DOE Order 435.1 Performance Assessment of WMA C Matt Kozak.pdfprotective of human health and the environment for all contaminants of concern, both radiological and non-radiological

Tank Operations Contract

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DOE Order 435.1Performance Assessment of WMA C

Overview

Performance and Risk Assessment Community of Practice Meeting

Marcel BergeronMatthew Kozak

Alaa Aly

October 19, 2016


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Hanford Site and Surrounding Area

WMA C

• Encompasses ~1,500 km2

(~586 mi2) northwest of the city of Richland along the Columbia River in southeastern Washington State

• Federal government acquired the Site in 1943 for the production of plutonium.

• Production of special nuclear materials continued until the 1980s.

• Since the 1990s, DOE has focused on environmental remediation of the Hanford Site.


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WMA C Location


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WMA C Operational History

• Constructed in 1943-1944

• Operated from 1946 through mid-1980s storing and transferring waste

• Due to long operational history, WMA C received waste generated by essentially all of the Hanford Site major chemical processing operations

100-Series SSTs

200-Series SSTs

C-301 catch tank


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WMA C Tanks and Associated Infrastructure

• Twelve 100 series tanks each with a waste capacity of 530,000 gals

• Four 200-series tanks each with a waste capacity of 50,000 gals and

• Related ancillary equipment that includes:

• C-244 CR-Vault containing 4 tanks

• C-301 catch tank• Seven diversion boxes• About 7 miles of waste

transfer pipelines


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WMA C Operational Period Releases*

Summary of Past Releases

C-101 37,000 GalC-104 28,000 GalC-105 2,000 GalC-108 18,000 GalC-110 2,000 GalC-112 7,000 GalUPR-81 36,000 GalUPR-82 2,600 GalUPR-86 17,000 Gal

Total Releases 149,600 Gal* RPP-ENV-33418, 2014, Hanford C-Farm Leak Assessments Report, Rev. 3.

UPR-82

UPR-81UPR-86

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APPENDIX I - Hanford Federal Facility Agreement and Consent Order (HFFACO)

• Defines “Single-Shell Tank System Waste Retrieval and Closure Process”

• Section 2.5 – Appendix I Performance Assessment (IPA)– A single performance assessment for the purposes of

evaluating whether SST system closure conditions are protective of human health and the environment for all contaminants of concern, both radiological and non-radiological.

– Documents by reference relevant performance requirements defined by:

• RCRA, HWMA, Clean Water Act, Safe Drinking Water Act, • Atomic Energy Act of 1954 (AEA), and • Any other performance requirements that might be ARARs

under CERCLA.


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Elements of Appendix I Required Analyses

DOE O 435.1 Performance Assessment

- Radionuclides

RCRA Closure Analysis- Dangerous chemicals/

Hazardous chemicals

Baseline Risk

Assessment- Current Impacts

(Rev. 0)- Current and future

Impacts (Rev. 1)

Analysis of Past Leaks

-Future impacts- Other cumulative

impacts from other sites

Landfill Closure of Tanks & Ancillary Equipment Residual

Waste Impacts

RCRA Corrective Action of Soil Contamination

(RFI/CMS)

Updates to Rev. 1 of BRA

RPP-ENV-58782

Appendix I Performance Assessment Synopsis- High-Level Summary of Four Documents

RPP-RPT-59625

RPP-ENV-58806 RPP-RPT-58329 RPP-RPT-59197


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DOE O 435.1 Performance Assessment

Radiological Impacts from Waste Residuals in Tanks and Ancillary Equipment


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Background

• A scoping process was conducted as a series of working sessions sponsored by ORP and WA State Department of Ecology during fiscal years 2009 – 2010

– Solicit input from the working session participants– Obtain a common understanding concerning the scope,

methods, and data to be used– Participating members from DOE, Ecology, EPA, NRC, Tribal

Nations, and other stakeholders groups– Included agreements to perform a number of specific

calculations• Funding hiatus (2011 – 2013)• Upon restart, the performance assessment took

account of updated information developed after scoping– Retrieval status– New data and hydrogeological interpretations


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WMA C Safety Functions (Section 1 and Appendix H)


