Last edited on 2011-04-23 08:24:18 by stolfi

Fukushima Daiichi
Plots of reactor data
Units #1, #2, #3

Jorge Stolfi
2011-04-20

The following plots show the partial time 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). Note also that the vertical scale in the Time × Pressure plots is logarithmic.

Another set of plots of the same data can be found in a wordpress site called FNPP1 reactor parameters maintained by user Daniel "dgr4quake".

Plots

Reactor 1

Time plots	PC × PD	PD × PS	TCn × PC	TCb × PC

Reactor 2

Time plots	PC × PD	PD × PS	TCn × PC	TCb × PC

Reactor 3

Time plots	PC × PD	PD × PS	TCn × PC	TCb × PC

Quantities and events

The precise meaning of the quantities plotted above (including the nature, placement, range, and calibration of the sensors) is unknown at this time. Here is what is known:

Core pressure (PC)

This quantity is the absolute pressure in the inner reactor pressure vessel ("RPV"), in kilopascals (kPa). Two readings are available, "A" and "B" (the latter sometimes labeled "C" for unit #2 and "D" for unit #3).

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 in past versions of this page only one reading was plotted. For data between mar/14 (NISA release 23) and apr/17 (NISA 98) we had chosen to plot the "B" reading for unit #1, "A" for #2 and #3. For data which did not came the NISA releases, it is not clear which reading was given in the original documents.

Drywell pressure (PD)

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

Torus pressure (PS)

This quantity is the absolute pressure (kPa) in the surge suppression chamber ("S/C"), 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 (RPV), taken somewhere near the water 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) taken somewhere near the bottom of the reactor's inner pressure vessel (RPV). The upper limit of the sensor's range (400 C) was exceeded on some occasions.

Drywell temperature

This quantity is the temperature (Celsius) in/of the drywel. NISA began publishing this quantity on release 99 (18/apr 08:00), as two separate readings: "RPV" (pressure vessel's bellows) and "HVH" (hydrogen venting head).

Torus temperature

This quantity is the temperature (Celsius) in/of the surge suppression torus. NISA began publishing this quantity on release 98 (17/apr 14:00), as two separate readings "A" and "B".

Drywell radiation

This quantity is the radiation level (Sievert per hour) in the drywell, as measured by the CAMS instrument. Since release 98 (17/apr 14:00) NISA started giving two CAMS readings, "A" and "B"; the previous readings apparently were all from the "A" meter. Note:The plot scale is logarithmic.

Torus radiation

This quantity is the radiation level (Sievert per hour) in the surge suppresion torus, as measured by the CAMS instrument. Since release 98 (17/apr 14:00) NISA started giving two CAMS readings, "A" and "B"; the previous readings apparently were all from the "A" meter. Note:The plot 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. There are two readings, "A" and "B". Note that in previous versions of this page only one reading was plotted ("B" for units #1 and #3, "A" for unit #2; uncertain for some sources).

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.

In the NISA press releases, this quantity is updated sparsely, only every few days. It is not clear what happens between readings; presumably the rate remains constant until a new reading is released.

Explosions

The orange diamonds indicate the time of the explosions in reactors #1 and #3, and the explosion-like sound heard from reactor #2. The vertical position of the dot is arbitrary.

Dark smoke

The large greenish-gray dots (or thick horizontal bars) show the approximate times when black, gray, or grayish smoke was observed coming from reactor #3. White "smoke" (steam) is not marked. The vertical position of the markers is arbitrary.

Data sources

Some values of core pressure, drywell pressure, and water level of reactor #1 (only) between 2011-03-11 22:00 and 2011-03-12 15:28 were eyeballed from a graph found on a Physics Forum post by user "Fred".

The water level and pressure data from 2011-03-12 15:30 through 2011-03-17 were taken from a PDF document titled 'Condition of the plants of the unit 1-3 at FI site', fetched from the Nuclear Information and Resource Service (NIRS) site on 2011-03-22. That site attributes the data to the Citizens' Nuclear Information Center in Tokyo. Core pressures in that document were gauge readings relative to atmospheric pressure ("MPa g"), 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.

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: pressures (format changed on apr/18).
• wlev-un1.txt, wlev-un2.txt, and wlev-un3.txt: water levels (added apr/18).
• heat-un1.txt, heat-un2.txt, and heat-un3.txt: temperatures (format changed on apr/17,apr/18).
• cams-un1.txt, cams-un2.txt, and cams-un3.txt: radiation levels (format changed on apr/17,apr/18).
• boom-un1.txt, boom-un2.txt, and boom-un3.txt: explosions and other events (added apr/18).

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 (A) 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.
• Reactor #3, 2011-04-16, 12:00, the drywell CAMS (A) reading was given in NISA's Release 97 as "2.00×10¹ Sv/h", but adjacent values suggest that the correct reading should be around 1.6×10¹ Sv/h.
• Reactor #1, starting 2011-04-17, 12:00 (NISA's Release 98), the drywell CAMS reading (A) dropped by almost exactly a factor of 10 compared to previous values: it was given as "1.07×10⁰ Sv/h" but previous values suggest that the correct reading should be "1.07×10¹ Sv/h". This may have been incorrect carry-over of exponent from previous reading, "9.92×10⁰ Sv/h". The (B) reading is around 2.00 Sv/h, and readings have changed a lot recently, so it is not clear which exponent is correct. The drop in the factor of 10 persisted in several subsequent NISA releases, so perhaps the exponent error was in all previous readings instead.
• Reactor #3, starting 2011-04-20, 00:02 (NISA's Release 103), the drywell CAMS reading (A) dropped by almost exactly a factor of 100 compared to previous value (NISA's Release 102) from "5.47×10¹ Sv/h" to "5.44×10^-1 Sv/h". Since the (B) reading is 5.88×10^-1 Sv/h resumably the exponent of all previous readings was wrong.

Plotting

The plots were created with gnuplot and other GNU/Linux tools, within these shell scripts:

• plot-reactor.sh - time plots.
• plot-pressure-tracking.sh - pressure × pressure plots.
• recompute-times.sh - convert date+hour to elapsed hours.

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.