Method for draining and filling a single fuel channel of a heavy water nuclear power plant

Abstract

The application relates to a heavy water reactor nuclear power plant single fuel channel dewatering and water filling operation method, which comprises the following steps: step 1, emptying the nuclear fuel of the fuel channel; step 2, installing a fuel channel cutoff tool to realize cutoff; step 3, implementing ice plug isolation to carry out fuel channel dewatering operation; step 4, installing a temporary shielding plug to establish a maintenance condition; step 5, fuel channel water filling operation; and step 6, nuclear fuel reloading of the fuel channel. The application establishes necessary conditions for single fuel channel fault treatment, and after the fault treatment is completed, the fuel channel is water filled, the nuclear fuel is reloaded and the like, so that the standard configuration of the single fuel channel is restored; thus, the maintenance can be safely and smoothly carried out, the operation risk is reduced, the work efficiency is improved, and the personnel radiation safety and the reactor safety are ensured.

Description

TECHNICAL FIELD

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

[0002] The core of the heavy water reactor is composed of a plurality of horizontally arranged fuel channels, each of which has two shielding plugs, two sealing plugs and twelve nuclear fuels; the two sealing plugs are used for sealing the fuel channel and ensuring the integrity of the pressure boundary; the two shielding plugs are used for supporting and fixing the twelve nuclear fuels in the fuel channel.

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

[0004] The inlet and outlet branch pipes of each fuel channel are connected to the total inlet and outlet header, and there is no separate isolation measure. When the end part, pressure tube, heat transfer branch pipe joint and other equipment parts of the single fuel channel have a leakage failure, it will cause the leakage of the heavy water coolant, which seriously affects the safe operation of the reactor. At this time, necessary operation methods need to be taken to establish the maintenance conditions, so as to safely and smoothly carry out the maintenance.

[0005] Since the single fuel channel is installed with twelve nuclear fuels, the radiation dose is high and cannot be directly handled, and the shielding plug, pressure tube and other components are in long-term contact with the nuclear fuel, which also has a high radiation dose, resulting in high requirements for this maintenance, great operation difficulty and great nuclear safety risk. After the equipment failure of the fuel channel occurs, the twelve nuclear fuels in the fuel channel must be emptied and unloaded, and the fuel channel must be cut off, isolated and drained, so that personnel can carry out maintenance. Therefore, an operation method for draining and filling water in a single fuel channel of a heavy water reactor is needed to empty the nuclear fuel, accurately locate the fault, drain the fuel channel and establish necessary conditions for the fault handling of the fuel channel. At the same time, after the fault handling is completed, the fuel channel is filled with water, the nuclear fuel is reloaded, and the standard configuration of the single fuel channel is restored, so as to ensure the safe and smooth maintenance, reduce the operation risk, improve the work efficiency, and ensure the radiation safety of personnel and the safety of the reactor. SUMMARY

[0006] The present application relates to the technical field of heavy water reactor maintenance, in particular to a method for draining and filling water in a single fuel channel of a heavy water reactor.

[0007] To achieve the above object, the present application provides the following technical solutions.

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

[0009] Step 1, emptying the nuclear fuel in the fuel channel;

[0010] Step 2, installing a flow blocking tool to achieve flow blocking of the fuel channel;

[0011] Step 3, implementing ice plug isolation to perform fuel channel draining operation;

[0012] Step 4, installing a temporary shielding plug to establish maintenance conditions;

[0013] Step 5, fuel channel water filling operation;

[0014] Step 6, refueling the nuclear fuel in the fuel channel.

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

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

[0017] Step 1.2, loading the emptying tool into the upstream loading and unloading machine: dismounting the push rod adapter, spare sealing plug and spare shielding plug in the loading and unloading machine bin; installing a K tube liner, installing an RGA tool, 6 extension pieces and a FAE tool in the loading and unloading machine bin; dismounting the spare shielding plug in the downstream loading and unloading machine;

[0018] Step 1.3, emptying 12 nuclear fuels in the fuel channel to the downstream loading and unloading machine: clamping the upstream and downstream loading and unloading machines to the fuel channel; dismounting the upstream sealing plug and shielding plug of the upstream loading and unloading machine and pushing in the emptying tool; dismounting the downstream sealing plug and shielding plug of the downstream loading and unloading machine and receiving 12 nuclear fuels; respectively reinstalling the shielding plug and sealing plug of the upstream and downstream loading and unloading machines to complete the emptying operation of the nuclear fuel;

[0019] Step 1.4, dismounting 12 nuclear fuels from the downstream loading and unloading machine to the spent fuel pool: moving the downstream loading and unloading machine to the spent fuel channel and clamping; dismounting the nozzle plug, installing the guide sleeve and lowering the liquid level; dismounting the 12 nuclear fuels in the loading and unloading machine bin to the spent fuel pool; dismounting the guide sleeve, reinstalling the nozzle plug and raising the liquid level to restore the system.

