制备放射性标准物质用SiO2基质中放射性核素比活度的测定

摘要

The lower limit of activity detection as low as mBq is used to measure SiO2,which is commonly used in the preparation of radioactive reference materials.The detection efficiency of the spectrometer system was calibrated with the standard source,and the specific activity of the natural radionuclide contained in the sample was determined by selfabsorption and coincidence summing correction as well as the evaluation of uncertainty.The measuring results show that on the condition of the measuring time is up to 559200s and the uncertainty of specific activity of the natural radionuclide lower than 10％ (k=2),the specific activity of SiO2 in uranium series,thorium series and actinium series is under 10 Bq/kg individually.The specific activity of radionuclide K-40 is 27.3 Bq/kg,which shows that the effect of the content of radionuclide in the matrix needs to be taken into consideration when preparing standard materials with low specific activity.%应用活度探测下限低至mBq/kg量级的γ谱仪,对放射性标准物质制备常用的基质SiO2进行分析测量.用标准源校准了谱仪系统的探测效率,通过自吸收和符合相加修正最终确定了所测样品中的天然放射性核素比活度,在测量时间达到559 200 s,天然放射性核素比活度分析结果不确定度低于10％(k=2)的情况下,所测SiO2样品中铀系、钍系、锕系核素的比活度均低于10 Bq/kg,核素K-40的比活度为27.3 Bq/kg,由此表明,在研制低比活度标准物质时,基质材料中的放射性核素含量影响需要纳入考虑.