JP2004309363A - Device and method for extracting test sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample extraction device (70) of an electric discharge machining style for extracting a material sample (212) from structure components in a boiling water reactor. <P>SOLUTION: In an illustrative practice pattern, the sample extraction device (70) includes a base plate (72), a motor (74) mounted on the base plate (72) and an electrode assembly (76)coupled with the base plate (70) so that it can rotate and operatively joined to the motor (74). The electrode assembly includes an outer wall (128) forming an almost semicylindrical hollow cavity (126). The outer wall (128) includes a first conductive arc part (130), a second conductive arc part (132) and a third nonconductive arc part (134) located between the first and the second arc parts and coupled with them. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to nuclear reactor inspection, and more specifically to an electrical discharge machining (EDM) apparatus for obtaining a material sample inside a reactor pressure vessel.
[0002]
[Prior art]
The reactor pressure vessel (RPV) of a boiling water reactor (BWR) generally has a generally cylindrical shape and is closed at both ends, for example, by a bottom head and a removable top head. The upper guide member is generally spaced above the core plate in the RPV. A core shroud or shroud generally surrounds the core and is supported by a shroud support structure. Specifically, the shroud has a generally cylindrical shape and surrounds both the core plate and the upper guide. Between the cylindrical reactor pressure vessel and the cylindrically shaped shroud there is a space, ie an annular space.
[0003]
During operation, the internal structure of the BWR is susceptible to various types of corrosion and cracking. Stress corrosion cracking (SCC) is one well-known phenomenon that occurs in reactor components such as structural members, piping, fasteners, and welds that are exposed to hot water. Reactor components may be subject to other causes, such as differential expansion, operating pressure required to contain reactor cooling water, and residual stresses from welding, cold working and other non-uniform metallization. Subject to various related stresses. In addition, water chemistry, welding, heat treatment and radiation can increase the incidence of SCC on component metals.
[0004]
[Problems to be solved by the invention]
If cracks occur in these internal structures, it is desirable to characterize the mechanism of crack initiation by taking a small sample of the test material to perform a metallurgical evaluation. Metallurgical evaluation helps to understand the causes of corrosion and cracking, and thus to identify ways to mitigate further deterioration of the reactor internals.
[0005]
[Means for Solving the Problems]
In one form, an electrical discharge machining sample removal apparatus for removing a material sample from a structural component in a boiling water reactor is provided. The reactor includes a reactor pressure vessel and a shroud. The apparatus includes a base plate, a motor mounted to the base plate, and an electrode assembly rotatably coupled to the base plate and operatively coupled to the motor. The electrode assembly includes an outer wall that forms a substantially semi-cylindrical hollow cavity. An outer wall is disposed between the first and second arcuate portions, the first and second arcuate portions being conductive, the second arcuate portion being conductive, and the first and second arcuate portions. A non-conductive third arcuate portion coupled to the arcuate portion.
[0006]
In another aspect, an electrical discharge machining electrode assembly for a sample removal device is provided. The electrode assembly includes an outer wall forming a substantially semi-cylindrical hollow cavity. An outer wall is disposed between the first and second arcuate portions, the first and second arcuate portions being conductive, the second arcuate portion being conductive, and the first and second arcuate portions. A non-conductive third arcuate portion coupled to the arcuate portion.
[0007]
In another aspect, an electrical discharge machining sample removal apparatus for removing a material sample from a structural component in a boiling water reactor is provided. The reactor includes a reactor pressure vessel and a shroud. The apparatus includes a base plate, a motor mounted to the base plate, and an electrode assembly rotatably coupled to the base plate and operatively coupled to the motor. The electrode assembly has a first end and a second end, and has a first electrode hub located at the first end, and a second electrode located at the second end. A hub, a conductive first electrode wing portion extending from the first and second electrode hubs; a conductive second electrode wing portion extending from the first and second electrode hubs; An electrode insulator extending between the electrode wing portions and coupled to the first and second electrode hubs. The first and second electrode wing portions and the electrode insulator form a substantially semi-cylindrical hollow cavity having an outer wall.
