Last updated on March 1, 2013
Update 15:00(UTC)/16:00(CET)/00:00(JST)
NISA has released their update, link 1, link 2, link 3. I have also reattached the earlier JAIF figures at the bottom of the last update to see if it will fix the bug that gives an error when one clicks on the pictures.
As usual the NISA figures are between (). The NISA data is 3 hours older than the JAIF data.
Reactor 1:
Water level in the core: 1.65(1.65) meters below the top of fuel assemblies
Flow rate of injected water: 7.2 cubic meters per hour
Core pressure: 476 (477) kPa
Containment pressure: 270 (270) kPa *note, in the last update I misstakenly wrote 370 kPa as containment pressure.
Core temperature(feedwater nozzle): 195.3 Celsius
Core temperature(bottom head) 146.3 Celsius
Dose rate within containment: 35.1 Sv/hour
Reactor 2:
Water level in the core: 1.1 (1.1) meters below the top of fuel assemblies
Flow rate of injected water: 18.6 cubic meters per hour
Core pressure: unknown
Containment pressure: 116 (115) kPa
Core temperature(feedwater nozzle): 107 Celcius
Core temperature(bottom head): 100 Celsius
Dose rate within containment: 43.4 Sv/hour
Spent fuel pool temperature: 57 Celsius
Reactor 3:
Water level in the core: 2.3 meters below the top of fuel assemblies
Flow rate of injected water: 14.5 cubic meters per hour
Core pressure: 139 (139) kPa *note, I wrote the wrong pressure in the last update
Containment pressure: 106.6 (106.6) kPa
Core temperature(feedwater nozzle): 37.6 Celsius (sounds like an error on equipment)
Core temperature(bottom head): 106.1 Celsius
Dose rate within containment: 36.1 Sv/hour
Due to my error with containment pressure in the last update I withdraw my speculation that its hard to control the pressure in number 1. Rather it seems like the situation is fairly stable. Otherwise not much new information.
The US Department of Energy has done some arial surveys around Fukushima Daiichi and released the data. I have one pictures from it below(hats of to http://neutroneconomy.blogspot.com/ where I found the pictures). The dose rate unit used on the picture is millirad. 1 millirad=10 microgray =* 10 microsievert
*that equality between gray and sievert is only valid for gamma radiation. Gray measures the energy deposited while sievert is weighted in such a way that it expresses a cancer risk. For gamma the weighting factor is 1.
Update 12:00(UTC)/13:00(CET)/21:00(JST)
No NISA updates have been released yet today, JAIF has released their update as usual(one hour old as of writing this).
Reactor 1:
Water level in the core: 1.65 meters below the top of fuel assemblies
Core pressure: 476 kPa
Containment pressure: 370 kPa
Core temperature(feedwater nozzle): no new data
Core temperature(bottom head) no new data
Dose rate within containment: no new data
Reactor 2:
Water level in the core: 1.1 meters below the top of fuel assemblies
Core pressure: unknown
Containment pressure: 116 kPa
Core temperature(feedwater nozzle): no new data
Core temperature(bottom head) no new data
Dose rate within containment: no new data
Reactor 3:
Water level in the core: 2.3 meters below the top of fuel assemblies
Core pressure: 202 kPa
Containment pressure: 106.6 kPa
Core temperature(feedwater nozzle): no new data
Core temperature(bottom head) no new data
Dose rate within containment: no new data
All 3 reactors are now cooled with freshwater instead of sea water. It seems hard for them to get the pressure in the number one reactor under complete control. In JAIF’s written update they say lights are on in all control rooms now. Levels of radioactive materials in the seawater around the plant is climbing. TEPCO is releasing updates on activity in both sea and air, I have attached levels as pictures in the bottom of this update.
The ground deposits of I-131 the prefectures around Fukushima ranges from less than 1 to 16 kBq per square meter. The cesium ground deposits ranges from less than 0.1 to 1.9 kBq per square meter(here are the last 3 MEXT updates on ground deposts link 1, link 2, link 3). The data form the worst effected prefectures are however omitted, we hope MEXT will make those figures available asap! As a comparison the ground deposits of cesium due to Chernobyl ranged from a couple of hundreds to a couple of thousand kBq per square meter.
Update, March 26, 12:00 (UTC) / 13:00 (CET) / 21:00 (JST)
Not much to add today. The radiation levels in the sea outside Fukushima I are sky-high. The long term effects are hard to predict now since a sea contamination is entirly different from a land contamination, where land is basicly a 2D area, which leads to a thin and high concentration on the surface, and where rains soon concentrate the contamination to “hotspots”. The sea on the other hand is a 3D volume where currents quickly dilute any contaminant by dispersing them over very wide areas.
The JAIF updates from 10:00, 16:00 and 21:00 (JST) for March 26 are pretty much uniform. The big news is that freshwater injection to the cores of 1, 2 and 3 has started as opposed to using salty sea water. Apart from that nothing new. The radiation readings at the main gate (1 km out) has stayed at 170 μSv/h all day. The west gate read 147 μSv/h at 13:30.
NISA has not said anything new since last night.
Links(english):
BBC We should stop running away from radiation
Hufftington post US brings fresh water to japan nuclear plant
NY Times Japan presses nuclear plant repair as more damage is found
Rod Adams Shaken, flooded, stressed by power outages, Fukushima Daiichi moves into second place
The Independent Fear and devastation on the road to Japan’s nuclear disaster zone
Links(swedish):
Röda berget
Dr Angels blog
DN Radioaktivt jod tusen gånger tillåten nivå i havet
Aftonbladet Strålningen ökar runt Fukushima
SvD Radioaktivt vatten i reaktorer
Tänkvärt? Eller inte!
Grön horizont
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Links to all the pictures above seems broken (at least in Chrome).
