November 12, 2009 

MEMORANDUM TO: Gregory Suber, Chief 

 Low-Level Waste Branch 

 Environmental Protection 

 and Performance Assessment Directorate 

 Division of Waste Management 

 and Environmental Protection 

 Office of Federal and State Materials 

 and Environmental Management Programs 

THRU: Christepher McKenney, Chief /RA/ 

 Performance Assessment Branch 

 Environmental Protection 

 and Performance Assessment Directorate 

 Division of Waste Management 

 and Environmental Protection 

 Office of Federal and State Materials 

 and Environmental Management Programs 

FROM: David Esh, Senior Systems Performance Analyst /RA/ 

 Performance Assessment Branch 

 Environmental Protection 

 and Performance Assessment Directorate 

 Division of Waste Management 

 and Environmental Protection 

 Office of Federal and State Materials 

 and Environmental Management Programs 

SUBJECT: TECHNICAL REVIEW: SALTSTONE VAULT #2 INTERIOR 

LINING REVIEW 

 On November 25, 2008, the U.S. Department of Energy (DOE), Savannah River 

Operations Office, provided the subject report for review by the U.S. Nuclear Regulatory 

Commission (NRC) staff pursuant to Section 3116(b) of the Ronald W. Reagan National 

Defense Authorization Act for Fiscal Year 2005. The subject report is available on NRC’s 

Agencywide Documents Access and Management System at accession number ML083400060. 

This report was reviewed in accordance with monitoring activities described in “NRC Plan for 

Monitoring the DOE Salt Waste Disposal at the Savannah River Site in Accordance with the
G. Suber 2 

National Defense Authorization Act for Fiscal Year 2005” (ML070730363). The staff’s technical 

review summary is enclosed for your use. 

Docket No.: PROJ0734 

Enclosure: Technical Review Summary 
G. Suber 2 

National Defense Authorization Act for Fiscal Year 2005” (ML070730363). The staff’s technical 

review summary is enclosed for your use. 

Docket No.: PROJ0734 

Enclosure: Technical Review Summary 

DISTRIBUTION: 

KPinkston GAlexander ARidge CGrossman LHoward/CNWRA 

ML093100197 

OFC DWMEP DWMEP DWMEP DWMEP:BC 

NAME DEsh NDevaser AWalker-Smith CMcKenney 

DATE 11/12/09 11/12/09 11/12/09 11/12/09 

OFFICIAL RECORD COPY
 

Technical Review Summary 

SALTSTONE VAULT #2 INTERIOR LINING REVIEW 

Review Completed: November 2009 

Reviewer(s): D. Esh 

Document(s): T.E. Skidmore, and K.D. Billings, Saltstone Vault #2 Interior Lining 

Review, WSRC-TR-2008-00090, Rev. 0, Savannah River National 

Laboratory. May, 2008. ADAMS Accession # ML083400060 

Evaluation

The subject report provided a review of lining options for the interior of the new Saltstone Vault 

#2 design. The objectives for the lining materials are to improve the probability that the new 

vault design will meet long-term performance goals in a 10,000 year performance period by 

protecting the concrete vault from sulfate attack and other degradation mechanisms associated 

primarily with the initial interaction of the vault concrete with the saltstone wasteform. The 

desired service life of the materials selected is 100 years, because current DOE analysis 

suggests the impact of sulfate-containing bleedwater decreases as the bleedwater is removed 

from the system as the saltstone cures. 

The report provides an overview of the vault lining requirements and saltstone characteristics. 

The primary function of the lining materials is mitigation of sulfate attack from short-term 

saltstone bleedwater (10,900 mg/L SO4

-

) penetration through surface cracks and by capillary 

suction, and diffusion of sulfate from the pore fluid of the cured saltstone. The coating must be 

resistant to chemical and radiation damage at elevated temperatures. In addition, the coating 

should exhibit a minimum elongation value of 2%, provide a long-term barrier for diffusion, be 

easily applied to joints and penetrations, and generate limited amounts of flammable gases. 