[0008]
In another form, a method is provided for hollowing out a material sample from a structural component in a nuclear reactor. The nuclear reactor includes a reactor pressure vessel and a shroud with an annular space between the pressure vessel and the shroud. The method includes disposing an electrical discharge machining sample removal device in an annular space and adjacent a shroud, and activating the sample removal device to cut a material sample from the shroud. The sample removal device includes a base plate, a motor attached to the base plate, and an electrode assembly rotatably coupled to the base plate and operatively coupled to the motor. The electrode assembly has a first end and a second end, and has a first electrode hub located at the first end, and a second electrode located at the second end. A hub, a conductive first electrode wing portion extending from the first and second electrode hubs; a conductive second electrode wing portion extending from the first and second electrode hubs; An electrode insulator extending between the electrode wing portions and coupled to the first and second electrode hubs. The first and second electrode wing portions and the electrode insulator form a substantially semi-cylindrical hollow cavity having an outer wall.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An electrical discharge machining (EDM) sample extraction device that can obtain a material sample from a shroud structure of a boiling water reactor will be described in more detail below. The EDM sample removal device is easily placed in the reactor between the shroud and the reactor pressure vessel, and can maintain the position in the reactor and perform the process of cutting out material from the shroud structure.
[0010]
Referring to the drawings, FIG. 1 is a cross-sectional view showing a part of a pressure vessel (RPV) 10 of a boiling water reactor in a cutaway manner. The RPV 10 has a generally cylindrical shape, with one end closed by a bottom head 12 and the other end closed by a removable top head 14. Side walls 16 extend from bottom head 12 to top head 14. The side wall 16 has an upper flange 18. Top head 14 is attached to upper flange 18. A cylindrical core shroud 20 surrounds the core 22. Shroud 20 includes a shroud head 26 supported at one end by shroud support 24 and removable at the other end. An annular space 28 is formed between the shroud 20 and the side wall 16. A ring shaped pump deck 30 extends between the shroud support 24 and the RPV sidewall 16. The pump deck 30 has a plurality of circular holes 32, each of which houses a jet pump 34. The jet pumps 34 are circumferentially distributed around the core shroud 20. An inlet riser 36 is connected to the two jet pumps 34 by a transition assembly 38. Each jet pump 34 includes an inlet mixer 40 and a diffuser 42. The inlet riser 36 and the two connected jet pumps 34 form a jet pump assembly 44.
[0011]
Heat is generated in the core 22 including the fuel assembly 46 made of fissile material. The water circulated through the core 22 is at least partially converted to steam. The steam separation device 48 separates steam from circulating water. Residual water is removed from the steam by steam dryer 50. Steam exits the RPV 10 through a steam outlet 52 near the top head 14 of the pressure vessel.
[0012]
The amount of heat generated in the core 22 is adjusted by inserting and withdrawing control rods 54 made of a neutron absorbing material such as, for example, boron carbide. Depending on the extent to which control rod 54 is inserted into fuel assembly 46, control rod 54 absorbs neutrons that would otherwise be used to promote a chain reaction that generates heat within core 22. During insertion and withdrawal, control rod guide tube 56 maintains vertical movement of control rod 54. The control rod driving device 58 inserts and pulls out the control rod 54. Control rod drive 58 extends through bottom head 12.
[0013]
The fuel assemblies 46 are aligned by a core plate 60 located at the bottom of the core 22. The upper guide member 62 aligns the fuel assembly 46 as it is lowered into the core 22. Core plate 60 and upper guide member 62 are supported by core shroud 20.
