fiannaFailMan writes "An international plan to build a nuclear fusion reactor is being threatened by rising costs, delays and technical challenges. 'Emails leaked to the BBC indicate that construction costs for the experimental fusion project called Iter have more than doubled. Some scientists also believe that the technical hurdles to fusion have become more difficult to overcome and that the development of fusion as a commercial power source is still at least 100 years away. At a meeting in Japan on Wednesday, members of the governing Iter council will review the plans and may agree to scale back the project.' Iter will be a Tokamak device, a successor to the Joint European Torus (JET) in England. Meanwhile, an experiment in fusion by laser doesn't seem to be running into the same high profile funding problems just yet."