Text

SRMC-CWDA-2023-00008, Rev. 0, Fy 2022 Annual Review of the Saltstone Disposal Facility (Z-Area) Performance Assessment
	ML23107A291
Person / Time
Site:	PROJ0734
Issue date:	03/31/2023
From:	Harry Felsher; NRC/NMSS/DDUWP/LLWPB, Savannah River Mission Completion LLC
To:	;
	Felsher H
References
	89303322DEM000068 SRMC-CWDA-2023-00008, Rev. 0
	Download: ML23107A291 (75)
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Prepared by: Savannah River Mission Completion Waste Disposal Authority Aiken, SC 29808 Prepared for U.S. Department of Energy Under Contract No. 89303322DEM000068 SRMC-CWDA-2023-00008 Revision 0 FY2022 ANNUAL REVIEW OF THE SALTSTONE DISPOSAL FACILITY (Z AREA)

PERFORMANCE ASSESSMENT March 2023

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 1 of 74 EXECUTIVE

SUMMARY

The Saltstone Disposal Facility (SDF) presently consists of Saltstone Disposal Units (SDUs) 1, 2, 3, 4, 5, 6 and 7 as described in the Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site (SRR-CWDA-2019-00001). Future SDUs are planned to be 375-foot diameter SDUs, similar to SDU 7 completed in 2021. Construction of SDUs 8 and 9 is in progress.

Project activities are in progress for SDUs 10 through 12.

The U.S. Department of Energy (DOE), through DOE O 435.1, requires an active maintenance program for the 2019 SDF Performance Assessment (PA), which is satisfied in the Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program - FY2022. [SRMC-CWDA-2022-00006] A maintenance program is required to continue to reduce uncertainty in the inputs and assumptions in order to provide greater confidence in the results of the analyses and in the long-term plans for public and environmental protection.

DOE O 435.1 also requires an approved Radioactive Waste Management Basis (RWMB).

Potential changes identified during the annual review must be evaluated for impact to the SDF RWMB which consists of facility controls and analyses to demonstrate near-and long-term protection of the public, workers, and the environment. Examples of these controls include facility safety documents, waste certification programs, facility waste acceptance criteria (WAC) requirements, low level waste disposal facility closure plans, PAs, Composite Analyses (CAs),

and other facility-specific processes, procedures, and analyses made to comply with DOE O 435.1 and its manual. The current SDF RWMB is Q-RWM-Z-00001, Rev. 9; however, DOE has not yet approved this latest revision, so Q-RWM-Z-00001, Rev. 8 is the most recently approved SDF RWMB. [WDPD-21-29]

The 2019 SDF PA was issued in FY2020. The 2019 SDF PA was reviewed by the DOE Low Level Waste Disposal Facility Federal Review Group (LFRG) and SRR received a letter from DOE in June 2020 approving the PA and authorizing continued operation of the SDF. [WDPD-20-32] A revised operating Disposal Authorization Statement (DAS) was issued by DOE-Headquarters to Savannah River Remediation (SRR) through DOE Savannah River Operations (DOE-SR) as an attachment to the authorization letter.

Since July 2020, the U.S Nuclear Regulatory Commission (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_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 four letters with Requests for Additional Information (RAIs). [ML21040A492, ML21133A296, ML21341A551, ML22026A391] The first letter (ML21040A492), issued in March 2021, had twelve RAIs as well as six Clarifying

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 2 of 74 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, issued in July 2021.

The NRC issued the second letter in June 2021 (ML21133A296) with 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. Once the responses to the remaining RAIs and CCs were completed, SRR-CWDA-2021-00072 was revised to include the complete set of RAI and CC responses. Revision 1 was issued in November 2021.

The NRC issued the third letter (ML21341A551) in December 2021 and that letter included an additional twenty RAIs and four CCs. On March 22, 2022, a complete set of responses to this third set of NRC RAIs and CCs was issued via SRMC-CWDA-2022-00003, Comment Response Matrix for the Third 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.

The NRC issued the fourth letter (ML22026A391) in February 2022 and that letter included an additional thirteen RAIs and ten CCs. On April 25, 2022, a complete set of responses to this fourth and final set of NRC RAIs and CCs was issued via SRMC-CWDA-2022-00016, Comment Response Matrix for the Fourth 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.

The 2019 SDF PA establishes controls to govern waste operations and monitoring performance of the SDF. The mechanisms to demonstrate that operations are within the bounds of the DAS (WDPD-20-32), the RWMB (Q-RWM-Z-00001), and the PA are the WAC, an Unreviewed Waste Management Question (UWMQ) program, periodic inspections of disposal unit integrity, routine engineering evaluation of inventory and operations, and a comprehensive environmental monitoring program. [X-SD-Z-00004, Manual S4 Procedure ENG.46, SRR-CWDA-2020-00006, WSRC-TR-2005-00257] Data relevant to the critical features, limits, and predictions of the PA are used to evaluate the performance in the previous fiscal year (FY). The performance evaluation conducted for FY2022 made the following determinations:

The current performance evaluation conducted on SDU 1, SDU 4, SDU Cells 2A/2B, SDU Cells 3A/3B, SDU Cells 5A/5B, SDU 6, and SDU 7 indicates SDF operations through FY2022 were within the performance expectations of the 2019 SDF PA.

The total inventory of radionuclides accumulated in SDU 1, SDU 4, SDU Cells 2A/2B, SDU Cells 3A/3B, SDU Cells 5A/5B, SDU 6, and SDU 7 through FY2022 was within the range of acceptable inventory values considered in the 2019 SDF PA.

Research was completed in FY2022 with respect to several ongoing studies on properties considered critical to the performance of saltstone. A more in-depth discussion of on-going

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 3 of 74 and future studies can be found in the Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program - FY2022. [SRMC-CWDA-2022-00006]

The routine groundwater monitoring analytical results do not contradict the SDF modeling estimates.

The current performance evaluation conducted on SDU 1, SDU 4, SDU Cells 2A/2B, SDU Cells 3A/3B, SDU Cells 5A/5B, SDU 6, and SDU 7 indicates SDF operations through FY2022 were within the performance expectation of the 2019 SDF PA and complies with the DAS, the RWMB, and DOE O 435.1 requirements.

To demonstrate compliance with pertinent requirements of DOE O 435.1 and its associated Manual and Guide, the Performance Assessment Monitoring Plan for the Saltstone Disposal Facility at the Savannah River Site (SRR-CWDA-2020-00006) (hereinafter referred to as the SDF Monitoring Plan) was prepared. The SDF Monitoring Plan, that complies with DOE M 435.1-1, must be maintained and modified as needed to reflect facility changes. The SDF Monitoring Plan is reviewed annually to determine if a revision is required. The SDF Monitoring Plan was updated in FY2020 to capture changes in the recently revised 2019 SDF PA and to incorporate ongoing activities as required by the DAS and no revision was necessary in FY2022.

A Special Analysis (SA) has been prepared entitled, Fiscal Year 2020 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, SRR-CWDA-2020-00064, to address the new SDU Concrete Mix 3B and cement-free saltstone. The SA is hereinafter referred to as the FY2020 SDF SA. The FY2020 SDF SA was issued in 1QFY21. 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 May 2021.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 4 of 74 TABLE OF CONTENTS EXECUTIVE

SUMMARY

.......................................................................................................... 1 LIST OF TABLES........................................................................................................................ 5 LIST OF FIGURES...................................................................................................................... 5 ACRONYMS................................................................................................................................. 6

1.

Purpose of Review............................................................................................................. 8

2.

Changes Potentially Affecting the PA, CA, DAS, OR RWMB................................... 11 2.1 Special Analyses and Unreviewed Waste Management Question Evaluations...... 11 2.1.1 Special Analyses.................................................................................................... 11 2.1.2 Unreviewed Waste Management Question Evaluations....................................... 11 2.2 Update the Closure Plan.............................................................................................. 11 2.3 Update the SDF Monitoring Plan............................................................................... 12

3.

Cumulative Effects of Changes...................................................................................... 13

4.

Waste Receipts................................................................................................................ 14 4.1 Waste Volumes and Radionuclide Inventories.......................................................... 14 4.1.1 Waste Volumes...................................................................................................... 17 4.1.2 Waste Inventory.................................................................................................... 20

5.

Monitoring....................................................................................................................... 42 5.1 Reason for Monitoring................................................................................................. 42 5.2 SDF Monitoring Plan................................................................................................... 42 5.3 Evaluation of Monitoring Data................................................................................... 46

6.

Research and Development............................................................................................ 52 6.1 Long-Term Radiological Lysimeter Program........................................................... 55 6.2 Radionuclide Leaching Characteristics from Saltstone Monolith........................... 57 6.3 Toxicity Characteristic Leaching Procedure (TCLP) Testing and X-Ray Absorption Spectroscopy (XAS) of Cement-Free Saltstone............................................... 61

7.

Planned or Contemplated Changes............................................................................... 64 7.1 Revise the Closure Plan............................................................................................... 64 7.2 Revise the SDF Monitoring Plan................................................................................. 64 7.3 Special Analyses............................................................................................................ 64 7.4 Unreviewed Waste Management Question Evaluations........................................... 64 7.5 Revise the Performance Assessment........................................................................... 65 7.6 Studies........................................................................................................................... 65 7.7 Performance Assessment Monitoring......................................................................... 65

8.

Status of DAS Conditions, Key and Secondary Issues................................................ 66

9.

Composite Analysis Summary....................................................................................... 67

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10.

Certification of Continued Adequacy of the PA, CA, DAS, and RWMB and Conclusion................................................................................................................................... 68

11.

References........................................................................................................................ 69 LIST OF TABLES Table 4.1-1: Saltstone Disposal Unit Waste Receipts Through FY2022............................... 16 Table 4.1-2: FY2022 Tank 50 Salt Solution Historical Data.................................................. 18 Table 4.1-3: FY2022 Tank 50 Salt Solution Disposed............................................................ 19 Table 4.1-4: Saltstone Disposal Facility SDU 1 Inventory..................................................... 22 Table 4.1-5: Saltstone Disposal Facility SDU 4 Inventory..................................................... 24 Table 4.1-6: Saltstone Disposal Facility SDU Cell 2A Inventory........................................... 26 Table 4.1-7: Saltstone Disposal Facility SDU Cell 2B Inventory........................................... 28 Table 4.1-8: Saltstone Disposal Facility SDU Cell 5A Inventory........................................... 30 Table 4.1-9: Saltstone Disposal Facility SDU Cell 5B Inventory........................................... 32 Table 4.1-10: Saltstone Disposal Facility SDU Cell 3A Inventory Comparison.................. 34 Table 4.1-11: Saltstone Disposal Facility SDU Cell 3B Inventory Comparison................... 36 Table 4.1-12: Saltstone Disposal Facility SDU Cell 6 Inventory Comparison..................... 38 Table 4.1-13: Saltstone Disposal Facility SDU Cell 7 Inventory Comparison..................... 40 Table 5.2-1: Summary Monitoring Table................................................................................ 43 Table 5.2-2: SDUs with Associated Background Monitoring Wells...................................... 45 Table 5.3-1: SDF Monitoring Wells Downgradient of SDU 4 with Detected Concentrations in 2022.......................................................................................................................................... 47 Table 6.0-1: Summary of FY2022 R&D Activities................................................................. 52 Table 6.1-1: Contaminant Leaching Study Summary............................................................ 58 Table 6.1-2: Effective Diffusivities (De) and Leachability Index (LI) for EPA Method 1315 Experiments................................................................................................................................. 59 LIST OF FIGURES Figure 4.1-1: Saltstone Facility Aerial View (November 2021)............................................. 14 Figure 5.2-1: SDF Existing Monitoring Well Locations for Z Area...................................... 44

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 6 of 74 ACRONYMS ARP Actinide Removal Process CA Composite Analysis CC Clarifying Comment CF (or CF 60/40)

Cement-Free [Saltstone]

CFR U.S. Code of Federal Regulations CRESP Consortium for Risk Evaluation with Stakeholder Participation CY Calendar Year DAS Disposal Authorization Statement De Effective Diffusivity DLM Dynamic Leaching Method DMA Direct Mercury Analysis DOE U.S. Department of Energy DOE-SR U.S. Department of Energy Savannah River Operations DSA Documented Safety Analysis EPA U.S. Environmental Protection Agency FA Fly Ash FTF F-Area Tank Farm FY Fiscal Year GGBFS Ground Granulated Blast Furnace Slag GSA General Separations Area GWMP Groundwater Monitoring Plan GWPS Groundwater Protection Standard HDPE High-Density Polyethylene HQ Headquarters HTF H-Area Tank Farm Kd Distribution Coefficient LAZ Lower Aquifer Zone LFRG Low Level Waste Disposal Facility Federal Review Group LI Leachability Index LLW Low-Level Waste LW Liquid Waste LWO Liquid Waste Organization MCL Maximum Contaminant Level MCU Modular Caustic Side-Solvent Extraction Unit MDL Method Detection Limit MOP Member of the Public MPAD Most Probable and Defensible N/A Not Applicable NDAA Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 NRC U.S. Nuclear Regulatory Commission NVB Nonvolatile beta ODAS Operating Disposal Authorization Statement PA Performance Assessment

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 7 of 74 PPCO Polypropylene Co-Polymer PQL Practical Quantitation Limit PSD Particle Size Distribution PTFE Polytetrafluoroethylene RadFLEx Radionuclide Field Lysimeter Experiment RAI Request for Additional Information RCRA Resource Conservation and Recovery Act RSI Request for Supplemental Information RWMB Radioactive Waste Management Basis R&D Research and Development SA Special Analysis SCDHEC South Carolina Department of Health and Environmental Control SDF Saltstone Disposal Facility SDI Salt Disposition Integration SDU Saltstone Disposal Unit SPF Saltstone Production Facility SREL Savannah River Ecology Laboratory SRMC Savannah River Mission Completion LLC SRNL Savannah River National Laboratory SRR Savannah River Remediation LLC SRS Savannah River Site SWPF Salt Waste Processing Facility TCCZ Tan Clay Confining Zone TCLP Toxicity Characteristic Leaching Procedure UAZ Upper Aquifer Zone UTRA Upper Three Runs Aquifer UWMQ Unreviewed Waste Management Question UWMQE Unreviewed Waste Management Question Evaluation WAC Waste Acceptance Criteria XAS X-Ray Absorption Spectroscopy XRD X-Ray Diffraction

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

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1. PURPOSE OF REVIEW In Fiscal Year (FY) 2022 the Saltstone Disposal Facility (SDF) at the Savannah River Site (SRS) was managed by Savannah River Remediation LLC (SRR) for the U. S. Department of Energy (DOE) until February 2022. On February 27, 2022, management of the SDF was transitioned to Savannah River Mission Completion LLC (SRMC) under the direction of the DOE. For work completed prior to the transition to SRMC in February 2022, the contractor is still referred to as SRR for historical context. The SDF presently consists of Saltstone Disposal Units (SDUs) 1, 2, 3, 4, 5, 6, and 7 as described in the Performance Assessment (PA) for the Saltstone Disposal Facility at the Savannah River Site (SRR-CWDA-2019-00001), heretofore known as the 2019 SDF Performance Assessment (PA). Future SDUs are planned to be 375-foot diameter SDUs, similar to SDU 7 completed in 2021. Construction of SDUs 8 and 9 is in progress. Project activities are in progress for SDUs 10 through 12.

The 2019 SDF PA was issued in FY2020. The 2019 SDF PA was reviewed by the DOE Low Level Waste Disposal Facility Federal Review Group (LFRG) and SRR received a letter from DOE in June 2020 approving the PA and authorizing continued operation of the SDF. [WDPD-20-32] A revised operating Disposal Authorization Statement (DAS) was issued by DOE-Headquarters to SRR through DOE Savannah River Operations (DOE-SR) as an attachment to the authorization letter.

Since July 2020, the U.S. Nuclear Regulatory Commission (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_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 four letters with Requests for Additional Information (RAIs). [ML21040A492, ML21133A296, ML21341A551, ML22026A391] 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, 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. Once the responses to the remaining RAIs and CCs were completed, SRR-CWDA-2021-00072 was revised to include the complete set of RAI and CC responses. Revision 1 was issued in November 2021.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 9 of 74 The NRC issued the third letter (ML21341A551) in December 2021 and that letter included an additional twenty RAIs and four CCs. On March 22, 2022, a complete set of responses to this third set of NRC RAIs and CCs was issued via SRMC-CWDA-2022-00003, Comment Response Matrix for the Third 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.

The NRC issued the fourth letter (ML22026A391) in February 2022 and that letter included an additional thirteen RAIs and ten CCs. On April 25, 2022, a complete set of responses to this fourth and final set of NRC RAIs and CCs was issued via SRMC-CWDA-2022-00016, Comment Response Matrix for the Fourth 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.

The 2019 SDF PA evaluates potential dose impact on a future hypothetical member of the public (MOP), an inadvertent intruder, as well as impacts to the environment from the Low-Level Waste (LLW) disposal facility. [SRR-CWDA-2019-00001] In addition, the 2019 SDF PA demonstrates a reasonable expectation of compliance with pertinent performance objectives as identified in Chapter IV of DOE Manual 435.1-1 and Title 10, of the U.S. Code of Federal Regulations (CFR)

Part 61, Licensing Requirements for Land Disposal of Radioactive Waste, Subpart C (10 CFR 61) as required by the Ronald W. Reagan National Defense Authorization Act (NDAA) for Fiscal Year 2005, Section 3116 (NDAA_3116).

A PA Maintenance Plan is prepared and updated annually and submitted to the DOE-SR to confirm the continued adequacy of the Liquid Waste (LW) PAs (which includes F-Area Tank Farm [FTF],

H-Area Tank Farm [HTF], and the SDF) and to increase confidence in the results of the LW PAs.

The preparation and execution of the plan is consistent with the Disposal Authorization Statement and Tank Closure Documentation Technical Standard (DOE-STD-5002-2017).

The active maintenance program for the 2019 SDF PA is satisfied in the Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program - FY2022. [SRMC-CWDA-2022-00006] The SDF Maintenance Program is required to continue to reduce uncertainty in the inputs and assumptions in order to provide 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 operations and/or discoveries (e.g., new waste forms, change in disposal unit design) is required to ensure that proposed changes do not adversely affect SDF performance.

