[ RadSafe ] RMS check source question

[JOHN.RICH at sargentlundy.com]

Hi all, 

ANSI N323D-2002 provides a "permissive" for using the background count 
rate in lieu of a check source as follows. 

"An instrument's response to ambient background radiation may be used in 
lieu of a check source provided
a) The instrument's application primarily involves a point of interest 
that is near the level of ambient background radiation;
b) The instrument's response to ambient background radiation is 
characterized and documented;
c) The instrument's response to ambient background radiation is routinely 
monitored; and
d) Provisions are made for removing the instrument from service if the 
instrument's response to ambient background radiation changes by an amount 
that cannot be attributed to expected changes in the background level."

Has anybody used this, or any other approach, to eliminate active check 
sources? 

We're looking at replacing some radiation monitors for a client, and there 
are a couple of monitors where maintaining a check source would be 
difficult due to the location.  It would be great  if the background, or a 
non-moving keep-alive source, could be used instead.  I'm not sure how the 
NRC would react.  However, it seems like the new detectors and electronics 
are so much more reliable than the equipment of the 60's that detector 
failures, electronic failures, and drift, would be in the same range as 
other instrument loops, and RMS channels could be run 18 months between 
calibration and maintenance.  Thus it shouldn't be necessary to trigger a 
check source once a month to confirm OPERABILITY.

thx in advance  - -jmr


John Rich
312-269-3768