US20040076254A1 - Control rod for boiling water reactor and method for manufacturing the same - Google Patents
Control rod for boiling water reactor and method for manufacturing the same Download PDFInfo
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- US20040076254A1 US20040076254A1 US10/274,040 US27404002A US2004076254A1 US 20040076254 A1 US20040076254 A1 US 20040076254A1 US 27404002 A US27404002 A US 27404002A US 2004076254 A1 US2004076254 A1 US 2004076254A1
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- Prior art keywords
- tie rod
- sheath
- sheaths
- welding
- rod
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C7/00—Control of nuclear reaction
- G21C7/06—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
- G21C7/08—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
- G21C7/10—Construction of control elements
- G21C7/113—Control elements made of flat elements; Control elements having cruciform cross-section
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
- B23K26/24—Seam welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/32—Bonding taking account of the properties of the material involved
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K33/00—Specially-profiled edge portions of workpieces for making soldering or welding connections; Filling the seams formed thereby
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
- G21C21/18—Manufacture of control elements covered by group G21C7/00
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/02—Iron or ferrous alloys
- B23K2103/04—Steel or steel alloys
- B23K2103/05—Stainless steel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Definitions
- the present invention relates to a control rod for controlling the power of a boiling water reactor and a method for manufacturing the same.
- the control rod typically has a structure wherein a handle is attached to an axially upper part of a tie rod having a substantially cruciform cross section; a lower part support member (or velocity limiter) is attached to at an axially lower part of the tie rod; and four sheaths, each of which incorporates a reaction rate controlling material, are fixed at a lower end of the handle, an upper end of the lower part support member and ends of the substantially cruciform of the tie rod by welding.
- a perfect weld penetration by the TIG welding has been performed for welding the sheaths to the ends of the handle, the lower part support member and the tie rod.
- control rod moves upward and downward in the narrow gap secured among the fuel assemblies during operation of the reactor. Therefore, a high degree of machining precision is required in manufacturing the control rod.
- a contact area of the step of the tie rod with the tip of the sheath must be sufficiently large to satisfactorily transfer the heat of the laser beam to the tie rod. Therefore, the step of the tie rod must be machined to achieve a precise rectangular shape. More specifically, if an R shape (round portion) is formed at a corner of the step of the tie rod, the contact area of the tie rod with the sheath becomes small to fail to provide the satisfactory heat transfer, and such imprecision may cause the melt-down of the sheath, resulting in the welding failure.
- the prior art requires a high precision control of the laser beam for the prevention of the deviation of the laser beam irradiating position from the overlap and a high precision machining of the step of the tie rod.
- a high precision control of the laser beam for the prevention of the deviation of the laser beam irradiating position from the overlap and a high precision machining of the step of the tie rod.
- An object of the present invention is to provide a control rod for boiling water reactor and a method for manufacturing the control rod for boiling water reactor, whereby the manufacturing process can be simplified and the production cost can be decreased.
- a tie rod having a cruciform cross section is provided with steps for fixing sheaths at tips of cruciform arms of the tie rod; the tips of each of sheaths are fitted onto the steps of the tie rod, each of the sheaths having a U-shaped cross section; and each of the sheaths is fixed to the tie rod by performing a laser welding using a YAG laser beam or a CO 2 laser beam with the sheath being fitted onto the tie rod to achieve a continuous weld of at least a part of the tie rod in a longitudinal direction thereof.
- An axial center position of the beam is shifted from an end face position of the step of the tie rod at least toward an axis center of the tie rod.
- the laser beam is not irradiated directly on the sheath, but firstly on a surface of the tie rod so that heat is transferred from the surface of the tie rod to the sheath which is being brought into contact with the tie rod step via the tie rod step. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, the heat is transferred to the sheath after passing the contact portion of the step with the sheath without fail, thereby eliminating possibility of a welding failure which is caused by the melt-down of the sheath.
- the present invention prevents the melt-down of the sheath to secure a good weldability without high precision control of the beam axial center position which has been performed in the conventional method. Therefore, the present invention facilitates the laser welding control as well as the manufacture of the control rod, and achieves a reduction in manufacturing cost.
- steps of a tie rod are formed by a drawing process, each of sheaths is fixed to the tie rod by performing a laser welding using a laser beam with the sheath being fitted onto the tie rod to achieve a continuous weld of at least a part of the tie rod in a longitudinal direction thereof.
- the melt-down of the sheath can be prevented to thereby secure the good weldability even if the tie rod step is not machined into a precise rectangular shape and thereby an R-shape or the like remains on a corner of the step.
- a machining step from a typical control rod manufacturing method comprising a process step of forming the drawn tie rod having a substantially cruciform cross section by a drawing process and a process step of machining of the steps to achieve the rectangular shapes, thereby making it possible to manufacture a multiple of the tie rods each provided with the steps at one time by the drawing process only. Therefore, the present invention facilitates the manufacture of the control rod by a process corresponding to the machining process omitted, to thereby achieve a reduction in manufacturing cost.
- a step for fixing sheaths is formed on a lower end of a handle attached to an axially upper part of a tie rod; an upper edge of each of the sheaths is fitted onto the step of the handle; and each of the sheaths is fixed to the handle by performing a laser welding using a laser beam with the sheath being fitted onto the handle to achieve a continuous weld of at least a part extending along the upper edge of the sheath.
- An axial center position of the beam is shifted from an end face position of the step of the handle to a side opposite to the sheath.
- the laser beam is not irradiated directly on the sheath, but firstly on a surface of the handle so that heat is transferred from the surface of the handle to the sheath which is being brought into contact with the handle step via the handle. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, there is no possibility of a welding failure which is caused by the melt-down of the sheath. Therefore, the same effect as that in Item (1) is obtained.
- a step for fixing sheaths is formed on an upper end of a lower part support member or a velocity limiter attached to an axially lower part of a tie rod; a lower edge of each of the sheaths is fitted onto the step of the lower part support member or the velocity limiter; and each of the sheaths is fixed to the lower part support member or the velocity limiter by performing a laser welding using a laser beam with the sheath being fitted onto the lower part support member or the velocity limiter to achieve a continuous weld of at least a part extending along the lower edge of the sheath.
- An axial center position of the beam is shifted from an end face position of the step of the lower part support member or the velocity limiter to a side opposite to the sheath.
- the laser beam is not irradiated directly on the sheath, but firstly on a surface of the lower part support member so that heat is transferred from the surface of the lower part support member to the sheath which is being brought into contact with the step of the lower part support member via the lower part support member. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, there is no possibility of a welding failure which is caused by the melt-down of the sheath. Therefore, the same effect as that in Item (1) is obtained.
- FIG. 1 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a first embodiment of the present invention
- FIG. 2 is a cross-sectional view taken along the section plane indicated by II-II in FIG. 1;
- FIG. 3 is a process-drawing showing manufacturing steps of the control rod of FIG. 1;
- FIG. 4A shows a top view or a bottom view of a drawn tie rod
- FIG. 4B is a top view or a bottom view of a cut tie rod
- FIG. 5 is a conceptual block diagram showing a general construction of a YAG laser welding machine used for a laser welding in FIG. 3;
- FIG. 6 is an enlarged perspective view showing a part of a welding portion of a sheath on a tie rod in FIG. 3;
- FIG. 7 is a cross-sectional view taken along the section plane indicated by VII-VII in FIG. 6;
- FIG. 8 is an enlarged perspective view showing a part of a welding portion of a sheath on a handle in FIG. 3;
- FIG. 9 is a cross-sectional view taken along the section plane indicated by IX-IX in FIG. 8;
- FIG. 10 is an enlarged perspective view showing a part of a welding portion of a sheath on a velocity limiter in FIG. 3;
- FIG. 11 is a cross-sectional view taken along the section plane indicated by XI-XI in FIG. 10;
- FIG. 12 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a second embodiment of the present invention.
- FIG. 13 is a process drawing showing process steps for manufacturing the control rod in FIG. 1;
- FIG. 14 is a partly enlarged perspective view showing a welding portion of a sheath on a drawn tie rod in FIG. 13;
- FIG. 15 is a cross-sectional view taken along the section plane indicated by XV-XV in FIG. 14;
- FIG. 16 shows a range of the welding conditions
- FIG. 17 shows a relationship between a heat input parameter Po and an analysis parameter P
- FIG. 18 is a conceptual block diagram showing a general construction of an automatic YAG laser welding machine used for performing an automatic sheath welding of a method for manufacturing a control rod for boiling water reactor according to a third embodiment of the present invention
- FIG. 19 shows a scanning method of a laser scanning two dimensional displacement sensor
- FIG. 20 is a cross-sectional view taken along the section plane indicated by XX-XX in FIG. 19;
- FIG. 21 is a longitudinal sectional view taken along the section plane indicated by XXI-XXI in FIG. 19;
- FIG. 22 is a partly enlarged perspective view showing an automatic welding portion of a sheath on a tie rod according to a third embodiment of the method for manufacturing a control rod for boiling water reactor of the present invention.
- FIG. 23 is a cross-sectional view taken along the section plane indicated by XXIII-XXIII in FIG. 22.
- FIG. 1 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a first embodiment of the present invention.
- FIG. 2 is a cross-sectional view taken along the section plane indicated by II-II in FIG. 1, in which fuel assemblies N are also shown.
- a control rod 1 for boiling water reactor is provided with a control rod supporting structural body 2 and four blades 3 each of which extends from an axis center 2 A of the control rod supporting structural body 2 (or an axis center 4 A of a tie rod 4 to be described later in this specification) toward four directions.
