Nuclear fuel element handling head processing method and apparatus

Abstract

The present disclosure belongs to the technical field of nuclear power and particularly relates to a nuclear fuel element operating head processing method and device and a structure before chromium nitriding. The present disclosure determines the structure of the operating head before chromium nitriding through a large number of design, processing and welding tests, mills the structure at the welding position after chromium nitriding, eliminates the influence of the chromium nitriding coating on welding and X-ray detection, mills out the sodium hole size and the marking plane, guarantees the size accuracy of the sodium hole and the reading effect of the marking identification, meets the technical condition requirements, solves the key technologies of the chromium nitriding workpiece structure and manufacturing process, and provides technical support for the smooth development and production of the demonstration fast reactor nuclear fuel element.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nuclear power, and particularly relates to a processing method and device for a nuclear fuel element operating head. BACKGROUND

[0002] A fast reactor nuclear power station is a nuclear power station using fast neutrons to cause nuclear fuel fission reactions. The operating head is a structural component in a demonstration fast reactor nuclear fuel element. In the reactor, the operating head is clamped by hoisting equipment to perform fuel element loading and unloading operations. The operating head is made of CN-1515 stainless steel. The surface of the operating head needs to be locally treated by chromium nitriding to prevent self-welding of the element in the reactor and to increase the wear resistance of the surface of the operating head. After the operating head is fully sized and processed, chromium nitriding is performed. However, the following problems exist:

[0003] 1. The chromium nitriding layer at the welding position of the operating head and the outer sleeve will affect the subsequent assembly welding process, and in the welding process, defects such as inclusions and pores will occur.

[0004] 2. When X-ray detection is performed after assembly welding of the operating head, the chromium nitriding layer at the inner hole position of the operating head will affect the X-ray detection result.

[0005] 3. The chromium nitriding layer has a certain brittleness, and the point needle type marking will have a cracking phenomenon, which affects the identification effect of the operating head after marking.

[0006] 4. The operating head will withstand high temperature deformation and coating thickening during the chromium nitriding process, which will cause the size of the sodium outlet hole to be out of tolerance. SUMMARY

[0007] To overcome the problems in the related art, a nuclear fuel element operating head processing method is provided.

[0008] According to an aspect of an embodiment of the present disclosure, a nuclear fuel element operating head processing method is provided, which includes:

[0009] The body material of the marking plane and the design structure of the sodium outlet hole before chromium nitriding is thickened by at least 0.5 mm, and the thinnest body material of the welding position design structure before chromium nitriding is thickened by at least 0.5 mm;

[0010] The welding process platform structure is not processed with a margin left in the welding position design structure before chromium nitriding, and the welding process platform structure is processed to remove the coating after the welding position design structure is chromium nitrided;

[0011] Step one: design and process the sodium outlet hole and marking plane structure of the chromium nitriding operation head, install a numerical control indexing head and tailstock tooling on the workbench of the vertical machining center, clamp the top end of the chromium nitriding operation head with the numerical control indexing head, support the inner hole of the other end of the chromium nitriding operation head with the tailstock center, and use a milling cutter to mill to realize automatic control of the numerical control indexing head, automatic loosening and tightening of the tailstock, and automatic milling.

[0012] Step two: weld structure processing; install a main shaft large hole numerical control indexing head on the workbench of the horizontal machining center, clamp the middle part of the chromium nitriding operation head, and tightly position the top part of the device. The main shaft of the horizontal machining center is on the front of the workpiece. A vertical milling cutter is used to rotate and mill the six-sided weld structure and end face around the workpiece. A boring cutter is used to process the inner hole circle. Then, the workbench is rotated, and a forming tool is used to process the inclined groove of the weld structure. This can realize automatic clamping, indexing, and processing functions.

[0013] For the weld structure of the chromium nitriding operation head, the minimum processing allowance for removing the chromium nitriding coating is determined. The removal amount of the chromium nitriding coating is not less than 0.5mm.

[0014] In one possible implementation, in step one, one-time clamping is adopted for processing. A numerical control indexing head is used for clamping. After each sodium outlet hole is processed, the machine tool program automatically rotates to process the subsequent sodium outlet hole.

