RU150156U1 - INSTALLATION FOR CLEANING LIQUID RADIOACTIVE WASTE FROM TRITIUM - Google Patents

Abstract

1. Installation for the purification of liquid radioactive waste from tritium, containing a distillation column equipped with a vapor condenser and an evaporator, a cold chemical isotope exchange column connected by a pipe to the distillation column, a hot chemical isotope exchange column, a line for hydrogen circulation through cold and hot chemical isotopic columns exchange, an additional column of chemical isotope exchange, connected by a pipeline to a cold column of chemical isotope exchange, is connected with an additional column of chemical isotope exchange, a catalytic burner connected to a hot column of chemical isotope exchange by a pipe, connected to an additional column of chemical isotope exchange, an electrolyzer connected by a line for oxygen transfer with a catalytic burner and a line for hydrogen transfer with an additional column of chemical isotope exchange, characterized in that the evaporator and condenser are equipped with heat exchangers connected by a line for circulation With a compressor and an expansion valve installed on it, and a hot column of chemical isotopic exchange by a pipe is connected to the evaporator. 2. Installation according to claim 1, characterized in that the electrolyzer is equipped with a container for the selection of aqueous tritium concentrate.

Description

The invention relates to the field of radioactive waste management and can be used to clean tritium from liquid radioactive waste.

Large volumes of tritium-containing liquid radioactive waste are generated at nuclear power plants, SNF reprocessing plants and in the production of tritium-labeled compounds. To clean heavy water waste from tritium (heavy water D ₂ O containing tritium) in a number of countries: France, Canada, South Korea, large industrial plants have been created and are being operated [B.M. Andreev, Y.D. Zelvensky, S.G. Katalnikov. Heavy hydrogen isotopes in nuclear technology. Publ. M., 2000 g]. Installations of this type (the so-called CECE type) include a liquid phase catalytic isotope exchange (LPCE) column filled with a water-hydrogen isotope exchange catalyst connected at the bottom to an electrolytic cell for electrolytic decomposition of the treated water into hydrogen (deuterium, tritium) through a pipeline for supplying water from the column to the electrolyzer and a gas line for supplying hydrogen from the electrolyzer to the column, and connected in the upper part to a burner for oxidizing hydrogen to water through a pipeline for transferring water and burner in a column and the gas pipeline for supplying hydrogen from the column to the burner. The column is additionally equipped with a tritium-contaminated water supply line in the central or lower part, a purified water withdrawal line in the upper part, and a tritium concentrate extraction line [John P. Butler et al., US Patent 4190515 A, Atomic Energy Of Canada Limited, 05/18/1978, 02/26/1980]. Installations of this design make it possible to achieve a high degree of purification from tritium with small dimensions, but it requires large expenditures for water electrolysis - $ 13 thousand or more per 1 liter of purified water [Robert H. Drake. Recovery of Tritium from. Tritiated Waste Water. Cost-Effectiveness Analysis. LA-UR-97-3767, Los Alamos National Laboratory, June 1997, 9 pp.]. Therefore, the use of this type of installation is justified in the processing of only such valuable raw materials as heavy water and is not economically feasible when cleaning tritium from ordinary, light water.

When treating ordinary water contaminated with tritium, plants of a more complex design are used, combining devices with high throughput for preliminary extraction and low concentration of tritium with devices for final, high concentration of tritium, designed to process already small volumes of tritium-containing products. These designs can reduce energy costs for the cleaning process and reduce the accumulation of intermediate products having a high tritium content.

Thus, there is a known installation for purifying water from tritium, containing a column for vapor-phase catalytic exchange of water-hydrogen (VPCE), having in its upper part a pipe for supplying tritiated water and in the lower part a pipe for collecting purified water, and equipped with counterflow lines circulation through a hydrogen column, which are connected to a cascade of gas diffusion columns (GD), at the outlet of which there are pipelines for transferring tritium-enriched hydrogen to thermal diffusion columns (TD) equipped with a sampling line Exposure to extreme concentrated tritium [A. Busigin, US Patent 7815890 B2, Process for tritium removal from water by transfer of tritium from water to an elemental hydrogen stream, followed by membrane diffusion tritium stripping and enrichment, and final tritium enrichment by thermal diffusion, Special Separations Application, Inc., 19.10 .2010]. The installation allows you to process large flows in the gas diffusion cascade, providing pre-concentration of tritium, and to carry out the final concentration of tritium in the thermal diffusion cascade. However, the installation of this design requires large expenditures of expensive materials (palladium, silver) for the gas diffusion cascade, and the gas diffusion process itself is extremely energy-intensive.

