ML21300A378

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Ril 2021-12 Proceedings of the Subsurface Soil Surveys Public Workshop
ML21300A378
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RIL 2021-12 PROCEEDINGS OF THE SUBSURFACE SOIL SURVEYS PUBLIC WORKSHOP July 14-15, 2021 Date Published: October 2021 U.S. Nuclear Regulatory Commission Rockville, MD 20852 T.H. Aird, NRC Project Manager Research Information Letter Office of Nuclear Regulatory Research

Disclaimer Legally binding regulatory requirements are stated only in laws, U.S. Nuclear Regulatory Commission (NRC) regulations, licenses, including technical specifications, or orders; not in Research Information Letters (RILs). A RIL is not regulatory guidance, although NRCs regulatory offices may consider the information in a RIL to determine whether any regulatory actions are warranted.

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ABSTRACT The U.S. Nuclear Regulatory Commission (NRC) is developing the technical basis for guidance on conducting and evaluating surveys of residual radioactivity in the subsurface soils of licensee sites. The NRC began to address this technical issue in NUREG/CR 7021, A Subsurface Decision Model for Supporting Environmental Compliance, issued January 2012. As part of this research effort, the agency held a public workshop in July 2021 to present current research results and solicit feedback from stakeholders and interested members of the public.

These workshop proceedings transmit the agenda and presentation materials for the Subsurface Soil Surveys Public Workshop held virtually July 14-15, 2021, using Web conference software. Attendees included members of the public; NRC technical staff, management, and contractors; staff from other Federal agencies; and members of academia.

The workshop began with an introductory session that included perspectives and research program highlights from NRC staff members, NRC contractors, and industry representatives.

Invited Federal and public speakers gave technical presentations and participated in various styles of panel discussion during the 2-day workshop. The workshop included four main topic areas for discussion:

(1) geospatial and statistical methods (2) subsurface derived concentration guideline levels or cleanup levels (3) subsurface hot spots (4) surveys of subsurface materials (including surveys of excavations, backfill materials, suspect areas, and hard-to-access areas) iii

TABLE OF CONTENTS 1 INTRODUCTION ..................................................................................................................... 1-1 1.1 Background ...................................................................................................................... 1-1 1.2 Workshop Objectives ....................................................................................................... 1-2 1.3 Workshop Scope.............................................................................................................. 1-2 1.4 Organization of Workshop Proceedings .......................................................................... 1-3 1.5 Reference Material........................................................................................................... 1-3 2 WORKSHOP AGENDA .......................................................................................................... 2-1 3 PROCEEDINGS ...................................................................................................................... 3-1 3.1 Day 1: Introductory Presentations ................................................................................... 3-1 3.1.1 NRC Overview Presentation (ADAMS Accession No. ML21208A213)............ 3-1 3.1.2 Overview of Guidance on Surveys for Subsurface Radiological Contaminants (ADAMS Accession No. ML21208A214) ....................... 3-8 3.1.3 Nuclear Energy Institute Presentation ............................................................ 3-36 3.2 Day 1: Geospatial and Statistical Methods.................................................................... 3-36 3.2.1 EPRI Presentation: Experiences with Geospatial and Statistical Based Surveys of Subsurface Soil (ADAMS Accession No. ML21208A215) .................................................................................... 3-36 3.2.2 VSP Geospatial Statistical Methods to Support Decommissioning (ADAMS Accession No. ML21208A216) ............................................ 3-50 3.3 Day 2: Opening Presentations ....................................................................................... 3-58 3.3.1 MARSSIM Subsurface Background ................................................................ 3-58 3.3.2 A Graded Approach to Subsurface Characterization and Remediation and Related Tools and Methods (ADAMS Accession No. ML21208A217) .................................................................................... 3-58 3.4 Day 2: Workshop Topic on Subsurface DCGLs ............................................................ 3-69 3.4.1 Development of Derived Concentration Guideline Levels (DCGLs or clean-up levels) for Subsurface Residual Radioactivity (ADAMS Accession No. ML21208A218)............................................................ 3-69 3.4.2 Subsurface DCGL: Effects of Thickness, Area, and Cover (ADAMS Accession No. ML21208A219)............................................................ 3-74 3.5 Day 2: Workshop Topic on Subsurface Hot Spots ........................................................ 3-80 3.5.1 Elevated Areas or Hot Spots in the Subsurface (ADAMS Accession No. ML21208A220) .......................................................................... 3-80 3.5.2 Subsurface Hot Spots (ADAMS Accession No. ML21208A221) .................... 3-84 3.6 Day 2: Workshop Topic on Surveys of Subsurface, Including Surveys of Excavations, Backfill Materials, Suspect Areas, and Hard-to-Access Areas........... 3-93 3.6.1 Survey Issues with Excavations from Recent Decommissionings (ADAMS Accession No. ML21208A222) ............................................ 3-93 3.6.2 Low Level Radioactive Objects at a Former Department of Defense Facility (ADAMS Accession No. ML212108A223) ............................ 3-101 3.6.3 Surveys of Survey Units with Low-Levels of Radioactivity (ADAMS Accession No. ML21208A224).......................................................... 3-103 4 Workshop Participants ......................................................................................................... 4-1 5 Summary and Conclusions.................................................................................................. 5-1 iv

