Technical Meeting of the International Nuclear Data Evaluation Network (INDEN) on Actinide Evaluations in the Resonance Region

21-24 October 2019, IAEA, Vienna

Scope

Reactivity prediction of critical thermal assemblies, particularly solution systems and lattices, is strongly affected by the PFNS, by nubar energy dependence, and by the detailed shape of the cross sections below 10eV (i.e., by the energy dependence of alpha). Newly evaluated PFNS for thermal-neutron induced fission of U-235, Pu-239 and U-233 (within the Neutron Standards Project) resulted in lower PFNS average energy by about 30 keV. It is well established that a softer PFNS significantly increases the reactivity of the high-leakage solution benchmarks by 0.7-1.2 percent. The Thermal Neutron Constants from the new Standards-2017 also strongly affect the reactivity of thermal systems. Significant differences between abovementioned quantities remain in newly released ENDF/B-VIII.0 and JEFF-3.3 libraries compared to older evaluations. Additionally, it has been found that temperature dependent of criticality is also strongly influenced by the same quantities in the same energy region.
Additionally, differences between measured cross sections and contents of evaluated libraries remain in the URR for all major actinides.

Objectives of the Meeting

The main objective is to:
- Review the current status of the resonance parameter evaluations including the URR of the major actinides and suggest possible/meaningful modifications.
- Check the impact of the new Standards-2017 and the softer PFNS of the fissile actinides on the criticality of thermal systems.
- Define strategies to use new PFNS combined with new RP evaluations for U-233, U-235 and Pu-239.
The overall objective is to co-ordinate the activities in different laboratories with the final goal of obtaining consistent evaluated data files that respect the differential data (particularly the thermal constants of Standards-2017, softer PFNS and cross section measurements) and preserve good performance in criticality benchmarks, especially regarding the trends as a function of the above-thermal leakage fraction (ATLF) as well as temperature dependence of criticality.

Agenda

The Agenda is available from here.

Presentations