August 23, 2013 

Ms. Jean Ridley, Director 

Waste Disposition Programs Division 

U.S. Department of Energy 

Savannah River Operations Office 

P.O. Box A 

Aiken, SC 29802 

SUBJECT: U.S. NUCLEAR REGULATORY COMMISSION JUNE 26-27, 2013, ONSITE 

OBSERVATION VISIT REPORT FOR THE SAVANNAH RIVER SITE SALTSTONE 

DISPOSAL FACILITY (DOCKET NO. PROJ0734) 

Dear Ms. Ridley: 

The enclosed report describes the U.S. Nuclear Regulatory Commission (NRC) onsite 

observation visit on June 26-27, 2013, at the Savannah River Site (SRS) Saltstone Disposal 

Facility (SDF). The visit was conducted in accordance with Section 3116(b) of the Ronald W. 

Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA), which requires NRC 

to monitor certain disposal actions taken by the U.S. Department of Energy (DOE) for the 

purpose of assessing compliance with the performance objectives set out in 10 CFR Part 61, 

Subpart C. The activities conducted during the visit were consistent with those described in the 

NRC monitoring plan for salt waste disposal at SRS (dated May 3, 2007) and the NRC staff 

guidance for activities related to waste determinations (NUREG-1854, dated August 2007). 

On every onsite observation visit to SRS, NRC is focused on assessing compliance with four 

performance objectives in 10 CFR Part 61, Subpart C: (1) protection of the general population 

from releases of radioactivity (§61.41), (2) protection of individuals from inadvertent intrusion 

(§61.42), (3) protection of individuals during operations (§61.43), and (4) stability of the disposal 

site after closure (§61.44). 

On April 30, 2012, NRC issued both a Technical Evaluation Report (TER) [available via the 

NRC’s Agencywide Documents Access and Management System (ADAMS) at Accession 

Number ML121020140] and a Type IV Letter of Concern [ML120650576] pertaining to waste 

disposal at the SRS. The TER concluded that NRC did not have reasonable assurance that salt 

waste disposal at the SDF met the performance objective §61.41. The Type IV Letter of 

Concern formally communicated NRC’s concerns to both DOE and the South Carolina 

Department of Health and Environmental Control. DOE provided responses to the Type IV 

Letter to NRC in two submittals. These submittals included an updated technetium-99 (Tc-99) 

inventory projection for the newly constructed SRS saltstone disposal structures1

; and 

information about DOE Case K and K1 uncertainty and sensitivity analyses. In August 2012, 

NRC issued a letter of acknowledgement [ML12213A447] stating that a letter to the U.S. 

Congress (Type II) is not needed at this time. Based on the NRC’s TER analyses and DOE’s 

revised Tc-99 inventory, the staff determined that, if DOE’s new projected Tc-99 inventory for 

 

1

 Inventory projections described in DOE’s response to NRC’s Type IV Letter are listed in reference to Disposal 

Structures (Cells) 2A, 2B, 3A, 3B, 5A, and 5B. Throughout this report, these structures will be referred to as the 

“newly constructed” saltstone disposal structures. 
J. Ridley 2 

the newly constructed disposal structures is correct, then it is unlikely that the salt waste 

disposal would cause an off-site peak dose exceeding the requirements of §61.41 

(i.e., 0.25 mSv/yr (25 mrem/yr)). 

The June 2013 onsite observation visit focused on technical concerns described in the NRC 

2012 TER. There are no new open issues resulting from this visit. Open issues that had been 

identified earlier have been rolled into the concerns identified by NRC in the 2012 TER. All 

NRC concerns will be rolled into the monitoring factors in the revised monitoring plan that is 

being prepared by NRC. 

The observation addressed a subset of the concerns raised in the 2012 TER. During the 

observation, staff was encouraged by DOE’s progress in research on technetium solubility in 

saltstone and saltstone core testing methodologies. Results from these research activities will 

provide useful information about risk-significant aspects related to SDF performance. The DOE 

and NRC continue to work in the monitoring process to resolve all outstanding issues that led to 

issuance of the Type IV Letter of Concern. In accordance with the requirements of NDAA, NRC 

will continue to monitor DOE disposal actions at SRS. 

If you have any questions or need additional information regarding this report, please contact 

Mr. Nishka Devaser of my staff at (301) 415-5196. 

Sincerely, 

/RA/ 

Aby Mohseni, Deputy Director 

Environmental Protection and 

 Performance Assessment Directorate 

Division of Waste Management 

 and Environmental Protection 

Office of Federal and State Materials 

 and Environmental Management Programs 

Enclosure: 

NRC Onsite Observation Visit Report 

cc w /enclosure: 

WIR Service List 
J. Ridley 2 

the newly constructed disposal structures is correct, then it is unlikely that the salt waste 

disposal would cause an off-site peak dose exceeding the requirements of §61.41 

(i.e., 0.25 mSv/yr (25 mrem/yr)). 

The June 2013 onsite observation visit focused on technical concerns described in the NRC 

2012 TER. There are no new open issues resulting from this visit. Open issues that had been 

identified earlier have been rolled into the concerns identified by NRC in the 2012 TER. All 

NRC concerns will be rolled into the monitoring factors in the revised monitoring plan that is 

being prepared by NRC. 

The observation addressed a subset of the concerns raised in the 2012 TER. During the 

observation, staff was encouraged by DOE’s progress in research on technetium solubility in 

saltstone and saltstone core testing methodologies. Results from these research activities will 

provide useful information about risk-significant aspects related to SDF performance. The DOE 

and NRC continue to work in the monitoring process to resolve all outstanding issues that led to 

issuance of the Type IV Letter of Concern. In accordance with the requirements of NDAA, NRC 

will continue to monitor DOE disposal actions at SRS. 

If you have any questions or need additional information regarding this report, please contact 

Mr. Nishka Devaser of my staff at (301) 415-5196. 

