Neutron energy dependence of delayed neutron yields and its assessments

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.

Energy Dependent Calculations of Fission Product, Prompt, and Delayed Neutron Yields for Neutron Induced Fission on $^{235}$U, $^{238}$U, and $^{239}$Pu

“…Ohsawa et al [19,20] introduced the multimodal random neck-rupture model [21] and fission mode fluctuations [22] to explain the energy-dependence. Minato [23] proposed a model to reproduce the energydependence of ν d based on the fission yield using Katakura's systematics [24]. Although an explicit statistical decay was not performed in Minato's model --hence the calculated ν p and ν d are independent of one another --it also supports Alexander's observation: the odd-even effect in the the charge distribution is important.…”

Development of a Reference Database for Beta-Delayed Neutron Emission

“…The least square fitting was thus performed only for α, β, and ξ for the above-mentioned actinides. The parameters obtained from fitting the new evaluated CRP data are listed in Table V, The differences observed between the values in this table and those in Table 3 of [265] re-FIG. 29.…”

“…In Ref. [265], a new method for evaluating the incident neutron energy dependence of total delayed neutron yields using least square fitting was presented. The model adopted the incident neutron energy dependence of fission product yields, the multi-chance fission, and the evaluated decay data of Ref.…”

“…Figure 35 shows the delayed neutron activities for the fast neutron fission of 235 To conclude, the incident neutron energy dependence of the delayed neutron yields of uranium and plutonium isotopes was re-estimated with the model of Ref. [265] using the new evaluated CRP data introduced in Sect. III.…”

Recent activities in the field of radiation, accelerator, and beam technologies

“…[13], neutron total and capture cross section of 241 Am in the eV region were measured. Moreover, important theoretical studies for fission and delayed neutron have been published [14,15].…”