JPH01302200A - Decommissioning of nuclear reactor - Google Patents

Abstract

PURPOSE:To enable a removal of a large sized nuclear reactor, by constructing a temporary tank and a tank at an inside and an outside of a reactor building, respectively, and by transporting a main body of the nuclear reactor cut off from a structural body of the building in a floating condition on a liquid in each tank. CONSTITUTION:In a building 1, a liquid W0 is fed into a temporary tank, and then a main body 10 of a nuclear reactor is cut off in a water of a lower foundation 2 part, at a hung-down condition of the reactor by jacks 32. After that, the main body 10 is put down onto a carriage 35 stationed on rails 33 by disengaging the hung-down condition by the jacks 32 and, at the same time, water is fed into an inter-mediate tank 41 to raise its water level to the same level W1 as that of the tank 30. Then, after pulling up a water gate 91, the main body 10 is transported to the tank 41 by the carriage 35 and water W0 in the tanks 30 and 41 flows into a treatment tank 42 to make its water level be a level W2, by pulling up a water gate 44. Moreover, after transferring the main body 10 into a tank 42, a water gate 45 is pulled up and therewith the liquid W0 in the tank 42 flows out into a discharge tank 43 and the main body 10 settles down to a floor in the tank 42. After those procedures, the liquid W0 is solidified and, buried for ever with the main body 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for decommissioning a nuclear reactor main body, and specifically, after cutting the reactor main body from a building structure, moving it outside the building, This concerns a method of decommissioning a nuclear reactor by burying it underground for permanent disposal.

[Conventional technology] The lifespan of a nuclear reactor building is said to be approximately 40 years.

Japan Atomic Energy Research Institute's JRR-3 is the only example of decommissioning that has been experienced in Japan. In this example.

To remove the reactor body from the reactor building, first separate the reactor body from the surrounding structures, build a temporary frame around it, and lift it up using jacks that absorb the reaction force and a temporary runway. and moved. This method is applicable to the patent application (Japanese Patent Application No. 1156/1986) relating to the applicant's earlier invention.
No. 83, entitled "Method for Decommissioning a Nuclear Reactor").

This method focuses on removing the entire reactor body while keeping the main reactor internals inside the main shielding body.This method generates less radioactive waste and is more effective for controlling radiation for workers and for the environment. Not only is it suitable because it can prevent the spread of
Because no other alternative methods have been proposed, and because the building can be reused, it is thought that this method will remain the mainstream demolition method for the time being. but,
Because this JRR-3 nuclear reactor was on the scale of a research reactor,
This was possible only when the weight of the target reactor body was approximately 2.250 tons, but for larger reactors such as commercial reactors that will be targeted in the future, the above It must be said that this method also has some difficulties, and no proposals based on this perspective are known.

[Problems to be Solved by the Invention] The biggest issues regarding the removal of nuclear reactors during decommissioning are, firstly, the need for safety against radiation, and secondly, the large scale of the reactor. Therefore, in order to remove the reactor from the reactor building, move it, and dispose of it safely, it is necessary to not only prevent radiation from spreading into the environment, but also to prevent workers from being exposed to radiation from the contaminated reactor body. It is important that radioactive waste is not generated during demolition, and that large-scale structures must be handled efficiently.

Among the reactors currently in operation in Japan, Ibaraki-based Tokai No. 1 reactor (TK-
Including 1), the issue of decommissioning commercial-scale nuclear reactors in the near future is a matter that should be considered in the future, and the thermal output is approximately 50 times greater than the previous example.

The weight of the reactor body is about 10 times greater. Furthermore, the subsequent version will need to cover 300 times more of the target, and many problems remain, so it is necessary to start technical studies in a concrete manner as soon as possible.

[Means for Solving the Problems] The present invention aims to solve the above-mentioned problems in the method of decommissioning a nuclear reactor, and has been achieved through intensive research. Move the reactor body,
Although it is intended for final disposal at the destination, it is designed to be moved efficiently, especially for large reactor bodies.The existing reactor building is used as a temporary water tank, and the reactor The gist of the device is to float the main body on liquid so that it can be easily moved using buoyancy. The technical means adopted for this purpose are
In the decommissioning method of a nuclear reactor, the reactor to be decommissioned is removed from the reactor building in the form of the reactor body including the biological shield and buried underground for disposal. A temporary water tank is constructed indoors, and another water tank is constructed outside the building, and the reactor body, which has been cut from the building structure, is floated on the liquid in each tank and moved using buoyancy for final disposal. It is characterized by

[Example] The method for decommissioning a nuclear reactor of the present invention will be described in detail based on drawings showing examples. FIG. 1 is a schematic sectional view of a nuclear reactor building in which the present invention is implemented, and is intended for the above-mentioned TK-1.

