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No-Entry Zones, Planned Evacuation Zones, etc.
Airborne monitoring results ?
Airborne monitoring results (Unmanned helicopter) ?
Distribution Map of Radiation Dose, etc. ?
Distribution Map of Radiation Dose, etc. (Vehicle-Borne Survey) ?
Land use
Population
Primary and junior high schools
Airborne monitoring map:
Using high-sensitivity radiation detectors installed on helicopters, second-by-second measurements are taken of the gamma rays emitted from radioactive substances deposited in circles of a diameter approximately twice the flight altitude (target altitude: 150 to 300 m) centering around ground locations right below the flight trajectories. Then, a dedicated software program is used to determine the hourly air dose rate (μSv/hour) 1 m above the ground surface at each location based on the value of gamma rays measured up in the air and the reading of the survey meter on the ground.
Meanwhile, the deposition density of radioactive cesium per unit area of ground surface (Bq/m2) is determined, using another dedicated software program, from the relationship between the results of ground surface measurement by a Ge semiconductor detector and the air dose rate 1 m above the ground surface. Note that values for points not flown (i.e., points not present on the flight trajectories) are determined by interpolation from measurement values obtained from points flown.
Airborne monitoring map:
As for measurements using an unmanned helicopter, the values converted on the basis of the results of measurements carried out once a second are displayed on the map.
[Measurement method]
Measurements using an unmanned helicopter installed with radiation measuring instruments (NaI scintillation type survey meter etc.).
*The detection section of the survey meter was installed on the bottom surface of the unmanned helicopter.
Distribution Map of Radiation Dose, etc.:
The hourly air dose rate (μSv/hour) 1 m above the ground surface at each reading point is determined as follows: individual reading points are identified using commercially available GPS devices; then, at each location with an air dose rate of 30 μSv per hour or less, measurements are taken using a calibrated NaI(Tl) scintillation survey meter; and measurements are taken using a calibrated ion chamber survey meter at each location with an air dose rate exceeding 30 μSv per hour.
Soil samples taken from up to five spots in each reading point are agitated in suspension for nuclide analysis using a calibrated Ge semiconductor detector. The averaged results of the nuclide analysis provide the basis for the surface deposition densities of iodine-131 and cesium-134 and 137 per unit area (Bq/m2) at each reading point.
Vehicle-Borne Survey:
The KURAMA System (Kyoto Univ. RAdiation MApping System) connected to on-vehicle NaI(Tl) scintillation survey meters is used to determine the hourly air dose rate (μSv/hour) 1 m above the road surface (as measured aboard). The values shown on the map as air dose rates measured by the on-vehicle survey meters are determined by factoring in the shielding effect of the construction of the monitoring cars, the installation height of the survey meters, and by multiplication with the correction coefficient for the air dose rates measured inside and outside the cars.
TEPCO Fukushima Daiichi Nuclear Power Plant TEPCO Fukushima Daiichi Nuclear Power Plant
Area 1 : Areas to which evacuation orders are ready to be lifted Area 1 : Areas to which evacuation orders are ready to be lifted
Area 2 : Areas in which the residents are not permitted to live Area 2 : Areas in which the residents are not permitted to live
Area 3 : Areas where it is expected that the residents have difficulties in returning for a long time Area 3 : Areas where it is expected that the residents have difficulties in returning for a long time
30km zone
50km zone
100km zone
150km zone
250km zone
350km zone
450km zone
Refer to the latest updated results to check the influences of current radiation levels.








































































































*This map shows air dose rates partially attributable to natural nuclides.
For example, 1.0 μSv/hour is equivalent to approximately 5 mSv/year.
* 10 k Bq = 10,000 Bq (Becquerel)
* The radioactive cesium deposition map identifies areas where no significant energy spectrum of radioactive cesium has been detected and represents these areas as being in the lowest (10 kB/m2) of the nine value ranges.
*The grey represents areas covered with snow. Due to the shielding effect of snow, the air dose rate 1 m above the ground surface of these areas may be lower than when there is no snow cover.
*The grey represents areas covered with snow. The amounts of radioactive cesium deposition in these areas are estimated on the basis of measurement values of air dose rate reduced by the shielding effect of snow and hence may be less than when there is no snow cover.
*Measurement results outside the 80 km radius area from Fukushima Daiichi Nuclear Power Plant obtained on May 7, 2012, were attenuation-corrected to the values as of June 28, 2012. The influence of migration of radioactive substances due to natural environment such as rain and wind was not taken into consideration.
