[en] After fission or fusion reactor shutdown the activated structure emits decay photons. For maintenance operations the radiation dose map must be established in the reactor building. Several calculation schemes have been developed to calculate the shutdown dose rate. These schemes are widely developed in fusion application and more precisely for the ITER tokamak. This paper presents the rigorous two steps (R2S) methodology implemented at CEA (first step: neutron transport + depletion calculation, second step: decay gamma transport). This methodology is based on the TRIPOLI-4 Monte Carlo code for particle transport and the inventory code MENDEL for depletion calculation. This paper presents a numerical benchmark: the ITER shutdown dose rate benchmark (ITER SDR benchmark) in which the steel and water region represent a typical experimental device of ITER cooled by water. Results are in good agreement with the other participant (UNED). Improvement of the R2S scheme are planned: to accelerate the calculation (MENDEL parallelization), to propagate the statistical error of the first step and to handle different materials in a mesh-cell