[en] The next stage in the Indian nuclear power programme consists of building 700 MWe Indian Pressurized Heavy Water Reactor (IPHWR) units. This involves up-rating of all the plant equipment like reactor, steam generators (SGs), turbo-generator, major pumps, etc. The SG used in the current generation of IPHWRs, which have an electrical power of 540 MWe, is a mushroom type, inverted U-tube, natural-circulation SG. The 700 MWe SG design has the same the tube diameter, tube pitch and outer diameter of the steam generator sections as the 434 MWth SG, with certain changes in geometry of the feed header, flow restrictor in the downcomer and flow distribution plate. The changes resulted in a 30% increase in steam flow rate while maintaining the same circulation ratio. The paper describes detailing of these changes using a CFD code for optimizing the flow field. (author)

[en] The new flow limiter design, which is integral with the 700 MWe Steam Generator (SG) steam outlet nozzle, was executed to improve safety margins and reduce forces on the tubes and egg crates during a postulated Main Steam Line Break (MSLB) accident. Computational fluid dynamics (CFD) Code was used to model the complex geometry involved and calculate the pressure drop. A flow limiter is required to maximize safety margins on steam generator internal components during a hypothetical full guillotine rupture of the main steam line leading from the steam generator to the turbine generator. In addition the flow limiter limits the rate at which steam would be released inside the containment building during the progression of the event. (author)