ML22227A002

Overview of the Safety Case for Low-Level Radioactive Waste Disposal Facilities

ML22227A002
Person / Time
Issue date:	07/20/2022
From:	Chris Mckenney NRC/NMSS/DDUWP/RTAB
To:
Christepher McKenney, 301-415-6663
Shared Package
ML22227A001	List: ML22227A002 ML22227A003 ML22227A004
References
Download: ML22227A002 (19)

Text

NEA Workshop on Overview of the Safety Case for Developing Safety Cases Low-Level Radioactive Waste for Various Radioactive Waste Disposal Facilities Disposal Facilities July 20-22, 2022 Chris McKenney Risk and Technical Analysis Branch Division of Decommissioning, Uranium Recovery, and Waste Programs Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission

Low-Level Radioactive Waste Disposal International Safety Case Framework Regulatory Approach and Framework Safety Case Development Stakeholder Interactions 2

International Framework 3

Relevant Documents Relevant Documents

• RS-G-1.9 Categorization of Radioactive Sources

• RS-G-1.10 The Safety of Radiation Generators and Sealed Radioactive Sources

• GSG-1 Classification of Radioactive Waste

• SSG-1 Borehole Disposal Facilities for Radioactive Waste (under revision by DS512)

• SSG-14 Geological Disposal Facilities for Radioactive Waste

• SSG-29 Near Surface Disposal Facilities for Radioactive Waste

• SSG-23 The Safety Case and Safety Assessment for the Disposal of Radioactive Waste

• SSG-31 Monitoring and Surveillance of Radioactive Waste Disposal Facilities

• SSG-44 Establishing the Infrastructure for Radiation Safety

• SSG-45 Predisposal Management of Radioactive Waste from the Use of Radioactive Material in Medicine, Industry, Agriculture, Research and Education

• WS-G-6.1 Storage of Radioactive Waste

Basis for all aspects of safety case provided for licensing process

• May be updated throughout lifecycle Regulatory

• Regulator provides oversight Approach and (inspections)

Framework Framework

• Regulations & guidance

• Prospective licensee submits information, regulator documents review and makes licensing decision Public interactions throughout licensing process 6

Regulatory Review of the Safety Case

• Regulatory body should be involved at all steps of the safety case

• The role and function of the regulatory body is encoded in IAEA documents

• Credibility is important. Must have technical competency, clarity of decision making, generate adequate records, and involve stakeholders

• Goal of the regulatory review is to verify that the facility or activity will not cause unacceptable adverse impacts on human health or safety, or on the environment, both now and in the future

Regulatory Review of the Safety Case:

General Considerations

• Manage the review of the safety case as a project where standard principles of good project management apply

• It may be necessary to establish a dedicated team of personnel to conduct the review

• The regulatory review may be conducted by the regulatory body with or without support from external organizations. Results of the review are the responsibility of the regulatory body

• The regulatory body should establish clear and consistent regulatory requirements, guidance and expectations. The regulatory review process must be independent

Describe the safety-relevant aspects of the site, the facility, and the managerial and regulatory controls Demonstrate the operator will provide Safety Case for the protection of people and the Development environment Provide assurance to the regulatory body and other interested parties that safety requirements will be met Demonstrate that consideration has been given to all steps in the management of the waste, from its generation to its disposal 9

Safety Case Content

• Context - regulatory requirements, purpose, system characteristics, philosophy, timeframes, endpoints

• Strategy - integrated approach, intended safety functions, management strategy

• System Description - information and system understanding, basis for safety assessment, characterization data, engineering studies

• Safety Assessment - quantification of impacts (scenarios, models, data, calculations, interpretation of results) 10

Safety Case Content (continued)

• Iteration and Design Optimization - dynamic process with changes expected

• Management of Uncertainty - compile, assess, and mitigate uncertainties

• Limits, Controls, Conditions - limits on inventory, controls on engineering components, conditions for operation or monitoring

• Integration of Safety Arguments - results comply with requirements using multiple lines of reasoning.

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Example: Safety Assessment - Post-closure Mathematical model (abstraction)

Real system Estimated future performance 1.E+0 1.E-1 Tc99 Tc99 I129 1.E-2 I129 Np237 Np237 Dose (mSv/yr)

Sn126 Model 1.E-3 Se79 Sn126 Se79 Pu239 1.E-4 C14 Pb210 Support 1.E-5 1.E-6 Pu240 Ra226 Ac227 0.6 1.E-7 Pa231 0.5 0.4 1.E-8 0.3 0 2000 4000 6000 8000 10000 0.2 Time(yr) 0.1 0

12 0 .0 3 0 .1 0 .3 1 3 10 30 35 100 300 1000 3000 10000 30000 Kd (ml/g)

Example: Iteration and Design 13

Important to learn from experience

• Must document observations!

• Must have systems to manage information!

Continual

• Knowledge management is a challenge Learning and Example: TableCalculator Improvement 14

Lessons Hydrology Issues Learned

• Water Retention in Disposal Cells ->

from Early Bathtubbing Experience

• Unidentified Fast Flow Groundwater Paths in the U.S. Waste Inventory Concerns for Near-

• Appropriate Concentration Limits Surface

• Waste Forms Performance

• Presence of Hazardous Material Issues

• Presence and Treatment of Liquids See NUREG-1853, History and Framework of Commercial Low-Level Radioactive Waste Management in the United States, https://www.nrc.gov/reading-rm/doc-15 collections/nuregs/staff/sr1853/index.html

Human Intrusion Scenarios Near surface more accessible for potential intrusion Loss of knowledge of sites still an issue with near surface disposal Larger variety of methods of disturbance 16

Often of the outreach managed by the licensee/developer/operator

• May establish citizen advisory panels Community

• Work with local organizations Outreach Regulators focus and

• Explaining regulations and allowing Involvement public comment

• Identifying hearing opportunities

• Discussing the decision-making process

• Announcing review findings and decisions 17

• Approaches and considerations for Safety Cases are similar for geologic and near-surface facilities

• Near surface facilities likely have:

• A greater range of waste streams and waste forms that will be co-disposed

• Less reliance on specific waste form characteristics for containment Conclusions

• Greater concerns of future human actions disturbing the facility barriers or resulting in direct contact with waste

• Knowledge management over the long period of siting, construction, operation, and post-closure a challenge for any waste disposal facility 18

Contact Chris McKenney, US NRC Christepher.McKenney@nrc.gov

+1-301-415-6663 19