Effect of Neutron Irradiation on Thermal Conductivity of Carbon/Carbon Fiber Materials at 400 and 600°C in the Fluence Range 1 × 1022 to 1 × 1024 m-2

Abstract

Because of their low atomic number and excellent thermal conductivity, carbon/ carbon fiber materials are seen as potential candidates for plasma-facing components, such as divertors, in Tokamak fusion devices. In the technology phase of Next European Torus (NET) or International Thermonuclear Experimental Reactor (ITER), the surface of a divertor will operate between 400 and 1000°C, and the materials will accumulate a lifetime neutron fluence equivalent to a dpa damage of 0.1. Low doses of neutron irradiation cause a significant decrease in the thermal conductivity of graphitic materials at low temperatures. To quantify the effect, candidate materials such as fine- and superfine-grained graphites (as reference materials), carbon/carbon fiber composites, and an oriented pyrolytic carbon (PyC) were irradiated at 400 and 600°C up to 0.1 dpa. At this fluence and at 400°C, the thermal conductivity (/) is reduced by 40 to 60%, whereas irradiation at 600°C caused a reduction of the l-values at irradiation temperature by about 20 to 40%. This spread seems to be caused by material differences but could be due to the uncertainties in the measurement and neutron fluence.