POWER October 2013 - 77

Nuclear Power
1. Reactor building. The fuel pool and control room are housed below ground level, enhancing
safety. Courtesy: NuScale
ator tubes cools the primary coolant and the
secondary coolant is heated in the process of
this heat exchange by conduction through the
tube walls. As the primary coolant cools, it
becomes more dense, which causes it to be
drawn by gravity back to the bottom of the
reactor vessel, where the natural circulation
process begins all over again. Water in the reactor
system (primary coolant) is physically
separate from water in the steam generator
system (secondary coolant), which prevents
cross-contamination.
The secondary coolant inside the steam
generator tubes is heated to steam and exits
the reactor vessel. The steam spins turbines,
which are attached by a single shaft to the
electrical generator. After passing through
the turbines, the steam loses its energy. It is
cooled back into liquid form in the condenser
and then pumped by the feedwater pump
back to the steam generator, where it begins
the cycle again.
Key NuScale power module specifications
would back NuScale's bid to commercialize
its SMR technology globally and will help
NuScale's submission to DOE's Funding
Opportunity Announcement, a federal initiative
aimed at bringing bring a scalable, SMR
reactor to market by 2025.
NuScale describes itself as the only U.S.based
company established solely for the
commercialization of its SMR. Using light
water reactor (LWR) technology, the NuScale
power module is cooled by natural circulation,
is entirely self-contained, and is
installed underwater and underground (Figure
1), which the developers say maximizes
safety. The NuScale design claims to enable
the reactor to safely shut down and self-cool
indefinitely, with no operator action, no AC
or DC power, and no additional water.
NuScale has pursued what it characterizes
as an aggressive pre-application program
with the NRC, consisting of nearly 40 technical
meetings and submittals covering a range
of technical and regulatory topics such as
safety analysis, nuclear fuel, test programs,
seismic analysis, and control room staffing.
Every February the NRC requires from
SMR designers a regulatory information
summary that is used for resource planning
purposes at the federal agency. " In our case,
we've provided thorough input " to help the
NRC plan for its review of the NuScale
design, said Michael S. McGough, chief
commercial officer. He said the company is
" pleased " with the level of resources the NRC
has allocated to its SMR review process.
The objectives of the pre-application process
are to inform the NRC of the unique
NuScale Power Module and power plant
design features and approach, resulting in
October 2013 | POWER
review criteria applicable to NuScale in the
form of an NRC-issued NuScale DSRS. Preapplication
engagement will continue through
design certification application (DCA) submittal,
currently forecast for 2015.
While the DCA review process is under
way, NuScale expects an applicant to file a
combined construction and operating license
application (COLA), allowing the design and
COLA review processes to move ahead on
parallel paths. The design ultimately certified
by the NRC will be incorporated in the
COLA. This supports a likely commercial
date in the early 2020s.
Design Specifications
Each NuScale power module is intended to
be a self-contained module that operates independently
of the other modules in a multimodule
configuration (Figure 2). However,
all modules are managed from a single control
room. The reactor itself would measure
65 feet tall x 9 feet in diameter. It would sit
within a containment vessel, and the reactor
and containment vessel would operate inside
a water-filled pool built below grade.
The reactor is designed to operate using
the principles of natural circulation; hence,
no pumps are needed to circulate water
through the reactor. Instead, the system uses
natural forces of physics-convection, conduction,
and gravity. To begin the process,
primary coolant water is heated as it passes
over the core. As it heats up, buoyancy forces
cause the water to rise through a riser tube
within the interior of the vessel. The riser
tube is surrounded by steam generator tubes,
which contain cooler water called secondary
coolant. The cooler water in the steam generwww.powermag.com
77
include:
■
Thermal capacity: 160 MWt
■ Electrical capacity: >45 MWe in modules
that can be scaled to reach 540 MWe in size
■ Capacity factor: >95%
■ Dimensions: 82' x 15' cylindrical containment
vessel module containing reactor
and steam generator
2. Reactor module. The light water reactor
NuScale Power Module is cooled by natural
circulation and is entirely self-contained.
Courtesy: NuScale

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POWER October 2013

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