ML22178A066

SRMC-CWDA-2022-00006, Rev. 0, Fiscal Year 2022 Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program

ML22178A066
Person / Time
Site:	PROJ0734
Issue date:	05/24/2022
From:	Harry Felsher Office of Nuclear Material Safety and Safeguards
To:
Felsher H
References
SRMC-CWDA-2022-00006, Rev 0
Download: ML22178A066 (164)

Text

SRMC-CWDA-2022-00006 Revision 0 Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program FY2022 Approved by:

Date: 2022.05.24 13:02:46 -04'00' Aaron Staub Waste Disposal Authority May 2022 Prepared by: Savannah River Mission Completion Waste Disposal Authority Aiken, SC 29808 Prepared for U.S. Department of Energy Under Contract No. 89303322DEM000068

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................. 2 LIST OF TABLES ........................................................................................................................ 4 LIST OF FIGURES ...................................................................................................................... 4 ACRONYMS/ABREVIATIONS ................................................................................................. 5

1.0 INTRODUCTION

................................................................................................................. 8 2.0 SALTSTONE DISPOSAL FACILITY.............................................................................. 15 2.1 Saltstone Disposal Facility Monitoring ............................................................................ 15 2.2 Saltstone Disposal Facility Performance Assessment Testing & Research Activities ..... 15 2.2.1 Contaminant Leaching Characteristics from Saltstone Monolith..............................18 2.2.2 Ongoing Studies..........................................................................................................22 2.2.3 To Be Determined Out-Year Testing ..........................................................................30 2.3 Saltstone Disposal Facility Performance Assessment Planned Review, Analysis, and Schedules .................................................................................................................................. 30 2.3.1 Maintain Saltstone Disposal Facility Performance Assessment Control through Unreviewed Waste Management Question Process ..............................................30 2.3.2 Prepare Annual Update to Performance Assessment Maintenance Program ...........31 2.3.3 Provide General Technical Support on Saltstone Disposal Facility Performance Assessment Issues...................................................................................................31 2.3.4 Develop and Maintain Performance Assessment Model Archive and Revision Control ...................................................................................................................32 2.3.5 Conduct Annual Saltstone Disposal Facility Performance Assessment Validation ...33 2.3.6 Maintain Saltstone Disposal Facility Performance Assessment Closure Plan ..........33 2.3.7 Maintain Saltstone Disposal Facility Performance Assessment Monitoring Plan ....34 2.3.8 Status of DAS Conditions/Limits ................................................................................34 2.3.9 LFRG Key and Secondary Issues ...............................................................................34 2.4 Saltstone Disposal Facility Performance Assessment Development/Revisions ............... 35 2.4.1 Prepare Out-Year Saltstone Disposal Facility Performance Assessment Revisions ................................................................................................................35 2.4.2 Saltstone Disposal Facility Performance Assessment Maintenance Activities ..........35 2.4.3 Saltstone Disposal Facility Special Analyses .............................................................37 2.5 Summary Table for the SDF PA Maintenance Program .................................................. 38 3.0 F-AREA AND H-AREA TANK FARMS.......................................................................... 40 3.1 Tank Farm Facilities Monitoring ...................................................................................... 40 3.2 Tank Farm Performance Assessment Testing & Research Activities .............................. 40 3.2.1 Tank Residual Characterization .................................................................................41 3.2.2 CLSM Testing .............................................................................................................46 3.2.3 Tank Farm Closure Cap Design.................................................................................47 3.2.4 To Be Determined Out-Year Testing ..........................................................................48 3.3 Tank Farm Performance Assessment Planned Review, Analysis, and Schedules ........... 48 Page 2 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 3.3.1 Maintain Tank Farm Performance Assessment Control through Unreviewed Waste Management Question Process ...................................................................48 3.3.2 Prepare Annual Update to Performance Assessment Maintenance Program ...........49 3.3.3 Provide General Technical Support on Tank Farm Performance Assessment Issues ......................................................................................................................49 3.3.4 Develop and Maintain Performance Assessment Model Archive and Revision Control ...................................................................................................................50 3.3.5 LFRG Key and Secondary Issues ...............................................................................50 3.4 Tank Farm Performance Assessment Development/Revisions ........................................ 50 3.4.1 Prepare Out-Year F-Area Tank Farm Performance Assessment Revisions ..............50 3.4.2 Prepare Out-Year H-Area Tank Farm Performance Assessment Revisions ..............51 3.4.3 Tank Farm Special Analyses ......................................................................................55 3.5 Summary Table for the Tank Farm PA Maintenance Program ........................................ 56

4.0 REFERENCES

.................................................................................................................... 57 APPENDIX A .............................................................................................................................. 73 APPENDIX B .............................................................................................................................. 75 APPENDIX C ............................................................................................................................ 102 Page 3 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 LIST OF TABLES Table 2.2-1: Contaminant Leaching Study Summary.................................................................. 19 Table 2.2-2: Effective Diffusivities (De) & Leachability Index (LI) for EPA 1315 Experiments

............................................................................................................................ 20 Table 2.2-3: Radionuclide Field Lysimeter Experiment (RadFLEx) Lysimeters........................ 27 Table 2.5-1: Summary for the Saltstone Disposal Facility Performance Assessment Maintenance Program ($K) ..................................................................................................... 39 Table 3.4 HTF PA Modeling Reports Issued in 2021 ............................................................. 53 Table 3.5-1: Summary for the Tank Farm Performance Assessment Maintenance Program ($K)

............................................................................................................................ 56 LIST OF FIGURES Figure 1.0-1: Disposal Document Activities for Saltstone Disposal Facility .............................. 13 Figure 1.0-2: Closure Document Development Activities for the Tank Farms........................... 14 Figure 2.2-1: Saltstone Research, Development, and Testing Program Elements ...................... 16 Figure 2.2-2: Critical Property Testing Strategy.......................................................................... 17 Page 4 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 ACRONYMS/ABREVIATIONS ARP Actinide Removal Process ASR Alkali-Silica Reactivity ADMP Advance Design Mixer Pump ALARA As Low As Reasonably Achievable APR Air Pathway Release ASTM American Society for Testing and Materials BFS Blast Furnace Slag CA Composite Analysis CAB Citizens Advisory Board CBP Cementitious Barriers Partnership CC Clarifying Comment CFR Code of Federal Regulations CLSM Controlled Low Strength Material CZ Contamination Zone DAS Disposal Authorization Statement De Effective Diffusivity DLM Dynamic Leaching Method DO Dissolved Oxygen DOE U.S. Department of Energy DOE-SR U.S. Department of Energy Savannah River Operations Office Eh Measure of Reduction (or Oxidation) Potential EPA U.S. Environmental Protection Agency FDB F-Area Diversion Box FEPs Features, Events, and Processes FFA Federal Facility Agreement FTF F-Area Tank Farm FY Fiscal Year GCL Geosynthetic Clay Liner GGBFS Ground Granulated Blast Furnace Slag GSA General Separations Area GWB Geochemists Workbench HDPE High Density Polyethylene HRR Highly Radioactive Radionuclide HTF H-Area Tank Farm ICM Integrated Conceptual Model ICP-MS Inductively Coupled Plasma - Mass Spectrometry Page 5 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 IHI Inadvertent Human Intruder Kd Distribution Coefficient LFRG Low-Level Waste Disposal Facility Federal Review Group LI Leachability Index LLW Low-Level Waste LW Liquid Waste LWO Liquid Waste Organization MCC Moisture Characteristic Curve MCU Modular Caustic Side-Solvent Extraction Unit MEP Maximum Extent Practical MF Monitoring Factor MOP Member of the Public N/A Not Applicable NDAA National Defense Authorization Act NEA Nuclear Energy Agency NRC U.S. Nuclear Regulatory Commission OPC Ordinary Portland Cement OU Operable Unit PA Performance Assessment PARC Performance Assessment Review Committee pH Measure of Acidity or Alkalinity of a Solution PMP Probable Maximum Precipitation PNNL Pacific Northwest National Laboratory POC Point of Compliance RADFLEx Radionuclide Field Lysimeter Experiment RAI Request for Additional Information ROD Record of Decision RSI Request for Supplemental Information RUSLE Revised Universal Soil Loss Equation SA Special Analysis SAP Sampling and Analysis Plan SCDHEC South Carolina Department of Health and Environmental Control SDF Saltstone Disposal Facility SDU Saltstone Disposal Unit SPF Saltstone Production Facility SHC Saturated Hydraulic Conductivity SOW Statement of Work SREL Savannah River Ecology Laboratory Page 6 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRMC Savannah River Mission Completion SRNL Savannah River National Laboratory SRNS Savannah River Nuclear Solutions, LLC SRR Savannah River Remediation LLC SRS Savannah River Site SWPF Salt Waste Processing Facility TCG Tank Closure Grout TER Technical Evaluation Report TFF Tank Farm Facilities TTQAP Task Technical and Quality Assurance Plan TRR Technical Review Report UTRA-LAZ Upper Three Runs Aquifer-Lower Aquifer Zone UWMQ Unreviewed Waste Management Question UWMQE Unreviewed Waste Management Question Evaluation VSL Vitreous State Laboratory WAC Waste Acceptance Criteria WD Waste Determination WDA Waste Disposal Authority WRM Waste Release Model XRD X-Ray Diffraction XRF X-Ray Fluorescence Page 7 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022

1.0 INTRODUCTION

The U.S. Department of Energy (DOE), through Order 435.1, Radioactive Waste Management, and Manual 435.1-1, Radioactive Waste Management Manual, requires the ongoing maintenance of all Performance Assessments (PAs) and Composite Analyses (CAs). Because PA and CA results, in part, are based on data that is uncertain due to utilization of projected conditions thousands of years into the future, a maintenance program is needed to continue to reduce uncertainty in the inputs and assumptions, providing greater confidence in the results of the analyses and in the long-term plans for public and environmental protection. Additionally, a disciplined process to address potential changes in disposal and/or closure operations (e.g., change in disposal unit design, new residual material characterization) is needed to ensure that new information or proposed changes do not adversely affect conclusions reached using PA results.

The PAs for the Savannah River Site (SRS) Saltstone Disposal Facility (SDF), F-Area Tank Farm (FTF), and H-Area Tank Farm (HTF) are managed by Savannah River Mission Completion (SRMC) for the DOE. [SRR-CWDA-2019-00001, SRS-REG-2007-00002, SRR-CWDA-2010-00128] These PAs assess the calculated dose impact on a future, hypothetical member of the public (MOP) and an inadvertent human intruder, as well as environmental impacts from the respective facilities after final closure as required by DOE Order 435.1. In addition, the PAs are used to support demonstration of compliance with pertinent requirements of the Ronald W. Reagan National Defense Authorization Act (NDAA) for Fiscal Year 2005, Section 3116 (hereinafter referred to as NDAA Section 3116).

The Savannah River Site DOE 435.1 Composite Analysis (hereinafter referred to as SRS CA) is a management tool required to assist DOE in assessing the possible impacts on the public and environment from multiple sources of legacy radioactive material at a DOE site (e.g., SRS) in order to determine where DOE may need to focus attention or take mitigating actions. The development and maintenance of the SRS CA is the responsibility of the SRS Management and Operations contractor, Savannah River Nuclear Solutions, LLC (SRNS). [SRNL-STI-2009-00512]

The purpose of the Liquid Waste (LW) PA Maintenance Program is to confirm the continued adequacy of LW PAs and to increase confidence in the results of the LW PAs. The elements of the LW PA Maintenance Program are:

• Testing and applied research

• Monitoring

• Unreviewed Waste Management Questions (UWMQs)/Performance Assessment Review Committee (PARC)

• Special Analyses (SAs)

• PA revisions This program Implementation Plan is prepared and updated annually and submitted to the DOE Savannah River Operations Office (DOE-SR). The preparation and execution of the plan is consistent with the Disposal Authorization Statement and Tank Closure Documentation Technical Standard (DOE-STD-5002-2017). Beginning with the FY2010 Implementation Plan (SRR-CWDA-2010-00015), the LW PA Maintenance Program activities for the SRS LW Facilities have been contained in a separate implementation plan from that for the E-Area Low-Level Waste Page 8 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Facility and the SRS CA. The purpose for this change was to better align the documents with the current SRS contract structure. A summary of LW maintenance activities for the individual PAs are summarized in Tables 2.5-1 and 3.5-1. Appendix A, Table A.1-1, contains a roll-up cost estimate summary of all LW PA Maintenance activities. This document reflects the PA-related activities completed last fiscal year (FY) or earlier in some cases, planned for the current FY, and captured out-year activities for estimation and planning purposes. Actual work performed in the out-years will be adjusted based on new program information and will be dependent on the contract baseline funding and associated actual allocated budget for that year.

Section 2.0 includes a summary of the LW PA Maintenance Program activities for the SDF and Section 3.0 contains the activities for FTF and HTF. Each section includes activities relating to the following areas:

• Monitoring

• Research and Development

• Planned Review and Analysis o Status of Disposal Authorization Statement (DAS) Conditions/Limits o Low-Level Waste Disposal Facility Federal Review Group (LFRG) Key and Secondary Issues o Unreviewed Waste Management Question Evaluations (UWMQEs) o SAs o LFRG PA Reviews o Annual Summary Report Reviews

• Planned Annual Maintenance Activities and Schedules

• Revisions to DAS Documents (PA)

Saltstone Disposal Facility Overview As shown in Figure 1.0-1, the development and review of the SDF disposal documentation has been ongoing for many years. The Section 3116 Determination for Salt Waste Disposal at the Savannah River Site, and the supporting Basis Document, were issued by DOE in January 2006.

[DOE_01-17-2006, DOE-WD-2005-001] Issuance of these documents was supported by a Vault 4 SA and the SDF Performance Objective Demonstration Document. [WSRC-TR-2005-00074, CBU-PIT-2005-00146] The 2009 SDF PA, Revision 0, which introduced a new 150-foot diameter Saltstone Disposal Unit (SDU) design, was issued in October 2009. [SRR-CWDA-2009-00017]

Three SAs utilizing new technical information, including another SDU design revision, were issued against the 2009 SDF PA. The first SA (the FY2013 SDF SA) was issued in October 2013 and approved in December 2013. [SRR-CWDA-2013-00062, WDPD-14-08] The second SA (the FY2014 SDF SA) was issued in September 2014 and approved in October 2014. [SRR-CWDA-2014-00006, WDPD-15-05] The FY2014 SA evaluated the performance of the current 375-foot diameter SDU design. The FY2016 SDF SA was issued in October 2016 and approved by DOE in November 2016. [SRR-CWDA-2016-00072, WDPD-17-05] The FY2016 SDF SA re-evaluated the performance of the current 375-foot diameter SDU design to reflect observed field conditions (SDU 6), to incorporate lessons learned (SDUs 7 through 12), and to incorporate new physical locations for SDUs. A full PA revision (SRR-CWDA-2019-00001) was issued in May 2020 and replaced the 2009 SDF PA and its associated SAs.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Figure 1.0-1 also provides an overview of primary documentation issued in support of the U.S.

Nuclear Regulatory Commission (NRC) consultation and monitoring role for SDF under NDAA Section 3116. Issuance of the current revision to the DOE DAS for SDF, along with DOE approval of the SDF PA, occurred in June 2020. [WDPD-20-32]

Since July 2020, the NRC has been reviewing the 2019 SDF PA as part of the NRCs monitoring role under Section 3116(b) of the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA Section 3116).

The NRC provided a set of Requests for Supplemental Information (RSIs) in October 2020 (ML20254A003). These RSIs requested that additional models be developed to better enhance the understanding of combined uncertainties related to the long-term performance and potential degradation of various components and features associated with the SDF closure system. Due to the sequential nature of the RSIs, wherein some RSIs had to be responded to as prerequisites to other RSIs, the preparation of the responses to the RSIs was performed sequentially, resulting in multiple documents being prepared from March to August 2021, which are summarized in Summary of RSI Response Documents for the SDF PA, SRR-CWDA-2021-00068.

In addition, as part of their review, the NRC has issued two letters as of the end of FY21 with Requests for Additional Information (RAIs). [ML21040A492, ML21133A296] The first letter had twelve RAIs as well as six Clarifying Comments (CCs). Those RAIs and CCs were addressed in SRR-CWDA-2021-00047, Comment Response Matrix for the First Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Revision 1, issued in July 2021.

The NRC issued the second letter in June 2021 and that letter included an additional sixteen RAIs and fourteen CCs. On August 18, 2021, an initial round of responses to this second set of NRC RAIs and CCs was issued via SRR-CWDA-2021-00072, Comment Response Matrix for the Second Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Revision 0. SRR-CWDA-2021-00072 was subsequently revised to include the complete set of RAI and CC responses and Revision 1 was issued in November 2021.

In FY2020, an SA was initiated to evaluate the following new information relative to potential impacts on the long-term performance of the SDF:

1. An improved normative analysis was developed to better determine the chemical and mineralogical constituents for concrete used in constructing SDUs and for the cementitious waste form known as saltstone.

2. Modeling properties have been developed to evaluate the performance of two proposed cementitious materials (SDU Concrete Mix 3B and Cement Free Saltstone) which are currently being considered for deployment.

3. An equivalent set of normative analyses for two new cementitious materials (SDU Concrete Mix 3B Concrete and Cement Free Saltstone) was also developed.

4. The normative analyses were used to update cementitious degradation rates for existing cementitious materials and for the new cementitious materials.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 The primary driver for evaluating this new information is to determine the potential impacts from using the two proposed cementitious materials (SDU Concrete Mix 3B Concrete and Cement Free Saltstone). The FY2020 SDF SA (SRR-CWDA-2020-00064) was issued in 1QFY2021. The FY2020 SDF SA evaluated the performance of SDU Concrete Mix 3B and Cement Free saltstone relative to the 2019 SDF PA.

The DOE-SR approved the FY2020 SDF SA (WDPD-21-40) and minor edits were incorporated as Revision 1 to address observations that were identified during the DOE-SR review. Revision 1 of the FY2020 SDF SA, was issued in April 2021.

F-Area and H-Area Tank Farms Overview As shown in Figure 1.0-2, Tank Farm closure document development has also been ongoing for many years.

The current FTF PA, Revision 1, was issued in March 2010. [SRS-REG-2007-00002] Issuance of the Section 3116 Determination for Closure of F-Tank Farm at the Savannah River Site (DOE-WD-2012-001) and supporting Basis Document for FTF occurred in March 2012. [DOE/SRS-WD-2012-001] In March 2012, DOE also approved the FTF Tier 1 Closure Plan including its referenced FTF PA, Revision 1. [DOE_03-28-2012, SRR-CWDA-2010-00147] Along with approval of the FTF Tier 1 Closure Plan, DOE approved the Tanks 18 and 19 Tier 2 Closure Plan, including the SA specific to Tanks 18 and 19. [WDPD-12-39, SRR-CWDA-2011-00015, SRR-CWDA-2010-00124] An SA for Tanks 5 and 6 was prepared in support of operational closure of Tanks 5 and 6 and Revision 1 of the SA was issued in January 2013. [SRR-CWDA-2012-00106]

DOE approved the Tanks 5 and 6 Tier 2 Closure Plan, including the Tanks 5 and 6 SA, in May 2013. [WDPD-13-56, SRR-CWDA-2013-00014]

The FTF F-Area Diversion Box (FDB)-5 and FDB-6 Special Analysis (SRR-CWDA-2020-00055, FDB-5 and FDB-6 Special Analysis for the Performance Assessment for the F-Tank Farm at the Savannah River Site) was issued in 2021. This SA describes the approaches used to assign inventories at closure for FDB-5 and FDB-6 for use in FTF transport modeling. The FDB-5 and FDB-6 SA reports that the results and conclusions presented in the FTF PA and supporting SAs are not impacted by new information regarding the final residual inventories that are planned to be grouted in-place in FDB-5 and FDB-6.

The current HTF PA, Revision 1, was issued in November 2012. [SRR-CWDA-2010-00128]

Issuance of the Section 3116 Determination for Closure of H-Tank Farm at the Savannah River Site (DOE-WD-2014-001) and supporting Basis Document for HTF occurred in December 2014.

[DOE/SRS-WD-2014-001] In December 2014, following issuance of the HTF Section 3116 Waste Determination (WD), DOE approved the HTF Tier 1 Closure Plan includ ing its referenced HTF PA, Revision 1. [DOE-OS-2015-04-27-01, SRR-CWDA-2014-00040]

An SA for Tank 16 was prepared in support of operational closure of Tank 16 and Revision 1 of the SA was issued in February 2015. [SRR-CWDA-2014-00106] DOE approved the Tank 16 Tier 2 Closure Plan, including the Tank 16 SA, in May 2015. [WDPD-15-42, SRR-CWDA-2015-00009] An SA for Tank 12 was prepared in support of operational closure of Tank 12 and Revision 0 of the SA was issued in August 2015. [SRR-CWDA-2015-00073] DOE approved the Tank 12 Tier 2 Closure Plan, including the Tank 12 SA, in September 2015. [SRR-CWDA-2015-00119, WDPD-16-17] An SA specific to the HTF Type I and Type II Tanks was prepared and issued in Page 11 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 August 2016 (SRR-CWDA-2016-00078) and received DOE approval in June 2017. [WDPD 34] This SA updated the radiological and chemical inventories for the Type I and Type II tanks in the HTF (incorporating lessons learned from the final waste tank characterization results to date) and includes an extensive series of sensitivity analyses that provide additional information that can inform decisions regarding HTF Type I and Type II tank closure operations.

A revision of the HTF PA was initiated in FY2020 and is schedule to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure). Unless otherwise noted in the HTF PA, the revision will include the following items at a minimum:

• Analyses and results contained in all SAs that have been completed to date;

• Analyses and results of all UWMQEs completed to date;

• Consideration of new information generated through research and development;

• Changes in site future land use plans or closure plans;

• Changes to PA guidance documents requirements; and

• Modeling improvements as identified in the Quality Assurance report for the HTF PA (SRR-CWDA-2012-00070).

A document which outlines the activities and data needed to revise the FTF and HTF PAs (SRR-CWDA-2019-00104, Strategy for Updating the SRS Tank Farm Performance Assessments) was issued in December 2019. An extensive update of the HTF compliance case PORFLOW model was completed in FY2021.

Figure 1.0-2 also provides an overview of primary documentation issued in support of the NRC consultation and monitoring role for FTF and HTF under NDAA Section 3116.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Figure 1.0-1: Disposal Document Activities for Saltstone Disposal Facility Page 13 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Figure 1.0-2: Closure Document Development Activities for the Tank Farms Page 14 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 2.0 SALTSTONE DISPOSAL FACILITY Monitoring is an essential part of ensuring a facility is performing as outlined in the PA and in ensuring compliance with performance objectives/measures.

2.1 Saltstone Disposal Facility Monitoring The SDF PA Monitoring Plan has been developed to meet the requirements for monitoring Low-Level Waste (LLW) disposal facilities according to DOE Order 435.1 (DOE O 435.1) and its associated manual and implementation guidance. This SDF PA Monitoring Plan considers actual performance versus projected performance for the SDF at the SRS as they relate to the requirements of the current DAS for the SDF. [WDPD-20-32] The SDF PA Monitoring Plan is intended to detect changing trends in performance in order to apply a graded approach to corrective actions prior to exceeding any performance objectives.

The SDF Monitoring Plan includes guidance for:

• Ensuring compliance with the current DAS issued for the SDF,

• Providing a general description of the location of the facility and the relevant aspects of the environmental setting for the facility,

• Describing the SDF and associated waste form,

• Identifying pertinent documents that govern or monitor the SDF,

• Monitoring approaches, including media to be monitored; types, locations, and frequencies of sampling; and analytical information, and

• Data evaluation, management, and reporting.

As part of this PA maintenance program, the SDF PA Monitoring Plan is evaluated annually, or as conditions at the facility change (e.g., the installation of new groundwater monitoring wells) and an update to the SDF PA Monitoring Plan, if required, will be submitted for DOE approval as necessary. The latest version of the SDF PA Monitoring Plan is SRR-CWDA-2020-00006, updated in August 2020. Additional information on the SDF PA Monitoring Plan is provided in Section 2.3.7.

2.2 Saltstone Disposal Facility Performance Assessment Testing & Research Activities This section contains the PA-related testing and research activities that are being performed as (1) part of the ongoing maintenance activities aimed at reducing uncertainty in the SDF PA and SA models, or (2) verification sampling and analysis of material properties used in the PA (i.e.,

verification of emplaced saltstone properties and properties of saltstone cured under temperature and humidity conditions that reflect the actual disposal environment). As ongoing research provides new information or reduces uncertainty, this information will be evaluated (via the UWMQ [Section 2.3.1] or SA process [Section 2.4.3]) against the information used as a basis for modeling.

Resources have been and continue to be prioritized to support research activities related to measuring and/or modeling key parameters of the saltstone waste form and the disposal units (Figure 2.2-1). Figure 2.2-2 depicts how testing and research activities and ongoing testing of the saltstone waste form are being selected using an integrated, systematic approach.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Figure 2.2-1: Saltstone Research, Development, and Testing Program Elements Page 16 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Figure 2.2-2: Critical Property Testing Strategy Page 17 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Funding estimates have been made for each ongoing or anticipated activity. While actual work performed is always dependent on current funding and priorities, Table 2.5-1 provides a general idea of the work expected to be performed over the next several years.

In September 2013, the NRC revised their NDAA Section 3116 monitoring plan for SDF, with a monitoring plan supplement issued in 2019 [ML19150A295]. This NRC SDF Monitoring Plan provides expectations for closing Technical Evaluation Report (TER) issues. Note that the monitoring factors in the NRC SDF Monitoring Plan cover both the NRC concerns from the 2012 NRC TER and the previous Open Issues that had not been closed from an earlier version (Revision

0) of their NRC SDF Monitoring Plan. [ML13100A113] Appendix B of this FY2022 update provides a summary of monitoring factors in the context of testing and research activities related to the SDF.

2.2.1 Contaminant Leaching Characteristics from Saltstone Monolith

Description:

The purpose of this study is to characterize the leaching behavior of saltstone samples spiked with Tc-99 and I-129 in addition to saltstone cores retrieved from SDU Cell 2A. Test methods to be employed include a standardized semi-dynamic leaching test, U.S.

Environmental Protection Agency (EPA) Method 1315, Mass Transfer Rates of Constituents in Monolithic or Compacted Granular Materials Using a Semi-Dynamic Tank Leaching Procedure, and a dynamic leaching test that was developed as part of this scope.

[EPA_Method_1315] The dynamic leaching method (DLM) uses a flexible-wall permeameter apparatus that is more commonly used for measuring the saturated hydraulic conductivity (SHC) of saltstone. The intent is to force leachate through the interior of the saltstone monolith to mimic the eventual ingress of water into saltstone and subsequent pore volume exchange to establish the dynamic leaching behavior of saltstone contaminants. This task provides empirical leaching (diffusion and solubility) data for Tc-99, I-129, and potentially other saltstone contaminants that are used as direct inputs to the SDF PA models. In addition, the development of a dynamic leaching test provides new information regarding the leaching of saltstone associated with multiple pore volume exchanges. Table 2.2-1 summarizes the saltstone samples that have been prepared and tested to date. Table 2.2-2 provides a summary of the EPA Method 1315 data.

Expected Benefit: This task provides empirical leaching (diffusion and solubility) data for Tc-99, I-129, and potentially other saltstone contaminants that can be used as direct inputs to the saltstone PA models. In addition, the development of a dynamic leaching test provides new information regarding the leaching of saltstone associated with multiple pore volume exchanges.

FY2014: Contaminant mass transfer for I- and Re- spiked monoliths was evaluated using EPA Method 1315. [EPA_Method_1315]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Table 2.2-1: Contaminant Leaching Study Summary GGBFS Saltwaste DLM Batch EPA FY Report Reduction Solution Spike EPA 1315 Notes DLM DLM Notes Status as Sample a 1315 Capacity (µeq/g) f Simulant g of FY2021 SREL-R-14-0006, I-127, 1-month cure (x1); 5 short-term experiments H45:45:10 b 861 ARP-MCU Yes Yes Removed FY2014 Re 3-month cure (x1) to develop DLM method.

SREL-R-15-0003, I-127, 3-month cure (x1);

H45:45:10 b 861 ARP-MCU Yes No N/A N/A FY2015 Re 6-month cure (x1)

SREL-R-15-0003, 3-month cure (x1);

H45:45:10 713 ARP-MCU Tc-99 Yes Yes 6-month cure (x1) Removed FY2015 6-month cure (x1)

SREL-R-16-0003, H45:45:10 713 ARP-MCU Tc-99 Yes 3-month cure No N/A N/A FY2016 SREL-R-16-0003, 3-month cure (x1);

L45:45:10 1,600 ARP-MCU Tc-99 Yes No N/A N/A FY2016 6-month cure (x2)

SREL-R-16-0003, SDU 2A - Tank 50 21-month cure Not Measured N/A Yes Yes 21-month cure (x1) Running FY2016 Sample A c Actual (x1)

SREL-R-16-0003, SDU 2A - Tank 50 21-month cure Not Measured N/A Yes Yes 21-month cure (x1) Removed FY2016 Sample B d Actual (x1)

SREL-R-16-0003, SDU 2A - Tank 50 21-month cure Not Measured N/A Yes No N/A N/A FY2016 Sample C e Actual (x1)

SRRA099188-000005, 1.5-month cure H45:45:10 713 ARP-MCU I-129 Yes No N/A N/A FY2018 (x1)

SRRA099188-000005, 1.5-month cure 6-month cure (x1);

L45:45:10 Not Measured ARP-MCU I-129 Yes Yes Removed FY2018 (x1) 13-month cure (x1)

SRRA099188-000005, L45:45:10 Not Measured ARP-MCU Tc-99 No N/A Yes 3-month cure (x2) Removed FY2018 SRRA099188-000010, Tc-99, 10-month cure (x1);

L45:45:10 870 SWPF Yes 9-month cure (x1) Yes Running FY2019 I-129 11-month cure (x1)

SRRA099188-000010, Tc-99, L60:40 870 SWPF Yes 9-month cure (x1) Yes 10-month cure (x2) Running FY2019 I-129 (a) SDU 2A samples with a 45:45:10 designation were prepared using dry-feed material ratio of 45 wt% ground granulated blast furnace slag (GGBFS), 45 wt% FA, and 10 wt% OPC. Samples with a 60:40 designation, prepared using a dry-feed material ratio of 60 wt% GGBFS and 40 wt% FA. All samples prepared using water-to-dry-feed mass ratio of 0.6. SDU samples starting with an "H" were made using Holcim Grade 100/120 GGBFS, samples starting with an "L" were made using Lehigh Grade 100/120 GGBFS.

(b) FY2015 samples are from the same batch as the FY2014 samples, just cured for longer. FY2014 report provided EPA 1315 data for the 1-month and 3-month cured samples but no Effective Diffusivity (De). De coefficient for the 3-month and 6-month cured Re/I spiked saltstone samples is provided in the FY2015 report.

(c) Taken from core SDU2A-0931-C-1-U-2 (see Attachment 2 in SRR-CWDA-2015-00066).

(d) Taken from core SDU2A-0931-C-1-U-5 (see Attachment 2 in SRR-CWDA-2015-00066).

(e) Taken from core SDU2A-0931-C-2-U-2 (see Attachment 2 in SRR-CWDA-2015-00066).

(f) Reduction capacity measured using the Ce(IV) method of Angus and Glasser (1985).

(g) The composition of the saltwaste solution simulants can be found in Table 2 of SRRA099188-000010 (SREL DOC No. R-20-0002). The SDU 2A core samples were made with actual salt waste from Tank 50.

ARP - Actinide Removal Process; FA - Fly Ash, MCU - Modular Caustic Side-Solvent Extraction Unit; OPC - Ordinary Portland Cement, SWPF - Salt Waste Processing Facility Page 19 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Table 2.2-2: Effective Diffusivities (De) & Leachability Index (LI) for EPA 1315 Experiments Curing Tc-99 Re NO3 Iodine c Batch FY Report Duration De De De Sample a LI d LI d De (cm2/s) LI d LI d (months) (cm2/s) (cm2/s) (cm2/s)

SREL-R-15-0003, H45/45/10 b 3 2.40E-10 9.9 3.00E-08 7.6 4.40E-08 7.6 2.90E-08 7.7 FY2015 SREL-R-15-0003, H45/45/10 b 6 2.80E-10 9.7 3.30E-08 7.6 1.60E-08 7.9 3.00E-08 7.7 FY2015 SREL-R-16-0003, H45/45/10 3 3.00E-10 9.6 N/A N/A 3.70E-07 6.7 N/A N/A FY2016 SREL-R-16-0003, L45/45/10 3 2.60E-11 10.6 N/A N/A 4.80E-08 7.5 N/A N/A FY2016 SREL-R-16-0003, L45/45/10 6 5.70E-12 11.3 N/A N/A 6.60E-08 7.2 N/A N/A FY2016 SREL-R-16-0003, L45/45/10 6 3.80E-11 10.4 N/A N/A 2.10E-07 6.7 N/A N/A FY2016 SREL-R-16-0003, SDU 2A -

21 6.40E-11 10.2 N/A N/A 1.30E-08 8 1.00E-08 8 FY2016 Sample A SREL-R-16-0003, SDU 2A - 21 5.80E-11 10.3 N/A N/A 4.40E-09 8.5 2.50E-09 8.6 FY2016 Sample B SREL-R-16-0003, SDU 2A -

21 5.20E-11 10.3 N/A N/A 5.50E-09 8.5 5.50E-09 8.4 FY2016 Sample C SRRA099188-H45/45/10 1.5 N/A N/A N/A N/A 9.50E-08 7 2.80E-08 7.6 000005, FY2018 SRRA099188-L45/45/10 1.5 N/A N/A N/A N/A 8.20E-09 8.1 1.40E-08 8 000005, FY2018 SRRA099188- 3.30E-L45/45/10 9 5.30E-11e 10.4 N/A N/A 9.20E-09e 8.2 8.8 000010, FY2019 09e SRRA099188- 4.40E-L60/40 9 5.70E-11e 10.5 N/A N/A 7.40E-09e 8.2 8.5 000010, FY2019 09e (a) Refer to Table 2.3-1 for additional information on batch samples.

(b) Two different batches of H45/45/10 saltstone were used in EPA 1315 tests, one spiked with Re/I-127, and the other spiked with Tc-99 (see Table 2.3-1). For convenience the data from these experiments has been consolidated into one row.

(c) For all SDU 2A samples and lab prepared saltstone samples made after FY2015, I-129 was used as the spike. Prior to that time, I-127 was used.

d LI = -log10 (De )

e The diffusivities and LI values reported in Table 6 of SRRA099188-000010 reflect the average of all incremental sampling intervals, hence the LI value reported in the table will not necessarily coincide with the negative log of the reported De value. In other words, the De and LI value was calculated at each sampling interval and the average of these values is presented in this table.

FY2015: EPA Method 1315 was used to evaluate the leaching characteristics of Tc-spiked saltstone samples cured for three and six months. The leaching rate of Tc-99 was observed to decrease over the course of testing but exhibited no clear response to either curing duration (3 or 6 months) or test atmosphere (oxic, anoxic, and anoxic reducing).

Dynamic leaching tests utilizing the method developed using Re-spiked samples in FY2014 were conducted on Tc-spiked samples in FY2015. Like the EPA measurements, technetium, iodine, and rhenium were spiked at levels equivalent to those measured in Tank 50 waste.

[SREL Doc. R-15-0003]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2016: EPA Method 1315 testing continued in FY2016 on Tc-99 spiked saltstone samples.

Tc-99 leaching rates appeared to be sensitive to curing duration and the reduction capacity of the ground granulated blast furnace slag (GGBFS) used in making the grout. Due to supply cessation of a historically utilized GGBFS, an alternate blast furnace slag (BFS) source was sought and approved for use in processing future saltstone batches at SRS. Longer curing times and higher reduction capacity for the as-received GGBFS resulted in lower effective diffusivities.

FY2017: At the end of FY2017, four samples had been evaluated on this revised DLM system and while the desired flow rates were set between 0.2 and 1.5 mL/day all samples were operating at rates at or below 0.1 mL/day. As such it was not possible to determine residence time effects on leachate chemistry with that experimental set up. These samples had less than a pore volume exchanged and as such it was too early to make any determinations with respect to sample-to-sample similarities or differences.

FY2018: In FY2018, EPA 1315 leachates collected from two I-129 spiked saltstone simulants were analyzed to obtain effective diffusivities for iodine in saltstone. The two saltstone simulants utilized the same dry feed composition, salt solution simulant, and curing time (1.5 months) but differed regarding the GGBFS source used (Lehigh versus Holcim). The resulting effective diffusivities for iodine from this work were comparable to previous EPA 1315 tests conducted in FY2015 on saltstone simulants cured for 3 months and 6 months. These effective diffusivities are noticeably higher than those measured from actual SDU 2A cores which were cured in SDU 2A for approximately 20 months prior to sampling.

FY2019: Four new DLM experiments were started in FY2019. The experiments employed saltstone simulants spiked with both Tc-99 and I-129 and prepared using Lehigh GGBFS to better understand what impact the new slag has on the saltstone hydraulic (i.e., SHC) and transport (i.e., release rates) properties. [SRR-CWDA-2020-00008]

• In February of 2019, four new DLM experiments began.

o These new DLM experiments were designed to better understand what impact the down-selected 60:40 cement-free formulation (SRR-CWDA-2019-00003) would have on the saltstone hydraulic (i.e., SHC) and transport (i.e., release rates) properties.

o Results to date suggest that the 60:40 cement-free formulation is comparable in performance, from a PA perspective, to the historically used 45:45:10 saltstone.

FY2020: Efforts in FY2020 were hindered by the Covid-19 pandemic and additional research projects ongoing at the Savannah River Ecology Laboratory (SREL) (e.g., aqueous and solid phase analysis of waste tank grouts (SRRA151648-000003), mercury leaching from saltstone (SRRA099188-000011)). The end result was that planned activities for FY2020 (i.e.,

monitoring and analysis of ongoing DLM experiments, saltstone degradation analysis, and studies analyzing curing time effects on saltstone properties) were suspended until a future date.

FY2021: In FY2021, X-Ray Diffraction (XRD) spectroscopy and X-Ray Fluorescence (XRF) spectroscopy analyses on pre- and post- DLM saltstone cores was initiated to better understand how saltstones chemical and phase composition evolve over time.

Page 21 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 In addition, in FY2021 work began to develop a detailed XRD user manual (with practical examples) for alternate sample preparation techniques, phase ID, and quantification of cementitious samples using XRD and associated software.

FY2022: Plans for FY2022 focus on collecting empirical data capturing saltstones weathering process and are presented in SRR-CWDA-2021-00087. In particular, analysis of pre- and post-DLM saltstone cores using XRF spectroscopy and powder XRD spectroscopy will be conducted to better understand how saltstones chemical and phase composition evolve over time. A technical report detailing the results of this testing will be issued in FY2022.

In addition, work will continue on development of an XRD user manual initiated in FY2021.

Deliverable: Annual Technical Reports Expected Completion Date: FY2022 Responsibility: SRMC Waste Disposal Authority (WDA), (SREL)

Estimated Cost: FY2022 $150K, FY2023 $150K, FY2024 $150K, FY2025 through FY2026

$0K 2.2.2 Ongoing Studies PA models rely on a number of input parameters to make informed predictions about a systems behavior over long periods of time. It is therefore desirable to reduce uncertainty in these parameters whenever possible. The 2019 SDF PA (SRR-CWDA-2019-00001) suggests that the parameters most important with respect to SDF performance are: infiltration (i.e., High Density Polyethylene [HDPE] and closure cap performance), the hydraulic conductivity of saltstone, water ingestion rate of the receptor, technetium solubility, and saltstone oxidation.

Several of the maintenance activities discussed below are intended to reduce uncertainty around some of these more critical parameters.

WDA has identified multiple areas of interest in regard to research and development activities to be conducted by SREL during FY2022 detailed in SRR-CWDA-2021-00087.

Additional maintenance activities presented in this section focus on meeting information needs relevant to these other aspects of system performance. Various programs discussed below include:

• Long-term behavior of radionuclides in lysimeters

• Cementitious materials degradation due to radiation exposure

• Closure cap performance 2.2.2.1 Long-Term Radiological Lysimeter Program

Description:

Understanding the long-term behavior of radionuclides in soil and cementitious materials is essential to models that project this behavior over thousands of years. The objective of this task is to measure the release from radioactive sources emplaced in lysimeters that are exposed to the outside environment. To this end, a multi-year study is being performed at the Radionuclide Field Lysimeter Experiment Facility (RadFLEx) to evaluate radionuclide fate and transport from sources emplaced in lysimeters that are exposed to the outside Page 22 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 environment. The study will provide additional information about long-term geochemical and transport phenomena that will be used to support the waste release and transport models used in the SDF and Tank Farm PAs.

