JP4398929B2 - Spent fuel storage container - Google Patents

Description

  The present invention relates to a spent fuel storage container used for transporting and storing spent fuel assemblies generated from the core of a light water reactor, and in particular, spent fuel for a boiling water reactor (BWR (Boiling Water Reactor)). The present invention relates to a spent fuel storage container suitable for use in transportation and storage of assemblies.

  After being used for a certain period in the nuclear reactor nuclear reactor core, the spent fuel assembly removed from the core is stored in the spent fuel storage pool in the power plant for a predetermined cooling period, and thereafter, uranium, plutonium, etc. In order to recover the reusable nuclear fuel material, it is stored in a spent fuel storage container such as a cask having a radiation shielding performance and transported to a fuel reprocessing facility by a trailer, a ship or the like. In addition, intermediate storage with spent fuel storage containers is being implemented or planned at the radioactive material storage facility until it is transported to the fuel reprocessing facility.

  Generally, a spent fuel storage container such as a cask is composed of a trunk portion having a storage portion provided with a lattice-like basket for partitioning and storing spent fuel assemblies one by one, and an upper portion of the trunk portion. It is comprised from the primary lid and secondary lid which are attached to opening, and it is constituted so that the sealed state of a container may be maintained by sealing the primary lid and secondary lid to a trunk (for example, Patent Document 1).

  BWR spent fuel assemblies are used in a nuclear reactor with a channel box installed, but when stored in a cask or the like after use, they may be stored with the channel box installed. , The channel box is removed and stored in two ways. Here, the used fuel assembly to which the channel box is attached has an outer dimension larger than that of the spent fuel assembly from which the channel box is removed because the channel box is attached.

  By the way, the size of the basket lattice is preferably as small as possible in order to improve the storage efficiency. However, as described above, the outer dimensions of the spent fuel assembly differ depending on the presence or absence of the channel box. Therefore, if the basket lattice is formed corresponding to these, the manufacturing cost of the spent fuel storage container is increased. I'll be stuck. Therefore, conventionally, a basket lattice is formed in accordance with the external dimensions of the spent fuel assembly with the channel box attached, and the spent fuel assembly with the channel box attached and the channel box are removed with one cask. It was designed to accommodate the storage of both fuel assemblies. Similarly, in the canister as a spent fuel storage container used in the concrete cask method or the vault storage method, the lattice of the basket is formed in accordance with the outer dimensions of the spent fuel assembly equipped with the channel box. It was designed to be able to accommodate both spent fuel assemblies with and without boxes.

JP 2001-83289 A

  However, in a spent fuel storage container that accommodates both spent fuel assemblies with and without a conventional channel box, a basket lattice is formed in accordance with the outer dimensions of the spent fuel assembly with the channel box attached. Therefore, when storing the spent fuel assembly with the channel box removed, a gap is formed between the inner wall of the basket compartment and the spent fuel assembly, and it is used within the range of the gap. There was a risk that the spent fuel assembly would move due to rattling. For this reason, the evaluation of subcriticality in the spent fuel storage container has been performed on the assumption that the spent fuel assembly has moved to the strictest position within the moving range.

  In general, the position of the most severe spent fuel assembly in the subcritical state is a position where the spent fuel assembly is shifted to the central portion side (the central portion side of the trunk portion) of the basket in the partition portion of the basket. In other words, in the spent fuel assembly with the channel box removed, the position of the spent fuel assembly where the fuel rods of each spent fuel assembly are in contact with the partition wall close to the center side in each partition of the basket is the most severe. In the past, evaluation was performed assuming that the spent fuel assembly moved to such a position. Therefore, there is a problem that the subcritical value becomes stricter as compared with the general evaluation performed when only the spent fuel assembly with the channel box attached is accommodated.

  Further, when storing the spent fuel assembly with the channel box removed, as described above, a gap is formed in the compartment of the basket, so that the decay heat generated by the fuel rods of the spent fuel assembly is transmitted to the basket. As a result, the temperature of the spent fuel assembly may be increased.

  In addition, the spent fuel assembly with the channel box removed may have a reduced shielding function due to the absence of the channel box compared to the spent fuel assembly with the channel box installed. A spent fuel storage container was desired.

