JPS5815758B2 - Reactor control rod guide tube crud removal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiling water nuclear reactor (hereinafter abbreviated as BWR reactor).

) relates to a device for removing crud accumulated at the bottom of the guide tube of a control rod.

Generally, in a BWR reactor, control rods are inserted into and removed from the reactor core from the bottom of the pressure vessel to control the output. In this case, the control rods move up and down while being guided within a guide tube. It is.

However, when such a device is operated for a long time, radioactive crud gradually accumulates at the bottom of the guide tube, and the pressure vessel tends to become highly radioactive.

However, in the past, there were few effective means to remove the radioactive crud, and the only way to do so was to suck it up with a drainage pump.

Therefore, there are problems in that it is very difficult to sufficiently remove the cladding at the bottom of the guide tube located in the lower vessel portion of the pressure vessel where the water is deep.

In view of these points, it is an object of the present invention to provide a crud removal device for a reactor control rod guide tube that can reliably remove crud in the guide tube with a relatively simple device.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

Reference numeral 1 in the figure indicates a bottom wall portion of the pressure vessel, and a control rod drive mechanism housing 2 is inserted through and attached to the bottom wall portion 1 of the pressure vessel.

A control rod guide tube 3 is attached to the top end of the control rod drive mechanism housing 2, and the control rod guide tube 3 is guided along the inner wall of the guide tube 3 via guide rollers 4 within the guide tube 3 to move up and down. A control rod 5 is provided (only its lower end is shown in the figure).

The control rod 5 is usually connected to the control rod drive mechanism housing 2.
The control rod is moved up and down by a control rod drive mechanism (removed in the figure) attached to the lower part of the guide tube 3. In the retracted position, the control rod is moved against the tapered seat surface 3a provided on the bottom surface of the guide tube 3. The unlatch portion 5a provided at the lower end of the slanted portion 5b formed at the outer circumferential portion of the upper end is seated.

By the way, the reference numeral 10 in the figure indicates the control rod drive mechanism housing 2 for mounting the control rod drive mechanism after the control rod drive mechanism is removed when the cladding inside the guide tube 3 is removed.
A push-up rod 11 whose top end can be engaged with the unlatch portion 5a of the control rod 5 is inserted and inserted into the bearing member 10 so as to be slidable in the axial direction. ing.

A water supply channel 12 extending in the axial direction is bored in the center of the push-up rod 11, and a plurality of water spray nozzles 13 are provided on the side surface near the top end of the push-up rod 11, communicating with the water supply channel 12 and facing diagonally downward. A guide member 14 is provided on the side wall of the push-up rod 11 and is capable of slidingly contacting the inner surface of the control rod drive mechanism housing 2 .

On the other hand, the upper end of a piston rod 16 of the push-up rod drive device 15 is removably attached to the lower end of the push-up rod 11.

That is, the push-up rod drive device 15 has a frame 19 equipped with wheels 18 so as to be able to run on a platform 17 in the lower part of the pressure vessel 1, and a cylinder 20 extending in the vertical direction is fixed to the frame 19. A piston 21 is disposed within the cylinder 20 so as to be able to move up and down.

The piston 21 is provided at both upper and lower ends of the cylinder 20.
A metal housing 22a that also serves as a bearing and an end cover for the piston rod 16 projects upward and downward from the metal housing 22a.

22b is attached in a fitting manner, and the flange-like mounting seat 23 provided at the top end of the piston rod 16 is brought into contact with the lower surface of the flange-like projection 24 fixed to the lower end of the push-up rod 11, and the above-mentioned Flange-shaped mounting seat 23
By screwing a cap nut 25 that engages with the flange-like projection 24, the piston rod 16 and the push-up rod 11 can be connected to each other on the same axis.

The cylinder 20 also has an upper cylinder chamber 20.
a, and pipe fittings 26.27 connected to the lower cylinder chamber 20b, respectively, are attached, and flexible tubes 28.2 connected to the pipe fittings 26, 27 are attached.
a water pressure source for actuating the piston 21 via 9 (
(not shown).

On the other hand, the bearing member 10 has an annular cavity 30 formed at its top portion that communicates with the annular gap between the inner circumferential surface of the housing 2 and the push-up rod 11, and two annular cavities 30 that communicate with the annular cavity 30. Pipe joints 31 and 32 are provided, and an air vent valve 33 such as a check valve is connected to the pipe joint 31.
An outflow pipe 34 is attached to the other pipe joint 32.

Further, an axial communication hole 35 communicating with the water supply channel 12 of the push-up rod 11 is bored at the top end of the piston rod 16, and a side portion of the piston rod near the bottom of the communication hole 35 is bored. A pipe joint 36 communicating with the communication hole 35 is attached to the pipe joint 36, a pressure water supply pipe 37 is connected to the pipe joint 36, and each pipe joint 32, 36 of the outflow pipe 34 and the pressure water supply pipe 37 is connected to the pipe joint 36. The vicinity of the bypass valve 38
Bypass pipe 4 that can be expanded and contracted via a pipe joint 39
They are connected to each other by 0.

Further, a water suction pump (not shown) is appropriately provided at the end of the outflow pipe 34.

Next, its effect will be explained.

In order to remove the crud accumulated in the control rod guide tube 3, first remove the control rod drive mechanism installed at the lower part of the control rod drive mechanism housing 2, and attach the crud according to the present invention to the flange 2a of the housing 2. The bearing member 10 of the removal device is attached, and the upper half of the push-up rod 11 attached to the bearing member 10 is inserted into the housing 2.

