Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[SteveElbows]

Humm, personnaly i see some visual global correlation between temps on this graphic, don't you?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11053106_temp_data_3u-e.pdf

The last large increase in temps was i think stopped when they injected boron (or MORE boron?) in N°3, at least it has been discussed about that here.

Yes, many of the temps correlate, I was just pointing out that 'RPV Bellows air' had a big spike in temperature in April, during which time most other temps did not rise dramatically, so I do not like to pay attention to this temperature on its own.

Certainly I would not dream of describing the temperature situation at reactor 3 as stable, and there have been some signs of increasing temperatures in recent days. But its not clear that these will keep on climbing, so its too early for me to declare that temperatures at 3 are going crazy again. But I think its safe to say that these temperatures are not as low as TEPCO would like, and the pattern at reactor 3 is quite different to reactors 1 & 2.

As for the explanation for these events, I am just not sure. As I've said previously, injection of boron was done at same time as they were rapidly increasing water flow rates, so I find it hard to judge what was responsible for getting the temperatures somewhat under control in may.

 

[MiceAndMen]

In this case I don't want to know what wouldn't be "exemplary"

Exemplary conduct would have started with being honest about the data they had from day 1, and a good followup would have been a "roadmap" plan not rooted in fantasy. Look at the IAEA's mission statement: http://www.iaea.org/About/mission.html

develops nuclear safety standards and, based on these standards, promotes the achievement and maintenance of high levels of safety in applications of nuclear energy, as well as the protection of human health and the environment against ionizing radiation;

With their statements in the Bloomberg article cited earlier, they are promoting imaginary achievements in Japan. I'll leave the rest for the other thread.

 

[jlduh]

If you stick to facts, this is one of the best places for animals in Europe:

http://www.nsrl.ttu.edu/chornobyl/wildlifepreserve.htm

See also:

http://news.bbc.co.uk/2/hi/europe/4923342.stm

I you stick to facts Borek, many animals live much better where there is no human

So in a sense, we could call nature park every place where human had to leave because of industrial mess for example, but this can become a kind of novlang, don't you think? Don't want to argue on this subject on this thread, but as you answered me, let say that I'm just a little bored of greenswashing speak to wash dirty stuff. You know that words are describing more than facts very often (this was an article in a newspaper). That's why they are so powerful...

 

[zapperzero]

Here we are again, discussing politics. Nature of the animal, it seems. To all those who commented on the IAEA report: for my sins, I am quite familiar with the kind of language used. Here's my analysis, feel free to discuss:

https://www.physicsforums.com/showpost.php?p=3332836&postcount=219

EDIT: also see the post above...

 

[Jorge Stolfi]

Yes, many of the temps correlate, I was just pointing out that 'RPV Bellows air' had a big spike in temperature in April, during which time most other temps did not rise dramatically, so I do not like to pay attention to this temperature on its own.

How could the temperature near the top of the drywell be highter than the temperatures measured on the RPV? Two hypotheses that I can think of:

* There is a leak from the drywel near that place, say through the diaphragm/bellows into the refueling space above, or through a broken pipe into the gap between drywell and concrete. As the hot hydrogen-rich steam comes in contact with the air, the hydrogen burns (with an invisible flame) heating up the drywell wall.

* The temperature inside the RPV is actually much higher than what the RPV sensors show, as the RPV wall is being cooled from the outside by water leaking from the injection pipes. But there is a relatively small leak near the top that blows hot steam from inside the RPV into the top region of the drywell, heating it locally.

Of course you can explain anything with the magic words "instrument malfunction". But it is hard to see how a thermocouple could give a reading just a few tens of degrees higher than the correct value. I would expect it to either drop to zero volts (if the wires are severed) or give a lower-than-correct voltage (if the insulation of the wires is compromised).

 

[NUCENG]

Here we are again, discussing politics. Nature of the animal, it seems. To all those who commented on the IAEA report: for my sins, I am quite familiar with the kind of language used. Here's my analysis, feel free to discuss:

https://www.physicsforums.com/showpost.php?p=3332836&postcount=219

EDIT: also see the post above...

Maybe it wasn't all a rosy picture.

http://www.google.com/hostednews/afp/article/ALeqM5iuTRMDEJRz--IfEm_cg_iFlvNQGg?docId=CNG.9e4977e7a1dedbfd01785d2d4b7cb668.791

Here is the summary report:

http://www.nisa.meti.go.jp/english/files/en20110601-1.pdf

 

[biggerten]

How could the temperature near the top of the drywell be highter than the temperatures measured on the RPV? Two hypotheses that I can think of:

* There is a leak from the drywel near that place, say through the diaphragm/bellows into the refueling space above, or through a broken pipe into the gap between drywell and concrete. As the hot hydrogen-rich steam comes in contact with the air, the hydrogen burns (with an invisible flame) heating up the drywell wall.

* The temperature inside the RPV is actually much higher than what the RPV sensors show, as the RPV wall is being cooled from the outside by water leaking from the injection pipes. But there is a relatively small leak near the top that blows hot steam from inside the RPV into the top region of the drywell, heating it locally.

Of course you can explain anything with the magic words "instrument malfunction". But it is hard to see how a thermocouple could give a reading just a few tens of degrees higher than the correct value. I would expect it to either drop to zero volts (if the wires are severed) or give a lower-than-correct voltage (if the insulation of the wires is compromised).

