Nuclear Power Plant Load Following: Problem Definition and Application

The general opinion about nuclear power plants is that they are not flexible generating units characterized with low or no load following capabilities. Therefore they should be used as baseline units only. Given the economic perspective of this issue, it is clear that the reasons for use of nuclear power plants as baseline units are purely economic. They have the lowest variable costs compared with the other thermal generating units. It is of crucial importance to note that the flexibility and reliability of the power system directly depends on the flexibility and reliability of the generating units. Therefore it is very important to have flexible units which will be available to follow load in any time of the day. This is especially important in power systems where nuclear power has great portion in the power production. In such case the conventional units which are used for load following may not be enough to secure reliable operation of the power system. The objective of this paper is to investigate the parameters from nuclear safety, which may be affected by load following manoeuvres. For this purpose an existing probabilistic safety assessment model of nuclear power plant from generation III+ is used. The first step is identification of components and systems from the nuclear power plant which are affected from the load following and subsequent adaptation of the existing probabilistic model. The second step is testing of the model for any changes in core damage frequency. The expected results indicate no significant decrease in core damage frequency due to the extensive use of load following.