JP2001356192A - Radioactive material dry storage method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool efficiently radioactive material in storage pipes. SOLUTION: A horizontal dividing wall part 10 is arranged between a ceiling slab 9 and a floor slab 8. Many storage pipes 6 are extended toward the floor slab 8, penetrating the horizontal dividing wall part 10. Cooling passages are formed respectively between the horizontal dividing wall part 10 and the ceiling slab 9 and between the horizontal dividing wall part 10 and the floor slab 8. Cooling air flowing in each cooling passage cools the storage pipes 6. Canisters 2 in which the radioactive material is stored and caked bodies 1 are preferably stored in the storage pipes 6 from the storage pipe 6 positioned on the outlet opening 31A, 31B sides of the cooling passages toward the storage pipe 6 positioned on the inlet opening 30A, 30B sides sequentially. The radioactive material having a large heating value just brought into a radioactive material dry storage chamber 38 is cooled by the cooling air having the lowest temperature in the cooling passages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactive material dry storage method, and more particularly to a radioactive material dry storage method suitable for storing high-level radioactive materials such as spent fuel generated from a nuclear power plant. It concerns storage methods.

[0002]

2. Description of the Related Art High-level radioactive material, which is a residue after reprocessing of a spent fuel assembly generated from a nuclear power plant, is packed in a canister as a vitrified material, stabilized, and then stored in a radioactive material dry storage. Stored for a long time.
This radioactive material dry storage has a large number of cylindrical steel sleeves (storage tubes) arranged in a canister storage room, as shown in Japanese Patent Application Laid-Open No. 17500/1990, and these storage tubes have a plurality of canisters inside. It has a length that allows stacking. Decay heat from the vitrified body in the canister is formed between the ceiling slab holding the upper end of the steel sleeve and the floor slab located below the ceiling slab and holding the lower end of the steel sleeve. It is cooled by the air flowing in the cooling air passage. The cooling air guided into the cooling air passage is outside air taken in from outside the radioactive substance dry storage. Cooling air is supplied by natural ventilation.

The radioactive material dry storage disclosed in Japanese Utility Model Application Laid-Open No. 62-22600 also includes a plurality of canisters containing a vitrified high-level radioactive material, similar to Japanese Patent Application Laid-Open No. 17500/1990. Disclosed is to stack and store in a bottomed cylindrical pit (storage tube). The upper end of the bottomed cylindrical pit is held in the upper slab, and the lower end is held in the lower slab located below the upper slab. A cooling passage through which cooling air flows surrounds and surrounds the bottomed cylindrical pit. The decay heat generated from the vitrified material in the bottomed cylindrical pit is
It is cooled by the air flowing upward in the cooling channel. The supply of the cooling air into the cooling channel is natural ventilation.

[0004] In the radioactive material dry storage disclosed in JP-A-3-273193, canisters storing spent fuel assemblies are stacked in a plurality of stages in a storage pipe. A cooling channel for guiding the cooling air taken in from outside the radioactive material dry storage upward is formed around the storage pipe between the storage pipe and the outer pipe surrounding the storage pipe, as in Japanese Utility Model Laid-Open No. 22600/1987. . The storage tube is held by the ceiling slab. The supply of the cooling air into the cooling channel is natural ventilation. Further, a forced ventilation means is provided in the storage pipe for sucking outside air by a blower and guiding the air into the storage pipe.

[0005]

In order to reduce the site area of the radioactive material dry storage, a plurality of canisters may be stacked in the storage tube as shown in the above-mentioned publications. By further increasing the number of canisters, the area of the dry radioactive storage can be reduced accordingly.

[0006] However, in the radioactive substance dry storage disclosed in Japanese Patent Application Laid-Open No. 2-17500, the temperature of the upper portion of the cooling air passage rises by further increasing the number of stacked canisters. That is, the cooling air flowing in the horizontally extending cooling air passage formed between the ceiling slab and the floor slab is heated by removing the decay heat of the radioactive substance in the canister. The heated cooling air rises toward the upper part of the cooling air passage. For this reason, the temperature of the upper part of the cooling air passage increases. This leads to suppression of cooling of radioactive material in the canister located above the storage tube, and limits an increase in the number of stacked canisters in the storage tube.

[0007] Japanese Utility Model Application Laid-open No. Sho 62-22600 and JP-A-3-273.
As disclosed in Japanese Patent Publication No. 193, when a cooling passage formed between the storage tube and the annular body and surrounding the storage tube with an annular body to guide cooling air upward is formed, the pressure loss of the cooling passage is Since the flow passage area is small, the larger the number of stacked canisters in the storage tube, the larger the size. Such an increase in the pressure loss reduces the amount of cooling air flowing into the cooling passage. In particular, the supply of the cooling air is performed using natural force without being forcedly performed by using a blower or the like, so that an increase in pressure loss greatly affects a decrease in the supply amount of the cooling air. Therefore, an increase in pressure loss acts in a direction to suppress an increase in the number of stacked canisters. In addition, since it is necessary to provide the above-mentioned annular body in order to form an annular cooling passage around each of the storage pipes, it is necessary to provide an annular cooling passage.
The radioactive material dry storage disclosed in JP-A-3-273193 and JP-A-3-273193 has a more complicated structure than that disclosed in JP-A-2-17500.

