When
the first atomic bomb test, code-named “Project Trinity,” was conducted on July
16, 1945, civilization moved from the chemical era—during which atomic energy
was outsourced to the sun—to the nuclear era, when induced atomic reactions on
Earth could produce energy. Humanity’s relationship with the atom may be about
to change again, into an age of controlled nuclear fusion for electricity
generation. If
handled skillfully and with sufficient political will, fusion could reduce the
threat of both nuclear weapons proliferation and climate change, the two risks
that academic Noam Chomsky claims have the greatest chance of ending
our very existence in the 21st century. But the transition from
fission-generated electricity to fusion will be precarious if appropriate
safeguards are not taken. A new
energy source is clearly needed, considering the five- to seven-fold increase
in electrical demand predicted to occur between the years 2000 and 2100 and the
potentially devastating impacts of man-made climate change caused by consuming
fossil fuels to meet this demand. To overcome these challenges, nuclear energy
may be part of the solution—however reluctant society may be to consider it. When
we think of nuclear energy, we have an overwhelming tendency to think of
fission. There may be an even better source of nuclear energy, however, in the
form of fission’s close cousin: fusion. Nuclear
fusion could come into play as soon as 2050, depending upon funding, the
success of upcoming fusion experiments, and the viability of other
alternatives, says a position paper published by the European Fusion
Development Agreement in November 2012. And considering the problems involved
with fission, the sooner we move to fusion, the better. Fusion
benefits regarding proliferation. In the most likely nuclear fusion reaction
contemplated for use in energy production, atoms of two isotopes of hydrogen
join, creating a helium isotope and throwing off energy. (In comparison,
fission generates energy by splitting a heavy atom into several lighter atoms.) A
reactor using fusion to generate electricity is intrinsically safe: First, a runaway
nuclear chain reaction cannot take place, under any circumstances. Second, no
long-lived, highly radioactive products are created. Third, of those magnetic
confinement fusion reactors that will require radioactive fuels such as
tritium, both the radioactive fuel requirements and fuel half-life are orders
of magnitude lower than their fission counterparts. In
contrast, a fission reactor is inherently more dangerous: If its safety systems
fail, it can undergo a fatal chain reaction; significant quantities of spent,
radioactive fuel are produced; and the re-fuelling and disposal of waste
requires that highly radioactive materials be transported. Another
bonus of fusion power is that there is enough raw material on Earth to supply
the needs of fusion reactors for hundreds of thousands—if not millions—of years
at current consumption levels, according to David Mackay, professor of
engineering at Cambridge University and author of Sustainable Energy. With
these potential benefits in mind, there have been significant research and
development efforts on fusion power since the 1950s. At present, the device
most widely backed by physicists and engineers is the tokamak, a toroidal
(doughnut-shaped) vacuum chamber that uses magnetic fields to confine plasma
inside the device. This plasma is heated up to very high temperatures, giving
the atoms within enough velocity to overcome the forces of electric coulomb
repulsion and fuse together, releasing energy in the process. First-generation
tokamak reactors generating electricity
for the grid will use the heavy hydrogen isotopes of deuterium and tritium as
fuels; deuterium is abundant in nature and stable, while tritium is extremely
rare and radioactive, with a half-life of 12 years. Decades
of tokamak research has led to the construction of the International
Thermonuclear Experimental Reactor, or ITER, in southeastern France. This
international collaboration, with an estimated €13 billion ($18.9 billion) in
construction costs, is designed to prove once and for all the feasibility of
the tokamak design for energy generation. While there are other contenders,
including stellarators (mechanisms in a figure-eight shape that control plasmas
via magnetic confinement, much like a tokamak), and inertial confinement
devices (mechanisms that compress and heat fuel, typically by using lasers),
the tokamak probably most closely fits the bill for a first-generation,
commercially viable fusion reactor. Not
that other areas of research are standing still. Investigators announced a
major advance in fusion research in the February 12, 2014 issue of the journal
Nature, when the National Ignition Facility used a powerful assembly of lasers
to extract more energy from a controlled fusion reaction than was absorbed by
the fuel to trigger it, an important symbolic milestone. But because this
fusion reaction only showed a minimal net gain—it released about one percent of
the total energy required to power the lasers that caused the reaction—laser
inertial confinement fusion still needs to make profound scientific and
technological advances before becoming commercially viable. In contrast, the
world’s largest operating tokamak, the Joint European Torus, or JET, is already
close to producing as much energy as is put in. Meanwhile, ITER is expected to
produce 10 times as much energy as is put into it. Fusion
and weapons. From the standpoint of controlling nuclear weapons proliferation,
the tokamak has several important plusses. First,
tokamak reactor cores are surrounded by a “lithium blanket,” which absorbs
escaping neutrons to breed more tritium for use as reactor fuel. While this
approach could theoretically be used to enrich fuel to weapons grade level by
inserting thorium or uranium, researchers Robert J. Goldston and Alexander
Glaser concluded that it would not be realistic for anyone to do so surreptitiously.
