[ RadSafe ] Lethal Amount of Po-210 - any gamma?

Tue Dec 12 21:31:29 CST 2006

Thanks Jim!

It turned out to be radioactive material in cargo. I was under the 
(apparently mistaken) impression that radioactive material was not supposed 
to go on passenger planes. Otherwise, I would have asked the pilot right 
away.

I considered a bunch of alternative explanations, but was able to eliminate 
most of them: I waited until every one else got off the plane, to make sure 
the reading was not originating from one of the passengers. I made sure the 
reading returned to normal as soon as I got off the plane to eliminate the 
possibility of equipment failure or a temporary increase in cosmic/solar 
rays.

BTW, if your GammaWatch gives you strange readings, its a good idea to turn 
off the alarm and turn on the audio. You get a beep every time a photon is 
detected. That way, you eliminate the possibility of the microprocessor 
going screwy without actually receiving any pulses. It also eliminates the 
possibility that the microprocessor received hundreds of pulses in a short 
time (perhaps due to some interference ...) and that it just takes a long 
time for the display to go back to normal. The displayed value responds 
quickly to increases in radiation, but takes some time to go low, once the 
radiation level is decreased. There is no such delay when you listen to the 
frequency of the beeps.

Whenever I observed unexpected higher readings, the reading was usually real 
and not due to equipment failure. However, there is always that possibility.

Best Regards,
Kai

----- Original Message ----- 
From: "Jim Hardeman" <Jim_Hardeman at dnr.state.ga.us>
To: <franz.schoenhofer at chello.at>; <radsafe at radlab.nl>; <eic at shaw.ca>
Sent: Tuesday, December 12, 2006 5:49 PM
Subject: Re: [ RadSafe ] Lethal Amount of Po-210 - any gamma?

Kai --

Just a guess, but take a look at 
http://www.sec.noaa.gov/ftpmenu/plots/proton.html ... looks like the flux of 
high-energy solar protons has been elevated by several orders of magnitude 
since sometime on 12/5 and is just now coming back down to normal. For 
example, the flux of 100+ Mev protons (as measured by the GOES 11 satellite) 
normally runs around  0.1 protons per square centimeter-second-steradian ... 
where over the past few days the peak flux was around 20 protons per square 
centimeter-second-steradian. Similarly, the flux of 50+ MeV protons went 
from 0.3 up to around 100 ... and the flux of 10+ MeV protons went from 
around 0.5 up to around 2,000 (same units as above).

I noticed a similar phenomenon with my GammaWatch a few years back ... I was 
sitting in my office when I heard the alarm going off (it was set at 100 
uR/hr) ... I looked at it, and it was measuring 250 - 350 uR/hr ... stayed 
at that level for about 30 minutes ... every other radiation detection 
instrument we had in the office was measuring normal background (10-15 
uR/hr). One of my staff looked at the website above, and to the best we 
could determine, the increase was due to an increase in solar proton flux. 
Why the little GM in this watch would respond to these protons so well, when 
no other instruments in the office (other GM instruments, NaI-based micro-R 
meters, etc.) does I don't know.

Of course, the other possibility is that you were seeing shine from one or 
more radioactive packages in the cargo hold. Airlines don't like to admit 
it, but it's by no means uncommon for radioactive packages to be transported 
aboard passenger aircraft.

My $0.02 worth for the day ...

Jim Hardeman
Jim_Hardeman at dnr.state.ga.us

>>> Kai Kaletsch <eic at shaw.ca> 12/12/06 6:11 PM >>>
Dear Franz,

To answer your question: Yes, I have heard about cosmic rays.

However, I am not sure how your question of "Ever heard about cosmic
rays???????!!!!!!!" relates to either a lethal dose of Po-210, or to
elevated radiation readings on a plane BEFORE take-off and AFTER landing.
(The plane is not that tall.) I'm also not sure how it relates to seeing a
noticeable increase ABOVE normal cosmic ray dose rate for that route DURING
the flight.

Best Regards,
Kai

----- Original Message ----- 
From: "Franz Schönhofer" <franz.schoenhofer at chello.at>
To: "'Kai Kaletsch'" <eic at shaw.ca>; <radsafe at radlab.nl>
Sent: Tuesday, December 12, 2006 2:16 PM
Subject: AW: [ RadSafe ] Lethal Amount of Po-210 - any gamma?

Ever heard about cosmic rays???????!!!!!!!

Franz Schoenhofer
PhD, MR iR
Habicherg. 31/7
A-1160 Vienna
AUSTRIA
phone -43-0699-1168-1319

> -----Ursprüngliche Nachricht-----
> Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im
> Auftrag von Kai Kaletsch
> Gesendet: Montag, 11. Dezember 2006 16:13
> An: radsafe at radlab.nl
> Betreff: [ RadSafe ] Lethal Amount of Po-210 - any gamma?
>
> Po-210 emits a gamma ray, but at a very low branching ratio. I did a quick
> calculation and concluded that you would not be able to see a gamma field
> above background, even a very small distance away from a lethal dose of
> Po-210, or even a few tens of lethal doses of Po-210 (it doesn't seem like
> those guys were particularly stingy with the stuff).
>
> I would appreciate it if anyone in radsafe land could tell me if this
> conclusion is correct.
>
> History:
>
> I was on a plane yesterday and noticed elevated gamma readings on my
> radiation detecting watch. (5 to 20 times normal BG before take-off and
> after landing and noticeably higher than what I am used to during flight.)
> Was told afterward that there were medical isotopes in cargo. But, you
> have
> a lot of time to consider possible scenarios during a 4 hour flight.
>
> BTW, it's a pretty strange experience trying to tell an airline that their
> plane is radioactive. You don't know who to talk to and you are not sure
> if
> they are going to stick you in a straight jacket. Especially, at a time
> when
> all you hear on the news is ted. The first few people you talk to do not 
> know
> that there is radioactive material in cargo.
>
> Kai
>
>
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