Impact of load follow operation on the chemistry of the primary and secondary circuit of a pressurized water reactor

Germany decided to abandon nuclear energy and to switch to renewables. According to the renewable energy act, renewable energies have priority to be fed to the grid. The support of wind and solar energy demands more and more load follow operation of the remaining nuclear power plants to stabilise the grid. This report summarises first experience with load follow operation in 2 pressurised water reactors (KKP 2 and GKN I) with regard to chemistry and radiology. The most important mechanisms of dose rate built-up on the primary side are described. Goal of the primary side chemistry is to avoid or at least to delay the dose rate built-up as far as achievable. The secondary circuit is operated according the H-AVT chemistry (high-pH, treatment with volatile chemicals) to minimise the release of metals from carbon- and low alloy steels. The impact of load follow operation on the corrosion protection of the carbon- and low alloy steels on the secondary side due to changes of physico-chemical conditions is discussed. (orig.)