Hmm, same here (Android). I’ll look at when I get home.
Now it should work! I screwed up a bit when copying and pasting 🙂
Is it possible to say something yet about the high radiation levels in the sea? What could the cause be? How much leakage could it correspond to?
I have no idea… but coupled with the overexposure of the workers, and the measured isotope composition published yesterday it seems likely that they have a containment breach somewhere.
Har man verkligen hittat Klor-38 (37 minuters halveringstid) i turbinbyggnaden till reaktor 1?
“Regarding the result of concentration measurement in the stagnant water on the basement floor of the turbine building of Unit 1 of Fukushima Dai-ichi Nuclear Power Station
Radioactive Nuclide Concentration (Bq/cm3)
Cl-38 1.6×106 ”
Från http://www.nisa.meti.go.jp/english/files/en20110325-6.pdf March 25th, 2011
Finns det något sätt som Cl-38 kan produceras på, som inte innebär höga neutronflöden?
Med mina amatörmässiga kunskaper, så ser det ut som om kedjereaktionen inte är stoppad.
(Thank you dio82, in the forum thread at: http://arstechnica.com/civis/viewtopic.php?f=26&t=1139141&start=1400 )
The measured chlorine-38 is something that baffled me as well yesterday when I saw it. No decay chain that I am aware of leads to Cl-38 and the half life means it has been created recently. But the temperature measurements of the vessel in reactor one doesn’t seem consistent with a re-criticality.
Maby one could imagine there was a re-criticality during the pressure and temperature spike 2 days ago. I don’t see any other reason for why it all of a sudden would start to run so hot. One can not in any way exclude that.
If I am allowed to speculate freely then it’s possible part of the control rods have melted or fractured and dropped down to the bottom of the vessel while the fuel at the same level might be fairly intact. Then re-criticality in parts of the core is possible. They have to make sure to borate the water properly.
Lets hope they get some of the neutron detectors working again so they can monitor the situation more carefully!
A re-criticality will be quite limited though. The water in the part that goes critical will boil of fairly rapidly and the chain reaction will die before there is a chance to build up any significant new short lived fission product inventory. I would bet they are borating the living hell out of the water they are pumping in now as well.
Could you please something about the borated water they have used? Could it have something to do with a possible criticality? What other function does it have here?
Bor is a neutron absorber so its only function is to prevent criticality. I am sure they are putting borated water into all of the cores just as a precaution, so one can not draw any real conclusion from that.
They haven’t really stated how many ppm bor they put into the water or anything like that.
Disclaimer: I am not a nuclear engineer at all, kindly do not use my reasoning for something important before checking with a real engineer 🙂
Suppose the measurements of Cl-38 are correct, then:
For a given number of Cl-38 atoms to exist, you need a certain amount of neutrons to colide with Cl (In this case seawater, or most probably a somewhat more concentrated saline solution. A more concentrated saline solution would lower the amount of neutrons needed)
Since the half life of Cl-38 is only 37,23 minutes, the number of neutrons needs to be a lot higher, if the re-criticality was not recent. 24 hours is 38.678 half lives for Cl-38.
Or more exactly, 2^38.678 = 0.44E12 times higher for each day further back in time.
In the thread I linked, there are 2 different rough calculations by different people
dio82’s post is at:
http://arstechnica.com/civis/viewtopic.php?p=21474153#p21474153
pietkuip’s post is at:
http://arstechnica.com/civis/viewtopic.php?p=21474415#p21474415
Regarding the re-criticality not consistent with temperature measurements of the vessel in reactor one, unless there is another way to get Cl-38, the temperature measurements must be considered suspect or interpreted in a erroneous way.
A very brief re-criticality would require a corresponding increase in neutron flux.
One factor that is hard to estimate is the total current number of Cl-38 atoms, since we do not know the volume.
Anyhow, someone with a bit more knowledge should be able to supply some back-of-the envelope calculations for the amount of heat produced for the required number of neutrons.
Another possibility is that they fumbled the measurements and got it wrong. Disussing this on our mailinglists this possibility has been brought up.
The thermal neutron absorption cross section of Cl-37 is quite tiny
http://www.nndc.bnl.gov/sigma/getPlot.jsp?cursor_x=2.4857E7&cursor_y=4.2227E-1&submit=Update+Plot&xmin=0.001&xmax=1E4&xscale=log&ymin=2.80161E-5&ymax=30.51118&yscale=log&renorm=1.0
So I think I take back my earlier comment, I don’t think there has been a re-criticality. Or even if there had been one it seems unlikely it would form a lot of Cl-38.
A better check would be to compare the level of I-131 and Cs-137 and estimate how long ago they would have formed to create the current ratio given the assumption that both has escaped from the core with equal ease.
Or even better, compare the different Cs isotope ratios.
So, is there any other possible source of Cl-38 than from Cl-37 + a neutron? This question should be possible to give a a definite answer to.
Not that I have been able to find. No decay paths lead to Cl-38 except from S-38, but S-38 has a half life of only 117 minutes and there is no way for it to form that I am aware of.
I did some calculations and the needed neutron flux in the core to create the Cl-38(assuming a thousand times dilution between core and basement) is on the order of 1*10^12 neutrons/cm^2*s.
The neutron flux in a LWR is usually somewhere around 10^14 neutrons/cm^2*s
So it seems like if the reactor went critical and was running at some fraction of its full power then its plausible to form the amount of Cl-38 seen.
I guess one can conclude that if there is no other common nuclide that gives similar gamma energies then the reactor must have reached criticality again not so long ago.
Cosmoskitten, I made a new blog post where I give my reasons for believing they are reporting the concentration wrong. You might find it interesting http://nuclearpoweryesplease.org/blog/2011/03/27/regarding-the-contaminated-water-in-turbine-buildings/