JPS6067899A - Method of washing radioactivity contaminated vessel - 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] [Field of Application of the Invention] The present invention relates to a pressure suppression chamber (
This article relates to a method for cleaning when the inner walls and internal structures of a donut-shaped container such as a torus are contaminated with radioactive substances.

[Background of the invention]

In nuclear power plants, cleaning of pressure suppression chambers contaminated with radioactive materials has been reported in the United States.
A suction port is attached to the tip of a ~6m ball, and the contaminated water sucked up by the operation of a worker in the pressure suppression chamber is filtered through an external filter, and the filtered water is returned to the pressure suppression chamber. It's a method.

After removing the general contaminants, drain the water in the pressure suppression chamber,
Finish cleaning is carried out by spraying high-pressure water inside the pressure suppression chamber through manual operation by a worker. In the cleaning method reported in the United States, in order to work over a wide area under the water surface from about 5 meters above the surface to be cleaned, depending on the sense of the worker, the water level is lowered while the contaminated material remains and the next step is carried out. There is a risk of moving to. If contaminants remain, there is a risk of the following, so it is necessary to minimize the amount of contaminants remaining.

Danger if contaminants reach the water surface.

1) Water, which is effective for shielding, will be discharged and the dose will increase, potentially exposing workers to radiation.

2) Fine contaminant particles attached to the surface of internal structures come out onto the water surface, where the moisture dries and partially diffuses into the air, which may cause internal radiation exposure to workers.

[Purpose of the invention]

In order to deal with the risk of worker exposure to radioactive substances mentioned above, the purpose of the present invention is to install an automatic cleaning device above the liquid level at a time when a water shielding effect can be expected before it is contaminated with radioactivity or before it is drained. This system provides a safe cleaning method by installing a container and operating it from outside the container.

[Summary of the invention]

Conventionally, general container inner surfaces are cleaned using a device called a cleaning ball, which is a collection of many injection nozzles, or
An omnidirectional automatic cleaning nozzle, etc., which sequentially moves the nozzle jet direction in all directions three-dimensionally by rotating and revolving around its axis, was attached to the tip of the universal joint to perform automatic cleaning. The above method was devised for cleaning relatively small and simple containers, 1 and was not applicable to cleaning the inside of large donut-shaped containers.

In the present invention, a large number of omnidirectional automatic cleaning nozzles or reversing spray nozzles, etc. are installed on a ring-shaped virtual line connecting the center points of each cross section of the donut on the liquid surface, or a mole rail, etc. for moving the spray nozzles is installed. However, by operating from the outside of the container, the risk of worker exposure to radiation is minimized and the inside of the donut-shaped container can be easily cleaned.

[Embodiments of the invention]

An embodiment of the method for cleaning a container according to the present invention when the inner bottom of the container is contaminated by deposition of radioactive substances will be described below in detail.

FIG. 1 is a perspective view of a donut-shaped container to be cleaned, and FIG. 2 is a plan view.

In FIGS. 1 and 2, the donut-shaped container 4 has a diameter of about 8 mm.
It is a doughnut-shaped pipe with a center diameter of about 30 meters, and about 1,700 meters of fluid enters inside. A walkway 9 is installed around the entire circumference above the internal liquid level. A drainage pump 2 is installed at the bottom of the container. At the same time, the discharge pipe 1
3 is connected to the discharge pipe 6, a large number of automatic sprayers 1 are installed on the liquid surface, and the pressure water introduction pipe 14 is connected to the water supply pipe 5.

The above describes the operation of the electric circuit for pump operation and the electric water supply adjustment valve 10 so that the automatic spray and drainage can be divided into four parts and operated one quarter at a time as shown in A, B, C, and D shown in Fig. 2. Form a circuit.

After the above preparations are completed, the drainage pumps are started in the order of A, B, C, and D for a certain period of time by operation from outside the container.
The fluid at the bottom of the container is passed through a drain pipe 6, radioactive solids are separated by a filter 3 installed outside, and then the fluid is discharged to a predetermined location.

