Optimization of the upper plenum of a PBMR to enhance thermal performance in the reactor core

An upper plenum of a PBMR type gas cooled nuclear reactor has been optimized using three-dimensional Reynolds-averaged Navier–Stokes (RANS) analysis and surrogate modeling technique. Shear stress transport turbulence model is used as a turbulence closure. Two geometric design variables viz., ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to that at outlet, are used as design variables for the optimization. Design points are selected by Latin-hypercube sampling. The objective function is defined as a linear combination of uniformity of temperature distribution in the core and pressure drop through the upper plenum. The optimal point is determined through surrogate-based optimization method which uses RANS derived calculations at design points. The results show that the optimization improves considerably both the temperature uniformity and the friction performance.