It’s not easy to make nuclear weapons, build missiles to carry them long distances, and to produce highly enriched uranium or plutonium. It’s even harder to keep nuclear weapons safe so they do not detonate except under orders from a National Command Authority. If a single mushroom cloud appears at a time of crisis or warfare because of an accident, inadvertent or unauthorized use, escalation control will be extremely difficult and all of the presumed benefits of nuclear deterrence can be lost.
Nuclear safety and security techniques and practices are designed to prevent these eventualities. Gates and guards and personnel reliability programs help with nuclear security. All states with nuclear weapons employ these practices. Nuclear weapon design features and other safety techniques help provide insurance against accidental, inadvertent, or unauthorized detonations. Nuclear safety and security reinforce each other. Sometimes these categories merge. For example, authorization codes required to arm and use a nuclear weapon — permissive action links — can be considered as essential for both nuclear safety and security. Additional design features, including the use of insensitive high explosives, are required besides PALs to prevent unwanted mushroom clouds.
The United States has a “one-point safety” standard for all of its nuclear weapons. This standard means that the probability of achieving a nuclear yield greater than four pounds of TNT must not exceed one in a million for any event involving the initiation of the warhead’s high explosive at a single point on its periphery. The United States achieved this exacting safety standard after decades of effort, significant investment, and a learning curve derived from nuclear testing.