ABSTRACT

We perform energy-dependent calculations of independent and cumulative fission product yields for ${ }^{235}\mathrm{U}$, ${ }^{238}\mathrm{U}$, and ${ }^{239}\mathrm{P}\mathrm{u}$ in the first chance fission region. Starting with the primary fission fragment distributions taken from available experimental data and analytical functions based on assumptions for the excitation energy and spin-parity distributions, the Hauser-Feshbach statistical decay treatment for fission fragment de-excitation is applied to more than 1,000 fission fragments for the incident neutron energies up to 5 MeV. The calculated independent yields are then used as an input of $\beta$-decay calculations to produce the cumulative yield, and summation calculations are performed. Model parameters in these procedures are adjusted by applying the Bayesian technique at the thermal energy for ${ }^{235}\mathrm{U}$ and ${ }^{239}\mathrm{P}\mathrm{u}$ and in the fast energy range for ${ }^{238}\mathrm{U}$. The calculated fission observable quantities, such as the energy-dependent cumulative yields, and prompt and delayed neutron yields, are compared with available experimental data. We also study the possible impact of the second chance fission opening on the energy dependence of the delayed neutron yield by on the opening of second chance fission on the energy dependence calculation.

摘要

我们对独立和累积裂变产物产量进行能量相关计算 ${ }^{235}\mathrm{你}$, ${ }^{238}\mathrm{你}$， 和 ${ }^{239}\mathrm{磷}\mathrm{你}$在第一次机会裂变区。从基于激发能量和自旋平价分布假设的可用实验数据和分析函数中获取的初级裂变碎片分布开始，对裂变碎片去激发的 Hauser-Feshbach 统计衰减处理应用于 1,000 多个裂变碎片，用于入射中子能量高达 5 MeV。然后将计算出的独立收益率用作输入$\beta$- 衰减计算以产生累积产量，并执行求和计算。这些程序中的模型参数通过在热能处应用贝叶斯技术来调整${ }^{235}\mathrm{你}$ 和 ${ }^{239}\mathrm{磷}\mathrm{你}$ 并且在快速能量范围内 ${ }^{238}\mathrm{你}$. 计算的裂变可观测量，例如与能量相关的累积产额、瞬发和延迟中子产额，与可用的实验数据进行了比较。我们还通过二次裂变的开口对能量依赖计算的影响，研究了二次裂变开口对延迟中子产额的能量依赖的可能影响。