Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

<..>
But these smoke events appear to come too late, because the peak was already showing up as early as at 6 a.m. on that morning in Mito <..>

All right. During the night between March 20th and March 21st, the Hyper Rescue Unit of the Tokyo Fire Department had a long-lasting operation on the plant, it lasted almost 6 hours, and finished about 4 am on the 21st. According to Tepco press relases the unit were doing spraying to the spent fuel pool of unit 3.

(Note: it is my impression that in this period 'spraying to SFP3' could well have been indicated, while the actual spraying was done to the NW corner of unit3, i.e. the opposite corner from the SFP. I haven't figured out why that corner of the building has been needing so much douching).

 

[AntonL]

Underground water is a very sensitive compartment, because it can travel a very long way at quite small speeds, with wery little possibilties to treat the contamination. Then it means pollution of soils and of all the usages by humans of this underground water (drinkable water, agricultural use in the fields, etc.). Depending on the phreatic structure in the area, you can also have pollution of the rivers of course.This is a very tricky situation which is far from "quiet". If you intend "quiet" as no "big boum", yes it is quiet. But some quietness and silence can be worse than impressive images in medias right after the beginning of the catastroph. Tchernobyl has been a high pace disaster (with long consequences), Fukushima turns to be a much smaller pace disaster but with very very long consequences.

Underground water has been analysed once and then conveniently forgotten, at the time of the release of sub-drain or underground water analysis the headlines was the leak into the ocean.

On 31 March Tepco published underground water (or sub-drain) water http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110331e18.pdf

On 4th April following sketch was published by meti explaining sub-drain http://www.meti.go.jp/press/2011/04/20110404003/20110404003-5.pdf which basically is a sub soil drain below foundation level, as we can see from the results major leaking of contaminated water is taking place into the the sub-soil and subsequently into the underground water.

 

[tsutsuji]

All right. During the night between March 20th and March 21st, the Hyper Rescue Unit of the Tokyo Fire Department had a long-lasting operation on the plant, it lasted almost 6 hours, and finished about 4 am on the 21st. According to Tepco press relases the unit were doing spraying to the spent fuel pool of unit 3.

(Note: it is my impression that in this period 'spraying to SFP3' could well have been indicated, while the actual spraying was done to the NW corner of unit3, i.e. the opposite corner from the SFP. I haven't figured out why that corner of the building has been needing so much douching).

It is a pity that the Radiation dose measured in the Fukushima Daiichi Nuclear Power Station[/url] data have a gap between March 20th 3 p.m. : http://www.tepco.co.jp/en/nu/monitoring/11032001a.pdf
and March 21st 0 a.m. : http://www.tepco.co.jp/en/nu/monitoring/11032101a.pdf

 

[rowmag]

On 4th April following sketch was published by meti explaining sub-drain http://www.meti.go.jp/press/2011/04/20110404003/20110404003-5.pdf which basically is a sub soil drain below foundation level, as we can see from the results major leaking of contaminated water is taking place into the the sub-soil and subsequently into the underground water.

I wonder if that could have been a leakage path for hydrogen from, say, Unit 3 to Unit 4...
Though, if so, it seems like hydrogen should also have leaked into the turbine hall. Guess there will be no way of knowing without a full map of underground conduits on-site.

 

[rowmag]

Does anyone know about the use of hydrogen peroxide in BWR's during shutdown. I'm interested in storage (in or out of reactor building), added concentrations in reactor and SFP.

For example:

"Appropriate biocides (hydrogen peroxide) at concentrations up to 1000 ppm were added (to the pool water) to control biofouling."

From: http://www-pub.iaea.org/MTCD/publications/PDF/te_0944_scr.pdf

Also anyone with knowledge about what chemicals might be stored/used (in or near reactor) during BWR shutdown that might interact with hydrogen peroxide (powerful oxidizer).

I have a feeling that hydrogen peroxide may have played a role in the explosion at the Fukushima Diiachi #4 reactor building.

Reactor 4 was undergoing shroud replacement, which uses apparently uses oxalic acid and hydrogen permanganate for decontamination:
http://www.toshiba.co.jp/nuclearenergy/english/maintenance/replace/shroud04.htm

Oxalic acid "reacts explosively with strong oxidizing materials"...
http://www.jtbaker.com/msds/englishhtml/o6044.htm

?

 

[rowmag]

The expertise deployed on this forum to understand the processes which reduced four multi billion dollar reactors to steaming scrap is laudable.
For an outside observer, it would be wonderful if this expertise were also employed looking forward, to help evaluate and understand the challenges and risks posed by the clean up plan.
For instance, Areva is scheduled to have a water processing plant built by the end of June that will process 1200 tons of water/day. There are nearly 70,000 tons currently in the facility, increasing at 500tons/day, so there will be 100,000 tons by the time the plant is operational.
The plant will start to whittle down the flood at about 700 tons/day net once it starts, so it will take 150 days to drain the facility, if all goes well.
That says the cleanup will not begin until very late this year at the earliest.
Is this a plausible schedule? How does it tie into the TEPCO indication that the immediate crisis should be stabilized within 9 months? What are the risks that should be of most concern?

