Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Astronuc]

In monitoring failed fuel, the industry typically measures Xe-133, Xe-135, Xe-138, Kr-85m, Kr-87 and Kr-88, and I-131,132,133,134,135.

Cs-134 and Cs-137 are also measured and the ratio can give some estimate of burnup.

Np-239 is measured and is an indicator for tramp fuel particles or released fuel from breached fuel rods.

 

[JUrban]

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside? This looks an odd way of doing it, considering that there was a risk of explosion. Why inside instead of outside? This looks strange to me and i find no analysis or answer on this point.

It's being reported that after one of the disasters (don't remember which one) the US forced reactor retrofits for hardened vents to avoid venting into the buildings, but it's a good chance the Japanese did not follow suit.

 

[JUrban]

The fresh water idea sounds essential and should have been actioned 10 days ago.

Thanks. Yeah for better or worse fairly obvious ideas still need all the pieces to come together to emerge from the darkened idea space, and for disaster situations like this, that fact is scary.

 

[TCups]

REGARDING THE PHOTOGRAPHIC EVIDENCE AND NATURE OF EXPLOSIONS, UNIT 1,3, 4

I am updating some of the earlier photo analysis that took place earler amongst the forum participants and that may not yet have been reviewed by those newer posters who have recently joined.

Look again, carefully, at the photos that AntonL referenced from Der Spiegel (page 23, post #363)

http://www.spiegel.de/images/image-193170-galleryV9-njkp.jpg
Reactor 4

http://www.spiegel.de/images/image-193230-galleryV9-ovfc.jpg
Reactor 4

http://www.spiegel.de/images/image-193230-galleryV9-ovfc.jpg
Reactor 4

http://www.spiegel.de/images/image-193165-galleryV9-kzvg.jpg
Reactor 3

http://www.spiegel.de/images/image-193254-galleryV9-gmmj.jpg
Reactor 3 (corrected, original post says Reactor 1)

from MSNBC
http://msnbcmedia3.msn.com/j/MSNBC/Components/Photo/_new/110312-reactor-vlg-5p.grid-4x2.jpg
Reactor 1

I don't know how I missed this before, but here is what I think I see. The building designs and overhead cranes in 3 and 4 are different than in 1. The overhead cranes in 3 and 4 are mounted atop massive steal beams that run north-south, and that are supported, indeed have to be supported by the reinforced concrete columns on the east and west sides of the building. The weight and size of the beams that are the tracks for the crane, in turn, reinforce the bearing weight-bearing columns of the top floor of bldgs 3, 4.

The hydrogen explosion in the top floor of 4 spares most of the roof and all of the columns on the east and west sides because of this relationship to the construction and weight-bearing functions mentioned. After the explosion, you can see that the structural damage to the roof and most of the structural damage to the side walls of Bldg 4, are therefore most severe at the north and south ends of the building.

The same holds true for Bldg 3, except that

1) the explosion at Bldg 3 was much more powerful, and
2) the explosion at Bldg 3 results in the north wall weight-bearing columns buckling and the crane structure itself sliding or being blown off of the rails and falling from the top floor of Bldg 3 to the top of the smaller, adjoining building below on the north side of Bldg 3.

The fuel handling machenery (green) still sits atop the SFP of Bldg 4, but not at Bldg 3. The SFPs are at the southeast corner of both Bldg 3 and 4 as has already been confirmed.

The concrete panels between the structural weight bearing columns of Bldg 3, because of the much larger size and power of the blast in Bldg 3, resulted in the concrete panels between the weight bearing columns on the east and west sides becoming more effective "bullets" when they blew out en mass, from between the columns, doing the damage to the adjacent roofs of Turbine Bldg 3 and the building in back, on the west side of Bldg 3. The size and power of the blast also did much more damage to the superstructure of the roof girders of 3 than 4, but it would still appear that the roof girders over the drywall containment plug of Bldg 3 are not completely destroyed after the explosion. Hence, the drywall containment plug was not blow straight upward.

The annotated image below was modified from the original, at DigitalGlobe.com

The larger explosion at Bldg 3 is annotated. The short arrows are the paths of the "bullet-like" blow out of the east and west side panels of Bldg 3.

The long arrow shows the damage to the north-side structures adjacent to Bldg 3 done by the falling crane, visibly absent at Bldg 4.

