Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[AntonL]

Unfortunately not - they are talking about the water in the trench being "only" 1-10% radioactive - which they refer to as "low compare to a core in action"

"
The Nuclear and Industrial Safety Agency says the levels of radioactive
substances detected are low, at one-to-ten percent of those occurring in an
operating nuclear reactor"

English is not the first language of the Japanese - this is water compared with water, one sample of reactor water normal conditions measured in a lab and one sample from the trench also measured in the lab,

To understand Japanglish you need to know the problem as well as the subject.

 

[|Fred]

I value Arnie Gundersen assesment, and as mentioned earlier, I'm having hard time to figure what can be done at this point. Considering the breach of the containment Breach linked to the Emergency cooling protocol and flooding of PCV and cooling of RCV

 

[rmattila]

Unfortunately not - they are talking about the water in the trench being "only" 1-10% radioactive - which they refer to as "low compare to a core in action"

"
The Nuclear and Industrial Safety Agency says the levels of radioactive
substances detected are low, at one-to-ten percent of those occurring in an
operating nuclear reactor"

They seem to use rather confusing units in describing activity inventories found in water. If I've understood correctly, this reference level of "water in a reactor operating normally" is some kind of a typical value of primary coolant activity in some fictitious representative reactor running with no fuel leakages (and excluding the N-16 gammas). Similarly, they give the iodine activities discovered in sea outside the plant as a multiplies of a reference value 40 Bq/kg, the basis of which is somewhat unclear at least to me and those I've talked to.

The way I see it, it would be much more clear if they would simply give the activities in Bq/kg and do the comparisons to some practical reference levels separately, if such are needed.

 

[shogun338]

Tokyo Electric pronounced it would proceed Thursday spraying Kuricoat C-720G, which envelops dust to try and knock down. It will be sprayed up sides of the reactors and all around reactors. If the three-week exam is successful, the spraying will go upon for as prolonged as necessary . Does anyone know if Kuricoat C-720G burns ? One website called it fake creosote . You know how creosote burns . If they cover everything in this stuff and it catches fire there making a bigger problem .

 

[Astronuc]

This diagram should help with identifying the recirculation and feedwater systems. It also shows the relative locations of the reactor cleanup and feedwater cleanup (filter demins).

 

[StrangeBeauty]

Hi everyone -- I'm new so please be kind. :)

First I'd like to thank everyone for freely giving their expertise and opinions here. I especially thank the mods/admins/helpers because that job has extra facets and work load attached to it ;) It can be difficult to remain calm and civil with this tragedy unfolding before our eyes, while trying to do analysis and speculation based on very incomplete info and no control by which to obtain more -- so thanks for that also.

Speculation leading to a question:
--Assuming there is a breach/leakage in RCVs #2 and #3 (which I think has been implied by the odd pressure readings in those for days [as opposed to pressure readings in #1; (not saying there is no breach there, just that the current pressure readings are much higher) Q: what is the normal pressure reading for cold shutdown?]
--and assuming the pressure measurement equipment is functioning somewhat normally)
--and trying to determine where the breach/leakage might be
I notice something consistent over the past week or so: no matter how much water they've pumped into the RCVs, the water level has remained about stable in each of the reactors. I do not believe this has been by design since a significant portion of the fuel assemblies are exposed.
Which leads to some speculative questions: Could the breach/leakage in each RCV be at/near the height of the water in each of the RCVs since they can't seem to get the water level any higher? What penetrations of the RCVs are at those various levels?

My second question is reiterating an earlier question about ongoing fission products. Is it true that it appears that fission is still occurring somewhere in one of the buildings (or what is the degree of certainty that this is the case)? I've not yet seen an alternative scenario for the production of those products associated with fission.

Thanks for any response, and please keep up the good work.

