JP4154463B2 - Underwater remote drilling tool and method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an underwater remote drilling tool, and more particularly to an underwater remote drilling tool for drilling a core shroud support plate between two jet pump diffusers in a reactor vessel.
[0002]
[Prior art]
It is sometimes necessary to machine existing internal components in order to maintain and modify the reactor vessel components. One such repair involves the addition of several (usually four) restraining rods that are anchored to the lower shroud support plate area and extend upwardly on the top of the shroud cylinder. Connected to The design of each system will vary somewhat due to the different shapes of each plant, but common to most designs is the need to drill holes in the shroud support plate near the jet pump diffuser to install repair parts. is there. The dominant nature of the reactor vessel internals is that substantially all work is done in the field, ie in the water (depth reaching 100 feet), while keeping the operator's radiation exposure to a minimum. Foreign matter exclusion (FME) is extremely important because foreign matter adversely affects nuclear fuel, monitoring devices, coolant / moderator flow, and the like. Since the work area is usually very small, all tools must be compact and remotely operated.
[0003]
A conventional method for processing a reactor vessel internal component uses a metal removal method called electric discharge machining (EDM). The generation of electric sparks across the small gap between the electrode and the workpiece causes the material to be substantially eroded and produces by-product chips. As already known, the chips left after the EDM process do not present a harmful problem as foreign matter. Since there is no actual mechanical reaction between the workpiece and the electrode, the developed tools do not have to be very rigid and therefore tend to place multiple tools in a narrow crowded area.
[0004]
The EDM method is widely used but is a very slow and time consuming method. The typical best time to drill a 7.6 cm (3 inch) diameter hole in a 3.8 cm (1.5 inch) thick workpiece is 16 hours or more. The effects of tool failure due to ambient pressure, side arcing, electrode wear, drilling, chip flushing, and long dive times can all lead to excessive delays during the EDM process. In addition, inherent to the EDM method is the rapid heating and cooling cycle that occurs with each spark. This rapid heating and cooling creates a recast layer on the work surface. Depending on the material being processed, it is sometimes necessary to perform grinding or honing of the recast layer to remove detectable microcracks.
[0005]
Traditional machining in reactor vessels has historically not been attempted due to the generation and retention requirements of the generated chips. Therefore, it is necessary to improve the machining productivity and method reliability of the reactor vessel internal components.
[0006]
OBJECT OF THE INVENTION
Accordingly, it is an object of the present invention to provide an underwater remote drilling tool and method that reduces the processing time of existing components within a reactor vessel. Another object of the present invention is to provide an underwater remote drilling tool that utilizes standard tool usage, while maintaining control of all foreign objects and minimizing adverse effects on the material being drilled. Another object of the present invention is to provide an underwater remote drilling tool with improved tool reliability.
[0007]
SUMMARY OF THE INVENTION
These and other objects of the present invention are achieved by providing a support base that can be inserted between two jet pump diffusers in a reactor vessel including a core shroud and a core shroud support plate to support a processing tool. Is done. The support base includes a first leg having a first extendable member that can be engaged with the core shroud, a second leg having a second extendable member that can be engaged with one of the two jet pump diffusers, And a third leg having a third extendable member that can engage with the other of the jet pump diffuser. The support base can be positioned on the core shroud support plate and the support base does not substantially move between the vessel wall and the core shroud when the first, second and third extendable members are extended. To be fixed. The support base may include a centering device disposed substantially between the second and third legs, the centering device positioning the support base in the middle between the two jet pump diffusers.
[0008]
According to another aspect of the present invention, a support base for supporting a processing tool has a first leg having a first extendable member, and a second leg spaced from the first leg and having a second extendable member. And a third leg separated from the first and second legs and having a third extendable member, wherein the first, second and third extendable members are selectively extended by a hydraulic drive. Can be withdrawn and retracted. In a preferred configuration, the support base is provided with an additional element, for example a substantially centrally provided opening to allow access to the support base support surface of the processing tool, substantially coaxial with the opening and the A sealing member disposed between the opening and the support surface and a leveling structure for leveling the support base on the support base support surface may be included. The support base may further include a structure for receiving at least one positioning dowel of the processing tool and a structure for receiving at least one securing member of the processing tool. Further, the support base can include a centering device disposed substantially between the second and third legs. This centering device positions the support base in the middle between both jet pump diffusers.
[0009]
Also provided is a method for securing a support base for a processing tool between two jet pump diffusers in a reactor vessel. The method includes positioning the support base between the core shroud and the vessel wall, positioning the support base between both jet pump diffusers, and first, second and third extendable members with a hydraulic drive. Extending the first leg into engagement with the core shroud and the second and third legs into engagement with both jet pump diffusers, respectively.