The rectangles show the location of the highest rates of measured radioactivity, presumably at ground level, adjacent to Bldg 3, and taken from this Diagram, posted earlier by jlduh (#957), original reference not known.

http://www.monsterup.com/upload/1300925395929.jpg

This suggests to me, but it has not been confirmed, that the debris blasted from Unit 3 carried radioactive contaminants, either from the SFP or from the Unit 3 reactor core, or from both.

And this close-up of steam venting in the region of the SFP of Unit 3, I believe, reinforces the opinion (speculation on my part) that the containment of Unit 3, more specifically, the drywall containment at the location of the fuel transfer gate(s) and chute to the SFP is the source of the breech and the venting steam (diagram following).

This image of debris atop Bldg 3 suggests to some (myself included) that the blast displaced spent fuel rods from Unit 3's SFP, but this has not been confirmed.

 

[AntonL]

NHK reported that water in basement 3 has 10000 x the radioactivity as the water inside a normal operating reactor, hence the assumption that unit 3 containment may be breached, leaking water into basement 3.



This is the slide displayed while above was being reported.

This slide also confirms to me that the design parameter of a 5.7m Tsunami wave was an afterthought. The height as I in a previous mail suggested is determined by design need to keep basements above seawater levels as can be seen above That height dictates a maximum Tsunami wave such that pump cabins for coolant do not get destroyed. Ground level at reactor is about 15 metres as per earlier Tepco releases.

 

[TCups]

NHK reported that water in basement 3 has 10000 x the radioactivity as the water inside a normal operating reactor, hence the assumption that unit 3 containment may be breached, leaking water into basement 3.

Could one not just as easily conclude that the contamination comes from damaged fuel rods in the SFP with the leakage coming from the damaged SFP, or from dispersed fuel rods outside of the SFP that had been spayed with water over the last several days?

 

[Bodge]

Nobody has commented on my analysis, so I'll post it again. I was honestly startled.

The IAEA have just measured very high beta/gamma contamination 4,900,000 beq / metre squared in Fuk. Pref.

"At distances between 30 and 32 kilometers from the Fukushima Nuclear Power Plant, in a north westerly direction from the site, dose rates between 16 and 59 microsievert per hour were measured. At these locations, the results of beta-gamma contamination measurements ranged from 3.8 to 4.9 Megabecquerel per square metre. At a location of 21 km from the Fukushima site, where a dose rate of 115 microsieverts per hour was measured, the beta-gamma contamination level could not be determined."

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

Here is a map of Chernobyl's "Zone of Alienation"

I converted 40 curies / square km to 1.48 Megabeq / square metre

Also 1.48 is mentioned here:

http://books.google.com/books?id=g3...age&q=chernobyl cs soil contamination&f=false

We seem to have 4.9 Megabecquerels in Japan

edit: Forgot to mention not all of the radiation detected yesterday by the IAEA was from Cs137, there will be Iodine,Strontium,Cobalt etc and maybe Plutonium too. Also one site was "unmeasureable", but mSv was highest at that point !

 

[AntonL]

Could one not just as easily conclude that the contamination comes from damaged fuel rods in the SFP with the leakage coming from the damaged SFP, or from dispersed fuel rods outside of the SFP that had been spayed with water over the last several days?

Makes more sense to me as water does not flow uphill - see basement levels of torus and turbine building of slide posted earlierTCups please note location of reactor relative to upper structure

 

[TCups]

Nobody has commented on my analysis, so I'll post it again. I was honestly startled.

If the original data are correct and your analysis of the data is correct, then, the obvious comment is "gee, that is really hot!"

Do we know which were the source of the radionuclides emitting that level of radioactivity and how long their half lives are? If these represent the volatile components, brought to ground by rain or settling dust, for example I-131 with a half life of 8 days, then the radioactivity will be very different a few weeks from now. If, on the other hand, there are longer half-lived fission byproducts from the damaged fuel rods in the core or SFP, then the contamination will by its nature, be much worse and a much more long-lasting problem. Chernobyl was the later. As far as is yet know, Fukushima will be the former.

 

[Bodge]

If the original data are correct and your analysis of the data is correct, then, the obvious comment is "gee, that is really hot!"

