At 8 p.m. EDT March 15, a dose rate of 1,190 millirem per hour was observed. Six hours later, the dose rate was 60 millirem per hour, IAEA said.
About 150 residents near the Fukushima Daiichi site have been checked for radiation and 23 have been decontaminated.
Japanese authorities have distributed potassium iodide tablets to evacuation center (see this page for more information on potassium iodide). If taken within several hours of ingesting radioactive iodine, potassium iodide can protect the thyroid gland.
UPDATE AS OF 9:15 A.M. EDT, TUESDAY, MARCH 15:
Fukushima DaiichiUnits 1 and 3 at Fukushima Daiichi are stable and cooling is being maintained through seawater injection. Primary containment integrity has been maintained on both reactors.
The Japan Atomic Energy Agency (JAEA) reported an explosion in the suppression pool at Fukushima Daiichi Unit 2, at 7:14 p.m. EDT on March 14. Reactor water level was reported to be at 2.7 meters below the top of the fuel. The pressure in the suppression pool decreased from 3 atmospheres to 1 atmosphere. Radiation readings at the site increased to 96 millirem per hour.
Dose rates at Fukushima Daiichi as reported at 10:22 p.m. EDT on March 14 were:
- Near Unit 3 reactor building 40 rem/hr
- Near Unit 4 reactor building 10 rem/hr
- At site boundary 821 millirem/hr.
- Kitaibaraki (200 km south of site) 0.4 millirem/hr.
We are working on getting updated information on radiation and dose rates at and near the plant.
Station personnel not directly supporting reactor recovery efforts have been evacuated, leaving approximately 50 staff members at the site. Operators are no longer in the main control room due to high radiation levels.
Safety relief valves were able to be re-opened and seawater injection into the reactor core was restarted around 1 a.m. EDT on March 15 and is continuing.
At Unit 4 on March 14 at approximately 8:38 p.m. EDT, a fire was reported in the reactor building. It is believed to have been from a lube oil leak in a system that drives recirculation water pumps. Fire fighting efforts extinguished the fire. The roof of the reactor building was damaged.
Fukushima DainiAll four reactors at Fukushima Daini are being maintained with normal cooling using residual heat removal systems.
UPDATE AS OF 10:25 P.M. EDT, MONDAY, MARCH 14:Yukio Edano, Japan’s Chief Cabinet Secretary, during a live press conference at 10 p.m. EDT, said there is a fire at Fukushima Daiichi 4 that is accompanied by high levels of radiation between Units 3 and 4 at the site. The fire began burning at Unit 4 at around 6 a.m. Japan time on March 14 and is still burning. Fire fighters are responding to the fire. The reactor does not have fuel in the reactor, but there is spent fuel in the reactor (pool) and Edano said that he assumes radioactive substances are being released. “The substances are coming out from the No. 4 reactor and we are making the utmost effort to put out the first and also cool down the No. 4 reactor (pool).”
Edano said that a blast was heard this morning at Unit 2 at about 6:30 a.m. A hole was observed in the number 2 reactor and he said there is very little possibility that an explosion will occur at Unit 2.
“The part of the suppression chamber seems to have caused the blast,” Edano said. A small amount of radioactive substance seems to have been released to the outside.
TEPCO workers continue to pump sea water at 1, 2 and 3 reactors. “The biggest problem is how to maintain the cooling and how to contain the fire at No. 4.” At 10:22 a.m. Japan time, the radiation level between units 2 and 3 were as high as 40 rem per hour. “We are talking about levels that can impact human health.” Edano said.
Of the 800 staff that remained at the power plant, all but 50 who are directly involved in pumping water into the reactor have been evacuated.
UPDATE AS OF 9:40 P.M. EDT, MONDAY, MARCH 14: An explosion in the vicinity of the suppression pool at Fukushima Daiichi 2 just after 6:20 a.m. Japan Standard Time (5:20 p.m. EDT) may have damaged a portion of the reactor’s primary containment structure.
Pressure in the suppression pool has been reported to have decreased to ambient atmospheric pressure shortly after the blast. Plant operator Tokyo Electric Power Co. (TEPCO) has reported possible damage to the reactor’s pressure-suppression system. Radiation levels at local monitoring stations have risen but are still in flux. TEPCO has evacuated some workers from all three Fukushima reactors with the exception of approximately 50 workers involved in sea water pumping activities into the reactors as part of emergency cooling efforts.
Residents within a 20-kilometer (12.5 mile) zone around the plant were ordered to evacuate on Saturday following a hydrogen explosion at Unit 1. Another hydrogen explosion occurred this morning (U.S. time) at Unit 3.
Efforts to inject sea water into Unit 2 have been complicated by a faulty pressure relief valve. The fuel at Unit 2 has been exposed at least twice, before being re-covered with sea water.
Japan's Chief Cabinet Secretary, Yukio Edano, has said a partial defect has been found inside the containment vessel of reactor 2 at the Fukushima Daiichi nuclear power plant.
UPDATE AS OF 5:30 P.M. EDT, MONDAY, MARCH 14: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 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.
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 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.
Administration, NRC Response to the Accident
At a White House briefing, press secretary Jay Carney said that information is still coming in on the status of nuclear plants in Japan, but that the Obama administration is committed to keeping nuclear energy as part of the U.S. energy portfolio.
Energy Department Deputy Secretary Daniel Poneman said nuclear energy “continues to play an important role in providing a low-carbon future.”
Gregory Jaczko, chairman of the Nuclear Regulatory Commission, said at the briefing that analysis of the damage, the type of reactor and the distances involved indicate a “very low likelihood” that any potential fallout from Japan might reach Hawaii or Western states.
U.S. nuclear power plants are built to endure the strain of natural phenomena like hurricanes, earthquakes and tornadoes, Jaczko said. “Right now, we continue to believe that nuclear power plants in this country operate safely and securely,” he said.
UPDATE AS OF 4:20 P.M. EDT, MONDAY, MARCH 14:
NEI has posted a new document, "Radiation in Perspective," which describes where radiation comes from and how it is measured.
My comments:
As for the dose rates listed in the above article. 40 rem/hr is a lot and any unshielded extended exposure could cause severe sickness and or death
As for the 821mrem/hour...........at 1000ft from there the dose rate would be less than 1 mrem/hr which is insignificant and poses no threat to the public. Granted number one priority at any nuclear site is to prevent the public from any exposure no matter how small.
Now these numbers are radiation exposure dose rates..........the real concern would be contamination which is different. Contamination is little particals that are radioactive that could be ingested or inhaled and therefore give you exposure internally until they are removed via the normal methods you get anything out of your body......sweat or other biological functions in the bathroom...
The fuel that has been and may still be uncovered was spent fuel in a spent fuel pool. This fuel is still generating heat but at a significantly slower rate than fuel that has recently been irradiated. If you will note they said the dose rates near the uncovered fuel were less than 100 mrem/hr.....If they continue to put water in the reactors eventually the dose rates will drop. Hopefully before fuel begins to leave the containment.
This event is definitely bad but it could have been so much worse.....One thing to remember is that this was not a failure of the personnel at the plant but a natural disaster.
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