 

[RealWing]

Hi everyone -- I'm new so please be kind. :)

First I'd like to thank everyone for freely giving their expertise and opinions here. I especially thank the mods/admins/helpers because that job has extra facets and work load attached to it ;) It can be difficult to remain calm and civil with this tragedy unfolding before our eyes, while trying to do analysis and speculation based on very incomplete info and no control by which to obtain more -- so thanks for that also.

Speculation leading to a question:
--Assuming there is a breach/leakage in RCVs #2 and #3 (which I think has been implied by the odd pressure readings in those for days [as opposed to pressure readings in #1; (not saying there is no breach there, just that the current pressure readings are much higher) Q: what is the normal pressure reading for cold shutdown?]
--and assuming the pressure measurement equipment is functioning somewhat normally)
--and trying to determine where the breach/leakage might be
I notice something consistent over the past week or so: no matter how much water they've pumped into the RCVs, the water level has remained about stable in each of the reactors. I do not believe this has been by design since a significant portion of the fuel assemblies are exposed.
Which leads to some speculative questions: Could the breach/leakage in each RCV be at/near the height of the water in each of the RCVs since they can't seem to get the water level any higher? What penetrations of the RCVs are at those various levels?

My second question is reiterating an earlier question about ongoing fission products. Is it true that it appears that fission is still occurring somewhere in one of the buildings (or what is the degree of certainty that this is the case)? I've not yet seen an alternative scenario for the production of those products associated with fission.

Thanks for any response, and please keep up the good work.

If I were there, I would not put a lot of trust in the level measurements of the water in the core without doing some checks at the level transmitters. Some things that could cause erroneous readings are:
- reference legs not full
- salt deposits in the impulse lines between reactor and the transmitter
- re-solidified material in the core which may have blocked the impulse lines.
-Transmitters damaged

There is a big difference between "fission" (which is always occurring) and the reactor being critical.

 

[hbjon]

Brand new to this site and can tell I will be visiting it on a regular basis to read the fascinating and enlightening posts. Please accept my humble apologies if these questions have been answered too many times, but I was wondering does anyone know the quantities of fissible matter that is available to the reactors 1,2, and 3? And can someone take a stab at the worst case scenerios again? I just read that 1gm U235 has the same potential as 2000 tons of coal.

 

[tadjik]

Hi everyone -- I'm new so please be kind. :)

First I'd like to thank everyone for freely giving their expertise and opinions here. I especially thank the mods/admins/helpers because that job has extra facets and work load attached to it ;) It can be difficult to remain calm and civil with this tragedy unfolding before our eyes, while trying to do analysis and speculation based on very incomplete info and no control by which to obtain more -- so thanks for that also.

Speculation leading to a question:
--Assuming there is a breach/leakage in RCVs #2 and #3 (which I think has been implied by the odd pressure readings in those for days [as opposed to pressure readings in #1; (not saying there is no breach there, just that the current pressure readings are much higher) Q: what is the normal pressure reading for cold shutdown?]
--and assuming the pressure measurement equipment is functioning somewhat normally)
--and trying to determine where the breach/leakage might be
I notice something consistent over the past week or so: no matter how much water they've pumped into the RCVs, the water level has remained about stable in each of the reactors. I do not believe this has been by design since a significant portion of the fuel assemblies are exposed.
Which leads to some speculative questions: Could the breach/leakage in each RCV be at/near the height of the water in each of the RCVs since they can't seem to get the water level any higher? What penetrations of the RCVs are at those various levels?

My second question is reiterating an earlier question about ongoing fission products. Is it true that it appears that fission is still occurring somewhere in one of the buildings (or what is the degree of certainty that this is the case)? I've not yet seen an alternative scenario for the production of those products associated with fission.

Thanks for any response, and please keep up the good work.

Like you, I've been wondering why the water level is stable.
From what I've read all around, I tend to think (pure speculation of mine) that they can wish to maintain it stable since they don't know the géometrical configuration of the fuel in the upper part of the core (most things have melt in this upper part).
So, if they raise the level of water, I think (if I've properly understood the explanations here), that they take the risk to have a criticity incident (which can be provoked by the presence of liquid water) ... in other terms, they would take the risk to reactive the reactor.
If the level is so stable, it maybe because they do not dare to raise it; instead, they could prefer to cool the upper part by maintaining the water level 2 meters below the upper part of the fuel rods which still allows to cool the system by the vapor (I read somewhere here that vapor gives cooling effect up to 1,8m above the water level).

