Method for assembling and welding silver-indium-cadmium absorption rod

Abstract

The invention belongs to the technical field of nuclear fuel manufacturing for nuclear power stations, and particularly relates to an assembling and welding method for a silver-indium-cadmium absorption rod. The cladding pipe is positioned and cut off through a turning tool, and burrs are removed; the surfaces of the end plug and the absorption rod spring are free of stains after being cleaned; cleaning the nitriding pipe with a lower end plug: putting the nitriding pipe on a cleaning table, and wiping the inner wall of the nitriding pipe by using a cotton swab or silk cloth dipped with acetone; wiping the end face and the outer wall of the nitriding pipe by using silk dipped with acetone; a silver-indium-cadmium rod is firstly installed, then a spring is installed, and the silver-indium-cadmium rod is located at the lower end of the rod; the inside of the nitriding pipe needs to be evacuated before plug pressing, then helium is filled into the pipe for plug pressing, and the pressure of the helium filled into the rod is one atmospheric pressure; welding the nitriding pipe; carrying out X-ray inspection on the absorption rod; carrying out helium leak detection on the absorption rod; the surface of the absorption rod is free of scratches, gouges and pits, and the length and bounce meet the technical requirements. The manufacturing technical problem of assembling and welding of the domestic absorption rod is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear fuel manufacturing for nuclear power plants, and in particular relates to an assembly and welding method of a silver-indium-cadmium absorption rod. Background Art

[0003] The CF control rod assembly is a domestically designed control rod assembly for a million-kilowatt nuclear power unit. The silver-indium-cadmium absorber rod (abbreviated as absorber rod) is an important component of the control rod assembly. The assembly and welding process of the absorber rod includes cutting, installing, plugging, ring welding and other process contents. The welding material of the absorber rod is made of domestic stainless steel, of which the material of the control rod end plug is 022Cr21Ni10, the material of the absorber rod cladding tube is 022Cr17Ni12Mo2, and the welding method is TIG welding. At present, except for our company, there are no related domestic enterprises manufacturing this type of absorber rod, and there is no report on the manufacturing method of this type of absorber rod abroad. Summary of the invention

[0004] The purpose of the present invention is to provide a method for assembling and welding a silver-indium-cadmium absorption rod, so as to solve the manufacturing technical problems of assembling and welding the domestic absorption rods.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for assembling and welding a silver-indium-cadmium absorption rod,

[0007] Step 1: Cut the nitriding tube to a fixed length with a lower end plug welded: Use a turning tool to position and cut the cladding tube and remove the burrs;

[0008] Step 2: The end plug and the absorber rod spring are cleaned and there is no stain on the surface; Cleaning of the nitriding tube with the lower end plug: Place the nitriding tube on the cleaning table and wipe the inner wall of the nitriding tube with a cotton swab or silk cloth dipped in acetone; Wipe the end face and outer wall of the nitriding tube with a silk cloth dipped in acetone;

[0009] Step 3: Install the absorber rod into the tube: first install the silver-indium-cadmium rod, then install the spring, with the silver-indium-cadmium rod at the lower end of the rod;

[0010] Step 4: Press the end plug: Before pressing the nitriding tube, the tube must be evacuated first, and then filled with helium to press the plug. The helium pressure filled in the rod is one atmosphere;

[0011] Step 5: Welding of nitriding tube: Open the valves of argon / helium and compressed air pipelines to put the welder into the pre-welding state; set TIG welding process parameters for welding; the oxidation color on the weld surface can be removed by grinding with an ultra-clean scouring pad, and grinding of the pipe wall outside the welding area is not allowed; the ring gauge should pass freely through the weld of the end plug; visually check that the weld has no oxidation color exceeding the technical conditions;

[0012] Step 6: X-ray inspection with absorption rod;

[0013] Step 7: Perform helium leak detection with the absorption rod;

[0014] Step 8: There are no scratches, dents or pits on the surface of the absorption rod, and the length and runout meet the technical requirements.

[0015] The maximum chamfer of the outer pipe mouth is 0.05mm; the maximum chamfer of the inner pipe mouth is 0.05mm×0.13mm. After cutting the pipe, use metallographic sandpaper to polish the inner wall of the pipe mouth.

[0016] After cutting the tube, check the appearance and size of the cladding tube. The nitriding tube shall meet the requirement of inner diameter ≥ Ф8.72mm.

[0017] Use a cotton swab or silk cloth dipped in acetone to wipe the inner wall of the nitriding tube, with a wiping depth of at least 10mm from the tube end face; use a silk cloth dipped in acetone to wipe the end face and outer wall of the nitriding tube, with a wiping depth of at least 50mm from the tube end face.

[0018] After the vacuum reaches 30Pa, continue to pump for at least 3 minutes.

[0019] The helium filling time is at least 30 seconds, and the plugging force is controlled within the range of 0.2 to 0.3 MPa.

[0020] Step 4: Check the ovality of the clamping part of the nitriding tube, and limit the ovality to within 0.05mm.

