About an hour and a half before the explosion, yellow smoke began to escape from the tank, which was noticed by the technician on duty. He, along with the manager and three duty officers, decided to check the condition of the tank. The corridor leading to the tank was filled with smoke, so the technicians only made a quick verification of the electrical system.
Despite the increasingly poor visibility and rising temperatures in the building, the technicians decided that there was no danger.
They started ventilation to lower the temperature and abandoned further inspection. The manager noted the incident in the logbook but omitted to examine the radiation index, which exceeded acceptable standards many times over.
Inside the tank, most of it was a mixture of sodium acetate and nitrate. When the tank was heated to 300 degrees Celsius, an explosion occurred. The force of the explosion is estimated to be at least 70 tons in TNT equivalent or more than 290 gigajoules.