  The objective of this invention is providing the spent fuel storage container which solves an above described subject.

In order to solve the above-described problems, in the present invention, two compartments that are adjacent to each other are located on the side close to the central part of the body part in the compartment part that divides and stores the spent fuel assemblies one by one. The restriction member is detachably disposed along the wall, and the position of the spent fuel assembly is brought close to the inner wall on the side opposite to the inner wall on the side where the restriction member is disposed. It is possible to store the spent fuel assemblies that are not present near one side of the compartment, and to restrict the movement of the spent fuel assemblies within the compartment. Thereby, it can control that a spent fuel assembly moves to the position where subcriticality becomes severe, and subcriticality can be secured. In this case, by arranging the regulating member along the inner wall located on the side closer to the central part of the storage part in the partition part, the spent fuel assemblies are respectively positioned on the side away from the central part of the storage part in the partition part. It is possible to secure subcriticality more reliably.
Moreover, since the spent fuel assembly is arranged by the restricting member so as to maintain a constant interval from the central portion toward the outer periphery of the trunk portion, subcriticality can be ensured more reliably.

In addition, since the gap between the spent fuel assembly and the inner wall in the compartment can be narrowed by the regulating member, the decay heat generated in the fuel rod of the spent fuel assembly is easily transmitted to the inner wall in the compartment, Increases heat removal. Here, heat removal can be further improved by forming at least a part of the inner wall with a heat transfer member having good heat conductivity.
Furthermore, by forming the regulating member with a shielding material, it is possible to shield a spent fuel assembly without a channel box, and a spent fuel storage container having an improved shielding function can be obtained.

  According to the present invention, in the spent fuel storage container corresponding to the storage of the spent fuel assemblies with and without the channel box, the subcriticality when the spent fuel assemblies without the channel box are stored is sufficient. It is possible to obtain a spent fuel storage container that can guarantee the heat dissipation, improve the heat removal performance, and further improve the shielding performance.

Next, the spent fuel storage container of the present invention will be described in detail with reference to the drawings as appropriate. In the present embodiment, a metal cask C that stores spent fuel generated from a nuclear power plant as a spent fuel storage container will be described. In the following description, “upper” and “lower” are based on the state in which the cask C is set up (the state in FIG. 1).
As shown in FIG. 1, the cask C includes a cylindrical body portion 10 having a bottom and a primary lid 11 and a secondary lid 12 that are attached to an upper opening of the trunk portion 10. The trunk | drum 10 consists of materials, such as carbon steel, and is provided with the surrounding wall 13, the bottom part 14, and the accommodating part 20 which consists of the cylindrical space enclosed by these surrounding walls 13 and the bottom part 14. As shown in FIG.

  The peripheral wall 13 includes an outer cylinder 13A, an inner cylinder 13B, and a neutron shielding body 13C as a shielding member provided between the outer cylinder 13A and the inner cylinder 13B. The neutron shielding body 13 </ b> C is embedded in substantially the entire circumferential wall 13 in the circumferential direction. Here, γ rays generated from a spent fuel assembly (not shown) are mainly shielded by the inner cylinder 13B, and neutron rays are shielded by the neutron shield 13C. As the neutron shielding body 13C, for example, a resin that is generally available, a polymer resin such as polypropylene or polyethylene mixed with boron, or a neutron moderator such as boric acid water (hydrogen H, carbon C, etc.) A substance containing a neutron absorbing material (such as boron B) can be used. The thicknesses of the inner cylinder 13B and the neutron shielding body 13C are appropriately determined in consideration of the characteristics of the spent fuel assembly to be stored. In the cask C of the present embodiment, a similar neutron shielding body 15 is also provided on the primary lid 11 and the bottom portion 14 of the trunk portion 10.

A plurality of trunnions 13E used for lifting and suspending the cask C and the like are provided on the upper and lower portions of the peripheral wall 13 at a predetermined interval in the circumferential direction. In this embodiment, four (only two are shown in the figure) are provided in the upper part, and two are provided in the lower part, but the number and shape can be arbitrarily set.
Moreover, as shown to Fig.2 (a), between the outer cylinder 13A and the inner cylinder 13B of the surrounding wall 13, the heat-transfer fin 13D is provided in the state which crosses the neutron shielding body 13C. The heat transfer fins 13D serve to transfer the heat of the inner cylinder 13B to the outer cylinder 13A, and at least a part of the heat transfer fins 13D supports the outer cylinder 13A.

