At around 11.40 a.m., a fire broke out on a 15m³ mixture of aluminium swarf at a metal waste treatment centre. The heap was in the open air and isolated in a concrete bay. The contact of a grab weighing 1.5t on the heap caused an explosion with the ejection of molten metal to a height of 7-8m. The “fireball'” type reaction lasted 13 seconds. Ejections of small solid debris were noticeable as far as the site entrance located 60m away as the crow flies. The grab operator was severely burned. The firefighters arrived on site quickly and took care of the grab operator. They extinguished the fire with sand while maintaining a protective hydraulic system. At around 3.20 p.m., the fire was brought under control. A mixed volume of 63t of sand and 12t of waste rested for five days without stirring, with checks by thermal imaging camera performed every 4 hours.
12t of metal waste burned or were ejected up to 50m around.
The investigation by the BEA-RI (Bureau d’Enquêtes et d’Analyses sur les Risques Industriels, i.e., industrial risk investigation and analysis bureau) showed the presence of magnesium and magnesium oxides in the residues, which tends to prove contamination of the heap of aluminium by magnesium. Friction with the grab created sufficient energy to initiate combustion of the magnesium present. Pollution of a heap of aluminium with 10% magnesium can produce this type of ignition.
The operator took the following action:
- reminder that it is forbidden to accept waste with magnesium;
- ban on purchases of aluminium turnings from private individuals;
- identification of suppliers who also use magnesium;
- for the latter, obligation to provide a guarantee certifying that there is no magnesium in their waste;
- for the latter, insertion of a specific instruction in the existing acceptance procedure to verify the effective absence of magnesium.
