Two Tepco employees may have surpassed their 250 milliSievert exposure limit due to high thyroid doses from I-131

If the employees ingested Iodine, then they surely ingested other isotopes as well. What are Tepco's estimates for Cesium and Strontium contributions to these worker's total body dose? How much cpm did the whole body counter indicate? There is more to this story..  From AFP:

TOKYO — Two workers from Japan's stricken Fukushima nuclear plant have been contaminated by high levels of radioactive iodine, the operator said Monday, prompting fears over their long-term health.

The workers, reportedly men in their 30s and 40s, may have already been exposed to radiation levels higher than the recently boosted official annual limit, Japanese media suggested.

Tokyo Electric Power Company (TEPCO) said it had been measuring the internal exposure to radiation of all employees involved in emergency work at the Fukushima Daiichi plant crippled by the March 11 earthquake and tsunami.

Internal exposure occurs when people take radioactive substances into their bodies through tainted air or food and drink.

The company notified the governmental atomic energy agency of the possible problem and the agency confirmed that "the thyroid glands of two male employees showed high levels of radiation (iodine-131)", TEPCO said in a statement.

The Jiji Press news agency said the two workers had stopped working at the plant and were not sick at the moment. They will undergo further check-ups.

The inspection by the government agency found 9,760 and 7,690 becquerels of iodine-131 in the thyroid glands of the workers, 10 times higher than other workers at Fukushima, reports said.

The two men were working at a variety of locations at Fukushima Daiichi, including the central control room, in March and April, including on March 11 and during the following days.

The tests sparked fears that their radiation exposure had been several hundred millisieverts, Jiji said.

A few days after the disaster, the government boosted the annual limit of radiation exposure for emergency workers to 250 millisieverts from 100 as the nation battled the world's worst nuclear crisis since Chernobyl in 1986.

No workers have been confirmed to have been exposed radiation higher than the annual limit since the disaster.

Radioactive iodine is known to accumulate in the thyroid gland.

Are strong winds from tropical storm Songda dropping in-air radiation readings around Fukushima?

Iitate, Fukushima, Japan

Over the last few weeks, readings from this geiger counter are usually between 3-4 microSv/hr during the day. You can see it shaking from the wind. It will be interesting to see what it reads after the storm passes, when the winds calm down.

Edit:  Looks like readings are back in the normal range again. Levels were between .75 and 1.5 all day on Monday.

Samples from an entire 300 km stretch of seafloor off the Fukushima coast indicate radioactivity 50-100 times higher than normal

As far as 30 kilometers out

Perhaps MEXT realized that Greenpeace was making them look bad by being so conscientious about testing sea life near Dai-ichi, so they conducted their own measurements of the seabed off the coast of Fukushima. From NHK:

Japan's science ministry has detected extraordinarily high levels of radioactive cesium in seafloor samples collected off Miyagi and Ibaraki Prefectures.

Experts say monitoring should be stepped up over a larger area to determine how fish and shell fish are being affected.

The ministry collected samples from 12 locations along a 300-kilometer stretch off Fukushima prefecture's Pacific coast between May 9th and 14th. It hoped to get an idea about the spread of nuclear contamination caused by the accident at the Fukushima Daiichi nuclear power plant.

Radioactive substances were found in all locations, including those off Miyagi and Ibaraki Prefectures, which had not been previously investigated.

Radioactive cesium 137, measuring 110 becquerels per kilogram or about 100 times the normal level, was found in samples collected from the seabed 30 kilometers off Sendai City and 45 meters beneath the surface.

Samples collected from the seabed 10 kilometers off Mito City and 49 meters beneath the surface measured 50 becquerels or about 50 times the normal level.

Professor Takashi Ishimaru of the Tokyo University of Marine Science and Technology says plankton most probably absorbed the radioactive substances carried by the current near the sea surface, and then sank to the seabed.

He said monitoring must be stepped up over a larger area, as radioactive materials in the seabed do not dissolve quickly, and can accumulate in the bodies of larger fish that eat shrimp and crabs that live on the seafloor.

Saturday, May 28, 2011 22:21 +0900 (JST)

In light of those findings, the combination of radioactivity in seawater and high tides will pose problems for Miyagi and Ibaraki

Shinomaki, Miyagi, Japan. (Asahi Shimbun via Getty Images)

I haven't heard any reporting on it yet, but aren't higher concentrations of isotope in ocean water a cause for concern in Miyagi, Ibaraki and other port areas around Fukushima?  Twice a day, every day, the high tide brings in fish and debris right up to the front doorsteps of residents homes.

I would imagine this as a potential health hazard and cause for evacuation.  Since they haven't done so yet, maybe they should start investigating amounts of radioactivity in water at high tide.  These people tread through it everyday. These communities will face permanent, regular flooding because the Japan earthquake shifted the local geography.  Miyagi is 1.2 meters lower than it used to be.

Typhoon Songda strengthens, and as luck would have it - heads straight for Fukushima

Source: Hurricanezone.net

Source:  Guam Loop

Bloomberg: "Songda’s winds increased to 241 kilometers (150 miles) per hour from 213 kph yesterday, the U.S. Navy Joint Typhoon Warning Center said on its website. The storm’s eye was about 240 kilometers east of Aparri in the Philippines at 8 a.m. today, the center said. Songda was moving northwest at 19 kph and is forecast to turn to the northeast and cross the island of Okinawa by 9 p.m. local time tomorrow before heading for Honshu."

