JP2009052955A - Decontamination liquid, decontamination method, and decontamination system of radioactive contaminant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decontamination liquid, a decontamination method and a decontamination system of a radioactive contaminant capable of performing simple decontamination processing, and reducing a load imposed on an environment. <P>SOLUTION: The decontamination liquid of the radioactive contaminant wherein water is used as a solvent, includes as organic acids as much as 0.4-50% in total, one or two or more species of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid. In the decontamination method, the radioactive contaminant is dipped into the decontamination liquid. The decontamination system of the radioactive contaminant has a determination means 2 for determining a radioactive contamination level of the radioactive contaminant 5; a multi-stage cleaning tank 3 into which the decontamination liquid 1 is injected, wherein the radioactive contaminant 5 selected corresponding to determination is dipped and subjected to multi-stage cleaning; and a means 4 enabling reuse of the decontamination liquid 1 used for decontamination. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radioactive contaminant decontamination solution, a decontamination method, and a decontamination system, and in particular, a decontamination solution, a decontamination method, and a decontamination system for a radioactive contamination tool used in a radiation control area such as a nuclear power plant. In particular, the present invention relates to a decontamination solution, a decontamination method, and a decontamination system for making a tool used and contaminated in a radiation management area reusable in the management area.

  When working in radiation control areas such as nuclear power plants, dedicated tools are rented out. Some tools returned after work are contaminated with radiation at a low level. Currently, contaminated tools are stored in a controlled area, and are finally drummed as radioactive waste. As a result, the amount of radioactive waste is increasing. Therefore, it is considered to decontaminate and reuse the contaminated tool.

  The invention of Patent Document 1 relates to a radioactive decontamination reagent. In this document, a radioactive radioactive decontamination agent mainly composed of orange oil is applied to radioactive contaminants and then wiped off with gauze. A dyeing method has been proposed.

  The invention of Patent Document 2 relates to a method and an apparatus for decontaminating radioactive contaminants. In this document, an organic solvent containing methylene chloride as a main component is injected while the radioactive contaminants are accommodated in a decontamination treatment tank. The NTA-based chelating agent is mainly used for radioactive contaminants that are exposed to radioactive contaminants, promote softening and thinning of radioactive materials and coatings attached to radioactive contaminants, and expose the surface. A decontamination method for removing a metal oxide by bringing a derusting agent into contact therewith has been proposed.

  The invention of Patent Document 3 relates to a radioactive material decontamination method and a chemical decontamination apparatus. In the same document, an alkali decontamination using an alkali decontamination agent (such as sodium silicate) is performed on a decontamination target generated from a nuclear facility. And an acid decontamination step using an acid decontamination agent that combines 0.1 to 0.3% organic acid (such as citric acid) and 0.5 to 1.5% inorganic acid (such as sulfuric acid). Combined radioactive material decontamination methods have been proposed.

JP 62-165199 A JP-A-6-59094 JP 2006-78336 A

  According to the radioactive decontamination method of the above-mentioned Patent Document 1, there is a problem that the cleaning power of orange oil mainly composed of limonene is not sufficient, and it is difficult to wipe a complicated shape because the decontamination agent is creamy. There is a problem that it takes time to dispose of the gauze.

  According to the method for decontaminating radioactive contaminants in Patent Document 2, since an organic solvent is used, there is a problem in that the waste liquid treatment is troublesome and the decontamination apparatus is enlarged.

  According to the radioactive substance decontamination method of the above-mentioned Patent Document 3, since two steps of an alkali decontamination step and an acid decontamination step are required, it takes time to prepare two kinds of liquids and waste liquid treatment. For this reason, there is a problem that the apparatus for the purpose is enlarged.

  An object of the present invention is to provide a decontamination solution, a decontamination method, and a decontamination system for radioactive contaminants that simplify the decontamination process and reduce the load on the environment.

In the first aspect, the present invention includes 0.4 to 50% in total of one or more of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid as the organic acid, Provided is a decontamination solution for radioactive contaminants whose solvent is water.
In the second aspect, the present invention provides a radioactive contaminant as an organic acid, and a total amount of one or more of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid is 0.4 to Provided is a method for decontaminating radioactive contaminants which is immersed in a radioactive contaminant decontamination solution containing 50% of water as a solvent.
In a third aspect, the present invention provides a decontamination system for radioactive contaminants, a determination means for determining the radioactive contamination level of radioactive contaminants, and organic acids such as malic acid, citric acid, formic acid, oxalic acid, One or two or more of glyceric acid, tartaric acid and glycolic acid is contained in a total amount of 0.4 to 50%, and the solvent is water. A radioactive contaminant decontamination solution is injected and selected according to the above determination. Provided is a radioactive contaminant decontamination system having a multistage cleaning tank in which the radioactive contaminant is immersed and subjected to multistage cleaning, and means for reusing the decontamination liquid used for the decontamination. .

