(Ed. note: The information provided below is based on a variety of sources, but I cannot verify its accuracy. It is likely that much of the information currently in play will change or be subject to revision in the coming hours and days.)
UPDATE: March 15, 2011.
@0:44UTC Japan’s Nuclear and Industrial Safety Agency says an explosion was heard early Tuesday morning at the No.2 reactor of the disaster-hit Fukushima No.1 nuclear power plant. Agency officials told reporters that the blast was heard at 6:10 AM local time on Tuesday. Chief Cabinet Secretary Yukio Edano earlier told a news conference that a reactor facility, called the suppression pool, has been damaged. But agency officials said they have no detailed information yet about the report. They said that depending on where the damage is done, either liquid or air could leak out of the suppression pool. The suppression pool is linked to the reactor containment vessel and is designed to prevent radioactive material from leaking outside. Experts say a breach to this crucial facility has raised the possibility of a radioactive leak. The Nuclear and Industrial Safety Agency also said that nuclear fuel rods inside the No.2 reactor are exposed above water by about 2.7 meters. That’s about half the length of the fuel rods. Agency officials said that radiation levels around the nuclear power plant reached 965.5 microsieverts following the explosive sound. They say the figure later dropped slightly to 882 microsieverts. The officials said they believe the rise in radiation level is due to the breach in the suppression pool, but that they cannot say for sure. They said they are monitoring the situation closely. The officials added that the monitored level of radiation would not immediately pose a health threat. Tokyo Electric Power Company that operates the power station briefly evacuated workers from the facility following the sound of the blast.
Earlier: Fuel rods at the Number Two reactor at a power plant in quake-hit Fukushima Prefecture remain exposed. Earlier, the Tokyo Electric Power Company said the valve to vent steam and reduce pressure inside the reactor closed at 11 PM on Monday. It said the increased pressure at the reactor made it impossible to pump water in. The water level dropped sharply, possibly fully exposing the fuel rods. The company managed to open the valve to reduce pressure and let seawater into the reactor at around 1 AM on Tuesday. But as of 3 AM, the water level remains low and the fuel rods remain exposed. The company says there has been no pressure increase inside the reactor, and no major change in radioactivity levels on the edge of the plant’s compound. A company official says there is no imminent danger. A similar problem hit the reactor earlier on Monday, but the company managed to reactivate the pump, bringing the water level to the middle of the fuel rods. The company is battling to raise the water level, as the protracted exposure of the fuel rods could cause them to melt.
The Tokyo Electric Power Company says there is a possibility of fuel rods melting in the Number Two reactor at its Fukushima Number One plant. A company official said at a news conference on Tuesday that the level of cooling water is now too low to measure. He indicated that the fuel rods may have overheated and begun melting.
Tokyo Electric Power Company says radiation levels reached 8,217 microsieverts per hour near the front gate of the Fukushima No.1 nuclear power station at 8:31 AM Tuesday. Anyone in this kind of environment would be exposed to more than 3 years’ worth of naturally occurring radiation within a single hour.
The United States has revealed that Japan asked for their assistance in cooling reactors at the nuclear power plant that were damaged by Friday’s earthquake. Chairman of the US Nuclear Regulatory Commission, Gregory Jaczko and Deputy Secretary of the Department of Energy Daniel Poneman spoke at a news conference at the White House on Monday.
Jaczko said the agency has sent 2 experts to Japan and is watching the situation closely. He said they were officially requested by the Japanese government for technical assistance to bring down temperatures in the reactors. He said they will assist with the request as much as possible. Poneman said the US has prepared for all possible scenarios in its nuclear program, based on its experience at the Three Mile Island accident in 1979. He said the US government will continue to gather information to promote its nuclear program, indicating there will no dramatic changes in policy.
UPDATE: March 14, 2011.
@8:53UTC The Nuclear and Industrial Safety Agency says a reactor at a power plant in quake-hit Fukushima Prefecture has lost all its cooling capability. The agency said on Monday that Tokyo Electric Power Company notified the agency of an emergency at the Number Two reactor at its Fukushima Number One power station. This is the second emergency notice for the reactor. The utility firm told the agency shortly after the quake on Friday that the reactor’s emergency cooling power system had failed. Since then, the company tried to cool the reactor by circulating water by steam power, instead of electricity. But an attempt to lower the temperature inside the vessel that houses the reactor did not work well.
