Sources of Radiation (EO1) - hdbk1131-98reaffirm0086

DOE-HDBK-1131-98

General Employee Radiological Training

Student's Guide

B. Sources of Radiation (EO1)

People have always been exposed to radiation. Radiation, simply defined, is

energy emitted through space and matter. We are exposed to radiation from

naturally-occurring sources in our environment, man-made sources, and even

from materials inside our bodies.

The average annual radiation dose to a member of the general population

is about 360 millirem/year. This amount is a combination of both natural

background and man-made sources of radiation.

1. Natural background sources of radiation

Natural background radiation is by far the largest contributor (about 300

millirem/year) to radiation doses. The main sources of natural background

radiation are listed below:

a. Cosmic radiation - radiation from the sun and outer space, varies with

altitude, (e.g., Denver would be higher than Miami).

b. Radon - (the principal source of background radiation exposure.) A

gas from naturally-occurring uranium in the soil.

Terrestrial radiation from naturally-occurring radioactive material found

in the earth's crust , such as uranium found in rocks and soil.

d. Materials present in our bodies. These come from naturally-occurring

radioactive material present in our food, such as Potassium -4 0 .