A method for servicing a reactor core neutron flux measurement system

Abstract

The application discloses a kind of overhaul method of reactor core neutron flux measuring system, including step one to step twelve, the safety of overhaul is improved by the control of overhaul step and overhaul moment, and the risk of overhaul is reduced.

Description

Technical Field

[0001] This invention relates to the field of nuclear power technology, and in particular to a maintenance method for a reactor core neutron flux measurement system. Background Technology

[0002] The neutron flux measurement system in the reactor core is a crucial component of the nuclear testing system. Equipment within this system, such as the guide tube, finger sleeves, and sealing section, forms part of the reactor's primary coolant circuit pressure boundary, serving as the second line of defense for nuclear safety. The guide tube primarily provides a safe passage for the insertion of the finger sleeves, which in turn provide a safe measurement path for the neutron flux detector. The sealing section's main function is to seal the primary coolant between the outer wall of the finger sleeves and the interior of the guide tubes. Therefore, maintenance and repair of this system are critical for the safe operation of a nuclear power plant.

[0003] The following problems have been identified during the current maintenance process:

[0004] 1. The finger sleeve is a hollow tube closed at one end, inserted into the measurement channel along the guide tube. The measurement channel is located at the center of the fuel assembly. During unit power operation, the outer wall of the finger sleeve is in the primary coolant. The flow of coolant in the pressure vessel causes friction between the finger sleeve and the fuel assembly, resulting in thinning of the finger sleeve wall and posing a risk of breakage. Breakage of the finger sleeve will directly prevent the measurement path from completing the neutron flux measurement, and there is also a risk of primary coolant leakage.

[0005] 2. The front of the detector consists of three parts: a welded end plug, a coaxial shell, and a measuring body, and it cannot be bent. The rear part is connected to a flexible coaxial cable, which is used for both conduction and driving. During the detection process, the detector needs to enter the reactor core through equipment such as the path and group selector and the finger sleeve. It may get stuck in the connecting tube due to the torque limiter failure, the fixed guide chain failure, or the reel position sensor failure, which will prevent the channel from measuring.

[0006] 3. During each refueling overhaul, the in-core finger sleeves need to be removed before unloading the reactor fuel assemblies. Before removing the finger sleeves, the mechanical equipment in the core instrument room of the core neutron flux measurement system needs to be disassembled to make room for the finger sleeves. After pushing the finger sleeves in, the in-core equipment needs to be restored. If the system restoration fails or the maintenance is insufficient, it may affect the normal operation of the system and make it impossible to measure the core power distribution. On the one hand, the unit will face the risk of deactivation; on the other hand, maintenance personnel will enter the nuclear island for maintenance while the unit is at power, which poses a significant radiation risk. Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned technical problems and provide a maintenance method for a reactor core neutron flux measurement system. This invention improves the safety of maintenance and reduces maintenance risks by controlling the maintenance steps and maintenance torque.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a maintenance method for a reactor core neutron flux measurement system, comprising the following steps:

[0009] Step 1: Before removing the finger sleeve, dismantle the components of the reactor core neutron flux measurement system;

[0010] Step 2: Inspect the dismantled equipment;

[0011] Step 3: Check the internal rotor rotation and the electrical performance of the synchro, the slip assembly, and the drive motor. After the guide chains of the synchro and / or the slip assembly and / or the drive motor are restored, use a feeler gauge to check that the spacing of the guide chains of the synchro and / or the slip assembly and / or the drive motor is between 0.8mm and 1.2mm.

[0012] Step 4: Check the route selector and group selector, and remove the ball positioner from the route selector and group selector. Check the condition of the ball positioner and the transmission gear system. The working torque of the transmission gear system should be between 0.22 da N·m and 0.29 da N·m.

[0013] Step 5: Use a dummy detector with a spiral cable to check the position of the micro switch, check the operation of the cam and the positioned micro switch, and ensure that the micro switch in each device functions normally.

[0014] Step 6: Check the clutch clearance, and use a dummy detector to check the selector's setting accuracy, setting status after each action, and setting cycle;

[0015] Step 7: Check for boron crystals inside the electric valve. Use a special probe to check the opening and closing of the electric valve, the alignment of the electric valve when it is open or closed, and the timing of opening or closing the valve.

[0016] Step 8: Disassemble and inspect the leak detector, replace the leak detector and its gasket, clean the inside of the leak detector, and reassemble the leak detector after inspection.

[0017] Step 9: When pulling out the finger sleeves, pull out the finger sleeves one by one in sequence. After completion, use a torque wrench to tighten the upstream nut of the sealing section.

[0018] Step 10: After the fuel assemblies are reloaded into the reactor, the finger sleeves are pushed back into the core.

[0019] Step 11: Reinstall the sealing section nut brake pad and the sealing section, the leakage detector and gasket of the electric valve, restore the connecting pipes between each section, and test each connecting pipe with a dummy detector to confirm that the detector can pass through the measurement channel smoothly.

[0020] Step 12: Reconnect the cable plugs and grounding wires of the electric valve, circuit selector, group selector, and drive mechanism.

