63Ni in Chernobyl 'ruthenium hot particles' and in forest soil samples

Results of 63Ni and 60Co determination in forest litter samples collected in 2007 in highly contaminated Chernobyl exclusion zone as well as in isolated ''ruthenium hot particles'' collected in 1986 in Northeastern Poland are presented. In case of bulk samples relatively complicated radiochemical procedure was necessary for nickel separation from matrix elements and other radioisotopes present. The main steps in radiochemical operations were cobalt separation on Dowex 1 x 8 anion-exchange resin and separation of most of the matrix elements under basic conditions. Nickel was precipitated with sodium sulfide and when dissolved in aqua regia, Ni-DMG complex was formed, extracted with chloroform and back-extracted with hydrochloric acid. 63Ni activity was measured with a liquid scintillation spectrometer, and the chemical yields were controlled by means of AAS method. A significant correlation between 60Co and 63Ni was found for both sets of samples, and the 63Ni/60Co mean ratio (decay corrected) is comparable for the two sets of samples. (orig.)