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Re: xenon behavior
THE ANSWER TO THE QUESTION CAN BEST BE SEEN WHEN CONSIDERING THE
DISTRIBUTION OF RADON IN THE ATMOSPHERE. It decreases to half its surface
concentration at about 1 Km altitude, whereas for nitrogen and oxygen,
this altitude is a few Km. These heights can easily be derived with basic
physics. --B. Cohen
On Fri, 3 Nov 1995, Joel T. Baumbaugh wrote:
> Ed,
>
> At one time I worked at a university where at one time (for
> months at a time) a P.I. was using both X-133 and K-85 in an
> interesting animal study (assessing/preventing stroke damage in
> primates).
>
> Needless to say, even with all of our precautions (we
> THOUGHT we'd thought of everything) - (more than once), we had
> leaks develop in the tubing/mixing bag between both the supply
> bottle and the patient and the breathing exhaust tubing to an
> activated charcoal container (note: the activated charcoal worked
> GREAT!).
>
> Under the circumstances (upon discovering I had a leak), I
> was unable to totally evacuate the room as we'd loose a valuable
> research subject (there was surgery involved). Of course, I was
> concerned with human personnel uptake from the xenon and/or
> krypton.
>
> Needless to say, I performed rapid "emergency" surveys of
> the room with both a collimated (lead wrapped) scintillation
> probe and a G.M. pancake probe. Note: With the scintillation
> probe I would wrap the outside with lead foil to cut down on side
> photons and I even tried loosely looping lead foil around the
> front of it to make a (sort of) open "gas chamber" so I could
> measure the xenon/krypton gas levels within a given
> area/elevation without being influenced by photons from across
> the room.
>
> Under all cases (although there appeared to be some mixing
> with air turbulence when I evacuated all non-critical personnel)
> the xenon/krypton did tend to displace the nitrogen and sink to
> the floor. Once it had sunk to the floor, it eventually left
> the room (under the locked door) - and slowly dispersed into the
> hallway and down the stairs (we were next to stairs and an
> elevator on the 4th floor). It dispersed "VERY" rapidly.
>
> After the first "accident" I was prepared for the next
> "whoops" and was ready and able to take air samples to check for
> actual gas levels at different elevations and in different
> locations and can happily say that the projected/calculated
> intakes to personnel were WAY below the ALI (WHEW!).
>
> I'm sorry I was so "wordy" in my reply, but wanted to give
> you (or anyone else reading this) a feel for the situation - hope
> this helps,
>
>
> Joel Baumbaugh (baumbaug@nosc.mil)
> Naval Research and Development
> San Diego, CA
>
> Std Disclaimer - the opinions above are mine and do not
> necessarily reflect those of my boss, the Navy or the Federal
> Govt.
> _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _M_e_s_s_a_g_e_ _S_e_p_a_r_a_t_o_r_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
>
>
>
> Date: Thu, 2 Nov 95 17:26:15 -0600
> Sender: radsafe@romulus.ehs.uiuc.edu
> From: LEIDHOLDT.EDWIN@FORUM.VA.GOV
> To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject: xenon behavior
>
> I have a question regarding the behaviour of xenon gas in a room,
> specifically Xe-133, which is used for lung ventilation studies
> in nuclear medicine. Some people claim that it "sinks" in a room
> so that the xenon concentration is higher toward the floor; other
> people say that it remains at approximately a uniform
> concentration throughout the room. This is an issue regarding
> the placement of exhaust ducts in a room. Does anyone know
> whether the xenon concentration is markedly higher toward the
> floor?
>
> I will be grateful for any help with this issue.
>
> Ed Leidholdt
> US Department of Veterans Affairs
> San Francisco
> Leidholdt.Edwin@FORUM.VA.GOV
> 415-744-6243
>
>
>
>