In the present configuration of the calandria for the 700 MWe Kakrapara Nuclear Power Plant, moderator inlet diffusers are directed upwards and the outlet is from the bottom of the ca­landria. Moderator circulation patterns and temperature distri­bution needs to be predicted to ensure adequate cooling margin for all channels. This study consists of two steps: at first, an op­timized calculation scheme is obtained by comparison of the predicted results with the experimental data and by evaluating the fluid flow and temperature distribution. Then, in the second step, the analysis for the real 700 MWe IPHWR moderator un­der normal operating conditions has been performed with the optimized scheme. The present paper describes the methodolo­gy used for predicting the circulation pattern and temperature distribution in the moderator during normal operation using CFD code CFD-ACE+. The matrix of the calandria tubes in the core region is simplified to a porous media in which the momentum resistance model is used for pressure loss. The buoyancy effects due to internal heating and jet momentum ef­fects through inlet nozzles have been considered in the analy­sis. The results show that the maximum temperature observed in the calandria is within the design limits during normal op­eration.