Chapter 11 Radiation Protection
Mini-Switch LB 471
11.2 Radiation Dose Calculations
When preparing work on radiometric measuring systems, it is im-
portant to calculate the radiation exposure to be expected in ad-
vance, for this has consequences on the required safety precau-
tions. 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.
11.3 Calculation with a given Dose Rate
In general, the shieldings of measuring systems are designed such
that the limit of the controlled area runs in a given distance (in
most case less than one meter) around the shielding. A simplified
calculation of the radiation exposure during assembly of the shield-
ing is possible with sufficient accuracy by using the dose rate value
stated on the type label. This value states the dose rate measured
in 1 m distance from the shielding. The radiation exposure D can
then be calculated using the following formula:
D = DR * t * 4
D accumulated dose during assembly (µSv)
DR dose rate stated on the type label of the shielding (µSv/h)
t time needed for assembly (h)
4 safety factor
In case of exact preparation, one may expect a working time of
less than 20 minutes for carrying out work such as assembling the
shielding or operating the shutter.
DR: 3 µSv/h
t: 20 min (1/3 h)
D = 3 µSv/h * 1/3 h * 4 = 4 µSv
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