JP5260410B2 - Method and apparatus for preventive maintenance of in-furnace equipment - Google Patents

Description

  The present invention relates to a preventive maintenance method for stress corrosion cracking in a reactor pressure vessel in a nuclear power plant.

  As a preventive maintenance method for the outer surface welded portion of the in-furnace equipment such as an in-core instrument tube, a water jet peening method using high pressure water containing cavitation bubbles (Japanese Patent Laid-Open No. 2006-201141) has been proposed. This water jet peening method improves the residual stress in the vicinity of the surface of the metal material by utilizing the generated impact pressure when the cavitation bubble collapses. The conventional preventive maintenance method based on the water jet peening method was devised as a method for preventing stress corrosion cracking that occurs in or near the weld when a metal material such as a nickel-base alloy (600 alloy) is placed in high-temperature water. It is a thing. It is said that stress corrosion cracking occurs under conditions where material, stress, and environmental factors are superimposed as factors of occurrence, and the water jet peening method is a technology that eliminates stress factors from these three factors to prevent stress corrosion cracking. is there.

  Further, as a preventive maintenance method for surface modification by overlay welding using a welding material having corrosion resistance from the viewpoint of material factors, JP 2002-90494 A, Atom A preventive maintenance method described in Japanese Patent Application Laid-Open No. 2001-124888 has been proposed for a welded portion of a furnace.

JP 2006-141141 A JP 2002-90494 A JP 2001-124888 A

  The above-mentioned technique is extremely effective as a preventive maintenance method for the outer surface of an in-core instrument tube that stands at the bottom of the reactor pressure vessel. The construction is not considered.

  In addition, the above-mentioned technology for the inner surface of the in-core instrumentation cylinder is an effective means for surface modification of the inner surface of the in-core instrumentation cylinder. There is no consideration for construction in the event of a crack.

  Moreover, in the preventive maintenance method of surface modification by overlay welding for the welded portion in the reactor described above, although there is a description from the material aspect, an actual nuclear reactor intended for an operating plant during the service period There is no consideration for construction when applying to the reactor internal structure, and in terms of shortening the construction period from the economical point of view when there are many workable parts for complex shaped parts and preventive maintenance target devices. Not considered. Also, there is no consideration for the presence or absence of cracks in the preventive maintenance target part, and no consideration is given to construction in the event of a crack.

  Therefore, the problem to be solved by the present invention is to provide a preventive maintenance method having excellent reliability after construction.

  In order to solve the above-mentioned problems, the present invention is a preventive maintenance method for in-core equipment that prevents stress corrosion cracking of a reactor pressure vessel by build-up welding having excellent corrosion resistance, and is attached to the inner surface of the reactor pressure vessel by welding. Inspecting the in-reactor equipment or the welded portion of the reactor pressure vessel, and changing the build-up welding conditions according to the inspection result.

By the above means, it is possible to provide a preventive maintenance method that is excellent in reliability after construction and shortens the construction period .

The preventive maintenance method flow which is one Example of this invention is shown. The welding construction figure with respect to the presence or absence of a crack which is one Example of this invention is shown. The welding condition setting flow which is one Example of this invention is shown. The crack growth evaluation procedure which is one Example of this invention is shown. 1 shows a cross section of a reactor pressure vessel to which the present invention is applied. 1 shows an apparatus configuration for surface polishing, which is an embodiment of the present invention. The apparatus structure of welding which is one Example of this invention is shown. The welding torch operation | movement figure which is one Example of this invention is shown. 1 shows an apparatus configuration of a penetrant flaw inspection (PT) which is an embodiment of the present invention. 1 shows an apparatus configuration of water jet peening according to an embodiment of the present invention. The outline of the watertight seal which is one example of the present invention is shown. The apparatus structure of the welding torch with a local watertight seal which is one Example of this invention is shown. 1 shows an outline of a common access device according to an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a work procedure of a preventive maintenance method by overlay welding which is an embodiment of the present invention.

