JPS60211396A - Method of preventing permeation of radioactive contamination - 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 the prevention of secondary contamination during the demolition of radioactively contaminated concrete structures such as shielding walls and reactor foundations in nuclear power plants.

The useful life of a nuclear power plant is said to be 30 to 40 years), and it is expected that the number of nuclear power plants reaching the end of their service life will increase in Japan in the future. Nuclear power plants contain a large amount of radioactivity, so it is not possible to tear them down like a normal building.The only way to dispose of a power plant that has reached the end of its lifespan is to manage it in a sealed manner or shield it. However, from the standpoint of securing land for a future power plant, it is desirable for Japan to demolish and remove the site and construct a new power plant on the site.

However, when it comes to dismantling, it is often problematic to simply apply conventional demolition techniques for buildings and structures.In particular, biological shielding walls and thermal shielding walls surrounding the reactor body are susceptible to radioactive contamination. It is conceivable that the degree of radioactivity may be significant, and that the decay period of radioactivity may extend over a long period of time. The structure near the reactor core is composed of a combination of metal liner and reinforced concrete, and is highly contaminated by radioactivity.

When dismantling such a structure, in addition to debris and dust from metal walls and reinforced concrete near the reactor core, which are highly radioactively contaminated, water, oil, fats, and
Or, the smoke and gases generated by demolition work come into contact with low-contamination areas or debris, spreading the radioactively contaminated area, or increasing the radioactive contamination, so-called secondary damage. Contamination occurs.

Figures 1 and 2 show an example of the structure of a nuclear reactor shielding wall to explain the above-mentioned problems. It is a detailed sectional view.

The living body or heat shielding wall surrounding the reactor body 10 is composed of a metal wall 1 made of a steel plate or a stainless steel plate and a reinforced concrete structure 2, 3.4, where 2 and 3 are the reactor body 10.
4 is a highly contaminated area close to the furnace body 10, and 4 is a low contaminated area far from the furnace body 10.

Due to the risk of radioactive contamination, workers cannot directly remove the children during this dismantling process, and the work must be carried out by remote control or robots. In addition, the debris generated by this demolition naturally has different degrees of contamination, such as the demolition debris 1', 2', 3' in the area with a high degree of contamination and the demolition debris 41 in the area with a low degree of contamination. Since the treatment methods are also different, it is necessary to avoid mixing highly contaminated fragments and fragments with low contamination. At the same time, highly contaminated fragments 1', 2', 3'
Contact with reinforced concrete 4 in areas with a low degree of contamination must also be avoided. Therefore, during demolition, it is necessary to carry out the demolition in a sequential manner to avoid mixing or contact of highly contaminated metal and concrete pieces with less contaminated items. It is extremely difficult to carry out demolition in such a way that the water, oils and fats used, as well as the smoke and gases generated during demolition work, do not come into contact with low-contamination areas.

The present invention was made in order to solve the problem of secondary contamination during demolition as described above, and the method includes:
Anti-pollution paint is applied to exposed concrete surfaces before and during demolition using a painting device equipped with a remotely operated spray gun and a television camera to confirm the application location.
This is a method for preventing permeation of radioactive contamination, in which dismantling is carried out sequentially while preventing secondary contamination due to fluids and scattered powder particles.An example of the method will be explained below with reference to the drawings.

FIG. 3 is a drawing showing a side sectional view of the reactor building after the reactor main body 10 has been removed, 11 is the external foundation, and the external shielding wall 12 is assembled on this foundation 11. It will be done.

A machine loading hole 13, an entrance/exit 14, etc. are provided on the side of this external shielding wall 12, and an overhead lane 15 is provided in the upper part of the building. There are 10 reactor bodies in the building.
A living body shielding wall 16 is provided surrounding the body, and a portion of the inner surface of this living body shielding wall 16 facing the reactor body 10 is constituted by a metal wall 17 for lining, and a portion immediately on the outer periphery of this metal wall 17 is constructed of a metal wall 17 for lining. Reinforced concrete walls 18 and 19 are reactor body 1
Metal wall 17 in areas exposed to high concentration of radiation
The reinforced concrete walls 18 and 19 are areas with a high degree of radiation contamination, and the surrounding reinforced concrete walls 20 are areas with a low degree of radiation contamination.

