JP3425624B2 - Reactor removal method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing a reactor pressure vessel from a reactor building.

[0002]

2. Description of the Related Art There is an urgent need to establish a safe and rational method for dismantling and removing a reactor pressure vessel associated with the decommissioning of a commercial nuclear reactor. As a construction method for dismantling and removing the reactor pressure vessel (hereinafter abbreviated as pressure vessel), other than the method of subdividing the pressure vessel and accommodating it in a disposal vessel and sequentially removing and disposing it, A method of removing it from the reactor building is also under consideration.

As a construction method for removing the pressure vessels in a lump, a reactor shielding wall (so-called γ
A method of taking out a pressure vessel from the inside of a shield (hereinafter simply referred to as a shielding wall) and covering the whole with a shielding steel plate, taking out the pressure vessel from the inside of the shielding wall and accommodating it in a shielding container, A method of filling, a method of dismantling and removing the shielding wall and covering the entire pressure vessel with a shielding steel plate,
Etc. have been proposed.

[0004]

However, none of the above proposed construction methods has been satisfactory in terms of construction period and construction cost, and the pressure vessel is first taken out from the inside of the shielding wall. Alternatively, it is necessary to dismantle and remove the shielding wall, so sufficient measures are essential in terms of ensuring work safety.

[0005]

In view of the above-mentioned circumstances, the invention of claim 1 is to remove the reactor pressure vessel from the reactor building while the shielding wall containing the pressure vessel is left as it is. A shielding container made of a steel plate for accommodating the pressure container is assembled inside the wall, and the inside of the shielding container is filled with mortar as a shielding material.

According to a second aspect of the present invention, when assembling the shielding container, an opening for working is provided in the shielding wall, and a steel plate welding operation is performed from the outside of the shielding wall through the opening.

According to a third aspect of the present invention, when the mortar as a shielding material is filled in the shielding container, the high activation portion is filled with mortar having a higher specific gravity than the other mortars.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, the most basic embodiment will be described with reference to FIGS. In the figure, reference numeral 1 is a reactor building, 2 is a reactor pressure vessel to be removed, and 3 is a reactor shielding wall (γ shield) provided around it. Conventionally, when attempting to collectively remove the pressure vessel 2 from the reactor building 1, the pressure vessel 2 is first taken out from the inside of the shield wall 3 or the shield wall 3 is disassembled. However, in the present embodiment, Without removing the pressure vessel 2 from the shield wall 3 and without removing the shield wall 3 in advance, the shield vessel 4 for accommodating the pressure vessel 2 is placed inside the shield wall 3 by a work from the outside of the shield wall 3. The main purpose is to assemble in.

The shielding container 4 in the present embodiment is made of a steel plate, and has an annular bottom plate portion 4a attached to the lower portion of the pressure container 2 and a cylindrical side plate portion 4b which is raised from the outer peripheral edge portion of the bottom plate portion 4a. It consists of The shielding container 4 has a shielding ability by itself, and also has a function as a mold for filling the mortar 5 as a shielding material inside.

Specifically, first, as shown in FIG. 2, an opening 6 for working is provided in the lower portion of the shield wall 3. 2A is a plan view of the shielding wall 3, and FIG. 2B is a developed view thereof.
As shown in (b), the openings 6 having a size of, for example, about 500 mm × 500 mm are provided at about 12 places at equal intervals.
The openings 6 can be provided without trouble by a wire saw or core boring, for example. It should be noted that by providing the opening portion 6 to this extent, there is no concern that the shielding wall 3 will collapse, and a stable self-standing state can be maintained as it is. In addition, these openings 6 are shielded steel plates 7 as shown in FIG. 1A except when it is necessary to open them for work.
It is preferable to block it.

Next, the bottom plate portion 4a of the shielding container 4 is attached to the lower portion of the pressure container 2. For this purpose, a fan-shaped steel plate 4c obtained by dividing the bottom plate portion 4a is hung between the shield wall 3 and the pressure vessel 2 by using an existing overhead crane 8, and the steel plate 4c is opened from the outside of the shield wall 3 to the above opening portion. Steel plate 4c which is welded to the lower portion of the pressure vessel 2 by the operation through 6 and is adjacent to the pressure vessel 2.
Weld one after another. The welding here may be performed with such an accuracy that the mortar 5 to be filled in the subsequent process does not leak out.

