Civil Engineering Reference
In-Depth Information
Fig. 5.10
EPR double containment with RPV, cooling systems and molten core spreading area [
1
]
steam generator fails in addition and its secondary-side water content is taken up by
the containment. Finally, also the steam needs to be taken into account which is
produced as a result of the emergency cooling water taking part of the energy stored
in the secondary water of the steam generators [
13
]. This leads to design values of
approx. 0.6 MPa, depending on the volume of the containment. The design criteria
of the outer containment with respect to primary and secondary stresses are similar
or identical to those applying to the reactor pressure vessel. The required leak rate
of e.g., 0.25 % per day must be verified prior to commissioning and during reactor
operation at prescribed intervals. Pressure tests must be conducted at regular
intervals before startup and afterwards.
5.6.5.1 Different Designs for Reactor Containments
The containments of PWR and BWR plants have some characteristic differences in
design:
- There are containments made of prestressed concrete with an inner steel liner,
and containments made entirely out of steel (see Chap.
3
).
For protection against external impacts, the reactor containment is,
e.g. additionally surrounded in Germany by a thick steel reinforced prestressed
concrete shell which sustains
- an impulse-type load associated with, e.g. a postulated airplane crash,
- a pressure wave in connection with, e.g. a postulated chemical explosion.
This design also covers other external impacts, such as tornados, hurricanes,
flooding or tsunamis. In more recent plants, the outer concrete shell has a wall
thickness of 1.80 m (Kraftwerk Union PWR or BWR) or about 2.6 m (EPR). It also
