A BULLEETITINN - Fusion Energy - INTERNATIONAL ATOMIC ENERGY AGENCY - Reporterre
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
IAEE A BULLE
IA BULLE TI
TINN
INTERNATIONAL ATOMIC ENERGY AGENCY
IAEA’s flagship publication | May 2021 | www.iaea.org/bulletin
Fusion Energy
What is fusion, and why is it so difficult to achieve? page 4
ITER: The world’s largest fusion experiment, page 10
Uniting countries through fusion research and cooperation, page 22
The International Atomic Energy Agency’s mission is to prevent the
spread of nuclear weapons and to help all countries — especially in
the developing world — benefit from the peaceful, safe and secure
use of nuclear science and technology.
Established as an autonomous organization under the United
Nations in 1957, the IAEA is the only organization within the UN
system with expertise in nuclear technologies. The IAEA’s unique
specialist laboratories help transfer knowledge and expertise to
IAEA Member States in areas such as human health, food, water,
IAEA BULLETIN
industry and the environment.
is produced by the
Office of Public Information The IAEA also serves as the global platform for strengthening
and Communication (OPIC) nuclear security. The IAEA has established the Nuclear Security
International Atomic Energy Agency Series of international consensus guidance publications on nuclear
Vienna International Centre security. The IAEA’s work also focuses on helping to minimize the
PO Box 100, 1400 Vienna, Austria
risk of nuclear and other radioactive material falling into the hands
Phone: (43-1) 2600-0
of terrorists and criminals, or of nuclear facilities being subjected to
iaeabulletin@iaea.org
malicious acts.
Managing Editor: Michael Amdi Madsen
Editor: Miklos Gaspar The IAEA safety standards provide a system of fundamental
Design and production: Ritu Kenn safety principles and reflect an international consensus on what
constitutes a high level of safety for protecting people and the
IAEA BULLETIN is available online at
environment from the harmful effects of ionizing radiation. The
www.iaea.org/bulletin
IAEA safety standards have been developed for all types of nuclear
Extracts from the IAEA material contained in the facilities and activities that serve peaceful purposes, as well as for
IAEA Bulletin may be freely used elsewhere provided protective actions to reduce existing radiation risks.
acknowledgement of their source is made. If the
attribution indicates that the author is not an IAEA The IAEA also verifies through its inspection system that Member
staff member, permission to republish other than for States comply with their commitments under the Nuclear
the use of review must be sought from the author or Non-Proliferation Treaty and other non-proliferation agreements
originating organization.
to use nuclear material and facilities only for peaceful purposes.
Views expressed in any signed article appearing in
The IAEA’s work is multi-faceted and engages a wide variety
the IAEA Bulletin do not necessarily represent those
of the International Atomic Energy Agency and the of partners at the national, regional and international levels.
IAEA accepts no responsibility for them. IAEA programmes and budgets are set through decisions of its
policymaking bodies — the 35-member Board of Governors and
Cover: the General Conference of all Member States.
In a tokamak, plasma particles — heated to hundred
of millions of degrees and confined by magnetic
The IAEA is headquartered at the Vienna International Centre.
fields — fuse together producing energy.
Field and liaison offices are located in Geneva, New York, Tokyo
(Shutterstock.com)
and Toronto. The IAEA operates scientific laboratories in Monaco,
Follow us on Seibersdorf and Vienna. In addition, the IAEA supports and
provides funding to the Abdus Salam International Centre for
Theoretical Physics, in Trieste, Italy.
Foreword
Helping make fusion a reality
By Rafael Mariano Grossi, Director General, IAEA
W hen senior IAEA officials attended the
second United Nations International
Conference on the Peaceful Uses of Atomic
also called DEMOs, which aim to produce
electricity from fusion for the first time.
Energy in 1958, they witnessed the release The IAEA is at the forefront of DEMO
of what until then had been State secrets development, facilitating international
— attempts by countries to harness the coordination and sharing best practices in
power of nuclear fusion. According to those projects globally (see article, page 12). The
disclosures, fusion promised to provide near IAEA is fostering discussion on DEMOs
limitless energy for society. Fusion requires and advancing broad-ranging international
nuclei to be brought together in a process that dialogue, in order to overcome highly
releases much more energy from the same technical challenges and make fusion energy
amount of fuel than nuclear fission, where a reality.
atoms are split.
Nuclear Fusion, a scientific journal
In the late 1950s, when fossil fuels’ future published by the IAEA, bears testimony
still seemed limitless and climate change was to our commitment to fusion research. It is
not yet being considered, fusion was seen as the longest running and most authoritative “The current level
‘nice to have’: a vision of energy generation fusion journal in the world. It supports fusion of international
for the distant future. How different the world researchers and engineers globally, receives commitment is bringing
we live in is today, with demand for clean half a million full text downloads each year us closer to a fusion
energy outstripping supply. This has made and is consistently the highest impact journal
clean sources of energy, such as fusion, of in its field. future than ever before.”
interest to policymakers, investors and the — Rafael Mariano Grossi,
wider public. In this Bulletin, we present the efforts of Director General, IAEA
governments and the growing involvement
Fusion generates four times more energy per of the private sector in fusion. The increasing
kilogram of fuel than fission, and nearly four interest from investors and major energy
million times more energy than burning oil producers show that the technical advances
and coal. The current level of international needed to make a fusion a reality are
commitment is bringing us closer to a fusion accelerating.
future than ever before.
