What is the smallest-yield nuclear blast possible?

Question

Or rather, what is the minimum blast from a nuclear bomb? Instead of levelling a city, could you level a football field, or a small room?

Answer 1

The minimum size is determined by what's called the "critical mass". If the fission core is below this, neutrons leak out too fast for a chain reaction to allow the neutron flux to grow exponentially. I image the tacticals are about as small you can get.

Answer 2

I'd think that would be possible. The trick is to hold enough material together long enough to initiate the reaction. As you use less material, it would tend to not initiate since it depends on enough neutrons firing randomly back through the material. At a certain point, you'll get a self-sustaining reaction. You can throttle back the power by not containing it as efficiently, in which case there's some energy released by the reaction but the energy throws the material apart so that it can't continue. So I'd think that such a small reaction would tend to be a very "dirty" one.

Answer 3

Exact amount i do not know. But, I would think it is somewhere between modern nuclear reactors and the yield of the bombs dropped in WWII-which are/were fission devices, not modern nuclear fusion devices. The smallest yield one could make happen would be the splitting of one nucleus. This yields about 200 million eV of energy.

Answer 4

I asked that a while back myself and couldn't get any good answers. But I read that the exact amount is top secret.