JP5787591B2 - Foreign matter removing apparatus, foreign matter removing method, uranium oxide pellet and fuel assembly manufacturing method - Google Patents

Description

This invention relates to a method for producing a foreign matter removing apparatus and the foreign matter removing method, and uranium oxide pellets and fuel assemblies, and more particularly, excellent foreign matter removing cleanability with uranium oxide powder or et foreign matter can be efficiently removed The present invention relates to an apparatus, a foreign matter removing method, and a method for producing uranium oxide pellets or fuel assemblies capable of producing high quality uranium oxide pellets or fuel assemblies with a high yield.

Uranium oxide pellets made of uranium oxide powder as a raw material are sealed in the fuel rods constituting the light water reactor fuel assembly. The uranium oxide powder forming the uranium oxide pellets is required to have high purity in order to produce high quality uranium oxide pellets or fuel assemblies with a high yield. It is required not to. However, in reality, metallic foreign matters or nonmetallic foreign matters may be mixed in the uranium oxide powder, and these foreign matters may also be mixed in the uranium oxide pellets. If foreign matter mixed in the uranium oxide pellets is found in the fuel rod inspection process, the fuel rod becomes defective, but the fuel rod is sealed and welded, so it takes time to disassemble the fuel rod, and the inside of the fuel rod Since the uranium oxide pellets taken out from can not be reused, it becomes scrap. Further, when the mixed foreign matter is a metallic foreign matter such as a magnetic substance, the magnetic susceptibility is measured for determining the gadolinia concentration in the fuel rod inspection process (also referred to as a Gd ₂ O ₃ concentration test). Since the metal foreign matter affects the measurement result, even if the gadolinia concentration is within a normal range, there is a possibility that it is judged as defective due to noise caused by the metal foreign matter.

  By the way, as an apparatus for removing metallic foreign matter from powder, for example, Patent Document 1 discloses that "a permanent magnet in which a plurality of permanent magnets having a longitudinal axis and whose surface is covered with a protective layer are arranged in parallel with a predetermined gap. The column has a structure in which a plurality of rows are stacked one above the other at a predetermined interval, and when the bulk particles containing foreign particles pass through the gaps of the permanent magnets at each step, the foreign particles are attracted to the permanent magnets. A foreign matter removing device characterized in that it is removed from a bulk particle group is described. Further, Patent Document 2 discloses that “a rotatable horizontal cylindrical magnet, a driving unit for rotating the magnet, a flow path for powdery material close to the curved surface of the magnet, and a powdered material connected to the flow path. A precision magnetic separator comprising a funnel for guiding the flow of the above, an opening / closing plate capable of reducing the diameter of the opening of the funnel, and a receiver for the powdery substance, wherein the magnet is housed in the flow path Is described.

  A sieve is mentioned as another apparatus which removes the foreign material mixed in the powder easily.

JP 2002-273264 A JP 2006-116453 A

  Since the foreign matter removing device of Patent Literature 1 and the precision magnetic separator of Patent Literature 2 are devices that remove metallic foreign matter, they can remove metallic foreign matter in the powder, but cannot remove nonmetallic foreign matter.

  On the other hand, when a sieve is used, if the sieve opening is too large, that is, too coarse, foreign matter cannot be sufficiently removed. On the other hand, if the sieve opening is too small, that is, too fine, it takes time to separate the sieves. In some cases, uranium oxide powder adhered or clogged, making it difficult to clean the sieve.

  By the way, since it is necessary to make the uranium enrichment of the uranium oxide pellets different in the fuel rod encapsulating the uranium oxide pellets formed with the uranium oxide powder, a different uranium enrichment is usually set for each production lot of the uranium oxide pellets. There is a special circumstance where it is necessary to prevent contamination with uranium oxide powder used or manufactured in other production lots.

  However, the foreign matter removing apparatus of Patent Document 1 and the precision magnetic separator of Patent Document 2 adsorb and remove metallic foreign substances by magnetic force, so that the metallic foreign substances adsorbed after processing the uranium oxide powder are separated from these apparatuses against the magnetic force. The metal foreign matter that is difficult to remove and removed from the powder tends to remain in the apparatus, and there is a possibility that the uranium oxide powder used or manufactured immediately before is mixed. In particular, in the precision magnetic separator of Patent Document 2, uranium oxide powder may not be removed if uranium oxide powder adheres or penetrates into the gap in the vicinity of the mounting portion of the rotatable cylindrical magnet. On the other hand, with a sieve, it is difficult to remove the uranium oxide powder remaining in the sieve after passing the uranium oxide powder, and there is a possibility that the uranium oxide powder used or produced immediately before is mixed. In particular, when the mesh is fine, it takes a long time to remove the adhered or clogged uranium oxide powder, and it may not be sufficiently removed.

  Thus, when producing a fuel assembly for a light water reactor using uranium oxide powder, due to its special circumstances, the foreign matter remaining together with efficient removal of foreign matter that may be mixed in the uranium oxide powder and There is also a demand for excellent cleaning properties that can easily remove uranium oxide powder.

The present invention is to provide an excellent foreign matter removing apparatus and the foreign matter removing method in cleanability with uranium oxide powder or et foreign matter can be efficiently removed, and an object.

  Another object of the present invention is to provide a method for producing uranium oxide pellets or fuel assemblies capable of producing high quality uranium oxide pellets or fuel assemblies with a high yield.

