Table 18.8 - Severe nuclear accidents (level 6 to 7 of INES scale)

Source: IAEA, 1991; SCOPE, 1993

Location Kyshtym (Eastern Urals) Chernobyl (Ukraine)
Date September 1957 April 1986
Estimated radioactivity release (TBq) 740 000 2 million
Nature of plant Chemical processing Electricity generation
Main radionuclides of concern Ce-144, Pr-144 (short term) Sr-90 (long term) I-131, Cs-134, Cs-137 and rare earths
Mode of release Instantaneous (chemical explosion) Over some days (criticality explosion and subsequent phenomena)
Significantly contaminated area Some 20 000 km2 Some 20 000 km2
Affected area ­ Northern hemisphere
People evacuated 11 000 116 000 (first year after accident)