Nuclear
RAS Alloy supplies nuclear-grade nickel alloys for PWR steam generator tubing, reactor internals and core support structures. Materials are supplied with full nuclear QA documentation, grain size control and UT/ET/PMI per ASME Section III NCA-3800 requirements.
Typical Alloy Grades
690 / 600 / X-750 / 718 / 625
PWR steam generator tubing
Inconel 690 (30% Cr for SCC immunity)
Reactor vessel internals and core barrel components
Inconel 600, Inconel 625
Control rod drive mechanism springs
Inconel X-750 (aged condition)
Primary coolant pump shafts and fasteners
Inconel 718
Spent fuel storage canister materials
Inconel 625, Inconel 690
Applicable Standards
PWR Steam Generator Tube SCC — Alloy 600 Degradation
Operating PWR plants worldwide experienced primary water stress-corrosion cracking (PWSCC) in Alloy 600 MA steam generator tubing, requiring costly plugging and replacement programs.
Alloy 600 (15% Cr) is susceptible to intergranular SCC in primary water at operating temperatures >300°C. The chromia passive film becomes unstable under PWR primary water conditions, allowing grain boundary oxidation and crack initiation at regions of high residual stress.
The industry migrated to Inconel 690 (30% Cr) with demonstrated PWSCC immunity for >30 years of PWR service. RAS Alloy supplies IN690 tubing with controlled grain size (ASTM 7-9), low inclusion content and full eddy-current testing to ASME Section III requirements.