Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Borek]

I am not an engineer, but does "end of the design life" in the case of the concrete structure mean it loses its strength? I honestly don't know, just asking.

What I am more afraid of is the fact that these buildings were not only damaged by the earthquake (taken into account in the design) but also shocked and shattered by the explosions (NOT taken into account). Still, I don't see a viable alternative to the TEPCO plan.

 

[joewein]

I am not an engineer, but does "end of the design life" in the case of the concrete structure mean it loses its strength? I honestly don't know, just asking.

What I am more afraid of is the fact that these buildings were not only damaged by the earthquake (taken into account in the design) but also shocked and shattered by the explosions (NOT taken into account). Still, I don't see a viable alternative to the TEPCO plan.

I'm not a structural engineer either, but to my knowledge the problem with concrete is not age as such, but effects of cracks from frost or mechanical strain and resulting corrosion of steel reinforcement bars.

If cracks penetrate from the surface down to steel (which is normally protected by the alkaline milieu of the concrete) then carbon dioxide, water and oxygen can start their work of turning the steel into rust and that damages the structural integrity of the concrete.

The presence of large amounts of salt from sea water cooling makes the corrosion problem worse. It would be bad enough given the proximity of the ocean at Fukushima Daiichi.

We know there are cracks in the concrete at other locations around the reactors, such as near the trench where water flow was stopped using liquid glass. Wherever there are cracks in the concrete, be suspicious of the state of the reinforcement bars inside, which are needed to make the structure resilient against quakes.

Looking at units 3 and 4 there is no shortage of exposed reinforcement bars sticking out from shattered concrete after the explosions. We don't know what the bottom of unit 2 looks like, where the suppression chamber is assumed to have exploded.

In future a lot more added support structures may be needed like the pillars added under the SFP in one unit, to make up for the earthquake and corrosion damage.

 

[Rive]

It's not like they are not at the end of their design life, you know?

Those buildings were designed for ~40 years of operation and undefined years till decommission. So they are far from their out-of-op lifetime :-)

Regarding cracks and damages: such concrete structures can be repaired effectively. Apart from the technical details (heavy cranes and scaffolds will be needed, evenly for the cleanup and for the restoration - and to be honest those will be the most dangerous tasks there, not the ones in high rad environment) there is no problem here.

 

[zapperzero]

I am not an engineer, but does "end of the design life" in the case of the concrete structure mean it loses its strength? I honestly don't know, just asking.

What I am more afraid of is the fact that these buildings were not only damaged by the earthquake (taken into account in the design) but also shocked and shattered by the explosions (NOT taken into account). Still, I don't see a viable alternative to the TEPCO plan.

www.inl.gov/technicalpublications/Documents/2906947.pdf[/URL]
and this for an overview of other common causes of concrete fatigue
[PLAIN]www.ornl.gov/~webworks/cppr/y2001/pres/108732.pdf[/URL]

TL;DR: It's not clear at all what concrete does and does not do when exposed to radiation. However, we do know it doesn't fare well at all when exposed to heat and/or seawater. Concrete left by itself gets stiffer with age (more crack-prone). Cracks from corrosion (such as acid rain) and/or mechanical stresses that occur during normal operation (such as earthquakes, temp changes, shifting of heavy loads etc) are hard/impossible to fix, so a lot of thought and study goes into "how much longer can we safely afford to keep this building up".

 

[tsutsuji]

Second: OK, water is often used for radiation shielding - but am I right that water with high amounts of radioactive cesium in it is not the best for this purpose?

I see no real way to 'wash out' all the cesium from the corium before opening the RPV cap.

I don't know the answer, but wasn't there a similar problem at Three Mile Island?

(TBS news) Unit 3 RPV bottom reached 98.4 °C at 5:00 AM on on 5 September. An alternative cooling method is going to be implemented at unit 2 too.

