Irradiation Performance of Coated Fuel Particles with Fission Product Retaining Kernel Additives

Four irradiation experiments for testing the efficiency of fission-product-retaining kernel additives in coated fuel particles are described. The evaluation of the obtained experimental data led to the following results: 1. Alumina-silica kernel additives reduce the inpile release of ⁹⁰Sr and ¹⁴⁰Ba from BISO-coated particles at temperatures of ∼1200°C by two orders of magnitude, and the cesium release from kernels by about one order of magnitude. 2. Effective transport coefficients including all parameters that contribute to kernel release for (Th,U)O₂ mixed oxide kernels and low-enriched UO₂ kernels containing 5 wt% alumina-silica additives are given by the equations: and 3. Alumina-silica kernel additives are ineffective for retaining ^110m Ag in coated particles. However, an intact silicon carbide interlayer was also found to be ineffective at temperatures >1200°C. 4. The penetration of fission-product-containing eutectic additive melts into the buffer layer during irradiation can be avoided by using additives that consist of alumina and mullite without an excess of silica. 5. Annealing of LASER-failed irradiated particles and results of the irradiation test FRJ2-P20 indicate that the efficiency of alumina-silica kernel additives is not altered if the coating becomes defective.