FIG. 4 is an enlarged view of the bio-shielding wall 16, showing a state in which anti-contamination paint is being applied to the reinforced concrete wall 20 which is being dismantled. In this figure, 21 is a coating device, and this coating device 21 includes a control section 22 and two operating cylinders 23, 23.
' A horizontal arm 24 that can be rotated;
a vertical arm 25 that is attached to the tip of the vertical arm 25 and is extendable and retractable in a downward vertical direction;
It is composed of a painting spray gun 26 that can be moved up and down and a television camera 27 that confirms the painting position. The rotation of the horizontal arm 24, the extension and contraction of the vertical arm 25, and the spray gun 26. The operation of the television camera 27 is controlled by a control unit 22, and the control unit 22 is further controlled remotely or externally by a remote control device 28 provided separately. Paint, water, compressed air, and power are introduced into the control unit 22 through an introduction pipe 29, and the power is supplied to the horizontal arm 24. Vertical arm 25, spray gun 26. It is supplied as an operating power source for the television camera, and paint, water, and compressed air are supplied to the spray gun 26 according to the operation of the spray gun 26.
In the dismantling of the biological shielding wall 16, the coating device 21 is selectively supplied with O.
is installed on the top surface 30 of the biological shielding wall 16, and is remotely controlled to apply anti-contamination paint to the inner and outer surfaces of the structure of the biological shielding wall 16, exposed concrete surfaces such as the top surface, and the surface of the metal wall 17. After applying the paint used here,
Use a paint that hardens quickly and is insoluble and impermeable to water, such as vinyl or epoxy. Next, the living body shielding wall 16 is dismantled, and for this disassembly, the living body shielding wall 16 is cut and dismantled into blocks using, for example, a cutting jet made by mixing an abrasive with a high-pressure water jet. 31) in the figure are sequentially removed to lane 15 for overhead running. Next, the above-mentioned resin-based paint is applied to the fractured surface 31' of the concrete and metal wall by the coating device 21. In this case, the area where the degree of contamination by radiation is the same, that is, the metal wall 17 and the reinforced concrete wall 18.1
After all the demolition in the area 9 is completed, a resin-based paint may be applied to the broken surface of the demolition. In addition, if a high-pressure water jet is used as the cutting means used during cutting and disassembly, the broken surface may have moisture and chips attached to it, making it difficult for resin-based paint to adhere to it. Pretreatment is required, such as spraying fresh water using the resin coating spray gun 26 to clean the coated surface, and spraying dry air with the other spray gun 26 to dry the coated surface. In this case, the pretreatment status and coating status of the coated surface are imaged by the television camera 2T, which is displayed on the image receiver of the remote control device 28 and confirmed before proceeding to the next step. The above-mentioned method is repeated sequentially to proceed with the dismantling work. In this embodiment, the case where the biological shielding wall 16 is dismantled by a high-pressure water jet is explained, but this seepage prevention method This also applies when a vehicle is dismantled using mechanical cutting, blasting, etc.
Anti-contamination paint is sequentially applied to the broken surfaces of the demolition.

As explained above, the method of preventing permeation of radioactive contamination according to the present invention is effective in preventing radioactive contamination from seeping through.

It is particularly effective in preventing secondary contamination due to adhesion, leakage, and seepage of dust, water, oil, and smoke and gas generated during demolition work, and it can be operated remotely. If done safely, the degree of contamination can be easily determined by color, and post-processing of radioactive demolition blocks, debris, etc. based on the degree of contamination is easy. However, this method is also effective in terms of work management.

[Brief explanation of drawings]

Figure 1 is a side sectional view explaining the structure of the reactor shielding wall, Figure 2
The drawings are a detailed partial sectional view of FIG. 1, FIG. 3 is a side sectional view illustrating the dismantling of the reactor shielding wall, and FIG. 4 is a partial side sectional view illustrating the painting procedure. 10... Reactor main body 12... External shielding wall 13...
- Loading hole 14... Entrance/exit 15... Lane for ceiling running 16... Living body shielding wall 17... Metal wall 18
, 19, 20...Reinforced concrete wall 21...Painting device 22...Control unit 24...Horizontal arm 2
5... Vertical arm 26... Spray gun 2T...
・TV camera 28...Remote control device 29...Introduction pipe 31...Dismantled block 31'...Fracture surface Applicant Hazama Co., Ltd. Patent attorney Yuji Taka, -" Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] During the demolition of concrete structures contaminated with radioactivity, the exposed surfaces of the concrete are coated with paint equipment equipped with a remotely operated spray gun and a television camera to confirm the application location before and during demolition. A method to prevent radioactive contamination from penetrating by applying anti-contamination paint and gradually dismantling buildings while preventing secondary contamination from fluids and scattered particles.