Short-lived fission product release from UO2: Annular versus solid pellets

We have irradiated, in a “dual sweep” test assembly, one element containing solid UO₂ pellets with four, $\text{1 × 1}$ mm surface slots and one element containing annular UO₂ pellets with a central hole two mm in diameter. Data are reported for a linear power range of 17–57 kW/m; thermocouples monitored operating temperatures. He-2%H₂ carrier gas swept short-lived fission products from both elements past independent spectrometers for identification and measurement. The releases from the solid and annular fuel were power-dependent from 17–57 kW/m, with the annular fuel release up to eight times greater than that for solid fuel. The annular fuel also showed a larger released iodine inventory in fuel and sheath areas with access to the carrier gas.