JP2010038842A - Boiling water reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow access from an exposed part to a welding HAZ part of a core shroud, and to perform work of applying compressive residual stress by making an execution device of shot peening approach a HAZ. <P>SOLUTION: This boiling-water reactor has a low-pressure water filling pipe that is welded and bonded horizontally between a reactor pressure vessel and a core shroud at a position above the core and fills cooling water to the core. The welded and bounded section 110 between the core shroud 105 and the low-pressure water filling pipe 100 is exposed both to the inside and outside of the core shroud. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a boiling water reactor, and in particular to improve the low-pressure water injection pipe for introducing coolant into the core shroud in order to reflood the core in the event of loss of coolant such as a main steam pipe breakage accident. Related to the furnace.

  A general configuration of the low-pressure water injection pipe of the boiling water reactor will be described with reference to a schematic longitudinal sectional view of FIG.

  As shown in FIG. 10, the boiling water reactor has a core shroud 105 that constitutes a core by opening a predetermined gap inside the reactor wall of a reactor pressure vessel (hereinafter abbreviated as “RPV”) 101. I have. A core shroud upper shell 105a is provided on the upper portion of the core shroud 105, and a low-pressure water injection pipe 100 is disposed from the core shroud upper shell 105a toward the furnace wall side.

  The low-pressure water injection pipe 100 is installed horizontally between the reactor wall of the reactor pressure vessel 101 and the core shroud 105, and performs reflooding of the core in the event of loss of coolant such as a main steam pipe breakage accident. The coolant has a function of guiding the coolant into the core shroud 105.

  During the operation of the reactor, the cooling water passes through the low-pressure water injection nozzle 102 of the RPV 101 and then passes through the low-pressure water injection pipe 100 installed horizontally between the RPV 101 and the core shroud 105 to penetrate the core shroud upper body 105a. Released into the shroud 105.

  The low-pressure water injection pipe 100 has two slip joints so that it can absorb the thermal expansion difference between the RPV 101 and the core shroud 105, the displacement difference due to the internal pressure, etc., and it can be expanded and contracted in the axial direction and in all directions. Can be freely rotated.

  The low-pressure water injection pipe 100 is mainly composed of austenitic stainless steel, and this material is stress-corrosion cracked when three conditions of tensile residual stress, corrosive environment, and material (formation of chromium-deficient layer) are satisfied. It is assumed that stress corrosion cracking occurs and is damaged. This stress corrosion cracking phenomenon is known to be difficult to occur if even one of the three conditions is excluded.

  Here, a standard attachment procedure at the time of plant construction of the low-pressure water injection pipe 100 that is horizontally attached between the furnace wall of the RPV 101 and the core shroud 105 will be described with reference to FIGS. 10, 11, and 12.

  FIG. 11 is a perspective sectional view of the low-pressure water injection pipe 100, and FIG. 12 is a side view showing a part of the low-pressure water injection pipe 100 as a cross section.

  a) First, the low pressure water injection nozzle 102 and the RPV side flange neck 103 are attached to the RPV 101 shown in FIG. 10 via the ring 106 shown in FIG.

  b) A core shroud 105 is installed in the RPV 101 as shown in FIG. As shown in FIGS. 11 and 12, the core shroud upper body 105a is previously provided with a hole 105b for attaching the low-pressure water injection pipe 100 to the orientation and elevation facing the RPV side flange neck 103. For this reason, in the state where the core shroud 105 is installed on the RPV 101, the centers of the RPV side flange neck 103 and the hole 105b are arranged on substantially the same line.

  c) In addition, a ring 106 is disposed at a position along the axis extension line of the RPV side flange neck 103 so as to close the hole 105b, and this ring 106 is formed of the hole 105b formed in the upper body 105a on the core shroud 105 side. It is welded and fixed by the welding part 110 around. Note that the ring 106 has a mating dimension that can be attached to the outer surface of the upper shell 105a of the core shroud 105 with a slight misalignment.

  d) The core shroud side flange neck 104 is fixed to the ring 106 by welding.

  e) On the other hand, the flanges 103a and 103b, the sleeve 103c, the bellows 103d, the bellows cover 103e, and the pin 103f installed between the RPV side flange neck 103 and the core shroud side flange neck 104 are preliminarily assembled together in advance (hereinafter referred to as “below”) This assembly part is abbreviated as “pipe central member”).

  f) The piping center member is held so as to be sandwiched between the RPV side flange neck 103 and the core shroud side flange neck 104.

  g) The RPV side flange neck 103 and the core shroud side flange neck 104 are attached by the lower half clamp 107 and the upper half clamp 108 so as to cover the sleeve 103c from below and above, respectively.

  h) The lower half clamp 107 and the upper half clamp 108 are tightened by combining eye bolts, nuts, pins 103f and the like. Grooves 109 are provided inside the lower half clamp 107 and the upper half clamp 108, respectively, and these grooves 109 press the outer slopes of the flange necks 103b and 104b, thereby bringing the flange surfaces into close contact with each other.