After the bottom plate portion 4a is annularly attached as shown in FIG. 1 (b), the side plate portion 4 is continuously attached as shown in FIG.
Attach b. To this end, a steel plate 4d manufactured in advance in the shape of a cylindrical divided body is hung between the shielding wall 3 and the pressure vessel 2 also using the overhead crane 8, and the lower end thereof is welded to the outer peripheral edge of the bottom plate portion 4a. And adjacent steel plate 4d
The parts are sequentially welded to each other to form the cylindrical side plate part 4b.

When the shielding container 4 is completed by assembling the bottom plate portion 4a and the side plate portion 4b as described above and the entire pressure container 2 is accommodated therein, the work stage 9
A mortar pressure-feeding device 10 is arranged on the upper side, and from there, a mortar 5 is filled as a shielding material in the shielding container 4 by a pressure-feeding hose 11, that is, in the entire annular space between the shielding container 4 and the pressure container 2 (of the mortar 5). (See FIG. 5 and FIG. 6).

After the mortar 5 has hardened, it is removed from the reactor building 1 by lifting the entire shielding container 4 accommodating the pressure container 2 or by disassembling the shielding wall 3 and then moving it horizontally. Then, if necessary, the main welding is performed again on the welded portion of the shielding container 4 to secure the structural strength and shielding performance of the shielding container 4.

According to the above construction method, excellent shielding performance can be ensured by the shielding container 4 and the mortar 5 filled in the shielding container 4, and the operation of accommodating the pressure container 2 in the shielding container 4 is left with the shielding wall 3 left. Since the work is performed from the outside, the shielding work for the pressure vessel 2 and the subsequent removal work can be safely performed, and cost reduction, exposure reduction, and shortening of the construction period compared to other conventionally conceived construction methods. Can be achieved.

The basic embodiment of the present invention has been described above, but a supplementary explanation and other embodiments will be listed below.

The size of the shielding container 4 for accommodating the pressure container 2 may be determined so as to secure a desired shielding thickness of the mortar 5, but normally the outer diameter of the pressure container 2 is 6.7 m.
The pressure vessel 2 and the shield wall 3 have a distance of 1 m.
Since there is a space between them, it is realistic to set the diameter of the shielding container 4 to about 7.7 m and the filling thickness of the mortar 5 to about 0.5 m. In addition, the total weight at the time of removal (the total weight of the storage container 4, the pressure container 2 and the mortar 5 inside thereof) exceeds about 1,000 tons, and as will be described later, the pressure container 2
Even if the inside is filled with mortar, the maximum amount is about 1,500 tons.

Prior to assembling the shielding container 4, it is necessary to attach a steel plate or the like to the nozzles for connecting pipes and other openings provided in the pressure container 2 for shielding. Also,
It is also preferable to fill the entire interior of the pressure vessel 2 or the high activation part with mortar as a shielding material as necessary. For that purpose, for example, the upper lid 2a of the pressure vessel 2 is opened as shown in FIG. , Mortar pumping equipment 1 inside
It is sufficient to fill mortar from 0.

Although the entire pressure vessel 2 is housed in the shielding vessel 4 in the above-described embodiment, a part of the pressure vessel 2 may be disassembled and removed in advance without causing any trouble. For example, as shown in FIG. 5 or FIG. 6, the upper lid of the pressure vessel 2 having a relatively low degree of activation and a part of its internal mechanism are removed in advance, and the remaining portion is used as a target for the bottom plate portion 4 by the above method.
a, the side plate portion 4b and the upper lid 4e are attached to the pressure vessel 4
Can be completed, which can reduce the total weight and size at the time of removal. FIG. 7 shows an example of the removal process in that case. (A) shows an opening 13 for removal provided in the ceiling slab of the reactor building 1 and is lifted by a crane 14 from there (b) ) Is one in which an opening 15 is provided on the wall surface of the reactor building 1 and is horizontally moved from there to be carried out.

The thickness of the steel plates 4c and 4d forming the shielding container 4 may be determined in consideration of the desired structural strength and the shielding performance of itself, but as shown in FIGS. It is also conceivable to increase the thickness of the steel plate 4d of the side plate portion 4b for the activation portion (for example, around the core shroud) to enhance the shielding performance there. It is also possible to attach a shielding steel plate 12 to the bottom of the pressure vessel 2 as needed, as shown in FIGS.

