Good article. Worth the read.
In Stricken Fuel-Cooling Pools, a Danger for the Longer Term
By WILLIAM J. BROAD and HIROKO TABUCHI
Published: March 14, 2011
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The good news is that the Japanese have a relatively long time to deal with the problem. Nuclear experts estimate the timeline for serious problems that could lead to a reactor meltdown as minutes to hours, and put the comparable time for cooling pools at days to weeks.
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Were the spent fuel rods in the pools to catch fire, nuclear experts say, the high heat would loft the radiation in clouds that would spread the radioactivity.
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A 1997 study by the Brookhaven National Laboratory on Long Island described a worst-case disaster from uncovered spent fuel in a reactor cooling pool. It estimated 100 quick deaths would occur within a range of 500 miles and 138,000 eventual deaths.
The study also found that land over 2,170 miles would be contaminated and damages would hit $546 billion.
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http://www.nytimes.com/2011/03/15/world/asia/15fuel.html