RU147659U1 - INSTALLATION OF LIQUID RADIOACTIVE WASTE CLEANING - Google Patents

Abstract

Installation for cleaning liquid radioactive waste, containing a series-connected phase separation unit, a purification unit for mechanical impurities, a double reverse osmosis unit, connected by a line for transferring permeate to the sorption filter unit, an evaporation unit for salt concentrate obtained as waste at the output of the reverse osmosis unit, made in the form of an evaporation apparatus for obtaining purified distillate and paste-like concentrate, connected by a line for supplying concentrate to the device for cement and a container for collecting and controlling the purified solution, characterized in that the phase separation unit and the mechanical impurities cleaning unit are combined into a single unit that performs the indicated operations by tangential ultrafiltration, the evaporation unit is made in the form of an evaporator with heat recovery, and the installation contains in addition, a line for transferring hydrocarbon and mechanical impurities to the cementing unit from the ultrafiltration unit, a line for transferring distillate to the sorption filter unit and a line for I am dosing the coagulant in the capacity of the stock solution.

Description

The utility model relates to the field of radioactive waste management, namely, to devices for the treatment of liquid radioactive waste (LRW). The utility model can be used in LRW storage and processing facilities, as well as in places of their formation: nuclear power plants, radiochemical enterprises, and in decommissioning of nuclear facilities.

Various types of plants for processing LRW are known [B.E. Ryabkov, Treatment of liquid radioactive waste. - M .: DeLi print, 2008, 391 s], which combine filtration, sorption, membrane and reagent treatment units (Eco-1, -2, 3, MMSU, Aqua-express, etc.) in different sequences. The indicated installations additionally incorporate pumping and capacitive equipment, with the help of which the initial LRW is collected and transferred between individual nodes. In some cases, the plants (ECO-ZM, MMSU) also have a secondary waste management unit — a cementing unit in which liquid salt concentrates and sorbents formed during the cleaning of LRW from radionuclides solidify [Yu. V. Karlin, V. Yu. Chuikov Reprocessing of liquid radioactive wastes using mobile modular systems, Atomic Energy, Vol. 90, No. 1, 2001]. Modern installations include, as a rule, a double reverse osmosis device as the main unit. In the specified device, the solution previously purified from mechanical impurities is processed to obtain purified water and salt concentrate containing the bulk of radionuclides and other toxic impurities [OM Slyunchov, P.A. Bobrov, P.V. Kozlov, et al., Results of resource tests for the treatment of liquid low-level waste from the Techen cascade of water bodies. Abstracts of the 6th Russian Conference on Radiochemistry, Radiochemistry 2009, Moscow, RIC VRB Federal State Unitary Enterprise PO Mayak, 2009, p. 276]. Additional purification is carried out through the use of selective sorption or ion exchange units. The water purified in such installations has a salinity of 1 mg / l, the residual radionuclide content is below the level of intervention (HC) and can be discharged without restrictions into an open hydraulic network.

The disadvantages of these plants are the insignificant degree of reduction in the volume of waste (the ratio of the volume of the initial LRW and the volume of the secondary radioactive waste) associated with the production of double reverse osmosis as secondary radioactive waste in significant quantities of liquid salt concentrates. As a rule, this ratio cannot fundamentally exceed 5-6, which is associated with the possibilities of reverse osmotic concentration [Yu.I. Dygaer, reverse osmosis and ultrafiltration. - M: "Chemistry", 1978. 352].

To reduce the volume of secondary radioactive waste generated during the processing of LRW, a liquid radioactive waste treatment plant is proposed, in which, for additional concentration of salt concentrates from the reverse osmosis unit, an evaporation unit is used [B&W Nuclear Environmental Services Inc., document No. B & W-10294 edition 01, - Vladivostok: B&W, 1999 - 12 s]. The drawing shows the installation (Fig. 1), which in its composition has four series-connected functional units. The node 1 contains a device for separating hydrocarbon impurities, including a sludge tank and a phase separator. Node 2 is a device for removing mechanical impurities from LRW and includes a sludge tank, coarse solids separator and fine filters. Node 3 is a device for pre-concentration of the purified LRW solution by double reverse osmosis. Permeate on the M1 line is fed for purification to the block of sorption filters. Node 4 is an evaporation apparatus for producing purified distillate and paste-like concentrate, which is supplied for cementing along the m2 highway. The purified solution from nodes 3 and 4 is collected in a container for monitoring and collecting purified industrial water.

This installation in design is the closest to the claimed and we have chosen as a prototype. The disadvantages of this design are:

1. large volumes of equipment associated with the presence in the installation of tanks - sedimentation tanks. This determines its bulkiness and leads to the accumulation of a large number of radioactive substances in the equipment;

2. low productivity, since separation in nodes 1, 2 is carried out by the settling method;

3. high energy consumption, determined by the cost of evaporation.

