JPH06294891A - Storage facility for spent fuel - Google Patents

Abstract

PURPOSE:To provide a spent fuel storage facility wherein spent fuel can be safely stored with a simple system and a construction cost can be reduced in a case where a period of time in which spent fuel waits for reprocessing is long. CONSTITUTION:A spent fuel storage facility includes a storage pit 1 for storing a spent fuel assembly 3 in a condition to submerge it in a pool, a cooling pit 4which is provided in the neighborhood of the storage pit 1 and whose upper and lower parts communicate with the storage pit 1 respectively and a heat tube 7 wherein a heat-absorbing part 7a is submerged in the pool of the cooling pit 4 and the heat of the cooling pit 4 is radiated in the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spent fuel storage facility for storing spent fuel.

[0002]

2. Description of the Related Art In general, spent fuel used in a nuclear reactor is planned to be dismantled and reprocessed. However, the uranium fuel used in the reactor is
If the price is reduced due to excessive supply, or the commercialization of the fast breeder reactor is delayed, it may be disadvantageous to immediately reprocess the spent fuel from the economical point of view.

[0003] Conventionally, a storage method has been adopted in which spent fuel is temporarily stored in a fuel pool or the like in a nuclear power plant until the final disposal or the start of its treatment. Due to the above-mentioned circumstances, if the chance of not going to the reprocessing cycle increases, the storage facility such as the fuel pool may become full.

[0004]

In order to deal with such a situation, spent fuel is stored in a canister and hermetically sealed, the canister containing the spent fuel is loaded into the storage pipe, and the storage pipe is A method for storing spent fuel, which can cool the spent fuel sufficiently and safely store it for a long period of time by forcibly replacing the internal air, was proposed and filed (Japanese Patent Application Laid-Open No. 3-273193).

However, with the above storage method,
The air inside the storage tube is forcibly replaced by using the driving force of a blower or the like. The warm air discharged from the storage tube is once purified through a filter and then released to the atmosphere.

On the other hand, the spent fuel is stored in a state of being submerged in pool water, the heat of pool water is released to an intermediate heat exchanger provided in the primary circulation system, and the heat of this heat exchanger is secondary circulation system. It is possible to release it to the outside through a seawater heat exchanger or the like provided in the above. However, such a storage method requires two primary and secondary circulation systems, so the system itself becomes complicated, It has the disadvantage of high cost.

The present invention has been made in view of the above circumstances, and safely stores spent fuel with a simple system even when the waiting period until the spent fuel is reprocessed is long. It is an object of the present invention to provide a storage facility for spent fuel, which can be manufactured at a reduced cost.

[0008]

In order to achieve the above object, the present invention has a storage pit for storing spent fuel in a state of being submerged in pool water, and an upper portion and a lower portion provided adjacent to the storage pit. Is provided with a cooling pit that communicates with each storage pit, and a heat pipe that inserts a heat absorbing portion below the pool water surface of the cooling pit to release the heat in the cooling pit to the outside.

[0009]

When the spent fuel is stored in the storage pit, the pool heat in the storage pit is warmed by the decay heat generated from the radioactive material contained in the spent fuel. The heated pool water rises due to the specific gravity, and moves into the cooling pit through the part communicating with the cooling pit. On the other hand, the heated pool water that has moved into the cooling pit is cooled by the heat pipe and moves to the lower portion. Then, the pool water that has moved to the lower portion of the cooling pit moves to the storage pit from the lower communication portion that connects the cooling pit and the storage pit, and is heated again by the fuel and rises. By circulating such pool water, the decay heat released from the spent fuel is removed, and the spent fuel is safely stored for a long period of time.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spent fuel storage pool according to the present invention will be described below with reference to the drawings. In the drawings, reference numeral 1 is a storage pit, 2 is a fuel rack, 3 is a spent fuel assembly, 4 is a cooling pit, 5 is a cooling channel, and 6
Is a partition that separates the storage pit 1 from the cooling pit 4, 7 is a heat pipe, 8 is a discharge tower, 9 is an air supply port, 10 is an exhaust port, 1
1 is an unloading pit and 12 is a cask.

The spent fuel storage facility of the present embodiment has a storage pit 1 for storing the spent fuel assembly 3 in a state of being submerged in pool water, and an upper portion and a lower portion provided adjacent to the storage pit 1. A basic structure comprising a cooling pit 4 communicating with the storage pit 1 and a heat pipe 7 in which a heat absorbing portion is inserted below the pool water surface of the cooling pit 4 to release the heat in the cooling pit 4 to the outside. It has become.

The spent fuel assembly 3 is stored in the fixed fuel rack 2 below the storage pit 1. The fuel rack 2 is constructed by stacking shaped steel or stainless steel materials assembled in a lattice shape in a multi-tiered manner, and the spent fuel assemblies are housed in an upright state in each lattice-shaped space. ing. The bottom plate of the fuel rack 2 is formed in a plate shape or a wire mesh shape having a large number of holes so that pool water can enter and exit.

The partition wall 6 is provided between the storage pit 1 and the cooling pit 4 adjacent to the storage pit 1.
The partition wall 6 and the fuel rack 2 are attached to the upper side of the cooling channel 5 which is arranged in the lower part of the storage pit 1 and the cooling pit 4 so as to interrogate them, and below the partition wall 6, A lower communication portion 13 that allows the flow of pool water between the cooling pit 4 and the storage pit 1 is formed. Further, the height of the partition wall 6 is set to a position lower than the height of the water surface Wa of the pool water by a predetermined amount, so that the pool water between the cooling pit 4 and the storage pit 1 is also above the partition wall 6. An upper communication portion 14 that allows the flow is formed.

