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氡-220体积活度参考标准是氡-220测量装置刻度校准的基本要件。国内急需建立一个特性良好的氡-220体积活度参考标准。用存放40年以上的硝酸钍通过离子交换法制备钍射气源;设计制作温湿度及气流可调控的内源式钍射气室,保证稳定性与均匀性;通过更换不同232Th活度的钍射气源来调节钍射气室内220Rn的体积活度水平;研制闪烁室探测器测量装置,以模拟计算和国际比对刻度结果确定其探测效率;钍射气室内220Rn的体积活度值经闪烁室探测器定值,作为氡-220体积活度参考标准。实验结果显示,该参考标准的短时间稳定性(2天以上)与长时间稳定性(约半年)均很好;其空间不均匀程度不超过5.5%;其活度浓度在500–20 000 Bq·m-3范围内可逐级调节;闪烁室探测器刻度系数为53.02 Bq·m-3·min。该研究建立了一个体积活度量值准确、稳定、均匀,浓度可调的氡-220体积活度参考标准,可用于氡-220测量装置的刻度与校准。
The Radon-220 Volume Activity Reference Standard is a basic element for calibration of Radon-220 measurement devices. Domestic urgent need to establish a good radon-220 volume activity reference standard. Thorium gas source prepared by ion exchange method with thorium nitrate stored for more than 40 years; design and manufacture endogenous thoron gas chamber with temperature, humidity and gas flow regulation, to ensure stability and uniformity; by changing thorium activity with different 232Th activity, A gas source to regulate the volume activity level of 220Rn in a radon chamber; a measuring device for a scintillation chamber detector was developed to determine its detection efficiency based on simulation calculation and international comparison calibration results; the volume activity value of 220Rn in the thoron chamber was blinking Room detector settings, as radon-220 volumetric activity reference standard. The experimental results show that the short-term stability (more than two days) and long-term stability (about six months) of the reference standard are very good; the spatial heterogeneity does not exceed 5.5%; the activity concentration is between 500 and 20 000 Bq · Within the range of m-3 can be adjusted step by step; Scintillation chamber detector scale factor is 53.02 Bq · m-3 · min. The study established an accurate, stable, uniform and adjustable reference volume of radon-220 volumetric activity, which can be used for calibration and calibration of radon-220 measurement devices.