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Nuclear Weapons: Safety Measures
Mrs. Cryer: To ask the Secretary of State for Defence what procedures are in place with regard to the (a) design and (b) handling of nuclear weapons to ensure that there is no popcorning or accidental explosion; what procedures are in place to ensure public safety in the event of popcorning; and if he will make a statement. 
Des Browne: The theoretical phenomenon known as "popcorning" is a process whereby a series of accidental detonations of a number of warheads' conventional explosives could lead to some nuclear yield. This is extremely unlikely and could occur only if the warheads were located in close proximity to each other without mitigation. Warheads are designed such that there cannot be a nuclear detonation without authorisation.
Warhead handling, transit and storage facilities, and processes are designed to reduce the risk of popcorning to ‘As Low As Reasonably Practicable’ levels by, for example, separating stored warheads and having physical shielding between them. Similarly, moves of warheads are planned and executed to minimise the proximity of warheads to each other.
Safety in the nuclear weapons programme is of paramount importance. There are well-rehearsed generic response plans in place to protect workers and the general public in the unlikely event of an accident; all measures are taken to ensure acceptable levels of safety throughout the life cycle of the Trident warhead.