U.S. Nuclear Regulatory Commission Plan 

for Monitoring Disposal Actions Taken by 

the U.S. Department of Energy at the 

Savannah River Site F-Area Tank Farm Facility 

in Accordance With the National Defense 

Authorization Act for Fiscal Year 2005 

January 2013 

U.S. Nuclear Regulatory Commission 

Office of Federal and State Materials 

 and Environmental Management Programs 

Washington, DC 20555-0001 
U.S. Nuclear Regulatory Commission Plan 

for Monitoring Disposal Actions Taken by 

the U.S. Department of Energy at the 

Savannah River Site F-Area Tank Farm Facility 

in Accordance With the National Defense 

Authorization Act for Fiscal Year 2005 

January 2013 

U.S. Nuclear Regulatory Commission 

Office of Federal and State Materials 

 and Environmental Management Programs 

Washington, DC 20555-0001 
ii 

CONTENTS 

Section Page 

FIGURES ..................................................................................................................................... iv 

TABLES ....................................................................................................................................... iv 

ACRONYMS AND ABBREVIATIONS ........................................................................................... v 

DEFINITIONS .............................................................................................................................. vi 

EXECUTIVE SUMMARY ............................................................................................................ viii 

1 MONITORING PROCESS ................................................................................................... 1-1 

 1.1 Background .............................................................................................................. 1-1 

 1.2 Objective .................................................................................................................. 1-2 

 1.3 Roles and Responsibilities ....................................................................................... 1-2 

 1.4 Coordination With the State of South Carolina ......................................................... 1-4 

 1.5 Monitoring Approach ................................................................................................ 1-5 

 1.5.1 Technical Reviews ....................................................................................... 1-5 

 1.5.2 Data Reviews ............................................................................................... 1-5 

 1.5.3 Onsite Observation Visits ............................................................................. 1-5 

 1.6 Annual Compliance Monitoring Report ..................................................................... 1-6 

 1.7 Notification Letters .................................................................................................... 1-6 

 1.8 Monitoring Plan ........................................................................................................ 1-6 

 1.8.1 Linkage Between Recommendations in the Technical Evaluation Report 

 and Monitoring Factors ............................................................................................. 1-8 

 1.8.2 Closing Monitoring Factors ........................................................................... 1-8 

2 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.40 ...................................... 2-1 

3 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.41 ...................................... 3-1 

 3.1 Monitoring Area 1 “Inventory” ................................................................................... 3-6 

 3.1.1 Monitoring Factor 1.1: Final Inventory and Risk Estimates ......................... 3-7 

 3.1.2 Monitoring Factor 1.2: Residual Waste Sampling ....................................... 3-9 

 3.1.3 Monitoring Factor 1.3: Residual Waste Volume .......................................... 3-9 

 3.1.4 Monitoring Factor 1.4: Ancillary Equipment Inventory ............................... 3-10 

 3.1.5 Monitoring Factor 1.5: Waste Removal (As It Pertains to ALARA) ............ 3-11 

 3.2 Monitoring Area 2 “Waste Release” ....................................................................... 3-11 

 3.2.1 Monitoring Factor 2.1: Solubility Limiting Phases/Limits and Validation 

 (Applies to Tank 18, May Apply to Other Tanks Later) ............................... 3-14 

 3.2.2 Monitoring Factor 2.2: Chemical Transition Times and Validation ............ 3-15 

 3.3 Monitoring Area 3 “Cementitious Material Performance” ....................................... 3-16 

 3.3.1 Monitoring Factor 3.1: Concrete Vault Performance (As It Relates to 

 Steel Liner Corrosion) ................................................................................. 3-19 

 3.3.2 Monitoring Factor 3.2: Groundwater Conditioning ..................................... 3-20 

 3.3.3 Monitoring Factor 3.3: Shrinkage and Cracking ........................................ 3-22 

 3.3.4 Monitoring Factor 3.4: Grout Performance ................................................ 3-23 

 3.3.5 Monitoring Factor 3.5: Basemat Performance ........................................... 3-23 

 3.3.6 Monitoring Factor 3.6: Use of Stabilizing Grout (As It Pertains 

 to ALARA) ................................................................................................... 3-24 

 3.4 Monitoring Area 4 “Natural System Performance” ................................................. 3-25 

 3.4.1 Monitoring Factor 4.1: Natural Attenuation of Plutonium ........................... 3-25 

 3.4.2 Monitoring Factor 4.2: Calcareous Zone Characterization ........................ 3-26 
iii 

CONTENTS (continued) 

Section Page 

 3.4.3 Monitoring Factor 4.3: Environmental Monitoring ...................................... 3-27 

 3.5 Monitoring Area 5 “Closure Cap Performance” ...................................................... 3-29 

 3.5.1 Monitoring Factor 5.1: Long-Term Hydraulic Performance of the 

 Closure Cap ................................................................................................ 3-29 

 3.5.2 Monitoring Factor 5.2: Long-Term Erosion Protection Design .................. 3-30 

 3.5.3 Monitoring Factor 5.3: Closure Cap Functions That Maintain 

 Doses ALARA ............................................................................................. 3-30 

 3.6 Monitoring Area 6 “Performance Assessment Maintenance” ................................. 3-31 

 3.6.1 Monitoring Factor 6.1: Scenario Analysis .................................................. 3-32 

 3.6.2 Monitoring Factor 6.2: Model and Parameter Support .............................. 3-32 

 3.6.3 Monitoring Factor 6.3: F-Tank Farm Performance 

 Assessment Revisions ............................................................................... 3-33 

4 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.42 ...................................... 4-1 

 4.1 Monitoring Area 1 “Inventory” ................................................................................... 4-2 

 4.2 Monitoring Area 2 “Waste Release” ......................................................................... 4-3 

 4.3 Monitoring Area 3 “Cementitious Material Performance” ......................................... 4-4 

 4.4 Monitoring Area 4 “Natural System Performance” ................................................... 4-5 

 4.5 Monitoring Area 5 “Closure Cap Performance” ........................................................ 4-5 

 4.6 Monitoring Area 6 “Performance Assessment Maintenance” ................................... 4-6 

5 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.43 ...................................... 5-1 

 5.1 Monitoring Factor 7.1: Protection of Workers During Operations ............................ 5-2 

 5.2 Monitoring Factor 7.2: Air Monitoring ...................................................................... 5-2 

 5.3 Monitoring Factor 7.3: As Low As Is Reasonably Achievable ................................. 5-3 

6 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.44 ...................................... 6-1 

 6.1 Monitoring Factor 8.1: Settlement ........................................................................... 6-1 

 6.2 Closure of MA 8 “Site Stability” ................................................................................ 6-2 

7 REFERENCES ..................................................................................................................... 7-1 

8 LIST OF CONTRIBUTORS .................................................................................................. 8-1 

APPENDIX A—MONITORING FACTORS 

APPENDIX B—OPEN ITEMS DURING CONSULTATION 

APPENDIX C—MONITORING AREA 2 “WASTE RELEASE” 

APPENDIX D—MONITORING AREA 3 “CEMENTITIOUS MATERIAL PERFORMANCE” 

APPENDIX E—MONITORING AREA 4 “NATURAL SYSTEM PERFORMANCE” 
iv 

FIGURES 

Figure Page 

1-1 Paths to Noncompliance With the Performance Objectives in 10 CFR Part 61, 

 Subpart C ....................................................................................................................... 1-8 

3-1 Potential Pathways of Exposure to a Member of the Public and Points of 

 Compliance for 10 CFR 61.41 (100 m) and 61.42 (1 m) Analyses ................................ 3-2 

3-2 Approximate 1 m and 100 m Boundaries Where the U.S. Department of Energy 

 Evaluates Compliance in Its PORFLOW Model Domain................................................ 3-3 

3-3 F-Tank Farm Barriers in the U.S. Department of Energy’s F-Tank Farm Performance 

 Assessment Reference Case ......................................................................................... 3-5 

3-4 Barriers to Timing in the U.S. Department of Energy’s F-Tank Farm Reference 

 (or Best Estimate) Performance Assessment Case ..................................................... 3-13 

3-5 Tank Grout Features Important to Performance .......................................................... 3-18 

3-6 Proposed F-Tank Farm Groundwater Monitoring Locations ........................................ 3-28 

TABLES 

Table Page 

ES–1 List of Monitoring Areas and Associated Performance Objectives ................................... xi 

ES–2 NRC Prioritization of Monitoring Factors That Support 10 CFR 61.41 and 61.42 ............ xii 

1-1 Types of Notification Letters ........................................................................................... 1-7 

3-1 Relative Risk and Contributions of F-Tank Farm Barriers to Reducing Risk for 

 Three Key Radionuclides (Tc, Pu, and Np) .................................................................... 3-8 
v 

ACRONYMS AND ABBREVIATIONS 

ALARA As Low As Is Reasonably Achievable 

ASR Alkali Silica Reaction 

CERCLA Comprehensive Environmental Response Compensation and Liability Act 

CFR Code of Federal Regulations 

CNWRA® Center for Nuclear Waste Regulatory Analyses 

CY Calendar Year 

DOE United States Department of Energy 

EDS Energy Dispersive Spectroscopy 

EPA United States Environmental Protection Agency 

EXAFS Extended X-Ray Absorption Fine Structure 

FEPs Features, Events, and Processes 

FFA Federal Facility Agreement 

FTF F-Tank Farm or F-Area Tank Farm 

FY Fiscal Year 

GCL Geosynthetic Clay Liner 

GCP General Closure Plan 

GSA General Separations Area 

HDPE High Density Polyethylene 

HLW High-Level Waste 

HRR Highly Radioactive Radionuclide 

HTF H-Tank Farm or H-Area Tank Farm 

Kds Distribution Coefficients 

LLRW Low-Level Radioactive Waste 

LLW Low-Level Waste 

MA Monitoring Area 

MF Monitoring Factor 

NDAA Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 

NRC United States Nuclear Regulatory Commission 

PA Performance Assessment 

PO 

POC 

Performance Objective 

Point of Compliance 

RAI Request for Additional Information 

SCDHEC South Carolina Department of Health and Environmental Control 

SEM Scanning Electron Microscopy 

SRS Savannah River Site 

TER Technical Evaluation Report 

UTRA Upper Three Rivers Aquifer 

WD Waste Determination 

WIR Waste Incidental to Reprocessing 

XANES X-Ray Absorption Near Edge Structure 

XRD X-Ray Diffraction 
vi 

DEFINITIONS 

As Low As (Is) Reasonably Achievable (ALARA): From 10 Code of Federal Regulations 

(CFR) 20.1003—Making every reasonable effort to maintain exposures to radiation as far below 

the dose limits as is practical, consistent with the purpose for which the licensed activity is 

undertaken, taking into account the state of technology, the economics of improvements in 

relation to the state of technology, the economics of improvements in relation to benefits to 

public health and safety, and other societal and socioeconomic considerations, and in relation to 

utilization of nuclear energy and licensed materials in the public interest. 

Disposal: The isolation of radioactive wastes from humans and the environment. 

Follow-Up Action: Items identified during monitoring that require additional effort by DOE to 

resolve. Examples include DOE providing answers to questions generated during technical 

reviews or DOE providing results of a particular experiment once it becomes available. 

Follow-up actions are less risk-significant than Open Issues. 

High-Level Radioactive Waste (HLW): (i) irradiated reactor fuel; (ii) liquid wastes resulting 

from the operation of the first cycle solvent extraction system, or equivalent, and the 

concentrated wastes from subsequent extraction cycles, or equivalent, in a facility for 

reprocessing reactor fuel; and (iii) solids into which such liquids have been converted. 

Highly Radioactive Radionuclides (also called Key Radionuclides): Those radionuclides 

that contribute most significantly to risk to the public, workers, and the environment. In the 

context of the U.S. Nuclear Regulatory Commission (NRC) reviews of DOE Waste 

Determinations (WDs) conducted under the Ronald W. Reagan National Defense Authorization 

Act for Fiscal Year 2005 (NDAA), the term is not limited to radionuclides with high-specific 

activity. NRC staff considers the term “highly radioactive radionuclides,” as used in the context 

of the NDAA, to be equivalent to the term “Key Radionuclides” used in the manual for DOE 

Order 435.1 (DOE M 435.1-1), the West Valley Policy Statement, and in some NRC reviews of 

DOE WDs. 

Indeterminate: Insufficient information is currently available to assess compliance with the 

Performance Objectives (POs) in 10 CFR Part 61, Subpart C. Additional information is 

forthcoming from DOE within a reasonable timeframe to allow NRC staff to assess compliance 

with POs. 

Monitoring Area (MA): General features or aspects of the disposal action identified by NRC 

as being important to DOE’s ability to meet the POs of 10 CFR Part 61, Subpart C. MAs are 

further divided into more specific monitoring factors (MF). 

Monitoring Factor (MF): Specific features of the disposal action (e.g., conceptual model 

assumptions, mathematical modeling assumptions, or parameter values) DOE uses in its 

performance demonstration that NRC has determined to be important to demonstrating 

compliance with POs of 10 CFR Part 61. NRC typically identifies MFs through the review of a 

DOE WD, performance assessment (PA), information DOE generates during monitoring 

(e.g., technical reports on laboratory or field experiments), or other information collected during 

monitoring (e.g., during NRC observations). MFs are a subset of MAs and tracked as open or 

closed. When NRC staff determines that an MF is no longer applicable or technical issues or 

uncertainties are resolved, then the MF is closed. 
vii 

Onsite: Areas of the DOE site where monitoring activities will be carried out. This may include 

areas that have some relationship to, but are outside the physical boundaries of a particular 

Waste Incidental to Reprocessing (WIR) related facility. 

Onsite Observation: A formal, preannounced site visit to a DOE WIR related facility by NRC 

staff for purposes of observing DOE facilities, activities, processes, or experiments related to 

compliance with 10 CFR Part 61 POs. 

Open Issue: An issue that NRC staff identifies during monitoring activities, which requires 

additional information from DOE to address questions that NRC staff has raised regarding 

DOE disposal actions. Open Issues can include MFs that DOE has not taken sufficient action 

to address or instances where data collected by DOE are not consistent with assumptions 

(e.g., conceptual model assumptions, mathematical assumptions, or parameter values) made in 

the PA. Open Issues are more risk significant than follow-up actions, and the term Open Issues 

indicates items that could lead to noncompliance with the POs. 

Operations: The time frame during which DOE carries out its waste disposal actions, through 

the end of the institutional control period. For the purpose of this monitoring plan, DOE actions 

involving waste disposal are considered to include PA development (analytical modeling), waste 

removal, grouting, stabilization, observation, maintenance, or other similar activities. 

Performance Assessment: A type of systematic (risk) analysis that addresses (i) what can 

happen, (ii) how likely it is to happen, (iii) what the resulting impacts are, and (iv) how these 

impacts compare to specifically defined standards. 

Performance Objectives: One of the 10 CFR Part 61, Subpart C, requirements for low-level 

waste (LLW) disposal facilities, which are (i) general requirement (10 CFR 61.40), (ii) protection 

of the general population from releases of radioactivity (10 CFR 61.41), (iii) protection of 

individuals from inadvertent intrusion (10 CFR 61.42), (iv) protection of individuals during 

operations (10 CFR 61.43), and (v) stability of the disposal site after closure (10 CFR 61.44). 

Recommendations: NRC suggestions DOE might consider to further enhance its approach for 

management of incidental waste. Recommendations are typically made during the consultation 

phase. Unlike follow-up actions and Open Issues, recommendations are not tracked during 

monitoring. 

Technical Review: NRC technical staff review of reports, studies, analyses, experiments, and 

other information prepared by DOE, South Carolina Department of Health and Environmental 

Control, or other stakeholders that may confirm or refute DOE’s ability to meet 10 CFR Part 61 

POs with respect to its WIR disposal activities. 

Waste Determination (or Non-High-Level Waste Determination): DOE documentation 

required by Section 3116 of the NDAA that demonstrates that a specific waste stream 

is not HLW. 

Worker: DOE personnel or contractors who carry out operational activities at the 

disposal facility. 
viii 

EXECUTIVE SUMMARY 

The Ronald Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA) 

authorizes the U.S. Department of Energy (DOE) in consultation with the U.S. Nuclear 

Regulatory Commission (NRC) to determine whether certain radioactive waste related 

to reprocessing of spent nuclear fuel is not high-level waste (HLW), provided certain 

criteria are met. The NDAA applies specifically to DOE facilities in South Carolina and 

Idaho and not to similar DOE facilities located in other states. The NDAA also requires 

NRC to coordinate with the covered state (i.e., South Carolina or Idaho) to monitor DOE 

disposal actions to assess compliance with the Performance Objectives (POs) for low-level 

waste (LLW) in 10 Code of Federal Regulations (CFR) Part 61, Subpart C. These POs 

include (i) general requirement (10 CFR 61.40), (ii) protection of the general population from 

releases of radioactivity (10 CFR 61.41), (iii) protection of individuals from inadvertent intrusion 

(10 CFR 61.42), (iv) protection of individuals during operations (10 CFR 61.43), and (v) stability 

of the disposal site after closure (10 CFR 61.44). This monitoring plan details the NRC’s path 

forward to assessing DOE’s compliance with each of these POs for residual waste remaining 

in the HLW tanks at the Savannah River Site (SRS) near Aiken, South Carolina, at the time of 

facility closure. 

In fiscal year 2010, DOE issued a draft Waste Determination (WD) that concluded that stabilized 

waste residuals in F-Area Tank Farm facility (FTF) tanks and auxiliary components, as well as 

the tanks and auxiliary components themselves, could meet NDAA criteria for Waste Incidental 

to Reprocessing at the time of closure and as such could be managed as LLW. As required by 

the NDAA, DOE consulted with NRC regarding the conclusions in its draft WD for FTF. Results 

of a multi-year consultative review culminated in NRC staff’s issuance of a Technical Evaluation 

Report (TER) in October 2011 (NRC, 2011). As DOE is in the early years of closure for FTF, 

limited information regarding important factors influencing facility performance has been 

generated. Therefore, rather than reaching conclusions regarding DOE’s ability to meet the 

POs in 10 CFR Part 61, Subpart C, NRC staff instead provided a series of comments and 

recommendations in its TER (NRC, 2011). If addressed by DOE, NRC staff expects these 

comments and recommendations will improve DOE’s compliance demonstration. NRC staff 

reasons that sufficient time is available for DOE to implement many of these recommendations 

as FTF closure progresses. 

In limited cases, NRC staff recommended actions that it deemed critical to DOE’s compliance 

demonstration in the short-term. These more critical recommendations generally involved 

issues associated with one tank at FTF, Tank 18, which was scheduled for closure in calendar 

year (CY) 2012. Tank 18 is predicted by DOE models to produce overall peak doses 

significantly above the POs in 10 CFR 61.41 and 61.42 considering longer performance periods 

beyond 10,000 years. Given the magnitude of the dose predictions and uncertainty in the timing 

of the peak dose, NRC staff recommended that technical issues associated with Tank 18 

(e.g., support for release and natural attenuation assumptions) should be resolved prior to tank 

grouting to inform closure of this single tank as well as future FTF tank closures. 

Notwithstanding NRC staff’s recommendation to delay grouting of Tank 18, DOE issued a final 

WD in March 2012 (DOE/SRS–WD–2012–001) and commenced grouting of Tanks 18 and 19 in 

April 20121

. DOE indicated in its final WD that it considered the assumptions, conclusions, and 

recommendations documented in NRC’s TER (NRC, 2011). In fact, a number of studies were 

 

1

NRC staff concluded in its TER (NRC, 2011), that due to the relatively low residual inventory and risk associated 

with Tank 19, DOE could proceed with closure of Tank 19. 
ix 

conducted by DOE between NRC’s issuance of its TER and DOE’s issuance of its final WD 

to address NRC staff’s technical concerns. Because DOE conducted significant work on 

reducing the technical uncertainties associated with Tank 18 prior to issuance of the final WD 

for FTF, NRC staff is in the process of reviewing the additional information DOE generated in 

support of the final WD to reach a conclusion regarding the ability of the FTF to meet the POs in 

10 CFR Part 61, Subpart C. Where appropriate, NRC staff lists specific monitoring activities 

related to Tank 18, including technical reviews of documents and activities generated or 

performed by DOE during the interim period between NRC’s issuance of its TER and DOE’s 

final WD for FTF, as well as future planned activities that have not yet occurred for Tank 18 and 

the larger FTF. 

In accordance with the NDAA, NRC will assess FTF compliance with the POs in 

10 CFR Part 61, Subpart C. A performance assessment (PA) is typically used to 

demonstrate compliance with two of the four POs, 10 CFR 61.41, “Protection of the 

General Population From Releases of Radioactivity,” and 61.42, “Protection of Individuals 

From Inadvertant Intrusion,” which are assessed using dose-based criteria. A PA is a type 

of systematic risk analysis that addresses (i) what can happen, (ii) how likely it is to happen, 

(iii) what the resulting impacts are, and (iv) how the impacts compare to specifically defined 

standards. Considering the long time period over which long-lived radionuclides pose a hazard 

to human health, a robust PA is needed to establish that the POs will be met for releases from 

the FTF that may occur many thousands of years in the future. NRC considers sufficient PA 

model support, coupled with an observation of disposal actions that are carried out in 

conformance with detailed closure plans, necessary for NRC to have reasonable assurance that 

the POs can be met. Many key features of DOE’s disposal facility design are important to the 

FTF compliance demonstration, as documented in the FTF PA. These key features are the 

focus of NRC staff’s monitoring efforts. 

NRC’s monitoring plan focuses on the most risk-significant aspects of DOE disposal actions. 

These risk-significant aspects were identified in eight monitoring areas (MA). The first six MAs 

relate to general public and intruder protection. NRC staff developed MA 1, “Residual Waste 

Inventory” to ensure that the final post cleaning inventory that is developed for each cleaned 

tank is consistent with assumptions made in DOE’s final WD and PA regarding the final waste 

inventory at closure. NRC also will perform monitoring activities related to engineered and 

natural features of the disposal facility that also are found to be important to meeting the POs. 

NRC staff developed MA 2 “Waste Release” to ensure that releases of key radionuclides remain 

low for long periods of time. NRC staff developed MA 3 “Cementitious Material Performance” to 

ensure that cementitious materials act as effective barriers to fluid flow, mitigate or attenuate 

releases of radioactivity from the tanks, and otherwise perform consistent with DOE PA 

assumptions. NRC staff developed MA 4 “Natural System Performance” to ensure the 

hydrogeological system acts as an effective natural barrier to attenuate key radionuclide 

releases. Additionally, under MA 4, NRC staff will review environmental data collected by DOE 

as an additional assurance that the FTF is operating as predicted by DOE models. NRC staff 

developed MA 5 “Closure Cap Performance” to evaluate key features of the closure cap 

identified in NRC staff’s review. All of these MAs are directly related to the facilities’ long-term 

ability to limit or mitigate releases of contaminants from the FTF that could result in adverse 

human health impacts. Items of lower risk significance or longer-term activities are addressed 

in MA 6 “PA Maintenance.” PA maintenance also is necessary to ensure that a mechanism is in 

place to consider new and significant information that may be collected in the future that might 

significantly alter results presented in DOE’s PA. 
x 

While DOE relies on a PA to demonstrate compliance with POs related to general public and 

intruder protection, NRC can evaluate compliance with 10 CFR 61.43, “Protection of Individuals 

During Operations,” through direct observation of DOE closure activities. NRC plans to perform 

a graded review of DOE’s radiological protection program while observing DOE’s most risk 

significant closure activities (e.g., tank cleaning and grout placement activities) to assess 

compliance with 10 CFR 61.43. For example, NRC staff will review radiation records and 

environmental data or reports and possibly conduct interviews during closure activities to 

assess compliance with 10 CFR 61.43 addressed under MA 7 “Protection of Individuals 

During Operations.” 

Finally, monitoring activities to assess compliance with 10 CFR 61.44, “Stability of the 

Disposal Site After Closure,” partially overlap those activities developed to support 

assessment of compliance with 10 CFR 61.41 and 61.42. NRC considers unique factors 

affecting stability of the disposal site not already discussed under 10 CFR 61.41 and 61.42 

under MA 8 “Site Stability.” 

To prepare this monitoring plan, NRC staff began by comprehensively considering all of its 

previous comments and recommendations on each FTF PA and WD review and cross-walked 

each of the items to one of the eight MAs described above that NRC considers important to 

DOE’s compliance demonstration2

. This cross-walk is provided in Appendix A. As such, this 

monitoring plan will serve as the starting point from which NRC staff will assess compliance with 

the POs in 10 CFR Part 61, Subpart C in fulfillment of its monitoring responsibilities under the 

NDAA. As discussed in the preceding paragraphs, the eight MAs are: 

• MA 1 “Residual Waste Inventory” 

• MA 2 “Waste Release” 

• MA 3 “Cementitious Material Performance” 

• MA 4 “Natural System Performance” 

• MA 5 “Closure Cap Performance” 

• MA 6 “PA Maintenance” 

• MA 7 “Protection of Individuals During Operation” 

• MA 8 “Site Stability” 

MAs are supported by a number of monitoring factors (MFs). MFs are smaller, more specific 

items that NRC staff will investigate in more detail. MFs will help facilitate monitoring by 

providing specific activities for NRC staff to focus on. These MFs will be tracked as open or 

closed. If issues arise related to MFs, NRC staff may develop an “open issue” to document 

concerns related to the MF. In this way, NRC staff will have a mechanism to communicate to 

DOE early in the process the need for corrective action, prior to issuance of a notification letter 

of concern or noncompliance. NRC staff will note the status of each MF in the periodic 

monitoring compliance reports, currently prepared annually, for the Idaho National Laboratory 

and SRS, NUREG–1911. 

Because Congress directed NRC to monitor DOE disposal actions to assess compliance with 

the POs in 10 CFR Part 61, Subpart C, this monitoring plan is first organized by PO, with four 

chapters each devoted entirely to one of the four POs. As indicated above, NRC staff evaluates 

what key MAs are important to DOE’s demonstration of compliance with each PO—MAs are, 

 

2

NRC recognizes that some of its previous review comments and recommendations are less risk-significant or may 

require longer time periods to address than others. Lower risk or long-term activities are binned into MA 6 titled 

“PA Maintenance.” 
xi 

therefore, listed directly beneath each PO and support NRC staff’s assessment of FTF facility 

compliance with the POs, as required by the NDAA. As stated above, each MA supports one or 

more POs. If the MA supports multiple POs, the monitoring plan will indicate whether the MA 

and underlying factors are an exact duplicate of a previously listed MA (in which case the MA 

and factors will not be repeated) or if there are unique aspects of the MA or underlying factors 

that pertain to just that PO (in which case only the unique aspects of the area and relevant 

factors will be discussed under the PO). Table ES–1 lists each MA and indicates the POs each 

MA supports. 

Table ES–2 provides NRC staff’s prioritization of each MF under MAs 1–5 developed to support 

the 10 CFR 61.41 PO. Many of these factors also support the 10 CFR 61.42 PO because an 

inadvertent intruder also is assumed to be exposed to FTF waste through the groundwater 

pathway. MA 6, “Performance Assessment Maintenance,” MFs are not listed in Table ES–2 

because PA Maintenance items are considered items of lower risk significance or longer-term 

monitoring activities by default. Each of these MFs is developed in more detail in the chapters 

that follow. 

This monitoring plan also provides information regarding the types of monitoring reports NRC 

plans to prepare to document its monitoring activities. For example, NRC plans to issue a 

report following each onsite observation and will summarize monitoring activities and changes 

to the status of its monitoring activities in periodic reports. If NRC is unable to conclude POs 

are met, NRC will notify DOE, the covered State, and Congress, as required by the NDAA. 

The types of notification letters related to a finding of non-compliance are listed in Section 1.9 of 

this document. 

Table ES–1. List of Monitoring Areas and Associated Performance Objectives 

MA Monitoring Areas 

10 CFR Subpart C 

Performance Objective 

61.41 61.42 61.43 61.44 

1 Inventory X X 

2 Waste Release X X 

3 Cementitious Material Performance X X 

4 Natural System Performance X X 

5 Closure Cap Performance X X 

6 Performance Assessment Maintenance X X 

7 Protection of Individuals During Operations X 

8 Site Stability X 

 
xii 

Table ES–2. NRC Prioritization of Monitoring Factors 

That Support 10 CFR 61.41 and 61.42

MA 1 

Inventory

MA 2 

Waste Release

MA 3 

Cementitious 

Material 

Performance

MA 4 

Natural System 

Performance

MA 5 

Closure Cap

1.1— 

Final 

Inventory 

and Risk 

Estimates†

2.1— 

SolubilityLimiting 

Phases/Limits 

and Validation§

3.1— 

Cement Vault 

Performance (As It 

Impacts Steel Liner 

Corrosion)‡

4.1— 

Natural 

Attenuation of 

Pu§

5.1— 

Long-Term 

Hydraulic 

Performance*

1.2— 

Residual 

Waste 

Sampling†

2.2— 

Chemical 

Transition 

Times‡

3.2— 

Groundwater 

Conditioning‡

4.2— 

Calcareous Zone 

Characterization†

5.2— 

Long-Term 

Erosion 

Protection 

Design*

1.3— 

Residual 

Waste 

Volume†

3.3— 

Shrinkage and 

Cracking†

4-3— 

Environmental 

Monitoring†

1.4— 

Ancillary 

Equipment 

Inventory*

3.4— 

Grout Performance†

1.5— 

Waste 

Removal 

(As It 

Impacts As 

Low As Is 

Reasonably 

Achievable)*

3.5— 

Basemat 

Performance‡

 3.6— 

Grout Stabilization 

(As It Impacts As Low 

As Is Reasonably 

Achievable)*

 

*Lower Priority

†Medium Priority

‡High Priority Dependent or More Difficult (The monitoring factors in orange‡ are risk-significant to the U.S. 

Department of Energy’s performance assessment, but the need for their implementation may be dependent on 

results of other monitoring factors. Because the monitoring factors in orange‡ are also expected to be more 

difficult to study or support, work on monitoring factors in red§ are recommended first.)

§High Priority Recommended
xiii 

References 

DOE/SRS–WD–2012–001, Rev. 0, “Basis for Section 3116 Determination for Closure of F-Tank 

Farm at Savannah River Site.” Washington, DC: U.S. Department of Energy. 2012. 

NRC. “Technical Evaluation Report for F-Area Tank Farm Facility, Savannah River Site, 

South Carolina—Final Report.” ML112371715. Washington, DC: U.S. Nuclear Regulatory 

Commission. 2011. 

DOE/SRS–WD–2012–001, Rev. 0, “Basis for Section 3116 Determination for Closure of F-Tank 

Farm at Savannah River Site.” Washington, DC: U.S. Department of Energy. 2012. 
1-1 

1 MONITORING PROCESS 

1.1 Background 

The Savannah River Site (SRS) is an 803 square kilometer (310 square mile) facility developed 

in the 1950s as part of the country’s growing weapons program. Many activities took place 

at the site, including the reprocessing of spent nuclear fuel in reinforced concrete buildings 

called canyons. Liquid waste from the reprocessing process was managed in 51 underground 

storage tanks. The F-Area Tank Farm (FTF), the subject of this monitoring plan, contains 22 of 

these tanks. 

The U.S. Department of Energy (DOE) is engaged in an expansive campaign to clean, 

stabilize and close 20 of the 22 underground waste storage tanks at the FTF. DOE 

closed two FTF tanks (Tanks 17 and 20) in the 1990’s prior to U.S. Nuclear Regualtory 

Commission (NRC) involvement in the Ronald W. Reagan National Defense Authorization Act 

for Fiscal Year 2005 (NDAA). DOE clean up activities also include support ancillary structures 

(i.e., evaporators, pump pits, pump tanks, diversion boxes, transfer valve boxes, and piping) 

used to store, treat, and transfer generated waste. The waste tanks and ancillary structures are 

several decades old. The original service life for these tanks was projected as 40 years; 

however, several of the aging FTF waste tanks are approaching 60 years of service life. 

Given the inherent risks of exhuming the aging waste tanks and disposing them as high-level 

waste (HLW), DOE plans to clean, grout and close the FTF waste tanks and ancillary structures 

that are in place to reduce the risks to the workers, the public, and the environment. 

In accordance with Section 3116 of the NDAA, the Secretary of Energy, in consultation with 

NRC on March 27, 2012, made a determination that waste remaining within the tanks and 

ancillary facilities in FTF does not have to be considered or managed as HLW, to be disposed in 

a geologic repository. Rather, it can be disposed of, in place, as low-level waste (LLW). 

NRC’s consultation included the review of a draft waste determination (WD) basis document, 

which DOE submitted in September 2010. A detailed site performance assessment (PA) 

accompanied the basis document (SRS–REG–2007–00002, Rev. 1). During the review 

process, NRC staff held a number of technical exchange meetings with DOE and submitted a 

written Request for Additional Information regarding certain aspects of the DOE basis document 

(NRC, 2010). DOE completed its response to NRC in the summer of 2011. NRC staff 

completed a technical evaluation report (TER) in October 2011 (NRC, 2011). In its TER, NRC 

staff provided a number of recommendations to DOE that, if implemented, would increase the 

likelihood that NRC would find the FTF in compliance with the 10 Code of Federal Regulations

(CFR) Part 61, Subpart C performance objectives (POs). DOE submitted additional information 

regarding several NRC TER recommendations prior to completing the final WD 

(DOE/SRS–WD–2012–001) and has plans to address other NRC recommendations, as 

indicated in its “Savannah River Site Liquid Waste Facilities Performance Assessment 

Maintenance Program, fiscal year 2012 Implementation Plan” (SRR–CWDA–2012–00020). 

NRC assumed its monitoring role, per the NDAA, once DOE issued its WD in March 2012 for 

the remaining tanks and ancillary structures at the FTF facility. The NDAA provides a very 

specific responsibility for NRC to monitor disposal operations to ensure DOE disposal actions 

comply with the POs in 10 CFR Part 61. While NRC staff reviewed and provided comments on 

DOE’s PA and the entire FTF WD, NRC’s TER (NRC, 2011) included a more detailed 

evaluation of the effectiveness of completed waste removal activities for Tanks 18 and 19 and 
1-2 

provided recommendations related specifically to the closure of those two tanks that were 

further along in the closure process and for which DOE provided more detailed closure 

information. This is important to note since the monitoring plan will include 20 tanks in FTF, 

including 16 tanks for which little or no waste removal has occurred. Over the next several 

decades, DOE will complete many activities to affect tank cleaning and closure in accordance 

with its responsibilities under the Federal Facility Agreement (FFA) to which NRC is not a party. 

NRC’s monitoring activities will focus on heel removal after much of the bulk removal of waste 

from the tanks has been completed. 

1.2 Objective 

In accordance with Section 3116 of NDAA, after the Secretary of Energy has made a 

determination that some residual waste does not have to be managed as HLW, NRC is required 

to monitor subsequent disposal activities to assess compliance with the POs in 10 CFR Part 61, 

Subpart C. NRC must coordinate these monitoring activities with the South Carolina 

Department of Health and Environmental Control (SCDHEC), the primary site regulator. 

This monitoring plan describes monitoring activities to be conducted in the context of their 

relationship with the ability for DOE to comply with the 10 CFR Part 61, Subpart C POs. In most 

cases, compliance or potential noncompliance with the POs must be demonstrated through 

indicators of future performance. The monitoring plan identifies eight Monitoring Areas (MAs) 

that NRC and SCDHEC finds to be important to demonstrating compliance with the POs. DOE 

activities associated with disposal of tanks and associated waste will take decades to complete. 

NRC anticipates that implementation of this monitoring plan will take place concurrently with 

DOE closure activities. NRC staff activities related to the MAs will include the following: 

• Technical reviews of DOE work products, experiments, and analyses tied to one or more 

MAs, including collection of environmental data. 

• Periodic onsite (quarterly or less frequent) observations of aspects of DOE disposal 

activities and, as appropriate, related experiments. 