- the control rod 1 as a whole has a cruciform cross section.
- the control rod supporting structural body 2 is provided with a tie rod 4 having the cruciform cross section, a handle 5 fixed to an upper end of the tie rod 4 and a velocity limiter 6 fixed to a lower end of the tie rod 4 .
- Each of the blades 3 comprises hafnium flat tubes 7 serving as a neutron absorbing member and sheaths 8 covering the hafnium flat tubes 7 .
- Each of the blades 3 is provided with four hafnium flat tubes 7 , two of which being provided in a direction of the axis center 2 A of the control rod supporting structural body 2 , other two of which being provided in a direction extending outward from the axis center 2 A of the control rod supporting structural body 2 .
- hafnium flat tubes 7 which are provided at an upper part are fixed to the handle 5 with pins (not shown), lower ends of the hafnium flat tubes 7 which are provided at a lower part are fixed to a base member 6 a of the velocity limiter 6 with pins (not shown), and the sheaths 8 press the hafnium flat tubes 7 to fix the hafnium flat tubes 7 to the control rod supporting structural body 2 .
- Each of the sheaths 8 is prepared by bending a stainless steel plate, for example, to form a U-shape, and each of tips of the sheath 8 is provided with projections 8 a and recesses 8 b.
- the projections 8 a are welded to each of tips 4 a of the arms of the tie rod 4
- an upper edge 8 c of the sheath 8 is welded to a lower end 5 a of the handle 5
- a lower edge 8 d of the sheath 8 is welded to an upper end 6 a 1 of the velocity limiter base member 6 a, to thereby fix the sheath 8 to the control rod supporting structural body 2 .
- Each of the sheaths 8 is provided with a plurality of cooling holes 9 which serve as paths for a coolant.
- a plate 10 is prepared by rolling a material in Step 10 of FIG. 3.
- the plate 10 is cut in such a manner as to form the projections 8 a and the recesses 8 b, and then punched to form the cooling holes 9 , to thereby obtain a flat sheath 11 .
- the sheath 8 is obtained by bending the flat sheath 11 in such a manner as to form a U-shape using a press machine.
- a drawn tie rod 12 is formed by drawing a material in Step 40 of FIG. 3, and then the drawn tie rod 12 is cut in Step 50 to give a tie rod 4 (hereinafter, for the distinction from the drawn tie rod 12 , the tie rod 4 will be referred to as cut tie rod 4 when so required). Details of shapes of the drawn tie rod 12 and the cut tie rod 4 will be described below with reference to FIGS. 4A and 4B.
- FIG. 4A is a top view or a bottom view of the drawn tie rod 12
- FIG. 4B is a top view or a bottom view of the cut tie rod 4
- the drawn tie rod 12 is the tie rod formed by drawing a material in Step 40 , which is provided with steps 12 b formed at both sides of a tip 12 a of each of arms.
- a corner 12 b 1 of each of the steps 12 b is slightly R-shaped (curved).
- the cut tie rod 4 is provided with steps 4 b formed at both sides of a tip 4 a of each of arms like the drawn tie rod 12 . It is formed by cutting each of the steps 12 b of the drawn tie rod 12 in Step 50 to eliminate the R-shape of the corner 12 b 1 . Thus, each of the steps 4 b has a precise rectangular shape.
- the steps 4 b are provided for the purpose of fitting the projections 8 a of the tips of the sheath 8 thereonto at the time of welding the sheath 8 to the tie rod 4 in Step 110 which will be described later.
- the handle 5 , velocity limiter 6 and other members constituting the control rod 1 for boiling water reactor are manufactured by subjecting materials to machining, assembling, welding and so forth in Step 60 .
- Step 70 of FIG. 3 the handle 5 manufactured in Step 60 is fixed to an upper end of the cut tie rod 4 by an assembly welding; the velocity limiter 6 manufactured in Step 60 is fixed to a lower end of the cut tie rod 4 in the same manner; and other members are properly assembled and welded, so that the control rod supporting structural body 2 is completed.
- a hafnium plate 13 is formed by rolling a material in Step 80 . Both ends of each of two hafnium plates 13 are bent, and then, in Step 90 , the hafnium plates are assembled in such a manner as to face each other, followed by welding seams thereof, so that a hafnium flat tube 7 is completed.
- the hafnium flat tube 7 which has been manufactured in Step 90 in the manner described in the item (5), is fixed to the control rod supporting structural body 2 which has been manufactured in Step 70 in the manner described in the item (4).
- the upper and lower ends of each of the hafnium flat tubes 7 to be provided in the upper and lower parts are fixed to the handle 5 and the base member 6 a of the velocity limiter 6 with pins as described above, respectively.
- the hafnium tubes 7 fixed to the four positions as described above are then covered with the sheaths 8 , respectively, in such a manner that the sheaths 8 respectively incorporate the hafnium tubes 7 from a tip of the U-shape, and the projections 8 a of each of the sheaths 8 are fitted onto the steps 4 b of each of the arms of the tie rod 4 .
- the lower end 5 a of the handle 5 and the upper end 6 a 1 of the base member 6 a of the velocity limiter 6 are provided with a step 5 b (see FIG. 9) and a step 6 ab (see FIG. 11) similar to the steps 4 b, and an upper edge 8 c and a lower edge 8 d of each of the sheaths 8 are fitted onto the steps 5 b and 6 ab, respectively.
- Step 110 fitting portions of the projections 8 a in the steps 4 b, the upper edges 8 c in the step 5 b, and the lower edges 8 d in the step 6 ab are subjected to a laser welding.
- the sheaths 8 are fixed to the control rod supporting structural body 2 , so that the control rod 1 for boiling water reactor is completed.
- the greatest characteristic is that, in performing the laser welding with the projections 8 a, the upper edge 8 c and the lower edge 8 d of each of the sheaths 8 being fitted onto the steps 4 b, the step 5 b and the step 6 a 1 , a beam axial center position of the laser beam is shifted from an end face position of the sheath 8 to a side opposite to the sheath 8 to weld them.
- a beam axial center position of the laser beam is shifted from an end face position of the sheath 8 to a side opposite to the sheath 8 to weld them.
- FIG. 5 is a conceptual block diagram showing a general construction of a YAG laser welding machine used in the laser welding.
- a YAG laser welding machine 14 is provided with a machining table 15 on which the tie rod 4 and the sheath 8 are placed, a holding fixture 16 for holding the sheath 8 , a laser beam machine 17 , a laser oscillator 18 for emitting a YAG laser beam 23 which will be described later and a control device 19 .
- the laser welding machine 17 is provided with rails 17 a, a frame 17 b capable of moving in directions indicated by the arrow A, a support member 17 c having a substantially L shape which is mounted on the frame 17 b, a slider 17 d capable of moving in directions indicated by the arrow C, a support rod 17 e extending downward from the slider 17 d and a machining head 17 f capable of moving in directions indicated by the arrow B along the support rod 17 e.
- the machining head 17 f can move in three axial directions of A, B and C with respect to the machining table 15 .
- the control device 19 is connected with the frame 17 b of the laser beam machine 17 and with the laser oscillator 18 respectively by a signal line 20 and a signal line 21 , while the laser oscillator 18 is connected with the machining head 17 f by an optical fiber 22 . Further, an operation panel (not shown) is connected with the control device 19 , so that an operator uses the operation panel to control a position of the machining head, laser output and so forth.
- the projections 8 a constitute the tips of the U-shape of each of the sheaths which are recited in the appended claims.
- FIG. 6 is a perspective view showing an enlarged part of welded portion of the sheath 8 and the tie rod 4 which are welded using the YAG laser welding machine 14
- FIG. 7 is a cross-sectional view taken along the section plane indicated by VII-VII in FIG. 6.
- the operator uses the operation panel, while moving the machining head 17 f in a longitudinal direction (in a direction of the arrow D) of the tie rod 4 , to perform a continuous laser welding of the projection 8 a of the sheath 8 on the step 4 b of the tie rod 4 .
- a shield gas 24 is fed from the machining head 17 f at the same time with the irradiation of the YAG laser beam 23 to prevent oxidization of the welded portion.
- a trailer gas 26 is blown to the welding bead from a trailer nozzle 25 to prevent the oxidization.
- the axial center position 23 A (see FIG. 7) of the YAG laser beam 23 is shifted from an end face 4 b 1 of the tie rod step 4 b toward the tie rod 4 (to the side opposite to the sheath 8 ) to irradiate a surface of the tie rod 4 directly with the YAG laser beam 23 for laser welding.
- the surface of the tie rod 4 is firstly irradiated with the YAG laser beam 23 , and then heat generated by the irradiation is transferred from the surface of the tie rod 4 to the sheath 8 via the tie rod step 4 b. Accordingly, even if a small error in the axial center position 23 A of the YAG laser beam occurs and the YAG laser beam slightly deviates from the target position, the heat is transferred to the sheath 8 after passing the contact portion of the tie rod step 4 b with the sheath 8 without fail, to thereby prevent the welding failure which otherwise would be caused by the melt-down of the projection 8 a of the sheath 8 .
- the present embodiment prevents the melt-down of the sheath 8 to secure a good weldability without controlling the axial center position 23 A of the YAG laser beam 23 with high precision.
- the present embodiment facilitates the laser welding control and the manufacture of the control rod 1 for boiling water reactor, and achieves a reduction in manufacturing cost.
