Evaluation of Concrete Permeability After 25 Years Exposure to Nuclear Operating Environment

Abstract

Permeability tests on cores recovered from concrete which had been in service for 25 years in the Nuclear Power Demonstration (NPD) reactor showed rates of mass transfer of gas and water which were slightly greater than those observed previously for younger concrete specimens of the same proportions. The permeability of the NPD concrete was also two orders of magnitude greater than that of comparable concrete which had been stored in the laboratory atmosphere for 19 years. Analysis of the effluent in water permeability tests revealed the presence of unusual amounts of soluble materials, mainly Na and K but little Ca, in the reactor concrete. This suggested service-related deterioration of the concrete rather than the release of soluble Ca by continuing hydration of cement. Overall, the tests did not reveal any serious deterioration of the measured properties of the specimens taken from the NPD concrete structure after 25 years of service.