An object of the present invention is to provide a radioactive substance dry storage method capable of efficiently cooling a radioactive substance in a storage tube.

[0009]

A first feature of the present invention that achieves the object of the present invention is that a storage pipe located at an outlet side of a cooling gas passage is directed toward the storage pipe located at an inlet side of the cooling gas passage. Thus, the present invention resides in storing the canister in the storage pipe.

A second feature of the present invention that achieves the object of the present invention is that the first feature is disposed between the first slab and the second slab.
A cooling gas passage formed between the slab and the second slab is divided into a plurality of cooling passages in a vertical direction, and a partition member through which each storage pipe passes is disposed between the first slab and the second slab. Storing the canister in the storage pipe from the storage pipe located on the outlet side of the cooling gas passage toward the storage pipe located on the inlet side of the cooling gas passage in the dried radioactive material storage facility It is in.

A feature of the first preferred embodiment is that a canister containing a radioactive substance is placed in a lower part of a storage pipe, and a canister containing a radioactive substance having a smaller calorific value than the radioactive substance in the canister is placed in an upper part of the storage pipe. It is to arrange in.

A feature of the second preferred embodiment of the radioactive substance dry storage facility is that a cooling gas passage formed between the first slab and the second slab is divided into a plurality of cooling passages in the vertical direction, and each storage is provided. In other words, the pipe has a partition member therethrough.

A feature of the third preferred embodiment of the radioactive material dry storage facility is that the height of each cooling passage is substantially equal to the height of the canister.

A feature of a fourth preferred embodiment of the radioactive material dry storage facility is that the steady rest provided on the second slab is located around the lower end of the storage tube and limits the lateral vibration of the lower end of the storage tube. It has a means.

A feature of the fifth preferred embodiment of the radioactive substance dry storage facility is that a gap is formed between the partition member and the storage pipe.

The feature of the sixth preferred embodiment of the radioactive substance dry storage facility is that the radioactive substance dry storage facility is provided between the lower end of the storage tube and the second slab.
An object of the present invention is to form a space that can at least absorb thermal expansion in the axial direction of the storage tube.

The feature of the seventh preferred embodiment of the radioactive substance dry storage facility can be achieved by providing the storage tube with a pad at a portion facing the partition member and the steady rest means, respectively.

A feature of the eighth preferred embodiment of the radioactive substance dry storage facility is that the radioactive substance dry storage facility is provided with a deformable support member which is attached to the partition member and the storage pipe and suppresses the horizontal vibration of the storage pipe.

The feature of the ninth preferred embodiment of the radioactive substance dry storage facility is that the partition member is made of a heat insulating material.

[0020] The tenth preferred dry storage facility for radioactive materials
A feature of the embodiment is that a convection suppressing member is arranged between a plurality of canisters stored in the storage tube in the axial direction.

A feature of the eleventh preferred embodiment resides in that flow rate adjusting means for adjusting the flow rate of the cooling gas is provided in each cooling passage.

Preferred twelfth of the radioactive material dry storage facility
The feature of the embodiment is that the cross section of the storage pipe is polygonal, and the corners of the cross section are arranged toward the inlet of the cooling passage.

Preferred thirteenth radioactive material dry storage facility
The feature of the embodiment is that the cross section of the storage tube is either a square or a hexagon.

Preferred No. 14 of the dry storage facility for radioactive materials
A feature of the embodiment is that the cross section of the canister stored in the storage tube is substantially similar to the shape of the cross section of the storage tube.

Preferred fifteenth dry storage facility for radioactive materials
A feature of the embodiment is that it moves between the storage tubes in the cooling passage,
The maintenance inspection of the outer surface of the storage tube is provided with the maintenance inspection means.

Preferable 16th dry storage facility for radioactive materials
A feature of the embodiment is that a means for cleaning the inside of the cooling air intake pit is provided in the cooling air intake pit that communicates the inlet of each cooling passage with the atmosphere.

Preferable 17th radioactive material dry storage facility
The feature of the embodiment is that in a canister provided with a container portion in which an upper portion is opened and a radioactive substance is stored therein and a lid portion that seals an upper end portion of the container portion, a cross section of the container portion and the lid portion is polygonal. That you are doing.

Preferred No. 18 of Dry Storage Facility for Radioactive Materials
The feature of the embodiment is that the material of the container and the lid is a boron-added alloy.

[0029]

According to the first aspect of the present invention, since the canisters are sequentially stored in the storage pipe from the storage pipe located on the outlet side of the cooling gas passage to the storage pipe located on the inlet side thereof, the dry storage of the radioactive substance is performed. The canister storing the radioactive substance having a large calorific value just brought into the facility is located in the storage pipe located at the most upstream side among the storage pipes storing the canister. Therefore, the radioactive substance having a large calorific value in the storage tube is efficiently cooled by the low-temperature cooling gas. Since the radioactive material stored in the storage pipe located on the outlet side of the cooling gas passage has passed over the radioactive material dry storage facility and has a small calorific value, the canister must be located upstream from it. Cooling is also possible with cooling gas whose temperature has risen due to cooling of the stored storage tube. Thus, according to the first aspect, the radioactive substance in the storage tube can be efficiently cooled.