Thereafter, the push-up rod driving device 15 is moved on the platform 17 and brought to a position below the push-out rod 11, and the flange-like projection 24 and the flange-like mounting seat 23 are brought into contact with each other, and the cap nut 23 is fixed to the flange-like projection. 2
They are connected to each other by screwing into 4.

Therefore, the frame 1 of the push-up rod drive device 15
9 and the platform 17, the lifting rod drive device 15 is prevented from moving, and the wheels 18 are lifted from the platform 17, so that the control rod 5 can be moved during work.
A piece of wood 41 is inserted in order to support heavy loads such as their own weight and water pressure applied thereto.

Next, the tips of flexible tubes 28 and 29 connected to a water pressure pump (not shown) placed on the pedestal floor or the like below the platform 17 are respectively connected to the pipe joints 26 and 27 of the cylinder 20, and further, Bearing member 1
The outflow pipe 34 and the pressure water supply pipe 37 are connected to the pipe joint 32 provided at the piston rod 0 and the pipe joint 36 provided at the piston rod 16, respectively.
and are connected via a bypass tube 40 using a pipe joint 39.

Note that in this case, the bypass valve 38 is kept closed.

Therefore, by supplying pressure water to the lower cylinder chamber 20b via the flexible tube 29, the piston 2
1 upward, and the top end of the push-up rod 11 is connected to the control rod 5.
The control rod 5 is brought into contact with the unlatch portion 5b of the control rod 5, and the control rod 5 is further lifted from the seat surface 3a by the push-up rod 11 (as shown).

On the other hand, at the same time, pressurized water is supplied by the pressure water supply pipe 37 into the water supply channel 12 inside the push-up rod 11 .

The pressure water supplied to the water supply channel 12 is then jetted from the water nozzle 13 toward the bottom wall of the control rod guide tube 3, and the jetted water agitates the crud that had accumulated in the control rod guide tube 3. The cladding is suspended together with the reactor water flowing into the control rod drive mechanism housing 2 from the seating surface 3a opened by the upward movement of the control rod 5.
It flows out into the annular gap between the housing 2 and the push-up iron, and is further discharged to a predetermined location via the outflow pipe 34.

In this case, since a water suction pump is provided at the tip of the outflow pipe 34, the floating crud is immediately sucked in together with the outflowing reactor water and is discharged very quickly.

Alternatively, a clad separator may be attached to the tip of the outflow pipe 34 to separate the clad from the reactor water and take it out.

Once the crud inside the control rod guide tube 3 is removed in this way, pressurized water is supplied to the upper cylinder chamber 20a of the push-up rod drive device 15 to lower the piston 21,
As a result, the push-up rod 11 is lowered via the piston rod 16.

Therefore, the control rod 5 is also lowered and its inclined portion 5b is lowered to the seat surface 3.
When seated in a, self-shielding of the relevant part is performed by the reactor water pressure.

Therefore, when the supply of pressure water to the pressure water supply pipe 37 is stopped and the bypass valve 38 is opened, the water in the control rod drive mechanism housing 2 and the water supply channel 12 of the push-up rod 11 is discharged by the water suction pump.

Note that in this case, air is sucked into the control rod drive mechanism housing 2 through the air vent valve 33, and the area does not become a vacuum.

Therefore, the cap nut 25 is loosened to release the connection between the push-up rod 11 and the piston rod 16, and at the same time, the connection between the bearing member 10 and the control rod drive mechanism housing 2 is released.
Also, remove the pipes connected to each of them,
Separate the bearing members, etc. and the push-up rod drive device, etc.
The control rod is carried to the lower part of the guide tube, and the cladding inside the guide tube is removed again in the same manner as described above.

Since the present invention is configured as described above, the bearing members etc. can be pushed up and the rod drive device etc. can be easily disassembled from each other, and therefore it can be relatively easily carried into a narrow work area below the pressure vessel. Moreover, since the crud accumulated inside the guide tube is suspended by the jet of pressurized water and discharged together with the reactor water, the crud can be removed quickly and reliably, and it is also possible to prevent workers from being exposed to radiation during work. This has the effect of reducing the high radioactivity caused by Clara in the lower vessel of the pressure vessel.

[Brief explanation of drawings]

The drawing is a schematic configuration diagram showing the crud removal operation of the reactor control rod guide tube crud removal device of the present invention. DESCRIPTION OF SYMBOLS 1... Bottom wall of the pressure vessel, 2... Control rod drive mechanism housing, 3... Control rod guide tube,
5... Control rod, 10... Bearing member, 1
1...Pushing rod. 12... Water supply channel, 13... Water nozzle, 14... Guide member, 15... Push-up rod drive device, 16... Piston rod,
20... Cylinder, 21... Piston, 25... Cap nut, 34... Outlet pipe, 37... Pressure water supply pipe.

Claims (1)

[Scope of Claims] 1. A bearing member that is detachably attached to the lower part of the control rod drive mechanism housing, and a bearing member that is inserted through the bearing member so as to be slidable in the axial direction, and is formed at the bottom of the control rod guide tube by the upward movement of the bearing member. a push-up rod that can lift a control rod from a seat surface; a push-up rod drive device that collapses a piston rod that is movably disposed on a platform and that can be connected to the lower end of the push-up rod; A water supply channel extending in the axial direction is formed in the push-up rod, and a plurality of pipes are connected to the water supply channel near the top end and are directed toward the bottom of the guide tube when the control rod is pushed up. A water spray nozzle is provided, and a pressure water supply pipe is attached to the water supply channel, and an outflow water drainage pipe is detachably attached to the lower end of the annular gap formed between the housing and the push-up rond. A nuclear reactor control rod guide tube crud removal device characterized by: 2. The crud removal device for a reactor control rod guide tube according to claim 1, wherein the push-up rod drive device is a hydraulic piston device.