A flammable cleaning solvent was used at the workplace where an explosion occurred at Hanwha Aerospace's Daejeon plant, it has been confirmed.
According to a "Workplace Environment Measurement Results" report on Hanwha Aerospace's Daejeon plant, submitted to the office of Rep. Cho Ji-yeon of the People Power Party, a member of the National Assembly's Environment and Labor Committee, by the Korea Occupational Safety and Health Agency, 8,240 kilograms of cleaning solvent was used per month in the second half of last year at Building 56, where the accident occurred. The report was submitted on Tuesday.
The cleaning solvent used was 1,2-dichloroethylene. The substance is a volatile organic solvent with a low flash point, and is known as a flammable material that can ignite when its vapor is present in the air above a certain concentration. In particular, the accident risk can increase when it comes into contact with high-risk materials such as propellant residue, aluminum powder, or static electricity.
The report states that Building 56 handles 36,000 kilograms of propellant and 730 liters of byproduct fuel oil annually. However, Hanwha Aerospace explained that "this process is not a process that uses propellant, but a process that cleans propellant," adding that "while waste propellant can be generated during the cleaning process, the amount is less than 3,600 kilograms."
However, experts point out that the cleaning process can also constitute high-risk work. Chae Jin, a professor of fire and disaster prevention at Mokwon University, said, "In the process of cleaning tools used to manufacture solid propellant, there is a possibility that propellant residue such as aluminum powder remains." He added, "It is high-risk work that requires strict safety management against static electricity, friction, and volatile cleaning solvent vapor."
Meanwhile, an explosion of unknown cause occurred Tuesday at the cleaning room of Building 56 at Hanwha Aerospace's Daejeon plant, killing five workers and leaving two with serious to minor injuries. At this plant, a 2018 explosion killed five people and a 2019 explosion killed three people. As serious accidents have recurred, controversy over poor safety management is growing. Police and relevant authorities are investigating the exact cause of the explosion and whether safety regulations were observed.
