A sealing welding treatment method for damaged spent fuel assembly

Abstract

The present invention relates to a sealing welding processing method for damaged spent fuel assemblies. The method provided by the present invention can effectively solve the sealing, storage and subsequent decommissioning and transportation problems of damaged spent fuel assemblies. By designing special equipment such as inclined conveyors, water tank operators, transfer cranes, sealing tank operating devices, thin-walled tube operating devices, transfer grippers and manipulators, the remote transportation of damaged component sealing tanks, damaged components, thin-walled tubes and other objects can be realized. The sealing welding, transportation and storage of damaged spent fuel assemblies can be handled entirely by remote operation, thereby effectively preventing operators from being exposed to radiation. At the same time, the present invention can solve the problem of environmental pollution caused by fission gases and other radioactive substances released by damaged assemblies during transportation, and also takes into account factors such as the influence of component heating; it is also applicable to other processing objects with sealing requirements and remote operation requirements.

Description

Technical Field

[0001] The invention belongs to the field of processing damaged spent fuel assemblies and relates to a sealing welding processing method for damaged spent fuel assemblies. Background Art

[0002] There is a possibility of component damage during reactor operation. In order to balance reactor safety and economic operation, damaged components are usually treated by evaluation, repair and reuse. For damaged spent fuel components that cannot be repaired, a treatment process for damaged spent fuel components is required. At present, the China Experimental Fast Reactor uses rubber rings for sealing and underwater storage to treat damaged spent fuel components. The sealing index and reliability are not high. There are also certain difficulties in the subsequent transportation, storage, and external transportation of damaged spent fuel components when the power plant reactor is decommissioned.

[0003] In order to prevent environmental pollution, the first thing that needs to be solved in the storage and transportation process of damaged spent fuel assemblies is the sealing problem of radioactive gases and other radioactive materials released by damaged spent fuel assemblies; at the same time, since damaged spent fuel assemblies are highly radioactive, in order to avoid operators being exposed to radiation, the treatment process also needs to be able to achieve remote operation. In addition, since damaged spent fuel assemblies continue to generate heat, the design of the treatment process should also take into account the impact of the heat generated by damaged spent fuel assemblies.

[0004] The treatment of damaged fast reactor spent fuel assemblies is still rarely reported in China, and the relevant treatment process is still blank. Therefore, it is necessary to propose a treatment method suitable for the structural characteristics of damaged fast reactor spent fuel assemblies to solve the problems of sealing, storage and subsequent decommissioning and transportation of damaged spent fuel assemblies, which can effectively prevent operators from being exposed to radiation and also take into account the impact of heating of damaged spent fuel assemblies. Summary of the invention

[0005] In view of the defects existing in the prior art, the purpose of the present invention is to provide a sealing welding processing method for damaged spent fuel assemblies, so as to establish an effective and reliable sealing welding processing method for damaged spent fuel assemblies, so as to solve the problems of sealing, storage and subsequent decommissioning and transportation of damaged spent fuel assemblies, while effectively preventing operators from being exposed to radiation.

[0006] To achieve this object, the present invention provides a sealing welding processing method for a damaged spent fuel assembly, the method comprising the following steps:

[0007] (1) Use a transfer sealed container to temporarily seal the damaged spent fuel assembly;

[0008] (2) Underwater transport of the sealed transport container containing damaged spent fuel assemblies;

[0009] (3) Open the sealed transfer container, take out the damaged spent fuel assembly, and transfer the damaged spent fuel assembly into the welded sealed cylinder;

[0010] (4) closing the inner cover of the welding sealing cylinder, and evacuating the welding sealing cylinder and filling it with helium;

[0011] (5) closing the outer cover of the welding sealing cylinder and welding and sealing the welding sealing cylinder;

[0012] (6) transporting the welded sealing tube to a helium leak detection station for leak detection;

[0013] (7) The welded sealing cylinder that passes the leak test is transferred to an inclined conveyor and transported to a receiving tank for storage.

[0014] Furthermore, the welding sealing cylinder that fails the leak detection in step (6) is subjected to the welding sealing and leak detection operations of steps (5) and (6) again until it passes the leak detection and then is transported to the receiving water tank for storage.

