Berthold LB 444 - Instrument Description

Density Meter LB 444 SECTION 2. SYSTEM DESCRIPTION
7
2.4 Instrument Description
Radioactive Source
Radioactive sources for industrial applications are always „encapsulated radio-
active substances“ which are tightly welded into a sturdy stainless steel capsule,
so that the radioactive substance cannot leak out. Contamination is therefore not
possible. Moreover activation of the product being measured by the source used
is also not possible. (Laws of Physics).
The following point-shaped Gamma sources can be used for these measuring
configurations.
241
Am,
60
Co,
137
Cs,
244
Cm,
85
Kr,
90
Sr.
The following isotopes are primarily used for density measurements:
a)
60
Co
has a relatively high energy of 1.17 and 1.33 MeV, respectively. It is
used for density measurements when measuring distances are very long
and/or the radiation has to pass through very thick pipe or vessel walls. Its
half-life period is 5.27 years.
b)
137
Cs
is the isotope most frequently used for density measurements. Its
energy of 0.660 MeV is sufficient to penetrate commonly used pipe and
container walls. Due to the lower energy, the measuring effect is better
than with Co-60. Also, the shielding costs for a Cs-137 source are lower
than for a Co-60 source. The half-life period of Cs-137 is approx. 30
years.
*
*
According to NBS, half-life is defined as “Time for the activity of any particular
radioisotope to be reduced to half its initial value”.
Please note the Radiation Protection Guidelines in Section 9.