Crevice flushing procedures and experience: Point Beach Nuclear Plant, Units 1 and 2

In August 1979, large numbers of crevice defects were detected during a shutdown of Unit 1 and subsequent eddy current inspection. During a refueling shutdown in October to November 1979, additional defects were detected and sample tubes were pulled from the hot leg side for analysis. The analyses indicated general intergranular attack of the tube material to within 1/2 inch of the top of the tubesheet. Analysis of tube deposits indicated highly alkaline conditions within the tubesheet crevice. In an attempt to minimize further progression of the crevice attack, a crevice flushing procedure was developed by Wisconsin Electric for use at Point Beach. This procedure involves the creation of steam bubbles in the crevice at low temperatures to remove soluble material from the crevices