ICP-MS analysis of plutonium activities and 240Pu/239Pu ratio in alpha spectrometry planchet deposits

Plutonium isotopes were measured by alpha-spectrometry and ICP-MS in sediment samples from two European lakes: Blelham Tarn in U.K. and Stechlin lake in Germany. The ICP-MS measurements were made after alpha-spectrometry counting of the planchets. The planchets were prepared by traditional electrodeposition method after radiochemical extraction, separation and purification of the Pu fraction. A short radiochemical separation using plutonium selective resin, between the two spectrometry measures, is presented. The results show that these two complementary methods are in good agreement, the plutonium activity concentrations are the same. Alpha-spectrometry allows the 238Pu determination and ICP-MS individual measurement of 239Pu and 240Pu. 238Pu/239+240Pu and 240Pu/239Pu ratios are calculated to determine the plutonium contamination source. With the results of these two techniques, it could be demonstrate that the plutonium is of global fallout origin.