PREPARATION AND VALIDATION OF NEW TYPE OF LARGE SIZE DRIED SPIKES

A new type of large size dried spike for determinations of uranium and plutonium in input solution of spent fuel from reprocessing plants by isotope dilution mass spectrometry has been prepared at the Institute for Reference Materials and Measurements. The new dried spike contains about 50mg of uranium (with a 19.7% 235U enrichment) and 2mg of plutonium (with a 97.8% 239Pu abundance), and is covered with cellulose acetate butyrate as a new type of organic stabilizer. Certified reference materials uranium metal EC-101, 93% enriched uranium metal NBL CRM-116 and plutonium metal CETAMA MP2 were used to prepare a synthetic mother solution with a concentration of about 20 mgU/g and 0.8 mgPu/g. Aliquots of the mother solution were dried to give large size dried spikes and a solution of cellulose acetate butyrate in acetone was added and carefully dried to cover the dried materials. Spikes treated like this can resist shocks encountered during transportation and prevent flaking off over long-term storage as well. It was found that the cellulose acetate butyrate will prevent flaking-off and confers good resistance against shocks, but is readily soluble on heating with nitric acid solution. The large size dried spike containing cellulose acetate butyrate was certified as reference material IRMM-1027f with certified quantities, 235U and 239Pu amounts and uranium and plutonium amount ratios.