Hong Kong background radiation is higher than most parts of Japan

The Hong Kong Observatory is reporting radiation readings that are essentially unchanged since April 1, at 0.14 microSv/hr.  Official numbers from the Tokyo Metropolitan Institute of Public Health show radiation levels in central Tokyo reached a high of 0.109 microsieverts per hour in Shinjuku Ward yesterday. The article doesn't state the typical background levels for Hong Kong prior to the Fukushima incident.  Story here

This infographic is useful overall, just disregard the banana equivalent dose at the very top. No respectable research source should be caught comparing banana doses these days. 

Protests by Fukushima parents pay off - Radiation limits for students will be revised lower, and topsoil will be removed from Fukushima schools

If you recall what transpired last month, education board officials overseeing schools in the Fukushima Prefecture jacked up permissible doses for school children from the standard 1 milliSievert/year to a very difficult to accept 20 milliSievert/year.  Angry parents have been protesting ever since, and have succeeded in forcing the Ministry of Education to acquiesce to their demands.  From the NYT:

"The education minister, Yoshiaki Takaki, said Friday that the government would, for the time being, revert to the original limit of 1 millisievert a year. Mr. Takaki said the government would pay for local schools with radiation levels above that limit to remove contaminated topsoil from their grounds.

“We will provide financial support to schools for measures to deal with soil in schoolyards as a way to lower radiation levels for children,” Mr. Takaki said at a news conference."

It was a tough call.  Education officials - weighing radiation safety vs Japan's high educational expectations - facilely cited a 2009 recommendation from the International Commission on Radiological Protection (ICRP) that addresses this sort of scenario.  During emergencies, the ICRP Publication 109 states that populations can be exposed to 20 to 100 mSv per year for short periods of time. The education ministry calculated that children could spend 8 hours a day in a schoolyard exposed to as much as 3.8 microsieverts per hour, and 16 hours a day indoors exposed to 1.52 microsieverts per hour.  Under these circumstances, annual doses would come in just under the 20-mSv limit.

Mext had recently conducted measurements at 58 public schools, and said none of them exceeded 3.8 microSeiverts per hour.  After the removal of topsoil, municipality officials are stating that doses in some areas will be reduced to just 0.6 microSievert/hour.

Here's a note of concern: ICRP recommendations, along with official exposure measurements are taken "in air", and are likely read with the equipment some distance from the ground.  If activity is as high as 600,000 becquerels per square metre in some areas like the IRSN recently reported, foot and ankle doses could be higher than official numbers by a factor of 2-4 due to beta contribution and principles of inverse square law.

If you measure the distance from ground to gonads for younger children (Kinder through Grade 6), you begin to appreciate why they should make the distinction.  In addition to the generic 'in air' reading, it's helpful to see the exposure numbers taken at 5cm, 20 cm and 1 meter levels from the soil.

Despite excessive Cesium found in tea leaves, some local growers still ship out

From NHK:

Radioactive substances detected in tea leaves

"Radioactive contamination has been found in tea leaves in Chiba and Gunma prefectures, about 200 kilometers from the crippled Fukushima Daiichi nuclear plant. Similar contamination has been found over a wide area around Tokyo including Ibaraki, Kanagawa, Saitama and Shizuoka prefectures.

Chiba authorities say up to 763 becquerels per kilogram of radioactive cesium were detected in tea leaves picked on Tuesday in Narita and 3 other cities. The provisional state limit is 500 becquerels per kilogram.

The Chiba government on Wednesday requested tea growers in the 4 cities to voluntarily halt shipments, and asked dealers not to sell the tea produced in the areas.

But 2 tea growers in Narita City reportedly shipped their tea leaves, and dealers sold some processed tea to local consumers. Radioactive materials in tea leaves exceeding the legal limit was earlier detected in other areas in the prefecture.

In Gunma Prefecture, 780 becquerels per kilogram of radioactive cesium were detected in tea leaves picked on Tuesday in Shibukawa City.

The Gunma government on Wednesday asked farm cooperatives to halt shipment of tea leaves.
This is the first tea contamination case reported in Gunma Prefecture."

Thursday, May 26, 2011 07:45 +0900 (JST)

Still not allowed within 20km of Dai-ichi, Greenpeace measures sea life radioactivity in unrestriced areas and still comes up with high numbers

I recall assumptions made by pro-nuc apologists that it's a big ocean out there, and that once in ocean current, dilution and dispersion would take care of any high concentrations of reactor contaminants coming from Fukushima.  Nevertheless, the ever vigilant (and pesky) Greenpeace continues to gather its own independent data, and recently discovered some pretty high levels of radioactivity in certain varieties of sea life further than 20km from the plant.  AFP:

"Greenpeace said it detected radiation levels in seaweed 50 times higher than official limits, which it charged raised "serious concerns about continued long-term risks to people and the environment from contaminated seawater".

It also said that tests, which it said were independently verified by French and Belgian laboratories, showed above-legal levels of radioactive iodine-131 and caesium-137 in several species of fish and shellfish.

"Our data show that significant amounts of contamination continue to spread over great distances from the Fukushima nuclear plant," said Jan Vande Putte, a Greenpeace radiation expert, at a Tokyo news conference.

Japan's seafood safety limit for caesium-137 is 500 Becquerels per kilogram (227 per pound).
Greenpeace said it found levels of 740 Becquerels per kilogram in oysters, 857 in a fish species, 1,285 in sea cucumber and 1,640 in seaweed.

The maximum iodine-131 limit is 2,000 Becquerels per kilogram for seaweed, but Greenpeace said it found a level of 127,000 Becquerels per kilogram in the seaweed species Sargassum Horneri (please see below).

The group said that "eating one kilo of highly contaminated seaweed sampled by Greenpeace could increase the radiation dose by 2.8 millisievert -- almost three times the internationally recommended annual maximum".

The amount of radioactivity released into the ocean from Dai-ichi is not trivial. In early May alone, 250 tons containing about 20 terabecquerel leaked from a pit near reactor 3.  From April 1-6, 500 tons of contaminated water containing 4,700 terabecquerel leaked from reactor 2.

