Drainage and water filling operation method for single fuel channel of heavy water reactor nuclear power station

Abstract

The invention particularly relates to a drainage and water filling operation method for a single fuel channel of a heavy water reactor nuclear power station. The drainage and water filling operation method comprises the following steps that 1, nuclear fuel in the fuel channel is emptied; 2, a fuel channel closure tool is installed to achieve closure; 3, ice plug isolation is carried out to carry out fuel channel drainage operation; 4, installing a temporary shielding plug to establish a maintenance condition; step 5, filling water into a fuel channel; and step 6, reloading the nuclear fuel in the fuel channel. According to the method, necessary conditions are established for fault processing of the single fuel channel; meanwhile, after fault processing is finished, operations such as fuel channel water filling and nuclear fuel reloading are carried out, and the standard configuration of a single fuel channel is recovered; therefore, safe and smooth maintenance is ensured, operation risks are reduced, working efficiency is improved, and personnel radiation safety and reactor safety are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of heavy water reactor maintenance, in particular to a method for draining and filling a single fuel channel of a heavy water reactor. Background Art

[0002] The core of a heavy water reactor consists of multiple horizontally arranged fuel channels. Each fuel channel has 2 shielding plugs, 2 sealing plugs and 12 nuclear fuels. The 2 sealing plugs are used to seal the fuel channels to ensure the integrity of the pressure boundary; the 2 shielding plugs are used to support and fix the 12 nuclear fuels in the fuel channels.

[0003] The heavy water coolant enters each fuel channel from the inlet header through the main pump and flows out from the outlet header, transferring the decay heat of the nuclear fuel to the steam generator, thereby achieving cooling and flow circulation of the nuclear fuel.

[0004] The inlet and outlet branches of each fuel channel are connected to the main inlet and outlet headers without separate isolation measures. When leakage occurs in the end parts, pressure pipes, heat transfer branch pipe joints and other equipment components of a single fuel channel, it will cause the leakage of heavy water coolant, seriously affecting the safe operation of the reactor. At this time, necessary operating methods need to be taken to establish maintenance conditions in order to carry out maintenance safely and smoothly.

[0005] Since 12 nuclear fuels are installed in a single fuel channel, the radiation dose is high and cannot be handled directly. In addition, the shielding plug, pressure tube and other components are in long-term contact with the nuclear fuel, and there is also a high radiation dose, which leads to high maintenance requirements, high difficulty in operation and high nuclear safety risks. After a fuel channel equipment failure occurs, the 12 nuclear fuels in the fuel channel must be emptied and unloaded, and the fuel channel must be intercepted, isolated and drained before personnel can carry out maintenance. Therefore, it is necessary to invent an operation method for draining and filling a single fuel channel of a heavy water reactor, to empty the nuclear fuel, accurately locate the fault, drain the fuel channel and other operations, and establish the necessary conditions for handling the fuel channel fault; at the same time, after the fault handling is completed, the fuel channel is filled with water, the nuclear fuel is reinstalled and other operations are carried out to restore the standard configuration of the single fuel channel; to ensure that the maintenance is carried out safely and smoothly, reduce the operation risk, improve work efficiency, and ensure the radiation safety of personnel and the safety of the reactor. Summary of the invention

[0006] The purpose of the present invention is to provide a method for draining and filling a fuel channel of a heavy water reactor, to perform operations such as emptying nuclear fuel, accurately locating faults, draining the fuel channel, and the like, so as to establish necessary conditions for handling fuel channel faults; at the same time, after the fault handling is completed, operations such as filling the fuel channel with water and reinstalling nuclear fuel are performed to restore the standard configuration of a single fuel channel; so as to ensure that maintenance is carried out safely and smoothly, reduce operational risks, improve work efficiency, and ensure radiation safety of personnel and reactor safety.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant comprises the following steps:

[0009] Step 1: Empty the fuel channel of nuclear fuel;

[0010] Step 2: Install the cut-off tool to cut off the fuel channel;

[0011] Step 3: Implement ice plug isolation to drain the fuel channel;

[0012] Step 4: Install temporary shielding plugs to establish maintenance conditions;

[0013] Step 5: Filling the fuel channel with water;

[0014] Step 6: Reinstall the nuclear fuel in the fuel channel.