[0015] Furthermore, the transfer sealed container is transferred to the receiving pool via an inclined conveyor, and the operation and docking of the inclined conveyor are controlled by remote operation in the fuel operation room.

[0016] Furthermore, the underwater transfer of the transfer sealed container in the receiving water tank is achieved by remotely operating the water tank operating machine. The transfer sealed container is provided with docking positioning requirements at each docking station. The repeated positioning accuracy is achieved through the mechanical positioning coordination between the transfer sealed container and the fixed tooling, and a transfer gripper with grasping adaptability is used to envelop the positioning deviation of the transfer sealed container. At the same time, the transfer grabbing process is remotely observed and monitored through cameras and peep windows to confirm the reliability of the transfer grabbing process.

[0017] Furthermore, the transportation process of the transport sealed container, damaged spent fuel assembly and welded sealing cylinder is achieved by remote operation.

[0018] Furthermore, the transport sealed container is a reusable sealed can of a damaged spent fuel assembly; and the welding sealing cylinder is a thin-walled cylinder for welding sealing.

[0019] Furthermore, a sealing structure is provided between the upper cover and the cylinder of the damaged spent fuel assembly sealed can; and the damaged spent fuel assembly sealed can is provided with a safety valve.

[0020] Furthermore, the operation of opening the sealed transport container and taking out the damaged spent fuel assembly is controlled by remote operation instructions and implemented at the sealed tank cover opening station in the welding and sealing process room;

[0021] The vacuuming-helium filling and sealing welding operations are controlled by remote operation instructions and are implemented at the thin-walled tube helium filling welding station in the welding and sealing process room;

[0022] The helium leak detection station is a thin-walled cylinder helium filling welding station in the welding and sealing process room;

[0023] The welding and sealing process room is provided with a sealed tank cover opening station, a thin-walled cylinder helium filling welding station, a thin-walled cylinder helium leak detection station, and a thin-walled cylinder and sealed cylinder tank temporary storage station.

[0024] Furthermore, the operation of transferring the damaged spent fuel assembly into the welding sealing cylinder is performed by issuing a remote operation command in the shielded room, using a transfer gripper, a transfer crane, and a manipulator with grasping adaptability to transfer the damaged spent fuel assembly to the thin-walled cylinder helium filling welding station, and placing the damaged spent fuel assembly into the thin-walled cylinder for welding sealing on the thin-walled cylinder helium filling welding station.

[0025] Furthermore, the opening and closing of the damaged spent fuel assembly sealed can is achieved by a damaged spent fuel assembly sealed can operating device, which is jointly designed with the damaged spent fuel assembly sealed can. The damaged spent fuel assembly sealed can operating device receives remote operation instructions to overcome the spring sealing pressure of the sealing structure or load the spring sealing pressure of the sealing structure, thereby respectively achieving the corresponding upper cover opening or closing sealing function of the damaged spent fuel assembly sealed can.

[0026] The beneficial effect of the present invention is that the sealing welding treatment method of the damaged spent fuel assembly provided by the present invention can effectively solve the sealing, storage and subsequent decommissioning and transportation problems of the damaged spent fuel assembly, and the remote transportation of damaged assembly sealed cans, damaged components, thin-walled tubes and other objects can be realized by designing special equipment such as inclined conveyors, pool operators, transfer cranes, sealed tank operating devices, thin-walled tube operating devices, transfer grippers and manipulators, so that the sealing welding, transportation and storage of damaged spent fuel assemblies can be handled entirely by remote operation, thereby effectively avoiding the operator from being exposed to radiation. The method provided by the present invention can solve the problem of environmental pollution caused by fission gas and other radioactive substances released by damaged assemblies during transportation (including receiving pools for storage, etc.). At the same time, the method provided by the present invention also takes into account factors such as the influence of component heating and the influence of fission gas release on the pressure change in the transport sealed container, and is also applicable to other processing objects with sealing requirements and remote operation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart of the sealing method for damaged spent fuel assemblies provided by the present invention.

[0028] Figure 2 A schematic flow chart of a method for sealing a damaged spent fuel assembly provided in an embodiment of the present invention.

