Abstract
Recent advances in the calculation of fission barriers and in the experimental determination of beta strength functions make it possible to derive reliable estimates of the effect of beta-delayed fission in the decay of very heavy nuclides far from the line of beta-stability. The model presented here is used to calculate the amount of delayed fission during the decay back of nuclides produced in the astrophysical decay r-process. An interesting feature of these calculations is that they reproduce the reversal of the odd-even effect found for the yield of beta-stable nuclides obtained in the thermonuclear explosions. The preliminary results from the r-process calculations indicate that the effect of delayed fission has to be considered when the yield of very heavy beta stable nuclides from this process is estimated.