Evaluation of the fission gas release behavior from fast reactor mixed oxide fuel based on local concentration measurement of retained xenon

An advanced model for grain face diffusion transport in irradiated UO2 fuel. Part 1: Model formulation

“…A similar behaviour was observed in the tests [28] with the MOX fuel from Japanese fast reactor JOY0 MK-I, where precipitation of intergranular gas bubbles in the central zone (so-called ''gas bubble region") of the fuel pellets under reactor irradiation conditions occurred significantly later than commencement of gas release from this zone (detected by puncturing tests). At 30 GWd/t, for example, fission gas release takes place at a local fuel temperature of 1080°C, and face bubble formation becomes visible with the optical microscope above 1360°C.…”

“…Threshold temperatures for fission gas release and for bubble formation as functions of burn-up (from Ref. [28]). …”

Fission gas release and swelling in uranium–plutonium mixed nitride fuels

“…Thus, the fraction of fission gas retained in the fission gas bubbles is estimated as about 15%. The fraction of Xe retained in the intragranular region is higher than that of MOX fuel pins irradiated to the same degree of burn-up [6].…”

“…In this study, the outermost part of the MOX fuel irradiated to low burn-ups at low temperature in the JOYO MK-II core was applied as the standard specimen, assuming that all the Xe produced in the fuel region was retained. This method was similar to one described elsewhere [6]. The specimen surface was polished using standard metallographic techniques.…”