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Hybrid Approach to Safety Functions and FEPs

• Addresses issues with FEP-based structuring of performance assessment

• Combines top-down safety function approach with bottom-up FEP approach


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Categories of WMA C Sensitivity Analysis Cases Evaluated (Section 8.2)

Safety Function categories (no. of cases) Key ParametersSurface Barrier Flow (5 cases) RechargeVadose Zone Flow & Dispersion (5 cases) Hydraulic properties and

dispersionAquifer Dilution (3 cases) Aquifer water fluxGrout Flow (3 cases) Diffusion and advectionResidual Chemistry (1 case) Waste release Tank Flow (3 cases) Timing of tank degradationResidual Inventory (1 case) Bounding inventory


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All Pathway

OFFICIAL USE ONLY


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DOE Order 435.1Performance Objectives and Measures

Performance Objectives

All Pathways: Groundwater + Air Pathways 25 mrem/yr EDE

Air Pathway 10 mrem/yr EDE

Radon Flux 20 pCi.m-2.s-1 radon flux(at surface of disposal facility)

Performance Measures

Acute Inadvertent Intruder 500 mrem EDE

Chronic Inadvertent Intruder 100 mrem/yr EDE

Groundwater Protection (water resources)

(40 CFR 141)

Beta-gamma dose equivalent ≤ 4 mrem/yr

Gross alpha activity concentration (excluding radon

and uranium) ≤ 15 pCi/L

Combined Ra-226 and Ra-228 concentration ≤ 5 pCi/L

Uranium concentration ≤ 30 μg/L

Sr-90 concentration ≤ 8 pCi/L

H-3 concentration ≤ 20,000 pCi/L

EDE = Effective Dose Equivalent


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Complimentary Use of Process- Level & System-Level Models


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Modeling Approach

Groundwater Pathway Analysis

Air Pathway Analysis

Analysis of DirectContact with Waste

Model Abstraction


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Conceptual Evolution of WMA C


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WMA C Tank Retrieval Status and Basis for Inventory

Three Single Shell Tanks Retrieval Ongoing Inventory estimated from

chemical process knowledge and estimated volume at closure

Ten Single Shell Tanks Retrieval complete Inventory based on sampled

residuals and final residual volumes

Seven tanks with release rate studies*

Three Single Shell Tanks Retrieval complete and

sampling underway Inventory estimated from

chemical process knowledge and final residual volumes

* PNNL has completed release rate studies on tank residuals for tanks C-103, C-106, C-108, C-203, C-203, C-204, and is starting on C-104 TOC-PRES-16-4687


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Source Term – Tanks

• Residual Waste left in bottom of tanks

• Tanks, diversion boxes, and pits filled with grout

• Release of constituents from tank controlled by diffusion through tank base mat

Alternative sensitivity analysis cases evaluating differing assumptions


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Source Term – Pipelines

• Approx. 7 miles of pipelines in WMA C

• Residual waste left in flushed pipelines

• Pipelines buried in place without grouting

• Release of constituents from pipelines controlled by combination of advection and diffusion


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Hanford (Hf2) sandsHanford (Hf2) sandsHanford (Hf3) unsat. gravelsHanford (Hf3) unsat. gravels

Hanford (Hf3) sat. gravelsHanford (Hf3) sat. gravelsColumbia River BasaltsColumbia River Basalts

BackfillBackfillHanford (Hf1) gravelsHanford (Hf1) gravels

* RPP-RPT-56356, 2014, Development of Alternative Digital Geologic Models of Waste Management Area C, Rev. 0

Hydrogeologic Framework


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Alternative Hydrogeologic Frameworks (1)

Hanford H2 sandsHanford H2 sands

Hanford H2 Coarse Gravelly SandHanford H2 Coarse Gravelly SandHanford H2 Silty SandHanford H2 Silty Sand

Hanford (Hf3) unsat. gravelsHanford (Hf3) unsat. gravels

Columbia River BasaltsColumbia River Basalts

Hanford (Hf3) sat. gravelsHanford (Hf3) sat. gravels

Hanford (Hf1) gravelsHanford (Hf1) gravels

BackfillBackfill


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Alternative Hydrogeologic Frameworks (cont.)

