食品样品中低水平^(137)Cs活度浓度测量的两种方法比较

Comparison of two methods for determination of low level^(137)Cs activity concentration in food sample

目的比较食品中^(137)Cs的γ能谱分析法和放射化学分析法,并探讨两种方法的适用性。方法采用γ能谱分析方法和放射化学分析方法(磷钼酸铵分离-β计数法)测量不同类型食品中的^(137)Cs,比较两种方法所需样品量、预处理制样过程以及测量探测下限,并以肉类样品为例,对比两种方法测量肉类样品中^(137)Cs的活度浓度及不确定度评估。结果能谱分析法与磷钼酸铵分离-β计数法的测量结果一致,两种方法测量肉类样品的相对扩展不确定度分别是18.0%和8.0%,γ能谱分析法样品制备简单,但样品用量大预处理过程耗时,磷钼酸铵分离-β计数法的样品用量小,但需要分离纯化过程,两种方法的探测下限分别是10.6 mBq/kg(样品质量11.7 kg)和5.1 mBq/kg(样品质量2.1 kg)。结论两种方法测量食品中低水平^(137)Cs结果一致,适用于食品中^(137)Cs的监测。

Objective To study the applicability of conventional detection method,gamma spectrometry and radiochemical analysis,for the determination of^(137)Cs activity concentratons in food samples and to compare the difference of such two methods for this purpose.Methods By using bothγspectrometry and radiochemical analysis,the activity concentrations of^(137)Cs in different types of food were determined,to compare the required sample amounts,the sample pretreatment and preparation processes and the lower detection limits.With meat samples as a case study,the two method were compared for assessing the activity concentrations of^(137)Cs in meat samples and evaluating the uncertainties.Results The deviation of measurement result obtained in meat by using gamma spectrometry and ammonium phosphomolybdate⁃βcounting method is consistent,with relative extended uncertainties of 18.0%and 8.0%,respectively.The pretreatment process forγspectrometry is characterized by its simplicity,but large sample amount required and time⁃comsuming process,while the ammonium phosphomolybdate method requires a small amount of sample but in need of separation and purification process.The detection limits of the two methods are 10.6 mBq/kg(sample mass 11.7 kg)and 5.1 mBq/kg(sample sample 2.1 kg),respectively.Conclusions The results of two methods for determinationf of the low activity concentrations of^(137)Cs in food samples are consistent.Therefore,when monitoring low activity concentrations of^(137)Cs in food samples,the appropriate detection method can be selected based on the specific objective and requirements of the monitoring study.