Stress corrosion cracking of AISI 316LN stainless steel in ITER primary water conditions

The susceptibility of the 316LN-IG stainless steel (ITER Grade) to stress corrosion cracking (SCC) in ITER primary water coolant conditions was investigated by slow strain rate testing and constant deformation testing. Unirradiated 316LN-IG specimens were tested at temperatures ranging from 90 to 360 C in different chemical environments simulating possible water radiolysis scenarios and ITER operation conditions. In-pile corrosion testing was performed at 200 C in pure water on 316LN-IG specimens irradiated to about 3 dpa. No specimen failed from SCC in pure water whatever the test conditions. However, detrimental effect of acidic solutions containing chloride and sulphate was demonstrated since all the specimens failed from transgranular SCC at 340 C. Thus, to avoid such a possible aggressive environment in ITER, a recommendation for baking the in-vessel components should be a procedure with liquid water and at lower temperature. (orig.)