[0010]
According to another aspect of the invention, a drilling tool is provided for drilling holes in the shroud support plate. The drilling tool includes a rotatable spindle, a substantially cylindrical drill bit coupled to the spindle, a sleeve that surrounds the drill bit and is non-rotatably secured so as not to rotate with the bit, A chip collecting system for collecting chips generated therein. A guide ring can be provided around the connection area between the spindle and the drill bit, and the chip collection system includes a fluid inlet in communication with the guide ring and the spindle. The drill bit may include the following grooves: a groove having a groove inlet at the cutting end of the drill bit and a groove outlet at the spindle end of the drill bit. The guide ring includes a ring outlet disposed near the groove outlet, and the chip collection system further includes the groove and the ring outlet. The chip collection system may further include a mesh chip basket in communication with the ring outlet. The mesh chip basket has a shape that collects chips generated during drilling.
[0011]
A housing may be provided that surrounds the spindle, drill bit, and sleeve. The housing includes a drilling tool substrate and has a positioning pot facing the shroud support plate. The positioning dowel is formed to fit within a corresponding positioning hole in the support base fixed to the shroud support plate. The drilling tool substrate further includes a mounting member that secures the drilling tool to the support base, and may alternatively or additionally include a hydraulic swing clamp configured to penetrate the swing clamp hole of the support base.
[0012]
The drilling tool can be further provided with a DC servo motor and a feed motor. Both motors are operatively connected to the spindle and serve to rotate the spindle and drill bit and feed the spindle and drill bit, respectively. The rotation speed and feed speed of the spindle and drill bit are variable. A controller communicates with the DC servo motor and the feed motor and controls the feed rate based on the rotational speed.
[0013]
A method is also provided for drilling a core shroud support plate using a drilling tool. In this method, the drilling tool is fixed near the core shroud support plate, water is pumped to flow between the cutting end of the drill bit and the shroud support plate, and the drill bit is turned to the hole in the shroud support plate. Including opening. The water preferably enters the inlet, flows through the spindle, flows into the center of the drill bit, flows between the cutting end of the drill bit and the shroud support plate, enters the groove inlet of the drill bit, and flows out of the groove outlet. Flow into the mesh chip basket.
[0014]
According to another aspect of the invention, an electrical discharge machining (EDM) tool is provided that can be inserted into a reactor vessel to machine a portion of a shroud support plate. The EDM tool includes a support frame, a carriage assembly movably coupled to the support frame, and a spindle assembly rotatably coupled to the carriage assembly. The EDM tool includes additional elements, for example, a first drive mechanism that drives the carriage assembly in the axial direction along the support frame, a second drive mechanism that rotatably drives the spindle assembly, the carriage assembly, and the spindle assembly. At least one radial bearing that facilitates rotation of the spindle assembly relative to the carriage assembly, a vacuum structure that sucks chips while the cutting electrode processes the shroud support plate, and is movably mounted on the support frame A collet assembly including a connected collet carriage and a collet extension attached to the collet carriage. The collet extension is formed to fit within the spindle assembly, and when the collet extension is disposed within the spindle assembly, the collet carriage rests on the carriage assembly.
[0015]
The support frame can include a rail to which the carriage assembly is coupled. The EDM tool may further include a linear bearing disposed between the rail and the carriage assembly. This linear bearing facilitates axial translation of the carriage assembly along the rail. The spindle assembly can include a substantially cylindrical cutting electrode disposed at one end thereof and capable of rotating with the spindle assembly. The cutting electrode is formed to process the shroud support plate.
[0016]
A counterbore assembly may be coupled to one end of the spindle assembly and a counterbore positioning mechanism coupled to the carriage assembly. The counterbore assembly includes an EDM electrode that is formed to form a counterbore surface on the opposite side of the shroud support plate from the EDM tool. The EDM electrode is preferably pivotable between a transport position and a counterbore position, the counterbore positioning mechanism including a pivot finger, coupled to the drive mechanism and capable of passing through the opening of the EDM electrode. The drive mechanism drives the pivot finger to cause displacement between the EDM electrode transport position and the counterbore position. The drive mechanism may include an air cylinder and an air cylinder shaft, and the counterbore positioning mechanism may further include a bearing assembly attached to one end of the air cylinder shaft. A pivot finger is rotatably connected to the bearing assembly and can rotate about an air cylinder axis.
[0017]
A method for processing a shroud support plate is also provided. The method includes inserting the EDM tool into a substantially cylindrical hole previously formed in the shroud support plate, machining the shroud support plate using the EDM tool, and removing the slag from the shroud support plate. Forming holes in the shroud support plate. A method of forming a counterbore surface is also provided.
[0018]
The present invention can remove material in about 5% of its material removal time compared to conventional EDM methods. Furthermore, foreign matter elimination (chip retention) is achieved by providing a fully closed tool housing that acts as a container for chips generated during machining. In addition, the present tool and method provide an excellent surface finish (compared to conventional EDM methods) so that subsequent grinding can be omitted.
[0019]
These and other aspects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings.
[0020]
[Description of Examples]
FIG. 1 is a perspective view showing a nuclear reactor vessel, which is partially cut away to show the internal components of the vessel. A core shroud 10 is supported on a core shroud support plate 14 by a core shroud support assembly 12. A plurality of holes 16 are formed circumferentially along the outer periphery of the core shroud support plate 14 and receive a corresponding plurality of jet pump diffusers 18 which are disposed between the vessel wall 20 and the core shroud 10. ing.