According to a second aspect of the present invention, there is provided a radioactive substance dry storage facility capable of making the temperature distribution in the axial direction of the storage tube more uniform with a simple structure in which the partition member is disposed, and to efficiently cool the radioactive substance in the storage tube. it can.

In the first embodiment, the canister containing a radioactive substance having a smaller calorific value than the radioactive substance in the canister disposed at the lower part of the storage pipe is disposed at the upper part of the storage pipe. Can be reduced. The temperature of the cooling gas in the upper portion of the cooling gas passage, which tends to increase in temperature, also decreases.

In the second embodiment, since the partition member is disposed between the first slab and the second slab, the cooling gas moves in each cooling passage formed by the partition member, and The cooling gas heated in the cooling passage below the member is significantly suppressed from rising into the cooling passage above the partition member. For this reason, the temperature rise of the cooling gas in the cooling passage above the partition member is suppressed, so that the storage pipe is efficiently cooled also in this cooling passage above. Therefore, the temperature distribution in the axial direction of the storage tube can be made more uniform with a simple structure in which the partition member is disposed. In particular, the number of stacked canisters can be further increased as compared with the radioactive substance dry storage facility disclosed in JP-A-2-17500.

In the third embodiment, since the height of each cooling passage is substantially equal to the height of the canister, the cooling of the canister can be performed efficiently without obstructing the cooling of the canister in the height direction. When the partition member is disposed at a position crossing the canister, the cooling gas flowing in the cooling passage does not directly hit the portion of the storage pipe facing the partition member, and cooling of this portion is hindered. When the canister is located at a position crossing the partition member in the storage tube, it goes without saying that cooling of the crossing portion is hindered by the partition member. The present invention solves such a problem.

In the fourth embodiment, since the second slab is provided with a steadying means for restricting the lateral vibration of the lower end of the storage tube, the lower end of the storage tube can be prevented from swaying during an earthquake. The seismic resistance of the pipe can be improved.

In the fifth embodiment, a small amount of cooling gas flows into the cooling passage above the partition member from the cooling passage below the partition member through the gap formed between the partition member and the storage tube. The temperature difference between the upper surface of the partition member and the lower surface of the partition member is reduced. For this reason, the thermal stress generated in the partition member penetration portion of the storage tube can be reduced.

In the sixth embodiment, a space is formed between the lower end of the storage tube and the second slab so that at least thermal expansion in the axial direction of the storage tube can be absorbed. Even in this case, the storage tube can extend downward. For this reason, damage due to buckling of the storage tube due to restraint of downward expansion due to thermal expansion of the storage tube can be prevented.

In the seventh embodiment, the storage tube is provided with pads at portions facing the partition member and the steadying means, respectively, so that the strength of those portions can be increased. The deformation of the storage tube due to collision with the storage tube can be suppressed.

In the eighth embodiment, since the deformable support member is disposed between the partition member and the storage pipe, the horizontal vibration of the storage pipe can be suppressed, and the earthquake resistance of the storage pipe can be improved.

In the ninth embodiment, since the partition member is made of a heat insulating material, the heat of the cooling gas in the cooling passage below the partition member, particularly the heat of the high-temperature cooling gas above the cooling passage, is reduced. Transmission to the cooling gas in the cooling passage above the partition member is suppressed. Therefore, the temperature rise of the cooling gas in the cooling passage above the partition member is suppressed.

In the tenth embodiment, since the convection suppressing member is arranged between the plurality of canisters accommodated in the accommodating tube in the axial direction, the convection of the gas in the accommodating tube caused by the heating by the decay heat of the radioactive substance is suppressed. It is limited to the area where one canister is located. For this reason, the temperature rise in the upper part in the storage tube is suppressed, and the temperature distribution in the axial direction in the storage tube can be made more uniform.

In the eleventh embodiment, the flow rate adjusting means for adjusting the flow rate of the cooling gas is provided in each cooling passage, so that the flow rate of the cooling gas in the cooling path can be adjusted by the flow rate adjusting means. The temperature distribution in the axial direction of the storage tube can be more easily made uniform even when the temperature distribution of the storage tube becomes unbalanced.

In the twelfth embodiment, since the corners of the storage tube having a polygonal cross section in the cross section are arranged toward the inlet of the cooling passage, the resistance to the flow of the cooling gas is reduced. The pressure loss in the cooling passage can be reduced.

In the thirteenth embodiment, since the cross section of the storage pipe is either a square or a hexagon, the flow of contraction and expansion between adjacent storage pipes is eliminated, and the stagnation of the cooling gas flow is reduced. Cooling passage can be formed. For this reason, the cooling capacity of the storage tube can be improved.

In the fourteenth embodiment, since the cross section of the canister housed in the storage tube is substantially similar to the shape of the cross section of the storage tube, it is formed between the storage tube and the canister. The width of the gap becomes uniform, and the cooling efficiency of the radioactive material can be improved.

In the fifteenth embodiment, a maintenance and inspection means for moving between the storage pipes in the cooling passage is provided.
Maintenance and inspection of the outer surface of the storage tube can be easily performed.

In the sixteenth embodiment, since the cooling air intake pit cleaning means is provided in the cooling air intake pit for communicating the inlet of each cooling passage with the atmosphere, each cooling passage is provided together with the cooling air from the external atmosphere. Foreign matter that has entered the passage communicating the air and the outside atmosphere and accumulated in this passage can be easily removed.

