원전 비상디젤발전기실에의 미분무수 소화설비 적용 연구

An Application Study of Water Mist Fire Extinguishing System in Emergency Diesel Generator Room of Nuclear Power Plant

Because carbon dioxide is heavier than air, it is easy to penetrate deep into the fire, and the latent heat of vaporization is large, so it has excellent fire extinguishing ability in a confined space. For this reason, fire extinguishing systems using carbon dioxide are installed in emergency diesel generator (EDG) rooms of most domestic nuclear power plants. However, flooding type carbon dioxide fire extinguishing systems applied to the EDG rooms are difficult to meet the fire extinguishing performance test standards and may negatively affect human safety. Since the water mist fire extinguishing system uses water as the fire extinguishing agent, it is environmentally friendly and does not adversely affect the human body. Thus, it has been replacing gas-based fire extinguishing systems such as carbon dioxide and Halon. In addition, since it has effective fire extinguishing performance even with a small amount, its application is being expanded to industrial facilities where it is difficult to supply a large amount of water. For example, the use of water mist fire extinguishing systems has been increasing in aircraft, naval warships, submarines, subways, machine rooms of ground industrial facilities, and substations. The field in which the water mist fire extinguishing system is most actively applied is in the ship field. International Maritime Organization (IMO) has developed IMO MSC/circ 1165 as a standard to approve the performance of the water mist fire extinguishing system in engine rooms of ships. Therefore, in order to apply a water mist fire extinguishing system to a ship, this standard must be satisfied. The U.S. Nuclear Regulatory Commission Regulatory Guide (USNRC RG 1.189) permit the use of the water mist fire extinguishing systems in accordance with NFPA 750. However, there are no technical standards and approval procedures for the performance test of water mist fire extinguishing systems specialized in nuclear power plant design. Therefore, in this study, the performance of the water mist nozzle applicable to the nuclear power plant was numerically evaluated using the IMO 1165 standard for the purpose of applying the water mist fire extinguishing system to a nuclear power plant. The performance evaluation of the water mist nozzle was performed using FDS (Fire Dynamics Simulator) 6.5.2 developed by NIST. As a result of the simulation, the water mist fire extinguishing system satisfies both the fire extinguishing time of 15 minutes (900 seconds), which is the performance standard of IMO 1165, and the room temperature within 100℃.