Polyethylene (PE) material is chemically inert and does not corrode. It is a preferred material choice for many piping applications including the service water pipe in nuclear power plants. With an outstanding field service record for 5 decades for both gas and water distribution, recently a 36 SDR 9 PE4710 pipe received approval for Release Request from the U.S. Nuclear Regulatory Committee (NRC) and was installed in 2008 by a major US utility to replace the steel pipe for the safety related nuclear water pipe application. The PE pipe industry uses a maximum 10% scratch as a rule of thumb for scratched pipes. As the pipe diameter increases, the stress intensity increases for the same 10% of scratch depth. It is a concern for the regulators how the increased stress intensity affects the long term performance of the scratched pipe against slow crack growth (SCG) failure. The SCG resistance depends on the resin material, stress intensity and testing temperature. The stress intensity is controlled by pipe geometric factors, the applied stress, and the notch depth. In order to achieve the equivalent SCG performance for all pipe sizes, the following actions may be taken: (1) use a resin material that has higher SCG resistance to compensate impact from the increased stress intensity; (2) reduce the scratch depth and (3) reduce the pipe hoop stress so that the increased stress intensity is decreased. The minimum SCG resistance requirement that eliminates the need for action (2) and (3) needs to be determined. ASTM F1473 has addressed the equivalent pipe sizes from 1 SDR 11 to 8 SDR 11 pipe. This paper investigates the dependence of SCG resistance on the geometric factors for the pipe diameters from 2 to 44. The recent PE4710 nuclear water pipe installation is also discussed.

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