[0021] Step 5: The welding electrode is cerium tungsten Ce-W; the electrode diameter is Φ2.0mm; the electrode taper is 30°; the cooling time is ≥5s; the welding speed is 12r / min; the welding time is 12s; the welding current is 22A±2A; the inter-electrode spacing is 0.6mm±0.1mm; the electrode deviates from the weld center by -0.1mm~0.1mm.

[0022] Step 5: Use a ring gauge with a diameter of 9.82mm and a length of 20mm to freely pass through the weld of the end plug.

[0023] Step 6: meet the following conditions: a) the weld penetration is not less than 90% of the minimum theoretical wall thickness of the pipe, 0.43mm; b) the remaining wall thickness of the pipe due to gas expansion is not less than 90% of the minimum theoretical wall thickness of the pipe, 0.43mm; c) inclusions or pores with a diameter not greater than 0.25mm are allowed; Step 7: the leakage rate is less than 10 -9 Pa·m3 / s.

[0024] The beneficial effects achieved by the present invention are:

[0025] The present invention is applied to the assembly and welding of nitriding absorber rods made of domestic materials for the first time. The mass production of absorber rods is realized. The manufacturing method has been applied to the mass production of absorber rods, and the data of various test quantities are in line with expectations. The batch absorber rods have been put into operation with good results. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the silver-indium-cadmium absorption rod;

[0027] In the figure: 1 - control rod upper end plug; 2 - absorption rod spring; 3 - silver-indium-cadmium rod; 4 - nitriding tube with welded lower end plug. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The structure and appearance of the absorption rod are as follows Figure 1 As shown. The silver-indium-cadmium absorber rod consists of an upper end plug, a nitriding tube with a welded lower end plug, a silver-indium-cadmium rod, and an absorber rod spring. The upper end plug of the control rod is connected to the nitriding tube by TIG welding. The end plug is made of domestic stainless steel material 022Cr21Ni10, and the nitriding tube is made of domestic material 022Cr17Ni12Mo2. Its manufacturing process includes pipe installation process, plug pressing process, ring welding process, etc. Among them, the ring welding process adopts TIG welding method. The absorber rod produced according to the manufacturing process, its appearance size and physical and chemical results of the sample meet the technical requirements.

[0030] Cutting of nitriding tubes with welded lower end plugs → Cleaning of the tube ends with welded lower end plugs → Tube installation → Helium filling and upper end plug pressurization → Circumferential welding → Weld inspection → X-ray inspection → Helium mass spectrometer leak detection → Appearance and size inspection.

[0031] The implementation steps are as follows:

[0032] Step 1: Cutting the nitriding tube to length with the lower end plug welded

[0033] a) Use a turning tool to cut the cladding tube and remove the burrs. The maximum chamfer of the tube mouth is 0.05mm; the maximum chamfer of the tube mouth is 0.05mm×0.13mm. After cutting the tube, use metallographic sandpaper to polish the inner wall of the tube mouth.

[0034] b) After cutting the tube, the appearance and size of the cladding tube should be checked, and the nitriding tube should meet the requirement of inner diameter ≥ Ф8.72mm.

[0035] Step 2: Parts cleaning

[0036] The end plug and the spring of the absorbent rod have been cleaned and there are no stains on the surface. Cleaning of nitriding tubes with lower end plugs: Place the nitriding tube on the cleaning table; Wipe the inner wall of the nitriding tube with a cotton swab or silk cloth dipped in acetone, the wiping depth: at least 10mm from the end face of the tube; Wipe the end face and outer wall of the nitriding tube with a silk cloth dipped in acetone, the wiping depth: at least 50mm from the end face of the tube.

[0037] Step 3: Install the absorber rod into the tube

[0038] First install the silver-indium-cadmium rod, and then install the spring. The silver-indium-cadmium rod is at the lower end of the rod.

[0039] Step 4: Press on the end plug

[0040] Before the nitriding tube is plugged, the tube must be evacuated (after the vacuum reaches 30Pa, it must be evacuated for at least 3 minutes), and then filled with helium before plugging. The helium pressure filled in the rod is one atmosphere (the helium filling time is at least 30 seconds). The plugging force is controlled within the range of 0.2-0.3Mpa.

[0041] Check the ovality of the clamping part of the nitriding tube, and the ovality should be limited to within 0.05mm.

[0042] Step 5: Welding of nitriding tube

[0043] Open the valves of argon / helium and compressed air pipelines to put the welder into the pre-welding state;

[0044] Set TIG welding process parameters and start welding.

[0045] The welding electrode is cerium tungsten Ce-W; the electrode diameter is Φ2.0mm; the electrode taper is 30°; the main welding process parameters are as follows:

[0046] Cooling time: ≥5s; welding speed: 12r / min; welding time: 12s; welding current: 22A±2A; inter-electrode spacing: 0.6mm±0.1mm; electrode deviation from weld center: -0.1mm~0.1mm.

