RU126185U1 - INSTALLATION FOR CLEANING LIQUID RADIOACTIVE WASTE FROM TRITIUM - Google Patents

Abstract

1. Installation for the purification of liquid radioactive waste from tritium, containing a container for the initial solution, connected to a distillation column equipped with a vapor condenser and a cube-evaporator, a storage tank for tritium-enriched water, a cold isotope chemical exchange column, a hot isotope chemical exchange column, a main for the circulation of hydrogen through columns of a two-temperature isotopic chemical exchange, a line for supplying water from a column of hot isotopic chemical exchange to the head process, an additional column of cold isotope chemical exchange, the input of which is connected by a line with the output of the column of cold isotope chemical exchange, an electrolyzer and a container for collecting hydrogen enriched with tritium, characterized in that a catalytic burner is installed at the outlet of the upper part of the additional column of cold isotope chemical exchange the combustion of hydrogen, which is communicated by a highway for returning the formed water for purification to a column of hot isotopic chemical exchange.2 . Installation according to claim 1, characterized in that the cell has a line for supplying oxygen from the cell to the catalytic burner. Installation according to claim 1, characterized in that the line for supplying water from a cold isotope chemical exchange column to the process head is connected to a distillation column at a point located between the supply point of the initial solution and the selection point of tritium-enriched water. Installation according to claim 1, characterized in that the cube-evaporator of the distillation column is equipped with a tank for collecting salt concentrate

Description

This utility model relates to the field of radioactive waste management and can be used to clean tritium from liquid radioactive waste.

Tritium - a radioactive isotope of hydrogen - is formed during the operation of enterprises of the nuclear fuel cycle and is characterized by high radiotoxicity. Therefore, at present, most of the leading nuclear energy companies have created and operate special facilities designed to remove tritium from waste solutions of nuclear power plants and radiochemical enterprises. The Canadian Atomic Energy Agency (AECL) - Darlington, Ontario - has been using a single-temperature chemical isotope exchange system in a water-hydrogen system (CECE process) since 1998 to clean tritium from liquid wastes [WRC Graham et al., 6 ^th . International Conference on Tritium Science and Technology, Tsukuba, Ibaraki, Japan, 2001 November 11-161]. Similar facilities exist in the United States, South Korea, Japan, and Russia. The installation includes a column of chemical isotope exchange, an electrolyzer as the lower unit of circulation and a burner as the upper unit of circulation. The disadvantage of this installation is the very high energy costs required for the electrolytic decomposition of the entire stream of treated water.

The General Electric industrial enterprise (GE-Hitachi) - Cardiff, UK - uses a tritium-free light water treatment plant, including a water distillation column (WD process) to produce purified water and pre-concentrate tritium, and a catalytic conversion reactor enriched tritium of water into hydrogen enriched with tritium (PMR - process) and thermal diffusion columns for the final concentration of tritium (TD - process) - [I. Bonnett et al. US Patent 7470350, December 30, 2008]. The disadvantages of this design are the need for a high degree of separation in the distillation column and the accumulation of significant amounts of tritium concentrate as a result, which is not rational for reasons of radiation safety, and significant energy costs in the catalytic conversion unit.

For use as part of the International Thermonuclear Reactor (ITER) (Cadarache, France), the Trit ∗ Ex® installation [A. Bonnet., Fusion Science and Technology, 2008, Vol.54, pp.209-214], including rectification columns (WD process), isotope exchange columns with an electrolyzer (CECE process), and a cascade of gas diffusion columns (GD process). Such an installation is designed to obtain highly enriched tritium and requires large energy costs for the electrolysis process. This makes it irrational to use it to clean tritium of large streams of water with a relatively low tritium content.

To reduce the energy costs of electrolysis, which are the main component of the cost of purification from tritium, installations are proposed that use column devices for two-temperature chemical isotope exchange (BWH - process) [W.R.C. Graham et al., US Patent No. 6858190, 02.22.2005; A.V. Demin et al., Patent Ru for utility model No. 112842, 08/16/2011]. This allows you to abandon the electrolytic decomposition of the entire stream of processed water and significantly reduce the cost of processing.

