Spent fuel storage facility

Abstract

The invention relates to a cavity-type spent fuel (SNF) dry storage facility for temporarily storing spent fuel to reduce the waste heat release of the fuel prior to delivery to a field storage facility for long-term storage or reprocessing. The spent fuel storage depot comprises a storage cavity with an integral reinforced concrete protection wall, a spent fuel tank provided with a spent fuel assembly, a top partition plate, a bottom partition plate and a natural ventilation system, the natural ventilation system comprises a vertical exhaust pipe, a vertical air inlet pipe provided with an air inlet device and horizontal air inlet and exhaust manifolds, and the bottom partition plate is arranged between the manifolds. An embedded pipe is installed in the bottom partition plate, an embedded pipe coaxial with the embedded pipe in the bottom partition plate is installed in the top partition plate, and an isolation plug is inserted into the embedded pipe to isolate the storage warehouse from a room provided with a loading machine. The spent fuel tanks are inserted into the embedded pipes in the bottom partition plate, and each embedded pipe is provided with a spent fuel tank filled with spent fuel or a spent fuel tank provided with a sealing plug in an inserted mode. All the embedded pipes in the bottom partition plate are sealed before canning. The cold air inlet is located at a height to prevent surface water from entering the air manifold.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power, and particularly to a cavity type spent nuclear fuel (SNF) dry storage facility for temporarily storing spent fuel to reduce the release of fuel residual heat before it is sent to the on-site storage facility for long-term storage or reprocessing. Background Art

[0002] Patent document RU2273067C1 discloses a spent fuel storage facility, which includes a shaft with a cofferdam at the upper part of the well, a container (lattice) arranged in the well and carrying spent fuel cans, and a well ventilation system. The container is cylindrical, with a perforated part at the bottom, and is vertically installed at the bottom of the well. The spent fuel cans are stacked vertically in the container. At the same time, at least one empty container is arranged in the well, and the cofferdam at the upper part of the well is installed below the top port of the container. The containers with spent fuel cans are arranged along the perimeter of the well, and the empty containers are installed between these containers and are located in the middle of the well.

[0003] In the above storage facility, the spent fuel cans are stacked in strings and loaded into the container, fixed at a certain height in the container using a partition, and maintained at the center of the container using a centering device. The heat released during the storage of spent fuel is discharged into the atmosphere by natural ventilation. Cold air enters the interior of the container through the perforated part of the container, rises after being heated, and is discharged into the atmosphere. If it is necessary to remove the lower spent fuel can for maintenance or reprocessing, the spent fuel can with the spent fuel assembly above is transferred to the empty container without being taken out to the surface.

[0004] The disclosed storage facility has the following deficiencies: Atmospheric air descends along the well and enters the space between the containers. Since the cross-section of the space between the containers is large, the air flow descends slowly. Therefore, the air enters the perforated part of the container only after being preheated by the container wall, which will cause its density to decrease, thereby forming an air density difference at the bottom and top of the well, and then resulting in a decrease in the natural ventilation force.

[0005] Therefore, especially in summer, the decrease in the natural ventilation force may cause the temperature of the spent fuel can with the spent fuel assembly to rise, and the heat transfer efficiency of the spent fuel assembly to the atmosphere is low because the heat flow needs to overcome not only the thermal resistance of the air in the spent fuel can against the air in the container, but also the thermal resistance of the air in the container against the atmosphere.

[0006] The bottom of the lattice (cell) is provided with a perforated part, so the lattice (cell) cannot be used as an auxiliary safety barrier.

[0007] Patent document RU2572361C1 discloses a spent fuel storage facility. The storage facility includes a storage cavity with an integral reinforced concrete protective wall, and a plurality of grids are provided on the top and bottom plates within the protective wall. These grids are provided with protective plugs, and the protective plugs are installed on the grids by welding after loading two spent fuel cans; the protective plugs are also provided with sampling pipes, and the inner cavity of the grid is connected to the maintenance area through a shut-off valve. The storage cavity is provided with equipment for remotely loading the spent fuel cans into the storage grids and installing the protective plugs in the grids. The natural ventilation system includes embedded pipes installed in the bottom cofferdam of the storage cavity, connecting the storage cavity to the space below the storage cavity, and the space below the storage cavity is sequentially connected to the air intake device. The top of the storage cavity is connected to the exhaust pipe through an exhaust duct, and the exhaust pipe is located at the top of the storage cavity.

