During the relatively quiet period of nuclear power development over the last
15 years, there has been a consolidation of expertise in relation to nuclear
power reactor design and development so that today several significant new designs,
all evolved from previous and mostly well-tested antecedents, are available.
In fact, utilities looking around for up-to-date nuclear power plants have
quite a lot to choose from. Designs have become more international than last
time most of them had their checkbooks out. There are some innovations, as well
as the designs which have steadily evolved from the 400-plus workhorses of today.
Several generations of reactors are commonly distinguished. Generation I reactors
were developed in the 1950-60s, and outside the United Kingdom, none is still
running today. Generation II reactors are typified by the present U.S. fleet
and most in operation elsewhere. Generation III are the advanced reactors discussed
here. The first of these are in operation in Japan and others are under construction
or ready to be ordered. Generation IV designs are still on the drawing board
and will not be operational before 2020 at the earliest.
About 85 percent of the worlds nuclear electricity is generated by reactors
derived from designs originally developed for naval use (see Figure 1). These
and other second-generation nuclear power units have been found to be safe and
reliable. In the last decade, the capacity of many has been marginally increased
and the actual kilowatt-hour output from that capacity has risen remarkably.
In addition, many have had operating licenses extended to 60 years (see Figure
2). However, they are being superseded by better designs.
Reactor suppliers in North America, Japan, Europe, Russia and South Africa
have a dozen new nuclear reactor designs at advanced stages of planning, while
others are at a research and development stage. Fourth-generation reactors are
at concept stage.
Third-generation reactors have:
- a standardized design for each type to expedite licensing, reduce capital
cost and reduce construction time;
- a simpler and more rugged design, making them easier to operate and less
vulnerable to operational upsets;
- higher availability and longer operating life typically 60 years;
- reduced possibility of core melt accidents;
- minimal effect on the environment;
- increased efficiency through higher burn-up to reduce fuel use and the amount
of waste; and
- burnable absorbers (poisons) to extend fuel life.
The greatest departure from second-generation designs is that many incorporate
passive or inherent safety features which require no active controls or operational
intervention to avoid accidents in the event of malfunction, and may rely on
gravity, natural convection or resistance to high temperatures.
In the United States, the Department of Energy (DOE) and the commercial nuclear
industry in the 1990s developed four advanced reactor types. Two of them fall
into the category of large evolutionary designs which build directly on the
experience of operating light water reactors in the United States, Japan and
One is an advanced boiling water reactor (ABWR) derived from an earlier General
Electric design. Four 1300-1380 MWe examples are in commercial operation in
Japan, with another under construction there and two in Taiwan. Four more are
planned in Japan and perhaps another in the United States, which was bid for
the fifth Finnish reactor in 2003.
The other type, System 80+, is an advanced pressurized water reactor (PWR),
which was ready for commercialization but is not now being promoted for sale.
But eight System 80 reactors in South Korea incorporate many design features
of the System 80+, which is the basis of the Korean Next Generation Reactor
program, specifically the larger APR-1400 which is expected to be in operation
soon after 2010, and marketed worldwide.
The U.S. Nuclear Regulatory Commission (NRC) gave final design certification
for both in 1997, noting that they exceeded NRC safety goals by several orders
of magnitude. The ABWR has also been certified as meeting European requirements
for advanced reactors.
Another, more innovative U.S. advanced reactor is smaller 600 MWe and has
passive safety features. The Westinghouse AP-600 gained NRC final design certification
in 1999 (AP = Advanced Passive).
These NRC approvals were the first such generic certifications to be issued
and are valid for 15 years. As a result of an exhaustive public process, safety
issues within the scope of the certified designs have been fully resolved and
hence will not be open to legal challenge during licensing for particular plants.
U.S. utilities will be able to obtain a single NRC license to both construct
and operate a reactor before construction begins.
Separate from the NRC process and beyond its immediate requirements, the U.S.
nuclear industry selected one standardized design in each category the large
ABWR and the medium-sized AP- 600 for detailed first-of-a-kind engineering
work. The $200 million program was half funded by the DOE. It means that prospective
buyers now have firm information on construction costs and schedules.
