Design, Simulation and Hardware Implementation of SMPS based High Current Rectifier Simulating Thermal Hydraulic Transients for Nuclear Research

A regulated high current DC power is supplied to nuclear fuel rod simulators of experimental research facilities to simulate various types of thermal hydraulic transients e.g. critical heat flux temperature pattern, thermal profile due to occurrence of loss of coolant accident, typical reactor setback and step back power patterns, decay heat curve immediately after reactor trip/shutdown, etc. expected in nuclear reactors. The heat source for generating these transients in nuclear reactor is fission reaction whereas in experimental research facilities it gets simulated by high response, high current controlled rectifiers powering nuclear fuel rod simulators. To attain desired temperature/power transients, conventional thyristor controlled rectifier configurations have been first choice, however, to feed low ripple precise DC power to fuel rod simulators, switched mode power supply based high current rectifiers have been designed using insulated gate bipolar transistor as control element for delivering controlled voltage, current or power output as required. The control system for rectifier is based on proportional integral derivative control utilizing pulse width modulation switching for inverter. The triggering circuit incorporating voltage/current/power is controlled through an error signal derived from difference of output DC parameter and reference value of respective control parameter. The closed loop feedback control system has been designed for switched mode power supply based rectifier for obtaining the desired selectable output DC voltage/current/power. The paper present design configuration, parametric design considerations, circuit simulation including pulse width modulation control topology of switched mode power supply based 500 Amp, 12 Volt rectifier feeding fuel rod simulator in experimental research facility simulating heat flux relevant to thermal hydraulic transients. Paper also analyzes feasibility of connecting 4 rectifier units each of 500 Amp, 12 Volt, in parallel to achieve 2000 Amp, 12 Volt.