To paraphrase Lev Artsimovich, a famous
A prime example of this is ITER, the world’s Soviet era physicist, “Fusion will be ready
largest fusion experiment (see article, page when society needs it.” That time of need is
10) which unites scientists from 35 countries now. Addressing climate change has become
in a quest to achieve a self-sustaining fusion a global priority and decarbonizing our
reaction. Construction is under way, and, energy sources is one of our most important
when complete, ITER promises to usher in tasks. Harnessing fusion energy offers
the next phase of fusion energy development humanity a clean energy future that is closer
— demonstration fusion power plants, than ever before.
(Photo: ITER) (Photo: ITER) (Photo: Freepik.com)
IAEA Bulletin, May 2021 | 1
Contents
1 Helping make fusion a reality
4 What is fusion, and why is it so difficult to achieve?
6 Magnetic fusion confinement with tokamaks and
stellarators
8 Exploring alternatives to magnetic confinement
10 ITER: The world’s largest fusion experiment
12 Demonstration fusion plants
A stepping stone to large-scale, commercial
electricity production
14 Safety in fusion
An inherently safe process
2 | IAEA Bulletin, May 2021
Contents
16 How IAEA databases help advance research towards the
commercial use of fusion
18 Burning plasma
A critical stepping stone towards fusion power
20 Closing fusion’s materials and technology gaps
22 Uniting countries through fusion research and cooperation
Q&A
24 Fusion: Ready when society needs it
World View
26 Moonshots and Sure Shots
Why Fusion Needs Enterprises and Start-ups
— By Simon Woodruff
IAEA Updates
28 IAEA News
32 Publications
IAEA Bulletin, May 2021 | 3
Fusion Energy
What is fusion, and why is it so
difficult to achieve?
By Irena Chatzis and Matteo Barbarino
F ive hundred years ago, the Aztec
civilization in today’s Mexico believed
that the sun and all its power was sustained
The amount of energy produced from
fusion is very large — four times as
much as nuclear fission reactions — and
by blood from human sacrifice. Today, we fusion reactions can be the basis of future
know that the sun, along with all other stars, fusion power reactors. Plans call for first-
is powered by a reaction called nuclear generation fusion reactors to use a mixture
fusion. If nuclear fusion can be replicated of deuterium and tritium — heavy types of
on earth, it could provide virtually limitless hydrogen. In theory, with just a few grams
clean, safe and affordable energy to meet the of these reactants, it is possible to produce a
world’s energy demand. terajoule of energy, which is approximately
the energy one person in a developed
So how exactly does nuclear fusion work? country needs over sixty years.
Simply put, nuclear fusion is the process by
which two light atomic nuclei combine to form
a single heavier one while releasing massive Reaching for the stars
amounts of energy. Fusion reactions take place While the sun’s massive gravitational force
in a state of matter called plasma — a hot, naturally induces fusion, without that force a
charged gas made of positive ions and free- higher temperature is needed for the reaction
moving electrons that has unique properties to take place. On earth, we need temperatures
distinct from solids, liquids and gases. exceeding 100 million degrees Celsius and
intense pressure to make deuterium and
To fuse on our sun, nuclei need to collide tritium fuse, and sufficient confinement to
with each other at very high temperatures, hold the plasma and maintain the fusion
exceeding ten million degrees Celsius, reaction long enough for a net power gain,
to enable them to overcome their mutual i.e. the ratio of the fusion power produced to
electrical repulsion. Once the nuclei the power used to heat the plasma.
overcome this repulsion and come within a
very close range of each other, the attractive While conditions that are very close to
nuclear force between them will outweigh those required in a fusion reactor are now
the electrical repulsion and allow them to routinely achieved in experiments, improved
fuse. For this to happen, the nuclei must be confinement properties and stability of the
confined within a small space to increase the plasma are needed. Scientists and engineers
chances of collision. In the sun, the extreme from all over the world continue to test new
pressure produced by its immense gravity materials and design new technologies to
create the conditions for fusion to happen. achieve fusion energy.
The sun, along with all other stars, is powered by a reaction
called nuclear fusion. If this can be replicated on earth,
it could provide virtually limitless clean, safe and affordable
energy to meet the world’s energy demand.
(Image: NASA/SDO/AIA)
4 | IAEA Bulletin, May 2021
Fusion Energy
Nuclear fusion and plasma physics research
are carried out in more than 50 countries,
and fusion reactions have been successfully
achieved in many experiments, albeit without
demonstrating a net fusion power gain. How
long it will take to recreate the process of the
stars will depend on mobilizing resources
through global partnerships and collaboration.
A history of collaboration
Ever since nuclear fusion was understood
in the 1930s, scientists have been on a quest
to recreate and harness it. Initially, these
attempts were kept secret. However, it soon
became clear that this complex and costly
research could only be achieved through
collaboration. At the second United Nations deposited with the IAEA Director General. A mixture of deuterium and
International Conference on the Peaceful After ITER, demonstration fusion power tritium — two hydrogen
Uses of Atomic Energy, held in 1958 in plants, or DEMOs are being planned to isotopes — will be used to
Geneva, Switzerland, scientists unveiled show that controlled nuclear fusion can fuel future fusion power
nuclear fusion research to the world. generate net electrical power. The IAEA plants. Inside the reactor,
hosts workshops on DEMOs to facilitate deuterium and tritium
The IAEA has been at the core of collaboration in defining and coordinating nuclei collide and fuse,
international fusion research. The IAEA regular DEMO programme activities releasing helium and
launched the Nuclear Fusion journal in 1960 around the world (see article, page 12). neutrons.
to exchange information about advances (Image: IAEA/M. Barbarino)
in nuclear fusion, and it is now considered It is expected that fusion could meet
the leading periodical in the field. The humanity’s energy needs for millions of years.
first international IAEA Fusion Energy Fusion fuel is plentiful and easily accessible:
Conference was held in 1961 and, since 1974, deuterium can be extracted inexpensively
the IAEA convenes a conference every two from seawater, and tritium can be produced
years to foster discussion on developments from naturally abundant lithium. Future fusion
and achievements in the field. reactors will not produce high activity, long
lived nuclear waste, and a meltdown at a
After two decades of negotiations on the fusion reactor is practically impossible.
design and location of the world’s largest
international fusion facility, ITER was Importantly, nuclear fusion does not emit
established in 2007 in France, with the aim of carbon dioxide or other greenhouse gases into
demonstrating the scientific and technological the atmosphere, and so along with nuclear
feasibility of fusion energy production (see fission could play a future climate change
article, page 10). The ITER Agreement is mitigating role as a low carbon energy source.