Do we know which were the source of the radionuclides emitting that level of radioactivity and how long their half lives are? If these represent the volatile components, brought to ground by rain or settling dust, for example I-131 with a half life of 8 days, then the radioactivity will be very different a few weeks from now. If, on the other hand, there are longer half-lived fission byproducts from the damaged fuel rods in the core or SFP, then the contamination will by its nature, be much worse and a much more long-lasting problem. Chernobyl was the later. As far as is yet know, Fukushima will be the former.

The IAEA simply had this to say:

"Measurements will be taken to determine more precisely the actual radionuclides that have been deposited."

 

[83729780]

Could one not just as easily conclude that the contamination comes from damaged fuel rods in the SFP with the leakage coming from the damaged SFP, or from dispersed fuel rods outside of the SFP that had been spayed with water over the last several days?

What do you make of the fact that the exposure took place inside the turbine building that had debris smash through its roof after the explosion?

 

[TCups]

What do you make of the fact that the exposure took place inside the turbine building that had debris smash through its roof after the explosion?

I don't know for sure. On consideration, though, if the exposure were from pooled water in the building floor, it seems more likely that the contamination came in with the water, not from falling debris. That said, I believe there might have been rain there. Rain or sprayed water leaking through a large hole in the roof could easily be one route, if not the main rout for water accumulating in the building, versus, for example, ground water seepage from a crack in the foundation.

What do you think?

 

[AntonL]

I don't know for sure. On consideration, though, if the exposure were from pooled water in the building floor, it seems more likely that the contamination came in with the water, not from falling debris. That said, I believe there might have been rain there. Rain or sprayed water leaking through a large hole in the roof could easily be one route, if not the main rout for water accumulating in the building, versus, for example, ground water seepage from a crack in the foundation.

What do you think?

I would guess that most of the water is still from the Tsunami, contaminated later.

 

[TCups]

The IAEA simply had this to say:

"Measurements will be taken to determine more precisely the actual radionuclides that have been deposited."

Exactly. It may be correct that "the sky is falling!", but it depends on what is in the sky that was the "fallout" that will determine whether or not it will be a long term problem. It's certainly not yet time to swallow the gun.

 

[TCups]

I would guess that most of the water is still from the Tsunami, contaminated later.

Good point -- yes, there was that source of water, also. ()

 

[wasteinc]

A colleague indicated it was apparently unintended for the hydrogen and steam from containment to be vented into the secondary or upper containment (metal structure). He indicated that duct work to carry to the appropriate stack had ruptured, and the hydrogen leaked into the upper containment area. As far as I know, one would not design a system to vent H₂ into the upper containment, precisely in order to prevent what did happen.

Salty seawater, which I expect has a fairly good soluble oxygen content, is problematic because it corrodes SS304. I imagine the intrusion produced a crud burst - crud being oxides of Fe, Cr, Ni, etc, and that could deposit on the fuel as it boils dry. Any crud on the fuel would be transportable in the seawater, which would explain the increase in Co-58,60 activity.

I'm curious about the behavior of UO₂ oxidation in seawater. I'm not aware of any studies.

I second that

TEPCO want us to believe it has some kind of control over the situation. So that was about all the narrative that they vented the H2 to the upper part in order to relieve pressure. Which is probably ********. The "venting" according to those guys http://www.ustream.tv/recorded/13410573" was the result of the extreme 8bar pressure inside the containment vessel, that made the lid of the containment vessel to give and relieve the pressure exactly as the lid of a cooker would have made. (we are talking about the second containment vessel).

As far as their presentation goes, the venting from the pressure cooker (containment 1), is done inside the containment 2 as long as the pressure goes over a certain point (if I remember they said it was around 80-88bar). There the radioactive steam cools down and becomes water again in the torus relieving pressure. In their explanation there was no way you could "vent by design" the second containment.

probably they had the explosions and then baptised them controlled releases to save face.

and thank all of you for the invaluable info and insights we get

 

[83729780]

is there any explanation for the temperature rising in the Common Use Spent Fuel Pool (the big one)?

status after 23/03:

In addition to pools in each of the plant's reactor buildings, there is another facility - the Common Use Spent Fuel Pool - where spent fuel is stored after cooling at least 18 months in the reactor buildings. This fuel is much cooler than the assemblies stored in the reactor buildings. Japanese authorities confirmed as of 18 March that fuel assemblies there were fully covered by water, and the temperature was 57 °C as of 20 March, 00:00 UTC. Workers sprayed water over the pool on 21 March for nearly five hours, and the temperature on 23 March was reported to be 57 °C.

http://www.iaea.org/newscenter/news/2011/fukushima240311.html

status on 24/03:

At the Common Spent Fuel, the power supply was restored as of 24 March, 06:37 UTC and cooling started again 28 minutes later. Work is now under way for the recovery of the lighting and instrumentation systems. As of 24 March, 09:40 UTC, the water temperature of the pool was around 73 °C.

