An Interpretation of Energy Dependence of Delayed Neutron Yields in the Resonance Region for ²³⁵U and ²³⁹Pu

Possible fluctuation in the delayed neutron yields (DNYs) in the resonance region was predicted on the basis of experimental data of mass distribution of fission fragments at resonances. Analyzed according to the multimodal random neck rupture model of fission, the small variations in the experimental mass distribution were attributed to fluctuations in the branching ratios to different modes of fission. Using the results of analysis of measured data for ²³⁵U and ²³⁹Pu, the DNYs were calculated for each resonance by the summation method, considering 271 precursors and evaluated data of delayed neutron emission probability. It was found that the DNYs should have local dips for ²³⁵U and spikes for ²³⁹Pu at resonances.