IAEA Bulletin, May 2021 | 5
Fusion Energy
Magnetic fusion confinement with
tokamaks and stellarators
By Wolfgang Picot
T he first fusion reactions in a laboratory
were achieved in 1934 — a major
breakthrough at the time. Today, however,
Fusion power
Fusion power exploits energy released from
the ‘fusion’ of light atomic nuclei. When two
achieving a fusion reaction is not particularly such particles merge, the resulting nucleus is
difficult: in 2018, a twelve-year-old entered slightly lighter than the sum of the originals.
the Guinness World Records as the youngest The difference, rather than disappearing, is
person to successfully create a fusion converted into energy. Amazingly, this tiny
experiment at home. loss of mass translates into a tremendous
amount of energy that makes the pursuit of
Unfortunately, such experiments produce fusion energy highly worthwhile.
bursts lasting just fractions of seconds,
and achieving and sustaining these fusion There are three states of matter: solid, liquid
reactions for prolonged periods remains a and gas. If a gas is subjected to very high
major challenge. Only by developing a steady temperatures, it becomes a plasma. In plasma,
and reliable way of producing fusion power electrons are stripped from the atoms. An
can fusion become a commercially viable atom with no electrons orbiting around the
energy source. nucleus is said to be ionized and is called an
How a tokamak works:
The electric field induced by a
transformer drives a current (big
red arrows) through the plasma
column. This generates a
poloidal magnetic field that
bends the plasma current into
a circle (green vertical circle).
Bending the column into a
circle prevents leakage and
doing this inside a doughnut-
shaped vessel creates a
vacuum. The other magnetic
field going around the length of
the doughnut is referred to as
toroidal (green horizontal circle).
The combination of these two fields
creates a three-dimensional curve, like a
helix (shown in black), in which the
plasma is highly confined.
6 | IAEA Bulletin, May 2021
Fusion Energy
ion. As a result, plasma is made Same challenge, different
of ions and free electrons. In this solutions
state, scientists can stimulate ions so that As stellarator configurations are
they smash into one another, challenging to build, most fusion
fuse and release energy. experiments today are tokamaks
(a short form for a Russian expression
Keeping plasmas stable in order that translates as ‘toroidal chamber with
to extract energy is difficult. They magnetic coils’). About 60 tokamaks and
are chaotic, super-hot and prone to 10 stellarators are currently operating.
turbulence and other instabilities.
Understanding, modelling and Both reactor types have certain
controlling plasma is extremely advantages. While tokamaks are better
complex but researchers have made at keeping plasmas hot, stellarators are
great strides over the past decades. better at keeping them stable. Despite
Twisting the magnets can
also produce the helical
shape without the need for a
transformer — this kind of
configuration is called a
stellarator.
(Images: Max Planck Institute for Plasma
Physics, Germany)
Scientists use magnetic confinement the tokamak’s current prevalence, it is
devices to manipulate plasmas. The most still possible that stellarators could one
common fusion reactors of that kind are day become the preferred option for a
tokamaks and stellarators. Currently, prospective fusion energy plant.
these are the most promising concepts
for future fusion energy plants. Researchers have made great strides
in magnetic confinement fusion and
Both reactor types make use of the fact can now achieve plasmas of very high
that charged particles react to magnetic temperatures with ease. They have
forces. Strong magnets in the reactors developed powerful magnets to handle
keep the ions confined. Electrons are plasmas and novel materials that can
also bound by the reactors’ forces and withstand the challenging conditions
play a role in the surroundings. The in the reactor vessels. Advances in
magnetic forces constantly spin the experimentation, theory, modelling
particles around their doughnut-shaped and simulation have led to a deeper
reactor chambers to prevent them from understanding of the behaviour of
escaping the plasma. plasmas, and experimental tokamak and
stellarator devices like will be central
to proving the scientific and technical
viability of fusion energy production.
IAEA Bulletin, May 2021 | 7
Fusion Energy
Exploring alternatives to magnetic
confinement
Laser fusion, linear devices and advanced fuels
By Aleksandra Peeva
L aser fusion is a method of igniting
nuclear fusion reactions and is a potential
alternative to magnetic confinement (see
“We have made significant progress at NIF
over the past five years and are now able to
produce two and a half to three times more
article, page 6). It does this through inertial energy than what we put into the hot spot of
confinement, using high-power lasers to the fuel,” said Brian Spears, Deputy Lead for
heat and compress tiny spherical capsules Modelling in Inertial Confinement Fusion at
containing fuel pellets made up of hydrogen NIF. “Getting to the 30 times amplification
isotopes such as deuterium and tritium. gain is still a major goal, but this is a
non-linear process and we have already taken
The intense heating of the capsule surface many important technical steps to get there.”
