Thermal storage system requirements and ramp-up considerations to maintain electrical grid stability in the event of tokamak disruption*

Fusion reactors will need to be connected to the electrical grid, which is a delicate system. As observed in Texas in 2021, grid stability can be threatened by extreme weather conditions and aging infrastructure.¹ Additionally, incorporation of renewables has already posed some challenges to grid stability due to unpredictable power outputs.² Modeling of transient events, which can in part be caused by sudden connection or disconnection, is particularly useful for probing grid stability.

Grid stability can inform the design stage of fusion reactors to ensure reliability and adherence to operational standards. Fusion poses unique challenges to grid stability due to its behavior as a significant load during startup. We use a multi-bus model to probe grid stability in the event of tokamak disruption and subsequent ramp-up. Each bus is a synchronous machine with an exciter and turbine-governor for stability controls. We use DEMO specifications to inform the model tokamak initial values of ramp-rates and startup power.^3,4 The tokamak was modeled to include a steam generation system connected to the synchronous machine. A molten salt storage system was included and total storage was varied to determine the minimum possible thermal storage capacity necessary to enable stability recovery in the event of disruption.⁵ Ramp rates on startup were also varied to evaluate impact and inform future reactor designs.

1 Lin, Ning et al. 2021

2 Smith, O. et al. 2022

3 Minucci, S. et al. 2020

4 Takeda et al. 2015

5 Schwartz et al. 2023