Fully-coupled transient simulation for RCS and SPCS of an integral reactor plant

Design features of SMART such as a built-in once-through steam generator (OTSG) and a close interaction between the feedwater flow rate and steam pressure controls leads to the necessity of fully-coupled transient analysis tools of the reactor coolant system (RCS) and the steam and power conversion system (SPCS) for the purpose of a plant control system development. A fully-coupled transient simulation tool, MMS/SMART, was developed to test the capability of the plant control system for the normal load-following event and the anticipated abnormal events. The MMS/SMART was composed of several interacting MMS modules with numerical data, each of which represented a component of the SMART plant and a control logic. The RCS and the SPCS with their control logics were modeled using default modules such as a pipe, pump and tank. The developed MMS/SMART was validated by using the scaled-down experimental data and the analysis result from the TASS/SMR code. A simulation result for the 100-50-100% load-following operation with a 25%/min rate shows that the feedwater flow rate and the steam pressure are controlled well as expected, except for small-amplitudes of steam pressure fluctuation at the lower power operating region. The loss of turbine load event was also simulated and the result shows that the plant can be operated stably with the steam bypass control system.