Most nuclear power plants are designed for constant power output, so they still need some other thing (like batteries?).
Some are engineered for changing their output power quicker, but that means higher costs (lower usage), more complicated design and for short periods (<30 Minutes) some other energy source/sink while the power is adjusted.
Some are engineered for changing their output power quicker, but that means higher costs (lower usage), more complicated design and for short periods (<30 Minutes) some other energy source/sink while the power is adjusted.