Neutron-Use Optimization with Virtual Experiments to Facilitate Research-Reactor Conversion to Low-Enriched Fuel

摘要

For almost three decades,there have been significant international e?orts to convert research reactors from weapon-usable highly enriched fuel to a fuel based on uranium enriched to less than 20% in the isotope U-235(LEU).The most challenging type of reactors to convert are high-flux research reactors,which,along with some spallation sources,are the most important neutron sources for modern neutron scattering experiments.Advanced Monte-Carlo computer codes are now available that make it possible to track neutrons from the reactor core,through a beam tube,to the instrument and detector.These“virtual experiments”allow optimizing the performance of a research facility as a whole instead of the reactor alone.This may open additional reactors for conversion and could significantly accelerate the“global cleanout”of civilian HEU.This article briefly reviews performance gains obtained for high-flux reactors during previous facility-upgrades.The Monte-Carlo code VITESS is used to compare results for typical neutron scattering experiments using obsolete versus state-of-the-art technologies.The analysis shows that performance gains due to instrument upgrades or neutron guide renewals dwarf potential neutron flux losses due to conversion to low-enriched fuel.