The problem to which the claimed utility model is directed is to eliminate these drawbacks.

The technical result of this solution is to reduce the dimensions of the installation, increase its productivity and reduce specific energy costs for processing.

The technical result is achieved by the fact that in the known installation of liquid radioactive waste treatment, containing a series-connected unit for phase separation, a unit for cleaning mechanical impurities, including a separator for coarse solids and fine filters, a double reverse osmosis unit connected by a line for transferring permeate to the unit sorption filters, evaporation unit, made in the form of an apparatus for obtaining purified distillate and paste-like concentrate, connected by a line for supplying concentrate in the device for cementing, and a container for collecting and controlling the purified solution. In order to reduce the dimensions of the installation, increase its productivity and reduce specific energy costs for processing, the phase separation unit and the mechanical impurities purification unit are combined into a single device that performs the indicated operations by tangential ultrafiltration, the evaporation unit is made in the form of an evaporator with heat recovery, and the installation additionally contains a trunk for transmission to cementing hydrocarbon and mechanical impurities from an ultrafiltration unit, a trunk for gears distillate per unit sorption filter and line for dosing coagulant to the vessel LRW starting solution.

In the drawing of FIG. 2 presents a diagram of the claimed installation of liquid radioactive waste treatment, where:

- nodes 1 (purification from carbon impurities) and 2 (purification from mechanical impurities) are combined into a single device that performs the indicated operations by tangential ultrafiltration;

- node 3 - reverse osmosis system;

- node 4 - evaporator - made in the form of an evaporator with heat recovery;

- the installation is equipped with additional lines:

m3 - for transmission to cementing hydrocarbon and mechanical impurities;

M4 - to transfer the distillate to the block of sorption filters;

m5 - for dosing the coagulant into the capacity of the initial LRW solution.

The installation works as follows: the stream of the initial LRW enters node 1-2 - to remove hydrocarbon and mechanical impurities. Node 1-2 contains a tangential ultrafiltration device, the input of which along the m5 highway receives a solution with a coagulant. The clarified solution from unit 1-2 enters unit 3, and the concentrate of hydrocarbon and mechanical impurities is sent to cementation along the m4 line. Node 3 processes the clarified solution in a reverse osmosis device to produce desalted purified water (permeate) and a salt concentrate containing the entire amount of salts and radioactive impurities. Permeate on the M1 line is sent for purification to a block of sorption filters, consisting of filters with selective sorbents and activated carbon filters. The concentrate enters node 4. Node 4 is an evaporator made in the form of an evaporator with heat recovery to obtain purified distillate and paste-like concentrate, which is fed through cementing line m2, where an impurity concentrate is also collected from node 1-2. The distillate from unit 4 along the m3 line is fed to a block of sorption filters and a container for collecting and monitoring purified water.

The technical solution is illustrated by the following example. The installation (Fig. 2) is mounted in a 40-foot container, with overall dimensions of 12192 × 2438 × 2591 mm, and includes the following equipment:

Node 1-2 - tangential filtering system is a metal case with a diameter of 150 mm, inside which there are 7 ultrafiltration membranes. Membranes - hollow ceramic rods with a diameter of 55 mm and a length of 1035 mm with a pore size of 0.1-0.05 microns. The initial LRW enter the gap between the housing and the outer surface of the filtering membranes. The circulation pump provides the circulation of the solution at a speed of 7 m / s at a pressure of 3.5 MPa along the surface of the membranes. The result is a separation of the water stream. Part of the water, passing radially through the membrane, is freed from hydrocarbon and mechanical impurities and enters the reverse osmosis unit. Another part of the flow, passing along the membrane surface, washes away the accumulated sediment from it and is periodically dumped into the cementing tank. Node productivity - 2 m ³ / hour. The power consumption of the node is 4.85 kW. Node 1-2 at the inlet has a line for supplying the initial LRW flow and a coagulant dosing line M5, at the exit it has a line for transferring clarified solution to node 3 and an M4 line for dumping the concentrate for cementing. On the m5 line, a coagulant solution - aqueous iron chloride with a concentration of 250 mg / l in an amount of 40 l / h is fed into the LRW input stream using a metering pump.

Node 3 - reverse osmosis system (manufacturer - supplier - Aquatoria LLC) consists of three reverse osmosis stages connected in series, operating respectively at a pressure of 15, 25 and 10 bar. Each stage has a pressure head housing with reverse osmosis membranes (type - CPA5-LD-4040) and a high pressure circulation pump. Overall dimensions of the unit 3 - 3032 × 1874 × 500 mm. The clarified solution from unit 1-2, is sent to the first stage of the reverse osmosis membranes using a high-pressure pump. As a result of the diffusion of water molecules through the membrane, the flow is divided into a filtrate (desalted water passing through the membrane) and a concentrate (water with a high salt content). The concentrate from the 1st stage serves as the source water for the 2nd stage of reverse osmosis. Then, respectively, the concentrate obtained by desalting water in 2 stages enters stage 3. The first stage operates on the source water with a filtrate / concentrate ratio of 6/4. The second stage works on concentrate with a filtrate / concentrate ratio of 6/4. The third stage works according to the concentrate of the second stage with a ratio of filtrate / concentrate - 1/1. Thereby, the total ratio of the filtrate (permeate) / concentrate is reached ~ 10-11 with a node productivity of the initial solution of up to 2 m ³ / h. Power consumption is 6.0 kW.