Also described is a water purification apparatus for tritium, operating at the General Electric enterprise (GE-Hitachi), including a water distillation column (WD - process) for producing purified water and preliminary concentration of tritium, connected in its middle part to the contaminated supply line water in the upper part connected to the vacuum line and the selection line for purified water and in the lower part connected to the electrolytic cell (or reactor for catalytic conversion), the cathode part of which, in turn, is connected to a hydrogen supply line with a thermal diffusion column having a high enriched tritium sampling line in the lower part and a low enriched tritium sampling line in the upper part [I. Bonnett and A. Busigin, US Patent No. 7,470,350, Ge Healthcare Uk Limited, Process for tritium removal from light water. 12/30/2008].

The installation developed by Special Separations Applications Inc. has a close design. (SSAI) and GE-Hitachi [A. Bonnet, A. Busigin and A. Shapiro, Tritium Removal and Separation Technology Developments, Fusion Science and Technology, 2008, Vol. 54, pp. 209-214], including water distillation columns (WD - process), connected to catalytic isotope exchange columns, equipped with electrolysers in their lower part (CECE - process), the hydrogen lines of which are connected to the cascade of gas diffusion columns (GD - process).

In both of the above plants, distillation columns are used to process large incoming streams of tritium-contaminated water, the energy of which can be supplied using cheap energy, for example, spent steam. Distillation columns are connected by transmission lines of a solution pre-enriched with tritium to electrolyzers or catalytic conversion reactors designed to transfer tritium from the liquid phase (water) to the gas phase (hydrogen) and to concentrate tritium in the gas phase. Electrolyzers or catalytic conversion reactors, in turn, have pipelines for supplying tritium-enriched hydrogen to gas diffusion or thermal diffusion columns for the final concentration of tritium. In plants of this type, electrolyzers or catalytic conversion reactors are extremely energy-intensive, which is a drawback of these designs. In addition, gas diffusion or thermal diffusion columns, which are part of the plants, require large volumes with an increased level of radiation hazard for their placement, which leads to a significant increase in the cost of the installation as a whole.

Recently, in order to reduce energy consumption for the cleaning process, more efficient plants have been proposed that also use distillation columns to process incoming water streams, but exclude energy-intensive devices for electrolysis or catalytic conversion from the design. Instead of these energy-intensive apparatuses, series-connected columns of a catalytic chemical isotope exchange of water-hydrogen are used, operating at high temperature (so-called hot columns) and low temperature (so-called cold columns) [W.R.C. Graham, US Patent No. 6858190, AECL, Heavy Water Production Process and Apparatus, 02/22/2005; A.V. Demin et al., RF patent for utility model No. 112842, Installation for the purification of tritium condensate from tritium. 01/27/2012; A.I. Kostylev et al., RF patent for utility model No. 126185, Installation for the purification of liquid radioactive waste from tritium, 03/20/2013]. This design allows you to drastically reduce energy costs. Additionally, in the design indicated, instead of gas diffusion or thermal diffusion columns, water-hydrogen chemical isotope exchange columns are used, which reduces the dimensions of the equipment.

The most effective of these three designs is the installation for the purification of liquid radioactive waste from tritium, described in the patent of the Russian Federation for utility model No. 126185. The installation according to this patent incorporates a distillation column equipped with a vapor condenser and an evaporation cube and connected by pipelines with series-connected water-hydrogen chemical isotope exchange columns operating at high temperature (hot column) and low temperature (cold column) and equipped with a main for the circulation of hydrogen in the specified cold and hot columns. Serially connected hot and cold water-hydrogen chemical isotope exchange columns are connected, in turn, to an additional chemical isotopic exchange column equipped with an electrolyzer in the lower part, a catalytic burner in its upper part and a container for collecting tritium concentrate.

This installation in design is the closest to the claimed and we have chosen as a prototype.

The disadvantage of this design is, first of all, the high energy consumption for distillation of water. The energy costs of this process practically determine the cost of cleaning tritium from radioactive waste (water) in this installation and amount to about 20 kWh per 1 liter of purified water.

Also technically difficult to operate and quite expensive is a device for the selection and fixation of tritium concentrate in the form of titanium tritide.

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

- to reduce energy costs for distillation of water, determining the total energy consumption for the treatment process;

- to increase the manufacturability of the operation of selection and fixation of tritium concentrate.

