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RE: In-flight radiation doses
Well, The last Concord plane has been grounded already, so my remark is of theoretical value only (if any...). I can't understand the reason why those Concords were ordered to lower altitude in the event of a solar flare. While changing altitude from about 80000 feet to 39000 feet, lowering the exposure to half the dose per unit of time, they had to cut the speed and doubling the flight (=exposure)time . The net change in radiation exposure would be about 0.I have raised that question to FAA men during the IRPA 2000 they gave me a twisted answer that the most logical part of it was that it only happaned once and that Concord flights are phasing out anyway...
Dov (Dubi) Brickner MD
Beer-Sheva ISRAEL
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu [mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of Franz Schoenhofer
Sent: Friday, July 09, 2004 12:37 PM
To: John Jacobus; radsafe@list.vanderbilt.edu
Subject: In-flight radiation doses
There was a paper on this topic in Health Physics about 10 years ago. Since
the Concord(e)s flew so high up (wasn't it 18 000 meters?), that the doses
from solar flares were regarded as not negligible, a measurement device was
working automatically during flight to warn in the case of elevated doses,
whereupon the plane flew to a lower altitude.
More on this topic:
There is still little known about the exact doses from cosmic rays,
especially about the quality factors for larger particles. The neutron
component of the cosmic radiation plays an important role and even this part
of the radiation can only be measured with more sophisticated
instrumentation than a TLD dosimeter or a Geiger counter would be, not to
talk about the other components.
In light of this fact it is difficult for me to understand, that - though
radiation doses cannot be easily and/or exactly determined - there exist
regulations, depending on radiation doses. The European Union Directive
obliges the member states to install regulations for in-flight doses. The
regulations of member states which I know use the concept, which is used
also for regulations with respect to Naturally Occurring Radioactive
Material (NORM): Members of the public are not supposed to receive doses
above 1 mSv/y. If professional of the flight crew (which are not regarded as
radiation workers!) probably or likely are to exceed 6 mSv/y, they have to
be monitored. The employer has to care for reduction of the doses. In any
case 20 mSv/y must not be exceeded.
Regarding "monitoring" of flight crews: Since it is not possible to have a
simple device like a TLD for measurement (see above), a totally different
approach has to be chosen:
Despite the above described inherent problems to accurately determine a
"real" dose, really a lot of research has been done on the aspect of
in-flight doses, both on behalf of air lines, national organisations and
international organisations like the European Union. The basic facts are
relatively well known, one being the variation of cosmic radiation intensity
with elevation, latitude, season etc. So an overall pattern is known. The
sun activity is very well monitored by astronomers and the cycles governing
it on a large scale is well known. I know of British Airways that they use
computers to calculate the expected doses according to the flight routes. A
few BA airplanes carry measurement devices and can transmit instantly
changes like big solar flares. This enables BA to assign doses to every
single member of a crew. Crew members approaching their 6 mSv/y will be
assigned to flights with lower expected doses. According to estimates from
BA the crew of long-haul flights will normally receive between 5 and 8
mSv/y, so the problem is not really dramatic and can be rather easily
overcome, making special "personal" monitoring unnecessary. Crews working on
short-haul flights are according to several national studies not at all at
risk to exceed 6mSv/y.
There is a web-site, which you can use to calculate your dose on your next
flight, but I do not have the address at hand. Anybody interested in details
is welcome to contact me and I will do my best to find material in my still
unsorted records. An alternative is of course to use Google or another
Search Engine ("in-flight radiation"), though they usually do not yield
highly scientific information.
Best regards,
Franz
--------------------------------------------------------------------------
-----Ursprüngliche Nachricht-----
Von: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]Im Auftrag von John Jacobus
Gesendet: Freitag, 09. Juli 2004 15:45
An: radsafe@list.vanderbilt.edu
Betreff: Re: CNN article
I believe that the Concorde jetliners had pressurized
ion chambers in the crew's cabin to provide real-time
exposure results. If a solar event occurred, the crew
were supposed to reduce their altitude, which I
believe only occurred once. I have yet to find any
indication if the exposure data was every recorded.
--- JGinniver@AOL.COM wrote:
>
> In a message dated 7/7/04 1:04:47 am,
> rujohnso@nmsu.edu writes:
>
>
> > I'm curious now what the actual doses are to
> full-time international
> > airline crews. Does anyone know, per flight or per
> annum? I've been asked this
> > question before in the radiation safety class I
> teach, but I don't know. If
> > european agencies monitor crew doses, then they
> must fly with TLD or similar
> > badges.
> >
>
> There is quite a good summary by the UK National
> Radiological Protection
> Board at the following URL
>
>
http://www.nrpb.org/publications/bulletin/no4/editorial.htm
>
> It as my understanding that doses to aircrew could
> not be accurately
> estimated using simple passive detectors such as
> TLDs. Instead special monitoring
> equipment has been developed by the NRPB which is
> carried on the aircraft to
> provide dosimetric information and that by using
> different routes/flight
> paths/altitudes it is possible to estimate the doses
> to aircrew.
>
> Regards,
> Julian
>
=====
+++++++++++++++++++
"To be persuasive, we must be believable,
To be believable, we must be credible,
To be credible, we must be truthful."
Edward R. Murrow
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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