JP5787496B2 - Repair method for nozzle - Google Patents

Description

  The present invention relates to a method for repairing a reactor vessel nozzle, and particularly relates to repair of a welded portion.

In a nuclear reactor vessel equipped with a vessel made of carbon steel or low alloy steel, a nozzle made of stainless steel or nickel base alloy is attached to a spherical mirror at the bottom by welding. Specifically, as shown in FIG. 2, in order to prevent deterioration of the nozzle due to welding, overlay welding is performed on the spherical mirror 5 side with stainless steel or a nickel-based alloy material and post-weld heat treatment is performed. The nozzle is attached to the spherical mirror 5 by welding.
The welding parts 13 and 14 by the build-up welding and J-welding described above may be damaged by aging such as stress corrosion cracking (SCC). Therefore, when the welded part by overlay welding and J welding is damaged or when there is a possibility of damage, the nozzle 2 is repaired.
As a method of repairing the nozzle 2, conventionally, the existing nozzle 2 and the welded portions 13 and 14 are all removed, the removed groove is refilled by welding, a new nozzle is inserted, and rejoined by welding. For example, in recent years, the existing nozzle 2 and the welded portions 13 and 14 are removed, and overlay welding is performed on the carbon steel or low alloy steel surface, and after the joint welding process is performed, the nozzle 2 is installed. Thus, a method of performing joint welding has been proposed (see, for example, cited document 1).

Japanese Patent No. 2530011

  By the way, since the inside of the reactor vessel described above is an underwater environment or an aerial environment with a high radiation dose, it is desirable to perform welding, processing work, etc., related to the nozzle repair with an automatic device, and the conventional nozzle repair In the method, since the existing welding parts 13 and 14 have a complicated shape such as a three-dimensional saddle, and the nozzle 2 is in a narrow environment where the spherical mirror 5 is erected, the existing welding parts 13 and 14 When trying to restore to the same structure as that of No. 14, there is a problem that it is not easy to automate the operation because a small and very high performance welding apparatus that can perform three-dimensional welding in a narrow environment is required.

  This invention is made in view of the said situation, and provides the nozzle repair method which can automate repair work of a welding part easily and can aim at a worker's burden reduction.

The present invention adopts the following configuration in order to solve the above-described problems and achieve the object.
A repair method for a nozzle according to the present invention includes a method for repairing an existing nozzle that penetrates a lower portion of a reactor vessel in a vertical direction and is fixed to the reactor vessel via a built-up portion and a welded portion. The upper portion and the welded portion are divided into a plurality of areas in a top view, and a predetermined groove shape is set in advance for each area, and the highest point in the inclination of the lower part of the reactor vessel around the nozzle When the direction along the line connecting the lowest point is the height direction, the groove shape of the mountain side area that is higher than the nozzle is set to a trapezoidal shape in a top view, and among the plurality of areas Identifying the area including the damaged portion of the build-up portion and the welded portion, cutting and removing the area with a predetermined groove shape set in advance, and cutting and removing the cut portion by build-up repair And a backfilling process. .
According to the repair method of the nozzle according to the present invention, the built-up portion including the damaged portion and the welded portion are cut and removed by the groove shape set in advance for each area and backfilled by the built-up repair, Since welding and processing work related to the repair of the nozzle can be simplified, for example, there is no need for skill in welding and processing work inside the reactor vessel such as underwater environment or air environment with high radiation dose. Remote repair using the device becomes possible. In addition, since it is repaired by cutting into a preset groove shape, complicated cutting work and welding work are not required even in a narrow environment where the nozzle is standing in a narrow area. The work can be automated without using a small, high-performance automatic apparatus capable of three-dimensional welding.

Further, the nozzle repair method of the present invention may be provided by dividing the plurality of areas in the circumferential direction of the nozzle in the nozzle repair method of the present invention.
By configuring in this way, even if the wall surface of the reactor vessel around the nozzle is inclined, for example, the inclination of the wall surface such as a groove shape for a mountain side or a groove shape for a valley side After the cutting and removal with the optimum shape corresponding to the above, the cut and removed portion can be backfilled by overlay repair.

