BERTHOLD TECHNOLOGIES LB 480 - Page 117

SENSseries LB 480 Level measurement
BERTHOLD TECHNOLOGIES GmbH & Co. KG
1 – 117
Volume 1 9 Radiation Protection
1
9.2.3 Radiation Dose Calculations
When preparing work on radiometric measuring systems, it is
important to pre-calculate the radiation exposure to be expected,
since this has consequences on the required safety precautions.
The expected radiation exposure can be calculated quite easily and
with sufficient accuracy, provided you know the isotope and the
activity of the source used. You can take this information from the
source documentation, or from the type label on the shielding.
The radiation exposure to be expected for a shielded source is cal-
culated as follows:
A is the activity of the source and k the respective specific Gamma
radiation constant (see table below). The distance from the measur-
ing point to the source is r and the duration of stay at this point is
T. s is the shielding factor of the shielding used, which is indicated
on the information sheet of the shielding or which can be calculated.
It is listed in the shielding brochure or can be calculated. s = 1 when
calculating the dose rate for work with an unshielded source.
Calculation example Calculate the dose in a distance of 50 cm from a Co-60 source with
an activity of 350 MBq and a time of 30 minutes. The source is
installed in a shielding with a shielding factor of 30:
Nuclide k Dimensions
Co-60
0.35
Cs-137
0.09
Dose D =
A x k x T
r
2
x s
µSv x m
2
h x MBq
Dose D =
350MBq x 0.35µSv x m
2
x 0.5h
(0.5m)
2
x h x MBq x 30
= 8.2µSv