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

 

[|Fred]

According to the Japanese authority (NISA) , taking into consideration the result of there analysis of that water that they found in the turbine building , it is very likely that it comes from the reactor core, although they can not exclude that is might come from the SFR.

They were not able to determine how the water came there.. Radiation mesure fo the water is 3.9×10^6 Bq/cm^3 (unit 3)

on the 25 At 3.10 am JST Unit 1 reactor containment vessel pressure went up to 6 atm (source NHK Japan)

[PLAIN]http://k.min.us/im0bGQ.jpg

 

[Lefteris]

Hello all, I am a graduate student of the University of Tokyo, from Greece and am currently living in Tokyo. I am studying precision engineering there (electronics/robotics). I have to admit I am overwhelmed by the things I hear both from the news and from various websites.

We were told that tap water has become unfit for infants 2 days ago with a level of 210 Bq/l but today the warning was lifted with a reported level of 79 Bq/l. Meanwhile I am watching the environmental radiation levels from my university's page http://www2.u-tokyo.ac.jp/erc/index_e.html" and I see elevated values, especially at the campus my lab is located at, Kashiwa campus.

I am not a physicist and I don't understand these values. I would like to ask the people here if they know what kind of values would be safe .. and what would prolonged exposure to values such as this (assuming I go to my lab daily) would mean?

Moreover about these radioactive substances such as iodine and caesium that have been detected. I heard that caesium has a half-life of 30 years. Doesn't that make it the most dangerous substance released, since it would mean that the contamination will stay in the environment for generations?

Sorry for the number of dizzying questions, but as with most people here in Tokyo we are trying to understand what to do with this situation. And going back home is a very hard option since all our lives/careers are here.

Thanks in advance!

 

[AntonL]

I would guess that most of the water is still from the Tsunami, contaminated later.

Good point -- yes, there was that source of water, also. ()

http://www.spiegel.de/panorama/0,1518,753058,00.html]Die[/PLAIN] Männer hatten am Donnerstag I am Untergeschoss eines Turbinengebäudes von Block 3 gearbeitet. Nachdem dort am Vortag weder Wasser noch erhöhte Strahlung festgestellt worden war, hatten sie bei ihren Arbeiten keine Schutzstiefel an - das radioaktiv belastete Wasser lief ihnen in die Schuhe.

translated means:
The men had worked on Thursday in the basement of a turbine building block 3. As on the previous day no water or increased radiation had been found, they did not wear protection boots - the radioactively contaminated water ran into into their shoes.

30cm water in basement is a huge quantity, possibly they stepped into a cable trench that was not pumped dry and accumulated contaminated water.

 

[Borek]

I am not a physicist and I don't understand these values. I would like to ask the people here if they know what kind of values would be safe .. and what would prolonged exposure to values such as this (assuming I go to my lab daily) would mean?

Compare these values with http://xkcd.com/radiation/

And read footnotes on the university page - they say what values are considered to be safe/normal. Note that in many places in he world natural levels of radiation are much higher, yet people living there have no traces of radiation related diseases. See http://en.wikipedia.org/wiki/Natural_background_radiation

 

[jensjakob]

http://www3.nhk.or.jp/daily/english/25_19.html

Propably damaged #3 RV :-(

 

[artax]

Joe NEUBARTH: i asked several times here if we were talking about relative pressures or absolute pressures and got no answer. On the METI doc that you link, i think you'll find an answer if you go down a little bit, to the line "D/W design service pressure". You will read a first pressure number and then the second is defined as "abs" -absolute. So all the numbers you have in this report otherwise specified are relative pressure i think, which explain why it can be negative.

But, it means that on reactors 2 and 3, those pressures are below atmospheric pressure, which is kind of strange and... scary?

