Prototype tokamak fusion reactor based on SiC/SiC composite material focusing on easy maintenance

If the major part of the electric power demand is to be supplied by tokamak fusion power plants, the tokamak reactor must have an ultimate goal, i.e. must be excellent in construction cost, safety aspect and operational avail ability (maintainability and reliability), simultaneously. On way to the ul timate goal, the approach focusing on the safety and the availability (incl uding reliability and maintainability) issues must be the more promising st rategy. The tokamak reactor concept with the very high aspect ratio configu ration and the structural material of SiC/SiC composite is compatible with this approach, which is called the DRastically Easy Maintenance (DREAM) app roach. This is because SiC/SiC composite is a low activation material and a n insulation material, and the high aspect ratio configuration leads to a g ood accessibility for the maintenance machines. As the intermediate steps a long this strategy between the experimental reactor such as international t hermonuclear experimental reactor (ITER) and the ultimate goal, a prototype reactor and an initial phase commercial reactor have been investigated. Es pecially for the prototype reactor, the material and technological immaturi ties are considered. The major features of the prototype and commercial typ e reactors are as follows. The fusion powers of the prototype and the comme rcial type are 1.5 and 5.5 GW, respectively. The major/minor radii for the prototype and the commercial type are of 12/1.5 m and 16/2 m, respectively. The plasma currents for the prototype and the commercial type are 6 and 9. 2 MA, respectively. The coolant is helium gas, and the inlet/outlet tempera tures of 500/800 and 600/900 degreesC for the prototype and the commercial type, respectively. The thermal efficiencies of 42 and 50% are obtainable i n the prototype and the commercial type, respectively. The maximum toroidal field strengths of 18 and 20 tesla are assumed in the prototype and the co mmercial type, respectively. The thermal conductivities of 15 and 60 W/m pe r K are assumed in the prototype and the commercial type, respectively. (C) 2000 Elsevier Science S.A. All rights reserved.