As means for solving the problems,
According to the first aspect of the present invention, the uranium oxide powder having a set enrichment is allowed to pass through to remove metallic foreign matters in the uranium oxide powder, and the bar magnets are arranged in a plurality of rows in the direction intersecting the passage direction and in a plurality of stages in the passage direction. Foreign matter removal having a magnetic force removing part arranged in the passage of the uranium oxide powder and a sieve arranged upstream or downstream in the passing direction with respect to the magnetic force removing part. A device,
The rod-shaped magnet is configured such that a magnet row in which magnet pieces and yokes are alternately arranged is removably accommodated in a stainless outer tube whose outer peripheral surface is mirror-finished, and in the passage of the uranium oxide powder. It is a foreign matter removing device characterized in that the uranium oxide powder is disposed so as not to rotate so that there is no gap for the uranium oxide powder to enter,
A second aspect of the present invention is the foreign substance removing apparatus according to the first aspect, wherein the bar-shaped magnets arranged in the second and subsequent stages in the passage direction have a pointed teardrop shape toward the upstream side in the passage direction. Yes,
Claim 3, wherein the sieve is a foreign matter removing apparatus according to claim 1 or 2 is disposed on the downstream side,
Claim 4 is the foreign matter removing apparatus according to any one of claims 1 to 3, further comprising a foreign matter collecting portion disposed on the downstream side in the passing direction with respect to the magnetic force removing portion.
Claim 5 is the foreign matter removing apparatus according to claim 4, wherein the foreign matter collecting part is a plate-like member.
Claim 6 is the foreign matter removing apparatus according to claim 4 or 5, wherein the foreign matter collecting part is disposed integrally with the sieve.
Claim 7 is a foreign matter removing method for removing foreign matter from uranium oxide powder having a step of passing the uranium oxide powder through the foreign matter removing device according to any one of claims 1 to 6,
Claim 8 is a step of passing the uranium oxide powder through the foreign matter removing apparatus according to any one of claims 1 to 6, a step of forming the uranium oxide powder passed through the foreign matter removing device, and a molded body formed. And a method of producing uranium oxide pellets having a step of firing
Claim 9 is a process of housing the uranium oxide pellets produced by the method for producing uranium oxide pellets according to claim 8 in a fuel cladding tube made of a zirconium alloy and sealing the sealed fuel rods. The manufacturing method of the fuel assembly which has these.

The foreign matter removing apparatus according to the present invention intersects the passing direction with a rod-shaped magnet in which a magnet array in which magnet pieces and yokes are alternately arranged is removably stored in a stainless steel outer tube whose outer peripheral surface is mirror-finished. Since it has a magnetic force removal portion and a sieve that are arranged in a plurality of rows in the direction and in a plurality of stages in the passing direction, and so as not to rotate so that there is no gap into which the uranium oxide powder enters, the metal Foreign matter can be removed with a magnetic force removal part, metallic foreign matter and non-metallic foreign matter can be removed with a sieve, and there is no moving part and there is no gap for the uranium oxide powder to enter, so it is easy to remove the remaining uranium oxide powder and foreign matter from the bar magnet. By removing the magnet row, the metal foreign matter adsorbed by the magnetic force can be easily dropped. Further, the foreign matter removing method of removing the uranium oxide powder or et foreign matter according to the present invention (hereinafter, referred to as foreign matter removing method according to the present invention.) Is the step of passing the foreign matter removing apparatus according uranium oxide powder in the present invention Have. Therefore, according to this invention can provide an excellent foreign matter removing apparatus and the foreign matter removing method in cleanability with uranium oxide powder or et foreign matter can be efficiently removed.

The method for producing uranium oxide pellets according to the present invention includes a step of passing uranium oxide powder through the foreign matter removing apparatus according to the present invention, a step of molding the uranium oxide powder passed through the foreign matter removing apparatus according to the present invention, and a molding and it could be produced with little uranium oxide pellets or et foreign matter and a step of firing the shaped body, a method of manufacturing a fuel assembly according to the present invention, uranium oxide according to the present invention according to the present invention little oxidation if we foreign matter and a step of focusing the steps a closed welded fuel rod sealing welding uranium oxide pellets produced by the production method of pellets housed in the fuel cladding tube made of zirconium alloy A fuel assembly having uranium pellets can be manufactured. Therefore, according to this invention, the manufacturing method of the uranium oxide pellet or fuel assembly which can manufacture a high quality uranium oxide pellet or fuel assembly with a high yield can be provided.

FIG. 1 is a schematic sectional view showing an example of a foreign matter removing apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view taken along line AA in FIG. FIG. 3 is a schematic cross-sectional view showing an example of a bar-shaped magnet that constitutes a magnetic force removing portion of the foreign matter removing apparatus according to the present invention. FIG. 4 is a schematic view showing an example of an apparatus for handling uranium oxide powder equipped with the foreign matter removing apparatus according to the present invention.

Foreign matter removing apparatus according to the present invention, there is provided an apparatus for removing foreign material of uranium oxide powder is passed through a uranium oxide powder, apparatus for handling uranium oxide powder, for example, mixers uranium oxide powder, molding and the like It is attached to the slot etc. As an apparatus provided with the foreign substance removal apparatus according to the present invention, for example, FIG. 4 shows a molding machine 8 for molding uranium oxide powder and a foreign substance removal apparatus according to the present invention attached to the inlet of the molding machine 8. An apparatus for handling uranium oxide powder is shown, which includes a foreign substance removal apparatus 1 as an example and a hopper 9 that is connected to the foreign substance removal apparatus 1 and guides the uranium oxide powder to the foreign substance removal apparatus 1. This is the system for handling uranium oxide powder equipped with foreign matter removing apparatus according to the invention uranium oxide powder not mixed uranium oxide powder be substantially also foreign material other production lot is turned on. Therefore, the foreign matter removing apparatus according to the present invention may be referred to as device both the uranium oxide powder other production lot is not mixed with the removal of foreign material in the uranium oxide powder.

