JP2007225437A - Boiling water reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiling water reactor capable of reducing possibility of a potential coolant loss accident of a pressure vessel lower part without requiring installation of a through port on the reactor pressure vessel lower part, and improving economical efficiency by miniaturizing a reactor container. <P>SOLUTION: This reactor includes a plurality of control rods 107 inserted from the upside toward the downside between a plurality of bodies of a fuel assembly 105 constituting a core 102, and subjected to extraction operation from the downside to the upside; a control rod driving mechanism 108 provided on the upper lid part of the reactor pressure vessel 101, for connecting the control rods 107 to a control rod driving shaft 109 and operating them; and an elongated fuel channel 110 formed by elongating a fuel channel for fixing and protecting the plurality of arranged bodies of the fuel assembly 105 constituting the core 102, and having a function for guiding the control rods. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a boiling water reactor that does not require a through hole at the lower part of a reactor pressure vessel and can improve safety.

  A conventional boiling water reactor will be described with reference to FIG. 6 using an improved boiling water reactor called ABWR as an example.

  In a conventional boiling water reactor, a shroud 104 that houses a core 102 is provided in a reactor pressure vessel 101. A core support plate 103 and an upper lattice plate 106 are disposed at the lower and upper portions of the shroud 104, respectively. A large number of fuel assemblies 105 are installed between the core support plate 103 and the upper lattice plate 106. Yes. A shroud head 112 is provided on the upper part of the 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 / water separator 114.

  A control rod guide tube 127 that houses the control rod 107 inserted into the core 102 and a control rod drive mechanism 108 for driving the control rod 107 are installed below the core support plate 103. A plurality of internal pumps 124 are arranged on the outer periphery of the lower part of the reactor pressure vessel 101 so as to be spaced apart from each other in the circumferential direction.

  On the other hand, a main steam pipe 118 that guides steam generated in the core 102 to the turbine is connected to the wall 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 standpipe 113 of the reactor pressure vessel 101.

  In the conventional 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 shroud 104 and the reactor pressure vessel 101, and passes through the bottom of the reactor. At 102, steam is generated, passes through the stand pipe 113, the steam separator 114, and the steam dryer 117, and travels toward the turbine through the main steam pipe 118. And the steam which turned the turbine is cooled with the main condenser, turns into water, and is the circulation which returns from the feed water piping 119 to the reactor pressure vessel 101 upper part. The shroud 104 is erected from the lower part of the reactor pressure vessel 101 by a shroud support 125 and a pump deck 126, and supports in-core equipment such as the core 102, the shroud head 112, and the steam-water separator 114.

  In such a conventional boiling water reactor, a large number of control rod drive mechanisms and core instrumentation tubes penetrate the lower part of the reactor pressure vessel, resulting in potential coolant loss at the lower part of the reactor pressure vessel. It was a factor that increased the likelihood of an accident (LOCA).

On the other hand, in order to realize a highly economical nuclear power plant, the fuel assembly in the reactor pressure vessel is stored as effectively as possible to reduce the size of the reactor pressure vessel, and further to the atomic vessel that contains the reactor pressure vessel. It is necessary to reduce the volume of the reactor containment vessel and the reactor building that contains it. However, the conventional boiling water reactor requires a large number of control rod drive mechanisms and core instrumentation tubes suspended in the lower part of the reactor pressure vessel, their cables, and a drawing space. However, it was one of the effective means for downsizing the containment vessel.
JP 2002-55189 A

  The present invention has been made to solve the above-described problems, and it is not necessary to provide a through-hole in the lower part of the reactor pressure vessel, reducing the possibility of a potential loss of coolant accident (LOCA) in the lower part of the pressure vessel. In order to improve safety and to reduce the size of the containment vessel and improve economy, the control rod drive mechanism is installed on the upper part of the pressure vessel, and the nuclear instrumentation tube in the reactor is located above the core of the reactor pressure vessel. The purpose is to provide a concrete in-reactor support structure and in-reactor equipment for realizing them.

