Taking into consideration a possibility of accelerated application of nuclear fusion for energy generation a computational research was undertaken to optimise the project guidelines of a fusion hybrid reactor blanket designated, among others, for production of fission reactor fuel. A symbiotic system of fission reactors and a fusion hybrid one, rejuvenating the spent fuel from the former has been proposed. The idea of a hard neutron spectrum blanket with the breeding zone moved away from the first wall, was adopted to maximize the fuel production and/or waste transmutation rates per unit power. Moreover, thorium, an element of large easily accessible resources and many other advantages, was selected as fertile material. The cross section corretions for self-shielding effects, both in homogeneous and heterogeneous geometry, were introduced to the calculations resulting in their improved accuracy. Th-U and U-Pu fuel cycles were compared. For thorium based fuel higher production rates were obtained, resulting in shorter time of enrichment and better economy of thorium blankets. The obtained support ratios exceeded 10.