Validation of Constraint Based Methodology in Structural Integrity – VOCALIST: Experimental Programme

The aim of VOCALIST (Validation of Constraint-Based Assessment Methodology in Structural Integrity) is to develop and validate innovative procedures for assessing the level of, and possible changes to, constraint-related safety margins in ageing pressure boundary components [1]. An iterative process of experiment and analysis will address this overall objective. The experimental investigations within VOCALIST are performed on three different materials representing the as new state of materials used for components of nuclear power plants as well as a state representing an in service degraded state of RPV materials. Within the experimental programme fracture mechanics specimens with different constraint situations are tested in order to quantify the influence of the constraint on the specimens failure behaviour as a basis for the advanced components integrity assessment. The investigations are performed on small laboratory specimens as well as on biaxially loaded cruciform specimens and large piping components. Within this contribution the experimental programme of VOCALIST is introduced. The investigated materials are characterized in terms of their mechanical properties. Special consideration is given to results of fracture mechanics specimens highlighting the constraint effect via the shallow crack effect and its contribution to a shift of the master curve.