Pollution
Humain
Environnement
Economique

During the destruction of sparking tubes, an unexpected denotation took place on the firing range of a plant set up to: produce munitions, distribute industrial explosives, and remove the charges from explosive materials and objects. The sparking tubes (containing 110 g of tetritol in a thin-walled steel tube) were laid out in packets of 30 spaced 40 cm apart on two 20-m rows. Each stack was connected by a propellant trail; equipment preparation lasted 2 hours and was performed in range B, a flat parcel without cover vegetation and concreted (30*20 m) with surrounding 4-m high barricades. The two employees responsible for firing the sockets each had 15 years experience with a unit specialised in the safe treatment and neutralisation of weapons and munitions on polluted sites. Around 4:45 pm, a detonation felt near the site occurred just a short while after ignition. The alarm was sounded and a safety perimeter set up around range B would be kept in place until the end of the firing phase at 5:30 pm. On the following day, a deformation (in the form of a crater) could be observed over a 6-m length and 60-cm width on the range B concrete surface. This width decreased in the direction of the shockwave propagation, given that the detonation had not been transmitted throughout the entire row length: 15 kg of sparking tubes actually detonated and 10 kg were burnt. Minor property damage was recorded: a loosened light fixture in Building B41, loss of roofing material on Building I22 which was undergoing remodelling work (yet without any debris strewn outside the range). The certified explosives technician admitted to committing an error by positioning the stack at a distance of 40 cm and not 80 cm minimum, as indicated in the operational specification. The propellant seemed to have combusted with a greater energy release than usual: the faster ignition of the contiguous stacks could have increased their sensitivity to the detonation. This accident demonstrated that the concrete flooring, which had been in place for several months, splintered in the event of detonation and required correcting the non-transmission distance. Remedial measures were adopted: systematic placement of the stacks using a rod, controlled by the explosives technician, followed by validating the placement of explosives prior to ignition by a unit manager. The preventive measures adopted called for modifying distances and updating safety practices. An ongoing awareness-building campaign aimed at personnel was intended to avoid a lethargic attitude, synonymous with a lack of vigilance.