Experimental and analytical study on heat dissipation mechanisms during spent fuel unloading in sodium fast reactor

Abstract In a sodium-cooled fast reactor spent fuel assemblies (SFAs) are unloaded from the reactor sodium pool after certain period of temporary storage. During unloading a spent fuel assembly is transferred through argon atmosphere where heat dissipation from SFA to argon is of great concern to avoid cladding damage which is strictly prohibited. With a 37-element rod array the steady-state experiments are carried out to investigate heat transfer under different environment temperatures and power levels. The rod array is installed vertically in a pressure vessel filled with argon. It is found that the circulation flow rate through the rod array driven by buoyancy is negligible. Instead of convection, conduction plays an important role in the radial heat transfer in the rod bundle. The Manteufel-Todreas model is proved to give satisfactory prediction for in-wrapper heat transfer. Natural convection on the outer wrapper surface can be reasonably predicted with the Yang model.