Problems concerned with local erosion-corrosion of welded connections in the pipelines of a power unit at a nuclear power station

Results from a study aimed at analyzing the damageability and determining the mechanism due to which thinning occurs in the metal of welded connections in the feed water supply control assemblies used in power units of nuclear power stations equipped with RBMK-1000 reactors are presented together with the outcomes from calculation studies aimed at analyzing the effect of hydrodynamic characteristics on the kinetics characterizing the thinning of a welded joint and adjacent elements of a pipeline. Data from a calculation of the erosion-corrosion rate of welded connections in the divergent parts of assemblies controlling the supply of feed water in power units of nuclear power stations equipped with RBMK-1000 reactors are given.     

Water chemistry in power units at nuclear power stations equipped with RBMK-1000 reactors

The modified standards for the water chemistry at nuclear power stations equipped with RBMK-1000 reactors for the entire service life of power units are presented. Stages through which the information-analytical system Center for Providing Chemical Support to Nuclear Power Stations was established and developed and its current structure are described. An example of analyzing the water chemistry of coolant used in the multiple forced circulation loop and operational data obtained through the communication channels with the above-mentioned system is given, and the main objectives pursued by the Center for Providing Chemical Support to nuclear power stations equipped with RBMK reactors are described in the part of conducting their water chemistry and using means and systems for maintaining water chemistry parameters.     

Preventing inadmissible erosion-corrosion thinning from occurring in the diffuser segments of feedwater supply control systems of power units at nuclear power stations equipped with RBMK-1000 reactors

Results obtained from investigations of erosion-corrosion processes that occur during operation of the feedwater supply control systems used in power units of nuclear power stations equipped with RBMK-1000 reactors and the sensitivity of these processes to variations in the chemical composition of metal and in the flow path geometry are presented. It is found that local erosion-corrosion thinning of the walls in the diffuser segments of feedwater supply control systems occur mainly due to intense mass transfer in the near-wall region taken in combination with a low content of chromium. Hydrodynamic simulation was carried out, and it was shown based on its results that local erosion-corrosion thinning of the walls of pipeline segments downstream of the valves controlling the supply of feedwater to power units of nuclear power stations equipped with RBMK-1000 reactors can be prevented by subjecting them to appropriate modernization. It is found that the above mentioned diffuser parts can be made more resistant to erosion-corrosion wear by keeping the content of chromium in the main metal and weld joints at a level of no less than 0.25% and concurrently reducing the hydrodynamic effect in the zones of weld connections.     

The TOMAS software system for approximate analysis of emergency situations at nuclear power stations

The TOMAS software system for carrying out prompt analysis of different emergency situations in power units of nuclear power stations equipped with VVER-1000 and RBMK-1000 reactors is described. This software system can be used by experts of crisis centers for evaluating various situations, as well as for teaching students in higher schools specializing in the appropriate disciplines.     

Erosion-corrosion wear of the components of pipeline systems at nuclear power stations equipped with RBMK-1000 reactors

The erosion-corrosion wear of components of pipeline systems at nuclear power stations equipped with RBMK-1000 reactors is analyzed. It is shown that the mechanism of erosion-corrosion wear involves two parallel processes: thinning of pipeline walls in some sections and sedimentation of corrosion products in the other sections.     

Calculated and experimental substantiation of operating conditions under which adequate erosion resistance of valves used in power units at nuclear power stations is ensured

A procedure for revealing factors causing damage to metal and the dominating mechanism through which this damage occurs that was developed earlier is applied for substantiating the operating conditions of valves with D _nom = 800 mm installed in the multiple forced circulation loop of power units at nuclear power stations equipped with RBMK-1000 reactors under which their resistance to erosion is ensured. Operating conditions under which cavitation erosion may occur are established, and practical proposals on how to prevent damage to the metal of a throttle-control valve’s body are presented.     

An investigation of the effect of hydrodynamics of flow on erosion-corrosion resistance of components of a feedwater control assembly used in power units of nuclear power plants equipped with RBMK-1000 reactors

The results of computational hydrodynamic simulation of the flow of a working medium in the flow path of the feedwater control assembly used in power units of nuclear power plants (NPPs) equipped with the reactors of the RBMK-1000 type are presented It was established that the rate of control valve opening has an influence on the position of the areas of the intense local erosion-corrosion thinning of metal of the diffuser section downstream of the valve.     

Operative management of activities on monitoring the erosion-corrosion state of elements used in the condensate-feedwater path of a nuclear power station

New principles, methods, and measures used for preventing the occurrence of failures in elements, pipelines, and equipment of nuclear power stations and making them more resistant to erosion-corrosion wear during operation are outlined. Results obtained from comprehensive work on optimizing operational monitoring of the main metal of pipelines used in the condensate-feedwater path of power units at nuclear power stations equipped with VVER-1000 reactors are presented. The main directions and stages of work on elaborating normative documents and software systems for supporting the personnel of nuclear power stations are determined.     

Problems connected with polishing turbine condensate of power units at nuclear power stations equipped with VVER reactors and ways of improving its quality

Experience gained from operation of the turbine condensate polishing system used at existing nuclear power stations equipped with VVER reactors is analyzed. The optimal scheme of polishing turbine condensate intended for use at newly designed nuclear power stations is substantiated.     

