Thermal and fission neutron-produced defect configurations in platinum

An experimental procedure employing resistivity measurements was used to observe the production of free interstitials and vacancies in platinum by atomic recoils produced from thermal neutron capture and fission neutron collision. For thermal neutrons, which produce damage much like fast electrons, free defect production increased nearly a factor of two with increasing irradiation temperature from 30 to 2800K. This is attributed to the increasing thermal dissociation of correlated pairs into free defects. From low-temperature recovery studies it is known that thermal neutrons produce damage which has a large I/sub D/ recovery substage indicating an abundant production of correlated pairs. Although the correlated pair population is less in similar recovery studies of the high-energy atomic recoils associated with fission neutron damage, it is still large enough that one would expect to observe the effects of thermal dissociation, or in other terms, the temperature dependence of the I-V recombination volume. In contrast to the thermal neutron case, virtually no temperature dependence of free defect production was found for fission neutron damage produced over the same temperature range. This result suggests that correlated pairs are present in the vacancy-rich central region of the fission neutron displacement cascade, but upon thermal dissociation the interstitial partner is annihilated before reaching a stable trapping site outside the cascade