The role of neutron importance in bilinear weighted cross sections for burnup evaluation

•Calculation of isotopic concentration considering neutron importance is performed.•Bilinear weighted cross sections are used for burnup evaluation.•A module has been developed and implemented into the IRBURN code system.•Calculations have been evaluated in comparison with OECD/NEA benchmark problem.•Bilinear weighting is more accurate than standard linear weighting for most nuclides.

This work presents the development and implementation of bilinear weighted cross-sections for improving the accuracy of isotopic concentration calculations, considering neutron importance function in burnup evaluation. Monte Carlo based MCNIC method is used for calculation of the required neutron importance function. A module is developed for this purpose and is implemented into the IRBURN code system. Role of the neutron importance function in accuracy and precision of the burnup calculation is evaluated. An OECD/NEA experimental benchmark problems is used for this evaluation. The results are indicative of the fact that using the bilinear weighted cross-sections give a better estimation of the isotopic concentration in the burnup calculation for most isotopes.