[0008] The disclosed spent fuel storage facility has the following drawbacks: Air flows along the storage grids (pipes) with empty spent fuel cans, thereby reducing the cooling effect of the spent fuel cans with spent fuel assemblies.

[0009] The main requirements for a spent fuel storage facility include:

[0010] - Ensure nuclear safety during the storage of spent fuel and its transportation and technological operations;

[0011] - Ensure the radiation safety of personnel and protect the environment;

[0012] - Monitor the release of residual heat, ensure the integrity of the fuel cladding, and the safety of the fuel within the storage facility.

[0013] The radiation safety of a spent fuel storage facility mainly depends on the state of the fuel cladding.

[0014] When using dry storage, the temperature of the fuel cladding is a key factor affecting the integrity of the spent fuel. Therefore, it is necessary to improve the cooling efficiency of the spent fuel within the storage facility. Summary of the Invention

[0015] The present invention aims to solve the problem of improving the safety of spent fuel storage.

[0016] By implementing the present invention, the following technical effects can be achieved: improving the cooling efficiency of the spent fuel cans within the storage facility and improving the radiation safety.

[0017] The above technical effects are achieved through the following method: A spent fuel storage facility includes a storage cavity with multiple integral reinforced concrete protective walls, multiple spent fuel cans for configuring spent fuel assemblies, a top plate partition and a bottom plate partition, and a natural ventilation system. The natural ventilation system includes a vertical exhaust pipe and a vertical intake pipe provided with an intake device, as well as a horizontal intake manifold and a horizontal exhaust manifold. A bottom plate partition is provided between the horizontal intake manifold and the horizontal exhaust manifold, and multiple embedded pipes are installed in the bottom plate partition to ensure that the air flow direction only passes through the multiple embedded pipes. In the top plate partition, multiple embedded pipes coaxial with the multiple embedded pipes in the bottom plate partition are installed, and the multiple embedded pipes are inserted with multiple isolation plugs to isolate the storage facility from the room equipped with a charging machine; the multiple spent fuel cans are inserted into the multiple embedded pipes in the bottom plate partition, and each embedded pipe is inserted with a spent fuel can containing spent fuel or an empty spent fuel can with a sealing plug; and, the cold air intake is located at a certain height to prevent surface water from entering the air manifold.

[0018] All the embedded pipes in the bottom plate partition are closed before canning.

[0019] Before canning, all the embedded pipes in the bottom plate partition are closed with empty spent fuel cans provided with sealing plugs.

[0020] The embedded pipes in the bottom plate partition are inserted with spent fuel cans containing spent fuel or empty spent fuel cans provided with sealing plugs.

[0021] The spent fuel cans are arranged at intervals to ensure nuclear storage safety.

[0022] The spent fuel can is cylindrical, and its tank body is provided with fins to increase the heat transfer surface area of the spent fuel can, thereby improving its cooling efficiency.

[0023] The upper surface of the isolation plug is provided with a grasping device, and the grasping device is closed with a lid; a sealing member is provided at the shoulder of the isolation plug; and, a heat insulation layer is provided at the bottom of the isolation plug.

[0024] The spent fuel can containing spent fuel is filled with lead to improve the heat dissipation efficiency of the fuel rod. The narrow part at the bottom of the spent fuel can serves as a shock absorber; a clamping device for fixing the spent fuel is provided at the bottom of the tank body of the spent fuel can; and, the lid of the spent fuel can is provided with a mushroom-shaped grasping device.

[0025] The spent fuel is loaded into the spent fuel can pre-filled with liquid lead by a standard loading device. The clamping device of the spent fuel can prevents the spent fuel from spilling.

