2 is positioned under the first wire grid 1, as is the case in the sensor according to the first embodiment of the invention. There will be just a limited or not significant flow through the other wire grid, i.e. if the main fluid flow goes through the second wire grid 2, there will only be a minor flow through the first wire grid 1, because it is positioned perpendicular to the main direction of the flow as the slits 3 of both wire grids 1, 2 are positioned in planes which are substantially parallel with respect to each other. The advantage of this is that the most efficient binding of luminophores occurs in a region that has the most efficient luminescence, e.g. fluorescence, detection and excitation, i.e. on the sides of the wires 4 of the second wire grid 2, which is located closest to the detector 17. In the above-described embodiment, the first wire grid 1 was positioned on the top surface 7 of the second wire grid 2. However, in some cases it can be advantageous that, in between the first wire grid 1 and the second wire grid 2, the luminescence sensor, e.g. fluorescence sensor, furthermore comprises a gap 20, causing a distance d between the first wire grid 1 and the second wire grid 2 (see FIG. 6). An example of such a case is where a larger luminescence, e.g. fluorescence, signal is needed because, for example, the luminescence, e.g. fluorescence, detector is not sensitive enough. Typically this may occur in applications where the concentration of luminophores, e.g. fluorophores, is somewhat lower, for example single-molecule detection. Thus, in a second embodiment, the luminescence sensor, e.g. fluorescence sensor, again comprises a first wire grid 1 comprising slits 3 and wires 4 extending in a first direction 5 and a second wire grid 2 comprising slits 3 and wires 4 extending in a second direction 6, the first direction 5 and the second direction 6 being substantially perpendicular with respect to each other. The slits 3 may have a smallest dimension which may be smaller than the wavelength of the excitation radiation in the fluid the sensor is immersed in. The immersion fluid may be a liquid or a gas but may also be vacuum comprising at least one luminescent particle to be detected. The wire grids 1, 2 may be formed in a substrate by conventional techniques known by persons skilled in the art. The substrates may, for example, be metal substrates, e.g. gold substrates, or semiconductor substrates, e.g. silicon substrates. In between the first wire grid 1 and the second wire grid 2 a gap 20 is present causing a distance d between the first wire grid 1 and the second wire grid 2. The distance d may have any suitable value and may typically be between 100 nm and 100 μm, and may optionally be variable by mounting wire grid 1 and wire grid 2 independently from each other. According to this second embodiment, luminophores, e.g. fluorophores, may, similar to the first embodiment, preferably be positioned at the second wire grid 2 or within the medium, e.g. fluid, filling the gap 20. In FIG. 7 the basic principle of the sensor configuration of the second embodiment is illustrated. This figure shows the first and second wire grids 1, 2 with the gap 20 present between the bottom surface 21 of the first wire grid 1 and the top surface 7 of the second wire grid 2, hence causing a distance d between the first wire grid 1 and the second wire grid 2. The sensor is irradiated with excitation radiation 11, e.g. excitation light, through the top surface 8 of the first wire grid 1. Similar to the first embodiment, the polarization of the excitation radiation 11, e.g. excitation light, may be such that it is not substantially suppressed, or not suppressed at all, by the first wire grid 1 and is thus substantially only suppressed by the second wire grid 2. The advantage of this second embodiment is that the full distance between the wire grids 1, 2 can be used for excitation. This means that there is an increased excitation volume, which can be tuned by varying the distance between the wire grids 1, 2. As the excitation of luminescence, e.g. fluorescence, is occurring within the gap 20, the length of this gap determines the excitation volume. Therefore, the excitation volume can be tuned by varying the distance between the wire grids 1, 2. Luminophores, e.g. fluorophores, may be positioned in the gap 20 but it is also possible that the luminophores, e.g. fluorophores, are floating within the medium, e.g. fluid, that fills the gap 20. In a third embodiment of the invention, the luminescence sensor, e.g. fluorescence sensor, furthermore comprises a third wire grid 22 formed of a transparent material, for example vitreous or glass-like materials. The third wire grid 22 is positioned between the first wire grid 1 and the second wire grid 2, the first wire grid 1 comprising slits 3 and wires 4 extending in a first direction 5 and the second wire grid 2 comprising slits 3 and wires 4 extending in a second direction 6, the first and second direction 5, 6 being substantially perpendicular with respect to each other. The slits 3 may have a smallest dimension which may be smaller than the wavelength of the excitation radiation 11 in the fluid the sensor is immersed in. The immersion fluid may be a liquid or a gas but may also be vacuum comprising at least one luminescent particle to be detected. The third wire grid 22 also comprises wires 4 and slits 3, which are aligned in such a way that the wires 4 of the third wire grid 22 are positioned under or above, parallel to and running in the same direction as the slits 3 of the first wire grid 1 respectively the second wire grid 2. In one possible implementation, as illustrated in FIG. 8, the third wire grid 22 may be positioned on top of the second wire grid 2 such that the wires 4 of the third wire grid 22 are positioned above the slits 3 of the second wire grid 2. A gap may be present between the second wire grid 2 and third wire grid 22. However, preferably the distance between the second wire grid 2 and the third wire grid 22 is as small as possible. Optionally, a gap 20 may be present between the first wire grid 1 and the third wire grid 22. In a second possible implementation, not illustrated in the figures, the third wire grid 22 may be positioned at the bottom surface 21 of the first wire grid 1 such that the wires 4 of the third wire grid 22 are positioned under the slits 3 of the first wire grid 1, and run parallel thereto and in the same direction. According to embodiments of the invention, a gap may be present between the first wire grid 1 and the third wire grid 22. However, in other embodiment, there may be no gap between the first wire grid 1 and the third wire grid 22. Optionally, a gap 20 may be present between the third wire grid 22 and the second wire grid 2. When the luminophores, e.g. fluorophores, are preferably bound to the third wire grid 22, the source of luminescence, e.g. fluorescence, is now placed at the location with optimized luminescence, e.g. fluorescence, excitation and detection. This is done because the excitation radiation, intensity and luminescence detection efficiency, is highest within the gap 20. The reason for using the third wire grid 22 is to give a method to place the luminophores, e.g. fluorophores, within the gap 20 between the wire grids. Hence, the main function of the third wire grid 22 is to provide binding sites for the luminophores, e.g. fluorophores, and to place these sites at the most suitable location. This results in a better sensitivity of the biosensor. In the above-described embodiments, the wire grids 1, 2 are formed in a substrate. According to the invention, however, these wire grids 1, 2 may also be positioned on top of a bearing substrate (not shown in any of the figures). The bearing substrate may be made of a material that is transparent for the excitation radiation, e.g. excitation light, and the luminescence, e.g. fluorescence, radiation, in contrast with the wire grid material or substrate from which the wire grids are formed, which are made of a material that is non-transparent for the excitation radiation, e.g. excitation light, and the luminescence, e.g. fluorescence, radiation. The luminescence sensor according to the invention has the following advantages over prior art luminescence sensors: The excitation volume is very small, i.e. below the diffraction limit, in at least two dimensions. This is achieved because the combination of the two wire grids 1, 2 forms sub-wavelength apertures 10. In the depth some extra distance is achieved because the excitation radiation 11, e.g. excitation light, is not suppressed by the first wire grid 1 and because some of the luminescence, e.g. fluorescence, generated within this first wire grid 1 will be able to transmit to the second wire grid 2 and is then able to reach the detector 17. By small excitation volume is meant that, in practice, the slits 3 or apertures 10 formed by the combination of the first and second wire grid 1, 2 only transmit excitation radiation 11 into a small volume localized around the position of the aperture 10 or slit 3. This may be utilized for localized probing of the luminescence radiation 14, 15 and for minimizing the ratio of the luminescence radiation 14, 15 generated behind the aperture 10 or slit 3 and the luminescence radiation 14, 15 generated inside the aperture 10 or slit 3. Automatic separation of excitation radiation 11 and luminescence, e.g. fluorescence, radiation 14, 15. Background luminescence, e.g. fluorescence, generated at the side of the sensor opposite to the side on which a detector 17 is positioned is unable to transmit through the aperture 10, improving the signal-to-background ratio. Background luminescence, e.g. fluorescence, generated on the side of the combination of wire grids 1, 2 opposite to the detector side will need to travel through both wire grids 1, 2 and will therefore be suppressed. Easy to align and use. Alignment is very simple, but the polarization of the excitation radiation 11 needs to be controlled. However, a small misalignment in the polarization may be allowed because it will only cause minor losses in the excitation radiation 11, e.g. excitation light, when travelling through the first wire grid 1. Assuming TE polarized excitation radiation, e.g. TE polarized light, is fully blocked, the transmittance of the wire grid 1, 2 may be determined by (cos(angle of misalignment))2. Luminescence, e.g. fluorescence, can efficiently reach the detector 17 which also means that excitation can be done efficiently. According to the invention, at least 50% of the generated luminescence, e.g. fluorescence, is able to reach the detector side of the wire grids 1, 2, i.e. that side of the sensor at which a detector 17 is positioned. An additional advantage of this is that luminescence, e.g. fluorescence, generated at the top of the second wire grid 2 (where the excitation beam is the most intense) can reach the detector side just as easily. This means that next to more efficient luminescence, e.g. fluorescence, detection, also excitation can be done more efficiently. It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention.
039768341	summary	BACKGROUND OF THE INVENTION This invention relates to nuclear reactors and more particularly to an emergency core coolant system for cooling the core of a nuclear reactor. In the event of an accident in which there is a break in the reactor coolant system, it has been postualted that the entire coolant medium which absorbs and removes the heat generated in the nuclear core will be lost or at least considerably decreased. Although control elements are inserted into the core to terminate the fission process upon the occurrence of such an accident, decay heat generated by the already formed fission products is capable of causing fuel or clad melting if sufficient cooling is not supplied to the fuel. Furthermore, the overheating of the fuel cladding can result in a severe adverse chemical reaction with its environment, which may not be reversed by later cooling procedures. Accordingly, it is necessary to provide a sufficient coolant flow immediately to insure that this heating of fuel and cladding does not occur. In some prior art systems, emergency core coolant water is normally injected into the inlet nozzles of the reactor and allowed to flow downwardly along the normal coolant path to the bottom of the vessel, and then upwardly to the nuclear core. Obviously, with such a system there is necessarily a time delay since the emergency coolant must first flood the bottom of the reactor before flowing upward into the core. Furthermore, the coolant injected into the reactor generates large quantities of steam which may create a pressure buildup in the core and outlet plenum of the reactor, thereby impeding further coolant from reaching the core. In other prior art systems a special plenum for distributing the emergency coolant fluid is provided in a active region of the reactor. This plenum is fluid coupled to an external source of fluid and means are provided for discharging the coolant supplied to the plenum into the affected regions of the reactor. In these systems the inactive region is normally located above the outlet flow region of the reactor with the special plenum being defined by the reactor vessel and the upper plate of the guide structure or by a separate header component positioned above the guide structure. It is to an improved form of the special plenum type of emergency core cooling system that the present invention is directed. SUMMARY OF THE INVENTION According to the present invention there is provided an emergency core cooling system for use in reactor systems which includes a reactor vessel having a nuclear core therein and a guide structure supported in the vessel in spaced relationship from the core, and having means for guiding control elements which are adapted for vertical reciprocal movement into and out of the core. A main reactor coolant flow path is defined in the reactor vessel for directing coolant fluid during normal operation through the core and then up through one of the spaced plates of the guide structure into the region between the two spaced plates. The emergency core cooling system of the present invention includes a third plate which substantially overlies the core. The plate is supported in vertical spaced relation from one of the two plates of the guide structure to define a plenum therebetween. Means are provided for substantially sealing the plenum from the main coolant flow path. A source of emergency coolant fluid is flow coupled to the plenum to introduce emergency core coolant into the plenum upon the loss of cooling accident. Means are fluid connected to the plenum for discharging emergency coolant therein into the core of the nuclear reactor. The emergency core cooling injection manifold or plenum of the present invention provides an efficient means of dispersing pressurized coolant fluid into the core of the reactor to prevent overheating of fuel elements therein during and after a loss of cooling accident. Furthermore, as will be more apparent hereinbelow, there is flexibility with respect to the location of dispersement into the core. Still further, there is no greater time delay or additional procedures required for removal of reactor hardware above the reactor core for refueling, since the emergency core cooling injection manifold is integrally attached to and forms a part of the existing guide structure.
	claims	1. A particle beam therapy system comprising:an irradiation nozzle that scans a particle beam supplied from an accelerator and irradiates the particle beam in such a way as to enlarge an irradiation field;a multileaf collimator in which a pair of leaf rows, each being composed of a plurality of leaf plates laminated in a thickness direction, is arranged in such a way as to interpose a beam axis of the particle beam, in which respective side faces of the plurality of leaf plates, that face the beam axis, are driven in an approaching or in a departing direction with respect to the beam axis so that a predetermined opening shape (i) is formed, and that conforms the particle beam emitted from the irradiation nozzle to an irradiation subject and (ii) emits the particle beam; andan image-capturing unit that takes images of outer ends, of respective downstream side faces of the plurality of leaf plates in irradiation direction of the particle beam, that are distal with respect to the beam axis, whereinthe image-capturing unit is provided for each of the pair of leaf rows, in such a way as to be situated at a position that is at an outer side of the irradiation field of the particle beam that has passed through the multileaf collimator and downstream of the multileaf collimator, andthe image-capturing unit is adjusted in such a way that a foot of a perpendicular line from a viewpoint, of the image-capturing unit, to the downstream side face of a leaf plate, is situated at a position that is at an inner side of a position of an outer end of the leaf plate when the leaf plate is maximally driven in the departing direction. 2. The particle beam therapy system according to claim 1, wherein the image-capturing unit has a mirror that reflects an image of the outer end of the leaf plate and an image-capturing device provided apart from the mirror,and arrangement of the mirror and the image-capturing device is adjusted, based on a virtual image of the viewpoint of the image-capturing device, that is caused by reflection of the mirror. 3. The particle beam therapy system according to claim 2, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is moved to a middle of driving range than to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction. 4. The particle beam therapy system according to claim 3, wherein each of the plurality of leaf plates is formed in such a way that at least a portion, of an outer side face of the leaf plate, that is adjacent to the downstream side face, has an acute angle with respect to the downstream side face. 5. The particle beam therapy system according to claim 4, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 6. The particle beam therapy system according to claim 3, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 7. The particle beam therapy system according to claim 2, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction than to a position of the outer end at a time when the leaf plate is moved to a middle of driving range. 8. The particle beam therapy system according to claim 7, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 9. The particle beam therapy system according to claim 2, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 10. The particle beam therapy system according to claim 1, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular in from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is moved to a middle of driving range than to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction. 11. The particle beam therapy system according to claim 10, wherein each of the plurality of leaf plates is formed in such a way that at least a portion, of an outer side face of the leaf plate, that is adjacent to the downstream side face, has an acute angle with respect to the downstream side face. 12. The particle beam therapy system according to claim 11, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 13. The particle beam therapy system according to claim 10, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 14. The particle beam therapy system according to claim 1, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction than to a position of the outer end at a time when the leaf plate is moved to a middle of driving range. 15. The particle beam therapy system according to claim 14, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 16. The particle beam therapy system according to claim 1, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape.
	summary
	description	FIG. 1 is a schematic and perspective view for explaining reflection of parallel light impinging on a reflection type integrator having convex cylindrical surfaces. FIG. 2 is a schematic and sectional view of the reflection type integrator having cylindrical surfaces. FIG. 3 is a schematic view for explaining reflection of X-rays at a cylindrical surface of a reflection type integrator having convex cylindrical surfaces. FIG. 4 is a schematic view for explaining an angular distribution of X-rays reflected by a cylindrical surface of a reflection type integrator having cylindrical surfaces. In these drawings, denoted at 5 is a reflection type integrator having convex cylindrical surfaces. An X-ray beam of substantially parallel light emitted from an X-ray light source is projected on the reflection type integrator 5 having a plurality of cylindrical surfaces, and secondary light sources are defined by this integrator. The X-rays emitted from these secondary light sources have an angular distribution of a conical surface shape. A reflector having a focal point placed at the secondary light source position reflects the X-rays to illuminate a mask. For explanation of the function of such a reflection type integrator having cylindrical surfaces, first the action of reflection light in a case where parallel light impinges on one cylindrical surface reflector will be described with reference to FIG. 3. As shown, parallel light is incident on one cylindrical surface at an angle xcex8 with respect to a plane perpendicular to the central axis thereof. If the light ray vector of the projected parallel light is R1=(0, xe2x88x92cos xcex8, sin xcex8) and the vector of a normal to the reflection surface of the cylindrical surface is n=(xe2x88x92sin xcex1, cos xcex1, 0) then the light ray vector of the reflection light is R2=(cos xcex8xc3x97sin 2xcex1 cos xcex8xc3x97cos 2xcex1, sin xcex8). Here, if the light ray vector of the reflection light is plotted in a phase space, the result is a circle of a radius cosxcex8 on an X-Y plane as shown in FIG. 4. That is, the reflection light is formed into divergent light of a conical surface shape, and the secondary light source is located at the position of an apex of this conical surface. If the cylindrical surface comprises a concave surface, the secondary light source is placed outside the reflection surface. If the cylindrical surface comprises a convex surface, the secondary light source is placed inside the reflection surface. Also, if the reflection surface is limitedly provided by a portion of a cylindrical surface and the central angle thereof is 2xc3x8, then as shown in FIG. 4 the light ray vector of reflection light is arcuate with a central angle 4xc3x8 upon the X-Y plane. Next, a case wherein parallel light is projected on a reflection mirror provided by a portion of a cylindrical surface, wherein a reflection mirror having a focal length f and a focal point placed at the position of this secondary light source, and wherein a mask is placed at the position away from this reflection mirror by a distance f, will be considered. The light emitted from the secondary light source is divergent light and, after it is reflected by the reflection mirror of a focal length f, it is transformed into parallel light. The reflection light here is formed into a sheet beam of an arcuate sectional shape with a central angle 4xc3x8, at a radius fxc3x97cosxcex8. Thus, only an arcuate region upon the mask, having a radius fxc3x97cos xcex8 and a central angle 4xc3x8 can be illuminated. While one cylindrical surface reflection mirror has been explained above, a cylindrical surface integrator such as shown in FIG. 1 will now be considered. That is, as shown, parallel light of a diameter D is projected on a reflection mirror of a wider area, having a number of cylindrical surfaces arrayed in parallel in a one-dimensional direction. If the reflection mirror and the mask are disposed in the same manner as in the foregoing example, the angular distribution of light reflected by the reflection mirror, with a number of cylindrical surfaces arrayed in parallel, is essentially the same as in the preceding case. Thus, an arcuate region on the mask with a radius fxc3x97cos xcex8 and a central angle 4xc3x8 is illuminated. Since the light which impinges on a single point on the mask comes from the whole illumination region on the reflection mirror provided by cylindrical surfaces arrayed in parallel, the angular extension of it is D/f. That is, the numerical aperture of the illumination optical system is D/(2f). If the mask-side numerical aperture of the projection optical system is NAp1, the coherence factor is "sgr"=D/(2fNAp1). Therefore, in accordance with the thickness (size) of the parallel light, an optimum coherence factor "sgr" can be set. Next, embodiments of the present invention which use a reflection type integrator with plural cylindrical surfaces will be explained with reference to some drawings. FIG. 5 is a schematic view of an X-ray reduction projection exposure apparatus according to a first embodiment of the present invention. FIG. 6 is a schematic and perspective view of a reflection type integrator with convex cylindrical surfaces, usable in the first embodiment of the present invention. FIG. 7 is a schematic view for explaining an illumination region on the surface of a mask, in the first embodiment of the present invention. Denoted in these drawings at 1 is a light emission point for X-rays, and denoted at 2 is an X-ray beam. Denoted at 3 is a filter, and denoted at 4 is a first rotational parabolic surface mirror. Denoted at 5 is a reflection type convex cylindrical surface integrator, and denoted at 5 is a second rotational parabolic surface mirror. Denoted at 7 is a mask, and denoted at 8 is a projection optical system. Denoted at 9 is a wafer, and denoted at 10 is a mask stage. Denoted at 11 is a wafer stage, and denoted at 12 is an arcuate aperture. Denoted at 13 is a laser plasma X-ray light source, and denoted at 14 is a laser collecting optical system. Denoted at 15 is an illumination region on the mask surface, and denoted at 16 is an arcuate region through which the exposure is to be performed. Denoted at 17 is a vacuum chamber. The X-ray reduction projection exposure apparatus of the first embodiment of the present invention comprises a laser plasma X-ray light source 13, an illumination optical system 8, a wafer 9, stages 10 and 11 on which the mask or wafer is placed, an alignment mechanism for precisely aligning the positions of the mask and wafer, a vacuum chamber 17 for keeping the optical arrangement as a whole in a vacuum to prevent X-ray attenuation, and an evacuation device, for example. The illumination optical system comprises a first rotational parabolic surface mirror 4, a reflection type convex cylindrical surface integrator 5, and a second rotational parabolic surface mirror 6. The mask 7 comprises a multilayered film reflection mirror on which a transfer pattern is defined by a non-reflective portion, provided by an X-ray absorptive material. The X-ray beam as reflected by the mask 7 is imaged by the projection optical system 8 upon the wafer 9 surface. The projection optical system 7 is so designed that good imaging performance is provided within a narrow arcuate region off the axis. For example, with a reduction magnification of 1:5, good imaging performance is assured with respect to a region on the mask 7 surface at 200 mm off the axis, and to a region on the wafer 9 surface at 40 mm off the axis, with a width of 1 mm. In order that the exposure process is performed only by use of this narrow arcuate region, an aperture 12 having an arcuate opening is disposed just before the wafer 9. For transfer of the pattern on the whole surface of the mask 7 having a rectangular shape, the mask 7 and the wafer 9 are scanningly moved simultaneously, at a predetermined speed ratio. The projection optical system 8 has two multilayered film reflection mirrors, and it serves to project the pattern of the mask 7 onto the wafer 9 in a reduced scale. The reduction magnification corresponds to the scan speed ratio between the mask and the wafer. The projection optical system 8 comprises a telecentric system. The X-ray beam 2 emitted from the light emission point 1 of the laser plasma X-ray source 13 passes a shield filter 3 of the target, for prevention of particle scattering, and it is reflected by the first rotational parabolic surface mirror 4, whereby it is transformed into a parallel beam. This beam is then reflected by the reflection type integrator 5 with convex cylindrical surfaces, whereby a number of secondary light sources are produced. The X-rays from these secondary light sources are reflected by the second rotational parabolic surface mirror 6, and then illuminate the mask 7. Both of the distance from the secondary light source to the second rotational parabolic surface mirror 6 and the distance from the second parabolic surface mirror 6 to the mask 7 are equal to the focal length of the second rotational parabolic surface mirror. Thus, the conditions for Koehler illumination are satisfied. The reflection type convex cylindrical surface integrator 5 comprises a total reflection mirror having such a shape that a number of small convex cylindrical surfaces are arrayed one-dimensionally such as shown in FIG. 6. In the sectional shape of the integrator 5, each arcuate portion has a radius of 0.5 mm and a central angle of 30 deg. When parallel light impinges on it, on a plane inside the reflection surface at a distance of 0.25 mm, there is formed a virtual image of linear secondary light sources, arrayed in parallel, that is, of the laser plasma X-ray light source 13. In this embodiment, the parallel X-ray beam has a thickness of 20 mm, and the incidence angle of the parallel X-ray beam upon the integrator 5 is 85 deg. The second rotational parabolic surface mirror 6, having a focal length f=2300 mm, has its focal point disposed at the position of the secondary light sources, as the linear secondary light sources arrayed in parallel are defined on a plane spaced by 0.25 mm from the reflection surface when parallel light is projected on the integrator 5. Also, the mask 7 is disposed at a distance 2300 mm from the second rotational parabolic surface mirror 6. Light emitted from one point on the secondary light source is divergent light having an angular distribution like a conical surface. It is reflected by the second rotational parabolic surface mirror 6 having a focal length f=2300 mm, and it is transformed into parallel light. Then, as shown in FIG. 7, an arcuate region 16 on the mask 7 having a radius 2300 mmxc3x97cos 85(deg)xe2x88x92200 mm and a central angle 30 deg.xc3x972=60 deg. is illuminated. Here, the numerical aperture of the illumination optical system is 20/(2xc3x972300)=0.0043. If the numerical aperture of the projection optical system is 0.01 on the mask side and 0.05 on the wafer side, the coherence factor is 0.43. On the mask 7 surface, an arcuate region 16 of a radius 200 mm and a central angle 60 deg. is illuminated, and the pattern within this region is projected in a reduced scale onto the resist surface of the wafer 9. If the reduction magnification is 1:5, an arcuate region on the wafer 9 having a radius 40 mm and central angle 60 deg. is illuminated at once. With the scan of the mask 7 and the wafer 9, a square region of 40 mm square, for example, can be exposed with good precision. As described, this embodiment uses a reflection type convex cylindrical surface integrator 5 having a reflection surface provided by a number of small convex cylindrical surfaces arrayed one-dimensionally, by which the region on the mask 7 to be illuminated can be defined with an arcuate shape and, simultaneously, an optimum value for a coherence factor of the illuminate optical system can be set. Also, the shape of the illumination region 15 on the mask 7 surface is restricted to the vicinity of the arcuate region 16 with which the exposure process is performed actually. Wasteful illumination of X-rays to a wide area outside the exposure region, such as shown in FIG. 14, is prevented. Thus, the loss of light quantity is reduced, the exposure time can be shortened and throughput can be improved. FIG. 8 is a schematic view of an X-ray reduction projection exposure apparatus according to a second embodiment of the present invention. FIG. 9 is a schematic and perspective view of a reflection type integrator with concave cylindrical surfaces, usable in the second embodiment of the present invention. Denoted in these drawings at 801 is an undulator X-ray light source, and denoted at 802 is an X-ray beam. Denoted at 803 is a concave surface mirror, and denoted at 804 is a first concave surface mirror. Denoted at 805 is a reflection type integrator with concave cylindrical surfaces, and denoted at 806 is a second concave surface mirror. Denoted at 807 is a mask, and denoted at 808 is a projection optical system. Denoted at 809 is a wafer. Denoted at 810 is a mask stage, and denoted at 811 is a wafer stage. Denoted at 812 is an arcuate aperture, and denoted at 817 is a vacuum chamber. The X-ray reduction projection exposure apparatus according to the second embodiment of the present invention comprises an undulator X-ray light source 801, an illumination optical system, a mask 807, a projection optical system 808, a wafer 809, stages 810 and 811 having the mask or wafer placed thereon, an alignment mechanism for precisely aligning the positions of the mask and wafer, a vacuum chamber for keeping the optical arrangement as a whole in a vacuum for preparation of X-ray attenuation, and an evacuation device, for example. The illumination optical system of this embodiment comprises an undulator X-ray light source 801, a convex surface mirror 803, a first concave surface mirror 804, a reflection type concave cylindrical surface integrator 805, and a second concave surface mirror 806. The mask 807 comprises a multilayered film reflection mirror on which a transfer pattern is defined by a non-reflective portion, provided by an X-ray absorptive material. The X-ray beam as reflected by the mask 807 is imaged by the projection optical system 808 upon the wafer 809 surface. The projection optical system 808 is so designed that good imaging performance is provided in a narrow arcuate region off the axis. In order that the exposure process is performed only by use of this narrow arcuate region, an aperture 812 having an arcuate opening is disposed just before the mask 807. For transfer of the pattern on the whole surface of the mask 807 having a rectangular shape, the mask 807 and the wafer 809 are scanningly moved simultaneously. The projection optical-system 808 has three multilayered film reflection mirrors, and it serves to project the pattern of the mask 807 on to the wafer 809 in reduced scale. The X-ray beam 802 emitted from the light emission point of the undulator X-ray light source 801 is a narrow and substantially parallel beam. It is reflected by the convex surface mirror 803 and the first concave surface mirror 804, whereby it is transformed into a thick parallel beam. This beam is reflected by the reflection type concave cylindrical surface integrator 805 of the structure that concave cylindrical surfaces with multilayered films for increased X-ray reflectivity are arrayed in parallel. By this, a number of secondary light sources are produced. Light emitted from a single point on the secondary light source is divergent light of a conical surface shape and, after being reflected by the second concave surface mirror 806, it is transformed into parallel light. Then, an arcuate region on the mask 807 is illuminated. As described above, this embodiment uses a reflection type concave cylindrical surface integrator 805 having a number of small concave cylindrical surfaces arrayed one-dimensionally, by which the region on the mask 807 to be illuminated can be made arcuate and, additionally, an optimum value for the coherence factor of the illumination optical system can be set. Also, the shape of the illumination region on the mask 807 surface is restricted to an arcuate region with which the exposure is to be done actually. Wasteful X-ray illumination to those areas outside the exposure region is prevented. Thus, the loss of light quantity is reduced, the exposure time can be shortened and the throughput can be improved. The X-ray illumination optical system and X-ray reduction exposure apparatus described above assure, with use of a reflection type integrator having a reflection mirror of a wide area provided by a number of cylindrical surfaces arrayed in parallel, illumination of only an arcuate region on a mask. Also, it enables setting the numerical aperture of the illumination system to provide an optimum coherent factor "sgr". The shape of the illumination region on the mask is restricted to an arcuate region with which the exposure is to be done actually, and wasteful X-ray illumination to those areas other than the exposure region is prevented. Thus, loss of light quantity is reduced, the exposure time can be shortened and the throughput can be enhanced. The reflection surface of the reflection type integrator may be provided with a multilayered film, to provide higher X-ray reflectivity. [Embodiment of a Device Manufacturing Method] Next, an embodiment of a device manufacturing method for producing semiconductor devices, for example, which uses an exposure apparatus such as described above, will be explained. FIG. 10 is a flow chart of a procedure for the manufacture of microdevices such as semiconductor chips (e.g., ICs or LSIs), liquid crystal panels, and CCDs, for example. Step 1 is a design process for designing a circuit of a semiconductor device. Step 2 is a process for making a mask on the basis of the circuit pattern design. Step 3 is a process for preparing a wafer by using a material such as silicon. Step 4 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed by step 4 is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step 6 is an inspection step wherein an operation check, a durability check and so on for the semiconductor devices provided by step 5, are carried out. With these processes, semiconductor devices are completed and they are shipped (step 7). FIG. 11 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. With these processes, high density microdevices can be manufactured. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.
	claims	1. A method for the compensation of image disturbances in the course of radiation image recording caused by defocusing of an antiscatter grid, arranged in the beam path between a beam source and a digital radiation image receiver and focused with respect to a specific distance from a focus of the beam source, the image disturbances being caused by a defocusing-dictated attenuation of primary radiation incident on the radiation image receiver, the digital radiation image receiver including radiation-sensitive pixels arranged in matrix form and a device for pixelwise amplification of the radiation-dependent signals, the method comprising:amplifying at least some of the signals supplied by the digital radiation image receiver in pixelwise fashion, in a manner dependent on an actual distance of the antiscatter grid from the focus. 2. The method as claimed in claim 1, wherein pixel-related gain factors, by which the at least some of the signals are amplified, are determined computationally for the given actual distance of the antiscatter grid from the focus relative to the original focusing distance. 3. The method as claimed in claim 2, wherein only the pixel signals of those pixels whose signals, relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid, lie below a predetermined threshold value are amplified. 4. The method as claimed in claim 3, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 5. The method as claimed in claim 2, wherein the signals are amplified by the gain factors to a predetermined threshold value. 6. The method as claimed in claim 5, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 7. The method as claimed in claim 5, wherein the threshold value is adjustable. 8. The method as claimed in claim 1, wherein pixelwise gain factors, by which the at least some of the signals are amplified, are chosen from a table assigned to the actual distance of the antiscatter grid from the focus. 9. The method as claimed in claim 8, wherein, in the case of a difference between the actual distance and the distance on which the table is based, the gain factors are adapted computationally. 10. The method as claimed in claim 9, wherein only the pixel signals of those pixels whose signals, relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid, lie below a predetermined threshold value are amplified. 11. The method as claimed in claim 10, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 12. The method as claimed in claim 8, wherein only the pixel signals of those pixels whose signals, relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid, lie below a predetermined threshold value are amplified. 13. The method as claimed in claim 12, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 14. The method as claimed in claim 1, wherein only the pixel signals of those pixels whose signals, relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid, lie below a predetermined threshold value are amplified. 15. The method as claimed in claim 14, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 16. The method as claimed in claim 14, wherein the threshold value is adjustable. 17. An apparatus for radiation image recording, comprising:a beam source including a focus;a digital radiation image receiver with radiation-sensitive pixels arranged in matrix form with an assigned device for the pixelwise amplification of the pixel signals; andan antiscatter grid, arranged between the beam source and the digital radiation image receiver, the antiscatter grid being focused with respect to a specific distance from the focus of the beam source, wherein the assigned device is designed for compensation of image disturbances caused by a defocusing of the antiscatter grid, the image disturbances being caused by a defocusing-dictated attenuation of the primary radiation incident on the digital radiation image receiver, for pixelwise amplification of at least some of the signals supplied by the digital radiation image receiver in a manner dependent on the actual distance of the antiscatter grid from the focus. 18. The apparatus as claimed in claim 17, wherein the assigned device is designed for the computational determination of pixel-related gain factors, by which the at least some of the signals are amplified, for the given actual distance of the antiscatter grid from the focus relative to the original focusing distance. 19. The apparatus as claimed in claim 17, wherein at least one table with pixel-specific gain factors, assigned to at least one specific distance of the antiscatter grid from the focus and by which the at least some of the signals are amplified,, is stored in the assigned device, the assigned device choosing the pixelwise gain factors from a table assigned to the actual distance of the antiscatter grid from the focus. 20. The apparatus as claimed in claim 19, wherein the assigned device is designed for the computational adaptation of the gain factors taken from the chosen table in the case of a difference between the actual distance and the distance on which the table is based. 21. The apparatus as claimed in claim 17, wherein the assigned device is designed for the amplification of the pixel signals only of those pixels whose signals, relative to the defocusing-dictated signal attenuation exclusively of the antiscatter grid, lie below a predetermined threshold value. 22. The apparatus as claimed in claim 21, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 23. The apparatus as claimed in claim 21, wherein the threshold value is adjustable. 24. The apparatus as claimed in claim 21, wherein the antiscatter grid is at least one of a linear grid with focused absorption lamellae and a cell grid with a carrier structure defining the focused rectangular cells with a beam passage opening with an absorption coating applied to the inner sides of the carrier structure which face the beam passage openings. 25. The apparatus as claimed in claims 17, wherein the assigned device is designed for the amplification of the signals to a predetermined threshold value. 26. The apparatus as claimed in claim 25, wherein the threshold value defines a defocusing-dictated attenuation of 40% or less. 27. The apparatus as claimed in claim 25, wherein the threshold value is adjustable. 28. The apparatus as claimed in claim 17, wherein the antiscatter grid is at least one of a linear grid with focused absorption lamellae and a cell grid with a carrier structure defining the focused rectangular cells with a beam passage opening with an absorption coating applied to the inner sides of the carrier structure which face the beam passage openings. 29. A method, comprising:amplifying at least some of signals supplied in pixelwise fashion from a radiation image receiver, in a manner dependent on an actual distance of an antiscatter grid from a focus of a source of a beam; andcompensating for image disturbances in a radiation image recording based upon the amplifying, the image disturbances being caused by defocusing of the antiscatter grid, arranged in a beam path and focused with respect to a specific distance from the focus of the source of the beam, and by a defocusing-dictated attenuation of primary radiation incident on the radiation image receiver. 30. An apparatus for radiation image recording, comprising:means for generating a beam including a focus;means for detecting the beam, including radiation-sensitive pixels arranged in matrix form, and including means for the pixelwise amplification of the pixel signals; andan antiscatter grid, arranged between the means for generating a beam and the means for detecting, the antiscatter grid being focused with respect to a specific distance from the focus of the means for generating the beam, wherein the means for the pixelwise amplification is designed for compensation of image disturbances caused by a defocusing of the antiscatter grid, the image disturbances being caused by a defocusing-dictated attenuation of primary radiation incident on the means for detecting, for pixelwise amplification of at least some of the signals supplied by the means for detecting in a manner dependent on the actual distance of the antiscatter grid from the focus.
