Chosen for this description of the selected Kraftwerk Union (KWU) pressurized water reactor units were Obrigheim [KWO, 345 MW(e)], Stade [KKS, 662 MW(e)], Borselle [KCB, 477 MW(e)], and Biblis [KWB-A, 1204 MW(e)]. The experience at these plants shows that with a special startup procedure and a proper chemical control of the primary heat transport system that influences general corrosion, selective types of corrosion, corrosion product activity transport and resulting contamination, and radiation-induced decomposition, KWU units have no basic problems.