[0014]
FIG. 2 is a left front perspective view of the EDM sample extraction device 70 according to the embodiment of the present invention. 3 is a right front perspective view of the device 70, FIG. 4 is a left rear perspective view of the device 70, FIG. 5 is a right rear perspective view of the device 70, and FIG. It is a bottom perspective view. Referring to FIGS. 2-6, in an exemplary embodiment, the device 70 includes a base plate 72, a motor 74 attached to the base plate 72, a motor 74 rotatably coupled to the base plate 72 and And an electrode assembly 76 operatively coupled to the electrode assembly 76.
[0015]
Specifically, the reversible stepper motor 74 is attached to the motor attachment bracket 78 with the fastener 80. The motor mounting bracket 78 includes a bracket substrate 82, and a bracket support plate 84 is mounted on the bracket substrate 82. The bracket support plate 84 extends at substantially 90 degrees from an end 86 of the bracket substrate 82. Gusset plates 88 and 90 extend between the support plate 84 and the bracket substrate 82 and are attached to both ends of the bracket substrate 82 and the support plate 84. The bracket substrate 82 is attached to the base plate 72 by a fastener 92 that passes through the base plate 72 and an oval fastener opening 94 in the bracket substrate 82. The oblong opening 94 allows the position of the motor 74 to be adjusted. A drive shaft 96 extends from motor 74 through an opening 98 that extends through bracket support plate 84. A motor pulley 100 is attached to the motor drive shaft 96.
[0016]
A motor output belt 102 extends between and operatively couples the motor pulley 100 and the first reduction pulley 104. A second reduction pulley 106 and a first reduction pulley 104 are coupled to both ends of a shaft 107, and the shaft 107 is mounted on a base plate 72 by a fastener 92 for a reduction mechanism bearing block 108. It is rotatably mounted inside. In another embodiment, the bearing block 108 is attached to the base plate by any suitable method, for example, by welding. A drive belt 110 extends between and operatively couples the second reduction pulley 106 and the electrode assembly 76.
[0017]
Referring also to FIG. 7, the electrode assembly 76 has a first end 112 and a second end 114 and includes a first electrode hub 116 located at the first end 112 and a first electrode hub 116. A second electrode hub 118 located at the second end 114; a conductive first electrode wing portion 120 extending from the first and second electrode hubs 116 and 118; and a first and second electrode hub. A conductive second electrode wing portion 122 extending from 116 and 118 and an electrode extending between the first and second electrode wing portions 120 and 122 and coupled to the first and second electrode hubs 116 and 118 An insulator 124. The first and second electrode wing portions 120 and 122 and the first and second electrode hubs 116 and 118 form an EDM electrode 125. The electrode wing portions 120 and 122 and the electrode insulator 124 form a substantially semi-cylindrical hollow cavity 126 having an outer wall 128. In one embodiment, the EDM electrode 125 is formed integrally, and in another embodiment, the EDM electrode 125 is formed from a plurality of parts joined together.
[0018]
The outer wall 128 includes a conductive first arcuate portion 130, a conductive second arcuate portion 132, and a non-conducting portion disposed between the first and second arcuate portions 130 and 132. And a third arcuate portion 134 that is conductive. The outer wall 128 further includes a first end portion 136 and a second end portion 138, each of the end portions 136 and 138 being a conductive first end section 140 extending from the first arc-shaped portion 130. And a conductive second end section 142 extending from the second arc-shaped portion 132 and a non-conductive third end section 144 extending from the third arc-shaped portion 134. The first and second end sections 140 and 142 of the first end portion 136 extend from the first electrode hub 116 and the first and second end sections 140 and 142 of the second end portion 138. Extends from the second electrode hub 118. The third end section 144 of the first end portion 136 is coupled to the first electrode hub 116, and the third end section 144 of the second end portion 138 is connected to the second electrode hub 118. Be combined.
[0019]
Each of the first and second electrode wing portions 120 and 122 includes a plurality of flushing holes 146 and a plurality of interconnecting holes 148 through the outer wall 128. Each of the interconnect holes 148 extends between and interconnects at least two flush holes 146.
