Nuclear operations with a high penetration of renewables: the case of France

Nuclear and intermittent renewables (wind and solar) are generally regarded as the only scalable technologies producing low-carbon electricity. However, the extent to which these technologies can co-exist in a reliable power system depends on whether nuclear units can adjust their operations to renewable output fluctuations. Using hourly data from the French power system, we find that nuclear units are operated quite flexibly, and that the foregone energy production due to "load following" actions (relative to the counterfactual of operating at full capacity during load following events) is currently limited. However, we find that an additional load following event is associated with a slightly higher likelihood of a unit failure. We also find that unit-level minimum output constraints are binding more frequently as system-wide renewable generation increases, especially so for units most exposed to solar generation. In 2024, hours during which available nuclear flexibility was exhausted are associated with non-positive hourly day-ahead prices.