[0020] In the present application, step 2, installing a flow blocking tool to achieve flow blocking of the fuel channel, comprises the following steps:

[0021] Step 2.1, unload empty tool in upstream loading and unloading machine: unload 1 RGA tool, 6 extension pieces and 1 FAE tool in the loading and unloading machine bin of the upstream; unload K tube liner;

[0022] Step 2.2, remove the shielding plug in the upstream and downstream fuel channel: the upstream and downstream loading and unloading machine clamps to the fuel channel, removes the sealing plug and shielding plug; the upstream and downstream loading and unloading machine re-installs the sealing plug; the removed shielding plug is unloaded through the spent fuel channel to the spent fuel pool;

[0023] Step 2.3, install the cutoff tool in the loading and unloading machine: the cutoff side loading and unloading machine clamps to the auxiliary channel, removes the nozzle plug and installs the guide sleeve; the cutoff tool is installed in the bin; the guide sleeve is removed, the nozzle plug is re-installed, and it is confirmed that the cutoff tool has been installed in the cutoff side loading and unloading machine bin;

[0024] Step 2.4, install the cutoff tool in the fuel channel to achieve cutoff: the cutoff side loading and unloading machine clamps to the fuel channel; the nozzle plug and the sealing plug are removed and the guide sleeve is installed; the cutoff tool is installed in the fuel channel; the guide sleeve is removed and the nozzle plug is installed, and the total flow data of the loading and unloading machine is recorded, at which time the cutoff operation of the fuel channel is achieved.

[0025] In the present application, step 3, ice plug isolation is implemented for fuel channel dewatering operation, comprising the following steps:

[0026] Step 3.1, implement ice plug operation on the inlet and outlet branch pipes of the fuel channel: ice plug jackets are respectively installed on the inlet and outlet branch pipes of the fuel channel to perform ice plug freezing operation until the ice plug is completely formed;

[0027] Step 3.2, remove the cutoff tool to demonstrate ice plug formation: the cutoff side loading and unloading machine removes the nozzle plug, confirms that the fuel channel pressure is stable at 0.8 MPa, installs the guide sleeve, removes the cutoff tool, checks the total flow data of the loading and unloading machine, which is completely consistent with the data of step 2.4, and verifies that the ice plug has been formed;

[0028] Step 3.3, perform fuel channel pressure increasing and decreasing operation through the loading and unloading machine: slowly increase the pressure of the bin pressure controller and the heavy water supply controller to increase the fuel channel pressure to 7 MPa; check various parameters for accurate fault positioning; slowly decrease the pressure of the controller to decrease the fuel channel pressure to 0.8 MPa;

[0029] Step 3.4, perform fuel channel dewatering operation through the loading and unloading machine: after confirming that the dewatering pipeline is connected with the dewatering station, remove the guide sleeve, stop the heavy water pump, and isolate the loading and unloading machine; open the high-pressure dewatering valve and the bin exhaust valve to perform fuel channel dewatering until the cofferdam liquid level indicator lights up, indicating that the fuel channel dewatering operation is completed.

[0030] In the present application, step 4, installing temporary shielding plugs to establish maintenance conditions, comprises the following steps:

[0031] Step 4.1, removing the sealing plug of the other side fuel channel: after the dewatering is completed, the dewatering side charging and discharging machine does not install the sealing plug of the fuel channel, and directly releases the clamping from the fuel channel; the sealing plug of the other side fuel channel is manually removed, and at this time, the sealing plugs of the two sides of the fuel channel have been removed;

[0032] Step 4.2, installing temporary shielding plugs in the upstream and downstream fuel channels: after the sealing plugs of the two sides are removed, temporary shielding plugs are installed in the upstream and downstream fuel channels to provide radiation shielding for the maintenance personnel;

[0033] Step 4.3, discharging the intercepting tool in the charging and discharging machine: the intercepting side charging and discharging machine is clamped to the auxiliary channel, the nozzle plug is removed, the guide sleeve is installed, the intercepting tool is discharged from the stock bin, the guide sleeve is removed, the nozzle plug is reinstalled, and it is confirmed that the intercepting tool has been discharged from the charging and discharging machine stock bin;

[0034] Step 4.4, processing defects of the fuel channel: the fault maintenance conditions have been established, and the ice plug freezing operation needs to be continued until the defect processing is completed.