Just my opinion ...
PS : sorry for the approximative english (not my mother tongue)

 

[jensjakob]

#4 was build by a different company than 1+2+3:
http://www.bloomberg.com/news/2011-03-17/japan-s-nuclear-disaster-caps-decades-of-faked-safety-reports-accidents.html

(And there is a story about the CV being "fixed" in production.)

What I am looking at - is which kind of fuel was being refueled into #4.

 

[TCups]

REACTOR ACCESS FLOOR LAYOUT?


Can anyone here add to or correct anything I may have wrong here, please. These are annotated images from drone fly over posted earlier by Fred with what I "think" may be the layout of the reactor access level floors. As can be seen, this will substantially affect how the remainder of the damages might be interpreted.

Blue Rectangle = Pools
Orange Ovals, Circles = Dry Well Cap and approximate positon of Dry Well Plug on floor
Red Rectangle = Building Footprint
Green Rectangle = Lift Shaft

Important points that I am not certain about some basic layout aspects:
1) Are the floor layouts exactly the same in the two buildings?
2) Is there indeed a smaller pool off the side of the SFP between the SFP and Lift Shaft?

Note that the Dry Well Cap has been removed from Reactor 4 but (I believe) would still be in place on Reactor 3. I use it as a relative gauge of the size of where the footprint of the Dry Well Plug would have to be on the floor. Thanks.

ADDENDUM:

I add the "Oyster Creek" Reactor Diagram referenced in several earlier posts.

http://i306.photobucket.com/albums/nn270/tcups/Oyster-Creek-reactor.gif

 

[Astronuc]

For each 10 m of water, the pressure increases about 1 atm (0.10133 MPa, or 14.7 psia).

If the core were open to the atmosphere and the top of the core was at a depth of 10 m, the pressure at the top of the core would be ~ 2atm. The core height is about 3.8 m (150 inches). The core proper is the height of the fuel. The fuel rods are a little longer - about a 10 inch plenum atop the fuel stack, and endplugs and tie plates at each end.

If there is a leak at or below the core, and there is steam in the upper part, then it's possible that the pressure is between 1 and 2 atm, or roughly equal to containment pressure.

This might be of interest to folks
http://sustainableenergytoday.blogspot.com/2011/03/post-31-bwr-severe-accidents-primer.html

The RPV doesn't need to be breached for fission products to escape. There could be a breach in any number of pipes, valve, or pump, in the recirculation system, reactor water cleanup, CRDM, or feedwater system. As far as I remember, the FW inlet to the RPV is above core level in order to avoid loss of coolant below that level.

and this - IAEA chief proposes nuclear safety meeting
29 March 2011
http://www.world-nuclear-news.org/RS-IAEA_chief_proposes_nuclear_safety_meeting-2903114.html

 

[Joe Neubarth]

We are hearing of meltdowns, breaches of the reactors and flooded containment and cracked sides and this and that. If any or all of this is true, the reactor level could be determined by the leaks in the vessel structure and the containment structure. We know that the water they are pumping in is ending up in the turbine room structures so we know it is getting there some way and some how.

 

[tadjik]

Yes, there are leaks; anyway, from reports I read (maybe NISA), I've seen that water injection is apparently not permanent, so I suppose they could, in fact, raise the water level, even tough they have oubviously leaks at every reactor.

 

[jensjakob]

REACTOR ACCESS FLOOR LAYOUT?


Can anyone here add to or correct anything I may have wrong here, please. These are annotated images from drone fly over posted earlier by Fred with what I "think" may be the layout of the reactor access level floors. As can be seen, this will substantially affect how the remainder of the damages might be interpreted.

