Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[etudiant]

I strongly doubt that. Cesium is created in the form of just nucleus, ejected during fission. It grabs any electrons it can from the surroundings. I doubt it gets more electrons than needed to become Cs⁺. Counterions are whatever happened to be in the vicinity and was not keeping its electrons strong enough.

Thank you for the extra information. I had not known the sequence of how one gets from a fission fragment to
a fission product. So cesium metal never forms even if the intact fuel.
Must be a real nuclear dance inside the fuel rods, with highly charged fission fragments competing for available counterions.

 

[radio_guy]

cesium is an alkaline metal and will react powerfully with water to form an hydroxide. The presence of iodine will cause cesium iodide to form in preference to the hydroxide, but cesium iodide also dissolves very well in water.
The cesium fission product is in metal form afaik in the fuel tubes, as long as the tube remains intact.
When the zirconium is destroyed because of the loss of coolant, the cesium metal boils out of the hot fuel assemblies. The cesium vapor will deposit all over, on pretty much every surface that is cold enough, so it is a serious contaminant, not easily flushed because it is so reactive.
Afaik, the Japanese helicopters that did the water drops early in the crisis were very badly contaminated and their cleanup required special equipment provided by the US military, because the conventional cleanings failed to dislodge the cesium embedded in the helicopters paint.

some light reading, just to clarify all thjs.


http://www.epa.gov/radiation/radionuclides/cesium.html
http://en.wikipedia.org/wiki/Caesium

 

[SteveElbows]

The reactors had clearly failed by the morning of Mar 12. However, the venting had not yet started, at least afaik, when these measurements were made 6 km away. That would seem to show an earthquake generated leak in the containment, which is something that was unclear previously.

I still don't see why this means it has to be earthquake generated. Surely the state of the reactor due to core melting is enough to cause problems by this stage.

There are not a huge number of pressure readings from the early hours of the situation at the reactors, but there are some. Reactor 1 seems most interesting of the 3 during the early hours of the 12th. At some point the reactor pressure goes from 6.9 MPa at 20:07 on the 11th to 0.8 Mpa by 02:45 on the 12th. Drywell is 0.6 MPa at 01:05 on the 12th, 0.84 Mpa at 02:30, 0.78 by 04:19, then tends to fluctuate around 0.74 and 0.75 until its time for steeper declines in the afternoon.

In my mind this means I can construct alternatives to earthquake damage to explain releases in this period. Extreme pressure or temperatures may have caused certain small drywell failures at reactor 1 by around 4am on the 12th.

 

[etudiant]

I still don't see why this means it has to be earthquake generated. Surely the state of the reactor due to core melting is enough to cause problems by this stage.

There are not a huge number of pressure readings from the early hours of the situation at the reactors, but there are some. Reactor 1 seems most interesting of the 3 during the early hours of the 12th. At some point the reactor pressure goes from 6.9 MPa at 20:07 on the 11th to 0.8 Mpa by 02:45 on the 12th. Drywell is 0.6 MPa at 01:05 on the 12th, 0.84 Mpa at 02:30, 0.78 by 04:19, then tends to fluctuate around 0.74 and 0.75 until its time for steeper declines in the afternoon.

In my mind this means I can construct alternatives to earthquake damage to explain releases in this period. Extreme pressure or temperatures may have caused certain small drywell failures at reactor 1 by around 4am on the 12th.

Thank you, that is most helpful data. The sharp loss of pressure in reactor 1 before 2.45 am on Mar 12 would fit nicely with the timeline recording reactor products 6 km away a few hours later.
As you point out, the leak does not appear to be directly from the quake, but rather a subsequent pressure generated failure. Still, it indicates that the integrity of the facility was materially compromised even before the explosions.

 

[MiceAndMen]

Congratulations to the people at the sharp end of this situation.

It may only be a small solution in a mass of big problems, but the establishment of closed loop cooling for the SFP in Unit 2 is a turning point I think and it gives me a sense of optimisim that we will have improved success in working our way through this.