creates a micro-implosion of the fuel, and, as
a result, the pellet’s surface layer is ablated Increasing the central pressure inside the
and explodes. The inertia created by this fuel hot spot to several billion times of
process keeps the fuel confined for long atmospheric pressure is key to achieving
enough for fusion reactions to take place. commercially viable fusion. NIF has made
substantial progress in this area by shifting
Experiments in the field of laser fusion began from plastic to micro crystalline, high density
in the 1970s. Today, the National Ignition carbon capsules, improving engineering
Facility (NIF) at the Lawrence Livermore features used to support the capsules and
National Laboratory in the United States of enhancing the structures used to fill the
America has 192 laser beams and is easily the capsule with fusion fuel. This allowed experts
world’s biggest laser facility. At NIF, lasers to significantly increase the energy coupling
heat the inner walls of a cylindrical golden efficiency from the energy produced by the
container, called a hohlraum, that holds the laser to the energy absorbed by the capsule,
capsule containing the deuterium–tritium and ultimately produce more energy.
fuel pellet. The laser–hohlraum interaction
generates X-rays, which heat up and compress “Major scientific challenges still lie ahead,
the capsule, creating a central hot spot inside but recent advancements at NIF and other
the pellet, where fusion reactions take place. facilities prove that we are getting closer to
achieving the ignition threshold via laser
To achieve ignition — the point at which fusion,” said Spears.
fusion becomes completely self-sustaining
— NIF’s capsules should release around 30 In 2020, the IAEA launched a new
times more energy than they absorb. coordinated research project (CRP),
8 | IAEA Bulletin, May 2021Fusion Energy
entitled “Pathways to Energy from Inertial Therefore, it has to be ‘bred’ in a nuclear
Fusion: Materials Research and Technology reaction between the fusion-generated
Development”. The project, which involves neutrons and lithium surrounding the reactor
24 institutes from 17 countries and is the wall. The energy of these neutrons also
fourth instalment in a CRP series on this presents significant challenges regarding the
field, focuses on developing high-gain materials in the reactor vacuum vessel, since,
capsule designs to achieve completely self- when the neutrons collide with the reactor
sustaining fusion. walls, its structures and components become
radioactive. This necessitates additional
considerations in radiation safety and waste
Fusion from colliding beams disposal (see article, page 14).
Another alternative to laser and magnetic
confinement approaches is using ion beams To bypass the challenges caused by the use
generated by particle accelerators and of tritium, there are now experiments using
targeting them at each other, with fusion alternative or advanced fusion fuels, such
taking place at their collision point. A big as proton–boron-11 (p–B-11). Boron-11 is
disadvantage of this method is that the non-radioactive and comprises around 80
probability of the particles bouncing off one percent of all boron found in nature, so it
another without fusing and producing energy is readily available. However, the major
is high. problem with p–B-11 fusion is that it would
require the plasma to be a hundred times
The private US company TAE Technologies hotter than plasma containing deuterium and
(TAE) uses a linear device: a 25-metre-long tritium. Fortunately, with laser ignition or
cylindrical reactor. Fusion is achieved by linear devices, heating is constrained to the
firing off two plasmas from each end of the hot spots, without the overall plasma having
reactor, which collide and merge in a cloud to be significantly hotter.
in the centre. Deuterium atoms are then fired
into the cloud to make it spin, thus keeping “P–B-11 is the cleanest, most
the plasmas hot and stable. environmentally friendly fuel source on
Earth, with no harmful by-products and
enough natural supply to sustain the planet
From alternative confinement to for millennia. Together, these factors can
advanced fuels maximize the safety, economics, efficiency Operators of the National
Another advantage of fusion through lasers and durability of fusion power plants,” said Ignition Facility (NIF)
or linear devices is that these methods could Michl Binderbauer, TAE’s Chief Executive inspect a final optics
more easily adapt to the use of fuels other Officer. “The main difficulty with p–B-11 is assembly during a routine
than deuterium and tritium. Traditionally, a that it requires higher temperatures than other maintenance period.
mixture of these hydrogen isotopes has been fuel cycles to sustain the fusion reaction. TAE NIF is the world’s largest
used to achieve fusion because they reach the has developed an alternative confinement and highest-energy laser
highest reaction rate at a lower temperature concept to address this challenge.” system and is located at
than other fuels. the Lawrence Livermore
Advanced fuels could thus provide a more National Laboratory.
However, tritium is radioactive and does not effective and efficient way to produce fusion (Photo: Lawrence Livermore National
Laboratory)
occur naturally in any significant quantities. energy in the future.
IAEA Bulletin, May 2021 | 9Fusion Energy
ITER: The world’s largest fusion
experiment
By Wolfgang Picot
W eighing 23 000 tonnes and standing at
nearly 30 metres tall, ITER will be an
impressive sight to behold. This nuclear fusion
As for the question of size, larger tokamaks
provide better insulation and confine the
fusion particles for longer, thus producing
reactor will sit at the heart of a 180-hectare more energy than smaller devices.
site, together with auxiliary housing and
equipment. The immense scale of ITER, Latin A significant indicator of a reactor’s
for “the way”, will considerably outsize the performance is its fusion power gain, or the
largest experimental fusion reactors currently ratio between the fusion power produced and
in operation — the Joint European Torus the power injected into the plasma to drive the
(JET) in the United Kingdom and the joint reaction. It is expressed by the symbol ‘Q’.
European–Japanese JT-60SA in Japan.
To date, JET has achieved the best gain,
But what is ITER’s potential, and, in an era with a Q value of 0.67, by producing
of miniaturization and optimization, why is it 16 megawatts (MW) of fusion power from
necessary to build a research device on such a 24 MW of heating power. Much higher
gigantic scale? Q values will be needed for electricity
production, however.