Sincerely, 

Aby Mohseni, Deputy Director 

Environmental Protection and 

 Performance Assessment Directorate 

Division of Waste Management 

 and Environmental Protection 

Office of Federal and State Materials 

 and Environmental Management Programs 

Enclosure: 

NRC Onsite Observation Visit Report 

cc w /enclosure: 

WIR Service List 

DISTRIBUTION: GAlexander KPinkston HArlt HFelsher 

ML13199A434 

OFC DWMEP:PM DWMEP:TR DWMEP:LA DWMEP:BC DWMEP:BC DWMEP:DD

NAME NDevaser ARidge AWalkerSmith CMcKenney JJessie AMohseni 

DATE 7/30/13 7/30/13 7/30/13 8/11/13 8/22/13 8/23/13 

OFFICIAL RECORD COPY
Enclosure 

U.S. NUCLEAR REGULATORY COMMISSION JUNE 26-27, 2013, ONSITE OBSERVATION 

VISIT REPORT FOR THE SAVANNAH RIVER SITE SALTSTONE DISPOSAL FACILITY 

EXECUTIVE SUMMARY:

The U.S. Nuclear Regulatory Commission (NRC) staff conducted its 14th onsite observation 

visit, Observation 2013-01, to the Saltstone Disposal Facility (SDF) at the Savannah River Site 

(SRS) on June 26-27, 2013. On every onsite observation visit to SRS, NRC focuses on 

assessing compliance with four performance objectives in 10 CFR Part 61, Subpart C: 

(1) protection of the general population from releases of radioactivity (§61.41), (2) protection of 

individuals from inadvertent intrusion (§61.42), (3) protection of individuals during operations 

(§61.43), and (4) stability of the disposal site after closure (§61.44). 

During Observation 2013-01, NRC focused on information regarding the April 30, 2012, NRC 

Technical Evaluation Report (TER) and associated Type IV Letter of Concern, where NRC 

concluded that it did not have reasonable assurance that salt waste disposal at the SDF met the 

performance objectives in 10 CFR Part 61, specifically §61.41. NRC performs monitoring 

activities in coordination with the State, so staff from the South Carolina Department of Health 

and Environmental Control (SC DHEC) also participated in this visit. 

During Observation 2013-01, NRC staff and U.S. Department of Energy (DOE) staff (including 

DOE contractors, Savannah River Remediation (SRR) throughout this report), discussed salt 

waste processing and the details of recent research conducted by DOE, related to issues 

identified in NRC’s 2012 TER. In addition, DOE provided NRC staff a tour of the saltstone 

processing facility (SPF), including views of the controls room. This report provides a 

description of the NRC activities during Observation 2013-01, including observations that NRC 

staff made during the visit. 

There are no new Open Issues2

 resulting from Observation 2013-01. NRC staff received 

documents and a DOE presentation that pertained to the activities to be observed prior to the 

observation. The presentation that DOE provided to NRC staff and the documents provided by 

DOE for discussion at the observation are accessible via the NRC’s document repository, the 

Agencywide Documents Access and Management System (ADAMS), via accession numbers 

listed below: 

SRR-CWDA-2013-00093, Onsite Observation Documents - DOE 

Presentation during June 26-27 Observation, Rev. 1 

ML13189A050 

SRNL-STI-2012-00769, Solubility of Technetium Dioxides in Reducing 

Cementitious Material Leachates, Rev. 1 

ML13070A135 

SRNL-STI-2013-00118, Degradation of Cementitious Materials 

Associated with Saltstone Disposal Units 

ML13189A205 

 

2

 The previous Open Issues are now rolled into the concerns identified by NRC in the 2012 TER. Those 

NRC concerns will be rolled into the monitoring factors in the revised monitoring plan that is being drafted 

by NRC. 
2 

Observation 2013-01 addressed a subset of the concerns raised in the 2012 TER. During the 

observation, staff was encouraged by DOE’s progress in conducting research that provides 

useful information. The DOE and NRC continue to work in the monitoring process to resolve all 

outstanding issues that led to issuance of the NRC’s Type IV Letter of Concern. 

A summary of NRC staff observations and conclusions in those areas is provided below: 

Saltstone Production Facility Operations and Discussion of Processing Cycle

• DOE provided NRC staff with details of saltstone disposal into the new disposal structures. 

In addition, DOE provided NRC staff a tour of the SPF, including views inside the control 

room. DOE described new process monitoring capabilities, which included video 

monitoring in the grout hopper, a humidity sensor in the vapor space of SDS 2A, and a 

new wet grout sample line installed in the process room. 

• DOE and NRC technical staff discussed physical and chemical characteristics of blast 

furnace slag as it is received and when it is used in saltstone. NRC and DOE staff 

discussed quality assurance procedures for components of the saltstone dry feed (i.e., 

slag, fly ash, and cement). 

Technical Discussion - Update on DOE’s Special Analysis for Saltstone and the DOE 

Performance Assessment Maintenance Plan (SRR-CWDA-2013-00049)

• DOE described its new approach of coordinating and prioritizing research projects across 

the three liquid waste facilities performance assessment (PA) maintenance programs. 

DOE provided an overview of the PA maintenance plan elements related to saltstone 

divided into critical property testing (e.g., initial hydraulic conductivity and sorption 

coefficients), degradation studies, and emplaced saltstone testing. Specific aspects of the 

special analysis (SA) were also discussed and are summarized in the report (e.g., 

humidity effects on saltstone curing, saltstone oxidation front). 

• DOE described potential sources of uncertainty in flow that were evaluated in sensitivity 

analyses. These factors included infiltration rates through the closure cap (as calculated 

by the HELP model), timing of complete physical degradation, initial hydraulic conductivity, 

and flow through construction joints. NRC staff commented that documentation and visual 

presentation of the deterministic sensitivity analyses are likely to be important for aspects 

of the analysis that are evaluated primarily with deterministic analyses. Sensitivity 

analysis results can reveal interrelationships of processes and provide significant insights 

and understanding. DOE described the status and expected schedule for the SA. DOE 

indicated that the SA would be reviewed by the low-level waste disposal facility federal 

review group (or LFRG) from July-September 2013. 