I think it's foolish to assume that once the isotope-laden water mixes with ocean current, it gets evenly distributed in nice, conveniently negligible quantities. High concentrations of isotope are certain to drift around without appreciably dispersing, and will end up depositing in random areas.  Sea life, possessing typical biology that depend on different elements for survival, take in cesium and iodine and continue to do so regularly.  This problem will continue until Tepco figures out a way to decontaminate and re-circulate reactor water, and that's where Areva comes in.

Here's some comic relief - I had trouble finding out if the species of seaweed Sargassum Horneri was actually edible.  Resorting to YouTube, i typed in "Sargassum Horneri Japan".  The results of that query:

An expert from the Nuclear Waste Management Organization of Japan has calculated more alarming radioactive contamination estimates for the surrounding Fukushima area

With Tepco releasing reliable data the way Enron disclosed its financials on the way down, independent experts have felt compelled to calculate and come forward with various estimates of their own. At a recent policy setting meeting with the Japan Atomic Energy Commission, Dr. Tomio Kawata, utilizing whatever reliable isotope release data he could get his hands on (the non-Tepco variety), shed further light on how heavily contaminated the soil is in areas northwest of the plant.

"According to Kawata, soil in a 600 square kilometer area mostly to the northwest of the Fukushima plant is likely to have absorbed radioactive cesium of over 1.48 million becquerels per square meter, the yardstick for compulsory migration orders in the 1986 Chernobyl catastrophe.

Kawata also said soil in a 700 square km area is likely to have absorbed 555,000-1.48 million becquerels per square meter, which was a criteria for temporary migration during the Chernobyl disaster.

Kawata estimated the soil contamination using data on radiation levels in the air monitored by the Ministry of Education, Culture, Sports, Science and Technology.

The size of the contaminated areas in the Fukushima crisis is one-tenth to one-fifth of those polluted in the Chernobyl disaster, Kawata said.

While the expected radiation exposure from 1.48 million becquerels of cesium is around five millisieverts a year, below the government’s benchmark of 20 millisieverts for evacuation orders, decontamination will still be necessary before evacuees can return as radioactive cesium binds strongly to soil, making it hard to reduce radiation levels, Kawata said."

Since this seems to be as legit as the Fukushima-Chernobyl comparisons get, let's pull up a map of the Chernobyl control-zone to get a visual idea of Dr. Kawata's numbers and their implications:

1.48 million Becquerels/m² = 40 Curies/km²

600 km² of area in the Fukushima Prefecture have radioactivity equivalent to the confiscated/closed zones on this map (red).  An additional 700 km² of area fit the "permanent control zone" criteria (dark pink), as it stands in Chernobyl today.

Edit:  Here's a recently released French IRSN map based on MEXT data.  This map breaks down the isotope concentration in the Fukushima and surrounding area:

Source:  IRSN.fr

How long will it take for Cs-137 to work it's way out of the environment?  Considering the Chernobyl situation further, we can see from the following chart that a long, slow slog in dose rate reduction is ahead for Japan as well. Measurements are in air, with Cs-137 as the main contributor.

Source: Wikipedia

Read the original story here

France's Institute for Radiological Protection and Nuclear Safety (IRSN) says 70,000 more people outside the exclusion zone should evacuate

Iitate is most likely the area of concern

From the TimesofIndia:

"Radioactivity levels in this area range from several hundred becquerels per square metre to thousands or even several million bequerels per square metre, the IRSN report, issued late Monday, said.

The 10 mSV derives from a calculation of exposure to at least 600,000 becquerels per square metre, emitted by caesium 137 and 134, which are long-lasting radioactive elements.

Of the 70,000 people in the zone identified in the IRSN report, more than 26,000 could be exposed to doses of more than 16mSv in the first year after the disaster.

Around 70,000 people, including 9,500 children aged up to 14, live in the area, "the most contaminated territory outside the evacuation zone," the agency said."

Live readings from Iitate, Japan.  An average of 3 microSv/hr over a years time comes out to just over 26 millSievert

If the IRSN studied the MEXT map shown above, they would realize that they may actually be under-calculating doses. Some areas outside the exclusion zone are expected to get as high as 20-50 mSv/yr or more.

The IAEA investigation team arrives in Japan just in time to witness radioactive water maxing out all available storage areas at the plant

I find this picture just classic

From NHK:

"A team of experts from the UN's nuclear watchdog group has arrived in Japan to investigate the accident at the Fukushima Daiichi nuclear power plant and has met with Japan's industry minister Banri Kaieda.

Kaieda met the team from the International Atomic Energy Agency in Tokyo on Tuesday evening. The team of nuclear experts from Britain, France and other nations arrived in Japan earlier in the day.

Kaieda said his government will fully cooperate with the team's investigations.

Team leader Mike Weightman said his agency wants to make use of lessons from the accident to improve the safety of nuclear power plants across the globe."

Meanwhile, a makeshift storage area with a capacity of 10,000 tons of water is filling up fast, and will reach capacity in 5 days.  As of Monday morning,  the building contained 8,700 tons of water. At the current transfer rate of 12 tons per hour, the facility will be full by the end of the week, at which point the water removal operation will stop until a treatment facility is complete.

Remember that French company Areva, and how they scored that big contract to decontaminate water in Dai-ichi? Their engineers have spent the last month designing a treatment system for the plant that will use a chemical process to remove radioactive contaminants and salt from the water.

Once installed, Areva and Tepco are touting their new system's technological efficiency at 50 treated tons of water per hour, which will then be used to cool reactors instead of seawater or fresh water brought from off site. TEPCO has indicated it expects treatment to begin in June.

