JP2012255701A - Transport container for nuclear fuel pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transport container for nuclear fuel pellet in which high neutron absorption effects can be maintained by suppressing a neutron absorber plate from being broken or cracked by impulse to the neutron absorber plate.SOLUTION: A transport container for nuclear fuel pellet comprises an inner container which is accommodated in an outer container and includes a plurality of pellet storage container housing chambers each housing a pellet storage container therein, and a neutron absorber plate made of boron-added stainless steel which is disposed while being fixed between an inner surface of the inner container and the pellet storage container housing chambers. A fixing strength of the neutron absorber plate is set to such a magnitude that the neutron absorber plate is removed from a fixture spot by a force from the outside before the neutron absorber plate is broken by the force from the outside, thereby preventing the neutron absorber plate from being broken, and ensuring subcriticality of stored substances.

Description

  The present invention relates to a nuclear fuel pellet transport container for transporting nuclear fuel pellets used in a fuel assembly for nuclear power generation fuel.

  Fuel assemblies used for nuclear power generation fuel are usually manufactured from nuclear fuel pellets to fuel assemblies in a unit in a nuclear fuel factory. However, there are cases in which fuel rods and fuel assemblies are manufactured by carrying nuclear fuel pellets manufactured at other nuclear fuel factories because of the relationship with the production capacity and manufacturing schedule of the factories.

  In this case, it is necessary to transport nuclear fuel pellets. However, in transport, it is necessary to use transport containers that ensure subcriticality that satisfies legal standards, and various proposals have been made regarding transport containers ( For example, Patent Documents 1 and 2).

  As a specific example, a transport container for nuclear fuel pellets such as uranium dioxide uses a boron-added stainless steel plate (neutron absorber plate) having high neutron absorption capability to ensure subcriticality. .

  Such a nuclear fuel pellet transport container has a double structure in which a stainless steel inner container is housed inside a stainless steel outer container via a buffer material, and the nuclear fuel pellets are housed in the inner container. Two pellet storage containers can be stored side by side.

  And subcriticality is ensured by arrange | positioning the neutron absorption board made from a boron addition stainless steel between the whole inner surface of an inner container, and two pellet storage containers.

JP 2002-202397 A Special Table 2000-509809

  However, since the neutron absorber plate made of boron-added stainless steel is more brittle than normal stainless steel, if the transport container receives a large impact due to an accident such as dropping during transport or handling of the transport container, the neutron absorber plate There is a risk of cracks and cracks.

  The boron-added stainless steel in which cracks and cracks have occurred may have a reduced or lost function as a neutron absorbing plate and may not be able to obtain a predetermined neutron absorbing ability.

  In particular, a boron-added stainless steel neutron absorber plate is disposed in the vicinity of a heavy pellet pellet container (nuclear fuel region), so that the possibility of occurrence of cracks and cracks increases.

  Therefore, it may be possible to reduce the impact and suppress the occurrence of cracks and cracks by placing a boron-added stainless steel neutron absorber plate away from the nuclear fuel region. In this case, however, the neutron absorption effect (neutron absorption capability) ) Decreases.

  Therefore, in view of the above problems, the present invention suppresses the generation of cracks and cracks in the neutron absorber plate due to the impact received by the neutron absorber plate, and transports nuclear fuel pellets capable of maintaining a high neutron absorption effect near the nuclear fuel region. It is an object to provide a container.

  The present inventor has found that the above problems can be solved by the inventions described in the following claims, and has completed the present invention. Hereinafter, each claim will be described.

The invention described in claim 1
An outer container,
An inner container having a plurality of pellet storage container storage chambers for storing the pellet storage container, and being housed in the outer container;
A nuclear fuel pellet transport container comprising a boron-added stainless steel neutron absorbing plate disposed between the inner surface of the inner container and the pellet storage container storage chamber,
The fixing force of the neutron absorber plate is set such that the neutron absorber plate is detached from the fixed portion by an external force before the neutron absorber plate is damaged by an external force. It is a transport container for nuclear fuel pellets.

