Shiny Choudhury
University of California San Diego
Seminar Information
Engineering Building Unit 2 (EBU2)
Room 479
Seminar Recording Available: Please contact seminar coordinator, Jake Blair at (j1blair@ucsd.edu)
Increasing renewable energy in the electric grid puts tremendous pressure on thermal generators, including nuclear power plants, to ramp their power. Nuclear reactors can operate somewhat flexibly and do so in markets where it is allowed, like in France. But stringent regulations and nuclear cost structure have resulted in their primarily baseload operation. Most energy system models represent nuclear as inflexible thermal units, but that assumption needs revision. Nuclear plants are flexible for a large fraction of their fuel cycle. However, they encounter challenges towards the end due to Xenon-poisoning, which induces escalating minimum power levels and increasing downtimes. Xenon, a powerful neutron absorber, requires careful management to maintain power maneuverability. Additional flexibility can be derived by operating individual reactors as a fleet. This study introduces a novel physics-informed formalism for nuclear fleet dispatch by tracking reactivity levels and imposing Xenon-poisoning induced constraints. The model is applied to compare the dispatchability of large reactor fleets (GW class) with small modular reactor (SMR) fleets operating at varying shares of variable renewable energy (VRE).
As VRE shares increase, we find that SMR fleets are better suited to offer dispatchable power. SMR designs are intrinsically more flexible, and their smaller units allow for more flexible fleet operations. SMR fleet also results in higher reliability by significantly reducing unmet load across all scenarios. Xenon-poisoning induced inflexibilities become apparent more quickly in the GW fleet. In contrast, SMR reactors, with their longer refueling timelines, experience these inflexibilities for a negligible fraction of their dispatch. Startup/shutdown costs and minimum power levels are the most sensitive parameters for dispatchability. The study highlights mitigation of the so-called `solar paradox,' which suggests that curtailment saturates when solar penetration exceeds a certain threshold. We demonstrate that SMR fleets with lower startup/shutdown costs reduce curtailment across all solar penetration levels. These dispatch and reliability benefits come at the cost of reduced fleet capacity factor, but SMRs could compensate for this as they fulfill considerably more reserve. This study demonstrates SMR fleets' technical capability to support highly decarbonized grids, and given the right market conditions, this potential can be fully harnessed.
Shiny Choudhury is a PhD student in the MAE Department at UC San Diego, where she is co-advised by Professor George Tynan and Professor Michael Davidson. Her research focuses on understanding the potential of advanced fission and fusion reactors in highly decarbonized grids. She hopes to inform the nuclear industry on design choices for their reactors and policymakers on correctly valuing the capabilities of these technologies. Shiny was a part of the winning team for the 2023 USAEE Case Competition and runner-up for the 2023 NREL Geothermal Collegiate. She has presented her research at many prestigious venues, most recently in Vienna, Austria, at the first SMR Conference at the International Atomic Energy Agency (IAEA). In her Master's at UC Irvine, she was a part of the California Energy Commission's study on hydrogen-blended natural gas combustion for stationary devices. She also developed a deep learning load forecast model for UC Irvine central campus.