JPH0344274B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a boiling water reactor (hereinafter referred to as BWR).
In particular, the present invention relates to an improvement of a lid for closing an upper opening of a nuclear reactor pressure vessel.

[Technical background of the invention]

Generally, in a BWR, there is a water supply pipe that supplies coolant into the reactor pressure vessel, a main steam pipe that takes out the steam generated in the reactor pressure vessel and introduces it to the turbine system, and a forced circulation reactor that circulates the coolant forcibly. In the reactor pressure vessel, recirculation piping with a recirculation pump inserted is connected to the reactor pressure vessel. Piping rupture accidents may occur in these water supply piping, main steam piping, recirculation piping, etc. In the unlikely event that a pipe rupture accident occurs, the reactor must be brought to an emergency shutdown, and coolant containing radioactive materials may leak out, resulting in a secondary disaster. Therefore, it has been considered to reduce the probability of pipe rupture accidents by eliminating the water supply pipe and the main steam pipe from among these pipes. Further, the entire steam generation system including the heat exchanger has been made more compact, for example, a nuclear reactor with a built-in heat exchanger is being considered, in which the heat exchanger is placed inside the reactor pressure vessel.

The nuclear reactor with a built-in heat exchanger will be described below with reference to FIGS. 1 to 3. Reference numeral 1 in FIG. 1 indicates a reactor pressure vessel. The reactor pressure vessel 1 has a lower diameter smaller than the upper part from the viewpoint of improving space utilization. This reactor pressure vessel 1 is supported by a reactor building 3 via a ring garter 2.

A coolant 4 is housed in the reactor pressure vessel 1, and a lid 5 is provided to close the upper opening 1A. Reference numeral 6 in the figure indicates a bolt that fixes the lid 5 to the reactor pressure vessel 1. A reactor core 8 made up of a plurality of fuel assemblies (not shown), control rods 7, etc. is disposed in the lower part of the reactor pressure vessel 1 and is supported by a core support mechanism 9. A core upper mechanism 10 is provided above the core 8 so as to penetrate through the lid 5. The upper core mechanism 10 is composed of a control rod guide tube 11, a control rod drive mechanism (hereinafter referred to as CRD) 12 that moves the control rods 7 up and down along the control rod guide tube 11, and a fuel exchanger (not shown). ing. A lower shroud 13A is fixed to the reactor pressure vessel 1 between the reactor core 8 and the reactor pressure vessel 1, and an intermediate shroud 13A is provided between the reactor core upper mechanism 10 and the reactor pressure vessel 1. A shroud 13B is provided above the lower shroud 13A, and an upper shroud 13 is provided above the intermediate shroud 13B.
C is provided. This upper shroud 13C
A plurality of openings 14A are formed in the opening 14A. Further, between the upper shroud 13C and the reactor pressure vessel 1, a plurality of primary heat exchangers 15 are supported by a support member 16 and penetrate through the lid body 5 at equal intervals in the circumferential direction (for example, as shown in FIG. 2). A heat exchanger flange 1 is provided (eight units) and closes the opening 5A of the lid body 5.
Its upper end is fixed to 5A. A guide pipe 17 is provided on the lower outer periphery of the primary heat exchanger 15 and is supported by the reactor pressure vessel 1 . Code 15 in the figure
B indicates a heat exchanger tube, and reference numeral 18 indicates a bolt fixing the heat exchanger flange 15A to the lid 5.

In the above configuration, the coolant 4 rises from the bottom to the top of the reactor core 8 as shown by the arrow in the figure, and is boiled at this time. Then, it flows out above the reactor core 8 and flows out into the vicinity of the primary heat exchanger 15 through the opening 14A of the upper shroud 13C. There, it is cooled by heat exchange with the secondary side coolant and flows again below the core 8.
This cycle is then repeated. All of this is done through natural circulation.

Next, another example will be explained with reference to FIG. That is, in the example shown in FIG. 1, the primary heat exchanger 15 is provided to penetrate the lid 5 and is supported by the lid 5, whereas in the example shown in FIG. The reactor pressure vessel 15 is completely housed within the reactor pressure vessel 1 and is fixed to the inner circumferential wall of the reactor pressure vessel 1 via a support member 19. The rest of the configuration is the same as the example shown in FIG. 1, so a description thereof will be omitted.