  First, a pre-inspection of the in-core instrument tube 5 weld located at the bottom of the reactor pressure vessel 1 is performed to check for cracks. As a preliminary inspection, a visual inspection (VT) is first performed, and if a crack is found by the visual inspection (VT), a detailed inspection is performed by an ultrasonic inspection (UT) and an eddy current inspection (ECT). Identify the position, length and depth of the. FIG. 1 shows the procedure for carrying out visual inspection (VT). However, visual inspection (VT) is omitted and eddy current inspection (ECT) is performed to confirm the presence or absence of cracks and specify the position, and then ultrasonic inspection ( In some cases, depth measurement is performed by UT). If it is determined that there is no crack in these preliminary inspections, preventive maintenance work, which is the next process, is selected in order to prevent the occurrence of stress corrosion cracking in the weld. Move on. In addition, if it is determined that there is a crack based on the results of the preliminary inspection, based on the reference position for overlay welding for repair purposes and the reference position, based on the data on the position, length and depth of the crack. Set the welding range, evaluate the amount of crack propagation to the build-up welding side, set the thickness of build-up welding, and move on to the next process, repair and preventive maintenance.

  Next, the preventive maintenance work will be described by taking the outer surface welded portion of the in-core instrument tube as an example of the in-furnace equipment. The preventive maintenance work when there is no crack and the repair and preventive maintenance work when there is a crack are many of the same work, so they are described collectively below.

  First, the surface of the welded portion of the target in-core instrumentation cylinder 5 is polished to remove oxide film, dust, clad, etc. adhering to the surface, and then the shape dimensions before welding are measured in advance. Next, overlay welding is performed. As welding conditions at this time, a welding operation is performed by setting a reference position, a welding range, and a welding thickness as a condition reflecting the result of the preliminary inspection. After the welding is completed, the surface is polished to remove the oxide film by welding, and the dimensions of the weld are measured using a dimension measuring device. In this operation, the overlay thickness is also checked. In particular, when there is a crack, the build-up thickness is obtained from the crack propagation amount as described above, and therefore it is confirmed that the required value of the build-up weld thickness is satisfied. After that, surface inspection (post-welding inspection) after build-up welding is performed by penetration inspection (PT) or eddy current inspection (ECT), and water jet peening (WJP) is performed to reduce residual stress in the vicinity of the weld. To do.

  FIG. 2 (a) shows welding with cracks, and FIG. 2 (b) shows welding with no cracks. FIG. 3 shows a welding condition setting flow.

  When there is a crack, overlay welding (with crack) 3 is performed on the entire surface where the crack 2 exists. At that time, the position coordinates are set by using data acquired by eddy current inspection (ECT), and the build-up weld length L2 is wider than the length L1 of the crack 2. The build-up welding length is calculated by adding a certain length to the starting point coordinate and the end point coordinate of occurrence of crack 2, and calculating the coordinates of the build-up welding start position and end position, and inputs them to the welding control apparatus as welding conditions. Here, the build-up weld thickness t1 is determined by using the crack growth evaluation result obtained by adding the subsequent plant operation time to the crack measurement result, and the crack is formed on the build-up weld side during the operation period of the plant. Set as a thickness that does not penetrate and penetrate. FIG. 4 shows a procedure for crack growth evaluation. In the evaluation procedure, an initial crack is set, a load condition is set, and a build-up weld thickness is set, and fatigue crack growth evaluation is performed based on the conditions. This evaluation depends on the build-up weld thickness. Therefore, fracture evaluation of the entire structure is performed in consideration of the crack length after fatigue crack growth after build-up. The build-up weld thickness is set so as to be within the range of the overall structure fracture evaluation (a range where fracture does not occur). The initial crack is set by using the results obtained in the ultrasonic inspection (UT) and eddy current inspection (ECT) performed in the preliminary inspection. In setting the load condition, the number of repetitions of the load load during the evaluation period is set from the operation results. The build-up weld thickness t1 is initially set to an assumed value. Fatigue crack growth evaluation is performed by adding the cyclic load obtained by setting the load condition to the residual crack after build-up welding and analyzing the crack growth amount with respect to the operating years. Fracture evaluation of the entire structure is performed for fracture length considering fatigue crack growth evaluation, and it is evaluated by analysis that all the operating conditions during plant operation and that no damage occurs during an earthquake. This crack growth evaluation uses the method disclosed in the nuclear power generation equipment standard maintenance standard. Based on the above evaluation results, the operation years are assumed, and the build-up weld thickness t1 that does not penetrate the crack during that period and can ensure the strength of the entire structure is set. Next, the required number of weld layers is calculated from the weld thickness per layer with respect to the build-up weld thickness t1, and is input as a welding condition to the welding power source and the control device. The build-up weld length L2 that is wider than the length of the crack 2 is the same as the build-up weld thickness t1, and the crack length is determined in consideration of the fatigue crack growth evaluation, and the crack position is measured. It is set from the extra length that adds the accuracy and position accuracy of overlay welding.

