Design of Steam Generator for 700 MWe IPHWR

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 434 MWth SG used in the current generation 540 MWe IPHWRs, is a mushroom type, inverted U tube, natural circulation steam generator. The challenge, for evolution of the 540 MWth SG design, was to keep the tube diameter, tube pitch and outer diameter of the steam generator sections identical to the 434 MWth SG as far as possible. Further, the temperature difference between the primary inlet and outlet temperatures from SG was also to be maintained equal to that of 434 MWth SG. The paper describes the thermal hydraulic studies carried out for arriving at an optimal process design of 540 MWth SG. The studies were carried out using the validated 1-D code developed in house. The paper covers the issues like, extraction of the extra 106 MWth power, maintenance of a good circulation ratio under all operating conditions, additional capacity requirements of steam separators and accommodation of internals in the given space. (authors)