[0015] In the present invention, step 1, emptying the fuel channel of nuclear fuel, comprises the following steps:

[0016] Step 1.1, the reactor enters the guaranteed shutdown mode: the reactor enters the guaranteed shutdown mode and maintains the guaranteed shutdown mode for more than 24 hours;

[0017] Step 1.2, empty the tool and load it into the upstream loader: remove the push rod adapter, spare sealing plug and spare shielding plug in the upstream loader bin; install the K-tube liner, install an RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; remove the spare shielding plug in the downstream loader;

[0018] Step 1.3, 12 nuclear fuels in the fuel channel are emptied to the downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped on the fuel channel; the upstream loading and unloading machine removes the upstream sealing plug and shielding plug, and pushes in the emptying tool; the downstream loading and unloading machine removes the downstream sealing plug and shielding plug, and receives 12 nuclear fuels; the upstream and downstream loading and unloading machines reinstall the shielding plug and sealing plug respectively, and complete the nuclear fuel emptying operation;

[0019] Step 1.4, the downstream loader and unloader unloads 12 nuclear fuels into the spent fuel pool: the downstream loader and unloader moves to the spent fuel channel and clamps it; removes the nozzle plug, installs the guide sleeve, and lowers the liquid level; unloads the 12 nuclear fuels in the downstream loader and unloader silo into the spent fuel pool; removes the guide sleeve, reinstalls the nozzle plug, and raises the liquid level to restore the system.

[0020] In the present invention, step 2, installing a shutoff tool to shut off the fuel channel, includes the following steps:

[0021] Step 2.1, unload the emptying tool in the upstream loader: unload 1 RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; unload the K pipe liner;

[0022] Step 2.2, remove the shielding plugs in the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines clamp onto the fuel channel, remove the sealing plugs and shielding plugs; the upstream and downstream loading and unloading machines reinstall the sealing plugs; the removed shielding plugs are unloaded into the spent fuel pool through the spent fuel channel;

[0023] Step 2.3, Load the cut-off tool into the loader: Hold the cut-off side loader on the auxiliary channel, remove the nozzle plug, and install the guide sleeve; install the cut-off tool into the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the cut-off tool has been loaded into the silo of the cut-off side loader;

[0024] Step 2.4, the shut-off tool is installed in the fuel channel to realize shut-off: the loader and unloader on the shut-off side clamps onto the fuel channel; removes the nozzle plug and the sealing plug, and installs the guide sleeve; installs the shut-off tool in the fuel channel; removes the guide sleeve, installs the nozzle plug, and records the total flow data of the loader and unloader. At this time, the shut-off operation of the fuel channel is realized.

[0025] In the present invention, step 3, implementing ice plug isolation to drain the fuel channel, includes the following steps:

[0026] Step 3.1, perform ice plugging operation on the inlet and outlet branches of the fuel channel: install ice plug jackets on the inlet and outlet branches of the fuel channel respectively to perform ice plug freezing operation until the ice plug is completely formed;

[0027] Step 3.2, remove the cut-off tool to verify the formation of ice plug: remove the nozzle plug of the loader and unloader on the cut-off side to confirm that the pressure in the fuel channel is stable at 0.8MPa; install the guide sleeve and remove the cut-off tool; check the total flow data of the loader and unloader, which is completely consistent with the data in step 2.4, verifying that the ice plug has been formed;

[0028] Step 3.3, perform fuel channel pressure increase and decrease operations through the loader and unloader: slowly increase the pressure of the silo pressure controller and the heavy water supply controller to raise the fuel channel pressure to 7MPa; check various parameters to accurately locate the fault; slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa;

[0029] Step 3.4, drain the fuel channel through the loader and unloader: After confirming that the drain pipeline is connected to the drain station, remove the guide sleeve, stop the heavy water pump, and isolate the loader and unloader; open the high-pressure drain valve and the silo exhaust valve to drain the fuel channel until the cofferdam liquid level indicator lights up, indicating that the fuel channel draining work is completed.