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

[0036] Step 5.1, installing sealing plugs in the upstream and downstream charging and discharging machines: the upstream and downstream charging and discharging machines are clamped to the auxiliary channel respectively, and the standby sealing plug on the auxiliary channel is installed into the charging and discharging machine stock bin;

[0037] Step 5.2, performing fuel channel water filling operation: the upstream and downstream charging and discharging machines are clamped to the fuel channel at the same time; the isolation of the water filling side charging and discharging machine is released, the high-pressure dewatering valve is closed, and the stock bin exhaust valve is opened; the heavy water pump is started to perform water filling operation, when the backflow flow is established, the stock bin exhaust valve is closed, the pressure of the fuel channel is kept at 0.8 MPa, and it is indicated that the water filling operation is successful;

[0038] Step 5.3, performing fuel channel pressure increasing and decreasing operation and reinstalling the sealing plug: after the sealing plug of one side charging and discharging machine is reinstalled, the pressure of the stock bin pressure controller and the heavy water supply controller of the other side charging and discharging machine is slowly increased, the pressure of the fuel channel is increased to 7 MPa; after it is confirmed that the fault processing is completed and each parameter is normal, the pressure of the controller is slowly decreased, the pressure of the fuel channel is decreased to 0.8 MPa, and then the sealing plug is reinstalled;

[0039] Step 5.4, releasing the ice plug operation: after it is confirmed that the sealing plugs of the two sides of the fuel channel have been installed, the ice plug operation is released, the fuel channel is isolated, and at this time, the fuel channel is communicated with the main heat transfer system.

[0040] In the present application, step 6, fuel channel nuclear fuel back loading, comprises the following steps:

[0041] Step 6.1, install upstream and downstream fuel channel shielding plugs: the upstream and downstream fuel handlers are clamped to the auxiliary channel respectively, receive the standby shielding plugs into the bunker; the upstream and downstream fuel handlers are clamped to the fuel channel; the upstream and downstream fuel handlers remove the nozzle plug and the sealing plug, install the guide sleeve; install the shielding plug; the upstream and downstream fuel handlers remove the guide sleeve respectively, and back load the sealing plug, confirm that the shielding plug has been correctly back loaded;

[0042] Step 6.2: the downstream fuel handler receives 12 new nuclear fuels: the downstream fuel handler is clamped to the new fuel channel, and receives 12 new nuclear fuels;

[0043] Step 6.3: back load 12 nuclear fuels in the fuel channel: the downstream fuel handler is clamped to the fuel channel, and the nozzle plug, the sealing plug and the shielding plug are removed; 12 nuclear fuels are back loaded into the fuel channel in reverse; the shielding plug, the sealing plug and the nozzle plug are back loaded, and it is confirmed that the nuclear fuels are back loaded in place;

[0044] Step 6.4: the reactor resumes normal operation mode: after the back loading of the nuclear fuels is completed, the main heat transfer system slowly increases the temperature and pressure to the normal operation state, and the reactor is put back into the full power operation mode.

[0045] The beneficial technical effects of the present application are as follows:

[0046] The heavy water reactor nuclear power plant single fuel channel drainage and water filling operation method of the present application is convenient to use, practical, safe and reliable, and has high economic benefits, can ensure that the single fuel channel equipment maintenance work is safely and smoothly completed, reduces the operation risk, improves the work efficiency, ensures the radiation safety of the maintenance personnel and the safety of the unit, provides a new fuel channel pressure increasing method after the ice plug is established, provides a new scheme for accurately judging and positioning the fault pressure pipe through the change of the annular gap gas dew point, and can be popularized to similar and same power plants at home and abroad. BRIEF DESCRIPTION OF DRAWINGS

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

[0048] Figure 2 It is a flowchart of the heavy water reactor nuclear power plant single fuel channel drainage and water filling operation method;

[0049] Figure 3 It is a heavy water reactor nuclear power plant single fuel channel nuclear fuel emptying schematic diagram;

[0050] Figure 4 It is a heavy water reactor nuclear power plant single fuel channel drainage and water filling operation schematic diagram.

