JPS5987400A - Cutting and dismantling system for pressure vessel in waste reactor - 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] [Utilization of the Invention] The present invention relates to the decommissioning of a nuclear reactor, and particularly to a method for efficiently cutting and dismantling a reactor pressure vessel (hereinafter referred to as RPV).

[Prior art]

As shown in Figure 1 (a), conventionally, the cutting and dismantling of RPV1 involves directly cutting the RPVI into pieces using a plasma arc.
It was stored in a package at a fuel pool (not shown) and transported. However, as shown in FIG. )X(1
Since it was necessary to cut by the length of (the number of thinly cut objects 6 in each round slice) x (the number of round slices), it was necessary to cut approximately twice as long as when only round cutting was performed. When cutting and dismantling RPVI during decommissioning, the RPV
Since there is an irradiation dose rate of 500 mR/h or more around the area 1, cutting work is performed by fully automatic remote control using a cutting torch 2 attached to a manipulator 3. If the cutting machine consisting of the manipulator 3, cutting torch 2, etc. breaks down, it will take a considerable amount of man-hours to repair it, and the complicated cutting work described above will take a long time. Of course, the longer you do it, the higher the chance of failure.)
Since the cutting position of RPVI is in the air above the water surface 4, there is a drawback that a large amount of fume is generated.

In addition, in the figure, 5 indicates a hole for an ω-shaped fitting, and 7 indicates a service floor.

[Purpose of the invention]

The purpose of this invention is to eliminate the above-mentioned drawbacks of the prior art;
It is an object of the present invention to provide a cutting method capable of efficiently cutting and disassembling an RPV and reducing the generation of fumes.

[Summary of the invention]

In short, this invention provides that the RPV is
This is a cutting method in which PV is cut into rings, cut into small pieces in a spent fuel pool with a low irradiation dose rate, stored in a package, and transported, and the cutting position is set to RPV in order to absorb the fumes during cutting into water. Cut to match the water surface inside.
However, in the fuel pool, cutting is performed underwater.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIG. 2. Note that the same or equivalent parts as in FIG. 1 are given the same reference numerals. Figure 2 shows a conceptual diagram of cutting and dismantling a decommissioned RPV installed in a nuclear power plant.
As shown in FIG. 2(A), in the above-mentioned installed state of the RPVI, the PVI is sliced into rounds at a point that coincides with the water surface 4 using a cutting torch 2 to obtain a sliced product 8 as shown in FIG. 2(B). Hook the hanging fitting 9 into the hanging fitting hole 5 provided in the shaft-cut workpiece 8, and lift it up by the wire rope 1o in the direction of arrow C in FIG. 1(A), and in the direction of arrow d. The fuel pool 11 with a low irradiation dose rate is placed next to the RPVI and suspended in the water as shown by the arrow e, and placed at the bottom of the fuel pool 11. Cut into small pieces. The shredded material 6 thus obtained is stored in a package (not shown) in the fuel pool 11 and carried out.

Another embodiment of the present invention is the system shown by the broken line in FIG. 2(A). Since the RPVI has a stainless steel coating applied to the inner surface of the soft iron body, the method of cutting the RPVI into rounds from the inner surface using the cutting torch 2 as in the above embodiment takes a somewhat long cutting time. Therefore, it takes less time to cut or make the hole 5 for the hanging fixture from the outside of the 1'LPV 1 using the manipulator 3' and the cutting torch 2' as in this embodiment.

As a third embodiment of the present invention, the fuel pool 11
Similar to the method of cutting the round cut object 8 into small pieces in water, after the shaft cut object 8 is transferred into a sealed dryer separator pool, the round cut object 8 is cut into small pieces in the dryer separator pool. This is a method to do so.

〔Effect of the invention〕

Cutting work in areas with high radiation dose rates is limited to circular cutting within one plane, so the cutting length is approximately % of that of conventional methods, making remote control work easier and reducing work time, as well as improving work reliability. It has the effect of improving sex.

In addition, by aligning the cutting position of the RPV with the water surface, a portion of the fume generated by the cutting is absorbed by the water, reducing the amount of heat rising toward the service floor. Reduced air conditioning and ventilation equipment on the floor 4.

There is an effect that it can be done.

Furthermore, since the cutting of the round pieces in the fuel pool is done underwater, approximately 50% of the total cutting work is underwater cutting, which has the effect of significantly reducing the amount of fumes generated compared to conventional methods. Some 0

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of RPV cutting during decommissioning of a nuclear reactor. FIG. 2 is a conceptual diagram of the above-mentioned PV cutting according to the present invention. Explanation of symbols 1... RPV, 2... Cutting torch, 3... Manipulator, 6... Thinly cut object, 7... Service floor, 8... Round cut object, 11... Fuel Pool representative patent attorney Junnosuke Nakamura 1 Figure (a) 0 units) 1
-Figure 2 (A) ゛(Rof)

Claims (1)

[Claims] In the reactor pressure vessel cutting and disassembly method for decommissioning a nuclear reactor, water is poured into the reactor pressure vessel, the cutting position matches the water surface, the reactor pressure vessel is cut into rings, and the pieces are placed in the spent fuel pool or dryer. Reactor pressure vessel cutting and disassembly method for decommissioning a nuclear reactor, which is characterized by transferring it into a separator pool, cutting it into pieces, storing it in a package, and transporting it □