After weeks of 'no detection', radionuclides suddenly pop up in San Luis Obispo Milk

The date of collection was on May 2nd, and there is a lag time in getting results back to the public due to testing.  Levels are low, and the California Dept. of Public Health does a good job of concisely explaining the potential absorbed doses in their report.

Source: CDPH

For your future reference, here's an EPA chart that converts isotope concentrations in water to absorbed dose.

Many residents in Iitate and Kawamata Prefectures (just outside the exclusion zone) are refusing to relocate

They've weighed the pros and cons and made their decision

From NHK:

"About half the residents living in parts of Fukushima Prefecture where an evacuation order is in place have still not left one week before the government-set deadline runs out.

On April 22nd, the government ordered people in Iitate Village and a part of Kawamata Town to leave by the end of this month because of radiation exposure from the Fukushima Daiichi nuclear power plant.

Officials have been placing priority on evacuating households with infants and small children.
But only about half of the 7,800 residents have followed the order one month after it was issued.

Some residents remaining in the areas say emergency shelters are far from their work places and their children's schools. Others say they will lose their jobs if they move away.
People in areas with relatively low levels of radiation hope to delay their evacuation until temporary housing is completed in the summer.

The officials say they will continue to urge the remaining residents to leave. But meeting the deadline will be difficult, as the evacuation order is not legally binding.

The 2 communities are located outside the 20 kilometer radius around the crippled nuclear plant. The central government earlier instructed residents living inside the 20 kilometer zone to evacuate.

Monday, May 23, 2011 11:46 +0900 (JST)"

Fortunately, this handy map by MEXT can help people in these areas understand what their yearly cumulative exposures will total  by March 11, 2012.  Suffice to say, these values are likely on the conservative side.

Source:  Mext

_________________________________________________________________________________

Parents demand lower radiation limit for children

"A group of parents of school children is calling for lowering the government-set radiation limit for children.

The group is from Fukushima Prefecture, where a crippled nuclear power plant is posing the danger of nuclear contamination.

On Monday, members of the group visited the education ministry and submitted a petition bearing more than 15,000 signatures.

The parents have been pointing out that the government safety level is too high for children and are demanding that it be lowered to 1 millisievert per year."

Referencing the map above, it's clear that these parents will have to change reality for their '1 mSv/yr' wish to be realized.  Sad, but true.  Read the story here

More info on ingested Cesium, internal doses, and the efficacy of whole body counters in determining absorbed dose

Cs-137 and Co-60

Here's what the NRRPT (referencing the  International Commission on Radiological Protection (ICRP)) has to say:

"From the case examined above, it can be seen that even though the intake estimate rises using the new dosimetry models, the organ dose has fallen by approximately 50% and the whole body dose is lower by 63%, from 51 mSv to 19 mSv.

This reduction in assessed doses is as expected. The new Respiratory Tract Model is now based on greatly improved understanding of the processes that occur in the airways, and the tissues that make up this organ. The new model also takes account of differences in radiosensitivity of respiratory tract tissues. In vivo and autopsy measurements, following accidental intakes, show that there is a degree of very long term retention in the lungs. The long term component of the ICRP 66 model is 7000 days compared with 500 days for the ICRP 30 model, so that a percentage of material in the lungs is released much more slowly using the new model.

Apportionment factors have now been assigned to each region of the respiratory tract. These factors relating to risks of cancer incidence weight certain tissues more than others according to their radiosensitivity. This means that certain areas of the respiratory tract can receive much higher doses but with a very low risk of cancer. For these reasons a higher intake does not necessarily lead to higher doses received by the lungs as a whole."

The value with the information above is in the dose estimates, where it was additionally stated that 810 Bq = 4860 dpm.  Regarding whole body counts:

"Co-60 and Cs-137 are two nuclides that make up a large portion of most radioactive profiles. These isotopes also put out gamma radiation that is easily seen by the whole body counter.  We need to scale in hard to detects for a couple of reasons.

The “hard to detects” (alpha, beta, low activity gamma) cannot be seen by the whole body counter because it can’t penetrate outside the body or it’s just too low activity that it’s washed out by background, other nuclides, or noise.

The “hard-to-detects” are the major dose contributor. A small fraction of alpha emitters may give 50% of the exposure."

See the info, prepared by Chesapeake nuclear services here

More revelations about radiation exposures from Fukushima are surfacing

Please bear with this lengthy post so you can understand what doses these people mentioned in the article are receiving.  Part of the story from the Daily Mainichi:

Nuclear plant workers suffer internal radiation exposure after visiting Fukushima

The government has discovered thousands of cases of workers at nuclear power plants outside Fukushima Prefecture suffering from internal exposure to radiation after they visited the prefecture, the head of the Nuclear and Industrial Safety Agency said. 

Most of the workers who had internal exposure to radiation visited Fukushima after the nuclear crisis broke out following the March 11 quake and tsunami, and apparently inhaled radioactive substances scattered by hydrogen explosions at the Fukushima No. 1 Nuclear Power Plant.
The revelation has prompted local municipalities in Fukushima to consider checking residents' internal exposure to radiation.

Nobuaki Terasaka, head of the Nuclear and Industrial Safety Agency, told the House of Representatives Budget Committee on May 16 that there were a total of 4,956 cases of workers suffering from internal exposure to radiation at nuclear power plants in the country excluding the Fukushima No. 1 Nuclear Power Plant, and 4,766 of them involved workers originally from Fukushima who had visited the prefecture after the nuclear crisis. Terasaka revealed the data in his response to a question from Mito Kakizawa, a lawmaker from Your Party. 