Measurements target solubility and distribution coefficient (K d ) values in soil and cementitious materials, and colloidal transport of various radionuclides. The total exposure time (in some cases) is anticipated to be as long as 10 years. Releases are determined from the lysimeter leachates collected and analyzed regularly (i.e., monthly or quarterly) in addition to solid phase analysis (i.e., destructive analysis) of select lysimeters after specified environmental exposure times. Lysimeter effluent testing in conjunction with solid phase analysis of the lysimeter cores and source material provides researchers with a robust data set specific to the SRS that can provide less ambiguous assignment of transport mechanisms and bolster confidence in PA modeling assumptions. The radionuclide treatments studied at RadFLEx consist of: 1) an anion group (Tc-99, I-127, and I-129), 2) a cationic gamma group (Co-60, Ba-133, Cs-137, and Eu-152), 3) neptunium (Np-237), 4) plutonium (Pu-239, Pu-240, and Pu-241), and 5) radium (Ra-226).

Radionuclide sources are prepared in the laboratory in two physical forms: 1) filter pita pockets and 2) cementitious pucks. For the filter pita pockets, a liquid radionuclide source is spiked onto a 47mm glass fiber filter and then covered with a second glass fiber filter. The filters are then stitched together using Teflon thread with the radionuclide source sandwiched between the two. Since the glass fiber filters are chemically inert and have limited physical interference, the filter pita pocket sources are representative of soil contamination.

Cementitious pucks (1.25 inches diameter, 0.5 inches thick) are prepared in the laboratory both with and without GGBFS. Radionuclide sources are spiked into the salt solution simulant used in making the cementitious pucks.

To date, lysimeter experiments performed at RadFLEx have proven fruitful, yielding both qualitative (improved mechanistic understanding of the fate and transport of certain radionuclides) and quantitative (sorption coefficients) results. In particular:

• Np breakthrough for both Np(IV) and Np(V) sources has been observed in lysimeter effluent. Np(V) release is two to four orders of magnitude higher than that observed for Np(IV). This data supports the idea that Np(V) mobility is controlled primarily by sorption of the radionuclide to the surrounding environment while Np(IV) release is solubility controlled.

• The concentration of Pu in lysimeter effluents is on the order of E-15 to E-13 mol/L, close to the solubility limits for Pu(IV) hydroxide phases. This data strongly supports the idea that Pu migration is solubility limited.

o The concentration of Pu in lysimeter effluents is below the detection limit for the standard Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) measurement and a low-level radioanalytical technique was used to perform these measurements.

• The spatial distribution of Pu in two field lysimeters that were removed and dissected for analysis, the first with a colloidal PuO 2 (s) source and the second with an emplaced Pu(V)NH 4 (CO 3 )(s) source, both demonstrated greater downward migration than previously observed for PuCl3 , Pu(NO 3 )4 , and Pu(C2 O4 )2 bearing lysimeters. Researchers Page 23 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 have proposed multiple working hypotheses to explain the enhanced transport observed for the PuO 2 (s) and Pu(V)NH 4 (CO 3 )(s) lysimeters.

o Working Hypothesis #1: Transport of Pu as PuO 2 (s) colloids. The Pu(V)NH 4 (CO 3 )(s) source transforms to a PuO 2 (s) phase similar to the one found in Lysimeter 44 (colloidal PuO 2 (s) source, SRRA021685-000008). The Pu colloids allow for enhanced transport of the radionuclide.

o Working Hypothesis #2: Transport is due to differing solubility values in the Pu source material. Evidence from the literature strongly suggests that the oxidized Pu present in Pu(V)NH 4 (CO 3 )(s) will rapidly reduce to Pu(+IV), perhaps as a PuO 2 (s) phase similar to that found in Lysimeter 44 (colloidal PuO 2 (s) source, SRRA021685-000008). Some of the Pu(+IV) present in the PuO 2 (s) phase oxidizes over time to the more mobile Pu(+V) oxidation state and is transported a short distance through the soil prior to being re-reduced and once again forming a PuO 2 (s) phase. The plutonium continues to undergo cycles of re-oxidation followed by re-reduction thereby allowing it to slowly traverse down the lysimeter column.

This mechanism is analogous to the one proposed for mobilization of Np observed in the NpO 2 (s) lysimeter (Lysimeter 32, SRRA021685-000011).

• Desorption experiments using Pu contaminated soils retrieved from the PuO 2 (s) and Pu(V)NH 4 (CO 3 )(s) lysimeters provided conditional desorption distribution coefficients of log K = 4.4 +/- 0.3 mL/g and log K = 3.2 +/- 0.2 mL/g, respectively. There was no apparent difference between unfiltered and ultra-filtered samples during the desorption experiments indicating that either 1) colloids are not present in these samples as hypothesized or 2) colloids sorb strongly to the soil and do not desorb.

Desorption experiments for gamma-emitting radionuclides (Co-60, Ba-133, Cs-137, and Eu-152) sorbed to SRS sediment (Lysimeter 26 at RadFLEx) generated conditional sorption coefficients (29 mL/g, 29 mL/g, 2,200 mL/g, and 4,300 mL/g, respectively) that can be utilized in PA modeling. [SRRA021685-000012] In addition, the study revealed the potential for aging effects on sorption, with both Cs-137 and Eu-152 demonstrating increased affinity for SRS sediment with time. With the exception of cobalt (K d of 29 mL/g measured vs. 40 mL/g modeled in SDF PA), the sorption coefficients determined from this study are favorable (i.e.,

higher) compared to the values currently used in PA modeling. Given this fact and Co-60s negligible contribution to the overall dose predicted in the PA (Table 5.5-2 of SRR-CWDA-2019-00001), the findings of this experimental work should only improve the dose results presented in the 2019 SDF PA. [SRR-CWDA-2019-00001].

Expected Benefit: This task is expected to provide actual site-specific K d values in soil and cementitious materials and colloidal transport measurements for various radionuclides. It will provide additional information about long-term geochemical and transport phenomena that will be used to support the waste release and transport models used in the SDF, FTF, and HTF PAs.

FY2012: Completed the installation of the lysimeter and initiation of the sample collection program. [SRNL-STI-2012-00603]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2013: The concentrations of radionuclides and stable iodine were measured in the effluents from the field lysimeters. [SRR-CWDA-2013-00121]

FY2014: The concentrations of radionuclides (leached from either filter pita pockets or cementitious monoliths) were measured in the effluents from the field lysimeters.

[SRRA021685]

FY2015: Key findings with respect to plutonium and cobalt transport are essentially the same as FY2014. Similarly, lysimeters 29 and 30 had measurable effluent concentrations of Np-237 corresponding to 1.56% and 13.1% of the initial activity added to the source. This was consistent with the higher mobility of pentavalent Np(V), which is the source lysimeters 29 and 30. No breakthrough was apparent for lysimeters 31 and 32 which contained neptunium in the less mobile tetravalent state (Np(IV)). [SRRA021685-000007]

FY2016: Key observations for FY2016 are as follows [SRRA021685-000008]:

• The concentration of Pu in lysimeter effluents were on the order of E-15 to E-13 mol/L.

This was below the detection limit for the standard ICP-MS measurement and a low-level radioanalytical technique was used to perform these measurements.

• Lysimeters containing pentavalent Np(V) sources had measurable breakthrough corresponding to 2.5% and 18.6% of the initial activity added to the source. The variability in these numbers was hypothesized to be caused by heterogeneous flow of water through the lysimeter. During work in FY2016, Np was also observed in the effluent of lysimeter 32, which contains a relatively insoluble NpO 2 source. The observation of Np in the effluent from this lysimeter implies that the NpO 2 was becoming oxidized and releasing Np(V) which can transport through the lysimeter with a relatively low K d .

• Similar to previous years, Co-60 was measured in the effluent of all lysimeters containing gamma emitting radionuclides. However, the concentrations were much lower than previous sampling events. The majority of the Co-60 was released within the first two years of the experiment and concentrations are now close to detection limits. For all lysimeters containing the gamma suite of radionuclides, the concentration of Co-60 in the lysimeter effluent was lowest for those with a filter pita pocket source.

• There was a high degree of variability in the amount of water flowing through each lysimeter. It was hypothesized this was due to heterogeneous flow of water through the soil and variations in the localized climate (i.e., wind and rain patterns) above the four-inch diameter lysimeter opening.

FY2017: Two reports were issued in September 2017.

The first report (SRRA021685-000008) documented concentrations measured in field lysimeter effluents during FY2017. The trends/findings concerning Np(V) and Np(IV) release, Co-60 effluent concentrations, and heterogeneous flow reported in FY2016 continued in FY2017.

The second report (SRRA021685-000009) documented the detailed solid phase analysis of a field lysimeter with an emplaced colloidal PuO 2 (s) source.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2018: Two reports were issued in September 2018.

The first report (SRRA021685-000011) documented concentrations measured in field lysimeter effluents from the fourth quarter of FY2017 and the second quarter of FY2018. The trends/findings concerning Np(IV) and Np(V) release, Co-60 effluent concentrations, and heterogeneous flow reported in FY2016 and FY2017 continued in FY2018 with the one caveat being that Co-60 was only present in measurable concentrations in Lysimeter 4 and 5s effluent. (Note that these two lysimeters possess a cementitious puck source without GGBFS).

The second report (SRRA021685-000010) documented the detailed solid phase analysis of a field lysimeter (Lysimeter 41) with an emplaced Pu(V)NH 4 (CO 3 )(s) source.

FY2019: In FY2019, new radionuclide sources were prepared for deployment lysimeters (installed in FY2020). Lysimeter effluent continued to be collected and analyzed during FY2019 and desorption experiments for gamma-emitting radionuclides (Co-60, Ba-133, Cs-137, and Eu-152) sorbed to SRS sediment were initiated.

FY2020: In FY2020, fifteen new lysimeters, containing plutonium, neptunium, iodine, or radium sources were installed at RadFLEx (see highlighted rows in Table 2.2-3). Effluent samples were collected at least quarterly from the field lysimeters and transported to Clemson University for analysis. Monthly sampling and analysis were performed for lysimeters where radionuclides have previously been detected in the leachate (i.e., Lysimeter 30 and Lysimeter 32 which utilize a Np(V) and a Np(IV) source, respectively).

Two reports were issued in FY2020.

The first report (SRRA021685-000013) documented concentrations measured in field lysimeter effluents from the third quarter of FY2018 through the fourth quarter of FY2019.

The second report (SRRA021685-000012) documented desorption experiments for gamma-emitting radionuclides sorbed to SRS sediment. The study used sediment taken from a previously removed lysimeter (Lysimeter 26 at RADFLEx) and generated conditional sorption coefficients (i.e., K d values) for Co-60, Ba-133, Cs-137, and Eu-152 of 29 mL/g, 29 mL/g, 2,200 mL/g, and 4,300 mL/g, respectively, that can be utilized in future PA modeling. In addition, the study revealed the potential for aging effects on sorption, with both Cs-137 and Eu-152 demonstrating increased affinity for SRS sediment with time. With the exception of cobalt (K d of 29 mL/g measured vs. 40 mL/g modeled in FY2019 SDF PA), the sorption coefficients determined from this study are favorable (i.e., higher) compared to the values currently used in PA modeling. Given this fact and Co-60s negligible contribution to the overall dose predicted in the PA (Table 5.5-2 of SRR-CWDA-2019-00001), the findings of this experimental work should only improve the dose results presented in the 2019 SDF PA.

[SRR-CWDA-2019-00001]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Table 2.2-3: Radionuclide Field Lysimeter Experiment (RadFLEx) Lysimeters Description Lysimeter Description Lysimeter Empty 1-3 Pu(IV)-oxalate, grass 13/9 Empty 2-3 Pu(V)NH4 (CO3)/OM, 2 yr 14-2 Cement Control 3 Saltstone Control 15 Cement gamma suite 4 Saltstone gamma suite 16 Cement gamma suite 5 Saltstone gamma suite 17 Cement gamma Suite 6 Saltstone gamma suite 18 Cement Tc & I (capped) 7 Saltstone Tc & I (capped) 19 Np(IV)O 2 , 2 yr 8-2 Pu(V)NH4 (CO3)/OM, 4 yr 20-2 Ra-226/Sand 9-2 Pu(V)NH4 (CO3)/OM, 10 yr 21-3 Pu(IV)-oxalate, grass 10 Pu(V)NH4(CO3)/OM 22 Pu(IV)-oxalate, grass 11 Pu(V)NH4(CO3)/OM 23 Grass control 12 Instrumented control 24 Sediment Control 25 Instrumented Control 37 Ra-226 26-2 Pu(V)NH4 (CO3)/Sand, 2 yr 38-3 gamma suite 27 Pu(IV)oxalate 39 gamma suite 28 Pu(IV)oxalate 40 Np(IV)O 2 , 6 yr 29-2 Pu(V)NH4 (CO3)/Sand, 4 yr 41-3 Np(V)nitrate 30 Pu(V)NH4(CO3) 42 Np(V)-nitrate, 2 yr 31-2 Pu(V)NH4(CO3) 43 Np(IV)O 2 32 Pu(V)NH4 (CO3)/Sand, 10 yr 44-3 Np(V)-nitrate, 6 yr 33-2 Pu colloids 45 Pu(III)oxalate 34 Pu colloids 46 Pu(III)oxalate 35 I-129 Cement 47-2 Ra-226 36 I-129 Cement 48-2 FY2021: In FY2021, effluent continued to be collected and analyzed for RadFLExs active lysimeters (including the 15 new lysimeters installed in FY2020). Additionally, a technical memo (SRRA175647-000002) detailing different analytical techniques for measuring radium and iodine in lysimeter effluent, was issued by Clemson University in support of the RadFLEx project. The memo discusses the detection limits, ease, and cost associated with each analytical method allowing the Liquid Waste Organization (LWO) to make an informed decision regarding what analytical method best suits the needs of the research both scientifically and financially.

FY2022: For FY2022, nine RadFLEx lysimeters will undergo retrieval and solid phase analysis. Four gamma suite lysimeters (lysimeters containing a Ba 137, Eu-152, Co-60, and Cs 137 source) are to undergo non-destructive analysis. The five remaining lysimeters, all possessing a Pu source, will undergo destructive analysis (i.e., soil dissection, soil digestion, and analytical measurements on the resulting digestate). Solid phase analysis of these nine lysimeters will generate high pedigree PA data and justification for selection of geochemical conceptual models.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Deliverable: Annual Leachate Report Expected Completion Date: FY2030 Responsibility: SRMC WDA (Savannah River National Lab [SRNL] and Clemson)

Estimated Cost: FY2022 through FY2026 $110K/yr 2.2.2.2 Studies Related to Cementitious Materials Degradation Due to Radiation Damage

Description:

Saltstone is a cementitious waste form. As such, damage to cementitious materials from radiolytic mechanisms must be understood. A literature search will be conducted to gain a better understanding of the potential degradation of cementitious materials exposed to radiation.

Expected Benefit: This activity is expected to produce a baseline of knowledge concerning cementitious degradation due to radiolytic mechanisms over long periods to inform degradation assumptions. The data provided from this effort will also inform the HTF and FTF modeling.

FY2022: A technical report documenting the results of the literature search will be issued in FY2022.

Deliverable: Technical Report Expected Completion Date: FY2022 Responsibility: SRMC WDA Estimated Cost: FY2022 $7K, FY2023 through FY2025 $0/yr 2.2.2.3 Closure Cap Long-Term Performance

Description:

This task involved research and development regarding the long-term performance of the closure cap as performed by the University of Virginia. The work is intended to derive analysis results to replace the current engineered closure cap baseline for the SDF from the design defined in SRR-CWDA-2018-00087 (which assumes the material properties as documented in WSRC-STI-2008-00244). Particular emphasis will be directed towards the following scope:

• Establishing infiltration rates through the bottom of the engineered closure cap system over time that can be utilized as an upper boundary condition to vadose zone flow and transport modeling.

• Determining uncertainty ranges in the infiltration rates that can be utilized in alternate infiltration scenarios for PA modeling.

• Providing recommendations for any improvements to the methods currently employed to degrade the performance of the sand drainage layer above the SDUs.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022

• Comparison to alternate calculation methods/codes or to measured/literature values to provide model support for baseline analysis.

Expected Benefit: This effort will validate assumptions in the PAs concerning the rate of closure cap infiltration as well as the behavior of the drainage layer above each SDF disposal unit.

FY2018: A Closure Cap document (SRRA107772-000009, Predicting Long-Term Percolation from the SDF Closure Cap) was issued in FY2018. This report updated the inputs and assumptions from the 2008 estimates (WSRC-STI-2008-00244) and developed a revised model using WinUNSAT-H (a variably saturated flow code that has been used extensively over the past two decades for predicting the hydrology of covers for waste containment systems). During report development, it was determined that a number of assumptions used to develop the 2008 estimates had no supporting bases and therefore had utilized very conservative assumptions. These assumptions were re-evaluated, and more realistic assumptions were developed based on field observations, recent laboratory analyses, and subject matter expertise. Justifications for the revised assumptions, and the updated modeling inputs were documented in SRRA107772-000009. The resulting infiltration (or percolation) estimates was used in the SDF PA modeling for the 2019 SDF PA revision. Updating the inputs and assumptions from the 2008 estimates provides lower infiltration rates used in the 2019 SDF PA revision.

FY2021: Closure cap analyses to address NRC RSIs (ML20254A003) include additional literature reviews and modeling to better characterize and evaluate uncertainties associated with the long-term performance of the closure cap. To support this work updates to the probable maximum precipitation (PMP) estimate and erosion rates are also being evaluated.

The resulting infiltration (or percolation) estimates will be used in the upcoming FTF and HTF PA revisions (See Section 3.4).

The FTF and HTF closure caps are primarily intended to provide physical stabilization of the site, minimize infiltration, and provide a deterrent to intrusion. The layers and materials of the current closure cap design are based on the FTF Closure Cap Concept and Infiltration Estimates (WSRC-STI-2007-00184). The design was updated to apply to the HTF via H-Area Tank Farm Closure Cap and Infiltration (SRNL-ESB-2008-00023). The geometry and the layout of the closure caps were further updated (SRR-CWDA-2019-00080; SRR-CWDA-2019-00081) to incorporate an increased slope at the surface (i.e., 4% slope instead of 1.5%

slope) to meet closure requirements specified in the regulation SWM: Solid Waste Landfills and Structural Fill (SCDHEC R.61-107.19). FTF and HTF closure cap performance over time was analyzed in SRRA162682-000002, Predicting Long-Term Percolation From the HTF and FTF Closure Caps, Report No. GENV-20-09. The Tank Farm closure cap designs are preliminary; however, they provide sufficient information for planning purposes, evaluating the closure cap configuration relative to its constructability and functionality, and for estimating infiltration rates over time through modeling.

SRR-CWDA-2021-00043, Erosion Analysis for the H-Tank Farm and F-Tank Farm Facilities, has been issued building upon the FTF and HTF closure caps designs and the previously issued SDF analysis, SRR-CWDA-2021-00035, Erosion Analysis for the Saltstone Disposal Facility.

The analysis utilizes the Revised Universal Soil Loss Equation (RUSLE) to determine the Page 29 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 average annual rate of soil loss due to erosion. SRR-CWDA-2021-00076, Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates was issued in September 2021 and provides a range of infiltration rates for use in the PA models.

FY2022: No Closure Cap design activities planned in FY2022.

Deliverable: Technical Report for Tank Farm Closure Cap, Section 3.2.3 Completion Date: FY2021 Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0/yr 2.2.3 To Be Determined Out-Year Testing

Description:

For FY2023 and beyond, testing has not been finalized. Future testing will be determined based on information needs identified in the SDF PA revision (discussed in Section 2.2.1).

Responsibility: SRMC WDA Estimated Cost: FY2023 through FY2026 $0/yr 2.3 Saltstone Disposal Facility Performance Assessment Planned Review, Analysis, and Schedules DOE M 435.1-1 requires the ongoing maintenance of all PAs. This maintenance includes a series of activities that must be performed on an annual basis. This section describes the activities required every year in support of the SDF PA. All cost estimates are assumed bounding so no increases due to escalation are applied.

2.3.1 Maintain Saltstone Disposal Facility Performance Assessment Control through Unreviewed Waste Management Question Process

Description:

A formal system to evaluate disposal practice changes and proposed actions is in place for the SRS LW Facilities and is known as the UWMQ process. For SDF, the UWMQ process consists of providing UWMQEs of proposed activities or new information to ensure that the assumptions, results, and conclusions of the current PA, any current SAs, the 3116 Waste Determination, and the CA remain valid, and the changes are within the bounds of the DAS.

If identified through the UWMQ process that a proposed activity or new information is outside the bounds of the current analyses, new SAs are prepared to update the technical baseline.

UWMQEs and SAs will continue to be required throughout the life of the facility. For planning purposes, the estimated cost assumes that 12 UWMQEs will be prepared in FY2022 (assumptions remaining at 12 for each out-year). The estimated cost does not reflect the cost of any emergent SDF SAs. Any planned PAs/SAs for SDF are captured in Section 2.4.

One UWMQE was performed in FY2021 for the SDF. The UWMQE was entitled Evaluation of the Assumed 40,000 gallons of Saltstone Produced with Noncompliant Slag (SRR-UWMQE-2021-00001). On January 21, 2021, new information was discovered that the slag Page 30 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 in the dry feed silos at the Saltstone Production Facility (SPF) did not meet procurement specifications. Specifically, the slag provided by the vendor was actually a mixture of materials: slag (50% to 70%), cement (16% to 39%), and limestone (8% to 11%) (SRR-UWMQE-2021-00001). Prior to identification of this noncompliance, approximately 36,000 gallons of saltstone grout had been produced with the noncompliant slag and was disposed of into SDU 6 (X-CLC-Z-00092). For added conservatism, this UWMQE assumes a volume of 40,000 gallons of saltstone grout was produced with the noncompliant slag and disposed of into SDU 6 (X-CLC-Z-00092).

Deliverable: Provide UWMQEs and UWMQ procedure support, as needed to support SDF operations Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $85K/yr 2.3.2 Prepare Annual Update to Performance Assessment Maintenance Program

Description:

The purpose of the LW PA Maintenance Program is to support the continued adequacy of the current PA and SAs and to increase confidence in the results. Every year the annual LW PA Maintenance Program FY update is prepared and provided to DOE. Plan preparation will include review of outstanding PA and SA comments and recommendations (noted in Sections 2.2.1 and 2.2.2). The update outlines planned work for each FY. The cost of preparing the update will be shared between SDF, FTF, and HTF. See the activities described in Section 3.1.2 for FTF and HTF.

Deliverable: Issue a FY LW PA Maintenance Program Annual Update Expected Completion Date: 2Q-3QFY (issued annually)

Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $15K/yr 2.3.3 Provide General Technical Support on Saltstone Disposal Facility Performance Assessment Issues

Description:

This task is to provide general technical and programmatic support on SDF PA and SA issues, NRC 3116 monitoring activities, and other regulatory issues that affect SDF operations. Activities include testing and research activity support, general project and operations support, supporting NRC on-site observation visits and technical reviews, responding to NRC RSIs, RAIs, and development of resolution path forward for NRC open items. Research activity support includes monitoring of research done by outside agencies (e.g., academic research, work conducted for Hanford) as well as research performed on-site (e.g., SRNL, SREL). These activities also include support on interactions with South Carolina Department of Health and Environmental Control (SCDHEC), SRS Citizens Advisory Board (CAB), the LFRG, National Academy of Sciences, and other regulatory and stakeholder bodies.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Since July 2020, the NRC has been reviewing the 2019 SDF PA as part of the NRCs monitoring role under Section 3116(b) of the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA Section 3116).

The NRC provided a set of RSIs in October 2020 (ML20254A003). These RSIs requested that additional models be developed to better enhance the understanding of combined uncertainties related to the long-term performance and potential degradation of various components and features associated with the SDF closure system. Due to the sequential nature of the RSIs, wherein some RSIs had to be responded to as prerequisites to other RSIs, the preparation of the responses to the RSIs was performed sequentially, resulting in multiple documents being prepared from March to August 2021, which are summarized in Summary of RSI Response Documents for the SDF PA, SRR-CWDA-2021-00068.

In addition, as part of their review, the NRC has issued two letters as of the end of FY21 with RAIs. [ML21040A492, ML21133A296] The first letter had twelve RAIs as well as six CCs.

Those RAIs and CCs were addressed in SRR-CWDA-2021-00047, Comment Response Matrix for the First Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, issued in July 2021.

The NRC issued the second letter in June 2021 and that letter included an additional sixteen RAIs and fourteen CCs. On August 18, 2021, an initial round of responses to this second set of NRC RAIs and CCs was issued via SRR-CWDA-2021-00072, Comment Response Matrix for the Second Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Revision 0. SRR-CWDA-2021-00072 was subsequently revised to include the complete set of RAI and CC responses and Revision 1 was issued in November 2021.

Deliverable: Provide ongoing technical support on regulatory and policy issues/activities affecting SDF operations Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $575K/yr 2.3.4 Develop and Maintain Performance Assessment Model Archive and Revision Control

Description:

This task established software and hardware resources for archiving development and final PA modeling files to a read-only storage medium. In FY2014, capital infrastructure improvements were enacted on the site network, allowing for faster communication between SRNLs high performance computing network and SRMC WDA servers. This improvement increased the rate for file transfers between the two systems. SDF modeling files (for both PORFLOW and GoldSim) were copied to electronic storage devices. The storage devices are maintained onsite by SRMC WDA, within a cipher-locked facility. The properties of the electronic files were set to read-only. Copies of files can be provided upon request. As needed, Page 32 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 additional storage devices will be purchased to provide sufficient disk space for maintaining a record of all related model files.

Deliverable: Establish process (completed in FY2014) and maintain after implementation Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $5K/yr 2.3.5 Conduct Annual Saltstone Disposal Facility Performance Assessment Validation

Description:

The purpose of the LW PA Maintenance Program is to confirm the continued adequacy of the SDF PA and to increase confidence in the results of that PA. A requirement of the maintenance program is to conduct an annual review of the disposal facility activities.

The annual PA review is conducted in a systematic manner that incorporates the following considerations:

1. Radionuclide inventories, waste volumes, and waste types disposed throughout the year

2. Testing and research activities performed during the year

3. Results of PA monitoring conducted in accordance with the SDF PA Monitoring Plan for the SDF The above factors are reviewed annually to confirm the adequacy of the current facility PA, and to evaluate the need to conduct SAs or prepare a revision to the PA. The results of the review are documented in an annual summary report for the current SDF PA and submitted to DOE.

Deliverable: Issue a FY PA annual summary report Expected Completion Date: 2QFY (issued annually)

Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $15K/yr 2.3.6 Maintain Saltstone Disposal Facility Performance Assessment Closure Plan

Description:

The closure plan that complies with DOE M 435.1-1 for SDF must be maintained and modified as needed to reflect facility changes. The SDF closure plan is reviewed annually to determine if a revision is required.

An update of the SDF Closure Plan (SRR-CWDA-2020-00005) was issued in August 2020 based on issuance of the SDF PA (SRR-CWDA-2019-00001) in May 2020.

Deliverable: Review closure plan annually and revise as necessary Expected Completion Date: Reviewed annually Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $5K/yr Page 33 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 2.3.7 Maintain Saltstone Disposal Facility Performance Assessment Monitoring Plan

Description:

The SDF PA Monitoring Plan that complies with DOE M 435.1-1 must be maintained and modified as needed to reflect facility changes. The SDF PA Monitoring Plan is reviewed annually to determine if a revision is required.

An update of the SDF PA Monitoring Plan (SRR-CWDA-2020-00006) was issued in August 2020 based on issuance of the SDF PA (SRR-CWDA-2019-00001) in March 2020 to capture changes in the recently revised 2019 SDF PA and to incorporate ongoing activities as required by the DAS. [WDPD-20-32].

Deliverable: Review the SDF PA Monitoring Plan annually and revise as necessary Expected Completion Date: Review annually Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $5K/yr 2.3.8 Status of DAS Conditions/Limits In FY2021 there were three DAS conditions in effect for SDF (per WDPD-20-32):

1. Changes to SDF Waste Acceptance Criteria shall be conservatively based on the Performance Assessment Retreating Closure Cap case analysis and any increase of I -129 concentrations shall be limited by a factor of 2. All Waste Acceptance Criteria (WAC) changes must be reviewed and approved by the Site LFRG member prior to implementation.

2. A Closure PA, including final closure cap design and appropriate erosion analysis, shall be developed and submitted to the LFRG for review and approval prior to closure cap construction.

3. Within 365 days of the DAS issuance, SRS shall submit to DOE Headquarters revised technical basis documents (monitoring plan, maintenance plan, WAC, etc.) for review or a justification provided as to why the existing documents are consistent with the PA.

Condition 3 pertains to implementation of the 2019 SDF PA. Conditions 1 and 2 were applied in response to one Secondary Issue, SDFS06PA1202 (LFRG_03-02-2020), which is the only remaining open issue.

Conditions 1 and 3 were closed in FY2020 with the issuance of the technical basis documents.

2.3.9 LFRG Key and Secondary Issues The LFRG review of the 2019 SDF PA initially identified 2 Key Issues and 11 Secondary Issues; with the exception of SDFS06PA1202, all of the other Key Issues and Secondary Issues were addressed and closed prior to issuing the 2019 SDF PA. The remaining open issue, SDFS06PA1202: Preliminary Cap Design Does Not Include Adequate Erosion Analysis, will be closed once an adequate erosion analysis has been completed for the proposed closure cap, and any potential impacts from future erosion are evaluated.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 2.4 Saltstone Disposal Facility Performance Assessment Development/Revisions The 2019 SDF PA provides the technical basis and results to be used in subsequent documents to demonstrate compliance with pertinent requirements of DOE M 435.1-1 and associated references and Title 10 Code of Federal Regulations (CFR) Part 61, Subpart C as required by NDAA Section 3116. The revised 2019 SDF PA (SRR-CWDA-2019-00001) was issued in March 2020 and issuance of an updated DAS was received in June 2020. [WDPD-20-32]

2.4.1 Prepare Out-Year Saltstone Disposal Facility Performance Assessment Revisions

Description:

The initial SDF PA was issued and implemented in 2009. In FY2018, work was begun to update and revise the SDF PA. The revised 2019 SDF PA (SRR-CWDA-2019-00001) was issued in March 2020 and issuance of an updated DAS was received in June 2020.

[WDPD-20-32] The SDF PA (SRR-CWDA-2019-00001) includes the following:

• Analyses and results contained in all SAs that have been completed to date;

• Analyses and results of all UWMQEs completed to date;

• Consideration of new information generated through applied research, including updated information about the material properties of saltstone and the transport behavior of I-129 and Tc-99 (from DLM testing);

• Updates to disposal unit design;

• Revised infiltration rates based on updated closure cap modeling from expert elicitation;

• Revised cementitious degradation rates based on upd ated material properties and recommended approaches informed by expert elicitation;

• Incorporation of an updated General Separations Area Flow Model using calibration targets from wells in Z Area;

• Changes in site future land use plans or closure plans; and

• Changes to PA guidance documents requirements.

No future PA revisions are scheduled at this time.

Deliverable: PA LFRG review draft issued - Complete PA Revision 0 issuance - Complete Expected Completion Date: FY2019 (PA LFRG review draft) - Summer 2019 - Complete FY2020 (PA Revision 0) - March 2020 - Complete Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0/yr 2.4.2 Saltstone Disposal Facility Performance Assessment Maintenance Activities The LFRG performed a review of the revised 2019 SDF PA (SRR-CWDA-2019-00001, Revision B). The Review Team evaluated the SRS SDF PA and associated WAC and Change Control procedure against the requirements in DOE Manual 435.1-1, Radioactive Waste Page 35 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Management, and the guidance provided in the DAS and Tank Closure Documentation Technical Standard (DOE-STD-5002-2017).

WDA has committed to performing several maintenance activities in support of resolving Secondary Issue SDF-S06-PA12-02 [Lack of Cap Design Including Proper Erosion Analysis]

and additional Observations identified as part of the LFRG review of the SDF PA (LFRG_03-02-2020):

• Update the PMP event value o Document the development of the value via technical report.

• Use updated PMP value to perform an erosion/stability analysis based on the current closure cap design.

o Erosion analysis should consider the most plausible erosion conditions and closure cap evolution o Erosion analysis should consider head-cut erosion/gully or channel formation o Erosion analysis should consider potential impacts from clogged drainage layers o Based on the erosion/stability analyses, consider if the current design requires any changes and implement the changes.

o Document analyses via technical report.

• If the erosion analysis indicates that significant erosion is probable, develop a more appropriate set of infiltration rates for Compliance Case, Realistic Case, and Pessimistic Case conditions.

o Document development of new erosion rates via technical report.

• Perform a literature review to develop a better understanding of diffusion in partially saturated media (soils) o Document the literature review and enhanced understanding via a technical report.

o Based on enhanced understanding of diffusion in partially saturated media, consider whether changes need to be implemented in the PA models

• Review the SDF GoldSim Model to:

o Identify parameters related to features or processes that may perform better than expected (or better than modeled) o Identify time-dependent events that could impact model results (e.g., possible step changes) o Determine if parameters or conditions could be modeled differently within the probabilistic simulations in ways that could provide insights related to superior performance affects Page 36 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 For example, if the SDUs are better barrier to release, then suddenly fail in some way, how might that impact results?

o Document changes to the SDF GoldSim Model via memo and Changed Model Check form.

• Analyze historical well data at or near SRS to quantify the temporal and spatial probabilities of drilling o Document analysis via technical report.

o Use the analysis to develop appropriate stochastic model inputs for probabilistic simulation with respect to Inadvertent Human Intruder (IHI) events.

• Based on the above actions, revise models and re-run Compliance Case, Realistic Case, and Pessimistic Case (for both MOP and IHI results) and rerun the Probabilistic realizations and analyses. Document all new mod eling and model analyses via UWMQE or SA, as appropriate.

Deliverable: Incorporate LFRG issue resolutions into PA models - FY2022 Expected Completion Date: FY2022 Responsibility: SRMC WDA Estimated Cost: FY2022 $50K, FY2023 through FY2026 $0/yr 2.4.3 Saltstone Disposal Facility Special Analyses In FY2020, an SA was initiated to evaluate the following new information relative to potential impacts on the long-term performance of the SDF:

1. An improved normative analysis was developed to better determine the chemical and mineralogical constituents for concrete used in constructing SDUs and for the cementitious waste form known as saltstone.

2. Modeling properties have been developed to evaluate the performance of two proposed cementitious materials (SDU Concrete Mix 3B and Cement Free Saltstone) which are currently being considered for deployment.

3. An equivalent set of normative analyses for two new cementitious materials (SDU Concrete Mix 3B Concrete and Cement Free Saltstone) was also developed.

4. The normative analyses were used to update cementitious degradation rates for existing cementitious materials and for the new cementitious materials.

The primary driver for evaluating this new information is to determine the potential impacts from using the two proposed cementitious materials (SDU Concrete Mix 3B Concrete and Cement Free Saltstone). The FY2020 SDF SA (SRR-CWDA-2020-00064) was issued in 1QFY2021. The FY2020 SDF SA evaluated the performance of SDU Concrete Mix 3B and Cement Free saltstone relative to the 2019 SDF PA.

Page 37 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 The DOE-SR approved the FY2020 SDF SA (WDPD-21-40) and minor edits were incorporated as Revision 1 to address observations that were identified during the DOE-SR review. Revision 1 of the FY2020 SDF SA, was issued in May 2021.

No additional new SAs are scheduled to be initiated in FY2022.

Deliverable: Technical Report - FY2020 SDF SA (SRR-CWDA-2020-00064)

Expected Completion Date: Complete Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0/yr 2.5 Summary Table for the SDF PA Maintenance Program Table 2.5-1 summarizes the estimated expenditures by activity and FY. Table A.1-1 contains a summary of the combined estimated expenditures for all the LW facility PA maintenance activities. This Implementation Plan reflects the PA related activities in the annual operating plan for the current FY and the projected out-year activities for estimation purposes.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Table 2.5-1: Summary for the Saltstone Disposal Facility Performance Assessment Maintenance Program ($K)

Section Maintenance Activity FY22 FY23 FY24 FY25 FY26 Contaminant Leaching Characteristics from 2.2.1 150 150 150 0 0 Saltstone Monolith 2.2.2.1 Long-Term Radiological Lysimeter Program 55 55 55 55 55 Studies Related to Concrete Degradation Due to 2.2.2.2 7 0 0 0 0 Radiation Damage Closure Cap Drainage Layer Long-Term 2.2.2.3 0 0 0 0 0 Performance 2.2.4 To Be Determined Out-Year Testing 0 0 0 0 0 Testing and Research Total 212 205 205 55 55 Maintain SDF PA Control Through UWMQ 2.3.1 85 85 85 85 85 Process Prepare Annual Update to PA Maintenance 2.3.2 15 15 15 15 15 Program Provide General Technical Support on SDF PA 2.3.3 575 575 575 575 575 Issues Develop and Maintain PA Model Revision 2.3.4 5 5 5 5 5 Archive and Revision Control 2.3.5 Conduct Annual SDF PA Validation 15 15 15 15 15 2.3.6 Maintain SDF Closure Plan 5 5 5 5 5 2.3.7 Maintain SDF PA Monitoring Plan 5 5 5 5 5 Annual Tasks Total 705 705 705 705 705 2.4.1 Prepare Out-Year SDF PA Revisions 0 0 0 0 0 2.4.2 SDF PA Maintenance Activities 50 0 0 0 0 2.4.3 SDF Special Analyses 0 0 0 0 0 PA Development/Revisions Total 50 0 0 0 0 SDF PA COMPILED TOTAL 917 910 910 760 760 Page 39 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 3.0 F-AREA AND H-AREA TANK FARMS 3.1 Tank Farm Facilities Monitoring As required by the Consolidated General Closure Plan for F-Area and H-Area Waste Tank Systems (SRR-CWDA-2017-00015), groundwater sampling will be conducted during the interim period from the time individual waste tanks and ancillary equipment are removed from service, through post-closure groundwater monitoring as defined in final Record of Decision (ROD) documents for the FTF and HTF Operable Units (OUs). In December 2012, the EPA and SCDHEC approved new Sampling and Analysis Plans (SAPs) for both FTF and HTF. The approved F-Area Tank Farm Groundwater Sampling and Analysis Plan (SRNS-RP-2012-00287) and the H-Area Tank Farm Groundwater Monitoring Plan and Sampling and Analysis Plan (SRNS-RP-2012-00146) provide specific details of the groundwater monitoring programs.

Monitoring is performed by SRNS with the latest groundwater monitoring results for the Tank Farms contained in the report, 2021 Annual Groundwater Monitoring Report for the F- and H-Area Radioactive Liquid Waste Tank Farms, SRNS-RP-2022-00076 issued in March 2022.

3.2 Tank Farm Performance Assessment Testing & Research Activities This section of the LW PA Maintenance Program contains PA-related testing and research activities identified as part of the ongoing maintenance of the FTF and HTF PAs. The PA testing and research discussion within this section is intended to address combined testing and research activities for both FTF and HTF. No testing and research activities unique to a specific Tank Farm have been identified at this time.

Issuance of the FTF PA and the Basis for Section 3116 Determination for Closure of F-Tank Farm at the Savannah River Site (DOE/SRS-WD-2012-001) occurred in FY2012. In the U.S. Nuclear Regulatory Commission Planned Monitoring Activities for F-Area Tank Farm at the Savannah River Site (ML12345A322), the NRC made recommendations, with respect to the various monitoring factors identified by the NRC, for DOE to consider during maintenance and monitoring of the FTF PA (documented in Appendix A of ML12345A322). Subsequent to issuance of the FTF Monitoring Plan, the NRC issued an HTF TER. The recommendations included in the HTF TER and associated transmittal letter (provided subsequent to the FTF Monitoring Plan) were considered by DOE within the Nuclear Regulatory Commissions H-Tank Farm Technical Evaluation Reports Recommendations - Department of Energys Activity Summary Matrix.

[SRR-CWDA-2014-00080]

The NRC revised the NRC issued Monitoring Plan for FTF to include both FTF and HTF in 2015.

The revised plan addresses the key monitoring areas for both tank farms. [ML15238A761] In the context of testing and research activities related to the FTF and HTF, the revised Monitoring Plan includes recommendations from the initial NRC FTF Monitoring Plan (ML12345A322) and any NRC TRRs issued subsequent to the NRC Monitoring Plan (see Appendix C). These recommendations will require further evaluation to determine how and when they should be addressed. The NRC recommendations are provided in Appendix C of this LW PA Maintenance Program Implementation Plan in the context of testing and research activities related to the FTF and HTF. In addition, Appendix C also contains NRC recommendations captured from NRC TRRs.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 3.2.1 Tank Residual Characterization These tasks involve measurements and methods that will improve upon current knowledge of materials remaining in the waste tanks at operational closure. Some maintenance activities established under the SDF maintenance program (Section 2.0) may also inform the FTF PA and HTF PA such as those concerning cementitious degradation, soil parameters, and fracture formation.

