Determination of plutonium in nuclear materials with the combination of alpha and gamma spectrometry

Alpha-particle spectrometry (AS) and high-resolution gamma spectrometry (HRGS) are jointly used for the determination of plutonium concentration in various materials containing this element. With AS the alpha activity ratios of 238Pu/(239Pu + 240Pu) in spiked and unspiked samples and with HRGS the isotopic composition of plutonium in unspiked samples have been measured. The plutonium concentrations are calculated from the isotope dilution formula and are compared with the results from isotope dilution mass spectrometry (IDMS). The relative differences between the results of both methods are within ± 1%. Several factors such as the quality of alpha sources, sample size and the errors in HRGS affect the results and they are discussed in detail.