Appendix F - Development Of Heterogeneous Media Model And Comparison To Base Case Model Results For Waste Management Area C Performance Assessment


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Process-level Model Based on STOMP with Points of Calculation (100 m Distance)


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System Level Model Based on GoldSim

• Implemented using GoldSim• Used for:

– Source Term Release– One-Dimensional Fate and Transport Model for

Groundwater Pathway based on flow abstraction from STOMP process-level model

– Air Pathway Transport and Radon Flux Calculations

– Dose Calculations– Uncertainty Analysis & Selected Sensitivity

Analyses


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Model Abstraction – Vadose Zone


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Source Loading Zone in AquiferSource Loading Zone in Aquifer

Point of Calculation

at 100 m distance

Point of Calculation

at 100 m distance

WMA C Fenceline

WMA C Fenceline

Model Abstraction – Saturated Zone


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Exposure Scenarios for Dose Calculations

All–Pathways Exposure


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Inadvertent Intrusion Into Tanks and Ancillary Equipment

• Qualitative treatment of the likelihood of intrusion the primary purpose of intrusion

analyses is to establish waste classification

Intended as hypothetical analyses to people living in the future under extreme scenarios of uncertain but generally very low likelihood

Potential for misinterpretation

• Intrusion into grouted tanks differs from pipelines Mechanical difficulty of drilling through

the tank dome and the grout infill would likely deter intrusion by drilling

Tanks represent “robust intrusion barriers” (NUREG-1854)

Intrusion into tanks assumed at 500 years, pipelines at 100 years


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DOE Order 435.1 Performance Assessment Summary and Conclusions

• All performance objectives and measures are – Met for 1000-year Compliance Time Period (CY 2020 to 3020) – Also met during 9000 –year Post-Compliance Period (CY 3020 to

12020)

• Performance objectives for all-pathways dose met in results of probabilistic analysis performed to evaluate the impact of parameter uncertainty on dose

• Results for tank residual waste impacts demonstrate the robustness of Landfill Closed WMA C where the key safety functions are degraded compared to the base case (i.e sensitivity cases)


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Compliance Period(2020-3020)

Post-Compliance Period

(3020-12020)

Performance Objectives

All Pathways(Groundwater + Air Pathway) 25 mrem/yr EDE 4E-3 mrem/yr 0.1 mrem/yr

Air Pathway 10 mrem/yr EDE 4E-3 mrem/yr 2E-5 mrem/yr

Radon Flux 20 pCi.m-2.s-1 radon flux(at surface of disposal facility) 2E-04 pCi.m-2.s-1 7E-3 pCi.m-2.s-1

Performance Measures

Acute Inadvertent Intruder 500 mrem EDE 36 mrem 11.1 mrem

Chronic Inadvertent Intruder 100 mrem/yr EDE 8.2 mrem/yr 7E-02 mrem/yr

Groundwater Protection (Water Resources)

(40 CFR 141)

Beta-gamma dose equivalent ≤ 4 mrem/yr 5E-4 mrem/yr 0.13 mrem/yr

Gross alpha activity concentration (excluding radon and uranium)

≤ 15 pCi/L0 pCi/L 1E-10 pCi/L

Combined Ra-226 and Ra-228 concentration ≤ 5 pCi/L 0 pCi/L 7E-7 pCi/L

Uranium concentration ≤ 30 μg/L 0 μg/L 0.05 μg /LSr-90 concentration ≤ 8 pCi/L Not applicable Not applicable

H-3 concentration ≤ 20,000 pCi/L 0 pCi/L 1E-10 pCi/L

Comparison of WMA C PA Results with DOE O 435.1 Performance Objectives and Measures

EDE = Effective Dose Equivalent


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Backup Supporting Material


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Groundwater Pathway Dose (Section 7)

Key Results for GW Pathway:• Peak dose – 0.1 mrem/yr• 250 times below 25 mrem/yr

performance objective • Primarily from Tc-99

Technetium-99

Selenium-79

Tin-126

U-Isotopes

Radium-226

Iodine-129

Performance Objective (All Pathways) 25 mrem/yr

Peak Total Dose – 0.1 mrem/yr


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Results of the PA Analysis – Base Case (Section 7)

