JPS6166999A - Method of overhauling construction of nuclear reactor vessel - 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] [Field of Application of the Invention] The present invention applies to boiling water, for example! Reactor vessel (RPV) of nuclear reactor (BWR), reactor vessel (RV) of pressurized water reactor (PWII) and other nuclear reactors (hereinafter referred to as these RPV, R
This invention relates to a method for dismantling a nuclear reactor vessel by cutting and removing the reactor vessel (V collectively referred to as the reactor vessel) from the installed state.

[Technical background of the invention and its problems]

Atomic lightning blasting blunts built in various locations in Japan and overseas have already reached the operational stage, and various dismantling methods are being developed for dismantling the plants after a certain useful life has passed. In particular, since the reactor vessel becomes highly radioactive waste (7), it is considered desirable to divide it into small pieces that can be enclosed in small processing vessels, and it is considered desirable to cut and separate the reactor vessel to the extent that it can be disassembled from the installed state. is being considered.

As shown in FIG. 2, during the operation of a nuclear power plant, the reactor vessel 1 contains a reactor core 2, and is exposed to high radiation radiation from the reactor core 2. The periphery of the reactor vessel 1 is covered with a reactor heat shielding wall (hereinafter also referred to as R3W) 3, and R3W is installed on the bed desk 4F. This R
Regarding 8W3, the DJ line from the reactor core 2 is prevented from having an adverse effect on surrounding equipment and equipment, or on work during periodic inspections. When dismantling the reactor vessel 1, it is desirable to work inside the reactor containment vessel with R3W3 installed from the viewpoint of preventing the spread of contamination. In addition, various piping 5 such as a coolant circulation system and an emergency core cooling system are connected to the reactor vessel 1, and these piping 5 are inserted into the through hole 6 of R8W3. When dismantling the reactor vessel 1, it is also necessary to cut and remove these pipes 5.

By the way, the methods of dismantling atoms or containers that have been considered so far include aerial cutting and underwater cutting. In air cutting, the cutting tool 7 is inserted into the inside of the reactor vessel 1 and the cutting operation is performed in the air, as shown in Fig. 3.
There is no need for troublesome T-culms etc. However, although it is a desirable countermeasure, there are concerns about environmental deterioration due to the spread of radioactive smoke, dross, gas, etc. that are expected to be emitted during cutting, and the spread of radioactive contamination. do not have.

On the other hand, for underwater cutting, as shown in Fig. 4, the reactor vessel 1 is submerged with R3W filling water 9, and the cutter I is submerged in water.
The reactor vessel 1 is cut with an iT shell 10. In this underwater cutting, J, Rudo, Cut at 1lJi! 1-Hi 1
-Most of the dross and dross are retained in the water, and the environment 1'j
It is thought that there is no risk of staining.

However, in this case, in order to accommodate water in R8W3, all the piping was cut and removed inside R3W as a preliminary work, and the N through hole 6 for piping insertion formed in R8W3 and the pedestal 4 were removed. It is necessary to seal the area with the watertight seal member 11 once a month. It is expected that cutting the pipes and sealing multiple locations inside the R8W will take a great deal of time and effort, and also from the perspective of preventing radiation exposure for workers.
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Therefore, the demolition methods known so far are considered to have problems in terms of environmental pollution or poor workability.

(Objective of the Invention) An object of the present invention is to provide a method for dismantling a nuclear reactor vessel that is free from the risk of scattering of radioactive materials, has good work efficiency, and is the most desirable from both safety and work system standpoints.

[Summary of the invention]

The reactor vessel dismantling method according to the present invention is a method of sequentially cutting and removing the installed reactor vessel surrounded by the reactor heat shielding wall from the top. The method is divided into a pre-cutting step in which the reactor vessel is cut to a predetermined depth from the inner circumference side toward the outer circumference side, and a post-cutting step in which the outer circumferential portion of the reactor vessel that remains uncut in the pre-cutting step is completely cut. In the pre-cutting step, underwater cutting is performed with the water level in the reactor vessel higher than the cutting line, and the quick cutting T
At the culm, the water level in the reactor vessel is lowered below the 1lyi line and an aerial cut is performed.

[Embodiments of the invention]

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

Since the arrangement of the reactor vessel and its surroundings is the same as in FIG. 2, the same parts in the figure will be described using the same reference numerals 8 as in FIG. 2.

FIG. 1(a) shows the pre-cutting step. That is, only the inside of the reactor vessel 1 is filled with water, but R8W3 is not filled with water.

From this, it is not necessary to seal the N through hole 6 and the pedestal 4 of R8W3 watertight.

As for the preparation work, the piping 5 is cut outside R3W3, and only the cut portion is sealed with the watertight seal part 012. The water level of the water 13 contained in the reactor vessel 1 is set higher than the required cutting line 14. Then, the cutting tool 15 is inserted into the reactor vessel 1 in a submerged state, and cuts from the inner circumferential side of the reactor vessel 1 toward the outer circumferential side to a predetermined depth. Note that in this case, the cutting shell 15 is an arc cutting tool, and arc cutting is performed.

