Two-phase pressure drop studies for 37-rod fuel bundles of Indian PHWR

Pressurized Heavy Water Reactor (PHWR) is a heavy water moderated and heavy water cooled nuclear reactor which employs short fuel bundles stacked one after another inside each of the horizontal channels. The 540 MWe reactors, under operation in India, employ 37- rod bundles. Presently, up rating of 540 MWe reactors to 700 MWe is taken up which allows boiling of the coolant, at the exit of channels. However, this provision affects the pressure drop of the coolant as it passes through different geometries, as pressure drop is a function of flow geometry besides other parameters. It is of prime interest and requirement to estimate the pressure drop across 37-rod fuel bundle under two-phase conditions. In the present study, experiments have been conducted in existing 3 MW Boiling Water Loop (BWL) at BARC for different flows and qualities at a pressure of 70 bar across the simulated fuel channel of 700 MWe PHWR. The results obtained for pressure drop across fuel bundle have been analyzed to evaluate the two-phase friction multipliers. (author)