As much as I try to understand what has happened, this is the question that really concerns me. What I really want to know is, when can I stop worrying about this? Right now it seems like they are juggling chainsaws while standing on a banana peel, and the chainsaws are leaking gas. Not yet a stable equilibrium.

As far as I can see, any notion of cleaning things up enough to allow people to do work inside the reactor buildings is hopeless for the time being, which means they will have to restore some kind of cooling loop from the outside before they can even start to think about how to take things apart. Perhaps that means just filtering water from the drainage trenches and feeding that back into the reactors, using some system such as proposed by Areva. I don't know. I really wish I had a brighter idea.

 

[WhoWee]

I wonder if that could have been a leakage path for hydrogen from, say, Unit 3 to Unit 4...
Though, if so, it seems like hydrogen should also have leaked into the turbine hall. Guess there will be no way of knowing without a full map of underground conduits on-site.

Blueprints would be helpfulbut not certain. Any estimate of the leakage rate required as per your idea?

 

[tsutsuji]

Some more details on what they plan to do :

At the No. 4 reactor, it is necessary to reinforce the structure below the temporary storage pool for spent nuclear fuel rods to prevent any possible spillage. However, this task is also expected to be fraught with difficulty.

Apr. 19, 2011
http://www.yomiuri.co.jp/dy/national/T110418004891.htm

 

[jarvik]

Does anyone know the definition of "daily deposition" as mentioned in http://www.slideshare.net/iaea/radiological-monitoring-and-consequences-19-april-2011 ? Is it the difference of the measured radioactivity from soil samples between that day and the day before ? How do "daily depositions" and "gamma dose rates" relate with each other ?

Looking at the slides, daily deposition is in Bq/m2 or decays per second per m2 for ¹³¹I (slide 4) and ¹³⁷Cs (slide 5) which are two fission products that are both produced in abundance by U fission and easy to measure via Gamma ray spectrometry. These and other radioactive isotopes (natural and fission sourced) will contribute a portion of the total gamma dose rate shown in slides 2 and 3. There are of course other fission (⁹⁰Sr ) and natural sourced radioisotopes that will also be present but do not emit gamma rays (i.e. pure beta emitters) and therefore do not contribute to the total gamma dosage.

I assume they have some sort of surface film on a collecting surface to capture the radioisotopes falling down and this is changed and counted in a gamma ray spectrometer on a daily basis.

Looking at ¹³⁷Cs for Ibaraki the cumulative fallout for the time period of April 1-19 is ~2000 Bq/m2. For a frame of reference the cumulative ¹³⁷Cs activity I find in sediment cores from various places (mostly in North America) tends to be 170-1700 Bq/m2. This ¹³⁷Cs is primarily from bomb testing from the 60s so at the time of deposition it would be about double what I measure now so I don't think that level of ¹³⁷Cs deposition seen in April for Ibaraki is likely to be a big issue. Though I'd be interested in the cumulative ¹³⁷Cs activity in Ibaraki since the beginning of the accident and not just since Aprils 1st, and of course all the other radioisotopes that might be coming down (Tc and Sr come to mind).

 

[AntonL]

OFF TOPIC: Farm animals starve in Fukushima exclusion zone - be warned a very disturbing video

 

[jlduh]

Thanks AntonL for the source data concerning contamination of the sub drain water. I heard reported in the medias that I-131 in high concentration was found in the water table 15 meters below ground level of reactor 1, but in fact the table you posted shows that the situation is much worse than that, because some other values (other elements) are also very high, but not only under 1 reactor but under the six ones, even the ones that are not damaged and leaking (5 and 6)! The value of 430 Becquerels/cm3 at reactor 1 is 10 000 times the limit for underground water, so you have an idea of the numbers we are talking about...

The fact that there is also highly contaminated water under 5 and 6 (which are at some fair distance -severel hundred meters- at the north side of the plant, on a second platform) shows that the contamination has already spread around the initial sources throughout the ground water. What would be important now to know is the direction of flow of this water table, especially if it is flowing inland.

Concerning the hypothesis that the reason why there is water in the basement of 5 and 6 turbines building could be an increase of the level of the water table because of cooling water leakage, i would be very surprised (and scared) if it was the case, because it would mean that a huge volume of this water has already gone into the table. Again, that would be very surprising. Not saying i cannot be the case, but really that would be a very bad news.

