Influence of interstitial impurities on defect production and recovery in niobium neutron-irradiated at 4.6 K

Pure niobium and niobium doped with 1700 ppm nitrogen and with 3900 and 4200 ppm oxygen were irradiated at 4.6 to 7 K in the reactor up to a neutron dose of 3 × 1018 cm−2. The measured increase of max. 15.3% in the damage production rate of the doped samples is mainly due to the reduction of radiation-annealing processes because of trapping reactions at the foreign atoms. The strong suppression of the recovery in the doped samples up to about 28 K is also explained by trapping reactions of the self-interstitials which already have to cover rather large distances. The recovery behaviour is influenced by the foreign atoms in the whole measuring range up to 354 K and can be interpreted in terms of well known recovery models for f.c.c. metals.