BERTHOLD TECHNOLOGIES LB4710-050, User Manual

Page: 102 / 227

Chapter 11 Radiation Protection
Mini-Switch LB 471
102
11.4
Activity-based Calculation
The exact calculation of the radiation exposure to be expected for
a
shielded source is carried out using the following equation:
A source activity
k specific radiation constant
r distance between measuring point and source
T duration of stay
s attenuation factor of shielding
see technical data on page
108 .
When working with an unshielded source; s is set equal to 1 for
calculation of the dose rate.
Nuclide k Dimensions
Co-60 0.35 µSv*m 2
h*MBq
Cs-137 0.09
The dose in a distance of 50 cm of a Co-60-source with a activity
of 350 MBq and a time span of 30 min. has to be calculated. The
source is installed in a shielding with a shielding factor of 30:
Sv 8.2 =
30 * Mbq * h * (0.5m)²
0.5h * m² * Sv 0.35 * 350Mbq
=


D
Gamma ray constant
Calculation example:
Dose D =
A * k * t
r² * s