Again, it's very difficult to draw a conclusion based on some numbers but to me this could (i say could) mean that the 2 and 3 reactors are dead from their confinement standpoint... and that N°1 is still rising...

All three reactors had explosions, n°1 seemed to bit quite "clean" (outer walls). N°2 had an explosion that nobody saw, it has been said that it was in the suppression pool and that it was leaking. N°3 had 3 simultaneous big explosions (the most impressive) and some here expressed concerns about it's current state.

Concerning the explanation given of why venting in the building instead of outside: ok that's what i heard BUT would you do it deliberately a second time (N°3) after having experienced the first time an explosion in the building (where the pools are!) because of H2 presence? Notice that venting in a room that explodes ends up with everything in the atmosphere + a severe explosion... That's a strange thing.

Like you I was confused by the pressure data, but one RV was stated as having 0MPa which I assume means atmospheric. As absolute 0MPa is rather difficult to achieve! And any negatives must be relative to atmosphere, but then again they seem to be very inconsistent with their use of units and change from millisieverts to micro, and then chuck in per hour when it suits them!

 

[jensjakob]

Pressure - interesting to see on #1 that the pressure is allmost identical between RV, drywell and Torus. And that the radiation is also allmost identical.

 

[DrDu]

Moreover about these radioactive substances such as iodine and caesium that have been detected. I heard that caesium has a half-life of 30 years. Doesn't that make it the most dangerous substance released, since it would mean that the contamination will stay in the environment for generations?

Caesium is very soluble so that it gets washed away quickly. It also has a short biological half live time, i. e. it leaves the body within several hundred days after incorporation.
Incorporating 80000 Bq of Caesium results in a body dose of 1 mSv.
Caesium gets stored especially in mushrooms and in the soil of forests for a long time.
So you should reduce your dayly intake of local Matsutake mushrooms if you could afford them at all :-)
Increased levels of iodine are potentially more worrysome as iodine accumulates in the tyroid gland and there are clear indications of induction of cancer by irradiation of the tyroid in epidemiologic studies.

 

[artax]

Hello all, I am a graduate student of the University of Tokyo, from Greece and am currently living in Tokyo. I am studying precision engineering there (electronics/robotics). I have to admit I am overwhelmed by the things I hear both from the news and from various websites.

We were told that tap water has become unfit for infants 2 days ago with a level of 210 Bq/l but today the warning was lifted with a reported level of 79 Bq/l. Meanwhile I am watching the environmental radiation levels from my university's page http://www2.u-tokyo.ac.jp/erc/index_e.html" and I see elevated values, especially at the campus my lab is located at, Kashiwa campus.

I am not a physicist and I don't understand these values. I would like to ask the people here if they know what kind of values would be safe .. and what would prolonged exposure to values such as this (assuming I go to my lab daily) would mean?

Moreover about these radioactive substances such as iodine and caesium that have been detected. I heard that caesium has a half-life of 30 years. Doesn't that make it the most dangerous substance released, since it would mean that the contamination will stay in the environment for generations?

Sorry for the number of dizzying questions, but as with most people here in Tokyo we are trying to understand what to do with this situation. And going back home is a very hard option since all our lives/careers are here.

Thanks in advance!

Studied some nuclear chemistry at uni a long time ago hence my interest but I would have to research those isotopes.
However the news here did mention that the ALLOWED UK levels for infants in tap water used for drinking (making up milk) are 5 TIMES HIGHER than those allowed in Japan... so I wouldn't worry at all.
The main reason Iodine is important is because the body has some in it always (thyroid gland) and can't tell the difference between the active isotopes and the natural ones. So if you take the Iodide pills, the iodide atoms (ions) just displace the radio ones very quickly before they've been their long enough to have any effect.
I'm pretty sure the authorities are tellining the truth about the tap water, and washing with it will be no problem at all... and drinking!
If I was in Japan now, I would just avoid the exclusion zone and don't go swimming in the sea!

 

[|Fred]

New video material has been released to the public including close up on the roof of unit 3, 4, 2 and 1

I estimate that the footage give some evidences that the debris that we though were rod are not.

 

[jensjakob]

New video material has been released to the public including close up on the roof of unit 3, 4, 2 and 1

I estimate that the footage give some evidences that the debris that we though were rod are not.

Link?