  According to the present invention, an aqueous decontamination solution containing a predetermined concentration of a predetermined organic acid can be used to sufficiently remove a tool to which a radioactive substance has adhered without actively adding an inorganic acid, a strong alkali, or an organic solvent. Can be dyed. Moreover, according to this invention, it is easy to adjust the density | concentration of an organic acid according to a radioactive contamination level. Therefore, the decontamination solution according to the present invention has a small environmental load and is easy to handle, collect and reuse. Thereby, according to the decontamination method and decontamination system using the decontamination liquid by this invention, a decontamination process and an apparatus structure become simple and the load given to an environment reduces.

  The decontamination liquid according to a preferred embodiment of the present invention has a total amount of organic acid of 0.4 to 50%, more preferably 0.4 to 30%, more preferably 0.4 to 20%, and still more preferably. 0.4 to 10%, or 1 to 20%, more preferably 1 to 10%. By adjusting the concentration in this way, radioactive contaminants of various contamination levels can be decontaminated to a degree that can be reused.

  In the decontamination liquid according to a preferred embodiment of the present invention, the organic acid includes one or more of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid. Such organic acids are easy to handle and have a low environmental impact.

  The decontamination solution according to the present invention can exhibit a sufficient decontamination capability without substantially containing inorganic acids such as sulfuric acid, nitric acid and nitric acid, or without actively adding them. Such inorganic acids require care in handling, take time for waste liquid treatment, and give a load to the environment.

  The decontamination solution according to the present invention can exhibit a sufficient decontamination capability without containing a strong alkali or without actively adding it. Such a strong alkali requires careful handling, takes time for waste liquid treatment, and places a burden on the environment.

  The decontamination liquid which concerns on preferable embodiment of this invention contains fruit acid (The organic acid derived from a fruit, for example, malic acid, a citric acid, tartaric acid etc.) as an organic acid. For example, the decontamination solution according to the present invention contains fruit acid alone or other organic acid in addition to fruit acid so that the total amount of organic acid is within the above range.

  The decontamination solution according to the present invention allows additives or auxiliaries to enhance the cleaning effect. For example, the decontamination solution according to the present invention may contain additives such as amide sulfonic acid, EDTA, NTA-3Na, a surfactant and amide sulfonic acid.

  In the decontamination method according to a preferred embodiment of the present invention, radioactive contaminants are immersed in the decontamination solution and washed with water.

  Radioactive contaminants that are the subject of the present invention include all radioactively contaminated ones, preferably tools, piping, waste materials, waste or equipment used in radiation control areas such as power plants, more preferably Tools, piping, waste materials, and more preferably tools.

  An embodiment of the present invention will be described below. In one embodiment of the present invention, after being used for work in a radiation control area of a nuclear power plant, a contaminated tool stored in the area is replaced with a decontamination solution according to one embodiment of the present invention. It was investigated whether the contaminated tool could be cleaned to a level where it could be transported out and reused outside the radiation control area.

[Test method]
(1) Object: radioactive contamination tool (driver, monkey wrench (hereinafter referred to as “monkey”), file, etc.).
(2) Decontamination liquid: Citric acid, malic acid, tartaric acid and formic acid were selected as organic acids so as to contain 5% in total amount, and the first to third decontamination liquids were prepared as the remaining water.
(3) Test method: The object is immersed in a decontamination solution in a beaker. When washing with water, use the stirrer method.
(4) Cleaning effect confirmation method: The surface contamination density of the object was measured by a GM tube survey meter.

[Test 1 (normal temperature test)]
It was 1000 cpm when the surface contamination density of the radioactive contamination tool (triangle file) before washing | cleaning was measured. This tool is immersed in the decontamination solution set at room temperature and washed with water by a magnetic stirrer (hereinafter referred to as “stirrer”) method, every 2, 4, 6, 8, 24 and 26 hours (number of samples). When the surface contamination density was measured in 1 to 7), the surface contamination density was less than the detection limit value in the measurement after 26 hours, and the tool was carried out of the radiation control area. FIG. 1 is a graph showing the change over time of the surface contamination density of the radioactive contamination tool according to Test 1. FIG. In this test and the following tests, the detection limit value varies depending on the background level, but is approximately 100 cpm.