Technical Discussion – Recent Research Activities

• NRC and DOE staff discussed NRC questions about recently published research on the 

solubility of technetium dioxides in reducing cementitious material leachates 

(SRNL-STI-2012-00769). NRC questions focused primarily on how the values 

recommended in SRNL-STI-2012-00769 will be used in future PAs, and included 

questions related to the text and figures in the document and how they were developed 

from its supporting references. DOE staff described the approach that was going to be 

used in the SA for modeling the release of Tc. 
3 

• NRC and DOE staff discussed the results of recently published research on the 

degradation of cementitious materials associated with saltstone (SRNL-STI-2013-00118). 

NRC questioned why mechanical degradation mechanisms (e.g., shrinkage, thermal 

loading, differential settlement) were not considered in the report. The NRC staff also 

asked for additional technical bases for the values identified as Best Estimates, Nominal 

Values, and Conservative Estimates. DOE replied that the values were based on 

engineering judgment. DOE showed NRC staff selected intermediate model results from 

the DOE draft Fiscal Year (FY) 2013 SA related to saltstone and disposal structure 

degradation. 

1.0 BACKGROUND:

Section 3116 of the National Defense Authorization Act for Fiscal Year 2005 (NDAA) authorizes 

DOE, in consultation with NRC, to determine that certain radioactive waste related to the 

reprocessing of spent nuclear fuel is not high-level waste, provided certain criteria are met. The 

NDAA also requires NRC to monitor DOE disposal actions related to those determinations to 

assess compliance with the performance objectives in 10 CFR Part 61, Subpart C. 

To carry out its monitoring responsibility under the NDAA, NRC, in coordination with the State 

site regulator – SC DHEC, performs three types of activities: (1) technical reviews, (2) onsite 

observation visits, and (3) data reviews. Those activities focus on key assumptions identified in 

the NRC monitoring plan. Technical reviews generally focus on reviewing additional model 

support for assumptions that DOE made in its PA that are considered important to the DOE 

compliance demonstration. Onsite observation visits generally are performed to: (1) observe 

the collection of data (e.g., observation of waste sampling used to generate radionuclide 

inventory data) and review the data to assess consistency with assumptions made in the waste 

determination; and (2) observe key disposal or closure activities related to technical review 

areas (e.g., slag/other material storage, grout formulation, preparation, or placements). Data 

reviews supplement technical reviews by focusing on monitoring data that may indicate future 

system performance or by reviewing records or reports that can be used to directly assess 

compliance with the performance objectives. 

On March 31, 2005, DOE submitted to NRC the Draft Section 3116 Determination for Salt 

Waste Disposal Savannah River Site (DOE-WD-2005-001, Rev. 0) to demonstrate compliance 

with the NDAA criteria, including demonstration of compliance with the performance objectives 

in 10 CFR Part 61, Subpart C. In its consultation role, NRC staff reviewed the draft waste 

determination. In the TER issued in December 2005 (NRC, 2005), NRC documented the 

results of its review and concluded that there was reasonable assurance that the applicable 

criteria of NDAA could be met, provided certain assumptions made in the DOE analyses were 

verified via monitoring. Taking into consideration the assumptions, conclusions, and 

recommendations in the NRC 2005 TER, DOE issued the final waste determination in 

January 2006 (DOE-WD-2005-001, Rev. 1). 
4 

DOE submitted a revised PA to NRC in 2009 (SRR-CWDA-2009-00017). NRC reviewed 

SRR-CWDA-2009-00017, including holding public meetings, sending requests for additional 

information, and reviewing the DOE responses. On April 30, 2012, NRC issued both the TER 

(NRC, 2012a) and the Type IV Letter of Concern (NRC, 2012b). In the 2012 TER, NRC 

concluded that it did not have reasonable assurance that salt waste disposal at the SDF met the 

performance objectives in 10 CFR Part 61, specifically §61.41. The Type IV Letter of Concern 

formally communicated the NRC concerns to both DOE and the SC DHEC. 

In July 2012, DOE responded to the Type IV Letter to NRC (DOE, 2012a; DOE, 2012b). DOE’s 

response included information about an updated technetium-99 (Tc-99) inventory projection for 

the newly constructed disposal structures and information about the DOE Case K and K1 

uncertainty and sensitivity analyses. In response to DOE’s submittal, NRC issued a letter of 

acknowledgement, dated August 31, 2012, stating that a (Type II) Letter to the U.S. Congress is 

not needed at this time. Based on the NRC’s TER analyses and DOE’s revised Tc-99 

inventory, the NRC staff determined that, if DOE’s new projected Tc-99 inventory for the newly 

constructed disposal structures is correct, then it is unlikely to cause an off-site peak dose 

exceeding the requirements of §61.41 (i.e., 0.25 mSv/yr (25 mrem/yr)). 

2.0 NRC ONSITE OBSERVATION VISIT ACTIVITIES:

Observation 2013-01 began with a short briefing on the agenda and site safety procedures 

presented by DOE and attended by representatives from DOE, NRC, and SC DHEC. 

Discussions that followed included details of the recent saltstone production and disposal into 

Saltstone Disposal Structure (SDS) 2B, a tour of the saltstone production facility, research 

results from experiments conducted in accordance with DOE’s PA maintenance program (as 

they relate to issues identified in NRC’s 2012 TER), and an update on DOE’s upcoming SA, 

which includes a revised conceptual model. This report summarizes those discussions. 

Prior to Observation 2013-01, DOE provided NRC staff with two documents (listed below) on 

research related to issues identified in NRC’s TER (NRC, 2012a). 

