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DEVICES AND METHODS OF PROCESSING AND DISPOSAL OF RADIOACTIVE, CHEMICAL AND PETROCHEMICAL WASTES
INVENTION
Patent of the Russian Federation RU2286612

METHOD FOR PROCESSING LIQUID RADIOACTIVE WASTE

METHOD FOR PROCESSING LIQUID RADIOACTIVE WASTE

The name of the inventor: Gennady Moiseevich Chechelnitsky (RU); Tishkov Victor Mikhailovich (RU); Cheremiskin Vladimir Ivanovich (RU); Mukhin Nikolay Alexandrovich (RU); Nemtsova Anna Vasilievna (RU)
The name of the patent holder: Ermakov Nikolai Ivanovich (RU); Mukhin Nikolay Alexandrovich (RU); Nemtsova Anna Vasilievna (RU); Tishkov Victor Mikhailovich (RU); Trusov Lev Ilich (RU); Cheremiskin Vladimir Ivanovich (RU); Chernikov Oleg Georgievich (RU); Chechelnitsky Gennady Moiseevich (RU)
Address for correspondence: 119313, Moscow, PO Box 38, G.M. Chechelnitsky
Date of commencement of the patent: 2005.03.10

The invention relates to the technology of handling liquid radioactive waste of the nuclear fuel-energy cycle and can be used in the process of processing liquid radioactive waste (LRW). The process comprises preconcentration, ozonation, microfiltration of the bottoms with separation into permeate and concentrate fractions and ion-selective purification of the permeate with an ion-selective sorbent, the microfiltration being carried out in at least two stages, the permeate of each previous microfiltration stage being directed to microfiltration as the feed solution for the subsequent Microfiltration stage, and in the final stage of microfiltration, the permeate from the microfiltration is sent for recycling, the concentrate obtained in each subsequent microfiltration step is mixed with the stock solution for the previous microfiltration stage and the concentrate obtained in the first stage of microfiltration is directed to conditioning and disposal, the ion-selective sorbent Add to the permeate of the previous stage of microfiltration before the final stage of microfiltration. The object of the invention is to reduce the volume of radioactive waste by deep purification of LRW with high salt content from radionuclides and isolation of the latter in a compact form of hardly soluble compounds, with a corresponding increase in the purification rate of the salts released during the treatment of the bottoms, reduction and optimization of the flow interacting with the initial solution, A and with subsequent permeate and concentrate.

DESCRIPTION OF THE INVENTION

The invention relates to the technology of handling liquid radioactive waste from the nuclear fuel-energy cycle and can be used in the process of processing liquid radioactive waste (LRW) to minimize their volumes and remove radionuclides with their concentration in the solid phase and / or the release of radionuclides in the form of sparingly soluble compounds , In the processing of which by existing methods reliable localization of radioactive substances from the environment is ensured.

Processing of liquid radioactive waste is aimed at solving two main tasks: purification of the bulk of waste from radionuclides and concentrating the latter in a minimal amount.

A solution is known for RU 2066493, MPC G 21 F 9/08, 13.11.1995, "METHOD FOR PROCESSING LIQUID RADIOACTIVE WASTE FROM NPP".

- the method involves pre-evaporating them to form condensate and bottoms, ozonizing the bottom residue, separating the radioactive sludge generated, and concentrating the filtrate by deep evaporation. In this case, the ozonization of the bottom residue is carried out immediately after preliminary evaporation at a solution pH of 12 to 13.5. After separation of radioactive sludge, the filtrate is passed through a filter container with an inorganic sorbent selective to cesium, then the spent filter container is sent for storage or disposal.

And the technical solution for patent RU 2226726, the IPC G 21 F 9/08, G 21 F 9/12, 27.04.2002 is known. "METHOD OF PROCESSING LIQUID RADIOACTIVE WASTE FROM THE NUCLEAR POWER PLANT"

- the method involves pre-evaporating them to form condensate and bottoms, ozonizing the bottom residue, separating the radioactive sludge generated, and concentrating the filtrate by deep evaporation. In this case, the ozonization of the bottom residue is carried out immediately after the preliminary evaporation of the solution. After separation of radioactive sludge, the filtrate is passed through a filter container with an inorganic sorbent selective to cesium, then the spent filter container is sent for storage or disposal.

The shortcomings of the known method include a low purification rate of the salts released during the treatment of the bottom residue, a significant and irrational consumption of the reactants interacting with the initial solution, and with the subsequently obtained permeate and concentrate of reagents.

The objective of the invention is to reduce the volume of radioactive waste due to deep purification of LRW with high salt content from radionuclides and isolation of the latter in a compact form of hardly soluble compounds, with a corresponding increase in the purification rate of the salts released during the treatment of the bottoms, reduction and optimization of the flow interacting with the initial solution, and And with the resulting permeate and concentrate of reagents. This task is solved using the necessary and sufficient set of essential features, namely:

  • A method for processing liquid radioactive waste, including pre-concentration thereof to form condensate and bottoms, ozonization, microfiltration of the bottoms with separation into permeate and concentrate fractions, and ion-selective purification of the permeate with an ion selective sorbent, the microfiltration being carried out in at least two stages,
  • The permeate of each previous stage of microfiltration is directed to microfiltration as a stock solution for the subsequent microfiltration stage, and in the final stage of microfiltration, the permeate from the microfiltration is sent for recycling,
  • The concentrate obtained in each subsequent microfiltration step is mixed with the stock solution for the previous microfiltration step and the concentrate obtained in the first microfiltration step is sent for conditioning and disposal, the ion selective sorbent is added to the permeate of the previous microfiltration step before the final microfiltration stage.