According to this arc cutting, for example, meat used in a 1,100 MWe class nuclear power plant η11)0#ll++
Even the reactor vessel described above can be sufficiently cut. However, in the case of a reactor vessel with a small wall thickness, it is also possible to use mechanical cutting such as a cutter or gas cutting.

In this pre-cutting T culm, the reactor vessel 1 is not completely cut, but the cutting operation is stopped in the middle of the cut to avoid leaving a wall thickness that can be mechanically cut on the outer circumferential side. This will cause it to emit when disconnected!
1- Hiccomb, dross, or sulfur are taken into the contained water 13 and are not scattered around.

After the required cutting, the water level of the contained water 13 in the reactor vessel 1 is lowered, as shown in FIG. 1(b), and the water level is lower than the cutting line 14, as shown in FIG. 1(C). Stop the water level drop at a certain point. Furthermore, when the water level is falling, piping placed above the water level will be cut and removed. The ((, (transition to the clear stage process.

FIG. 1(C) shows the post-cutting process. In this step, the shell 16 is mechanically cut using a cutter, etc., and the cut line 1 exposed above the water level of the contained water 13 is inserted into the reactor vessel 1.
The outer periphery of the reactor vessel 1, which was left uncut by the culm from the previous cut, is completely cut 1- along the /I by mechanical cutting. Although not shown, to prevent the cut part from falling into the complete cut opening),
Support the cut part using hanging tools, etc. After this I
In the Wi11 culm, the cutting depth m is small, and since the cutting is done mechanically, there is little scattering of the hem etc. Furthermore, since the water level of the accommodated water 13 is lower than the cut line 14J, there is no risk of the accommodated water 13 overflowing across the cut line 11i. After cutting, the cut portion is removed and stored in a pool (not shown) or the like.

After that, as shown in FIG. 1(d), the arc cutting tool 15 is reintroduced into the contained water 13, and the process proceeds to the next stage of pre-cutting T culm in the same manner as in FIG. 1 <8>. Thereafter, the dismantling cycle in combination with the same post-cutting process as described above is repeated.

According to this method of dismantling the reactor vessel, the conventional method of underwater cutting is prohibited, and only the reactor vessel 1 is filled with water, R8W is not filled with water, so the pipes connected to the reactor vessel 1 are There is no need to perform preliminary work such as cutting 5 etc. inside the R8W3, and there is no need to stop the Q through hole 6 or the pedestal 4 of the R8W3. Therefore, the labor involved in these tasks can be omitted, and the amount of radiation exposure can be reduced at the same time. The piping can be cut outside R3W3 at the same time as the reactor vessel 1, and the work can be reduced.

In addition, arc cutting, which generates a lot of hichomes and dross, is done underwater, so there is no scattering.Mechanical cutting, on the other hand, generates less of these when cutting in the air, which prevents the spread of radioactive contamination. This will be effective in maintaining environmental safety.

(Effects of the invention) As described above, the reactor vessel dismantling method according to the present invention is as follows:
Filling only the inside of the reactor vessel with water and changing the water level, combining the pre-cutting process with underwater cutting and the post-cutting process with aerial cutting, prevents the scattering of radioactive materials and eliminates the troublesome preparation work for water shutoff. With this in mind, the cutting operation itself can be carried out efficiently.

Therefore, it satisfies both the demands of ensuring safety through radiation exposure prevention and improving work efficiency, and the disposal of nuclear reactor equipment Ij1
It has the effect of dealing with 11 problems.

[Brief explanation of the drawing]

Figures 1 (a) to (d) are explanatory diagrams showing one embodiment of the present invention; Figure 2 is a layout diagram showing the reactor vessel and peripheral equipment; Figures 3 and 4; Each of the figures is an explanatory view of the operation showing a conventional example. 1... Reactor vessel, 3... Reactor shielding wall, 15.1
6... Cutting tool, 13... Accommodated water. Applicant's agent Hisashi Hatano -10 -

Claims (1)

[Scope of Claims] 1. In a method for dismantling a nuclear reactor vessel in which the installed reactor vessel surrounded by a reactor heat shield wall is sequentially cut and removed from the top, the inside of the reactor vessel is filled with water, and the cutting step This process is divided into a pre-cutting process in which the reactor vessel is cut from the inner circumference to the outer circumference to a predetermined depth, and a post-cutting process in which the outer circumference of the reactor vessel that is left uncut in the pre-cutting process is completely cut. ,
In the pre-cutting step, the water level in the reactor vessel is made higher than the cutting line to perform underwater cutting, and in the post-cutting step, the water level in the reactor vessel is lowered than the cutting line to perform aerial cutting. A method for dismantling nuclear reactor vessels. 2. The method for dismantling a nuclear reactor vessel according to claim 1, wherein arc cutting is used in the underwater cutting in the pre-cutting step. 3. The method for dismantling a nuclear reactor vessel according to claim 1, wherein mechanical cutting is used in the aerial cutting in the post-cutting process.