The 10CrMoNbV Manet II cast has been selected as the reference ferritic-martensitic steel in the framework of the European Fusion Technology Programme. Charpy impact tests have been carried out in the ductile to brittle transition temperature range of this steel, such that a dynamic quasi-equilibrium has been achieved in the process zones of investigated specimens before brittle failure. This type of testing enables the evaluation of dynamic Weibull moduli and, consequently, dynamic Weibull master curves. Thus, Weibull parameters have been calculated for normal size and subsize Charpy impact specimens. The evaluated, geometry dependent dynamic Weibull master curves facilitate computation of the failure probability densities of the investigated steels as functions of scaled critical crack sizes or scaled initial defect sizes. MST/4585.