High Thermal Performance CFC Divertor

Abstract

The paper presents the conceptual study of an innovative divertor plate for the physical phase of the ITER/NET reactor. The main distinguishing feature of the new concept is the use of a single material, a Carbon Fibre reinforced Carbon (CFC) composite with ultra-high-thermal conductivity carbon fibres, for the whole structure, i.e. for the protective armour, heat sink and cooling channels. The main potential advantages of such a solution are perceived to be: elimination of the severe joint-interface problems inherent to other multimaterial solutions; weak interaction with runaway electrons; low-activation properties; reduction of mechanical stresses induced by electromagnetic transient. Moreover, the use of helium as a coolant leads to the following additional advantages: avoidance of the risk of burn-out; flexibility towards different operating scenarios; ease of baking at high temperature; lower tritium inventory in the CFC material; avoidance of the sharp pressure rise in cooling circuit because of water evaporation due to runaway electron impact. The thermal performance assessment shows that the maximum surface temperature can be kept below the threshold for radiation enhanced sublimation with comparable pumping power with that required by water cooling with turbulence promoters. After this study, which has to be considered as a first step in the iterative process for the development of a new component, the issue of the manufacturing feasibility in close collaboration with the composite industry will be addressed.