The technical result of this technical solution is to reduce the energy costs of the cleaning process. This result was obtained due to the use of a heat pump circuit as part of the distillation column, which ensures the recovery of heat spent on the evaporation of water in the evaporator and in the condenser due to the circulation of the heat carrier-freon. The selection and fixation of tritium concentrate in the form of water from the cell increases the safety and manufacturability of this operation and the installation as a whole. This is an additional result of the claimed technical solution.

In addition, the proposed utility model allows you to expand the arsenal of technical equipment designed for the purification of liquid radioactive waste from tritium.

The technical result of the proposed solution is achieved in that the installation for the purification of liquid radioactive waste from tritium contains a distillation column equipped with a vapor condenser located on top of the distillation column and an evaporator located at the bottom of the distillation column. In the particular case of execution, the evaporator may be a cube.

To reduce the energy costs of the tritium purification process, the evaporator is equipped with a heating heat exchanger, and the condenser is equipped with a cooling heat exchanger. In the particular case of execution, the heat exchangers of the evaporator and condenser can be made in the form of coils. The evaporator and condenser heat exchangers are connected by a line with a compressor installed on it and an expansion valve for circulating the coolant. Freon can be used as a heat carrier. The circulation of the coolant-freon according to the claimed solution provides a high degree of saving of energy spent on the evaporation of water in the distillation column due to the return of heat generated by water vapor during condensation in the condenser to the evaporator.

The distillation column is connected via a pipeline to the inlet of a cold chemical isotope exchange column operating at low temperature. The installation also contains a hot column of chemical isotopic exchange, operating at high temperature. The output of the hot column of chemical isotopic exchange is connected by a pipe to the evaporator. Cold and hot columns of chemical isotope exchange are combined by a highway for the circulation of hydrogen through them.

The output of the cold column of chemical isotopic exchange is connected by a pipe to the input of an additional column of chemical isotopic exchange. The electrolyzer is connected to an additional column of chemical isotope exchange in such a way that it receives liquid waste (for example, water) from the additional column, and hydrogen obtained as a result of electrolysis returns to the column. That is, the input of the electrolyzer is connected in the liquid phase (water) to the output of the additional column of chemical isotope exchange, and the output of the electrolyzer is connected in the gas phase (hydrogen) to the input of the additional column. The electrolyzer is also connected to the catalytic burner by a line for transferring the oxygen resulting from electrolysis to the catalytic burner. The catalytic burner, in turn, is connected to an additional column of chemical isotope exchange in such a way that hydrogen from the additional column enters the catalytic burner. That is, the first burner inlet is connected in the gas phase (oxygen) with the outlet of the electrolyzer, and the second burner inlet is connected in the gas phase (hydrogen) with the output of the additional column. The exit of the catalytic burner is connected by a pipeline to the inlet of the hot column of chemical isotopic exchange.

In addition, in the particular case of the implementation of the claimed design, a container connected to the electrolyzer is used to withdraw tritium concentrate in the form of water from the installation.

The utility model is illustrated by a specific embodiment with reference to the drawing, where in FIG. a generalized installation diagram is presented.

In the drawing figure, the following notation:

1 - distillation column;

2 - evaporator;

3 - vapor condenser;

4 - pipeline supply of the original tritiated water;

5 - pipeline selection purified from tritium water;

6 - a pipeline for supplying tritium-enriched water from a distillation column to a cold column of chemical isotope exchange;

7 - cold column of chemical isotopic exchange;

8 - hot column of chemical isotopic exchange;

9 - line for the circulation of hydrogen through a cold and hot column of chemical isotopic exchange;

10 - a pipeline for supplying tritium-enriched water from a cold column to an additional column of chemical isotope exchange;

11 - a pipeline for supplying water from a catalytic burner to a hot column of chemical isotopic exchange;

12 - a pipeline for supplying tritium-containing water from a hot column of chemical isotope exchange into a cube-evaporator of a distillation column;

13 - an additional column of chemical isotopic exchange;

14 - electrolyzer;

15 - a catalytic burner for burning hydrogen entering the column 13 from the electrolytic cell 14, in oxygen coming from the electrolytic cell 14 through the line 16;

16 - line for supplying oxygen from the electrolyzer to the catalytic burner;

17 - container for tritium concentrate;

18 - heating coil-heat exchanger of the heat pump, providing boiling water;

19 - cooling coil-heat exchanger of the heat pump, providing condensation of water vapor;

20 - highway circulation of the coolant-freon circuit of the heat pump, connecting the heating and cooling coils;

21 - a compressor that circulates the coolant-freon;

22 - expansion valve on the coolant circulation line.