Furthermore, the method for repairing a nozzle according to the present invention provides a method for repairing the nozzle according to the above-described method for repairing a nozzle according to the present invention, in a case where a damaged or possibly damaged portion extends over the whole of the build-up portion and the weld portion. A step of cutting and removing the upper portion, a step of cutting and removing the entire area of the build-up portion and the welded portion with a predetermined groove shape set in advance, and a back-filling of the cut and removed groove by the build-up repair You may make it provide the process and the process of joining a new nozzle top to the backfill part backfilled by this build-up repair.
By configuring in this way, in addition to the case where the damaged portion is clear, even if there is no obvious damaged portion in the built-up part and the welded part, such as when the nondestructive inspection is difficult, the cutting removal The upper part of the nozzle that is in the way of cutting is cut and removed, and the entire build-up part and welded part that may be damaged are all cut and removed in a preset groove shape to repair the build-up on the groove After that, by joining the upper part of the new nozzle, it is possible to cut and remove the entire build-up part and welded part that may be damaged, and to cut and remove the whole build-up part and welded part. Remote repair using an automatic device can be performed by simplifying welding and processing operations.

And the repair method of the nozzle stub of this invention WHEREIN: In the repair method of the said nozzle stub, it is good also considering the backfill amount of the said groove as a backfill amount smaller than before the said removal by cutting.
By comprising in this way, compared with the case where it welds only as much as the build-up part before repair and the weld part before repair, a welding amount can be reduced, for example, the welding amount at the time of build-up repair is reduced. It can be minimized.

Furthermore, the repair method of the nozzle stub of this invention WHEREIN: The said overlay repair is good also as welding by a temper bead method in the repair method of the said nozzle stub.
By comprising in this way, at the time of overlay repair, for example, compared to the case of forming the weld after forming the overlay, it is not necessary to perform post-weld heat treatment performed after the overlay is formed. The work process is reduced, and the work can be automated more easily.

According to the repair method of the nozzle according to the present invention, welding and processing work related to the repair of the nozzle are simplified, for example, welding and processing inside the reactor vessel such as an underwater environment or an air environment with a high radiation dose. Since no skill is required for the work and the like, remote repair using an automatic device is possible, so that the work time can be shortened and the burden on the repair worker can be reduced.
In addition, since complicated cutting work and welding work are not required, the work can be automated without using a high-performance automatic device that is compact and capable of three-dimensional welding. This can reduce the burden on the user.

It is a fragmentary sectional view of the reactor vessel lower part in a 1st embodiment of the present invention. It is a cross-sectional view which shows the attachment structure of a nozzle. It is a figure explaining each area set around a nozzle. It is a figure which shows the process of cutting and removing the trough side of a nozzle, and forming a groove | channel, Comprising: (a) is a cross-sectional view, (b) is sectional drawing which follows the AA line of (a). It is a figure which shows the process of forming a repair built-up part and a repair J weld part in the groove | channel of FIG. 4, Comprising: (a) is a cross-sectional view, (b) is sectional drawing which follows the BB line of (a). It is. It is a figure which shows the groove shape matched with the area of the valley side of a nozzle, Comprising: (a) is a cross-sectional view, (b) is a top view. It is a figure which shows the groove shape matched with the area of the mountain side of a nozzle, Comprising: (a) is a cross-sectional view, (b) is a top view. It is a figure which shows the groove shape matched with the area on the right side of a nozzle, Comprising: (a) is a cross-sectional view, (b) is a top view. It is a figure which shows the process of cutting and removing the whole region around a nozzle base in 2nd Embodiment of this invention, Comprising: (a) is a cross-sectional view, (b) is CC of (a). It is sectional drawing which follows a line. It is a figure which shows the process of forming a repair built-up part and a repair J weld part in the groove | channel of FIG. 9, Comprising: (a) is a cross-sectional view, (b) is sectional drawing which follows the DD line | wire of (a). It is. It is a figure which shows the process of forming a screw hole part and a through-hole in the repair J weld part of FIG. 10, Comprising: (a) is a cross-sectional view, (b) is sectional drawing which follows the EE line of (a). is there. It is a figure which shows the process of fixing a nozzle top to the screw hole part of FIG. 11, Comprising: (a) is a cross-sectional view, (b) is sectional drawing which follows the FF line of (a). It is sectional drawing which shows the case where the curvature radius of the corner part of a groove shape is 10 mm in 3rd Embodiment of this invention. FIG. 15 is a view corresponding to FIG. 14 when the radius of curvature of the corner portion of the groove is 20 mm. It is a graph which shows the intensity | strength of the surrounding spherical mirror in the case where the curvature radius of a corner part at the time of using a temper bead method is 10 mm, and 20 mm.

