Density Meter LB 444 SECTION 9. RADIATION PROTECTION
87
5. If necessary, clean and grease the threading on the source holder and the
shielding.
6. Using a pair of pliers, take the new source out of the transport shielding and
firmly fix it onto the source holder together with the locking washer.
7. Put the source holder with the source again into the shielding and fix it using
the socket wrench.
8. Check the proper OPEN/CLOSED function. Survey and wipe-test the shield-
ing. Test shutter operation. Lock in the closed position. Update the labels and
complete the records.
9. Carefully survey the transport shielding again, after you have placed the old
source into the transport shielding. The special regulations regarding labeling
and transport of the shielding back to the manufacturer must be observed.
9.2 Radiation Dose Calculations
When preparing work on radiometric measuring systems, it is important to cal-
culate the radiation exposure to be expected in advance, for this has conse-
quences on the required safety precautions.
The expected radiation exposure can be calculated quite easily and with suffi-
cient 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 calculated as
follows:
Dose D =
A k t
rs
2
⋅⋅
⋅
A is the activity of the source and k the respective specific Gamma radiation
constant (see the table below). The distance from the measuring 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; it is listed in the shielding brochure or can be calculated. s =
1 when calculating the doserate for work with an unshielded source.
NUCLIDE
k DIMENSIONS
Co-60 0.35
Cs-137 0.09
Sv * m
h * MBq
µ
2
Examples of calculations:
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