1. Chernobyl Nuclear Power Plant, Pripyat, Ukraine.
International Nuclear Event Scale Level: 7.

2. Fukushima Nuclear Power Plant, Fukushima, Japan.
International Nuclear Event Scale Level: 7.

3. Mayak Nuclear Fuel Reprocessing Plant, Ozyorsk, Russia.
International Nuclear Event Scale Level: 6.

4. Three Mile Island Nuclear Power Plant, Pennsylvania, USA.
International Nuclear Event Scale Level: 5.

5. Windscale Piles, Cumberland (Now Cumbria), UK.
International Nuclear Event Scale Level: 5.

6. JCO Uranium Reprocessing Facility, Tokai, Japan.
International Nuclear Event Scale Level: 4.

7. Bohunice Nuclear Power Plant, Trnava District, Slovakia.
International Nuclear Event Scale Level: 4.

8. Lucens Reactor, Vaud, Switzerland.
International Nuclear Event Scale Level: 4.

9. National Reactor Testing Station, Idaho, USA.
International Nuclear Event Scale Level: 4.

10. Davis-Besse Nuclear Power Station, Ohio, USA.
International Nuclear Event Scale Level: 3.

Source: Tech Graffiti
Photo by Pedro Moura Pinheiro