[0021]
Holes may need to be formed in the core shroud support plate 14 between the jet pump diffusers 18 to maintain and modify the reactor vessel components. As can be seen from FIG. 1, any machining operation of the shroud support plate 14 must be carried out in water in a very limited working area.
Referring to FIG. 2, the present invention provides an underwater remote drilling tool that quickly and efficiently forms holes in the core shroud support plate 14. The present invention includes a support base 100 that can be securely attached to the shroud support plate 14 between two jet pump diffusers 18. The support base 100 has a shape that supports a drilling tool 200 that forms a first hole in the core shroud support plate 14 and an EDM tool 300 that forms a second hole in the core shroud support plate 14. The support base 100, the drilling tool 200, and the EDM tool 300 will be described in detail with reference to FIGS. In these drawings, the same reference numerals are used to represent the same elements.
[0022]
3A is a plan view of the support base 100, and FIG. 3B is a cross-sectional view taken along line III-III in FIG. 3A.
The support base 100 is substantially a T-shaped member and includes a first leg 102 that forms a T-shaped base, and a second leg 104 and a third leg 106 that form a T-shaped lateral portion. . An opening 108 is provided at a substantially central position between the second and third legs 104, 106 and is axially aligned with the first leg 102. The opening 108 helps the drilling tool 200 and EDM tool 300 access the shroud support plate 14 when the support base 100 is secured in place.
[0023]
After positioning the support base 100 between the two diffusers 18, the support base 100 is positioned at the center between the two diffusers 18 by the centering device 110. The centering device 110 includes a pair of centering arms 110A, 110B that move parallel together to abut against both diffusers 18 and position the support base 100 in the middle between the diffusers 18. The centering device 110 is a known device, and any structure that positions the support base in the middle between the diffusers 18 can be used. Therefore, detailed description of the centering device 110 is omitted.
[0024]
In order to properly process the shroud support plate 14 using the support base 100, the support base 100 must be placed horizontally on the surface of the shroud support plate 14. The support base 100 includes a plurality (preferably three) threaded leveling feet 112 that can be displaced axially to level the support base 100. The leveling feet 112 preferably have hexagonal openings 113 that are shaped to receive adjustment tools (not shown). In addition, the support base 100 includes two bubble levels 114 disposed on the second and third legs 104, 106 to ensure that the support base 100 is level before processing. During the operation, after the support base 100 is lowered between the two diffusers 18, an operator who is at least 24 m (80 feet) above the shroud support plate 14 uses a sighting device (not shown) to set the bubble level 114. While checking, the horizontal adjustment foot 112 is adjusted with an adjustment tool.
[0025]
The support base 100 is lowered into the reactor vessel, and when the support base 100 is supported by the shroud support plate 14, the first leg 102 faces the core shroud 10 and the second and third legs 104, 106 are adjacent. Partially enclosing the jet pump diffuser 18 and the outer surfaces of the second and third legs 104, 106 (ie, the T-shaped lateral portion) face the container wall 20. The first leg 102 includes a first extendable member 116, preferably operated hydraulically. The first extendable member 116 can extend to engage the core shroud 10. The second leg 104 includes a second extendable member 118 which is also preferably hydraulically operated and engages one of the jet pump diffusers 18. The third leg 106 includes a similar extendable member 120 that can engage the other of both jet pump diffusers 18. After the support base 100 is centered by the centering device 110 and placed horizontally by using the leveling feet 112 and the bubble level 114, the first, second and third extendable members 116, 118 and 120 are operated with hydraulic pressure to securely fix the support base 100 in place between the two diffusers 18.
[0026]
The support base 100 also has two positioning dowels 122 disposed on either side of the opening 108. The positioning dowel hole 122 has a shape for receiving a positioning dowel (described later) fixed to the drilling tool 200 and the EDM tool 300. As the tool positioning dowel enters the positioning dowel hole 122, the tool is secured to the support base 100 by screwing a threaded bolt into the respective screw hole 124 of the support base 100. Another opening 126 located approximately in the middle between the second and third legs 104, 106 is formed in the support base 100 and receives a swing clamp (described later) of the processing tool.
[0027]
The cable 128 is swingably attached to the support base 100, thereby lowering the support base 100 into the reactor vessel. When the support base 100 is lowered into the reactor vessel, the support base 100 is oriented in a substantially vertical direction, so that it can be easily placed between the vessel wall 20 and the core shroud 10. As the support base approaches the shroud support plate 14, a second cable 130 is used to change the orientation of the support base 100 in the horizontal direction. These cables may be of any form and the present invention is not limited to that illustrated and described.
[0028]
Referring to FIG. 3B, a generally circular sealing member 132 is disposed coaxially with the opening 108 and radially outward thereof. The sealing member 132 prevents a material generated as a result of the processing operation from contaminating water in the reactor vessel. The first, second and third extendable members 116, 118, 120 are disposed above the opening 108 and the sealing member 132 so that the extendable members 116, 118, 120 are hydraulically operated. When this occurs, the sealing member 132 is pressed by a downward force to make a sealing engagement with the shroud support plate 14.
