1 Analytical Technique for Tritium in Soil Richard Conatser Calvert Cliffs Constellation Energy Group June 2007.

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Analytical Analytical Technique for Technique for Tritium in SoilTritium in Soil

Richard ConatserRichard ConatserCalvert CliffsCalvert Cliffs

Constellation Energy GroupConstellation Energy Group

June 2007June 2007

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OutlineOutline

Introduction Objectives for the method Soil sampling Analytical Method Calculations LLDs and Reporting Levels Regulations and Use of Soil Results Conclusion

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Method’s Method’s ObjectivesObjectives

Rapid analytical technique Minimal impact on Chem

Techs/Staff Collect samples from small areas Want results to be pCi/kg soil Results should be simple to report Results should be easy to interpret

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Types of Soil Types of Soil SamplingSampling

Sample soil vapors Solar still Direct soil sample Direct reading instrument

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CCNPP Analytical CCNPP Analytical MethodMethod

Sample soil Measure %moisture (w/w%) Quantitatively add soil to

“container” Add carrier DI water to dry samples Allow soil-water to equilibrate Distill, and Count on LSC Calculate the results

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Method AssumptionsMethod Assumptions

Soil sample is representative All tritium originates from the soil All tritium is in the water fraction If DI water (carrier) is added, all

tritium enters the liquid phase Vapor pressure H-3 & H2O are equal

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CalculationsCalculations

AS = AW * [M% + (VDI / MS)]Where,

AS = Activity in soil, pCi/kg soil

AW = Activity in water, pCi/l distillate

M% = Moisture fraction in soil sample

VDI = Mass of DI water, grams

MS = Mass of soil sample, grams

Tritium in Soil With Soil Vapor of 20,000 pCi/l -- No Water AddedAssumes (1) All Tritium is Available in the Water Fraction, and (2) 100 g "Wet" Soil Sample

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0 1 2 3 4 5 6 7 8 9 10

Moisture in Wet Soil, w/w%

So

il T

riti

um

, p

Ci/

kg

For a soil sample that's 5% moisture, the tritium concentration with respect to the soil would be 1,000 pCi/kg

The method is based on a 100 g wet soil sample and it takes about 5 ml of water to do tritium analysis At CCNPP.

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LLD (no carrier)LLD (no carrier) CCNPP LLD for water is ~ 350 pCi/l Assume distillate is 350 pCi/l Assume the soil moisture is 5% Convert water LLD to soil LLD

AS = AW * [M% +(VDI / MS)]

AS = 350 pCi/l * 0.05

AS = 18 pCi/kg

LLD of Analytical Method -- No Water AddedAssumes (1) All Tritium is Available in the Water Fraction, and (2) LLD of Water Fraction = 350 pCi/l

0

10

20

30

40

0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10%

Moisture in Wet Soil, w/w%

So

il T

riti

um

, p

Ci/

kg

For a soil sample that's 5% moisture, the LLD corresponds to 18 pCi/kg of soil when no DI water is added to the samle.

The method is based on a 100 g wet soil sample and it takes about 5 ml of water to do tritium analysis At CCNPP.

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< LLD

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% Moisture in Soil% Moisture in Soil

If M%is unknown a bias will exist Soil tritium will be mis-reported

If M% is assumed 15%, reduce bias Determine moisture analytically

gravimetrically moisture tester

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Low Soil MoistureLow Soil Moisture

Some samples may be “dry.” DI water can be added as a

carrier This is necessary IF analysis is

needed Water added dilutes sample’s H-3

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Just Add WaterJust Add Water As water is added, soil is diluted Adding water required for dry soil If no water is added, LLD=350 pCi/l As water is added, LLD suffers Can natural soil moisture be ignored? Use the calculation model to test The following graph demonstrates

effect

Effect of Ignoring Soil MoistureIf Calculations Ignore Vol of Soil's Moisture, When it is Actually 15% Moisture @1422 pCi/l

1

13

25 3

6

53

85

122

164

186

210 213

0

50

100

150

200

250

0.0 0.1 1.0 10.0 100.0 1000.0 10000.0

DI Water (Carrier) Added to Soil Sample, Grams

Tri

tiu

m A

ctiv

ity

in S

oil

(p

Ci/

kg) pCi/kg calc

AS = AW * [M% + (VDI / MS)]X

Soil would be reported as 1422 pCi/kg soil if no carrier is added and the natural soil moisture is ignored.

1422 pCi/kg

With 0.1 ml DI water (carrier) added, the calculated result would be 1 pCi/kg soil.

With 10,000 ml DI water (carrier) added, the theoretically calculated result would be 213 pCi/kg soil, which is the correct value.

