Lessons learned from the Barracas accident: Ammonium nitrate explosion during road transport

Abstract

On March 9, 2004, a lorry transporting ammonium nitrate (AN) overturned. The load caught fire and exploded due to the self-sustaining decomposition reactions of the AN. The consequences were two deaths, five injuries, and significant material damage in the form of destruction to vehicles and the highway. This article delves into the causes of the accident through root cause analysis techniques, such as fishbone, AcciMap and events and causal factors charting, which have demonstrated that the causes were not only physicochemical but also of an organizational nature. The explosion caused a crater 18 m in diameter, which would be equivalent to one caused by 11.4 tonnes of TNT. Through the relevant models, we have established the overpressure-distance map, explaining the breakage of lorry windscreens located 100 m from the accident site, and the vibration of glass planes at a distance of some 4 km. This accident underscored the need to comply with the safety measures handed down by competent bodies: (a) avoid contamination of AN, especially with fuels; (b) prevent the AN from being exposed to heat; (c) isolate for a minimum distance of 800 m in all directions around the accident site; (d) in case of fire, flood the area from a distance and stay away from the fire.