[0029]
After fixing the support base 100 in place between the jet pump diffusers 18, the drilling tool 200 is lowered into the container 100 to the base 100 and the machining operation is started. FIG. 4 is a front view of the drilling tool 200. As described above, the drilling tool is attached to the support base 100 fixed in advance between the jet pump diffusers 18 in the reactor vessel. The drilling tool 200 includes a tool housing 201 having a drilling tool substrate 202 at the lower end thereof. Two positioning dowels 204 are fixed to the bottom of the substrate 202 and are received in the positioning dowel holes 122 of the support base 100. The drilling tool substrate 202 also includes a swing clamp 206 that is received in the swing clamp receiving opening 126 of the support base 100. The swing clamp 206 is a stop clamp operated by hydraulic pressure. The swing clamp 206 is inserted into the swing clamp opening 126 and then rotated and retracted by hydraulic pressure to sandwich the support base 100. A pair of set screws 208 are provided on the upper surface of the drilling tool substrate 202 so as to engage with the screw holes 124 of the support base 100. The set screw 208 is tightened by an operator in a position above the reactor vessel using a set tool. After the drilling operation is complete, the tool is removed by reversing the order of the steps described above.
[0030]
Referring to FIG. 5, a rotatable spindle 222 is disposed in the housing 201 of the drilling tool 200 and is connected to a DC servo motor. An industry standard trepan drill bit 224 is fixed to the rotatable spindle 222 and can rotate with the spindle 222. The standard drill bit includes two carbide inserts that define an inner cutter 226 and an outer cutter 228. The drill bit 224 is cylindrical and has a hollow cylindrical central portion. At least one groove 230 is cut in the drill bit. Inner cutter 226 is secured adjacent to the inner surface of the drill bit and outer cutter 228 is secured adjacent to the outer surface of the drill bit. During rotation, the areas machined by the inner and outer cutters 226, 228 overlap and form a continuous workpiece. A stainless steel sleeve 232 is secured against rotation around the drill bit 224. During the drilling process, the stainless steel sleeve 232 is fed with the drill bit 224.
[0031]
A guide ring 234 surrounds the bottom of the spindle 222 and the top of the drill bit 224 and surrounds an area where the spindle 222 and the drill bit 224 are connected. The guide ring 234 has a water inlet 212 and a water outlet 216 described below. An inlet 212 is formed in the guide ring 234 and the spindle 222 and guides water into the central tubular area 236 of the drill bit 224. Water reaches the work surface through the central cylindrical area 236 and acts as a blade lubricant on the surface of the shroud support plate 14 (to make the tool hydroplaning). Conventional lubricants cannot be used due to restrictions on the introduction of harmful elements into the reactor environment.
[0032]
As high pressure and large amounts of water pass over the surface to be machined, chips generated as a result of the drilling operation enter the groove inlet 238 through small notches near the carbide inserts, the inner and outer cutters 226, 228. Carried. Water and chips in the groove inlet 238 flow to the groove outlet 240 at the spindle end of the drill bit and through the outlet 216. The amount of water flowing through the drill bit is preferably in the range of about 227-303 liters (60-80 gallons) per minute (lpm (gpm)) and the pressure is in the range of about 414-552 kpa (60-80 psi). It is in. As a result of this structure and a large amount of high-pressure water, all the chips generated during the drilling operation are flowed to the chip basket and do not adversely affect the reactor vessel.
[0033]
An important advantage of the present invention is that the feed rate can be varied according to the rotational speed of the drill bit. The DC servo motor and the feed motor are controlled by a basic control device 221 that controls the feed speed in accordance with the rotational speed of the drill bit. In the preferred embodiment, the drill bit has a diameter of about 11 cm (4.3 inches). Spindle 222 is rotated in the range of 90-140 rpm and fed in the range of 6350-11430 m (250,000-450,000 inches) per minute.
[0034]
4 and 5, the drilling tool 200 includes an improved chip receptacle 210. The chip housing 210 includes a water inlet 212 that guides water from the water hose 214 to the drill bit 224 and the surface to be machined. Chips generated during the machining operation are carried to the outlet 216 by a large amount of high-pressure water. Water and chips flow through the outlet hose 218 and into the chip basket 220. Chip basket 220 is a mesh basket having a mesh size of about 1550 holes per square centimeter (10000 holes per square inch). As a result, the chips are accommodated in the chip basket 220 and the water can continue to flow. If very small chips escape from the chip basket 220, such chips are probably very small and will not have an adverse effect.
[0035]
FIG. 6 is an exploded sectional view of the shroud support plate 14. The shroud support plate 14 is generally formed of three materials. The first layer 14A of the shroud support plate 14 is typically made of Inconel, the second layer 14B comprising the majority of the shroud support plate 14 is formed of a low alloy, such as carbon steel, and the third layer 14C of the shroud support plate 14 is Generally made of stainless steel. The drilling tool 200 forms a substantially circular hole 15 in the shroud support plate 14 over approximately 90% of the thickness of the shroud support plate 14. After removing the drilling tool 200 from the hole 15 and away from the support base 100, the EDM tool 300 is lowered into the reactor vessel. Similar to the drilling tool 200, the EDM tool 300 includes a structure that is adapted to be received by the support base 100, thereby securing the EDM tool to the support base 100.
