It is now a year since the devastating Tohoku earthquake and tsunami triggered
the Fukushima disaster, the largest nuclear accident since Chernobyl.
Inevitably, the episode has prompted renewed debate about nuclear
Since Fukushima, important developments have taken place. Germany
has decided to shut down its fission plants. Moreover, in a referendum, 95
percent of the Italian public opposed plans to restart a nuclear program in the
country. However, the United States (where public support for nuclear power is
growing) and the United Kingdom have committed to building two fission power
Meanwhile, China is continuing with a massive program of nuclear
power reactor construction, and Turkey has re-committed to building its first
nuclear power plant. South Africa is also reportedly soon to announce an
expansion of its nuclear power program.
A danger in the occasionally
polarized international debate is that nuclear energy is often portrayed as a
single, undifferentiated energy source. This is wrong and risks losing the
opportunity to explore the role that new nuclear technologies can play in the
Indeed, those who seek to write nuclear energy off completely
are missing what could be remarkable developments on the horizon with hybrid
technologies potentially reshaping the way we think about nuclear
The starting point for debate should be the daunting energy
problems many countries face. With growing challenges to energy security,
the range of energy sources must be broadened, with greenhouse gas emissions
reduced. There is also a pressing need to reduce pollution by coal and oil
extraction and combustion (which continue to cause more deaths per year than
nuclear power has in its entire history).
Renewables are a key part of
the solution, but no country can be sure of the reliability of energies such as
wind or solar in 20 to 50 years, given changing climatic conditions. Relying on
neighboring countries for power also carries risks.
There seems to be no
alternative but to include nuclear in the energy mix for the foreseeable
future. So, what do new generations of fission, fusion and hybrid offer?
Modern power stations using fission, which harnesses energy from the
radioactive decay of uranium and other fissile materials, are considerably safer
than older ones such as Fukushima. This is because of stronger containment
structures, more secure storage of spent fuel rods and emergency systems to
prevent overheating. Future developments will greatly reduce the volumes of
radioactive waste produced.
As the supply of uranium is limited, there
are controversial plans in some countries to construct fast breeder reactors to
recycle waste and use the fuel more efficiently. However, there are
proliferation dangers associated with the plutonium by-product.
will only continue to be acceptable if the immediate risks of the systems are
reduced. Despite improved safety, the rare but catastrophic failures of
operations such as Chernobyl cannot be dismissed. As Fukushima showed,
there are also remaining risks from natural hazards and even aircraft crashes –
plus the dangers of fission associated with the storage of waste for over 10,000
The principle of controlled thermonuclear fusion is to
extract energy from processes similar to those occurring inside the Sun, where
hydrogen atoms are fused together to form helium. This is a “clean” process with
negligible long-lived radioactive waste.
In the United States, President
Barack Obama’s budget request for the magnetic fusion program for fiscal year
2013 was $400 million. However, the overall US domestic program was stripped
back to increase funding for the International Thermonuclear Experimental
Reactor (ITER) project, whose budget, $26 billion, has increased by a factor of
three in the past five years.
Taken overall, because of the great size
needed for a “pure” fusion reactor and the unsolved problem of fabricating
materials to withstand the materials requirement, the development challenges are
substantial and may take decades to overcome.
The long-term future
of nuclear energy may therefore lie with combining nuclear fission (atoms
splitting) and fusion (atoms merging) in a hybrid reactor. Indeed, governments,
agencies and research institutes are already moving tentatively in this
Hybrid fusion was first proposed by the American Nobel
laureate Hans Bethe to enable more widely available reserves of nuclear fuels
other than uranium, such as thorium, to be used. Hybrid could become a reality
within the next two decades – the International Atomic Energy Authority has
started a project on conceptual development of steady state compact fusion
neutron sources, and the Institute of Plasma Physics in China is planning to
build a hybrid fusion proof-of-principle prototype experiment by 2025.
International experiments are underway into the critical fusion parts of such a
The basic principle is that neutrons generated by fusion in the
plasma core stimulate fission in the outer blanket that contains uranium or
other fissile materials (which could include nuclear waste). Because
there is relatively less energy extracted from the plasma than in pure fusion,
continuous operation can be engineered more readily.
The fission is well
below critical mass and only operates when there is a current flowing in the
plasma, which can be switched off at a moment’s notice. This is why the system
is safer, especially in regions where earthquakes and tsunamis can
A major advantage of hybrid reactors for countries without uranium
is that they use a wider range of fuels. And they do not produce the long-lived
waste produced in fission reactors because the high-energy neutron flux from the
fusion process transmutes these into isotopes that decay over a hundred years,
rather than tens of thousands.
Not only does this eliminate some nuclear
waste problems, it helps to rid the world of weapons-grade materials.
Furthermore, if thorium is used, it cannot be converted into weapons-grade
While even modest-sized hybrid reactors could provide affordable
and almost limitless energy, their power output can be controlled through the
fusion process. Thus the operation is safe enough for a power station to be
located even in countries prone to natural hazards.
controllability would allow fusion-fission power to be used either as base load
or more flexibly in combination with renewable energy, which is inherently more
Many aspects of hybrid nuclear require further intense
research; current collaboration between groups in Russia, China, the United
States, South Korea and Britain needs to involve more countries. While
workable hybrid technology is still some way off, time-frames could be
accelerated with the right commitments from the public and private
Taken overall, this emerging hybrid option deserves wider
understanding and support if we are going to have the maturity of debate we need
about the role that nuclear energy can play in the future.
Hunt, a former fusion technology researcher, is a visiting professor at Delft
University of Technology. Graham O’Connor is a former senior scientist at ITER.