5.1 Summary .......................................................................................................................... 5-1 5.2 Conclusions...................................................................................................................... 5-1 6 Acknowledgements .............................................................................................................. 6-1 v

1 INTRODUCTION This research information letter (RIL) details the proceedings of the Subsurface Soil Surveys Public Workshop held virtually July 14-15, 2021. It provides the agenda, speaker information, and presentation materials. Attendees included members of the public; U.S. Nuclear Regulatory Commission (NRC) technical staff, management, and contractors; staff from other Federal agencies; and members of academia.

The workshop began with an introduction from Trish Holahan, Director, Division of Decommissioning, Uranium Recovery, and Waste Programs in the Office of Nuclear Material Safety and Safeguards (NMSS). Following these opening remarks, staff members from the Office of Nuclear Regulatory Research (RES) and an NRC contractor (SC&A, Inc.) provided an overview of the results of current research. Additionally, Bruce Montgomery from the Nuclear Energy Institute (NEI) gave industry perspectives during this introductory session.

Technical sessions followed the introduction session. Most sessions included several technical presentations and concluded with a panel of all speakers, who discussed the session topic in general. At the end of each day, participants provided feedback and asked generic questions related to that days discussion topics.

1.1 Background

Dose modeling is used to determine cleanup levels or derived concentration guideline levels (DCGLs) that meet regulatory criteria for license termination. After remediation has been completed, final status surveys are conducted to confirm that residual radioactivity remaining at the site meets license termination rule (LTR) radiological criteria. The NRC has issued guidance for characterization and final status surveys of residual radioactive material in surface soils and structures in NUREG-1575, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), and NUREG-1757, Consolidated Decommissioning Guidance. MARSSIM includes procedures for these surveys and the statistical approaches used for their analysis for surficial contamination. However, this guidance applies only to contaminants in surficial materials (i.e., the top 15 centimeters of soils) and is not appropriate for use on subsurface soils (i.e., below 15 centimeters).

The NRC and industry expect an increasing number of complex decommissioning sites to become active soon. Many of these are reactor sites that can be expected to contain areas of residual radioactivity in subsurface soils. Moreover, instead of entering long-term storage before decommissioning (SAFSTOR), some reactor sites are now being decommissioned soon after shutdown. These facilities will need to be surveyed and have a determination made on the need for subsurface remediation. Statistical methods are needed to determine acceptable numbers and distributions of soil samples (or other subsurface media) taken at depth, to maintain appropriate coverage while keeping costs of sampling and analysis reasonable. Therefore, the NRC needs guidance on characterization and final status survey procedures for subsurface contamination.

