Fracture mechanics evaluation of reactor coolant pump failure at Crystal River-3

On January 1, 1986, one of the reactor coolant pumps at Florida Power Corporation's Crystal River Unit-3 failed due to a broken pump shaft. An exhaustive failure analysis was launched to investigate the root cause of the shaft failure. During the disassembly of this pump, some shallow axial cracks were found in the thermal barrier region on both the cover bore and the shaft. Therefore, the investigation was extended to include the thermal fatigue cracks on the shaft as well as the cover. In parallel, field crack measurements were made using a dye-penetrant method and eddy current tests on the cover thermal barrier region, and extensive destructive examination of the shaft. Also, some of the cut shaft material was used for fatigue crack growth testing to determine actual crack growth rate. This paper compares the results of fracture mechanics analysis with the field measured crack depths. The analytical models developed here well predict the observed crack patterns and crack depths. (orig.)