[0051] 1, sealing plug; 2, sealing ring; 3, inlet and outlet branch pipe; 4, inner liner pipe; 5, end piece body; 6, outer side support bearing; 7, separation ring; 8, nuclear fuel; 9, pressure pipe; 10, discharge pipe; 11, end shield inner side plate; 12, inner side support bearing; 13, shield plug; 14, end shield filler; 15, end shield liner pipe; 16, end shield outer side plate; 17, bellows; 18, positioning assembly; 19, upstream loading and unloading machine; 20, fuel channel; 21, upstream loading and unloading machine push rod; 22, RGA tool; 23, extension piece; 24, FAE tool; 25, downstream loading and unloading machine; 26, downstream loading and unloading machine push rod; 27, heavy water collection tank; 28, drain hose; 29, ice plug device; 30, shutoff tool. DETAILED DESCRIPTION

[0052] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0053] In the description of the present application, it should be noted that the terms "left end", "right end", "upper", "lower", "outer side", "inner side" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0054] Referring to Figure 1 , a structural schematic diagram of a single fuel channel of a heavy water reactor nuclear power plant is shown. There are 2 sealing plugs, 2 shield plugs and 12 nuclear fuels in each fuel channel. The 2 sealing plugs are used for sealing the fuel channel to ensure the integrity of the pressure boundary, and the 2 shield plugs are used for supporting and fixing the 12 nuclear fuels in the fuel channel. The 12 nuclear fuels are located between the 2 shield plugs and are tightly against the downstream shield plug under the action of the heavy water flow. The fuel channel is horizontally arranged, and the inside is configured from left to right with an upstream sealing plug, an upstream shield plug, 12 nuclear fuels, a downstream shield plug and a downstream sealing plug, respectively.

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

[0056] Referring to Figure 2The embodiment provides a method for draining and filling water in a single fuel channel of a heavy water reactor nuclear power plant, and creates necessary conditions for troubleshooting of the single fuel channel of the heavy water reactor nuclear power plant.

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

[0058] Step 1, emptying nuclear fuel in the fuel channel;

[0059] Step 2, installing a flow blocking tool to achieve flow blocking of the fuel channel;

[0060] Step 3, implementing ice plug isolation to perform fuel channel draining operation;

[0061] Step 4, installing a temporary shielding plug to establish troubleshooting conditions;

[0062] Step 5, fuel channel filling water operation;

[0063] Step 6, reloading nuclear fuel in the fuel channel.

[0064] In the embodiment, step 1, emptying nuclear fuel in the fuel channel, comprises the following steps:

[0065] Step 1.1, entering the reactor into a 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, loading the emptying tool into the upstream loading and unloading machine: dismounting the push rod adapter, the spare sealing plug and the spare shielding plug in the loading and unloading machine bin of the upstream loading and unloading machine; installing a K tube liner, installing an RGA tool, six extension pieces and an FAE tool in the loading and unloading machine bin of the upstream loading and unloading machine; and dismounting the spare shielding plug in the downstream loading and unloading machine;

[0067] Step 1.3, emptying 12 nuclear fuels in the fuel channel to the downstream loading and unloading machine: clamping the upstream and downstream loading and unloading machines to the fuel channel; dismounting the sealing plug and the shielding plug at the upstream of the upstream loading and unloading machine and pushing in the emptying tool; dismounting the sealing plug and the shielding plug at the downstream of the downstream loading and unloading machine and receiving 12 nuclear fuels; respectively reloading the shielding plug and the sealing plug of the upstream and downstream loading and unloading machines, and completing the emptying operation of the nuclear fuel;

[0068] Step 1.4, dismounting 12 nuclear fuels from the downstream loading and unloading machine to the spent fuel pool: moving the downstream loading and unloading machine to the spent fuel channel and clamping; dismounting the nozzle plug, installing the guide sleeve, and lowering the liquid level; dismounting 12 nuclear fuels in the loading and unloading machine bin of the downstream loading and unloading machine to the spent fuel pool; dismounting the guide sleeve, reloading the nozzle plug, and raising the liquid level to restore the system.