[0029] Figure 3 A flow chart of the sealing process for a damaged spent fuel assembly during a welding sealing process provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] like Figure 1-3 As shown, a sealing welding method for a damaged spent fuel assembly of a fast reactor comprises the following steps:

[0032] (1) Temporarily seal the damaged spent fuel assembly: The temporary sealing and transportation of damaged spent fuel assemblies needs to meet the requirements of remote operation; the transport sealed container should be reusable, and the design of the transport sealed container should consider the impact of the heating of the assembly on the performance of the transport sealed container, and the impact of the fission gas release on the pressure change in the transport sealed container;

[0033] In this embodiment, a reusable sealed canister of a damaged spent fuel assembly is used as a transport sealed container to temporarily seal and transport the damaged spent fuel assembly. The sealed canister of the damaged spent fuel assembly is a reusable container. A sealing structure with high temperature resistance and radiation resistance is arranged between the upper cover and the cylinder of the sealed canister of the damaged spent fuel assembly to ensure the sealing reliability of the sealed canister of the damaged spent fuel assembly under the conditions of heating of the assembly and / or radiation of radioactive waste during the transport process. The sealing structure is regularly inspected and replaced to ensure the sealing stability of the sealed canister of the damaged spent fuel assembly itself and meet the requirements of reuse.

[0034] In the present embodiment, the opening and closing of the damaged spent fuel assembly sealed can is realized by the damaged spent fuel assembly sealed can operating device, which is jointly designed with the damaged spent fuel assembly sealed can. The damaged spent fuel assembly sealed can is sealed by the spring in the sealing structure. The damaged spent fuel assembly sealed can operating device can overcome the spring sealing pressure of the sealing structure or load the spring sealing pressure of the sealing structure by receiving the remote operation command, thereby realizing the corresponding opening or closing sealing function of the damaged spent fuel assembly sealed can respectively.

[0035] At the same time, the design of sealed cans for damaged spent fuel assemblies should take into account the effect of component heating on the performance of transport sealed containers. Composite materials with high temperature resistance and radiation resistance should be selected when designing sealed cans for damaged spent fuel assemblies to ensure that under conditions of component heating and / or radioactive waste radiation, the strength of the sealed can material can meet the material strength requirements of the design of sealed cans for damaged spent fuel assemblies; and reasonable inspection and maintenance procedures should be formulated.

[0036] The design of the sealed canister for damaged spent fuel assemblies should also fully consider the impact of fission gas release and assembly heating on pressure changes in the transport sealed container. Assembly heating and fission gas release will cause changes in temperature and pressure in the sealed canister. The pressure requirements of the sealed canister for damaged spent fuel assemblies should be determined through relevant calculations, and the pressure bearing capacity of the sealed canister for damaged spent fuel assemblies should be matched and designed, and a safety valve should be installed to ensure the safety of the sealed canister for damaged spent fuel assemblies.

[0037] (2) Underwater transfer of the sealed transfer container containing the damaged spent fuel assembly: The underwater transfer of the sealed transfer container is achieved through remote operation. During the transfer of the sealed transfer container, the repeat positioning accuracy of the sealed transfer container at each workstation and the envelope of the relevant transfer grippers are fully considered to ensure that the sealed transfer container can be reliably grasped and transferred.

[0038] In this embodiment, after the damaged spent fuel assembly sealed canister is remotely sealed in the spent fuel assembly receiving room by the damaged spent fuel assembly sealed canister operating device, the damaged spent fuel assembly sealed canister is transferred from the spent fuel assembly receiving room to the spent fuel assembly receiving pool by the spent fuel assembly inclined conveyor, and the operation and docking of the spent fuel assembly inclined conveyor can be remotely controlled in the fuel operation room; the damaged spent fuel assembly sealed canister is remotely transferred in the spent fuel assembly receiving pool by the pool operating machine.

[0039] There are docking positioning requirements at each docking station. The repeated positioning accuracy is achieved through the mechanical positioning coordination between the transfer object (i.e. the transfer sealed container, the damaged spent fuel assembly sealed can used in this embodiment) and the fixed tooling, to ensure the repeated positioning accuracy of the transfer object before or after each grabbing or lowering. At the same time, the gripper used for grabbing has certain grabbing adaptability and enveloping properties. The automatic transfer gripper used in this embodiment has a maximum grabbing contour that can envelop the positioning deviation of the transfer object after the gripper is opened, to achieve reliable grabbing and lowering of the transfer object. In addition, the transfer grabbing process can be remotely observed through cameras and peep windows to perform secondary confirmation of the grabbing.

