Re: Contaminated Hosp Pipes

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

	While I was never explicitly taught this in my formal, didactic radiation
safety training which was drenched in the LNT hypothesis, my experience
over the years has imparted to me the seemingly obvious lesson that mere
"detectability does not necessarily mandate or logically guarantee that a
personnel radiation safety HAZARD actually exists."  For example, one can
swipe a lab bench top for H-3 and count say 200,000 dpm/100 cm^2, but if
so, does that necessarily constitute a personnel health hazard?  The point
is that many more things must be considered in addition to mere
radiological detectability before a given unique situation can be
considered to constitute a radiation safety "hazard."

	It is noted that you have measured low-level external dose rates of 5
microgray (0.5 mrad) per hour and 30 microgray (3 mrad) per hour from a
relatively short half-life radionuclide.  If workers are actually being
exposed to a 0.5 mR/hr radiation field, how long per day are they being so
exposed, are the SAME workers always exposed to the field in the room each
day, is the exposure rate relatively constant, do they sustain an annual
external dose equivalent exceeding the standard for a "member of the
public" (which in the U.S. is 100 mrem/yr), or are they "radiation workers"
with a much higher annual permissible dose, etc.

	I don't think it is possible to offer considered advice until the
existence/magnitude of the  potential personnel radiation safety "hazard"
is described in a bit more detail.

REGARDS David W. Lee, Los Alamos National Laboratory (lee_david_w@lanl.gov). 

At 10:35 AM 18-06-97 -0500, you wrote:
>General thoughts,
>
>Organic crud probably is accumulating iodine, and it
>is likely that corrosion centers/pits/etc. are
>also accumulating iodine.  Some of this is chemical,
>some mechanical, all of it is very difficult to 
>remove in situ.  If you don't feel comfortable
>waiting for decay to happen, a good "roto-rooter"
>job likely will help some.
>
>The only alternative that I have heard of involves
>removal of all the piping (most expensive and
>disruptive).
>
>The drain pipe clean-out will probably reduce the
>levels, presently about 0.5 mR/h general area and 3 mR/h
>at the pipe--using the ancient exposure rate units--which presumably are
>the highest levels found in the surveys.  
>How accessible are these pipes? If members of the general
>public can't readily get access, perhaps some labels
>warning against loitering or prolonged contact would
>suffice.  If there are areas with levels greater than 
>5 mR/h at 30 cm from the surface of the pipe, posting as a
>radiation area would be required in the USA.
>
>For the long term, you might consider, if possible 
>in your hospital, placing radionuclide therapy 
>patients in rooms on lower floors.
>
>Good Luck,
>
>MikeG.
>
>At 08:26 AM 6/18/97 -0500, you wrote:
>>ANY THOUGHTS ON THIS PLEASE:
>>
>>Patients receive up to 7.4GBq (200mCi) I-131 for Ca-thyroid radionuclide 
>>therapy. This is administered on the 6th floor of our hospital. 
>>
>>Excreted I-131 from these patients passes through cast ...
>
>
>
>
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