CURRENT RESEARCH ON I-129 IMMOBILIZATION

Radioactive 129 I has a half-life of 1.57x10 7 years and is produced in the nuclear fuel cycle. One method of conditioning 129 I is to adsorb it from a gas stream heated at ~ 200 0 C onto a AgNO3 impregnated ceramic to form Ag 129 I. A range of commercial porous AgNO3-impregnated porous alumina and silica sorbents are available for this purpose. Once 129 I is incorporated as Ag 129 I then the long term immobilization is a challenging problem because of the long half-life of 129 I and its volatility during processing. In this paper we review the work carried out by various investigators in attempting to contain this Ag 129 I and our current program. It covers the immobilization of AgI in glasses, ceramics and other matrices by sintering, hot pressing or hot isostatically pressing (HIPing). The volatilization of AgI above its melting point of ~ 552 0 C entails that HIPing in a can is a very good option to produce a dense material. The matrix selected has to densify at low temperatures to prevent the AgI volatilization. The selection of the matrix, the HIPing temperature and the aqueous durability of the matrix will determine the best solution for the immobilization of 129 I via AgNO3-impregnated sorbents.