Effect of Geometry Variation on Temperature Prediction in the TN-32 Used Nuclear Fuel Storage Cask

Abstract

During vacuum drying, low pressures in combination with the relatively high heat generation rate may cause the temperatures of the fuel cladding to exceed the limit of roughly 400°C set by the Nuclear Regulatory Commission. The low pressures (rarefied gas) conditions within the cask may induce an additional thermal resistance for heat transfer by conduction at the solid-gas interface, and it is this resistance, also called “temperature-jump,” that causes the temperature of the used nuclear fuel assemblies to increase considerably.The objective of this work is to accurately predict the peak cladding temperature during the low-pressure conditions associated with vacuum drying. Other models and experimental results indicate that the peripheral basket-rail gap is the most sensitive component in peak cladding temperature (PCT) prediction within the continuum regime, and its sensitivity is even more pronounced for rarefied conditions. Several geometrically-accurate two-dimensional computational fluid dynamics (CFD) models were built in order to predict PCTs under conditions associated with vacuum drying while taking into account a variety of probable gap geometries.