Neutronic design of a very high temperature reactor core with low graphite content

► A relevant issue concerning VHTRs is the accumulation of radioactive graphite. ► In this study most of the graphite reflector was replaced with steel. ► The core was modified and simulated with MCNPX. ► The neutron multiplication factor and reactivity coefficients perform well. ► More than 1000 m3 of irradiated graphite are saved.