  As shown in FIG. 2A, the storage unit 20 includes a basket 21 corresponding to storage of both spent fuel assemblies (not shown) with and without a channel box. The basket 21 is formed by assembling flat metal plates including a neutron absorber in a lattice shape in plan view. As the metal plate, in addition to boron-containing stainless steel, a boron-containing aluminum alloy having a high thermal conductivity is used. Each partition section 22 partitioned in a lattice shape is provided in a rectangular tube shape in the longitudinal direction of the trunk section 10 (see FIG. 1), and can store a spent fuel assembly in which a channel box (not shown) is mounted. It has a size. Specifically, it has dimensions that are several millimeters larger than the external dimensions of the channel box (not shown) in consideration of warpage and distortion so that the spent fuel assembly with the channel box can be smoothly stored and taken out. Is formed. Thus, since the partition part 22 is formed according to the size of the spent fuel assembly to which the channel box is mounted, the spent fuel assembly from which the channel box has been removed is stored in the partition part 22. In some cases, a gap is formed around the spent fuel assembly because there is no channel box. Therefore, in the present embodiment, as a member that narrows this gap, the restricting member 30 is detachably disposed in each partition portion 22.

  The restricting member 30 has a substantially L-shaped plan view shape and a cross-sectional shape (not shown). As shown in FIG. 2B, each of the inner side walls adjacent to each other in each partition portion 22. It is formed in the size arrange | positioned along the side surfaces 22a and 22a. Specifically, as shown in FIG. 3, the regulating member 30 is made of a material such as carbon steel capable of shielding radiation (mainly γ rays or the like), and the side surfaces 22 a and 22 a of the inner wall of the partition part 22. Two rows of support portions 31 that are elongated in the longitudinal direction are provided on the surface facing (see FIG. 2B). In addition, the criticality prevention capability of the spent fuel assembly 40 can be enhanced by forming the regulating member 30 by including a neutron absorber or the like.

Such a restricting member 30 is a member for narrowing the above-described gap, and at the same time, as shown in FIG. 4A, the restricting member 30 is disposed in the partition portion 22 and is outside the channel box. The used fuel assembly 40 is moved toward the inner wall opposite to the inner wall on the side where the regulating member 30 is disposed. That is, as shown in FIG. 4B, the spent fuel assembly 40 is moved to the adjacent inner side walls 21B and 21B on the side opposite to the adjacent inner side walls 21A and 21A on the side where the regulating member 30 is disposed. In this state, it is stored in the partition unit 22.
By the way, as described above, as long as the regulating member 30 is an inner wall adjacent to each other in the partition part 22, any adjacent inner wall can be disposed along the side surface. In the embodiment, each regulating member 30 is disposed along each side surface 22a, 22a of the inner wall located on the side close to the central portion (the central portion of the storage portion 20) O of the trunk portion 10 in each partition portion 22. It is made to do.

Here, when the evaluation of subcriticality in the storage of the spent fuel assembly 40 without using the regulating member 30 is illustrated, the spent fuel assembly 40 is arranged as shown in FIG. That is, as described above, the evaluation of subcriticality is performed assuming that the spent fuel assemblies 40 are brought close to the central portion O of the storage unit 20 that is the most severe position in subcriticality. Particularly, in the central portion O, the spent fuel assemblies 40 are arranged close to each other (the central portion O shown in FIG. 5A has the same position as the central portion O shown in FIG. 4A). This also applies to FIG. For this reason, the subcritical value becomes severe. In contrast, in the evaluation of subcriticality in the present embodiment, as shown in FIG. 5B, the side where the spent fuel assemblies 40 are separated from the central portion O (side surfaces 22b and 22b side), specifically Are stored in a state of being brought close to the peripheral wall 13 side of the body portion 10 (see FIG. 4A), so that the subcritical value does not become severe. Therefore, the subcriticality can be sufficiently ensured, and in addition, the spent fuel assemblies 40 as much as possible can be stored with high density while maintaining a constant interval by regular position regulation by the regulating member. Cask C is obtained.
Further, as shown in FIG. 5 (b), the spent fuel assembly 40 is brought closer to the inner side walls 21B and 21B by the regulating member 30, so that the spent fuel assembly 40 and the inner side walls 21B and 21B are brought into contact with each other. Can be increased. Thereby, the heat from the fuel rod of the spent fuel assembly 40 is easily transmitted to the inner side walls 21B and 21B (basket 21), and the heat removal action is enhanced.

