Fukushima Japan earthquake - contamination & consequences outside Fukushima NPP

[tsutsuji]

Tepco is being careful not to release the ground water that leaked into the basement of unit 6 into the sea, and stores that water into tanks : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110602_01-e.pdf

Have Tepco or the Japanese authorities or independent researchers published data about the radiation released into the sea through rain and rivers ? Or can we be confident enough that the radioactive materials are staying in the ground once they have deposited ?

Isn't there a contradiction between, on the one hand, storing the plant's ground water into tanks, and on the other hand, letting the ground water from elsewhere in Fukushima Prefecture flow to the sea ?

 

[Luca Bevil]

Tepco is being careful not to release the ground water that leaked into the basement of unit 6 into the sea, and stores that water into tanks : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110602_01-e.pdf

Meanwhile, I guess most rivers in nearby areas are releasing "low level radioactive materials" in perhaps much lower concentrations, but in larger amounts.

Have Tepco or the Japanese authorities or independent researchers published data about the radiation released into the sea through rain and rivers ? Or can we be confident enough that the radioactive materials are staying in the ground once they have deposited ?

Well I would say that we can be confiddent that just the opposite is true.
Mitigation shuld be the name of the game, instead what I see are limited measures and slipping schedules.

Chernobyl was a tragedy, likely it will remain the worst accident in industrial history but at least you got a sense of an "all-out" effort being carried out after the fact.

for Fukushima I often feel efforts and resources are employed on a "we can no longer delay this" basis

 

[swl]

Plenty of radioactive material has shown up in sewage sludge in Tokyo, so I am going to assume that there is plenty of Cesium being washed into the groundwater and ocean.

TEPCO and the government might wish they could avoid the contradiction, (of stopping contaminated water from the plant vs letting the contaminated water outside the plant flow unobstructed) but they can do nothing to stop the rain and snow water from rinsing the radiation down to the sea or underground. On second thought, maybe they are hoping that the rain will help reduce their cleanup costs in areas outside the plant.

As someone has already mentioned, the final containment vessel is the ocean.

 

[jlduh]

It seems that I'm not the only person worried about possible inadequate assessment of global human contamination (including inhalated and ingested contamination) through only external measurements in mSv/h, currently used to decide where to evacuate...

Fukushima prefecture is going to make more whole body scans, but they have only... ONE equipment to do it!

http://www3.nhk.or.jp/daily/english/02_27.html

Fukushima to check internal radiation exposure

Fukushima Prefecture has decided to check the internal radiation exposure of residents near the crippled Fukushima Daiichi nuclear power plant and adjacent areas with high radiation levels.In Fukushima, there are mounting concerns among locals over the health effects of radiation after the nuclear accident at Fukushima Daiichi plant.

The prefecture had already decided to conduct health checks on all citizens, but will now assess residents' internal exposure to radiation from breathing and eating.

The targets will be residents near the plant and people who live in adjacent areas with high radiation levels.A device called a "whole-body counter" will be used to precisely measure radiation.But the prefecture currently has only one device and can screen just 10 people per day. It is urging research institutes and others with the device outside the prefecture to help them.

 

[jlduh]

A clear example that the way external radiation is measured doesn't always reflect the total dose including internal radiation ingested or inhalated:http://www3.nhk.or.jp/daily/english/03_32.html

2 TEPCO workers exposed to radiation above limit

Experts say 2 workers at the troubled Fukushima Daiichi nuclear power plant have been exposed to high levels of radiation exceeding the safety limit set by the government.

[...]

The test by the National Institute of Radiology Sciences shows the estimated internal radiation absorbed by one man in his 30s is between 210 and 580 millisieverts, while another man in his 40s received between 200 and 570 millisieverts.

An earlier test showed the younger man had received about 74 millisieverts of external radiation and the other about 89 millisieverts.

The latest test results indicate that the amounts of radiation for the both workers exceeded the limit of 250 millisieverts set for emergency situations. The limit was raised by the government from 100 millisieverts soon after the accident.

[...]

TEPCO says safety measures, such as wearing protective clothing and masks, may have been inadequate just after the accident. It says it wants to conduct detailed tests on about 150 workers who were involved in similar operations.

 

[ThomS]

http://ex-skf.blogspot.com/2011/06/radiation-in-tokyo-as-measured-by.html

http://www.jcptogidan.gr.jp/html/menu5/2011/20110525195904.html

Simply wow! Regardless of the source or if the JCP has other political motivation, this data is worrisome.

