Remedial Design for D&D and Environmental Restoration

IAEA/Argonne Training Course on Decontamination, Decommissioning, and Environmental Remediation of

Radiologically-Contaminated Facilities and SitesApril 2011

Lawrence Moos, P.E.Argonne National Laboratory

Introduction

Present process of remedial design and remedy selection Synthesis of topics covered in last week and a half Process depends on accurate information

– Site characterization– Dose  calculations– Risk assessment 

Complex process– Multiple conflicting priorities and constraints– Many non‐technical factors– Decision is often out of your hands

Integrated approach  – Address both facility D&D and environmental cleanup

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What is Environmental Remediation?

Response to release of radioactive materials and/or chemicals to the outdoor environment– Mill tailings from mining– Improper waste disposal – Fire or explosion– Leaks or spills

Contaminants migrate from source to a receptor– Air ‐ inhalation or emersion– Water ‐ ingestion,  food contamination– Soil ‐ dermal contact, ingestion– Direct radiation

Cause of major human health, ecological, economic, or political consequences

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Remedial Action Process

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Define problem

Determinedesired

end-state

Developoptions

Selectaction

Implementaction

Evaluatesuccess

Reevaluateapproach

Step 1 Define the Problem

How big is the problem?– Obtain and review historical information and worker knowledge– Conduct site assessment – identify contaminants of concern

• Visual reconnaissance (Phase 1),  • Sample collection and analysis (Phase 2)

– Fully characterize nature and extent of contamination– Compare results with applicable criteria– Characterize site hydrology, geology, and hydrogeology– Assess potentially impacted human and natural receptors

Develop Site Conceptual Model – Describes the problem and communicate the problem to stakeholders– Various formats and complexity

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Step 2 Define Desired End-state

What is the desired future use of the site (End‐use)– Completely clean, unrestricted future use (greenfield)– Some contamination  in place, restricted use (brownfield)– Waste contained and land‐use restricted (landfill)– Isolate area and leave as‐is (abandonment)

Affected by political and economic factors– Resources available to achieve desired end‐use?

• If not, modify end‐use or set interim goals

– Consider wishes of the land owner– Influenced by higher‐level goals – institutional, regional, national,      

or international

Requires input from stakeholders End‐use goal must be technically feasible

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Develop Remediation Objectives

Defines what needs to be done to achieve desired end state  Based on allowable level of residual risk Determines acceptable levels of contamination to leave in 

place – major cost driver Determined by working with regulators and site stakeholders

– Political and socioeconomic factor as well as technical

Numeric or non‐numeric goals

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Example of Remedial Action Objectives

Numeric– Remove Cs‐137 contamination above 10 pCi/g– Remove contaminated groundwater until residual H‐3 concentration is 

less than 20,000 pCi/L– Reduce residual risk levels from all pathways to less than 1 in 100,000.

Non‐numeric– Prevent migration of contaminated groundwater from beneath the 

reactor building– Provide an alternate drinking water supply– Prevent contact with contaminated soil– Prevent residential and agricultural use of land

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Risk Assessment and Reduction

Baseline risk assessment is critical– Quantifies current risk level– Based on conceptual model– Identifies completed pathways to target– Prioritizes actions to gain most risk reduction for money spent

Should include risk for both radiological and chemical contaminants

Address risk to wildlife and ecosystems Degree of risk reduction tied to remedial objectives

– Risk reduction key element of remedy selection

Consider increased risk to remediation workers, residents, and environment – What is net benefit?

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Step 3 Develop Options

How can the remedial objectives be achieved?– Set of actions, technologies and administrative controls

Begins with considering “No Action” alternative– What happens if you do nothing?– Is clean‐up necessary to achieve desired end‐use?– Are there alternatives to cleaning up the site?

Search for technical solutions to achieve objectives– Technology screening tools available– D&D and remedial actions should be integrated– May  require bench‐scale and pilot scale testing

• Develop critical design parameters 

– Develop cost estimates and schedules for feasible alternatives

Compare expected results with No Action alternative

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Remedial Technologies for Radiologically Contaminated Sites Natural attenuation

– Radioactive decay– Dilution

Removal and off‐site disposal Containment

– Encapsulation – grout injection– Caps and engineered barrier– Hydraulic containment

In‐situ treatment– Chemical treatment– Vitrification

Ex‐situ treatment– Soil washing– Groundwater treatment

Step 4 – Select Alternative

Which approach should be recommended? Selection criteria evaluated in side‐by‐side comparison

– Anticipated effectiveness at achieving remediation objectives– Technical feasibility, reliability and implementability– Cost , schedule, and other resource requirements– Availability of materials, equipment, and personnel– Risk reduction achieved– Increased risk to workers, public, and environment– Project risk and uncertainty– Public and regulator acceptance– Socioeconomic impacts

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CERCLA/Superfund Alternative Selection Criteria

Overall protection of human health and the environment Compliance with appropriate regulatory requirements Long‐term effectiveness and permanence Reduction of toxicity, mobility, or volume Short‐term effectiveness Implementability Cost State acceptance Community acceptance

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Remedy Selection

Are any of the options technical feasibility?– Can any achieve all the desired objectives?– If not, reevaluate remediation objectives or end‐use

Quantify every option’s ability to satisfy each criteria so alternatives can be compared objectively– Include weighting factor for each criteria – what is most important?– Alternatives evaluation matrix– Cost‐benefit analysis

Select best alternative and propose to stakeholders– Stakeholder comments may change recommendation– Iterative process to achieve final selection

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Step 5 Implement the Solution

Conduct planned remedial actions Develop suitable project management tools

– Project  team• Project plan• Manage scope, cost, and schedule

Put project support tools in place– Financial management– Procurement– Contractor oversight– Waste management– Health and safety– Emergency response– Public information– Records management

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Step 6 Performance Monitoring and Long-Term Stewardship

Operate and maintain remedial systems Maintain land use restrictions and site security Inform regulators and public about effectiveness of the 

remedial approach Site‐specific environmental monitoring program

• Measure contaminant concentrations vs. clean–up criteria• Verify hydraulic containment• Document cap integrity

Periodically reassess overall effectiveness– Anticipated completion date– Revise remedial approach, if necessary, to achieve objectives– Revise end‐use and remediation objectives

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Uncertainty

Many sources – Incomplete or incorrect information used to design approach– Changing regulatory requirements

• New contaminants of concern• Lower clean‐up criteria

– Technical performance less than anticipated– New or changed expectations of stakeholders

Major consequences– Increased cost– Delayed clean‐up– Changed end‐use, increased site constraints

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