Ceramic Matrix Composites Based on Lanthanum Orthophosphate for Disposal of High-Level Radioactive Waste

Abstract

Abstract Ceramic matrix composites for solidification and disposal of actinide-rare-earth fraction of high-level waste (HLW) were prepared by sintering of nanosized powders of 0.8LaPO4–0.2Al2O3, 0.8LaPO4–0.2Y2O3 and 0.8LaPO4–0.2ZrO2 obtained from 0.8LaPO4 · nH2O–0.2Al(OH)3, 0.8LaPO4 · nH2O–0.2Y(OH)3 and 0.8L-aPO4 · nH2O–0.2ZrO(OH)2 precursors. These powders-precursors were synthesized via sol-gel technique. After heat treatment at 850°C powders of 0.8LaPO4–0.2Al2O3, 0.8LaPO4–0.2Y2O3 and 0.8LaPO4–0.2ZrO2 were obtained. Further powdered compositions were stepwise sintered to prepare ceramic composites which were supposed to be used as matrices for storage of HLW. Rate of La3+, Al3+, Y3+ and Zr4+ leaching from ceramic matrix composites in strength aqueous solutions of NaCl and Na2SO4 simulating underground brine typical for proposed location of HLW geological repository was estimated.