BERTHOLD TECHNOLOGIES LB4710-080 - 11.4 Activity-based Calculation

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 * Sv0.35 * 350Mbq
= 

D
Gamma ray constant
Calculation example:
Dose D =
A * k * t
r² * s