Next, the nozzle 2 in the first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a plurality of nozzles 2 are attached to a spherical mirror 5 at the bottom of a reactor vessel 1 made of carbon steel or low alloy steel. The nozzle 2 is formed in a pipe shape made of stainless steel or Ni-base alloy, and is provided so as to penetrate the spherical mirror 5 in the vertical direction. These nozzles 2 are fixed to the reactor vessel 1 by welding to a groove 6 formed on the inner periphery (upper surface side in FIG. 1) of the through hole 7 of the spherical mirror 5. On the outer peripheral edge of the container of the through hole 7, the build-up welded portion 3 that does not involve groove processing is formed. In FIG. 1, reference numeral 9 is a safe end of the in-core instrument tube, reference numeral 10 is a conduit tube, and reference numeral 11 is a stainless steel weld for fixing the safe end 9 to the conduit tube 10.

  As shown in FIG. 2, through the through hole 7 formed in the spherical mirror 5, the nozzle top 2 a of the nozzle 2 is arranged inside the reactor vessel 1, and the bottom of the nozzle 2 is outside the reactor vessel 1. Be placed. The reactor vessel 1 includes a stainless steel layer 8 having a mirror finish on its inner surface, and the nozzle 2 is fixed by welding to a groove 6 formed on the inner peripheral side of the spherical mirror 5 of the through-hole 7. Are attached to the spherical mirror 5. For welding to the groove 6, first, a build-up portion 13 is formed on the inner surface of the groove 6 cut as the groove processing by stainless steel or Ni-based alloy material, and then the spherical mirror 5 is formed. A heat treatment after welding is performed to ensure strength, and then a J weld 14 is formed on the build-up portion 13 by welding with stainless steel or a Ni-based alloy material, and the nozzle 2 and the spherical mirror are formed by the J weld 14. 5 is connected and fixed. Here, the build-up portion 13 and the J-welded portion 14 may be damaged such as stress corrosion cracking (SCC) due to deterioration over time, and repair is performed when damage occurs. For convenience of illustration, in FIG. 2, the build-up weld 3 on the outer periphery of the through hole 7 is omitted.

The nozzle 2 in this embodiment has the above-described mounting structure. Next, a method for repairing the nozzle 2 attached to the spherical mirror 5 will be described with reference to the drawings.
First, a plurality of areas obtained by dividing an existing welded part (the build-up part 13 and the J weld part 14) around the nozzle 2 in a top view are set, and a damaged area is specified among these areas. Here, as shown in FIG. 3, for example, when the direction along the line connecting the highest point and the lowest point in the inclination of the spherical mirror 5 around the nozzle 2 is assumed to be the height direction, the plurality of areas are assumed to be the height direction. In addition, the area on the side lower than the nozzle 2 (0 degree side in FIG. 3), the area on the side higher than the nozzle 2 (180 degree side in FIG. 3), the left side of the nozzle 2 (in FIG. 3, Four areas are set: an area on the 90 ° side and an area on the right side (270 ° side in FIG. 3) of the nozzle 2. Hereinafter, a side lower than the nozzle 2 is referred to as a “valley side”, and a side higher than the nozzle 2 is referred to as a “mountain side”.

