Martensitic steels were examined, using transmission electron microscopy, after bombardment with fast neutrons at 420C to a fluence of 7.8 x 1026/m2 (about 35dpa). Before irradiation, the tempered martensitic microstructures of the steels contained a high dislocation density. Voids were found in the bombarded specimens, but swelling remained lower than 1%. A 9Cr-1MoVNb steel exhibited the highest void density. Although a 12Cr-1MoVW steel had the highest swelling resistance, it also contained the highest density of radiation-induced new phases. Reduced-activation steels exhibited a very stable behavior under irradiation, with a high density of dislocation loops replacing the original high dislocation density. Moderate void swelling also occurred.

J.J.Kai, R.L.Klueh: Journal of Nuclear Materials, 1996, 230[2], 116-23