Foreign Affairs

Last edited Thu Sep 25, 2025, 04:06 AM - Edit history (1)

Here’s a list of the major nuclear reactor accidents since the 1940s, focusing on those with fatalities, large releases of radiation, or long-term consequences:


---

1940s–1950s

SL-1 (Idaho, USA, 1961) – A U.S. Army experimental reactor suffered a steam explosion due to improper rod withdrawal, killing 3 operators.

Mayak / Kyshtym Disaster (Soviet Union, 1957) – Not a reactor core accident but a waste storage tank explosion at Mayak. Released large amounts of radioactive material; estimated thousands exposed.

Windscale Fire (UK, 1957) – Graphite-moderated reactor fire in Cumbria released radioactive contamination, especially iodine-131. Milk in nearby areas was destroyed.



---

1960s–1970s

Lucens Reactor (Switzerland, 1969) – Experimental underground reactor suffered partial core meltdown. Contained within cavern, but major contamination of facility.

Leningrad Nuclear Power Plant (Soviet Union, 1975) – RBMK reactor experienced partial meltdown; significant local contamination.

Three Mile Island (USA, 1979) – Partial meltdown in Pennsylvania due to cooling system failures and operator error. Large hydrogen bubble formed, but containment held. Public exposure was minimal, but it caused widespread alarm and changed nuclear regulation.



---

1980s

Saint-Laurent Nuclear Power Plant (France, 1980) – Partial meltdown of graphite gas-cooled reactor fuel assemblies. No major release outside containment.

Chernobyl Disaster (Soviet Union, 1986) – Worst nuclear accident in history. RBMK reactor exploded during a botched safety test. Massive release of radioactive materials across Europe. Immediate deaths: 2 workers that night, ~28 firefighters/plant staff later from acute radiation syndrome. Long-term health effects continue. The Chernobyl Nuclear Power Plant and the nearby abandoned city of Pripyat are located in northern Ukraine, close to the border with Belarus. When the accident happened in April 1986, the region was part of the Soviet Union (the Ukrainian SSR). After the USSR dissolved in 1991, it became part of independent Ukraine.
------>Chernobyl is now in Ukraine.


---

1990s

Tomsk-7 (Seversk, Russia, 1993) – Explosion during reprocessing of spent fuel at a plutonium production plant, releasing radioactive gas cloud.

Tokaimura Criticality Accident (Japan, 1999) – Fuel preparation facility workers caused uncontrolled chain reaction. Two workers died of radiation sickness; many others exposed.



---

2000s

Fukushima Daiichi (Japan, 2011) – Triggered by a massive earthquake and tsunami. Loss of power led to meltdowns in 3 reactors, hydrogen explosions, and major radioactive releases into air and sea. Tens of thousands displaced.



---

2010s–2020s

No large-scale new civil reactor disasters reported after Fukushima (2011). Smaller incidents and near-misses have occurred, but not on the scale of Chernobyl or Fukushima.



---

Summary of Major Reactor Core Accidents (since 1940s):

SL-1 (1961, USA)

Lucens (1969, Switzerland)

Leningrad Unit 1 (1975, USSR)

Three Mile Island (1979, USA)

Saint-Laurent (1980, France)

Chernobyl (1986, USSR)

Tokaimura (1999, Japan) – technically a fuel accident, not reactor core

Fukushima Daiichi (2011, Japan)