Design and application of a large-volume sample cassette for nuclear radiation emergency monitoring
Objective To develop a large-volume sample cassette in the shape of a formalin cup suitable for portable HP-Ge γ spectrometer,to determine the detection limits of the cassette at different detection times through fresh sample measure-ments,and to provide a reference for responding to and monitoring of nuclear and radiation emergencies.Methods Ac-cording to the formula for calculation of detection limit described in the GB/T 16145-2022,131I and 137Cs were measured using the sourceless efficiency calibration software Angle and the portable HPGe γ spectrometer for the optimization of the large-volume sample cassette.Fresh salmon samples were measured using a formalin cup-shaped large-volume sample cas-sette.The detection times were 2,4,6,8,10,19,19,22,and 24 hours.The relationship between detection time and detection limit was assessed.Results Using sample cassettes with 15 cm radius and 10 L volume,the simulated detection efficiency of the formalin cup-shaped large-volume sample cassette was 30%-46%higher and the detection limit was lower as com-pared with the cake-shaped large-volume sample cassette.The detection limit obtained by measuring fresh salmon samples decreased with the extension of the detection time.These results provided a reference for the detection limits of measuring fresh samples for nuclides of concern in nuclear contaminated water with different detection times.Conclusion The form-alin cup-shaped large-volume sample cassette developed by combining the optimization of detection limit provides a geo-metry for quantitative analysis in on-site monitoring of γ nuclides in the case of emergencies.Measurement of fresh samples using the cassette with different detection times showed that 8-10 hours of detection was optimal in balancing the detection limit and the detection time.
Detection limitLarge-volume sample cassetteSourceless efficiency calibrationDetection time
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