Jeff Cady, CHP, Dresden Station Earlier this year, I polled the international operating reactors through the ISOE occupational dose program ( NEA and IAEA) regarding the alpha self absorption or transmission factors. Here are the responses so far for utility distribution only.
By the way, Harry Bush, Dresden RPM, at last weeks US NRC Region III RPM meeting announced that Dresden 2,3 is being nominated for the 2010 ISOE NATC World Class ALARA Award competition. Good Luck! David W. Miller NATC ISOE Regional Director Radiation Protection Dept. Cook Nuclear Plant American Electric Power One Cook Place Bridgman, Michigan 49106 1 269 466-3428 1 269 466 3389 fax 1 217 855 3238 cell Edit post Report this post Reply with quote Re: Counting of Alpha Contamination Smears by millerdw » 17 May 2010 16:54 David Miller - NATC, Below are Cook ( PWR Westinghouse) responses: When counting alpha contamination smears, 1) Do you use a self absorption factor? We purchase alpha calibration sources made in a simulated filter paper matrix to mimic the smear and air sample self absorption encountered in the sample. We found the calibration filter source to give alpha counts a factor of two lower than an electroplated source of equal activity (e.g. an apparent self absorption factor of two). Therefore we do not apply a self absorption factor because it is already considered in the counting instrument calibration. 2) If yes, what value do you use? See answer above. The vendor reported alpha efficiency for the Ludlum 3030P is ~40% with an electroplated source, but we only get ~19%. The same is true for our Canberra S5E alpha/beta proportional counter. Joe Beer, CHP Staff Health Physicist Cook NPP [email protected] millerdw Posts: 14 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by renn » 18 May 2010 08:20 Sizewell B NPP (UK), Westinghouse 4-Loop 2nd Generation responds as follows: We do not use a self absorption factor. Qualitatively we recognise the difficulty of assessing the alpha activity content in surfaces and for the potential for some self absorption. Another issue we regularly face is in differentiating true alpha activity from "beta breakthrough" in samples with very high levels of beta-gamma activity. renn Posts: 11 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by svedberg » 18 May 2010 08:38 David, At Ringhals NPP we use self absorption factors according to ISO standard 7503-1 (Evaluation of surface contamination - Part 1 Beta emitters and alpha emitters). Therefore we use a factor of 4 (50 % absorbtion and 50 % solid angel included will result in a factor of 4) regarding the self absorbtion and angle dependence for Alpha as well as for Beta (< 0,4 MeV), [ISO 7503-1: 1998 (E), point A.4.2 in included Annex]. Yours sincerlely Torgny Svedberg Ringhals AB Dept. RTAR [email protected] Last edited by svedberg on 19 May 2010 05:51, edited 1 time in total. svedberg Posts: 18 Joined: 01 Jan 1970 00:00 MSNM/WLM Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by rosellh » 18 May 2010 11:27 In our plant, Almaraz NPP (Spain, PWR), we don´t use a self absorption factor, but alpha measuring is an interesting issue for future RP´s meetings. Regards, Borja Rosell Herrera rosellh Posts: 6 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by brunnerr » 18 May 2010 16:18 Information sent by Email on 18 May 2010 Dear David, we calibrate our equipment at NPP Isar to the standard DIN ISO 7503. Therefore we consider self absorption for alphas by an epsilon-s of 0.25. Freundliche Grüße/Kind regards Ralph Brunner Leiter/Head of Strahlenschutz/Health Physics T +49-8702-38-4282 F +49-8702-38-4921 [email protected] E.ON Kernkraft GmbH Kernkraftwerk Isar Postfach 11 26 D-84049 Essenbach brunnerr Posts: 8 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by dascenzo » 18 May 2010 16:22 Information sent by Email on 18 May 2010 Dear Mr Miller, Nutronic AB received this question from our contact Mr Johan Uljons at the Forsmark NPP in Sweden. Our answer reflects our experience in this matter and is not to be taken as an official statement. As a manufacturer of smear test instruments we follow the recommendations in the standard ISO 7503-1, "Evaluation of surface contamination - Part 1: Beta-emitters (maximum beta energy greater than 0,15 MeV) and alpha-emitters". In this standard the factor is referred to as the source efficiency. In a 2pi measuring geometry the the source efficiency should be 0,25 for alpha samples and beta samples in the energy range 0,15 meV < Ebmax < 0,4 MeV. For higher beta energies the the source efficiency should be 0,5. Previously in Swedish NPP:s the source efficiency was *not* used. At a meeting between the NPP:s in 2005 it was decided to start to use source efficiency, effectively increasing measured alpha contamination values with a factor of 2. The standard nuclide for beta calibration in Swedish NPP:s is Tc-99 (Ebmax 0.294 MeV) and this falls within the beta energy range that should also have a source efficiency of 0,25 so measured beta contamination also increased by a factor of 2. It may also be noted that ISO 7503-1 recommends to calibrate surface contamination meters based on the surface emission rate from the reference source rather that the activity. >From 7503-1: "The calibration based on activity will ? yield a calibration factor which is not unique but depends critically on the source construction; a wide range of values may be obtained using reference sources containing the same activity of a given radionuclide but having a different construction". In Swedish NPP:s, in 2010, surface contamination meters are calibrated based on the source activity so the 7503-1 standard is not followed in this case. This gives a 4pi measuring geometry so the source efficiency must be recalculated to 0,5. This is used for both alpha and beta. As a manufacturer of health physics instruments, especially of smear (wipe) test instrument we have included a setting for the source efficiency in all our software. Please refer to our website www.nutronic.se for more information on our products. Best regards, Lars Peterson International Sales Manager Nutronic AB dascenzo Posts: 9 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by breznik » 25 May 2010 07:41 Information sent by Email on 21 May 2010 Dear David, Please, find below the answers and explanation to the questions. With my best regards, Borut When counting alpha contamination smears, In case of control of equipment or surfaces related to primary system or refueling. 1) Do you use a self absorption factor? We are aware about self absorption but this problem is solved in our case by purchasing a specially prepared filter paper alpha calibration source (Analytics). It is assumed that self absorption of the sample is the same in the both cases. In fact our focus is on gross alpha air monitoring. The same source is used also for the calibration of the alpha smear monitors. 2) If yes, what value do you use? breznik Posts: 5 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by obermoser » 25 May 2010 08:22 Information sent by Email on 21 May 2010 Dear Mr. Miller! Please find our answers hereafter kind regards Bernhard Obermoser Head Radiation Protection Axpo AG - Kernenergie NPP Beznau | CH-5312 Döttingen T +41 56 266 78 70 | F +41 56 266 77 01 [email protected] | http://www.axpo.ch When counting alpha contamination smears, 1) Do you use a self absorption factor? Yes 2) If yes, what value do you use? 0.25 obermoser Posts: 2 Joined: 01 Jan 1970 00:00 Top Report this post Reply with quote Re: Counting of Alpha Contamination Smears by rittera » 25 May 2010 08:26 Information sent by Email on 21 May 2010 In KKM we don?t measure alpha contamination for personal monitors. When we measure with CoMo 170 the smears, then its possible to detect alpha contamination, but I don?t know where is the value for the self absorbtion calibrated. Maybe Christoph Schuler, chef calibration, Paul Scherrer Institut (PSI) can answer your question. mit freundlichen Grüssen BKW FMB Energie AG Kernkraftwerk Mühleberg Andreas Ritter Strahlenschutz-Techniker Tel. ++41 (0)31 754 74 09 Fax ++41 (0)31 754 71 22 e-mail [email protected] ---------------------------------------------------------------- This e-mail message and all attachments transmitted with it from the Nuclear Generation Group of American Electric Power are for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
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