Neutronic design issues of the WCLL and HCPB power plant models

This work addresses neutronic design issues of the two near term reactor models of the EU Power Plant Conceptual Study (PPCS) employing the water cooled lithium lead (WCLL) and the helium cooled pebble bed (HCPB) blankets for the tritium and the power production. Detailed three-dimensional torus sector models have been developed for the two PPCS reactor variants to enable proper design calculations with the MCNP Monte Carlo code. It is shown that both blanket concepts can provide tritium self-sufficiency although the tritium breeding potential of the HCPB concept is higher. The HCPB blanket also shows a higher energy multiplication which results, together with a higher thermal efficiency in the power conversion system, in a smaller fusion power required for the same net electrical power. The shielding efficiency of the two reactor models is shown to be similar. A total thickness of 1 m in for the inboard blanket/shield system is required to allow the operation of the power reactor over the anticipated lifetime of 40 full power years.