Separation of thorium from uranium in support of particle reference material production

This work investigated the utility of UTEVA and TEVA extraction resins for the separation of Th from U. The ²³⁰Th/²³⁴U radiochronometer is one 'fingerprint' of nuclear material used to verify a State's compliance with non-proliferation treaties or bi-lateral agreements. Reference materials with suitable particle densities, geometries, compositions and well-documented purification dates are continually needed. Legacy uranium inventories can be used as feedstock to produce younger reference materials, if the U and Th are quantitatively separated to reset the age of the material and allow new model ages to be developed by adding known quantities of ²³⁰Th (e.g. SRM4325). High recoveries, > 90% of U were achieved using UTEVA but ∼ 0.5% of Th remained with the U. The TEVA double stack showed quantitative recoveries of U and removal of Th below ICP-MS detection limits. (author)