초록
Many safety facilities are installed and operated in nuclear power plants. In particular, at the nuclear power plant, the gaseous radioactive waste which is exhausted in ventilation of the facility or generated in the power plant is emitted from the exhaust stack after filtering out the radioactive materials. The safety of equipment that monitors the emission of gaseous radioactive materials is very important. ANSI N13.1, the technical standard for emission gas radiation monitoring sampling design, was amended in 1999. There has been a need to verify that the sampling system meets the revised technical standards. It was difficult to directly carry out these evaluations in the field of nuclear power plants. Therefore, the efficiency of the HVAC duct was compared with that of the actual HVAC duct after shrinking (reduction ratio: 2.032 : 1) in the laboratory. The circular duct model and the scale down model were suitable for the sample collection position by satisfying all the flow rate, flow angle, particle distribution, trace gas distribution, and trace gas maximum values, which are the five sample collection position acceptance conditions of ANSI N13.1. The COVs of the real duct model, the flow velocity uniformity scale, and the Reynolds number equal-scale scale down model were 4.6%, 5.3% and 4.1%, respectively, and the COV difference between the actual duct model and the scale down model was less than 5%. The scale down model was validated. ANSI N13.1 (1999) confirmed that the scale-down model validity condition was satisfied. It is now possible to build other types of HVAC ducts in a miniature way to perform an empirical test of the performance of gas radiation monitors. This study was the first case that the actual HVAC duct was evaluated by the scale down model and its effectiveness was evaluated in Korea.