SRNL-STI-2012-00769, Solubility of Technetium Dioxides in Reducing 

Cementitious Material Leachates, Rev. 1 

ML13070A135 

SRNL-STI-2013-00118, Degradation of Cementitious Materials 

Associated with Saltstone Disposal Units 

ML13189A205 

2.1 Saltstone Production Facility Operations and Discussion of Processing Cycle: 

2.1.1 Observation Scope:

The staff’s interest in discussing operations at the SPF is to ensure that the production of 

saltstone grout at the SDF is consistent with the assumptions made in the 2009 PA. 
5 

NRC staff monitors salt waste processing which is critical to grout quality. Section 3.2.2, “Waste 

Sampling”, Section 3.2.3, “Vault Construction”, Section 3.2.4, “Grout Formulation and 

Placement”, and Section 5, “Monitoring to Assess Compliance with §61.43 – Protection During 

Operations” of the May 2007 monitoring plan (NRC, 2007a) provide details of the basis for NRC 

staff review areas on the topic. 

2.1.2 Observation Results:

DOE provided an update of salt waste processing, including details of recent saltstone 

processing in Cell 2B. The following bullets provide a highlight of the discussion: 

• DOE described new monitoring capabilities. 

o Video monitoring in the grout hopper will allow DOE to monitor grout physical 

characteristics during production and may allow DOE to optimize production 

parameters. For example video monitoring will allow DOE to assess the need for 

anti-foaming agents. This improved monitoring capability may provide a way to 

simplify the saltstone mixture and resolve an NRC question about the effects of 

admixtures on radionuclide leaching from saltstone. Action Item: DOE to 

provide to NRC information on all current admixtures in use. 

o Humidity sensor in the vapor space of SDS 2A will reduce uncertainty in curing 

conditions. 

o A new wet grout sample line was installed in the process room. 

• DOE noted there are currently no plans to fill the remaining space in Vault 4 with 

saltstone because the drain system would need to be upgraded before the space could 

be used. 

• NRC and DOE technical staff discussed the blast furnace slag used in saltstone. 

o DOE and NRC technical staff discussed physical and chemical characteristics of 

the slag as it is received and when it is used in Saltstone. DOE technical staff 

described that, although the slag has a small mesh size (e.g., similar to powder), 

it is microscopically crystalline. DOE indicated that the slag becomes more 

porous and its surface area per unit mass increases significantly (e.g., by 

approximately a factor of 10) when it is mixed with the high-pH simulated salt 

solution. Action Item: DOE to evaluate information available regarding 

blast furnace slag properties and provide to NRC (crystalline versus glass, 

proportion of slag oxide types, age of slag from time of grinding, 

temperature during storage). 

o NRC and DOE staff discussed quality assurance procedures for components of 

the saltstone dry feed (i.e., slag, fly ash, and cement). Action Item: DOE to 

evaluate previously provided information regarding Quality Assurance (QA) 

for dry feeds and will provide updated information, if any, to NRC. DOE to 

supply NRC with the written QA procedures. DOE confirmed that the QA 

program is based on vendor analysis showing the product meets the DOE 

product specification (i.e., DOE does not perform third party analysis). 
6 

• The residence time of the dry feed materials in the hoppers is typically about 2 days 

while SPF is operating, but material does sit in the hoppers for longer periods (i.e., tens 

of days to months) during SPF outages. 

2.1.3 Conclusions and Follow-up Actions:

The NRC staff will continue to monitor SPF activities, including any changes in the SPF 

production schedule, as the SPF continues its current processing cycle and as DOE transfers 

saltstone grout to the newly constructed disposal structures. There were three follow-up actions 

resulting from these discussions. 

2013-01-1. DOE to provide to NRC information on all current admixtures in use. 

2013-01-2. DOE to evaluate information available regarding blast furnace slag properties 

and provide to NRC. 

• Crystalline versus glass 

• Proportion of slag oxide types 

• Age of slag from time of grinding 

• Temperature during storage 

2013-01-3. DOE to evaluate previously provided information regarding QA for dry feeds. 

Provide updated information, if any, to NRC. 

2.2 Technical Discussion - Update on DOE’s Special Analysis for Saltstone and the DOE PA 

Maintenance Plan (SRR-CWDA-2013-00049): 

2.2.1 Observation Scope:

The objective of this monitoring activity is for DOE to provide NRC staff with an update on 

recent activities related to the Saltstone SA and the implementation plan for DOE’s PA 

maintenance plan. 

Based on technical information available from PA maintenance activities, DOE is in the final 

stages of developing a new SA that incorporates recently available technical data and modeling 

lessons learned from other activities to resolve uncertainties and address TER (NRC, 2012a) 

issues. DOE uses its PA maintenance program to both satisfy DOE internal requirements and 

address technical topics in the NRC monitoring plan. 

DOE Manual 435.1-1 (DOE, 2001a) requires DOE to implement a PA maintenance program to 

evaluate changes that could affect the performance, design, and operating bases for the SDF. 

DOE Order 435.1 (DOE, 2001b) states that the PA maintenance program must include the 

conduct of research, field studies, and monitoring needed to address uncertainties or gaps in 

existing data. In addition to fulfilling those internal DOE requirements, DOE uses PA 

maintenance activities to address technical topics in the NRC monitoring plan. The SA is a part 

of those PA maintenance activities. 
7 

As part of monitoring under the NDAA, NRC is responsible for reviewing updates to the DOE PA 

and associated analyses (such as an SA). Section 3.1.2 “Oxidation of Saltstone,” Section 3.1.3, 

“Hydraulic Isolation of Saltstone,” and Section 3.1.4, “Model Support” of the May 2007 

monitoring plan (NRC, 2007a) provide details of the basis for the NRC staff review areas. 

2.2.2 Observation Results:

DOE presented details of both the PA maintenance plan (SRR-CWDA-2013-00049) and an 

update on the details of its SA. The bulleted list below provides the major points of the 

discussion. The reader is advised to refer to DOE’s presentation (SRR-CWDA-2013-00093) for 

more specific details on the bullets below. 

PA Maintenance Plan - General topics 

• DOE described its new approach of coordinating and prioritizing research projects 

across the PA maintenance program for the three liquid waste facilities (i.e., F-Tank 

Farm, H-Tank Farm and the SDF) 

• DOE provided an overview of the PA maintenance plan elements related to saltstone 

divided into critical property testing (e.g., initial hydraulic conductivity and sorption 

coefficients), degradation studies, and emplaced saltstone testing. NRC staff asked if all 

of the experiments planned for this year related to the representativeness of saltstone 

samples focused on initial conditions, and DOE replied that they did. 

