Neutronic design optimisation of modular HCPB blankets for fusion power reactors

Neutronic design optimisation analyses based on three-dimensional Monte Carlo calculations have been conducted with the MCNP code as part of the development work for the modular helium cooled pebble bed (HCPB) blanket for a fusion power reactor of the model B-type of the European power plant conceptual study (PPCS). Design variants with breeder pebble beds parallel and perpendicular to the first wall have been investigated with the objective to assess and optimise their tritium breeding efficiency. Although both configurations are feasible, the latter design solution was shown to provide a superior performance in terms of the required blanket thickness, the beryllium inventory and the 6Li enrichment due to a better utilisation of the space available for the breeder and the beryllium pebbles.