3.2.1.1 Waste Release Studies

Description:

Through the NDAA Section 3116(a) consultation process, the NRC observed that uncertainties associated with the FTF PA doses might prevent DOE from meeting the 10 CFR Part 61, Subpart C performance objectives, particularly with regard to plutonium-related modeling assumptions. The NRC staffs primary concern was that the timing of the FTF PA peak dose could be shifted into their period of performance (10,000 years) if certain assumptions were incorrect. This peak dose is principally associated with the residual Pu-239 inventory in Tank 18. The NRCs TER recommends that DOE provide additional model support to further reduce the uncertainty surrounding PA assumptions that, if found to be significantly non-conservative, could result in this peak dose shifting into a 10,000-year performance period. [ML112371715]

FY2013: An experimental plan was developed in FY2013 to provide additional information regarding the residual waste solubility assumptions used in the FTF and HTF PA waste release models (WRMs). This task was to be performed in two parts, the first part being development of the test plan and methods and the second part being conducting the actual waste testing with simulants and tank samples. The first part was completed in FY2013. [SRNL-RP-2013-00203]

FY2014: The overall objective of the task is to provide additional information regarding the residual waste solubility assumptions used in the FTF and HTF PA WRMs by developing a series of analytic methods to be used to test the solubility of plutonium, neptunium, uranium, and technetium under various simulated waste tank chemistry conditions using actual waste tank residuals. Waste release testing using simulants was initiated and the results were documented in Determining the Release of Radionuclides from Tank Waste Residual Solids.

[SRNL-STI-2014-00456]

FY2015: Waste release testing was performed in FY2015 in the areas of pore water development (including testing to understand and control stabilities of Oxidized Region II and Oxidized Region III) and surrogates solid testing (zero-head space and open-head space with O 2 and CO 2 present for Oxidized Region II and Oxidized Region III). The results of this testing were documented in an FY2015 testing report (Determining the Release of Radionuclides from Tank Waste Residual Solids: FY2015 Report, SRNL-STI-2015-00446) in anticipation of actual waste testing in FY2016.

FY2016: Testing of actual waste (i.e., Tank 18 residuals) was performed in FY2016 using the methodologies developed to date. The solubilities of Pu, Np, U, and Tc were tested under simulated waste tank chemistry conditions using Tank 18 residual waste samples, with the results documented in Determining the Release of Radionuclides from Tank Waste Residual Solids: FY2016 Report (SRNL-STI-2016-00432).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2017: Based on the successful testing of Tank 18 residuals in FY2016, the decision was made to test the residual solids from Tank 12. Tank 12 was an acid -cleaned tank versus the mechanical-only cleaning conducted on Tank 18 thus providing additional waste release data for comparison. In addition, Tank 12 is the tank which drives currently calculated doses in HTF modeling. Since I-129 is the radionuclide that drives the calculated dose peak, iodine was also analyzed in addition to Pu, Np, U and Tc as done for Tank 18. In FY2017 the Technical Task Request was generated by SRR, Waste Release Testing Program (G-TTR-H-00014), and the Task Technical and Quality Assurance Plan (TTQAP) was generated by SRNL, Task Technical and Quality Assurance Plan for Tank 12 Waste Residual Radionuclide Release Testing (SRNL-RP-2017-00411). The scope defined by the TTQAP in FY2017 included procurement of test equipment and initial chemical preparation of the Tank 12 solids.

New equipment procurement was necessary as the equipment used for Tank 18 testing had been discarded during the SRNL High-Level Caves renovations.

FY2018: The remaining scope of the TTQAP was completed in FY2018. Testing of a Tank 12H residual waste sample was performed in FY2018 using the same basic methodology used for the Tank 18F residual waste testing, with some minor changes made to incorporate lessons learned. The test setup modifications and the initial Tank 12H waste release testing results are documented in Determining the Release of Radionuclides from Tank 12H Waste Residual Solids Following Tank Closure (SRNL-STI-2018-00484).

FY2019: SRNL-STI-2018-00484, Revision 1 (Determining the Release of Radionuclides from Tank 12H Waste Residual Solids Following Tank Closure) was issued in FY2019. This revision captured the final Tank 12H waste release testing results and addressed outstanding comments against the waste release testing reports. An evaluation of the testing results, in particular the I-129 results, were documented in a revision to Evaluation of Waste Release Testing Results against the Tank Farm Performance Assessment Waste Release Model (SRR-CWDA-2016-00086). The measured solubilities for the tested elements are consistent for the residuals from both Tanks 18F and 12H, with the Tank 12H solubilities tending to be less soluble. The updated experimental results (including 12H testing) continue to indicate there may be some variance between the actual waste solubilities and the WRM assigned solubilities.

The results indicate that I-129 in the Tank 12H residual waste sample is relatively insoluble, under both reduced and oxidized conditions, compared to the WRM which conservatively assumed no solubility control for iodine. If the Tank 12 derived iodine solubility values were used in the PA model, the HTF peak dose within 10,000 years would decrease significantly.

The new waste release data can be integrated into the next revision to the FTF and HTF PAs.

FY2020: No real waste testing was performed in FY2020.

FY2021: The Waste Tank Chemistry Dynamics Testing in Section 3.2.1.2 provide additional inputs for the Tank Farm WRM, and was incorporated into an updated WRM (SRR-CWDA-2021-00042, Recommended Solubilities for Tank Closure Performance Assessment) in FY2021.

FY2022: No real waste testing planned in FY2022.

Deliverable: Test Plan (SRNL-RP-2013-00203) - Complete Residual Solids Technical Report (SRNL-STI-2014-00456) - Complete Page 42 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Residual Solids Technical Report (SRNL-STI-2015-00446) - Complete Waste Testing Technical Report (SRNL-STI-2016-00432) - Complete Tank 12 Waste Testing Technical Report (SRNL-STI-2018-00484) - Complete Waste Testing Evaluation (SRR-CWDA-2016-00086, Rev. 1) - Complete Expected Completion Date: FY2013 (Test Plan) - Complete FY2014 (Residual Solids Report) - Complete FY2015 (Residual Solids Report) - Complete FY2016 (Waste Testing Reports) - Complete FY2017 (Test Plan) - Complete FY2018 (Waste Testing Report, Rev.0) - Complete FY2019 (Waste Testing Report, Rev.1) - Complete Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0K/yr 3.2.1.2 Waste Tank Chemistry Dynamics Testing

Description:

The FTF and HTF PA Integrated Conceptual Models (ICMs) simulate radiological and chemical contaminant release from the waste tanks. An independent conceptual WRM was used to simulate stabilized contaminant release from the grouted waste tanks based on various chemical conditions in the waste tank which control solubility and thereby affect the timing and rate of release of contaminates from the residual waste layer (designated as the contamination zone (CZ) in the Tank Farm PA modeling). The current Tank Farm WRM is described in detail in Evolution of Chemical Conditions and Estimated Solubility Controls on Radionuclides in the Residual Waste Layer during Post-Closure Aging of High-Level Waste Tanks (SRNL-STI-2012-00404).

The WRM has not been updated since 2012 and does not incorporate solubility test data obtained from Tank 12 and Tank 18 real waste testing (documented in SRR-CWDA-2016-00086). Incorporating this data into the WRM would help to reduce the overall PA uncertainty, especially with respect to the radionuclides that drive peak doses (e.g., I-129, Pu-239). In addition, there are several NRC Monitoring Factors (MFs) regarding WRM chemistry dynamics that are best addressed through update of the WRM (the MFs are documented in Appendix C). The issues touched on in the MFs are areas where additional empirical data would be useful in reducing WRM uncertainty. It would be prudent to address the other WRM areas of concern (such as those raised in the NRC MFs) when the real waste test data is incorporated. To achieve this, it is proposed that testing be performed on various grout formulations to provide additional information regarding: 1) the impact of infiltrating ground water on grout pore water chemistry (e.g., pH and Eh) through time, 2) the ranges of tank grout pore water measure of acidity or alkalinity of a solution (pH) and measure of reduction (or oxidation) potential (Eh) to be expected in waste tanks, initially and through time following many pore volume flushes, and 3) the mineralogy of tank fill grouts, initially and through time following many pore volume flushes.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Another objective is to assess the performance of alternative tank grout formulas and ground water chemistries relative to baseline assumptions, to provide for flexibility within the WRM.

This WRM flexibility would help for account for potential variability within the infiltrating water chemistry (i.e., infiltrating fresh rainwater versus infiltrating ground water from an aquifer above the tank bottom) and could also potentially be used to allow for operating flexibility in the future (e.g., use of Controlled Low Strength Material (CLSM) versus the current grout formula).

The testing will involve placing tank fill grout in test columns which are subject to pore water exposure for a set time frame. Infiltrating water and grout will interact with the net effect being that both the infiltrating water and grout chemistries are expected to evolve over the duration of the test. Multiple grout test columns will be used for testing. Some of the grout configurations involve sealed systems while others allow the infiltrate water to flow through the grout column. The infiltrate water will be placed in different columns with various grout forms and formulations with the column sealed for the duration of the test. For the other grout configurations, the infiltrate water will be run through the columns with the column output monitored during the duration of the test. Data will be obtained over time regarding infiltrating water chemistry and grout minerology evolutions. Empirical data on infiltrating water and grout evolution could be used to supplement and/or replace inputs used in the Geochemists Workbench (GWB) simulation and better define the tank chemistry conditions after closure.

The tank chemistry conditions could be used to refine the WRM and to better bound the waste release conditions. An improved WRM would reduce the uncertainty in the FTF and HTF PA models.

FY2019: A detailed test plan, outlining the final scope and goals for the water chemistry and grout minerology testing, was issued in FY2019 as well as starting testing. Testing will be completed and a Technical Report outlining the results will be issued in FY2020. The proposed scope for the testing is outlined in the following.

Request for quote went out March 2019 on a Statement of Work (SOW) for Aqueous and Solid Phase Characterization of Potential Tank Fill Materials. WDA performed a technical evaluation of the three vendor quotes received on this SOW and the University of Georgia Research Foundation was selected to perform this work in April 2019. An SREL Test Plan was issued in FY2019.

The three grout formulations used in the batch and column tests completed a 90-day cure and most of the paste samples were size-reduced to at least the granularity of coarse sand and mixed in clean quartz sand in the proportion of the production grout mixes. Batch tests performed under oxic (bench-top) and anoxic (glove box) exposure conditions were initiated with approximately one-half of the sample material. SREL performed mockups of additional column tests to calibrate probes and troubleshoot the overall apparatus. Column tests using both oxic and anoxic infiltrates started in October 2019. The pH and Eh was monitored in the batch and column tests for at least 20 weeks. The results of the testing are presented the report, Aqueous and Solid Phase Characterization of Potential Tank Fill Materials, SREL-R 0001, issued in August 2020.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 A memorandum entitled Application of Characterization of the Aqueous and Solid Phase Chemistry of Closure Grouts, SRR-CWDA-2020-00061, was issued by WDA in August 2020 summarizing the results of the testing.

A report related to Waste Tank Chemistry Dynamics Testing (ML19105B156, Tank Grout Water-Conditioning TestsStatus Report) was issued in FY2019 and a follow-up report, ML20126G298 was issued in FY2020, both by the Center for Nuclear Waste Regulatory Analyses under contract for the U.S. Nuclear Regulatory Commission. Grout water conditioning tests performed during FY2018 and early FY2019 investigated the effects of the reducing tank grout in consuming Dissolved Oxygen (DO) and on the pH and Eh of simulated SRS ground water, as well as the effect of grout surface area on these three parameters. The DO consumption test demonstrated that reducing grout could consume DO from the SRS water, a pre-requisite for producing reducing conditions in water contacting the grout.

WDA has completed a review of both these report and found the test results to be consistent with the current Tank Farm PA modeling approaches and supportive of the proposed Waste Tank Chemistry Dynamics Testing.

FY2020: In August 2020, SREL issued the technical report, Aqueous and Solid Phase Characterization of Potential Tank Fill Material, SREL-R-21-0001. SREL conducted a series of batch and column studies to address uncertainty in the realistic pH and Eh ranges associated with the grouted waste tank systems, including an evaluation of three candidate Tank Closure Grout (TCG) paste formulations.

The observed results generally agreed with previous laboratory tests aimed at defining achievable Eh and pH conditions in tank waste grouted systems. The pH results were predominantly consistent with both the values derived from geochemical modeling and more recent laboratory testing.

FY2021: In FY2021, WDA updated the WRM (SRR-CWDA-2021-00042, Recommended Solubilities for Tank Closure Performance Assessment) to capture refined equilibrium chemistry. SRR-CWDA-2021-00042 includes comprehensive update of solubilities recommended for elements in the residual waste layer based on 1) new and updated aqueous solutions; 2) current thermodynamic databases including the international Nuclear Energy Agency database; and 3) experimental studies. This report utilizes a consulting report from Dr. Miles Denham entitled Recommended Updates to Solubility Controls for Modeling Leaching of Technetium, Uranium, Neptunium, Plutonium, and Iodine from the Residual Waste Layer of Closed Savannah River Site High-Level Waste Tanks (IEI 2024-002). The recommendations contained in IEI 2024-002 are based on an updated Nuclear Energy Agency (NEA) thermodynamic database published in 2020, and insights gained from review of laboratory experiments involving real tank waste samples conducted over the past decade.

FY2022: No Waste Tank Chemistry Dynamics Testing planned in FY2022.

Deliverables: WDA Waste Release Model update (SRR-CWDA-2021-00042, Recommended Solubilities for Tank Closure Performance Assessment)

Expected Completion Date: FY2019 (Test Plan) - Complete Page 45 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2020 Test Technical Report (SREL-R-21-0001) -

Complete WDA Memorandum (SRR-CWDA-2020-00061) -

Complete WDA Waste Release Model update (SRR-CWDA-2021-00042)

Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0/yr 3.2.2 CLSM Testing

Description:

A key step in closing a radioactive liquid waste tank at the Savannah River Site is filling void spaces in the emptied and cleaned tank with grout. The fill grout stabilizes the structure, serves as a barrier to inadvertent intrusion, limits moisture contact with residual waste, chemically conditions the waste (e.g., high pH, low Eh) generally hindering radionuclide release, and inhibits corrosion of impermeable steel liners maintaining containment of the residual waste. Several different grout mixes have been used since 1997 as the bulk fill material for waste tank closure, with additional mixes used for specialized purposes, such as filling cooling coils. The various grouts all have different attributes and features that make them better or worse with respect to the bulk fill grout function.

FY2020: Grout testing was performed in FY2020 in order to:

• Identify the grout attributes affecting performance as a liquid waste tank bulk fill material (e.g., slump flow, bleed water, etc.),

• Define performance metrics and associated requirements and goals,

• Identify additional CLSM characterization needed to support Tank Farm PA revisions,

• Assess the pros and cons of the reference sample LP#8-16 and candidate CLSM mixes on an attribute-by-attribute basis, and

• Recommend next steps toward selecting a bulk fill grout for the next tank closure.

Results of the CLSM testing is contained in Test Report- CLSM Proposed TCG Hydraulic Conductivity Test; Subcontract No. 0000441257, Delivery Order No.4; Specification K-SPC-G-00013, Rev. 15; Wood E&IS Project No. 6162-19-1253.04 (Wood E&IS 2020) issued in May 2020.

An evaluation memo of the results of the CLSM Test Report entitled Characterization and Assessment of CLSM Grouts for Potential Use in Waste Tank Operational Closures, SRR-CWDA-2020-00045 was issued by WDA in June 2020.

FY2021: For FY2021, SREL performed three tasks evaluating Zero-Bleed CLSM; 1) calculating saturated hydraulic conductivity, 2) measure diffusion of Na+ and NO3- from solution into the monolith, and 3) obtain Moisture Characteristic Curves (MCCs) for Zero-Bleed CLSM. A report was issued in FY2021 documenting the results of this CLSM testing.

[SRRA099188-000015].

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 FY2022: For FY2022, no additional effort is proposed for testing CLSM.

Deliverables: Test Technical Report and WDA Evaluation Expected Completion Date: Test Technical Report (Wood E&IS 2020) - Complete WDA Evaluation (SRR-CWDA-2020-00045) - Complete SREL - CLSM Characterization: Data Report (SRRA099188-000015) - Complete Responsibility: SRMC WDA (SREL)

Estimated Cost: FY2022 through FY2026 $0/yr.

3.2.3 Tank Farm Closure Cap Design

Description:

The Tank Farm Closure Cap Concepts used in the FTF PA (SRS-REG-2007-00002, Rev. 1) and HTF PA (SRR-CWDA-2010-00128, Rev. 1) are being updated. The general Tank Farm Closure Cap Concepts used in the PAs are currently detailed in reports WSRC-STI-2007-00184 (FTF) and SRNL-ESB-2008-00023 (HTF). The Tank Farm closure cap designs set forth in these documents will be used in the updated designs except with a nominal 4% closure cap slope (i.e., the closure cap assumptions regarding cap component dimensions, facility locations, and topography are not changed). The change from a 2% to 4%

slope was made in compliance with SCDHEC requirements (SCDHEC requires the closure cap to have at least a 3% but not greater than 5% surface slope, graded to promote positive drainage). In addition, lessons learned from a Closure Cap degradation document (Predicting Long-Term Percolation from the SDF Closure Cap, SRRA107772-000009) issued in 2018 will be incorporated into the updated Tank Farm Closure Cap Concepts. This SDF Closure Cap degradation document captured research that provided improved insights related to HDPE/

Geosynthetic Clay Liner (GCL) degradation. As a result of this, infiltration through the closure cap is expected to be lower, resulting in very different flow fields in the vadose zone, relative to previous modeling efforts.

In FY2020, updated predictions were prepared for the percolation rate emanating from the base of the engineered closure cap anticipated for closure of the FTF and HTF at the SRS.

[SRRA162682-000002] Simulations were conducted with meteorological conditions representing wet conditions in the current climate and two climate change scenarios corresponding to wet and very wet conditions. Predictions were made for conditions where the drainage layer and composite barrier continue to function as intended, and where degradation of the drainage layer and composite barrier occur due to clogging of the drainage layer, oxidation of the geomembrane, or severe gully erosion that penetrates down to the composite barrier. [SRRA162682-000002]

FY2021: The FTF and HTF closure caps are primarily intended to provide physical stabilization of the site, minimize infiltration, and provide a deterrent to intrusion. The layers and materials of the current closure cap design are based on the FTF Closure Cap Concept and Infiltration Estimates (WSRC-STI-2007-00184). The design was updated to apply to the HTF via H-Area Tank Farm Closure Cap and Infiltration (SRNL-ESB-2008-00023). The geometry and the layout of the closure caps were further updated (SRR-CWDA-2019-00080; SRR-CWDA-2019-00081) to incorporate an increased slope at the surface (i.e., 4% slope instead of Page 47 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 1.5% slope) to meet closure requirements specified in the regulation SWM: Solid Waste Landfills and Structural Fill (SCDHEC R.61-107.19). FTF and HTF closure cap performance over time was analyzed in SRRA162682-000002, Predicting Long-Term Percolation From the HTF and FTF Closure Caps, Report No. GENV-20-09. The Tank Farm closure cap designs are preliminary; however, they provide sufficient information for planning purposes, evaluating the closure cap configuration relative to its constructability and functionality, and for estimating infiltration rates over time through modeling.

SRR-CWDA-2021-00043, Erosion Analysis for the H-Tank Farm and F-Tank Farm Facilities, has been issued building upon the FTF and HTF closure caps designs and the previously issued SDF analysis, SRR-CWDA-2021-00035, Erosion Analysis for the Saltstone Disposal Facility.

The analysis utilizes the RUSLE to determine the average annual rate of soil loss due to erosion. SRR-CWDA-2021-00076, Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates was issued in September 2021 and provides a range of infiltration rates for use in the PA models.

Deliverables: FTF and HTF Closure Cap Documents FY2022: No Closure Cap design activities planned in FY2022.

Responsibility: SRMC WDA Expected Completion Date:

Erosion Analysis - Complete Closure Cap Erosion Analysis (SRR-CWDA-2021-00043) - Complete Closure Cap Uncertainty Analysis (SRR-CWDA-2021-00076) - Complete Estimated Cost: FY2022 $50K, FY2023 through FY2026 $0/yr.

3.2.4 To Be Determined Out-Year Testing

Description:

For FY2023 and beyond, testing has not been finalized.

Responsibility: SRMC WDA Expected Completion Date: Ongoing Estimated Cost: FY2023 through FY2026 $0/yr.

3.3 Tank Farm Performance Assessment Planned Review, Analysis, and Schedules DOE M 435.1-1 requires the ongoing maintenance of all PAs. This maintenance involves a series of activities that must be performed on an ongoing or annual basis. The activities in this section 3.3.1 Maintain Tank Farm Performance Assessment Control through Unreviewed Waste Management Question Process

Description:

Similar to the process set up for evaluating disposal related questions in SDF, a UWMQ process was established for waste tank closure activities. The UWMQ process consists of providing UWMQEs of proposed activities or new information to ensure that the assumptions, results, and conclusions of the approved PA, CA, and SAs remain valid.

Page 48 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 If identified through the UWMQ process that a proposed activity or new information is outside the bounds of the approved NDAA Section 3116 Basis Document, PA, CA, or SAs, new SAs are prepared to update the technical baseline. UWMQEs and SAs will continue to be required throughout the life of the facility. For planning purposes, the estimated cost assumes that four UWMQEs will be prepared each year in the out-years. The estimated cost does not reflect the cost of any emergent Tank Farm PA or SA revisions. Currently planned PA and SA revisions are captured in Section 3.2.

FY2020: No UWMQEs were completed for the Tank Farms in FY2021.

Deliverable: Provide UWMQEs and UWMQ procedure support, as needed to support closure of FTF and HTF.

Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $170K/yr 3.3.2 Prepare Annual Update to Performance Assessment Maintenance Program

Description:

The purpose of the LW PA Maintenance Program is to confirm the continued adequacy of the current PA and SAs, and to increase confidence in the results. Every year the annual LW PA Maintenance Program FY Implementation Plan is prepared and provided to DOE-SR. Plan preparation will include review of outstanding PA and SA comments and recommendations (noted in Sections 3.2.1 and 3.2.2). The Implementation Plan will outline planned work for each FY. The cost of preparing the Implementation Plan will be shared between SDF and the Tank Farms. See Section 2.3.2 for SDF maintenance activities.

Deliverable: Issue a FY update to the LW PA Maintenance Program Expected Completion Date: 2Q-3QFY (issued annually)

Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $30K/yr 3.3.3 Provide General Technical Support on Tank Farm Performance Assessment Issues

Description:

This task is to provide general technical and programmatic support on Tank Farm PA and SA issues, NRC activities, and other regulatory issues that affect waste tank closure.

Activities include testing and research activity support, general project support, review of annual groundwater monitoring data, supporting NRC on-site observation visits and technical reviews, and development of resolution path forward for NRC open items. Tier 2 Closure Plans are developed for each waste tank prior to closure activities and include reviews of actual tank residual impacts on long-term conditions. Research activity support includes monitoring of research done by outside agencies (e.g., academic research, Hanford activities) as well as research performed on-site (e.g., SRNL, SREL). These activities also include support on interactions with SCDHEC, SRS CAB, LFRG, National Academy of Sciences, and other regulatory and stakeholder bodies.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Deliverable: Provide ongoing technical support on regulatory and policy issues/activities affecting waste tank closure activities.

Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $370K/yr 3.3.4 Develop and Maintain Performance Assessment Model Archive and Revision Control

Description:

This task established software and hardware resources for archiving development and final PA modeling files to a read-only storage medium. In FY2014, capital infrastructure improvements were enacted on the site network, allowing for faster communication between SRNLs high performance computing network and SRMC WDA servers. This improvement increased the rate for file transfers between the two systems. FTF and HTF modeling files (for both PORFLOW and GoldSim) were copied to electronic storage devices. The storage devices are maintained onsite by SRMC WDA, within a cipher-locked facility. The properties of the electronic files were set to read-only. Copies of files can be provided upon request. As needed, additional storage devices will be purchased to provide sufficient disk space for maintaining a record of all related model files.

Deliverable: Establish process (completed in FY2014) and maintain after implementation Expected Completion Date: Ongoing Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $10K/yr 3.3.5 LFRG Key and Secondary Issues There are currently no open LFRG Key or Secondary issues associated with the Tank Farm PAs.

3.4 Tank Farm Performance Assessment Development/Revisions The FTF and HTF PAs provide the technical basis and results to be used in subsequent documents to demonstrate compliance with performance objectives of Radioactive Waste Management Manual, Licensing Requirements for Land Disposal of Radioactive Waste, as required by NDAA Section 3116, Federal Facility Agreement for the Savannah River Site (FFA), Standards for Wastewater Facility Construction, and Proper Closeout of Wastewater Treatment Facilities.

[DOE M 435.1-1, 10 CFR 61, WSRC-OS-94-42, SCDHEC R.61-67, SCDHEC R.61-82]

3.4.1 Prepare Out-Year F-Area Tank Farm Performance Assessment Revisions

Description:

In March 2012, following issuance of the Section 3116 Determination for FTF Closure (DOE-WD-2012-001), DOE approved the Tier 1 Closure Plan for FTF (SRR-CWDA-2010-00147) including its referenced FTF PA, Revision 1 (Tier 1 authorization letter, DOE_03-28-2012, was received March 28, 2012). The FTF PA, Revision 1, has been issued and implemented. A future revision of the FTF PA will be scheduled as required and agreed Page 50 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 upon by DOE. Unless otherwise noted in the FTF PA, the future FTF PA revision will include the following items at a minimum:

• Updated modeling to make the PA more consistent with the more current modeling approaches (i.e., at a minimum, consistent with the HTF PA);

• Analyses and results contained in all SAs that have been completed to date;

• Analyses and results of all UWMQEs completed to date;

• Consideration of new information generated through research and development;

• Changes in site future land use plans or closure plans; and

• Changes to PA guidance documents requirements.

Future FTF PA revisions will also consider the following:

• LFRG items from the PA review team report (LFRG_08-13-2008);

• Comment Responses to SCDHEC and EPA on Revision 1 of the FTF PA (SRR-CWDA-2011-00164, SRR-CWDA-2011-00175);

• Responses to RAIs posed by the NRC (SRR-CWDA-2011-00054);

• NRC recommendations in the U.S. Nuclear Regulatory Commission Plan for Monitoring Disposal Actions Taken by the U.S. Department of Energy at the Savannah River Site F-Area and H-Area Tank Farm Facilities in Accordance with the National Defense Authorization Act for Fiscal Year 2005 (ML15238A761), as discussed in detail in Section 3.3; and

• Information generated to support other PAs and SAs.

• Incorporation of applicable Technical Review Reports (TRRs) from the NRC.

Furthermore, the future FTF PA revisions shall be in alignment with the most current revision of the LW System Plan.

A document which outlines the activities and data needed to revise the F-Tank Farm and the H-Tank Farm PAs (SRR-CWDA-2019-00104, Strategy for Updating the SRS Tank Farm Performance Assessments) was issued in December 2019.

Deliverable: Issue PA revision Expected Completion Date: FY2024 Responsibility: SRMC WDA Estimated Cost: FY2022 $150K, FY2023 $300K, FY2024 $400K, FY2025 $0, FY2026 $0 3.4.2 Prepare Out-Year H-Area Tank Farm Performance Assessment Revisions

Description:

The HTF PA was submitted for DOE review in November 2010. Revision 1 of the HTF PA, incorporating FTF PA lessons learned and comments on HTF PA Revision 0, was dated November 2012. DOEs Draft NDAA Section 3116 Basis Document for HTF was prepared in FY2013 and was provided, along with the HTF PA Revision 1, to the NRC to initiate HTF NDAA Section 3116 Consultation in FY2013. Final HTF PA approval and implementation was achieved in FY2015.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 A revision of the HTF PA was initiated in FY2020 and is schedule to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure). Unless otherwise noted in the HTF PA, the revision will include the following items at a minimum:

• Analyses and results contained in all SAs that have been completed to date;

• Analyses and results of all UWMQEs completed to date;

• Consideration of new information generated through research and development;

• Changes in site future land use plans or closure plans;

• Changes to PA guidance documents requirements; and

• Modeling improvements as identified in the Quality Assurance report for the HTF PA (SRR-CWDA-2012-00070).

In late FY2020, as part of the HTF and future FTF PAs, a report entitled Features, Events, and Processes for the F-Area and H-Area Tank Farm Performance Assessments, was initiated.

The information presented within the report informs an upcoming revision to the PAs. As part of a PA, models are used to simulate the release and transport of radionuclides and chemical contaminants from post-closure facilities and to estimate exposure and consequence to potential receptors. Due to the complex nature of PA models, a structured methodology is necessary to ensure that relevant components are adequately addressed during model development. Therefore, PA models must be developed within defined boundaries and with appropriate consideration of relevant (site-specific) features, events, and processes (FEPs), as derived from a complete set of FEPs. The FEPs report was issued in March 2021.

The HTF PA revision will also consider the following:

• Comment Responses to SCDHEC and EPA on Revision 0 of the HTF PA (SRR-CWDA-2011-00135, SRR-CWDA-2012-00166);

• NRC recommendations from the Technical Evaluation Report for H-Area Tank Farm Facility, Savannah River Site, South Carolina (ML14094A496) and addressed within the Nuclear Regulatory Commissions H-Tank Farm Technical Evaluation Reports Recommendations - Department of Energys Activity Summary Matrix (SRR-CWDA-2014-00080);

• NRC recommendations in the U.S. Nuclear Regulatory Commission Plan for Monitoring Disposal Actions Taken by the U.S. Department of Energy at the Savannah River Site F-Area and H-Area Tank Farm Facilities in Accordance with the National Defense Authorization Act for Fiscal Year 2005 (ML15238A761), as discussed in detail in Section 3.3; and

• Information generated to support other PAs and SAs.

• Incorporation of applicable TRRs from the NRC.

A document which outlines the activities and data needed to revise the F-Tank Farm and the H-Tank Farm PAs (SRR-CWDA-2019-00104, Strategy for Updating the SRS Tank Farm Performance Assessments) was issued in December 2019. An extensive update of the HTF compliance case PORFLOW model was completed in FY2021. Key PA reports and studies issued in 2021 in support of the updated HTF PA are summarized in Table 3.4-1. Using the issued reports shown in Table 1, WDA has documented which parameters from the completed modeling reports will be used in the different HTF PA modeling cases/sensitivity analyses and Page 52 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 has updated the HTF PORFLOW compliance case model to be able to use those parameters and incorporate any physical changes (e.g., add new ancillary structures or model the tank liner in multiple segments). The HTF PORFLOW model update involved defining the elements/configurations that must be included in the model and how the various cases are differentiated.

Table 3.4 HTF PA Modeling Reports Issued in 2021 Document Number Document Topic SRR-CWDA-2021-00004 SRR-CWDA-2021-00004, Conceptual Model Development for the H-Area Tank Farm Facility Performance Assessment, was issued in March 2021.

The purpose of the HTF PA Conceptual Model Report is to document: 1) the methods used in the development of the conceptual models for the new HTF PA; 2) a description of the recommended modeling scenarios and conceptual models; and 3) a discussion of how all the relevant FEPs relate to the conceptual models, either through explicit modeling descriptions or through other approaches.

SRNL-STI-2021-00017 SRNL issued SRNL-STI-2021-00017 Geochemical Data Package for Performance Assessment Calculations Related to the Savannah River Site in 2021. This report documents updates to solute Kd and solubility limit recommendations for soils and cementitious materials.

SRR-CWDA-2021-00025 SRR-CWDA-2021-00025, Tank Farm Closure Inventory For use in Performance Assessment Modeling was issued in March 2021. This document presents the assigned inventories of radiological and chemical constituents in the residual material in both the HTF and FTF waste tanks and ancillary equipment at the presumed time of closure to support PA modeling.

SRR-CWDA-2021-00034 SRR-CWDA-2021-00034, Chemical and Physical Evolution of Tank SREL Doc.: R-21-0001 Closure Cementitious Materials was issued in April 2021. This study analyzes the chemical evolution of tank concrete and fill grout due to long-term environmental exposure to vadose zone soil moisture and groundwater.

The predicted mineral composition, pH, and Eh variations through time are key inputs to solubility analysis in the Waste Release Model and transport property transitions in the Vadose Zone Transport Model. The study also forecasts the physical degradation of concrete and grout over time due to decalcification, carbonation, and reinforcing bar corrosion. This report utilized the results of grout studies documented in SREL Doc.: R-21-0001, Aqueous and Solid Phase Characterization of Potential Tank Fill Materials.

SRNL-STI-2021-00187 SRNL issued a technical report on steel tank liner and concrete reinforcing bar corrosion entitled Corrosion of Steel in Evolving Concrete Environments (SRNL-STI-2021-00187). This study was coordinated with Chemical and Physical Evolution of Tank Closure Cemen titious Materials (SRR-CWDA-2021-00034) and provides failure times for the key steel components within closed waste storage tanks based on consideration of multiple potential modes of corrosion (anoxic, chloride-induced, carbonation-induced, etc.).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRR-CWDA-2021-00042 SRR-CWDA-2021-00042, Recommended Solubilities for Tank Closure IEI 2024-002 Performance Assessment, was issued in May 2021. This report includes comprehensive update of solubilities recommended for elements in the residual waste layer based on 1) new and updated aqueous solutions; 2) current thermodynamic databases including the international Nuclear Energy Agency database; and 3) experimental studies. This report utilizes a consulting report from Dr. Miles Denham entitled Recommended Updates to Solubility Controls for Modeling Leaching of Technetium, Uranium, Neptunium, Plutonium, and Iodine from the Residual Waste Layer of Closed Savannah River Site High-Level Waste Tanks (IEI 2024-002). The recommendations contained in IEI 2024-002 are based on an updated NEA thermodynamic database published in 2020, and insights gained from review of laboratory experiments involving real tank waste samples conducted over the past decade.

SRR-CWDA-2021-00043 SRR-CWDA-2021-00043, Erosion Analysis for the H-Tank Farm and F-Tank Farm Facilities, has been issued building upon the previously issued SDF analysis, SRR-CWDA-2021-00035, Erosion Analysis for the Saltstone Disposal Facility. The analysis utilizes the RUSLE to determine the average annual rate of soil loss due to erosion.

SRR-CWDA-2021-00045 SRR-CWDA-2021-00045, Air Pathway Release Model for the F-Area and H-Area Tank Farm Facility Performance Assessments was issued in May 2021. This technical report documents the development and benchmarking of Air Pathway Release (APR) models created for HTF and FTF using GoldSim simulation software. APR models for HTF and FTF are designed to evaluate the air-phase transport of potentially volatile radionuclides present in the Tank Farms residual waste. The ra dionuclides partitioned into the air phase may be released to the accessible environment (the atmosphere) via diffusion through the waste tank grout, the tanks roof, and the closure cap barriers.

SRR-CWDA-2021-00076 SRR-CWDA-2021-00076, Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates was issued in September 2021. This report provides a range of infiltration rates for use in the PA models.

SRR-CWDA-2021-00078 SRR-CWDA-2021-00078, Saturated Hydraulic Conductivities for F-Area and H-Area Tank Farm Cementitious Materials was issued in September 2021. This report evaluates available data related to the initial saturated hydraulic conductivity of Tank Farm cementitious materials and selects a set of appropriate values for use in PA modeling.

SRR-CWDA-2013-00058, Rev 3 SRR-CWDA-2013-00058, Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, Revision 3 was issued in January 2022. This document updates the dose calculation methodologies in support of the HTF PA. As part of this update, a thorough review of the references has been performed. Since the last HTF PA was issued, a number of key references for the dose calculations have been revised and this new information needs to be incorporated into the HTF PA dose calculator.

HTF Porflow Simulations performed in 2021 were limited to the Compliance Case within the Central Scenario. Subsequent PORFLOW model updates will be completed in 2022 to cover the remaining Central Scenario cases, several alternate modeling cases, and sensitivity analysis (as needed) as discussed in SRR-CWDA-2021-00004, Conceptual Model Development for the H-Area Tank Farm Facility Performance Assessment. The HTF Goldsim Model will be also be updated in FY2022.

Page 54 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Deliverable: Issue supporting input documents and HTF PA revision Expected Completion Date: Supporting Documents and Input Documents - FY2021; HTF PA Models Updated - FY2022 HTF PA Revision - FY2023 Responsibility: SRMC WDA Estimated Cost: FY2022 $400K, FY2023 $300K, FY2024 though FY2026 $0/yr 3.4.3 Tank Farm Special Analyses

Description:

SAs are performed to evaluate the significance of new information or new analytical methods to the results and associated conclusions of a PA. As waste tanks and ancillary equipment are cleaned, final residual inventories will be used to update the PA fate and transport modeling, allowing for evaluation of the difference between the projected and final waste tank inventories to determine if the results and conclusions of the PA and supporting SAs remain valid.

FY2020: In FY2020, an SA was initiated to support operational closure of F-Area Diversion Box (FDB)-5 and FDB-6, which are no longer needed in support of FTF operations. This reanalysis allows for evaluation of the difference between the projected and final FTF inventories to determine if the results of the FTF PA transport modeling, and the conclusions reached based on the FTF PA information, remain valid.

This SA will describe the approaches used to assign inventories at closure for FDB-5 and FDB-6 for use in FTF transport modeling. The analytes used for the inventory determination are the same 60 radionuclides and 18 chemicals used for ancillary equipment inventory assignment in the FTF PA. The methodology used to assign the FDB-5 and FDB-6 inventories is similar to the approach used in the FTF PA to determine the FTF piping systems residual inventory.

Using this approach results in there being several conservatisms inherent in the final FDB-5 and FDB-6 inventories. Camera inspection confirmed that the FDB-5 and FDB-6 vault and sump walls are clean with a minimal accumulation of material on the vault floor of only FDB-6, as would be expected in FDBs cleaned by flushing. To account for any uncertainty associated with volume determination through visual inspection, the radiological and chemical inventory assigned to FDB-5 and FDB-6 conservatively assumed a non-negligible accumulation of residue on the FDB surfaces (jumper internals and floors) most likely to have collected material after flushing.

FY2021: The FTF FDB-5 and FDB-6 Special Analysis (SRR-CWDA-2020-00055, FDB-5 and FDB-6 Special Analysis for the Performance Assessment for the F-Tank Farm at the Savannah River Site) was issued in February 2021. The FDB-5 and FDB-6 SA reports that the results and conclusions presented in the FTF PA and supporting SAs are not impacted by new information regarding the final residual inventories that are planned to be grouted in-place in FDB-5 and FDB-6.

Deliverable: Technical Report - SRR-CWDA-2020-00055 Completion Date: FY2021 Responsibility: SRMC WDA Estimated Cost: FY2022 through FY2026 $0/yr Page 55 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 3.5 Summary Table for the Tank Farm PA Maintenance Program Table 3.5-1 summarizes the estimated expenditures by activity and FY. Table A.1-1 contains a summary of the combined estimated expenditures for all the LW facility PA maintenance activities. This Implementation Plan reflects the PA related activities in the annual operating plan for the current FY and the projected out-year activities for estimation purposes.

Table 3.5-1: Summary for the Tank Farm Performance Assessment Maintenance Program ($K)

Section Maintenance Activity FY22 FY23 FY24 FY25 FY26 2.2.2.1 Long-Term Radiological Lysimeter Program 55 55 55 55 55 3.2.1.1 Waste Release Studies 0 0 0 0 0 3.2.1.2 Waste Tank Chemistry Dynamics Testing 0 0 0 0 0 3.2.2 CLSM Testing 0 0 0 0 0 3.2.3 Closure Cap Design 50 0 0 0 0 3.2.4 To Be Determined Out-Year Testing 0 0 0 0 0 Testing and Research Total 105 55 55 55 55 Maintain Tank Farm PA Control Through UWMQ 3.3.1 170 170 170 170 170 Process Prepare Annual PA Maintenance Program 3.3.2 30 30 30 30 30 Implementation Plan Provide General Technical Support on Tank Farm 3.3.3 370 370 370 370 370 PA Issues Develop and Maintain PA Model Revision Archive 3.3.4 10 10 10 10 10 and Revision Control Annual Tasks Total 580 580 580 580 580 3.4.1 Prepare Out-Year FTF PA Revisions 150 300 400 0 0 3.4.2 Prepare Out-Year HTF PA Revisions 400 300 0 0 0 3.4.3 Tank Farm Special Analyses 0 0 0 0 0 PA Development/Revisions Total 550 600 400 0 0 TANK FARM PA COMPILED TOTAL 1,235 1,235 1,035 635 635 Page 56 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022

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SRNL-ESB-2008-00023, H-Area Tank Farm Closure Cap and Infiltration, Savannah River Site, Aiken, SC, Rev. 0, May 21, 2008.

SRNL-RP-2013-00203, Hobbs, D.T. et. al, Task Technical and Quality Assurance Plan for Determining the Radionuclide Release from Tank Waste Residual Solids, Savannah River Site, Aiken, SC, Rev. 3, October 7, 2015.

SRNL-RP-2017-00411, King, W.D., Task Technical and Quality Assurance Plan for Tank 12 Waste Residual Radionuclide Release Testing, Savannah River Site, Aiken, SC, Rev. 0, August 2017.

SRNL-STI-2008-00421, Dixon, K., et al., Hydraulic and Physical Properties of Saltstone Grouts and Vault Concretes, Savannah River Site, Aiken, SC, November 2008.

SRNL-STI-2009-00419, Dixon, K., et al., Hydraulic and Physical Properties of ARP/MCU Saltstone Grout, Savannah River Site, Aiken, SC, May 2010.

SRNL-STI-2009-00473, Kaplan, D.I., Geochemical Data Package for Performance Assessment Calculations Related to the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, July 22, 2016.

