Safety regulations regarding to water chemistry in Russia's NPPs

The basic directions of further improvement of the regulatory documents with respect to NPP water chemistry (WC) in Russia are considered. Necessity of optimizing of water chemistry regulation is caused by the requirement to ensure the integrity, reliability and availability of the main plant structures, systems and components that have a bearing on safety. For Russia's NPP are determined the limits of safe operation related to coolant quality. These limits for NPP with WWER-1000, WWER-440 and RBMK-1000 are regulated by WC standards and norms prepared by operating organization. The principles, which are used as the basis for regulation of WC quality indicators and main quality standards of coolant for NPPs are considered. Performance data are also provided on chemical indicators of water chemistry quality of operating NPP units. The issues of justification and application of most advanced water chemistries are dealt with. The report describes the current state of Russia's NPP operation safety regulation with regard to water chemistry. The paper describes a tendency of development of regulatory document requirements related to maintenance of NPP unit WC. The Russia Federal Rules and Regulations (FRRs) in the field of nuclear energy use establish a number of requirements to NPP water chemistry (WC) and to systems required for WC maintenance. The objective of these FRRs includes supporting the integrity of various barriers due to the potential corrosion of components, reducing occupational exposures and limiting releases of radioactivity and chemicals into the environment. The structure of documents specifying requirements to water chemistry at nuclear power plants is considered. It's shown, that the realization of the Program of power generation increasing at the nuclear power plants, adopted by Federal Atomic Energy Agency of Russia, including power up rating, life extension and the prospects of commissioning of the advanced power units with WWER-1200 demands the development of new guidelines on water chemistry. (author)