PNNL

Abstract

Volatile loss of technetium (Tc) during vitrification of Hanford low-activity wastes is a technical challenge to treating and immobilizing large volume of radioactive and hazardous wastes at the U.S. Department of Energy’s (DOE) Hanford Site. Various research efforts are being pursued to develop technologies that can be implemented for cost effective management of Tc, including studies to understand the behavior of Tc during vitrification, eventually to increase Tc retention in glass. One of such studies has been identifying the form or species of Tc and Re (surrogate for Tc) that evolve during waste to glass conversion process, which is important for understanding the mechanism of Tc volatilization. In this paper, available literature information were collected and critically evaluated to clarify the volatile species of Tc and Re, more specifically, whether they volatilize as alkali pertechnetate and perrhenate or volatilize as technetium and rhenium oxides after decomposition of alkali pertechnetate and perrhenate. The evaluated data ranged from the mass spectrometric identification of species volatilized from pure and binary alkali pertechnetate and perrhenate salts to the structural and chemical analyses of volatilized materials during crucible melting and scaled melter processing of simulated wastes.