IN-PILE FISSION-GAS-RELEASE BEHAVIOR OF ALUMINA-COATED UO2 PARTICLES IRRADIATED TO HIGH BURNUP

摘要

Several types of coated-particle fuel materials and coated-graphite fuel elements were irradiated at temperatures up to about 1350 F to a total uranium burnup of about 6 a/o. The fission-gas-release behavior of one of these materials, 100 to 140-μ-diameter UO2 particles coated with 40 μ of vapor-deposited Al2O3, was studied in detail.nThe fission gas released by this material was brought by a flowing stream of helium from the specimen to a point where it was sampled intermittently so that the amount released could be determined. Stainless steel mesh traps were placed close to the capsule from time to time to trap the solid decay products of the short-lived fission gases.nThe fission-gas retention of this material was extremely good at low burn-up when the particle coatings were intact. Deterioration was first noted at 1 a/o burnup, and became relatively severe at between 3 and 5 a/o burnup. Cracking of particle coatings was the cause of deterioration. Fission-gas release initially was approximately 10-7 and at about 6 a/o burnup was 10-2 for the long-lived fission gases and below 10-4 for most of the shorter lived ones.