In a recent project, buried cast-iron pipe carrying cooling water at the UK's Hunterston A magnox nuclear power plant was replaced with high-density polyethylene (HDPE) pipe.
The Reactor Cooling Water (RCW) system draws water from the cooling water pump house and routes it to safety-related plant and equipment via the turbine house. The link from the pump house to the turbine was subject to periodic problems due to pipe failures.
(Pictured: Hunterston nuclear power plant, Scotland).
Boulting Group replaced it with a new raised pipeline consisting of sections in HDPE, stainless steel and glass flake-lined carbon steel. All of the sections were flanged, and all of the pipe connections were made flange-to-flange. (No plastic butt-welding was used on site). The pipeline consisted of 24 sections of HDPE pipe (250m total length), five sections of super duplex (stainless steel) pipe (40m), and 25 sections of glass flake-lined carbon steel pipe. Pipes were about 620mm in diameter.
Stainless steel sections were used near storage tanks outside of the turbine hall to avoid the risk of melting in the (unlikely) event of a tank explosion. Carbon steel pipes were installed inside the turbine hall to reduce the risk to them posed by a potential fire.
The different expansion coefficients of the metal and plastic pipe sections required calculations to be peformed of the whole length of the pipeline rather than section-by-section; those calculations determined where pipeline anchors were placed.
The 15-month job, which included site surveys, design, equipment qualification, procurement, fabrication, delivery, inspection and testing, commissioning, documentation and warranty, finished in March 2013.
It is now starting work to replace primary and secondary containment Active Effluent Discharge pipe work (AETP) at the Dungeness Power Station with HDPE piping.