Water chemistry during hot functional testing of WWER reactors

In contrast to the major sets of PWR chemistry guidelines, which follow similar water chemistry' control principles, the position with WWER guidelines is that there is no single document that describes the rationales for controlling individual chemical species and the limit values recommended. There are standards produced by design and research organizations, but no document has been prepared by a wider chemistry community that includes plant chemists from different WWER operating countries, which addresses operational chemistry optimization issues and is available to WWER operators in all countries. Thus sources of information concerning the water chemistry during HFT of WWERs are sparse and a systematization of the available information on the process is needed. In the present report, the main principles of the controlled primary water chemistry applied during the hot functional tests are reviewed and importance of the water chemistry, technological and other relevant parameters is emphasized regarding the quality of the passive layer formed on the primary system surfaces. The first perational experience obtained in recently commissioned WWER units is presented with respect to the corrosion products in the coolant and surface activities. Effect of the initial passivation performed during hot functional tests and the primary water chemistry on corrosion products radioactivity level and radiation situation is discussed.