[0069] In the embodiment, step 2, installing a flow blocking tool to achieve flow blocking of the fuel channel, comprises the following steps:

[0070] Step 2.1, unload empty tool in upstream loading and unloading machine: unload 1 RGA tool, 6 extension pieces and 1 FAE tool in the loading and unloading machine bin of the upstream loading and unloading machine; unload K tube liner;

[0071] Step 2.2, remove the shielding plug in the upstream and downstream fuel channels: the upstream and downstream loading and unloading machines are clamped to the fuel channels, the sealing plug and the shielding plug are removed; the upstream and downstream loading and unloading machines are reloaded with the sealing plug; the removed shielding plug is unloaded through the spent fuel channel to the spent fuel pool;

[0072] Step 2.3, load the cutoff tool in the loading and unloading machine: the cutoff side loading and unloading machine is clamped to the auxiliary channel, the nozzle plug is removed and the guide sleeve is installed; the cutoff tool is installed in the bin; the guide sleeve is removed, the nozzle plug is reinstalled, and it is confirmed that the cutoff tool has been loaded into the cutoff side loading and unloading machine bin;

[0073] Step 2.4, load the cutoff tool into the fuel channel to achieve cutoff: the cutoff side loading and unloading machine is clamped to the fuel channel; the nozzle plug and the sealing plug are removed and the guide sleeve is installed; the cutoff tool is installed into the fuel channel; the guide sleeve is removed and the nozzle plug is installed, and the total flow data of the loading and unloading machine is recorded, at which time the cutoff operation of the fuel channel is achieved.

[0074] In this embodiment, step 3, ice plug isolation is implemented to perform fuel channel dewatering operation, including the following steps:

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

[0076] Step 3.2, remove the cutoff tool to demonstrate ice plug formation: the cutoff side loading and unloading machine removes the nozzle plug, confirms that the fuel channel pressure is stable at 0.8 MPa, installs the guide sleeve, removes the cutoff tool, checks the total flow data of the loading and unloading machine, which is completely consistent with the data of step 2.4, and verifies that the ice plug has been formed;

[0077] Step 3.3, perform fuel channel pressure increasing and decreasing operation through the loading and unloading machine: slowly increase the pressure of the bin pressure controller and the heavy water supply controller to increase the fuel channel pressure to 7 MPa; check the parameters for fault positioning; slowly decrease the pressure of the controller to decrease the fuel channel pressure to 0.8 MPa;

[0078] Step 3.4, perform fuel channel dewatering operation through the loading and unloading machine: after confirming that the dewatering pipeline is connected to the dewatering station, remove the guide sleeve, stop the heavy water pump, and isolate the loading and unloading machine; open the high-pressure dewatering valve and the bin exhaust valve to perform fuel channel dewatering until the cofferdam liquid level indicator lights up, indicating that the fuel channel dewatering operation is completed.

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

[0080] Step 4.1, remove the sealing plug on the other side of the fuel channel: after the dewatering is completed, the dewatering side of the charging and discharging machine does not install a sealing plug on the fuel channel, and the sealing plug is directly released from the fuel channel; the sealing plug on the other side of the fuel channel is manually removed, and 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 the sealing plugs on both sides are removed, temporary shielding plugs are installed in the upstream and downstream fuel channels to provide radiation shielding for maintenance personnel;

[0082] Step 4.3, unload the intercepting tool from the charging and discharging machine: the intercepting side of the charging and discharging machine is clamped to the auxiliary channel, the nozzle plug is removed, the guide sleeve is installed, the intercepting tool is unloaded from the silo, the guide sleeve is removed, the nozzle plug is reinstalled, and it is confirmed that the intercepting tool has been unloaded from the charging and discharging machine silo;

[0083] Step 4.4, perform defect treatment on the fuel channel: the fault maintenance conditions have been established, and the ice plug freezing operation needs to be continued until the defect treatment is completed.

