Studies on the age determination of trace plutonium

An isotope dilution multicollector inductive coupled plasma mass spectrometry (ID-MC-ICP-MS) method for determining age of trace Pu through measuring Pu-241/Am-241, Pu-240/U-236 ratio was established. At the same time, other two methods-alpha-spectrometry combined with MC-ICP-MS and liquid scintillator combined with alpha-spectrometry through measuring Pu-241/Am-241 ratio to determine the age of trace Pu were also studied. The techniques were explored for the age determination of nanogram grade Pu sample on the basis of Pu/Am, Pu/U separation. The ages of two Pu samples-one with known and the other with unknown age-were determined by the three methods. The determined ages by the three methods were all in agreement with the reference value. The established methods for determining the age of trace Pu could be adopted in the verification activities of nuclear safeguards and nuclear arms control.