[0021] The dummy detector refers to a 1:1 replica of the detector, used to verify whether the detector's working path is smooth. The detector is only used after it is confirmed to be working correctly.

[0022] In step six, the accuracy of the positioning, the positioning status after each action, and the positioning cycle are determined by using a dummy detector to complete the work at the designated position and observing whether the completion is correct. The selector mentioned in step six includes a path selector and a group selector.

[0023] Preferably, step one includes the following: removing and placing the drive unit, route selector, group selector, electric valve, and power cable; removing and marking the metal connecting pipes between the electric valve and the group selector, between the group selector and the route selector, and between the electric valve and the sealing section assembly; removing the leak detectors and gaskets from the sealing section and the electric valve and storing them separately; removing the nut brake pad from the sealing section and loosening the upstream and downstream nuts of the nut brake pad; removing the drive unit and pulling the detector drive cable out from the tail and wrapping it for placement.

[0024] Preferably, step two includes the following: inspecting each disassembled core instrumentation line to check for any damage; inserting a dummy detector into each disassembled core instrumentation line to verify that the detector drive cable passes smoothly without jamming; replacing any jammed core instrumentation lines; and applying lubricant to the removed and stored detector drive cables to prevent them from jamming.

[0025] Preferably, the spacing of the guide chains in step three is 1.0 mm or 1.1 mm.

[0026] Preferably, the torque of the ball positioner and the transmission gear system in step four is 0.24 da N·m, 0.25 da N·m, 0.26 da N·m, or 0.27 da N·m.

[0027] Preferably, step eight includes the following: after inspection, reinstall the leak detector with a torque of 1 daN·m.

[0028] Preferably, step nine includes the following: using a torque wrench to tighten the upstream nut of the sealing section to a torque of 1 da N·m.

[0029] Preferably, step ten includes the following: first loosen the upstream nut of the sealing section, push the finger sleeve back, and then use a torque wrench to tighten the upstream nut and the downstream nut to a torque of 6 da N·m.

[0030] Preferably, step eleven includes the following: restoring the connecting pipes between the sections and tightening each connecting pipe joint to a torque of 5 da N·m.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention improves maintenance safety and reduces maintenance risks by controlling maintenance steps and maintenance torque;

[0033] 2. The present invention inspects the components before the finger sleeve is pulled out. During the finger sleeve pulling operation, the finger sleeves are pulled out one by one in sequence. By precisely controlling the torque, the risk of thinning and breakage of the finger sleeve wall is reduced.

[0034] 3. This invention uses a dummy detector to verify whether the detector's working path is smooth, avoiding the risk that the channel cannot be measured due to the dummy detector getting stuck in the connecting pipe because of torque limiter failure, fixed guide chain failure, or reel position sensor failure. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments.

[0036] This invention discloses a maintenance method for a reactor core neutron flux measurement system, comprising the following steps:

[0037] Step 1: Before removing the finger sleeve, dismantle the components of the core neutron flux measurement system, including the drive unit, path selector, group selector, electric valve, and power cable, and place them aside; dismantle the metal connecting pipes between the electric valve and the group selector, between the group selector and the path selector, and between the electric valve and the sealing section assembly, and mark and store them; remove the leak detectors and gaskets from the sealing section and the electric valve, and store them separately; remove the nut brake pads from the sealing section, and loosen the upstream and downstream nuts of the nut brake pads; dismantle the drive unit and pull the detector drive cable from the tail end, wrap it, and place it in the corner of the core instrument room; push the path selector and electric valve trolley along the track to leave sufficient path for the finger sleeve to be removed;

[0038] Step 2: Inspect the dismantled equipment. Check each dismantled core instrumentation line for any damage. Use a dummy detector to insert into each dismantled core instrumentation line to verify that the detector drive cable passes smoothly without jamming. Replace any jammed core instrumentation lines. Apply lubricant to the dismantled and stored detector drive cables to prevent jamming. Perform electrical and mechanical performance checks on the drive units, route selectors, group selectors, and electric valves.

[0039] Step 3: Check the internal rotor rotation and the electrical performance of the synchro, the slip assembly, and the drive motor. After the guide chains of the synchro and / or the slip assembly and / or the drive motor are restored, use a feeler gauge to check that the spacing of the guide chains of the synchro and / or the slip assembly and / or the drive motor is 1.0mm or 1.1mm.

[0040] Step 4: Check the route selector and group selector, and remove the ball positioner from the route selector and group selector. Check the condition of the ball positioner and the transmission gear system. The working torque of the transmission gear system should be 0.24daN·m, 0.25daN·m, 0.26daN·m, or 0.27daN·m.

[0041] Step 5: Use a dummy detector with a spiral cable to check the position of the micro switch, check the operation of the cam and the positioned micro switch, and ensure that the micro switch in each device functions normally.

[0042] Step 6: Check the clutch clearance, and use a dummy detector to check the selector's setting accuracy, setting status after each action, and setting cycle;

[0043] Step 7: Check for boron crystals inside the electric valve. Use a special probe to check the opening and closing of the electric valve, the alignment of the electric valve when it is open or closed, and the timing of opening or closing the valve.

