JP5885596B2 - Control rod guide tube cleaning device - Google Patents

Description

  The present invention relates to a cleaning device for a control rod guide tube used in a nuclear power plant, particularly, a boiling water reactor.

  In the boiling water reactor, as shown in FIG. 5, a plurality of bar drive mechanism housings 6 (hereinafter referred to as “CRD housings”) are attached through the bottom of the reactor pressure vessel 7. A control rod drive mechanism 3 is inserted into the housing 6 from below the housing. The control rod drive mechanism 3 engages with the lower portion of the control rod 5, and the control rod 5 moves up and down in the gap between the plurality of fuel assemblies 1 and in the control rod guide tube 2 by the control rod drive mechanism 3. The reactor reactivity is controlled, and in the event of an emergency, all reactors are inserted and the reactor is shut down. Further, the fuel assembly 1 is placed on a fuel support fitting 4 installed on the core lower plate 8.

  Incidentally, dust 16 (hereinafter referred to as “cladding”) adheres or accumulates on the bottom of the control rod guide tube 2 as the operation period becomes longer. In particular, since the bottom surface of the control rod guide tube 2 is concave, the clad 16 tends to accumulate.

  During periodic inspection of the bar drive mechanism 3, the reactor water in the CRD housing 6 to be inspected is drained, and the high-dose control rod drive mechanism 3 is disassembled, inspected and cleaned, so that the dose in the CRD housing 6 is removed. Becomes lower. However, the clad 16 accumulated for many years is accumulated in the upper control rod guide tube 2, and the clad 16 penetrates into the control rod drive mechanism 3 after the inspected control rod drive mechanism 3 is attached, and the seal 16 is sealed. Sliding resistance increases due to clad biting on a ring (not shown), and as a result, there is a possibility that the driving speed of the control rod drive mechanism 3 is lowered and fine adjustment becomes difficult. There is.

  Further, when the control rod 5 is fully pulled out and separated from the control rod drive mechanism 3, the clad bites into the bottom of the control rod guide tube 2 and the metal touch portion (not shown) of the seating portion of the control rod 4, thereby When removing and installing the control rod drive mechanism, water leakage will increase and the work environment may deteriorate.

  Furthermore, if the clad 16 adheres to an O-ring (not shown) between the flanges where the control rod drive mechanism 3 and the CRD housing 6 are joined, the pressure resistance of the reactor pressure vessel 7 is impaired, and in some cases the reactor water May leak from the control rod drive mechanism 3.

  Therefore, in a conventional nuclear power plant, after removing the control rod drive mechanism 3 at the regular inspection, a cleaning device is inserted into the control rod guide tube 2 to remove the clad 16 attached or deposited on the bottom of the control rod guide tube 2. Things have been done. As shown in FIG. 6, the cleaning device includes a cylindrical rod member 35 and a water absorption nozzle 36 that is rotatably provided on the upper portion of the rod member 35, and the rod member 35 is placed in the CRD housing 6 during cleaning. The clad 16 attached or deposited on the bottom of the control rod guide tube 3 is removed by inserting and sucking the water in the control rod guide tube 2 and the clad 16 through the water absorption nozzle 36 by the water absorption pump 28 ( Patent Document 1).

JP 2001-42084 A

  By the way, the above-described conventional control rod guide tube cleaning device removes the clad by suction, and the clad slightly attached to the bottom of the control rod guide tube or the light weight clad in the floating state can be removed. It is difficult to remove a clad that is firmly attached to the bottom surface or inner wall surface of the control rod guide tube or a clad that is heavy. For this reason, there are problems such as that the working environment is deteriorated by radiation, and the function of the control rod drive mechanism and the airtightness of the reactor pressure vessel are impaired by the cladding.

  The present invention has been made to solve the above-mentioned problems, and reliably and efficiently removes a clad adhering or depositing on the bottom surface or inner wall surface of the control rod guide tube, particularly a strongly adhering clad or a heavy clad. It is an object of the present invention to provide a cleaning device for a control rod guide tube.

