Convection influence on the modelisation of the fire test on a radioactive material transport package

International audienceNuclear transport packages are used for the protection and transportation of nuclear material by road, train or boat. Therefore, the packages containing the most dangerous materials have to go through many reglementary tests, including a fire test of 30 minutes at 800 °C.To demonstrate the safety of the package, such a test may be performed on a model of the package, or numerically, with boundary conditions representative of the fire (surface emissivity, environment temperature, convection coefficient…).The guidelines of the regulation give a value of the convection coefficient during the fire, 10 W/m²/K. Recent research suggests that this value may not be representative of such a fire, and may have to be scaled up. But does a higher convection coefficient necessarily have an impact on the temperatures of the package? In order to answer that question, IRSN has performed calculations on a dummy transport package. This package, 7 m high and a 3 m diameter, is used for the transportation of nuclear materials with a high thermal power.To attest (or contest) the influence of the convection coefficient, this coefficient will take its value within a range from 0 (no convection) to 80 W/m²/K. The temperature in the package during the fire phase, as well as during the cooling phase which follows the fire, will be observed and the influence of the convection coefficient will be analysed