Fatigue evaluation by positron annihilation lineshape analysis

Aiming at non-destructive evaluation of fatigue stored in a stainless steel (SUS316) pipe of the primary cooling water in pressurized water reactors (PWR) before generation of cracks, we tried to apply positron annihilation lineshape analysis to fatigue evaluation. 68Ge was used as a positron source and decrement of energy spread of the annihilation gamma ray peak was observed. As a result, it was found that the energy decrement parameter increased with stored stress for the case in which stress amplitude was higher than 200 MPa. Thereby, the possibility to evaluate the degree of fatigue in stainless steel by the positron annihilation lineshape analysis above some stress amplitude was shown. (author)