ITER is expected to take about a decade to build. And closing JET such a long time before ITER is operational would severely disrupt preparations for the new reactor, critics of the closure proposal contend.

Some 200 million (US$230 million) of the EU's 750-million fusion budget for 2002–06 has been earmarked for ITER's construction. If work begins before 2006, officials will have to cut funding to existing projects to make ends meet. Because JET consumes the single biggest chunk of EU fusion money — about 55 million per year — researchers fear that it may be selected for closure. "There is a possibility that JET will have to close by 2006," confirms Pascal Lallia, an energy adviser with the European Commission's research directorate.

Fusion researchers accept that cuts must be made to allow ITER to be built, but they are split on whether JET should be spared. Supporters point out that JET is the closest in size to ITER of Europe's fusion reactors, and is the ideal place for fusion scientists to work while ITER is being built. "JET could help develop a generation of fusion researchers to run ITER," says David Baldwin, head of fusion research at General Atomics in San Diego, California.

Others note that research at JET over the past decade has helped to streamline ITER's design. Future experiments at JET, to increase understanding of the turbulence in the plasma contained in the reactor and how to control it, for instance, are likely to help guide ITER's early work, they add. "It's in the collective interest of European fusion researchers to keep JET going," says Steven Cowley, a plasma physicist at Imperial College London.

But shutting JET might be simpler than cutting funds to several of the 12 other national fusion projects that receive money from the same EU funding stream, and which could also be used to train researchers for ITER. "In an ideal world we would keep JET going," says Alexander Bradshaw, scientific director of the Max Planck Institute for Plasma Physics in Garching, Germany. "But if we are short of money for financing the EU contribution to ITER construction, it would be more sensible to shut it."

Negotiations about which facility to close will begin in earnest once a site has been chosen for ITER, which received a boost last week when South Korea announced that it would be joining the project. An expert group of scientists and engineers, led by David King, the UK government's chief scientific adviser, is assessing the merits of proposed sites in France and Spain and will report in September. ITER's international partners will then compare the European site with two others in Canada and Japan, and a final decision could be made by the end of this year.