061309265	claims	1. An apparatus for recirculating charged particles through a single target location, the apparatus comprising: a cyclotron having a center and at least one resonator for acting upon charged particles drawn into the cyclotron at the center thereof so that the charged particles increase in energy and are moved along a path which spirals radially outward from the center of the cyclotron in conjunction with the increase in energy of the charged particles; and target means positionable in the radially-outward spiral path of the charged particles so that the charged particles strike the target means and wherein the target means permits the charged particles to pass therethrough following an absorption by the target of a small portion of the energy of the charged particles so that upon passing through the target means, the charged particles possess a reduced amount of energy and begin to spiral radially-inwardly of the cyclotron; and the at least one resonator, the energy absorbed by the target means, and the distance of the target means from the at least one resonator are coordinated so that the at least one resonator restores energy to the reduced-energy charged particles after the particles pass through the target means so that the charged particles of reduced-energy increase in energy and once again begin to spiral radially outward from the center of the cyclotron toward the target means. a cyclotron having a center and at least one resonator for acting upon charged particles drawn from a source into the center of the cyclotron so that the charged particles increase in energy and are moved along a path which spirals radially outward from the center of the cyclotron in conjunction with the increase in energy of the charged particles; and target means positionable in the radially-outward spiral path of the charged particles so that the charged particles impinging upon the target means in a first pass to undergo nuclear reactions with the target material, wherein the target means permits the charged particles to pass therethrough following an absorption by the target means of a small portion of the energy of the charged particles so that upon passing through the target means, the charged particles possess a reduced amount of energy and begin to spiral radially-inwardly of the cyclotron; and the at least one resonator, the energy absorbed by the target means, and the distance of the target means from the at least one resonator are coordinated so that the at least one resonator restores energy to the reduced-energy charged particles after the particles pass through the target means so that the charged particles of reduced-energy increase in energy and once again begin to spiral radially outward from the center of the cyclotron and strike the target means again. 2. The apparatus as defined in claim 1 wherein the cyclotron is adapted to act upon charged particles which are drawn into the center of the cyclotron in a chain of pulses or in a substantially continuous manner so that the target means is struck by charged particles in a chain of pulses or substantially continuously. 3. The apparatus as defined in claim 2 wherein the apparatus is adapted to continually recirculate charged particles through the target means so that a closed ring of a large number of charged particles accumulate in the cyclotron. 4. The apparatus as defined in claim 1 wherein the charged particles which strike the target means comprise a beam of cross-sectional area and the target means has a cross-sectional area which is larger than the cross-sectional area of the charged particle beam, and the apparatus includes means for moving the target means relative to the charged particle beam so that different regions of the target means are continually moved into and out of registry with the charged particle beam. 5. The apparatus as defined in claim 4 wherein the target means includes a foil portion and is mounted adjacent the cyclotron for rotation relative thereto about an axis so that the foil portion is maintained in registry with the charged particle beam, and the means for moving the target means includes means for rotating the target means about the rotation axis so that while the foil portion is maintained in registry with the charged particle beam, different regions of the foil portion are moved into and out of registry with the charged particle beam. 6. The apparatus as defined in claim 5 wherein the apparatus further includes a rotatable shaft upon which the target means is mounted for rotation about the rotation axis and means for cooling the shaft as the shaft is rotated about the rotation axis. 7. The apparatus as defined in claim 6 wherein the shaft defines an interior passageway along its length, and the cooling means includes means for routing a liquid coolant through the interior passageway. 8. The apparatus as defined in claim 1 wherein the target means includes at least two targets which are spaced from one another along the radially-outward spiral path of the charged particles. 9. The apparatus as defined in claim 8 wherein the charged particles which strike the target means comprise a beam, and the apparatus further includes means for moving the target means relative to the charged particle beam so that different regions of the target means are continually moved into and out of registry with the charged particle beam, and the means for moving includes a rotatable shaft upon which the at least two targets are mounted and means for rotating the shaft about an axis so that different regions of the at least two targets are continually moved into and out of registry with the charged particle beam. 10. The apparatus as defined in claim 1 wherein the target means is adapted to reduce the energy of the charged particles which strike the target means by no more than about ten percent of the total energy of the charged particles. 11. An apparatus for producing an increased number of nuclear reactions with a target nuclide comprising: 12. The apparatus as defined in claim 11 wherein the cyclotron is adapted to act upon charged particles which are drawn into the center of the cyclotron in a chain of pulses or in a substantially continuous manner so that charged particles undergo nuclear reactions with the target means during a first pass of the charged particles in a pulsed or substantially continuous manner and charged particles undergo nuclear reactions with the target means during a second pass of the charged particles in a pulsed or substantially continuous manner. 13. The apparatus as defined in claim 11 wherein the charged particles which strike the target means comprise a beam of cross-sectional area and the target means has a cross-sectional area which is larger than the cross-sectional area of the charged particle beam, and the apparatus includes means for moving the target means relative to the charged particle beam so that different regions of the target means are continually moved into and out of registry with the charged particle beam. 14. The apparatus as defined in claim 13 wherein the target means includes a foil portion and is mounted adjacent the cyclotron for rotation relative thereto about an axis so the foil portion is maintained in registry with the charged particle beam, and the means for moving the target means includes means for rotating the target means about the rotation axis so that while the foil portion is maintained in registry with the charged particle beam, different regions of the foil portion are moved into and out of registry with the charged particle beam. 15. The apparatus as defined in claim 14 wherein the apparatus further includes a rotatable shaft upon which the target means is mounted for rotation about the rotation axis and means for cooling the shaft as the shaft is rotated about the rotation axis. 16. The apparatus as defined in claim 15 wherein the shaft defines an interior passageway along its length, and the cooling means includes means for routing a liquid coolant through the interior passageway. 17. The apparatus as defined in claim 11 wherein the target means includes at least two targets which are spaced from one another along the radially-outward spiral path of the charged particles. 18. The apparatus as defined in claim 17 wherein the charged particles which strike the target means comprise a beam, and the apparatus further includes means for moving the target means relative to the charged particle beam so that different regions of the target means are continually moved into and out of registry with the charged particle beam, and the means for moving includes a rotatable shaft upon which the pair of targets are mounted and means for rotating the shaft about an axis so that different regions of the pair of targets are continually moved into and out of registry with the charged particle beam. 19. The apparatus as defined in claim 11 wherein the target means is adapted to reduce the energy of the charged particles which strike the target means by no more than about ten percent of the total energy of the charged particles. 20. The apparatus as defined in claim 11 wherein the charged particles drawn into the center of the cyclotron for being acted upon by the cyclotron are protons, and the target means includes beryllium. 21. The apparatus as defined in claim 11 wherein the charged particles drawn into the center of the cyclotron for being acted upon by the cyclotron are protons, and the target means includes rhodium 103. 22. The apparatus as defined in claim 11 wherein the cyclotron includes four pairs of sectors and four pairs of valleys wherein the return path for closing the magnetic circuit are located opposite each other and a vacuum tank having walls within which the cyclotron is mounted. 23. A cyclotron according to claim 22 wherein the angular extents of all sectors is 45.degree..
053012151	claims	1. A building for enclosing a nuclear reactor comprising: a containment vessel for surrounding said reactor; a wetwell disposed inside said containment vessel and including an inner wall, an outer wall, a floor, and a roof defining a wetwell pool, for containing wetwell water at a predetermined level from said wetwell floor, and a suppression chamber disposed above said wetwell pool; said wetwell and said containment vessel defining a drywell for surrounding said reactor, said drywell including a gas; a plurality of vents disposed in said wetwell pool and in flow communication with said drywell for channelling steam releasable in said drywell from said reactor for condensing said steam; a shell disposed inside said wetwell and extending into said wetwell pool to define a dry gap devoid of said wetwell water and disposed in flow communication with said suppression chamber; said shell being spaced from at least one of said wetwell inner and outer walls to define said dry gap; said shell extending from said wetwell floor and into said suppression chamber; and said wetwell roof comprising a slab disposed above a plurality of spaced apart support beams, said beams defining therebetween an auxiliary chamber disposed in flow communication with said suppression chamber. a containment vessel for surrounding said reactor and sized for containing a maximum pressure therein; a wetwell of predetermined size disposed inside said containment vessel and including an inner wall, an outer wall, a floor and roof defining a wetwell pool, for containing wetwell water at a predetermined level above said wetwell floor, and a suppression chamber disposed above said predetermined level of the wetwell water in the wetwell pool of a predetermined volume such that a pressure margin between an actual pressure in the suppression chamber and the maximum pressure is maintainable; said wetwell and said containment vessel defining a drywell for surrounding said reactor, said drywell including a gas; a plurality of vents disposed in said wetwell pool and in flow communication with said drywell for channeling steam releasable in said drywell from said reactor to said wetwell pool for condensing said steam; and a shell disposed inside said wetwell and extending into said wetwell pool to define a dry gap devoid of said wetwell water and disposed in flow communication with said suppression chamber, said dry gap extending a vertical height substantially corresponding to the vertical height of said wetwell including said wetwell pool and said suppression chamber and at a corresponding elevation as said wetwell such that the volume of the suppression chamber is increased by said dry gap from said predetermined volume to a volume in excess thereof and the pressure margin in the suppression chamber given said actual pressure is increased without change in the sizes of the containment vessel and the wetwell. 2. A nuclear reactor building according to claim 1 wherein said shell extends upwardly to said support beams and said dry gap is disposed in flow communication with said auxiliary chamber. 3. A nuclear reactor building according to claim 2 wherein said shell is spaced inwardly from said wetwell outer wall to define said dry gap therebetween. 4. A nuclear reactor building according to claim 3 wherein said wetwell and said shell are annular, and said dry gap extends circumferentially therebetween. 5. A nuclear reactor building according to claim 4 wherein said support beams are equiangularly circumferentially spaced apart from each other and extend from said wetwell inner wall to said wetwell outer wall. 6. A nuclear reactor building according to claim 5 wherein said shell includes a top edge disposed adjacent to bottom ends of said support beams and spaced inwardly from said wetwell outer wall to define an annular inlet therebetween, said inlet being disposed in flow communication with said auxiliary chamber. 7. A nuclear reactor building according to claim 6 wherein said wetwell has a predetermined volume and contains said wetwell water, said wetwell water has a predetermined minimum level above said horizontal vents, and said predetermined minimum level with said shell displaying a portion of said wetwell water is substantially the same as a predetermined minimum level without said shell within said wetwell. 8. A building for enclosing a nuclear reactor comprising: 9. A nuclear reactor building according to claim 8 wherein said wetwell roof comprises a slab disposed above a plurality of spaced apart support beams, said beams defining therebetween an auxiliary chamber disposed in flow communication with said suppression chamber. 10. A nuclear reactor building according to claim 9 wherein said shell extends upwardly to said support beams and said dry gap is disposed in flow communication with said auxiliary chamber. 11. A nuclear reactor building according to claim 8 wherein said shell is spaced inwardly from said wetwell outer wall to define said dry gap therebetween. 12. A nuclear reactor building according to claim 8 wherein said wetwell and said shell are annular, and said dry gap extending circumferentially therebetween. 13. A nuclear reactor building according to claim 8 wherein said wetwell roof comprises a slab disposed above a plurality of spaced apart support beams, said beams defining therebetween an auxiliary chamber disposed in flow communication with said suppression chamber, said support beams being equiangularly circumferentially spaced apart from each other and extending from said wetwell inner wall to said wetwell outer wall. 14. A nuclear reactor building according to claim 13 wherein said shell includes a top edge disposed adjacent to bottom ends of said support beams and spaced inwardly from said wetwell outer wall to define an annular inlet therebetween, said inlet being disposed in flow communication with said auxiliary chamber. 15. A nuclear reactor building according to claim 8 wherein said wetwell has a predetermined volume and contains said wetwell water, said wetwell water having a predetermined minimum level above said horizontal vents, and said predetermined minimum level with said shell displacing a portion of said wetwell water is substantially the same as a predetermined minimum level without said shell within said wetwell. 16. A nuclear reactor building according to claim 8 wherein said suppression chamber is sealed from said drywell.
	abstract	A treatment method for a used ion exchange resin, includes: bringing a used ion exchange resin into contact with a reaction solution, the used ion exchange resin having an ion exchange group with at least a radionuclide or a heavy metal element adsorbed thereon, and the reaction solution containing an iron compound, hydrogen peroxide, and ozone; separating at least a part of the reaction solution in contact with the used ion exchange resin from the used ion exchange resin; and decomposing an organic component contained in the reaction solution separated from the used ion exchange resin.
048470430	claims	1. In a nuclear reactor having forced circulation jet pumps for causing pumped flow of reactor water coolant through the core of said reactor in forced circulation, said reactor further including a steam outlet for providing steam to a power source and a feedwater inlet communicated from a feedwater system for replacing said outflowing steam with a corresponding supply of water coolant for generation into steam, the improvement to said jet pumps comprising: a jet pump having an inlet, a mixer section and a diffuser section said inlet and said diffuser communicated to water coolant to be force circulated within said reactor; a nozzle communicated to said mixer for entraining water coolant into said inlet and transferring momentum to said water coolant in said mixer for discharge of pumped water coolant in forced circulation through the core of said reactor, said nozzle including a first water jet communicated from the feedwater inlet of said nuclear reactor for receiving said feedwater at a temperature below the saturation temperature of said reactor and discharging water in an accelerated fluid stream; pump means communicated to said feedwater inlet for intake from said feedwater system and discharge through said nozzle for introducing feedwater into said reactor; said nozzle further including a second stream jet communicated from the saturated steam outlet of said reactor, said feedwater jet and said steam jet discharging their respective flows in the direction of the nozzle of said jet pump; a mixing chamber configured to receive said steam jet and said water jet, said mixing chamber communicated to water interior of said nuclear reactor for forced circulation within said nuclear reactor, said mixing chamber having a sufficient length dimension to allow condensation of said steam jet on said water jet whereby the momentum of said steam is transferred to said water interior of said mixing chamber of said jet pump to accelerate said water; said jet pump further including a discharge section for discharging said water and steam forced circulation interior of said reactor. providing a forced circulation loop for water flow interior of said reactor for pumping water in a loop through said reactor core; providing at least one jet pump body including an inlet, a mixer selection and a diffuser section; placing said jet pump body in the water of said reactor to be circulated through said core with said inlet and diffuser communicated to water to be force circulated within said reactor; providing a jet from said water of said feedwater system for circulating water through said jet pump body, said jet directed to said inlet and thereafter passing through said mixer and diffuser sections of said jet pump body, said provided jet including a water jet communicated from said feedwater system having a temperature less than the saturation temperature of steam within said reactor; providing a steam jet from the steam produced by said reactor at the saturation temperature of said reactor; aligning said steam jet and said water jet to output fluid through the nozzle of said jet pump into the mixer section of said provided jet pump; providing a nozzle mixing chamber communicated to said steam jet to permit said steam jet to condense to said water jet to thereby transfer momentum to said water jet; and discharging the flow from said jet to the mixer section of said jet pump body in the direction from said inlet to said diffuser section whereby a water jet of water interior of said reactor of increased momentum from the discharge section of said nozzle mixing chamber drives said jet pump to force circulate said water in said reactor. a jet pump having an inlet, a mixer section, and a diffuser section; said inlet and diffuser section communicated to water interior of said steam generator for forced circulation; a nozzle communicated to said mixer section for entraining water from said inlet and transferring momentum to water in said mixer for discharge of pumped coolant in said loop through said diffuser section, said nozzle including a first water jet communicated from the feedwater system of said steam generator for receiving said feedwater at a temperature below the saturation temperature of said steam generator and discharging water in an accelerated fluid stream; pump means for intake from said feedwater system and discharge through said feedwater inlet to said nozzle for introducing feedwater back into said generator; said nozzle further including a second steam jet communicated from the saturated steam outlet of said steam generator, said feedwater jet and said steam jet discharging their respective flows in the direction of the nozzle of said jet pump; a mixing chamber configured to receive said steam jet, said water jet, and said entrained water from said steam generator, said mixing chamber having a sufficient length and dimension to allow condensation of said steam jet on said water jet whereby the momentum of said steam is transferred to said water interior of said steam generator to accelerate said water; said jet pump further including a discharge section for discharging said water and condensed steam into forced circulation interior of said steam generator. 2. A process of forced circulation of water within a boiling water reactor, said reactor having a core, a steam outlet, a turbine, a condenser for condensing steam from said turbine into water, and a feedwater system for taking water from said condenser and introducing said water back into said reactor; said process comprising the steps of: 3. In a steam generator having forced circulation jet pumps for causing pump flow of coolant through the steam generator in a pattern of forced circulation, said steam generator further including a steam outlet for providing steam to a power source and a feedwater inlet communicated to a feedwater system for replacing said outflowing steam to the corresponding supply of water for generation into steam, the improvement to said jet pumps comprising; 4. The invention of claim 3 and wherein said steam generator constitutes a nuclear reactor.
	claims	1. A method for prognostics of a structure subject to loads, particularly an aircraft structure, comprising performing on a processor the steps of:providing a first database linking possible loads acting on the structure in operating conditions with a modified state of the structure, including values of a quantity indicative of the state of the structure as modified in the presence of said loads in a predetermined number of relevant points;providing a second database linking changes of the state of the structure induced by pre-established defects in a predetermined number of relevant points of the structure, with possible classes of defects; and,iteratively:detecting the values of said quantity indicative of the state of the structure in a first plurality of primary detection points and in a second plurality of additional detection points;determining from the first database the loads acting on the structure starting from the detected values of the state quantity;estimating, based on the determined loads, the values of the state quantity in the additional detection points; whereincomparing between the estimated values and detected values of the state quantity in the additional detection points;wherein a condition of integrity of the structure is determined if the difference between the detected values and the estimated values of the state quantity in the additional detection points are within a predetermined tolerance, and a condition of defectiveness of the structure is determined if the differences between the detected values and the estimated values of the state quantity are outside a predetermined tolerance. 2. A method according to claim 1, wherein said quantity indicative of the state of the structure is the local strain of the structure. 3. A method according to claim 2, wherein a population of the first database comprises a bi-unique association between values of typical loads acting on the structure in operating conditions and measured or simulated strain values of the structure subject to said loads. 4. A method according to claim 2, wherein a population of the second database comprises a bi-unique association between measured values of the changes of strain in the structure induced by a same load vector in the presence of a defect in the structure and data of identification of a possible defect of the structure. 5. A method according to claim 1, comprising identifying a defect of the structure by associating the changes between the detected values and the estimated values of the state quantity with a type of defect in the second database. 6. A method according to claim 5, wherein the type of defects includes at least one of data of: the defect class; the defect dimension; the position of the defect in the structure. 7. A method according to claim 1, wherein said relevant points of the structure are selected from a plurality of points of identification of the structure which are defined based on a predetermined mathematical model of said structure. 8. A method according to claim 7, wherein said relevant points on the structure are selected among the points that, according to said model, are capable of identifying a state condition of the structure which can be associated univocally with a load condition, with concentration in proximity of regions of greater structural criticality. 9. A method according to claim 1, including estimating the contribution to the change of the state of the structure in said detection points due to changes in the properties of the structure material induced by the operating temperature. 10. A non-transitory computer readable medium encoded with a computer program or set of programs to be run on a processor, comprising one or more code modules for carrying out a method for prognostics of a structure subject to loads according to claim 1. 11. A system for prognostics of a structure subject to loads, particularly an aircraft structure, comprising:a first and a second plurality of detection sensors, located in primary detection points and additional comparison detection points, respectively;first storage comprising a first database linking possible loads acting on the structure in operating conditions with a modified state of the structure, including values of a quantity indicative of the state of the structure as modified in the presence of said loads in a predetermined number of relevant points;second storage comprising a second database linking changes of the state of the structure induced by pre-established defects in a predetermined number of relevant points of the structure, with possible classes of defects; anda processor configured for iteratively:detecting the values of said quantity indicative of the state of the structure in a first plurality of primary detection points and in a second plurality of additional detection points;determining from the first database the loads acting on the structure starting from the detected values of the state quantity;estimating, based on the determined loads, the values of the state quantity in the additional detection points; whereincomparing between the estimated values and detected values of the state quantity in the additional detection points;determining a condition of integrity of the structure if the difference between the detected values and the estimated values of the state quantity in the additional detection points are within a predetermined tolerance, anddetermining a condition of defectiveness of the structure if the differences between the detected values and the estimated values of the state quantity are outside a predetermined tolerance. 12. A system according to claim 11, wherein said detection sensors include sensors of the strain in the structure. 13. A system according to claim 11, comprising temperature sensors positioned in proximity of said detection points. 14. A system according to claim 11, wherein said processor is arranged for identifying a class of defect of the structure, concentrated or distributed, selected from the group of surface or bulk modifications comprising a hole, a filled hole, the insertion of a connection member, a damage due to a crash, delamination, porosity, a region of the structure differently rich in resins or fibres.
060875461	claims	1. A method of decommissioning a nuclear reactor vessel comprising the steps of: a. lifting the reactor vessel into a cylindrical open-ended shell by using existing reactor closure head attachment stud holes, b. providing inward lugs on the shell, the lugs having vertical holes, c. bolting the reactor vessel within the shell using studs extending through the vertical holes engaging existing reactor closure head attachment stud holes, d. securing a bottom wall on the shell to form a container; e. filling any clearance space between the vessel and the container with concrete, and f. securing a top wall in the container. a. a steel outer container having top and bottom walls and a continuous side wall shell therebetween, the side wall shell having secured thereto and extending inward therefrom a plurality of support lugs having vertical bores therethrough, the lugs all being at the same level, b. a reactor vessel defined by a cup-shaped reactor shell having an upwardly facing annular lip, containing and supporting operating components and a closure head sitting on the lip, the head being vertically apertured above the lip and the lip of the vessel being bored and formed with internal threads in alignment with the apertures, the vessel being disposed in the outer container, the outer container and the reactor vessel defining between them a clearance space, c. a plurality of threaded studs engaging the threads in the bores in the lip respectively, extending up through the respective apertures in the head and through the respective lugs, d. a plurality of threaded nuts disposed on the respective studs above the lugs, each compressing the lug and the closure head against the lip of the reactor shell to secure the vessel in the outer container, and e. a mass of concrete substantially filling the clearance space. 2. A method as claimed in claim 1 which packages all portions of the reactor vessel internal components, including the portion of internal components which would otherwise be classified as Greater-Than-Class-C radioactive waste if removed individually. 3. A nuclear reactor disposal package comprising: 4. A disposal package as claimed in claim 3 wherein a portion of the side wall is covered with a layer of steel shielding. 5. A disposal package as claimed in claim 4 wherein the steel shielding is at the level of the operating components. 6. A disposal package as claimed in claim 3 wherein a mass of low-density cellular concrete is disposed within the reactor vessel. 7. A disposal package as claimed in claim 3 wherein the top wall and bottom wall are secured to the side wall by a bead of welding. 8. A disposal package as claimed in claim 3 wherein the outer container is provided with lifting trunnions.
	description	The present application is a continuation of U.S. patent application Ser. No. 13/515,073, filed on Jun. 11, 2012 and issued as U.S. Pat. No. 8,565,503 on Oct. 22, 2013, which is the U.S. national stage of International App. No. PCT/US2011/039173, filed on Jun. 3, 2011, which claims priority to U.S. Provisional Patent App. No. 61/396,971, filed on Jun. 4, 2010, all of which are hereby incorporated herein by reference in their entireties. 1. Field of the Invention The present invention relates to the field of digital pathology and more particularly relates to the assessment of image quality based on complexity and spatial frequencies and the presentation of said assessment using both visual and quantitative results. 2. Related Art The cornerstone of pathology is the glass microscope slide with its biologic specimen. Traditionally, a pathologist used a conventional microscope to inspect the specimen. The pathologist would navigate the field of view by moving the slide underneath the microscope's lens and increase or decrease the field of view by selecting lenses of different magnifications. To adjust for the variable thickness of a specimen, the pathologist would adjust the focus by moving the optics up and down and modify the brightness by adjusting the light aperture. In this manner, the pathologist interactively adjusts for acceptable image quality. Similarly, the cornerstone of digital pathology is the digitized microscope slide (“digital slide”), an image file of the entire slide. Digital pathology scans the microscope glass slide at a high magnification, automating the pathologist's actions of focus and dynamic range adjustment as it captures the image and stores the digital slide. The pathologist inspects the digital slide using viewing software. It is critical that the image is scanned without fault because the viewing software simply displays the captured digital slide and cannot re-focus the image or offer dynamic range adjustments. Common problems that plague scanning software include, but are not limited to, out of focus scans and the introduction of scan-hardware related artifacts into images. Manually reviewing each image for sufficient scan quality is time consuming because a given digital slide image may be very large (e.g., as large as 200K×100K pixels). Additionally, in many cases only an expert may be able to properly judge variations in the quality of a digital slide and these judgments are highly subjective. For example, scan artifacts can make distinct sub-cellular structures apparent in one slide region but difficult to distinguish in a nearby region. Scan artifacts can also change tissue architecture from a crisply patterned texture to a smooth plane. Furthermore, even a properly scanned digital slide may lack sufficient quality for proper analysis and review. Accordingly, there exists a need for a system that is capable of measuring the quality of the digital slide image and identifying scan-related artifacts. Determination of image quality is a difficult task for a computer system, whereas an expert may readily distinguish between a good quality image and a bad quality image. Particularly, an expert may judge the content and context of an image and see differences in focus and contrast. However, research shows that no single metric stands out as the dominant indicator of image quality for a wide variety of imagery. Instead, combinations of metrics in classification schemes prove themselves more reliable indicators yet have not been proven to operate well in digital pathology. In digital pathology, the imagery is limited to biologic specimens. The look of a specimen is complex and its nature varies from patient to patient. However, areas of interest in most specimens are generally “busy” areas of activity with respect to tissue and cell structures, as illustrated in FIG. 6. These “busy” areas of activity translate mathematically into the presence of spatial frequencies. The digital slide quality determination system and method use the spatial frequencies that are present in a high quality pathology image. By determining the presence of certain spatial frequencies in the image, the system generates a quantifiable assessment of the digital slide image quality. By analyzing the images based on complexity and spatial frequencies, an example embodiment described herein provides visual feedback on the quality of the whole slide by overlaying the image in the viewing software with a color coded “heat map” of local area quality. Thus, the user is presented with both an absolute quality measure for the whole image and the ability to see the quality variability of local areas at a glance. Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings. Certain embodiments disclosed herein provide systems and methods for assessment of image quality based on complexity and spatial frequencies and the presentation of said assessment using both visual and quantitative results. For example, one method disclosed herein allows for analyzing digital slide images based on complexity and spatial frequencies to provide visual feedback on the quality of the whole slide by overlaying the image in the viewing software with a color coded “heat map” of local area quality and thereby provide the user with both an absolute quality measure for the whole image and the ability to see the quality variability of local areas at a glance. After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention as set forth in the appended claims. Since digital slide content is diverse, as illustrated in FIG. 7, measuring the spatial frequencies of the whole image would not characterize the image quality well. Pathology imagery contains considerable white space, fragmented specimens of no import, and cover slip edges and air bubbles. An expert reviewing a given image intuitively ignores these issues and does not consider them material to the image quality. Therefore, the present system similarly discounts them. FIG. 14 illustrates examples of different variations in digital slide content that result from protocol differences, stain kit selection, and pathologist staining preferences. Biologic samples present extraordinary differences between patients, pathology and organs resulting in image variations. Slide preparation also varies the digital slide content by producing tissue folds, adding foreign matter, microtome blade chatter and different sample thicknesses. The digital slide capture process is conducted at a wide range of resolutions. Additionally the digital slide capture process may employ various image compression techniques (e.g. JPEG, JPEG2000), each of which may have settings uniquely tailored to establish a desired compression quality. In order to tolerate the variability of a given specimen, the example embodiment of the slide quality determination system executes a two-part analysis: a micro-analysis process followed by a macro-analysis process. Micro-Analysis The micro-analysis process evaluates the whole image by breaking it down into small parts (referred to herein as “regions or blocks”) and performing quality analysis on each of those parts. FIG. 1 illustrates an example embodiment of a micro-analysis process 100 performed by a slide analysis system in accordance with the present invention. Micro-Analysis process 100 begins at step 105. At step 110, process 100 may evaluate the image as a grid of small images called blocks or regions. The size of a given block may be dependent upon the resolution of the image. For example, a block may be large enough to contain one or more cells. Empirically, a block size may be an n×n block with edge lengths in the range of 32-96 pixels, such as for example, 32, 64, or 96 pixels. However, various embodiments may exist with pixel squares having dimensions greater than 96 pixels or less than 32 pixels. Furthermore, the blocks are not limited to squares but may include various other shapes capable of making up an image slide, including, but not limited to, rectangular blocks, stripes, polygonal regions, circular regions, etc. At step 115, process 100 may qualify each block. The qualification step serves to determine which blocks have proper specimen content. For example, a block containing too much white space may be classified as “background”, or a block that is too dark or light may be classified as “not-processed”. Further metrics may determine whether a block contains sufficient edge activity, contrast, etc. At step 120, qualified blocks may be analyzed with frequency transforms. This may include analyzing the blocks' spatial frequency content. The analysis may include performing a two dimensional Fast Fourier Transform (“FFT”), Discrete Fourier Transform (“DFT”), Discrete Cosine Transform (“DCT”) or Discrete Sine Transform (“DST”). The present example embodiment is illustrated using a DCT. However, the use of DCT in the present example is not intended to illustrate a preference of bias towards or against the use of DCT, or any other viable single or combination of frequency transforms. At step 120, a plurality of DCTs may be performed in a grid pattern over the blocks. An overlapping pattern could also be performed in which case modified-DCT (“MDCT”) is performed. DCTs within an image block may be referred to as “partial-DCTs.” In the example embodiment, the partial-DCT size may be set such that at least 4 partial-DCTs may fit within an image block. For example, a 32×32 pixel image block can use an 8×8 or 16×16 partial-DCT. FIG. 2A illustrates an example embodiment with 8×8 partial-DCTs in a 32×32 pixel image block. FIG. 2B illustrates a second example embodiment with a 16×16 partial-DCTs in a 32×32 pixel image block. At step 125, process 100 may combine the multiple frequency transforms into a Block Score. Process 100 may consolidate the partial-DCTs into a “block-DCT.” The block-DCT may have the same two dimensional size of the block. During the consolidation, partial-DCTs with values that are above a given threshold may contribute to the corresponding block-DCT. The amount each partial-DCT contributes to the block-DCT may be based on the magnitude of the partial-DCT. Alternatively, each partial-DCT may contribute a preset uniform value, such that the block-DCT may become a count value for the number of partial-DCTs in the block that exceeded a predetermined threshold. A quality score for the block may be generated from the block-DCT. The block-DCT may be required to meet a minimum magnitude to indicate the presence of a frequency. For example, the ratio of partial-DCTs above a threshold forming the block-DCT may be representative of the amount of frequency content in the image block. This value may be determined by dividing the number of partial-DCTs above a threshold forming the block-DCT by the number of partial-DCTs making up the block. Alternatively each partial-DCT may be weighted to emphasize the contributions of one frequency range; for example, the higher frequencies could be weighted more than the lower frequencies. The weighted sum of the partial-DCTs of a given frequency may then be normalized by the sum of the weights to produce a value between 0 and 1. Multiplying the value by 100 provides a score from 0 to 100. A score of 70 may indicate that 70% of the possible spatial frequencies were present. An excellent quality image block may score in the 80's or 90's. An acceptable quality block may score in the 60's or 70's. A poor quality image block may score in the 50's or below. Table 1 illustrates an example numeric block score range that can serve to score the different blocks. TABLE 1Block ScoreScore DescriptionMarkup Image Color100-85 ExcellentBlue84-75GoodGreen74-65DecentYellow64-55LowOrange54-0 PoorRed At step 125, process 100 may generate a markup image from the qualified blocks. The markup image, also known as an overlay image, may be generated by blending each block's original image converted to gray scale with a block of color related to the block's score. Any scheme could be devised, such as, for example, the color coding scheme presented in Table 1. FIG. 8 illustrates an example embodiment of a markup image of color coded image block quality scores. A benefit of the example embodiment is that a glance at the markup image gives the reviewer an instant visual understanding of the whole slide quality. FIG. 9 illustrates an example of a high resolution cut out of a markup image of a low quality area. The red and orange areas are indications of lower quality and yellow areas are passable. FIG. 10 illustrates an example of a high resolution cut out of a markup image of a high quality area. When the markup image is predominantly blue and green the slide quality is very good. FIG. 11 illustrates an example of a high resolution cut out of the markup image displaying an edge effect from scanning. The small block sizes provide accurate determination of image capture artifacts, shown by a sparse red line of poor quality mixed with blocks of varying quality. At step 135, process 100 generates a score map that is compiled for use by a macro-analysis process, as exemplified below. The dimensions of the score map are compared to the image size scaled by the image block size. Each of its pixel values may represent the block's quality score, ranging from 0 to 100 or an indication that the block was classified as white space or was not processed. Process 100 ends at step 140. Macro-Analysis The Macro-analysis process summarizes the slide quality, the amount of specimen measured and the location of scan-hardware related artifacts. The macro-analysis compiles informational trends among all of those small image parts to form the slide quality score. FIG. 3 illustrates an example embodiment of a macro-analysis process 300 performed by a slide analysis system in accordance with the present invention. Macro-analysis process 300 begins at step 305. In the example embodiment, prior to beginning process 300, all image blocks are analyzed in micro-analysis process 100. Macro-analysis process 300 receives the score map, described in step 135 above. Alternatively, the system may function in parallel, pipelining the image blocks from micro-analysis process 100 to macro-analysis process 300 as the necessary blocks are processed. At step 305, process 300 pre-processes the blocks. Pre-processing builds on block qualification step 115 from micro-analysis process 100. Previously, step 115 labeled blocks containing questionable content (e.g., the blocks included folds, saturated specimen, foreign materials) as not processed. Step 305 removes the scores on the specimen edges and fragments in the score map so that they are ignored in the subsequent steps in macro-analysis process 300. At step 310, process 300 determines the percentage of specimen analyzed. This percentage may serve as an indicator of specimen artifacts. The percentage value may also be used as a confidence measure for the final whole slide quality score. For example, if only 70% of the specimen was deemed fit to process, it might be recommended that a quality control technician review the digital slide and its markup image to make a final decision upon the slide's readiness for pathologist diagnosis. Also, an average score can be directly computed from the preprocessed score map. However, one limitation of this approach is that locales of poor focus (i.e., low scores) may not significantly impact an image with blocks with average values of overwhelmingly high scores. For example, the average quality score for the digital slide may be 71 when considered on a scale of 0 to 100. However, the average score of 71 may not reflect the slide's poor quality with respect to specific areas. At step 320, process 300 performs artifact detection and degradation scoring. digital pathology scanners have common and unique hardware capture related artifacts that they may introduce into the digital slide. For example, a scanner may capture areas of the slide out of focus, have blurred edges along the capture field of view, or introduce light reflections or illumination fluctuations that cause photometric variations and motion blur. Step 320 may detect these artifacts and measure their impact (degradation) upon the slide quality. The following example embodiment illustrates example of two types of artifacts (i.e. image capture and local area artifacts). However, various other artifacts may be detected and the scoring thereby adjusted appropriately. Image Capture Artifacts: digital pathology scanners use either area or linear cameras to receive the image in the optical field of view and digitize it. Area cameras capture snapshots that are tiled together in a mosaic format to produce the large digital slide. Linear cameras continuously capture strips along one dimension of the image and assemble each strip adjacent to the next. A scanner based upon an area camera can have both horizontal and vertical striping along the two dimensions of the captured tile. The striping can be caused by optical fall off that degrades the image focus, tilt between the camera's focal plane and the stage holding the glass slide, and other such optical-mechanical design issues. A scanner based upon a linear camera will only have a striping effect along one dimension, the direction of motion. A search for score discontinuity trends along the horizontal and vertical dimensions in the score map is performed by assembling score profiles. The score profiles computed in the horizontal and vertical directions can identify area or linear camera related edge defects. However, the score map may be further partitioned and those partitions independently examined for defects. For example, four vertical profiles could be created by partitioning the score map into four (4) horizontal regions. The gradient magnitude of each discontinuity in each profile is measured. Those with large enough magnitudes are flagged as defective. The magnitude and the proportion of the area of the image that is affected by the discontinuity are factored into a degradation score for each of the detected image capture related artifacts. Local Area Artifacts: A region of the digital slide with poor quality is apparent on the markup image as a local area with a higher density of red and orange colored blocks. Poor quality regions appear in the score map as areas with high densities of low scores. The areas that have a predetermined density of low score and size requirements are flagged as defective. The region size and its density of poor scores are factored into a degradation score for each of the detected local area artifacts. One additional step is taken by each artifact detection algorithm. If an artifact is detected, the affected area in the score map is labeled such that the subsequent artifact detection algorithm will not integrate it. FIG. 12 illustrates an example of bounding box outlines around the edge of area artifacts detected on a sample scan. The long, thin boxes contain image capture edge artifacts and the smaller rectangles contain local area artifacts. It is notable that the right side of each edge artifact outline is part of the area affected by the defect and is not illustrated in this diagram. There are many other kinds of scanner artifacts that can be identified and their severity judged. For example, motion artifacts that shift red color planes, instrument resonance, and scan velocity ripple may manifest themselves as patterns in the score map. At step 325, process 300 computes the