The method of cleaning surfaces from radioactive contamination

 

The invention relates to the field of decontamination of objects. The inventive method of cleaning the surface from radioactive contamination by handling contaminated surface water decontamination solution with the subsequent removal of spent decontamination solution. When handling contaminated surfaces is carried out in a confined space decontamination solution by exposure to contaminated surface cavitating flow decontamination solution. The difference between the pressure of the flow of the decontamination solution and the static pressure of the closed volume of the decontamination solution is 0.4-0.6 MPa, and the treatment of contaminated surface is conducted at the temperature of the decontamination solution 18-22°C. advantages of the invention lie in the fact that provide fast and high-quality processing of the contaminated surface. 1 C.p. f-crystals, 2 Il.

The invention relates to a method of cleaning surfaces from radioactive contamination, namely the internal decontamination of closed surfaces of technological equipment at nuclear technology.

Currently the key, is a closed surface heat exchangers, process piping, tanks, etc., during operation on the inner surfaces of this equipment appear combined deposits, which consist of salt deposits circulating solutions, while simultaneously containing radioactive contamination. During repair, maintenance or replacement of such equipment is necessary to clean the internal surfaces of equipment, such as from radioactive contamination - decontamination and other polluting sediments.

Existing methods of decontamination on the mechanism of their action can be divided into three groups:

- based on mechanical removal of dirt;

- based on partial dissolution of radioactive substances in the surface water or organic solvents;

based on the physico-chemical processes.

Physico-chemical methods of decontamination include the surface treatment of complex decontamination solutions.

The well-known "Method of decontamination of metal surfaces in nuclear power reactors" (MKI G 21 F 9/00, EPO application No. 0138289, publ. 1985). The method is carried out by processing zahrt water, and then treated with an aqueous alkaline solution at a temperature of 70-200°C.

Also known "Method of decontamination of metal surfaces" (MKI G 21 F 9/30, Pat. France No. 2644618, publ. 1990). The method consists of sequentially performed operations lasting two hours each, and provides a surface treatment first oxidizing aqueous solution, and then recovery. The process is conducted at a temperature of 70-95°C.

The well-known "Method of decontamination equipment (MCI G 21 F 9/30, Japan's bid No. 60-50320, publ. 1985). Cleaning contaminated surfaces carry out chemical or mechanical method using water under pressure and the subsequent formation on the cleaned surface oxide film.

The disadvantages of these methods of decontamination include:

- the duration of the decontamination process;

- the need for heat decontamination composition and maintaining the process temperature at least 70°C.

- the complexity of processing the resulting liquid radioactive waste (LRW) and solid radioactive waste (SRW).

A known process for the decontamination of surfaces using aqueous decontamination solutions (C. M. Gorodinsky, D. S. Goldstein. Decontamination polymeric material is contaminated surface water decontamination solution and subsequent removal of spent decontamination solution, including radioactive contamination.

The disadvantages of this technology should include the fact that when washing contaminated surface transition radioactive component in the decontamination solution is only of a very thin outer layer in contact with the decontamination solution. The process of decontamination in such conditions is very slow only due to chemical reaction and subsequent removal of the reaction products of spent decontamination solution.

Cleaning of surfaces from other contaminants that do not have a radioactive component, carried out in other ways.

Known "Method of cleaning hole PCB" from micro inclusions due to exposure to contaminated surface cavitating jet stream of fluid at a certain pressure drop (patent RF №2074537, IPC H 05 To 3/26, publ. 24.01.94).

Reasons preventing the use of this method are:

- the possibility of secondary radioactive contamination on the surfaces due to the low capacity of binding of radionuclides in the cleaning liquid;

the inability to clean the surface with a large layer of fat, as this method is recommended for cleaning only microsc the deposits" (RF application No. 99110613, IPC In 08 In 9/04, publ. 13.05.99). The method consists in the generation of shock waves at the entrance to the pipeline, sharp applying pulses of compressed air under high pressure and discharge of contaminated liquid and the filling and discharge are carried out through the set in a single closed loop.

The disadvantages that hinder the use of the present invention is the possibility of secondary radioactive contamination of surfaces of pipelines.

The closest way to clean the surfaces of radioactive contamination to the claimed combination of essential features is the method of cleaning surfaces described in the information source "Decontamination of polymeric materials" authors S. M. Gorodinsky, D. S. Goldstein, who is selected as a prototype.

Thus, the problem to which the present invention is directed, is formulated as follows: clean closed surface from radioactive contamination and at the same time from other deposits of non-radioactive nature

- reduction of time of the process;

- carrying out the process at room temperature (18-22°C);

- the absence of secondary radioactive contamination of the surface being cleaned;

- the possibility of the material) layers of sediment.

The technical result from use of the present invention is to significantly reduce time to decontamination works in a confined space through a combination of decontamination and cavitation flow properties. The internal surfaces of the equipment and pipelines at the same time clear of various types (including different thicknesses) of contaminants, including radioactive. Simultaneously, significantly reduces energy costs and consumption decontamination solution due to its repeated use. There is no secondary radioactive contamination of the cleaned surface, which significantly increases the efficiency of decontamination. Using a closed loop circulation decontamination solution allows you to create environmentally safe decontamination process.