[0036]
The EDM component of the apparatus removes material ligaments that remain after the drilling operation is completed. This ligament is about 1.9 cm (3/4 inch) from the bottom of the shroud support plate to be drilled. The exact thickness is obtained by ultrasonic testing (UT) of the shroud support plate prior to the start of drilling and by setting the desired depth in the tool controller. The EDM method begins after removal of the drilling component and after complete chip removal by aspiration and includes a visual inspection. Chip removal prior to hole formation by EDM in the support plate ensures chip-free penetration. As described below, the EDM tool engages and captures the slag top area for slag removal after cutting.
[0037]
Referring to FIGS. 7A and 7B, the EDM tool 300 has two forms: a cut form and a counterbore form. The cutting mode will be described with reference to FIGS. 7A, 8 and 9. FIG.
The cutting configuration mainly includes a spindle assembly 302 and a collet assembly 304. As shown in FIG. 9, the spindle assembly 302 includes a carriage assembly 306. Each form includes a support frame 301 and has a pair of rails 303. A structure for attaching the EDM tool 300 to the support base 100 is attached to the bottom plate of the support frame 301. The carriage assembly 306 includes a pair of radial bearings 308 and is shaped to slide axially along the rail 303. A spindle 310 is rotatably supported by a carriage assembly 306. A radial bearing 308 is provided between the carriage assembly 306 and the spindle 310. In the cutting configuration, the cutting electrode 314 is fixed to one end of the spindle assembly 310. The carriage assembly 306 is preferably moved along the rail 303 by a ball screw driven by a motor, and the second motor rotates the spindle assembly 310 within the carriage assembly 306. Those skilled in the art will envision alternatives for driving the carriage assembly 306 along the rail 303 and rotating the spindle assembly 310.
[0038]
The collet assembly 304 includes a collet carriage 316 and a collet extension 318 coupled to the collet carriage 316. Collet extension 318 is adapted to be non-rotatably inserted into spindle 310 of spindle assembly 302 and includes a linear bearing 320 that rests on rail 303 of the support frame similar to linear bearing 308 of carriage assembly 306. Yes. Collet carriage 316 is free to move on rail 303 and rests on carriage assembly 306 by gravity. FIG. 7A shows the carriage assembly and spindle assembly 302 configured as a unit in a cut configuration.
[0039]
The support frame 301 further includes a stop bar 322 to limit the axial displacement of the collet assembly. During operation, the collet carriage 316 is free to move on the rail 303 so that the collet assembly moves with the spindle assembly.
Collet extension 318 includes a substantially cylindrical collet 324 at one end, the collet being divided into four segments and shaped to grip a slag of material cut from the shroud support plate. . The collet 324 is operated by a hydraulic cylinder 326 that drives the tubular member 328 onto the collet 324. After the collet 324 is positioned on the slag, the hydraulic cylinder 326 is operated to drive the tubular member 328 downward onto the collet 324 and deflect the collet inward to grip the slag. The outer surface of the collet 324 preferably has a 10 degree taper and the tubular member 328 is formed to have a corresponding 10 degree taper.
[0040]
The process of the EDM tool 300 in the cutting mode will be described with reference to FIGS. 10A to 10D.
The EDM tool 300 is lowered into the reactor vessel and connected to the support base 100 using a positioning dowel 204 and a swing clamp 206 fixed to the support frame 301. The collet assembly 304 inserted into the spindle assembly 302 follows the spindle assembly 302 and enters the hole 15 formed by the drilling tool 200 due to the axial displacement of the spindle assembly 302 by the ball screw. In FIG. 10B, the axial displacement of the collet assembly 304 is stopped by a stop bar 322. The stop bar 322 has a shape that stops the collet assembly 304 so that the collet 324 surrounds the top of the slug. By operating the hydraulic cylinder 326 and pressing the tubular member 328 onto the collet 324, the collet 324 is bent radially inward to grip the slag.
[0041]
The spindle assembly 302 continues axial displacement into the bore 15 until the cutting electrode 314 is positioned near the remainder of the shroud support plate 14. The spindle assembly 302 with the cutting electrode 314 attached is then rotated to apply the conventional EDM method to the remainder of the shroud support plate 14. Since the EDM method is a publicly known method, further explanation of its details is omitted. Known suction tools aspirate chips during the EDM process. Referring to FIG. 10D, when the EDM process is complete and the shroud support plate 14 has been punctured, the spindle assembly 302 is driven axially upward to move the collet assembly 304 to the retracted position, thus allowing the slug to flow into the shroud support plate 14. Remove from.
[0042]
As an alternative to the EDM method of machining the final portion of the shroud support plate 14, a drilling tool is further developed to perform a “can opener” type of finish cut that drills and rotates the final thickness of metal instead of removing the material by machining. You may go. Monitor the exact depth of cut (perform initial thickness measurement using UT) to help drill the remaining ligaments.