  The present invention provides a core having a core shroud, a core support plate, an intermediate grid plate, an upper grid plate, and a fuel assembly supported by the core shroud, a core support plate, and a fuel assembly supported by the core shroud. A plurality of control rods inserted between the fuel assemblies from above to below and pulled out from below to above, and provided on the reactor pressure vessel, the control rods being connected to the control rod drive shaft A control rod drive mechanism that is connected and operated at the same time, an extended fuel channel that is formed by extending a fuel channel that fixes and protects the fuel assembly, and has a function of guiding a control rod, and this extended fuel channel A shroud head that closes the upper end opening of the core and passes the plurality of control rod drive shafts in a vertically movable manner, and a shroud head provided above the shroud head, A plurality of steam separators for separating the steam generated in the two-phase flow generated from the reactor core, and a dryer provided in the reactor pressure vessel and passing through the steam generated from the reactor core and drying. Features.

  In the present invention, it is preferable to enable natural circulation of cooling water in the furnace.

  In the present invention, it is preferable that piping and nozzles connected to the reactor pressure vessel are disposed above the core position.

  In the present invention, it is preferable that the nuclear instrumentation wiring lead portion of the nuclear reactor is disposed in the trunk portion of the reactor pressure vessel above the core position.

  In this invention, it is preferable that the said shroud is remotely installed in the shroud support part installed in the lower mirror of the said reactor pressure vessel.

  In the present invention, when the control rod is rapidly inserted, it is preferable that the control rod is configured to fall freely with the control rod alone or the control rod drive shaft connected to the control rod and the control rod.

  In the present invention, it is preferable to install a lateral support of a shroud capable of absorbing a difference in thermal expansion in the vertical direction in the trunk portion of the reactor pressure vessel.

  In the present invention, it is preferable that a steam drying portion of the dryer is disposed on the inner surface of the reactor pressure vessel so as to be spaced apart in the circumferential direction.

  In the present invention, it is preferable that a buffer mechanism for absorbing an impact when the control rod is rapidly inserted is disposed at a lower end portion of the control rod and a lower portion of the core support plate.

  In the present invention, a control rod drive shaft lower guide tube rising from the shroud head and a control rod drive shaft upper guide tube installed on the pressure vessel upper lid are connected, and a two-phase flow generated from the reactor core It is preferable to prevent leakage to other than the separator.

  In the present invention, in addition to the inside of the core, it is preferable to dispose nuclear instrumentation outside the shroud or outside the reactor pressure vessel.

  In the present invention, it is preferable that a steam guide tube is suspended from directly below the shroud head.

  According to the present invention, a core provided at the inner bottom portion of a reactor pressure vessel and having a core shroud, a core support plate, an intermediate lattice plate, an upper lattice plate, and a fuel assembly supported by the core shroud, and constitutes the core A plurality of control rods inserted between a plurality of fuel assemblies from the top to the bottom and pulled out from the bottom to the top, and provided at the upper part of the reactor pressure vessel, the control rods being provided as control rods A control rod drive mechanism connected and operated by a drive shaft, an extended fuel channel formed by extending a fuel channel for fixing and protecting the fuel assembly, and having a control rod guide function, and this extension A shroud head that closes the upper end opening of the core above the fuel channel and through which the plurality of control rod drive shafts can move up and down, and a shroud head provided above the shroud head. A plurality of steam separators for separating the two-phase steam generated from the core, and a dryer provided in the reactor pressure vessel and allowing the steam generated from the core to pass through and drying. Therefore, there is no need to provide a through-hole in the lower part of the reactor pressure vessel, and the possibility of potential loss of coolant accident (LOCA) in the lower part of the pressure vessel can be reduced. Can be improved.

  When natural circulation of the cooling water in the furnace is enabled, a recirculation pump is not required, so that the configuration can be made extremely compact and the cost can be reduced.

  When piping and nozzles connected to the reactor pressure vessel are arranged above the core position, a potential coolant loss accident at the bottom of the reactor pressure vessel is prevented and a highly safe reactor is obtained. be able to.

  When the nuclear instrumentation wiring lead-out part of the nuclear reactor is arranged in the trunk of the reactor pressure vessel above the core position, the number of through-holes in the lower part of the reactor pressure vessel can be reduced. Can be improved.

