Re: INSTRUMENT CALIBRATION

["Riasp Medora"<riasp.medora@fernald.gov>]

     Kenny:
     
     As far as calibration and use in field conditions refer to ANSI 
     N42.17A-C. This is required by 835. As far as verifying the sources 
     annually, is something new. Typically we try to have sources 
     re-certified every three years. M&TE equipment such as pulsers and 
     multimeters are calibrated annually. Also what do you consider field 
     conditions? The statement that efficiencies change and are determined 
     daily seems ,to be a practice that is not typically seen at most 
     facilities.
     
     Riasp Medora
     riasp_medora@fernald.gov


______________________________ Reply Separator _________________________________
Subject: INSTRUMENT CALIBRATION 
Author:  <radsafe@romulus.ehs.uiuc.edu> at FE-INTERNET
Date:    9/17/1998 4:09 PM


I recently had a peer come up and ask a question regarding calibration of 
portable instruments.  A debate began over whether portable instruments 
could be "calibrated" outside of a laboratory environment (e.g., in the 
field).  We've all had the opportunity in the past or present of conducting 
source checks and "calibrating" instruments in areas that would most 
definitely not be considered to be a lab.  ANSI N323A-1997 defines several 
terms:  calibrate, national standard, secondary standard, and tertiary 
standard.  The standard provides good information in Section 4 about 
calibration.
     
The questions I'm providing are how legitimate is it to conduct "field 
calibrations" (typically using one source at on one range) and use the 
subsequent efficiency to determine activity?  (This instrument may have been 
calibrated by the manufacturer/vendor to a different source and then field 
calibrated.)  If it is legitimate to calibrate in the field, is it necessary 
to send instruments to manufacturers or other calibration vendors to be 
calibrated, we can still calibrate in the field on an annual basis?  From my 
read on calibration and a discussion with the ANSI N323A working group chair, 
a calibration must take place in a location that maintains at a minimum NIST 
traceable, tertiary standards and these standards need to be part of a 
managed QA program which are sent off routinely (say once a year) to be 
verified.
     
Also at issue was the interchangeability of separate detectors onto a 
ratemeter.  This subject is discussed in the Standard.  Probes are allowed 
to be changed without recalibration if the variation between the new and 
previous baseline reading is within 20%.  The calibrated efficiency (from 
the manufacturer) is intended to remain the same unless you can show that 
the standards used to calibrate are part of QA program.  This may be news to 
many field hounds, but this is message I was given. 
     
Obviously, I'm more concerned operationally about survey technique because 
this in itself is the largest variable in a survey.  I'd be interested in 
how others view this subject regarding calibration.  If there are any 
regulators (either DOE, NRC, or Agreement State) looking at this I'd much 
appreciate how you would view this if you came upon a site where 
efficiencies changed on a daily basis.  With this I'll call it a week and 
await any responses.
     
This message is most definitely mine alone.
     
     
Kenny Fleming CHP CSP
FUSRAP Radiological Control Supervisor 
knflemin@bechtel.com
(423) 220-2306
(423) 220-2464 FAX
     
************************************************************************ 
The RADSAFE Frequently Asked Questions list, archives and subscription 
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
     

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html