Design parameters in an annular, prismatic HTGR for passive decay heat removal

Highlights: •Inner reflector improves reactor safety feature. •Annular cylinder reactor is safer than solid cylinder one. •Uniform power density profile throughout a core enhances the passive safety margin. •Longer life cycle is assured for annular reactor compared to solid cylinder one. -- Abstract: We studied the capability of an annular, prismatic HTGR to remove decay heat passively. The purpose of the study was to obtain the design parameters relationship of the annular, prismatic HTGR with passive decay heat removal depending on power density profile and to compare them with those for solid cylinder one. The results showed that the safety feature of the annular reactor is improved a lot compared with that of cylinder one. The safety margin could be increased further by flattening the power density profile. Then fundamental neutronic analysis was performed for the annular reactor whose design parameters are obtained from the condition.