Such a regulating member 30 may be arranged in advance in each partition 22 of the basket 21 (see FIG. 2A) when the cask C is manufactured. For example, when the cask C is placed vertically (the state shown in FIG. 1) by a crane or the like before the spent fuel assembly 40 is stored, the cask C shown in FIG. Prior to storing the spent fuel assembly 40 in a pool (not shown), the fuel assemblies 40 may be arranged in each partition 22.
It should be noted that if the regulating member 30 is removed from each compartment 22, a spent fuel assembly with a channel box (not shown) can be accommodated in each compartment 22.

  As shown in FIG. 7, the regulating member 30 can also be used for the similar basket 21 provided in the metal canister C1, and stores the spent fuel assembly 40 with the channel box removed. Can be suitably performed.

Below, the effect acquired in this embodiment is demonstrated.
(1) Corresponding to storage of both spent fuel assemblies (40) with and without channel boxes by one cask C by a simple configuration in which the regulating member 30 is attached to and detached from each partition 22 of the basket 21. Can do.
(2) The regulating member 30 is detachably disposed along the side surfaces 22a and 22a of the adjacent inner side walls in each partitioning portion 22, and regulates the position of the spent fuel assembly 40 from which the channel box is removed. Since it is configured to approach the inner side walls 21B, 21B on the side opposite to the inner side walls 21A, 21A on the side where the member 30 is disposed, the spent fuel assembly 40 is moved closer to one side in the partition portion 22 and stored. The movement of the spent fuel assembly 40 in the partition part 22 can be restricted. Thereby, it can control that the spent fuel assembly 40 moves to the position where subcriticality becomes severe, and subcriticality can be sufficiently secured.
(3) Since the regulating member 30 is disposed along the inner side walls 21 </ b> A and 21 </ b> A located on the side close to the central portion O of the storage portion 20 in the partition portion 22, the restriction member 30 is separated from the central portion O in each partition portion 22. The spent fuel assemblies 40 can be positioned on the sides, and the subcriticality can be more reliably ensured.
In particular, in the central portion O of the storage section 20 with severe subcriticality, it becomes possible to store the spent fuel assemblies 40 with an interval between them, and the subcriticality can be sufficiently ensured.
(4) Since the clearance between the spent fuel assembly 40 and the inner side walls 21B and 21B in the partition portion 22 can be narrowed by the regulating member 30, the decay heat generated by the fuel rods of the spent fuel assembly 40 is separated from the compartment. It becomes easy to be transmitted to the inner side walls 21B and 21B in the part 22, and the heat removal property is enhanced.
Moreover, since the spent fuel assembly 40 is positioned on the side away from the central portion O of the storage portion 20 in each partition portion 22 by the regulating member 30, the heat removal performance of the basket 21 is flattened.
(5) Since the regulating member 30 is formed of a shielding material that shields radiation, the spent fuel assembly 40 without a channel box shields radiation equivalent to or equal to or more than the spent fuel assembly with a channel box. As a result, a cask C having an improved shielding function can be obtained.
(6) Since the regulating member 30 plays a role of narrowing the gap formed around the spent fuel assembly 40, when the vibration external force such as an earthquake is applied to the cask C, the spent fuel assembly 40 is partitioned. It is possible to suitably suppress the occurrence of a collision load by colliding with the inner surface of 22. This eliminates the need to design the basket 21 and the like with a wall thickness corresponding to the collision load, and contributes to reducing the size and weight of the cask C.

