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方法采用塑料闪烁晶体β低本底测量装置直接测定了高放废液样品40 keV以上β射线的总β放射性活度。装置的β效率曲线采用与被测样品相同质量厚度、不同β能量的一系列标准源刻度。样品测量的β放射性对装置的总β效率是根据各个样品的放射性核素组成、各核素β射线能量对应于β效率曲线值以及各核素β放射性活度占样品总β放射性活度的比例加权平均计算求得。在测定样品各核素β放射性活度占总β放射性活度的比例时,方法对具有γ衰变的核素采用直接γ能谱法;对纯β衰变核~(90)Sr-~(90)Y,采用了半衰期近似法;对纯β衰变核~(147)Pm,采用了表观冷却时间近似替代法对高放废液样品测量的不确定度约为±15%。测量结果与化学分离各核素测得的结果在误差范围内符合。
Methods The total β radioactivity of β-rays above 40 keV in high-level liquid waste samples was directly determined by using a plastic low-background β measuring apparatus with scintillation crystal. The beta efficiency curve of the device uses a series of standard source calibrations with the same mass thickness and different beta energies as the measured sample. The total β efficiency of the β-radioactivity measured on the sample is based on the radionuclide composition of each sample. The β-ray energy of each nuclide corresponds to the value of the β-efficiency curve and the ratio of the β-radioactivity of each nuclide to the total β-radioactivity of the sample Weighted average calculated. In the determination of the ratio of radioactive activity of each nuclide in the sample to the total beta activity, direct gamma spectrometry was used for the nuclides with gamma decay. The effect of pure beta decay nuclear ~ (90) Sr- ~ (90) Y, the half-life approximation method was adopted. The uncertainty of the measurement of high-level liquid waste samples was approximately ± 15% for the pure β-decay nuclear ~ (147) Pm using the approximate cooling time approximation method. The results of the measurement and the chemical separation of the nuclides are within the error range.