[Problems with background technology]

In the case of the configuration shown in FIG. 1, for example, when removing the lid 5 to perform fuel exchange, the primary heat exchanger 15 must also be removed at the same time, and at least the heat transfer tube 15B of the primary heat exchanger 15 must be removed. Therefore, residual heat cannot be removed after the reactor is shut down, and a long-term fuel exchange operation cannot be started until the temperature of the coolant 4 has decreased. Further, when removing the primary heat exchanger 16 that is integrated with the lid body 5, large-sized equipment such as a crane is required, and the work is difficult. In the configuration shown in FIG. 3, for example, when performing maintenance and inspection of the primary heat exchanger 15, the CRD 12 is removed at the same time as the lid 5 is removed.
The primary heat exchanger 15 must also be removed, and the installation and removal of the primary heat exchanger 15 and maintenance and inspection work cannot be said to be easy.

[Purpose of the invention]

An object of the present invention is to provide an upper cover for removing the heat exchanger and an upper cover for fuel exchange independently, so that the heat exchanger can be arbitrarily removed with easy operation when performing maintenance and inspection of the heat exchanger. It is an object of the present invention to provide a boiling water nuclear reactor that can prevent loss of cooling capacity by leaving the heat exchanger as it is during fuel exchange, and can remove residual heat at that time.

[Summary of the invention]

A boiling water reactor according to the present invention includes a reactor pressure vessel containing a coolant, a lid body provided to close an upper opening of the reactor pressure vessel, and a lid body housed in the reactor pressure vessel. A boiling water reactor comprising a reactor core, a core upper mechanism provided above the core by penetrating the lid, and a heat exchanger provided between the core upper mechanism and the reactor pressure vessel. In the type nuclear reactor, the lid body consists of an upper lid for removing the heat exchanger and an upper lid for fuel exchange, each of which is provided independently.

Therefore, when performing maintenance and inspection of the heat exchanger, only the upper cover for removing the heat exchanger can be removed, and since the upper cover for fuel exchange is not integrated as in the past, it is possible to remove the heat exchanger. The top cover for removal is small and lightweight, and removal work is easy. On the other hand, when performing fuel exchange work, it is necessary to similarly remove only the fuel exchange top cover, and the work is easy. Further, since work can be carried out with the heat exchanger as it is, residual heat can be removed without worrying about loss of cooling capacity.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 4 and 5. Reference numeral 101 in FIG. 4 indicates a reactor pressure vessel. The reactor pressure vessel 101 has a lower diameter smaller than the upper part from the viewpoint of improving space utilization. This reactor pressure vessel 101 is a ringata 1
It is supported by the reactor building 103 via 02. A coolant 104 is contained within the reactor pressure vessel 101 . Further, a reactor core 108 composed of a plurality of fuel assemblies (not shown), control rods 107, etc. is disposed in the lower part of the reactor pressure vessel 101 and is supported by a core support mechanism 109. A core upper mechanism 110 is provided above the reactor core 108, penetrating through a refueling top cover 120 provided to close the upper opening 101A at the center of the reactor pressure vessel 101. The upper core mechanism 110 includes a control rod guide tube 111 and a control rod guide tube 11
The control rod drive mechanism (hereinafter referred to as CRD) 112 moves the control rod 107 up and down along the CRD. The reactor core 108 and the reactor pressure vessel 1
01, a lower shroud 113A is fixed to the reactor pressure vessel 101, and an intermediate shroud 113B is provided between the upper core mechanism 110 and the reactor pressure vessel 101 above the lower shroud 113A. Further, an upper shroud 11 is provided above the intermediate shroud 113B.
3C is provided. A natural circulation flow path is formed by the lower shroud 113A, the intermediate shroud 113B, and the upper shroud 113C. Further, the intermediate shroud 113B has a function of supporting the control rod guide tube 111, and is configured to be detachable from the lower shroud 113 at the time of fuel exchange. Upper shroud 113
A plurality of openings 114A are formed in C. The above upper shroud 113C and the reactor pressure vessel 10
1, a primary heat exchanger 115 is supported by a support member 116 fixed to the inner circumferential wall of the reactor pressure vessel 101, and is fixed to heat exchanger flanges 121 provided independently. A plurality (for example, eight as shown in FIG. 5) are provided at equal intervals in the circumferential direction. Note that the heat exchanger flange 121
is provided independently from the fuel exchange upper cover 120, and is connected to the reactor pressure vessel 1 by bolts 118.
It is fixed at 01. The above primary heat exchanger 115
A guide pipe 117 is provided on the outer periphery of the lower part of the reactor pressure vessel 10.
It is supported by 1. That is, the primary heat exchanger 115 is configured to be restrained from being displaced in the horizontal direction during an earthquake or the like by the guide tube 117 and the support member 116. Code 115B in the figure
indicates a heat exchanger tube through which a secondary coolant flows.

