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 Lab SOCS 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 ²²⁸ Ra were detected in some samples. Conclusion: The source-less calibration technique based on Lab SOCS 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'. (authors)