Sensitivity Studies and Experimental Evaluation for Optimizing Transcurium Isotope Production

This work applies to recent initiatives at the Radiochemical Engineering Development Center at Oak Ridge National Laboratory to optimize the production of transcurium isotopes in the High Flux Isotope Reactor in such a way as to prolong the use of high-quality heavy curium feedstock. By studying the sensitivity of fission and transmutation reaction rates to the neutron flux energy spectrum, a flux filtering methodology is explored for increasing the fraction of (n,γ) reactions per neutron absorption. Filter materials that preferentially absorb neutrons at energies considered detrimental to optimal transcurium production are identified, and transmutation rates are examined with high-energy resolution. Experimental capsules are irradiated employing filter materials, and the resulting fission and activation products are studied to validate the filtering methodology. Improvement is seen in the production efficiency of heavier curium isotopes in ²⁴⁴Cm and ²⁴⁵Cm targets and potentially in the production of ²⁵²Cf from mixed californium targets. Further analysis is recommended to evaluate longer-duration irradiations more representative of typical transcurium production.