An alternate hypothesis is that the basements of the different buildings are in fact built into the water table (so there is underground water around the basement in normal conditions). A little bit surprising when you know the difficulties to have concrete waterproof over years in these conditions, but who knows... The fact that the article cited this morning was saying that Tepco was already pumping leaked water from the outside in 5 and 6 basements BEFORE the accident (and that they then stopped because of other priorities on site) could reinforce this hypothesis.

A third hypothesis can also be that the tsunami has modified the water table level and increased its level... That's an other possible factor.

Concerning the calculation done for the time necessary to treat this daily ongoing flooding of contaminated water on site, yes it shows that this Fukushima story is going to last MUCH LONGER than the Tchernobyl one (as far as "liquidation" process) where the sarcophage was in place one year after the explosion (but with almost 1 million workers who have gone through the site to build it in between). Don't know how many workers are now on Fukushima site, but this is a very different scenario, although in the first class mess category...

At the time of the Tchernobyl accident, all the western experts from nuclear industry where criticizing the russians for their inexperience and stupidity, and their "low tech" of course (meaning: ours is far better of course...).

Well, it seems that time has come for all these brilliants minds to demonstrate that they are far more clever, but also far more EFFICIENT than these silly russians...

 

[PietKuip]

A third hypothesis can also be that the tsunami has modified the water table level and increased its level... That's an other possible factor.

The earthquake may have diminished the elevation of the nuclear power plant.

 

[M. Bachmeier]

Reactor 4 was undergoing shroud replacement, which uses apparently uses oxalic acid and hydrogen permanganate for decontamination:
http://www.toshiba.co.jp/nuclearenergy/english/maintenance/replace/shroud04.htm

Oxalic acid "reacts explosively with strong oxidizing materials"...
http://www.jtbaker.com/msds/englishhtml/o6044.htm

?

Now the question is, would it have been considered safer (prior to earthquake) to store a hydrogen peroxide tank at (50-70% concentration) in the reactor building (which has good filtered ventilation)? I believe hydrogen peroxide (small leak by itself) has a flash point of 70 degrees Celsius without a source of ignition. Not 100% certain?

 

[AntonL]

here is the latest Radiological Assessment estimates published by NNSA
http://www.slideshare.net/energy/ra...ta-from-fukushima-area-04182011?from=ss_embed and reported by http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/04/21/20110421p2a00m0na016000c.html

[PLAIN]http://k.min.us/imWXac.jpg

 

[Borek]

I believe hydrogen peroxide (small leak by itself) has a flash point of 70 degrees Celsius without a source of ignition. Not 100% certain?

Hydrogen peroxide is not combustible.

 

[IowaNewbie]

here is the latest Radiological Assessment estimates published by NNSA
http://www.slideshare.net/energy/ra...ta-from-fukushima-area-04182011?from=ss_embed and reported by http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/04/21/20110421p2a00m0na016000c.html

{IMG}

To put into perspective - 2,000 mrems is 40% of max radiation worker allotment in US - 4x that of the allotment for a minor (under age 18).

http://web.mit.edu/newsoffice/1994/safe-0105.html"

 

[jlduh]

To remember: 1 millisievert = 100 mrem.

The maximal limit considered safe for human (general public) is 1 millisievert/year. So everything on this map in an other color than grey is above this limit (the red is 20 times this limit). This shows that the 30kms evacuation zone set by japanese government is far from appropriate.

As i was out for two weeks, i missed some infos but I've read somewhere that the japanese governement had raised the 14th of April the maximal limit for adults to 20 millisieverts/year and 10 millisieverts for children! Can someone confirm this?

This would be a new demonstration that really that kind of decision concerning limits is just ******** and reverse science (if any science at all): get the conclusion first ("don't evacuate further") then set the limits...

I just want to mention that there is also some debate about the influence of low doses but over long periods of time, which may be underestimated (as their influence is more difficult to prove, with long term diseases diffciult to analyze).

 

[etudiant]

here is the latest Radiological Assessment estimates published by NNSA
http://www.slideshare.net/energy/ra...ta-from-fukushima-area-04182011?from=ss_embed and reported by http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/04/21/20110421p2a00m0na016000c.html

[PLAIN]http://k.min.us/imWXac.jpg[/QUOTE]

Very helpful map. Thank you!
One question.
Does this assume that the full year dose is from a constant irradiation at the level measured during the survey flights?
If not, what assumptions were made regarding the decay profile of the radioactivity that was measured?
Very different public health conclusions emerge depending on the answer.

 

[jlduh]

Etudiant, you have all the answers in page 4 of the study, under assumptions paragraph...

Decay is taken into acount. The dose takes into account an estimate of radiation from particulates deposited on the ground and also from inhalated ones. On the other hand it is assumed that people are outdoors during the 365 days , which is of course not the case...

