SIC-FISSION PRODUCT REACTIONS IN HTGR TRISO UC2 AND UCXOY FISSILE FUEL .1. KINETICS OF REACTIONS IN A THERMAL-GRADIENT

The potential for SiC‐lanthanide fission product reactions on the cool side of TRISO‐coated UC2 and UC4.3O1.3 fuel particles was studied in postirradiation thermal‐gradient heating experiments. The kinetics of the reactions were obtained by determining the rate of decrease in SiC thickness as‐a function of temperature and fission density. Reaction rates are independent of the fission density for UC2 kernel burnups >5% FIMA. The rate of change in SiC thickness for TRISO UC2 in a temperature gradient isX (μm/h) = 4.2×107 exp(‐3.283×105/8.313T). No reduction in SiC thickness was observed in TRISO UC4.3O1.3fuel; the rates of SiC fission product reactions are at least an order of magnitude slower than those observed in UC2. No metallic fission product release from TRISO particles was indicated until the SiC layer thickness was reduced by 50%. Copyright © 1979, Wiley Blackwell. All rights reserved