  When there is no crack, build-up welding (no crack) 4 is performed for the purpose of surface modification, and the build-up weld thickness t2 considers the amount of crack propagation to the build-up welding side of the cracked case There is no need to do this, it is only necessary to consider dilution by welding to the overlay welding side of the material to be built up, and depending on the welding heat input, if the heat input is about 2 kJ / cm, about 1 mm It is enough. In this case, the range of overlay welding is set to the entire surface of the existing welded portion of the in-core instrument tube 5 and the range covered by the weld heat affected zone. In addition, as a build-up welding material with and without cracks, the corrosion resistance of the weld metal 82 alloy used for clad welding of the conventional 600 series nickel base alloy or 690 series nickel base alloy is further improved. 52 alloy is used.

  Note that the welding condition needs to be a heat input amount in consideration of prevention of deformation of the in-core instrument tube 5. Therefore, the welding heat input when there is no crack is a low heat input of 5 kJ / cm or less, more preferably 2 kJ / cm or less. As an example of the setting range, a welding current of 130 to 175 A, a voltage of 8 to 10 V, and a welding speed of 45 To 70 cm / min. In the case where cracks are confirmed, the welding condition range used for general Inconel TIG overlay welding is about 3 to 20 kJ / cm. As a result, at about 20 kJ / cm, the weld is at the end of the overlay bead. Since dents (undercuts) were observed, it was set to 15 KJ / cm or less, and about 5 to 15 kJ / cm was set as an appropriate welding condition range. Examples of the setting range include a welding current of 100 to 180 A, a voltage of 9 to 11 V, and a welding speed of 8 to 11 cm / min. The welding current, voltage, and welding speed are input to the control device and the welding power source as welding conditions. This eliminates dents and the like at the end of the built-up bead, and can provide a highly reliable preventive maintenance method considering deformation prevention.

  Here, the TIG welding can be replaced with laser welding. In the case of laser welding, the amount of heat input is set by laser output power (kW = kJ / s) and welding speed (cm / min) corresponding to the welding current, voltage, and welding speed, which are TIG welding conditions.

  The effect of these examples is that the construction of the preventive maintenance method can be performed with the same welding machine by carrying out the inspection of the construction site in advance and changing the overlay welding conditions depending on the presence or absence of cracks. It is possible to carry out preventive maintenance that also serves as a repair in a relatively short period of time, even if a crack is discovered, by eliminating the need for repair using another processing machine. Moreover, the preventive maintenance method excellent in the reliability after construction can be provided.

  FIG. 5 shows a cross section of the reactor pressure vessel 1 that is the subject of this construction method.

  A large number of in-core instrumentation cylinders 5 stand through the reactor pressure vessel lower mirror 6. The target of preventive maintenance is the welded portion of the penetration portion of the reactor pressure vessel lower mirror 6 and the outer peripheral portion of the in-core instrument tube 5, and the shape of the welded portion reflects the hemispherical shape of the lower mirror 6 and is three-dimensional. It has a shape. Therefore, a device used for preventive maintenance work requires a mechanism corresponding to the shape of the welded portion. An example of the apparatus is shown below.

  FIG. 6 shows an example of surface polishing.

  As a device for accessing the grinding wheel 11 to the outer periphery welded portion of the in-core instrumentation cylinder 5, in a configuration having a head turning drive unit 8 and a head lifting drive unit 9, a polishing arm 10, a polishing drive unit 12 and a grinding wheel are provided at the tip. 11 is provided. The grinding wheel 11 is used for the purpose of removing oxide film, dust and clad adhering to the surface. For example, a grinding wheel in which abrasive grains are uniformly applied and bonded to a wire brush or a non-woven fabric is used. Polishing operation is performed by the rotational force. The polishing arm 10 swivels around the in-furnace instrumentation cylinder 5 as a reference to cover a range of 360 °.

