Discussion The presently reported value of the Pa231 half-life, 34,300 years, is higher than any appearing in the literature. The closest correspondence is found with the 1932 value of von Grosse, namely, 32,000 years4 This value was obtained from presumedly pure macro amounts of the isotope; the values given in the earlier literature are based on growth into purified uranium of the protactinium. These early determinations depend on measuring ...