whole slide quality score. The whole slide quality score may be computed as the average score minus each artifact degradation score. The whole slide quality score (“WSQ score”) ranges from 100 to 0. At step 330, the system provides for the interpretation of the WSQ score, as determined by a study comparing an expert's quality rating against that of the system. The provided comparative score may be established by generating a comparative scoring system based on expert rating as compared with system rating executed on the digital slide set. The interpreted results may include a summarized result set including a WSQ score, a whole slide average score, an artifact degradation score, the percentage of specimen analyzed, a markup image of color coded score distributions, and annotated defective artifacts. A user of the system may choose to work with one or more these results. For example, the WSQ score may suffice to pass, fail, or visually inspect a slide. Alternatively, the mere presence of an artifact may be enough to require visual review. In one embodiment, the WSQ score (or even the average score) may be required to exceed a threshold to pass a quality control inspection. In another alternative embodiment, instead of using any of the three scores, a user may always want to visually interpret the markup image to find artifacts that may not have been quantified. For example, in one application, after computing an overall score for each scan in the range of 1-100, the system may determine whether the slide is satisfactory or needs further inspection by comparing the overall score to a threshold value; this provides a significant savings in laboratory technician time since the majority of slides may prove satisfactory. If the score is lower than a given threshold, the slide is considered unsatisfactory and may be rescanned. In this case, the slide may be rescanned “manually” by the lab technician in order to obtain a better result, or unsatisfactory slides may be auto-scanned in a batch, and then only those slides that fail to rescan successfully may be manually scanned. In further alternative embodiments, the system may tag certain slides as neither satisfactory nor unsatisfactory, if the slides results fall between two thresholds, representative of satisfactory and unsatisfactory slides. These mid-range slides, representing a small fraction of the scanned slides may be manually inspected by lab technicians. In application, the system may be employed in various aspects. During assembly of the slide scanner, the system may provide quantitative and visual feedback as technicians assemble the slide scanner, identifying scan artifacts that cue the technician to necessary alignment tasks. During scanner manufacturing, the processes may provide quantitative acceptance criteria and provide quality assurance. In a field service scenario, the system may aid in preventive maintenance checks or after service calls. That is, aside from operating in its pathology aimed purpose, the system may provide a means to verify that the scanner is operating within acceptable ranges by scanning a master glass slide and verifying quantitative and visual performance. In an operational scenario, the system may identify locations of poor focus and instruct the scanner to automatically rescan the slide and add special focus to those areas. In a clinical laboratory, the quantitative score may serve as an automatic quality control assessment. Also, a screening technician could use the combination of the quantitative score and the visual heat map to judge the image quality. FIG. 4A is a network diagram illustrating an example scanner system 400 according to an embodiment of the invention. In the illustrated embodiment, the system 400 comprises a scanning system 440 that is configured with a data storage area 445. The scanning system 440 is communicatively coupled with a user station 430, and an image server system 450 via a data communication network 460. Each of the user stations 430 and image server systems 450 are configured with a data storage area 425, 435 and 455, respectively. The data storage areas 425, 435, 445 and 455 may include volatile and persistent storage including for example, random access memory and hard disk drives. The network 460 can be any of a variety of network types including wired and wireless, public and private, or any combination of communication networks, such as the Internet. In operation, the scanning system 440 may digitize a plurality of samples to create a corresponding plurality of digital slide images that can be stored on the scanning system 440 or on the image server system 450. The scanning system 440 may be operated directly or remotely by an operator at the operator station 420. The digital slide images located at the scanning system 440 or the image server system 450 may be viewed by a user at the user station 430, where the digital image data is provided to the user station 430 via the network 460. While the example embodiment of scanning system 400 is presented as a distributed system linked via network 460, the system can also be arranged as a single computer system, or may include a large number of disparate systems for scanning and storing the digital image slides. FIG. 4B is a block diagram illustrating an example set of modules in scanner system 440 according to an embodiment of the invention. In the illustrated embodiment, the scanner system 440 may include a tissue sample acquisition module 505, a micro-analysis module 510, a macro-analysis module 515, and a visualization module 520. In certain combinations, the various illustrated modules collaborate to perform whole slide analysis, in accordance with previously described processes. Tissue sample acquisition module 505 operates to obtain an initial digital slide image from a microscope slide scanner or another source. This may include management of the scanner during scanning to handle automatic focus, exposure control, etc. Alternatively, the tissue sample acquisition module 505 may retrieve a digital sample slide from an available database. Micro-analysis module 510 evaluates the whole image by breaking it down into extraordinarily small parts and performing quality analysis on each of those parts. This evaluation may be performed in accordance with micro-analysis process 100 in FIG. 1. Macro-analysis module 515 summarizes the slide quality, the amount of specimen measured, and the location of scan-hardware related artifacts. The macro-analysis compiles informational trends among all of those small image parts to form the slide quality score. This process may be performed in accordance with the macro-analysis process 300 in FIG. 3. Visualization module 520 operates to facilitate viewing of the digital slide image file. Image viewing adjustments such as brightness, contrast, gamma and false coloring are automatically determined using the stored image descriptors and the acquisition settings. In one embodiment, viewing adjustments can be made by a user at the user station 430 for the individual images and/or for a fused image (i.e., the combined image of two or more individual channel images). In addition, when viewing a fused image, the relative translation and rotation corrections may be adjusted. Interactive image exploration tools may also be enabled by the digital visualization module 520 to instantly access responses on a cellular basis. Additionally, predetermined regions of interest may contain annotation that can be displayed to a user at the user station 430 to indicate meaningful biologic responses or to automatically quantitatively analyze responses. Additionally, the visualization and analysis module 520 may provide a user at the user station 430 with tools to annotate regions of interest and then store such annotations in the digital slide image file in relation to the base layer image. Advantageously, such annotations can be a useful to guide to document artifacts in an image, regions of interest in an image, or to identify a region of an image for reporting or quantitative analysis. Additionally, the visualization module 520 may use predetermined or otherwise identified image features to locate similar image data or patterns using content based image retrieval techniques. Advantageously, this utility can provide a user at the user station 30 with related case information and image data. In one embodiment, a client-server architecture permits a user at the user station 30 to view a digital slide image located at the image server system 50 or the scanning system 40 by requesting the compressed image tiles at a specified pyramid level on an as-needed basis and by performing client side caching of tiles in anticipation of user requests. The digital visualization and analysis module 520 additionally operates to facilitate whole slide quantitative analysis of the digital slide images, whether the image is a quadrant style image or a fused style image. In one embodiment, the digital visualization and analysis module 520 can facilitate a quantitative analysis of a particular region of interest instead of the entire digital slide image. Analysis results can be stored in a data storage area such as data storage areas 445, 455, or 435 for use with data management and reporting. FIG. 5A illustrates a block diagram of a preferred embodiment of an optical microscopy system 10 according to the present invention is shown. The heart of the system 10 is a microscope slide scanner 11 that serves to scan and digitize a specimen or sample 12. The sample 12 can be anything that may be interrogated by optical microscopy. For instance, the sample 12 may be a microscope slide or other sample type that may be interrogated by optical microscopy. A microscope slide is frequently used as a viewing substrate for specimens that include tissues and cells, chromosomes, DNA, protein, blood, bone marrow, urine, bacteria, beads, biopsy materials, or any other type of biological material or substance that is either dead or alive, stained or unstained, labeled or unlabeled. The sample 12 may also be an array of any type of DNA or DNA-related material such as cDNA or RNA or protein that is deposited on any type of slide or other substrate, including any and all samples commonly known as a microarrays. The sample 12 may be a microtiter plate, for example a 96-well plate. Other examples of the sample 12 include integrated circuit boards, electrophoresis records, petri dishes, film, semiconductor materials, forensic materials, or machined parts. The scanner 11 includes a motorized stage 14, a microscope objective lens 16, a line scan camera 18, and a data processor 20. The sample 12 is positioned on the motorized stage 14 for scanning. The motorized stage 14 is connected to a stage controller 22 which is connected in turn to the data processor 20. The data processor 20 determines the position of the sample 12 on the motorized stage 14 via the stage controller 22. In the presently preferred embodiment, the motorized stage 14 moves the sample 12 in at least the two axes (x/y) that are in the plane of the sample 12. Fine movements of the sample 12 along the optical z-axis may also be necessary for certain applications of the scanner 11, for example, for focus control. Z-axis movement is preferably accomplished with a piezo positioner 24, such as the PIFOC from Polytec PI or the MIPOS 3 from Piezosystem Jena. The piezo positioner 24 is attached directly to the microscope objective 16 and is connected to and directed by the data processor 20 via a piezo controller 26. A means of providing a coarse focus adjustment may also be needed and can be provided by z-axis movement as part of the motorized stage 14 or a manual rack-and-pinion coarse focus adjustment (not shown). In the presently preferred embodiment, the motorized stage 14 includes a high precision positioning table with ball bearing linear ways to provide smooth motion and excellent straight line and flatness accuracy. For example, the motorized stage 14 could include two Daedal model 106004 tables stacked one on top of the other. Other types of motorized stages 14 are also suitable for the scanner 11, including stacked single axis stages based on ways other than ball bearings, single- or multiple-axis positioning stages that are open in the center and are particularly suitable for trans-illumination from below the sample, or larger stages that can support a plurality of samples. In the presently preferred embodiment, motorized stage 14 includes two stacked single-axis positioning tables, each coupled to two millimeter lead-screws and Nema-23 stepping motors. At the maximum lead screw speed of twenty-five revolutions per second, the maximum speed of the sample 12 on the motorized stage 14 is fifty millimeters per second. Selection of a lead screw with larger diameter, for example five millimeters, can increase the maximum speed to more than 100 millimeters per second. The motorized stage 14 can be equipped with mechanical or optical position encoders which has the disadvantage of adding significant expense to the system. Consequently, the presently preferred embodiment does not include position encoders. However, if one were to use servo motors in place of stepping motors, then one would have to use position feedback for proper control. Position commands from the data processor 20 are converted to motor current or voltage commands in the stage controller 22. In the presently preferred embodiment, the stage controller 22 includes a 2-axis servo/stepper motor controller (Compumotor 6K2) and two 4-amp microstepping drives (Compumotor OEMZL4). Microstepping provides a means for commanding the stepper motor in much smaller increments than the relatively large single 1.8 degree motor step. For example, at a microstep of 100, the sample 12 can be commanded to move at steps as small as 0.1 micrometer. A microstep of 25,000 is used in the presently preferred embodiment of this invention. Smaller step sizes are also possible. It should be obvious that the optimum selection of the motorized stage 14 and the stage controller 22 depends on many factors, including the nature of the sample 12, the desired time for sample digitization, and the desired resolution of the resulting digital image of the sample 12. The microscope objective lens 16 can be any microscope objective lens commonly available. One of ordinary skill in the art will realize that the choice of which objective lens to use will depend on the particular circumstances. In the preferred embodiment of the present invention, the microscope objective lens 16 is of the infinity-corrected type. The sample 12 is illuminated by an illumination system 28 that includes a light source 30 and illumination optics 32. The light source 30 in the presently preferred embodiment includes a variable intensity halogen light source with a concave reflective mirror to maximize light output and a KG-1 filter to suppress heat. However, the light source 30 could also be any other type of arc-lamp, laser, or other source of light. The illumination optics 32 in the presently preferred embodiment include a standard Köhler illumination system with two conjugate planes that are orthogonal to the optical axis. The illumination optics 32 are representative of the bright-field illumination optics that can be found on most commercially available compound microscopes sold by companies such as Carl Zeiss, Nikon, Olympus, or Leica. One set of conjugate planes includes (i) a field iris aperture illuminated by the light source 30, (ii) the object plane that is defined by the focal plane of the sample 12, and (iii) the plane containing the light-responsive elements of the line scan camera 18. A second conjugate plane includes (i) the filament of the bulb that is part of the light source 30, (ii) the aperture of a condenser iris that sits immediately before the condenser optics that are part of the illumination optics 32, and (iii) the back focal plane of the microscope objective lens 16. In the presently preferred embodiment, the sample 12 is illuminated and imaged in transmission mode, with the line scan camera 18 sensing optical energy that is transmitted by the sample 12, or conversely, optical energy that is absorbed by the sample 12. The scanner 11 of the present invention is equally suitable for detecting optical energy that is reflected from the sample 12, in which case the light source 30, the illumination optics 32, and the microscope objective lens 16 must be selected based on compatibility with reflection imaging. One possible embodiment may therefore be illumination through a fiber optic bundle that is positioned above the sample 12. Other possibilities include excitation that is spectrally conditioned by a monochromator. If the microscope objective lens 16 is selected to be compatible with phase-contrast microscopy, then the incorporation of at least one phase stop in the condenser optics that are part of the illumination optics 32 will enable the scanner 11 to be used for phase contrast microscopy. To one of ordinary skill in the art, the modifications required for other types of microscopy such as differential interference contrast and confocal microscopy should be readily apparent. Overall, the scanner 11 is suitable, with appropriate but well-known modifications, for the interrogation of microscopic samples in any known mode of optical microscopy. Between the microscope objective lens 16 and the line scan camera 18 are situated the line scan camera focusing optics 34 that focus the optical signal captured by the microscope objective lens 16 onto the light-responsive elements of the line scan camera 18. In a modern infinity-corrected microscope the focusing optics between the microscope objective lens and the eyepiece optics, or between the microscope objective lens and an external imaging port, consist of an optical element known as a tube lens that is part of a microscope's observation tube. Many times the tube lens consists of multiple optical elements to prevent the introduction of coma or astigmatism. One of the motivations for the relatively recent change from traditional finite tube length optics to infinity corrected optics was to increase the physical space in which the optical energy from the sample 12 is parallel, meaning that the focal point of this optical energy is at infinity. In this case, accessory elements like dichroic mirrors or filters can be inserted into the infinity space without changing the optical path magnification or introducing undesirable optical artifacts. Infinity-corrected microscope objective lenses are typically inscribed with an infinity mark. The magnification of an infinity corrected microscope objective lens is given by the quotient of the focal length of the tube lens divided by the focal length of the objective lens. For example, a tube lens with a focal length of 180 millimeters will result in 20× magnification if an objective lens with 9 millimeter focal length is used. One of the reasons that the objective lenses manufactured by different microscope manufacturers are not compatible is because of a lack of standardization in the tube lens focal length. For example, a 20× objective lens from Olympus, a company that uses a 180 millimeter tube lens focal length, will not provide a 20× magnification on a Nikon microscope that is based on a different tube length focal length of 200 millimeters. Instead, the effective magnification of such an Olympus objective lens engraved with 20× and having a 9 millimeter focal length will be 22.2×, obtained by dividing the 200 millimeter tube lens focal length by the 9 millimeter focal length of the objective lens. Changing the tube lens on a conventional microscope is virtually impossible without disassembling the microscope. The tube lens is part of a critical fixed element of the microscope. Another contributing factor to the incompatibility between the objective lenses and microscopes manufactured by different manufacturers is the design of the eyepiece optics, the binoculars through which the specimen is observed. While most of the optical corrections have been designed into the microscope objective lens, most microscope users remain convinced that there is some benefit in matching one manufacturers' binocular optics with that same manufacturers' microscope objective lenses to achieve the best visual image. The line scan camera focusing optics 34 include a tube lens optic mounted inside of a mechanical tube. Since the scanner 11, in its preferred embodiment, lacks binoculars or eyepieces for traditional visual observation, the problem suffered by conventional microscopes of potential incompatibility between objective lenses and binoculars is immediately eliminated. One of ordinary skill will similarly realize that the problem of achieving parfocality between the eyepieces of the microscope and a digital image on a display monitor is also eliminated by virtue of not having any eyepieces. Since the scanner 11 also overcomes the field of view limitation of a traditional microscope by providing a field of view that is practically limited only by the physical boundaries of the sample 12, the importance of magnification in an all-digital imaging microscope such as provided by the present scanner 11 is limited. Once a portion of the sample 12 has been digitized, it is straightforward to apply electronic magnification, sometimes known as electric zoom, to an image of the sample 12 in order to increase its magnification. Increasing the magnification of an image electronically has the effect of increasing the size of that image on the monitor that is used to display the image. If too much electronic zoom is applied, then the display monitor will be able to show only portions of the magnified image. It is not possible, however, to use electronic magnification to display information that was not present in the original optical signal that was digitized in the first place. Since one of the objectives of the scanner 11 is to provide high quality digital images, in lieu of visual observation through the eyepieces of a microscope, it is important that the content of the images acquired by the scanner 11 include as much image detail as possible. The term resolution is typically used to describe such image detail and the term diffraction-limited is used to describe the wavelength-limited maximum spatial detail available in an optical signal. The scanner 11 provides diffraction-limited digital imaging by selection of a tube lens focal length that is matched according to the well know Nyquist sampling criteria to both the size of an individual pixel element in a light-sensing camera such as the line scan camera 18 and to the numerical aperture of the microscope objective lens 16. It is well known that numerical aperture, not magnification, is the resolution-limiting attribute of a microscope objective lens 16. An example will help to illustrate the optimum selection of a tube lens focal length that is part of the line scan camera focusing optics 34. Consider again the 20× microscope objective lens 16 with 9 millimeter focal length discussed previously and assume that this objective lens has a numerical aperture of 0.50. Assuming no appreciable degradation from the condenser, the diffraction-limited resolving power of this objective lens at a wavelength of 500 nanometers is approximately 0.6 micrometers, obtained using the well-known Abbe relationship. Assume further that the line scan camera 18, which in its preferred embodiment has a plurality of 14 micrometer square pixels, is used to detect a portion of the sample 12. In accordance with sampling theory, it is necessary that at least two sensor pixels subtend the smallest resolvable spatial feature. In this case, the tube lens must be selected to achieve a magnification of 46.7, obtained by dividing 28 micrometers, which corresponds to two 14 micrometer pixels, by 0.6 micrometers, the smallest resolvable feature dimension. The optimum tube lens optic focal length is therefore about 420 millimeters, obtained by multiplying 46.7 by 9. The line scan focusing optics 34 with a tube lens optic having a focal length of 420 millimeters will therefore be capable of acquiring images with the best possible spatial resolution, similar to what would be observed by viewing a specimen under a microscope using the same 20× objective lens. To reiterate, the scanner 11 utilizes a traditional 20× microscope objective lens 16 in a higher magnification optical configuration, in this example about 47×, in order to acquire diffraction-limited digital images. If a traditional 20× magnification objective lens 16 with a higher numerical aperture were used, say 0.75, the required tube lens optic magnification for diffraction-limited imaging would be about 615 millimeters, corresponding to an overall optical magnification of 68×. Similarly, if the numerical aperture of the 20× objective lens were only 0.3, the optimum tube lens optic magnification would only be about 28×, which corresponds to a tube lens optic focal length of approximately 252 millimeters. The line scan camera focusing optics 34 are modular elements of the scanner 11 and can be interchanged as necessary for optimum digital imaging. The advantage of diffraction-limited digital imaging is particularly significant for applications, for example bright field microscopy, in which the reduction in signal brightness that accompanies increases in magnification is readily compensated by increasing the intensity of an appropriately designed illumination system 28. In principle, it is possible to attach external magnification-increasing optics to a conventional microscope-based digital imaging system to effectively increase the tube lens magnification so as to achieve diffraction-limited imaging as has just been described for the present scanner 11; however, the resulting decrease in the field of view is often unacceptable, making this approach impractical. Furthermore, many users of microscopes typically do not understand enough about the details of diffraction-limited imaging to effectively employ these techniques on their own. In practice, digital cameras are attached to microscope ports with magnification-decreasing optical couplers to attempt to increase the size of the field of view to something more similar to what can be seen through the eyepiece. The standard practice of adding de-magnifying optics is a step in the wrong direction if the goal is to obtain diffraction-limited digital images. In a conventional microscope, different power objectives lenses are typically used to view the specimen at different resolutions and magnifications. Standard microscopes have a nosepiece that holds five objectives lenses. In an all-digital imaging system such as the present scanner 11 there is a need for only one microscope objective lens 16 with a numerical aperture corresponding to the highest spatial resolution desirable. The presently preferred embodiment of the scanner 11 provides for only one microscope objective lens 16. Once a diffraction-limited digital image has been captured at this resolution, it is straightforward using standard digital image processing techniques, to present imagery information at any desirable reduced resolutions and magnifications. The presently preferred embodiment of the scanner 11 is based on a Dalsa SPARK line scan camera 18 with 1024 pixels (picture elements) arranged in a linear array, with each pixel having a dimension of 14 by 14 micrometers. Any other type of linear array, whether packaged as part of a camera or custom-integrated into an imaging electronic module, can also be used. The linear array in the presently preferred embodiment effectively provides eight bits of quantization, but other arrays providing higher or lower level of quantization may also be used. Alternate arrays based on 3-channel red-green-blue (RGB) color information or time delay integration (TDI), may also be used. TDI arrays provide a substantially better signal-to-noise ratio (SNR) in the output signal by summing intensity data from previously imaged regions of a specimen, yielding an increase in the SNR that is in proportion to the square-root of the number of integration stages. TDI arrays can comprise multiple stages of linear arrays. TDI arrays are available with 24, 32, 48, 64, 96, or even more stages. The scanner 11 also supports linear arrays that are manufactured in a variety of formats including some with 512 pixels, some with 1024 pixels, and others having as many as 4096 pixels. Appropriate, but well known, modifications to the illumination system 28 and the line scan camera focusing optics 34 may be required to accommodate larger arrays. Linear arrays with a variety of pixel sizes can also be used in scanner 11. The salient requirement for the selection of any type of line scan camera 18 is that the sample 12 can be in motion with respect to the line scan camera 18 during the digitization of the sample 12 in order to obtain high quality images, overcoming the static requirements of the conventional imaging tiling approaches known in the prior art. The output signal of the line scan camera 18 is connected to the data processor 20. The data processor 20 in the presently preferred embodiment includes a central processing unit with ancillary electronics, for example a motherboard, to support at least one signal digitizing electronics board such as an imaging board or a frame grabber. In the presently preferred embodiment, the imaging board is an EPIX PIXCID24 PCI bus imaging board, however, there are many other types of imaging boards or frame grabbers from a variety of manufacturers which could be used in place of the EPIX board. An alternate embodiment could be a line scan camera that uses an interface such as IEEE 1394, also known as Firewire, to bypass the imaging board altogether and store data directly on a data storage 38, such as a hard disk. The data processor 20 is also connected to a memory 36, such as random access memory (RAM), for the short-term storage of data, and to the data storage 38, such as a hard drive, for long-term data storage. Further, the data processor 20 is connected to a communications port 40 that is connected to a network 42 such as a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), an intranet, an extranet, or the global Internet. The memory 36 and the data storage 38 are also connected to each other. The data processor 20 is also capable of executing computer programs, in the form of software, to control critical elements of the scanner 11 such as the line scan camera 18 and the stage controller 22, or for a variety of image-processing functions, image-analysis functions, or networking. The data processor 20 can be based on any operating system, including operating systems such as Windows, Linux, OS/2, Mac OS, and Unix. In the presently preferred embodiment, the data processor 20 operates based on the Windows NT operating system. The data processor 20, memory 36, data storage 38, and communication port 40 are each elements that can be found in a conventional computer. One example would be a personal computer such as a Dell Dimension XPS T500 that features a Pentium III 500 MHz processor and up to 756 megabytes (MB) of RAM. In the presently preferred embodiment, the computer, elements which include the data processor 20, memory 36, data storage 38, and communications port 40 are all internal to the scanner 11, so that the only connection of the scanner 11 to the other elements of the system 10 is the communication port 40. In an alternate embodiment of the scanner 11, the computer elements would be external to the scanner 11 with a corresponding connection between the computer elements and the scanner 11. The scanner 11, in the presently preferred embodiment of the invention, integrates optical microscopy, digital imaging, motorized sample positioning, computing, and network-based communications into a single-enclosure unit. The major advantage of packaging the scanner 11 as a single-enclosure unit with the communications port 40 as the primary means of data input and output are reduced complexity and increased reliability. The various elements of the scanner 11 are optimized to work together, in sharp contrast to traditional microscope-based imaging systems in which the microscope, light source, motorized stage, camera, and computer are typically provided by different vendors and require substantial integration and maintenance. The communication port 40 provides a means for rapid communications with the other elements of the system 10, including the network 42. The presently preferred communications protocol for the communications port 40 is a carrier-sense multiple-access collision detection protocol such as Ethernet, together with the TCP/IP protocol for transmission control and internetworking. The scanner 11 is intended to work with any type of transmission media, including broadband, baseband, coaxial cable, twisted pair, fiber optics, DSL or wireless. In the presently preferred embodiment, control of the scanner 11 and review of the imagery data captured by the scanner 11 are performed on a computer 44 that is connected to the network 42. The computer 44, in its presently preferred embodiment, is connected to a display monitor 46 to provide imagery information to an operator. A plurality of computers 44 may be connected to the network 42. In the presently preferred embodiment, the computer 44 communicates with the scanner 11 using a network browser such as Internet Explorer from Microsoft or Netscape Communicator from AOL. Images are stored on the scanner 11 in a common compressed format such a JPEG which is an image format that is compatible with standard image-decompression methods that are already built into most commercial browsers. Other standard or non-standard, lossy or lossless, image compression formats will also work. In the presently preferred embodiment, the scanner 11 is a webserver providing an operator interface that is based on webpages that are sent from the scanner 11 to the computer 44. For dynamic review of imagery data, the currently preferred embodiment of the scanner 11 is based on playing back, for review on the display monitor 46 that is connected to the computer 44, multiple frames of imagery data using standard multiple-frame browser compatible software packages such as Media-Player from Microsoft, Quicktime from Apple Computer, or RealPlayer from Real Networks. In the presently preferred embodiment, the browser on the computer 44 uses the hypertext transmission protocol (http) together with TCP for transmission control. There are, and will be in the future, many different means and protocols by which the scanner 11 could communicate with the computer 44, or a plurality of computers. While the presently preferred embodiment is based on standard means and protocols, the approach of developing one or multiple customized software modules known as applets is equally feasible and may be desirable for selected future applications of the scanner 11. Further, there are no constraints that computer 44 be of any specific type such as a personal computer (PC) or be manufactured by any specific company such as Dell. One of the advantages of a standardized communications port 40 is that any type of computer 44 operating common network browser software can communicate with the scanner 11. If one so desires, it is possible, with some modifications to the scanner 11, to obtain spectrally resolved images. Spectrally resolved images are images in which spectral information is measured at every image pixel. Spectrally resolved images could be obtained by replacing the line scan camera 18 of the scanner 11 with an optical slit and an imaging spectrograph. The imaging spectrograph uses a two-dimensional CCD detector to capture wavelength-specific intensity data for a column of image pixels by using a prism or grating to disperse the optical signal that is focused on the optical slit along each of the rows of the detector. FIG. 5B illustrates a block diagram of a second embodiment of an optical microscopy system 10 according to the present invention is shown. In this system 10, the scanner 11 is more complex and expensive than the currently preferred embodiment shown in FIG. 1. The additional attributes of the scanner 11 that are shown do not all have to be present for any alternate embodiment to function correctly. FIG. 2 is intended to provide a reasonable example of additional features and capabilities that could be incorporated into the scanner 11. The alternate embodiment of FIG. 2 provides for a much greater level of automation than the presently preferred embodiment of FIG. 1. A more complete level of automation of the illumination system 28 is achieved by connections between the data processor 20 and both the light source 30 and the illumination optics 32 of the illumination system 28. The connection to the light source 30 may control the voltage, or current, in an open or closed loop fashion, in order to control the intensity of the light source 30. Recall that the light source 30 is a halogen bulb in the presently preferred embodiment. The connection between the data processor 20 and the illumination optics 32 could provide closed loop control of the field iris aperture and the condenser iris to provide a means for ensuring that optimum Köhler illumination is maintained. Use of the scanner 11 for fluorescence imaging requires easily recognized modifications to the light source 30, the illumination optics 32, and the microscope objective lens 16. The second embodiment of FIG. 2 also provides for a fluorescence filter cube 50 that includes an excitation filter, a dichroic filter, and a barrier filter. The fluorescence filter cube 50 is positioned in the infinity corrected beam path that exists between the microscope objective lens 16 and line scan camera focusing optics 34. One embodiment for fluorescence imaging could include the addition of a filter wheel or tunable filter into the illumination optics 32 to provide appropriate spectral excitation for the variety of fluorescent dyes or nano-crystals available on the market. The addition of at least one beam splitter 52 into the imaging path allows the optical signal to be split into at least two paths. The primary path is via the line scan camera focusing optics 34, as discussed previously, to enable diffraction-limited imaging by the line scan camera 18. A second path is provided via an area scan camera focusing optics 54 for imaging by an area scan camera 56. It should be readily apparent that proper selection of these two focusing optics can ensure diffraction-limited imaging by the two camera sensors having different pixel sizes. The area scan camera 56 can be one of many types that are currently available, including a simple color video camera, a high performance, cooled, CCD camera, or a variable integration-time fast frame camera. The area scan camera 56 provides a traditional imaging system configuration for the scanner 11. The area scan camera 56 is connected to the data processor 20. If two cameras are used, for example the line scan camera 18 and the area scan camera 56, both camera types could be connected to the data processor using either a single dual-purpose imaging board, two different imaging boards, or the IEEE1394 Firewire interface, in which case one or both imaging boards may not be needed. Other related methods of interfacing imaging sensors to the data processor 20 are also available. While the primary interface of the scanner 11 to the computer 44 is via the network 42, there may be instances, for example a failure of the network 42, where it is beneficial to be able to connect the scanner 11 directly to a local output device such as a display monitor 58 and to also provide local input devices such as a keyboard and mouse 60 that are connected directly into the data processor 20 of the scanner 11. In this instance, the appropriate driver software and hardware would have to be provided as well. The second embodiment shown in FIG. 2 also provides for a much greater level of automated imaging performance. Enhanced automation of the imaging of the scanner 11 can be achieved by closing the focus control loop comprising the piezo positioner 24, the piezo controller 26, and the data processor 20 using well-known methods of autofocus. The second embodiment also provides for a motorized nose-piece 62 to accommodate several objectives lenses. The motorized nose-piece 62 is connected to and directed by the data processor 20 through a nose-piece controller 64. There are other features and capabilities of the scanner 11 which could be incorporated. For example, the process of scanning the sample 12 with respect to the microscope objective lens 16 that is substantially stationary in the x/y plane of the sample 12 could be modified to comprise scanning of the microscope objective lens 16 with respect to a stationary sample 12. Scanning the sample 12, or scanning the microscope objective lens 16, or scanning both the sample 12 and the microscope objective lens 16 simultaneously, are possible embodiments of the scanner 11 which can provide the same large contiguous digital image of the sample 12 as discussed previously. The scanner 11 also provides a general purpose platform for automating many types of microscope-based analyses. The illumination system 28 could be modified from a traditional halogen lamp or arc-lamp to a laser-based illumination system to permit scanning of the sample 12 with laser excitation. Modifications, including the incorporation of a photomultiplier tube or other non-imaging detector, in addition to or in lieu of the line scan camera 18 or the area scan camera 56, could be used to provide a means of detecting the optical signal resulting from the interaction of the laser energy with the sample 12. FIG. 5C is a block diagram of a third embodiment of an optical microscopy system 10 according to the present invention. In this system 10, the scanner 11 is optimized for scanning fluorescent microscope samples. The additional attributes of the scanner 11 in this embodiment including the various software and hardware elements do not all have to be present for operation of the fluorescence scanner to function correctly. FIG. 3 illustrates a reasonable example of additional features and capabilities that could be incorporated into the scanner 11 for scanning fluorescent microscope samples. FIG. 13 is a block diagram illustrating an example computer system 550 that may be used in connection with various embodiments described herein. For example, the computer system 550 may be used in conjunction with the digital pathology system and the computer and display monitors used in conjunction with the viewing software described herein. However, other computer systems and/or architectures may be used, as will be clear to those skilled in the art. The computer system 550 preferably includes one or more processors, such as processor 552. Additional processors may be provided, such as an auxiliary processor to manage input/output, an auxiliary processor to perform floating point mathematical operations, a special-purpose microprocessor having an architecture suitable for fast execution of signal processing algorithms (e.g., digital signal processor), a slave processor subordinate to the main processing system (e.g., back-end processor), an additional microprocessor or controller for dual or multiple processor systems, or a coprocessor. Such auxiliary processors may be discrete processors or may be integrated with the processor 552. The processor 552 is preferably connected to a communication bus 554. The communication bus 554 may include a data channel for facilitating information transfer between storage and other peripheral components of the computer system 550. The communication bus 554 further may provide a set of signals used for communication with the processor 552, including a data bus, address bus, and control bus (not shown). The communication bus 554 may comprise any standard or non-standard bus architecture such as, for example, bus architectures compliant with industry standard architecture (“ISA”), extended industry standard architecture (“EISA”), Micro Channel Architecture (“MCA”), peripheral component interconnect (“PCI”) local bus, or standards promulgated by the Institute of Electrical and Electronics Engineers (“IEEE”) including IEEE 488 general-purpose interface bus (“GPIB”), IEEE 696/S-100, and the like. Computer system 550 preferably includes a main memory 556 and may also include a secondary memory 558. The main memory 556 provides storage of instructions and data for programs executing on the processor 552. The main memory 556 is typically semiconductor-based memory such as dynamic random access memory (“DRAM”) and/or static random access memory (“SRAM”). Other semiconductor-based memory types include, for example, synchronous dynamic random access memory (“SDRAM”), Rambus dynamic random access memory (“RDRAM”), ferroelectric random access memory (“FRAM”), and the like, including read only memory (“ROM”). The secondary memory 558 may optionally include a hard disk drive 560 and/or a removable storage drive 562, for example a floppy disk drive, a magnetic tape drive, a compact disc (“CD”) drive, a digital versatile disc (“DVD”) drive, etc. The removable storage drive 562 reads from and/or writes to a removable storage medium 564 in a well-known manner. Removable storage medium 564 may be, for example, a floppy disk, magnetic tape, CD, DVD, etc. The removable storage medium 564 is preferably a computer readable medium having stored thereon computer executable code (i.e., software) and/or data. The computer software or data stored on the removable storage medium 564 is read into the computer system 550 as electrical communication signals 578. In alternative embodiments, secondary memory 558 may include other similar means for allowing computer programs or other data or instructions to be loaded into the computer system 550. Such means may include, for example, an external storage medium 572 and an interface 570. Examples of external storage medium 572 may include an external hard disk drive or an external optical drive, or and external magneto-optical drive. Other examples of secondary memory 558 may include semiconductor-based memory such as programmable read-only memory (“PROM”), erasable programmable read-only memory (“EPROM”), electrically erasable read-only memory (“EEPROM”), or flash memory (block oriented memory similar to EEPROM). Also included are any other removable storage units 572 and interfaces 570, which allow software and data to be transferred from the removable storage unit 572 to the computer system 550. Computer system 550 may also include a communication interface 574. The communication interface 574 allows software and data to be transferred between computer system 550 and external devices (e.g. printers), networks, or information sources. For example, computer software or executable code may be transferred to computer system 550 from a network server via communication interface 574. Examples of communication interface 574 include a modem, a network interface card (“NIC”), a communications port, a PCMCIA slot and card, an infrared interface, and an IEEE 1394 fire-wire, just to name a few. Communication interface 574 preferably implements industry promulgated protocol standards, such as Ethernet IEEE 802 standards, Fiber Channel, digital subscriber line (“DSL”), asynchronous digital subscriber line (“ADSL”), frame relay, asynchronous transfer mode (“ATM”), integrated digital services network (“ISDN”), personal communications services (“PCS”), transmission control protocol/Internet protocol (“TCP/IP”), serial line Internet protocol/point to point protocol (“SLIP/PPP”), and so on, but may also implement customized or non-standard interface protocols as well. Software and data transferred via communication interface 574 are generally in the form of electrical communication signals 578. These signals 578 are preferably provided to communication interface 574 via a communication channel 576. Communication channel 576 carries signals 578 and can be implemented using a variety of wired or wireless communication means including wire or cable, fiber optics, conventional phone line, cellular phone link, wireless data communication link, radio frequency (RF) link, or infrared link, just to name a few. Computer executable code (i.e., computer programs or software) is stored in the main memory 556 and/or the secondary memory 558. Computer programs can also be received via communication interface 574 and stored in the main memory 556 and/or the secondary memory 558. Such computer programs, when executed, enable the computer system 550 to perform the various functions of the present invention as previously described. In this description, the term “computer readable medium” is used to refer to any media used to provide computer executable code (e.g., software and computer programs) to the computer system 550. Examples of these media include main memory 556, secondary memory 558 (including hard disk drive 560, removable storage medium 564, and external storage medium 572), and any peripheral device communicatively coupled with communication interface 574 (including a network information server or other network device). These computer readable mediums are means for providing executable code, programming instructions, and software to the computer system 550. In an embodiment that is implemented using software, the software may be stored on a computer readable medium and loaded into computer system 550 by way of removable storage drive 562, interface 570, or communication interface 574. In such an embodiment, the software is loaded into the computer system 550 in the form of electrical communication signals 578. The software, when executed by the processor 552, preferably causes the processor 552 to perform the inventive features and functions previously described herein. Various embodiments may also be implemented primarily in hardware using, for example, components such as application specific integrated circuits (“ASICs”), or field programmable gate arrays (“FPGAs”). Implementation of a hardware state machine capable of performing the functions described herein will also be apparent to those skilled in the relevant art. Various embodiments may also be implemented using a combination of both hardware and software. Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and method steps described in connection with the above described figures and the embodiments disclosed herein can often be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. In addition, the grouping of functions within a module, block, circuit or step is for ease of description. Specific functions or steps can be moved from one module, block or circuit to another without departing from the invention. Moreover, the various illustrative logical blocks, modules, and methods described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (“DSP”), an ASIC, FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, the steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium including a network storage medium. An exemplary storage medium can be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can also reside in an ASIC. The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.