 

[razzz]

The link is to ex-skf.blogspot.com...
http://ex-skf.blogspot.com/2011/06/fukushima-nuke-accident-wspeedi-shows.html"

When it comes to fallout data, either TEPCO has to stop throwing people under the bus or get a bigger bus.

 

[clancy688]

The link is to ex-skf.blogspot.com...
http://ex-skf.blogspot.com/2011/06/fukushima-nuke-accident-wspeedi-shows.html"

When it comes to fallout data, either TEPCO has to stop throwing people under the bus or get a bigger bus.

In my opinion, EX-SKF misunderstands the data he found. Those are only mathmatical simulations as for how a cloud of Krypton-85 would've behaved if there would've been one.

There are only two things we can derive from those images: Direction of a possible Krypton-85 plume that day and densitiy over distance based on initial release.
It doesn't show us what really happened.

Krypton-85 is a noble gas. It has a very, very, very short biological half life (the body throws it out as soon as it gets in) and is a beta decayer (it's only a problem if it's inside), so there is probably little to none significance for any health damage.
The nuclear waste facilities Sellafield and La Hague are releasing Krypton gas in the magnitude of hundreds of PBq every year. The converted release of C137 and I131 at Fukushima was 630 PBq. The conversion factor for noble gases (Krypton-85) is zero. (according to the INES manual)
So IAEA is apparently thinking of Krypton-85 as "not dangerous at all".

 

[razzz]

In my opinion, EX-SKF misunderstands the data he found. Those are only mathmatical simulations as for how a cloud of Krypton-85 would've behaved if there would've been one.

There are only two things we can derive from those images: Direction of a possible Krypton-85 plume that day and densitiy over distance based on initial release.
It doesn't show us what really happened.

Krypton-85 is a noble gas. It has a very, very, very short biological half life (the body throws it out as soon as it gets in) and is a beta decayer (it's only a problem if it's inside), so there is probably little to none significance for any health damage.
The nuclear waste facilities Sellafield and La Hague are releasing Krypton gas in the magnitude of hundreds of PBq every year. The converted release of C137 and I131 at Fukushima was 630 PBq. The conversion factor for noble gases (Krypton-85) is zero. (according to the INES manual)
So IAEA is apparently thinking of Krypton-85 as "not dangerous at all".

Do you think those wind pattern arrows are made up? We already know what happened, just waiting for the forthcoming confirmation. Maybe in another month or two if ever.

 

[clancy688]

Do you think those wind pattern arrows are made up? We already know what happened, just waiting for the forthcoming confirmation. Maybe in another month or two if ever.

Nope, they are real. What's unreal is the actual dose or amount of the radioactive source.

If there's a 1Bq/h release we get ~ 1^-12 Bq/m² in Tokio. I don't know if that scale is linear, but let's assume it is. Then for 1000000 Bq/m² Kr-85/I-129/Cs-137 you'd need a release of 10^18 Bq/h.
So if we'd actually KNOW how much material the reactors were spitting out EVERY HOUR during the first two weeks, we could make use of these cards and calculate what radiation hit Tokio. But we don't. And so those cards tell us nothing except "the wind was blowing in direction x at time z" - which we already know.

But again we're straying offtopic with something which fits better in the contamination and consequences thread...

 

[etudiant]

Nope, they are real. What's unreal is the actual dose or amount of the radioactive source.

If there's a 1Bq/h release we get ~ 1^-12 Bq/m² in Tokio. I don't know if that scale is linear, but let's assume it is. Then for 1000000 Bq/m² Kr-85/I-129/Cs-137 you'd need a release of 10^18 Bq/h.
So if we'd actually KNOW how much material the reactors were spitting out EVERY HOUR during the first two weeks, we could make use of these cards and calculate what radiation hit Tokio. But we don't. And so those cards tell us nothing except "the wind was blowing in direction x at time z" - which we already know.

But again we're straying offtopic with something which fits better in the contamination and consequences thread...

The charts show the level of dilution for a 1 bq/hr source term and suggests that the source level was diluted by about 10**12th by the time it reached Tokyo. Perhaps that is enough information for someone who was monitoring the actual levels reached in Tokyo to work back to derive the corresponding emission level at the source.

 

[clancy688]

The charts show the level of dilution for a 1 bq/hr source term and suggests that the source level was diluted by about 10**12th by the time it reached Tokyo. Perhaps that is enough information for someone who was monitoring the actual levels reached in Tokyo to work back to derive the corresponding emission level at the source.