Since thermocouples require good connections, I can see corrosion introducing offset quite easily. High temperatures, saltwater, steam, oh, I can see error possibilities indeed.

 

[~kujala~]

A nice article in allthingsnuclear about spent fuel pools:

http://allthingsnuclear.org/
(Fission Stories #42: Air Error)

When workers manipulate valves on reactor systems, a second worker must verify the proper configuration is achieved. Valves on spent fuel pool systems don’t require checking.

Instruments monitoring key parameters on reactor systems require backups to ensure the parameters are monitored 24/7. Instruments monitoring key parameters in the spent fuel pools neither require backups nor even to be working themselves.

If we continue to treat irradiated fuel in spent fuel pools so cavalierly, we risk someday having lots of dead cavaliers.

 

[Bandit127]

[URL]http://www.tepco.co.jp/en/news/110311/images/110601_01.jpg[/URL]

I presume this is the heat exchanger for the Unit 2 SFP. Again, ingenuity at work and good to see.

The larger diameter pipes will be bringing in coolant (probably seawater) in an open loop and this will cool the heat exchanger. The smaller pipes will be a closed loop system that circulates clean(er) water around the fuel pool, thus removing heat to the heat exchanger.

As others have suggested, they seem to be taking advantage of pre existing piping for the closed loop part.

It doesn't look great and may not survive another tsunami but it is good engineering given the circumstances and it is a good example of how we are going to engineer our way out of this situation.

In time more elegant and robust solutions will be found, but right now this is (in my opinion) perfect.

Well done the guys and girls at the front line for a big step in the right direction.

 

[etudiant]

The well informed site Atomic Power Review here suggests these are absorption towers for cleaning some of the water.
http://atomicpowerreview.blogspot.com/2011/06/fukushima-daiichi-update-june-1st.html

Not sure which is right, but had thought that the absorption was just one part of a series of process steps,
so this may indeed be a heat exchanger.
Can anyone tell for sure?

 

[Bandit127]

The well informed site Atomic Power Review here suggests these are absorption towers for cleaning some of the water.
http://atomicpowerreview.blogspot.com/2011/06/fukushima-daiichi-update-june-1st.html

Not sure which is right, but had thought that the absorption was just one part of a series of process steps,
so this may indeed be a heat exchanger.
Can anyone tell for sure?

Good info and thanks. Looking at it, I suspect you are right.

I will reduce my hope and optimism that we have closed loop cooling somewhere in Units 1-4 until we have some more information.

 

[MadderDoc]

Good info and thanks. Looking at it, I suspect you are right.

I will reduce my hope and optimism that we have closed loop cooling somewhere in Units 1-4 until we have some more information.

I think the equipment in the photo may be for removing cesium from the contaminated sea water in the unit 3 screen area, as referenced in:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110521e2.pdf

 

[etudiant]

Is it even possible to selectively remove cesium contamination at the part per 10 million level from sea water? Would not the overwhelmingly more numerous sodium ions saturate the zeolite in short order?

 

[tsutsuji]

[URL]http://www.tepco.co.jp/en/news/110311/images/110601_01.jpg[/URL]

I presume this is the heat exchanger for the Unit 2 SFP. Again, ingenuity at work and good to see.

It is the "Sea water circulatory purification system" aimed at purifying the harbor : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110531_01-e.pdf

 

[htf]

That makes sense. I don't like the idea to use some kind of rubber hoses for the cooling system. Something more temperature and pressure resistant would give me a better feeling.

 

[WhoWee]

It is the "Sea water circulatory purification system" aimed at purifying the harbor : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110531_01-e.pdf

How much water can they hope to purify with this unit - does the intake target problem areas?

 

[Bandit127]

It is the "Sea water circulatory purification system" aimed at purifying the harbor : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110531_01-e.pdf

Sadly, I concede that you are right - my optimism is popped like a balloon with a pin.

...I wonder how such a small system will cope with the millions of liters of water in the harbour. Those small hoses can probably take 200 l/min at 3 bar. (An informed guesstimate).

For the volume in the harbour, I guess 15m of depth, 300m out to the harbour wall and 1000m width along the seafront and I get 4.5 x 10^6 m3 of harbour water. Or 4.5 x 10^9 litres.

With my guess of 200 l/min, we would pass 4.5 x 10^9 l through in 2.25 x 10^7 minutes. That's about 42 years to pass the water in the harbour through once.
Better I reckon to use it to treat the water that will form the closed loop part of the Unit 2 SFP cooling system.

And - once they have gained the skills to do it with the Unit 2 SFP, the closed loop cooling water for the rest of the SFPs and beyond from there.

(Oops - my unbounded opimism is bouncing back. Apologies...)

 

[Atomfritz]

Hmm, I asked myself, how much cesium did they get into the these water masses in the buildings they want to decontaminate.

1 gram of Cs-134 (half life 2.0648 y) makes up 1293 curies.
1 gram of Cs-137 (half life 30.17 y) makes up 86.55 curies.

(Calculated according to the formula described http://www.bautforum.com/showthread...odine-in-nuclear-waste?p=1893658#post1893658".)

So ...
...one megacurie of Cs-134 weighs about 773.4 g.
...one megacurie of Cs-137 weighs about 11.55 kg.

So, if we have about, say, 12000 tons of water with 1 megacurie Cs-134 and Cs-137 each, then this would be a ppm cesium (weight 12kg total), I think.