• DOE explained that it would ensure that lab samples reflected the curing conditions of 

emplaced saltstone, and specifically indicated they would refer to the temperature profile 

from SDS 2B at an elevation of 3.2 m (10.5 ft.) as well as humidity data from the 

headspace in SDS 2A. 

PA Maintenance Plan - Specific topics 

• Humidity Effects on Saltstone Curing. NRC and DOE staff discussed diurnal variations 

in the observed humidity in the headspace of SDS 2A 30 days after emplacement. DOE 

noted that it expected the humidity to remain more constant during saltstone runs 

(i.e., when grout was being poured on a daily basis). 

• Osmotic Pressure Effects on Contaminant Transport. This task consists of a literature 

search to better understand the potential effects of osmotic pressure on contaminant 

transport. 

• Saltstone Leachate Impacts. DOE will perform experiments to assess the effects of 

leachate from cementitious materials on the Kd of various actinides and fission products 

in site-specific soil. DOE mentioned separate consideration of selenate, selenite, 

niobium, and radium in Z-area soil. The effect would be quantified as a “leachate impact 

factor”. DOE indicated it would assess the effects of four different solutes: (1) leachate 

saturated with Ca(OH)2 to represent young material (pH 12), (2) leachate representative 

of more weathered saltstone (pH 11-12), (3) leachate at equilibrium with CaCO3 (pH 8) 

representing aged saltstone, and (4) artificial SRS ground water. 
8 

• Saltstone Oxidation Front. DOE indicated it would evaluate the time-dependent depth 

profile of saltstone oxidation (i.e., the movement of an oxidation front into saltstone) over 

a 5-42 month curing period. The position of the oxidation front would be determined 

through 2 methods: (1) thin-section leaching and subsequent ICP-MS analyses and 

(2) XANES analysis of Cr and S speciation of sample cross-sections. These studies will 

use Cr as a redox surrogate at concentrations of 500, 250, 100, and 20 mg Cr per 

kilogram saltstone. Studies would look at both Cr and S speciation. 

• Degradation Studies. In response to an NRC question, DOE indicated that all of the 

work planned for this year in this area is method development. 

• Non-Saturated Hydraulic Conductivity Measurements. DOE indicated it would develop 

and assess various techniques to measure unsaturated hydraulic conductivity of 

fractured and non-fractured saltstone. Specifically, DOE indicated it would assess the 

applicability of an unsaturated flow apparatus (UFA) for measuring hydraulic conductivity 

in intact unsaturated samples using ASTM D6527. If DOE finds the UFA method can be 

applied to unsaturated saltstone, it will apply the UFA method and a multistep overflow 

extraction method to samples with known fracture pathways. If DOE finds it can apply 

these methods to samples with known fracture pathways, it will establish methods for 

inducing saltstone fracturing and will assess whether the UFA and multistep overflow 

extraction methods can be applied to fractured saltstone. 

• Saturated Hydraulic Conductivity: Alternate Measurement Techniques. DOE indicated it 

would compare two methods for measuring saltstone saturated hydraulic conductivity. 

Specifically, DOE indicated it would compare the use of a flexible wall permeameter 

(ASTM method D5084) with a centrifuge technique (ASTM D6527). The purpose of the 

evaluation is to determine if the centrifuge method can be used for measuring hydraulic 

conductivity in saltstone because it is a faster technique. DOE indicated it would 

analyze eight replicate samples by each technique, and a third party laboratory using the 

flexible wall permeameter technique would conduct additional confirmatory analyses. 

• Saltstone Field-to-Laboratory Property Comparison: DOE described a new approach for 

evaluating how well laboratory-produced samples represent field-emplaced samples. 

Specifically, DOE described its approach of breaking the comparison into the following 

three groups to isolate the source of any discrepancies: (1) saltstone made with 

simulated salt waste mixed and cured in the laboratory, (2) saltstone made with salt 

waste directly from tank 50 and mixed with the full scale SPF mixer (i.e., samples pulled 

from the SPF process room downstream of the grout hopper) but cured in a mold in the 

laboratory, and (3) samples cored from field-emplaced saltstone in locations (i.e., lift 

heights) that correspond to the fresh grout samples that were cured in molds in items (1) 

and (2). DOE noted it would take and archive a salt waste sample from tank 50 at the 

same time as pulling the process room samples, item (2), so they can refer to a sample 

of the salt waste involved if necessary. NRC staff stated the logical approach to 

demonstrating the representativeness of laboratory samples for field-emplaced saltstone 

appeared to be well planned and seemed as if it would provide very useful results. 
9 

Update on Special Analysis 

• DOE described the status and expected schedule for the SA. DOE indicated that the SA 

would be reviewed by the low-level waste disposal facility federal review group, or 

LFRG3

 from July-September 2013. 

• DOE described potential sources of uncertainty in flow that were evaluated in sensitivity 

analyses included in the SA. These factors included infiltration rates through the closure 

cap (as calculated by the HELP model), timing of complete physical degradation, initial 

hydraulic conductivity, and flow through construction joints. 

• To assess the potential effects of fracturing, DOE will model oxygen generation in 

randomly selected blocks in the model. NRC staff commented that it would assess the 

conservatism of the fraction of saltstone represented by those blocks. 

• NRC staff commented that documentation and visual presentation of the deterministic 

sensitivity analyses are likely to be important for aspects of the analysis that are 

evaluated primarily with deterministic analyses. Sensitivity analysis results can reveal 

interrelationships of processes and provide significant insights and understanding. 

2.2.3 Conclusions and Follow-up Actions:

The NRC will continue to monitor DOE’s PA maintenance program as it applies to NRC’s 

monitoring responsibilities under the NDAA. In addition, NRC looks forward to reviewing the 

DOE’s revised SA when it is completed. No open issues or follow-up actions resulted from this 

discussion. 

