Development of an efficient approach to perform neutronics simulations for plutonium-238 production

Conversion of ²³⁸Pu decay heat into usable electricity is imperative to power National Aeronautics and Space Administration (NASA) deep space exploration missions; however, the current stockpile of ²³⁸Pu is diminishing and the quality is less than ideal. In response, the US Department of Energy and NASA have undertaken a program to reestablish a domestic Pu production program and a technology demonstration sub-project has been initiated. Neutronics simulations for ²³⁸Pu production play a vital role in this project because the results guide reactor safety-basis, target design and optimization, and post-irradiation examination activities. A new, efficient neutronics simulation tool written in Python was developed to evaluate, with the highest fidelity possible with approved tools and improved computational speed, the time-dependent nuclide evolution and heat deposition rates in ²³⁸Pu production targets irradiated in the High Flux Isotope Reactor (HFIR). The Python Activation and Heat Deposition Script (PAHDS) was developed specifically for experiment analysis in HFIR and couples the MCNP5 and SCALE 6.1.3 software quality assured tools to take advantage of an existing high-fidelity MCNP HFIR model, the most up-to-date ORIGEN code, and the most up-to-date nuclear data. Three cycle simulations for the ²³⁸Pu production targets were performed with PAHDS using ENDF/B-VII.O, ENDF/B-VII. 1, and the Hybrid Library GPD-Rev0 cross-section libraries. The ²³⁸Pu production results were compared with VESTA-obtained results and the impact of various cross-section libraries on the calculated metrics were assessed.