FRP Retrofit of the Ring-Beam of a Nuclear Reactor Containment Structure

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Title: FRP Retrofit of the Ring-Beam of a Nuclear Reactor Containment Structure

Author(s): M. Demers, A. Popovic, K. W. Neale, S. Rizkalla, and G. Tadros

Publication: Special Publication

Volume: 215

Issue:

Appears on pages(s): 303-316

Keywords: concrete repair; fiber optic sensors; nuclear power plant; structural monitoring; surface-bonded FRPs

Date: 8/1/2003

Abstract:
The Gentilly-1 nuclear power plant, in Quebec, Canada, was decommissioned in 1978. Since that time, the containment structure has been used for the storage of the moderately contaminated nuclear reactor. The enforcement of more rigorous environmental regulations, as well as economic considerations, have raised the decommissioning period from 40 to 100 years, thus severely increasing the durability requirements for the structure. The containment structure, constructed of thick prestressed concrete, was in good condition except for the secondary concrete. The latter is a keystone for the durability of the structure because it fills the recesses and protects the terminations of the tendons against corrosion. The differential shrinkage caused cracking and debonding and, with freeze-thaw cycling over the years, the secondary concrete had to be removed and replaced. The ringbeam, at the top of the containment structure, was severely affected because the numerous tendons of the roof terminate at that level. The retrofit of the ring-beam consisted of replacing the secondary concrete with highquality shrinkage-compensated mortar and concrete, followed by FRP wrapping. The layout of the FRP wrap was designed to mitigate the adverse effects of the new secondary concrete shrinking-induced cracks. Most of the concrete cold joints were covered by the FRP wrap, which was anchored on the dome roof to provide an effective support.