NRC monitoring activities will be accomplished by NRC headquarters and regional personnel. 

In general, NRC staff will work in concert with SCDHEC personnel regarding accomplishment of 

monitoring tasks supportive of each organization’s program. 

1.3 Roles and Responsibilities 

U.S. Department of Energy 

The SRS FFA (WSRC–OS–94–42), a formal agreement between DOE, Region IV of the 

U.S. Environmental Protection Agency (EPA), and SCDHEC specifies the order and time in 

which FTF waste tanks are closed. The organizations who are parties in the FFA have 

regulatory authority over certain activities at SRS. NRC is not a party to the FFA and does not 

have regulatory authority over waste disposal activities. 

The FFA establishes that, among other things, the SRS waste tanks that do not meet secondary 

containment standards (older style tanks, specifically Types I and IV in FTF) must be removed 

from service according to the FFA schedule. The current FFA calls for operational closure of 

Tanks 18 and 19 by December 2012 and staggered operational closure of the other eight 
1-3 

FTF (Type I) waste tanks (tank numbers not specified in the FFA) by September 2022 

(WSRC–OS–94–42). DOE addresses the closure of the remaining FTF tanks 

(Types III and IIIA) and ancillary structures in the SRS Liquid Waste System Plan 

(SRR–LWP–2009–00001). 

DOE will, pursuant to its authority, pursue closure of the FTF and monitor its activities to ensure 

compliance with all requirements. DOEs relevant authority stems from the Atomic Energy Act of 

1954, as amended, and applicable DOE Orders, manuals and policies. Furthermore, DOE uses 

a documented process to review and resolve any disposal questions and develop any mitigation 

measures, as appropriate. Tank waste storage and removal operations are governed by an 

SCDHEC industrial wastewater construction permit (DHEC–01–25–1993). DOE will carry out 

removal from service and stabilization of the FTF waste tanks and ancillary structures pursuant 

to a State-approved closure plan, the FTF General Closure Plan, which contains the overall plan 

for removing from service and stabilizing the FTF waste tanks and ancillary structures 

(LWO–RIP–2009–00009). A specific Closure Module for each waste tank or ancillary structure 

or groupings of waste tanks and ancillary structures will be developed and submitted to the 

State of South Carolina for approval. Final waste tank stabilization activities shall not proceed 

until the State of South Carolina grants approval. Stabilization of individual FTF waste tanks 

and ancillary structures is anticipated to take place after individual component cleaning 

is complete. 

South Carolina Department of Health and Environmental Control 

SCDHEC is the primary regulator of DOE closure activities at SRS. The FTF waste storage and 

removal operations are governed by an SCDHEC industrial wastewater construction permit, 

issued January 25, 1993 (DHEC–01–25–1993). The State issued the permit under the authority 

of the South Carolina Pollution Control Act (State of South Carolina, 1985, Section 48-1-10) and 

all applicable regulations implementing the Act. The State of South Carolina has authority for 

approval of wastewater treatment facility operational closure under Chapter 61, Articles 67 

and 82 of the SCDHEC Regulations (SCDHEC R.61-67, SCDHEC R.61-82). 

The FTF GCP addresses the State’s regulatory authority relevant to removing the FTF 

waste tanks and ancillary structures from service. The GCP sets forth the general protocol 

by which DOE intends to remove from service the FTF waste tanks and ancillary structures 

to protect human health and the environment. The SCDHEC approved the FTF GCP on 

January 24, 2011. Prior to approval by SCDHEC, the FTF GCP was made available to the 

public for review and comment (LWO–RIP–2009–00009). 

U.S. Environmental Protection Agency 

As previously stated, the FFA is an agreement between the EPA, DOE, and the State of 

South Carolina. EPA is a party to the FFA pursuant to its authority in accordance with the 

Comprehensive Environmental Response Compensation and Liability Act (CERCLA), also 

known as Superfund, under which EPA is tasked with protecting citizens from the dangers 

posed by abandoned or uncontrolled hazardous wastes. EPA’s involvement with the State is 

focused on ensuring that proper disposal actions are taken, assisting the state with the design 

and installation of those actions, and monitoring and evaluating their effectiveness. 

Executive Order 12580 delegates the responsibility to implement the provisions in CERCLA to 

DOE and the U.S. Department of Defense. CERCLA also names DOE and DOD as the lead 

agencies for their respective areas. DOE has several facilities in EPA’s Region IV. EPA added 
1-4 

SRS to the Superfund National Priorities List in December 1989, which also is the year that SRS 

was required to have an FFA with the State and EPA. 

U.S. Nuclear Regulatory Commission 

Section 3116 of the NDAA authorized the Secretary of Energy to manage and dispose of 

certain waste associated with facility clean-up in Idaho and South Carolina as LLW, in 

accordance with POs in NRC regulations. Prior to such a determination, DOE is required to 

consult with NRC regarding its WD. Following the Secretary’s WD, NRC is required to monitor 

disposal activities in coordination with the covered State. 

NRC’s role in monitoring DOE’s closure activities derives from Section 3116 of the NDAA. 

While NRC is not given a formal regulatory role, the NDAA requires that NRC monitor, in 

coordination with SCDHEC, DOE disposal activities to assess compliance with the POs in 

10 CFR Part 61. Thus, DOE complies with a subset of NRC regulations in 10 CFR Part 61 

“Licensing Requirements Land Disposal of Radioactive Waste” in carrying out such disposal 

activities. The regulations in Part 61 establish, for land disposal of radioactive waste, 

procedures, criteria, and terms and conditions upon which NRC issues licenses for the disposal 

of radioactive wastes containing byproduct, source, and special nuclear material received from 

other persons. 

NRC recognizes that many of the activities that DOE must carry out prior to tank closure are 

beyond the scope of NRC monitoring authority. For instance, NRC is concerned with and will 

monitor aspects of residual waste inventory in each tank because of its direct relationship to 

compliance with the POs. However, NRC staff will focus only on more risk-significant activities 

related to the residual waste inventory. For example, while NRC staff will monitor heel removal 

activities insofar as these activities pertain to as low as is reasonably achievable provisions in 

10 CFR 61.41, NRC staff does not plan to monitor more routine inventory-reducing activities, 

such as bulk waste removal. 

This monitoring plan articulates NRC’s role to ensure DOE disposal activities associated 

with residual waste covered by the Secretary of Energy’s WD are in compliance with the POs 

of 10 CFR Part 61. 

1.4 Coordination With the State of South Carolina 

Per Section 3116 of NDAA, NRCs monitoring role includes coordination with State of South 

Carolina. During the WD review, NRC staff began coordinating with SCDHEC by conducting 

discussions to determine the types of activities that the State monitors under its regulatory 

authority. These discussions also enabled the State to get a better understanding of NRC’s 

activities. NRC continues to coordinate with the SCDHEC throughout the monitoring process by 

consulting with SCDHEC in the development of this monitoring plan and reviewing the State’s 

Environmental Surveillance and Oversite Program for use as a source of information to 

supplement NRC’s monitoring plan. SCDHEC uses a holistic monitoring approach with regard 

to overall performance and safety of SRS. The NRC objective with this NDAA monitoring 

program is limited to assessment of DOE’s compliance with the 10 CFR Part 61 POs. 

Ultimately, NRC and SCDHEC are concerned with the potential for environmental contamination 

in ground and surface water, air, milk, and meat. While it is unlikely that any contribution to 

 
1-5 

such contamination from FTF could manifest itself offsite in the foreseeable future, it is 

important to consider, and evaluate to the extent practicable, the utility of environmental 

monitoring in assessing compliance with the POs. 

During the monitoring phase, NRC activities will be closely coordinated with SCDHEC. To the 

extent practical, NRC will request SCDHEC’s assistance in following up on certain monitoring 

activities that require a local or onsite presence (e.g. activities related to daily tank grouting 

activities). SCDHEC also will be invited to contribute to the development of monitoring reports 

as well as the overall monitoring plan. 

NRC will keep the State abreast of the status of monitoring activities at the site, including any 

potential findings of noncompliance that require a notification letter as described in Section 1.7 

of this Monitoring Plan. At least two business days prior to the release and dissemination 

of any notification letters, SCDHEC officials will be briefed, in detail, on the reasons for 

such notification. 

1.5 Monitoring Approach 

Monitoring is an ongoing process consisting of technical reviews, data reviews, and periodic 

(i.e., quarterly or less frequently) onsite observation visits of DOE disposal activities related to 

compliance with the 10 CFR Part 61 POs. 

1.5.1 Technical Reviews 

Technical reviews by NRC include review and evaluation of analyses conducted by DOE or 

others that confirm one or more aspects of site performance. Also, reviews are used to obtain 

additional model support for assumptions made by DOE in the PA that are considered important 

to DOE compliance demonstration. NRC will document each review, which will be publicly 

available (e.g., Note to File and report for an Onsite Observation Visit). 

1.5.2 Data Reviews 

Data reviews focus on real-time monitoring data that may indicate future system performance 

or a review of records or reports that can be used to directly assess compliance with POs 

(e.g., review of radiation records). NRC will document each review, which will be publicly 

available (e.g., Note to File and report for an Onsite Observation Visit). 

1.5.3 Onsite Observation Visits 

As described in NUREG–1854 (NRC, 2007), onsite observation visits are opportunities for 

NRC to observe and review certain operations as they are being performed. Onsite 

obseravtions visits are performed by NRC staff or a representative and may include a variety 

of specific activities that could be used to assess an aspect of current or future site 

performance. A visit is generally performed to either (i) ensure data collected for a technical 

review are of sufficient quality or (ii) observe key disposal actions that are important to DOE’s 

compliance demonstration. 

Prior to each onsite observation visit, NRC will prepare an Observation Guidance Memorandum 

that discusses the scope and specific activities that will be monitored during the visit in more 

detail than is described in this monitoring plan. The activities NRC selects will be based on 
1-6 

many aspects, such as completion of DOE technical reports, emergent issues, timely DOE 

actions related to a monitoring factor (MF), availability of staff (i.e., NRC, SCDHEC, DOE), 

availability of locations at the site, length of time since reviewing an item in an MF, scheduled 

follow-up actions to previous visits, and available NRC resources. NRC will coordinate with 

SCDHEC in development of the memorandum to take into account areas that SCDHEC is 

interested in and availability of SCDHEC experts in those areas of interest. NRC plans to 

provide the final memorandum to DOE within 30 calendar days prior to the visit. The final 

memorandum will be publicly available. During a visit, the agenda may change based on what 

happens during the visit (e.g., new areas of interest are identified) or unforeseen circumstances. 

Each visit will be documented in an observation report. The report will include, for the actual 

areas covered during the visit, specific activities, results of discussions, status of any open 

issues/follow-up actions, and any NRC conclusions. The areas covered may differ 

somewhat from the areas of interest identified in the Observation Guidance Memorandum. 

NRC plans to finalize each report within 60 calendar days after the visit. The final report will be 

publicly available. 

1.6 Annual Compliance Monitoring Report 

NRC will publish an Annual Compliance Monitoring Report [i.e., currently, NUREG–1911 

(NRC, 2012)] to document the major findings associated with the monitoring activities during 

each calendar year (CY). The report will be for the entire NRC NDAA program for that CY and 

will be publicly available. 

1.7 Notification Letters 

In accordance with NRC guidance in NUREG–1854 (NRC, 2007), there are five types of 

notification letters. Three of the letters are non-compliance letters (i.e., Types I to III) that NRC 

developed to implement the authority it has inferred from the statutory language in Section 3116 

of the NDAA and two other types of letters that NRC may issue as an interim step when 

identifying or resolving major issues. NRC may issue a Type IV letter to express a concern and 

a Type V letter to confirm resolution of a concern. Table 1-1 describes each of the five letters, 

including NRC’s reason for issuing the letter, who at NRC signs the letter, and who receives the 

letter. The information in Table 1-1 is similar to the information in NUREG–1854 (NRC, 2007, 

Table 10-2), but is supplemented by information that reflects current experiences and lessons 

learned from previous monitoring activities. 

Figure 1-1 shows the types of noncompliance with the POs in 10 CFR Part 61, Subpart C, which 

are based on the collection of indirect and direct evidence. 

1.8 Monitoring Plan 

This monitoring plan presents the basic framework for NRC to perform monitoring activities in 

accordance with the NDAA for the FTF. The monitoring plan starts with the high level 

consideration of the four POs. Under each PO, the relevant MAs are identified. Each MA 

contains a set of MFs important to DOE’s compliance demonstration. New MAs are not 

expected in the future; but, they may be identified and added to the monitoring plan. The MFs 

were created from the concerns identified in NRC’s TER (NRC, 2011). These concerns will now 

be addressed under the MFs in this monitoring plan. 

 
1-7 

Table 1-1. Types of Notification Letters

Type Description/Notification Signature Distribution 

Non-Compliant Performance Objective Notifications 

I 

Evidence Performance Objective Is Not Met

NRC staff concludes that direct evidence 

(e.g., environmental sampling data) exists 

that indicates DOE disposal actions do not 

meet one or more performance objectives in 

10 CFR Part 61, Subpart C. 

Notification: NRC will issue a Type I letter of 

noncompliance if DOE cannot demonstrate that 

disposal actions currently meet the requirements 

specified in the performance objectives. 

Chairman DOE, Covered State, 

and Congress 

II Lack of Compliance Demonstration

NRC staff concludes that indirect evidence 

(e.g., experimental data on a key modeling 

assumption) exists that indicates DOE disposal 

actions do not meet one or more of the 

performance objectives in 10 CFR Part 61, 

Subpart C. 

Notification: NRC will issue a Type II letter of 

noncompliance if DOE cannot adequately 

address NRC technical concerns. 

Chairman DOE, Covered State, 

and Congress 

III Insufficient Information

NRC staff concludes that insufficient information 

is available to assess whether DOE 

disposal actions meet the performance 

objectives in 10 CFR Part 61, Subpart C. It is 

not clear to NRC staff that DOE (i) has plans to 

or (ii) is able to provide the information in a 

reasonable timeframe to allow NRC staff to 

assess compliance. 

Notification: NRC will issue a Type III letter of 

noncompliance if DOE cannot adequately 

address NRC technical concerns. 

Chairman DOE, Covered State, 

and Congress 

Other Notification Letters 

IV Concern

NRC staff has concerns with the 

performance demonstration. 

NRC Staff 

Management 

DOE and 

Covered State 

V Resolution

DOE has provided sufficient information to 

resolve NRC staff’s concerns with the 

performance demonstration. 

NRC Staff 

Management

DOE and 

Covered State 

Note: If practical, NRC staff will attempt to issue a notification letter of concern (Type IV letter) to allow DOE 

sufficient time to respond to NRC staff concerns prior to issuance of one of the three notification letters of 

noncompliance (Types I to III) listed above. 
1-8 

Figure 1-1. Types of Non-Compliance With the Performance Objectives in 

10 CFR Part 61, Subpart C

The identification, description, and status (i.e., open or closed) of each MF will evolve as 

monitoring activities continue in the future. New MFs are expected to be added 

to the monitoring plan in the future, as more information is known about the future DOE 

disposal actions and experiments. After each onsite observation visit, NRC will issue a 

report that will document status of each open MF or open issue. NRC expects to issue more 

revisions to the monitoring plan in the future to address such items as an updated DOE PA or a 

new NRC TER. 

1.8.1 Linkage Between Recommendations in the Technical Evaluation 

 Report and Monitoring Factors 

Appendix A provides a crosswalk between each consultative review comment or 

recommendation to the MAs and factors developed in this monitoring plan. Appendix A 

also provides a crosswalk between NRC staff’s PA maintenance items binned under MA 6 and 

DOE’s Performance Assessment Maintenance Plan (SRR–CWDA–2012–00020). 

1.8.2 Closing Monitoring Factors 

NRC will document closure of MFs (e.g., TER, technical review memorandum, or annual 

monitoring compliance report). To the extent practical, the information needed by NRC staff to 

close an MF is provided in Chapters 3 through 6, following each MF identified herein. NRC 
1-9 

anticipates that as DOE tank farm closure activities continue, it will identify additional MFs. In 

general, DOE must provide transparent and technically robust reports, studies, analyses, or 

experiments that specifically address the technical issues associated with each MF. 
2-1 

2 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.40 

Land disposal facilities must be sited, designed, operated, closed, and controlled after closure 

so that reasonable assurance exists that exposures to humans are within the limits established 

in the performance objectives (PO) in 10 Code of Federal Regulations (CFR) 61.41 through 

61.44.

The requirements in 10 CFR Part 40 are general requirements for near-surface disposal of 

low-level waste. The Department of Energy (DOE) disposal actions at F-Area Tank Farm (FTF) 

are unique in that the site and the waste are preexisting. Consequently, certain activities 

specified in the POs are limited in applicability. Siting requirements do not apply and design is 

only applicable with respect to the prospective design features of waste disposal, as described 

in the waste determination (WD). These might include such things as design of the grout mix 

introduced to the tanks and the site cover. Other activities (i.e., operations, use, closure, and 

postclosure) are applicable as they relate to disposal of waste covered by the WD. 

This section requires reasonable assurances that exposures to humans are within the limits 

established in the other four POs (i.e., 10 CFR 61.41 through 61.44). If DOE provides 

reasonable assurance that it will meet the other four POs, then DOE will likely have met 

10 CFR 61.40. If DOE does not provide reasonable assurance that it will meet the other four 

POs (i.e., 10 CFR 61.41 through 61.44), then DOE will likely not have met 10 CFR 61.40. 

Therefore, there are no specific monitoring areas (MAs) or monitoring factors for 10 CFR 61.40 

in this monitoring plan. 

With the exception of 10 CFR 61.43, the ability to observe and measure any direct violation of 

the POs will be very limited in the foreseeable future. The public will have limited and 

controlled access to environmental media (air or water) that could be contaminated by residual 

FTF waste until the federal government cedes the site. Similarly, a successor resident is 

expected to have low probability of directly intruding upon residual waste. Finally, while current 

activities could result in long-term stability concerns, major activities that will impact long-term 

stability, (i.e., emplacement of the site cover) will not occur for many years. Therefore, the 

U.S. Nuclear Regualtory Commission will rely on indirect indicators, referred to as key MAs, to 

ascertain DOE’s ability to affect continued compliance with POs as it proceeds with closure 

operations over the next several decades. The key MAs, rationale for their relevance, and 

specific monitoring activities related to them are summarized herein. 
3-1 

3 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.41 

Concentrations of radioactive material which may be released to the general environment 

in groundwater, surface water, air, soil, plants, or animals must not result in an annual dose 

exceeding an equivalent of 25 millirems to the whole body, 75 millirems to the thyroid, and 

25 millirems to any other organ of any member of the public. Reasonable effort should be made 

to maintain releases of radioactivity in effluents to the general environment as low as is 

reasonably achievable (ALARA). 

Protection of the general population from releases of radioactivity is a dose-based standard that 

considers potential releases of radioactivity from a low-level waste (LLW) disposal facility, such 

as the F-Tank Farm (FTF) facility into the general environment. These releases may cause a 

receptor to be exposed through direct or indirect contact with various environmental media such 

as soil, water, air, and plant or animal products (Figure 3-1). Direct pathways include direct 

radiation exposure or inhalation of buried waste residuals that may migrate to the surface. 

Indirect (groundwater) pathways include ingestion of crops irrigated with contaminated water, 

ingestion of animals or animal products exposed to contaminated water and fodder (grown in 

soil irrigated with contaminated groundwater), ingestion of contaminated groundwater, and 

incidental ingestion of soil (irrigated with contaminated water). Because FTF waste is located 

several meters below grade underneath a closure cap, the primary pathway of exposure of 

potential receptors to residual waste at the FTF disposal facility is through leaching of 

radionuclides into groundwater. Shielding of buried radiation by engineered barriers lowers the 

potential dose from direct radiation exposure. Transport of buried radioactivity from FTF 

components to the surface in the vapor phase also is considered a less risk-significant process. 

Therefore, direct radiation exposure from buried contamination and releases of radioactivity to 

air and subsequent transport to the surface are not a focus of the U.S. Nuclear Regulatory 

Commission’s (NRC) staff’s monitoring under 10 Code of Federal Regulations (CFR) 61.41. 

Review of air monitoring data is, however, an aspect of NRC’s evaluation of 10 CFR 61.43 as it 

pertains to protection of members of the public, particularly during active disposal facility 

operations such as cleaning and grouting of the high-level waste (HLW) tanks when the risk of 

airborne releases are the greatest. 

Because the 10 CFR 61.41 evaluation is prospective, a performance assessment (PA) analyst 

must select an evaluation period. However, the time period over which the evaluation should be 

conducted is not specified in the rule. LLW and waste incidental to reprocessing (WIR) 

guidance found in NUREG–1573 (NRC, 2000) and NUREG–1854 (NRC, 2007) suggests that 

generally a 10,000 year period of performance is sufficient to demonstrate compliance with the 

performance objective (PO). However, longer evaluation periods may be necessary to capture 

the peak dose and provide insights on facility (natural and engineered) performance for certain 

long-lived wastes. The 10 CFR 61.41 standard also has an ALARA component to ensure that 

operations and closure are optimized to achieve the lowest overall risk to members of the 

public, workers, and the environment. 

NRC staff evaluates compliance with 10 CFR 61.41 using more recent internal dosimetry 

methods than available when the Part 61 rule was developed. In lieu of using whole body and 

individual organ dose limits specified in the 10 CFR Part 61 rule, NRC uses a single dose 

criterion of 0.25 mSv/yr (25 mrem/yr) total effective dose equivalent to evaluate compliance with 

10 CFR 61.41. This departure from the 10 CFR 61.41 rule is explained further in NUREG–1854 

(NRC, 2007) and is consistent with the “Disposal of High-Level Radioactive Wastes in a 

Proposed Geologic Repository at Yucca Mountain, Nevada” rulemaking (66 FR 55752). 
3-2 

Figure 3-1. Potential Pathways of Exposure to a Member of the Public and Points of 

Compliance for the 10 CFR 61.41 (100 m) and 61.42 (1 m) Analyses 

To determine the dose to a potential receptor, NRC also must select a point of compliance 

(POC). NRC guidance in NUREG–1854 (NRC, 2007) indicates that after the end of the 

institutional control period,3

 the receptor evaluated to demonstrate compliance with the 

10 CFR 61.41 PO is assumed to be located at the point of highest projected dose beyond a 

100 m buffer zone surrounding the disposal facility (see Figure 3-2 that denotes the 100 m 

and 1 m boundaries, the points at which the dose-based standards in 10 CFR 61.41 and 

10 CFR 61.42 are assessed in the U.S. Department of Energy’s (DOE) FTF PA, respectively). 

 

3

Before the end of the institutional control period, the point of compliance is located on the larger site boundary over 

which DOE maintains access control. 

Direct Pathways—Direct 

Radiation and Inhalation; Indirect 

Pathways—Ingestion of Plant, 

Animal/Products, Water, and Soil 

Additional 

Surface 

Water 

Pathways: 

Fish 

Ingestion 
3-3 

Figure 3-2. Approximate 1 m and 100 m Boundaries Where the U.S. Department of 

Energy Evaluates Compliance in Its PORFLOW Model Domain 

(Adapted from DOE, 2008, Figure 5.2-5)

Considering the specific objectives and established paradigms for assessing compliance with 

10 CFR 61.41, NRC staff identified key aspects of disposal facility performance that have the 

largest impact on the 10 CFR 61.41 compliance demonstration based on information provided in 

DOE’s PA. NRC staff found that several monitoring areas (MAs) are important to meeting the 

10 CFR 61.41 PO. For example, the residual inventory remaining in the cleaned tanks is a 

good indicator of the potential risk associated with each tank (Section 3.1 on MA 1 

“Residual Inventory”). 

However, the extent to which the inventory of key radionuclides affects facility risk also is 

strongly influenced by the assumed rate of release of the inventory from the tanks. Because the 

key radionuclides are highly concentrated in a very small volume of waste, solubility limits apply 

100 m boundary 

1 m boundary 
3-4 

for many key radionuclides. In some cases, solubility control of the radionuclides is the single 

most important factor controlling release and dose. Therefore, NRC staff established waste 

release as a key MA (Section 3.2 on MA 2 “Waste Release”). 

For both solubility and nonsolubility controlled radionuclides, releases cannot occur from the 

tanks until the steel liners (i.e., the tanks) fail. Furthermore, even after release from the tanks, 

key radionuclides must traverse the concrete basemats underneath the tanks. Because DOE 

assumes the concrete vaults that house the high-level radioactive waste tanks (i) provide a 

passive environment that drastically slows corrosion of the tanks and (ii) because the floor of the 

concrete vaults (i.e., tank basemats) attenuate or provide a barrier to the release of 

radionuclides out of the tank, NRC staff established cementitious material performance as a key 

MA (Section 3.3 on MA 3 “Cementitious Material Performance”). 

Following release from the tanks, the final barrier to waste release is the natural environment 

surrounding the disposal facility. The natural environment acts as a barrier because it interacts 

with radioactivity leaving the tanks and causes key radionuclides to move at a slower rate than 

water and in some cases decreases concentrations in a down-gradient well where a potential 

receptor may be exposed. Dilution of key radionuclides leaching from the FTF tanks into the 

aquifer below also is an important natural attenuation mechanism that NRC staff will monitor. 

Therefore, NRC staff created MA 4 “Natural System Performance” as a key MA (Section 3.4). 

Figure 3-3 provides details regarding the assumed capabilities of each FTF barrier described 

above in limiting or mitigating long-term releases from the closed FTF HLW tanks. 

NRC staff also established MAs to address more routine or longer-term monitoring activities 

including the following:

• MA 5 “Closure Cap Performance” 

• MA 6 “Performance Assessment Maintenance” 

Although NRC staff concluded that the FTF closure cap is a redundant barrier4

 in DOE’s FTF 

PA, NRC staff nonetheless established MA 5 “Closure Cap Performance” as an MA for FTF 

because staff concluded that in certain cases, the FTF closure cap could be important to 

mitigating risk from the disposal facility and in maintaining doses ALARA. Therefore, NRC staff 

created MA 5 as an MA, given the potential for the closure cap to serve as an important barrier 

that may help ensure compliance with each of the 10 CFR Part 61, Subpart C, POs. 

Section 3.5 contains additional details on the monitorin factor (MF) related to the closure cap. 

NRC staff binned all comments and recommendations from its TER (NRC, 2011) that were of 

relatively lower risk-significance or required long-term action to address in a single category, 

MA 6 “Performance Assessment Maintenance.” The MA 6 term “Performance Assessment 

 

4

NRC staff concluded that DOE’s reference or best-estimate PA case shows the FTF closure cap is a redundant 

hydraulic barrier as other, more robust hydraulic barriers such as the steel liners and tank grout used to fill the 

cleaned tanks are present and expected to outperform the closure cap for longer periods of time under most 

scenarios, including the reference case used by DOE in its FTF PA. However, it is important to note that the closure 

cap is the only barrier assumed to provide long-term infiltrating-reducing capabilities, albeit at modest levels. 

Figure 3-4 shows barriers to timing of tank farm releases in DOE’s reference case. The dark blue barrier represents 

the closure cap that is assumed in DOE’s PA to be fully or nearly fully effective for less than 1,000 years before its 

performance drops off rapidly compared to the light blue (tank grout) or green (steel liner) barriers that last in most 

cases for tens of thousands of years following disposal facility closure. However, it is important to note that after a 

few thousand years, infiltration through the closure cap is assumed in DOE’s PA to stabilize to a constant rate of 

approximately 30 cm/yr [12 in/yr] for all time, less than the background infiltration rate of 37 cm/yr [15 in/yr], while no 

other barrier serves to permanently reduce infiltration. 
3-5 

Figure 3-3. F-Tank Farm Barriers in the U.S. Department of Energy’s F-Tank Farm 

Performance Assessment Reference Case
3-6 

Maintenance” should not be confused with a similar, but broader, term used by DOE to describe 

all of the short-term and longer-term activities it plans to undertake to maintain its PA, including 

planned research and tank characterization activities, the results of which may be reflected in a 

future PA revision. In other words, DOE’s PA maintenance plan encompasses all activities 

NRC staff might discuss under each key MA, as well as lower priority activities NRC staff 

discusses under MA 6 “Performance Assessment Maintenance.” In contrast, only those items 

of lower risk-significance or longer term PA maintenance activities are discussed by NRC staff 

under MA 6 “Performance Assessment Maintenance.” 

3.1 MA 1 “Inventory” 

Inventory for key radionuclides is important to the compliance demonstration because inventory 

is linearly related to dose for those radionuclides that are not solubility limited. Even for key 

radionuclides that are solubility controlled, in some cases (e.g., when solubility control is not the 

primary barrier to release from the engineered disposal system) doses also can be very 

sensitive to inventory. This is true because with higher inventory more activity can accumulate 

in a down gradient barrier (e.g., concrete basemats underneath the tanks that may control 

release for certain key radionuclides). For those radionuclides that are solubility limited, 

inventory also can be important from a mass depletion perspective. For example, the inventory 

of a key radionuclide could be released at very low concentrations over a long period of time, 

such that little to no activity remains when the solubility of the key radionuclide increases to 

risk-significant values. In these cases, a higher inventory could lead to significantly higher peak 

releases and dose from the engineered system than would occur from a lower inventory. 

Inventory can be very risk-significant for both solubility-controlled and nonsolubility controlled 

constituents and, therefore, is listed as an MA for FTF. 

Based on DOE’s PA, the key risk drivers under 10 CFR 61.41 for the FTF over longer 

evaluation periods are as follows: Technetium (Tc)-99, Plutonium (Pu)-239, 

Neptunium (Np)-237, and Radium (Ra)-226. Type IV Tank 18 contains the largest inventory 

of Pu-239 in FTF, leading to a peak dose of approximately 5 mSv/yr [500 mrem/yr] within 

40,000 years in DOE’s reference or best-estimate PA case5

. Type I tanks contain the highest 

assumed inventory of Tc-99, leading to the overall peak dose of approximately 6 mSv/yr 

[600 mrem/yr] after 20,000 years in DOE’s reference or best-estimate PA case. All tanks 

contain risk-significant quantities of Np-237 or Am-241 (parent of Np-237) that could lead to 

doses similar to the 10 CFR 61.41 standard evaluated at 0.25 mSv/yr [25 mrem/yr]. The key 

radionuclide Ra-226 is a significant but lower-risk, highly radioactive radionuclide (HRR) 

compared to Tc-99, Pu-239, and Np-237 in DOE’s reference case. Ra-226 is produced at the 

FTF via radioactive decay of its parents, Th-230, U-234, and Pu-238. The highest concentration 

of Ra-226 parents is found in Tank 18, although other tanks also have significant quantities of 

Ra-226 predecessors. 

Because facility risk is sensitive to key radionuclide inventory, in most cases a threshold 

inventory exists below which a key radionuclide ceases to be important to the compliance 

demonstration. For some key radionuclides (e.g., relatively long-lived and mobile), it may be 

more cost effective to remove additional activity from the tanks than it would be to provide 

additional information to support a key modeling assumption relied on for compliance. In fact, 

 

5

The FTF PA, Rev. 1 (SRS-REG-2007-00002, Rev. 1) dose estimates were updated in Tanks 18 and 19 special 

analyses (SRR-CWDA-2010-000124, Rev. 0). A range of dose values was included in the special analyses using 

updated solubility and sorption data. Some values were similar to previous estimates, while other values were 

significantly below previous estimates. 
3-7 

NRC staff indicated in the request for additional information (RAIs) and in its technical 

evaluation report (TER) (NRC, 2011) its position that it would be difficult for DOE to provide 

supporting information for the assumption that 100 percent of Tc is co-precipitated with iron 

mineral phases in the tank waste. In response to NRC staff’s RAIs, DOE provided additional 

information from Tanks 5 and 6 to support a significantly lower inventory estimate for Tc-99 in 

Type I tanks. Until then, Tc-99 had been regarded as the single most risk significant 

radionuclide for FTF over longer periods of performance in DOE’s base case analysis, owing to 

its relatively high mobility in the environment. If DOE can show the residual Tc-99 inventory is 

below levels of concern, then no additional support for the iron co-precipitation model for Tc will 

be needed. NRC staff will monitor progress on Type I tank closures to ensure the inventory of 

Tc-99 is reduced to non-risk-significant levels. If Tc-99 inventory cannot be reduced to these 

low levels, then other barriers to waste release for Tc-99 will become increasingly important. 

Table 3-1 indicates NRC staff’s current thinking that inventory is the likely one of the most 

effective ways of providing support for the 10 CFR 61.41 compliance demonstration with respect 

to Tc-99 and Np-237 doses. It is important to note that the inventory of Am-241, parent to 

Np-237, should be considered in determining whether or not Np-237 will be produced at 

risk-significant levels over time. 

NRC Monitoring Under MA 1 “Inventory”

As listed in Appendix A and documented in more detail in NRC’s TER (NRC, 2011), NRC staff 

will consider the following MFs related to inventory that are considered important to meeting the 

10 CFR 61.41 PO: 

• Final Inventory and Risk Estimates. 

The following factors support development of the final inventory (e.g., sampling and volume 

data are used to estimate a final inventory) and also are listed as MFs under MA 1 “Inventory.” 

• Waste Sampling, 

• Waste Volume, and 

• Ancillary Equipment Inventory. 

The following factor, related to the final tank inventory, is important to meeting ALARA criteria in 

10 CFR 61.41 and will, therefore, be listed as an MF under MA 1 “Inventory”: 

• Waste Removal As It Pertains to ALARA. 

3.1.1 Monitoring Factor 1.1: Final Inventory and Risk Estimates 

DOE has committed to sample each tank following waste retrieval activities. During the 

monitoring period, NRC staff will review special analyses performed for tanks as they are 

cleaned. NRC staff will assess the degree to which DOE demonstrates the FTF will meet the 

POs with the new projected radionuclide inventories, if inventory exceeds the predicted 

inventory used to support the determination. NRC staff will assess the degree to which DOE’s 

special analyses evaluate uncertainty in the revised inventory. NRC staff should independently 

verify whether the change in inventory is likely to significantly affect the dose to a hypothetical 

receptor {a 0.25 mSv/yr [25 mrem/yr]} limit to a member of the public under 10 CFR 61.41 or an 

applied 5 mSv/yr [500 mrem/yr] limit to an intruder under 10 CFR 61.42}. NRC staff should 

review the reasonableness of DOE’s approach to developing inventory multipliers used in the 
3-8 

uncertainty analysis. NRC staff will review these special calculations for each cleaned tank to 

ensure that PA is sufficiently bounding. This factor can be closed following NRC review of the 

last tank or equipment specific special analysis prepared by DOE for FTF. 

Table 3-1. Relative Risk and Contributions of F-Tank Farm Barriers to Reducing Risk 

for Three Key Radionuclides (Tc, Pu, and Np)*

Tc Pu Np Notes 

1 

Total Barrier 

Performance 

Needed (Function 

of Inventory)† 

6‡ 

(Type 1) 

9 

(Type IV, 

 Tank 18) 

6‡ 

(Type I) 

Factor reduction in concentration 

needed to meet the 10 CFR 61.41 

dose standard. The tank/type 

producing the highest dose for 

each key radionuclide is provided 

in parentheses. 

Engineered System 

2a Solubility Control 0‡ 2‡ 1 to 2‡ Final solubility 

2b (9 to 11)§ (9 to 11 )§ (5 to 6) Initial solubility 

3 

Basemat 

Attenuation 

(Sorption) 

<1 2§ 2§ Very important for Pu and Np. 

Can compensate for solubility. 

4 

Near-Field 

Diffusion or 

Dispersion‡ 

2^ 1§ 1§ 

Additional reduction in 

concentration due to upward 

diffusion into tank grout, large cell 

size, or dispersion. 

Natural System 

5 Aquifer Dilution 1 1 1 Based on simple aquifer mixing 

model; comparison of 

concentrations between vadose 

zone and saturated zones; and 

between source and POC. 

Pu sorption can compensate for 

other barrier underperformance. 

