Incidents
Chernobyl (1986)
Steam explosion and fire during a poorly conducted safety test destroyed Reactor 4. Positive void coefficient of RBMK design allowed runaway power surge. 31 direct deaths (2 from explosion, 29 from acute radiation syndrome). Estimated 350,000+ evacuated. Exclusion zone remains.
Fukushima Daiichi (2011)
9.0 Mw Tōhoku earthquake and tsunami disabled cooling systems at four BWR units. Units 1–3 experienced fuel meltdowns; Unit 4 spent fuel pool at risk. ~154,000 evacuated. No direct radiation deaths; significant economic and psychological impact. Cleanup expected to take decades.
Three Mile Island (1979)
Partial core meltdown caused by cooling system malfunction and operator error. Approximately 700,000 gallons of radioactive water released into the Susquehanna River. No direct deaths attributed. Unit 2 permanently shutdown; cleanup completed by 1993. TMI-1 continued operation until 2019.