The way malariacontrol decontamination

 

(57) Abstract:

The invention relates to nuclear power and can be used to remove radioactive contaminants from the internal surfaces of the circuits of nuclear power plants. The method of decontamination is processing power equipment with a solution of nitrous acid 45-100 mg/l at a temperature of 80-100oFor 5-17 including Nitrous acid is obtained directly in the circuit by passing the solution of salt of nitrous acid through the ion exchange resin or the introduction of a solution of salt of nitrous acid, nitric acid or gidrolizuacy salt of nitric acid. Effect: increase the effectiveness of decontamination and simplify technology. 1 C.p. f-crystals, 3 tables.

The invention relates to nuclear power and can be used to remove radioactive contaminants from the internal surfaces of the circuits of nuclear power plants, such as contours of the multiple forced circulation reactor high power channel (FRC RBMK), the first loop water-to-water energetic reactor (WWER), etc.

In modern nuclear power for the purpose of decontamination is the most widely ispolzovav enter activator - fluorides, hydrogen peroxide, hydrazine, etc. /1/.

The disadvantages of these methods are

1. High concentration of chemicals, resulting after decontamination produce large quantities of waste requiring further processing.

2. Highly corrosive solutions, resulting items of equipment, made of pearlitic steels, are destroyed.

3. The multistage processing.

4. Chemical activation of metal surfaces, resulting in the steel become prone to corrosion degradation.

5. Increased sorption of radionuclides on chemically activated surfaces.

Known methods malariacontrol decontamination. Unlike traditional "chemical" decontamination, which produce large quantities of radioactive waste, malariagen decontamination is less efficient from the point of view of removal of radioactive corrosion products.

However malariagen washing has several advantages over traditional "chemical" decontamination.

These are

1. Bezoekadres (removal of radionuclides from des.solutions to ionoobmenom.

4. Does not require any preparation and can be performed during each reactor shut-down.

A known method of removing radioactive corrosion products /2/ used in the shutdown of the reactor type CAND", which consistently uses the following cycle of operations:

1. the temperature cycle is reduced and the temperature rise of the coolant;

2. hydrodynamic cycle - change the mode of operation of the equipment, changing the speed and flow;

3. the redox cycle of the alternation of recovery mode with an excess of N2and oxidative mode with the addition of O2to a concentration of 50-100 mg/l

As noted by the authors, this method shows good results only for surfaces made of alloy "Monel". Surface made from other metals, washed badly.

The first outlines of Ukrainian NPPs alloy "Monel" is not produced and therefore this method is not used. In addition, the disadvantages of this method include the complex system of operations to create cycles, enter the path of the gases, the need for prior training.

Known also adopted for the nearest equivalent way to remove the radio the CSOs and the temperature to 60oWith continuous circulation of coolant to reduce the concentration of H2in the circuit less than 4 mg/l, then increase the pressure up to several atmospheres and to add coolant oxygenated solution having a content of ABOUT2more than contouring the water, and then reduce the pressure and coolant serves on the treatment facility to remove corrosion products, and the cleaned fluid return circuit /3/.

This method has the following disadvantages:

1. The concentration of oxygen in the water is greater than its solubility at atmospheric pressure. To prevent the gas pressure in the circuit increases up to several atmospheres. With increasing temperature the solubility of oxygen in water decreases, and almost all of the injected oxygen is concentrated in the steam space of the drum-separators.

2. Boiling channel reactors have developed a system of water and steam communication, which leads to uneven distribution of oxygen concentration in the circuit.

3. Additional hardware required to implement the dosing of oxygen.

The aim of the invention is to increase the efficiency of des is determined as being the solution, containing nitrous acid 45-100 mg/l at a temperature of 80-100oFor 5-17 hours.

Because nitrous acid by industry is not available (due to the low stability), it is synthesized directly in the path

a) passing a salt of nitrous acid through the ion exchange filter (for example, through resin grade KU 2-8 CSN in the N+-form);

b) adding to the solution of salt of nitrous acid, nitric acid;

c) adding to the solution of salt of nitrous acid gidrolizuyushchie salts with acidic reaction, such as aluminum nitrate.

