United States Nuclear Regulatory Commission - Protecting People and the Environment

Final Report-Assessment of Potential Phosphate Ion-Cenmentitious Materials Interactions (NUREG/CR-6938)

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Publication Information

Manuscript Completed: November 2006
Date Published: June 2007

Prepared by:
D.J. Naus, C.H. Mattus, and L.R. Dole

Oak Ridge National Laboratory
Managed by UT-Battelle, LLC
P.O. Box 2008
Oak Ridge, TN 37831-6283

H. L. Graves, NRC Project Manager

Prepared for:
Division of Fuel, Engineering and Radiological Research
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code N6002

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The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants.

An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.

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