Small modular reactors (SMRs) offer a promising avenue for revolutionizing the traditional role of nuclear plants, transforming them from serving as baseload to flexible contributors in both power generation and ancillary services. This paper develops a steady-state model for SMRs, with a focus on incorporating constraints related to â\euro˜xenon poisoningâ\euro™. These constraints are essential to prevent issues during nuclear plant ramp-up following a ramp-down event. These â\euro˜xenon poisoningâ\euro™ constraints have been integrated into a multi-timescale power system operation framework, which also encompasses the formu- lation of inter-temporal coupling constraints. A comprehensive investigation is undertaken to evaluate the impact of integrating SMRs into a power grid with a high penetration of renewable en- ergy, specifically the NREL-118 bus system. A capacity expansion planning analysis is first conducted over multiple years to identify the optimal locations and sizes for deploying SMRs across the network. Additionally, weâ\euro™ve developed various reserve rules that adapt to the ramping status of the SMRs and include different â\euro˜hold-timeâ\euro™ for â\euro˜xenon poisoningâ\euro™ mitigation. Results obtained from a day-long simulation illustrate that the implementation of minimal â\euro˜xenon poisoningâ\euro™ hold-time, coupled with a steady- state guided reserve provision rule, yields the highest revenue â\euro“ approximately 4.14% more than the base case.Â

This study explores how sector coupling via In- tegrated energy systems (IES) can improve the operational flexibility of the power grid, while hydrogen is gaining traction as a versatile energy carrier. Specifically, we have evaluated the operational benefits of integrating two electrolytic processes for hydrogen generation, namely low-temperature electrolysis (LTE) and high-temperature steam electrolysis (HTSE), into a nuclear- renewable IES using a 3-cycle power system operation frame- work. Detailed steady-state models of the electrolytic hydrogen generating facilities are constructed, with the HTSE process represented using standard transient models to account for the steam-bypass scheme from the nuclear reactor. These models are then integrated into a renewable-intensive power network model (specifically, the NREL 118-bus system). To simulate the operation of the integrated system across multiple timescales, a multi-timescale scheduling and dispatch tool is employed. Results indicate that while both electrolytic processes contribute to signif- icant flexibility enhancement and renewable energy curtailment reduction, the LTE process offers more operational benefits than the HTSE process across multiple timescales.