One of ITER’s primary goals is to prove that
fusion reactions can produce significantly
more energy than the energy supplied to Prerequisites for power
initiate the reaction process — resulting in Over the past 50 years of fusion
an overall gain in power. Reactors like ITER experimentation, the performance of fusion
are called tokamaks (see article, page 6), devices has increased by a factor of 100
and use a combination of heating systems, 000, but a further increase by a factor of 5 is
strong magnets, and other devices to create needed to arrive at the level of performance
energy-releasing fusion reactions in super-hot required for a power plant. To achieve
plasmas. The resulting magnetic fields bind this, researchers are working to optimize
and spin the charged particles around the the plasma’s condition through changes in
doughnut-shaped reactor vessel so that these temperature, density and confinement
can fuse and produce fusion energy. ime (see article on page 8).
10 | IAEA Bulletin, May 2021Fusion Energy
Some of these improvements have been most of them still coordinate, cooperate, or
the result of experimental fusion reactors collaborate with the ITER Organization.
becoming larger. With ITER’s height and
radius being twice that of JET’s, its plasma The IAEA and the ITER Organization have had
volume will increase tenfold. Applying a close relationship from the very beginning,
novel designs and innovative materials, particularly in the areas of nuclear fusion
ITER will also integrate some of the most research, knowledge management, human
powerful plasma-heating devices ever used. resources development, and educational
With the injection of just 50 MW heating activities and outreach. The IAEA also
power into the plasma, it aims to produce helps the ITER Organization share their
500 MW of fusion power — giving a experiences in nuclear safety and radiation
Q value of at least 10 — in pulses that are protection with IAEA Member States,
each roughly 5–10 minutes long. including those not participating in the project.
This year, the ITER Organization, together with
ITER’s peak performance will be impressive, the French Alternative Energies and Atomic
but it will only be reached for a very short Energy Commission (CEA), will co-host the
amount of time. To become a steady source 28th IAEA Fusion Energy Conference.
of electricity, future fusion power plants will
need to operate continuously. A Q value of It is hoped that ITER will prove the scientific
five represents a critical threshold, above and technological feasibility of fusion power
which the plasma starts heating itself to production and, under its staged-approach
sustain the fusion reaction on its own. To research plan, will start conducting its first
better understand how to achieve this self- experiments in 2025. Full-power experiments
sustaining reaction, ITER aims to eventually should commence in 2035. If successful,
generate and maintain Q values of five for these developments will be a significant
periods much longer than ten minutes. milestone and will represent a historic bridge
between experimental research and the
first demonstration fusion power plants, or
A global collaboration DEMOs (see article, page 12). Envisioned
ITER’s 35 participating nations represent DEMOs will achieve a net electrical energy
more than half of the world’s population gain. Multiple preliminary concepts for
and 85 per cent of global gross domestic DEMO-type reactors are already under
product (GDP). While many other smaller consideration. If everything goes according
fusion experiments are under way globally, to plan, they could be in operation by
ITER construction site.
mid-century. (Photo: ITER)
IAEA Bulletin, May 2021 | 11Fusion Energy
Demonstration fusion plants
A stepping stone to large-scale, commercial
electricity production
By Irena Chatzis and Matteo Barbarino
T he aim of ITER, the world’s largest
fusion experiment, is to prove how to
create net energy from a fusion reaction.
breed and extract tritium. Challenges in the
fuelling, exhausting, confining, extracting
and separating of tritium will also need to
Demonstrating that net electricity can be be resolved.
produced from fusion energy will then
be the next significant step. This is where Another major difference between DEMO-
demonstration fusion power plants, or type and existing experimental reactors will
DEMOs, will come in. be the addition of appropriate systems and
technologies to capture and convert fusion
DEMOs require the DEMO-type reactors are more of a design power into electricity.
development of concept than a particular fusion machine
new materials and configuration. Preliminary designs for “DEMO-type machines require the design
publicly funded DEMOs, under development and integration of complex components
technologies.” in several countries, are yet to be finalized. and systems that are not part of existing
— Elizabeth Surrey, This will be done following results of the fusion experimental machines. Components
Head of Technology, ITER experiments. such as tritium breeding blankets, power
United Kingdom’s Atomic Energy generation, burn control, and so on, are
Authority DEMOs are planned to operate almost all required,” said Elizabeth Surrey, Head
continuously to produce more than of Technology at the United Kingdom’s
50 megawatts (MW) of net electrical gain. Atomic Energy Authority. “The operating
The key challenge they will set out to address conditions of a DEMO are particularly
is how to keep the fusion plasma stable for hostile to materials, as the burning plasma
long enough to produce energy on an generates a high flux of neutrons and high-
ongoing basis. power densities on the walls. DEMOs require
the development of new materials and
While a lot about DEMOs are still undecided, technologies.”
a public DEMO will likely be a tokamak-
type reactor and will use heavy hydrogen
isotopes — deuterium and tritium — as fuel. The role of the IAEA
However, the world’s available supply of Groups of researchers in various countries are
tritium is limited, and DEMOs themselves exploring DEMO concepts and approaches.
will need to produce sufficient tritium The IAEA facilitates international
supplies through so-called ‘blankets’ that coordination and the sharing of best practices
12 | IAEA Bulletin, May 2021Fusion Energy
through a series of Technical Meetings, India has announced plans to begin building
and, since 2012, through its regular DEMO a device called SST-2 to qualify reactor
Programme Workshops. These platforms concepts and components for a DEMO
foster discussion on physics and technology around 2027 and will then start construction
issues, facilitate the sharing of strategies for of a DEMO in 2037.
DEMO programmes and analyse potential
courses of action. Over time, the topical The Japanese Joint Special Design Team for
emphasis has shifted from broad visions to Fusion DEMO is currently working on the
the detailed technical challenges that must conceptual study of a steady state DEMO
be overcome. (JA DEMO), with construction planned to
start around 2035.
