Speciation of actinides in groundwater samples collected near deep nuclear waste repositories.

Actinide binding to colloidal particles of different nature was studied under oxic and anoxic conditions of an underground nuclear waste disposal site using successive micro- and ultrafiltration techniques. According to the actinide redox speciation, under oxic conditions they were present in high oxidation states except for plutonium, for which a significant part was found in the tetravalent state. In case of the anoxic conditions, the share of An (IV) was proportional to the total U(IV) concentration.

Determination of Np-237 by radiochemical neutron activation analysis combined with extraction chromatography.

A procedure for determination of 237Np, 238Pu, 239,240Pu and 241Pu in environmental samples is described. Neptunium-237 is determined using radiochemical neutron activation analysis with pre- and post-irradiation chemistry based on solvent extraction and extraction chromatography. 238Pu, 239,240Pu is determined using alpha spectrometry and 241Pu by liquid scintillation spectrometry.