Progress on the chemical separation of fission fragments from Np-236 produced by proton irradiation of natural uranium target

摘要

The aim of the current work is to develop and validate a radiochemical separation scheme capable of separating both Np-236g and Pu-236 from a uranium target of natural isotopic composition (similar to 1 g uranium) and 200 MBq of fission decay products. A target containing 1.2 g of UO2 was irradiated with a beam of 25 MeV protons with a typical beam current of 30 mu A for 19 h in December 2013 at the University of Birmingham Cyclotron facility. Using literature values for the production cross-section for fusion of protons with uranium targets, we estimate that an upper limit of approximately 250 Bq of activity from the Np-236 ground state was produced in this experiment. Using a radiochemical separation scheme, Np and Pu fractions were separated from the produced fission decay products, with analyses of the target-based final reaction products made using Inductively Couple Plasma Mass Spectrometry (ICP-MS) and high-resolution a particle and gamma-ray spectrometry.