Two units of Fukushima Daiini have now achieved cold shutdown with full cooling capabilities. They are currently working on the third. This is the equivalent to the train coming to a stop from full speed. Kudos to TEPCO, not that it would or should be any another way and may the rest of the units follow soon.
A new update from NEI (I am supplementing in italics):
Tokyo Electric Power Co. reported at 3:00 p.m. EDT that work had resumed to pump seawater into Fukushima Daiichi 2 to maintain safe cooling water levels after the utility was able to vent steam from the pressure vessel. The fuel had been exposed for 140 minutes Monday night due to a malfunctioning pressure relief valve. Water levels later went up to cover more than half of the rods. (The extent of fuel damage (total speculation on my part) will likely not be known until later when the plant is decommissioned.)
The U.S. Nuclear Regulatory Commission reports that the Japanese government has formally asked for assistance from the United States on nuclear power plant cooling issues triggered by the March 11 tsunami.
The agency has already sent two experts on boiling water reactor issues to Japan as part of a U.S. Agency for International Development disaster relief team. The experts now are in Tokyo providing technical assistance. The U.S. NRC is also monitoring the Japanese reactor events around the clock from its headquarters operations center in Rockville, Md.
Prior to the second exposure of the rods around 11 p.m., March 14 local time in Japan, radiation at the plant site was detected at a level twice the maximum seen so far – 313 millirem per hour, according to TEPCO. (This is the highest yet and too high to work in for long. Levels beyond the site periphery are still low.)
Chief Cabinet Secretary Yukio Edano said he believes the problem at the plant ''will not develop into a situation similar to Chernobyl,” even in the worst case. (The problem is is that no layperson understands what happened at Chernobyl and Three Mile Island. The majority believe that meltdown = death and cancer for all which is a poor misnomer. Much of the misinformation has to do with media hype and movies. Perhaps I'll dig up some old notes and see if I can find anything of use from those accidents.)
The utility said a hydrogen explosion at the nearby No. 3 reactor that occurred Monday morning may have caused a glitch in the cooling system of the No. 2 reactor.
The hydrogen explosion at reactor 3 on March 14 injured 11 people: seven TEPCO workers at the site and four members of the country’s Self-Defense Forces. The reactor's containment vessel was not damaged and the reactor remains safely contained in its primary containment.