Use of Appendix VIII Qualification Data to Determine Procedures Capability to Measure Remaining Ligament
P. Ashwin, EPRI, USA
ABSTRACT
The 1989 addenda of the ASME Boiler and Pressure Vessel Code, of Section XI, introduced new requirements for the performance demonstration of ultrasonic procedures, equipment and personnel. These requirements are described in Appendix VIII, "Performance Demonstration Requirements for Ultrasonic Examination Systems" and apply to piping, bolting and selected regions on the reactor pressure vessel. Staring in the early 1990's the United States Nuclear Utility industry's has organized a project aimed at implementing the requirements of ASME Section XI, Appendix VIII on a uniform basis. This project is commonly referred to as the PDI - Performance Demonstration Initiative and includes representatives from all US utilities as well as some foreign organizations that also utilize ASME. The EPRI NDE Center provides support to PDI and among the many roles EPRI provides to PDI is that of the Performance Demonstration Administrator (PDA). In this role EPRI organizes, oversees and maintains the records for all PSI qualifications. On September 22, 1999, that the US Nuclear Regulatory Commission (NRC) issued their final ruling on the implementation of ASME Section XI, Appendix VIII. Within the NRC ruling a schedule was included for Nuclear Plant licensees to comply with the requirements. Additionally the ruling included supplementary requirements to those specified by ASME. In anticipation of expanded the requirements PDI has proactively engaged in qualifying NDE procedures and personnel in accordance with a program that complied with the full requirements of the NRC ruling. Even so, both Appendix VIII and the supplementary requirements included within the NRC ruling omitted to specifically evaluate a procedures capability and reliability to resolve and accurately measure the ligament between a planar flaw and the surface of the component. This oversight may be because of the ligament is normally only considered important during ISI when a flaw has been detected and is evaluated in accordance with the ASME requirements. This paper describes how through an evaluation of results obtained during procedure qualifications carried out to the PDI program, assurance can be obtained that a qualified procedure has the capability to resolve and measure the remaining ligament of a flaw, if present in the RPV shell to shell examination volume.
Publication Source: 3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, November 14-16, 2001, Seville Spain. Publisher: Tecnatom s.a. - [Homepage]
