Neutron Irradiation Effects on Carbon and Graphite Cloths and Fibers

Because of the interest in using carbon or graphite cloth between the plasma and the first structural wall of fusion reactors, cloth and fiber samples were irradiated to neutron fluences of 3.5, 7.3, and 10 X 10²¹ cm^-2 at 743 K. Dimensional changes of the fibers in the radial direction ranged from -19 to +33% and in the axial direction from -18 to -27%, roughly ten times greater than dimensional changes found for typical nuclear graphites. Despite these large dimensional changes, all but one of the two-dimensional cloths remained essentially unchanged in overall physical appearance. On the other hand, the three-dimensional cloths deteriorated, apparently because these types of weaves were less able to accommodate the large axial fiber shrinkages.