  In order to solve the above problems, a control rod guide tube cleaning device according to the present invention includes a control rod drive mechanism housing and a water absorption pipe that can be inserted into the control rod guide tube, and a water injection pipe installed in the water absorption pipe. A control part guide comprising: a main body comprising a pipe; a water absorption cap provided at a distal end of the water absorption pipe and having a plurality of openings around; and a cleaning nozzle provided at the front end of the water injection pipe. During cleaning of the pipe, high-pressure washing water is jetted from the washing nozzle into the control rod guide pipe through the opening, and the high-pressure washing water is sucked together with the clad through the opening through the opening and discharged to the outside. It is characterized by that.

  According to the present invention, the clad adhered or deposited on the bottom surface or inner wall surface of the control rod guide tube, in particular, the firmly adhered clad or heavy clad can be removed reliably and efficiently.

The whole block diagram of the cleaning device of the control rod guide tube concerning the embodiment of the present invention. The enlarged view of the control-rod guide pipe lower part at the time of the cleaning which concerns on embodiment of this invention. (A), (b) is a block diagram of the water injection nozzle which concerns on embodiment of this invention. (A), (b) is a block diagram of the water absorption cap which concerns on embodiment of this invention. The block diagram of a control rod guide tube and a control rod drive mechanism. Schematic of the conventional cleaning apparatus.

  Hereinafter, an embodiment of a control rod guide tube cleaning device according to the present invention will be described with reference to FIGS. 1 to 4.

(Constitution)
As shown in FIG. 1, the control rod guide tube cleaning device according to this embodiment includes a cylindrical water absorption pipe 22 inserted into the CRD housing 6 during cleaning and a water injection pipe 21 installed therein. A main body 20, a water injection nozzle 25 attached to the front end of the water injection pipe 21, a water absorption cap 24 provided at the front end of the water absorption pipe 22 so as to cover the water injection nozzle 25, and water injection connected to the water injection pipe 21 The connecting pipe 21b and the high pressure jet cleaning unit 26, the water absorbing connecting pipe 22b and the water absorbing pump 28 connected to the water absorbing pipe 22, the drain pipe 23b connected to the lower part of the CRD housing 6, and the main body 20 can be moved up and down. And an elevating device 27 that is operated to

  The main body 20 of the cleaning device has a double pipe structure in which a water absorption pipe 22 and a water injection pipe 21 are inserted therein, is guided by a guide flange 23, and slides up and down by a lifting device 27.

  A conical water absorption cap 24 having a rounded tip is attached to the front end of the water absorption pipe 22 so that the control rod 5 can be pushed up, and a water injection nozzle that injects high-pressure washing water into the water absorption cap 24. 25 is stored.

  As shown in FIGS. 3 (a) and 3 (b), the water injection nozzle 25 attached to the tip of the water injection pipe 21 has a plurality of nozzle openings 25a so that water in the water injection pipe 21 can be uniformly injected around. Is provided.

  Further, as shown in FIGS. 4A and 4B, the water absorption cap 24 provided at the tip of the water absorption pipe 22 is provided with a plurality of slit-shaped openings 24a around the openings 24a. The high pressure cleaning water is injected and the clad 16 and the high pressure cleaning water are absorbed.

(Function)
In the control rod guide tube cleaning apparatus configured as described above, when cleaning the inside of the control rod guide tube 2, after removing the control rod drive mechanism 3 from the CRD housing 6, the guide flange 23 is attached to the CRD housing 6. The main body 20 of the cleaning device is inserted into the CRD housing 6 from the lower side of the reactor pressure vessel 7. At that time, as shown in FIG. 1, the lower end of the main body 20 is pushed up by a predetermined length by an elevating device 27, whereby the water absorption cap 24 provided at the tip of the water absorption pipe 22 pushes up the control rod 5, and the water absorption cap 24 is located at the lower end of the control rod guide tube 2.

  Since the main body 20 is designed to have the same outer shape and dimensions as the control rod drive mechanism 3, an exchange device or the like used when replacing the control rod drive mechanism 3 can be used. Therefore, the control rod guide tube cleaning device can be easily attached and detached in the same manner as the control rod drive mechanism 3.

  Next, when the water absorption cap 24 is positioned at the lower end portion of the control rod guide tube 2, the water injection valve 21 a is opened and the high pressure cleaning water from the high pressure jet cleaning unit 26 is supplied to the water injection nozzle 25 through the water injection pipe 21. At the same time, the water absorption valve 22a is opened and the water absorption pump 28 is operated.

