Degradation of raw water piping systems is a major issue facing nuclear power plant owners. High density polyethylene (HDPE) is a cost-effective alternative to corrosion resistant alloys and has been found to perform well in power plant applications for over 10 years. When used above ground, fire resistance may be an issue. HDPE starts to melt at ∼235°F (115°C) and has an auto-ignition temperature of ∼662°F (350°C). Additionally, toxic gasses are released when it burns.
The paper summarizes the development of a method that can be used to protect HDPE piping from postulated fire events is situations where the system must remain operable or not contribute to the fire load. The method was demonstrated using a proof-of-concept fire test of four piping subassemblies that contained many of the fittings that are commonly found in HDPE piping systems. The assemblies were subject to a 3-hour fire test following the guidance of ASTM E119 followed by a hose stream test following the guidance of ASTM E2226. All four specimens survived the test, with each retaining its overall geometry, cross section, and structural and pressure boundary integrity.