The report provides physical characteristics of saltstone, referencing the 1992 performance 

assessment. More recent data is acknowledged, though a reference is not provided. Although 

the physical characteristics of saltstone are not essential to the content of this report, they may 

influence the preliminary assessment performed in 2007 (reference 1 in the document) which 

identified the desired service life. If this report were to be revised, U.S. Nuclear Regulatory 

Commission (NRC) staff recommends that more recent information for the physical 

characteristics of saltstone be provided and that the assessment of the impact of liner coatings 

on preventing, mitigating, or delaying sulfate attack of concrete be reevaluated. 

The impact of radiation on different liner materials was evaluated. Cs-137 was the primary 

contributor to the total dose rate from all radionuclides. The Cs-137/Ba-137m concentration 

was assumed to be 0.1 Ci/gal. From review of saltstone inventory reports, NRC staff concludes 

that the assumption of 0.1 Ci/gal may not be realistic or sufficiently conservative. Review of the 

saltstone inventory reports show that quarterly averaged concentrations of saltstone can exceed 

0.15 Ci/gal. In addition, batch to batch variability would likely result in locally higher 

concentrations. NRC staff recommends that the assessment of radiation damage should 

consider variability in the source concentrations of saltstone. NRC staff agrees that the 
2 

ARP/MCU and SWPF waste streams are projected to have concentration less than 0.1 Ci/gal; 

however, DOE should evaluate the fraction of waste that may be above 0.1 Ci/gal. 

Mat-reinforced epoxy-novolac thermosetting linings were recommended based on the 

assessment of experience with different lining materials, comparison of the materials to the 

design requirements, and recommendations from vendors, among other factors. The report 

recommends mat-reinforced epoxy-novolac thermosetting linings, but acknowledges that 

service life prediction is complex, long-term performance data are limited, and that performance 

is based on several assumptions that would require verification. These assumptions include: 

limited oxidation, gradual temperature decline, tolerable radiation dose with minimal dose rate 

effects, minimal differential settlement and proper installation. Numerous vendors were 

contacted by DOE for recommendations of coating systems given the design parameters. 

Throughout section 5.4 of the subject report is a discussion of lining degradation mechanisms 

and in particular dose rate effects. Processes that are rate-limited have the potential to not be 

identified in testing or from examination of performance data of a period of time that is shorter 

than the anticipated service life. In addition, the materials may exhibit cliff response where 

performance is relatively stable until a condition is achieved, where performance deteriorates 

relatively quickly. An example would be depletion of antioxidants in a polymer. 

Teleconferences and Meetings

This report has not yet been discussed in a teleconference or meeting. 

Open Issues

No open issues were identified as part of this review. 

Conclusion

The NRC staff believes that this report was a sufficient assessment of lining systems that could 

be used to reduce the impact of sulfate attack on saltstone vault concrete. NRC staff concludes 

the primary vault lining requirements have been appropriately identified. The report adequately 

discussed lining degradation mechanisms, factors that could affect performance and key 

assumptions. 

NRC staff would note that while the report did a good job of assessing different lining materials 

and evaluating their potential performance given the design goals and expected service 

environment, the actual performance of thermosetting lining materials would need to be verified 

for this particular application. If credit is taken for the thermosetting lining performance in the 

performance assessment the NRC staff recommends: 

1) Performance of additional testing and research. The testing and research should 

consider how dose rate effects could be addressed. 

2) Providing conceptual diagrams of the systems and conditions, including a description of 

how the system would avoid osmotic blistering and moisture vapor transmission. 
3 

3) Completion of the accelerated-aging test program noted in the report to validate 

conclusions and provide a model for lining service life prediction for this application. 

4) Providing a more detailed description of the quality assurance (QA) processes, 

procedures, and controls for the lining systems selected for use in this application. 

5) Evaluating the potential for waste to exceed 0.1 Ci/gal, and if necessary revise the lining 

assessment and selection process and associated testing. 

References

WSRC. Radiological Performance assessment for the Z-Area Saltstone Disposal Facility, 

WSRC-RP-92-1360, Westinghouse Savannah River Company. 1992,