[0020]
Each of electrode hubs 116 and 118 is coupled to electrode mount 150, and each of electrode mounts 150 is coupled to main shaft 152. Each of the main shafts 152 is received in a bearing block 154 mounted on the base plate 72, thereby rotatably coupling the electrode assembly 76 to the base plate 72. The opening 156 in the base plate 72 is sized and shaped to receive the electrode assembly 76, and the bearing block 154 is dimensioned across the opening 156 to position the electrode assembly 76 within the opening 156. Has been.
[0021]
Axial holes 158 and 160 extend through electrode hubs 116 and 118, respectively. 8 and 9, an axial hole 162 extends through each electrode mount 150 and an axial hole 164 extends through each main shaft 152. Each axial hole 164, 162 and 158 in the main shaft 152 coupled to the electrode mount 150 coupled to the first electrode hub 116 is aligned and extends from inside the electrode assembly cavity 126 to outside the cavity 126. A first passage 166 extending is formed. Each axial hole 164, 162 and 160 in the main shaft 152 coupled to the electrode mount 150 coupled to the second electrode hub 118 extends in alignment from inside the electrode assembly cavity 126 to outside the cavity 126. A second passage 168 is formed.
[0022]
Debris formed during the EDM process is called swarf. Chips generated during the EDM cutting process as well as dissociated hydrogen and oxygen are removed either by washing with water or by suction through flushing holes 146 and interconnect holes 148. This network of flushing holes 146 and interconnecting holes 148 communicates the electrode assembly cavity 126 with the first and second passages 166 and 168 to remove chips from the cutting area. Also, since the flushing holes 146 extend through the outer wall 128, chips are further removed from the area outside the cavity 126 and adjacent to the electrode 125. Piping (not shown) from a chip collector (not shown) is mounted at the end of each spindle 152 in communication with passages 166 and 168, and chips generated during EDM cutting operations as well as dissociated hydrogen And remove oxygen. A pipe restrainer 170 and a pipe cover 172 are attached to the base plate 72 to protect the chip collection pipe (not shown).
[0023]
A brush 174 is mounted adjacent to the electrode assembly 76 in a brush holder 176 coupled to the base plate 72. Brush 174 is coupled to an electrical wire (not shown) and engages electrode hubs 116 and 118 to supply voltage to electrode wing portions 120 and 122. The electrode mount 150 is made of a non-conductive material to electrically insulate the EDM electrode 125.
[0024]
Apparatus 70 also includes a clamp assembly 178 coupled to base plate 72. The clamp assembly 178 is a telescoping fixation sized and configured to engage the reactor pressure vessel 10 to secure the device 70 in place between the reactor pressure vessel sidewall 16 and the shroud 20. Includes cylinder 180. A cylinder mounting assembly 182 is coupled to the base plate 72. The cylinder mounting assembly includes frame members 184 and 186 coupled to and extending substantially perpendicular to the base plate 72. A beam member 188 extends between and is coupled to the frame members 184 and 186. A cylinder mounting bracket 190 is coupled to the beam member 188, and a locking cylinder 180 is pivotally mounted to the mounting bracket 190. The stop bracket 192 is connected to the fixing cylinder 180. The stop bracket 192 engages the beam member 188 to limit pivoting of the locking cylinder 180. The cylinder receiving bracket 194 mounted on the base plate 72 receives the fixing cylinder 180 when the fixing cylinder 180 is pivoted to the storage position (see FIG. 10). An adjustable leveling stud 196 extends from the bottom surface of the base plate 72. When the locking cylinder 180 is actuated to extend the plunger 198 into contact with the RPV sidewall 16, the generated force is transmitted to the leveling stud 196, which is pressed onto the curved surface of the shroud 20. Leveling stud 196 is adjusted prior to mounting device 70 to accommodate the curved surface of shroud 20. Adjustment of the leveling stud 196 also allows for fine adjustment to the depth of cut made by the EDM electrode 125 in the shroud 20. An eyebolt 200 is attached to the base plate 72 and the tether assembly 202 is coupled to the fixing cylinder 180. The eyebolt 200 and tether assembly 202 are sized to allow the installation of ropes used to lower and suspend the device 70 within the reactor annulus 28.