  Next, for example, the case where damage is present in the welded portion on the valley side with respect to the nozzle 2 described above will be described as an example, as shown in FIGS. 4 (a) and 4 (b). The built-up portion 13 and the J weld portion 14 are cut and removed by an end mill or the like with the predetermined groove shape. This cutting removal operation is automatically performed by setting and inputting information on the cutting position and the groove shape to a cutting machine (not shown). In addition, you may make it shape | mold the inner surface of the groove | channel 6 with a rubber grindstone etc. after cutting.

  When the above-described cutting and removal work is completed, repair welding is then performed. Specifically, as shown in FIGS. 5 (a) and 5 (b), a laminar repair overlay 15 is formed on the entire inner surface of the groove 6 by a dedicated welding device (not shown). A post-weld heat treatment is performed to heat the spherical mirror 5 around the repair build-up portion 15, and a repair J weld portion 16 is formed inside the repair build-up portion 15 by the above welding apparatus. The repaired J welded portion 16 is refilled until it becomes equal to the welding amount before cutting removal. In the build-up repair work for forming the repair build-up portion 15 and the repair J weld portion 16, since the groove shape is set for each area in advance, information on the groove shape and the cutting position is set in the welding apparatus. This is done automatically by typing.

FIGS. 6-8 has shown the part cut and removed by the groove shape set for every area mentioned above.
6 (a) and 6 (b) show a case where cutting and backfilling are performed with a groove shape corresponding to the valley side area of the nozzle 2 out of the groove shapes set in advance for each area. 7 (a) and 7 (b) show a case where cutting and backfilling are performed with a groove shape corresponding to the mountain-side area of the nozzle 2 out of the groove shapes set in advance for each area. . FIGS. 8A and 8B show a case where cutting and backfilling are performed with a groove shape corresponding to the area on the right side of the nozzle 2. In the case of FIGS. 7A and 7B, the groove shape on the mountain side has a larger area in a top view (see the figure) than the valley side because the inner surface on the mountain side of the spherical mirror 5 interferes with the work during cutting. It is set to a substantially trapezoid. 8A and 8B, the groove shape on the right side is a substantially trapezoid whose upper side and lower side are shorter than the trapezoidal shape of the groove shape on the mountain side when viewed from above, and the center is It is set to shift slightly to the mountain side. The left-side groove shape is a symmetric shape with respect to the right-side groove shape and the nozzle 2 as described above, and is omitted.

  The groove shape in any of the above-described areas is set to a cutting depth corresponding to the depth of the original build-up portion 13 and the J-welded portion 14 before cutting in order to completely remove the damaged portion. In addition, since the overlay repair is often performed while swinging the torch of the welding apparatus, the bottom of each groove shape is formed so that the cross-sectional shape in the longitudinal direction when viewed from above is a curve with a relatively large radius of curvature. Is done. In addition, in this embodiment, although the case where damage exists in any one of the four areas mentioned above was explained, when there is damage in a plurality of areas individually, with respect to each damaged part Perform the above-mentioned repairs individually. In addition, when a damaged portion exists in a portion where the two areas overlap, a groove shape that is suitable for removing and repairing the damaged portion is selected.

  Therefore, according to the repair method of the nozzle 2 in the above-described embodiment, the build-up portion 13 and the J-welded portion 14 including the damaged portion are cut and removed by the groove shape set for each area in advance. By performing overlay repair, welding and processing work related to repair of the nozzle 2 can be simplified, so welding and processing inside the reactor vessel 1 such as underwater environment or air environment with high radiation dose. Skills such as work become unnecessary, and remote repair using an automatic device becomes possible. As a result, the work time can be shortened and the burden on the repair worker can be reduced.

  In addition, since it is cut and repaired so as to have a groove shape set for each area in advance, even in a narrow environment where the nozzle 2 stands in a narrow area, complicated cutting work or Since no welding work is required, the work can be automated without using a small, high-performance automatic device capable of three-dimensional welding. As a result, it is possible to reduce the burden on the operator while suppressing an increase in cost.

