Last edited on 2011-04-02 02:35:18 by stolfi

Plots of reactor data - Fukushima Daiichi - Units #1--#3

Jorge Stolfi
2011-03-23 02:40

The following plots show the partial evolution of physical quantities in the Fukushima Daiichi reactors #1, #2, and #3, after the march/2011 earthquake and tsunami. Note that the incident started on 2011-03-11 (friday), two days before the start of the plots.

Plots

Reactor 1	Reactor 2	Reactor 3

Quantities

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. Note also that the tic spacing in the top half of the plot is 10 times that of the bottom half.

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 surge suppression chamber, 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. 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. The upper limit of the sensor's range (400 C) was exceeded on some occasions.

Drywell radiation

This quantity is the radiation level (Sievert per hour) in the drywell, as measured by the CAMS instrument. Note:The scale is logarithmic.

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".

Water injection rate

This quantity is the rate at which water was pumped into the (inner) reactor pressure vessel, in liters per minute. Some of it was saltwater, some freshwater; some was injected through the fire extinguisher lines, some through the water feed line.

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 attributes the data to the 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).

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, injection rate, pressure, and temperature) come from the Nuclear and Industrial Safety Agency (NISA) News Releases, either the English version or the Japanese version.

For further information please contact the document authors.

Data files

The data was copied by hand from the source documents into a separate text file fo each reactor, namely:

• flow-un1.txt, flow-un2.txt, and flow-un3.txt: water injection rates.
• data-un1.txt, data-un2.txt, and data-un3.txt: water levels and pressures.
• heat-un1.txt, heat-un2.txt, and heat-un3.txt: temperatures.
• cams-un1.txt, cams-un2.txt, and cams-un3.txt: radiation levels.

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

Some data were almost certainly typos and were corrected (hopefully) as follows:

• Reactor #1, 2011-03-16, 6:00, the core pressure was given as "0.62 MPa" in the NIRS table. Corrected to "0.162 MPa".

• Reactor #2, 2011-03-20, 15:00, the CAMS reading in the drywell was given as "6.25×10^-1 Sv/h" in NISA's Release 37. Corrected to "6.25×10¹ Sv/h".

A few other values in the original source documents are so different from their neighbors (both before and after them) that they must be errors too. However it is not clear what 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 #1, 2011-03-17, 12:50, the CAMS reading in the drywell is given as "4.10×10^-3 Sv/h" in NISA's Release 28. May be "4.10×10⁰ Sv/h" or "4.10×10¹ Sv/h".
• Reactor #1, 2011-03-18, 03:00, the CAMS reading in the drywell is given as "3.80×10^-3 Sv/h" in NISA's Release 29. May be "3.80×10⁰ Sv/h" or "3.80×10¹ Sv/h".
• Reactor #1, 2011-03-18, 07:55, the CAMS reading in the drywell is given as "3.75×10^-3 Sv/h" in NISA's Release 30. May be "3.75×10¹ Sv/h" or "3.75×10¹ Sv/h".
• Reactor #1, 2011-03-20, 15:00, the CAMS reading in the drywell is given as "1.20×10¹ Sv/h" in NISA's Release 36. May be "1.20×10² Sv/h" or "4.20×10¹ Sv/h".
• 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.

Plotting

The plots were created by a gnuplot-based Linux shell script.

Disclaimer

IMORTANT: These plots, scripts, and data files are provided "as is", for the reader's convenience, with no guarantee whatsoever. There may be errors in the original document and/or in my processing of it.

This page is NOT an official document of the State University of Campinas (UNICAMP). Neither its author (me) nor UNICAMP should be held responsible for any damages that may result from the use of this information. Corrections and suggestions are welcome.