[0025]
Apparatus 70 also includes a trap door assembly 204 movably coupled to base plate 72. The trap door assembly 204 includes a door operating cylinder 206 connected to the base plate 72 and a trap door 208 connected to the door operating cylinder 206. Door 208 is movable from an open position to a closed position to capture a sample cut from shroud 20.
[0026]
Apparatus 70 is used to cut a material sample from shroud 20. The locking cylinder 180 is disengaged from the cylinder receiving bracket 194 and pivoted to an operative position where the stop bracket 192 engages the beam member 188 of the mounting assembly. With the rope attached to the eyebolt 200 and the rope assembly 202, the device 70 is lowered into the reactor annular space 28 and adjacent to the shroud 20 so that the bracket 210 is positioned in engagement with the shroud 20. Be placed. In one embodiment, locating bracket 210 engages one of the shroud flanges (not shown) extending into annular space 28. In another embodiment, the locating bracket engages other shaped portions of the shroud 20. The locking cylinder 180 is activated, thereby causing the plunger 198 to extend and contact the RPV sidewall 16. The force generated by the locking cylinder is transmitted to the leveling stud 196 which is pressed against the curved surface of the shroud 20, securing the device in place such that the electrode assembly 76 is adjacent to the shroud 20. .
[0027]
An electric current is supplied to the EDM electrode 125 and the motor 74 is operated to rotate the electrode 125 to a position where the shroud 20 is cut. Electrode 125 is first rotated such that first electrode wing section 120 cuts shroud 20. When approximately half of the cut is completed, motor 74 is reversed and electrode 125 is rotated such that second electrode wing portion 122 cuts shroud 20. When the cutting path of the second wing section 122 just coincides with the cutting path already performed by the first wing section, the door operating cylinder 206 is actuated to move the trapping door 208 and the electrode insulator 124 between the trap door 208 and the electrode insulator 124. The trap door 208 is moved to a closed position to capture the sample 212 cut from the shroud 20 (see FIG. 11).
[0028]
The locking cylinder 180 is deactivated, thereby retracting the plunger 198, releasing the device 70 from engagement with the shroud 20. The device 70 is then withdrawn from the annular space 28 so that the sample 212 captured between the trap door and the electrode insulator 124 is also removed from the annular space 28.
[0029]
Although the present invention has been described in terms of various specific embodiments, it will be apparent to one skilled in the art that the present invention may be practiced with modification within the spirit and scope of the appended claims. Would. Reference numerals described in the claims are for easy understanding, and do not limit the technical scope of the invention to the embodiments.
[Brief description of the drawings]
FIG. 1 is a sectional view in which a part of a boiling water reactor pressure vessel is cut away.
FIG. 2 is a left front perspective view of the sample removing device according to the embodiment of the present invention.