SRNL-STI-2009-00512, Savannah River Site DOE 435.1 Composite Analysis, Volumes I and II, Savannah River Site, Aiken, SC, Rev. 0, June 10, 2010.

SRNL-STI-2011-00551, (SUPERSEDED) Stefanko, D.B. and C.A. Langton, Tanks 18 and 19-F Structural Flowable Grout Fill Material Evaluation and Recommendations, Savannah River Site, Aiken, SC, Rev. 0, September 2011.

Page 63 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRNL-STI-2011-00661, Dixon, K., Moisture Retention Properties of High Temperature Cure ARP/MCU Saltstone Grout, Savannah River Site, Aiken, SC, Rev. 0, December 2011.

SRNL-STI-2011-00665, Reigel, M.M., et al., Operational and Compositional Factors that Affect the Performance Properties of ARP/MCU Saltstone Grout, Savannah River Site, Aiken, SC, Rev.

0, February 2012.

SRNL-STI-2011-00672, Almond, P.M., et al., Variability of Kd Values in Cementitious Materials and Sediments, Savannah River Site, Aiken, SC, Rev. 0, January 2012.

SRNL-STI-2011-00716, Estes, S.L., et al., Technetium Sorption of Cementitious Materials Under Reducing Conditions, Savannah River Site, Aiken, SC, Rev. 0, January 2012.

SRNL-STI-2012-00087, Denham, M., Evolution of Chemical Conditions and Estimated Plutonium Solubility in the Residual Waste Layer During Post-Closure Aging of Tank 18, Savannah River Site, Aiken, SC, Rev. 0, February 2012.

SRNL-STI-2012-00404, Evolution of Chemical Conditions and Estimated Solubility Controls on Radionuclides in the Residual Waste Layer during Post-Closure Aging of High-Level Waste Tanks, Savannah River Site, Aiken, SC, Rev. 0, August 2012.

SRNL-STI-2012-00468, Langton, C.A., et al., Method Evaluation and Field Sample Measurements for the Rate of Movement of the Oxidation Front in Saltstone, Savannah River Site, Aiken, SC, Rev. 0, August 2012.

SRNL-STI-2012-00558, Reigel, M.M., et al., Process Formulations and Curing Conditions that Affect Saltstone Properties, Savannah River Site, Aiken, SC, Rev. 0, September 2012.

SRNL-STI-2012-00596, Estes, S.L., et al., Technetium Sorption by Cementitious Materials Under Reducing Conditions, Savannah River Site, Aiken, SC, Rev. 0, September 2012.

SRNL-STI-2012-00603, Bagwell, L., et al., SRNL Radionuclide Field Lysimeter Experiment Baseline Construction and Implementation, Savannah River Site, Aiken, SC, Rev. 0, October 18, 2012.

SRNL-STI-2013-00522, Dixon, K.L. and Nichols, R.L., Method Development for Determining the Hydraulic Conductivity of Fractured Porous Media, Savannah River Site, Aiken, SC, Rev. 0, September 2013.

SRNL-STI-2013-00533, Nichols, R.L. and Dixon, K.L., Saltstone Osmotic Pressure, Savannah River Site, Aiken, SC, September 2013.

SRNL-STI-2014-00456, Miller, D.H., et al., Determining the Release of Radionuclides from Tank Waste Residual Solids, Savannah River Site, Aiken, SC, Rev. 0, September 2014.

SRNL-STI-2015-00446, King, W.D. and Hobbs, D.T., Determining the Release of Radionuclides from Tank Waste Residual Solids: FY2015 Report, Savannah River Site, Aiken, SC, Rev. 0, September 2015.

SRNL-STI-2016-00432, Determining the Release of Radionuclides from Tank Waste Residual Solids: FY2016 Report, Savannah River Site, Aiken, SC, Rev. 0, August 2016.

SRNL-STI-2018-00484, Determining the Release of Radionuclides from Tank Waste Residual Solids Following Tank Closure, Savannah River Site, Aiken, SC, Rev. 1, November 2018.

Page 64 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRNL-STI-2018-00643, Updated Groundwater Flow Simulations of the Savannah River Site General Separations Area, Savannah River Site, Aiken, SC, Rev. 0, January 2019.

SRNL-STI-2021-00017, Geochemical Data Package for Performance Assessment Calculations Related to the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, February 2021.

SRNL-STI-2021-00187, Corrosion of Steel in Evolving Concrete Environments, Savannah River Site, Aiken, SC, Rev. 0, April 2021.

SRNS-RP-2012-00146, H-Area Tank Farm Groundwater Monitoring Plan and Sampling and Analysis Plan, Savannah River Site, Aiken, SC, Rev. 1, November 2012.

SRNS-RP-2012-00287, F-Area Tank Farm Groundwater Sampling and Analysis Plan, Savannah River Site, Aiken, SC, Rev. 1, December 2012.

SRNS-RP-2022-00076, 2021 Annual Groundwater Monitoring Report for the F- and H-Area Radioactive Liquid Waste Tank Farms, Savannah River Site, Aiken, SC, Rev. 0, March 2022.

SRNS-STI-2008-00045, Kaplan, D.I., et al., Saltstone and Concrete Interactions with Radionuclides: Sorption (Kd), Desorption, and Reduction Capacity Measurements, Savannah River Site, Aiken, SC, October 30, 2008.

SRRA021685, Witmer, M. and Powell, B.A., Determination of Constituent Concentrations in Field Lysimeter Effluents FY14 Final Report, Clemson University, Clemson, SC, Rev. 0, September 25, 2014.

SRRA021685-000007, Pope, R. et al., Determination of Constituent Concentrations in Field Lysimeter Effluents, Clemson University, Clemson, SC, September 30, 2015.

SRRA021685-000008, Powell, B. Determination of Constituent Concentrations in Field Lysimeter Effluents, Clemson University, Clemson, SC, Rev. B, November 2017.

SRRA021685-000009, Powell, B.A., et al., Analysis of Plutonium Soil Concentrations in Field Lysimeter Experiments, Clemson University, Clemson, SC, September 28, 2017.

SRRA021685-000010, Powell, B.A., Analysis of Plutonium Soil Concentrations in Field Lysimeter Experiments FY18 Reports, Clemson University, Clemson, SC, Rev. A, October 2018.

SRRA021685-000011, Powell, B.A., Determination of Constituent Concentrations in Field Lysimeter Effluents FY18 Report, Clemson University, Clemson, SC, Rev. A, October 2018.

SRRA021685-000012, Powell, B.A., Partitioning of Cesium-137 and Other Gamma-Emitting Radionuclides to SRS Sediments Recovered from Field Lysimeter Experiments at the Savannah River Site, Clemson University, Clemson, SC, Rev. A, October 2018.

SRRA021685-000013, Powell, B.A., et al., Determination of Constituent Concentrations in Field Lysimeter Effluents - FY19 Report, Clemson University, Clemson, SC, Rev. A, August 2020.

SRRA042328-000002, Arai, Y. and Powell, B.A., Examination of Tc, S, and Fe Speciation within Saltstone (SRRA042328SR), Clemson University, Clemson, SC, September 25, 2014.

SRRA099188-000005, Seaman, J., et al., Contaminant Leaching from Saltstone Simulants for FY 2018, (SREL-R-18-0006), Savannah River Site, Aiken, SC, Rev. 0, November 2018.

Page 65 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRRA099188-000010, Seaman, J., et al., Contaminant Leaching from Saltstone Simulants:

Summary of EPA 1315 and Dynamic Leaching Method Results for FY2019, (SREL DOC No. R-20-0002), Savannah River Site, Aiken, SC, Rev. 1, October 2019.

SRRA099188-000011, Seaman, J.,SREL Test Plan: Extractable Mercury in Saltstone Derived from Various Dry Feed Materials, (SREL Doc. R-20-0004), Savannah River Site, Aiken, SC, Rev.

1, March 2020.

SRRA099188-000015, Seaman, J., CLSM Characterization: Data Report (SREL-Doc. R 0003), Savannah River Site, Aiken, SC, Rev. 0, September 2021.

SRRA107772-000009, Benson, C. H. et al., Predicting Long-Term Percolation from the SDF Closure Cap, University of Virginia, Charlottesville, VA, April 23, 2018.

SRRA110110-000004, Brown, K. et al., Predicting the Hydraulic Conductivity Over Time for Degrading Saltstone Vault Concrete - Task 5 (Subcontract Number SRRA110110), Vanderbilt University, Nashville, TN, December 2017.

SRRA151648-000003, Seaman, J., et al., Aqueous and Solid Phase Characterization of Potential Tank Fill Materials, (SREL Doc No. R-21-0001), Savannah River Site, Aiken, SC, August 2020.

SRRA162682-000002, Benson, C. and Gustitus, S.A., Predicting Long-Term Percolation From the HTF and FTF Closure Caps (GENV-20-09), University of Virginia, Charlottesville, VA, June 24, 2020.

SRRA175647-000002, Powell, B.A., Technical Memo: Discussion of Radium and Iodine Detection Limits, Clemson University, Clemson, SC, August 26, 2021.

SRR-CWDA-2009-00017, Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, October 29, 2009.

SRR-CWDA-2009-00054, Comment Response Matrix for NRC Comments on Revision 0 of SRS-REG-2007-00002, Performance Assessment for F-Tank Farm, Savannah River Site, Aiken, SC, Rev. 0, February 19, 2010.

SRR-CWDA-2010-00015, Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program, FY2010 Implementation Plan, Savannah River Site, Aiken, SC, Rev. 0, March 31, 2010.

SRR-CWDA-2010-00124, Tank 18/Tank 19 Special Analysis for the Performance Assessment for the F-Area Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, February 2012.

SRR-CWDA-2010-00128, Performance Assessment for the H-Area Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, November 14, 2012.

SRR-CWDA-2010-00147, Tier 1 Closure Plan for the F-Area Waste Tank Systems at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, March 20, 2012.

SRR-CWDA-2011-00015, F-Area Tank Farm Tanks 18 and 19 Tier 2 Closure Plan, Savannah River Site, Aiken, SC, Rev. 0, March 22, 2012.

SRR-CWDA-2011-00054, Comment Response Matrix for United States Nuclear Regulatory Commission Staff Comments on the Draft Basis for Section 3116 Determination and Associated Page 66 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Performance Assessment for the F-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, October 25, 2011.

SRR-CWDA-2011-00135, Responses to South Carolina Department of Health & Environmental Control Comments on Performance Assessment for the H-Area Tank Farm at Savannah River Site (SRR-CWDA-2010-00128, Rev. 0 March 2011) Received March 24, 2011, Savannah River Site, Aiken, SC, Rev. 1, February 6, 2012.

SRR-CWDA-2011-00164, Comment Response Matrix for South Carolina Department of Health and Environmental Control (SCDHEC) Comments on: Performance Assessment for the F-Tank Farm, SRS-REG-2007-00002, Revision 1, March 31, 2010, Savannah River Site, Aiken, SC, Rev.

0, February 2012.

SRR-CWDA-2011-00175, Comment Response Matrix for United States Environmental Protection Agency Comments on: Performance Assessment for the F-Tank Farm, SRS-REG-2007-00002, Revision 1, March 31, 2010 and Comment Response Matrix for United States Environmental Protection Agency Comments on Revision 0 of the F-Tank Farm Performance Assessment SRR-CWDA-2009-00055, Revision 0, February 16, 2010, Savannah River Site, Aiken, SC, Rev. 0, February 2012.

SRR-CWDA-2012-00022, Evaluation of the Features, Events, and Processes in the F-Area Tank Farm Performance Assessment, Savannah River Site, Aiken, SC, Rev. 0, February 7, 2012.

SRR-CWDA-2012-00070, Performance Assessment for the H-Area Tank Farm at the Savannah River Site: Quality Assurance Report, Savannah River Site, Aiken, SC, Rev. 0, August 30, 2012.

SRR-CWDA-2012-00106, Tanks 5 and 6 Special Analysis for the Performance Assessment for the F-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, January 2013.

SRR-CWDA-2012-00166, Responses to EPA Comments on Responses to EPA Comments On Performance Assessment for the H-Area Tank Farm At the Savannah River Site SRR-CWDA-2010-00128, Rev 0 March 2011, Savannah River Site, Aiken, SC, Rev. 0, November 2012.

SRR-CWDA-2012-00170, Tanks 18 and 19 Final Configuration Report for F-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, June 2013.

SRR-CWDA-2013-00014, F-Area Tank Farm Tanks 5 and 6 Tier 2 Closure Plan, Savannah River Site, Aiken, SC, Rev. 0, May 2013.

SRR-CWDA-2013-00058, Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, July 2014.

SRR-CWDA-2013-00058, Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 3, January 2022.

SRR-CWDA-2013-00062, FY2013 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 2, October 2013.

SRR-CWDA-2013-00121, Witmer, M. and Powell, B.A., Determination of Constituent Concentrations in Field Lysimeter Effluents, FY13 Final Report - Task 2: Lysimeter Leachate Chemistry, Clemson University, Clemson, SC, Rev. 0, September 6, 2013.

Page 67 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRR-CWDA-2013-00123, Examination of Cr and S Speciation within Saltstone Monoliths, Savannah River Site, Aiken, SC, Rev. 0, September 2013.

SRR-CWDA-2014-00006, FY2014 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 2, September 2014.

SRR-CWDA-2014-00040, Tier 1 Closure Plan for the H-Area Waste Tank Systems at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, December 2014.

SRR-CWDA-2014-00060, Updates to the H-Area Tank Farm Stochastic Fate and Transport Model, Savannah River Site, Aiken, SC, Rev. 2, June 2016.

SRR-CWDA-2014-00080, Nuclear Regulatory Commissions H-Tank Farm Technical Evaluation Reports Recommendations - Department of Energys Activity Summary Matrix, Aiken, SC, Rev.

0, December 2014.

SRR-CWDA-2014-00106, Tank 16 Special Analysis for the Performance Assessment for the H-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, February 2015.

SRR-CWDA-2014-00108, Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program FY2015 Implementation Plan, Savannah River Site, Aiken, SC, Rev. 0, January 2015.

SRR-CWDA-2015-00009, H-Tank Farm Tank 16 Tier 2 Closure Plan, Savannah River Site, Aiken, SC, Rev. 0, May 2015.

SRR-CWDA-2015-00066, Summary of Saltstone Disposal Unit Cell 2A Core Drill Activities, Savannah River Site, Aiken, SC, Rev. 0, May 2015.

SRR-CWDA-2015-00073, Tank 12 Special Analysis for the Performance Assessment for the H-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, August 2015.

SRR-CWDA-2015-00077, Evaluation of I-129 Concentration Data to Improve Liquid Waste Inventory Projections, Savannah River Site, Aiken, SC, Rev. 2, February 26, 2018.

SRR-CWDA-2015-00119, H-Tank Farm Tank 12 Tier 2 Closure Plan, Savannah River Site, Aiken, SC, Rev. 0, September 2015.

SRR-CWDA-2015-00123, Evaluation of Tc-99 Concentration Data to Improve Liquid Waste Inventory Projections, Savannah River Site, Aiken, SC, Rev. 2, March 28, 2018.

SRR-CWDA-2015-00158, H-Tank Farm Type I and Type II Tank Special Analysis Base Case Model Inputs, Savannah River Site, Aiken, SC, Rev. 1, March 4, 2016.

SRR-CWDA-2016-00051, Property Data for Core Samples Extracted from SDU Cell 2A, Savannah River Site, Aiken, SC, Rev. 0, April 2016.

SRR-CWDA-2016-00072, FY2016 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, October 2016.

SRR-CWDA-2016-00078, Type I and II Tanks Special Analysis for the Performance Assessment for the H-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, August 2016.

Page 68 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRR-CWDA-2016-00086, Evaluation of Waste Release Testing Results Against the Tank Farm Performance Assessment Waste Release Model, Savannah River Site, Aiken, SC, Rev. 1, November 2018.

SRR-CWDA-2016-00119, SRS Liquid Waste Facilities Performance Assessment Maintenance Program - FY2017 Implementation Plan, Savannah River Site, Aiken, SC, Rev. 0, January 2017.

SRR-CWDA-2017-00015, Consolidated General Closure Plan for F-Area and H-Area Waste Tank Systems, Savannah River Site, Aiken, SC, Rev. 1, April 2017.

SRR-CWDA-2017-00019, Updated Sorption Constants for use in Performance Assessment Modeling, Savannah River Site, Aiken, SC, Rev. 0, February 2017.

SRRCWDA201700057, Features, Events, and Processes for the Saltstone Disposal Facility Performance Assessment, Savannah River Site, Aiken, SC, Rev. 0, August 2017.

SRRCWDA201800006, Conceptual Model Development for the Saltstone Disposal Facility Performance Assessment, Savannah River Site, Aiken, SC, Rev. 0, May 2018.

SRR-CWDA-2018-00087, Saltstone Disposal Facility Closure Cap Concept Update for Large-Scale Disposal Units, Savannah River Site, Aiken, SC, Rev. 1, April 2019.

SRR-CWDA-2019-00001, Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, March 2020.

SRR-CWDA-2019-00003, Cement-Free Formulation Down-Select Report, Savannah River Site, Aiken, SC, Rev. 0, March 5, 2019.

SRR-CWDA-2019-00080, 2019 PA HTF Tank Farm Closure Concepts, Savannah River Site, Aiken, SC, Rev. 0, September 2019.

SRR-CWDA-2019-00081, 2019 PA FTF Tank Farm Closure Concepts, Savannah River Site, Aiken, SC, Rev. 0, September 2019.

SRR-CWDA-2019-00104, Strategy for Updating the SRS Tank Farm Performance Assessments, Savannah River Site, Aiken, SC, Rev. 0, December 2019.

SRR-CWDA-2020-00005, Closure Plan for the Z-Area Saltstone Disposal Facility, Savannah River Site, Aiken, SC, Rev. 1, August 2020.

SRR-CWDA-2020-00006, Performance Assessment Monitoring Plan for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, August 24, 2020.

SRR-CWDA-2020-00008, Cement-Free Saltstone Down-Selection Report Follow-up, Savannah River Site, Aiken, SC, Rev. 0, February 4, 2020.

SRR-CWDA-2020-00045, Characterization and Assessment of CLSM Grouts for Potential Use in Waste Tank Operational Closures, Savannah River Site, Aiken, SC, Rev. 0, June 2020.

SRR-CWDA-2020-00055, FDB-5 and FDB-6 Special Analysis for the Performance Assessment for the F-Tank Farm at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, February 2021.

SRR-CWDA-2020-00061, Application of Characterization of the Aqueous and Solid Phase Chemistry of Closure Grouts, Savannah River Site, Aiken, SC, August 2020.

Page 69 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRR-CWDA-2020-00064, FY2020 Special analysis for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, April 2021.

SRR-CWDA-2020-00074, Features, Events, and Processes for the F-Area and H-Area Tank Farm Performance Assessments, Savannah River Site, Aiken, SC, Rev. 0, March 2021.

SRR-CWDA-2021-00004, Conceptual Model Development for the H-Area Tank Farm Facility Performance Assessment, Savannah River Site, Aiken, SC, Rev. 0, March 2021.

SRR-CWDA-2021-00024, Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program FY2021, Savannah River Site, Aiken, SC, Rev. 0, May 2021.

SRR-CWDA-2021-00025, Tank Farm Closure Inventory For use in Performance Assessment Modeling, Savannah River Site, Aiken, SC, Rev. 0, March 2021.

SRR-CWDA-2021-00034, Chemical and Physical Evolution of Tank Closure Cementitious Materials, Savannah River Site, Aiken, SC, Rev. 0, April 2021.

SRR-CWDA-2021-00035, Erosion Analysis for the Saltstone Disposal Facility, Savannah River Site, Aiken, SC, Rev. 0, March 2021.

SRR-CWDA-2021-00042, Recommended Solubilities for Tank Closure Performance Assessment, Savannah River Site, Aiken, SC, Rev. 0, May 2021.

SRR-CWDA-2021-00043, Erosion Analysis for the H-Tank Farm and F-Tank Farm Facilities, Savannah River Site, Aiken, SC, Rev. 0, April 2021.

SRR-CWDA-2021-00045, Air Pathway Release Model for the F-Area and H-Area Tank Farm Facility Performance Assessments, Savannah River Site, Aiken, SC, Rev. 0, May 2021.

SRR-CWDA-2021-00047, Comment Response Matrix for the First Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, July 2021.

SRR-CWDA-2021-00068, Summary of RSI Response documents for the SDF PA, Savannah River Site, Aiken, SC, Rev. 0, August 2021.

SRR-CWDA-2021-00072, Comment Response Matrix for the Second Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 0, August 2021.

SRR-CWDA-2021-00072, Comment Response Matrix for the Second Set of U.S. Nuclear Regulatory Commission Staff Requests for Additional Information on the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, November 2021.

SRR-CWDA-2021-00076, Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates, Savannah River Site, Aiken, SC, Rev. 0, September 2021.

SRR-CWDA-2021-00078, Saturated Hydraulic Conductivities for F-Area and H-Area Tank Farm Cementitious Materials, Savannah River Site, Aiken, SC, Rev. 0, September 2021.

Page 70 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 SRR-CWDA-2021-00087, FY2022 Plans for Research Conducted by Savannah River Ecology Laboratory as Part of Subcontract SRRA200036, Savannah River Site, Aiken, SC, Rev. 0, November 2021.

SRS-REG-2007-00002, Performance Assessment for F-Tank Farm at the Savannah River Site Savannah River Site, Aiken, SC, Rev. 1, March 31, 2010.

SRR-UWMQE-2021-00001, Evaluation of the Assumed 40,000 gallons of Saltstone Produced with Noncompliant Slag, Aiken, SC, Rev. 0, February 2021.

U-ESR-H-00107, Clark, D.J., Tank 16H: Preliminary Evaluation of Cessation of Annulus Waste Removal Activities, Savannah River Site, Aiken, SC, Rev. 0, March 2013.

VSL-13R3010-1, Papathanassiu, A.E., et al., Oxidation Rate Measurement and Humidity Effects on Saltstone, Vitreous State Laboratory, The Catholic University of America, Washington, DC 20064, August 22, 2013.

VSL-14R3210-1, Papathanassiu, A.E., et al., Final Report - Saltstone Curing Assessment, Vitreous State Laboratory, The Catholic University of America, Washington, DC 20064, Rev. 0, March 27, 2014.

WDPD-12-39, [Letter, Langton to Moody] Request for Contracting Officer Approval - Closure Documents Required for Operational Closure of Tanks 18 and 19, U.S. Department of Energy, Savannah River Site, Aiken, SC, March 29, 2012.

WDPD-13-56, [Letter, Moody to Schlismann] Contract DE-AC09-09SR22505 - Request for Contracting Officer Approval - Closure Documents Required for Operational Closure of Tanks 5 and 6 (Ltr, Schlismann to Smith, SRR-CAA-2013-00160, 5/13/13), U.S. Department of Energy, Savannah River Site, Aiken, SC, May 17, 2012.

WDPD-14-08, [Letter, Spears to Camper], Transmittal of Fiscal Year 2013 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site SRR-CWDA-2013-00062, Rev. 2, U.S.

Department of Energy, Aiken, SC, December 5, 2013.

WDPD-15-05, [Letter, Folk to Camper], Transmittal of Fiscal Year 2014 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site SRR-CWDA-2014-00006, Rev. 2, U.S.

Department of Energy, Aiken, SC, October 29, 2014.

WDPD-15-42, [Letter, Moody to Bair] Contract DE-AC09-09SR22505 - Request for Contracting Officer Approval - Closure Documents Required for Operational Closure of Tank 16 (Ltr, Bair to Smith, SRR-CAA-2015-00141, 5/4/15), U.S. Department of Energy, Savannah River Site, Aiken, SC, May 17, 2012.

WDPD-16-17, [Letter, Smith to Bair], Contract DE-AC09-09SR22505 - Request for Contracting Officer Approval Closure Documents Required for Operational Closure of Tank 12H, U.S.

Department of Energy, Savannah River Site, Aiken, SC, December 2015.

WDPD-17-05, [Letter, Ridley to Fortenberry], Contract DE-AC09-09SR22505 - Department of Energy (DOE) Approval of the FY2016 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site (SRR-CWDA-2016-00072), Revision 0, October 2016), U.S. Department of Energy, Savannah River Site, Aiken, SC, November 21, 2016.

Page 71 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 WDPD-17-34, [Letter, Folk to Foster], Contract DE-AC09-09SR22505 - Department of Energy (DOE) Approval of the Type I and II Tanks Special Analysis for the Performance Assessment for the H-Tank Farm (HTF) at the Savannah River Site (SRR-CWDA-2016-00078, Revision 0, August 2016), U.S. Department of Energy, Savannah River Site, Aiken, SC, June 27, 2017.

WDPD-20-32, Folk, J., Disposal Authorization Statement for the Savannah River Site Saltstone Disposal Facility, Savannah River Site, Aiken, SC, Rev. 0, June 2020.

WDPD-21-40, [Letter, Clark to Thomas], Department of Energy (DOE) Approval of Special Analysis: FY2020 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, SRR-CWDA-2020-00064 Revision 0, dated January 2021, U.S. Department of Energy, Savannah River Site, Aiken, SC, April 22, 2021.

Wood E&IS 2020, Test Report- CLSM Proposed TCG Hydraulic Conductivity Test; Subcontract No. 0000441257, Delivery Order No.4; Specification K-SPC-G-00013, Rev. 15; Wood E&IS Project No. 6162-19-1253.04, May 2020.

WSRC-OS-94-42, Federal Facility Agreement for the Savannah River Site, Savannah River Site, Aiken, SC, August 16, 1991.

WSRC-STI-2007-00184, Jones, W.E. and Phifer, M.A., FTF Closure Cap Concept and Infiltration Estimates, Savannah River Site, Aiken, SC, Rev. 2, October 2007.

WSRC-STI-2008-00244, Jones, W.E. and Phifer, M.A., Saltstone Disposal Facility Closure Cap Concept and Infiltration Estimates, Savannah River Site, Aiken, SC, Rev. 0, May 2008.

WSRC-TR-2005-00074, Cook, J.R., et al., Special Analysis: Revision of Saltstone Vault 4 Disposal Limits, Savannah River Site, Aiken, SC, Rev. 0, May 26, 2005.

X-CLC-Z-00092, Hunter, H.M., Bounding Volume of Grout Produced from Noncompliant Slag, Savannah River Site, Aiken, SC, Rev. 0, February 2021.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 APPENDIX A Summary Table for the Liquid Waste Facilities Performance Assessment Maintenance Program FY2022 Page 73 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 A.1 Summary Table for the LW PA Maintenance Program Table A.1-1 contains a summary of the combined estimated expenditures for all the LW facility PA maintenance activities, summarized from Tables 2.5-1 and 3.5-1. This Maintenance Program reflects the PA related activities in the annual operating plan for the current FY and the projected out-year activities for estimation purposes.

Table A.1-1: Summary for the Liquid Waste Performance Assessment Maintenance Program ($K)

LW PA Maintenance Program FY22 FY23 FY24 FY25 FY26 SDF PA Maintenance Program Totals 917 910 910 760 760 Tank Farm PA Maintenance Program Totals 1,235 1,235 1,035 635 635 COMPILED TOTAL 2,152 2,145 1,945 1,395 1,395 Page 74 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 APPENDIX B U.S. Nuclear Regulatory Commission Monitoring Factors for Saltstone Disposal Facility Page 75 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Appendix B: U.S. Nuclear Regulatory Commission Monitoring Items for the Saltstone Disposal Facility Factors are colored by current NRC priority and a symbol is included with each Monitoring Factor (MF) number to ensure clarity. Changes from previous year are indicated by red text. A legend containing a description of the NRC ranking is provided at the end of the table. [ML13100A113]

Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments Monitoring Activity (MA 1) - Inventory Section 2.3.5 - Conduct Saltstone Disposal Facility Performance Assessment Validation Contaminant inventories are determined NRC expects to close MF 1.01 after DOE has Inventory in based on sample analysis and to ensure 1.01 completed waste disposal at the SDF and DOE will continue to revise inventory estimates as Disposal compliance with the Saltstone WAC.

§ determined the final inventory in each disposal part of waste disposal activities.

Structures The SDF inventory will be updated structure.

based on the results of quarterly sample results and transfer volumes. Annual review reports including updated actual inventory will be provided to the NRC.

Final inventory will be determined prior to SDF closure. PA Maintenance Plans indicate that a Section 2.3.5 - Conduct Saltstone future revision of the SDF PA will be scheduled Disposal Facility Performance as required. This activity was performed as part Assessment Validation of the 2019 SDF PA and included revised Contaminant inventories are determined NRC expects to close MF 1.02 after DOE has assessments of inventories to use in modeling. In Methods Used based on sample analysis and to ensure 1.02 completed waste disposal at the SDF and FY2017 estimates of total Tc-99 and I-129 to Assess compliance with the Saltstone WAC.

determined the final inventory in each disposal inventories were completed (SRR-CWDA-2015-Inventory The SDF inventory will be updated structure. 00123, SRR-CWDA-2015-00077).

based on the results of quarterly sample results and transfer volumes. Annual Supernate from five tanks estimated to contain a review reports including updated actual significant fraction of the total Tc and I inventories inventory will be provided to the NRC.

were analyzed in FY2018 and the previous reports were revised to incorporate the new data.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 2 - Infiltration and Erosion Control Section 2.2.2.3 - Closure Cap Long-Term Performance Research began in FY2017 and concluded in Research will validate assumptions in the FY2018 to validate PA assumptions concerning the modeling concerning the rate of rate of closure cap infiltration as well as the pluggage of the closure cap drainage drainage layer behavior. DOE incorporated updated layer as well as the drainage layer above closure cap modeling into the 2019 SDF PA, NRC expects to close MF 2.01 after NRC each SDU. including sensitivity cases to evaluate risks Hydraulic determines that the hydraulic performance of the associated with the preliminary closure cap design.

2.01 Performance as-built closure cap is adequate. Given the Section 2.3.3 - Provide General DOE will revise closure cap modeling assumptions of Closure importance of construction activities on the Technical Support on Saltstone and support once a final closure design has been Cap performance of the cap, MF 2.01 will not be Disposal Facility Performance determined.

closed prior to construction of the cap.

Assessment Issues To address RSIs from the NRC, literature In FY2018, the NRC recommended increasing the reviews are currently underway to better priority of MF 2.01 (Hydraulic Performance of evaluate uncertainties associated with the Closure Cap) from Low to Medium priority.

hydraulic performance of the closure (ML18002A545, ML18107A161) cap.

DOE will revise closure cap modeling assumptions Section 2.3.3 - Provide General and support once a final closure design has been Technical Support on Saltstone NRC expects to close MF 2.02 after NRC determined. DOE incorporated updated closure Erosion Disposal Facility Performance determines that the physical stability of the final cap modeling into the 2019 SDF PA, including Control of the Assessment Issues closure cap is adequate. Given the importance sensitivity cases to evaluate risks associated with SDF To address RSIs from the NRC, literature of construction activities on the performance of the potential erosion.

2.02 Engineered reviews are currently underway to better Surface Cover the cap, MF 2.02 will not be closed prior to evaluate uncertainties associated with the construction of the cap. In FY2018, the NRC recommended modifying MF and Adjacent hydraulic performance of the closure 2.02 to clarify that areas adjacent to the future SDF Area cap, including an evaluation of the closure cap will be under the NRC monitoring potential for erosion in areas adjacent to activities at the SDF. (ML18002A545, the SDF closure cap.

ML18107A161)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 3 - Waste Form Hydraulic Performance Saltstone testing of measured hydraulic conductivities is ongoing. A variety of laboratory testing has completed, including one in which samples were cured under conditions similar to Section 2.2.1 - Contaminant Leaching those expected for field-emplaced saltstone. The Characteristics from Saltstone results were incorporated into the FY2014 SDF Monolith SA.

Hydraulic Laboratory prepared and process room Conductivity NRC expects to close MF 3.01 after NRC samples will have physical properties Multiple cores were extracted via a wet core 3.01 of Field- determines that model support for the SHC of testing performed to determine the drilling process in FY2015 approximately 20

+/-

Emplaced field-emplaced saltstone is sufficient. hydraulic conductivity, Kd, bulk cured months after the saltstone of interest was processed Saltstone density, porosity, and microstructure/ in the SPF and subsequently emplaced in SDU Cell phase analysis. Future testing will 2A. The physical property data for SDU-emplaced compare these properties to those and laboratory-prepared samples is summarized in measured from emplaced core sampling. the SDU Cell 2A Core Sampling Report (SRR-CWDA-2016-00051), with values for SDF model inputs provided in the report where applicable.

Based on these results, NRC closed this monitoring factor in June 2017 per ML17097A351.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments Saltstone testing of measured hydraulic Section 2.2 - Saltstone Disposal conductivities is ongoing. A variety of laboratory Facility Performance Assessment testing has completed, including one in which Testing & Research Activities samples were cured under conditions similar to Previous testing and research activities those expected for field-emplaced saltstone. The were carried out to define the operating results were incorporated into the FY2014 SDF conditions (e.g., water-to-premix ratio, SA.

dry feeds variability, and the curing temperature) required to meet or exceed Variability of saltstone hydraulic conductivities PA expectations of saltstone was evaluated in the FY2014 SDF SA through the NRC expects to close MF 3.02 after NRC Variability of performance. use of parametric flow cases that applied average, determines that saltstone production, placement, 3.02 Field- upper bounding, and lower bounding values.

and curing conditions that significantly affect

+/- Emplaced saltstone hydraulic properties are well Section 2.2.1 - Contaminant Leaching Saltstone Characteristics from Saltstone Multiple cores were extracted via a wet core controlled. drilling process in FY2015 approximately 20 Monolith months after the saltstone of interest was processed Laboratory prepared and process room in the SPF and subsequently emplaced in SDU Cell samples will have physical properties 2A. The physical property data for SDU-emplaced testing performed to determine the hydraulic conductivity, Kd, bulk cured and laboratory-prepared samples is summarized in the SDU Cell 2A Core Sampling Report (SRR-density, porosity, and microstructure/

CWDA-2016-00051), with values for SDF model phase analysis. Future testing will inputs provided in the report where applicable.

compare these properties to those Based on these results, NRC closed this monitoring measured from emplaced core sampling.

factor in June 2017 per ML17097A351.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments The saltstone sampling and analysis plan established a strategy for studies to reduce PA uncertainty in the area of SHC, and for correlating grout properties between laboratory-prepared samples and core-drilled samples from actual NRC expects to close MF 3.03 after NRC emplaced grout. A variety of laboratory testing has determines that representing the hydraulic completed, including one in which samples were properties of field-emplaced saltstone with the Section 2.2.1 - Contaminant Leaching cured under conditions similar to those expected hydraulic properties of laboratory-produced Characteristics from Saltstone for field-emplaced saltstone. The results were samples is adequate. That assessment should Monolith incorporated into the FY2014 SDF SA.

Applicability account for the range of expected disposal Laboratory prepared and process room of Laboratory conditions of field-emplaced saltstone as well as samples will have physical properties Multiple cores were extracted via a wet core 3.03 Data to Field- effects of scale. testing performed to determine the drilling process in FY2015 approximately 20

+/-

Emplaced hydraulic conductivity, Kd, bulk cured months after the saltstone of interest was processed Saltstone Alternately, MF 3.03 may be closed if NRC density, porosity, and microstructure/ in the SPF and subsequently emplaced in SDU Cell determines that DOE bases the hydraulic phase analysis. Future testing will 2A. The physical property data for SDU-emplaced properties of saltstone on the properties of an compare these properties to those and laboratory-prepared samples is summarized in appropriate range of samples of field-emplaced measured from emplaced core sampling. the SDU Cell 2A Core Sampling Report (SRR-saltstone, rather than on measurements of CWDA-2016-00051), with values for SDF model laboratory-produced samples. inputs provided in the report where applicable.

Based on these results, NRC narrowed the scope of this monitoring factor in June 2017 per ML17097A351 to the understanding of changes in hydraulic conductivity in the short term between laboratory-prepared and field-emplaced saltstone.

Saltstone testing of measured hydraulic conductivities is ongoing. A variety of laboratory Section 2.2 - Saltstone Disposal NRC expects to close MF 3.04 after NRC testing has completed, including one in which Facility Performance Assessment Effect of determines that projected SDF performance is samples were cured under conditions similar to Testing & Research Activities Curing based on estimates of the hydraulic properties of those expected for field-emplaced saltstone. The Previous testing and research activities 3.04 Temperature saltstone (e.g., hydraulic conductivity and results were incorporated into the FY2014 SDF were carried out to define the operating

+/- on Saltstone diffusivity) that are well-supported. That SA. The physical property data for SDU-emplaced conditions (e.g., water-to-premix ratio, Hydraulic support should account for the range of curing and laboratory-prepared samples is summarized in dry feeds variability, and the curing Properties conditions (i.e., temperatures values, humidity the SDU Cell 2A Core Sampling Report (SRR-temperature) required to meet or exceed values) experienced by field-emplaced saltstone. CWDA-2016-00051). Based on the test results, PA expectations of performance.

NRC closed this monitoring factor in June 2017 per ML17097A351.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 4 - Waste Form Physical Degradation Section 2.2.2.2 - Studies Related to Cementitious Materials Degradation Due to Radiation Damage The degradation models for concrete and saltstone A literature search will be conducted to grout were revised for the FY2014 SDF SA to gain a better understanding of the incorporate greater conservatisms and to modify NRC expects to close MF 4.01 after NRC potential degradation of cementitious inputs to implicitly model fractures in the matrix.

Waste Form 4.01 determines that support for modeled changes in materials exposed to radiation. The 2019 SDF PA incorporated the revised Matrix

+/- the SHC and diffusivity during the performance and degradation model and updated input values based Degradation period is sufficient. Section 2.4.1 - Prepare Out-year on recent research and development. The PA also Saltstone Disposal Facility considered variations of the input values to better Performance Assessment Revisions evaluate risks associated with saltstone This section describes future revisions to degradation.

the PA that will incorporate improvements to conceptual modeling.

Section 2.2 - Saltstone Disposal The degradation models for concrete and saltstone Facility Performance Assessment grout were revised based on FY2013 test data for NRC expects to close MF 4.02 after NRC Testing & Research Activities the FY2014 SDF SA to incorporate greater Waste Form 4.02 determines that model support for the assumed Previous testing and research activities conservatisms and to modify inputs to implicitly Macroscopic

+/- formation of macroscopic fractures during the were carried out to provide a better model fractures in the matrix. The 2019 SDF PA Fracturing performance period is sufficient. understanding of degradation explicitly includes sensitivity cases to examine the mechanisms and fracturing. [SRNL-STI- potential effects from assumed macroscopic 2013-00522] fractures through saltstone and SDU concrete.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 5 - Waste Form Chemical Degradation In June of 2015, the NRC issued a TRR titled Technical Review: Oxidation of Reducing Cementitious Waste Forms, Docket No. PROJ0734.

Section 2.2.2.1 - Long-Term The TRR is related to MFs 5.01, 5.02, 5.03, and Radiological Lysimeter Program 5.05. [ML15098A031]

This task is expected to provide Kd values in soil and cementitious materials Studies to better quantify radionuclide release from and additional information about long-field-emplaced saltstone have been complete.

term geochemical and transport Multiple cores were extracted via a wet core phenomena that will be used to support drilling process in FY2015 approximately 20 the waste release and transport models.

months after the saltstone of interest was processed Radionuclide NRC expects to close MF 5.01 after NRC in the SPF and subsequently emplaced in SDU Cell Release from Section 2.2.1 - Contaminant Leaching 5.01 determines that measurements of radionuclide 2A. The physical property data for SDU-emplaced Field- Characteristics from Saltstone

+/- release rates from field-emplaced saltstone used and laboratory-prepared samples is summarized in Emplaced Monolith in the PA are reliable. the SDU Cell 2A Core Sampling Report (SRR-Saltstone Laboratory prepared and process room CWDA-2016-00051), with values for SDF model samples will have physical properties inputs provided in the report where applicable.

testing performed to determine the Ongoing work related to hydraulic conductivity hydraulic conductivity, Kd, bulk cured and Tc-99 and I-129 release from field-emplaced density, porosity, and saltstone is discussed in Section 2.2.1. The microstructure/phase analysis. Future updated 2019 SDF PA incorporated this new testing will compare these properties to information to improve the modeling of Tc-99 and those measured from emplaced core I-129 releases.

sampling.

