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The Pacific Northwest Laboratory is conducting a four-phase program for measuring and evaluating the effectiveness and reliability of in-service inspection (lSI} performed on the primary system piping welds of commercial light water reactors (l..WRs). Phase I of the program is complete. A survey was made of the state of practice for ultrasonic rsr of LWR primary system piping ·Nelds. Fracture mechanics calculations 'Nere made to establ-ish required nondestru:tive testing sensitivities. In general, it was found that fatigue flaw·s less t11an 25% of wall :hic!

Copies of industry codes and standards used in a substantive manner in the NRC regulatory procars y are maintained at the NRC Library, 7920 Norfolk A w e , Bothria, MHyland, and are available "3 there for reference ure by the public. Codes and standards are k l l y copyrighted and may be 4 .! purchased from the originating organization or, if thy are A m i o n National Standards, from the

Results from the research have been used to support development of NRC guidance for implementation of risk-informed ISI of piping. The results have also been used in the development of PFM tools to generate failure probabilities for vessels that has been used in regulatory decision making.