JP4776361B2 - Boiling water reactor - Google Patents

Description

  The present invention relates to a boiling water reactor, and more particularly to a boiling water reactor having an improved connection structure between a core shroud and a shroud support.

  A conventional example of a boiling water reactor will be described with reference to FIG. FIG. 5 is an overall cross section showing the configuration of an improved boiling water reactor (ABWR). As shown in FIG. 5, a reactor core shroud 104 that houses a reactor core 102 is installed in the reactor pressure vessel 101. A core support plate 103 and an upper lattice plate 106 are disposed below and above the core shroud 104, and a large number of fuel assemblies 105 are installed between the core support plate 103 and the upper lattice plate 106. ing. A shroud head 112 is disposed on the upper part of the core shroud 104, and an air / water separator 114 is installed on the upper part of the shroud head 112 via a stand pipe 113. A steam dryer 117 is installed above the steam separator 114.

  Below the core support plate 103, a control rod guide tube 127 that accommodates the control rod 107 inserted into the core 102 and a control rod drive mechanism 108 for driving the control rod 107 are installed. A plurality of internal pumps 124 are disposed in the circumferential direction below the reactor pressure vessel 101. A main steam pipe 117 that guides steam generated in the core 102 to the turbine is connected to the wall surface of the reactor pressure vessel 101 on the side of the steam dryer 117. A water supply pipe 119 for supplying cooling water to the reactor pressure vessel 101 is connected to the side of the stand pipe 113 of the reactor pressure vessel 101.

  In the boiling water reactor configured as described above, the cooling water in the upper part of the reactor is sucked into the internal pump 124 from the annular space surrounded by the core shroud 104 and the reactor pressure vessel 101, and passes through the bottom of the reactor and the core 102. It becomes steam. The steam passes through the stand pipe 113, the steam separator 124, and the steam dryer 117 and travels to the turbine through the main steam pipe 118. The steam that has worked in the turbine is cooled by the main condenser and becomes water to supply water. The circulation structure is such that it returns from 119 to the top of the reactor pressure vessel 101.

  A shroud support 125 is erected at the lower part of the reactor pressure vessel 101, and the core shroud 104 is connected and supported on the shroud support 125 by welding or the like. In-core equipment such as the core 102, the shroud head 112, and the steam separator 114 is supported by the core shroud 104.

Conventionally, the core shroud extends upward from the bottom of the reactor pressure vessel so that the core shroud and the pump deck can be easily removed or replaced when damaged or the like requires repair or replacement. A technique for removably fixing to a support leg is proposed (for example, see Patent Document 1).
JP-A-8-254591

  In the conventional boiling water reactor, the lower end portion of the core shroud 104 is welded to the shroud support 125, and the shroud support 125 is welded to the lower mirror portion of the pressure vessel 101. Therefore, even when the core shroud needs to be replaced due to aging, there is a problem that it cannot be easily removed.

  The reactor pressure vessel 101 is made of carbon steel, and the core shroud 104 is made of stainless steel. At the reactor operating temperature (about 300 ° C.), stainless steel has a higher coefficient of thermal expansion than carbon steel, which may cause a difference in radial elongation. This difference in elongation cannot be solved even by a known technique in which the shroud support 125 and the core shroud 104 are fitted with bolts or the like.

  The present invention has been made in view of such circumstances, and allows radial expansion at the connection portion between the lower end portion of the core shroud and the reactor pressure vessel, while maintaining radial and axial directions due to external forces such as earthquakes. An object of the present invention is to provide a boiling water nuclear reactor that can restrain displacement and can easily remove and reattach a core shroud.

In order to achieve the above object, according to the present invention, a shroud support is erected at the lower part of the reactor pressure vessel, and a protrusion provided on the inner peripheral side of the lower end of the core shroud is mounted on the support. A boiling water nuclear reactor in which the core and the shroud support are detachably coupled to each other by a coupling means, wherein the projecting portion on the inner peripheral side of the lower end of the core shroud is a flange or a plurality of brackets, Bolt insertion holes are formed in the flange or the bracket along the vertical direction, and the shroud support is formed with a bolt accommodation hole longer than the length of the bolt insertion hole in the direction from the center of the core shroud to the bolt accommodation hole. The bolt in the direction from the center of the core shroud to the bolt receiving hole is formed at the bottom of the bolt receiving hole. A stud bolt having a diameter smaller than the length of the socket receiving hole and having a diameter approximately equal to the length of the bolt receiving hole in the circumferential direction of the core shroud in the bolt receiving hole is attached, and the stud bolt is attached to the bolt insertion hole of the flange or the bracket. A boiling water nuclear reactor characterized in that the flange or the bracket and the shroud support are coupled by inserting and screwing the upper end side of the stud bolt from the upper surface side of the flange or the bracket with a nut. I will provide a.