  During this tightening, the flange surfaces may gradually shift, so the flange outer surface facing each other is observed from the gap between the lower half clamp 107 and the upper half clamp 108, and it is confirmed that there is no position shift. The half clamps 107 and 108 are tightened.

Conventionally, the integrity of all in-furnace structures is ensured by removing the in-furnace structures and using a combination of replacement, partial repairs, and preventive maintenance methods according to the difficulty of re-installation. On the other hand, techniques for removing and re-installing relatively easily have been proposed (see, for example, Patent Document 1).
JP 05-080187 A

[Problem 1]
Specifically, the site of stress corrosion cracking in austenitic stainless steel is a portion (HEAT AFFECTED ZONE (hereinafter abbreviated as “HAZ”)) that is affected by heat in the vicinity of the weld. Since residual stress is often generated by welding, it is considered effective methods to reduce residual stress, forcibly apply compressive residual stress, and to change the shape to reduce the weld line itself as countermeasures against stress corrosion cracking. It has been.

  Among these methods, as a specific measure for excluding the tensile residual stress, a method of applying forced compressive stress by performing shot peening on the HAZ is effective. However, in the low-pressure water injection pipe 100 described above, the weld back side of the core shroud upper shell 105a and the ring 106 is a narrow portion, and the shot peening apparatus cannot be brought close to each other, so that compressive residual stress cannot be applied.

[Problem 2]
Further, the low-pressure water injection pipe 100 is installed in the order of (a) to (h) shown in the above-described conventional example in order to install the pipe horizontally, and among these, (g) the half clamp attachment and ( The confirmation of the displacement between the flange surfaces in h) is an operation performed by a worker entering between the RPV 101 and the core shroud upper shell 105a in the vicinity of the low-pressure water injection pipe 100 during plant construction. These operations can be easily performed at the time of plant construction. However, in the low pressure water injection pipe re-installation in the operation plant, there is a problem that the operations are difficult from the viewpoint of preventing the exposure of workers because RPV is activated. is there.

  The present invention has been made in view of such circumstances, and includes a low-pressure water injection pipe that is welded and joined horizontally between a reactor pressure vessel and a core shroud at a position above the core, and injects cooling water into the core. In a boiling water reactor, a boiling water reactor characterized in that a welded joint between the core shroud and the low-pressure water injection pipe is exposed to both the inside and the outside of the core shroud. provide.

  According to the present invention, the welded joint between the core shroud and the low-pressure water injection pipe is exposed to both the inside and the outside of the core shroud, so that the access to the welded HAZ part of the core shroud is possible from the exposed part. Thus, it is possible to perform an operation of applying a compressive residual stress by bringing a construction apparatus for shot peening to the HAZ close to the apparatus, and the first problem can be solved. That is, according to the present invention, as a means for solving the problem that the welding HAZ when the low-pressure water injection pipe is attached to the core shroud, which is the problem 1, the welding of the core shroud and the low-pressure water injection pipe is performed. By adopting a structure in which the joint is exposed to both the inside and outside of the core shroud, it is possible to approach the shot peening equipment to the HAZ, and to integrate parts as another countermeasure against stress corrosion cracking It becomes possible to provide a boiling water nuclear reactor that is basically free of HAZ.

  Moreover, the low pressure water injection which solves the problem accompanying the exposure of the worker during the installation work in the operation plant, which is the problem 2, and can be easily installed even if the worker does not enter between the RPV and the core shroud. Piping shapes can be provided. Further, in the operation of re-installing the low-pressure water injection pipe in the operation plant, the low-pressure water injection pipe can be attached in a short time without requiring access to the reactor pressure vessel.

  Hereinafter, with reference to FIGS. 1-9, embodiment of the boiling water reactor which concerns on this invention, especially a core shroud is demonstrated concretely. In addition, FIGS. 10-12 is also referred for the structure of the whole reactor and low-pressure water injection piping.

First Embodiment (FIGS. 1 and 10)
FIG. 1 is an enlarged cross-sectional view showing a main configuration of a core shroud of a boiling water reactor according to a first embodiment of the present invention.

  As shown in FIG. 1, in the present embodiment, the peripheral portion of the ring 1 is attached to the circular furnace wall side (outside (left side in the drawing)) formed on the core shroud upper shell 105 a by the welded portion 2. A core shroud side flange neck 104 is attached to the ring 1.