In FY2018, the NRC recommended no changes to MF 5.01. (ML18095A122)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In November of 2013, the NRC issued a TRR titled Technical Review: Solubility of Technetium Dioxides in Reducing Cementitious Material Leachates, A Thermodynamic Calculation, Docket No. PROJ0734. The TRR is related to MFs 5.02 and 5.05. [ML13304B159] In June of 2015, the NRC issued a TRR titled Technical Review:

Oxidation of Reducing Cementitious Waste Forms, Docket No. PROJ0734. The TRR is related to MFs 5.01, 5.02, 5.03, and 5.05. [ML15098A031]

A robust suite of tests has been performed and Section 2.2 - Saltstone Disposal additional tests are planned in order to develop a Facility Performance Assessment detailed understanding of Tc behavior with respect Testing & Research Activities to releases via chemical reductions. Based on the NRC expects to close MF 5.02 after NRC Studies to support modeled assumptions most current data available, the FY2014 SDF SA determines that: (1) model support for the for Tc release behavior.

applied a modified approach for modeling Tc Chemical chemical reduction of Tc(VII) to Tc(IV) is release. The physical property data for samples is 5.02 Reduction of robust; and (2) this reduced state is maintained Section 2.2 - Saltstone Disposal summarized in the SDU Cell 2A Core Sampling Technetium under field conditions. NRC expects that DOE Facility Performance Assessment Report (SRR-CWDA-2016-00051) Dynamic by Saltstone will inform NRC what the ranges of those Testing & Research Activities leaching and EPA Method 1315 testing were conditions are expected to be during the Measurement of cured saltstone grout performed in FY2016 and encompassed evaluation performance period. samples are expected to validate PA of radionuclide-spiked saltstone simulants and assumptions concerning the movement actual saltstone cores extracted from SDU Cell 2A.

of oxidation fronts through cementitious The data from these studies is provided in SREL materials.

Doc. R-16-0003. Work continued in FY2017 and FY2018, as documented in SREL Doc. R-17-0005, SREL Doc. R-18-0004, and SREL Doc. R 0006. The updated 2019 SDF PA incorporated this new information to improve the modeling of Tc-99 releases.

In FY2018, the NRC recommended decreasing the priority of MF 5.02 from High to Medium to reflect the NRC staff reduced concern about technetium (Tc) oxidation by trace concentrations of oxygen.

(ML18095A122, ML18219B035)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In June of 2015, the NRC issued a TRR titled Technical Review: Oxidation of Reducing Cementitious Waste Forms, Docket No. PROJ0734.

The TRR is related to MFs 5.01, 5.02, 5.03, and 5.05. [ML15098A031]

A review of measured test data resulted in a revised reduction capacity for saltstone (from 0.822 meq e-/g to 0.607 meq e-/g). Pore volume data was revised to apply this more conservative value for the FY2014 SDF SA. In addition, sensitivity Section 2.2 - Saltstone Disposal models were developed to better understand the Facility Performance Assessment effects of varying the initial oxidation conditions in NRC expects to close MF 5.03 after NRC Testing & Research Activities saltstone. These sensitivity models showed that a Reducing determines that information for the initial 5.03 Measurement of cured saltstone grout significant percentage of the saltstone monolith Capacity of reducing capacity of saltstone and the expected samples are expected to validate PA would need to be initially oxidized to significantly Saltstone evolution of redox conditions over time is assumptions concerning the movement alter dose results within 10,000 years. An updated adequate.

of oxidation fronts through cementitious evaluation of the reducing capacity of saltstone has materials. been incorporated into the 2019 SDF PA. The PA also included sensitivity cases to better evaluate the effects associated with reducing capacity uncertainties. The 2019 SDF PA also provides the basis for the assumption that saltstone oxidation prior to closure cap emplacement will be minimal.

In FY2018, the NRC recommended decreasing the priority of MF 5.03 from Medium to Low to reflect the NRC staff reduced concern about technetium (Tc) oxidation by trace concentrations of oxygen.

(ML18095A122, ML18219B035)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone Disposal Facility, Docket No. PROJ0734. The TRR is related to MFs 5.04, 6.01, 7.01, 10.04, 10.06, and 10.09. [ML16342C575]

Due to the relative importance of Kd values, studies are ongoing to improve estimates for site-specific conditions. Studies focus on radionuclides that are expected to contribute significantly to dose risks.

The FY2014 SDF SA applied the latest available NRC expects to close MF 5.04 after NRC values and future modeling will consider all determines that model support for the sorption available data. In FY2016, DOE produced a coefficients assumed for radium and selenium comprehensive report of Kd values, including for saltstone is adequate. Section 2.2.2.1 - Long-Term improved documentation for the rationale for Radiological Lysimeter Program values used in modeling.

Certain Risk- MF 5.04 may be closed based on DOE This task is expected to provide Kd 5.04 Significant Kd measurements on either field-emplaced or values in soil and cementitious materials Responses to the NRC RAIs on the FY2014 SDF Values for simulated saltstone. and additional information about long- SA were documented in FY2016, including Saltstone term geochemical and transport additional Kd sensitivity analyses. Results indicated NRC could close MF 5.04 (and open a new MF phenomena that will be used to support that Kd value variability did not impact the ability for selenium) if NRC determines that the the waste release and transport models. to meet performance objectives.

inventory of Ra-226 and its ancestors is consistent with the revised inventory assumed in The NRC recommended expanding the scope of Case K under MFs 1.01 and 1.02. MF 5.04 (Certain Risk-Significant Kd Values for Saltstone), MF 6.01 (Certain Risk-Significant Kd Values in Disposal Structure Concrete), and MF 7.01 (Certain Risk-Significant Kd Values in Site Sand and Clay) to now include iodine sorption in saltstone, disposal structure concrete, and soils, respectively. (ML18158A172)

The 2019 SDF PA incorporates the latest Kd values as recommended in the FY2016 Kd report (SRR-CWDA-2017-00019). The PA also updated the saltstone Kd based on an SREL study of actual I-129 release from saltstone simulant samples.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In November of 2013, the NRC issued a TRR titled Technical Review: Solubility of Technetium Dioxides in Reducing Cementitious Material Leachates, A Thermodynamic Calculation, Docket No. PROJ0734. The TRR is related to MFs 5.02 and 5.05. [ML13304B159] In June of 2015, the NRC issued a TRR titled Technical Review:

Oxidation of Reducing Cementitious Waste Forms, Docket No. PROJ0734. The TRR is related to MFs 5.01, 5.02, 5.03, and 5.05. [ML15098A031]

NRC expects to close MF 5.05 after NRC determines that model support for the exclusion A Pacific Northwest Laboratory (PNNL) study of rinse-release phenomenon from the found that short-term oxidation of Tc in saltstone Potential for Section 2.2.1 - Contaminant Leaching conceptual model assumed in the DOE 2009 can be overcome (i.e., re-reduced) in a fairly short Short-Term Characteristics from Saltstone 5.05 SDF PA is adequate. amount of time. In addition, sensitivity models Rinse-Release Monolith were developed in the FY2014 SDF SA to better from Studies to support modeled assumptions Alternately, MF 5.05 may be closed after NRC understand effects of varying the initial oxidation Saltstone for Tc release behavior.

determines that the phenomenon is well- conditions in saltstone. The physical property data understood and the effect on the projected dose for SDU-emplaced and lab-prepared samples is is well supported. summarized in the SDU Cell 2A Core Sampling Report (SRR-CWDA-2016-00051), with values for SDF model inputs provided in the report where applicable. Based on these results, NRC narrowed the scope of this monitoring factor in June 2017 per ML17097A351 to the understanding of changes in hydraulic conductivity in the short term between laboratory-prepared and field-emplaced saltstone.

In FY2018, the NRC recommended closing MF 5.05. (ML18095A122, ML18219B035)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 6 - Disposal Structure Performance In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone Disposal Facility, Docket No. PROJ0734. The NRC expects to close MF 6.01 after NRC TRR is related to MFs 5.04, 6.01, 7.01, 10.04, determines that DOE information about radium 10.06, and 10.09. [ML16342C575]

and selenium sorption in disposal structure concrete is appropriate. Ra-226 information Due to the importance of Kd values, studies were could include either material-specific performed to improve estimates for site-specific measurements of radium sorption to disposal conditions with focus on radionuclides that structure concrete or additional support for the contribute significantly to dose risks. The revised lower inventory estimates for Ra-226 geochemical data package (SRNL-STI-2009-and Th-230 that DOE used in Case K. Se-79 00473) used to identify a justified set of information could include additional model geochemical data inputs for the various transport support (e.g., results of laboratory experiments) modeling at SRS was updated in July 2016 (it was for the appropriate sorption coefficient for Section 2.2.2.1 - Long-Term last revised in March 2010). This update Certain Risk- selenium in oxidized disposal structure concrete. Radiological Lysimeter Program incorporated the numerous experiments and Significant Kd This task is expected to provide Kd geochemical measurements that have been 6.01 Values in Alternately for radium and selenium, if the DOE values in soil and cementitious materials conducted since 2010, resulting in new Disposal dose projection changes, NRC could determine and additional information about long-recommended input values for modeling, Structure that the potential dose from radium and term geochemical and transport integrating recent documented geochemical results, Concrete selenium is appropriate without sorption in the phenomena that will be used to support including radionuclide Kd values, solubility values, disposal structure concrete. DOE may provide the waste release and transport models.

and cementitious impact factors, and includes a additional model support (e.g., results of critical evaluation of these values with respect to laboratory experiments) to demonstrate that the existing values to assess potential impacts. The sorption coefficient for selenium in oxidized 2019 SDF PA incorporates the latest Kd values as disposal structure concrete reflects the sorption recommended in the FY2016 Kd report (SRR-of selenate rather than selenite.

CWDA-2017-00019).

For either Ra-226 or Se-79, if appropriate The NRC recommended expanding the scope of information for one of those radionuclides is MF 5.04 (Certain Risk-Significant Kd Values for provided by DOE, but not the other Saltstone), MF 6.01 (Certain Risk-Significant Kd radionuclide, then NRC could close MF 6.01 Values in Disposal Structure Concrete), and MF and open a new MF for the other radionuclide.

7.01 (Certain Risk-Significant Kd Values in Site Sand and Clay) to now include iodine sorption in saltstone, disposal structure concrete, and soils, respectively. (ML18158A172)

Page 87 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments Based upon new information, the FY2014 SDF SA (SRR-CWDA-2014-00006) incorporated a dual dependency model for Tc-99 solute transport (using both the redox state and the solid-phase concentration of Tc-99, via the solubility limit).

NRC expects to close MF 6.02 after NRC Additionally, the degradation model for determines that Kd values for technetium in cementitious materials has been revised. Together, reduced and oxidized disposal structure concrete Section 2.2 - Saltstone Disposal Technetium these modeling improvements significantly are well-supported. Facility Performance Assessment Sorption in changed the expected transport (and dose results) 6.02 Testing & Research Activities Disposal for Tc-99 within the first 10,000 years after SDF

+/- Alternately, if the DOE dose projection changes, A summary of already completed studies Structure closure.

then NRC could determine that the potential support modeled assumptions for Tc Concrete dose from technetium is appropriate without sorption.

The updated 2019 SDF PA incorporated new technetium sorption in disposal structure information related to the modeling of Tc-99 concrete.

releases. Specifically, the solubility limit was revised.

In FY2018, the NRC recommended closing MF 6.02. (ML18095A122, ML18219B035)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 In April of 2017, the NRC issued a TRR titled Technical Review: Performance of the High Density Polyethylene Layer, High Density Polyethylene/Geosynthetic Clay Liner Composite Layer, and the Lower Lateral Drainage Layer, Docket No. PROJ0734. The TRR is related to MFs 6.03 and 10.02. [ML17081A187]

Section 2.2.2.2 - Studies Related to Infiltration into saltstone is influenced by closure Cementitious Materials Degradation cap performance and roof degradation. Closure Due to Radiation Damage cap performance is addressed in the discussions A literature search will be conducted to associated with MFs 2.01 and 2.02. The roof gain a better understanding of the degradation is addressed through the revised potential degradation of cementitious degradation analysis for cementitious materials.

materials exposed to radiation.

The flow cases in the FY2014 SDF SA provide and additional insights by varying the infiltration rates NRC expects to close MF 6.03 after NRC Section 2.2.2.3 - Closure Cap Long-and the degradation of cementitious materials.

determines that model support for the amount of Term Performance Furthermore, the linear degradation rate for Performance water that DOE expects to be diverted by the Research will validate assumptions in the cementitious materials results in less diversion of of Disposal lower lateral drainage layer, including support PAs concerning the rate of pluggage of water around the SDUs.

6.03 Structure for the hydraulic conductivity of the relevant the closure cap drainage layer as well as Roofs and engineered layers, is sufficient. the drainage layer above each SDU.

Research was begun in FY2017 to improve insights HDPE/GCL related to SDS concrete and high-density Layers Alternately, NRC could close MF 6.03 if DOE Section 2.3.3 - Provide General polyethylene/geosynthetic clay liner (HDPE/GCL) conservatively assumes less diversion around Technical Support on Saltstone degradation. A Closure Cap degradation document the disposal structures in the PA model. Disposal Facility Performance (Predicting Long-Term Percolation from the SDF Assessment Issues Closure Cap, SRRA107772-000009) and SDU To address RSIs from the NRC, literature concrete degradation document (Predicting the reviews are currently underway to better Hydraulic Conductivity Over Time for Degrading evaluate uncertainties associated with the Saltstone Vault Concrete - Task 5, SRRA110110-hydraulic performance of the closure 000004) were issued in FY2018.

cap, including an evaluation of the long-term performance of HDPE and GCL The updated 2019 SDF PA revised the modeling of materials.

HDPE/GCL materials based on this research. As a result of this, infiltration through the closure cap is expected to be lower, resulting in very different flow fields in the vadose zone, relative to previous modeling efforts. Due to these new flow fields, the amount of infiltrating water that is diverted by the lower lateral drainage layer is expected to be minimal.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments For the FY2014 SDF SA, the model assumes a linear degradation rate for cementitious materials.

This assumption conservatively approximates the hydraulic effects of fracturing. The FY2016 SDF Sections 2.2 - Saltstone Disposal SA (SRR-CWDA-2016-00072) addresses cracks in Facility Performance Assessment the SDU roof/floor. Research was begun by Testing & Research Activities Vanderbilt University in FY2017 to improve Previous testing and research activities insights in this area. The intent of the work is to NRC expects to close MF 6.04 after NRC were carried out to provide a better gain an enhanced understanding of mechanisms determines that support for the amount of understanding of degradation potentially associated with the degradation of SDU Disposal fracturing of the disposal structure floor and mechanisms and fracturing. [SRNL-STI- concrete and utilize that information to recommend 6.04 Structure walls expected to occur during the performance 2013-00522] Additional research is an alternative degradation profile to the currently Concrete period is adequate or if NRC determines that the being carried out to establish key utilized, and conservative, linear profile.

Fracturing estimate that DOE uses in the PA model is degradation mechanisms for SDU conservative. concrete based on long-term, realistic The 2019 SDF PA explicitly includes sensitivity service conditions and incorporating cases to examine the potential effects from credible, chronic exposure scenarios. assumed macroscopic fractures through saltstone and SDU concrete.

An SDU concrete degradation document (Predicting the Hydraulic Conductivity Over Time for Degrading Saltstone Vault Concrete - Task 5, SRRA110110-000004) was issued in FY2018.

NRC expects to close MF 6.05 after NRC determines that support for the assumed The FY2014 SDF SA and the 2019 SDF PA performance of non-cementitious materials used Integrity of modeled non-cementitious materials as gravel and in the disposal structures is adequate. For 6.05 Non- demonstrates that joints have a negligible impact example, DOE may perform accelerated testing N/A cementitious on performance, even when modeled with to estimate long-term performance.

Materials conservative moisture characteristic curves (MCCs).

Alternately, DOE may be able to use a conservative estimate in the PA model.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 7 - Subsurface Transport In December of 2016, the NRC issued a TRR titled Technical Review of Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, SRR-CWDA-1013-00058, Rev. 1, July 2014, Docket No.

PROJ0734. The TRR is related to MFs 7.01, 10.07, 10.08 and 10.09. [ML16277A060]

In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone NRC expects to close MF 7.01 after NRC Disposal Facility, Docket No. PROJ0734. The determines that site-specific measurements for TRR is related to MFs 5.04, 6.01, 7.01, 10.04, the Kd value for selenium in sand and clay are 10.06, and 10.09. [ML16342C575]

appropriate. Those measurements should consider the potential effect of the higher pH Section 2.2.2.1 - Long-Term Due to the relative importance of Kd values, studies conditions that are likely to exist downgradient Radiological Lysimeter Program were performed to improve estimates for site-Certain Risk- specific conditions with focus on radionuclides that of the SDF. This task is expected to provide Kd Significant Kd contribute significantly to dose risks. The FY2014 7.01 values in soil and cementitious materials Values in Site SDF SA applied the latest available values. The Alternatively, MF 7.01 may be closed if NRC and additional information about long-Sand and geochemical data package (SRNL-STI-2009-determines that selenium Kd values for SRS term geochemical and transport Clay 00473) used to identify a justified set of sand and clay do not have the potential to phenomena that will be used to support significantly affect the dose to an off-site MOP. the waste release and transport models. geochemical data inputs for the various transport That determination should consider the modeling at SRS was updated July 2016 (it was uncertainty in other key parameters related to last revised in March 2010).

selenium release and transport (i.e., MFs 5.04 and 6.01). The 2019 SDF PA incorporates the latest Kd values as recommended in the FY2016 Kd report (SRR-CWDA-2017-00019).

The NRC recommended expanding the scope of MF 5.04 (Certain Risk-Significant Kd Values for Saltstone), MF 6.01 (Certain Risk-Significant Kd Values in Disposal Structure Concrete), and MF 7.01 (Certain Risk-Significant Kd Values in Site Sand and Clay) to now include iodine sorption in saltstone, disposal structure concrete, and soils, respectively. (ML18158A172)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 8 - Environmental Monitoring Section 2.3.3 - Provide General Technical Support on Saltstone Disposal Facility Performance Assessment Issues NRC expects to close MF 8.01 after the leak 8.01 Leak Activities include supporting NRC on- DOE will provide routine/requested information to detection system ends operation or after final

§ Detection site observation visits and technical NRC as it becomes available. (ML18219B035) waste disposal occurs, whichever comes later.

reviews, general project support, testing and research activity support, and development of resolution path forward for NRC open items.

Section 2.3.3 - Provide General Technical Support on Saltstone Disposal Facility Performance DOE will provide routine/requested information to Assessment Issues NRC as it becomes available.

NRC does not expect to close MF 8.02 because 8.02 Groundwater Activities include supporting NRC on-NRC will monitor groundwater data for the

§ Monitoring site observation visits and technical In FY2018, the NRC recommended not changing duration of NRC monitoring at the SDF.

reviews, general project support, testing either the priority or the status of MF 8.02.

and research activity support, and (ML18117A494, ML18219B035) development of resolution path forward for NRC open items.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments NRC staff identified the following concerns regarding the groundwater monitoring system in the Z Area: (1) the locations and the number of groundwater monitoring wells in the upper part of the aquifer system in order to detect saltstone disposal structure leaks or any unintentional In FY2018, the NRC recommended adding the new release to the subsurface relatively early; (2) the MF 8.03 (Identification and Monitoring of locations and the number of groundwater Groundwater Plumes in the groundwater monitoring wells to adequately follow the monitoring well network). (ML18117A494, development of the plume within the Z Area, ML18219B035)

Identification and (3) the lack of groundwater wells to obtain and background concentration values from the 8.03 Monitoring of The SRS groundwater model (General Separations Upper Three Runs Aquifer-Lower Aquifer N/A Area [GSA] Model) has been updated using recent

+/- Groundwater Zone (UTRA-LAZ).

Plumes in the well data and improved modeling techniques Z Area (SRNLSTI2018-00643). This revised GSA The NRC staff expects to close MF 8.03 when Model showed good agreement with known the NRC staff determines that the groundwater contaminant plumes at the GSA, including the Z monitoring system in the Z Area can: (1) Area plume. The 2019 SDF PA uses this updated identify saltstone contaminants in the GSA Model to simulate groundwater flow and groundwater in the SDF at no more than 150 ft transport.

[46 m] from a disposal structure; and (2) track the movements of the groundwater plume (e.g.,

know the horizontal and vertical extent of the plume; be able to follow the approximate path of the peak of the plume).

MA 9 - Site Stability NRC expects to close MF 9.01 after NRC determines that the projections of settlement in the recent geotechnical investigations will not Settlement adversely affect SDF performance.

Geotechnical evaluations for current and planned 9.01 Due to N/A SDUs indicate that settlement will not be Increased Alternately, DOE may provide NRC significant.

Overburden information that allows NRC to determine that the new DOE settlement projections are consistent with the values assumed in the DOE 2009 SDF PA.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments Geotechnical evaluations for current and planned SDUs indicate that settlement will not be significant.

The Georgia Institute of Technology (GIT) was contracted by the Department of Energy (DOE) to provide an independent evaluation of the soft zones and their implications at the SRS (K-ESR-G-00023, K-TRT-G-00008, K-ESR-K-00008). These studies suggest that the risk of settlement due to dissolution of calcareous sediment is less likely in the GSA where subsurface clastic materials are more dominant than carbonates, compared to areas in the southeast portion of the SRS where the Settlement NRC expects to close MF 9.02 after NRC subsurface carbonates are more dominant than the Due to assesses a new DOE projection of the likelihood 9.02 clastic material.

Dissolution of of the formation of sinks during the period of N/A Calcareous performance at the SDF and any resulting Note that in a geotechnical investigation for the Sediment effects on site stability.

future site of SDU 9 (K-ESR-Z-00010), it was determined that a limited portion of the near-surface soil material beneath the SDU 9 footprint may not provide adequate stability to support the SDU. To mitigate this, the unsuitable material was over-excavated down to approximately 252 feet above mean sea level (msl) and backfilled with structural aggregate fill material back up to an elevation of 262 feet above msl (C-CG-Z-00134).

Regardless, to ensure defensibility, the 2019 SDF PA assumed that SDU 9 would be constructed at a lower elevation of 250 feet above msl as the SDF PA models were performed prior to this site preparation work.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 10 - Performance Assessment Model Revisions The 2019 SDF PA identified multiple conceptual NRC expects to close MF 10.01 after DOE Section 2.4.1 - Prepare Out-year models. These conceptual models were developed Implement- updates the PA and NRC determines that Saltstone Disposal Facility to address specific conditions or to ensure that 10.01 ation of intermediate model results are consistent with Performance Assessment Revisions specific FEPs were addressed (as informed by

+/- Conceptual the conceptual models, quality assurance This section describes future revisions to SRRCWDA201700057 and SRRCWDA2018 Models methods used are appropriate, and parameter the PA that will incorporate 00006). In many cases, various sensitivity cases values and uncertainty ranges are appropriate. improvements to conceptual modeling. were developed to evaluate possible variations of the conceptual models.

In April of 2017, the NRC issued a TRR titled Technical Review: Performance of the High Density Polyethylene Layer, High Density Polyethylene/Geosynthetic Clay Liner Composite Layer, and the Lower Lateral Drainage Layer, Docket No. PROJ0734. The TRR is related to MFs 6.03 and 10.02. [ML17081A187]

Section 2.4.1 - Prepare Out-year Saltstone Disposal Facility The 2019 SDF PA identified multiple conceptual Defensibility NRC expects to close MF 10.02 after DOE 10.02 Performance Assessment Revisions models. These conceptual models were developed of Conceptual updates the PA and NRC determines that the

+/- This section describes future revisions to to address specific conditions or to ensure that Models conceptual models are appropriate.

the PA that will incorporate specific FEPs were addressed (as informed by improvements to conceptual modeling. SRRCWDA201700057 and SRRCWDA2018 00006). In many cases, various sensitivity cases were developed to evaluate possible variations of the conceptual models.

In FY2018, the NRC recommended not changing either the priority or the status of MF 10.02.

(ML18095A122, ML18107A161)

Section 2.2 - Saltstone Disposal The 2019 SDF PA incorporates updated effective Facility Performance Assessment diffusions coefficients based on studies by SREL.

NRC expects to close MF 10.03 after DOE Testing & Research Activities The 2019 SDF PA also provides the basis for the Diffusivity in updates the PA and NRC determines that the 10.03 Measurement of cured saltstone grout assumption that saltstone oxidation prior to closure Degraded diffusivity information, including the model of samples are expected to validate PA cap emplacement will be minimal. This includes Saltstone the movement of the oxidation front, is well-assumptions concerning the movement observations of SDU 2A cores which showed little supported.

of oxidation fronts through cementitious to no evidence that the field-emplaced saltstone materials. was being oxidized.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone Disposal Facility, Docket No. PROJ0734. The TRR is related to MFs 5.04, 6.01, 7.01, 10.04, 10.06, and 10.09. [ML16342C575]

Section 2.2.2.1 - Long-Term Due to the relative importance of Kd values, studies Radiological Lysimeter Program were performed to improve estimates for site-NRC expects to close MF 10.04 after DOE This task is expected to provide Kd specific conditions, with focus on radionuclides updates the PA and NRC determines that the Kd 10.04 Kd Values for values in soil and cementitious materials that contribute significantly to dose risks. The values for saltstone for any radionuclides that Saltstone and additional information about long- FY2014 SDF SA applied the latest available values become risk-significant in the updated PA are term geochemical and transport and future modeling will consider all available well-supported.

phenomena that will be used to support data. The geochemical data package (SRNL-STI-the waste release and transport models. 2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010).

The 2019 SDF PA incorporates the latest Kd values as recommended in the FY2016 Kd report (SRR-CWDA-2017-00019).

In March of 2017, the NRC issued a TRR titled Technical Review: Saltstone Waste Form Section 2.2 - Saltstone Disposal Hydraulic Performance, Docket No. PROJ0734.

NRC expects to close MF 10.05 after DOE Facility Performance Assessment The TRR is related to MF 10.05. [ML17018A137, updates the PA and NRC determines that the Testing & Research Activities ML19150A295]

MCCs are well-supported. Previous testing and research activities Moisture 10.05 investigated the impact of curing The FY2014 SDF SA and the 2019 SDF PA Characteristic Alternatively, MF 10.05 may be closed if, in an temperature on the moisture retention applied revised MCCs to incorporate data from the Curves updated PA, DOE assumes the relative properties in saltstone. Characteristic latest studies. The 2019 SDF PA also includes a permeability is 1, which means that DOE does curves for high cure temperature samples sensitivity case that assumes the relative not use MCCs in the updated PA. were compared to those based on permeability is 1, which means that the MCCs saltstone cured at room temperature. were not used. This sensitivity case showed no change in the results relative to the Compliance Case.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone Disposal Facility, Docket No. PROJ0734. The TRR is related to MFs 5.04, 6.01, 7.01, 10.04, 10.06, and 10.09. [ML16342C575]

Section 2.2.1 - Contaminant Leaching Characteristics from Saltstone Due to the relative importance of Kd values, studies Monolith Emplaced Core Sample were performed to improve estimates for site-NRC expects to close MF 10.06 after DOE Laboratory prepared and process room Kd Values for specific conditions, with focus on radionuclides updates the PA and NRC determines that the Kd samples will have physical properties 10.06 Disposal that are expected to contribute significantly to dose values for disposal structure concrete for any testing performed to determine the Structure risks. The FY2014 SDF SA applied the latest radionuclides that become risk-significant in the hydraulic conductivity, Kd, bulk cured Concrete available values and future modeling will consider updated PA are well-supported. density, porosity, and microstructure/

all available data. The geochemical data package phase analysis. Future testing will (SRNL-STI-2009-00473) used to identify a compare these properties to those justified set of geochemical data inputs for the measured from emplaced core sampling.

various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010).

The 2019 SDF PA incorporates the latest Kd values as recommended in the FY2016 Kd report (SRR-CWDA-2017-00019).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In December of 2016, the NRC issued a TRR titled Technical Review of Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, SRR-CWDA-2013-00058, Rev. 1, July 2014, Docket No.

PROJ0734. The TRR is related to MFs 7.01, NRC expects to close MF 10.07 after DOE 10.07, 10.08, and 10.09. [ML16277A060]

updates the PA and NRC determines that the soil Kd values are well-supported in the soil Calculation of For the FY2014 SDF SA and the 2019 SDF PA, 10.07 build-up calculation (i.e., if DOE chose Build-Up in N/A DOE developed a revised dose calculator that conservative low Kd values in the transport Biosphere Soil incorporated the latest available data related to calculation, then the soil Kd values may not be exposure factors and also included a soil-build up the same Kd values used in the transport calculation with the most recent Kd values. The calculation).

dose calculator (SRR-CWDA-2013-00058) was updated again in early FY2019 for use in the SDF PA revision. Additionally, the 2019 SDF PA also includes a number of sensitivity cases to better evaluate risks associated with alternative Kd values for soil build-up calculations.

In December of 2016, the NRC issued a TRR titled Technical Review of Dose Calculation Methodology for Liquid Waste Performance Section 2.2.3 - Prepare Out-year Assessments at the Savannah River Site, SRR-Consumption Saltstone Disposal Facility CWDA-2013-00058, Rev. 1, July 2014, Docket No.

NRC expects to close MF 10.08 after DOE Factors and Performance Assessment Revisions PROJ0734. The TRR is related to MFs 7.01, updates the PA and NRC determines that the 10.08 Uncertainty This section describes future revisions to 10.07, 10.08, and 10.09. [ML16277A060]

values of consumption factors and uncertainty Distributions the PA that will incorporate the latest distributions for transfer factors are well-for Transfer available information with respect to For the 2019 SDF PA the dose calculator (SRR-supported.

Factors consumption factors, transfer factors, and CWDA-2013-00058) was updated. This update to uncertainty distributions. the dose calculator provided additional support for the consumption factors and removed the unsupported uncertainty distributions associated with the transfer factors.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments In December of 2016, the NRC issued a TRR titled Technical Review of Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site, SRR-CWDA-1013-00058, Rev. 1, July 2014, Docket No.

PROJ0734. The TRR is related to MFs 7.01, 10.07, 10.08, and 10.09. [ML16277A060]

In January of 2017, the NRC issued a TRR titled Technical Review: Iodine Sorption Coefficients for Use in Performance Assessments for the Saltstone Section 2.2.2.1 - Long-Term Disposal Facility, Docket No. PROJ0734. The Radiological Lysimeter Program TRR is related to MFs 5.04, 6.01, 7.01, 10.04, NRC expects to close MF 10.09 after DOE This task is expected to provide Kd 10.06, and 10.09. [ML16342C575]

10.09 updates the PA and NRC determines that the Kd Values for values in soil and cementitious materials site-specific Kd values for any radionuclides that SRS Soil and additional information about long- Due to the relative importance of Kd values, studies become risk-significant in the updated PA are term geochemical and transport were performed to improve estimates for site-well-supported.

phenomena that will be used to support specific conditions, with focus on radionuclides the waste release and transport models. that are expected to contribute significantly to dose risks. The FY2014 SDF SA applied the latest available values and future modeling will consider all available data. The geochemical data package (SRNL-STI-2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010).

The 2019 SDF PA incorporates the latest Kd values as recommended in the FY2016 Kd report (SRR-CWDA-2017-00019).

Section 2.3.3 - Provide General The SRS groundwater model (GSA Model) has Technical Support on Saltstone been updated using recent well data and improved NRC expects to close MF 10.10 after DOE Disposal Facility Performance modeling techniques (SRNLSTI2018-00643).

Far-Field 10.10 updates the PA and NRC determines that the Assessment Issues This revised GSA Model showed good agreement Model far-field model calibration, particularly in the To address RSIs from the NRC, with known contaminant plumes at the GSA, Calibration area near the SDF, is adequate. additional ground water modeling will be including the Z Area plume. The 2019 SDF PA developed to support improved far-field uses this updated GSA Model to simulate model calibration. groundwater flow and transport.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments Far-Field NRC expects to close MF 10.11 after DOE 10.11 Model Source updates the PA and NRC determines that the No new activities have been performed to address N/A Loading far-field source loading approach in the model is this monitoring factor.

Approach adequate.

NRC expects to close MF 10.12 after DOE In response to the RAIs for the FY2013 SDF SA, updates the PA and NRC determines that the Far-Field DOE has performed sensitivity modeling to 10.12 grid refinement used in any hydrological model Model N/A evaluate the potential impacts from dispersivity supporting the updated PA does not increase Dispersion variability. A similar sensitivity case was also modeled dispersion beyond the expected incorporated into the 2019 SDF PA.

physical dispersion.

Impact of NRC expects to close MF 10.13 after DOE Geotechnical evaluations for current and planned Calcareous investigates potential preferential pathways due SDUs indicate that subsurface calcareous zone will 10.13 Zones on to subsurface calcareous zones and NRC be minimal or not present in Z Area. Regardless, N/A Contaminant determines that the DOE representation of any the 2019 SDF PA includes a sensitivity case to Flow and preferential pathways due to calcareous zones is evaluate the potential impacts should preferential Transport adequate. flow paths be present.

In FY2018, the NRC recommended adding the new MF 10.14 (Scenario Development and Defensibility) as Medium priority to reflect the NRC would monitor DOE consideration of NRC staff distinguishing conceptual model plausible alternative scenarios in future PA uncertainty from scenario uncertainty.

development because of the potential (ML18158A172)

Scenario importance of plausible alternative scenarios to 10.14 Development dose projections and continue to monitor the N/A The 2019 SDF PA identified multiple conceptual and scenario development and defensibility of the models. These conceptual models were developed Defensibility central scenario. The NRC expects to close MF to address specific conditions or to ensure that 10.14 after the DOE updates the PA and the specific FEPs were addressed (as informed by NRC determines that the evaluated scenarios are SRRCWDA201700057 and SRRCWDA2018 appropriate 00006). In many cases, various sensitivity cases were developed to evaluate possible variations of the conceptual models.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as MF # 1 Factor NRC Expectations2 Described in this Document Comments MA 11 - Radiation Protection Program Section 2.3.3 - Provide General Technical Support on Saltstone Disposal Facility Performance Dose to Assessment Issues 11.01 Individuals NRC expects to close MF 11.01 at the end of Activities include supporting NRC on- DOE will provide routine/requested information to

§ During the institutional control period. site observation visits and technical NRC as it becomes available.

Operations reviews, general project support, testing and research activity support, and development of resolution path forward for NRC open items.

Section 2.3.3 - Provide General Technical Support on Saltstone Disposal Facility Performance Assessment Issues Activities include supporting NRC on-11.02 Air NRC expects to close MF 11.02 at the end of site observation visits and technical DOE will provide routine/requested information to

§ Monitoring the institutional control period. reviews, general project support, testing NRC as it becomes available.

and research activity support, and development of resolution path forward for NRC open items.

Y = Yes N= No N/A = Not applicable 1

Monitoring Factors are color-coded based on NRC-determined prioritizations in NRC SDF Monitoring Plan. [ML13100A113]. Symbols are included for clarity.

+/- Red = High Green = Low Yellow = Medium § Blue = Periodic Purple = Closed 2

NRC expectations are from the NRC SDF Monitoring Plan. [ML13100A113]. Subsequent to issuance of the NRC SDF Monitoring Plan, NRC has issued various TRRs related to SDF monitoring activities. [ML13304B159, ML15098A031, ML16196A179, ML16277A060, ML16342C575, ML17018A137, ML17081A187, ML18002A545, ML18033A071, ML18095A122, ML18117A494, ML18158A172, ML19031B221]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 APPENDIX C U.S. Nuclear Regulatory Commission Monitoring Items for F-Area Tank Farm and H-Area Tank Farm Page 102 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Appendix C: U.S. Nuclear Regulatory Commission Monitoring Items for the F-Area Tank Farm and H-Area Tank Farm Factors are colored by NRC priority and a symbol is included with each MF number to ensure clarity. Changes from previous year are indicated by red text. A legend containing a description of the NRC ranking is provided at the end of the Table.

Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 1 - Inventory General NRC Monitoring Activities [ML15238A761]

During the monitoring period, NRC staff will review special analyses typically performed Section 3.4.3 - Tank Farm SA at the time of closure of each tank that provide updated inventories and risk estimates for Each tank is sampled following waste retrieval the entire tank farm that is the subject of the special analysis. NRC staff will assess the operations. For each waste tank an SA will be degree to which DOE demonstrates the tank farm meets the performance objectives with performed to evaluate the impact of the final residual the new projected radionuclide inventories and will assess other PA updates. As part of inventory on the conclusions of the PAs. SAs will be the evaluation, NRC staff will assess the degree to which DOEs special analyses evaluate available to the NRC in support of NRCs monitoring uncertainty in the revised inventory. NRC staff should independently verify whether the role. An SA specific to the HTF Type I and Type II change in inventory, or changes to other modeling parameters, are expected to lead to an Tanks was prepared and issued in August 2016.

exceedance of the dose-based performance objectives (i.e., a 0.25 mSv/yr [25 mrem/yr]

[SRR-CWDA-2016-00078] This SA updated the limit to a MOP under 10 CFR 61.41 or an applied 5 mSv/yr [500 mrem/yr] limit to an radiological and chemical inventories for the HTF intruder under 10 CFR 61.42). NRC staff will review special analyses to ensure intruder Type I and Type II tanks, incorporating lessons risks reported in the tank farm PAs are appropriately assessed and evaluated.

learned from the final waste tank characterization results to date.

This factor can be closed following NRC review of the last tank or equipment-specific Final Inventory special analysis prepared by DOE for FTF and HTF.

1.1 and Risk Section - N/A Estimates Recommendation [FTF and HTF TERs - As Tanks Are Cleaned and Sampled]

DOE has committed to sampling of each tank In the FTF and HTR TERs, NRC staff recommended DOE sample each tank following following waste retrieval operations. This activity is waste retrieval operations for the purpose of developing a final inventory.

covered as part of the individual tank project work (Duplicate, also applies to MF 1.2) scope.

Section - N/A Recommendation [FTF and HTF TERs - When Developing Highly Radioactive Each tank will be sampled following waste retrieval Radionuclide (HRR) List and When Characterizing Residuals] operations and an SA will be performed to evaluate In the FTF and HTR TERs, NRC staff recommended that DOE continue to evaluate its the impact of the final residual inventory on the HRR list and provide sufficient justification for any changes as additional information conclusions of the applicable PA. Development of becomes available. The HRR list should be evaluated especially where it is used to the final tank residual inventory, including selection inform decisions, such as the selection of radionuclides characterized in residual waste, of radionuclides to be analyzed, is covered as part of selection of treatment technologies, and the screening of radionuclides for the purpose of the individual tank project work scope. This detailed PA calculations. recommendation will be considered in development (Duplicate, also applies to MF 1.2) of future inventory determinations and documentation.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.3- Tank Farm SA Each tank is sampled following waste retrieval operations. An SA will be performed to evaluate the impact of the final residual inventory on the conclusions of the applicable PA. This Recommendation [HTF TER] recommendation will be considered in development In the HTF TER, NRC staff recommended DOE revise its annulus inventory assumptions of future SAs. An SA specific to the HTF Type I and in the HTF PA if plans to clean the annuli of Tanks 9H, 10H, and 14H change. Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA updated the radiological and chemical inventories for the HTF Type I and Type II tanks, incorporating lessons learned from the final waste tank characterization results to date.

Section 3.4.3 - Tank Farm SA Final Inventory Each tank is sampled following waste retrieval 1.1 operations. An SA will be performed to evaluate the and Risk impact of the final residual inventory on the Estimates conclusions of the applicable PA. This recommendation will be considered in development of future SAs. Under Monitoring Factor 1.1, the NRC concluded that the Tank 12H SA adequately evaluated deviations in the Tank 12H final inventory Recommendation [ML13273A299]

compared to forecasted inventories used in earlier PA DOE should evaluate whether it has appropriately managed inventory uncertainty.

calculations. [ML17277B235]

An SA specific to the HTF Type I and Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA updated the radiological and chemical inventories for the HTF Type I and Type II tanks, incorporating lessons learned from the final waste tank characterization results to date.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.3 - Tank Farm SA Each tank is sampled following waste retrieval operations. An SA will be performed to evaluate the impact of the final residual inventory on the conclusions of the applicable PA. This Recommendation [ML13273A299] recommendation will be considered in development DOE should provide a stronger technical basis for projected inventory multipliers. of future SAs. An SA specific to the HTF Type I and Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA updated the radiological and chemical inventories for the HTF Type I and Type II tanks, incorporating lessons learned from the final waste tank characterization results to date.

General NRC Monitoring Activities [ML15238A761]

NRC staff will review sampling and analysis plans developed for each tank. NRCs technical review should include, but may not be limited to, the following considerations:

• Consideration of intratank waste variability that is important to the sampling design, including the basis for assumptions regarding homogeneity and the number of samples to be collected

• Use of floor concentration samples for assigning residual waste inventory for tank walls

• DOEs support for assumptions regarding normality of radionuclide concentration when developing deterministic and probabilistic inventory parameters Section 3.3.3 - Provide General Technical

• Sampling of HRRs or basis for removal of HRRs from the list of radionuclides to be Support on Tank Farm PA Issues 1.2 Residual Waste sampled Ongoing support of NRCs monitoring role will be Sampling In addition to review of sampling and analysis plans, NRC staff also will conduct its own provided as necessary.

independent assessment to verify the list of HRRs in DOEs assessment is complete. If additional HRRs are identified, NRC staff will meet with DOE to resolve the discrepancies in the list and suggest actions, as appropriate, that DOE could take to ensure that risks are appropriately assessed and managed. NRC staff will review sampling and analysis plans to ensure all HRRs are sampled or a basis for exclusion of an HRR is provided.

