Re: Exposure to Phograhic Film in Airport X-ray Scanners

[Ted de Castro <tdc@xrayted.com>]

I have checked out one of those Pb bags.

At altitude they would offer no shielding to the higher energies and
might even be worse due to secondary particle production from cosmic
rays.

Similarly on low energy xrays they offer 10% to 20% shielding - BUT the
x-ray units are auto brightness - so REGARDLESS of the operator - the
exposure goes up when the Pb bag gets in there.  ALSO - if they don't
think they got a good look - they can stop the belt but keep the xrays
on.

So - any slight shielding the bag MIGHT confer is easily negated by the
system and or the operator.

As everyone else said - hand check!

Also - I don't know why no one else suggested it - but buy and develop
your film at the destination!  Maybe I am not enough of a photographer
to understand why not - but then I use a digital camera on the RARE
occasion that I might take a picture.

Bob Flood wrote:
> 
> I may be the cause of this thread - I answered a post in a photography
> newsgroup about 10 days ago and made a statement that the exposure of the
> film in US and Eurpoean airports would be a fraction of a millirem per pass
> through the gate security xray machines. I also said that the dose at
> cruising altitude for a transcontinental flight would be a few millirem each
> way, and an intercontinental flight (the subject of the newsgroup
> discussion) would be correspondingly higher.
> 
> The original post to the newsgroup wondered if there was any value in
> placing film in lead-lined bags. Such bags are made for this purpose and
> sold in major camera stores and mail-order houses. The discussion had raised
> the question of the xray machnine operator turning up the intensity and
> thereby undoing the protection the bag offered.
> 
> I replied to that group that the operator doesn't have much adjustment
> available, mainly so that the shielding of the xrays isn't "undone"
> resulting in higher than desired exposure of the staff that work the machine
> 40 hours a week. There would also be some benefit in xray tube life
> expectancy to limiting the operator's latitude in adjustment. But the real
> benefit of the lead-lined bag in reducing radiation exposure to your film
> would be at cruising altitude, since that's where the large majority of dose
> would be received, especially for intercontinental travel. I deliberately
> ran 3 of our Panasonic UD-802 dosimeters through the gate xray at SFO
> International a few years ago and the processing results show evidence of
> xrays but the dose was too small to quantify. This result is consistent with
> claims of a fraction of a millirem per pass.
> 
> One fact that may not be common knowledge on this list is that US FAA rules
> grant to the passenger the right to have photographic film hand-inspected at
> the gate security post instead of passing it thru the xray machine. This
> right does not exist outside the US, however. The newgroup discussion
> included quite a few useful "war stories" from those traveling outside the
> US on how cooperative the security people are or aren't in various places
> around the world, and how best to help them be cooperative. In general, it
> seems that removing each roll of film from its box and plastic capsule (if
> it has one) and placing it all in clear plastic bags for easy inspection
> dramatically increases your chances of getting a hand-inspection overseas.
> It stands to reason - doing some preparation to make it easier for the
> security guard do what you want may well bear some fruit. But not always -
> apparently some airports are getting famous for being uncooperative.
> 
> Another issue raised had to do with checked baggage. US airports now use the
> CTX machines to inspect all checked bags. The machine can do a single pass
> xray just like the gate machine, although exposure levels are undoubted
> higher (SFO wouldn't say, this is my estimation) - the machine will
> encounter larger, thicker bags, so it will have a need to, and it won't have
> a crowd of workers and civilians around it, so there's no reason not to.
> According to SFO security people, if the operator of the CTX sees anything
> unidentifiable or suspicious looking, they back up the belt and a full CT
> scan is done, allowing them to examine the contents of the bag in detail
> without opening the bag. This is also done of very infrequent random
> samples, too. It will, however, thoroughly ruin your film, whether it has
> been exposed yet or not. NEVER put your film in your check-in luggage.
> ============================
> Bob Flood
> Dosimetry Group Leader
> Stanford Linear Accelerator Center
> bflood@slac.stanford.edu
> 
> ************************************************************************
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html