VOCALIST (Validation of Constraint Based Methodology in Structural Integrity) is a shared cost action project co-financed by the European Commission under the Fifth Framework of the European Atomic Energy Community (EURATOM). The motivation for VOCALIST is based on the observation that the pattern of crack-tip stresses and strains causing plastic flow and fracture in components is different to that in test specimens. This gives rise to the so-called constraint effect. Crack-tip constraint in components is generally lower than in test specimens. Effective toughness is correspondingly higher. The fracture toughness measured on test specimens is thus likely to underestimate that exhibited by cracks in components. The purpose of VOCALIST is to develop validated models of the constraint effect, and associated best practice advice, with the objective of achieving (i) an improved defect assessment methodology for predicting safety margins; (ii) improved lifetime management arguments. The work is intended to be of benefit to both plant operators and their regulators. The project started in October 2000 and all experimental and analytical work was completed by February 2004. The final report and an updated Best Practice Handbook are currently being prepared. This paper provides an overview of VOCALIST, describes its various Work Packages, and provides an up-to-date summary of results.

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