JPH0523399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to a method for decommissioning a nuclear reactor.

"Prior Art" In boiling water nuclear power plants, etc., the reactor is stored in a steel containment vessel in case of an accident, and the outer surface of this containment vessel is Additionally, a thick concrete shielding wall has been installed. The shape of this containment vessel and shielding wall is often so-called flask-shaped, with a cylindrical upper part and a hollow spherical lower part, and the reactor has a pedestal ( It is generally supported and placed on a pedestal.

By the way, it is expected that in the future it will be necessary to take decommissioning measures for the nuclear reactors currently in operation due to aging or model changes. being done.

To date, the generally accepted method for decommissioning a nuclear reactor is to dismantle the reactor and radioactive shielding walls by remotely controlling manipulators while monitoring with television cameras. The idea is to divide it into small blocks, store these blocks in a container that can shield them from radioactivity, and then transport them to a final disposal site or storage site.

``Problems to be solved by the invention'' However, the method of decommissioning the reactor by dividing it into small blocks as described above requires extremely complex and highly precise equipment to perform most of the work remotely. (cutting equipment, handling equipment, etc.) is required, and a huge number of containers are required to store the cut blocks, making the decommissioning work complex and large-scale, and the cost increases significantly. be.

This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a method for decommissioning a nuclear reactor with simple work and at low cost, without dividing the reactor and shielding wall into small blocks. shall be.

``Means for Solving the Problems'' This invention provides a method for decommissioning a nuclear reactor that is supported by a pedestal and housed within a shielding wall consisting of an upper cylindrical part and a lower hollow spherical part. The pedestal is removed and the reactor is located inside the spherical part of the shielding wall, and then the cylindrical part and the spherical part of the shielding wall are edged, and the edge is cut off. lowering the cylindrical part to position it around the reactor located inside the spherical part;
Thereafter, the upper opening of the spherical part is closed and the spherical part is transported outside the reactor building.

"Operation" The decommissioning method of this invention utilizes the spherical part at the bottom of the shielding wall as a transfer container, stores the nuclear reactor in this spherical part without dismantling it, and at the same time removes radioactively contaminated reactors. The cylindrical part at the top of the shielding wall can also be stored and transported without being dismantled.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.

Figures 1 to 5 are diagrams explaining the steps of the decommissioning method of this embodiment in the order of the steps, and Figure 1 shows the state of the reactor to be decommissioned before decommissioning work begins. FIG. In FIG. 1, reference numeral 1 is a nuclear reactor, and this nuclear reactor 1 has a pedestal 2.
It is supported by and stored in the containment vessel 3. The containment vessel 3 is formed of a steel plate in the shape of a so-called flask, and a shielding wall 4 of a predetermined thickness made of concrete is formed on the outer surface of the containment vessel 3. This shielding wall 4 has a flask shape similar to the containment vessel 3, and has an upper cylindrical portion 4a.
and a lower spherical portion 4b. The lower part of this shielding wall 4 is integrated with the foundation 5a of the reactor building 5, and the slabs 5b of each floor of the reactor building 5 are attached to the sides.

From the state shown in Fig. 1, as shown in Fig. 2,
First, the top of the containment vessel 3 is dismantled, and the pedestal 2 is removed from the top using a manipulator or the like, and the reactor 1 is lowered inside the lower spherical portion 4b of the shielding wall 4. Then, the reactor 1 is supported by appropriate means and erected at the center of the spherical portion 4b.

Next, as shown in FIG. 3, the cylindrical portion 4a and the spherical portion 4b of the shielding wall 4 are edged using a concrete cutter or the like from the outside of the shielding wall 4, and the cylindrical portion 4a is The edges of the attached slabs 5b of the reactor building 5 and the cylindrical portion 4a are cut. Further, the vicinity of the bottom surface of the spherical portion 4b is cut out according to the shape of the lower end portion of the cylindrical portion 4a.

Then, as shown in FIG. 4, the cut-off cylindrical portion 4a is lowered inward of the spherical portion 4b,
It is placed around the nuclear reactor 1 which was previously placed inside the spherical portion 4b.

Thereafter, as shown in FIG. 5, the upper opening 4c of the spherical portion 4b (the portion where the cylindrical portion 4a is edged) is hermetically closed with a concrete slab 6. Next, the slab 5b attached to the spherical part 4b is edged, and the outer wall and foundation of the building 5 are dismantled to secure an exit path. Then, the ground below the spherical part 4b is excavated, the spherical part 4b is supported by the rails 7, rollers 8, etc., and the spherical part 4b is transferred in the direction of the arrow shown in the figure by an appropriate means such as a hydraulic jack. and transport it to the storage location.

As described above, in this decommissioning method, without dismantling the reactor 1, the spherical part 4b that becomes the transfer container can be removed.
At the same time, the cylindrical part 4a of the shielding wall 4, which is contaminated with radioactivity, is also transported at the same time without being cut into pieces.

As a result, in this decommissioning method, it is not necessary to dismantle the reactor 1, and the dismantling work of the shielding wall 4 is very small. cutting work)
This decommissioning can be carried out from outside the shielding wall 4 using a relatively simple device (for example, a cutter for dismantling concrete structures that has been widely used in the past. Therefore, in this decommissioning method, it is possible to In addition to significantly simplifying reactor work, the huge number of shielding containers that were required in conventional decommissioning methods can be minimized, and the costs required for decommissioning work can also be reduced. Of course, since the spherical portion 4b used as a transfer container has sufficient shielding ability, there is no risk of workers being exposed to radiation during the transportation of the spherical portion 4b or during subsequent storage.

The spherical part 4b that has been transported to the storage location may be stored there for a long period of time or may be treated as appropriate, and the disposal value of the building 5 after the spherical part 4b is taken out is You can either demolish it and construct a new building, or if possible, repair it and reuse it.

"Effects of the Invention" As explained in detail above, according to the present invention, the nuclear reactor and the cylindrical part of the shielding wall are housed inside the spherical part of the shielding wall, and the spherical part is used as a transfer container. This eliminates the need to divide the reactor and shielding wall into small blocks, eliminating the need for high-precision, large-scale equipment and a huge number of shielding containers, and simplifying the work and reducing maintenance costs. This has the effect of reducing the cost required for decommissioning work.

[Brief explanation of the drawing]

Figures 1 to 5 are explanatory diagrams showing the steps of the embodiment of the present invention in the order of the steps. 3 shows a state in which the cylindrical part and the spherical part are separated, FIG. 4 shows a state in which the cylindrical part is lowered, and FIG. 5 shows a state in which the spherical part is transferred. FIG. DESCRIPTION OF SYMBOLS 1... Nuclear reactor, 2... Pedestal, 4... Shielding wall, 4a... Cylindrical part, 4b... Spherical part, 4c
...Opening, 5...Reactor building, 6...Concrete slab.

Claims (1)

[Claims] 1 A method for decommissioning a nuclear reactor that is housed within a shielding wall consisting of an upper cylindrical part and a lower hollow spherical part, supported by a pedestal, in which the pedestal is removed and the atom The furnace is positioned inside the spherical portion of the shielding wall, and then the cylindrical portion of the shielding wall and the spherical portion are edged, and the edged cylindrical portion is lowered to remove the spherical portion. located around the reactor, which is located inward, and then
A method for decommissioning a nuclear reactor, comprising closing the upper opening of the spherical part and transporting the spherical part to the outside of the reactor building.