What’s the dose up there?

The best thing with plane trips is that they’re a great way to test your Geiger counter. If you don’t have one you can also look out the window or catch up with your crappy movies stack but you’re then missing out on all the fun.

Typical dose rate on a plane: 3.4 µSv/h

At an altitude of 10 000 m the typical dose rate is indeed around 3 µSv/h instead of the 0.1 µSv/h that is commonly observed at ground level. The culprit is of course the atmosphere layer that gets thinner as the plane flies higher and can thus absorb less cosmic radiation.

That is not a problem for passengers who are flying only occasionally but for pilots and cabin crews the dose may be more than negligible. Since 1996 EU legislation thus requires airline companies to monitor their employees’ exposure. In the industry or medical field this is usually done through dosimeters but for a reason that will be explained later it would be far too impractical here. The chosen solution is thus different: all flights performed by pilots or cabin attendants are registered in an online database from which the received doses can be computed thanks to a model that is updated periodically with data provided by the IRSN (Institut de Radioprotection et de Sûreté Nucléaire) and Observatoire de Paris.

Where it gets even more interesting is that this system called S.I.E.V.E.R.T. (Système Informatisé d’Évaluation par Vol de l’Exposition au Rayonnement cosmique dans les Transports aériens) can also be accessed by anybody. All that are needed are the departure and arrival cities as well as the take off and landing dates and times and the website spits out the corresponding flight dose.

Thanks to a recent trip in Japan I have also been able to carry out my own measurements in flight. The whole gear was initially meant to perform land surveys but since I had it with me I thought I might as well use it. Here are the tools:

Gammascout (left) and GPS logger (right)

  • Gammascout : Geiger counter with a nifty feature that allows to periodically log activity and dose rate (for example every 1 or 10 minutes).
  • GPS logger: As the name says it continuously records the GPS coordinates (latitude, longitude, altitude) it is sitting at.

Based on the recorded times it is then possible to correlate the Geiger counter measurements with the GPS coordinates and thus infer all dose rates throughout the flight. By summing all these values we can even compute the total dose and compare it to the one derived from the SIEVERT system.

Departure City
Arrival City
Flight duration
SIEVERT Dose (µSv)
Measured Dose (µSv)
Total Dose (µSv)151.946.4

My computation’s order of magnitude is more or less correct but the actual figure is quite off. How come that there is such a large difference between the two figures? Did I screw up somewhere? Is the SIEVERT system too pessimistic in its dose estimation? Answers will come in due time, most probably in the next post.

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3 Responses to What’s the dose up there?

  1. Râle says:

    rhoooo le teasing,
    La suite, la suite !!!

  2. Adri says:

    10000 km d’altitude, ça me parait beaucoup ^^