No more radiation washed out or steamed off of at least part of the site.

Good news.

Credit where credit is due, I agree. Of course they would be worthy of much more credit if they had started doing this weeks ago. They've allowed things to get worse by delaying prompt action, and that nullifies whatever praise they're otherwise deserving of this week. But it is a step in the right direction.

 

[etudiant]

Credit where credit is due, I agree. Of course they would be worthy of much more credit if they had started doing this weeks ago. They've allowed things to get worse by delaying prompt action, and that nullifies whatever praise they're otherwise deserving of this week. But it is a step in the right direction.

Is this actually the case?
My impression, from looking at the stuff that is getting deployed, is that we are seeing a lot of custom built gear, rather than a lot of off the shelf equipment. It is pretty impressive, to conjure this up in a couple of months. At a minimum, it proves that the TEPCO road map did actually reflect some serious engineering effort.
Maybe it has been ' a day late and a dollar short', but there is a real effort.

Short of making this a global effort, it is hard to see what TEPCO could have done additional.
Presumably, the global effort option was rejected both for operational as well as political reasons, ie how do you coordinate a nuclear emergency with a polyglot crew that cannot talk to each other?.

 

[SteveElbows]

Thank you, that is most helpful data. The sharp loss of pressure in reactor 1 before 2.45 am on Mar 12 would fit nicely with the timeline recording reactor products 6 km away a few hours later.
As you point out, the leak does not appear to be directly from the quake, but rather a subsequent pressure generated failure. Still, it indicates that the integrity of the facility was materially compromised even before the explosions.

I forgot to include TEPCOs own thoughts on containment damage which came out in the 2nd half of may as part of a very long Japanese report that had not been fully translated into english last time we talked about it, and I presume it still hasnt. But there were some press stories about it which we talked about here, and I computer-translated a few paragraphs that were related to the timing of containment failures.

Their assumptions, which were apparently based on things such as pressure readings, don't exactly match what I've been saying, although they are not too far off for some reactors.

For reactor 1 they estimated a leak equivalent to a 3cm hole in drywell 18 hours after quake. Worsening to 7cm by 50 hours after quake. So here they are already admitting to some containment damage by the morning of 12th, although some 4 hours later than I guestimated based on a few pressure readings.

For reactor 2 they estimated a leak equivalent to a 10cm hole in drywell 21 hours after quake. Suppression chamber damage obviously followed at a later date, when the 'strange sound was heard. Drywell damage at 21 hours after quake is late on morning of 12th, a bit too late to blame this for the data 6km away.

I suppose it is possible that these '18 hours' and '21 hours' estimates that TEPCO mentioned are not supposed to be the exact starting times for containment failure, but rather an indication of how bad the damage may be at that moment. eg if damage equivalent to 3cm at around 8:30, maybe there could have been damage equivalent to 1cm at 5am. I cannot tell until I see full translation, and even then I would not be surprised if this remains a little unclear. Its not as if when I study what pressure data is available to us, the times TEPCO said fit perfectly with a dramatic event shown in data at precisely these times.

Anyway TEPCOs analysis of reactor 3 may be of particular interest to those seeking possible earthquake damage, because as discussed when press articles appeared on this subject some days ago, TEPCO seem to be suggesting that some piping system may have been damaged at reactor 3 by the earthquake itself. Again I wait in hope of full document translation, and I have no idea whether such early damage may be responsible for any of the radiation being picked up on morning of march 12th.

 

[~kujala~]

I updated my https://www.physicsforums.com/showpost.php?p=3270265&postcount=5081" with some new references and ideas. First it looked like a simple case, then it got complicated. Even now there are many explanations and possibilities. Nothing new from TEPCO for a long time...

