Improvement of evaluation of replacement cost of a fusion power plant

A new model to evaluate the plant availability of a fusion reactor by considering the required cooling time before starting the scheduled replacement of in-vessel components was developed and incorporated in the tokamak system design code TPC-SCONE. Plant availability strongly depends on the electric output and decreases with increasing electric output. The plant availability does not much improve by advances in the physics or engineering design conditions. Consequently, the effect of the increase in the electric output on reducing the cost of electricity is diminished. Thus, proper selection of the electric output of a fusion reactor (especially for a DEMO reactor) is likely required to achieve the plant availability target.