Civil Engineering Reference
In-Depth Information
• Radiation exposure of the involved workers
• Damage to the environment
• Costs
• Social and ethical aspects
• Communication with and expectations from the public
For many of the late phase measures other than relocation identified in [
4
], there
is only a limited time window in the order of days or weeks after the accident where
they stay efficient, so that the effectiveness of a given measure in general will
depend on the delay until carrying-out becomes possible by radiological, logistical
or other reasons. Moreover, agricultural measures also depend very much on the
time of year when the accident takes place, the types of radionuclides released, the
local soil types, and the given food item.
The aim of agricultural measures is to reduce the activity concentration in a
given foodstuff below a given limit so that the product can be marketed. Typical
limits in the European Union are in the range of a few hundred to several thousand
Bq/kg fresh weight; they were introduced after the Chernobyl accident [
5
,
6
] and
are under discussion again after the Fukushima accident in 2011.
Measures against the contamination of milk by iodine or cesium, which are
typical fission products present in accidental releases from reactors, have to be
initiated at a very early stage. When milk cows are grazing outside, the peak
contamination of iodine in the milk, for example, occurs already after a few days
after the deposition on pasture grass. Apart from banning the consumption, mea-
sures can also be taken for reducing the transfer of the contamination from the cows
into the milk (by feeding sorbents), or for reducing the contamination of the
end-product by processing the milk to cheese or milk powder.
Another important fact with respect to the timing is that it is the effect of direct
deposition of activity on existing vegetation that causes high activities in food stuffs
and feed stuffs, so consumption bans are mostly needed only in the 1st year. In the
following years, the activity is transmitted to the plants only by means of root
uptake, which reduces the effectiveness of uptake by at least one or two orders of
magnitude [
7
].
Decontamination measures in urban areas can be subdivided into two categories:
• Measures shielding the population from the contamination
• Measures removing contamination from the area as far as possible
Measures applied in Chernobyl, now under discussion also for Fukushima,
include in particular the removal of top soil and the cleaning of paved or solid
surfaces, such as roads, sidewalks, walls, and roofs. However, decontamination in
urban environments clearly requires always aggregates of measures for the variety
of surfaces present in a given area. Depending on the level of urbanization, specific
surfaces will contribute most to the dose. In low-density areas and especially in
suburbs, for example, the doses of the local population can be dominated by
contributions from plants in the surroundings, such as trees, shrubs, and lawns [
8
].