Closest to the claimed utility model is the installation according to the Ru patent for utility model 112842, selected as a prototype, which incorporates a vessel with tritium condensate, a distillation column equipped with a condenser located in its upper part and a heating chamber in the lower part, with a capacity for collecting tritium concentrate, cold and hot isotope chemical exchange columns, an additional cold isotope chemical exchange column, an electrolyzer and a container for fixing tritium. The initial tritium condensate is fed into the middle section of the distillation column, while purified water is taken from the column condenser, and water pre-enriched with tritium through a container for collecting tritium concentrate is fed to the column for irrigation of cold isotopic chemical exchange. From the lower section of the cold isotope chemical exchange column, water with intermediate tritium enrichment enters the irrigation of the hot isotope chemical exchange column and an additional cold isotope chemical exchange column. Tritium depleted water is drawn from the lower section of the hot isotopic chemical exchange column and returned to the tritium condensate tank for purification. Water preliminarily enriched with tritium passes through an additional column of cold isotopic chemical exchange and decomposes in the electrolyzer into hydrogen and oxygen. Enriched with tritium, hydrogen is partially taken at the outlet of the electrolyzer and enters a container for fixing tritium, partially enters an additional column of cold isotopic chemical exchange, and then is discharged into the atmosphere.

The disadvantage of this design are:

- a low degree of concentration of tritium in an additional column of cold chemical isotope exchange, since it does not ensure the completeness of the circulation of hydrogen and water flows (there is no upper node of the circulation of flows). The low concentration of tritium in this column leads to an increase in the flow of tritium-enriched hydrogen and, accordingly, the volume of containers for fixing tritium and an increase in the volume of waste to be disposed of;

- discharge of hydrogen containing tritium. At the output of an additional column of cold isotopic chemical exchange, hydrogen is not processed into water, which can be returned for further treatment, but is released into the atmosphere.

The task to which this technical solution is directed is to eliminate these shortcomings, namely:

- increasing the degree of concentration of tritium and thereby reducing the volume of waste to be disposed of without increasing energy costs;

- elimination of tritium emissions with hydrogen into the environment.

To solve this problem, we propose a facility for the purification of liquid radioactive waste from tritium, containing a container for the initial solution, a distillation column equipped with a vapor condenser and a cube-evaporator, a storage tank for tritium-enriched water, a cold isotope chemical exchange column and a hot isotope chemical exchange column, line for the circulation of hydrogen through columns of cold and hot isotopic chemical exchange, an additional column of cold isotopic chemical th exchange, an electrolyzer and a container for collecting hydrogen enriched in tritium. To ensure conditions of a high degree of concentration and to prevent the release of hydrogen containing tritium into the environment, an additional cold isotope chemical exchange column in its upper part is equipped with a catalytic burner designed to burn hydrogen to water, and a line to return the resulting water for treatment to a hot column isotopic chemical exchange. In addition, for the withdrawal of salt concentrate, the installation is equipped with a tank for collecting salt concentrate. Otherwise, during the accumulation of salt concentrate in the evaporator cube, the installation may fail.

The technical result of this technical solution is to reduce the amount of solid radioactive waste generated by increasing the concentration of tritium, eliminating the release of hydrogen containing tritium into the atmosphere, and increasing the life of the installation.

In the drawing (Fig.) Presents a diagram of the installation, which contains:

1 - capacity for the initial solution;

2 - distillation column;

3 - vapor condenser;

4 - cube-evaporator;

5 - storage tank for tritium-enriched water;

6 - column of cold isotopic chemical exchange;

7 - column of hot isotopic chemical exchange;

8 - an additional column of cold isotopic chemical exchange;

9 - electrolyzer;

10 - a container for collecting hydrogen enriched with tritium;

11 - catalytic burner for burning hydrogen;

12 - capacity for collecting salt concentrate.

The installation is equipped with a line for the circulation of hydrogen through columns 6 and 7, a line for supplying oxygen from the electrolyzer 9 to the catalytic burner 11.

