Congress is questioning the need to bring fresh bombs into the US nuclear stockpile. Credit: P. SHAMBROOM/NUKEPHOTO.COM

Congress is losing its appetite for the Reliable Replacement Warhead (RRW), a nuclear bomb conceived as a way to allow weapons physicists to ply their trade in a weapons-ban world. Instead, Capitol Hill is calling for a full review of the US nuclear programme.

After its 4 July recess, the House of Representatives will vote on a bill that would eliminate funding for the RRW from the 2008 budget. The Bush administration had requested $89 million for the project. And committees in both the House and the Senate are drafting legislation that would limit work on the new design to feasibility and cost assessments. That legislation would also call for a review of the need for nuclear weapons.

Until last autumn, the RRW programme enjoyed bipartisan, if tentative, support in Congress. The project, which aims to design a weapon more robust than its predecessors but that requires no testing (see Nature 442, 18–21; 2006), was seen by congressional appropriators as a way to cut the cost of maintaining the nuclear stockpile. Some also liked the idea that it could reduce the size of the stockpile.

But a costly plan released in December on the future of the nuclear weapons complex suggested it would be hard to realize any savings from the RRW. And a study showing that existing warheads will last for at least another 50 years (see Nature 444, 660–661; doi:10.1038/444660a 2006) made the new bomb seem less necessary. Billions have been spent on 'stockpile stewardship' to prolong the lives of current warheads, Congressman Pete Visclosky (Democrat, Indiana) said on 19 June. Now, he said, “We are told: 'Let's do something else'.”

“I don't think it is asking too much for a comprehensive nuclear strategy before we build a new nuclear weapon,” added Visclosky, who chairs the subcommittee that withdrew the RRW funding.

A separate defence bill working its way through Congress might provide such a strategy. Versions of the authorization bill, which would set out policy but not funding, call for a comprehensive review of US nuclear policy. This would assess whether the size of the stockpile is appropriate in the post-cold-war era and whether an RRW would be necessary for a credible deterrent.

Arms-control advocates are elated by the move. “What Congress has done is really stunning,” says Philip Coyle, a senior adviser at the Center for Defense Information, a think-tank in Washington DC. The current US stockpile is far too bloated, he adds.

But supporters of the RRW say that Congress has undercut the weapons programme. Expertise will be lost unless a new generation can design weapons, says Paul Robinson, former director of Sandia National Laboratories in Albuquerque, New Mexico. He notes that the House budget for nuclear weapons is also $400 million lower than that enacted for 2007. “I feel absolutely sure that members of Congress have not looked at the strategic consequences of what they are doing,” he says.

The RRW is not done yet. This week, the Senate begins drafting its own version of the appropriations bill. Senator Pete Domenici (Republican, New Mexico) has vowed to win back support for the programme. A final version of the bill, to be worked out between the House and Senate, is expected sometime in the autumn.