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Fukushima review: a complex disaster and disastrous response

March 4, 2012 at 9:13 am By Roz Potter

From the Bulletin of the Atomic Scientists:  Link

Conclusion of the report:

At Fukushima Daiichi, the problems were not with the law or the manual, but with the humans who formulated  the anticipated risks that fell in line with corporate and political will but did not represent the actual risks  the nuclear plant faced and posed.

Other excerpts:

It is clear from our investigation of the Fukushima Daiichi accident that, even in the technologically advanced country of Japan, the government and the plant operator, Tokyo Electric Power Company (Tepco), were astonishingly unprepared, at almost all levels, for the complex nuclear disaster that started with an earthquake and a tsunami. And this grave oversight will affect the Japanese people for decades.

***

The Fukushima crisis revealed the dangers of building multiple nuclear reactor units close to one another. This  proximity triggered the parallel, chain-reaction accidents that led to hydrogen explosions blowing the roofs off of  reactor buildings and water draining from open-air spent fuel pools, a situation that was potentially more  dangerous than the loss of reactor cooling itself.

***

The nuclear accident was itself a compound disaster, with meltdowns of reactor cores at Units 1, 2, and 3 and  problems with the cooling of spent fuel pools at Units 1 through 4 of the six-unit plant. A hydrogen explosion at  Unit 1 on the second day of the crisis exposed a spent-fuel pool to the open air, released radioactive material into  the environment, and deteriorated the situation at the plant, causing delays in cooling Unit 3.

An ensuing  hydrogen explosion at Unit 3 then damaged seawater injection lines and vent lines for Unit 2, producing delays in  cooling there. In other words, an accident at one unit inevitably hampered responses to the situation at another, leading to parallel chain reactions of accidents and radiation releases.

***

As the crisis deepened, Prime Naoto Kan secretly instructed Shunsuke Kondo, chairman of the Japan Energy Commission (AEC), to draw up a worst-case scenario for the nuclear accident.

***

If the sixth stage of the scenario is reached, the contingency document says, all residents living within 170 kilometers or more of the Fukushima plant might need to be relocated, and relocation might need to be advised for those living within 250 kilometers, since their annual exposure to radiation would be much higher than normal atmospheric levels.

If such a worst-case scenario becomes a reality, the document suggests, evacuation of the 30 million residents in the Tokyo metropolitan area become necessary, depending upon wind direction.

***

Many human errors were made at Fukushima, a point elaborated on in great detail in the interim report of the Japanese government’s Investigation Committee on the Accident at the Fukushima Nuclear Power Stations, and   our investigative commission has incorporated some of these findings in its report as well.

But the role of human error in the Fukushima nuclear accident was not limited to the misjudgment of any one worker, like the  one who misjudged the backup cooling situation at Unit 1. The technical chief, the plant director, and the nuclear energy section of Tepco’s headquarters all failed to ascertain the true operational situation of the IC system at Unit 1.

***

When on-site workers referred to the severe accident manual, the answers they were looking for simply were not  there. And those who misjudged the condition of the emergency cooling system had never actually put the  system into service; they were thrown into the middle of a crisis without the benefit of training or instructions.

To read more,  Link

Fukushima reactor temperature reading as high as 102C raises concerns

February 12, 2012 at 11:14 pm By Roz Potter

From UK’s the Guardian,   Link

Excerpts:

Concern is growing that the Fukushima Daiichi nuclear plant in Japan is no longer stable after temperature readings suggested one of its damaged reactors was reheating.

The plant’s operator, Tokyo Electric Power (Tepco), said the temperature inside No 2 reactor – one of three that suffered meltdown after last year’s earthquake and tsunami – may have reached 82C on Sunday.

***

Given that Tepco assumes a margin of error of 20C, the actual temperature could have risen to 102C.

***

Confirmation that the temperature has risen above 80C could force the government to reverse its declaration two months ago that the crippled plant was in a safe state known as cold shutdown.