- FIG. 8 is a perspective view showing an enlarged part of a welding portion in the welding of the sheath 8 on the handle 5 using the YAG laser welding machine 14 .
- FIG. 9 is a cross-sectional view taken along the section plane indicated by IX-IX in FIG. 8.
- FIGS. 8 and 9 those also shown in FIGS. 6 and 7 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
- the machining head 17 f is moved in a direction along the upper edge 8 c of the sheath 8 (in a direction indicated by the arrow E) to perform a continuous laser welding of the upper edge 8 c of the sheath 8 on the step 5 b (see FIG. 9) of the lower end 5 a of the handle 5 as shown in FIGS. 8 and 9.
- the axial center position 23 A of the YAG laser beam 23 is shifted from an end face 5 b 1 (see FIG.
- the present embodiment prevents the melt-down of the sheath 8 to secure the good weldability without controlling the axial center position 23 A of the YAG laser beam 23 with high precision.
- the present embodiment facilitates the laser welding control and the manufacture of the control rod 1 for boiling water reactor, and achieves the reduction in manufacturing cost.
- FIG. 10 is a perspective view showing an enlarged part of the welding portion of the sheath 8 on the base member 6 a of the velocity limiter 6 which are welded by using the YAG laser welding machine 14 .
- FIG. 11 is a cross-sectional view taken along the section plane indicated by XI-XI in FIG. 10.
- FIGS. 10 and 11 those also shown in FIGS. 6 and 7 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
- the machining head 17 f is moved in a direction along the lower edge 8 d of the sheath 8 (in a direction indicated by the arrow F in FIG. 10) to perform a continuous laser welding of the lower edge 8 d of the sheath 8 on the step 6 ab (see FIG. 11) of the upper end 6 a 1 of the velocity limiter base member 6 a as shown in FIGS. 10 and 11.
- the axial center position 23 A of the YAG laser beam 23 is shifted from an end face 6 ab 1 (see FIG.
- the present embodiment prevents the melt-down of the sheath 8 to secure the good weldability without controlling the axial center position 23 A of the YAG laser beam 23 with high precision.
- the present embodiment facilitates the laser welding control and the manufacture of the control rod 1 for boiling water reactor, and achieves the reduction in manufacturing cost.
- a welding rod may be used for promotion of fusion (see FIG. 23).
- the welding rod since the welding rod is irradiated with the YAG laser beam 23 , heat generated by the irradiation is transferred from the welding rod (more precisely, a melted welding rod) to the sheath 8 to prevent the melt-down of the sheath 8 , thereby achieving the good weldability.
- control rod for boiling water reactor is manufactured by using the above-described drawn tie rod 12 which is formed only by drawing, or, without the cutting process.
- FIG. 12 is a partly exploded perspective view showing a general structure of the control rod for boiling water reactor according to the present embodiment.
- FIG. 12 those also shown in FIG. 1 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
- a control rod 1 ′ for boiling water reactor is provided with a control rod supporting structural body 2 ′ comprising the drawing tie rod 12 , a handle 5 which is fitted onto an upper end of the drawing tie rod 12 and a velocity limiter 6 which is fixed to a lower end of the drawn tie rod 12 .
- Steps 10 to 30 for manufacturing sheaths 8 , Step 40 for manufacturing the drawn tie rod 12 and Step 60 for manufacturing the handle 5 , velocity limiter 6 and other members are the same as those of the first embodiment.
- Step 50 Although the cutting process is performed in Step 50 succeeding to Step 40 in the first embodiment as shown in FIG. 3, the cutting process is not performed in the present embodiment.
- the handle 5 and the velocity limiter 6 are fixed to the upper end and the lower end of the drawn tie rod 12 , respectively by an assembly welding, and the other members are assembled and welded as required in Step 70 , so that the control rod supporting structural body 2 ′ is completed.
- Steps 80 and 90 for manufacturing hafnium flat tubes 7 , Steps 100 and 110 for manufacturing the control rod 1 ′ for boiling water reactor are the same as those of the first embodiment.
- the drawn tie rod 12 constitutes the tie rod for fixing the sheaths which is prepared by drawing and provided with steps at each of the tips of the arms of the cruciform as recited in the appended claims.
- a machining head 17 f is moved in a longitudinal direction of the drawn tie rod 12 (in a direction indicated by the arrow G) to perform a continuous laser welding of the projection 8 a of the sheath 8 on the step 12 b of the drawn tie rod 12 in the present embodiment.
- an axial center position 23 A (see FIG.
- a YAG laser beam 23 is shifted toward the drawn tie rod 12 (to the side opposite to the sheath 8 ) from an end face 12 b 2 of the drawn tie rod step 12 b to directly irradiate a surface of the drawn tie rod 12 with the YAG laser beam 23 for laser welding.
- each of corners 12 b 1 (see FIG. 15) of the step 12 b of the drawn tie rod 12 is in a slightly R-shape due to the omission of the cutting process as described above, the projection 8 a of the sheath 8 is not completely fitted onto the end face 12 b 2 of the step 12 b. More specifically, an overlap L 2 (see FIG. 15) in the present embodiment is narrower than the overlap L 1 of the sheath 8 with the cut tie rod 4 of the first embodiment.
- the present embodiment since the surface of the drawn tie rod 12 is irradiated with the YAG laser beam 23 , heat generated by the irradiation is transferred from the surface of the drawn tie rod 12 to the sheath 8 via the drawn tie rod step 12 . Therefore, the present embodiment prevents the melt-down of the projection 8 a of the sheath 8 and the welding failure even if a small error in the irradiation position of the YAG laser beam 23 occurs.
- the present embodiment facilitates the manufacture of the control rod by a step corresponding to the omitted machining process, which leads to a reduction in manufacturing cost.
- the welding rod described in the first embodiment may be used also in the present embodiment for promotion of fusion (see FIG. 23). In this case, too, it is possible to achieve the above-described effects of the present embodiment.
- FIGS. 16 to 23 a third embodiment of the method for manufacturing a control rod for boiling water reactor of the present invention will be described with reference to FIGS. 16 to 23 .
- weldings of sheath 8 on the tie rod 4 , the sheath 8 on the handle 5 , the sheath 8 on the velocity limiter base member 6 a are automated.
- FIG. 16 shows a range of the welding conditions.
- states after the weldings are broadly classified into three states of a state wherein a penetration bead is not formed and the perfect weld penetration is not achieved, a state wherein the perfect weld penetration is achieved and a state wherein the sheath 8 is melted down.
- G represents a gap (mm) between an inner surface 8 a 5 (see FIG. 21) of a sheath projection 8 a and a base 4 b 3 of a tie rod step 4 b in a state where the sheath projection 8 a is fitted onto the tie rod step 4 b;
- A represents a distance (mm) (hereinafter referred to as “laser irradiation position A” when so required) from an axial center position 23 A of a YAG laser beam 23 to an edge 8 a 1 (see FIG.
- H heat input (kj/cm) by the YAG laser beam 23
- D represents a beam converging diameter (mm) of the YAG laser beam 23
- W represents a supply (g/m) of a welding rod 30 for one meter of welding length
- L represents an overlap (mm) (see FIG. 20) of the inner surface 8 a 5 of the sheath projection 8 a with the base 4 b 3 of the tie rod step 4 b in the state where the sheath projection 8 a is fitted onto the tie rod step 4 b.
- FIG. 17 shows a relationship between the heat input parameter Po and the analysis parameter P.
- the heat input parameter Po becomes 0 when the analysis parameter P is in the range of ⁇ 0.5 to 0.5 to achieve the perfect welding. More specifically, as can be seen from FIG. 17, if values for the gap G, laser irradiation position A, heat input H, beam converging diameter D, control rod supply W and overlap L are given, it is possible to find out the state after welding by the heat input parameter Po since the heat input parameter Po is dependent on the analysis parameter P.
- the most satisfactory conditions of the above values are in the following range: 0 to 0.3 mm of the gap G; 0 to ⁇ 0.5 mm of the laser irradiation position A; 0.89 ⁇ 0.2 kj/cm of the heat input H; 0.57 to 0.6 mm of the beam converging diameter D; 3.16 to 4.06 g/m of the welding rod supply W; and 0.3 to 0.6 of the overlap L.
- FIG. 18 is a conceptual block diagram showing a general construction of an automatic YAG laser welding machine which performs the automatic welding using the above analysis parameter P.
- FIG. 18 those also shown in FIG. 5 of the first embodiment are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
- FIG. 18 is a conceptual block diagram showing a general construction of an automatic YAG laser welding machine which performs the automatic welding using the above analysis parameter P.
- the automatic YAG laser welding machine 27 is provided with a laser scanning two-dimensional displacement sensor (not shown) attached to the machining head 17 f, an welding rod supply device (not shown) for performing an automatic supply of a welding rod 30 , which is to be described later in this specification, as being attached to the machining head 17 f, a processor 29 which is connected with the control device 19 via a signal line 28 , and a servo motor (not shown) for moving the machining head 17 f to a welding start position and a welding completion position which are instructed by the control device 19 .
- the processor 29 calculates the welding start position, welding completion position, gap G and overlap L from values detected by the laser scanning two dimensional displacement sensor, and further calculates the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W from the gap G and overlap L using the analysis parameter P.
- FIG. 19 shows a scanning method of the laser scanning two dimensional displacement sensor
- FIG. 20 is a cross-sectional view taken along the section plane indicated by XX-XX in FIG. 19
- FIG. 21 is a longitudinal sectional view taken along the section plane indicated by XXI-XXI in FIG. 19.