This technical result is achieved by the fact that the applied method of cleaning the surface from radioactive contamination by handling contaminated surface water decontamination solution with the subsequent removal of spent decontamination solution, and the treatment of contaminated surface is carried out in a confined space decontamination solution through between the pressure of the flow of the decontamination solution and the static pressure of the closed volume of the decontamination solution is 40-60 ATM (0.4-0.6 MPa), and handling contaminated surfaces are at a temperature of decontamination solution 18-22°C.

If you want to ensure closed-loop cleanup with reuse decontamination solution, preferably after removal of the spent decontamination solution is recycled for separation of radioactive and mechanical components of the contamination, and after processing, decontamination solution re-directed to the treatment of contaminated surfaces.

The characteristics specified in the claims, are necessary and sufficient, i.e., are essential.

The proposal is not known from available sources of information, is not obvious from the prior art and thus is industrially applicable as a method of decontamination, i.e. meets all the eligibility criteria under the current legislation.

The proposed method (schematically) is illustrated by drawings:

In Fig.1 is a schematic representation of the cycle of implementation of the decontamination of the inner closed surface of the pipeline. In Fig.2 presents a vicious cycle, where:

1 - generator cavitation flow;

2 - pipe;

3, the internal surface of truboprovodservice);

6 - system processing of spent decontamination solution;

7 - supercharger decontamination solution.

The method is implemented as follows.

Generator cavitation stream 1 is introduced, for example, by means of rod, pipe 2, the inner surface 3 of which is to be cleaned (decontaminated). Decontamination solution 4, the temperature of which 20±2°With, served in the volume of the pipeline 2 for decontamination its inner surface 3 using the supercharger decontamination solution 7. At a certain value (0.4-0.6 MPa) difference between the pressure of the flow of the decontamination solution 7 from the nozzle hydro-cavitation generator 1 and the static pressure of the closed volume of the decontamination solution of 4 formed through the device to ensure zatoplennoe 5, the formation of gas bubbles which are in contact with the surface being cleaned collapse with the formation of small explosions, due to which there is intense destruction of deposits on the surface. Moreover, the surface remains intact.

The process of decontamination of the inner surface 3 of the pipe 2, depending on the type of sediment is carried out at a speed of 0.1-1.0 m/min the speed>the ATEM spent decontamination solution is removed (Fig.1) the volume of cleaned pipe 2.

To implement closed loop (Fig.2) decontamination of spent solution sent for recycling 6 to separate radioactive and various salt deposits. Recycled decontamination solution is recycled through the compressor 7 in the cleaned pipe 2 or in another volume of cleaned equipment.

In the present invention the optimum conditions for the process of decontamination is provided at a pressure drop of 0.4-0.6 MPa.

Experimental studies show that when the differential pressure below 0.4 MPa intensity of the process of cavitation erosion sharply.

When the difference is above 0.6 MPa intensity process does not increase and therefore does not make sense to increase the differential pressure.

Changing the solution temperature does not lead to abrupt changes in the efficiency of the process, so the cost of heating the solution impractical.

As a result of application of the proposed method of cleaning does not occur secondary radioactive contamination of surfaces.

In this way the possible cleaning of surfaces with a high degree of relationship to the thickness of the contamination to the diameter of the ü surfaces does not exceed the values specified in the norms of radiation safety NRB-99 for the accepted premises.

The traditional method of decontamination using liquid decontamination solutions is carried out for ~4-6 hours before the establishment of chemical equilibrium, the proposed method of decontamination is carried out in several minutes.

In the proposed method of decontamination in comparison with the prototype of the decontamination efficiency in 100-1000 times higher. (Kdthe decontamination factor, and its value determines the efficiency of cleaning the surface from contamination and the presence of secondary contamination).

Using the proposed method allows to carry out the process without heating, to repeatedly clean one solution to reduce the time of the decontamination process and to exclude secondary radioactive contamination of the processed surfaces.

These results are achieved by a combination of decontamination properties of the solution and properties of the cavitating flow at a certain value of the differential pressure and low temperature (18-22°C).

Thus, the present invention aims at solving the problem and meets all the eligibility criteria under the current legislation.

Way Coho region and Smolensk NPP.

Claims

1. The method of cleaning the surface from radioactive contamination by handling contaminated surface water decontamination solution with the subsequent removal of spent decontamination solution, characterized in that the treatment of contaminated surface is carried out in a confined space decontamination solution by exposure to contaminated surface cavitating flow decontamination solution, the dierence between the pressure of the flow of the decontamination solution and the static pressure of the closed volume of the decontamination solution is 40-60 ATM (0.4-0.6 MPa), and the treatment of contaminated surface is conducted at the temperature of the decontamination solution 18-22°C.

2. The method according to p. 1, characterized in that after removal of the spent decontamination solution is recycled for separation of radioactive mechanical components of the contamination, and after processing, decontamination solution re-directed to the treatment of contaminated surfaces.



 

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