JPH011999A - Reactor drainage system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention guides reactor water flowing out from an in-core housing when replacing a neutron instrumentation tube in a boiling water nuclear reactor, and The present invention relates to a nuclear reactor drainage system that controls the flow of water, and particularly to a nuclear reactor drainage system that can remotely control the flow of reactor water.

<Prior art> In general, in a boiling water reactor, the neutron flux distribution within the reactor is monitored, and by monitoring the neutron flux distribution, the neutron flux distribution within the reactor is always kept in an appropriate state during the operation period. Retained. This neutron flux distribution is monitored by a plurality of neutron instrumentation tubes installed inside the reactor.

FIG. 2 is a sectional view showing a state in which a neutron instrumentation tube is installed in a nuclear reactor. Reference numeral 1 in FIG. 2 is a reactor pressure vessel, inside which a shroud 2 is disposed integrally with the reactor pressure vessel 1, and inside the shroud 2 a core support plate 3 is provided horizontally. . Furthermore, an in-core housing 4 is provided to penetrate the lower part of the reactor pressure vessel 1 .

This in-core housing 4 is connected to an in-core guide pipe 5 within the reactor pressure vessel 1, and the upper part of the in-core guide pipe 5 is fixed to the core support plate 3.

A neutron instrumentation tube 6 is provided in the opening 5A of the in-core guide tube 5.
is removably inserted into the neutron instrumentation tube 6, and the lower end of the neutron instrumentation tube 6 is housed in the in-core housing 4. The upper end of the neutron instrumentation tube 6 is engaged with the bottom of the intersection of the upper grid plate 7 by a spring action.

An in-core flange 9 is bolted to the lower end of the in-core housing 4, and a drive device 11 for driving the drive tube 10 up and down is provided below the in-core flange 9. A cable guard 12 is provided at the bottom of the drive bag @11, and a signal cable 13 from a central control room is connected to this cable guard 12.

The neutron instrumentation tube 6 is provided with a neutron detection section and an Ml cable in a dry tube 15. The surface of the neutron detection part is coated with uranium 235, and this uranium 235 absorbs thermal neutrons from the fuel assembly 16'8, splits into fragments, and rips the argon gas inside the detector.
Let go, this? [ffl flow enters each electrode resulting in an ionization signal proportional to the number of neutrons. This ionization signal is transmitted to the central control room, and the neutron flux distribution within the reactor can be monitored from the central control room.

When the neutron instrumentation tube 6 is operated for a long period of time in a nuclear reactor, the uranium 235 coated in the neutron detection section is depleted, resulting in a decrease in detection sensitivity.

The neutron instrumentation tube 6 whose detection sensitivity has decreased is replaced with a new neutron instrumentation tube 6 during periodic inspection.

In this replacement work, first remove the bolts at the bottom of the in-core flange 9, then remove the drive unit 11 and cable guard 1.
2 and drive tube 10, etc., and then pull out the neutron instrumentation tube 6 from above the reactor, but when it is pulled out, reactor water passes through the in-core guide tube 5 and in-core housing 4 and flows out of the reactor. A drainage system is installed to guide reactor water to the rad pit.

FIG. 3 is a configuration diagram showing a conventional drainage device published in Japanese Patent Application Laid-Open No. 53-99194. This drainage device consists of a straight pipe 20 that is screwed onto the in-core flange 9, a ball valve 21 that is connected to the straight pipe 20, and a transparent vinyl hose 23 that is connected to the ball valve 21 with a one-touch joint 22. , directly from the in-core flange 9! ! (2
This guides the reactor water flowing into the rad pit and discharges it from the transparent vinyl hose 23 to the rad pit.

(Problems to be Solved by the Invention) During the replacement work of the neutron instrumentation tube, the in-core guide tube 5 and the in-core housing 4 are latched by the flow of reactor water discharged through the drainage system, and the By flushing, sewage and dirt accumulated in the in-core guide pipe 5 and in-core housing 4 are discharged to the rad pit.

