Fuel handling control system for TAPP-3,4

The fuel handling system is required for loading of new fuel bundles in the reactor, to retrieve spent fuel bundles and move them to the storage bay during online condition. The Fuel Handling operations involve a large number of steps that are to be executed automatically in a specified and sequential manner. Each step includes checking of permissive and issuing the required commands. The commands effect the selection of process set points, accurate positioning of mechanical rams at pre-calibrated discrete positions, advancing/ retracting of hydraulic cylinders, opening/ closing of valves, energizing or de-energizing of relays and provide adequate indications or messages. There are large number of inputs and outputs in the control system and an extensive logic relates the output to input. The system provides ON-POWER refueling at any selected reactor coolant channel; the operation is completely synchronized between two sides fueling machines. A comprehensive status of system is presented on OIS. It also permits manual interventions to complete the execution of current step or continue sequence operation. The overall design of the control system is such as to ensure safety under various conditions of postulated failures. (author)