Too bad Tepco doesn't publish salinity data, so we can only guess the ratio of Cs and seawater salt. But appears to be sure that there is salt in the magnitude of at least tens of tons.
So my layman's estimate is that the ratio seawater salt:cesium in the T/B water could be 10000s-1000s:1.

Does anybody know whether Areva's plant also precipitates salt or is selective to cesium, and if, how much?

 

[Jorge Stolfi]

Since thermocouples require good connections, I can see corrosion introducing offset quite easily. High temperatures, saltwater, steam, oh, I can see error possibilities indeed.

But, can those errors be positive?

I know about theormocouples only from theory, not from practice. AFAIK corrosion of electric wires or terminals near the sensing junction should only increase the resistance of the loop, not the net electric potential generated by the junction. Thus the temperature reading (basically a measure of voltage at the other end of the wires) should be diminished, not increased. Similarly, any damage to the insulation along the wires would create another junction at that spot; if the temperature there is lower than at the normal junction, the reading again will be lowered, not increased. Is this correct?

One possibility for positive errors is electrical "leaks" into the thermocouple wires from other nearby wires. Are there any others?

 

[Borek]

https://www.physicsforums.com/showpost.php?p=3230258&postcount=2885

 

[Jorge Stolfi]

To complement the plots posted yesterday, here are two plots of the pressures in unit #3 spanning from mar/20 to mar/22. The first one is based on a consolidated table of water levels, pressures and CAMS readings recently posted by TEPCo (http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf).

The second plot uses the pressure readings from the faxes that TEPCo sent to NISA and were distributed by NISA at the time, as part of their periodic press releases (http://www.meti.go.jp/press/).

Note that the large transient in the core pressure "A", quite conspicuous in the first graph, is entirely absent in the second graph --- even though the latter uses a subset of the data points of the former. Note also that the max pressure recorded by TEPCo during that transient (11.67 MPa) exceeds the maximum design pressure of the RPV; and that peak is confirmed by three readings over the space of one full hour.

 

[GJBRKS]

If there is about 100,000 tons of similarly contaminated water in the entire plant, that would suggest about 12Pbq *100,000/2700 = about 440 Pbqs of Cesium at Fukushima.
Seems that AREVA really has a job to do.
Has anyone any idea whether their selective precipitation techniques have a prayer of working on this minute quantity of cesium, ( about 0.05 gram/ton) from a salt water solution? They claimed 99.9% to 99.99% removal, but that seems just heroic to me, based on my long ago chemistry background.

They wouldn't get the contract if not ...
A 99.99% cleanup on a contamination of 100mSv/hour would still amount to .01 mS/hour .
That would be 87 mSv / year , 87 times the public allowed dose

 

[etudiant]

They wouldn't get the contract if not ...
A 99.99% cleanup on a contamination of 100mSv/hour would still amount to .01 mS/hour .
That would be 87 mSv / year , 87 times the public allowed dose

Afaik, the water is much more contaminated than that, so even the treated material will be painfully dirty, maybe 1000-10,000x the allowable limit. Still way better than 1,000,000x the limit or more as at present.
The question though is whether there is any experience with selective cesium removal in the presence of an overwhelming amount of sodium. It seems unlikely that anyone has ever needed such a process before, so while the AREVA facility may be the best or perhaps the only option TEPCO had, it may not be a very effective solution.
What is plan B?

 

[DaveC426913]

Thought I'd be the first to point out that this thread just cleared 1 million views.

 

[SteveElbows]

Note that the large transient in the core pressure "A", quite conspicuous in the first graph, is entirely absent in the second graph --- even though the latter uses a subset of the data points of the former. Note also that the max pressure recorded by TEPCo during that transient (11.67 MPa) exceeds the maximum design pressure of the RPV; and that peak is confirmed by three readings over the space of one full hour.

Its very annoying that the B pressure reading over the same time period does not do anything interesting, because it makes it hard to be too confident that the pressure really rose to the extent that A reading indicates. What the various pressure readings were doing in the week before the 21st don't really help me get a sense of exactly what may have happened either, eg its not clear to me whether the rpv could attain such high pressures again given how the pressure was for days before the 21st?

But if you added some temperature data to your graph, I think you would end up with a stronger looking indication that something happened that night, since some temperatures peak near or soon after that time, and certain temp sensors go on to give wacky negative values after this event.

As for why the 3 interesting datapoints are missing from the status snapshots that were published a few times a day, it seems inevitable to me because of what time they tended to take readings to publish vs the time of day that the pressure A spike happened. So I am very happy that we have more comprehensive data available to us for some weeks now, its just a shame it isn't enough to draw strong conclusions. Maybe we can be reasonably confident that significant stuff happened early on the 21st and possibly on a few other occasions that week as well, but I do wonder whether we will ever find out what. I don't imagine there is much further data from that time period, so our only hope may be to wait until better idea about state of core & containment are known, and then see if we can get this to match any theories about what happened around the 21st. CAMS data doesn't seem to help in this case, and from memory I think the times that neutron readings went above <0.01 in published data tended to be much earlier on in the crisis, but I will go and double-check this now.

 

[SteveElbows]

CAMS data doesn't seem to help in this case, and from memory I think the times that neutron readings went above <0.01 in published data tended to be much earlier on in the crisis, but I will go and double-check this now.

