Civil Engineering Reference
In-Depth Information
Chapter 7
Light Water Reactor Design Against
External Events
Abstract
LWRs must be designed against earthquakes, air plane crashes, chemical
explosions, flooding, tsunamis and tornados. The design of LWRs against earth-
quakes must meet certain guidelines required by regulatory authorities. These
distinguish between the design basis earthquake and the safe shut down earthquake.
The design basis earthquake is the highest intensity earthquake which can occur
according to scientific findings at the site of the nuclear power plant. In a safe shut
down earthquake the fundamental safety functions of the LWR must remain
fulfilled. The mechanical loads and stresses acting on nuclear power plants in an
earthquake are determined by horizontal and vertical displacements and accelera-
tions as well as the associated frequencies of vibration and the duration of the
earthquake. Besides the rules recommended by regulatory authorities also two- and
three-dimensional finite-element codes are employed on the mechanical analysis of
the plant. Where horizontal or vertical displacements and the resultant stresses are
too high, pipings and components may be supported by means of damping ele-
ments. Also the entire nuclear plant may be built on thousands of damping elements
located in the foundation bottom concrete slab of the reactor building. LWR plants
are designed against air plane (military or commercial) crashes into the plant.
Impulse models and experiments form the basis for a shock load versus time
curve which has to be applied for the design of the plant.
LWRs must also be designed against a given pressure wave resulting from
chemical explosions in the vicinity of the plant.
The risk of flooding by a maximum-level flood must be taken into account on the
basis of scientific findings about floods for the past 10,000 years. Similar require-
ments exist for tsunamis and for tornados.
Nuclear power plants are designed against the impacts of external events, such as
earthquakes, airplane crashes, chemical explosions, flooding, or tsunamis and
tornados.