The installation for cleaning the cleaning of liquid radioactive waste (water) from tritium works as follows: the source of tritium-contaminated water flows through line 4 (stream F with tritium concentration x _F ) to a distillation column, in the lower part of which there is evaporator 2. In the evaporator, water evaporates , in the form of steam passes through the distillation column 1 and condenses in the condenser 3. The resulting water flows through the distillation column 1 into the evaporator 2. When the countercurrent movement of water and liquid vapors is repeated many times 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.

The water coming from the condenser 3 into the upper section of the column and is practically free of tritium is taken through line 5 in the form of a stream of purified water P, x _p .

To achieve a high degree of purification of water from tritium, the process of evaporation of water in the evaporator 2 and its condensation in the condenser 3 should be repeated many times. This means that the energy for water evaporation is constantly supplied to the evaporator 2 in the form of, for example, electricity, and in the condenser 3 this energy is dissipated (taken away and irretrievably lost) with cooling water circulating through the condenser. To save energy spent on evaporation, in the proposed design, the evaporator is equipped with an additional heating coil-heat exchanger 18 of the heat pump, providing boiling of water due to compression by the compressor 21 of the coolant-freon. After heat transfer in the evaporator 2, the freon evaporates through the expansion valve 22, is cooled and enters the cooling coil-heat exchanger 19 of the condenser 3. Water vapor in the condenser 3 condenses on the coil-heat exchanger 19, transferring its heat to the freon. Freon, having taken the heat from condensing water vapor, enters the compressor inlet 21. The circulation of the heat carrier-freon in line 20 ensures the operation of the heat pump: the heat stored in the water vapor is returned from the condenser back to the evaporator.

Water preliminarily enriched with tritium from the lower section of the distillation column 1 via pipeline 6 is fed to the irrigation column 7 of a chemical isotope exchange operating at low temperature (the so-called cold column). The cold column 7 is connected to the hot column 8 (i.e., operating at high temperature) by a line 9, through which hydrogen is circulated through the columns 7 and 8. As a result of the chemical isotopic exchange between water and hydrogen, additional enrichment of water with tritium is achieved in the lower section of the cold column 7, and depletion of tritium in the lower section of the hot column 8. The tritium-enriched water from the column 7 through the pipeline 10 is supplied to irrigate an additional column of chemical isotope exchange 13, and the tritium-rich water through the pipe 12 is returned to the evaporator 2.

The tritium-enriched water entering the additional column 13 through line 10 passes through the column and enters the cell 14, where it decomposes into hydrogen and oxygen. The hydrogen evolved is returned to the column 13 and is burned to the water in the catalytic burner 15 at the outlet of the column. For hydrogen, oxygen is used that is released in the electrolysis cell 14 during electrolysis of water and enters the catalytic burner through line 16. The resulting tritium-containing water is returned for tertiary treatment at the entrance to the hot column 8 through the pipe 11. When countercurrent movement of water and hydrogen in the column 13 as a result of chemical isotopic exchange between water and hydrogen, the concentration of trit in the lower section of the column and in the electrolyzer. Water with a high concentration of tritium (flow W, x _W ), as tritium is accumulated in it, is withdrawn at the outlet of the electrolyzer 14 to container 17. In container 17, water with a high tritium content (up to 10-50 Ci / l) is fixed on alumina, magnesium oxide or other adsorbent.

The installation according to this technical solution provides water purification from tritium with a low level of energy costs and has a high degree of manufacturability and safety.

The technical solution is illustrated by the following example. The installation for water purification from tritium includes the following equipment:

- distillation column 1 with a diameter of 300 mm and a height of 15 m, filled with mass transfer devices in the form of a Levin nozzle [Auth. testimonial. USSR N 75115, C12F 1/00, publ. 1949] with dimensions of 2.5 × 2.5 × 0.2 mm, made of oxidized stainless steel. The operating parameters of the column: temperature / pressure in the head of the columns is 60-65 ° C / 0.02 MPa, in the lower part of the column is 70-75 ° C / 0.045 MPa. The column has a pipe 4 for supplying source water with a flow rate of up to 6 l / h, a pipeline for sampling purified water with a flow rate of up to 6 l / h, pipelines 6 and 12 for transferring and selecting a solution to the chemical isotope exchange columns 7 and 8 with a flow rate of up to 10 l / hour;