  When the shroud is remotely fixed to a shroud support portion installed in a lower mirror of the reactor pressure vessel, the shroud can be easily installed, and is also earthquake resistant by being directly fixed to the pressure vessel. Can be improved.

  When the control rod is rapidly inserted, when the control rod is configured to fall freely with the control rod alone or with the control rod and the control rod drive shaft connected to the control rod, the hydraulic control is performed as in the past. It is possible to provide a control rod drive mechanism that does not require a unit and is therefore excellent in reliability and economy.

  In the boiling water reactor of the present invention, a control rod drive mechanism is installed in the reactor pressure vessel upper lid, and the upper end opening of the reactor core is closed, and the drive shafts of a plurality of control rods are inserted in a vertically movable manner. A plurality of steam separators installed on the upper end of the shroud head via a stand pipe for separating the two-phase steam generated from the reactor core, and the inner periphery of the reactor pressure vessel above the steam separator And a steam dryer that dries the steam separated by the steam separator, and allows the control rod to be pulled out and inserted and the through hole at the bottom of the reactor pressure vessel to be reduced. Below, the form of the boiling water reactor of this invention is demonstrated in detail with reference to FIG. 1 thru | or FIG.

First Embodiment FIGS. 1, 2 and 3 are schematic views of a reactor pressure vessel according to a first embodiment of the present invention.

  As shown in FIG. 1, in the present embodiment, a core 102 is provided at the lowest end position in the reactor pressure vessel 101.

  A shroud 103 and a core support plate 104 are provided in the vicinity of the bottom of the reactor pressure vessel 101, and a large number of fuel assemblies 105 are erected and supported on the core support plate 104 in a square lattice arrangement. The upper end portion is fixed by the upper lattice plate 106, and thereby the core 102 is configured. The control rod 107 is a cross-shaped control rod, and is regularly arranged corresponding to each of the four fuel assemblies 105. The control rod 107 is inserted from the upper part of the core 102 by a control rod drive shaft 109 connected to a control rod drive mechanism 108 installed on the upper cover of the reactor pressure vessel 101.

  The core shroud 103 has a structure in which an upper lattice plate 106, an intermediate lattice plate 111, and a core support plate 104 can be installed from the upper part of the reactor pressure vessel 101, and the core support plate 104 protects the fuel assembly 105. An extended fuel channel 110 is installed and a fuel assembly 105 is installed therein.

  The upper portion of the extended fuel channel 110 extends to the upper lattice plate 106. As a result, the control rod 107 is guided by the extended fuel channel 110 and inserted into the core 102 from above. The upper part of each extended fuel channel 110 opens upward, and the gas-liquid two-layer flow generated in the core 102 rises through the two-layer flow region inside the extended fuel channel 110.

  A shroud head 112 is provided above the extended fuel channel 110, and a control rod drive shaft lower guide tube 116 for guiding the control rod drive shaft 109 is installed at the upper end of the shroud head 112. Further, a stand pipe 113 is installed at the upper end of the shroud head 112 so as not to interfere with the control rod drive shaft lower guide pipe 116, and this stand pipe 113 is separated into the two-phase flow of steam generated from the core 102. A plurality of steam separators 114 for performing the above are provided. Further above, a steam dryer is provided along the inner periphery of the reactor pressure vessel 101 so as not to interfere with the control rod drive shaft upper guide tube 115 and the control rod drive shaft lower guide tube 116 for guiding the control rod drive shaft 109. 117 is disposed.

  The control rod drive shaft lower guide tube 116 rising from the shroud head 112 and the control rod drive shaft upper guide tube 115 installed from the upper cover of the reactor pressure vessel 101 are connected, and the two-phase flow generated from the reactor core 102 is a steam-water separator. It prevents leaking to other than 114.

  Further, an in-core nuclear instrumentation 122 for detecting a neutron flux is provided in the core 102, and the electrical wiring from the in-core nuclear instrumentation 122 can be drawn from the lower part of the core 102, and the wiring can be routed inside. It is routed through the in-core nuclear instrumentation wiring guide tube 120 installed with a large bending radius. This electrical wiring is taken out from an outlet 121 installed in the trunk of the reactor pressure vessel 101 above the core 102.