“By concentrating on identifying problems
and discussing ongoing research and In 2012, the Republic of Korea initiated a
development, the IAEA Technical Meeting conceptual design study for ‘K-DEMO’,
series and DEMO Programme Workshops targeting construction by 2037, with the
enable the community to define requirements potential for electricity generation starting
and analyse possible solutions in a in 2050. In its first phase (2037–2050),
collaborative manner. One example is the K-DEMO will be used to develop and test
emergence of plasma control as a major issue components, and will then utilize these
for DEMO-type machines when long, or near components. In its second phase, after
continuous plasma operation is required,” 2050, it is hoped that it will demonstrate net
said Surrey, who served as chair for the electricity generation.
last three DEMO Programme Workshops,
between 2016 and 2019. The Russian Federation is planning a fusion–
fission hybrid facility called DEMO Fusion
Neutron Source (DEMO-FNS), which
Plans around the world will harvest fusion-produced neutrons to
While various paths are still being explored turn uranium into nuclear fuel and destroy
to reach fusion-based electricity, the science radioactive waste. The DEMO-FNS is
and technology issues to be resolved are planned to be built by 2023 and is part of the
broadly agreed. Individual countries have country’s fast-track strategy to establishing a
different timelines, but the general consensus fusion power plant by 2050.
among scientists is that they can have an
electricity-producing DEMO-type reactor Fusion experts in the United States of
built and operating by 2050. America recently issued two reports that
Artist’s concept of a
recommend starting a national research and
fusion power plant
In China, significant progress has been made technology programme, including public–
converting the heat of
in planning for the China Fusion Engineering private partnerships, to ultimately bring
fusion into heat and
Test Reactor (CFETR). This device will help fusion to commercial viability. It aims to do
electricity.
bridge the gap between ITER and DEMOs. this in the period 2035–2040, with the aim of (Source: EUROfusion)
Construction of the CFETR will start in the positioning the country as a leader in fusion
2020s and will be followed by construction of and speeding up its transition to low carbon
a DEMO in the 2030s. energy by 2050.
In Europe, EUROfusion is responsible for In parallel, numerous privately funded
developing the design of a DEMO. The commercial enterprises are also making
project is currently in its conceptual design strides in developing concepts for fusion
phase (2021–2027) and aims to demonstrate power plants, drawing on the know-how
the technological and economic viability of generated over years of publicly funded
fusion by producing several hundred MWs of research and development and proposing
net electricity. even more aggressive timelines.
IAEA Bulletin, May 2021 | 13Fusion Energy
Safety in fusion
An inherently safe process
By Carley Willis and Joanne Liou
W hile nuclear fission derives energy
from splitting atomic nuclei, nuclear
fusion does so by joining them, releasing
the wall, generating tritium that can then be
reinjected into the machine.”
energy in the process. Though both atomic However, fusion and fission facilities do
reactions produce energy by modifying share some similarities, such as in how
atoms, their fundamental differences have radioactive material is handled and how
broad implications for safety. cooling systems are used. “Regulatory bodies
have vast experience in the realm of safety
The conditions required to start and maintain and security for fission. We are working with
a fusion reaction make a fission-type them to ensure that all applicable knowledge
accident or nuclear meltdown based on a is transferred to fusion,” González de Vicente
chain reaction impossible. Nuclear fusion said. “Not everything can be translated
power plants will require out-of-this-world one-to-one, however, and the differences
conditions — temperatures exceeding 100 with fusion, such as the reduced amount
million degrees Celsius to achieve high and variety of radioactive material, the
enough particle density for the reaction to impossibility of core meltdown conditions
take place. As fusion reactions can only and the lack of long lived waste, should
take place under such extreme conditions, be identified and addressed. The IAEA is
a ‘runaway’ chain reaction is impossible, helping to facilitate these efforts.”
explained Sehila González de Vicente,
Nuclear Fusion Physicist at the IAEA.
International collaboration
Fusion reactions depend on the continuous ITER, the world’s largest fusion experiment
input of fuel, and the process is highly has gathered experts from 35 countries to work
sensitive to any variation in working towards making fusion energy sources a reality,
conditions. Given that a fusion reaction could while also helping to solve fusion’s safety and
come to a halt within seconds, the process security challenges as the project develops.
is inherently safe. “Fusion is a self-limiting
process: if you cannot control the reaction, it A high degree of safety can be ensured
stops by itself,” she added. by applying relevant safety requirements
for fission, such as the IAEA safety
Furthermore, fusion does not produce highly standards, to fusion. For example, just as
radioactive, long lived nuclear waste. “Fusion with nuclear fission reactors, proposed
produces only low level radioactive waste fusion plants must also consider dose
and does not pose any serious danger,” said regulations, and installations should be
González de Vicente. Contaminated items, designed so that the minimum dose is ‘as
such as protective clothing, cleaning supplies low as reasonably achievable’, or ALARA.
