Irradiation Annealing in Graphite. [Part] 2. Activation Processes

The rate of annealing due to primary neutron-carbon atom collisions transferring 3 to 25 ev to the recoil atoms is much too slow to accouat for irradiation annealing rates observed in pile annealing experiments. It is necessary to assume that much of the annealing is accomplished by the slowing down of carbon atoms produced by high energy neutrons. The fraction of primary recoil energy going into arealing reactions is estimated to be about four per cent. Irradiation annealing occurs before vibrational equilibrium is established with the lattice and should not be considered as equivalent to additional thermal arealing. Irradiation damage to the properties of graphite should saturate when the irradiation damage rate equals the irradiation and thermal annealing rates. The effects of irradiation annealing on the damage distribution function are discussed. (auth