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

Saturday, March 12, 2011

FACTS: How does the Japan evacution compare to US plants?

-In the case of Fukushima Daiichi site, the evacuation area at last report included a zone with roughly a 12.5 mile radius and included between perhaps 170,000 and 200,000 people

-Reactors in many countries are sited closer to populated areas than they are in the United States

-AEC document TID-14844 in the APRA library gave basic guidelines by the AEC for the siting recommendations for nuclear power plants based on how much radioactive material a core could possibly contain (this was calculated based on the power output of the core in MWt or Megawatts thermal) and the necessary radius of population to prevent serious effects in case of an accident

-Fukushima Daiichi 1 is rated at roughly 1380 MWt.. if we look at the TID-14844 siting recommendations, we find that this falls between the 1200 MW and 1500 MW listings. Let's look at these briefly:

1200 MW plant recommended exclusion (no population) area of .77 miles, low population zone radius of 11.5 miles, nearest population center 15.3 miles

1500 MW plant recommended exclusion area of .88 miles, low population zone radius of 13.3 miles, nearest population center 17.7 miles

-Without going into detail on all of the meanings in precise terms we have just mentioned, it suffices to say that the Japanese reactors are sited in an area far more heavily populated than US regulations would allow

-Further, there is not just one reactor at that site, but six. Three were operating at the time of the quake, and because of the nature of a major natural disaster there is not just one "beyond design basis accident" series of potential events occurring at one plant alone (like there would be if there had been a serious system failure on a normal day) but serious problems simultaneously at three reactors on the same site with an aggregate total output at power of over 3000 MW

-This is one reason why very few US sites include more than two reactor plants on one power plant site

-In the years following dissemination of those initial concepts of reactor siting it was determined through a variety of avenues, not the least of which were public hearings with local citizens and local governments, that siting of some plants in some areas inside earlier recommended radii was safe enough to be acceptable and economically beneficial. So far in the United States, even at Three Mile Island, this policy of only very rare, careful rule relaxation has proven safe and effective

Written by Will Davis for Atomic Power Review. Do not copy or quote without credit.

9:30 PM Saturday 3/12

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