Complex sentence: Nuclear power plants in France and in Germany operate in load-following mode, i.e. they participate in the primary and secondary frequency control, and some units follow a variable load programme with one or two large power changes per day.
Split into simpler sentences: Nuclear power plants in France and in Germany operate in load-following mode and so participate in the primary and secondary frequency control. Some units follow a variable load programme with one or two large power changes per day.