FUNDAMENTAL STUDIES OF RADIATION DAMAGE IN GRAPHITE

Graphite expands linearly with irradiation at temperatures below 250 deg C and develops stored energy of the lattice because of interstitial and vacancy defects. Radiation changes such as stored energy and dimensional expansions can be removed by thermal annealing in which the graphite is removed from the radiation field and heated to a temperature above the irradiation temperature. The thermal annealing of irradiated graphites shows that the greater the irradiation dose, the greater is the recovery obtained at a given temperature. In periodically irradiated graphites, the 200 deg C stored energy no longer increases as it does in continuously irradiated graphites. Thermal annealing not only removes radiation damage but redistributes and creates it. (H.G.G.)