Civil Engineering Reference
In-Depth Information
Fig. 3.32
Main features of
ABWR-II Plant-System
[
22
]
Large K-lattice
bundle
Large sized
SRV/MSIV
Hydrogen recombiner
system
Passive residual heat
removal system
Control rod
drives
The ABWR-II core has a larger fuel element, a somewhat modified emergency
core cooling system (ECCS) and additional passive heat removal systems for
accidental (beyond design basis) conditions.
3.4.5.1 ABWR-II Core Design and Coolant System
The larger ABWR-II fuel element box consists of four subbundles (Fig.
3.33
). Each
of the four subbundles has an 8
8 fuel rod arrangement. A so-called K-lattice
control rod concept (Fig.
3.33
) allows the number of control rods in the core to be
increased. As a consequence the ABWR-II core has only 424 fuel element boxes
and 197 control elements. The dimensions of the fuel rods and the cladding
materials are equal to those of the ABWR.
The control rod drive system consists of the fine motion control rod drive
mechanisms, the hydraulic control unit and the control rod drive hydraulic sub-
systems. Compared to the ABWR design an improvement was made by introducing
a magnetic coupling which transmits torque between the control rod drive motor
and the control rod drive shaft through the pressure boundary at the bottom of the
reactor pressure vessel.
The ABWR-II has four main steam lines and 14 safety/relief valves in the main
steam lines. The discharge capacity during depressurization was increased by 70 %
compared to the ABWR design.
