A case study in plutonium radiochronometry using multiple isotope systems

Radiochronometry analyses of two Pu metals were performed using the ²³⁷Np-²⁴¹Am-²⁴¹Pu, ²³24U-²³⁸Pu, ²³⁵U-²³⁹Pu, and ²³⁶U-²⁴⁰Pu decay series. For one sample, all radiochronometers yield concordant model dates in 1959-1960, indicating that the aqueous processing method used to purify Pu effectively removed U, Am and Np decay products from the bulk Pu. The second sample yields discordant model dates that are also older than the known production date in 1982. The excess U, Am and Np present in the sample indicate that the sample was purified during at least two different episodes, using a combination of aqueous methods and molten salt extraction. (author)