An application of acoustic emission techniques to the study of tensile deformation behaviors in neutron irradiated zirconium and other nuclear materials

The effects of neutron irradiation upon the acoustic emission (AE) characteristics were investigated in neutron irradiated zirconium and reactor pressure vessel steels, A533B and A542. Results showed that a great number of burst type AE signals were detected in un-irradiated zirconium specimen, in which AE activity steeply increased near the yield point. The dependence of AE activity on the strain rate was remarkable in the early stage of the plastic deformation. Whereas in the irradiated zirconium specimens, results showed that the AE activity extremely decreased due to the neutron irradiation up to dose of 4 x 1019 n/cm2 (E > 1 MeV). This indicates that the neutron irradiation of this amount has the effect to suppress the formation of the deformation twinning during tensile testing at room temperature. According to the recovery behaviors in both the tensile properties and the AE characteristics due to the post-irradiation-annealing, the major recovery stage was clearly observed at the same temperature; 5000C. At this temperature, therefore, irradiation-induced defects almost can be annealed out. On the other hand, the results obtained in reactor pressure vessel steels showed that the dependence of the AE activity upon neutron irradiation in A533B steel specimens was very different from that of A542 steel specimens. Namely, the AE parameters, E/N and V/N increased monotonously with increase of neutron fluence in A542 steel specimens, while in A533B steel specimens, they had the maximum at the neutron fluence of 6.3 x 1018 n/cm2 (F > 1 MeV) and decreased with increase of the neutron fluence, where E/N and V/N are the averaged energy and amplitude in the amplitude distribution, respectively. (author)