Another purpose of the PA maintenance program is to confirm the continued adequacy of the PA through annual reviews of the disposal facility activities. In accordance with the DOE Standard, Disposal Authorization Statement and Tank Closure Documentation (DOE-STD-5002-2017), the reviews evaluate and document that SDF operations comply with the DAS (WDPD-20-32) and DOE M 435.1-1 requirements and determine if the 2019 SDF PA remains valid or if additional actions are required. A review of the 2019 SDF PA was conducted in a systematic manner that incorporates all the following considerations.

1. Radionuclide inventories, waste volumes, and waste types - The review of waste radionuclide inventories and waste volumes includes a comparison of the actual waste receipts to the evaluated inventory.

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2. Research and development (R&D) - The R&D activities are primarily documented in technical reports. The R&D activities are designed and funded to provide additional information for further reduction in the uncertainties associated with PAs results. In addition, Special Analyses (SAs) or Unreviewed Waste Management Question Evaluations (UWMQEs) may be conducted to provide new information or to understand impacts of potential or actual changes to the physical facility, operations, or disposal inventory.

3. PA monitoring - The current monitoring program (SRR-CWDA-2020-00006) includes sampling of the salt waste feed stream in Tank 50 to characterize inventory, evaluation of final waste form composition, periodic sampling of grout raw materials, and monitoring of groundwater to detect changing trends in performance. Physical inspections of structures ensure SDU conditions are consistent with model inputs. Monitoring of system parameters help ensure that the system produces a grout with physical and chemical properties that are consistent with that described in the PA.

To demonstrate compliance with pertinent requirements of DOE O 435.1 and its associated Manual and Guide, the Performance Assessment Monitoring Plan for the Saltstone Disposal Facility at the Savannah River Site (SRR-CWDA-2020-00006) (hereinafter referred to as the SDF Monitoring Plan) was prepared. The SDF Monitoring Plan, that complies with DOE M 435.1-1, must be maintained and modified as needed to reflect facility changes. The SDF Monitoring Plan is reviewed annually to determine if a revision is required. The SDF Monitoring Plan was updated in FY2020 to capture changes in the recently revised 2019 SDF PA and to incorporate ongoing activities as required by the DAS and no revision was necessary in FY2022. [WDPD-20-32]

DOE O 435.1 also requires an approved Radioactive Waste Management Basis (RWMB).

Potential changes identified during the annual review must be evaluated for impact to the SDF RWMB which consists of facility controls and analyses to demonstrate near-and long-term protection of public, workers, and the environment. Examples of these controls include facility safety documents, waste certification programs, facility waste acceptance requirements, low level waste disposal facility closure plans, monitoring plans, PAs, Composite Analyses (CAs), and other facility-specific processes, procedures, and analyses made to comply with DOE O 435.1 and its manual. The current DOE approved SDF RWMB is Q-RWM-Z-00001, Rev. 8. [WDPD-21-29]

All these factors are reviewed annually to evaluate the need to conduct special studies or to prepare a revision of the 2019 SDF PA.

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2. CHANGES POTENTIALLY AFFECTING THE PA, CA, DAS, OR RWMB 2.1 Special Analyses and Unreviewed Waste Management Question Evaluations 2.1.1 Special Analyses No Special Analyses (SA) were performed to ensure compliance with SDF PA in FY2022.

2.1.2 Unreviewed Waste Management Question Evaluations One UWMQE was performed in FY2022 for the SDF. The UWMQE was entitled Evaluation of Saltstone Disposal Unit (SDU) 6 Leakage (SRMC-UWMQE-2022-00001). In March of 2022, the East Sump of the SDU 6 leak detection system was discovered to contain low levels of contamination. The leak detection sumps are enclosed within the SDU 6 high-density polyethylene (HDPE) liner system, and previous sampling of the east sump had never identified detectable levels of radionuclides. Prior to the discovery of this contamination, it was believed that the water within the SDU 6 leak detection sumps came almost exclusively from rainwater intrusion and/or construction activities. The presence of radiological contamination within the sump implied the existence of a hydraulic flow path or diffusive link from the cell interior through the disposal unit floor. Before continuing to dispose of saltstone in SDU 6, the potential for leakage from the interior of the SDU 6 disposal cell into the leak detection sump had to be evaluated to determine impacts relative to the SDF PA.

Results of the UWMQE indicate that any impacts from the limited quantity leakage from SDU 6 is bounded by the SDF PA modeling assumptions for flow through the floor of SDU 6. The SDF PA (SRR-CWDA-2019-00001) already assumed the SDU 6 floor will be more permeable than similar units based on observed post-construction cracking and subsequent leak testing.

In other words, the SDF PA already modeled SDU 6 as leaking, and the results of the PA show that this condition does not present a significant risk relative to performance objectives. No other PA assumptions are impacted by the observed contamination in the east sump of SDU 6, so the performance objectives of the SDF PA are not impacted.

2.2 Update the Closure Plan Management of SRS LLW is regulated under DOE M 435.1-1, Radioactive Waste Management Manual. A DAS (WDPD-20-32) revision was issued by DOE in June 2020 authorizing continued operations of the SDF. The DAS specifies 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. The Closure Plan for the Z-Area Saltstone Disposal Facility, SRR-CWDA-2020-00005, was updated in FY2020 to capture changes in the recently revised 2019 SDF PA. This Closure Plan provides information for planning, initial design, and a basis for PA assumptions related to the final closure configuration of the SDF and no revision was necessary in FY2022.

The Savannah River Site Land Use Plan (SRNS-RP-2014-00537) provides the framework for integrating the SRS mission and vision with ecological, economic, cultural, and social factors in a regional context and to support decision-making for near-term and long-term use of the site, including the SDF. The Savannah River Site Land Use Plan describes the current site conditions, defines a vision for the evolution of the site, outlines actions to achieve the vision, and guides the

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 12 of 74 allocation of resources toward attainment of that vision. This plan provides guidance and direction for the future physical development of the site and provides a framework within which detailed analyses will be conducted to determine the courses of action required to reach optimum site configuration. The plan is based on specific assumptions. If these assumptions were to change, the plan would be updated to reflect the changed conditions. The Savannah River Site Land Use Plan was issued in November 2014 and no modifications have occurred to the plan, therefore there are no impacts to the current SDF PA/SA.

2.3 Update the SDF Monitoring Plan The SDF Monitoring Plan (SRR-CWDA-2020-00006) demonstrates compliance with pertinent requirements of DOE O 435.1 and its associated Manual and Guide. The SDF Monitoring Plan that complies with DOE M 435.1-1 must be maintained and modified as needed to reflect facility changes. The SDF Monitoring Plan is reviewed annually to determine if a revision is required.

The SDF Monitoring Plan was updated in FY2020 to capture changes in the recently revised 2019 SDF PA and to incorporate ongoing activities as required by the DAS and no revision was necessary in FY2022. [WDPD-20-32]

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

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3. CUMULATIVE EFFECTS OF CHANGES No SAs were issued in FY2022 against the 2019 SDF PA. One UWMQE was performed in FY2022 against the 2019 SDF PA and the results indicated there would be no impact to the conclusions of the 2019 SDF PA.

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4. WASTE RECEIPTS 4.1 Waste Volumes and Radionuclide Inventories Construction of rectangular shaped SDUs 1 and 4 was completed between February 1986 and July 1988. The Saltstone Production Facility (SPF) started radioactive operations June 1990. Disposal into SDU 1 occurred intermittently from June 1990 to September 1996. Disposal into SDU 4 began in January 1997 and completed in FY2012.

Initially constructed cylindrical SDUs (2A/2B, 3A/3B and 5A/5B) include cells, 150 feet in diameter by 22 feet high. Future SDUs are anticipated to consist of single cells, 375 feet in diameter and 45 feet high, such as SDU 7 which was approved for operation in 2021. Figure 4.1-1 shows the August 2022 configuration of SDUs at the SDF, including the ongoing construction efforts for SDUs 8 and 9.

Figure 4.1-1: Saltstone Facility Aerial View (August 2022)

Disposal into SDU Cell 2B commenced in September 2012 and disposal into SDU Cell 2A commenced in December 2012. SDU Cells 2A and 2B have a slightly less nominal useable volume for grout disposal due to an additional one foot of clean pour (sulfate resistant concrete) having been placed on the floor. The pour was performed to address suspected compromised areas detected during water tightness testing. Disposal into SDU Cell 2A concluded in June 2014 and disposal into SDU Cell 2B concluded in July 2014. Disposal into SDU Cell 5B commenced in August 2014 and concluded in February 2017 and disposal into SDU Cell 5A commenced in August 2015 and concluded in August 2016. Disposal into SDU Cell 3A commenced in February 2017. The first disposal into SDU 6 was in August 2018 and continued through FY2022. The first disposal into SDU 7 was in March 2022 and continued through FY2022. [X-CLC-Z-00096]

The first disposal into SDU Cell 3B was in April 2022 and continued through FY2022.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 15 of 74 Table 4.1-1 summarizes the SDU waste receipts (i.e., salt solution disposed and saltstone grout emplaced in each SDU) through FY2022. Table 4.1-1 also provides both the PA-estimated disposal capacity and the operational capacity for each SDU. The PA-estimated disposal capacity is the assumed grout disposal capacity for the SDU used in the PA; while the operational capacity is the actual grout disposal capacity based on operational limits imposed by the Saltstone Facility Documented Safety Analysis (DSA) (WSRC-SA-2003-00001).

Table 4.1-1 provides two approaches for estimating the amount of saltstone emplaced in each SDU and for estimating the volume percent filled based on operational capacity. The first approach is to multiply the volume of the salt solution disposed by a salt solution-to-grout volume scaling factor (assumed to be 1.76 per SRR-LWP-2009-00001); this approach does not account for volumes of clean cap material of processing/flush water, so it is expected to underestimate the volume in the SDU (minimum estimated volume of saltstone in SDU and minimum percent filled).

The second approach is based on observed fill heights within the SDU; the reported fill heights are based on peak heights, so these estimates do not account for mounding or low points that may form as grout is poured into the SDUs, so this approach is expected to provide an overestimate.

The maximum estimates for SDUs 1, 2A, 2B, and 4 are based on earlier assumptions and are higher than the values estimated based on current fill heights (maximum estimated volume of saltstone in SDU and maximum percent filled). The volume assumptions do not affect the estimates for the total curies disposed.

Future SDUs will be constructed, as needed, in coordination with salt processing production rates.

The anticipated quantity and need dates for future SDUs are outlined in the Liquid Waste System Plan. [SRR-LWP-2009-00001] The Liquid Waste System Plan is updated as necessary to align with the most recent operational, budgetary, and regulatory requirements of the overall Liquid Waste System at SRS. The current revision to the plan is Revision 22.

During FY2022, no additional saltstone was disposed in SDU 1, SDU 4, SDU Cells 2A/2B, or SDU Cells 5A/5B, therefore the inventories for these SDUs are presented in this annual review to reflect only current decayed inventories (i.e., end of FY2022 [September 30, 2022]), and decayed inventories at closure (i.e., October 1, 2037).

In FY2022 alone, 2,803 kgal of low-level salt waste was transferred from Tank 50 to the SPF. A total of 4,428 kgal of saltstone containing 1.27 kCi was emplaced in the SDF. Saltstone was emplaced in SDUs 3A, 3B, 6, and 7. The entire SDF inventory underwent a total of 8.58 kCi of decay during FY2022, resulting in a net decrease of 7.31 kCi to the SDF current inventory at the end of FY2022.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 16 of 74 Table 4.1-1: Saltstone Disposal Unit Waste Receipts Through FY2022 SDU Salt Solution Disposed Volume (gal) to date Estimated Volume (gal) of Disposed Saltstone to datea PA-Estimated Disposal Capacity (gal)b Opera-tional Capacity (gal)c Volume Percent Filledd Total Curies Disposed to date (kCi)

PA/CA Impacts Min.

Max.

Min.

Max.

1 2,030,082 3,572,944 5,450,000 10,900,000 10,900,000 32.8%

50.0%

158 None 2A 1,467,168 2,582,216 2,800,000 2,830,000 2,800,000 92.2% 100.0%

13.6 None 2B 1,469,584 2,586,468 2,800,000 2,830,000 2,800,000 92.4% 100.0%

16.9 None 3A 899,850 1,583,736 1,665,210 2,830,000 2,800,000 56.6%

59.5%

2.32 None 3B 785,205 1,381,961 1,632,559 2,830,000 2,800,000 49.4%

58.3%

0.29 None 4e 8,533,444 15,018,861 19,070,000 21,800,000 20,000,000 75.1%

95.4%

414 None 5A 1,566,197 2,756,507 2,808,001 2,830,000 2,800,000 98.4% 100.3%

9.16 None 5B 1,556,147 2,738,819 2,775,349 2,830,000 2,800,000 97.8%

99.1%

17.0 None 6

5,074,410 8,930,962 10,610,812 33,700,000 32,800,000 27.2%

32.4%

24.6 None 7

336,538 592,307 1,848,672 34,500,000 33,600,000 1.8%

5.5%

0.13 None Notes: The Sum of Fractions or Total curie vs PA Curie Limit column outlined in the DOE Standard (DOE-STD-5002-2017) is not presented in this table as the individual SDUs do not have a PA curie limit placed on them.

a.

There are two approaches for estimating the disposal inventories. The first approach is to multiply the volume of the salt solution disposed by a salt solution-to-grout volume scaling factor (assumed to be 1.76 per SRR-LWP-2009-00001); this approach does not account for volumes of clean cap material of processing/flush water, so it is expected to underestimate the volume in the SDU. The second approach is based on observed fill heights within the SDU; the reported fill heights are based on peak heights, so these estimates do not account for mounding or low points that may form as grout is poured into the SDUs, so this approach is expected to provide an overestimate. The maximum estimates for SDUs 1, 2A, 2B, and 4 are based on earlier assumptions and are higher than the values estimated based on current fill heights. The volume assumptions do not affect the estimates for the total curies disposed.

b.

PA-estimated disposal capacities are from SRR-CWDA-2017-00032, Table 2.3-1, SDU Fillable Volume.

c.

Operational capacities for SDUs 1 and 4 are based on earlier assumptions. For SDUs 2, 3, and 5, the operational capacities are based on a fill height of 21.25 feet (X-CLC-Z-00070, X-CLC-Z-00078, X-CLC-Z-00080, X-CLC-Z-00085). For SDUs 6 and 7, the operational capacities are based on a fill height of 41 feet (SRR-SDU-2017-00003, C-CLC-Z-00143).

d.

Volume percent filled is based on comparison of the estimated volume of disposed saltstone to date relative to the operational capacity.

e.

Instead of saltstone, SDU 4 Cell A contains 10,032 United States Naval Fuel Material Facility 55-gallon drums emplaced in Cell A (SRMC-CWDA-2022-00056).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 17 of 74 4.1.1 Waste Volumes The salt solution production history through FY2022 is presented in Table 4.1-2 and includes new waste receipts into the SDF in FY2022, detailed in Table 4.1-3.

SDU 1 is currently at approximately 50% of its operational capacity with Cells A, B, and C being full. SDU 1 Cells D, E, and F are empty. Currently, there are no plans to use SDU 1 Cells D, E, and F for saltstone disposal in the future. [SRR-LWP-2009-00001]

SDU Cell 2A has reached 100% of its operational capacity (21.25 ft of height used relative to 21.25 ft of height available). [X-CLC-Z-00070] SDU Cell 2B has reached 100% of its operational capacity (21.25 ft of height used relative to 21.25 ft of height available). [X-CLC-Z-00070]

Based on Table 4.1-1 and Table 4.1-3, SDU Cell 3A has reached 60% of its operational capacity, with 1,134,790 gallons of remaining disposal space based on the maximum estimated volume of saltstone disposed to date. SDU Cell 3B has reached 58% of its operational capacity, with 1,167,441 gallons of remaining disposal space based on the maximum estimated volume of saltstone disposed to date.

SDU 4 has reached 95% of its operational capacity (930,000 gallons of remaining disposal volume of the 20-million-gallon capacity), not including final clean cap installation. [X-CLC-Z-00052] No additional saltstone was disposed in SDU 4 during FY2022 and there are no plans to dispose of additional saltstone in SDU 4 in the future. SDU 4 Cell A contains 10,032 drums (added to SDU 4 in the 1990s) of cementitious waste generated from the U. S. Naval Fuel Material Facility. [ESH-FSS-9000373] The void space surrounding the drums in SDU 4 Cell A is filled with clean grout.

SDU Cell 5A has reached 100% of its operational capacity (21.25 ft of height used relative to 21.25 ft of height available). [X-CLC-Z-00078] SDU Cell 5B has reached 100% of its operational capacity (21.25 ft of height used relative to 21.25 ft of height available). [X-CLC-Z-00080]

Based on Table 4.1-1 and Table 4.1-3, SDU 6 has reached 32% of its operational capacity, with 22,189,188 gallons of space available for saltstone disposal based on the maximum estimated volume of saltstone disposed to date.

Based on Table 4.1-1 and Table 4.1-3, SDU 7 has reached 6% of its operational capacity, with 31,751,328 gallons of space available for saltstone disposal based on the maximum estimated volume of saltstone disposed to date.

All SDF disposal operations are limited by the WAC, as specified in Waste Acceptance Criteria for Transfers to the Z-Area Saltstone Production Facility During Salt Disposition Integration (SDI) (X-SD-Z-00004).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 18 of 74 Table 4.1-2: FY2022 Tank 50 Salt Solution Historical Data SDU 1 SDU 4 SDU 2 SDU 3 SDU 5 SDU 6 SDU 7 Total Salt Solution Disposed (gal) 2,030,082 8,533,444a 2,936,752 1,685,056 3,122,344 5,074,410 336,538 Total Salt Solution Disposed Through End of September 2022:

23,590,488

[SRMC-CWDA-2022-00056] N/A = Not Applicable

a. This volume is only the gallons of Tank 50 salt solution processed to SDU 4. The volume presented does not include the 10,032 United States Naval Fuel Material Facility 55-gallon drums emplaced in Cell A as the waste was not from Tank 50 salt solution processing.

b. The volume of saltstone emplaced in each SDU in FY2022 is based on a ratio of salt solution to grout (0.633) per the methodology in X-CLC-Z-00096. Volumes prior to FY2022 were estimated using the appropriate ratios based on the available processing data, so the totals may vary slightly from totals estimated using the data in Table 4.1-1.

