with the number of nuclear weapons in the world now, and how old a lot are, how is it possible we’ve never accidentally set one off?

Question

Title says it. Really curious how we’ve escaped this kind of occurrence anywhere in the world, for the last ~70 years.

In: Engineering

Answer 1

Almost all nuclear weapons ever built are plutonium implosion weapons. 

You take a ball of plutonium and squash it in a very specific way and it goes bang. 

You do anything else with that plutonium and not much happens.

The device to squash it is called an ‘explosive lens’. It’s a set of explosives around the plutonium that have to go off in exactly the right way to squash it. Any other form of explosion and nothing happens. So even accidentally making those explosives go off won’t cause the nuclear explosion.

There is a type of nuclear bomb that could be accidentally detonated – a ‘gun type’ uranium bomb. In this type of bomb a cylinder of uranium is fired into a hollow tube. This does not need complex explosives, and so a simple accident could make it go bang. This is one of the reasons only a very small number of these were built, and they are all now decommissioned.