  According to the present invention, the radial shroud is allowed to extend at the connection portion between the lower end portion of the core shroud and the reactor pressure vessel, while the axial and radial displacement due to an external force such as an earthquake can be restrained. Can be easily removed and reattached.

  Hereinafter, an embodiment of a boiling water reactor according to the present invention will be described with reference to FIGS. 1 to 3 show an embodiment of a boiling water reactor according to the present invention, and FIG. 4 shows a modification. In addition, the same code | symbol as the code | symbol shown in FIG. 5 is attached | subjected and demonstrated about the part which is the same as that of the conventional structure, or respond | corresponds.

  FIG. 1 is a longitudinal sectional view showing the overall configuration of the in-furnace structure. As shown in FIG. 1, in the improved boiling water reactor (ABW) of this embodiment, a core shroud 104 that houses a core 102 is installed in a reactor pressure vessel 101. A core support plate 103 and an upper lattice plate 106 are disposed below and above the core shroud 104, and a large number of fuel assemblies 105 are installed between the core support plate 103 and the upper lattice plate 106. . A shroud head 112 is disposed on the upper part of the core shroud 104, and an air / water separator 114 is installed on the upper part of the shroud head 112 via a stand pipe 113. A steam dryer 117 is installed above the steam separator 114.

  Below the core support plate 103, a control rod guide tube 127 that accommodates the control rod 107 inserted into the core 102 and a control rod drive mechanism 108 for driving the control rod 107 are installed. A plurality of internal pumps 124 are disposed in the circumferential direction below the reactor pressure vessel 101. A main steam pipe 117 that guides steam generated in the reactor core 102 to the turbine is connected to the wall of the reactor pressure vessel 101 on the side of the steam dryer 117. Further, a water supply pipe 119 for supplying cooling water to the reactor pressure vessel 101 is connected to the side of the stand pressure 113 of the reactor pressure vessel 101.

  Cooling water at the top of the reactor is sucked into the internal pump 124 from an annular space surrounded by the core shroud 104 and the reactor pressure vessel 101, and becomes steam at the core 102 through the bottom of the reactor. The steam passes through the stand pipe 113, the steam separator 124, and the steam dryer 117 and travels to the turbine through the main steam pipe 118. The steam that has worked in the turbine is cooled by the main condenser and becomes water to supply water. The circulation structure is such that it returns from 119 to the top of the reactor pressure vessel 101.

In such a configuration, a shroud support 125 is erected at the lower part of the reactor pressure vessel 101, and a core shroud 104 separate from the shroud support 125 is detachably supported via a shroud fixing flange 130. Has been. A pump deck 126 is attached to the outer peripheral side of the lower end of the core shroud 104 as an integral structure, and an internal pump 124 is supported on the pump deck 126.

  FIG. 2 is an enlarged cross-sectional view showing an enlarged joint (A portion in FIG. 1) between the shroud support 125 and the core shroud 104 shown in FIG. As shown in FIG. 2, the core shroud 104 is arranged in a cylindrical shape so as to surround the core 102, and the lower end portion of the core shroud 104 is configured to be thicker than the upper side portion. A shroud fixing flange 130 is provided on the inner peripheral side of the lower end portion of the core shroud 104 as a horizontal protrusion for fixing the shroud. Further, a shroud support 125 that supports a shroud fixing flange 130 as a projecting portion is provided at the lower portion of the reactor pressure vessel 101.

The shroud fixing flange 130 is formed over the entire inner peripheral side of the lower end portion of the core shroud 104, and the inner peripheral surface of the shroud fixing flange 130 is substantially the same vertical surface as the outer peripheral surface of the shroud support 125. . The outer peripheral surface of the shroud fixing flange 130 is larger in diameter than the outer peripheral surface of the shroud support 125. A stud bolt 131 is vertically provided at the upper end portion of the shroud support 125, and the upper end portion of the stud bolt 131 protrudes above the shroud fixing flange 130. A nut 132 is screwed onto the upper end of the stud bolt 131, and the upper surface of the shroud fixing flange 130 is fastened and fixed on the shroud support 125 by the nut 132. That is, the shroud fixing flange 130 as the projecting portion and the shroud support 125 are detachably coupled by the stud bolt 131 and the nut 132 as the coupling means.

