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Question on Noble Gas Monitors



Dear  Radsafers,

Noble gas monitors are usually installed at the stacks of containment and 
other buildings to measure radioactivity of noble gases.
According to  ANSI N42.18-1980(or, N13.10-1974), noble gas monitors shall 
have a minimum concentration limit of 5 x 10(-7) muCi/cc for Xe-133 and 3 x 
10 (-7) for Kr-85.
However, table 4.11-2 of NUREG-1301 (i.e. GL 89-01 Supplement No. 1) 
 states that LLD for continuous noble gas monitor  is 1 x 10 (-6) muCi/cc. 
In addition, reg. Guide 1.97 states that lower operating range of noble gas 
monitor is 1 x 10 (-6) muCi/cc.

I would like to know something described below;
  - Which values of measuring ranges of noble gas monitors are specified in 
your design documents such as FSAR or Tech. Spec. ?
 - Which  level of detection limit for noble gas monitor is required by 
regulatory body ?
 - Finally, how to derive in detail the minimum concentration limit of ANSI 
N42.18 and  the  LLD of NUREG-1301 ?

Thanks in advance.


Si Young Jang
k244jsy@kins.re.kr

KINS
P.O.Box 114, Yusung
Taejon, Korea


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