 

[MJRacer]

www.inl.gov/technicalpublications/Documents/2906947.pdf[/URL]
and this for an overview of other common causes of concrete fatigue
[PLAIN]www.ornl.gov/~webworks/cppr/y2001/pres/108732.pdf[/URL]

TL;DR: It's not clear at all what concrete does and does not do when exposed to radiation. However, we do know it doesn't fare well at all when exposed to heat and/or seawater. Concrete left by itself gets stiffer with age (more crack-prone). Cracks from corrosion (such as acid rain) and/or mechanical stresses that occur during normal operation (such as earthquakes, temp changes, shifting of heavy loads etc) are hard/impossible to fix, so a lot of thought and study goes into "how much longer can we safely afford to keep this building up".[/QUOTE]

FRP Composites are an alternative to repair/strengthen existing/damaged concrete structures. [PLAIN]http://www.quakewrap.com/frp%20papers/Case-Study-of-Application-of-FRP-Composites-in-Strengthening-the-Reinforced-Concrete-Headstock-of-a-Bridge-Structure.pdf" is a random paper on the subject.

 

[Rive]

I don't know the answer, but wasn't there a similar problem at Three Mile Island?

Good point.

(TBS news) Unit 3 RPV bottom reached 98.4 °C at 5:00 AM on on 5 September. An alternative cooling method is going to be implemented at unit 2 too.

Yeah. But with the actual water injection rate (6m³/h through feedwater line and 3 m³/h through Core Spray) the temperatures are stabilizing after the first rapid fall. So this won't be enough, as it seems. Something is still missing.

Maybe some boron?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11090612_temp_data_3u-e.pdf

 

[zapperzero]

FRP Composites are an alternative to repair/strengthen existing/damaged concrete structures. http://www.quakewrap.com/frp%20papers/Case-Study-of-Application-of-FRP-Composites-in-Strengthening-the-Reinforced-Concrete-Headstock-of-a-Bridge-Structure.pdf" is a random paper on the subject.

Yea, good luck lining a PCV with that stuff. For bonus points, you have to do it underwater, with teleoperated manipulators.

EDIT: I find this kind of thing often happens, when interacting with people in my line of work as well. The possibilities offered by contemporary technology are as wide, as to appear boundless. They are not. Constraints of time, energy and complexity still apply.

 

[zapperzero]

Maybe some boron?

Don't say that. You'll be assured in the haughtiest of tones (as I was) that recriticality in the corium is un-possible. Nevermind the fact that TEPCO's decomissioning plan includes a need to develop ways of preventing it while all the cutting and moving is done. Nevermind that it happened at Chernobyl. Nevermind that it may have happened at TMI, but no-one had the gumption to check.

Bitter? Me? Yeah, a bit.

 

[NUCENG]

Don't say that. You'll be assured in the haughtiest of tones (as I was) that recriticality in the corium is un-possible. Nevermind the fact that TEPCO's decomissioning plan includes a need to develop ways of preventing it while all the cutting and moving is done. Nevermind that it happened at Chernobyl. Nevermind that it may have happened at TMI, but no-one had the gumption to check.

Bitter? Me? Yeah, a bit.

It shows, zz. I remember a number of people, including me, that have said that recriticality was possible, but that we did not have proof that it had or had not occurred. If anyone said it was impossible they would have to explain how they made that finding. If TEPCO failed to include measures to prevent criticality then that would be a valid point of concern. They have included it so you use that to prove an opinion that is equally unprovable. The fact is we just don't know, yet.

I have been thinking of ways to determine if recriticality has occurred and have come up with one possibility. We suspect that signicficant relocation of fuel has happened. If recriticality has occurred, it is possible that structures and components would have undergone neutron activation in areas not normally exposed to high neutron flux during normal operation.

At TMI the debris remained inside the RPV which probably would have made this effect difficult to detect. I have no idea how this would translate to a carbon moderated RBMK like Chernobyl. But if there is "core on the floor" at Fukushima this may be possible to detect.

 

[Dmytry]

It shows, zz. I remember a number of people, including me, that have said that recriticality was possible, but that we did not have proof that it had or had not occurred. If anyone said it was impossible they would have to explain how they made that finding. If TEPCO failed to include measures to prevent criticality then that would be a valid point of concern. They have included it so you use that to prove an opinion that is equally unprovable. The fact is we just don't know, yet.

I have been thinking of ways to determine if recriticality has occurred and have come up with one possibility. We suspect that signicficant relocation of fuel has happened. If recriticality has occurred, it is possible that structures and components would have undergone neutron activation in areas not normally exposed to high neutron flux during normal operation.

At TMI the debris remained inside the RPV which probably would have made this effect difficult to detect. I have no idea how this would translate to a carbon moderated RBMK like Chernobyl. But if there is "core on the floor" at Fukushima this may be possible to detect.

