First lessons of the Toulouse ammonium nitrate disaster, 21st september 2001, AZF plant, France
Résumé
A terrible explosion of ammonium nitrate occurred on 21st September 2001, in Toulouse, in AZF plant belonging to Grande Paroisse Company, TotalFinaElf Group. The manufactured chemicals in the plant were mainly ammonium nitrate, ammonium nitrate-based fertilisers and other chemicals including chlorinated compounds. The explosion took place in a storage warehouse where roughly 400 tons of rejected off-spec materials were stored. These materials were both coming from ammonium nitrate for explosives and from high nitrogen content single fertilisers manufactured on site. The TNT equivalent mass of the explosion was estimated by INERIS in a range of 20 to 40 tons of TNT. The human effects of the explosion were 30 persons killed (8 from the public) and up to 2242 people injured. The plant was located in the suburbs of Toulouse (750 000 inhabitants) and the extent of damages was very large both on and off site with a cost estimated by insurers of 1500 million Euro. The origin of the explosion is still under investigation one year and a half after the accident, and few possible causes are mainly on debate, in particular between the Justice and the company's investigations. The IGE's (General Inspectorate for the Environment) asked INERIS to lend its technical assistance during the administration (kind of public) enquiry set up after the explosion, in order to report one month later to the French Prime Minister. The aim of this paper is to share a global overview that is not exhaustive upon lessons of the disaster that have been identified until now. As far as the direct or immediate causes of the explosion are not established yet, the identification of some factors that contributed to the disaster enabled to debate on changes at the different level of the socio-technical system as described by Rasmussen and Svedung (1997) that manages the risk. It will deal mainly with facts and changes on different aspects such as ammonium nitrate hazards, safety studies, land use planning, accident investigation, safety regulation, public communication... All these points could deserve more details.