 

[dave2004]

I found this forum searching for discussions about facts of what is happening in Japan, and have been reading it for nearly a week now. I am glad to see so many people interested in what actually is happening instead of the scare mongering done by the media...

I wanted to add a perspective on the max. levels in food/water I found:
1) German newspaper:
some hot springs have up to 2700 Becquerel, in Germany baby food is allowed up to 370 and the EU proposes a limit of 500 to 1000 for drinking water in case of a nuclear accident (why only in case of an accident? don't ask me)
2) French government:
they seem to be based on a calculated yearly dose of 0.1 microSv of water contributing to the total yearly dose.

sources:
http://www.tagesspiegel.de/weltspiegel/wie-die-havarie-das-leben-veraendert/3982686.html

"Ein noch verträglicher Wert für Strahlenbelastung sei 300 Becquerel. Und „einige heiße Quellen in Kurbädern haben bis zu 2700 Becquerel.“ Das trinke dann natürlich niemand, aber trotzdem werden Werte eben gesetzt, willkürlich. Die Becquerel-Grenzen für Säuglingsnahrung in Deutschland liegt bei 370, die EU schlägt I am Falle eines Reaktorunglücks für Trinkwasser Grenzwerte von 500 bis 1000 Becquerel vor. "

and
http://www.sante.gouv.fr/IMG/pdf/bil0809-2.pdf
page 3:
Dose Totale indicative (DTI) 0,1 mSv/an

 

[jlduh]

Hi all,

i think that the news at not very good this morning from this damned plant.

Here in France some big newspaper like Le Monde (one of the main newspaper) are finally now step by step going towards the idea that the reactor (REACTOR) vessel of N°3 "could be damaged"...

http://www.lemonde.fr/asie-pacifiqu...-radioactifs_1498180_3216.html#ens_id=1493258

For me, with the last elements compiled here (especially the water on the basement 10 000 times more contaminated than in a normal functionning, but also the presence of strange elements that shoudn't be outside but ARE outside, ...) i have no more doubts about this fact: the reactor core has exploded the 14th of March, period.

And i think a lot of things that have been told (the controlled releases, the containment intact, the fact that it's no way like Tchernobyl, ...) has been a kind of cover up of the real situation, and this is really a problem when you think that offcially, people between 20 and 30 kms are still adviced to stay confined in their homes as i didn't see new info on that. I sincerely consider that it has everything to become worse than Tchernobyl :

-because the potential source is much bigger -we're talking about a complete plant with multi reactors and pools and not a single reactor, with all the domino effects we can anticipate - the number of dominos involved can be adjusted to your mood, more or less optimistic.

-because the density of population is terribly high in Japan

-because of the presence of the ocean which is already contaminated by the rejects of the cooling, and very quicky of all the **** which will be drained from the plant

In the article of Le Monde, it is reported that TEPCO is saying that bringing back the "normal" (what does it mean really as the situation is clearly more and more abnormal) cooling system "will last maybe more than one month, who knows?" ("Cela pourrait prendre encore plus d'un mois, qui sait"). If this sentence has been correctly reported, it shows that they are submerged by much more than a tsunami i think.

Bodge, i didn't react but the measurements you indicated are really bad of course and confirm that the contamination is not just from "controled releases" (which i doubted of very few days after the the start of the accident, the explosion of n°3 was the key moment for me). I personnaly suspect that a big part of the explosion could be from the suppression chamber based on the images i analysed, but we'll see.Now, we now that there is a fair amount of water at the basement and we will fairly quick hear about the word Corium to my opinion. The engineer from the CNIC conference (on USTREAM) in the video i posted and that has been reposted here a few hours ago (he has worked on the design of reactor N°4, his name is TANAKA) was saying in this video that one of the big problems with this design (relatively small containment chamber with the use of suppression chamber which is essentielly a big pool) implies a very high quantity of water below or near the core... which is not the safest idea in case of a fusion of the core. That's the next big question in the domino game: will corium meet water and have a big and violent love affair?

Before the TMI accident, almost nobody in the nuclear industry was seriously considering the practical possibility of a complete meltdown of the core. That's also why the TMI has been a so big surprise historically for the nuclear industry (50% of the core discovered melted when opened 5 years later). This design of BWR Mark I is from the mid sixties, so nothing has been anticipated for this scenario of core meltdown. This is no good news.