- cube-evaporator 2 connected to the distillation column 1 and equipped with a coil-heat exchanger 18 with an evaporation surface of 3.6 m;

- a condenser 3 connected to a distillation column and equipped with a coil-heat exchanger 19 with a condensation surface of 7.2 m;

- a heat pump circuit, including a line 20 for circulating the coolant-freon (R407, R134, etc.), an expansion valve 22 with a receiver, a compressor 21 with a power of 15 kW;

- cold column 7 of chemical isotopic exchange with a height of 6 m and a diameter of 200 mm, filled with a hydrophobic catalyst [J. Li et al., US 7153486 B2, Wetproofed catalysts for hydrogen isotope exchange, AECL, 12.26.2006]. Operating temperature - 60 ° C, pressure - 0.1 MPa; Hot column 8 of chemical isotopic exchange 6 m high and 200 mm in diameter, filled with a hydrophobic catalyst [J. Li et al., US 7153486 B2, Wetproofed catalysts for hydrogen isotope exchange, AECL, 12.26.2006]. Operating temperature - 130 ° C, pressure - 1.0 MPa. The columns are equipped with pipelines 11 and 10 for the transfer of tritium-enriched solution with a flow rate of up to 6 l / h and line 9 for hydrogen circulation with a flow rate of up to 50 m / h;

- column 13 of chemical isotopic exchange 3 m high and 100 mm in diameter, filled with a hydrophobic catalyst [J. Li et al., US 7153486 B2, Wetproofed catalysts for hydrogen isotope exchange, AECL, 12.26.2006]. Operating conditions - temperature - 60 ° C, pressure - 0.1 MPa. The column is connected to the electrolytic cell 14 with a hydrogen capacity of up to 1000 l / h of type МЭl 500 and a catalytic burner 15 with heat generation up to 10 MJ / h with a cooling circuit with running water with a flow rate of 100 l / h;

- a container for collecting and fixing tritium - a stainless steel vessel with a capacity of 5 l, equipped with connecting fittings.

The plant processes water contaminated with tritium to a level of ~ 1 · 10 ⁶ Bq / l. Productivity of the installation is 5 l / h in the source water. During the operation of the plant, tritium-free water is formed in an amount of ~ 5 l / h (the residual tritium content is ~ 300-500 Bq) and tritium concentrate, which is selected in the form of tritium-containing water at a rate of ~ 0.5 ml / h from the electrolyzer and fixed on aluminum oxide in a container for disposal (5-6% mass). The concentration (activity) of tritium in the concentrate is ~ 1 · 10 ¹⁰ Bq / l.

The installation in this design has a capacity of 5 l / h, provides water purification from tritium to discharge norms (degree of purification more than 2000) and concentration of tritium 10,000 times in comparison with its initial content. Power consumption of the installation - no more than 20 kW. The consumed electric power of the installation according to the prototype is at least 120 kW (estimate).

Thus, the installation for water purification from tritium according to this technical solution has advantages in comparison with the technical solution of the prototype in terms of energy consumption: the inventive installation is about 6 times more efficient than the installation of the prototype.

The installation also has increased safety and manufacturability in comparison with the prototype, since highly active tritium concentrate is taken in the form of water.

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 installation can be successfully used to clean tritium from liquid radioactive waste.

Claims (2)

1. Installation for the purification of liquid radioactive waste from tritium, containing a distillation column equipped with a vapor condenser and an evaporator, a cold chemical isotope exchange column connected by a pipe to the distillation column, a hot chemical isotope exchange column, a line for hydrogen circulation through cold and hot chemical isotopic columns exchange, an additional column of chemical isotope exchange, connected by a pipeline to a cold column of chemical isotope exchange, is connected with an additional column of chemical isotope exchange, a catalytic burner connected to a hot column of chemical isotope exchange by a pipe, connected to an additional column of chemical isotope exchange, an electrolyzer connected by a line for oxygen transfer with a catalytic burner and a line for hydrogen transfer with an additional column of chemical isotope exchange, characterized in that the evaporator and condenser are equipped with heat exchangers connected by a line for circulation It has a compressor and an expansion valve installed on it, and a hot column of chemical isotope exchange is connected to the evaporator by a pipeline. 2. Installation according to claim 1, characterized in that the electrolyzer is equipped with a container for the selection of aqueous tritium concentrate.

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