[0044] Step 8: Disassemble and inspect the leak detector, replace the leak detector and its gasket, clean the inside of the leak detector, and reassemble the leak detector with a torque of 1 da N·m after inspection.

[0045] Step 9: When pulling out the finger sleeves, pull out the finger sleeves one by one in sequence. After completion, use a torque wrench to tighten the upstream nut of the sealing section to a torque of 1 da N·m.

[0046] Step 10: After the fuel assembly is reinstalled into the reactor, first loosen the upstream nut of the sealing section, push the finger sleeve back, and then use a torque wrench to tighten the upstream and downstream nuts to a torque of 6 da N·m.

[0047] Step 11: Reinstall the sealing section nut brake pad and the sealing section, the leakage detector and gasket of the electric valve, restore the connecting pipes between each section, tighten each connecting pipe joint to a torque of 5 da N·m, and test each connecting pipe with a dummy detector to confirm that the detector can pass through the measurement channel smoothly.

[0048] Step 12: Reconnect the cable plugs and grounding wires of the electric valves, route selectors, group selectors and drive mechanisms, and restore the equipment in the core instrument room to its pre-disassembly state.

[0049] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0050] It should be noted that when a component is referred to as "fixed on" or "set on" another component, it can be located directly on or indirectly on the other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to the other component.

[0051] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicating orientation or positional relationships are only for the convenience of describing the present invention, and do not indicate that the device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or the number of technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

Claims

1. A method for overhauling a reactor core neutron flux measurement system, characterized in that: Includes the following steps: Step 1: Before removing the finger sleeve, dismantle the components of the reactor core neutron flux measurement system; Step 2: Inspect the dismantled equipment; Step 3: Check the internal rotor rotation and the electrical performance of the synchro, the slip assembly, and the drive motor. After the guide chains of the synchro and / or the slip assembly and / or the drive motor are restored, use a feeler gauge to check that the spacing of the guide chains of the synchro and / or the slip assembly and / or the drive motor is between 0.8mm and 1.2mm. Step 4: Check the route selector and group selector, and remove the ball positioner from the route selector and group selector. Check the condition of the ball positioner and the transmission gear system. The working torque of the transmission gear system should be between 0.22 da N·m and 0.29 da N·m. Step 5: Use a dummy detector with a spiral cable to check the position of the micro switch, check the operation of the cam and the positioned micro switch, and ensure that the micro switch in each device functions normally. Step 6: Check the clutch clearance, and use a dummy detector to check the selector's setting accuracy, setting status after each action, and setting cycle; Step 7: Check for boron crystals inside the electric valve. Use a special probe to check the opening and closing of the electric valve, the alignment of the electric valve when it is open or closed, and the timing of opening or closing the valve. Step 8: Disassemble and inspect the leak detector, replace the leak detector and its gasket, clean the inside of the leak detector, and reassemble the leak detector after inspection. Step 9: When pulling out the finger sleeves, pull out the finger sleeves one by one in sequence. After completion, use a torque wrench to tighten the upstream nut of the sealing section. Step 10: After the fuel assemblies are reloaded into the reactor, the finger sleeves are pushed back into the core. Step 11: Reinstall the sealing section nut brake pad and the sealing section, the leakage detector and gasket of the electric valve, restore the connecting pipes between each section, and test each connecting pipe with a dummy detector to confirm that the detector can pass through the measurement channel smoothly. Step 12: Reconnect the cable plugs and grounding wires of the electric valve, circuit selector, group selector, and drive mechanism.

2. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: Step one includes the following: Remove and store the drive unit, route selector, group selector, electric valve, and power cable; remove and label the metal connecting pipes between the electric valve and the group selector, between the group selector and the route selector, and between the electric valve and the sealing section assembly; remove the leak detectors and gaskets from the sealing section and the electric valve and store them separately; remove the nut brake pads from the sealing section and loosen the upstream and downstream nuts of the nut brake pads; remove the drive unit and pull the detector drive cable from the tail end, wrap it, and store it.

3. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: Step two includes the following: Inspect each disassembled core instrumentation line, observing for any damage. Use a dummy detector to insert into each disassembled core instrumentation line to verify that the detector drive cable passes through smoothly without any jamming. Replace any jammed core instrumentation lines and apply lubricant to the removed and stored detector drive cables.

4. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: In step three, the spacing of the guide chains is 1.0mm or 1.1mm.

5. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: In step four, the torque of the ball positioner and the transmission gear system is 0.24 da N·m, 0.25 da N·m, 0.26 da N·m, or 0.27 da N·m.

6. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: Step eight includes the following: After inspection, reinstall the leak detector with a torque of 1 da N·m.

7. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: Step nine includes the following: using a torque wrench to tighten the upstream nut of the sealing section to a torque of 1 da N·m.

8. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: Step 10 includes the following: First, loosen the upstream nut of the sealing section, push the finger sleeve back, and then use a torque wrench to tighten the upstream and downstream nuts to a torque of 6 da N·m.

9. The maintenance method for the reactor core neutron flux measurement system according to claim 1, characterized in that: In step eleven This includes the following: restoring the connecting pipes between each section and tightening each connecting pipe joint to a torque of 5 da N·m.