[en] The invention concerns a steam generator for a nuclear plant where feed water is preheated before mixing to recirculated water. This preheating allows a better use of the exchange surface and an increase in thermal efficiency of the generator. This result is obtained by directing an important fraction of recirculated water toward the hot leg of the tube bundle, the remainder beeing mixed to the whole of feed water. This fractionation is produced by the pressure-drop created by a flange and two distribution plates with different permeabilities placed respectively in the hot leg and in the cold leg

[en] Prismatic sectional files, staggered one behind the other, enclose the tubes of the feedwater piping system. These sectional files of the steam moisture separator are dimensioned in such a way that the gaps between the individual rods of the files become tighter in the direction from the flowing - in steam towards the feedwater heater. With their lower end the sectional files are arranged on a plate with rim and water drain. By these measures there will be achived that the stagnation of the heating steam does not immediately affect the piping system. (DG)

[en] An integral part of the feedwater heater condition assessment program consists of an inspection program performed on a periodic basis to help extend the availability of feedwater heaters. If applied effectively, NDE can extend the life of feedwater heaters by eliminating insurance plugs, minimizing tube leaks, assisting where necessary with design modifications and improved water chemistry, and repairing defective tubes for safety and remedial reasons. By performing inspection on a periodic basis, more realistic, up-to-date heater conditions can be obtained for a planned and timely heater replacements. This paper presents essential components of an effective NDE program to better prepare and assist utilities with reliable feedwater heater inspections

[en] The flow rate due to an accidental clean failure in a vaporizing bundle tube of steam generator is derived. The optimal diameter of a pipe of drain transfer of the feedwater heaters in a thermal power plant was also calculated

[en] The ASME Performance Test Code (PTC) 12.1-1978 for the performance testing of feedwater heaters is being revised extensively and updated. The committee anticipates that the final draft of the proposed Code will be ready for industry review in 1993. This Code revision will greatly enhance the usefulness and cost effectiveness of feedwater heater performance testing. This paper has been prepared to report on the progress of the committee and to disseminate information on the nature of the revision. Included in this paper are some of the notable changes intended for the Code. The most extensive change is the calculation method, which is described in step-by-step detail. An approach is also described for using ultrasonic flow techniques to test individual or split-string feedwater heaters, when flow nozzles are not available. Additionally some educational information on the use and limitations of ultrasonic measurement instrumentation is included. Discussion is also included on the required uncertainty analysis. 3 refs., 2 figs., 2 tabs

[en] A total of 22 steam generators with integral preheaters have been supplied or are currently being completed for KWU nuclear stations. The preheater concept was introduced to improve the thermal efficiency of steam generators by preheating the main portion of the incoming feedwater with heat from primary coolant passing through the cold leg of the generator, thus improving overall thermal efficiency by approximately one percent. The design of the KWU preheater is outlined in this paper. (U.K.)

[en] This invention concerns the generation of steam by bringing the water to be vaporised into indirect thermal exchange relation with the heating steam which condenses when passing in series, along alternate routes, through bundles of tubes immersed in a vaporising chamber. A number of steam generators working on this principle already exist. The purpose of the invention is to modify the operating method of these steam generators by means of a special disposition making it possible to build a compact unit including an additional bundle of tubes heated by the condensates collected at the outlet of each bundle through which the heating steam passes

[en] The invention concerns a steam generator, especially for PWRs, with a U-tube bundle to the cold leg of which is assigned a feedwater heater which has two parallel flow paths for the feedwater, running in one case in the same and in the other case opposite to the direction of the primary medium flowing through the U-tube bundle. The distribution is done by means of a separating wall in the feedwater heater running across the tubes of the U-tube bundle. It is proposed to provide - preferably in the area of the separating wall - a passage between the two flow paths which may be closed and which may, if necessary, distribute the feedwater among both flow paths to the degree required. The normally closed passage may be opened by twisting a ring enclosing the shell of the U-tube bundle. This permits the steam generator to be operated preferably in the range of the separating wall, the feedwater heater being practically excluded. (UWI)

[en] The description is given of a feed water preheater for a nuclear power station, located between a feed pump and a reactor. The preheater is in the shape of a vertical exchanger vessel containing a bundle of tubes in which the feed water circulates and around which there is a casing in which the heating steam passes at various different pressures and coming from different parts of the installation. The lower part of the vessel is in the shape of an expansion tank for that part of the heating steam having a higher pressure than that of the remainder of the input steam

[en] The invention proposes to improve the inlet zone of the condensates in the heater vessel. So, the mixture water-vapor is separated in good conditions; the upward vapor outflow and the downward liquid phase flow are improved, what reduces the condensate volume rate and, thus its velocity along the inner walls of the shell. The cross baffles arranged in the passage zones contributes to dissipate the kinetic energy of the inlet condensate flux. Finally, it allows to improve considerably the flow conditions along the walls and to get a distribution of velocities compatible with the nature of materials which constitute these walls, reducing by this way the erosion-corrosion risks