Pollution
Humain
Environnement
Economique

An explosion occurred at around 10:52 a.m., in a centre specialising in the recovery and treatment of metals and end-of-life vehicles when a metal cylinder was being cut with a torch. The projections started a fire in the company’s storage warehouse and in the vegetation around the site. A significant plume of smoke was released. A second explosion occurred.

A 500 m security perimeter was established. The site and the surrounding plants, a retirement home and a school were evacuated. The fire was extinguished at around 12:40 p.m.

Consequences

The 2 subcontractors performing the cutting operation were killed in the explosion. A local resident, 4 employees and 3 residents of the retirement home were injured. The medical services examined around 100 people and 40 received counselling by a psychological assistance unit.

The explosion left a crater measuring 2.5 m long, 1.2 m wide and 1.6 m deep in the reinforced concrete slab. The cylinder was pulverised, and everything within a 10-meter radius of the crater was damaged by the blast. The operating building, located 40 m from where the cutting took place, was very severely damaged: the roof was destroyed, the walls were deformed and cracked, the interior was ruined. The radioactivity detection gantry was partially destroyed.

A cable on an HV line, cut during the first explosion, fell to the ground. Twenty residential apartments in 4 buildings were damaged (windows and joinery). The retirement home suffered significant damage which was estimated at €250,000. As the site was located in a dense industrial zone, the explosion impacted a total of 19 companies (blast damage to facades, deformed cladding, windows blown out within a 200 m radius, damaged roofs, damaged vehicles). The activity of 15 or so of these companies was disrupted, 31 employees were placed on temporary leave, including 4 at the site where the accident occurred.

Follow-up

The inspection authorities for classified facilities visited the site on the day of the accident.

The site’s activity was suspended by prefectoral decree, and emergency measures were taken:

  • site security (access to the site was secured, and permanent surveillance was set up);
  • waste management and disposal (after finalisation of the expert evaluations):
    • scrap metal;
    • gas cylinders used for cutting (made safe and then disposed of according to a protocol validated by their manufacturer);
    • fibre cement waste from the collapsed roof of the building (characterisation of the waste, ambient air measurements to ensure the absence of asbestos fibres in suspension, disposal in accordance with regulations).

Causal analysis

The cutting station was located outside, in the scrap metal yard, 15 m from the property limits and the road running alongside the site. The cutting operations on the metal cylinder (roll measuring 0.40 m in diameter by 2 m long) was performed using a torch fed by 2 propane cylinders and several oxygen racks to supercharge the combustion.

According to an employee who witnessed the accident, a fire started on the cylinder just before the explosion. In accordance with the procedure, one of the two subcontractors went to report the incident to the operator. The explosion occurred when he returned to his workstation.

An expert evaluation was conducted by the specialised services and the forensic police. It would appear that the origin of the explosion was caused by the accidental cutting of high-calibre military ammunition (a TNT load of 200 to 300 kg). The ordnance was an English submarine mine from the Second World War. The mine had become damaged over time which rendered it more unstable. Since the explosive had been kept in a sealed chamber, and therefore without contact with the air, it was still active. Unlike a civilian explosive, which produces a blast effect, this ordnance created a downward detonation which resulted in a large crater.

Following the investigation, several other hypotheses were excluded. It had been thought that the cylinder was a roller from an agricultural facility and that the explosion was related to the residual presence of fertilizer. The hypothesis of an explosion of one or more gas cylinders was also rejected owing to the violence of the blast and to the damage caused. In addition, propane cylinders were found several metres from the crater, pierced by projectiles but without any trace of an internal explosion.

The operator updated the plant’s hazard study to take into account feedback from the event.