Flammability Limits of H2 Based Mixtures in Conditions Relevant to Waste Management in Containment - 18032

The aim of the present work is to assess the risk of explosion in closed containments used for the transportation of nuclear materials or nuclear waste. Indeed, it is very well-known that hydrogen can be produced due to (i) the radiolysis of different materials within the containment, (ii) the thermal decomposition of mainly the organic part in the containment. Since hydrogen has a very low ignition energy and a very wide flammability domain, it is important to determine the risk of ignition of the subsequent mixture produced by the aforementioned mechanisms. The quantity of the hydrogen that can be produced can vary depending on the containment type and on the state of the material/waste being transported. It is then mandatory to have a very good knowledge not only of the flammability domain of hydrogen in air diluted with water vapor. To do so, an experimental work on the flammability domain of multiple ternary mixtures containing H₂/air/H₂O_vap is being conducted at the CNRS-ICARE laboratory within collaboration with the CEA. The present work will focus on the experimental determination of the lower flammability limit of H₂/air/H₂O_vap using the spherical method. These experiments have been carried out for an initial temperature of 200 deg. C and at three different initial pressures: 0.3, 1 and 2 bar. The monitoring of the flammability conditions has been conducted using fast flame imaging and pressure measurements. (authors)