[0030] In the present invention, step 4, installing a temporary shielding plug to establish maintenance conditions, includes the following steps:

[0031] Step 4.1, remove the sealing plug of the fuel channel on the other side: after the drainage is completed, the loader and unloader on the drainage side does not install the sealing plug of the fuel channel, and directly releases the clamp from the fuel channel; manually remove the sealing plug of the fuel channel on the other side, at this time, the sealing plugs on both sides of the fuel channel have been removed;

[0032] Step 4.2, install temporary shielding plugs in the upstream and downstream fuel channels: After removing the sealing plugs on both sides, install temporary shielding plugs in the upstream and downstream fuel channels to provide radiation shielding for maintenance personnel;

[0033] Step 4.3, unload the shut-off tool in the loader and unloader: clamp the loader and unloader on the shut-off side to the auxiliary channel, remove the nozzle plug, and install the guide sleeve; unload the shut-off tool from the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the shut-off tool has been unloaded from the silo of the loader and unloader;

[0034] Step 4.4: Carry out fuel channel defect treatment: The fault repair conditions have been established, and the ice plug freezing operation needs to be maintained until the defect is repaired.

[0035] In the present invention, step 5, the fuel channel water filling operation, includes the following steps:

[0036] Step 5.1, install sealing plugs in the upstream and downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and the spare sealing plugs on the auxiliary channels are installed in the silos of the loading and unloading machines;

[0037] Step 5.2, perform water filling operation on the fuel channel: the upstream and downstream loaders and unloaders are simultaneously clamped on the fuel channel; the isolation of the loaders and unloaders on the water filling side is released, the high-pressure drain valve is closed, and the silo exhaust valve is opened; the heavy water pump is started for water filling operation, and when the reflux flow is established, the silo exhaust valve is closed, and the fuel channel pressure is maintained at 0.8MPa, indicating that the water filling operation is successful;

[0038] Step 5.3, perform fuel channel pressure increase and decrease operations and reinstall the sealing plug: After reinstalling the sealing plug on one side of the loader and unloader, slowly increase the pressure of the silo pressure controller and the heavy water supply controller of the loader and unloader on the other side to raise the fuel channel pressure to 7MPa; after confirming that the fault handling is completed and all parameters are normal, slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa, and then reinstall the sealing plug;

[0039] Step 5.4, release the ice plug operation: After confirming that the sealing plugs on both sides of the fuel channel have been installed, release the ice plug operation and release the isolation of the fuel channel. At this time, the fuel channel is connected to the main heat transfer system.

[0040] In the present invention, step 6, reloading the nuclear fuel in the fuel channel, comprises the following steps:

[0041] Step 6.1, install the shielding plugs of the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and receive the spare shielding plugs into the silo; the upstream and downstream loading and unloading machines are clamped to the fuel channels; the upstream and downstream loading and unloading machines remove the nozzle plugs and sealing plugs, and install the guide sleeves; install the shielding plugs; the upper and lower loading and unloading machines remove the guide sleeves respectively, and reinstall the sealing plugs, and confirm that the shielding plugs have been correctly reinstalled;

[0042] Step 6.2: The downstream loader receives 12 new nuclear fuels: The downstream loader clamps onto the new fuel channel and receives 12 new nuclear fuels;

[0043] Step 6.3: Reinstall 12 nuclear fuels in the fuel channel: The downstream loading and unloading machine clamps onto the fuel channel, removes the nozzle plug, sealing plug and shielding plug; reversely reinstalls 12 nuclear fuels into the fuel channel; reinstalls the shielding plug, sealing plug and nozzle plug, and confirms that the nuclear fuel has been reinstalled in place;

[0044] Step 6.4: The reactor returns to normal operating mode: After the nuclear fuel is reloaded, the main heat transfer system slowly heats up and pressurizes to normal operating state, and the reactor returns to full power operation mode.

[0045] Beneficial technical effects of the present invention:

[0046] The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant of the present invention is easy to use, highly practical, safe and reliable, and highly economical. It can ensure that the maintenance work of the single fuel channel equipment is completed safely and smoothly, reduce operating risks, improve work efficiency, and ensure the radiation safety of maintenance personnel and the safety of the unit. It provides a new fuel channel pressurization method after the ice plug is established, and provides a new solution for accurately judging and locating the faulty pressure pipe through the change of the annular gap gas dew point, which can be promoted to similar power plants at home and abroad. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the structure of a single fuel channel in a heavy water reactor nuclear power plant;

[0048] Figure 2 The schematic diagram of the process of draining and filling a single fuel channel of a heavy water reactor nuclear power plant;

[0049] Figure 3 Schematic diagram of emptying nuclear fuel from a single fuel channel in a heavy water reactor nuclear power plant;

[0050] Figure 4 This is a schematic diagram of the drainage and filling operations of a single fuel channel in a heavy water reactor nuclear power plant.

