DEVELOPMENT OF CERAMIC WASTE FORMS FOR ACTINIDE-RICH WASTE - RADIATION STABILITY OF PEROVSKITE AND PHASE AND CHEMICAL STABILITIES OF ZR-BASED AND AL-BASED CERAMICS

Ceramics are considered as most promising materials for conditioning o f long-lived radionuclides because of their outstanding durability for long term. The Japan Atomic Energy Research Institute (JAERI) has dev eloped ceramic waste forms, e.g. Synroc and zirconia-based ceramics, f or the actinide-rich wastes arising from partitioning and transmutatio n processes. In the present study, alpha-decay damage effects on the d ensity and leaching behavior of perovskite (one of three main minerals forming Synroc) were investigated by an accelerated experiment using the actinide doping technique. A decrease in density of Cm-doped perov skite reached 1.3% at a dose of 9 x 10(17) alpha-decays.g(-1). The lea ch rates (MCC-1 leach test in pH similar to 2 solution at 90 degrees C for 2 months) of perovskite specimens with accumulated doses of 1.6 x 10(17), 4.0 x 10(17) and 8.3 x 10(17) alpha-decays.g(-1) were 1.7, 2. 3 and 3.0 g.m(-2).day(-1), respectively. Application of zirconia- and alumina-based ceramics for incorporating actinides was also investigat ed by the experiments using non-radioactive elements (Ce and Nd) with an emphasis on crystallographic phase stability and chemical durabilit y. The yttria-stabilized zirconia was stable crystallographically in t he wide ranges of Ce and/or Nd content and had excellent chemical dura bility. (C) 1997 Published by Elsevier Science Ltd.