Cold shutdown is achieved when the temperature inside the reactors remains below 100C and there is a significant reduction in radiation leaks.

Plant workers are unable to take accurate readings of the temperature inside the damaged reactor because radiation levels are still too high for them to enter and examine the state of the melted fuel, which is thought to be resting at the bottom of the reactor’s pressure vessel.

***

Tepco said it did not know the cause of the apparent temperature rise, but speculated that it might be due to problems with the supply of coolant or a faulty thermometer.

“We believe the state of cold shutdown is being maintained,” said Junichi Matsumoto, a company spokesman. “Rather than the actual temperature rising, we believe there is high possibility that the thermometer concerned is displaying erroneous data.”

Tepco was forced to inject additional cooling water into the same reactor last week after the temperature started rising at the beginning of the month.

Eye-opening Frontline documentary on Fukushima, nuclear power and energy

January 18, 2012 at 3:19 am By Roz Potter

From PBS:  Link

A look at nuclear power,  energy, Fukushima, the Indian Wells nuclear plant near New York City, a near-disaster at the Fort Calhoun nuclear power plant in Nebraska last year, and other threats. Link


Ocean radioactivity from Fukushima: largest release ever is ongoing, affecting seaweed and shellfish

October 8, 2011 at 12:42 pm By Roz Potter

From the NYT: Link

A private foundation funded this study, after governments refused.

Excerpts:

Six months after the accident at Fukushima Daiichi, the news flow from the stricken nuclear power plant has slowed, but scientific studies of radioactive material in the ocean are just beginning to bear fruit.

The word from the land is bad enough. As my colleague Hiroko Tabuchi reported on Saturday, Japanese officials have detected elevated radiation levels in rice near the crippled reactors. Worrying radiation levels had already been detected in beef, milk, spinach and tea leaves, leading to recalls and bans on shipments.

Off the coast, the early results indicate that very large amounts of radioactive materials were released, and may still be leaking, and that rather than being spread through the whole ocean, currents are keeping a lot of the material concentrated.

Most of that contamination came from attempts to cool the reactors and spent fuel pools, which flushed material from the plant into the ocean, and from direct leaks from the damaged facilities.

The leakage very likely isn’t over, either. The Tokyo Electric Power Company, the operator of the plant, said Sept. 20 that it believed that something on the order of 200 to 500 tons a day of groundwater might still be pouring into the damaged reactor and turbine buildings.

Ken Buesseler, a scientist at the Woods Hole Oceanographic Institution, who in 1986 studied the effects of the Chernobyl disaster on the Black Sea, said the Fukushima disaster appeared to be by far the largest accidental release of radioactive material into the sea.

Chernobyl-induced radiation in the Black Sea peaked in 1986 at about 1,000 becquerels per cubic meter, he said in an interview at his office in Woods Hole, Mass. By contrast, the radiation level off the coast near the Fukushima Daiichi plant peaked at more than 100,000 becquerels per cubic meter in early April.

Before Fukushima, in 2010, the Japanese coast measured about 1.5 becquerel per cubic meter, he said.

Working with a team of scientists from other institutions, including the University of Tokyo and Columbia University, Mr. Buesseler’s Woods Hole group in June spent 15 days in the waters off northeast Japan, studying the levels and dispersion of radioactive substances there and the effect on marine life.

The project, financed primarily by the Moore Foundation after governments declined to participate, continued to receive samples from Japanese cruises into July.

While Mr. Buesseler declined to provide details of the findings before analysis is complete and published, he said the broad results were sobering.

“When we saw the numbers — hundreds of millions of becquerels — we knew this was the largest delivery of radiation into the ocean ever seen,’’ he said. ‘‘We still don’t know how much was released.’’

