APR: your source for nuclear news and analysis since April 16, 2010

Friday, March 18, 2011

Accident Level 5

Let's just briefly take a look at the upgrading of the Fukushima Daiichi Accident to the INES scale Level 5.

First let's link a pdf file from IAEA describing the levels of incidents and accidents. Be sure to notice the two actual reactor accidents that are listed as Level 5 events; you've seen both mentioned on this site before.


That's right - Windscale, and TMI-2. Frankly I can't see how these are identical events in terms of release. For example, one of the elements we've been seeing mentioned widely is iodine... TMI-2 released between 13 and 17 Curies of iodine to the atmosphere. Windscale released 20,000 curies of iodine.

Total population dose is estimated for the TMI-2 accident at somewhere between 500 and 3300 man-Rem. The total population dose from Windscale was about 25,000 man-Sieverts. Since 1 Sievert equals 100 Rem, the Windscale dose in the older and more familiar Rem (Roentgen Equivalent Man) units would be 2,500,000 man-Rem.

For my source on this check the stand-alone page on Fukushima Accident sources and find "The Second Nuclear Era."

The only reason one might guess that this could be raised to a 5 is the finding of small amounts of radioactive contamination on some items shipped outside of Japan after the accident... but the effects of this are minor.

Of course Level 7, which is the worst, is Chernobyl and this is absolutely nothing like that at all. But we also think that Windscale is a lot more like Chernobyl in the sense that after Windscale apparently according to WASH-1250 milk over 200 square miles was destroyed (probably the cows were eating contaminated grass, etc) and nothing of that scale occurred with TMI-2.

6:45 PM Eastern Friday 3/18

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