Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 2019
An AMS method for measurement of Radium-226 in drinking water
Abstract
Abstract Radium-226 is a naturally occurring radionuclide resulting from the radioactive decay of 238U. The aquifers used for drinking water may contribute to the source of 226Ra in water supplies. To accommodate the needs of 226Ra assessments, we developed a new, rapid and sensitive method for measuring 226Ra in drinking waters utilizing Accelerator Mass Spectrometry (AMS). 226Ra was co-precipitated with BaBeF4, which is known for its insoluble attribute and high stability. Mixed with a large excess amount of PbF2 and compressed into a copper target holder, such sputter targets have adequate electrical and thermal conductivity in the Cs+ sputter ion source used in AMS. Due to the difficulty to obtain a suitable Ra isotope for measurement normalization, we performed an external calibration with 226Ra alone, covering the final co-precipitation and measurement steps. A good linearity was attained in the dilution series with an external error of 5%. The detection limit of this method was 3\u202ffg (∼0.1\u202fmBq) in an AMS-ready target at present, using a low Cs+ sputter ion flux that produced >0.02 226Ra3+ ion counts per second (CPS) per fg. With this BaBeF4 co-precipitation method, we performed a rapid survey of 226Ra concentration in local tap water and several bottled waters. The results suggested that the 226Ra concentrations in all the tested samples were less than the limit set by the Canadian water quality guidelines.