Introduction of water chemistry conditions of the secondary coolant circuit with metering organic amines at nuclear power stations equipped with VVER-1000 reactors

Results from introduction of new water chemistry conditions involving metering of organic amines (morpholine and ethanolamine) at nuclear power stations equipped with VVER-1000 reactors are presented.     

Measurement instruments for automatically monitoring the water chemistry of reactor coolant at nuclear power stations equipped with VVER reactors. Selection of measurement instruments and experience gained from their operation at Russian and foreign NPSs

An analytical review is given of Russian and foreign measurement instruments employed in a system for automatically monitoring the water chemistry of the reactor coolant circuit and used in the development of projects of nuclear power stations equipped with VVER-1000 reactors and the nuclear station project AES 2006. The results of experience gained from the use of such measurement instruments at nuclear power stations operating in Russia and abroad are presented.     

The influence of the high-temperature coolant purification system at nuclear power stations equipped with VVER-1000 reactors on the formation of dose burdens

It is shown that the effectiveness of using high-temperature filters for purifying the coolant at nuclear power stations equipped with VVER-1000 reactors is mainly determined by the precipitation constant of activated corrosion products dispersed in the coolant.     

The capacities of a corrosion-fatigue monitoring system in managing the service life of steam generators operating at nuclear power stations equipped with a VVER-1000M reactor

We consider the possibilities of using a corrosion-fatigue monitoring system for operatively monitoring the corrosion of heat-transfer tubes in steam generators operating at nuclear power stations equipped with VVER reactors. It is proposed that this system be tested on a power unit built around a VVER-1000 reactor.     

Improving the transient stability of VVER-1000 reactor-based nuclear power plant units

Ensuring transient stability of nuclear power plant units in transient modes of their operation is one of the goals aimed at achieving enhanced safety and reliability of nuclear power plants. Field experience shows that for nuclear power plants equipped with VVER-1000 reactors, matters relating to transient stability in modes involving disconnection of the power unit main equipment, such as reactor coolant pumps, turbine-driven feedwater pumps, and turbine generator, are of most concern. Specialists of the Institute for Nuclear Power Plant Research perform comprehensive investigations of the technological processes aimed at working out measures for achieving better transient stability of nuclear power plant units. The article presents the results of joint activities carried out by specialists of the Institute for Nuclear Power Plant Research and the Novovoronezh nuclear power plant on enhancing the transient stability of Unit 5 at the Novovoronezh nuclear power plant.     

Thermal and chemical tests of the steam generator of unit 3 at the Kalinin nuclear power station

The results obtained from combined thermal and chemical tests of the steam generator of Unit 3 at the Kalinin nuclear power station are summarized. The obtained data are compared with the results of thermal and chemical tests carried out on steam generators at other nuclear power stations equipped with VVER-1000 reactors, and recommendations on selecting the steam-generator blowdown schedule are given.     

Basic Ways of Making Nuclear Power Stations Equipped with VVER Reactors More Efficient

Basic lines of work for achieving efficient generation of electric energy at nuclear power stations equipped with VVER reactors are determined. Comparative characteristics and technical-economic indicators of different power-generating units are given.     

The application of computational fluid dynamics for determining the hydraulic characteristics of pipelines at nuclear power stations

The application of computational fluid dynamics for calculating the hydraulic resistances of elements of the pipeline system for steam and gas discharges at a nuclear power station equipped with an RBMK-1000 reactor is demonstrated. It is shown that the interaction of local resistances along the flow path that are situated close to one another at distances insufficient for the flow to become stabilized causes the total hydraulic resistance coefficient of pipelines to be smaller as compared with the reference data.     

Specific features of corrosion damage to heat-transfer tubes of steam generators used at nuclear power stations equipped with VVER-1000 reactors

Specific features of corrosion damage occurring to the heat-transfer tubes of steam generators used at nuclear power stations equipped with VVER-1000 reactors are considered. The results obtained from metallographic studies of flaws found in samples cut out from steam-generator tubes are analyzed. Regularities with which flaws of steam-generator tubes are distributed over the tube bundle volume are discussed. Approaches for assessing the technical state and remaining service life of steam-generator tubes are presented.     

Conducting water chemistry of the secondary coolant circuit of VVER-based nuclear power plant units constructed without using copper containing alloys

The secondary coolant circuit water chemistry with metering amines began to be put in use in Russia in 2005, and all nuclear power plant units equipped with VVER-1000 reactors have been shifted to operate with this water chemistry for the past seven years. Owing to the use of water chemistry with metering amines, the amount of products from corrosion of structural materials entering into the volume of steam generators has been reduced, and the flow-accelerated corrosion rate of pipelines and equipment has been slowed down. The article presents data on conducting water chemistry in nuclear power plant units with VVER-1000 reactors for the secondary coolant system equipment made without using copper-containing alloys. Statistical data are presented on conducting ammonia-morpholine and ammonia-ethanolamine water chemistries in new-generation operating power units with VVER-1000 reactors with an increased level of pH. The values of cooling water leaks in turbine condensers the tube system of which is made of stainless steel or titanium alloy are given.     

Measures for ensuring reliable operation of the welded joint connecting the reactor coolant circuit’s header to the shell of a steam generator used at a VVER-1000 reactor-based nuclear power station

Problems that arose around the weld joint connecting the reactor coolant circuit’s header to the steam generator shell during operation of steam generators at nuclear power stations equipped with VVER-1000 reactors are considered. Works on studying the defects occurred in the header’s metal are described, and ways for preventing their development are determined.