*Measurement results inside the 80 km radius area from Fukushima Daiichi Nuclear Power Plant obtained on November 16, 2012, were attenuation corrected to the values as of December 28, 2012.
*The grayed zone represents places having been exposed to snowfall. Air dose rates in and around these regions may be reduced in comparison with those in the season without snowfall because of the shielding effect of snow.
*The grayed zone represents places having been exposed to snowfall. The deposition density of radioactive cesium in and around these regions may be reduced in comparison with those in the season without snowfall because of the shielding effect of snow.
Refer to the latest updated results to check the influences of current radiation levels.



































*This map shows air dose rates partially attributable to natural nuclides.
For example, 1.0 μSv/hour is equivalent to approximately 5 mSv/year.
* 10 k Bq = 10,000 Bq (Becquerel)
* The radioactive cesium deposition map identifies areas where no significant energy spectrum of radioactive cesium has been detected and represents these areas as being in the lowest (10 kB/m2) of the nine value ranges.
*The grey represents areas covered with snow. Due to the shielding effect of snow, the air dose rate 1 m above the ground surface of these areas may be lower than when there is no snow cover.
*The grey represents areas covered with snow. The amounts of radioactive cesium deposition in these areas are estimated on the basis of measurement values of air dose rate reduced by the shielding effect of snow and hence may be less than when there is no snow cover.
*Measurement results outside the 80 km radius area from Fukushima Daiichi Nuclear Power Plant obtained on May 7, 2012, were attenuation-corrected to the values as of June 28, 2012. The influence of migration of radioactive substances due to natural environment such as rain and wind was not taken into consideration.
*The grayed zone represents places having been exposed to snowfall. Air dose rates in and around these regions may be reduced in comparison with those in the season without snowfall because of the shielding effect of snow.
*The grayed zone represents places having been exposed to snowfall. The deposition density of radioactive cesium in and around these regions may be reduced in comparison with those in the season without snowfall because of the shielding effect of snow.
Double-click the left mouse button at the measurement point on the map. The measured value at that point will be displayed.
Expression "E**" means "x10 to the power of **."
(Example: 1.60E−001=1.60x10−1 = 0.16)
*This map shows air dose rates partially attributable to natural nuclides.
  For example, 1.0 μSv/hour is equivalent to approximately 5 mSv/year.
* 10 k Bq = 10,000 Bq (Becquerel)
*Assuming that the ratio of the deposition density of plutonium 238 to that of plutonium 239 + 240 observed nationwide during 11 years from 1999 to 2009 is expressed by a logarithmic normal distribution, and estimating there is a high possibility that the zones where the ratio of deposition density of plutonium 238 to that of plutonium 239 + 240 exceeds 0.053 are affected by the accident at the Fukushima Daiichi Nuclear Power Plant, the zones are marked with circles.
Double-click the left mouse button at the measurement point on the map. The measured value at that point will be displayed.
Expression "E**" means "x10 to the power of **."
(Example: 1.60E−001=1.60x10−1 = 0.16)
The eleventh Vehicle-borne survey
(From November 2 to December 18, 2015)
The tenth Vehicle-borne survey
(From June 29 to August 4, 2015)
The ninth Vehicle-borne survey
(From November 4 to December 5, 2014)
The eighth Vehicle-borne survey
(From June 23 to August 8, 2014)
The seventh Vehicle-borne survey
(From November 5 to December 12, 2013)
The sixth Vehicle-borne survey
(From June 12 to August 8, 2013)
The fifth Vehicle-borne survey
(From November 11 to December 10, 2012)
The fourth Vehicle-borne survey
(From August 20 to October 12, 2012)
Results of second and third vehicle-borne surveys
(From December 5 to 28, 2011 and
  from March 13 to 30, 2012)
The second Vehicle-borne surve
(From December 5 to 28, 2011)
The first Vehicle-borne survey
(From June 4 to 13, 2011)
*This map shows air dose rates partially attributable to natural nuclides.
  For example, 1.0 μSv/hour is equivalent to approximately 5 mSv/year.
*The grey represents areas covered with snow. Due to the shielding effect of snow, the air dose rate 1 m above the ground surface of these areas may be lower than when there is no snow cover.
*The measurement results of the second vehicle-borne survey have been corrected taking into account the reduction in the air dose rate resulting from the physical attenuation of radioactive cesium during the period (three months) between the second vehicle-borne survey and the investigation this time. The influence of the migration of radioactive substances due to the natural environment, such as wind and rain, was not taken into account.
* When a map is expanded, data is displayed.
* When a map is expanded, data is displayed.
* When a map is expanded, data is displayed.
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