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Tritium in Water: Hydrology and Health Implications

Tritium is a radioactive isotope of hydrogen with a physical half-life of 4500±8 days that behaves like stable hydrogen and is usually found attached to molecules replacing hydrogen. This radioactive isotope is directly incorporated into the water molecule (H3HO or HTO) and therefore it can be detected in all waters. This radionuclide occurs in nature, originating from natural and anthropogenic sources. Natural tritium is produced in the atmosphere from the interaction of cosmic radiation with atmospheric nitrogen. Anthropogenic production has disturbed the natural levels of tritium by nuclear weapons tests and, in addition to that tritium is being released into the atmosphere through weapons manufacturing, the operation of nuclear power plants (NPP) and reprocessing of nuclear fuels. The average natural concentration of tritium in environmental waters has been estimated to range from 0.12 Bql-1 to 0.9 Bql-1. The stable isotopes oxygen-18 (δ18O) and deuterium (δ2H) and the radioactive isotope tritium (3H) are rare components of the water molecule. Knowing the isotopic composition (δ18O, δ2H, and 3H activity) in surface and groundwater have found wide application in hydrology, such as determination of mean residence time of water in aquifers, the determination of recharge areas, the interconnections between aquifers and the origin of groundwater. The IAEA Global Network of Isotopes in Precipitation (GNIP) consists of data on isotopic composition of the mentioned isotopes with the aim to determine temporal and spatial variations of those isotopes in precipitations. Tritium is an important tool not only in isotope hydrology (studies of the origin and dynamics of surface and groundwaters), but also in studies related to atmospheric circulation and paleoclimatic investigations. Although occurring naturally on Earth, significant amounts of tritium are also generated through human activity. NPPs routinely and accidentally release tritium into the air and water. No economically feasible technology exists to filter tritium from gaseous and liquid emissions from a nuclear power plant into the environment. Routine releases and accidental spills of tritium from nuclear power plants are a growing concern for public health and safety. Most of the tritium that is released from NPP goes to surface waters which raises a concern that tritium can enter into drinking water in wells. As NPPs are usually located on rivers and/or lakes this issue is exceptionally important. Concerning the relative biological effectiveness (RBE) of tritium and therefore health implications that may arise, international and national regulations require the constant control in releasing tritium from NPPs into the environment, especially into natural waters by constant monitoring of the activity concentrations of tritium in surface waters. This chapter will present importance of tritium measurement in water (precipitation, surface, and groundwater) from the application point of view and also as a health concern.

tritium ; water ; hydrology ; precipitation ; groundwater ; surface water ; health implications

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