Next, a method for repairing a nozzle according to a second embodiment of the present invention will be described with reference to the drawings. Since the repair method of the nozzle 2 of this 2nd Embodiment is a repair method performed when the damage location of the build-up part 13 and the J weld part 14 before repair cannot be specified, or there exists a possibility of damage to the whole. The same parts as those in the first embodiment described above are denoted by the same reference numerals.
First, as shown in FIG. 9, while cutting the nozzle top 2a to prevent interference with the welding apparatus, the entire area around the nozzle 2 is different from the plurality of areas of the first embodiment described above. All the welded parts consisting of the built-up portion 13 and the J welded portion 14 are cut and removed by a predetermined groove shape set corresponding to. The groove 21 formed by this cutting is set to be slightly larger than the built-up portion 13 and the J welded portion 14 before cutting. The groove 21 is formed by expanding the side wall 23 from the bottom wall 22 upward. The angle formed between the bottom wall 22 and the side wall 23 of the groove 21 is set to, for example, about 60 degrees so as to conform to the automatic cutting and automatic welding conditions of the cutting device and the welding device.

  Next, after forming a built-up portion (not shown) on the entire inner surface of the groove 21 cut and removed by welding and performing post-weld heat treatment, as shown in FIG. Overlay repair is carried out by forming a repaired J weld 25 with a small welding amount. This welding amount is set to such a degree that a sufficient strength can be obtained when the nozzle top 2a is attached. Further, the upper surface 26 of the repair J weld 25 is formed substantially horizontally along the radial direction of the nozzle 2.

  Further, as shown in FIG. 11, the through hole 27 and the screw hole portion 28 for screwing the nozzle top portion 2a are respectively cut into the repair J weld portion 25 on the extension of the axis of the nozzle bottom portion 2b. Form. And finally, as shown in FIG. 12, the male thread part 31 corresponding to the said screw hole part 28 formed in the bottom part of the new nozzle top 2a is screwed in the said screw hole part 28, and a nozzle stand The upper part 2 a is fixed to the repair J weld 25. Thereby, the nozzle top 2a and the nozzle bottom 2b are communicated with each other through the through hole 27.

  Therefore, according to the repair method of the nozzle 2 of 2nd Embodiment mentioned above, it is clear to the buildup part 13 and the J weld part 14 in the case where a nondestructive inspection is difficult in addition to the case where a damage location is clear. Even if no damage is observed, the upper portion 2a of the nozzle base that is obstructive at the time of cutting and removing is cut and removed, and the entire area of the build-up portion 13 and the J weld portion 14 that may be damaged is set in advance. After cutting and removing all of the groove shape and repairing the build-up on the groove 21, the whole of the build-up portion 13 and the J weld portion 14 that may be damaged can be obtained by joining a new nozzle top 2 a. Since it can be removed by cutting, and the remote repair using an automatic device can be performed by simplifying the welding and processing work when cutting and removing the entire area of the build-up portion 13 and the J-welded portion 14, a repair worker Can be further reduced.

In addition, when all of the built-up parts 13 and J welds 14 are replaced with materials having better SCC resistance (for example, 690 Ni-base alloy), the risk of damage recurrence after repair is reduced. can do.
Furthermore, by setting the welding amount by the build-up repair to a welding amount smaller than the build-up portion 13 and the J weld portion 14 before being removed by cutting, for example, the necessary minimum weld amount, the build-up portion before the repair Compared with the case where the welding amount is the same as 13 and the J-welded portion 14 before repair, the work time can be shortened while ensuring the strength, so that it is possible to further reduce the burden on the repair worker.

Next, a nozzle repair method according to a third embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and demonstrated to the same part as 1st Embodiment and 2nd Embodiment.
The method of repairing the nozzle according to the third embodiment is different only in that the overlay repair performed by the method of repairing the nozzle according to the first embodiment and the second embodiment described above is performed by the temper bead method. . Specifically, after performing the work of cutting and removing the build-up portion 13 and the J-welded portion 14 as in the first and second embodiments described above, build-up repair is performed by the temper bead method.

