JPS646436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cleaning device for cleaning the inside of an in-core monitor housing and a guide tube.

[Technical background of the invention]

In general, a boiling water reactor (hereinafter referred to as BWR) has a reactor pressure vessel 1, for example, as shown in Figure 1.
A large number of control rod drive mechanism housings (hereinafter referred to as CRD housings) 2 are installed through the bottom wall 1a of the CRD housing 2, and control rod guide tubes 3 are connected to these CRD housings 2. The control rod is driven up and down in the control rod guide tube 3 by a control rod drive mechanism (hereinafter referred to as CRD) installed in the CRD housing 2. Further, a cylindrical shroud 4 is housed within the reactor pressure vessel 1, and an upper grid plate 5 is provided at the upper end of the shroud 4, and a core support plate 6 is provided at the lower end. A fuel assembly (not shown) is loaded between the upper grid plate 5 and the core support plate 6. In addition, in order to understand the neutron flux distribution state inside the reactor during reactor operation,
An in-reactor neutron flux monitor (hereinafter referred to as an in-core monitor) 7 is provided. This in-core monitor 7 is inserted into the reactor core through an in-core monitor housing (hereinafter simply referred to as in-core housing) 8 and an in-core monitor guide tube (hereinafter simply referred to as in-core guide tube) 9, and as shown in FIG. The head 7a of the monitor 7 is fitted into the locking recess 10 of the upper grid plate 5 so as to stand upright.
The head 7a is configured to be able to protrude and retract upwardly with respect to the main body 7b, and is biased in the protruding direction by a spring 11. The lower stepped portion 7b of the in-core monitor 7 is connected to the inner seat portion 12 of the in-core flange 12 of the in-core housing 8.
a to form a self-shield and prevent reactor water from flowing out.

The in-core monitor 7 having the above configuration is replaced with a new in-core monitor 7, for example, at the time of periodic inspection. At this time, before installing the new in-core monitor 7, the inside of the in-core housing 8 and the in-core guide tube 9 are cleaned. This is because there is a possibility that fine radioactive dust containing oxidized metals and slurry-like crud such as scale may adhere to the inside of the in-core housing 8 and the in-core guide pipe 9, and especially on the seat portion 12a of the in-core flange 12. If crud is attached, the lower stepped portion 7 of the in-core monitor 7
There is a possibility that the sheet with b may be incomplete and a sheet leak may occur. Therefore, before installing a new in-core monitor 7 during periodic inspection, the inside of the in-core housing 8 and in-core guide tube 9 are cleaned to remove the crud. As a cleaning method, for example, a drainage device (not shown) is attached to the in-core housing 8 from below, and reactor water is allowed to flow down into the in-core guide pipe 9 and the in-core housing 8 by opening the on-off valve of this drainage device. The structure is such that the crud in the in-core guide pipe 9 and in-core housing 8 is removed by the flow of this reactor water. Further, when fixing the in-core flange 12 to the in-core housing 8, the bolts 13 are carefully tightened to prevent damage to the seat portion 12a.

[Problems with background technology]

With the above configuration, it may not be possible to reliably remove the crud, and if crud remains on the seat portion 12a of the in-core flange 12,
The bolts 13 must be tightened carefully, which prolongs the work, and in view of the radiation exposure of the workers, it is necessary to remove the crud reliably.

[Purpose of the invention]

The object of the present invention is to be able to reliably remove crud in the in-core guide pipe and in-core housing, thereby reducing the work time required to remove the crud and further reducing the work time required to replace the in-core monitor, thereby exposing workers to radiation. It is an object of the present invention to provide a cleaning device for an in-core monitor housing and a guide tube that can reduce the amount of waste.

[Summary of the invention]

The in-core monitor housing and guide tube cleaning device according to the present invention includes a pipe-shaped main body that is provided so as to be able to enter and exit the in-core monitor guide pipe and the in-core monitor housing from above the reactor core, and a cleaning device that is connected to the upper part of the main body and has a cleaning water inside the main body. a cleaning nozzle provided at the lower end of the main body; a positioning member provided in the main body for positioning the main body by engaging with a core structure; This structure includes a drainage device which is detachably provided and drains the cleaning water containing the removed crud.

That is, for example, at the time of periodic inspection, before installing a new Incore monitor, the main body is placed into the Incore monitor guide pipe and the Incore monitor housing, and the washing water is supplied to the main body from the washing water supply mechanism, and the Incore monitor is supplied through the cleaning nozzle to the main body. Clean the inside of the monitor guide tube and in-core monitor housing.

