Gauging nuclear disasters

Concept image about dangerous radioactivity levels in Japan.


A nuclear accident is defined by the International Atomic Energy Agency (IAEA) as an incident in which people died or property damage topped $50,000. In 1990, IAEA introduced the International Nuclear and Radiological Event Scale (INES) to rate and rank nuclear accidents. INES is a logarithmic scale that consists of seven levels: 0 (Deviation, no safety significance), 1 (Anomaly), 2 (Incident), 3 (Serious incident), 4 (Accident with local consequences), 5 (Accident with wider consequences), 6 (Serious accident) and 7 (Major accident). The scale is not very quantitative, and it is often long after an event that an accident’s level is estimated.

Some well-known nuclear accidents include an INES level 4 accident at the Sl-1 reactor in Idaho in 1961, the INES level 5 accident at Three Mile Island in Pennsylvania in 1979 and the INES level 7 event in Chernobyl in Ukraine in 1986. By mid-April, Japan’s Fukushima accident was rated an INES level 7 because of the total hazard that the radiation leakage has caused to human health and the environment.

In addition, a list of 99 nuclear accidents that occurred between 1952 and 2009, compiled by Benjamin Sovacool of the National University of Singapore, shows that more than half have occurred since the 1986 Chernobyl disaster. Out of the world’s 442 reactors, 263 were built before 1986, and thus are 25 to 40 years old.

Rasoul Sorkhabi

Sorkhabi is a research professor at the University of Utah’s Energy & Geoscience Institute. Email: The views expressed are his own.

Tuesday, May 31, 2011 - 11:00