[0051] In the figure, 1. sealing plug; 2. sealing ring; 3. inlet and outlet branches; 4. inner liner; 5. end component body; 6. outer support bearing; 7. separation ring; 8. nuclear fuel; 9. pressure pipe; 10. discharge pipe; 11. inner plate of end shield; 12. inner support bearing; 13. shielding plug; 14. end shielding filler; 15. end shielding liner; 16. outer plate of end shield; 17. bellows; 18. positioning assembly; 19. upstream loader and unloader; 20. fuel channel; 21. upstream loader and unloader push rod; 22. RGA tool; 23. extension; 24. FAE tool; 25. downstream loader and unloader; 26. downstream loader and unloader push rod; 27. heavy water collection box; 28. drain hose; 29. ​​ice plug device; 30. interception tool. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by terms such as “left end”, “right end”, “above”, “below”, “outside”, and “inside” are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0054] See also Figure 1 , shows a schematic diagram of the structure of a single fuel channel of a heavy water reactor nuclear power plant. Each fuel channel has 2 sealing plugs, 2 shielding plugs and 12 nuclear fuels. The 2 sealing plugs are used to seal the fuel channel to ensure the integrity of the pressure boundary, and the 2 shielding plugs are used to support and fix the 12 nuclear fuels in the fuel channel. The 12 nuclear fuels are located between the 2 shielding plugs, and under the action of the heavy water flow, they are tightly attached to the downstream shielding plug. The fuel channel is arranged horizontally, and the internal configuration from left to right includes an upstream sealing plug, an upstream shielding plug, 12 nuclear fuels, a downstream shielding plug, and a downstream sealing plug.

[0055] Under the action of the main pump, the heavy water coolant enters the fuel channel from the inlet header through the inlet branch pipe, flows out of the fuel channel from the outlet branch pipe and enters the outlet header, transferring the decay heat of the nuclear fuel to the steam generator, thereby realizing the cooling and flow circulation of the nuclear fuel. The inlet and outlet branches of each fuel channel are connected to the main inlet and outlet header, and there is no separate isolation facility.

[0056] See also Figure 2This embodiment provides a method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant, creating necessary conditions for fault inspection and repair of a single fuel channel of a heavy water reactor nuclear power plant.

[0057] The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant described in this embodiment includes the following steps:

[0058] Step 1: Empty the fuel channel of nuclear fuel;

[0059] Step 2: Install the cut-off tool to cut off the fuel channel;

[0060] Step 3: Implement ice plug isolation to drain the fuel channel;

[0061] Step 4: Install temporary shielding plugs to establish maintenance conditions;

[0062] Step 5: Filling the fuel channel with water;

[0063] Step 6: Reinstall the nuclear fuel in the fuel channel.

[0064] In this embodiment, step 1, emptying the fuel channel of nuclear fuel, includes the following steps:

[0065] Step 1.1, the reactor enters the guaranteed shutdown mode: the reactor enters the guaranteed shutdown mode and maintains the guaranteed shutdown mode for more than 24 hours;

[0066] Step 1.2, empty the tool and load it into the upstream loader: remove the push rod adapter, spare sealing plug and spare shielding plug in the upstream loader bin; install the K-tube liner, install an RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; remove the spare shielding plug in the downstream loader;

[0067] Step 1.3, 12 nuclear fuels in the fuel channel are emptied to the downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped on the fuel channel; the upstream loading and unloading machine removes the upstream sealing plug and shielding plug, and pushes in the emptying tool; the downstream loading and unloading machine removes the downstream sealing plug and shielding plug, and receives 12 nuclear fuels; the upstream and downstream loading and unloading machines reinstall the shielding plug and sealing plug respectively, and complete the nuclear fuel emptying operation;

[0068] Step 1.4, the downstream loader and unloader unloads 12 nuclear fuels into the spent fuel pool: the downstream loader and unloader moves to the spent fuel channel and clamps it; removes the nozzle plug, installs the guide sleeve, and lowers the liquid level; unloads the 12 nuclear fuels in the downstream loader and unloader silo into the spent fuel pool; removes the guide sleeve, reinstalls the nozzle plug, and raises the liquid level to restore the system.

