POWER November 2010 - 43

PLANT DESIGN
3. Simplified plant design. There are six major plant structures in the standard
ESBWR plant design. Passive safety features eliminate the need for safety-grade pumps
and AC power. This allows a significant reduction in overall building volumes and plant
footprint. The reactor building (left) houses safety-related structures, systems, and components
(SSC), except for the main control room, safety-related distributed control, and
information system equipment rooms in the control building and the spent fuel storage
pool and associated auxiliary equipment in the fuel building. The reactor building includes
the reactor, primary containment, auxiliary equipment, and the refueling area. The control
building (located in the foreground in front of the reactor building) houses the main
control room and safety-related controls outside of the reactor building. The fuel building
(located to the left of the reactor building) houses the spent fuel storage pool, its associated
auxiliary equipment, and the fuel transfer machine. The turbine building (located on
the right) houses equipment associated with the main turbine and generator plus their
auxiliary systems and equipment, including the condensate purification system and the
process off-gas treatment system. The radwaste building (not shown) houses equipment
associated with the collection and processing of solid and liquid radioactive waste
generated by the plant. The electrical building (not shown) houses the two non-safetyrelated
standby diesel generators and their associated auxiliary equipment as well as the
solid-state adjustable-speed-drive units powering pump motors in the feedwater system
and other plant systems. Source: GE Nuclear Energy
Natural Circulation Is Critical
The ESBWR vessel design enhances natural
circulation (Figure 4), which provides
simplification over previous BWR and all
pressurized water reactor designs that rely
on forced circulation. The main features of
the natural circulation reactor design are:
■ A partitioned chimney above the reactor
core to promote natural circulation flow
and to direct the steam and water flow
above the core.
■ A correspondingly taller, open downcomer
annulus that reduces flow resistance and
provides additional driving head, pushing
the water to the bottom of the core.
This fundamental design improvement
removes recirculation pumps and associated
motors, piping, valves, heat exchangers,
controls, and electrical support systems
that are required with forced circulation
designs, thus contributing to an expected
20% reduction in operation and maintenance
costs. Natural circulation in the
ESBWR also eliminates the risk of flow
disturbances resulting from recirculation
pump anomalies. (See " Retrofitting BWR
4. Natural circulation. Because hot
water is less dense than cold water, it rises
through the core while the cool water flows
down to the bottom of the core. These natural
differences in density circulate the fluid to
produce steam without the need of pumps.
Source: GE Nuclear Energy
Saturated water
Subcooled water
Saturated steam
Table 4. Comparison of key design features. Source: GE Hitachi
Parameter
BWR/4
Power (MWt/MWe)
Vessel height/diameter (m)
Fuel bundles (number)
Active fuel height (m)
Power density (kW/L)
Recirculation pumps
Number/type of control rod
drives
Safety system pumps
Safety diesel generators
Alternate shutdown
Control and instrumentation
3,293/1,100
21.9/6.4
764
3.7
50
2, external
185/LP
9
2
2 standby liquid
control (SLC) pumps
Analog single
channel
Core damage (frequency/year) 10-5
42
BWR/6
3,900/1,360
21.8/6.4
800
3.7
54.2
2, external
193/LP
9
3
2 SLC pumps
Analog single
channel
10-6
ABWR
3,926/1,400
21.1/7.1
872
3.7
51
10, internal
205/FM
18
3
2 SLC pumps
Digital multiple
channel
1.6 x 10-7
ESBWR
Dryers
4,500/1,600
27.7/7.1
1132
3
54
269/FM
2 SLC
accumulators
Digital multiple
channel
1.7 x 10-8
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POWER| November 2010
Core
Chimney
Main steam
Steam
separators
Feedwater
Annulus

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POWER November 2010

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