The Nuclear and Industrial Safety Agency said it received the data from power companies across the country that measured the workers' internal exposure to radiation with "whole-body counters" and recorded levels of 1,500 counts per minute (cpm) or higher. In 1,193 cases, workers had internal exposure to radiation of more than 10,000 cpm. Those workers had apparently returned to their homes near the Fukushima No. 1 Nuclear Power Plant or had moved to other nuclear power plants from the Fukushima No. 1 and 2 nuclear power plants.

Now, what are 'counts per minute', and can we convert them to an absorbed dose?  A counts per minute reading is a measure of radioactivity.  It is the amount of photons a geiger counter is able to detect after entering the gm tube of the device (calibrated to Cs-137).  Each photon is presumed to have arisen from the decay of a radioactive isotope.

Although the 'counts per minute' value tries hard to indicate the amount of disintegrations per minute coming from a radioactive source, the two terms should not be confused.  Most geiger counters have limitations, and will not detect all disintegrations taking place from a source, but will give you a good idea of the radioactivity originating in air, or coming from an object.

Nuclear disintegrations taking place within an atom are tied to the definition of the Becquerel.  One becquerel = one disintegration per second.  60 counts per minute, theoretically, indicates 1 Becquerel of activity.

The readings mentioned in the article above stated a range of 1,500 to 10,000 cpm.  Thus, they are reading between 25 to 166 becquerel of activity (assuming whole body), per person.   The exact isotopes that NISA equipment is sensitive to is not mentioned in the article, but is also probably rated for Cesium.

We have the inferred activity, but what doses are these people getting?  Take a look at the specifications stated on the back of a Radalert geiger counter:

For Gamma, the device detects x-rays down to 10 keV through end window, or 40 keV through case. Calibration is 1000 CPM = 1 mR Cs-137 per hour (indicated in the picture above).  So for example, if we were measuring cpm with this particular unit, we will be able to establish a range of absorbed dose readings based on what was mentioned in the article.  Most geiger counters are calibrated similarly, thus these people are receiving:

1500 cpm = 1.5 milliREM per hour.  That is 15 microSv/hr, or 131 milliSv/year.
10,000 cpm = 10 milliREM per hour.  That equals 100 microSv/hr, or 876 milliSv/year.

Some of these people will break 1 Sievert a year if readings are calculated from just part of the body and/or do not take all isotopes into account.

How's that "nobody has exceeded 250 milliSievert" claim doing, Tepco?   Many of these guys most assuredly have, or will exceed that dose very soon now.
_________________________________________________________________________________

Recommended exposure limits from the NRC:

"The NRC adopted the 100 mrem per year dose limit from the 1990 Recommendations of the International Commission on Radiological Protection (ICRP). The ICRP is an organization of international radiation scientists who provide recommendations regarding radiation protection related activities, including dose limits. These dose limits are often implemented by governments worldwide as legally enforceable regulations. The basis of the ICRP recommendation of 100 mrem per year is that a lifetime of exposure at this limit would result in a very small health risk and is roughly equivalent to background radiation from natural sources (excluding radon) (ICRP, 1991).

100 mrem/yr = 1 mSv/yr 

Tepco sends workers into reactor 1 again, gathers info to assess the plausibility of their water recirculation plan

Two brave souls entered reactor #1 to get an ocular on the basement situation today and confirmed that water levels are indeed at least 4 meters deep. Tepco is preparing to set up a cooling system that will pump water out of the basement, decontaminate it, and send it back into the reactor.

The idea is to reduce the need to pump high volumes of fresh water from outside that just winds up leaking out of the reactor and into other undesirable locations within the plant.  The two employees spent "about one hour" making observations and gathering info, which is about the longest period of time i can remember a person spending in any of the units as of late.

The article also mentions that "4 other workers later took over and spent about 90 minutes on the ground floor using a gamma camera to measure the spread and densities of radiation."  I get the sense that Tepco is getting as serious as cancer about making progress, but found it unusual that they reported the amounts of time their employees spent inside the reactor without providing associated exposure information.

This data is usually provided to the media.  For example, an article on May 5th indicated that two workers installing a ventilation system in that same reactor stayed for 25 minutes and received 2 milliSieverts.  Todays employees were exposed for 1-1½ hours. They probably received a manageable dose, but based on an exposure chart for unit 1 released this past weekend (above left), radiation levels measured at different locations within the unit were still considerably high.  Hopefully, Tepco will clarify how much exposure these guys actually got.

Read the story here

Just another typical day in Dai-ichi - Head-scratching, uncertainty predominate

Just in time to offset the Tepco Execs 'cold shutdown in 6 months' drivel, it was recently discovered that the water level in a tunnel linked to the Number 3 reactor has been rising several centimeters a day for the past week. The water is expected to rise to about one meter below the ground level soon.  It works out great.  At that rate, the highly radioactive water should completely fill the basement and reach ground level at about the same time cold shutdown is achieved.

Perhaps Tepco has a problem grasping the law of conservation of matter.  Water goes in, water must come out.  For how long now; massive, drought-inducing, crop-shriveling amounts  have been pumped into reactors with known leaks. Tepco has to expect water to pop up at different locations, however remote that possibility may appear (see next paragraph), but they always seem surprised when it happens.

Tepco is also confirming that radioactive water levels are also rising - if you can believe it - in the Number 5 and 6 turbine buildings. Also, TEPCO says an estimated 67,500 tons of contaminated water are now in the Number 1, 2 and 3 reactors alone, "hampering efforts to restore the reactors' cooling systems".

In a stroke of luck, workers entering the unit 2 building for the first time since the explosion discovered lower amounts of radiation than expected, at 10 to 50 milliSieverts/hr.  This will enable each worker to spend 20 minutes a day instead of just 10 minutes a day in the unit.  What they will be able to accomplish in that greatly expanded time frame is hard to say - maybe installation of some air purification system that reduces radiation by 96%, but in actuality, only reduces it 5-10%. 

