Reactor Engineers Struggle To Maintain Progress
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The Science Of Japan's Nuclear Crisis
An exploration of the science and health questions raised by the situation in Japan
The U.S. Nuclear Regulatory Commission says American nuclear plants need to be better prepared for the sudden and continued loss of electric power. Above, the Limerick Generating Station, a nuclear power plant in Pottstown, Pa.
Commission: U.S. Must Make Nuclear Plants Safer
()In the aftermath of the disaster at the Fukushima Dai-ichi nuclear power plant, the U.S. Nuclear Regulatory Commission says American nuclear reactors need new safeguards to ensure that the kind of accident that damaged the Japanese reactors doesn't happen in the U.S.
April 11, 2011
Day 32
Japan's nuclear regulators raised the severity level of the crisis at a stricken nuclear plant Tuesday to rank it on par with the 1986 Chernobyl disaster, citing the amount of radiation released in the accident. The regulators said the rating was being raised from 5 to 7 - the highest level on an international scale overseen by the International Atomic Energy Agency. However, there was no sign of any significant change at the tsunami-stricken Fukushima Dai-ichi nuclear plant.
April 9, 2011
Day 30
Japan's government has announced it will "ban farmers from planting rice in soil contaminated by radiation from the tsunami-flooded nuclear power plant, adding another food central to Japanese culture to the list of items raising concerns. The ban will apply to any soil found to contain high levels of radioactive cesium, and farmers who cannot grow rice will be compensated.
April 8, 2011
Day 29
The 7.1-magnitude aftershock on April 7 caused blackouts in nearly one million homes in northeast Japan. Officials reported that two people were killed.
April 7, 2011
Day 28
A magnitude 7.1 earthquake hit off the northeast coast of Japan, near the city of Honshu. TEPCO officials say there is no additional damage to the plant at the time and all workers have been accounted for.
April 6, 2011
Day 27
Using liquid glass, workders have stopped at least one route that contaminated water was taking from the nuclear power plant to the sea. Meanwhile, TEPCO continues to intentionally discharge mildly radioactive water from storage tanks into the ocean to make space for more highly contaminated water. Workers are also pumping nitrogen gas into a reactor vessel, which should help to prevent an explosion that could be caused by hydrogen gas that's building up there.
April 5, 2011
Day 26
The Japanese government set its first radiation safety standards for fish today after thed istressed nuclear power plant reported radioactive contamination in nearby seawater measuring at several million times the legal limit. The Tokyo Electric Power Co., which operates the plant, insisted that the radiation will rapidly disperse and that it poses no immediate danger.
April 4, 2011
Day 25
TEPCO plans to release 10,000 tons of radioactive water into the ocean in a move to clear space in a waste storage building for water that is even more highly contaminated than the dumped water. Chief Cabinet Secretary Yukio Edano called it an "unavoidable" step. Officials say the water must be disposed of before the normal cooling systems can be brought back on line, and intentionally draining some of it into the ocean is the best option.
April 3, 2011
Day 24
A Japanese safety agency spokesman said it could take several more months for engineers to get the tsunami-ravaged plant under control. Bringing the reactors at the plant under control will require permanently restoring cooling systems that prevent reactors from dangerously overheating.
April 2, 2011
Day 23
Highly radioactive water was leaking into the sea from a crack discovered in a maintenance pit at the facility. Water flowing into the ocean from the 8-inch crack was expected to dissipate quickly and not cause any health hazard, officials said. Soon after discovering the crack TEPCO officials bean trying to fill the pit with cement.
April 1, 2011
Day 22
Japan's Nuclear and Industrial Safety agency ordered the Tokyo Electric Power Co. to review its latest radiation measurements taken in air, seawater and groundwater samples around the disabled Fukushima Dai-ichi plant, saying they seemed suspiciously high. TEPCO says it may have misstated radiation levels in water near the plant, officials said Friday.
March 31, 2011
Day 21
Radiation levels continue to rise in the ocean, offshore from the nuclear power plant. Officials are also evaluating whether to expand the mandatory evacuation area after the report of high levels of radiation in the village of Iitate, 25 miles from the plant. Workers also continue to struggle with pooling radioactive water; they must keep pumping water to cool the reactors, but storage of contaminated water is becoming problematic.
March 30, 2011
Day 20
Japanese officials say seawater outside of the Fukushima Dai-ichi nuclear power plant contains more than 3,300 times the normal amount of radioactive iodine. The country's nuclear safety agency says it's a "concern" — but not necessarily an immediate threat. Workers at the plant are continuing to battle large amounts of radioactive water that has flooded parts of the facility; tanks to store contaminated water are beginning to fill up.
March 29, 2011
Day 19
Highly toxic plutonium has been detected in the soil outside the nuclear power plant. Safety officials say the amounts are low and do not pose a risk to humans, but the finding supports suspicions that radioactive water is leaking from damaged nuclear fuel rods inside the plant.
March 28, 2011
Day 18
Plant officials report that highly radioactive water has filled a series of underground tunnels at the damaged power plant, raising concerns that the contaminated water could start spilling out into the ocean. Experts say that the water is a result of frantic efforts to cool overheated reactors and spent fuel pools.
March 27, 2011
Day 17
Workers flee the Unit 2 reactor after TEPCO officials erroneously report a reading of radiation levels nearly 10 million times above normal. "The number is not credible," Tokyo Electric Power Co. spokesman Takashi Kurita later said. "We are very sorry." Officials acknowledge the presence of radioactive water in each of the four most troubled reactors.
