D
–
2
R
R
a
a
d
d
i
i
a
a
t
t
i
i
o
o
n
n
T
T
h
h
e
e
o
o
r
r
y
y
A more detailed discussion of radiological theory can be found
in the
Troxler Nuclear Gauge Safety Training Program
manual,
provided at the Troxler Safety Class.
Atomic Structure
All matter is made up of atoms. For example, water has two
atoms of hydrogen (H) and one atom of oxygen (O), which in
chemical notation is written
H
2
O
.
An atom is made up of a dense nucleus, consisting of positively
charged protons and uncharged neutrons, surrounded by a
cloud of negatively charged electrons. Under normal
circumstances, the number of electrons in an atom equals the
number of protons. The number of protons in the atom is called
the
atomic number
(Z). A chemical element consists of all atoms
having the same atomic number.
The number of protons plus neutrons in the nucleus is called the
atomic mass
(A). Atoms of a given chemical element can exist in
slightly different variants called
isotopes
that have different
atomic masses. For example, carbon-12 (C-12) is non-
radioactive and carbon-14 (C-14) is radioactive. Isotopes that
are radioactive are termed radioisotopes or radionuclides.
Figure 14 depicts a helium atom consisting of two protons and
two neutrons in the nucleus and two orbiting electrons.
ELECTRONS
NEUTRON
PROTON
Figure 14. Diagram of an Atom
Summary of Contents for RoadReader 3430
Page 14: ...1 6 Figure 1 Model 3440 Gauge and Accessories...
Page 19: ...Model 3440 2 3 Figure 2 Direct Transmission Geometry Figure 3 Backscatter Geometry...
Page 20: ...2 4 Figure 4 Backscatter Surface Density Effects Top Layer Effect Curves...
Page 22: ...2 6 Figure 5 Effect of Moisture on Depth of Measurement...
Page 164: ...F 2 STANDARD COUNT LOG Gauge Serial Number _____________ Date MS DS Date MS DS...
