CFD simulation of flow blockage through a coolant channel of a typical material testing reactor core

Two-dimensional simulations of partial and total channel blockage of the IAEA 10 MW generic reactor is performed under both hot and average channel conditions using the CFD code, Fluent. Three adjacent coolant channels of a fuel assembly and their fuel plates are modeled, one of which is subjected to partial blockage as a sequence of continuous area contractions due to buckling of its fuel-plates inwards. The simulation is performed under the hot channel condition up to 90% blockage where boiling is predicted. Whereas under the average channel conditions, the simulation is performed up to 100% blockage, where the predicted temperatures are always below boiling even for total blockage. The hydraulic resistance of the obstructed channel resulted in the redistribution of the coolant among the three channels. The obstructed (left) channel received less flow and the adjacent (middle) channel more flow while the flow in the third (right) channel did not change appreciably. This has impacted the temperature distributions of the fuel plates and the coolant channels in the model. The velocity and temperature profiles through the obstructed channel and the other channels as well as the streamlines at the entrance are presented and discussed for each blockage case. The CFD analysis provides an in-depth investigation to the interplaying thermal–hydraulic processes involved in this system that are usually missed when using lumped analysis 1D codes.

► CFD investigation of heat transfer in partially blocked channel is considered for MTR reactors.
► Both the hot and average channel scenarios were considered.
► Results show that, for the hot channel, boiling may occur for blockage more than 85%.
► For the average channel, no boiling is reported even for full blockage.
► Interesting patterns is investigated and highlighted.