Radiation Monitoring
 

I'm a Capt for a Middle East airline on long-haul. We currently have no Radiation Monitoring for crews. I would be interested to know what monitoring is done by other airlines. Do you use Monitoring Cards for example which register the dosage of radiation on a continuous basis??

Ours is calculated by the crewing control system so its only working on theoretical data based on route and time in the air. Apparently its pretty accurate, you can look at your monthly dose whenever you want to.

Same thing here, calculated for each individual by the rostering system. I don´t recall the numbers but heard our Union Health rep recently give a speech regarding the annual dosage, and in the context he gave it, it seemed quite low given that a lot of our flying is in the high northerly latitudes.

At one time, Concorde crews received the highest routine dose of any industry including Nuclear Reactor charge face workers. Fortunately the inverse square law works wonderfully well to prevent crews of 'ordinary' airliners at a mere 42,000 ft, from receiving anything more than a dose at the top end of 'acceptable background radiation'.

A holiday in Cornwall or a week or two in Aberdeen would put my radiation film badge - not actually a film any more, it's a TLD (Thermo Luminescent Dosimeter) - into the 'inquiry' region. Although my day job often involves working with x-ray equipment, I am not routinely expected to absorb any more than background for the general public and it has always surprised me slightly that flight crews are not obliged to wear the same TLD that I do. Inverse square law notwithstanding.

Monitoring your radiation dose by extrapolating from your 'at altitude hours' is okay, up to a point. Coronal flares and changing solar activity makes a substantial difference to the dose at altitude and the ISL can only do so much.

Roger.

This is an important subject that affects the health of us all and in many quarters is being ignored by our employers. Radiation levels in the environment is on the increase and much contantamination is present suspended in the air at the levels we operate at. This combined with Cosmic Radiation is having it affects. Roster monitoring is from what I have read and understand is completely useless and is merely there to show 'concern'

We are going to present our facts to our airline and need ammunition regarding the efforts of other companies. If you have the Dose Meters could you let me know and if at all possible what company you work for. On the other hand if you only have roster monitoring could you let me know and again if possible tell me which company you work for.

Not a physicist and hate to nit-pick, however.....

I think the inverse square law of which you speak actually has very little effect in reducing the radiation dose between concorde altitudes and boeing altitudes.

The reduction is due to the attenuating affect of the thicker layer of atmosphere above the boeing, compared to the concorde.

Does anyone know what the day / night variation is in radiation dose? I've always assumed i was not being slow cooked at FL410 at night, in the earths shadow. Is this a correct assumption, or is there some perverse reason why it doesn't work like that?

@Landroger, TLDs cannot reliably measure cosmic radiation which is the main radiation source for flying personnel. Therefore it is calculated only as measurements cost too much money. By the way, according to our yearly radiation training flying personnel is still considered the highest dosed worker group, even compared to nuclear plant workers. The total dose is still low though. For the 8 months before January i had around 2 mSv with around 490 hours flown over the last 12 months from today.

I am reliably informed that this is only a possible problem in the high (polar) latitudes. Our ops people check the predictions and actual warnings for flights SYD-EZE (Buenos Aries) and SYD-JNB. It comes down to how many air molecules are between you and space to put it simply.

This area of science has a lot to yet discover, in fact one of our pilots earned a PhD in this field some years back.

Radiation Exposure...
 

Several years ago I wrote a 'white-paper' for an operator with regards to flight crew being exposed to radiation at altitude.

The most accurate form of measurement is found here:

CARI-6: Radiobiology Research Team

Those operating under EASA/EU Ops/TC are required to provide radiation monitoring for all of their crews...pilots and flight attendants.

Research has shown that solar radiation is not significant in our environment however; solar flares that cannot be forecast, are significant.

There is more harm in heading off to the beach to do some sun worship on layovers and taking a drag on a 'cancer stick'.

Go fly!

Warpspeedmrsulu
 

Of course it is the attenuation of the thicker atmosphere between 60K ft and 40K ft, but the ILS is always working in your favour when dealing with radiation. Although I don't work with active sources as do my Gamma Camera/ Nuclear Medicine colleagues, I have to know about spills and dealing with accidents involving sources. In this the teaching says; 'the only thing better than 8 feet away, is 12 feet away.'