- the automatic YAG laser welding machine 27 detects coordinates of an edge 8 b 1 (see FIG. 20) of a recess 8 b of the sheath 8 and an outer corner 4 b 2 (see FIG. 20) of the step 4 b near a tip of the tie rod 4 by automatically scanning in a direction indicated by the arrow H in FIG. 19. Also, the automatic YAG laser welding machine 27 detects coordinates of both edges 8 a 2 and 8 a 3 (see FIG. 21) of the projection 8 a of the sheath, a height of the base 4 ba (see FIG. 21) of the step 4 b of the tie rod 4 and a height of an outer surface 8 a 4 of the sheath projection 8 a by scanning in a direction indicated by the arrow I in FIG. 19.
- the processor 29 calculates the gap G between the sheath 8 and the tie rod 4 and the overlap L of the sheath 8 with the tie rod 4 from the data which are obtained by the two scannings of the laser scanning two dimensional displacement sensor as well as a length of the sheath projection 8 a (a distance between the edge 8 a 1 of the sheath projection 8 a and the edge 8 b 1 of the sheath recess 8 b ) and a thickness of the sheath 8 which are inputted by, for example, the operator.
- the coordinates of the both edges 8 a 2 and 8 a 3 of the projection 8 a of the sheath 8 which are obtained by the above scanning are used as the welding start position and the welding completion position as they are.
- the processor 29 calculates the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W to achieve the analysis parameter P of not less than ⁇ 0.5 to not more than 0.5 by using the thus obtained gap G and overlap L.
- a value of the laser irradiation position A is set to a negative value (i.e. to be shifted in a direction toward the tie rod 4 ) in advance of the calculation by, for example, the operator in view of the prevention of the melt-down of the sheath 8 similarly to the first and the second embodiment.
- the control device 19 which has obtained from the processor 29 the welding start and completion positions, gap G, laser irradiation position A, heat input H, beam converging diameter D, welding rod supply W and overlap L, controls the laser welding machine 17 and the laser oscillator 18 , and performs the automatic laser welding of the sheath 8 on the tie rod 4 , so that the welding rod 30 is irradiated with the YAG laser beam 23 as being placed at a position corresponding to the axial center position 23 A of the YAG laser beam 23 which is shifted toward the tie rod 4 (in a direction opposite to the sheath 8 ) from the end surface 4 b 1 of the tie rod step 4 b as shown in FIGS. 22 and 23, thereby automatically achieving the perfect weld penetration.
- the automatic YAG laser welding machine 27 performs the laser welding to automatically achieve the perfect weld penetration by calculating the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W, it is possible to prevent the melt-down of the sheath 8 more securely to achieve the good weldability. Moreover, owing to the automatic laser welding, effects such as a reduction in workload of welding operators and improvements in productivity of control rods are achieved.
Abstract
Description
- The present invention relates to a control rod for controlling the power of a boiling water reactor and a method for manufacturing the same.
- The control rod typically has a structure wherein a handle is attached to an axially upper part of a tie rod having a substantially cruciform cross section; a lower part support member (or velocity limiter) is attached to at an axially lower part of the tie rod; and four sheaths, each of which incorporates a reaction rate controlling material, are fixed at a lower end of the handle, an upper end of the lower part support member and ends of the substantially cruciform of the tie rod by welding. In this case, a perfect weld penetration by the TIG welding has been performed for welding the sheaths to the ends of the handle, the lower part support member and the tie rod.
- The control rod moves upward and downward in the narrow gap secured among the fuel assemblies during operation of the reactor. Therefore, a high degree of machining precision is required in manufacturing the control rod.
- However, the conventional TIG welding has such drawbacks that it requires a large amount of heat input and tends to increase deformation due to welding. Thus, in order to suppress the deformation caused by welding, a method employing a laser welding, which requires a less amount of heat input, has been proposed in Japanese Patent Laid-open No. 2000-329885.
- In the aforementioned prior art literature, the perfect weld penetration is carried out in the following manner. Steps are provided on each of tips of arms of the tie rod to fit a U-shaped tip of each of the sheaths thereonto, and each of tips of the sheath are directly irradiated with a laser beam in such a manner that the axial center position of the beam is shifted from an end face of the step of the tie rod to a side opposite to the axis center of the tie rod by 0.1 to 2.0 mm.
- The above-described prior art has the following problems. Specifically, since a width of the step at the tip of each of the arms of the tie rod is typically about 0.5 mm, an overlap of the step of the tie rod with the tip of the sheath is about 0.5 mm. Therefore, if an error occurs in the axial center position of the laser beam and the laser beam is deviated from the very narrow overlap portion, the sheath is heated to melt down due to a slow heat transfer of the laser beam to the tie rod, to thereby cause a welding failure.
- Further, even if the irradiation position of the laser beam is located within the overlap, a contact area of the step of the tie rod with the tip of the sheath must be sufficiently large to satisfactorily transfer the heat of the laser beam to the tie rod. Therefore, the step of the tie rod must be machined to achieve a precise rectangular shape. More specifically, if an R shape (round portion) is formed at a corner of the step of the tie rod, the contact area of the tie rod with the sheath becomes small to fail to provide the satisfactory heat transfer, and such imprecision may cause the melt-down of the sheath, resulting in the welding failure.
- In order to prevent the above problems, the prior art requires a high precision control of the laser beam for the prevention of the deviation of the laser beam irradiating position from the overlap and a high precision machining of the step of the tie rod. Thus, it has been difficult to simplify the manufacturing process of the control rod, and, also, the production cost has been undesirably increased in the prior art.
- An object of the present invention is to provide a control rod for boiling water reactor and a method for manufacturing the control rod for boiling water reactor, whereby the manufacturing process can be simplified and the production cost can be decreased.
- (1) According to an aspect of the present invention, a tie rod having a cruciform cross section is provided with steps for fixing sheaths at tips of cruciform arms of the tie rod; the tips of each of sheaths are fitted onto the steps of the tie rod, each of the sheaths having a U-shaped cross section; and each of the sheaths is fixed to the tie rod by performing a laser welding using a YAG laser beam or a CO2 laser beam with the sheath being fitted onto the tie rod to achieve a continuous weld of at least a part of the tie rod in a longitudinal direction thereof. An axial center position of the beam is shifted from an end face position of the step of the tie rod at least toward an axis center of the tie rod.
- In this case, the laser beam is not irradiated directly on the sheath, but firstly on a surface of the tie rod so that heat is transferred from the surface of the tie rod to the sheath which is being brought into contact with the tie rod step via the tie rod step. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, the heat is transferred to the sheath after passing the contact portion of the step with the sheath without fail, thereby eliminating possibility of a welding failure which is caused by the melt-down of the sheath. Thus, the present invention prevents the melt-down of the sheath to secure a good weldability without high precision control of the beam axial center position which has been performed in the conventional method. Therefore, the present invention facilitates the laser welding control as well as the manufacture of the control rod, and achieves a reduction in manufacturing cost.
- (2) According to another aspect of the present invention, steps of a tie rod are formed by a drawing process, each of sheaths is fixed to the tie rod by performing a laser welding using a laser beam with the sheath being fitted onto the tie rod to achieve a continuous weld of at least a part of the tie rod in a longitudinal direction thereof.
- As described in the above item (1), by shifting the laser beam axial center position toward the tie rod axis center, the melt-down of the sheath can be prevented to thereby secure the good weldability even if the tie rod step is not machined into a precise rectangular shape and thereby an R-shape or the like remains on a corner of the step. Thus, it is possible to omit a machining step from a typical control rod manufacturing method comprising a process step of forming the drawn tie rod having a substantially cruciform cross section by a drawing process and a process step of machining of the steps to achieve the rectangular shapes, thereby making it possible to manufacture a multiple of the tie rods each provided with the steps at one time by the drawing process only. Therefore, the present invention facilitates the manufacture of the control rod by a process corresponding to the machining process omitted, to thereby achieve a reduction in manufacturing cost.
- (3) According to further aspect of the present invention, a step for fixing sheaths is formed on a lower end of a handle attached to an axially upper part of a tie rod; an upper edge of each of the sheaths is fitted onto the step of the handle; and each of the sheaths is fixed to the handle by performing a laser welding using a laser beam with the sheath being fitted onto the handle to achieve a continuous weld of at least a part extending along the upper edge of the sheath. An axial center position of the beam is shifted from an end face position of the step of the handle to a side opposite to the sheath.
- In this case, the laser beam is not irradiated directly on the sheath, but firstly on a surface of the handle so that heat is transferred from the surface of the handle to the sheath which is being brought into contact with the handle step via the handle. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, there is no possibility of a welding failure which is caused by the melt-down of the sheath. Therefore, the same effect as that in Item (1) is obtained.
- (4) According to a still further aspect of the invention, a step for fixing sheaths is formed on an upper end of a lower part support member or a velocity limiter attached to an axially lower part of a tie rod; a lower edge of each of the sheaths is fitted onto the step of the lower part support member or the velocity limiter; and each of the sheaths is fixed to the lower part support member or the velocity limiter by performing a laser welding using a laser beam with the sheath being fitted onto the lower part support member or the velocity limiter to achieve a continuous weld of at least a part extending along the lower edge of the sheath. An axial center position of the beam is shifted from an end face position of the step of the lower part support member or the velocity limiter to a side opposite to the sheath.
