Load-following capability of German nuclear power plants (NPPs)

Amid the discussion whether the Lifetime Extension of the existing NPPs supports or constrains the increasing use of renewable energy sources in electricity generation, it is partially alleged that the NPPs as typical base load power plants could only be operated at a more or less constant power output. Actually, NPPs in Germany have been designed in the seventies to compensate large load changes. The design included the following specific characteristics: a partial load diagram with a constant coolant temperature (PWR) or recirculation control (BWR) in the upper partial load range; a special control rod assembly drive concept (PWR), intricate measurement devices; special I and C for controlling and limitation of power and power density as well as consideration of a large number of load changes in the design process against fatigue of components. The operational experience available today unambiguously confirms that the design of the existing NPPs is well suited for compensating of load changes due to wind fluctuations in case of further significant expansion of wind power. Furthermore, evaluation of the operational experience using up to date knowledge demonstrates that there are no technical safety aspects standing against routine load-following operation of the existing NPPs. Insofar, continued operation of the NPPs can (if needed) support expansion of the renewable energy sources in electricity generation. (orig.)