061920959	abstract	Radioactive stents used in angioplasty on sclerotic coronary arteries without the risk of restenosis can be produced by ion injecting .sup.133 Xe into the surfaces of stents as a nuclide that has a shorter half-life and emits a smaller maximum energy of .beta.-rays than .sup.32 p Uniform ion injection is accomplished using an apparatus capable of uniform irradiation of the stents with .sup.133 Xe ion beams. The source of .sup.133 Xe is a nuclear fission product generated from .sup.235 U in the fuel rods in nuclear reactor.
	description	The invention related to the field of high-precision positioning. More specifically, this invention relates to the field of piezo-driven inertial positioners. Another aspect of this invention relates to field of accurate determination of position by the principle of light interference and position-sensing light detectors. Another aspect of this invention relates to positioners integrated with optical instruments for the purpose of accurate control of position and motion. High-precision positioner is an enabling component of many scientific and industrial instruments. Such instruments are widely used in a variety of fields, for example, in optical microscopy and spectroscopy, electron microscopy, scanning probe microscopy, nanotechnology, wafer inspection, microassembly, optical fiber alignment methods in optoelectronics, and many others. A design of one known type of such positioner is disclosed in the 1993 World Intellectual Property Organization Publication WO/1993/019494 by Shuheng Pan. Described therein is a piezoelectric step positioner. This positioner comprises six shear-piezo actuators that hold a movable element. Motion can be achieved in two different ways: by slip-stick actuation or by locomotion. Different arrangements effecting linear, x-y planar, and rotational motion are described. This device is reliable, rigid, and capable of performing in many environments. However, when used for the design of a multi-axis positioner, this invention lacks optimal implementation of several necessary functions, as follows. The embodiment of the invention that comprises a stack of two or three independent single-axis positioners lacks compactness which limits the rigidity, and thus the performance of the instrument. Another embodiment of Pan's invention provides simultaneous motion in two dimensions, but such motion is not independent along Cartesian axes and makes the readout of coordinates difficult. Another type of positioner relevant to our invention is described in the U.S. Pat. No. 5,912,527 by Karrai. This positioner is arranged in such a way that a movable member is set in motion by a stick-slip mechanism, the driving motor of which is the extending and contracting piezo-stack. The preferred embodiment of this invention allows a compact multi-axis positioning assembly, but such assembly is not rigid enough for many applications, for example, its low mechanical resonant frequency limits its use in scanning probe microscopy. This invention does not teach a method of measuring coordinates of a movable member. In U.S. Pat. No. 6,130,427 Park et al. disclose an optical setup for measuring xyz coordinates of a movable cartridge carrying a scanning microscope probe. The cartridge is affixed to the top of a piezoelectric tube having multiple electrodes Application of appropriate voltages across the electrodes, produces displacement in the plane of the top surface (xy) and along the axis of the tube (z). In this prior art, displacements x and y of the cartridge are measured by the spot where a probing beam of light impinges on a 4-quadrant photodetector positioned in the xy plane. Axial displacement z is measured separately requiring two additional bi-cell photodetectors positioned along z axis, and two additional probing beams of light. The resulting setup is quite complex and difficult to manufacture, as it requires a complicated alignment. An alternative instrument that reads all three coordinates while requiring a single beam of light and a single detector affixed to the movable element would be a clear advantage over this prior art. Therefore, there is a need for an improved three-dimensional positioning instrument integrated with a reliable instrument for accurate determination of coordinates: compact and rigid, applicable to a variety of uses, cost-efficient, and straightforward to machine and assemble. Sufficient rigidity is necessary for achieving mechanical resonant frequency on the order of 10 kHz or higher, which will make the instrument ideally suited for probe microscopy, micro-manipulation and nano-lithography. For example, such instrument will enable scanning probe microscopy with atomic resolution in a real-world environment, where mechanical vibrations are not entirely suppressed. We invented an instrument for precise positioning of objects using an inertial actuator and an optical instrument for accurate determination of the object position in 3 dimensions. The micro-positioner is compact and rigid with the lowest mechanical resonant frequency in excess of 10 kHz. The optical instrument for position readout and control is a compact interferometric module comprising a position-sensing detector as one of the arms of the interferometer. A single incident beam of light is required for position readout in 3 dimensions in all disclosed embodiments of the instrument. We further invented a mounting assembly suitable for carrying and swapping a microdevice or a sample by a disclosed positioner or another instrument. We now turn to the detailed description of this invention. I. An Inertial Positioner In FIG. 1a through FIG. 4a series of embodiments of a single-axis inertial positioner is presented. Turning to FIG. 1a, the represented positioner is an essentially rigid construction comprising a frame having as frame elements: a base 1, a carrier 2, and an inertial actuator 4 which is disposed on base 1 of the positioner; further comprising a movable platform 3 to which an object to be positioned is affixed. Base 1 may be a platform of another positioner, or any other suitable rigid object. One surface of the actuator is bonded to the base, while the other surface is bonded to the carrying element. In this invention, a preferred embodiment of an inertial actuator 4 is a piezo-electric actuator, more preferably a stack of piezo-electric elements. Less preferred embodiments of an inertial positioner comprise a magnetostrictive or an electromagnetic actuator. The piezo-electric actuator 4 is supplied with electrical contacts so as to apply voltage causing sheer stress to the actuator. The waveform of applied voltage is chosen in such a way as to move the carrier 2 with respect to the base 1 fast enough to cause a slipping motion of the platform 3 with respect to the carrier along the interface 6; and then to retract the carrier to bring it back to a starting position with respect to the base slowly enough for the platform to remain at rest with respect to the carrier. An example of a suitable waveform is presented in FIG. 7. Such process is routinely referred to as the “slip-stick” motion. The positioner further comprises a plurality of constraining surfaces 5 housing a plurality of rollers 7 which are capable of rolling between said surfaces. The rollers are pressed against the platform to ensure that the motion of the platform is along the direction set by containing surfaces; and to further ensure a loaded frictional contact of the carrier and the platform along the common interface 6. A preferred roller is ball-shaped; another preferred roller is cylindrical. Possible embodiments of rollers are not limited to spherical balls and cylinders; other shapes and arrangements known in the art of rolling bearings may be used in a positioner of this invention. Containing surfaces may be formed by guiding grooves 5, as represented in FIG. 1a through 1g. One containing surface may be the surface of the carrier 2, as represented in FIG. 1a and FIG. 1b. In another embodiment, such surface is the surface of the base 1 of the positioner, as represented in FIG. 1c and FIG. 1d. Two embodiments of a positioner with guiding grooves 5 disposed in the platform are represented in FIG. 1a and FIG. 1c. In another embodiment represented in FIG. 1b, a guiding groove is disposed in the carrier. In yet another embodiment represented in FIG. 1d, a guiding groove is disposed in the base. In yet another embodiment, a plurality of guiding grooves may be disposed in one or more of the elements comprising a positioner: a base, a carrier, and a platform. A piezo-electric actuator 4 may be a stack of sheer planar piezos 4a or a plurality thereof, as shown in FIG. 1e. In an embodiment represented in FIG. 1f a plurality of carriers 2, each mounted onto and rigidly attached to surfaces of piezo stacks, is disposed in a frictional engagement with the platform 3. In yet another embodiment represented in FIG. 1g the frame of a positioner is comprised of a base and a plurality of piezo stacks without a separate carrier; the frictional engagement is made directly between surfaces of piezo stacks 4a and the platform 3. The advantage of the last embodiment is the increased compactness and rigidity of a positioner. Numerous other embodiments of an inertial positioner will be immediately obvious to anyone skilled in the field. Another example from a multitude of embodiment within the scope of this invention is shown in FIG. 1h. In this embodiment, containing surfaces 5 are formed in the platform 3 and in the base 1, and a plurality of carriers 2 is mounted onto and rigidly attached to surfaces of piezo stacks 4a. Yet another example of an embodiment shown in FIG. 1j comprises cylindrical rollers 7a housed in a plurality of grooves formed in a carrier 2. In yet another embodiment of a positioner represented in FIG. 1k spherical balls 7 are housed and rolling in a space formed by containing surfaces of base 1 and platform 3. Rollers employed in these embodiments for the purpose of aligning the motion of the platform along the direction set by containing surfaces and creating a loaded frictional contact between the platform and a frame, can be machined from a number of rigid materials, such as alumina, tungsten carbide, stainless steel, or another refractory material, preferably the ones having Vickers hardness exceeding 1000 MPa. Surfaces of frictional engagement may formed by alumina, sapphire, titanium, lead zirconate titanate (PZT), and various ceramics. Inertial positioner in this invention is preferably a piezoelectric stack positioner made of lead zirconate titanate (PZT) or lithium niobate crystals (LiNbO3). A base or a carrier of the positioner may be supplied with a spring-loaded mechanism, the function of which is to allow tuning the pressure on the interface between the carrier and the platform. Similarly, a carrier may be supplier with such spring-loaded mechanism. By varying this pressure, the shape of the voltage pulse required to cause a slipping motion of the platform with respect to the carrier, may be adjusted to specification. By way of example and not by way of limitation, a spring-loaded mechanism is represented in FIG. 2. According to this embodiment, a carrier 2 is comprised of a first element 2a, a second element 2b disposed to make a slip-fit contact to the first element, brought into contact with the first element by a plurality of screws 2c, spring-loaded by tightening a plurality of spring elements 2d. By turning the screws one achieves the target pressure between the carrier and the platform along the common interface 6. It will be obvious to anyone ordinarily skilled in the art of mechanical design that many spring-loaded arrangements will allow tuning the pressure on the interface between the carrier and the platform, and that such arrangements will fall into the scope of the present invention. A graphical projection of a single-axis positioner wherein roller-containing surfaces comprise guiding grooves disposed in the carrier is presented in FIG. 3. An interface of frictional engagement 6 can be a planar surface. In another embodiment, said interface comprises a cylindrical portion. One such embodiment is represented in a cross-sectional view of FIG. 4a. Base 1 is a block onto which a piezoelectric actuator 4 is rigidly mounted. Actuator 4 is preferably a stack of hollow piezo elements allowing the insertion of a hollow carrier 2 rigidly attached to the actuator 4. In a less preferred embodiment, the actuator 4 is a piezo tube. Platform 3 is inserted into the carrier and makes contact to it along interface 6 between the cylindrical outer surface of 3 and cylindrical inner surface of 2. By way of illustration and not by way of limitation, grooves 5 are disposed in the platform 3; each housing a ball 7. A spring element 2d presses on the balls 7 and thereby provides a pressure between the carrier and the platform along their common interface 6. A graphical projection of the positioner of FIG. 4a is shown in FIG. 4b. The spring member and the piezo stack are not shown in this figure so as not to obscure guiding grooves 5 and balls 7. The spring member 2d in FIG. 4c is inserted into the carrier 2 and is held in place by retainers 8 formed in the carrier 2. The spring member 2d is pressing on balls 7 disposed in grooves 5, ensuring a loaded frictional contact between the platform and the carrier. Another embodiment of a positioner having an interface of frictional contact comprising a cylindrical portion is represented in FIG. 4d. Here frictional engagement is created between the inner surface of platform 3 and the outer surface of carrier 2 inserted into platform 3. Two single-axis positioners can be stacked together by rigid attachment between a platform of a first single-axis positioner and a base of a second single-axis positioner, resulting in an instrument for positioning an object in 2 dimensions. Three invented single-axis positioners can be stacked together by rigid attachment between a platform of a first single-axis positioner and a base of a second single-axis positioner, and further between a platform of a second single-axis positioner and a base of a third single-axis positioner resulting in an instrument for positioning an object in 3 dimensions. The platform of a first single-axis positioner may serve as a base of a second single-axis positioner, and similarly, the platform of a second single-axis positioner may serve as a base of a third single-axis positioner. Two embodiment of such instrument are presented in the graphical projection in figures FIG. 5 and FIG. 6. The preferred embodiment of FIG. 5 comprises two positioners in which common interface of frictional engagement is planar, and another positioner in which said interface comprises a cylindrical portion. The advantage of multi-axis positioners obtained by stacking single-axis positioners disclosed above is their compactness and rigidity. The latter property is important for achieving high mechanical resonant frequencies on the order of or higher than 10 kHz. For example, at a mechanical resonant frequency of 50 kHz, which is attainable in a multi-axis positioner assembled from disclosed single-axis positioners, the platform is capable of translational motion at a typical speed of 1 mm/sec. Rigidity is also necessary for achieving the desired insensitivity to ambient mechanical vibrations. Low profile of a positioner is important for attaining rigidity and is achieved by choosing height of an inertial positioner between 0.1 and 0.75 of the square root of the product of its footprint. The invention of a positioner disclosed herein is not limited to geometries illustrated in FIGS. 1 through 6. It will be appreciated by anyone skilled in the art of positioning instruments that a multitude of other embodiments comprising an inertial actuator and rollers which are employed to press on an interface of frictional engagement between a moving element and a frame element of a positioner will fall into the scope of this invention. II. An Optical Instrument for Determining Coordinates Another aspect of the invention is the optical instrument for determining coordinates to enable position control. A preferred embodiment of an optical position-measuring apparatus is represented in FIG. 8a. In this embodiment, the apparatus requires substantially one beam of light, preferably a laser light, to probe all coordinates in a 3-dimensional space. Turning to the representation in FIG. 8a, a beam of light 10 is emanating from the collimating lens 9 which is coupled to an optical fiber 15, at a direction normal to the surface of a quadrant (4-cell) position-sensitive light detector 11a. The collimating lens 9 is preferably a gradient refractive index lens or another collimating optical element or a plurality thereof. A reference beam 10r resulting from reflection of beam 10 by the inside surface of the collimating lens, or by a separate element with a semi-reflecting surface, is directed toward the analyzer 13. Probing beam 10p is resulting from reflection of beam 10 by the surface of the detector 11a and is thus directed to reenter the fiber 15 and to interfere with the reference beam 10r. Hence, partially reflective surface of the quadrant light detector 11a plays the role of a sensing arm, while partially reflective surface of the collimating lens 9 plays the role of a reference arm of the interferometric part of this apparatus. The intensity of interfering beams 10r and 10p depends on phase accumulation caused by displacement of the detector 11a with respect to the fiber end; and hence the position of the photo detector 11a along the axis of the fiber end can be inferred by the analyzer 13. The center of a photo detector with respect to x,y position of the light spot formed on the surface of the detector by the incoming beam 10 can be inferred from its electrical signals at electrodes 12. Another embodiment of a position-measuring apparatus is represented in FIG. 8b. In this embodiment, the position-sensitive photodetector is a continuous rectangular light detector 11b, operating on the basis of current spreading. The photocurrent generated by the incoming beam 10 is spreading to electrodes 12 along resistive paths defined by the location of the spot where beam 10 impinges on the detector 11b, thus relating voltage outputs at electrodes 12 of the detector to its x,y position with respect to the fiber end. A disclosed instrument for position readout and control comprises a probing beam of light 10, a position-sensing detector 11a, and an interference analyzer 13. This enables determination of all 3 coordinates of the photo-detector 11a with respect to the fiber end. Alternative embodiments for creating a probing beam and a reference beam are shown in FIG. 8c and FIG. 8d. In FIG. 8c a conventional lens 16 is used for beam collimation and a separate planar element with a semi-reflective surface 14 is introduced to create a reference beam reentering the fiber 15. In FIG. 8d a spherical mirror with a semi-reflective surface 14 is introduced to reflect diverging light emanating from a fiber end back into the fiber, thus creating a reference beam, while the collimation of light emanating from a fiber end is achieved by two curved mirrors 17a and 17b as shown schematically in FIG. 8d. These alternative embodiments require precise alignment and are therefore less preferred than those represented in FIGS. 8c and 8d. The advantages of the disclosed instrument illustrated in FIGS. 8a and 8b with respect to the existing position-sensing instruments are many. The number of components comprising the position-measuring apparatus is minimal: a single source of collimated light is required for positional readout and control in all 3 dimensions; a single position-sensitive photodetector for reading x and y coordinates also serves as a sensing arm of a fiber interferometer for reading z. Furthermore, integration of such instrument with a positioner is straightforward, as illustrated by graphical projections in FIG. 9 and FIG. 10. An integrated instrument is a stack of single-axis positioners; and an interferometric/position-sensitive module for coordinate readout and control disclosed above. The x and y positioners which are shown in FIG. 5 are omitted in FIG. 9 for clarity of representation of the position-measuring apparatus. A collimating lens 9 is affixed to the base 1x of the first positioner in the stack, while the position-sensitive photodetector 11a is disposed at the right angles with respect to the direction of the probing beam 10 and is affixed to the platform 3z of the last positioner in the stack. Thus, the optical module is reading the position of the platform 3z with respect to the base 1x. A preferred embodiment represented in FIG. 9 is characterized by compactness and small footprint, in part due to enclosing an optical module for determining coordinates within a 3-axis positioner. III. A Mounting Assembly Another aspect of the current invention is a mounting assembly. A disclosed assembly may be suitable for carrying various objects on a platform of a positioner disclosed above. An assembly comprises a receiving member, possibly affixed to a platform of a mechanical stage or a positioner; and a holder that may carry a variety of objects, for example, a scanning probe for SFM, STM or other microscopy; a micromanipulator; a micro-machined SEM; a microdispenser, a micro- or nano-indenter, and many other types of samples, probes or devices. If voltage is applied across electrodes formed in the holder and the receiving member, which are brought into close proximity of each other, an electrostatic clamping force is created between these electrodes, holding the assembly together. Further, electrode pairs are formed in the holder and the receiving member. These can be insertion electrodes of the pin-receptacle type, pogo pin type electrodes, or other similar electrode pairs. Input and output terminals of a device carried by the holder can be permanently connected to holder-side electrodes; when a holder and a receiving member are joined to form an assembly, the connection between these terminals and electrodes on the receiving member is made, facilitating control or probing of the carried device. Electrode pairs of insertion type ensure alignment between the holder and the receiving member. Alternatively, separate aligning elements may be formed in the assembly. An exemplary electrostatically clamped mounting assembly comprising a receiving member 18 and a holder 19 is represented in two graphical projections in FIG. 11. In one embodiment, a receiving member 18 comprises a plurality of electrically conductive pins and a plurality of clamping electrodes disposed on a preferably insulating surface. Such receiving member may be affixed to the platform 3z of a last positioner in a positioner stack comprising a three-axis positioner, a preferred embodiment of which is shown in FIG. 9. or to any other suitable carrier, stage, positioner, robotic arm or a pick-and-place tool. Holder 19 comprises a plurality of receptacles for making electrical connection to the conductive pins of the receiving member 18 and a plurality of clamping electrodes disposed on its insulating surface. In this embodiment one pin-receptacle pair is necessary for clamping action. For example, a pin electrode formed in the receiving member may be electrically connected to a source of electric field. A receptacle in the holder corresponding to this pin electrode is connected to a clamping electrode of the holder. A clamping electrode on the surface of the receiving member may be grounded. Alternatively, a clamping electrode on the holder surface may be grounded. Application of electric filed between clamping electrodes on the receiving member side and on the holder side results from insertion of the pin into the receptacle, effecting attractive force between clamping electrodes and securely clamping the holder to the receiving member. Another pin-receptacle pair may be used for making electrical connections to an object mounted on the holder, which may be a scanning probe, a manipulator, a dispenser, a micro-machine, an optical probe, an indenter, or any other suitable device. Now turning to the preferred embodiments of a receiving member and a holder presented in FIG. 12 and FIG. 13, respectively, a plurality of clamping electrodes 24 is disposed on the electrically insulating surface 23 of the receiving member, and similarly, a plurality of clamping electrodes 24′ is disposed on the electrically insulating surface 23′ of the holder. A layer of an insulator, preferably made from a high dielectric permittivity material, covers clamping electrodes 24 of the receiving member. In another embodiment of the mounting assembly, an insulating layer, preferably a high dielectric permittivity material, covers clamping electrodes 24′ of the holder. Spring members 22 aid reliable electrical and mechanical contact between pin 20 and the conducting inner surface of receptacle 25; and pin 21 and inner surface of receptacle 26, respectively. Pins and receptacles provide alignment of holder 19 and receiving member 18 with respect to each other during insertion, minimizing tilt and rotational (in-plane) misalignment. In this embodiment, receptacle 26 formed in the holder is wired to clamping electrodes 24′. Pin 21 of the receiving member is permanently connected to clamping electrodes 24. When the assembly is put together, pin 21 is inserted into receptacle 26. By applying a potential difference between electrodes 21 and 24 of the receiving member, the electric field is created between electrodes 24 and 24′, effecting electrostatic clamping of the holder to the receiving member. While pin 21 is used to engage electrostatic clamping, pin 20 can be used for applying electrical signals to or measuring characteristics of the carried object via electrical connection to receptacle 25 if this receptacle is wired to a terminal of said object. A receiving member can be affixed to a platform of an inertial positioner, providing a convenient way of securely locking the holder to the platform, and allowing either manual or automatic swapping of various devices mounted on holders by disengaging electrostatic clamping. Such automatic swapping can be achieved, for example, by a robotic arm or an automated picking and placing tool. Further, a receiving member of the mounting assembly affixed to a platform of a three-axis positioner can play a role of a picking and placing tool. For example, a worn probe or a microdispenser, or another device disposed on a holder of the assembly may be removed from the work area, disengaged and discarded or stored, then a new device on a holder may be picked up by the receiving member by reengaging electrostatic clamping, a brought into the work area. This embodiment has an additional advantage of allowing automatic swapping of holders safely, away from the work area by retracting the holder over a macroscopic distance. This is possible because the available throw of the positioner disclosed above substantially exceeds 1 mm. As an alternative to an embodiment represented in FIG. 12 and FIG. 13, one or more pins may be disposed on the holder while the corresponding receptacles may be formed in the receiving member. The number of pin-receptacle pairs in the disclosed mounting assembly can be as many as necessary for applying electrical signals to or probing an object carried by the holder. Another embodiment of a mounting assembly is shown in a cross-sectional representation in FIG. 14a. Receptacle electrodes 25a formed in the receiving member and spring-loaded electrodes 28 formed in the device holder have guiding surfaces 30 that guide the holder into receiving member during insertion. In this present embodiment guiding surfaces are conical. A variety of surfaces having a guiding function will be immediately obvious to anyone ordinarily familiar with mechanics: they may comprise spherical, cylindrical, pyramid-like, or more complex shapes. A electrical potential difference is provided by a source 29 between a guiding electrode in the receiving member 25a and a spring loaded electrode 28 formed in the holder; the latter electrode is permanently wired to a clamping electrode 24′ which is brought into close proximity of clamping electrode 24, thus creating electrostatic clamping of the holder to the receiving member. Polarity of the source 29 is inessential and is such as shown by way of example only. A layer of insulating material 27, preferably made of a high permittivity dielectric or a piezoelectric, is disposed on the clamping electrode 24. In an alternative embodiment a layer of electrically insulating material 27 is covering a holder-side clamping electrode 24′. Another pair of electrodes 25a and 28 may be used for transmitting electrical signals between the receiving member 18 and a device carried by the holder 19. Not all available pairs of electrodes 25a-28 necessarily provide guiding of the holder into receiving member during insertion. For example, all but two electrode pairs may be such that their receptacle electrodes are substantially flat and therefore do not have guiding function. Guiding surfaces disclosed above make the mounting assembly particularly suitable for automated holder placement, by reducing sensitivity to placement inaccuracy such as misalignment, in-plane rotation, and tilt. For example, a picking and placing tool that carries a holder by vacuum suction could place it over a receiving member with an offset, which will be corrected by self-aligning function of guiding surfaces. Another embodiment of a mounting assembly comprising a holder and a receiving member, wherein electrodes 25a are formed in a holder 19, while spring-loaded contacts 28 are formed in a receiving member 18 is represented in FIG. 14b. Guiding surfaces 30 guide the holder into receiving member during insertion. In another embodiment of a mounting assembly represented in FIG. 14c electrode pairs comprising pad-like electrodes 25b do not have a guiding function. Instead, guiding, alignment, and minimization of in-plane rotational placement inaccuracy during joining of the assembly is provided by separately formed guiding elements having surfaces 30. By way of example, surfaces 30 of this embodiment are concave and convex pairs, preferably spherical. Many other types of guiding surfaces comprising spherical, conical, cylindrical, planar, and combinations thereof, as well as other shapes fall within the scope of this invention. Guiding surfaces 30 may be formed on spring-loaded guiding members, as represented in FIG. 14d. Yet another embodiment of an assembly capable of minimizing inaccuracy of placement during joining of the assembly is represented in FIG. 14e. Guiding surfaces having conical shapes 30 are formed by standoffs on the holder side and corresponding cutouts in the receiving member. Yet another embodiment of a mounting assembly is represented in FIG. 14f. In this embodiment clamping of the holder 19 to the receiving member 18 is achieved by applying a potential difference between split electrodes 32 formed in the receiving member. As a result of capacitive coupling between electrodes 32 and 32′ the electric field and the associated with it clamping force is created between holder and receiving member. Since an electrical connection to holder-side electrode 32′ is not necessary in this embodiment, all available electrode pairs 28-25a can be used for applying electrical signals to or probing the carried object. In yet another embodiment of a mounting assembly clamping electrodes 24 and 24′ have a frame or ring-like shape, as shown in a cross-sectional representation of the assembly in FIG. 14h. A similarly shaped insulating layer 27 covers a clamping electrode 24 on the receiving member of the assembly. In an alternative embodiment, insulating layer 27 covers a holder-side clamping electrode 24′. This embodiment is particularly useful if a line of sight to an object carried by holder 19 is desirable, for example, for optical probing of said object. Light can be guided through transparent path, for which purpose optional cutouts 18h and 19h can be made in the assembly. Many other embodiments of the disclosed mounting assembly will be obvious to anyone skilled in the art of the field of this invention. Embodiments which are capable of making electrical connection to an object mounted onto a holder, clamping of a holder to a receiving member electrostatically, and maintain alignment between parts of an assembly, will fall within the scope of this invention. Other less preferred ways of creating a clamping force are possible, for example, clamping may be effected magnetically. Embodiments of a mounting assembly disclosed above are suitable for automatic handling by a robotic tool. For example, a device on a holder may be picked up by a robotic arm and discarded after use or picked up and removed from the receiving member for further analysis, and a new device on another holder can be brought in and clamped to a receiving member. For another example, a positioner of the present invention with a receiving member attached to it may discard a worn device by unclamping its holder, move to another location, and pick up a new device on a holder by reengaging clamping. Figures illustrating embodiments of a mounting assembly show a holder above a receiving member by way of example. Orientation of the assembly in space is inessential to its operation and can be chosen to suit a particular application. An exemplary mounting assembly in FIG. 15 comprises a receiving member 18 disposed above a holder 19 which is affixed to a positioner 33. Holder 19 carries a probe 34 that may have one or more electrical terminals. An example terminal is electrically connected by wire 35 to a holder-side electrode 25a. When the holder and the receiving member are joined to form an assembly, a signal may be applied to or read from device 34 by connecting to electrode 28 formed in the receiving member, as shown in this figure. Another electrode 28 is used to apply clamping voltage to the assembly, as shown. In this example, clamping electrode 24′ on the surface of holder 19 is grounded when the holder is joined to the receiving member. Positioner 33 in this example is a 3-axis positioner disclosed above, but other types of positioners may be used to position the mounting assembly. It should be noted that a 3-axis positioner with an integrated optical positioning control instrument preferred embodiments of which are shown in FIG. 9 or FIG. 10 in combination with a disclosed mounting assembly make up a tool ideally suited for in-situ replacement of worn or contaminated probes in scanning probe microscopy, and for numerous other applications. Any application requiring compactness, rigidity and precision of positioning, as well as hot-swapping of micro-machined instruments, probes or arrays of probes, micro-manipulators, microdispensers, or other devices—where reproducible return after swapping is necessary, will greatly benefit form this invention. A probing station comprising a positioner with an integrated optical positioning control instrument of the present invention or a plurality thereof, may be used for a variety of tasks, for example, to characterize using a scanning probe sub-microscale devices, nanoassemblies or molecules.
	abstract	A radiation attenuation system suitable for use in radiological examinations includes a first portion comprising a radiation attenuation material and a second portion comprising a relatively non-radiation attenuation buffer region between the radiation attenuation material and an article undergoing the examination. The radiation attenuation system may be positioned over, under, near, or otherwise about the article. According to one embodiment, the radiation attenuation system is intended to be positioned over a target area on the article and coincident with the primary radiation beam.
	abstract	A ventilated apparatus for storing and/or transporting high level radioactive waste. In one aspect, the invention is a ventilated apparatus comprising: an overpack body having an inner surface forming a cavity about a longitudinal axis. A bottom portion of the overpack body is formed by a plurality of segments. Each of the segments extends from a first end wall having a projection to a second end wall having a channel. The segments circumferentially surround a longitudinal axis and are arranged in an intermeshing and spaced-apart configuration such that the projections of the first end walls of the segments project into the channels of the second end walls of adjacent ones of the segments, thereby forming inlet ducts between adjacent ones of the segments. The inlet ducts form air inlet passageways from the external atmosphere to a bottom portion of the cavity.
	summary
	abstract	A leakage testing device for testing leakage of a nuclear fuel assembly (18) by sipping. The device includes a collection assembly (32) that is configured to close an upper end (24A) of a cell (24) of a storage rack (22) for storing nuclear fuel assemblies discharged from a nuclear reactor (4). The closing prevents water contained in the cell from escaping via the upper end of the cell. The collection assembly is configured to collect products containing possible fission products released by a nuclear fuel assembly contained in the cell.
	abstract	An electron beam apparatus that includes a vacuum chamber, a large-area cathode disposed in the vacuum chamber, and a first power supply connected to the cathode. The first power supply is configured to apply a negative voltage to the cathode sufficient to cause the cathode to emit electrons toward a substrate disposed in the vacuum chamber. The electron beam apparatus further includes an anode positioned between the large-area cathode and the substrate. The anode is made from aluminum. The electron beam apparatus further includes a second power supply connected to the anode, wherein the second power supply is configured to apply a voltage to the anode that is positive relative to the voltage applied to the cathode.
044302924	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a main condenser 10 is disposed downstream of a steam turbine, not shown, and an air extractor 11 is connected to the upper portion of the main condenser 10 to extract radioactive gaseous wastes staying in the upper portion thereof. The air extractor 11 is communicated with an inlet of a recombining unit 13 including a preheater 12 and a recombiner 14, which are aligned vertically with a slight space therebetween. The recombining unit 13 is usually a cylindrical container and is dividable into upper and lower halves at substantially the intermediate portion of the container 13 as shown by flanges 40 so that the recombiner 14 is disposed in the upper half and the preheater 12 in the lower half when the container 13 is disassembled. The preheater 12 serves to heat the gaseous wastes to a temperature suitable for effectively disposing of the wastes, and the preheated gaseous wastes passing through the preheater 12 is fed into the recombiner 14 in which the oxygen and the hydrogen in the gaseous wastes are recombined into vapour. A condenser 15 is connected to an outlet of the recombining unit 13 downstream thereof, and in the condenser 15, the recombined water vapour and steam from the turbine system for driving the air extractor 11 are cooled into condensed water. A device 16 for holding up the radioactive gaseous wastes with activated carbon is connected downstream of the condenser 15 for attenuating the radioactivity of the radioactive gaseous wastes to a level below a permissible radioactivity. The outlet of the hold-up device 16 is connected to gas discharging stack 17 for discharging the waste gas having substantially no radioactivity or a radioactivity below the permissible level into atmosphere. A pipe line 19 is also arranged to feed cooling water from the main condenser 10 to the condenser 15 by means of a pump 18. Thus, the cooling water flows in a closed loop. Referring now to FIG. 2 in which the condenser 15 and the recombining unit 13 are installed on a common skid 50 as one assembly 20. The recombining unit 13 essentially comprises an inlet pipe 21 through which the gaseous wastes from the main condenser 10 are introduced, the preheater 12, the recombiner 14, and an outlet pipe 22. The preheater 12 is of a shell and tube type heat exchanger and comprises a plurality of heat transfer tubes 23 which utilize steam flowing from an inlet pipe 21 towards an outlet pipe 25 as a heating medium. Usually a trap 26 is connected to the outlet pipe 25. The outlet pipe 22 of the recombining unit 13 is connected to an inlet pipe 27 of the condenser 15 through an expansion joint 37. The condenser 15 comprises a cooling water injector 28, a baffle 29 located below the injector 28, an outlet pipe 30 disposed at the bottom of the condenser 15 for discharging condensed water and used cooling water, and a gaseous waste outlet pipe 31 on the side wall of the condenser 15. To the outlet pipe 31 is connected a steam separator 32 provided with a gaseous waste outlet pipe 33 at the upper end thereof and a drain duct 34 at the lower end thereof. Water level controlling means 35 which adjusts the water level of the condensed water and cooling water in the condenser 15 is installed in a by-pass line disposed at the lower portion of the condenser 15. A valve 36 for adjusting the flow of the condensed water from the condenser 15 is provided downstream of the outlet pipe 30. In a case where a recombining unit of the type utilizing a catalyst is used, a wire net 38, shown in FIG. 2, may be provided within the recombining unit 13 for preventing the catalyst from dispersing towards the downstream side. The radioactive gaseous waste disposing system according to this invention operates as follows. The gaseous wastes passing through the air extractor 11 enters into the recombining unit 13 through the inlet pipe 21. The wastes are heated in the preheater 12 by steam fed through the steam inlet pipe 24 so as to efficiently combine the oxygen with the hydrogen in the gaseous wastes at a time when it is fed into the recombiner 14 without heat loss. The preheater 12 and the recombiner 14 are vertically aligned in the recombining unit 13 so that preheated gas flows directly upwardly to effectively contact the catalyst 38. The recombined water vapour and the gaseous wastes are then fed into the condenser 15 through the outlet pipe 22. The steam for heating the gaseous wastes enters into the outside of the heat transfer tubes 23 through the inlet pipe 24 and the steam transfers its heat to the gaseous wastes in the tubes 23. In this heat exchanging step, a portion of the steam changes into condensed water. The steam containing the condensed water flows out through the outlet pipe 25 and the condensed water is separated from the steam by the trap 26 and discharged to the outside of the system. The cooling water fed from the main condenser 10 by means of the pump 18 for circulating the cooling water is injected through the injector 28 into the condenser 15 and cools the gaseous wastes in direct contact thereto, thereby condensing the water vapour contained in the gaseous wastes into the condensed water, which will be recovered into the main condenser 10. The heat transfer efficiency between the cooling water and the gaseous wastes in the condenser 15 will be increased by using a spraying device as the injector 28 which sprays the cooling water or by using a wire net or a flat plate for enlarging the area of contacting the cooling water to the gaseous wastes. The heat transfer efficiency attained by the direct contact, described above, can be considerably improved in comparison with the use of a conventional shell and tube heat exchanger. In addition, the preheater 12 can be made to be compact by directly contacting the gaseous wastes to the cooling water over a relatively wide area, and the latent heat of evaporation of the cooling water makes it possible to use a smaller quantity of cooling water than that in the conventional system. The condensed water obtained in the condenser 15 is returned to the main condenser 10 under a head similar to that in the conventional system. Thus, since the water in the main condenser 10 can be utilized as a cooling water, it is not necessary to supply the cooling water into the condenser 15 from an external source. The fact that the cooling water does not flow out of the waste disposing system efficiently prevents leakage of the cooling water having radioactivity to the outside of the system. Namely, in a case where the conventional shell and tube type heat exchanger is used as the condenser 15, if a portion of a pipe for supplying the cooling water were broken, the radioactive gaseous wastes would leak into the cooling water and the contaminated cooling water flows out of the system. However, according to the system of this invention, the possibility of the breaking of the pipe for supplying the cooling water is considerably low and even if the pipe were accidentally broken, the smaller amount of the contaminated cooling water flows into the main condenser 10 and does not flow out of the system. Although the gaseous wastes also contain mist, it is caught by the steam separator 32 connected to the outlet pipe 31 of the condenser 15, and the gaseous wastes containing substantially no mist is fed into the hold-up device 16 for adsorbing the radioactive gaseous wastes with the activated carbon. The water level of the water containing the condensed water and the used cooling water in the condenser 15 is maintained at a predetermined level by level controlling means 35 and the level adjusting valve 36. It will of course be understood that although the steam separator 32, the water level control means 35, and the adjusting valve 36 were incorporated into the assembly 20 comprising the recombining unit 13 and the condenser 15 as shown in the embodiment of FIG. 2, it is possible to install them on the outside of the assembly 20. According to the radioactive gaseous waste disposing system of this invention, a recombining unit and a condenser are installed on a common skid and combined as one assembly, so that the pipes connecting these equipment can be eliminated thereby making compact the system and minimizing the space for installation thereof. The constructional advantages allow workers to use a wide space for maintenance and operation of the system. The direct contact of the cooling water to the radioactive gaseous wastes in the condenser allows to use a small amount of the cooling water and prevents the wastes from leaking out of the system, thus providing the safe and reliable system. In addition, the elimination of the pipes necessary to connect respective equipments of the system makes simple the installation works in the field without connecting the pipes by welding, etc. Moreover, since the cylindrical containers are constructed to be dividable into two upper and lower parts so that the recombiner is disposed in the upper half and the preheater is disposed in the lower half when the recombining unit is disassembled, the periodical maintenance or inspection of the preheater and the recombiner can be performed independently, and these members are arranged vertically, so that the water vapour formed in the recombiner drops and does not stay there. Thus, if a catalyst is used, it will not be damaged by the water vapour.
	abstract	A radiation shielding sheet formed by filling a shielding material into an organic polymer material. The shielding material is an oxide powder containing at least one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu) and gadolinium (Gd). The oxide powder has an average grain size of 1 to 20 μm, and a volumetric ratio of the shielding material filled in the radiation shielding sheet is 40 to 80 vol. %.
	abstract	A locking mechanism for securing hatches internal to a steam generator that is made up of only mechanical locking elements with fully captured moving parts. The mechanism employs a locking pin with redundant mechanisms to secure the pin in the closed position. The moving parts of the device can be attached directly to a removable hatch so that installation and repairs that may be required can be performed outside of the pressure vessel of the steam generator.