  In the invention of this claim, the fixing force is such that the neutron absorber plate is detached from the inner container before the neutron absorber plate is cracked or cracked due to deformation of the inner container due to external force or impact of the pellet container. Therefore, the neutron absorber plate can be prevented from cracking or cracking due to external force. For this reason, the neutron absorption effect can be maintained while arranging the neutron absorber plate in the vicinity of the nuclear fuel region. The fixing means here includes the adhesive, screw, tread groove and the like described in the embodiment of the present invention.

The invention described in claim 2
A gap is formed between the pellet storage container and the inner container that is accommodated in the inner container so as to restrict the movement of the neutron absorbing plate that is out of the fixed position of the inner container to the extent that the neutron absorption effect reaches. 2. The nuclear fuel pellet transport container according to claim 1, wherein an inner dimension of the inner container is set.

  In the invention of this claim, even when the neutron absorber plate is detached from the inner vessel by an external force, an appropriate space in which the movement of the neutron absorber plate within the inner vessel is regulated within a range in which the neutron absorption effect is exerted. Therefore, the neutron absorbing plate can be held at a position where the neutron absorption effect is high.

The invention according to claim 3
3. The nuclear fuel pellet transport container according to claim 1, wherein the neutron absorber plate is formed by laminating a plurality of boron-added stainless steel thin plates.

  In the invention of this claim, in addition to the neutron absorber plate coming off from the inner vessel before the neutron absorber plate is cracked or cracked due to deformation of the inner vessel due to external force or collision of the pellet container, a plurality of By laminating a single sheet of boron-added stainless steel, the flexibility of the neutron absorber plate as a whole is enhanced, so that the generation of cracks and cracks in the neutron absorber plate due to external force can be further suppressed. .

  According to the present invention, it is possible to maintain a high neutron absorption effect in the vicinity of the nuclear fuel region, and to suppress the generation of cracks and cracks in the neutron absorber plate against the impact received by the neutron absorber plate. A nuclear fuel pellet transport container can be provided.

It is a perspective view which shows the state by which the pellet storage container was accommodated in the transport container of the nuclear fuel pellet in one embodiment of this invention. It is a figure which shows the inner container of the transport container of the nuclear fuel pellet in one embodiment of this invention, Comprising: (a) is a perspective view, (b) is a partial expanded sectional view. It is a figure which shows the inner container of the transport container of the nuclear fuel pellet in one embodiment of this invention, Comprising: (a) is a perspective view, (b) is a partial expanded sectional view. It is a figure which shows the inner container of the transport container of the nuclear fuel pellet in one embodiment of this invention, Comprising: (a) is a perspective view, (b) is a partial expanded sectional view. It is an expanded sectional view which shows the partial cross section of the inner container of the transport container of the nuclear fuel pellet in one embodiment of this invention.

  Hereinafter, based on an embodiment, the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a perspective view illustrating a state in which a pellet storage container is stored in a nuclear fuel pellet transport container according to an embodiment. 2-4 is a figure which shows the inner container of the transport container of the nuclear fuel pellet in one embodiment of this invention, respectively, (a) is a perspective view, (b) is a partial expanded sectional view. FIG. 5 is an enlarged cross-sectional view showing a partial cross-section of the inner container of the nuclear fuel pellet transport container according to the embodiment.

1. 1. Overall configuration of nuclear fuel pellet transport container As shown in FIG. 1, the nuclear fuel pellet transport container 1 has a heat insulating material 3a and a buffer material 3b disposed inside an outer container 2 made of stainless steel. The stainless steel inner container 4 is housed.

  The outer container 2 includes a housing 2a having an upper opening and an outer container upper lid 2b that is screwed to the housing 2a.

  The inner container 4 stores two pellet storage containers for storing a casing 4a having an open top, an inner container upper lid 4b screwed to the casing 4a, and two pellet storage containers 5 in an array. A chamber 4c is provided.

  As shown in FIGS. 2 (a), 3 (a), and 4 (a), a neutron absorbing plate 6 for side wall made of boron-added stainless steel is fixed to the inner side surface of the inner container 4, and 2 One pellet storage container storage chamber 4c is partitioned by a partitioning neutron absorbing plate 7 made of boron-added stainless steel.

  A protective plate 8 made of a buffer material such as rubber is attached to the neutron absorbing plate 6 for the side wall and the neutron absorbing plate 7 for the partition.