In the seventeenth embodiment, since the cross section of the container and the lid is polygonal, the waste space in the canister when storing a spent fuel assembly having a polygonal cross section is stored. Can be reduced. For this reason, the space efficiency of the canister can be improved.

In the eighteenth embodiment, since the material of the container and the lid is a boron-added alloy, criticality management when the spent fuel assembly is stored in the container becomes easy.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radioactive substance dry storage according to a preferred embodiment of the present invention will be described with reference to FIGS. 1, 2, 3 and 4. FIG.

The radioactive material dry storage 38 has an outer wall portion 13 which is mostly underground, a floor slab 8 constituting the bottom of the outer wall portion 13, a ceiling slab 9 located above the floor slab 8,
It has an outer wall portion 47 located above the ground 45, an inner wall portion 46 located inside the outer wall portion 13, and the horizontal partition wall portion 10. The inner wall portion 46 is provided on the floor slab 8 inside the outer wall portion 13.
Attached to. Ceiling slab 9 and horizontal partition wall 1
0 is installed on the inner wall portion 46. Horizontal partition wall 10
Is located between the ceiling slab 9 and the floor slab 8, specifically, in the middle. The outer wall 47 is provided above the inner wall 46.

The canister transfer chamber 42 is formed in the outer wall 47 above the ceiling slab 9. Canister transfer chamber 4
2 is covered by a ceiling provided on the outer wall 47. The overhead traveling crane 40 is installed in the canister transfer chamber 42 and is installed on a traveling rail provided on the outer wall 47.

The inlet duct 19 includes the outer wall 13 and the inner wall 4.
6 and open to the atmosphere outside the radioactive dry storage 38 by an air intake 11. The air discharge duct 12 is connected to the outer wall 13 on the opposite side of the inlet duct 19.
And the inner wall portion 46. Air exhaust duct 12
Is communicated to the atmosphere outside the radioactive substance dry storage 38 via a passage in the exhaust pipe 41.

The area below the ceiling slab 9 and inside the inner wall 46 is a canister storage room. A plurality of storage tubes 6 for storing a plurality of canisters therein are arranged in the canister storage chamber. The canister storage compartment is divided into two cooling passages by a horizontal partition wall 10. One of them is a cooling passage 32A formed between the ceiling slab 9 and the horizontal partition wall portion 10. The other is a cooling passage 32B formed between the horizontal partition wall 10 and the floor slab 8.
It is. The cooling passage 32A is connected to the inlet duct 19 through a plurality of inlet openings 30A provided in the inner wall portion 46, and is connected to the air discharge duct 12 through a plurality of outlet openings 31A provided opposite the inner wall portion 46. . The cooling passage 32B located below the cooling passage 32A is connected to the inlet duct 19 through a plurality of inlet openings 30B provided in the inner wall 46, and through a plurality of outlet openings 31B provided facing the inner wall 46. Air discharge duct 1
Contact 2 Each of the cooling passages 32A and 32B is a part of the outer wall 13 and the inner wall 4 as shown in FIGS.
It is located between a pair of side wall portions 36 orthogonal to 6. Louver 18
Are rotatably provided in the inlet openings 30A and 30B and the outlet openings 31A and 31B, respectively. Louver 18
Although not shown, is opened and closed by a motor.

Each storage tube 6 is suspended from the floor slab 9 and penetrates the horizontal partition wall 10. That is, each storage pipe 6 crosses the cooling passage 32A in the vertical direction, and
It extends within 32B. An annular steady rest 16 is provided on the upper surface of the floor slab 8. The lower end of the storage tube 6 is
6 is inserted. The pad 17 is used for the horizontal partition wall 10.
And it is provided in the storage tube 6 at a position facing the steady rest 16. The thickness of the portion of the pad 17 is larger than that of the other portion of the storage tube 6. The storage pipe 6 suspended from the ceiling slab 9 is, as shown in FIG.
0 allows pulling out upwards. An inclined surface having a guide function is formed on the inner surface of the upper end of the steady rest 16 so that the lower end of the storage tube 6 can be smoothly inserted into the steady rest 16.

The storage tube 6 has a circular cross section. The storage tubes 6 are arranged in a regular triangular lattice in a horizontal section of the canister storage room.

The horizontal partition wall 10 has a plurality of circular holes through which the storage tube 6 passes. These holes are arranged in a regular triangular lattice at the same arrangement pitch as the storage tube 6. The intermediate steady rest 15 is provided on the horizontal partition wall 10 so as to face the pad 17 of the storage tube 6. Intermediate steady rest 15
An inclined surface serving as a guide when the storage tube 6 is inserted is formed inside. A gap is formed between the outer surface of the pad 17 and the intermediate steady rest 15.
Is formed between The width of this gap is slightly larger than the amount of thermal expansion of the pad 17 in the radial direction. The width of the gap formed between the pad 17 and the steady rest 16 at the lower end of the storage tube 6 is also slightly larger than the thermal expansion of the pad 17 in the radial direction.

