Studies of Ceramic Fuels with the Use of Fission Gas Release Loop, (I)

Fission Gas Release from UO₂-Graphite Mixture during Irradiation

Abstract

Fission gas release from a UO₂-graphite mixture was studied during irradiation with the use of the Fission Gas Release Loop in the JRR-3 reactor. The release rates of fission krypton and xenon increased proportionally with neutron flux (6×10¹⁰-6×10¹²n/cm²•sec) and exponentially with temperature (400°-1, 000°C). A burst of fission gas was observed when the specimen was abruptly heated to a higher temperature. These results can be explained by a mechanism whereby fission gas is trapped in defects created in graphite by fission fragments and released through annealing of the defects.