Just to confirm that neutron readings are indeed uninteresting around this event, with the ones of interest being recorded in periods 13th march 05:30 to 10:50, and then another batch between 21:00 on march 14th and 01:40 march 15th.

 

[Jorge Stolfi]

I have updated again my plots, to NISA release 156 (jun/01 12:00).
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

Its very annoying that the B pressure reading over the same time period does not do anything interesting, because it makes it hard to be too confident that the pressure really rose to the extent that A reading indicates.

The RPV B gauge was acting strange since mar/19 00:00, when apparently it started to correlate more to the drywell pressure than to the RPV A pressure. As soon as the RPV A transient began on mar/21 ~01:25, the B gauge started to drop on its own, going from ~150 kPa just before the transient to ~60 kPa just after it. So while it does not confirm the 11 MPa surge, it does indicate that something special happened a that time.

Moreover I cannot imagine what sort of malfunction could have caused a pressure gauge to register ~10MPa (~100 times atmospheric pressure) for over an hour. My understanding is that those gauges are basically pipes that convey the RPV pressure to the dial on the control room by purely mechanic/hydraulic means. Thus I cannot see how the gauge could register 10 MPa, unless something somewhere was under 10 MPa. And where else could one have such pressures, if not in the RPV?

But if you added some temperature data to your graph, I think you would end up with a stronger looking indication that something happened that night

I will look into that. (The TEPCo documents I just transcribed do not list the temperatures, hopefully some other document does.)

As for why the 3 interesting datapoints are missing from the status snapshots that were published a few times a day, it seems inevitable to me because of what time they tended to take readings to publish vs the time of day that the pressure A spike happened.

Still I would expect that a Nuclear and Industrial Safety Agency would at least comment on the RPV pressure apparently exceeding the max design pressure. Would't such an event automatically trigger some bureaucratic response from them? I suppose that either NISA knew of the peak and decided that it was not important/significant; or TEPCo forgot to tell NISA about it.

 

[etudiant]

I have updated again my plots, to NISA release 156 (jun/01 12:00).
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html


The RPV B gauge was acting strange since mar/19 00:00, when apparently it started to correlate more to the drywell pressure than to the RPV A pressure. As soon as the RPV A transient began on mar/21 ~01:25, the B gauge started to drop on its own, going from ~150 kPa just before the transient to ~60 kPa just after it. So while it does not confirm the 11 MPa surge, it does indicate that something special happened a that time.

Moreover I cannot imagine what sort of malfunction could have caused a pressure gauge to register ~10MPa (~100 times atmospheric pressure) for over an hour. My understanding is that those gauges are basically pipes that convey the RPV pressure to the dial on the control room by purely mechanic/hydraulic means. Thus I cannot see how the gauge could register 10 MPa, unless something somewhere was under 10 MPa. And where else could one have such pressures, if not in the RPV?


I will look into that. (The TEPCo documents I just transcribed do not list the temperatures, hopefully some other document does.)


Still I would expect that a Nuclear and Industrial Safety Agency would at least comment on the RPV pressure apparently exceeding the max design pressure. Would't such an event automatically trigger some bureaucratic response from them? I suppose that either NISA knew of the peak and decided that it was not important/significant; or TEPCo forgot to tell NISA about it.

I'm a bit confused by this. We had earlier had extensive discussions about the inability of the RPV to hold high pressures because the seal at the top would give at fairly modest levels.
Now we have a damaged reactor holding 100x atmospheric for over an hour. Am I the only one to be disconcerted by this?

 

[Jorge Stolfi]

I'm a bit confused by this. We had earlier had extensive discussions about the inability of the RPV to hold high pressures because the seal at the top would give at fairly modest levels. Now we have a damaged reactor holding 100x atmospheric for over an hour. Am I the only one to be disconcerted by this?

The normal operating pressure of the RPV is ~70 bar (= 70x atmospheric ~ 7 MPa), and it is supposedly tested at over ~100 bar (~10 MPa). So the seal definitely is tight up to that much.

Between mar/13 noon and the transient on mar/21 midnight, the RPV of reactor #3 appears to have been communicating in some way with the drywell, since their pressures wandered up and down between 100 kPa (1 bar) and 500 kPa (5 bar) more or less together. (In this period the RPV presure was quite consistently ~75 kPa (0.75 bar) below that of the drywell. This pressure difference corresponds to a water depth of 7 meters, so perhaps there is a communicating-vessels-type explanation for that behavior.)

After the mar/21 transient and the black smoke inident, the drywell seems to have been continuously open to the atmosphere, with the pressure constant at 1 bar exactly; and the torus remained steady at 2 bar, as if its gauge was under 10 meters of water. The slow but steady pressure fall in the RPV could be explained perhaps by closure of the RPV-drywell connection, and condensation of the steam inside the RPV.

I still cannot fgure out where the RPV pressure gauges A and B are located exactly. Is it possible that the space inside the RPV got partitioned by the meltdown into two fairly airtight spaces, with one gauge in each?

 

[jim hardy]

Jorge on the anomalous pressure readings around 21 March, from my recollections at the time (i noticed it too):
I think they were inferring pressure from a gage on a pipe through which they were pumping water. Possibly a gage on a fire truck pump.
Check your newspaper reports back then. On about 20th there were phrases "unable to overcome pressure might have to vent again" and on 21st a NYTimes article had phrases "Condition has stabilized" with no explanation. I think they opened a valve. I wouldn't have admitted it either.
Thereafter the two pressure readings came back together and tracked injection flow per your plots (which i were admiring).
Of course i wasn't there so that's a guess , just what i surmised at the time.