In the figure, 1 is the building that houses the reactor, and the foundation 2
A large-scale structure 3 is constructed on top, and a nuclear reactor 5 consisting of a reactor core and a containment vessel is housed inside a heavy biological shield 4. 6 is an overhead crane above the nuclear reactor 5, 7 is a demolition shielding wall used for dismantling the nuclear reactor 5, and 8 is a demolition manipulator. Reference numeral 10 denotes a reactor body, and in the present invention, the inner part of the cut aC shown by a broken line in the figure, including the biological shielding wall 4 and the reactor 5, is collectively referred to as the reactor body.

To explain FIG. 1 in more detail, inside building 1,
Using the structures 3 of various parts around the reactor body 1o, reinforcing bodies 20 are constructed at various locations outside the cutting gc in preparation for cutting the reactor body 1o. In addition, this reinforcing body 20
A watertight structure is formed so as to form a temporary water tank 30 including the bottom plate. Therefore, as shown by the dotted line, the temporary water tank 3
The reinforcing wall 2o serving as the side wall of the liquid W injected into the inside
.

The water level shall be set at a height equal to or higher than the water level W. The part of the foundation 2 below the reactor 5 is reinforced by supplementing the thickness with concrete blocks 21, etc. below the slab.

In addition to putting lead plates, appropriate support posts 22 were installed in preparation for radiation.
I support it. Also, in the case of the reactor 5, the openings that will occur in each penetrating member such as ducts and piping due to dismantling will be closed watertight to prevent liquid from flowing into the reactor body 10, and the reinforcement of each part will be completed. For example, disassembly of the nuclear reactor 5 is started, and the reactor main body 1o is cut at the position of the cut 1c and separated from the structure 3. The demolition residue is loaded onto the transport vehicle T and discharged from the opening 23. However, in order to cut vertical members under the reactor body 10 under its own weight,
Since temporary support by the support columns 22 is difficult and requires a large number of supports, this cutting operation may be performed underwater after pouring water, which will be described later.

[Function] Next, the method for decommissioning a nuclear reactor of the present invention will be explained according to its steps with reference to FIG. (1) The figure schematically shows the first stage of starting the removal of the reactor main body 10.
The reactor main body 10 is separated from the foundation 2 and the structure part 3, and 9 is the TR of the building 1.

(2) The figure shows a temporary girder 31 spanning the structure 3 of the building 1 or another bridge above the reactor main body 10, and equipped with jacks 32 as lifting equipment to assist in levitation. Two stages are shown, and on the other hand, a state is shown in which the liquid W0 is injected into the temporary water tank 30 to a predetermined depth. Seawater is the most economically suitable liquid W0.
According to the inventor's estimate, the total weight of the reactor body 1o is approximately 2
1,000 tons, and its volume is approximately 36,000 cubic meters, so the depth of the temporary water tank 30 may be formed to be less than approximately 60% of the height of the reactor body 10. The temporary opening 23 in FIG. 1 is of course closed. At this stage, the operating part of the jack 32 is attached to the upper part of the reactor main body 10, and seawater is introduced into the temporary water tank 30 under its support, and the reactor main body is fixed while using the jack for assistance and adjustment. 1o is brought to the surface. On the outer wall of TR9 of the temporary water tank 30,
A water gate 91 is provided or left as an opening so as to be connected to a water tank 40 which will be described later.

(3) The figure shows a reactor main body 10 on one side adjacent to building 1.
This figure shows the third stage in which the aquarium 4o was formed. Water tank 40
is connected to or close to the building 1, has a side wall with a height higher than the water level W0 of the temporary water tank 3o, and is deeper than the temporary water tank 30; It consists of a large disposal water tank 42 with sufficient depth and width to completely bury the furnace body 10 under the ground, and a drainage tank 43, which will be described later.
The disposal water tank 42 is arranged so that the movement of the reactor body 10 is preferably in a straight line, and the liquid W in the temporary water tank 30 is removed by the water gate 91.

are now communicating. A water gate 44 and a water gate 45 are provided in the partition walls between the intermediate water tank 41 and the disposal water tank 42 and between the disposal water tank 42 and the drainage tank 43, respectively, and the water levels in the water tanks on both sides are adjusted by raising and lowering the water gates. be.

On the other hand, inside the building 1, liquid W0 is injected into the temporary water tank 30, and while the reactor main body 10 is suspended by the jack 32, the lower foundation 2 portion is cut underwater.

Next, a rail 33 for movement is laid from the floor of the building 1 below the reactor main body 10 to the middle stage of the intermediate water tank 41, and between the bottom of the intermediate water tank 41 and the disposal water tank 42, a rail 33 for movement of the lower stage is laid. rails 34 will be laid. At this point, release the jack 32 and move the reactor body 10 onto the rail 33.
Lower it onto the cart 35 above. Next, water is poured into the intermediate water tank 41 to the same water level W1 as the temporary water tank 30, and
The water gate 91 between the outer wall of the building and the intermediate water tank 41 is raised to equalize the water level W1 in both tanks, and while taking a reaction force to the building 1, the moving jack 36 is operated to move the cart 35 to the inside of the intermediate water tank 41. let Since the reactor body 10 on the trolley 35 is still under buoyancy, this moving work is carried out by the jack 3.
6. It does not require much force and can be easily moved by simply changing the position gradually. In the intermediate water tank 41, the rail 33 and the truck 35 are removed from below the reactor body 10, and the truck 35 is moved onto the lower rail 34. Next, water gate 4
4 gradually raise the seawater W inside the temporary tank 3o and the intermediate tank 41. is caused to flow into the disposal water tank 42. Therefore, when the water levels in the intermediate water 141 and the disposal water tank 42 reach W2,
The setting is such that all the seawater in the temporary water tank 30 is discharged. Here, the reactor main body 10 gradually sinks, reaches the bottom in the intermediate water tank 41, and is placed on the one carriage 35, as shown by the arrow.