  FIG. 7 shows an example of welding.

  In the head structure in which the entire welded portion of the in-core instrument tube 5 rising from the reactor pressure vessel lower mirror 6 is covered with a watertight seal 19, a welding torch 17, a mechanism of a torch swinging motion 20, a head turning motion 14 and a head are contained therein. The mechanism of the raising / lowering operation | movement 13 and the welding wire feeder 18 are provided. The operation of each mechanism is performed by each device installed on the operation floor above the reactor pressure vessel, and includes a control device 15b, a welding power source 21, a cooling water circulation device 22, a camera controller, and a monitor 16b. Here, since the reactor pressure vessel 1 is in a full water state, a watertight seal 19 is used in order to locally bring the welded portion into the air environment.

  As shown in the welding condition control flow in FIG. 4, the present apparatus uses the controller 15 to control the driving operation of the apparatus according to the welding condition input value set according to the presence or absence of cracks. Do. Here, the information on the position and range to be welded is used for controlling the torch swinging motion 20, the head turning motion 14 and the head lifting / lowering motion 13, and is operated by positioning the tip of the welding torch 17 within a predetermined range. Further, the information on the build-up weld thickness is similarly used to control the torch swinging motion 20, the head turning motion 14 and the head lifting / lowering motion 13, but here is set as a condition of the number of layers of the build-up. FIG. 8A and FIG. 8B show an example of the operation procedure of the welding torch. The welding torch 17 is moved to the welding start point 46 with respect to the welded portion 45 of the in-core instrument tube 5, and the position coordinates are taught. Subsequently, the welding torch 17 is moved to the welding start point 46 and the position coordinates are taught. An interpolated path between the taught welding start point 46 and the welding end point 47 is created, the welding torch 17 is moved to the welding start point 46 again, and overlay welding 48 is performed between the welding end points 47. When there is no crack, this operation is repeated 360 ° around the circumference of the in-core instrumentation cylinder 5, and the entire surface of the weld is welded. Further, when there is a crack, the range corresponding to the build-up welding length L2 is set to the welding start point 46 and the welding end point 47, and the process is performed. The welding heat input is a condition related to the welding current, welding voltage, and welding speed, and is input to the control device 15 b and the welding power source 21. The welding current and welding voltage are set by the welding power source 21, and the welding speed is set by the control device 15b. The trajectory of the welding torch is calculated from the conditions of the welding position and range in advance, and is distributed to the respective operating speeds of the torch swinging movement 20, the head turning movement 14 and the head lifting movement 13 so that a predetermined welding speed is obtained at that time. Control the operation.

  Here, when the configuration in the TIG welding is replaced with laser welding, the welding torch 17 and the welding power source 21 correspond to the laser welding nozzle and the laser transmitter, and the transmission between the laser welding nozzle and the laser transmitter is an optical fiber cable. By connecting, a system can be achieved as well.

  The effect of these examples is that the welder has a function to create a local air environment, so that preventive maintenance work can be performed with reactor water filled in the reactor pressure vessel, and the exposure of workers can be reduced. That preventive maintenance can be performed. Furthermore, the work period can be shortened because the work can be performed with the reactor water filled.

  Surface polishing after welding is shared with the surface polishing apparatus.

  FIG. 9 shows an example of a penetrant inspection (PT).

  In the head structure in which the entire welded portion of the in-core instrument tube 5 rising from the reactor pressure vessel lower mirror 6 is covered with a water-tight seal 19, a head turning drive unit 8 and a head lifting drive unit 9 are built in, and a penetrant flaw inspection is provided beyond that. A (PT) liquid coating / cleaning / drying nozzle head 23 and a camera (mirror) swing mechanism 25 having a camera at the tip are provided. The operation of each mechanism is performed by each device installed on the operation floor above the reactor pressure vessel. The control device 15c, the PT solution / washing water / air supply unit 28, the PT solution / washing water recovery unit 29, It comprises a dry hot air supply unit 30, an observation camera, a controller, and a monitor 16c. Here, a water-tight seal is used in order to make the inspection surface of the penetrant inspection (PT) locally in the air environment as in the case of welding.

