What is critical mass of uranium and what connection does it have with atomic blast??

Question

What is critical mass of uranium and what connection does it have with atomic blast??

Answer 1

Uranium 233 critical mass is 15 kg
Uranium 235 critical mass is 50 kg

Until detonation is desired, a nuclear weapon must be kept subcritical. In the case of a uranium bomb, this can be achieved by keeping the fuel in a number of separate pieces, each below the critical size either because they are too small or unfavorably shaped. To produce detonation, the uranium is brought together rapidly. In Little Boy, this was achieved by firing a smaller piece of uranium down a gun barrel into a corresponding hole in a larger piece, a design referred to as a gun-type fission weapon.

Answer 2

Uranium 233 - 15Kg

Uranium 235 - 50Kg

The critical mass is amount of fissile material that is required to for a sustained nuclear reaction, meaning once you set it off and leave it you have a nuclear bomb.