Error analysis of approximations and treatments commonly made in multi-group library and self-shielding calculation based on NECP-X

Approximations and treatments commonly applied in multi-group library and self-shielding calculation of conventional neutronics calculation codes are analyzed based on a numerical nuclear reactor physics code NECP-X. The numerical results show that the approximations and treatments introducing largest errors for UO2 pin cell problems are narrow resonance (NR) approximation, ignorance of multi-group (MG) equivalence effect, Bondarenko iteration method and using average fission spectra. For MOX pin cell problems, the approximations and treatments introducing largest errors are ignorance of thermal resonance, NR approximation, resonance interference factor method, ignorance of MG equivalence effect and in-flow transport correction. These analysis provide references and help to improve the conventional methods and legacy codes.