051031035	abstract	A switchable shield which precludes transmission or receipt of radio frequency or microwave energy. The shield comprises a substrate of highly transmissive material with an active film layer disposed on the substrate. This active film layer is switchable upon heating from a high transmissivity, high resistivity mode which permits transmission or receipt of rf or microwave radiation, to a low transmissivity, low resistivity mode which precludes transmission or receipt of rf or microwave radiation through the shield.
051026155	summary	BRIEF SUMMARY OF THE INVENTION The invention is directed to a container for storing, transporting and disposing radioactive material comprising a vessel and cap each having walls with a core of radioactive shielding material enveloped and isolated within a continuous metal lining. In the operation of nuclear power stations spent fuel is generally stored in short term storage on the power station site until such radioactive materials have decayed to a state where long term storage or disposal is desirable due to space limitations as material accumulates, and transport to locations off-site does not entail unacceptable risks. To this end containers have been developed for storing and transporting radioactive material encased within a shell of radioactive shielding material such as concrete for example. Although lead has superior shielding capabilities, due to its high weight, toxicity, and cost, other preferable shielding materials have been developed including high density concrete. To provide corrosion and leakage resistance as well as structural strength to the shell of shielding material, conventional containers often include inner or outer metal liners. Conventional containers having a core of lead are described in the following U.S. Pat. Nos. 3,229,096 to Bonilla et al; 2,514,909 to Strickland; and 4,666,659 to Lusk et al. A hollow concrete-shielded steel outer walled container with a steel inner liner is described in U.S. Pat. No. 3,448,859 to Hall et al. for use in association with liquid wastes. Conventional containers which utilize lead as a shielding material suffer from disadvantages when compared to concrete shielded containers since lead is relatively expensive. Lead is toxic and therefore requires more careful handling during construction. Lead has a low melting point and low structural strength which are disadvantageous due to the heat generated by radioactive decay. Lead also has significantly different thermal expansion characteristics compared to the associated composite metal liners used, requiring the designs to incorporate means to allow for differential expansion. Concrete as a shielding material is preferred therefore since it is less costly and is easily prepared and handled. Concrete also has similar thermal expansion characteristics to steel enabling the use of steel liners and internal reinforcing bars, without the necessity of accommodating differential expansion. However, concrete typically contains pockets of water that has not reacted with the cement powder and therefore concrete is a relatively porous material. Concrete also cracks under thermal or other stresses and upon impact. As a result therefore concrete often allows contaminated fluid to migrate through it reducing its effectiveness as a radioactive shield. Spent fuel elements are often stored under water in short term storage pools within the power station. To minimize the risk of contamination, loading of spent fuel into long term storage containers is preferably carried out under water within the short term storage pools. The water within such pools contains radioactive material and therefore containers with concrete shielding material which is exposed to such contaminated water during loading are unsuitable since the shielding material may become permeated with contaminated water through the cracks and pores of the concrete. Conventional containers generally comprise a vessel with a central cavity to house the radioactive material and a cap which is bolted to the vessel to seal the cavity. Although bolted caps may be preferred if repeated access is desired, bolted caps and associated flexible gasket seals are often unreliable in the long term due to gasket and bolt corrosion. Bolted caps are also difficult to install since an evenly distributed compressive force is required to seal the flexible gaskets. Frequent inspection is required to ensure initial sealing and maintenance of the seal when bolted caps are used, increasing the associated costs and risks. The present invention relates to a novel container for storing and transporting radioactive material which overcomes the above disadvantages of conventional containers. In accordance with the invention is provided a container for storing and transporting radioactive material comprising: a vessel, having an upwardly open cavity for accommodating said radioactive material, said vessel having walls with a core of concrete shielding material enveloped and isolated within a continuous metal lining; and a cap, covering the top surface of said vessel sealing said cavity, said cap having a core of concrete shielding material enveloped and isolated within a continuous metal lining, the lower outer peripheral edge of said cap being continuously welded to the upper outer peripheral edge of said vessel.
	description	In accordance with the present invention, a system is provided for collimating and optionally focusing light, such as preferably light in the x-ray spectrum or light with wavelengths less than about 13 nanometers. Other wavelengths of light also can be collimated or optionally focussed in accordance with the present invention, as well, so long as the light is within the reflective or collimating range of the reflector or guide channel. In this description, the term xe2x80x9clightxe2x80x9d will be used synonymously with the term xe2x80x9cradiationxe2x80x9d to refer to the wavelengths that are collimated and/or focused in the present invention, for example, in the x-ray spectrum or in wavelengths less than about 13 nanometers. As illustrated in FIGS. 1-5, a source 10, such as an x-ray or other light source is provided. The figures illustrate an x-ray source, such as would be used in an x-ray lithography system in which a plasma target, located approximately at the point indicated by source 10 is excited by a beam source, such as a high energy laser, electron beam, proton beam or photon beam. The source 10 emits light in the desired wavelengths. In the figures, the emitted light is depicted diagrammatically with arrows 20. Light, such as x-rays, emitted from the source 10 is collected by the collimator 30. The collimator includes a reflector apparatus 40 and a guide channel apparatus 50. The reflector serves to gather and reflect in a desired fashion the light 20 from the source 10 that is outside the guide channel 50, but still within the reflector 40, such in the region between the guide channel 50 and the reflector 40, as illustrated in FIGS. 1-3. Any suitable reflector can be used that can reflect the light 20 from the source 10. In the preferred embodiment, the reflector 40 is adapted to reflect x-rays. In one embodiment, a conical, parabolic resonance reflector or grazing incidence reflector with a shape similar to the guide channel 50 is used to increase the solid angle collected and produce a circular, square, etc. annular x-ray beam whose inside dimensions are approximately equal to the exit dimensions of the polycapillary collimator. It should be understood that any shaped reflector 40 (for example parabolic resonance reflector or grazing incidence reflector) can be used that can achieve collimating and/or focusing the portions of the incoming light that are received and reflected by it. The shape of the exit beam generated can be any shape and does not necessarily need to match the shape of the guide channel 50, although in the preferred embodiment, the exit beam from the reflector 40 does generally match that of the guide channel 50. In the preferred embodiment, a grazing incidence reflector or resonance reflective optic can be used as the reflector 40. The reflector 40 is shaped to reflect light into a collimated orientation. In operation, a portion of the incident light 20 hits the reflective inner surface 45 of the reflector 40 and is reflected in a more linear fashion, i.e. it is collimated. The collimated light exiting collimator 30 is illustrated with arrows 60 in FIG. 1. As illustrated, the exiting light 60 preferably has a substantially collimated profile. The output beam shape, intensity profile and/or collimation angle can be adjusted, if desired, using an absorber 65. For example, an absorber 65 positioned towards the exit end 140 of the collimator 30 can adjust the intensity profile. In one embodiment, the intensity of the light exiting the collimator 30 close to the reflector 40 at the exit 140 is less intense than that slightly further away from the reflector 40 at the exit 140, but still outside the guide channel 50. Accordingly, in this embodiment, the light intensity gradually increases with distance from the reflector 40. In order to generate a flat intensity profile a graduated absorber may be used. In other words, the absorber 65 absorbs less light close to the reflector. The use of such an absorber 65 is particularly beneficial where it is desired to have a uniform intensity profile in the exiting light 60. The guide channel apparatus 50 serves to gather and transmit in a collimated fashion light 20 from the light source 10 that reaches the beginning 70 of the guide channel 50. Any suitable guide channel 50 can be used that gather the incoming light 20 and transmit it in a collimated fashion. In the preferred embodiment, the guide channel 50 is adapted to gather and transmit x-rays. In the preferred embodiment, plural guide channel elements 80 are in the guide channel 50. The guide channel elements 80 preferably include polycapillary tubes, or microchannel plates, or a combination of polycapillary tubes and microchannel plates are used in the guide channel apparatus 50. The guide channel collimates or focuses the central portion of the x-ray beam in a desired shape, such as circular, elliptic, square, or rectangular shape. The individual guide channel elements (i.e. polycapillary tubes and/or microchannel plates) are referenced with number 80 in the figures. The polycapillary tubes or microchannel plates 80 are arranged in any pattern to collect incoming light 80 and transmit it to a desired location. The individual polycapillary tubes 80 within the guide channel 50 can optionally be tapered, such as having a changing width over the length of the tube. In addition, the polycapillary tubes 80 can be monolithic such as by being bonded or melted together, or formed within a matrix. As illustrated in FIG. 1, the light 60 exiting the collimator 30 is collimated by the guide channel apparatus 50. In one embodiment, as illustrated in FIG. 1, there is a gap 85 between the guide channel elements 80 (such as polycapillary tubes or microchannel plates 80) and the reflector 40. In this embodiment, a portion of the exit beam 60 comes from the reflector and a portion from the guide channel 50. In another embodiment, as illustrated in FIG. 2, the elements 80 of the guide channel 50 extend to the reflector 40. In this embodiment, the exit beam 60 comes from the guide channel 50. In operation, a portion of the incoming light 20 is reflected off the reflector 40 and is received in one or more of the guide channel elements 80, i.e. those which are closer to the reflector 40 and oriented to receive light reflected by the reflector 40. Any geometry of the polycapillary tubes or microchannel plates 80 can be used. In the embodiment illustrated in FIG. 4, a half of a generally square cross-sectional arrangement of polycapillary tubes 80 is provided. Alternatively, a circular arrangement can be used as indicated by arc 90 in FIG. 4. One exemplary application of the collimator 30 of the present invention is in x-ray lithography or microlithography. In such lithography operations, the collimated light 60 exiting from the collimator 30 is received by a mask/photoresist on a wafer or other substrate to be processed. In a typical embodiment, the collimated light 60 is directed using directing optics and/or focusing optics to a desired location. In an alternative embodiment, it is desired to focus the emitted light. This embodiment is illustrated in FIG. 3. In this embodiment, the reflector is shaped as a focusing optic and will be referred to as a xe2x80x9cfocusing optic 42xe2x80x9d. Any shape can be selected for the focusing optic 42, which will receive the incoming light and reflect it to a focus location 120. In one embodiment, a generally elliptical cross-sectional shape is used for the focusing optic 42. In a preferred embodiment, the focusing optic 42 includes two generally parabolic reflectors 40 linearly arranged. In the embodiment where two reflectors 40 are used, the reflectors optionally may have the same profile, or alternatively may have different profiles. The upstream reflector portion 46 preferably has the same profile as the downstream reflector portion 48, resulting in a reflection of the light towards a focus point 120. Using a focusing optic 42 is of particular use in non-lithography applications, such as tomography, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray microscopy and x-ray flourescence. It should be noted that, for ease of illustration and discussion, FIGS. 1-4 illustrate a cross-section of a top portion of collimators in accordance with the present invention. A full cross-section of the embodiment illustrated in FIG. 1 is shown in FIG. 5. In operation, incident light 20, such as x-rays, is received by the collimator, such as through an aperture 130. A portion of the incident light 20 is reflected off reflector 40 and exits via exit aperture 140. Another portion of the incident light 20 is received within and guided through the guide channel and exits via exit aperture 140. The intensity of the exiting light 60 can be adjusted such as by absorber 65, which preferably is positioned at or near the exit aperture 140. In the x-ray embodiment, the exit light can be used for x-ray lithography, such as in the manufacture of integrated circuits and other electronic components. Thus, it is seen that an apparatus and method for collimating light, such as x-rays or other wavelengths is provided. One skilled in the art will appreciate that the present invention can be practiced by other than the preferred embodiments, which are presented in this description for purposes of illustration and not limitation. It is noted that various equivalents for the particular embodiments discussed in this description may practice the invention as well.
	claims	1. A transport or storage cask, comprising:a cask body;a modular thermal conducting and shielding system that includes a modular fin and a modular neutron shield, the modular fin being disposed between the modular neutron shield and the cask body, the modular fin being capable of dissipating thermal energy from the cask body, the modular fin including a base and an arm, the base being capable of coupling to the cask body, the arm of the modular fin having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the modular fin and the distal end of the arm extending away from the cask body, the modular neutron shield being disposed on top of the base of the modular fin, the distal end of the arm having slots that enables air flow to facilitate dissipation of thermal energy conducted from the cask body;a mechanical attachment that retains the modular thermal conducting and shielding system to the cask body; anda conductive cover in which the modular neutron shield is disposed between the modular fin and the conductive cover, the modular neutron shield being capable of shielding radiation generated within the cask body,wherein the modular thermal conducting and shielding system further comprising the conductive cover that is disposed on top of the modular neutron shield, the conductive cover including a base, a first arm and a second arm, the base being capable of covering the modular neutron shield, each of the first and second arms having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the conductive cover and the distal end of the arm extending away from the cask body, the distal end of the arm having slots that are aligned with the slots of the modular fin to enable air to flow through the slots of the modular fin and the conductive arm, each of the first and second arms being capable of engaging the arm of the modular fin, the conductive cover being capable of facilitating dissipation of thermal energy conducted from the cask body. 2. The cask of claim 1, further comprising a neutron-shield enclosure that encapsulates the modular neutron shield and protects the modular neutron shield from exposure to particular environments. 3. The cask of claim 1, wherein the modular neutron shield has a shape of a trapezoid and the modular fin has a shape of an elongated letter V, the modular neutron shield being retained to the cask body by way of the mechanical attachment. 4. The cask of claim 3, wherein the modular thermal conducting and shielding system further comprising a second modular neutron shield having a shape of a trapezoid, the second modular neutron shield being retained to the cask body by way of the elongated V-shaped fin. 5. The cask of claim 1, wherein the mechanical attachment includes stud, washer, and nut. 6. A transport or storage cask, comprising:a cask body;a modular thermal conducting and shielding system that includes a plurality of modular fins and a plural of modular neutron shields, each modular fin being disposed between the respective modular neutron shield and the cask body, each modular fin being capable of dissipating thermal energy from the cask body, each modular fin including a base and an arm, the base being capable of coupling to the cask body, the arm of the modular fin having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the modular fin and the distal end of the arm extending away from the cask body, each modular fin being placed adjacent to another modular fin; andmechanical attachments that retain the modular thermal conducting and shielding system to the cask body. 7. The cask of claim 6, further comprising a plurality of neutron-shield enclosures each encapsulating the respective neutron shield and protects the respective neutron shield from exposure to particular environments. 8. The cask of claim 7, wherein each modular neutron shield has a shape of a trapezoid and each modular fin has a shape of an elongated letter V, each modular neutron shield being retained to the cask body by way of the mechanical attachment. 9. The cask of claim 7, wherein the modular thermal conducting and shielding system further comprising a plurality of second modular neutron shields having a shape of a trapezoid, each second modular neutron shield being retained to the cask body by way of the elongated V-shaped fin. 10. The cask of claim 6, wherein the mechanical attachment includes stud, washer, and nut. 11. The cask of claim 6, further comprising a plurality of conductive covers in which each modular neutron shield is disposed between the respective modular fin and the respective conductive cover, each modular neutron shield being capable of shielding radiation generated within the cask body. 12. The cask of claim 11, wherein the distal end of the arm having slots that enables air flow to facilitate dissipation of thermal energy conducted from the cask body. 13. The cask of claim 12, wherein the modular thermal conducting and shielding system further comprising the conductive cover that is disposed on top of the modular neutron shield, the conductive cover including a base, a first arm and a second arm, the base being capable of covering the modular neutron shield, each of the first and second arms having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the conductive cover and the distal end of the arm extending away from the cask body, the distal end of the arm having slots that are aligned with the slots of the modular fin to enable air to flow through the slots of the modular fin and the conductive arm, each of the first and second arms being capable of engaging the arm of the modular fin, the conductive cover being capable of facilitating dissipation of thermal energy conducted from the cask body. 14. A transport or storage cask, comprising:a cask body;a thermal conducting and shielding system that includes a plurality of fins and a plurality of neutron shields, each fin being disposed between the respective neutron shield and the cask body, each fin being capable of dissipating thermal energy from the cask body, each fin including a base, a first arm and a second arm, each of the first and second arms having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the fin and the distal end of the arm extending away from the cask body, the neutron shield being disposed on top of the base of the fin, each fin being separate and independent of another fin; anda mechanical attachment that retains the thermal conducting and shielding system to the cask body. 15. The cask of claim 14, further comprising a plurality of neutron-shield enclosures each encapsulating the respective neutron shield and protecting the respective neutron shield from exposure to particular environments. 16. The cask of claim 14, further comprising a plurality of conductive covers in which the respective neutron shield is disposed between the respective fin and the respective conductive cover, each neutron shield being capable of shielding radiation generated within the cask body. 17. The cask of claim 16, wherein the distal end of the first and second arms having slots that enables air flow to facilitate dissipation of thermal energy conducted from the cask body. 18. The cask of claim 17, wherein the thermal conducting and shielding system further comprising the conductive cover that is disposed on top of the neutron shield, the conductive cover including a base, a first arm and a second arm, the base being capable of covering the neutron shield, each of the first and second arms of the conductive cover having a distal end and a proximal end, the proximal end of the arm being integrally connected to the base of the conductive cover and the distal end of the arm of the conductive cover extending away from the cask body, the distal end of the arm of the conductive cover having slots that are aligned with the slots of the fin to enable air to flow through the slots of the fin and the conductive arm, each of the first and second arms of the conductive cover being capable of engaging the arm of the fin, the conductive cover being capable of facilitating dissipation of thermal energy conducted from the cask body. 19. The cask of claim 14, wherein each neutron shield has a shape of a trapezoid and the fin has a shape of an elongated letter V, each neutron shield being retained to the cask body by way of the mechanical attachment. 20. The cask of claim 19, wherein the thermal conducting and shielding system further comprising a plurality of second neutron shields having a shape of a trapezoid, each second neutron shield being retained to the cask body by way of the elongated V-shaped fin. 21. The cask of claim 14, wherein the mechanical attachment includes stud, washer, and nut.
061447161	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to nuclear reactor fuel element support grids and more particularly to support grids that include diagonal retaining springs. 2. Background Information Fuel assemblies for nuclear reactors are generally formed from an array of elongated fuel elements or rods maintained in a laterally spaced relationship by a skeletal support structure, including a plurality of longitudinally spaced support grids, a lower end fitting, and an upper end fitting. The fuel assembly skeleton also includes guide tubes and instrumentation thimbles, which are elongated tubular members symmetrically interspersed among and positioned coextensive with the fuel element locations. The guide tubes and instrumentation thimbles are fixedly connected to the support grids to provide the structural coupling between the other skeletal members. The support grids each define an array of fuel rod support compartments or cells and have a perimeter that is configured in one of a number of alternate geometrical shapes that is dictated by the reactor core design. Nuclear fuel grids for commercial pressurized water reactors employing square fuel assemblies can typically have between 14 and 17 cells per side. Other polygonal array designs are also employed, such as the hexagonal array illustrated in U.S. Pat. No. 5,303,276, issued Apr. 12, 1994. One typical fuel element support grid design includes a generally polygonal perimeter surrounding an interior lattice array. A plurality of fuel element compartments or cells within the perimeter are defined by a number of evenly spaced, slotted, interlocked lattice forming members or straps, which are welded to the perimeter and joined to each other by small nugget welds at the ends of their lines of interception along the slotted locations. Each interior lattice forming member is slotted over one half of its width along its lines of intersection with the other grid forming members of the array. The members are assembled and interlocked at the lines of intersection with the slot in one member fitting into the opposing slot in the crossing member in an "egg-crate" fashion. This egg-crate design provides a good strength to weight ratio without severely impeding the flow of coolant that passes through the grid in an operating nuclear reactor. The lattice-forming members typically include projecting springs and dimples for engaging and supporting the fuel elements within some of the grid compartments. The springs provide axial, lateral and rotational restraint against fuel rod motion during reactor operation under the force of coolant flow, during seismic disturbances, or in the event of external impact. These spacer grids also act as lateral guides during insertion and withdrawal of the fuel assemblies from the reactor. One of the operating limitations on current reactors is established by the onset of film boiling on the surfaces of the fuel elements. The phenomenon is commonly referred to as departure from nuclear boiling (DNB) and is affected by the fuel element spacing, system pressure, heat flux, coolant enthalpy and coolant velocity. When DNB is experienced, there is a rapid rise in temperature of the fuel element due to the reduced heat transfer that occurs under these conditions as a result of the gaseous film that forms on portions of the fuel element surface, which can ultimately result in failure of the fuel element if it was to continue. Therefore, in order to maintain a factor of safety, nuclear reactors must be operated at a heat flux level somewhat lower than that at which DNB occurs. This margin is commonly referred to as the "thermal margin." Nuclear reactors normally have regions in the core that have a higher neutron flux and power density than other regions. The variation in flux and power density can be caused by a number of factors, one of which is the presence of control rod channels in the core. When the control rods are withdrawn, these channels are filled with coolant, a moderator, which increases the local moderating capacity and thereby increases the power generated in the adjoining fuel. In these regions of high power density known as hot channels, there is a higher rate of enthalpy rise than in other channels. These hot channels set the maximum operating conditions for the reactor and limit the amount of power that can be generated, since it is in these channels that the critical thermal margin is first reached. The prior art has attempted to reduce the variation in power density across the core and thus increase the DNB performance by providing coolant flow deflector vanes as an integral part of the fuel support grids. The vanes improve performance by increasing heat transfer between the fuel rods and the coolant downstream of the vane locations. The vanes are especially beneficial in the regions adjoining the hot channels, which are the fuel element positions adjacent to the control rod guide tube locations. To take full benefit of the vanes, it is also desirable to streamline the remaining grid components, i.e., the lattice straps, including the springs, dimples and welds, to reduce the turbulence generated upstream from the vanes. Other objectives in optimizing fuel grid designs include minimizing grid pressure drop and maximizing grid load carrying strength. The springs, which provide the force for holding the fuel rods in position, are normally formed from cut-out sections of the lattice forming members that protrude into the fuel rod support compartments. The spring force applied is designed as a balance between the forces necessary to provide the axial, lateral and rotational restraint required to hold the fuel elements in position and that which will score or otherwise damage the surface of the fuel element as it is threaded into the assembly during manufacture. To both avoid damage to the fuel element and provide maximum restraining forces it is desirable to maximize the contact area that the spring has with the fuel rod as well as the flexure of the spring. A preferred method for achieving maximum contact area is to provide a diagonal spring which extends from a lower portion of one of the walls of the fuel support compartment to a diagonally opposed upper portion of the same wall as illustrated in the prior art design illustrated in FIG. 2. FIG. 2 shows a single wall section of a grid lattice strap 110 with a diagonal spring 112. The cut-out sections 114 protrudes into an adjacent fuel element support compartment and forms the dimple for providing point contact support for an adjacent fuel rod which is pressed against the dimple by a similarly formed spring extending inwardly from the opposite wall of that adjacent compartment. Typically a fuel rod support compartment is provided with springs on at least two walls and dimples on the opposing walls to center the fuel rods and provide maximum coolant flow around their surface. The prior art also provided cut-out sections 116, shown in FIG. 2, to reduce the mass of wall material around the spring and thus increase it flexibility. As shown in patent application Ser. No. 08/887,017 (Docket ARF96-003 it is desirable to locate the mixing vanes 120 over the grid compartments that support the fuel element, to enhance heat transfer. It has been found however, that the vanes increase the pressure drop in the fuel support compartments. That creates a pressure differential between the fuel support compartments that adjoin the control rod guide tube and instrument thimble locations and the tube and thimble locations, that do not have mixing vanes. As a result, during operation the coolant flowing through the grid compartments adjoining the guide tube and thimble locations tends to seek the path of least resistance and flow out the windows 116 on either side of the diagonal 112 spring and up through the thimble and guide tube locations. The result is reduced heat transfer in the area that most needs it and less efficient use of the vanes. Accordingly, an improved grid structure is desired that improves DNB performance. It is an object of this invention to achieve that result by minimizing the leakage path around the grid springs, while maintaining the spring's flexibility. It is a further object of this invention to improve upon the flexibility of the diagonal spring design without reducing the crushable strength of the grid. SUMMARY OF THE INVENTION The structure of this invention overcomes some of the deficiencies of prior art grid spring designs by reducing the area open to cross flow in the fuel support cells while maintaining the flexibility of the grid springs. In accordance with this invention the spring is formed from narrow, diagonal, parallel slits in the lattice walls. In the preferred embodiment added spring flexibility is achieved by extending the vertical slits in the lattice straps to more than half of the width of the strap, at the points of intersection with the orthogonal straps. In addition, in a diagonal spring configuration the slits in the lattice walls that form the springs are extended at their terminations, in a direction parallel with the line of intersection of the adjacent wall and away from the spring. Thus the flexibility of the springs are enhanced with reduced open wall area available for cross flow. These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following description when taken in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention.
	abstract	Projection-optical systems are disclosed that reduce OoB radiation doses on the wafer while reducing deterioration of optical properties of the systems. An exemplary system includes a first reflector having a reflectance for light of a second predetermined wavelength, different from light of a first predetermined wavelength, that is less than a predetermined reflectance. The system also includes a second reflector having a reflectance for light of the second wavelength which is greater than the predetermined reflectance. When the reflectors in the system are classified as reflectors having a high percentage of overlap for the reflecting regions corresponding to two different points on the wafer, and reflectors having a low percentage of overlap for the reflecting regions, then, among the reflectors having a lower percentage of overlap for the reflecting regions, the most upstream reflector in the light path of the system is the second reflector.
	claims	1. For use with an irradiation system comprising a radiation source operable to produce a radiation beam towards a target, a beam modulator comprising:a flexible, deformable container at least partially filled with a radiation attenuating fluid;a non-deformable first contacting surface in contact with a first portion of said container, said first contacting surface pivotable about a first axis; anda positioner operable to rotate said first contacting surface about said first axis, wherein as said first contacting surface rotates about said first axis, said first contacting surface deforms said container. 2. The beam modulator according to claim 1, wherein said first axis is generally perpendicular to a propagation axis of the radiation beam. 3. The beam modulator according to claim 1, further comprising a non-deformable second contacting surface in contact with a second portion of said container different from said first portion, said second contacting surface pivotable about a second axis, and a positioner operable to rotate said second contacting surface about said second axis, wherein as said second contacting surface rotates about said second axis, said second contacting surface deforms said container. 4. The beam modulator according to claim 3, wherein said second axis is generally perpendicular to a propagation axis of the radiation beam. 5. The beam modulator according to claim 3, wherein said second axis is different than said first axis. 6. The beam modulator according to claim 3, wherein said second axis is generally perpendicular to said first axis. 7. The beam modulator according to claim 3, wherein said positioner that positions said first contacting surface is the positioner that positions said second contacting surface. 8. The beam modulator according to claim 3, wherein said positioner that positions said first contacting surface is separate from the positioner that positions said second contacting surface. 9. The beam modulator according to claim 3, wherein said positioner is operable to translate at least one of said first and second contacting surfaces. 10. The beam modulator according to claim 3, wherein said first and second contacting surfaces are generally radiation transparent. 11. The beam modulator according to claim 1, wherein said positioner is in communication with an orientation changer, wherein said orientation changer is operable to change an orientation of the beam and the target. 12. The beam modulator according to claim 1, wherein said container is made of an elastomeric material. 13. For use with an irradiation system comprising a radiation source operable to produce a radiation beam towards a target, a beam modulator comprising:a flexible, deformable container at least partially filled with a radiation attenuating fluid;a plurality of non-deformable contacting surfaces in contact with a plurality of portions of said container, said contacting surfaces pivotable about a plurality of pivot axes; anda positioner system operable to rotate said contacting surfaces about said pivot axes, wherein as said contacting surfaces rotate about said pivot axes, said contacting surfaces deform said container. 14. An irradiation system comprising:a radiation source operable to produce a radiation beam towards a target; anda beam modulator comprising:a flexible, deformable container at least partially filled with a radiation attenuating fluid;a plurality of non-deformable contacting surfaces in contact with a plurality of portions of said container, said contacting surfaces pivotable about a plurality of pivot axes; anda positioner system operable to rotate said contacting surfaces about said pivot axes, wherein as said contacting surfaces rotate about said pivot axes, said contacting surfaces deform said container.
	abstract	A collimator module (10A) comprises a plurality of collimator single plates (11) having a pair of long sides and a pair of short sides and a pair of blocks (12) including a plurality of first grooves (125) extending along an irradiation direction of the X-rays. The short sides are inserted into the first grooves to support the collimator single plates. A supporting member is configured to cover the long sides from an incident side and an emission side of the X-rays. The supporting member includes an incident side fixing sheet (13) and an emission side fixing sheet (15) each having a plurality of second grooves into which the long sides are inserted to support the plurality of collimator single plates. The fixing sheets cover the first grooves and at least a portion of each of the long sides.
