Bimetallic welds (BMWs) play a critical and indispensable role in the primary heat transport piping system of nuclear reactors. The primary heat transport system itself is the critical part of a nuclear reactor. Any failure of this system can lead to very grave consequences, not only speaking of huge monetary losses resulting from non-utilization of the reactor setup, but also immensely valuable and irreparable loss of human life. This paper describes the experimental efforts towards estimation of Gurson material parameters of base metal and weld metal regions of a BMW so as to use the micromechanical modelling approach for addressing the structural integrity issues in BMWs. © IMechE 2008.