More
attention has been given of late to recent announcements of nuclear
power plant closures and threatened shutdowns than to the pursuit of new
nuclear technology. Despite current economic challenges to the nuclear
power industry, many experts support the ongoing development of nuclear
power as an essential part of the mix for long-term world energy needs.
Recent polling shows that the majority of Americans still favor the use
of nuclear energy to generate electricity and 81 percent of those
surveyed stated that nuclear power will be important in meeting the
country’s future energy needs.
Given current
economics, however, it would be easy to question the ability of the U.S.
to build new nuclear plants and make use of advanced nuclear designs.
This question was recently answered when the industry achieved an
historic milestone in the construction of new nuclear power. In March,
South Carolina Electric and Gas (SCG&E) and Georgia Power poured the
first new construction “nuclear concrete” in over 30 years at the
Summer and Vogtle construction sites, respectively. The historic
completion of over 7,000 cubic yards of basemat structural concrete at
each site by CB & I (formerly Shaw Group) serves as the foundation
for the nuclear island structures, such as the containment and auxiliary
buildings.
Georgia Power and SCG&E (and
their co-owners) are building two Westinghouse AP1000 reactors at each
of the Vogtle and Summer locations. Westinghouse and CB&I are even
further along in building four AP1000s in China. Design certification of
the AP1000 by the NRC was issued in December 2011 and the licenses for
construction and operation (COLs) were issued in February 2012 for
Vogtle and March 2012 for Summer.
The building of
these advanced reactors in Georgia and South Carolina is significant
and demonstrates that nuclear power will continue to play an important
role in the U.S. energy mix. Their presence also reinforces the need for
key stakeholders to support and continue to invest in nuclear reactor
technology. According to the World Nuclear Association (WNA), the
certification of the AP1000 required 1,300 person-years of work and $440
million for the design and testing program.
Notably,
at the time of the Fukushima disaster, the Westinghouse AP1000 was not
yet fully certified and the COL had not yet been issued by the NRC. The
passive safety features of the AP1000 design provide 72 hours of cooling
by way of stored energy and gravity in the case of a major event, which
protects public safety as well as the asset. Russ Bell, the Senior
Director of New Plant Licensing at the Nuclear Energy Institute (NEI),
points out that one year after Fukushima, the NRC was able to proceed
with the licensing of the AP1000 at Vogtle and Summer in part because of
the robustness of its enhanced safety features. “There is a lot of
credit to go all around—Southern Nuclear, SCANA (SCE&G’s parent
company), Westinghouse, the NRC, and many others.”
TERRAPOWER’S TRAVELING WAVE REACTOR PROTOTYPE
At
least one high-profile investor, Microsoft Corp co-founder and Chairman
Bill Gates, touts the benefits of nuclear power and calls for more
investment in nuclear energy research. At the international energy
executives’ conference in March—CERAWeek, Gates endorsed nuclear power
as the best long-term solution to meeting rising world energy needs
while addressing climate change because only nuclear provides reliable,
high capacity, low-carbon energy in a way that can significantly reduce
global warming. Gates also discussed how after the Fukushima accident,
there is a greater demand for more stable nuclear energy technology with
improved nuclear power reactor designs with greater inherent safety
features. There are multiple improvements in nuclear reactor technology
already being realized—and there are dozens of new reactor designs being
pursued and significant innovations on the horizon.
THE VOGTLE UNIT 3 REACTOR VESSEL IN FRONT THE UNITY 4 CONTAINMENT VESSELL BOTTOM HEAD, MAY 2013. COURTESY OF GEORGIA POWER.
GENERATIONS OF NUCLEAR TECHNOLOGY
The
U.S. Department of Energy (DOE) has adopted a nomenclature to
categorize various stages of advancement in the development of nuclear
energy technology. The progression from one “generation” to the next
tells a story of technology evolving to meet needs for increased safety
and economy as well as proliferation resistance and reduced nuclear
waste material.
VOGTLE UNIT 3 COOLING TOWER CONSTRUCTION, MAY 2013. COURTESY OF GEORGIA POWER.
•Generation
I reactors were the prototypes, the first civil reactors developed in
the 1950s and 60s that moved the technology from research and military
uses to commercial power. They were typically small and lacked the
redundant safety systems and non-proliferation aspects of current
designs. Exelon’s Dresden Unit 1 (now retired) is of the first
generation.
• Generation II reactor designs
comprise the vast majority of nuclear plants in operation in the world
today. These are commercial nuclear power reactors designed to be
economical and reliable and built primarily in the late 1960s through
the 90s worldwide. They include the boiling water reactor (BWR),
pressurized water reactor (PWR), and the Canadian CANDU reactors. In the
west, most were built by Westinghouse, GE and Framatone (ARE-VA). They
use active safety features, as opposed to passive, that involve
electrical and mechanical operations initiated automatically and/or by
the unit operators.
•Generation III and Gen III+
reactor designs reflect significant design improvements and are referred
to as Advanced Nuclear Power Reactors. There are dozens of third
generation designs that are under development, going through the
licensing and certification process or under construction (some Gen III
units have been in operation in Japan). According to the World Nuclear
Association, third generation reactor designs have the following
improvements:
• Standardized design—reducing capital cost, construction time and expediting licensing.