It's so long, I made it directly as HTML:
http://varasto.kerrostalo.huone.net/unit4_theory.html

 

[hbjon]

I strongly doubt that. Cesium is created in the form of just nucleus, ejected during fission. It grabs any electrons it can from the surroundings. I doubt it gets more electrons than needed to become Cs⁺. Counterions are whatever happened to be in the vicinity and was not keeping its electrons strong enough.

I would like to see the math on how Cs is created in a fuel rod. Exactly how long does it take for a fresh fuel rod to produce a gram of the stuff. Since U238 and U235 have approximately that number of electrons AFAIK, doesn't Cs take its share of them after the products decay? Btw, I am not an expert on the chemical properties of isotopes or nuclear physics. I guess I am just an annoying "backseat driver". <-----My disclaimer

 

[SteveElbows]

Thank you, that is most helpful data. The sharp loss of pressure in reactor 1 before 2.45 am on Mar 12 would fit nicely with the timeline recording reactor products 6 km away a few hours later.

I should also point out that I am not sure that particular pressure drop, of the reactor itself, gives a proper indication of release of radioactive substances to outside world. I am not especially knowledgeable about this stuff, but I assumed that drop of reactor pressure vessel tells us that stuff has gone from pressure vessel to containment vessel. It sets the situation up for trouble, but its a drop in containment pressure that we should look for when thinking about when exactly this material escapes into the wider world. So for my crude estimations of radioactive release timing I was looking for even slight falls in containment pressure.

 

[SteveElbows]

There is another piece of data from early on March 12th which demonstrates radioactive release. It is mentioned in TEPCO document that analyses situation at plant in first hours. In the reactor 3 status table at the very end of the document, in the final row about emissions, it says:

Exhaust stack radioactive monitor : noise was confirmed after reactor scram, but it was stable rate until termination of recording From around 5:00 on March 12th, it showed temporarily gradual increase. Since it is assumable that the water level of the reactor of Unit 3 at that time was above flooded level to cover the fuel, increase in dose is effected by the other units at the site.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110524e13.pdf

 

[Borek]

Since U238 and U235 have approximately that number of electrons AFAIK, doesn't Cs take its share of them after the products decay?

Number of electrons in uranium atom is exactly the same as number of electrons needed for fissions products. Trick is, when fission products run apart they do it very fast. They can be able to take some of the electrons from the original uranium atom with them, I am not sure about details, but basically these are two massive, highly charged ions going through the fuel rod and ionizing everything on their way. Electrons don't need much time to get back "in place", but it is a messy process. Final products (in chemical sense) are ions - like Cs⁺ and I^-, but they are put in random places in the original lattice of uranium oxide, creating local defects, so they can be hardly described as specific compounds.

 

[LabratSR]

More storage capacity to be brought on site.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110603_02-e.pdf

 

[etudiant]

More storage capacity to be brought on site.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110603_02-e.pdf

Hope that these are just the specs for the product, because they need at least two of each of those every day
just to hold the injected water at the current rate.
TEPCO is reportedly putting in a 100,000 ton storage tank underground, but it will not be ready until August.
Provided the AREVA treatment plant starts operating by mid June as expected, TEPCO might have just enough capacity to avoid an overflow of highly contaminated water. It does not look however as though they will be able to store the treated water unless there is some tanker storage planned. So there will of necessity be a further ocean disposal of contaminated water.

 

[Astronuc]

I would like to see the math on how Cs is created in a fuel rod. Exactly how long does it take for a fresh fuel rod to produce a gram of the stuff. Since U238 and U235 have approximately that number of electrons AFAIK, doesn't Cs take its share of them after the products decay? Btw, I am not an expert on the chemical properties of isotopes or nuclear physics. I guess I am just an annoying "backseat driver". <-----My disclaimer

By successive beta decay, Te -> I -> Xe -> Cs -> Ba -> La (all having the same A, but different Z. Some Cs is born as a fission product. Te, I, Xe are also born as fission products, and decay by beta emission as shown.