This study gives a rough view of the extension of the contamination, and of the global levels at which the people can be exposed. But there is always a lot of variation between various people at the same place, depending on their activities and habits. For example, someone who will eat vegetables or milk or mushrooms coming from this area will have a dose greater that the one who will eat stuff coming from outside of the area. These variations (and many other ones) are outside of the scope of this study...

 

[etudiant]

Hydrogen peroxide is not combustible.

High purity hydrogen peroxide is very potent stuff.
It may not be combustible, but it will generate tremendous heat/steam on decomposition over a silver catalyst.
It is potent enough to have been used as a rocket fuel oxidizer.
So even a 50% H2O2 solution would be capable of doing serious damage if combined with some fuel such as oil or rubber or plastics.

 

[etudiant]

Etudiant, you have all the answers in page 4 of the study, under assumptions paragraph...

Thank you.
That is actually quite ugly.
It indicates that there is now a substantial public health experiment in process, on a largely involuntary basis, across a broad age profile.

 

[jlduh]

And the experiment continues with this info:

http://www3.nhk.or.jp/daily/english/21_35.html

Is the numbers seem high to you, it is because they ARE high...

 

[Jorge Stolfi]

"to feed the dog with something" that is how the public is feeling about the information "policy" of TEPCO. But why are they doing so?

Two other possibilities:
- The plant and the disaster operations are actually being managed by subcontractors, who are not used/capable/keen of talking to public or other specialists;
- TEPCO (and GE, Areva, ...) may be afraid that any detail they reveal about the plant or their actions may be used to criticize or sue them.

 

[AntonL]

A M5.6 earthquake with epicenter about 30km NE of Fukushima was reported at at 01.11 AM 22 April Japan time

 

[jarvik]

To remember: 1 millisievert = 100 mrem.

The maximal limit considered safe for human (general public) is 1 millisievert/year. So everything on this map in an other color than grey is above this limit (the red is 20 times this limit). This shows that the 30kms evacuation zone set by japanese government is far from appropriate.

Actually if you read the whole slide show the average US citizen receives 620 mrem / year and a whole body CT scan is 1000 mrem so I don't know where your safe limit of 100 mrem/year is coming from but I'll guess pretty much no one on this planet doesn't exceed your suposed safe annual limit.

This is a bad situation but let's not make stuff up to worry about.

Edit: Current US federal occupational limit of exposure per year above background +medical stuff is 5000mrem or 500mrem if you are pregnant.

 

[AntonL]

"to feed the dog with something" that is how the public is feeling about the information "policy" of TEPCO.

But why are they doing so?
To hide the real size of the disaster? -> It's INES 7 already.
To secure "engineering secrets"? -> I do not belief the Iran like to copy this crap.
TEPCO itself do not have more data, pictures and information? -> God forbid.

Two other possibilities:
- The plant and the disaster operations are actually being managed by subcontractors, who are not used/capable/keen of talking to public or other specialists;
- TEPCO (and GE, Areva, ...) may be afraid that any detail they reveal about the plant or their actions may be used to criticize or sue them.

the real reason is Japanese mentality - (i have a 12 year very close professional relationship with a Japanese company) and believe me they do not disclose anything voluntary one really needs to force the information out of them. You are only told what they want to tell you. What I have experienced in the last 12 years on a small scale I am witnessing here in a mega scale so rest assured a lot more is happening behind the scenes and much of the criticism which is easily aired from our armchairs is unfounded - we just have to live with the drip drip information policy.

And Tepco will only report what is required by law - nothing more

 

[|Fred]

The maximal limit considered safe for human (general public) is 1 millisievert/year. So everything on this map in an other color than grey is ...

Is not, 1 mSv/y is a threshold, threshold allowance of "artificial" radiation to the general public. Living in France expose you to 3.7mSv /year, moving to Sweden ? Double that. (and 6.4mSv for our US friends)

Perspective..

So, if you don't think you should be scare by moving to Sweden, then there is no reason why you should think 1mSv is the annual dose limit considered to be safe. Having said that It's a good conservative value that you should wish not to be exceeded by "artificial" radiation. Because we wish things to be as safe as possible..

 

[Borek]

High purity hydrogen peroxide is very potent stuff.
It may not be combustible, but it will generate tremendous heat/steam on decomposition over a silver catalyst.
It is potent enough to have been used as a rocket fuel oxidizer.
So even a 50% H2O2 solution would be capable of doing serious damage if combined with some fuel such as oil or rubber or plastics.

I was just referring to the fact there is no flash point for hydrogen peroxide. I know it is a dangerous stuff.

