BBC News By Paul Rincon Published image captionArtwork: Mast Upgrade has been testing an innovative design Initial results from a UK experiment could help clear a hurdle to achieving commercial power based on nuclear fusion, experts say. The researchers believe they now have a way to remove the excess heat produced by fusion reactions. This intense heat can melt materials used inside a reactor, limiting the amount of time it can operate for. The system, which has been likened to a car exhaust, resulted in a tenfold reduction in the heat. The tests were carried out at the Mast (Mega Amp Spherical Tokamak) Upgrade nuclear fusion experiment at Culham in Oxfordshire. The £55m device began operating in October last year, after a seven-year build.