In a nuclear power plant, a single metallic component may be fabricated from different materials. For example, RPV components are made from ferritic steel, whereas some of the connecting pipelines are fabricated from austenitic stainless steel. As a consequence different components often need to be connected by so-called dissimilar metal welds (DMW).Despite extensive research in Euratom Framework projects such as BIMET and ADIMEW, further work is needed to quantify the structural performance of ageing DMWs.The first purpose of this project shall be to gather relevant information from field experience: typical locations of DMWs in Western as well as Eastern LWRs will be identified and their characteristics considered, as well as applicable assessment methods. Micro-mechanical modelling of ductile failure processes will be used as an innovative technique to augment current numerical methods for structural integrity assessment of DMWs. The modelling will take account of ageing related phenomena and realistic stress distributions in the weld area and be supported by a comprehensive material test program. A procedure for measuring fracture toughness in DMWs will be developed. The work will also include an assessment of Leak Before Break (LBB) behaviour.Overall the project will serve to promote common understanding of structural integrity assessment of DMWs in existing and future NPPs of EU member states. This will be the technical basis towards the development of harmonised European codes and standards for multi-metal components, which is currently not available.