Covariance Matrices for Differential and Angle-Integrated Neutron-Induced Elastic and Inelastic Scattering Cross Sections of 56Fe

Shengli Chen,David Bernard,Gilles Noguere,Pascal Archier,Pierre Tamagno,Cyrille De Saint Jean,O Serot,A Chebboubi

doi:10.1051/epjconf/201921107002

Abstract

Correlations between neutron inelastic scatterings angular distributions are not included in the Joint Evaluated Fission and Fusion (JEFF) nuclear data library, while they are key quantities for uncertainty propagation of nuclear data. By reproducing the angle-integrated cross sections and uncertainties of JEFF-3.1.1, the present work obtains covariance matrix between high energy model parameters using the least square method implemented in the CONRAD code. With this matrix, it is possible to generate correlations between angle-integrated cross sections and angular distributions, which are usually presented by Legendre coefficients. As expected, strong correlations are found, for example, between the Legendre coefficients of elastic and first-level-inelastic scatterings and the angle-integrated total, elastic, total inelastic cross sections.

Highlights

In the nuclear industry, both Reactor Pressure Vessels (RPVs) for Pressurized Water Reactors (PWRs) and fuel cladding in Sodium-cooled Fast Reactors (SRFs) are Stainless Steel (SS), which is a candidate cladding material for PWR Accident Tolerant Fuel (ATF) [1], [2]
The fluctuations from experimental data of Joint Evaluated Fission and Fusion (JEFF)-3.1.1 cannot be reproduced by the Optical Model (OM) and the Statistical Model (SM), but the global correspondence between our results and JEFF-3.1.1 is ensured, especially for incident energy above 6 MeV
It is noticeable that the OM parameters should be improved to compute the cross sections below 4 MeV for 56Fe. Such an approach is sufficient for producing suitable covariance information for nuclear applications on atomic displacement and fast neutron flux in RPVs

Summary

Introduction

Both Reactor Pressure Vessels (RPVs) for Pressurized Water Reactors (PWRs) and fuel cladding in Sodium-cooled Fast Reactors (SRFs) are Stainless Steel (SS), which is a candidate cladding material for PWR Accident Tolerant Fuel (ATF) [1], [2]. The analyses of covariance matrices of 56Fe are necessary for both neutronic investigations and studies of neutron irradiation in materials. The angular distribution of scattering reactions, called as the differential scattering cross section, is one of the most important quantities in nuclear data evaluation. The angular distribution of neutrons determines directly the neutron spectrum. The recoil energy of a Primary Knock-on Atom (PKA) is deduced from the angular distributions, while the former is the basis for investigating the irradiation damage of materials

Methods

Results

Conclusion