  The procedure of the penetration inspection (PT) is as follows.

  The first procedure is cleaning of the weld surface. In this method, the PT liquid application / cleaning / drying nozzle head 23 is positioned on the welding surface by using the head turning drive unit 8 and the head lifting / lowering drive unit 9, and then pretreatment cleaning is performed by spraying cleaning water. Then, dry hot air is fed to remove moisture from the cleaning surface.

  The second procedure is penetration inspection (PT) solution application. This is because, after positioning the PT liquid application / cleaning / drying nozzle head 23 to the target site, a penetrant flaw detection (PT) liquid is sprayed from the tip of the nozzle, and after a predetermined time has elapsed, the cleaning liquid is then sprayed and penetrated. Rinse the test (PT) solution. At this time, the penetrant flaw detection (PT) liquid and the cleaning water are collected by suction by the PT liquid / cleaning water recovery unit 29. Then, dry hot air is fed to remove moisture from the cleaning surface.

  The third procedure is a penetration inspection (PT) determination. This is done by irradiating the welding surface with ultraviolet (UV) light and scanning the entire surface using an observation camera to confirm that there is no significant indication pattern at that time.

  FIG. 10 shows an example of water jet peening.

  Water jet peening is performed on the entire surface of the in-core instrument tube 5 in order to reduce the residual stress in the welded portion. As a device for accessing the water injection nozzle 43 to the built-up welded portion of the in-core instrumentation cylinder 5, in the configuration having the head turning drive unit 8 and the head lifting drive unit 9, the nozzle arm 49 and the water injection nozzle 43 are provided at the tip. Prepare. The nozzle arm 49 rotates 360 ° around the in-core instrument tube 5 and adjusts the direction and distance of the water injection nozzle 43 by the head lifting / lowering operation 13 and the water injection nozzle swinging operation 44 to spray high-pressure water. . In the case where there is no crack, overlay welding is performed in accordance with the existing welding shape. However, in the case where there is a crack, the shape is partially different depending on the overlay welding thickness t1 in FIG. 2A described above. Then, the operation of the water jet nozzle 43 following the overlay shape is performed. This operation can be achieved by teaching in advance the position coordinates of the change point (start point, end point, and a plurality of intermediate points) of the build-up shape and teaching back. As a result, it is possible to reduce the residual stress at the site where overlay welding is performed.

  FIG. 11 shows an example of the watertight seal 19.

  Among these methods, welding and penetration testing (PT) need to be locally in the air, so a watertight seal is used. At this time, since the in-core instrumentation cylinder 5 stands in the spherical shape of the reactor pressure vessel lower mirror 6, the contact with the seal at the lower mirror surface becomes a three-dimensional curved surface, and its shape changes greatly in the tilt direction depending on the position. To do. Since this shape changes in size for each plant and also changes depending on the position, if it is prepared for each target in-core instrumentation cylinder 5, a huge amount is required. For this reason, in order to obtain a structure that can be used in common, the following structure is adopted.

  The watertight seal has a plurality of divided structures in the circumferential direction, has a mechanism that moves up and down on each divided surface, and presses the lower seal surface against the furnace bottom by its own weight or cylinder. FIG. 11 is a diagram showing an example in which a total of 12 divisions of 6 wide and 6 wide are used. A metal seal plate 33 having a circumferential rubber seal 27 at the lower end is provided on one divided surface, a guide rod 34 is provided on the upper portion of the metal seal plate 33, and the guide rod 34 is matched to the curvature of the reactor pressure vessel lower mirror 6. Moves up and down to bring the circumferential rubber seal 27 into close contact with the reactor pressure vessel lower mirror 6. In addition, a side surface circumferential rubber seal 32 is provided on the side surface of one divided surface to ensure water tightness so that no gap is generated even when it moves up and down.

  In this structure, when the watertight seal 19 is suspended from the upper part, it is set in the reactor pressure vessel lower mirror 6 with the inside purged with gas, but the water inside cannot be completely removed by purging. Therefore, after setting the reactor pressure vessel lower mirror 6, purging is continued and the internal water is completely removed, and then welding or penetration inspection (PT) is performed.

