Airborne Uranium -- Summary of Responses

["David W. Lee" <lee_david_w@lanl.gov>]

Group:

	Radsafer Mike McNaughton earlier asked about the logic behind the DAC
values in 10 CFR 835, noting that the Class W inhalation DAC value for
U-238 was 15 times larger than the value for Class Y, and that the Class Y
inhalation DAC value for Pu-239 was 3 times larger than the value for Class W.

	The following is a summary from the responses received from Radsafers
Jerry Hunt, Liz Brackett, Otto Raabe, and Vince King.


	U-238	Class D (UO2; U3O8)
		Class W (UO3; UF4; UCl4)
		Class Y (UO2F2; OU2(NO3)2; UF6)

		Organs of Ultimate Deposition:  Sometimes kidney, sometimes mineralized
(compact) bone

		Chemical toxicity typically overrides radiotoxicity for Class D forms of
U-238. Insoluble (Class Y) forms are removed from the lung more slowly;
hence, they reside in the lung longer to irradiate lung tissue; thus the
Class Y inhalation DAC is smaller (implying greater radiological hazard)
than the value for Class W.

	Pu-239	Class Y (all Pu-oxides)
		Class W (all other chemical forms)

		Organ of ultimate deposition:  bone surfaces

		Since Class W Pu-239 once inhaled would be cleared from the lung faster
than a Class Y chemical form, Class W will get into the blood sooner and
transfer to bone surfaces sooner than Class Y.  Thus, the Class W
inhalation DAC is smaller (implying greater radiological hazard) than the
value for Class Y.

REGARDS  David W. Lee, (lee_david_@lanl.gov); Los Alamos National
Laboratory, Los Alamos, NM  87545
David W. Lee
Los Alamos National Laboratory
Radiation Protection Services Group (ESH-12)
PO Box 1663, MS K483
Los Alamos, NM  87545
PH:   (505) 667-8085
FAX:  (505) 667-9726
lee_david_w@lanl.gov