The concentrate from unit 3 enters unit 4, and demineralized water (permeate) is transferred via line M1 to the block of sorption filters.

Node 4 — the evaporation system — has a line at the entrance for supplying salt concentrate after a reverse osmosis unit, and at the exit, a line for removing distillate to the block of sorption filters and paste-like concentrate to the cementation block. Node 4 is made in the form of an evaporator (type LOFT LE70) with overall dimensions of 1900 × 1800 and a power of 7.5 kW, operating under vacuum at a working pressure of 0.2-0.25 bar with forced circulation of the evaporated solution. Heat recovery according to the heat pump scheme is achieved by heat exchange of water vapor, the circulation of which is provided by the compressor, and supplied to evaporate the solution in a vertical tubular heat exchanger. The plant productivity is 70 l / h, energy consumption for the process is no more than 130 W-h / l of the initial concentrate. When processing in node 4 receive distillate and one stripped off salt concentrate (up to 400 g / l). The distillate passes through the m3 line to the block of sorption filters, and one stripped off salt concentrate is discharged along the m2 line to the cementing device.

A cementing device with overall dimensions of 900 × 1800 × 500 mm includes an electric drive paddle mixer made of crude metal (power 2 kW), a system for manual dosing of cement, a system for supplying hydrocarbon and mechanical impurities concentrate from unit 1-2 and salt concentrate from unit 4, a weight table for installation of replaceable 200 l barrels for the preparation of cement compound. Accumulated waste from units 1-2 and 4 is pumped to a cementing barrel using a submersible pump-based supply system (Grundfos brand). In the process of filling the barrel, cement is dosed and the mixer is working. The ratio of saline / cement = 3: 7. Cement compound complies with GOST Ρ 51883-2002.

The block of sorption filters (size 550 × 550 × 170 mm) consists of three columns (case diameter 150 mm, height 550 mm), two of which are loaded with the FS-10 sorbent for additional extraction of radionuclides, and one with activated carbon for trapping traces of organic substances.

The tank for collecting and controlling purified water has a volume of 1000 liters.

The water lines of the installation are made of PVC pipe, the equipment is interconnected by means of flanges and threaded fittings, PTFE-4 is used as a seal, valves DN 20 ΡΝ 16 bar and DN 20 ΡΝ 25 bar are used as control (shut-off) valves, circulation and supply liquids are carried out by Grundfos brand pumps.

For example, 16 m ³ LRW with salinity up to 1500 mg / dm ³ and radionuclide content: Sr-90 up to 1400 Bq / l, Cs-137 up to 3500 Bq / l, Ri-239 up to 8 hours of continuous operation were processed at the installation 150 Bq / l, At-241 up to 25 Bq / l, uranium -1 mg / l. The productivity of the installation was 2 m ³ / hour for the source water. As a result of processing, ~ 15.7 m ^{3 of} purified water and 0.4 m ^{3 of} cement compound were obtained.

The degree of reduction of RW volume (initial LRW / cement compound) -40. Purified water had the following composition:

Salinity - 5 mg / l;

The sum of β-emitting nuclides is not more than 1 Bq / l;

The sum of α-emitting nuclides is not more than 0.25 Bq / l;

The uranium content is not more than 0.005 mg / l.

According to the content of chemical impurities, the water of this composition meets the requirements for discharge into fishery bodies of water of a radionuclide content below the level of intervention (HC) according to NRB-99/2009. The specific energy consumption was about 3.1 kW · h / l.

Claims (1)

Installation for cleaning liquid radioactive waste, containing a series-connected phase separation unit, a unit for cleaning mechanical solids, a double reverse osmosis unit, connected by a line for transferring permeate to the sorption filter unit, an evaporation unit for salt concentrate obtained as waste at the output of the reverse osmosis unit, made in the form of an evaporation apparatus for obtaining purified distillate and paste-like concentrate, connected by a line for supplying concentrate to the device for cement and a container for collecting and controlling the purified solution, characterized in that the phase separation unit and the mechanical impurities cleaning unit are combined into a single unit that performs the indicated operations by tangential ultrafiltration, the evaporation unit is made in the form of an evaporator with heat recovery, and the installation contains in addition, a line for transferring hydrocarbon and mechanical impurities to the cementing unit from the ultrafiltration unit, a line for transferring distillate to the sorption filter unit and a line for I am dosing the coagulant in the capacity of the stock solution.

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