Re: Use of Portable Radiation Monitoring Equipment

[James Reese <jreese@smtpgate.ddrw.dla.mil>]

     I do not believe you would want to rely totally on the area monitor 
     for ensuring the beam is "off".  Most of the applications I have seen 
     with large Co-60 irradiators require the operator to enter with a 
     portable dose rate indicating meter as well as verify the beam is off 
     by the area monitor.  This is usually a conditional requirement of 
     either the license or radiation program manual/procedures.  NRC 
     regulations rarely get that specific.
     
     I believe the reasoning is that eventhough there are numerous periodic 
     quality checks required to ensure the area monitor is operational, 
     defense-in-depth is desired.
     
     Just my thoughts.
     
     Jim Reese
     Defense Logistics Agency
     jreese@ddrw.dla.mil


______________________________ Reply Separator _________________________________
Subject: Use of Portable Radiation Monitoring Equipment 
Author:  <radsafe@romulus.ehs.uiuc.edu > at SMTPGATE
Date:    9/19/97 12:00 PM


GROUP:
     
        I wish to respectfully solicit the advice/expertise of RADSAFERS on the
following issue.  I pose this issue to RADSAFERS because I have been out of 
the NRC and medical world for some time and am not current as to the 
subtleties of some present radiation safety practices in that arena.  I 
presently work in the DOE (industrial? -- certainly non-medical) world.
     
        Radiation safety for industrial x-ray devices in the DOE world is
expected
to be provided in accordance with guidance contained in ANSI N43.3, 
American National Standard for General Radiation Safety -- Installations 
Using Non-Medical X-Ray and Sealed Gamma-Ray Source, Energies Up To 10 MeV, 
January 1993.  In the case of what this standard calls "Shielded 
Installations," the x-ray machine operator is required to carry a 
calibrated portable radiation monitoring instrument, such as an Eberline 
Model RO-2, into and out of the x-ray exposure room each and every time 
he/she enters/exits the x-ray room.  The intent of using such a portable 
x-ray detector is to provide the operator an additional means, apart from 
the various kVp meters, mA meters already on the x-ray control panel, of 
verifying that the x-ray beam truly of "off."
     
        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.  This part also 
requires the radiation safety organization that has jurisdiction over such 
a unit to have portable radiation detection survey instrumentation 
sufficient to perform the various radiation surveys specified in 35.641. 
But I note that 10 CFR 35.600 does NOT contain any explicit requirement for 
the Co-60 machine operator to carry and use a portable radiation monitoring 
instrument anytime he/she enters/exits the treatment room.
     
        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"?
     
        I do not wish to seem to be splitting semantic hairs here.  In my
non-medical, DOE world, the question has now come up as to whether a 
properly placed, calibrated area radiation monitor properly installed 
inside the x-ray exposure room can/should be regarded as the serving the 
same function as an operator carrying and using a portable radiation 
monitoring instrument upon each entry/exit of the exposure room.
     
        This question may not be of wide interest to the general RADSAFE
community; therefore, I leave it to your judgment as to whether or not you 
wish to post your response to the RADSAFE net or merely respond to me 
individually.
     
Thank-you.
     
Best regards  David 
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