  The effect of these embodiments is that the build-up welder is provided with a telescopic seal mechanism that follows the sphere R of the reactor pressure vessel lower mirror, so that many reactors in the reactor pressure vessel lower mirror can be The preventive maintenance work on the outer surface of the instrumentation cylinder can be performed in a single furnace setting without changing the seal of the welding machine, so that a large number of preventive maintenance works can be performed, and the preventive maintenance with a shortened construction period can be performed.

  The above procedure and apparatus configuration is an example of a pressurized water reactor, but the boiling water reactor also has an inner instrument tube and a control rod drive mechanism (CRD) housing that penetrates the lower mirror and welds the outer periphery. Since the shape of the welded portion is also a three-dimensional shape reflecting the hemispherical shape of the lower mirror, the preventive maintenance method can be applied with the same apparatus configuration. However, the in-core instrument tube 5 of the pressurized water reactor has a short distance from the reactor pressure vessel weld to the upper end as shown in FIG. 7 and can be covered with a watertight cover from above. The in-core instrument tube 5 of the nuclear reactor cannot be covered from above because it has a length up to the vicinity of the central part of the core. In such a case, there is an embodiment shown in FIG. 12 as a method for locally covering the welded portion. In the embodiment of FIG. 11, the watertight seal is fixed and the welding torch is moved. However, the embodiment of FIG. 12 is a method of moving the watertight seal and the welding torch at the same time, and this method can be used. Become. The welding torch 17 has a local water-tight seal 50 at the tip, and a welding electrode 51 and a welding wire guide 52 therein. As the local watertight seal 50, a heat-resistant silicone sponge that follows the shape of the welded portion of the pressing surface is suitable. Further, a gas purge supply system 53 is connected to the side surface so that the inside of the welding torch 17 is always purged with gas. In the welding torch 17 having the above-described structure, the welding electrode 51 of the welding torch 17 is taught the position coordinates of the welding start point 46 and the welding end point 47, respectively. An interpolated path between the taught welding start point 46 and the welding end point 47 is created, the welding torch 17 is moved to the welding start point 46 again, the gas purge flow rate is increased, and the local watertight seal 50 is accumulated. After removing the water and replacing it with a gas atmosphere, build-up welding is performed up to the welding end point 47. At this time, the operation of the welding torch 17 can be achieved by using the mechanism of the torch swing operation 20 of FIG. 7 described above, the mechanism of the head turning operation 14 and the head lifting / lowering operation 13, and the welding wire feeder 18.

  The effect of these embodiments is that preventive maintenance can be performed in consideration of the shortening of the construction period from the viewpoint of economy when there are many workability and preventive maintenance target devices for complex shaped parts.

  Next, FIG. 13 shows an example of an apparatus for efficiently performing work by combining the surface polishing, welding, and penetration inspection (PT). This is an example assuming a pressurized water reactor. In the case of boiling water reactors, there are structures inside the reactor, so surface polishing, welding, penetration flaw detection (PT) and water jet peening should be set by hanging the equipment from the top of the reactor. However, in the case of a pressurized water reactor, since it is possible to remove the structure in the reactor, space constraints are greatly reduced during the operation. An embodiment for improving workability using this advantage will be described below.

  The common access device 35 set in the core support metal 7 includes a table device 40 lowered to a pedestal supported by the core support metal 7, an arm device 41 swiveled by the table device 40, and a diameter attached to the arm device 41. The head driving device 42 moves in the direction.

  Various apparatus heads are exchanged and used according to the purpose, and are suspended from the upper part of the nuclear reactor and set remotely in the head driving apparatus 42. At that time, there are a plurality of heads to be used according to the method to be selected, but it is assumed that the arm device 41 and the head driving device 42 to be swiveled have the necessary number.

  An example of carrying out repair welding will be described below.

  A polishing device head 36, a welder head 37, a penetrant inspection (PT) device head 38, and a dimension measuring device head 39 are attached to a head drive device 42 having four heads of a cross-shaped arm device remotely underwater and welded. Perform the work. The procedure of repair welding is as follows.

