Absolute Branching Ratios of Prominent γ Rays Following α Decay of 233U

Abstract

The absolute γ-ray branching ratios (emission probabilities) for 19 prominent peaks in the α decay of ²³³U are reported with energies ranging from 97 to 366 keV. The branching ratios were obtained from α-γ coincidence measurements, normalized to the α singles. The high-purity ²³³U material ($>99.98\text{\%}$) was separated from its decay products before preparation of a 4.74-$\text{mg}/{\text{cm}}^2$ uranyl nitrate foil with a 6-mm diameter. This is the first report on the absolute normalization of the branching ratios since 1984 and it is the only measure by α-γ coincidences, where the $\alpha \text{-}\gamma /\alpha$ ratio removes several potential systematic biases. Overall, the results are consistent with the adopted literature and they validate the quantities most relevant to the non-destructive assay of fissile ²³³U material, which is relevant to the thorium fuel cycle and associated safeguards.