Influence of the convection coefficient on the numerical modeling of a fire test on a nuclear transport package

International audienceTo be approved, a package dedicated to the transport of radioactive material must withstand severaltests required by the IAEA SSR-6 regulations, one of which is a 30-minute 800 °C fire test. Todemonstrate the safety of the package, such a test may be performed on a package mock-up ornumerically with boundary conditions representative of the fire. IAEA regulations specify values forflame emissivity and package surface absorptivity. However convection is addressed in the IAEASSG-26 guidelines with a suggested coefficient of 10 W.m-2K"1 correlated with a range of flamevelocity between 5 and 10 m.s-1. Recent research [REF 2] suggests that this value may not alwaysbe representative of such a fire and could be scaled up. What could be the influence of higherconvection coefficients on the temperature of the package?In order to answer that question, IRSN performed sensitivity calculations on transport packagesmodels and studied the influence of the convection coefficient over a range from 0 (no convection)to 100 W.m"2.K-1 (very high convection, not necessarily representative of real fires). Thetemperatures in the package models during the fire and cooling phases were analyzed and put inperspective with safety issue