  The first procedure is welding zone polishing. This removes oxide film, dust, and cladding adhering to the surface of the weld. Therefore, the polishing apparatus head 36 is aligned with the coordinates of the target in-core instrumentation cylinder 5 by the turning operation of the table device 40 and the radial operation of the head drive device 42, and the entire outer periphery of the welded portion is polished. .

  The second procedure is welding. Similarly, the position of the welder head 37 is aligned with the coordinates of the target in-core instrumentation cylinder 5 by the turning operation of the table device 40 and the radial operation of the head drive device 42. In the case where the above range is overlay welding, or when there is no crack, overlay welding for the purpose of surface modification is performed.

  The third procedure is a penetrant inspection (PT). After welding is completed, the penetration inspection (PT) device head 38 is aligned with the coordinates of the target in-core instrumentation cylinder 5 by the turning operation of the table device 40 and the radial operation of the head drive device 42, and the welding surface Perform penetration inspection (PT).

  The fourth procedure is to measure the weld dimensions. After the penetration inspection (PT) is completed, the dimension measuring device head 39 is aligned with the coordinates of the target in-core instrumentation cylinder 5 by the turning operation of the table device 40 and the radial operation of the head driving device 42, and welding is performed. Measure the thickness.

  Welding is performed according to the above procedure, and the mounting positions of various apparatus heads are arranged according to the procedure. Further, when welding is built up on a plurality of layers, a penetration inspection (PT) is performed each time. In this case, by having the welding machine head 37 and the penetrant flaw detection (PT) apparatus head 38 in the same apparatus, the head can be switched in a short time, and the work can be performed efficiently. In other words, when performing work such as welding machines used in preventive maintenance work, surface polishing before and after welding, and penetration inspection (PT), preventive maintenance work can be performed by efficiently switching various work heads. Preventive maintenance with a shortened construction period can be performed.

  So far, the procedure and method for performing overlay welding by changing the welding conditions depending on the presence or absence of cracks have been described. On the other hand, it is also possible to apply a preventive maintenance method that does not require prior inspection, in which surface modification is performed on the entire surface of the welded portion under cracked conditions. This eliminates preliminary inspections such as visual inspection (VT) and ultrasonic flaw inspection (UT) of the work procedure shown in FIG. 1, and implements steps corresponding to repair and preventive maintenance welding for cracked conditions as preventive maintenance work In consideration of the fact that there are many welds of in-core equipment in the reactor pressure vessel and there are several tens of in-core instrument tubes depending on the reactor power, all of these welds are pre-inspected. It can be expected to shorten the work period.

  In this method, the welding condition flow of FIG. 3 can be applied as it is. The calculation of the overlay welding range is performed on the entire welded portion where preventive maintenance is performed regardless of the presence or absence of cracks, and the overlay welding start position and end position are calculated. Next, the build-up weld thickness t2 is calculated by performing fatigue crack growth evaluation assuming that the crack depth is the maximum penetration crack, and the number of build-up weld layers is set based on the result. Also, the amount of heat input is assumed to be a cracked condition, the welding current, voltage and welding speed are calculated, and each condition is input to the welding control device and the welding power source. Since the apparatus configuration is the same as the method with cracks, the apparatus configuration shown in FIGS. 6 to 10 can be applied as it is.

1 Reactor pressure vessel 2 Crack 3 Overlay welding (with crack)
4 Overlay welding (no cracks)
5 In-core instrumentation cylinder 6 Reactor pressure vessel lower mirror 7 Core support hardware 8 Head turning drive unit 9 Head lifting drive unit 10 Polishing arm 11 Polishing wheel 12 Polishing drive unit 13 Head lifting operation 14 Head turning operations 15a, 15b, 15c , 15d Control device 16a, 16d Controller, monitor 16b Camera controller 16c Camera for observation, controller, monitor 17 Welding torch 18 Welding wire feeder 19 Watertight seal 20 Torch swing motion 21 Welding power supply 22 Cooling water circulation device 23 PT liquid application / cleaning Dry nozzle head 24 PT liquid / cleaning liquid recovery 25 Camera (mirror) swing mechanism 25b Camera swing operation 26 Dry hot air supply 27 Circumferential rubber seal 28 PT liquid / cleaning liquid / air supply unit 29 PT liquid / cleaning liquid recovery unit 30 Dry hot air supply unit 31 Axial direction Museal 32 Side circumferential rubber seal 33 Metal seal plate 34 Guide rod 35 Common access device 36 Polishing device head 37 Welding machine head 38 PT device head 39 Dimension measuring device head 40 Table device 41 Arm device 42 Head drive device 43 Water injection nozzle 44 Water Injection nozzle swinging operation 45 In-furnace instrumentation tube welding part 46 Welding start point 47 Welding end point 48 Overlay welding 49 Nozzle arm 50 Local watertight seal