- In this case, the laser beam is not irradiated directly on the sheath, but firstly on a surface of the lower part support member so that heat is transferred from the surface of the lower part support member to the sheath which is being brought into contact with the step of the lower part support member via the lower part support member. Accordingly, even if a small error in the beam axial center position occurs to cause a slight deviation from the target position, there is no possibility of a welding failure which is caused by the melt-down of the sheath. Therefore, the same effect as that in Item (1) is obtained.
- FIG. 1 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a first embodiment of the present invention;
- FIG. 2 is a cross-sectional view taken along the section plane indicated by II-II in FIG. 1;
- FIG. 3 is a process-drawing showing manufacturing steps of the control rod of FIG. 1;
- FIG. 4A shows a top view or a bottom view of a drawn tie rod, and FIG. 4B is a top view or a bottom view of a cut tie rod;
- FIG. 5 is a conceptual block diagram showing a general construction of a YAG laser welding machine used for a laser welding in FIG. 3;
- FIG. 6 is an enlarged perspective view showing a part of a welding portion of a sheath on a tie rod in FIG. 3;
- FIG. 7 is a cross-sectional view taken along the section plane indicated by VII-VII in FIG. 6;
- FIG. 8 is an enlarged perspective view showing a part of a welding portion of a sheath on a handle in FIG. 3;
- FIG. 9 is a cross-sectional view taken along the section plane indicated by IX-IX in FIG. 8;
- FIG. 10 is an enlarged perspective view showing a part of a welding portion of a sheath on a velocity limiter in FIG. 3;
- FIG. 11 is a cross-sectional view taken along the section plane indicated by XI-XI in FIG. 10;
- FIG. 12 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a second embodiment of the present invention;
- FIG. 13 is a process drawing showing process steps for manufacturing the control rod in FIG. 1;
- FIG. 14 is a partly enlarged perspective view showing a welding portion of a sheath on a drawn tie rod in FIG. 13;
- FIG. 15 is a cross-sectional view taken along the section plane indicated by XV-XV in FIG. 14;
- FIG. 16 shows a range of the welding conditions;
- FIG. 17 shows a relationship between a heat input parameter Po and an analysis parameter P;
- FIG. 18 is a conceptual block diagram showing a general construction of an automatic YAG laser welding machine used for performing an automatic sheath welding of a method for manufacturing a control rod for boiling water reactor according to a third embodiment of the present invention;
- FIG. 19 shows a scanning method of a laser scanning two dimensional displacement sensor;
- FIG. 20 is a cross-sectional view taken along the section plane indicated by XX-XX in FIG. 19;
- FIG. 21 is a longitudinal sectional view taken along the section plane indicated by XXI-XXI in FIG. 19;
- FIG. 22 is a partly enlarged perspective view showing an automatic welding portion of a sheath on a tie rod according to a third embodiment of the method for manufacturing a control rod for boiling water reactor of the present invention; and
- FIG. 23 is a cross-sectional view taken along the section plane indicated by XXIII-XXIII in FIG. 22.
- Embodiments of a method for manufacturing a control rod for boiling water reactor and a control rod for boiling water reactor according to the present invention will hereinafter be described with reference to the accompanying drawings.
- FIG. 1 is a partly exploded perspective view showing a general structure of a control rod for boiling water reactor according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the section plane indicated by II-II in FIG. 1, in which fuel assemblies N are also shown.
- In FIGS. 1 and 2, a
control rod 1 for boiling water reactor is provided with a control rod supportingstructural body 2 and fourblades 3 each of which extends from anaxis center 2A of the control rod supporting structural body 2 (or anaxis center 4A of atie rod 4 to be described later in this specification) toward four directions. Thecontrol rod 1 as a whole has a cruciform cross section. - The control rod supporting
structural body 2 is provided with atie rod 4 having the cruciform cross section, ahandle 5 fixed to an upper end of thetie rod 4 and avelocity limiter 6 fixed to a lower end of thetie rod 4. - Each of the
blades 3 comprises hafniumflat tubes 7 serving as a neutron absorbing member andsheaths 8 covering the hafniumflat tubes 7. Each of theblades 3 is provided with four hafniumflat tubes 7, two of which being provided in a direction of theaxis center 2A of the control rod supportingstructural body 2, other two of which being provided in a direction extending outward from theaxis center 2A of the control rod supportingstructural body 2. Here, upper ends of the hafniumflat tubes 7 which are provided at an upper part are fixed to thehandle 5 with pins (not shown), lower ends of the hafniumflat tubes 7 which are provided at a lower part are fixed to abase member 6 a of thevelocity limiter 6 with pins (not shown), and thesheaths 8 press the hafniumflat tubes 7 to fix the hafniumflat tubes 7 to the control rod supportingstructural body 2. - Each of the
sheaths 8 is prepared by bending a stainless steel plate, for example, to form a U-shape, and each of tips of thesheath 8 is provided withprojections 8 a and recesses 8 b. Theprojections 8 a are welded to each oftips 4 a of the arms of thetie rod 4, anupper edge 8 c of thesheath 8 is welded to alower end 5 a of thehandle 5, and alower edge 8 d of thesheath 8 is welded to anupper end 6 a 1 of the velocitylimiter base member 6 a, to thereby fix thesheath 8 to the control rod supportingstructural body 2. Each of thesheaths 8 is provided with a plurality ofcooling holes 9 which serve as paths for a coolant. - The method for manufacturing each of main parts of the thus-structured control rod for boiling water reactor according to the first embodiment of the present invention will be described with reference to FIG. 3.
- A
plate 10 is prepared by rolling a material inStep 10 of FIG. 3. Next, inStep 20, theplate 10 is cut in such a manner as to form theprojections 8 a and therecesses 8 b, and then punched to form the cooling holes 9, to thereby obtain aflat sheath 11. InStep 30, thesheath 8 is obtained by bending theflat sheath 11 in such a manner as to form a U-shape using a press machine. - A drawn
tie rod 12 is formed by drawing a material inStep 40 of FIG. 3, and then the drawntie rod 12 is cut inStep 50 to give a tie rod 4 (hereinafter, for the distinction from the drawntie rod 12, thetie rod 4 will be referred to ascut tie rod 4 when so required). Details of shapes of the drawntie rod 12 and thecut tie rod 4 will be described below with reference to FIGS. 4A and 4B. - FIG. 4A is a top view or a bottom view of the drawn
tie rod 12, and FIG. 4B is a top view or a bottom view of thecut tie rod 4. In these drawings, the drawntie rod 12 is the tie rod formed by drawing a material inStep 40, which is provided withsteps 12 b formed at both sides of atip 12 a of each of arms. Acorner 12b 1 of each of thesteps 12 b is slightly R-shaped (curved). - In turn, the
cut tie rod 4 is provided withsteps 4 b formed at both sides of atip 4 a of each of arms like the drawntie rod 12. It is formed by cutting each of thesteps 12 b of the drawntie rod 12 inStep 50 to eliminate the R-shape of thecorner 12b 1. Thus, each of thesteps 4 b has a precise rectangular shape. Thesteps 4 b are provided for the purpose of fitting theprojections 8 a of the tips of thesheath 8 thereonto at the time of welding thesheath 8 to thetie rod 4 in Step 110 which will be described later. - Referring back to FIG. 3, the
handle 5,velocity limiter 6 and other members constituting thecontrol rod 1 for boiling water reactor are manufactured by subjecting materials to machining, assembling, welding and so forth inStep 60. - In
Step 70 of FIG. 3, thehandle 5 manufactured inStep 60 is fixed to an upper end of thecut tie rod 4 by an assembly welding; thevelocity limiter 6 manufactured inStep 60 is fixed to a lower end of thecut tie rod 4 in the same manner; and other members are properly assembled and welded, so that the control rod supportingstructural body 2 is completed. - In FIG. 3, a
hafnium plate 13 is formed by rolling a material inStep 80. Both ends of each of twohafnium plates 13 are bent, and then, inStep 90, the hafnium plates are assembled in such a manner as to face each other, followed by welding seams thereof, so that a hafniumflat tube 7 is completed. - In FIG. 3, the hafnium
flat tube 7, which has been manufactured inStep 90 in the manner described in the item (5), is fixed to the control rod supportingstructural body 2 which has been manufactured inStep 70 in the manner described in the item (4). Here, the upper and lower ends of each of the hafniumflat tubes 7 to be provided in the upper and lower parts are fixed to thehandle 5 and thebase member 6 a of thevelocity limiter 6 with pins as described above, respectively. - The
hafnium tubes 7 fixed to the four positions as described above are then covered with thesheaths 8, respectively, in such a manner that thesheaths 8 respectively incorporate thehafnium tubes 7 from a tip of the U-shape, and theprojections 8 a of each of thesheaths 8 are fitted onto thesteps 4 b of each of the arms of thetie rod 4. Here, thelower end 5 a of thehandle 5 and theupper end 6 a 1 of thebase member 6 a of thevelocity limiter 6 are provided with astep 5 b (see FIG. 9) and astep 6 ab (see FIG. 11) similar to thesteps 4 b, and anupper edge 8 c and alower edge 8 d of each of thesheaths 8 are fitted onto thesteps - In Step110, fitting portions of the
projections 8 a in thesteps 4 b, theupper edges 8 c in thestep 5 b, and thelower edges 8 d in thestep 6 ab are subjected to a laser welding. Thus, thesheaths 8 are fixed to the control rod supportingstructural body 2, so that thecontrol rod 1 for boiling water reactor is completed. - In the method for manufacturing the
control rod 1 for boiling water reactor through the above-described process steps, the greatest characteristic is that, in performing the laser welding with theprojections 8 a, theupper edge 8 c and thelower edge 8 d of each of thesheaths 8 being fitted onto thesteps 4 b, thestep 5 b and thestep 6 a 1, a beam axial center position of the laser beam is shifted from an end face position of thesheath 8 to a side opposite to thesheath 8 to weld them. Hereinafter, details of the laser welding will be described taking an example when welding thesheath 8 on thetie rod 4. - FIG. 5 is a conceptual block diagram showing a general construction of a YAG laser welding machine used in the laser welding. In FIG. 5, a YAG