[0040] (3) Unsealing the sealed transfer container in the welding and sealing process room: After the sealed transfer container is transferred to the sealed can cover opening station in the welding and sealing process room, the sealed transfer container is opened;

[0041] In this embodiment, after the damaged spent fuel assembly sealed can is transported to the sealed can cover opening station in the welding and sealing process room, the damaged spent fuel assembly sealed can operating device receives the remote operation command, overcomes the spring sealing pressure of the sealing structure, and opens the upper cover of the damaged spent fuel assembly sealed can.

[0042] The welding and sealing process room is equipped with a sealed tank cover opening station, a thin-walled cylinder helium filling and welding station, a thin-walled cylinder helium leak detection station, and a thin-walled cylinder and sealed cylinder tank temporary storage station.

[0043] (4) taking out the damaged spent fuel assembly from the transport sealed container, transporting it to the thin-walled cylinder helium filling welding station in the sealing welding process room, and placing the damaged spent fuel assembly into the thin-walled cylinder for welding and sealing at the thin-walled cylinder helium filling welding station;

[0044] In this embodiment, the following operations are performed in the shielded room by issuing remote operation commands: the damaged spent fuel assembly is grabbed by a transfer gripper with a certain grasping adaptability, and then the damaged spent fuel assembly is transferred to the thin-walled cylinder helium filling welding station in the sealing welding process room, and then the damaged spent fuel assembly is placed downwardly into the thin-walled cylinder for welding sealing on the thin-walled cylinder helium filling welding station.

[0045] (5) closing the inner cover of the thin-walled tube for welding and sealing, and evacuating and filling the thin-walled tube for welding and sealing with helium;

[0046] (6) closing the outer cover of the thin-walled tube for welding and sealing, and welding and sealing the thin-walled tube for welding and sealing;

[0047] (7) The welded sealing thin-walled tube is transported to the helium leak detection station for leak detection;

[0048] (8) If the leak test is qualified, that is, the leak test results show that the welding seal is qualified, the thin-walled cylinder for welding seal is transferred to the spent fuel assembly inclined conveyor and transported to the spent fuel assembly receiving pool for storage;

[0049] Since the treatment object is a damaged spent fuel assembly with high radioactivity, the treatment process is all remotely operated to avoid radiation exposure. In this embodiment, the thin-walled tube for welding and sealing that passes the leak detection is transported to the spent fuel assembly receiving pool for storage by the spent fuel assembly inclined conveyor. The thin-walled tube for welding and sealing has the same transport interface as the sealed tank of the damaged spent fuel assembly, and the same transport method can be used.

[0050] (9) If the leak detection result is unqualified, repeat the welding, sealing and leak detection operations of steps (6) to (8) until it passes the test and then transfer it to the spent fuel assembly receiving pool for storage.

[0051] The temporary sealing and transportation of damaged spent fuel assemblies need to meet the requirements of remote operation to avoid radiation exposure to operators. In this embodiment, the remote transportation of damaged spent fuel assembly sealed cans, damaged spent fuel assemblies, thin-walled tubes for welding and sealing, etc. is mainly achieved by designing special equipment, for example, 1) a spent fuel assembly inclined conveyor is used from the spent fuel assembly receiving room to the spent fuel assembly receiving pool, and the operation and docking of the spent fuel assembly inclined conveyor can be remotely controlled in the fuel operation room. 2) A pool operator is used for remote transportation in the spent fuel assembly receiving pool. 3) In the shielded room, remote operation / control instructions can be used to control the shielded room transfer crane, transfer gripper and manipulator to remotely transport damaged spent fuel assemblies and thin-walled tubes for welding and sealing.

[0052] The treatment scheme provided in this embodiment has been verified by relevant experiments and applied in the 600MW demonstration fast reactor project. Figure 3 shown.