[0069] In this embodiment, step 2, installing a shutoff tool to shut off the fuel channel, includes the following steps:

[0070] Step 2.1, unload the emptying tool in the upstream loader: unload 1 RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; unload the K pipe liner;

[0071] Step 2.2, remove the shielding plugs in the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines clamp onto the fuel channel, remove the sealing plugs and shielding plugs; the upstream and downstream loading and unloading machines reinstall the sealing plugs; the removed shielding plugs are unloaded into the spent fuel pool through the spent fuel channel;

[0072] Step 2.3, Load the cut-off tool into the loader: Hold the cut-off side loader on the auxiliary channel, remove the nozzle plug, and install the guide sleeve; install the cut-off tool into the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the cut-off tool has been loaded into the silo of the cut-off side loader;

[0073] Step 2.4, the shut-off tool is installed in the fuel channel to realize shut-off: the loader and unloader on the shut-off side clamps onto the fuel channel; removes the nozzle plug and the sealing plug, and installs the guide sleeve; installs the shut-off tool in the fuel channel; removes the guide sleeve, installs the nozzle plug, and records the total flow data of the loader and unloader. At this time, the shut-off operation of the fuel channel is realized.

[0074] In this embodiment, step 3, implementing ice plug isolation to drain the fuel channel, includes the following steps:

[0075] Step 3.1, perform ice plugging operation on the inlet and outlet branches of the fuel channel: install ice plug jackets on the inlet and outlet branches of the fuel channel respectively to perform ice plug freezing operation until the ice plug is completely formed;

[0076] Step 3.2, remove the cut-off tool to verify the formation of ice plug: remove the nozzle plug of the loader and unloader on the cut-off side to confirm that the pressure in the fuel channel is stable at 0.8MPa; install the guide sleeve and remove the cut-off tool; check the total flow data of the loader and unloader, which is completely consistent with the data in step 2.4, verifying that the ice plug has been formed;

[0077] Step 3.3, perform fuel channel pressure increase and decrease operations through the loader and unloader: slowly increase the pressure of the silo pressure controller and the heavy water supply controller to raise the fuel channel pressure to 7MPa; check various parameters to accurately locate the fault; slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa;

[0078] Step 3.4, drain the fuel channel through the loader and unloader: After confirming that the drain pipeline is connected to the drain station, remove the guide sleeve, stop the heavy water pump, and isolate the loader and unloader; open the high-pressure drain valve and the silo exhaust valve to drain the fuel channel until the cofferdam liquid level indicator lights up, indicating that the fuel channel draining work is completed.

[0079] In this embodiment, step 4, installing a temporary shielding plug to establish maintenance conditions, includes the following steps:

[0080] Step 4.1, remove the sealing plug of the fuel channel on the other side: after the drainage is completed, the loader and unloader on the drainage side does not install the sealing plug of the fuel channel, and directly releases the clamp from the fuel channel; manually remove the sealing plug of the fuel channel on the other side, at this time, the sealing plugs on both sides of the fuel channel have been removed;

[0081] Step 4.2, install temporary shielding plugs in the upstream and downstream fuel channels: After removing the sealing plugs on both sides, install temporary shielding plugs in the upstream and downstream fuel channels to provide radiation shielding for maintenance personnel;

[0082] Step 4.3, unload the shut-off tool in the loader and unloader: clamp the loader and unloader on the shut-off side to the auxiliary channel, remove the nozzle plug, and install the guide sleeve; unload the shut-off tool from the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the shut-off tool has been unloaded from the silo of the loader and unloader;

[0083] Step 4.4: Carry out fuel channel defect treatment: The fault repair conditions have been established, and the ice plug freezing operation needs to be maintained until the defect is repaired.