and even medical tubes or swabs, are short However, given the fundamental differences
lived, low level radioactive waste that can be in the risk of accidents, the application of
safely handled with basic precautions. a graded approach is necessary to avoid
overregulating the fusion process. “The
Most current experimental fusion devices problem with all existing safety standards
use a mix of deuterium and tritium as fuel. is that they are geared towards fission,”
Tritium is a radioactive isotope of hydrogen said Stéphane Calpena, Deputy Head of
with a half-life of 12.3 years. As a result of the Safety & Quality Department at the
the fusion reaction, neutrons are released, ITER Organization. “We need to extract the
which impact and are absorbed by the wall standards that are relevant to fusion and apply
surrounding the reactor core, said González them in a manner commensurate with risk
de Vicente, making it radioactive. “The to make sure that the technology is not only
neutrons react with lithium contained in feasible, but that it is truly safe. Fusion is a
14 | IAEA Bulletin, May 2021Fusion Energy
new way to create energy, and is still very potential types and amounts of radioactive
much a young technology.” or hazardous material that could be released
into the environment at fusion facilities, as
The IAEA is helping to foster this technology well as on preparing publications equivalent
by holding Technical Meetings for experts to to IAEA Safety Standards Series Nos SSR-4
share knowledge that can aid in overcoming and SSG-12 for fusion. The meeting covered
challenges in fusion and ensure the safety topics such as risk criteria for, and the One of ITER’s vacuum
of fusion facilities. The First Joint IAEA– design and operation of fusion facilities. The vessel sectors is installed
ITER Technical Meeting on Safety and Workshop on Waste Management for Fusion, — a 440-tonne piece that
Radiation Protection for Fusion, chaired scheduled for October 2021, will look at will help contain the
by Calpena in November 2020, focused on how radioactive waste from fusion energy device’s plasma.
developing a methodology to determine the production is classified and disposed of. (Photo: ITER)
IAEA Bulletin, May 2021 | 15Fusion Energy
How IAEA databases help advance
research towards the commercial
use of fusion
By Aleksandra Peeva
T he promise of harnessing nuclear
fusion’s abundant energy potential
through commercial fusion requires a better
— compromising the integrity of the wall
material or causing the material to sputter
back into the plasma and cool it.
understanding of plasmas — superheated
ionized gases — and the development A reactor’s materials should also absorb as
of high-performance reactor materials. little tritium — one of the hydrogen isotopes
By supporting scientists studying plasma of the fusion’s fuel — as possible. Absorbed
behaviour, and modelling the properties of tritium fuel is lost fuel for the reaction. But
“Only with reliable materials used in fusion energy research, more importantly, tritium is radioactive, and
IAEA databases are helping to advance to minimize the amount and radiotoxicity
data from accurate research towards eventual energy production of the eventual nuclear waste generated, the
computation and on a commercial scale. reactor’s walls should ideally not absorb
experiments can the tritium and become radioactive in the process.
relevant properties of Central to developing fusion energy is
achieving and then maintaining the extreme
candidate materials be Exploring plasma behaviour
conditions needed for ‘fusion ignition’ — the
predicted.” point at which a fusion reaction is sustained A deep understanding of how plasma
— Christian Hill, Head, IAEA’s Atomic by its own generated energy. This requires behaves in a reactor is necessary to increase
and Molecular Data Unit the reaction’s plasma fuels to be confined in the length of time it can be confined by
a space for long enough to allow fusion to magnetic forces. IAEA databases hold
develop and heat itself to self-sufficiency. information on the processes occurring in
core plasma and edge plasma, as well as
Ignition also requires engineers to develop in neutral beam injection systems used to
high-performance reactor wall materials able heat the plasma towards ignition. They also
to withstand the steady flux of energy in contain data on the properties of various
the form of released heat and neutrons. This impurities that are deliberately injected into
energy heats up the walls, and the neutron the plasma for diagnostic purposes and to
bombardment can lead to material damage mitigate instabilities.
16 | IAEA Bulletin, May 2021Fusion Energy
The IAEA’s ALADDIN database is a of the IAEA’s Atomic and Molecular
searchable repository of evaluated collisional Data Unit. “Only with reliable data from
data for fusion-relevant processes. It is accurate computation and experiments can
used by the research community to perform the relevant properties of candidate materials
plasma diagnostics and learn about important be predicted.”
plasma parameters, such as temperature and
density. Using ALADDIN, scientists can Researchers use IAEA databases in fusion
better understand the collisional–radiative energy research and other plasma science and
properties of ions that are critical for reliable technology applications. Data are collected
plasma diagnostics. and evaluated by the IAEA through its
networks, coordinated research projects and
Technical Meetings, and distributed through
Modelling materials for fusion its free, searchable and curated online
A lack of facilities that replicate the extreme databases.
conditions of a fusion reactor makes creating
new materials for future fusion power plants “The value in a curated, international
complex. Using computational modelling database is in its role as a permanent,
techniques, high-performance computing trusted and accessible repository of evaluated
platforms and analytical experimental data that can be freely used by the fusion
characterization tools, experts are able to community. The IAEA’s Atomic and
design materials that can perform well in a Molecular Data Unit is unique in other
fusion energy environment. ways, too: it has existed for more than
40 years, which is pretty old in ‘fusion-data
Through modelling, new materials are being years’,” said Hill.
discovered and the reliability of existing
materials can be predicted. This is especially The IAEA’s databases are continuously
important for the reactor’s innermost wall, improved and expanded based on the
which is located closest to the plasma in specific data needs of researchers, including
the reactor vessel and protects the vessel the quantification and implication of
components from plasma-induced damage. uncertainties in data, and techniques for data
validation, curation and dissemination.
“The extreme environment of a nuclear
fusion reactor’s first wall demands a A visualization of the
careful choice of materials which must cascade of collisions leading
withstand high temperatures and particle to damage in a crystalline
bombardment without becoming eroded, All fusion-related databases maintained material.
brittle or radioactive, and without retaining by the IAEA can be accessed at: (Image: courtesy of Andrea Sand/
the hydrogen fuel,” said Christian Hill, Head amdis.iaea.org/databases Aalto University)
IAEA Bulletin, May 2021 | 17Fusion Energy
Burning plasma
A critical stepping stone towards fusion power
By Matteo Barbarino
I n our sun’s core, extreme temperatures and
the immense pressure created by massive
gravitational forces create ideal conditions for
this heating is critical to harnessing fusion
power,” said Matthew Hole, Professor at the
Australian National University.
nuclear fusion.