I'm not sure if that was discussed there:
http://www.pnas.org/content/early/2011/08/11/1109449108
the sulphur-35 detected in San Diego which may have been produced when seawater was irradiated in a criticality.

Note by the way that even though the result is in m^-2, this has little to do with fluence but is an result of multiplying airborne concentration (m^-3) by penetration depth and the factor related to cross section. It would be interesting to see more sensible analysis as it doesn't seem to make sense to estimate the airborne concentration, rather than total amount, based on the data after such a massive dilution.

I'd think the criticality would have been easy to detect on-site by isotope analysis, but it also would be equally easy not to detect the criticality if they did not want to.

 

[Rive]

Don't say that. You'll be assured in the haughtiest of tones (as I was) that recriticality in the corium is un-possible.

Let's cut it to pieces.

- recriticality as the reason of some unusual isotope levels detected in early samples is un-likely, because a chain-reaction which could produce the required amount of isotopes would produce too much heat:

- recriticality as the primary reason of any explosions there is un-likely because of the nature of the recriticality itself:

- recriticality as a reason of unusual temperatures in RPVs is possible but cannot be proven.

As I see it.

 

[NUCENG]

I'm not sure if that was discussed there:
http://www.pnas.org/content/early/2011/08/11/1109449108
the sulphur-35 detected in San Diego which may have been produced when seawater was irradiated in a criticality.

Note by the way that even though the result is in m^-2, this has little to do with fluence but is an result of multiplying airborne concentration (m^-3) by penetration depth and the factor related to cross section. It would be interesting to see more sensible analysis as it doesn't seem to make sense to estimate the airborne concentration, rather than total amount, based on the data after such a massive dilution.

I'd think the criticality would have been easy to detect on-site by isotope analysis, but it also would be equally easy not to detect the criticality if they did not want to.

I would love to see the full report from San Diego to see how they treated atmospheric dispersion. They claim that 0.7% of the S-35 generated onsite in Fukushima was detected at the Scripps Institute pier in San Diego. If so it was basically a point source and would be subject to inverse square law behavior as it expands away from the site. Even if this only applied as the plume expanded up into the atmosphere to the jet stream, that is impossible to believe. Atmospheric dispersion models generally show a reduction by a factor of 10E-4 to 10E-5 over a mile or so from an elevated release. There prediction shows 7E-3 over 5000 miles.

Another question comes from the summary of the study where they state that they could rule out cosmogenic S-35 and that the source could only be Fukushima. I saw no justification or details of how they reached that conclusion.

They acknowledge that there is cosmogenic production of S-35, but the summary does not explain how that contribution at the Scripps Pier was treated.

Finally the whole discussion of stating the source was derived from a neutron flux (n/m^2) is highly dependent on how that are term was related to the S-35 concentration at high elevations over Fukushima. There was insufficient description of their method, and my attempts to perform similar calculations have not come out anywhere near their results. The people that performed this analysis have previously studied cosmogenic generation of radio-sulfer which is basically a deep planar source over the upper atmosphere and for that source at 10E-3 dispersion to the surface is probably reasonable. I have never seen details of "moving box" atmospheric models in relation to atmospheric dispersion of the accident source term.

If anyone has seen any peer review results of the study, please post a link. I have participated in chemical marker testing of control room pressure envelopes that use extremely low concentrations of the marker chemical. I believe that this approach may have merit in tracking the radiation releases from Fukushima, but I'm not sure S-35 is the right marker.

 

[Dmytry]

I would love to see the full report from San Diego to see how they treated atmospheric dispersion. They claim that 0.7% of the S-35 generated onsite in Fukushima was detected at the Scripps Institute pier in San Diego. If so it was basically a point source and would be subject to inverse square law behavior as it expands away from the site. Even if this only applied as the plume expanded up into the atmosphere to the jet stream, that is impossible to believe. Atmospheric dispersion models generally show a reduction by a factor of 10E-4 to 10E-5 over a mile or so from an elevated release. There prediction shows 7E-3 over 5000 miles.

Yes the math there is terrible... I mean, why is concentration over Fukushima is per cubic meter rather than total amount? That does not make slightest sense, at Fukushima this was being diluted by many orders of magnitude within first few kilometers from smokestack, the concentrations at source are meaningless. At most you can have 'concentration' at the simulator cell size, but this actually corresponds to amount and not any real world concentration.