The maintenance inspection robot travels along the traveling rail 33 provided between the storage pipes 6 on the lower surface of the ceiling slab 9 and the horizontal partition wall 10. The maintenance and inspection robot includes a traveling vehicle 22 engaged with the traveling rail 33, a vertically extending vertical guide rail 34 provided on the traveling vehicle 22,
And a maintenance and inspection unit 35 that moves up and down along the vertical guide rail 34.

The pit 20 is provided at the lower end of the entrance duct 19. A cleaning robot 21 is installed in the pit 21.

The solidified product 1, which solidified high-level radioactive waste,
A large spent fuel assembly 3 from a pressurized water reactor sealed in a canister 2, a small spent fuel assembly 4 from a boiling water reactor sealed in a canister 2, and a canister 2
The radioactive materials such as the spent fuel rods 5 which are dismantled pieces of the spent fuel assemblies hermetically sealed are stored and stored in the storage pipe 6. After storing the canister 2 and the like, the storage tube 6 is sealed at the upper end with the storage lid 7. The storage tube 6 can be pulled out upward from the ceiling slab 9 as described above, and is useful for replacement and inspection. In addition, not only the same type of radioactive substance but also various radioactive substances can be stored in the storage tube 6 in combination as illustrated in FIGS. 1B to 1D. A partition plate 14 that is a heat insulating material is arranged between the canisters 2 stacked in each storage tube 6 and the like. The installation level of the partition plate 14 is the same as the installation level of the horizontal partition wall 10. As the partition plate 14, an on-plate block of stainless steel or ceramics may be used. The partition plate 14 is larger than the lateral dimensions of the canister 2 and the solidified body 1 in order to suppress convection in the storage pipe 6. The upper end of the storage tube 6 in which the canister 2 and the like are stored is sealed with a storage lid 7.

The outside air taken in from the air intake 11 descends in the inlet duct 19 as cooling air, and flows into the cooling passages 32A and 32B through the inlet openings 30A and 30B. The cooling air that has flowed into each of the cooling passages 32A and 32B passes between the storage pipes 6 and exits 31A and 31B.
B is led into the air discharge duct 12. The cooling air is discharged to the outside of the radioactive substance dry storage 38 through the exhaust pipe 41. Such a flow of the cooling air is not forcibly performed by a blower or the like, but is naturally generated by using the chimney effect of the exhaust stack 41. The decay heat of the radioactive substance stored in the canister 2 stored in the storage pipe 6 is removed by natural cooling with cooling air.

In the present embodiment, the cooling air flows through each of the cooling passages 32A and 32B formed by disposing the horizontal partition wall portion 10 between the ceiling slab 9 and the floor slab 8. The cooling air heated in the lower cooling passage 32B is:
The horizontal partition wall 10 significantly suppresses ascending into the upper cooling passage 32A. That is, the temperature rise of the cooling air in the cooling passage 32A due to the flow of the warm cooling air above the cooling passage 32B into the cooling passage 32A is suppressed. For this reason, the cooling of the storage pipe 6 is efficiently performed also in the cooling passage 32A. Therefore, in this embodiment, the temperature distribution in the axial direction of the storage tube 6 can be made more uniform than that of the radioactive substance dry storage shown in Japanese Patent Application Laid-Open No. 2-17500 with a simple structure in which the horizontal partition wall 10 is disposed. . This leads to a further increase in the number of stacked canisters as compared with the radioactive substance dry storage facility disclosed in JP-A-2-17500. The horizontal partition wall section 10 not only uniforms the temperature distribution as described above, but also
It also has a function of suppressing the lateral swing of the storage tube 6 in the middle part in the height direction. For this reason, the seismic strength of the storage tube 6 increases. In particular, the intermediate steady rest 15 suppresses the roll.

The height of each cooling passage 32A, 32B is substantially equal to the height of the canister 2. this is,
The cooling air always comes into contact with the portion of the storage pipe 6 where the canister 2 is located, so that the cooling of the canister 2 is not hindered by the horizontal partition wall 10. The canister that is heated by the decay heat of the stored radioactive material is efficiently cooled. If the horizontal partition wall 10 is arranged at a position intersecting with the canister 2, the cooling air flowing in the cooling passage will not directly hit the portion of the storage pipe 6 facing the horizontal partition wall 10, and cooling of this portion Is inhibited.

Since the horizontal partition walls 10 are made of concrete, which is a heat insulating material, the heat of the cooling air in the cooling passage 32B, particularly, the heat of the high-temperature cooling air in the upper part of the cooling passage 32B is reduced by the heat in the cooling passage 32A. Suppresses transmission to cooling air. Therefore, the temperature rise of the cooling air in the cooling passage 32A is suppressed, and the storage pipe 6 in the cooling passage 32A can be efficiently cooled. The horizontal partition wall portion 10 may be made of a stainless steel plate having a small thermal conductivity and functioning as a heat insulating material, or a combination of an earthquake-resistant structure and a heat insulating material.

The cooling passage 32A is provided below the cooling passage 32A through the gap formed as described above between the intermediate steady rest 15 provided on the horizontal partition wall portion 10 and the storage pipe 6.
A small amount of cooling air flows in from 32B. This flow of the cooling air reduces the thermal stress generated in the penetrating portion of the horizontal partition wall portion 10 of the storage pipe 6 by the cold cooling air that contacts the upper surface of the horizontal partition wall portion 10 and the warm cooling air that contacts the lower surface of the horizontal partition wall portion 10. it can. If the amount of cooling air passing through this gap increases, the temperature above the cooling passage 32A rises,
The cross-sectional area of the gap needs to be set appropriately.

