Question on Noble Gas Monitors

[=?EUC-KR?B?wOW9w7+1?= <k244jsy@pinpoint.kins.re.kr>]

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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