I'm collecting some data about how many fuel assemblies were at Fukushima
Tomorrow (Wed) I'll post my calculations about the Cesium-137 contained in those assemblies.
I was pleased today to find a report detailing how many assemblies were at the plant in 2010. This report may not be new, and I know other people have discussed it, but it has some valuable information that I can use for estimating how much radiation is at various places in the plant.
The report is titled Integrity Inspection of Dry Storage Casks and Spent Fuels at Fukushima Daiichi Nuclear Power Station. 16 November 2010. Yumiko Kumano, Tokyo Electric Power Company
The report states "Approximately 700 spent fuel assemblies are generated every year" (p. 9)
The assemblies are stored in spent fuel pools and also in dry casks. Each reactor building has a spent fuel pool and there is also a common spent fuel pool.
On page 9 there is a nice table detailing the amount of fuel assemblies in storage at the plant as of March 2010.
STORAGE METHOD STORAGE AMOUNT CAPACITY
Spent Fuel Pool at Each Reactor 3,450 assemblies in each pool 8,310
Dry Cask 408 assemblies 408
Common Spent Fuel Pool 6,291 6,840
Total 10,149 as of March 2010 15,558
There is also a chart for Storage Amount (ton-U) as of March 2010 (page 4)
Fukushima Daiichi had 1,760 (ton-U) as of March 2010
I found two other sources of information for spent fuel stored at Daiichi plant:
MacKenzie of New Scientist reported in March 2011 that “the Fukushima plant has around 1760 tonnes of fresh and used nuclear fuel on site, and an unknown amount has been damaged. The Chernobyl reactor had only 180 tonnes.”
Austrian researchers have used a worldwide network of radiation detectors – designed to spot clandestine nuclear bomb tests – to show that iodine-131 is being released at daily levels 73 per cent of those seen after the 1986 disaster. The daily amount of caesium-137 released from Fukushima Daiichi is around 60 per cent of the amount released from Chernobyl." (MacKenzie http://www.newscientist.com/article/dn20285-fukushima-radioactive-fallout-nears-chernobyl-levels.html )
Eliot Marshall and Sara Reardon on 17 March 2011. How Much Fuel Is at Risk at Fukushima? Science Insider http://news.sciencemag.org/scienceinsider/2011/03/how-much-fuel-is-at-risk-at-fukushima.html?rss=1
“The most damaged Daiichi reactor, number 3, contains about 90 tons of fuel, and the storage pool above reactor 4, which the Nuclear Regulatory Commission's (NRC's) Gregory Jaczko reported yesterday had lost its cooling water, contains 135 tons of spent fuel. The amount of fuel lost in the core melt at Three Mile Island in 1979 was about 30 tons; the Chernobyl reactors had about 180 tons when the accident occurred in 1986."