This means that in a fusion-only era, any “horizontal proliferation”—the
process by which non-nuclear states or entities obtain nuclear weapons—would
become significantly harder. While in theory pure-fusion weapons could be
created that release a lethal neutron dose within a radius of several hundred
meters, this has not been achieved in practice. Second,
the tokamak device itself inhabits only a small part of an entire tokamak
reactor site. A large number of non-nuclear external systems are required to
run it, such as vacuum systems, cryogenics, and power supplies; to fit them in,
the ITER “platform” housing all the scientific apparatus is 42 hectares in size
(approximately 104 acres)—a landmass more than five times larger than New York
City’s Rockefeller Center. The sheer geographic size of a tokamak reactor
complex drastically lowers the possibility of any clandestine fusion plant
construction, Goldston and Glaser say. What’s
more, once a fusion plant has been built, the detection of any weapons-grade
fissile material produced there should be simple. By monitoring the lithium
blanket for traces of fissile material, it should be easy to detect if a fusion
plant is diverting some of its material to illegal weapons enrichment. Most
likely, only a very small amount could be enriched, hardly enough for making a
bomb, before attracting attention. If
such illicit activity is detected, disabling a tokamak would be relatively
straightforward, due to that vast array of essential support systems. Even if
the entire fusion reactor had to be destroyed—by dropping conventional bombs on
it, for example—the radioactive fallout would be negligible, due to the low
levels of fuel in the reactor at any given time (just a few grams). The worst
damage would come from the destruction of the tritium storage system, which
would release two-to-four kilograms of tritium—a substance with a 12.3-year half-life. Because
of these factors, it would be relatively easy to quickly and safely disable a
fusion facility and eliminate any nuclear weapons grade materials located on
site. Therefore, in a world powered only by fusion, it would be significantly
harder to clandestinely enrich fissile material, putting the brakes on nuclear
proliferation. (This is based on the assumption that no new clandestine
enrichment technologies come onboard by that time; while centrifuges are fairly
easy to detect, laser enrichment, for example, may be harder to monitor. Transition
risks. The period during which both fission and fusion plants coexist could be
dangerous, however. Just a few grams of deuterium and tritium are needed to
increase the yield of a fission bomb, in a process known as “boosting.” Because
a full-sized fusion reactor would use about 250 kilograms of fuel per year that
is half tritium and half deuterium, this would significantly increase the
amount of material available for such activities. Assuming that a one-gigawatt
fusion plant uses 125 kilograms of tritium per year, and allowing for a very
conservative one-percent level of uncertainty in the amount of tritium produced
in the lithium blanket, a country with 10 one-gigawatt fusion reactors would
have as many as 12.5 kg of tritium unaccounted for each year, or enough for
several thousand boosted weapons. Thus,
it would not be feasible to monitor and control tritium supplies down to the
tiny levels required to boost a bomb. Another
problem during transition lies in the ever-increasing sophistication of
advanced facilities to simulate the effects of the explosion of nuclear weapons
at laboratories such as the US National Ignition Facility. As the technology
for computerized simulation of nuclear weapons becomes more widespread, more
countries will be able to build and design increasingly powerful boosted
weapons without actual testing, and at a pace that would be much faster than
before. Consequently, the number of high-yield nuclear weapons and the number
of countries that own them could increase substantially during the period of
overlap between the eras of fission and fusion. As a
result, if humanity does decide to have fusion play a major role in energy
generation, it should complete the changeover swiftly, before the capacity to
build boosted and thermonuclear weapons becomes widespread. Even if only a
handful of countries have the technology, resources, and willpower to construct
facilities for making boosted and thermonuclear weapons, their very existence
is a liability. Will Fusion
be Affordable? Some physicists and engineers have expressed concerns that
even if a fusion reactor that produced significantly more energy than it
consumes could be built, it still might not be economically viable within the
current pricing framework. While the costs of a demonstration fusion reactor
are fairly well known, first-generation tokamak electrical plants could be
unaffordable when compared to nuclear fission, conventional fossil fuels, and
even renewables. But
economic viability depends upon one’s point of view. The price of a fusion
reactor (or any product for that matter) contains significant negative or
positive external costs, or “externalities,” which distort one’s perceptions of
its value. For example, greenhouse gases emitted by fossil fuels carry
significant externalities, in the form of carbon emissions into the atmosphere,
although they are typically not included in the price of electricity that a
customer sees on a monthly electric bill. Rather, future generations pay those
costs. As long as carbon is not priced or heavily underpriced, fossil fuel
technologies will continue to appear cheap compared to cleaner sources such as
fusion. However,
even with these distortions, an extensive US study called ARIES-AT found that
first-generation fusion reactors would be competitive with renewables and
fossil fuel, even without a carbon tax. Since it is likely that such a
carbon-pricing mechanism will be enacted by the time fusion reactors come
online, there is a strong likelihood that fusion will be very economically
attractive. If by
2050 there is a choice between building large numbers of fast breeder reactors
(which could clandestinely provide fission fuel for thousands of nukes per
year), or emitting an extra several billion tons of carbon dioxide into the
atmosphere, the decision will not be easy. To avoid this dismal choice, then
widespread, commercially viable fusion is required—assuming there are no other
viable technologies. There
comes a critical point in a civilization’s development when its resource and
energy consumption are so great that exploiting the atom may well be the only
way to maintain a high level of advance. While nuclear technology has the
potential to terrify, dehumanize, and exterminate, if used wisely it also has
the potential to liberate human civilization from the shackles of fossil fuels.
A swift transition from fission to fusion not only would allow us to escape the
worst medium- to long-term environmental and social ramifications of climate
change, it also would enable the creation of a more stable and credible
equilibrium in a world with no nuclear weapons. A world without nuclear weapons
but with fissile material will always be in fragile equilibrium; a world
without both would be far more sustainable.
Humanity’s
past failure to wield the double-edged nuclear sword skillfully has been
permanently etched into the annals of history, from the bombing of Hiroshima
and Nagasaki, to the world build-up to 65,000 nuclear weapons, to dozens of
seriousnear-misses,
during which nuclear war was only narrowly averted. Reaching and navigating the
fusion era, an advanced step in the progression of nuclear technology, would be
a testament to humanity’s foresight and organization, as well as a catalyst for
nuclear weapons abolition and the curtailing of the extremes of climate
change. |
Powered by Discuz! X3.2 © 2001-2013 Comsenz Inc.