Mitsubishi Heavy Industries, Ltd. (MHI) has recently developed new blades for nuclear turbines, in order to achieve higher efficiency and higher reliability. The three-dimensional aerodynamic design for 41-inch and 46-inch blades, their one piece structural design (integral shrouded blades: ISB), and the verification test results using a model steam turbine are described in this paper. The predicted efficiency and lower vibratory stress have been verified. On the basis of these 60Hz ISB, 50Hz ISB series are under development using "the law of similarity" without changing their thermodynamic performance and mechanical stress levels. Our 3D-designed reaction blades which are used for the high pressure and low pressure upstream stages, are also briefly mentioned.