Discussion: Thermal reactor materials

Opening the discussion on irradiation effects in pressure vessel steels. Dr. R.W. Nichols referred to Dr. Little's comment that French workers had recently reported irradiation embrittlement at copper levels as low as 0.03%. In view of the two papers indicating the interaction of copper and sulphur he wondered whether Dr. Little knew if the French low copper material was also very low in sulphur. Dr. Little said that the principal evidence for interactions between copper and sulphur was based on studies of high copper (0.2%) low alloy steel weld metals, in which copper sulphide inclusion formation, generally in association with manganese silicide particles, was observed.