Radiation dose at Shirasawa branch office, Motomiya - Absorbed dose rate
07 Sep 2012 00:00
- 07 Oct 2012 00:00
Data source: Dataset 4 (see below)
: absorbed dose rate [μGy/h]
Data source - Absorbed dose rate
- In cases of x-rays and gamma rays and electrons absorbed by human tissue Gray is often converted into Sievert by assuming
1 Gy/h = 1 SV/h (see information below).
Roentgen equivalent in man (rem): 1 Sv = 100 rem
- Please note: The y-axis displaying the absorbed dose rate and accumulation plots can vary depending on location and time frame.
||since 13.3.2011 or 15.3.2011
10 minute data
10 minute data
different sources with 10 minute data or hourly averages
|Minimum value (Vmin) and maximum value (Vmax) from usual value band: "Usual value band means a range of the maximum and minimum value observed before the earthquake" [MEXT: e.g. pdf])
||Minimum value (Vmin) and maximum value (Vmax) calculated with the data of the respective locations from 1.1.2010 to 10.3.2011 (from hourly averages)
||no value band
||no value band
Sometimes data is not transmitted due to maintenance or for other reasons. Missing data is not bridged by lines.
Only values refering to sequential hours are connected.
Accumulated absorbed dose rate
||Dataset 1, Dataset 2, Dataset 3 and Dataset 4
|Accumulated dose rate = summation of hourly averages of absorbed dose rate
Accumulation period: 13.3.2011 up to today
||❚Accumulation of original data
❚Accumulation of interpolated data:
Missing values are approximated since original data of average absorbed dose rate is not available for every hour. Missing data points are computed by linear interpolation.
∅Missing data at the beginning of the period:
All data taken into account in the accumulation is shown in the graph ‘interpolated raw data’ (top left button above the graph).
|The red graph shows the accumulation of 0,114 μGy/h
based on an estimated average for Japan of 1000 μGy per year (equates 0,114 μGy/h *24 hours * 365 days). The accumulation starts with the first available value of the data set after 13.3.2011 (see missing values above).
|The green graph shows the accumulation of Vmax.
The accumulation starts with the first available value of the data set after 13.3.2011 (see missing values above).
||< 10 * Vmax
||< 100 * Vmax
||> 100 * Vmax
The colour scale is based on the maximum Value (Vmax) measured at the location of the Geiger counter prior to the accident. Therefore allowing to spell out the changes in comparison to the values prior to the accident.
Units: absorbed dose rate [Gy/h]
Absorbed dose [Gy]:
The unit gray, [Gy], measures radiation which is absorbed into any
Equivalent dose [Sv]:
The unit sievert, [Sv], specifically measures radiation
which is absorbed by a person.
The equivalent dose to a person is found by
multiplying the absorbed dose, in gray, by a radiation weighting factor (WR
The radiation weighting factor WR
is introduced to allow for the different relative biological effects of
different types of ionizing radiation on human tissue.
In terms of SI base units:
1 Sv = 1 Gy ⋅ WR
where Sv=sievert, Gy=gray, WR
=weighting factor specific
to each type of radiation and tissue.
Radiation weighting factor (WR ):
Effective dose [Sv]:
For x-rays and gamma rays and electrons absorbed by human tissue, WR is 1.
For alpha particles it is 20. To compute Sieverts from Grays, simply
multiply by WR . This is obviously a simplification. The radiation weighting
factor WR approximates what otherwise would be very complicated
computations. The values for WR change periodically as new research refines
the approximations .
The probability of a harmful effect from radiation exposure depends on what part or parts of the body are exposed. Some organs are more sensitive to radiation than others.
A tissue weighting factor is used to take this into account. When an equivalent dose to an organ is multiplied by the tissue weighting factor for that organ the result is the
effective dose to that organ. If more than one organ is exposed then the effective dose, is the sum of the effective doses to all exposed organs .