An effective method for the determination of ¹⁰⁶Ru in seawater by γ-spectrometry

¹⁰⁶Ru is a product originating from the fission reactions of uranium (²³⁵U) and plutonium (²³⁹Pu). ¹⁰⁶Ru represents a potential source of radioactive marine contamination since it makes up 70-90% of the total radioactivity of liquid effluents from fuel reprocessing plants; thus, it is important to effectively determine the quantity of ¹⁰⁶Ru in the natural environment. In this study, a simple and effective method was developed for the determination of ¹⁰⁶Ru in seawater by γ-spectrometry using NiS coprecipitation. In addition, the amounts of S^2- and Ni²⁺ added, Ru³⁺ carrier addition, pH, salinity, and sample volume were tested, and accordingly, optimal conditions were proposed. With the optimized conditions, the recovery of ¹⁰⁶Ru in seawater ranged from 85.3% to 92.3%, with an average of 88.1 ± 4.2%. The method proposed in the present study can also be applied to seawater samples with various salinities and volumes. For 20 L seawater and 24 h counting time on a γ-spectrometer, the limit of detection for ¹⁰⁶Ru in seawater was 5.74 mBq/L. In contrast to the traditional CoS method, the usage of NiS does not require any heating process; thus, the pretreatment time is substantially reduced. In addition, by using our method, ¹⁰⁶Ru can be determined in the presence of other radionuclides, further enhancing processing efficiency.