Number of electrons in uranium atom is exactly the same as number of electrons needed for fissions products. Trick is, when fission products run apart they do it very fast. They can be able to take some of the electrons from the original uranium atom with them, I am not sure about details, but basically these are two massive, highly charged ions going through the fuel rod and ionizing everything on their way. Electrons don't need much time to get back "in place", but it is a messy process. Final products (in chemical sense) are ions - like Cs⁺ and I^-, but they are put in random places in the original lattice of uranium oxide, creating local defects, so they can be hardly described as specific compounds.

The fission products do not go far - only a few microns (2-6 um) with the heavier nuclide going shorter distances, and the lighter one going longer. The Te - Cs are the heavier ones, and Se->Br->Kr->Rb->Sr->Y are the lighter ones.

Edit/update: The grains in the polycrystalline UO₂ ceramic are on the order of 10 microns, and actually 2 to 20 microns. At temperature, the smallest grains basically reform as part of larger grains (the atoms at the grain boundaries migrate from small grains to large grains).

 

[jlduh]

I thought it was now common knowledge that all three reactors melted down before the explosions. That in fact the explosions were the result of catastrophic failure of the reactors.

Isn't that the latest version of what happened?

It seems that the three cores melted quickly, agree. But The containment was not supposed to leak in the morning of March 12. So how did this Tellurium go out of the cores, out of the RPV, out of the containment, to deposit 6 kms away from Daichi?

Did they already vent? Tepco said no (as a matter of fact Kan was visiting the plant that morning and was upset that no venting had been done despite official governement approval). So how did this Tellurium come out?

Either Tepco already vented, or the containment was already breached, the earthquake being possibly the only credible explanation to explain some leak in the containment...

 

[LabratSR]

Hope that these are just the specs for the product, because they need at least two of each of those every day
just to hold the injected water at the current rate.
TEPCO is reportedly putting in a 100,000 ton storage tank underground, but it will not be ready until August.
Provided the AREVA treatment plant starts operating by mid June as expected, TEPCO might have just enough capacity to avoid an overflow of highly contaminated water. It does not look however as though they will be able to store the treated water unless there is some tanker storage planned. So there will of necessity be a further ocean disposal of contaminated water.

If I read it right under "Transportation Duration" they are planning on delivering up to 6 a day of the bigger ones for a month and 4 a day of the smaller ones for 2 months.

 

[jlduh]

Hope that these are just the specs for the product, because they need at least two of each of those every day
just to hold the injected water at the current rate.
TEPCO is reportedly putting in a 100,000 ton storage tank underground, but it will not be ready until August.
Provided the AREVA treatment plant starts operating by mid June as expected, TEPCO might have just enough capacity to avoid an overflow of highly contaminated water. It does not look however as though they will be able to store the treated water unless there is some tanker storage planned. So there will of necessity be a further ocean disposal of contaminated water.

Hummm, 100 000 tons underground storage installed in August? Do you have a idea of how big this is? How can they dig a hole that big and install a tank that big in so little time? That's putting below the ground a tanker, not exactly an easy task! And where?

I don't understand this statement.

 

[etudiant]

Hummm, 100 000 tons underground storage installed in August? Do you have a idea of how big this is? How can they dig a hole that big and install a tank that big in so little time? That's putting below the ground a tanker, not exactly an easy task! And where?

I don't understand this statement.

World Nuclear News here
http://www.world-nuclear-news.org/RS_cooling_success_while_water_builds_up_0306111.html
notes that TEPCO is moving to install 3 tanks on the site, a 10,000 ton unit for highly contaminated water, a 19,400 ton one for mid level contaminated water and a 140,000 ton low level contaminated water tank. No completion dates are given and no construction details.

 

[hbjon]

That explanation makes me think there is a complex stew of isotopes unwinding towards the zone of stability, decaying at various halflives, and converting mass to energy in the process. One thing that I cannot get my mind around is when you say "Te, I, and Xe are born by fission." Would that be U235 or P239?

 

[MiceAndMen]

Hope that these are just the specs for the product, because they need at least two of each of those every day just to hold the injected water at the current rate.