Fiscal Year Salt Solution Disposed (gal)

Saltstone Disposed Based on Ratio (gal)b Saltstone Disposal Unit Fiscal Year Salt Solution Disposed (gal)

Saltstone Disposed Based on Ratio (gal) b Saltstone Disposal Unit 1990 246,660 389,668 SDU 1 2010 1,013,770 1,601,532 SDU 4 1991 651,279 1,028,877 SDU 1 2011 1,486,842 2,348,882 SDU 4 1992 105,391 166,494 SDU 1 2012 811,710 1,282,322 SDU 4 1993 28,020 44,265 SDU 1 439,740 694,692 SDU 2 1994 261,058 412,414 SDU 1 2013 2,005,340 3,167,994 SDU 2 1995 129,900 205,213 SDU 1 2014 491,672 768,521 SDU 2 1996 607,774 960,148 SDU 1 680,146 1,074,480 SDU 5 1997 212,370 335,498 SDU 4 2015 828,128 1,308,259 SDU 5 1998 339,310 536,035 SDU 4 2016 1,506,010 2,379,163 SDU 5 1999 0

0 N/A 2017 61,600 97,314 SDU 3 2000 0

0 N/A 108,060 170,711 SDU 5 2001 0

0 N/A 2018 268,384 423,987 SDU 3 2002 263,830 416,793 SDU 4 116,875 184,637 SDU 6 2003 1,292,474 2,041,823 SDU 4 2019 703,300 1,111,058 SDU 6 2004 0

0 N/A 2020 0

0 NA 2005 0

0 N/A 2021 3,015,006 4,816,304 SDU 6 2006 0

0 N/A 2022 1,355,072 2,140,714 SDU 3 2007 244,480 386,224 SDU 4 1,111,091 1,755,278 SDU 6 2008 1,342,930 2,121,532 SDU 4 336,538 534,815 SDU 7 2009 1,525,728 2,410,313 SDU 4

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 19 of 74 Table 4.1-3: FY2022 Tank 50 Salt Solution Disposed Time Period Salt Solution Disposed (gal)

SDU 1st Quarter FY2022 640,506 SDU 6 2nd Quarter FY2022 470,585 SDU 6 2nd Quarter FY2022 168,981 SDU 7 3rd Quarter FY2022 264,932 SDU Cell 3B 3rd Quarter FY2022 167,557 SDU 7 4th Quarter FY2022 569,867 SDU Cell 3A 4th Quarter FY2022 520,273 SDU Cell 3B Total FY2022 Receipts 2,802,701 Total

[SRMC-CWDA-2022-00056]

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 20 of 74 4.1.2 Waste Inventory A disposed radionuclide inventory estimate was developed for use in PA modeling. The 2019 SDF PA, based on these inventory estimates, met performance objectives. Determination of SDF Inventories through 9/30/2022 (SRMC-CWDA-2022-00056) includes both the original inventory disposed of at the SDF and the current inventory through FY2022. The current inventory includes decay and ingrowth for SDF operations beginning in 1990 through FY2022.

As of the end of FY2022, 656 kilocuries (kCi) have been disposed in the SDF. This is 5 kCi less than what was reported in the FY21 inventory report (SRR-CWDA-2021-00100). This is due to updates to the special methods for inventory assignment. The special methods are used to estimate disposal concentrations based on relationships with other radionuclides. These special methods are only used when characterization analyses yield values that are below applicable detection limits or when characterization data from direct waste sampling and analysis is otherwise unavailable. Methodology updates are discussed in detail in the FY2022 SDF inventory report (SRMC-CWDA-2022-00056). The current inventory as of the end of FY2022, accounting for decay and daughter ingrowth, is 379 kCi. [SRMC-CWDA-2022-00056]

The current inventories were decayed to 10/1/2037 to match the basis date for closure used in the 2019 SDF PA. For SDU 1 and SDU 4, as well as SDU Cells 2A/2B and SDU Cells 5A/5B, no additional saltstone was disposed in FY2022 in these units and there are no plans to place additional saltstone in these units in the future; therefore, Tables 4.1-4 through 4.1-9 provide only current inventories as of 09/31/2022 and inventories decayed to 10/1/2037 for the SDUs listed above.

The total inventory of radionuclides in SDU 1, SDU 4, SDU Cells 2A/2B, and SDU Cells 5A/5B through FY2022 was used in the 2019 SDF PA modeling and therefore do not contradict the performance objectives of the 2019 SDF PA.

For SDU Cell 3A (Table 4.1-10), for SDU Cell 3B (Table 4.1-11), for SDU 6 (Table 4.1-12),

and for SDU 7 (Table 4.1-13), the current FY2022 inventory (decayed to 10/1/2037) was divided by the 2019 SDF PA inventory to generate a ratio. This ratio helps in evaluating the inventory that will be in each SDU upon completion of filling.

The comparison ratios presented in Table 4.1-10 indicate that the current SDU 3A inventories for 9 radionuclides (Ac-227, Cm-243, Cm-245, Pa-231, Pd-107, Pt-193, Ra-226, Th-230, and U-232) are currently trending higher than would be expected for SDU 3A relative to the Most Probable and Defensible (MPAD) inventory values that were evaluated in the 2019 SDF PA (SRR-CWDA-2019-00001).

The comparison ratios presented in Table 4.1-11 indicate that the current SDU 3B inventories for 11 radionuclides (Ac-227, Cf-251, Cm-243, Cm-245, Cm-247, Pa-231, Pd-107, Pt-193, Ra-226, Th-230, and U-232) are currently trending higher than would be expected for SDU 3B relative to the Most Probable and Defensible (MPAD) inventory values that were evaluated in the 2019 SDF PA (SRR-CWDA-2019-00001).

As of the end of FY2022, per Table 4.1-1, SDU 3 is approximately 50% to 60% filled. Some variability is to be expected in the waste concentrations during disposal operations, and with 40% to 50% of the SDU volume still available, it is too early to draw conclusions based on the current values; however, these values will continue to be monitored and evaluated, as

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 21 of 74 necessary. These radionuclides fall within the ranges of uncertainty that were considered within the 2019 SDF PA (SRR-CWDA-2019-00001). In addition, because the radionuclides that are trending higher than the MPAD inventory values are not significant dose contributors, and because SDU Cells 3A and 3B are both significantly smaller than the 375-foot diameter SDUs, and because they are located above a subsurface groundwater divide, these radionuclides are unlikely to become a significant contributor to the total dose results. Therefore, these higher-than-expected concentrations of 9 radionuclides in SDU Cell 3A and 11 radionuclides in SDU Cell 3B are not expected to be risk-significant.

The comparison ratios presented in Table 4.1-12 indicate that the current SDU 6 inventories for 13 radionuclides (Ac-227, Cf-249, Cf-251, Cm-243, Cm-245, Cm-247, Pa-231, Pd-107, Pt-193, Ra-226, Th-230, U-232, and U-233) are currently trending higher than would be expected for SDU 6 relative to the MPAD inventory values that were evaluated in the 2019 SDF PA (SRR-CWDA-2019-00001). As of the end of FY2022, 27% to 32% of the SDU 6 volume has been filled. Some variability is to be expected in the waste concentrations during disposal operations, and with 68% to 73% of the SDU volume still available, it is too early to draw conclusions based on the current values, however, these values will continue to be monitored and evaluated, as necessary. Nevertheless, because SDU 6 is further from the 100-meter boundary than other SDUs, slightly higher concentrations in SDU 6 of radionuclides that are insignificant dose contributors in the PA are unlikely to significantly affect the long-term performance of the SDF, because any potential releases from SDU 6 will undergo plume spreading before reaching the points of assessment along the 100-meter boundary.

The comparison ratios presented in Table 4.1-13 indicate that the current SDU 7 inventories for 5 radionuclides (Ac-227, Cf-251, Cm-247, Pa-231, and Pt-193) are currently trending higher than would be expected for SDU 7 relative to the MPAD inventory values that were evaluated in the 2019 SDF PA (SRR-CWDA-2019-00001). As of the end of FY2022,1.8% to 5.5% of the SDU 7 volume has been filled. Some variability is to be expected in the waste concentrations during disposal operations, and with more than 94% of the SDU volume still available, it is too early to draw conclusions based on the current values, however, these values will continue to be monitored and evaluated, as necessary. Nevertheless, because SDU 7 is further from the 100-meter boundary than other SDUs, slightly higher concentrations in SDU 7 of radionuclides that are insignificant dose contributors in the PA are unlikely to significantly affect the long-term performance of the SDF, because any potential releases from SDU 7 will undergo plume spreading before reaching the points of assessment along the 100-meter boundary.

The total inventory of radionuclides accumulated in SDU 1, SDU 4, SDU Cells 2A/2B, SDU Cell 3A/3B, SDU Cells 5A/5B, SDU 6, and SDU 7 through FY2022 was within the range of acceptable inventory values considered in the 2019 SDF PA. The inventories in each operational SDU will continue to be monitored and trended to evaluate if the results are within the uncertainty values modeled in the SDF PA. If monitoring indicates a potential impact to the conclusions of the PA, a UWMQE, or other appropriate evaluation, may be performed to determine actual impacts.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 22 of 74 Table 4.1-4: Saltstone Disposal Facility SDU 1 Inventory Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 2.46E-04 2.14E-04 Al-26 2.78E-02 2.78E-02 Am-241 2.08E-03 2.70E-03 Am-242m 4.79E-04 4.47E-04 Am-243 1.34E-04 1.34E-04 Ba-137mb 5.34E+00 3.85E+00 C-14 1.31E+00 1.31E+00 Cf-249 1.28E-08 1.25E-08 Cf-251 2.11E-10 2.09E-10 Cl-36 8.70E-06 8.70E-06 Cm-243 2.13E-03 1.52E-03 Cm-244 3.56E-04 2.06E-04 Cm-245 2.19E-02 2.18E-02 Cm-247 1.85E-05 1.85E-05 Cm-248 2.86E-13 2.86E-13 Co-60 2.28E-04 3.48E-05 Cs-135 2.28E-02 2.28E-02 Cs-137 5.66E+00 4.07E+00 Eu-152 2.28E-04 1.10E-04 Eu-154 3.44E-04 1.09E-04 H-3 1.03E+01 4.61E+00 I-129 2.01E-01 2.01E-01 K-40 2.27E-03 2.27E-03 Nb-93m 8.07E-02 8.31E-02 Nb-94 1.92E-03 1.92E-03 Ni-59 2.28E-03 2.28E-03 Ni-63 1.16E-01 1.05E-01 Np-237 3.94E-03 3.94E-03 Pa-231 1.58E-04 1.59E-04 Pd-107 5.12E-01 5.11E-01 Pt-193 1.11E+02 9.10E+01 Pu-238 6.92E-03 6.19E-03 Pu-239 1.43E-02 1.43E-02 Pu-240 1.26E-02 1.26E-02 Pu-241 3.25E-02 2.72E-02 Pu-242 1.64E-03 1.64E-03 Pu-244 7.84E-06 7.84E-06 Ra-226 3.21E-06 5.06E-06 Ra-228 2.22E-06 1.85E-06

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 23 of 74 Table 4.1-4: Saltstone Disposal Facility SDU 1 Inventory (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037a (Ci)

Se-79 3.44E-01 3.44E-01 Sm-151 5.33E-03 4.78E-03 Sn-126 1.22E+00 1.22E+00 Sr-90 9.74E-03 6.92E-03 Tc-99 4.93E+01 4.93E+01 Th-229 1.42E-03 2.09E-03 Th-230 2.65E-04 3.41E-04 Th-232 1.78E-06 1.78E-06 U-232 2.67E-02 2.31E-02 U-233 5.33E-01 5.33E-01 U-234 5.84E-01 5.84E-01 U-235 3.88E-03 3.88E-03 U-236 1.11E-02 1.11E-02 U-238 2.55E-02 2.55E-02 Y-90b 9.75E-03 6.92E-03 Zr-93 8.82E-02 8.82E-02 a Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 24 of 74 Table 4.1-5: Saltstone Disposal Facility SDU 4 Inventory Radionuclide Current Inventorya 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 3.99E-03 3.38E-03 Al-26 4.55E-01 4.55E-01 Am-241 2.08E+01 2.15E+01 Am-242m 1.85E-02 1.71E-02 Am-243 5.16E-01 5.15E-01 Ba-137mb 1.43E+05 1.01E+05 C-14 6.52E+00 6.50E+00 Cf-249 2.75E-01 2.67E-01 Cf-251 9.27E-02 9.16E-02 Cl-36 1.21E-03 1.21E-03 Cm-243 4.61E+00 3.22E+00 Cm-244 2.69E+01 1.51E+01 Cm-245 8.02E-01 8.01E-01 Cm-247 8.07E-02 8.07E-02 Cm-248 1.23E-12 1.23E-12 Co-60 3.02E-02 4.19E-03 Cs-135 1.77E+00 1.77E+00 Cs-137 1.52E+05 1.07E+05 Eu-152 7.09E-01 3.29E-01 Eu-154 2.12E+00 6.31E-01 H-3 1.87E+01 8.03E+00 I-129 2.78E-01 2.78E-01 K-40 5.09E-02 5.09E-02 Nb-93m 1.22E+03 1.96E+03 Nb-94 4.38E-02 4.38E-02 Ni-59 9.21E-02 9.20E-02 Ni-63 2.73E+00 2.46E+00 Np-237 2.47E-01 2.47E-01 Pa-231 2.32E-03 2.39E-03 Pd-107 2.26E+00 2.26E+00 Pt-193 4.92E+02 4.00E+02 Pu-238 3.00E+02 2.67E+02 Pu-239 5.86E+01 5.86E+01 Pu-240 7.28E+01 7.27E+01 Pu-241 6.81E+01 3.334E+01 Pu-242 6.25E-01 6.25E-01 Pu-244 3.19E-03 3.19E-03 Ra-226 1.38E-01 1.37E-01 Ra-228 5.32E-04 2.45E-04

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 25 of 74 Table 4.1-5: Saltstone Disposal Facility SDU 4 Inventory (Continued)

Radionuclide Current Inventorya 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Se-79 1.03E+01 1.03E+01 Sm-151 1.12E+01 9.97E+00 Sn-126 1.98E+00 1.98E+00 Sr-90 2.11E+03 1.47E+03 Tc-99 6.36E+02 6.36E+02 Th-229 7.97E+01 7.96E+01 Th-230 3.57E-03 4.82E-03 Th-232 1.89E-04 1.89E-04 U-232 1.41E-01 1.21E-01 U-233 8.89E+00 8.89E+00 U-234 9.02E+00 9.03E+00 U-235 9.41E-02 9.41E-02 U-236 8.16E-02 8.16E-02 U-238 8.01E-02 8.01E-02 Y-90b 2.11E+03 1.48E+03 Zr-93 8.53E+00 8.53E+00 a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 26 of 74 Table 4.1-6: Saltstone Disposal Facility SDU Cell 2A Inventory Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 1.25E-04 1.10E-04 Al-26 9.01E-04 9.01E-04 Am-241 7.11E-02 9.11E-02 Am-242m 4.20E-04 3.91E-04 Am-243 2.32E-03 2.31E-03 Ba-137mb 5.25E+03 3.78E+03 C-14 2.42E+00 2.42E+00 Cf-249 1.77E-02 1.72E-02 Cf-251 1.34E-02 1.32E-02 Cl-36 1.98E-05 1.98E-05 Cm-243 3.59E-02 2.55E-02 Cm-244 1.63E-01 9.45E-02 Cm-245 1.46E-02 1.46E-02 Cm-247 3.89E-04 3.89E-04 Cm-248 2.11E-13 2.11E-13 Co-60 4.88E-04 7.46E-05 Cs-135 9.10E-02 9.10E-02 Cs-137 5.56E+03 4.01E+03 Eu-152 3.58E-03 1.73E-03 Eu-154 5.63E-03 1.78E-03 H-3 1.78E+00 7.98E-01 I-129 7.33E-02 7.33E-02 K-40 9.35E-03 9.35E-03 Nb-93m 2.34E-01 2.47E-01 Nb-94 1.90E-03 1.90E-03 Ni-59 1.02E-03 1.02E-03 Ni-63 3.64E-02 3.30E-02 Np-237 4.25E-03 4.25E-03 Pa-231 8.52E-05 8.55E-05 Pd-107 3.89E-01 3.89E-01 Pt-193 8.40E+01 6.90E+01 Pu-238 5.52E+00 4.93E+00 Pu-239 5.29E-01 5.29E-01 Pu-240 5.29E-01 5.28E-01 Pu-241 1.33E+00 6.72E-01 Pu-242 1.87E-02 1.87E-02 Pu-244 3.42E-04 3.42E-04 Ra-226 3.83E-03 3.81E-03 Ra-228 4.99E-05 1.93E-05

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 27 of 74 Table 4.1-6: Saltstone Disposal Facility SDU Cell 2A Inventory (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Se-79 1.34E-01 1.34E-01 Sm-151 1.61E-01 1.44E-01 Sn-126 7.65E-01 7.65E-01 Sr-90 1.50E+01 1.06E+01 Tc-99 1.15E+02 1.15E+02 Th-229 2.56E-03 3.75E-03 Th-230 8.10E-04 8.91E-04 Th-232 1.26E-05 1.26E-05 U-232 1.32E-02 1.14E-02 U-233 9.55E-01 9.55E-01 U-234 6.18E-01 6.18E-01 U-235 9.97E-04 9.97E-04 U-236 6.39E-03 6.39E-03 U-238 2.25E-02 2.25E-02 Y-90b 1.50E+01 1.06E+01 Zr-93 2.68E-01 2.68E-01 a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 28 of 74 Table 4.1-7: Saltstone Disposal Facility SDU Cell 2B Inventory Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 1.75E-04 1.50E-04 Al-26 8.56E-04 8.56E-04 Am-241 8.43E-02 1.03E-01 Am-242m 4.25E-04 3.97E-04 Am-243 2.61E-03 2.61E-03 Bk-249 6.43E+03 4.63E+03 C-14 2.44E+00 2.44E+00 Cf-249 1.46E-02 1.42E-02 Cf-251 1.08E-02 1.07E-02 Cl-36 2.21E-05 2.21E-05 Cm-243 3.58E-02 2.55E-02 Cm-244 1.85E-01 1.07E-01 Cm-245 2.22E-02 2.22E-02 Cm-247 4.45E-04 4.45E-04 Cm-248 2.12E-13 2.12E-13 Co-60 5.45E-04 8.32E-05 Cs-135 1.11E-01 1.11E-01 Cs-137 6.82E+03 4.91E+03 Eu-152 6.37E-03 3.07E-03 Eu-154 1.00E-02 3.17E-03 H-3 1.50E+00 6.75E-01 I-129 6.83E-02 6.83E-02 K-40 8.73E-03 8.73E-03 Nb-93m 3.07E-01 3.24E-01 Nb-94 1.63E-03 1.63E-03 Ni-59 9.61E-04 9.61E-04 Ni-63 3.42E-02 3.11E-02 Np-237 4.47E-03 4.47E-03 Pa-231 1.07E-04 1.08E-04 Pd-107 3.89E-01 3.89E-01 Pt-193 8.42E+01 6.91E+01 Pu-238 5.23E+00 4.67E+00 Pu-239 5.19E-01 5.19E-01 Pu-240 5.19E-01 5.18E-01 Pu-241 1.25E+00 6.38E-01 Pu-242 1.83E-02 1.83E-02 Pu-244 1.60E-03 1.60E-03 Ra-226 3.23E-02 3.21E-02 Ra-228 5.64E-05 2.12E-05