  When backfill welding is performed by the temper bead method, the hardness of the spherical mirror 5 after temper bead welding is lower than 350 HV, for example, from the viewpoint of securing the toughness of the carbon steel and low alloy steel of the spherical mirror 5. For this purpose, it is necessary to equalize the pitch between the welding passes. And in order to equalize the pitch between welding passes, it is necessary to optimize the groove shape. For example, in the case of the groove shape in the second embodiment, the angle of the corner portion C of the groove 21 is fixed at 60 degrees, and the radius of curvature of the corner portion C composed of the bottom wall 22 and the side wall 23 is set as shown in FIG. When set to 10 [mm], as shown in the graph of FIG. 15, the hardness exceeds 350 HV at a position about 3 mm away from the center of the corner portion C. On the other hand, as shown in FIG. 14, when the radius of curvature of the corner portion C is set to 20 [mm], the hardness is 350 HV even if it is about 3 [mm] away from the center of the corner portion C as shown in the graph of FIG. Is not exceeded. Although illustration is omitted, the increase in hardness tends to be suppressed as the radius of curvature becomes larger than 20 [mm].

  Therefore, according to the repair method of the nozzle 2 of the third embodiment described above, by using the temper bead method, after the build-up portion 13 is formed in the build-up repair, the post-weld heat treatment is performed and the repair is performed. Compared with the case where the J welds 16 and 25 are formed, it is not necessary to perform post-weld heat treatment after the repair build-up part 15 or the like is formed, so that the work process is reduced and the work can be automated more easily. be able to.

In addition, this invention is not restricted to the repair method of the nozzle 2 of embodiment mentioned above, A design change is possible in the range which does not deviate from the summary.
For example, in the third embodiment described above, the case where repair welding by the temper bead method is performed on the groove 21 obtained by cutting and removing all of the built-up portion 13 and the J weld portion 14 has been described as an example. Thus, it is applicable also when it cuts with the groove shape for every area, and does not cut and remove the nozzle top 2a. In this case, the groove shape is preferably constituted by a curved surface or a flat surface having a curvature radius of 20 [mm] or more.

  Further, in the first embodiment, the spherical mirror 5 has an inclination with the nozzle 2 as the center, and there is a mountain side and a valley side, and each area is set based on the inclination as an example. When the crest side and the trough side do not exist as in the vicinity of the lowermost part of the spherical mirror 5, a groove shape for cutting removal in the vicinity of the lowermost part is set in advance, and the groove 6 is formed around the damaged part. What is necessary is just to form.

DESCRIPTION OF SYMBOLS 1 Reactor vessel 2 Tubular head 2a Tubing upper part 6 Groove (cutting part)
13 Overlaying part 14 J welded part (welded part)
15 Repair overlay 16 Repair J weld 21 Groove (total cutting)

Claims (5)

In the repair method of the existing nozzle that penetrates the lower part of the reactor vessel in the vertical direction and is fixed to the reactor vessel via the overlay and the weld,
The build-up portion and the welded portion are divided into a plurality of areas in a top view and a predetermined groove shape is set in advance for each area, and the highest in the inclination of the lower portion of the reactor vessel around the nozzle When the direction along the line connecting the point and the lowest point is the height direction, the groove shape of the area on the mountain side that is higher than the nozzle is set to a trapezoid in a top view, and the plurality of areas Among these, identifying the area including the damaged portion of the build-up portion and the welded portion, and cutting and removing the area with a predetermined groove shape set in advance,
And a step of refilling the cut and removed cutting portion by build-up repair.   The method of repairing a nozzle according to claim 1, wherein the plurality of areas are divided in a circumferential direction of the nozzle. In the case where the damaged or possibly damaged portion extends over the entire area of the build-up portion and the welded portion,
Cutting and removing the top of the nozzle,
In a predetermined groove shape set in advance, the step of cutting and removing the entire area of the build-up portion and the welded portion;
A step of refilling the entire area cut portion removed by cutting by overlay repair;
A method of repairing a nozzle according to claim 1 or 2, further comprising a step of joining a new nozzle upper part to a backfill portion backfilled by the build-up repair.   The method of repairing a nozzle according to claim 3, wherein the backfilling amount of the whole area cutting portion is a backfilling amount smaller than that before the cutting and removal.   The method of repairing a nozzle according to any one of claims 1 to 4, wherein the build-up repair is welding by a temper bead method.

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