	description	This patent application is a continuation of U.S. patent application Ser. No. 15/225,279, filed Aug. 1, 2016, and titled Atomic Number (Z) Grade Shielding Materials and Method of Making Atomic Number (Z) Grade Shielding, and claims the benefit of and priority to U.S. Provisional Patent Application No. 62/199,032, filed on Jul. 30, 2015, and titled “Additional Methods of Making Z-Grade,”; U.S. Provisional Patent Application No. 62/240,604, filed on Oct. 13, 2015, and titled “Additional Methods of Making Z-Grade,”; and U.S. Provisional Patent Application No. 62/368,248, filed on Jul. 29, 2016, and titled “Additional Methods of Making Z-Grade,” where the contents of each application are hereby incorporated by reference in their entirety. The invention described herein was made in part by an employee of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. In some aspects, this disclosure relates to improved Atomic Number (Z) grade (“Z-grade”) materials, such as those used for shielding, systems incorporating such materials, such as Z-grade vaults, Z-grade electronic enclosures, and processes of making Z-grade materials. Satellites and instruments, among other things, may require shielding or spot shielding when in orbit or in other environments where there is exposure to radiation. Thus, shielding may increase the lifetime of ionizing radiation sensitive components. Other applications may include piping, housing, or suits designed to protect persons or materials from radiation. In various applications, shielding may help provide hardware design for increased orbital lifetimes, and enable out of low earth orbit (LEO) missions by using shielding for sensitive components. For geotransfer orbit (GTO), however, the radiation levels are around at least 10 times the level of LEO. In Jovian environments, the amount of radiation is still higher. Z-shields made from Z-grade material may provide cost-effective shielding for such systems by utilizing sheets or pieces of metal with different materials/densities, and thus including different atomic numbers (Z). For example, a higher density metal and lower density metal may be used together. The low atomic number materials slow high energy protons and electrons via collision more effectively without the production of Bremmstrahlung radiation. At lower energies, high atomic number materials can also slow protons and electrons with reduced Bremmstrahlung radiation. At the same time, the ability to use the high atomic number material may reduce the thickness of the overall shielding. As one example, known shielding applications utilize a typical outer skin of larger spacecraft with around 300 mils of aluminum, and combines this with additional spot shielding using higher atomic number materials that takes advantage of inherent low atomic number shielding on the outside surface. For smaller enclosures, known products may utilize a 50 mil thick aluminum skeleton or shell with limited shield potential. For an enclosure that must last for three to six months (as in many standards missions) or longer, this may be insufficient or may only last for these limited periods. While some Z-grade applications are known, additional compositions, applications, and synthesis methods may be desired. This Summary provides an introduction to some general concepts relating to this disclosure in a simplified form, where the general concepts are further described below in the Detailed Description. In some aspects, this disclosure relates to improved Z-grade materials and synthesis methods. For example, in one aspect, a Z-grade alloy material is disclosed. In some examples, the Z-grade material includes a high atomic number material, a low atomic number material, where the atomic number of the low atomic number material is lower than the atomic number of the high atomic number material (in some examples, if alloys or other combinations are used for either material, any atomic numbers of the low atomic number material are lower than any atomic numbers of the higher atomic number material). The low atomic number material may be bonded to the high atomic number material. The Z-grade material may include a diffusion zone, the diffusion zone including a mixed metallic alloy material, the alloy material including both the high atomic number material and the lower atomic number material. The use of the disclosed Z-grade materials allows for a one-piece shielding that has sufficient mass thickness (areal density) while reducing the physical thickness (volume) of the shielding. This provides the ability to provide effective radiation shielding in reduced volume or thickness applications such as, for example, small satellites, instrumentation, confined spaces and dimensions, etc. In some examples, the diffusion zone of the Z-grade material is at least 0.5 mil in thickness, in others it is at least 5 mil in thickness, and in others at least 10 mil in thickness. In certain examples, the thickness of the diffusion zone is equal to at least 10% of a thickness of the thinner of the high atomic number material and the low atomic number material (or both, if they have equal or essentially equal thickness). In other examples, it is essentially equal to the thinner of the two. In still other examples, the diffusion zone is actually thicker than the thinner of the two. In some embodiments, the high atomic number material comprises one or more of tantalum, tungsten, or a copper-tungsten alloy. In certain examples, the low atomic number material comprises one or more of aluminum or titanium. In some examples, the Z-grade material also includes an aluminum layer bonded the Z-grade material (e.g. bonded to the low atomic number material). In certain examples, the density of the diffusion zone is between or varies between around 4.4 g/cm3 and about 16.7 g/cm3 along the gradient. In some examples, the diffusion zone is a graded metallic alloy. In some examples, the Z-grade alloy material has an areal density of at least about 3.0 g/cm2. In various examples, the alloy material has an overall thickness of the Z-grade alloy material of about 240 mils or less, about 190 mils or less, about 140 mils or less, or about 100 mils or less. In accordance with another aspect, systems are disclosed. In some examples, the system is a housing, a vault, shield, or an enclosure (such as an electronic enclosure). In some examples, the system is a Z-grade vault. The Z-grade vault may include one or more surfaces of Z-grade material, where the one or more surfaces may include a high atomic number material and a low atomic number material, where the atomic number of the low atomic number material is lower than the atomic number of the high atomic number material, and where the low atomic number material is diffusion bonded to the high atomic number material. In some examples, the areal density of the Z-grade material is at least about 2.5 g/cm2, and wherein an overall thickness of the Z-grade alloy material is about 240 mils or less, about 190 mils or less, about 140 mils or less, or about 100 mils or less. In some examples, the areal density of the one or more surfaces of Z-grade material is at least about 3.0 g/cm2. In various embodiments, the Z-grade material further comprises an aluminum layer bonded to the low atomic number material. In accordance with another aspect, processes are disclosed. In some examples, the process may include combining a high atomic number material and a low atomic number material, where the atomic number of the low atomic number material is lower than the atomic number of the high atomic number material, and bonding the high atomic number material and the low atomic number together using diffusion bonding to form a Z-grade material. In various examples, the diffusion bonding includes vacuum pressing the high atomic number material and the lower atomic number material at an elevated temperature. In some examples, the method further includes (in addition to the diffusion bonding) vacuum pressing the Z-grade material at an elevated temperature. In certain examples, the elevated temperature is near a softening or melting point of the low atomic number material. In various embodiments, the process also includes cooling the Z-grade material under vacuum. In some embodiments, the diffusion bonding includes plasma spraying the low atomic number material onto a sheet of the higher atomic number material. In certain examples, the diffusion bonding includes welding the low atomic number material onto a sheet of the higher atomic number material using an electronic beam gun. In various embodiments, the diffusion bonding includes heating the low atomic number material under an inert atmosphere or a vacuum to its melting temperature, and coating a sheet (or other piece) of the high atomic number material with the melted low atomic number material. In some examples, the diffusion bonding includes ultrasonic layering of the low atomic number material onto the high atomic number material. In various examples of the process, the high atomic number material includes one or more of tantalum, tungsten, or a copper-tungsten alloy, and the low atomic number material comprises one or more of aluminum, titanium and vanadium. In certain examples, the formed Z-grade material includes a diffusion zone, where the diffusion zone includes a mixed metallic alloy material, the alloy material including both the high atomic number material and the lower atomic number material. These summary descriptions are merely provide examples of the processes and/or process steps that may be performed in one or more embodiments. In certain embodiments, materials and methods include additional combinations or substitutions. To that end, other details and features will be described in the sections that follow. Any of the features discussed in the embodiments of one aspect may be features of embodiments of any other aspect discussed herein. Moreover, additional and alternative suitable variations, features, aspects and steps will be recognized by those skilled in the art given the benefit of this disclosure. These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. The examples, materials and methods of described herein provide, inter alia, Z-grade materials, shielding components or systems, and processes of making the same. These and other aspects, features and advantages of the disclosure or of certain embodiments of the disclosure will be further understood by those skilled in the art from the following description of example embodiments. In the following description of various examples, reference is made to the accompanying drawings, which form a part hereof. It is to be understood that other modifications may be made from the specifically described methods and systems without departing from the scope of the present disclosure. It is also to be understood that the specific material, systems, devices and processes illustrated in the attached drawings, and/or described in the following specification, are simply exemplary embodiments. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting. Moreover, the figures of this disclosure may represent the scale and/or dimensions according to one or more embodiments, and as such contribute to the teaching of such dimensional scaling. However, the disclosure herein is not limited to the scales, dimensions, proportions, and/or orientations shown in the figures. In some aspects, this disclosure relates to improved Z-grade materials such as a Z-grade alloy material. FIG. 1 shows an example schematic view of a Z-grade material including a high atomic number material 101, a low atomic number material 102, where the atomic number of the low atomic number material is lower than the atomic number of the high atomic number material (in some examples, if alloys or other combinations are used for either material, any atomic numbers of the low atomic number material are lower than any atomic numbers of the higher atomic number material). The low atomic number material may be bonded to the high atomic number material. The Z-grade material in this example also includes a diffusion zone 103, the diffusion zone including a mixed metallic alloy material, the alloy material including both the high atomic number material and the lower atomic number material. In some examples, the diffusion zone includes a gradient of materials. For example, the example schematic of FIG. 1 shows a region with a relatively higher concentration of the high atomic number material 104, and a region with a relatively higher concentration of the low atomic number material 105. In some examples, the composition of the diffusion zone may be relatively uniform, however. In some examples, the diffusion zone of the Z-grade material is at least 0.5 mil in thickness, at least 1 mil, at least 2.5 mil, at least 4 mil, at least 5 mil, or at least 7.5 mil, while in others it is at least 10 mil in thickness, 25 mil, at least 40 mil, and in others at least 50 mil or 75 mil thickness. In some examples, it is 1-2.5, 1-5, 1-10, 5-10, 10-50 or 10-20 mil in thickness. In certain examples, the thickness of the diffusion zone equal to at least 10% of a thickness of the thinner of the high atomic number material and the low atomic number material (or both, if they have equal or essentially equal thickness). In other examples, it is essentially equal to the thinner of the two. In still other examples, the diffusion zone is actually thicker than the thinner of the two. As one example, a titanium layer may be approximately 100 mil, a tantalum layer approximately 8-10 mil, and the diffusion zone between the two is approximately 10 mil. In some examples, any of the layers may be between 1-500 mil, such as 1-100, 10-100, 1-10, 1-5, 5-10, 1-25, 5-25, or 50-100 mil. The Z-grade material may have an overall thickness suitable for its particular application, expected radiation levels, and/or applicable volume constraints. In some examples, the overall Z-grade material is at least 100 mil thick, in others at least 200, and in others at least 300. In other examples, the material provides the desired shielding characteristics while remaining under 400 mil, or under 300 mil, under 250 mil, under 200 mil, or under 150 mil. In comparison an aluminum (Al) shielding at 3.0 g/cm2 has a thickness of 434 mils and a titanium (Ti 6-4) shielding at 3.0 g/cm2 has a thickness of 267 mils. In some embodiments, the high atomic number material comprises one or more of tantalum, tungsten, or a copper-tungsten alloy. In certain examples, the low atomic number material comprises one or more of aluminum, titanium and vanadium. In various examples, aluminum and/or titanium materials are used to form an alloy with tantalum. Suitable example materials include Al 6061 or Ti6-4. In some examples, the Z-grade material also includes an aluminum layer bonded the Z-grade material (e.g. bonded to the low atomic number material, such as being bonded to titanium after a titanium/tantalum Z-grade material is formed). The optional addition of aluminum by diffusion bonding with titanium or brazing enables another lower atomic number material to be added. This may be advantageous for fast electron shielding where the Bremstrahlung critical energy can be increased, so as to reduce Bremstrahlung formation, when comparing aluminum to titanium. Titanium may also be used as an adhesive interlayer between aluminum and tantalum (or other high/low atomic number materials). In certain examples, the density of the diffusion zone is between or varies between around 4.4 g/cm3 and about 16.7 g/cm3 along the gradient. In some examples, the diffusion zone is a graded metallic alloy. In some examples, the density is at least 4.0 g/cm3 and up, 6.0 g/cm3 and up, 8.0 g/cm3 and up, 10.0 g/cm3 and up, or 12.0 g/cm3 and up. In various examples, the areal density of the entire Z-grade material is between 1.5 and 2.25 g/cm2 or between 2.5 and 3.0 g/cm2, or between 2.9 and 3.1 g/cm2. In some examples, it is 2.0 g/cm2, 2.25 g/cm2, 2.5 g/cm2, 2.75 g/cm2, 2.9 g/cm2, 3.0 g/cm2, or 3.1 g/cm2 or above, while in others it is between 1.6 and 1.7 g/cm2, and other between 1.5 and 2.0 g/cm2. The Z-grade materials may provide an integrated, single piece of shielding as opposed to prior systems using, e.g., additional spot shield of the second high atomic number material. This may be particularly useful for small satellites, or small instruments housing applications where shielding is needed in one or more areas, or to enclose an entire device/satellite/instrument/etc., but where there are volume constraints affecting the amount and type of shielding that may be utilized. By reducing shielding thickness through use of a high atomic number material (and optionally, as described herein, by making the low atomic number material denser via elevated temperature processes) the Z-grade materials may help enable shielding of small structures with less volume impact, when compared to typical aluminum shielding. Indeed, for one application example, the significant reduction in spacecraft volume will benefit from one piece Z-grade shields, as larger thickness aluminum shields would prohibit the incorporation of standard electronic cards in an enclosure, due to volume constraints. The Z-grade materials may have high densities for each material layer (as compared to layers obtained through prior formation methods), be flat and thus easy to incorporate into various systems, and have a strong weld or interface between layers. In some examples, a Z-grade material (such as one with Al/Ta or Ti/Ta, i.e. an aluminum/tantalum or titanium/tantalum material) a can reduce the overall thickness in half compared to standard (e.g. aluminum only) shielding but providing same areal density. As illustrated in FIG. 13, the electron shielding of an example Z-grade material is modeled having 30% greater shielding effectiveness and about the same proton shielding effectiveness compared to an aluminum shield. Specifically, the Z-shield properties have been estimated, using The Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have ˜30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The diffusion zone may enable a shielding property between that of a high Z material and a low Z material, without having to add another material layer. This can not only provide additional shielding benefits, but can help lower thickness and volume. Example Material Characteristics The remaining Figures of the application illustrate example properties that the Z-grade material and/or its constituent materials may provide. FIG. 2 is a graph illustrating the stopping power of Z-grade by modeling the energy loss of a 49.3 MeV proton beam, with varying materials having varying densities and thicknesses, and illustrating how the Z-grade materials may provide essentially equivalent shielding in conjunction with thinner materials. FIGS. 3-5 are EDAX images showing diffusion of titanium and vanadium into tantalum, and illustration a very uniform gradient of the Ti and Ta in the bonding area interface. FIG. 6 is a back scattered SEM image of diffusion bond formed over 256 hours between Ti and Ta. FIG. 7 is a EDAX image and data illustrating a diffusion zone of 124 microns and a higher CPS intensity for the titanium material for the material shown in FIG. 6. FIG. 8 illustrates the microhardness/Knoop hardness test (KHN) for a various layers (Ti, diffusion zone, and Ta) for 4, 16, and 256 hour diffused Ta—Ti interface, where the diffusion zone was about 130 microns. FIG. 9 illustrates the microhardness/Knoop hardness test (KHN) for a 256 hour diffused Ta—Ti interface, where the diffusion zone was about 130 microns. FIGS. 10A and 10B illustrate the microhardness/Knoop hardness test (KHN) for a 4 hour diffused Ta—Ti interface, where the diffusion zone was about 15 microns (FIG. 10A) and a 16 hour diffused Ta—Ti interface, where the diffusion zone was about 30 microns (FIG. 10B). FIGS. 11A-11C are scanning electronic microscope images of a Ti—Ta diffusion zone after 4 hours at 890° C. (FIG. 11A), 16 hours (FIG. 11B) and 256 hours (FIG. 11C) and with 50 mPa of pressure (which is an example possible value but not required). The lightest top layer is Ta, which most dramatically shows diamond scoring marks resulting from additional hardness tests, as it is a softer material. The diffusion zone is in the intermediate medium grey, which clearly increases in size as time increases, and the bottom, dark grey layers in these examples is Ti6-4, which is a harder material and therefore only has smaller scoring marks. FIGS. 12A-12C are spectra of various areas of a Ti/Ta Z-grade material. FIG. 12A is the Ti layer (Ti6-4) which has around 88.5% Ti, around 5.9% Al, and around 2.4% V (in other examples the V content may be around 4%). FIG. 12B shoes the spectra for the diffusion zone, where the amount of Ti is around 59.2% and the amount of Ta is about 28%, illustrating that Ti may diffuse more readily compared to Ta. FIG. 12C shows the spectra for the Ta layers, which was around 90.1% Ta. FIG. 13(a.) shows that with expected ionizing dose of 10-400 MeV protons, the Al/Ta has similar shielding performance to Al at approximately half the thickness. In FIG. 13(b.), a expected ionizing dose of 4-6.5 MeV electrons shows greater than 30% improvement in shielding effectiveness for Al/Ta over Al. The predominant radiation dose received behind the shielding samples originated from the proton ionizing dose. In FIG. 13(a.), the dose levels appear below 1 kRad for Al and Al/Ta at areal densities above 1.7 g/cm2, whereas Ta appears higher. In FIG. 13(b.), the electron radiation dose at areal densities above 1.7 g/cm2 appear below 200 Rad for Al/Ta and Ta. At areal densities greater than 2 g/cm2, the electron ionizing dose for the Al/Ta appears to be reduced almost completely. Overall, the expected accumulated total ionizing dose behind 3 g/cm2 shielding will originate from proton radiation. FIG. 14 is an electron image of an example Ti64/Ta material, with the Ti material at the top of the image, a diffusion zone in the intermediate part of the image, and the Ta material at the bottom of the image. Making the Z-Grade Material In accordance with another aspect, processes are disclosed. These may utilize metallurgy techniques to make one piece radiation shielding with layers of differing atomic numbers. In some examples, the process may include combining a high atomic number material and a low atomic number material, where the atomic number of the low atomic number material is lower than the atomic number of the high atomic number material, and bonding the high atomic number material and the low atomic number together using diffusion bonding to form a Z-grade material. In various examples, the diffusion bonding includes vacuum pressing the high atomic number material and the lower atomic number material at an elevated temperature. In some examples, the method further includes (in addition to the diffusion bonding) vacuum pressing the Z-grade material at an elevated temperature. In certain examples, the elevated temperature is near a softening or melting point of the low atomic number material. In various embodiments, the process also includes cooling the Z-grade material under vacuum. For some specific examples, vacuum pressure diffusion bonding is used, where layers of titanium (Ti) and tantalum (Ta) are bonded at elevated temperatures underneath the melt temperature of the Ti6-4 titanium material. As another example, Aluminum (Al) and a previously formed Ti/Ta material is vacuum pressured diffusion bonded to make Al/Ti/Ta Z-grade. This additional bonding uses welding at a relatively lower temperature under vacuum, under the melt temperature of aluminum. These examples utilize layering and diffusion bonding. For another specific example, a diffusion gradient Z-grade may be formed with titanium/tantalum. A Ti6-4/Ta sample may be produced via diffusion bonding at elevated temperature for extended time periods to allow a large diffusion zone between titanium and tantalum to take place. This improves the gradient of the Z-grade by having a greater distribution of titanium and tantalum in the diffusion zone (again, different suitable materials and metal or metallic alloys may be used in this and all other examples specifically identifying a material, and the elevated temperatures may be adjusted accordingly relative to the different melt temperature). This maximizes the Z-grade of the low atomic number to high atomic number by creating an extended diffusion gradient of the alloys between majority titanium to majority tantalum to form a graded diffusion zone alloy. In some examples, the density gradually increases between the two starting materials. The diffusion zone can thus be expanded, for example to 5 mils, which is 10 times thicker than typical bonding applications. This additional diffusion zone may create a new shielding layer with an actual atomic number gradient. This can be further exploited to create intermediate densities of graded alloys between a low atomic number and high atomic number material. In turn, this will shield fast electrons and heavy ions, such that the radiation can be even further reduced with a simpler material lay-up while retaining the benefit of thickness reductions. The addition of aluminum on Ti/Ta has substantially improved the atomic number Z-grade with the addition of low atomic number aluminum. The use of an additional aluminum layer (or simply Z-grade utilizing aluminum) reduces Bremstrahlung radiation in shielding applications for fast electron applications for the Jovian environment where the energy critical point for Bremstrahlung formation, i.e. Ecollision loss=Eradiative loss, is estimated at 51.0 MeV. Therefore the dominant 30 MeV Jovian electrons can be slowed down with reduced Bremstrahlung formation. The critical energy for titanium is estimated at 34.5 MeV. These critical energy calculations are from pg. 41, W. R. Leo, “Techniques for Nuclear and Particle Physics Experiments, 2nd Edition, Spring Verlag, Berlin, 1194, page 378 (which is expressly incorporated by reference). In short, there is a significant reduction in Bremstrahlung formation with the incorporation of Al to Ti/Ta for fast electron shielding applications. Any important feature of this disclosure is that for Ti/Ta Z-grade materials (and others) these can be manufactured much more simply by using high temperature vacuum press diffusion bonding. In this case there are also radiation shielding benefits available by being able to shape the material using diffusion bonding techniques through use of, e.g. Ti and Ta. For example, one may add separate faces of a cube and/or frame pieces together (or other shapes/components) and under pressure (e.g. by screws) form a shaped structure such as an electronic enclosure to create a seamless joint, as a result of the diffusion bonding, as self-welding that can occur at the joints. For high energy particle radiation shielding, the low atomic number material can be used to shield fast electrons such as the 30 MeV electrons found in the Jovian environment or the earth electron belt. It can also shield high energy protons, such as ones found from solar radiation or the earth inner proton belt with reduced Bremstrahlung formation. In many vault applications or enclosure applications 3 g/cm2 aluminum has been used in the past, where this past example is often about 434 mil thick. A Z-grade with Al/Ta or Ti/Ta can reduce the thickness in half (or even more, as described below, e.g. by around 70% or 80%) with the same areal density. The electron shielding of the Z-grade with 50% thickness reduction is modeled having 30% greater shielding effectiveness and about the same proton shielding effectiveness. Recent shielding modeling (FIG. 2) show that Al/Ti/Ta and Ti/Ta Z-grades had slightly lower stopping powers Al/Ti/Ta (10.1 MeV cm2/g) and Ti/Ta (9.4 MeV cm2/g) compared to baselines Al (13.8 MeV cm2/g) and Ti (11.5 MeV cm2/g). The proton shielding models show that Ti/Ta and Al/Ti/Ta could be used as a substitute for Al shielding applications. The Ti may also add a structural component. Another advantage of the process is the vacuum pressing at elevated temperature is a relatively cheap technique. The other welding techniques such as ultrasonic and friction stir welding and electron beam freeform fabrication can make the shielding materials additively using powder, wire, foil, and sheet. These other methods take advantage of welding, diffusion bonding methods. The additive approaches also enable making 3D and multilayer constructions. As mentioned above, another unique feature of this disclosure is the ability to make an extended diffusion zone, which may create a graded alloy between two materials. For example, extending the diffusion times in high vacuum oven at an elevated temperature (e.g. 890° C., but other appropriate temperatures based on the material may be used) may create an extended diffusion zone. These times may be 2 hours or hour, 4 hours or more, 8 hours or more, 12 hours or more, 16 hours or more, 1 day or more, two days or more, 4 days or more, 7 days or more, or 10 days or more. In some examples, 4 hours of diffusion time at 890° C. resulted in a 17 micron diffusion zone. Raising the temperature (such as to 1200 or 1300° C.), can further enhance the diffusion zone extension. For example, raising the temperature from 890° C. to 1200° C. will increase the diffusion rate for the thermal dependence on the Arrhenius equation. It will also increase because titanium will be in the beta phase, a BCC structure. In cases, the diffusivities differ between BCC and HCP between 1 and 2 orders of magnitude. In some examples, a limiting factor in increasing the area of the diffusion zone is the diffusion coefficient of the tantalum and Ti-6-4 in the alpha phase, hexagonal close pack phase, at 890° C. The diffusion rates of a hexagonal close packed phase can be up to 5 times slower than in a body centered cubic phase. Tantalum is in a body centered cubic phase. Therefore increasing the temperature for the diffusion bonding may increase the inter-diffusion between tantalum and titanium and increase the size of the diffusion zone. If the temperature is raised to 1200-1300° C., for example, the diffusion rate will increase. Other suitable temperatures are around 900, 950, 1000, 1100° C. (or above). The only trade-off is that the titanium will have to go through a phase transition and on cooling the tantalum/titanium layered material may curl or warp slightly. But when this occurs, the material may be flattened, for example at a slightly elevated temperature, as illustrated below. Increasing the temperature and diffusing in the beta phase of titanium will also contribute to conditions for making a larger Z-grade in a shorter amount of time. By providing an extended diffusion zone, this results in a new shielding approach where the Z-grade occurs with an actual density gradient. Current Z-grade systems are at best systems using multiple and separate layers: such as spacecraft skin, avionics case, and a single layer or two layer spot shield. For example, in formation of a Ti/Ta Z-grade material using extended diffusion times of 256 hours, this makes a new intermediate density material between Ti6-4 density of about 4.43 g/cm3 and Ta density of about 16.69 g/cm3. This enables a shielding property between that of a high Z material and a low Z material, without having to add another material layer. And the addition of aluminum by diffusion bonding with Ti or brazing enables a yet another lower atomic number material to be added. This is significant for fast electron shielding where the Bremstrahlung critical energy can be increased, so as to reduce Bremstrahlung formation, when comparing Al to Ti. In these examples, the titanium can also be used as an adhesive interlayer between Al and Ta. This has been demonstrated with an Al/Ti/Ta material sample as described herein. First, a Ti/Ta material is diffusion bonded together using Ti and Ta sheets at elevated temperatures at 850-890° C. (as an example). Then Al can be diffusion bonded to the Ti sheet of Ti/Ta in order to take advantage of Al being able to bond with Ti at a lower temperature, underneath the melting point of Ti. Therefore, low atomic number materials such as Al or alloys of Al can be adhesively bonded with Ti or similar reactive materials of higher melting point with tantalum or other refractory materials such as tungsten or tungsten alloys, such as tungsten copper. The benefits of these Z-grade shielding arc for applications with small satellites or instrument enclosures where volume reduction is important and the need to effectively shielding high energy particles necessitates a layered approach for volume and shielding effectiveness. In some embodiments, the diffusion bonding includes thermal spaying, such as plasma spraying, the low atomic number material onto a sheet of the higher atomic number material. The thermal spraying may include plasma spraying or RF plasma spraying. RF plasma spraying titanium or aluminum onto a tantalum sheet has a high chance of welding at the interface. Both titanium and aluminum are known to alloy with tantalum once the aluminum or titanium is added to the tantalum. The titanium or aluminum layered tantalum can then be vacuum hot pressed near the softening points of the low atomic numbered materials, e.g. the aluminum or titanium, to increase the density of the low atomic number material on top of the tantalum sheet. Al 6061 or Ti6-4 plasma spray powder may be used to take advantage of its alloy property. In certain examples, the diffusion bonding includes welding the low atomic number material onto a sheet of the higher atomic number material using an electronic beam gun. This may utilize a wide feed (e.g. a dual wire feed) and the electron beam gun to depositing the material. For example, the process may use Electron Beam Freeform Fabrication (EBF3) aluminum or titanium wire layered onto tantalum material (e.g. a sheet). This process would take advantage of the welding technology of the EBF3. The EBF3 method allows another way of adding a dense layer of low atomic number material or alloy onto the higher atomic number material, such as tantalum or tungsten, which are refractory metals and hard to melt. After the process is done, the layered sheet material may have warped in shape due to the thermal stresses of the welded EBF3 material. This bilayer material can then be added to a vacuum hot press just below the melt temperature of the aluminum or titanium to soften and cool in the vacuum press to remove the warp. Again, Al 6061 or Ti6-4 may be used to take advantage of its alloy property. In various embodiments, the diffusion bonding includes heating the low atomic number material under an inert atmosphere or a vacuum to its melting temperature, and coating a sheet of the high atomic number material with the melted low atomic number material. As an example, the bonding may include casting Al or Ti on top of tantalum or tungsten or CuW sheet. This process may be by accomplished by heating Al or Ti or alloys thereof under an inert atmosphere or in vacuum to the melting temperature. The molten Al or Ti would then coat over the tantalum or tungsten material (e.g. a sheet). Al and Ti can form alloys with tantalum and thus make a strong interface with these materials (e.g. a sheet of the material). On cooling, if the tantalum or tungsten sheet warps due to thermal stress, then the resulting Al or Ti coated tantalum or tungsten sheet can be placed into a vacuum hot press and heated until Al or Ti softens, just below the melt temperature, such that the pressure straightens the bilayer sheet. Then it is cooled while under pressure to retain the flatness. In some examples, the diffusion bonding includes ultrasonic layering of the low atomic number material onto the high atomic number material. For example, the bonding may include ultrasonic layering of (a) Aluminum or Titanium foil onto tantalum or tungsten or CuW sheet, (b) tantalum or tungsten or CuW foil onto aluminum or titanium sheet, (c) tantalum or tungsten foil onto aluminum or titanium foil, or (d) aluminum or titanium foil onto tantalum or tungsten foil. A forged or high density layer may be formed. In some examples, a larger area is made, e.g. at least 10 v. 10 cm, or having at least 100 cubic centimeters in area (but larger or smaller squares, rectangles, or other geometric or none geometric shapes are suitable for the Z-grade materials (made via this example process or others), such areas as 200 cubic centimeters or more, 500 or more, 1000 or more, and so on). In some examples, the layers are flat, so the layered materials may be placed in a vacuum hot press to just below the melt temperature of the low atomic number material, such as aluminum or titanium. This may provide a strong interface (good weld), a flat large area sheet, and high densities for each elemental material or alloy. In this manner, however the initial Z-grade material is made (e.g. ultrasonic v. plasma spraying or others), additional desirable characteristics may be obtained. In various examples of the process, the high atomic number material includes one or more of tantalum, tungsten, or a copper-tungsten alloy, and the low atomic number material comprises one or more of aluminum or titanium. In certain examples, the formed Z-grade material includes a diffusion zone, where the diffusion zone includes a mixed metallic alloy material, the alloy material including both the high atomic number material and the lower atomic number material. Example Applications and Systems The applications of the Z-grade material are numerous, but these improved materials may be particular advantages for satellites or other space applications such as shuttles. For example, a research payload could be made with the Z-graded radiation shields of varying thicknesses. As another example, an engineered Z-grade radiation shielding vault may protect a system's electronic boards. Other housings, encloses, surfaces, or spot shields may be made. In some examples, one or more surfaces and/or other pieces of Z-grade material may be fastened, attached, bonded or joined to each other, a frame pieces or entire frame, or another object to form a partial or full enclosure. In other examples, there may be a skin or surface on the exterior of a satellite or shuttle comprising the Z-grade material, or a housing enclosing one or more parts or components, that comprise the Z-grade material in the entire housing or in one or more sections of the housing. The improves processes described herein enable cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. This in turn may provide for increased mission lifetimes, and enable, for example, out of low earth orbit (LEO) missions. For example, the Al/Ta Z-grade material may offer a thickness reduction approaching half of a typical 3 g/cm2 (1.1 cm) Al shield. With materials dimensions of approximately 10 cm×10 cm×10 cm (1000 cm3) the loss of electronics card volume area and cable volume would be 295 cm3 or −30% of the volume. A shielding thickness of a 0.5 cm Z-grade would only have a volume reduction of −14%. At the same time, the Z-grade material performs similar to Al for the proton environment and over 30% more effective at areal densities of 1.7 to 2.2 g/cm2 for an electron environment. The addition of Z-grade shielding thus can offer the reduction of total ionizing dose on sensitive electronic components, such as memory cards and CMOS devices. The near complete elimination of electron radiation at areal densities greater than 2 g/cm2 reduces the chance of internal charging effects on electronic that causes anomalies. The use of the Z-grade radiation shielding enables shielding applications in volume constrained small satellites and instrument enclosures, where typical aluminum shielding is volume prohibitive. As another example, a Ti/Ta Z-grade material may offer a thickness reduction compared to known shielding materials (e.g. the standard 434 mil Al shield) of up to about 70% of a typical 3 g/cm2 (1.1 cm) Al shield, or even about 80%. In some embodiments, a Ti/Ta material has an overall thickness of about 140 mils (i.e. about 0.36 cm) and an areal density of 3.0 c/cm2, where the Ti layer is about 105 mils (i.e. about 0.27 cm) and the Ta layer is about 40 mils (i.e. about 0.09 cm). For an example incorporating the additional Al layer, a Z-grade material with (at least) the desired areal density has an Al layers of 0.23 cm, a Ti layers of 0.16 cm and a Ta layer of 0.09 (i.e. about 90 mils, about 63 mils, and about 40 mils). In some examples, a relatively thin Ti (or other low atomic number materiel) layer is used, diffusion bonded to a high atomic number material, and then an additional Al layer is brazed on (e.g. after the materials are cleaned). The diffusion zone may relatively extended to make the e.g. Ti layer even thinner by extending the gradient and lengthening the diffusion zone incorporating the high atomic number material. As another example, the diffusion conditions may be such that the large amounts (e.g. 50% or more, 70% or more, or 90% or more) or even essentially the entire high atomic number material diffuses into the lower atomic number material, providing increased density while lowering overall thickness. For these relatively thin materials (e.g. having a total thickness of about 190 mils or less, 160 mils or less, 150 mils or less, 140 mils or less, 125 mils or less, 110 mils or less, 100 mils or less, 95 mils or less or 90 mils or less), that still provide an areal density sufficient for shielding (e.g. around 3.0 or at least 3.0) one of more sheets of the materials may be connected to form a vault or housing (e.g. to define a square or rectangular area, or any other shape as needed for a particular electric component or other object that requires shielding). Where high degrees of thinness is needed, the amount of Tantalum (or other high atomic number material) may be increased and formed into an alloy with a low atomic number material (e.g. Titanium) to form a thin but dense layer. While this may not be as strong structurally as other examples, another layer of e.g. Ti (or another low atomic number material) may be added and more briefly diffused in to help the mechanical properties of the material. For example, an initial Ti layer with a 10-20 mils diffusion interface, where Ta is diffused all the way through the interface to form an alloy, and then another Ti layer is added but diffused less (e.g. so the additional interface is less) to provide structural support. Thus, the low atomic number material (or different low atomic number materials) may be diffusion bonded twice, once to form an alloy, and the second time primarily for structural reinforcement. As further illustrative embodiments, one example material is 145 mil (0.363 cm) thick, with Ti (105 mil)/Ta (40 mil). Another material (e.g. for use in a shield or vault or housing) is 125 mil (0.317 cm) thick, with 50 mil Ta (2.15 g/cm2)/35 mil Ti (0.393 g/cm2) that are initially diffusion bonded over extended periods of time, and then another Titanium layer that is diffusion bonded to the Ti/Ta alloy, that is 40 mil (0.461 g/cm2). The additional Ti has greater strength than the Ti in the extended diffusion bonded layer. The densities of these materials are Ti-6−4=4.43 g/cm3, Ta=16.68 g/cm3. As yet another example, a material (e.g. shield material) is 97 mil (0.248 cm) thick, with 60 mil Ta (2.58 g/cm2)/37 mil Ti (0.42 g/cm2). This is a Ti/diffusion gradient alloy/Ta Z-grade created by diffusion bonding over extended periods of time. The densities of these materials are Ti-6-4=4.43 g/cm3, Ta=16.68 g/cm3. As yet another example, a Al/Ti/Ta material may have dimensions of about 190 mil (0.483 cm) and an areal density of 3.0 g/cm2′ In this examples, the Al material is about 89 mils (˜0.226 cm/0.610 g/cm2), the Ti material is about 63 mils (0.160 cm/0.71 g/cm2) and about 40 mil Ta (0.102 cm/1.72 g/cm2), for total properties of about 0.488 cm thickness/3.04 g/cm2. This example may be made by the Ti/Ta diffusion bonding and then brazing Al to Ti. For another example material, a Al/Ti/Ta material may have a thickness of about 240-250 mil at about 3.0 g/cm2, with a very thin Ti layer that acts as interface material for the Al layer (e.g. about 40 mils or less, about 30 mils or less, about 20 mils or less, about 15 mils or less, about 10 mils or less, or about 5 mils or less). Thus, this example is almost only composed of Al and Ta, with only Ti being used as an interface. One may ultrasonic weld the Al to Ta directly and this is preferable to diffusion bonding the Al to Ta, as the Al may melt before diffusion bonding can occur with Ta, which has a very high melting point. Ti working as an interface, however, can more easily allow the creation of materials with the desired characteristics. The use of Ti for diffusion and compatibility with the Al brazing is extremely important at bringing together metals that can't go to high temperatures. Still other materials may be used for the Z-shielding systems, such a nickel-cobalt alloy, or a nickel-cobalt iron alloy (optionally with small amounts of other materials such as carbon, silicon, and/or Mn). For example, the commercially available Kovar® allow has been used for some single layer shielding applications because it can be used for hermetic sealing of spot shields. This material may also braze to aluminum and diffusion bond with Titanium. As illustrated here, any group IV metal (or metals) with the necessary thermal properties may be used as the low atomic number material or materials as long as other detrimental properties (e.g. poor mechanical characteristics, toxicity, and the like) are present. Other high atomic number materials may also be used, such as Group VI metals (with the same caveats noted about regarding e.g. mechanical properties), such as Tungsten and Tungsten-Copper alloys, or Tantalum alloys such as Ta/W alloys. To illustrate a vault system and the benefits of the above example materials, a vault may enclose an electronic board. In some examples, the board may have outer dimensions of about 9-10 cm×9-10 cm. Using the example materials above, and assuming board dimensions of 9.0 cm and 9.6 cm, and an outer housing dimension of 9.98 cm, the follow calculations illustrate the benefits of lowering thinness while retaining shielding capability. First, using the 145 mil Z-grade, a 9.98 cm outer dimension minus the 0.363 cm for the shielding material thickness gives 9.617 cm. Subtracting the 9.6 cm board dimension effectively leaves no additional space, but another surface of shielding material is needed to enclose the board. Thus, using these example dimensions, it is necessary to obtain an additional 0.346 cm of space from reduction of board dimension through shaving off pieces, removing corners, and the like, rather than using the standard size. For the second example material (125 mil), using the 0.319 cm shielding thickness (and using the same calculation), 0.256 cm of additional space is needed. For the third example material (97 mil), using the 0.248 cm shielding thickness, only 0.116 cm of additional space is needed. By providing increased density, vaults and enclosures can be made for a relatively small investment compared to the high costs for other equipment utilized in typical missions (e.g. system electronics, solar panels, etc.). At the same time, these systems and materials can extend mission lifetimes up to ten years for low earth orbits and eight years for geostationary orbits (compared to typical designed lifespan on the order of months) with typical electronic cards, allowing the systems to forego more expensive radiation tolerant cards. Thus, the systems advantageously allow a reduction in volume while enabling longer duration missions. These materials, systems and process descriptions are merely examples. In certain embodiments, the materials and systems includes additional combinations and/or substitutions of some or all of the components described above. Moreover, additional and alternative suitable variations, forms and components for the materials and systems will be recognized by those skilled in the art given the benefit of this disclosure. Finally, any of the features discussed in the example embodiments of the processes may be features of embodiments of the materials and/or systems (or components thereof), and vice versa (e.g. any material examples can be used in any system (such as but not limited to vaults, housings, enclosures, and spot shields) and any example materials described in reference to a system may be utilized as a stand-alone material or for other purposes than those discussed in the example system).
041586395	summary	BACKGROUND This application relates to a process for the storing of gas by high temperature and pressure absorption, aadsorption or reaction with a capturing solid bed. In particular, the process relates to storing radioactive krypton (.sup.85 Kr) and other gases absorbed in zeolites. Other applications will become apparent to those skilled in the art. The encapsulation of gases in zeolites is known and it has been taught that the encapsulation of radioactive krypton (.sup.85 Kr) takes place under high temperatures and pressures. (See Brown et al. ".sup.85 Kr Storage by Zeolite Encapsulation," 14th ERDA Air Cleaning Conference). Following the absorption and cooling, the pressure may be lowered without the loaded zeolite releasing the krypton. The process suggested to date for encapsulation has a distinct drawback; namely, it cannot be carried out without contamination of the autoclave reaction vessel; and/or the atmosphere. For example, it has been proposed to place the zeolite in a mesh basket, to lower the basket into an autoclave and to pressurize the autoclave with krypton. After loading the zeolite, the excess krypton is pumped out of the autoclave and the basket is removed through the atmosphere and placed in a sealable container for storage. The possibilities for contamination of the atmosphere are many. Worse yet, the loaded zeolite can be exposed to moisture in the air. As krypton 85 decays, rubidium 85 is produced which can react with the absorped moisture to form a strong caustic and hydrogen. The caustic can cause corrosion of the container and the hydrogen can result in gas pressure buildup in the container. It is an advantage according to this invention to provide a process for the encapsulation of radioactive gas or the like without exposing the atmosphere or even the interior of the autoclave to the dangerous gas. The process has application where it is desired to react gases with capturing solids at elevated temperatures and pressures. SUMMARY OF THE INVENTION Briefly, according to this invention, there is provided a process of storing gas by high temperature and pressure absorption, adsorption or reaction with the bed of capturing solids comprising a first step of placing the capturing solids in a relatively thin-walled container having an opening therein connectable to a conduit. The container need only be able to withstand small pressures across its body of say 25 psi. Preferably the container has a relatively large opening at the top for introducing the capturing solids to the container and a lid sealing the large opening. Built into the lid is a valve which, when opened, provides communication between the interior of the container or canister and a fitting connectable to a conduit. A second step of the process comprises placing the thin-walled container in a pressurizable autoclave. A third step comprises bringing the interior of the thin-walled canister into communication with a conduit extending through the walls of the autoclave and communicating with a source of the gas to be stored. Typically, this comprises a connection between the fitting above described and a fitting in the wall of the autoclave. A fourth step comprises simultaneously pressurizing the autoclave and the interior of the thin-walled vessel by pumping gas to be stored into the thin-walled vessel and inert gas into the autoclave external the thin-walled vessel. The gas to be stored is continuously pumped into the thin-walled vessel as it is being absorbed, adsorbed or reacted with the capturing solids. When the bed of solids can no longer capture additional gas, a fifth step comprises first cooling and thereafter depressurizing the autoclave and the thin-walled vessel. In a final step, the autoclave is opened; the conduit from the thin-walled vessel disconnected; the vessel is sealed and removed to provide a substantially nonpressurized container loaded with absorbed, adsorbed or reacted gases.
	description	1. Field of Invention This invention relates to an ion implantation method and, in particular, the method can improve the uniformity of ion implantation. 2. Background of the Related Art The different stages of an implantation method according to the prior art are shown in FIG. 1a˜FIG. 1d. An ion beam scans a substrate S along a scan path to implant ions onto the substrate surface and forms a plurality of parallel ion implantation scan lines on the surface of the substrate S, that is called an ion implantation scan pass. As shown in FIG. 1a for explaining the execution of one ion implantation scan pass, the ion beam implants ions on the substrate S along a first direction, the direction parallel to that of a first scan path 21, to form an ion implantation scan line. And then the ion beam shifts with a scan pitch T in a second direction perpendicular to the first direction. Continuously, the ion beam implants ions onto the substrate S along the reverse direction of the first direction to form another ion implantation scan line. The procedure is repeated to form a plurality of ion implantation scan lines on the substrate till the scan area covers the whole substrate S. In FIG. 1a, the plurality of ion implantation scan lines is marked 1 and the arrow mark 100 represents the orientation of the substrate S. Next, the substrate is rotated by 90 degree on the plan of the substrate S, and the ion beam is shifted with an interlace pitch T/2 (half scan pitch) along the second direction. And then the procedure of the ion implantation scan pass is repeated to form a plurality of ion implantation scan lines 2, which is perpendicular to the direction of the plurality of ion implantation scan lines 1, and the dotted lines represent the second scan path 22 as shown in FIG. 1b. The step shown in FIG. 1b is then further repeated two times, so as to complete the third time and the forth time of the ion implantation scan pass to form another plurality of ion implantation scan lines 1 and 2, as shown in FIG. 1c and FIG. 1d, respectively. Rotate the substrate S by 180 degree (i.e. continuous two rotations of 90 degree). The ion implantation scan lines formed by the first time of the ion implantation scan pass overlaps the ion implantation scan lines formed by the third time, and the ion implantation scan lines formed by the second time overlaps the ion implantation scan lines formed by the forth time. Therefore the third time and the forth time of the ion implantation scan pass are still marked 21 and 22, and the plurality of ion implantation scan lines formed are also still marked 1 and 2. The dose of the ion implantation on the surface of the substrate S is illustrated in FIG. 2, where D(x) represents the distribution variation function of the dose. The larger value of D(x) is, and the worse the uniformity is. On contrary, the smaller value of D(x) is, the better the uniformity is. For one ion implantation scan line, the farther the ion beam is away from the center of the ion implantation scan line, the smaller the dose of the ion implantation is. The first time of the ion implantation scan pass overlapping the third time of the ion implantation scan pass and the second time of the ion implantation scan pass overlapping the forth time of the ion implantation scan pass renders a larger value of the distribution variation function D(x), resulting in a poor uniformity. It is an object of this invention to provide an ion implantation method, which can improve the uniformity of the dose of the ion implantation. The method shifts the ion beam with an interlace pitch in the direction perpendicular to the scan direction, and the interlace pitch makes that ion implantation scan lines formed on substrate at 0 orientation degree do not overlap ion implantation scan lines formed on substrate at 180 orientation degree, and the uniformity is thus improved. For understanding this invention better, a quad ion implantation method according to an embodiment of this invention is illustrated and shown in FIG. 3a-FIG. 3d. As shown in FIG. 3a, ion beam finishes an ion implantation scan pass along a ion scan path 210, and ions are implanted onto the surface of a substrate S to form a plurality of ion implantation scan lines 10, where the arrow mark 100 represents the orientation of the substrate S. The ion implantation scan pass is illustrated as follows. First, the ion beam scans the substrate S along a first direction of a scan path 210 to implant the ions onto the surface of the substrate S to form an ion implantation scan line. And then the ion beam shifts with a scan pitch T along a second direction, which is perpendicular to the first direction and parallel to the plan of the substrate S. Continuously, the ion beam implants the ions onto the substrate S along the reverse direction of the first direction to form another ion implantation scan line. The procedure is repeated to form another plurality of parallel ion implantation scan lines and so on till the scan area contains the whole substrate S. Next, the substrate S is rotated by 90 degree, and then a second time of the ion implantation scan pass follows along the scan path 220, as shown FIG. 3b. Before proceeding the second time of the ion implantation scan pass, the ion beam is shifted with an interlace pitch T/4 (quarter of the scan pitch T) so as to form another plurality of ion implantation scan lines 20 after the second time of the ion implantation scan pass. The plurality of ion implantation scan lines 20 is perpendicular to the plurality of ion implantation scan lines 10. Continuously, the substrate is rotated by 90 degree again, and then ion beam is shifted with an interlace pitch T/4, and a third time of the ion implantation scan pass follows along the scan path 230 as shown in FIG. 3c. The plurality of ion implantation scan lines 30 are formed and parallel to the plurality of ion implantation scan lines 10. The similar procedure is preceded again. Rotate the substrate S by 90 degree, and shift the ion beam with the interlace pitch T/4, and a forth time of ion implantation scan pass follows along the scan path 240 as shown in FIG. 3d. A plurality of ion implantation scan lines 40 are formed and parallel to the plurality of ion implantation scan lines 20. The plurality of ion implantation scan lines 10 shown in FIG. 3a and the plurality of ion implantation scan lines 30 shown in FIG. 3c are parallel to each other but interlaced by an interlace space T/2. In the same reason, it can be understood that the plurality of ion implantation scan lines 20 shown in FIG. 3b and the plurality of ion implantation scan lines 40 shown in FIG. 3d are parallel to each other but interlaced by an interlace space T/2 also. It is noted that the motion of shifting the ion beam during an ion implantation scan pass is achieved by the movement of either the ion beam or the substrate S itself. The uniformity of the dose is shown in FIG. 4 and illustrated as follows. The parallel pluralities of ion implantation scan lines are interlaced by an interlace T/2, so the value of distribution variation function D(x) is reduced, and therefore the uniformity is enhanced. The quad ion implantation method can be extended to any orientation of the substrate S. The point is that, after rotating the substrate S by 180 degree, the formed ion implantation scan line must lie between two ion implantation scan lines formed before substrate S was rotated i.e. when the orientation of S is 0 degree. The general method is explained as follows. At the 0 degree orientation of the substrate S, an ion implantation scan pass is proceeded. Continuously, the substrate S is rotated by 180/n degree and the ion beam is shifted with an interlace pitch T/2 n, where n is a positive integer equal to or larger than 2 and T is the ion scan pitch. One ion implantation scan pass is proceeded for each rotation of the substrate S, and that is repeated for 2 n−1 times till covering the whole substrate S. The method is called 2 n ion implantation method, for example, the method is called quad ion implantation method as n=2. Although this invention has been explained in relation to its preferred embodiment, it is to be understood that modifications and variation can be made without departing the spirit and scope of the invention as claimed.
