How the IAEA scores nuclear incidents

Eventually, this Japanese incident will be assigned a final numerical rating according to a scale devised by the IAEA.  The scale, called INES (for International Nuclear and Radiological Event Scale), breaks down the severity of nuclear events into bloodless, regimented categories.  Each event ultimately gets a ranking from 1 to 7.

The anomalies, incidents, and accidents of our nuclear world,  CNNMoney.com, 11 April 11 From simple leaks to sudden deaths, Fukushima to Pennsylvania, our world’s brief history of nuclear power is rife with mishaps and tragedy. By Shelley DuBois, reporter

 The nuclear crisis in Japan, the aftermath of an 9.0 magnitude earthquake, including a 7.1 magnitude aftershock yesterday, and a tsunami on March 11, adds to a long list of major nuclear accidents, all of which stem from some combination of human error, insufficient safety procedure, or outdated equipment….

Eventually, this Japanese incident will be assigned a final numerical rating according to a scale devised by the IAEA.  The scale, called INES (for International Nuclear and Radiological Event Scale), breaks down the severity of nuclear events into bloodless, regimented categories.  Each event ultimately gets a ranking from 1 to 7.

A rating of 1 is applied to “an anomaly.” That includes situations in which a person is exposed to a higher level of radiation than the annual limit set by regulators, but does not necessarily develop health problems…..

Level 2 is an “incident” and Level 3 is a “serious incident.”  Which designation applies depends on the extent of security problems, the number of people exposed to radiation, and the dosage they receive.

Levels 4-7 on the INES scale are officially called “accidents” and often, but not always, signal that one or more fatalities from radiation exposure have occurred. The INES ranking scale doesn’t cover deaths at nuclear facilities from non-radioactive chemical leaks or explosions…

level 5, which signifies that there is severe damage to the reactor core and that members of the public will probably be exposed to some level of radiation….

History’s second-most damaging nuclear accident occurred in 1957 at Russia’s Mayak plant in the Kyshtym province.  Caused by the explosion of a tank that contained radioactive waste, this crisis is recorded as a Level 6 “serious accident” on the INES scale. The explosion spewed roughly 75 tons of radioactive waste into the atmosphere, according to the World Nuclear Association, and caused an estimated 200 people to develop fatal cancer.

There has only been one Level 7 “major accident,” and that, of course, was at Chernobyl, located in what is now called Ukraine….
surge of power caused a chain reaction that set the reactor core on fire.  It burned for 10 days and released a cloud of radioactive matter that spread over a wide area of the USSR.

At the plant, 134 emergency workers were exposed to high doses of radiation that killed 28 of them in that same year, 1986.

To that toll of about 30 deaths must be added the indirect effects of Chernobyl—deaths caused, for example, by that radioactive cloud, which is estimated to have exposed more than 5 million people to abnormal doses of radiation.

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