Therefore, the crud inside the in-core monitor guide pipe and the in-core monitor housing can be reliably removed, and in particular, the crud in the seat part of the in-core flange can be reliably removed, making it easier to tighten the in-core flange, which has traditionally been done carefully. The required time can be shortened, and the time required for the crud removal work can also be shortened, reducing radiation exposure to workers and improving safety.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 3 to 6. 3 to 6 are diagrams showing the configuration of the cleaning device. In the figure, 21 indicates the main body of the cleaning device. This main body 21 has almost the same shape as the in-core monitor 7, is suspended from above the reactor core by a gripper 22, and is inserted into the in-core guide pipe 9 and the in-core housing 8. A wash water supply mechanism 23 consisting of a quick fitting 24, a water hose 25, a submersible pump (not shown), etc. is connected to the upper part of the main body 21. A plurality of cleaning nozzles 26 are formed in the lower end of the main body 21 in the circumferential direction so as to face the seat portion 12a of the in-core flange 12. Also, the main body 2
1. An insertion guide 27 is provided to protrude downward. This insertion guide 27 has a guiding function when inserting the main body 21 into the in-core guide tube 9 and the in-core housing 8, and the upper part of this insertion guide 27 protrudes into the main body 21 so that the washing from the washing nozzle 26 can be carried out. The water jet is adjusted properly. That is, the main body 21 is held by the gripping tool 22.
is inserted into the suspended in-core guide tube 9 and in-core housing 8. At that time, click the quick fitting 2.
Cleaning water is supplied into the main body 21 from a submersible pump connected via a water hose 25 and a water hose 25, and is injected from a cleaning nozzle 26 to inject water into the in-core guide pipe 9.
Also, the inside of the in-core housing 8 is cleaned to remove crud. Further, the main body 21 is provided with a positioning member 28, and when the main body 21 is inserted into the in-core guide tube 9 and the in-core housing 8, this positioning member comes into contact with the upper surface of the core support plate 6 to determine the position of the main body 21. It is.
At this time, the cleaning nozzle 26 of the main body 21 is configured to face the seat portion 12a of the in-core flange 12. In addition, 29A in the figure indicates a joint fitting, and 2
9B indicates a guide. This guide 29B maintains a distance between the main body 21 and the in-core housing 8.

The gripping tool 22 is constructed as shown in FIG. In the figure, numeral 30 denotes a latch portion which is made by dividing an elongated cylinder into several pieces and imparting spring characteristics to the divided pieces, and grips the head portion 7a of the in-core monitor 7. A guard sleeve 31 is provided on the outer periphery of the latch portion 30 for controlling the opening of the latch portion 30. The latch portion 30 and guard sleeve 31 are connected by a connecting portion 32 and connected to a hoist mechanism (not shown) via a wire rope 33.

Next, the drainage device 34 will be explained with reference to FIG. In the figure, 35 indicates a drain pipe connected to the in-core flange 12. A ball valve 38 is connected to the drain pipe 35 via a connector 36 and a quick fitting 37. A transparent hose 40 is connected to this ball valve 38 via a hose fitting 39, and this transparent hose 40 is piped to a rad pit 41. That is, the ball valve 38 is opened and the cleaning water containing the crud removed in the in-core guide pipe 9 and the in-core housing 8 is drained into the rad pit 41. At this time, the structure allows the removed crud to be confirmed by visually observing the transparent hose 40.

The operation of the in-core monitor housing and guide tube cleaning device configured as above will be explained. For example, the in-core monitor 7 is replaced during periodic inspection. At that time, first, the drain pipe 35 is connected to the in-core flange 12 and the drain device 34 is installed. At this time, the ball valve 38 is closed. Next, the existing in-core monitor 7 is pulled out using a puller (not shown). Then, the main body 21 of the cleaning device is suspended and inserted into the in-core guide tube 9 and the in-core housing 8 using the hoist mechanism via the gripping tool 22 . At this time, cleaning water is supplied from the submersible pump into the main body 21 through the water hose 25 and the quick fitting 24, and is injected from the cleaning nozzle 26 to remove crud in the inner core guide pipe 9 and the inner core housing 8. Then, the ball valve 38 is opened and the cleaning water containing the crud is poured into the rad pit 41.
Drain to. At this time, the removed crud can be confirmed by visually observing the transparent hose 40, and it can be seen that the crud has been reliably removed by cleaning. Then, when the main body 21 is further inserted, the positioning member 28 comes into contact with the core support plate 6,
Insertion of the main body 21 is stopped. At this time, the cleaning nozzle 26 is located at a position facing the seat portion 12a of the in-core flange 12, so that the sheet portion 12a can be cleaned and the crud can be reliably removed. Then, when the transparent hose 40 is visually observed and it is determined that the crud removal has been completed, the cleaning is stopped and the ball valve 38 is closed. Then, the main body 21 is pulled up and a new in-core monitor 7 is attached.

