Abstract
The main aim of the current study is to analyze advantages and shortcomings of horizontal and vertical types of steam generator design. Design solutions and experience of operation of steam generators of horizontal type accepted in Russia and of vertical type applied by Westinghouse, Combustion Engineering, Siemens, Mitsubishi, Doosan were analyzed within the framework of the present study. It was established that steam generator equipment of horizontal type is characterized by disadvantages of design, technological and operational nature. Thus, horizontal steam generators with dimensions permissible for railroad transportation and, for VVER-1200 with reactor vessel diameter equal to 5 m, by water transport as well, have exhausted the possibilities for further significant increase of the per unit electric power. The demonstrated advantages of vertical-type steam generators are as follows: 1) absence of stagnant zones within the second cooling circuit; 2) uniformity of heat absorption efficiency of the heating surface that ensures improved conditions for moisture separation; 3) increased temperature drop with parameters of generated steam elevated by 0.3 – 0.4 MPa. Conclusion was made on the advisability of introduction of steam generators with vertical-type layout in the Russian nuclear power generation.
Highlights
Steam generator is one of the most important elements of a nuclear power installation
Russian NPPs equipped with VVER-1000 reactors have four-loop cooling configuration, i.e. each power unit incorporates four steam generators occupying significant space inside the containment shell of the reactor unit
Steam generators of horizontal type are used on NPPs with VVER reactors from the moment of initiation of development of nuclear power generation [6]
Summary
Steam generator is one of the most important elements of a nuclear power installation. A significant part of emergency shutdowns of NPPs is caused, in particular, by failures of steam generators [3, 4]. Steam generator for VVER-1000 power unit (Figure 1) is a large-sized equipment with vessel length of 14.5 m and diameter up to 4.2 – 4.3 m. Russian NPPs equipped with VVER-1000 reactors have four-loop cooling configuration, i.e. each power unit incorporates four steam generators occupying significant space inside the containment shell of the reactor unit. Containment shell must be strong enough, i.e. it must be capable to withstand excess pressure of steamwater mixture in case of an accident accompanied with a failure of pressurization in the primary cooling circuit. The larger is the diameter of the shell which is a pressurized vessel, the more difficult it becomes to ensure its strength. Comparative analysis of contemporary design of steam generators and earlier design configurations presented, for instance, in [5], demonstrated that during the period of development of “large-scale” nuclear power generation industry beginning from the time of its initiation, design layouts of steam generators remain practically unchanged
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