Papers by Keyword: Steam Generator

Abstract: Extending the lifetime of energy facilities is extremely important today. This is especially true of nuclear power plants, the closure (or modernization) of which poses enormous financial and environmental problems. High-quality repair of reactors can significantly extend their service life. One of the critical parts is heat exchangers, the tubes of which quite often fail. Sealing, as a type of repair of heat exchanger tubes by the plugs, is promising provided that the joint quality is high. Practical experience in the use of welding to solve this problem has shown the need to search technological solutions associated with increasing the depth of penetration and reducing the area of thermal effect. The aim of the work was to develop a highly efficient technology for repair and extension of service life of heat exchangers of nuclear power plants based on the results of studying the technological features of laser welding of joints of dissimilar austenitic steels AISI 321 and AISI 316Ti in the vertical spatial position. Based on the results of the analysis of mechanical test data, visual and radiographic control, impermeability tests and metallographic studies of welded joints, the appropriate modes of laser welding of plugs have been determined. The principal causes of defects during laser welding of annular welded joints of dissimilar stainless steels are determined and techniques for their elimination and prevention of their formation are proposed. Based on the results of the research, technological recommendations for laser welding of plugs in the heat exchange tube of the collector are formulated, which significantly improves the technology of repair of steam generators of nuclear power plants and extends the service life of reactors.

Abstract: By the non-destructive testing of a dissimilar weld joint (DWJ) of cold collector DN 1100 (CC) on a steam generator, indications were found on inner-side cold collector’s surface at the root position of the examined weld. All the identified indications were very similar in shape and form, therefore, it was decided to cut out a part of the damaged site from this type of DWJ DN 1100 and get the obtained ring (real piece of material) for complex metallographic analysis. This paper briefly describes the results and recommendations found for the future reference during the next long‑term operation induced ageing and degradation of critical steam generator parts in NPP Bohunice Unit 4. There are summarized the results obtained from evaluation of original DWJ material.

Abstract: Indications were detected on dissimilar metal welds (DMW) of steam generators (SG) after 20 years of operation during NDT inspections. Indications started slowly growth every year. DMW on SGs had to be repaired. Paper describes experimental analysis and degradation mechanism of SG weld joints failures.

Abstract: The main reason of appearance and growth of corrosion damages of the nuclear steam generator heat exchanger tubes is the process of stress-corrosion cracking of metal under the influence of residual tensile stress.The article contain the suggestion of the method that combines the operation of heat processing and straightening of pipes by stretching. The approbation of the method was carried out in the laboratory conditions. There is described the construction and working principle of a trial installation. During the experiments different parameters of electrocontact heating with stretching were tested. Approbation showed that the proposed method can reduce the level of tensile residual stresses or get compressive residual stresses in the wall of the tubes, which increases their resistance to corrosion.Keywords:Steam generator, heat exchange tubes, stress corrosion cracking, intercrystalline corrosion, residual stresses

Abstract: Medical facilities and similar types of medical centres providing surgical or ambulant care are nowadays unable to manage without a strict hygienic sterilization of medical instruments. The clean steam, necessary for the requested sterilizations, must meet the requirements of European Standard EN 285 and that is particularly from the point of quality, pressure and requested volume in random time period. Production of clean steam is technically and financially very demanding. This contribution is aimed on newly developed Pure Steam system with STEAMEX clean steam generator.

Abstract: Water level control of the steam generator is an important indicator of the safe operation of nuclear power plant. The traditional PID controller system has the disadvantages of large amount of overshoot, long adjusting time, etc. Steam generator has complex, nonlinear and time-varying characteristics. This article proposes the adopting the BP neural network intelligent control algorithm. The simulation experiments results indicated that: Comparing with traditional PID control it has smaller overshoot and shorter adjustment time, more ideal control effect c.

Abstract: In the steam generator with water level control system of nuclear power plant, there are various uncertainties in the controlled devices. Any actual system had certain nonlinear. Because of the steam generator is very important equipment in nuclear power plants, water level control plays a decisive role for the safe operation of nuclear power plant and it required stable operation and fast response of the whole system. For the highly complex, non-linear system , the traditional cascade PID control had been used cannot obtain satisfactory control effect, this paper try to use RBF neural network to optimize the PID parameters. The simulation experiments show that: the rbf neural network optimized controller made the control system’s robustness and control quality superior than the traditional PID controller, and described the method can be applied more widely.