Radioactive isotope used for age dating
Radioactive isotope used for age dating - updating 2016 arctic cat m7
The two most important chains providing nuclides of significance in NORM are the thorium series and the uranium series: Another major source of terrestrial NORM is potassium 40 (K-40).The long half-life of K-40 (1.25 billion years) means that it still exists in measurable quantities today.
Since most cosmic radiation is deflected by the Earth’s magnetic field or absorbed by the atmosphere, very little reaches the Earth’s surface and cosmogenic radionuclides contribute more to dose at low altitudes than cosmic rays as such.
Terrestrial NORM consists of radioactive material that comes out of the Earth’s crust and mantle, and where human activity results in increased radiological exposure.
The materials may be original (such as uranium and thorium) or decay products thereof, forming part of characteristic decay chain series, or potassium-40.
Excluding uranium mining and all associated fuel cycle activities, industries known to have NORM issues include: Another NORM issue relates to radon exposure in homes, particularly those built on granitic ground.
Occupational health issues include the exposure of flight crew to higher levels of cosmic radiation, the exposure of tour guides to radon in caves, exposure of miners to radon underground, and exposure of workers in the oil & gas and mineral sands industries to elevated radiation levels in the materials they handle.
By contrast, terrestrial NORM – especially radon – contributes to the majority of natural dose, usually over 1000 microsieverts (1 m Sv) per year.
Some of the main comsogenic nuclides are shown in Table 1, carbon-14 being important for dating early human activities.For most human activities involving minerals and raw materials, the levels of exposure to these radionuclides are not significantly greater than normal background levels and are not of concern for radiation protection.However, certain work activities can give rise to significantly enhanced exposures that may need to be controlled by regulation.It beta decays, mostly to calcium-40, and forms 0.012% of natural potassium which is otherwise made up of stable K-39 and K-41.Potassium is the seventh most abundant element in the Earth’s crust, and K-40 averages 850 Bq/kg there.All minerals and raw materials contain radionuclides of natural origin.