laser welding machine 14 is provided with a machining table 15 on which thetie rod 4 and thesheath 8 are placed, a holdingfixture 16 for holding thesheath 8, alaser beam machine 17, alaser oscillator 18 for emitting aYAG laser beam 23 which will be described later and acontrol device 19. Thelaser welding machine 17 is provided withrails 17 a, aframe 17 b capable of moving in directions indicated by the arrow A, asupport member 17 c having a substantially L shape which is mounted on theframe 17 b, aslider 17 d capable of moving in directions indicated by the arrow C, asupport rod 17 e extending downward from theslider 17 d and amachining head 17 f capable of moving in directions indicated by the arrow B along thesupport rod 17 e. Owing to this structure, themachining head 17 f can move in three axial directions of A, B and C with respect to the machining table 15. - The
control device 19 is connected with theframe 17 b of thelaser beam machine 17 and with thelaser oscillator 18 respectively by asignal line 20 and asignal line 21, while thelaser oscillator 18 is connected with themachining head 17 f by anoptical fiber 22. Further, an operation panel (not shown) is connected with thecontrol device 19, so that an operator uses the operation panel to control a position of the machining head, laser output and so forth. Here, theprojections 8 a constitute the tips of the U-shape of each of the sheaths which are recited in the appended claims. - Next, details of the first embodiment of the method for manufacturing a control rod for boiling water reactor using the
cut tie rod 4 of the above-described structure will be described with reference to FIGS. 6 and 7. FIG. 6 is a perspective view showing an enlarged part of welded portion of thesheath 8 and thetie rod 4 which are welded using the YAGlaser welding machine 14, and FIG. 7 is a cross-sectional view taken along the section plane indicated by VII-VII in FIG. 6. - In FIGS. 6 and 7, according to the present embodiment, the operator uses the operation panel, while moving the
machining head 17 f in a longitudinal direction (in a direction of the arrow D) of thetie rod 4, to perform a continuous laser welding of theprojection 8 a of thesheath 8 on thestep 4 b of thetie rod 4. In this laser welding, ashield gas 24 is fed from themachining head 17 f at the same time with the irradiation of theYAG laser beam 23 to prevent oxidization of the welded portion. Further, since a welding bead (not shown) immediately after the welding is susceptible to the oxidization, atrailer gas 26 is blown to the welding bead from atrailer nozzle 25 to prevent the oxidization. It is the greatest characteristic of the present embodiment that, theaxial center position 23A (see FIG. 7) of theYAG laser beam 23 is shifted from anend face 4b 1 of thetie rod step 4 b toward the tie rod 4 (to the side opposite to the sheath 8) to irradiate a surface of thetie rod 4 directly with theYAG laser beam 23 for laser welding. - In the conventional technique, wherein the axial center position of the beam is shifted toward the sheath8 (in a side opposite to the tie rod 4) from the
end face 4b 1 of thetie rod step 4 b, it is necessary to control an irradiation position of theYAG laser beam 23 to be located in a very narrow overlap L1 (see FIG. 7) as mentioned above. If an error in theaxial center position 23A of theYAG laser beam 23 occurs to irradiate a portion which is shifted from the overlap L1 toward thesheath 8 with theYAG laser beam 23, thesheath 8 is heated too much since heat generated by the irradiation of theYAG laser beam 23 is difficult to be transferred to thetie rod 4. Thus, in the conventional technique, theprojection 8 a of thesheath 8 has been melted down, resulting in a welding failure in some cases. - By contrast, according to the present embodiment, the surface of the
tie rod 4 is firstly irradiated with theYAG laser beam 23, and then heat generated by the irradiation is transferred from the surface of thetie rod 4 to thesheath 8 via thetie rod step 4 b. Accordingly, even if a small error in theaxial center position 23A of the YAG laser beam occurs and the YAG laser beam slightly deviates from the target position, the heat is transferred to thesheath 8 after passing the contact portion of thetie rod step 4 b with thesheath 8 without fail, to thereby prevent the welding failure which otherwise would be caused by the melt-down of theprojection 8 a of thesheath 8. Therefore, as compared with the conventional technique, the present embodiment prevents the melt-down of thesheath 8 to secure a good weldability without controlling theaxial center position 23A of theYAG laser beam 23 with high precision. Thus, the present embodiment facilitates the laser welding control and the manufacture of thecontrol rod 1 for boiling water reactor, and achieves a reduction in manufacturing cost. - Description has been made on an example in the welding of the
sheath 8 on thetie rod 4, while the following describes an example in the welding of thesheath 8 on thehandle 5. FIG. 8 is a perspective view showing an enlarged part of a welding portion in the welding of thesheath 8 on thehandle 5 using the YAGlaser welding machine 14. FIG. 9 is a cross-sectional view taken along the section plane indicated by IX-IX in FIG. 8. Among the elements shown in FIGS. 8 and 9, those also shown in FIGS. 6 and 7 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description. - In the welding of the
sheath 8 to thehandle 5, themachining head 17 f is moved in a direction along theupper edge 8 c of the sheath 8 (in a direction indicated by the arrow E) to perform a continuous laser welding of theupper edge 8 c of thesheath 8 on thestep 5 b (see FIG. 9) of thelower end 5 a of thehandle 5 as shown in FIGS. 8 and 9. Here, in the same manner as in the welding of thesheath 8 on thetie rod 4 described above, theaxial center position 23A of theYAG laser beam 23 is shifted from anend face 5 b 1 (see FIG. 9) of thehandle step 5 b toward the handle 5 (to the side opposite to the sheath 8) to directly irradiate a surface of thehandle 5 with theYAG laser beam 23 for laser welding. In this case, too, heat generated by the irradiation of theYAG laser beam 23 is transferred from the surface of thehandle 5 to thesheath 8 via thehandle step 5 b. Therefore, similarly to the above described welding of thesheath 8 on thetie rod 4, the present embodiment prevents the melt-down of thesheath 8 to secure the good weldability without controlling theaxial center position 23A of theYAG laser beam 23 with high precision. Thus, the present embodiment facilitates the laser welding control and the manufacture of thecontrol rod 1 for boiling water reactor, and achieves the reduction in manufacturing cost. - Next, the welding of the
sheath 8 on thebase member 6 a of thevelocity limiter 6 will be described. FIG. 10 is a perspective view showing an enlarged part of the welding portion of thesheath 8 on thebase member 6 a of thevelocity limiter 6 which are welded by using the YAGlaser welding machine 14. FIG. 11 is a cross-sectional view taken along the section plane indicated by XI-XI in FIG. 10. Among the elements shown in FIGS. 10 and 11, those also shown in FIGS. 6 and 7 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description. - In the welding of the
sheath 8 on the velocitylimiter base member 6 a, themachining head 17 f is moved in a direction along thelower edge 8 d of the sheath 8 (in a direction indicated by the arrow F in FIG. 10) to perform a continuous laser welding of thelower edge 8 d of thesheath 8 on thestep 6 ab (see FIG. 11) of theupper end 6 a 1 of the velocitylimiter base member 6 a as shown in FIGS. 10 and 11. Here, in the same manner as in the welding of thesheath 8 on thetie rod 4 described above, theaxial center position 23A of theYAG laser beam 23 is shifted from anend face 6 ab 1 (see FIG. 11) of thestep 6 ab of the velocitylimiter base member 6 a toward the velocitylimiter base member 6 a (to the side opposite to the sheath 8) to directly irradiate a surface of the velocitylimiter base member 6 a with theYAG laser beam 23 for laser welding. - In this case, too, heat generated by the irradiation of the
YAG laser beam 23 is transferred from the surface of the velocitylimiter base member 6 a to thesheath 8 via the velocity limiterbase member step 6 ab. Therefore, similarly to the above described welding of thesheath 8 on thetie rod 4, the present embodiment prevents the melt-down of thesheath 8 to secure the good weldability without controlling theaxial center position 23A of theYAG laser beam 23 with high precision. Thus, the present embodiment facilitates the laser welding control and the manufacture of thecontrol rod 1 for boiling water reactor, and achieves the reduction in manufacturing cost. - In addition, although the
tie rod 4, thehandle 5 and the velocitylimiter base member 6 a as members to be welded are directly irradiated with theYAG laser beam 23 in the first embodiment of the present invention, a welding rod may be used for promotion of fusion (see FIG. 23). In this case, since the welding rod is irradiated with theYAG laser beam 23, heat generated by the irradiation is transferred from the welding rod (more precisely, a melted welding rod) to thesheath 8 to prevent the melt-down of thesheath 8, thereby achieving the good weldability. - Next, a method for manufacturing a control rod for boiling water reactor and the control rod for boiling water reactor according to a second embodiment of the present invention will be described with reference to FIGS.12 to 15. In the present embodiment, the control rod for boiling water reactor is manufactured by using the above-described
drawn tie rod 12 which is formed only by drawing, or, without the cutting process. - FIG. 12 is a partly exploded perspective view showing a general structure of the control rod for boiling water reactor according to the present embodiment. Among the elements shown in FIG. 12, those also shown in FIG. 1 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
- In FIG. 12, a
control rod 1′ for boiling water reactor is provided with a control rod supportingstructural body 2′ comprising the drawingtie rod 12, ahandle 5 which is fitted onto an upper end of the drawingtie rod 12 and avelocity limiter 6 which is fixed to a lower end of the drawntie rod 12. - Process steps for manufacturing the control rod for boiling water reactor according to the second embodiment of the present invention will be described with reference to FIG. 13. Among the elements shown in FIG. 13, those also shown in FIG. 3 are denoted by the same reference numerals, and explanations therefor will be omitted in the following description.