  A foreign matter removing apparatus 1 as an example of the foreign matter removing apparatus according to the present invention will be described. This foreign matter removing apparatus 1 includes a rod-shaped magnet 10 in which a magnet array 12 in which permanent magnet pieces 14 and yokes 15 are alternately arranged is removably accommodated in a stainless steel outer tube 11 whose outer peripheral surface is mirror-finished. A magnetic force removing unit 3 disposed in the passage of the uranium oxide powder, which is arranged in a non-rotatable manner so as to have a plurality of rows in the direction intersecting the passing direction and a plurality of stages in the passing direction, and a magnetic force removing unit 3, a sieve 4 disposed upstream or downstream in the passing direction, and a foreign matter collecting unit 5 disposed downstream in the passing direction with respect to the magnetic force removing unit 3. In addition, since the foreign material collection | recovery part 5 is not mounted | worn with the foreign material removal apparatus 1 shown by FIG. 1, a mounting state is shown with a broken line.

  As shown in FIG. 1 and FIG. 2, the magnetic force removing unit 3 has a bar-shaped magnet 10 </ b> A and a bar-shaped magnet 10 </ b> B (collectively referred to as a bar-shaped magnet 10) arranged so as not to rotate. First, the bar magnet 10 will be described. As shown in FIGS. 3A and 3B, the rod-shaped magnet 10 is housed in a stainless steel outer tube 11 whose outer peripheral surface is mirror-finished, and the outer tube 11 so as to be detachable. And a magnet array 12.

  The outer tube 11 is a tube formed of stainless steel and having one end opened. The outer tube 11 is mirror-finished on its outer peripheral surface. If the outer peripheral surface of the outer tube 11 is a mirror surface, the uranium oxide powder is difficult to deposit on the outer peripheral surface of the outer tube 11, and can be easily removed even if temporarily deposited, and the cleaning performance of the magnetic force removing unit 3 is improved. The dimensions of the outer tube 11 are set as appropriate. For example, the axis length only needs to be long enough to install the foreign substance removing device 1, and the outer diameter of the outer tube 11, in particular, the direction arranged in a plurality of rows on the same stage. These dimensions, specifically the dimensions in the horizontal direction in FIG. 1, are also set appropriately. If the wall thickness of the outer tube 11 is too thin, the durability and strength may be inferior. On the other hand, if the wall thickness is too thick, the surface magnetic flux density is lowered.

  In the outer tube 11A of the rod-shaped magnet 10A arranged at the first stage with respect to the passing direction of the uranium oxide powder and the outer tube 11B of the rod-shaped magnet 10B arranged at the second and subsequent steps with respect to the passing direction, The cross-sectional shape in the vertical plane is not particularly limited, and examples thereof include a circle, an ellipse, a polygon, and a teardrop shape. In the present invention, the cross-sectional shape of the outer tube 11B of the rod-shaped magnet 10B is directed toward the upstream side in the passing direction of the uranium oxide powder in that the uranium oxide powder is difficult to deposit on the outer tube 11B and is excellent in cleaning performance of the magnetic force removing portion 3. For example, a polygonal shape or a teardrop shape is preferable, and a teardrop shape is particularly preferable. The cross-sectional shape of the outer tube 11A of the rod-shaped magnet 10A is substantially circular.

  As shown in FIGS. 3 (a) and 3 (b), the magnet row 12 has a permanent magnet piece 14 and a yoke 15 that are alternately arranged through the shaft body 13 and the shaft body 13. As shown in FIG. doing. The shaft body 13 integrally supports the permanent magnet piece 14 and the yoke 15 so that they can be inserted into and removed from the outer tube 11, that is, can be taken out. The shaft body 13 has a longer axial length than the outer tube 11. The yoke 15 is also called a spacer, and generates a magnetic line of force together with the permanent magnet piece 14. The yoke 15 is formed in a ring shape from a metal material such as stainless steel, and has a shaft hole through which the shaft body 13 passes. The cross-sectional shape in the plane perpendicular to the axial direction of the yoke 15 is preferably the same as the cross-sectional shape of the outer tube 11 in that the bar-shaped magnet 10 exhibits a high surface magnetic flux density. It is particularly preferred that the cross-sectional shape and dimensions are as follows. The thickness of the yoke 15 is appropriately determined in consideration of the thickness of the permanent magnet piece 14, the surface magnetic flux density of the rod-shaped magnet 10, and the like. The permanent magnet piece 14 generates magnetic lines of force together with the yoke 15 and has a shaft hole that is formed in a ring shape from a magnet material and through which the shaft body 13 passes. The permanent magnet piece 14 is formed as a permanent magnet of a magnet material such as a rubber magnet, a ferrite magnet, a rare earth magnet, for example, a samarium cobalt rare earth magnet, a neodymium rare earth magnet, etc. The magnetic force is adjusted so that The cross-sectional shape in a plane perpendicular to the axial direction of the permanent magnet piece 14 is preferably formed in the same manner as the yoke 15. Dimensions other than the thickness of the permanent magnet piece 14 are basically the same as those of the yoke 15. The thickness of the permanent magnet piece 14 is appropriately determined in consideration of the thickness of the yoke 15, the surface magnetic flux density of the rod-shaped magnet 10, and the like.

  The magnet row 12 is formed by arranging the permanent magnet pieces 14 and the yokes 15 so as to be alternately adjacent to each other. Specifically, the eight yokes 15 and the seven pieces of the yokes 15 are positioned so that the yokes 15 are located at both ends. The permanent magnet piece 14 is arranged so that the permanent magnet piece 14 is positioned between the yoke 15. And the permanent magnet piece 14 and the yoke 15 have the shaft body 13 penetrated through the shaft holes, and are integrally supported by the shaft body 13 as shown in FIG. It is stored in. The magnet row 12 has a lid 16 that closes the opening of the outer tube 11 at its end. None of the shaft body 13, the permanent magnet piece 14, and the yoke 15 are fixed to the outer tube 11, but merely inserted and arranged, so that the end of the shaft body 13 protruding from the end of the outer tube 11 is used. The magnet row 12 can be accommodated in the outer tube 11 or taken out from the outer tube 11 by operating the unit. That is, in the rod-shaped magnet 10, the magnet row 12 is housed or loaded in the outer tube 11 so as to be detachable. The process of taking out the magnet array 12 from the outer tube 11 is shown in FIG.