[0026] The inlet part of the bottom air manifold can be U-shaped, and a drain port is provided at the bottom of the inlet part for draining the water entering the U-shaped pipe.

[0027] The space between the body of the spent fuel canister and the embedded pipe within the bottom partition forms a vertical air passage through which cold air flows. An empty spent fuel canister with a plugging stopper is installed in the embedded pipe within the bottom partition to block the embedded pipe, thereby increasing the flow rate of cooling air in the embedded pipe containing the spent fuel canister.

[0028] The embedded pipe ensures that the air flow only passes through the space between the body of the spent fuel canister and the embedded pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following will briefly introduce the drawings required to describe the present invention. These drawings show one possible embodiment of the present invention.

[0030] Figure 1 Shows a general layout of the spent fuel storage facility;

[0031] Figure 2 Shows the spent fuel canister; and

[0032] Figure 3 Shows the spent fuel canister with a temporary plugging stopper.

[0033] The storage facility includes a storage cavity with an integral reinforced concrete wall, an exhaust pipe and an intake pipe, as well as a top partition and a bottom partition. Embedded pipes are coaxially installed within the top partition and the bottom partition.

[0034] To cool the spent fuel canister installed in the embedded pipe within the bottom partition, the storage facility is provided with a cooling system based on natural ventilation. DETAILED DESCRIPTION OF THE INVENTION

[0035] The following describes one possible embodiment of the present invention, but not the only embodiment.

[0036] The storage facility may consist of multiple chambers for storing spent fuel. Each chamber ( Figure 1 ) includes a vertical exhaust pipe 1, a vertical intake pipe 2, a horizontal intake manifold 3 and a horizontal exhaust manifold 4, a top partition 5 and a bottom partition 6 provided with an embedded pipe 7, a spent fuel canister 8 containing spent fuel, an empty spent fuel canister 9 with a plugging stopper 10, and a spacer plug 11. A drain port 12 is installed at the bottom of the air duct for discharging water entering the U-shaped pipe. Each spent fuel canister is located within a corresponding cell.

[0037] The embedded pipe 7 within the bottom partition 6 is used to arrange the spent fuel canisters within the storage facility in an orderly manner and to guide the cooling air to flow along the fins of the spent fuel canister 8.

[0038] The isolation plug 11 is used for biological protection of the staff, preventing the spent fuel canister 8 containing spent fuel from emitting ionizing radiation, and preventing the cooling air from entering the central hall. The isolation plug 11 is installed in the top partition of the storage chamber, above the corresponding cell of the spent fuel canister 8 containing spent fuel.

[0039] The isolation plug 11 is a cylinder made of metal, with a shoulder for installation in the top partition 5. The isolation plug 11 can be filled with packing. The upper surface of the isolation plug 11 is provided with a grasping device (not shown in the figure), which can be sealed with a lid and is similar to the grasping device of the lid of the spent fuel canister 8. A seal is provided at the shoulder of the isolation plug 11. A heat-insulating layer is provided at the bottom of the isolation plug 11.

[0040] The spent fuel canister 8 (9) containing spent fuel 21 Figure 2 ) is a metal tube 14, the bottom of which is closed and filled with lead 15 inside. The narrow part at the bottom of the spent fuel canister 8 (9) serves as a shock absorber 16 to prevent damage to the fuel inside when loading the spent fuel into the spent fuel canister. A clamping device 17 is provided at the bottom of the canister body of the spent fuel canister 8 (9) to fix the spent fuel assembly 21 in the spent fuel canister 8 (9) to prevent it from spilling. The lid 18 of the spent fuel canister 8 (9) is provided with a mushroom-shaped grasping device 19. To increase the heat transfer area, fins 20 are provided on the canister body of the spent fuel canister 8 (9).

[0041] The spent fuel canister 8 is loaded into the embedded pipe 7, and the embedded pipe is installed in the bottom partition 6.

[0042] The blanking plug 10 on the empty spent fuel canister 9 ( Figure 3 ) is a detachable metal structure, consisting of two identical elements that are sleeved on the empty spent fuel canister 9 to block the air flow through the embedded pipe 7 in the bottom partition 6.