  As shown in FIG. 2, the high-pressure washing water is sprayed from the plurality of nozzle ports 25 a of the water injection nozzle 25 toward the lower part and the inner wall surface of the control rod guide tube 2 through the openings 24 a. The clad 16 adhering to the lower and inner wall surfaces is peeled off, and the adhering or floating clad 16 is washed into the sump pit 30 through the opening 24a, the water absorption pipe 22 and the water absorption connection pipe 22b together with the cleaning water by the suction force of the water absorption pump 28. Discharge.

  The guide flange 23 attached to the CRD housing 6 serves to guide the insertion of the main body 20 of the cleaning device, and the reactor pressure vessel 7 accumulated in the CRD housing 6 via the drain valve 23a and the drain hose 23b. The water leaked from the water is drained into the sump pit 30. Thereby, the water in the CRD housing 6 is drained before the cleaning work, thereby preventing the workability from being deteriorated due to water leakage from the CRD housing 6.

  As described above, the cleaning process according to the present embodiment includes (1) removal of the control rod drive mechanism 3 → (2) attachment of the guide flange 23 → (3) attachment and insertion of the main body 20 → (4) high pressure washing water The removal of the clad 16 in the control rod guide tube 2 by spraying and suction is performed in the order of (5) removal of the main body 20 → (6) attachment of the control rod drive mechanism 3.

  Further, since the clad 16 is attached not only to the bottom surface of the control guide tube 2 but also to the inner wall surface, the injection position of the high-pressure washing water is appropriately changed by moving the main body portion up and down appropriately by the lifting device during cleaning. It may be.

(effect)
According to the present embodiment, the high pressure cleaning water is jetted and sucked onto the bottom surface and the inner wall surface of the control rod guide tube, so that the clad adhered or deposited on the bottom surface and the inner wall surface of the control rod guide tube, particularly firmly adhered. Cladding and heavy cladding can be removed reliably and efficiently. Thereby, it is possible to prevent a decrease in the function of the control rod drive mechanism due to the cladding, a decrease in pressure resistance of the reactor pressure vessel, a deterioration of the working environment due to radiation, and the like.
Further, since the outer shape and dimensions of the cleaning device are made the same as those of the control rod drive mechanism, it is possible to use an existing exchange device for the control rod drive mechanism together, and the cleaning device can be easily attached and detached.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, combinations, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Fuel assembly, 2 ... Control rod guide tube, 3 ... Control rod drive mechanism, 4 ... Fuel support bracket, 5 ... Control rod, 6 ... Control rod drive mechanism housing, 7 ... Reactor pressure vessel, 8 ... Lower core Plate: 16 ... Clad, 20 ... Main body, 21 ... Water injection pipe, 22 ... Water absorption pipe, 23 ... Guide flange, 24 ... Water absorption cap, 24a ... Opening, 25 ... Water injection nozzle, 25a ... Nozzle port, 26 ... High pressure jet Cleaning unit, 27 ... lifting device, 28 ... water absorption pump, 30 ... sump pit, 35 ... rod member, 36 ... water absorption nozzle.

Claims (4)

A main body part consisting of a water absorption pipe that can be inserted into the control rod drive mechanism housing and the control rod guide pipe, and a water injection pipe installed inside the water absorption pipe, and a plurality of surroundings provided at the tip of the water absorption pipe A water absorption cap having an opening, and a cleaning nozzle provided at the tip of the water injection pipe,
When cleaning the control rod guide tube, high-pressure washing water is jetted from the washing nozzle into the control rod guide tube through the opening, and the high-pressure washing water is sucked together with the clad through the opening through the opening. A cleaning device for a control rod guide tube which is discharged to the outside.   The control rod guide tube cleaning according to claim 1, further comprising an elevating device that moves the main body up and down, and changing the injection position of the high-pressure washing water by moving the elevating device up and down during cleaning. apparatus.   3. The control rod guide pipe cleaning device according to claim 1, wherein the water injection pipe is connected to a high-pressure jet cleaning unit via a water injection valve.   4. The control rod guide tube cleaning device according to claim 1, wherein a drainage device for discharging water inside the control rod drive mechanism housing is attached to the control rod drive mechanism housing. .

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