  The rod-shaped magnet 10 can efficiently remove metallic foreign matters from the uranium oxide powder and, for example, has a surface magnetic flux density of 0.2 to 1.5 Tessler (T) in that it does not easily drop the metallic foreign matters once adsorbed. Can be set. Specifically, it can be set to 0.2 Tessler in the case of a ferrite magnet and 1.5 Tessler in the case of a neodymium rare earth magnet or the like.

  As shown in FIG. 1 and FIG. 2, the magnetic force removing unit 3 is arranged in the uranium oxide powder passage so as to have a plurality of rows in the direction intersecting with the passing direction of the uranium oxide powder and a plurality of stages in the passing direction. Has been. Specifically, the magnetic force removing unit 3 includes a first stage with respect to the passage direction of the uranium oxide powder in which five rod-shaped magnets 10A having a substantially circular cross section are arranged in parallel in the passage of the uranium oxide powder, and the cross sectional shape. Has a second stage with respect to the passing direction in which four teardrop-shaped rod-shaped magnets 10B are arranged in parallel. The first stage of the magnetic force removing unit 3 has five bar-shaped magnets 10A hung on the housing of the foreign matter removing apparatus 1 in a direction intersecting the passing direction of the uranium oxide powder, that is, in a direction substantially perpendicular to the passing direction. Has been passed. Further, the second stage of the magnetic force removing unit 3 includes four bar-shaped magnets 10B in a direction crossing the passing direction of the uranium oxide powder, that is, in a direction substantially perpendicular to the passing direction, as shown in FIG. When viewed in a plan view, it is stretched over the housing of the foreign matter removing apparatus 1 so as to be positioned between the rod-shaped magnets 10A. In the second stage, as shown in FIG. 1, the rod-shaped magnets 10 </ b> B are arranged substantially in parallel so that the teardrop-shaped cusps are directed upstream in the passage direction of the uranium oxide powder, that is, toward the first stage. . When the rod-shaped magnets 10B are arranged in this way, the uranium oxide powder does not accumulate or stay on the rod-shaped magnet 10B, and the cleaning property is excellent.

  As shown in FIG. 2, the arrangement interval of the bar-shaped magnets 10A and the bar-shaped magnets 10B along the horizontal direction of the first stage and the second stage is positioned between the other bar-shaped magnets 10 when viewed in plan view. Preferably, the setting is made so that the interval 17 with the other rod-shaped magnet 10 is small, or when there is no interval 17 with the other rod-shaped magnet 10 when viewed in plan, and a portion overlaps the other rod-shaped magnet 10. Is done. In this example, the distance 17 from the other rod-shaped magnet 10 is set to be small. As described above, when the bar magnets 10 arranged in a plurality of stages are alternately arranged in a so-called “staggered” shape as shown in FIG. 1, the uranium oxide powder passing through the magnetic force removing unit 3 uniformly contacts the bar magnet 10. Metal foreign matter mixed in uranium oxide powder can be adsorbed efficiently.

  In this magnetic force removing portion 3, a bar magnet 10 having a magnet row 12 covered with an outer tube 11 is disposed so as not to rotate. Thus, when the magnet row 12 is covered with the outer tube 11 and the rod-shaped magnet 10 is spanned over the casing of the foreign matter removing device 1 so as not to rotate, there is no gap in the rod-shaped magnet 10 and the rod-shaped magnet. Since there is no movable part in 10 and a housing | casing, the uranium oxide powder adhering to a housing | casing or the rod-shaped magnet 10 can be easily removed, without a uranium oxide powder invading a clearance gap and a movable part, and cleaning property improves.

  The sieve 4 is detachably disposed on the downstream side in the passing direction of the uranium oxide powder with respect to the magnetic force removing unit 3. The sieve 4 removes metal foreign matters that have not been removed by the magnetic force removing unit 3 and / or non-metallic foreign matters mixed in the uranium oxide powder. Therefore, when the sieve 4 is provided in addition to the magnetic force removing unit 3, the metal foreign matter removing performance can be improved as an auxiliary removing device of the magnetic force removing unit 3, and the foreign matters different between the magnetic force removing unit 3 and the sieve 4. It is possible to remove various foreign matters such as metallic foreign matters and non-metallic foreign matters at once.

  The sieve 4 only needs to have a sieve opening to the extent that foreign matter in the uranium oxide powder can be removed. For example, # 100 (a sieve opening of 0.150 mm) to # 40 (a sieve opening of 0.0. 425 mm) is appropriately selected according to the foreign matter to be removed. For example, if non-metallic foreign matter is to be removed separately from the magnetic force removing unit 3, the opening is set to be smaller than the non-metallic foreign matter when mixing is assumed. If the metallic foreign matter is to be removed as an auxiliary to 3, the mesh opening is set smaller than the metallic foreign matter expected to be mixed. The USA mesh # 40 corresponds to a # 35 Tyler mesh if the mesh opening is the same. The sieve 4 may be produced for the foreign matter removing apparatus 1 or a known sieve may be adopted.