The Westinghouse AP-1000, scaled up from the AP-600, received final design
certification from the NRC in December 2005 the first generation 3+ type to
do so. It represents the culmination of a 1,300 man-year and $440 million design
and testing program. Overnight capital costs are projected at $1,200 per kilowatt
and modular design will reduce construction time to 36 months. The 1100 MWe
AP-1000 generating costs are expected to be less than $3.5 cents/kWh and it
has a 60-year operating life. It is under active consideration for building
in China, Europe and the United States.
General Electric has developed the ESBWR of 1390 MWe with passive safety systems,
from its ABWR design. This then grew to 1550 MWe and has been submitted for
NRC design certification in the United States. Design approval is expected by
2007. It is favored for early U.S. construction as the Economic & Simplified
Also Ready for Action
Europe, designs have been developed to meet the European Utility Requirements
of French and German utilities, which have stringent safety criteria.
Framatome ANP has developed a large (1600 and up to 1750 MWe) European Pressurized
Water Reactor, which was confirmed in 1995 as the new standard design for France
and received French design approval in 2004. It is derived from the French N4
and German Konvoi types and is expected to provide power about 10 percent cheaper
than the N4. It will operate flexibly to follow loads, have high fuel utilization
and the highest thermal efficiency of any light water reactor, at 36 percent.
Availability is expected to be 92 percent over a 60-year service life. The first
unit is being built at Olkiluoto in Finland; the second is planned at Flamanville
in France. The U.S. EPR is also undergoing review in the United States with
intention of a design certification application in 2007.
Together with German utilities and safety authorities, Framatome ANP also developed
another evolutionary design, the SWR 1000, a 1000-1290 MWe boiling water reactor
which was bid for Finland in 2003. The design was completed in 1999 and development
continues, with U.S. design certification being sought. As well as many passive
safety features, the reactor is simpler overall and uses efficient fuels, giving
it refueling intervals of up to 24 months. It is ready for commercial deployment.
In Russia, Gidropress 1000 MWe V-392 (advanced VVER-1000) units with enhanced
safety are planned for Novovoronezh and are being built in India. A transitional
VVER-91 (1000 MWe) was developed with Western control systems two are being
built in China at Jiangsu Tianwan (the first started up in December) and it
was bid for Finland.
The larger VVER-1500 V-448 model is being developed by OKBM, and two units
each are planned as replacement plants for Leningrad and Kursk. It will have
high fuel efficiency and enhanced safety. Design is expected to be complete
in 2007 and the first units commissioned in 2012-13.
Canada has had two designs under development which are based on its reliable
CANDU-6 reactors, the most recent of which are operating in China.
The main one is the Advanced Candu Reactor (ACR). While retaining the low-pressure,
heavy water moderator, it incorporates some features of the pressurized water
reactor. Adopting light water cooling and a more compact core reduces capital
cost, and because the reactor is run at higher temperature and coolant pressure,
it has higher thermal efficiency.
The ACR-700 is 750 MWe but is physically much smaller, simpler and more efficient
as well as 40 percent cheaper than the CANDU-6. But the ACR-1000 of 1200 MWe
is now the focus of attention by AECL. It has more fuel channels (each of which
can be regarded as a module of about 2.5 MWe). Projected overnight capital cost
of $1,000/kWe and operating costs of 3 cents/kWh have been claimed. The ACR
will run on lowenriched uranium (about 1.5 to 2.0 percent U-235) with high efficiency,
extending the fuel life by about three times and reducing high-level waste volumes
accordingly. Regulatory confidence in safety is enhanced by changes in the reactor
physics, and it utilizes other passive safety features. Units will be assembled
from prefabricated modules, eventually cutting construction time to three years.
Development is under way and the project is expected to be ready to build soon.
Meanwhile it is moving toward design certification in Canada, with a view to
following in China, the United States and the United Kingdom. The first ACR-1000
unit is expected to be operating in 2014 in Ontario.
In Japan, the first two GE-Hitachi-Toshiba ABWRs have been operating since
1996 and are expected to have a 60-year life. Two more started up in 2004 and
2005 and others are under construction in Japan and Taiwan. Also a large (1500
MWe) advanced PWR (APWR) is being developed by four utilities together with
Westinghouse and Mitsubishi. The first two are planned for Tsuruga. It is simpler,
combines active and passive cooling systems to greater effect, with high fuel
efficiency. Design work continues and will be the basis for the next generation
of Japanese PWRs. In addition, Mitsubishi is participating in development of
Westinghouses AP-1000 reactor.