Effect of Ignoring Soil MoistureIf Calculations Ignore Vol of Soil's Moisture, When it is Actually 15% Moisture @1422 pCi/l

1

13

25 3

6

53

85

122

164

186

210 213

0

50

100

150

200

250

0.0 0.1 1.0 10.0 100.0 1000.0 10000.0

DI Water (Carrier) Added to Soil Sample, Grams

Tri

tiu

m A

ctiv

ity

in S

oil

(p

Ci/

kg) pCi/kg calc

AS = AW * [M% + (VDI / MS)]X

1422 pCi/kg

46

g c

arr

ier

dil

ute

s s

oil

m

ois

ture

to

35

0 p

Ci/

l

Effect of Ignoring Soil MoistureIf Calculations Ignore Vol of Soil's Moisture, When it is Actually 15% Moisture @1422 pCi/l

1

13

25 3

6

53

85

122

164

186

210 213

0

50

100

150

200

250

0.0 0.1 1.0 10.0 100.0 1000.0 10000.0

DI Water (Carrier) Added to Soil Sample, Grams

Tri

tiu

m A

ctiv

ity

in S

oil

(p

Ci/

kg) pCi/kg calc

AS = AW * [M% + (VDI / MS)]X

1422 pCi/kg

46

g c

arr

ier

dil

ute

s s

oil

m

ois

ture

to

35

0 p

Ci/

l

< LLD

Effect of Ignoring Soil MoistureIf Calculations Ignore Vol of Soil's Moisture, When it is Actually 15% Moisture @1422 pCi/l

1

13

25 3

6

53

85

122

164

186

210 213

0

50

100

150

200

250

0.0 0.1 1.0 10.0 100.0 1000.0 10000.0

DI Water (Carrier) Added to Soil Sample, Grams

Tri

tiu

m A

ctiv

ity

in S

oil

(p

Ci/

kg)

pCi/kg calc

AS = AW * [M% + (VDI / MS)]X

1422 pCi/kg

46

g c

arr

ier

dil

ute

s s

oil

m

ois

ture

to

35

0 p

Ci/

l

< LLD161

213

-25% bias if no correction is applied for the natural moisture

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Limitations of the Limitations of the ModelModel

Previous example was one case: 15% moisture Took 46 ml DI water to be <LLD

LLD will be dependent on M%

Graph shows family of lines

Volume of DI Water Equivalent to Analytical LLDBased on 100 g Soil Sample, LLD = 350 pCi/l in distillate

0

50

100

150

200

0

500

1,00

0

1,50

0

2,00

0

2,50

0

3,00

0

3,50

0

4,00

0

4,50

0

5,00

0

H-3 in Water Fraction of Soil Sample, pCi/l

DI w

ate

r re

qu

ire

d t

o d

ilu

te t

riti

um

to

LL

D,

gra

ms

2% Moisture

8% Moisture

15% Moisture50% Moisture100% Moisture

With

no

wat

er a

dded

, the

LLD

is 3

50 p

Ci/l

iter

Example Case: 46 ml water added to 100 grams soil with 15% moinsture at 1422 pCi/l in water fraction diluted the distillate to 350 pCi/l.

Volume of DI Water Equivalent to Analytical LLDBased on 100 g Soil Sample, LLD = 350 pCi/l in distillate

0

50

100

150

200

0

500

1,00

0

1,50

0

2,00

0

2,50

0

3,00

0

3,50

0

4,00

0

4,50

0

5,00

0

H-3 in Water Fraction of Soil Sample, pCi/l

DI w

ate

r re

qu

ired

to

dil

ute

tri

tiu

m t

o L

LD

, gra

ms

2% Moisture

8% Moisture

15% Moisture

50% Moisture100% Moisture

< LLD

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LLDLLD

The LLD with respect to soil: As good as 18 pCi/kg of soil Up to 350 pCi/kg of soil

The LLD with respect to soil vapor: As good as 350 pCi/liter of vapor May be over 18,000 pCi/liter of

vapor

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Regulations and UseRegulations and Use

No regulatory LLDs for H-3 in soil No NRC regulatory reporting level NEI guidance to report spill results What does this mean to managers? Use soil H-3 as remediation criteria?

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Potential Potential EnhancementsEnhancements

Microwave digestion of soil Oxidizer or reducer

(permanganate) Use more than 100 g soil Use DI water carrier sparingly Combine with other methods

Solar Still Tritium in soil vapor

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ConclusionsConclusions

Tritium in soil can be an easy analysis The method can get more complex The focus needs to be on using the results Using the results can be problematic Tritium in soil needs to be tailored to the

site At Waterford 3, it may not make sense For coastal sites on hillsides with no drinking

water, it may not make sense Best use may be for remediation criteria

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Questions?Questions?