[0043] The storage facility of the present invention operates in the following manner.

[0044] Before starting to load all the spent fuel canisters 8 into the embedded pipes in the bottom partition, except for one embedded pipe, empty spent fuel canisters 9 with blanking plugs 10 should be inserted to ensure that the air flow only passes through the embedded pipes containing the spent fuel canisters 8.

[0045] The water entering the bottom U-shaped air pipe 2 is discharged through the drain port 12 under the action of gravity.

[0046] During the subsequent loading process of the storage facility, the empty spent fuel canisters 9 with blanking plugs 10 are taken out in sequence, and then the spent fuel canisters 8 containing spent fuel are loaded. During these operations, the isolation plug 11 is first taken out from the top partition 5, and after installing the spent fuel canister 8 with the spent fuel assembly, the isolation plug is reinstalled.

[0047] The spent fuel canister 8 filled with spent fuel is loaded into the storage facility by the loading machine 13. Using the loading machine 13 can provide biological protection for the staff, prevent the fuel from being heated beyond the allowable temperature during fuel transportation, and prevent the fuel from overheating in case of an emergency.

[0048] Overpressure is maintained in the space above the top partition 5 to prevent air from entering the space from the storage facility.

[0049] After welding the lid 18, the tightness of the spent fuel canister 8 filled with spent fuel is detected.

[0050] When spent fuel is stored in the reactor storage facility, the air temperature in the exhaust pipe is monitored.

[0051] Industrial applicability

[0052] The technical solution according to the present invention can be used for dry storage of spent fuel before it is sent to the on-site storage facility for long-term storage or reprocessing.

Claims

1. A spent fuel storage facility, comprising a storage cavity having a plurality of integral reinforced concrete protective walls, a plurality of spent fuel cans for configuring spent fuel assemblies, a top partition and a bottom partition, and a natural ventilation system. The natural ventilation system includes a vertical exhaust pipe and a vertical intake pipe provided with an intake device, as well as a horizontal intake manifold and a horizontal exhaust manifold. A bottom partition is provided between the horizontal intake manifold and the horizontal exhaust manifold, and a plurality of embedded pipes are installed in the bottom partition. Characterized in that, a plurality of embedded pipes coaxial with the plurality of embedded pipes in the bottom partition are installed in the top partition, and a plurality of isolation plugs are inserted into the plurality of embedded pipes to isolate the storage facility from a room equipped with a charging machine; the plurality of spent fuel cans are inserted into the plurality of embedded pipes in the bottom partition, and each of the plurality of embedded pipes is inserted with a spent fuel can containing spent fuel or an empty spent fuel can provided with a sealing plug; and, the plurality of embedded pipes in the bottom partition are closed before canning, and the cold air intake is located at a certain height to prevent surface water from entering the air manifold.

2. The spent fuel storage facility according to claim 1, Characterized in that, the plurality of spent fuel cans are arranged at intervals to ensure nuclear storage safety.

3. The spent fuel storage facility according to claim 1, Characterized in that, the plurality of spent fuel cans are cylindrical, and fins are provided on the tank body.

4. The spent fuel storage facility according to claim 1, Characterized in that, before canning, the plurality of embedded pipes in the bottom partition are all closed with the empty spent fuel cans provided with the sealing plugs.

5. The spent fuel storage facility according to claim 1, Characterized in that, a grasping device is provided on the upper surface of the isolation plug, and the grasping device is closed with a lid; a sealing member is provided on the shoulder of the isolation plug; and, a heat insulation layer is provided at the bottom of the isolation plug.

6. The spent fuel storage facility according to claim 1, Characterized in that, lead is filled in the spent fuel can containing the spent fuel.

7. The spent fuel storage facility according to claim 1, Characterized in that, the narrow part at the bottom of the spent fuel can serves as a shock absorber; a clamping device for fixing the spent fuel is provided at the bottom of the tank body of the spent fuel can; and, a mushroom-shaped grasping device is provided on the lid of the spent fuel can.

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