RU27731U1 - DEVICE FOR GLAZING LIQUID RADIOACTIVE WASTE - Google Patents

Description

Vitrification apparatus for liquid radioactive waste

The inventive utility model relates to the field of environmental protection, and in particular to devices for the disposal of liquid radioactive waste (LRW) by fixing them into glass-like matrices.

Known devices in which the processes of vitrification of LRW in one or two stages.

In a single-stage process, all LRW processing operations are carried out in one apparatus - a melter, which is very important when handling radioactive products. In this apparatus, the LRW melter is sequentially dehydrated, the salts decompose to oxides, which melt and are part of the molten glass. (Phosphate glasses with radioactive waste. Edited by A.A. Vashman and A.S. Polyakov, M., TsNIIatominform, 1997, p. 10).

In a single-stage treatment of LRW, it is necessary to have a developed surface of the glass melt in order to evaporate a large amount of water from the LRW. A disadvantage of the analogue is that industrial melters of this type have large dimensions, while the problem of disposal of spent melters is currently not resolved in Russia.

A known installation for vitrification of LRW, in which the operations of the first stage is carried out in a dryer, and in the second stage, the vitrification of the products is carried out in a separate apparatus - melter (Japanese application No. 60-24440, class C21P 9/16, 1985). The first stage of the process is proposed to be carried out either in a spray dryer or in a tubular rotary kiln.

The disadvantage of the spray dryer is its large dimensions with industrial productivity. A rotary tube furnace with a free core inside the workspace, like any moving mechanisms, is not suitable for use in the zone of high levels of radioactivity due to limited resource, complexity of maintenance, dismantling and disposal.

The device for vitrification of radioactive waste proposed in the patent of the Russian Federation No. 2115182, class 021P 9/16, 1997 contains a dehydration apparatus — a vertical rotor concentrator (VRK).

The drawbacks of the WRC are a small resource in conditions of high radiation fields, a low degree of dehydration of LRW.

The closest in technical essence to the claimed utility model is the LRW vitrification device described in the report (A.V. Demin et al., Use of the induction heating method in a cold crucible for solidification of highly fuels waste. Proceedings of the international conference MRS-2000, Sydney). In this device, the evaporator and separator of the concentrated and combined-gas phases are combined in one housing. A cylindrical separator is located inside the main body of the evaporator, which makes the apparatus very compact. In the annular space of the apparatus

Between the outer casing and the separator there is a spiral tubular coil, into which LRW is continuously supplied, and a coolant is supplied to the annular space - water vapor under pressure. One end of the coil is in communication with the capacity of the initial LRW, and the other end of the coil is brought to the bottom of the separator. The separator is connected with the bottom with the melter, and with the top with the condenser of water vapor and nitric acid. In the separator, LRW concentrate is separated from the vapors. The concentrate, which is a fluid melt of salts with a moisture content of about 20%, flows into the melter, where the final dehydration, decomposition of salts, melting and formation of glass melt take place. The vapor-gas phase passes in the separator from the bottom up, being separated from the droplets of the melt, and through the steam pipe enters the condenser.

The advantage of this device is its compactness, high specific productivity for evaporated moisture, the absence of moving mechanisms, the possibility of remote dismantling and disposal for disposal in a standard protective container.

The disadvantage of the prototype is the need for periodic cleaning of the surface of the separator from deposited on it and dried drops of LRW melt. For several hours of continuous operation, a solid sediment layer forms on the walls of the separator, which reduces the cross-sectional area of the separator. As a result, the speed of the gas-vapor flow in the separator increases and, as a result, the amount of product carried away by the gas-vapor flow to the condenser increases, which is undesirable. It is necessary to periodically stop the main process for cleaning the separator.

The task to which the proposed utility model is directed is the creation of a device for vitrification of radioactive waste, which will ensure continuous operation, increase overall productivity, and improve operational safety.

This problem is solved in that the device for vitrification of LRW includes a LRW preparation unit, a direct-flow LRW concentrator, a glass melter, a glass melt receiver, a gas purification unit, a piping system, remote connectors and valves, and a direct-flow concentrator consists of a remotely separated direct-flow evaporator and a concentrated and combined-gas separator phases, the evaporator is made of series-connected sections "pipe in pipe, the input of the first section is connected to the LRW capacity, and the output of the last section is tangent Flax introduced into the separator which is a vertical cylindrical body with a hemispherical cover and the outer water cooling jacket, within the housing of the separator is an annular pocket with a pipe for collecting condensate. The separator is located above the melter and is connected by steam and gas supply to the gas treatment unit.