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 29 of 74 Table 4.1-7: Saltstone Disposal Facility SDU Cell 2B Inventory (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Se-79 1.23E-01 1.23E-01 Sm-151 1.40E-01 1.26E-01 Sn-126 6.83E-01 6.83E-01 Sr-90 1.83E+01 1.30E+01 Tc-99 1.37E+02 1.37E+02 Th-229 5.57E-03 7.21E-03 Th-230 3.57E-04 4.69E-04 Th-232 1.36E-05 1.36E-05 U-232 1.27E-02 1.10E-02 U-233 1.32E+00 1.32E+00 U-234 8.54E-01 8.54E-01 U-235 1.27E-03 1.27E-03 U-236 8.85E-03 8.85E-03 U-238 2.65E-02 2.65E-02 Y-90b 1.83E+01 1.30E+01 Zr-93 3.52E-01 3.52E-01 a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 30 of 74 Table 4.1-8: Saltstone Disposal Facility SDU Cell 5A Inventory Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 1.48E-04 1.45E-04 Al-26 1.02E-03 1.02E-03 Am-241 2.71E-01 6.04E-01 Am-242m 8.35E-04 7.78E-04 Am-243 2.53E-03 2.53E-03 Ba-137mb 3.23E+03 2.33E+03 C-14 3.18E+00 3.17E+00 Cf-249 2.21E-02 2.15E-02 Cf-251 1.68E-02 1.66E-02 Cl-36 5.22E-04 5.22E-04 Cm-243 1.12E-01 7.96E-02 Cm-244 8.06E-02 4.67E-02 Cm-245 1.50E-02 1.50E-02 Cm-247 4.32E-04 4.32E-04 Cm-248 2.26E-13 2.26E-13 Co-60 1.28E-02 1.96E-03 Cs-135 6.23E-02 6.23E-02 Cs-137 3.43E+03 2.47E+03 Eu-152 1.63E-03 7.85E-04 Eu-154 2.56E-03 8.09E-04 H-3 4.32E+00 1.94E+00 I-129 1.39E-01 1.39E-01 K-40 1.67E-02 1.67E-02 Nb-93m 2.66E-01 2.80E-01 Nb-94 2.61E-03 2.60E-03 Ni-59 1.36E-03 1.36E-03 Ni-63 4.85E-02 4.40E-02 Np-237 4.22E-03 4.22E-03 Pa-231 1.40E-04 1.40E-04 Pd-107 4.15E-01 4.15E-01 Pt-193 8.97E+01 7.36E+01 Pu-238 7.30E+01 6.52E+01 Pu-239 1.86E+00 1.86E+00 Pu-240 1.86E+00 1.85E+00 Pu-241 2.09E+01 1.05E+01 Pu-242 6.41E-02 6.41E-02 Pu-244 2.98E-04 2.98E-04 Ra-226 3.64E-06 5.23E-06 Ra-228 6.81E-05 2.31E-05

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 31 of 74 Table 4.1-8: Saltstone Disposal Facility SDU Cell 5A Inventory (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Se-79 2.72E-01 2.72E-01 Sm-151 2.48E-01 2.22E-01 Sn-126 1.65E+00 1.65E+00 Sr-90 4.37E+02 3.10E+02 Tc-99 1.75E+02 1.75E+02 Th-229 8.40E-04 2.30E-03 Th-230 2.13E-04 3.13E-04 Th-232 1.33E-05 1.33E-05 U-232 1.38E-02 1.19E-02 U-233 1.17E+00 1.17E+00 U-234 7.57E-01 7.60E-01 U-235 1.53E-03 1.53E-03 U-236 7.82E-03 7.82E-03 U-238 3.28E-02 3.28E-02 Y-90b 4.37E+02 3.11E+02 Zr-93 3.05E-01 3.05E-01 a Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 32 of 74 Table 4.1-9: Saltstone Disposal Facility SDU Cell 5B Inventory Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Ac-227 1.65E-04 1.46E-04 Al-26 8.59E-04 8.59E-04 Am-241 1.01E-01 2.11E-01 Am-242m 7.48E-04 6.97E-04 Am-243 2.04E-03 2.03E-03 Ba-137mb 6.69E+03 4.81E+03 C-14 3.78E+00 3.77E+00 Cf-249 1.82E-02 1.77E-02 Cf-251 1.51E-02 1.49E-02 Cl-36 2.39E-05 2.39E-05 Cm-243 4.47E-02 3.19E-02 Cm-244 9.15E-02 5.30E-02 Cm-245 1.31E-02 1.31E-02 Cm-247 3.86E-04 3.86E-04 Cm-248 2.24E-13 2.24E-13 Co-60 5.91E-04 9.04E-05 Cs-135 1.17E-01 1.17E-01 Cs-137 7.08E+03 5.10E+03 Eu-152 1.86E-03 8.97E-04 Eu-154 2.93E-03 9.27E-04 H-3 2.66E+00 1.19E+00 I-129 8.68E-02 8.68E-02 K-40 9.40E-03 9.40E-03 Nb-93m 2.52E-01 2.65E-01 Nb-94 2.05E-03 2.05E-03 Ni-59 6.62E-04 6.62E-04 Ni-63 2.36E-02 2.14E-02 Np-237 4.10E-03 4.10E-03 Pa-231 1.14E-04 1.14E-04 Pd-107 4.12E-01 4.12E-01 Pt-193 8.91E+01 7.32E+01 Pu-238 2.52E+01 2.25E+01 Pu-239 7.39E-01 7.39E-01 Pu-240 7.39E-01 7.38E-01 Pu-241 6.92E+00 3.48E+00 Pu-242 2.59E-02 2.59E-02 Pu-244 1.20E-04 1.20E-04 Ra-226 3.26E-06 4.74E-06 Ra-228 1.07E-04 3.76E-05

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 33 of 74 Table 4.1-9: Saltstone Disposal Facility SDU Cell 5B Inventory (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Se-79 1.68E-01 1.68E-01 Sm-151 2.01E-01 1.80E-01 Sn-126 9.47E-01 9.47E-01 Sr-90 1.09E+02 7.73E+01 Tc-99 1.20E+02 1.20E+02 Th-229 7.78E-04 2.11E-03 Th-230 1.97E-04 2.87E-04 Th-232 2.26E-05 2.26E-05 U-232 1.88E-02 1.63E-02 U-233 1.07E+00 1.07E+00 U-234 6.87E-01 6.88E-01 U-235 1.27E-03 1.27E-03 U-236 7.18E-03 7.18E-03 U-238 2.85E-02 2.85E-02 Y-90b 1.09E+02 7.74E+01 Zr-93 2.88E-01 2.88E-01 a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 34 of 74 Table 4.1-10: Saltstone Disposal Facility SDU Cell 3A Inventory Comparison Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Ac-227 1.71E-04 1.33E-04 1.45E-05 9.19E+00 Al-26 3.06E-04 3.06E-04 3.54E-01 8.63E-04 Am-241 9.25E-02 2.69E-01 2.06E+02 1.31E-03 Am-242m 4.26E-04 3.97E-04 1.00E-01 3.97E-03 Am-243 8.07E-04 8.06E-04 8.34E-02 9.66E-03 Ba-137mc 8.54E+02 6.15E+02 N/A N/A C-14 2.12E+00 2.11E+00 8.21E+00 2.57E-01 Cf-249 8.74E-04 8.50E-04 8.50E-04 9.99E-01 Cf-251 6.08E-04 6.01E-04 6.01E-04 1.00E+00 Cl-36 2.27E-05 2.27E-05 1.33E-02 1.71E-03 Cm-243 5.41E-02 3.85E-02 4.48E-04 8.60E+01 Cm-244 8.80E-03 5.10E-03 1.48E+00 3.44E-03 Cm-245 4.04E-03 4.03E-03 2.74E-03 1.47E+00 Cm-247 1.50E-04 1.50E-04 8.39E-04 1.78E-01 Cm-248 1.30E-13 1.30E-13 N/A N/A Co-60 5.60E-04 8.56E-05 1.11E-01 7.71E-04 Cs-135 1.99E-02 1.99E-02 2.35E-02 8.45E-01 Cs-137 9.04E+02 6.51E+02 3.70E+03 1.76E-01 Eu-152 1.34E-03 6.45E-04 1.16E-01 5.56E-03 Eu-154 1.65E-03 5.21E-04 1.07E+00 4.87E-04 H-3 4.91E+00 2.20E+00 4.54E+01 4.85E-02 I-129 8.63E-02 8.63E-02 1.92E-01 4.49E-01 K-40 7.73E-03 7.73E-03 1.33E-02 5.81E-01 Nb-93m 9.24E-02 9.70E-02 1.36E+00 7.13E-02 Nb-94 1.05E-03 1.05E-03 2.33E-03 4.51E-01 Ni-59 5.92E-04 5.92E-04 N/A N/A Ni-63 2.11E-02 1.91E-02 2.90E+00 6.60E-03 Np-237 2.44E-03 2.44E-03 1.79E-01 1.36E-02 Pa-231 6.71E-05 6.73E-05 4.55E-06 1.48E+01 Pd-107 2.38E-01 2.38E-01 1.41E-02 1.69E+01 Pt-193 5.15E+01 4.23E+01 1.23E+00 3.44E+01 Pu-238 3.66E+01 3.27E+01 2.12E+03 1.54E-02 Pu-239 9.75E-01 9.75E-01 1.31E+02 7.44E-03 Pu-240 9.75E-01 9.74E-01 2.77E+01 3.51E-02 Pu-241 1.10E+01 5.53E+00 2.51E+02 2.20E-02 Pu-242 3.37E-02 3.37E-02 1.05E-01 3.21E-01 Pu-244 1.57E-04 1.57E-04 4.86E-04 3.22E-01 Ra-226 2.08E-06 2.83E-06 1.18E-06 2.40E+00 Ra-228 3.08E-05 8.76E-06 3.78E-03 2.32E-03 Se-79 1.65E-01 1.65E-01 1.35E+00 1.22E-01 Sm-151 1.17E-01 1.05E-01 5.67E+01 1.85E-03

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 35 of 74 Table 4.1-10: Saltstone Disposal Facility SDU Cell 3A Inventory Comparison (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Sn-126 1.66E+00 1.66E+00 5.58E+00 2.97E-01 Sr-90 4.29E+01 3.04E+01 5.31E+04 5.73E-04 Tc-99 1.49E+02 1.49E+02 3.63E+02 4.10E-01 Th-229 2.15E-04 5.25E-04 1.09E-03 4.82E-01 Th-230 1.04E-04 1.42E-04 1.01E-04 1.41E+00 Th-232 3.96E-06 3.96E-06 3.78E-03 1.05E-03 U-232 7.95E-03 6.89E-03 2.73E-03 2.52E+00 U-233 2.49E-01 2.49E-01 3.24E-01 7.68E-01 U-234 2.92E-01 2.93E-01 3.83E-01 7.66E-01 U-235 6.66E-04 6.66E-04 7.08E-03 9.40E-02 U-236 4.15E-03 4.15E-03 1.65E-02 2.52E-01 U-238 7.32E-03 7.32E-03 2.27E-01 3.22E-02 Y-90c 4.29E+01 3.05E+01 N/A N/A Zr-93 1.05E-01 1.05E-01 1.35E+00 7.79E-02 N/A - Not Applicable. Radionuclide not evaluated in the 2019 SDF PA a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Evaluated MPAD inventories from 2019 SDF PA (SRR-CWDA-2019-00001).

c Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 36 of 74 Table 4.1-11: Saltstone Disposal Facility SDU Cell 3B Inventory Comparison Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Ac-227 2.44E-04 1.99E-04 1.95E-06 1.02E+02 Al-26 2.95E-03 2.95E-03 4.22E-01 7.00E-03 Am-241 5.58E-03 5.96E-02 2.46E+02 2.42E-04 Am-242m 5.08E-04 4.74E-04 1.19E-01 3.98E-03 Am-243 5.47E-04 5.46E-04 9.92E-02 5.51E-03 Ba-137mc 3.82E+01 2.75E+01 N/A N/A C-14 1.86E+00 1.86E+00 9.14E+00 2.03E-01 Cf-249 0.00E+00 0.00E+00 7.66E-13 0.00E+00 Cf-251 8.58E-11 8.49E-11 2.69E-14 3.16E+03 Cl-36 1.92E-05 1.92E-05 1.55E-02 1.24E-03 Cm-243 1.32E-02 9.41E-03 4.55E-04 2.07E+01 Cm-244 2.59E-03 1.50E-03 1.77E+00 8.47E-04 Cm-245 5.67E-03 5.67E-03 1.34E-03 4.23E+00 Cm-247 9.98E-05 9.98E-05 1.38E-13 7.23E+08 Cm-248 1.13E-13 1.13E-13 N/A N/A Co-60 4.74E-04 7.24E-05 1.33E-01 5.44E-04 Cs-135 3.46E-03 3.46E-03 2.09E-02 1.65E-01 Cs-137 4.04E+01 2.91E+01 3.84E+03 7.58E-03 Eu-152 5.81E-04 2.80E-04 1.38E-01 2.03E-03 Eu-154 5.83E-04 1.84E-04 1.28E+00 1.44E-04 H-3 4.15E+00 1.86E+00 5.36E+01 3.47E-02 I-129 5.86E-02 5.86E-02 1.88E-01 3.12E-01 K-40 7.39E-03 7.39E-03 1.55E-02 4.77E-01 Nb-93m 9.11E-02 9.55E-02 1.53E+00 6.24E-02 Nb-94 1.44E-03 1.44E-03 2.37E-03 6.08E-01 Ni-59 4.25E-04 4.25E-04 N/A N/A Ni-63 1.51E-02 1.37E-02 3.44E+00 3.99E-03 Np-237 1.95E-03 1.95E-03 2.00E-01 9.73E-03 Pa-231 1.19E-04 1.19E-04 5.03E-06 2.37E+01 Pd-107 2.08E-01 2.08E-01 1.55E-02 1.34E+01 Pt-193 4.50E+01 3.69E+01 1.20E+00 3.08E+01 Pu-238 8.28E+00 7.40E+00 2.51E+03 2.95E-03 Pu-239 2.71E-01 2.71E-01 1.55E+02 1.75E-03 Pu-240 1.37E-01 1.37E-01 3.23E+01 4.24E-03 Pu-241 3.34E+00 1.68E+00 2.95E+02 5.68E-03 Pu-242 9.57E-03 9.57E-03 5.23E-02 1.83E-01 Pu-244 4.45E-05 4.45E-05 2.42E-04 1.84E-01 Ra-226 5.49E-06 7.15E-06 1.12E-06 6.38E+00 Ra-228 8.50E-05 2.24E-05 4.51E-03 4.97E-03 Se-79 1.33E-01 1.33E-01 1.58E+00 8.39E-02 Sm-151 1.35E-01 1.21E-01 6.76E+01 1.78E-03

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 37 of 74 Table 4.1-11: Saltstone Disposal Facility SDU Cell 3B Inventory Comparison (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Sn-126 1.18E+00 1.18E+00 6.13E+00 1.92E-01 Sr-90 1.37E+01 9.76E+00 6.34E+04 1.54E-04 Tc-99 1.20E+02 1.20E+02 3.80E+02 3.17E-01 Th-229 3.46E-05 2.59E-04 9.05E-04 2.87E-01 Th-230 2.60E-04 2.90E-04 7.86E-05 3.69E+00 Th-232 8.81E-06 8.81E-06 4.51E-03 1.95E-03 U-232 8.53E-03 7.39E-03 6.21E-04 1.19E+01 U-233 1.80E-01 1.80E-01 2.02E-01 8.93E-01 U-234 2.31E-01 2.31E-01 3.36E-01 6.87E-01 U-235 1.14E-03 1.14E-03 8.20E-03 1.39E-01 U-236 4.82E-03 4.82E-03 1.83E-02 2.64E-01 U-238 3.78E-03 3.78E-03 2.66E-01 1.42E-02 Y-90c 1.37E+01 9.76E+00 N/A N/A Zr-93 1.03E-01 1.03E-01 1.55E+00 6.67E-02 N/A - Not Applicable. Radionuclide not evaluated in the 2019 SDF PA a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Evaluated MPAD inventories from 2019 SDF PA (SRR-CWDA-2019-00001).

c Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 38 of 74 Table 4.1-12: Saltstone Disposal Facility SDU Cell 6 Inventory Comparison Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Ac-227 7.11E-04 6.40E-04 2.28E-05 2.81E+01 Al-26 6.25E-03 6.25E-03 4.92E+00 1.27E-03 Am-241 2.66E-01 1.08E+00 2.87E+03 3.77E-04 Am-242m 1.88E-03 1.75E-03 1.39E+00 1.26E-03 Am-243 5.38E-03 5.37E-03 1.16E+00 4.63E-03 Ba-137mc 9.27E+03 6.68E+03 N/A N/A C-14 8.59E+00 8.58E+00 1.07E+02 8.01E-02 Cf-249 1.07E-08 1.04E-08 8.95E-12 1.16E+03 Cf-251 5.55E-10 5.49E-10 3.14E-13 1.75E+03 Cl-36 1.04E-04 1.04E-04 1.81E-01 5.72E-04 Cm-243 2.67E-01 1.90E-01 5.31E-03 3.58E+01 Cm-244 1.16E-01 6.73E-02 2.06E+01 3.27E-03 Cm-245 4.55E-02 4.55E-02 1.56E-02 2.91E+00 Cm-247 7.96E-04 7.96E-04 1.61E-12 4.94E+08 Cm-248 7.31E-13 7.31E-13 N/A N/A Co-60 2.58E-03 3.94E-04 1.55E+00 2.54E-04 Cs-135 5.33E-02 5.33E-02 2.44E-01 2.18E-01 Cs-137 9.82E+03 7.07E+03 4.48E+04 1.58E-01 Eu-152 4.27E-03 2.06E-03 1.61E+00 1.28E-03 Eu-154 6.73E-03 2.13E-03 1.49E+01 1.43E-04 H-3 1.84E+01 8.26E+00 6.26E+02 1.32E-02 I-129 4.09E-01 4.09E-01 2.20E+00 1.86E-01 K-40 4.32E-02 4.32E-02 1.81E-01 2.39E-01 Nb-93m 1.11E+00 1.17E+00 1.79E+01 6.53E-02 Nb-94 6.75E-03 6.74E-03 2.76E-02 2.44E-01 Ni-59 8.63E-03 8.62E-03 N/A N/A Ni-63 3.07E-01 2.79E-01 4.02E+01 6.93E-03 Np-237 1.32E-02 1.32E-02 2.33E+00 5.67E-03 Pa-231 5.17E-04 5.18E-04 5.87E-05 8.83E+00 Pd-107 1.35E+00 1.35E+00 1.81E-01 7.43E+00 Pt-193 2.91E+02 2.39E+02 1.40E+01 1.71E+01 Pu-238 1.57E+02 1.41E+02 2.93E+04 4.80E-03 Pu-239 5.07E+00 5.07E+00 1.81E+03 2.80E-03 Pu-240 4.93E+00 4.92E+00 3.77E+02 1.31E-02 Pu-241 5.07E+01 2.55E+01 3.44E+03 7.40E-03 Pu-242 1.75E-01 1.75E-01 6.11E-01 2.87E-01 Pu-244 8.14E-04 8.14E-04 2.82E-03 2.89E-01 Ra-226 5.05E-05 5.78E-05 1.30E-05 4.45E+00 Ra-228 4.53E-04 1.26E-04 5.26E-02 2.39E-03 Se-79 4.97E-01 4.97E-01 1.84E+01 2.70E-02 Sm-151 8.76E-01 7.85E-01 7.89E+02 9.94E-04

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 39 of 74 Table 4.1-12: Saltstone Disposal Facility SDU 6 Inventory Comparison (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Sn-126 5.76E+00 5.76E+00 7.15E+01 8.06E-02 Sr-90 1.59E+03 1.13E+03 7.40E+05 1.52E-03 Tc-99 6.47E+02 6.47E+02 4.43E+03 1.46E-01 Th-229 1.19E-03 6.06E-03 1.06E-02 5.71E-01 Th-230 1.07E-03 1.41E-03 9.18E-04 1.53E+00 Th-232 5.42E-05 5.42E-05 5.26E-02 1.03E-03 U-232 5.00E-02 4.33E-02 7.25E-03 5.98E+00 U-233 3.91E+00 3.91E+00 2.36E+00 1.66E+00 U-234 2.61E+00 2.62E+00 3.92E+00 6.68E-01 U-235 5.09E-03 5.09E-03 9.57E-02 5.31E-02 U-236 3.13E-02 3.13E-02 2.14E-01 1.46E-01 U-238 3.98E-02 3.98E-02 3.10E+00 1.29E-02 Y-90c 1.59E+03 1.13E+03 N/A N/A Zr-93 1.27E+00 1.27E+00 1.81E+01 7.00E-02 N/A - Not Applicable. Radionuclide not evaluated in the 2019 SDF PA a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Evaluated MPAD inventories from 2019 SDF PA (SRR-CWDA-2019-00001).

c Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 40 of 74 Table 4.1-13: Saltstone Disposal Facility SDU Cell 7 Inventory Comparison Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Ac-227 1.31E-04 1.12E-04 2.28E-05 4.92E+00 Al-26 2.55E-03 2.55E-03 4.92E+00 5.18E-04 Am-241 2.61E-03 2.72E-02 2.87E+03 9.49E-06 Am-242m 2.15E-04 2.00E-04 1.39E+00 1.44E-04 Am-243 2.01E-04 2.01E-04 1.16E+00 1.73E-04 Ba-137mc 1.92E+01 1.38E+01 C-14 7.55E-01 7.54E-01 1.07E+02 7.05E-03 Cf-249 0.00E+00 0.00E+00 8.95E-12 0.00E+00 Cf-251 3.68E-11 3.64E-11 3.14E-13 1.16E+02 Cl-36 9.54E-06 9.54E-06 1.81E-01 5.27E-05 Cm-243 5.92E-03 4.21E-03 5.31E-03 7.94E-01 Cm-244 1.71E-03 9.89E-04 2.06E+01 4.80E-05 Cm-245 3.82E-03 3.82E-03 1.56E-02 2.45E-01 Cm-247 2.77E-05 2.77E-05 1.61E-12 1.72E+07 Cm-248 4.85E-14 4.85E-14 Co-60 0.00E+00 0.00E+00 1.55E+00 0.00E+00 Cs-135 2.61E-04 2.61E-04 2.44E-01 1.07E-03 Cs-137 2.03E+01 1.46E+01 4.48E+04 3.26E-04 Eu-152 1.29E-04 6.22E-05 1.61E+00 3.86E-05 Eu-154 2.03E-04 6.41E-05 1.49E+01 4.30E-06 H-3 1.38E+00 6.18E-01 6.26E+02 9.88E-04 I-129 2.50E-02 2.50E-02 2.20E+00 1.14E-02 K-40 3.96E-03 3.96E-03 1.81E-01 2.19E-02 Nb-93m 5.51E-02 5.78E-02 1.79E+01 3.23E-03 Nb-94 9.04E-04 9.04E-04 2.76E-02 3.28E-02 Ni-59 1.84E-04 1.84E-04 Ni-63 6.55E-03 5.94E-03 4.02E+01 1.48E-04 Np-237 8.28E-04 8.28E-04 2.33E+00 3.55E-04 Pa-231 7.95E-05 7.97E-05 5.87E-05 1.36E+00 Pd-107 8.92E-02 8.92E-02 1.81E-01 4.93E-01 Pt-193 1.93E+01 1.58E+01 1.40E+01 1.13E+00 Pu-238 3.74E+00 3.35E+00 2.93E+04 1.14E-04 Pu-239 1.21E-01 1.21E-01 1.81E+03 6.67E-05 Pu-240 8.89E-08 2.10E-06 3.77E+02 5.57E-09 Pu-241 1.52E+00 7.64E-01 3.44E+03 2.22E-04 Pu-242 4.26E-03 4.26E-03 6.11E-01 6.98E-03 Pu-244 1.98E-05 1.98E-05 2.82E-03 7.02E-03 Ra-226 3.92E-06 5.07E-06 1.30E-05 3.90E-01 Ra-228 6.45E-05 1.71E-05 5.26E-02 3.25E-04 Se-79 3.92E-02 3.92E-02 1.84E+01 2.13E-03 Sm-151 6.99E-02 6.27E-02 7.89E+02 7.94E-05

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 41 of 74 Table 4.1-13: Saltstone Disposal Facility SDU 7 Inventory Comparison (Continued)

Radionuclide Current Inventory a 09/30/2022 (Ci)

Current Inventory Decayed to 10/1/2037 a (Ci)

Evaluated Total Inventory per SDUb 10/1/2037 (Ci)

Comparison Ratio Sn-126 3.48E-01 3.48E-01 7.15E+01 4.87E-03 Sr-90 7.47E+00 5.31E+00 7.40E+05 7.17E-06 Tc-99 4.85E+01 4.85E+01 4.43E+03 1.10E-02 Th-229 1.28E-05 1.72E-04 1.06E-02 1.62E-02 Th-230 1.85E-04 1.98E-04 9.18E-04 2.16E-01 Th-232 6.80E-06 6.80E-06 5.26E-02 1.29E-04 U-232 4.64E-03 4.02E-03 7.25E-03 5.54E-01 U-233 1.27E-01 1.27E-01 2.36E+00 5.40E-02 U-234 9.98E-02 9.99E-02 3.92E+00 2.55E-02 U-235 7.64E-04 7.64E-04 9.57E-02 7.99E-03 U-236 2.55E-03 2.55E-03 2.14E-01 1.19E-02 U-238 1.73E-03 1.73E-03 3.10E+00 5.59E-04 Y-90c 7.47E+00 5.31E+00 N/A N/A Zr-93 6.26E-02 6.26E-02 1.81E+01 3.46E-03 N/A - Not Applicable. Radionuclide not evaluated in the 2019 SDF PA a

Inventories account for decay and ingrowth from SRMC-CWDA-2022-00056.

b Evaluated MPAD inventories from 2019 SDF PA (SRR-CWDA-2019-00001).

c Data included for inventory only. Doses for these short-lived radionuclides are implicitly accounted for in the 2019 SDF PA by applying modified dose conversion factors based on assuming secular equilibrium with longer-lived parents (SRR-CWDA-2019-00001, Section 4.4.8.3).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 42 of 74

5. MONITORING The environmental monitoring and disposal unit inspection programs were developed to be consistent with the 2019 SDF PA. The monitoring data evaluation is presented in this section.

5.1 Reason for Monitoring Per the requirements in the DAS issued for the SDF (WDPD-20-32), a monitoring plan shall be written, approved, and implemented within one year of issuance of the DAS and updated at least every five years. This monitoring plan includes annual data review and evaluation. Following this annual data review and evaluation, any modifications to this monitoring plan that may be applicable will be noted and the plan updated as necessary. The SDF Monitoring Plan (SRR-CWDA-2020-00006) satisfies this monitoring plan requirement.

Monitoring to be performed as part of this plan is intended to meet the requirements of DOE O 435.1 and its associated implementation Manual and Guide. These documents require disposal facilities to monitor for compliance with the conditions of the DAS. In particular, the following must be addressed:

The site-specific 2019 SDF PA (SRR-CWDA-2019-00001), associated CA (SRNL-STI-2009-00512), and the DSA (WSRC-SA-2003-00001) were used to determine the media, locations, radionuclides, and other substances to be monitored.

The environmental monitoring program includes measuring and evaluating releases, migration of radionuclides, SDU subsidence, and changes in disposal facility and disposal site parameters, which may affect long-term performance.

The environmental monitoring program is capable of detecting changing trends in performance to allow application of any necessary corrective action prior to exceeding the PA performance objectives (DOE M 435.1-1).

5.2 SDF Monitoring Plan Table 5.2-1 summarizes the monitoring implemented to assess the SDF compliance with the pertinent performance objectives as presented in the SDF Monitoring Plan. Figure 5.2-1 shows the monitoring locations. [SRNS-TR-2022-00338]

In addition to exposure pathways, certain facility features are relevant to monitoring the release of constituents to the surrounding environment. Per the existing SDF Monitoring Plan, quarterly visual inspection of the SDU integrity is sufficient to indicate conditions that may affect SDU integrity. [SRR-CWDA-2020-00006] The SDF has met this requirement by creating an Inspection Program Plan for Z-Area Vault 4 (LWO-LWE-2008-00023) for SDU 4 due to its existing condition. In-service inspection of SDU 4 was performed to provide a historical photographic record of the external SDU condition. Inspections are made of SDU 4 to document SDU cell wall coatings and wall conditions, including baseline inspections. SDUs 2, 3, and 5 are buried such that inspections of the roof are performed during routine operator rounds. The roof and walls of SDUs 6 and 7 are inspected during routine operator rounds.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 43 of 74 Table 5.2-1: Summary Monitoring Table Pathway/

Relevant Feature Media Features/

Inspection Monitoring Location Radionuclide/Other Substance Sampling Frequency Sampling Method Analytical Method Minimum Detectable Activity/Method Detection Limit WAC Transfer Compliance Tank 50 content in compliance with Saltstone WAC Completed evaluation on file in the Control Room Tank 50 content as provided in the Waste Characterization System prior to transfer to Salt Solution Receipt Tanks WAC Evaluation complete prior to transfer from Tank 50 to Salt Solution Receipt Tanks N/A N/A Tank 50 content in compliance with Saltstone WAC SDU integrity Visual and video inspection of SDUs Periphery and interior, if accessible, of SDUs N/A Monthly, at a minimum Visual inspections, Video camera N/A N/A Monitoring Well integrity Visual inspection of wells Well enclosure and well integrity N/A Twice per year Visual inspections N/A N/A Water resource protection Groundwater Wells ZBG 1 through ZBG020D Nitrate/nitrite Gross alpha Nonvolatile beta Beta/photon emitters I-129 Technetium-99 Tritium Twice per year Well sampling As designated in the groundwater monitoring plan (WSRC-TR-2005-00257)

As designated in the groundwater monitoring plan (WSRC-TR-2005-00257)

Wells ZBG 1 through ZBG020D Radium-226 Radium-228 Benzene Toluene Tetrachloroethylene Trichloroethylene Once every two years (odd Fiscal years, e.g.,

FY2022)

Well sampling As designated in the groundwater monitoring plan (WSRC-TR-2005-00257)

As designated in the groundwater monitoring plan (WSRC-TR-2005-00257)

N/A - Not Applicable

[SRR-CWDA-2020-00006]

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 44 of 74 Figure 5.2-1: SDF Existing Monitoring Well Locations for Z Area SRNS-TR-2022-00338 Table 5.2-2 lists the SDUs present or under construction at the SDF, associated downgradient monitoring wells, associated upgradient background wells, SDU status, and if there have been known historical releases from the SDU. The wells are all identified with ZBG identifiers for Z Area background.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 45 of 74 Table 5.2-2: SDUs with Associated Background Monitoring Wells SDU Monitored Monitoring Wells Associated

Background

Well Status Comments SDU 1 ZBG 6, 7, 8 ZBG015D Fulla Wells for SDU 4 are also downgradient of SDU 1, known historical releases SDU 2 ZBG009D, 010D, 011D ZBG 1 Full No known releases SDU 3A/B ZBG012D, 013D, 014D ZBG 1 Partial Fill Cell 3A partially full, Cell 3B empty no known releases SDU 4 ZBG 3, 4, 5, 002D, 002C, 020D ZBG015D Fulla Well ZBG 2 abandoned, replaced by ZBG002D, known historical releases SDU 5A/B ZBG012D, 13D, 14D ZBG 1 Full No known releases SDU 6 ZBG017D, 18D, 19D ZBG 1 Partial Fill Although contaminants have been detected in a sump beneath SDU 6 (SRMC-UWMQE-2022-00001), the monitoring wells have not detected any releases.

SDU 7 Not Installed Yet ZBG 1 Partial Fill SDU 8 Not Installed Yet ZBG 1 Under Construction SDU 9 Not Installed Yet ZBG 1 Under Construction SDU 10 Not Installed Yet ZBG 1 Future SDU 11 Not Installed Yet ZBG 1 Future SDU 12 Not Installed Yet ZBG 1 Future Sedimentation Basin #4 ZBG016C, 016D ZBG 1, ZBG015D Ongoing Wells installed to monitor potential releases from Sedimentation Basin #4 a - Although SDU 1 and SDU 4 are in operation standby and are not technically full, there are no current plans for continued disposal into any of the vaults in either SDU 1 or SDU 4.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 46 of 74 5.3 Evaluation of Monitoring Data Previous operational upsets have resulted in minor groundwater contamination being detected downgradient of SDUs 1 and 4. In addition, in 2014, due to concerns of potential groundwater contamination from Sedimentation Basin No. 4, a shallow well (ZBG016D) and a deeper well (ZBG016C) were installed to monitor perched water in the vadose zone and the saturated zone. In 2017, four additional wells (ZBG017D, ZBG018D, ZBG019D, and ZBG020D) were added to the SDF monitoring network. Wells ZBG017D, ZBG018D, and ZBG019D were added to monitor SDU 6, and in the future, SDUs 7 and 8. These wells helped establish background chemistry as SDU 6 was just placed into service in August 2018. Well ZBG020D provides additional downgradient groundwater monitoring of SDU 4. The SDF groundwater monitoring well network and monitoring plan, Groundwater Monitoring Plan (GWMP) for the Z-Area Saltstone Disposal Facility, WSRC-TR-2005-00257, are designed to effectively detect any release associated with SDUs in the SDF. The movement of contaminants within the Upper Three Runs Aquifer are consistent with the expectations of the PA groundwater modeling. Results of groundwater monitoring downgradient from SDU 4 do not have any impact on PA assumptions or the ability to meet compliance objectives for the SDF.

Per, the Z-Area Saltstone Disposal Facility Groundwater Monitoring Midyear Report for 2022 (SRNS-TR-2022-00338), groundwater samples were collected during 1Q Calendar Year (CY) 2021 from 21 of the 22 wells monitoring the SDF (monitoring well ZBG016D was dry). The Z-Area groundwater well samples were sent to a South Carolina Department of Health and Environmental Control (SCDHEC) certified lab for analyses.

Groundwater monitoring results were compared to Practical Quantitation Limits (PQLs),

background concentrations, and Groundwater Protection Standards (GWPS) contained in the Groundwater Monitoring Plan for the Z-Area Saltstone Disposal Facility, WSRC-TR-2005-00257. PQLs are indicators of laboratory instrument sensitivity, but are not regulatory limits, nor are they risk-based. The PQL is the lowest concentration of an analyte which can be reliably quantified in a given sample. Background concentrations are based on historical data from two wells (ZBG 1 and ZBG015D) upgradient of the SDF. Data from ZBG015D is used for background comparisons to monitoring data collected at wells downgradient of SDUs 1 and 4. Data from ZBG 1 is used for background comparisons to monitoring data collected at wells downgradient of SDUs 2A, 2B, 3A, 3B, 5A, 5B, and 6. Wells ZBG017D, ZBG018D, ZBG019D, and ZBG020D were sampled after installation in the second quarter of 2017. The second quarter 2017 samples from ZBG017D through ZBG019D helped establish background groundwater chemistry for SDUs 6, 7, and 8.