Compliance assessments for surface and subsurface residual radioactivity have similar objectives, in that both focus on demonstrating that LTR radiological criteria are met. These criteria consider residual radioactivity (1) averaged over the entire site or survey unit and (2) potentially elevated concentrations in smaller areas of the site or survey unit. However, the 1-1

subsurface presents substantial challenges that add to the complexity of these surveys. First, access to subsurface soils is limited, and surveying subsurface soils is much more expensive compared to surface soils. Continuous scanning techniques, which are commonly used to provide fast and detailed surveys of the surface, cannot be conducted for subsurface soils unless the soils are exposed. Second, subsurface soils can be expected to be heterogeneous in ways that may not be evident. Third, the development of DCGLs for subsurface soils is more complex and often involves consideration of various intrusion events to bring subsurface residual radioactivity to the surface, where a receptor could be exposed. In this regard, ground water exposure pathways also appear to be more important for subsurface contaminants than for contaminants found at the surface. At complex sites that operated over an extended period, mobile radionuclides may have been transported deep in the vadose zone and into ground water or fractured rock, further adding to the difficulty of characterizing subsurface residual radioactivity. For these reasons, guidance is needed for the design and implementation of radiological surveys of the subsurface that includes statistical methods to determine acceptable sample distributions in three dimensions. The NRC hopes that licensees will be able to use this guidance to demonstrate the adequacy of site characterization and final status surveys by providing reasonable assurance of compliance with radiological criteria while limiting overly conservative approaches.

The NRC has sponsored some previous work on this topic, as described in NUREG/CR-7021, A Subsurface Decision Model for Supporting Environmental Compliance, issued January 2012. While NUREG/CR-7021 outlines an approach that overcomes obstacles to detailed subsurface surveys, it does not detail methods and statistical tests for use in the subsurface. Limitations of access to and sampling of the subsurface require an approach that, as stated in NUREG/CR-7021, maximizes the available information, technologies, and expertise; addresses and mitigates sources of uncertainty; and is meaningful within a compliance setting. Guidance is needed to provide licensees with acceptable approaches to subsurface surveys. Ultimately, this guidance may become associated with a modeling tool that can be used to process data, visualize contaminant distributions, interpolate and extrapolate data to areas where no data exist, consider subsurface structures (natural and anthropogenic) that may influence contaminant flow and transport, and help assess the radiological status of the site for comparison against the criteria for license termination.

1.2 Workshop Objectives The Subsurface Soil Surveys Public Workshop had two main objectives: (1) to inform and solicit feedback from internal NRC stakeholders, partner Federal agencies, industry, and the public about research in this topic area, and (2) to provide a forum for the presentation and discussion of notable U.S. activities in this area.

1.3 Workshop Scope The workshop included four main topic areas for discussion:

(1) geospatial and statistical methods (2) subsurface derived concentration guideline levels or cleanup levels (3) subsurface hot spots 1-2

(4) surveys of subsurface materials (including surveys of excavations, backfill materials, suspect areas, and hard-to-access areas)

Within these main topics, the scope of the workshop presentations and discussions generally included the following:

  • subsurface radiological surveys, ranging from historical site assessments, scoping, characterization, remedial action, and confirmatory and final status surveys
  • DCGLs for contaminants in the subsurface and the use of multiple DCGLs for surface and subsurface layers
  • evaluation of elevated areas or hot spots (DCGLEMC) for potential doses to receptors, including the inadvertent intruder
  • evaluation of sites with geospatial and statistical methods

- statistical methods and geospatial modeling tools and software to analyze contaminant distributions and optimize sampling and scanning of the subsurface

- methods to determine the sample density, spatial distributions, depths, and volume to achieve a level of confidence and limit decision errors

- applicability of MARSSIM statistical tests and other alternative methods

- treatment of uncertainty and data sufficiency

- applicability of composite sampling or surrogate ratios

  • applicability of Scenario B for subsurface residual radioactivity and demonstrating indistinguishability from background
  • methods to survey large subsurface soil excavations and survey of soils for reuse in large excavations, including the use of conveyor belts and other methods 1.4 Organization of Workshop Proceedings Section 2 of this RIL includes the agenda for this workshop. The agenda is also available in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML21208A212.

Section 3 presents the proceedings for the workshop, including speaker information and presentation materials. The complete workshop presentation package is available at ADAMS Package Accession No. ML21208A206.

Section 4 lists the workshop registrants, and Section 5 summarizes the workshop.

1.5 Reference Material The following three references provide helpful background on this topic:

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  • Executive Summary, Guidance on Surveys for Subsurface Radiological Contaminants, Draft Technical Letter Report, SC&A, Inc., issued April 2021 (ADAMS Accession No. ML21123A229) 1 0F
  • NUREG/CR-7021, A Subsurface Decision Model for Supporting Environmental Compliance, issued January 2012 (ADAMS Accession No. ML12026A022) 1 The Executive Summary report was prepared by the same contractor that supported this public workshop.

