EBW of nuclear pressure vessel steels

Part of the mission for the Nuclear Advanced Manufacturing Research Centre (Nuclear AMRC) is to develop, mature and deploy advanced manufacturing technologies in the nuclear manufacturing industry. Electron beam welding (EBW) is widely considered to be one of the game-changing technologies which could reduce pressure vessel fabrication lead time, unit cost and manufacturing risk, while maintaining or improving quality & component integrity. This paper presents development work for the use of EBW as a joining technique for nuclear pressure vessel (NPV) steel walls of up to 100 mm thickness. SA508 Grade 3 as well as the higher strength type SA508 4N with increased hardenability were investigated. It has been demonstrated that EBW has the capability of joining these sections in a single pass, with elementary microstructural and mechanical examinations underpinning the basic performance support for such capability. Two-thirds scale components, such as those typical of a Small Modular Reactor (SMR) have demonstrated this processing duty-cycle further with the joint being completed in 26 minutes. This work will strengthen the viability of EBW applied to primary circuit safety-critical components, and will support a future ASME III code case.