Fears of a hydrogen explosion at the vessel housing building are growing as the water level of the reactor is falling. A reaction with the steam and exposed fuel rods generates a large amount of hydrogen. Hydrogen blasts have occurred at two other reactors at the plant. The government’s top spokesperson Yukio Edano said the power company is preparing to pour seawater into the container.
What appears to be another hydrogen blast has occurred at a nuclear power plant in Fukushima. No damage to the reactor chamber has been reported, but 11 people have been injured. The Nuclear and Industrial Safety Agency says what it believes was a hydrogen blast occurred at 11:01 AM on Monday at the No.3 reactor of Tokyo Electric Power Company’s Fukushima No.1 nuclear power plant. The agency says it has so far observed no abnormal rise in radiation around the compound of the plant. The company says the blast injured 11 people, including 4 of its employees and 4 Self-Defense Force members. The Nuclear and Industrial Safety Agency has advised anyone remaining within 20 kilometers of the power plant to take shelter inside buildings as soon as possible. About 500 people are thought to be still in the area. A similar hydrogen blast occurred at the No.1 reactor at the same plant on Saturday. Chief Cabinet Secretary Yukio Edano told reporters that he has received a report that the latest blast has left the container of No.3 reactor intact. He said the likelihood of large volumes of radioactive materials being dispersed in the air is low.
Video footage shows that the top of the building housing the reactor has been blown off, as in Saturday’s blast. Fears of an explosion grew when the water level of the No. 3 reactor dropped, exposing fuel rods, and a reaction with the steam generated a large amount of hydrogen. The Nuclear and Industrial Safety Agency says that even if the top of the building has blown off, the reactor chamber will not be affected.
UPDATE: March 13, 2011.
Japan’s Meteorological Agency says the magnitude of Friday’s earthquake that hit the Pacific coast of northeastern Japan was 9.0 instead of 8.8 as earlier announced. The agency made the correction on Sunday morning after analyzing seismic waves and other data. The magnitude is equivalent to that of the 2004 earthquake off Sumatra, Indonesia, which triggered massive tsunamis in the Indian Ocean. The agency says the focal zone of Friday’s quake was about 500 kilometers long and 200 kilometers wide. Destructive movement along the fault continued for more than 5 minutes. The Meteorological Agency says only 4 other quakes in the world have recorded magnitudes of 9 or over. The largest was the magnitude 9.5 quake that hit the Chilean coast in 1960, killing more than 1,600. The quake also triggered tsunamis in Japan, leaving 142 people dead. The 2004 quake off Sumatra registered a magnitude of 9.1. Subsequent giant tsunamis killed more than 200,000 people.
Chief Cabinet Secretary Yukio Edano says that a hydrogen explosion may occur at the No.3 reactor building of No.1 power plant in Fukushima prefecture. But he emphasized that an explosion should not cause health problems for evacuated residents. He said at a news conference on Sunday afternoon that a large amount of hydrogen may have accumulated in the top portion of the No.3 reactor building because cooling of the reactor was insufficient at one point. Edano said a valve was opened to ease pressure in the reactor and fresh water was injected to cool it down. He said because of trouble with the pump, seawater was pumped in instead, but the flow became unstable, causing the water level to drop dramatically. He said although the water began to rise again, a large amount of hydrogen may have been generated inside the reactor building while cooling was insufficient. Edano said that a similar explosion as the one which occurred at the No.1 reactor building on Saturday may take place. He emphasized that even if an explosion occurs, the impact should not affect the pressure vessel and containment vessel.
Fukushima prefectural government says on Sunday 70,000 to 80,000 people living near the Fukushima No.1 and No.2 Nuclear Plants are subject to an evacuation advisory. They live in 10 cities and towns near the nuclear plants including Minamisouma-city, Tamura-city, and 8 towns. About 62,000 people are confirmed to have already evacuated.
