Nuclear Reactor Pressure Vessel Welds: A Critical and Historical Review of Microstructures, Mechanical Properties, Irradiation Effects, and Future Opportunities

The nuclear reactor pressure vessel (RPV) is the most critical pressure boundary and safety structure in a nuclear power plant, as it contains the reactor core and coolant. RPVs, which are fabricated from low-alloy steel, are exposed to irradiation damage at moderate temperatures, and thus experience irradiation embrittlement in service. Since the 1960s, commercial reactor designs and construction have sought to minimize beltline-region welds in RPVs to limit the more extreme irradiation embrittlement found in these arc welds. But recent advancements in welding, compounded by long lead times and astronomical costs for single-forging RPVs, have prompted the nuclear industry to reconsider RPV welds. To design and deploy improved RPV welds, a scientific understanding of their structure–property relationships must be attained. However, many studies report only on microstructure or mechanical properties, hampering a rigorous mechanistic understanding. Additionally, RPV weld irradiation embrittlement data enables researchers to more accurately evaluate the risk of RPV welds and design modern RPV welds with enhanced irradiation stability and structural integrity.