  The assembly of the in-core nuclear instrumentation wiring guide tube 120 is performed in a state of good workability before the shroud 103 is installed in the reactor pressure vessel 101. Thereafter, with the assembly of the core support plate 104, the intermediate lattice plate 111, the upper lattice plate 106, and the in-core nuclear instrumentation wiring guide tube 120 completed, the shroud 103 can be tightened with bolts that can be remotely tightened to the lower part of the reactor pressure vessel 101. Fixed. The shroud 103 is fixed at the lower part and supported at the upper part. That is, a support 129 is provided on the trunk of the reactor pressure vessel 101, and the shroud is also supported by this support 129. This support 129 absorbs the vertical displacement due to the thermal expansion difference of the shroud, but prevents the movement in the lateral direction, prevents blurring during an earthquake, and controls by bending of the control rod drive shaft 109. Abnormal driving of the rod 107 does not occur.

  By configuring in this way, the control rod drive mechanism 108 penetrating part, the main steam pipe 118, the feed water pipe 119, and the in-core nuclear instrumentation wiring guide pipe 120 outlet 121 are respectively located above the core 102 of the reactor pressure vessel 101. Arranged. Therefore, no through-holes, pipes, valves, drive mechanisms, etc. can be provided below the core 102, and a very safe nuclear reactor can be obtained.

  In the reactor pressure vessel 101 having such a configuration, during operation, the two-layer flow generated in the core 102 rises through the internal space of each extended fuel channel 110, and the steam is a steam-water separator 114 and a steam dryer 117. And is sent from the main steam pipe 118. On the other hand, the water descends along the inner surface of the reactor wall of the reactor pressure vessel 101 via the steam separator 114 or the steam dryer 117 and naturally circulates in the core 102. Therefore, according to the present embodiment, the chimney effect is generated due to the presence of the extended fuel channel 110 on the core 102 while the core 102 is located in the lower part of the reactor pressure vessel 101, thereby causing strong natural circulation. Power can be obtained, and a nuclear reactor as a natural circulation reactor is achieved.

  Further, since the recirculation pump in the conventional reactor pressure vessel is not required, the configuration can be made extremely compact, and a greater economic effect can be obtained for cost reduction. On the other hand, since the control rod drive mechanism 108 is installed on the upper part of the reactor pressure vessel 101 and the control rod 107 is inserted / removed from the upper part of the reactor core 102, water pressure control is performed against the pressure in the reactor as in the prior art. It is not necessary to scram the control rod from below using the unit, and it is possible to adopt a gravity drop type. Therefore, it is possible to provide the control rod drive mechanism 108 that is excellent in reliability and economy.

  The control rod scram has a method of separating the control rod 107 at the lower end of the control rod drive shaft 109 and allowing it to fall naturally, and a method of naturally dropping the control rod drive shaft 109 and the control rod 107 together. Moreover, you may arrange | position the buffer mechanism which absorbs the impact force at the time of a scram to the control rod 107 lower end and the core support plate 103 lower part as needed.

Second Embodiment FIG. 4 is a schematic sectional view according to a second embodiment of the present invention. In the first embodiment of the present invention, in-core nuclear instrumentation 122 is arranged on the outer periphery of the shroud 104 and in the core 102 or on the outer periphery of the reactor pressure vessel 101 to implement the nuclear instrumentation of the core 102. According to the present embodiment, the in-core nuclear instrumentation wiring guide tube 120 required in the first embodiment and the outlet 121 installed in the trunk of the reactor pressure vessel 101 above the core 102 are provided. Therefore, a simple nuclear reactor having a cheaper structure can be provided.

Third Embodiment FIG. 5 is a longitudinal sectional view of a reactor pressure vessel according to a third embodiment of the present invention. In the first embodiment of the present invention, the extended fuel channel 110 is changed to a chimney-structured steam guide tube 128 suspended from directly below the shroud head 112. The steam guide tube 128 has an integral structure, and can be removed from the shroud during maintenance to access the core 102. Further, by adopting the chimney structure, the fuel assembly 105 having the same structure as that used in the current boiling water reactor can be used, and an inexpensive nuclear reactor can be provided.

