Multi-objective optimization of sub-assemblies design towards static mechanical equilibrium of sodium-cooled fast reactor core
Abstract
In the framework of Sodium-cooled Fast Reactors, core design studies are performed at CEA. A new methodology based on core multi-objective optimization is proposed taking into account the geometrical uncertainties on sub-assemblies regarding manufacturing tolerances for core static mechanical equilibrium analysis. This methodology relies on feedback from past reactors, especially PHENIX and SUPERPHENIX. As an example, the optimization is performed on a reduced number of parameters (distance across flats of pads, natural core restraint by reflectors sub-assemblies, pads axial position and stiffness).The thermal-mechanics core HARMONIE V2 code and the uncertainties URANIE platform are applied to define a first set of optimal features of the sub-assemblies. The core behaviour is analysed during nominal conditions, fuel handling operations and unprotected transients (i.e. with complete failure of all automatic shutdown systems).First results tend towards to give priority to high pads flexibility in order to minimise friction between sub-assemblies during handling operations. Pads on the whole of sub-assemblies, including reflectors, should be preferred for core restraint requirements. The effect of pads axial position over the core static mechanical equilibrium is limited, but pads located close to the top of fuel pins favour the pads effect during an unprotected transient.
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