And no wonder they've been putting cows down outside the exclusion zone.  It's in the grass - 1,530 becquerels of radioactive cesium per kilogram were found in a sample collected last Wednesday from a farm in southern town of Marumori in Miyagi Prefecture. That is 5 times the legal limit of 300 becquerels.

350 becquerels of cesium were also detected in a sample from a prefectural farm in the northern city of Osaki.

Amazing photos of the tsunami hitting the Fukushima Dai-ichi nuclear plant

From TEPCO's site: Tsunami situation Fukushima Daiichi Nuclear Power Station (March 11, 2011 Place Taken: East Slope solid waste storage facility (near the No. 5 (south)

See more images here

Bloomberg article nails Tepco about making promises on timelines without even knowing if they can back those promises up

I want to plaster this article somewhere on the blog permanently, but i have such limited sidebar space. From Bloomberg:

Tepco Misleading Public Over Nuclear Crisis

"Tokyo Electric Power Co. has made misleading statements about when it will stabilize its nuclear reactors crippled by the March 11 earthquake and tsunami, said Tetsuo Ito, head of the Atomic Energy Research Institute at Kinki University in western Japan.

The company, known as Tepco, yesterday reiterated the schedule on its so-called road map announced a month ago to achieve cold shutdown of the three radiation-leaking reactors as early as October. Setting a timetable without knowing the condition of the reactor cores doesn’t make sense, Ito said in a phone interview from Osaka.

“Only after understanding what’s going on inside the buildings and reactors, will it be clear what parts of the timetable are achievable,” Ito said. “Devising a road map without that will give the public a false sense of security.”

On May 15, or more than two months after the disaster at the Fukushima Dai-Ichi plant, Tepco said conditions were worse than expected in reactor No. 1 when it found all uranium fuel rods had melted.

Today it sent four workers into reactor No. 2 for the first time since March 14 to measure radiation levels and assess whether work can be done to fix gauges that will show the condition of the core. “It’s highly likely No. 2 and No. 3 reactors are worse than thought,” Ito said.

“Tepco devised the first (road map) before fully grasping the situation inside the reactor buildings; a scientist wouldn’t do such a thing.”
Ito has headed the institute, which started running Japan’s first university-based nuclear reactor in 1961, for more than five years. He has spent 35 years in nuclear engineering research.

Targets Achievable

Tepco officials believe the targets remain achievable, spokeswoman Ryoko Sakai said by phone today. She declined to comment on Ito’s other remarks.
When asked whether Tepco has sought the advice of nuclear engineering academics, Vice President Sakae Muto said yesterday the company has talked to experts, nuclear companies and government bodies around the world.

Tepco has also been criticized by government officials for responding too slowly to the crisis that unfolded at Fukushima after the tsunami washed ashore.
The utility plans to build self-circulating cooling systems in reactor buildings damaged by explosions after the earthquake and tsunami knocked out power and pumping equipment to cool fuel rods and spent pools.

This is to achieve a cold shutdown, where the core temperature in the three damaged reactors falls to below 100 degrees Celsius (212 degrees Fahrenheit).
Forced Evacuations

Beside radiation leaks into the atmosphere forcing about 50,000 families near the plant to evacuate, more than 10 million liters (2.6 million gallons) of contaminated water have leaked or been released into the sea.

Millions of liters of radiated water have also filled basements and trenches at the station from leaking reactor vessels and piping.

Since the accident, Tepco shares have lost 82 percent of their value. They traded at 392 yen at 2:32 p.m. in Tokyo today compared with 2,153 yen on March 10.

Japan’s government in April raised the severity rating of the Fukushima crisis to the highest on an international scale, the same level as the Chernobyl disaster in 1986. The station, which has withstood hundreds of aftershocks, may release more contamination than Chernobyl before the crisis is contained, Tepco officials have said."

'We are not in control of the situation in Fukushima, nor are we sure how we will get in control of the situation there, but don't worry... we just know we'll be in control soon' - is what it amounts to.

MEXT just released an updated map showing predicted radiation exposures for a year ending March 11, 2012, in areas near the Fukushima No. 1 Nuclear Power Plant

Values are cumulative up to 3/11/12. View the pdf here

Let's presume that this forecast is based on Tepco's firm resolve to achieve cold shutdown by January.  Any unforeseen surprises or delays could substantially change the optimistic dose distribution calculations presented herein.

What to do with all those Cesium-fortified tea leaves

Adding insult to  injury, farmers in Kanagawa prefecture are not only stuck with acres of unsellable, hazardous tea leafage, but have been tasked to round it all up for transportation and disposal.  NHK mentions that "The prefectural government has asked farmers to place the harvested leaves as far as possible from the trees until it decides with the central government how to dispose of them". 

At 550 Bq/kg, you can bet some hefty exposures are emanating from the same amount of leaves you could rake up from a big back yard.  It will be interesting to see what happens when the new crop of tea leaves come out.  I'm sure these farmers - whose livelihoods depend on selling the leaf - are hoping that levels of Cesium will be below the danger threshold when the next crop turns up.  Water measurements per prefecture posted at atmc.jp didn't predict this problem, so soil sample measurements would probably not help much either.  Farmers will just have to wait and see.

I think the reason the local government has asked them to set all the leaf away from everything and wait for further instruction is because they have absolutely no experience with this kind of problem, and are clueless about how to handle it.  Cs-137, with a half-life of 30 years, makes this stuff a health hazard for a very long time.  Where should they dump it?  Or bury it?

The last thing they want to do is burn or incinerate it.  The isotope won't get destroyed, and everything goes airborne, just to travel to different locations and contaminate everything else there.

