Industrialising Local Vacuum Electron Beam Welding for Nuclear Applications

Sheffield Forgemasters (SF) has actively supported the development of materials and processes for the nuclear and defence sectors throughout the years. Safety-critical components (e.g. castings and forgings) have been successfully produced using conventional methods, and when possible, more advanced manufacturing techniques such as hot-isostatic pressing (e.g. ASME code case 2564-5) and advanced metal-forming have been successfully implemented.

With the increasing demand for efficient and reliable welding techniques in the field of nuclear

applications, and the need to save cost and time, the use of local vacuum electron beam (LVEBW) technology has emerged as a promising solution.

This work highlights developments at SF on designing, building, and commissioning a production-ready machine capable of local vacuum welding, eliminating the need for large and expensive vacuum chambers. The machine incorporates key enabling technologies to develop a robust set of welding parameters and hardware, resulting in the manufacture of a full-scale demonstrator. Welding parameters have been developed to achieve indication-free welds in 200mm thick sections, including steady state, slope-in and slope-out regions. Finite element modelling and dimensional inspection have predicted and verified minimal vessel distortion due to the highly localised and consistent heat input. Extensive material analysis and mechanical testing were conducted to demonstrate superior properties of the weld region compared to traditional arc-based fabrication methods. Multiple non-destructive testing techniques have been applied to evaluate detection capabilities and facilitate the rapid development of welding parameters.

The development and qualification of this welding process play a crucial role in ensuring acceptability, particularly in defence and advanced modular reactors. Current efforts on this front are also highlighted.