Theoretical Yields for ¹⁸⁸W Production in the High Flux Isotope Reactor

Accurately predicting the production yield of ¹⁸⁸W and ¹⁹¹Os from enriched 186W metal rings irradiated in HFIR is not straightforward. Two key factors can lead to significant uncertainty or inaccuracy in yield predictions: The effect of neutron flux depression in the dense tungsten metal target. Inaccuracy of the currently published ¹⁸⁷W thermal neutron absorption cross section. This manuscript reports the calculated yields for ¹⁸⁸W, ¹⁹¹Os, and total osmium mass for the NM-888 target that was irradiated in High Flux Isotope Reactor (HFIR) Cycles 487 and 488. Three different yield calculation methods were used and are described herein. The results are presented in terms of total yield and in terms of yield per target mass. This allows for an approximate estimation of yields for future targets of varying mass loading but with similar irradiation profiles. For more accurate prediction yields, target-specific models that account for target loading, target positioning within HFIR, and accurate HFIR cycle data are required.