That is, when replacing the in-core monitor during periodic inspection, the drainage device 34 is connected to the lower part of the in-core housing 8, while the main body 21 is inserted into the in-core guide pipe 9 and the in-core housing 8 from above the core, and at that time, cleaning water is supplied from the submersible pump. Supply cleaning nozzle 2
6 to clean the inner core guide pipe 9 and the inner core housing 8 and remove crud.

Therefore, the crud can be removed more reliably than in the conventional cleaning method, such as by letting reactor water flow down, and in particular, the positioning member 28 comes into contact with the core support plate 6 to position the main body 21. When the cleaning nozzle 26 is in a position facing the seat portion 12a of the in-core flange 12, the crud on the seat portion 12a can be reliably removed. Thereby, the trouble of having to carefully tighten the bolts 13 when connecting the in-core flange 12 to the in-core housing 8 can be eliminated, and the working time can also be shortened. In addition, the work time required for cleaning work is also shortened, making it possible to reduce the exposure of workers to radiation.

Note that the same items are indicated by the same reference numerals.

〔Effect of the invention〕

The in-core monitor housing and guide tube cleaning device according to the present invention includes a pipe-shaped main body that is provided so as to be able to enter and exit the in-core monitor guide pipe and the in-core monitor housing from above the reactor core, and a cleaning device that is connected to the upper part of the main body and has a cleaning water inside the main body. a cleaning nozzle provided at the lower end of the upper main body; a positioning member provided in the main body for positioning the main body by engaging with the core structure; This structure includes a drainage device which is detachably provided and drains the cleaning water containing the removed crud.

That is, for example, at the time of periodic inspection, before installing a new Incore monitor, place the main body into the Incore monitor guide tube and the Incore monitor housing,
Cleaning water is supplied from the cleaning water supply mechanism to the main body to clean the inside of the in-core monitor guide pipe and the in-core monitor housing through the cleaning nozzle.

Therefore, the crud inside the in-core monitor guide pipe and the in-core monitor housing can be reliably removed, and in particular, the crud in the seat part of the in-core flange can be reliably removed, so the tightening work of the in-core flange, which was previously performed carefully, can be removed. This method has great effects, such as reducing the time required for cladding removal work, reducing radiation exposure to workers, and improving safety.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams referred to in explaining the conventional example, and Figure 1 is a diagram showing a part of the configuration of a nuclear reactor.
The figure shows the installation state of the in-core monitor, and Figures 3 to 6 are diagrams showing one embodiment of the present invention.
The figure shows the structure of a part of the main body and the wash water supply mechanism, FIGS. 4 and 5 are partially enlarged views of FIG. 3, and FIG. 6 shows the structure of the drainage device. 7...Incore monitor, 8...Incore monitor housing, 9...Incore monitor guide pipe, 21
... Main body, 23 ... Washing water supply mechanism, 26 ... Washing nozzle, 28 ... Positioning member, 34 ... Drainage device.

Claims (1)

[Scope of Claims] 1. A pipe-shaped main body that can enter and exit the in-core monitor guide pipe and the in-core monitor housing from above the reactor core, and a wash water supply mechanism that is connected to the upper part of the main body and supplies wash water into the main body. a cleaning nozzle provided at the lower end of the main body; a positioning member provided on the main body for positioning the main body by engaging with a core structure; 1. A cleaning device for an in-core monitor housing and a guide pipe, comprising: a drainage device for draining cleaning water containing contaminated crud. 2. The in-core according to claim 1, wherein the cleaning nozzle is provided so as to face the seat portion of the in-core monitor housing and the in-core monitor with the main body positioned by a positioning member. Monitor housing and guide tube cleaning device.