To the student in Japan who posted on this thread, i would just say that i don't know (personally) of any career more important than health and life for you and your family and friends. That's easier to say that from a place 17 000 kms away from Japan (less on the other side but I'm counting distances related to atmospheric movements in the last days) , for sure. But it is still true. Then, you have to make your own assesment of the situation there, and of the way it develops in the next days/weeks/months. But clearly, the situation at the plant is not good. Really not good. A few days after the start of the crisis, i adviced a friend (french) who was working in Tokyo to leave as quickly as possible when it was possible. But maybe I was too pessimistic of course (i would prefer to be pessimistic in fact, instead of realistic sometimes)...

 

[|Fred]

@Jakob HD NHK Japan..
this is the best I could find online but the quality of the feed is bad http://www3.nhk.or.jp/news/genpatsu-fukushima/movie/chapter_42.html .

 

[intric8]

Hello all, I am a graduate student of the University of Tokyo, from Greece and am currently living in Tokyo. I am studying precision engineering there (electronics/robotics). I have to admit I am overwhelmed by the things I hear both from the news and from various websites.

We were told that tap water has become unfit for infants 2 days ago with a level of 210 Bq/l but today the warning was lifted with a reported level of 79 Bq/l. Meanwhile I am watching the environmental radiation levels from my university's page http://www2.u-tokyo.ac.jp/erc/index_e.html and I see elevated values, especially at the campus my lab is located at, Kashiwa campus.

I am not a physicist and I don't understand these values. I would like to ask the people here if they know what kind of values would be safe .. and what would prolonged exposure to values such as this (assuming I go to my lab daily) would mean?

Moreover about these radioactive substances such as iodine and caesium that have been detected. I heard that caesium has a half-life of 30 years. Doesn't that make it the most dangerous substance released, since it would mean that the contamination will stay in the environment for generations?

Sorry for the number of dizzying questions, but as with most people here in Tokyo we are trying to understand what to do with this situation. And going back home is a very hard option since all our lives/careers are here.

Thanks in advance!

____________

I131 contribution 4.6483 microsieverts/day, based on 2 litres a day consumption. Reports are tap water levels dropping to 70 becquerel/kg as of today

http://falloutphilippines.blogspot.com/2011/03/current-levels-of-iodine-131-in-tokyo.html

 

[rhody]

Local News Radio is reporting the core for reactor #1 is compromised and will complicate efforts to contain radiation. A quick scan of local cybernews came up empty. Personally, I am surprised since the explosion at reactor #3 was greatest. On second thought though, imagine you sneezing and trying to suppress it to contain it, that may do more damage than letting it fly. I hope they (media source ) are incorrect. I reported this in the tsunami thread as well and am repeating it here.

Rhody...

P.S. Unlike Chernobyl, the 6 reactors are close to water, and one would assume, the water table. If I remember correctly they pumped liquid nitrogen near the burning core from wells driven at an angle to converge below where the core was. Might this be a desperate measure now given consideration, given the circumstances ?

Finally, I would think they would be considering using heroic, self-sacrificial robots to do some of the dirty work of inspection at deeper levels, (if possible) to assess reactor integrity and containment around it. It may not be possible given the situation, but it was a thought.

Edit: 6:38 am The same radio news reiterated the story 15 minutes later with an official audio newsclip of what sounded like a Japanese reporter who said it was reactor #3, not reactor #1 as I reported above. In the race to be the first, sometimes these folks get it wrong.

Thanks Astronuc for your explanation on Mox fuel many posts ago, but I know you already know that.

 

[jlduh]

@FRED: yes the quality of the video in not very good, but on the reactor 3 what is shown is not, in my opinion, the "things" that has been extracted from the first video (the supposed rods), i only see here (seeing means guessing on this video) structural steel from the roof. The sticks had a different appearence and were on one side (if i remember) of the building, ready to fall down. I would need to see the good quality video, probably soon on youtube anyway.

 

[jensjakob]

More on the possible breach:
http://translate.google.dk/translat...2&eotf=1&sl=ja&tl=en&u=http://www3.nhk.or.jp/

Assumed a valve or a pipe - and the pumping of water into the CV raises the level so it flows throug a broken pipe.

This is a bit less sinister than a breached CV - but still bad - though not "breached CV due to molten core"