Nuclear Energy Insight
Summer 2011—The severity of the nuclear event at Fukushima Daiichi has been rated 7 on the International Nuclear and Radiological Event Scale (INES), the highest level and the same as the 1986 Chernobyl nuclear power plant accident.
It may appear that Fukushima Daiichi is just as serious an accident as Chernobyl, but there are significant differences.
Chernobyl is the only accident in the history of commercial nuclear power to cause deaths from radiation. Twenty-eight reactor staff and emergency workers died from radiation and thermal burns within four months of the accident, and 19 more died by the end of 2004. Japanese authorities estimate that the amount of radioactivity released at Fukushima is only 10 percent of the amount released from the Soviet-era plant and many times less than U.S. radiation protection standards.
INES was created by the International Atomic Energy Agency in an effort to facilitate consistent communication on the safety significance of nuclear and radiological events.
INES levels 1–3 are called “incidents” and levels 4–7 “accidents.” Each level of the scale indicates that an event is 10 times more severe than the level below it.
The IAEA compares INES to the Richter scale, which measures the relative intensity of earthquakes. But according to Barbara Hamrick, the radiation safety officer at the University of California’s Irvine Medical Center and secretary-elect of the Health Physics Society, that comparison can be misleading. She adds that there is a “great deal of subjectivity involved in the final assessment of any nuclear event.”
Hamrick said that countries use the scale “to communicate a very rough approximation of the potential consequences [of an event].”
“I’m not sure that adding levels would make a lot of difference in how the international nuclear safety community would react or respond, which is really the reason the scale was created,” Hamrick said.
On the INES scale, Level 7 describes an accident serious enough to require a country to implement countermeasures to protect the public from the health and environmental effects of radiation, but it does not mean that these effects have occurred.
Both Chernobyl and Fukushima required countermeasures, thus setting both events at Level 7. However, the differences between government responses to the two accidents are striking.
Efforts by the Soviet Union to hide the Chernobyl accident from its people and the world made its potential effects worse. The Soviet Union did not evacuate the population around the plant for several days or attempt to mitigate health effects.
Japan, on the other hand, moved quickly to evacuate the area within 12.5 miles of the Fukushima facility and halt food shipments from the area, limiting potential health effects. Unlike the Soviets, the Japanese government also distributed potassium iodide to residents near the facility to prevent their thyroid glands from absorbing radiation.
The Japanese government is continually monitoring and reporting radiation levels to citizens as well as providing information and health protection instructions.
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