Measurements of ¹²⁹I in a nuclear power reactor by accelerator mass spectrometry

The method of accelerator mass spectrometry is applied to measurements of concentrations of the long-lived volatile fission product ¹²⁹I (t _{1 2} = 1.6 × 10⁷ a) in the primary heat transport (PHT) system and irradiated fuel bay (IFB) of a commercial nuclear power reactor. Concentrations of (8.1 ± 1.1) × 10^{12 129}I atoms per gram and between 10¹¹ and 10^{13 129}I atoms/L were measured in an ion-exchange resin and in the heavy water (PHT) system, respectively. The corresponding value for the IFB system water samples was 5-6 × 10^{12 129}I atoms/L. These measurements, based on very small size samples (of the order of 0.5 mL) emphasize the advantage of the present method where a simple chemical process for the iodine extraction enables a direct measurement of the ¹²⁹I atom content of the samples. In view of the physical and chemical properties of iodine and their important implications in the environment, the method is likely to find even wider applications for the monitoring of ¹²⁹I and the study of long-range nuclear waste storage.