As to the thermocouples: there's one more failure mode, wet insulation.
Being dissimilar metals they produce microvolts per degree along any part of the wire with a temperature gradient (google peltier and seebeck)... so they make a predictable micro-voltage proportional to difference between hot and cold ends as you know very well.
Well, being dissimilar metals they'll also make a battery if placed in an electrolyte. That electrochemical effect makes tens of millivolts and will cause substantial error if the insulation gets compromised and water gets to the conductors. The chemical millivolts overwhelm and bury the temperature microvolts. Try it yourself - take a coffee cup of tapwater add a shake of salt and dip two pieces of bare thermocouple wire in it and i bet you get close to 100 millivolts . Then twist the ends together to make a thermocouple and you still get millivolts because the battery effect is stronger than the thermocouple effect.
Given all the steam in there it could be a wet terminal block in a flooded junction box. Might dry out and start working on its own.

 

[htf]

Moreover, given we now know the reactors were doomed within a day of the loss of power, it is not clear any great harm was done by the TEPCO stonewalling during the early days after the accident. Or am I missing something?

I am not so sure. Maybe early venting would have avoided the hydrogen explosions? What if they immediately started sea water injection? Let's wait for the "lessons learned" in the final report.

 

[htf]

As to the thermocouples: there's one more failure mode, wet insulation.

Great explanation! But why are all those sensor readings published without assessment by TEPCO or NISA? Are they afraid of drawing wrong conclusions?

 

[tsutsuji]

The water level in the basement of unit 1 reactor building has decreased by 7.9 cm over the last 24 hours : http://www3.nhk.or.jp/news/html/20110602/t10013272611000.html

The firm is gauging radioactivity in underground water around the No. 1 reactor and checking if radioactive water is leaking from the building.
http://www3.nhk.or.jp/daily/english/02_03.html

 

[AntonL]

http://www3.nhk.or.jp/daily/english/31_03.html][/PLAIN]
Tokyo Electric Power Company detected 2 million becquerels of radioactive cesium per cubic centimeter of water in the basement of the No. 1 reactor building.

It speculates that radioactive substances from the melted fuel have leaked from the pressure vessel encasing the reactor core.

That is 2x10⁹ Bq/Litre and safe limit is 60 or 90 Bq/L for Cs-134 and 137 respectively.

Why are Tepco reporting sea water contamination in Bq/L and ground water, basement water etc as Bq/cm³?Tepco released these images of their temporary tank farms, note the plastic wrap as additional protection against drips at joints. (click image for high res original)

How do plastic polymers stand up to radiation, UV usually makes plastics go brittle with time. While transporting radioactive substances in plastic pipes, the radiation intensity and energy is higher than the UV radiation from sunlight, so I suspect these pipes will deteriorate with time (possibly faster than expected) and laying these pipes on rough surfaces with sharp stones is also not a good idea as induced vibration of the flowing water on a sharp point load could lead to puncturing.

Are there studies on plastic polymer decay and radiation?

http://www.tepco.co.jp/en/news/110311/images/110602_01.jpg"

http://www.tepco.co.jp/en/news/110311/images/110602_03.jpg"

http://www.tepco.co.jp/en/news/110311/images/110602_02.jpg"

(Photo credits: Tokyo Electric Power Co.)

 

[dh87]

Hmm, I asked myself, how much cesium did they get into the these water masses in the buildings they want to decontaminate.

1 gram of Cs-134 (half life 2.0648 y) makes up 1293 curies.
1 gram of Cs-137 (half life 30.17 y) makes up 86.55 curies.

(Calculated according to the formula described http://www.bautforum.com/showthread...odine-in-nuclear-waste?p=1893658#post1893658".)

So ...
...one megacurie of Cs-134 weighs about 773.4 g.
...one megacurie of Cs-137 weighs about 11.55 kg.

So, if we have about, say, 12000 tons of water with 1 megacurie Cs-134 and Cs-137 each, then this would be a ppm cesium (weight 12kg total), I think.

Too bad Tepco doesn't publish salinity data, so we can only guess the ratio of Cs and seawater salt. But appears to be sure that there is salt in the magnitude of at least tens of tons.
So my layman's estimate is that the ratio seawater salt:cesium in the T/B water could be 10000s-1000s:1.

Does anybody know whether Areva's plant also precipitates salt or is selective to cesium, and if, how much?

Salinity data are here: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110522_04-e.pdf

The conductivities show that the salinities are 0.5 - 0.8X that of seawater. The potassium may be a larger problem for a cesium-specific ion exchanger than the sodium, even though its concentration is lower, and there are plenty of other cations to interfere with the process.

 

[dh87]

Is it even possible to selectively remove cesium contamination at the part per 10 million level from sea water? Would not the overwhelmingly more numerous sodium ions saturate the zeolite in short order?

The 99+% removal of Cs+ will require very high affinity for Cs+. At the same time, affinity for Na+, K+, Mg++, and other ions has to be low. I can't find numbers for zeolite, if that's what they're using. I think that there are technologies that might have the high affinity and selectivity required (such as crown ethers), but there doesn't seem to be any certainty about what they're actually doing (maybe they don't know either).

