Environmental Engineering Reference
In-Depth Information
for longer than our planet has existed and continually
bombard us. Its intensity depends on altitude, and at a
high altitude, in the city of Denver for example, it is more
than double that at sea level. The medical portion can be
higher or lower, but the number used here is typical for
the United States.
The second line in the table,
sur-
prises most people. Our bodies contain traces of the
elements potassium-
“
Natural in body,
”
is
very long-lived and, like uranium and thorium, has been
with us since the planet was formed. Carbon-
and carbon-
. Potassium-
is con-
tinually produced by the same cosmic rays that have been
bombarding everything since the beginning of time. The
radioactive forms of carbon and potassium are present in
trace amounts in the food we eat and the air we breathe.
Most of the
radiation dose comes from
the potassium in our bones. The annual dose listed in the
table is for a
“
natural in body
”
pound) person: the dose
is roughly proportional to body weight. If you sleep
in a double bed you will get a few extra mR from your
companion.
The comparison between natural radiation and a
properly operating nuclear plant
kilogram (
is striking. We get
times the radiation from natural sources than we
would from living next to a nuclear plant and
times
as much from material in our own bodies. Coal-
red
power plants generate about as much radiation as nuclear
plants from impurities in the coal. Radiation from a power
plant is not signi
cant compared with what we get all the
time from natural sources, and we should stop worrying
about it. The concern should be directed to reactor acci-
dents and their consequences.
