I think the base setting is to subtract 2.75 beta/alpha. I've heard Eberline say you might get a false alarm early on if since you're not subtracting out beta from Rn. I've never had a CAM false alarm early because of low counts variance since some amount of data is needed to ensure you meet the fast and slow alarm MDC valued.
At our power plants, I seem to recall we're typically set for ~186 dpm/ft^3 for Co-60 0.3 DAC for slow alarm at 1860 dpm/ft^3 for fast alarm. Co-60 is going to be conservative for essentially every mix in the plant. We have had some cases where we calculated an effective DAC and put that in the monitor to manage the conservatism of the monitor. In general, we always find the alarm of the AMS-4 to be conservative to the gamma spec of the real air sample. I leave the value as-is since the default value doesn't seem to help or hurt the monitor. The big thing to focus on is the gamma subtract factor and keeping it accurate. This is number one adverse condition we can cause for monitor response. If the automated source check routine shows a change in bias, something in the surrounding environment has changed and you need to reset the ratio. Glen Vickers, CHP Exelon Corp RP Technical Lead 815-216-2723 (work/cell) From: Creamer, Charles E [mailto:[email protected]] Sent: Tuesday, August 22, 2017 1:06 PM To: 'Voss, Tom'; 'Bradley A Krupp'; [email protected] Cc: Brian G Gonia Subject: [EXTERNAL] [powernet] RE: AMS-4 remote monitoring We have not looked at the Alpha subtract function of the AMS-4 From: Voss, Tom [mailto:[email protected]] Sent: Tuesday, August 22, 2017 12:22 PM To: Creamer, Charles E; 'Bradley A Krupp'; [email protected]<mailto:[email protected]> Cc: Brian G Gonia Subject: RE: AMS-4 remote monitoring TVA External Message. Please use caution when opening. Hi All Does anyone use the "Alpha Subtract" function of the AMS-4 to get an alpha cpm rate ? The detectors are sealed gas proportional and there is a separate beta and alpha channel in the AMS-4s. It is not straight forward to access the alpha channel and the count rate is only kept inside the AMS-4 memory for a few hours. But the alpha cpm value might have some use in assessing the potential for airborne alpha contamination NOT DUE TO RADON/THORON. A simple ratio of alpha cpm to beta cpm might be of use also. Here at LANL we did NOT use that alpha cpm information and only extracted it from operating AMS-4s a few times. Tom From: Creamer, Charles E [mailto:[email protected]] Sent: Tuesday, August 22, 2017 10:37 AM To: 'Bradley A Krupp' <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> Cc: Brian G Gonia <[email protected]<mailto:[email protected]>> Subject: [powernet] RE: AMS-4 remote monitoring Brad, Browns Ferry uses GEDDS as well as the AMS-4. You can contact me for more information. Chuck Creamer Health Physicist Radiation Protection Tennessee Valley Authority; Browns Ferry Nuclear Plant P.O. 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If you are not the intended recipient, be aware that any disclosure, copying, distribution, or use of the content of this information is prohibited. If you have received this communication in error, please notify me immediately by email and delete the original message. From: Bradley A Krupp [mailto:[email protected]] Sent: Tuesday, August 22, 2017 8:56 AM To: [email protected]<mailto:[email protected]> Cc: Brian G Gonia Subject: [powernet] AMS-4 remote monitoring TVA External Message. Please use caution when opening. Fermi is in the process of upgrading our remote monitoring software to GEDDS. Would like feedback and contact information from peers who have integrated remote monitoring of their Eberline AMS-4's. Thanks in advance for your assistance. Brad Krupp This Email message and any attachment may contain information that is proprietary, legally privileged, confidential and/or subject to copyright belonging to Exelon Corporation or its affiliates ("Exelon"). 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