Claims (8)

In preventive maintenance method for the weld between the reactor pressure vessel and the furnace device which prevents the meat Mori溶 contact in the reactor pressure vessel and the reactor internal equipments and excellent member surface corrosion resistance to stress corrosion cracking of the weld,
And line Cormorant step testing of the welded portion between the furnace device which is attached by welding to the inner surface of the reactor pressure vessel the reactor pressure vessel,
After that, according to the inspection result , on the portion where the crack of the welded portion is not confirmed, build-up welding is performed on the surface of the member for the purpose of surface modification with a predetermined thickness, and the crack of the welded portion is confirmed. In the part, with a thickness considering the amount of crack propagation to the overlay welding side of the crack, performing the overlay welding on the surface of the member for the purpose of surface modification that also serves as repair of the crack ;
When performing the overlay welding, preventive maintenance how to wherein a welding heat input of cracks was confirmed part of the high heat input than if no cracks. In the preventive maintenance method of Claim 1,
The preventive maintenance method according to claim 52, wherein the material for overlay welding uses 52 alloy. In the preventive maintenance method as described in any one of Claim 1 to Claim 2,
The preventive maintenance method, wherein the reactor pressure vessel is constructed in a state where reactor water is filled. In the preventive maintenance method according to any one of claims 1 to 3,
A preventive maintenance method comprising forming a local air environment and performing the overlay welding. In the preventive maintenance method according to any one of claims 1 to 4,
A preventive maintenance method for improving residual stress by injecting high pressure water accompanied by generation of cavitation bubbles from an injection nozzle to a region exceeding the overlay welding range after the overlay welding step. In the preventive maintenance method of Claim 4,
The preventive maintenance method according to claim 1, wherein the local aerial environment causes the ball R of the reactor pressure vessel lower mirror to follow a telescopic seal mechanism. Installing in the reactor pressure vessel a common access device comprising a table device supported by a core support metal in the reactor pressure vessel, and a head drive device fixed to the table device and driven to turn and radially. ,
Inspecting the welded portion between the reactor pressure vessel and the in-reactor equipment attached to the inner surface of the reactor pressure vessel by the inspection head set in the common access device;
By the welder head set in the common access device, on the part where the crack of the welded portion is not confirmed from the inspection result, build-up welding is performed on the surface of the member for the purpose of surface modification with a predetermined thickness, In the part where the crack of the welded part is confirmed, the thickness of the crack is increased in consideration of the amount of crack propagation toward the build-up weld side of the crack, and on the surface of the member for the purpose of surface modification that also repairs the crack. Performing overlay welding,
A preventive maintenance method characterized in that, when performing build-up welding, the weld heat input at a portion where cracks are confirmed is higher than that when there is no crack. A table device supported by a core support metal in the reactor pressure vessel;
A common access device having a head drive device fixed to the table device and driven in a turning and radial direction;
An inspection head that is set in the common access device and inspects a welded portion between the reactor pressure vessel and the in-reactor equipment attached to the inner surface of the reactor pressure vessel by welding,
A welder head set in the common access device;
An inspection result in the inspection head is received, and on the portion where no crack of the welded portion is confirmed on the welding head, overlay welding is performed on the surface of the member for the purpose of surface modification with a predetermined thickness, and the welded portion In the part where the crack is confirmed, the thickness of the crack considering the amount of crack propagation to the overlay welding side of the crack, and the overlay welding on the surface of the member for the purpose of surface modification that also repairs the crack A processing device that transmits an instruction to perform;
The said processing apparatus is a preventive maintenance apparatus which makes the welding heat input of the part in which the crack confirmed the welding heat input higher than the case where there is no crack when performing the build-up welding.

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