Upscaling and downscaling the heat transfer process coupled with neutronic reflected core for sodium-cooled fast nuclear reactor

The heat transfer phenomena are crucial in nuclear reactors' design and safety analysis due to the feedback effects with the neutronic processes for power generation. Nuclear reactors are heterogeneous systems containing hundreds of thousands of fuel pins that exhibit power distribution through the space, and the temperatures between the coolant fluid and pins are different. This work analyzes the heat transfer process in liquid metal-cooled fast nuclear reactors with two upscaled energy equations based on the volume averaging method, which is widely applied for the analysis of transport in multiphase systems. The upscaled heat transfer model is coupled with a neutronic reflected core model including feedback effects from the nuclear fuel and liquid metal temperatures. The coupled mathematical models are employed within a called downscaling procedure , which represents a novel methodology with scopes beyond conventional problems in heat transport processes in nuclear reactors. The downscaling process allows us to increase the degree of resolution in the reactor core since this considers the scale of the fuel assembly and that of individual pins at the smallest scale, i.e. a single fuel pin surrounded by liquid metal. This point is crucial for analyzing hot spots in the reactor core. (c) 2022 Elsevier Ltd. All rights reserved.