Model-Based Load Following Control for Helical-Coiled Supercritical Steam Generator of MHTGR

The modular high-temperature gas-cooled reactor (MHTGR) nuclear power plant incorporates a helical-coiled supercritical once-through steam generator (OTSG) to facilitate efficient heat transfer between the primary and secondary circuits. This complex nonlinear system is operated in load following mode to improve safety and economic performance. By comprehensively investigating the thermal hydraulic characteristics of the novel helical-coiled supercritical OTSG, this study develops a lumped parameter model with movable boundaries, which is formulated based on the fundamental conservation of mass, energy and momentum. The thermophysical properties specific to helium and water, as well as the empirical correlations for pressure drop and heat transfer of fluid flows are discussed. Furthermore, a tailored simultaneous approach is introduced to efficiently solve the model and facilitate model applications of dynamic simulation and optimization. The model accuracy is verified by conducting numerical simulations of the steady operating point and dynamic step response under full load conditions. The model-based load following control scheme is finally implemented to allow for rapid and smooth load changes in the supercritical OTSG.