Civil Engineering Reference
In-Depth Information
Chapter 3
The Design of Light Water Reactors
Abstract
This chapter describes the designs and safety concepts of presently
operating and more recently developed (future) LWRs. The chapter concentrates
on LWR plants (PWRs and BWRs) with 1,300-1,700 MW(e) power output
manufactured in Europe, the USA and Japan. As a presently operating PWR the
standard PWR of 1,300 MW(e) of KWU (Germany) is chosen. As more recent
(future) PWR designs the Advanced Pressurized Water Reactor AP1000 and the
US-APWR (1,700 MW(e)) developed by Westinghouse (USA) and Mitsubishi
(Japan) are described. In addition the European Pressurized Water Reactor (EPR)
with 1,600 MW(e) power output of AREVA (France) is presented too.
The fuel elements, the control elements, the core design, the pressure vessel, the
design characteristics of the primary system, the steam generators and steam
conditions for the turbine-generator system are all very similar for all these
PWRs. Most of the PWRs with 1,300 MW(e) and more power output have four
redundant coolant circuits. Their emergency core and afterheat cooling systems are
also fourfold redundant. An exception is AP1000 with only two redundant coolant
circuits and two redundant emergency core and afterheat cooling systems. All
PWRs provide emergency core cooling at three different pressure levels (high
pressure (core make up tanks), medium pressure (accumulator) and low pressure).
Whereas in the older KWU PWR-1,300 design the primary system can be
depressurized manually by the operator, this is realized automatically by the
automatic depressurization system (ADS) in the more recent designs of AP1000,
US-APWR and EPR. Emergency cooling water is taken from the building sump in
case of the KWU PWR-1,300, whereas the more recent designs AP1000,
US-APWR and EPR are equipped with a large water volume in-containment
refueling water storage tank (IRWST). The afterheat can be removed in case of a
severe core melt accident either passively through the inner steel containment wall
(AP1000) or by using sprinkler systems in connection with containment heat
removal systems (EPR and US-APWR). In case of a core melt accident water of
the IRWST can be drained into the reactor cavity (AP1000). This water cools the
reactor pressure vessel from the outside and prevents the core melt from penetrating
through the pressure vessel wall. In case of EPR a molten core spreading and