 

[Bandit127]

here is the latest Radiological Assessment estimates published by NNSA
http://www.slideshare.net/energy/ra...ta-from-fukushima-area-04182011?from=ss_embed and reported by http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/04/21/20110421p2a00m0na016000c.html

[PLAIN]http://k.min.us/imWXac.jpg[/QUOTE]

Assuming a very rough Gaussian distribution and that the blue represents the tails of that, the red area has chopped the peak off by a long way. The peak radiation in the area marked red could be an order of magnitude greater than 2000 mrem.

 

[jlduh]

Well, maybe i should have written maximal ALLOWED dose for general population (defined by french safety coden but that is the limit in many countries for artificial radiation). Which i expect is a "safe limit" by the way ;o)

The fact is that we see on the map that outside of a certain perimeter, the measures (in grey) are below 1 mSv/year (100 mrem/year).

So maybe you have an example Jarvik about who is leaving with a dose of less than 1 mSv/year on this planet ;o) . In fact, this last remark let me conclude that we don't know if this study is separating artificial radioactivity from "natural" one?

A whole body scanner gives you even more than 10 mSv, the measured values go up often to 20 mSv, which is the maximal equivalent dose of a worker in nuclear industry in France!

But this doesn't mean that there is no risk, in 2010 the president of the french ASN indicated that the radiation doses received by people from medical examinations (mostly X rays and Scanners) increased by 50% in the last 5 years! He was considering this as a scary trend and was insisting in investing more in MRI equipment than scanners to reduce this tendency.

So i don't think that giving that kind of comparison -with doses coming from medical exams- is also very relevant, because one can also say that medical examination is not a normal process for everybody, it is a process with a benefit/risk consideration when somebody has a significant disorder.

Here we are talking about average doses (the real doses have to be better assessed, taking into account food and water ingestion, and many other parameters) for a COMPLETE population, including old and youngs, healthy and sick people.

And in their case, they have absolutely not benefit in taking these extra doses, right?

Coming back on the map showed (and this sketch was already the general tendency 4 weeks ago) I don't undertsand why japanese government stayed with a basic 20 or 30 kms circular zone. Data are available to show that the risk area could be more finely tuned (especially at the north west side)...

Very low tech method, to say the least...

 

[biffvernon]

Note that the map is dated 8th April. Up until then the wind had been almost totally out to sea. On Sunday last and Tuesday 19th when it rained, the wind was from the east, blowing the plume inland. They have been very lucky with the westerly winds so far. If the power-station is still leaking into the air as we move into the typhoon season those numbers could get much higher.

 

[Jorge Stolfi]

I was just referring to the fact there is no flash point for hydrogen peroxide. I know it is a dangerous stuff.

Biological control should not require large quantities of H2O2 of KMnO4. The typical dose (e.g. for sanitizing vegetables) is a few drops per gallon. A few tens of kg should be enough for years.

 

[Rive]

Note that the map is dated 8th April. Up until then the wind had been almost totally out to sea. On Sunday last and Tuesday 19th when it rained, the wind was from the east, blowing the plume inland. They have been very lucky with the westerly winds so far. If the power-station is still leaking into the air as we move into the typhoon season those numbers could get much higher.

The actual aerial release rate is not high enough to cause any radical change on that map.

The sea and the groundwater is a different story, of course.

 

[Caniche]

Why is Speedi not giving any info when it costs 12.8 million yen pa ; why is Rimnet not communicating; why has Radnet crashed? For Speedi ,2 published forecasts out of 2000 produced, since 11/3 seems a poor return . I'm sure there is a perfectly acceptable explanation(- :

 

[biffvernon]

The actual aerial release rate is not high enough to cause any radical change on that map.

The sea and the groundwater is a different story, of course.

Hmm... It's not sea or groundwater that produced the map pattern but stuff blown on the wind on the very few days that the wind has blown onshore. That map may need revision when the wind changes.

 

[jlduh]

new data from Tepco website on underground water contamination:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110419e11.pdf

and pdf with time curves for all reactors samples:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110419e12.pdf

 

[Dmytry]

Just because you have Cs and I in the water, it does not mean that they will stick together as CsI. Each ion (Cs⁺ and I^-) will go is way and interact with all the other crud in the pool.
Fresh seawater is slightly alkaline, but boric acid was added to it. It is a weak acid, but presumably enough to allow the much smaller amount of iodide to form HI and leave with the steam.

However it seems that iodide in water easily reacts with oxygen to form neutral iodine I2, which is volatile too. The pH does not seem to matter in this case.

On the other hand cesium has no volatile compounds that I know of, so it can only leave the liquid carried by droplets, as you say --- which will only form if the water if boiling or blasted away.