In this embodiment, since the louvers 18 are provided at the inlet opening and the outlet opening for each cooling passage, the cooling air flow in the cooling passages 32A and 32B is adjusted by adjusting the angle of the corresponding louver 18. Thus, they can be controlled separately. Therefore, even when the axial distribution of the storage pipe 6 arranged over the different cooling passages is unbalanced, the axial distribution of the storage pipe 6 can be easily adjusted by adjusting the angle of the louver 18. Can be made more uniform. Although not shown, the temperature in each of the cooling passages 32A and 32B is measured, and the control device controls the rotation of the above-described motor so that the temperature becomes the set temperature, and the angle of the louver 18 can be adjusted. It is.

It is also known that metal materials cause low-temperature embrittlement. When the radioactive material dry storage is built in the northern region, it may be necessary to limit the amount of outside air taken in to prevent low-temperature brittle destruction of the storage tube 6 and the like due to supercooling in a severe winter. At this time, even if an unbalance occurs between the calorific value of the radioactive substance stored in the canister 2 located in the cooling passage 32A and the calorific value stored in the canister 2 located in the cooling passage 32B, By adjusting the angle of the corresponding louver 18, the cooling air flow rates in the cooling passages 32A and 32B can be independently and appropriately controlled.

Furthermore, if the amount of leaking air flowing through the gap for reducing thermal stress generated in the penetrating portion of the horizontal partition wall 10 of the storage pipe 6 increases, the balance of the cooling air flow in the cooling passages 32A and 32B becomes unbalanced. Become appropriate. In order to eliminate this state, the angle of the louver 18 provided at the openings of the cooling passages 32A and 32B is controlled so that the flow rate of the cooling air in one of the cooling passages does not become insufficient.

The partition plate 14 is arranged between the plurality of canisters 2 stacked in the storage tube 6 because the storage tube generated by heating by the heat (decay heat of the radioactive substance) released from the solidified body 1 and the canister 2. The convection of the gas in 6 is restricted to the area where one canister 2 is located. For this reason,
The temperature rise in the upper part inside the storage tube 6 is suppressed, and the temperature distribution in the axial direction inside the storage tube 6 can be made more uniform. Partition plate 1
Since 4 is a heat insulating material, heat transfer via the partition plate 14 is reduced.

The storage tube 6 thermally expands in the axial direction by heating by the decay heat of the radioactive substance. Between the lower end of the storage tube 6 and the floor slab 8, specifically, between the lower end of the storage tube 6 and the bottom surface of the cylindrical steady rest 16, there is a space capable of absorbing the thermal expansion of the storage tube 6 in the axial direction. Is formed. For this reason, the storage pipe 6
Since the downward expansion due to the thermal expansion is not restricted, damage due to buckling of the storage tube 6 can be prevented.

The steady rest 16 is provided for the storage pipe 6 during an earthquake.
Of the lower end of the vehicle. For this reason, the earthquake resistance of the storage tube 6 is improved.

The storage tube 6 has pads 17 at portions facing the horizontal partition wall portion 10 and the steady rest 16 respectively. The formation of the pad 17 can increase the strength in those parts, and the intermediate steady rest 1 during an earthquake
The deformation of the storage tube 6 due to the collision with the storage tube 5 and the steady rest 16 can be suppressed.

Among the foreign substances such as dust and flying foreign substances contained in the air flowing into the inlet duct 19 from the air inlet 11, relatively large and heavy foreign matters accumulate in the pit 20 provided at the lower end of the inlet duct 19. . Inlet openings 30A, 30B
Are located above the pits 20 and are not blocked by the accumulation of those foreign substances. The suction type cleaning robot 21 installed in the pit 20 periodically cleans the pit 20 and discharges foreign matters accumulated in the pit 20 to the outside. Therefore, foreign substances accumulated in the pits 20 can be easily removed.

Among the foreign substances contained in the air flowing into the inlet duct 19, relatively small and light foreign matters such as dust flow into the cooling passages 32 A, 32 B through the inlet openings 30 A, 30 B and out of the storage pipe 6. Attaches to surface. This lowers the cooling efficiency of the storage pipe 6 with the cooling air. Therefore, it is necessary to remove the foreign matter attached to the storage tube 6. Also, when the outer surface of the storage tube 6 is corroded, the heat removal performance is deteriorated, so that the outer surface of the storage tube 6 may need to be polished. In the unlikely event that the corrosion of the storage tube 6 is severe,
It may be necessary to repair the storage tube 6 by welding or the like. For this reason, a maintenance inspection robot is provided as described above. The maintenance and inspection unit 35 inspects the outer surface of the storage tube 6 as the maintenance and inspection robot is periodically moved along the traveling rail 33. When it is found that the above situation has occurred in the storage pipe 6, maintenance and repair are performed by the maintenance and inspection unit 35. The maintenance and inspection of the outer surface of the storage tube 6 can be easily performed by the maintenance and inspection robot.