6 Sorption <<1 1‡ <<1 

7 Additional 

Dispersion to POC 1-2§ 1§ 1§ 

8 Total Barrier 

Performance 5 8 6 to 7 Sum of rows 2a, 3-7. 

9 Calculated 

Safety Margin -1 -1 0 to 1 Difference Between Row 8 and Row 1. 

Tc–Technetium, Np–Neptiunium, Pu–Plutonium

*All values in the table are approximate (order of magnitude). Values only are intended to provide relative 

information on the contributions of various barriers in DOE’s FTF PA and are not expected to be exact. Many 

of the values for the various barriers were estimated based on tracking the concentrations of the three key 

radionuclides from the contaminated zone to the point of compliance in DOE’s PORFLOW models for the tank/type 

listed in Row 1. 

†The “total barrier performance needed” is calculated by assuming the entire FTF tank inventory is located in 

the pore water of the contaminated zone. While virtually impossible, assuming the total inventory is available to a 

potential receptor is necessary to provide a starting point from which to evaluate the contributions of various barriers 

to reducing risk and to gauge the relative residual risk associated with each key radionuclide listed based on 

inventory and groundwater pathway dose conversion factor (measure of risk) of each radionuclide. The 

contaminated zone is assumed to be one inch thick with a porosity of 0.27. For example, a value of “6” for Tc in 

the first row corresponds to a factor of 106, or 1,000,000, the factor by which the concentration in the waste zone 

needs to be reduced to produce a groundwater concentration at the point of compliance equivalent to 0.25 mSv/yr 

[25 mrem/yr] total effective dose equivalent based on DOE biosphere modeling in the FTF PA. 

‡Most tractable 

§Potentially optimistic 

║Dispersion is used in a broad sense to describe diffusion, numerical, and physical dispersion in DOE’s PA 

models. Because Tc is ultimately assumed to be highly soluble and mobile in DOE’s PA model, almost all the 

attenuation of Tc is due to dilution and dispersion. No solubility control is assumed for Tc upon transition to the final 

chemical state. 
3-9 

3.1.2 Monitoring Factor 1.2: Residual Waste Sampling 

To accurately estimate the post-cleaning inventory that will be stabilized in FTF tanks, DOE 

must sample and analyze the residual waste concentration in each tank after it is cleaned, as 

well as characterize the solids density and estimate residual waste volumes. NRC staff will 

review sampling and analysis plans developed for each tank, as they are cleaned. 

NRC’s technical review of sampling and analysis plans should include, but may not be limited 

to, the following considerations: 

• Consideration of intratank waste variability that is important to the sampling design, 

including the basis for assumptions regarding homogeneity and the number of samples 

to be collected. 

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

• DOE’s support for assumptions regarding normality of radionuclide concentration when 

developing deterministic and probabilistic inventory parameters. 

• Sampling of HRRs or basis for removal of HRRs from the list of radionuclides to 

be sampled.6

In addition to review of sampling and analysis plans, NRC staff also will conduct its own 

independent assessment to verify the list of HRRs in DOE’s assessment is complete. 

If additional HRRs are identified, NRC staff will meet with DOE to resolve the discrepancies in 

the list and suggest actions, as appropriate, that DOE could take to ensure that FTF risks are 

appropriately assessed and managed. Technical review efforts under this MA should be 

coordinated with onsite observations of waste sampling to evaluate whether samples are being 

collected in accordance with sampling analysis plan and the quality of data is sufficient to meet 

data quality objectives. 

This MF can be closed following review of the last sampling and analysis plan for an FTF tank 

and following the last planned onsite observation of sampling of an FTF tank (may occur prior to 

the last tank or ancillary equipment being sampled). 

3.1.3 Monitoring Factor 1.3: Residual Waste Volume 

Residual waste volume is multiplied by density and radionuclide concentrations to estimate the 

residual inventory and is, therefore, important to development of the final inventory. As 

documented in its TER (NRC, 2011), NRC staff noted there is significant uncertainty in DOE’s 

current material mapping approach used for volume estimation. NRC staff recommended DOE 

explore methods to improve the process by which it estimates residual waste volumes and 

 

 

6

In its TER (NRC, 2011), NRC staff recommended DOE continue to characterize samples for radionuclides that are 

important to risk. The HRR list is used to target radionuclides for waste characterization. Thus, the HRR list is 

important for determining accurate inventories for the FTF and adequately assessing risk. DOE eliminated certain 

radionuclides from the initial HRR list based on Tank 18 and 19 inventories (Cs-135, U-233, Th-229, and Ra-226). 

Unless DOE can show that the inventories will not be significantly different for other tanks DOE should continue to 

characterize samples for these radionuclides. NRC staff will review sampling and analysis plans to ensure that all 

HRRs are sampled or a basis for exclusion of an HRR is provided. 
3-10 

associated uncertainty, including evaluation of the costs and benefits of alternative technologies 

available for mapping. For example, NRC noted in its TER (NRC, 2011) the following potential 

improvements: 

• DOE could improve the process by which it estimates volume in areas of cleaned tanks 

where relative objects used to make depth comparisons are not available. For example, 

in certain areas in Tanks 18 and 19, which could not be accessed by the Mantis and 

could not be mapped due to lack of relative objects for depth comparison, the mapping 

team applied weights based on other areas that were deemed similar. In the case of 

Tanks 18 and 19, it was not clear if DOE could have obtained access to certain areas of 

the tanks by removing obstacles or creating new points of access. DOE also could have 

more clearly described the process. 

• DOE also could improve the method of characterizing uncertainty and variability in depth 

of waste across the tank floor. For tank volume in Tanks 18 and 19, DOE fit a normal 

distribution to the data. NRC staff notes that artificially fitting a normal distribution for the 

volume may not properly take into account the variability of the depths of residual 

material on the tank floor. Alternatively, DOE also could have assessed the uncertainty 

by looking at the variability in the depths estimated through material mapping and 

developing distribution models based on the specific sample population (weighted for the 

area of each sample). 

In lieu of improving the method by which DOE estimates residual waste volume, DOE could 

manage inventory uncertainty with conservative estimates (i.e., volume estimates that clearly 

err on the side of higher values). 

DOE indicates its intent to improve the method of estimating residual volumes in its PA 

Maintenance Plan (SRR–CWDA–20012–00022). NRC staff will monitor DOE’s progress in this 

area. NRC staff also will attempt to observe DOE’s use of video and photographic records to 

develop residual waste volumes during an onsite observation. This factor will be closed once 

NRC staff concludes DOE has taken steps to improve the process by which it estimates residual 

volumes or shows that DOE has appropriately managed volume uncertainty. The factor may be 

re-opened if NRC staff identifies issues with DOE’s approach to developing or consideration 

of uncertainty in volumes estimates. 

3.1.4 Monitoring Factor 1.4: Ancillary Equipment Inventory 

The low risk significance of ancillary equipment to meeting the 10 CFR 61.41 PO is predicated 

on the assumed inventory for key radionuclides in DOE’s PA. Therefore, the inventory for 

ancillary equipment should be confirmed to support NRC staff’s understanding of the low risk 

significance of these FTF components. DOE indicated, in response to NRC comment 

(SRR–CWDA–2009–00054, Rev. 0), its intent to verify PA assumptions regarding transfer line 

inventories consistent with Section 8.2, “Further Work” in DOE’s PA (SRS–REG–2007–00002, 

Rev. 1). NRC staff will discuss with DOE its schedule for characterization of transfer lines to 

ensure conclusions regarding the relatively low risk estimates for transfer lines are confirmed. 

Additionally, transfer line inventories are important for the intruder analysis because DOE 

assumes an intruder can more easily access the residual inventory in a transfer line than in a 

tank. Transfer line inventories are discussed in more detail in Chapter 4, which includes 

information on MFs related to assessing compliance with the 10 CFR 61.42 PO. 

 
3-11 

This MF can be closed once NRC staff concludes that DOE characterization has confirmed the 

low risk of ancillary components. 

3.1.5 Monitoring Factor 1.5: Waste Removal (As It Pertains to ALARA) 

In the final FTF waste determination (WD), DOE cites its ability to meet the the Ronald Reagan 

National Defense Authorization Act for Fiscal Year 2005 (NDAA) criteria “removal of HRRs to 

the maximum extent practical” as the primary means by which it meets the ALARA criteria in 

10 CFR 61.41. NRC will evaluate removal to the maximum extent practical for each cleaned 

tank to ensure DOE disposal actions are consistent with ALARA criteria. NRC staff will assess 

DOE compliance with ALARA objectives through review of DOE documentation completed in 

conjunction with the federal facility agreement closure process. As provided in NRC guidance 

[NUREG–1854 (NRC, 2007)], NRC staff also should pay special attention to the distribution of 

residual inventory in the cleaned tanks to ensure compliance with ALARA (e.g., removal of 

waste from areas susceptible to preferential pathways, such as tank walls). 

This MF can be closed once all FTF tanks are cleaned and NRC staff has reviewed DOE 

documentation of removal to the maximum extent practical. 

Closure of Monitoring Factors Related to MA 1 “Inventory” 

NRC staff expects that MFs related to inventory will be closed after tank cleaning activities and 

subsequent post-cleaning sampling activities are completed for FTF tanks. 

3.2 MA 2 “Waste Release” 

Importance of MA 2 “Waste Release” 

In the PA reference (or best-estimate) case, DOE assumes for many key radionuclides that 

concentrations released from the tanks are limited to low values for long periods of time. Key 

radionuclide concentrations in the waste zone are limited through solubility control and the 

imposition of solubility (or concentration) limits. If waste zone concentrations are limited to low 

values, then exposure to a member of the public that may result from use of contaminated 

groundwater at the points of compliance (maximum concentrations on the 1 or 100 m 

boundaries) also will be limited. Solubility (or waste release) assumptions are, therefore, 

important to DOE’s demonstration of compliance with the 10 CFR 61.41 PO and are considered 

a key component of NRC staff’s monitoring program. 

The solid phases that are assumed to be present in the waste (or contaminated) zone dictate 

the solubility (or concentration) limits of key radionuclides. The key radioelements that are

(i) important to dose and (ii) sensitive to solubility limits are Tc, Np, and Pu. Solubility limits for 

these elements are modeled, in DOE’s PA, for (i) pure phases consisting only of the key 

radionuclide itself as a precipitated solid and (ii) in the case of Tc and Pu, as co-precipitated7

with iron-bearing mineral solids in the waste residue. NRC staff will, therefore, focus on these 

three elements, their assumed solubility-limiting phases, and associated solubility limits during 

FTF monitoring under MA 2. 

 

7

DOE uses the term “co-precipitated” in a broad sense to refer to the incorporation of key radionuclides into a solid 

iron mineral (rather than being a pure solid comprised of just that key radionuclide). The solubility of the key 

radionuclide is assumed to be controlled by the solubility of the iron mineral. 
3-12 

In addition to the solubility limiting phases and associated solubility limits for key radionuclides, 

assumptions regarding the length of time that key radionuclides remain in a low solubility phase 

also are important to the compliance demonstration from a timing perspective (i.e., DOE relies 

on the two largest key radionuclide peak doses of approximately 58

 and 69 mSv/yr 

[500 and 600 mrem/yr] from Pu-239 and Tc-99, respectively, occurring after the 10,000 year 

compliance period because the peak doses from Pu-239 and Tc-99 are both greater than the 

PO of 0.25 mSv/yr [25 mrem/yr]. DOE assumes groundwater infiltrating the tank system will be 

conditioned by the tank grout used to stabilize the waste residuals through which it must first 

flow10 to get to the contaminated zone. Conditioning is assumed to occur for thousands to tens 

of thousands of years (purple barriers in Figure 3-4). Conditioning of the groundwater through 

its interactions with tank grout is important because DOE assumes the chemical properties of 

the conditioned groundwater in its models to help maintain the low solubility of key radionuclides 

in the contaminated zone. It is not until the beneficial tank grout components, which help 

maintain the low solubilities, are depleted through their interactions with infiltrating groundwater 

that Eh11 increases and pH12, decreases allowing the most risk-significant radionuclides at FTF 

to be released at higher solubilities and rates in DOE’s reference PA case. Therefore, the 

longevity of the chemical conditioning of infiltrating groundwater that maintains low solubility is a 

function of both (i) the flow path of water movement through the grout mass (e.g., bypass flow 

through preferential pathways with minimal contact of water with grout or matrix flow through the 

grout monolith with maximum contact of water with the grout) and (ii) the geochemical 

interactions between the water and the contacted grout mass. The assumptions regarding the 

movement of infiltrating water through the grout mass are discussed further in MA 3 

“Cementitious Material Performance,” Section 3.2. Assumptions regarding the longevity of 

reducing conditions and high pH that are based on DOE’s geochemical modeling are the 

subject of this MA and are discussed in more detail under MF 2.2. 

 

8

 DOE provided an updated dose projection around 2.5 mSv/yr [250 mrem/yr] for Pu-239 in Tanks 18 and 19 special 

analyses (SRR-CWDA-2010-000124, Rev. 0), “conservative Eh” case. 

9

As documented in its TER, DOE has provided information to support a significantly lower inventory for Tc-99 at FTF. 

Therefore, the peak dose from Tc-99 is likely over-estimated. 10This is true for DOE’s reference or best-estimate PA case. However, in an alternative conceptual model, not 

explicitly modeled by DOE, the groundwater table may periodically rise above the bottom of the tanks and lead to 

limited or unconditioned release of key radionuclides from the contaminated zone. NRC staff discusses this 

alternative conceptual model for waste release under MA 3 “Cementitious Materials Performance.” 11Eh is a measure of oxidation-reduction potential or electron activity (or concentration). Eh is measured in millivolts 

and varies from approximately -500 to +800 in natural environments. Many key radionuclides are less mobile or less 

soluble at lower values of Eh or what is referred to as “reducing conditions.” Solubility of many key radionuclides 

increases when Eh value rises (e.g., Pu solubility increases significantly when Eh rises above a value of around 

+0.45 volts in DOE’s updated solubility modeling (Denham, 2012) or when the system becomes “oxidized”). 

Oxidation signals the transition from a chemical state that DOE refers to as Reduced Region II to a chemical state 

referred to as Oxidized Region II. The transition from reduced to oxidized conditions is marked in Figure 3-4 by the 

vertically oriented green-dashed line. 

12Measure of hydrogen ion activity (or concentration) or measure of acidity. The pH is a unitless number calculated 

as the negative of the log of the hydrogen ion concentration that is measured in mol/L. The pH of the Upper Three 

Runs aquifer at SRS ranges from 5.2 to 7.7 (Prikryl and Pickett, 2007). Undegraded cementitious materials tend to 

increase pH to values as high as 12.5. In DOE’s reference (or best-estimate) case, a decrease in pH to 

approximately eight or nine generally leads to increases in solubility limits or releases from the tanks. When pH 

decreases to that value, a chemical transition is assumed to occur from what DOE refers to as Oxidized Region II to 

Oxidized Region III. The Eh-based chemical transition discussed in the preceding footnote occurs prior to the 

pH-based chemical transition, with the two transitions delineating the three chemical states, with a solubility specified 

for each key radionuclide and chemical state, which DOE assumes in its PA. 
3-13 

Figure 3-4. Barriers to Timing in the U.S. Department of Energy’s F-Tank Farm Reference 

(or Best Estimate) Performance Assessment Case
3-14 

NRC Monitoring Under MA 2 “Waste Release” 

As listed in Appendix A and documented in more detail in NRC’s TER (NRC, 2011), NRC will 

consider the following MFs related to waste release that are considered important to meeting 

the 10 CFR 61.41 PO: 

• Solubility Limiting Phases/Limits and Validation. 

Due to DOE’s reliance on timing of peak dose to demonstrate compliance, NRC staff also will 

monitor the following factor, which is considered necessary for DOE to demonstrate compliance 

with the 10 CFR 61.41 PO: 

• Chemical Transition Times and Validation. 

More detailed discussion regarding NRC’s MFs related to waste release is available in 

Appendix C. 

3.2.1 Monitoring Factor 2.1: Solubility Limiting Phases/Limits and 

 Validation (Applies to Tank 18, May Apply to Other Tanks Later) 

Given its importance to the timing and magnitude of peak dose, in its TER, NRC staff 

recommended DOE conduct waste release experiments to increase support for key modeling 

assumptions related to (i) chemical forms of key radionuclides in residual wastes and (ii) 

expected solubility of key radionuclides under a range of environmental or service conditions 

that the contaminated zone is expected to be exposed to over time. 

For Tank 18, which has been cleaned and was scheduled for near-term closure in calendar 

year (CY) 2012, NRC continues to recommend that DOE design and perform waste release 

experiments using actual tank residual samples as soon as practical. DOE staff should discuss 

its plans with NRC to ensure experiments are designed to optimize their potential usefulness in 

supporting the 10 CFR 61.41 compliance demonstration. This monitoring activity is considered 

to be the highest priority by NRC staff at this time from both a timing and importance 

perspective. Furthermore, as indicated in Table 3-1, NRC staff thinks that in addition to being 

one of the most important barriers in the FTF PA, determining the solubility of Pu is expected to 

be one of the more tractable key technical issues. Given its importance to Tank 18 risk and 

overall tank closure, DOE also should consider performing solubility experiments for Np-237 at 

this time. Although NRC staff did not identify any issues with DOE’s assumed Np-237 

solubilities, DOE has not provided sufficient support for the assumed level of performance of the 

basemats in its FTF PA. DOE also assumes lower solubilities for Np-237 in its H-Area Tank 

Farm (HTF) PA compared to those assumed in the FTF PA, and if supported through 

experimentation, could alleviate the burden of providing additional support for other Np-237 

barriers, such as the vault basemats. Table 3-1 shows the importance of the basemat in 

meeting the 10 CFR 61.41 PO. If the basemat does not perform as well as assumed in DOE’s 

reference of “best estimate” case, data on solubility control may assist in demonstrating that 

POs can be met. 

For tanks that have not been cleaned, DOE should consider the effects of reagents (e.g., oxalic 

acid) used to remove radionuclides from the tank residue, including formation of new 

compounds that may alter leachability of key radionuclides. Execution of this monitoring 

activity may be contingent on results of other analyses. For example, final Tc-99 inventories 

in Type I tanks, as described in Section 3.1, may determine the need for Tc-99 waste 
3-15 

release experiments. 

This MF can be closed once DOE provides experimental support for the assumed solubilities of 

key radionuclides relied on for performance. The results of near-term waste release 

experiments may inform the extent to which additional recommendations made in NRC’s TER 

(NRC, 2011) would need to be implemented by DOE. Should the results of the experiments 

indicate less than favorable performance, NRC staff expects DOE to assess the impact of the 

results on the PA. NRC staff also will assess the need for additional experiments, data 

collection, and modeling to provide support for key barriers in DOE’s PA that might serve to 

mitigate underperformance of chemical barriers. If the results of the experiments show that key 

radionuclides are strongly retained in the residual waste, NRC staff expects that in addition to 

this MF, other MAs or MA components will become less important and can be closed. 

3.2.2 Monitoring Factor 2.2: Chemical Transition Times and Validation 

DOE relies on barriers that delay the timing of peak dose to demonstrate compliance with the 

POs in 10 CFR 61.41, therefore, PA assumptions regarding the timing of transition of key 

radionuclides to higher solubility phases are important to the FTF compliance demonstration. 

DOE relies on geochemical modeling to estimate the time at which two key chemical transitions 

take place: (i) the transition from reduced to oxidized conditions reflected in an increase in Eh 

(see bright green, vertically oriented dashed lines in Figure 3-4), and (ii) the transition from a 

relatively high to a relatively low pH (see red, vertically oriented dashed lines in Figure 3-4) as 

the cementitious materials continue to degrade over time. In its TER (NRC, 2011), NRC staff 

discussed concerns with the geochemical modeling results, which may be attributable to 

assumptions such as (i) the characteristics of the infiltrating groundwater, (ii) the solid phases 

that comprise the tank grout, (iii) uncertainties in the thermodynamic data used in the modeling, 

or (iv) assumptions regarding the ability of grout components to react with and condition 

infiltrating groundwater and the residual waste. 

As part of this MF, NRC staff also will evaluate the efficacy of DOE’s use of two chemical 

transitions, three chemical states, and no more than three solubilities for each key 

radionuclide with solubility changes assumed in DOE’s PA to occur at the same time for 

each key radionuclide for a given tank type. It may be more reasonable to assume that 

solubility of each key radionuclide has a unique sensitivity to Eh and pH, making it difficult to 

make generalizations about the manner in which solubility changes over time. This 

assumption is important because the timing of transition to higher solubility and releases may 

be critical to DOE’s compliance demonstration, as indicated above. The adequacy of DOE’s 

approach to modeling solubility changes will be evaluated through NRC review of the literature, 

DOE-generated geochemical modeling, or through independent geochemical modeling. 

NRC staff also may observe DOE experiments related to this MF in conjunction with an 

onsite observation at the FTF. This MF can be closed when (i) DOE shows that chemical 

transition times are no longer important to its compliance demonstration (i.e., predicted dose is 

less than the dose standards for all time) or (ii) DOE provides adequate (e.g., experimental 

validation) support for its assumptions regarding chemical transition times. 

Closure of the Group of Monitoring Factors Related to MA 2 “Waste Release” 

The MF regarding chemical transition times can be closed when DOE completes experiments to 

study the evolution of pH and Eh in the tank grout over time to provide more accurate 

estimates of chemical transition times to higher solubility chemical conditions. Alternatively, 
3-16 

this MF can be closed if DOE can provide support that the highest solubility for each key 

radionuclide developed under MF 2.1, under any relevant geochemical condition will not lead 

to an exceedance of the 10 CFR 61.41 PO (i.e., DOE no longer relies on timing of the peak 

dose to demonstrate compliance) or adequate support for other barriers relied on to delay 

the timing or reduce the magnitude of peak dose for key radionuclides is generated to 

demonstrate compliance. 

Depending on the results of initial waste release experiments and other factors (e.g., expected 

final inventories for Tc-99 in Type I tanks), the factors in this MA can be closed in the short-term 

following Tank 18 waste release experiments. Likewise, if closed, NRC could reopen the MFs 

in this MA as additional information is obtained on expected final tank inventories or the 

performance of other important barriers. 

3.3 MA 3 “Cementitious Material Performance” 

Importance of MA 3 “Cementitious Material Performance” 

As illustrated in Figure 3-4 (see dark green barrier), the steel liners (or tanks) serve as an 

important barrier significantly delaying the timing of releases from FTF tanks for thousands to 

tens of thousands of years. In the case of Types I and III/IIIA tanks, DOE assumes the tanks do 

not fail until after the 10,000 year compliance period. The longevity of the steel liners is directly 

related to PA assumptions regarding the capability of the concrete vaults, which house the steel 

liners, to provide an effective barrier to fluid flow, thereby minimizing the transport of corrosive 

agents such as chloride, oxygen, and carbon dioxide to the surface of the steel liners. 

Therefore, NRC staff considers assumptions regarding the hydraulic performance of the 

concrete vaults under conditions of both infiltrating water from above or flooding groundwater 

from below an important component of DOE’s compliance demonstration. Type IV tanks at FTF 

are particularly susceptible to early corrosion due to the fact that the tanks (i) have a thin layer 

of concrete applied using a technique known as Shotcrete, (ii) do not have an annulus between 

the “Shotcrete” and liner, (iii) do not have a tank top, (iv) have bottoms located in close proximity 

to the water table, (v) have experienced groundwater in-leakage in the past, and (vi) have the 

thinnest steel liners. 

As discussed in MA 2 “Waste Release,” DOE relies on the timing of peak dose occurring 

after the 10,000 year compliance period to meet the 10 CFR 61.41 PO in its reference (or best 

estimate) PA case13. Therefore, any barrier that delays the timing of peak dose is important to 

DOE’s compliance demonstration for the FTF. The reducing tank grout and contaminated zone 

chemical barriers (represented by a single purple barrier in Figure 3-4) are two of the most 

effective barriers in DOE’s FTF PA in delaying the timing of the peak dose. Chemical transition 

times are directly dependent on the nature of water flow through the grouted tanks and on the 

likelihood and frequency of tank flooding due to water table rise. For example, NRC staff has 

technical concerns related to the potential for: (i) groundwater to bypass or have minimal 

contact with the reducing tank grout as a result of flow via preferential pathways such as cracks 

or shrinkage gaps and (ii) water table rise above the tank bottoms.14 NRC staff is concerned 

 

13Type I tanks and Tank 18 are the sources of exceedance of the 10 CFR 61.41 standard in DOE’s FTF PA. DOE 

thinks the Type I tank inventories of Tc-99 that led to the exceedance were overestimated in the FTF PA. Updated 

special analyses show the peak dose from Tank 18 may be above or below the 0.25 mSv/yr [25 mrem/yr] dose 

standard, depending most significantly on assumed solubility of Pu-239. NRC staff will evaluate the updated 

modeling under MA 2. 

14Water table rise is especially important for Type IV tanks, which have bottoms located at or near the water table and 

for Type I tanks (Amidon, et al., 2012).
3-17 

because these scenarios could lead to a situation where relatively oxidized and acidic 

groundwater has minimal contact with the tank grout that DOE’s PA assumes will condition the 

groundwater to higher pH and lower Eh, thereby maintaining the low solubility of key 

radionuclides in the contaminated zone. If the infiltrating groundwater is not well-conditioned, 

key radionuclides may have higher solubility and be released at significantly higher 

concentrations, much earlier in time. In fact, the peer review group tasked by DOE to review 

DOE’s Pu solubility modeling indicated that flow through cracks in the grout should be expected 

(Cantrell, et al., 2011). Therefore, NRC staff will monitor DOE’s FTF PA assumptions related to 

the nature of water flow into the contaminated zone, including assumptions regarding the extent 

to which in-tank water is conditioned by the tank grout, the timing of chemical transitions, and 

the magnitude of key radionuclide releases and dose. 

Additionally, because preferential flow through the tank grout is a strong function of the extent 

to which FTF tank grout shrinks and cracks, NRC staff also will monitor DOE FTF PA 

assumptions regarding shrinkage and cracking. Specifically, NRC staff will monitor DOE’s 

efforts to minimize tank grout shrinkage through additional shrinkage compensating admixtures. 

Shrinkage of grout away from tank walls and intratank components may lead to formation of 

preferential flow pathways. The Center for Nuclear Waste Regulatory Analyses (CNWRA®) 

staff, who have developed and tested physical analog models of NDAA-type grout monoliths, 

have observed shrinkage between grout lifts and flow lobes15 with both horizontally and 

vertically oriented, imperfectly bonded seams that form at their interfaces when placing relatively 

viscous formulations that tend to form lobes (Figure 3-5), enhancing preferential flow through 

the grout monolith. 

Because temperature rise and gradients that form due to grout curing can lead to thermal 

cracking, NRC staff will monitor DOE’s assessment and, as applicable, plans to reduce the 

potential for thermal cracking. NRC staff also will monitor other FTF design features to minimize 

adverse conditions such as alkali silica reaction (ASR) that results in dissolution of silica phases 

and cracking due to alkali silicate gel formation and expansion. The risk of ASR-based 

dissolution and cracking increases in the presence of cement or externally introduced alkalis, 

amorphous silica phases of certain concrete aggregates, and moisture. Although the final 

formulation used for Tanks 18 and 19 has relatively low cement content compared to other 

concretes used in construction applications, DOE’s final formulation uses an aggregate 

potentially susceptible to ASR. Current standards calling for short-term testing (16 day tests) 

may not be sufficiently robust to evaluate the potential for long-term degradation associated with 

ASR. Finally, NRC staff will monitor FTF design features to minimize cracking of the tank grout 

due to differential settlement. Differential settlement may occur due to loading stresses 

imposed by the weight of the closure cap and may be enhanced by dissolution of calcareous 

zone materials at depth and subsequent collapse of overlying materials (see Chapter 6). 

Because the DOE FTF PA made a number of assumptions regarding the chemical and 

hydraulic properties of the as-emplaced tank grout used to fill the HLW, NRC will monitor DOE’s 

efforts to develop and test grout formulations that will meet PA requirements. Additionally, NRC 

staff will monitor DOE’s efforts to deliver a high-quality grout from design placement in the field 

that performs as well as DOE assumed in its FTF PA. 

After releases occur through the steel liners, the tank basemats are estimated by DOE’s FTF 

PA to serve as an important barrier for many key radionuclides. In fact, in some cases, the 

tank basemats have savior characteristics in DOE’s PA (i.e., basemats can compensate for 

 

15A grout flow lobe is a fan-shaped mass of grout that forms on a slope by the changing direction of flow.
3-18 

Panel A 

Panel B 

Figure 3-5. Tank Grout Features Important to Performance: 

Panel A is a Close-In View of Grout Seams and Gaps (Dinwiddie, et. al., 2012, Figure 3-8) 

and Panel B is an Example of Grout Lobes From F-Tank Farm Tank 18 Grouting 

(Photo Taken During June 12, 2012 Onsite Observation)

 
3-19 

other failures or act in isolation to mitigate releases from the tanks when all other engineered 

barriers have failed). For instance, the basemats may serve as the most effective barrier in 

the FTF PA after long periods of time when the closure cap, steel liner, and tank grout have all 

failed as hydraulic barriers and key radionuclide solubility limits are a their highest levels 

(Oxidized Region III). However, anecdotal and other evidence exists that preferential flow 

pathways may be present in the tank basemats and that these pathways may have a significant 

impact on contaminant flow and transport. 

For example, in 1960, waste leaked from HTF Tank 16 is thought to have breached the 

concrete vault and entered the surrounding soil (Davis, 1977). Tank documentation suggests 

that groundwater has historically intruded into FTF tank vaults following water table rise 

(McNatt, 1982). Therefore, NRC staff are concerned that assumptions regarding the ability of 

the concrete vaults to reduce radionuclide releases from the FTF tanks are overly optimistic. 

For these reasons, NRC staff will monitor assumed basemat performance for key radionuclides 

such as Pu and Np at FTF. 

NRC Monitoring Under MA 3 “Cementitious Material Performance” 

As listed in Appendix A and documented in more detail in NRC’s TER (NRC, 2011),16 NRC staff 

will consider the following MFs related to cementitious material performance that are considered 

important to meeting the 10 CFR 61.41 PO: 

• Concrete Vault Performance (As it Relates to Steel Liner Corrosion), 

• Grout Conditioning, 

• Shrinkage and Cracking, 

• Grout Performance, 

• Basemat Performance, and 

• Waste Stabilization (As It Pertains to ALARA). 

More detailed discussion regarding NRC’s concerns related to some of the aforementioned MFs 

is available in Appendix D. 

3.3.1 Monitoring Factor 3.1: Concrete Vault Performance 

 (As It Relates to Steel Liner Corrosion) 

DOE assumes the grouted17 concrete vaults that house the HLW tanks at FTF act as hydraulic 

barriers to fluid flow and provide a relatively passive environment for the steel liners or tanks, 

significantly limiting tank corrosion following closure. In some cases (for Types I and III tanks), 

DOE assumes steel liners are a barrier to fluid flow and prevent significant releases from the 

tanks during the entire performance period. Therefore, NRC staff will review reports, analog 

studies, and other information used to support DOE’s assumption regarding initial conditions 

and performance of the concrete vaults. For example, NRC staff will review annual tank 

inspection reports that provide information regarding trenching, scarifying, and cracking of the 

concrete vaults, as well as information about groundwater intrusion into the tank vaults. NRC 

staff will review reports related to previous events that led to potential releases or groundwater 

 

16Monitoring factors related to cementitious material performance are described in NRC staff’s TER (NRC, 2011) 

except for monitoring factor 3.3 related to FTF tank grout design measures to minimize shrinkage and cracking. 

Mitigation of cracking is important to minimizing the occurrence of preferential flow pathways through the tank 

system, which is, however, discussed in detail in NRC staff’s TER. 

17Type IV tanks have no annulus and are, therefore, not grouted at the time of closure. 
3-20 

in-leakage through joints or cracks in the concrete vaults. Analog studies could include review 

and evaluation of information obtained from West Valley or other analog sites to better 

understand the potential for and rates of corrosion of HLW tanks/components, as well as 

mitigative design measures. As part of this MF, NRC staff also will consider the potential for 

earlier steel liner failure than assumed in DOE’s PA due to corrosion of steel components 

(e.g., rebar) in the concrete vaults that are close to the vault surface. 

If DOE performs additional modeling or experiments to study the potential for transport of 

deleterious species into the tank vaults and subsequent corrosion of steel liners or tanks, NRC 

staff will review the documentation or provide input on the design and results of the 

experiments. Experiments to study steel liner corrosion are expected to be relatively difficult to 

implement with unknown benefit compared to other experimental investigations recommended 

in NRC’s TER and discussed in this monitoring plan. Therefore, NRC staff does not consider 

these experiments to be a high priority at this time. NRC staff will assume steel liners will not be 

effective at mitigating releases for the long time periods DOE relies on the steel liners for 

performance in the FTF PA and will investigate the support for the performance of other barriers 

to ensure POs can be met until such support for steel liner performance is provided. Should 

results of other investigations indicate FTF barriers that DOE relies on in its reference (or 

best-estimate) PA case are not expected to perform as well as assumed, NRC will give more 

thought to methods by which DOE could obtain additional support for steel liner performance 

assumptions. 

3.3.2 Monitoring Factor 3.2: Groundwater Conditioning 

As stated above, DOE assumes that infiltrating groundwater is able to flow through every pore 

space of the grout monolith, rather than coming into contact with a relatively small volume of 

potentially armored18 tank grout along crack or fracture faces. Reactions between the infiltrating 

groundwater and tank grout cause the pH to increase from approximately 5 to 12 and the Eh to 

decrease from as high as +500 mV to as low as -600 mV. Tank groundwater conditioning to 

high pH and low Eh is important to maintaining low solubility, concentrations, and dose, 

because the chemistry of the groundwater dictates the solubility limits assigned to key 

radionuclides in the contaminated zone in DOE’s reference PA case. If the infiltrating 

groundwater that has a drastically different chemistry than DOE assumed in the PA is able to 

contact the radioactivity in the contaminated zone, then concentrations leached from the tanks 

could be significantly higher than predicted much earlier in time. 

Because groundwater table rise and preferential flow through the tank grout may lead to higher 

solubilities and releases from the tanks, NRC staff will monitor DOE experiments to study the 

potential for groundwater flow through cracks that may form in the tank grout (the potential for 

cracking is addressed in MF 3.3). If DOE cannot rule out bypass flow through the tank grout 

under MF 3.3 or water table rise above the bottom of FTF tanks under this MF, then it will be 

important for DOE to demonstrate the extent to which groundwater is conditioned when flow is 

primarily through preferential pathways through the tank grout. Although DOE assumes little to 

no conditioning in Configuration19 G, a tank grout bypass scenario evaluated in response to 

 

18Armoring may occur through precipitation of calcium carbonate on fracture and crack faces through a concrete 

degradation process referred to as carbonation. Armoring may preclude interaction of infiltrating groundwater with 

tank grout components interior to fracture faces that serve to condition the groundwater and maintain low solubilities 

or concentrations of key radionuclides. 

19The term “configuration” is used in DOE’s PA to describe various scenarios that are generally run to evaluate 

differences in waste release model and parameter assumptions. 
3-21 

NRC RAIs,20 the dose prediction in Configuration G exceeded the 10 CFR 61.41 PO within the 

10,000 year compliance period. Although DOE assumes the likelihood of Configuration G is 

low, NRC staff thinks the likelihood of this scenario may be underestimated. Therefore, more 

credit for groundwater conditioning may be needed in this alternative flow scenario to 

demonstrate compliance with the PO. 

NRC staff will monitor DOE experiments or perform its own independent experiments to better 

understand the nature of flow through the tank grout as it impacts the extent to which infiltrating 

groundwater interacts with and is conditioned by the tank grout (this factor is closely related to 

MF 2.221). If NRC staff concludes that bypass flow through preferential pathways in the tank 

grout is significant, DOE should implement an alternative conceptual model consistent with 

preferential flow through the tank grout to compute chemical transition times. 

