RE: xenon behavior

[Free Spirit <FRANK@rover.bsd.uchicago.edu>]

>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 do know that it flows down-hill.

	Some years ago we suddenly had a CO-60 area monitor go off in our
	department, (radiation therapy,) which is on the first floor. The CO60
	the unit was fine, according to electrical and mechanical indicators.
	It was finally traced to Nuclear Medicine, (one floor ABOVE.) 

	They had just done a study and turned off their exhaust fan before it 
	had time to vent the exhaust stack, (which went up eight more floors.)

	All the Xenon came back down the stack, thru the study room in
	Nuclear Medicine, down a conveniently located back stairway,
	under a door, down a short corridor, down a hall, down a second
	stairway, and into our ventillation system, where it quickly was 
	circulated throughout one section of our department, including the 
	room containing the CO60 unit.

	N.B. Figuring this out was mainly due to some superb detective work by
	     a very astute RSO.

Frank R. Borger - Physicist     ___     "I promise you we won't build an
Michael Reese - U of Chicago   |___     airport in Lake Michigan, if it 
Center for Radiation Therapy   | |_) _  bothers one resident of the lake!"
net: Frank@rover.uchicago.edu    | \|_) - Daley the elder, (former Mayor
ph: 312-791-8075 fa: 791-2517       |_) of the City of Chicago.)