Installation works as follows. The initial solution flows from tank 1 (stream X ₀ ) into a distillation column 2, which is equipped with a vaporizer 4 and a vapor condenser 3. In a vaporizer, water evaporates and condenses in a storage tank to receive water pre-enriched with tritium 5. During countercurrent movement of the vapor water and liquid during the phase isotopic exchange, enrichment of water with tritium in the lower section of the column and purification of water from tritium in the upper section of the column are achieved. Water flowing from the vapor condenser 3 to the upper section of the distillation column 2 and practically free of tritium is taken in the form of a stream Xp of purified water. Pre-enriched with tritium water (stream X ₁ ) from the bottom section of the column through the storage tank for enriched with tritium water 5 is fed to the irrigation column 6. In countercurrent to the movement of water in the columns 6 and 7 organized the movement of hydrogen. As a result of the chemical isotope exchange between water and hydrogen in columns 6 and 7, tritium enrichment of water at the outlet of column 6 and depletion of tritium of water in the lower section of column 7 are achieved. Water with intermediate tritium enrichment (stream X ₂ ) is supplied from the lower section of column 6 at column 8, irrigation, and water (stream Y _1), depleted of tritium, which is withdrawn from the lower section of the column 7, is supplied to post-treatment in a distillation column 2. Pre tritium enriched water (stream X ₁₎ passes through the column 8 and is decomposed in the electron olizere 9 into hydrogen and oxygen. The evolved hydrogen (main stream) is returned to the column 8 and, at the outlet of the column, it is burned to water in a catalytic burner 11. For the combustion of hydrogen, the oxygen released in the electrolysis cell 9 during electrolysis of water is used. The combustion of hydrogen in a catalytic burner 11 eliminates the release of tritium into the atmosphere and ensures complete phase reversal in the column 8, which is a necessary condition for achieving a high degree of concentration. The tritium-containing water obtained in the burner 11 is returned to the column 7 for further purification. When countercurrent water and hydrogen move in the column 8 as a result of isotopic chemical exchange, tritium is concentrated in the lower section of the column and in the electrolyzer. Hydrogen with a high concentration of tritium (stream X ₃ ) is partially taken at the outlet of the electrolyzer 9 before entering the column 8 and enters the container 10. In the container 10, tritium mixed with hydrogen is fixed in the form of metal hydride and sent for storage or disposal. To achieve the optimal treatment and concentration in column 2, the flow of waste water Y ₁ from column 7 is introduced into the cross section of distillation column 2 located between the input point of the source water and the point of selection of the concentrate. The evaporator cube 4 is additionally equipped with a tank 12 for periodic selection of salt concentrate that accumulates during evaporation of water during operation. This increases the life of the installation.

The technical solution is illustrated by the following example. The installation for the purification of liquid radioactive waste from tritium includes the following equipment:

1 - capacity for the initial solution with a volume of 1000 l;

2 - two parallel distillation columns with a diameter of 150 mm and a height of 18 m, filled with a spiral-prismatic nozzle with element sizes of 3.5 × 3.5 × 0.2 mm according to TU 2873-001-780401001-2009. The vacuum in the column is maintained using the NVBM-10 vacuum pump. The operating parameters of the column: temperature / pressure in the head of the columns -60 ° C / 0.02 MPa, in the lower part of the column -75 ° C / 0.045 MPa;

3 - vapor condenser in the form of a tubular heat exchanger cooled by running water with a condensation area of 1.25 m ² . Cooling water consumption -300 l / h;

4 - cube - evaporator with electric heating up to 20 kW;

5 - storage tank for tritium-enriched water with a volume of 40 l;

6 - column of cold isotopic chemical exchange 4 m high and 100 mm in diameter, filled with a hydrophobic catalyst (TU 2172-001-470301001-2009) to a height of 2.5, equipped with a thermostatic jacket to maintain an operating temperature of 50 ± 1 ° С;

7 - column of hot isotopic chemical exchange 4 m high and 100 mm in diameter, filled with a hydrophobic catalyst (TU 2172-001-470301001-2009) to a height of 2.5 m, equipped with a thermostatic jacket to maintain a working temperature of 100 ± 1 ° С. Hydrogen circulation in columns 6 and 7 is provided by a hydrogen compressor of the grade AD 162C at a pressure of 0.1 MPa;

8 - an additional cold isotope chemical exchange column with a height of 1.5 m and a diameter of 30 mm filled with a mixture (1: 1) of a hydrophobic catalyst of the РХТУ-3СМ / ⌀2 brand and a spiral-prismatic packing with element sizes 2.0 × 2.0 × 0.2 (TU 2873-001-780401001-2009) to a height of 1.5 m, equipped with a thermostatic jacket to maintain a working temperature of 60 ± 1 ° C;

9 - an electrolyzer of the brand "Color-Chrome 60" with a hydrogen productivity of 60 l / h;

10 - a container for collecting hydrogen enriched with tritium - a metal vessel made of stainless steel with a height of 250 mm and a diameter of 30 mm filled with sponge titanium of the ТГ100 grade in accordance with GOST 17746-96 (Specifications “Container for storage of tritium containing titanium hydride. КТТ. ТУ 69 68 -001-07625447-2010);

11 - burner for the combustion of hydrogen of a catalytic type with a cooling circuit.

