Civil Engineering Reference
In-Depth Information
Table 4.2
Tissue weighting
factors w
T
for determination
of the effective dose
according to ICRP 60 (1991)
[
5
] and ICRP 103 (2007) [
7
]
Issue
ICRP 60
ICRP 103
Tissue organ weighting factors, w
T
Gonads
0.20
0.08
Breast
0.05
0.12
Red bone marrow
0.12
0.12
Lung
0.12
0.12
Thyroid
0.05
0.04
Bone surfaces
0.01
0.01
Colon
0.12
0.12
Stomach
0.12
0.12
Bladder
0.05
0.04
Oesophagus
0.05
0.04
Liver
0.05
0.04
Brain
++
0.01
Kidney
++
++
Salivary glands
++
0.01
Skin
0.01
0.01
0.05
+
0.12*
+
see ICRP 60, *see ICRP 103,
++
included in Remainder
Remainder
radiation dose is roughly a factor of 8-100 higher than the mean background dose
on earth of 2.4 mSv/year [
8
-
11
].
In the Federal Republic of Germany,
given here as an example—, the
corresponding average background whole body dose is 2.1 mSv/year (Table
4.3
)
[
12
,
13
].
4.3.1 Natural Background Exposure from Natural Sources
in Germany
A major source of external radiation exposure consists of both cosmic (0.3 mSv/
year) and external terrestrial radiation (0.4 mSv/year) from the natural radionuclide
K-40 (half-life 1.28
10
9
year) together with the radionuclides of the natural decay
chains of U-238 and Th-232. The internal component of radiation exposure is
largely caused by the inhalation of the natural noble gas radon and its daughter
nuclides (1.1 mSv/year), and partially also by the intake of natural radioactive
substances with drinking water and food (0.3 mSv/year).
The annual mean value of the radon activity concentration in occupied spaces is
about 50 Bq/m
3
, which corresponds to a mean annual effective dose of about
0.9 mSv/year. Outdoors inhalation of radon and its progeny leads to about
0.2 mSv/year [
12
,
13
]. The natural background radiation in Germany is given as
an example in Table
4.3
; in other countries the natural background exposure is
similar.
