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

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

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

Tritium

• Naturally occurring in rainwater at 40-150 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

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 1952.

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 1970’s• Greater Than 50(162pCi/l) TU Dominantly 1960 recharge

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)

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]

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

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)

NRC 10CFR20 Table 2 Effluent Values

EPA MCL ValuesEPA MCL• H-3 20,000 pCi/l• C-14 2,000 pCi/l• Sr-90 8 pCi/l• Tc-99 900 pCi/l• Ni-63 50 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

Analytical Methods for H-3

• H-3 decays by -, Emax 0.018 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

H-3 Beta Spectrum

H-3 in Water

0

2

4

6

8

10

1 101 201 301 401 501 601 701 801 901

Channel

Co

un

ts

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)

361-4100

Analytical Methods for C-14

• C-14 Decays by -, Emax 0.160 MeV

• Liquid Scintillation

• Acid Digested to remove all carbon as CO2

• The CO2 is collected on a chemical trap and determined using liquid scintillation counting

• Typical MDAs for this test are 50 pCi/l

C-14 Beta Spectrum

S P E C T R U M P L O TUSER 17 - C-14

0

5

10

15

20

25

0 100 200 300 400 500 600 700 800 900 1000

Channel Number (Log)

Cou

nts

Analytical Methods for Sr-90

• Sr-90 in secular equilibrium with Y-90

• Both decay by -, Emax 0.546Sr and 2.3Y MeV

• Gas Flow Proportional Counting

• Sr-90 is removed via EPA method 905.0 “Drinking Water Method”

• Typical MDA is 2 pCi/l for Sr-90

Analytical Methods for Tc-99

• Tc-99 Decays by -, Emax 0.294 MeV

• Liquid Scintillation

• The sample is oxidized to pertechnetate and removed via resin extraction

• Typical MDA is 50 pCi/l

Tc-99 Beta Spectrum

Tc-99 Beta Spectrum

0

50

100

150

200

250

1 101 201 301 401 501 601 701 801 901

Channel

Co

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Analytical Methods for Ni-63

• Ni-63 Decays by -, Emax 0.067 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

Ni-63 Beta Spectrum

Ni-63

05

1015

20253035

1 101 201 301 401 501 601 701 801 901

Channel

Co

un

ts