2.3 Technical Discussion – Recent Research Activities

2.3.1 Observation Scope:

This section of the observation focused primarily on two technical reports (shown below) on 

research related to issues identified in NRC’s TER (NRC, 2012a). 

SRNL-STI-2012-00769, Solubility of Technetium Dioxides in Reducing 

Cementitious Material Leachates, Rev. 1 

ML13070A135 

SRNL-STI-2013-00118, Degradation of Cementitious Materials 

Associated with Saltstone Disposal Units 

ML13189A205 

As noted in Section 3.1.2, “Factor 1 – Oxidation of Saltstone” of the May 2007 monitoring plan 

(NRC, 2007a), saltstone oxidation is considered to be important to compliance with the 

performance objectives primarily because oxidation can lead to increased releases of 

technetium from the wasteform. The release of Tc-99 from the wasteform is an important factor 

in the compliance with the performance objective identified in §61.41, “Protection of the General 

 

3

 The LFRG assists DOE-Environmental Management senior managers in the review of documentation 

that supports the approval of PAs and associated analyses (such as an SA). 
10 

Population from Releases of Radioactivity” and §61.42 “Protection of Individuals from 

Inadvertent Intrusion.” 

As noted in Section 3.1.3, “Factor 2 – Hydraulic Isolation of Saltstone” of the May 2007 

monitoring plan (NRC, 2007a), performance of the wasteform and concrete vault barriers is 

important to meet the performance objective in §61.41, “Protection of the General Population 

from Releases of Radioactivity” and §61.42 “Protection of Individuals from Inadvertent 

Intrusion.” The methods used to analyze the long-term performance of the SDF must account 

for potential mechanisms of contaminant release from the facility and the potential mechanisms 

for loss of integrity of the SDF engineered barriers. 

2.3.2 Observation Results:

DOE provided presentations on each topic with authors of each technical report present at the 

observation. Slides from the presentations are in SRR-CWDA-2013-00093. The bulleted list 

below provides the details of the technical discussion on each topic. The discussion of 

SRNL-STI-2012-00769 below was guided by a list of questions (NRC, 2013a) provided to DOE 

following a technical exchange phone call on April 30, 2013 (NRC, 2013b) and in preparation for 

this observation. The staff’s full conclusions about SRNL-STI-2012-00769 will be documented 

in a technical review memo. 

SRNL-STI-2012-00769, Solubility of Technetium Dioxides and Primary References 

• DOE staff explained that the proposed solubility value for moderately aged cement 

(1x10-8 M) (Table 11, SRNL-STI-2012-00769) was based on a combination of an 

experimental value of 4.5x10-10 M (pH 10.9 and Eh -0.40 V) (SRNL-STI-2012-00596) and 

expert judgment. DOE explained that expert judgment was used to adjust the 

experimental value, based on considerations of ionic strength in a closed experiment as 

compared to a flow-through system, as well as consideration of the relative values 

applicable under different conditions represented in Table 11 (i.e., oxidizing and 

reducing conditions of young, middle age, and old cementitious materials). In response 

to NRC questions, DOE explained that, although the experiments were conducted with 

young cement, the experimental conditions mimicked “moderately aged” conditions 

because the permeate pH was controlled at approximately 10.5. 

• NRC and DOE staff discussed the uncertainty in the geochemical modeling due to the 

high ionic strengths present in early pore volumes that could lead to a higher solubility of 

Tc. DOE staff stated that the model uses the Debye-Hückel equation, which is valid up 

to an ionic strength of 1 M. DOE staff estimated that the number of pore volumes before 

the ionic strength decreases to less than 1 M, which NRC and DOE staff referred to as 

the “very early” time period, is on the order of ones. DOE staff also stated that the 

experimental values represented in the model were derived from experiments that 

included the very early time period in which the pore solution had an ionic strength 

greater than 1 M. 

• DOE noted the results of synchrotron data (PIT-MISC-0017) on the speciation of Tc in 

reduced grout. DOE stated that over time the amount of Tc that was oxidized decreased 

to around 4% after 30 months of curing. 
11 

SRNL-STI-2012-00769, Solubility of Technetium Dioxides, Use of Results in PA 

• DOE staff described the approach that was going to be used in the SA for modeling the 

release of Tc. They stated that the saltstone was initially modeled as being reduced and 

moderately-aged (2nd stage) and having a Tc solubility limit of 1x10-8 mol/L. At later 

times, the Tc was modeled as having a Kd value of 0.5 mL/g, which represents oxidized 

aged cement (3rd stage). Oxidized moderately-aged saltstone was not explicitly included 

in the model because the Kd value for this (0.8 mL/g) is similar to the Kd value for 

oxidized aged cement and the use of the lower Kd value for oxidized aged saltstone is 

conservative. NRC staff stated that it is only appropriate to exclude the young cement 

(1st stage) from the model if the properties of the young and moderately-aged saltstone 

are similar and if this simplification does not lead to an underestimation of the dose. 

• NRC staff asked if the model used in the SA accounted for the possibility that the 

reduced sulfur is present in a more soluble form and is leached out. DOE staff stated 

that in the model, the reductant is only consumed by oxygen and the model does not 

include any leaching of the sulfur reductant. 

• In response to an NRC question, DOE staff stated that the Tc solubility limit would not be 

modeled probabilistically in the new SA, but sensitivity cases were run in which the 

solubility limit was increased and decreased by an order of magnitude. 

SRNL-STI-2013-00118, Degradation of Cementitious Materials 

• NRC staff made the general comment that the topic report does not address why 

mechanical degradation mechanisms (e.g., shrinkage, thermal loading, differential 

settlement) were not considered. The NRC staff noted that the subject report included 

the following basis for the selection of degradation mechanisms discussed: 

Previous studies of cementitious material degradation in the context of 

low-level waste disposal have identified sulfate attack, carbonation 

influenced steel corrosion, and decalcification (primary constituent 

leaching) as the primary chemical degradation phenomena of most 

relevance to SRS exposure conditions (NUREG/CR-5542, 

WSRC-STI-2007-00607, SRNL-STI-2010-00035, and 

CBP-TR-2009-002-C4). (emphasis added) 

NRC staff indicated it expected to ask DOE for more of a basis for why mechanical 

degradation mechanisms were not incorporated into the SA. 