2 MARSSIM Revision 2 has been issued for public comment and is available at https://www.epa.gov/radiation/multi-agency-radiation-survey-and-site-investigation-manual-marssim-proposed-revision-2.

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2 WORKSHOP AGENDA The workshop agenda is also available at ADAMS Accession No. ML21208A212.

DAY 1 AGENDA: WEDNESDAY, JULY 14, 2021 Time Topic Speaker 10:00-10:05 Welcome, Webinar Logistics Ken Hamburger, Trish Holahan, NRC 10:05-10:20 NRC Overview Presentation Tom Aird, NRC 10:20-11:20 Overview of Guidance on Carl Gogolak, SC&A, Inc.

Surveys for Subsurface Radiological Contaminants +

Q&A 11:20-12:00 NEI Presentation + Q&A Bruce Montgomery, Nuclear Energy Institute (NEI) 12:00-13:00 1-hour Break Workshop Topic: Geospatial and Statistical Methods 13:00-13:30 EPRI Presentation: Experiences Richard Reid, Electric Power Research with Geospatial and Statistical Institute (EPRI)

Based Surveys of Subsurface Soil 13:30-14:00 VSP Geospatial Statistical Debbie Fagan, Pacific Northwest National Methods to Support Laboratory (PNNL)

Decommissioning 14:00-14:10 10-minute Break 14:10-15:50 Open discussion on the evaluation of sites with geospatial and statistical methods:

- applicability of MARSSIM statistical tests and other methods

- treatment of uncertainty and data sufficiency.

- methods to determine the sample density, spatial distributions, depths, and volume to achieve a level of confidence and limit decision errors 15:50-16:00 Daily Wrap-up 2-1

DAY 2 AGENDA: THURSDAY, JULY 15, 2021 Time Topic Speaker 10:00 Day 2 Welcome NRC Staff 10:00-10:30 Presentation: MARSSIM Subsurface Background Kathryn Snead, EPA Presentation: A Graded Approach to Subsurface Matt Darois, RSCS Characterization and Remediation and Related Tools and Methods 10:30-11:15 Discussion Topic: Subsurface DCGLs Short Presentations:

Development of Derived Concentration Guideline Levels Cynthia Barr, (DCGLs or clean-up levels) for Subsurface Residual NRC/NMSS Radioactivity Subsurface DCGL: Effects of Thickness, Area, and Charley Yu, Argonne Cover National Laboratory

--specific discussion on this topic--

11:15-12:30 Discussion Topic: Subsurface Hot Spots Short Presentations:

Elevated Areas or Hot Spots in the Subsurface Cynthia Barr, NRC/NMSS Subsurface Hot Spots Carl Gogolak, SC&A

--specific discussion on this topic--

12:30-13:30 1-hour Break 13:30-15:00 Discussion Topic:

Surveys of subsurface, including surveys of excavations, backfill materials, suspect areas, and hard-to-access areas Short Presentations:

Survey Issues with Excavations from Recent Bruce Watson, Decommissionings NRC/NMSS Low Level Radioactive Objects at a Former Department Matthew Wright, of Defense Facility California Department of Public Health Surveys of Survey Units with Low-Levels of Claude Wiblin, SC&A Radioactivity

--specific discussion on this topic--

15:00-15:15 15-minute Break 15:15-16:00 Discussion Topic:

Surveys of subsurface, including surveys of excavations, backfill materials, suspect areas, and hard-to-access areas 2-2

Specific discussion on subsurface survey topics, including but not limited to:

- dose calculations for backfill materials

- applicability of Scenario B for subsurface residual radioactivity

- methods to survey large subsurface soil excavations 16:00 Workshop Wrap-up NRC Staff 2-3

3 PROCEEDINGS 3.1 Day 1: Introductory Presentations 3.1.1 NRC Overview Presentation (ADAMS Accession No. ML21208A213)

Speaker: Thomas Aird, NRC Office of Nuclear Regulatory Research 3.1.1.1 Presentation Materials 3-1

3-2 3-3 3-4 3-5 3-6 3-7 3.1.2 Overview of Guidance on Surveys for Subsurface Radiological Contaminants (ADAMS Accession No. ML21208A214)

Speaker: Carl Gogolak, SC&A, Inc.

