ULTRASONIC INSPECTION OF A SECTION OF THE NS SAVANNAH PRIMARY PIPING SYSTEM

A section of NS Savannah primary pipe and part of a primary system gate valve were examined ultrasonically to determine whether a fluctuating flow of low- temperature makeup water entering through a nozzle in the valve hsnd damaged the components during service. Examination was prompted by failure of a Vallecitos Boiling Water Reactor (VBWR) recirculating pipe in which makeup water was introduced under conditions similar to those in the Savannah. The ultrasonic equipment was calibrated on spare components. The calibration standards, 11-mil- deep chisel marks in the pipe and 25-mil-deep marks in the valve, were more stringent than those used to calibrate equipment for inspection of components at the time of manufacture. The inspections of components conducted aboard ship are therefore thought to be more exacting than those performed on the original equipment. Ultrasonic inspections of the failed VBWR pipe completely defined the areas of defective material that led to the failure. The VBWR results, together with experience gained by Babcock & Wilcox, indicate that the inspections of Savannah's components were both applicable andd definitive. Since no indications of discontinuities were found in the valve or the pipe, both components are considered to be sound and unaffected by service. (auth