  A pump deck 126 is provided on the outer peripheral surface side of the core shroud 104 at a position slightly higher than the shroud fixing flange 130. The pump deck 126 is provided integrally with the core shroud 104 over the entire circumference of the core shroud 104, and an internal pump 124 is supported on the pump deck 126. That is, a pump deck 126 facing the inner peripheral surface of the reactor pressure vessel 101 is provided on the outer peripheral side of the core shroud 104, and a seal ring 134 is provided on the outer peripheral portion of the pump deck 126. It is configured to contact the inner surface of the reactor pressure vessel 101.

  FIG. 3 is an enlarged cross-sectional view showing in more detail the coupling means of the shroud fixing flange 130 which is the protruding portion on the inner peripheral side of the lower end portion of the core shroud 104 shown in FIG. That is, the connection structure between the shroud fixing flange 130 and the shroud support 125 of the core shroud 104 is shown in more detail.

  As shown in FIG. 3, the shroud fixing flange 130 has a bolt insertion hole 136 extending in the vertical direction. The shroud support 125 is formed with a bolt receiving hole 135 having an upper end opening communicating with the bolt insertion hole 136. A length b in the radial direction of the bolt receiving hole 135 is formed to be longer than a length c in the same direction of the bolt insertion hole 136. A stud bolt 131 having a diameter smaller than the radial length b of the bolt receiving hole 135 and a diameter substantially equal to the circumferential length of the bolt receiving hole 135 is attached to the bottom of the bolt receiving hole 135. The stud bolt 131 is inserted into the bolt insertion hole 136 of the shroud fixing flange 130. Then, the upper end side of the stud bolt 131 is fastened by screwing the nut 132 from the upper surface side of the shroud fixing flange 130, thereby connecting the shroud fixing flange 130 and the shroud support 125.

  As described above, the upper end side of the shroud support 125 is formed with the bolt receiving hole 135 that opens upward in the axial direction of the reactor pressure vessel 101 and is long in the radial direction of the reactor pressure vessel 101. Between the support 125 and the stud bolt 131, even if the stud bolt 131 is deformed, the generated stress has a gap having a length that does not exceed the allowable value on the strength of the stud bolt 131. The stud bolt 131 can be deformed in the radial direction from the core side.

  In this configuration, in this embodiment, the coupling means including the stud bolt 131 and the nut 132 restrains the core shroud 104 in the axial direction and the circumferential direction of the reactor pressure vessel 101, but radiates from the center of the core shroud 104. It is a means for enabling movement in the direction.

  And according to the coupling | bonding means of such this embodiment, the following specific problems can be solved. That is, when the reactor pressure vessel 101 is made of carbon steel and the core shroud 104, the shroud fixing flange 130, and the pump deck 126 are made of stainless steel, the reactor operating temperature (about 300 ° C.) is stainlesser than carbon steel. Since steel has a higher coefficient of thermal expansion, it is necessary to absorb the difference in elongation in the radial direction.

  In this case, according to the configuration of the present embodiment, the core shroud 104 can absorb about 2 mm (one side) in the radial direction, and the floating of the core shroud 104 due to the differential pressure in the core is tightened by the stud bolt 131. Can be surely restrained. That is, according to the present embodiment, the coupling means including the stud bolt 131 and the nut 132 restrains the core shroud 104 in the axial direction and the circumferential direction of the reactor pressure vessel 101, but in the radial direction from the center of the core shroud 104. In this case, it is possible to reliably restrain the bolt by fastening with the stud bolt 131 by means for enabling movement.

  Further, in the present embodiment, a pump deck 126 facing the inner peripheral surface of the reactor pressure vessel 101 is provided on the outer peripheral side of the core shroud 104. And the seal ring 134 is provided in the outer peripheral part of the pump deck 106 over the whole circumferential direction of the reactor pressure vessel 101, for example in two steps of upper and lower sides. These seal rings 134 are in contact with the inner surface of the reactor pressure vessel 101 so that a good sealing function can be maintained.