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

[0085] Step 5.1, install sealing plugs in the upstream and downstream charging and discharging machines: the upstream and downstream charging and discharging machines are clamped to the auxiliary channel, and the standby sealing plug on the auxiliary channel is installed in the charging and discharging machine silo;

[0086] Step 5.2, perform fuel channel water filling operation: the upstream and downstream charging and discharging machines are clamped to the fuel channel at the same time; the isolation of the water filling side of the charging and discharging machine is released, the high-pressure dewatering valve is closed, and the silo exhaust valve is opened; the heavy water pump is started to perform water filling operation, and when the backflow flow is established, the silo exhaust valve is closed, the fuel channel pressure is maintained at 0.8 MPa, and it is indicated that the water filling operation is successful;

[0087] Step 5.3, perform fuel channel pressure increasing and decreasing operation and reinstall the sealing plug: after the sealing plug is reinstalled on one side of the charging and discharging machine, the pressure of the other side of the charging and discharging machine silo pressure controller and the heavy water supply controller is slowly increased to increase the fuel channel pressure to 7 MPa; after confirming that the fault treatment is completed and all parameters are normal, the pressure of the controller is slowly decreased, the fuel channel pressure is decreased to 0.8 MPa, and then the sealing plug is reinstalled;

[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, the ice plug operation is released, and the fuel channel is isolated; at this time, the fuel channel is connected with the main heat transfer system.

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

[0090] Step 6.1, install upstream and downstream fuel channel shielding plugs: the upstream and downstream load handlers are clamped to the auxiliary channel respectively, receive the standby shielding plugs into the silo; the upstream and downstream load handlers are clamped to the fuel channel; the upstream and downstream load handlers remove the nozzle plug and the sealing plug, install the guide sleeve; install the shielding plug; the upstream and downstream load handlers remove the guide sleeve respectively, and back load the sealing plug, confirm that the shielding plug has been correctly back loaded;

[0091] Step 6.2: the downstream load handler receives 12 new nuclear fuels: the downstream load handler is clamped to the new fuel channel, and receives 12 new nuclear fuels;

[0092] Step 6.3: back load 12 nuclear fuels in the fuel channel: the downstream load handler is clamped to the fuel channel, and the nozzle plug, the sealing plug and the shielding plug are removed; 12 nuclear fuels are back loaded into the fuel channel in reverse; the shielding plug, the sealing plug and the nozzle plug are back loaded, and it is confirmed that the nuclear fuels are back loaded in place;

[0093] Step 6.4: the reactor resumes normal operation mode: after the nuclear fuel back loading is completed, the main heat transfer system slowly increases the temperature and pressure to the normal operating state, and the reactor reenters the full power operation mode.

[0094] Referring to Figure 3 , a single fuel channel nuclear fuel emptying schematic diagram of a heavy water reactor nuclear power plant is shown.

[0095] Before emptying, the upstream load handler is loaded with emptying tools, including RGA tools, extension pieces and FAE tools; in the shutdown mode, the upstream load handler push rod is not long enough to push all 12 nuclear fuels into the downstream load handler, so 6 extension pieces and 1 FAE tool are needed to extend the length of the upstream load handler push rod, and therefore the emptying tools are loaded into the upstream load handler.

[0096] When emptying, the upstream and downstream load handlers are clamped to the same fuel channel; the upstream load handler removes the sealing plug and the shielding plug in the upstream fuel channel and pushes in the emptying tools; the downstream load handler removes the sealing plug and the shielding plug in the downstream fuel channel; then the upstream and downstream load handlers cooperate with each other to receive 12 nuclear fuels; the upstream and downstream load handlers back load the shielding plug and the sealing plug respectively, and complete the emptying operation of 12 nuclear fuels.

[0097] After emptying, the downstream load handler moves to the spent fuel channel and is clamped, and 12 nuclear fuels in the silo are unloaded to the spent fuel pool.

[0098] Referring to Figure 4, shows the heavy water reactor nuclear power plant single fuel channel drainage, water filling operation schematic diagram. After all the nuclear fuel emptying is completed, there is still heavy water flow in the fuel channel, which cannot be directly isolated by ice plug, and a cutoff tool with sealing device needs to be installed to realize the flow cutoff of the fuel channel. The fuel handling machine installs the cutoff tool into the fuel channel to realize the cutoff of the fuel channel.

[0099] After the cutoff, the ice plug device on the inlet and outlet branch pipes is used to freeze the pipeline to realize complete isolation by freezing; after the isolation is completed, the fuel handling machine removes the cutoff tool; according to the need, the pressure of the fuel channel can be raised and lowered by the heavy water control system of the fuel handling machine to confirm the defect condition of the fuel channel.

[0100] After the ice plug isolation, the fuel handling machine opens the valve to lower the liquid level, and the heavy water in the fuel channel will flow into the heavy water collection box through the hose to complete the drainage of the fuel channel.

