J Korean Soc Environ Eng. 2016; 38(1): 42-46.
Published online 2016 January 31.
A Case Study about Counting Uncertainty of Radioactive Iodine (131I) in Public Waters by Using Gamma Spectrometry
Geum River Environment Research Center, National Institute of Environmental Research
Received 2015 October 05; Accepted 2016 January 25.
ABSTRACT
The radioactive iodine (131I) presents in the environment through the excrete process of nuclear medicine patients. In the detecting of low level of 131I in the public water, the counting uncertainty has an effect on the accuracy and reliability of detecting 131I radioactivity concentration. In this study, the contribution of sample amount, radioactivity concentration and counting time to the uncertainty was investigated in the case of public water sample. Sampling points are public water and the effluents of a sewage treatment plant at Sapkyocheon stream, Geumgang river. In each point, 1, 10 and 20 L of liquid samples were collected and prepared by evaporation method. The HPGe (High Purity Germanium) detector was used to detect and analyze emitted gamma-ray from samples. The radioactivity concentration of 131I were in the range of 0.03 to 1.8 Bq/L. The comparison of the counting uncertainty of the sample amount, 1 L sample is unable to verify the existence of the 131I under 0.5 Bq/L radioactivity concentration. Considering the short half-life of 131I (8.03 days), a method for measuring 1 L sample was used. However comparing the detecting and preparing time of 1, 10 L respectively, detecting 10 L sample would be an appropriate method to distinguish 131I concentration in the public water.
Keywords :
Radioactive Iodine (131I), Counting Uncertainty, Environmental Radiation, Gamma Spectrometry
