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Saturday, July 16, 2011

TEPCO replaces dry well pressure gauges

TEPCO apparently agreed with this author (without consultation, I might add) that its pressure indications at No. 2 and No. 3 plant for dry well pressure were suspicious and has replaced the pressure gauges. The new readings are not only improved but encouraging.

Below are the reactor plants, the volume of nitrogen injected in total so far, and the most up to date dry well pressure readings.

No. 1 - 66300 m³ nitrogen - pressure 142.4 kPa absolute
No. 2 - 5500 m³ nitrogen - pressure 127 kPa absolute
No. 3 - 500 m³ nitrogen - pressure 101.6 kPa absolute

Most encouraging is the reading at No. 2 plant whose dry well integrity is suspected as compromised by hydrogen explosion.

4:05 PM Eastern Saturday July 16, 2011


  1. Should've skipped up and offered yourself as a freelance consultant weeks ago, Will! :D

    Good job!

    James Greenidge

  2. @James: Thank you very much. That's actually one of the plans I started all this with.

  3. For those of you who still think in terms of psi (like me), according to the unit conversion website I use:
    142.4 kPa = 20.65 psi
    127 kPa = 18.42 psi
    101.6 kPa = 14.735 psi

    Atmospheric pressure is 14.696 psi or so.

    The N2 injection is harmless, I suppose, but what are the chances of another hydrogen explosion? The tops of the reactor buildings are pretty much already blown apart (for #1,#3 and #4). Even though the containment vessels might be holding in some N2, the operators have still not been successful in getting the fuel covered with water.


  4. @T: If you say that the cores are not covered with water, then the reason for nitrogen injection into the dry wells is all too obvious.

  5. I don't completely understand the N2 injection. Is this continuous, as a way of flushing the containment vessels (and preventing an H2 buildup)? If so, what is the significance of the pressure readings --- that they are maintaining a positive pressure difference with the outside? If not continuous, then is this just diluting any H2 present --- that doesn't really make sense to me.

  6. @stevek9: Nitrogen injection to the dry well is performed in this case as an accident mitigation step to attempt to inert the environment to prevent further combustion or deflagration of accumulated hydrogen gas. The injection is absolutely continuous; the hope is to see some indication of a pressure rise in the dry wells which eventually would mean that the atmosphere inside will be so oxygen-poor that further burn of hydrogen gas cannot take place. At the moment, there is no rock solid guarantee that great amounts of hydrogen are being generated, but anyone familiar with any seriously considered accident scenarios (like the decades' worth run by Oak Ridge) will tell you that N2 injection continuously to the dry wells is very prudent.

  7. Any idea how does the volume injected compare to the expected pressures? My physics isn't good enough to work it out ...

    Can see the R2 change on the latest TEPCO csv exports, but the R3 don't show up yet. Be interesting to see a trend, currently it just shows a step change to a new value ... are they still continually injecting?

    Keep up the good work Will.


  8. @sheff/Ian: No idea at this moment what exactly we might expect for pressures due solely to the nitrogen injection, considering the unknown quantity of pressure vessel failure and thus steam release into the dry wells. However, what you'd hope for is that with temperature stable, and thus pressure simply due to that temperature stable assuming a fixed leak rate, that with the nitrogen injection pressure would start to increase even if only slightly and slowly. Nitrogen injection will be continuous at all three plants until some time in the future when they begin to take further action to obtain access to the cores. Thanks for the kudos.

  9. Not seen any changes on the TEPCO csv data dumps. The R1 step change is all it was and the R2/3 haven't altered readings at all. The temps for R1 and R3 are starting to come down nicely though, so perhaps that explains them (expansion related of reactor and air density?). R2 doesn't appear to have done anything at all, if anything slightly higher temps.