Blue Rectangle = Pools
Orange Ovals, Circles = Dry Well Cap and approximate positon of Dry Well Plug on floor
Red Rectangle = Building Footprint
Green Rectangle = Lift Shaft

Important points that I am not certain about some basic layout aspects:
1) Are the floor layouts exactly the same in the two buildings?
2) Is there indeed a smaller pool off the side of the SFP between the SFP and Lift Shaft?

Note that the Dry Well Cap has been removed from Reactor 4 but (I believe) would still be in place on Reactor 3. I use it as a relative gauge of the size of where the footprint of the Dry Well Plug would have to be on the floor. Thanks.

Your annotations looks spoton and are briliant to nail some facts.

 

[turbo]

This might be of interest to folks
http://sustainableenergytoday.blogspot.com/2011/03/post-31-bwr-severe-accidents-primer.html

Thanks for the link. His previous blog entry addressed spent fuel storage issues.

http://sustainableenergytoday.blogspot.com/2011/03/post-33-spent-fuel-storage-pool.html

 

[shogun338]

Some good info and updates posted on wikipedia. http://en.wikipedia.org/wiki/Fukushima_I_nuclear_accidents

 

[ivars]

http://www.reuters.com/article/2011/03/30/us-japan-nuclear-iaea-idUSTRE72T5JR20110330"

(Reuters) - Radiation measured at a village 40 km from Japan's crippled nuclear plant exceeded a criterion for evacuation, the U.N. nuclear watchdog said on Wednesday, the latest sign of widening consequences from the crisis.

The finding could increase pressure on Japan's government to extend the exclusion zone beyond 20 km (12 miles) around the Fukushima power plant, which has leaked radioactive particles since it was hit by a huge earthquake and tsunami on March 11.

Criticized for weak leadership during Japan's worst crisis since World War Two, Prime Minister Naoto Kan has said he is considering enlarging the evacuation area to force 130,000 people to move, in addition to 70,000 already displaced.

"The first assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village," Denis Flory, a deputy director general of the International Atomic Energy Agency (IAEA), said.

"We have advised (Japan) to carefully assess the situation and they have indicated that it is already under assessment," he told a news conference.

Greenpeace this week said it had confirmed radiation levels in this village northwest of the plant high enough to evacuate. But Japan's nuclear safety agency on Monday rebuffed a call by the environmental group to widen the evacuation zone.

 

[rhody]

For your information:

http://www.reuters.com/article/2011/03/30/us-japan-nuclear-germany-idUSTRE72T5OI20110330"

German Chancellor Angela Merkel has offered Japanese Prime Minister Naoto Kan "to make available special radio-controlled equipment from Germany that can be used for cleanup and repairs of reactors," her spokesman Steffen Seibert said in a statement.

Japan was considering the offer, the statement said on Wednesday. A government spokesman could not immediately verify which devices could be sent.

Rhody...

 

[M. Bachmeier]

@Astronuc:

SOUTH FACE BLDG 4

See image:
http://i306.photobucket.com/albums/nn270/tcups/SouthUnit4.png

With reference to the visible external ridge on Bldg's 1-4 at the level of the reactor access floor, part of that ridge is clearly visible on this image of the south face, Bldg 4. With that as a reference point, it seems to me that the visible damage below that ridge may extend two floors below the ridge (?), and that the depth of the damage below the ridge would be consistent with the depth of the SFP4. Again, not confirmed, but perhaps suggested by the images.

Is there a separate pool (new fuel?) to the west of the larger SFP, and are the intact walls below the ridge at the SE corner indicative of an intact exterior at the level of SFP4?

I realize I'm still relativistically not up to date (still catching up posts), but the area by the equipment bay resembles a hot spot. i.e., the area in a fire that is the original source (greater damage, more metal fatigue etc.) What are the odds that a very full SFP might be bypassed for storage of more active fuel during shutdown/changeover?
Wonder if that's common or a violation of safety protocols?

