Re: Radiation Units

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

"Frohne, Vickie" wrote:

> ... Commercial planes generally fly at 30,000 to 35,000 feet,
> so the 96 mR at 9000 ft. from the mentioned chart will indeed
> be an underestimate for commercial pilots.

Good point. What fraction of air atmosphere is above 30,000 ft?
Probably only 20% or less. Therefore I would expect the
dependence of the dose on elevation to be less strong than near the
ground level (where is is about 70 mR per 10,000 feet, according
to the chart you posted). In the spirit of exaggerating the dose let
me assume that the dose versus elevation dependence is linear
(This would be wrong near the ionization belt.)

Under that assumption the previous estimate of 80 mR/yr would
have to be multiplied by 3. In other words, the expected dose
would be 240 mR, provided 8760 hrs (10% of the total time of
one year) is spent at the high elevation. But let see what Google
knows about this. I will finish this message later.

With the query phrase: radiation dose commercial pilots

I got this September 2001 report from a conference of
the WORLD METEOROLOGICAL ORGANIZATION.

They say: "At typical flying altitude (FL320), the radiation
dose reaches 2000-3000 nSv/hr." This is 2 to 3 mSv/hr, or
0.025 mrem/hr. The conversion factors are: 1 Gy=100 R
and 1 Sv=100 rem. Suppose the pilot flies, on the average,
5 hr per day. This translates into 1825 hrs. Thus the average
dose is 1825*0.025=45 mrem ~=45 mR. This is about 1/2
of the 80 mR estimate I made before (unrealisyically
assuming 8760 hrs of flying). Thanks, Google.
Ludwik Kowalski