Measurement of 129I Level Around a Nuclear Power Plant by Accelerator Mass Spectrometer

¹²⁹I is a long-lived (15.7M year) radioisotope of iodine. It can be used as a tracer for monitoring nuclear proliferation and the ¹²⁹I/¹²⁷I ratio can be used to evaluate the radiation contamination level. Nowadays a great number of nuclear power plants will be built in China, but the data of ¹²⁹I concentration in environmental samples around nuclear power plants are limited. Accelerator Mass Spectrometer (AMS) whose detection limit is about 10⁻¹⁴, is one of the best instruments for analyzing environmental samples. The methods of making ¹²⁹I target samples for AMS measurement from different type samples were studied, and the processing system for water and soil samples were established. Six surface seawater samples were collected at different distance away from a nuclear power plant in China. These samples were measured by Xi’an AMS. The ratios of ¹²⁹I/¹²⁷I in the seawater samples are between 0.829 × 10⁻¹⁰ and 9.451 × 10⁻¹⁰, and the average value is about 3.518 × 10⁻¹⁰. The ratios of ¹²⁹I/¹²⁷I in these samples are compared with other measurement results under different circumstances in other parts of the world. The results show that this nuclear power plant has not released superfluous ¹²⁹I into environment after several years’ operation. Since the AMS and sample processing system are established, we will do much work on nuclear technology application with ¹²⁹I tracer.