NRC staff also will review information regarding water table rise to evaluate the likelihood of 

this alternative conceptual model for waste release. Based on the results of the water table 

rise investigation, an alternative conceptual model may be proposed for a subset of FTF 

tanks to assess the impact on the compliance demonstration. Specifically, NRC staff will 

review historical water table elevation data for FTF wells to assess the likelihood of water table 

rise above the bottom of FTF tanks. NRC staff also will review design and construction of any 

DOE mitigation measures used to ensure that the water table remains below the bottom of FTF 

tanks. The water table is most likely to rise above Type IV tank bottoms, followed by Type I 

tank bottoms because of the lower elevations at which these tanks were constructed (Amidon, 

et al., 2012). 

In the case where flow is primarily through preferential pathways, such as shrinkage gaps and 

cracks, DOE should design experiments to provide information on the expected level of 

groundwater conditioning for this type of flow. DOE has designed and constructed a lysimeter 

field experiment at the Savannah River Site (SRS) to study the mobility of various radionuclides 

in a saltstone waste form. This experiment could be leveraged to study the potential for 

groundwater conditioning for what is expected to be a relatively impermeable cementitious 

waste form. If infiltrating groundwater is not conditioned, DOE could design and construct 

column experiments with cracked FTF grout to study the extent to which groundwater may be 

conditioned by the tank grout under what is currently considered a more realistic scenario by 

NRC staff. 

NRC will review documentation provided by DOE to support assumptions regarding the extent 

of groundwater conditioning for as-emplaced FTF tank grout. NRC staff may conduct the 

technical review activities in conjunction with an onsite observation to observe any laboratory or 

field experiments in this area. If results of waste release experiments conducted under MF 2.1 

show key radionuclides in waste residuals have sufficiently low solubility when in contact with 

unconditioned SRS groundwaters, MF 3.2 related to the extent of conditioning (and 2.2 related 

to the longevity of conditioning) will no longer be needed by DOE to support the compliance 

 

20Configuration G is evaluated in DOE RAI responses (SRR-CWDA-2009-00054, Rev. 1) and discussed in more 

detail in NRC staff’s TER (NRC, 2011). 

21The difference between MF 2.2 and MF 3.2 is that MF 2.2 focuses on the actual geochemical reactions that are 

occurring between groundwater and tank grout components that determine how the chemistry of the groundwater 

changes over time, whereas MF 3.2 assesses how groundwater flows through the tank grout. In other words, MF 2.2 

is focused on the chemical aspects of how groundwater and tank grout components interact, while MF 3.2 is focused 

on the extent to which the nature (fracture or matrix) and rates of flow through the grout impact the ability of the 

groundwater to interact with the tank grout. Because MF 3.2 may influence the extent of reaction; it also may 

influence chemical transition times and is therefore closely related to MF 2.2. 
3-22 

demonstration and can be closed. If MF 2.1 results indicate unconditioned flow may lead to 

unacceptably high doses, then this MF will need to be evaluated by NRC and can be closed 

after DOE (i) shows matrix flow through the grout will dominate waste release or (ii) provides 

information to support assumptions regarding the level of groundwater conditioning for 

degraded (cracked) grout. 

3.3.3 Monitoring Factor 3.3: Shrinkage and Cracking 

As discussed, there are many mechanisms that could lead to cracking or creation of void space 

in the tank grout, which increases the likelihood of early, risk-significant releases and doses 

from the FTF tanks including the following: 

• Steel Component Corrosion, 

• Shrinkage Gap Development and Poor Grout-Bond Quality, 

• Thermal Cracking, 

• ASR, and 

• Differential Settlement and Related Cracking. 

DOE should consider design measures to minimize the occurrence of negative features, events, 

or processes that may promote shrinkage or cracking. For example, DOE should consider 

removal of in-tank equipment that could lead to development of shrinkage-induced annuli 

around equipment or corrosion of steel components and associated cracking due to corrosion 

product expansion. DOE also should promote the ability of the tank grout to fill all void spaces 

(e.g., grout should be self-leveling) to minimize imperfectly bonded grout seams and voids that 

may form in between grout pours. DOE should research and evaluate shrinkage compensating 

agents for use in its grout formulations to minimize shrinkage, shrinkage gap formation, and 

creation of annuli and void space within the tank grout. DOE should ensure temperature 

gradients are sufficiently low to prevent excessive thermal cracking. Calculations could be 

conducted to evaluate potential thermal gradients and/or instrumentation could be used to 

evaluate as-emplaced thermal evolution of the tank grout. Finally, DOE should ensure the tank 

grout is designed to consider the potential for cracking due to differential settlement (see 

Chapter 6 on site-stability for more detailed discussion). It also may be useful for DOE to 

research and deploy methods of detecting early crack development within tanks (e.g., through 

use of devices such as acoustic sensors). 

NRC staff will review grout formulations, calculations, research, test methods, and results to 

ensure the disposal facility is designed to minimize fast flow path development. NRC staff may 

conduct technical reviews in conjunction with onsite observations that could include such 

activities as video inspections of grout pours, observations of grout tests, and inspection of 

test specimens. 

It is important to note the intended low matrix hydraulic conductivity of the grout monolith may 

accentuate fast crack or bypass flow through the system because the grout matrix is expected 

to be quite impermeable to water flow, particularly for Type IV tanks that do not have cooling 

coils and are assumed, therefore, to degrade more slowly than grout in tanks containing internal 

fixtures. If it becomes clear that (i) it will be difficult to prevent preferential pathways from 

forming in the system, (ii) these preferential pathways may conduct a significant amount of 

unconditioned water, and (iii) unconditioned releases may exceed the dose standard, then it 

might be useful for DOE to explore methods under MF 3.2 to enhance contact of infiltrating 
3-23 

water with the tank grout if such contact is shown to condition infiltrating groundwater and limit 

releases from the tanks to non-risk-significant levels. 

MF 3.3 can be closed when DOE demonstrates (i) preferential fast flow into the waste zone will 

not occur or (ii) preferential fast flow into the waste zone will not adversely impact performance 

(e.g., the PO can be met under all chemical conditions as discussed in more detail under MA 2 

“Waste Release”). 

3.3.4 Monitoring Factor 3.4: Grout Performance 

After issuance of NRC’s TER (NRC, 2011), DOE generated a number of documents developing 

and testing a final grout formulation for closure use in Tanks 18 and 19. NRC will perform 

technical review activities related to DOE’s testing and development of grout formulations to 

meet design specifications. Additionally, NRC will monitor DOE’s efforts to deliver a grout mix 

of sufficient quality to meet performance assumptions in DOE’s FTF PA from design to 

as-emplaced conditions in the field. NRC staff will review relevant procedures and 

documentation related to such items as grout material procurement, production, testing, 

acceptance and placement in FTF components. NRC staff will perform technical review 

activities in conjunction with onsite observations. Onsite observations will include such activities 

as observations of grout material storage, tests, and acceptance of grout materials, live video 

streams of grouting operations, review of archived video footage, review of batch tickets for 

accepted and rejected loads, tour of the command center, and observation of mock-up tests or 

visual examination of test specimens. NRC staff can close this MF after it completes (i) review 

of DOE-generated grouting documentation and (ii) monitoring of grouting operations. If NRC 

identifies any issues, DOE also must adequately address the issues or provide plans to address 

the issues under another MF. 

3.3.5 Monitoring Factor 3.5: Basemat Performance 

The basemat is the last engineered defense against releases from FTF tanks. For some key 

radionuclides such as Np and Pu, it is the most effective barrier, limiting peak releases and 

doses in DOE’s reference PA case. Because the basemats are, in most cases, more than 

50 years old and have supported the weight of the waste-filled HLW tanks for many years, it is 

expected the basemats are chemically degraded and cracked. Additionally, tank vaults may 

contain features conducive to by-pass flow (e.g., leak detection channels or construction joints). 

Because attenuation of Np and Pu in the basemat is very important to the compliance 

demonstration and may be less than assumed in DOE’s PA in the case of (i) flow through 

cracks or other preferential pathways, or (ii) if sorption potential for these two constituents is 

overestimated, NRC staff will monitor DOE efforts to study basemat sorption for these two 

constituents. DOE should address technical issues that experiments used to support basemat 

distribution coefficients (Kds) for Pu and Np were flawed in that they represented solubility rather 

than sorption. DOE also should address the potential for degradation of the attenuating 

properties of the basemats over time (i.e., old, cracked concrete materials may be less sorptive 

than newer, uncracked concrete materials). NRC staff will review documentation and any 

analog studies that may provide additional information regarding the ability of the concrete 

basemats to attenuate release from FTF tanks, including information regarding groundwater 

inleakage for FTF tanks and release from HTF Tank 16. 

This MF can be closed when sufficient information is available to support assumptions regarding 

attenuation of Np and Pu in the basemats, or when DOE provides sufficient information to show 
3-24 

that Np and Pu doses will be below the dose limits prescribed in the POs with little to no 

performance from the concrete basemats (e.g., solubility limits for unconditioned groundwater 

are sufficiently low or natural attenuation of Pu is sufficiently high to compensate for 

underperformance of the basemat). 

3.3.6 Monitoring Factor 3.6: Use of Stabilizing Grout (As It 

 Pertains to ALARA) 

DOE considers tank and vault grouting consistent with ALARA criteria. In its final WD 

(DOE/SRS–WD–2012–001), DOE explains that residual material remaining in the waste tanks 

after key radionuclides have been removed to the maximum extent practical will be stabilized 

with reducing grout, a chemically reducing environment known to minimize the mobility of the 

contaminants after closure. DOE indicates that waste tank grout fill is designed to have a low 

matrix permeability to enhance its ability to limit the migration of contaminants after closure. 

DOE also indicates that waste tank concrete vaults serve to significantly retard water flow 

through the waste tanks. In addition, DOE will fill the waste tank liners and annular space 

between liner and vault, if applicable, with cementitious material to further limit the amount of 

water infiltration into the waste tanks. 

Consistent with WIR guidance in NUREG–1854 (NRC, 2007), NRC staff will review use of 

stabilizing materials to determine if DOE has made a reasonable effort to optimize mixing or 

encapsulating the waste with the stabilizing material. DOE should evaluate options to move or 

stabilize the waste present along the edge of the tanks that may present a relatively higher risk, 

including options to minimize shrinkage along the tank wall, if deemed ALARA. NRC staff will 

evaluate DOE’s use of stabilizing materials to grout features of the tank and vault system that 

might otherwise lead to preferential flow through the engineered system and into the 

environment (e.g., grouting of leak detection channels and sumps contained within the 

concrete basemats). 

NRC staff will conduct technical reviews and onsite observations under MFs 3.1 to 3.5, bearing 

in mind the additional function of the stabilizing grout to maintain doses ALARA. NRC staff can 

close MF 3.6 when MFs 3.1 through 3.5 are closed, and if NRC staff finds DOE’s use of 

stabilizing cementitious materials consistent with ALARA criteria. 

Closure of the Group of Monitoring Factors Related to MA 3 “Cementitious 

Material Performance” 

MF 3.1 is contingent on the results of other studies. MFs 3.2 and 3.3 can be closed after DOE 

demonstrates that preferential pathways will not occur or will not significantly alter the 

compliance demonstration. MF 3.4 can be closed following grouting of the FTF tanks. MF 3.5 

can be closed when DOE demonstrates that concrete basemats can effectively immobilize key 

radionuclides Np and Pu that are released from the tanks or that solubility control is effective at 

reducing Pu releases to non-risk-significant levels or that natural system attenuation is sufficient 

to compensate for underperformance of the concrete basemats. MF 3.6 will be closed when 

MFs 3.1 through 3.5 are closed, if NRC staff finds stabilization operations consistent with 

ALARA criteria. 

 
3-25 

3.4 MA 4 “Natural System Performance” 

Importance of MA 4 “Natural System Performance” 

The hydrogeological system at FTF performs as a significant natural barrier, helping to 

attenuate key radionuclide releases from FTF tanks to groundwater through such processes as 

dilution, dispersion, sorption,22 and decay.23 Natural attenuation can serve to (i) delay the 

timing of the peak dose and (ii) reduce concentrations and dose at the POC. Therefore, NRC 

staff will monitor natural system performance to assess compliance with the 

10 CFR 61.41 PO. 

NRC staff made two primary recommendations related to natural system performance in its TER 

(NRC, 2011): (i) DOE should obtain support for averaging Kds of multiple oxidation states to 

simulate the transport of Pu in the natural environment and (ii) DOE should provide additional 

data from tracer tests and calcareous zone outcrop locations to allow NRC and DOE to evaluate 

the significance of calcareous zone dissolution on flow and transport from the FTF. As shown in 

Figures 3-3 and 3-4 and Table 3-1, DOE assumes a significant amount of performance is 

achieved for sorption of Pu in the natural system (i) an approximately 10,000-year delay in the 

timing of the peak dose due to travel times in the vadose and saturated zones (Figure 3-4) and 

(ii) a reduction in the peak dose from Pu due to sorption in the natural system by approximately 

a factor of 10 (Table 3-1). The risk significance of the Pu Kds is evident. Regarding 

characterization of the calcareous “soft zones” that are located in the lower portion of the Upper 

Three Runs Aquifer (UTRA), NRC staff is concerned these zones could act as conduits for fast 

groundwater flow, decreasing travel times and potentially minimizing dilution and natural 

attenuation in the aquifer. Site-specific sorption coefficients for the calcareous zones have not 

been developed and it is not clear the extent to which key radionuclide mobility will be affected 

by the presence of these zones. Faster travel times could lead to less decay, higher 

concentrations and earlier peak doses; less dilution and natural attenuation also could lead to 

higher predicted concentrations and doses at the POC. 

NRC Monitoring Under MA 4 “Natural System Performance” 

As listed in Appendix A and documented in more detail in its TER (NRC, 2011),24 NRC staff will 

consider the following MFs related to natural system performance that it considers important to 

meeting the 10 CFR 61.41 PO: 

• Natural Attenuation of Pu, 

• Characterization of Calcareous Zones, and 

• Environmental Monitoring. 

3.4.1 Monitoring Factor 4.1: Natural Attenuation of Plutonium 

Depending on the Kds of Pu assumed in the natural environment, travel times from Tank 18 

to the 1 m or 100 m points of compliance used in the intruder and member of the public dose 

 

22Sorption is used in a broad sense to describe the association of a groundwater contaminant with subsurface 

materials that can (i) lead to longer travel times or (ii) decreased concentration at the point of compliance. 23Decay can be significant when travel times to a well are expected to be similar to the half-life of key radionuclides 

[e.g., for key radionuclides such as Pu-239, Sr-90, and Cs-137 in DOE’s reference (or best-estimate) PA case]. 24This is true except for monitoring factor 4.3 related to environmental monitoring. NRC staff will review data 

collection and associated documentation to ensure the disposal facility is performing as intended. 
3-26 

assessments, respectively, could range from hundreds to tens of thousands of years. NRC staff 

concludes that DOE has not addressed issues associated with its Kds averaging approach,25

with site-specific studies indicating a range of Kds anywhere from a few (three) L/kg to 

thousands (1,000s) L/kg for different oxidation states of Pu, with higher oxidation states of Pu 

tending to be more mobile. Furthermore, DOE has not provided sufficient information regarding 

the expected chemical form of Pu released from the tanks (see discussion under MA 2) and 

potential sorption of Pu released from the tanks in the sediments below. If arguments based on 

travel times are relied on to demonstrate compliance with the POs, then DOE should 

demonstrate that more mobile forms of Pu that can be transported to the 1 or 100 m points of 

compliance in hundreds of years cannot exist in risk-significant quantities in the subsurface at 

SRS. If arguments based on magnitude of peak dose are relied on to demonstrate compliance 

with the POs, then DOE should show that a combination of barriers that may include sorption of 

Pu to natural sediments leads to a dose below the dose-based standards. 

NRC staff will perform technical reviews of DOE research and documentation related to Pu 

sorption in the subsurface of SRS including a recently prepared document re-evaluating vadose 

zone Pu Kds prepared between issuance of NRC’s TER and DOE’s final WD (Almond, et al., 

2012). NRC staff will review results of analog studies, such as the lysimeter studies related to 

Pu release from a saltstone waste form. Although the lysimeter studies consider releases from 

saltstone grouts, the lysimeter studies may provide useful information regarding the potential 

mobility of Pu in the natural soils located above and below the saltstone waste form. However, 

DOE should consider performing experiments that are more relevant to FTF that take into 

account the chemical forms of Pu expected to be leached from the tanks, as well as the impact 

of grout leachate on Pu Kds. 

Technical review activities may be conducted in conjunction with onsite observations of 

any experiments developed to study the attenuation of Pu in SRS soils. This MF can be 

closed when DOE provides support for its treatment of Pu sorption in the subsurface at FTF 

or DOE shows that Pu sorption in the subsurface is not needed to support its compliance 

demonstration (e.g., solubility control effectively limits Pu releases into the natural environment 

to non-risk-significant levels). 

3.4.2 Monitoring Factor 4.2: Calcareous Zone Characterization 

Another source of uncertainty in DOE’s far-field model is the treatment of the calcareous “soft 

zones,” located in the lower portion of the UTRA. The focus of studies related to calcareous 

zones has been facility or site stability. NRC staff observed that DOE studies appear to give 

less attention to the hydrogeologic properties of these zones that may impact contaminant flow 

and transport from the FTF. DOE argues that monitoring data have not revealed any noticeable 

impacts on hydraulic heads or contaminant transport to date, but no tracer testing has been 

performed to improve understanding of transport within the pseudo-karst-like soft zones, nor 

has downhole imaging of water velocities been performed at known soft zone locations. 

DOE could monitor flow velocities at screen levels both consistent and inconsistent with known 

existing soft zones to assess local fast flow path gradients of soft zones to provide additional 

confidence that current PA groundwater modeling treatment is acceptable. To date, mapping of 

surface water seeps from the UTRA-Lower Zone rocks along Upper Three Runs Creek and 

Four Mile Branch has not focused on surface seeps or other features associated with these 

 

25 In lieu of modeling different oxidation states of Pu that may be present in the natural system, DOE averages the 

Kds of multiple oxidation states together in assigning a Kds for a single Pu species. 
3-27 

zones, but DOE has suggested they are willing to perform both tracer testing and outcrop 

mapping of seeps. 

NRC staff should observe field tests and review and evaluate results of tracer tests and field 

mapping DOE may conduct to ascertain the significance of existing calcareous “soft” zones on 

flow and transport from the FTF. Staff will review relevant geotechnical logs acquired in the 

vicinity of FTF to stay informed of the potential for and characteristics of soft zones that may be 

identified in the future. Finally, if DOE opts to employ downhole visualization or other methods 

to monitor local groundwater velocities associated with soft zones, NRC staff will review and 

evaluate DOE’s analysis of these data. NRC may conduct technical review activities in 

conjunction with onsite observations of field activities, such as calcareous zone outcrop 

mapping on Upper Three Runs Creek. This MF can be closed when DOE has provided NRC 

sufficient information to show its treatment of calcareous zones in the FTF PA is reasonable or 

adequate to assess risk. If NRC concludes that DOE’s treatment of calcareous zones in the 

FTF PA is not reasonable or appropriate, DOE should evaluate the risk-significance of a more 

adequate representation. 

3.4.3 Monitoring Factor 4.3: Environmental Monitoring 

NRC staff will review any data collected by DOE for the FTF facility for the purpose of evaluating 

FTF disposal facility performance. While early releases from the disposal facility are not 

expected, groundwater monitoring can serve as a valuable tool for early detection of potential 

issues with the disposal facility design to allow sufficient time to institute mitigative measures. 

Additionally, groundwater monitoring data can provide useful validation data from which to 

assess the adequacy of DOE PA models in evaluating risk from the FTF disposal facility. For 

these reasons, NRC staff will review and evaluate groundwater monitoring data as a technical 

review activity under this MF. 

DOE monitors FTF groundwater, as described in the FTF Groundwater Monitoring Plan 

(SRNS–RP–2011–00995). DOE currently monitors eleven wells at FTF. Nine of the 11 wells 

are older wells (constructed between 1972 and 1984), screened in the upper zone of UTRA: 

FTF-15 to -23. Two newer wells, FTF-28 and -29, constructed in 2002, are located a little 

further down gradient and are screened in the lower zone of UTRA. Field parameters and 

constituents monitored include pH, conductivity, temperature, turbidity, depth to water, gross 

alpha, non-volatile beta, tritium, nitrate/nitrite, chromium, and Tc-99.26 Tc-99 has been detected 

in well FTF-28 at significant concentrations (e.g., 900–1,000 pCi/L) that has been attributable to 

a documented release from Tank 8 that occurred in 1961.27 

DOE (SRNS–RP–2011–00995) notes the monitoring network could be improved by (i) 

increasing coverage on the northwest corner of the FTF, (ii) increasing well coverage in the 

 

26Tc-99 is only monitored at wells FTF-28 and -29. 27It is significant to note that FTF-28 is not located along the center-line of flow paths from Tank 8. This means that 

either (i) concentrations could be substantially higher along the center-line with the concentrations at FTF-28 being a 

result of lateral dispersion or (ii) Tank 8 is not the only possible source of the FTF-28 groundwater plume. It is also 

significant to note that Tc-99 is very mobile in the environment and would not be expected to be present in the aquifer 

50 years after its release into the vadose zone at FTF unless it were held up in an engineered system. An alternative 

hypothesis is that leaks from the sewer lines resulted in UTRA contamination at wells FTF-28 and FSL-11C (FSL-11C 

is part of the larger general separations area monitoring well network). However, well FTF-28 is screened in the 

lower zone of the UTRA. Because the well is also located in close proximity to the sewer lines, it is not clear that 

contamination could be vertically transported to the lower zone of the UTRA over such a small lateral distance. 

Therefore, NRC may perfrom backwards particle tracking from FTF-28 to identify potential source areas during 

monitoring. 
3-28 

lower aquifer zone, and (iii) installing upgradient wells to establish background conditions. SRS 

plans to install six new wells to implement these improvements, including two background 

wells, and four downgradient wells located in both the upper zone (two wells) and the lower 

zone (two wells) of the UTRA. The locations of the new wells are circled in Figure 3-6. 

Sampling of wells FTF 15–18 will be discontinued. Additional analyses under the proposed 

monitoring plan include: cadmium, manganese, sodium, and, if above gross alpha or 

non-volatile beta trigger levels alpha, beta, or gamma speciation may be conducted by DOE.28 

NRC staff will evaluate the FTF monitoring well network and associated data collection as a 

technical review activity under this MF. 

Figure 3-6. Proposed F-Tank Farm Groundwater Monitoring Locations 

(SRNS-RP–2011–00995) 

Closure of the Group of Monitoring Factors Under MA 4 “Natural System Performance” 

NRC may conduct technical review activities for this monitoring activity in conjunction with 

onsite observations related to groundwater sampling, well construction, and other field activities. 

South Carolina Department of Health and Environmental Control oversight may be leveraged in 

this area to ensure the quality of data collected. This MF will remain open and will not be 

closed. However, once MF 4.1 and 4.2 have been closed, the MA will be changed to 

environmental monitoring. MA 4 will be renamed “Environmental Monitoring” once MF 4.1 and 

4.2 have been closed. MA 4 will remain open indefinitely. 

 

28DOE (SRNS–RP–2011–00995, p. 22) lists I-129 as a constituent to be monitored at FTF; however, Table 3 in the 

same report does not appear to list I-129 in the analyte column. 
3-29 

3.5 MA 5 “Closure Cap Performance” 

Importance of MA 5 “Closure Cap Performance” 

Although DOE’s sensitivity and uncertainty analyses indicate the closure cap has minimal 

impact on peak dose and in most cases serves as a redundant barrier,29 NRC staff concluded 

that in certain cases, the FTF closure cap could be important to mitigating risk from the disposal 

facility and in maintaining doses ALARA. In fact, DOE’s barrier analysis shows that if other 

barriers do not perform as well as expected, the closure cap could become a more important 

barrier limiting release from the disposal facility. Over long periods of time, DOE also assumes 

that the closure cap limits infiltration rates to 30.5 cm/yr [12 in/yr], below the background 

infiltration rate of 38 cm/yr [15 in/yr]. Longer-term lowering of the infiltration rate helps to

(i) decrease releases of key radionuclides from the disposal facility and (ii) prolong transition 

times to higher solubility of many key radionuclides. Based on the potential importance of the 

closure cap in meeting the POs in 10 CFR Part 61 and the limited support that has been 

provided by DOE for this barrier in its FTF PA, NRC staff will monitor closure cap performance. 

NRC Monitoring Under MA 5 “Closure Cap Performance” 

As listed in Appendix A and documented in more detail in its TER (NRC, 2011), NRC staff will 

consider the following MFs related to waste release that are considered important to meeting 

the 10 CFR 61.41 PO: 

• Long-Term Hydraulic Performance of the Closure Cap, 

• Long-Term Erosion Protection Design, and 

• Closure Cap Functions as They Pertain to ALARA. 

3.5.1 Monitoring Factor 5.1: Long-Term Hydraulic Performance 

 of the Closure Cap 

In its TER (NRC, 2011), NRC staff discussed (i) the uncertainty in the processes being modeled 

for the FTF closure cap and (ii) the limited support for several of the closure cap assumptions. 

DOE should provide additional support for the long-term hydraulic conductivity of the foundation 

layer, which acts to reduce the long-term infiltration to the disposal facility. DOE assumed the 

foundation layer would limit the infiltration rate to 30.5 cm/yr [12 in/yr], slightly less than the 

estimated background infiltration rate of 38 cm/yr [15 in/yr]. NRC will monitor additional 

information to support the assumed long-term hydraulic conductivity of the foundation layer. 

In addition, NRC staff will monitor construction quality and settlement at the FTF to help ensure 

assumed performance of the High Density Polyethylene/Geosynthetic Clay Liner (HDPE/GCL) 

composite layer is not adversely impacted. Although the HDPE/GCL composite layer does not 

significantly contribute to the long-term hydraulic performance of the closure cap, DOE assumes 

it is a significant barrier to infiltration for several hundred years after site closure. Because the 

performance of the HDPE/GCL layer is sensitive to construction quality and differential 

 

29NRC staff concluded that DOE’s reference (or best-estimate) PA case shows the FTF closure cap is a redundant 

hydraulic barrier because other, more robust hydraulic barriers, such as the steel liners and tank grout used to fill the 

cleaned tanks, are present and expected to outperform the closure cap for longer periods of time under most 

scenarios, including the reference case DOE used in its FTF PA. However, it is important to note the closure cap is 

the only barrier assumed to provide long-term infiltrating-reducing capabilities, albeit at modest levels. Figure 3-4 

shows barriers to timing of tank farm releases in DOE’s reference case. 
3-30 

settlement, NRC will monitor the quality assurance/quality control for closure cap construction 

and settlement data collected during FTF operations as well as nearby facilities. NRC also will 

review relevant studies and tests related to HDPE/GCL performance. This MF can be closed 

after DOE’s construction of the closure cap and demonstration of its hydraulic performance. 

3.5.2 Monitoring Factor 5.2: Long-Term Erosion Protection Design 

As documented in its TER (NRC, 2011), NRC staff recommended that DOE provide additional 

support for the long-term erosion of the topsoil layer and conduct a preliminary evaluation of 

erosion protection designs. Long-term maintenance of the topsoil and vegetative closure cap is 

important to closure cap performance, because evapotranspiration dominates the modeled 

water balance distribution for SRS precipitation. DOE should evaluate potential loss of soil and 

development of gullies due to cumulative effects of soil loss from frequent rainfall events. 

Effects of high frequency and low intensity events can dominate long-term erosion processes. 

In addition, DOE did not evaluate the resistance of a degraded vegetation cover to gully erosion. 

A Bahia grass, bamboo, or pine forest vegetative cover could be degraded by fire or extended 

drought, thereby affecting the capability of the engineered cover to resist erosion. NRC staff will 

review and evaluate information pertaining to erosion processes of the vegetative and topsoil 

layers, including cover maintenance activities. 

DOE should conduct a preliminary evaluation of erosion protection designs (e.g., evaluation of 

an acceptable rock source, the ability of an integrated drainage system to accommodate design 

features) to verify assumptions related to closure cap performance can be met. The design of 

perimeter drainage structures that convey runoff and infiltration from the cover and divert runoff 

from surrounding areas will affect resistance of these structures to erosion that could also affect 

the stability of the cover side slopes and the cover itself. If the vertical hydraulic conductivity of 

the native soil, on which the perimeter drainage channel is constructed, is not sufficiently high to 

allow ponded water to infiltrate vertically, it could flow toward the tanks. The final design for the 

cover and associated drainage structures should consider their performance and degradation 

during the long, post-institutional control period. If DOE performs simulations of the influence of 

clogging and ponding in the perimeter drainage structures on flow in the vadose zone, NRC will 

review results of these simulations to evaluate risk significance of the uncertainties in the 

long-term performance of the perimeter drainage structure. This MF can be closed after DOE’s 

construction of the closure cap and demonstration of its physical stability. 

3.5.3 Monitoring Factor 5.3: Closure Cap Functions That Maintain 

 Doses ALARA 

DOE lists the infiltration reducing function of the closure cap as part of its ALARA demonstration 

under 10 CFR 61.41. In addition to reducing short-term, as well as long-term infiltration rates, 

the closure cap serves many functions that are not specifically discussed in DOE’s FTF PA. For 

example, the closure cap provides defense in depth to ensure relatively high specific activity 

radionuclides are present in significant quantities, such as Sr-90 and Cs-137, are not released 

from FTF tanks and ancillary equipment before they decay to negligible levels. During the 

period of a few hundred years after FTF closure, the closure cap may reasonably be assumed 

to be effective in minimizing infiltration through the disposal facility. 

Although not specifically discussed in DOE’s PA, another important function of the closure cap 

is that it may limit infiltration and transport of deleterious species into the engineered disposal 

system such as carbon dioxide, oxygen, chloride, sulfate, and slightly acidic groundwater that 
3-31 

could accelerate material degradation of cement vaults, as well as accelerated corrosion of the 

HLW tanks. Therefore, construction of a well-designed closure cap also may benefit the 

longevity of other engineered barriers at the FTF. 

Finally, the closure cap may have a minor but detectable impact on water table elevations local 

to FTF. Barriers constructed to reduce the likelihood of periodic water table rise above the 

bottom of the tanks may be needed to support the compliance demonstration and may be 

considered ALARA. The alternative waste release configuration where the water table rises and 

falls above and below the tank bottoms is especially important for Type IV tanks that are located 

at or in close proximity to the water table, based on historical water table data because the 

configuration could lead to accelerated corrosion and higher release rates of key radionuclides 

to the UTRA. 

For these reasons and other closure cap functions listed in Chapter 4, related to the 

10 CFR 61.42 PO, NRC staff will monitor DOE’s disposal actions as they pertain to FTF closure 

cap design, construction, and maintenance consistent with ALARA criteria. 

Closure of the Group of Monitoring Factors Under MA 5 “Closure Cap Performance” 

This MA will remain open throughout DOE’s development, construction, and completion of a 

final closure cap, unless final design information indicates the MFs are not risk-significant. 

When DOE develops a final closure cap design, NRC will revise the monitoring plan, as 

appropriate, to describe the monitoring activities relevant to the final design. NRC staff will 

monitor DOE’s development of specific designs for the closure cap and determine if these 

designs are likely to significantly alter DOE and NRC conclusions regarding the conceptual 

design analyzed in the PA. Prior to any construction activities, NRC staff will review 

specifications for closure cap construction materials and quality assurance/quality control 

procedures for assuring these materials meet specifications. During construction, NRC staff 

should observe the placement of these materials and the quality control testing to assure the 

as-built closure cap will meet design specifications. NRC staff also will evaluate available data 

from similar covers built on the larger SRS site and other humid sites. 

3.6 MA 6 “Performance Assessment Maintenance” 

Importance of MA 6 “Performance Assessment Maintenance” 

DOE Manual 435.1-1, Change 1, (DOE, 2001) requires DOE PAs to be maintained to evaluate 

changes that could affect the performance, design, and operation bases for the facility. DOE 

Manual 435.11-1 (DOE, 2001) requires the maintenance to include research, field studies, and 

monitoring necessary to address uncertainties or gaps in existing data. DOE prepares an 

annual PA maintenance program implementation plan that summarizes activities related to the 

following areas for the FTF: (i) annual maintenance program activities; (ii) PA development or 

revisions; and (iii) research and testing activities. The implementation plan for fiscal year 2012 

is documented in SRR–CWDA–2012–00020. 

NRC used risk insights to prioritize the recommendations identified in its TER (NRC, 2011) and 

anticipates that DOE, as part of its PA maintenance program, might use a graded approach to 

focus on development of support for key modeling assumptions, such as those identified under 

other MAs (e.g., MA 2) to enhance confidence in the PA. NRC will monitor DOE’s PA 

maintenance activities related to key modeling assumptions under other MAs identified in this 

monitoring plan. The insights generated from focusing on key modeling assumptions would 
3-32 

then inform the need for further data collection, experimental studies, and modeling to address 

MFs identified under this MA. 

NRC Monitoring Under MA 6 “Performance Assessment Maintenance” 

Under this MA, NRC will monitor DOE activities associated with the FTF PA maintenance 

program that are related to NRC recommendations to improve model support and parameter 

justification, including representation of uncertainty in models and parameters. Appendix A 

provides a cross-walk of specific NRC recommendations identified in its TER (NRC, 2011) that 

fall under this MA. Specifically, NRC will consider the following MFs related to DOE’s PA 

maintenance activities for recommendations that NRC, based on the current understanding, 

identifies as lower significance to demonstrating compliance with the POs or may require a 

longer time horizon to complete based on current information: 

• Scenario Analysis, 

• Model and Parameter Support, and 

• FTF PA Revisions. 

3.6.1 Monitoring Factor 6.1: Scenario Analysis 

During the monitoring period, NRC staff will review PA revisions to evaluate adequacy of 

scenarios considered. Specifically, NRC staff will review the DOE methodology for 

identification, screening, and dispositioning of features, events, and processes (FEPs) and the 

formation of scenarios considered in the PA. NRC staff should verify FEPs identified by DOE, 

including all FEPs having a potential to influence compliance with POs. NRC staff should 

examine the technical basis for screening FEPs from further consideration in the PA. NRC staff 

also should examine DOE bases for the formation of scenarios considered in the PA to 

determine whether they include all FEPs that have not been screened from further 

consideration. 

Since NRC issued its TER (NRC, 2011), DOE has documented an evaluation of FEPs for 

the FTF PA. NRC staff will review and comment on the evaluation as a technical review activity. 

NRC will close this MF when DOE demonstrates that all risk-significant FEPs have been (or will 

be under another MF) adequately evaluated in PA documentation. 

3.6.2 Monitoring Factor 6.2: Model and Parameter Support 

As documented in NRC’s TER (NRC, 2011), NRC staff provided a number of recommendations 

regarding the technical bases for model selection and justification of parameter ranges and 

distributions. NRC staff will review DOE’s PA revisions to evaluate the selection of models and 

justification of parameters. Specifically, NRC staff will examine information DOE generates, 

including experimental and site characterization data and information from literature, to support 

model selection and justify parameters. NRC staff also will review DOE methods to 

characterize data and model uncertainty and propagate the uncertainty through the PA. NRC 

staff will use a graded approach to focus on aspects of most importance to demonstrating 

compliance with the POs. This MF can be closed when DOE provides sufficient information to 

support risk-significant models and/or model parameters listed in Appendix A related to MF 6.2. 
3-33 

3.6.3 Monitoring Factor 6.3: F-Tank Farm Performance 

 Assessment Revisions 

It is anticipated that DOE will update its current FTF PA (SRS–REG–2007–00002, Rev. 1) in the 

future, to incorporate new and significant information collected since preparation of its 2010 FTF 

PA. NRC staff will review the revised PA and issue a TER documenting the results of its review. 

