In case of a hypothetic severe accident in a PWR, the loads generated by the hydrogen combustion process increase the containment atmosphere pressure and temperature and may threaten the containment building, internal walls and equipments integrity or availability. The evaluation of such loads needs 3D CFD codes. However, before such codes can be used with a high level of confidence, a thorough validation process on well-instrumented experimental data is necessary. The original vertical facility ENACCEF (Enceinte d’Accéleration de Flamme) has been built to fulfil these objectives. This facility is highly instrumented and divided in 2 parts: the lower one, acceleration tube, measures 0.15 m i.d. and 3.2 m long while the top one, the dome, is 0.75 m i.d. and 1.7 m long. The present work deals with TONUS validation based on ENACCEF flame acceleration tests characterized by a H2 gradient. Comparison between experimental data and full multi-dimensional calculations is given.