Management of Commercially Generated Radioactive Waste - U.S. ...

3.26
3.3 NATURALLY OCCURRING RADIATION AND STANDARDS FOR EXPOSURE TO MAN-MADE RADIATION
Although public awareness regarding radiation has grown markedly in recent years, many
readers may not be aware of all of the kinds and quantitites of naturally occurring radia-
tion around them. Because of this and because naturally occurring radiation can often be
used as a meaningful perspective for evaluating radiation exposure from other sources, a
summary of radiation from naturally occurring sources is provided.
To protect workers and the public from excessive exposure to man-made radiation sources
and yet realize the benefit from the use of these radiation sources, standards or limits of
exposure for various circumstances have been established by several authoritative bodies.
Exposures up to these standards are believed not to result in undue risk to the individual.
Regardless, the practice of keeping exposures as low as reasonably achievable is fundamental
in the radiation protection field. As a consequence, in many facilities the average expo-
sure is not more than one-tenth of the occupational standard. Because of the importance of
standards in the control of radiation exposure, a summary of presently applicable standards
is also presented.
3.3.1 Natural Radioactivity and Radiation Dose(a)
Depending on their activities and location, people are exposed in varying degrees to
several sources of ionizing radiation found in nature. Cosmic radiation entering the
earth's atmosphere and crust is one natural source of exposure. Also, nuclear interactions
of cosmic rays with matter produce radiation and radionuclides to which'people are exposed.
Other sources exposing people to radiation are naturally occurring radioelements in the
earth's crust.
Natural radioactivity includes all ionizing radiations and radionuclides except those
that have been produced by man's activities, such as that produced by nuclear weapons, bom-
bardment of targets by ion accelerator beams, in nuclear reactors, and from medical and
dental x-rays. Sometimes a distinction is made between natural radioactivity in an unmined
uranium ore body and "enhanced radioactivity" in mine or mill tailings, for example, radio-
activity left on the earth's surface.
The following discussion of dose(b) and dose rate to the U.S. population from
natural radioactivity is presented as perspective for dose estimates associated with man-
agement of commercial radioactive wastes in the LWR fuel cycles. No contention is made
that exposure to natural radioactivity is or is not harmful. However, when doses associ-
ated with waste management are small fractions of natural background dose, such doses
would probably be viewed as insignificant.
(a) The discussion of natural radioactivity was taken largely from Natural Background
Radiation in the United States, NCRP Report No. 45, Washington, DC, 1975.
(b) Throughout this Statement, the term "dose" may generally be taken to mean the more
rigorous term "dose-equivalent." The latter; expressed in units of rem or millirem
(one one-thousandth of a rem), implies a consistent basis for estimates of consequential
health risk, regardless of rate, quantity, source, or quality of the radiation
exposure. Unless otherwise specified, dose is that for the whole body.