Base Load vs Peak Load Power Plants
Nuclear power plants may take many hours, if not days, to startup or to change their power output. Modern power plants can and do operate as load following power plants and alter their output to meet varying demands. But base load operation is the most economical and technically simple mode of operation. It is primarily due to the fact, they require a long period of time to heat up the nuclear steam supply system and the turbine-generator to operating temperature. From this point of view power plant generally are divided into two basic categories:
Base Load Power Plant
In general, nuclear power plants (NPPs) have been considered as base load sources of electricity as they rely on a technology with low variable costs and high fixed costs. This is the most economical and technically simple mode of operation. In this mode, power changes are limited to frequency regulation for grid stability purposes and shutdowns for safety purposes. Different plants and technologies may have differing capacities to power changes on demand. Base load power plants are generally run at close to maximum output (100% of rated power) continuously (apart from maintenance, refueling outages). During refueling, every 12 to 18 months, some of the fuel – usually one third or one quarter of the core – is replaced by a fresh fuel assemblies. After refueling the reactor is usually started up and operated again at nominal power.
Although most of nuclear power plants were designed as base load power plants, today, 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. It is due to the share of nuclear power in the national electricity mix of some countries has become large, and due to the significant increase renewable energy sources.