  The foreign matter removing apparatus 1 has a foreign matter collecting portion 5 disposed on the downstream side in the passing direction of the uranium oxide powder with respect to the magnetic force removing portion 3 and the sieve 4. The foreign matter collecting unit 5 is attached to the foreign matter removing device 1 when cleaning the foreign matter removing device 1 or the device having the foreign matter removing device 1, and the inside of the device comprising the foreign matter removing device 1, for example, a molding machine 8 (see FIG. 4). .) Prevents uranium oxide powder, metallic foreign matter and non-metallic foreign matter from falling inside. Accordingly, the foreign matter collecting unit 5 is arranged on the most downstream side when cleaning the foreign matter removing device 1 and is arranged so as not to function when the foreign matter removing device 1 is operated, that is, when uranium oxide powder is allowed to pass through. Not installed. As shown by a broken line in FIG. 2, the foreign matter collecting part 5 is a plate-like member that is detachably disposed integrally with the foreign matter removing device 1 or its housing adjacent to the downstream side of the sieve 4, It does not have holes to allow uranium oxide powder and foreign materials to pass through.

  The foreign matter removing apparatus 1 has a guide plate 6 disposed on the upstream side in the passing direction of the uranium oxide powder with respect to the magnetic force removing portion 3. The guide plate 6 is disposed on the upstream side of the magnetic force removing unit 3 and guides the uranium oxide powder to the magnetic force removing unit 3 so that the uranium oxide powder does not pass through the gap between the foreign matter removing device 1 and the magnetic force removing unit 3. . Therefore, the guide plate 6 is also called a baffle plate. The shape and dimensions of the guide plate 6 are not particularly limited as long as the uranium oxide powder can be guided. For example, as shown in FIG. 1, a rod-shaped magnet 10 is stretched over the side wall forming the casing of the foreign matter removing apparatus 1. A pair of flat plates provided on the side walls that are not disposed along the axial direction of the rod-shaped magnet 10 such that the distance between them becomes shorter in the direction of passage of the uranium oxide powder.

Next, the foreign matter removing method according to the present invention will be described. Foreign matter removing method according to the present invention is a method for removing uranium oxide powder or et foreign matter, has a step of passing the foreign matter removing apparatus according uranium oxide powder in the present invention.

  In the foreign matter removing method according to the present invention, the prepared uranium oxide powder is put into the foreign matter removing device according to the present invention, for example, the foreign matter removing device 1. Then, the uranium oxide powder and the mixed foreign matter are guided by the guide plate 6 and reach the magnetic force removing unit 3. Then, the uranium oxide powder and the non-metallic foreign matter guided by the guide plate 6 and reaching the magnetic force removing portion 3 pass through the magnetic force removing portion 3 without being adsorbed by the rod-shaped magnet 10, and the metallic foreign matter is the rod-shaped magnet 10 of the magnetic force removing portion 3. And does not pass through the magnetic force removal unit 3. At this time, since the bar-shaped magnet 10 is disposed in the magnetic force removing unit 3 as described above, the metal foreign matter uniformly contacts the bar-shaped magnet 10 and most of the metal foreign body is efficiently adsorbed. The foreign metal once adsorbed does not interfere with the passage of the uranium oxide powder due to the passage of the uranium oxide powder and the like, and does not impede the passage of the uranium oxide powder. In addition, the metal foreign material which went around to the downstream side of the rod-shaped magnet 10 does not fall off from the rod-shaped magnet 10 having the surface magnetic flux density.

  On the other hand, the uranium oxide powder and the non-metallic foreign matter that have not been attracted to the bar-shaped magnet 10 and have passed through the magnetic force removing unit 3 reach the sieve 4. As a result, the non-metallic foreign matter and the metallic foreign matter that has not been adsorbed by the bar magnet 10 are larger than the sieve opening of the sieve 4, so that they cannot pass through the sieve 4 and remain on the sieve 4 and do not pass through the sieve 4. On the other hand, since the uranium oxide powder usually has a particle size smaller than the opening of the sieve 4, it passes through the sieve 4 and is installed in a device such as a molding machine 8 (see FIG. 4) where the foreign matter removing device 1 is mounted. To reach.

  In this way, the foreign matter can be efficiently removed from the uranium oxide powder mixed with the foreign matter by the foreign matter removing device 1 including the magnetic force removing unit 3 and the sieve 4.

  After the uranium oxide powder passes through the foreign matter removing apparatus 1, the foreign matter removing apparatus 1 is cleaned. In the magnetic force removing unit 3, since the first stage bar-shaped magnet 10A is close to the opening of the foreign matter removing apparatus 1, the uranium oxide powder deposited or staying on the bar-shaped magnet 10A can be easily cleaned by a cleaning tool or air blowing. . On the other hand, since the cross-sectional shape of the second-stage bar-shaped magnet 10B is a teardrop shape, almost no uranium oxide powder is deposited on the magnet, and normal cleaning is not required. Further, since the magnet row 12 is covered with the outer tube 11 and all the bar-shaped magnets 10 are disposed so as not to rotate, the bar-shaped magnet 10 has no gap, and the bar-shaped magnet 10 and the casing have a movable part. The uranium oxide powder remaining in the magnetic force removal unit 3 can be easily removed. In this way, the uranium oxide powder remaining in the magnetic force removal unit 3 can be easily and effectively cleaned.

  On the other hand, in order to clean the metal foreign matter adsorbed by the bar magnet 10 of the magnetic force removing unit 3, for example, after the foreign matter collecting unit 5 is installed on the downstream side of the magnetic force removing unit 3, as shown in FIG. Then, the shaft body 13 is pulled out from the outer tube 11 of the bar magnet 10 and the magnet row 12 is removed. That is, a cleaning process is performed in which the magnet row 12 of the bar-shaped magnet 10 is removed from the outer tube 11 and the metal foreign matter adsorbed on the bar-shaped magnet 10 is removed. Then, the surface magnetic flux density of the rod-shaped magnet 10 disappears, and the metal foreign matter adsorbed on the outer tube 11 of the rod-shaped magnet 10 falls due to gravity. In this way, the metallic foreign object can be easily dropped from the bar magnet 10. The metal foreign matter dropped off from the rod-shaped magnet 10 is captured by the sieve 4 or the foreign matter recovery unit 5 and remains in the device to which the foreign matter removing device 1 is attached, such as the molding machine 8 (see FIG. 4) and the foreign matter removing device 1, Mixing into the uranium oxide powder to be processed next is prevented.

