Radioactive material, naturally occurring exposure

It is widely accepted by the scientific community that the risk of negative effects occurs on the health of workers as a result of their exposure to low doses of ionizing radiation. Sometimes this exposure results from the proximity or handling radioactive materials that occur naturally in the environment. It is therefore of utmost importance to identify these radioactive materials, assess their danger to exposed workers and to take measures to protect them against this exposure. 

This very long half-life (1.25x1(r years) isotope comprises 0.0117 percent of all potassium. Thus, this isotope is present in all of us and has always been so. In addition, the materials around us, including the soil and the building materials, contain both potassium and the heavy naturally occurring radioactive elements thorium and uranium that contribute to a level of radiation to which we are all continuously exposed. Thus, there is always radiation exposure to the general public and we must understand the exposure due to radon in this context. The amount of radioactivity is described in units of activity. The activity is the number of decay events per unit time and is calculated as follows... 

NAS/NRC (1999a). National Academy of Sciences/National Research Council. Evaluation of Guidelines for Exposures to Technologically Enhanced Naturally Occurring Radioactive Materials (National Academy Press, Washington). 

Small quantities of radioactive materials occur naturally in the air we breathe, the water we drink, the food we eat, and even in our own bodies. Radiation that goes inside our bodies causes what we refer to as internal exposure. 

External exposure is from radiation from sources outside our body, such as radiation from sunlight and man-made and naturally occurring radioactive materials. 

Naturally occurring radioactive materials A method for assessing the risk of exposure... 

Birky, B.K., Tolaymat, T., Warren, B.C. (1998). Evaluation of Exposure to Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) in the Phosphate Industry. Florida, USA Florida Institute of Phosphate Research. 

Occupational exposure due to radioactive materials ean oeeur as a result of various human activities. These include woik associated with the different stages of the nuclear fuel cycle, the use of radioactive sourees in medicine, scientific researeh, agriculture and industry, and occupations which involve the handling of materials containing enhanced concentrations of naturally occurring radionuclides, fir order to control this expostrre, it is necessary to be able to assess the magrritude of the doses involved. 

One feature of reprocessing plants which poses potential risks of a different nature from those ia a power plant is the need to handle highly radioactive and fissionable material ia Hquid form. This is necessary to carry out the chemical separations process. The Hquid materials and the equipment with which it comes ia contact need to be surrounded by 1.5—1.8-m thick high density concrete shielding and enclosures to protect the workers both from direct radiation exposure and from inhalation of airborne radioisotopes. Rigid controls must also be provided to assure that an iaadvertent criticahty does not occur. 

Recently there has been interest in the sorptive behavior of natural clays toward metal ions potentially present in radioactive wastes. Initial studies of the transplutonium elements have been carried out to define their sorption behavior with such materials ( ). However, it is also important to understand the stability of the clay-actinide product with regard to radiation damage and to be able to predict what changes in behavior may occur after exposure to radiation, so that accurate transport models may be constructed. 

Radon (Rn-222) is an odorless and colorless natural radioactive gas. It is produced during the radioactive decay of radium-226, itself a decay product of uranium-238 found in many types of crustal materials, that is, rocks and soils. Rn-222 has a short half-life (3.8 days) and decays into a series of solid particulate products, known as radon progeny or radon daughters, all of which have even shorter half-lives ( 30 min or less). Other isotopes of radon also occur naturally, but due to differences in half-life and dosimetry their health significance is minimal compared to that from exposure to Rn-222. 

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