In Fukushima Daiichi the wreaked reactors and fuel pools still need cooling and will continue to need it for many month. Cooling is currently done with water which leaks after running through the 'hot' areas. The immense amount (110,000 metric tons) of contaminated water is a huge problem. Each hour additional 25 tons of water are added. Some water decontamination equipment was set up over the last weeks but it has yet to work properly:
Operators of Japan's Fukushima nuclear plant have suspended an operation to clean contaminated water hours after it began due to a rapid rise in radiation.
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The teams at the plant suspect the radiation rise may be linked to sludge flowing into the machinery intended to absorb caesium or the pipes surrounding it.
All three reactors are still too hot to get significant work done inside of them. The plans to somehow stop the leaks and to implement closed cooling cycles will likely be delayed and and then take longer than anticipated.
There is some weird behavior visible in the radiation level measurement in reactor 1. Every three to four days it jumps between some 50 Sievert and 250 Sievert. As the temperature measurements show no change I have no explanation for this weird behavior.
Reactor 3 has also shown some life over the last weeks with the temperature increasing from 100 Centigrade to nearly 200 Centigrade without obvious changes in the cooling situation. The temperature is now slowly coming down again. I have found no explanation for this phenomenon.
Work to implement a closed loop cooling at the no 4 spent fuel pool is delayed as a site survey found the pipes needed to get it installed got ripped off the walls when the no 4 building exploded.
The three reactor and the four spent fuel pools continue to release radioactive substances into the environment. Japan will need a long time to overcome this catastrophe.
People in the U.S. seem concerned about the Missouri flood which threatens the Missouri, at the Fort Calhoun Nuclear Power Station near Blair, Nebraska. The reactor is cooled down but the spent fuel is quite full and a long, three to four days, station blackout event with no electricity available at the site could lead to problems. But unless there is a breach of one of the upper river dams I see no danger of that occurring.
Additional resources:
AllThingsNuclear Union of Concerned Scientists
Bulletin of the Atomic Scientists
Atomic power review blog
Digital Globe Sat Pictures
IAEA Newscenter
NISA Japanese Nuclear Regulator
Japan Atomic Industry Forum (regular updates)
Japanese government press releases in English
Kyodo News Agency
Asahi Shimbun leading Japanese newspaper in English
NHK World TV via Ustream
Status reports for the German Federal Government by the Gesellschaft für Reaktorsicherheit in German language