Nuclear- Notable Plant Accidents


3 MILE ISLAND  (March 2001minor update Jan 2012)

– In 1979 at Three Mile Island nuclear power plant in USA a cooling malfunction caused part of the core to melt in the # 2 reactor. The TMI-2 reactor was destroyed.

– Some radioactive gas was released a couple of days after the accident, but not enough to cause any dose above background levels to local residents.

– There were no injuries or adverse health effects from the Three Mile Island accident.
enlarge graphic>>    DYK NUCLEAR 3 MILE

– The chain of events during the Three Mile Island Accident
– Cooling Restored, radioactive releases to air
– The Hydrogen Bubble
– Cold Shutdown and investigation
– Public concern and confusion
– No Radiological Health Effects
– The TMI-2 Cleanup
– TMI-1: Safe and World-Class
– Training improvements
– Increased safety & reliability
– Summary

CHERNOBYL  (Updated November 2016)
– The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel.
– The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the atmosphere and downwind – some 5200 PBq (I-131 eq).
– Two Chernobyl plant workers died on the night of the accident, and a further 28 people died within a few weeks as a result of acute radiation poisoning.
– UNSCEAR says that apart from increased thyroid cancers, “there is no evidence of a major public health impact attributable to radiation exposure 20 years after the accident.”
– Resettlement of areas from which people were relocated is ongoing. In 2011 Chernobyl was officially declared a tourist attraction.


– The Chernobyl site and plant
– The 1986 Chernobyl accident
– Immediate impact of the Chernobyl accident
– Environmental and health effects of the Chernobyl accident
– Progressive closure of the Chernobyl plant
– Chernobyl today
– Resettlement of contaminated areas
– What has been learned from the Chernobyl disaster?

FUKUSHIMA–  (Updated April 2017)
– Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident on 11 March 2011. All three cores largely melted in the first three days.
– The accident was rated 7 on the INES scale, due to high radioactive releases over days 4 to 6, eventually a total of some 940 PBq (I-131 eq).
– Four reactors were written off due to damage in the accident – 2719 MWe net.
– After two weeks, the three reactors (units 1-3) were stable with water addition and by July they were being cooled with recycled water from the new treatment plant. Official ‘cold shutdown condition’ was announced in mid-December.
– Apart from cooling, the basic ongoing task was to prevent release of radioactive materials, particularly in contaminated water leaked from the three units. This task became newsworthy in August 2013.
– There have been no deaths or cases of radiation sickness from the nuclear accident, but over 100,000 people had to be evacuated from their homes to ensure this. Government nervousness delays their return.
– Official figures show that there have been well over 1000 deaths from maintaining the evacuation, in contrast to little risk from radiation if early return had been allowed.

The Great East Japan Earthquake of magnitude 9.0 at 2.46 pm on Friday 11 March 2011 did considerable damage in the region, and the large tsunami it created caused very much more. The earthquake was centred 130 km offshore the city of Sendai in Miyagi prefecture on the eastern cost of Honshu Island (the main part of Japan), and was a rare and complex double quake giving a severe duration of about 3 minutes. Japan moved a few metres east and the local coastline subsided half a metre. The tsunami inundated about 560 sq km and resulted in a human death toll of over 19,000 and much damage to coastal ports and towns with over a million buildings destroyed or partly collapsed….>>

– The two Fukushima plants and their siting
– Events at Fukushima Daiichi 1-3 & 4
– Inside the Fukushima Daiichi reactors
– Fuel ponds: developing problems
– Radioactive releases to air
– Radiation exposure on the plant site
– Radiation exposure and fallout beyond the plant site
– Return of evacuees
– Managing contaminated water
– IRID and NDF involvement
– Fukushima Daiichi 5&6
– Remediation on site and decommissioning units 1-4
– Fukushima Daini plant
– International Nuclear Event Scale assessment
– Accident liability and compensation
– Inquiries and reports
– “Stress Tests” on Japanese reactors and new regulatory authority