3.1.2.1 Presentation Materials 3-8

3-9 3-10 3-11 3-12 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 3-21 3-22 3-23 3-24 3-25 3-26 3-27 3-28 3-29 3-30 3-31 3-32 3-33 3-34 3-35 3.1.3 Nuclear Energy Institute Presentation Speaker: Bruce Montgomery, NEI

    • No presentation materials (e.g., Microsoft PowerPoint slides) exist for this presentation**

3.2 Day 1: Geospatial and Statistical Methods 3.2.1 EPRI Presentation: Experiences with Geospatial and Statistical Based Surveys of Subsurface Soil (ADAMS Accession No. ML21208A215)

Speakers: Rick Reid and Rich McGrath, EPRI 3.2.1.1 Presentation Materials 3-36

3-37 3-38 3-39 3-40 3-41 3-42 3-43 3-44 3-45 3-46 3-47 3-48 3-49 3.2.2 VSP Geospatial Statistical Methods to Support Decommissioning (ADAMS Accession No. ML21208A216)

Speaker: Debbie Fagan, PNNL 3.2.2.1 Presentation Materials 3-50

3-51 3-52 3-53 3-54 3-55 3-56 3-57 3.3 Day 2: Opening Presentations 3.3.1 MARSSIM Subsurface Background Speaker: Kathryn Snead, U.S. Environmental Protection Agency (EPA)

    • No presentation materials (e.g., Microsoft PowerPoint slides) exist for this presentation**

3.3.2 A Graded Approach to Subsurface Characterization and Remediation and Related Tools and Methods (ADAMS Accession No. ML21208A217)

Speaker: Matt Darois, Radiation Safety and Control Services Inc. (RSCS) 3.3.2.1 Presentation Materials 3-58

3-59 3-60 3-61 3-62 3-63 3-64 3-65 3-66 3-67 3-68 3.4 Day 2: Workshop Topic on Subsurface DCGLs 3.4.1 Development of Derived Concentration Guideline Levels (DCGLs or clean-up levels) for Subsurface Residual Radioactivity (ADAMS Accession No. ML21208A218)

Speaker: Cynthia Barr, NRC/NMSS 3.4.1.1 Presentation Materials 3-69

3-70 3-71 3-72 3-73 3.4.2 Subsurface DCGL: Effects of Thickness, Area, and Cover (ADAMS Accession No. ML21208A219)

Speaker: Charley Yu, Argonne National Laboratory 3.4.2.1 Presentation Materials 3-74

3-75 3-76 3-77 3-78 3-79 3.5 Day 2: Workshop Topic on Subsurface Hot Spots 3.5.1 Elevated Areas or Hot Spots in the Subsurface (ADAMS Accession No. ML21208A220)

Speaker: Cynthia Barr, NRC/NMSS 3.5.1.1 Presentation Materials 3-80

3-81 3-82 3-83 3.5.2 Subsurface Hot Spots (ADAMS Accession No. ML21208A221)

Speaker: Carl Gogolak, SC&A, Inc.

3.5.2.1 Presentation Materials 3-84

3-85 3-86 3-87 3-88 3-89 3-90 3-91 3-92 3.6 Day 2: Workshop Topic on Surveys of Subsurface, Including Surveys of Excavations, Backfill Materials, Suspect Areas, and Hard-to-Access Areas 3.6.1 Survey Issues with Excavations from Recent Decommissionings (ADAMS Accession No. ML21208A222)

Speaker: Bruce Watson, NRC/NMSS 3.6.1.1 Presentation Materials 3-93

3-94 3-95 3-96 3-97 3-98 3-99 3-100 3.6.2 Low Level Radioactive Objects at a Former Department of Defense Facility (ADAMS Accession No. ML212108A223)

Speaker: Matthew Wright, California Department of Public Health 3.6.2.1 Presentation Materials 3-101

3-102 3.6.3 Surveys of Survey Units with Low-Levels of Radioactivity (ADAMS Accession No. ML21208A224)

Speaker: Claude Wiblin, SC&A, Inc.

