食品放射性测量中马林杯干样与圆柱盒灰样探测限比较研究

摘要

目的：加强食品放射性监测中样品制备和测量方法学研究，建立快捷的预处理方法。方法：将圆柱盒灰样改为马林杯干样，采用低本底γ能谱仪测量蔬菜、大米、牛肉及海产品等10类食品样品中的放射性核素，采用无源效率刻度(LabSOCS)与有源刻度验证结合法，计算马林杯样品对应的效率。将分析得到的最小可探测浓度(MDC)值与圆柱盒灰样比较。结果：与圆柱盒灰样对应的灰化法相比，样品的预处理时间由7 d左右缩短至1～3 d，可以自动低温烘干完成且不产生明火和烟雾，测量72 h，对137Cs的MDC范围为0.02～0.180 Bq/kg。结论：采用马林杯干样可极大缩短样品预处理时间，而对应的MDC与圆柱型灰样在同一量级范围内，能满足监测精度要求。%Objective:To improve methods of sample preparation and radioactivity monitoring of food, and to establish fast method of sample pretreatment and radioactivity analyses.Methods: By changing the method of cylindrical backer filled with ash samples to Marinelli backer filled with powder samples, radionuclides in ten kinds of food samples, such as in spinach, carrots, beef, rice, tea, dried small shrimps, prawns, milk powder, seaweed and mushrooms, were analyzed by using gamma spectrometry. The minimum detectable concentration (MDC) obtained by the method were compared with that of cylindrical backer filled with ash samples.Results: Compared with that method of cylindrical backer filled with ash samples, pretreatment time for sample in this work can be shortened from seven days to one or three days under condition of automatically low-temperature drying, which also do not emit smoke or have flame, the MDC of the present methods are in the range of 0.02-0.180 Bq/kg for the137Cs if measure it for 72 hours.Conclusion: The time for sample pretreatment can be greatly shortened after use method of Marinelli backer filled with powder samples, and the corresponding MDC can be kept in the same order of magnitude with that method of using cylindrical backer filled with ash samples, so it can meet the requirements of monitoring.