JPH0229200B2 - - Google Patents

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.

FIG. 1 is a sectional view of a nuclear reactor showing a conventional cutting and dismantling method.

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 gamma shield that surrounds the reactor pressure vessel 1 and shields it from radiation; 4 is the reactor pressure vessel 1
This is water injected into the tank. 5 is reactor pressure vessel 1
The manipulator 6 inserted therein is a cutting torch attached to the manipulator 5.

To cut the reactor pressure vessel 1, first, water is filled in the vessel 1 from which the internal structure has been removed, and the manipulator 5 is
This is done by moving the cutting torch 6 along the inner wall of the container 1 by operating the . In such cutting, since the stainless steel clad 2 is stretched inside, the oxygen acetylene gas cutting method cannot be used. Therefore, the following cutting methods have conventionally been considered for cutting the reactor pressure vessel.

(1) Cut using plasma arc cutting method.

(2) After removing the stainless steel cladding 2 by the arc gouging method, it is cut by the oxygen acetylene 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,
The thickness of the reactor pressure vessel for commercial reactors is over 300 mm, so it cannot be cut using current technology and is therefore unusable. Furthermore, 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.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
To provide a method for cutting and disassembling a nuclear reactor pressure vessel, which allows the reactor pressure vessel to be cut and dismantled reliably and stably by remote control.

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 stretched inside the container can also be cut using the oxidation heat.

Hereinafter, the present invention will be explained based on 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. Ru. 8 indicates a planned cutting line along which the reactor pressure vessel 1 is cut.

First, water 4 is filled in the reactor pressure vessel 1 up to the vicinity of the planned cutting line 8 . 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 cladding 2 provided 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 8, the fuselage flange portion 1a of the reactor pressure vessel 1 is cut.
can be cut. After removing the cut fuselage flange portion 1a, as shown in FIG.
and the gamma shield 3, and the body of the reactor pressure vessel 1 is subsequently cut along the new planned cutting line 8.

As described above, in this embodiment, the reactor pressure vessel is cut from the outside of the vessel, and the inner stainless steel cladding can be heated and made ready for cutting by the oxidation heat generated during cutting of the outer steel plate.
Oxygen acetylene gas, which is the most stable and reliable cutting method, can be used, allowing stable and reliable cutting and disassembly of the reactor pressure vessel. 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 water 9 can be injected by watertightly sealing the opening of the γ shield 3. In this example as well, cutting is carried out from outside the container using oxygen acetylene gas as in the previous example. After the fuselage flange portion 1a of the reactor pressure vessel 1 is cut and removed, the manipulator 5 and cutting torch 6 are inserted between the reactor pressure vessel 1 and the gamma shield 3 to cut and disassemble the next fuselage portion. However, in this embodiment, water 9 is spread above the new planned cutting line 8, so that the cutting torch 6 is submerged in the water and the body is cut underwater. be.

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

As described above, in the present invention, since the reactor pressure vessel is cut from the outside using oxygen acetylene gas, the reactor pressure vessel can be cut and dismantled reliably and stably.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a nuclear reactor showing a conventional method for cutting and disassembling a reactor pressure vessel, and FIGS. 2 and 3 are cross-sectional views showing 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 disassembling a reactor pressure vessel according to another embodiment of the present invention. 1... Reactor pressure vessel, 2... Stainless steel cladding, 5... Manipulator, 6... Cutting torch,
8... Planned cutting 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. How to cut and dismantle a reactor pressure vessel.