Equilibrium leach testing and on-line, nondestructive strength prediction methods as cemented radioactive waste form qualification procedures

Abstract

The disposal of solidified radioactive wastes requires physical, chemical, and radiological characterization to ensure safety. Two quantities important to physical characterization include compressive strength and leach resistance. It is desirable to monitor strength development on-line in processing whenever possible. Therefore, the ability of nondestructive evaluation techniques to predict the long term compressive strength of waste forms during their processing was theoretically and experimentally evaluated. It was determined that the compressive strength of the mixture could be predicted through analysis of both rheological behavior and maturity development. Ultrasonic methods were shown to be less effective. Leach testing requires destructive analysis. The ability of neutron activation analysis to increase the detection limit of leached cobalt from cement waste forms containing EDTA was experimentally examined. A detection limit approaching 53 parts per billion was found. EDTA concentration had a measurable effect on the cobalt release due to cobalt chelation and matrix degradation.