Investigating Load Follow Operation for a Typical Nuclear Power Plant using Multi-Physics Analysis

Most Nuclear Power Plants (NPPs) are designed for baseload operation, maintaining a constant power output of 100% except for planned maintenance and refueling. In countries like France, Slovakia, and Korea, where nuclear energy is the primary source of electricity, integrating nuclear power with intermittent renewable sources is essential for stable electricity generation. This integration requires NPPs to perform daily power adjustments as a response to grid requirements, known as Load Follow Operation (LFO). LFO reflects the strong interconnectedness between thermal-hydraulics and neutron-physics, accompanied by the three-dimensional movement of Control Element Assemblies (CEA), which introduces safety challenges due to variations in power distribution within the core. To address these issues, a Multi-Physics approach is adopted using the two-way implicit coupling between RELAP5/SCDAPSIM/MOD3.4 and 3DKIN. In this analysis, power control strategy for LFO consisting of both CEA movement altogether with soluble boron concentration adjustments has proven to be successful in keeping important safety parameters, such as axial offset (AO) within its safety margins of ± 30 % and 3D peaking factor below 2.43. The results demonstrates the safe and reliable daily LFO with a sliding average temperature control mode.