Information in spectra from sources containing "aged" Am-241 as from TRU waste

The Ge gamma-ray spectra of Am-241 were studied using sources of Am-241 tha t had not been purified from their daughter activities for many years. In s pite of the fact that the first member of the Am-241 decay chain, Np-237, h as a half-life of 2.14x10(6) years, the grow-in of the second member of the Am-241 decay chain, 27-day Pa-233 could be clearly observed. This unexpect ed observation is possible when the parent emits low-intensity gamma-rays w hile the progeny emits high-intensity y-rays. A calculation of the ratio of the parent to daughter gamma-ray emission rates for the 241Am 322-keV gamm a-ray and the Pa-233 312-keV gamma-ray as a function of time from purificat ion verifies that this is the case for the 322-keV Am-241 gamma-ray and the 312-keV Pa-233 gamma-ray. These gamma-rays may be used in the assay of tra nsuranic waste to determine its age, when Am-241 is present In the waste, a nd also to assay for Np-237 in excess of that expected from grow-in of its 241Am parent. Published by Elsevier Science Ltd.