IMPROVED ULTRASONIC INSPECTION METHOD FOR STAINLESS STEEL PIPING.

This document is a compendium of reports on nuclear power plant ultrasonic inspection development sponsored by the Electric Power Research Institute (EPRI) to improve the equipment available for detecting intergranular stress corrosion cracking (IGSCC) in nuclear plant stainless steel piping. An advanced transducer optimized for detection of IGSCC near circumferential pipe butt welds was developed and has gained wide acceptance in nuclear plant inspection throughout the world. This document, prepared for those concerned with such inspection, summarizes the history, development and evaluation testing of this ultrasonic inspection equipment. Transducer specifications for normally expected plant pipe sizes and a theoretical analysis that should aid in adapting the transducer to alternate applications are included. The document consists of a brief assessment of the IGSCC incidents followed by a summary of the overall EPRI ultrasonic transducer reliability improvement program and abstracts of contractor-prepared design and evaluation reports. The results of this work suggest that a substantial detection reliability increase can be expected from proper equipment design. This point is perhaps most dramatically illustrated by comparison testing on a flawed specimen removed from a foreign reactor. IGSCC not readily detected by conventional, high-frequency transducers was readily observed using the optimized unit. The comparison is of particular significance in that the field experience with the reactor in question has been responsible for substantial concern over ultrasonic transducer detection adequacy.