Spontaneous Nuclear Fission

The spontaneous nuclear fission rate is the probability per second that a given atom will fission spontaneously--that is, without any external intervention.

If a spontaneous fission occurs before the bomb is fully ready, it could fizzle. Plutonium 239 has a very high spontaneous fission rate compared to the spontaneous fission rate of uranium 235. Scientists had to consider the spontaneous fission rate of each material when designing nuclear weapons.

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