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News and training for radiation workers at Northwestern
University Number 70 March, 2004
Survey Meter Calibration and Maintenance
About 30% of all compliance citations and safety
observations that are recorded by ORS inspectors on laboratory survey reports
pertain to the calibration and maintenance of survey meters. A troubling aspect
of this is that the observation sometimes is noted on sequential survey
reports, potentially meaning that no corrective action was taken and that 3
months could have elapsed without a functioning or calibrated survey meter on
hand.
Labs are required to do regular contamination
checks, which would be impossible if a meter has dead batteries. And while one
can do a contamination check with an uncalibrated survey meter, how is one to
interpret the results?
Survey meter calibration and repair keeps your meter operating at peak
performance. ORS provides free calibration service for portable survey meters
in University laboratories. We check switches, batteries and high voltage, use
an electronic pulser to calibrate the various ranges, and check detector
operation with a source of radiation. We provide a copy of the survey report
and schedule another calibration for next year. Check the calibration sticker
on your instrument; if it is missing or more than a year old, call ORS to
arrange for calibration.
Daily operational checks
of radiation survey
instruments are important because they tell you whether your survey meter is
functioning correctly before you use it. The best method is to use a small,
long-lived check source counted in the same geometry each time. Other sources
can be used such as a thorium lantern-mantle (now in short supply) or a
FiestawareÔ plate. When no other source is available
you can aim the detector at a stock vial or waste container and see if you get
a response. If you don't, make sure the instrument is turned on and the
batteries are OK and try it again. If you still don't get a response, call us
and arrange for getting your instrument repaired.
Common problems
include shorting cables, punctured tube windows, and leaking batteries. We've
also seen meter window glass fall out and knobs come off. While we can make
some minor repairs, in many cases we will help you get the parts or service you
need from the manufacturer.
Make sure the
meter has fresh batteries before you bring it in. We cannot do a calibration if
the batteries are dead or weak, and labs are responsible for this aspect of
maintenance.
Use this NUtrino as a training tool for new workers and required
annual refresher training for current workers. Circulate it among the radiation
workers in your group and have them sign and date the training form on the
back. File it with your authorization and other radiation safety documents for
review during regulatory inspections. Discuss it during laboratory meetings. We
have back issues, or you can print them off the web at
http://research.northwestern.edu/ors/safety/radation/nutrino.html
.
Office for Research Safety -
Office for Research - Radiation Safety Committee
Ward B-106 Chicago Campus, phone 3-8300 Tech NG71
Evanston Campus, phone 1-5581