  In this way, the uranium oxide powder and metal foreign matter remaining from the magnetic force removing unit 3 can be easily discharged out of the foreign matter removing apparatus 1, that is, removed.

  In the sieve 4, for example, the non-metallic foreign matter or the metallic foreign matter supplemented by the sieve 4 is removed by removing the foreign matter collecting unit 5 from the housing of the foreign matter removing apparatus 1 after installing the foreign matter collecting unit 5. The foreign matter removing device 1 can be discharged out of the foreign matter removing device 1 without remaining in the apparatus, for example, the molding machine 8 (see FIG. 4) and the foreign matter removing device 1, for example. In this way, non-metallic foreign matters or metallic foreign matters can be easily removed from the sieve 4.

  The foreign matter collected by the foreign matter collecting unit 5 can be discharged out of the foreign matter removing device 1 by removing the foreign matter collecting unit 5 from the housing of the foreign matter removing device 1 before or after the cleaning of the sieve 4. It can be removed without remaining in the mounted device, for example, the molding machine 8 (see FIG. 4) and the foreign matter removing device 1. In this way, the foreign matter can be easily removed from the foreign matter collection unit 5.

  As described above, the foreign matter removing apparatus 1 including the magnetic force removing unit 3, the sieve 4, and the foreign matter collecting unit 5 having the rod-shaped magnet 10 in which the magnet row 12 is removably accommodated in the outer tube 11 is provided with a magnet from the outer tube 11. By removing the column 12 and removing the sieve 4 and the foreign matter collecting part 5 from the foreign matter removing apparatus 1, the uranium oxide powder and the foreign matter can be easily removed from the foreign matter removing apparatus 1 without remaining in the foreign matter removing apparatus 1. Can be discharged. Therefore, according to the foreign matter removing apparatus according to the present invention and the foreign matter removing method according to the present invention, even if uranium oxide powder having a stable quality free from foreign matters and uranium oxide powders having different concentrations are continuously passed through, High quality uranium oxide powders substantially free of different uranium oxide powders can be provided.

  Subsequently, the manufacturing method of the uranium oxide pellet which concerns on this invention is demonstrated. The method for producing uranium oxide pellets according to the present invention includes a step of passing uranium oxide powder through the foreign matter removing apparatus according to the present invention, a step of molding the uranium oxide powder passed through the foreign matter removing apparatus according to the present invention, and a molding And a step of firing the formed body.

  In the method for producing uranium oxide pellets according to the present invention, preferably, before the step of passing the uranium oxide powder through the foreign matter removing apparatus according to the present invention or after the step of passing the uranium oxide powder, A cleaning process is performed in which the magnet row 12 is removed from the outer tube 11 to remove the metal foreign matter adsorbed on the rod-shaped magnet 10. This cleaning step is basically the same as the “cleaning step of removing the metal foreign matter adsorbed on the bar magnet by removing the magnet row of the bar magnet from the outer tube” in the foreign matter removing method according to the present invention described above. Omitted. By carrying out this cleaning step, it is possible to prevent the mixing of uranium oxide powders having different concentrations that have been used or manufactured immediately before.

  In the method for producing uranium oxide pellets according to the present invention, a step of passing the uranium oxide powder through the foreign matter removing apparatus according to the present invention is performed. Since this step is basically the same as the “step of passing the uranium oxide powder through the foreign matter removing apparatus according to the present invention” in the foreign matter removing method according to the present invention described above, the description thereof is omitted.

  In the method for producing uranium oxide pellets according to the present invention, a step of forming the obtained high-quality uranium oxide powder into pellets is then performed. In forming, it is preferable to add other additives to the uranium oxide powder and mix them uniformly. The mixture thus prepared is molded into a predetermined shape. Various molding methods can be adopted for molding, and known molding conditions selected for producing pellets of uranium oxide powder can be adopted as molding conditions.

  In the method for producing uranium oxide pellets according to the present invention, a step of firing the molded body is then performed. For the firing of the molded body, a known firing method and firing conditions selected for producing pellets of uranium oxide powder can be appropriately selected.

  In the method for producing uranium oxide pellets according to the present invention, an appearance inspection of the obtained uranium oxide pellets is performed as desired. In the present invention, since the uranium oxide pellets are manufactured with the uranium oxide powder from which the metal foreign matters are removed, the manufactured uranium oxide pellets can be accurately inspected, and the yield of the uranium oxide pellets is increased.

  The uranium oxide pellets produced in this way are stable and high quality uranium oxide powders that are obtained by allowing the uranium oxide powder to be used to pass through the foreign matter removing apparatus according to the present invention. And has a high quality substantially free of uranium oxide powders having different concentrations. Therefore, according to the method for producing uranium oxide pellets according to the present invention, it is possible to provide uranium oxide pellets having a stable and high quality free from foreign matters at a high yield.

  A method for manufacturing a fuel assembly according to the present invention will be described. The method for producing a fuel assembly according to the present invention includes a step of enclosing the uranium oxide pellets produced by the method for producing uranium oxide pellets according to the invention according to the invention in a fuel cladding tube made of a zirconium alloy and hermetically welding the uranium oxide pellets. And focusing the fuel rods that are hermetically welded.

  In the fuel assembly manufacturing method according to the present invention, uranium oxide pellets manufactured by the uranium oxide pellet manufacturing method according to the present invention are prepared. Since the manufacturing method of the uranium oxide pellet according to the present invention is as described above, the description thereof is omitted.

