PNNL

Abstract

Radiation effects from alpha-decay events in crystalline oxides, which are proposed for the immobilization of actinides, often lead to amorphization, macroscopic swelling and order-of-magnitude increases in dissolution rates for all of the phases currently under consideration. However, the results of systematic experimental studies using short-lived actinides and ion-beam irradiations, studies of radiation effects in U- and Th-bearing minerals, and the development of new models of the damage process over the past 20 years have lead to a substantial increase in the understanding of the processes of damage accumulation in apatite, zircon, perovskite, zirconolite, and pyrochlore/fluorite structures. This fundamental scientific understanding now provides a basis for the selection of nuclear waste forms based on their predicted performance in a radiation field. One of the recent successes of these studies has been the discovery of a class of radiation-resistant pyrochlore/fluorite structures that can serve as highly durable, radiation-resistant host phases for the immobilization of actinides.