[0015] In one possible implementation, the chromium nitriding sodium outlet hole and marking plane processing tooling are installed on the machine tool workbench. The machine tool workbench is the workbench of a vertical machining center. In the processing process, automatic clamping is adopted. The tightening and loosening of the tailstock are controlled by the machine tool program. The tailstock is installed on the tailstock guide and can automatically move according to the program control.

[0016] In one possible implementation, the workbench is the workbench of a horizontal machining center. The chromium nitriding weld processing tooling is installed on the workbench.

[0017] In one possible implementation, the weld structure is a six-sided structure. To ensure the relative position accuracy of processing, one-time clamping is adopted for processing. A numerical control indexing head is used for clamping. After each weld structure is processed, the machine tool program automatically rotates to process the subsequent weld structure.

[0018] In one possible implementation, a plurality of chromium nitriding operation heads are batch processed. A positioning device is designed at the left end of each chromium nitriding operation head to ensure that each workpiece is clamped in the same position.

[0019] According to another aspect of the embodiments of the present disclosure, a nuclear fuel element operating head processing device is provided, and the method described above is implemented based on the device. In the device, a numerical control indexing head and a tailstock tool are installed on the workbench of the vertical machining center machine tool. The numerical control indexing head clamps the top end of the operating head after chromizing, and the tailstock center supports the inner hole of the other end of the operating head after chromizing. Milling is performed by using a milling cutter to realize automatic control of the numerical control indexing head, automatic loosening and tightening of the tailstock, and automatic milling.

[0020] A main shaft large hole numerical control indexing head is installed on the workbench of the horizontal machining center to clamp the middle part of the operating head after chromizing, and the top part is tightly attached to the positioning device. The main shaft of the horizontal machining center is on the front surface of the workpiece. A vertical milling cutter is used to rotate and mill the hexagonal welding structure and the end face around the workpiece. A boring cutter is used to process the inner hole circle. Then, the workbench is rotated by degrees, and a forming cutter is used to process the inclined groove of the welding structure.

[0021] The present disclosure has the beneficial effects that the milling of the welding structure after chromizing eliminates the influence of the chromizing coating on welding and X-ray detection, and the sodium hole size and the marking plane are milled to ensure the size accuracy of the sodium hole and the reading effect of the marking identification, meet the technical requirements, solve the key technology of the chromizing workpiece structure and manufacturing process, and provide technical support for the smooth development and production of the demonstration fast reactor nuclear fuel element. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a schematic diagram of a finished nuclear fuel element operating head.

[0023] Figure 2 FIG. 2 is a schematic diagram of an operating head before chromizing.

[0024] Figure 3 FIG. 3 is a schematic diagram of the design structure of the welding part before chromizing.

[0025] Figure 4 FIG. 4 is a schematic diagram of the sodium hole and the marking plane processing tooling after chromizing.

[0026] Figure 5 FIG. 5 is a schematic diagram of the welding part processing tooling after chromizing.

[0027] In the drawings:

[0028] 1, marking plane; 2, sodium hole; 3, welding structure;

[0029] 4, marking plane and sodium hole design structure before chromizing;

[0030] 5, welding part design structure before chromizing;

[0031] 6, welding process platform structure; 7, chromizing processing allowance;

[0032] 8, chromium nitriding operation head; 9, numerical control indexing head; 10, machine tool workbench; 11, tailstock guide;

[0033] 12, tailstock; 13, workbench; 14, indexing head; 15, positioning device; DETAILED DESCRIPTION

[0034] The present application will be further described in conjunction with the accompanying drawings and specific embodiments.

[0035] Figure 1 A finished product diagram of a nuclear fuel element operation head, Figure 2 A schematic diagram of the operation head before chromium nitriding is shown in Figure 1 The method comprises the following steps:

[0036] In the related art, the operation head needs to be added with a chromium nitriding coating according to the design requirements to increase the wear resistance and self-welding resistance of the operation head. According to the welding test, welding after chromium nitriding will cause defects such as inclusions and pores in the weld, and the coating will affect X-ray detection.