With any radiation, the inverse square law operates. If it is nuclear radiation, you want to be far away from it and each doubling of the distance increases the protection as the square of the distance. If you want an emergency transmission to get to someone who can help, the ISL works against you in exactly the opposite manner.

After reading 777AV8R's post, it looks like CARI-6 is your best bet, because it seems to fold in all the solar stuff I mentioned, but it is still not measuring, it is educated guessing. Denti points out that my TLD does not measure Cosmic radiation reliably, although I'm not sure why. The crystal registers any ionizing radiation, although does not give information about source or duration, which my old film badge used to. Progress?

Roger.

Landroger:

The Inverse Square Law isn't relevant for radiation from the sun, since the distance from the sun doesn't change significantly whether you're at 60,000 feet or sea level... of course if dealing with muon showers initiated in the upper atmosphere, it's different. In any case the ISL only holds in the absence of absorption, if absorption is present the radiation will decay faster than inverse square. So "12 feet better than 8" is always true, but not necessarily because of the ISL.

Regarding the TLD's and cosmic rays, I came across this link. I didn't read the paper but the abstract says it all:

The response of LiF thermoluminescence dosimeters to the ground-level cosmic-ray background

http://www.sciencedirect.com/scidirimg/alertIcon.gif


This article is not included in your organization's subscription. However, you may be able to access this article under your organization's agreement with Elsevier.



Keran O'Briena

aEnvironmental Measurements Laboratory, U.S. Department of Energy, New York, NY 10014, U.S.A.


Received 7 December 1977;
accepted 21 February 1978.
Available online 3 October 2002.

Abstract

Monte-Carlo calculations of the response of LiF thermoluminescence dosimeters to cosmic radiation have been carried out and indicate that the dosimeter, when calibrated against gamma radiation in air, registers 0.83 of the muon-produced ionization. This is due both to the density effect and to the large proportion of muon-electron energy transfer that takes place when the cosmic-ray muons interact with the thermoluminescent material. The result is a systematic underestimate of the environmental radiation exposure rate of about 0.5 μR/hr.


The International Journal of Applied Radiation and Isotopes
Volume 29, Issue 12, December 1978, Pages 735-739

Fizz57
 

Thanks for that clarification, which changes some long held misconceptions. I thought the inverse square law would operate locally, as well as 'globally'. In other words, attenuation in air will also increase according to the ISL and is much easier to quantify horizontally. Vertically it is more complicated because of the change in density. Of course, the difference between 60k and 40k is miniscule compared to the distance from Earth to the Sun, but given that a finite amount of radiation arrives at the limits of atmosphere, it will still decay from that level according to the ISL, as well as be the action of the atmosphere?

As for my TLD, my eyes are well and truly opened. I simply hadn't realised it was so inaccurate when measuring 'background' effectively. I know the old film badges had to be specially calibrated for places like Aberdeen, with its high concentration of granite buildings.

Thanks again for the information.

Roger.

attenuation should be proportional to the mass of air between the point of interest and the source. however, at the smaller scales of measurement you were referring to in this instance, on the earth, the inverse square law will also be significant in reducing the flux density the further you are from the source. Both effects count.


thats always true, however in this case that is very much a second order effect, compared to the atmospheric attenuation (because the delta distance from upper to lower atmosphere is small compared to the orbital radius of the earth about the sun).

Current research
 

I've just stumbled across this forum and i'm very interested in some of the posts. There is a lot of misinformation generally on this topic and plenty of debate even amoung the "informed".

I am a physicist working directly in this field so i'd just like to clarify a few fundamentals: the radiation dose received by aircrew (and some frequent flying passengers) is indeed typically higher than workers at nuclear power stations - this is in large part becuase their dose is much more closely monitored and controlled. It is true that the dose received is not something to panic about - typically two to three times the average UK background level - but it is not true to say that it is unimportant. European legislation recognises air crew as radiation workers and airlines typically apply rostering to avoid exceeding an operational threshold which would require them to apply regular health checking.