NRC anticipates results of the review, as documented in NRC’s TER, will be used by NRC to 

update this monitoring plan in the future. NRC staff will pay special attention to supporting 

documentation generated since the last PA revision, including results of experiments, analog 

studies, models, and peer reviews conducted to support the key MAs listed in this monitoring 

plan, as well as lower priority items listed under MA 6 “PA Maintenance.” 

Closure of the Group of Monitoring Factors Under MA 6-PA Maintenance 

NRC staff expects the PA Maintenance MA will remain active until all recommendations have 

been resolved (or are deemed unnecessary to the compliance demonstration), and possibly for 

the entire duration over which DOE performs maintenance activities related to the FTF PA. 

Alternatively, NRC staff could close this group of MFs, if it determines DOE’s PA maintenance 

program is sufficient to evaluate new and significant information related to FTF compliance with 

10 CFR 61.41 in the futre. 
4-1 

4 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.42 

Design, operation, and closure of the land disposal facility must ensure protection of any 

individual inadvertently intruding into the disposal site and occupying the site or contacting the 

waste at any time after active institutional controls over the disposal site are removed. 

Protection of individuals from inadvertent intrusion considers the potential risks to individuals 

who are unknowingly exposed to radiation from disposed waste while engaging in normal 

activities while occupying the site. Generally, compliance with the waste classification system at 

10 Code of Federal Regulations (CFR) 61.55 ensures protection of inadvertent intruders. 

However, for waste streams that were not considered in the development of 10 CFR Part 61 

[NUREG–0945 (NRC, 1982)], such as the residual waste projected to remain in F-Tank Farm 

(FTF), it would be prudent to assess the performance of the disposal facility to limit radiological 

exposures to inadvertent intruders to demonstrate compliance with the performance 

objective (PO). 

Exposures to radiation can be through direct contact with the waste or indirect exposure to the 

radiation from buried waste while onsite. Direct contact could occur as a result of an activity 

that disturbs the waste zone directly. Examples of activities that could lead to direct contact of 

radioactivity by an inadvertent intruder include excavation during dwelling construction and well 

drilling. The U.S. Department of Energy (DOE) rules out excavation for dwelling construction in 

its performance assessment (PA) because DOE assumes a minimum of 3-m [10-ft] clean cover 

is present and most residential dwellings disturb less than 3-m [10-ft] of soil. Although well 

drilling was considered a potential direct intrusion event in DOE’s PA, well drilling into a 

high-level waste (HLW) tank was considered unlikely in DOE’s PA, given the presence of 

multiple redundant barriers such as the closure cap, tank grout, and steel liner that would make 

drilling more difficult and based on regional experience would likely alert a driller accustomed to 

drilling into softer materials to the potential hazards of the disposal facility. Instead, DOE 

considered intrusion into transfer lines more likely. Nonetheless, because FTF waste is located 

several meters below grade underneath a closure cap, DOE also considers exposures resulting 

from indirect contact with contaminated onsite groundwater as a more likely exposure scenario 

for an inadvertent intruder. The basis for the 10 CFR 61.42 compliance demonstration is 

therefore calculations of potential dose to a well driller who intrudes into the FTF transfer lines 

and the potential dose to a groundwater receptor. 

Because 10 CFR Part 61 relies on the waste classification system to ensure protection of 

inadvertent intruders, the regulation does not specify a time period for an assessment. 

Low-level waste and waste incidental to reprocessing guidance found in NUREG–1573 

(NRC, 2000) and NUREG–1854 (NRC, 2007) suggest a 10,000 year period of performance is 

generally sufficient for demonstration of compliance with 10 CFR 61.41. Likewise, the 

U.S. Nuclear Regulatory Commission (NRC) considers this time period appropriate for 

assessment of compliance with 10 CFR 61.42. However, longer evaluation periods may be 

necessary to capture the peak dose and provide insights on facility (natural and engineered) 

performance for certain long-lived wastes. 

To determine the dose to a potential receptor, DOE also must select a point of compliance 

(POC). NRC assumes in the development of 10 CFR Part 61 [NUREG–0945 (NRC, 1982)] the 

intruder excavated into a disposal cell or extracted water from a well located at the boundary 

of the disposal area after the end of the institutional control period. DOE assumes the 

inadvertent intruder installs a well located 1 m from the boundary of the disposal facility. 

 
4-2 

NRC staff considers this appropriate to assess potential inadvertent intruder exposures to 

contaminated groundwater. 

NRC staff evaluated DOE’s assessment of key FEPs associated with disposal facility 

performance that are estimated to have the largest impact on the 10 CFR 61.42 compliance 

demonstration based on the criteria discussed above. NRC staff found several monitoring 

areas (MAs) are important to meeting the 10 CFR 61.42 PO. Because the groundwater 

pathway is evaluated for both the 10 CFR 61.41 and 61.42 POs, with the only difference being 

the POC (100 m versus 1 m, respectively) and the allowable dose {0.25 mSv/yr [25 mrem/yr]} 

versus 5.0 mSv/yr [500 mrem/yr], each MA that is important for demonstrating compliance with 

10 CFR 61.41 also is important for demonstrating compliance with 10 CFR 61.42. In general, 

NRC staff expects that compliance with the 10 CFR 61.41 PO will be bounding for the 10 CFR 

61.42 evaluation. This is true because the factor difference between the dose standards (20 

times higher for the 10 CFR 61.42 evaluation) is greater than the difference in concentrations 

between the 1 m and 100 m points of compliance for most key radionuclides (e.g., 

concentrations of key radionuclides are around 10 times greater at 1 m than they are at 100 m 

for relatively sorbing Pu-239). 

However, because DOE relies on timing of the peak dose to demonstrate compliance with the 

POs in its reference (or best-estimate) PA case, the 10 CFR 61.42 compliance demonstration 

could be bounding for those radionuclides whose travel times are assumed to be prolonged 

between the 1 and 100 m points of compliance (e.g., Pu-239). Additionally, because 

10 CFR 61.41 does not consider a direct intrusion case (e.g., intrusion into the transfer lines), 

constituents important to the 10 CFR 61.42 evaluation may not be important for the 

10 CFR 61.41 evaluation and will be highlighted in MA 1 “Residual Inventory.” In general, NRC 

staff considers MA and MA factors discussed in Chapter 3 with respect to 10 CFR 61.41 

applicable to 10 CFR 61.42 discussed in Chapter 4 and will not be repeated. However, special 

considerations are discussed below for each MA. 

4.1 MA 1 “Inventory” 

Monitoring Factor 1.1: Final Inventory and Risk Estimates (Additional Considerations) 

The FTF PA reports a peak 20,000-year dose for the chronic intruder of 0.75 mSv/yr 

[75 mrem/yr] due to groundwater dependent pathways with most of the dose from vegetable 

and water ingestion from Np-237.30 Other important radionuclides from the groundwater 

pathway include Th-229 and U-233, although DOE indicated its plans to eliminate these two 

radionuclides from the list of highly radioactive radionuclides (HRRs) that is used to identify 

constituents in the waste residue to be sampled by DOE, following cleaning based on low 

inventories of these two radionuclides in cleaned Tanks 18 and 19. NRC staff will review 

special analyses prepared for each cleaned tank to ensure intruder risks reported in the FTF PA 

are appropriately assessed and evaluated under monitoring factor (MF) 1.1. This MF can be 

closed after NRC staff reviews each special analysis developed by DOE for FTF tanks and 

concludes that DOE has adequately evaluated the risk to the inadvertent intruder. 

Monitoring Factor 1.2: Residual Waste Sampling (Additional Considerations)

DOE’s conclusion that inventories of Th-229 and U-233, which may be important to the 

10 CFR 61.42 analysis, were overestimated in the PA, is based on analyses of these 

 

30The peak of the mean dose in the probabilistic analysis is 6.4 mSv/yr [640 mrem/yr]. 
4-3 

radionuclides in cleaned Tanks 18 and 19. However, as stated in NRC’s technical evaluation 

report (NRC, 2011), unless DOE can show that final inventories in other tanks are similar to final 

inventories in Tanks 18 and 19, DOE should continue to characterize samples for these 

radionuclides. NRC staff will review sampling and analysis plans to ensure all HRRs are 

sampled, or a basis for exclusion of an HRR is provided. This MF can be closed when NRC 

concludes that DOE has provided sufficient information to support its list of HRRs (or provides 

sufficient basis for removal of radionuclides from its list of HRRs) for each FTF tank. 

Monitoring Factor 1.3: Residual Waste Volume 

There are no special considerations under MF 1.3 for the 10 CFR 61.42 analysis. 

Monitoring Factor 1.4: Ancillary Equipment Inventory 

Short-lived radionuclides Sr-90/Y-90 and Cs-137/Ba-137 that may not be considered important 

by DOE or NRC to the 10 CFR 61.41 evaluation could be important for the 10 CFR 61.42 

analysis, because the 10 CFR 61.42 analysis considers direct intrusion into the FTF transfer 

lines at 100 years, when these radionuclides may still be present in risk-significant quantities.31 

In fact, the peak dose within 10,000 years for the chronic intruder scenario is 0.73 mSv/yr 

[73 mrem/yr], with the most important pathway being the ingestion of vegetables contaminated 

with drill cuttings at the time of intrusion at 100 years, due to relatively short-lived radionuclides 

Sr-90/Y-90 (56 percent) and Cs-137/Ba-137 (44 percent). However, because the estimated 

does is significantly below the 5 mSv/yr [500 mrem/yr] dose standard, inventory of these 

radionuclides could potentially be higher, while still maintaining compliance with the dose 

standard. NRC staff should ensure risks associated with these relatively short-lived 

radionuclides are bounded by the PA or a special analysis is performed to assess the increased 

risk associated with a higher than assumed inventory, once final estimates of transfer line 

inventories are assessed through additional characterization. DOE indicated in response to 

NRC comment (SRR–CWDA–2009–00054, Rev. 0) its intent to verify PA assumptions 

regarding transfer line inventories and listed this activity under Section 8.2 “Further Work” in its 

FTF PA (SRS–REG–2007–00002, Rev. 1). NRC staff will monitor DOE’s efforts in this area to 

ensure the assumed transfer line inventories are sufficiently bounding or that increased risk is 

assessed. This MF can be closed when NRC staff concludes that DOE has adequately 

assessed the risk associated with transfer lines. 

Monitoring Factor 1.5: Waste Removal (As It Pertains to ALARA) 

MF 1.5 related to as low as is reasonably achievable (ALARA) does not apply to the 10 CFR 

61.42 evaluation. 

4.2 MA 2 “Waste Release” 

Monitoring Factor 2.1: Solubility Limiting Phases/Limits and Validation 

There are no special considerations under MF 2.1 for the 10 CFR 61.42 analysis. 

 

 

31The 10 CFR 61.41 analysis is dominated by groundwater dependent pathways and releases from FTF components 

are not assumed to occur for 100s to 1,000s of years, allowing sufficient time for decay of relatively short-lived 

radionuclides, such as Cs-137 and Sr-90. 
4-4 

Monitoring Factor 2.2: Chemical Transition Times and Validation 

There are no special considerations under MF 2.2 for the 10 CFR 61.42 analysis. 

4.3 MA 3 “Cementitious Material Performance” 

Monitoring Factor 3.1: Concrete Vault Performance (Additional Considerations) 

Because DOE relies on grouted tanks and vaults in the FTF PA to deter inadvertent intrusion 

into the HLW tanks32, NRC staff will perform routine monitoring of DOE’s reliance on 

cementitious materials to ensure FTF PA assumptions regarding the ability of the tank vaults to 

serve as a recognizable and durable barrier to intrusion are valid. This MF will be reviewed in 

conjunction with MF 3.4 and can be closed following closure of FTF tanks. 

Monitoring Factor 3.2: Groundwater Conditioning 

There are no special considerations under MF 3.2 for the 10 CFR 61.42 analysis. 

Monitoring Factor 3.3: Shrinkage and Cracking 

There are no special considerations under MF 3.3 for the 10 CFR 61.42 analysis. 

Monitoring Factors 3.4: Grout Performance (Additional Considerations)

Because DOE relies on the grouted tanks and vaults in the FTF PA to deter inadvertent 

intrusion into the HLW tanks33, grouting activities under MA 3 “Cementitious Materials 

Performance” will also be monitored under 10 CFR 61.42. NRC will perform routine monitoring 

of DOE’s use of grout materials to stabilize HLW tanks to ensure FTF PA assumptions 

regarding the ability of the grouted tank and vaults to serve as a recognizable and durable 

barrier to intrusion remain valid. This MF will be reviewed in conjunction with MF 3.1 and can 

be closed following closure of FTF tanks. 

Monitoring Factor 3.5: Basemat Performance 

There are no special considerations under MF 3.5 for the 10 CFR 61.42 analysis. 

Monitoring Factor 3.6: Use of Stabilizing Grout (As it Pertains to ALARA) 

MF 3.6 related to ALARA does not apply to the 10 CFR 61.42 evaluation (there are no ALARA 

provisions in 10 CFR 61.42). 

 

 

32DOE only considers intrusion into the HLW tanks in sensitivity analyses due to assumed robustness of the grouted 

tank and vault system. 

33DOE only considers intrusion into the HLW tanks in sensitivity analyses due to assumed robustness of the grouted 

tank and vault system. 
4-5 

4.4 MA 4 “Natural System Performance” 

Monitoring Factor 4.1: Pu Distribution Coefficients (Kds) and Averaging (Additional 

Considerations) 

Due to potential reliance on travel time of Pu to the 100 m POC for the 10 CFR 61.41 

analysis, NRC will specifically consider whether the shorter distance and travel time to the 1 m 

POC for the 10 CFR 61.42 analysis makes compliance with the latter PO bounding. As 

discussed in Section 3.4.1, NRC staff has concerns with the Kd averaging approach used by 

DOE that tends to delay travel times to the 10 CFR 61.41 and 61.42 POCs. NRC staff will 

review information generated by DOE and perform independent modeling to assess whether 

more mobile forms of Pu, if evaluated explicitly in DOE’s PA modeling, could reach the 

inadvertent intruder POC within 10,000 years. This MF can be closed when NRC staff 

concludes that DOE has adequately assessed the timing and magnitude of Pu-239 release and 

transport to the 1 m POC. 

Monitoring Factor 4.2: Calcareous Zone Characterization

NRC staff does not think calcareous zone characterization is as important to the 10 CFR 61.42 

analysis because contaminant plumes emanating from the FTF are less likely to traverse the 

lower zone of the UTRA where the calcareous zone is present during their travel to the (1 m) 

POC, where the inadvertent intruder dose is assessed. Therefore, there are no special 

considerations under MF 4.2 for the 10 CFR 61.42 analysis. 

Monitoring Factor 4.3: Environmental Monitoring

There are no special considerations under MF 4.3 for the 10 CFR 61.42 analysis. 

4.5 MA 5 “Closure Cap Performance” 

Monitoring Factor 5.1: Long-Term Erosion Protection Design

There are no special considerations under MF 5.1 for the 10 CFR 61.42 analysis. 

Monitoring Factor 5.2: Long-Term Erosion Protection Design (Additional Considerations) 

DOE relies on the erosion barrier to maintain a minimum 3 m [10 ft] clean cover to prevent 

intrusion into FTF waste (DOE/SRS–WD–2012–001), thereby eliminating certain shallow 

intrusion scenarios from analysis in DOE’s PA (SRS–REG–2007–00002, Rev. 1). DOE also 

considers the erosion barrier part of a system of durable engineered barriers that would 

cause a regional driller, not accustomed to encountering hard materials to change location 

(SRS–REG–2007–00002, Rev. 1). For these reasons, NRC will specifically monitor use of the 

engineered closure cap as a barrier to intrusion. This MF can be closed after construction of the 

closure cap. 

Monitoring Factor 5.3: Closure Cap Functions that Maintain Doses ALARA

MF 5.3 related to ALARA does not apply to the 10 CFR 61.42 evaluation. 
4-6 

4.6 MA 6 “Performance Assessment Maintenance” 

Monitoring Factor 6.1: Scenario Analysis (Additional Considerations) 

NRC will pay particular attention to DOE’s consideration of various scenarios related to 

inadvertent intrusion into FTF components in its review of DOE’s FEPs analysis 

(SRR–CWDA–2012–00022). NRC staff can close this MF when it concludes that DOE has 

adequately addressed FEPs related to inadvertent intrusion in its PA documentation. 

Monitoring Factor 6.2: Model and Parameter Support 

There are no special considerations under MF 6.2 for the 10 CFR 61.42 analysis. 

Monitoring Factor 6.3: F-Tank Farm Performance Assessment Revisions (Additional 

Considerations)

NRC will evaluate DOE’s revision to the FTF PA to ensure all relevant FEPs pertaining to 

inadvertent intrusion into FTF components were properly evaluated in the 10 CFR 61.42 

analysis. This MF can be closed when NRC staff concludes that DOE has adequately 

evaluated FEPs important to the inadvertent intrusion analysis in its PA documentation and that 

its PA maintenance program is sufficient to evaluate new and significant information related to 

inadvertent intrusion in the future. 
5-1 

5 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.43 

Operations at the land disposal facility must be conducted in compliance with the standards 

for radiation protection set out in Part 20 of this chapter, except for releases of radioactivity 

in effluents from the land disposal facility, which shall be governed by 10 Code of Federal 

Regulations (CFR) 61.41 of this part. Every reasonable effort shall be made to maintain 

radiation exposures as low as is reasonably achievable (ALARA). 

The U.S. Nuclear Regulatory Commission (NRC) interprets the term “operations” as those 

U.S. Department of Energy (DOE) activities related to waste retrieval (i.e., heel removal), 

grouting, stabilization, observation, maintenance, or other similar activities. NRC intends to 

evaluate this performance objective (PO) from the time that DOE issues its final waste 

determination (WD) until the end of the institutional control period. For workers performing 

duties on a controlled DOE site, under DOE’s radiation protection program, the 50 mSv/yr 

[5 rem/yr] radiation worker dose limit applies. For members of the public, including workers 

performing limited activities not covered under a DOE radiation protection program, the 

1 mSv/yr [100 mrem/yr] dose limit for members of the public applies from sources other than 

effluents.34 10 CFR 20.1101(d) further specifies that the maximum annual dose that a member 

of the public can receive from airborne emissions is 0.10 mSv [10 mrem/yr]. DOE also must 

demonstrate that dose in any one hour in an unrestricted areas is less than 0.02 mSv [2 mrem]. 

DOE has a radiation protection program to ensure protection of individuals during operations. In 

DOE’s 2010 F-Tank Farm (FTF) WD (DOE/SRS–WD-–2012–001), DOE provided a cross-walk 

of the relevant DOE regulation or limit consistent with that provided in 10 CFR 20 to 

demonstrate that the DOE regulation provides an equivalent level of protection. 

During operations associated with FTF disposal at the Savannah River Site (SRS), the primary 

pathway of concern will be through the air. No significant releases to the subsurface or surface 

water from the waste in the FTF tanks are expected during the time of operations. Additionally, 

the release of radionuclides from FTF to the subsurface is being monitored in assessment of 

compliance with 10 CFR 61.41 (Chapter 3) and 10 CFR 61.42 (Chapter 4). Any leaching of 

contaminants from the vaults observed while the FTF is still in operation may indicate the ability 

of the waste form to retain the radionuclides is worse than expected and that 10 CFR 61.41 and 

10 CFR 61.42 may not be met. 

Importance of MA 7 “Protection of Individuals During Operations” 

The Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA) 

requires NRC, in coordination with the State of South Carolina, to monitor DOE disposal actions 

to assess compliance with the POs in 10 CFR Part 61, Subpart C. 10 CFR 61.43 is related to 

protection of individuals during operations, including workers and members of the public. NRC 

expects the following DOE activities to incur the largest risks to workers and members of the 

public during FTF closure operations: (i) tank cleaning, (ii) waste stabilization, and (iii) other 

maintenance activities. Tank cleaning activities could include use of high pressure water that 

has the potential to lead to releases or radioactivity into secondary containment and the 

environment. Radioactivity also may be released to the tank vapor space during tank grouting 

activities. Modification and maintenance of tank equipment and ventilation systems are 

 

34The public dose limit is 1 mSv/yr. However, 10 CFR 61.43 indicates that effluents will be addressed under 10 CFR 

61.41. The 10 CFR 61.41 dose based standard is 0.25 mSv/yr [25 mrem/yr]. The point of compliance during active 

disposal facility operations under 10 CFR 61.41 is the larger SRS site boundary. 
5-2 

expected to incur worker dose. Therefore, NRC may observe installation and removal of 

equipment from high-level waste (HLW) tanks during an onsite observation, as practical. 

NRC Monitoring Under MA7 “Protection of Individuals During Operations” 

NRC staff has developed the following monitoring factors (MFs) related to protection of 

individuals during operations 

• Protection of Workers During Operations 

• Air Monitoring 

• ALARA 

5.1 Monitoring Factor 7.1: Protection of Workers 

 During Operations 

Compliance with the dose requirements for protection of individuals during operations is 

expected to be assessed by NRC through the use of dosimetry and the monitoring of radiation 

data and radiation records. NRC staff should review, on at least an annual basis, DOE reports 

and records that are related to dose during waste disposal operations to assess whether doses 

are within the limits found in 10 CFR Part 20 and are ALARA. 

NRC staff should periodically confirm programs and policies presented in the WD 

(DOE/SRS–WD–2012–001) continue to be in effect during the operational period. In particular, 

NRC staff should verify personnel involved in waste disposal operations are provided dosimetry 

and are familiar with requirements of the radiation protection program. NRC will leverage staff 

in Region I with experience in radiation protection inspections to support onsite observations in 

this area. Any NRC staff participating in an onsite observation should obey DOE’s onsite 

radiation protection program requirements, as well as obtain dosimetry from NRC’s Office of 

Administration, if not already assigned, prior to the onsite observation. 

This factor will be closed at the end of the assumed 100 year institutional control period or after 

operational doses are expected to be reduced to non-risk-significant levels following tank 

closure activities. 

5.2 Monitoring Factor 7.2: Air Monitoring 

DOE monitors air quality at SRS using air sampling stations located at the site boundary as well 

as in other locations throughout the site. NRC staff should review air monitoring data to 

determine whether activity released in the air, as a result of FTF disposal facility activities, could 

cause a member of the public located at the SRS site boundary to receive an annual dose of 

greater than 0.10 mSv/yr [10 mrem/yr] through the air pathway. 

NRC staff should periodically confirm the air monitoring program continues to 

adequately assess the risk of FTF operations. As part of this review, NRC staff should evaluate 

whether sampling locations and sampling methodologies are adequate to assess airborne 

emissions from the FTF or rely on independent verification from the South Carolina Department 

of Health and Environmental Control. NRC staff expects the dose from airborne emissions to 

be small. If the airborne emissions dose becomes more risk significant, then NRC staff will 

need to evaluate the air monitoring program in greater detail. 

 
5-3 

This factor will be closed at the end of the assumed 100 year institutional control period or when 

operational doses are expected to be reduced to non-risk-significant levels following tank 

closure activities. 

5.3 Monitoring Factor 7.3: As Low As Is Reasonably Achievable

The NRC regulation at 10 CFR 20.1003 defines ALARA in relevant part: 

ALARA ... means making every reasonable effort to maintain exposures to radiation as far 

below the dose limits ... as is practical consistent with the purpose for which the ... activity 

is undertaken...[.] 

10 CFR 835 and relevant DOE Orders, which establish DOE regulatory and contractual 

requirements for DOE facilities and activities establish a similar requirement to 10 CFR 20.1003. 

DOE regulation at 10 CFR 835.2 defines ALARA as “... the approach to radiation protection to 

manage and control exposures (both individual and collective) to the work force and to the 

general public to as low as is reasonable, taking into account social, technical, economic, 

practical, and public policy considerations.” 

Furthermore, the DOE regulation at 10 CFR 835.101(c) requires the contents of each RPP to 

include formal plans and measures for applying the ALARA process to occupational exposure. 

As such, NRC staff’s monitoring of ALARA under 10 CFR 61.43 will be carried out through 

monitoring of the Radiation Protection Program and related activities. 

NRC staff should periodically (or at the appropriate time relevant to each measure) review 

documents associated with the following measures for ensuring ALARA (i) a documented RPP; 

(ii) a Documented Safety Analysis (DSA); (iii) design of the FTF; (iv) regulatory and contractual 

enforcement mechanisms; and (v) access controls, training, and dosimetry. These measures 

are described in the WD or basis document (DOE/SRS–WD–2012–001). 

This factor will be closed at the end of an assumed 100 year institutional control period or when 

operational doses are expected to be reduced to non-risk-significant levels following tank 

closure activities. 
6-1 

6 MONITORING TO ASSESS COMPLIANCE WITH 10 CFR 61.44 

The disposal facility must be sited, designed, used, operated, and closed to achieve long-term 

stability of the disposal site and to eliminate, to the extent practicable, the need for ongoing 

active maintenance of the disposal site following closure so that only surveillance, monitoring, or 

minor custodial care are required. 

These requirements relate to both stability of the disposal site and control of releases within 

acceptable limits. Ensuring site stability helps to minimize the access of water to the residual 

waste by helping to maintain the performance of the closure cap. In addition, site stability is 

important in protecting against inadvertent intrusion. 

The monitoring area (MA) for site stability includes features, events, and processes (FEPs) that 

are external to the individual disposal facility components (e.g., settlement of the subsurface) 

that may impact individual barrier performance. FEPs that are internal to the individual 

components (e.g., grout shrinkage, erosion of the topsoil layer) are discussed under the 

respective performance objectives (POs) and MAs. 

Importance of MA 8 “Site Stability” 

Site stability is an integral aspect to limiting the infiltration through the disposal site and in 

maintaining an adequate barrier to intrusion. The key attributes responsible for providing 

stability of the F-Tank Farm (FTF) are the grouting of the high-level waste (HLW) tanks and 

annular spaces and the erosion protection designs associated with the closure cap. The 

U.S. Department of Energy (DOE) assumes that tank grout used to fill the tanks will create 

a solid monolith with little void space and eliminate differential settlement due to structural 

collapse of the tanks. 

Site stability could be affected by settlement. Settlement could lead to cracking of the vault 

concrete and tank grout. Cracking is not expected to result in significant structural tank 

collapse; however, the integrity of the vault concrete and tank grout is important to steel liner 

performance and waste release, as discussed under monitoring factor (MF) 3.1. Settlement 

may impact the hydraulic performance of the closure cap due to (i) modifications of the closure 

cap slope and surface drainage patterns and (ii) disruption to closure cap components 

[e.g., high density polyethylene/geosynthetic clay liner (HDPE/GCL) composite layer, foundation 

layer, lateral drainage layer]. The erosion protection design is important in maintaining a 

minimum of 3 m [10 ft] of clean material above the tanks and significant ancillary equipment, 

which is discussed in Chapter 4. 

NRC Monitoring Under MA 8 “Site Stability” 

Because other MFs related to site stability are discussed in the preceding chapters, monitoring 

activities to assess compliance with 10 Code of Federal Regulations (CFR) 61.44 will focus 

on settlement. 

6.1 Monitoring Factor 8.1: Settlement 

Settlement could result from (i) increase in overburden from the tank grout and closure cap and 

(ii) the ongoing dissolution of calcareous sediment in the lower portion of the Upper Three 

Rivers Aquifer (UTRA) (i.e., the Santee Formation). Increased loading resulting from the 
6-2 

increase in overburden may lead to compression of subsurface layers and consequently, 

differential settlement. Differential settlement has the potential to disrupt the HDPE/GCL 

composite layer, which acts as a significant barrier to infiltration in the early part of the 

performance period. Hydraulic isolation of the residual waste during this period is important in 

the retention of short-lived radionuclides before they are substantially decayed. Differential 

settlement also may affect the performance of the foundation layer and lateral drainage layer, 

both of which act as long-term barriers to infiltration. DOE should account for the potential 

effects of the additional overburden of the engineered barriers onsite stability. Technical 

reviews and onsite observations of settlement will be conducted by the U.S. Nuclear Regualtory 

Commission (NRC) staff to assess compliance with 10 CFR 61.44. Reviews will focus on

(i) settlement data collected during FTF closure operations, (ii) settlement data collected from 

analogous sites, and (iii) updated settlement modeling investigations. 

In addition to settlement from loading, settlement may result from the dissolution of calcareous 

sediment. Elevated bicarbonate ion concentrations and relatively high pH groundwater in and 

near the Santee Formation suggests ongoing dissolution of the calcareous zones within the 

lower zone of the UTRA (U.S. Army Corps of Engineers, 1952). Although dissolution of 

calcareous sediment may be a very slow process, DOE has not demonstrated that dissolution 

will be insignificant to site stability throughout the performance period. Such dissolution 

previously has created a soil structure that is characterized by arching, under-consolidation, and 

historic, periodic collapses. The U.S. Army Corps of Engineers (1952) identified seven surface 

depressions (i.e., Carolina Bays) thought to be sinks within F-Area, including one sink located 

within the 100 m [330 ft] compliance boundary. DOE’s calculations do not account for the 

stability of calcareous soft zones in the Santee Formation, given the additional overburden that 

is to be contributed by waste-stabilizing grout and the engineered closure cap, or for additional 

subsidence that could occur as a result of future dissolution of subsurface material during the 

performance period. DOE should account for the potential effects of future dissolution of 

calcareous zones on ground subsidence over the long-term period of performance or 

demonstrate that future dissolution of calcareous sediment will be insignificant to site 

performance. Technical reviews related to the risk significance of calcareous zones will be 

conducted to assess compliance with 10 CFR 61.44. Reviews will focus on (i) processes that 

have resulted in the formation of sinks at the Savannah River Site (SRS) and specifically at the 

FTF at the General Separations Area (GSA), (ii) the potential for these processes to affect site 

stability throughout the performance period, and (iii) the potential dose consequences from 

subsidence related to dissolution of calcareous sediment. DOE stated that it will consider 

static-loading-induced settlement, seismically induced liquefaction and subsequent settlement, 

and seismic-induced slope instability in the final design of the closure cap. NRC staff will review 

DOE’s consideration of these processes, as information is made available. 

Compliance or noncompliance with the PO for 10 CFR 61.44 is associated with the status of the 

aforementioned monitoring activities. If surveillance, monitoring, and custodial care are carried 

out after closure, NRC staff expects DOE to inform it of changes to features in the immediate 

area that might affect site stability. These changes may include (i) vegetation denudation at the 

surface due to fires or storms; (ii) erosion features caused by extreme precipitation events or 

long-term processes; or (iii) visible surface changes due to significant biotic intrusion, 

earthquakes, or other geological processes. 

6.2 Closure of MA 8 “Site Stability” 

To assess compliance with 10 CFR 61.44, NRC staff will visually observe the facility for obvious 

signs of degeneration of the facility. For example, evidence of ponded water on the cap surface 
6-3 

may be a sign of differential settlement. Surface fractures may be evidence of underlying 

displacement. NRC staff also may plan site visits to observe the facility after severe weather 

events (e.g., storms, tornados) to ascertain how well the facility can withstand these events. 

DOE is expected to carry out an active maintenance program for the facility through the end of 

the institutional control period; therefore, DOE should repair any obvious signs of facility 

degradation. However, such degradation can provide insights on potential long-term facility 

performance. NRC staff should also discuss any maintenance activities that are performed at 

the disposal facility (e.g., repairs to engineered surface barriers) with SCDHEC. This monitoring 

activity is expected to remain open indefinitely. 
7-1 

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Vol. 1. Washington DC: U.S. Nuclear Regulatory Commission. November 1982. 

Prikryl, J.D. and D.A. Pickett. “Recommended Site-Specific Sorption Coefficients for Reviewing 

Non-High-Level Waste Determinations at the Savannah River Site and Idaho National 

Laboratory.” San Antonio, Texas: Center for Nuclear Waste Regulatory Analyses. 2007. 

SRR–LWP–2009–00001, Rev. 17. “Savannah River Site Liquid Waste System Plan.” 

Washington, DC: U.S. Department of Energy. 2012. 

SRR–CWDA–2009–00054, Rev. 0. “Comment Response Matrix for Nuclear Regulatory 

Commission (NRC) Comments on the F-Tank Farm Performance Assessment.” Aiken, South 

Carolina: Savannah River Remediation LLC, Closure and Waste Disposal Authority. 2010. 

SRR-CWDA-2012-00020, Rev. 0. “Savannah River Site Liquid Waste Facilities Performance 

Assessment Maintenance Program, FY2012 Implementation Plan,” Aiken, South Carolina: 

Savannah River Remediation, LLC. 2012. 

SRR–CWDA–2012–00022, Rev. 0. “Evaluation of Features, Events, and Processes in the FArea Tank Farm Performance Assessment.” Aiken, South Carolina: Savannah River 

Remediation, LLC. 2012. 

SRS–REG–2007–00002, Rev. 1. “Performance Assessment for the F-Tank Farm at the 

Savannah River Site.” Aiken, South Carolina: Savannah River Remediation, LLC, Closure and 

Waste Disposal Authority. 2010. 

SRNS–RP–2011–00995, Rev. 1. “F-Area Tank Farm Ground Water Monitoring Plan.” Aiken, 

South Carolina: Savannah River Nuclear Solutions, LLC. 2012. 

State of South Carolina. “South Carolina Pollution Control Act.” 1985. 

<http://www.scstatehouse.gov/code/t48c001.php>. (22 June 2012). 
7-3 

U.S. Army Corps of Engineers. “Geologic Engineering Investigations.” Vicksburg, Mississippi: 

Waterways Experiment Station, U.S. Army Corps of Engineers. 1952. 

WSRC–OS–94–42, “Federal Facility Agreement for the Savannah River Site.” Washington DC: 

U.S. Department of Energy. 1993. 
8-1 

8 LIST OF CONTRIBUTORS 

U.S. Nuclear Regulatory Commission 

James Shaffner 

(Project Manager) 

Project Manager–Low-Level Radioactive Waste (LLRW) 

M.S., Civil Engineering, University of Maryland 

B.S., Civil Engineering, Drexel University 

30 years experience in LLRW management 

Janelle B. Jessie 

(Project Manager) 

Project Manager–LLRW 

B.S., Mechanical Engineering, Tulane University 

B.A., Physics, Xavier University of Louisiana 

Cynthia S. Barr 

(Technical Lead) 

Sr. Systems Performance Analyst 

M.S., Environmental Systems Engineering, Clemson University 

B.S., Mathematics, College of Charleston 

B.A., Political Science (Pre-Law), College of Charleston 

15 years experience in nuclear environmental analysis and 

risk assessment 

Christopher Grossman 

(Technical Co-Lead) 

Systems Performance Analyst 

M.S., Environmental Engineering and Science, Clemson University 

B.S., Civil Engineering, Purdue University 

10 years experience in radioactive waste management and 

performance assessment 

Mark Fuhrmann Geochemist 

Ph.D., Geochemistry, State University of New York at Stony Brook 

M.S., Geology, Adelphi University 

B.S., Marine Science, State University of New York, Empire College 

30 years experience in geochemistry of contaminants 

George Alexander Systems Performance Analyst 

Ph.D., Energy and Geo-Environmental Engineering, Pennsylvania 

State University 

M.S., Energy and Geo-Environmental Engineering, Pennsylvania 

State University 

B.S., Geo-Environmental Engineering, Pennsylvania State 

University 

Leah Spradley Parks Systems Performance Analyst 

Ph.D., Environmental Management, Vanderbilt University 

M.S., Environmental Engineering, Vanderbilt University 

B.S., Systems and Information Engineering, University of Virginia 

Southwest Research Institute®

Center for Nuclear Waste Regulatory Analyses 

Roberto T. Pabalan Institute Scientist 

Ph.D., Geochemistry and Mineralogy, Pennsylvania State University 

B.S., Geology, University of the Philippines 

35 years experience in geology and geochemistry 

25 years experience in nuclear waste management applications

David A. Pickett Sr. Program Manager (geochemistry, radionuclide release, 

and transport) 

Ph.D., Geology, California Institute of Technology 

M.S., Geology, California Institute of Technology 

B.A. Geology, Rice University 

20 years experience in nuclear waste disposal analyses 
8-2 

Southwest Research Institute®

Center for Nuclear Waste Regulatory Analyses (continued) 

Cynthia Dinwiddie, P.G. Principal Engineer (hydrogeology) 

Ph.D., Environmental Engineering and Science, Clemson University 

M.S., Environmental Systems Engineering, Clemson University 

B.S.E., Mechanical Engineering, Walla Walla College 

11 years experience in nuclear waste disposal analyses 

Gary R. Walter Manager (hydrology, hydrogeology, and environmental 

risk assessment) 

Ph.D., Hydrology, University of Arizona 

M.A., Geology, University of Missouri–Columbia 

B.A., Chinese and Sociology, University of Kansas 

35 years consulting experience 

10 years experience in nuclear waste management 

Biswajit Dasgupta Staff Engineer (structural/geotechnical engineering and 

risk assessment) 

Ph.D., Structural Engineering, University of Minnesota 

M. Tech., Structural Engineering, Indian Institute of Technology, 

Mumbai, India 

B. Tech., Civil Engineering, Indian Institute of Technology, 

Kharagpur, India 

12 years experience in nuclear waste disposal analyses 

Lane D. Howard Principal Engineer (nuclear engineering, health physics, and 

performance assessment) 

M.S., Nuclear Engineering, Texas A&M University 

B.S., Civil Engineering, Texas A&M University 

25 years nuclear industry experience 

10 years experience in nuclear waste disposal analyses 
APPENDIX A 

MONITORING FACTORS 
A–1 

APPENDIX A 

MONITORING FACTORS

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

MA 1 “Inventory”

1§ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE sample each tank following waste retrieval operations for the purpose of developing a final inventory. 