When the radioactive substance is stored in the storage pipe 6, the use of the canister 2 is not necessarily required. However, the canister 2 serves as a barrier to contain radioactive materials such as nuclear fuel material. Further, by using a boron-added alloy such as boron-added stainless steel or boron-added aluminum as the material of the canister 2, its excellent neutron absorption ability is advantageous for criticality control. That is, criticality management when the spent fuel assemblies are stored in the canister 2 is facilitated.

The storage of the radioactive substance in the storage pipe 6 may be performed as follows from the cooling of the radioactive substance and the temperature distribution in the axial direction of the storage pipe 6.

First, the canister 2 containing the radioactive substance and the solidified body 1 are connected to the outlet opening 31 of the cooling passage.
From the storage tubes 6 located on the A, 31B side, sequentially toward the storage tubes 6 located on the entrance openings 30A, 30B side.
It is better to store in the storage tube 6. For this reason, the canister 2 and the like in which the radioactive substance having a large calorific value just stored in the radioactive substance dry storage 38 is stored in the storage pipe 6 sequentially from the downstream side of the cooling passages 32A and 32B. Therefore, the radioactive substance having a large calorific value is always located in the most upstream storage pipe 6 among the storage pipes 6 storing the radioactive substance. In other words, the radioactive substance having a large calorific value just brought into the radioactive substance dry storage 38 is cooled by the cooling air having the lowest temperature in the cooling passage. This is very convenient for cooling a radioactive substance having a large calorific value. The radioactive substance having a large calorific value stored in the storage pipe 6 is efficiently cooled by the low-temperature cooling air. Conversely, as the period elapses, the radioactive substance stored in the storage pipe 6 located on the side of the outlet openings 31A and 31B of the cooling passage generates a smaller amount of heat, so that the canister is stored upstream of the radioactive substance. Cooling is also possible with cooling air whose temperature has increased due to cooling of the storage tube.

By adopting such a storage method, even if the radioactive substance is not moved between the storage tubes 6 according to the calorific value, the radioactive substance is taken into the radioactive substance dry storage 38 as the period elapses. The radioactive material that has just generated a large amount of heat is stored in the storage tube on the upstream side, and the radioactive material whose calorific value has been reduced by being brought into the radioactive material dry storage box 38 in the early next stage is stored in the storage tube on the downstream side. Become.

In the second storage method, a radioactive substance having a smaller calorific value than the radioactive substance stored in the lower part of the storage pipe 6 (for example, in a state of being stored in the canister 2). ). Thereby, the temperature of the upper part of the storage tube 6 can be reduced.

These first and second storage methods can also be applied to a radioactive substance dry storage having no horizontal partition wall 10 as shown in FIG. 1 of JP-A-2-17500.

Another embodiment of the canister and the storage tube will be described below.

Conventionally, when a spent fuel assembly is transported from a radioactive material dry storage to a reprocessing facility, the canister must be opened and the spent fuel assembly removed to reload the spent fuel transport cask. This leads to an increase in the amount of work. To solve this problem, a canister and a storage tube shown in FIG. 5 were considered. Canister 2
Has a container part for storing the radioactive substance, and a lid part for sealing the upper end of the container part. The canister 2 of the present embodiment includes:
The cross section of the container part and the lid part has a square shape. The cross section of the storage tube 6 for storing the canister 2 is also substantially square (the corners are deformed to reduce backlash). Four small spent fuel assemblies 4 can be stored in the canister 2. In addition to the small spent fuel assemblies 4, the large spent fuel assemblies 3 and the spent fuel rods 5 obtained by disassembling the spent fuel assemblies may be stored. Such a canister 2 is suitable for directly loading the spent fuel transport cask. If copper or a copper alloy is used as the material of the canister 2, it is advantageous in terms of heat transfer. Since the canister 2 of the present embodiment has a square cross section, it is possible to reduce unnecessary space inside when the spent fuel assembly is stored. For this reason, the space efficiency of the canister can be improved. In the present embodiment, since the canister 2 containing the radioactive material is loaded into the spent fuel transport cask while being sealed and is carried out of the radioactive material dry storage, the work of carrying out the radioactive material in the storage tube can be performed in a short time. Can be.

The storage pipe 6 shown in FIG. 5 is arranged with the corner in the cross section of the storage pipe crossing the inlet direction of the cooling air as shown in FIG. That is, the storage tube 6 is disposed with its corner portion facing the side wall portion 36. Since the corner in the cross section of the storage pipe 6 is arranged toward the inlet direction of the cooling passage, the resistance of the storage pipe 6 to the flow of the cooling air is reduced, and the pressure loss in the cooling passage can be reduced. When the cross section of the storage tubes is circular, cooling air stagnates in a cooling passage formed between the storage tubes, and a flow of cooling air that does not contribute to cooling occurs. In this embodiment, since the cross section of the storage tube 6 is square, the width of the cooling passage formed between the adjacent storage tubes 6 can be made uniform. For this reason, since the stagnation of the cooling air flow is reduced, the cooling capacity of the storage pipe 6 can be increased. Furthermore, since the cross sections of both the canister 2 and the storage tube 6 are substantially the same as a square,
The width of the gap formed between the storage tube 6 and the canister 2 becomes uniform, and the cooling efficiency of the radioactive substance can be improved.

