CFD analysis of flow blockage in MTR coolant channel under loss-of-flow transient: Hot channel scenario

In this work 2D, CFD analysis of the fast loss-of-flow accident in the IAEA 10 MW generic research reactor is conducted under the hot channel condition with one channel subject to a sequence of area contractions up to 80%. While the previous work on this system under normal operating conditions shows that the system may be safe up to blockage ratio of approximately 85%, this work shows that boiling is inevitable particularly for blockage ratio more than 20%. Three channels are considered for the CFD simulations. Results for the unblocked scenario are compared with those published in literatures and good agreement is obtained. The interesting phenomenon of flow inversion is highlighted and investigated. The onset of flow inversion is found to be different amongst the three channels for different blockage ratio. Whereas, for the unblocked channel scenario, the onset of flow reversal is found to be identical in the three channels. This is a manifestation of the effect in the hydraulic resistance for the different cases and also to the buoyancy forces. The interesting flow and heat transfer regimes involved in this system are highlighted and investigated.