Metallic Fission Product Retention of Coated Particles with Ceramic Kernel Additives

Abstract

The retention of metallic fission products in coated particles with ceramic kernel additives is studied out-of-pile and in-pile. The ceramic additives are easily introduced without any significant change of kernel fabrication processes. The excellent efficiency of alumina-silica kernel additives for retaining 90Sr and 140Ba is demonstrated in-pile: The fractional release is reduced by two orders of magnitude. Silver-110m is not retained by the kernel additives. Cesium forms compounds in the alumina-silica additives, which become unstable at temperatures above 1400°C (1673 K). At normal high-temperature gas-cooled reactor operation temperatures [1000 to 1200°C (1273 to 1473 K)], the diffusion coefficient of cesium in oxide kernels with alumina-silica additives is reduced by about two orders of magnitude. The effective diffusion coefficients in these kernels are given by the equation