High-Strength Steels and Welding Filler Metals for Small Modular Reactor Pressure Vessels

This paper reviews SA-508 Grade 3 Class 2 low-alloy steel and Type XM-19 austenitic stainless steel as high-strength candidate materials for SMR pressure vessels, covering their material specifications and application status, with particular emphasis on filler metal development. For SA-508 Grade 3 Class 2, the key challenges include developing high-strength filler metals and evaluating the neutron irradiation embrittlement behavior of the base metal and weld metal for beltline applications. For Type XM-19, the establishment of manufacturing technologies for large forgings is needed for its application to nuclear pressure vessels. Although a dedicated filler metal is available, further verification of weld metal performance under reactor operating conditions is necessary, while optimization of the filler metal composition may be required.