Liquid radioactive waste concentration methods

Methods for concentrating liquid radioactive wastes (LRW) - an important step in waste processing procedures aimed at reducing hazards to personnel and the public - are reviewed, and some of their advantages and drawbacks pointed out. Chemical LRW-treatment methods include coagulation (by aluminium sulfate, ferric chloride, etc.), soda-lime softening of water, as well as techniques based on specific reactions with particular nuclides. By addition of sorbents (clay, activated charcoal, etc.) the chemical scavenging effect is enhanced, while use of flocculating agents (sodium polyalginate, polyacrylamide, synthetic polymers, etc.) produces accelerated deposition of resulting precipitates. A second major LRW-concentration method is evaporation, which is relatively expensive and, moreover, inapplicable in the case of volatile radionuclides escaping into the fume-and-vapor phase. It is emphasized that to overcome difficulties due to presence of contaminants such as saponaceous, organic or mineral oil matter, use of defoaming agents is indicated. A third important LRW-concentration method is that by ion exchange; synthetic is well as natural organic ion exchan.gers are in use. There are a number of other methods that also find application, such as biological techniques, electrodialysis, embedding in bitumen or asphalt, sand filtration, etc. (A.B.)