Patent GB-1141196-A (GB)
Title: Method of, and apparatus for, purifying gases contaminated with radioactive substances
IPC: G21F9/02
Filed: 1966-02-17
Abstract: 1,141,196. Purifying radioactive gases. SIEMENS-SCHUCKERTWERKE A.G. 17 Feb., 1966 [17 Feb., 1965], No. 7115/66. Heading G6R. [Also in Divisions B1 and B2] A gas contaminated with radio-active substances is purified by increasing its moisture content, cooling it and thereafter or simultaneously passing it through dust extraction and/ or filtering means which also act simultaneously as a moisture separator. The gas is preferably heated before or during the moistening operation. In a simple form of apparatus, Fig. 1, the gas is passed through a tube 1 and water is sprayed through a nozzle 2. The moistened gas then passes successively through a cooler 3 and a filter 4. In another embodiment, Fig. 2, each of two filters 41, 42 which are preceded by coolers 31, 32 and spraying nozzles 2 is alternately traversed by the gas to be purified and by air for drying the filter so that when gas is flowing through one filter, drying air is flowing through the other. The filters in the above two embodiments may be of the activated charcoal type or they may be constituted by cyclone dust extractors, electrostatic precipitators, Venturi washers or cloth, woven fabrics or paper filters. In a further embodiment, Fig. 3, the gas to be purified is fed via a tube 11 (in which it is moistened by means of a sprayer 20) into a vertical tubular helical flow dust extractor 12. Cool auxiliary gas 14, which is the same as the gas being treated but in a pure condition, is supplied through a jacket 13 and passes through latteral nozzles 16 into the interior of the extractor 12 where it creates a potential flow 161 (see Specification 933,224) which gives rise to a rotary flow 100 initiated by a drop-shaped streamlined body 19. The radioactive substances are separated by a vortex source which forms at the lower end of the body 19 and are carried by the potential flow into a bunker 21. The purified gas 18 flows through an upper nozzle-like aperture 17. A number of extractors may be connected in series. To improve separation, additional condensation nuclei may be produced by electrostatic corona discharges or by irradiation of the gas with ultra-violet light. In the latter case, a mercury vapour low-pressure lamp may be axially mounted in the extractor chamber 12 and to improve irradiation the inside surface of the wall of the chamber may be made, or coated with a layer, of stainless steel, Ni, Cr or Al. Alternatively, the wall of the chamber and the body 19 may be coated with a material which emits α- particles or may be made of a radiating material which can be activated in a nuclear reactor. In both cases, the material chosen must not itself comprise any gaseous isotopes in its radio-active series. Separation efficiency may also be increased by mixing with the gas solid or liquid, non-radioactive substances which absorb or adsorb radioactive substances or gases. Where the particles to be separated are volatile, chemicals may be added to the water spray to convert the particles to non-volatile chemical compounds. Alternatively, the inside wall of the extractor chamber 12 may be sprayed or sprinkled with a solution containing such chemicals or the inside walls of the chamber and of the gas supply pipe may be made of a material which effects the necessary chemical conversion.