We use the Ludlum 3030P which has the PIPS semiconductor detector. Still need a count rate limit to do smear-of-a-smear to prevent false beta and alpha at high count rates. If the photon count rate is too high, the mV pulses in one count period will get added together and create a combined mV that may be high enough to exceed the threshold for a beta count. If the beta activity is too high you can create false alpha counts. We use 500 kdpm as our limit. You'll also want to disable the beta-to-alpha crosstalk to not subtract any alpha counts. Someone suggested lowering the upper mV window for alpha to try to filter out Rn at ~6 MeV, but that's where we have Cm-242, so don't doodle with the alpha windows or you'll also filter out real alpha.
I like the detector because of it's response. As an example you might think the beta pulse height is linear based upon energy; however beta being a medium LET radiation type will only deposit so much energy in the thin active volume and the remainder escapes. So, even if you go from Tc-99 to Sr-90 beta energy, you can't get a pulse height high enough to get into the alpha channel. We've seen handheld probes have false alpha counts at relatively low beta-gamma radiation levels compared to some benchtop counters, so you'd want to validate those limitations before you bought a bunch of any specific portable probe model. Every instrument will have limitations. I would go to all 3030P units and save my portable alpha frisker for that case where I have a level 3 alpha are with a b/a ratio <50 and have to frisk personnel. I'd also be comfortable with SAC-4 units til they pass on. Every instrument has limitations, so verify them yourself. SAC-4 still a good instrument if you have any around, but we're happy with the 3030P transition. Glen Vickers, CHP Exelon RP Technical Lead From: Powernet <[email protected]> On Behalf Of Rolph, James Thomas Jr via Powernet Sent: Tuesday, February 05, 2019 12:11 PM To: '[email protected]' <[email protected]> Cc: Rolph, James Thomas Jr <[email protected]> Subject: [EXTERNAL] [Powernet] Industry pulse on alpha instrument used to counts smears for alpha in the field We would like to conduct a short pulse within the industry of what portable instrument (meter and detector model) your site uses to count smears for alpha in the field. Thank you in advance, James (JT) Rolph, CHP Superintendent, RP Technical Support Radiation Protection Tennessee Valley Authority; Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, TN 37379 423-843-8115 (w) 423-521-9169 (m) [email protected]<mailto:[email protected]> [https://lakeinfo.tva.gov/web/images/tva_logo_32b.png]<https://tva.com/> [https://lakeinfo.tva.gov/web/images/blue_line.png] [https://lakeinfo.tva.gov/web/images/facebook2.png]<https://www.facebook.com/TVA/>[https://lakeinfo.tva.gov/web/images/twitter2.png]<https://twitter.com/tvanews>[https://lakeinfo.tva.gov/web/images/instagram2.png]<https://instagram.com/tva>[https://lakeinfo.tva.gov/web/images/youtube2.png]<https://www.youtube.com/user/TVANewsVideo>[https://lakeinfo.tva.gov/web/images/linkedin2.png]<https://www.linkedin.com/company/tva>[https://lakeinfo.tva.gov/web/images/flickr2.png]<https://www.flickr.com/photos/tennesseevalleyauthority/> NOTICE: This electronic message transmission contains information that may be TVA SENSITIVE, TVA RESTRICTED, or TVA CONFIDENTIAL. Any misuse or unauthorized disclosure can result in both civil and criminal penalties. 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. 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"). This Email is intended solely for the use of the person(s) to which it is addressed. If you are not an intended recipient, or the employee or agent responsible for delivery of this Email to the intended recipient(s), you are hereby notified that any dissemination, distribution or copying of this Email is strictly prohibited. If you have received this message in error, please immediately notify the sender and permanently delete this Email and any copies. Exelon policies expressly prohibit employees from making defamatory or offensive statements and infringing any copyright or any other legal right by Email communication. Exelon will not accept any liability in respect of such communications. -EXCIP
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