  And as shown in FIG.3 (b) and FIG.4 (b), the neutron absorber plate 6 for side walls has the laminated structure which laminated | stacked the several thin plate 6a made from a boron addition stainless steel, in order to exhibit a softness | flexibility. It has become.

  Further, as shown in FIG. 2B, the partitioning neutron absorbing plate 7 has a laminated structure in which a plurality of thin plates 7a made of boron-added stainless steel are laminated in the same manner as the neutron absorbing plate 6 for side walls.

  Since the side wall neutron absorber plate 6 and the partitioning neutron absorber plate 7 have a laminated structure, the flexibility of the neutron absorber plate as a whole is enhanced, so that the generation of cracks and cracks can be suppressed. The absorption effect can be sufficiently maintained.

  Hereinafter, the mode for fixing the neutron absorber plate will be described separately for the side wall neutron absorber plate 6 and the partitioning neutron absorber plate 7.

2. Aspect for fixing side wall neutron absorber plate (first aspect)
In the first embodiment, the neutron absorber plate 6 for side walls is bonded to the inner side surface of the inner container 4 with an adhesive or a solvent having an equivalent function. The adhesive strength of the adhesive or the like is set so that the side wall neutron absorbing plate 6 is detached from the inner side surface of the inner container 4 when the nuclear fuel pellet transport container 1 receives an impact force exceeding a predetermined value. Thereby, before the side wall neutron absorption plate 6 is damaged by the impact force, the side wall neutron absorption plate 6 is detached from the inner container 4, and the neutron absorption effect can be maintained.

  As the adhesive or the like to be selected, an adhesive or the like in a use environment suitable for the environment such as the maximum temperature to be considered in the analysis is selected. In addition, an adhesive having an appropriate adhesive force is selected in consideration of the assumed deformation and impact of the transport container 1. In addition, when the time of high temperature is assumed to the transport container 1, the adhesive agent etc. which ignite flammable gas are not used. The application area of the adhesive or the like is determined in consideration of the assumed deformation of the inner container 4 or the strength of the adhesive or the like. In particular, when the timing at which the neutron absorbing plates 6 and 7 are peeled off is controlled by the coating area, the area at the time of bonding is controlled.

(Second aspect)
In the second mode, as shown in FIG. 2, the side wall neutron absorbing plate 6 is attached to the inner surface of the inner container 4 by screws 9. The strength of the screw 9 is set such that when the nuclear fuel pellet transport container 1 receives an impact force exceeding a predetermined value, the screw 9 is broken and the side wall neutron absorbing plate 6 is detached from the inner surface of the inner container 4. Is done. Thereby, the neutron absorption effect can be maintained as in the first embodiment.

  The material, size and number of the screws 7 are determined based on the impact and deformation assumed in the analysis. Further, the screw holes formed in the neutron absorber plate 6 for the side wall are processed in consideration of not causing a decrease in strength of the neutron absorber plate 6 for the side wall.

(Third aspect)
In the third aspect, as shown in FIG. 3, the side wall neutron absorbing plate 6 is fixed by a stopper 10, and the stopper 10 is fixed to the inner surface of the inner container 4 by welding or the like. Regarding the fixing force of the side wall neutron absorber plate 6 by the stopper 10, the side wall neutron absorber plate 6 comes off from the inner surface of the inner container 4 when the nuclear fuel pellet transport container 1 receives an impact force exceeding a predetermined value. Is set as follows. Thereby, the neutron absorption effect can be maintained as in the first embodiment.

  The shape and the position of the stopper 10 are determined so as not to damage the neutron absorber plate 6 for the side wall even when the nuclear fuel pellet transport container 1 receives an impact. Further, the welding strength of the stopper 10 is determined based on the impact and deformation assumed in the analysis. Moreover, it attaches so that the heat | fever at the time of welding of the stopper 10 may not affect the neutron absorption board 6 for side walls.

