Abstract
The performance of irradiated TRISO UC2 and TRISO UC4.301.3 HTGR fissile fuel particles was studied by postirradiation isothermal heating at 1600° to 2000°C to evaluate HTGR fuel performance models. Test conditions were similar to reactor conditions predicted for hypothetical core heatup events evaluated during safety and licensing studies. Less than 2% of the particles experienced failure of all coating layers with rapid gaseous and metallic fission product release (pressure vessel failure). Lanthanide fission product, Cs‐137, and Kr‐85 release occurred in the remaining particles by diffusion through intact outer pyrocarbon layers after SiC‐lanthanide fission product reactions had penetrated the SiC layers. The rates of SiC‐fission product reactions depended on the fission density of the test samples and were less than or equal to those observed in a thermal gradient. Test results showed the HTGR fuel performance models to be very conservative.
Published Version
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