[Test 2 (Heating test)]
When the surface contamination density of the radioactive contamination tool (three monkeys) before cleaning was measured, it was 250 to 450 cpm. These radioactive contamination tools were immersed in the decontamination solution heated to 70 degrees, washed with water using a stirrer method, and the surface contamination density was measured every 2 hours (number of samples 1 to 3). After 6 hours In this measurement, the surface contamination density was less than the detection limit value, and it was possible to carry the object out of the radiation control area.

[Test 3 (normal temperature test)]
The surface contamination density of the radioactive contamination tool (ratchet wrench (hereinafter referred to as “ratchet”), shackle and monkey) before cleaning was measured and found to be 200 to 700 cpm. These radioactive contamination tools were immersed in the decontamination solution set at room temperature, washed with water using a stirrer system, and the surface contamination density was measured before decontamination and after 2, 4 and 16 hours. Measurement after 4 hours The surface contamination density was about 100 cpm, and in the measurement after 16 hours, all the surface contamination densities were less than the detection limit value, and it was possible to carry out the radioactive contamination tool outside the radiation control area. Moreover, after washing | cleaning, discoloration did not generate | occur | produce in the plating and coating of the target object. FIG. 2 is a graph showing the change over time of the surface contamination density of the radioactive contamination tool according to Test 3.

[Test 4 (warming test)]
When the surface contamination density of the radioactive contamination tool (ratchet, shackle and monkey) before cleaning was measured, it was 170 to 1500 cpm. These radioactive contamination tools were immersed in the decontamination solution set at 70 degrees, washed with water using a stirrer method, and the surface contamination density was measured every 2 hours. Became less than the detection limit, making it possible to carry out the radioactive contamination tool outside the radiation control area. However, after washing, some of the plating was discolored and some of the ratchet paint was peeled off.

[Test 5 (normal temperature test)]
It was 200-700 cpm when the surface contamination density of the radioactive contamination tool (single-end spanner, number wire cutter, single-end spectacle wrench) before washing was measured. These objects were immersed in the decontamination solution set at room temperature, washed with water using a stirrer method, and the surface contamination density was measured every 2 hours. In the measurement, the surface contamination density became less than the detection limit value, and it was possible to carry out the radioactive contamination tool outside the radiation control area. Moreover, after washing | cleaning, discoloration did not generate | occur | produce in the plating and coating of the target object.

  From the above test results, the contaminated tool can be reused as a tool in a general area by washing the decontamination solution with water, for example, at room temperature. Was confirmed. Further, it was confirmed that the decontamination solution can be decontaminated without having a practical effect on the metal. The concentration of the decontamination solution takes into consideration factors such as the degree of contamination of radioactive contaminants (tools, etc.), material and shape complexity, plating and coating surface properties, set decontamination time, water flow rate and flow rate. Thus, it can be variably set as necessary within the framework of the present invention.

[Decontamination system for radioactive contaminants (tools used in radiation control areas)]
FIG. 3 is a block diagram of a radioactive contaminant decontamination system according to an embodiment of the present invention. Referring to FIG. 3, the decontamination system includes a determination means 2 for determining the radioactive contamination level of the contaminated tool 5, and a decontamination liquid 1 according to the present invention, and the contaminated tool 5 selected in accordance with the determination. It has a multistage washing tank 3 that is immersed and washed in multiple stages, and a reuse means 4 that makes it possible to reuse the decontamination liquid 1 used for the decontamination. In reusing the decontamination liquid, only water in the decontamination liquid may be reused, or a part other than water may be reused.

  The operation of this decontamination system will be described. The radioactive contamination level of the tool 5 used in the radioactive contamination, for example, the radiation control area is determined by the determination unit 2 such as a GM tube survey meter. In response to this determination, a contaminated tool 5 having a contamination level within a predetermined range is put into the multistage washing tank 3. The multi-stage cleaning layer 3 is partitioned into, for example, first to third tanks 3a to 3b, and the decontamination liquid 1 is injected so that the water cleaning can be performed. The contamination tool 5 is put into each tank in the order of the first to third tanks 3a to 3b and gradually decontaminated. The concentration of the decontamination solution can be set sequentially or uniformly for each tank. If the concentration is uniform, the supply of the decontamination solution to each tank can be easily achieved by the once-through mode. The used decontamination liquid 1 is stored in a reuse means 4, for example, a tank, and is reused as appropriate. This decontamination system can be operated automatically.