During this flushing, a worker needs to operate the ball valve 21, etc., and in order to do this, the worker enters the reactor support pedestal, which is a high lam area, and performs the flushing work inside the reactor support pedestal. must be done.

Furthermore, in the 11112 work on the in-core flange 9 of the drainage system, it is necessary for a worker to perform the work within the reactor support pedestal. In addition, during neutron instrumentation tube replacement work, there are many opportunities for workers to enter the reactor support pedestal, and there is a risk that radiation waves [ffl] for workers may increase.

The present invention has been made in consideration of the above-mentioned circumstances, and it reduces the work that a worker has to do inside the reactor support pedestal when replacing a neutron instrumentation tube, while increasing the efficiency of the work done inside the reactor support pedestal. The purpose of the present invention is to provide a drainage system for a nuclear reactor that can reduce the time that workers spend inside the reactor support pedestal and protect the workers from radiation exposure.

(Structure of the Invention) (Means for Solving the Problems) The present invention provides a method for guiding reactor water flowing out from an in-core housing when replacing a neutron instrumentation tube, and for controlling the flow of the reactor water. In the device, a straight pipe that is detachable from an in-core flange fixed to the in-core housing, a manually operable first ball valve connected to the straight pipe, and a remote control connected to the first ball valve by a one-touch joint. It has an operable second ball valve and a transparent tube connected to the second ball valve by a one-touch joint.

(Function) When replacing a neutron instrumentation tube, first prepare a plurality of straight pipes and first ball valves that are integrally connected (hereinafter referred to as first ball valve parts), and replace each first ball valve part. to each in-core flange fitted with a neutron instrumentation tube to be replaced.

Next, prepare one or a few pieces of the second ball valve (hereinafter referred to as the second ball valve section) in which the second ball valve and the transparent pipe are integrally connected by a one-touch joint, and use the second ball valve section for neutron instrumentation. It is connected by a one-touch joint to the first ball valve part attached to the in-core flange from which the pipe is pulled out. At this time, the first ball valve is opened, the second ball valve is left open, and the reactor remains in this state while waiting outside the reactor support pedestal.

After that, the neutron instrumentation tube is pulled out from above the reactor, and the second ball valve is opened by remote control in response to a communication from above the reactor, and reactor water is drained from the in-core housing through the drainage device. Ru. Then, the inside of the in-core guide pipe and the in-core housing are flushed by the flow of reactor water. After that, it is confirmed on a monitor TV etc. that the reactor water is no longer cloudy, and the second ball valve is closed by remote control. Enter the intrusion reactor support pedestal, remove the second ball valve part from the first ball valve part, and then attach it to the first ball valve part attached to the in-core flange fitted with the neutron instrumentation tube to be replaced. Connect with one-touch fitting.

In this way, since the second ball valve can be remotely controlled,
There is no need for workers to wait inside the lower reactor pedestal during flushing work, and the second ball valve can be operated from outside the reactor support pedestal, which is a low-level intoxication area. Furthermore, since the second ball valve part can be easily attached to and removed from the first ball valve part by a one-touch joint, work efficiency is improved and the time required for workers to enter the reactor support pedestal can be shortened. Furthermore, since it is sufficient to prepare one or a small number of second ball valve parts and sequentially attach and detach them to the first ball valve part, it is not necessary to install a large number of second ball valve parts in the reactor support pedestal in advance. The work space inside the reactor support pedestal can be expanded without
The working environment will be improved.

In addition, if a large number of second ball valve parts are prepared, the first ball valve part and the second ball valve part should be attached in advance to all in-core flanges into which the neutron instrumentation tube to be replaced is fitted. This makes it possible to first handle the neutron instrumentation tubes that need to be replaced one after another, perform the handling work all at once, and then perform the work of installing new neutron instrumentation tubes all at once. Therefore, the replacement work of the neutron instrumentation tube can be performed efficiently, and the work time is shortened.

(Embodiment) An embodiment of a nuclear reactor drainage system according to the present invention will be described with reference to FIG.

