Examination and refinement of fine energy group structure for high temperature reactor analysis

•Fine energy group structure improvement increased the accuracy of the reaction rates.•Fine energy group structure (SHEM-361) was improved to SHEM_TPN-531 and (SHEM-281) was improved to SHEM_TPN-407.•Uncertainty about the applicability of SHEM energy group structures to HTRs has been addressed.•Depletion analysis were conducted to predict the economic performance of HTRs.