Another question comes from the summary of the study where they state that they could rule out cosmogenic S-35 and that the source could only be Fukushima. I saw not justification or details of how they reached that conclusion.

I think all we could do about the natural S-35 is to look at measurement data at other times (especially the past solar maximum) and see if this kind of peak is very much outside the normal range. Then calculate the source term, not as meaningless concentration but as amount.

They acknowledge that thjere is cosmogenic production of S-35, but the summary does not explain how that contribution at the Scripps Pier was treated.

Finally the whole discussion of stating the source was derived from a neutron flux (n/m^2) is highly dependent on how that are term was related to the S-35 concentration at high elevations over Fukushima. There was insufficient description of their method, and my attempts to perform similar calculations have not come out anywhere near their results. The people that performed this analysis have previously studied cosmogenic generation of radio-sulfer which is basically a deep planar source over the upper atmosphere and for that source at 10E-3 dispersion to the surface is probably reasonable. I have never seen details of "moving box" atmospheric models in relation to atmospheric dispersion of the accident source term.

Well, yea. I actually did some bit of atmospheric modelling a while back (for entirely different purposes though) and this just doesn't make a lot of sense.

If anyone has seen any peer review results of the study, please post a link. I have participated in chemical marker testing of control room pressure envelopes that use extremely low concentrations of the marker chemical. I believe that this approach may have merit in tracking the radiation releases from Fukushima, but I'm not sure S-35 is the right marker.

Could still be a useful marker, not a lot of natural around

 

[NUCENG]

Yes the math there is terrible... I mean, why is concentration over Fukushima is per cubic meter? That does not make slightest sense, at Fukushima this was being diluted by many orders of magnitude within first few kilometers from smokestack, the concentrations at source are meaningless. At most you can have 'concentration' at the simulator cell size, but this actually corresponds to amount and not any real world concentration.

I think all we could do about the natural S-35 is to look at measurement data at other times (especially the past solar maximum) and see if this kind of peak is very much outside the normal range.

Well, yea. I actually did some bit of atmospheric modelling a while back (for entirely different purposes though) and this just doesn't make a lot of sense.

Could still be a useful marker, not a lot of natural around

I'm open to correction of my concerns about this study. A typical BWR neutron flux at the RPV wall at full power is on the order of 10e9 n/cm^2 or 10e13 n/m^2. If the atmosphere dispersion is really on the order I expect from previous experience, the neutron flux from a recriticality at Fukushima would have had to be near as high as full power.

Anyway, that study is still a good topic for discussion, thanks.

 

[zapperzero]

It shows, zz. I remember a number of people, including me, that have said that recriticality was possible, but that we did not have proof that it had or had not occurred. If anyone said it was impossible they would have to explain how they made that finding. If TEPCO failed to include measures to prevent criticality then that would be a valid point of concern. They have included it so you use that to prove an opinion that is equally unprovable. The fact is we just don't know, yet.

I have been thinking of ways to determine if recriticality has occurred and have come up with one possibility. We suspect that significant relocation of fuel has happened. If recriticality has occurred, it is possible that structures and components would have undergone neutron activation in areas not normally exposed to high neutron flux during normal operation.

At TMI the debris remained inside the RPV which probably would have made this effect difficult to detect. I have no idea how this would translate to a carbon moderated RBMK like Chernobyl. But if there is "core on the floor" at Fukushima this may be possible to detect.

At Chernobyl some plutonium pooled in a corner and went critical when rain water infiltrated the basement. Much higher enrichment than here, to be sure.

Re: detection. Perhaps senior workers on-site would be willing to donate their wedding rings for science? Other small items may also serve. Some dosimeters? If new/unused ones were brought in after the accident, the should show no neutron activation, yes?

Re: my attitude. I am just relieved that the possibility is recognized. I would not go as far as to say that it's proven when it obviously is not.

 

[nikkkom]

At Chernobyl some plutonium pooled in a corner and went critical when rain water infiltrated the basement.

Wow. Never heard of that. Googled a bit but found nothing. Do you have a link?

 

[zapperzero]

Wow. Never heard of that. Googled a bit but found nothing. Do you have a link?