***

The international team also collected plankton samples and small fish for study. Mr. Buesseler said there were grounds for concern about bioaccumulation of radioactive isotopes in the food chain, particularly in seaweed and some shellfish close to the plants. A fuller understanding of the effect on fish that are commercially harvested will probably take several years of data following several feeding cycles, he said.

To read more… Link

Highly toxic plutonium and strontium detected in soil 45 and 79 km away from Fukushima nuclear complex

October 1, 2011 at 7:11 pm By Roz Potter

From The Mainichi Daily News:  Link

Excerpts:

The Ministry of Education, Culture, Sports, Science and Technology announced on Sept. 30 that it had detected highly-toxic plutonium apparently from the crippled Fukushima No. 1 Nuclear Power plant in soil at six locations including Iitate village in Fukushima Prefecture.

It is the first discovery of the highly-toxic radioactive substance outside the nuclear plant since the outbreak of the disaster in mid-March. The ministry also said radioactive strontium was detected in a wide swath of Fukushima Prefecture within a radius of 80 kilometers from the troubled nuclear power plant, underscoring the fact that the nuclear crisis has been affecting wide areas.

The ministry conducted inspections on soil at 100 locations within a radius of 80 kilometers from the crippled nuclear power plant in June and July. Plutonium-238, believed to have come from the crippled nuclear plant, was detected in six locations including Iitate, Futaba and Namie. Plutonium-239 and -240 were also detected in many locations, but the ministry said it was not clear whether they were directly linked to the Fukushima nuclear crisis.

According to the ministry, the levels of radiation in the plutonium detected fall below the levels of radiation in plutonium believed to have come from atmospheric nuclear tests conducted in the past. But because very little plutonium-238 had been detected before the outbreak of the nuclear crisis, the ministry concluded that it had come from the Fukushima nuclear power plant.

***

Meanwhile, the ministry said it had detected radioactive strontium-89 in nearly half of the locations inspected, including Shirakawa, about 79 kilometers from the nuclear plant. Because the half life of strontium-89 is only about 50 days, the ministry concluded that all the findings of the radioactive substance were linked to the Fukushima nuclear power plant.

Namie registered the highest level of radiation, with 22,000 becquerels per one square meter of soil. Noting differences in distribution between the plutonium and radioactive cesium from the Fukushima nuclear power plant, the ministry plans to carry out more inspections because strontium can easily builds up in bones.

Experts concerned about massive radiation leaks from Fukushima

September 20, 2011 at 12:53 pm By Roz Potter

From the Washington Blog:  Link

Excerpts:

[A] study [by University of Texas engineering professor Steven Biegalski  and researchers at the Pacific Northwest National Laboratory] reports that more radioxenon was released from the Fukushima facilities than in the 1979 meltdown at the Three Mile Island Nuclear Generating Station in Pennsylvania and in the 1986 Chernobyl nuclear disaster in the Ukraine.

“As the measurements came in sooner and at higher concentrations than we initially expected, we quickly came to the conclusion that there were some major core melts at those facilities,” Biegalski said. “I remember being in the lab thinking, ‘Wow, if this is all true we have a far more bigger accident than what we’re hearing right now.’”

The thought was confirmed by data collected by he and PNNL researchers. Their study reports that more radioxenon was released from the Fukushima facilities than in the 1979 meltdown at the Three Mile Island Nuclear Generating Station in Pennsylvania and in the 1986 Chernobyl nuclear disaster in the Ukraine.

Biegalski said the reason for the large release in Fukushima, when compared to the others, is that there were three nuclear reactors at the Japan facilities rather than just one.

***

Nuclear expert Arnie Gundersen notes:

New TEPCO data measured on August 19 & 20 shows severe damage to the spent fuel in Fukushima Daiichi Units 1, 2, and 3…. This TEPCO data clearly contradicts and refutes the July assertion by the NRC the Fukushima Daiichi spent fuel pools were not damaged in this tragic accident.

