~(237)Np originates in environment from atmospheric nuclear tests, nuclear fuel reprocessing and from single nuclear events, which all have released ~(237)Np, ~(241)Am (mother nuclide) or ~(241)Pu (grandparent nuclide) to environment. Np is more mobile than other actinides in environment having several, easily changeable valence states. Furthermore, in the distant future ~(237)Np will be the dominating transuranium isotope in the environment due to its long, 2.16 million years, half-life and constantly increasing inventory from both direct ~(237)Np emissions and production by the decay chain ~(241)Pu -> ~(241)Am -> ~(237)Np. The aim of the work was to determine total amount of ~(237)Np, deposited from nuclear weapons testing in 1950-1960's and the Chernobyl accident, in Finland. Regional distribution of ~(237)Np in Finland was also sought. Furthermore, two analytical methods were tested, one based on ~(235)Np-tracer and other ~(242)Pu-tracer in ~(237)Np analysis. Samples utilized in this study were collected from peat bogs in Southern and Central Finland immediately after Chernobyl accident. Previously activity concentrations of Pu isotopes, ~(243)Am and ~(244)Cm have been determined from same samples [1,2]. Separation method included wet ashing with concentrated acids, co-precipitation with calcium oxalate and TEVA~(~R) column separation. Concentration of ~(237)Np in sample was determined by ICP-MS. Recovery was determined either by measuring activity of low-energy photons/x-rays from ~(235)Np with Quantulus 1220 or concentration of ~(242)Pu with ICP-MS. Activity concentration of ~(237)Np in peat at different bogs, total ~(237)Np deposition in Finland and differences between two analytical methods will be presented in more detail.
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