Fermi response:
Do you currently have alpha contamination at your plant?
Yes; I think some level of long lived alpha contamination will probably be seen at all plants if extended alpha counts are done on high activity smears.
If so what is your average or typical Beta/Gamma to Alpha ratios? e.g., > 1000, 100 to 1000, < 100
Fermi 2's ratios are highly variable, but almost always >30,000 (Level 1); average is perhaps 100,000. Ratios slightly less than 30,000 have been seen occasionally but never confirmed by other smear counts in the same area. However ratios at Fermi 1, which is being decommissioned, are frequently <30,000; average is perhaps 10,000. This is because the usual beta-gamma emitters, other than Cs-137, have decayed away.
What is the lowest Beta/Gamma to Alpha ratio that you have seen?
18,000 at Fermi 2; 2900 at Fermi 1 (possibly lower in some areas)
If you have alpha contamination areas with ratios < 50:1 do you require that all items removed from the area have a direct frisk with an alpha contamination instrument? NA
What instrument do you use to direct alpha frisking?
Due to low absolute alpha activity and higher beta/gamma to alpha ratios, Fermi does not use direct alpha frisking.
What is the RDA for the instrument? NA
What instrument do you use to count smears for alpha?
Ludlum 43-10 alpha counter
For smears counted in a scalar, do you have an upper limit on activity levels to prevent cross- contamination or cross-talk?
Nominal upper limit is 1,000,000 dpm beta-gamma activity; counter is located in a hood in the Chemistry lab to facilitate counting high activity smears without contaminating other equipment.
Do you have a specific posting for areas that contain alpha contamination?
Level 2 and 3 alpha areas would be posted if >20 dpm/100 cm2 alpha is present.
At what level do you post these areas? e. g., > 20 dpm/100 cm2: See above.
Do you perform routine in-vitro analysis for personnel working in alpha contamination areas or only when there are indications that that a potential intake has occurred?
Due to prevalent alpha levels, Fermi only attempts to determine alpha uptakes when there is indication of an airborne intake. We use 1) scaling factors (to Co-60) for all non-detectables (Fe-55 is the most significant HTD nuclide at Fermi); 2) alpha scaling factors based on an applicable air sample, if available, for the incident being evaluated; 3) in cases of significant internal exposure in vitro sampling such as 3 day cumulative fecal samples would be considered.
Tom VanderMey, CHP
Principal Radiological Engineer
DTE Energy, Fermi 2
734-586-1539
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Principal Radiological Engineer
DTE Energy, Fermi 2
734-586-1539
To: [email protected]
From: [email protected]
Sent by: [email protected]
Date: 09/09/2010 05:14PM
cc: [email protected]
Subject: Powernet: Alpha MonitoringPalo Verde requests some information pertaining to alpha monitoring at other stations:Do you currently have alpha contamination at your plant? If soWhat is your average or typical Beta/Gamma to Alpha ratios? e.g., > 1000, 100 to 1000, < 100What is the lowest Beta/Gamma to Alpha ratio that you have seen?If you have alpha contamination areas with ratios < 50:1 do you require that all items removed from the area have a direct frisk with an alpha contamination instrument?What instrument do you use to direct alpha frisking?What is the RDA for the instrument?What instrument do you use to count smears for alpha?For smears counted in a scalar, do you have an upper limit on activity levels to prevent cross- contamination or cross-talk?Do you have a specific posting for areas that contain alpha contamination?At what level do you post these areas? e. g., > 20 dpm/100 cm2Do you perform routine in-vitro analysis for personnel working in alpha contamination areas or only when there are indications that that a potential intake has occurred?**********************************************************************
Seth J. Kanter, CHP, RPT
Sr. Health Physicist
Palo Verde Nuclear Generating Station
Mail Sta. 7397
5801 S. Wintersburg Rd.
Tonopah, AZ 85354
Phone (623) 393-3130
Fax (623) 393-2487
Unless otherwise noted, all opinions are my ownLiviu Librescu**********************************************************************Email Firewall made the following annotations
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