Here you go.
http://www.osti.gov/bridge/servlets/purl/263918-f2Q5cb/webviewable/263918.pdf

 

[Dmytry]

I'm open to correction of my concerns about this study. A typical BWR neutron flux at the RPV wall at full power is on the order of 10e9 n/cm^2 or 10e13 n/m^2.

you mean n/(m^2*s) ?
If it was at ~1/1000 the power for few hours...

 

[MJRacer]

Yea, good luck lining a PCV with that stuff. For bonus points, you have to do it underwater, with teleoperated manipulators.

EDIT: I find this kind of thing often happens, when interacting with people in my line of work as well. The possibilities offered by contemporary technology are as wide, as to appear boundless. They are not. Constraints of time, energy and complexity still apply.

There are three large reactor buildings that have been severely damaged by hydrogen explosions. Working inside those buildings, given probable continued seismic activity as well as corrosion is going to be a hazard over the foreseeable time period (10 to 20 years). It would seem FRP composites may serve well to stabilize the structures of these buildings, as well as reduce future corrosion of reinforcing elements by sealing cracks. From the structural point of view, that is what first comes to mind when looking at these buildings. The specialized application that leads you to wholesale dismiss the whole idea is not representative of the many conventional uses of this technology that are well within the proven experience in structural repair in non-nuclear applications.

 

[zapperzero]

There are three large reactor buildings that have been severely damaged by hydrogen explosions. Working inside those buildings, given probable continued seismic activity as well as corrosion is going to be a hazard over the foreseeable time period (10 to 20 years). It would seem FRP composites may serve well to stabilize the structures of these buildings, as well as reduce future corrosion of reinforcing elements by sealing cracks. From the structural point of view, that is what first comes to mind when looking at these buildings. The specialized application that leads you to wholesale dismiss the whole idea is not representative of the many conventional uses of this technology that are well within the proven experience in structural repair in non-nuclear applications.

Or you could just prop them up with steel trusses and not have to worry about the accelerated aging of polymer resins in radioactive environments, the many hours of skilled labor needed and so on and so forth.

And still, the integrity of the RPVs is the bigger problem, long term.

EDIT: to clarify. I emphasize skilled labor because most of the work on site is and will be, necessarily, done by jumpers, who are unskilled labor by definition.

 

[NUCENG]

you mean n/(m^2*s) ?
If it was at ~1/1000 the power for few hours...

Yes the /s is important as well - if that is the right unit. Add that to my list of errors :tongue:. I have done calculations of activation rates from neutron flux, and well as participated in neutron irradiation of vessels and internals. I have forwarded the summary of the study to othe colleagues and none of us have been able to figure out how they reached their numbers and conclusions.

Specifically, they counted their samples for 4 hours and came up with 1502 atoms of S-35. Is that the peak activity - 1502 decays per second (Bq) of S-35? Or is it 1502 total atoms of S-35 detected over the four hour count? With that kind of uncertainty should it be n/m^2*s or /hr or /fortnight? All we can tell for sure is that whatever they measured was higher than they have seen previously and the concluded that the source of that peak was Fukushima.

Any help deciphering that study would be appreciated. At a minimum they should get a big fat F- on the abstract or summary they wrote. Any ideas, Dmytry?

 

[Rive]

Dmytry, NUCENG: there was some information leakage regarding that PNAS article. Here is what I've found - I hope it helps:

http://www.pnas.org/content/suppl/2011/08/15/1109449108.DCSupplemental/pnas.1109449108_SI.pdf

http://www.docstoc.com/docs/9146110...measurements-of-radioactive-35S-in-California

Ps.: I don't know if it's legal or not - Moderators, if must please delete or modify the links/post.

 

[etudiant]

Yes the /s is important as well - if that is the right unit. Add that to my list of errors :tongue:. I have done calculations of activation rates from neutron flux, and well as participated in neutron irradiation of vessels and internals. I have forwarded the summary of the study to othe colleagues and none of us have been able to figure out how they reached their numbers and conclusions.

Specifically, they counted their samples for 4 hours and came up with 1502 atoms of S-35. Is that the peak activity - 1502 decays per second (Bq) of S-35? Or is it 1502 total atoms of S-35 detected over the four hour count? With that kind of uncertainty should it be n/m^2*s or /hr or /fortnight? All we can tell for sure is that whatever they measured was higher than they have seen previously and the concluded that the source of that peak was Fukushima.

