Princeton

Government officials have indicated that the United States is ready to rejoin ITER, the international project to build an experimental magnetic fusion reactor.

Speaking at celebrations to mark Princeton Plasma Physics Laboratory's fiftieth birthday on 6 June, energy under-secretary Robert Card said that a decision on whether to return to ITER will come “within weeks rather than months”.

“We've more or less decided to re-enter talks” with ITER's current participants, says presidential science adviser John Marburger. But, he adds, the United States needs to have a firmer understanding of the project's costs and implications before making a firm financial commitment to it.

The United States could yet take part in ITER — but it has ruled out hosting the reactor itself. Credit: ITER

The extent of the United States' planned involvement remains an open question, but Marburger says that the country will not offer to pay the $1 billion or more needed to host the experimental reactor. “We're not interested in having ITER in the United States,” he says. Observers say that US participation would probably involve a commitment of about $500 million over 10 years.

The United States and the Soviet Union started ITER, then known as the International Thermonuclear Experimental Reactor, as part of détente in 1988. But just over a decade later, when the engineering phase yielded a design that could have cost up to $10 billion to build, Congress instructed the energy department to withdraw from the project. This withdrawal was accompanied by sharp cuts in the domestic fusion budget, leaving US researchers with no prospect of building a large fusion experiment of their own.

Subsequently, the remaining ITER participants — Russia, Canada, Japan and the European Union — have developed a slimmed-down version of the design, which is now expected to cost about $4 billion to build. At a meeting in Cadarache, France, on 6 June, the project members formally announced four potential sites for the reactor — two in Europe, one in Canada and one in Japan.

In the past year, both members of Congress and the Bush administration have steadily warmed to the idea of once again participating in ITER (see Nature 415, 247–248; 2002)

US researchers reacted with a mixture of caution and optimism to the prospect of the United States rejoining ITER. “I think this is an opportunity for the United States to re-engage with the international programme,” says Rob Goldston, director of the Princeton Plasma Physics Laboratory in New Jersey. “But I think it is critical that the United States strengthens its domestic programme as part of such an initiative.”

The domestic US fusion-research programme “is still pretty fragile”, says Gerry Navratil, a physicist at Columbia University. He is worried that its management will be distracted by negotiations over ITER, and even questions whether US scientists will gain full access to data from the international experiment. He wants the United States to establish a firm withdrawal date should the negotiations prove not to be fruitful, and to continue working on its own, more modest, plasma experiment.

As ITER negotiators begin discussing their choice of site, US researchers will debate the relative merits of ITER and a domestic experiment next month at a conference in Snowmass, Colorado. Goldston hopes that the negotiations abroad and discussion at home will bring the United States closer to the ultimate goal of building a viable fusion reactor. “Between vision and reality a number of steps remain,” he says, “but I think it's possible.”

→ http://www.iter.org