Africa's 2-billion-year-old nuclear reactor

Humans develop most nuclear reactors.

They're manmade and artificial, meant to halt nuclear fission and provide alternative energy to coal

Nuclear reactors aren't human-made, however. As of this writing, just one naturally occurring nuclear reactor has been found. 

Nuclear reactors create dangerous radioactive waste. Nuclear waste stays radioactive for millions of years, despite being cleaner than coal.

EPA says nuclear scientists' biggest challenge is securely storing nuclear waste.

This unusual creation has helped researchers comprehend nuclear fission and prospective approaches for properly storing nuclear waste in the future.

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