Any help deciphering that study would be appreciated. At a minimum they should get a big fat F- on the abstract or summary they wrote. Any ideas, Dmytry?

The initial report is here: http://environmentalresearchweb.org/cws/article/yournews/46920

The measurement was to collect airborne contaminants for 4 days and then to measure the radioactive sulfur levels in the sulfates captured during that interval.
The detected amounts, equivalent to 1501 atoms of radioactive sulfur/ m**3, is about 60% more than the peak atmospheric level of 950 atoms found after cosmic ray surges.
Does that help any?

 

[Borek]

Ps.: I don't know if it's legal or not - Moderators, if must please delete or modify the links/post.

Looks OK to me, both documents are hosted on what looks like legitimate sites, and you don't quote (excessive parts of the) documents.

 

[NUCENG]

Dmytry, NUCENG: there was some information leakage regarding that PNAS article. Here is what I've found - I hope it helps:

http://www.pnas.org/content/suppl/2011/08/15/1109449108.DCSupplemental/pnas.1109449108_SI.pdf

http://www.docstoc.com/docs/9146110...measurements-of-radioactive-35S-in-California

Ps.: I don't know if it's legal or not - Moderators, if must please delete or modify the links/post.

The second one looks new to me. I'll take a look. Thanks.

 

[Caniche]

Don't say that. You'll be assured in the haughtiest of tones (as I was) that recriticality in the corium is un-possible. Nevermind the fact that TEPCO's decomissioning plan includes a need to develop ways of preventing it while all the cutting and moving is done. Nevermind that it happened at Chernobyl. Nevermind that it may have happened at TMI, but no-one had the gumption to check.

Bitter? Me? Yeah, a bit.

Well I wasn't going to mention it ,but it does seem odd that Tepco are so concerned about the critical stuff when some of our learned contributors or adamant that you need precise geometric configuration to have a hope in hell of getting a spark. They could save Tepco millions.
That "pnas' report is dynamite though, radiation 368 times above normal ,blimey

 

[jim hardy]

I too am suspect of the sulfur's origin. Was it really Japan?



"The detected amounts, equivalent to 1501 atoms of radioactive sulfur/ m**3, is about 60% more than the peak atmospheric level of 950 atoms found after cosmic ray surges.
Does that help any?"

Only 60% larger?

There were unusually lage solar eruptions on Feb 15 and March 9 of this year.


old jim

 

[StrangeBeauty]

I too am suspect of the sulfur's origin. Was it really Japan?

"The detected amounts, equivalent to 1501 atoms of radioactive sulfur/ m**3, is about 60% more than the peak atmospheric level of 950 atoms found after cosmic ray surges.
Does that help any?"

Only 60% larger?

There were unusually lage solar eruptions on Feb 15 and March 9 of this year.

old jim

Not unusually large, just sizeable and typical for the active part of the solar cycle; X1 and X2 magnitude flares. We had a much larger X7 (log scale) in Aug - any sulfur reported from that? The X2 in Feb did produce some good auroras (CME was more Earth directed).

http://www.spaceweather.com/archive.php?view=1&day=07&month=09&year=2011

X-flares of Solar Cycle 24: There have been only a small number of X-flares since the beginning of new Solar Cycle 24. Here is a complete list so far: Feb. 15, 2011 (X2), March 9, 2011 (X1), Aug. 9, 2011 (X7), Sept. 6, 2011 (X2). Before these four, the previous X-flare occurred on Dec.14, 2006, (X1) during old Solar Cycle 23.

The X2 flare is believed to have launched a CME toward Earth which should hit on the 8th-10th. Anyone have sources for relevant sulfur measurements over the next couple of days? Was sulfur seen after the Feb 9th timeframe? What's expected? What would be out of normal expectations?

I share the skepticism of the origin of the sulfur in any case - more data please.

I continue to follow the admirable work here. Please keep it up as the most people seem to have forgotten/want to forget that this tragedy has decades at the least left to fully unfold.

 

[Rive]

By the actual temperature data some temperatures started to rise again as the water flow through the feedwater line was reduced to 5m³/h.

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11090806_temp_data_3u-e.pdf

- Is this a kind of evidence, that the water from feedwater line also reaches at least some parts of the core debris? IMHO yes.