FIG. 3 is a right front perspective view of the apparatus shown in FIG. 2;
FIG. 4 is a left rear perspective view of the device shown in FIG. 2;
FIG. 5 is a right rear perspective view of the apparatus shown in FIG. 2;
FIG. 6 is a bottom perspective view of the apparatus shown in FIG. 2;
FIG. 7 is a perspective view of an electrode shown in the apparatus shown in FIG. 2;
FIG. 8 is a sectional view of an electrode mount shown in the apparatus shown in FIG. 2;
FIG. 9 is a sectional view of a main shaft shown in the apparatus shown in FIG. 2;
FIG. 10 is a left front perspective view of the apparatus shown in FIG. 2 with the clamp assembly in the stowed position;
FIG. 11 is a perspective view of a sample taken out of the shroud shown in FIG. 1 by the apparatus shown in FIG. 2;
[Explanation of symbols]
70 EDM type sample removal device 72 Base plate 74 Motor 76 Electrode assembly 102 Motor output belt 104 First reduction pulley 106 Second reduction pulley 110 Drive belt 140 First end section 142 Second end section 144 3 end section 178 clamp assembly 180 locking cylinder 192 restraining bracket 194 cylinder receiving bracket 198 plunger 202 tether assembly 204 trap door assembly 210 positioning bracket

Claims (10)

An electrical discharge machining type sample removal device (70) for removing a material sample from a structural component in a boiling water reactor provided with a reactor pressure vessel (10) and a shroud (20),
A base plate (72);
A motor (74) mounted on the base plate;
An electrode assembly (76) rotatably coupled to the base plate and operatively coupled to the motor;
Wherein the electrode assembly includes an outer wall (128) forming a substantially semi-cylindrical hollow cavity (126), the outer wall comprising:
A first conductive arc-shaped portion (130);
A second conductive arc-shaped portion (132);
A non-conductive third arcuate portion (134) disposed between and coupled to the first and second arcuate portions;
An apparatus (70), comprising: And a clamp assembly (178) coupled to the base plate (72) for securing the device in place between the reactor pressure vessel and the shroud (20). The apparatus (70) of any preceding claim, comprising an extendable locking cylinder (180) sized and shaped to engage the reactor pressure vessel (10). The apparatus (70) of any preceding claim, further comprising a trapdoor assembly (204) movably coupled to the base plate (72). The trap door assembly (204) includes a door operating cylinder (206) coupled to the base plate (72) and a trap door (208) coupled to the door operating cylinder, the door comprising a sample ( Device (70) according to claim 3, characterized in that it is movable from an open position to a closed position for capturing (212). The apparatus (70) of any preceding claim, further comprising at least one drive belt (110) operatively coupling the motor (74) to the electrode assembly (76). The outer wall (128) further includes a first end portion (136) and a second end portion (138), wherein each of the first and second end portions is
A conductive first end section (140) extending from the first arc-shaped portion (130);
A conductive second end section (142) extending from the second arc-shaped portion (132);
A non-conductive third end section (144) extending from the third arcuate portion (134);
A conductive electrode hub (116);
Including
The first and second end sections extend from the electrode hub, and the third end section is coupled to the electrode hub;
Device (70) according to claim 1, characterized in that: First end sections (140) of the first and second end portions (136, 138) and the first arc-shaped portion (130) form a first electrode wing (120). And the second end section (142) of the first and second end portions and the second arc-shaped portion (132) form a second electrode wing (122); A third end section (144) of the first and second end portions and the third arc-shaped portion (134) form an electrode insulator (124) and the first and second arc portions (124). Each of the electrode wings includes a plurality of flushing holes (146) penetrating the outer wall and a plurality of interconnecting holes (148) each interconnecting at least two of the flushing holes. Apparatus (70) according to claim 6 ,. Each of the electrode hubs (116, 118) is coupled to an electrode mount (150), each of the electrode mounts is coupled to a main shaft (152), and each of the main shafts is rotatably coupled to the base plate (72). Apparatus (70) according to claim 6, characterized in that: Each of the electrode hubs (116, 118), each of the electrode mounts (150) and each of the main shafts (152) include a longitudinal hole therethrough and at the first end portion (136). Each longitudinal hole in the main shaft coupled to the electrode mount coupled to the electrode hub is aligned with a first passage extending from inside the cavity of the electrode assembly to outside of the cavity. (166) wherein each longitudinal hole in the main shaft coupled to the electrode mount coupled to the electrode hub at the second end portion (138) is aligned with the electrode assembly. Device (70) according to claim 8, characterized in that it forms a second passage (168) extending from inside the cavity to outside the cavity. The device (70) of claim 8, wherein each of the electrode mounts (150) comprises a non-conductive material.

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