Last month North Korea carried out its fourth nuclear test. As with the previous test, three years ago, the yield was equivalent to between six and nine kilotons of TNT. Yet while the first three tests were undoubtedly atomic bombs – the explosive energy came from the fission of the nucleus of plutonium-239 – this time North Korea announced that it had tested a hydrogen bomb. An H-bomb’s energy comes from the fusion of the nuclei of the hydrogen isotopes deuterium and tritium. Whereas A-bombs attain yields measured in kilotons, H-bombs typically attain megaton yields. They are also known as thermonuclear bombs because the nuclei must be heated to a temperature as hot as the centre of the sun in order to initiate the fusion process.
On 29 January 2002, George W. Bush designated Iran part of the ‘Axis of Evil’, despite Iranian co-operation in Afghanistan the previous year. In summer 2002, the US told the International Atomic Energy Agency (IAEA) that two nuclear sites were under construction in Iran, at Natanz and Arak, neither of which had been declared to the IAEA as required by the Nuclear Non-Proliferation Treaty (NPT) to which Iran was a signatory. To defuse the situation, President Khatami offered to discuss Iran’s nuclear programme with the EU3 (France, Germany and the UK). Jack Straw, Joschka Fischer and Dominique de Villepin visited Tehran in October 2003. Iran’s nuclear negotiator, Hassan Rouhani, agreed to suspend the enrichment facility at Natanz and the construction of a heavy water reactor at Arak, and to sign the IAEA’s Additional Protocol, which provides for more intrusive inspections of nuclear sites than the NPT does.
At five o’clock on Tuesday morning, Yasser Arafat’s body was disinterred in Ramallah and tissue samples extracted for analysis by French, Swiss and Russian scientists. One of the things they’ll be testing for is polonium poisoning. But can a meaningful result be hoped for eight years after Arafat’s death? The half-life of Po-210 in vacuo is 138 days (i.e. half the original Po-210 nuclei would decay on average in 138 days) but in the body it’s rather less, between two and three months (i.e. on average half the Po-210 atoms would have passed through the body after this time). Either way, a definitive result for Arafat would be difficult to obtain now, since after eight years the initial quantities of any Po-210 would be diluted by a factor of a million. As a spokesperson for the University of Lausanne's Institute of Radiation Physics has said, the traces of polonium they found on Arafat's clothes a few months ago could be a more recent contamination and don't prove anything.
Among the evidence for ‘possible military dimensions to Iran’s nuclear programme’ in the new Report from the International Atomic Energy Agency (IAEA) is that a foreign expert... who, a Member State has informed the Agency, worked for much of his career... in the nuclear weapon programme of his country of origin... was in Iran from about 1996 to 2002, ostensibly to assist Iran in the development of a facility and techniques for making ultra-dispersed diamonds, where he lectured also on explosion physics and its applications.
On 22 September 1979 at about 1 a.m. GMT, a US Vela satellite passing over the South Atlantic detected a double flash of light in the vicinity of Prince Edward Island. The satellite had been launched in 1969 in order to detect atmospheric nuclear tests. When a nuclear weapon explodes in the atmosphere, the heat of the fireball strips the electrons off the atoms and molecules of the surrounding air. For a fraction of a second the ionised air is opaque, until the blast blows it away. The resulting double flash is the signature of a nuclear explosion. At the time the Vela had successfully detected 41 such explosions. Guy Barasch of Los Alamos, the laboratory which ran the Vela programme, concluded that ‘naturally occurring signals would not be mistaken for that of a nuclear explosion’ and that