3. Aspect for fixing the partitioning neutron absorber plate (fourth aspect)
In the fourth aspect, as shown in FIG. 4, the partitioning neutron absorbing plate 7 is fixed to the side surface and the bottom surface of the inner container 4 with a stopper 11 and a screw 12. The stopper 11 is attached to the side surface and the bottom surface of the inner container 4 by welding. Regarding the fixing force of the partitioning neutron absorbing plate 7 by the stopper 11 and the screw 12, the partitioning neutron absorbing plate 7 is detached from the inner container 4 when the nuclear fuel pellet transport container 1 receives an impact force exceeding a predetermined value. Is set as follows. Thereby, the neutron absorption effect can be maintained as in the first embodiment.

  The welding strength of the stopper 11 and the material, size, and number of the screws 12 are determined based on the shock that is assumed in the analysis. The stopper 11 may have a plurality of functions such as serving as a guide when the pellet storage container 5 is taken in and out.

(Fifth aspect)
In the fifth aspect, as shown in FIG. 5, a pair of trench grooves 13 are formed on the inner surface of the inner container 4, and both side edges of the partitioning neutron absorbing plate 7 are fitted into the trench grooves 13. A partitioning neutron absorbing plate 7 is fixed to the inner container 4. The trench groove 13 is a groove formed on the inner surface of the opposing side wall plate of the inner container 4 over the entire length in the vertical direction.

  Regarding the fixing force of the partitioning neutron absorbing plate 7 by the trench groove 13, the side wall neutron absorbing plate 6 comes off the inner surface of the inner container 4 when the nuclear fuel pellet transport container 1 receives an impact force exceeding a predetermined value. Thus, the depth, width, cross-sectional shape and the like of the trench groove 13 are set. Thereby, the neutron absorption effect can be maintained as in the first embodiment.

4). Setting of the inner dimension of the inner container By appropriately setting the inner dimension of the inner container 4, the movement of the neutron absorbing plates 6 and 7 detached from the inner container 4 as described above can be restricted. Specifically, by forming a gap having a size capable of restricting the movement of the neutron absorber plate 6 for the side wall between the pellet container 5 and the inner vessel 4, the neutron absorber plate 6 for the side wall can be applied by an external force. Even when the neutron absorber plate 6 is detached from the inner vessel 4, the movement of the neutron absorber plate 6 for the side wall within the inner vessel 4 is restricted, and the neutron absorber plate 6 for the side wall can be kept at a position where the neutron absorption effect is high.

  About the partitioning neutron absorber plate 7 detached from the inner container 4, even if the partitioning neutron absorber plate 7 is removed by appropriately setting the size of the gap between the two pellet storage containers 5. The movement of the partitioning neutron absorber plate 7 in the vessel 4 is restricted, and the neutron absorption effect can be maintained.

  As mentioned above, although this invention was demonstrated based on one Embodiment, this invention is not limited to said one Embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Transport container of nuclear fuel pellet 2 Outer container 2a Outer container housing 2b Outer container top lid 3a Heat insulating material 3b Buffer material 4 Inner container 4a Inner container housing 4b Inner container top lid 4c Pellet container storage chamber 5 Pellet container 6 Side wall Neutron absorber plate 6a Thin neutron absorber plate for sidewall 7 Neutron absorber plate for partition 7a Thin plate of neutron absorber plate for partition 8 Protection plate 9, 12 Screw 10, 11 Stopper 13 Trench groove

Claims (3)

An outer container,
An inner container having a plurality of pellet storage container storage chambers for storing the pellet storage container, and being housed in the outer container;
A nuclear fuel pellet transport container comprising a boron-added stainless steel neutron absorbing plate disposed between the inner surface of the inner container and the pellet storage container storage chamber,
The fixing force of the neutron absorber plate is set such that the neutron absorber plate is detached from the fixed portion by an external force before the neutron absorber plate is damaged by an external force. Transport container for nuclear fuel pellets.   A gap is formed between the pellet storage container and the inner container that is accommodated in the inner container so as to restrict the movement of the neutron absorbing plate that is out of the fixed position of the inner container to the extent that the neutron absorption effect reaches. The nuclear fuel pellet transport container according to claim 1, wherein an inner dimension of the inner container is set.   3. The nuclear fuel pellet transport container according to claim 1, wherein the neutron absorber plate is formed by laminating a plurality of boron-added stainless steel thin plates.

Images