Comment Not the most powerful (Score 2) 299
The B53 was not the most powerful bomb the US had in service. the B41 (https://secure.wikimedia.org/wikipedia/en/wiki/B41_nuclear_bomb) had a theoretical maximum yield of 25 megatons, making it more powerful than even the Castle Bravo Shrimp device which had a yield of 15 megatons. The only stronger detonation was the Soviet RDS-220, or "Tsar Bomba", which had a yield of 57 megatons, reduced from 100 by replacing the uranium tamper with a lead one in order to reduce fallout.