Investigations on the flow and temperature distribution downstream of local coolant blockages in rod bundle subassemblies

Experimental and theoretical investigations are reported on the flow and temperature distribution in local recirculating flows in rod bundles, downstream of a blockage. A mean coolant temperature in this recirculation zone can be calculated from the dimension of the recirculation zone and the mass exchange rate with the main flow. Similarity analysis for recirculating flow in a simple geometry without rods shows that with a sufficiently high Reynolds number, similar geometry and similar heat distribution, the dimensionless temperature fields in recirculating flows are equal and independent of the Reynolds and Prandtl numbers. This result is also observed to be true for rod bundles, justifying temperature distribution measurements to be performed with water instead of sodium. Typical results are given.