|Safe, clean, cost-competitive, versatile and adaptable. These,
in a nutshell, are the features of South Africa's Pebble Bed Modular
Reactor (PBMR ™).
Locally, the PBMR technology has the potential to provide South Africa
with competitive power generation in coastal areas.
Internationally it will be competitive with virtually all other forms of
|Most of South Africa's coal-fired electricity is generated by
large-scale plants built near the pit-heads of two extensive
coal-producing areas, both of them far inland on the eastern side of the
country. This requires long power lines from the coal-rich areas
to load centres away from the pit-heads, which in turn implies high
capital costs and transmission losses.
|New power stations have to be built to ensure that the country's
capacity keeps up with demand. In addition, Eskom's older power
stations reach the end of their design life after 2025. South
Africa will, therefore, need to access and use all natural resources to
meet the additional demand that will be needed by 2025 (over and above
the currently installed 39 000 MW).
|A typical coal-fired power station requires a construction lead time
of four to six years, and could result in the installation of surplus
capacity if economic growth is not as expected. Shorter lead times
would enable power utilities to drastically shorten their
decision-making horizon for the addition of new capacity, and to add
capacity in smaller increments.
|Eskom, like most utilities worldwide, also experiences short, sharp
demand peaks in winter that are difficult to accommodate with the slow
ramping characteristics of the existing large power stations.
|These factors prompted Eskom to investigate small electricity
generation plants that can be placed near to the points of demand.
The PBMR concept, which has a short construction time, low operating
cost and fast load-following characteristics, is such an option.
|While open-cycle gas turbines, coal-fired plants and conventional
nuclear reactors are all good options in the short and medium term, the
PBMR could play a crucial role to help meet the countries' energy
requirements from the next decade onwards. Its inherent safe
characteristics and positive attributes from an environmental point of
view, add immensely to the attractiveness of this technology.
|It was therefore envisaged that - should the technology be
successfully demonstrated - at least 20 percent of Eskom's potential new
nuclear build programme of about 20 000 MW will consist of PBMRs (24
modules generating 165 MV each).
|Since the technology has not previously been commercialised, the
intention was to build and operate a single module at Koeberg near Cape
Town, and a fuel plant at Pelindaba near Johannesburg. Successful
demonstration was to be followed by commercialisation.
|Process Heat Applications
|While PBMR's design and development efforts were initially focused
mainly on electricity generation, it has become increasingly apparent
that the high-temperature gas-cooled reactor technology will also enable
access to markets that call for process heat applications.
|Heat from the PBMR can be used for a variety of industrial process
applications, including process team for cogeneration applications,
in-situ oil sands recovery, ethanol applications, refinery and
petrochemical applications. The high temperature heat can also be
used to reform methane to produce syngas (where the syngas can be used
as feedstock to produce hydrogen, ammonia and methanol); and to
produce hydrogen and oxygen by decomposing water thermochemically.
The waste heat of the PBMR can furthermore be applied to produce water
|In South Africa, there is interest in the possible use of PBMR
technology in petro-chemical complexes, notably for the South African
synthetic fuels giant Sasol, to either produce process steam and/or
hydrogen to upgrade coal products. In Canada, there is interest
from oil sands producers to use the PBMR to produce the temperature and
associated pressure needed to extract bitumen from oil sands instead of
|In the USA, PBMR was a partner in the Westinghouse-led consortium
which has been awarded a contract by the US Department of energy to
consider the PBMR technology as heat source for producing non-carbon
|Small and Adaptable
|The PBMR is based on the philosophy that the new generation of
nuclear reactors should be small. Each module would be sized to
produce 400 MWth (165 MWe nominal), which is about 18 percent of the
output of conventional reactors such as the ones at Koeberg near Cape
|The main building and generator of a module will cover an area of
about 4 320 m2 (108m x 40m), which means that two modules would fit on a
soccer field. The height of the building will be 66m, more than a
third (23m) of which will be below ground level.
|In addition, the PBMR can be used both as a base-load or
load-following station and can be configured to the size required by the
community it serves.
|The PBMR has a simple design basis, with inherent safety features
that require no human intervention, and which cannot be bypassed or
rendered ineffective in any way. If a fault occurs during
reactor operations, the system, at worst, will shut down and merely
dissipate heat on a decreasing curve without any core failure or release
of radioactivity to the environment.
|Green House Gas Reductions
|The PBMR can provide an economic mitigation strategy for greenhouse
gas reductions, since nuclear power generation produces no carbon
dioxide emissions, smoke or any other gases. France's carbon
dioxide emissions from electricity generation fell by 80 percent between
1980 and 1987 as its nuclear capacity increased, and Germany's nuclear
power programme has saved the emission of over two billion tons of
carbon dioxide from fossil fuels since it began in 1961.
|Compared with the huge atmospheric emissions from fossil-fuel
energy, nuclear wastes exist in small, highly manageable amounts that
can be stored without harm to people or the environment.
|One kilogram of uranium in the PBMR fuel has a greater energy output
than 430 tons of the best coal with an ash content (waste) of up to 40
percent. A large coal-fired power station uses about 2 200
trainloads of coal per year (six a day), while only 2 truckloads of fuel
per week will be required for 24 PBMR nuclear power stations of
equivalent capacity. For the PBMR demonstration unit at Koeberg,
10 truckloads would have been needed for the initial load, and only 4 truckloads
per year for the replacement of spent fuel.
|A 165 MWe PBMR module will generate about 32 tons of spent fuel
pebbles per annum, about 1 ton of which is uranium. The storage of
PBMR spent fuel should be easier than for fuel elements or rods from
conventional nuclear reactors, as no safety graded cooling systems are
needed to prevent fuel failure.
|The PBMR system has been designed to deal with nuclear waste
efficiently and safely. There will be enough room for the spent
fuel to be stored at the PBMR plant for the power station's expected
40-year operational life, during which time no spent fuel will have to
be removed from the site. After the plant has been shut down, the
spent fuel can be safely stored on site for another 40 years before
being set to a final repository.