Irradiation Response of the New IAEA Correlation Monitor Material JRQ Measured by Fracture Mechanical Properties

The irradiation response of the extensively evaluated Japanese pressure vessel plate material, JRQ, offered by IAEA as a correlation monitor material for international use, has been measured. Charpy V-notch and precracked specimens of 3-point-bend (3-PB) geometry for J-Δa curve measurement have been irradiated in the surveillance position of the Loviisa NPP at a flux of 2 × 10¹¹ neutrons/(cm² ∙ s) into a fluence of 2.1 × 10¹⁹ neutrons/cm², E > 1 MeV, at a temperature of 265°C.

The irradiation-induced transition temperature shifts measured with Charpy V-notch and fracture mechanics specimens are correlated by using indexed temperature values.

The shapes of the brittle fracture transition curves, measured with 3-PB specimen geometry for irradiated and reference material states, are compared using a statistical brittle fracture model. Both the shape of the average curve and the scatter of the measured points are considered.

The effect of irradiation on the ductile fracture behavior based on the measured fracture resistance curves (J-Δa) is presented. The 3-PB specimen geometry is used also for measuring the fracture resistance curves.