-
Steps 10 to 30 formanufacturing sheaths 8,Step 40 for manufacturing the drawntie rod 12 andStep 60 for manufacturing thehandle 5,velocity limiter 6 and other members are the same as those of the first embodiment. - Although the cutting process is performed in
Step 50 succeeding to Step 40 in the first embodiment as shown in FIG. 3, the cutting process is not performed in the present embodiment. Thehandle 5 and thevelocity limiter 6 are fixed to the upper end and the lower end of the drawntie rod 12, respectively by an assembly welding, and the other members are assembled and welded as required inStep 70, so that the control rod supportingstructural body 2′ is completed. -
Steps flat tubes 7,Steps 100 and 110 for manufacturing thecontrol rod 1′ for boiling water reactor are the same as those of the first embodiment. - Here, the drawn
tie rod 12 constitutes the tie rod for fixing the sheaths which is prepared by drawing and provided with steps at each of the tips of the arms of the cruciform as recited in the appended claims. - Next, details of the method for manufacturing the control rod for boiling water reactor of the present embodiment will be described. As shown in FIGS. 14 and 15, a
machining head 17 f is moved in a longitudinal direction of the drawn tie rod 12 (in a direction indicated by the arrow G) to perform a continuous laser welding of theprojection 8 a of thesheath 8 on thestep 12 b of the drawntie rod 12 in the present embodiment. Here, in the same manner as in the first embodiment, anaxial center position 23A (see FIG. 15) of aYAG laser beam 23 is shifted toward the drawn tie rod 12 (to the side opposite to the sheath 8) from anend face 12b 2 of the drawntie rod step 12 b to directly irradiate a surface of the drawntie rod 12 with theYAG laser beam 23 for laser welding. - Since each of
corners 12 b 1 (see FIG. 15) of thestep 12 b of the drawntie rod 12 is in a slightly R-shape due to the omission of the cutting process as described above, theprojection 8 a of thesheath 8 is not completely fitted onto theend face 12b 2 of thestep 12 b. More specifically, an overlap L2 (see FIG. 15) in the present embodiment is narrower than the overlap L1 of thesheath 8 with thecut tie rod 4 of the first embodiment. - In the conventional technique, wherein the laser welding is performed with the
axial center position 23A being shifted toward the sheath 8 (in a direction opposite to the drawn tie rod 12) from theend face 12b 2 of thestep 12 b, it is necessary to control the irradiation position of theYAG laser beam 23 to be located inside the very narrow overlap L2 which is yet narrower than the overlap L1 in the first embodiment, to thereby increase the possibility of the melt-down of thesheath 8 due to an error in controlling the laser irradiation position. Also, since a thermal transfer from thesheath 8 to the drawntie rod 12 is smaller due to the narrowed overlap L2, the possibility of the melt-down of thesheath 8, which results in a welding failure, is further increased in the conventional technique. - By contrast, in the present embodiment, since the surface of the drawn
tie rod 12 is irradiated with theYAG laser beam 23, heat generated by the irradiation is transferred from the surface of the drawntie rod 12 to thesheath 8 via the drawntie rod step 12. Therefore, the present embodiment prevents the melt-down of theprojection 8 a of thesheath 8 and the welding failure even if a small error in the irradiation position of theYAG laser beam 23 occurs. - More specifically, according to the present embodiment, by shifting of the irradiation position of the
YAG laser beam 23 toward the drawn tie rod 12 (in a direction opposite to the sheath 8), it is possible to prevent the melt-down of thesheath 8 and to secure the good weldability even if the drawntie rod 12 is not machined into the precise rectangular shape and remains the R-shape on thecorner 12b 1. Thus, it is possible to omit the machining step from a typical tie rod manufacturing process consisting of the process steps of formation of the drawntie rod 12 from a material by drawing and machining of thesteps 12 b to achieve the rectangular shape, thereby enabling thecontrol rod 1′ for boiling water reactor to be manufactured by using the drawntie rod 12 prepared only by the drawing process. Therefore, the present embodiment facilitates the manufacture of the control rod by a step corresponding to the omitted machining process, which leads to a reduction in manufacturing cost. - In addition, the welding rod described in the first embodiment may be used also in the present embodiment for promotion of fusion (see FIG. 23). In this case, too, it is possible to achieve the above-described effects of the present embodiment.
- Next, a third embodiment of the method for manufacturing a control rod for boiling water reactor of the present invention will be described with reference to FIGS.16 to 23. In the present embodiment, weldings of
sheath 8 on thetie rod 4, thesheath 8 on thehandle 5, thesheath 8 on the velocitylimiter base member 6 a are automated. - For the purpose of automating the laser welding, the inventors of the present invention have conducted welding experiments using the
sheath 8 and thetie rod 4 under various welding conditions to find out a welding condition under which a prevention of the melt-down of thesheath 8 as well as a perfect weld penetration are achieved. FIG. 16 shows a range of the welding conditions. As a result of the welding experiments, states after the weldings are broadly classified into three states of a state wherein a penetration bead is not formed and the perfect weld penetration is not achieved, a state wherein the perfect weld penetration is achieved and a state wherein thesheath 8 is melted down. - Then, the inventors have converted the three states onto numerical values by using a heat input parameter Po which relates to an amount of heat input. More specifically, the state wherein the perfect weld penetration is not achieved due to an insufficient heat input is represented by Po=−1, the state wherein the perfect weld penetration is achieved is represented by Po=0, and the state wherein the
sheath 8 is melted down is represented by Po=1. - Further, the inventors have conducted multiple regression analyses of welding conditions associated with the above three states to obtain an analysis parameter P represented by the following equation:
- P=0.184+1.11×G+0.964×A+1.07×H−1.17×D−0.11×W−0.807×L
- where G represents a gap (mm) between an
inner surface 8 a 5 (see FIG. 21) of asheath projection 8 a and abase 4b 3 of atie rod step 4 b in a state where thesheath projection 8 a is fitted onto thetie rod step 4 b; A represents a distance (mm) (hereinafter referred to as “laser irradiation position A” when so required) from anaxial center position 23A of aYAG laser beam 23 to anedge 8 a 1 (see FIG. 20) of thesheath projection 8 a on the premise that a direction toward thesheath 8 is a positive direction and a direction toward thetie rod 4 is a negative direction; H represents heat input (kj/cm) by theYAG laser beam 23; D represents a beam converging diameter (mm) of theYAG laser beam 23; W represents a supply (g/m) of awelding rod 30 for one meter of welding length; and L represents an overlap (mm) (see FIG. 20) of theinner surface 8 a 5 of thesheath projection 8 a with thebase 4b 3 of thetie rod step 4 b in the state where thesheath projection 8 a is fitted onto thetie rod step 4 b. - FIG. 17 shows a relationship between the heat input parameter Po and the analysis parameter P. According to FIG. 17, the heat input parameter Po becomes 0 when the analysis parameter P is in the range of −0.5 to 0.5 to achieve the perfect welding. More specifically, as can be seen from FIG. 17, if values for the gap G, laser irradiation position A, heat input H, beam converging diameter D, control rod supply W and overlap L are given, it is possible to find out the state after welding by the heat input parameter Po since the heat input parameter Po is dependent on the analysis parameter P. According to the inventors' research, the most satisfactory conditions of the above values are in the following range: 0 to 0.3 mm of the gap G; 0 to −0.5 mm of the laser irradiation position A; 0.89±0.2 kj/cm of the heat input H; 0.57 to 0.6 mm of the beam converging diameter D; 3.16 to 4.06 g/m of the welding rod supply W; and 0.3 to 0.6 of the overlap L.