 

[ivars]

http://www.lex18.com/news/un-high-radiation-outside-japan-s-exclusion-zone"

Elena Buglova, an official from the International Atomic Energy Agency, said the reading was 2 megabecquerels per square meter at the village of Iitate, adding that "as a ratio it was about two times higher" than levels at which the agency recommends evacuations.
Iitate is about 25 miles (40 kilometers) from the Fukushima complex where emergency crews are battling to keep radioactivity from spreading.

Japanese officials have told residents to evacuate within a 12-mile (20-kilometer) zone and to stay indoors within 18 miles (30 kilometers) of the damaged complex, but U.S. officials have recommended citizens stay at least 50 miles (80 kilometers) away.

The officials emphasized that the readings at the village of Iitate were sporadic and only at one measuring point. They did not say exactly when the readings were taken but mentioned them along with radiation measurements of iodine 131 and cesium 137 in soil samples between March 18 and March 26.

 

[jensjakob]

http://www.scribd.com/doc/50775386/Areva-Fukushima-la-licence-d-exportation-de-MOX

Notice "Reload fuel for Reactor 1,2,3,4,5".
~35 tons of Uranium dioxide.

Will it be possible to research whether the plan was to reload #4 with MOX?

 

[PietKuip]

There is a big difference between "fission" (which is always occurring) and the reactor being critical.

There is almost no difference. Without a chain reaction, there will only be spontaneous fission, which is quite rare in uranium.

The high levels of shortlived iodine-134 were retracted as erroneous. I suspect that the reported levels of chlorine-38 were due to the same error in evaluating data of old samples. However, I have not seen any correction of those results. The data is still http://www.nisa.meti.go.jp/english/files/en20110325-6.pdf" .

 

[liamdavis]

I'm pretty sure it's not just suspended solids that become radioactive, it's any soluble ions too which is why de ionised water is used.
However I'm pretty sure the 'polishers' will be ion exchange filters or resins and will be able to 'remove' the majority of radiation from the water.

The problem is the collection of the water after it's been pumped into the building,... beacuse like the missing fuel at chernobyl... they've no idea where it's going as there's no seals/containment anymore!

Ok, de ionizing will have to be done as well. Thank you.

Actually, the hydrogen in the water can absorb a neutron and become deuterium, and some deuterium can absorb a neutron and become tritium. Leaking (cracked) control blades also release some tritium.

There are filters (resin beds, not HEPA filters) in the reactor water and feedwater clean up systems. Without power to the feedwater pumps and recirculation systems, which may be damaged (if the drywell is flooded then the recirculation pumps are underwater (seawater)), then I would expect that the filtering is not working - at least not properly or efficiently if at all.

Thank you. Yes, I am thinking that the existing equipment cannot be counted on for use.
I realize that these filter systems are not sitting on a shelf to be delivered. I am looking at it from the perspective of someone who has people come to him and say "can we make something that will do...?" and then we sketch something out and I construct it.

I am picturing a skid mounted reactor water polisher with its own pumps, that could be fabricated off site and then placed by a forklift on site. Plumbed into the contaminated water storage system, which has a finite capacity, any decontaminated water that can be discharged makes room for other contaminated water that has to be removed, allows for the use of water for flushing of contaminants in a way that does not allow them to be dust particles floating about.

It gives the people on site more latitude in the use of water as a problem solving tool. A robot directing a clean water stream around a contaminated basement area may not render it safe but may reduce the danger to workable levels more quickly than addressing each square inch of surface directly.

This unit does not have to be anything but functional and can be controlled by any length of wire that can be attached to it. A stationary unit, plumbed in, is what I would start with followed by a portable/movable unit that could work the trench.
liam

PS The diagram, post 2083, was helpful.

