Civil Engineering Reference
In-Depth Information
Fig. 6.6
Results of the
US-Risk Study WASH-
1400 [
1
] for 100 nuclear
reactor plants
10
-4
10
-5
10
-6
10
-7
10
10
2
10
3
10
4
Fatalities
Source: Wash-1400
Figure
6.6
shows the complementary, cumulative frequency distribution of early
fatalities, determined by the WASH-1400 Risk Study [
1
], which could be caused by
radiation exposure after accidental radioactivity release. Results of the German
Risk Study, Phase A [
2
,
10
] are similar.
Of course, a large number of early fatalities will occur if major releases are
encountered on sites with high population densities, the wind blows in the direction
of the sector with the highest population density, and rain falls in the immediate
vicinity, thus creating high radioactivity concentration levels on the ground.
In the US and the German Risk Studies [
1
,
2
,
10
] late fatalities at all dose levels
are reported since a linear dose rate (Sect.
10.5.1
) without threshold value was
assumed according to ICRP (1977). The occurrence of late fatalities is therefore not
restricted to only the immediate vicinity of the reactor plant, as in case of early
fatalities. Also a considerable fraction of the late fatalities determined in the Risk
Studies [
1
,
2
] was due to low radiation exposures of
50 mSv (The average natural
background radiation on earth is about 2.4 mSv per year or 170 mSv over 70 years
<
6.9.1 Use of Results of Reactor Risk Studies
The value of Reactor Risk Studies should not be exaggerated or misinterpreted or
even used for forecasts in which time periods core melt accidents could occur. As
their methodology is based on probabilistic considerations their results can only be
used for
- comparison with the results of risk studies for other energy production systems
(coal, oil, gas etc.) which are based on the same probabilistic methodology
- for the optimization of the design of the different safety systems to reach a well
balanced overall safety concept for that nuclear plant for which the probabilistic
safety analysis was performed.