053575547	description	DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, a radiographic system 10 includes an X-ray tube 11 directed to project a beam of X-rays 14 through soft tissue 16 toward a conventional X-ray sensitive medium 18. After passing through the medium 18, the X-rays are detected by an exposure detector 20, such as that described in U.S. Pat. No. 4,970,398 entitled "Focused Multi-Element Detector For X-Ray Exposure Control." A radiographic grid assembly 22 is located between the soft tissue 16 being imaged and the medium 18 to block scattered X-rays. The grid assembly 22 is composed of a grid 26 formed by a series of spaced apart X-ray absorbing vanes 24 which are aligned or "focused" to the X-ray tube 11. The vanes 24 form channels of a given width and height which prevent scattered X-rays from reaching the medium 18. One side of grid 26 rides on base members 28 which permit the grid to move in the reciprocal directions indicated by arrows 30. A U-shaped drive bracket 32 is attached to the opposite side of the grid 26 from members 28. A support 34 on fixed base 49 is positioned within the opening of the drive bracket 32 and has rods 36 and 38 extending outwardly therefrom through apertures in each leg of the bracket. The drive bracket 32 is able to slide on the rods 36 and 38 as the grid 26 reciprocates in the directions indicated by arrows 30. One leg 40 of drive bracket 32 has a threaded aperture therethrough which receives a threaded shaft 42 of a bidirectional stepper motor 44 that is attached to base 49. As the stepper motor 44 drives shaft 42, the radiographic grid 26 moves in one of the directions indicated by arrows 30 depending upon the direction of rotation of that shaft. As is well-known, stepper motors provide a very accurate incremental movement of a shaft as will be described each time the motor is driven by a step signal. The grid assembly contains a mercury tilt switch 46 which closes when the grid assembly 22 is tilted into vertical orientation as occurs when the X-ray apparatus 10 is swiveled orthogonally to the orientation shown in FIG. 1. The tilt switch 46 is positioned at an angle of approximately 20 degrees from horizontal in the orientation of the system 10 shown in FIG. 1. When the edge 45 of the grid 26 is above the motor 44 by a given amount, the tilt switch 46 closes, providing a signal to a control circuit for the motor, as will be described. The grid assembly 22 also contains a electro-optic sensor 48 which produces a signal when the grid 26 is at either of the two extremes of its travel, known as "home positions." The electro-optic sensor 48 is mounted on base 49 of the grid assembly 22 and is a standard device having a light emitting diode and a phototransistor with a gap therebetween, as shown in FIG. 2. A shutter plate 47 is mounted on the grid 26 so as to pass between the diode and phototransistor of the electro-optic sensor 48 as the grid moves. The shutter plate 47 is shown schematically in FIG. 2 and is slightly shorter than the maximum travel of the grid 26. Thus, when the grid is at either end of its travel, the shutter plate 47 will clear the electro-optic sensor 48 allowing the diode to illuminate the phototransistor, which produces a signal designated HOME. FIG. 2 depicts a control circuit 50 for operating the stepper motor 44. Control circuit 50 includes microcomputer 52 that contains a microprocessor, random access memory, read only memory and associated components. The program for controlling the operation of the grid assembly 22 is stored within the read only memory of the microcomputer 52. The microcomputer 52 receives an EXPOSURE signal via line 53 from a conventional main control system (not shown) of the radiographic system 10. This EXPOSURE signal goes to an active logic level when the main control system initiates an X-ray exposure and remains at the active logic level until the main control system determines that the X-ray exposure should be terminated. The main control system for the radiographic apparatus 10 receives a signal designated AT SPEED from the microcomputer 52 indicating that the grid 26 has reached a normal operating speed. This signal may be produced a given interval of time after the microcomputer 52 begins activating the stepper motor 44. In another implementation of the present invention, the microcomputer 52 ramps up the speed of stepper motor 44, in which case the AT SPEED signal is produced when microcomputer 52 has ramped the stepper motor up to the full operating speed. The microcomputer 52 also receives the signal from tilt switch 46 and a HOME signal from the opto-sensor 48 which indicates when the grid 26 is in one of the home positions. The microcomputer 52 responds to these input signals by producing a set of output signals which controls the direction and speed of the stepper motor 44. The application of power to the stepper motor 44 is governed by a conventional stepper motor driver 54. The microcomputer 52 produces an ON/OFF signal which activates the stepper motor driver 54. The direction in which the stepper motor 44 is to rotate shaft 42 is determined by a DIRECTION signal from the microcomputer 52 and each time that the stepper motor is to incrementally advance in that designated direction, the microcomputer sends a STEP signal pulse to the stepper motor driver 54. The stepper motor driver 54 responds to these signals from the microcomputer 52 by applying power to the appropriate coils of the stepper motor 44. The common terminals for the coils of the stepper motor 44 are connected by resistors 55 and 56 to node 58. Another resistor 60 is connected to node 58 to form a voltage divider with resistors 55 and 56 between the stepper motor 44 and a source of positive voltage V.sup.+. A switch 62 of relay 64 is connected across resistor 60. When the relay switch 62 is in an open position, the voltage divider formed by resistors 55, 56 and 60 applies a relatively low voltage to the stepper motor 44. Whereas when the relay switch 62 is closed and resistor 60 is shorted, a higher voltage is applied to the stepper motor 44. The level of voltage applied to the stepper motor determines the energy and thus the force that is exerted by the stepper motor on the grid 26. As will be seen, the force will be varied in order to compensate for the gravitational effects on the grid 26. Relay 64 is controlled by a digital ENERGY signal from the microcomputer 52. The logic level of the ENERGY signal is stored within a latch 68 which has an output that drives the coil 66 of relay 64. The stepper motor 44 must move the grid 26 fast enough so that the grid vane pattern is sufficiently blurred to be indiscernible on the exposed radiograph. Since the grid vane pattern is uniformly repetitive, the minimum required velocity is inversely proportional to the spacing between the adjacent vanes of the grid. The greater the vane spacing, the faster the grid must move. This relationship is given by the mathematical expression V.sub.min =C/(T.sub.ex S), where V.sub.min is the minimum threshold grid velocity, T.sub.ex is the exposure time, and S is the grid vane spacing. C is a proportionality constant that is dependent upon, among other things, characteristics of medium 18, film development processing and the specific X-ray apparatus employed. A value for C is derived from empirical test data for the specific configurations of the X-ray apparatus 10. The relationship of grid velocity to exposure time is plotted by the dashed line in FIG. 3. As can be seen, the shorter the exposure time, the greater the required velocity of the grid apparatus. Thus, to adequately blur the vane shadows, the stepper motor control circuit 50 must be capable of a velocity range which is sufficiently great to accommodate the entire range of possible exposure times. In conventional radiographic systems, the duration of the exposure is controlled by a feedback loop in which detector 20 senses radiation flowing through the medium 18 and produces a signal indicative of the level of radiation. The detector signal is used by the main control system to determine when a proper exposure has occurred and when to shut off the X-ray tube 11. Therefore, at the commencement of a given X-ray exposure, the duration of that exposure is unknown. In order to accommodate this unknown exposure duration, the grid 26 is initially moved at a relatively high velocity which decreases over the exposure time as shown by the solid line in FIG. 3. With reference to FIG. 4A, the speed of the grid 26 is determined by the control program which is executed by the microcomputer 52. The initial section of the program ensures that the grid is placed into the proper home position in expectation of an X-ray exposure. The orientation of the grid 26 at the start of an exposure is important as it is undesirable to initially move the grid upward against the force of gravity. Therefore, between X-ray exposures, the microcomputer 52 monitors the TILT signal to detect the orientation of the grid assembly 22. The state of the tilt switch 46, as indicated by the logic level of the TILT signal, is checked at step 100 in order to sense the orientation of the grid assembly 22. If the tilt switch is not closed, the grid assembly is in either the horizontal position or an angular position with the motor above edge 45. In this case the home position to be used is toward the motor and the program execution advances to step 102. At that point the microcomputer activates the stepper motor driver 54 to retract the grid 26 into a home position. During retraction, the grid 26 moves toward the stepper motor 44 until the vane 47 on the grid clears the electro-optic sensor 48 so that the sensor produces an active HOME signal. Then at step 103, the microcomputer 52 reverses the DIRECTION signal for the stepper motor driver 54 to prepare for movement upon the start of an exposure. At this time the grid no longer moves, as STEP signal pulses are not being applied to the stepper motor driver 54. If the tilt switch 46 is found closed at step 100, as occurs when the grid assembly 22 begins to be tilted vertically with edge 45 significantly above the stepper motor 44, the program branches to step 104. In this event, the grid 26 is advanced away from the stepper motor and into the home position at the opposite end of grid travel, where the electro-optic sensor 48 produces an active HOME signal. Thereafter, the DIRECTION signal is set at step 106 to produce movement of the grid 26 toward the stepper motor 44. Once the grid is in the appropriate home position, the microcomputer 52 checks for an active EXPOSURE signal at program step 108. When this signal is inactive, the program execution returns to step 100 to monitor the tilt switch 46. At the beginning of an X-ray exposure, the microcomputer 52 receives an active EXPOSURE signal on line 53 from the main X-ray system controller. This causes the program to advance to step 109 where variables and counters used in controlling the stepper motor 44 are initialized. Then a "step" routine is called at program step 112 to produce incremental movement of the stepper motor 44. The step routine is shown in FIG. 5 and commences at program step 121 to check whether the main X-ray system computer is signalling that the exposure should continue, as indicated by an active EXPOSURE signal. Microcomputer 52 turns off the stepper motor 44 at step 122 if an exposure is not occurring, and the program returns to step 100. Otherwise during an exposure, the subroutine branches to step 124 where the microcomputer 52 produces a pulse of the STEP signal which causes the stepper motor driver 54 to move the stepper motor 44 one fixed increment in the direction indicated by the DIRECTION signal. A count of the steps during each movement cycle of the grid is maintained in the memory of microcomputer in order to know the position of the grid 26. At the commencement of the exposure, this count was zero and thereafter is incremented by one each time program step 125 is executed. The rate of grid movement is determined by the interval of time between STEP signal pulses, the shorter the interval the faster the rate. The pulse interval is determined by a delay timer that is implemented as a conventional software routine executed by the microcomputer 52. This timer is loaded at step 126 with a delay period. At the beginning of the exposure (step 109), this delay period is set to a very short interval so as to produce maximum velocity of the grid as determined by the shortest allowable exposure time. As will be described, the delay period is incremented by a given amount in the early portion of the exposure so as to decrease the speed of the motor 44 and thus the grid 26 during the exposure time. Then at step 128, the delay timer is repeatedly inspected until it reaches zero, at which time the step routine terminates and returns to the point in the main program on FIG. 4A at which it was called. Upon returning at this time, the program execution enters step 114 where the microcomputer 52 determines whether it is time to reverse the direction of the grid 26. Since each pulse of the STEP signal produces a fixed incremental movement of the stepper motor 44, the count of the step pulses indicates how far the grid 26 has moved. Thus, the number of pulses between the home position and the point of movement at which direction reversal should begin is known. Therefore, at step 114, that number of pulses is compared to the value in the step counter, called STEP COUNT. If the two values are not equal, the program execution advances to step 116. At this time, the microcomputer 52 checks a flag which during the initial stage of the grid movement (prior to point 61 on FIG. 3) has a zero value. This causes step 118 to be executed where the step period is incremented by a given amount to slow the grid speed, as shown by the solid line in FIG. 3. Once the step period has been incremented, the program execution returns to step 112 to once again call the step routine to incrementally advance the stepper motor 44 and thus the grid 26. This loop through program steps 112-118 continues until the STEP COUNT reaches a value which indicates that reversal of the grid 26 should begin. Reversal of the grid 26 starts at point 61 in FIG. 3 when the grid is approaching the extreme end of its travel from the home position. Then, the program execution advances to step 120 where the step period is set to a much shorter fixed value designated as "FAST." This significantly shorter step period approximately doubles the grid velocity between points 61 and 62 as shown in FIG. 3. At program step 130, the step routine is called once again to produce movement of the stepper motor and grid at this faster speed. This action results in movement of the grid 26 at an increased speed near the ends of travel in order to prevent grid lines in the X-ray image due to dwell of the grid at the extreme points. During the reversal procedure at the ends of grid travel, a separate count of movement steps is maintained in a memory location designated "reverse count." At step 132, the reverse count is incremented by one. Operation at the FAST speed continues for a number of motor steps, for example eight. During this time, the program repeatedly loops through steps 130-134. When eight steps at the FAST speed have occurred, program execution advances from step 134 to step 136. It is now time to reverse the direction of the grid 25 and the microcomputer 52 changes the logic level of the DIRECTION signal at step 136. As noted previously, if the grid assembly 22 has been tilted significantly from the horizontal, higher energy must be applied to the stepper motor 44 when the grid 26 is travelling upward against the force of gravity. Thus, if the TILT signal is active, the ENERGY signal must be set at step 138 to indicate high energy is required due to reversal of the movement direction. The reversal of the grid direction occurs at time 62 in FIG. 3 and as illustrated, the initial operation in the reverse direction occurs at even a faster speed than was occurring prior to time 62. Thus, at program step 140, microcomputer 52 sets the step period to an even shorter value designated "VERY FAST." The fixed values for FAST and VERY FAST are stored in a data table within the internal ROM of the microcomputer. At steps 142 and 144, the step routine is called to produce an incremental movement of the grid 26 at this higher speed and the reverse count is incremented by one. The VERY FAST speed occurs for a relatively short period of time, for example four movement steps, which is sufficiently long to ensure blurring of the vanes 24 at the turn-around location. Thus, when the step count reaches a value of 12 at step 146, as occurs at time 63, the program execution advances to step 150 on FIG. 4B. The step period is once again set to the FAST value to decrease the speed of the grid. Then at steps 152, 154 and 156, eight more steps at this intermediate speed occur as indicated between points 63 and 64 in FIG. 3. Time 64 occurs at the end of the reversal process, where the reverse count is zeroed at step 158 to prepare for the next reversal process. Then, grid speed is reduced dramatically by setting the step period to a relatively large value, designated SLOW, at step 160 to move the grid even slower than occurred immediately prior to the direction reversal at time 61. The speed maintained constant at this SLOW level by setting the flag to one at step 162 so that the step period will no longer be incremented at program step 118 as happens prior to time 61. Movement at this fixed SLOW speed is accomplished by continuously calling the step routine at program step 164 until the step count indicates at step 166 that the direction of the grid should be reversed again as it is approaching the home position. When the step count indicates that the grid is a fixed distance, for example eight steps, from the home position, the program execution advances to step 168 where the step period is once again set to the FAST value. The step routine is called at step 170 to advance the grid one increment of the stepper motor. Following the step routine, the reverse count is incremented and a determination is made at step 174 whether the grid has reached the home position as indicated by the HOME signal from the electro-optic sensor 48. The program execution continues looping through step 170-174 until the home position is reached. Upon reaching the home position, microcomputer 52 acts as a comparator by comparing the STEP COUNT to a value designated CYCLE COUNT, which is the nominal number of movement steps which occur during a cycle of grid 26. If the actual STEP COUNT is not within a given tolerance, e.g. .+-.10, of the CYCLE COUNT, the microcomputer sets an error indicator at step 178. In either event, the program execution then advances to step 180 to once again reverse the direction of the grid 26 by changing the logic level of the DIRECTION signal to the stepper motor driver 54. Then at step 82, if the TILT signal is active, the ENERGY signal is set to a low logic level to decrease the energy applied to the stepper motor 44 since the new direction of travel will be downward and not against the force of gravity. Then the step period is set to the VERY FAST value at step 184 and steps 186, 188 and 190 produce four increments of movement at that very fast speed. Then the step period is set to the FAST value at step 192 and at steps 194, 196 and 198, eight steps, for example, occur at the fast speed. When those steps have been completed, the grid may once again travel at the slow speed. Therefore, the reverse count is zeroed at step 200 and the step period is set to the SLOW value at step 202. The program execution then returns to step 112 to begin another reciprocal cycle of the grid movement. As can be seen from the graph of FIG. 3, the motor speed increases just before reversal of the grid direction. Immediately following the reversal, the grid is moved at an even higher speed for a short amount of time and then at an intermediate speed, before returning to a normal slow speed. This rapid movement of the grid before and after direction reversal, eliminates the shadows which previously occurred due to dwell of the grid at the points of reversal. Furthermore, the comparison of the actual number of movement steps to the nominal amount for a grid cycle provides an indication of when the grid is not moving satisfactorily.
	description	This claims priority to U.S. Provisional Patent Application Ser. No. 61/445,878, filed Feb. 23, 2011, which is incorporated herein by reference in its entirety. X-ray windows can be used for enclosing an x-ray source or detection device. The window can be used to separate air from a vacuum within the enclosure while allowing passage of x-rays through the window. X-ray windows can include a thin film supported by a support structure, typically comprised of ribs supported by a frame. The support structure can be used to minimize sagging or breaking of the thin film. The support structure can interfere with the passage of x-rays and thus it can be desirable for ribs to be as thin or narrow as possible while still maintaining sufficient strength to hold the thin film. The support structure is normally expected to be strong enough to withstand a differential pressure of around 1 atmosphere without sagging or breaking. Information relevant to x-ray windows can be found in U.S. Pat. Nos. 4,933,557, 7,737,424, 7,709,820, 7,756,251 and U.S. patent application Ser. Nos. 11/756,962, 12/783,707, 13/018,667, 61/408,472 all incorporated herein by reference. It has been recognized that it would be advantageous to provide a support structure for an x-ray window that is strong but also minimizes attenuation of x-rays. The present invention is directed to an x-ray window that satisfies the need for strength and minimal attenuation of x-rays by providing larger ribs for strength of the overall structure which support smaller ribs. The smaller ribs allow for reduced attenuation of x-rays. The x-ray window can comprise a support frame with a perimeter and an aperture. A plurality of ribs can extend across the aperture of the support frame and can be supported or carried by the support frame. Openings exist between ribs to allow transmission of x-rays through such openings with no attenuation of x-rays by the ribs. A film can be disposed over and span the ribs and openings. The film can be configured to pass radiation therethrough, such as by selecting a film material and thickness for optimal transmission of x-rays. The ribs can have at least two different cross-sectional sizes including at least one larger sized rib with a cross-sectional area that is at least 5% larger than a cross-sectional area of at least one smaller sized rib. As used herein, the term “about” is used to provide flexibility to a numerical range or value by providing that a given value may be “a little above” or “a little below” the endpoint. As used herein, the term rib “cross-sectional area” means the rib width times the rib height. As used herein, the term “linear” or “linearly”, as referring to the rib pattern, means that the rib or ribs extends substantially straight, without bends or curves, as the rib extends across the aperture of the support frame. “Non-linear” means that the rib does bend or curve. As used herein, the terms “larger ribs,” “larger rib,” “largest ribs,” and “largest rib” mean larger or largest in cross-sectional area of the ribs, and does not refer to the length of the ribs. As used herein, the terms “smaller ribs,” “smaller rib,” “smallest ribs,” and “smallest rib” mean smaller or smallest in cross-sectional area of the ribs, and does not refer to the length of the ribs. As used herein, the term “substantially” refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is “substantially” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained. The use of “substantially” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. As illustrated in FIG. 1, an x-ray window 10 is shown comprising a support frame 12 with a perimeter and an aperture 15. A plurality of ribs 11 can extend across the aperture 15 of the support frame 12 and can be supported or carried by the support frame 12. Openings 14 exist between ribs 11 to allow transmission of x-rays through such openings with no attenuation of x-rays by the ribs 11. A film 13 can be disposed over and span the ribs 11 and openings 14. The film 13 can be carried by the ribs 11. The film 13 can contact the ribs 11. The film 13 can be configured to pass radiation therethrough, such as by selecting a film material and thickness for optimal transmission of x-rays. The ribs 11 can have at least two different cross-sectional sizes including at least one larger sized rib with a cross-sectional area that is at least 5% larger than a cross-sectional area of at least one smaller sized rib. This design with some ribs having a larger cross sectional area and other ribs having a smaller cross sectional area can have high strength provided by the larger ribs while allowing for minimal attenuation of x-rays by use of smaller ribs. The change in cross-sectional area between larger and smaller ribs can be accomplished by a change in rib width w and/or a change in rib height h. For example, in FIG. 1, rib 11b has a width w2 that is greater than a width w1 of rib 11a, but both ribs have approximately equal heights h1, and thus rib 11b has a greater cross-sectional area than rib 11a. As another example, rib 11c has a height h2 that is greater than a height h1 of rib 11a, but both ribs have approximately equal widths w1, and thus rib 11c has a greater cross-sectional area than rib 11a. As another example, rib 11d has a height h3 that is greater than a height h1 of rib 11a and a width w3 that is greater than a width w1 of rib 11a, and thus rib 11d has a greater cross-sectional area than rib 11a. As another example not shown, one rib may have a greater width, but a lesser height, than another rib. Whichever rib has a greater value of width times height has a greater cross-sectional area. In the various embodiments described herein, tops of the ribs 11 can terminate substantially in a common plane 16. “Tops of the ribs” is defined as the location on the ribs 11 to which the film 13 is attached. It can be beneficial for tops of the ribs 11 to terminate substantially in a common plane 16 to allow for a substantially flat film 13. FIGS. 2-9 show schematic top views of x-ray window support structures, with some ribs having a larger cross-sectional area and other ribs having a smaller cross-sectional area. Ribs with a smallest cross-sectional area are designated as 11e, ribs with a larger cross-sectional area than ribs 11e are designated as 11f, ribs with a larger cross-sectional area than ribs 11f are designated as 11g, ribs with a larger cross-sectional area than ribs 11g are designated as 11h, and ribs with a larger cross-sectional area than ribs 11h are designated as 11i. Ribs with larger cross-sectional area are shown with wider lines. A wider line does not necessarily mean that the rib is wider, only that the cross-sectional area is larger, which may be accomplished by a larger width, a larger height, or both, than another rib. In one embodiment, each larger sized rib can have a cross-sectional area that is at least 5% larger than a cross-sectional area of smaller sized ribs Area ⁢ ⁢ of ⁢ ⁢ larger ⁢ ⁢ rib - Area ⁢ ⁢ of ⁢ ⁢ smaller ⁢ ⁢ rib Area ⁢ ⁢ of ⁢ ⁢ smaller ⁢ ⁢ rib > 0.05 . In another embodiment, each larger sized rib can have a cross-sectional area that is at least 10% larger than a cross-sectional area of smaller sized ribs. In another embodiment, each larger sized rib can have a cross-sectional area that is at least 25% larger than a cross-sectional area of smaller sized ribs. In another embodiment, each larger sized rib can have a cross-sectional area that is at least 50% larger than a cross-sectional area of smaller sized ribs. In another embodiment, each larger sized rib can have a cross-sectional area that is at least twice as large as a cross-sectional area of smaller sized ribs. In another embodiment, each larger sized rib can have a cross-sectional area that is at least four times as large as a cross-sectional area of smaller sized ribs. Some figures show only two different cross-sectional area size ribs, but more cross-sectional area sizes are within the scope of the present invention and are only excluded from the figures for simplicity. Also, more than the five different cross-sectional area size ribs shown are within the scope of the present invention and are only excluded from the figures for simplicity. As illustrated in FIG. 2, an x-ray window 20 is shown with ribs 11e-g having at least three different cross-sectional areas. The smallest ribs 11e are formed into repeating hexagonal shapes and define hexagonal-shaped openings. The next larger ribs 11f are formed into repeating structures comprising seven of the small hexagonal shapes. The pattern of the larger ribs 11f can be aligned with the part of the hexagonal pattern of the smaller sized ribs 11e. Larger ribs 11g can extend across the aperture of the support frame 12 to provide extra strength to the smaller sized ribs 11e-f. The pattern of the larger ribs 11g can be aligned with part of the pattern of the smaller sized ribs 11e-f. The ribs 11e-f can extend non-linearly across the aperture of the support frame 12. As illustrated in FIG. 3, an x-ray window 30 is shown with ribs 11e-f having at least two different cross-sectional areas. The smallest ribs 11e are formed into repeating hexagonal shapes and define hexagonal-shaped openings. The larger ribs 11f provide extra strength to the smaller sized ribs 11e. The ribs 11e-f can extend non-linearly across the aperture of the support frame 12. The pattern of the larger ribs 11f can be aligned with part of the hexagonal pattern of the smaller sized ribs 11e. As illustrated in FIG. 4, an x-ray window 40 is shown with ribs 11e-f having at least two different cross-sectional areas. The smallest ribs 11e are formed into repeating hexagonal shapes and define hexagonal-shaped openings. The larger ribs 11f extend across the aperture of the support frame 12, in a cross-shape, to provide extra strength to the smaller sized ribs 11e. The larger-sized ribs 11f, along with the support frame, separate the smaller sized ribs 11e into separate and discrete sections 43a-d. Note that the smaller sized ribs 11e extend non-linearly across the aperture of the support frame 12 while larger sized ribs 11f extend linearly across the support frame 12. A portion of the pattern of the larger sized ribs 11f can be aligned with a portion of a pattern of the smaller sized ribs 11e, such as at location 44. This alignment can optimize strength by continuing with the larger ribs 11f, a portion of a pattern of the smaller ribs 11e. As illustrated in FIG. 5, an x-ray window 50 is shown with ribs 11e-f having at least two different cross-sectional areas and defining hexagonal-shaped openings. The smallest ribs 11e are formed into repeating hexagonal shapes. The larger ribs 11f extend across the aperture of the support frame 12 to provide extra strength to the smaller sized ribs 11e. The ribs 11e-f can extend non-linearly across the aperture of the support frame 12. As illustrated in FIG. 6, an x-ray window 60 is shown with ribs 11e-f having at least two different cross-sectional areas. The smallest ribs 11e are formed into repeating hexagonal shapes and define hexagonal-shaped openings. The larger ribs 11f extend across the aperture of the support frame 12 to provide extra strength to the smaller sized ribs 11e. The larger-sized ribs 11f, along with the support frame, separate the smaller sized ribs 11e into separate and discrete sections 63a-c. The ribs 11e-f can extend non-linearly across the aperture of the support frame 12. As illustrated in FIG. 7, an x-ray window 70 is shown with ribs 11e-f having at least two different cross-sectional areas. The smallest ribs 11e are formed into repeating hexagonal shapes and define hexagonal-shaped openings. The larger ribs 11f extend across the aperture of the support frame 12 to provide extra strength to the smaller sized ribs 11e. The ribs 11e-f can extend non-linearly across the aperture of the support frame 12. As illustrated in FIG. 8, an x-ray window 80 is shown with substantially parallel ribs 11e-i having at least five different cross-sectional areas. The ribs 11e-i extend linearly from one side of the support frame to an opposing side of the support frame 12. At least one of the larger sized ribs 11i can have a longer length than all smaller sized ribs 11e-h. Also, at least one of the larger sized ribs 11i can span a greater distance across the aperture of the support frame 12 than all smaller sized ribs. As illustrated in FIG. 9, an x-ray window 90 is shown with ribs 11e-h having at least four different cross-sectional areas. Some of the ribs 11e-h are substantially parallel with respect to each other and some of the ribs 11e-h ribs intersect one another. The intersecting ribs 11e-h can be oriented non-perpendicularly with respect to each other and can define non-rectangular openings 14. As illustrated in FIG. 10, an x-ray detection system 100 is shown comprising an x-ray window 101 hermetically sealed a mount 102. The x-ray window 101 can be one of the various x-ray window embodiments described herein. An x-ray detector 103 can also be attached to the mount 102. The window 101 can be configured to allow x-rays 104 to impinge upon the detector 103. This may be accomplished by selection of window materials and support structure size to allow for transmission of x-rays and orienting the window 101 and detector 103 such that x-rays 104 passing through the window 101 will impinge upon the detector 103. As illustrated in FIG. 11, an x-ray source 110 is shown comprising a hermetically sealed enclosure formed by an x-ray window 111, an x-ray tube 114, a cathode 112, and possibly other components not shown. An electron emitter 113 can emit electrons 115 towards the window 111 and the window 111 can be configured to emit x-rays 116 in response to impinging electrons, the x-rays 116 can exit the x-ray source 110. The x-ray window 111 can be one of the various x-ray window embodiments described herein and can have a coating of target material, such as silver or gold, to allow for production of the desired energy of x-rays 116. As illustrated in FIG. 12, an x-ray window 120 is shown with a portion of the support frame 12 and a portion of the ribs 11 all disposed in a single plane 126. The plane 126 can be substantially parallel with the film 13 and can have a thickness 127 of less than 5 micrometers. How to Make: The film 13 can be comprised of a material that will result in minimal attenuation of x-rays and/or minimal contamination of the x-ray signal passed through to an x-ray detector or sensor. The film can be comprised of a polymer, graphene, diamond, beryllium, or other suitable material. The window can have a gas barrier film layer disposed over the film. The gas barrier film layer can comprise boron hydride. The film can be attached to the support structure by an adhesive. The support structure can be comprised of a polymer (including a photosensitive polymer such as a photosensitive polyimide), silicon, graphene, diamond, beryllium, carbon composite, or other suitable material. The support structure can be formed by pattern and etch, ink jet printer or inkjet technology, or laser mill or laser ablation. In one embodiment, ribs can have a width w between 25 μm and 75 μm and a height h between 25 μm and 75 μm. In one embodiment, largest ribs can have a width w between about 50 μm and about 250 μm. In another embodiment, smallest ribs can have a width w between about 8 μm and about 30 μm. In another embodiment, intermediate sized ribs can have a width w between about 20 μm and about 50 μm. All ribs in this described in this paragraph can have the same height h or they can be different heights h. All ribs in this described in this paragraph can have heights h as described in the following paragraph. In one embodiment, largest ribs can have a height h between about 20 μm and about 300 μm. In another embodiment, smallest ribs can have a height h between about 20 μm and about 60 μm. In another embodiment, intermediate sized ribs can have a height h between about 20 μm and about 100 μm. All ribs in this described in this paragraph can have the same width w or they can be different widths. All ribs in this described in this paragraph can have widths as described in the previous paragraph. In one embodiment, openings 14 between the ribs 11 can take up about 81% to about 90% of a total area within the aperture of the support frame 12. In another embodiment, openings 14 between the ribs 11 can take up about 71% to about 80% of a total area within the aperture of the support frame 12. In another embodiment, openings 14 between the ribs 11 can take up about 91% to about 96% of a total area within the aperture of the support frame 12. Opening 14 area can be dependent on the width w and height h of the ribs 11, the pattern of the ribs, and the number of different sizes of ribs. It is to be understood that the above-referenced arrangements are only illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention. While the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment(s) of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth herein.
	claims	1. A method for separating at least one first chemical element E1from at least one second chemical element E2coexisting in a mixture in the form of oxides, comprising the following steps:a) a step to solubilise a powder of one or more oxides of said at least one first chemical element E1and a powder of one or more oxides of said at least one second chemical element E2in a medium comprising at least one molten salt of formula MF—AlF3, where M is an alkaline element, resulting after this step in a mixture comprising said at least one molten salt, a fluoride of said at least one first chemical element E1, and a fluoride of said at least one second chemical element E2; andb) a step to contact the mixture resulting from step a) with a medium comprising a metal in the liquid state, the said metal being a reducing agent capable of predominantly reducing said at least one first chemical element E1 relative to said at least one second chemical element E2, resulting after this step in a two-phase medium comprising a first phase which is a metal phase comprising said at least one first chemical element E1 in oxidation state 0, and a second phase which is a saline phase comprising the least one molten salt of above-mentioned formula MF—AlF3, and a fluoride of the said at least one second chemical element E2. 2. The process according to claim 1, wherein the element(s) E1 are selected from the group formed by the actinides, transition elements, and the element(s) E2 are selected from the group not comprising any actinides. 3. The process according to claim 2, wherein the element(s) E2 are selected from the group formed by the lanthanides, transition elements other than those of E1, alkaline or alkaline-earth elements, and/or pnictogenic elements. 4. The process according to claim 1, further comprising reprocessing spent nuclear fuel, transmutation targets used for nuclear physics experimentation, or refractory matrixes included in the composition of nuclear reactors, using said steps a) and b). 5. The process according to claim 1, wherein the molten salt is a salt of formula LiF—AlF3. 6. The process according to claim 1, wherein AlF3 is contained in the molten salt up to a molar content of 10 to 40 mole %. 7. The process according to claim 1, wherein the metal in the liquid state at step b) is selected from among aluminium and the alloys thereof. 8. The process according to claim 7, wherein the alloy is an alloy of aluminium and copper. 9. The process according to claim 1, further comprising, before step a), a step to prepare the mixture of powders intended to be used at step a). 10. The process according to claim 9, wherein, when the process relates to the reprocessing of uranium oxide spent nuclear fuel, said step to prepare the mixture of powders further comprises:an operation for mechanical treatment of the spent fuel to form a powder of oxide(s); anda heat treatment operation by voloreduction to remove volatile fission products. 11. The process according to claim 9, wherein, when the process relates to the reprocessing of uranium oxide spent fuel, said step to prepare the mixture of powders comprises a voloxidation operation after which uranium oxide UO2 is converted to uranium oxide U3O8. 12. The process according to claim 1, wherein above-mentioned step a) and step b) are performed successively. 13. The process according to claim 12 which, wherein, step a) and step b) are performed successively, further comprises a digestion step of elements selected from among the platinum-group elements and/or molybdenum contained in the mixture resulting from step a), said digestion step being performed after step a) and before step b). 14. The process according to claim 13, wherein the digestion step consists of contacting the mixture resulting from step a) with a medium comprising a metal in the liquid state, said metal being capable of selectively absorbing the platinum-group elements and/or molybdenum relative to the elements E1 and E2 contained in the at least one molten salt, the following being obtained after this step:the mixture of step a) being free of said platinum-group element(s) and/or molybdenum; anda metal phase comprising the above-mentioned metal in the liquid state and the said platinum-group element(s) and/or molybdenum. 15. The process according to claim 14, further comprising, after the digestion step, a step to separate the mixture of step a) and the metal phase. 16. The process according to claim 1, further comprising, after step b), a step c) to separate the metal phase from the saline phase. 17. The process according to claim 16, wherein when the process relates to the reprocessing of spent fuel, the metal phase thus separated is subjected to the following successive treatments:a back-extraction step of the actinide(s) by contacting the metal phase with a molten chloride medium in the presence of an oxidizing agent belonging to the chloride family to convert the actinides in the metal state to actinide chloride(s), after which there subsists a metal phase free of actinide(s) and a chloride saline phase; anda step to convert the actinide chloride(s) to actinide oxide(s). 18. The process according to claim 16, wherein the saline phase derived from separation step c) is subjected to the following successive treatments:a distilling step, to regenerate the medium comprising at least one molten salt of MX—AlF3 type; anda vitrifying step of elements E2 removed from the saline phase after the distillation step. 19. The process according to claim 1, wherein above-mentioned step a) and step b) are performed simultaneously. 20. The process according to claim 13, wherein the platinum-group elements comprise Ru, Rh, or Pd.