  That is, the core shroud 104 and the pump deck 126 are integrated, and it is necessary to absorb the difference in thermal expansion coefficient between the pump deck 126 and the reactor pressure vessel 101. In the present embodiment, the core shroud 104 and the pump deck 126 are integrated, and the seal ring 134 is installed on the outer peripheral surface of the pump deck 126, so that the expansion in the radial direction of the pump deck 126 can be absorbed.

  FIG. 4 shows a modification of the present embodiment. That is, a modification of the connection structure between the shroud fixing flange 130 and the shroud support 125 of the core shroud 104 is shown.

As shown in FIG. 4, in this embodiment, the shroud support 125 is formed with a digging capable of installing a nut 132 and spherical washers 133 and 136. The nut 132 is configured to fasten the stud bolt 17 via the upper and lower spherical washers 133. About another structure, it is the same as that of embodiment shown in FIGS. 1-3.

  As described above, according to the configuration of FIG. 4 in which the shroud support 125 and the shroud fixing flange 130 are detachably coupled with the stud bolt 131 and the nut 132 via the spherical washer 133, the core shroud 104 and the shroud fixing flange 130 are provided. When the stud bolt 131 is inclined by thermal expansion in the radial direction, the elongation can be absorbed by the inclination of the stud bolt 131.

  According to the above embodiment, if the core shroud 104 is damaged, it can be repaired by replacing the core shroud 104 or taking it out from the reactor pressure vessel 101 by a simple method.

  In the above embodiment, the horizontal shroud fixing flange 130 is integrally provided on the outer peripheral surface of the lower end portion of the core shroud 104. However, in the present invention, a plurality of configurations are provided along the outer peripheral surface of the lower end portion of the core shroud 104. It is good also as a structure which provides these brackets integrally with a fixed space | interval, and fastens these brackets with the above-mentioned stud bolt 131.

  In addition, the present invention is not limited to the new and improved boiling water reactor (ABWR) as in the above-described embodiment, but the in-core structure replacement technique including the core shroud of the existing boiling water reactor (BWR). Can be applied as

1 is a schematic cross-sectional view showing a configuration of a boiling water reactor according to an embodiment of the present invention. The A section enlarged view of FIG. The expanded sectional view which expands and shows the principal part of FIG. Sectional drawing which shows the modification of one Embodiment of this invention. The schematic sectional drawing which shows the conventional boiling water reactor.

Explanation of symbols

101 reactor pressure vessel 102 core 103 core support plate 104 core shroud 105 fuel assembly 106 upper lattice plate 107 control rod 108 control rod drive mechanism 112 shroud head 113 stand pipe 114 steam separator 117 steam dryer 118 main steam pipe 119 Water supply piping 120 In-core nuclear instrumentation wiring guide pipe 121 Outlet 122 In-core nuclear instrumentation 124 Internal pump 125 Shroud support 126 Pump deck 127 Control rod guide pipe 130 Shroud fixing flange 131 Stud bolt 132 Nut 133 Spherical washer 134 Seal ring 135 Bolt Housing hole 136 Bolt insertion hole

Claims (3)

A shroud support is erected at the lower part of the reactor pressure vessel, and a protrusion provided on the inner peripheral side of the lower end of the core shroud is mounted on this support, and these protrusions and the shroud support are detachably connected by a coupling means. A boiling water reactor,
The projecting portion on the inner peripheral side of the lower end portion of the core shroud is a flange or a plurality of brackets, and the coupling means drills a bolt insertion hole along the vertical direction in the flange or the bracket,
Forming a bolt housing hole longer than the length of the bolt insertion hole in the direction from the center of the core shroud to the bolt housing hole in the shroud support;
The bottom of the bolt housing hole has a diameter smaller than the length of the bolt housing hole in the direction from the center of the core shroud to the bolt housing hole and the length of the bolt housing hole in the circumferential direction of the core shroud in the bolt housing hole. Install stud bolts of approximately equal diameter,
By inserting the stud bolt into the bolt insertion hole of the flange or the bracket, and screwing the upper end side of the stud bolt from the upper surface side of the flange or the bracket with the nut, the flange or the bracket and the shroud support A boiling water reactor characterized by combining Boiling water reactor according to claim 1, wherein coupled removably with the flange or the and said bracket and the shroud support via a spherical washer stud bolt and the nut. A pump deck facing the inner peripheral surface of the reactor pressure vessel is provided on the outer peripheral side of the core shroud, and a seal ring is provided on the outer peripheral portion of the pump deck, and this seal ring is in contact with the inner surface of the reactor pressure vessel. The boiling water reactor according to claim 1 .

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