JPS5815759B2 - Nuclear reactor control rod guide tube cleaning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for cleaning control rod guide tubes of a boiling water nuclear reactor.

The control rods of a boiling water reactor are configured to be inserted into the reactor core from below while being guided by control rod guide tubes erected from the bottom of the reactor vessel.

By the way, so-called crud, such as corrosion products of reactor internal components, adheres to the inside of the control rod guide tube, so it is necessary to periodically remove this crud.

For this reason, conventionally, during regular maintenance of the control rod drive mechanism, the control rod drive mechanism was removed, a push rod was inserted into the lower part of the control rod guide tube through the control rod drive mechanism housing, and the upper end of the push rod was inserted into the control rod guide tube. the control rod, and push up the lower end of the push-up rod with a screw jack or the like to push up the control rod.
The control rod is floated from a seating surface provided at the bottom of the control rod guide tube to form a gap, and reactor water is drained through the control rod guide tube, the gap, and the control rod drive mechanism housing;
Along with this drain water, the crud that had adhered to the inside of the control rod guide tube was removed.

However, in this type of reactor, crud removal relies on the natural flow of reactor water, so a large amount of reactor water must be drained to remove crud, and the treatment equipment must have a large capacity. The problem was that the work efficiency was poor and it took a long time, resulting in a large amount of radiation exposure for the workers.

Additionally, this type of control rod guide tube has a problem in that the crud attached to the bottom corner of the control rod guide tube cannot be completely removed.

The present invention was made based on the above circumstances, and its purpose is to be able to efficiently perform crud removal work in a short time, to completely remove crud, and to drain reactor water. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An object of the present invention is to obtain a control rod guide tube cleaning device for a nuclear reactor that requires a small amount of cleaning.

In the figure, reference numeral 1 denotes a lower mirror portion of a reactor vessel of a boiling water reactor, and a control rod drive mechanism housing 2 is provided passing through the lower mirror portion 1.

The control rod drive mechanism housing 2 protrudes several meters outside the reactor vessel 1 and also protrudes several meters into the reactor vessel 1, and a thermal sleeve 3 is inserted into the control rod drive mechanism housing 2.

A control rod guide tube 4 is attached to the upper end of the control rod drive mechanism housing 2, and a control rod 5 is inserted into the control rod guide tube 4 and slidably guided.

A control rod drive mechanism is provided within the control rod drive mechanism housing 2 and is coupled to the latch portion 6 of the control rod 5, but the control rod drive mechanism is not shown in the figure. The control rod drive mechanism is not shown.

In addition, when this control rod drive mechanism is removed, the control rod 5
is lowered by its own weight, and its lower end is seated on the seating surface 7 formed at the bottom of the control rod guide tube 4 to maintain watertightness and prevent reactor water from leaking into the control rod drive housing 2. There is.

Next, the control rod guide tube cleaning device of the present invention will be described in detail.

Reference numeral 8 in the figure indicates a flange member, and this flange member 8 is configured to be detachably attached to a bolt or the like to a flange portion 9 provided at the lower end of the control rod drive mechanism housing 2. Between part 9 and O
A ring 10 is interposed to ensure watertightness.

A push-up tube 11 is provided slidably penetrating the center of the flange member 8, and an O-ring 12° 12 is interposed in the penetrating portion of the push-up tube 11 to ensure watertightness. .

This push-up tube 11 is inserted into the control rod drive mechanism housing 2, and its upper end reaches the lower end of the control rod guide tube 4, and a nozzle 13 and a control rod fitting part 14 are formed at this upper end. .

The control rod fitting portion 14 is configured to fit into the latch portion 6 of the control rod 5 and push up the control rod 5 via the push-up tube 11.

Further, the nozzle 13 is formed with a nozzle hole 15 that opens obliquely downward in the radial direction, and this nozzle hole 15 communicates with the inside of the push-up tube 11 .

Further, this push-up tube 11 is composed of a plurality of unit tubes 16..., and these unit tubes 16... are detachably connected via joints 17....

In addition, plate-shaped guide plates 18 and 18 are attached to the upper end of the push-up tube 11, and these guide plates 18 and 18 slide on the inner surface of the thermal sleeve 3 of the control rod drive mechanism housing 2, so that the push-up tube 11 It is configured to guide the upper end.

Note that through holes 19 are formed in these guide plates 18, 18.

