JPH0229199B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to the decommissioning of nuclear reactors, and particularly to a method for efficiently cutting and disassembling a reactor pressure vessel (hereinafter referred to as RPV).

[Prior art]

As shown in FIG. 1A, conventionally, the RPV 1 was cut and dismantled by directly cutting the RPV 1 into pieces using a plasma arc, storing it in a package in a fuel pool (not shown), and transporting it. However, this method
As shown in FIG. Since it was necessary to cut the length equal to (number of thinly cut objects 6) x (number of round slices), it was necessary to cut approximately twice as long as when only round cutting was performed. When cutting and dismantling RPV1 during decommissioning, the applicable
Since the area around the RPV 1 has an irradiation dose rate of 500 mR/h or more, the cutting work is performed by fully automatic remote control using a cutting torch 2 attached to the manipulator 3. Because the above-mentioned complicated cutting work has to be performed at a location for a long time, if the cutting machine consisting of the above-mentioned manipulator 3, cutting torch 2, etc. breaks down, it will take a considerable amount of man-hours to repair it (as above-mentioned complicated cutting work). (Of course, if the work is done for a long time, the probability of failure increases.) Since the cutting position of RPV 1 is in the air above the water surface 4, there is a drawback that a large amount of fume is generated. In the figure, 5 indicates a hole for a hanging metal fitting, and 7 indicates a service floor.

[Purpose of the invention]

An object of the present invention is to provide a cutting method that eliminates the drawbacks of the prior art described above, efficiently cuts and disassembles an RPV, and reduces the generation of fumes.

[Summary of the invention]

In short, this invention is a cutting method in which the RPV is cut into rounds at the RPV installation location, cut into small pieces in a spent fuel pool with a low irradiation dose rate, stored in a package cage, and transported. In order to absorb the fume into the water, the cutting position is aligned with the water surface inside the RPV, and the cutting is done underwater in the fuel pool.

[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 disassembling the decommissioned RPV1 installed in a nuclear power plant. 2, the part that coincides with the water surface 4 is sliced into rings to obtain a round cut piece 8, and as shown in FIG.
Hook the hanging fitting 9 to the wire rope 10, lift it up in the direction of arrow c in FIG. After hanging the fuel as shown in FIG. 1 and leaving it stationary at the bottom of the fuel pool 11, the cutting torch 2 is used to cut the fuel into small pieces in the axial direction. 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. 2A. Since the RPV1 has a stainless steel coating on the inner surface of its soft iron body, it can be cut with the cutting torch 2 as in the above embodiment.
The method of cutting into rings from the inner surface of RPV1 takes a little longer to cut. Therefore, it takes less time to cut or make the hole 5 for the hanging fixture from the outside of the RPV 1 using the manipulator 3' and the cutting torch 2' as in this embodiment.

As a third embodiment of the present invention, similarly to the method in which the cut pieces 8 are cut into small pieces underwater in the fuel pool 11, the cut pieces 8 are transferred to a sealed dryer separator pool, and then the cut pieces 8 are transferred to the dryer separator pool. This is a method in which the round cut object 8 is cut into small pieces within a separator.

〔Effect of the invention〕

Cutting work in areas with high radiation dose rates is limited to circular cutting within a single plane, so the cutting length is approximately 1/2 that of conventional methods, making remote control work easier and reducing work time. This has the effect of improving reliability.

In addition, by aligning the RPV's cutting position with the water surface, some of the fume generated by the cutting is absorbed by the water, reducing the amount of fume that rises to the service floor.
This has the effect of saving air conditioning and ventilation system equipment on the service floor.

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. be.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the conventional RPV disconnection during decommissioning of a nuclear reactor, and Fig. 2 is a conceptual diagram of the above method according to the present invention.
A conceptual diagram of RPV disconnection is shown. Explanation of symbols, 1...RPV, 2...cutting torch,
3... Manipulator, 6... Shredded object, 7...
Service floor, 8...Cut into rings, 11...
fuel pool.

Claims (1)

[Claims] 1. 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 is aligned with the water surface, the reactor pressure vessel is cut into rings, and the slices are placed in the spent fuel pool or A method for cutting and dismantling a nuclear reactor pressure vessel during decommissioning of a nuclear reactor, which is characterized by transferring it into a dryer separator pool, cutting it into pieces, storing it in a package, and transporting it.