AbstractThe present study concerns the 3-D geometry evaluations of the tritium breeding ration of the breeder-in-tube helium-cooled ceramic blanket performed at CEA and ENEA in the framework of the recently released DEMONET specifications. For the calculations the nuclear data have all been derived by the European Fusion File (EFF-1), but different Monte Carlo codes, and different design variants and geometrical models have been used. A benchmark calculation has been defined in order to better analyse the results; such an exercise has shown that TBR differences of a few percent could be due to the calculation methods. The determined global TBR ranges from 1.06 in the CEA results to 1.15 in the ENEA results, the expected difference being mainly due to the greater neutron coverage of the ENEA variant of the design. Heat deposition density and He production in beryllium are also given.