This MF can be closed when NRC concludes that DOE has provided sufficient information to support its list of HRRs and following review of the last sampling and analysis plan for a tank and following the last planned onsite observation of sampling of a tank (may occur prior to the last tank or ancillary equipment being sampled).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section - N/A Recommendation [FTF and HTF TERs - As Tanks Are Cleaned and Sampled]

DOE has committed to sampling of each tank In the FTF and HTF TERs, NRC staff recommended DOE sample each tank following following waste retrieval operations. This activity is waste retrieval operations for the purpose of developing a final inventory.

covered as part of the individual tank project work (Duplicate, also applies to MF 1.1) scope.

Section - N/A Recommendation [FTF TER - As Tanks Are Sampled and SAs are Prepared]

Each tank will be sampled following waste retrieval In the FTF TER, NRC staff recommended DOE better explain intratank waste variability operations and an SA will be performed to evaluate that influences waste characterization and uncertainty evaluation. NRCs comments were the impact of the final residual inventory on the expressed in the context of Tank 18 sampling, but also pertain to future characterization of conclusions of the applicable PA. Development of other tanks. Specifically, NRC commented on (i) lack of explanation regarding the final tank residual inventory is covered as part of differences between past and current sample variability, (ii) potential lack of consideration the individual tank project work scope. This and explanation of the unexpectedly high tank wall concentrations for Pu-238, and (iii) recommendation will be considered in development lack of basis for assumptions regarding normality of sample concentrations and volume of future inventory determinations and estimates when calculating inventory multiplier to be used in the probabilistic analysis. documentation.

Section - N/A Recommendation [FTF and HTF TERs - When Developing HRR List and When Each tank will be sampled following waste retrieval Characterizing Residuals] operations and an SA will be performed to evaluate In the TERs for FTF and HTF, NRC staff recommended DOE continue to evaluate its the impact of the final residual inventory on the HRR list and provided sufficient justification for any changes as additional information conclusions of the applicable PA. Development of becomes available. The HRR List should be evaluated especially where it is used to the final tank residual inventory, including selection inform decisions, such as the selection of radionuclides characterized in residual waste, of radionuclides to be analyzed, is covered as part of selection of treatment technologies, and the screening of radionuclides for the purpose of the individual tank project work scope. This detailed PA calculations. recommendation will be considered in development (Duplicate, also applies to MF 1.1) of future inventory determinations and documentation.

1.2 Residual Waste Recommendation [HTF TER - When Characterizing Residuals]

Sampling Section 3.3.3 - Provide General Technical In the HTF TER, the NRC repeated recommendations from the Inventory TRR for Tanks 5F and 6F related to sampling (ML13085A291). These recommendations include: Support on Tank Farm PA Issues

1. DOE should consider, in its tank sampling design, historical information on tank These recommendations apply to the overall waste waste receipts, and information related to the alteration and redistribution of waste due tank residual sampling program and are not tank-to cleaning operations that may impact horizontal and vertical waste heterogeneity, specific. These recommendations will be evaluated

2. DOE should evaluate the option to composite samples within segments (or strata) to as funding becomes available.

preserve information about segment (or strata) variance,

3. DOE should evaluate and present information on the relative contributions of various Under Monitoring Factor 1.2, the NRC concluded forms of uncertainty in its estimation of mean tank concentrations, that the DOE methodology used to develop final inventory estimates for high-level waste tanks in the

4. DOE should also consider how it can better assure sample representativeness by Tank 12H SA was acceptable. [ML17277B235]

improving tank sampling designs, collection tools and instructions.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.3.3 - Provide General Technical General NRC Monitoring Activities [ML15238A761]

Support on Tank Farm PA Issues DOE indicates its intent to improve the method of estimating residual volumes in its LW Ongoing support of NRCs monitoring role will be PA Maintenance Programs (e.g., SRR-CWDA-2012-00022 and SRR-CWDA-2014-provided as necessary.

00108). NRC staff will monitor DOEs progress in this area. NRC staff also will attempt to observe DOEs use of video and photographic records to develop residual waste With respect to volume estimation (Monitoring volumes during an onsite observation. NRC staff will monitor DOEs visual inspection of Factor 1.3), the NRC found DOE implementation of internal surfaces to ensure no significant inventory is overlooked (e.g., Pu-238 on the the tank mapping methodology for Tank 12H 1.3 Residual Waste walls of Tank 18F). In the Tank 16H Final Inventory TRR (ML15301A830), NRC adequate for the purpose of developing radionuclide Volume reiterated that DOE needs to improve documentation of its volume estimation approach, as inventories for use in PA calculations, although well as validate methods used to estimate the residual volumes whether through sampling, several areas of potential improvement were noted, measurement or through more qualitative methods (e.g., visual evidence).

particularly related to timing of solids mapping and consideration of uncertainty in volume estimates.

This factor will be closed once NRC staff concludes DOE has taken steps to improve the Additional technical issues relevant to volume process by which it estimates residual volumes or shows that DOE has appropriately estimation were listed in the Tank 16H inventory managed volume uncertainty. This factor may be reopened if NRC staff identifies issues TRR (ML15301A830) and were not repeated.

with DOEs approach to developing or considering uncertainty in volumes estimates.

[ML17277B235]

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [FTF and HTF TERs - 1 to 5 Years, Next Tank Mapping]

In the FTF TER, NRC staff recommended DOE consider improvements to residual material mapping and consideration of uncertainty in volume estimates. In the HTF TER, NRC repeated recommendations related to volume estimations from the Inventory TRR for FTF Tanks 5 and 6. [ML13085A291] NRC expects DOE to address the following technical concerns when estimating residual tank waste volumes in the future: Section 3.3.3 - Provide General Technical

1. DOE should better understand the accuracy of mapping team height estimates through Support on Tank Farm PA Issues additional field validation activities for a range of solid material heights. Ongoing support of NRCs monitoring role will be

2. DOE should clearly communicate how it determines the size of areas to be mapped provided as necessary. These recommendations and how it manages uncertainty related to height estimates for discretized areas in its apply to the overall waste tank residual sampling deterministic analysis. Likewise, DOE should clarify how it represents uncertainty in program and are not tank-specific. These 1.3 Residual Waste the assignment of high and low end heights to these areas (e.g., does it use a height recommendations will be evaluated as funding Volume that is clearly below/above the non-uniform surface of the delineated areas). becomes available.

3. DOE should consider uncertainty in the volume estimates resulting from the transfer of data from photographic and video evidence to hand contoured maps (and then to Excel spreadsheets with a finer discretization). Section - N/A

4. DOE should be more transparent with respect to its approach to (i) mapping annular DOE will stay up to date with advances in volume volumes including use of a crawler to inspect internal surfaces and (ii) estimating measurement applications.

residual waste volumes in ventilation ducts. DOE should consider uncertainty in annulus volume estimates.

In lieu of improving the method by which DOE estimates residual waste volume, DOE could manage inventory uncertainty with conservative estimates (i.e., volume estimates that clearly err on the side of higher values).

Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues General NRC Monitoring Activities [ML15238A761]

Ongoing support of NRCs monitoring role will be DOE indicated, in response to NRC comment (SRR-CWDA-2009-00054), its intent to provided as necessary.

verify PA assumptions regarding transfer line inventories consistent with Section 8.2, Further Work, in DOEs PA (SRS-REG-2007-00002). NRC staff will meet with DOE Section 3.4.3 - Tank Farm SA to discuss DOEs schedule for characterization of transfer lines to ensure conclusions In FY2021, an SA was issued to support operational Ancillary regarding the relatively low risk estimates for transfer lines are confirmed. Additionally, 1.4 closure of FDB-5 and FDB-6, which are no longer Equipment transfer line inventories are important for the intruder analysis because DOE assumes an

• needed in support of FTF operations. The FDB-5 Inventory intruder can more easily access the residual inventory in a transfer line than in a tank.

and FDB-6 SA reports that the results and NRC staff will monitor DOEs efforts in this area to ensure the assumed transfer line conclusions presented in FTF PA and supporting SAs inventories are sufficiently bounding or that increased risk is assessed. are not impacted by new information regarding the final residual inventories that are planned to be This MF can be closed once NRC staff concludes that DOE characterization has grouted in-place in FDB-5 and FDB-6 and the confirmed the low risk of ancillary components.

conclusions reached based on the FTF PA information, remain valid.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.3 - Tank Farm SA In FY2021, an SA was issued to support operational closure of FDB-5 and FDB-6, which are no longer needed in support of FTF operations. The FDB-5 Recommendation [FTF and HTF TERs - 1 to 5 Years]

Ancillary and FDB-6 SA reports that the results and 1.4 DOE indicates, in response to NRC comment (SRR-CWDA-2009-00054) its intent to Equipment conclusions presented in FTF PA and supporting SAs

• verify PA assumptions regarding transfer line inventories consistent with Section 8.2, Inventory are not impacted by new information regarding the Further Work in DOEs PA (SRS-REG-2007-00002).

final residual inventories that are planned to be grouted in-place in FDB-5 and FDB-6 and the conclusions reached based on the FTF PA information, remain valid.

General NRC Monitoring Activities [ML15238A761]

NRC will evaluate removal to the maximum extent practical (MEP) for each cleaned tank to ensure DOE disposal actions are consistent with as low as reasonably achievable Section 3.3.3 - Provide General Technical (ALARA) criteria. NRC staff will assess DOE compliance with ALARA objectives Support on Tank Farm PA Issues through review of DOE documentation completed in conjunction with the federal facility Ongoing support of NRCs monitoring role will be agreement closure process. provided as necessary.

This factor can be closed once all tanks are cleaned and NRC staff has reviewed DOE documentation of removal to the MEP.

Waste Removal 1.5 Recommendation [FTF and HTF TERs - As Tanks Are Cleaned]

(As It Pertains

• In the FTF TER, NRC staff recommended DOE more fully evaluate costs and benefits of to ALARA) additional HRR removal, including (i) consideration of benefits of additional HRR Section - N/A removal over longer performance periods (and considering uncertainty in the timing of Development of cost-benefit analyses related to HRR peak doses), (ii) justification for assumptions regarding alternative cleaning technology removal are covered as part of the individual tank effectiveness, and (iii) comparison of costs and benefits of additional HRR removal to project work scope. This recommendation will be similar DOE activities. In the HTF TER, NRC staff indicated that DOE provide a clear considered in development of future cost-benefit linkage between the Criterion 2 evaluation and the PA results, including consideration of analyses.

the long-term risks associated with the HTF facility, and indicated that sufficient detail was not provided in the waste determination to ensure consistent format and appropriate content for future cost-benefit analyses.

Page 109 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.2 - Prepare Out-Year HTF PA Revisions This recommendation will be considered in the next PA revision. An SA specific to the HTF Type I and Recommendation [HTF TER] Type II Tanks was prepared and issued in August In the HTF TER, NRC staff indicated that it does not have confidence that DOE has 2016. [SRR-CWDA-2016-00078] This SA updated adequately evaluated the risk associated with the projected inventory of the Tank 16H the radiological and chemical inventories for the HTF annulus. The NRC staff recommended DOE evaluate a waste release scenario due to Type I and Type II tanks, incorporating lessons groundwater in-leakage into and out of the annular region and contacting the high- learned from the final waste tank characterization solubility waste in the annuli of those tanks. results to date.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Section - N/A Recommendation [ML13080A401]

Development of cost-benefit analyses related to In the Cost Benefit Analysis for Tanks 18 and 19, the NRC noted that many additional Highly Radioactive Radionuclide (HRR) removal are costs were due to the length of time that had passed between the decision to cease removal covered as part of the individual tank project work activities and the time at which the cost-benefit analysis was performed. DOE does not scope. This recommendation will be considered in expect this lapse in time for future cost-benefit analysis for other tanks. development of future cost-benefit analyses.

Section - N/A Recommendation [ML13080A401] Development of cost-benefit analyses related to HRR In the Cost Benefit Analysis for Tanks 18 and 19, the NRC noted issues with the removal are covered as part of the individual tank collective dose comparison, which only included 1 person for 50 years, although NRC project work scope. This recommendation will be also noted problems with use of collective dose. considered in development of future cost-benefit Waste Removal analyses.

1.5 (As It Pertains

• Section - N/A to ALARA)

Recommendation [ML13080A401] Development of cost-benefit analyses related to HRR In the Cost Benefit Analysis for Tanks 18 and 19, the NRC staff questioned DOEs removal are covered as part of the individual tank criteria that additional waste removal be more cost beneficial than other similar DOE project work scope. This recommendation will be activities. considered in development of future cost-benefit analyses.

Recommendation [ML13080A401] Section - N/A In the Cost Benefit Analysis for Tanks 18F and 19F, the NRC staff also questioned DOEs Development of cost-benefit analyses related to HRR separate consideration of cost and benefit uncertainty in its sensitivity analysis removal are covered as part of the individual tank (cumulative impact of uncertainty in the costs and benefits was not considered). project work scope. This recommendation will be Additionally, higher removal rates (e.g., 75 percent) could have been evaluated in considered in development of future cost-benefit sensitivity analysis. analyses.

Page 110 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 2 - Waste Release Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues Testing of actual waste (i.e., Tank 18 and Tank 12 residuals) was performed in FY2016 and FY2018.

The solubilities of I, Pu, Np, U, and Tc were tested under simulated waste tank chemistry conditions using Tank 18 and Tank 12 residual waste samples.

Data was collected via measured concentrations (or General NRC Monitoring Activities [ML15238A761]

solubilities) over a multi week testing period under NRC continues to recommend that DOE design and perform waste release experiments different chemical conditions (pH and Eh were using actual tank residual samples as soon as practical. DOE staff should continue to varied). The chemical conditions reflect a range of discuss its plans with NRC to ensure experiments are designed to optimize their potential states such that the test results can be used to better usefulness in supporting the 10 CFR 61.41 compliance demonstrations. This monitoring understand the impact of transitory waste tank activity is considered to be the highest priority by NRC staff at this time from both a Solubility- chemical conditions on solubility. As discussed in timing and importance perspective. NRC staff encourages DOE to continue the work that 2.1 Limiting Evaluation of Waste Release Testing Results against was initiated in FY2014 with respect to obtaining support for the assumed solubility limits

§ Phases/Limits the Tank Farm Performance Assessment Waste of key radionuclides in tank farm waste. Pending results of the waste release experiments, and Validation Release Model (SRR-CWDA-2016-00086), the NRC will evaluate the need for additional experiments for other tank waste.

experimental results indicate there may be some variance from the actual waste solubilities and the This factor can be closed once DOE provides experimental support for the assumed WRM assigned solubilities. For example, Np and I solubilities of key radionuclides relied on for performance. The results of waste release was in all cases more insoluble than assigned in the experiments may inform the extent to which additional recommendations would need to WRM. The other three elements (Pu, Tc and U) be implemented.

appeared in most instances to be potentially more soluble than was assumed in the WRM. For example, Pu was relatively insoluble when oxidized, but was still more soluble than calculated by the WRM. Even if the experimental results were conservatively accepted into the WRM, the newly assigned solubilities would have a negligible impact on peak doses in 1,000 or 10,000 years.

Page 111 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.1.1 - Waste Release Studies Recommendation [FTF and HTF TERs - Short-to-immediate term]

This task focuses on reducing uncertainty In the FTF TER, NRC staff recommended DOE perform experiments to verify validity of surrounding WRM assumptions. The first step is to Geochemists Workbench calculations used to determine solubility-limiting phases, attempt to determine solubility values based on actual solubility limits, and chemical transition times. These experiments should study (i) pH waste samples for key radionuclides. Testing of and Eh evolution of the grout pore water over time, (ii) controlling solubility-limiting actual waste (i.e., Tank 18 and Tank 12 residuals) phases, and (iii) static and dynamic leach tests to study the mobility of HRRs, including was performed in FY2016 and FY2018. The consideration of alteration of tank residuals following chemical cleaning with reagents, solubilities of I, Pu, Np, U, and Tc were tested under such as oxalic acid. In the HTF TER, NRC staff reiterates its FTF recommendation that simulated waste tank chemistry conditions using DOE conduct waste release experiments to (i) distinguish between releases from high Tank 18 and Tank 12 residual waste samples, with solubility compounds and low solubility compounds via semi-dynamic leach tests and (ii) the results documented in Evaluation of Waste determine constant concentrations of elements of concern under conditions of exposure to Release Testing Results against the Tank Farm local groundwater and grout leachate via static tests.

Performance Assessment Waste Release Model (Duplicate, also applies to MF 2.2)

(SRR-CWDA-2016-00086).

Section 3.2.4 - To Be Determined Out-Year Solubility- Testing 2.1 Limiting An SA specific to the HTF Type I and Type II Tanks

§ Phases/Limits was prepared and issued in August 2016. [SRR-and Validation CWDA-2016-00078] This SA updated the radiological and chemical inventories for the HTF Recommendation [ML12272A082] Type I and Type II tanks, incorporating lessons DOE should provide additional information to support assumptions regarding longevity of learned from the final waste tank characterization reducing conditions in the contaminated zone. Recent studies (Cantrell and Williams, results to date.

2012) suggest that the reducing capacity of the tank grout could be depleted much earlier DOE has evaluated potential activities in this area than assumed in the FTF PA (SRS-REG-2007-00002) and in more recent plutonium based on the waste release testing experimental work solubility modeling performed for Tank 18 (SRNL-STI-2012-00087). Uncertainty in the performed in support MF 2.1. Testing is being normative mineralogy assumed in geochemical modeling should be considered under this performed on various grout formulations to provide action. additional information regarding: 1) the impact of (Duplicate, also applies to MF 2.2) infiltrating ground water on grout pore water chemistry (e.g. pH and Eh) through time, 2) the ranges of tank grout pore water pH and Eh to be expected in waste tanks, initially and through time following many pore volume flushes, and 3) the mineralogy of tank fill grouts, initially and through time following many pore volume flushes.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing DOE has evaluated potential activities in this area based on the waste release testing experimental work Recommendation [ML12272A082]

performed in support MF 2.1. Testing is being DOE should provide additional support for the assumption that the Eh of infiltrating water performed on various grout formulations to provide will remain below a critical threshold at which plutonium solubility will increase to a risk additional information regarding: 1) the impact of significant value (e.g., updated geochemical modeling indicates a dramatic increase in infiltrating ground water on grout pore water plutonium solubility occurs at Eh greater than +0.45 V). Uncertainty in the critical chemistry (e.g. pH and Eh) through time, 2) the threshold and the Eh of infiltrating groundwater should be considered under this action.

ranges of tank grout pore water pH and Eh to be (Duplicate, also applies to MF 2.2) expected in waste tanks, initially and through time following many pore volume flushes, and 3) the mineralogy of tank fill grouts, initially and through time following many pore volume flushes.

Page 113 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML18242A259]

In the Tank 18F Waste Release Testing TRR, NRC staff concluded that additional waste release testing and updated geochemical modeling are needed for NRC staff to have confidence in the PA results. The NRC staff offered the following additional conclusions and comments related to waste release testing.

• Although DOE only used a single sample (FTF-1) for the Tank 18F waste release testing, their rationale (e.g., good characterization, and high concentrations of key radionuclides) is reasonable. In future waste release Testing of actual waste (i.e., Tank 18 and Tank 12 testing, if testing of multiple samples is impractical, DOE should consider residuals) was performed in FY2016 and FY2018.

compositing samples to get representative results for the entire tank contents The solubilities of I, Pu, Np, U, and Tc were tested rather than just a small portion of the waste. under simulated waste tank chemistry conditions

• DOE should consider the impact of waste treatment methods, grout additives, using Tank 18 and Tank 12 residual waste samples.

and other chemical constituents that may increase radionuclide solubility (e.g., The NRC conclusions and comments relating to oxalates and carbonates) in designing and evaluating the results of future waste release testing were incorporated into the Tank 12 testing to the extent practical and will be experiments.

addressed further in any future testing.

• In future testing, DOE should consider water rinses with synthetic SRS ground Solubility-water in addition to grout conditioned ground water to study the impact of grout 2.1 Limiting DOE has also evaluated other potential activities in bypass on waste release results. DOE should also consider evaluating the change

§ Phases/Limits this area based on the waste release testing in concentration over time for the rinse solutions.

and Validation experimental work performed in support MF 2.1.

• DOE should continue to conduct solid phase analysis of residual waste to inform Testing is being performed on various grout waste release assumptions for other tanks.

formulations to provide additional information

• As recommended by an independent peer review group, DOE should consider regarding: 1) the impact of infiltrating ground water conducting spectroscopic analyses of plutonium (Pu) and other metals such as on grout pore water chemistry (e.g. pH and Eh) iron (Fe) in waste residues.

through time, 2) the ranges of tank grout pore water

• DOE should analyze all major ions, alkalinity, and appropriate trace components pH and Eh to be expected in waste tanks, initially and (e.g., Pu, Fe, and sulfide). through time following many pore volume flushes,

• DOE should consider the following: (1) comparison of the experimental and 3) the mineralogy of tank fill grouts, initially and conditions against those for which the Nuclear Energy Agencys (NEAs) through time following many pore volume flushes.

thermodynamic database is based to better understand differences in the modeled and experimental results, and (2) updating the assumed phases and geochemical modeling as warranted.

• DOE should consider performing updated geochemical modeling using information gained from characterization of the tanks, and knowledge gained from comparisons of the experimental to previously modeled results.

Page 114 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Recommendation [ML19298A092]

In the Tank 12H Waste Release Testing TRR, NRC stated that DOE should consider the following items to enhance its waste release testing.

• NRC staff supports DOEs recommendation to conduct additional leach testing on other tank waste (N-ESR-H-00040).

• DOE should consider evaluation of the impact of waste type, waste treatment methods, grout additives, & other chemical constituents that may increase radionuclide solubility (e.g., oxalates & carbonates) in designing/evaluating the results of future experiments.

• In future waste release testing, if testing of multiple tank samples is impractical, DOE should develop support for the use of composite samples and discuss the limitations of use of a composite sampling approach. Ideally supporting information for use of a composite leach test sample would include solid phase characterization and aqueous phase concentrations of individual samples to better understand tank waste variability.

• As stated in the Tank 18F TRR (ML18242A259), in future testing, DOE should consider water rinses with synthetic SRS groundwater in addition to grout conditioned groundwater to study the impact of grout bypass on waste release results.

• DOE should conduct solid phase analysis on tank waste residuals, including Tank 12H. Recommendations were provided in an independent peer review group report Waste release testing is being performed on various Solubility- (LA-UR-2012-00079) with potential analysis methods. grout formulations to provide additional information.

2.1 Limiting

• DOE should analyze all major ions, alkalinity, and appropriate trace components (e.g., The topics addressed in this recommendation will be

§ Phases/Limits Pu, Fe, and sulfide). If possible, an anion/cation balance should be calculated to considered in any future waste release testing and in and Validation determine if an important component has been missed. updates to the Waste Release Modeling.

• DOE should consider the following: (1) comparison of the experimental conditions against those for which the NEAs thermodynamic database is based to better understand differences in the modeled and experimental results, and (2) updating the assumed phases and geochemical modeling as warranted.

• DOE should consider performing updated geochemical modeling using information gained from characterization of the tanks, and knowledge gained from comparisons of the experimental to previously modeled results. DOE should also consider how the inability to meet the target Eh endpoints assumed in modeling affect the results.

• DOE should develop additional model support that calcium carbonate maintains pH in the simulated cement-reacted solutions, both oxidizing and reducing, and how the leaching results might have been affected by this assumption.

• DOE should develop additional model support to refer to the results of the experiments (i.e., aqueous phase concentrations) as solubilities. Without a conceptual understanding of controls on radionuclide concentrations in the engineered system, it would be difficult to extrapolate the results to other conditions.

• DOE should discuss how the RRII and ORII conditions targeted in the leach testing differ from Conditions C and D assumed in the HTF PA for Tank 12H, and how the use of a higher pH affects the applicability of the experimental results.

Page 115 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML19298A092]

In the Tank 12H Waste Release Testing TRR, NRC stated that DOE should consider the following items to continue to address uncertainties in the current PA models and support future PA models.

• DOE should perform probabilistic or multi-variate sensitivity analysis considering uncertainty in performance of multiple barriers, including scenarios that evaluate Solubility-basemat bypass, early hydraulic failure due to water table rise or preferential flow 2.1 Limiting The topics addressed in this recommendation will be through the system, and consider the impact of higher mobility forms of Pu in the

§ Phases/Limits considered in any future PA models.

natural system.

and Validation

• DOE should continue to study and develop alternative conceptual models to account for the various oxidation states of Pu in the natural system including models that consider two fractions of Pu (relatively high mobility and low mobility forms) as well as the potential for oxidation and reduction reactions affecting the mobility of Pu in the subsurface along the flow paths away from the tanks to the 1 m and 100 m compliance points.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML18242A259]

In the Tank 18F Waste Release Testing TRR, NRC staff concluded that additional waste release testing and updated geochemical modeling are needed for NRC staff to have confidence in the PA results. The NRC staff offered the following additional conclusions and comments related to waste release testing and PA modeling.

• DOE should consider a larger range of uncertainty in key radionuclide solubility due to experimental limitations (e.g., substantial metal losses of uranium during leach testing which compromised the utility of the uranium data collected from Section 3.4.1 - Prepare Out-Year FTF PA Revisions the experiments and apparent lack of ability to achieve equilibrium conditions Section 3.4.2 - Prepare Out-Year HTF PA particularly for Pu and Tc).

Revisions

• DOE should perform probabilistic or multi-variate sensitivity analysis Future revisions to the FTF PA will be provided to considering uncertainty in performance of multiple barriers including scenarios NRC for review in support of NRCs monitoring that evaluate basemat bypass, early hydraulic failure due to water table rise or role.

preferential flow through the system, and consider the impact of higher mobility Solubility-forms of Pu in the natural system.

2.1 Limiting Testing of actual waste (i.e., Tank 18 and Tank 12

• DOE should explain differences in PORFLOW and GoldSim modeling results

§ Phases/Limits residuals) was performed in FY2016 and FY2018.

(e.g., Pu peak doses of around 5 mSv/yr (500 mrem/yr) in the Tanks 18/19 SA and Validation The solubilities of I, Pu, Np, U, and Tc were tested (SRR-CWDA-2010-00124) versus 7 mSv/yr (700 mrem/yr) in SRR-CWDA- under simulated waste tank chemistry conditions 2016-00086). using Tank 18 and Tank 12 residual waste samples.

• DOE should evaluate the impact of the early, high concentration release of Pu or The NRC conclusions and comments relating to justify why the rinse sample results are not applicable to alternative conceptual waste release testing were incorporated into the Tank models involving water table rise or preferential flow through the system.

12 testing to the extent practical and will be

• DOE should continue to study and develop models to account for higher addressed further in any future testing.

mobility forms of Pu in the natural system including models that consider two fractions of Pu (relatively high mobility and low mobility forms) as well as the potential for oxidation and reduction reactions affecting the mobility of Pu in the subsurface along the flow paths away from the tank to the 1 m and 100 m compliance points.

DOE should evaluate the impact of transport of key radionuclides from the waste zone up into the tank grout, and if found to be risk-significant, provide additional support for the transport mechanism(s).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues DOE has evaluated potential activities in this area based on the waste release testing experimental work performed in support MF 2.1. In August 2020, General NRC Monitoring Activities [ML15238A761]

SREL issued the technical report, Aqueous and Solid NRC staff will evaluate the efficacy of DOEs use of two chemical transitions, three Phase Characterization of Potential Tank Fill chemical states, and no more than three solubilities for each key radionuclide with Material, SREL-R-21-0001. SREL conducted a solubility changes assumed in DOEs PAs to occur at the same time for each key series of batch and column studies to address radionuclide for a given tank type. NRC will perform this evaluation through NRC review uncertainty in the realistic pH and Eh ranges Chemical of literature, DOE-generated geochemical modeling, or through independent geochemical 2.2 associated with the grouted waste tank systems, Transition Times modeling. NRC staff also may observe DOE experiments related to this MF in including an evaluation of three candidate Tank and Validation conjunction with an onsite observation of the FTF or HTF.

Closure Grout (TCG) paste formulations. The observed results generally agreed with previous This factor can be closed when (i) DOE shows that chemical transition times are no longer laboratory tests aimed at defining achievable Eh and important to its compliance demonstration (i.e., predicted dose is less than the dose pH conditions in tank waste grouted systems. The standards for all time) or (ii) DOE provides adequate experimental support for its pH results were predominantly consistent with both assumptions regarding chemical transition times.

the values derived from geochemical modeling and more recent laboratory testing.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.1.1 - Waste Release Studies DOE has evaluated potential activities in this area based on the waste release testing experimental work performed in support MF 2.1. In August 2020, Recommendation [FTF and HTF TERs - Short-to-Immediate Term] SREL issued the technical report, Aqueous and Solid In the FTF TER, NRC staff recommended DOE perform experiments to verify validity of Phase Characterization of Potential Tank Fill Geochemists Workbench calculations used to determine solubility limiting phases, Material, SREL-R-21-0001. SREL conducted a solubility limits, and chemical transition times. These experiments should study (i) pH series of batch and column studies to address and Eh evolution of the grout pore water over time, (ii) controlling solubility limiting uncertainty in the realistic pH and Eh ranges phases, and (iii) static and dynamic leach tests to study the mobility of HRRs, including associated with the grouted waste tank systems, consideration of alteration of tank residuals following chemical cleaning with reagents, including an evaluation of three candidate Tank such as oxalic acid. In the HTF TER, NRC staff reiterated its FTF recommendation that Closure Grout (TCG) paste formulations. The DOE conduct waste release experiments to (i) distinguish between releases from high observed results generally agreed with previous solubility compounds and low solubility compounds via semi-dynamic leach tests and (ii) laboratory tests aimed at defining achievable Eh and determine constant concentrations of elements of concern under conditions of exposure to pH conditions in tank waste grouted systems. The local groundwater and grout leachate via static tests. pH results were predominantly consistent with both (Duplicate, also applies to MF 2.1) the values derived from geochemical modeling and more recent laboratory testing.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results.

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Recommendation [HTF TER - Immediate-Term]

Section 3.4.2 - Prepare Out-Year HTF PA The NRC staff recommends DOE include dissolved oxygen concentrations in its modeling Revisions that are consistent with measurements of unimpacted groundwater across SRS or collect DOE has evaluated potential activities in this area additional dissolved oxygen measurements within the HTF at locations and elevations that based on the waste release testing experimental work are in closer proximity to the tanks.

performed in support MF 2.1. No work related to this recommendation is currently being performed.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing DOE has evaluated potential activities in this area based on the waste release testing experimental work performed in support MF 2.1. In August 2020, SREL issued the technical report, Aqueous and Solid Phase Characterization of Potential Tank Fill Recommendation [ML12272A082] Material, SREL-R-21-0001. SREL conducted a DOE should provide additional information to support assumptions regarding longevity of series of batch and column studies to address reducing conditions in the contaminated zone. Recent studies (PNNL-21723) suggest that uncertainty in the realistic pH and Eh ranges Chemical 2.2 the reducing capacity of the tank grout could be depleted much earlier than assumed in the associated with the grouted waste tank systems, Transition Times FTF PA (SRS-REG-2007-00002) and in more recent plutonium solubility modeling including an evaluation of three candidate Tank and Validation performed for Tank 18 (SRNL-STI-2012-00087). Uncertainty in the normative Closure Grout (TCG) paste formulations. The mineralogy assumed in geochemical modeling should be considered under this action. observed results generally agreed with previous (Duplicate, also applies to MF 2.1) laboratory tests aimed at defining achievable Eh and pH conditions in tank waste grouted systems. The pH results were predominantly consistent with both the values derived from geochemical modeling and more recent laboratory testing.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing DOE has evaluated potential activities in this area based on the waste release testing experimental work performed in support MF 2.1. In August 2020, SREL issued the technical report, Aqueous and Solid Phase Characterization of Potential Tank Fill Material, SREL-R-21-0001. SREL conducted a Recommendation [ML12272A082]

series of batch and column studies to address DOE should provide additional support for the assumption that the Eh of infiltrating water uncertainty in the realistic pH and Eh ranges will remain below a critical threshold at which plutonium solubility will increase to a risk associated with the grouted waste tank systems, significant value (e.g., updated geochemical modeling indicates a dramatic increase in including an evaluation of three candidate Tank plutonium solubility occurs at Eh greater than +0.45 V). Uncertainty in the critical Closure Grout (TCG) paste formulations. The threshold and the Eh of infiltrating groundwater should be considered under this action.

observed results generally agreed with previous (Duplicate, also applies to MF 2.1) laboratory tests aimed at defining achievable Eh and pH conditions in tank waste grouted systems. The pH results were predominantly consistent with both the values derived from geochemical modeling and more recent laboratory testing.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 3 - Cementitious Material Performance General NRC Monitoring Activities [ML15238A761]

NRC staff will review reports, analog studies, and other information used to support DOEs assumption regarding initial conditions and performance of the concrete vaults to protect the steel liner and limit releases of radioactivity from the annulus. For example, NRC staff will review annual tank inspection reports that provide information regarding trenching, scarifying, and cracking of the concrete vaults, as well as information about groundwater intrusion into the tank vaults. NRC staff will review reports related to previous events that led to potential releases or groundwater in-leakage through joints or cracks in the concrete vaults. Analog studies could include review and evaluation of information obtained from West Valley or other analog sites to better understand the potential for and rates of corrosion of high-level waste tanks/components, as well as mitigative design measures. As part of this MF, NRC staff also will consider the potential for earlier steel liner failure than assumed in DOEs PA due to corrosion of steel components (e.g., rebar) in the concrete vaults that are close to the vault surface or that may be physically separated but electrically connected. If DOE performs additional Hydraulic modeling or experiments to study the potential for transport of deleterious species into the Performance of tank vaults or the separation of iron dissolution and oxygen reduction and subsequent Concrete Vault corrosion of steel liners or tanks, NRC staff will review the documentation or provide Section 3.3.3 - Provide General Technical 3.1 and Annulus (As input on the design and results of the experiments. Experiments to study steel liner Support on Tank Farm PA Issues it Relates to Steel corrosion are expected to be relatively difficult to implement with unknown benefit Ongoing support of NRCs monitoring role will be Liner Corrosion compared to other experimental investigations recommended in NRCs TERs and provided as necessary.

and Waste discussed in this Monitoring Plan. Therefore, NRC staff does not consider these Release) experiments to be a high priority at this time. Until such time that DOE provides additional support for the estimated lifetimes of the steel liners, NRC staff (i) will assume steel liners will not be effective at mitigating releases for the long time periods DOE relies on the steel liners for performance in the tank farm PAs and (ii) will investigate the support for the performance of other barriers to ensure performance objectives can be met until such support for steel liner performance is provided.

NRC staff will perform routine monitoring of DOEs reliance on cementitious materials to ensure tank farm PA assumptions regarding the ability of the tank vaults to serve as a recognizable and durable barrier to intrusion are valid. In the Cementitious Barriers Partnership Toolbox (CBP) TRR (ML16196A179), the NRC identified QA gaps and limitations in the documentation associated with software development and in the technical basis for the conceptual and mathematical models for the CBP Toolbox.

This MF will be reviewed in conjunction with MF 3.4 and can be closed following closure of tanks at FTF and HTF.

Page 122 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [FTF and HTF TERs - Long-Term Activity with need contingent on Section 3.2.4 - To Be Determined Out-Year other factors] Testing In the FTF and HTF TERs, NRC staff recommended DOE consider uncertainty in initial No work related to this recommendation is currently conditions and performance lifetime of concrete vaults, because they impact uncertainty in being performed.

the calculated steel liner failure times.

Section 3.2.4 - To Be Determined Out-Year Hydraulic Testing Performance of Recommendation [HTF TER - Short- and Immediate-Term]

An SA specific to the HTF Type I and Type II Tanks Concrete Vault In the HTF TER, NRC staff indicated that DOE should conduct a more comprehensive was prepared and issued in August 2016. [SRR-3.1 and Annulus (As analysis of contaminant release from the annular regions of Types I and II tanks. Dose CWDA-2016-00078] This SA updated the it Relates to Steel projections from the potential release of the radionuclides in the annuli and sand pads are radiological and chemical inventories for the HTF Liner Corrosion likely to be very sensitive to several key assumptions, which should be well supported.

Type I and Type II tanks, incorporating lessons and Waste These assumptions include, but are not limited to, (i) the assumed release scenario; (ii) the learned from the final waste tank characterization Release) chemical composition of the infiltrating water; (iii) the volumetric flow rate through results to date.

grouted tanks, including shrinkage gaps and cracks; and (iv) the solubility of the annulus and sand pad waste. NRC staff also indicated that if the possibility of rise and fall of the A revision of the HTF PA was initiated in FY2020 water table in the vicinity of the Types I and II tanks cannot be excluded, DOE should and is scheduled to be completed in FY2023. This evaluate a scenario where water drains from any gaps in the annulus and sand pad regions.

PA will include a more comprehensive analysis of (Also applies to MFs 3.2, 3.3, and 3.5) contaminant release from the annular regions of Types I and II tanks.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

NRC staff will monitor DOE experiments to study the potential for groundwater flow through cracks that may form in the tank grout. NRC staff will monitor DOE experiments or perform its own independent experiments to better understand the nature of flow through the tank grout as it impacts the extent to which infiltrating groundwater interacts with and is conditioned by the tank grout. NRC staff also will review information Section 3.3.3 - Provide General Technical regarding water table rise to evaluate the likelihood of this alternative conceptual model Support on Tank Farm PA Issues for waste release. Based on the results of the water table rise investigation, an alternative Ongoing support of NRCs monitoring role will be conceptual model may be proposed for a subset of tanks to assess the impact on the provided as necessary. DOE has evaluated potential compliance demonstration. Specifically, NRC staff will review historical water table activities in this area based on the waste release elevation data for wells to assess the likelihood of water table rise above the bottom of the testing experimental work performed in support MF tanks. NRC staff also will review design and construction of any DOE mitigation 2.1. In August 2020, SREL issued the technical measures used to ensure that the water table remains below the bottom of the tanks.

report, Aqueous and Solid Phase Characterization of Under contract with the NRC, Center for Nuclear Waste Regulatory Analyses is Potential Tank Fill Material, SREL-R-21-0001.

conducting experiments to study the extent of groundwater conditioning when flow is SREL conducted a series of batch and column studies Groundwater primarily through preferential pathways or through a cracked grout specimen. The to address uncertainty in the realistic pH and Eh 3.2 Conditioning via objectives of these experiments are to understand the extent to which infiltrating water ranges associated with the grouted waste tank Reducing Grout chemistry (primarily pH and Eh) is modified by contact with the tank grout and how the systems, including an evaluation of three candidate tank grout buffering capacities for pH and Eh may change with contact to infiltrating Tank Closure Grout (TCG) paste formulations. The water. Documentation of results of these experiments are expected in CY2015. NRC will observed results generally agreed with previous also review documentation provided by DOE to support assumptions regarding the extent laboratory tests aimed at defining achievable Eh and of groundwater conditioning for as-emplaced tank grout. NRC staff may conduct the pH conditions in tank waste grouted systems. The technical review activities in conjunction with an onsite observation to observe any pH results were predominantly consistent with both laboratory or field experiments in this area.

the values derived from geochemical modeling and more recent laboratory testing.

If results of waste release experiments conducted under MF 2.1 show key radionuclides in A revision of the HTF PA was initiated in FY2020 waste residuals have sufficiently low solubility when in contact with unconditioned SRS and is scheduled to be completed in FY2023. This groundwaters, MF 3.2 related to the extent of conditioning (and 2.2 related to the PA will incorporate these testing results.

longevity of conditioning) will no longer be needed by DOE to support the compliance demonstration and can be closed. If MF 2.1 results indicate unconditioned flow may lead to unacceptably high doses, then this MF will need to be evaluated by NRC and can be closed after DOE (i) shows matrix flow through the grout will dominate waste release or (ii) provides information to support assumptions regarding the level of groundwater conditioning for degraded (cracked) grout.

Page 124 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4- To Be Determined Out-Year Testing No work related to this recommendation is currently being performed. DOE will evaluate potential activities in this area pending final resolution of experimental work performed in support MF 2.1.

In August 2020, SREL issued the technical report, Aqueous and Solid Phase Characterization of Recommendation [FTF and HTF TERs - Intermediate- to Long-Term Activity with need Potential Tank Fill Material, SREL-R-21-0001.

contingent on other factors] SREL conducted a series of batch and column studies In the FTF and HTF TERs, NRC staff recommended DOE obtain greater support for its to address uncertainty in the realistic pH and Eh assumption regarding flow through the tank grout (i.e., fracture versus matrix) flow as it ranges associated with the grouted waste tank impacts the timing of chemical transition or time to release of HRRs at risk-significant systems, including an evaluation of three candidate solubility. If found to be risk-significant, DOE should consider the appropriateness of Tank Closure Grout (TCG) paste formulations. The using MCCs for matrix materials to simulate fracture flow. In the HTF TER, NRC staff observed results generally agreed with previous recommended DOE provide more support for the assumption that the engineered system laboratory tests aimed at defining achievable Eh and will not interfere with the ability of the overlying grout to sufficiently condition the pH conditions in tank waste grouted systems. The infiltrating water for the fully and partially submerged tanks. pH results were predominantly consistent with both Groundwater (Duplicate, also applies to MF 3.3) the values derived from geochemical modeling and 3.2 Conditioning via more recent laboratory testing.

Reducing Grout A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results and address assumptions regarding flow through the tank grout (i.e., fracture versus matrix) flow and hoe these assumptions may impact the timing of chemical transitions.

