Complete Chronological Analysis Of Fukushima Reactor 1 - 3 Data

Tyler Durden's picture

With TEPCO unwilling (or unable) to disclose consolidated detailed information about the status of its reactors, the task has fallen on third party analysts. Luckily, Jorge Stolfi of the state university of the State University of Campinas in Brazil, has compiled what is probably the most comprehensive data dump of all key Fukushima reactor indicators including water level, core, drywell and torus pressure, as well as temperature at the core bottom and nozzle. Below are the detailed results for each of the fuel loaded reactors since the start of the crisis.

Reactor 1

Reactor 2

Reactor 3

Further details on the legend and methodology:

Water level

This quantity is the water level inside the (inner) reactor
pressure vessel, in millimeters, measured from the top of the
fuel elements. Negative values mean that the fuel is partly out of
the water. The "B" reading is used in preference to "A".

Core pressure

This quantity is the absolute pressure in the inner reactor pressure
vessel, in kilopascals (kPa). The "B" reading is used in preference to "A" or "C".
Note that 101 kPa is approximately 1 bar (one atmosphere) i.e. the pressure inside
the core is the same as that of air outside the building.

Drywell pressure

This quantity is the absolute pressure (kPa) in the "drywell", the outer pear-shaped
steel container that surrounds the reactor. A value of 101 kPa means
the same as outside air pressure.

Torus pressure

This quantity is the absolute pressure (kPa) in the suppression container, the
torus (donut) shaped chamber below the drywell container. A value
of 101 kPa means the same as outside air pressure.

Core noz. temperature

This quantity is the temperature (Celsius) of the
reactor's (inner) pressure vessel, taken at the injection nozzles. Note:The
value is multiplied by 10 for clarity. The upper limit of the sensor's range
(400 C) was exceeded on some occasions.

Core bot. temperature

This quantity is the temperature (Celsius) at the bottom of the
reactor's (inner) pressure vessel. Note:The
value is multiplied by 10 for clarity. The upper limit of the sensor's range
(400 C) was exceeded on some occasions.

Data sources

The water level and pressure data through 2011-03-17 come from the
NIRS PDF document titled
'Condition
of the plants of the unit 1-3 at FI site
', fetched from
the Nuclear
Information and Resource Service
site on 2011-03-22. That site
says

Here is a document on the condition of Units 1, 2 & 3 from March 13-17,
showing water levels and containment pressure, obtained through Citizens'
Nuclear Information Center in Tokyo.

Core pressures in that document were relative to atmospheric
pressure, so they were incremented by 101 kPa to match the
other pressures (all absolute).

Data from 2011-03-22 onwards comes from the Nuclear and Industrial
Safety Agency (NISA) News Releases.

The temperature readings from 2011-03-19 06:30 to 2011-03-22 15:30 were obtained from
a scanned
worksheet
presumably prepared by TEPCO. After 2011-03-22 the data
weer taken from the NISA bulletins (see above).

Data from 2011-03-22 onwards (water level, pressure, and temperature) come
from the Nuclear and Industrial
Safety Agency (NISA) News Releases
.

For further information please contact the document authors.

Data files

The water level and pressure data was entered by hand into
a separate text file fo each reactor, namely data-un1.txt,
data-un1.txt, and data-un1.txt.
The emperature data was placed in separate text files heat-un1.txt,
heat-un1.txt, and heat-un1.txt.

Values that were missing in the original documents are encoded as
"99999" in these files. Entries that were marked "down scale" are encoded as "88888".
(It seems that many of these may be "over scale" instead.)
Missing and out-of-scale values appear as gaps in the plots.

Corrections

The core pressure of reactor #1 on 2011-03-16 6:00 was given as
"0.62 MPa" in the NIRS table.
That must be a typo. I have corrected (hopefully) the value to "0.162 MPa".

A few other values in the original source documents sand so far out from
the neighbors (both before and after them) that they must be errors too.
However it is not clear which are the correct values:

  • Reactor #1, 2011-03-24, 11:00, the given temperature "175C" is too low. Perhaps "225C"?
  • Reactor #2, 2011-03-13, 9:55 and 10:35, the core pressures given
    as "1.283 MPa" and "1.263 MPa" are much lower than the previous value
    (6.08 MPa at 9:25) and the next one (5.85 MPa at 16:00).
    Interpolation of the smooth trend would give around 5.9--6.0 MPa.
    On the other hand, there seem to be sudden transient excursions in the
    drywell and torus pressures at that same time; so the data may be
    correct after all.
  • Reactor #2, 2011-03-16, 14:00, the drywell pressure is given as
    "400 kPA" in the NIRS table,
    dropping to 75 kPA at midnight.
    But NISA's
    News Release 26
    claims that the pressure had already dropped to "40 kPA" at
    12:25. perhaps the time of the NIRS table is incorrect: instead
    of 14:00 it should be 12:00?
  • Reactor #2, 2011-03-17, 11:25, the water level is given as
    "-1800 mm" in NISA's Release 28.
    That may be a typo; the correct value seems to be -1400 mm.
    Note that -1800 mm is the correct water level for reactor #1.
  • Reactor #3, 2011-03-20, 11:00, the water level in the core is
    given as "-2350 mm" in NISA's Release 36.
    That is a dip of 350 mm from the adjacent values. However the
    torus pressure at that time went off scale (greater than 400 kPa).
  • Reactor #3, 2011-03-20, 15:20, the presure in the suppression torus
    is given as "800 kPa, ~ down scale" in NISA's Release 37.
    However the previous report gave "400 kPa ~ over scale", so the
    two values may be guesses for some unknown value above 400 kPa.
    Indeed most readings between 2011-03-14 and 2011-03-24 are
    given as "down scale", but seem to be "over scale" instead.

Source.

h/t Jeroen