Civil Engineering Reference
In-Depth Information
Chapter 10
Assessment of Risk Studies and Severe
Nuclear Accidents
and consequences of the severe nuclear accidents of Chernobyl and Fukushima
were assessed. The severe nuclear accidents of Chernobyl and Fukushima resulted
in contamination of large areas and in the evacuation of the population of large
areas.
It is concluded that LWRs in Europe are built and operated in densely populated
areas with cities of several 100,000 inhabitants. It is impossible to evacuate cities of
that size in due time and their contamination is beyond anybody's imagination.
Therefore, the KHE safety concept was proposed around 1990 to build future
LWRs such that the main accident path of the risk studies leading to the high
number of deaths and to the large contamination of land should be eliminated by the
safety design concept of the plant. The probabilistic safety studies leading to low
frequencies of core melt in the range of 10
6
per year should be retained. However,
the present risk concept should not be applicable any more to LWR plants built in
future in Europe. It was concluded that the consequences of the most severe
accidents in risk studies should be managed by the inner and outer containment
of the reactor plant. A severe accident research program of the Research Center
Karlsruhe, Germany, lasting for about two decades showed that it is possible to
fulfill the requirements of the KHE concept. The KHE concept was essentially
accepted by the German and French Safety Commissions and also incorporated in
the German Atomic Law in 1994.
The main findings of the Karlsruhe research program for severe accidents were
as follows:
- A large scale steam explosion in the reactor pressure vessel of a PWR would not
jeopardize the mechanical integrity of the reactor pressure vessel. Consequently
a steam explosion followed by failure of the integrity of the reactor pressure
vessel and of the containment as assumed in WASH-1400 and the German Risk
study can be considered impossible.
- A large scale hydrogen detonation after core melt in the spherical containment of
a KWU PWR-1300 reactor plant cannot jeopardize the integrity of the steel