Fascinating... it never occurred to me to calculate backwards in order to get the source term. Thanks for that hint.

Does somebody know where to find airborne activity measurements for Tokio...?


P.S.
thx @ Borek for moving :)

 

[jlduh]

Fascinating... it never occurred to me to calculate backwards in order to get the source term. Thanks for that hint.

Does somebody know where to find airborne activity measurements for Tokio...?


P.S.
thx @ Borek for moving :)

I have this table with data it seems from CTBTO measurement network, but as i don't speak japanese i cannot give precisions of where it was measured, i just read the numbers for the various isotopes!

http://www.cpdnp.jp/pdf/110603Takasaki_report_May30.pdf

But this is interesting as you can see that there has been three spikes in the measurements:

- One (the biggest) between March 15 and 16
- One between March 20 and 21 (which fits the "black smoke coming from N°3" period)
- One between March 29 and 30

For Tokyo I had a nice curve but i don't find it anymore, damn...

You have also these graphs (but not for Shibuya is Tokyo), but difficult to read:

http://www.netimago.com/image_207151.html

http://www.netimago.com/image_207151.html

You find the same pattern here:

http://tkynt2.phys.s.u-tokyo.ac.jp/news_internal/graph_0603v1_all_eng.pdf

Basically, Tokyo was around 0,37 micro Sv/h for March 16, and then 0,17 micro Sv/h after the event of March 21 st.



Found from this page with a lot of links, maybe you'll find what you need:

https://sites.google.com/site/radmonitor311/top_english#11

 

[clancy688]

Nice... but despite what I wrote before I am being indecisive as to how to apply those measures and cards and stuff exactly...

I'm sure what ZAMG did was basically the same... they got a source term of 4 * 10^16 for C137 on March 14th.

 

[onkeljonas]

Regarding the thresholds for cleanup of contaminated soil in areas with children:
As far as I understand, the quoted doserates are calculated purely for external exposure.
If true, this ignores that children (especially small children) ingest significant amounts of soil compared to most adults. The obvious (if not only) reason for this, is the fact that children at certain ages simply eat soil.

So my question is: Given known concentrations of radioisotopes in topsoil, how would we calculate dose estimates (from internal exposure) for different amounts of ingested soil?

P.S. First post here - glad to have found a forum concerned with reality more than spin :)

 

[swl]

From the power plant thread...

My understanding is that the reported number DO NOT include releases to the Ocean and only air releases and thus the statement that the worse is over. When they consider the true releases to the Ocean, my gross napkin calculations say that they already got Gold!

I don't know about the overall gold, but it seems like this accident is already the ocean contamination champion.

Does anyone know how ocean contamination from Fukushima compares to contamination from bomb testing in and above the ocean?

My wife was recently reading an article from a Japanese women's magazine that was advising readers to avoid eating seafood bones and shells because of the risk of Strontium contamination. It is impressive how so much food/water from so many areas is contaminated now. It makes it that much more difficult to feed the kids (here in Japan) a healthy diet.

 

[etudiant]

From the power plant thread...



I don't know about the overall gold, but it seems like this accident is already the ocean contamination champion.

Does anyone know how ocean contamination from Fukushima compares to contamination from bomb testing in and above the ocean?

My wife was recently reading an article from a Japanese women's magazine that was advising readers to avoid eating seafood bones and shells because of the risk of Strontium contamination. It is impressive how so much food/water from so many areas is contaminated now. It makes it that much more difficult to feed the kids (here in Japan) a healthy diet.

No easy answer, unfortunately.
Airborne bomb testing ended 50 years ago, with only about 500 tests, most of which were fairly small and involved around 100kg of nuclear material or less. There were some big multi megaton tests, involving tons of uranium and plutonium to give the hydrogen fusion its kick, but these were few, less than 50.
By contrast, Fukushima involves about 250 tons of melted reactor fuel, probably an amount equal to all the atmospheric A bomb tests put together. Plus Fukushima just happened, so the radiation is at its peak.
The complicating issue is that the former USSR had a very relaxed attitude to nuclear power. Old nuclear submarine reactors were scrapped by dumping them into the ocean, along with other nuclear wastes. There are some horror stories of nuclear waste casks getting pounded with hammers to help them fit on some waste fuel barges. Norway and Japan both helped fund cleanups of some of the worst pollution, but the records of what was dumped are very suggestive that a lot was missed.
So the impact of this disaster is a step on a continuum, it is not a new dimension in pollution.