It seems to say they are going to be moving 6 x 120m³ and 4 x 100m³ tanks every day for several weeks. Better late than never.

 

[etudiant]

Hummm, 100 000 tons underground storage installed in August? Do you have a idea of how big this is? How can they dig a hole that big and install a tank that big in so little time? That's putting below the ground a tanker, not exactly an easy task! And where?

I don't understand this statement.

My bad.
The underground tank is for high level wastes and is only 10,000 tons, according to Yomiuri here
http://www.yomiuri.co.jp/dy/national/T110603005358.htm

I do not know where the large 140,000 ton tank will go.

 

[jim hardy]

""I would like to see the math on how Cs is created in a fuel rod. Exactly how long does it take for a fresh fuel rod to produce a gram of the stuff. ""

i'm a beginner at this but here's what i do

really you don't need more than high school chemistry and physics and an introduction to chart of nuclides.

Here's brief into for beginners like me:

get this page open in browser (i use firefox)
http://www.nndc.bnl.gov/chart/reZoom.jsp?newZoom=7
you should see a white box with diagonal multicolored stripe, pink below and blue above center.
If it's not pink and blue click in top line the box "Decay Mode".

What you see is a graph of all known nuclides, sort of an expanded periodic table of the elements but showing all isotopes. It is a mosaic of teeny squares, one for every known nuclide. Hydrogen is lower left corner, up and right is progressively heavier atoms.

Vertical axis is atomic number (which is number of protons), horizontal axis is number of neutrons.
So any row represents all the isotopes of one element.
Black stripe along center is stable nuclei, all others are decaying toward that line with various half-lives.

near upper right corner click on box "235U FY" which stands for U235 fission yield
the colors change to mostly red and yellow and clump toward center

The color of any little square tells the likelihood that a U235 atom will split into that square.
Note deepest red is in two areas, U235 tends to split into smaller atoms in those areas.

On right side about midway up is a little box labelled "Nucleus". Type in there 137Cs and click GO.

Now click, above Nucleus box, zoom = 1.
Note center square says Cs137 and is red.
The number at bottom is probability of getting that nucleus from a fission. 6E-4 means out every 10,000 fissions you'll get 6 of it.

Now click in top row "Decay Mode" and colors turn mostly purple .
Purple means, from legend at right, the isotope decays by emission of a beta ray which is an electron from the nucleus.
Shedding that electron caused one neutron to change into a proton, which moved it one square up and one square left. Try it - one more proton, one less neutron means one up and one to left. Cs137 decays into Ba137 with halflife 30.08 years.

But notice that Xe137 decays into Cs137 with 8 minute halflife. So all the Xe137 will soon enough be Cs137.
And I-137 decays into 137Xe with 24.5 sec halflife, from there to Cs... And so on.
You get Cs137 by two paths - direct fission yield and decay of other fission fragments.

Now click 235UFY again, notice Xe137 is a more likely fission product than Cs137 its yield is 0.0319. So out of the same 10,000 fissions you'd expect 6 Cs137's, 319Xe137's, and 262 I-137's. etc etc.
So as you said it's chaotic...


You might estimate how long to make a gram from production rate
To get production rate you have to figure out fission rate, number of fissions per second to make full core power. I think it's around 200 MEV/fission and Google will give MEV/sec to Watts ...
Fissions/sec X fission yield equals production rate.
add up production rates of Cs, I , Xe, Te and Sb 137 they'll all be Cs soon enough..

have fun!

 

[jim hardy]

"""One thing that I cannot get my mind around is when you say "Te, I, and Xe are born by fission." Would that be U235 or P239?""

Both. in chart above, click 239Pu FY..

have fun!

 

[robinson]

So, is the cesium a metal or an oxide?

 

[Astronuc]

That explanation makes me think there is a complex stew of isotopes unwinding towards the zone of stability, decaying at various halflives, and converting mass to energy in the process. One thing that I cannot get my mind around is when you say "Te, I, and Xe are born by fission." Would that be U235 or P239?

