The Combination of Finely Divided Inorganic Ion Exchangers and Ultrafiltration for the Treatment of Low- and Medium-Level Waste

Summary

The Harwell Laboratory is engaged in the design and development of processes to reduce the radioactivity present in low and intermediate level waste streams to a very low level. Three types of process are being examined, precipitation, ultrafiltration and ion-exchange using Inorganic absorbers; these processes are used singly or in combination depending on the composition of the waste and the extent of decontamination required.

Modern cross-flow filtration techniques allow the removal of very fine particles of solid material from aqueous streams. When the streams contain radionuclides, some small additional activity removal may be achieved by cross-flow filtration even after the stream has been treated by conventional filtration and ion-exchange, and despite the concentration of radionuclides being exceedingly small. Much greater activity removal may be achieved, however, if the stream is dosed with additives which absorb or coprecipitate the radionuclides. This paper describes the development and characterisation of several such seed materials (finely divided Inorganic ion-exchange materials) and an investigation of factors which influence their effectiveness.