Flare test evaluation and stress prediction of PWRs steam generator tubes

Alloy 600 and 690 steam generator tubes fabricated in Korea were evaluated by flare tests according to ASTM standards. The stress acting in the tube elements during the tests was predicted. All the tubes, including alloys 600 and 690, satisfied the requirement of a 30 percent or 35 percent O.D expansion. Flow curves obtained from the flare test were found to be higher in alloy 690 tubes than in the alloy 600 ones. The difference between alloy 600 and 690 tubes increased gradually with flaring percentage (F.P,percentage). An effective stress corresponding to mean yield stress was introduced and calculated. It showed that the prediction values were in good agreement with the measured ones for all the 690 and 600 alloy tubes. It became possible to predict the amount of acting stresses within tubes during expansion process. (author)