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:


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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.



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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.



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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.


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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.



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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.



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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.



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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)

Chernobyl happened when I was in the US Army, stationed in Germany.

We knew something had happened within a couple of days - but not really how bad it was. I remember local farmers having to throw out milk that was contaminated- the rain had left many fields full of fallout, cows ate the grass. Our Army equipment detected something- but not really a lot of radiation. It was spotty - some places little hotspots turned up.

No one ever tracked the history of the US military stationed there- to see cancer patters, or anything. We had about 350,000 U.S. military folks in the area, including large numbers in areas where fallout was reported.

It the cap is cracking- it’s going to be very hazardous again.

Russian troops were idiotically running tanks and personnel vehicles across grounds that were well within the Chernobyl "Exclusion Zone" and kicking up the topsoil (because they didn't used the designated roads) that had covered the contaminated soil over the past couple decades. Some idiots even dug trenches in that zone.

Quite educational on how they built the sarcophagus right after the 1986 disaster (something like in 200 days IIRC, its somewhere in the video) and its inadequacies, and so they built the big "NSC" (New Safe Confinement - the big dome over it all that we see today, and its weak points, even before the big hole blown all the way through. (I bold it because I use the "NSC" abbreviation throughout).

0:59: picture of the hole.

2:14: more on the hole. Occurred Feb 14 of this year, fire spread extensively, took 17 days of continuous water spraying to put it out.

4:09: extent of damage - about 5% of the dome's surface area (progree guess), almost all at the top (they show a picture so you can venture your own guess). Later on, they say there are additionally 300 holes created by fire crews.

Then how initially after the 1986 disaster, they built a "sarcophagus" to contain the 95% of destroyed reactor fuel that remained, and how it was problematical. So they built the big "NSC" over the sarcophagus. At 11:15 -- the steel rod structures holding up the NSC.

12:21 - the drone broke the air-tightness and why that's a problem (corrosion).

15:50 -The invasion and occupation of Chernobyl by Russians for a month - Russian soldiers even dug and lived in the trenches in the contaminated exclusion zone.

17:08 - Loss of most of the human capital / knowledge base. Also a lot of destruction of transportation infrastructure to the plant making efforts to deal with the problems much more difficult, despite Trump ending the war many months ago even before taking office because Putin respects him (OK that's not in the video),

18:55-if the sarcophagus (which is in a precarious position) collapses it would be disastrous in the situation with the NSC having holes in it. In the short run, they'll patch the holes..

18:54 Essentially they don't know what to do about repairing the NSC in the long-run, they are still exploring long-term solutions, but likely the result will not have the 100-year supposed lifetime of the original NSC.

It ends on an optimistic note about how the international community contributed so much money and expertise to the building of the original NSC and their high level of concern now.