A method of machining a nuclear reactor in-core component

Abstract

A kind of nuclear reactor internal component processing method, comprising the following method, cross center line is drawn on raw material and angle is marked, the center point of pie-shaped forging is drilled point hole positioning, is drilled to the point of punching with sleeve drill, the depth of hole is greater than half of plate thickness, wood wedge is driven into the hole that has completed half, the forging is turned over and is aligned and is punched positioning, drill hole sleeve is worn and the excess material mandrel in hole is lifted out;The processing mode of sleeve drill is used in the application and the processing method is optimized, the utilization rate of material can be effectively improved and the processing cost is reduced, and the processing quality is further improved.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor internals manufacturing technology, and more specifically to a method for processing nuclear reactor internals. Background Technology

[0002] In-core components are all the components inside the reactor pressure vessel except for fuel assemblies and their related components. They are the core main equipment of the nuclear island of a nuclear power plant. Their special function determines that the structure of the in-core components is complex. They include various plate parts such as the upper core plate, upper support plate, lower core plate, core support plate, and grid plate. These parts all have large through holes. At the same time, in order to meet the requirements of special operating conditions, the raw material of the in-core components is austenitic stainless steel, which has poor machinability, poor chip breaking and difficult chip removal.

[0003] For machining large-diameter deep holes with a diameter of φ225 and a depth of 368, the traditional process is drilling-reaming-boring.

[0004] 1. Drilling is usually done with an 80mm drill bit. A regular twist drill is selected, with cutting parameters of S=150~200r / min and F=10~15mm / min. The length-to-diameter ratio of the drill bit is about 4.6 times. The cutting parameters decrease as the drilling depth increases. During the entire machining process, the tool needs to be lifted and the chips need to be manually removed multiple times.

[0005] 2. When using a reamer for enlargement, the cutting parameters are S=80~150r / min and F=10-12mm / min. However, this method also suffers from poor rigidity and requires repeated tool lifting for chip removal.

[0006] 3. For boring, a double-sided boring bar is selected, with a cutting depth of 1.5-3 mm on each side, S=120-180 r / min, F=15-30 mm / min;

[0007] The drilling, reaming, and boring processes convert the entire core area of ​​the hole into iron filings, which is inefficient and has low material utilization, failing to meet product delivery cycle and cost control requirements. Summary of the Invention

[0008] In view of the technical problems existing in the background art, the present invention provides a method for processing nuclear reactor internals. By adopting a machining method with a nested drill and optimizing the machining method, the material utilization rate can be effectively improved and the machining cost can be reduced, and the machining quality can also be further improved.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A method for fabricating nuclear reactor internals includes the following steps:

[0011] Step 1: Draw a cross center line on the disc-shaped forging to be processed, and mark the angle on the disc-shaped forging with a vibrating pen, and extend the marking line to the outer circle;

[0012] Step 2: Drill a dotted hole at the center point of the disc-shaped forging to determine the positions of the remaining holes on the disc-shaped forging, and mark the dotted hole at the center position.

[0013] Step 3: After confirming the hole positions, use a nesting drill to drill the holes at the marked points. The drilling depth should be greater than half the thickness of the board. When drilling, a verified nesting tool and drilling plan should be used. During the processing, it is necessary to pay attention to whether the chip removal is normal.

[0014] Step 4: Drive wooden wedges into the half-completed hole. The female wooden wedges should be conical and fixed inside the hole.

[0015] Step 5: After the wooden wedges are firmly fixed, flip the disc-shaped forging over and align it with the cross center line as a reference. Repeat the work in Step 2 and drill holes for positioning on the reverse side of the disc-shaped forging.

[0016] Step 6: Repeat the work in Step 3 to drill through the hole;

[0017] Step 7: Mark the remaining material mandrel inside the hole, weld a nut to the end of the remaining material inside the hole, and then knock the wooden wedge out of the hole.

[0018] Step 8: Connect the nut at the end of the scrap material to the eye bolt, connect the other side of the eye bolt to the overhead crane, and use the overhead crane to lift the scrap material out.

[0019] In the preferred embodiment, in steps three and six, the nesting drill uses a vertical feed method for machining.

[0020] In the preferred embodiment, in steps three and six, the insert of the nesting drill is connected to the tool body through inner and outer tool holders. The tool body is provided with two spiral chip removal grooves, providing a large chip removal space. The middle part of the nesting drill is a cooling ring, the interface of which is consistent with the machine tool coolant pipe interface. During the drilling process, the coolant flows through the cooling ring and through the tool body, and is sprayed out from the bottom.

[0021] In the preferred embodiment, in steps three and six, when the drilling depth reaches 50mm, the cutting tool is lifted to remove chips, and the chip removal is done manually.

[0022] This patent can achieve the following beneficial effects:

[0023] 1. This invention, by employing a nested drilling process, can significantly reduce processing costs and effectively improve processing efficiency compared to the traditional drilling and boring process.

[0024] 2. After the invention is modified to be processed by nesting, the raw material of the mandrel inside the hole can be retained and can be used to process other materials of the stack components such as support column flanges and pins;

[0025] 3. This invention, by drilling holes on both sides, can effectively improve the problem of the cutting tool breaking after the die has penetrated deep into the casing, and also helps to remove the debris. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0027] Figure 1 This is a schematic diagram of the internal components structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the nesting drill bit structure of the present invention;

[0029] Figure 3 This is a flowchart of the processing method of the present invention; Detailed Implementation

[0030] Example: Drilling of the upper support plate of the internal components of Hualong One reactor (disc-shaped part, outer diameter φ3612mm, thickness 368mm, with 69-φ241 through holes and other small holes).

