Re: Use of Portable Radiation Monitoring Equipment

[tdc@ehssun.lbl.gov]

>January 1993.  In the case of what this standard calls "Shielded
>Installations," the x-ray machine operator is required to carry a
etc.

> I note that 10 CFR 35.600 in the NRC world requires Co-60 teletherapy
>rooms to be equipped with a room area radiation monitor.
 etc.

> Therefore, my question:  Is it correct in your judgment for me to
>conclude that having an area radiation monitor inside the treatment room
>is sufficient to exempt the Co-60 unit operator from having to carry and
>use a portable radiation monitoring instrument upon entering/exit of the
>room to verify that the radiation beam is "off"?

The difference is simple!  Since ANSI is a conscensus (however that is
spelled) standard there is no REQUIRED about it!  10 CFR on the other hand
is LAW.

Here at LBL we have a CO-60 irradiator and had an x-ray irradiator with
VERY robust interlocking, fixed monitoring and alarms such that we deemed
the survey meter unnecessary.  Visitors used to the survey meter find this
uncomfortable.

On the other hand fixed monitors get less abuse and are more likely to be
functioning and appropriately positioned than a portable meter AND they
function from the moment the unit is supposedly turned OFF which is BEFORE
entry.  Thus I consider the fix monitor approach better.  And - of course -
these monitors have keep alive sources and failure check circuitry.  The
fixed monitor is also not subject to the person forgetting, not wanting to,
or having hands full, or for whatever reason NOT bringing the portable
meter with them.

Ted de Castro
tdc@ehssun.lbl.gov
University of California Lawrence Berkeley Laboratory
Bldg 90 Rm 0026B
Berkeley, CA 94720
(510) 486-5256
(510) 486-6939 - FAX