What about smear geometry? I seem to remember a correction factor of 8 (was with an RO-2).
Dane R. Williams, CHP Team Leader Institute of Nuclear Power Operations [email protected] 770.644.8882 From: [email protected] [mailto:[email protected]] On Behalf Of Sorber, Bob Sent: Wednesday, January 04, 2012 1:02 PM To: [email protected] Subject: Powernet: RE: Beta Correction Factor for Handheld Ion Chamber Instruments Gordon, Duke Energy uses the following beta correction factors for the RO-20: * 4 for bare instrument. * 5 for single bagged instrument. * 6 for double bagged instrument. * 7 for a single bagged instrument measuring a noble gas atmosphere. These factors were developed using slab sources of Tc-99, Tl-204 and U-238 at contact. The sources were wider than the instrument beta window. Note that geometry is important. We measured significantly lower correction factors using on axis point sources. The beta correction factor for a bare instrument changes only slightly with changes in beta half value layer (energy) because the window thickness approximately equals the 7 mg/cm^2 depth at which skin dose is defined. Inspection of the detector geometry explains the measured bare instrument correction factor of 4. The anode blocks the rear half of the detector chamber making it insensitive to all but high energy beta radiation. This accounts for a correction factor of 2. Partial shielding of the space around the side walls of the chamber for radiation entering off axis brings the bare instrument correction factor to 4. We do not perform a beta calibration on each instrument since once the instrument's overall gamma response is accurately calibrated, the correction for beta is fixed since the beta correction factor depends only on the geometry of the chamber, the thickness of the anode and the thickness of the window. We do confirm the beta response of individual instruments. Bob Sorber 704-382-7259 _____________________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Wednesday, January 04, 2012 10:44 AM To: [email protected] Subject: Powernet: Beta Correction Factor for Handheld Ion Chamber Instruments Palo Verde requests the following information: What beta source is used to establish beta correction factors for handheld ion chambers (RO-20, RO-2/2A, RSO-50E) at your facility? Is a generic beta correction factor is assigned (such as 4 or 5) or is the specific value established during calibration assigned (such as 3.8)? Thanks Gordon Nelson Radiological Engineering Palo Verde Nuclear Generating Station Phone (623) 393-5200 Cell (623) 238-0542 Pager (877) 466-7534 [email protected]<mailto:[email protected]> ________________________________ .DISCLAIMER: This e-mail and any of its attachments may contain proprietary INPO or WANO information that is privileged, confidential, or protected by copyright belonging to INPO or WANO. This e-mail is intended solely for the use of the individual or entity for which it is intended. If you are not the intended recipient of this e-mail, any dissemination, distribution, copying, or action taken in relation to the contents of and attachments to this e-mail is contrary to the rights of INPO or WANO and is prohibited. If you are not the intended recipient of this e-mail, please notify the sender immediately by return e-mail and permanently delete the original and any copy or printout of this e-mail and any attachments. Thank you.