FIG. 8 shows a modification of the cask C of this embodiment. As shown in FIG. 8, the cask C of this modification is characterized in that a heat transfer member 35 having good heat conductivity is provided on a part of the inner wall of the basket 21. The heat transfer member 35 is, for example, a copper or aluminum alloy plate, and is integrally provided on each inner wall along the inner wall on the side opposite to the inner wall on the side where the regulating member 30 is disposed. In this example, the heat transfer member 35 is provided on the inner wall so as to exhibit a well shape in a plan view, and each regulating member 30 is arranged so that the spent fuel assembly 40 is brought close to the heat transfer member 35. ing.
By providing such a heat transfer member 35 on the inner wall, the heat of the spent fuel assembly 40 can be efficiently transferred to the inner wall, and a cask C that can improve the heat removal performance is obtained. .

  The heat transfer member 35 is not limited to the one provided on the inner wall in the state of having a well shape as described above, and is appropriately disposed on the inner wall opposite to the inner wall on the side where the regulating member 30 is disposed. Can be provided.

  9 to 11 show modifications of the regulating member 30 used in the cask C of this embodiment (refer to each figure as appropriate, the same applies hereinafter). The regulating member 30 shown in FIG. 9 has an upper end portion 32 provided with a locking portion 32A and a lower end portion 33 provided with a locking portion 33A. The locking portion 32 </ b> A provided on the upper end portion 32 can be locked in an engagement hole (not shown) provided on the inner wall of the partition portion 22 of the basket 21, and the locking portion provided on the lower end portion 33. 33A can be locked to a locking hole or a groove (not shown) provided in the bottom 14 of the storage unit 20. According to the cask C provided with such a restriction member 30, the restriction member 30 can be reliably locked to a predetermined position (inner wall) in the partition part 22, and the displacement of the restriction member 30 itself is restricted. Thus, smooth storage of the spent fuel assembly 40 is realized.

  Further, the regulating member 30 shown in FIG. 10 is provided with a plurality of square openings 34 at predetermined intervals in the longitudinal direction of the regulating member 30. According to the cask C provided with such a restriction member 30, the function of the restriction member 30 can be ensured while reducing the weight of the restriction member 30. Note that the shape and number of the openings 34 can be arbitrarily set.

  Furthermore, as shown in FIG. 11, the regulating member 30 may be composed of two flat plates 36, 36 that are separated. In addition, you may provide the opening part 34 as shown in FIG.

FIG. 12 shows a cask C of a reference example . In the cask C shown in FIG. 12, the regulating member 30 </ b> A is disposed along one inner wall in the partition part 22 of the basket 21. As shown in FIG. 13, the restriction member 30 </ b> A has a substantially U-shape in plan view (substantially U-shape in cross section), and is formed in a size that is arranged along one inner wall in the partition portion 22. Has been. Also in the cask C, the regulating member 30A is arranged along the side surface of the inner wall located on the side close to the central portion O of the storage unit 20 in each partitioning part 22, and the side on which the regulating member 30A is arranged. It plays the role which brings the spent fuel assembly 40 close to the inner wall opposite to the inner wall. As a result, the spent fuel assembly 40 is brought closer to the side away from the central portion O of the storage unit 20 in each partition unit 22 to ensure subcriticality and the cask C with improved heat removal performance. can get. Further, by forming the regulating member 30A from a shielding material capable of shielding radiation, it is possible to improve radiation shielding properties.

  The restriction members 30 and 30A described above are not limited to being integrally formed, and may be provided by joining a plurality of members. Further, the regulating members 30 and 30 </ b> A may be configured to be fixed to the inner wall in the partition portion 22 using bolts or other fixing means. Furthermore, the trunk | drum 10 is not restricted to a cylindrical thing, A square cylinder shape and a polygonal cylinder shape may be sufficient.