Examples of specific use.

Example 1: The proof for higher efficiency of decontamination of the proposed method compared with the method of the analogue and prove optimal concentration of nitrous acid.

When studying the decontamination properties of solutions used samples of steel 08KH18N10T and ST20, pre-aged in polluting the solution containing the radionuclides 137Cs, 60Co, se, SG in equal amounts with a total activity of 2108Bq/kg 270oWith over 150 hours Contaminated samples (3-5 specimens) was immersed in the test solution. The ratio between the area of the IMC (1200 m2and the area of its inner surfaces (38900 m2). The solution was found or in flasks under reflux or in a special autoclave connected through a gearbox with an oxygen tank. Temperature was maintained by immersing vessels in thermostat. Radiometric measurements were made on the radiometers BDBS-3-em and DS shipped with the detector SBT-10A, respectively, account and account and update the device PSO-2-4. Spectrometric analysis of radioactive solutions and samples was performed using the pulse analyzer AI-4096-3M-IN-100 and semiconductor detector DGDK-80B. The error value ratio should not exceed 25%. Processing of samples was made

1. By the method similar to the solution of 4 mg/kg of hydrogen at 60oC for 8 hours, then served with oxygen at a pressure of 4 ATM and processing continued at 110oC for 8 hours.

2. The proposed method

a) a Solution of HN0215-250 mg/l (missed NaNO2through a column filled with cation exchange resin KU - 2-8-es in the N+form)

b) a Mixture of HN3+NaN2in equal amounts. (Table 1 concentration of HNO3+NaNO2total).

Processing was carried out at a temperature of 95">

From the data presented in table 1, it is seen that the coefficients of decontamination when processing samples by the proposed method (PP a and b) is higher than when processed by the method similar (p. 1). To explain this effect, apparently, can the fact that the nitrite-ions form stable complex compounds [Co(NO2)6]-4. As you know, With60is at least 90% activity of sediments during operation of the reactor plant /1, S. 71/.

From the above data also shows that at concentrations of nitrous acid is less than 45 mg/l is a sharp decrease of decontamination properties of the solution. The concentration of nitrous acid should be limited to a value of 100 mg/l because at high concentrations can produce the conclusion of chemicals from the spent solution on a regular filters, the installation becomes impractical. In addition, the decontamination efficiency increases slightly. Optimal adopted the concentration range 45-100 mg/l

Example 2: Given to substantiate temperature processing.

Sample processing ST20 and 08KH18N10T, contaminated, spent a solution of HNO2concentration of 80 mg/l at temperatures 60, 70, 80, 90, 100, 120oWith in achierements presented in table 2.

From the data presented in table 2, it is seen that at a temperature of less than 80oWith a sharp reduction in the rate of deactivation, and at temperatures above 100oWith the increase in KD practically does not occur. Therefore, the optimal temperature testing adopted interval 80-100oC.

Example 3: Given to justify the processing time.

Sample processing ST20 and 08KH18N10T, contaminated, spent a solution of 80 mg/l of nitrous acid at 90oWith over 3, 5, 8, 12, 17, and 24 hours. Determined coefficient of decontamination. The results of the experiments are presented in table 3.

The data show that when the processing time less than 5 hours there is a sharp decrease in KD, while processing more than 17 hours zoom KD practically not observed. Therefore, the optimal processing time passed interval 5-17 hours.

Literature

1. Anpilogov N. And. and other Decontamination in nuclear power Meters, Energoizdat, 1982.

2. Atomic Enerde of Canada Limited, AECL 4223, Zuly, 1972.

3. U.S. patent 4042455 from 16.18.77,

1. The way malariacontrol decontamination power equipment oxidizing solutions, characterized in that the processing to produce restasis fact, that nitrous acid is obtained directly in the circuit by passing the solution of salt of nitrous acid through the ion exchange resin in the H+form, or the introduction of a solution of salt of nitrous acid, nitric acid or gidrolizuacy salt of nitric acid, for example, aluminum nitrate.

 

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