Improvement of the resonance scattering treatment in MCNP in view of HTR calculations

Full core models of the test reactors HTR-10 and HTTR are analyzed. As expected the impact of the improved kernel is low for the HTR-10 because of an enhanced thermal flux. However, for the HTTR the effective multiplication factor decreases by 200-400 pcm and Doppler reactivity becomes more negative by 14%.