  In the fuel assembly manufacturing method according to the present invention, the step of enclosing uranium oxide pellets in a zirconium alloy fuel cladding tube and hermetically welding is performed, and then the step of concentrating the hermetically sealed fuel rods is performed. . Both the hermetically welding step and the converging step in the method for manufacturing a fuel assembly according to the present invention can be performed by appropriately adopting known methods and conditions selected for manufacturing the fuel assembly.

In the method for producing uranium oxide pellets according to the present invention, the produced fuel assembly is inspected as desired. Examples of the fuel assembly inspection include a Gd ₂ O ₃ concentration inspection of the fuel assembly. Gd ₂ O ₃ concentration tests, _Gd 2 _{O 3} magnetization method utilizing the magnetic susceptibility of _Gd 2 _{O 3} is proportional to the _Gd 2 _{O 3} concentration of uranium oxide pellets are normally used. In this inspection, if metal foreign matter is mixed in the uranium oxide pellet, the measurement result of the magnetic susceptibility of Gd ₂ O ₃ is affected, and the accurate magnetic susceptibility of Gd ₂ O ₃ cannot be measured. Since the uranium oxide pellets are manufactured from the uranium oxide powder from which the metal foreign matter has been removed, the magnetic susceptibility of Gd ₂ O _{3 in} the fuel assembly can be accurately measured. Therefore, the manufactured fuel assembly can be accurately inspected, and the yield of the fuel assembly is increased.

  The fuel assembly produced in this way is a stable, high-quality uranium oxide pellet without foreign matter produced by the uranium oxide pellet production method according to the present invention. And has a high quality substantially free of uranium oxide powders having different concentrations. Therefore, according to the method for manufacturing a fuel assembly according to the present invention, it is possible to provide a fuel assembly having a stable and high quality with no foreign matter mixed in at a high yield.

Further, since the fuel assembly manufactured in this way is manufactured with a stable and high quality uranium oxide powder free from foreign matter, the magnetic susceptibility of Gd ₂ O ₃ can be accurately measured. Generation of defective products can be reduced, and high-quality nuclear fuel assemblies can be manufactured. In particular, in the inspection process, even if the measured value of the magnetic susceptibility of Gd ₂ O ₃ is within an allowable range, it is possible to suppress the occurrence of defective products that are determined to be defective. Therefore, according to the method for manufacturing a fuel assembly according to the present invention, a fuel assembly having no magnetic susceptibility abnormality can be manufactured with high yield.

  The method for producing uranium oxide pellets using the uranium oxide powder and the method for producing the fuel assembly are described in, for example, “Light Water Reactor Fuel Behavior” (Author: Light Water Reactor Fuel Behavior Editorial Committee, Publisher Name Nuclear Safety Research Foundation) Committee, publication date: July 1998).

  The foreign matter removing apparatus according to the present invention is not limited to the above contents, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, in the foreign matter removing apparatus 1, a rod-shaped magnet 10A having a substantially circular cross section is arranged in the first stage with respect to the passing direction of the uranium oxide powder. A teardrop-shaped rod-shaped magnet having a cusp-shaped cross-section toward the upstream side in the passage direction may be arranged in the first stage.

  In the foreign matter removing apparatus 1, in the magnetic force removing unit 3, the five bar magnets 10A are arranged in the first stage, and the four bar magnets 10B are arranged in the second stage. The number of rod-shaped magnets arranged in each stage is not particularly limited.

  In the foreign matter removing apparatus 1, the magnetic force removing unit 3 has a plurality of bar magnets 10 arranged in parallel in one direction. In this invention, the magnetic force removing unit has a plurality of bar magnets arranged in parallel in the other direction. Also good. For example, in the magnetic force removing unit, a plurality of bar magnets may be arranged in a so-called cross-beam shape in a plurality of stages in a direction perpendicular to each other.

  In the foreign matter removing apparatus 1, the bar-shaped magnet 10 includes a permanent magnet piece 14 as a permanent magnet. However, in the present invention, the bar-shaped magnet may include an electromagnet instead of the permanent magnet, and the permanent magnet and the electromagnet are combined. You may have. When an electromagnet is employed, the metal foreign matter adsorbed on the rod-shaped magnet is removed by interrupting energization to the electromagnet.

  In the foreign matter removing apparatus 1, one sieve 4 is arranged on the downstream side in the passing direction of the uranium oxide powder with respect to the magnetic force removing unit 3, but in this invention, a plurality of sieves may be arranged, One or a plurality of uranium oxide powders may be arranged on the upstream side in the passage direction of the uranium oxide powder, and one or more may be arranged on the upstream side and the downstream side in the passage direction.

  In the foreign matter removing device 1, the foreign matter collecting unit 5 is a plate-like member that is detachably disposed on the foreign matter removing device 1 or its casing. In this invention, the foreign matter collecting unit is provided integrally with the sieve. A foldable plate-like member may be used, and a foldable plate-like member arranged to be opened and closed separately from the sieve may be used.

  The foreign matter removing method according to the present invention, the method for producing uranium oxide pellets according to the present invention, and the method for producing a fuel assembly according to the present invention are not limited to the above contents, and the object of the present invention can be achieved. Various changes are possible as long as possible.

Example 1
A foreign matter removing apparatus 1 shown in FIGS. 1 to 3 was prepared. Details are shown below.