In summary, if hot water containing Cs and I is kept in an open container (like the #4 SFP, but unlike a normal reactor), I guess that the Cs:I ratio will gradually get skewed towards the former. Would that effect be enough to confuse the interpretation of the analysis, e.g. with regard to old x recent fission?
They took the sample with a bucket suspended from the concrete pump by a cable. The camera was mounted on the crane too. Radiation presumably was a bigger obstacle to human intervention than any heat level would be.

Yea. Two things to note about CsI :
a: in solution there is no such thing as CsI
b: CsI has approximately 1360 Bq of I to 1Bq of Cs ratio, i.e. the role of CsI in the transport of Cs is small. It's role in the transport of iodine might be big or not, but very little Bq of caesium get carried along with iodine as CsI .
The ratio being skewed over time towards Cs would make it look like criticality ended longer ago.

 

[MiceAndMen]

MARK

T plus 1,000 hours

1 x 10³ hours since TEPCO reported failure of the Emergency Core Cooling Systems to NISA, as reported here:
http://www.nisa.meti.go.jp/english/files/en20110416-9-1.pdf

A key benchmark value for many graphs I've seen that use log(time) for the abscissa.

 

[Dmytry]

on topic of criticality in SFP... why are we all (myself was a little guilty of that before in other forum) so sceptical about that? There's those boral plates
http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0933/sec3/196.html
which presumably are required to prevent criticality (or so NRC says). Is it a big stretch that aluminium would start melting if spent fuel gets uncovered? Possibly even before any zirconium fire, massive fuel damage, etc. Is it a big stretch that if enough of the boral plates fail, it would go critical if water is re-introduced (or even just having water nearby) ?
Then there's the issue of heavy stuff falling into SFP and damaging everything in unpredictable way. It is a safety issue, right? Shouldn't the burden of proof to be on whoever claims that re-criticality is impossible ? And shouldn't it be like this - if it can't be shown impossible, the water has to be borated more?
Then, the isotope analysis - was it not a priority to make sure there is no criticality? Why no short living isotopes data was released?

also, read the article about boral. It can make hydrogen quite well, according to that page.

 

[Dmytry]

Well, maybe i should have written maximal ALLOWED dose for general population (defined by french safety coden but that is the limit in many countries for artificial radiation). Which i expect is a "safe limit" by the way ;o)

The fact is that we see on the map that outside of a certain perimeter, the measures (in grey) are below 1 mSv/year (100 mrem/year).

So maybe you have an example Jarvik about who is leaving with a dose of less than 1 mSv/year on this planet ;o) . In fact, this last remark let me conclude that we don't know if this study is separating artificial radioactivity from "natural" one?

A whole body scanner gives you even more than 10 mSv, the measured values go up often to 20 mSv, which is the maximal equivalent dose of a worker in nuclear industry in France!

But this doesn't mean that there is no risk, in 2010 the president of the french ASN indicated that the radiation doses received by people from medical examinations (mostly X rays and Scanners) increased by 50% in the last 5 years! He was considering this as a scary trend and was insisting in investing more in MRI equipment than scanners to reduce this tendency.

So i don't think that giving that kind of comparison -with doses coming from medical exams- is also very relevant, because one can also say that medical examination is not a normal process for everybody, it is a process with a benefit/risk consideration when somebody has a significant disorder.

Here we are talking about average doses (the real doses have to be better assessed, taking into account food and water ingestion, and many other parameters) for a COMPLETE population, including old and youngs, healthy and sick people.

And in their case, they have absolutely not benefit in taking these extra doses, right?

Coming back on the map showed (and this sketch was already the general tendency 4 weeks ago) I don't undertsand why japanese government stayed with a basic 20 or 30 kms circular zone. Data are available to show that the risk area could be more finely tuned (especially at the north west side)...

Very low tech method, to say the least...

Yes, I've been wondering about that. Also, how many people did this 'stay indoors' order kill? It's just irresponsible to give stay indoors order and keep it in place for weeks. They had to map it properly (don't you map radiation from a plane?)

 

[default.user]

I found this article today.

http://www.glgroup.com/News/After-5...137-Suggests-Ongoing-Criticalities-53599.html

I used the google translator.

So, sorry my bad english. But a few people thinking, that Tepco has a lot of problems with the reactors.

http://www.businessweek.com/news/2011-03-31/tepco-workers-threatened-by-heat-bursts-sea-radiation-rises.html

At this week i saw this blue light often.
Is it possible that the neutron light can see through concrete?

 

[Joe Neubarth]

Yes, I've been wondering about that. Also, how many people did this 'stay indoors' order kill? It's just irresponsible to give stay indoors order and keep it in place for weeks. They had to map it properly (don't you map radiation from a plane?)

I believe most of the countryside was mapped from a plane or helicopter. I think Greenpeace or some organization like that was driving around into contaminated areas and taking measurements that were considerably higher that previously posted.