Geiger counter readings in Fukushima this morning

High

View this stream here

This video seems like it was recorded in a non-exclusion zone (okay to live) area to me.  Lots of cars are passing by in the background.  4.32 microSv/hr is a very high dose rate for the general population to be exposed to.  It comes out to 37.8 milliSv/yr.

20 milliSv/yr in air is supposedly the public limit in those areas, yes?

__________________________________________________________________________________

Recently it was Kanagawa, now it's Ibaraki with high Cesium levels in tea leaves

"The government said radioactive cesium of 894 becquerels per kilogram was detected in green tea leaves picked May 15 in Sakai and that of 570 becquerels per kilogram in Daigo in green tea leaves picked May 14, compared with the official interim limit of 500 becquerels per kilogram."

That May 8th venting was pretty uneventful, but...

This is kind of interesting

Amounts are still very, very low at 1/100,000 of a Becquerel per cubic meter.

Edit: More Tepco data to further support the theory:

Excellent article on how working conditions are deteriorating at Fukushima Dai-ichi

Here's part of a recent testimonial from a veteran worker at the plant. From Mainichi Japan:

"Safety rules and procedures at the stricken Fukushima No. 1 Nuclear Power Plant are being gradually relaxed, spreading anxiety and confusion amongst workers, according to a worker at the plant.

He says now that the weather has grown warmer, wearing the full set of protective equipment, mask and all, is "like wearing a sauna suit." After a while, sweat a few centimeters deep collects in the mask, and "many people have collapsed from heat exhaustion."

"We were told that if we start feeling like we can't take the heat anymore, we should 'squat, calm down and breathe deeply.' Really, though, the limit is only about two to three hours. Once summer comes, things will be even tougher," he said.

"Right now anything goes, because what's considered most important is to stop the situation at the plant from getting worse, even if that means some smaller things get overlooked," said the worker. He added, however, "It's frightening. I wonder how much radiation I'll be exposed to from here on.""

In any war, good morale is a crucial factor in achieving victory, and that's what worries me here.  Success will have to come by means of a sense of duty, because it doesn't seem like they can pay these guys enough.

More on why seawater infiltrated the cooling system at the Hamaoka plant

The above is a nice infographic from Asahi News and its associated article.  I wasn't aware of this yesterday, but seawater is used at the plant to condense (convert back to water) massive amounts of steam that are produced by the reactor.

Once the steam is converted back to water, that water is sent back into the reactor to resume the cooling process. The piping for each task is separate, one system is dedicated for water coming from the ocean and the other for the reactor, but they occupy a common area within the condenser.

Since there is always a risk of damage to pipes and possible entry of salt water into the fresh water reactor system, sensors and ion exchange purifiers are set-up to detect abnormal concentrations of saline, and eliminate very small amounts from solution until the problem can be fixed. 

The big questions here - what caused the leak, and why didn't the sensors pick it up sooner, resulting in 400++ tons of water contaminating the reactor side of the system?  Are the sensors also broken or was someone not paying attention to the computer screen?  My contention is that coming off the heels of Fukushima, this sort of oversight and poor reaction time should not be happening.  The way Murphy has made his rounds around the country, they are lucky it didn't escalate into a bigger problem.

The live streaming geiger counters located in Japan have some crazy range, jumpy behavior

View the live streams by clicking the link on the sidebar, or click here

Most of the readings from the locations above are usually within normal limits, save the Fukushima stream (bottom center).  There are times, however, when i notice massive 50-100% increases in levels within a very short time frame.  Just earlier today, i saw the Fukushima GC shoot up from the .30 level all the way above 1.5, bounce around erratically for a time, and then resume it's normal range of .20-.50.  A few of the Tokyo locations will occasionally increase or decrease 50% on a dime.

Observations with my unit here in the Philippines are steady rates that change in small increments (.01-.02 at the most).  Not much jumpiness at all, though indoors tends to read slightly higher than outdoors.  Although readings may be comparable here as with certain areas in Japan, there is definitely a different sort of stasis and dynamic with the air here vs there, and it's obvious.  The radioactivity in the air there is causing the volatility in readings.

If you want an appreciable exposure rate in Japan, you're better off obtaining a cumulative over a 24 hour period and dividing it up to get an average hourly rate.  The range is pretty nuts.

What is 400 tons of seawater doing in the cooling system at the Hamaoka nuclear plant?

Couldn't help but notice the waves. Might actually be surfable there

From NHK:

At the Hamaoka nuclear power plant in central Japan, seawater has been found in coolant at one reactor.

Five nuclear reactors at the Hamaoka plant in Omaezaki City, Shizuoka Prefecture, were all shut down on Saturday due to concern that a massive earthquake might hit the area. The move was in line with a request by Prime Minister Naoto Kan.

In the course of shutdown, plant operator Chubu Electric Power Company found impure substances in coolant water at the No.5 reactor.

The company reports damage to a pipe connected to a condenser, a system that turns the steam generated by a nuclear reactor to water through the use of seawater.  Chubu Electric Power Company says 400 tons of seawater may be mixed into the cooling water that goes through the reactor.

It says 400 tons would not severely affect the reactor, and that no radioactive substances were detected outside the building.

But in order to prevent the reactor being eroded by seawater, the operator will take measures to remove salt from the cooling water.

Edit:  Here's slightly more info about what happened:

"Chubu Electric Power Co. said Sunday that trouble with the cooling systems at the Hamaoka power plant prevented its No. 5 reactor from achieving a cold shutdown for about two hours but did not result in the release of radiation.

The problem at the coastal plant in Shizuoka Prefecture was caused by seawater that leaked into a steam condenser at the reactor. The condenser is a device used to cool the steam as it comes out of the turbines and turn it back into water.