All of the above are moderated and cooled by water, but an entirely different
approach is based on pioneering work in the United States and Germany. This
involves using helium cooling and much higher temperatures; hence, greater thermodynamic
South Africas Pebble Bed Modular Reactor (PBMR) is being developed by a consortium
led by the utility Eskom, and drawing on German expertise. It aims for a step
change in safety, economics and proliferation resistance. Production units will
be 165 MWe. They will have a direct-cycle gas turbine generator and thermal
efficiency of about 42 percent. Up to 450,000 fuel pebbles recycle through the
reactor continuously (about six times each) until they are expended, giving
an average enrichment in the fuel load of 4 to 5 percent. The pressure vessel
is lined with graphite and there is a central column of graphite as reflector.
Control rods are in the side reflectors and cold shutdown units in the central
column. Performance includes great flexibility in loads (40 to 100 percent),
with rapid change in power settings. Each unit will finally discharge about
19 tonnes/yr of spent pebbles to ventilated, on-site storage bins.
Construction costs (especially when in clusters of four to eight units) and
operating costs are expected to be low. Investors in the PBMR project are Eskom,
the South African Industrial Development Corporation and Westinghouse. A demonstration
plant is due to be built in 2007 (most contracts have already been let) for
commercial operation in 2010.
Chinas INET is rapidly progressing with a similar design, of 200 MWe, which
it plans to have running in 2010. It then hopes to build a plant comprising
18 of these at Weihai in Shandong province.
Beyond all these, two major international initiatives have been launched to
define future reactor and fuel-cycle technology, mostly looking further ahead
than what has been discussed so far.
Technology Always Changing
The Generation IV International Forum is a U.S.-led grouping established in
2001 which has identified six reactor concepts for further investigation with
a view to commercial deployment by 2030. Parallel to this, the IAEAs International
Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) is focused more
on the needs of developing countries, involving Russia rather than the United
States. It is now funded through the IAEA budget.
Along with development of new reactors in the medium- to long-term time frame
is a renewed focus on reprocessing used fuel from the reactors, both to extract
more energy value from it and to expedite the disposal of high-level wastes.
Since President Jimmy Carter, U.S. policy has turned away from this, but a major
change is now under way, and under the Advanced Fuel Cycle Initiative the Argonne
National Laboratory is planning an engineering-scale demonstration of a new
process for reprocessing used fuel. It is estimated that using this process,
the effective capacity of the Yucca Mountain repository could be increased fivefold
and much better utilization of uranium achieved. The policy change is strongly
supported by industry and the U.S. professional association.
So, there is a variety of reactor technology available or soon to be available,
and more still after 2020. These will take the world nuclear power industry
into an era of upgraded equipment which is safer, simpler, more economic and
more durable, while playing a major role in limiting world carbon dioxide emissions.
A doubling of nuclear capacity will reduce carbon dioxide emissions by almost
one-third of present levels from power generation.
But beyond simple economics and the related question of climate change is the
looming issue of energy security. Whereas the logistics of fossil fuel supply
are increasingly fraught, it is very easy and inexpensive to store a few years
supply of uranium or fabricated nuclear fuel.
it is up to governments to adopt sound policies regarding energy security and
the environment, the ball is then in the court of utilities and financiers to
invest wisely in plants which will perform economically and reliably for a long
Humankind cannot conceivably achieve the clean-energy revolution which is so
obviously necessary today without a rapid expansion of nuclear power. Initially
this is to generate electricity, but let us not lose sight of desalination and
the future supply of hydrogen for transport. I believe that this will require
a twenty-fold increase in nuclear energy during this century, from 440 to some
8,000 reactors. While this is a big challenge, it is certainly achievable given
the maturity of the technology involved.
- Traditional reactor safety systems are active in the sense that they involve
electrical or mechanical operation on command. Some engineered systems operate
passively (e.g., pressure relief valves). Both require parallel redundant
systems. Inherent or full passive safety depends only on physical phenomena
such as convection, gravity or resistance to high temperatures, not on functioning
of engineered components.