  The magnetic force removing unit 3 in the foreign matter removing apparatus 1 includes five rod-shaped magnets 10A (first stage) that are supported in parallel and non-rotatably with a distance between axes of 55 mm, and parallel and rotate with a distance between axes of 55 mm. The four rod-shaped magnets 10B (second stage) that were pivotally supported were arranged in a “staggered” manner so as to be staggered. The axis of each of the four bar-shaped magnets 10B is located at the center of the distance between the axes of two adjacent bar-shaped magnets 10A. The bar-shaped magnet 10A (first stage) and the four bar-shaped magnets 10B (two-staged) The distance between the axis and the eye) was 50 mm. Each of the five rod-shaped magnets 10A has an outer tube 11 in which a magnet array 12 in which permanent magnet pieces 14 and yokes 15 are alternately inserted into a shaft body 13 is circular in cross section (diameter 25 mm) and the outer peripheral surface is mirror-finished. It was stored so that it could be inserted and removed freely, and had the same shape and dimensions. The surface magnetic flux density of each of the rod-shaped magnets 10A was 1.00T. On the other hand, each of the four bar-shaped magnets 10B is basically the same as the bar-shaped magnet 10A except that the cross section has a teardrop shape. The guide plate 6 was installed diagonally above the rod-shaped magnet 10 </ b> A arranged on both sides of the first stage in the magnetic force removing unit 3.

  A sieve 4 having a mesh opening of # 100 is placed on the downstream side in the passing direction of the uranium oxide powder with respect to the magnetic force removing unit 3, and the plate-like foreign material collecting unit 5 is placed on the uranium oxide powder with respect to the sieve 4. It was detachably arranged on the downstream side in the passing direction.

  Next, the foreign matter collecting unit 5 of the foreign matter removing device 1 is removed, and about 5 t of uranium oxide powder is put into the foreign matter removing device 1 to pass through the magnetic force removing unit 3 and the sieve 4, and the oxidized deposited on the rod-shaped magnet 10A. Uranium powder was removed by dropping with a cleaning tool. Thereafter, the sieve 4 is removed, and the foreign matter collecting part 5 is mounted on the downstream side of the sieve 4, and the magnet array 12 of the bar magnet 10 </ b> A and the bar magnet 10 </ b> B is removed from the outer tube 11 and attracted to the bar magnet 10 </ b> A and the bar magnet 10 </ b> B. The foreign metal collected by the foreign material collecting unit 5 was supplemented. Thus, the metal foreign matter removed by the bar-shaped magnet 10A and the bar-shaped magnet 10B, that is, the magnetic force removing unit 3 and the sieve 4, was about 1.25 g. The uranium oxide powder was not mixed with nonmetallic foreign matters.

  In this foreign matter removing apparatus 1, cleaning of the uranium oxide powder deposited on the rod-shaped magnet 10A was easy, and almost no uranium oxide powder was deposited on the rod-shaped magnet 10B, so that cleaning was not necessary. On the other hand, the metal foreign matter adsorbed by the rod-shaped magnet 10 </ b> A and the rod-shaped magnet 10 </ b> B was easily dropped by removing the magnet row 12 from the outer tube 11. The foreign matter captured on the sieve 4 could be easily cleaned by removing the sieve 4 from the foreign matter removing apparatus 1.

The uranium oxide powder thus passed through the foreign matter removing apparatus 1 was molded and fired in accordance with a known molding method and firing method to produce uranium oxide pellets. According to a known method, the uranium oxide pellets were housed in a zirconium alloy fuel cladding tube and hermetically sealed, and then fuel rods were focused to produce a plurality of fuel assemblies. A plurality of fuel rods manufactured in this manner were subjected to a Gd ₂ O ₃ concentration test. As a result, fuel assemblies having almost the same concentration and having no magnetic susceptibility abnormality could be manufactured with good yield.

DESCRIPTION OF SYMBOLS 1 Foreign material removal apparatus 3 Magnetic force removal part 4 Sieve 5 Foreign material collection | recovery part 6 Guide plate 8 Molder 9 Hopper 10, 10A, 10B Bar-shaped magnet 11, 11A, 11B Outer tube 12 Magnet row 13 Shaft body 14 Permanent magnet piece 15 Relay ( Spacer)
16 Lid 17 Interval

Claims (9)

The uranium oxide powder having a set enrichment is passed through to remove metallic foreign matters in the uranium oxide powder, and the bar magnets are arranged in a plurality of rows in the direction intersecting the passing direction and in a plurality of stages in the passing direction. A foreign matter removing device having a magnetic force removing portion arranged in the passage of the uranium oxide powder, and a sieve arranged upstream or downstream in the passing direction with respect to the magnetic force removing portion ,
The rod-shaped magnet is configured such that a magnet row in which magnet pieces and yokes are alternately arranged is removably accommodated in a stainless outer tube whose outer peripheral surface is mirror-finished, and in the passage of the uranium oxide powder. A foreign matter removing device, wherein the foreign matter removing device is arranged so as to be non-rotatable so that there is no gap through which the uranium oxide powder enters.   The foreign matter removing apparatus according to claim 1, wherein the bar-shaped magnets arranged in the second and subsequent stages in the passage direction have a pointed teardrop shape toward the upstream side in the passage direction. The sieve, the foreign matter removing apparatus according to claim 1 or 2 is disposed on the downstream side.   The foreign substance removal apparatus of any one of Claims 1-3 which has the foreign material collection | recovery part arrange | positioned with respect to the said magnetic force removal part in the downstream of the said passage direction.   The foreign matter removing apparatus according to claim 4, wherein the foreign matter collecting unit is a plate-like member.   The foreign matter removing apparatus according to claim 4, wherein the foreign matter collecting unit is disposed integrally with the sieve.   A foreign matter removing method for removing foreign matter from uranium oxide powder, comprising a step of passing the uranium oxide powder through the foreign matter removing device according to any one of claims 1 to 6.   A step of passing the uranium oxide powder through the foreign matter removing apparatus according to any one of claims 1 to 6, a step of molding the uranium oxide powder passed through the foreign matter removing device, and firing the molded body. And a method for producing uranium oxide pellets.   A fuel comprising: a step of enclosing uranium oxide pellets produced by the method for producing uranium oxide pellets according to claim 8 in a zirconium alloy fuel cladding tube and hermetically welding; and a step of focusing hermetically welded fuel rods. A method for manufacturing an assembly.

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