Below is a great video explaining what is going on and what the risks are:
Must See: Interview about spent fuel pools with former White House official
No water in spent fuel pool of Unit 4
AP reports that there is no water in spent fuel pool of Japan plant.
NRC: No water in spent fuel pool of Japan plant
Mar 17, 12:42 AM EDT
WASHINGTON (AP) -- The chief of the U.S. Nuclear Regulatory Commission said all the water is gone from one of the spent fuel pools at Japan's most troubled nuclear plant, raising the possibility of widespread nuclear fallout…
"There is no water in the spent fuel pool and we believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures," NRC Chairman Gregory Jaczko said Wednesday at a U.S. House Energy and Commerce subcommittee hearing.
If Jaczko was correct, this would mean there was nothing to stop the fuel rods from heating and ultimately melting down. The outer shell of the rods could also ignite with enough force to propel the radioactive fuel inside over a wide area.
That country's nuclear safety agency and Tokyo Electric Power Co., which operates the six-unit Fukushima Dai-ichi complex, denied Jaczko's statements that the water is gone from the pool.
Utility spokesman Hajime Motojuku said the "condition is stable" at Unit 4, which was shut when the earthquake and tsunami hit last week.
After the hearing, Jaczko left some wiggle room. If he is wrong, it would represent a very embarrassing moment for the U.S. government.
"My understanding is there is no water in the spent fuel pool," he said. "I hope my information is wrong. It's a terrible tragedy for Japan."
Jaczko said the information came from NRC staff and experts in Tokyo who are working with the utility in Japan. He said NRC staffers continue to believe the spent fuel pool is dry. "They believe the information they have is reliable," he said.
Plutonium threat at Fukushima
CNET News reports about plutonium threat at Japan reactor.
March 14, 2011 10:48 AM PDT
Plutonium threat at Japan reactor, expert warns
by Tim Hornyak
At a press conference in Tokyo, Masashi Goto, who worked for Toshiba as a reactor researcher and designer, said the mixed oxide (MOX) fuel used in unit 3 of the Fukushima Daiichi nuclear plant contains plutonium, which is much more toxic than the fuel used in the other reactors.
Goto added that the MOX also has a lower melting point than the other fuels. The Fukushima facility began using MOX fuel last September, becoming the third plant in Japan to do so.
Japan decides radiation isn't that deadly
Zerohedge reports that Japan increases maximum "safe" radiation dose allowed to near-Chernobyl levels.
When All Else Fails, Change The Rules: Japan Increases Maximum "Safe" Radiation Dose Allowed For Nuclear Workers By 150% To Near-Chernobyl Levels
Submitted by Tyler Durden on 03/16/2011 10:42 -0400
… In order to deal with a new baseline level of radiation across Fukushima (which Japan still refuses to discloses to the world because it is "Under Survey"), the Japanese ministry of health labor has decided to take the unilateral act of scrapping years of safety data, and MORE THAN DOUBLED the maximum allowable exposure for nuclear workers from 100 millisieverts to 250 millisieverts. At least we now know that the radiation level around Fukushima is most likely bounded by this range. As to the reason for the increase, the ministry said it is "unavoidable due to the circumstances." In other words, when self-administered Seppuku will not work, just apply it to someone else.
Indicatively, here is how "safe" 250 millisieverts are:
About efforts to "restore power" to Fukushima
From Nikkei: Tepco To Build New Power Source To Aid In Cooling
Tokyo Electric Power Co. (9501) will on Thursday start work to build makeshift electric power sources within the Fukushima Daiichi nuclear power plant, a move intended to inject water more efficiently into the plant's crippled reactors, the company said at a dawn news conference.
Construction will start as soon as Thursday morning [it hasn't begun yet!], an official said, but it will be unclear how long the work will take to complete until it begins [sounds like this might not be done in time to make any difference…]. The work will be carried out at the same time as cooling efforts under way by police water cannon trucks.
Less than 48 hours to get things undercontrol…
U.S. Officials Alarmed By Japanese Handling of Nuclear Crisis, ABC News, March 16, 2011:
U.S. officials are alarmed at how the Japanese are handling the escalating nuclear reactor crisis and fear that if they do not get control of the plants within the next 24 to 48 hours they could have a situation that will be "deadly for decades."
"It would be hard to describe how alarming this is right now," one U.S. official told ABC News. …
"Urgent efforts are needed on the part of the Japanese to restore emergency operations to cool" down the reactors' rods before they trigger a meltdown. …
"They need to stop pulling out people—and step up with getting them back in the reactor to cool it. THERE IS A RECOGNITION THIS IS A SUICIDE MISSION," the official said. …
My reaction: The big developments:
1) There is no water in spent fuel pool of Unit 4. This is very, very bad.
2) Fukushima just started using a much more dangerous fuel (containing plutonium) last September. How nice.
3) Japan has increased the maximum "safe" radiation dose to near-Chernobyl levels.
4) Working at Fukushima is recognized as a suicide mission.
5) Construction on a makeshift electric power source will start as soon as Thursday (it hasn't begun yet!). How long the work will take (hours, days?) is unknown.
6) If they do not get control of the plants within the next 24 to 48 hours, no one is going to be living near Fukushima for a long while…