***

The following was reported in an earlier post by Defying Disaster, see Link :

As a radiation meteorology and nuclear safety expert at Kyoto University’s Research Reactor Institute, Hiroaki Koide [says]:

The nuclear disaster is ongoing.

At present, I believe that there is a possibility that massive amounts of radioactive materials will be released into the environment again.

At the No. 1 reactor, there’s a chance that melted fuel has burned through the bottom of the pressure vessel, the containment vessel and the floor of the reactor building, and has sunk into the ground. From there, radioactive materials may be seeping into the ocean and groundwater.

Japan radiation expert says possibility that new “massive amounts of radioactive materials will be released into the environment again”

September 14, 2011 at 8:32 pm By Roz Potter

From the Mainichi Daily News,  Link

As a radiation metrology and nuclear safety expert at Kyoto University’s Research Reactor Institute, Hiroaki Koide has been critical of how the government and Tokyo Electric Power Co. (TEPCO) have handled the nuclear disaster at the Fukushima No. 1 nuclear plant. Below, he shares what he thinks may happen in the coming weeks, months and years.

The nuclear disaster is ongoing. Immediately after the crisis first began to unfold, I thought that we’d see a definitive outcome within a week. However, with radioactive materials yet to be contained, we’ve remained in the unsettling state of not knowing how things are going to turn out.

Without accurate information about what’s happening inside the reactors, there’s a need to consider various scenarios. At present, I believe that there is a possibility that massive amounts of radioactive materials will be released into the environment again.

At the No. 1 reactor, there’s a chance that melted fuel has burned through the bottom of the pressure vessel, the containment vessel and the floor of the reactor building, and has sunk into the ground. From there, radioactive materials may be seeping into the ocean and groundwater.

The use of water to cool down the reactors immediately after the crisis first began resulted in 110,000 cubic meters of radiation-tainted water. Some of that water is probably leaking through the cracks in the concrete reactor buildings produced by the March 11 quake. Contaminated water was found flowing through cracks near an intake canal, but I think that’s just the tip of the iceberg.

I believe that contaminated water is still leaking underground, where we can’t see it. Because of this, I believe immediate action must be taken to build underground water barriers that would close off the nuclear power plant to the outside world and prevent radioactive materials from spreading. The important thing is to stop any further diffusion of radioactive materials.

The government and plant operator TEPCO are trumpeting the operation of the circulation cooling system, as if it marks a successful resolution to the disaster. However, radiation continues to leak from the reactors. The longer the circulation cooling system keeps running, the more radioactive waste it will accumulate. It isn’t really leading us in the direction we need to go.

34 points near Fukushima plant exceed radiation standard used for Chernobyl, map shows

August 30, 2011 at 8:42 am By Roz Potter

From the Mainichi News:  Link

Excerpts:

A government map of soil radiation levels mainly within a 100-kilometer radius of the disaster-hit Fukushima No. 1 Nuclear Power Plant shows 34 locations with levels of cesium-137 exceeding 1.48 million becquerels per square meter, the level that was used for determining bans on living near the Chernobyl plant.

The map was released on Aug. 29 by the Ministry of Education, Culture, Sports, Science and Technology (MEXT). Cesium-137 has a half-life of around 30 years. The greatest concentration was found in the town of Okuma, which holds part of the plant, at 15.45 million becquerels per square meter. The six municipalities with levels over the Chernobyl level are Okuma, Minamisoma, Tomioka, Futaba, Namie, and Iitate.

The distribution of cesium in the soil across the 100-kilometer radius zone was very close to that calculated from air samples taken in the same areas.

U. S. nuclear power plant locator map

August 23, 2011 at 6:22 pm By Roz Potter

For those of you anticipating the obvious from serious earthquakes, here’s an eye-opening map of U.S. nuclear power plants from Greenpeace,  Link

Excerpt:

Nationwide, 108 million people live within 50 miles of a nuclear plant, yet many do not know they may be at risk if an accident or terrorist attack led to the release of radiation.