 

[tsutsuji]

Sadly, I concede that you are right - my optimism is popped like a balloon with a pin.

...I wonder how such a small system will cope with the millions of liters of water in the harbour. Those small hoses can probably take 200 l/min at 3 bar. (An informed guesstimate).

For the volume in the harbour, I guess 15m of depth, 300m out to the harbour wall and 1000m width along the seafront and I get 4.5 x 10^6 m3 of harbour water. Or 4.5 x 10^9 litres.

With my guess of 200 l/min, we would pass 4.5 x 10^9 l through in 2.25 x 10^7 minutes. That's about 42 years to pass the water in the harbour through once.

The "circulatory sea water purification system" is described as being "experimental". They wanted to try it for 4 days and see the results after those 4 days. If the results are good enough, they will increase the number of purifying units : http://www.kfb.co.jp/news/index.cgi?n=201106019

It has been stopped on June 1st because of some bad cable that needs to be changed : http://www.asahi.com/national/jiji/JJT201106010117.html

Tepco released these images of their temporary tank farms, )

alongside a map showing their locations : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110602_01-e.pdf

note the plastic wrap as additional protection against drips at joints. (click image for high res original)

How do plastic polymers stand up to radiation, UV usually makes plastics go brittle with time. While transporting radioactive substances in plastic pipes, the radiation intensity and energy is higher than the UV radiation from sunlight, so I suspect these pipes will deteriorate with time (possibly faster than expected) and laying these pipes on rough surfaces with sharp stones is also not a good idea as induced vibration of the flowing water on a sharp point load could lead to puncturing.

These tanks are for water moved from units 5 and 6 which - as far as I understand - consists of sea water from the tsunami wave and ground water leaking inside basements through cracks. The sea was clean before the tsunami. So the remaining source of radiation is the ground water. I understand that this water is a concern for people and biological life as a potential health hazard, but is it so radioactive that plastic polymers will suffer ?

 

[MadderDoc]

Jorge on the anomalous pressure readings around 21 March<..>
Check your newspaper reports back then. On about 20th there were phrases "unable to overcome pressure might have to vent again" and on 21st a NYTimes article had phrases "Condition has stabilized" with no explanation. <..>

Right, Jim, but those newspaper reports were about the rise in containment vessel pressure. The DW pressure had started increasing on March 18th, and by early March 20th JST it reached design max limit, and had provoked a plan to vent the containment (presumably to avoid further calamity, having the events of March 14th in mind.)

However, on the morning of March 20th the containment vessel pressure started decreasing and it was announced that the plan to vent had been set on hold. There was a sustained decrease in containment vessel pressure throughout March 20th and 21st, ultimately leading to its being at atmospheric pressure, so there is little reason to think that the plan to vent was invigorated and enacted during this period.

 

[zapperzero]

Just to confirm that neutron readings are indeed uninteresting around this event, with the ones of interest being recorded in periods 13th march 05:30 to 10:50, and then another batch between 21:00 on march 14th and 01:40 march 15th.

I know this is speculation, but I can't help myself. Those readings... are they continuous? If not, it may be that any neutron spikes could have been "lost" just like the pressure/temp readings.

 

[zapperzero]

Are there any physicists in the house?

I had an idea a week ago. Turns out, as with nearly all my best ideas, someone else had had it before:

http://physicsworld.com/cws/article/news/44411

Now, for the questions. Would a prompt recriticality event at Fukushima produce enough neutrinos to be detected at the Super-Kamiokande? If so, could someone sift the recorded "noise" from the Super-Kamiokande looking for anti-neutrinos coming from there, or is the "spurious" data discarded in real-time, as it happens in, say, the LHC experiments?

 

[SteveElbows]

I will look into that. (The TEPCo documents I just transcribed do not list the temperatures, hopefully some other document does.)

As part of the same release of data some weeks back, there was temperature data in another file, covering a similar time period. This is the file for reactor 3:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_temp_data_3u.pdf

Unfortunately temperature data of this variety only became available on the 19th, so we don't get a great look at the temperature trends long before the 21st.

The picture is rather messy, but a few of the temps hit new highs around the 01:25 time on the 21st.

 

[SteveElbows]

I know this is speculation, but I can't help myself. Those readings... are they continuous? If not, it may be that any neutron spikes could have been "lost" just like the pressure/temp readings.

Well the data has long been available, I only looked at it again recently because TEPCO published some corrections & additional data. I don't think the corrections/additions make any difference to the neutron figures but I could be wrong, its been a while since I looked at the original data.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110528e14.pdf

Neutron readings during this period were mostly taken near the main gate every 10 minutes.

 

[GJBRKS]

That is 2x10⁹ Bq/Litre and safe limit is 60 or 90 Bq/L for Cs-134 and 137 respectively.

Why are Tepco reporting sea water contamination in Bq/L and ground water, basement water etc as Bq/cm³?

with a mean gamma ray energy of 662keV per decay ,

this would amount to 18.33 J/day per liter ,

or (230mSv / day) / ingested liter ( for a man of 80 Kg)

or (9.6 Sv / hour ) / ingested cubic meter ( for a man of 80 Kg)

http://www.wolframalpha.com/input/?i=2.0e09+bq+*+662+kev&a=*C.bq-_*Unit-&a=ListOrTimes_Times

(This is only the cesium component , there would be other additional sources , and not counting any betaradiation that would add to the Sv)

 

[jim hardy]

Jorge wrote:
"""However, on the morning of March 20th the containment vessel pressure started decreasing and it was announced that the plan to vent had been set on hold. There was a sustained decrease in containment vessel pressure throughout March 20th and 21st, ultimately leading to its being at atmospheric pressure, so there is little reason to think that the plan to vent was invigorated and enacted during this period.""