[0084] In this embodiment, step 5, the fuel channel water filling operation, includes the following steps:

[0085] Step 5.1, install sealing plugs in the upstream and downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and the spare sealing plugs on the auxiliary channels are installed in the silos of the loading and unloading machines;

[0086] Step 5.2, perform water filling operation on the fuel channel: the upstream and downstream loaders and unloaders are simultaneously clamped on the fuel channel; the isolation of the loaders and unloaders on the water filling side is released, the high-pressure drain valve is closed, and the silo exhaust valve is opened; the heavy water pump is started for water filling operation, and when the reflux flow is established, the silo exhaust valve is closed, and the fuel channel pressure is maintained at 0.8MPa, indicating that the water filling operation is successful;

[0087] Step 5.3, perform fuel channel pressure increase and decrease operations and reinstall the sealing plug: After reinstalling the sealing plug on one side of the loader and unloader, slowly increase the pressure of the silo pressure controller and the heavy water supply controller of the loader and unloader on the other side to raise the fuel channel pressure to 7MPa; after confirming that the fault handling is completed and all parameters are normal, slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa, and then reinstall the sealing plug;

[0088] Step 5.4, release the ice plug operation: After confirming that the sealing plugs on both sides of the fuel channel have been installed, release the ice plug operation and release the isolation of the fuel channel. At this time, the fuel channel is connected to the main heat transfer system.

[0089] In this embodiment, step 6, reloading the nuclear fuel in the fuel channel, includes the following steps:

[0090] Step 6.1, install the shielding plugs of the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and receive the spare shielding plugs into the silo; the upstream and downstream loading and unloading machines are clamped to the fuel channels; the upstream and downstream loading and unloading machines remove the nozzle plugs and sealing plugs, and install the guide sleeves; install the shielding plugs; the upper and lower loading and unloading machines remove the guide sleeves respectively, and reinstall the sealing plugs, and confirm that the shielding plugs have been correctly reinstalled;

[0091] Step 6.2: The downstream loader receives 12 new nuclear fuels: The downstream loader clamps onto the new fuel channel and receives 12 new nuclear fuels;

[0092] Step 6.3: Reinstall 12 nuclear fuels in the fuel channel: The downstream loading and unloading machine clamps onto the fuel channel, removes the nozzle plug, sealing plug and shielding plug; reversely reinstalls 12 nuclear fuels into the fuel channel; reinstalls the shielding plug, sealing plug and nozzle plug, and confirms that the nuclear fuel has been reinstalled in place;

[0093] Step 6.4: The reactor returns to normal operating mode: After the nuclear fuel is reloaded, the main heat transfer system slowly heats up and pressurizes to normal operating state, and the reactor returns to full power operation mode.

[0094] See also Figure 3 , showing a schematic diagram of nuclear fuel emptying from a single fuel channel in a heavy water reactor nuclear power plant.

[0095] Before emptying, the upstream loader and unloader are loaded with emptying tools, including RGA tools, extensions and FAE tools; in the shutdown mode, since the push rod of the upstream loader and unloader is not long enough, all 12 nuclear fuels cannot be pushed into the downstream loader and unloader, so 6 extensions and 1 FAE tool are required to extend the length of the push rod of the upstream loader and unloader, so the emptying tools need to be loaded into the upstream loader and unloader.

[0096] During emptying, the upstream and downstream loaders and unloaders clamp onto the same fuel channel; the upstream loaders and unloaders remove the sealing plugs and shielding plugs in the upstream fuel channel and push in the emptying tool; the downstream loaders and unloaders remove the sealing plugs and shielding plugs in the downstream fuel channel; then the upstream and downstream loaders and unloaders cooperate with each other to receive 12 nuclear fuels; the upstream and downstream loaders and unloaders respectively reinstall the shielding plugs and sealing plugs to complete the emptying operation of 12 nuclear fuels.

[0097] After emptying, the downstream loader and unloader moved to the spent fuel channel and clamped it, unloading the 12 nuclear fuels in the silo into the spent fuel pool.

[0098] See also Figure 4, showing a schematic diagram of the drainage and filling operation of a single fuel channel in a heavy water reactor nuclear power plant. After all the nuclear fuel is emptied, there is still heavy water flow in the fuel channel, which cannot be directly isolated by ice plugging. It is necessary to install a cut-off tool with a sealing device to achieve fuel channel flow cut-off. The loader installs the cut-off tool into the fuel channel to achieve fuel channel cut-off.

[0099] After interception, the pipeline is frozen through the ice plug device on the inlet and outlet branches to achieve complete freezing isolation; after isolation, the loader and unloader removes the interception tool; as needed, the pressure of the fuel channel can be increased and decreased through the loader and unloader's own heavy water control system to confirm the defects of the fuel channel.

[0100] After the ice plug is isolated, the loader opens the valve to lower the liquid level, and the heavy water in the fuel channel will flow into the heavy water collection tank through the hose, completing the drainage of the fuel channel.