This nuclear locator map allows you to learn more about the risks of nuclear power in your community: how close you live to a nuclear plant, the record of near misses at each reactor, and government estimates of how many people could be killed or injured in an accident.

Radioactivity at Fukushima spikes to highest ever recorded!

August 1, 2011 at 9:31 pm By Roz Potter

From NHK World news:  Link

Excerpt:

The operator of the Fukushima Daiichi nuclear power plant says it has detected 10,000 millisieverts of radioactivity per hour at the plant. The level is the highest detected there since the nuclear accident in March.

Workers of Tokyo Electric Power Company, or TEPCO, on Monday measured the extremely high level of radioactivity near pipes at the bottom of a duct between the No.1 and neighboring No.2 reactor buildings.

According to the science ministry’s brochure, if a human received 10,000 millisieverts, they would likely die within a week or two.

TEPCO has restricted access to the site and the surrounding area.

Cancer from radiation develops at lower doses than government-stated safe exposure limit

July 28, 2011 at 10:12 pm By Roz Potter

From the Mainichi Daily News, Japan,  Link

Excerpts:

Of 10 nuclear power plant workers who have developed cancer and received workers’ compensation in the past, nine had been exposed to less than 100 millisieverts of radiation, it has been learned.

The revelation comes amid reports that a number of workers battling the crisis at the Fukushima No. 1 Nuclear Power Plant were found to have been exposed to more than the emergency limit of 250 millisieverts, which was raised from the previous limit of 100 millisieverts in March.

According to Health, Labor and Welfare Ministry statistics, of the 10 nuclear power plant workers, six had leukemia, two multiple myeloma and another two lymphatic malignancy. Only one had been exposed to 129.8 millisieverts but the remaining nine were less than 100 millisieverts, including one who had been exposed to about 5 millisieverts.

To read more,  Link.

Radioactive contamination and testing of meat and milk

July 25, 2011 at 1:09 am By Roz Potter

This information is from the IAEA and FAO (International Atomic Energy Agency and the Food and Agricultural Agency of the United Nations). A future post from the same source will focus on the effects of radioactive contamination on soil and crops.  Link

Excerpts:

Reports from the Government of Japan indicate that several radionuclides of consequence to human health have been found in the soil, vegetation and in animals, or their products. These include Iodine-131 and Caesium-137 that have both been found in the soil, in milk and in leaf vegetables such as spring onions and spinach.

Some of the samples have been reported to be above the levels allowed by the Japanese food hygiene law for emergency monitoring criteria for intake of vegetables.

Where these radionuclides have contaminated grazing land, milk from livestock is affected, so it is possible that any beef cattle will begin to show radionuclides in the muscle tissues.

***

Caesium-137 spreads readily in the environment in soil, water and in the air. It can be ingested or inhaled and locates in muscle tissue, bones and fat. It has a half-life of 30 years and is extremely toxic.

Iodine-131 is a volatile radionuclide that emits beta and gamma rays and combines easily with organic materials and soil minerals. Water, grass, vegetables and animal fodder become contaminated. The half-life is 8 days, but in the thyroid it can last for 100 days potentially causing malignant tumors.

***

Sampling for measurement of radioactivity

Various procedures can be used for monitoring levels of radionuclides in milk and meat, and although there are no standardized methods it is essential that surveys take into account all aspects of contamination in relation to the environment, likely exposure, the animal species and their foraging habits. The following list indicates some of the procedures used to monitor animals exposed to radiation.

Live animals – cattle, sheep, goat, poultry

  • Live sampling with a hand held, battery operated monitor e.g. Canberra 10, calibrated for use with live sheep (as used in UK, Norway etc.). For cattle – place monitor on hindquarters for one minute. Small birds can be monitored by whole body measurement.