[0037] The welding position is designed as shown in Figure 3 The thickness of the inner hole is increased by 0.5 mm, and the thinnest part of the welding position is thickened by 0.5 mm. For the welding position structure 3 of the operation head, the minimum machining allowance for removing the chromium nitriding coating is determined, and the removal amount of the chromium nitriding coating is not less than 0.5 mm, which can eliminate the influence of the coating on welding and X-ray detection.

[0038] Referring to Figure 2 and Figure 3 , the welding process platform structure 6 is not machined with a remaining amount before chromium nitriding, and the welding process platform structure 6 is machined to remove the coating after chromium nitriding.

[0039] The structure of the sodium outlet hole 1 is designed. Since the size will change after chromium nitriding due to the increase of the coating, according to the test, if the sodium outlet hole 1 is machined first and then chromium nitriding, it will affect the size accuracy of the sodium outlet hole 1, and there is a risk of causing size out-of-tolerance and causing product scrap. To solve this problem, the design is to perform finish machining of the sodium outlet hole 1 after chromium nitriding.

[0040] The design of the marking plane 1 structure is shown in

[0041] Referring to Figure 4 and Figure 5After the machining allowance of the semi-finished product of the operating head is reserved, the chromium nitriding treatment is performed to form a chromium nitrided operating head 8, and further processing is required to remove the local coating.

[0042] The operating head is designed with six sodium outlet hole 1 structures. To ensure the relative position accuracy of the processing, one-time clamping is required for processing. A numerical control indexing head 9 is used for clamping, and after the processing of each sodium outlet hole is completed, the machine tool program controls the automatic rotation to sequentially process the subsequent sodium outlet hole.

[0043] The chromium nitrided sodium outlet hole and the marking plane processing tool are both installed on the machine tool workbench 10, which is the workbench of a vertical machining center.

[0044] Among them, automatic clamping is adopted during processing, and the tightening and loosening of the tailstock 12 are controlled by the machine tool program. The tailstock 12 is installed on the tailstock guide rail 11 and can automatically move according to the program control.

[0045] Since the chromium nitrided operating head 8 is about 600 mm long, in order to ensure the accuracy of the clamped workpiece, the tailstock 12 is used for self-centering support.

[0046] The workbench 13 is the workbench of a horizontal machining center, and the chromium nitrided welding site processing tool is installed on the workbench 13.

[0047] The welding site structure 3 is a hexagonal structure. To ensure the relative position accuracy of the processing, one-time clamping is required for processing. A dividing head 14 is used for clamping, and after the processing of each welding site structure 3 is completed, the machine tool program controls the automatic rotation to sequentially process the subsequent welding site structure 3.

[0048] Positioning device 15: Since the chromium nitrided operating head 8 needs to be processed in batches, in order to ensure the consistency of the clamping of each part, a positioning device is designed at the left end of the chromium nitrided operating head 8 to ensure that each workpiece is clamped at the same position, thereby ensuring the processing accuracy and efficiency of the parts.

[0049] In one possible implementation, a method for processing a nuclear fuel element operating head is provided. After the nuclear fuel element is subjected to chromium nitriding treatment, the following steps are used for processing.

[0050] Step one: sodium outlet hole 2 and marking plane 1 structure processing, numerical control dividing head 9 and tailstock 12 tooling are installed on the vertical machining center machine tool workbench 10, numerical control dividing head 9 clamps the top end of the chromium nitrided operating head 8, tailstock 12 supports the other end hole of the chromium nitrided operating head 8, and milling is performed to realize automatic control of the numerical control dividing head 9 for indexing, automatic loosening and tightening of the tailstock 12, and automatic milling.

[0051] Step two: welding structure 3 processing. Install the main shaft large hole numerical control indexing head 14 on the horizontal machining center workbench 13, clamp the middle part of the chromium nitriding operation head 8, and the top is close to the positioning device 15. The main shaft of the horizontal machining center is on the front surface of the workpiece. A vertical milling cutter is used to rotate and mill the hexagonal welding structure 3 and the end face around the workpiece. A boring cutter is used to process the inner hole circle. Then rotate the machine tool workbench 13 by 90 degrees. A forming tool is used to process the inclined groove of the welding structure 3. The functions of automatic clamping, indexing and processing can be realized.