Further, it is conceivable that the specific gravity of the mortar 5 to be filled in the shielding container 4 is changed according to the filling position. That is, it is desirable to use a mortar having a high specific gravity (for example, 2.0 or more) in order to improve the shielding performance, but when the entire shielding container 4 is filled with such a high mortar, the total weight is large. Therefore, as illustrated in FIGS. 5 and 6, the mortar 5a having a high specific gravity is filled only around the core shroud and the like, which requires high shielding performance, and is low in other portions where shielding performance is not so required. It is conceivable to fill the mortar 5b with a specific gravity (for example, about 0.7). By doing so, it is possible to reduce the weight while securing the necessary shielding performance as a whole.

[0022]

According to the invention of claim 1, when the reactor pressure vessel is dismantled and removed, a steel plate for accommodating the pressure vessel inside the shielding wall while leaving the shielding wall for accommodating the pressure vessel. Since the shielding container is assembled and the inside of the shielding container is filled with mortar as a shielding material, excellent shielding performance can be ensured by the shielding container and the mortar filled inside the shielding container, as well as the shielding work for the pressure container and the subsequent operation. The removal work can be performed safely, and the cost and exposure can be reduced compared to other conventional methods.
And the construction period can be shortened.

According to the second aspect of the present invention, when assembling the shielding container, an opening for working is provided in the shielding wall, and the welding work of the steel plate is performed from the outside of the shielding wall through the opening, so that the shielding work is safe. It can be done without any trouble.

In the third aspect of the present invention, when the mortar as a shielding material is filled in the shielding container, the high activation portion is filled with mortar having a higher specific gravity than others, so that the shielding required as a whole is obtained. Weight can be reduced while ensuring performance.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, which is a diagram showing a step of attaching a bottom plate portion of a shielding container to a lower portion of a pressure container.

FIG. 2 is a diagram showing an example of installation of openings on the shielding wall.

FIG. 3 is a diagram showing a process of attaching the side plate portion of the shielding container.

FIG. 4 is a diagram showing a step of opening the upper lid of the pressure vessel and filling the interior with mortar.

FIG. 5 is a diagram showing an example of a case where the upper lid of the pressure vessel is removed and is housed in a shielding vessel.

FIG. 6 is a view showing another example of the case where the upper lid of the pressure vessel and a part of the internal mechanism are removed and housed in the shielding vessel.

FIG. 7 is a diagram showing an example of a removing process of the pressure container housed in the shielding container.

[Explanation of symbols]

1 reactor building 2 Reactor pressure vessel 3 Reactor shielding wall 4 Shielding container 4a Bottom plate part 4b side plate 5,5a, 5b Mortar (shielding material) 6 openings

Front Page Continuation (72) Inventor Sei Muramatsu 821-100, Funakawa Ishikawa, Tokai-mura, Naka-gun, Ibaraki Prefecture Within the Japan Nuclear Facilities Decommissioning Research Association (72) In-house Hisao Otsuka 821 Ishikawa, Tokai-mura, Naka-gun, Ibaraki Prefecture 100 Incorporated foundation Japan Nuclear Facilities Decommissioning Research Association (72) Inventor Jyo Matsuo 1-32 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Yoshiyuki Sakazume 1-chome, Shibaura, Minato-ku, Tokyo No. 2-3 within Shimizu Construction Co., Ltd. (72) Inventor Toshiro Watanabe 1-3-2 Shibaura, Minato-ku, Tokyo Within Shimizu Construction Co., Ltd. (56) Reference JP-A-62-203097 (JP, A) JP-A-2000-162388 (JP, A) JP-A-2000-206294 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21F 9/30 G21C 19/02

Claims (3)

(57) [Claims] 1. When removing a reactor pressure vessel from a reactor building, a shielding steel plate container for accommodating the pressure vessel is provided inside the shielding wall while leaving the shielding wall accommodating the pressure vessel. A method for removing a nuclear reactor, comprising assembling and filling the inside of the shielding container with mortar as a shielding material. 2. The atom according to claim 1, wherein, when the shield container is assembled, a work opening is provided in the shield wall, and a welding work of a steel plate is performed from the outside of the shield wall through the opening. Furnace removal method. 3. The mortar as a shielding material is filled in the shielding container with a mortar having a higher specific gravity than that of other portions in the high activation portion. Reactor removal method.