This report presents the outcome of four fracture test series, addressing the ductile-to-brittle toughness behaviour of a nuclear reactor pressure vessel steel. Each test series corresponds to a specific test specimen geometry, tensile or three-point-bend, with a given degree of crack-tip constraint. A brief overview is given of available constraint-based fracture mechanics methodologies in the ductile-to-brittle transition range, including both engineering and local approach procedures. The obtained experimental data are analysed by means of the Master Curve standard ASTM E1921. Variability of the resulting reference temperature, T0, is successfully confirmed by a selection of constraint-based methodologies.JRC.DG.F.4-Safety of future nuclear reactor
