JPS5975199A - Method of cutting and dismantling reactor pressure 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 The present invention relates to a method for cutting and disassembling a reactor pressure vessel to be decommissioned in a nuclear power plant.

When decommissioning a nuclear reactor at a nuclear power plant, the reactor pressure vessel is cut and dismantled. Traditionally, this cutting was done from inside the container.

Is Figure 1 the conventional cutting and dismantling method? FIG.

In the figure, 1 indicates a reactor pressure vessel, and 1a is its fuselage flange. 2 is a stainless steel clad constructed inside the reactor pressure vessel 1 to maintain its corrosion resistance; 3 is a γ shield that surrounds the reactor pressure vessel 1 and shields radiation; 4
is the water injected into the reactor pressure vessel 1. 5 is a manipulator inserted into the reactor pressure vessel 1, and 6 is a cutting torch attached to the manipulator 5.

The cutting of the reactor pressure vessel 1 is carried out by first filling water into the vessel 1 from which the internal structure has been removed, and operating the manipulator 5 to move the cutting torch 6 along the inner wall of the vessel 1. In such cutting, since the stainless steel clad 2 is placed on the inside, the oxygen acetylene gas cutting method cannot be used. Therefore, conventionally, the following cutting methods have been considered for cutting the reactor pressure vessel.

(1) Cutting by plasma arc cutting method.

(2) After removing the stainless steel cladding 2 by an arc gouging method, it is cut by an oxyacetylene gas cutting method.

(3) The stainless steel cladding 2 is cut using an arc saw cutting method that can also cut the stainless steel cladding 2 at the same time.

By the way, with the plasma arc cutting method (1), the maximum thickness that can be cut is 150 mm, whereas the thickness of the reactor pressure vessel for commercial reactors is 300 mm or more, so current technology cannot cut it. It is completely unusable.

Further, the arc gouging method and oxygen acetylene gas cutting method (2), and the arc saw cutting method (3) all have the drawback of lacking stability and reliability.

An object of the present invention is to provide a method for cutting and dismantling a nuclear reactor pressure vessel, which eliminates the drawbacks of the above-mentioned prior art and allows the reactor pressure vessel to be cut and dismantled reliably and stably by remote control. be.

In order to achieve this objective, the present invention fills the reactor pressure vessel with water up to the vicinity of the planned cutting line, and uses a remotely controlled gas cutting torch from outside the reactor pressure vessel to cut the vessel. It is characterized in that the outer wall steel plate is cut, and the stainless steel cladding placed inside the container can also be cut using the oxidation heat.

The present invention will be explained below based on the illustrated embodiments.

FIGS. 2 and 3 are cross-sectional views of a nuclear reactor showing a method for cutting and disassembling a reactor pressure vessel according to an embodiment of the present invention.

In FIGS. 2 and 3, the same parts as those shown in FIG. 1 are given the same reference numerals. 7 is a service floor provided in the nuclear reactor.

In this embodiment, a remote-controlled manipulator 2 is installed on the service floor 7, and the installation position is such that the cutting torch 6 attached to the manipulator 2 faces the outer wall of the reactor pressure vessel 1. reactor. 8 indicates a planned cutting line along which the reactor pressure vessel 1 is cut.

First, water 4 is filled in the reactor pressure volume Bl up to near the planned cutting line 80. Next, oxygen acetylene gas is sent to the cutting torch 6, which is ignited to cut the steel plate outside the reactor pressure vessel 1. During this cutting, the outer steel plate generates high oxidation heat, and this heat heats the stainless steel clad 2 provided on the inside, making it ready for cutting. therefore,
The outer steel plate and the inner stainless steel cladding 2 can be cut together using oxygen acetylene gas. Slag and dross blown away during cutting fall into the water 4 and are cooled. By remotely controlling the manipulator 5 and moving the cutting torch 6 along the planned cutting line 8vc, the fuselage flange portion 1a of the reactor pressure vessel 1 can be cut. After removing the cut fuselage flange part 1a, as shown in FIG. 8
The body of the lock reactor pressure vessel 1 will then be cut along this line.

As described above, in this embodiment, the reactor pressure vessel is cut from the outside of the vessel, and the oxidation heat generated during cutting of the outer steel plate can heat the inner stainless steel cladding to a state where it can be cut. As a method, it is possible to use oxygen acetylene gas, which is the most stable and reliable method.
It is possible to perform stable and reliable cutting and dismantling of nuclear reactor pressure vessels. Furthermore, since the oxygen-acetylene gas cutting torch is lighter than other cutting machines, remote control using a manipulator is also facilitated.

FIG. 4 is a sectional view of a nuclear reactor showing a method for cutting and disassembling a reactor pressure vessel according to another embodiment of the present invention.

The same parts in FIG. 4 as those shown in FIGS. 2 and 3 are given the same reference numerals. 9 is water injected between the reactor pressure vessel 1 and the γ shield 3. The injection of water 9 is γ
This is possible by sealing the opening of the shield 3 watertight. In this example as well, the cutting is carried out from outside the container using oxygen acetylene gas, as in the case of the rabbit example. After the fuselage flange portion 1a of the reactor pressure vessel 1 is cut and removed, the manipulator 5 and the cutting torch 6 are inserted between the reactor pressure vessel 1 and the gamma shield 3 to cut and dismantle the next fuselage part. However, in this embodiment, by spreading water 9 above the new cutting line 8, the cutting torch 6
The machine is submerged in water so that the body can be cut underwater.

In this way, in this example, cutting is performed using oxygen acetylene gas from the outside of the container, so the same effect as in the rabbit example is achieved, and since the cutting is done underwater, the generation of fume etc. is absorbed in water, and the amount of secondary waste generated in the atmosphere can be reduced.

As stated above, in the present invention, the reactor pressure vessel is cut using oxygen acetylene gas from the outside.
Therefore, the solution is to reliably and stably cut and disassemble the reactor pressure vessel.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a nuclear reactor showing a conventional method for cutting and dismantling a reactor pressure vessel, and FIGS. 2 and 3 show a method for cutting and disassembling a reactor pressure vessel according to an embodiment of the present invention. FIG. 4 is a sectional view of a nuclear reactor showing a method for cutting and dismantling a reactor pressure vessel according to another embodiment f of the present invention. 1... Reactor pressure vessel, 2... Stainless steel clad, 5... Manipulator, 6...
...Cutting torch, 8... Cutting planned line.

Claims (1)

[Claims] 1. A nuclear reactor pressure vessel whose inner surface is made of stainless steel cladding is dismantled by cutting along a planned cutting line from the outside of the reactor pressure vessel using a remotely controlled gas cutting torch. Reactor pressure vessel cutting/
Disassembly method.