When draining reactor water via the control rod drive mechanism housing 2, the reactor water is configured to flow through these through holes 19.

The flange member 8 is provided with a push-up mechanism 20 for pushing up the push-up tube 11.

Reference numeral 21 denotes a base plate thereof, which projects downward from the lower surface of the flange member 8.

A hydraulic cylinder 22 is attached to the lower end of this base plate 21 with its piston rod 23 facing upward, and the upper end of this piston rod 23 is attached to the lower end of the push-up tube 11.

This hydraulic cylinder 22 is the holding valve 2.
4. Connected to a manual hydraulic pump 27 via a coupler 25 and a hydraulic hose 26.

The holding valve 24 includes a check valve mechanism that allows flow only toward the hydraulic cylinder 22, and a mechanism that manually controls the check valve mechanism.

Note that 28 is a pressure gauge of the hydraulic pump 27.

Further, a high pressure water supply chamber 29 is formed at the lower end of the push-up pipe 11, and a high pressure water coupler 30 is installed in this high pressure water supply chamber 29.
is installed.

A high pressure water hose 31 is connected to this high pressure water coupler 30, this high pressure water hose 31 is connected to a high pressure water supply mechanism 32, and the high pressure water hose 3 is connected to this high pressure water supply mechanism 32.
1. It is configured so that high-pressure water can be supplied into the push-up tube 11 via the high-pressure water supply chamber 29.

The high pressure water coupler 30 also includes the high pressure water hose 31.
Instead, a clean water hose 33 can be connected, and this clean water hose 33 is connected to a clean water supply mechanism 34, and by connecting this clean water hose 33 to a high pressure water coupler 30, the push-up pipe 11 It is designed to supply clean water inside the tank.

Further, the flange member 8 is provided with a drain coupler 35, a drain hose 36 is connected to the drain coupler 35, and this drain hose 36 is connected to the drain water treatment mechanism 3.
7, and the reactor water drained via the control rod drive mechanism housing 2 is configured to be sent to a drain water treatment mechanism 37 via this drain hose 36 for treatment.

Further, a vent pipe 38 is inserted into the push-up tube 11, and the vent pipe 38 protrudes outside the push-up tube 11 at the upper end of the push-up tube 11, and its tip is bent downward.

The lower end of this vent pipe 38 is connected to a vent coupler 39 provided through the lower end of the push-up pipe 11, and this vent coupler 39 is connected to a dummy coupler 4 that is open to the atmosphere.
0 is fitted, and when this dummy coupler 40 is removed, the vent coupler 39 is placed in a closed state, and when this dummy coupler 40 is fitted, the vent coupler 39 is placed in an open state.

Further, like the push-up tube 11, the vent pipe 38 is made by connecting a plurality of unit pipes 41 through joints 42, and can be divided into a plurality of pipes.

In one embodiment of the present invention constructed as described above, the control rod drive mechanism is removed from the control rod drive mechanism housing 2 and sent to a maintenance shop.

In this case, the lower end of the control shaft 5 is the seating surface 7 of the control rod guide tube 4.
The reactor water will not leak outside.

Next, the push-up tube 11 is inserted into the control rod 7 drive mechanism housing 2.
is inserted, and the prong rod fitting portion 14 at the tip thereof is fitted into the latch portion 6 of the control rod 5.

In this case, since the push-up tube 11 and the vent tube 38 are divided into a plurality of unit tubes 16..., 41..., these unit tubes 16..., 41... are inserted while being connected.

After the insertion of the push-up tube 11 is completed, the flange member 8 is fixed to the flange portion 9 of the control rod drive mechanism housing 2 with bolts or the like.

Next, the hydraulic pump 27 is activated, the piston rod 23 of the hydraulic cylinder 22 is extended, and the push-up tube 11 is pushed up.

Therefore, the control rod 5 is pushed up via this push-up tube 11 and separated from the seating surface 7 of the control rod guide tube 4.

In this case, the hydraulic cylinder 22 is provided with a holding valve 24, and this holding valve 24 is provided with a check valve mechanism, so that the hydraulic cylinder 22 is hydrolocked by the press-fitted hydraulic oil, and the control rod 5 is
The pressed up state is maintained.

Therefore, reactor water flows into the control rod drive mechanism housing 2 from the control rod guide pipe 4 and is sent to the drain water treatment mechanism 37 via the drain hose 36.

