Fission Gas Release from Nuclear Fuels, (II)

Fission Gas Release from Nuclear Fuels during Low Temperature, Low Dose Irradiation

抄録

The release behavior of fission gases in U-metal, UO₂ and uranium carbides, irradiated at arelatively low temperature (below 100°C) to low dosage, was studied by out-of-pile experiments.
It was found that fission gas (¹⁸³Xe) released from a specimen by fission fragment recoil is mostlycaptured in the wall of the irradiating capsule or in the capsule support material.
The amount of fission gas released into the void space of the capsule is proportional to thesurface area and to the fuel burn-up, and is controlled by a knock-out release mechanism. Thenumber of U atoms considered to take part in the knock-out mechanism by evaporation or displacement due to the intrusion of a recoil fission fragment, is estimated to be 1.4×10⁵-2.7×10⁵ atoms for U-metal and 5×10⁴-10×10⁴ atoms for UO₂ and uranium carbides.