That is a very confusing time.
I was and remain puzzled by that day.
Your graph shows i believe a LOT of water injection. Nootice the pressures track injection flow...


""""I still cannot fgure out where the RPV pressure gauges A and B are located exactly. Is it possible that the space inside the RPV got partitioned by the meltdown into two fairly airtight spaces, with one gauge in each? "

What i believe is they used local pressure gages on pipes that go into the RPV from whatever temporary pumps they had jury-rigged. One of those pipes i believe had a valve that was closed or nearly so, so the pump pressure was high and it took them a while to figure that out. when they opened it the situation "stabilized", so valve they opened was afill valve not a vent valve. That's my best guess at a hypothesis that fits observations.

amen to your torus sensor being under water.
What i did not realize until recently is how high above ground the reactor vessel is. My PWR was at ground level. I am wondering if the ~1.5 atm pressures in drywell could be from their flooding it , and the pressure indication due to pressure drop in the fill lines and elevation. Both pressures tracked injection flow for a while.

about a month ago i posted some thoughts about unit 3 and your charts here,
http://tickerforum.org/akcs-www?singlepost=2541679

at time i thought the rpv and containment were both open at top. Less convinced of that now.

 

[NUCENG]

Jorge wrote:
"""However, on the morning of March 20th the containment vessel pressure started decreasing and it was announced that the plan to vent had been set on hold. There was a sustained decrease in containment vessel pressure throughout March 20th and 21st, ultimately leading to its being at atmospheric pressure, so there is little reason to think that the plan to vent was invigorated and enacted during this period.""



That is a very confusing time.
I was and remain puzzled by that day.
Your graph shows i believe a LOT of water injection. Nootice the pressures track injection flow...


""""I still cannot fgure out where the RPV pressure gauges A and B are located exactly. Is it possible that the space inside the RPV got partitioned by the meltdown into two fairly airtight spaces, with one gauge in each? "

What i believe is they used local pressure gages on pipes that go into the RPV from whatever temporary pumps they had jury-rigged. One of those pipes i believe had a valve that was closed or nearly so, so the pump pressure was high and it took them a while to figure that out. when they opened it the situation "stabilized", so valve they opened was afill valve not a vent valve. That's my best guess at a hypothesis that fits observations.

amen to your torus sensor being under water.
What i did not realize until recently is how high above ground the reactor vessel is. My PWR was at ground level. I am wondering if the ~1.5 atm pressures in drywell could be from their flooding it , and the pressure indication due to pressure drop in the fill lines and elevation. Both pressures tracked injection flow for a while.

about a month ago i posted some thoughts about unit 3 and your charts here,
http://tickerforum.org/akcs-www?singlepost=2541679

at time i thought the rpv and containment were both open at top. Less convinced of that now.

For information, RPV Pressure instruments sense steam dome pressure on the reactor water level condensing chamber instrument tap outside of the shroud and dryer skirt at about the elevation of the tops of the steam separators. The instruments themselves are in the reactor building outside of containment'

 

[Jorge Stolfi]

Jorge on the anomalous pressure readings around 21 March, from my recollections at the time (i noticed it too): I think they were inferring pressure from a gage on a pipe through which they were pumping water. Possibly a gage on a fire truck pump.

There's one more failure mode, wet insulation.
Being dissimilar metals [...] they'll also make a battery if placed in an electrolyte. That electrochemical effect makes tens of millivolts and will cause substantial error if the insulation gets compromised and water gets to the conductors. The chemical millivolts overwhelm and bury the temperature microvolts. [...] Given all the steam in there it could be a wet terminal block in a flooded junction box. Might dry out and start working on its own.

Good explanation, thanks!

One thing I don't understand about theormocouples is why the bimetal wires are usually extended all the way to the voltmeter. Why couldn't they be extended only to some cooler place nearby (such as just outside the concrete enclosure), and then have the signal be carried by copper wires to the meter? That would result in lower resistance for the signal and reduced risk of electrochemical effects along the way.

Or is that in fact how it is done?

About a month ago i posted some thoughts about unit 3 and your charts here,
http://tickerforum.org/akcs-www?singlepost=2541679
at time i thought the rpv and containment were both open at top. Less convinced of that now.

Thanks for the compliments and for the thorough analysis. As for them being "open", there is a continuum between having a small leak and being wide open, so it may not be a simple yes/no question. Also, for a small leak, the degree of opening may be sensitive to pressure, temperature, flooding, clogging, etc., and so may vary erratically with time.

As part of the same release of data some weeks back, there was temperature data in another file, covering a similar time period. This is the file for reactor 3:
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_temp_data_3u.pdf

Thanks! I think I saw mention of it in this forum, but hadn't the time to check it out then.

[Gamma and neutron] data has long been available [...]
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110528e14.pdf

Thanks again. I am tempted to include those readings in my plots too, but first one question: do they reflect the conditions inside the reactor, or only of the external contamination? In other words, are those gammas and neutrons mostly created by fission and decay inside the reactor's concrete enclosure? If so, does the spent fuel in the SFP contribute to those readings?