It is a schematic cross section which shows the cask as a spent fuel storage container which concerns on embodiment of this invention. (A) is a schematic cross-sectional view of the cask of FIG. 1, (b) is a schematic enlarged view of a partition part. It is an expansion perspective view of a control member. (A) is a model cross-sectional view which shows the state which accommodated the spent fuel assembly in the cask of FIG. 1, (b) is a model enlarged view of a division part. (A) (b) is an operation explanatory view. It is a schematic diagram which shows a storage procedure. It is a schematic cross section which shows the canister as a spent fuel storage container. It is a model cross-sectional view of the cask provided with the heat-transfer member. It is a perspective view which shows the modification of a control member. It is a perspective view which shows the modification of a control member. It is a perspective view which shows the modification of a control member. It is a model cross-sectional view of the cask of a reference example . It is a perspective view of the control member used for the cask of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 trunk | drum 11 primary lid 12 secondary lid 13 peripheral wall 13A outer cylinder 13B inner cylinder 13C neutron shield body 20 storage part 21 basket 21A inner wall 21B inner wall 22 partition part 22a side 22b side 30 regulating member 35 heat transfer member 40 used Fuel assembly C cask

Claims (9)

A spent fuel storage container having a bottomed cylindrical body portion in which square cylindrical partition portions for storing and storing spent fuel assemblies one by one are arranged in a lattice pattern ,
A regulating member that is detachably disposed in the partition part and regulates a position of the spent fuel assembly in the partition part;
The regulating member is disposed along two inner side walls adjacent to each other and located on the side near the center of the body in the compartment , and the position of the spent fuel assembly in the compartment To the inner wall on the side opposite to the inner wall on the side where the restricting member is disposed ,
The spent fuel storage container , wherein the spent fuel assembly is arranged by the regulating member so as to maintain a constant interval from the central portion toward the outer periphery of the trunk portion . A bottomed cylindrical barrel having a receiving portion which partitions part of the square tube-shaped for housing and divides the spent fuel assemblies in each body is provided are arranged in a grid, in the peripheral wall of the body portion A spent fuel storage container, comprising: a shielding member that shields radiation from the spent fuel assembly; and a lid that is attached to an upper opening of the trunk portion and seals the storage portion;
A regulating member that is detachably disposed in the partition part and regulates a position of the spent fuel assembly in the partition part;
The regulating member is disposed along two inner side walls adjacent to each other and located on the side near the center of the body in the compartment , and the position of the spent fuel assembly in the compartment To the inner wall on the side opposite to the inner wall on the side where the restricting member is disposed ,
The spent fuel storage container , wherein the spent fuel assembly is arranged by the regulating member so as to maintain a constant interval from the central portion toward the outer periphery of the trunk portion . 3. The spent fuel storage container according to claim 1, wherein the regulating member is formed in an L-shaped cross section extending over the two inner side walls adjacent to each other. The spent fuel storage container according to any one of claims 1 to 3 , wherein the regulating member is locked to the inner wall. The spent fuel storage container according to any one of claims 1 to 4 , wherein a heat transfer member having good heat conductivity is provided on at least a part of the inner wall. 6. The spent fuel storage container according to claim 5 , wherein the heat transfer member is provided on the inner wall opposite to the inner wall on the side where the regulating member is disposed. The spent fuel storage container according to any one of claims 1 to 6 , wherein the restricting member is formed of a shielding material that shields radiation from the spent fuel assembly. In the compartment, a spent fuel assembly of a boiling water reactor equipped with a channel box can be stored as the spent fuel assembly in a state where the regulating member is removed from the compartment. The spent fuel storage container according to any one of claims 1 to 7 , wherein A spent fuel storage container having a bottomed cylindrical body portion in which square cylindrical partition portions for storing and storing spent fuel assemblies one by one are arranged in a lattice pattern,
  A regulation member that is detachably disposed in the partition part and regulates a position of the spent fuel assembly in the partition part; and a heat transfer member with good heat conductivity provided in the partition part,
  The regulating member is disposed along two inner walls adjacent to each other at a position close to the central part of the trunk part, at least in the partition part located around the central part of the trunk part, The position of the spent fuel assembly in the compartment is brought closer to the inner wall on the side opposite to the inner wall on the side where the regulating member is disposed,
  The heat transfer member is provided on the inner wall on the opposite side to the inner wall on the side where the regulating member is disposed, in all the partition portions,
  The spent fuel assembly is arranged so as to be moved toward the heat transfer member by the regulating member and to be kept at a constant distance from the central portion toward the outer periphery of the trunk portion. Fuel storage container.

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