The burner is a vertical cylindrical vessel with a diameter of 50 mm and a height of 400 mm, filled with a catalyst brand RKhTU-3SM. Hydrogen and oxygen are supplied to the burner through fittings equipped with flame arresters;

12 - a tank for collecting salt concentrate - a stainless steel vessel with a capacity of 5 l, equipped with connecting fittings.

The gas and water lines of the installation are made of 12X18H10T DN12 and DN6 pipes, the equipment is interconnected by means of flanges and threaded fittings, PTFE-4 is used as a seal, Du10 Ru10 bellows valves are used as control (shut-off) valves, the pumps are circulated and supplied with pumps membrane brands НР / 2АН.

The plant processes water contaminated with tritium to a level of 1.2 · 10 ⁷ Bq / l with a salt content of ~ 0.05 g / l. The productivity of the installation is 2 l / h in the source water. During the operation of the plant, tritium-free water is formed (the residual tritium content is less than 7600 Bq / l, which is lower than HC), which is discharged after control analyzes, and tritium concentrate, which is taken in the form of hydrogen from the electrolyzer and fixed in the form of titanium hydride in the container for burial. The concentration (activity) of tritium in the concentrate is 2.4 · 10 ¹¹ Bq / l. Salt concentrate (50 g / l) is taken from the evaporator cubes of the columns once a month in the amount of 1.0-1.5 l and transferred to the disposal site (after curing by cementing).

The installation in this design has a capacity of 2 l / h, provides water purification from tritium to discharge standards (purification degree more than 1500) and tritium concentration 20,000 times compared to its initial content. The main concentration of tritium in this unit occurs in column 8 due to the presence of an upper flow reversal unit — a burner: the concentration of tritium is 200. (In the absence of a burner, the concentration does not exceed 3.5). The design of the installation eliminates the release of tritium into the atmosphere with hydrogen or other products and is designed for long-term operation.

Thus, the installation for water purification from tritium according to this technical solution has advantages in comparison with the technical solution for the prototype in terms of the concentration of tritium (the degree of waste reduction compared to the prototype about 70 times) without increasing energy costs and ensures environmental safety of the production - eliminates emissions tritium into the environment. The installation also has an increased resource in comparison with the prototype. The effectiveness and efficiency of the proposed design indicate its technical and economic advantages in comparison with the design of the prototype and other well-known technical solutions. Therefore, the facility can be successfully used to clean tritium of radioactive waste generated during the operation of nuclear fuel cycle enterprises.

Claims (4)

1. Installation for the purification of liquid radioactive waste from tritium, containing a container for the initial solution, connected to a distillation column equipped with a vapor condenser and a cube-evaporator, a storage tank for tritium-enriched water, a cold isotope chemical exchange column, a hot isotope chemical exchange column, a main for the circulation of hydrogen through columns of a two-temperature isotopic chemical exchange, a line for supplying water from a column of hot isotopic chemical exchange to the head process, an additional column of cold isotope chemical exchange, the input of which is connected by a line with the output of the column of cold isotope chemical exchange, an electrolyzer and a container for collecting hydrogen enriched with tritium, characterized in that a catalytic burner is installed at the outlet of the upper part of the additional column of cold isotope chemical exchange the combustion of hydrogen, which is communicated by the line to return the formed water for purification to the column of hot isotopic chemical exchange. 2. Installation according to claim 1, characterized in that the cell has a line for supplying oxygen from the cell to the catalytic burner. 3. Installation according to claim 1, characterized in that the line for supplying water from a cold isotope chemical exchange column to the process head is connected to a distillation column at a point located between the supply point of the initial solution and the selection point of tritium-enriched water. 4. Installation according to claim 1, characterized in that the cube-evaporator of the distillation column is equipped with a tank for collecting salt concentrate.

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