In 2022, three constituents (nonvolatile beta [NVB], Tc-99, and nitrates) continued to have detected results from historical releases from SDU 4 consistent with expectations with previous years information in four monitoring wells all downgradient of SDU 4: ZBG002C (in the Lower Aquifer Zone of the Upper Three Runs Aquifer [LAZ], below the Tan Clay Confining Zone), and ZBG002D, ZBG 4, and ZBG020D (in the Upper Aquifer Zone of the Upper Three Runs Aquifer

[UAZ], above the Tan Clay Confining Zone). One constituent, nitrate, exceeded its maximum contaminant level (MCL) for the first time in FY2022. Results for the sampling from FY2022 for these three constituents downgradient of SDU 4 are summarized in Table 5.3-1. As conductivity is also an indication of potential contamination, its results are also included in Table 5.3-1.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 47 of 74 Table 5.3-1: SDF Monitoring Wells Downgradient of SDU 4 with Detected Concentrations in 2022 Well Consti-tuent Units Monitoring Results &

Trends Performance Objective Measure or Other Regulatory Limit Action Level Action Taken PA/CA Impact ZBG002D (UAZ)

NVB pCi/L 87.5 4 mrem/yr 8

None (result exceeded 30 pCi/L)

N/A 30 Well and background well ZBG015D resampled for constituents in Table 3 of the GWMP None. All results below respective detection limits.

Tc-99 pCi/L 192 900 900 None None Conductivity uS/cm 98 N/A N/A N/A None Nitrate mg/L 15.4 10 10 First exceedance, result reported to SCDHEC, groundwater characterization plan to assess the lateral and vertical extent of contamination to be implemented in FY2023 None ZBG002C (LAZ)

NVB pCi/L 28.6 4 mrem/yr 8

Well resampled for Sr-90 None. Result below detection limit.

30 None None Tc-99 pCi/L 58.4 900 900 None None Conductivity uS/cm 49 N/A N/A N/A None Nitrate mg/L 3.73 10 10 None None ZBG 4 (UAZ)

NVB pCi/L 8.34 4 mrem/yr 8

Well resampled for Sr-90 None. Result below detection limit.

30 None None Tc-99 pCi/L ND 900 900 None None Conductivity uS/cm 27 N/A N/A N/A None Nitrate mg/L 1.2 10 10 None None ZBG020D (UAZ)

NVB pCi/L 17.9 4 mrem/yr 8

Well resampled for Sr-90 None. Result below detection limit.

30 None None Tc-99 pCi/L 54.1 900 900 None None Conductivity uS/cm 25 N/A N/A N/A None Nitrate mg/L 1.73 10 10 None None SRNS-TR-2022-00338 LAZ - Lower Aquifer Zone of the Upper Three Runs Aquifer (below the Tan Clay)

UAZ - Upper Aquifer Zone of the Upper Three Runs Aquifer (above the Tan Clay)

N/A - Not Applicable ND - Not Detected Results that exceed Regulatory Limits or Action Levels indicated by shading

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 48 of 74 Water Table Wells Downgradient of SDU 4 In 1Q22, groundwater at well ZBG002D showed increases in Tc-99 (192 pCi/L), nonvolatile beta activity (87.5 pCi/L), nitrate concentration (15.4 mg/L) and specific conductance (98 S/cm) relative to the 3Q21 concentrations for Tc-99 (117 pCi/L), nonvolatile beta activity (44.6 pCi/L),

nitrate concentration (8.77 mg/L), and specific conductance (90 S/cm). The Tc-99, nonvolatile beta and nitrate contaminants are from the previously reported 2014 release from SDU 4. The 1Q22 results for ZBG002D are lower than the maximum ZBG002D concentrations in 2015 for nonvolatile beta activity (132 pCi/L), Tc-99 activity (230 pCi/L), and specific conductance (211 S/cm). In 1Q22, nitrate groundwater concentrations at well ZBG002D exceeded the previous maximum concentration in 2015 (6.8 mg/L) and the GWPS (10 mg/L) for the first time. Actions have been taken to confirm the nitrate exceedance, and actions (e.g., expanded monitoring and characterization plan) will be taken in accordance with the requirements of the Groundwater Monitoring Plan (WSRC-TR-2005-00257).

Nonvolatile Beta Speciation The 1Q22 nonvolatile beta results for ZBG 4, ZBG002C, ZBG002D and ZBG020D exceeded the 8 pCi/L threshold for nonvolatile beta initiating Sr-90 analyses for these well samples. All the Sr-90 sample results were below their method detection limits (MDLs) indicating that Sr-90 was not detected in these samples.

The ZBG002D nonvolatile beta results (87.5 pCi/L) exceeded the 30 pCi/L threshold for nonvolatile beta, so nonvolatile speciation was required for this sample and the background well ZBG015D sample. For well ZBG002D all speciated radionuclides were below their respective detection limits, with the exception of Tc-99, which was well below its GWPS. [SRNS-TR-2022-00338]

Any nuclides detected above the associated maximum background concentration of the GWPS will be added to the monitoring list in Table 2 of the groundwater monitoring plan, WSRC-TR-2005-00257. If the follow-up sampling exceeds the maximum background concentration and GWPS, a plan for assessing the lateral and vertical extent of the plume will be developed and submitted to SCDHEC within 60 days. [WSRC-TR-2005-00257]

In 2014, well ZBG002C was installed adjacent to ZBG002D with a screen zone below the Tan Clay Confining Zone (TCCZ) in the Upper Three Runs Aquifer (UTRA) - Lower Aquifer Zone (LAZ) to monitor groundwater in the LAZ. In 1QCY22, samples collected in the LAZ at wells ZBG002C and ZBG 4 had levels of nonvolatile beta groundwater concentrations (28.6 and 8.34 pCi/L, respectively) that exceeded the historic maximum nonvolatile beta value (2.17 pCi/L) for background well ZBG015D. The nonvolatile beta data indicates contamination below the TCCZ.

The SDF groundwater monitoring well network is adequately monitoring contaminants above and below the TCCZ per the Z-Area Saltstone Disposal Facility Groundwater Monitoring Midyear Report for 2022 (SRNS-TR-2022-00338).

Z-Area Sedimentation Basin No. 4 Two groundwater monitoring wells (ZBG016C and ZBG016D) have been installed downgradient of Sedimentation Basin No. 4, one to monitor perched water above the TCCZ (ZBG016D) and one to monitor the water table below the TCCZ (ZBG016C). The 1QCY22 data for ZBG016C indicates there not have been any impacts to the groundwater at Sedimentation Basin No. 4. The

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 49 of 74 screen zone for well ZBG016D has been dry since installation, indicating there was no perched water at this location in 1QCY22 (SRNS-TR-2022-00338). Analytical results from the groundwater sampling from 1QCY21 are presented in the Z-Area Saltstone Disposal Facility Groundwater Monitoring Midyear Report for 2022 (SRNS-TR-2022-00338). The groundwater analytical results to date do not contradict 2019 SDF PA model estimates.

Tc-99 In 1QCY22, the Tc-99 groundwater concentration (192 pCi/L) increased at well ZBG002D as compared to 3QCY21 (117 pCi/L) and had the highest observed Tc-99 result in 1QCY22, but the concentration remains below the GWPS (900 pCi/L). Previous results from this well have been higher, with a maximum of 230 pCi/L in third quarter 2015 (3QCY15). Well ZBG002D indicates the location of the highest concentration of the Tc-99 groundwater plume.

The sample from wells ZBG002C and ZBG020D also had a Tc-99 result (58.4 pCi/L and 54.1 pCi/L, respectively) above detection in 1Q22, which is consistent with the nonvolatile beta result from the same well samples and historical data. Previous and 1Q22 Tc-99 data from well ZBG002C (58.4 pCi/L) indicate Tc-99 contamination has migrated through the TCCZ, but at concentrations below the maximum contaminant level.

As demonstrated by the 2017 through 2022 data at wells ZBG002C, ZBG002D and ZBG020D, it is not uncommon for the Tc-99 results to be higher than the nonvolatile beta results for the same samples, as some Tc-99 is volatilized by the drying step in the nonvolatile beta analytical method.

In contrast, the Tc-99 analytical method does not include a drying step, thus avoiding any volatilization of Tc-99. [SRNS-TR-2022-00338]

Nitrates At SRS nitrogen in the groundwater is primarily in the form of nitrate, because the groundwater is typically well oxygenated, especially in the UTRA - Upper Aquifer Zone (UAZ).

Nitrates in the groundwater are determined using Nitrate - Nitrite as Nitrogen USEPA methods 353.1 or 353.2. At SRS nitrogen in the groundwater is primarily in the form of nitrate because the groundwater is typically well oxygenated, especially in the UAZ. The maximum nitrate concentration in background well ZBG015D is 1.3 mg/L. In 1QCY22, the sample from well ZBG002D had the highest nitrate groundwater concentration (15.4 milligrams/liter [mg/L]), while the sample from well ZBG002C had the second highest groundwater concentration (3.73 mg/L) for nitrate in 1QCY22. The elevated nitrate concentration in ZBG002C continues an increasing trend since 2014, indicating nitrate contamination is present in the LAZ.

The ZBG002D nitrate sample result continues a sharp increasing trend since the 3QCY20. Per the Groundwater Monitoring Plan for the Z-Area Saltstone Disposal Facility (WSRC-TR-2005-00257), nitrate is very mobile and abundant in saltstone and is a reliable early indicator of a vault release. The ZBG002D 1QCY22 nitrate result (15.4 mg/L) exceeded the GWPS (10 mg/L). The source of the nitrate is from an SDU 4 release first identified and reported in late 2014. In accordance with the requirements of the Groundwater Monitoring Plan, the GWPS exceedance was reported to SCDHEC via email correspondence on April 27, 2022. Resampling of ZBG002D was performed in May 2022 and the nitrate result (14.4 mg/L) confirms the nitrate exceedance of the GWPS (10 mg/L).

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 50 of 74 In accordance with the Groundwater Monitoring Plan for the Z-Area Saltstone Disposal Facility (WSRC-TR-2005-00257), the full list of GWPS analytes in Table 2 of the groundwater monitoring plan will be sampled for in the third quarter sampling event in 2022. The results of this event will be reported in the 2022 Annual Saltstone Groundwater Monitoring Report, submitted in January 2023. Additionally, the assessment monitoring plan in response to the nitrate exceedance will be submitted along with the 2022 Annual Saltstone Groundwater Monitoring Report.

Historically, nitrate groundwater concentrations at well ZBG019D have remained elevated.

Previously, the source of contamination was not considered related to saltstone material due to Tc-99 results below the MDL and nonvolatile beta results below the PQL. The nitrate concentration in ZBG019D has followed a decreasing trend since initial sampling in April 2017 (5.74 mg/L),

with the last four sampling results consistently around 1.15 mg/L (1.13 to 1.19 mg/L), being below the maximum nitrate value at background well ZBG 1 (2.03 mg/L). The 1QCY22 nitrate result at ZBG019D was 1.19 mg/L.

In 1Q22, nitrate groundwater concentrations increased to 1.14 mg/L at well ZBG 6, which is greater than the PQL, but less than the maximum nitrate background value (1.30 mg/L) at ZBG015D and the GWPS (10 mg/L).

Tritium Low concentrations of tritium are present in nearly all SDF monitoring wells, including the two background wells and does not appear to be related to activities associated with the SDF.

The maximum tritium concentration was 2.04 pCi/mL at background well ZBG015D in 1QCY22.

This concentration is below the historic maximum (4.02 pCi/mL) for background well ZBG015D and below the GWPS (20 pCi/mL). The older background well ZBG 1 has indicated steadily decreasing tritium concentration trends from 19.0 pCi/mL in 1987 to 1.72 pCi/mL in 1QCY22.

All of the SDF monitoring wells appear to be following this trend. Data from the background wells ZBG 1 and ZBG015D indicate the tritium in Z-Area is from an up-gradient source [SRNS-TR-2022-00338]

Summary In summary, groundwater concentrations in the UAZ downgradient of SDU 4 continued to decrease from 3Q15, when the highest historical concentrations were measured, and match expectations based on previous years results. Downgradient of SDU 4, contaminants (specifically Tc-99, nonvolatile beta, and nitrates) continue to be detected above their respective PQL, with Tc-99 and nonvolatile beta remaining below their respective MCL; however, nitrates exceeded its MCL (10 mg/L) at ZBG002D for the first time (15.4 mg/L). Actions have been taken to confirm the nitrate exceedance, and actions (e.g., expanded monitoring and characterization plan) will be taken in accordance with the requirements of the Groundwater Monitoring Plan. [WSRC-TR-2005-00257]

Also, downgradient of SDU 4, contaminants (specifically Tc-99, nonvolatile beta, and nitrates) have begun to move downward into the LAZ, but concentrations in the LAZ remain below their respective GWPS. The movement of contaminants within the Upper Three Runs Aquifer are consistent with the expectations of the PA groundwater modeling. Results of groundwater monitoring downgradient from SDU 4 do not have any impact on PA assumptions or the ability to meet compliance objectives for the SDF.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 51 of 74 There also have been no impacts to groundwater from Sedimentation Basin No. 4. Overall, no new contamination was identified at the SDF during 1QCY22.

Because nonvolatile beta exceeded action levels; however, additional sampling, required by the action level exceedances, resulted in no constituents exceeding their respective GWPS. [SRNS-TR-2022-00338]

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 52 of 74

6. RESEARCH AND DEVELOPMENT Several studies from FY2022 have continued research on properties considered critical to the performance of saltstone and are described in the sections below and summarized in Table 6.0-1.

Table 6.0-1: Summary of FY2022 R&D Activities R&D Document Number Results/Discussion PA/CA Impacts To Be Determined Long-Term Radiological Lysimeter Program Ongoing lysimeter effluent testing, in conjunction with solid phase analysis of the lysimeter cores and source material, provide both qualitative (e.g., relative importance of certain transport mechanisms) and quantitative (e.g., sorption coefficients, also known as distribution coefficients or Kds, for radionuclides placed in SRS soil) insights that can improve PA models.

For FY2022, nine Radionuclide Field Lysimeter Experiment Facility (RadFLEx) lysimeters underwent retrieval and solid phase analysis.

Four gamma suite lysimeters (lysimeters containing a Ba-137, Eu-152, Co-60, and Cs-137 source) underwent non-destructive analysis. The five remaining lysimeters, all possessing a Pu source, underwent destructive analysis (i.e., soil dissection, soil digestion, and analytical measurements on the resulting digestate). Solid phase analysis of these nine lysimeters generates high pedigree PA data and justification for selection of geochemical conceptual models. A report documenting this effort is scheduled for issue in the second quarter of FY2023.

The RadFLEx data will be compared against geochemical inputs and assumptions used in the PA to validate the current technical approach.

Should the field data imply that PA values are non-conservative, the information will be evaluated via the UWMQ process Note: Kd is a sorption or distribution coefficient defined as the quantity of a solute sorbed by a solid, per unit weight of solid, divided by the quantity of the solute dissolved in the water per unit volume of water.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 53 of 74 Table 6.0-1: Summary of FY2022 R&D Activities (Continued)

R&D Document Number Results/Discussion PA/CA Impacts SRMC-CWDA-2022-00017 Radionuclide Leaching Characteristics from Saltstone Monolith Dynamic Leaching Method (DLM) testing concluded in 2020 with the termination of five on-going experiments: one with a sample from an SDU Cell 2A core and four utilizing saltstone simulants spiked with both Tc-99 and I-129.

Initially the concentration of Tc-99 in the SDU 2A core leachate was fairly consistent around a value of 2E-07 mol/L but dropped to around 5E-08 mol/L once the pH of the leachate fell below 11. The consistency of the Tc-99 concentrations measured in the leachate, both before and after the pH drops below 11, supports the current modeling approach that Tc-99 release from saltstone is initially solubility controlled.

Regarding the four DLM experiments utilizing saltstone simulants, two of the samples were prepared using the historical saltstone formulation (i.e., 45 wt% Ground Granulated Blast Furnace Slag (GGBFS), 45 wt%

Class F Fly Ash (FA), and 10 wt% ordinary Portland cement (OPC))

while the other two were prepared using the cement-free formulation (i.e., 60 wt% GGBFS and 40 wt% FA) proposed in the Cement-Free Formulation Down-Select Report. [SRR-CWDA-2019-00003] Results from these experiments, as well as reduction capacity testing performed on non-spiked samples, suggest that the cement-free saltstone formulation is comparable in performance, from a PA perspective (i.e., leaching and saturated hydraulic conductivity), to the historically used 45 wt% GGBFS, 45 wt% FA, and 10 wt% OPC saltstone formulation. Furthermore, the cement-free saltstone formulations fresh properties (e.g., heat of hydration, bleed water, set time, etc.) were all found to meet the processing and short-term storage requirements of the SPF. These findings are captured in the Cement-Free Saltstone Down-Selection Report Follow-up (SRR-CWDA-2020-00008) that states the down-selected cement-free formulation exhibits acceptable and comparable near-and long-term performance to the standard GGBFS/FA/OPC 45/45/10 composition.

The final report, X-ray Diffractometry of Saltstone Samples Subjected to the Dynamic Leaching Method, (SRMC-CWDA-2022-00017) detailing the mineralogical evaluation of saltstone samples that had been subjected to leach testing via the DLM was issued in April 2022.

The DLM involves the continuous passage of simulated ground water through monolithic saltstone samples, and the subsequent analysis of the leachates for analytes of interest. During DLM testing the saltstone pore solution is exchanged multiple times, and the intent of this study was to determine how the pore solution exchanges impact the mineralogy of saltstone. As such, the crystalline phase composition of both post-DLM and non-DLM samples has been characterized by X-ray diffractometry (XRD).

The Dynamic Leaching Method (DLM) was developed by Savannah River Ecology Laboratory (SREL) and SRR (and, subsequently SRMC) to observe how pore solution chemistry in saltstone evolves as progressively more infiltrating water passes through the waste form. As infiltrating water flows through the saltstone pore space and interacts with the solid phase, the mineral composition of the waste form is expected to change. Currently, these changes to the mineralogy of saltstone are predicted in the Saltstone Disposal Facility (SDF)

Performance Assessment (PA) based on geochemical modeling.

Observations of post-DLM samples indicated phase changes consistent with the microstructure expected after multiple pore volume exchanges.