[0053] The above embodiments are merely illustrative of the present invention, and those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A sealing welding method for damaged spent fuel assemblies, characterized in that: The method comprises the following steps: (1) Use transfer sealed containers to temporarily seal damaged spent fuel assemblies; (2) Underwater transport of the sealed transport container containing damaged spent fuel assemblies; (3) opening the sealed transfer container, taking out the damaged spent fuel assembly, and transferring the damaged spent fuel assembly into a welding sealing cylinder; the welding sealing cylinder is a thin-walled cylinder for welding sealing; (4) closing the inner cover of the welding sealing cylinder, and evacuating the welding sealing cylinder and filling it with helium; (5) closing the outer cover of the welding sealing cylinder and welding and sealing the welding sealing cylinder; (6) transporting the welded sealing cylinder to a helium leak detection station for leak detection; (7) The welded sealing cylinders that have passed the leak test are transferred to an inclined conveyor and transported to a receiving pool for storage; the welded sealing cylinders that have failed the leak test in step (6) are subjected to the welding, sealing and leak test operations of steps (5) and (6) again until they pass the leak test and are then transferred to the receiving pool for storage; The underwater transfer of the transfer sealed container in the receiving water tank is achieved by remotely controlling the water tank operating machine. The transfer sealed container is provided with docking positioning requirements at each docking station. The repeatable positioning accuracy is achieved through the mechanical positioning cooperation between the transfer sealed container and the fixed tooling, and a transfer gripper with grasping adaptability is used to envelop the positioning deviation of the transfer sealed container. At the same time, the transfer grabbing process is remotely observed and monitored through a camera and a peep window to confirm the reliability of the transfer grabbing process. The operation of opening the sealed transfer container and taking out the damaged spent fuel assembly is controlled by remote operation instructions and implemented at the sealed tank cover opening station in the welding and sealing process room; The vacuuming-helium filling and sealing welding operations are controlled by remote operation instructions and are implemented at the thin-walled tube helium filling welding station in the welding and sealing process room; The helium leak detection station is a thin-walled cylinder helium filling welding station in the welding and sealing process room; The transportation process of the transport sealed container, the damaged spent fuel assembly and the welded sealing cylinder is all achieved by remote operation.

2. A sealing welding method for damaged spent fuel assembly according to claim 1, characterized in that: The transfer sealed container is transferred to the receiving pool via an inclined conveyor, and the operation and docking of the inclined conveyor are controlled by remote operation in the fuel operation room.

3. A sealing welding method for damaged spent fuel assembly according to claim 1 or 2, characterized in that: The transport sealed container is a reusable sealed canister of a damaged spent fuel assembly.

4. A sealing welding method for damaged spent fuel assembly according to claim 3, characterized in that: A sealing structure is arranged between the upper cover and the cylinder of the damaged spent fuel assembly sealed can; and a safety valve is arranged on the damaged spent fuel assembly sealed can.

5. A sealing welding method for damaged spent fuel assembly according to claim 4, characterized in that: The welding and sealing process room is provided with a sealed tank cover opening station, a thin-walled cylinder helium filling welding station, a thin-walled cylinder helium leak detection station, and a thin-walled cylinder and sealed cylinder tank temporary storage station.

6. A sealing welding method for damaged spent fuel assembly according to claim 5, characterized in that: The operation of transferring the damaged spent fuel assembly into the welding sealing cylinder is performed by issuing a remote operation command in the shielded room, using a transfer gripper, a transfer crane, and a manipulator with grasping adaptability to transfer the damaged spent fuel assembly to the thin-walled cylinder helium filling welding station, and placing the damaged spent fuel assembly into the thin-walled cylinder for welding sealing on the thin-walled cylinder helium filling welding station.

7. A sealing welding method for damaged spent fuel assembly according to claim 6, characterized in that: The opening and closing of the damaged spent fuel assembly sealed can is achieved by a damaged spent fuel assembly sealed can operating device, which is jointly designed with the damaged spent fuel assembly sealed can. The damaged spent fuel assembly sealed can operating device receives remote operation instructions to overcome the spring sealing pressure of the sealing structure or load the spring sealing pressure of the sealing structure, thereby respectively achieving the corresponding upper cover opening or closing sealing function of the damaged spent fuel assembly sealed can.

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