α-Particle and γ-ray spectrometry of a plutonium solution for impurity determination

A highly enriched 240Pu solution was measured by α-particle and γ-ray spectrometry to determine other radionuclides present in the material as impurities. Low activities of 238Pu, 241Am, 243Cm and 244Cm were determined by measuring thin sources, made from the original solution, in a high-resolution alpha-particle spectrometer. The sources were prepared by evaporating the plutonium solution on quartz plates in a vacuum chamber. From the ingrowth of 241Am in the original solution, the amount of 241Pu could be calculated. After radiochemical separation of 241Am, the plutonium was measured by high-efficiency alpha-particle spectrometry to determine the amount of 238Pu. The enriched 240Pu material was also measured by high-resolution gamma-ray spectrometry, using two different HPGe detectors to determine the impurities of 239Pu and 241Am. The preparation of the sources and the measurement methods are described and discussed. The measured impurities, given in % of the 240Pu activity, are compared with the values on the certificate.