Trident nuclear warheads damaged in a vehicle pile-up or a plane crash could partially detonate and deliver a lethal radiation dose, according to a newly declassified report from the UK Ministry of Defence obtained by New Scientist. The MoD has also revealed that an attack by terrorists on a nuclear weapons convoy could produce an even more disastrous outcome. "The consequences of such an incident are likely to be considerable loss of life," says a senior MoD official.
Trident warheads are regularly transported to weapons facilities in the US and the UK, where they are inspected to make sure that ageing materials don't render them unreliable or unstable. The MoD has always insisted that an accidental nuclear explosion could not happen in transit, because a warhead's plutonium core must be compressed symmetrically by conventional explosives. Bombs are designed to be "single point safe" so a knock at a single point should not trigger all the explosives around the core.
But according to the report extreme accidents could result in a nuclear explosion. A serious vehicle collision or an aircraft crash combined with multiple failures of the MoD's secret protective measures could mean that the weapon might not remain single-point safe. The report puts the overall yearly risk of an "inadvertent yield" in the UK at 2.4 in a billion, mainly due to the possibility of an aircraft crashing onto a convoy. Inadvertent yield suggests a partial nuclear explosion, also called fizzle yield, smaller than the full yield of up to 100 kilotons.
