India’s plutonium breeder reactor in Kalpakkam is nearly complete. Credit: Reuters/Babu

The Indian government has barred a group of nuclear scientists from meeting in New Delhi, where they planned to challenge key elements of the nation's nuclear programme, Nature has learned.

The International Panel on Fissile Materials (IPFM) is an independent group of two dozen scientists and policy analysts devoted to stirring debate on issues related to nuclear ma­terials. The group was formed in 2006 and is funded by the MacArthur Foundation, a philanthropic organization based in Chicago, Illinois. The panel's draft version of the Fissile Material Cutoff Treaty, a proposal that would ban production of weapons-grade nuclear material worldwide, has received backing from Japan, Canada and the Netherlands in United Nations disarmament discussions.

The IPFM had hoped to convene on 9 December to discuss technical and political issues associated with India's nuclear strategy. But the Indian Ministry of External Affairs, which must approve such meetings, has denied it the permission it needs. As Nature went to press, the ministry had not responded to e-mails about the incident, but R. Rajaraman, an emeritus professor of physics at Jawaharlal Nehru University in New Delhi and co-chairman of the IPFM, says that an official in the ministry blocked the group because individuals on the panel were supposedly "hostile to India". Rajaraman concedes that some of the views held by panel members clash with those of the government, but he says that the denial is at odds with India's democratic principles. "I'm hopping mad," he says.

The IPFM also works to reduce and safeguard civilian and military stocks of fissile materials, and is considered a reputable source for global inventories of uranium and plutonium. "They're providing data out there on the web, and it's solid stuff," says Sharon Squassoni, a non-proliferation expert at the Center for Strategic and International Studies in Washington DC. But panel members take a provocative stance against technologies that create more fissile material. They openly oppose nuclear reproces­sing, in which fuel is chemically separated and reused in either power reactors or nuclear weapons, and breeder reactors, which generate new nuclear fuel in addition to producing power. Many panel members believe that such technologies are not economically viable and increase the risk of nuclear war or terrorism.

India's nuclear ambitions are at odds with those views. The nation has refused to sign the Nuclear Non-Proliferation Treaty, which is designed to slow the spread of nuclear weapons. It is actively pursuing nuclear reprocessing, both for weapons and for power, and is near completion of a 500-megawatt plutonium breeder reactor in Kalpakkam, Tamil Nadu. That reactor will pave the way for future breeder reactors capable of converting the nation's vast thorium reserves into uranium-233 fuel.

The decision to bar the IPFM comes at a sensitive time for India as it looks for acceptance from other nuclear states after decades of isolation because of its weapons programme. In 2008, it signed a nuclear cooperation agreement with the United States, and is seeking entry into the Nuclear Suppliers Group, an international body that sets non-proliferation guidelines for exports of nuclear equipment and material. The IPFM affair should give other nations pause, says Squassoni. "Is this the kind of behaviour that you want in a nuclear supplier?" she asks.

Rajaraman says that the panel hoped to debate India's nuclear policies with scientists from the nation's government and nuclear establishment. Similar debates organized by the IPFM in the United Kingdom, China and the United States have often led to thought-provoking discussions, he says. But even if the Indian government relents now, Rajaraman doubts there will be a truly open meeting with the nation's nuclear leaders: "The spirit in which I wanted to have the discussion has been ruined."

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