[0052] The above has described various embodiments of the present disclosure, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A method of processing a nuclear fuel element handling head, characterized by, The method comprises: The body material of the marking plane and the design structure (4) of the sodium outlet hole before chromium nitriding is thickened by at least 0.5 mm, and the thinnest body material of the welding design structure (5) before chromium nitriding is thickened by at least 0.5 mm; The welding design structure (5) before chromium nitriding is left with a margin and is not processed into the welding process platform structure (6), and the welding design structure (5) is chromium nitrided and then the welding process platform structure (6) is reprocessed to remove the coating; Step one: the sodium outlet hole (2) and the marking plane (1) structure are processed for the marking plane and the design structure (4) of the sodium outlet hole of the operation head (8) after chromium nitriding, a numerical control indexing head (9) and a tailstock (12) tool are installed on a vertical machining center machine tool workbench (10), the numerical control indexing head (9) clamps the top end of the operation head (8) after chromium nitriding, the tailstock (12) top center supports the other end hole of the operation head (8) after chromium nitriding, and milling is performed by using a milling cutter to realize automatic control of the numerical control indexing head (9) for indexing, automatic loosening and tightening of the tailstock (12), and automatic milling; Step two: the welding structure (3) is processed; a main shaft large hole numerical control indexing head (14) is installed on a horizontal machining center workbench (13) to clamp the middle part of the operation head (8) after chromium nitriding, and the top is tightly attached to a positioning device (15); the horizontal machining center main shaft is on the front of the workpiece; a vertical milling cutter is used to rotate and mill the six-sided welding structure (3) and the end face around the workpiece; a boring cutter is used to process the inner hole circle; then the machine tool workbench (13) is rotated by 90 degrees; and a forming cutter is used to process the inclined surface groove of the welding structure (3) to realize automatic clamping, indexing and processing functions; For the welding structure (3) of the operation head (8) after chromium nitriding, the minimum processing margin of the chromium nitriding coating is determined, and the chromium nitriding coating removal amount is not less than 0.5 mm.

2. The method of claim 1, wherein, In step one, one-time clamping is adopted for processing, the numerical control indexing head (9) is clamped, and after each sodium outlet hole is processed, the machine tool program controls automatic rotation for subsequent sodium outlet hole processing.

3. The method of claim 1, wherein, The sodium outlet hole and the marking plane processing tool after chromium nitriding are all installed on the machine tool workbench (10), which is a vertical machining center workbench, and in the processing process, automatic clamping is adopted, the tightening and loosening of the tailstock (12) are controlled by the machine tool program, and the tailstock (12) is installed on the tailstock guide rail (11) and can automatically move according to the program control.

4. The method of claim 1, wherein, The workbench (13) is a horizontal machining center workbench, and the welding processing tool after chromium nitriding is installed on the workbench (13).

5. The method of claim 1, wherein, The welding structure (3) is a six-sided structure, and in order to ensure the relative position accuracy of processing, one-time clamping is adopted for processing, the indexing head (14) is clamped, and after each welding structure (3) is processed, the machine tool program controls automatic rotation for subsequent welding structure (3) processing.

6. The method of claim 1, wherein, Batch processing is performed on multiple operation heads (8) after chromium nitriding, a positioning device (15) is designed at the left end of each operation head (8) after chromium nitriding to ensure that each workpiece is clamped at the same position.

7. A nuclear fuel element handling head processing apparatus characterized by, Based on the device to achieve the method as claimed in any one of claims 1 to 6, in the device, vertical machining center machine tool table (10) on the installation of numerical control indexing head (9) and tailstock (12) tooling, numerical control indexing head (9) clamping chromium nitriding after operation head (8) top, tailstock (12) center support chromium nitriding after operation head (8) the other end hole, using milling cutter milling, to realize automatic control numerical control indexing head (9) indexing, tailstock (12) automatic release and tight, realize automatic milling; On the horizontal machining center worktable (13) install spindle large hole numerical control indexing head (14), clamping chromium nitriding after operation head (8) middle, top close to positioning device (15), horizontal machining center spindle in the front of the workpiece, using end mill around the workpiece rotary milling hexagonal welding structure (3) and end face, using boring tool processing hole circle, and then rotate the machine tool table (13) 90 degrees, using the forming tool processing welding structure (3) inclined groove.

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