  The ring 1 is configured to have a slightly larger diameter than the diameter of the upper body hole 105b. The outer peripheral edge of the ring 1 is welded to the core shroud upper body 105a from the outside along the oblique direction by the welded portion 2, The gap portion on the side of the body hole 105b is configured to be greatly opened.

  As a result, the joint between the core shroud 105 and the low-pressure water injection pipe 100 is exposed to both the inside (right side in the figure) and the outside (left side in the figure) of the core shroud upper trunk 105a.

  That is, the diameter of the upper trunk hole 105b of the core shroud 105 and the diameter of the groove of the ring 1 are approximate to each other (the diameter of the groove of the ring 1 is slightly larger). The welded HAZ, which is a part, is exposed along the oblique direction on the inner and outer surface sides of the core shroud upper shell 105a.

  With this configuration, it is possible to solve the problem 1 that the welding HAZ when the low-pressure water injection pipe is attached to the core shroud 105, which is a narrow portion, and the proximity of the shot peening apparatus to the HAZ is possible.

  Further, as another countermeasure against stress corrosion cracking, the components can be integrated, and the HAZ can be fundamentally eliminated.

  In addition, the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2 described above, can be solved, and the low-pressure water injection pipe can be easily obtained even if the worker does not enter between the RPV and the core shroud 105. Can be installed.

Second Embodiment (FIGS. 2 and 10)
FIG. 2 is an enlarged cross-sectional view showing a core shroud 105 of a boiling water reactor according to a second embodiment of the present invention. In the present embodiment, the boiling water reactor in which the inner diameter of the opening 105b formed in the core shroud 105 to which the low-pressure water injection pipe 100 is welded is gradually widened toward the inner surface side of the core shroud 105 is described. explain.

  As shown in FIG. 2, in the low-pressure water injection pipe 100 of the present embodiment, the peripheral portion of the ring 1 is welded to a circular furnace wall side (outside (left side in the drawing)) formed in the core shroud upper trunk 105a. The ring shroud side flange neck 104 is attached to the ring 1.

  The inner diameter of the core shroud upper trunk hole 105b is inclined toward the inner surface side of the core shroud upper trunk 105a and gradually increases.

  By adopting such a configuration, according to the present embodiment, the shot peening construction to the HAZ can be performed more easily, and there is a problem that the welded HAZ becomes a narrow portion when the low-pressure water injection pipe is attached to the core shroud 105. It is possible to solve this problem, and the proximity of the shot peening apparatus to the HAZ becomes possible.

  Moreover, in this embodiment, the ring 1 and the core shroud side flange neck 104 are integrated, and parts can be integrated as a countermeasure against stress corrosion cracking. With this configuration, HAZ can be eliminated fundamentally, and the problems associated with the exposure of workers during installation work in the operation plant can be solved, so that workers do not enter between the RPV 101 and the core shroud 105. Even low pressure water injection pipes can be installed easily.

[Third Embodiment] (FIGS. 3 and 10)
FIG. 3 is an enlarged cross-sectional view showing a core shroud 105 of a boiling water reactor according to a third embodiment of the present invention. In the present embodiment, a boiling water reactor in which the welding groove 3 between the low-pressure water injection pipe 100 and the core shroud upper body 105a is formed only on the inner surface of the core shroud will be described.

  As shown in FIG. 3, in the low-pressure water injection pipe 100 according to the present embodiment, the ring 3 and the groove 3 of the welded portion 2 of the core shroud upper body 105 a are open only on the inner surface of the core shroud 105.

  For this reason, when the operator welds the ring 1 to the core shroud upper shell 105a, it suffices to work from the inside (right side in the figure) of the core shroud 105, and there is no work under a high dose outside the core shroud. The amount of exposure can be reduced.

  According to the present embodiment, as a means for solving the problem 1 that the welding HAZ becomes a narrow portion when the low-pressure water injection pipe is attached to the core shroud 105, the proximity of the shot peening apparatus to the HAZ is as follows. It becomes possible. Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  In addition, the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2 described above, is solved, and the worker can easily attach it without entering between the RPV 101 and the core shroud 105. .

[Fourth Embodiment] (FIGS. 4, 5, and 10)
FIG. 4 is an enlarged sectional view showing the core shroud 105 of the boiling water reactor according to the present embodiment. In the present embodiment, a boiling water reactor in which a ring 1 is provided as a component of the low-pressure water injection pipe 100 and the outer surface or inner surface of the ring 1 and the core shroud upper trunk 105a are aligned on the same surface will be described. .