The cross sections of the canister 2 and the storage tube 6 may be hexagonal. In particular, when storing the spent fuel rods 5 obtained by disassembling the spent fuel assemblies, it is useful to seal the canisters 2 having a hexagonal cross section for compactness. It is preferable that such a canister is also loaded directly into the spent fuel transport cask. In this case, it is preferable in terms of heat removal that the cross section of the storage tube 6 is also a hexagon, which is a similar shape. The storage tube 6 having a hexagonal cross section, as shown in FIG.
The cooling passage is arranged with the corner in the cross section of the storage pipe facing the inlet direction of the cooling air. These storage tubes 6
They are arranged in a triangular lattice. These storage tubes 6 are shown in FIG.
As shown in the figure, one of the three diagonals is the other two.
One is longer than that. This longest diagonal line is oriented toward the inlet of the cooling air, and the dimension b in FIG.
By making the size 1.5 to 2.5 times the dimension, the flow path cross-sectional area between the storage tubes 6 is made uniform, and the pressure loss in the cooling passage is also reduced. Even when the cross sections of the canister 2 and the storage tube 6 are hexagonal, the same effects as in the embodiment of FIG. 5 can be obtained.

FIG. 8 shows another embodiment in the vicinity of the storage tube 6 and the horizontal partition wall 10 in the embodiment of FIG. In this embodiment, a bellows 24 is provided between the pad 17 provided on the storage tube 6 and the horizontal partition wall 10. The bellows 24 is joined to the storage pipe 6, and can prevent the leakage of the cooling air and can absorb the lateral vibration at the time of the earthquake. In this structure, thermal stress generated in the storage pipe 6 is small, and prevention of leakage of cooling air through the gap between the storage pipe 6 and the horizontal partition wall section 10 helps to secure a heat removal balance between the upper and lower cooling passages. Applies to cases. In this embodiment, the vibration of the storage tube 6 in the horizontal direction can be suppressed, and the earthquake resistance of the storage tube 6 can be improved.

[0085]

According to the first aspect of the present invention, the radioactive substance having a large calorific value just brought into the radioactive substance dry storage facility is located in the most upstream storage pipe among the storage pipes storing the radioactive substance. Therefore, the stored canister can always be stored upstream of the cooling gas passage. The radioactive material having a large calorific value can be efficiently cooled by a low-temperature cooling gas.

A second aspect of the present invention is to provide a radioactive substance dry storage facility capable of making the temperature distribution in the axial direction of the storage tube more uniform with a simple structure in which the partition member is disposed, and to efficiently cool the radioactive substance in the storage tube. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a radioactive material dry storage according to a preferred embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of the vicinity of a canister storage chamber in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a cross-sectional view of another embodiment of the canister and the storage tube of FIG. 1;

FIG. 6 is an explanatory view showing an arrangement state of storage tubes in FIG. 5;

FIG. 7 is an explanatory view showing an arrangement state of another embodiment of the storage tube.

FIG. 8 is a longitudinal sectional view of another embodiment in the vicinity of the horizontal partition wall and the storage tube of FIG. 1;

[Explanation of symbols]

2 ... canister, 6 ... storage pipe, 8 ... floor slab, 9 ... ceiling slab, 10 ... horizontal partition wall, 12 ... air discharge duct, 13 ... outer wall, 14 ... partition plate, 16 ... steady rest,
17 pad, 18 louver, 19 inlet duct, 21
... pit cleaning robot, 30A, 30B ... entrance opening,
31A, 31B: outlet opening, 32A, 32B: cooling passage,
35 ... maintenance inspection section, 38 ... radioactive material dry storage, 46 ... inner wall section.

Continuing from the front page (72) Inventor Shosho Matsuda 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Energy Research Laboratory, Hitachi, Ltd. (72) Inventor Hidetoshi Kanai 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture No. Hitachi, Ltd. Hitachi Factory (72) Inventor Takao Karita 3-2-2, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi New Clear Engineering Co., Ltd.

Claims (3)

[Claims] A first slab, a second slab located below the first slab and forming a passage through which the cooling gas flows, and a cooling slab installed in the first slab. A radioactive material dry storage facility comprising a plurality of storage pipes extending in a gas passage toward the second slab and storing a canister in which a radioactive material is stored, wherein the storage located at an outlet side of the passage. A radioactive substance dry storage method in which the canister is stored in the storage pipe from the pipe toward the storage pipe located on the entrance side of the passage. 2. A first slab, a second slab located below the first slab and forming a passage for cooling gas between the first slab and the first slab, and provided in the first slab for the cooling. A plurality of storage pipes extending in a gas passage toward the second slab and storing a canister having a radioactive substance stored therein; and a cooling gas disposed between the first slab and the second slab. In the radioactive substance dry storage facility, wherein the passage is divided into a plurality of cooling passages in the vertical direction, and a partition member through which each of the storage tubes penetrates, from the storage tube located on the outlet side of the passage. A dry storage method of a radioactive substance, wherein the canister is stored in the storage tube toward the storage tube located on the entrance side of the passage. 3. The canister containing the radioactive substance is placed below the storage tube, and the canister containing the radioactive substance having a smaller calorific value than the radioactive substance in the canister is placed above the storage pipe. The dry storage method for a radioactive substance according to claim 1 or 2.