Meat:

  • Meat – slaughter animals – samples 1.5×1.5×1.5 cm taken from muscle of two legs. Measurements of muscle samples from different parts of the same animal does not differ by more than 10%
  • Fresh meat samples from cattle of 20 – 100g
  • Fresh muscle samples of 20 – 25g from wild deer
  • Samples of 250 – 500g lean caribou meat collected and air dried in the sun, or by infra-red before analysis
  • Muscle sample from wild boar of at least 500g; samples frozen after collection

Milk:

  • Milk – bulk milk samples collected daily to average out physiological differences in the dietary habits of individual cows
  • In affected and sensitive areas – daily monitoring of milk for Sr-90/Cs-137/I-131
  • In areas at risk but not contaminated – sample as often as possible, but not less than 14 day intervals

Mitigating the effects of radionuclide contamination

Radioactive Contamination and Animal Production and Health Contamination can be mitigated by taking measures to the transfer of radioactive pollutants. It is important to reduce exposure wherever possible, especially in the immediate aftermath of contamination, i.e. by bringing livestock in from pasture and confining them to pens to prevent their grazing on contaminated pasture.

Animals should be fed with uncontaminated feed as soon as possible. Changing land use is effective in reducing transfer to man. A switch from milk production to beef or pigs can reduce radionuclide transfer by 5-fold.

To reduce radiocaesium in milk, cattle can be supplied with a caesium-binding compound such as ammonium ferric cyanoferrate (or AFCF, “Prussian Blue”) as a bolus into the rumen, in compounded concentrate feed, in salt licks, or simply sprinkled on the diet. AFCF reacts with consumed radiocaesium in the intestine to form a complex that is eliminated in the faeces.

In the case of meat-producing animals, moving to uncontaminated pastures and feeding uncontaminated feed may only be necessary close to the time of slaughter since the biological half-life of radiocaesium, for example, is of the order of two to four weeks depending on the species. In the case of wild boar meat, brining in sodium chloride and potassium nitrate can reduce caesium-137 levels by >70%.

Radioactive Contamination and Animal Production and Health The most salutary lesson learned in the past 25 years has been the need for the regulatory authorities in countries affected by contamination to take a much broader view of the environmental consequences and adopt a more holistic approach in addressing the situation.

Thus, the international scientific community has a more fundamental understanding and greater insight into the way in which different ecosystems are affected by nuclear contamination, which will provide the basis for predicting the risk to, and likely impact on, agriculture in the Fukushima incident.

Union of Concerned Scientists: What happened at Fukushima – can it happen here?

July 18, 2011 at 6:41 pm By Roz Potter

A video presentation by David Lochbaum the Union of Concerned Scientists and Arnie Gunderson, of Fairwinds Association.  Both are nuclear scientists.  Link

They walk, step-by-step, through the events of the Japanese meltdowns and consider how the knowledge gained from Fukushima applies to the nuclear industry worldwide. They discuss “points of vulnerability” in American plants, some of which have been unaddressed by the NRC for three decades. Finally, they concluded that an accident with the consequences of Fukushima could happen in the US.

This is an illuminating and fascinating presentation that becomes more interesting as it progresses. Don’t miss the slow-motion video of the hydrogen explosion.

Beef contaminated with radioactive cesium enters Japan’s food supply

July 18, 2011 at 5:40 pm By Roz Potter

From the Daily Yomiuri, Japan Link

Excerpt:

Officials of the Agriculture, Forestry and Fisheries Ministry have admitted they did not consider the possibility of cattle ingesting straw contaminated by radioactive substances emitted from the Fukushima No. 1 nuclear power plant.

“This is nothing less than a colossal blunder by our ministry. It was beyond our expectations that straw would become a source of radioactive contamination,” a ministry official said.

A total of 143 beef cattle suspected of being contaminated with radioactive cesium after ingesting straw that was stored outdoors have been shipped from Fukushima Prefecture and distributed to wholesalers, retailers and consumers in various prefectures.