3.6.3.1 Presentation Materials 3-103

3-104 3-105 3-106 3-107 3-108 4 WORKSHOP PARTICIPANTS Approximately 195 people registered to attend the July 2021 Subsurface Soil Surveys Public Workshop, with approximately 67 individuals from State agencies, 48 from industry and commercial companies, 36 from non-NRC federal organizations, 33 NRC staff members, 8 from the general public, and 3 from international organizations. The workshop had approximately 160 virtual workshop participants during each day.

External registrants came from the following organizations:

American Nuclear Insurers Argonne National Laboratory Barrick Bechtel Bestica, Inc.

BHP CDI Oyster Creek Curtiss-Wright Nuclear Duane Arnold Energy Center ENERCON EnergySolutions EPRI Exelon Geosyntec Consultants H3 Environmental, LLC Homestake Mining Company of California Iberdrola Nuclear Generation (Spain)

Los Alamos National Laboratory National Nuclear Security Administration Savannah River Site NEI NEIS.com Oak Ridge Associated Universities Omaha Public Power District PNNL RSCS San Onofre Decommissioning Solutions SC&A, Inc.

Southern California Edison Southern Nuclear State Scientific and Technical Center for Nuclear and Radiation Safety (Ukraine)

Tennessee Valley Authority Tidewater, Inc.

Town of Duxbury, MA, Nuclear Advisory Committee U.S. Air Force U.S. Army Corps of Engineers (USACE), Buffalo District U.S. Army Public Health Center U.S. Department of Energy (DOE), Office of Public Radiation Protection U.S. Department of Energy, Office of Environmental Management U.S. Department of Energy, Office of the Chief of Nuclear Safety U.S. Department of Energy, West Valley Demonstration Project 4-1

U.S. EPA National Center for Radiological Field Operations U.S. EPA Office of Radiation and Indoor Air U.S. EPA Region 2 U.S. Navy Wood PLC.

State agencies (e.g., Department of Public Health, Environment) from the following:

State of Alabama State of Arkansas State of California State of Colorado State of Connecticut State of Mississippi State of Nevada State of New Jersey State of New York State of North Carolina State of Tennessee State of Texas State of Utah State of Vermont State of Washington 4-2

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SUMMARY

AND CONCLUSIONS 5.1 Summary This report includes the agenda and presentations for the Subsurface Soil Surveys Public Workshop held in July 2021. Attendees of the virtual workshop included members of the public; NRC technical staff, management, and contractors; staff from other Federal agencies; and members of academia. Public attendees over the course of the workshop included industry groups, industry members, consultants, independent laboratories, and research institutions.

5.2 Conclusions As reflected in these proceedings, subsurface characterization of licensee sites undergoing decommissioning is a very active area of research for the NRC and other Federal agencies, industry, and academia. Readers of this report will have been exposed to current technical issues, research efforts, and accomplishments in this area within the NRC and the wider research community.

These proceedings represent the main efforts in the first phase (technical basis phase) of this research effort. As part of this technical basis phase, the NRC has initiated research into case studies that synthesize various technical basis results and lessons learned to demonstrate the development of realistic modeling and characterization of subsurface contaminants. The final phase (development of selected guidance documents) is an area of active discussion between RES and NRC licensing offices. The NRC staff looks forward to further public engagement in this area.

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6 ACKNOWLEDGEMENTS An organizing committee in the RES Division of Risk Analysis, Fire and External Hazards Analysis Branch, planned and executed this workshop with the assistance of NMSS staff and contractors from SC&A, Inc.

Organizing Committee Members: Mark Fuhrmann, Tom Aird, Sarah Tabatabai, Cynthia Barr, Carl Gogolak, Claude Wiblin, and Deborah Schneider Workshop NRC Facilitator: Kenneth Hamburger Several NRC offices contributed to this workshop and the resulting proceedings. The organizing committee would like to highlight the efforts of the RES administrative staff, as well as agency publishing staff. The organizers appreciated managerial direction and support from MarkHenry Salley, Mark Thaggard, Christian Araguas, and Trish Holahan.

Members of the NRC Subsurface Soil Surveys Research Group:

Tom Aird (RES), Mark Fuhrmann (RES), Sarah Tabatabai (RES), and Cynthia Barr (NMSS) 6-1

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