Neutron Energy Dependence of Delayed Neutron Yields and its Assessments

TL;DR

This paper investigates how delayed neutron yields from uranium and plutonium isotopes depend on incident neutron energy, using a summation calculation that aligns well with experimental data and offers insights for nuclear data evaluation.

Contribution

The study introduces an energy-dependent model for delayed neutron yields, improving the understanding and calculation of fission yields and decay heats.

Findings

Successfully reproduces energy dependence of delayed neutron yields

Provides assessment and comparison with existing nuclear data libraries

Achieves good agreement with experimental decay heat measurements

Abstract

Incident neutron energy dependence of delayed neutron yields of uranium and plutonium isotopes is investigated. A summation calculation of decay and fission yield data is employed, and the energy dependence of the latter part is considered in a phenomenological way. Our calculation systematically reproduces the energy dependence of delayed neutron yields by introducing an energy dependence of the most probable charge and the odd-even effect. The calculated fission yields are assessed by comparison with JENDL/FPY-2011, delayed neutron activities, and decay heats. Although the fission yields in this work are optimized to delayed neutron yields, the calculated decay heats are in good agreement with the experimental data. Comparison of the fission yields calculated in this work and JENDL/FPY-2011 gave an important insight for the evaluation of the next JENDL nuclear data.