An explosion occurred at around 6 pm in the reactor of an active ingredient manufacturing plant during a reprocessing campaign for non-compliant batches of morniflumate by recrystallisation in isopropanol. Written instructions had been produced for this unusual reprocessing operation; the product, which is liquid under normal operating conditions, was in powdered form in this situation. The workshop was defined as an ATEX area. At 5:35 pm, 2 technicians wearing personal protective equipment were loading 400 kg of powder. After loading the 7th barrel out of 8, the explosion occurred while the 4,000 l nitrogen-inerted stainless reactor contained 1,200 l of isopropanol at 20 °C mixed with morniflumate. The 2 slightly injured technicians were thrown backward and a cloud of smoke/white dust formed. In fact, 2 successive explosions had occurred; a flash blast in the hopper during loading, followed by a secondary explosion which spread to the workshop roof. A fire that had started in the hopper was put out by the automatic fire extinguishing system. The workshop was secured, a safety perimeter was set up and the internal emergency plan was activated. No external pollution was detected as the fire remained confined to the workshop. The explosive cloud resulted from the presence of finely separated morniflumate powder thoroughly mixed with air.

Following an appraisal, the accident was determined to be of electrostatic origin. Property damage was limited: roof and window components damaged within a radius of 5 m around the hopper, failure of a connection duct between the hopper and reactor, and the projection of metal sheet and boards on the ceiling. The inspection authorities for classified facilities requested the workshop to be shut down and recommended that the Prefect issue an emergency order making the resumption of operations subject to an analysis of the causes and the implementation of suitable corrective measures. Several provisions were made: suction to be restored in the loading hopper (out of order during the accident), better control of inerting, improvement of the loading stations by placing the technician further away from the hopper and using a tilt table, elimination of electrostatic charges (dissipator gloves, etc.), implementation of a set of alcohol vapour concentration measurements in the hopper and the pipe for loading morniflumate into the reactor, and a valve separating the hopper and nitrogen-inerted pipe.