R-process production ratios of long-lived radionuclides

The r-process production ratios of 232Th, 235U, 238U, and 244Pu, and their uncertainties, are estimated without dependence on specific r-process models. The estimates are based on similarities between nuclei of the same nuclear type in the rare-earth and actinide regions. All actinide alpha-series progenitors are assumed to be equally produced, and the uncertainties in this estimate are derived from the rms fluctuations of observed rare-earth even-even isotopic abundances about their mean. It is shown, however, that the systematic odd-even effect in rare-earth abundances cannot be applied reliably to the actinide region. Production ratios involving 235U are thus more uncertain than ratios between two even nuclides. The estimated production ratios and uncertainties are compared with previously published ones