The practical implementation of the claimed method for processing liquid radioactive waste (LRW) consists in the preliminary concentration of liquid radioactive waste with the production of condensate and bottoms, carrying out ozonation, microfiltration on membrane filters in the form of a bottoms residue with separation into permeate and concentrate fractions, and in ion-selective purification of permeate with ion-selective sorbent .

In carrying out the said technological operations, it is optimal to perform the microfiltration in at least two stages, the permeate of each previous stage of microfiltration is then directed to microfiltration as a starting solution for the subsequent microfiltration step, and in the final stage of microfiltration, the permeate from the microfiltration is sent for recycling.

The concentrate obtained in each subsequent microfiltration step is mixed with the stock solution for the previous microfiltration step and the concentrate obtained in the first microfiltration step is sent for conditioning and disposal, the ion-selective sorbent is added to the permeate of the previous microfiltration step before the final microfiltration stage.

This sequence and content of technological methods allow to ensure the solution of the technical task and contribute to the reduction of the volume of radioactive waste due to the deep purification of LRW with high salt content from radionuclides, the isolation of the latter in a compact form of hardly soluble compounds, with a corresponding increase in the purification coefficient of the salts released at the bottom residue treatment stage , And reduce and optimize the flow of reactants interacting with the initial solution, as well as with the resulting permeate and concentrate of reagents.

Examples of implementing the method for using, for example, three purification steps.

1. Activity of the initial liquid radioactive waste (LRW) for Cs is 2.1 × 10 5 Bq / liter. When the unit is started, the ion-selective sorbent at the rate of 2 g / liter is introduced already in the first purification stage, while the activity of the first stage permeate is reduced to 6 × 10 2 Bq / liter. In the second stage, fresh sorbent is introduced at a rate of 2 g / liter, while the activity of the second stage permeate is reduced to 11 Bq / liter, which is below the standard value in accordance with the current legislation, and it is sent for conditioning, for example, evaporation to dry salts, And storage as chemical waste. The second stage microfiltration concentrate (approximately 10% of the original volume) is mixed with the original LRW and microfiltration is carried out. The activity of the first stage permeate is 6 × 10 2 Bq / liter. Concentrate is directed to conditioning (for example, cementing) and disposal. A fresh sorbent is introduced into the permeate and microfiltration is carried out. The activity of the second stage permeate is 11 Bq / liter, then the process is repeated.

2. The activity of the initial LRW by Cs is 2.1 × 10 7 Bq / liter. When the unit is started, the ion-selective sorbent is calculated at the rate of 2 g / liter already in the first stage of purification, while the activity of the first stage permeate is reduced to 3 × 10 4 Bq / liter. In the second stage, a fresh sorbent is introduced at a rate of 2 g / liter, while the activity of the second stage permeate is reduced to 2 × 10 2 Bq / liter. When the fresh sorbent is introduced into the permeate of the second stage of microfiltration, the activity of the third stage permeate is reduced to a value of 9 Bq / liter. Concentrates of the first and second stages of microfiltration are directed to conditioning and disposal, the concentrate of the third stage is mixed with the initial LRW and sent to the first stage of microfiltration. The activity of the first stage permeate is reduced to a value of 3 × 10 4 Bq / liter. To continue the procedure for starting the plant, a fresh sorbent is added to the permeate of the second stage, while the activity of the second stage permeate is 2 × 10 2 Bq / liter. The second stage concentrate is mixed with the starting solution and sent to the first stage of microfiltration. A fresh sorbent is added to the permeate of the second stage of microfiltration and sent to the third stage of microfiltration. The activity of the third stage permeate is 9 Bq / liter. The third stage microfiltration concentrate (about 10% volume) is mixed with the first stage permeate and sent to the second microfiltration stage. The activity of the second stage permeate is 2 × 10 2 Bq / liter. The concentrate of the second stage of microfiltration is mixed with the initial LRW, a fresh sorbent is added to the permeate and sent to the third stage of microfiltration. The activity of the third stage permeate is 9 Bq / liter, and it is sent for conditioning and disposal as chemical waste, the concentrate of the third stage of microfiltration is mixed with the permeate of the first stage of microfiltration.

Further, the cleaning process is repeated, but the fresh sorbent is introduced only into the permeate of the second stage of microfiltration.

In the examples, the indicated consumption data for the sorbent have a rather wide range of possibilities, however, when further processing for solving particular problems, it is possible to specify these quantities.

CLAIM

A method for processing liquid radioactive wastes, including pre-concentrating them to form a condensate and a bottoms residue, ozonizing, microfiltration of the bottoms with separation into permeate and concentrate fractions, and ion-selective purification of the permeate with an ion-selective sorbent, characterized in that the microfiltration is carried out in at least two stages , The permeate of each previous stage of microfiltration is directed to microfiltration as a starting solution for the subsequent microfiltration stage, and in the final microfiltration stage, the permeate from the microfiltration is sent for recycling, the concentrate obtained in each subsequent microfiltration step is mixed with the stock solution for the previous microfiltration stage and the concentrate , Obtained in the first stage of microfiltration, is directed to conditioning and disposal, the ion-selective sorbent is added to the permeate of the previous stage of microfiltration before the final stage of microfiltration.

print version
Date of publication 11.12.2006гг