Development of a Simplified Model for Radionuclide Aerosol Removal Using a Containment Spray Including a Nonsprayed Region

After the accident at TEPCO’s Fukushima Daiichi Nuclear Power Stations on March 11, 2011, severe accident countermeasures and regulations have been discussed in various organizations as well as the Secretariat of the Nuclear Regulation Authority (S/NRA) in Japan. For severe accident management, spray systems or alternative spray systems have become increasingly important for reducing radionuclide release from the containment. In the present study, a simplified model was developed for aerosol removal by the spray system, considering a nonsprayed region in the containment. The effect of the nonsprayed region was estimated by the simplified model with a single volume, although multivolumes were used in the past. The model was verified through comparison with the analytical solutions for typical containment spray conditions.