Load-following operating mode at Nuclear Power Plants (NPPs) and incidence on Operation and Maintenance (O&M) costs : compatibility with wind power variability

In this report the capability of nuclear power plants to adapt to the demand is examined and several types of regulations needed for this are explained. From design there exists a power fluctuation margin and this is also an important characteristic of the design rules agreed upon by the European Utility Requirements (EUR rules) that should apply to the new builds in Europe. In the last chapter of this report the fluctuation margins as needed from wind farms are estimated from the experience gained in the wind turbines installations from Scandinavia and from the US. This allows an estimation of the compatibility of wind and nuclear generating units in a geographic area. A central point of this study was to consider to what extent the contribution of NPPs to grid regulation impairs their economical profitability due to possible higher O&M costs. In a liberalised electricity market price components are not communicated. Consequently no precise cost data were available and the study is based on personal communication and on aggregated data from an IAEA database collecting yearly average loss of production of NPPs worldwide. The study shows that the supplementary O&M costs due to load-following like operating mode can be majored by 2% of the theoretical available capacity of a power plant. These supplementary costs allow a power plant to be eligible for regulation which is associated with much higher electricity prices than if the unit is always producing base-load electricity. The conclusion may need to be reconsidered in case of a larger share of intermittent electricity generation. The decisive factor on this is the price at which reserve capacity is to be sold. This will be the adjustment factor and this last is more dependent on the share of the intermittent energy than of the nature of the backup plants.