Editor’s note: The importance of this contamination source should not be underestimated.  Beef is just one food source. The amount and variety of  foods and drinks potentially contaminated by radioactivity could add up to a large amount of internal radiation exposure over time, as an unsuspecting public ingests a variety of foods and drinks contaminated by radioactivity.

Food supply contamination from radiation: radioactive cesium found in green tea 355 km (220 miles) from Fukushima

June 12, 2011 at 4:43 pm By Roz Potter

From the Wall Street Journal:  Link , and a earlier related article in the UK Telegraph:  Link

Excerpt:

TOKYO—Japan’s recent discovery of tea leaves contaminated with radioactive material far from the crippled Fukushima Daiichi nuclear plant has cast a spotlight on how the country tests for fallout from the accident—and has sparked a backlash from local officials and tea growers who say too-rigid scrutiny could unnecessarily harm sales of the iconic product.

The controversy erupted last week when Shizuoka prefecture, which produces more than 40% of the green tea consumed in Japan, announced that a sample of dry tea leaves from a producer about 355 kilometers from the nuclear plant contained 679 becquerels of radioactive cesium per kilogram. That level exceed the maximum allowable amount of 500 becquerels set just this month by the government.

The prefecture requested the leaves’ producer halt shipments and is now testing other samples from the same area.

The announcement follows concerns since the March 11 accident about contamination to other staples of the Japanese diet, from the prospect of fish poisoned by the heavy amounts of radioactive material dumped into the sea off the country’s northeastern coast, to produce laced with radioactive material in one of the nation’s historic farming areas.

The reports of tea contamination so far from the nuclear plant have sparked worries over the seemingly broadening scope of contamination three months after the accident. But it also fueled an argument from the tea-growing region and opposition lawmakers in the national parliament over whether Japan’s testing is giving consumers an unnecessarily escalated sense of danger.

To read more…  Link

Widespread radioactive strontium contamination around Fukushima

June 9, 2011 at 12:29 pm By Roz Potter

From a June 9, 2011 NHK World report, which includes a video,  Link

From Mainichi News, Link

Also see my April 12, 2011 post on radioactive Strontium that was found 90 km from Fukushima at that time, Link

Strontium-90 is generated during the fission of uranium in fuel rods in reactors.

With a comparatively long half-life of 29 years, the radioactive substance poses a risk of accumulating in the bones if inhaled, because its properties are similar to those of calcium. If this happens, it could cause cancer.

The ministry says the survey revealed that strontium was detected even in the city of Fukushima about 60 kilometers from the plant, suggesting wide-spread contamination.

It says higher doses of strontium were spread northwestward from the plant, along with other radioactive substances, because of the prevailing winds.

The Nuclear Safety Commission says the detected doses of strontium were minimal, compared with those of cesium found in the region. It says the substance does not pose any immediate health threat.

Doctor Osamu Saito is a radiation expert at a hospital in Fukushima City. He says even though only small quantities of strontium-90 were detected in the survey, it still poses a high health risk because it can accumulate in the bones.

He is urging the government to increase the number of observation points throughout the prefecture, so as to help ease public anxiety.

The ministry says it is considering taking samples from additional locations in the next survey.

Japanese authorities: 3 Fukushima reactors likely had melt-through – more serious than meltdown

June 8, 2011 at 10:06 am By Roz Potter

From the UK’s Guardian,  Link

Excerpt:

Molten nuclear fuel in three reactors at the Fukushima Daiichi power plant is likely to have burned through pressure vessels, not just the cores, Japan has said in a report in which it also acknowledges it was unprepared for an accident of the severity of Fukushima.

It is the first time Japanese authorities have admitted the possibility that the fuel suffered “melt-through” – a more serious scenario than a core meltdown.

The report, which is to be submitted to the International Atomic Energy Agency (IAEA), said fuel rods in reactors No 1, 2 and 3 had probably not only melted, but also breached their inner containment vessels and accumulated in the outer steel containment vessels.