[0031] Step 1: Draw a cross center line on the disc-shaped forging to be processed, and use a vibrating pen to mark angles of 0°, 180°, 90° and 270° on the disc-shaped forging, with a character height of 12mm, and extend the marking line to the outer circle;

[0032] Step 2: Drill a dotted hole at the center point of the disc-shaped forging to determine the position of the 69-φ229 holes on the disc-shaped forging. Draw the φ224 / φ229 circumferential line of the 69-φ229 holes and drill dots at the center of the 69 hole positions.

[0033] Step 3: After confirming the hole positions are correct, use a nesting drill to drill φ225 holes at the marked locations, nesting 69 holes to the required φ225 size.

[0034] The drilling depth is 200mm. The nesting tool is Sandvik 250489232R136478_D2, and the insert is WCMX06T308-58 235. The cutting parameters are: V=100m / min, f=0.04~0.05mm / r. During the drilling process, the tool is lifted every 50mm and manual chip removal is performed.

[0035] Step 4: Drive 4 wooden wedges into the half-finished hole. The female wooden wedges are conical and fixed in the hole. Their main purpose is to fix the remaining core rod when it is inserted from the back, so as to prevent the core rod from falling and damaging the blade or the worktable.

[0036] Step 5: After the wooden wedges are firmly fixed, flip the disc-shaped forging over and align it with the cross center line as a reference. Repeat the work in Step 2 and drill holes on the reverse side of the disc-shaped forging for positioning.

[0037] Step 6: Repeat step 3 to pass through the φ225 hole;

[0038] Step 7: Mark the remaining material mandrel in the hole, weld a nut to the end of the remaining material in the hole, and then knock the wooden wedge out of the hole.

[0039] Step 8: Connect the nut at the end of the scrap material to the eye bolt, connect the other side of the eye bolt to the crane, and use the crane to lift the scrap material out.

[0040] Comparative analysis of the time and cost of traditional process and nesting drilling (taking the above support plate as an example)

[0041] Processing method machine tools Single-hole working time Number of holes Taiwan time fee Total cost Drilling and boring radial drilling machine 29h 69 60 yuan / hour 120,060 yuan Nesting drill boring and milling machine 2.5h 69 260 yuan / hour 44,850 yuan

[0042] The total reduction is approximately 75,210 yuan;

[0043] In addition, the core area has a specification of φ189×368, with a total of 69 pieces and a total weight of 5.2t. The unit price of nuclear power forging material is about 285,000 yuan / t, and the material cost is 1,482,000 yuan.

[0044] In summary, modifying the upper support plate hole machining to the solution of this invention can save approximately RMB 1.557 million in costs. Additionally, other plate-type parts within the reactor internals, such as the upper core plate, lower core plate, and core support plate, result in a total cost saving of RMB 4.2 million per unit.

[0045] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The various technical features described in the present invention can be combined with each other without conflict. The scope of protection of the present invention should be the technical solution described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for processing internal components of a nuclear reactor, characterized in that, Includes the following steps: Step 1: Draw a cross center line on the disc-shaped forging to be processed, and mark the angle on the disc-shaped forging with a vibrating pen, and extend the marking line to the outer circle; Step 2: Drill a dotted hole at the center point of the disc-shaped forging to determine the positions of the remaining holes on the disc-shaped forging, and mark the dotted hole at the center position. Step 3: After confirming the hole positions, use a nesting drill to drill the holes at the marked points. The drilling depth should be greater than half the thickness of the board. When drilling, a verified nesting tool and drilling plan should be used. During the processing, it is necessary to pay attention to whether the chip removal is normal. Step 4: Drive wooden wedges into the half-completed hole. The female wooden wedges should be conical and fixed inside the hole. Step 5: After the wooden wedges are firmly fixed, flip the disc-shaped forging over and align it with the cross center line as a reference. Repeat the work in Step 2 and drill holes for positioning on the reverse side of the disc-shaped forging. Step 6: Repeat the work in Step 3 to drill through the hole; Step 7: Mark the remaining material mandrel inside the hole, weld a nut to the end of the remaining material inside the hole, and then knock the wooden wedge out of the hole. Step 8: Connect the nut at the end of the scrap material to the eye bolt, connect the other side of the eye bolt to the overhead crane, and use the overhead crane to lift the scrap material out.

2. The method for processing nuclear reactor internals according to claim 1, characterized in that: In steps three and six, the nesting drill uses a vertical feed method for machining.

3. The method for processing nuclear reactor internals according to claim 1, characterized in that: In steps three and six, the insert of the nesting drill is connected to the tool body through inner and outer tool holders. The tool body is provided with two spiral chip removal grooves, providing a large chip removal space. The middle part of the nesting drill is a cooling ring, the interface of which is consistent with the machine tool coolant pipe interface. During the drilling process, the coolant flows through the cooling ring and through the tool body, and is sprayed out from the bottom.

4. The method for processing nuclear reactor internals according to claim 1, characterized in that: In steps three and six, when the drilling depth reaches 50mm, the cutting tool is lifted to remove chips manually.

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