spontaneous fission

uncountable

(physics) Nuclear fission that occurs spontaneously, instead of being induced by an external stimulus.

Japanese Meaning

自発核分裂：外部からの刺激によらず、核が自発的に分裂する物理現象

Scientists observed spontaneous fission in the old uranium rods, showing the material can undergo fission without an external trigger.

科学者たちは古いウラン棒で自発的な核分裂を観測し、外部からの刺激なしに核分裂が起き得ることを示した。

Sense（1）

(physics) Nuclear fission that occurs spontaneously, instead of being induced by an external stimulus.