[0043]
FIG. 7B shows a counterbore EDM tool 300. After the slag has been removed from the shroud support plate 14, the EDM tool is converted to a counterbore configuration to perform a counterbore action. The counterbore action forms a counterbore surface on the underside of the hole over a specific distance around the hole. The counterbore surface makes the bottom of the hole perpendicular to the hole axis.
Referring to FIGS. 7B and 11, the spot facing assembly 330 includes an EDM tool support frame 301 and a rail 303. The carriage assembly 306 of the spot facing assembly 330 is the same as the carriage assembly 306 of the spindle assembly 302. Further, the spindle 310 of the spot facing assembly is the same as the spindle 310 of the spindle assembly 302. The cutting electrode 314 is removed from the spindle 310 and a counterbore attachment 332 is attached to the end of the spindle 310.
[0044]
The counterbore mounting portion 332 includes a pivotable EDM electrode 334 that countersits the bottom surface of the shroud support plate 14. The electrode 334 can be pivoted between a transport position (FIG. 7B) and a counterbore position (FIG. 11) by a counterbore positioning mechanism 336 (described later). Referring to FIG. 12, the electrode 334 pivots about a central axis 338 and has an elongated opening 340 that receives a portion of the counterbore positioning mechanism 336.
Counterbore positioning mechanism 336 includes an air cylinder 342 and has an air cylinder shaft 347 attached to a bearing assembly 346. The positioning mechanism 336 is disposed within the spindle 310 and is fixed to the carriage assembly 306 so that it does not rotate with the spindle 310. A rotatable pivot finger 348 is attached to the bearing assembly 346 and engages an elongated slot 340 in the electrode 334. One end 350 of the pivot finger 348 has a cross member, which is provided perpendicular to the pivot finger 348 and engages the electrode 334, which causes the electrode 334 to sit against the transport position according to the position of the air cylinder 342. Pivot between positions. The bearing assembly 346 allows the pivot finger 348 to rotate with the spindle 310 and the electrode 334 and allows the air cylinder 342 to remain stationary. Members 344 and 345 limit the pivoting of electrode 334 in the transport position and the counterbore position, respectively.
[0045]
The operation of the spot facing EDM tool will be described with reference to FIGS. 13A to 13C. 13A to 13C show the shroud support plate 14 with the slag removed. The support frame 301 and the rail 303 of the EDM tool remain fixed to the support base 100 described above. When the counterbore assembly is held above the hole in the support plate 14, the air cylinder 342 is in its retracted position so that the cross member at the end 350 of the pivot finger 348 engages the elongated slot 340 in the electrode 334. The electrode 334 is held in its transport position.
[0046]
As shown in FIG. 13B, the carriage assembly 306 is lowered so that the counterbore assembly is inserted into the hole in the support plate 14. The carriage assembly 306 continues to move downward in the axial direction until the electrode 334 passes over the bottom surface of the support plate 14. At this time, the air cylinder 342 is operated to protrude the air cylinder shaft 347, thereby pivoting the electrode 334 to its counterbore position. Then, when the carriage assembly 306 is retracted, the counterbore electrode 334 is adjacent to the bottom surface of the shroud support plate 14 as shown in FIG. 13C. Next, a counterbore surface is formed on the bottom surface of the shroud support plate 14 by performing a conventional EDM method using a counterbore electrode (see FIG. 6). Chips generated during the EDM process are sucked by a conventional vacuum apparatus. After the EDM process is completed and the counterbore surface is formed, when the carriage assembly 306 lowers the counterbore mounting portion 332 below the bottom surface of the shroud support plate 14, the air cylinder 342 retracts the air cylinder shaft 347. The electrode can pivot to its transport position. The carriage assembly 306 is then displaced axially upward to remove the counterbore attachment 332 from the hole. This completes the process.
[0047]
As shown in FIG. 12, the electrode has a substantially circular shape with the parallel edges removed. The counterbore surface formed by the electrode 334 preferably has a slight radius at the boundary between the counterbore surface and the aperture of the hole (see FIG. 6). This small radius helps to accommodate the shape of the hardware that fits into the hole.
In an alternative configuration (not shown), the drilling tool is shaped to form a pair of holes in the top perimeter of the shroud. This drilling tool includes two independent spindles housed in a frame, allowing the formation of both holes in a single tool configuration.
[0048]
Tool positioning is achieved by supporting the frame away from the guide projections, which are oriented in the same orientation as the holes to be formed. The relationship between these holes is based on the distance from the shelf directly above the tool to the hole. Once supported by the guide projection, the tool is lifted and is in direct contact with the shroud shelf, providing a fixed position for the hole. In order to substantially support the tool (absolute stiffness is required due to the nature of the method, the reaction force applied, etc.), multiple telescopic cylinders (supported back to the required stroke) are extended horizontally. Press the tool face against the shroud wall. The tool is substantially fixed in place by the horizontal locking cylinder and the shroud shelf stop.