Your problem is that you are getting your seafood from Japanese waters, shortly after a major pollution event, with food safety supervised by a government that is very reluctant to sound the alarm just because some food is more contaminated than before. Afaik, the safest foods will be the pelagic fish, tuna, albacore etc, simply because they are caught far from Japan's shores. By contrast, shrimp, clams, mussels and similar coastal seafood may be problematical. Even seaweed, a wonderful food, may be best skipped for a couple of years, unless you can lay in a stash of pre March 11 product.
It is pointless imho to buy a geiger counter to check your food, the most damaging radiation is alpha particles, which is stopped even by a tissue and which is not detected that readily, but which is most likely to be harmful if ingested. The Russian dissident poisoned by polonium some years back died from the effects of internal alpha particle irradiation.

 

[razzz]

From the power plant thread...



I don't know about the overall gold, but it seems like this accident is already the ocean contamination champion.

Does anyone know how ocean contamination from Fukushima compares to contamination from bomb testing in and above the ocean?

My wife was recently reading an article from a Japanese women's magazine that was advising readers to avoid eating seafood bones and shells because of the risk of Strontium contamination. It is impressive how so much food/water from so many areas is contaminated now. It makes it that much more difficult to feed the kids (here in Japan) a healthy diet.

Better to read the site http://ex-skf.blogspot.com/" as he tries to keep up with all aspects of Japan dealing with nuclear power and fallout involving tea. seaweed, to cement, etc. Also. maybe check the Greenpeace site for information as they asked Japan for permission to test seawater and fish near the accident and were refused but try to keep track of the fallout.

On a sensor, the difference in readings from an adult holding it, to a child holding it, to laying on the ground can be 100 fold. Defenseless children are more susceptible to fallout just being nearer the ground as dust kicks up first to their level.

 

[SteveElbows]

http://www.zerohedge.com/article/ph...t-mortality-northwest-cities-meltdown-might-b
"The recent CDC Morbidity and Mortality Weekly Report indicates that eight cities in the northwest U.S. (Boise ID, Seattle WA, Portland OR, plus the northern California cities of Santa Cruz, Sacramento, San Francisco, San Jose, and Berkeley) reported the following data on deaths among those younger than one year of age:

4 weeks ending March 19, 2011 - 37 deaths (avg. 9.25 per week)
10 weeks ending May 28, 2011 - 125 deaths (avg.12.50 per week)

This amounts to an increase of 35% (the total for the entire U.S. rose about 2.3%), and is statistically significant. Of further significance is that those dates include the four weeks before and the ten weeks after the Fukushima Nuclear Power Plant disaster"

I took a look at the data and as a result I find this article to be a disgrace.

Im not sure why they picked the locations they did, just a handful from a very long list, and why for example they did not look at the data for the entire US region described as 'Pacific'.

If I look at data for the Pacific cities deaths of infants under 1 year of age:

4 weeks ending March 19 2011, there are an average of 23.5 deaths per week
10 weeks ending May 28 2011, there are an average 23.6 deaths per week

Now let's compare to 2010:

4 weeks ending March 20 2010, there are an average of 26.25 deaths per week
10 weeks ending May 29 2010, there are an average of 25.9 deaths per week

Now looking at the 2010 averages for just the cherry-picked cities they used:

4 weeks ending March 20 2010, there are an average of 11 deaths per week
10 weeks ending May 29 2010, there are an average of 12.2 deaths per week

And that 12.2 average is brought down by the fact that during this period 4 weeks of San Jose data is missing. If for example I assume that the number of <1 year deaths for the missing San Jose weeks is just 2 per week, then the average climbs to 13 deaths per week.

 

[SteveElbows]

I have this table with data it seems from CTBTO measurement network, but as i don't speak japanese i cannot give precisions of where it was measured, i just read the numbers for the various isotopes!

http://www.cpdnp.jp/pdf/110603Takasaki_report_May30.pdf

But this is interesting as you can see that there has been three spikes in the measurements:

- One (the biggest) between March 15 and 16
- One between March 20 and 21 (which fits the "black smoke coming from N°3" period)
- One between March 29 and 30

The Japanese report to IAEA makes mention of the March 15th stuff.

