Last edited on 2011-04-18 19:33:35 by stolfi

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

Jorge Stolfi
2011-04-18

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
Time plots: reactor 1 PC × PD plot: reactor 1 PD × PS plot: reactor 1 TCn × PC plot: reactor 1 TCb × PC plot: reactor 1

Reactor 2

Time plots PC × PD PD × PS TCn × PC TCb × PC
Time plots: reactor 1 PC × PD plot: reactor 2 PD × PS plot: reactor 1 TCn × PC plot: reactor 2 TCb × PC plot: reactor 1

Reactor 3

Time plots PC × PD PD × PS TCn × PC TCb × PC
Time plots: reactor 1 PC × PD plot: reactor 3 PD × PS plot: reactor 1 TCn × PC plot: reactor 3 TCb × PC plot: reactor 1

Quantities and events

The precise meaning of the quantitied plotted (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 recent data we used the "B" reading for unit #1, "A" for #2 and #3. For older data, 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, 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 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: "RSV" and "HVH".

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:

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:

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:

Plotting

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

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.