[0049]
The device is designed to feed all generated chips back into the tool housing with the tool securely fixed to the workpiece. Actual cutting is accomplished by using a “standard” Hougen Rotabroach tool bit. This type of cutter is an integral spiral grooved multi-tooth trepan type cutter. Having a large number of cutting teeth and making a core with that cutting is desirable given that it minimizes horsepower requirements (relatively reduces the tool package) and produces relatively few chips. is there. The generated chips are long helical. Due to the long helix shape of the chips (which can cause helical chips if folded or bent), this type of tool bit is ideal for applications with a thickness of 5.1 cm (2 inches) or less. A plurality of chip breakers are placed in the tool housing once the helical chip exits the cut to facilitate chip compaction. Without a chip breaker, helical chips tend to “bird nest” around the tool spindle. Below the spindle, the chips fall to the bottom of the tool housing. This lower part acts as a chip container.
[0050]
Another feature of this alternative tool / method is how to hold the slag. The cutting bit design leaves a flange on the outlet side of the slag. During the cutting process, water is introduced and passes through the center of the tool bit. This cools the cutting edge and facilitates chip discharge. Stop the flow near the end of the cut. By monitoring the back side of the surface to be cut, it is possible to visually know when the cut is complete. As soon as the cutting is completed, suction is performed through the tool bit. This suction pulls the slag back into the tool bit. The spindle is then retracted into the tool housing and a pneumatically operated door covers the opening. This process is repeated for both holes.
[0051]
Full chip containment is achieved with the slag trapped and chips accumulated in the lower container. The entire tool is then loosened and removed from the vessel annulus. Once in place, the pneumatically actuated door is opened and the slag is placed in the final trash bin. Similarly, the container portion of the tool also has a pneumatically actuated trap door that is opened to process chips collected in the container portion.
[0052]
The spindles are driven by hydraulic motors, these motors have a shape that is perpendicular to the spindle (by the surrounding area), and power is transmitted via the worm gear. The feed shaft is similarly provided, but the power is transmitted to the feed acme lead screw. The spindle rotation and feed shaft are powered by TEA (reactor compatible hydraulic fluid) from a single source hydraulic skid. There is a valve body / solenoid housing that is integral with the top of the tool, which is pre-calibrated and sends hydraulic media to each axis as needed.
[0053]
As described above, what has been considered as the optimum embodiment of the present invention has been described. However, the present invention is not limited to the disclosed embodiment, and various modifications and equivalent configurations are possible within the scope of the present invention. I want you to understand.
[Brief description of the drawings]
FIG. 1 is a perspective view of a nuclear reactor vessel, partly cut away to show the internal components of the nuclear reactor vessel.
FIG. 2 shows components of the underwater drilling tool of the present invention.
FIG. 3A is a plan view of a support base according to the present invention.
3B is a cross-sectional view taken along line III-III in FIG. 3A.
FIG. 4 shows the external components of a drilling tool according to the present invention.
FIG. 5 is a cross-sectional view of the drilling tool of the present invention.
FIG. 6 shows the hole shape of the shroud support plate after the hole is formed.
FIGS. 7A and 7B show an EDM tool in a cut configuration and a counterbore configuration, respectively.
FIG. 8 shows a collet assembly of an EDM tool according to the present invention.
FIG. 9 shows a spindle assembly of an EDM tool according to the present invention.
10A-10D show steps performed by an EDM tool in a cut form.
FIG. 11 shows a counterbore assembly of an EDM tool according to the present invention.
12 is a cross-sectional view taken along line XII-XII in FIG.
13A-13C show steps performed by a counterbore EDM tool.
