Civil Engineering Reference
In-Depth Information
cooling device (core catcher) provides long term cooling of the molten core. The
outer containment of PWRs protects the inner components in the inner containment
against external events (earthquakes, hurricanes etc.).
As presently operating standard BWR the BWR-1,300 of KWU (Germany) and
the ABWR built by General Electric (USA), TOSHIBA and HITACHI (Japan) are
described. In addition the more recently designed (future) SWR-1,000 (KERENA)
of AREVA (France) and the ABWR-II of General Electric (USA), TOSHIBA and
HITACHI (Japan) will be presented. The fuel elements, the control elements, the
core design etc. of the BWR-1,300, ABWR and SWR-1,000 (KERENA) designs
are very similar. The pressure suppression system with suppression pool, drywell
and the containment system of the BWR-1,300 and the ABWR are again very
similar. The threefold emergency core cooling and afterheat removal systems of
BWR-1,300 and ABWR show only little differences. In case of the SWR-1,000
(KERENA) with fourfold cooling and emergency cooling systems more passive
safety systems are installed. At depressurization the steam is discharged into four
interconnected core flooding pools. These core flooding pools serve as a passive
heat sink. The heat is transferred through four containment emergency condensers
to an upper shielding/storage pool. Additional passive heat transfer systems are the
emergency condensers within the four core flooding pools. The drywell with reactor
pressure vessel is flooded passively in case of drastic losses of coolant and danger of
core melt.
The ABWR-II design of General Electric (USA), TOSHIBA and HITACHI
(Japan) evolved from the ABWR. It has a larger fuel element, modified emergency
core cooling systems and passive core cooling as well as passive containment
cooling systems. In case of core melt through the bottom of the pressure vessel
the core melt can be cooled on a steel plated cavity underneath the pressure vessel.
3.1 Light Water Reactors
It was already mentioned in Chap.
1
that nuclear power generation is currently
mainly based (about 80 %) on Light Water Reactors (LWRs) designed as Pressur-
ized Water Reactors (PWRs) or Boiling Water Reactors (BWRs). LWRs use low
enriched uranium fuel, which makes for greater flexibility in the choice of reactor
core materials, especially allowing normal (light) water to be used as a coolant
and moderator. PWRs deliver the heat generated in their reactor core to water
circulating under high pressure in primary coolant circuits. From here the heat is
transferred to a secondary coolant system via steam generators to produce steam
driving a turbo-generator system. In BWRs the steam for the turbo-generator
system is generated right in the reactor core and sent directly to the turbo-generator.
PWRs and BWRs have been advanced to a high level of technical maturity. They
are built now in unit sizes up to 1,200 and 1,700 MW(e) [
1
].
