摘要目的:通过对γ能谱分析 226Ra的部分影响因素进行有针对性的测量，进一步优化γ能谱针对 226Ra活度的分析方法，以求得到更为精准的测量结果。 方法:利用实验室高纯锗γ能谱仪，开展样品密封时间的跟踪测量、铅室本底波动影响测量，分析方法与子体核素特征γ射线能峰选择等方面研究。结果:样品密封12 d后， 226Ra- 222Rn衰变系基本达到平衡。测量屏蔽铅室本底中 222Rn昼夜波动明显且无明显规律，向铅室内注入氮气的方式可降低或避免本底波动影响。针对31份密封23 d后测量的土壤样品，采用效率曲线法分析的结果表明，351.9 keV能峰计算的 226Ra结果普遍高于609.3 keV能峰，高出的比例范围为8.0%~20.7%；采用相对比较法分析的结果表明，两能峰偏差的比例范围为－4.1%~10.3%。 结论:在样品密封后第12天进行测量时，建议考虑由衰变系平衡因素引入约4%的不确定度。通过铅室内注入氮气避免本底波动时，须注意铅室内腔体积与氮气注入流量的匹配关系。采用效率曲线法分析 226Ra活度时， 214Bi(609.3 keV)能峰存在级联符合相加影响，应避免选用；采用相对比较法分析 226Ra活度时， 214Pb(351.9 keV)和 214Bi(609.3 keV)两个能峰均可采用。

abstractsObjective:To measure the influencing factors associated with the analysis of 226Ra gamma spectra in order to obtain more acurate and precise measuring result on a basis of further optimizing the gamma spectrometry method for 226Ra activity. Methods:A laboratory-based HPGe gamma spectrometer was used to carry out the studies on tracking measurement of sample sealing time, measurement of background fluctuation with lead shielding, analytical method, and selection of characteristic gamma ray energy peak of its daughter nuclides in 226Ra measurement. Results:After the sample was sealed for 12 d, the decay products of 226Ra- 222Rn basically reached equilibrium. The day and night fluctuations of 222Rn in the shielded lead room were obvious but had no obvious regularity. The way of filling nitrogen into the shielded lead room could reduce or avoid the influence of background fluctuations. For 31 soil samples measured after 23 days of sealing, the result of using the efficiency curve method showed that the 226Ra result calculated from the 351.9 keV energy peak were generally higher than the 609.3 keV energy peak, and the higher ratio ranged from 8.0% to 20.7%. The result of relative comparison method showed that the deviation ratio of the two peaks ranged from -4.1 % to 10.3 %. Conclusions:It is recommended to consider the uncertainty attributed from decay equilibrium about 4 % of measured at 12 d after the sample is sealed. When filling nitrogen through the shielded lead chamber to avoid background fluctuations, attention must be paid to the matching relationship between the volume of the lead chamber and the nitrogen filling flow. When the efficiency curve method is used to analyze the activity of 226Ra, the 214Bi ( 609.3 keV ) energy peak has the effect of cascade coincidence addition, so 214Bi(609.3 keV) energy peak should be avoided. When the relative comparison method is used to analyze the activity of 226Ra, both two energy peaks of 214Pb ( 351.9 keV ) and 214Bi ( 609.3 keV ) can be used.