This is consistent with the degradation mechanisms analyzed within the PA and thus has no PA impact.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 54 of 74 Table 6.0-1: Summary of FY2022 R&D Activities (Continued)

R&D Document Number Results/Discussion PA/CA Impacts SRMC-CWDA-2022-00034 Toxicity Characteristic Leaching Procedure (TCLP) Testing and X-Ray Absorption Spectroscopy (XAS) of Cement-Free Saltstone The investigations were conducted by the Savannah River Ecology Laboratory (SREL), and had the primary objective of evaluating materials, testing, and analysis variables that might impact the mercury (Hg) leaching data for saltstone when subjected to the Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure (TCLP) (EPA Method 1311). Testing was conducted on cement-free saltstone samples spiked with methylmercury hydroxide (CH3HgOH; also termed MeHgOH). The cement-free samples were composed of 60 wt% ground granulated blast furnace slag (GGBFS) and 40 wt% fly ash (FA) (referred to as CF 60/40) and mixed at a water-to-premix (w/pm) mass ratio of 0.60, which is approximately equivalent to a salt solution-to-premix (SS/pm) mass ratio of 0.82.

A secondary objective of the study was to determine potential sources for the significant disparity observed between TCLP-Hg extractant concentrations for samples prepared and tested at SREL compared to tests on similar samples conducted by the Savannah River National Laboratory (SRNL) (SRNL-STI-2020-00468). For SREL tests, the TCLP-Hg extractant concentrations (for samples prepared with similar MeHgOH-spike concentrations) were almost an order of magnitude higher than those measured by SRNL.

Data obtained from TCLP and XAS experiments can inform the geochemical conceptual models used in the PA.

While further leach testing on grout simulants was not able to fully resolve the disparity in mercury leach performance between SREL and SRNL methods, TCLP testing of actual waste grouts remain within regulatory limits. Retention behavior for mercury is not related to the retention behavior for dose-driving radionuclides within the PA and therefore there is no impact to the current PA.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 55 of 74 6.1 Long-Term Radiological Lysimeter Program Understanding the long-term behavior of radionuclides in the FTF, HTF, and the SDF is essential for PA models that project this behavior out over thousands of years. 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 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, FTF, and HTF PAs.

Measurements target solubility and Kd 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 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.

The spatial distribution of Pu in two field lysimeters that were removed and dissected for analysis, the first with a colloidal PuO2(s) source and the second with an emplaced Pu(V)NH4(CO3)(s) source, both demonstrated greater downward migration than previously observed for PuCl3, Pu(NO3)4, and Pu(C2O4)2 bearing lysimeters. Researchers

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 56 of 74 have proposed multiple working hypotheses to explain the enhanced transport observed for the PuO2(s) and Pu(V)NH4(CO3)(s) lysimeters.

o Working Hypothesis #1: Transport of Pu as PuO2(s) colloids. The Pu(V)NH4(CO3)(s) source transforms to a PuO2(s) phase similar to the one found in Lysimeter 44 (colloidal PuO2(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)NH4(CO3)(s) will rapidly reduce to Pu(+IV), perhaps as a PuO2(s) phase similar to that found in Lysimeter 44 (colloidal PuO2(s) source, SRRA021685-000008). Some of the Pu(+IV) present in the PuO2(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 PuO2(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 NpO2(s) lysimeter (Lysimeter 32, SRRA021685-000011).

Desorption experiments using Pu contaminated soils retrieved from the PuO2(s) and Pu(V)NH4(CO3)(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 (Kd 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].

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 detailing different analytical techniques for measuring radium and iodine in lysimeter effluent, was issued by Clemson University in support of the RadFLEx project. [SRRA175647-000002] 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 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 57 of 74 In FY2022, nine RadFLEx lysimeters underwent retrieval and solid phase analysis. Four gamma suite lysimeters (lysimeters containing a Ba-133, Eu-152, Co-60, and Cs-137 source) underwent non-destructive analysis. The five remaining lysimeters, all possessing a Pu source, underwent destructive analysis (i.e., soil dissection, soil digestion, and analytical measurements on the resulting digestate). Solid phase analysis of these nine lysimeters generated high pedigree PA data and justification for selection of geochemical conceptual models. A report documenting this effort is scheduled for issue in the second quarter of FY2023.

The RadFLEx data will be compared against geochemical inputs and assumptions used in the PA to validate the current technical approach. Should the field data imply that PA values are non-conservative, the information will be evaluated via the UWMQ process.

6.2 Radionuclide Leaching Characteristics from Saltstone Monolith 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 will provide 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 will provide new information regarding the leaching of saltstone associated with multiple pore volume exchanges. Table 6.1-1 summarizes the saltstone samples that have been prepared and tested to date. Table 6.1-2 provides a summary of the EPA Method 1315 data.

With respect to EPA Method 1315, Tc-99 leaching rates for the spiked saltstone samples appeared to be sensitive to curing duration and the reduction capacity of the ground granulated blast furnace slag (GGBFS) used in making the grout. Longer curing times and higher reduction capacity1 for the as-received GGBFS resulted in lower effective diffusivities. As anticipated, leaching rates and effective diffusivities from the simulant samples for poorly sorbing contaminants like NO3-were much higher than for Tc-99. Interestingly, the effective diffusivity measured for nitrate is comparable to that of iodine, suggesting that iodine is poorly retained in the saltstone matrix.

[SRRA099188-000005]

1 Reduction capacity can vary between different GGBFS sources due to differences in the concentrations of components, in particular sulfur and iron, which are known reductants.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 58 of 74 Table 6.1-1: Contaminant Leaching Study Summary FY Report Batch Sample a GGBFS Reduction Capacity (µeq/g) f Saltwaste Solution Simulant g Spike EPA 1315 EPA 1315 Notes DLM DLM Notes DLM Status as of FY2022 SREL-R-14-0006, FY2014 H45:45:10 b 861 ARP-MCU I-127, Re Yes 1-month cure (x1);

3-month cure (x1)

Yes 5 short-term experiments to develop DLM method.

Removed SREL-R-15-0003, FY2015 H45:45:10 b 861 ARP-MCU I-127, Re Yes 3-month cure (x1);

6-month cure (x1)

No N/A N/A SREL-R-15-0003, FY2015 H45:45:10 713 ARP-MCU Tc-99 Yes 3-month cure (x1);

6-month cure (x1)

Yes 6-month cure (x1)

Removed SREL-R-16-0003, FY2016 H45:45:10 713 ARP-MCU Tc-99 Yes 3-month cure No N/A N/A SREL-R-16-0003, FY2016 L45:45:10 1,600 ARP-MCU Tc-99 Yes 3-month cure (x1);

6-month cure (x2)

No N/A N/A SREL-R-16-0003, FY2016 SDU 2A -

Sample A c Not Measured Tank 50 Actual N/A Yes 21-month cure (x1)

Yes 21-month cure (x1)

Running SREL-R-16-0003, FY2016 SDU 2A -

Sample B d Not Measured Tank 50 Actual N/A Yes 21-month cure (x1)

Yes 21-month cure (x1)

Removed SREL-R-16-0003, FY2016 SDU 2A -

Sample C e Not Measured Tank 50 Actual N/A Yes 21-month cure (x1)

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

No N/A N/A SRRA099188-000005, FY2018 L45:45:10 Not Measured ARP-MCU I-129 Yes 1.5-month cure (x1)

Yes 6-month cure (x1);

13-month cure (x1)

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

Removed SRRA099188-000010, FY2019 L45:45:10 870 SWPF Tc-99, I-129 Yes 9-month cure (x1)

Yes 10-month cure (x1);

11-month cure (x1)

Removed SRRA099188-000010, FY2019 L60:40 870 SWPF Tc-99, I-129 Yes 9-month cure (x1)

Yes 10-month cure (x2)

Removed (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. 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

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 59 of 74 Table 6.1-2: Effective Diffusivities (De) and Leachability Index (LI) for EPA Method 1315 Experiments FY Report Batch Sample a Curing Duration (months)

Tc-99 Re NO3 Iodine c De (cm2/s)

LI d De (cm2/s)

LI d SREL-R-15-0003, FY2015 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 SREL-R-15-0003, FY2015 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 SREL-R-16-0003, FY2016 H45/45/10 3

3.00E-10 9.6 N/A N/A 3.70E-07 6.7 N/A N/A SREL-R-16-0003, FY2016 L45/45/10 3

2.60E-11 10.6 N/A N/A 4.80E-08 7.5 N/A N/A SREL-R-16-0003, FY2016 L45/45/10 6

5.70E-12 11.3 N/A N/A 6.60E-08 7.2 N/A N/A SREL-R-16-0003, FY2016 L45/45/10 6

3.80E-11 10.4 N/A N/A 2.10E-07 6.7 N/A N/A SREL-R-16-0003, FY2016 SDU 2A -

Sample A 21 6.40E-11 10.2 N/A N/A 1.30E-08 8

1.00E-08 8

SREL-R-16-0003, FY2016 SDU 2A -

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

Sample C 21 5.20E-11 10.3 N/A N/A 5.50E-09 8.5 5.50E-09 8.4 SRRA099188-000005, FY2018 H45/45/10 1.5 N/A N/A N/A N/A 9.50E-08 7

2.80E-08 7.6 SRRA099188-000005, FY2018 L45/45/10 1.5 N/A N/A N/A N/A 8.20E-09 8.1 1.40E-08 8

SRRA099188-000010, FY2019 L45/45/10 9

5.30E-11e 10.4 N/A N/A 9.20E-09e 8.2 3.30E-09e 8.8 SRRA099188-000010, FY2019 L60/40 9

5.70E-11e 10.5 N/A N/A 7.40E-09e 8.2 4.40E-09e 8.5 (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.

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Revision 0 Performance Assessment March 2023 Page 60 of 74 Regarding DLM testing, data reproducibility has proven difficult given the heterogeneity of the saltstone matrix. Despite this variability, the data collected to date has proven valuable in providing both qualitative and quantitative findings. In particular:

Although I-129 is not strongly bound to the saltstone matrix, the DLM data suggests that the radionuclide does have some affinity for the waste form and a non-zero Kd value. [SRR-CWDA-2018-00045]

o This retention was later quantified by means of an iodine Kd value estimated using a GoldSim-based optimization model. [SRR-CWDA-2018-00045] The Kd value derived from this approach was subsequently implemented into the 2019 SDF PA.

[SRR-CWDA-2019-00001]

The concentration of Tc-99 in the DLM leachate remains fairly constant above pH 11.

Once the pH falls below 11, the Tc-99 concentration transitions to a lower steady-state value. The consistency of the Tc-99 concentrations measured in the leachate, both before and after the pH drops below 11, supports the idea that Tc-99 release from saltstone is initially solubility controlled. [SRRA099188-000003]

o The concentration data provided from these DLM experiments allowed for the solubility values used in modeling Tc-99 release from saltstone to be updated for implementation in the 2019 SDF PA. [SRR-CWDA-2018-00046; SRR-CWDA-2019-00001]

Comparison of the DLM data collected from both the Tc-99 spiked saltstone simulants and SDU 2A core, with theoretical solubility curves for Tc solid phases, suggests that under reducing conditions Tc release from saltstone is solubility-controlled by one or more hydrated Tc(IV)-oxide solid phases (TcO2x(H2O)). [SRRA099188-000003]

DLM leaching data suggest that cement-free saltstone (i.e., 60 wt% GGBFS, 40 wt% FA) is comparable in performance, from a PA perspective, to the historically used saltstone formulation (i.e., 45 wt% GGBFS, 45 wt% FA, and 10 wt% OPC). [SRR-CWDA-2020-00008]

The final report, X-ray Diffractometry of Saltstone Samples Subjected to the Dynamic Leaching Method, SRMC-CWDA-2022-00017, detailing the mineralogical evaluation of saltstone samples that had been subjected to leach testing via the dynamic leaching method (DLM) was issued in April 2022. The DLM involves the continuous passage of simulated ground water through monolithic saltstone samples, and the subsequent analysis of the leachates for analytes of interest.

During DLM testing the saltstone pore solution is exchanged multiple times, and the intent of this study was to determine how the pore solution exchanges impact the mineralogy of saltstone. As such, the crystalline phase composition of both post-DLM and non-DLM samples has been characterized by X-ray diffractometry (XRD).

Observations of post-DLM samples indicated phase changes consistent with the microstructure expected after multiple pore volume exchanges. This is consistent with the degradation mechanisms analyzed within the PA and thus has no PA impact.

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Revision 0 Performance Assessment March 2023 Page 61 of 74 6.3 Toxicity Characteristic Leaching Procedure (TCLP) Testing and X-Ray Absorption Spectroscopy (XAS) of Cement-Free Saltstone These investigations were conducted by the Savannah River Ecology Laboratory (SREL), and had the primary objective of evaluating materials, testing, and analysis variables that might impact the mercury (Hg) leaching data for saltstone when subjected to the Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure (TCLP) (EPA Method 1311). Testing was conducted on cement-free saltstone samples spiked with methylmercury hydroxide (CH3HgOH; also termed MeHgOH). The cement-free samples were composed of 60 wt% ground granulated blast furnace slag (GGBFS) and 40 wt% fly ash (FA) (referred to as CF 60/40) and mixed at a water-to-premix (w/pm) mass ratio of 0.60, which is approximately equivalent to a salt solution-to-premix (SS/pm) mass ratio of 0.82.

A secondary objective of the study was to determine potential sources for the significant disparity observed between TCLP-Hg extractant concentrations for samples prepared and tested at SREL compared to tests on similar samples conducted by the Savannah River National Laboratory (SRNL) (SRNL-STI-2020-00468). For SREL tests, the TCLP-Hg extractant concentrations (for samples prepared with similar MeHgOH-spike concentrations) were almost an order of magnitude higher than those measured by SRNL.

The following observations were made, noting that comparative [TCLP-THg] percentages within

+/- 20% are likely within the analysis variability of the direct mercury analysis (DMA).

1. Cement-Free vs Standard Saltstone - the CF 60/40 and STD 45/45/10 saltstone formulations indicate similar [TCLP-THg]. With respect to the testing of CF 60/40 samples prepared with simulant solution, Hg retention was marginally enhanced in comparison to STD 45/45/10 samples. However, this trend was reversed for samples produced for regulatory testing with actual Tank 50 salt solution.

2. Salt Solution Hg-Spike Concentration - as [SS-THg] was increased, so the [TCLP-THg]

increased. For [SS-THg] of 64, 128, and 325 mgHg/LSS, the [TCLP-THg] were 0.079, 0.185, and 0.551 mgHg/LExt, respectively. Note that the Resource Conservation and Recovery Act (RCRA) limit for [TCLP-THg] is 0.2 mgHg/LExt, and, thus, the [TCLP-THg] for the 325 325 mgHg/LSS sample (i.e., the [SS-THg] SPF WAC Limit (X-SD-Z-00004)) exceeded the RCRA limit. This result potentially questions the current [SS-THg] WAC limit, noting, however, that SRNL data indicates RCRA TCLP compliance for samples with [SS-THg]

> WAC limit 325 mgHg/LSS (SRNL-STI-2020-00468).

3. Curing Duration - extending the saltstone curing duration from 28 to 90 days resulted in a marginal (15%) decrease in [TCLP-THg], though, in essence, the difference should be considered within the +/- 20% DMA equivalence range.

4. TCLP Extractant Type & pH - TCLP testing allows the use of two different extractants depending on the acidic or caustic nature of the waste; i.e., extractants #1 and #2 with initial pHs of 4.93 and 2.88, respectively. The use of extractant #1 resulted in a marginal 10%

decrease in [TCLP-THg]. As such, the extractant type and initial pH had no significant impact on [TCLP-THg].

5. SRNL DMA Verification - SRNL conducted parallel DMA testing on TCLP extractants derived from the SREL study. The [TCLP-THg] reported by SRNL was 19% higher than

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Revision 0 Performance Assessment March 2023 Page 62 of 74 the value measured by SREL. This was attributed to the use of a Si-Thiol Hg-scavenger by SRNL, which likely served to reduce the evaporation of Hg from the extractant samples as they awaited analysis in the DMA carousel. Ultimately, the SRNL testing served to validate

[TCLP-THg] DMA measurements performed at SREL.

6. Polytetrafluoroethylene (PTFE) vs Polypropylene Co-Polymer (PPCO) TCLP Container

- a previous SREL study (SRRA099188-000016) had indicated enhanced absorption of MeHg+ and Hg(II) to PPCO containers (in comparison to PTFE). However, it should be noted that the phenomenon was significantly more pronounced for Hg(II), which was ultimately not evaluated in this investigation. With respect to the MeHg+-spiked samples considered in this study, the comparative use of PPCO and PTFE containers for the 18-hour TCLP agitation step yielded identical [TCLP-THg]. However, it is, of course, still recommended that PTFE containers be used for simulant and regulatory TCLP testing since these have been shown to limit Hg-loss of both MeHg+ and Hg(II) species.

7. Post-TCLP/Pre-DMA Storage - different scenarios were evaluated with respect to the storage of the filtered post-TCLP extractants. For SREL testing, the extractants are typically loaded into the DMA within an hour of TCLP-testing cessation. In contrast, extractant samples associated with SRNL testing (SRNL-STI-2020-00468) are acidified, refrigerated, and stored in zero-headspace containers for up to 4 weeks. Ultimately, this study demonstrated no significant impact on [TCLP-THg] for the different storage protocols considered.

8. Saltstone Particle Size - not surprisingly, as the saltstone particle size decreases (and the particle surface area per unit mass increases), the [TCLP-THg] increases. [TCLP-THg] was almost tripled when testing particles <1.00 mm compared to those in the range of 1.00 -

9.53 mm. The effect of particle size has also been previously demonstrated by SRNL SRNL-STI-2019-00060). The phenomenon alludes to an Hg-retention mechanism in which soluble Hg-species are microencapsulated in the saltstone micropores. As the surface area increases, more of the micropores are directly exposed to the extractant and, thus, leaching of soluble Hg-species from the micropores is enhanced.

9. Saltstone Particle Attrition During TCLP Testing - after the 18-hour TCLP agitation step, the TCLP extractants contain noticeable amounts of fine particulates, which result from attrition of the larger saltstone pieces during end-over-end mixing. Since particle size has been shown to significantly impact [TCLP-THg], the abraded fines have the potential to exaggerate the leaching characteristics of saltstone. Testing to classify the abraded fines indicated that only 63 wt% remained in the starting range of 4.76 - 9.53 mm, and 7 wt%

and 30 wt% were abraded to 1.00 - 4.76 mm and <1.00 mm, respectively. The high proportion of fines (i.e., 30 wt%) produced in the TCLP sample would be expected to elevate [TCLP-THg], though it was impossible to quantify the potential impact without more comprehensive PSD data.