  As described above, this boiling water reactor is provided at the inner bottom portion of the reactor pressure vessel 101, and includes the core shroud 103, the core support plate 104, the intermediate grid plate 111, the upper grid plate 106, and the like. A plurality of cores 102 having supported fuel assemblies 105 and a plurality of fuel assemblies 105 constituting the cores 102 are inserted from above to below and pulled out from below to above. Control rod 107, a control rod drive mechanism 108 that is provided on the upper lid portion of the reactor pressure vessel 101 and is operated by connecting the control rod 107 with a control rod drive shaft 109, and a plurality of fuels arranged in the core 102. An extended fuel channel 110 formed by extending a fuel channel for fixing and protecting the assembly 105 and having a function of guiding a control rod, and this extended fuel channel A shroud head 112 that closes the upper end opening of the core 102 above the tunnel 110 and allows the plurality of control rod drive shafts to freely move up and down, and is erected on the upper end of the shroud head 112 via a stand pipe 113. , A plurality of steam separators 114 for separating the two-phase steam generated from the core 102, and a dryer steam drying provided in the reactor pressure vessel 101, through which steam generated from the core 102 passes and is dried. Since there is no need to provide a through-hole in the lower part of the reactor pressure vessel, the possibility of a potential coolant loss accident in the lower part of the pressure vessel can be reduced, and the reactor containment vessel can be downsized. Can improve economy.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view which shows the outline of the boiling water reactor which is the 1st Embodiment of this invention. The cross-sectional view which shows the cross section which follows the AA line in FIG. The cross-sectional view which shows the cross section which follows the BB line in FIG. It is a figure which shows the in-core nuclear instrumentation installation which is the 2nd Embodiment of this invention, Comprising: The cross-sectional view which shows the cross section of the position along CC line in FIG. The longitudinal cross-sectional view which shows the outline of the boiling water reactor which is the 3rd Embodiment of this invention. The longitudinal cross-sectional view which shows the outline of the conventional boiling water reactor.

Explanation of symbols

101 reactor pressure vessel 102 core 103 shroud 104 core support plate 105 fuel assembly 106 upper lattice plate 107 control rod 108 control rod drive mechanism 109 control rod drive shaft 110 extended fuel channel 111 intermediate lattice plate 112 shroud head 113 stand pipe 114 air Water separator 115 Control rod drive shaft upper guide tube 116 Control rod drive shaft lower guide tube 117 Steam dryer 120 In-core nuclear instrumentation wiring guide tube 121 Outlet 122 In-core instrumentation 125 Shroud support 128 Steam guide tube

Claims (5)

A reactor core provided with a core shroud, a core support plate, an intermediate grid plate, an upper grid plate, and a fuel assembly supported by the core shroud, provided at the inner bottom of the reactor pressure vessel;
A plurality of control rods inserted between the plurality of fuel assemblies constituting the core from the top to the bottom and being pulled out from the bottom to the top;
A control rod drive mechanism that is provided on the upper part of the reactor pressure vessel and operates by connecting the control rod with a control rod drive shaft;
An extended fuel channel formed by extending a fuel channel for fixing and protecting the fuel assembly, and having a function of guiding a control rod;
A shroud head that closes the upper end opening of the core above the extended fuel channel and through which the plurality of control rod drive shafts can move up and down;
A plurality of steam separators provided above the shroud head for performing steam separation of the two-phase flow generated from the core;
A dryer provided in the reactor pressure vessel and passing through the steam generated from the core and drying;
A boiling water reactor characterized by comprising:   The boiling water reactor according to claim 1, wherein the cooling water can be naturally circulated in the reactor.   2. The boiling water reactor according to claim 1, wherein piping and nozzles connected to the reactor pressure vessel are disposed above the core position.   2. The boiling water reactor according to claim 1, wherein the shroud is remotely installed on a shroud support portion installed on a lower mirror of the reactor pressure vessel.   The boiling water reactor according to claim 1, wherein when the control rod is rapidly inserted, the control rod alone or the control rod and a control rod drive shaft connected to the control rod are configured to fall freely. Boiling water reactor characterized by being made.

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