Load-following with nuclear power plants

T raditionally, nuclear power plants (NPPs) have been considered as baseload sources of electricity as they rely on a technology with high fixed costs and low variable costs. In the beginning of the nuclear era, the share of nuclear power in the overall energy mix was usually small, and adjustments of electric load in response to variations in electricity demand could be left to technologies with different economic and technological characteristics, most notably low fixed cost and high variable cost gas plants. However, this simple state of affairs no longer applies in all countries. The share of nuclear power in the national electricity mix of some countries has become so large that the utilities have had to implement or to improve the manoeuvrability capabilities of their NPPs in order to be able to adapt electricity supply to daily, seasonal or other variations in power demand. This is the case in France where more than 75% of electricity is generated by NPPs, and where some nuclear reactors operate in load-following mode (see Figure 1).