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Looking into ITER: this may be all we ever see of it, if the United States backs out. Credit: ITER

The US Congress is poised to pass legislation seeking an end to US participation in the International Thermonuclear Experimental Reactor (ITER). The move is likely to lead to the collapse of a 13-year global effort to design and build a prototype fusion reactor.

The agreement to design ITER, intended to demonstrate sustained fusion in a magnetically confined plasma, expired on 21 July. Japan is said to feel that a three-year extension is contingent on the participation of all four parties — the United States, Russia, the European Union and Japan.

Russia's political interest is liable to wane if the United States withdraws. Officials say that the collaboration will therefore lie in ruins if, as seems likely, Congress passes an appropriations bill next month which pointedly advises the US Department of Energy to withdraw from the project.

Even if this were to happen, however, there remains a possibility that Europe might decide to build a new fusion reactor either on its own, as it was planning before the ITER project was agreed on, or in a separate collaboration with Japan.

Energy department officials, backed by the US magnetic fusion research community, have been imploring members of the House energy and water appropriations subcommittee to withdraw the advice they inserted in their proposed 1999 appropriations bill.

The officials want the DoE to be allowed to sign the agreement, even if it cannot spend any money on ITER. They say this would at least allow the other partners, each of which has signed the extension agreement, to proceed. “We need to be able to sign, regardless of the money,” says Anne Davies, head of the magnetic fusion programme at the DoE.

Joseph McDade (Republican, Pennsylvania), chair of the energy and water appropriations subcommittee, believes that several questions about ITER need a better answer before the agreement is extended. According to a letter which he sent to Federico Peña, then the energy secretary, on 11 June, these include questions about “whether this construction project will ever be started”.

Last week, the energy and water appropriations subcommittees of both the House and the Senate were close to holding a conference at which, officials say, the language advising the DoE not to sign would have been confirmed. But they didn't get round to it before the Senate recessed on 31 July. This gives the ITER agreement a breathing space until their return in September, when a final version of the appropriations bill must be agreed and passed into law.

James Sensenbrenner (Republican, Wisconsin), chairman of the House Science Committee, is to fly to Tokyo on 9 August to talk to senior Japanese officials about fusion research and other fields of US-Japanese research collaboration. Some officials and fusion scientists see this visit as a possible rescue mission for US participation in ITER.

In the cases of the International Space Station and the Large Hadron Collider, they note, Sensenbrenner has enjoyed making international visits in which he has noisily banged the drum for American interests, scolded the Clinton administration for its alleged failure to protect these interests and then strongly supported both projects.

But sources close to the Wisconsin congressman are playing down such expectations in the case of ITER. During the five day trip, they say, he will try to soothe what are expected to be bruised Japanese feelings over the possible demise of the ITER agreement, find out if Japan is serious about a scaled down, incremental version of ITER, and look at possibilities for fusion research collaboration outside of ITER.

Although it is McDade — not Sensenbrenner — who is ready to kill the agreement, officials are nonetheless pinning their hopes on the latter. Asked if his trip could help save the agreement, Davies says: “I certainly hope so.”

The last ITER Council meeting in Vienna amply demonstrated the fragile status of agreement. After meeting on 21 July — the date on which the six-year agreement to conduct an engineering design assessment of ITER expired — Japanese officials contended that the legal basis for the council had expired, as its terms require all four parties to agree on the proposed three-year extension.

The officials at Vienna then met informally on 22 July and agreed to keep talking informally until October, by which time the US situation should be resolved.

ITER research in the United States is continuing, at least until the end of the financial year on 30 September. “In terms of the technical work we are continuing with business as usual,” says Charles Baker, head of the US ITER team based in San Diego, California.

But a senior scientist at one US fusion facility describes the situation as “a shambles”, while Baker admits: “Of course we are very concerned about the future”.

Despite the uncertainty, a “special working group” of 20 scientists from the four partners is pressing on with two tasks assigned to them by the ITER council. The first, which is more or less complete, determined that a smaller version of ITER — known as ‘ITER-Lite’ — costing $5.5 billion instead of $10 billion, could meet many of the project's technical objectives (see Nature 393, 406; 1998).

The second task, requiring the group to explore other collaborative experiments short of that, is proving more difficult to execute. At Vienna, the United States pushed for the group to formally spell out such options. But ITER advocates in Europe and Japan fear that such a step will undermine the case for any version of ITER.

For many of its supporters, ITER's symbolism as an example of international collaboration in science is at least as important as its technical objectives. It is on the basis of that broader significance that the energy department is now trying to save the agreement in the Congress.

President Bill Clinton will not, however, veto the energy and water appropriations bill in order to save the agreement. And its fate is likely to have little impact on support for the US magnetic fusion research programme, which will be funded next year at close to this year's level of $229 million.