This study presents the neutronic analysis of a high power density (DT) fusion-fission (hybrid) reactor fuelled with thorium fuel for an operation period of 48 months. The effect of the innovative coolants, Li20Sn80 and Flinabe, used to breed tritium as well as transfer nuclear heat out of the blanket on the neutronic performance of the hybrid reactor is investigated. For comparison to these two coolants, natural lithium is chosen to be used in the same blanket. Calculations are performed on a simple experimental hybrid blanket with the aid of SCALE4.3 by solving the Boltzmann transport equation with the XSDRNPM code in 238 groups and a S-8-P-3 approximation. Numerical results bring out that the blanket using Li20Sn80 or Flinabe shows higher neutronic performance with respect to energy multiplication and fuel enrichment than that with natural lithium. However, when Li20Sn80 or Flinabe is used as coolant, neutron multiplier material will be required to maintain tritium self-sufficiency for the fusion driver at startup condition of the reactor. (c) 2006 Elsevier Ltd. All rights reserved.