[0101] After the fault handling is completed, the fuel handling machine completes the water filling of the fuel channel, and after the water filling is completed, the pressure of the single fuel channel can be raised and lowered according to the need by the heavy water control system of the fuel handling machine to finally confirm the success of the defect treatment; after the defect treatment is completed, the ice plug isolation is removed; the upstream and downstream fuel handling machines complete the reloading of the fuel channel sealing plug and the shielding plug respectively; the downstream fuel handling machine reloads 12 new fuels to restore the standard configuration of the fuel channel.

[0102] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for draining and filling water into a single fuel channel in a heavy water reactor nuclear power plant, characterized in that, Includes the following steps: Step 1: Empty the nuclear fuel from the fuel passage; Step 2: Install flow control tools to block the fuel passage; Step 3: Perform ice plug isolation and dewatering operation in the fuel passage; Step 4: Install temporary shielding plugs to establish maintenance conditions; Step 5: Fill the fuel channel with water; Step 6: Reloading nuclear fuel into the fuel channel; Step 3, perform ice plug isolation and fuel passage drainage operation, including the following steps: Step 3.1: Implement ice plugging operation on the inlet and outlet branch pipes of the fuel passage: Install ice plug jackets on the inlet and outlet branch pipes of the fuel passage to carry out ice plug freezing operation until the ice plug is completely formed; Step 3.2: Remove the flow-blocking tool to verify ice block formation: Remove the nozzle plug from the loader / unloader on the flow-blocking side and confirm that the fuel channel pressure is stable at 0.8MPa; install the guide sleeve and remove the flow-blocking tool; check the total flow data of the loader / unloader to verify that ice block has formed; Step 3.3: Perform fuel channel pressure increase and decrease operations using the loading and unloading machine: Slowly increase the pressure of the silo pressure controller and heavy water supply controller to raise the fuel channel pressure to 7MPa; check various parameters to accurately locate the fault; slowly decrease the controller pressure to reduce the fuel channel pressure to 0.8MPa; Step 3.4: Perform drainage operation of the fuel channel using the loading and unloading machine: After confirming that the drainage pipeline is connected to the drainage station, remove the guide sleeve, stop the heavy water pump, and isolate the loading and unloading machine; open the high-pressure drainage valve and the silo exhaust valve to drain the fuel channel until the cofferdam level indicator light is lit, indicating that the fuel channel drainage work is completed. Step 5, 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 respectively clamped onto the auxiliary channel, and the spare sealing plugs on the auxiliary channel are installed into the loading and unloading machine hoppers; Step 5.2: Perform water filling operation for the fuel channel: The upstream and downstream loading and unloading machines are simultaneously clamped onto the fuel channel; release the isolation of the loading and unloading machine on the water filling side, close the high-pressure drain valve, and open the hopper exhaust valve; start the heavy water pump to perform water filling operation. After the return flow is established, close the hopper exhaust valve. If the fuel channel pressure is maintained at 0.8MPa, it indicates that the water filling operation is successful. Step 5.3: Perform fuel channel pressure increase / decrease operation and reinstall the sealing plug: After reinstalling the sealing plug on one side of the loading and unloading machine, slowly increase the pressure of the hopper pressure controller and heavy water supply controller on the other side of the loading and unloading machine to raise the fuel channel pressure to 7MPa; after confirming that the fault handling is completed and all parameters are normal, slowly reduce the controller pressure to lower the fuel channel pressure to 0.8MPa and then reinstall the sealing plug. Step 5.4, Ice plug removal: After confirming that the sealing plugs on both sides of the fuel passage have been installed, remove the ice plugs and disconnect the fuel passage. At this time, the fuel passage is connected to the main heat transfer system.

2. The method for draining and filling water into a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that, Step 1, nuclear fuel removal from the fuel passages, includes the following steps: Step 1.1: The reactor enters a guaranteed shutdown mode: The reactor enters a guaranteed shutdown mode and maintains the guaranteed shutdown mode for more than 24 hours; Step 1.2, Empty the tools and load them into the upstream loading and unloading machine: Remove the push rod adapter, spare sealing plug and spare shielding plug from the upstream loading and unloading machine hopper; install the K-tube liner, and install one RGA tool, 6 extension parts and 1 FAE tool in the upstream loading and unloading machine hopper; remove the spare shielding plug from the downstream loading and unloading machine; Step 1.3: Emptying 12 nuclear fuels from the fuel channel to the downstream loading and unloading machine: The upstream and downstream loading and unloading machines clamp onto 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 respectively reinstall the shielding plug and sealing plug to complete the nuclear fuel emptying operation; Step 1.4: The downstream loader unloads 12 nuclear fuels into the spent fuel pool: The downstream loader moves to the spent fuel channel and engages the clamp; the nozzle plug is removed, the guide sleeve is installed, and the liquid level is lowered; the 12 nuclear fuels in the downstream loader's hopper are unloaded into the spent fuel pool; the guide sleeve is removed, the nozzle plug is reinstalled, and the liquid level is raised to restore the system.

