Gamma Radiation during Flight between Schiphol Amsterdam - Tokyo Narita

Radiation level at sea level in Tokyo is currently 0.09 uSv/h which is similar to the pre-March 11 level. At higher altitudes, however, radiation levels are much larger due to cosmic radiation. To see the impact of altitude on radiation levels, we measured the in-flight gamma radiation dose rates aboard a KLM plane flying from Amsterdam Schiphol Airport to Tokyo Narita Airport.

Measurement Conditions

• Date: July 27, 2011
• Flight: KL861, AMS-NRT
• Seat: 12A
  
• Flight Duration: 11h00m
• Maximum Altitude: 33,000ft
• Route: Netherlands, Sweden, South of Nova Zembla, Jakutsk, Chabarovsk, Niigata, Narita
• Measurement Device: Polimaster PM1610
• Type of Radiation Measured: gamma
• Measurement Interval: 10m
  

Measurements
The graph below shows the dose rates measured. The vertical axis shows dose rate (uSv/h) and the horizontal axis time (hh:mm).

The total dose during the flight was 25 uSv. The flight started at 0:50 and ended at 12:10. Soon after taking off, radiation levels started to rise to 2 uSv/h. Three distinct radiation levels were recorded, each indicating a different altitude during the flight. A peak value of 3.1 uSv/h was reached close to Nova Zembla which was the most northern position during the flight. When the plane navigated southwards, we saw radiation levels gradually decreasing. Because incoming cosmic radiation particles are deflected by the Earth's magnetic field, the intensity of in-flight radiation is a function of altitude. In general, radiation shielding by the geomagnetic field is greatest at the equator and decreases as one goes north or south.

The top dose rate measured during the flight was about 30 times higher than the current levels in Tokyo. Does this mean that flying is dangerous? No, the accumulated radiation dose per year for five round trip flights between Europe and Japan add sea-level exposure would be approximately 1 mSv. This is well below any internationally alarm threshold levels.