Research Program to Investigate the Fundamental Chemistry of Technetium

Technetium ({sup 99}Tc, half-life = 2.13 x 10{sup 5} years, ?-emitter) is one of the radionuclides of major concern for nuclear waste disposal. This concern is due to the long half-life of {sup 99}Tc, the ease with which pertechnetate, TcO4{sup -}, migrates in the geosphere, difficulties in incorporating technetium into glass waste forms, and the corresponding regulatory considerations. The problem of mobility of pertechnetate in the environment is compounded by the fact that pertechnetate is the thermodynamically stable form of technetium in oxidizing environments. These factors present challenges for the separation and immobilization of technetium. The objective of this research project is to provide new knowledge about the chemical behavior of technetium so that the factors underlying technetium speciation in nuclear waste and in waste forms can be understood and the problems can be addressed. In particular, the behavior of technetium and rhenium in glass will be examined since rhenium is ofte n used as a non-radioactive surrogate to predict the behavior of technetium. In this project, glasses containing both rhenium and technetium will be prepared, so that the behavior of both metals can be compared under identical conditions.