高放废液总β放射性活度测量

MEASUREMENT OF GROSS BETA RADIOACTIVITY IN HIGH-LEVEL LIQUID WASTE

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。

Using beta plastic scintillation counter of low level background, gross beta radlioactivity of twelve samples for high-level liquid waste is determined directly. Beta efficiency curves of plastic scintillation counter for four mass thickness are calibrated in advance. Determining gross beta radioactivity, gross efficiency of the scintillation counter for various energy beta ray is calculated via weighted mean method with the ratio of radioactivity for each nuclide. The ratio of radioactivity for nuclides which havc gamma disintegration is determined in terms of the radioactivity measured by gamma spectrometer. The ratio of the radioactivity for ^(90)Sr which has purity beta disintegration is calculated in terms of halflife lime approximation. The ratio of the radioactivity for ^(147)Pm which also has purity disintegration is calculated by means of apparent cooling-time approximation. The uncertainty of results for the present work is about ±15%.