The following are radioactive concentrations in the air measured near the monitoring posts (MP1-8) at the site boundary of Fukushima Daiichi Nuclear Power Station.

Monitoring points

Monitoring point

Radiation concentration

Radiation concentration
  • *

    "-": the wind velocity is below 0.5 m/s

  • *

    Wind direction and speed are measured by a meteorological observation instrument, installed on the west side of the Seismic Isolation Building, at 10m above ground level.

  • *

    0.0E-○ signifies 0.0×10-○
    Example:1.0E-6 signifies 1.0×10-6(= 0.0000010).

  • *

    Lower limit:1.0E-6(Bq/cm3)

  • Fluctuation in Radioactive Concentrations in the Air The radioactive concentrations in the air for natural nuclides such as Radon may fluctuate during the day depending on weather conditions such as temperature, wind velocity, and rainfall.


  • *On March 30, 2021, archives were updated. Please click “Past measurement results (on and after March 25, 2021) are found here” for additional archives.
  • *Data may be missing due to regular inspections and cleanup work.
  • *Duplicate measurement near the MP 1 to 8 has been begun from December 19, 2018.

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