The following figures show the yields of several radionuclides for fission of U-235 and Pu-239.

Fission yields of Te isotopes:

Isotope  U235    Pu239
Te-131  0.00233 0.0087
Te-132  0.0153  0.0225
Te-133  0.0299  0.0289
Te-134  0.0622  0.044
Te-135  0.0322  0.022
Te-136  0.0132  0.005
Te-137  0.0039  0.0013

In fission of Pu-239, the yield of heavier elements shifts toward I and Xe isotopes, particularly Xe-136, Xe-137 and Xe-138. Te-134 and I-135 have nearly the same yield for fission of Pu-239

 

[Astronuc]

So, is the cesium a metal or an oxide?

Cs is an alkali metal in the same group as Rb, K, Na.

It forms compounds with halides, e.g., CsI, but also oxides Cs₂O, and more complex compounds with U and O, e.g., Cs₂UO₄ (cesium uranate).

 

[etudiant]

So, is the cesium a metal or an oxide?

pure cesium is an alkaline metal, in the same family as sodium and potassium.
It is very reactive and consequently not found pure in nature, but in the form of minerals and salts.
If refined, it must be kept under oil, because it reacts strongly with water, even from the ambient air, and will get quite hot. Like sodium or potassium, dump some on water and it will float while generating hydrogen from the water with enough heat that the hydrogen will burn spontaneously. The cesium hydroxide formed in this reaction dissolves very well in water, forming a very alkaline solution, very akin to lye, which is of course sodium hydroxide in solution.

 

[jlduh]

Don't know exactly where this video has been taken by packbot (N°1 Unit, but where precisely is not clear), but it's a new one (June 3) and this is showing some boiling water inside the building...

http://ex-skf.blogspot.com/2011/06/fukushima-i-nuke-plant-reactor-1.html

On June 4, TEPCO announced that the US-made robot "Packbot" confirmed and photographed the hot steam gushing through the space around the air duct that goes through the floor in the southeast corner of the 1st floor of the reactor building of the Reactor 1 at Fukushima I Nuclear Power Plant.

[...]

TEPCO thinks the steam comes from the warm (50 degrees Celsius) contaminated water leaking near the Suppression Chamber, and says the company will continue to monitor the situation.

(Steam coming from water 50°C? Doesn't make sense to me...)


Direct link to Tepco site to download video, the title is just this:
"Confirmation of steam situation at a reactor building of Fukushima Daiichi Nuclear Power Plant Unit 1 (ZIP 5.55MB)"
http://www.tepco.co.jp/en/news/110311/images/110604_09.zip

For the first time, we see for real a Boiling Water Reactor...

The ex-skf site speaks about 4Sv/h radiation in unit 1, is it based on this article?
http://www.yomiuri.co.jp/science/news/20110604-OYT1T00372.htm?from=main5

EDIT: Oups, NHK just released an article on this matter, it's here:

http://www3.nhk.or.jp/daily/english/04_16.html

The operator of the damaged Fukushima Daiichi nuclear plant says steam was observed coming out of the floor of the No.1 reactor building, and extremely high radiation was detected in the vicinity.Tokyo Electric Power Company inspected the inside of the No.1 reactor building on Friday with a remote-controlled robot.

TEPCO said it found that steam was rising from a crevice in the floor, and that extremely high radiation of 3,000 to 4,000 millisieverts per hour was measured around the area. The radiation is believed to be the highest detected in the air at the plant.

TEPCO says the steam is likely coming from water at a temperature of 50 degrees Celsius that has accumulated in the basement of the reactor building.

The company sees no major impact from the radiation so far on ongoing work, as it has been detected only within a limited section of the building.

 

[elektrownik]

And this ? This is ne pressure indicator, but it show correct values ?
http://www.tepco.co.jp/en/news/110311/images/110604_10.jpg