全膳食中放射性核素的γ能谱测量方法研究

目的 建立一套HP Geγ能谱仪测量全膳食中放射性核素活度浓度的方法。方法 利用"双份饭法"收集全膳食样品后,用BE 5030型宽能HP Geγ能谱仪进行测量。以大米粉标准源验证无源效率刻度的可靠性后,采用LabSOCS软件进行效率刻度,并计算样品中放射性核素的活度浓度和日均摄入量。结果 无源效率刻度验证结果在可接受范围内,所分析样品中均检测出了天然放射性核素²²⁶Ra和⁴⁰K,平均活度浓度分别为0.31和141 Bq/kg（干重）,日均摄入量分别为0.21和95 Bq/d;部分样品检出了²¹⁰Pb和²²⁸Ra;均未检出²³⁸U和人工放射性核素¹³⁷Cs。结论 基于LabSOCS软件的无源效率刻度方法能较好的模拟全膳食样品的探测效率,可以用于全膳食样品的效率刻度。样品中的所检测的放射性核素活度浓度均在国家标准限值内。解决全膳食样品不易混合均匀的制样方法以及"全膳食基质成分库"的建立有待进一步研究。

A study for measuring radionuclides in whole diet by gamma spectrometry

Objective Establishing a method for measuring the activity concentration of radionuclides in whole diet based on a broad-energy HPGe detector BE5030 model.Methods Whole diet samples were collected by "Dupllicate Portion Technique" and were measured by a broad-energy HPGe gamma spectrometer BE5030 model. The reliability of source-less efficiency calibration was verified by measuring a rice powder standard source with two different calibration methods. The efficiency calibration was carried out with LabSOCS software, and the activity concentration and daily intake of radionuclides in the samples were calculated.Results The results of source-less efficiency calibration were acceptable. Natural radionuclides ²²⁶Ra and ⁴⁰K were detected in all the samples, the average activity concentration were 0.31 and 141 Bq/kg (dry weight), and the average daily intake was 0.21 and 95 Bq/d, respectively. ²³⁸U and artificial radionuclide ¹³⁷Cs were not detected. ²¹⁰Pb and ²²⁸Ra were detected in some samples.Conclusion The source-less calibration technique based on LabSOCS software could better simulated the detection efficiency and could be used to calibrate the efficiency for whole diet samples. The activity concentration of all radionuclides detected were within the national standard limits. Further research remain to be done in order to homogenize whole diet samples better and establish a "whole diet element library".