Re: Survey Instrument calibration frequency

[magnum8@banet.net]

Jim,

I think Andy Karam and Tom O'Dou hit on one of the key points. A meter
calibrated in accordance with an accepted standard (e.g., ANSI N323A-1997)
should be used for legal, documented surveys. This provides for satisfaction of
regulatory requirements (whatever you are committed to in your license) as well
as affording protection in the event of (and I hope it never happens to you)
legal action. There is also the political survival issue of "managing
perception". Of course, this varies from place to place and must be assessed on
a case basis.

On the other hand, meters used "for information only" can be managed with far
less effort. I'm guessing here - since I'm not familiar with your working
environment or license conditions. I  assume you have many labs and researchers
(which I understand is typical of a large university), and you have friskers or
equivalent located in the labs for use by the researchers - basically to use
"for indication" to "keep them out of trouble". You probably have a limited few
RSTs that go through the labs and perform official surveys at a prescribed
frequency to verify proper control of RAM and smearable contamination. If this
is correct, I would think you could make a  good case for labeling the lab
meters "For Indication Only" and pull them out of the cal. program. Subject them
to  whatever periodic source response and functional checks you are comfortable
with (and your regulator will accept). Keep the few meters that your RSTs use in
a formal cal. program. If I'm all wet here, please hammer me. I can use the
education. In my world of power reactors, we occasionally use meters "for
indication only", but never to perform and document legal surveys. And I
wouldn't ever want to go to widespread use of same due to both level of
regulatory scrutiny and the probability that somebody would "foul" it up.

The issue of how "rigorous" the calibration needs to be for meters used for
"order of magnitude" or "gross indication" surveys is an interesting one. I hope
to hear views from others. I can offer that in some power plants, the effort is
made to determine the specific efficiency of each GM detector and he detector is
"married" to the meter (Note: ANSI N323-1997 specifically says this is NOT
required). In other power plants, they verify that the GM tube has a minimum
efficiency (usually 10%) for the energy of interest (based on plant spectrum)
and lets it go at that. Probes are then swapped between meters as necessary. The
assumption here is that this will be "close enough" for an "order of magnitude"
contamination survey in the plant. That's about the extent to which the reactors
have backed off - that I know of.

My thoughts/opinions only.

Chris Wend
Sr. Rad Engineer
christopher_wend@bedison.com
magnum8@banet.net

Jim F. Herrold wrote:

> Thank you everyone who has responded so far, particularly to Chris Wend and
> Bruce Busby, who reminded me to pull NCRP 112 off my shelf. I looked at it 6
> years ago when I was renewing my license LAST time. For license purposes, we
> use ANSI N323 because it's shorter. I like Appendix Q on NUREG 1556 vol. 11
> because it's shorter still.
>
> Anyway, NCRP 112, chapter 7 says: "The underlying reasons for performing
> surface activity measurements often do not necessitate particularly accurate
> measurements.... For purposes of common radiation control, routine
> measurements of surface contamination are made to fulfill regulatory
> requirements and to provide semiquantitative information on which to base
> further action (e.g., decontamination). Under such circumstances, a
> sophisticated and time-consuming calibration of a monitoring instrument is
> not justified." What's it mean by that? Any comments? I'm investigating
> further.
>
> I'm trying to do what I believe is the right thing, without burying myself
> with my own good intentions. What do I mean by that? A few years ago we were
> cited by NRC because our geiger counters were not calibrated within six
> months. This calibration frequency was our license condition, not based on
> ANSI, NCRP, or any other recommendation. The old RSO just did it that way. I
> soon changed that. Now I follow ANSI N323-1978, but I want to upgrade to the
> newer model (or an acceptable alternative).
>
> Jim Herrold
> Radiation Safety Officer
> University of Wyoming
>
> herrold@uwyo.edu
>
> -----Original Message-----
> From: Christopher_Wend@bedison.com [mailto:Christopher_Wend@bedison.com]
> Sent: Thursday, February 04, 1999 12:09 PM
> To: Multiple recipients of list
> Subject: Re: Survey Instrument calibration frequency
>
>
> Brief summary:
>
> ANSI N323A-1997, section 4.9, says: "Calibration shall be required at least
> annually..." There are also the usual words about calibration after
> maintenance,
> adjustment, etc. that can affect instrument performance. Also words about
> increasing cal. frequency due to extreme op, conditions, hard usage, etc.
> Essentially, there isn't any change (on this issue) from the 1978 version.
>
> NCRP 112, section 2.8 begins with: "Calibration frequencies suggested by
> various
> groups for portable radiological survey instruments vary from once every few
>
> weeks to once every year, with the most commonly suggested periods between
> calibrations ranging between quarterly and annually."
>
> ANSI N323A-1997, NCRP 112 and ISO 7503-1 all require daily source response
> checks (NCRP calls it a "performance check"). The source response checks
> should
> be based on a reference reading, normally established during calibration.
> Acceptance criteria should be +/-20% (ANSI N323A-1997, section 4.8).
>
> I'd be wary about taking your cal. freuency past 1 year. Recommend reviewing
> the
> discussion in NCRP 112, section 2.8. Probably not what you wanted to hear -
> but
> I hope it helps a little.
>
> My opinion only,
>
> Chris Wend
> Sr. Rad Engineer
> (508) 830-8158
> christopher_wend@bedison.com
> magnum8@banet.net
> ______________________________ Reply Separator
> _________________________________
> Subject: Survey Instrument calibration frequency
> Author:  "Jim F. Herrold" <Herrold@uwyo.edu> at Internet
> Date:    2/4/99 12:27 PM
>
> Howdy.
>
> Reading through Draft NUREG 1556 vol.11 I came across this statement under
> section 8.10.2, RADIATION MONITORING INSTRUMENTS:
>
> "Some instruments may only need to be checked periodically for operability
> and response to radiation rather than receive full calibration.  For
> example, Geiger-Mueller (G-M) type survey instruments used to identify
> contamination in laboratories may only need to be checked for ability to
> detect low level contamination."
>
> If this is true, it would have a HUGE impact on our calibration program. Is
> anybody else doing this? Does anybody know where the NRC got this guidance?
> Was it from ANSI N323A-1997? I don't have it yet, but am planning to obtain
> one as soon as possible. We have been following the old ANSI N323-1978, and
> don't remember any statements like the one above.
>
> We are in the process of renewing our license. Because NUREG 1556-11 is
> still in draft form, the NRC says I can't use it yet. However, if I can find
>
> another suitable reference for this statement, I could use it.
>
> Thanks.
>
> Jim Herrold, Radiation Safety Officer
> herrold@uwyo.edu
>
> University of Wyoming
> Environmental Health & Safety
> 303 Merica Hall
> Laramie, WY 82071-3413
>
> (307) 766-3277
>
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