University:
California State University, Northridge
Course:
PHYS 376 | Radiologic Physics
Academic year:

2024
Views:

239

Pages:

1
Author:

foummafiodifeugh

RADIATION SOURCES NATURAL SOURCES (also called background levels) in the U.S. add up to about 100 mrems/year. Even without human activities, these sources would still be present. They include the following sub-categories. 1. Terrestrial sources include all land based sources. U.S. community levels range from about 15 to 100 mrem/year. Globally, levels can be as high as 2 rems/year (e.g., parts of Brazil). Various materials contribute radiation, including granite, coal (especially in the western U.S.), and clay (brick homes have typically twice the radiation of wood homes). The most serious radiation exposure from terrestrial sources is usually radon, because it is a gas (i.e., inhalation exposure). 2. Cosmic radiation (also called extra-terrestrial sources) originates from deep space, from such sources as our own sun (a minor contribution) and supernovas. Primary cosmic radiation is mostly protons, some electrons, and various atomic fragments. When these sources hit our atmosphere, their impact creates secondary cosmic radiation, composed of mostly gamma rays, electrons, mesons, and neutrinos. Cosmic radiation varies from 40-160 mrem/year depending on three major factors: 1. altitude (e.g., one plane flight cross country can contribute 1 mrem, and Denver has about twice the cosmic radiation of L.A); 2. latitude (cosmic radiation is attracted to our magnetic poles); and 3. air pressure (as pressure increases, cosmic radiation decreases at ground level). ARTIFICIAL SOURCES add up to about 80 mrem/year on average. 1. Medical procedures are the major source, with a single chest X-ray contributing an average 200 mrem. Dental x-rays are far less than chest x-rays. 2. Nuclear power plants contribute, on average, about 1 mrem/year. However, this is only for residents closest to the facility. Of course, this does not include other concerns such as nuclear accidents and nuclear waste disposal.

Radiation Sources

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