Factors 1.1—Final Inventory and Risk Estimates Factor 1.2—Residual Waste Sampling 

Medium to High Risk Medium Difficulty As Tanks Are Cleaned 

(TER Pgs. 107, 178) 

2¶ 10 CFR 61.41 

10 CFR 61.42 Including ALARA 

NRC recommends DOE better explain intratank waste variability that influences waste characterization and uncertainty evaluation. NRC’s comments in this area were expressed in the context of Tank 18 sampling, but also pertain to future characterization of other tanks. Specifically, NRC commented on (i) lack of explanation regarding differences between past and current sample variability, (ii) potential lack of consideration and explanation of the unexpectedly high tank wall concentrations for Pu-238, and (iii) lack of basis for assumptions regarding normality of sample concentrations and volume estimates when calculating inventory multiplier to be used in the probabilistic analysis. 

Factor 1.2—Residual Waste Sampling 

Medium Risk Medium Difficulty As Tanks Are Sampled 

(TER Pgs. 43, 74, 76) 
A–2 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

3¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE provide evidence to support its intent to remove radionuclides from the list of nine radionuclides that were potentially considered as HRRs, based on Tanks 18 and 19’s sampling results. For example, DOE could show that Tanks 18 and 19’s residual waste is representative of waste in 

other tanks that DOE does not intend to sample for these HRRs. 

Factor 1.2—Residual Waste Sampling 

Low to Medium Risk Low Difficulty Before Dropping HRRs From Sampling 

(TER Pg. 51) 

4§ 10 CFR 61.41 

10 CFR 61.42 Including ALARA 

NRC recommends DOE consider improvements to residual material mapping and consideration of uncertainty in volume estimates. 

Factor 1.3—Residual Waste Volume 

Medium Risk Medium Difficulty 1 to 5 Years 

OID 41 (TER Pgs. 43, 48, 79) 

5¶ 10 CFR 61.41 

10 CFR 61.42 Including ALARA 

DOE indicates in response to NRC comment (SRR–CWDA–2009–00054, Rev. 0) its intent to verify PA assumptions regarding transfer line inventories consistent with Section 8.2, “Further Work” in DOE’s PA (SRS–REG–2007–00002, Rev. 1). 

Factor 1.4—Ancillary Equipment Inventory 

Low to Medium Risk Low Difficulty 1 to 5 Years 

(TER Pg. 49) 

6§ Criterion 2—

Removal to the Maximum Extent Practical 10 CFR 61.41 and 61.42 ALARA 

NRC recommends DOE more fully evaluate costs and benefits of additional HRR removal, including (i) consideration of benefits of additional HRR removal over longer performance periods (and considering uncertainty in the timing of peak HRR doses), (ii) justification for assumptions regarding alternative cleaning technology effectiveness, and (iii) comparison of costs and benefits of additional HRR removal to similar DOE activities. 

Factor 1.5—Waste Removal As It Pertains to ALARA 

Medium Risk Medium Difficulty As Tanks Are Cleaned 

(TER Pgs. 80, 81) 
A–3 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

MA 2 “Waste Release” 

7# 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE perform experiments to verify validity of Geochemist’s Workbench calculations used to determine solubility limiting phases, solubility limits, and chemical transition times. These experiments should study (i) pH and Eh evolution of the grout pore water over time, (ii) controlling solubility limiting phases, and (iii) static and dynamic leach tests to study the mobility of HRRs, including consideration of alteration of tank residuals following chemical cleaning with reagents, such as oxalic acid. 

Factor 2.1—Solubility-Limiting Phases/Limits and Validation Factor 2.2—Chemical Transition Times and Validation 

High Risk Medium to High Difficulty Short- to Intermediate-Term 

OID 1, 2, 8, 15, 16, and 17 (TER Pgs. 134, 178) 

8¶ 10 CFR 61.41 

10 CFR 61.42 

DOE should consider uncertainty in initial conditions and performance lifetime of FTF concrete vaults, as they impact uncertainty in the calculated steel liner failure times. 

Factor 3.1—Concrete Vault Performance (As It Impacts Steel Liner Corrosion) 

Medium to High Risk Medium Difficulty Long-Term Activity (need contingent on other factors) 

(TER Pgs. 120–128) 

9¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE obtain greater support for its assumption regarding flow through the tank grout (i.e., fracture versus matrix) flow as it impacts the timing of chemical transition or time to release of HRRs at risk-significant solubility. If found to be risk-significant, DOE should consider the appropriateness of using moisture characteristic curves for matrix materials to simulate fracture flow. 

Factor 3.2—Grout Conditioning Factor 3.3—Shrinkage and Cracking 

Medium to High Risk Medium to High Difficulty Intermediate to Long-Term (need contingent on other factors) 

OID 24 and 26 (TER Pgs. 126–127) 
A–4 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

MA 3 “Cementitious Material Performance” 

10§ 10 CFR 61.41 

10 CFR 61.42 

Given the wide range of values in the literature, NRC recommends DOE obtain additional support for basemat K

ds for Pu 

and Np, including consideration of solubility affects from previous evaluations and representativeness of experimentally derived values for aged concrete. 

Factor 3.5—Basemat Performance 

Medium to High Risk Medium to High Difficulty 1 to 5 Years 

OID 13, 14 and 20 (TER Pgs. 128, 178) 

MA 4 “Natural System Performance” 

11¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommended DOE evaluate appropriateness of averaging K

ds of 

multiple oxidation states to simulate the transport of Pu in the natural system. 

Factor 4.1—Pu Natural Attenuation 

Medium to High Risk Short-Term 

OID 45 (TER Pg. 129) 

12¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE continue to evaluate significance of calcareous zone dissolution on FTF flow and transport, including conduct of tracer studies and field mapping of seepage locations along Upper Three Runs Creek. 

Factor 4.2—Calcareous Zone Characterization 

Medium Risk Low to Medium Difficulty Next PA Update 

OID 28 and 29 (TER Pgs. 146, 147, 149, 150, 178) 

MA 5 “Closure Cap Performance” 

13¶ 10 CFR 61.41 

10 CFR 61.42 10 CFR 61.44 

NRC recommends DOE provide additional model support for (i) the long-term hydraulic conductivity of the upper foundation layer and lateral drainage layer and (ii) the long-term erosion of the topsoil layer. 

Factor 5.1—Long-Term Hydraulic Performance of the Closure Cap Factor 5.2—Long-Term Erosion Protection Design 

Low to Medium Risk Medium Difficulty Long-Term Activity 

OID 5 and 6 (TER Pgs. 104, 105) 

14¶ 10 CFR 61.41 

10 CFR 61.42 10 CFR 61.44 

NRC recommends DOE conduct a preliminary evaluation of erosion protection designs (e.g., assessment of an acceptable rock source, and the ability of an integrated drainage system to accommodate design features) prior to completing the final closure cap design. 

Factor 5.1—Long-Term Hydraulic Performance of the Closure Cap Factor 5.2—Long-Term Erosion Protection Design 

Low to Medium Risk Low Difficulty Long-Term Activity 

(TER Pgs. 104, 105) 
A–5 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

MA 6 “Performance Assessment Maintenance” 

15§ 10 CFR 61.41 

10 CFR 61.42 

DOE indicated in an RAI resolution meeting on June 28 2011 (Shaffner, 2011) that it would explain the differences in the inventory lists for tanks versus ancillary equipment in future PA documentation. 

Factor 6.2—Model and Parameter Support 

Low Risk Low Difficulty Next PA Update 

 (TER Pg. 49) 

16§ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE perform a systematic scenario analysis in which FEPs are identified, screened, and dispositioned using transparent and traceable documentation of the FEPs considered, the screening arguments, and how FEPs are implemented in the models to support future WD efforts. 

Factor 6.1—Scenario Analysis 

Medium Risk Medium Difficulty Next PA Update 

OID 40 (TER Pgs. 92, 93, 95, 178) 

17¶ 10 CFR 61.41 

10 CFR 61.42 

DOE should consider uncertainty in steel liner performance, including more aggressive service conditions and corrosion mechanisms than assumed in the PA, as well as a patch model for waste release, if deemed to be risk-significant. 

Factor 6.2—Model and Parameter Support 

Medium to High Risk Medium to High Difficulty Long-Term Activity (need contingent on other factors) 

OID 7, 9, 10, 11, 12, 21, and 25 (TER Pg. 121) 

1.8.3 8¶ 

1.8.4 10 CFR 61.41 1.8.5 10 CFR 61.42 

1.8.6 NRC recommends DOE obtain additional support for probabilistic parameter distributions, including solubility limiting phases, cement Kds (based on 

sediment variability), chemical transition times, basemat bypass, and configuration probability. 

1.8.7 Factor 6.2—Model and Parameter Support 

1.8.8 Medium Risk Intermediate-Term 

OID 18, 19, 22, 24, 46 (TER Pgs. 130–132) 

19¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE acquire FTF specific data to support material property assignments, including hydraulic conductivity, moisture characteristic curves, and Kds. 

Factor 6.2—Model and Parameter Support 

Low to Medium Risk Long-Term 

(TER Pgs. 128–129) 
A–6 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

20# 10 CFR 61.41 

10 CFR 61.42 

NRC will monitor DOE’s efforts to study the impact of cement leachate on radionuclide mobility. 

Factor 6.2—Model and Parameter Support 

Low to Medium Risk Long-Term 

OID 32 (TER Pg. 126) 

21¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE address the significant amount of dispersion evident in its near-field and far-field PORFLOW models, including evaluation of the need for mesh refinement to ensure that contaminant plumes are not artificially dispersed over the volume of the cells in the far-field model. Nonphysical dispersion may be attributable to large changes in adjacent element size and large differences in element sizes between the vadose zone and far-field models. DOE should evaluate the adequacy of the time discretization of the model(s) for swiftly moving constituents such as Tc-99. 

Factor 6.2—Model and Parameter Support 

Medium Risk Low to Medium Difficulty Next PA Update 

OID 34 (TER Pgs. 149–150) 

22¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE evaluate appropriateness of the assumed level of physical dispersion in the FTF model (longitudinal and transverse vertical). 

Factor 6.2—Model and Parameter Support 

Medium Risk Low to Medium Difficulty Next PA Update 

OID 31 and 34 (TER Pgs. 149, 179) 

23¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE provide greater transparency and traceability of far-field model calibration, including consideration of more extensive calibration focused strictly on the area of interest. 

Factor 6.2—Model and Parameter Support 

Medium Risk Medium to High Difficulty Next PA Update 

OID 35 (TER Pg. 178) 

24¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE evaluate compliance with POs in 10 CFR Part 61, Subpart C at the point of maximum exposure in the UTRA. 

Factor 6.2—Model and Parameter Support 

Medium Risk Low difficulty Next PA Update 

OID 33 (TER Pgs. 147–148) 
A–7 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

25¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE evaluate plant transfer factor uncertainty in future updates to its PA. DOE should consider the appropriateness of excluding common vegetable types in its assignment of plant transfer factors (DOE only considers root vegetable data) based on production data rather than household data that might be more appropriate for a resident gardener. 

Factor 6.2—Model and Parameter Support 

Low to Medium Risk Medium difficulty Next PA Update 

OID 43 (TER Pg. 153) 

26¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE evaluate appropriateness of assumptions related to drinking water consumption in future updates to its PA, such as partitioning consumption rates based on use of both bottled and community water. Biosphere parameters should be reasonably conservative and reflect the behavior of the average member of the critical group. 

Factor 6.2—Model and Parameter Support 

Low to Medium Risk Low Difficulty Next PA Update 

OID 44 (TER Pgs. 153–154) 

27¶ 10 CFR 61.41 

10 CFR 61.42 

DOE should better assess uncertainty in the timing of peak dose, given the inherent level of uncertainty associated with predicting doses over tens of thousands of years; key parameters, such as steel liner failure times and chemical transition times may be overly constrained. 

Factor 6.2—Model and Parameter Support 

Medium to High Risk Medium Difficulty Next PA Update 

OID 18 and 46 (TER Pgs. 167, 168, 169) 

28¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE provide additional support for the likelihood of its base case or expected Case A. 

Factor 6.2—Model and Parameter Support 

Medium to High Risk Medium to High Difficulty Next PA Update 

OID 39 and 46 (TER Pgs. 167, 168, 170) 

29¶ 10 CFR 61.41 

10 CFR 61.42 

NRC recommends DOE improve transparency and documentation of its benchmarking process. NRC recommends DOE apply a more methodical and systematic approach to the benchmarking process in future updates to its PA. 

Factor 6.2—Model and Parameter Support 

Medium Risk Medium Difficulty Next PA Update 

OID 34 (TER Pg. 171) 
A–8 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

30¶ 10 CFR 61.41 

10 CFR 61.42 

NRC suggests DOE consider consistency between the plotting interval and calculation time step size. DOE should correct errors in its probabilistic assessment (e.g., porosity of 1E–20). DOE also should present results for the point of maximum exposure. 

Factor 6.2—Model and Parameter Support 

Low to Medium Risk Low Difficulty Next PA Update 

(TER Pgs. 147–148) 

31¶ 10 CFR 61.41 

10 CFR 61.42 

NRC made a general comment that DOE could improve its parameter distribution assignments, hybrid modeling approach, benchmarking process, and evaluation and interpretation of probabilistic modeling results. With respect to parameter distributions, NRC included several items in its open items database, most of which are listed in other recommendations, with the exception of probability of basemat bypass flow. 

Factor 6.2—Model and Parameter Support 

Medium Risk Medium Difficulty Next PA Update 

OID 22, 23 and 39 (TER Pg. 151) 

MA 7 “Protection of Individuals During Operations” 

32¶ 10 CFR 61.43 DOE can demonstrate compliance 

with protection of individuals during operations. 

Factor 7.1—Protection of Workers During Operations Factor 7.2—Air Monitoring 

Low Risk Low to Medium Difficulty Ongoing 

(TER Pg. 174) 

MA 8 “Site Stability” 

33¶ 10 CFR 61.44 NRC recommends DOE continue to 

evaluate closure cap settlement and stability, including consideration of (i) increased overburden from the tank grout and closure cap on settlement and (ii) potential for subsidence associated with ongoing dissolution of calcareous sediment in the Santee Formation. 

Factor 8.1—Settlement Medium Risk 

Medium to High Difficulty 1 to 5 years 

OID 30 (TER Pg. 176) 
A–9 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

34¶ 10 CFR 61.44 NRC concluded that assumed long-term 

compressive strength of the grout monolith is not adequately supported and may be optimistic based on observations of vault cracks, discussed in TER Section 4.2.9.1 (NRC, 2011). While cracking of the vault concrete and tank grout is not expected to result in significant structural tank collapse, the integrity of the vault concrete and tank grout is important to steel liner performance and waste release. 

Factor 8.1—Settlement Medium Risk 

Medium to High Difficulty 1 to 5 Years 

Other TER Recommendations 

35¶ Criterion 2—

Technology Selection 

NRC recommends DOE specifically consider and evaluate HRR removal in its technology selection and effectiveness evaluations consistent with the NDAA. 

TER Recommendation Only 

NA (TER Pgs. 55, 56, 79) 

36¶ Criterion 2—

Technology Selection 

NRC recommends DOE continuously evaluate new technologies, participate in technology exchanges, and not default to previous evaluations for technology selection. 

TER Recommendation Only 

NA (TER Pgs. 77, 78, 79) 

37¶ Criterion 2—

Removal to the Maximum Extent Practical 

NRC recommends DOE include more specificity in its process for determining HRRs are removed to the maximum extent practical, including (i) defining the term end states versus removal goals and (ii) clarifying when conditions are sufficiently similar to warrant use of a previous technology evaluation. 

TER Recommendation Only 

NA (TER Pg. 79) 
A–10 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

38¶ Criterion 2—

Removal to the Maximum Extent Practical 

NRC recommends DOE more fully evaluate or document its consideration of 

alternatives to additional HRR removal, including (i) modifications to existing technologies (e.g., upgraded Mantis or enhanced chemical cleaning); (ii) modification to tank system components (e.g., installation of a new risers or removal of equipment from existing risers); (iii) sequential cleaning (e.g., sequencing of mechanical and chemical technologies in Tank 18); and (iv) alternative cleaning technologies (e.g., alternative reagents to leach HRRs out of residual heels). 

TER Recommendation Only 

NA (TER Pgs. 79, 81) 

39¶ Criterion 2—

Removal to the Maximum Extent Practical 

NRC recommends DOE better quantify technology effectiveness. For example, DOE should better characterize waste and residual tank inventory prior to deployment of cleaning technologies to better assess effectiveness. 

TER Recommendation Only 

NA (TER Pgs. 77, 79) 

ALAR–As Low As Is Reasonably Achievable, DOE–The U.S. Department of Energy, FTF–F-Tank Farm, HRR–Highly Radioactive Radionuclide, NRC–The U.S. Nuclear Regulatory Commission, PA–Performance Assessment, RAI–Request for Additional Information, TER–Technical Evaluation Report, UTRA–Upper Three Rivers Aquifer 

*The table is organized by Monitoring Area. The cross-walk from the consultative recommendation/comment to MFs is provided in the column “Monitoring Factor.” †NRC notes that NRC monitoring pertains to assessment of compliance with the POs in 10 CFR Part 61, Subpart C. Thus, comments or recommendations related to the NDAA criterion that waste has had HRR removed to the maximum extent practical or what NRC refers to as Criterion 2 under the NDAA is only monitored if the same comment or recommendation applies 

to the ability of the disposal facility to meet Criterion 3, compliance with the POs in 10 CFR Part 61, Subpart C, including the ALARA requirements found in 10 CFR 61.41 and 61.43. If 

Criterion 2 recommendations in NRC’s TER are not tied to Criterion 3, such as ALARA, then the TER recommendations are not carried forward into monitoring. ‡Table in Appendix B. 

§Listed in DOE’S PA Maintenance Plan. ¶Not currently listed in DOE’s PA Maintenance Plan or not executed. Issue is still risk-significant and outstanding without a path forward to address. #Listed in DOE’S PA Maintenance Plan or DOE already executed the recommendation, but preliminary indications suggest that the proposal or results may be lacking. SRR–CWDA–2009–00054. “Comment Response Matrix for Nuclear Regulatory Commission (NRC) Comments on the F-Tank Farm Performance Assessment.” Aiken, South Carolina: 

Savannah River Remediation, LLC, Closure and Waste Disposal Authority. 2010. SRS–REG–2007–00002. Rev. 1. “Performance Assessment for the F-Tank Farm at the Savannah River Site.” Aiken, South Carolina: Savannah River Remediation, LLC, Closure and Waste Disposal Authority. 2010. Shaffner, J. “Summary of Teleconference Between U.S. Nuclear Regulatory Commission Staff and U.S. Department of Energy Representatives Concerning Responses to RAIs Related to 

Closure of F-Tank Farm, Savannah River Site.” Memorandum to File PROJ0734. ML111920367. Washington, DC: U.S. Nuclear Regulatory Commission. 2011. 
A–11 

Table A–1. Cross-Walk Between Consultative Review Comments, 

Recommendations, and Monitoring Areas/Factors* (continued) 

ID 

Performance 

Objective Recommendation or Comment Monitoring Factor† 

Risk, Difficulty, 

and Timing 

Ranking 

Open Item Database 

(OID)‡ and/or 

(TER Page No.) 

NRC. “Technical Evaluation Report for F-Area Tank Farm Facility, Savannah River Site, South Carolina—Final Report.” ML112371715. Washington, DC: U.S. Nuclear Regulatory 

Commission. 2011. 
A–12 

Table A–2. Grouping of NRC’s Performance Assessment Maintenance Items in Table A–1 

and Cross-Walk to DOE’s Performance Assessment Maintenance Plan 

Recommendation or Comment 

Performance 

Objective TER Section 

DOE PA 

Maintenance 

Program Section 

3.1—Scenario Analysis 

NRC recommends DOE perform a systematic scenario analysis in which DOE identifies, screens, and dispositions FEPs using transparent and traceable documentation of the FEPs considered, the screening arguments, and how FEPs are implemented in the models to support future WD efforts. 

61.41 61.42 

4.2.3 4.2.3.2 4.4 (pgs. 92, 93, 95, 178) 

SRR–CWDA–2012–00022 

3.2—Model and Parameter Justification 

DOE indicated in an RAI resolution meeting on June 28, 2011 (Shaffner, 2011), that it would explain the differences in the inventory lists for tanks versus ancillary equipment in future PA documentation. 

61.41 61.42 

3.2.3 (pg. 49) 

Uncertainty in steel liner performance, including more aggressive service conditions and corrosion mechanisms than assumed in the PA should be considered, as well as a patch model for waste release, if deemed to be risksignificant. 

61.41 61.42 

4.2.9.2 (pg 121) 

NRC recommends DOE obtain additional support for probabilistic parameter distributions, including solubility limiting phases, cement Kds (based on sediment variability), chemical transition times, basemat bypass, and configuration probability. 

61.41 61.42 

4.2.9.4 (pgs. 130–132) 

FY12: 2.3.1.2, 2.3.1.7 

NRC recommends DOE acquire FTF specific data to support material property assignments, including hydraulic conductivity, moisture characteristic curves, and Kds. 

61.41 61.42 

4.2.9.4 (pgs. 128–130) 

2.3.1.2, 2.3.1.7, 2.3.2.1, 2.3.2.2, 2.3.3, 2.3.4.2 

NRC will monitor DOE’s efforts to study the impact of cement leachate on radionuclide mobility. 

61.41 61.42 

4.2.9.3 (pg. 126) SRNL–STI–2011–

00672 (Almond, et al., 2012) 

NRC recommends DOE investigate the significant amount of dispersion in its near-field and far-field models that may be attributable to large changes in adjacent element size and large difference in element sizes between the vadose zone and far-field models. DOE also should evaluate the adequacy of the time discretization for swiftly moving constituents, such as Tc-99. 

61.41 61.42 

4.2.11.5 4.2.11.6 (pgs. 148–150) 

FY12: 3.2.2 

NRC recommends DOE evaluate the appropriateness of the assumed level of physical dispersion in the FTF model (longitudinal and transverse vertical). 

61.41 61.42 

4.2.11.6 4.4 (pgs. 149, 179) 

FY12: 3.2.2 

NRC recommends DOE provide greater transparency and traceability of farfield calibration, including consideration of more extensive calibration focused on the area of interest. 

61.41 61.42 

4.4 (pg. 178) 

FY12: 3.2.2 
A–13 

Table A–2. Grouping of NRC’s Performance Assessment Maintenance Items in Table A–1 

and Cross-Walk to DOE’s Performance Assessment Maintenance Plan (continued) 

Recommendation or Comment 

Performance 

Objective TER Section 

DOE PA 

Maintenance 

Program Section 

NRC recommends DOE evaluate compliance with the POs in 10 CFR Part 61, Subpart C, at the point of maximum exposure in the UTRA. 

61.41 61.42 

4.2.11.4 (pgs. 147–148) 

NRC recommends DOE evaluate plant transfer factor uncertainty in future updates to its PA. DOE should consider appropriateness of excluding common vegetable types in its assignment of plant transfer factors (DOE only considers root vegetable data) based on production data rather than household data that might be more appropriate for a resident gardener. 

61.41 61.42 

4.2.17 (pg. 153) 

NRC recommends DOE evaluate appropriateness of assumptions related to drinking water consumption in future updates to its PA, such as partitioning consumption rates based on use of both bottled and community water. Biosphere parameters should be reasonably conservative and reflect behavior of the average member of the critical group. 

61.41 61.42 

4.2.17 (pgs. 153-154) 

DOE should better assess uncertainty in the timing of peak dose, given the inherent level of uncertainty associated with predicting doses over tens of thousands of years; key parameters, such as steel liner failure times and chemical transition times, may be overly constrained. 

61.41 61.42 

4.2.19 (pgs. 167–169) 

NRC recommends DOE provide additional support for the likelihood of its base case or expected Case A. 

61.41 61.42 

4.2.19 4.2.19.1 4.2.19.2 (pgs. 167–168, 170) 

NRC recommends DOE improve the transparency and documentation of its benchmarking process. NRC recommends DOE perform a more methodical and systematic approach to applying the benchmarking process in future updates to its PA. 

61.41 61.42 

4.2.19.3 (pg. 171) 

NRC suggests DOE consider consistency between the plotting interval and calculation time step size. DOE should correct errors in its probabilistic assessment (e.g., porosity of 1E–20). DOE also should present results for the point of maximum exposure. 

61.41 61.42 

4.2.19.34.2.19.4 (pgs. 170–171) 

NRC made a general comment that DOE could improve its parameter distribution assignments, hybrid modeling approach, benchmarking process, and evaluation and interpretation of probabilistic modeling results. With respect to parameter distributions, NRC included several items in its open items database, most of which are listed in other recommendations, with the exception of probability of basemat bypass. 

61.41 61.42 

4.2.19 4.4 (pg. 171) 

DOE–The U.S. Department of Energy, FEP–Features, Events, and Processes, FTF–F-Tank Farm, Kds –Distribution Coefficients, NRC–The U.S. Nuclear Regulatory Commission, PA–Performance Assessment, PO–Performance Objective, RAI–Request for Additional Information, TC–Techneium, UTRA–Upper Three Rivers Aquifer, WD–

Waste Determination 
A–14 

Table A–2. Grouping of NRC’s Performance Assessment Maintenance Items in Table A–1 

and Cross-Walk to DOE’s Performance Assessment Maintenance Plan (continued) 

Recommendation or Comment 

Performance 

Objective TER Section 

DOE PA 

Maintenance 

Program Section 

Almond, P.M., D.I. Kaplan, and E.P. Shine. “Variability of Kd Values in Cementitious Materials and Sediments.” Rev. 0. SRNL–STI–2011–00672. Aiken, South Carolina: Savannah River National Laboratory. 2012. SRR–CWDA–2009–00054, Rev. 0. “Comment Response Matrix for Nuclear Regulatory Commission (NRC) Comments on the F-Tank Farm Performance Assessment.” Aiken, South Carolina: Savannah River Remediation LLC, Closure and Waste Disposal Authority. 2010. SRR–CWDA–2012–00022. “Evaluation of Features, Events, and Processes in the F-Area Tank Farm Performance Assessment. Rev.0.” Aiken, South Carolina: Savannah River Remediation, LLC. 2012. Shaffner, J. “Summary of Teleconference Between U.S. Nuclear Regulatory Commission Staff and U.S. Department of Energy Representatives 

Concerning Responses to RAIs Related to Closure of F-Tank Farm, Savannah River Site.” Memorandum to File PROJ0734. ML111920367. Washington, DC: U.S. Nuclear Regulatory Commission. 2011. 
APPENDIX B 

OPEN ITEMS DURING CONSULTATION 
B–1 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

1 Identify Tc 

solubility limiting phases 

RAI–NF–8 RAI–NF–9 

Near-field 1 1 Solubility–CZ Identify solid phase key radionuclides are 

associated within various sludge types (sequential extractions or other methods). Conduct solubility studies on tank sludges. Characterize mineralogy of various sludge types in SRS tanks. 

Open 

7 

2 Identify Pu 

solubility limiting phases 

RAI–NF–8 RAI–NF–9 

Near-field 1 1 Solubility–CZ Identify solid phase key radionuclides are 

associated within various sludge types (sequential extractions or other methods). Conduct solubility studies on tank sludges. Characterize mineralogy of various sludge types in SRS tanks. 

Open 

7 

5 Infilling of lateral 

drainage layer with coarser sediments 

RAI–IE–2 Infiltration 2 2 Cap Rerun basecase with more technically 

defensible parameters, given current knowledge base. Conduct literature review. Look at natural analogs. 

Open 

13 

6 Basis for reduced 

infiltration rate, due to residual cap performance 

RAI–IE–3 Infiltration 2 2 Cap Rerun basecase with more technically 

defensible parameters, given current knowledge base 

Open 

13 

7 As-emplaced 

versus assumed cap performance 

CC–IE–1 Infiltration 3 2 Cap Rerun basecase with more technically 

defensible parameters, given current knowledge base 

Closed 

8 Longevity of 

reducing conditions 

RAI–NF–1 Near-field 1 1 Solubility–CZ Conduct experiments to study the 

conditioning of SRS groundwaters in cements w/varying levels of degradation 

Open 

7 

9 General versus 

localized corrosion, as dominant mechanism 

RAI–NF–2 Near-field 1 2 Steel Liner Collect analog data on carbon steel in 

contact with cement. Conduct experiments to study impact of various hydrologic configurations on corrosion rates [fully immersed, partially immersed (corrosion at liquid/air interface), wet/dry cycling]. Conduct accelerated corrosion experiments with carbon steel in contact with cements of varying levels of degradation. Rerun basecase with more technically defensible parameters, given current knowledge base. Conduct literature review. 

Open 

17 
B–2 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

10 Time invariant 

and low diffusion coefficients for CO2 (carbonation) and O2 (after chloride-induced corrosion) 

RAI–NF–3 

RAI–NF–13 

Near-field 1 2 Steel Liner Collect analog data on carbon steel in 

contact with cement. Conduct experiments to study impact of various hydrologic configurations on corrosion rates [fully immersed, partially immersed (corrosion at liquid/air interface), wet/dry cycling]. Conduct accelerated corrosion experiments with carbon steel in contact with cements of varying levels of degradation. Rerun basecase with more technically defensible parameters, given current knowledge base. Conduct literature review. 

Open 

17 

11 Assumption that 

corrosion only proceeds from one-side 

RAI–NF–4 Near-field 2 2 Steel Liner Rerun basecase with more technically 

defensible parameters, given current knowledge base. 

Open 

17 

12 Wet-dry cycling 

of tank bottoms 

RAI–NF–13 Near-field 1 1 Steel Liner Collect analog data on carbon steel in 

contact with cement. Conduct experiments to study impact of various hydrologic configurations on corrosion rates [fully immersed, partially immersed (corrosion at liquid/air interface), wet/dry cycling]. Rerun basecase with more technically defensible parameters, given current knowledge base. 

Open 

17 

13 Pu 

Kds in 

middle-aged and old-aged cementitious materials (basemat)–solubility limited 

RAI–NF–7 Near-field 2 2 Basemat Rerun basecase with more technically 

defensible parameters, given current knowledge base. Conduct additional experiments to study sorption of key radionuclides to basemat. Provide additional information justifying the approach. Conduct literature review. 

Open 

10 

14 Np 

Kds in 

middle-aged and old-aged cementitious materials (basemat)–

RAI–NF–7 Near-field 2 2 Basemat Rerun basecase with more technically 

defensible parameters, given current knowledge base. Conduct additional experiments to study sorption of key radionuclides to basemat. Provide additional information justifying the approach. Conduct 

Open 

10 
B–3 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

solubility limited literature review. 

15 Consideration of 

a more mobile fraction of Tc in CZ 

RAI–NF–8 Near-field 1 1 Solubility–CZ Identify solid phase key radionuclides are 

associated within various sludge types (sequential extractions or other methods). Conduct solubility studies on tank sludges. Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

7 

16 Consideration of 

a more mobile fraction of Pu in CZ 

RAI–NF–8 Near-field 1 1 Solubility–CZ Identify solid phase key radionuclides are 

associated within various sludge types (sequential extractions or other methods). Conduct solubility studies on tank sludges. Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

7 

17 Possibility of 

radionuclide release during iron phase transitions (from magnetite to hematite) 

RAI–NF–9 Near-field 1 1 Solubility–CZ Identify solid phase key radionuclides are 

associated within various sludge types (sequential extractions or other methods). Conduct solubility studies on tank sludges. Characterize mineralogy of various sludge types in SRS tanks. Rerun basecase with more technically defensible parameters, given current knowledge base. 

Open 

7 

18 Support for 

parameter distributions related to chemical transition times 

RAI–NF–10 Near-field 1 1 Solubility–CZ Conduct experiments to study the 

conditioning of SRS groundwaters in cements w/ varying levels of degradation. Expert elicitation on chemical transition times. 

Open 

7 

19 Support for 

likelihood of solubility limiting phases 

RAI–NF–11 Near-field 1 1 Solubility–CZ Conduct solubility studies on tank sludges. 

Expert elicitation on probability of various solubility limiting phases. Rerun basecase with more technically defensible parameters, given current knowledge base. Conduct literature review. 

Open 

18 

20 Support for use 

of young cements (40-year old) in 

Kds testing for 

basemats 

RAI–NF–12 Near-field 2 2 Basemat Provide additional information justifying 

the approach 

Open 

10 
B–4 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

21 Groundwater 

in-leakage into tanks, leading to unconditioned water and conditions closer to carbon steel in contact with soil 

RAI–NF–13 Near-field 1 2 Steel Liner Collect analog data on carbon steel in 

contact with cement. Conduct experiments to study impact of various hydrologic configurations on corrosion rates [fully immersed, partially immersed (corrosion at liquid/air interface), wet/dry cycling]. Conduct experiments to study the conditioning of SRS groundwaters in cements w/varying levels of degradation. 

Open 

17 

22 Basis for 

probability of basemat bypass 

RAI–NF–14 Near-field 1 2 Basemat Rerun basecase with more technically 

defensible parameters, given current knowledge base. Provide additional information justifying the approach. 

Open 

36 

23 Basis for lack of 

consideration of basemat bypass in basecase 

RAI–NF–14 Near-field 1 2 Basemat Rerun basecase with more technically 

defensible parameters, given current knowledge base. Provide additional information justifying the approach. 

Open 

31 

24 Probability and 

consequences of a Condition 2 waste release scenario 

RAI–NF–15 

CC–NF–10 

Near-field 1 2 Waste Release Expert elicitation on probability of various 

configurations of tank system evolution. Rerun basecase with more technically defensible parameters, given current knowledge base. 

Open 

9 

25 Consequences of 

early release due to partial failure of steel liner 

RAI–NF–16 Near-field 1 1 Waste Release Rerun basecase with more technically 

defensible parameters, given current knowledge base. Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

17 

26 Lack of support 

for moisture characteristic curves 

CC–NF–9 Near-field 2 2 Waste Release Rerun basecase with more technically 

defensible parameters, given current knowledge base. 

