ULTRASONIC INSPECTIONS OF FUEL ALIGNMENT PINS

As a remedy to the practical problem of defects in fuel alignment pins made of Inconel X750, an inspection technique has been developed whic h fully meets the requirements of detecting defects. The newly used fu el alignment pins made of austenite are easy to test and therefore sat isfy the necessity of further inspections. For the fuel alignment pins of the upper core structure a safe and fast inspection technique was made available. The inspection sensitivity is high and it is possible to give quantitative directions concerning defect orientation and dept h. After the required inspections had been concluded in 1989, a total of 18 inspections were carried out in various national and internation al nuclear power plants in the following years. During this time more than 6000 fuel alignment pines were examined. For the fuel alignment p ins the inspection technique provided could increase the understanding of the defect process. This technique contributed to the development of an adaptive and economical repair strategy.