- Was there any chemical analysis regarding the amount of boron in the water from the basement? I can't recall any.

- is there any way to recirculate the boron as they can recirculate the water?

 

[MJRacer]

Or you could just prop them up with steel trusses and not have to worry about the accelerated aging of polymer resins in radioactive environments, the many hours of skilled labor needed and so on and so forth.

And still, the integrity of the RPVs is the bigger problem, long term.

EDIT: to clarify. I emphasize skilled labor because most of the work on site is and will be, necessarily, done by jumpers, who are unskilled labor by definition.

The RPVs are made out of steel. Nobody has suggested using FRP composites on them. That is a straw man. Any structural repairs are going to require long hours of skilled labor, as well as long hours of unskilled labor. Steel trusses are an alternative also, as are steel plates, each of which will have its own difficulties and its own limitations. FRP composites give you another tool in your tool belt, so to speak. Different polymer resins will have different tolerances for radioactivity. Some polymers are even used in casks used for long-term storage of radioactive resins, where they need to pass certain specifications for a period of 300 years, IIRC.

In closing, I do not wish to belabor this issue further. Let's just agree to disagree.

 

[zapperzero]

Corium quenching and cooldown with overlying water pool:

http://www.sciencedirect.com/science/article/pii/S0029549306003062
http://www.sciencedirect.com/science/article/pii/S0029549307000222

Tl;DR:

The measured cooling rates were found to decrease with increasing concrete content and, contrary to expectations, are essentially independent of system pressure.

.

 

[zapperzero]

The RPVs are made out of steel. Nobody has suggested using FRP composites on them. That is a straw man. Any structural repairs are going to require long hours of skilled labor, as well as long hours of unskilled labor. Steel trusses are an alternative also, as are steel plates, each of which will have its own difficulties and its own limitations. FRP composites give you another tool in your tool belt, so to speak. Different polymer resins will have different tolerances for radioactivity. Some polymers are even used in casks used for long-term storage of radioactive resins, where they need to pass certain specifications for a period of 300 years, IIRC.

In closing, I do not wish to belabor this issue further. Let's just agree to disagree.

I should have written PCV, of course those are made of concrete.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110908/0455_osensui.html Tepco needs to create more waste storage space for the Areva system sludge, as the present storage area will become full by October 10. Utilization rates for the past week were 90.6% (Kurion-Areva) and 91.4 (SARRY) [I guess this is counting 100%=25 tons/hour, with SARRY line B only. I am still wondering what the status of SARRY line A is]. The 90% target has been reached for the first time.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110907/index.html Confirming that Daiichi units 1,2,3,4 will be decommissioned, Tepco president Toshio Nishizawa said the restarting or decommissioning of Daiichi units 5,6 and Daini four units will be "decided taking prefecture and local opinion into account".

http://www.asahi.com/english/TKY201109060349.html "No response was given to Paris about Fillon's proposal [to recycle Fukushima spent fuel], and the matter is still being considered by a government panel on energy and the environment."

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110906_01-e.pdf Fukushima Daini photograph series, right after disaster and now. Large size pictures are available at http://www.tepco.co.jp/en/news/110311/index-e.html

 

[etudiant]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110908/0455_osensui.html Tepco needs to create more waste storage space for the Areva system sludge, as the present storage area will become full by October 10. Utilization rates for the past week were 90.6% (Kurion-Areva) and 91.4 (SARRY) [I guess this is counting 100%=25 tons/hour, with SARRY line B only. I am still wondering what the status of SARRY line A is]. The 90% target has been reached for the first time.

Thank you, Tsutsuji-san, for your superb continued research. We are in your debt.

The progress of the water decontamination is a bit puzzling.
TEPCO reports that 80,000 cubic meters have been decontaminated and over 30,000 desalinated, but the stored volume yet to be treated, at 107,000, is down less than 20,000 from its peak of about 125,000. At this rate, it will take several years to drain the water from the plant, despite the addition of SARRY.
Meanwhile, the waste build up will accelerate as the spent SARRY columns add to the AREVA sludge and Kurion zeolites. That pile of very nasty material will need tending for many decades.
Are there any specifics on the storage space used? TEPCO does claim that this problem was adequately provided for, but no detail or photographs have been released, afaik.