On Hold 

9 

27 Impact of 

upwards diffusion in tank grout to results; in-tank hydraulics (diffusion or advection dominated) 

RAI–NF–10 Near-field 2 2 Waste Release Provide additional modeling results 

and evaluation 

Closed 
B–5 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

28 Impact of 

calcareous zone dissolution on flow 

RAI–FF–1 Far-field 2 2 Saturated Zone Provide additional information justifying the 

approach. Include additional complexity in modeling. Rerun models. Abstract process level model. Perform tracer tests at the seepline. 

Open 

12 

29 Impact of 

calcareous zone dissolution on transport 

RAI–FF–1 Far-field 2 2 

Kds -Saturated 

Zone 

Sorption experiments with groundwater in contact with calcareous zone sediments. Perform additional sorption studies to study Pu speciation & transport in the subsurface. Provide additional information justifying the approach. Perform geochemical modeling. 

Open 

12 

30 Impact of 

calcareous zone on site stability 

RAI–SS–3 Site Stability 2 2 Site Stability Provide additional information justifying the 

approach. Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

33 

31 Verify PORFLOW 

has an acceptable amount of hydrodynamic and numerical dispersion 

RAI–FF–3 Far-field 2 2 Saturated Zone Rerun basecase with more technically 

defensible parameters, given current knowledge base. Provide additional information justifying the approach. Sensitivity analysis to determine risk-significance. 

Open 

22 

32 Impact of grout 

leaching on saturated zone transport 

RAI–FF–4 Far-field 2 2 

Kds -Saturated 

Zone 

Provide additional information justifying the approach. Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

20 

33 Adequacy of the 

100 m point of compliance 

RAI–FF–5 Far-field 2 3 Saturated Zone Provide additional information justifying the 

approach. Provide additional modeling results and evaluation. 

Changed 

24 

34 Benchmarking 

issues (indicates PORFLOW results may be biased low); dispersivities 

RAI–FF–3 RAI–FF–6 

Far-field 2 2 Saturated Zone Rerun basecase with more technically 

defensible parameters, given current knowledge base. Provide additional information justifying the approach. Include additional complexity in modeling. Rerun models. abstract process level model. Provide additional modeling results and evaluation. 

Open 

22 and 

34 
B–6 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

35 Hydrogeological 

conceptual model uncertainty (vertical gradients, groundwater flow divide) 

CC–FF–11 Far-field 2 3 Saturated Zone Provide additional information justifying the 

approach. Sensitivity analysis to determine risk significance. Provide additional modeling results and evaluation. 

Open 

23 

36 C-14 

Kds in the 

saturated zone (used higher 

Kds

for batch experiments at longer equilibration times) 

CC–FF–7 Far-field 3 2 

Kds -Saturated 

Zone 

Rerun basecase with more technically defensible parameters, given current knowledge base. Provide additional information justifying the approach. 

Closed 

37 Np 

Kds in the 

saturated zone (higher for sand, lower for clay); clarify ranges used in PA 

CC–FF–8 Far-field 3 2 

Kds -Saturated 

Zone 

Rerun basecase with more technically defensible parameters, given current knowledge base. Provide additional information justifying the approach. Sensitivity analysis to determine risk-significance. 

Closed 

38 Location of clays 

in the SZ; impact of clay 

Kds

assignments on results 

CC–FF–6 Far-field 2 3 

Kds -Saturated 

Zone 

Rerun basecase with more technically defensible parameters, given current knowledge base. Provide additional information justifying the approach. Sensitivity analysis to determine risk-significance. 

Closed 

39 Conservatism of 

basecase in the face of large uncertainty 

RAI–PA–1 Performance 

Assessment 

1 1 Performance 

Assessment 

Peer review of DOE's basecase configuration Open 

28 and 

31 

40 Identification of 

FEPs 

RAI–PA–2 Performance 

Assessment 

2 1 Performance 

Assessment 

Conduct literature review Open 

16 

41 Basis for 

inventory uncertainty 

CC–IN–1 Uncertainty 3 3 Uncertainty Provide additional information justifying the 

approach. Collect sampling data. 

Open 

1, 2, 3, 4 
B–7 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

42 Support for 

barriers to intrusion over 10,000 year compliance period 

CC–IT–1 Intruders 2 3 Intruders Provide additional information justifying 

the approach 

Closed 

43 Lack of 

consideration of uncertainty in transfer factors/basis for selection of basecase values 

RAI–IT–1 RAI–IT–2 

Intruders 2 2 Biosphere 

Parameter 

Rerun basecase with more technically defensible parameters, given current knowledge base. Provide additional information justifying the approach. Conduct literature review. Sensitivity analysis to determine risk significance. 

Open 

5 

44 Drinking water 

ingestion rates 

RAI–IT–3 Intruders 3 3 Biosphere 

Parameter 

Rerun basecase with more technically defensible parameters, given current knowledge base. Provide additional information justifying the approach. Conduct literature review. 

Open 

26 

45 Pu Kds in the 

saturated zone 

CC–FF–9 Far-field 1 1 Kds -Saturated 

Zone 

Sorption experiments with groundwater in contact with calcareous zone sediments. Perform additional sorption studies to study Pu speciation & transport in the subsurface. Increase complexity of Pu transport modeling (e.g., consider various fractions of varying mobility and reactive transport). Include additional complexity in modeling. Rerun models. Abstract process level model. 

Open 

11 

46 Configuration 

development, configuration probabilities 

RAI–UA–1 Performance 

Assessment 

1 1 Performance 

Assessment 

Expert elicitation on probability of various configurations of tank system evolution 

Open 

27 and 

28 

47 Uncertainty in 

timing versus magnitude of peak dose 

RAI–UA–2 Uncertainty 3 3 Uncertainty Provide additional modeling results 

and evaluation 

Closed 

48 Configurations E 

and F (consider in the basecase) 

RAI–UA–4 Uncertainty 2 3 Uncertainty Provide additional modeling results 

and evaluation 

Open 

18 
B–8 

Table B–1. Open Items Database Data Transmitted to DOE Via Meeting Summary 

Held on February 17, 2011 (NRC, 2011) (continued) 

ID Open Item 

Related 

Comment 

Technical 

Category Priority 

Resolution 

Difficulty 

Technical 

Subcategory NRC Recommendation(s) to DOE 

Status 

Table 

A–1 ID 

49 Intruder 

sensitivity analysis 

CC–IT–2 CC–IT–3 

Intruders 2 3 Intruders Provide additional information justifying the 

approach. Sensitivity analysis to determine risk significance. Provide additional modeling results and evaluation 

Closed 

FEP–Features, Events, and Processes, Kds –Distribution Coefficients, RAI–Requests for Additional Information, SRS–Savannah River Site, Tc–Technetium NRC. “Summary of Teleconference Between the U.S. Nuclear Regulatory Commission Staff and the U.S. Department of Energy Representatives Concerning Requests for Additional 

Information Pertaining to the Draft Waste Determination and Related Performance Assessment Related to the Closure of the F-Area Tank Farm at the Savannah River Site.” Note to File (15 March 2011) From J. Shaffner (NRC). ML110700511. Washington, DC: U.S. Nuclear Regulatory Commission. 2011. 
APPENDIX C 

MA 2 “WASTE RELEASE” 
C–1 

APPENDIX C 

Monitoring Area (MA) 2 “WASTE RELEASE” 

The Department of Energy (DOE) relies on solubility controls in the residual waste to constrain 

aqueous phase concentrations of highly radioactive radionuclides (HRRs) released from the 

waste tanks and associated groundwater doses to a potential receptor. In DOE’s performance 

assessment (PA), solubility limiting phases and the resulting solubility limits are often a function 

of the chemical environment in the contaminated zone. The chemical environment of the 

contaminated zone is affected by chemical conditioning from the overlying grout, which is 

intended to ensure a high pH and low Eh chemical environment in the contaminated zone for 

thousands to tens of thousands of years, thereby delaying significant release of key HRRs 

beyond the 10,000-year period of performance. 

In its technical evaluation report (TER) (NRC, 2011), the Nuclear Regulatory 

Commission (NRC) staff presented a number of observations and recommendations. 

Staff’s primary recommendation related to Criterion 3, as stated in the Executive Summary, 

is as follows: 

NRC staff recommends DOE conduct waste release experiments to increase support for 

key modeling assumptions related to: (i) the evolution of pH and Eh in the grouted tank 

system over time; (ii) identification of HRR association with solid phases comprising the 

residual wastes; and (iii) expected solubility of HRRs under a range of environmental or 

service conditions that the residual wastes in the contaminated zone are expected to be 

exposed to over time. Implementation of this recommendation is deemed crucial for 

NRC staff to have reasonable assurance that the performance objectives (POs) in 10 

CFR Part 61, Subpart C, can be met. Given the risk-significance of Tank 18 to the 

overall PA and the short timeline for closure of this tank, DOE should initiate discussions 

with NRC staff regarding implementation of this recommendation for Tank 18 as soon as 

practical. Experiments to address this recommendation should be conducted prior to 

final closure of this single tank. Results of Tank 18 residual waste experiments will be 

evaluated by NRC staff to determine the need for additional data collection, experiments, 

and modeling. For Tank 18, as well as other F-Tank Farm (FTF) tanks, additional 

information regarding NRC staff’s recommendations in this area, including details on the 

suggested implementation of other recommendations listed below will be provided in 

NRC staff’s plan for monitoring the FTF later in fiscal year (FY) 2012. 

As a result, NRC has identified the following monitoring factors (MFs) related to waste release: 

• Solubility Limiting Phases/Limits and Validation (see Section 3.2.1) 

• Chemical Transition Times and Validation (see Section 3.2.2) 

Since DOE assumes the chemical transition to more soluble conditions occur for the most 

risk-significant HRRs in the DOE PA, both: (i) the nature of flow through the tank grout 

(e.g., fracture versus matrix flow) that dictates the reactive surface area and amount of grout 

available to condition infiltrating water, and (ii) the assumed rate of change of Eh and pH also 

are important to the compliance demonstration. Uncertainty related to flow through the tank 

grout is considered under MA 3, “Cementitious Material Performance,” which is concerned with 

the hydraulic (rather than the chemical) performance of cementitious materials mitigating FTF 

releases and doses. 
C–2 

Other NRC technical evaluation report (TER) recommendations related to waste release are 

binned under PA maintenance activities under MA 6 until overall facility performance is better 

understood and constrained. Should the results of the experiments indicate less than favorable 

performance, NRC staff expects DOE to assess the impact on the results of the PA. NRC staff 

also will assess the need for additional experiments, data collection, and modeling to provide 

support for key barriers in DOE’s PA that might serve to mitigate underperformance of chemical 

barriers. If the results of the experiments show that key radionuclides are strongly retained in 

the residual waste, NRC staff expects other MAs or MA components will become less important 

and may be closed as monitoring progresses. 

Special Considerations for Tank 18 

Since preparation of the FTF PA, DOE has performed additional analysis to study potential 

solubility of Pu in Tank 18 to support the final waste determination (WD) and near-term 

[calendar year (CY) 2012] closure of this tank (Denham, 2012). The analysis indicates that Pu 

may be present in the tank waste waters at risk-significant concentrations for what DOE 

describes as “conservative” or higher Eh conditions, or that Pu also can be relatively insoluble at 

what DOE describes as more “realistic” or lower Eh conditions. These results are important, as 

they show that peak doses could either be similar to those doses reported in DOE’s PA 

(i.e., hundreds of mrem/yr) or that the peak doses from Pu could be insignificant. However, only 

through additional analyses and experimental validation can DOE confirm the geochemical 

modeling results and present a more accurate measure of risk. It also is important to note that if 

higher Eh conditions prevail, DOE models predict releases from the tanks much earlier in time. 

In Figure 3-4, a green dashed line that dissects the tank grout and contaminated zone chemical 

barriers35 at around 10,000 years for Type IV tanks (including Tank 18)36 marks the first 

chemical transition from reducing to oxidizing conditions, corresponding to the time at which Pu 

is expected to be released at risk-significant rates based on DOE’s updated solubility modeling. 

Risk-significant release of Pu-239 at higher solubility are predicted by DOE PA models to occur 

much earlier in the updated solubility modeling than assumed in DOE’s PA (i.e., Pu-239 was 

previously assumed to be released at risk-significant rates only after the second chemical 

transition to lower pH marked with a red dashed line after 30,000 years in Figure 3-4). If 

performance of the tank grout, steel liner, or basemat is slightly less than assumed in DOE’s 

base case scenario, then release of Pu-239 into the surrounding environment could occur within 

the 10,000 year period of performance. 

Given the risk-significance of Tank 18 to the overall FTF PA and DOE’s planned near-term 

closure of Tank 18 in CY 2012, NRC staff recommended in its TER (NRC, 2011) that DOE 

initiate discussions with NRC staff regarding implementation of waste release experiments for 

Tank 18, as soon as practical. In its TER (NRC, 2011), NRC staff recommended experiments 

be conducted prior to closure of the tank. After issuance of NRC’s TER (NRC, 2011), a peer 

review group recommended DOE update its geochemical modeling and validate modeling 

results with follow-up experiments (Cantrell, et al., 2011) consistent with NRC 

recommendations. The peer review report, however, suggested that validation experiments 

could occur after tank grouting had been completed. Consistent with the peer review group 

recommendation, DOE decided to grout the tanks and perform follow-up experiments to study 

waste release later in CY 2012 (SRR–CWDA–2012–00020). 

 

35Tank grout and contaminated zone chemical barriers are combined and shown in purple in Figure 3-4. 36Type IV tanks are illustrated in the bottom set of three panels in Figure 3-4. 
C–3 

Monitoring Factor 2.1—Solubility-Limiting Phases/Limits and Validation 

The key radio-elements that are expected to significantly contribute to receptor dose and 

are sensitive to solubility limits are technetium (Tc), neptunium (Np), and plutonium (Pu). 

As discussed in NRC’s TER (NRC, 2011), DOE models solubility limits for these elements in 

the DOE PA, for pure phases and, in cases of Tc and Pu, as co-precipitates with iron 

oxyhydroxide minerals in the residual waste. NRC staff will, therefore, emphasize these 

elements in monitoring how DOE treats their concentration-limited release in PA. 

As mentioned above, NRC staff’s primary recommendation in its TER (NRC, 2011) was that 

DOE conduct waste release experiments to increase support for key modeling assumptions. 

Accordingly, NRC will monitor experiments conducted by DOE to address the primary 

recommendation. With respect to the experiments, DOE should develop a plan to analyze key 

radionuclides that rely on solubility for control, such as Pu, Tc, and Np. The experiments should 

consider the effects of reagents (e.g., oxalic acid) used to remove radionuclides from the tank 

residue, including formation of new compounds that may alter leachability of key radionuclides. 

DOE should determine the number of samples to be analyzed from each waste tank based on 

characterization results that show the homogeneity or lack thereof of residual waste remaining 

in the tanks. 

NRC recommends DOE perform experiments for residual waste from Tank 18 in the short-term 

and, based on the results of the first set of experiments and expected intertank variability, 

determine the need for additional experiments for remaining tanks. Decisions on additional 

experiments should be based on expected tank risk; HRRs targeted for these studies should be 

those that are the largest risk drivers and for which the reliance on chemical retention is 

greatest. The experiments should be representative of the final chemical and physical form of 

the waste (e.g., should reflect post chemical treatment for those tanks where chemical cleaning 

is selected as the preferred technology). 

While grouting of Tank 18 has been completed, DOE should conduct tests recommended by the 

peer review group (Cantrell, et al., 2011) using archived samples of the tank heels or additional 

samples were obtained before grouting commenced. The need for this information is important, 

especially when considering waste reactions with water and the subsequent interactions of this 

leachate with soil underlying the tanks. 

The remainder of this section will address, in turn, each of the three elements for which 

waste release is most significant to calculated dose. The Pu section exceeds the others in 

length mainly because recent information has become available that warranted discussion; 

the DOE efforts that led to much of the new information may eventually provide relevant data for 

Tc and Np. 

Technetium 

Under Oxidized Region III conditions, no solubility limit is placed on Tc in the DOE PA. 

Concerning Reduced Region II and Oxidized Region II, however, NRC staff still has questions 

regarding the applicability of the iron co-precipitation model for Tc. It appears these concerns 

will be moot if the tank Tc-99 inventories are reduced enough by cleaning, such that the Tc 

solubility limit is not risk-significant. If Tc-99 tank inventories continue to be sufficiently low, 

NRC staff may not need to monitor Tc solubility limit issues. 
C–4 

Neptunium 

NRC’s TER (NRC, 2011) observed that Np pure-phase solubilities used in the PA appeared 

reasonable. These solubility values, ranging from 1.6 × 10-9 to 1.1 × 10-4 M (SRS–REG–2007–

00002, Rev. 1, Table 4.2-10), have the potential to be risk-significant if release and chemical 

transitions occur before 10,000 years. In addition, there are indications that DOE may employ 

iron co-precipitation for Np release in later PA efforts. NRC staff will, therefore, continue to 

monitor the Np solubility topic, including the iron co-precipitation issue and any recalculations of 

solubility limits using thermodynamic models. 

DOE assumes the basemat is quite effective in limiting Np release in its FTF PA. Accordingly, 

monitoring activities concerning the Np Kds in the basemat (Cementitious Materials 

Performance MA3) are discussed under MA 3, “Cementitious Materials Performance,” as 

well as those concerned with flow through the basemat, which are discussed further under 

MA 5,”PA Maintenance.” 

Plutonium 

Pu release and, therefore, dose are highly sensitive to the contamination zone solubility limit. 

The DOE plot seen in Figure C–1 shows that, if timing is disregarded, any Pu solubility limit 

above 1 × 10-10 M could yield doses that exceed the 10 CFR 61.41 compliance limit. 

Independent NRC staff analyses corroborate DOE’s sensitivity analysis results and show that 

peak release rates (and therefore doses) are relatively insensitive to solubility at higher solubility 

levels but that, at some threshold value, tank waste solubility becomes increasingly controlling 

with respect to peak release and dose. Because NRC staff remains unconvinced of the timing 

of release, owing to uncertainty in chemical transition times and potential for tank grout bypass, 

a solubility limit exceeding 1 × 10-10 M, under any set of chemical conditions, has the potential to 

lead to an unacceptable dose within 10,000 years. Because Pu solubility limit is highly 

dependent on the iron co-precipitation model and on assumptions regarding any solubility 

limiting pure Pu phases, recommended waste release studies discussed earlier are particularly 

critical for Pu. 

Table C–1 also shows that a Pu solubility at the source of less than 1 × 10-10 M is not likely to be 

risk-significant, considering minimal credit for the performance of other FTF barriers. The 

concentrations were calculated based on the DOE-calculated pathway dose conversion factor 

for Pu-239 that provides the dose to groundwater concentration ratio for this key radionuclide. 

DOE convened a peer review group to assess recommendations and comments NRC made in 

its TER (NRC, 2011), specifically with regard to the technical justification for the assumptions 

and technical bases for modeling Pu release from tank residual wastes. Much of this effort 

focused on the solid phases of Pu in the waste and the modeling activities associated with 

assessing solubility of those phases. The peer review group’s report points out the DOE 

analysis of chemistry in the tanks only provides “possible clues as to the potential nature of Pu 

speciation in the precipitates and residues left in the tank after extensive cleaning” (Cantrell, et 

al., 2011, p. 7). In addition, the report states, “There is no real understanding of the nature of 

Pu speciation in tank precipitates” (Cantrell, et al., 2011, p. 8). The peer review team’s findings 

are based on several days of discussions with Savannah River Site (SRS) personnel, but 

presumably the peer review team was exposed to material similar to that contained in 

Hobbs (2012) report. 
C–5 

Figure C–1. Revised Tank 18/Tank 19 Special Analysis (SRR–CWDA–2010–00124, Rev. 0, 

Figure 6.3-23) Showing the Sensitivity of Calculated Dose to the Plutonium 

Solubility at the Waste Residue 

Table C–1. Risk-Significant Concentrations of Pu-239 in the Environment Based on 

DOE F-Tank Farm Performance Assessment Modeling 

Standard 

Concentration 

(pCi/L) 

Concentration 

(mol/L) 

Intruder 5 mSv/yr 1,100 7 × 10-11

Member of the Public 0.25 mSv/yr 55 4 × 10-12

Pathway Dose Conversion Factor = 4.5E-03 mSv/yr per pCi/L 

Specific Activity = 0.063 Ci/g 

1 pCi/L = 3.7 × 10-02 Bq/pCi 

(NRC has no information on the material presented to the peer review group, beyond what is 

stated in its report.) The peer review team stated that, to provide a stronger scientific foundation 

to justify the use of geochemical modeling in the tank closure PA, validation and verification of 

the model and assumptions are required. 

With respect to tank waste residues, the peer review group recommended: 

(1) Spectroscopic analyses [e.g., Extended X-Ray Absorption Fine Structure or (EXAFS)] of 

Pu and other metals in the waste residues. 
C–6 

(2) Leach tests that use leachant solutions representative of aged as well as fresh grout and 

deionized water. The recommended leach tests would include the following features: 

• Chemical analysis including all major ions, pH, alkalinity, Eh, and appropriate trace 

components (e.g., Pu, Fe, and sulfide). 

• Solids characterization after leaching, because new phases may have precipitated or 

some phases may have dissolved completely. 

• Geochemical modeling with the leachate data as input, in order to validate and verify the 

solubility model and certain assumptions used in the model. 

In addition to these peer review group recommendations, Hobbs (2012) recommended that if 

the presence of PuO(CO3)(am,hyd) is confirmed by X-ray absorption analysis, experiments be 

conducted to determine if Pu carbonates can be transformed back into PuO2(am,hyd) upon 

contact with grout. 

Many of the tests that were recommended by the peer review group are consistent with NRC’s 

TER (NRC, 2011) recommendations. These tests have not been conducted yet. With this in 

mind, NRC staff is not confident that DOE has adequately characterized tank waste residues, 

especially with respect to the forms and behavior of the transuranic elements, to allow 

reasonable assurance that releases from the tanks have been appropriately modeled. The 

complex behavior of Pu and the variety of tank configurations, materials, and potential pathways 

for water to short-circuit closure conditions suggest DOE should conduct carefully considered 

leaching studies coupled to site-specific soil interaction analysis. Specifically, DOE should 

conduct leaching studies to ascertain maximum solubilities and leach rates of key radionuclides 

from the tank heels. These tests should represent different scenarios of waste-grout 

interactions that control factors such as pH and speciation. DOE could use leachate from the 

experiments to define site-specific Kds values, based on waste-specific releases. 

Hobbs (2012) provides a discussion of the possible solid phases and aqueous species in which 

Pu may reside in residual SRS tank wastes, based on observations of Tank 18 residues, the 

tank operational history, and the literature. A variety of metals, including Pu, that precipitate 

from solution as acidic residues from spent fuel dissolution are made alkaline by addition of 

NaOH. Hobbs describes three forms that the Pu may take if it co-precipitates with other, much 

more abundant metals, such as iron and aluminum. One potential form is Pu substitution for 

another metal in a crystal lattice, a second is physical occlusion into a mass of precipitated 

material without becoming part of the structure, and a third is adsorption onto surfaces of the 

material. In each of these cases, Pu would be expected to be uniformly dispersed in the solid. 

However, recent Scanning Electron Microscopy (SEM) analyses of a single Tank 18 waste 

sample (Hay, et al., 2012) show Pu present as discrete, small (<1 μm) particles that are not 

evenly distributed within the precipitated matrix. The Pu mass represented by these particles 

seems to be smaller than total Pu in the sample, suggesting that some Pu also is 

co-precipitated. Perhaps more importantly, the concentrations of Pu in Tank 18 waste liquids 

(1 × 10-8 M and 3 × 10-8 M) were “well above the predicted solubilities for PuO2(am,hyd) and 

co-precipitated Pu(IV)” (less than 2 × 10-9 M) (Hobbs, 2012). 

Further, Hobbs (2012) discusses how the speciation of Pu in the waste may be impacted by 

changes in pH and ingress of CO2, resulting from continual active ventilation of the tanks to 

control hydrogen accumulation. The presence of CO2 gas over a strongly alkaline solution will 

result in accumulation of carbonates in solution, inducing the formation of PuO(CO3)xH2O(solid) or 
C–7 

Pu(OH)2(CO3)(solid) in the presence of aqueous Pu carbonate species. In fact, carbonate 

concentrations of about 0.04 M were measured in the aqueous phase of Tank 18 heels. 

A recent X-Ray Diffraction (XRD) analysis of Tank 18 heels shows the presence of 

Na4UO2(CO3)3 and calcite at about 10 percent of the crystalline solid phase material (Hay, 

et al., 2012). The presence of these solids and the measured aqueous carbonate 

concentrations strongly suggests that some Pu in the heels is in a carbonate form. These 

observations have important implications for how Pu solubility is modeled, because the solubility 

limits for these carbonate phases could differ substantially from the hydrated Pu oxides used in 

DOE models. If Pu is present as a carbonate solid, then at pH 9.8, Pu solubilities of around 

1 × 10-6 M can be expected (Hobbs, 2012). In addition, these observations mean that at least 

some of the Pu in the aqueous phase will be negatively charged carbonate complexes, which 

will have very low Kds values. 

In the recent special analyses for Tanks 18 and 19 (SRR–CWDA–2010–00124), DOE assumes 

that reaction of Pu carbonate species with the high pH of the grout will convert all Pu to the 

lower-solubility phases Pu(OH)4(am) or PuO2(am, hyd). Presumably, this would take place with free 

alkaline water released during grout setting or with water that percolated from the surface 

through the grout. In many release scenarios, water in the system will be alkaline before it 

contacts the waste residue. This seems reasonable for many situations. However, there are 

several important processes that may preclude the conditioning of water entering the 

contamination zone. Based on information presented in the PA, the Pu Peer Review Report, 

and Hobbs (2012), there are potential radionuclide release scenarios that may lead to greater 

leach rates than expected from the PA. 

The recent analysis of one sample of tank residue by SEM and XRD has altered the conceptual 

model presented in the PA. From Hobbs (2012), it is reasonable to think that Pu may be 

present in at least three forms in the heels, and the higher than expected concentrations of 

aqueous Pu highlight this point. This illustrates the importance of doing a characterization of the 

waste, as outlined above. Other radionuclides that cannot be detected by the solid phase 

analytical techniques may be better characterized by the leach tests. Moreover, release rates of 

Pu and other related elements as well as their speciation can be used by DOE to validate 

modeling of this system. 

In summary, DOE should characterize tank heels as recommended in NRC’s TER (NRC, 2011) 

and by the DOE peer review group. These analyses, to be conducted on multiple samples, 

include: XRD; SEM/Energy Dispersive Spectroscopy (EDS); synchrotron-based studies, such 

as X-Ray Absorption Near Edge Structure (XANES); synchrotron microprobe; and EXAFS for 

selected materials. Leach tests need to be conducted under differing environmental conditions. 

Analyses of the leachates should attempt to determine the aqueous speciation of Pu. Tests 

need to be conducted to assess the ability of fluids from the grout to transform Pu carbonate 

solids to Pu(OH)4(am) or PuO2(am, hyd). 

Monitoring Factor 2.2—Chemical Transition Times and Validation 

DOE relies on geochemical modeling to estimate the time at which two key chemical transitions 

take place (i) transition from reduced to oxidized conditions reflected in an increase in Eh 

and (ii) transition from relatively high to relatively low pH reflected in a decrease in pH. In 

Section 4.2.9.3 of its TER (NRC, 2011), NRC staff discussed its concerns with the geochemical 

modeling results, which may be attributable to assumptions such as the solid phases that 

comprise the tank grout, the characteristics of the infiltrating groundwater, uncertainties in the 

thermodynamic data used in the modeling, or assumptions regarding the ability of grout 
C–8 

components to react with and condition infiltrating groundwater. As illustrated in Figure C–2 

(NRC, 2011, Figure 4-5), NRC staff questioned the shape of the pH vs. time curve generated, 

using the results of DOE’s geochemical modeling. The experimental data presented in Figure 

C–2 suggest that DOE’s conceptual model or modeling results related to chemical transition 

times may be flawed. 

Chemical transition times also are dependent on the nature of flow through the grouted tanks. If 

flow is primarily through cracks, only a small fraction of the total mass of tank grout may come 

into contact with infiltrating water over time, thereby limiting the effective reductive and buffering 

capacity of the tank grout and hastening chemical transitions to higher solubility. MF 3.2—

Groundwater Conditioning and MF 3.3—Shrinkage and Cracking, discussed in Sections 3.3.2 

and 3.3.3 and Appendix D is concerned with the potential for preferential pathways to form 

that by-pass the tank grout, limit groundwater conditioning, and lead to faster chemical 

transition times. 

For these reasons, NRC staff does not believe a compelling case has been made yet that waste 

release or the chemical transition to Oxidized Region II will be limited to times after the 

10,000-year compliance demonstration period. For the purposes of waste release, NRC staff 

assumes releases and chemical transitions can occur before 10,000 years. Until DOE resolves 

questions of the timing of release and chemical transitions, the FTF compliance demonstration 

will depend on whether the highest solubility limits identified as result of monitoring activities 

conducted by DOE under MF 2.1 will lead to doses that meet or exceed the dose limits in 

10 CFR 61.41 and 61.42. 

Since preparation of DOE’s PA and NRC’s TER (2011), DOE has performed additional 

modeling (Denham, 2012) that updates the chemical transition times presented in DOE’s PA. 

As part of this MF, NRC will review information provided in the updated solubility report as a 

technical review activity. However, DOE should perform experiments to validate results of the 

Figure C–2. Experimental Versus Modeled Change in pH Versus Displaced Pore Volumes 

(Dimensionless Time) (NRC, 2011, Figure 4-5; Fuhrmann and Gillow, 2009) 
C–9 

updated geochemical modeling. As NRC staff has expertise in design and implementation of 

relevant experiments, DOE should discuss with NRC staff its plans to ensure that experiments 

are designed to optimize their usefulness in supporting the 10 CFR 61.41 compliance 

demonstration. NRC staff also may observe DOE experiments related to this MF in conjunction 

with an onsite observation at the FTF. This MF will be closed when DOE completes 

experiments to study the evolution of pH and Eh in the tank grout over time to provide more 

accurate estimates of chemical transition times to higher solubility. 

In addition to concerns regarding geochemical modeling results that show the evolution of pH 

and Eh over time, NRC staff also is concerned that the reducing capacity of the tank grout may 

not be readily transferable to the waste zone; DOE PA modeling assumes the waste zone 

remains in a reduced state for thousands of years (see purple barrier to the left of the green 

dashed line in Figure 3-4), based on conditioning from the overlying grout. NRC will, therefore, 

monitor the ability of FTF tank grout to maintain reducing conditions in the waste zone through 

experimentation or other support. 

References 

Cantrell, K., D.L. Clark, D.R. Janecky, J. Psaras, and W. Runde. “Plutonium Solubility Peer 

Review Report.” LA–UR–2012–00079. Los Alamos, New Mexico: Los Alamos National 

Laboratory. 2011. 

Fuhrmann, M. and J. Gillow. “Fate of Contaminants in Contact With West Valley Grouts.” 

BNL–82395. Upton, New York: Brookhaven National Laboratory. 2009. 

Hay, M.S., P.E. O’Rourke, and H.M. Ajo. “Summary of XRD and SEM Analysis of Tank 18 

Samples.” Rev. 0. Memorandum (February 23) to F.M. Pennebaker (NRC). 

SRNL–l3100–2012–00017. Aiken, South Carolina. Savannah River National Laboratory. 

2012. 

Hobbs, D.T. “Form and Aging of Plutonium in Savannah River Site Waste Tank 18, Savannah 

River National Laboratory.” SRNL–STI–2012–00106. Aiken, South Carolina: Savannah River 

Nuclear Solutions, LLC. 2012. 

SRR–CWDA–2010–00124, Rev. 0. “Tank 18/Tank 19 Special Analysis for the Performance 

Assessment for the F-Tank Farm at the Savannah River Site.” Aiken, South Carolina: 

Savannah River Remediation, LLC. 2012. 

SRS–REG–2007–00002, Rev. 1. “Performance Assessment for the F-Tank Farm at the 

Savannah River Site.” Aiken, South Carolina: Savannah River Remediation, LLC, Closure and 

Waste Disposal Authority. 2010. 
APPENDIX D 

MA 3 “CEMENTITIOUS MATERIAL PERFORMANCE” 
D–1 

APPENDIX D 

Monitoring Area (MA) 3 “CEMENTITIOUS MATERIAL PERFORMANCE” 

The Department of Energy (DOE) relies on the cementitious materials to (i) limit the transport of 

corrosive species to the steel tank liner, thereby promoting the longevity of the steel liner to limit 

water from entering the tanks and contacting the residual waste; (ii) condition the chemistry of 

the water contacting the residual waste, thereby limiting dissolution of radionuclides associated 

with the residual waste (see MA 2 for a discussion of dissolution of residual waste); (iii) retard 

transport of radionuclides released from the residual waste; and (iv) stabilize waste residuals. 

These capabilities are directly dependent upon the hydraulic performance of the cementitious 

materials. The Nuclear Regulatory Commission (NRC) has identified the following monitoring 

factors (MFs) related to the capabilities of the cementitious materials to limit or mitigate releases 

from the F-Tank Farm (FTF): 

• Concrete Vault Performance (As It Pertains to Steel Liner Corrosion Modeling) 

• Groundwater Conditioning 

• Shrinkage and Cracking 

• Grout Performance 

• Basemat Performance 

• Use of Stabilizing Grout [As It Pertains to As Low As Is Reasonably 

Achievable (ALARA)] 

Technical uncertainties related to the geochemical modeling performed to estimate the extent to 

which groundwater is conditioned by the tank grout and geochemical changes over time is 

addressed under MA 2 “Waste Release,” MF 2.2—Chemical Transition Times. MA 3 

“Cementitious Material Performance,” MF 3.2—Groundwater Conditioning, focuses on the 

nature of flow or the hydraulic performance of the tank grout. Both monitoring factors, however, 

pertain to the rate at which grout degradation proceeds and leads to changes in the chemistry of 

the infiltrating water over time and are therefore, closely related. 

Other NRC technical evaluation report (TER) recommendations related to cementitious material 

or steel liner37 performance are binned by NRC under performance assessment (PA) 

maintenance activities under MA 6 until NRC obtains a better understanding of overall FTF 

facility performance. Should the results of experiments conducted under MA 2 “Waste Release” 

or MA 3 “Cementitious Material Performance” indicate less than favorable results, NRC staff 

expects DOE to assess the impact on the results of the PA. NRC staff also will assess the need 

for additional experiments, data collection, and modeling to provide support for key barriers in 

DOE’s PA that might serve to mitigate underperformance of chemical and hydraulic barriers. 

If the results of waste release experiments show key radionuclides are strongly retained in 

the residual waste, NRC staff expects other MAs or MA components, including MA 3 

“Cementitious Material Performance,” will become less important and may be closed as 

monitoring progresses. 

Monitoring Factor 3.1—Concrete Vault Performance (As It Pertains to 

Steel Liner Corrosion) 

DOE relies on steel liners to limit water flow to the residual waste remaining in the tanks. 

 

37Steel liner performance is indirectly related to cementitious material performance under MF 3.1—Concrete 

Vault Performance. 
D–2 

DOE’s steel liner corrosion modeling relies on concrete vaults, which enclose the high-level 

waste (HLW) tanks, as barriers to fluid flow. DOE assumes the cementitious materials 

surrounding the steel liners will provide a passive chemical environment that will limit corrosion 

to a low general corrosion rate {1 μm/yr [0.04 mil/yr] in the base case scenario} prior to 

carbonation- or chloride-induced steel depassivation that can lead to higher corrosion rates. 

Because chemical species that induce corrosion (i.e., water, chloride, carbon dioxide, and 

oxygen) need to be transported through the cementitious materials, NRC staff finds that the 

uncertainty in steel tank liner longevity is related primarily to the hydraulic properties of the 

cementitious materials and their effect on the persistence of a chemical and physical 

environment that will limit corrosion of the steel liner. 

