Verification of Multi-Group Covariance Data Processing Module in RXSP Code

Abstract

The capability of multi-group covariance matrices has been developed in RXSP code to process correlation matrix data stored in Evaluated Nuclear Data Files for averaged number of neutrons per fission (MF31), resonance parameters (MF32), and neutron cross sections (MF33), and fission spectrum (MF35). MF31, MF33 and MF35 data blocks can be processed by multi-group neutron flux based weighting integral to compute self-shielded group-wise cross sections covariance matrices. However, MF32 only stores evaluated experimental measurements caused uncertainty for resonance parameters in resolved resonance range (RRR), for instance, the standard deviation of resonance level, elastic scattering, capture, fission reaction widths. In order to calculate uncertainties of cross sections in RRR from above resonance parameters uncertainty, the MF32 stored R-Matrix approximated resonance formulae should be used. NJOY code introduces covariance data processing method used initiated from ERRORJ code, which can handled all common used R-Matrix approximate resonance formulae, including Single-level Breit-Wigner, Multi-level Breit-Wigner and Reich-Moore. Posterior to the code development, the comparison of microscopic multi-group cross sections covariance matrices for 235U nuclide will be conducted between RXSP and NJOY code. Moreover, the multi-group covariance data library will be applied in benchmark using SCALE S/A and U/Q utility code package