  In addition, the used decontamination solution can be reused after being separated into water and an organic acid in the final stage of the treatment.

  FIG. 4 is a schematic view of a multi-stage cleaning apparatus for radioactive contaminants using a decontamination solution according to an embodiment of the present invention. Referring to FIG. 4, the multistage cleaning apparatus 10 includes a transport mechanism 11 for raising and lowering radioactive contaminants or a basket containing the radioactive contaminants and moving between the multistage cleaning tanks 12, and a decontamination liquid, and radioactive contaminants are injected. Connected to the water flow generating mechanism 13, a multi-stage cleaning tank 12 having a plurality of tanks that are immersed and decontaminated by a water flow, a water flow generating mechanism 13 that sends a decontamination solution to the multi-stage cleaning tank 12 and generates a water flow And a tank 14 for storing the decontamination liquid.

  The transport mechanism 11 includes a lift elevator 11a to which a car that contains radioactive contaminants is attached, and a horizontal transport mechanism 11b that moves the lift elevator 11a in the horizontal direction. The elevator 11a and the horizontal transport mechanism 11b can be constructed using rails, guides and rollers, screw mechanisms, or the like.

  The multi-stage washing tank 12 includes first to fourth tanks 12a to 12d, and radioactive contaminants housed in the cage are sequentially immersed in the first to fourth tanks 12a to 12d by the transport mechanism 11. Go.

  The water flow generation mechanism 13 includes a switching valve mechanism 13a having a plurality of switching valves for selectively supplying decontamination liquid to the first to fourth tanks 12a to 12d, and a decontamination liquid stored in the tank 14. And pumps 13b and 13c for delivering the.

  The operation of the multistage cleaning apparatus 10 will be described. After radioactive contaminants are put into the elevator elevator 11a, the multi-stage cleaning apparatus 10 is closed. Hereinafter, the radioactive contaminants are immersed in the first to fourth tanks 12a to 12d sequentially by the elevator 11a and the horizontal transport mechanism 11b by the automatic operation, and the water flow of the decontamination liquid generated by the water flow generation mechanism 13 is used. Each is washed. Part or all of the decontamination liquid stored in the tank 14 is reused.

  The decontamination solution, decontamination method and decontamination system according to the present invention are suitably used for cleaning tools, piping, waste materials, waste, equipment, or other radioactive contaminants used in radiation control areas such as power plants. This makes it possible to reuse the cleaned tools or carry them out of the radiation control area.

In one Example of this invention, it is a graph which shows a time-dependent change of the surface contamination density of the radioactive contamination tool which concerns on the test 1. FIG. In one Example of this invention, it is a graph which shows the time-dependent change of the surface contamination density of the radioactive contamination tool which concerns on the test 3. FIG. It is a block diagram of the decontamination system which concerns on one Example of this invention. It is a schematic diagram of the multistage washing | cleaning apparatus of the radioactive contaminant which uses the decontamination liquid which concerns on one Example of this invention.

Explanation of symbols

1 Decontamination solution 2 Judging means (GM tube survey meter)
3 Multi-stage washing tanks 3a, 3b, 3c 1st to 3rd tanks 4 Reuse means 5 Contaminated tools (radioactive contaminants)
DESCRIPTION OF SYMBOLS 10 Multistage washing | cleaning apparatus 11 Conveyance mechanism 11a Elevating elevator 11b Horizontal conveyance mechanism 12 Multistage washing tanks 12a-12d 1st-4th tank 13 Water flow generation mechanism 13a Switching valve mechanism 13b Pump 13c Pump 14 Tank

Claims (4)

As organic acid, malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid contain 0.4 to 50% in total,
The solvent is water,
A decontamination solution for radioactive contaminants.   Radioactive contaminants include 0.4 to 50% in total of one or more of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid as organic acids, and the solvent is water A method for decontaminating radioactive contaminants, comprising immersing in a decontamination solution for radioactive contaminants.   The decontamination method according to claim 2, wherein the radioactive contaminant is immersed in the decontamination solution and washed with water. A determination means for determining a radioactive contamination level of the radioactive contamination;
The organic acid contains 0.4 to 50% in total of one or more of malic acid, citric acid, formic acid, oxalic acid, glyceric acid, tartaric acid and glycolic acid, and the solvent is water. A multi-stage cleaning tank in which a decontamination liquid is injected, and the radioactive contaminants selected according to the determination are immersed and cleaned in multiple stages;
Means for reusing the decontamination solution used for the decontamination;
A decontamination system for radioactive contaminants, comprising:

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