The gearbox of nuclear-power-circulating water pump is installed in the three-circuit system of the nuclear power plant, and its role is to provide cooling water to condenser the steam turbine and auxiliary cooling water system. The gearbox is uniquely designed for the special working conditions of nuclear power plants and the extremely high reliability is required. Because of the large power transmission, it is featured by large volume, large mass, and complex structure. The gearbox adopts NGW structure and power split of herringbone planetary one-stage transmission.

Gearboxes of nuclear-power-circulating water pump are divided into HDBT and HDB series according to whether they can withstand the thrust generated by the water pump. At present, the designed transmission power is between 4700kW and 9000kW, and the transmission ratio range is 3.63:1～7.25:1.