The problem prompted the utility to switch to another system to cool and stabilize the reactor, which achieved cold shutdown status shortly past noon, it said."

How on earth did they allow seawater to leak in, especially since they have had months after the quake to safety check all systems?  Did they botch the shutdown procedure? After what they've learned from Fukushima, this should not be happening.

Latest reactor 1 temperatures, with diagram

Take note of the 'note'

Source: TEPCO

Basically, Tepco admits to the fact that it's hard to be confident with some of the data, but marginal data is always better than no data

_________________________________________________________________________________


More on the unit 3 reactor

The WSJ online reports that "substantial damage to the fuel cores at two additional reactors of Japan's Fukushima Daiichi nuclear complex has taken place", "further complicating the already daunting task of bringing them to a safe shutdown while avoiding the release of high levels of radioactivity".

It also mentions that "the pressure vessel a cylindrical steel container that holds nuclear fuel, "is likely to be damaged and leaking water at units Nos. 2 and 3", and that "there could be far less cooling water in the pressure vessels of Nos. 2 and 3, indicating there are holes at the bottom of these vessels, with thousands of tons of water pumped into these reactors mostly leaking out".

Units 1,2 and 3 may all be in the same boat.

Missing water located in the Unit 1 reactor basement

Unacceptably low levels of water within the unit 1 reactor pressure vessel have dogged TEPCO since the beginning of the crisis. After increasing rates of water injection for weeks on end with no appreciable increase in levels within the RPV or the containment vessel, Tepco engineers have been hard pressed to figure out where the water had gone. After initial reports that 3000 tons of water were 'missing', NHK now confirms that most of the water now occupies the unit 1 basement - and it's a whopping 4.2 meters deep.

Efforts to problem solve reactor woes are understandably difficult and dangerous, as seen by this recent chart of dose rates within the unit 1 reactor area.  The southeast corner is reading extremely high, as much as 2000 milliSievert/hour at one specific location.

In an interesting development, Tepco has plans to cover the unit 1 building with "a polyester sheet" that "will be attached to steel frames, enclosing the 50-meter-tall building. The company says the cover can withstand strong winds. TEPCO also says it will install a ventilator with a filter to capture radioactive materials that would otherwise be concentrated inside."

To minimize radiation exposure among its workers, the company says the steel frames will be pre-assembled as much as possible, shortening the set up time at the plant. Whether this tent and it's associated ventilation system will actually improve the working environment in unit 1 remains to be seen.  One thing it will certainly accomplish?  Block the public's view of what goes on at unit 1.

Update: You may want to pay attention to this development. Boric acid is now being injected into reactor 3, where temperatures have been rising and water levels have been falling. We need some follow up on that decision, and i hope it's not out of some fear of re-criticality.  Read the Tepco update here

Latest CTBTO monitoring registers another spike in radioactivity, possibly from venting that took place on May 8th

A third worker dies at Japan's troubled nuclear plant - Cause unknown

"(Reuters) - A worker at Japan's tsunami-crippled Fukushima Daiichi nuclear power plant died on Saturday, plant operator Tokyo Electric Power Co said, bringing the death toll at the complex to three since a massive earthquake and tsunami in March.

The cause of the death was unknown. The man, in his 60s, was employed by one of Tokyo Electric's contractors and started working at the plant on Friday. He was exposed to 0.17 millisieverts of radiation on Saturday, Tokyo Electric said.

The Japanese government's maximum level of exposure for male workers at the plant is 250 millisieverts for the duration of the effort to bring it under control.

The worker fell ill 50 minutes after starting work at 6:00 a.m. on Saturday (2100 GMT on Friday) and brought to the plant's medical room unconscious."

Was it due to heat exhaustion, a pre-existing medical condition exacerbated by difficult working conditions at the plant, or unknown and unaccounted for exposures to radiation?  The latter seems the least likely, but they better find the cause of death, and fast.

Read the story here

Update: Suspected cause of death is heart attack

That sludge radioactivity problem in Japan is apparently ongoing; more highly radioactive amounts were recently detected in Gunma Prefecture

Sludge treatment facility

First back in March, it was Koto Ward that shipped out sludge just buzzing with radioactivity at 170,000 Bq/kg.  Then in that same month, two other Tokyo Wards reported intense radioactivity coming from incinerator ash in the range of 100,000 to 140,000 Bq/kg.

This past Friday, a water sanitation facility in Maebashi, Gunma Prefecture detected radioactive Cesium at levels of 41,000 Bq/kg coming from incinerator ash that the water facility had collected earlier that week.  Monitoring is ongoing.

I hope the Japanese government will start dose monitoring these waste water treatment facility employees, because these circumstances may put them at risk of considerable exposure.  Ash gets easily airborne, travels everywhere in particulate form and poses a seriously risk of inhalation and ingestion to those exposed.

Not to mention the exposure dangers for employees who are loitering next to a truckload of sludge.

Story here

___________________________________________________________________________________

Another 6.2 earthquake near the area of Fukushima

550 Bq/kg of Cs-137 detected in Tea Leaves in Kanagawa Prefecture south of Tokyo

"TOKYO—A prefecture just south of Tokyo said it had detected higher-than-permissible amounts of radioactive material in tea leaves, in a reminder that Japan's radioactive-contamination problems are far from over.

According to Kanagawa officials, a sample of tea leaves collected May 9 from the city of Minamiashigara, in the western part of the prefecture, was found to contain 550 becquerels of cesium per kilogram in the first test; the second test of the same sample detected 570 becquerels. The difference between the two readings is within the margin of error in such tests, the officials said." Full story here

The interesting thing is, you would never know from Kanagawa's official water readings.