 

[jensjakob]

Some information about the cement-truck used for dousing the SFP's:
http://gearheads.in/showthread.php?...-on-its-way-to-save-Fukushima-s-No.-4-reactor

 

[|Fred]

From a pdf provided on the board http://ompldr.org/vN3VhMQ I extracted some layout of the improved Mk-1 used in Fukushima Unit 4 (for sure) and very likely on 2 and 3

It did not quite fit the look of the building we have in fujushima, So I figured (made the hypothesis) that the japanese sightly moded the upper level to make a nice rectangular building and got rid of some lower space.
(japanese design :red line vs blue) and got rid of some space on the (east wall)
based on my speculation i just corrected the perspective of the picture only based on external square structure and height of the 2 top floor..

 

[hbjon]

Remember the movie, Titanic? The engineer tells the captain, "From this point on there is nothing we can do, except prolong the inevitable". Of course, what they are doing will buy some time but, how much? Set up the logistics for entombment NOW! This thing could have been buried by now. Run some big *** pipes through the thing for future water circulation. Start sand bagging. Let's not get to the point where we say "Stand back, she's going to blow!

 

[razzz]

Some information about the cement-truck used for dousing the SFP's:
http://gearheads.in/showthread.php?...-on-its-way-to-save-Fukushima-s-No.-4-reactor

I read since at a normal job site you need a spotter with a remote control (and/or walkie talkie) to visually watch the discharge at the work area to control the the boom movements for placement, that the boom in this case was fitted with a camera to aid in maneuvering and spotting the discharge nozzle's target (mainly the spent fuel pond). I'm sure the view from that boom would be very telling.

 

[jlduh]

I wanted to give some information about results and measurement methods for iodine-131. The french CRIIRAD (which is a laboratory specialized in nuclear monitoring and is independant from french autorities) has published an article explaining how activity of this element in the air (in Bq/m3) has to measured. The important thing to remember is that some measurements methods (and more precisely some sampling methods) only show part of the total activity of the element in the air (which can then go to the soils and the fields when it's raining for example).

Iodine-131 can be present in the air either as:

a) particulates, which can be sampled with appropriate filters,
b) but it can also be present in the air under gazeous forms, and these WON'T BE CAPTURED BY THE SAME FILTERS, BUT NEED A SPECIFIC PROTOCOL OF SAMPLING WITH AIR CARTRIDGES containing charcoal.

IT IS IMPORTANT TO KNOW THAT THIS SECOND FORM (GAZEOUS IODINE 131) CAN BE 3 TO 14 TIMES MORE IMPORTANT THAN THE PARTICULATES FORM OF IODINE-131.

CRIIRAD is producing a report in which they show the example of recent measurements done by EPA on the air in the US after the fukushima accident.

The US report is here:

http://www.criirad.org/actualites/dossier2011/japon/radnet.pdf

I extract the paragraphs describing the two sampling methods used:

Results are presented from two types of air sampling: air canisters and air filters.
• Air Cartridge Sampling: RadNet deployable monitors pass air through a canister that contains charcoal. The cartridges collect radioactive particles and gases in much the same way that a home charcoal air filter traps cooking odors. The canisters are sent to an EPA laboratory for a sensitive laboratory analysis which can detect any radionuclides in the sample. The date on the table is the day that the canister was taken off the sampler.
• Filter Sampling: RadNet fixed or deployable monitors pass air through a filter which traps particulates. The filter is sent to an EPA laboratory for a sensitive laboratory analysis which can detect any radionuclides present. The date on the table is the day that the filter was taken off the sampler for analysis.

You can see in this other document (in french), in the colored results table (going down in the page):
http://94.23.16.204/criirad_telechargement_pdf/eau_de_pluie_iode_131.pdf

that the ratio between gazeous form/particulates form of iodine-131 can vary from 3 to 14 (for example, there was 14 times more gazeous form of iodine in the air at Dutch Harbour than there was in particulates form).

CRIIRAD is pushing a lot the information on this subject because in France the autorities give a lot of data about the iodine-131 activity in the air (through a network called teleray) BUT these numbers are based on a sampling method with filters which can just measure particulate form of iodine. So the numbers given can in fact be several times lower than reality because this network doesn't take into account gazeous forms.