Recommendation [HTF TER - Short- and Immediate-Term]

In the HTF TER, NRC staff indicated that DOE should conduct a more comprehensive Section 3.2.4 - To Be Determined Out-Year analysis of contaminant release from the annular regions of Types I and II tanks. Dose Testing projections from the potential release of the radionuclides in the annuli and sand pads are No work related to this recommendation is currently likely to be very sensitive to several key assumptions, which should be well supported. being performed. An SA specific to the HTF Type I These assumptions include, but are not limited to, (i) the assumed release scenario; (ii) the and Type II Tanks was prepared and issued in August chemical composition of the infiltrating water; (iii) the volumetric flow rate through 2016. [SRR-CWDA-2016-00078] This SA updated grouted tanks, including shrinkage gaps and cracks; and (iv) the solubility of the annulus the radiological and chemical inventories for the HTF and sand pad waste. NRC staff also indicated that if the possibility of rise and fall of the Type I and Type II tanks, incorporating lessons water table in the vicinity of the Types I and II tanks cannot be excluded, DOE should learned from the final waste tank characterization evaluate a scenario where water drains from any gaps in the annulus and sand pad regions. results to date.

(Also applies to MFs 3.1, 3.3, and 3.5)

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues Ongoing support of NRCs monitoring role will be provided as necessary. An SA specific to the HTF Type I and Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA updated the radiological and chemical inventories for the HTF Type I and Type II tanks, incorporating General NRC Monitoring Activities [ML15238A761]

lessons learned from the final waste tank NRC staff will review grout formulations, calculations, research, test methods, and results characterization results to date.

to ensure the disposal facility is designed to minimize fast flow path development. NRC staff may conduct technical reviews in conjunction with onsite observations that could Additional grout testing was performed in FY2020 include such activities as video inspections of grout pours, observations of grout tests, and with emphasis on CLSM formulations. An inspection of test specimens. The NRC staff will also continue to monitor the importance evaluation memo of the results of the CLSM Test of alkali-silica reactivity on cementitious material degradation. The NRC staff will Shrinkage and Reports entitled Characterization and Assessment of 3.3 continue to evaluate the potential for shrinkage- and cracking-induced preferential flow Cracking of CLSM Grouts for Potential Use in Waste Tank through the tank grout.

Reducing Grout Operational Closures, SRR-CWDA-2020-00045 was issued by WDA in June 2020.

MF 3.3 can be closed when DOE demonstrates (i) preferential fast flow into the waste zone of the tanks or through the waste in the annuli for Types I and II tanks at HTF will In FY2021, additional CLSM characterization was not occur or (ii) preferential fast flow into the waste zone of the tanks or through the performed which included evaluating Zero-Bleed annuli for Types I and II tanks at HTF will not adversely impact performance (e.g., the CLSM; 1) calculating saturated hydraulic performance objective can be met under all chemical conditions as discussed in more conductivity, 2) measure diffusion of Na+ and NO3-detail under MA 2, Waste Release).

from solution into the monolith, and 3) obtain MCCs for Zero-Bleed CLSM. The results are documented in SRRA099188-000015.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results and address preferential flow through the tank grout.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Recommendation [ML15238A761] Testing

• DOE should consider design measures to minimize the occurrence of negative features, Additional grout testing was performed in FY2020 events, or processes that may promote shrinkage or cracking with emphasis on CLSM formulations. An evaluation memo of the results of the CLSM Test

• DOE should consider removal of in-tank equipment that could lead to development of shrinkage-induced annuli around equipment or corrosion of steel components and Reports entitled Characterization and Assessment of associated cracking due to corrosion product expansion. CLSM Grouts for Potential Use in Waste Tank Operational Closures, SRR-CWDA-2020-00045 was

• DOE should promote the ability of the grout to fill all void spaces to minimize issued by WDA in June 2020.

imperfectly bonded grout seams and voids that may form between grout pours.

• DOE should research and evaluate shrinkage compensating agents for use in its grout In FY2021, additional CLSM characterization was formulations to minimize shrinkage, shrinkage gap formation, and creation of annuli performed which included evaluating Zero-Bleed and void space within grout.

CLSM; 1) calculating saturated hydraulic

• DOE should ensure temperature gradients are sufficiently low to prevent excessive conductivity, 2) measure diffusion of Na+ and NO3-thermal cracking. Calculations could be conducted to evaluate potential thermal from solution into the monolith, and 3) obtain MCCs gradients and/or instrumentation could be used to evaluate as-emplaced thermal for Zero-Bleed CLSM. The results are documented evolution of grout.

in SRRA099188-000015.

• DOE should ensure the grout is designed to consider the potential for cracking due to differential settlement. A revision of the HTF PA was initiated in FY2020

• It may be useful for DOE to research and deploy methods of detecting early crack and is scheduled to be completed in FY2023. This development in reducing grout used to fill tanks. PA will incorporate these testing results and address preferential flow through the tank grout.

Page 127 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing Additional grout testing was performed in FY2020 with emphasis on CLSM formulations. An evaluation memo of the results of the CLSM Test Reports entitled Characterization and Assessment of Recommendation [FTF and HTF TERs - Intermediate- to Long-Term Activity with need CLSM Grouts for Potential Use in Waste Tank contingent on other factors]

Operational Closures, SRR-CWDA-2020-00045 was In the FTF and HTF TERs, NRC staff recommended DOE obtain greater support for its issued by WDA in June 2020.

assumption regarding flow through the tank grout (i.e., fracture versus matrix) flow as it impacts the timing of chemical transition or time to release of HRRs at risk-significant In FY2021, additional CLSM characterization was solubility. If found to be risk-significant, DOE should consider the appropriateness of performed which included evaluating Zero-Bleed using MCCs for matrix materials to simulate fracture flow. In the HTF TER, NRC staff CLSM; 1) calculating saturated hydraulic recommended DOE provide more support for the assumption that the engineered system conductivity, 2) measure diffusion of Na+ and NO3-will not interfere with the ability of the overlying grout to sufficiently condition the from solution into the monolith, and 3) obtain MCCs infiltrating water for the fully and partially submerged tanks.

for Zero-Bleed CLSM. The results are documented (Duplicate, also applies to MF 3.2) in SRRA099188-000015.

Shrinkage and 3.3 A revision of the HTF PA was initiated in FY2020 Cracking of and is scheduled to be completed in FY2023. This Reducing Grout PA will incorporate these testing results and address preferential flow through the tank grout.

Section 3.2.4 - To Be Determined Out-Year Testing Recommendation [HTF TER - Short- and Immediate-Term] No work related to this recommendation is currently In the HTF TER, NRC staff indicated that DOE should conduct a more comprehensive being performed. An SA specific to the HTF Type I analysis of contaminant release from the annular regions of Types I and II tanks. Dose and Type II Tanks was prepared and issued in August projections from the potential release of the radionuclides in the annuli and sand pads are 2016. [SRR-CWDA-2016-00078] This SA updated likely to be very sensitive to several key assumptions, which should be well supported.

the radiological and chemical inventories for the HTF These assumptions include, but are not limited to, (i) the assumed release scenario; (ii) the Type I and Type II tanks, incorporating lessons chemical composition of the infiltrating water; (iii) the volumetric flow rate through learned from the final waste tank characterization grouted tanks, including shrinkage gaps and cracks; and (iv) the solubility of the annulus results to date.

and sand pad waste. NRC staff also indicated that if the possibility of rise and fall of the water table in the vicinity of the Types I and II tanks cannot be excluded, DOE should A revision of the HTF PA was initiated in FY2020 evaluate a scenario where water drains from any gaps in the annulus and sand pad regions. and is scheduled to be completed in FY2023. This (Also applies to MFs 3.1, 3.2, and 3.5)

PA will address contaminant release from the annular regions of Types I and II tanks.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML13269A365]

In the Tanks 18 and 19 Grout Documentation TRR, the NRC staff stated that DOE has not provided sufficient information to rule out preferential pathways from its reference case. Section 3.2.4 - To Be Determined Out-Year NRC staff expects DOE to provide additional information related to the extent and Testing performance impact of shrinkage. During its review of tank grouting video, NRC staff No work related to this recommendation is currently observed potential segregation of tank grout during placement that could enhance the being performed. DOE will evaluate potential extent of shrinkage along the periphery of the Type IV tanks. NRC staff also expects activities in this area when funding is available.

DOE to provide additional information on the potential for thermal cracking of the grout monolith for Tanks 18F and 19F.

Research was performed in FY2017 to improve Recommendation [ML12212A192, ML13269A365]

insights in this area. The intent of the work was to DOE indicated that it currently does not have plans to conduct shrinkage testing, but may gain an enhanced understanding of tank specific pursue tests in the future. The NRC staff concur with Stefanko and Langtons (SRNL-cementitious material properties. Overall results STI-2011-00551) recommendations for testing of admixtures and implementation of were inconclusive from the shrinkage testing and no measures to help mitigate tank grout shrinkage. further tests are planned in FY2021.

Recommendation [ML12212A192, ML13269A365]

The NRC staff believes DOEs conclusion that the temperature rise was sufficiently low Section 3.2.4 - To Be Determined Out-Year for bulk grouting of Tanks 18F and 19F based on a 1 cubic yard [0.8 m3] bulk scale-up test Testing and will continue to evaluate this technical issue in future onsite observations. A more No work related to this recommendation is currently Shrinkage and detailed thermal analysis that considers the specific grout pour sequence and geometry to being performed. DOE will evaluate potential 3.3 Cracking of determine the potential for thermal cracking of the tank grout would improve model activities in this area when funding is available.

Reducing Grout support.

Recommendation [ML12212A192, ML13269A365]

DOE did not document in the Final Configuration Report (SRR-CWDA-2012-00170) expected causes for the bulk fill grout deviations to mitigate potential concern over the formation of preferential pathways. The Final Configuration Report does provide Section 3.3.3 - Provide General Technical documentation regarding potential causes of significant deviations in equipment grout fill Support on Tank Farm PA Issues volumes, however, estimates of remaining void volumes are not provided (e.g., advance Ongoing support of NRCs monitoring role will be design mixer pump [ADMP]). This information could also be used to improve future provided as necessary.

volume estimates. NRC staff will continue to monitor DOE estimates of void volumes including whether there is additional information that would support a conclusion that the ADMP void spaces were completely filled.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing Additional grout testing was performed in FY2020 with emphasis on CLSM formulations. An evaluation memo of the results of the CLSM Test Reports entitled Characterization and Assessment of CLSM Grouts for Potential Use in Waste Tank Recommendation [ML14342A784] Operational Closures, SRR-CWDA-2020-00045 was In the Tanks 5 and 6 Grout Documentation TRR, the NRC staff stated that DOE has not issued by WDA in June 2020.

provided sufficient information and testing to exclude from its reference case preferential flow through the tank grout monolith. During its review of tank grouting video, NRC staff In FY2021, additional CLSM characterization was observed potential bleedwater segregation of tank grout during placement that could result performed which included evaluating Zero-Bleed in inhomogeneity of the monolith, which can affect flow patterns. The NRC staff will CLSM; 1) calculating saturated hydraulic continue to evaluate the potential for shrinkage- and cracking-induced preferential flow conductivity, 2) measure diffusion of Na+ and NO3-through the tank grout. from solution into the monolith, and 3) obtain MCCs for Zero-Bleed CLSM. The results are documented in SRRA099188-000015.

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate these testing results and address preferential flow through the tank grout.

Recommendation [ML12212A192, ML13269A365]

The NRC staff communicated its concern with the potential formation of cracks in the tank grout due to alkali-silica reactivity (ASR). The NRC staff is concerned that DOEs Section 3.2.4 - To Be Determined Out-Year criterion for acceptance of vendor supplied granite aggregate relies on short-term alkali Shrinkage and Testing 3.3 reactivity tests (ASTM Standard C1260-14), which is unlikely to predict the occurrence of Cracking of No work related to this recommendation is currently ASR over the very long period of performance for compliance with the performance Reducing Grout being performed. DOE will evaluate potential objective specified at 10 CFR 61.41. Evaluating potential ASR in tank grouts and its activities in this area when funding is available.

potential effect on long-term performance of the engineered barrier system would improve model support for the performance of the grout and understanding of the potential for cracking of the grout.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

NRC will perform technical review activities related to DOEs testing and development of grout formulations to meet design specifications. Additionally, NRC will monitor DOEs efforts to deliver a grout mix of sufficient quality to meet performance assumptions in DOEs PAs from design to as-emplaced conditions in the field. NRC staff will review relevant procedures and documentation related to such items as grout material procurement, production, testing, acceptance and placement in tank farm components.

NRC staff will perform technical review activities in conjunction with onsite observations.

Onsite observations will include such activities as observations of grout material storage, tests, and acceptance of grout materials; live video streams of grouting operations; review of archived video footage; review of batch tickets for accepted and rejected loads; tour of the command center; and observation of mock-up tests or visual examination of test specimens. NRC will perform routine monitoring of DOEs use of grout materials to stabilize high-level waste tanks to ensure tank farm PA assumptions regarding the ability of the grouted tank and vaults to serve as a recognizable and durable barrier to intrusion remain valid. The NRC staff will also continue to monitor void volumes in the emplaced grout to the extent information is available and the impact of limestone additions to the Section 3.3.3 - Provide General Technical 3.4 Grout grout mix on pH buffering of water contacting the emplaced grout. NRC continues to Support on Tank Farm PA Issues Performance monitor the potential for segregation of emplaced grout and its impacts on flow through Ongoing support of NRCs monitoring role will be the grout monolith and waste release. In the Tank 16H and Tank 12H Grouting TRR provided as necessary.

(ML16231A444), the NRC identified information that would enhance DOEs demonstration of grout performance:

• DOE should take reasonable measures to ensure a sufficient number of cement trucks are in rotation to optimize grout distribution throughout the tank and minimize mounding.

• DOE should address the potential for either a capillary or permeability barrier to form due to the varying hydraulic conductivity of the clean cap and bulk fill grout used in Tank 16H.

• DOE should provide additional information regarding the quantity and performance impact of the presence of standing water in Tank 12H during grouting.

• DOE should evaluate differences in hydraulic conductivity between the Grade 100 and Grade 120 slag used to fill Tank 12H and any resulting performance impact NRC staff can close this MF after it completes (i) review of DOE-generated grouting documentation and (ii) monitoring of grouting operations. This MF will be reviewed in conjunction with MF 3.1 and can be closed following closure of tanks at FTF and HTF.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML12212A192, ML13269A365]

The Tanks 18 and 19 Grout Documentation TRR stated that the NRC staff is concerned that the use of commercially-available Portland cements in Tanks 18 and 19 that differ Section 3.2.4 - To Be Determined Out-Year from the grout mix considered in the FTF PA (SRS-REG-2007-00002) because of Testing 3.4 Grout substitution of up to 5% by weight limestone would lower the pH buffering capacity of the No work related to this recommendation is currently Performance grout and could affect the timing of release of key radionuclides. Evaluating the effect of being performed. DOE will evaluate potential limestone substitution in Portland cement on the pH buffering capacity of the grout and activities in this area when funding is available.

the release of key radionuclides improves model support for the modeling of chemical states and transitions of water contacting the residual waste.

General NRC Monitoring Activities [ML15238A761]

NRC staff will monitor DOE efforts to study basemat sorption for plutonium and neptunium. NRC staff will review documentation and any analog studies that may provide additional information regarding the ability of the concrete basemats to attenuate release from the tanks or annuli of Types I and II tanks at HTF, including information regarding groundwater inleakage and release from construction joints or other discrete features such as those implicated in the release from HTF Tank 16H.

Section 3.3.3 - Provide General Technical Vault and 3.5 Support on Tank Farm PA Issues Annulus This MF can be closed when (i) sufficient information is available to support assumptions Ongoing support of NRCs monitoring role will be Sorption regarding attenuation of key radionuclides (e.g., plutonium, neptunium, cesium, strontium) provided as necessary.

in the basemats, vaults, or annular grout or (ii) DOE provides sufficient information to show that doses from key radionuclides will be below the dose limits prescribed in the performance objectives with little to no performance from the concrete basemats and vaults and annular grout (e.g., solubility limits for unconditioned groundwater are sufficiently low or natural attenuation of key radionuclides is sufficiently high to compensate for underperformance of the concrete basemat and vaults and annular grout).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing Recommendation [HTF TER - Short- and Immediate-Term]

No work related to this recommendation is currently In the HTF TER, NRC staff indicated that DOE should conduct a more comprehensive being performed. An SA specific to the HTF Type I analysis of contaminant release from the annular regions of Types I and II tanks. Dose and Type II Tanks was prepared and issued in August projections from the potential release of the radionuclides in the annuli and sand pads are 2016. [SRR-CWDA-2016-00078] This SA updated likely to be very sensitive to several key assumptions, which should be well supported.

the radiological and chemical inventories for the HTF These assumptions include, but are not limited to, (i) the assumed release scenario; (ii) the Type I and Type II tanks, incorporating lessons chemical composition of the infiltrating water; (iii) the volumetric flow rate through learned from the final waste tank characterization grouted tanks, including shrinkage gaps and cracks; and (iv) the solubility of the annulus results to date.

and sand pad waste. NRC staff also indicated that if the possibility of rise and fall of the water table in the vicinity of the Types I and II tanks cannot be excluded, DOE should A revision of the HTF PA was initiated in FY2020 evaluate a scenario where water drains from any gaps in the annulus and sand pad regions.

and is scheduled to be completed in FY2023. This (Also applies to MFs 3.1, 3.2, and 3.3)

PA will address contaminant release from the annular regions of Types I and II tanks.

Section 3.2.4 - To Be Determined Out-Year Testing The geochemical data package (SRNL-STI-2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010). This update incorporated the numerous experiments and geochemical Recommendation [FTF and HTF TERs - Intermediate-Term] measurements have been conducted since 2010, In the FTF and HTF TERs, NRC staff commented that given the wide range of values in resulting in new recommended input values for the literature, NRC staff recommends DOE obtain additional support for basemat Kds for modeling. The revised geochemical data package Vault and 3.5 plutonium and neptunium, including consideration of solubility affects from previous integrates recent documented geochemical results, Annulus evaluations and representativeness of experimentally derived values for aged concrete. including radionuclide Kd values, solubility values, Sorption DOE should continue to evaluate the appropriateness of selected transport parameters and cementitious impact factors, and includes a (e.g., cementitious material and soil Kds) and the selection of sorption models during the critical evaluation of these values with respect to monitoring period. existing values to assess potential impacts.

Two sorption reports were issued in September 2018.

The first report (SRRA021685-000011) documented concentrations measured in field lysimeter effluents from the fourth quarter of FY2017 and the second quarter of FY2018. The second report (SRRA021685-000010) documented the detailed solid phase analysis of a field lysimeter (lysimeter

41) with an emplaced Pu(V)NH4(CO3)(s) source.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

NRC staff will review use of stabilizing materials to determine if DOE has made a reasonable effort to optimize mixing or encapsulating the waste with the stabilizing material. NRC staff will evaluate DOEs use of stabilizing materials to grout features of the tank and vault system that might otherwise lead to preferential flow through the Section 3.3.3 - Provide General Technical Waste engineered system and into the environment (e.g., grouting of leak detection channels and Support on Tank Farm PA Issues 3.6 Stabilization (As sumps contained within the concrete basemats). NRC staff will conduct technical reviews Ongoing support of NRCs monitoring role will be

• it Impacts and onsite observations under MFs 3.1 to 3.5, bearing in mind the additional function of provided as necessary.

ALARA) the stabilizing grout to maintain doses ALARA.

NRC staff will close this factor when MFs 3.1 through 3.5 are closed, and if NRC staff finds DOEs use of stabilizing cementitious materials consistent with ALARA criteria.

No specific NRC staff recommendations identified. Section - N/A MA 4 - Natural System Performance General NRC Monitoring Activities [ML15238A761]

NRC will monitor DOEs efforts to develop site-specific sorption coefficients that consider the impact of cement-impacted leachate released from the tanks. NRC staff will review any DOE-generated reports or other documentation that provides additional information related to site-specific niobium Kd values. Technical review activities may be conducted in conjunction with onsite observations of any experiments developed to study the attenuation of plutonium, niobium, and other key radionuclides in SRS soils.

NRC staff will review information generated by DOE and perform independent modeling Section 3.3.3 - Provide General Technical Natural to assess whether more mobile forms of plutonium, if evaluated explicitly in DOEs PA Support on F-Area Tank Farm PA Issues 4.1 Attenuation of modeling, could reach the inadvertent intruder point of compliance (POC) within 10,000 Ongoing support of NRCs monitoring role will be

§ Key years. provided as necessary.

Radionuclides This MF can be closed when NRC staff concludes that DOE has adequately assessed the timing and magnitude of Pu-239 release and transport to the 1-m [3.28 ft] POC and DOE provides support for its treatment of plutonium, niobium, and other key radionuclide sorption in the subsurface at FTF or DOE shows that plutonium, niobium, and other key radionuclide sorption in the subsurface is not needed to support its compliance demonstration (e.g., solubility control effectively limits plutonium releases into the natural environment to non-risk-significant levels).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 2.2.2.1 - Long-Term Radiological Lysimeter Program This task is expected to provide Kd values (including for plutonium) in soil and cementitious materials and additional information about long-term geochemical and transport phenomena that will be used to support the waste release and transport models. The geochemical data package (SRNL-STI-2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010). This update incorporated the numerous experiments and geochemical measurements have been conducted since 2010 (including Lysimeter testing results), resulting in new recommended input Recommendation [FTF and HTF TERs - Short- and Intermediate-Term] values for modeling. The revised geochemical data In the FTF TER, NRC staff recommended DOE evaluate appropriateness of averaging Kds package integrates recent documented geochemical of multiple oxidation states to simulate the transport of plutonium in the natural system. results. Two sorption reports were issued in FY2018.

Natural Consistent with the recommendation in the FTF TER, in the HTF TER, NRC staff The first report (SRRA021685-000011) documented 4.1 Attenuation of indicated that a more accurate representation of the transport of multivalent plutonium concentrations measured in field lysimeter effluents

§ Key would be to treat the two species separately, assuming the oxidation state distribution from the fourth quarter of FY2017 and the second Radionuclides could be reasonably quantified. In the HTF TER, NRC staff also questioned the basis for quarter of FY2018. The second report the sandy sediment Kd for Pu of 650 mL/g derived from SRNL-STI-2011-00672, as well (SRRA021685-000010) documented the detailed as the cement leachate factors that were derived based on Hanford data (SRNL-STI-2009- solid phase analysis of a field lysimeter (lysimeter 00473). 41) with an emplaced Pu(V)NH4(CO3)(s) source.

Section 3.4.1- Prepare Out-Year FTF PA Revisions, Section 3.4.2 - Prepare Out-Year HTF PA Revisions An SA specific to the HTF Type I and Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA includes sensitivity analyses that provided additional information regarding the sensitivity of HTF dose results to Pu soil Kd values. The next PA revisions will include more analysis of plutonium attenuation. It is expected that sensitivity analyses will show that peak dose results within the performance period are not sensitive to the Natural Attenuation of plutonium given the SA sensitivity analyses.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Testing being performed in support of the SDF PA will be used for the FTF and HTF PAs as applicable.

The geochemical data package (SRNL-STI-2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016.

Recommendation [ML13273A299]

The Tanks 5F and 6F Special Analysis TRR stated that additional information related to Section 3.4.1 - Prepare Out-Year FTF PA the niobium Kd is needed to have reasonable assurance that DOE disposal actions at the Revisions FTF will meet the performance objectives in 10 CFR Part 61, Subpart C. Section 3.4.2 - Prepare Out-Year HTF PA Revisions The next PA revision will include more analysis of niobium attenuation. It is expected that sensitivity Natural analyses will show that peak dose results within the 4.1 Attenuation of performance period are not sensitive to the Natural

§ Key Attenuation of niobium.

Radionuclides Section 3.2.4 - To Be Determined Out-Year Testing An SA specific to the HTF Type I and Type II Tanks was prepared and issued in August 2016. [SRR-Recommendation [ML12272A124] CWDA-2016-00078] This SA includes sensitivity The Environmental Monitoring TRR stated that the NRC staff will continue to monitor the analyses that provided additional information Kd averaging approach used to simulate plutonium transport in the natural system at FTF. regarding the sensitivity of HTF dose results to Pu DOE could address the issue by modeling explicitly more mobile and less mobile forms of soil Kd values. The next PA revisions will include plutonium in future performance assessment calculations. more analysis of plutonium attenuation. It is expected that sensitivity analyses will show that peak dose results within the performance period are not sensitive to the Natural Attenuation of plutonium given the SA sensitivity analyses.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML12272A124] Section 3.2.4 - To Be Determined Out-Year The Environmental Monitoring TRR stated that the NRC staff will continue to monitor Testing support for cement leachate factors developed for plutonium (and other constituents). No work related to this recommendation is currently DOE could provide support for cement leachate factors by performing site-specific being performed. DOE will evaluate potential analyses. activities in this area when funding is available.

Recommendation [ML12272A124]

The Environmental Monitoring TRR stated that the NRC staff will continue to monitor the Section 3.2.4 - To Be Determined Out-Year basis for selection of the niobium Kd value of 160 L/kg used in the Tanks 5F and 6F Natural Testing Special Analysis. DOE could address the technical issues by verifying the batch 4.1 Attenuation of No work related to this recommendation is currently experiments did not exceed solubility limits and are representative of conditions at FTF

§ Key being performed. DOE will evaluate potential (e.g., plot solid phase versus aqueous phase concentration or Kd versus concentration; Radionuclides activities in this area when funding is available.

evaluate Kd for FTF aquifer soils) or perform additional experiments to verify the niobium Kd.

Section 3.4.1 - Prepare Out-Year FTF PA Recommendation [ML16277A060]

Revisions As a result of its review of the revised dose methodology for Liquid Waste PAs (SRR-Section 3.4.2 - Prepare Out-Year HTF PA CWDA-2013-00058, Revision 1), NRC identified a number of items that should be Revisions addressed in future HTF and FTF PAs revisions. The complete listing of items is These items will be considered in the next PA documented in the Dose Calculation Methodology TRR.

revision.

General NRC Monitoring Activities [ML15238A761]

NRC staff should observe field tests and review and evaluate results of tracer tests and field mapping DOE may conduct to ascertain the significance of existing calcareous soft zones on flow and transport from the tank farms. NRC Staff will review relevant geotechnical logs acquired in the vicinity of tank farms to stay informed of the potential for and characteristics of soft zones that may be identified in the future. Finally, if DOE Section 3.3.3 - Provide General Technical Calcareous opts to employ downhole visualization or other methods to monitor local groundwater 4.2 Support on Tank Farm PA Issues Zone Character- velocities associated with soft zones, NRC staff will review and evaluate DOEs analysis Ongoing support of NRCs monitoring role will be ization of these data. NRC may conduct technical review activities in conjunction with onsite provided as necessary.

observations of field activities, such as calcareous zone outcrop mapping on Upper Three Runs Creek.

This factor will be closed when DOE has provided NRC sufficient information to show its treatment of calcareous zones in the tank farm PAs is reasonable or adequate to assess risk.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Recommendation [ML15238A761]

Testing DOE could monitor flow velocities at screen levels both consistent and inconsistent with No work related to this recommendation is currently known existing soft zones to assess local fast flow path gradients of soft zones to provide being performed. DOE will evaluate potential additional confidence that current PA groundwater modeling treatment is acceptable.

activities in this area when funding is available.

Calcareous 4.2 Recommendation [FTF and HTF TERs - Next PA Update (Long-Term)]

Zone Character-In the FTF and HTF TERs, NRC staff recommended DOE continue to evaluate Section 3.2.4 - To Be Determined Out-Year ization significance of calcareous zone dissolution on FTF flow and transport, including conduct Testing of tracer studies and field mapping of seepage locations along Upper Three Runs Creek. No work related to this recommendation is currently Site-specific Kds may also need to be developed for the Upper Three Runs Aquifer-Lower being performed. DOE will evaluate potential Zone. activities in this area when funding is available.

(Duplicate, also applies to MF 6.2)

General NRC Monitoring Activities [ML15238A761]

NRC staff will review any data collected by DOE for the tank farms for the purpose of evaluating disposal facility performance. NRC staff will review and evaluate groundwater monitoring data as a technical review activity under this factor. NRC staff will continue to review the adequacy of the tank farm monitoring well network with respect to its ability Section 3.3.3 - Provide General Technical to detect releases from the tank farms. NRC may conduct technical review activities for Support on Tank Farm PA Issues this monitoring activity in conjunction with onsite observations related to groundwater Ongoing support of NRCs monitoring role will be sampling, well construction, and other field activities. SCDHEC oversight may be provided as necessary.

leveraged in this area to ensure the quality of data collected.

MA 4 will be renamed Environmental Monitoring once MF 4.1 and 4.2 have been 4.3 Environmental closed. MA 4 will remain open indefinitely.

Monitoring Recommendation [ML12272A124]

The Environmental Monitoring TRR stated that the NRC staff will continue to evaluate the source of elevated Tc-99 levels in well FTF 28. It is not clear that releases from the F-Area Inactive Process Sewer Line could migrate vertically to the lower zone of the Upper Section 3.2.4 - To Be Determined Out-Year Three Runs Aquifer in such a short distance from the source. This evaluation is important Testing to ensure that the hydrogeological system at FTF is well understood and that releases from No work related to this recommendation is currently the tanks could be detected by the monitoring well network. DOE could provide being performed. DOE will evaluate potential additional support for the source of contamination detected at well FTF 28 by performing activities in this area when funding is available.

particle tracking to better understand contaminant plume trajectories. DOE could also perform a more formal statistical analysis of FTF and Western Groundwater Operable Unit well data to correlate contaminant concentrations associated with various sources.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML12272A124]

The Environmental Monitoring TRR stated that the NRC staff will continue to monitor the Section 3.2.4 - To Be Determined Out-Year ability of the tank farm monitoring well network to detect releases from the tank farm Testing 4.3 Environmental facilities following closure. DOE could (i) evaluate the monitoring well network by No work related to this recommendation is currently Monitoring performing an analysis of the centerline of plumes emanating from tank sources should being performed. DOE will evaluate potential releases occur in the future and (ii) provide input on optimal well locations to ensure that activities in this area when funding is available.

future releases from the tank farm facility would be detected.

Recommendation [ML18051B009, ML19280A059]

The Environmental Monitoring TRR concluded the following:

1) DOE has performed environmental monitoring that provides useful information on the hydrogeological systems at FTF and HTF. This information can also be used to better understand contaminant flow and transport at the tank farm facilities (TFFs) and provide support for DOE Performance Assessment (PA) models, particularly the updated 2018 GSA PORFLOW model. Modeling and monitoring should be conducted iteratively as information is collected to help reduce hydrogeological uncertainties.

2) Significant uncertainty in the source of contaminant plumes detected via the FTF and HTF monitoring well networks exists. A better understanding of contaminant flow and transport processes at the TFFs through more extensive data analysis, modeling, and conceptual model development would provide additional confidence in modeling results. For example, geochemical data could be evaluated to better understand spatial Section 3.2.4 - To Be Determined Out-Year and temporal correlations, evaluate trends, and identify sources. Additional particle Testing tracking simulations could be conducted to help identify the source of contaminant 4.3 Environmental No work related to these recommendations is plumes and validate observed versus modeled travel times.

Monitoring currently being performed. DOE will evaluate

3) PA modeling and groundwater monitoring at the TFFs could be better integrated. PA potential activities in this area when funding is modeling could be used to determine key constituents and the types of field available.

monitoring data, which would provide the most useful information to evaluate performance of, and detect early releases from, the TFFs. Data from the monitoring program could be used to evaluate model performance and help develop conceptual models for contaminant flow and transport.

4) The latest GSA groundwater model should be used to establish the monitoring well network, particularly to inform vertical placement of wells when such opportunities for additions or other changes to the monitoring well network exist in the future.

5) Additional work is needed to better understand the significance of the observed mobile fraction of Plutonium (Pu) in the natural system.

6) DOE should justify its Pu Kd averaging approach, or explicitly model the various oxidation states of key radionuclides such as Pu in future PA documentation, because explicitly modeling the more mobile fraction of Pu could lead to risk-significant dose significantly earlier in time compared to the current modeling approach.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 5 - Closure Cap Performance General NRC Monitoring Activities [ML15238A761]

NRC will monitor additional information to support the assumed long-term hydraulic conductivity of the foundation layer. In addition, NRC staff will monitor construction quality and settlement at the tank farms to help ensure assumed performance of the high density polyethylene/geosynthetic clay liner (HDPE/GCL) composite layer is not Section 3.3.3 - Provide General Technical adversely impacted. NRC will monitor the quality assurance/quality control for closure Support on Tank Farm PA Issues cap construction and settlement data collected during tank farm operations as well as Ongoing support of NRCs monitoring role will be nearby facilities. NRC also will review relevant studies and tests related to HDPE/GCL provided as necessary.

performance.

This factor can be closed after DOEs construction of the closure cap and demonstration of its hydraulic performance.

Section 3.2.4 - To Be Determined Out-Year Testing Work was begun by the University of Virginia in Long-Term 5.1 FY2017 related to degradation of the closure cap Hydraulic Recommendation [FTF and HTF TERs - Long-Term Activity]

• layers and resulting infiltration rates based on new Performance In the FTF and HTF TERs, NRC staff recommended DOE provide additional model field information and calculation methodologies. A support for (i) the long-term hydraulic conductivity of the upper foundation layer and Closure Cap degradation document (Predicting lateral drainage layer and (ii) the long-term erosion of the topsoil layer.

Long-Term Percolation from the SDF Closure Cap, (Duplicate, also applies to MF 5.2)

SRRA107772-000009) was issued in FY2018. This document is being used as the basis for a planned update to the Tank Farm closure cap documents in FY2021.

Section 3.2.4 - To Be Determined Out-Year Recommendation [FTF and HTF TERs - Long-Term Activity] Testing In the FTF and HTF TERs, NRC staff recommended DOE conduct a preliminary No work related to this recommendation is currently evaluation of erosion protection designs (e.g., assessment of an acceptable rock source, being performed. DOE will evaluate potential and the ability of an integrated drainage system to accommodate design features) prior to activities in this area closer to the time when final completing the final closure cap design. closure cap design is being developed. An update to (Duplicate, also applies to MF 5.2) the Tank Farm closure cap documents is planned for FY2021.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

NRC staff will review and evaluate information pertaining to erosion processes of the vegetative and topsoil layers, including cover maintenance activities. If DOE performs simulations of the influence of clogging and ponding in the perimeter drainage structures Section 3.3.3 - Provide General Technical on flow in the vadose zone, NRC will review results of these simulations to evaluate risk Support on Tank Farm PA Issues significance of the uncertainties in the long-term performance of the perimeter drainage Ongoing support of NRCs monitoring role will be structure. NRC will specifically monitor use of the engineered closure cap as a barrier to provided as necessary.

intrusion.

This factor can be closed after DOEs construction of the closure cap and demonstration of its physical stability.

Long-Term Section 3.2.4 - To Be Determined Out-Year 5.2 Erosion Testing

• Protection No work related to this recommendation is currently Design being performed. DOE will evaluate potential activities in this area closer to the time when final closure cap design is being developed. Work was begun by the University of Virginia in FY2017 Recommendation [ML15238A761]

related to degradation of the closure cap layers and NRC staff recommends that DOE provide additional support for the long-term erosion of resulting infiltration rates based on new field the topsoil layer and conduct a preliminary evaluation of erosion protection designs.

information and calculation methodologies. A Closure Cap degradation document (Predicting Long-Term Percolation from the SDF Closure Cap, SRRA107772-000009) was issued in FY2018. This document is being used as the basis for a planned update to the Tank Farm closure cap documents in FY2021.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing No work related to this recommendation is currently being performed. DOE will evaluate potential activities in this area closer to the time when final closure cap design is being developed. Work was begun by the University of Virginia in FY2017 related to degradation of the closure cap layers and resulting infiltration rates based on new field information and calculation methodologies. A Closure Cap degradation document (Predicting Long-Term Percolation from the SDF Closure Cap, Recommendation [FTF and HTF TERs - Long-Term Activity]

SRRA107772-000009) was issued in FY2018.

In the FTF and HTF TERs, NRC staff recommended DOE provide additional model support for (i) the long-term hydraulic conductivity of the upper foundation layer and SRR-CWDA-2021-00043, Erosion Analysis for the lateral drainage layer and (ii) the long-term erosion of the topsoil layer.

H-Tank Farm and F-Tank Farm Facilities, has been (Duplicate, also applies to MF 5.1) issued building upon the FTF and HTF closure caps designs and the previously issued SDF analysis, SRR-CWDA-2021-00035, Erosion Analysis for the Saltstone Disposal Facility. The analysis utilizes the Revised Universal Soil Loss Equation (RUSLE) to determine the average annual rate of soil loss due to erosion. SRR-CWDA-2021-00076, Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates was issued in September 2021 and provides a range of infiltration rates for use in the PA models.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.2.4 - To Be Determined Out-Year Testing In FY2021, a report will be prepared to capture a design for a Probable Maximum Precipitation (PMP) event defined as the greatest amount of precipitation for a given duration meteorologically possible for a given size storm area at a particular location at a particular time of year will ensure that the closure cap is capable to withstand these rare rain events. Data for the PMP event was developed for SRS in 1998 using rainfall measurements from 1949 up to 1995. WDA will update the PMP values for SRS cover systems based on an extended record of rainfall measurements and the new PMP event will be incorporated into PA erosion analyses. This new Recommendation [FTF and HTF TERs - Long-Term Activity]

range of PMP values will be used to develop various In the FTF and HTF TERs, NRC staff recommended DOE conduct a preliminary Long-Term erosion and infiltration variables to determine the evaluation of erosion protection designs (e.g., assessment of an acceptable rock source, 5.2 Erosion influence of head-cut erosion and/or gullying, and the and the ability of an integrated drainage system to accommodate design features) prior to

• Protection potential for channel formation or clog formation completing the final closure cap design.

Design within the drainage layers, and appropriate riprap (Duplicate, also applies to MF 5.1) sizing.

The earthen material that comprises the vegetative cover, topsoil, and upper backfill layer, which provide water storage and help to promote evapotranspiration, are subject to degradation via erosion. Previous investigations on these layers note the lack of a formal study on side-slope failure and down-slope creep of riprap. The riprap material for the erosion barrier, side slope, and toe of the side slope will be sized to optimize drainage capabilities in the upper layers. The erosion analysis will focus on soil erosion by overland flow mechanisms in addition to fluvial processes and gravitational erosion mechanisms from landslides, debris flow, and potential stability issues. Seismic analysis provided by SRNS will be incorporated into the final report.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues Ongoing support of NRCs monitoring role will be provided as necessary. Work was begun by the General NRC Monitoring Activities [ML15238A761] University of Virginia in FY2017 related to NRC staff will monitor DOEs disposal actions as they pertain to tank farm closure cap degradation of the closure cap layers and resulting design, construction, and maintenance consistent with ALARA criteria. infiltration rates based on new field information and calculation methodologies. A Closure Cap This monitoring area will remain open throughout DOEs development, construction, and degradation document (Predicting Long-Term completion of final closure caps, unless final design information indicates the MFs are not Percolation from the SDF Closure Cap, risk significant. When DOE develops final closure cap designs, NRC will revise the SRRA107772-000009) was issued in FY2018.

Closure Cap Monitoring Plan, as appropriate, to describe the monitoring activities relevant to the final Functions That 5.3 designs. NRC staff will monitor DOEs development of specific designs for the closure SRR-CWDA-2021-00043, Erosion Analysis for the Maintains Doses caps and determine whether these designs are likely to significantly alter DOE and NRC H-Tank Farm and F-Tank Farm Facilities, has been ALARA conclusions regarding the conceptual design analyzed in the PA. Prior to any construction issued building upon the FTF and HTF closure caps activities, NRC staff will review specifications for closure cap construction materials and designs and the previously issued SDF analysis, quality assurance/quality control procedures for assuring these materials meet SRR-CWDA-2021-00035, Erosion Analysis for the specifications. During construction, NRC staff should observe the placement of these Saltstone Disposal Facility. The analysis utilizes materials and the quality control testing to assure the as-built closure cap will meet design RUSLE to determine the average annual rate of soil specifications. NRC staff also will evaluate available data from similar covers built on the loss due to erosion. SRR-CWDA-2021-00076, larger SRS site and other humid sites. Evaluation of the Uncertainties Associated with the F-Area and H-Area Tank Farm Closure Caps and Long-Term Infiltration Rates was issued in September 2021 and provides a range of infiltration rates for use in the PA models.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 6 - Performance Assessment Maintenance Section 3.3.3 - Provide General Technical Support on Tank Farm PA Issues Ongoing support of NRCs monitoring role will be provided as necessary.

