Troxler 3411-B, Manual Of Operation And Instruction

Page: 83 / 109

Model 3400-B Series Appendix B-7
LIMITING EXPOSURE
Current regulations for both NRC and Agreement States have
established a whole body occupational exposure limit of 5,000
millirem per year. Under normal conditions a full time operator
of a 3400 series will receive less than 200 millirem per year.
Taking advantage of all available means to limit radiation
exposure is always recommended. The three methods of
limiting exposure are:
Time
Distance
Shielding
These methods are a part of an "
ALARA
" (
A
s
L
ow
A
s
R
easonably
A
chievable) program.
TIME
The simplest way to reduce exposure is to keep the time spent
around a radioactive source to a minimum. If time is cut in half,
so is the exposure, with all other factors remaining constant.
DISTANCE
Distance is another effective means to reduce radiation
exposure. A formula known as the "inverse square law" relates
the radiation exposure rate to distance (Figure 15). Doubling
the distance from a radiation source reduces the exposure to
one-fourth its original value. If the distance is tripled, the
exposure is reduced by a factor of nine, etc.