In September 2017, Mitsubishi Hitachi Power Systems Co., LTD. (MHPS) successfully tested a 74 inch (1880mm) final rotor blade (74 inch ISB) for rotational vibration.  The 74in ISB is the longest nuclear turbine blade in the world.
 
MHPS began development of 74in ISB blades in 2005 and has completed various validation tests.  The rotary vibration test is the last step in blade development. 
 
 
 
The 74in ISB achieved an exhaust area of 27 square meters per flow. 
 
 
 
The integrated gird blade (ISB) structure achieves excellent vibration resistance, large roots and grooves achieve stress reduction, and full 3D design achieves high efficiency. 
 
 
 
A key feature of the 74in ISB is its ISB architecture.  This makes use of a "twisted" structure that accommodates large differences in circumferential velocities between tip and root. 
 
 
 
During operation, centrifugal force increases as the turbine speed increases, and each twisted blade reforms, avoiding blade distortion and locking in contact with adjacent blades to form a complete row of blades. 
 
 
 
In this configuration, friction on the contact surfaces produces significant mechanical damping, which reduces vibration-induced stress and improves efficiency and reliability. 
 
 
 
The design of the blade root, profile and girth as a whole provides the best design for the low-pressure part of the turbine blade, providing excellent vibration resistance and excellent damping characteristics.