The Wikipedia article says > The Mk-54 weighed about 51 lb (23 kg), with a yield equivalent to somewhere between 10 and 20 tons of TNT—close to the minimum pr

The Wikipedia article says > The Mk-54 weighed about 51 lb (23 kg), with a yield equivalent to somewhere between 10 and 20 tons of TNT—close to the minimum practical size for a fission warhead [footnote:] the theoretical minimum critical mass for 233U is close to 16 kg. Actually, the critical mass depends on how much you compress it (so surrounding the fissile core with more chemical explosives lets you use less plutonium), and how effective neutron reflectors you surround it with. A modern hydrogen bomb might use 3kg of plutonium in the fission primary core, but the weight of the whole assembly (including chemical explosives and so on) would be several hundred kgs.