Assessment of NDE Methods on Inspection of HDPE Butt Fusion Piping Joints for Lack of Fusion (NUREG/CR-7136, PNNL-20300)
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Manuscript Completed: October 2011
Date Published: May 2012
S. L. Crawford, S. R. Doctor, A. D. Cinson, M. W. Watts,
S. E. Cumblidge, T. E. Hall, and M. T. Anderson
Pacific Northwest National Laboratory
P.O. Box 999
Richland, WA 99352
W. E. Norris, NRC Project Manager
NRC Job Code N6398
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
The U.S. Nuclear Regulatory Commission (NRC) has a multi-year program at the Pacific Northwest National Laboratory (PNNL) to provide engineering studies and assessments of issues such as the nondestructive evaluation (NDE) of high-density polyethylene (HDPE) butt fusion joints. This work was begun in response to requests from commercial nuclear licensees to employ HDPE materials in nuclear power plant systems. HDPE has been widely used in low-pressure, low-temperature applications such as natural gas lines, water, sewer, and petrochemical applications. There are a number of issues related to its use at the higher temperatures that would be encountered in nuclear applications.
Materials issues associated with the use of HDPE at higher temperatures are being investigated under a separate contract. The work described in this report is being conducted by the NRC at PNNL to assess whether a volumetric inspection method can be applied to the fusion joint that may reliably detect lack-of-fusion (LOF) conditions. Temperatures at or exceeding the design temperature may result in the failure of piping due to LOF.
Twenty-four HDPE pipe specimens were butt fused in 3408 material to contain LOF conditions that could be used to assess the effectiveness of NDE methods applied. (It should be noted that 4710 became the material of choice after this study was initiated [in large part to address some of the issues associated with the higher temperature application]. The NRC plans to assess 4710 material.) A range of NDE measurements were performed using ultrasonic and electromagnetic methods. Destructive evaluations were conducted using several different methods, but eventually were focused on a side-bend test procedure. All of the NDE results and destructive test results have been analyzed and documented in this report.