Development of new scoop tube positioner for fluid drive of recirculation control system in BWR plant

As one of the measures for improving the rate of operation of nuclear power stations, the improvement and development of the controller for the fluid coupling used for the recirculation system of a BWR power station were carried out. Heretofore, the imported controllers have been used, but the development was made, aiming at the improvements of reliability, performance and maintenance. In this paper, the outline of the developed controller and its features, and the test results are reported. The power of BWR plants is controlled by the reactivity with control rods and adjusting the recirculating flow rate. The recirculating flow rate control system comprises a driving motor, a fluid coupling and a variable frequency generator, and the power source frequency for a motor driving a recirculating pump is regulated, and the number of revolution of the pump is changed. The oil quantity in a fluid coupling is adjusted with a scoop tube, and the controller adjusts the position of this scoop tube. The developed controller for a fluid coupling, the target of the development, the construction of the controller, the specifications and the features, and the performance test are described. (J.P.N.)