A Study on the In-growth of Uranium Daughters’ Gamma-rays from a Freshly Separated Uranium Gamma-ray Standard

摘要

Uranium gamma-ray isotopic analysis codes rely strongly on an assumption that the uranium daughtersare in secular equilibrium with their parents. Without a prior knowledge of the separation time, it ispossible that freshly separated natural uranium samples can be analyzed mistakenly as enriched uraniumsamples using only the gamma-ray signatures. In this study, we used a 1g 0.5% uranium standard fromthe National Bureau of Standards (NBS) and performed a chemical separation of uranium from theirdaughters. The separated uranium solution was dived equally into two samples, one counted on a coaxialHPGe (High-purity germanium) detector and the other counted on a planar HPGe detector. The gammaraydata were collected with list-mode data acquisition systems. We have analyzed the gamma-ray datawith MGA++ and observed the “time-dependent” uranium analysis results, and as expected, the resultsare ranging from highly enriched uranium to slightly enriched uranium. However, with a properknowledge of the separation time, the isotopic analysis results are in good agreement with the declaredvalues (i.e., depleted uranium). We also observed gamma-rays that were signatures from the separationchemistry.