The heat pipe 7 has a well-known structure in which a working fluid such as methanol or ammonia is enclosed in a closed container lined with a wick structure. Here, the heat pipe 7 is made to correspond to the heat removal amount of pool water. A support 1 in which a plurality of determined heat pipes 7 are provided with heat absorbing portions 7a to be inserted into the cooling pit 4 at predetermined vertical intervals.
It is supported and arranged by 5. The heat pipe 7 extends upward along the cooling pit 4 and
The exhaust heat section 7b at the tip is exposed in the exhaust tower 8 through the side wall 4a of the. The discharge tower 8 is provided at a position deviated laterally from directly above the cooling pit 4, and an air supply port 9 is provided at the lower part.
An outside air introduction passage 9 having a is continuously provided, and an exhaust port 10 is formed on the upper side wall.

In order to store the spent fuel assembly by the spent fuel storage facility thus constructed, the following procedure is performed. First, the cask 12 carried by a trailer or the like is unloaded at the unloading pit 11 using a cask crane.
And casks 1 at the unloading pit 11.
The spent fuel assembly 3 is taken out from 2. The taken-out spent fuel assembly 3 is lifted by a ceiling crane (not shown) in a range below the surface of the pool, moved through the communicating portion 1a between the storage pit 1 and the unloading pit 11 into the storage pit 11, and the fuel rack Insert into the storage part of 2.

When the spent fuel assembly 3 is stored in the storage portion of the fuel rack 2 and stored in the storage pit 1, decay heat generated from radioactive substances contained in the spent fuel assembly 3 causes the inside of the storage pit 1 to collapse. Pool water is warmed. The heated pool water rises due to the specific gravity, and moves to the cooling pit 4 through the upper communicating portion 14 above the partition wall 6.
On the other hand, the pool water that has moved to the cooling pit 4 is cooled by the heat pipe 7 and moves downward in the cooling pit 4. Then, the pool water that has moved to the lower portion of the cooling pit 4 flows into the storage pit 1 through the lower communication portion 13 below the partition wall, is warmed by the spent fuel assembly 3, and rises again.

The heat absorbed by the heat absorbing portion 7a of the heat pipe 7 is brought into contact with the outside air in the exhaust tower 8 where the exhaust heat portion 7b of the heat pipe 7 flows from the air supply port 9a through the outside air introduction passage 9. As a result, the outside air, which is released to the outside air and is warmed at the same time, rises in the discharge tower 8 and is released from the exhaust port 10 to the atmosphere. As described above, since the natural cooling is performed by natural ventilation without using a forced cooling means such as a blower, the running cost can be reduced. Further, since the heat pipe 7 is interposed between the pool water and the outside air to cool the pool water, the radiation substance is less likely to be emitted as compared with the case where the pool water is directly cooled by the outside air, and parts such as filters are also included. It becomes unnecessary.

In the above embodiment, the heat exhaust portion 7b at the upper portion of the heat pipe 7 is cooled by so-called natural ventilation utilizing the natural flow of air, but the invention is not limited to this. It may be cooled by so-called forced cooling in which air is forcedly sent by a fan. Further, in the above embodiment, the discharge tower 8 is provided at a position laterally offset from directly above the cooling pit 4, and correspondingly the middle of the heat pipe 7 is positioned in the upper discharge tower 8. However, the present invention is not limited to this, and conversely, the discharge tower 8 may be formed midway and positioned above the cooling pit 4, while the heat pipe 7 may be simply linear.

[0019]

As described above, according to the present invention, a storage pit for storing spent fuel in a state of being submerged in pool water, and a storage pit provided adjacent to the storage pit and having an upper portion and a lower portion, respectively. Since a cooling pit communicated with the cooling pit and a heat pipe that has an endothermic part inserted below the pool water surface of the cooling pit to release the heat in the cooling pit to the outside, The pool heat in the storage pit is warmed by the decay heat generated,
The heated pool water rises from the relationship of specific gravity and flows into the cooling pit through the upper communication part, where it is cooled by the heat absorption part of the heat pipe and moves downward, and again through the lower communication part to the storage pit. The moving pool water is circulated, the decay heat released from the spent fuel is removed by such pool water circulation, and the spent fuel can be safely stored for a long period of time, and Since the cooling pit is provided and the heat pipe is provided in association with this cooling pit, the construction cost can be reduced, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a spent fuel storage facility according to the present invention.

[Explanation of symbols]

 1 Storage Pit 2 Fuel Rack 3 Spent Fuel Assembly 4 Cooling Pit 5 Cooling Channel 6 Partition 7 Heat Pipe 7a Endotherm 7b Heat Exhaust 8 Exhaust Tower 9 Air Supply Port 10a Exhaust Port 11 Unloading Pit 12 Cask

Claims (1)

[Claims] 1. A storage pit for storing spent fuel in a state of being submerged in pool water, a cooling pit provided adjacent to the storage pit and having upper and lower portions connected to the storage pit, respectively, and the cooling pit. A storage facility for spent fuel, comprising a heat pipe that has an endothermic portion inserted below the water surface of the pool to release the heat in the cooling pit to the outside.