At Fermi we don't have a lot of hot air samples, but we have the "half-life method" of EPRI Report 1019500 Appendix C in our procedures: it uses one count at 15-30 minutes after collection and another at 1-2 hours after that to calculate the long lived alpha activity. I think this may be a little tricky in practice however. We also have an iSolo which is not yet in service. We've done preliminary testing and radon rejection seems good with regular filters, but much better with PTFE filters. I think this has a lot of promise. I'm not sure what you mean by having problems with the algorithm; there was an issue with very short sample to count intervals but this is solved by not using intervals shorted than 30 minutes, I think. Canberra has all the info on this; it seems that they've done a lot of good research in developing this counter. Another point I would make is that even if there appears to be significant alpha activity in an air sample, some or all of which may be due to radon progeny which can't be ruled out, controls may not have to be that restrictive if you project dose based on ingestion dose factors. Everything I've read, and our own experience, seems to indicate that any uptakes will predominantly follow the ingestion retention pattern. Therefore doses will be a lot lower than 2.5 mrem/DAC hour.
Tom VanderMey, CHP Principal Radiological Engineer DTE Energy, Fermi 2 734-586-1539 [email protected] wrote: ----- To: "'[email protected]'" <[email protected]> From: "Barber, Jerry" <[email protected]> Sent by: [email protected] Date: 02/28/2011 12:26PM Subject: Powernet: Alpha Counting of Air Samples Has anyone at a nuclear power plant found a good solution for quickly counting air samples for alpha radioactivity in the presence of significant Radon decay products? We would like a system that is simple to use but which can accurately distinguish TRU alpha emitters from Radon decay products without having to delay counting for decay. I understand that some sites are using the iSolo but I haven’t heard of anyone that isn’t having problems with the system’s algorithm working the way they want it to. If your site is using the iSolo or some other system to accurately and quickly determine TRU in the presence of Radon daughters on particulate air samples, I would really like to hear about it. Thanks, Jerry Barber Lead RC Specialist H.B. Robinson Nuclear Plant 843-857-1496 [email protected]