[0047] Weld grinding

[0048] The oxidation color on the weld surface can be removed by grinding with an ultra-clean scouring pad (the main components are nylon fiber, polyester fiber, and corundum). Grinding of the pipe wall outside the welding area is not allowed.

[0049] Weld visual inspection

[0050] Weld diameter inspection: A ring gauge with a diameter of Ф9.82mm and a length of 20mm should pass freely through the weld of the end plug.

[0051] Appearance inspection of welds: Visually inspect the welds to ensure that there is no oxidation color exceeding that specified in the technical conditions.

[0052] Step 6: X-ray examination

[0053] The absorption rod is used for X-ray inspection and the following conditions are met:

[0054] a) The weld penetration depth should not be less than 90% of the minimum theoretical wall thickness of the pipe (0.43mm);

[0055] b) The remaining wall thickness of the pipe due to inflation is not less than 90% of the minimum theoretical wall thickness of the pipe (0.43 mm);

[0056] c) Inclusions or pores with a diameter not exceeding 0.25 mm are allowed;

[0057] Step 7: Helium leak check

[0058] Helium leak test with absorber rod; the leakage rate should be less than 10 -9 Pa·m 3 / s.

[0059] Step 8: Check the appearance and dimensions of the absorber rod

[0060] The surface of the absorber rod has no scratches, dents or pits. The length and runout meet the technical requirements.

Claims

1. A method for assembling and welding a silver-indium-cadmium absorption rod, characterized in that: Step 1: Cut the nitriding tube to a fixed length with a lower end plug welded: Use a turning tool to position and cut the cladding tube and remove the burrs; Step 2: The end plug and the absorber rod spring are cleaned and there is no stain on the surface; Cleaning of the nitriding tube with the lower end plug: Place the nitriding tube on the cleaning table and wipe the inner wall of the nitriding tube with a cotton swab or silk cloth dipped in acetone; Wipe the end face and outer wall of the nitriding tube with a silk cloth dipped in acetone; Step 3: Install the absorber rod into the tube: first install the silver-indium-cadmium rod, then install the spring, with the silver-indium-cadmium rod at the lower end of the rod; Step 4: Press the end plug: Before pressing the nitriding tube, the tube must be evacuated first, and then filled with helium to press the plug. The helium pressure filled in the rod is one atmosphere; Step 5: Welding of nitriding tube: Open the valves of argon / helium and compressed air pipelines to put the welder into the pre-welding state; set TIG welding process parameters for welding; the oxidation color on the weld surface can be removed by grinding with an ultra-clean scouring pad, and grinding of the pipe wall outside the welding area is not allowed; the ring gauge should pass freely through the weld of the end plug; visually check that the weld has no oxidation color exceeding the technical conditions; Step 6: X-ray inspection with absorption rod; Step 7: Perform helium leak detection with the absorption rod; Step 8: There are no scratches, dents or pits on the surface of the absorption rod, and the length and runout meet the technical requirements.

2. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 1: The maximum chamfer of the outer pipe mouth is 0.05mm; the maximum chamfer of the inner pipe mouth is 0.05mm×0.13mm. After cutting the pipe, use metallographic sandpaper to polish the inner wall of the pipe mouth.

3. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 1: After cutting the tube, check the appearance and size of the cladding tube. The nitriding tube shall meet the requirement of inner diameter ≥ Ф8.72mm.

4. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 2: Use a cotton swab or silk cloth dipped in acetone to wipe the inner wall of the nitriding tube, with a wiping depth of at least 10mm from the tube end face; use a silk cloth dipped in acetone to wipe the end face and outer wall of the nitriding tube, with a wiping depth of at least 50mm from the tube end face.

5. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 4: After the vacuum reaches 30Pa, continue to pump for at least 3 minutes.

6. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 4: The helium filling time is at least 30 seconds, and the plugging force is controlled within the range of 0.2-0.3Mpa.

7. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 4: Check the ovality of the clamping part of the nitriding tube, and limit the ovality to within 0.05mm.

8. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 5: The welding electrode is cerium tungsten Ce-W; the electrode diameter is Φ2.0mm; the electrode taper is 30°; the cooling time is ≥5s; the welding speed is 12r / min; the welding time is 12s; the welding current is 22A±2A; the inter-electrode spacing is 0.6mm±0.1mm; the electrode deviates from the weld center by -0.1mm~0.1mm.

9. The method for assembling and welding the silver-indium-cadmium absorber rod according to claim 1, characterized in that: Step 5: Use a ring gauge with a diameter of 9.82mm and a length of 20mm to freely pass through the weld of the end plug.

10. The method for assembling and welding the silver-indium-cadmium absorption rod according to claim 1, characterized in that: Step 6: meet the following conditions: a) the weld penetration is not less than 90% of the minimum theoretical wall thickness of the pipe, 0.43mm; b) the remaining wall thickness of the pipe due to gas expansion is not less than 90% of the minimum theoretical wall thickness of the pipe, 0.43mm; c) inclusions or pores with a diameter not greater than 0.25mm are allowed; Step 7: the leakage rate is less than 10 -9 Pa·m3 / s.

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