[Explanation of symbols]
10 Core shroud
14 Core shroud support plate
15 holes
18 Jet pump diffuser
20 container wall
100 Support base
102 1st leg
104 Second leg
106 3rd leg
108 opening
110 Centering device
112 Leveling feet
116 First extendable member
118 Second Extendable Member
120 Third extendable member
122 Dowel Hole
124 Screw hole
126 opening
132 Sealing member
200 Drilling tool
201 housing
202 Drilling tool substrate
204 Dowel
206 Swing clamp
208 Set screw
210 Chip housing part
212 Water inlet
216 Water outlet
220 Chip basket
221 Basic controller
222 spindle
224 drill bit
230 groove
232 sleeve
234 induction ring
238 Groove entrance
240 Groove exit
300 EDM tool
301 Support frame
302 Spindle assembly
303 rails
304 Collet assembly
306 Carriage assembly
308 Radial bearing
310 spindle
312 Radial bearing
314 Cutting electrode
316 Collet carriage
318 Collet extension
320 Linear bearing
324 Collet
326 Hydraulic cylinder
330 Counterbore assembly
334 EDM electrode
336 Spot facing positioning mechanism
342 Air cylinder
348 Pivot finger

Claims (6)

In a drilling tool (200) for drilling a core shroud support plate (14) of a core shroud (10) placed in a nuclear reactor vessel on site,
A drilling tool (200) positioned in a drilling position by being positioned on a support base (100) positioned on the core shroud support plate (14),
A rotatable spindle (222), a substantially cylindrical drill bit (224) connected to the spindle, a non-rotatable fixed and drill bit (24) surrounding the drill bit and not rotating with the bit. 224), and a housing (201) that surrounds the spindle (222), the drill bit (224), and the sleeve (232), with a gap (230, 238, 240) secured between them, and the housing A drilling device (200) having a tool substrate (202) fixed to 201;
A chip collection system (210) for collecting chips generated during drilling, and a connection area between the basket (220) for collecting chips and the spindle (222) and the drill bit (224) A cylindrical guide ring (234) disposed around the fluid inlet, a fluid inlet (212) communicating with the guide ring (234) and the spindle (222), and a hose for injecting fluid into the inlet (212) ( 214), a chip collection system (210) having a fluid outlet (216) provided in the guide ring (234) , and a hose (218) communicating the fluid outlet with the basket (220), The tool substrate (202) has at least one dowel (for mounting the drilling device (200) to the support base (100) in the field during drilling operations ( 204, 206), a drilling tool (200) characterized in that it is integrated with the chip collection system (210). The drilling tool according to claim 1, wherein the tool substrate (202) further includes an attachment member (208) for securing the drilling tool (200) to the support base (100). A predetermined processing tool (200, 300) is remotely positioned and fixed on the core shroud support plate (14) supporting the core shroud (10) placed in the reactor vessel, and the fixed processing is performed. A method of processing the shroud support plate (14) with a tool (200, 300),
A support base (100) capable of positioning and fixing itself by remote control with respect to the jet pump diffuser and a processing tool (200, 300) capable of positioning and fixing itself on the support base (14) are used. The core shroud support plate (14) of the core shroud (10) once mounted is processed on site,
The machining tool (200) includes a rotatable spindle (222), a substantially cylindrical drill bit (224) connected to the spindle, a sleeve (232) surrounding the drill bit, and the spindle ( 222), a drill bit (224) and a sleeve (232) surrounding the housing (201), and a chip collection system (220) for collecting chips generated during drilling,
The chip collection system (220) includes a cylindrical guide ring (234) disposed around a connection area between the basket (220) for collecting chips and the spindle (222) and the drill bit (224). ), An inlet (212) communicating with the guide ring (234) and the spindle (222), a hose (214) for injecting water into the inlet (212), and water from the guide ring (234) An outlet (216) and a hose (218) communicating the water outlet with the basket (220);
The method
Wherein the supporting base (100) is lowered to the vicinity of the machining position of the reactor vessel, said protraction arm (116, 118, 120) of the support base (100) by Shin out by remote control the support base ( 100) positioning itself, and further, a support base positioning step for fixing the support base (100) to the shroud support plate (14);
The drilling tool (200) is lowered onto the support base (100), and a tool fitting member (204, 204, 206) provided in advance on the drilling tool (200) and the support base (100). The base fitting member (122, 122, 126) provided in advance is fitted and the drilling tool (200) is positioned on the support base (100), whereby the shroud support plate (14 ) A drilling tool positioning process for positioning and fixing to the upper drilling position;
Turning the drill bit (224) to pierce the shroud support plate (100);
In parallel with the step of drilling, water is pumped through the inlet (212) between the cutting end (226, 228) of the drill bit (224) and the shroud support plate (14), And a step of drilling the core shroud support plate (14), further comprising the step of flowing to the chip collection system (210). The chip collection system (210) has a mesh chip basket,
The sinking step is
Pouring the water from the inlet through the spindle (222) into the center of the drill bit (224);
4. The water is allowed to flow between the cutting end (226, 228) of the drill bit and the shroud support plate (14) and further into the chip basket (220) . The method described. The support base (100)
A first leg (102) having a first extendable member (116); a second leg (104) spaced from the first leg and having a second extendable member (118); A third leg (106) spaced from the second leg and having a third extendable member (120) and said first, second and third extendable members (118, 118, 120) Is configured to be selectively extendable and retractable by a hydraulic drive,
The support base positioning step includes:
Positioning the support base (100) between the core shroud (10) and the wall (20) of the reactor vessel ;
Positioning the support base (100) between the two jet pump diffusers (18, 18);
The hydraulic drive device engages the first, second and third extendable members (116, 118, 120), the first leg (102) with the core shroud (10), and the first Extending the second and third legs (104, 106) to engage with both jet pump diffusers (18, 18), respectively. . Following the step of opening the hole and the step of flowing water,
An electrical discharge machining (EDM) tool (300) including a support frame (301), a carriage assembly (306) movably coupled to the support frame, and a spindle assembly rotatably coupled to the carriage assembly And further comprising an EDM processing step of further processing the hole drilled in the step of drilling the hole using
This EDM processing process
The EDM tool (300) was fixed to the support base (100) adjacent to the shroud support plate (14), and the EDM tool (300) was formed on the shroud support plate (14) in the drilling step. Inserting into the hole;
Machining the holes in the shroud support plate (14) using the EDM tool (300);
Removing the slag from the shroud support plate (14).

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