Civil Engineering Reference
In-Depth Information
7.2 Design Against Airplane Crash
Since the 1970s, the protection of nuclear power plants against airplane crashes has
been a topic of discussion in Germany. At the same time, also underground designs
were analyzed and discussed [
30
,
31
]. Finally, however, preference was given to
construction above ground with an external concrete containment [
31
].
The main point of interest was the crash of a high-speed military aircraft and,
implicitly, the demand to protect against intentional impacts by third parties (such
as terrorist attacks) [
1
]. The probability of a commercial aircraft crashing into a
nuclear power plant was much lower, however. After lengthy debates, the decision
was taken to design the outer steel-reinforced concrete containment (outer contain-
ment) of a nuclear power plant in such a way that it withstood the crash of a
Phantom II military aircraft of the time (in the 1970s, this was the fastest and
heaviest military aircraft) weighing approximately 20 ton and reaching a crashing
speed of approx. 215 m/s or 774 km/h. This at the same time covered crashes of a
smaller aircraft [
1
,
32
-
35
].
On the basis of an impulse model by Riera [
36
,
37
], and after evaluation of
penetration and shock experiments with bullets fired at steel-reinforced concrete
walls, the shock load-vs.-time curve shown in Fig.
7.7
was defined and laid down
around 1977 for new nuclear power plants to be built [
10
].
The penetration tests at the time had shown that full protection, i.e. no penetra-
tion of such a military aircraft through the concrete wall, and no spallation of
concrete on the back of the steel-reinforced concrete wall between approx. 105 cm
and approx. 145 cm thick, would be ensured (depending on the stability of steel
reinforced concrete) [
32
,
35
]. Present-day pre-konvoy PWR, konvoy-PWR, and the
SWR-72 BWR line have concrete walls 180 cm thick (outer containment).
The area of impact of the Phantom II aircraft is assumed to be 7 m
2
in size
(circular). The angle of impact is assumed normal to the tangential plane of the
spherical or cylindrical reactor building. The vibrations caused by the impact of the
aircraft must be taken into account in the design of the nuclear power plant
(building and components) [
10
].
The shock load-vs.-time curve defined in the RSK-guidelines [
10
] as shown in
Fig.
7.7
was based on computer models by Riera [
36
,
37
] and Drittler [
32
-
34
]. In
1980, Riera showed a comparison of these models and findings. That comparison is
reflected in Fig.
7.8
. It is evident that the peak shock loads occurring were smoothed
for the shock load-vs.-time curve in Fig.
7.7
to be assumed in accordance with RSK
guidelines [
10
]. It is also seen that an aircraft not hitting the concrete wall in a
perpendicular direction (angle of impact 30
off the vertical direction (Fig.
7.8
,
right)) causes the shock load to be broken down into a smaller vertical and a still
smaller horizontal shock load.
The shock load-vs.-time curve laid down in Germany for the crash of a Phantom II
aircraft was tested by Sandia National Laboratories in Albuquerque, New Mexico,
USA in April 1988. The test was initiated by a Japanese research institute which had
been required to protect
the buildings of the Japanese reprocessing plant of