- FIG. 18 is a conceptual block diagram showing a general construction of an automatic YAG laser welding machine which performs the automatic welding using the above analysis parameter P. Among the elements shown in FIG. 18, those also shown in FIG. 5 of the first embodiment are denoted by the same reference numerals, and explanations therefor will be omitted in the following description. In FIG. 18, the automatic YAG
laser welding machine 27 is provided with a laser scanning two-dimensional displacement sensor (not shown) attached to themachining head 17 f, an welding rod supply device (not shown) for performing an automatic supply of awelding rod 30, which is to be described later in this specification, as being attached to themachining head 17 f, aprocessor 29 which is connected with thecontrol device 19 via a signal line 28, and a servo motor (not shown) for moving themachining head 17 f to a welding start position and a welding completion position which are instructed by thecontrol device 19. - The
processor 29 calculates the welding start position, welding completion position, gap G and overlap L from values detected by the laser scanning two dimensional displacement sensor, and further calculates the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W from the gap G and overlap L using the analysis parameter P. - Next, details of the method for manufacturing a control rod for boiling water reactor of the present embodiment using the above-described automatic YAG
laser welding machine 27 will be described. FIG. 19 shows a scanning method of the laser scanning two dimensional displacement sensor; FIG. 20 is a cross-sectional view taken along the section plane indicated by XX-XX in FIG. 19; and FIG. 21 is a longitudinal sectional view taken along the section plane indicated by XXI-XXI in FIG. 19. - Referring to FIGS.19 to 21, the automatic YAG
laser welding machine 27 detects coordinates of anedge 8 b 1 (see FIG. 20) of arecess 8 b of thesheath 8 and anouter corner 4 b 2 (see FIG. 20) of thestep 4 b near a tip of thetie rod 4 by automatically scanning in a direction indicated by the arrow H in FIG. 19. Also, the automatic YAGlaser welding machine 27 detects coordinates of bothedges 8 a 2 and 8 a 3 (see FIG. 21) of theprojection 8 a of the sheath, a height of thebase 4 ba (see FIG. 21) of thestep 4 b of thetie rod 4 and a height of anouter surface 8 a 4 of thesheath projection 8 a by scanning in a direction indicated by the arrow I in FIG. 19. - The
processor 29 calculates the gap G between thesheath 8 and thetie rod 4 and the overlap L of thesheath 8 with thetie rod 4 from the data which are obtained by the two scannings of the laser scanning two dimensional displacement sensor as well as a length of thesheath projection 8 a (a distance between theedge 8 a 1 of thesheath projection 8 a and theedge 8b 1 of thesheath recess 8 b) and a thickness of thesheath 8 which are inputted by, for example, the operator. The coordinates of the bothedges 8 a 2 and 8 a 3 of theprojection 8 a of thesheath 8 which are obtained by the above scanning are used as the welding start position and the welding completion position as they are. - Also, the
processor 29 calculates the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W to achieve the analysis parameter P of not less than −0.5 to not more than 0.5 by using the thus obtained gap G and overlap L. At this point, a value of the laser irradiation position A is set to a negative value (i.e. to be shifted in a direction toward the tie rod 4) in advance of the calculation by, for example, the operator in view of the prevention of the melt-down of thesheath 8 similarly to the first and the second embodiment. - The
control device 19, which has obtained from theprocessor 29 the welding start and completion positions, gap G, laser irradiation position A, heat input H, beam converging diameter D, welding rod supply W and overlap L, controls thelaser welding machine 17 and thelaser oscillator 18, and performs the automatic laser welding of thesheath 8 on thetie rod 4, so that thewelding rod 30 is irradiated with theYAG laser beam 23 as being placed at a position corresponding to theaxial center position 23A of theYAG laser beam 23 which is shifted toward the tie rod 4 (in a direction opposite to the sheath 8) from theend surface 4b 1 of thetie rod step 4 b as shown in FIGS. 22 and 23, thereby automatically achieving the perfect weld penetration. - According to the present embodiment described above, since the
YAG laser beam 23 irradiates thewelding rod 30, heat generated by the irradiation is transferred from thewelding rod 30 to thesheath 8. In particular, since thewelding rod 30 is irradiated with theYAG laser beam 23 which is shifted toward thetie rod 4 in the same manner as in the first and second embodiments, a surface of thetie rod 4 is irradiated with theYAG laser beam 23 if the irradiation position is erroneously deviated from thewelding rod 30. More specifically, heat generated by the irradiation transfers from the surface of thetie rod 4 to thesheath 8 via thetie rod step 4 b in the same manner as in the first embodiment. Therefore, according to the present embodiment, the melt-down of thesheath 8 is prevented without fail to achieve the good weldability. - Further, according to the present embodiment, since the automatic YAG
laser welding machine 27 performs the laser welding to automatically achieve the perfect weld penetration by calculating the laser irradiation position A, heat input H, beam converging diameter D and welding rod supply W, it is possible to prevent the melt-down of thesheath 8 more securely to achieve the good weldability. Moreover, owing to the automatic laser welding, effects such as a reduction in workload of welding operators and improvements in productivity of control rods are achieved. - Although the present embodiment is described in connection with the welding of the
sheath 8 on thetie rod 4, it is possible to perform the automatic weldings of thesheath 8 on thehandle 5, and thesheath 8 on the velocitylimiter base member 6 a by the same process steps to achieve the same effects.
Claims (12)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US10/409,124 US6882696B2 (en) | 2001-12-17 | 2003-04-09 | Control rod for boiling water reactor and method for manufacturing the same |
US10/798,354 US20050105668A1 (en) | 2001-12-17 | 2004-03-12 | Control rod for boiling water reactor and method for manufacturing the same |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2001-383262 | 2001-12-17 | ||
JP2001383262A JP3752451B2 (en) | 2001-12-17 | 2001-12-17 | Manufacturing method of control rod for boiling water reactor |
Related Child Applications (2)
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US10/409,124 Division US6882696B2 (en) | 2001-12-17 | 2003-04-09 | Control rod for boiling water reactor and method for manufacturing the same |
US10/798,354 Continuation US20050105668A1 (en) | 2001-12-17 | 2004-03-12 | Control rod for boiling water reactor and method for manufacturing the same |
Publications (2)
Publication Number | Publication Date |
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US20040076254A1 true US20040076254A1 (en) | 2004-04-22 |
US6735266B1 US6735266B1 (en) | 2004-05-11 |
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US10/274,040 Expired - Lifetime US6735266B1 (en) | 2001-12-17 | 2002-10-21 | Control rod for boiling water reactor and method for manufacturing the same |
US10/409,124 Expired - Fee Related US6882696B2 (en) | 2001-12-17 | 2003-04-09 | Control rod for boiling water reactor and method for manufacturing the same |
US10/798,354 Abandoned US20050105668A1 (en) | 2001-12-17 | 2004-03-12 | Control rod for boiling water reactor and method for manufacturing the same |
Family Applications After (2)
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US10/409,124 Expired - Fee Related US6882696B2 (en) | 2001-12-17 | 2003-04-09 | Control rod for boiling water reactor and method for manufacturing the same |
US10/798,354 Abandoned US20050105668A1 (en) | 2001-12-17 | 2004-03-12 | Control rod for boiling water reactor and method for manufacturing the same |
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JP (1) | JP3752451B2 (en) |
Cited By (1)
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JP2015031619A (en) * | 2013-08-05 | 2015-02-16 | 日立Geニュークリア・エナジー株式会社 | Method of manufacturing control rod for reactor |
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US7313617B2 (en) * | 2001-09-28 | 2007-12-25 | Dale Malik | Methods and systems for a communications and information resource manager |
DE102005001435A1 (en) * | 2005-01-07 | 2006-07-20 | Andreas Link | Absorber for a solar thermal collector and method for producing such an absorber |
JP4846392B2 (en) * | 2006-02-28 | 2011-12-28 | 株式会社東芝 | Underwater repair welding method |
JP4961154B2 (en) * | 2006-03-23 | 2012-06-27 | 日立Geニュークリア・エナジー株式会社 | Manufacturing method of control rod for boiling water reactor |
DE102006016096B3 (en) * | 2006-04-04 | 2007-12-13 | J. Eberspächer GmbH & Co. KG | Component arrangement and associated manufacturing method |
CA2551252C (en) * | 2006-06-22 | 2012-10-23 | 9031-1671 Quebec Inc. | Hollow pipe connector |
US8530777B2 (en) * | 2006-10-20 | 2013-09-10 | Swagelok Company | Welding purge control using electronic flow control |
JP4369493B2 (en) * | 2007-03-30 | 2009-11-18 | 日立Geニュークリア・エナジー株式会社 | Control rod |
JP5171151B2 (en) * | 2007-08-07 | 2013-03-27 | 日立Geニュークリア・エナジー株式会社 | Control rod for boiling water reactor |
US20090057373A1 (en) * | 2007-08-30 | 2009-03-05 | Gm Global Technology Operations, Inc. | Multi-Purpose End Effector for Welder |
US20090139969A1 (en) * | 2007-11-29 | 2009-06-04 | Global Nuclear Fuel - Americas Llc | Laser welding of castings to minimize distortion |
US8761331B2 (en) * | 2009-09-11 | 2014-06-24 | Hitachi-Ge Nuclear Energy, Ltd. | Control rod for boiling water reactor |
JP6242082B2 (en) * | 2013-05-31 | 2017-12-06 | 日立Geニュークリア・エナジー株式会社 | Control rod for boiling water reactor |
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US4473738A (en) * | 1981-10-05 | 1984-09-25 | Dayton Superior Corporation | Method and apparatus for hot forming a polygonal head on a snap tie rod |
JPS58147687A (en) * | 1982-02-26 | 1983-09-02 | 株式会社東芝 | Control rod for reactor |
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-
2001
- 2001-12-17 JP JP2001383262A patent/JP3752451B2/en not_active Expired - Lifetime
-
2002
- 2002-10-21 US US10/274,040 patent/US6735266B1/en not_active Expired - Lifetime
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- 2003-04-09 US US10/409,124 patent/US6882696B2/en not_active Expired - Fee Related
-
2004
- 2004-03-12 US US10/798,354 patent/US20050105668A1/en not_active Abandoned
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JP2015031619A (en) * | 2013-08-05 | 2015-02-16 | 日立Geニュークリア・エナジー株式会社 | Method of manufacturing control rod for reactor |
Also Published As
Publication number | Publication date |
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US6735266B1 (en) | 2004-05-11 |
US20050105668A1 (en) | 2005-05-19 |
US20040091077A1 (en) | 2004-05-13 |
JP3752451B2 (en) | 2006-03-08 |
US6882696B2 (en) | 2005-04-19 |
JP2003185777A (en) | 2003-07-03 |
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