Contribution of neutron-capture reactions to observed tungsten isotopic ratios

To study whether tungsten isotopic ratios observed in terrestrial samples relative to W ratios in an iron meteorite could be made by neutron-capture reactions in the iron meteorite, the fluxes of thermal and epithermal neutrons in a large iron meteoroid, Toluca, were calculated using Monte Carlo particle production and transport codes. Peak neutron-capture rates on W isotopes were calculated to occur at depths of 30–34 cm. The calculated changes in the 182W/183W due to neutrons are much less than those observed in terrestrial samples relative to iron meteorites, indicating a non-cosmogenic origin of the observed W isotopic ratios.