LANTHANIDE OXALATES AS A POSSIBLE FORM OF INTERMEDIATE SEPARATION FOR LONG-LIVED FISSION-PRODUCT NUCLIDES

摘要

The chemical composition of fission-product nuclides after their removal from a reactor after one year operation attracts attention by prevalence of rare earth elements (La, Ce, Pr, Nd, Pm, Y) together with alkaline (Cs) and alkaline-earth (Sr, Ba) elements. Their contribution to the total radioactivity increases with time and reaches up to 96% in 5 years. All lanthanides form some types of insoluble compounds, and oxalates are one of them. The solubility products of both normal (simple) oxalates and double REE oxalates with added alkaline cations are considered as a basis for possible intermediate operation of lanthanide group precipitation. Ba and Sr could be coprecipitated together with them, especially within a universal Ca-oxalate matrix. Long-lived actinides (Pu, Am, Np, Cm) form sparingly insoluble oxalates too, and they are discussed as probable participants of suggested technology.