March 26, 2011
Day 16
The U.S. Navy rushes to deliver fresh water to replace the corrosive salt water being used to cool the plant's nuclear reactors, as the Japanese government urges TEPCO to be more transparent in sharing information with the public. Radiation has been making its way into milk, seawater and 11 kinds of vegetables, including broccoli, cauliflower and turnips.
March 25, 2011
Day 15
The power plant operators say it's likely that radiation detected in water pooling in the basement of one reactor building came from the reactor's main vessel. This raises concerns that the reactor core may have been breached, but there have been conflicting accounts of this. Separately, the Japanese Nuclear Safety Commission widens a voluntary evacuation area around the plant to a radius of 18 miles.
March 24, 2011
Day 14
Two plant workers are hospitalized with injuries to their feet after coming in contact with radioactive water while laying electrical cables in the basement of a turbine building next to reactor No. 3. The two men were subcontractors for TEPCO. Food safety concerns linger in Japan, as residents begin stockpiling clean water with the news that radiation in tap water was above recommended levels for infants.
March 23, 2011
Day 13
Smoke is seen again at Unit 3. Tokyo water officials say they've found elevated radiation levels in the city's water supply. Testing found the amount of radioactive iodine was at twice the recommended limit for infants.
March 22, 2011
Day 12
Smoke is seen at Unit 3 and Unit 2. All six reactor units are connected to the power grid. Radioactive materials are detected in seawater near the plant.
March 21, 2011
Day 11
Smoke is emitted from Units 2 and 3. U.S. Nuclear Regulatory Commissioner says that the situation at the plant appears "to be on the verge of stabilizing."
March 20, 2011
Day 10
Seawater is injected into spent fuel pool at Unit 2. Reactors at Units 5 and 6 go into cold shutdown. Radiation levels higher than the legal limit are detected in spinach in several prefectures near the plant.
March 19, 2011
Day 9
Water spraying resumes at Unit 3. Elevated radiation levels are detected in milk and spinach from areas around power plant. Emergency power is restored to the cooling systems for the spent fuel ponds in Units 5 and 6.
March 18, 2011
Day 8
Unit 2 is connected to a power line. Water spraying continues. The International Atomic Energy Agency raises the International Nuclear and Radiological Event Scale rating from 4 to 5.
Related: Early Radiation Data From Near Plant Ease Health Fears
March 17, 2011
Day 7
Water levels at Unit 4's spent fuel pool run low and radiation levels at the plant are high. Workers attempt to spray the spent fuel pool at Unit 3 with helicopters, fire trucks and water cannons. Little water reaches the pool. The Tokyo Electric Power Corp. reports that 23 of its workers sustained injuries and 18 were contaminated with radiation from the events at the plant following the tsunami.
March 16, 2011
Day 6
Another fire at Unit 4 hinders efforts to get the reactors and spent fuel pools under control. Steam and smoke rise from Unit 3, due to evaporation of water in the spent fuel pool. Radiation levels surge. The U.S. government advises its citizens within 50 miles of the plant to evacuate.
March 15, 2011
Day 5
Unit 2 becomes the new focal point as a hydrogen explosion occurs there and its suppression pool is damaged. Explosion and fires also plague Unit 4, and leak radiation into the atmosphere. The government evacuates residents from the 12-mile (20-kilometer) radius around the plant.
March 14, 2011
Day 4
Crisis depeens at Fukushima Dai-ichi. The pressure and heat continue to build in Unit 3, resulting in a hydrogen explosion that destroys the outer containment building. Fuel rods at Unit 2 are fully exposed to air twice, worrying officials. Workers pump seawater into the cores of Units 1, 2 and 3.
March 13, 2011
Day 3
New problems appear at Unit 3, where workers vent steam to try to avoid another hydrogen explosion. Seawater pumped to Units 1 and 3.
March 12, 2011
Day 2
Engineers scramble to prevent a nuclear meltdown. Some of the reactors begin to grow hotter with their cooling systems disabled. A hydrogen explosion rocks Unit 1, causing a radiation leak. Workers furiously pump seawater into the reactor's core.
March 11, 2011
Day 1
A magnitude-9.0 earthquake and tsunami hit Japan's northeastern coast, knocking out power and swamping the backup diesel generators needed to cool the six reactors and spent fuel pools at the Fukushima Dai-ichi nuclear plant.
In Depth: Science
One Year Later, 'Inside Japan's Nuclear Meltdown'
An investigative reporter chronicles the aftermath of the disaster in a new Frontline documentary.
Reports: Why Things Fell Apart At Fukushima Plant
A lack of power, communication and risky conditions made it difficult to prevent the meltdowns.
Fukushima Vs. Chernobyl: Still Not Equal
Though both are level 7 nuclear accidents, the consequences in Japan to date are much less severe.
Cleaning Up Fukushima: A Challenge To The Core
Japan's nuclear crisis was raised to the highest level. Cleanup could take a decade or more.
In Japan, Shaken Soil Turned Soft After Quake
The phenomenon was particularly noticeable in areas built on land reclaimed from the sea.
In Depth: Health
Trauma, Not Radiation, Is Key Concern In Japan
Experts worry far more about the psychological toll from last year's tsunami and nuclear disaster.
One Year Later, 'Inside Japan's Nuclear Meltdown'
An investigative reporter chronicles the aftermath of the disaster in a new Frontline documentary.
Sushi Science: Fear, Not Radiation, Seen As Risk
An expert says the fish and seaweed that ends up on plates is unlikely to be contaminated.
Rapid Response Radiation Team Tends To Wounded
Within hours of the nuclear disaster, a team of radiation experts sprang into action.
Got Radiation? Only Harmless Traces Found In U.S. Milk
A small dose of radioactive iodine in milk from Washington state poses no health risk.
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