Key Base Case Results

• Peak Tc-99 Concentration

• 30 pCi/L (All Sources)

• 22 pCi/L (Tank C-105)

• MCL for Tc-99 – 900 pCi/L

Points of Calculation at 100 m


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Air Pathway Dose (Section 7)

Key Results for Air Pathway• Peak dose - 4e-03 mrem/yr• 2500 times below 10 mrem/yr

performance objective• Primarily from Tritium

Peak Dose - 4e-03 mrem/yr

Tritium

Iodine-129

Carbon-14


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All Pathway Dose (Section 7)

Technetium-99

Iodine-129

Selenium-79 Tin-126 U-Isotopes

Radium-226C-14

Tritium

Peak Total Dose 0.1 mrem/yr

(Post-compliance period)

Peak Total Dose 4E-03 mrem/yr

(Compliance period)


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Uncertainty Analysis (Section 8.1)

• Performed using System-level model based on GoldSim• Evaluated uncertainty estimates of about 130 model

parameters in the areas of:– Groundwater Pathway

• Recharge rates• Residual inventories• Source-term release • Vadose zone hydraulic properties• Vadose zone flow fields• Distribution coefficients (Kd)• Aquifer fluxes• Macrodispersivity in Vadose Zone and Groundwater

– Air pathway• Gas-phase tortuosity• Wind Speed


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Uncertainty Analysis of PA (Section 8)

GW Pathway: 300 Realizations All Pathways Mean Dose Calculation

• Uncertainty in parameters propagated using Monte Carlo sampling methodology

• All realizations remain below the Performance Objective (25 mrem/yr )

2.5 mrem/yr Performance Objective – 25 mrem/yr

Peak Total Mean Dose0.166 mrem/yr


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Sensitivity Analysis Examples(Section 8)

Varying Tank Grout Degradation Timing

• In all sensitivity cases, the Tc-99 concentration remains below MCL (900 pCi/l)

Tc-99 MCL - 900 pCi/l

42.5 pCi/l

26 pCi/l

30 pCi/l

44 pCi/l

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Sensitivity Analysis Examples(Section 8)

Tc-99 Upper Bound Inventory Sensitivity Analysis

For Upper Bound Tc-99 inventory sensitivity case, the groundwater concentration (~145 pCi/l) remains factor of ~6.5 below MCL (900 pCi/l)

145 pCi/l

30 pCi/lTc-99 MCL - 900 pCi/lC

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Inadvertent Intruder ScenariosInadvertent Intruder Scenarios

Acute Well Driller ScenarioAcute Well Driller Scenario Chronic Suburban Gardener ScenarioChronic Suburban Gardener Scenario

Chronic Rural Pasture ScenarioChronic Rural Pasture Scenario Chronic Commercial Farm ScenarioChronic Commercial Farm Scenario


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Inadvertent Intrusion Results For UngroutedFlushed Waste Transfer Pipelines

Doses from acute well driller scenario do not exceed performance measure of 500 mrem for acute exposure after assumed loss of institutional control

Performance Measure – 500 mrem

Acute Well Driller Expsure Scenario (Waste Transfer Pipeline)

Compliance period


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Inadvertent Intrusion Results For UngroutedFlushed Waste Transfer Pipelines (continued)

Doses from chronic exposure scenarios do not exceed performance measures of 100 mrem/yr after assumed loss of institutional control

Performance Measure – 100 mrem/yr

Chronic Rural Pasture Exposure Scenario (Waste Transfer Pipeline)

Chronic Suburban Gardener Exposure Scenario (Waste Transfer Pipeline)

Performance Measure – 100 mrem/yr

Compliance periodCompliance period


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Sensitivity Case: Long Term Groundwater Pathway Dose Evaluation* (Section 8)

* Tank considered degraded at 30,000 years

Technetium-99 (Tank Sources)

U-Isotopes (Pipelines)

Ra-226

0.1 mrem/yr

0.28 mrem/yr0.08 mrem/yr

1,000 10,000 100,000

Time after Closure (years400,000

U-Isotopes (Tank Sources)

Pb-210

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