Filter 3 is stored in a shielded container, and when the external surface reaches a specified dose, or when the differential pressure across the filter, which is an indicator of the maximum solids collection capacity of the filter, reaches a specified differential pressure. Replace filter 3 with a separately prepared spare filter.

At the same time as the drainage pump 2 is started, the liquid level drops and the radioactive particles adhering to the surface of the structure in the liquid dry up, and in order to prevent the spread of contamination into the air, automatic sprays 1 and A are applied. B, C, I') are activated sequentially for a certain period of time.

By setting the total discharge amount of the automatic spray 1 to J-amount from the total discharge amount of the drain pump 2, almost the entire amount of fluid is finally discharged, and at the same time, the cleaning of the structure surface is completed.

In order to confirm the cleaning method described above, a portion corresponding to about 1/60 of the donut-shaped container is shown in FIG.

The results of an experiment conducted by installing two automatic sprayers 1 and one drainage pump 2 in the horizontal container 15 are shown below.

Conditions 1) Input simulated contaminated particles 2) Automatic spray orifice diameter 6.4 Nozzle injection angle 80° Nozzle swing angle 180° Nozzle swing speed 4°/@l Spray pressure 6F-g/cm" Injection water amount 55t/drink / Unit operating time (a) Wet operation: Run for 3 minutes, stop for 5 minutes, and repeat several times.

(b) Cleaning operation: Run for 15 minutes, stop for 45 minutes, and repeat the cycle 8 times.

3) Drainage pump discharge capacity: 100 t/total shrine head: 12 m Operating method: As a result of experiments under conditions of continuous operation or higher, the removal rate was 88% when AlF 630 m was used as a simulated contaminant particle, and A2F e 203
When these particles were used as simulated contamination particles, the removal rate was 92%, and a very good decontamination effect was obtained.

Next, a modified example and an application example will be shown.

1) In Fig. 3, automatic spray 1 is > sloppy spray angle 8
Although 0' and 1800 inverted spray nozzles were used, it is possible to clean the upper inner surface of the container with a nozzle that moves three-dimensionally, that is, rotates and revolves at the same time.

2) In Fig. 2, automatic sprayer 1 and drain pump 2
Although the operation is divided into four parts such as A, B, C, and D, it is not necessarily divided into four parts, and other division plans may also be applied depending on the size of the container, the degree of contamination inside the container, and the water supply and drainage capacity. It is.

3) If there is not enough water supply and drainage capacity, it is possible to reduce the actual amount of water supply and drainage by using the return piping 7 shown in Figures 1 and 2 to make all or part of the drainage water into spray water. be.

4) In Fig. 1 and Fig. 2, the method of installing a large number of automatic sprayers 1 was explained, but as another method to obtain the same effect, as shown in Fig. A similar effect can be obtained by installing the movable spray 11 on the connecting point and automatically running the movable spray 11 on the mole rail.

〔Effect of the invention〕

According to the present invention, it is possible to safely and efficiently automatically clean the inside of the donut-shaped container from radioactive substance contamination by remote control from outside the container.

[Brief explanation of drawings]

FIG. 1 is a partial perspective view of the donut-shaped container, FIG. 2 is a plan view, and FIG. 3 is a perspective view showing an experimental situation using the donut-shaped container. 1... Automatic spray, 2... Drain pump, 3...
Filter, 4...Doughnut-shaped container, 5...Water supply piping, 6...Drainage piping, 7...Return) piping, 8...Manhole, 9...-Walkway, 10...Water supply Adjustment electric valve, 11...mobile spout ♀1 figure 2nd prisoner

Claims (1)

[Claims] 1. When fluid stagnates in the donut-shaped torus of a nuclear power plant and radioactive materials are deposited or attached to structures below the liquid surface and the inner walls of the container, a ring is automatically placed on the liquid surface near the center of the container. After installing a large number of cleaning devices or installing automatic cleaning devices on rails that can be moved in a ring shape, the fluid is discharged to the outside of the container by operation from outside the container, and at the same time, radioactive contaminants are removed by automatic cleaning. A method for cleaning radioactively contaminated containers, characterized by rinsing away radioactively contaminated containers.