This all primarily relates to cosmic rays. The additional hazard from some types of solar flare has only recently started gathering momentum in terms of industry awareness. Radiation from the largest of these flares can not only cause personal dose to exceed annual limits (though one of these has not occured for over twenty years) but they can also pose a threat to avionics via radiation effects on microelectronics. The radiation environment is mixed and complex and most radiation dosimeters do not adequately measure the dose (this includes TLDs incidentally). Altitude and latitude are the most important factors but inverse square law has no relevance at all.

Concorde was obliged to carry a monitor because of its high altitude, but in fact the dose on a subsonic flight between London and LA is higher than the dose on Concorde because of the higher latitude and greater duration. CARI-6 mentioned in another post, is a standard tool used for establshing dose on flights, but it is far from perfect and does not apply to solar flares. Research in this field is ongoing but awareness is poor.

Apologies for the lengthy post but I hope this clarifies a few things. For further information google "Advances in Measuring and Modeling the Atmospheric Radiation Environment" for a recent article and there are other papers. The European Cockpit Association published an open letter on this topic in September 2009 and this provides a reasonable summary.

I can provide further information to anyone who is interested - the more awareness this gets in the industry the better, especially as the legislation does not currently mandate any monitoring of frequent flying passengers.

Complete Agreement...so....
 

It would be VERY prudent for those flying in the next few days to heed the warnings about the Solar Flare event that is due to hit our atmosphere over the next few days.

For Space Weather Forcasts, it would be wise to have a look here:

NOAA / NWS Space Weather Prediction Center

No Polar ops gang!

Post on another MB stated that conversations with U.S. Space Weather Prediction Center revealed the current event is a 'G' type storm and aircrew health events are related to 'S' type storms.

R2
 

Sounds like we missed the brunt of it but rated at R2 right now:

R 2


Moderate


HF Radio: Limited blackout of HF radio communication on sunlit side, loss of radio contact for tens of minutes.

Navigation: Degradation of low-frequency navigation signals for tens of minutes.


M5
(5 x 10-5)


350 per cycle
(300 days per cycle)

2011 feb 18 1205 UTC

Solar flux 111 and mid-latitude A-index 2.
The mid-latitude K-index at 1200 UTC on 18 February was 3 (25 nT).

Space weather for the past 24 hours has been moderate.
Radio blackouts reaching the R2 level occurred.

Space weather for the next 24 hours is expected to be moderate.
Geomagnetic storms reaching the G1 level are expected.
Radio blackouts reaching the R2 level are expected.

Seems indeed that we passed the brunt of it. Well, i just lost my 10 hour block hour day tomorrow, so doesn't really worry me either way.

I concur with Handlesinc that not much is known about the radiation exposure of humans in alu-composite tubes at altitudes. I looked into this quite closely about a decade ago, although I am not a professional physicist.

First of all, the composition of the cosmic background radiation at specific altitudes is not necessarily very well understood. You have to sense it. Sensing it means stopping it, or getting it to react, with something in the sensor. Using silicon chips senses, well, gamma rays, but does it sense, say, neutrons? Not very well. What does? Water. Not very much of it will stop most, say about 6 ft / 2 m worth. Now think: what's made mostly of water and about 6 ft long/tall?

At higher altitudes, typical measurements say, for example, lots of electrons. But do those get through airplane skin? Probably not. The fuselage likely stops most of what there is that is charged. But not neutrons. This and other considerations led the Boeing Radiation Lab to posit that most SEUs at altitude were due to neutrons. My particle-physicist colleagues (and I) have our doubts.

Cosmic radiation in the atmosphere is also equidirectional. Its predominant types and intensities are not dependent simply on the amount of atmosphere above and below. The relation is much more complicated than that, and has to do with reaction by-products. Most of the stuff outside the atmosphere is alpha particles (helium nuclei, a couple of protons bound with a couple of neutrons). Get a little bit inside the atmosphere, and all that changes very fast.

Human activity (someone mentioned "contamination") has just about zero to do with radiation exposure at altitude, except for the business of physically putting you up there, or someone exploding something in the vicinity, which they don't any more.

The European Physical Journal C publishes an annual Review of Particle Physics, which has a chapter on Cosmic Rays, which is only 6 or so A4 pages long. It is worth scanning, to get an idea of what, and comparatively how little, is known. It is still difficult to get up there with the right stuff to find out! Most accurate radiation detection devices, such as used in ground-based particle accelerators, don't fit on aircraft, anywhere near!

PBL