As previously indicated, SREL TCLP data from this, and a previous (SRRA099188-000016),

study indicated significantly higher [TCLP-THg] compared to a study conducted on similar simulant saltstone samples by SRNL (SRNL-STI-2020-00468). Indeed, the SREL [TCLP-THg]

are almost an order of magnitude higher those measured by SRNL. It is important to note, however, that the SREL data, in particular the [TCLP-THg] for different particle size ranges, is

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Revision 0 Performance Assessment March 2023 Page 63 of 74 much better aligned with another SRNL study that also evaluated the impact of saltstone particle size on [TCLP-THg] (SRNL-STI-2019-00060). Nonetheless, part of this study sought to identify variables in TCLP sample testing and analysis that might account for the disparate SREL-SRNL data. The only variable considered that could potentially result in the order-of-magnitude higher SREL [TCLP-THg] is particle size, and specifically, the authors refer to the production of 30 wt%

fines due to particle attrition during the 18-hour TCLP-agitation step. However, it is ultimately impossible to assert particle attrition as a causal factor without knowledge regarding the extent to which this phenomenon might occur during SRNL TCLP testing. Of course, if similar degrees of particle attrition are observed for SRNL samples, then the explanation for the considerable SREL-SRNL data disparity lies elsewhere.

One final aspect of this study was to conduct X-ray absorption spectroscopy (XAS) on MeHgOH-spiked CF 60/40 samples to determine the predominant Hg phases that were formed during curing.

In a sample spiked at the SPF [SS-THg] WAC limit of 325 mgHg/LSS (or 0.012 wt% Hg/saltstone),

XAS indicated approximately 37 wt% unreacted MeHgOH, and 63 wt% HgS (red cinnabar). Note that small proportions of HgO may also have been present, but this was difficult to distinguish from the MeHgOH. This data confirms the assertion that sulfide in the GGBFS facilitates the precipitation of insoluble HgS, though it is somewhat surprising that such a significant portion of MeHgOH remained unreacted. This is especially the case since XAS phase data for samples with Hg concentrations up to 0.6 wt% Hg/saltstone would suggest that there is at least an order-of-magnitude more reactive sulfide in the cured saltstone than is needed to completely convert the MeHgOH to HgS in the 0.012 wt% Hg/saltstone sample. The authors tentatively suggest that the incomplete transformation of MeHgOH HgS may result from a degree of isolation between the reactive MeHg+ and S2-species as the saltstone transitions from a free-flowing particulate suspension to a viscous slurry and finally to a cured solid.

The final report documenting the results of this study, SRMC-CWDA-2022-00034, was issued in July 2022.

While further leach testing on grout simulants was not able to fully resolve the disparity in mercury leach performance between SREL and SRNL methods, TCLP testing of actual waste grouts remain within regulatory limits. Retention behavior for mercury is not related to the retention behavior for dose-driving radionuclides within the PA and therefore there is no impact to the current PA.

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7. PLANNED OR CONTEMPLATED CHANGES Sections 7.1 through 7.7 discuss planned work that are part of PA maintenance and monitoring activities. A PA Maintenance Plan is prepared and updated annually and submitted to the DOE-SR to confirm the continued adequacy of the LW PAs (which includes F-Area Tank Farm, H-Area Tank Farm, and the SDF) and to increase confidence in the results of the LW PAs. The preparation and execution of the plan is consistent with the Disposal Authorization Statement and Tank Closure Documentation Technical Standard (DOE-STD-5002-2017). The latest revision is the Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program -

FY2022. [SRMC-CWDA-2022-00006]

The DOE has performed a number of additional activities to support the 2019 revision to the SDF PA. The 2019 SDF PA includes model revisions, UWMQE analysis recommendations (i.e.,

General Separations Area [GSA] model updates), lessons learned, and incorporation of the latest input values as developed through ongoing studies (see Sections 6 and 7.6), as well as other recent literature reviews and analyses, as appropriate.

7.1 Revise the Closure Plan As stipulated in the SDF DAS (WDPD-20-32), and as part of the PA maintenance program, the SDF Closure Plan is reviewed annually to determine if additional revision is required. If a revision is required, then an update to the SDF closure plan will be submitted to DOE for approval.

The Closure Plan for the Z-Area Saltstone Disposal Facility, SRR-CWDA-2020-00005, was last updated in FY2020 to capture changes in the 2019 SDF PA. This Closure Plan provides information for planning, initial design, and basis for PA assumptions related to the final closure configuration of the SDF and no revision was necessary in FY2022.

7.2 Revise the SDF Monitoring Plan As stipulated in the SDF DAS (WDPD-20-32), and as part of the PA maintenance program, the SDF Monitoring Plan is reviewed annually to determine if additional revision is required. If a revision is required, then an update to the SDF Monitoring Plan will be submitted to DOE for approval.

An updated Performance Assessment Monitoring Plan for the Saltstone Disposal Facility at the Savannah River Site, SRR-CWDA-2020-00006, was issued in FY2020 to capture changes in the 2019 SDF PA and to incorporate ongoing activities as required by the DAS and no revision was necessary in FY2022. [WDPD-20-32]

7.3 Special Analyses Additional SAs for the SDF will be prepared in the future as new technological data warrant that may potentially impact the ability to meet SDF PA performance objectives.

7.4 Unreviewed Waste Management Question Evaluations A formal system to evaluate disposal practice changes and proposed actions is in place at the SDF.

The process consists of providing screening and if necessary UWMQEs of proposed activities and new information. The Unreviewed Waste Management Question (UWMQ) process will continue

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Revision 0 Performance Assessment March 2023 Page 65 of 74 to be required throughout the life of the facility. This process is implemented via Manual S4 Procedure ENG.46 Revision 5.

7.5 Revise the Performance Assessment In FY2020 a revision to the SDF PA was approved (SRR-CWDA-2019-00001). The timing of this PA revision was associated with four main drivers:

1. The design and layout of the SDF SDUs had undergone major changes since the last PA revision.

2. The breadth of research and development activities in recent years had provided new information and increased the confidence in key transport modeling inputs and assumptions.

3. Three Special Analyses had been conducted since the 2009 SDF PA and this information has been incorporated into the new PA revision, 2019 SDF PA.

4. DOE-STD-5002-2017 states that PAs should be revised at a minimum every ten years and the previous SDF PA was completed in 2009.

As part of PA implementation, related documents were updated to ensure that any performance-affecting assumptions or requirements within the updated PA will be protected. Such documents included, for example, the WAC, Closure Plan, and SDF Monitoring Plan. No PA revisions are currently planned.

7.6 Studies PA-related testing and research activities are being performed as part of the on-going maintenance activities aimed at reducing uncertainty in the 2019 SDF PA model or are verification sampling and analysis of materials properties used in the 2019 SDF PA. As ongoing research provides new information or reduces uncertainty, this information will be evaluated (via the UWMQ and SA process) against the information used as a basis for the 2019 SDF PA modeling.

Below is a brief list of testing and research activities currently planned for FY2023.

Long-term Radiological Lysimeter Program

Performance Assessment Monitoring 7.7 Performance Assessment Monitoring Per the requirements in the DAS issued for the SDF (WDPD-20-32), a monitoring plan shall be written, approved, and implemented within one year of issuance of the DAS and updated at least every five years. This monitoring plan includes annual data review and evaluation. Following this annual data review and evaluation, any modifications to this monitoring plan that may be applicable will be noted and the plan updated, as necessary and no revision was necessary in FY2022.

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8. STATUS OF DAS CONDITIONS, KEY AND SECONDARY ISSUES In FY2023 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 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 this Operating Disposal Authorization Statement (ODAS) issuance, SRS shall submit to DOE Headquarters (HQ) 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 and was completed in FY2020.

Conditions 1 and 2 were applied in response to one Secondary Issue, SDFS06PA1202, which is the only remaining open issue. 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 adequate stability and erosion analyses have been completed for the proposed closure cap, and any potential impacts from these analyses are evaluated.

For SDF-S06-PA12-02, recent modeling work that was performed in support of responses to the NRCs Requests for Supplemental Information (RSIs) addressed uncertainties associated with erosion and infiltration. [SRR-CWDA-2021-00036, SRR-CWDA-2021-00040] These models were revised to better reflect the expected long-term conditions for the SDF, and have been integrated into an probabilistic SDF model to determine the potential dose impacts as described in Evaluation of the Combined Uncertainties Associated with the Long-Term Performance of Saltstone Disposal Facility Flow Barriers (SRR-CWDA-2021-00066). Additionally, a subject matter expert with the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) is preparing a literature review and analysis (due 2QFY23) to better understand the potential for the silting-in (or clogging) of the sand drainage layer of the closure cap. Finally, to complete the closure of SDF-S06-PA12-02, an updated slope stability analysis of the SDF closure cap will be performed. The new stability analysis is expected to be completed in the 3QFY23. Upon completion of the silting-in paper and the slope stability analysis, all of the documentation related to long-term closure cap performance will be transmitted to the LFRG to support the resolution and closure of the Secondary Issue.

FY2022 SDF operations continue to comply with the DAS. [WDPD-20-32]

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9. COMPOSITE ANALYSIS

SUMMARY

The annual evaluation of the SRS CA (SRNL-STI-2009-00512) is covered by a separate report.

The latest evaluation as of the issuance of this review was issued in February 2023 for FY2022 (SRMC-CWDA-2023-00015). Based on the assessment presented within this annual review and collective engineering judgement, the conclusions of the CA remain valid and there is reasonable assurance that SRS will meet the performance objectives delineated in DOE O 435.1.

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10. CERTIFICATION OF CONTINUED ADEQUACY OF THE PA, CA, DAS, AND RWMB AND CONCLUSION The current performance evaluation conducted on SDU 1, SDU 4, SDU Cells 2A/2B, SDU Cells 3A/3B, SDU Cells 5A/5B, and SDU 6 indicates SDF operations through FY2022 were within the performance expectation of the 2019 SDF PA and comply with the DAS, the RWMB, and DOE O 435.1 requirements.

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11. REFERENCES 10 CFR 61, Energy, Title 10 Code of Federal Regulations, Part 61, Licensing Requirements for Land Disposal of Radioactive Waste, U.S. Nuclear Regulatory Commission, Washington DC, December 22, 2011.

Angus M.J. and Glasser F.P., The Chemical Environment in Cement Matrices, Materials Research Society Symposium Proceedings 50:547-556, 1985.

C-CLC-Z-00143, Swindle, M.V., SDU 7 Minimum Grout Containment Capacity, Savannah River Site, Aiken, SC, Rev. 0, May 2021.

DOE M 435.1-1, Radioactive Waste Management Manual., U.S. Department of Energy, Washington DC, Chg. 3, January 2021.

DOE O 435.1 Chg. 2, Radioactive Waste Management, U.S. Department of Energy, Washington DC, January 2021.

DOE-STD-5002-2017, DOE Standard Disposal Authorization Statement and Tank Closure Documentation, U.S. Department of Energy, Washington, DC, May 2017.

EPA Test Method 1311, Toxicity Characteristic Leaching Procedure (1992) (from EPA Manual SW-846), U. S. Environmental Protection Agency, Washington, DC, December 2015.

EPA_Method_1315, Mass Transfer Rates of Constituents in Monolithic or Compacted Granular Materials Using a Semi-Dynamic Tank Leaching Procedure (from EPA Manual SW-846), U. S.

Environmental Protection Agency, Washington, DC, January 2013.

ESH-FSS-9000373, Odum, J.V., Naval Fuel Material Facility (FMF) Settlement Agreement 89-06-SW, Item No. 3 Final Disposal of Saltcrete Drums, Savannah River Site, Aiken, SC, June 20, 1990.

LWO-LWE-2008-00023, Plummer, A.S., Inspection Program for Z-Area Vault 4, Savannah River Site, Aiken, SC, February 2008.

Manual S4 Procedure ENG.46, LW Unreviewed Waste Management Question (UWMQ),

Savannah River Site, Aiken, SC, Rev. 5, July 19, 2021.

ML20254A003, Letter from Koenick, S.S. to Folk, J.L., Preliminary Review of the U.S.

Department of Energys Submittal of the 2020 Savannah River Site Saltstone Disposal Facility Performance Assessment, U.S. Nuclear Regulatory Commission, Washington DC, October 5, 2020.

ML21040A492, Letter from Koenick, S.S. to Folk, J.L., Request for Additional Information Regarding the 2020 Savannah River Site Saltstone Disposal Facility Performance Assessment, U.S. Nuclear Regulatory Commission, Washington DC, March 1, 2021.

ML21133A296, Second Set of Request for Additional Information Regarding the 2020 Savannah River Site Saltstone Disposal Facility Performance Assessment, U.S. Nuclear Regulatory Commission, Washington DC, June 8, 2021.

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Revision 0 Performance Assessment March 2023 Page 70 of 74 ML21341A551, Hommel, S.P., Third Set of Request for Additional Information Regarding the 2020 Savannah River Site Saltstone Disposal Facility Performance Assessment, U.S. Nuclear Regulatory Commission, Washington DC, December 14, 2021.

ML22026A391, Hommel, S.P., Fourth Set of Request for Additional Information Regarding the 2020 Savannah River Site Saltstone Disposal Facility Performance Assessment, U.S. Nuclear Regulatory Commission, Washington DC, February 9, 2022.NDAA_3116, Public Law 108-375, Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005, Section 3116, Defense Site Acceleration Completion, U.S. Department of Energy, Washington DC, October 28, 2004.

Q-RWM-Z-00001, Petras, R.J., Savannah River Remediation (SRR) Saltstone Facility Radioactive Waste Management Basis, Savannah River Site, Aiken, SC, Rev. 8, December 2020.

Q-RWM-Z-00001, Petras, R.J., Savannah River Mission Completion (SRMC) Saltstone Facility Radioactive Waste Management Basis, Savannah River Site, Aiken, SC, Rev. 9, February 2022.

SREL-R-14-0006, Seaman, J., Chemical and Physical Properties of Saltstone as Impacted by Curing Duration, Savannah River Site, Aiken, SC, Rev. 1.0, September 2014.

SREL-R-15-0003, Seaman, J., Chemical and Physical Properties of 99Tc-Spiked Saltstone as Impacted by Curing Duration and Leaching Atmosphere, Savannah River Site, Aiken, SC, Rev.

0, October 2015.

SREL-R-16-0003, Seaman, J., Contaminant Leaching from Saltstone, Savannah River Site, Aiken, SC, Rev. 0, September 2016.

SRMC-CWDA-2022-00003, Hommel, S.P., Comment Response Matrix for the Third 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, March 2022.

SRMC-CWDA-2022-00006, Watkins, D.R., Savannah River Site Liquid Waste Facilities Performance Assessment Maintenance Program FY2022 Implementation Plan, Savannah River Site, Aiken, SC, Rev. 0, May 2022.

SRMC-CWDA-2022-00016, Hommel, S.P., Comment Response Matrix for the Fourth 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, April 2022.

SRMC-CWDA-2022-00017, Simner, S., X-ray Diffractometry of Saltstone Samples Subjected to the Dynamic Leaching Method, Savannah River Site, Aiken, SC, Rev. 0, April 2022.

SRMC-CWDA-2022-00034, Simner, S., Toxicity Characteristic Leaching Procedure (TCLP)

Testing and X-Ray Absorption Spectroscopy (XAS) of Cement-Free Saltstone, Savannah River Site, Aiken, SC, Rev. 0, July 2022.

SRMC-CWDA-2022-00056, Dixon, K.D., Determination of SDF Inventories through 9/30/2022, Savannah River Site, Aiken, SC, Rev. 0, March 2023.

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Revision 0 Performance Assessment March 2023 Page 71 of 74 SRMC-CWDA-2023-00015, Memo Hommel, S. to Staub A., Model Validation for the FY2022 SRS Composite Analysis Monitoring Plan, Savannah River Site, Aiken, SC, Rev. 0, February 2023.

SRMC-UWMQE-2022-00001, Hommel, S.P., Evaluation of Saltstone Disposal Unit (SDU) 6 Leakage, Savannah River Site, Aiken, SC, Rev. 0, June 2022.

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-2019-00060, Methylmercury Speciation and Retention Evaluation to Support Saltstone Waste Acceptance Criteria, Savannah River Site, Aiken SC, Rev. 0, 2021.

SRNL-STI-2020-00468, Tank 50 Simulant Grout and Toxicity Characteristic Leaching Procedure (TCLP) Results for Methylmercury Waste Acceptance Criteria (WAC) Limit, Savannah River National Laboratory, Aiken, SC, Rev. 0, 2021.

SRNS-RP-2014-00537, Savannah River Site Land Use Plan, Savannah River Site, Aiken, SC, November 2014.

SRNS-TR-2022-00338, Killeen, T.P., Z-Area Saltstone Disposal Facility Groundwater Monitoring Midyear Report for 2022, Savannah River Site, Aiken, SC, July 2022.

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

SRR-CWDA-2017-00032, Hommel, S.P., Recommended Saltstone Waste Acceptance Criteria for Implementing the Fiscal Year 2016 Saltstone Disposal Facility Special Analysis, Savannah River Site, Aiken, SC, Rev. 0, April 2017.

SRR-CWDA-2018-00045, Lester, B.H., Iodine Kds for Simulating I-129 Releases from Saltstone SDUs, Savannah River Site, Aiken, SC, Rev. 0, August 2018.

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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, Simner, S., Cement-Free Formulation Down-Select Report, Savannah River Site, Aiken, SC, Rev. 0, March 5, 2019.

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

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

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

SRR-CWDA-2020-00064, Hommel, S.P., Fiscal Year 2020 Special Analysis for the Saltstone Disposal Facility at the Savannah River Site, Savannah River Site, Aiken, SC, Rev. 1, April 2021.

FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

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SRR-CWDA-2021-00047, Hommel, S.P., Comment Response Matrix for the First Set of U.S.

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

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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 18, 2021.

SRR-CWDA-2021-00072, Hommel, S.P., 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 15, 2021.

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SRR-SDU-2017-00003, Brooks, T., SDU 6 Minimum Grout Containment Capacity, Savannah River Site, Aiken, SC, Rev. 0, February 2017.

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

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FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

Revision 0 Performance Assessment March 2023 Page 73 of 74 SRRA099188-000005, Seaman, J., SREL-R-18-0006, Contaminant Leaching from Saltstone Simulants for FY 2018, Savannah River Site, Aiken, SC, Rev. A, November 2018.

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FY2022 Annual Review of the SRMC-CWDA-2023-00008 Saltstone Disposal Facility (Z Area)

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