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2006 Nuclear Utility REMP Conference Isotopes Of Concern General Engineering Laboratories, LLC Environmental Levels And Methods For Monitoring H-3. C-

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Presentation on theme: "2006 Nuclear Utility REMP Conference Isotopes Of Concern General Engineering Laboratories, LLC Environmental Levels And Methods For Monitoring H-3. C-"— Presentation transcript:

1 2006 Nuclear Utility REMP Conference Isotopes Of Concern General Engineering Laboratories, LLC Environmental Levels And Methods For Monitoring H-3. C- 14. Sr-90, Fe-55, Tc- 99. Ni-63

2 Today We Will Review H-3 Levels in US ground water, surface water and drinking water Pick Your Background Level Compare NRC and EPA limits Look at H-3, C-14, Sr-90, Tc-99, Ni-63 analytical methods and typical detection limits

3 Tritium Naturally occurring in rainwater at pCi/L The Tritium Unit (TU) is defined as: –1 TU = 3.2 pCi Concentration varies as a function of upper atmospheric conditions, solar conditions, and age of the ground water

4 Environmental H-3 Levels In The United States (USGS Ground Water) USGS Lists 5 types of H-3 Ground Water Levels Based on age of recharge from surface water Less Than 0.8 TU (2.6 pCi/l) Submodern Prior to Analytically we call this dead water 0.8TU(2.6 pCi/l) To 4 TU(13pCi/l) Mixture between submodern and recent recharge 5TU(16pCi/l) to 15 TU(50pCi/l) Modern Less than 5 years to 10 Years Greater Than 30 TU(100pCi/l) Considerable Component of Recharge from 1960 to 1970s Greater Than 50(162pCi/l) TU Dominantly 1960 recharge

5 Environmental H-3 Levels In The United States (EPA Surface Water Testing 1994 to 2000) EPA testing of H-3 in drinking water taken from locations away from nuclear instillations list US H-3 levels ranging from 100 to 300 pCi/l EPA testing of H-3 in surface water taken downstream from operating nuclear facilities ranges from 100 to 2,900 pCi/l (most locations tested had results less than 300 pCi/l) A few of the sites that stand out are: 2,300 pCi/l (Savannah River ) and 2,900 pCi/l (Lake Robinson), 2,200 (North Anna River)

6 So What is The H-3 Background In The US USGS Data Shows Environmental H-3 ranging from 3 pCi/l to a high of 160pCi/l [GW] EPA H-3 Drinking Water Results dating January 1994 – March 1994 range from 100 to 300 pCi/l [SW]

7 I Think Its Safe To Say We Have More Than One H-3 Background Level H-3 in ground water aquifer is less than 160pCi/l H-3 in drinking water ranges from 100 to 300pCi/l

8 Can You Write Off H-3 At Low Levels As Environmental Only? Is your H-3 level above 160 pCi/l Do you have a good understanding of the hydro- geology of your site Can you have a radiological leak to the ground Is it time to look harder What To Do: Additional site wells, hydro- geology study of your site, and start looking for other isotopes (C-14, Sr-90, Tc-99, Ni-63)

9 NRC 10CFR20 Table 2 Effluent Values EPA MCL Values EPA MCL H-3 20,000 pCi/l C-14 2,000 pCi/l Sr-90 8 pCi/l Tc pCi/l Ni pCi/l NRC Values H-3 1E6 pCi/l C-14 3E4 pCi/l Sr-90 5E3 pCi/l Tc-99 6E4 pCi/l Ni-63 1E5 pCi/l

10 Analytical Methods for H-3 H-3 decays by -, E max MeV Liquid Scintillation Typical MDA without sample enrichment runs about 500 pCi/l and with extended 4 hr counts you can push this down to 200 pCi/l (but the uncertainty at this level is about 100% relative to the actual measurement) Typical MDA with sample enrichment runs about 3 pCi/l

11 H-3 Beta Spectrum

12 Analytical Methods For Very Low Tritium Detection For H-3 Analysis at levels less than 200 pCi/l the gold standard is H-3 sample enrichment Process takes 4 to 6 weeks Samples go through an electrolytic enrichment step Typical MDA is 0.1 TU or 0.3 pCi/l Tritium Laboratory University of Miami (305)

13 Analytical Methods for C-14 C-14 Decays by -, E max MeV Liquid Scintillation Acid Digested to remove all carbon as CO 2 The CO 2 is collected on a chemical trap and determined using liquid scintillation counting Typical MDAs for this test are 50 pCi/l

14 C-14 Beta Spectrum

15 Analytical Methods for Sr-90 Sr-90 in secular equilibrium with Y-90 Both decay by -, E max Sr and 2.3 Y MeV Gas Flow Proportional Counting Sr-90 is removed via EPA method Drinking Water Method Typical MDA is 2 pCi/l for Sr-90

16 Analytical Methods for Tc-99 Tc-99 Decays by -, E max MeV Liquid Scintillation The sample is oxidized to pertechnetate and removed via resin extraction Typical MDA is 50 pCi/l

17 Tc-99 Beta Spectrum

18 Analytical Methods for Ni-63 Ni-63 Decays by -, E max MeV Liquid Scintillation Analytical Chemistry to take all the nickel to nickel – DMG – precipitate. The precipitate is taken to a liquid phase via nitric acid Typical MDA is 50 pCi/l

19 Ni-63 Beta Spectrum


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