STP responds as follows to the questions below. STP records ED data for each entry to the nearest 0.1 mrem from the EDs. For reporting purposes, the data is summed, then rounded to the nearest mrem.
With respect to bias, EDs are biased +10% based on exposure to Cs-137 with the ED on phantom. Calibration verification is not performed on phantom but with a Cs-137 source. Our objective is to have two independent dosimetry systems, ED and TLD. TLD is used as dose of record unless TLD is lost, etc., in which case ED data is used. From here down, it's strictly my opinion. With respect to dose control and forcing ED readings to be greater than TLD readings in all cases, the conservative nature of most site's dose control program should preclude any regulatory problems irrespective of whether EDs are biased or not. A few of us old gray haired guys remember the days of pocket ionization chambers. We expected PIC results to be higher than TLD (or film) in most every case and based dose control on PICs. We also had higher individual doses back then and had to be careful not to exceed regulatory limits. The expected over estimate of dose from PIC data gave us a comfort level that we've found hard to give up with the advent of computerized access control, EDs, and instant summation of individual doses upon exit. How conservative do we need to be? Should every individual's ED dose be greater than his TLD (or OSL) dose? I don't think this is necessary since we're usually talking about doses below 20% of the regulatory limit. Regards, Leonard Earls Consulting Engineer 361-972-7759 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Barber, Jerry Sent: Thursday, December 16, 2010 07:57 To: '[email protected]' Subject: Powernet: Electronic Dosimeter Bias - "Rounding" In addition to June Scott's excellent follow up questions I would also like to ask the following - Do any other facilities round EAD data before bringing it over into their Official dose tracking/reporting database? The version of Passport Total Exposure that we use as our Official dose tracking/reporting database currently does not accept decimal data. Our interface software (WACs) has been configured to round EAD dose as follows: EAD reading Value Input into Database 0 - 0.4 0 0.5 - 1.4 1 1.4 - 2.4 2 ........and so on................. Question: Does your facility round EAD data in a similar fashion before input into your Official dose tracking/reporting system? Thanks to all of you who help make Powernet such a valuable Benchmarking tool (Merry Christmas and Happy New Year!!!) Jerry Barber Lead RC Specialist H.B. Robinson Nuclear Plant 843-857-1496 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Wednesday, December 15, 2010 3:28 PM To: [email protected] Subject: Re: Powernet: Electronic Dosimeter Bias Is this bias 7% the difference between TLD and EAD collective and individual dose after a read period? or is it the correction factor set on the calibrator compared to Cs-137 source? Do you irradiate on a phantom? or a box calibrator? or with a MG robot calibrator setup? How is your transfer cal performed? We have a over all bias factor after TLD reads of 7 to 8% with the EAD being high. To reach this we need to set the Cs-137 robot calibrator to 1.18 correction factor. This has been cross checked on a NVLAP phantom in open air geometry. I'd like to ensure we are comparing the same criteria. June L. Scott [email protected] Phone: 419-321-8555 Cell: 419-367-6651 Davis Besse Nuclear Power Station 5501 N State Route 2 Oak Harbor, Oh 43449 [email protected] om Sent by: To owner-power...@hp [email protected] s1.org cc Subject 12/15/2010 10:43 Re: Powernet: Electronic Dosimeter AM Bias Please respond to [email protected] Responses from San Onofre. We also use DMC-2000S electronic dosimeters. Regards, Eric 1. and 2. EDs are biased up 7% to more closely match TLD data. Not really over-responding. Really a correction for slight ED geometry and energy under-response compared to TLDs. 3. Not yet. We've had these EDs in service for about 5 years and only just recently implemented zinc injection. Will be completing another TLD/ED study after the current steam generator replacement outage. Eric M. Goldin, CHP Southern California Edison <[email protected]> From: "Courtenay, Christopher C" <[email protected]> To: "[email protected]" <[email protected]> Date: 12/14/2010 11:48 AM Subject: Powernet: Electronic Dosimeter Bias Sent by: [email protected] Duke Energy would like to know the following: 1. Do you bias your EDs to over-respond in the field? 2. What bias do you apply if you do? (5%, 10%, etc) 3. Have you noticed a change in ED response due to changing plant conditions (Co58/Co60 ratio changes due to Zinc injection, etc) or specific jobs (weld overlay, alloy 600, etc)? Point of reference – Duke uses the DMC2000S from Mirion. Chris Courtenay Engineer, Duke Energy 980-875-5005 "To the optimist, the glass is half full. To the pessimist, the glass is half empty. 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