The reactor drainage system includes an M pipe 25 that can be attached to the in-core flange 9 fixed to the in-core housing 4, and a manually operable first ball valve 26 connected to this straight pipe 25.
A remotely controllable second ball valve 28 is connected to the first ball valve 26 by a push-in joint 27, and a transparent tube 30 is connected to the second ball valve 28 by a push-in joint 29.

A male thread is formed at the tip of the straight pipe 25, and is screwed into the female thread of the in-core flange 9, and the other end of the straight pipe 25 is integrally connected to the first ball valve 26 having a manual lever 32 by screwing or the like. be done.

A second ball valve 28 is detachably connected to the first ball valve 26 via a one-touch joint 27 .

The second ball valve 28 has a manual lever 33 and an actuator 34, and the actuator 34 is connected to an operating device 36 via, for example, a pneumatic hose 35, and the operating device 36 is operated from outside the reactor support pedestal. By doing so, the second ball valve 28 can be freely opened and closed.

A transparent tube 30 is detachably connected to the second ball valve 28 by a one-touch joint 29, and the end of the transparent tube 30 is fixed on a Radvit (not shown). The transparent tube 30 is made of transparent vinyl chloride or the like so that the turbidity of the reactor water flowing inside can be visually confirmed, and when the vinyl chloride deteriorates, it is disposed of.

The inner diameters of the straight pipe 25, first and second ball valves 26, 28, push-in joints 27, 29, and transparent pipe 30 are such that reactor water flowing into the straight pipe 25 from the in-core housing 4 can be smoothly discharged to the rad pit without resistance. The inner diameter of the in-core housing 4 is approximately equal to that of the in-core housing 4.

Next, the operation of this embodiment will be explained.

When replacing the neutron instrumentation tubes 6, first, the straight tube 25 and the first ball valve 26 are integrally connected (hereinafter referred to as the first ball valve part A), and the number of neutron instrumentation tubes 6 to be replaced is determined. Prepare only. Then, each prepared first ball valve part A is screwed onto each in-core flange 9 into which the neutron instrumentation tube 6 to be replaced is fitted.

Next, prepare one or two pieces (hereinafter referred to as second ball valve part B) in which the second ball valve 28 and the transparent tube 30 are integrally connected by a one-touch joint 29, and prepare the second ball valve part B. is connected by a one-touch joint 27 to the first ball valve part A attached to the in-core flange 9 from which the neutron instrumentation tube 6 is extracted. At this time, the first ball valve 26 is opened and the second ball valve 28 is closed, and the reactor remains in this state and waits outside the reactor support pedestal.

Thereafter, when the neutron instrumentation tube 6 is handled from above the reactor, the reactor water, which had been watertightly sealed by the seat portion 37 between the sealing surface of the neutron instrumentation tube 6 and the seating portion of the in-core flange 9, flows into the straight pipe. 25 and reaches the second ball valve 28. After receiving a message from above the reactor,
Operate the operating device 36 from outside the reactor support pedestal to
When the ball valve 28 is opened, reactor water is discharged into the rad pit through the transparent pipe 30. The in-core guide pipe 5 and the in-core housing 4 are flushed by the flow of the reactor water, and the sewage, filth, etc. stored therein are discharged to the rad pit.

After opening the second ball valve 28 using the operating device 36, check the monitor TV from outside the reactor support pedestal to confirm that the reactor water flowing through the transparent tube 3o is no longer turbid, and then open the first ball valve 26. Closed by remote control. After the closing operation, a new neutron instrumentation tube 6 is hung from above the reactor and installed.

After installation, enter the reactor support pedestal, operate the first ball valve 26, and remove the seat part 3 of the in-core flange 9.
Confirm that there is no leak from 7. After that, the second ball valve part B is connected to the first ball valve part A by the one-touch joint 27.
The neutron instrumentation tube 6 to be replaced is then connected to the first ball valve part A attached to the in-core flange 9 fitted with the one-touch joint 27, and the neutron instrumentation tube 6 to be replaced is successively replaced. Proceed.