• Simpler and more rugged design—making them easier to operate and less vulnerable to error.
•Longer operating life—typically 60 years.
• Reduced possibility of core melt accidents.
•
Passive safety features and long grace period during a shutdown—passive
cooling and containment requires no active intervention.
•Greater fuel efficiency—longer fuel life and less fuel waste by-products.
• Resistance to serious damage and radiological release from an aircraft impact.
The
major difference between Gen III and Gen III+ designs is that the
latter incorporated significant safety improvements that do not require
active controls or operator intervention, but rely on gravity and
natural convection to mitigate the impact of an event. After the reactor
events at the Fukushima Daiichi units, the importance of passive,
naturally occurring safety features in the event of a loss of all
back-up power became patently clear. The AP1000 is a Gen III+ reactor
design.
Other third generation reactor designs
pursuing certification include the APR 1400 led by Korea Electric Power
Company (KEPCO), US EPR by Areva, the ABWR and ESBWR by GE Hitachi, and
the US-APWR by Mitsubishi Heavy Industries.
Small
Modular Reactors (SMRs) are third generation designs that have received
broad support. SMRs provide advantages in their modular construction
and smaller size, which impacts cost, time for construction, and
location. Most SMR designs employ advanced passive safety features. The
DOE awarded Babcock and Wilcox’s mPower a maximum of $452 million in
matching funding to support certification and licensing of its 180 MWe
SMR. mPower’s anticipated deployment is approximately 2022. The DOE is
taking applications for a second SMR design funding opportunity. Other
companies pursuing an SMR reactor design include Holtec International,
NuScale Power and Westinghouse.
VOGTLE
UNIT 3 CR10 “CRADLE” ON CONCRETE AND STEEL BASEMAT INSIDE THE “NUCLEAR
ISLAND,” VOGTLE 1 & 2 OPERATING UNITS IN THE BACKGROUND, MAY 2013.
COURTESY OF GEORGIA POWER.
Generation
IV reactor designs are in the concept stage, require extensive
fundamental research and could be built then commercially deployed
beginning in the late 2020s or the 30s. The Generation IV International
Forum (GIF) was formed in 2001 to bring global resources to bear on Gen
IV reactor research and development and to coordinate efforts for best
results. There are 12 member countries including the U.S. DOE. According
to the DOE, the objectives of the Gen IV designs are:
•Sustainability—meeting clean energy goals, utilizing fuel more effectively.
• Significantly reduced nuclear waste and long-term stewardship burden.
•
Safety and reliability—a low level of reactor core damage in the case
of an accident and reduced need for offsite emergency response.
•Economic competitiveness—with a lifecycle cost advantage over other energy sources.
• Proliferation resistance and physical protection.
With
any future regulatory effort to capture fees for carbon allowances,
nuclear power’s estimaed share of generation increases anywhere from
7-18%, taking the gains from coal.
Six reactor
technologies have been selected by GIF for further research and
development. Five of the designs recycle nuclear material and produce
less waste. China has begun construction of a prototype Gen IV reactor.
Bill
Gates has invested in TerraPower, a Bellevue, Washington-based company
that is working on the development of a Gen IV technology, the traveling
wave reactor (TWR). The TWR is a safer form of breeder reactor that
would have no fuel recycling or reprocessing needed because of an
intrinsically higher burn-up rate of waste byproduct. TerraPower is
working on a prototype reactor to be built around 2022, with an
ambitious goal of commercial operation in the late 2020s. The TWR-P
would possess all the safety and security benefits of the Gen III+
reactors, but would generate at least seven times less waste than
current reactor technology with 50 times the fuel efficiency.
But will we continue to need nuclear power?
The
National Renewable Energy Laboratory (NREL) recently released a study
that was interpreted by some as concluding that renewables such as wind
and solar can provide the vast majority of America’s electricity.
However, an April Washing-ton Post article analyzed the study and
reached different conclusions. The Post stated that the limits of
renewable energy reinforce the need to more aggressively explore next
generation nuclear technologies that can provide better safety, nuclear
waste, and security (non-proliferation) solutions that can be more
economical to build. Although renewables are and will continue to be an
important part of the U.S. energy portfolio, most experts conclude that
they will not be able to dominate the energy mix, though they certainly
can become a bigger play.
Looking at the
long-term energy picture reveals that nuclear power will continue to
have a key role. According to the U.S. Energy Information Administration
(EIA), nuclear power’s share of the electricity mix is expected to
decrease by only 2% by 2040, losing some ground to natural gas and
renewables, which will also absorb increases in demand. With any future
regulatory effort to capture fees for carbon allowances, nuclear power’s
estimated share of generation increases anywhere from 7-18%, taking the
gains from coal. Global long-term estimates show that nuclear power’s
overall proportion of electricity generation stays fairly constant, with
losses in Europe and gains in Asia, according to the International
Energy Agency.
In sum, nuclear power will
continue to be a significant electricity generator in the U.S. and
internationally. Advanced nuclear technologies currently being realized
bring significant advantages over current reactors. Future technologies
hold even more promise to enhance the safety, security and economics of
nuclear power while incorporating nuclear waste solutions( Source : Nuclear Power International )
0 nhận xét:
Đăng nhận xét