 

[Joe Neubarth]

I found this article today.

http://www.glgroup.com/News/After-5...137-Suggests-Ongoing-Criticalities-53599.html

I used the google translator.

So, sorry my bad english. But a few people thinking, that Tepco has a lot of problems with the reactors.

http://www.businessweek.com/news/2011-03-31/tepco-workers-threatened-by-heat-bursts-sea-radiation-rises.html

At this week i saw this blue light often.
Is it possible that the neutron light can see through concrete?

When high speed neutrons hit the nucleus's of large atoms they bounce off sort of like a ping pong ball does off of a bowling ball. Neutrons can make it through concrete and some air but it is difficult for them to travel far. The experts on radiation attenuation probably have charts that they can refer you to.

 

[TCups]

Regarding the radioactive contaminated underground water in the basements of Unit 5 and 6:

I have just read a very interesting post regarding this matter in a german Fukushima board - http://fukushima.physikblog.eu/discussion/33/radioaktivitaet-im-grundwasser-noch-so-ein-thema

It's very large, so I'll try translating the most vital parts. All thoughts come frome user Silene in the german forum, I'm only reciting. But I think it's very plausible.

Here is an image of the sweetwater/saltwater levels at coasts:

Notice that the saltwater is forming a wedge which's pressing inland. Since saltwater is more dense than sweetwater, sweetwater is pushed upwards near the coast, it's floating on the saltwater.
The water leak which was sealed earlier this month can't be responsible for the big seawater contamination which was measured since there was only a release of 7m³/h. It's more likely that the saltwater, which was previously used to cool the reactors, seeped through the ground, passed through the sweetwater (because it's denser) and mixed with the saltwater. That way, it could have gotten into the ocean.
Now the reators are cooled with sweetwater. The sweetwater is staying with the groundwater and the overall groundwater level is rising -> radioactive groundwater begins seeping into Units 5 and 6.

REGARDING GROUND WATER CONTAMINATION AT FUKUSHIMA - IS THIS RIGHT?!

After taking a day off just to step back and think about all of this, I am catching up. In that time and several pages of posts, I find the post from Clancy688 to be the most interesting and most alarming new information. If I understand the concept correctly (please correct me if I got it wrong) this is why:

1) the ongoing efforts to cool the reactor cores and the SFP4 are going to continue to release massive volumes of contaminated water for months to come.

2) the density gradient between the denser saltwater and lighter, fresh ground water forms, effectively, a dam-like barrier to the active mixing of fresh ground water with the ocean (though presumably there must be diffusion (osmosis) across the gradient based on the concentration of NaCl)

http://upload.wikimedia.org/wikiped...r_Intrusion.gif/440px-Saltwater_Intrusion.gif

3) The switch to using fresh water for cooling means that the waste water from the ongoing cooling is now differentially contaminating ground water more so than ocean water. So forget seepage into the basement of Units 5 and 6 -- as bad as the ongoing contamination of the ocean would be, contamination of the ground water in terms of long term adverse consequences to the Japanese population is going to be even worse and long lasting.

4) As long as the fuel remains "hot" and requires cooling, the water used to cool it is going to be contaminated at high levels.

5) The rate of that ongoing water-borne contamination will continue at the same rate at the flow of cooling water unless an effective containment, precipitation and filtration system for the waste water is devised.

Yikes!

 

[jlduh]

to come back to the groundwater subject, even if i didn't find any precise map of the area around the plant, but because of the proximity of ocean, it is very probable that the direction of flow of the fresh water table is towards the sea (discharge path). This is the normal case in costal areas at least. So it is IMHO very probable that ground water (and so radioactive contamination through it) won't move far inland (which would be a good news), but will finish in the ocean, like the direct leaks from the plant...

The sketch below is summarizing this process:

http://www.netimago.com/image_191926.html

So the sketch for the contamination move through groundwater could be close to this one:

http://www.netimago.com/image_191927.html

 

[TCups]

to come back to the groundwater subject, even if i didn't find any precise map of the area around the plant, but because of the proximity of ocean, it is very probable that the direction of flow of the fresh water table is towards the sea (discharge path). This is the normal case in costal areas at least. So it is IMHO very probable that ground water (and so radioactive contamination through it) won't move far inland (which would be a good news), but will finish in the ocean, like the direct leaks from the plant...

The sketch below is summarizing this process:

http://www.netimago.com/image_191926.html

So the sketch for the contamination move through groundwater could be close to this one:

http://www.netimago.com/image_191927.html

@jlduh

Thanks for that. Amazing all the stuff you can learn from a really big nuclear accident, isn't it? But in broad strokes, it would seem to me that the groundwater contamination problem will be just as big or bigger and just as complex if not more complex than the airborne contamination problem in the wake of the Fukushima events. Is that how you assess things as well? PS, welcome back. Hope you had a great holiday.