3. The method for draining and filling water into a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that, Step 2, install the flow control tool to achieve fuel channel flow control, including the following steps: Step 2.1: Remove the emptying tools from the upstream loading and unloading machine: Remove one RGA tool, six extension parts, and one FAE tool from the upstream loading and unloading machine's hopper; remove the K-tube liner; Step 2.2: Remove the shielding plugs in the upstream and downstream fuel channels: The upstream and downstream loading and unloading machines are clamped onto the fuel channels, and the sealing plugs and shielding plugs are removed; the upstream and downstream loading and unloading machines reinstall the sealing plugs; the removed shielding plugs are discharged into the spent fuel pool through the spent fuel channel. Step 2.3: Install the intercepting tool into the loading and unloading machine: The intercepting side loading and unloading machine clamps onto the auxiliary channel, remove the nozzle plug, and install the guide sleeve; install the intercepting tool into the hopper; remove the guide sleeve, reinstall the nozzle plug, and confirm that the intercepting tool has been installed into the hopper of the intercepting side loading and unloading machine; Step 2.4: Insert the flow-blocking tool into the fuel channel to achieve flow blocking: The loader / unloader on the flow-blocking side is clamped onto the fuel channel; the nozzle plug and sealing plug are removed, and the guide sleeve is installed; the flow-blocking tool is installed into the fuel channel; the guide sleeve is removed, the nozzle plug is installed, and the total flow data of the loader / unloader is recorded. At this time, the flow blocking operation of the fuel channel is achieved.

4. The method for draining and filling water into a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that, Step 4, install temporary shielding plugs to establish maintenance conditions, including the following steps: Step 4.1: Remove the fuel channel sealing plug on the other side: After the drainage is completed, the fuel channel sealing plug is not installed on the loader / unloader on the drainage side. The clamp is directly released from the fuel channel; the fuel channel sealing plug on the other side is manually removed. 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 passages: After removing the sealing plugs on both sides, install temporary shielding plugs in the upstream and downstream fuel passages to provide radiation shielding for maintenance personnel; Step 4.3: Remove the intercepting tool from the loading and unloading machine: Position the loading and unloading machine clamp on the intercepting side onto the auxiliary channel, remove the nozzle plug, and install the guide sleeve; remove the intercepting tool from the hopper; remove the guide sleeve, reinstall the nozzle plug, and confirm that the intercepting tool has been removed from the loading and unloading machine hopper; Step 4.4: Handle fuel passage defects: The fault repair conditions have been established, and the ice plug freezing operation should be maintained until the defect is resolved.

5. The method for draining and filling water into a single fuel channel of a heavy water reactor nuclear power plant according to claim 1, characterized in that, Step 6, nuclear fuel reloading in the fuel channel, includes the following steps: Step 6.1: Install upstream and downstream fuel channel shielding plugs: The upstream and downstream loading and unloading machines respectively clamp onto the auxiliary channel and receive the spare shielding plug into the hopper; The upstream and downstream loading and unloading machines clamp onto the fuel channel; 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 upstream and downstream loading and unloading machines respectively remove the guide sleeves and reinstall the sealing plugs, confirming that the shielding plugs have been correctly reinstalled; Step 6.2: 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: Refilling 12 nuclear fuels into the fuel channel: The downstream loader clamps onto the fuel channel, removes the nozzle plug, sealing plug, and shielding plug; refills 12 nuclear fuels into the fuel channel in reverse; Reinstall the shielding plug, sealing plug, and nozzle plug, and confirm that the nuclear fuel has been reinstalled in place; Step 6.4: Reactor returns to normal operating mode: After the nuclear fuel reloading is completed, the main heat transfer system slowly heats up and pressurizes to normal operating conditions, and the reactor is put back into full-power operation mode.

Images