Load cycling capabilities of German Nuclear Power Plants

In the debate on whether lifetime extension of existing nuclear power plants facilitates or impedes the increased use of renewable energy sources in power generation, one claim being made is that nuclear power plants can only be operated to meet base-load demand at more or less constant power output. In fact, as early as the seventies nuclear power plants in Germany were designed to compensate load changes over a large range.

In the debate on whether lifetime extension of existing nuclear power plants facilitates or impedes the increased use of renewable energy sources in power generation, one claim being made is that nuclear power plants can only be operated to meet base-load demand at more or less constant power output.

In fact, as early as the seventies nuclear power plants in Germany were designed to compensate load changes over a large range. The corresponding design included the following specific features: a part-load diagram with constant coolant temperature (PWR: Pressurized Water Reactor) or recirculation control (BWR: Boiling Water Reactor) in the upper load range, a special control rod maneuvering concept (PWR), complex measuring equipment, special instrumentation and control systems for regulating and limiting power and power density, and consideration of a large number of load cycles for the fatigue design of components.

Operating experience gained to date clearly confirms that the nuclear power plants designed for this cycling duty are well suited to compensating load changes such as are to be expected to result from wind fluctuations in the event of a further significant increase in wind power plant generating capacity. Furthermore, a review of operating experience and current know-how also shows that there are no safety-related concerns that preclude routine load cycling operation of existing NPPs. Consequently, this implies that the continued operation of NPPs can secure the increased use of renewable energy sources in power generation.