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_vi.pdf Page VI-3

An air dose rate of about 3 mSv/h was measured near MP-6 at 21:00 on March 14. This rate decreased once but increased again after 06:00 on March 15, and a dose rate of about 12 mSv/h was measured at 09:00 on the same day. In Unit 2, a decrease in D/W pressure was observed due to a wet venting at 21:00 on March 14, and it is estimated that radioactive materials were discharged from Unit 2 because of a blast sound from the unit at around 06:00 on March 15 and a subsequent S/C pressure decrease. At around the same time, however, an explosion occurred in the reactor building of Unit 4, thus a clear distinction cannot be made between them. Since wind often blew from the north in this period, the plume was very likely to have blown to the south, and agencies including the Japan Atomic Energy Agency (JAEA) in Tokai village, Ibaraki prefecture observed a rise in the dose rate and detected radioactive iodine, etc. in the atmosphere.

I have a particular interest in this stuff because early on they were prepared to acknowledge reactor 2 containment damage but not containment damage at other reactors, and also because their estimates of percentage of various substances released into environment seem to have a much wider range for reactor 2 than the others. So I ponder whether reactor 2 may have caused more environmental woe than the others.

 

[ElliotLake]

SteveElbows: I don't know about the Cali sites, but Portland and Seattle are large seacoast cities and.. Boise is I believe the only one in Idaho where there are sensors in use. Plus, standing under the Rockies, it catches Pacific weather as well. So, seem sensible to me to check those sites. Interpretation of data I couldn't say.

 

[clancy688]

I think that fits here better:

A discussion in https://www.physicsforums.com/showpost.php?p=3352430&postcount=121" thread raised the question whether the Hiroshima and Nagasaki contaminations were worse or not.

I searched for the answer and found a very interesting document by the US military:

http://www.dtra.mil/documents/ntpr/relatedpub/DNATR805512F.pdf

It's dealing with radiation doses for US occupational forces in late 1945 in Nagasaki. On page 58 they calculate surface contamination rates for several isotopes at a location one mile east of and 45 days after the blast. The location was shielded, so there's no neutron activation, only surface deposition.
They get 0.37 uCi/m², or ~14.000 Bq/m² Cs-137. In Fukushima, large areas are contaminated with 1.000.000 to 30.000.000 Bq/m² Cs-137...

Overall they get 340 uCi/m², which's around 13.000.000 Bq/m², but most of those isotopes are short living ones which are gone after 1-2 years.

So at least for me it looks like the Fukushima contamination is way worse than the Nagasaki bomb contamination. Apparently, the blast produced many short living fission products, but less long lived.

I think that's to be expected. A nuclear reactor's core load fissures over a period of months and creates a hundred or thousand times more energy a Nagasaki sized nuclear bomb releases during that interval.
Which means that there's a hundred or thousand times more fission products which accumulate, especially the long living ones. But I'd still be interested in more documents regarding the surface contamination of Hiroshima and Nagasaki.Btw: Don't know if it's been posted before, but the french report linked in the first post is available in english now.

http://www.irsn.fr/EN/news/Documents/IRSN-Fukushima-Report-DRPH-23052011.pdf

 

[Borek]

So at least for me it looks like the Fukushima contamination is way worse than the Nagasaki bomb contamination.

Hardly surprising. If not for other reasons, compare mass of the bomb with mass of the fuel in the reactor.

 

[clancy688]

Hardly surprising. If not for other reasons, compare mass of the bomb with mass of the fuel in the reactor.

Apparently it was surprising for a certain user who should know better... that's why I posted it here... ^^;

 

[clancy688]

I have one question regarding the IRSN evaluation I posted:

Do I understand correctly, that most of the paper is only about the population which's outside the 20km zone?
So there are up to ~70.000 people outside the 20km zone who are in need of evacuation and ~85.000 people inside the 20km zone who have already been evacuated? All in all 110.000 to 150.000 people who'll lose their homes forever?

 

[jlduh]

I have one question regarding the IRSN evaluation I posted:

Do I understand correctly, that most of the paper is only about the population which's outside the 20km zone?
So there are up to ~70.000 people outside the 20km zone who are in need of evacuation and ~85.000 people inside the 20km zone who have already been evacuated? All in all 110.000 to 150.000 people who'll lose their homes forever?