  As shown in FIG. 4, in the low-pressure water injection pipe 100 according to the present embodiment, the outer surface (left surface) of the ring 1 and the outer surface (also the left surface) of the core shroud upper body 105a are aligned as the same surface. The weld 2 appears only on the back side.

  Therefore, there is no step after welding on the front side of the core shroud upper shell 105a. For this reason, it is possible to easily reduce the residual stress or to apply the forced compressive residual stress by shot peening or the like.

  FIG. 5 is an enlarged cross-sectional view showing a modification of the core shroud 105 shown in FIG.

  As shown in FIG. 5, in the low-pressure water injection pipe 100 of the present embodiment, the inner peripheral surface of the core shroud upper trunk hole 105b is inclined toward the inner surface side of the core shroud upper trunk 105a, and gradually toward the outer peripheral side. Spreading.

  For this reason, according to this embodiment, it becomes a structure which can perform the shot peening construction to the HAZ more easily, and the problem that the welding HAZ when the low-pressure water injection pipe is attached to the core shroud 105, which is the problem 1, is a narrow portion. As a means for solving the problem, the proximity of the shot peening apparatus to the HAZ becomes possible.

  Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  Further, the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2 described above, is solved, and the worker can easily install it even if the worker does not enter between the RPV and the core shroud 105. .

[Fifth Embodiment] (FIGS. 6, 2, and 10)
FIG. 6 is an enlarged cross-sectional view showing a core shroud 105 of a boiling water reactor according to a fifth embodiment of the present invention.

  In the present embodiment, the core shroud side flange neck 104 and the ring 1 which are components of the low-pressure water injection pipe 100 are integrally configured. The ring 1 extends in a direction protruding outward (upward) from the core shroud, and its outer peripheral end is connected to the core shroud upper body 105a via the welded portion 2.

  Thus, the low-pressure water injection pipe 100 according to the present embodiment has a configuration in which the ring 1 and the core shroud side flange neck 104 are integrated. With this configuration, a structure without HAZ is obtained.

  According to this embodiment, it becomes a structure which can perform the shot peening construction to the HAZ more easily, and solves the problem that the welding HAZ when the low pressure water injection pipe is attached to the core shroud 105, which is the problem 1, is a narrow portion. As a means for this, the proximity of the shot peening apparatus to the HAZ becomes possible. Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  In addition, the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2 described above, can be solved, and the worker can easily install it without entering between the RPV and the core shroud 105. .

[Sixth Embodiment] (FIGS. 7 and 10)
FIG. 7 is an enlarged cross-sectional view showing a core shroud 105 of a boiling water reactor according to a sixth embodiment of the present invention. In the present embodiment, a configuration in which the core shroud side flange neck 104 and the ring 1 are integrally formed and further expanded in a tapered shape and connected in a direction protruding toward the outside of the core shroud will be described.

  As shown in FIG. 7, the low-pressure water injection pipe 100 according to the present embodiment is connected in a direction in which the integrated ring 1 protrudes to the outside of the core shroud upper body 105a.

  As a means for solving the problem that the welded HAZ becomes a narrow portion when the low-pressure water injection pipe is attached to the core shroud 105, which is the problem 1 described above, the shape to be easily machined by turning is achieved by this configuration. The proximity of the shot peening equipment becomes possible.

  Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  Furthermore, the low pressure which solves the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2, and can be easily attached even if the worker does not enter between the RPV and the core shroud 105. The shape of the water injection pipe can be provided.

[Seventh Embodiment] (FIGS. 8 and 10)
FIG. 8 is an enlarged perspective view showing a half clamp of the boiling water reactor according to the seventh embodiment of the present invention. This embodiment demonstrates the structure which formed the through-hole 5 in the upper end of the upper half clamp 108 which is a component of the low pressure water injection piping 100. FIG.

  As shown in FIG. 8, in the present embodiment, a through hole 5 is provided along the circumferential direction at the upper end of the upper half clamp 108 that is a component of the low-pressure water injection pipe 100. The upper half clamp 108 is connected to the lower clamp 107 via an eye bolt 109 via a flange portion 108a.

  Thereby, the shift | offset | difference of a flange surface becomes possible [an operator] visually recognizable via the through-hole 5 from upper direction. Therefore, it is not necessary for the worker to enter between the RPV 101 and the core shroud 105, and the exposure amount can be reduced when the low-pressure water injection pipe of the operation plant is reinstalled.

  As described above, since the fastening parts for fastening the half clamps 107 and 108 are simplified to the bolt 109 only, the assembly work efficiency of the lower half clamp 107, the upper half clamp 108, the bolt 109 and the nut 110 of the conventional shape is improved, and a short time is required. Since the low-pressure water injection pipe 100 can be attached, the exposure amount can be reduced when the low-pressure water injection pipe is reinstalled in the operation plant.