• NRC staff made the general comment that the subject report did not appear to provide 

adequate basis for the selection of the Best Estimates, Nominal Values, and 

Conservative Estimates. NRC staff indicated it understood a lengthy technical basis for 

parameter values would typically be unnecessary in an initial uncertainty analysis. 

However, NRC stated that, in general, it is not adequate to indicate only that one value 

of a parameter is greater than or less than another value. In a subsequent discussion, 

NRC staff noted slide 40 of DOE’s presentation (SRR-CWDA-2013-00093) as an 

example of the simple, physically-based reasoning and short explanation that might be 

appropriate in the context of the DOE degradation report. 
12 

• NRC staff asked for more information about the technical basis for the choice of Best 

Estimate, Nominal, and Conservative values for several parameters, including the 

fractional porosity, pore space open for gas transport, hydraulic gradient, water-tocement ratio, and the ratio of the interior concentration to boundary concentration (i.e., in 

the computation of the effective diffusion coefficient). DOE replied that the values were 

based on engineering judgment. 

• NRC staff noted that the use of the term “best estimate” in the degradation report 

appeared to differ from its meaning in the 2009 PA. NRC staff suggested that a formal 

definition for each term (Best Estimate, Nominal, and Conservative) would reduce 

misunderstandings and help focus future technical discussions. 

• DOE showed NRC staff selected intermediate model results from the DOE Fiscal Year 

2013 draft SA. DOE explained that it would assume disposal structure and saltstone 

hydraulic conductivity increased linearly as a function of time after an initial lag period. 

• NRC staff commented that it seemed the initial lag period, prior to the linear increase in 

hydraulic conductivity, did not account for potential mechanical degradation 

mechanisms, because DOE had not explained why it did not expect mechanical 

degradation to take place during that lag period. NRC staff also noted that the duration 

of the initial lag period appeared to have a significant effect on the timing of the projected 

peak dose. 

• DOE explained that “completely degraded” conditions meant the component degraded to 

the hydraulic characteristics of the surrounding soil. DOE addressed the potential 

concern that cementitious materials in contact with natural soil as compared to backfill 

(e.g., disposal structure floors as compared to disposal structure roofs) would have 

different degraded states. NRC staff commented that it understood this approach was 

designed to minimize modeling artifacts that could be created if the degraded barriers 

were dissimilar to the surrounding materials. 

2.3.3 Conclusions and Follow-up Actions

NRC staff found these discussions very helpful and will continue to monitor the progress of this 

research and its application in the upcoming SA and future revisions to the PA. The discussion 

on SRNL-STI-2012-00769 will provide direct benefit to the NRC staff’s publicly available 

technical review memo on the report expected within CY 2013. NRC staff expressed general 

concerns about the scope of degradation mechanisms considered in SRNL-STI-2013-00118 as 

well as the justification provided for Best Estimates, Nominal Values, and Conservative 

Estimates of parameters. No open issues or follow-up actions resulted from this discussion. 
13 

3.0 FOLLOW-UP ACTIONS AND OVERALL CONCLUSIONS:

3.1 Follow-up Actions from the Saltstone Production Facility Operations and Discussion of 

Processing Cycle

2013-01-1. DOE to provide to NRC information on all current admixtures in use. 

2013-01-2. DOE to evaluate information available regarding blast furnace slag properties 

and provide to NRC: 

• Crystalline versus glass 

• Proportion of slag oxide types 

• Age of slag from time of grinding 

• Temperature during storage 

2013-01-3. DOE to evaluate previously provided information regarding QA for dry feeds. 

Provide updated information, if any, to NRC. 

3.2 Follow-up Actions from the Update on DOE’s Special Analysis for Saltstone and the 

DOE PA Maintenance Plan

None. 

3.3 Follow-up Action from the Technical Discussion –Recent Research Activities

None. 

3.4 Overall Conclusions

There are no new Open Issues resulting from Observation 2013-01. The previous Open Issues 

are now rolled into the concerns identified by NRC in the 2012 TER (NRC, 2012a). Those NRC 

concerns will be rolled into the monitoring factors in the revised monitoring plan that is being 

drafted by NRC. Based on the results of Observation 2013-01, there is no change to the NRC 

conclusions in that TER – NRC continues to conclude that it does not have reasonable 

assurance that salt waste disposal at the SDF meets the performance objectives in 

10 CFR Part 61, specifically §61.41. However, the NRC is encouraged by the progress made 

since publication of the TER. 
14 

4.0 PARTICIPANTS:

U.S. NRC SC DHEC US. DOE SRR

George Alexander 

Hans Arlt 

Nishka Devaser 

Christepher McKenney 

Aby Mohseni 

Karen Pinkston 

A. Christianne Ridge 

Mark Roberts 

Justin Koon 

Robert McDaniel 

Gregory O’Quinn 

Scott Simons 

Daniel Ferguson 

Jean Ridley 

Sherri Ross 

Irvin Rubin 

Terry Spears 

Patricia Suggs 

Linda Suttora 

SRNL

Gregory Flach 

Daniel Kaplan 

Alex Baldwin 

Kim Hauer 

Bruce Long 

Mark Mahoney 

Larry Romanowski 

Kent Rosenberger 

Steven Simner 

Steven Smith 

Aaron Staub 

Steven Thomas 

5.0 REFERENCES:

10 CFR 61, Federal Register, Licensing Requirements for Land Disposal of Radioactive Waste. 

Code of Federal Regulations, Office of the Federal Register. Washington, DC. January 2001. 

CBP-TR-2009-002-C4, Rev. 0, Samson, E., P. Henocq, and J. Marchand, Chemical 

Degradation Review. Cementitious Barriers Partnership technical report. November 2009. 

DOE-WD-2005-001 Rev. 0, U.S. Department of Energy Draft Basis for Section 3116 

Determination Salt Waste Disposal at the Savannah River Site. DOE. Washington, DC. 