In the above configuration, the coolant 104 rises from the bottom to the top of the reactor core 108 as shown by the arrow in the figure, and is boiled at this time. and core 108
Flows upward to the opening 1 of the upper shroud 113C.
14A to the vicinity of the primary heat exchanger. There, the secondary coolant is cooled by heat exchange and flows into the lower part of the core 108 again, and this cycle is repeated thereafter. All of this is done through natural circulation.

Next, a case where fuel replacement and maintenance/inspection of the primary heat exchanger 115 are performed will be described. First, when performing fuel replacement, only the fuel replacement top cover 120 is removed and replacement work is performed using a fuel exchanger or the like. At that time, as in the past, the heat exchanger flange 12
Since it is not integrated with 1, removal work is easy. In addition, since the primary heat exchanger 115 can be maintained as it is, residual heat can be removed after the reactor is shut down, and therefore the fuel can be used for a long time until the temperature of the coolant 104 falls, unlike in the conventional case. There is no need to wait for the fuel replacement work to start, and the fuel replacement work can be started immediately, which greatly reduces work time and improves safety during work. can.

Next, a case in which maintenance and inspection work is performed on the primary heat exchanger 115 will be described. In this case, the flange 1 of any primary heat exchanger 115 to be inspected for maintenance.
It is only necessary to remove part 21, thereby removing part 1.
The secondary heat exchanger 115 can be removed. Therefore, it is not necessary to remove the fuel exchange top cover 120 as in the conventional case, and only the flanges 121 corresponding to each primary heat exchanger 115 need be removed, making the work extremely easy.

Next, another embodiment will be described with reference to FIG.
While the above embodiment is a natural circulation type reactor, the reactor shown in FIG. 6 is a forced circulation type reactor. That is, a plurality of jet pumps 122 are arranged between the lower shroud 113A and the reactor pressure vessel 101, and a recirculation pipe 125 and an inlet are provided with a recirculation pump (not shown) installed outside the reactor pressure vessel 101. It is connected via a nozzle 123 and an outlet nozzle 124. This recirculation pump supplies drive water to the jet pump 122 to forcefully circulate the coolant 104 into the core 108. Even when the present invention is applied to a forced circulation type nuclear reactor in this way, the same effects as in the embodiments described above can be achieved.

It should be noted that the same parts as in the previous embodiment are denoted by the same reference numerals, and the explanation of the same constituent parts is omitted.

〔Effect of the invention〕

A boiling water reactor according to the present invention includes a reactor pressure vessel containing a coolant, a lid body provided to close an upper opening of the reactor pressure vessel, and a lid body housed in the reactor pressure vessel. A boiling water reactor comprising a reactor core, a core upper mechanism provided above the core by penetrating the lid, and a heat exchanger provided between the core upper mechanism and the reactor pressure vessel. In the type nuclear reactor, the lid body consists of an upper lid for removing the heat exchanger and an upper lid for fuel exchange, each of which is provided independently.

Therefore, when performing maintenance and inspection of the heat exchanger, only the upper cover for removing the heat exchanger can be removed, and unlike in the past, the upper cover for fuel exchange is not integrated, so the heat exchanger can be removed. The top lid for removing the container is lightweight and small, making it easy to remove. On the other hand, when performing fuel exchange work, it is necessary to similarly remove only the fuel exchange top cover, and the work is easy. Further, since the heat exchanger can be operated as it is, there is no risk of loss of cooling capacity, and residual heat can be removed, which is a great advantage.

[Brief explanation of drawings]

1 to 3 are diagrams showing a conventional example, in which FIG. 1 is a longitudinal sectional view showing the configuration of a boiling water nuclear reactor, FIG. 2 is a plan view, and FIG. 3 is a longitudinal sectional view. 4 and 5 are diagrams showing one embodiment of the present invention, in which FIG. 4 is a longitudinal sectional view showing the configuration of a boiling water reactor, and FIG. 5 is a plan view. FIG. 6 is a longitudinal sectional view of a boiling water reactor showing another embodiment. 101... Reactor pressure vessel, 101A... Upper opening of reactor pressure vessel, 104... Coolant, 10
8... Core, 110... Core upper mechanism, 115...
...Primary heat exchanger, 120...Top cover for fuel exchange, 1
21...Flange for heat exchanger (upper cover for removing heat exchanger).

Claims (1)

[Claims] 1. A reactor pressure vessel containing coolant, a lid provided to close the upper opening of the reactor pressure vessel, a reactor core housed in the reactor pressure vessel, and the above reactor pressure vessel above the reactor core. In a boiling water reactor comprising a core upper mechanism provided through the lid, and a heat exchanger provided between the reactor top mechanism and the reactor pressure vessel, the lid is a boiling water nuclear reactor characterized by having an upper cover for removing a heat exchanger and an upper cover for replacing fuel, each of which is provided independently.