Biggest nuclear disasters
Today marks the 25th anniversary of the nuclear accident at Chernobyl. In light of that, and the story continuing to unfold at Japan's Fukishima plant, we'll look at three of the worst nuclear plant disasters. First, to give some context, here's how the International Nuclear and Radiological Event Scale (INES) classifies each type of event:
Level 7 disaster
Major release of radioactive material; widespread health and environmental effects
Level 6 accident
Significant release; requires planned countermeasures
Level 5 accident
Limited release; several deaths from radiation
Level 4 accident
Minor release
Level 3 incident
Exposure in excess of 10 times the annual limit for workers; possible burns from exposure
Level 2 incident
Exposure of statutory annual limits
Level 1: Anomaly
Definition:• Overexposure of a member of the public in excess of statutory annual limits.
• Minor problems with safety components with significant defence-in-depth remaining.
• Low activity lost or stolen radioactive source, device or transport package.
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