An additional tubular spiral vapor condenser and a separation cone are placed inside the separator, into which the evaporator pipe is introduced tangentially.

In FIG. 1 shows a diagram of the proposed ugroysgva, in FIG. 2 shows a diagram of a device with a vapor condenser, where: 1 - direct-flow evaporator; 2 - separator; 3 - coil; 4 - a melter; 5 - cooling shirt; 6 - LRW supply pipeline; 7 - heating steam supply pipe; 8ch-9 - cooling water inlet and outlet pipelines; 10 - pipeline for the concentrated phase;

11 - pipeline exit of the vapor-gas phase; 12 - LRW condensate outlet pipe; 13 - remote connector; 14 - an annular pocket; 15 - dividing cone; 16 - steam condensate outlet pipe.

The proposed device operates as follows. LRW through the pipeline (6) is pumped into the inner pipe of a once-through evaporator (1). Water vapor is supplied to the outer pipe of the evaporator through the pipe (7) at a temperature of 110-160 ° С, and steam condensate leaves through the pipe (16). LRW pass sequentially through the sections of the evaporator, turning into a mixture of concentrate (melt) and the vapor-gas phase, which through the remote connector (13) flows from the evaporator to the separator (2). In the separator, separation of the concentrate and steam occurs. The concentrate (10) flows into the melter (4), and the vapor-gas phase rises up the evaporator and enters the gas purification system through the pipe (11).

On the inner wall of the separator, the temperature of which is maintained at 80-90 ° С by supplying cooling water to the jacket (5) through the pipe (8), partial (1-5%) condensation of water vapor and nitric acid occurs. Condensate flows down the inner surface of the separator and flushes particles of fusion deposited on it into the annular pocket (14) and then through the pipe (12) into the condensate collector. Heated water exits the shirt through the pipe (9). The main part of the vapor-gas phase comes from the separator to the gas treatment system (11).

In the device (see FIG. 2), the separation of the concentrate and the vapor occurs in the separation cone (15), and the bulk of the vapor condenses on the coil (3). The condensate dissolves the particles of the melt deposited on the coil, flows into the annular pocket and then enters the condensate collector. The remainder of the vapor, along with non-condensable gases, escapes

separator through the steam line to the gas treatment unit. The use of a separating cone and a cooled coil inside the separator provides better conditions for the separation of concentrated and vapor-gas phases, however, the device according to this option is more complicated in design. A comparative experimental verification of the proposed device and prototype was carried out during vitrification of LRW simulators at a 2-stage vitrification stand. The test results are shown in the table.

Table

Tests have shown the advantages of the proposed device. Compared with the prototype, the entrainment of radioactive products into the gas treatment system is reduced by 1.6 times at the beginning of the process and 10 times after 8 hours.

The ablation of radioactivity in the prototype device during testing increased due to overgrowth of the separator by dried waste salts. As the separator overgrown, the speed of the vapor-gas phase increased

in the separator from 1.0 to 2.1 m / s, which led to increased entrainment of the product. After 8 hours, the ablation reached an unacceptable value of 5%, and a process stop was required to clean the separator from sublimates.

In the proposed device, the separator does not overgrow due to the fact that the sublimates are continuously washed off from the walls of the separator by condensing moisture. As a result, the entrainment of radioactivity into the gas purification system is reduced, and a periodic shutdown of the process for cleaning the separator is not required, and the operation safety is increased. As a result, the overall productivity of the installation increases by 10-20%.

Claims (2)

1. A device for vitrification of liquid radioactive waste, including a unit for preparing liquid radioactive waste, a direct-flow concentrator of liquid radioactive waste, a glass melter, a glass melter receiver, a gas cleaning unit, a piping system, remote connectors and fittings, characterized in that the direct-flow concentrator consists of a remotely-separated direct-flow an evaporator and a separator of concentrated and vapor-gas phases located above the melter and connected by a steam-gas pipeline to a gas purification unit , the evaporator is made of series-connected sections of the pipe-in-pipe type, the inlet of the first section is connected to the liquid radioactive waste tank, the output of the last section is tangentially introduced into the separator, which is a vertical cylindrical body with a hemispherical cap and an outer water cooling jacket, inside of which An annular pocket with a condensate collection pipe is located. 2. The device according to claim 1, characterized in that the tubular spiral vapor condenser and a separation cone are additionally placed inside the separator, into which the evaporator pipe is introduced tangentially.