 

[jlduh]

Hi TCups, thanks, yes vacations were fine (and isolated)!

Well, ground water contaminations are always complex matters (treating them is uneasy because they are... underground!). But obviously, the contaminations have to be assessed regarding what they can directly impact in the short to long term timeframe: so basically, 1) what will be their path and 2) what will they encounter along these path (in terms of usage of the water resource for example). In other words, which "targets" will the contamination hit in the next weeks, months, years, decennies...

If the flow of the groundwater is a discharge flow towards the sea at Fukushima, the targets won't be numerous because the path will be short. Of course, I'm only talking about ground water. Ocean water is an other department (of importance). In the Fukushima disaster, I'm afraid that the ocean is going to be the big garbage can of the contamination. To be more precise, ocean is big, BUT the coastal areas will be in my opinion the biggest target of the pollution. It seems that the currents are going south in this area of the Japan sea, so I wouldn't be surprise that the plume of contamination follow this costal line... But it is to early to be sure of that.

Don't forget also that with the typhoon season, huge amount of rain water is going to "wash" the big mess on the Fukushima plant (soils, buildings, reactors, etc.). And this water is going to finish its trip into... the ocean.

At Tchernobyl it has been estimated that because of the 1000m2 or so of cracks in the cover of the shelter (sarcophagus), around 10 000 m3 of rain water enter every year the sarcophagus, and that there is still 3000 m3 of water in the basements of the plant.

You can read also this article which treats this subject and come to a similar conclusion it seems:

http://www.groundwatergo.com/blog/nuclear-disasters-and-groundwater/

 

[rowmag]

Blueprints would be helpfulbut not certain. Any estimate of the leakage rate required as per your idea?

Good question, and maybe that is the one that can put this to rest.

Don't know proper dimensions, but a quick back of the envelope calculation of what kind of wind is needed to replace the air in a reactor building through, say, a 10 m^2 cross-section trench in one day suggests wind-tunnel-like air flow. So not likely, unless concentrated hydrogen were piped through, but
a) why would it be? and
b) in any case, robot videos of the inside of Unit 3 show the lower floors in pretty good shape, no obvious signs of hydrogen explosion down there, suggesting that the hydrogen in Unit 3 was largely confined to the top of the building, far from any underground conduit.

 

[Jorge Stolfi]

I've updated my plots of #Fukushima reactor variables, up to #NISA release 106 (21/apr 15:30) :

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

No big news. The drop by a factor of 10 in the CAMS (A) reading in the Unit #1 torus persists. Presumably it is the previous values that were wrong by 1 in the exponent. It is hard to tell
because the (B) redings are intermediate between the two (A) values, old and new, and both have
been changing a lot recently.

In release 103 there was another similar drop, by a factor of 100, in the CAMS (B) reading of Unit #3 torus. Here it is clear that it was a typo in the exponent, since the (A) and (B) readings were previously off by factor of 100 (exponent 1 instead of -1), and now they agree. The question is, are they now both correct, or both wrong?

In their release packet 105, NISA messed up their file names, so intead of the raw TEPCO fax we got a second copy of the redacted NISA press release. The latter does not give the CAMS readings, water pump flows, and core and drywell temperatures. But release 106 was OK.

 

[MiceAndMen]

I've updated my plots of #Fukushima reactor variables, up to #NISA release 106 (21/apr 15:30) :

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

No big news. The drop by a factor of 10 in the CAMS (A) reading in the Unit #1 torus persists. Presumably it is the previous values that were wrong by 1 in the exponent. It is hard to tell
because the (B) redings are intermediate between the two (A) values, old and new, and both have
been changing a lot recently.

In release 103 there was another similar drop, by a factor of 100, in the CAMS (B) reading of Unit #3 torus. Here it is clear that it was a typo in the exponent, since the (A) and (B) readings were previously off by factor of 100 (exponent 1 instead of -1), and now they agree. The question is, are they now both correct, or both wrong?

In their release packet 105, NISA messed up their file names, so intead of the raw TEPCO fax we got a second copy of the redacted NISA press release. The latter does not give the CAMS readings, water pump flows, and core and drywell temperatures. But release 106 was OK.

What do people think here? Is TEPCO/NISA sloppy with their reporting, or are the inconsistencies due to translation? I've seen plenty of Japanese electronics' users' guides in my day, and it seems there are plenty of Japanese - ostensibly employed as professionals - who do not read and write English as well as they think they do. Not to say all Japanese in general are like that; I know several who are fluent in English and they would not make such grievous errors. But it seems to be common that the first person who raises their hand when the boss asks, "Who can translate this into English?", always gets the job regardless of their actual level of fluency.

On the other hand it would not surprise me if they're just sloppy and careless with the numbers for Japanese consumption, too.