(4) The figure shows the final stage of the removal method of the present invention, and shows a drainage tank 43 having the same depth as the disposal tank 42,
A water gate 45 is provided between the disposal water tank 42 and the disposal water tank 42 . In this example, the drainage tank 43 is installed below the intermediate water tank 41 in a layered manner. Here, the reactor main body 1o is moved into the disposal water tank 42 on the rails 34. In this case as well, the jack 36 may be operated by applying a reaction force to the side wall of the intermediate water tank 41. When the movement is finished, remove the rail 34 and truck 35 from below the reactor body 10 and raise the water gate 45.
Seawater W0 in the disposal tank 42 flows into the drainage layer 43,
The water levels in both tanks drop to W, and the reactor body 10 reaches the bottom in the disposal water tank 42. At this time, the entire reactor body 10 is completely underground, but since the seawater W0 in each tank is gradually becoming contaminated with radiation, a gelling agent is added to solidify it, and together with the reactor body 10. , be permanently buried. Thereafter, an artificial ground 5o is constructed on the upper surfaces of the intermediate water tank 41 and the disposal water tank 42, aligned with the ground surface, and the removal and disposal work is completed. The seawater used for the above work is set so that the capacity of each tank is mutually distributed, and of course, it is ensured that it does not remain on the ground as contaminated water. In addition, the construction head seat does not have to be limited to the above order, and
The arrangement of each water tank is also not limited to this example.

In this embodiment, the intermediate water tank 41 is provided and the reactor body 10 is buried underground in the disposal water tank 42, but the disposal water tank 42 is connected to the reactor building without providing the intermediate water tank 41. It may also be implemented by providing a The method of moving the reactor body 10 in this case is the same as described above.

[Effects of the Invention] The present invention provides a nuclear reactor in which a nuclear reactor to be decommissioned is removed from a reactor building in the form of a reactor body including a biological shield, and disposed of by being buried underground. In the decommissioning method, a temporary water tank is constructed inside the reactor building, and a water tank is also constructed outside the building, and the reactor body, which has been cut from the structure of the building, is floated on the liquid in each tank to create buoyancy. The method is to move the used state for final disposal, and since this method is concretely achieved, large atomic A method for moving the furnace body as it is can be provided. In addition, the construction of the water tank will utilize the structure of the reactor building, and will be used in the Gregorian Group, which will permanently dispose of the reactor itself as it is for final disposal.
Since it will be used as a yard, the temporary facility will only require the construction of a water tank and a water gate, and these will make it possible to remove a large nuclear reactor, which is currently considered impossible. It can be worth it. Furthermore, the liquid used is water or seawater, and its buoyancy is utilized, so the cost is low, and large lifting equipment is not required, so its effects are noteworthy. .

[Brief explanation of the drawing]

The drawings show an example of the object of the decommissioning method of a nuclear reactor according to the present invention, and FIG. 1 is a cross-sectional view showing the entire reactor building, and each figure in FIG. It is a schematic sectional view explaining a process in order. 1... Reactor building, 2... Foundation, 3... Structure,
4... Biological shield, 9... Lower layer, 10... Reactor main body, 2°... Reinforcement body, 30... Temporary water tank, 32...
...lifting equipment, jack, 33,34...rail, 3
5... Trolley, 36... Jackpot, 40... Water tank,
41... Intermediate water tank, 42... Disposal water tank, 43...
Drainage tank, 44.45,...sluice gate, 50...artificial ground, 91...sluice gate, Wo...liquid, seawater, Wl, Wyo, W,...water level, C...cutting line. Fig. 1 1 Reactor building 7 Demolition shielding wall 2 Keiza 8 Manipulator 3 Purchased body 10 Reactor body 4 Raw 47$ shield
2o Reinforcement body 5 Haraze 30 A Reverse installation water I Tomoe 6
Overhead crane WO liquid, seawater C cutting line
W+ Tree grove 2nd figure and

Claims (1)

[Claims] (1) In a method of decommissioning a nuclear reactor, the reactor to be decommissioned is removed from the reactor building in the form of the reactor body including the biological shield, and disposed of by being buried underground. A temporary water tank is constructed inside the reactor building, and a water tank is also constructed outside the building, and the reactor body, which has been cut from the building structure, is floated on the liquid in each tank and moved using buoyancy. A method for decommissioning a nuclear reactor, characterized by final disposal.