Moderator flow and temperature distribution inside Indian PHWR Calandria- a case study

The Calandria of a Pressurized Heavy Water Reactor (PHWR) is essentially a large horizontal cylindrical vessel housing a matrix of horizontal tubes called Calandria tubes within which is contained the pressure tubes that house the fuel bundles. The Calandria is filled with heavy water moderator at a pressure slightly above the atmosphere. Due to complex geometry of Calandria and distributed heat source, the flow/temperature profile of moderator inside Calandria is complex, which is mainly governed by the combination of momentum force and the buoyancy force. The moderator flow within the Calandria manifests based on the balance of the momentum and buoyancy forces and the losses due to frictional and drags effects. The thermal boundary condition plays a significant role in the manifestation of the moderator flow. The two enveloping conditions in this scenario would be considering the adiabatic wall conditions implying no heat loss from the Calandria boundaries and considering realistic heat loss from the boundaries Two separate studies have been carried out to predict and compare the temperature distribution/magnitudes of moderator inside the Calandria. Prediction of flow/temperature distribution of moderator inside Calandria has been carried out using Computational Fluid Dynamics (CFD) simulation. (author)