For information, RPV Pressure instruments sense steam dome pressure on the reactor water level condensing chamber instrument tap outside of the shroud and dryer skirt at about the elevation of the tops of the steam separators. The instruments themselves are in the reactor building outside of containment'

Thanks, that is important information.

As for the temperature sensors, I have seen several diagrams showing their approximate location on the RPV, drywell and torus; but I still miss the key details. Namely, where precisely are the RPV temperature measured: on the outside surface of the RPV, or embedded into its wall? If the former, woud the reading be affected by the drywell atmosphere or by water leaks above the sensor? How far is the "water nozzle" temperature sensor from the nozzles and their feedpipes? And so on...

These details are important, for example, to analyze the pressure x temperature plots. The red boiling curve in those plots is relevant only if the temperature and pressure are measured at the same spot in the fluid. Barring gauge malfunctions, the pressure must be indeed that of the fluid at the gauge's intake point, which should be valid for the bulk space inside (except for the hydrostatic pressure gradient in the liquid-filled part). On the other hand, if the temperature is measured on the outside of a 15 cm thick wall, or even embedded into it, it will be some value intermediate between the temperatures of the two fluids in immediate contact with the wall. Thus, one can easily have superheated steam inside the RPV with a temperature reading well below the boiling curve, or (less likely) liquid water inside with a temperature reading well above the boiling curve.

 

[SteveElbows]

On the other hand, if the temperature is measured on the outside of a 15 cm thick wall, or even embedded into it, it will be some value intermediate between the temperatures of the two fluids in immediate contact with the wall. Thus, one can easily have superheated steam inside the RPV with a temperature reading well below the boiling curve, or (less likely) liquid water inside with a temperature reading well above the boiling curve.

The early NRC assessment that was leaked said 'Vessel temperature readings are likely metal temperature which lags actual conditions.'

http://cryptome.org/0003/daiichi-assess.pdf page 2 reactor 1 assessment first mentions this, I believe the same sentence is also used for reactors 2 & 3 later on in the document.

 

[Quim]

Here is a paper which discusses "aquifer recharge" which has been used to combat salt water intrusion into the underground aquifer in Japan. The Japanese have been fighting saltwater intrusion into their aquifer by injecting fresh water into wells and by creating freshwater ponds (basins) over porous stratum. This paper discusses the basin method of aquifer recharge.
http://www.igme.es/internet/Boletin/2009/120_2_2009/311-320.pdf

Current circumstance in Fukushima suggests that the corium have now reached (become at one with) the groundwater. This is a first ever, in this respect the accident in Fukushima has surpassed events in Chernobyle.

Possibly, it is time for those managing the accident to get ahead of events and do whatever is necessary to prevent the spread of contamination to the deeper stratum of groundwater in Honshu.

This forum is sorely lacking the expertise of a geologist as shown in the previous mudstone/bedrock discussion.

Could a poster from Japan find a knowledgeable contributer to join the discussion?

The "battle of Fukushima" would seem to now be an underground battle.

 

[biffvernon]

This forum is sorely lacking the expertise of a geologist as shown in the previous mudstone/bedrock discussion.

It's not so much the lack of a geologist as a lack of any detailed geological information about the site.

 

[jlduh]

Here is a paper which discusses "aquifer recharge" which has been used to combat salt water intrusion into the underground aquifer in Japan. The Japanese have been fighting saltwater intrusion into their aquifer by injecting fresh water into wells and by creating freshwater ponds (basins) over porous stratum. This paper discusses the basin method of aquifer recharge.
http://www.igme.es/internet/Boletin/2009/120_2_2009/311-320.pdf

Current circumstance in Fukushima suggests that the corium have now reached (become at one with) the groundwater. This is a first ever, in this respect the accident in Fukushima has surpassed events in Chernobyle.

Possibly, it is time for those managing the accident to get ahead of events and do whatever is necessary to prevent the spread of contamination to the deeper stratum of groundwater in Honshu.

This forum is sorely lacking the expertise of a geologist as shown in the previous mudstone/bedrock discussion.

Could a poster from Japan can find a knowledgeable contributer to join the discussion?

The "battle of Fukushima" would seem to now be an underground battle.

Welcome to the forum first!

I agree with your view that we are lacking specific knowledge about the geology and watertable in this area, I already mentionned it and personally, i haven't been able, despite some research on the net, to find precise information on this matter (in this specific area i precise). I just found that Tepco has conducted in 2008 and 2009 many tests with soil drilling and test explosions and shocks to better assess the seismic properties of the area regarding to resistance to earthquake of the Daichi plant, but I have not been able to find the reports and data of this studies.

I think that nothing says at this time that the corium/debris entered the water table and escaped from the containment, we just don't know where are relocated the cores that have melted, based on Tepco explanations. This is a serious problem not to know what's happening inside...

The only very factual element that let us think that maybe "some corium went through something" has been the black smoke from reactor 3, around March 21/23. I don't think we can say more than this.

But whatever the situation of the corium is, it is very important to have a better knowledge of the underground area around the reactors, also to better assess how the basements can leak and contaminate the surroundings or even the sea.

So if somebody knows someone in a University in Japan with some knowledge of the geology and or the aquifer there, just try to convince him or her to come on this forum!