Modular reactors have the potential to revolutionize the nuclear power industry by turning nuclear generating plants from major civil engineering projects to factory-produced commodities. Instead of being essentially one-offs, modular reactors have a standardized design, can be mass produced, installed in any number required to serve local needs, and don't require the incredibly expensive buildings conventional reactors depend upon.

The problem is that there are bottlenecks in how to build reactors of any size. One is welding the vessels used to contain the reactor core, isolating it from the outer environment. Using conventional techniques, this can take over a year, but Sheffield Forgemasters have reduced this to under a day using what is called Local Electron-Beam Welding (LEBW) to complete four thick, nuclear-grade welds.

LEBW is a revolutionary method to weld two pieces of metal together using a high-energy density fusion process centered on a high-powered electron gun operating in a local vacuum. This melts and fuses components to one another and allows for an efficiency of 95%, deep penetration, and a high depth-to-width ratio.

The upshot is that Sheffield Forgemasters was able to complete a vessel three meters (10 ft) in diameter with 200-mm (8-in) thick walls with what is claimed to be zero defects and at lower costs. In addition, the welding machine can handle innovative sloping-in and sloping-out techniques to start and finish the weld.

This demonstration, a world first, is a significant milestone for the British nuclear sector, which has been moribund for decades with advances only in reactors for nuclear submarines, a couple of showcase power plants, and nuclear fuel processing. Now, the UK government is looking toward a nuclear renaissance, with new plants planned – including 15 modular reactors to be constructed by Rolls-Royce.