26 June 2008 - YOU might think nuclear weapons have been carefully designed not to go off by accident. Yet more than 1700 of them have design flaws that could conceivably cause multiple warheads to explode one after another - an effect known as "popcorning" - according to a UK Ministry of Defence safety manual.A typical Trident nuclear missile contains from three to six warheads, and a US submarine might carry up to 24 missiles. Weapons builders aim to prevent accidental explosions of warheads by designing them to be "single-point safe". This means that a sudden knock at a single point - say if it were dropped from a crane while being unloaded from a submarine - should not detonate the plutonium core.
However, a nuclear-weapons safety manual drawn up by the MoD's internal nuclear-weapons regulator argues that this standard single-point design might not be enough to prevent popcorning. The document was declassified last month. More >>>
