[en] In assessing the safety of a liquid metal fast breeder reactor (LMFBR), a major concern is the behavior of concrete structures subjected to high temperatures. The potential of concrete cracking is an important parameter which could significantly influence the safety assessment of thermally attacked concrete. A new modified J-integral approach for the blunt crack model has been derived to provide a general procedure to accurately predict the direction of crack growth. This formulation has been incorporated into the coupled heat transfer-stress analysis finite element code TEMP-STRESS. A description of the formulation is presented in this paper. Results for the problems of a Mode I and mixed mode crack in a plate using regular and slanted meshes subjected to uniaxial and shear loading are presented