Civil Engineering Reference
In-Depth Information
4.1.1.2 Radioisotopes of Iodine
For releases from nuclear reactors the shortlived radioactive isotopes of iodine,
I-131 (half-life 8 days) and I-133 (half-life 20 h), are important fission products.
I-129 (half-life 1.7
10
7
year) remains an important radioisotope. Radioiodines in
the airborne effluents from a nuclear power plant occur partly as elemental iodine
and partly as an organic compound (e.g. methyl iodide). Airborne iodine is depos-
ited on the surfaces of grass or vegetables. If liquid effluents containing radioiodine
are discharged into rivers or lakes etc., a possible major pathway will be their
accumulation in fish or plants. The human body can take up radioiodine with the
inhalation of air, ingestion of vegetables or fish, and by drinking milk. The
radioiodine absorbed by the human body is concentrated mainly in the thyroid.
Radioiodine emits both
-radiations.
Iodine aerosols or organic iodine compounds may, in particular under abnormal
operating conditions, deposit on components and concrete walls in the reactor
building. These are usually covered by suitable paintings. Nevertheless this may
impair decommissioning of these parts of the reactor plant [
4
].
β
- and
γ
4.1.1.3 Strontium and Cesium
The fission product Sr-90 (half-life 29.1 year) can be released into the atmosphere
as aerosols during severe nuclear accidents or with liquid effluents into rivers
during nuclear accidents. Through the food chain (milk, vegetables, fish, meat
and drinking water), Sr-90 enters the human body. Like calcium, Sr-90 is deposited
preferably in bones, representing a major burden on the blood forming organs
because of the long biological residence times of 18 years and the
-radiation of
2.3 MeV maximum energy of the daughter product, Y-90 (half-life 2.7 days).
Releases of radioactive cesium by way of gaseous and liquid effluents during
severe nuclear accidents also cause radiological exposures of the human body
through the uptake of food, as in the case of strontium. Cs-134 (half-life 2.1 year)
and Cs-137 (half-life 30 year) also emit
β
-radiation.
Cesium can largely replace potassium in living organisms and, like the latter, is
distributed throughout the body in highly soluble compounds.
γ
-radiation in addition to
β
4.1.1.4 Plutonium Isotopes
Plutonium isotopes may be discharged into the atmosphere during severe nuclear
accidents with gaseous effluents as aerosols of PuO
2
or into rivers together with
liquid effluents. The following plutonium isotopes are of main interest: Pu-238
(half-life 87.8 year): Pu-239 (half-life 24,100 year); Pu-240 (half-life 6,450 year);
Pu-241 (half-life 14.4 year); Pu-242 (half-life 3.9
10
5
year). The highest burden
results from inhalation, in which case plutonium is deposited in the lung. Moreover,
