EXAMPLE

Pathways of Liquid Effluents in Pathways of Liquid Effluents in Groundwater and Surface WaterGroundwater and Surface Water

(Section 2.4.13 SAR)(Section 2.4.13 SAR)

EXAMPLE

Pathways of Liquid Effluents in Pathways of Liquid Effluents in Groundwater and Surface WaterGroundwater and Surface Water

(Section 2.4.13 SAR)(Section 2.4.13 SAR)

FRAMES-2.0 WorkshopU.S. Nuclear Regulatory Commission

Bethesda, MarylandNovember 15-16, 2007

Pacific Northwest National LaboratoryRichland, Washington

2

PurposePurposePurposePurpose

Demonstrate Hierarchical Modeling SSAR assessment: instantaneous mixing, advection, retardation,

decay Modeling: mass balance, advection, dispersion, retardation, decay

Instantaneous release Long-term release (20-yr leak)

Explore Conservative Assumptions Full mixing over the Aquifer Depth Largest Darcy Velocity No Dispersion

Register and use an Excel Spreadsheet

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Problem DescriptionProblem Description(direct quote from SAR)

Problem DescriptionProblem Description(direct quote from SAR)

“Reactor Coolant Storage Tank is postulated to rupture, and 80% of its liquid volume (92 m3) is assumed to be released in accordance with Branch Technical Position 11-6…Flow from the rupture is postulated to flood the building and migrate past the building containment structure and sump collection system and enter the subsurface at the top of the building slab…(V)ertical downward flow ensues. A pathway is created that would allow the entire 92 m3 to enter the groundwater system instantaneously.”

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Problem DefinitionProblem DefinitionProblem DefinitionProblem Definition

No vadose zone, aquifer only

Uses known tank concentrations

Instantaneously places 80% (not 100%) of the tank’s mass into only the aquifer’s effective pore space

Uses tank’s total liquid volume to estimate the plan view area of contamination

NOT an instantaneous release scenario, which requires mass balance checks on water and mass flux rates

Mixes contamination over the aquifer depth (conservative?)

Maximum Darcy velocity (noted as conservative)

Advection, Decay, and Retardation Only (noted as conservative)

No Dispersion (noted as conservative)

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With Dispersion

Fully Mixed

Upper Aquitard

Upper Aquifer Unit

Plume

Source

River

Upper Aquitard

Source

RiverPlume

Upper Aquifer Unit

FullyMixed

6

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ModulesModulesModulesModules

Source, Vadose Zone, and Aquifer Transport

FRAMES Constituent Database Selection

Source (User-defined source term) – WFF Vadose Zone Module

MEPAS 5.0 Aquifer Module

MEPAS 5.0 River Module

Exposure/Intake/Risk

MEPAS 5.0 Exposure Pathways Module

MEPAS 5.0 Receptor Intakes Module

MEPAS 5.0 Health Impacts Module

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Model InputModel Input

Registering an Registering an Excel WorksheetExcel Worksheet

(separate presentation)

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10

11

12

ConstituentDatabase

13

“Source-Term” Module

14

Aquifer Module

15

River Module

16

Chronic ExposureModule

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Intake Module

Impacts Module

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Output ResultsOutput Results

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exp5:Aquifer Constituent Concentration for IODINE-1 (I129)

0.00E+00

5.00E-06

1.00E-05

1.50E-05

2.00E-05

2.50E-05

3.00E-05

0 5 10 15 20 25 30 35

yr

pC

i/m

l

exp5:Aquifer Constituent Concentration for STRONTIU (SR90)

0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

3.00E-04

3.50E-04

4.00E-04

4.50E-04

0 50 100 150 200 250 300 350 400

yr

pC

i/m

l

exp5:Aquifer Constituent Concentration for TRITIUM (H3)

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

6.00E+02

0 5 10 15 20 25 30 35

yr

pC

i/m

l

Constituent Concentrations in

Aquifer at River’s Edge

pC

i/m

L

pC

i/m

L

pC

i/m

L

Years

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Comments & InvestigationsComments & InvestigationsComments & InvestigationsComments & Investigations

Modeling provides us with an opportunity to more fully understand the problem. SAR case ignores mass balance of water flux rate.

Maximum Darcy Velocity is conservative – Reduce SZ Darcy Velocity one order of magnitude

Fully mixed condition is conservative – Increase the aquifer depth

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Check to see if a maximum saturated zone Darcy velocity is conservative:Check to see if a maximum saturated zone Darcy velocity is conservative:

Reduce the saturated zone Darcy velocity by an order of magnitude (i.e., 1/10th)

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Reduced by 1/10th

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Reduced by 1/10th

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Reduced by 1/10th

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Reduced by 1/10th

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exp5:Aquifer Constituent Concentration for IODINE-129 (I129)

0.0E+00

5.0E-06

1.0E-05

1.5E-05

2.0E-05

2.5E-05

3.0E-05

0 50 100 150 200 250 300 350

yr

pC

i/m

L

exp5:Aquifer Constituent Concentration for STRONTIUM-90 (SR90)

0.0E+00

5.0E-08

1.0E-07

1.5E-07

2.0E-07

2.5E-07

3.0E-07

3.5E-07

0 200 400 600 800 1000 1200

yr

pC

i/m

L

exp5:Aquifer Constituent Concentration for TRITIUM (H3) (H3)

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140 160 180 200

yr

pC

i/m

L

Constituent Concentrations in Aquifer at River’s Edge at 1/10th

the Darcy Velocity

pC

i/m

L

pC

i/m

L

pC

i/m

L

Years

27

Hierarchical Modeling Results

28

Check to see if fully mixed conditions in the aquifer is conservative:Check to see if fully mixed conditions in the aquifer is conservative:

Increase the aquifer thickness.

This case was not run, but the modeling can provide insight on how aquifer depth can impact the conservative assumption.

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Rule-of-Thumb Relationships

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Rule-of-Thumb Relationship Definitions

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SummarySummarySummarySummary

Many important factors determine whether scenarios and assumptions are conservativeInterdependencies between parametersDuration of releaseTime of concentrationWater mass balanceContaminant mass balance