Concentrations of Natural Radionuclides in Drinking Water in Israel

Naturally occurring radioactive material migrates from uranium and thorium present in the Earth`s crust to groundwater through geochemical processes. Uranium and thorium radionuclides and their decay progenies are therefore found in groundwater wells that provide drinking water. The concentration of radionuclides in those wells depends on several parameters, including the soil/rock type and the solubility of the radionuclides. The Israeli Ministry of Health adopted in its Drinking Water Quality Regulations limits of activity concentrations for natural radionuclides, based on a reference level of 0.1 mSv per year.

The regulations also state that the radioactivity in drinking water is to be periodically measured in order to prove compliance with the limits. The Laboratory for Radioactivity in Drinking Water (LRDW) of the Radiation Safety Division at Soreq Nuclear Research Center performs measurements of activity concentrations of natural radionuclides in all sources of drinking water in Israel. The LRDW is accredited for ISO-17025 by the Israel Laboratory Accreditation Authority (ISRAC) and follows standard methods for sample preparation and measurement [Book of Standard Methods]. For screening purposes, activity concentrations of gross alpha- and gross beta emitting radionuclides in water samples are measured by a proportional counter (Eurysis-Mesures Model IN20). The limits of activity concentrations of gross alpha- and gross beta emitting radionuclides are 0.2 Bq/l and 1.0 Bq/l, respectively. For samples exceeding those values, further analysis is required to determine the activity concentrations of the contributing radionuclides. A series of chemical processes is involved to extract and isolate specific radionuclides (e.g. radium radioisotopes). Their quantification in the sample extracts is performed by dedicated measuring techniques, e.g., High-Purity Germanium (HPGe) spectrometry, liquid scintillation counting and Inductively-Coupled-Plasma Mass-Spectrometry (ICP-MS).

Activity concentrations of natural radionuclides in selected wells in Israel will be presented and compared to those in several locations worldwide.