Fréjus complementary report english summary
The report completes the provisional technical investigation report on the HGV fire in the Frejus tunnel on 4 June 2005, published in March 2006.
The provisional and complementary reports make up the final report.
The additional report is based mainly on a study carried out by the CETU and which concerned :
the digital reconstitution of the fire ;
the study of alternative smoke control scenarios ;
the study of scenarios illustrating the influence of the seat of the fire and atmospheric conditions.
This study enabled us to consider that a power of 60 MW would appear to be the most realistic hypothesis, albeit rather low, amongst the 3 simulated fire power hypotheses (30 MW, 60 MW, 90 MW). It revealed the importance of the rapid activation of the smoke control system which should normally be performed by the Automatic Fire Detection System which was installed in the tunnel following the accident.
This study also revealed the persistence of potentially dangerous situations in the event of fire, when the velocity of the initial draught is high. This is the case close to the ends of the tunnel, especially where there is a significant difference in atmospheric pressure between the two ends of the tunnel.
The tunnel operating instructions provide for the gradual reinforcement of preventive measures depending on this difference in atmospheric pressure ; nevertheless, the specific problem posed by the possible presence of coaches in the event of a fire under such circumstances requires special attention.
Accordingly, an additional recommendation was made to the concessionaires, the Intergovernmental Commission and the Prefect of Savoie, to improve the protection of the transit of coaches through the tunnel and check the efficiency of the arrangements made to protect coach passengers by asking the concessionaires to test them beforehand during exercises.