***

The report comes a day after Japan’s nuclear safety agency said the amount of radiation that leaked from Fukushima Daiichi in the first week of the accident may have been more than double that initially estimated by Tepco.

Fukushima dai-ichi reactors, containment vessels and radioactive water storage tanks all leaking radioactivity into the Pacific

May 26, 2011 at 6:41 pm By Roz Potter

From the blog of the online version of the esteemed journal Nature:  Link

Fukushima nuclear plant is leaking like a sieve - May 26, 2011

As more details leak out about the stricken Fukushima Daiichi nuclear power plant, it’s become clear that something else is leaking—radioactive water from the cores of three damaged reactors.

Leaks have been a persistent problem at the plant since it was struck by an earthquake and tsunami on 11 March. Three reactors operating at the time of the quake went into meltdown after the tsunami wiped out emergency generators designed to circulate water through the cores. TEPCO recently admitted that all three units probably suffered complete meltdowns before workers could flood them with seawater.

Since then, reactor operators have kept water flowing to the cores and several fuel storage pools above the reactors. That same water appears to be flowing out into the basements of buildings and eventually the Pacific Ocean, where environmentalists and scientists have raised concerns about possible contamination.

The Tokyo Electric Power Company (TEPCO), which runs the plant, hoped to rectify the problem by pumping water into storage tanks until it can be reprocessed, but today Reuters reports that the storage tanks appear to be leaking.

And that’s just the start of the bad news because the reactors themselves appear to be leaking as well. TEPCO initially hoped that the leaks were largely coming from pipes that could be repaired, but they now concede that both the reactors’ pressure vessels and primary containment vessels, which are designed to contain an accident, are probably leaking water.

The leaks will probably force TEPCO to abandon its plans to set up a recirculation system that can cool the reactor cores. That’s a serious blow to efforts to bring the reactors to a safe temperature within months.

To read on,  Link

Meltdowns at Fukushima Units 1,2 & 3 add significantly to total radiation released

May 24, 2011 at 10:48 am By Roz Potter

From the Union of Concerned Scientists, Link

Excerpt:

The melting fuel was released into the primary containment vessel. The molten fuel reacts with the concrete floor of the containment, creating additional radioactive gases. These are released into the atmosphere through a leak in the containments (editor: leaks have been admitted by TEPCO, the plant owners). This adds significantly to the total radiation released by the accident. (emphasis added)

Nuclear meltdown confirmed at Fukushima reactor #1 – also now presumed at #2 and #3

May 17, 2011 at 8:31 pm By Roz Potter

Fukushima reactor #1 meltdown, Excerpt from a UK Telegraph article:

Engineers from the Tokyo Electric Power company (Tepco) entered the No.1 reactor at the end of last week for the first time and saw the top five feet or so of the core’s 13ft-long fuel rods had been exposed to the air and melted down.

To read on, Link

Fukushima reactors #2 and #3 meltdowns, Excerpts from Asahi in Japan:

Data shows meltdowns occurred at the No. 2 and No. 3 reactors of the Fukushima No. 1 nuclear power plant, creating huge problems for the plant operator that had presented a more optimistic scenario.

And like the No. 1 reactor, the melted fuel appears to have created holes in the pressure vessel of the No. 3 reactor, according to the data of Tokyo Electric Power Co. released May 16.

Goshi Hosono, special adviser to Prime Minister Naoto Kan, acknowledged the likelihood of meltdowns at the No. 2 and No. 3 reactors.

“We have to assume that meltdowns have taken place,” Hosono said at a news conference May 16.

To read on, Link

From a Bloomberg article:

Holes have been found in the base of the pressure vessel, and most of the fuel has likely melted, Kyodo News reported yesterday, citing the utility. It’s possible the fuel has leaked into the containment vessel, which was damaged in the explosion, according to the report.

To read on, Link

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