Leaching of ¹³⁷Cs, ¹³⁴Cs, and ¹²⁹I from Irradiated UO₂ Fuel

The relationship between the quantity of iodine and cesium present in the fuel-sheath gap region and the amount of stable fission gas released from the fuel matrix has been investigated for typical natural UO₂ Canada deuterium uranium power reactor fuels. Two leaching techniques were employed to determine the fuel-sheath gap inventories of cesium and iodine, and their respective release fractions were derived from these. The ^I37Cs/Xe and ¹³⁴Cs/Xe release ratios were close to one over nearly three orders of magnitude of release fraction. Limited data suggest that ¹²⁹I may show similar behavior. The experiments were performed in support of the safety assessment of irradiated fuel disposal and may have further application to fuel storage and reactor safety studies.