The preparation and characterisation of a 1:1:1 mixture of 239Pu:240Pu:242Pu for use as a reference material for mass spectrometric analysis

A plutonium nitrate solution containing the isotopes 239Pu, 240Pu and 242Pu in a 1:1:1 atomic ratio has been produced at Harwell for use as a reference material for thermal ionisation mass spectrometric analysis. This reference material was prepared by blending weighed quantities of stock solutions of plutonium of high isotopic enrichment and accurately known plutonium concentration, established by controlled-potential coulometric measurement. The calculated atom ratios together with the associated uncertainties at the 95% confidence level are 240Pu to 239Pu 0.9999 ± 0.0006 and 242Pu to 239Pu 0.9999 ± 0.0010. (author)