Some days ago, there was a discussion on the forum about comparing the impacts between a majpr accident in a nuclear plant and any other industrial accident. I was saying that there is no other industrial accident that has a so big impact on social communities than a nuclear one (I'm talking about a big one like this one for example, which could have been much worse in fact, I think that even some professionals from nuke industry start to, hardly but finally i would say, recognize it -think of one or several completely explosed SFP with fuel thrown in the air and falling around, with all he domino effects to anticipate). Some people were arguing that chemical accident like Bhopal did more dead people immediatly than Fukushima, which is true if you consider the time factor.

But can you list one single other INDUSTRIAL accident that creates what you describe, currently 110 to 150 000 people losing their homes? I don't...

That's why in my mind, nuke industry is no way an industry like the others. The potential social impacts are too big.

 

[clancy688]

Isn't their line of thought being that populations should be evacuated according to the shapes on the maps rather than according to perfect round shapes centered on the plant ?

That's exactly why I'm confused... if you take a look at the LAST page of the paper, you'll find a comparison between Chernobyl and Fukushima.

They say there's an "inital evacuation zone at Chernobyl (30km, 135.000 people) and Fukushima (20km, 85.000 people).
And then there are "strictly controlled zones" or "evacuation zones" with 270.000 people at Chernobyl (that's the number they're often quoting in the text as being evacuated) and 70.000 at Fukushima (also often quoted).
It's my understanding now that those 135.000 and 85.000 from the "inital evacuation zones" do NOT include the numbers from the "strictly controlled zones".

They say the following on page 4:

The number of Japanese people living in the most contaminated areas outside the initial 20 km radius
evacuation zone around the Fukushima plant (874 km2 with caesium 134+137 deposits higher
than 600,000 Bq/m2) was estimated to 70,000 people including 9,500 children of 0-14 years in age.

My interpretation is that we're dealing with TWO zones, both at Chernobyl and Fukushima. The first one is a strict 30/20km perimeter which was evacuated IMMEADIATELY after the accident, regardless of actual radiation levels.
The second one is an extension of the first one based on actual radiation data. And while the first was evacuated within the first few days of the accidents, the second one was and will be evacuated over a course of months.
But both zones will stay off limits.

 

[tsutsuji]

I have one question regarding the IRSN evaluation I posted:

Do I understand correctly, that most of the paper is only about the population which's outside the 20km zone?
So there are up to ~70.000 people outside the 20km zone who are in need of evacuation and ~85.000 people inside the 20km zone who have already been evacuated? All in all 110.000 to 150.000 people who'll lose their homes forever?

table 1 page 18/28 (pdf page number 17 , http://www.irsn.fr/EN/news/Documents/IRSN-Fukushima-Report-DRPH-23052011.pdf ) says that the 69,400 population figure applies to "Affected population (excluded the no-entry zone)".

Conversely, among the people already evacuated from the no-entry zone, those from the North and those between 15 and 20 km away in the South-West where the contamination is low should be able to go back home. So you should ultimately subtract that number from the total displaced population.

 

[clancy688]

Conversely, among the people already evacuated from the no-entry zone, those from the North and those between 15 and 20 km away in the South-West where the contamination is low should be able to go back home. So you should ultimately subtract that number from the total displaced population.

Hm, let's do a "best case/worst case" calculation:

Let's say from those 70.000 mentioned in the report, only ~25.000 need to be evacuated (because the government tells <20mSv/a is still okay or something like this). In the 20km zone, the towns of Tomioka, Okuma, Futaba and Namie are probably in need of permanent abandonment. They have a total population of 55.000 people.

So the "best case" may be that 80.000 people lose their homes and the worst case 150.000.http://en.wikipedia.org/wiki/Futaba_District,_Fukushima" will probably nearly become a ghost district. Of all cities (total population: 75.000) only the villages of Kawauchi. Naraha and Hirono (only 17.000 people) lie outside the >1MBq/m² zone.

 

[tsutsuji]

To this contamination map by Yukio Hayakawa @ Gunma University:

http://maps.google.co.jp/maps/ms?ie...2043,140.097656&spn=3.203668,4.257202&t=p&z=8

In my opinion no one has officially explained nor factored in the full significance of the contaminated green tea from Shizuoka (150km south west of Tokyo) yet, however those SPEEDI plumes just kiss Shizuoka too.

Thank you for the link. I think the 0.5 μSv/h　spot centered in the North of Chiba prefecture, extending west on both sides of the Edogawa river could have a link with the 22 March water crisis when significant levels of contamination were found in the Kanamachi water purification plant, which takes water from the Edogawa.