Radon in water measurements by sampling with sunflower oil

A novel method for measuring radon in water is proposed. This method involves sampling radon from water into sunflower oil and subsequently measuring the radon in the oil using either Cherenkov counting or Liquid Scintillation (LS) counting. The high partition coefficient of radon between oil and water enables radon preconcentration in the oil, significantly improving the Minimum Detectable Activity Concentration (MDAC) compared to direct Cherenkov or LS measurements in water. The estimated MDACs for the method are 0.20 Bq/l using Cherenkov counting and 0.04 Bq/l using gross alpha/beta LS counting. The MDAC achieved with Cherenkov counting allows for radon-in-water measurements for the purposes of radiation protection, ecology, hydrology, and earth sciences without requiring LS cocktails. The MDAC for LS counting facilitates radium-in-water measurements (via radon measurement) for radiation protection without chemical pretreatment of the water sample. Additionally, the method enables direct estimation of the radon partition coefficient between water and oils. The partition coefficient of radon between sunflower oil and water at 20 °C is estimated at K_oil/w = 23.2(16).