	description	Computed tomography (CT) is an imaging technique that is widely used in the medical field. In general, an x-ray source and a detector are positioned on opposite sides of a patient. The x-ray source generates and directs an x-ray beam towards the patient, while the detector measures the x-ray absorption along different transmission paths. By taking many readings from multiple angles around the patient, relatively large amounts of data can be accumulated. That data can then be analyzed and processed to construct a three-dimensional representation of the patient's insides. While performing CT, a filter is generally placed between the patient and the x-ray source in order to, for example, reduce the intensity of the x-ray beam or shape the x-ray beam, thereby reducing the radiation dose experienced by the patient. One class of filter (e.g., beam hardening filters) may be used to change the beam's energy spectrum, and another class of filter (e.g., shape filters) may be used to change the beam's shape. Within each class of filter, there may be a number of different filters—that is, there may be a number of different beam hardening filters, and a number of different shape filters. Different filters are selected and used depending on, for example, the types of procedures to be performed. In one conventional implementation, a filter is selected and manually placed in a fixed position inside the beam path. To change the filter to a different one, an operator must enter the treatment room, manually remove the installed filter, and insert the new filter. Consequently, the process of setting up a different filter, including alignment and perhaps calibration, can take a relatively long time. From the patient's perspective, the wait may be both inconvenient and uncomfortable. In another conventional implementation, a motor is used to move a filter into a filtering position in the beam path. However, if a different filter is to be used, an operator must still enter the treatment room and manually replace that filter with another in a manner similar to that just described. There are other types of conventional implementations in use, but in general those implementations share the problems described above. According to embodiments of the invention, a filter changing assembly that can be used in, for example, a radiology system includes shape filters that can used to shape a radiation beam and that can be moved back-and-forth, for example. The filter changing assembly also includes beam hardening filters that can be used to change the energy spectrum of the radiation beam, and that also can be moved back-and-forth, for example. The filter changing assembly includes a control system that can be used to select at least one of the filters and automatically move the selected filter from one position to another position. In one embodiment, the filter changing assembly includes shape filters that can be moved between a first filtering position between a radiation source and a target and a first storage position that is outside of the radiation beam's path. The filter changing assembly also includes beam hardening filters that also can be moved between a second filtering position between the radiation source and the target and a second storage position that is outside of the radiation beam's path. The filter changing assembly includes a control system that can be used to select at least one of the filters and automatically move the selected filter from its storage position to its filtering position. The filter changing assembly can be used in a radiology system (e.g., a radiographic imaging system such as a computed tomography system) to scan the insides of an object (e.g., a piece of luggage) or a subject (e.g., a human patient). For medical procedures, the filter changing assembly can be used during diagnosis and/or treatment. There are a number of advantages associated with the disclosed filter changing assembly. For example, filters can be changed remotely and automatically so that the operator does not need to enter the treatment room, which speeds up the setup process. The position of each filter can be repeated, which also speeds up the setup process—for example, the radiology system can be calibrated with a certain filter in place in a particular position, and then that filter can be precisely returned to that position with a patient in place. Also, different combinations of filters can be selected and readily moved in and out of position. Furthermore, mechanical features of the filter changing assembly allow the position of each filter to be fine-tuned. Other mechanical features of the assembly prevent filters from being inadvertently dropped or from falling on a patient. Errors are reduced or even eliminated, because the possibility of installing an incorrect filter or combination of filters is reduced if not altogether eliminated. These and other objects and advantages of the various embodiments of the invention will be recognized by those of ordinary skill in the art after reading the following detailed description of the embodiments that are illustrated in the various drawing figures. Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the embodiments of the present invention. Some portions of the detailed descriptions, which follow, are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer-executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “receiving,” “selecting,” “causing,” “identifying,” “generating” or the like, refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. Some embodiments described herein may be discussed in the general context of computer-executable instructions or components residing on some form of computer-usable medium, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, data structures, etc., that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or distributed as desired in various embodiments. By way of example, and not limitation, computer-usable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital versatile disks (DVDs) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information. Communication media can embody computer-readable instructions, data structures, program modules or other data and includes any information delivery media. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency (RF), infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer-readable media. FIG. 1 illustrates elements of a radiology system 100 in an embodiment according to the invention. In one embodiment, the system 100 is a computed tomography (CT) system, specifically a cone beam CT (CBCT) system. The system 100 can be used for medical applications including diagnosis and treatment. However, the system 100 is not so limited and can be used to scan objects other than human subjects, such as luggage, for example. In the example of FIG. 1, the system 100 includes a support 14 (e.g., a flat surface such as a bed or table) for an object or subject 16 to be scanned (imaged) and/or treated. In operation, the support 14 and subject 16 are situated within an opening in a gantry 12. The system 100 also includes a radiation source 20 (e.g., an x-ray tube) that is attached to the gantry 12 and that projects a beam of radiation towards a target (e.g., to and through the subject 16, and to the detector 40). The radiation source 20 can generate beams at different energy levels (measured in keV). The detector 40 includes a number of sensor elements that can sense the intensity (e.g., amount and/or energy level) of the radiation that passes through the subject 16. The gantry 12 can rotate about the subject 16, and can move back and forth along the length of the subject 16 (or the position of the subject can be moved relative to the position of the gantry). The control system 18 can be used to control operation of the gantry 12, and can also be used to control the radiation source 20 and the filter changing assembly 30. The filter changing assembly 30 is positioned between the radiation source 20 and the detector 40. A blade (jaw) assembly (not shown), which contains some number of motorized and position-controlled blades (e.g., four blades), can be located between the radiation source 20 and the filter changer assembly 30, in order to narrow the beam so that no elements external to the active surface of the detector 40 are irradiated. The blades can be remotely controlled and respectively pre-programmed to any intermediate position either symmetrically or asymmetrically. The filter changing assembly 30 includes multiple (e.g., at least two) filter decks or sliders. In one embodiment, the filter changing assembly 30 includes a beam hardening (or foil) filter slider and a shape filter slider. The beam hardening filter slider includes multiple beam hardening filters, and the shape filter slider likewise includes multiple shape filters. Additional information is provided in conjunction with the discussion of FIGS. 2, 3, and 4, below. Continuing with reference to FIG. 1, a beam hardening (foil) filter is used to change the energy spectrum of the radiation beam. For example, a beam hardening filter can be used to filter out lower energy x-rays, changing the x-ray spectrum to a “harder” beam with a larger proportion of higher energy x-rays. The lower energy x-rays tend to get absorbed by the subject 16 and thus do not reach the detector 40 (and hence do not contribute to the resultant image), and so only increase the dose to the subject. By hardening the beam, the dose to the subject 16 can be reduced. The areas of the detector 40 that are not covered by the subject 16 get the direct beam (the part of the beam not attenuated by the subject), which will saturate those areas much sooner than the areas covered by the subject. Also, in a human subject, for example, the beam will have to penetrate through less tissue at the edges of the subject than it will toward the center of the subject. In that case, the beam can be less intense toward the edges of the subject 16; if the intensity is too high, unwanted scatter can increase in those areas. A shape filter (e.g., a bow-tie filter) can be used to better fit the x-ray dose distribution to the subject 16 in order to reduce (minimize) the dose to that subject, to improve scatter behavior, and to improve the dynamic range of the detector 40. Also, because the radiation source 20 (x-ray tubes, for example) may not have a totally flat distribution of dose over the whole radiation field, a shape filter can be used to correct the field to make it flatter (more homogeneous). In general, the filter changing assembly 30 can be used to provide different combinations of filters depending on the type of procedure to be performed or to modulate the radiation beam in different ways. For example, a particular beam hardening filter and a particular shape filter can each be selected and used together (in combination) to filter the radiation beam in a particular way, each filter hardening or shaping the beam in its own way, as described above. Also, the filter changing assembly 30 has the capability to automatically select a filter from one or both of the aforementioned filter sliders and automatically move the selected filter(s) into a respective position inside, or substantially inside, the beam's path. In other words, as will be seen from the discussion below, the filters are stored in a position that is entirely outside of, or at least partially outside of, the path of the radiation beam; that position may be referred to herein as the storage position. Also, selected filters are automatically moved from their respective storage positions into a position that is, at least in part or entirely, inside the beam's path between the radiation source 20 and the subject 16; the latter position may be referred to herein as the filtering position. Generally speaking, the filtering position refers to the position of a filter that allows that filter to filter the radiation beam to the extent required by a selected radiation procedure (e.g., scan, imaging, treatment), and the storage position refers to the position of the filter when it is not in the filtering position. A filter can also be placed in an intermediate position between the extreme filtering position and the extreme storage position. In one embodiment, the filters are selected and inserted depending on a selected radiation procedure. The control system 18 is capable of storing one or more positions for each filter to accommodate different beam profiles, different procedures, and different types of targets (e.g., different body shapes and sizes). For example, if an operator selects a pelvic CBCT scan, then the control system 18 automatically selects a beam hardening filter and a shape filter that were defined in advance for that type of scan, and then automatically causes those filters to be moved into a precise filtering position also defined in advance for that type of scan. Errors are reduced or even eliminated, because the possibility of installing an incorrect filter or combination of filters is reduced if not altogether eliminated. FIG. 2 illustrates an embodiment of a filter changing assembly 30 according to the invention. The bottom of the filter changing assembly 30 is shown. In other words, considering the orientation of the assembly in FIG. 2, a radiation beam would exit out of the page. In one embodiment, the filter changing assembly 30 includes a beam hardening filter slider (or deck) 202 and a shape filter slider (or deck) 204. In such an embodiment, the beam hardening filter slider 202 includes multiple filters (not shown), and the shape filter slider includes two shape filters 205 and 206. In the example of FIG. 2, a beam hardening filter 203 is situated in a filtering position over the beam exit, while the shape filters 205 and 206 are situated in their storage positions. Either of the shape filters 205 or 206 can be automatically moved to a position over the beam exit by means of, for example, a motor and spindle (e.g., the linear actuator 215). More specifically, in one embodiment, the shape filter slider 204 is moved along the linear guides 210 until one or the other of the shape filters 205 and 206 is positioned over the beam exit. Any of the positions in the slider 202 and the slider 204 can contain a “null” filter. Also, a filter in place in either of the sliders can be removed and replaced with a different filter. For example, a shape filter in the slider 204 can be removed and replaced with a different shape filter. Alternatively, a shape filter in the slider 204 can be removed and the position left empty—the unoccupied position is thus a null filter. In one embodiment, an encoder 220 and an absolute feedback element (resolver) 225 are used to measure and monitor the position of the shape filter slider 204. The linear actuator 215 can move the filters by relatively small (precise) amounts, and the encoder 220 can likewise accurately measure the positions of the filters, so that the positions of the filters can be fine-tuned as needed. The absolute feedback element 225 can be used for initial calibration and as a diverse, redundant feedback of the slider position. The encoder 220 and the absolute feedback element 225 may be referred to generally as position detectors. Fine tuning of the filter position can be performed remotely from outside the treatment room and during radiation exposure. The mechanical features of the filter changing assembly 30—specifically, the linear guides 210 and the encoder 220—ensure that the selected shape filter 205 or 206 is precisely located relative to the radiation beam and the beam exit. Similar mechanical features (not shown) ensure that the selected beam hardening filter 203 also is properly aligned with the beam exit. The precise nature of these mechanical features allows the filters to be positioned in virtually the same spot time-after-time. This repeatability is advantageous, particularly for use of the beam shaping filter. For example, the system 100 (FIG. 1) can first be calibrated with filters in place but without a subject 16 to be scanned (e.g., with the patient not present). For instance, the offset gain correction can be calculated with the selected filters in a filtering position but without a subject 16. Subsequently, with the subject 16 now present, the selected filters can be returned to the filtering position and the scan can be performed. The offset gain correction can be subtracted from the raw image data collected by the detector 40, in order to derive the data that represents only the scanned subject. In other words, effects introduced by, for example, the support 14 are subtracted from the raw data. Thus, repeatability can improve the quality of the image data. Furthermore, repeatability decreases setup time, especially from the perspective of a human patient. In other words, a human patient need not be present while the system 100 is set up and calibrated and therefore, from the patient's perspective, the amount of time needed for the scan, imaging, or treatment process is greatly reduced. In addition to the advantages just described, there are a number of other advantages associated with the filter changing assembly 30. For example, filters can be changed remotely and automatically so that an operator does not need to enter the treatment room, which further speeds up the setup process. Also, different combinations of filters can be selected and readily moved in and out of position. The shape and beam hardening filters are each securely mounted within the filter changing assembly 30. The filter changing assembly 30 itself may be enclosed within a housing. Accordingly, filters are prevented from being inadvertently dropped or from falling on the subject 16. As an alternative to the sliders 202 and 204 discussed above, a carousel type of structure can be used, in which the filters are rotated to and from their respective storage and filtering positions or any intermediate position. FIGS. 3 and 4 illustrate an embodiment of a filter changing assembly 30 and an x-ray tube 310 according to the invention. In the example of FIG. 3, a beam hardening filter 203 is situated over the beam exit, while the shape filters 314 and 315 are in their storage positions. In the example of FIG. 4, the shape filter slider 204 has been moved (as described above) so that the shape filter 314 is aligned over the beam hardening filter 203 (not visible in FIG. 4). In FIGS. 3 and 4, the filter changing assembly 30 is mounted transverse to the longitudinal axis of the x-ray tube 310; however, the invention is not so limited. In general, depending on how they are mounted, the filter sliders 202 and 204 can move in the axial or radial direction with respect to the orientation of the x-ray tube 310. The x-ray tube 310 can contain a pre-collimator that prevents the storage position from being exposed to radiation. Also, a blade (jaw) assembly, which contains some number of motorized and position-controlled blades (e.g., four blades), can be located between the x-ray tube 310 and the filter changer assembly 30. The blade assembly is used to narrow the beam so that no elements external to the active surface of the detector 40 (FIG. 1) are irradiated. FIG. 5 illustrates elements of an embodiment of a control system 18 according to the invention. In the example of FIG. 5, the control system 18 includes a controller 510 that is coupled to (in communication with) the controller area network (CAN) 505. However, embodiments according to the present invention are not limited to the CAN standard and protocol. The controller 510 can also be coupled to or include a memory 511. In one embodiment, a user interface 502 (e.g., a control console or the like) is coupled to the control system 18. With reference to FIG. 1, an operator at the user interface 512 can input commands to control operation of the filter changing assembly 30. Significantly, the user interface 512, and hence the operator, can be in a room other than the treatment room and still control the filter changing assembly 30. More specifically, as described above, an operator can remotely and automatically change, insert, and remove filters. The control system 18 can include one or more motors 512, one or more encoders 220, and one or more absolute feedback elements 225. A single motor and one feedback element may be sufficient, but one encoder 220 and one absolute feedback element 225 provide diverse redundancy and may be required by government regulations. As presented above, the encoder 220 is used to detect, measure, and monitor filter positions. The absolute feedback element 225 provides a diverse and redundant channel to the encoder 220 for position detection, and can be used to establish the initial position of the filter when the encoder is not yet initialized. More specifically, the encoder 220 provides positions based on differences (e.g., distance traveled). Thus, the evaluating electronics (e.g., counters) have to be set to an initial value at a well-defined absolute position. The shape filter slider 202 (FIG. 2) uses physical (mechanical) end stops as the well-defined absolute positions. The control system 18 uses values from the absolute feedback element 225 to locate the end stops in an accurate and reproducible way. Once the encoder 220 is initialized, it can serve as the primary (accurate) position read-out. During normal operation (once initialized), the controller 510 checks both the encoder 220 and the absolute feedback element 225 for plausibility. If they do not agree, then a possible mechanical problem has occurred, and the control system 18 goes into a safe state (e.g., it stops and notifies the operator). FIG. 6 is a flowchart 600 of a method of operating a radiology system (e.g., the system 100 of FIG. 1) according to an embodiment of the invention. Although specific steps are disclosed in the flowchart 600, such steps are exemplary. That is, the present invention is well-suited to performing various other steps or variations of the steps recited in the flowchart 600. In one embodiment, the method of the flowchart 600 is performed by, for example, the control system 18 of FIG. 5. In block 602 of FIG. 6, a control signal that identifies a type of radiation procedure (e.g., a scan, imaging, or treatment procedure) to be performed is received. Alternatively, the control signal can identify the filter or filters that are to be used to perform a particular type of radiation procedure. In general, as discussed above, filters can be selected and inserted depending on a selected type of scan, imaging, or treatment procedure. In block 604, once the control signal is received, then the control system 18 (FIG. 5) automatically selects a first filter (e.g., a beam hardening filter or a shape filter) that was defined in advance for the specified procedure. In one embodiment, the control signal is produced in response to a user-generated command that is input from a location outside a room (e.g., the treatment room) that houses the radiology system 100 (FIG. 1). In block 606 of FIG. 6, the control system 18 (FIG. 5) causes the selected filter to be moved into a precise filtering position that was also defined in advance for the specified procedure. The filter can be moved, and the filter position can be fine-tuned, remotely from outside the treatment room and during radiation exposure. In block 608 of FIG. 6, once the control signal is received, then the control system 18 (FIG. 5) automatically selects a second filter (e.g., a beam hardening filter or a shape filter) that was also defined in advance for the specified procedure, and causes the second selected filter to be moved into a precise filtering position that was also defined in advance for the specified procedure, such that the first and second filters can be used together to filter an incident radiation beam. The second filter can also be moved and its position fine-tuned remotely from outside the treatment room and during radiation exposure. In summary, embodiments according to the present invention provide a filter changing assembly that allows multiple filters to be automatically selected and moved into a filtering position inside the path of a radiation beam. Accordingly, it is not necessary for an operator to enter the treatment room to change filters or filter positions. Consequently, the process of setting up filters, including alignment and calibration, is significantly reduced. Embodiments according to the invention may also be used in combinations that include both moveable and fixed-position filters. For example, the disclosed filter changing assembly can be used in combination with a fixed-position flattening filter (used to flatten the dose of an x-ray beam, for example). Types of filters other than shape filters and beam hardening filters can be used in place of or in addition to those types of filters. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and many modifications and variations are possible in light of the above teaching. The embodiments described herein were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
043702953	abstract	A fusion-fission reactor having a plasma containing toroidal fusion region for producing high energy neutrons from fusion reactions and a region external to the fusion region containing material which is both fissile with respect to high energy neutrons and fertile with respect to low energy neutrons. The device comprises a toroidal field generating means and a region of fissile-fertile material positioned within the region of the toroidal field generating means. The toroidal field generating means is positioned substantially adjacent the toroidal fusion region.
059404698	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a radiation source for generating multi-chromatic, particularly di-chromatic x-radiation, having at least one cathode and an anode for generating x-ray bremsstrahlung and a target surrounded by the anode for converting the x-ray bremsstrahlung incident onto the target into fluorescence radiation. 2. Description of the Prior Art X-ray sources that generate a continuous x-ray spectrum are almost exclusively employed in medical diagnostics. For a number of applications, however, a monochromatic x-ray spectrum would be advantageous since additional material properties such as, for example, the discontinuous rise in the intensity attenuation at the absorption edges, could thereby be exploited. Although German OS 42 09 226 discloses a monochromatic x-ray source of the type initially described, this known x-ray source only generates x-radiation at a wavelength defined by the selection of the fluorescence target. Different wavelengths are required, however, for producing images using subtraction techniques. This subtraction method was therefore previously utilized in x-ray diagnostics by employing either x-radiators with continuous bremsstrahlung spectrum and two different acceleration voltages, or a di-chromatic synchrotron source. In the first method with two continuous bremsstrahl spectra shifted relative to one another, however, the absorption edge of the contrast agent is inadequately used. The second approach can be utilized only in conjunction with accelerator rings, and thus not at all in normal hospital use, and moreover requires the use of two-line detectors. SUMMARY OF THE INVENTION An object of the present invention is to provide a compact x-ray source having a number of rapidly switchable x-ray frequencies, preferably two rapidly switchable x-ray frequencies. This object is achieved in accordance with the invention in an x-ray source having a target composed in sections of different materials and wherein the sections can be optionally irradiated with the x-ray bremsstrahlung. In a first embodiment of the inventive radiation source, a needle-shaped target is employed which is divided in a longitudinal middle plane, and the two halves are composed of the aforementioned different materials, and the cathode is likewise divided and its sections are separately driveable so as to selectively irradiate two sections (maximally in the shape of a half-ring) of the anode lying opposite one another with electrons, from which x-rays only reach one target half. Dependent on which of the sub-sections of the anode is driven at the moment, thus, x-ray bremsstrahlung is generated only on one part of the anode surface, this is in turn irradiating only one target half composed of different materials, so that only the characteristic fluorescence radiation of this target half can be produced. The switching from one cathode section to the other is possible practically without inertia and without delay, so that the change between the two monochromatic x-ray frequencies can ensue very rapidly. Such a di-chromatic x-ray source is thus excellently suited for the subtraction techniques mentioned earlier, wherein one x-ray frequency lies somewhat above and the other x-ray frequency lies somewhat below the absorption edge of the material of interest. In a second embodiment of the invention, the target is divided in the middle plane of the anode ring perpendicularly to the ring axis; and the anode ring is provided with an inwardly projecting wedge ring symmetrical to the middle plane. Respective ring cathodes, each with a focusing arrangement, are arranged above and under the middle plane. These rings respectively irradiate only the upper or the lower ring surface of the wedge ring with electrons. By bringing the tip of the wedge ring close to the target and/or by fashioning the wedge angle smaller than or equal to twice the heel angle of the wedge ring, it can be assured that radiation from one of the ring surfaces of the wedge ring can exclusively reach either the upper half or the lower half of the target, so that an exactly monochromatic fluorescence radiation is generated dependent on whether the upper or the lower ring cathode is employed. In a further embodiment of the invention a fluid guide surface through which coolant flows is disposed in the hollow ring. This surface is preferably likewise wedge-shaped and inwardly projects into the hollow wedge ring and is spaced therefrom. The coolant also flows through the hollow wedge ring in which, of course, the principal heat quantity is generated due to the incidence of the electrons, and must also be removed therefrom. It also within the scope of the invention to provide a central x-ray exit window in a bottom plate of the anode ring lying opposite the target tip. The x-ray exit window is preferably arranged on a carrying pipe for the lower ring cathode projecting inwardly from a base opening and on the focusing coils thereof. Of course, the different divisions of the target could also be combined with one another, so that the target could be composed of four different sections in order to create a quadro-chromatic radiation source with four x-ray frequencies selectable optionally and in rapid sequence. Such an x-ray source with four different frequencies can be very advantageously utilized for other diagnostic purposes. For x-ray diagnostics systems making use of the subtraction method, however, a di-chromatic x-ray source is sufficient, i.e. only a single partition of the target into two sections.
	claims	1. A tritium-stripping apparatus in a nuclear reactor system including a nuclear reactor, a utilization means for utilizing heat energy generated by the nuclear reactor, and a flowing stream of molten salt for transferring the heat energy from the nuclear reactor to the utilization means, the tritium-stripping apparatus comprising:an outer containment structure;a tritium-separating membrane structure within the outer containment structure, the tritium-separating membrane structure including:a porous support selected from a group consisting of stainless steel and nickel-based alloy, and defining a first surface of the tritium-separating membrane structure;a nanoporous structural metal-ion diffusion barrier layer supported by and in contact with the porous support; anda gas-tight nonporous palladium-bearing separative layer supported by and in contact with the nanoporous structural metal-ion diffusion barrier layer, and defining a second surface of the tritium-separating membrane structure; anda sweep gas circulating between the outer containment structure and the first surface of the tritium-separating membrane structure;wherein the tritium-separating membrane structure is configured to receive the flowing stream of molten salt in contact with the gas-tight nonporous palladium-bearing separative layer so that tritium contained within the molten salt is absorbed by the gas-tight nonporous palladium-bearing separative layer and transported through the first surface and wherein the sweep gas circulates in contact with the porous support for collecting the transported tritium, and wherein the tritium-separating membrane structure is tubular and the first surface of the tritium-separating membrane structure is an outer surface of the tube and the second surface of the tritium-separating membrane structure is an inner surface of the tube. 2. The tritium-stripping apparatus in accordance with claim 1 wherein said porous support comprises 316 stainless steel. 3. The tritium-stripping apparatus in accordance with claim 1 wherein said structural metal-ion diffusion barrier layer comprises at least one material selected from the group consisting of yttrium-stabilized zirconia, scandia-stabilized zirconia, alumina, titania, chromia, and chromium nitride. 4. The tritium-stripping apparatus in accordance with claim 1 wherein said gas-tight nonporous palladium-bearing separative layer comprises a palladium alloy. 5. The tritium-stripping apparatus in accordance with claim 4 wherein said palladium alloy comprises a palladium-silver alloy. 6. The tritium-stripping apparatus in accordance with claim 1 wherein the outer containment structure is a tubular containment structure, wherein the sweep gas circulates between the tubular containment structure and the outer surface of the tubular tritium-separating membrane structure. 7. The tritium-stripping apparatus in accordance with claim 6 wherein the tubular tritium-stripping membrane structure is one of a plurality of tubular tritium-separating membrane structures within the tubular containment structure. 8. The tritium-stripping apparatus in accordance with claim 1 wherein the tritium-stripping system comprises a plurality of tubular tritium-separating membrane structures within the outer containment structure. 9. The tritium-stripping apparatus in accordance with claim 8 wherein the plurality of tritium-separating tubular membrane structures are U-shaped, and wherein the sweep gas circulates around the outer surface of the U-shaped tubular tritium-separating membrane.
	claims	1. A method for adjusting a charged particle beam traversing along a charged particle beam path, comprising the steps of:providing a charged particle system, comprising:an accelerator;a beamline from said accelerator to an output nozzle; anda tray assembly;inserting a first tray into a first slot of said tray assembly, said first tray configured with a first insert comprising a patient specific charged particle beam adjustment material, said step of inserting further comprising the steps of:inserting a second tray into a second slot of said tray assembly; andinserting a third tray into a third slot of said tray assembly;after said step of inserting, longitudinally retracting said tray assembly along the charged particle beam path into a zone circumferentially defined by said output nozzle, said step of retracting further comprising the step of:prior to operation of said charged particle system, moving said first slot, said second slot, and said third slot of said tray assembly into the zone circumferentially defined by said output nozzle;attaching a second insert to said second tray prior to said step of retracting; andattaching a third insert to said third tray prior to said step of retracting, wherein each of said first insert, said second insert, and said third insert comprise any of:a patient specific range shifter element comprising a standard thickness of a charged particle beam slowing material;a patient specific ridge filter, comprising a charged particle beam focusing element; anda patient specific blocking material comprising an aperture therethrough, said blocking material blocking the charged particle beam outside of the aperture. 2. The method of claim 1, said step of inserting further comprising the steps of:establishing a first electromechanical connection between a first identifier element, affixed to said first tray, and a first receiver, affixed to said tray assembly; andsaid first identifier element communicating at least one property of said first insert to said charged particle system via said first electromechanical connection. 3. The method of claim 2, said step of communicating further comprising the step of:identifying a patient specific insert installed in said first tray using information digitally stored in said first identifier. 4. The method of claim 2, said step of communicating further comprising the step of:identifying a blank insert installed in said first tray using information digitally stored in said first identifier. 5. The method of claim 2, said step of communicating further comprising the step of:identifying all of: occupancy, type of insert, and slot position to a main controller of said charged particle system. 6. The method of claim 1, said step of retracting further comprising the step of:moving said first slot and not said second slot and not said third slot of said tray assembly into a zone circumferentially defined by said output nozzle. 7. The method of claim 1, said step of retracting further comprising the step of:substantially removing steric limitation of said tray assembly between said output nozzle and a patient. 8. The method of claim 2, said step of communicating further comprising the step of: directly communicating with a main controller of said charged particle system without communication through a sub-assembly not directly in communication with said main controller. 9. An apparatus for adjusting a charged particle beam traversing a charged particle beam path, comprising:a charged particle system, comprising:an accelerator;a beamline from said accelerator to an output nozzle; anda tray assembly longitudinally retractable along the charged particle beam path into a zone circumferentially defined by said output nozzle; anda first tray insertable into a first slot of said tray assembly, said first tray configured with a patient specific charged particle beam adjustment insert during use;a second patient specific tray insertable into a second slot of said tray assembly; anda third patient specific tray insertable into a third slot of said tray assembly,wherein said first slot comprises a first height at least ten percent larger than said second slot, wherein a difference in slot height removes errors associated with a first tray intended for said first slot being inserted into said second slot. 10. The apparatus of claim 9, said first slot further comprising:a lateral orientation, relative to the charged particle beam path through said output nozzle, for insertion of said first patient specific tray.
050341847	summary	BACKGROUND OF THE INVENTION This invention relates to an apparatus for nuclear reactors, particularly to an apparatus for the acceleration and deceleration of the movement of a neutron absorbing control element of a nuclear reactor during its scram stroke. In many types of nuclear reactors the output and uniform fuel consumption of the reactors is controlled by inserting rods bearing a neutron absorbing material thereon into the reactor core. Shutdown or scram may be effected by releasing the control rods, and permitting them to fall with the force of gravity into the reactor core. In an emergency the control rods must enter into the reactor core sufficiently rapidly to effect an immediate power shut off, and the movement of the control rods must be slowed and stopped at the end of their strokes to prevent damage to the rods and to the core. Prior art methods such as those disclosed in U.S. Pat. No. 3,980,519, issued Sept. 14, 1976, to Taft, and U.S. Pat. No. 4,487,739 issued Dec. 11, 1984, to Thatcher et.al. have been devised to damp the motion of the free falling control rods prior to the point of impact. It is an object of this invention to provide a reliable and fast acting system for the insertion of control rods into a reactor core including both propulsion and damping of control rod movement. In the accomplishment of the foregoing object, it is another important object of this invention to provide a method for determining the accelerating pressure required to cause rapid insertion of a control rod as well as the decelerating pressure required to prevent damage to the control rod mechanism. It is another important object of this invention to provide a method for determining the rate at which decelerating pressure should be relieved to permit the control rod to move through a full stroke and come to rest safely without bouncing. It is a further object of this invention to present an improvement to a nuclear reactor control rod assembly which controls the movement of the control element throughout the scram stroke. Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention. SUMMARY OF THE INVENTION To achieve the foregoing and other objects, this invention comprises a high speed air cylinder in which the longitudinal movement of the piston within the air cylinder tube is controlled by pressurizing the air cylinder tube on the accelerating side of the piston and releasing pressure at a controlled rate on the decelerating side of the piston. The invention also includes a method for determining the pressure required on both the accelerating and decelerating sides of the piston to move the piston with a given load through a predetermined distance at the desired velocity, bringing the piston to rest safely without piston bounce at the end of its complete stroke.
054066018	claims	1. A transport and storage cask for spent nuclear fuel, comprising: a. a cask body having one open end; b. a basket formed from multiple layers of rowed plates that have complementary notches therein along the length of the plates such that the notches form fuel cell channels when the plates are assembled adjacent each other, said basket sized to be received in said cask body; c. centering keys on said cask body and said basket that maintain a gap between the inner surface of said cask body and the outer surface of said basket; and d. means for shielding and sealing the open end of said cask body. a. a shield plug received in the open end immediately above said basket; b. a shear ring installed in said cask body between said shield plug and the open end of said cask body; c. an inner lid seal welded in said cask body between said shear ring and the open end of said cask body; and d. an outer lid fastened to the open end of said cask body. 2. The transport and storage cask of claim 1, further comprising locating keys that extend the length of said basket and are received in notches in the mating surfaces of the plates forming said basket. 3. The transport and storage cask of claim 1, wherein said means for shielding and sealing the open end of said cask body comprises:
	abstract	The invention describes a storage and dispatch container for variable quantities of radioactive miniature radiation sources as well as a locking and opening device for the said storage and dispatch container and is applicable for the transport of radioactive miniature radiation sources in well organized and undamaged condition.
	summary
	abstract	Techniques are described that enhance power from an extreme ultraviolet light source with feedback from a target material that has been modified prior to entering a target location into a spatially-extended target distribution or expanded target. The feedback from the spatially-extended target distribution provides a nonresonant optical cavity because the geometry of the path over which feedback occurs, such as the round-trip length and direction, can change in time, or the shape of the spatially-extended target distribution may not provide a smooth enough reflectance. However, it may be possible that the feedback from the spatially-extended target distribution provides a resonant and coherent optical cavity if the geometric and physical constraints noted above are overcome. In any case, the feedback can be generated using spontaneously emitted light that is produced from a non-oscillator gain medium.
	summary
	claims	1. A thermal neutron capture reagent, comprising:a lithium-containing compound selected from a group consisting of: Li-3-phenylsalicylate, Li-3,5-di-tert-butylsalicylate, Li-acetylsalicylic acid, and combinations thereof,wherein the lithium-containing compound is soluble in a fluor,wherein the thermal neutron capture reagent exhibits an optical response signature for thermal neutrons. 2. A scintillator, comprising:a scintillator material;a primary fluor; anda Li-containing compound,wherein the Li-containing compound is soluble in the primary fluor,wherein the scintillator exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays,wherein the Li-containing compound is selected from a group consisting of: Li-3-phenylsalicylate, Li-3,5-di-tert-butylsalicylate, Li-acetylsalicylic acid, and combinations thereof. 3. The scintillator as recited in claim 2, wherein the scintillator material is optically transparent. 4. The scintillator as recited in claim 2, wherein the primary fluor is 2,5-diphenyloxazole (PPO). 5. The scintillator as recited in claim 2, further comprising a coordinating solvent, wherein the Li-containing compound is soluble in the coordinating solvent. 6. The scintillator as recited in claim 5, wherein the coordinating solvent is selected from a group consisting of: acetone, methanol, and dimethoxyethane. 7. The scintillator as recited in claim 2, further comprising a secondary fluor, wherein the secondary fluor has a longer wavelength than the primary fluor. 8. The scintillator as recited in claim 7, wherein the secondary fluor is present in an amount of less than 2 wt %. 9. The scintillator as recited in claim 7, wherein the secondary fluor is selected from a group consisting of: 9,10-diphenylanthracene and p-bis-(o-methylstyryl)-benzene. 10. The scintillator as recited in claim 2, wherein the scintillator material comprises a polymer matrix. 11. The scintillator as recited in claim 10, wherein the polymer matrix includes one or more aromatic groups. 12. The scintillator as recited in claim 10, wherein the polymer matrix is selected from a group consisting of: polystyrene, polyvinyltoluene, and poly(methylmethacrylate). 13. The scintillator as recited in claim 10, wherein the polymer matrix comprises an initiator and a cross-linker, wherein the initiator is present in an amount ranging from about 0.001 wt % to about 1 wt %, and wherein the cross-linker is present in an amount ranging from about 0.05 wt % to about 5 wt %. 14. The scintillator as recited in claim 2, wherein the scintillator material comprises a liquid scintillator material. 15. The scintillator as recited in claim 14, wherein the liquid scintillator material includes one or more aromatic groups. 16. The scintillator as recited in claim 14, wherein the liquid scintillator material includes a xylene-based liquid. 17. A system comprising:the scintillator of claim 2; anda photodetector for detecting the response of the scintillator to at least one or neutron and gamma ray irradiation. 18. A method for fabricating a scintillator, the method comprising:forming a precursor mixture; andheating the precursor mixture until a polymerization process is complete,wherein the precursor mixture comprises:a monomer;one or more fluors;a coordinating solvent; anda Li-containing compound selected from a group consisting of: Li-3-phenylsalicylate, Li-3,5-di-tert-butylsalicylate, Li-acetylsalicylic acid, and combinations thereof,wherein the Li-containing compound is soluble in at least one of the one or more fluors.
	abstract	A vacuum actuated and sustained ammonia feed system for the pH adjustment of power plant condensate and boiler feed water is described. This system can provide a safe means of providing anhydrous ammonia for pH adjustment to the condensate/feed water system of a power plant.

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