Comment Re:It might be worse than that. . . (Score 2) 234
"The decay heat, which is 7% of 1000 MW"
IIRC, the reactors were 1000MW *electrical* output. Because of thermal efficiencies of steam generators of around 35%, I believe that means the thermal output of each reactor would have been about 1000/.35 ~= 2800 MW thermal energy.
So, instead of 7% of 1000MW = 70MW, I think you're looking at 7% of 2800 = 196MW.
That's a LOT of heat to get rid of, even if it is a small percentage of the 2800MW full output.
http://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Power_Plant shows the plant #2 at 784MW for electrical power out.
Assuming 30% thermal efficiency (35% seems high for a 1973 reactor, but I am guessing honestly), then the full thermal load would be ~2600 MW. 7% of that would be 183MW. So, you aren't too far off.
Not sure what the water volume of the reactor would be, but if you ever have a hard time falling asleep the NRC has the standards for a BWR/4 reactor (plant #2) at this site http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1433/r3/v1/sr1433r3v1.pdf Note that page 1.1-5 talks about the RTP (Rated Thermal Power) of the heat transfer of the core to the coolant being 2436MW. Admittedly this is a US document but GE (the reactor designer) has usually made a point to support customer upgrades to US-NRC standards.
then you could figure the boil off rate assuming the 7% was unchanging (which it isn't, right off hand I don't recall the reported decay rate of that level). Truth is, 12 days later this won't even be close to 7% thermal load. 12 days later put the amount of Iodine through about 1.5 half lives so there would be much less Iodine left. Obviously other decay product would be on their own schedule. So, one might argue that the measurements show a restart, but if there was one, it is highly likely that it was a small localized one.
The physical laws do not lie or change, but I and others have been known to make errors in measurements and observations.
aside from this speculation of what went on based on the measurements they claim to have made.....
I find all this discusion about oceanic releases interesting since there are 5 USSR nuclear subs (3 of which had 2 reactors each), 2 US subs (with one 5SW reactor each) and one of the original 3 cores of the Lenin nuclear ice breaker all sunk in the ocean. Many of these 11 sunken reactors are in the Atlantic some up north nearer Russia, partially spent fuel and all.
Due to the US Department Of Defense plutonium breeding activities at the Hanford Nuclear Facilities many millions of curies were released into the Columbia River by primary coolant water used in the reactors there. http://en.wikipedia.org/wiki/Hanford_Site http://toxipedia.org/display/wanmec/River+Releases%2C+Columbia+River
then there is the release made by coal plants which according to this article is quite significant. http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html It makes an interesting point that the coal plants in the world release more uranium in their wastes than "...dozens of nuclear reactor fuel loadings...".
I respect the need for environmental controls, but I get annoyed by much of the 'sky is falling' 'the world is ending' mentality that seems to underlie much of popular news on this issue in general. Much of the science can be measured and thought about rationally. I appreciate the intention of this thread to actually put numbers to their discussion.