At the same time, high-pressure water is supplied from the high-pressure water supply mechanism 32 into the push-up tube 11 via the high-pressure water hose 31, and this high-pressure water is ejected obliquely downward in the radial direction from the nozzle 13.

Therefore, this jet stream hits the bottom corner of the control rod guide tube 4 and removes the crud attached to this part.

The removed crud is then discharged from the control rod guide pipe 4 together with the reactor water drained through the control rod drive mechanism housing 2.

When cleaning of the control rod guide tube 4 is completed, the supply of high pressure water is stopped and the holding valve 24 is operated to open the check valve mechanism.

Then, the hydraulic oil in the hydraulic cylinder 22 is returned to the reservoir of the hydraulic pump 27, the piston rod 23 is shortened, and the control rod 5 descends under its own weight and seats on the seating surface 7 of the control rod guide tube 4, discharging the reactor water. emission will stop.

Next, a dummy coupler 40 is fitted into the vent coupler 39 to communicate the vent pipe 38 with the atmosphere.

Therefore, since the atmosphere is introduced into the control rod drive mechanism housing 2 through the vent pipe 38, reactor water containing crud remaining in the control rod drive mechanism housing 2 is discharged by gravity.

Next, the high-pressure water hose 31 is removed from the high-pressure water coupler 30, and the clean water hose 33 is connected to supply clean water into the push-up pipe 11.

Therefore, this clean water is injected into the control rod drive mechanism housing 2 from the nozzle 13, and cleans the inner surface of the control rod drive mechanism housing 2, the push-up tube 11, etc.

This clean water is then discharged through the drain pipe 36.

In this case, the tip of the vent pipe 38 is bent downward, so that the clean water spouted from the nozzle 13 flows through the vent pipe 38.
There is no possibility that the liquid will flow into the 8 and leak to the outside.

After cleaning is completed, the flange member 8 is removed and the extruded tube 11 is removed.

With such a device, high-pressure water is injected toward the corner of the bottom of the control rod guide tube 4, where the crud is most difficult to remove, and the crud in this area is reliably removed, making the cleaning process quick and efficient. This can improve work efficiency and reduce radiation exposure for workers.

Furthermore, since the crud is forcibly removed by the jetted high-pressure water, the crud can be completely removed, and the amount of reactor water drained can be reduced.

Further, since a hydraulic cylinder is used as a mechanism for pushing up the push-up tube 11, the control rod 5 can be moved up and down smoothly, and the seating surface 7 of the control rod guide tube 4 will not be damaged.

Note that the present invention is not limited to the above embodiment.

For example, the mechanism for pushing up the push-up tube is not necessarily limited to the one described above.

Further, the push-up tube does not necessarily have to be divided into a plurality of pieces.

Further, the vent pipe does not necessarily need to be provided; when draining reactor water in the control rod drive mechanism housing, air may be introduced into the push-up pipe and this may also be used as a vent pipe.

As described above, in the present invention, a nozzle is provided at the tip of the push-up tube for pushing up the control rod to spray high-pressure water toward the bottom of the inner surface of the control rod guide tube.

Therefore, the high-pressure water spouted from this nozzle can forcibly remove the crud at the bottom of the control rod guide tube, making work faster and more efficient, reducing radiation exposure for workers, and ensuring crud removal. In addition, the amount of drain water from the reactor is small, and the processing equipment for it is small in capacity.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a longitudinal sectional view of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 2... Control rod drive mechanism housing, 4... Control rod guide tube, 5...
...Control rod, 8...Flange member, 11...
... Push-up tube, 13 ... Nozzle, 14 ...
... Control rod fitting part, 20 ... Push-up mechanism, 22.
... Hydraulic cylinder, 27 ... Hydraulic pump, 32 ... High pressure water supply mechanism, 38 ...
Vent pipe (vent passage).

Claims (1)

[Claims] 1. A push-up tube that is inserted into the lower end of the control rod guide tube through the control rod drive mechanism housing and whose upper end is coupled to the lower end of the control rod; a push-up mechanism that pushes up the control rod through the push-up tube; a nozzle provided at the upper end of the push-up tube that spouts high-pressure water toward the inner bottom of the control rod guide tube; A control rod guide pipe cleaning device for a nuclear reactor, comprising: a high-pressure water supply mechanism that supplies high-pressure water to a nuclear reactor. 2. A control rod guide tube cleaning device for a patented reactor, characterized in that the push-up tube can be divided into a plurality of tubes.