As described above, according to this embodiment, the second ball valve 28 can be remotely controlled, so there is no need for workers to hold the rock inside the reactor support pedestal during flushing work, and it is possible to operate the second ball valve 28 remotely in the low aω area. Second from outside a reactor support pedestal
Ball valve 28 can be operated. In addition, since the second ball valve part B can be easily removed from the first ball valve part A, work efficiency is improved when sequentially replacing the second ball valve part B with the first ball valve part A. Therefore, the time required for workers to perform work inside the reactor support pedestal can be shortened.

Furthermore, since it is sufficient to prepare one or two second ball valve parts B and sequentially attach and detach the first ball valve part Ak, it is necessary to install a large number of second ball valve parts B in the reactor support pedestal in advance. There is no need to keep the reactor supporting pedestal in place, and the working space within the reactor support pedestal can be expanded, improving the working environment.

Further, since the ball valves 26 and 28 are used in the above embodiment, it is possible to make the diameter of the flow passage cross section of the valve approximately equal to the inner diameter of the in-core housing 4. Therefore,
Compared to the case where a solenoid valve is used, which has a narrow flow path and high flow resistance, allowing only a small amount of water to pass through, reactor water can be dropped at a higher speed and the flushing effect can be enhanced. .

In the above embodiment, if the second ball valve parts A are prepared as many as the number of neutron instrumentation tubes 6 to be replaced, the second ball valve parts A are preliminarily attached to all in-core flanges into which the neutron instrumentation tubes 6 to be replaced are fitted. By installing the first ball valve part A and the second ball valve part B, you can first pull out the neutron instrumentation tube 6 that needs to be replaced one by one and perform the pulling operation all at once, and then install the new neutron instrumentation tube 6. can be done all at once. Therefore, the replacement work of the neutron instrumentation tube 6 can be performed efficiently and the work time can be shortened.

In this way, this embodiment has the effect of reducing the amount of time the workers spend working inside the reactor support pedestal, thereby protecting the workers from radiation exposure.

〔Effect of the invention〕

A nuclear reactor drainage system according to the present invention includes a straight pipe that can be connected to an in-core flange fixed to an in-core housing, a first ball valve that can be manually operated connected to the straight pipe, and a first ball valve that can be manually operated. Since it has a remotely controllable second ball valve connected by a one-touch joint, and a transparent pipe connected to the second ball valve by a one-touch joint,
By reducing the work that workers have to do inside the reactor support pedestal when replacing neutron instrumentation tubes, and at the same time improving the efficiency of work done inside the reactor support pedestal,
It reduces the amount of time workers spend inside the reactor support pedestal and protects them from radiation exposure.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing one embodiment of a nuclear reactor drainage system according to the present invention, Fig. 2 is a cross-sectional view showing a state in which a neutron instrumentation tube is installed in the reactor, and Fig. 3 is a conventional FIG. 2 is a configuration diagram showing a drainage system of a nuclear reactor. 4... In-core housing, 6... Neutron instrumentation tube,
9... In-core flange, 25... Straight pipe, 26...
・1st ball valve, 27.29... One-touch joint, 2
8... Second ball valve, 30... Transparent tube, 34...
Actuator, 35... pneumatic hose, 36... operating device. Applicant's agent Hisashi Hatano Figure 1

Claims (1)

[Claims] 1. In a nuclear reactor drainage system that guides reactor water flowing out from an in-core housing when replacing a neutron instrumentation tube and controls the flow of the reactor water, an in-core fixed to the in-core housing; A straight pipe that can be attached to and detached from the flange,
a manually operable first ball valve connected to the straight pipe;
A drainage system for a nuclear reactor, comprising: a remotely controllable second ball valve connected to the first ball valve by a push-in joint; and a transparent pipe connected to the second ball valve by a push-in joint. 2. The second ball valve has an actuator operated by compressed air, and the actuator is connected to an operating device via a pneumatic hose.
Nuclear reactor drainage system as described in Section.