Don't know how it is done in Japan but i thought this had to be presented here and known by people for correctly assessing the total activity of iodine-131 in the air. If you see activities of iodine-131 in Bq/m3, check or ask how measurements were done and if all the forms of iodine-131 (particulates AND gaz) have been sampled.

Measurements are not always an easy matter, this is an example of its tricks and of its complexity.

 

[TCups]

From a pdf provided on the board http://ompldr.org/vN3VhMQ I extracted some layout of the improved Mk-1 used in Fukushima Unit 4 (for sure) and very likely on 2 and 3

It did not quite fit the look of the building we have in fujushima, So I figured (made the hypothesis) that the japanese sightly moded the upper level to make a nice rectangular building and got rid of some lower space.
(japanese design :red line vs blue) and got rid of some space on the (east wall)
based on my speculation i just corrected the perspective of the picture only based on external square structure and height of the 2 top floor..

Fred:

This is excellent. We can now start to look at all the pictures again and make more informed assessments of the damages and possible mechanisms. But at a glance, on the south face of Bldg 4, the blown out panel(s) ARE NOT the area of the SFP, and they are BELOW the level of the reactor access floor, where, in Bldg 1 for sure and Bldg 3 with high probability, most of the hydrogen gas accumulated before the explosion. And the explosion at Bldg 4 DID NOT come from the reactor vessel or primary drywell containment. Hmmmm. . .

 

[Bodge]

Suprised that comments made by IAEA nuclear safety director Denis Flory have not been picked up on yet,

http://ecocentric.blogs.time.com/2011/03/30/has-fukushimas-reactor-no-1-gone-critical/

Scroll to the bottom for the comments made by the IAEA:

"It is not IAEA's final assesment...This may happen locally and possibly increase the releases.”

So in reactor 1, we have the oldest Mark 1 BWR-3, with rising pressures and high temperatures, 19 days after SCRAM.

Radiation levels in the secondary containment are an order of magnitude greater than in reactors 2 and 3 (~18 Sv/hr compared to ~1.2 Sv/hr) http://www.meti.go.jp/press/20110330007/20110330007-3.pdf

Reactor 1 has had high levels of water pumped into its core, but its heat output is increasing, possibly due to 'transient' criticalities in the IAEA's judgement.

Remember the "13 Neutron beams" (as of 23.03).

 

[Bodge]

"The risk to workers might be greater than previously thought because melted fuel in the No. 1 reactor building may be causing isolated, uncontrolled nuclear chain reactions, Denis Flory, nuclear safety director for the International Atomic Energy Agency, said at a press conference in Vienna. "

http://www.bloomberg.com/news/2011-03-30/record-high-levels-of-radiation-found-in-sea-near-crippled-nuclear-reactor.html

 

[Bodge]

Nobody has tackled this question. Reasoned speculation would be fine!

So, is it currently feasible for there to be a large steam explosion in (under) any of reactors 1-3?

Could there be corium in an unbreached RPV, suspended above a saturated area?

 

[0131413]

Another IAEA reading of Cs-137 in Iitate was reported to be 163 kBq/kg on Wed:
http://soafcom.com/m/Fukushima_I_Nuclear_Accident_Latest_News#24_March_2011

Since Bq/m² isn't easily convertible to Bq/kg, it's tough to tell how these readings might be related. Can anyone shed some light on a way to estimate one unit from the other and the pitfalls of doing so? I tried and fell into the "How do I know how much depth of soil the area measurement represents?" trap.

Unfortunately, the linked Reuters article doesn't specify if the reading was taken in the same place (or what was measured.) Does anyone have the original IAEA information? It's not on their news page: http://www.iaea.org/newscenter/news/

http://hps.org/publicinformation/ate/q7878.html

Apparently you need the penetration of the coring device...convenient.

 

[Joe Neubarth]

Nobody has tackled this question. Reasoned speculation would be fine!

We need to know what you think would be suspending it.