Fukushima Daiichi nuclear disaster on the International Nuclear Event Scale (INES). This scale runs from 0, indicating an abnormal situation with no safety consequences, to 7, indicating an accident causing widespread contamination with serious health and environmental effects. Prior to Fukushima, the Chernobyl disaster was the only level 7 event on record, while the Three Mile Island accident was rated as level 5. A 2012 analysis of the intermediate and long-lived radioactivity released found about 10–20% of that released from the Chernobyl disaster. Approximately 15 PBq of caesium-137 was released, compared with approximately 85 PBq of caesium-137 at Chernobyl, indicating the release of of
Radiation effects from the Fukushima Daiichi nuclear disaster in the unit-3 spent-fuel pool were reported at 140 kBq of radioactive caesium-134 per cubic centimeter, 150 kBq of caesium-137 per cubic centimeter, and 11 kBq per cubic centimeter of iodine-131 on 10 May. TEPCO have reported at three sites 500 meters from the reactors that the caesium-134 and caesium-137 levels in the soil are between 7.1 kBq and 530 kBq per kilo of undried soil. Small traces of plutonium have been found in the soil near the stricken reactors: repeated examinations of the soil suggest that the plutonium level is similar to the background level caused by atomic bomb