History's 10 Worst Nuclear Disasters

1. Chernobyl, Ukraine Level 7 - Chernobyl, the worst nuclear disaster in history, occurred in 1986 in Ukraine due to reactor flaws and safety lapses. It caused severe radiation, evacuations, and long-term uninhabitability.

2. Fukushima, Daiichi, Japan Level 7 - In 2011, a devastating 9.1 magnitude earthquake triggered a tsunami in Japan, disabling Fukushima Daiichi Nuclear Power Plant. Meltdown, evacuations, and ongoing displacement followed, prompting a temporary nuclear plant shutdown.

3. Kyshtym, Russia Level 6 - The third deadliest nuclear disaster occurred in Kyshtym, USSR, in 1957. A reactor malfunction led to a secret explosion, releasing radioactive materials, with an unknown death toll due to government cover-up.

3. 4. Windscale, UK Level 5 - In 1957, the UK also experienced the worst nuclear disaster in its history. The country had built two nuclear reactors in Windscale now part of Cumbria in the late 1940s. In 1957, one reactor overheated, rupturing uranium cartridges.

5. Three Mile Island, Pennsylvania, USA Level 5 - In 1979, a broken pressure valve in a nuclear reactor, at Three Mile Island in Pennsylvania, created panic among the plant workers. They made some errors in judgment, which led to the reactors partial meltdown. They also did not discover a radiation leak until more than 24 hours had passed.

6. First Chalk River, Canada Level 5 -Canada only experienced one nuclear accident in its history, and that was in 1952, at Chalk River Laboratories first nuclear research reactor. The reactor’s core got damaged because of a loss in coolant and it went through a partial meltdown.

7. Jaslovskè Bohunice, Czechoslovakia Level 4 - Czechoslovakia built its first nuclear power plant in Bohunice, with the objective that it would run on the uranium produced locally. Unfortunately, many accidents occurred in this facility, with the most serious one occurring in 1977.

8. SL-1 Experimental Power Station, Idaho, USA Level 4 - In 1961, the SL-1 nuclear reactor in Idaho exploded, resulting in the only fatal reactor accident in US history. The SL-1 was one of several reactors built in Idaho to learn about the process of creating nuclear energy.

9. Saint-Laurent, France Level 4 - France has experienced two level 4 nuclear accidents at the same nuclear facility of Saint-Laurent. The first time was in 1969 when the uranium in the reactor melted, causing a partial meltdown. Workers spent a year cleaning and repairing the reactor, in a highly toxic environment.

10. Tokaimura, Japan Level 4 - Japan had experienced a nuclear accident in 1999 as well. It occurred in a small plant where three workers were mixing two kinds of fuel to make uranyl nitrate for a nuclear reactor. Unfortunately, they misjudged the amounts they needed to mix and ended up using seven times the permitted amount of uranium.