  According to the present embodiment, as a means for solving the problem 1 that the welding HAZ becomes a narrow portion when the low-pressure water injection pipe is attached to the core shroud 105, the proximity of the shot peening apparatus to the HAZ is as follows. It becomes possible.

  Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  Moreover, the low pressure which solves the problem accompanying the exposure of the worker during the installation work in the operation plant, which is the problem 2, and can be easily attached even if the worker does not enter between the RPV and the core shroud 105. The shape of the water injection pipe can be provided.

[Eighth Embodiment] (FIGS. 9 and 10)
FIG. 9 is an enlarged cross-sectional view showing a core shroud 105 of a boiling water reactor according to an eighth embodiment of the present invention. In the present embodiment, a configuration in which the lower half clamp 107 and the flange neck 104 that are components of the low-pressure water injection pipe 100 are integrated will be described.

  As shown in FIG. 9, in this embodiment, the lower half clamp 107 and the flange neck 104 that are components of the low-pressure water injection pipe 100 are integrated.

  Then, it is not necessary for an operator to enter between the RPV 101 and the core shroud 105 in order to attach the lower half clamp 107, and after placing the pipe center member 111 on the integrated lower half clamp, the upper half clamp from above. Since it is possible to attach the low-pressure water injection pipe 100, the amount of exposure can be reduced when the low-pressure water injection pipe is reinstalled in the operation plant.

  As described above, according to the present embodiment, by integrating the lower half clamp 107 and the flange neck 104, the welding HAZ when attaching the low-pressure water injection pipe to the core shroud 105, which is the problem 1, is narrow. The problem which becomes a part can be solved, and the shot peening construction apparatus proximity | contact to HAZ can be enabled.

  Further, as another countermeasure against stress corrosion cracking, HAZ can be fundamentally eliminated by integrating components.

  In addition, the problem associated with the exposure of the worker during the installation work in the operation plant, which is the problem 2 described above, can be solved, and the worker can easily install it without entering between the RPV and the core shroud 105. .

The expanded sectional view showing a 1st embodiment of the present invention. The expanded sectional view which shows 2nd Embodiment of this invention. The expanded sectional view which shows 3rd Embodiment of this invention. The expanded sectional view which shows 4th Embodiment of this invention. The expanded sectional view which shows the modification of 4th Embodiment of this invention. The expanded sectional view which shows 5th Embodiment of this invention. The expanded sectional view which shows 6th Embodiment of this invention. The perspective view which shows 7th Embodiment of this invention. The expanded sectional view which shows 8th Embodiment of this invention. The schematic sectional drawing which shows the reactor pressure vessel of a boiling water reactor. The perspective sectional view showing low-pressure water injection piping. The side view which shows a part of low-pressure water injection piping as a cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ring, 2 Welded part, 3 ... Weld groove, 5 ... Through-hole, 101 ... Core shroud 105 reactor pressure vessel (RPV), 105a ... Core shroud upper trunk, 100 ... Low pressure water injection pipe, 106 ... Ring, 102 ... Low pressure water injection nozzle, 103 ... RPV side flange neck, 105b ... Hole, 110 ... Welded part, 104 ... Core shroud side flange neck, 103a, 103b ... Flange, 103c ... Sleeve, 103d ... Bellows, 103e ... Bellow cover, 103f ··· pins, 107 ··· lower half clamp, ································································· 109F, 103b, 104b Flange neck, 105b

Claims (5)

In a boiling water nuclear reactor having a low-pressure water injection pipe that is welded and joined horizontally between a reactor pressure vessel and a core shroud at a position above the core and injects cooling water into the core, the core shroud and the low-pressure water injection pipe The boiling water reactor is characterized in that the welded joint portion is exposed to both the inside and the outside of the core shroud. 2. The boiling water reactor according to claim 1, wherein an inner diameter of an opening formed in a core shroud in which the low-pressure water injection pipe is welded is gradually increased toward an inner surface side of the core shroud. Water reactor. The boiling water nuclear reactor according to claim 1, wherein a welding groove between the low-pressure water injection pipe and the core shroud is formed only inside the core shroud. The boiling water reactor according to claim 3, wherein a ring is provided as a component of the low-pressure water injection pipe, and the ring and the outer surface or the inner surface of the core shroud are arranged on the same surface. . The boiling water reactor according to any one of claims 1 to 4, wherein a flange neck and a ring, which are components of the low-pressure water injection pipe, are integrally configured.

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