Study on rapid measurement methods for clearance of nuclear ventilation filter frame

The metal frames of waste filters from the ventilation system are the main source of radioactive solid waste in nuclear power plants. Due to the slight radioactive contamination of waste filter metal frames from ventilation systems in nuclear power plants, some nuclear power plants have studied clearance and recycling technologies for waste filter metal frames through methods of laboratory measurement. Focusing on the problems existing in the clearance measurement of traditional methods, such as complex sampling of the metal frame of the filter, difficulty in guaranteeing the representativeness of the sampling, and cumbersome analysis and measurement process. This work designs two kinds of on-site rapid monitoring equipment for the metal frames of waste filters based on the plastic scintillator detector and high-purity germanium detector, which can achieve the purpose of non-destructive and rapid measurement of the whole filter frame. It solves the problems of traditional measurement methods and is more suitable for the recycling of filter metal frames from the ventilation system. The calculation models of the plastic scintillation detector and the high-purity germanium detector used in the monitoring equipment are verified by the comparison between experimental measurement and Monte Carlo simulation. Based on the confirmed detector model, the key parameters such as detection efficiency, background, and Minimum detectable activity (MDA) of the two-monitoring equipment are simulated and analyzed. The results show that the MDA of the two-monitoring equipment developed in this work is one to two orders below the clearance level for the common gamma nuclides that could be present in the filter metal frames. The research results can provide technical references for nuclear power plants to further encourage the minimization of radioactive solid waste.