In late FY2020, as part of the HTF and future FTF General NRC Monitoring Activities [ML15238A761] PAs, a report entitled Features, Events, and NRC staff will review PA revisions to evaluate adequacy of scenarios considered. Processes for the F-Area and H-Area Tank Farm Specifically, NRC staff will review the DOE methodology for identification, screening, Performance Assessments (SRR-CWDA-2020-and dispositioning of Features, Events, and Processes (FEPs) and the formation of 00074) was initiated. The information presented scenarios considered in the PAs. NRC staff should verify FEPs identified by DOE, within the report will inform an upcoming revision to including all FEPs having a potential to influence compliance with performance the PAs. As part of a PA, models are used to 6.1 Scenario objectives. NRC will also evaluate DOEs consideration of FEPs related to inadvertent simulate the release and transport of radionuclides

1. Analysis intrusion. NRC staff should examine the technical basis for screening FEPs from further and chemical contaminants from post-closure consideration in the PA. NRC staff also should examine DOE bases for the formation of facilities and to estimate exposure and consequence scenarios considered in the PAs to determine whether they include all FEPs that have not to potential receptors. Due to the complex nature of been screened from further consideration. PA models, a structured methodology is necessary to ensure that relevant components are adequately NRC will close this factor when DOE demonstrates that all risk-significant FEPs have addressed during model development. Therefore, PA been (or will be under another MF) adequately evaluated in PA documentation. models must be developed within defined boundaries and with appropriate consideration of relevant (site-specific) FEPs, as derived from a complete set of FEPs. The FEPs report was issued in March 2021.

This FEPs document is being used as a foundation for a revision of the HTF PA, scheduled to be completed in FY2023.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions The next PA revision will incorporate the results of FEP analysis updates and any additional information relative to FEPs available at that time.

Recommendation [FTF and HTF TERs - Next PA Update]

In the FTF TER, NRC staff recommended DOE perform a systematic scenario analysis in In late FY2020, as part of the HTF and future FTF which FEPs are identified, screened, and dispositioned using transparent and traceable PAs, a report entitled Features, Events, and documentation of the FEPs considered, the screening arguments, and how FEPs are Processes for the F-Area and H-Area Tank Farm implemented in the models to support future waste determination efforts. DOE performed Performance Assessments (SRR-CWDA-2020-a FEPs analysis to support the final waste determination for FTF. NRC staff reviewed the 00074), was initiated. The information presented FEPs analysis and documented the results of its review in a TRR. (ML13277A063; see within the report will inform an upcoming revision to also Table B-1) the PAs. As part of a PA, models are used to simulate the release and transport of radionuclides In the HTF TER, similar to the findings in the TRR for FTF, NRC staff recommended that and chemical contaminants from post-closure DOE include subject matter experts on the screening team in the specific engineering and facilities and to estimate exposure and consequence scientific disciplines that are pertinent to the professional judgments being made. NRC to potential receptors. Due to the complex nature of staff noted that the screening documentation could be more transparent. The NRC staff PA models, a structured methodology is necessary to also recommended that DOE improve the transparency and traceability of its ensure that relevant components are adequately implementation of FEPs to ensure comprehensive, accurate, and traceable links to clear addressed during model development. Therefore, PA descriptions of how included FEPs are actually implemented in the HTF PA.

models must be developed within defined boundaries and with appropriate consideration of relevant (site-specific) FEPs, as derived from a complete set of FEPs. The FEPs report was issued in March 2021.

This FEPs document is being used as a foundation for a revision of the HTF PA scheduled to be completed in FY2023.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions The next PA revision will incorporate the results of FEP analysis updates and any additional information relative to FEPs available at that time.

In late FY2020, as part of the HTF and future FTF Recommendation [ML13277A063] PAs, a report entitled Features, Events, and In the Review of FEPs TRR, the NRC staffs review of the DOE screening methodology Processes for the F-Area and H-Area Tank Farm finds that DOE properly focused on likelihood and impact as criteria for screening, but Performance Assessments (SRR-CWDA-2020-identifies several concerns with DOEs screening of FEPs, including the membership of 00074) was initiated. The information presented the FEPs screening team and the documentation of each subject matter experts basis for within the report will inform an upcoming revision to 6.1 Scenario judgment. The NRC staffs review also identifies questions with the screening process for the PAs. As part of a PA, models are used to

1. Analysis selected FEPs. Finally, the NRC staffs review finds that DOEs crosswalk of included simulate the release and transport of radionuclides FEPs has the potential to enhance transparency and traceability, while NRC staff identifies and chemical contaminants from post-closure multiple examples where transparency and traceability are reduced, which results in a loss facilities and to estimate exposure and consequence of confidence that all relevant FEPs are adequately considered in the FTF Performance to potential receptors. Due to the complex nature of Assessment. PA models, a structured methodology is necessary to ensure that relevant components are adequately addressed during model development. Therefore, PA models must be developed within defined boundaries and with appropriate consideration of relevant (site-specific) FEPs, as derived from a complete set of FEPs. The FEPs report was issued in March 2021 This FEPs document is being used as a foundation for a revision of the HTF PA scheduled to be completed in FY2023.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

NRC staff will review DOEs PA revisions to evaluate the selection of models and justification of parameters. Specifically, NRC staff will examine information DOE generates, including experimental and site characterization data and information from literature, to support model selection and justify parameters. NRC staff also will review Section 3.3.3 - Provide General Technical DOE methods to characterize data and model uncertainty and propagate the uncertainty Support on Tank Farm PA Issues through the PAs. NRC staff will use a graded approach to focus on aspects of most Ongoing support of NRCs monitoring role will be importance to demonstrating compliance with the performance objectives. provided as necessary.

This factor can be closed when DOE provides sufficient information to support risk-significant models and/or model parameters listed in Appendix A of the NRC Monitoring Plan related to MF 6.2.

Recommendation [FTF and HTF TERs - Next PA Update (Long-Term)]

Model and In the FTF and HTF TERs, NRC staff recommended DOE continue to evaluate Section 3.2.4 - To Be Determined Out-Year 6.2 Parameter significance of calcareous zone dissolution on FTF flow and transport, including conduct Testing Support of tracer studies and field mapping of seepage locations along Upper Three Runs Creek. No work related to this recommendation is currently Site-specific Kds may also need to be developed for the Upper Three Runs Aquifer-Lower being performed. DOE will evaluate potential Zone. activities in this area when funding is available.

(Duplicate, also applies to MF 4.2)

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Recommendation [FTF TER - Next PA Update] Revisions As documented in the FTF TER, DOE will explain the differences in the inventory lists The next PA revision will explain the differences in for tanks versus ancillary equipment in future PA documentation. DOE made this the inventory lists for tanks versus ancillary commitment in an NRC/DOE teleconference on the FTF RAIs held on June 28, 2011. equipment. A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023. This PA will incorporate additional ancillary equipment information.

Section 3.4.1 - Prepare Out-Year FTF PA Recommendation [HTF TER - Next PA Update]

Revisions In the HTF TER, NRC staff repeated an FTF TRR (ML13273A299) comment indicating Section 3.4.2 - Prepare Out-Year HTF PA that DOE should provide a stronger technical basis for the projected inventory multipliers Revisions Model and used in the probabilistic analysis. Given the significant fraction of the Tank 5F and 6F 6.2 The next PA revision will explain the differences in Parameter radionuclide inventories that were underestimated, it was not clear to the NRC staff that

1. the inventory lists for tanks versus ancillary Support the inventory multipliers should be biased at 100 times less and only 10 times higher.

equipment. A revision of the HTF PA was initiated NRC staff went on to state that DOE should analyze trends in projections versus actual in FY2020 and is scheduled to be completed in inventories by radionuclide to update the multiplier assumptions for the probabilistic FY2023. This PA will incorporate additional analysis.

ancillary equipment information.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [FTF and HTF TERs - Long-Term Activity with need contingent on other factors]

In the FTF TER, NRC staff recommended DOE consider uncertainty in steel liner Section 3.2.4 - To Be Determined Out-Year performance, including more aggressive service conditions and corrosion mechanisms Testing than assumed in the PA, as well as a patch model for waste release, if deemed to be risk No work related to this recommendation is currently significant. In the HTF TER, similar to previous FTF consultative comments, NRC staff being performed. DOE will evaluate potential questioned DOEs assumed time-invarient oxygen diffusivity of 106 cm2/s given activities in this area when funding is available.

expected degradation of concrete vaults over time and potential presence of bypassing pathways through the system.

Recommendation [FTF and HTF TERs - Intermediate-Term]

In the FTF TER, NRC staff recommended DOE obtain additional support for probabilistic Section 3.2.4 - To Be Determined Out-Year parameter distributions, including solubility limiting phases, cement Kds (based on Testing sediment variability), chemical transition times, basemat bypass, and configuration No work related to this recommendation is currently probability. In the HTF TER, NRC staff recommended DOE incorporate in probability being performed. DOE will evaluate potential distributions pessimistic values that exceed base case solubility limits and that DOE activities in this area when funding is available.

obtain support for the solubility and probability assignments Section 3.2.4 - To Be Determined Out-Year Recommendation [FTF TER - Long-Term] Testing In FTF TER, NRC staff recommended DOE acquire FTF specific data to support material No work related to this recommendation is currently property assignments, including hydraulic conductivity, MCCs, and KdS. being performed. DOE will evaluate potential activities in this area when funding is available.

Recommendation [HTF TER - Prior to final closure]

Section 3.2.4 - To Be Determined Out-Year In the HTF TER, NRC staff recommended DOE provide additional model support to Testing understand the effects of perimeter infiltration and focused infiltration in the drainage No work related to this recommendation is currently valley between the East and West Caps on near-field and far-field groundwater flow being performed. DOE will evaluate potential patterns and radionuclide transport. The analysis should include appropriate refinement of activities in this area when funding is available.

the grid cells receiving recharge and a well-supported value for the diversion of flow.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document The geochemical data package (SRNL-STI-2009-00473) used to identify a justified set of geochemical data inputs for the various transport modeling at SRS was updated in July 2016 (it was last revised in March 2010). This update incorporated the numerous experiments and geochemical measurements have been conducted since 2010, resulting in new recommended input values for Recommendation [FTF and HTF TERs - Long-Term] modeling. The revised geochemical data package In the FTF TER, NRC staff indicated that it would monitor DOEs efforts to study the integrates recent documented geochemical results, impact of cement leachate on radionuclide mobility. NRC reviewed cement leachate including radionuclide Kd values, solubility values, factors utilized in the HTF PA and listed several technical concerns in the HTF TER, most and cementitious impact factors, and includes a notably the lack of site-specific information and basis for some of the factors. critical evaluation of these values with respect to existing values to assess potential impacts.

In the Tank 16H Special Analysis TRR (ML15301A710), the NRC indicated that it needs Distribution Coefficient studies measured the Kds for DOE to provide additional information to support its selection of the iodine distribution various species under oxidizing and reducing coefficient. conditions in actual subsurface sediments retrieved at Model and SRS (actual SDF soils used). This will be applicable 6.2 to FTF and HTF modeling as well.

Parameter Support Section 3.2.4 - To Be Determined Out-Year Testing No work related to this recommendation is currently being performed. DOE will evaluate potential activities in this area when funding is available.

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Recommendation [FTF TER - Next PA Update] Section 3.4.2 - Prepare Out-Year HTF PA In the FTF TER, NRC staff recommended DOE address the significant amount of Revisions dispersion evident in its near-field and far-field PORFLOW models, including evaluation This recommendation will be considered in the next of the need for mesh refinement to ensure that contaminant plumes are not artificially PA revision.

dispersed over the volume of the cells in the far-field model. Nonphysical dispersion may be attributable to large changes in adjacent element size and large differences in element A revision of the HTF PA was initiated in FY2020 sizes between the vadose zone and far-field models. DOE should evaluate the adequacy and is scheduled to be completed in FY2023 (in of the time discretization of the model(s) for swiftly moving constituents such as Tc-99. support of Tank 15 operational closure, the next scheduled HTF tank closure).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions This recommendation will be considered in the next Recommendation [FTF TER - Next PA Update]

PA revision.

In the FTF TER, NRC staff recommended DOE evaluate the appropriateness of the assumed level of physical dispersion in the FTF model (i.e., dispersivities).

A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Section 3.4.1 - Prepare Out-Year FTF PA Recommendation [FTF and HTF TERs - Next PA Update] Revisions In the FTF TER, NRC staff recommended DOE provide greater transparency and Section 3.4.2 - Prepare Out-Year HTF PA traceability of far-field model calibration, including consideration of more extensive Revisions calibration focused strictly on the area of interest. In the HTF TER, NRC staff made This recommendation will be considered in the next Model and 6.2 recommendations similar to those in the FTF TER, but more strongly indicated that the PA revision.

Parameter

1. model may not be sufficiently calibrated local to HTF, and recommended specifically that Support DOE study uncertainty in calibration targets and provide support for hydraulic A revision of the HTF PA was initiated in FY2020 conductivity assignments (Kh was artificially lowered in elliptical regions during the and is scheduled to be completed in FY2023 (in calibration process), including consideration of conducting pumping tests to provide support of Tank 15 operational closure, the next support for the model and model parameters. scheduled HTF tank closure).

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions Recommendation [FTF and HTF TERs - Next PA Update]

This recommendation will be considered in the next NRC staff indicated in the FTF TER that Gordon Aquifer concentrations should not be PA revision.

used to demonstrate compliance with the performance objectives if higher concentrations are observed in another aquifer that can support groundwater-dependent pathways. These A revision of the HTF PA was initiated in FY2020 statements were repeated in the HTF TER.

and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions Recommendation [HTF TER- Next PA Update] This recommendation will be considered in the next In the HTF TER, NRC staff recommended DOE evaluate the compliance boundary and PA revision.

loading of the contaminant source cells (i.e., tank cells in the far-field model) to ensure that the dose estimates are not significantly underestimated. A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Section 3.4.1 - Prepare Out-Year FTF PA Recommendation [FTF and HTF TERs - Next PA Update] Revisions In the FTF TER, NRC staff recommended DOE evaluate plant transfer factor uncertainty Section 3.4.2 - Prepare Out-Year HTF PA in future updates to its PA. DOE should consider the appropriateness of excluding Revisions common vegetable types in its assignment of plant transfer factors (DOE only considers A review of the current HTF Base Case conceptual root vegetable data) based on production data rather than household data that might be model inputs was performed in 2016 to identify more appropriate for a resident gardener. In the HTF TER, NRC staff indicated that DOE inputs requiring revision (SRR-CWDA-2015-00158),

addressed the use of root vegetable transfer factors; however, uncertainty in plant transfer including a review of the dose calculator inputs factors was not addressed. (SRR-CWDA-2013-00058). This recommendation will be considered further in the next PA revision.

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Recommendation [FTF and HTF TERs - Next PA Update]

Section 3.4.2 - Prepare Out-Year HTF PA In the FTF TER, NRC staff recommended DOE evaluate appropriateness of assumptions Revisions Model and related to drinking water consumption in future updates to its PA, such as partitioning 6.2 A review of the current HTF Base Case conceptual Parameter consumption rates based on use of both bottled and community water. Biosphere

1. model inputs was performed in 2016 to identify Support parameters should be reasonably conservative and reflect the behavior of the average inputs requiring revision (SRR-CWDA-2015-00158),

member of the critical group. NRC staff reiterated the FTF TER recommendation in the including a review of the dose calculator inputs HTF TER.

(SRR-CWDA-2013-00058). This recommendation will be considered further in the next PA revision.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions Recommendation [FTF TER - Next PA Update]

This recommendation will be considered in the next In the FTF TER, NRC staff indicated that DOE better assess uncertainty in the timing of PA revision.

peak dose, given the inherent level of uncertainty associated with predicting doses over tens of thousands of years. Additionally, NRC staff indicated that key parameters, such as A revision of the HTF PA was initiated in FY2020 steel liner failure times and chemical transition times, may be overly constrained.

and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Recommendation [FTF and HTF TERs - Next PA Update]

In the FTF TER, NRC staff recommended DOE provide additional support for the likelihood of its base case or expected Case A. In the HTF TER, NRC staff went on to Section 3.4.1 - Prepare Out-Year FTF PA state the NRC staff thinks that additional information is needed to support the compliance Revisions case, Case A. Ideally, supporting information would be in the form of additional Section 3.4.2 - Prepare Out-Year HTF PA experimental or field data, natural analogs, peer review, expert elicitation, and other forms Revisions of model support. NRC staff stated that without this additional model support, it would be This recommendation will be considered in the next difficult to argue the relative likelihood of the base case compared to alternative cases. PA revision.

Additionally, NRC staff indicated that the uncertainty analysis results not be used to demonstrate compliance with the performance objectives because (i) there is limited A revision of the HTF PA was initiated in FY2020 support for the base case and (ii) there is limited support for the assignment of the and is scheduled to be completed in FY2023 (in likelihood of alternative cases and consequently, the averaging of alternative cases in the support of Tank 15 operational closure, the next All Cases model. NRC staff recommended DOE present the results of alternative cases scheduled HTF tank closure).

individually and provide qualitative information regarding the likelihood of alternative cases. Finally, NRC staff indicated that DOE should use the results of its probabilistic analysis to inform areas where additional model support is needed.

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Recommendation [FTF and HTF TERs - Next PA Update] Section 3.4.2 - Prepare Out-Year HTF PA Model and In the FTF TER, NRC staff recommended DOE improve transparency and documentation Revisions 6.2 Parameter of its benchmarking process. NRC recommends DOE apply a more methodical and The HTF benchmarking process was detailed in the Support systematic approach to the benchmarking process in future updates to its PA. In the HTF most recent HTF Goldsim model update (SRR-TER, NRC staff also noted that DOE could improve its benchmarking process. CWDA-2014-00060), with improved transparency and documentation. This recommendation will be considered further in the next PA revision.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Recommendation [HTF TER - Next PA Update] Revisions In the HTF TER, NRC staff noted that due to significant differences between the GoldSim This recommendation will be considered in the next and PORFLOW modeling results, the NRC staff plans to continue to evaluate the PA revision.

PORFLOW modeling assumptions and results for the compliance case (Case A) during the monitoring period to provide confidence that the timing of peak dose is not artificially A revision of the HTF PA was initiated in FY2020 delayed. This applies to the inadvertent intruder analysis. and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions Recommendation [FTF TER - Next PA Update] This recommendation will be considered in the next In the FTF TER, NRC staff suggested that DOE consider consistency between the plotting PA revision.

interval and calculation time step size. DOE should also correct errors in its probabilistic assessment (e.g., porosity of 1E-20). A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Recommendation [FTF TER - Next PA Update]

Revisions NRC made a general comment that DOE could improve its parameter distribution This recommendation will be considered in the next assignments, hybrid modeling approach, benchmarking process, and evaluation and PA revision.

interpretation of probabilistic modeling results. With respect to parameter distributions, NRC included several items in its open items database (see Appendix B in A revision of the HTF PA was initiated in FY2020 ML12212A192), most of which are listed in other recommendations, with the exception of and is scheduled to be completed in FY2023 (in probability of basemat bypass flow.

support of Tank 15 operational closure, the next scheduled HTF tank closure).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions Section 3.4.2 - Prepare Out-Year HTF PA Revisions Recommendation [ML16277A060] These items will be considered in the next PA As a result of its review of the revised dose methodology for Liquid Waste PAs (SRR- revision.

CWDA-2013-00058, Revision 1), NRC identified a number of items that should be addressed in future HTF and FTF PAs revisions. The complete listing of items is documented in the Dose Calculation Methodology TRR. A revision of the HTF PA was initiated in FY2020 and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next scheduled HTF tank closure).

Recommendation [ML19277H550]

DOE should consider the following in future updates to the GSA PORFLOW model to increase accuracy and reduce uncertainty in contaminant flow and transport modeling:

Section 3.4.1 - Prepare Out-Year FTF PA

• More extensive calibration in the areas of interest for waste disposal activities, including Revisions FTF and HTF, and evaluation of calibration statistics local to these areas.

Section 3.4.2 - Prepare Out-Year HTF PA

• Hydraulic conductivity measurements near HTF and other areas where additional data Revisions collection is important to model calibration to reduce uncertainty in calibrated These items will be considered in the next PA parameters. revision.

• Evaluation of more recent baseflow measurements for model validation consistent with the time over which water level measurements were averaged to develop calibration targets, and consideration of uncertainty in baseflow to Upper Three Runs Creek when A revision of the HTF PA was initiated in FY2020 evaluating model performance and is scheduled to be completed in FY2023 (in support of Tank 15 operational closure, the next

• Evaluation of the sensitivity of the results to changes in recharge, and other parameters.

scheduled HTF tank closure).

• Sensitivity analysis to identify observations and parameters most important to the results where additional data collection could be conducted to reduce model uncertainty.

• More extensive analysis of the impact of flow model and parameter uncertainty on the results of the PAs.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Section 3.4.1 - Prepare Out-Year FTF PA Revisions General NRC Monitoring Activities [ML15238A761]

NRC staff will review the revised PAs and issue a TER documenting the results of its Future revisions to the FTF PA will be provided to review. NRC staff will pay special attention to supporting documentation generated since NRC for review in support of NRCs monitoring the last PA revision, including results of experiments, analog studies, models, and peer role.

FTF PA reviews conducted to support key Monitoring Areas listed in the NRC Monitoring Plan.

6.3 Revisions NRC will evaluate any revisions to the tank farm PAs to ensure inadvertent intrusion into Section 3.4.2 - Prepare Out-Year HTF PA

1. (Additional tank farm components were properly evaluated in the 10 CFR 61.42 analyses.

Revisions Considerations)

This MF can be closed when NRC staff concludes that DOE has adequately evaluated A revision of the HTF PA was initiated in FY2020 FEPs and scenarios related to inadvertent intrusion in its PA documentation and that its and is scheduled to be completed in FY2023 (in LW PA Maintenance Program is sufficient to evaluate new and significant information support of Tank 15 operational closure, the next related to 10 CFR 61.41 and 10 CFR 61.42 in the future.

scheduled HTF tank closure).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [ML18242A259]

In the Tank 18F Waste Release Testing TRR, NRC staff concluded that additional waste release testing and updated geochemical modeling are needed for NRC staff to have confidence in the PA results. The NRC staff offered the following additional conclusions Section 3.4.1 - Prepare Out-Year FTF PA and comments related to waste release testing and PA modeling. Revisions

• DOE should consider a larger range of uncertainty in key radionuclide solubility due to experimental limitations (e.g., substantial metal losses of uranium during Future revisions to the FTF PA will be provided to leach testing which compromised the utility of the uranium data collected from NRC for review in support of NRCs monitoring the experiments and apparent lack of ability to achieve equilibrium conditions role.

particularly for Pu and Tc).

• DOE should perform probabilistic or multi-variate sensitivity analysis Section 3.4.2 - Prepare Out-Year HTF PA considering uncertainty in performance of multiple barriers including scenarios Revisions that evaluate basemat bypass, early hydraulic failure due to water table rise or preferential flow through the system, and consider the impact of higher mobility Testing of actual waste (i.e., Tank 18 and Tank 12 FTF PA forms of Pu in the natural system. residuals) was performed in FY2016 and FY2018.

6.3 Revisions

• DOE should explain differences in PORFLOW and GoldSim modeling results The solubilities of I, Pu, Np, U, and Tc were tested

1. (Additional (e.g., Pu peak doses of around 5 mSv/yr (500 mrem/yr) in the Tanks 18/19 SA under simulated waste tank chemistry conditions Considerations)

(SRR-CWDA-2010-00124) versus 7 mSv/yr (700 mrem/yr) in SRR-CWDA- using Tank 18 and Tank 12 residual waste samples.

2016-00086). The NRC conclusions and comments relating to

• DOE should evaluate the impact of the early, high concentration release of Pu or waste release testing were incorporated into the Tank justify why the rinse sample results are not applicable to alternative conceptual 12 testing to the extent practical and will be models involving water table rise or preferential flow through the system. addressed further in any future testing.

• DOE should continue to study and develop models to account for higher mobility forms of Pu in the natural system including models that consider two A revision of the HTF PA was initiated in FY2020 fractions of Pu (relatively high mobility and low mobility forms) as well as the and is scheduled to be completed in FY2023 (in potential for oxidation and reduction reactions affecting the mobility of Pu in the support of Tank 15 operational closure, the next subsurface along the flow paths away from the tank to the 1 m and 100 m scheduled HTF tank closure).

compliance points.

• DOE should evaluate the impact of transport of key radionuclides from the waste zone up into the tank grout, and if found to be risk-significant, provide additional support for the transport mechanism(s).

Page 157 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 7 - Protection of Individuals During Operations General NRC Monitoring Activities [ML15238A761]

NRC staff should review, on at least an annual basis, DOE reports and records that are related to dose during waste disposal operations to assess whether doses are within the limits found in 10 CFR Part 20 and are ALARA. NRC staff should periodically confirm programs and policies presented in the waste determination (DOE/SRS-WD-2012-001) continue to be in effect during the operational period. In particular, NRC staff should Section 3.3.3 - Provide General Technical verify personnel involved in waste disposal operations are provided dosimetry and are Support on Tank Farm PA Issues familiar with requirements of the radiation protection program. NRC will leverage staff in Ongoing support of NRCs monitoring role will be Protection of its Region I office with experience in radiation protection inspections to support onsite provided as necessary.

7.1 Workers During observations in this area.

+/-

Operations This factor will be closed at the end of the assumed 100-year institutional control period or after operational doses are expected to be reduced to non-risk-significant levels following tank closure activities.

Recommendation [FTF and HTF TERs - Ongoing]

No specific recommendations identified, NRC concluded DOE can demonstrate Section - N/A compliance with protection of individuals during operations and DOE provides adequate information that individuals will be protected during operations.

General NRC Monitoring Activities [ML15238A761]

NRC will review air monitoring data to determine whether activity released in the air, as a result of tank farm disposal activities, could cause a MOP located at the SRS boundary to receive a dose of greater than 10 mrem/yr through the air pathway. NRC staff should periodically confirm the air monitoring program continues to adequately assess the risk of tank farm operations. As part of this review, NRC staff should evaluate whether sampling Section 3.3.3 - Provide General Technical locations and sampling methodologies are adequate to assess airborne emissions from the Support on Tank Farm PA Issues tank farms or rely on independent verification from the SCDHEC. NRC staff expects the Ongoing support of NRCs monitoring role will be dose from airborne emissions to be small. If the airborne emissions dose becomes more 7.2 provided as necessary.

Air Monitoring risk significant, then NRC staff will need to evaluate the air monitoring program in greater

+/- detail.

This factor will be closed at the end of the assumed 100-year institutional control period or when operational doses are expected to be reduced to non-risk-significant levels following tank closure activities.

Recommendation [FTF and HTF TERs - Ongoing]

No specific recommendations identified, NRC concluded DOE can demonstrate Section - N/A compliance with protection of individuals during operations and DOE provides adequate information that individuals will be protected during operations.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document General NRC Monitoring Activities [ML15238A761]

Section 3.3.3 - Provide General Technical NRC staffs monitoring of ALARA under 10 CFR 61.43 will be carried out through Support on Tank Farm PA Issues monitoring of the Radiation Protection Program and related activities.

Ongoing support of NRCs monitoring role will be NRC staff should periodically (or at the appropriate time relevant to each measure) review provided as necessary.

documents associated with the following measures for ensuring ALARA: (i) a documented Radiation Protection Program; (ii) a Documented Safety Analysis; (iii)

Section 3.4.2 - Prepare Out-Year HTF PA radiological design for protection of occupational workers and the public; (iv) regulatory Revisions 7.3 and contractual enforcement mechanisms; (v) access controls, training, and dosimetry; and ALARA (vi) occupational radiation exposure history. These measures are described in the waste

+/- A revision of the HTF PA was initiated in FY2020 determination or basis documents (DOE/SRS-WD-2012-001 and DOE/SRS-WD-2014-and is scheduled to be completed in FY2023 (in 001).

support of Tank 15 operational closure, the next scheduled HTF tank closure). The new PA will This factor will be closed at the end of an assumed 100-year institutional control period or contain additional ALARA analyses.

when operational doses are expected to be reduced to non-risk-significant levels following tank closure activities.

No specific NRC recommendations identified. Section - N/A Page 159 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document MA 8 - Site Stability General NRC Monitoring Activities [ML15238A761]

Technical reviews and onsite observations of settlement will be conducted by the NRC staff to assess compliance with 10 CFR 61.44. Reviews will focus on (i) settlement data collected during closure operations of the tank farms, (ii) settlement data collected from analogous sites, and (iii) updated settlement modeling investigations. NRC Technical reviews related to the risk significance of calcareous zones will be conducted to assess compliance with 10 CFR 61.44. Reviews will focus on (i) processes that have resulted in the formation of sinks at the SRS and specifically at the tank farms at the General Separations Area, (ii) the potential for these processes to affect site stability throughout the performance period, and (iii) the potential dose consequences from subsidence related to dissolution of calcareous sediment. DOE stated that it will consider static-loading- Section 3.3.3 - Provide General Technical induced settlement, seismically induced liquefaction and subsequent settlement, and Support on Tank Farm PA Issues seismically induced slope instability in the final design of the closure cap. NRC staff will Ongoing support of NRCs monitoring role will be review DOEs consideration of these processes as information is made available. provided as necessary.

To assess compliance with 10 CFR 61.44, NRC staff will visually observe the facility for obvious signs of degeneration of the facility. For example, evidence of ponded water on the cap surface may be a sign of differential settlement. Surface fractures may be 8.1 Settlement evidence of underlying displacement. NRC staff also may plan site visits to observe the

1. facility after severe weather events (e.g., storms, tornados) to ascertain how well the facility can withstand these events. NRC staff should also discuss any maintenance activities that are performed at the disposal facility (e.g., repairs to engineered surface barriers) with SCDHEC.

This monitoring activity is expected to remain open indefinitely.

Recommendation [ML15238A761]

NRC staff expects DOE to inform it of changes to features in the immediate area that Section 3.3.3 - Provide General Technical might affect site stability. These changes may include (i) vegetation denudation at the Support on Tank Farm PA Issues surface due to fires or storms; (ii) erosion features caused by extreme precipitation events Ongoing support of NRCs monitoring role will be or long-term processes; or (iii) visible surface changes due to significant biotic intrusion, provided as necessary.

earthquakes, or other geological processes.

Recommendation [FTF and HTF TERs - Intermediate-Term] Section 3.2.4 - To Be Determined Out-Year In the FTF and HTF TERs, NRC staff recommended DOE continue to evaluate closure Testing cap settlement and stability, including consideration of (i) increased overburden from the No work related to this recommendation is currently tank grout and closure cap on settlement and (ii) potential for subsidence associated with being performed. DOE will evaluate potential ongoing dissolution of calcareous sediment in the Santee Formation. activities in this area when funding is available.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [FTF and HTF TERs - Intermediate-Term]

In the FTF and HTF TERs, NRC staff concluded that assumed long-term compressive Section 3.2.4 - To Be Determined Out-Year strength of the grout monolith is not adequately supported and may be optimistic based on Testing 8.1 Settlement observations of vault cracks, discussed in TER Section 4.2.9.1 (ML112371715). While No work related to this recommendation is currently cracking of the vault concrete and tank grout is not expected to result in significant being performed. DOE will evaluate potential structural tank collapse, the integrity of the vault concrete and tank grout is important to activities in this area when funding is available.

steel liner performance and waste release.

TER Recommendations Only Recommendation [FTF and HTF TERs]

In the FTF TER, NRC staff recommended DOE specifically consider and evaluate HRR removal in its technology selection and effectiveness evaluations consistent with the Section 3.3.3 - Provide General Technical NDAA. In the HTF TER, NRC staff recommended DOE provide more emphasis on Support on Tank Farm PA Issues removal of HRR in its technology selection process and provide a clear linkage between Ongoing support of NRCs monitoring role will be the HTF PA results, including information regarding the long-term risks associated with provided as necessary.

the HTF facility, and the demonstration that HRRs have been removed to the MEP per Criterion 2.

Recommendation [FTF and HTF TERs]

In the FTF TER, NRC staff recommended DOE continuously evaluate new technologies, participate in technology exchanges, and not default to previous evaluations for technology selection. In the HTF TER, NRC staff recommended DOE continue evaluating new technologies for future use as tank closure progresses, especially if N/A previously used technologies are no longer practical to use. Furthermore, for those tanks N/A Section 3.3.3 - Provide General Technical

1. in which conditions are dissimilar (e.g., Tank 48), the NRC staff would expect DOE to Support on Tank Farm PA Issues reevaluate technologies as opposed to relying on previously performed technology Ongoing support of NRCs monitoring role will be evaluations. The NRC staff also recommended DOE continue its efforts to participate in provided as necessary.

technology exchanges so that it can stay informed of potential new cleaning technologies.

New technologies or improvements to current technologies should be fully considered in the selection process for future tank cleaning. DOE should try to optimize operational parameters for existing technologies and technologies to be developed in the future to ensure that removal of HRRs is not hampered or made more difficult because of poor planning or lack of investment in waste characterization.

Recommendation [HTF TER]

Section 3.3.3 - Provide General Technical In the HTF TER, NRC staff indicated that DOEs approach to optimization of technology Support on Tank Farm PA Issues through sampling and monitoring during cleaning should be documented. The NRC staff Ongoing support of NRCs monitoring role will be also recommended DOE consider how it might better assess and optimize the provided as necessary.

effectiveness of selected technologies (e.g., obtain better baseline information).

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [HTF TER]

In the HTF TER, NRC staff noted that, although the results from mapping contain Section 3.3.3 - Provide General Technical uncertainties, performing the tank mapping methodology during multiple cleaning phases Support on Tank Farm PA Issues will provide additional information on the effectiveness of specific technologies. As such, Ongoing support of NRCs monitoring role will be the NRC staff recommended DOE perform the tank mapping consistently and as provided as necessary.

frequently as practical throughout the cleaning process.

Section 3.3.3 - Provide General Technical Recommendation [HTF TER]

Support on Tank Farm PA Issues In the HTF TER, NRC staff recommended DOE should obtain better baseline information Ongoing support of NRCs monitoring role will be from which it could better assess oxalic acid effectiveness. provided as necessary.

Recommendation [HTF TER] Section 3.3.3 - Provide General Technical In the HTF TER, NRC staff supported DOEs efforts to re-evaluate oxalic acid cleaning Support on Tank Farm PA Issues against downstream impacts to determine the future role of oxalic acid cleaning, as Ongoing support of NRCs monitoring role will be opposed to relying on previous evaluations of oxalic acid technology. provided as necessary.

Section 3.3.3 - Provide General Technical Recommendation [HTF TER]

Support on Tank Farm PA Issues In the HTF TER, NRC staff noted that each final characterization should be accompanied Ongoing support of NRCs monitoring role will be N/A by a Technical Task Request and a Quality Assurance and Quality Control Plan.

N/A provided as necessary.

Recommendation [HTF TER]

In the HTF TER, NRC staff indicated that to help overcome the limitations encountered Section 3.3.3 - Provide General Technical with cleaning Tanks 5 and 6 for the cleaning of future tanks, the NRC staff recommends Support on Tank Farm PA Issues that DOE evaluate the effectiveness of the submersible mixer pumps with respect to bulk Ongoing support of NRCs monitoring role will be sludge removal versus residual heel removal. The NRC staff also recommends that DOE provided as necessary.

compare the efficiency and effectiveness of the submersible mixer pump to previously used technologies or readily available technologies.

Recommendation [HTF TER]

Section 3.3.3 - Provide General Technical In the HTF TER, NRC staff noted that if oxalic acid is not available to be used for Support on Tank Farm PA Issues cleaning future tanks and a technology with similar proven effectiveness is not used as an Ongoing support of NRCs monitoring role will be alternative, DOE may need to reconsider the validity of assuming that the cooling coil and provided as necessary.

tank wall surface inventory is negligible.

Recommendation [HTF TER]

Section 3.3.3 - Provide General Technical In the HTF TER, NRC staff recommended DOE should develop separate site-specific Support on Tank Farm PA Issues factors for risk-significant annular waste versus tank waste sources in the future. Annular Ongoing support of NRCs monitoring role will be and tank sources would then be separately compared to adjusted waste classification provided as necessary.

concentration limits to determine the classification of HTF components.

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SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [HTF TER]

In the FTF TER, NRC recommended DOE more fully evaluate or document its consideration of alternatives to additional HRR removal, including (i) modifications to Section 3.3.3 - Provide General Technical existing technologies (e.g., upgraded Mantis or enhanced chemical cleaning); Support on Tank Farm PA Issues (ii) modification to tank system components (e.g., installation of new risers or removal of Ongoing support of NRCs monitoring role will be equipment from existing risers); (iii) sequential cleaning (e.g., sequencing of mechanical provided as necessary.

and chemical technologies in Tank 18F); and (iv) alternative cleaning technologies (e.g.,

alternative reagents to leach HRRs out of residual heels).

Recommendation [HTF TER]

In the FTF TER, NRC recommended DOE better quantify technology effectiveness. For example, DOE should better characterize waste and residual tank inventory prior to Section 3.3.3 - Provide General Technical deployment of cleaning technologies to better assess effectiveness. In the HTF TER, NRC Support on Tank Farm PA Issues staff recommended, to the extent practical, DOE consider obtaining data on HRR Ongoing support of NRCs monitoring role will be inventories prior to and following major cleaning campaigns (e.g., before and after provided as necessary.

treatment of Type I tanks with oxalic acid) to provide effectiveness measurements for chemical cleaning and mechanical feed-and-bleed.

Recommendation [HTF TER]

In the HTF TER, NRC staff noted that given the potential risk significance of the waste N/A remaining in the Tank 16 annulus, the NRC staff recommends that DOE more fully N/A

1. evaluate the practicality of additional radionuclide removal from the Tank 16H annulus Section 3.3.3 - Provide General Technical versus the long-term benefit of reduced risk considering uncertainty in the releases of Support on Tank Farm PA Issues radionuclides from the Tank 16 annulus. While DOEs HTF PA demonstrates that the risk Ongoing support of NRCs monitoring role will be from waste remaining in the annulus is reasonable, alternative waste release models may provided as necessary. An SA specific to the HTF lead to higher risk estimates. Type I and Type II Tanks was prepared and issued in August 2016. [SRR-CWDA-2016-00078] This SA NRC staff went on to note that at this stage, DOE has provided a rough order of updated the radiological and chemical inventories for magnitude cost-benefit analysis of additional HRR removal from the Tank 16H annulus to the HTF Type I and Type II tanks, incorporating the NRC staff (U-ESR-H-00107). The NRC staff acknowledges that DOE is still lessons learned from the final waste tank preparing the final removal report and recommends that DOE provide a more detailed cost characterization results to date.

benefit analysis to support the Criterion 2 demonstration for Tank 16H in the final removal report. NRC staff indicated that it would like to obtain a copy of the final removal report when it is complete.

Recommendation [HTF TER]

In the HTF TER, NRC staff noted that DOE improved the operating plan for Tank 12H by Section 3.3.3 - Provide General Technical requiring the availability of the transfer receipt tank to be confirmed prior to acid addition. Support on Tank Farm PA Issues The NRC staff encourages DOE to continue to analyze the lessons learned from these Ongoing support of NRCs monitoring role will be prior cleaning campaigns to prevent limitations of the liquid waste system from provided as necessary.

unexpectedly influencing the effectiveness of future cleaning campaigns.

Page 163 of 164

SRS Liquid Waste Facilities Performance Assessment SRMC-CWDA-2022-00006 Maintenance Program - FY2022 Revision 0 May 2022 Related PA Maintenance Activities as Described MF1 Factor NRC Monitoring Activities 2 / Recommendation(s) in this Document Recommendation [FTF and HTF TERs]

In the FTF TER, the NRC staff recommended DOE include more specificity in its process for determining HRRs are removed to the MEP, including (i) defining the term end states versus removal goals and (ii) clarifying when conditions are sufficiently similar to warrant Section 3.3.3 - Provide General Technical use of a previous technology evaluation. NRC staff also recommended DOE continue to N/A Support on Tank Farm PA Issues N/A better define the documented process to be used to demonstrate removal to the MEP to

1. Ongoing support of NRCs monitoring role will be ensure consistent (nonarbitrary) application of the criterion. In the HTF TER, NRC staff provided as necessary.

noted that Appendix B of the draft basis for the waste determination for HTF (DOE/SRS-WD-2013-001) outlines a general approach to demonstrate that the HRRs will be removed to the MEP. However, DOE could still improve the standardization of metrics for determining that the anticipated end states have been reached.

1 Monitoring Factors are color-coded based on NRC-determined prioritizations in NRC Monitoring Plan. [ML15328A761] Symbols are included for clarity.

§ High Priority Recommended

• Lower Priority High Priority Dependent or More Difficult +/- Not Prioritized - Periodic Medium Priority # Not Prioritized - Not Periodic 2

Recommendations noted by [FTF and HTF TER - timing] are from the NRC TERs for FTF [ML112371715] and HTF [ML14094A496]. Other recommendations are from the FTF and HTF Monitoring Plan Table A-1 [ML15238A761], which replaced the FTF Monitoring Plan [ML12212A192], or from other various NRC TRRs. [ML12272A082, ML12272A124, ML13273A299, ML13085A291, ML13269A365, ML13277A063, ML13100A230, ML13080A401, ML14342A784, ML15301A710, ML15301A830, ML16196A179, ML16231A444, ML16277A060, ML17277B235, ML18051B153, ML18242A259, ML19277H550, ML19280A059, ML19298A092]

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