DOE’s corrosion analyses use diffusion coefficients of carbon dioxide, chloride, and oxygen 

applicable to intact concrete to model the transport of these species through the concrete vault. 

Although earlier corrosion initiation times and corrosion rates significantly higher than the 

general corrosion rate could result if the corrosion analyses assume higher diffusion 

coefficients, higher values are applied by DOE, only in limited cases in its FTF probabilistic 

assessment (i.e., they are not considered in the base case assessment). Also, DOE assumes 

concrete vault degradation starts once carbonation reaches one-half the concrete thickness, 

even though steel reinforcements typically have only a few inches of concrete cover. Although 

rebar corrosion-induced cracking of concrete would be delayed relative to carbonation of the 

concrete cover, initiation of concrete vault degradation may initiate sooner than assumed in 

DOE’s concrete degradation analysis. 

Additionally, although groundwater in-leakage into the concrete vaults is evident at the 

Savannah River Site (SRS) site, DOE does not consider this phenomenon an important factor 

that could influence the expected performance of the concrete vaults and steel liner. DOE 

projects the steel liners for 18 of 22 tanks fail after 10,000 years in the FTF PA reference case. 

The steel liners of four Type IV tanks are projected by DOE to fail in the DOE PA after 

3,600 years and, thus, these tanks also provide a rather significant barrier to waste release. 

Because Type IV tank bottoms are near the water table, NRC staff also is concerned that 

intermittent flooding of the tank bottoms due to water table fluctuations over the long period of 

performance could (i) expose the tank liners periodically to corrosive environments and (ii) 

cause contaminants exiting the basemat to be released directly into the saturated zone. For 

example, DOE corrosion analyses conducted to support the H-Tank Farm (HTF) PA (SRR–

CWDA–2010–00128, Rev. 0) indicate that corrosion could be significantly enhanced if the tanks 

are exposed to groundwater. These analyses indicate the median time to failure for HTF Type I 

tanks decreases to 4,183 years in the presence of groundwater from 7,630 years in soils with no 

significant groundwater, and the median time to failure of HTF Type II tank decreases to 4,890 

years in the presence of groundwater from 13,600 years in soils with no significant groundwater. 

Also in the HTF PA, the contaminant flux leaving submerged or partially submerged waste tanks 

pass directly into the saturated zone. Given the risk significant barrier to waste release provided 

by the SRS FTF Type IV tanks, DOE should evaluate the potential effect of exposure of Type IV 

tanks to water table fluctuations on waste release. Amidon, et al. (2012) also notes that given 

the close proximity of Type I tanks to the water table, the likelihood that groundwater could 

come in contact with the grouted tanks is high since the average depth to water ranges from 

0.3 to 2 m [1 to 6 ft]. 

Given the risk significance of the steel liner barrier, DOE should provide additional support for 

the assumptions used in its base case assessment that concrete vaults will remain an effective 

fluid flow barrier that prevents exposure of the tanks to corrosive conditions for thousands to 

tens of thousands of years. A peer review panel that evaluated the DOE PA modeling of waste 
D–3 

release and transport noted that fracturing of the cement-based material with preferential flow 

through cracks would appear to be a more likely scenario that should be evaluated (Cantrell, et 

al., 2012). While referring to the waste release model, this statement by the peer review panel 

also applies to cementitious material degradation, suggesting that slow carbonation of 

cement-based material by diffusion of carbon dioxide seems like a low probability scenario. 

NRC staff will review reports, analog studies, and other information used to support DOE’s 

assumption regarding initial conditions and performance of the concrete vaults. For example, 

NRC staff will review annual tank inspection reports that provide information regarding 

trenching, scarifying, and cracking of the concrete vaults, as well as information about 

groundwater intrusion into the tank vaults. NRC staff will review reports related to previous 

events that led to potential releases for groundwater in-leakage through joints or cracks in the 

concrete vaults. Analog studies could include review and evaluation of information obtained 

from West Valley or other analog sites to better understand the potential for and rates of 

corrosion of HLW tanks/components, as well as mitigative design measures. As part of this MF, 

NRC staff also will consider the potential for earlier steel liner failure than assumed in DOE’s PA 

due to corrosion of steel components (e.g., rebar) in the concrete vaults that are close to the 

vault surface. 

If DOE performs additional modeling or experiments to study the potential for transport of 

deleterious species into the tank vaults and subsequent corrosion of the steel liners or tanks, 

NRC staff will review the documentation or provide input on the design and results of the 

experiments. Experiments to study steel liner corrosion are expected to be relatively difficult to 

implement with unknown benefit compared to other experimental investigations recommended 

in NRC’s TER (2011) and discussed in this monitoring plan. Therefore, these experiments are 

not considered a high priority by NRC staff at this time. NRC staff will assume the steel liners 

will not be effective at mitigating releases for the long periods of time relied on for performance 

in the FTF PA and will investigate the support for the performance of other barriers to ensure 

that the performance objectives (POs) can be met. Should results of other investigations 

indicate that FTF barriers relied on in DOE’s reference (or best-estimate) PA case are not 

expected to perform as well as assumed, then more thought will be given to methods for 

obtaining additional support for steel liner performance assumptions, including use of a patch 

model that could simulate such processes as partial failure and slower release rates from 

the tanks. 

NRC staff may conduct technical review activities listed above in conjunction with onsite 

observations that could help inform its assessment of the concrete vaults as a hydraulic barrier 

mitigating steel liner corrosion. If DOE conducts experiments to provide additional support for 

concrete vaults as effective hydraulic barriers, NRC staff may observe these experiments at 

SRS facilities. 

Monitoring Factor 3.2—Groundwater Conditioning 

The hydraulic performance of the tank grout is important to DOE’s compliance demonstration 

because it both limits infiltration and delays chemical transition times to higher solubility, thereby 

reducing and delaying waste release from the contaminated zone for long periods of time. The 

transitions in chemical conditions in the grout and residual waste that generally lead to higher 

solubility are directly dependent on how water flows through the grouted tanks and, potentially, 

from below the tanks. NRC staff has unresolved technical concerns regarding the potential for 

the existence or creation of fast flow paths through the grouted tanks. The potential for 

relatively rapid chemical modifications along these flow paths, and consequent chemical 
D–4 

transitions, have not been ruled out. For example, water may flow along cracks relatively 

rapidly and react with the grout lining the crack walls. This may lead to a chemical environment 

for percolating water that is quite different from that for water permeating through the bulk grout 

(e.g., lower pH, higher Eh, and higher aqueous carbonate—as a result of calcification of the 

crack walls). Furthermore, DOE has not provided information to rule out the potential for water 

table rise to the level of the tank bottoms in the future. This scenario could afford contact with 

the residual waste at the tank bottom with limited benefit of the buffering grout that lies above 

the residue. 

NRC staff is particularly concerned with DOE’s PA assumptions regarding the transition from 

reduced to oxidized conditions. For example, it is not clear to NRC staff that infiltrating 

groundwater will, in fact, be conditioned to low Eh by the tank grout. The Center for Nuclear 

Waste Regulatory Analyses (CNWRA®) has collected experimental data relevant to the 

saltstone disposal facility under contract with NRC. This data indicates that even if a significant 

portion of the system remains in a reduced state, minimal interaction between infiltrating 

groundwater and the reduced inner pore space of the waste form may occur, such that the Eh of 

the groundwater is more reflective of the incoming groundwater chemistry, rather than a 

groundwater conditioned by the waste form grout (Pabalan, et. al., 2012). Because flow rates 

used in CNWRA experiments are higher than might occur in the real system, it is possible that 

the experimental conditions might not be representative of the real system. Therefore, DOE 

should undertake experiments using grout formulations consistent with those used or planned 

for FTF tanks to confirm PA assumptions regarding groundwater conditioning and chemical 

transition times that are important to FTF compliance demonstration. NRC staff also will 

evaluate the efficacy of using data from lysimeter studies at SRS planned for fiscal year (FY) 

2012 to corroborate PA assumptions regarding groundwater conditioning for FTF. For example, 

the extent to which infiltrating water is conditioned by saltstone waste form present in the 

lysimeters may be used to support assumptions regarding conditioning of infiltrating water by 

FTF tank grout. 

For several tanks with bottoms located near the water table, including Tanks 18 and 19, 

groundwater from a rising aquifer (about pH 5.5) could intrude through corroded liners and 

contact waste along the bottom of the tank. This scenario is similar to Configuration E in DOE’s 

PA (SRS–REG–2007–00002, Rev. 1, p. 595). However, DOE did not consider the possibility of 

essentially unconditioned groundwater contacting the waste after passing through the corroded 

liner. It is interesting to note that in the HTF PA, DOE did consider such an unconditioned 

release scenario for tanks in a similar configuration (SRR–CWDA–2010–00128, Rev. 0). The 

lack of characterization of the waste, and especially the transuranic elements in it, will have 

substantial impact on the uncertainties presented by a water table rise scenario. NRC staff will 

evaluate the likelihood of this scenario under this monitoring factor through review of historical 

water table data. 

Another DOE FTF PA scenario is characterized by preferential pathways through the grout, 

along either cracks or shrinkage voids along the tank margins. In reality, carbonation of the 

grout can be expected to be relatively rapid along the preferential pathways. These 

calcite/aragonite coatings may inhibit conditioning of ingress water by the grout, such that the 

pH of the water is more likely conditioned by calcite rather than the grout hydroxide. In addition, 

the reducing capacity of the grout could decline relatively rapidly along these preferential 

pathways. DOE evaluated the performance impact of preferential pathways in Cases C, D, 

and G. Case G, developed in response to NRC requests for information (RAIs), also addressed 

other potential issues with DOE’s base case analysis. In all cases, peak doses were in the 

range of a few mSv/yr (100s of mrem/yr) from Pu-239 (SRS–REG–2007–00002, Rev. 1; SRR–
D–5 

CWDA–2009–00054, Rev. 1). The primary difference between these cases was the timing of 

the peak dose. Because Case G also considered an earlier transition to higher solubility limiting 

phases, this scenario resulted in peak doses that exceeded the dose standard in 10 CFR 61.41 

within 10,000 years. Therefore, if Case G is found to be more likely than assumed by DOE, the 

extent to which groundwater is conditioned under this scenario may become important to the 

compliance demonstration and will be evaluated under this monitoring factor. 

Monitoring Factor 3.3—Shrinkage and Cracking

As discussed in the preceding section, the hydraulic performance of the tank grout is important 

to DOE’s compliance demonstration because it both limits infiltration and delays chemical 

transition times to higher solubility chemical conditions, thereby reducing and delaying waste 

release from the contaminated zone for long periods of time. In the DOE PA model, the 

longevity of the chemical-barrier performance within Type IV tanks is greater than tanks in 

Types I or III/IIIA due to a combination of factors, including the (i) larger grout volume in Type IV 

tanks, (ii) lower hydraulic conductivity of Type IV tank grout for longer periods of time due to the 

absence of cooling coils that may fail the tank grout earlier due to corrosion-induced cracking, 

and (iii) shedding of water around the Type IV tanks due to a domed roof. But also an important 

factor in the longevity of the chemical-barrier performance within Type IV tanks is the DOE 

assumption that the infiltrate reaching the contaminated zone does not bypass the waste tank 

grout (via fast flow pathways). Instead, downward flow through the grout remains relatively 

uniform and significant across the plane of the contaminated surface. DOE should provide 

additional support for this assumption. NRC staff is concerned that in actual field conditions, 

only a fraction of the grout components may be accessible for reaction with the infiltrate, 

particularly if flow occurs through preferential fast pathways. Preferential fast flow pathways 

could include shrinkage gaps that form: 

• Between the Tank Grout and Steel Liner 

• Between the Gank Grout and Internal Fixtures 

• At Lift Interfaces 

• In Between Individual Grout Flow Lobes, Including the Pseudo-Cracks Formed at 

Internal Fixtures Where Grout Split by an Obstacle Into Two Lobes Merges Gack 

Together to Form a Vertical Seam on the Trailing Edge of the Obstacle 

CNWRA observed many of the features listed above through an independent, NRC-funded 

study of large grout monoliths (Walter and Dinwiddie, 2008; Walter, et al., 2009, 2010; 

Dinwiddie, et al., 2011; Dinwiddie, et al., 2012). The study is providing information to help 

assess the robustness of DOE assumptions regarding the nature of flow through the tank grout 

that affects the calculated chemical transition times. NRC conducts these analyses to 

independently inform its review rather than make conclusive findings because NRC recognizes 

these studies cannot fully duplicate conditions in waste tanks at SRS. DOE should consider 

conducting its own grout studies and inspections of the distribution, consistency, flowability, and 

topography of the grout, as it is placed in the tanks, as well as measurement of the in-place 

physical properties of the grout, including vertical distribution and temporal evolution of grout 

density, porosity, and permeability. These activities could provide the information necessary to 

support key FTF PA modeling assumptions. 
D–6 

DOE also should consider design measures to minimize the occurrence of negative features, 

events, or processes related to grout placement. For example, DOE should consider removal of 

in-tank equipment that could lead to development of shrinkage-induced annuli around 

equipment or corrosion of steel components and associated cracking due to corrosion product 

expansion. DOE also should ensure the ability of the tank grout to fill all void spaces (i.e., grout 

should be self-leveling) to minimize imperfectly bonded grout seams and voids that may form in 

between grout pours. DOE should research and evaluate shrinkage compensating agents for 

use in its grout formulations to minimize shrinkage, shrinkage gap formation, and creation of 

annuli and void space within the tank grout, as recommended in Stefanko and Langton (2011). 

Preferential fast flow pathways also include cracks that form due to thermal or mechanical 

stresses (e.g., those due to settlement or corrosion product expansion from steel component 

corrosion). NRC will request information regarding thermal gradients generated during tank 

grout curing and evaluate potential for thermal cracking in a future technical review activity or 

onsite observation. Cracking due to settlement is discussed in Section 6.2. 

NRC staff also is concerned with potential formation of cracks in the tank grout due to alkali 

silica reaction (ASR). ASR is a process whereby reactive aggregates breakdown under 

exposure to the highly alkaline pore solution in concrete, which can result in significant 

expansion and, in some cases, cause cracking of concrete. This concern arose because the 

grout being used to fill Tanks 18 and 19 include 3/8-inch granite “pea gravel” as aggregates, 

instead of using only sand aggregate, as described in the DOE PA document (SRS–REG–

2007–00002, Rev. 1), and because of recent observations of concrete cracking at the Seabrook 

Nuclear Power Plant in Seabrook, New Hampshire. In that facility, granite aggregates also were 

used in the concrete mix. ASR is a slow process and its occurrence at Seabrook became 

evident only decades after the plant was constructed. Grout fill mix in Tanks 18 and 19 contain 

less Portland cement than the concrete mix used at Seabrook and likely would be less 

susceptible to ASR. Nevertheless, NRC staff is concerned that DOE’s criterion for acceptance 

of vendor supplied granite aggregate relies on short-term alkali reactivity tests (ASTM C–1260), 

which is unlikely to predict the occurrence of ASR over the very long period of performance for 

compliance with PO 61.41. NRC staff will discuss this issue with DOE and evaluate the 

potential for ASR to negatively impact FTF performance in a future technical review activity or 

onsite observation. 

NRC staff will review grout formulations, calculations, research, test methods, and results to 

ensure the disposal facility is designed to minimize fast flow path development. NRC staff may 

conduct technical reviews in conjunction with onsite observations that could include such 

activities as video inspections of grout pours, observations of grout tests, and inspections of test 

specimens. 

Monitoring Factor 3.4—Grout Performance

During onsite observations, NRC staff will verify the actual grout formulation DOE 

uses is consistent with performance assumptions in the FTF PA (SRS–REG–2007–00002, Rev. 

1) and design specifications assumed in the final waste determination (WD) (DOE/SRS–WD–

2012–001). DOE should evaluate significant deviations from the design specifications to ensure 

expected grout performance will not be negatively affected. In addition, NRC staff will evaluate 

DOE’s program for sampling, testing, and accepting grout materials to ensure materials conform 

to DOE specifications and national standards, such as ASTM C–989. The verification program 

should incorporate a comprehensive record-keeping system to include, for example (i) plant 

operation records, (ii) vendor-provided test reports on the grout components, (iii) as-received 
D–7 

acceptance test reports on bleed, slump, and/or flow of each grout batch (e.g., ASTM C–232, 

ASTM C–143, ASTM C–1611) and records of any additional water or other components added 

onsite to meet the acceptance criterion prior to emplacement, (iv) DOE laboratory test results of 

composite or grab samples, and (v) certification of shipping records. 

Also, NRC staff will evaluate the adequacy of the verification program pertaining to DOE’s 

supply of grout components, such as blast furnace slag. NRC staff’s evaluation will be based, 

to the extent practicable, on direct observation of ongoing activities and interviews with key DOE 

personnel. The review will evaluate certain aspects of the program: 

• Representativeness of the Samples Collected 

• Adequacy of the Analytical Equipment 

• Calibration of the Analytical Equipment 

• Adequacy of Verification Records 

To minimize degradation in the quality and chemical reactivity of the slag and Portland cement, 

DOE must store the material in weather-tight silos or bins to prevent contact with moisture. 

During onsite observations, NRC staff will examine silos or bins for storage of the slag and 

cementitious materials. In addition to the grout formulation, curing conditions also are expected 

to have a significant effect on the short- and long-term performance of the emplaced grout. 

Numerous studies have shown that improper curing results in a variety of undesirable effects, 

such as lower strength, high permeability, and several types of cracking. For example, early 

age cracking could occur due to thermal and self-dessication stresses and uneven lift 

topography. DOE streamed live video (over the internet) of the initial grout pours into Tank 18, 

which provided important information regarding grout flowability and non-self-leveling grout 

behavior. The technology needed to observe most stages of grout emplacement has thus been 

proven and DOE should continue to use this technology during grout emplacement. NRC will 

review video footage of grout emplacement activities to (i) provide confidence that grout 

behavior during emplacement is understood and (ii) incorporate this information into NRC 

reviews of PA updates. Staff performing onsite observations will verify grout placement is 

conducted under proper temperature and humidity conditions or that steps are taken to ensure 

proper curing of the grout.

Monitoring Factor 3.5—Basemat Performance 

An additional NRC concern pertains to the hydraulic and chemical performance of the FTF 

concrete basemat, which NRC considers an important barrier to radionuclide release. Despite 

the relatively short transport pathway, sorption onto the concrete basemat attenuates release of 

highly radioactive radionuclides (HRRs), such as Np and Pu, by orders of magnitude in DOE’s 

PA. DOE barrier analyses indicate the presence of a fast flow path through the basemat causes 

a more rapid release of contaminants. This effect is more evident for Pu because of its high 

sorption coefficient in oxidized concrete. Notwithstanding results of the barrier analyses, a fast 

flow path through the basemat is not considered a likely scenario in the DOE PA base case. 

DOE needs to provide support for its base case assumption that the basemat will remain intact. 

In particular, the basemat underneath Type IV tanks is only 10 cm [4 in] thick and could be 

susceptible to cracking due to stress imposed by the mass of emplaced grout. 
D–8 

References 

Amidon, M.B., et al. “Alternative Risk Reduction Technologies in Support of F-Tank Farm 

Closure.” SRNL–STI–2012–00079. Aiken, South Carolina: Savannah River Site. 2012. 

Cantrell, K., D.L. Clark, D.R. Janecky, J. Psaras, and W. Runde. “Plutonium Solubility Peer 

Review Report.” LA–UR–2012–00079. Los Alamos, New Mexico: Los Alamos National 

Laboratory. 2011. 

Denham, M. “Evolution of Chemical Conditions and Estimated Plutonium Solubility in the 

Residual Waste Layer During Post-Closure Aging of Tank 18, Savannah River National 

Laboratory.” SRNL–STI–2012–00087. Aiken, South Carolina: Savannah River Nuclear 

Solutions, LLC. 2012. 

Dinwiddie, C.L., D.R. Bannon, M.K. Todt, G.R. Walter, and M.M. Roberts. “Draft Fiscal Year 

2012 Meso- and Intermediate-Scale Grout Monolith Test Bed Experiments: Results and 

Recommendations.” San Antonio, Texas: Center for Nuclear Waste Regulatory Analyses. 

2012. 

Dinwiddie, C.L., G.R. Walter, G. Light, S. Winterberg, D. Wyrick, D. Sims, and K. Smart. 

“Bonding and Cracking Behavior and Related Properties of Cementitious Grout in an 

Intermediate-Scale Grout Monolith.” San Antonio, Texas: Center for Nuclear Waste Regulatory 

Analysis. 2011. 

Pabalan, R.T., G.W. Alexander, and D.J. Waiting. “Experimental Study of Contaminant 

Release From Reducing Grout.” San Antonio, Texas: Center for Nuclear Waste Regulatory 

Analyses. 2012. 

SRR–CWDA–2009–00054, Rev. 1. “Comment Response Matrix for Nuclear Regulatory 

Commission (NRC) Comments on the Draft Basis for Section 3116 Determination and 

Associated Performance Assessment for the F-Tank at the Savannah River Site.” 

Aiken, South Carolina: Savannah River Remediation, LLC, Closure and Waste Disposal 

Authority. 2011. 

SRR-CWDA-2012-00020, Rev. 0. “Savannah River Site Liquid Waste Facilities Performance 

Assessment Maintenance Program, FY2012 Implementation Plan,” Aiken, South Carolina: 

Savannah River Remediation, LLC. 2012. 

SRS–REG–2007–00002, Rev. 1. “Performance Assessment for the F-Tank Farm at the 

Savannah River Site.” Aiken, South Carolina: Savannah River Remediation, LLC, Closure and 

Waste Disposal Authority. 2010. 

Stefanko, D.B. and C.A. Langton. “Tanks 18 and 19-F Structural Flowable Grout Fill Material 

Evaluation and Recommendations.” SRNL–STI–2011–00551. Rev. 0. Aiken, South Carolina: 

Savannah River National Laboratory. 2011. 

U.S. Army Corps of Engineers. “Geologic Engineering Investigations.” Vicksburg, Mississippi: 

Waterways Experiment Station, U.S. Army Corps of Engineers. 1952. 
D–9 

Walter, G.R., C.L. Dinwiddie, D. Bannon, G. Frels, and G. Bird. “Intermediate Scale 

Grout Monolith and Additional Mesoscale Grout Monolith Experiments: Results and 

Recommendations. San Antonio, Texas: Center for Nuclear Waste Regulatory 

Analyses. 2010. 

Walter, G.R., C.L. Dinwiddie, E.J. Beverly, D. Bannon, D. Waiting, and G. Bird. “Mesoscale 

Grout Monolith Experiments: Results and Recommendations.” San Antonio, Texas: Center for 

Nuclear Regulatory Analyses. 2009. 

Walter, G.R. and C.L. Dinwiddie. “Conceptual Design for Small-Scale Grout Monolith Tests.” 

San Antonio, Texas: Center for Nuclear Waste Regulatory Analyses. 2008. 
APPENDIX E 

MA 4 “NATURAL SYSTEM PERFORMANCE” 
E–1 

APPENDIX E 

Monitoring Area (MA) 4 “NATURAL SYSTEM PERFORMANCE” 

Monitoring Factor 4.1—Natural Attenuation of Pu 

The choice of appropriate distribution coefficient (Kds) values for radionuclides in the natural 

system is very important to performance assessment (PA) analyses and has been the subject of 

considerable effort at Savannah River Site (SRS). Sorption of Pu and other key radionuclides 

on the natural materials of the saturated zone is especially important for Type IV tanks, such as 

18 and 19, because of the very thin (or nonexistent) unsaturated zone underlying these tanks. 

As radionuclides are leached from the waste and released to the soil, Kds will be a critical barrier 

that will depend on a number of factors including pH, ionic strength of the solution, speciation of 

the radionuclides and their oxidation state(s). 

In the F-Tank Farm (FTF) PA (SRS–REG–2007–00002, Rev. 1), Pu is one of the most 

important radionuclides contributing to peak dose. For oxidized forms of Pu (V/VI) the “best” 

value for Kds is 16 mL/g. For reduced forms of Pu (III/IV) the “best” value for Kds is 300. 

Because Pu can exist in several redox states at the same time, a “combination” ”best” value 

was suggested as 290 mL/g. These values were taken from Kaplan (2010) as the “best” 

estimates for sandy sediment. As explained in the report, the combination value is a hybrid that 

is taken to describe fractions of Pu in two different oxidation states: 95 percent of reduced 

Pu (III/IV) and 10 percent oxidized (V/VI) [sic]. 

Subsequent to preparation of the Department of Energy’s (DOE’s) FTF PA (SRS–REG–2007–

00002, Rev. 1), Section 6.3.5.3.4 of the Tanks 18 and 19 Special Analyses (SRR–CWDA–

2010–00124, Rev. 0) explains that Pu Kds values were reevaluated. Section 6.3.6.1 of the 

special analyses (SRR–CWDA–2010–00124, Rev. 0) considers the impact of the new Kds

values on the deterministic model results. A statistical analysis of 65 Kds values (Almond 

et al, 2012) taken from many areas and materials around the SRS, was conducted in an attempt 

to reexamine Kds from a site-wide perspective. Almond (2012) only grossly considers chemistry 

in evaluating Kds for FTF (e.g., pH is binned into two categories; greater or less than 7 and Pu 

redox state is not considered). Almond (2012) recommends a Kds value of 650 L/kg for FTF 

based on the following: (i) information from a modeling analysis (Demirkanli et al., 2007) of 

long-term lysimeter studies (Kaplan et al, 2006) indicates that a Kds of 1800 L/kg should be 

used, and that (ii) the statistical analysis shows that the 290 L/kg value used in the FTF PA is in 

the lower quantile. The sediment in the lysimeter appears to have had more clay in it than 

typically found at FTF and so, the 1800 value was lowered to 650 L/kg. This value, in turn, was 

increased for the “near field” of the tanks, using a factor of two recommended in Kaplan (2010) 

to account for greater adsorption due to elevated pH resulting from grout component leaching. 

The work to analyze and model results of the SRS Pu lysimeters has led to a model in which a 

reduction rate and an oxidation rate drive concentrations of different Pu redox states at any 

given time (Kaplan, 2010; Kaplan, et al., 2006; Demirkanli, et al., 2007). This leads to a small 

fraction of mobile Pu and a large fraction of relatively recalcitrant Pu. To reproduce the profiles 

in the lysimeters, the two rates and the retardation factor needed to be adjusted. In lysimeters 

containing reduced Pu sources, a retardation factor of 15 was used for Pu in the small, mobile 

fraction, while a retardation factor of 10,000 was used for the larger fraction. Even with the high 

retardation of the large fraction, modeling was not able to capture the overall Pu distribution in 

the lysimeter by using a single species retardation factor (Demirkanli, et al., 2007). The small, 

mobile fraction caused the soil profile of Pu below the source. 
E–2 

The long-term lysimeter experiments conducted at SRS and other work referenced in 

Kaplan (2006) show that although most Pu is in the (IV) state, there is a small component, that 

at times, is in a much more mobile form. In fact, most Pu that is in solution (albeit a very small 

concentration) is in the Pu (V) form. Even PuO2(s), which had been considered a stable form of 

Pu (IV), has been shown to oxidize in the presence of water forming a substantial fraction 

(27 percent) of Pu (VI) (Haschke, et al., 2000). In SRS sediment, it is thought that Pu cycles 

repeatedly through the Pu (IV) and Pu (V) oxidation states in response to wet/dry cycles 

(Kaplan, 2003) 

From Kaplan (2010) the “best” Kds value for sandy soil for Pu (V/VI) is 16 mL/g, while for 

Pu (III/IV) the “best” value is 300 L/kg. Recognizing that Pu chemistry is especially complex and 

disproportionation presents a difficult problem; NRC staff suggests that averaging Kds values for 

different oxidation states is not appropriate, even if values are weighted for proportions of 

different redox states. 

A potential additional complication is the possibility that Pu (III) can be produced by certain 

common Fe (II) species, and that the Pu (III) form can be more soluble or mobile than Pu (IV). 

The finding by Felmy, et al. (2011) that Pu (IV) can be reduced to Pu (III) by Fe (II) and that the 

presence of certain Fe (III) minerals increases the reaction rate, suggests that for long-times a 

single Kds, steady-state adsorption model may not be appropriate. For the SRS lysimeters 

containing sources of reduced Pu, X-Ray absorption near edge structures (XANES) showed 

that in the soil, Pu was distributed approximately 37 percent Pu (III), 67 percent Pu (IV) 

0 percent Pu (V), and 0 percent Pu (VI) (Kaplan, et al., 2007). This distribution was essentially 

the same for both the Pu (III) and Pu (IV) lysimeters. In both cases, most Pu remained very 

close to the source over 11 years; however, a small but measurable quantity of Pu in the 

sediment had migrated to a maximum of 15 cm from the source, giving a concentration of about 

1 pCi/g. XANES is not sensitive to species that are less than about 5 percent abundance, so 

even if some Pu (V) were present, it would almost certainly not be observed. From the 

evidence based on research at SRS, it is apparent that in the presence of reduced Pu, some 

small fraction can be oxidized, enter solution, and become relatively mobile. This is probably an 

ephemeral process, with Pu (IV) and Pu (V) switching back and forth, but always heavily 

dominated by Pu (IV). Factors such as complexation of the aqueous phase and possibly 

microbiological activity will potentially influence this distribution in a currently unknown way. 

The use of a factor to adjust Kds for effects of higher pH due to grout is an arbitrary adjustment 

that will vary with pH, time, and aqueous speciation. It also depends on the scenario by which 

water intrudes into the tanks, with some conceptual models not involving water that has been 

conditioned by grout. While leachate that is influenced by cement chemistry is expected to have 

an impact on vadose zone Kds, as discussed in NRC’s comments on DOE’s Rev. 0 PA 

(comment FF-2) and DOE’s Rev. 1 PA (comment RAI-FF-4) (see [NRC, 2010]), the basis for 

what appears to be an arbitrary increase in the Kds is not clear. NRC staff’s evaluation of DOE’s 

updated Kds will be the subject of a future NRC technical review memorandum under this 

monitoring factor. 

Hobbs (2012) provides a discussion of the possible solid phases and aqueous species in which 

Pu may reside in residual tank wastes. Recent scanning electron microscopy (SEM) analysis 

(of a single waste sample) is reported (Hay et al., 2012) to show Pu present as discrete, small 

(<1 um) particles that are currently not characterized. The mass of these particles seems to be 

smaller than total Pu in the sample, suggesting that some Pu also is coprecipitated. Further the 

formation of PuO(CO3)xH2O(solid) or Pu(OH)2(CO3)(solid) in the presence of aqueous Pu carbonate 
E–3 

species in the tank heels is viewed as a likely possibility. In fact, carbonate concentrations of 

about 0.04 M were measured in the aqueous phase of Tank 18 heels. Recently, X-Ray 

diffraction (XRD) analysis of Tank 18 heels shows the presence of Na4UO2(CO3)3 and calcite at 

about 10 percent of the crystalline solid phase material (Hay, et al., 2012). The presence of 

these solids and the measured aqueous carbonate concentrations strongly suggests that some 

Pu in the heels is in a carbonate form. If Pu is present as a carbonate solid, then at pH 9.8, 

relatively high Pu solubilities of around 1 × 10-6 mol/L can be expected. Hobbs suggests that the 

OH⎯ from the grout, in contact with the heels, should convert the carbonate to less soluble 

Pu(OH)4(am) or PuO2(am, hyd). However, it is not clear if this process does in fact take place; 

Hobbs recommends experiments to verify the transformation. These observations suggest that 

at least some of the Pu in the aqueous phase in the heels will be negatively charged carbonate 

complexes of higher solubility. Hobbs (2012) reported that Pu(OH)2(CO3)2

-2 was the dominant 

solution Pu species between pH 9.4 and 10.1, while Pu(OH4)(CO3)2

-4 was the dominant Pu 

solution species when pH was between 12 and 13. If these species are present in leachate 

from the grouted tanks, then very low Kds values can be expected. The stability of these 

species under high pH and varying redox conditions is not clear. 

Therefore, based on the information presented above, NRC staff will monitor DOE’s efforts to 

conduct transport modeling that explicitly accounts for the multiple oxidation states of Pu that 

may be present or may form during transport through the FTF far-field. Kds for Pu should be 

developed based on sorption studies relevant to FTF (i.e., based on sorption to sediments 

encountered during transport from the FTF tanks to various points of compliance and 

considering important changes to geochemical conditions that may occur over space and time). 

References 

Demirkanli, D.I.,F.J. Molz, D.I. Kaplan, R.A. Fjeld, and S.M. Serkiz. “Modeling Long-Term 

Plutonium Transport in the Savannah River Site Vadose Zone.” Vadose Zone Journal. Vol.6. 

pp. 344–353. 2007. 

Felmy, A., D.A. Moore, K.M. Rosso, O. Qafoku, D. Rai, E.C. Bock, and E.S. Ilton. 

“Heterogenous Reduction of PuO2 With Fe(II): Importance of the Fe(III) Reaction Product.” 

Environmental Science and Technology. Vol. 45. pp. 3,952–3,958. 2011. 

Haschke, J.M., T.H. Allen, and L.A. Morales. “Reaction of Plutonium Dioxide With Water: 

Formation and Properties of PuO2+x.” Science. Vol. 287. pp. 285–287. 2000. 

Hay, M.S., P.E. O’Rourke, and H.M. Ajo. “Summary of XRD and SEM Analysis of 

Tank 18 Samples.” Rev. 0. Memorandum (February 23) to F.M. Pennebaker (NRC). 

SRNL–l3100–2012–00017. Aiken, South Carolina. Savannah River National 

Laboratory. 2012. 

Hobbs, D.T. “Form and Aging of Plutonium in Savannah River Site Waste Tank 18, Savannah 

River National Laboratory.” SRNL–STI–2012–00106. Aiken, South Carolina: Savannah River 

Nuclear Solutions, LLC. 2012. 

Kaplan, D.I. “Geochemical Data Package for Performance Assessment Calculations Related to 

the Savannah River Site.” SRNL–STI–2009–00473. Aiken, South Carolina: Savannah River 

Site. 2010. 
E–4 

Kaplan,D.I., B.A. Powell, M.C. Duff, D.I. Demirkanli, M. Denham, R.A. Fjeld, and F.J. Molz. 

“Influence of Sources on Plutonium Mobility and Oxidation State Transformations in 

Vadose Zone Sediments.” Environmental Science and Technology. Vol. 41, No. 21. 

pp. 7,417–7,423. 2007. 

Kaplan, D.I., I. Deniz, D.I. Demirkanli, L. Gumapas, B.A. Powell, R.A. Fjeld, F.J. Molz, and S.M. 

Serkiz. “Eleven Year Field Study of Pu Migration From Pu III, IV, and VI Sources.” 

Environmental Science and Technology. Vol. 40, No. 2. pp. 443–448. 2006. 

Kaplan,D.I. “Enhanced Plutonium Mobility During Long-Term Transport Through an 

Unsaturated Subsurface Environment.” WSRC–MS–2003–00889. Aiken, South Carolina: 

Savannah River Site. 2003. 

NRC. “U.S. Nuclear Regulatory Commission Staff Requests for Additional Information 

on the Draft Basis for Section 3116 Determination for Closure of F-Tank Farm at the 

Savannah River Site (Rev. 0) and on Performance Assessment for the F-Tank Farm for the 

Savannah River Site (Rev. 1).” DOE/SRS–WD–2010–001. Memorandum from L. Camper 

(NRC) to F. Marcinowski (DOE). ML103190402. Washington, DC: U.S. Nuclear Regulatory 

Commission. 2010. 

SRS–REG–2007–00002, Rev. 1. “Performance Assessment for the F-Tank Farm at the 

Savannah River Site.” Aiken, South Carolina: Savannah River Remediation, LLC, Closure and 

Waste Disposal Authority. 2010.