Cast Iron Pipe Rehabilitation with CFRP and CIPP in a Nuclear Power Generating Station

Circulating cooling water piping systems are critical to nuclear power station operations and overall safety. As nuclear power stations in the United States and around the world age and the piping systems reach their service life, utilities have initiated pipe replacement activities to comply with their NRC (nuclear regulatory commission) license commitments for safe operations and to ensure system performance doesn’t impact operations. Power plants need to consider their options on how to comply with life extension requirements of degraded pipe include dig and replace the piping systems as well as trenchless rehabilitation methods. The trenchless repair options include the design and installation of cured in place pipe (CIPP) and carbon fiber reinforced polymers (CFRP). Replacing a system often presents operational or construction challenges to nuclear power stations. In the case of a pipe rehabilitation project in a nuclear power station in the United States which this paper will review in details, the site’s design team was presented with the challenge of replacing a concrete encased cast iron piping system beneath the turbine building. Replacing the piping system was not operationally feasible and therefore, the repair method chosen for the pressure barrier replacement of the buried piping systems was a combination of CIPP and CFRP. This paper describes the successful design, planning, and implementation of a full structural rehabilitation of a cooling water piping system at the nuclear power station.