InstroTek
55
Man
- Weapons testing fallout
- Medical X-rays
- Nuclear Moisture/
Density Gauge
- 4 mRem
- 9-210 mRem
- 25 mRem/yr.
Fig 5.1 Natural Radiation and Annual Dose
Typical yearly totals are 123 mRem for someone living alone in a
wood house in San Francisco, and whom does not; fly, get sick,
or watch television, and 272 mRem for someone living in a
stone house in Denver, flying coast to coast 10 times per year,
watching television 4 hours per day, and getting one dental X-
ray (20 mRem).
There is no evidence to suggest that people living in regions of
higher natural radiation have poorer health as a result. Some of
the longest living people in the world live in high mountain
regions. (In areas of Brazil and India the natural radiation is ten
times greater than the average in other parts of the world).
The exposure limit set by the United States Radiation Protection
Authorities is 5000 mRem per year for radiation workers.
ALARA
A
s
L
ow
A
s is
R
easonably
A
chievable considering social and
economic matters.
No matter what the allowable legal limits are, the operator and
his company should review their procedures to determine if with
reasonable steps the dose could be reduced. This should be
taken considering all aspects, e.g. one could design a
density/moisture gauge with sufficient shielding that little or no