About 380,000 people have evacuated their homes in northeastern Japan after a major earthquake shook the region on Friday. NHK’s survey has found that 377,576 people were taking refuge at 2,047 evacuation centers in 6 Tohoku prefectures as of 11 AM on Sunday. The actual number of evacuees may be bigger. Municipalities in devastated areas are facing difficulties confirming the numbers. Temperatures dropped sharply during the night and the early morning in the quake-hit areas. Some evacuation centers are having difficulties keeping people warm due to heating fuel shortages.
UPDATE: March 12, 2011.
@22:56 UTC, The Japanese government rates the accident at the Fukushima Number One nuclear power plant at level 4 on an international scale of 0 to 7. Two radioactive substances, cesium and radioactive iodine, were detected near the Number One reactor at the plant on Saturday. Their presence indicates nuclear fission of uranium. The Nuclear and Industrial Safety Agency said that fuel in the reactor partially melted. It’s the first such accident in Japan. A level 4 on the International Nuclear and Radiologocal Event Scale includes damage to fuel and release of significant quantities of radioactive material within an installation. It’s the same level as a criticality accident at a nuclear fuel processing plant in Tokai Village in Ibaraki Prefecture, south of Fukushima, in 1999. (from NHK/World/)
@4:17EST, Reuters is reporting that the emergency cooling system has failed at reactor no.3, creating the same situation as had occured at no. 1. Japan is apparently experiencing critical issues at three of its nuclear reactor facilities, due to failure to cool the cores down as a result of damage from the 8.9 magnitude earthquake, subsequent strong aftershocks, and tsunami. It is reported from Twitter commenter Richard Parry that there has been an explosion (confimed) at the Fukushima nuclear plant No.1, with partial core meltdown (unconfirmed). Reuters reports that the roof blew off in the explosion but that containment facilities were not affected and any radiation leaks were low.
According to World Nuclear News 3 of 6 reactors at Fukushima Daiichi were operating when the earthquake hit. They apparently immediately went into emergency shutdown and began the cooling process, but the cooling pumps quit about an hour into the process, blamed on tsunami flooding. In order to contain building pressures in the vessels, the plant has been making low level releases of air and water vapour on no.1 and was preparing to do so on nos.2 and 3. Status updates of the situation are also being published on Nuclear Power Industry News, and by the Nuclear Energy Institute. The Fukushima plants are operated by TEPCO, Tokyo Electric, and their press releases are available.
NHK World is reporting that the Japanese government has just expanded the evacuation zone around Fukushima No.1 to a 20km radius and is maintaining a 10 km evacuation radius around Fukushima no.2. The No.2 plant is approximately 10 km south of the no.1 plant. Contrary to reports made earlier of a low radiation leak, the expanded evacuation zone suggests a higher risk level, and NHK is quoting confirmation of that from Fukushima Prefecture.
The LA Times is reporting that a failed cooling system has compromised three reactors at Fukushima #2 nuclear power plant. (Ed note: see the first comment below for an insider perspective on this situation).
The Japanese Prime Minister is publicly stating that the nuclear facilities were inadequate to sustain the hit of such a powerful earthquake, and the ECCS cooling system was unable to control the reactor heat. Seawater has been pumped into the facility to attempt to cool the core. Levels of radioactive cesium and iodine, products of the fission process, have apparently been found outside the facility.
March 10, 2011: An 8.9 magnitude earthquake has struck Japan today. The epicenter, located just off Japan’s Pacific coast near Sendhai, has triggered a 4 meter high tsunami which is devastating a large area of the adjacent coastline. Tsunami warnings are currently up for the entire North American west coast. A 4.5 magnitude earthquake has just been reported in Hawaii, although officials there don’t know if its associated with the Sendhai quake. Check in from time to time with the NOAA Pacific Tsunami Centre and the Pacific Disaster Center for recent alerts. NHK, the national broadcaster in Japan, is providing updating and contact information in English on NHK World. Please use the link sparingly so that people with a bona-fide need can access the link.
The Boston Globe has a good array of photos at their Big Picture blog series.
Magnitude 8.9 Earthquake - Japan
Technical discussions of this earthquake are available from the US Geological Survey, here.