[0101] After the fault is fixed, the fuel channel is filled with water through the loader and unloader. After the filling is completed, the pressure of a single fuel channel can be increased and decreased through the loader and unloader's own heavy water control system as needed to finally confirm that the defect is fixed successfully. After the defect is fixed, the ice plug isolation is released. The upstream and downstream loader and unloader complete the reinstallation of the fuel channel sealing plug and shielding plug respectively. The downstream loader and unloader reinstalls 12 new fuels to restore the standard configuration of the fuel channel.

[0102] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant, characterized in that: The steps include: Step 1: Empty the fuel channel of nuclear fuel; Step 2: Install the cut-off tool to cut off the fuel channel; Step 3: Implement ice plug isolation to drain the fuel channel; Step 4: Install temporary shielding plugs to establish maintenance conditions; Step 5: Filling the fuel channel with water; Step 6: Reinstall the nuclear fuel in the fuel channel.

2. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 1, emptying the fuel channel of nuclear fuel, includes the following steps: Step 1.1, the reactor enters the guaranteed shutdown mode: the reactor enters the guaranteed shutdown mode and maintains the guaranteed shutdown mode for more than 24 hours; Step 1.2, empty the tool and load it into the upstream loader: remove the push rod adapter, spare sealing plug and spare shielding plug in the upstream loader bin; install the K-tube liner, install an RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; remove the spare shielding plug in the downstream loader; Step 1.3, 12 nuclear fuels in the fuel channel are emptied to the downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped on the fuel channel; the upstream loading and unloading machine removes the upstream sealing plug and shielding plug, and pushes in the emptying tool; the downstream loading and unloading machine removes the downstream sealing plug and shielding plug, and receives 12 nuclear fuels; the upstream and downstream loading and unloading machines reinstall the shielding plug and sealing plug respectively, and complete the nuclear fuel emptying operation; Step 1.4, the downstream loader and unloader unloads 12 nuclear fuels into the spent fuel pool: the downstream loader and unloader moves to the spent fuel channel and clamps it; removes the nozzle plug, installs the guide sleeve, and lowers the liquid level; unloads the 12 nuclear fuels in the downstream loader and unloader silo into the spent fuel pool; removes the guide sleeve, reinstalls the nozzle plug, and raises the liquid level to restore the system.

3. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 2, installing the shutoff tool to shut off the fuel channel, includes the following steps: Step 2.1, unload the emptying tool in the upstream loader: unload 1 RGA tool, 6 extensions and 1 FAE tool in the upstream loader bin; unload the K pipe liner; Step 2.2, remove the shielding plugs in the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines clamp onto the fuel channel, remove the sealing plugs and shielding plugs; the upstream and downstream loading and unloading machines reinstall the sealing plugs; the removed shielding plugs are unloaded into the spent fuel pool through the spent fuel channel; Step 2.3, Load the cut-off tool into the loader: Hold the cut-off side loader on the auxiliary channel, remove the nozzle plug, and install the guide sleeve; install the cut-off tool into the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the cut-off tool has been loaded into the silo of the cut-off side loader; Step 2.4, the shut-off tool is installed in the fuel channel to realize shut-off: the loader and unloader on the shut-off side clamps onto the fuel channel; removes the nozzle plug and the sealing plug, and installs the guide sleeve; installs the shut-off tool in the fuel channel; removes the guide sleeve, installs the nozzle plug, and records the total flow data of the loader and unloader. At this time, the shut-off operation of the fuel channel is realized.

4. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 3, implementing ice plug isolation to drain the fuel channel, includes the following steps: Step 3.1, perform ice plugging operation on the inlet and outlet branches of the fuel channel: install ice plug jackets on the inlet and outlet branches of the fuel channel respectively to perform ice plug freezing operation until the ice plug is completely formed; Step 3.2, remove the cut-off tool to verify the formation of ice plug: remove the nozzle plug of the loader and unloader on the cut-off side to confirm that the pressure in the fuel channel is stable at 0.8MPa; install the guide sleeve and remove the cut-off tool; check the total flow data of the loader and unloader, which is completely consistent with the data in step 2.4, verifying that the ice plug has been formed; Step 3.3, perform fuel channel pressure increase and decrease operations through the loader and unloader: slowly increase the pressure of the silo pressure controller and the heavy water supply controller to raise the fuel channel pressure to 7MPa; check various parameters to accurately locate the fault; slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa; Step 3.4, drain the fuel channel through the loader and unloader: After confirming that the drain pipeline is connected to the drain station, remove the guide sleeve, stop the heavy water pump, and isolate the loader and unloader; open the high-pressure drain valve and the silo exhaust valve to drain the fuel channel until the cofferdam liquid level indicator lights up, indicating that the fuel channel draining work is completed.

5. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 4, installing a temporary shielding plug to establish maintenance conditions, includes the following steps: Step 4.1, remove the sealing plug of the fuel channel on the other side: after the drainage is completed, the loader and unloader on the drainage side does not install the sealing plug of the fuel channel, and directly releases the clamp from the fuel channel; manually remove the sealing plug of the fuel channel on the other side, at this time, the sealing plugs on both sides of the fuel channel have been removed; Step 4.2, install temporary shielding plugs in the upstream and downstream fuel channels: After removing the sealing plugs on both sides, install temporary shielding plugs in the upstream and downstream fuel channels to provide radiation shielding for maintenance personnel; Step 4.3, unload the shut-off tool in the loader and unloader: clamp the loader and unloader on the shut-off side to the auxiliary channel, remove the nozzle plug, and install the guide sleeve; unload the shut-off tool from the silo; remove the guide sleeve, reinstall the nozzle plug, and confirm that the shut-off tool has been unloaded from the silo of the loader and unloader; Step 4.4: Carry out fuel channel defect treatment: The fault repair conditions have been established, and the ice plug freezing operation needs to be maintained until the defect is repaired.

6. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 5, the fuel channel water filling operation, includes the following steps: Step 5.1, install sealing plugs in the upstream and downstream loading and unloading machines: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and the spare sealing plugs on the auxiliary channels are installed in the silos of the loading and unloading machines; Step 5.2, perform water filling operation on the fuel channel: the upstream and downstream loaders and unloaders are simultaneously clamped on the fuel channel; the isolation of the loaders and unloaders on the water filling side is released, the high-pressure drain valve is closed, and the silo exhaust valve is opened; the heavy water pump is started for water filling operation, and when the reflux flow is established, the silo exhaust valve is closed, and the fuel channel pressure is maintained at 0.8MPa, indicating that the water filling operation is successful; Step 5.3, perform fuel channel pressure increase and decrease operations and reinstall the sealing plug: After reinstalling the sealing plug on one side of the loader and unloader, slowly increase the pressure of the silo pressure controller and the heavy water supply controller of the loader and unloader on the other side to raise the fuel channel pressure to 7MPa; after confirming that the fault handling is completed and all parameters are normal, slowly reduce the pressure of the controller to reduce the fuel channel pressure to 0.8MPa, and then reinstall the sealing plug; Step 5.4, release the ice plug operation: After confirming that the sealing plugs on both sides of the fuel channel have been installed, release the ice plug operation and release the isolation of the fuel channel. At this time, the fuel channel is connected to the main heat transfer system.

7. The method for draining and filling a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that: Step 6, reloading the nuclear fuel in the fuel channel, includes the following steps: Step 6.1, install the shielding plugs of the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines are clamped to the auxiliary channels respectively, and receive the spare shielding plugs into the silo; the upstream and downstream loading and unloading machines are clamped to the fuel channels; the upstream and downstream loading and unloading machines remove the nozzle plugs and sealing plugs, and install the guide sleeves; install the shielding plugs; the upper and lower loading and unloading machines remove the guide sleeves respectively, and reinstall the sealing plugs, and confirm that the shielding plugs have been correctly reinstalled; Step 6.2: The downstream loader receives 12 new nuclear fuels: The downstream loader clamps onto the new fuel channel and receives 12 new nuclear fuels; Step 6.3: Reload 12 nuclear fuels into the fuel channel: The downstream loading and unloading machine clamps onto the fuel channel, removes the nozzle plug, sealing plug and shielding plug; reversely reloads 12 nuclear fuels into the fuel channel; Reinstall the shielding plug, sealing plug and nozzle plug, and confirm that the nuclear fuel is reinstalled in place; Step 6.4: The reactor returns to normal operating mode: After the nuclear fuel is reloaded, the main heat transfer system slowly heats up and pressurizes to normal operating state, and the reactor returns to full power operation mode.

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