February 2005. ML051020072. 

DOE-WD-2005-001, Rev. 1, U.S. Department of Energy Basis for Section 3116 Determination 

Salt Waste Disposal at the Savannah River Site. DOE. Washington, DC. January 2006. 

ML102850319. 

PIT-MISC-0017, Lukens, W.W., J.I. Bucher, D.K. Shuh, and N.M. Edelstein, Evolution of 

Technetium Speciation in Reducing Grout. Environmental Science and Technology, Vol. 39. 

pp. 8,064–8,070. 2005. ML052720213. 

NDAA, Congress, Public Law 108-375, Ronald W. Reagan National Defense Authorization Act 

for Fiscal Year 2005, Section 3116, Defense Site Acceleration Completion. U.S. Congress. 

Washington DC. October 2004. 

NUREG/CR-5542, Walton, J. C., L. E. Plansky, and R. W. Smith, Models for Estimation of 

Service Life of Concrete Barriers in Low-Level Radioactive Waste Disposal, September 1990. 

ML121240822. 

SRNL-STI-2010-00035, Rev. 0, Langton, C. A., Chemical Degradation Assessment for the HArea Tank Farm Concrete Tanks and Fill Grouts, January 2010. ML111220404. 

SRNL-STI-2012-00596, Rev. 0, Technetium Sorption by Cementitious Materials under 

Reducing Conditions. SRNL and Clemson. September 30, 2012. ML12345A134. 
15 

SRNL-STI-2012-00769, Rev. 1, Li, D. and Kaplan, D.I., Solubility of Technetium Dioxides in 

Reducing Cementitious Material Leachates. SRNL, Aiken, SC. February 1, 2013. 

ML13070A135. 

SRNL-STI-2013-00118, Flach, G. P. and Smith III, F. G., Degradation of Cementitious Materials 

Associated with Saltstone Disposal Units. SRNL, Aiken, SC. March 2013. ML13189A205. 

SRR-CWDA-2009-00017, Performance Assessment for the Saltstone Disposal Facility at the 

Savannah River Site. SRR, Aiken, SC. October 2009. ML101590008. 

SRR-CWDA-2012-00095, Rev. 1, Projected Technetium-99 Inventory in Saltstone Disposal 

Facility Units 2, 3, and 5. SRR. Aiken, SC. July 2012. ML12198A307. 

SRR-CWDA-2013-00049, Rev. 1, Savannah River Site Liquid Waste Facilities PA Maintenance 

Program, SRR, Aiken, SC. May 2013. ML13148A277. 

SRR-CWDA-2013-00093, Rev. 1, Onsite Observation Documents - DOE Presentation during 

June 26-27 Observation. SRR. Aiken, SC. June 2013. ML13189A050. 

U.S. Department of Energy (DOE), DOE Manual 435.1-1, Radioactive Waste Management 

Manual, Change 1. DOE, Washington, D.C. June 2001a. ML110800193. 

U.S. Department of Energy (DOE), DOE Order 435.1, Radioactive Waste Management. DOE. 

Washington, DC. August 2001b. ML101590125. 

U.S. Department of Energy (DOE), Response to Letter of Concern (Type IV) Regarding U.S. 

Department of Energy Disposal Activities at the Savannah River Site Saltstone Disposal Facility. 

DOE. Washington, DC. July 2012a. ML12198A258. 

U.S. Department of Energy (DOE), Additional Response to Technical Evaluation Report for 

Revised Performance Assessment for the Saltstone Disposal Facility at the Savannah River 

Site, South Carolina and the Letter of Concern. DOE. Washington, DC. July 2012b. 

ML12215A081. 

U.S. Nuclear Regulatory Commission (NRC), Technical Evaluation Report for Draft Waste 

Determination for Salt Waste Disposal. NRC. Washington, DC. December 2005. 

ML053010225. 

U.S. Nuclear Regulatory Commission (NRC), U.S. Nuclear Regulatory Commission Plan for 

Monitoring the U.S. Department of Energy Salt Waste Disposal at the Savannah River Site in 

Accordance with the National Defense Authorization Act for Fiscal Year 2005. NRC. 

Washington, DC. May 2007a. ML070730363. 

U.S. Nuclear Regulatory Commission (NRC), NRC Staff Guidance for Activities Related to U.S. 

Department of Energy Waste Determinations – Draft Final Report for Interim Use. NRC. 

Washington, DC. August, 2007b. ML072360184. 

U.S. Nuclear Regulatory Commission (NRC), Technical Evaluation Report for the Revised 

Performance Assessment for the Saltstone Disposal Facility at the Savannah River Site, South 

Carolina. NRC. Washington, DC. April 2012a. ML121020140. 
16 

U.S. Nuclear Regulatory Commission (NRC), Letter of Concern (Type IV) Regarding U.S. 

Department of Energy Disposal Activities at the Savannah River Site Saltstone Disposal Facility. 

NRC. Washington, DC. April 2012b. ML120650576. 

U.S. Nuclear Regulatory Commission (NRC), Letter to Terrel Spears of DOE, Acknowledging 

Receipt of July 12, 2012 Letter Regarding NRC's Letter of Concern (Type IV) Regarding 

Disposal at the Savannah River Site. NRC. Washington, DC. August 29, 2012c. 

ML12213A447. 

U.S. Nuclear Regulatory Commission (NRC), NRC Staff Questions on Technetium Solubility 

Research Related to Monitoring of the Saltstone Disposal Facility.. NRC. Washington, DC. 

June 26, 2013a. ML13211A329. 

U.S. Nuclear Regulatory Commission (NRC), April 30, 2013, Summary of Telephone 

Conference Call to Discuss Technetium Solubility Research Related to Monitoring of the 

Saltstone Disposal Facility.. NRC. Washington, DC. July 3, 2013b. ML13171A127. 

WSRC-STI-2007-00607, Rev. 0, Langton, C. A., Chemical Degradation Assessment of 

Cementitious Materials for the HLW Tank Closure Project (U), September 2007. ML081330358.