Safe and sustainable fusion power relies
Recreating that on earth, however, without on these charged alpha particles and their
the extreme gravitational forces of a star, energy to maintain the plasma at a constant
and by means of a fusion reactor, poses temperature, thus allowing the reactions to be
many technical challenges. The biggest of self-sustaining. Achieving this is essential to
these is keeping the heated fusion plasma operating a fusion reactor.
— a charged gas composed of ions and free
electrons in which the reaction takes place In the 1990s, experimental fusion reactors
— at over 100 million degrees Celsius, produced up to 16 megawatts (MW) of
confining its particles in a magnetic field power for a little less than a second. In those
“ITER will provide us and holding them together long enough for experiments, the alpha particles provided
reactions to take place and produce energy. only about ten per cent of the heat externally
with the opportunity to supplied. Understanding what happens when
study ‘burning plasmas’ Understanding and validating current alpha particles provide more of the heat will
in which at least 66 per hypotheses of how this hot fusion plasma be explored through initiatives like ITER
cent of the total heating behaves are among the key issues fusion — an international reactor-scale experiment
scientists and engineers must address to under construction in France (see article,
will come from fusion eventually produce electricity from fusion. page 10).
alpha particles.”
— Alberto Loarte, Head of the “ITER will provide us with the opportunity to
Science Division, ITER Organization
A super fuel for temperatures study ‘burning plasmas’ in which at least 66
hotter than the sun per cent of the total heating will come from
Fuel options for fusion are limited. The fuel fusion alpha particles. In these conditions,
with the highest performance potential on ITER will produce 500 MW of fusion power
earth is made from a mixture of deuterium for up to 500 seconds,” said Alberto Loarte,
and tritium ions — two heavier forms of Head of the Science Division at the ITER
hydrogen. When colliding under extreme Organization. He said his organization’s
temperatures, deuterium and tritium fuse to experiments will provide much-needed
generate charged particles with two protons answers to key questions in burning plasma
and two neutrons, known as alpha particles, physics, such as how to create a plasma
as well as free neutrons. While the neutrons that is self-sustained by the internal heating
escape the magnetic field and do not interact from its alpha particles, and how to find
with the plasma, the alpha particles are optimal operating conditions for high fusion
confined by the magnetic field and further performance that are compatible with the
heat the surrounding plasma. “Controlling power handling capabilities of the reactor wall.
18 | IAEA Bulletin, May 2021Fusion Energy
How to make plasma that would allow for high performance
self-sustaining without breaching operational boundaries
An important indicator of a fusion reactor’s for long periods. Breaching operational
performance is its ‘fusion power gain’, boundaries is problematic as it could lead to
which is determined by the plasma’s instabilities that can terminate the plasma in a
temperature, density, and energy confinement phenomenon known as plasma disruption.
time — a measure of how effectively the
magnetic field maintains the plasma energy “In a torus-shaped tokamak type reactor, like
over time. Creating a self-sustaining reaction ITER, a disruption could rapidly terminate
requires three conditions: a temperature of the plasma over a few milliseconds and
about 100 million degrees Celsius; a density generate substantial thermal and mechanical
that is one million times less that of air; stress to the reactor’s components,” said
and the energy confinement time of just Michael Lehnen, Scientific Coordinator for
a few seconds. ITER Organization’s Stability & Control
Section. “The IAEA is helping to avoid this
Although the conditions required are well scenario by fostering information exchange
understood, how they can be reached on experimental, theoretical and modelling
simultaneously is far from obvious. For work in this area, with special emphasis in
example, increasing the plasma density is the next few years on developing a solid
advantageous in principle, as it increases the basis for the design of ITER’s disruption
likelihood of fusion reactions. However, as mitigation system.”
the density approaches its maximum, many
experiments show that plasma confinement Recent experiments and modelling efforts
degrades more than expected, says Richard incorporating artificial intelligence-
Hawryluk, Associate Director for Fusion at based methods are shedding light on the
the Princeton Plasma Physics Laboratory in requirements for effective plasma control —
the United States of America. helping to pave the way for the safe design
and operation of future fusion power plants.
For the ITER experiment to succeed, “Powerful advanced statistics and machine
solutions to these problems need to be found, learning approaches applied to disruption
and much of the research to do so requires research can help identify significant patterns
international cooperation. Through its series and reveal hidden information in years’
of Technical Meetings on energetic particle worth of experimental data,” said Cristina
physics, plasma control, and fusion data Rea, Research Scientist at the Massachusetts
acquisition, validation and analysis, the IAEA Institute of Technology (MIT) Plasma
provides a platform for the exchange of Science and Fusion Center.
scientific and technical results, and is helping
to develop modelling tools that can be used A productive synergy among control
to predict the behaviour of fusion plasma in physicists, modellers, scenario developers
ITER and future fusion power reactors. and data engineers is emerging, where new
solutions are being designed to avoid these
A visualization of high
disruptive boundaries. More work must be
Finding the ‘sweet spot’ done to evaluate the applicability of these
energy particles, in the form
of plasma, flowing through a
One of the greatest challenges is finding data-driven methodologies for projects
tokamak-type reactor.
optimal operating conditions with such as ITER, but the results thus far are (Photo: Shutterstock)
maximum fusion power and plasma control encouraging, Rea said.
IAEA Bulletin, May 2021 | 19Fusion Energy
Closing fusion’s materials and
technology gaps
By Matteo Barbarino
T he most challenging science and
engineering endeavour on earth is
arguably fusion. Building a fusion reactor,
“The energy of the fusion-generated neutrons
poses serious challenges to the fusion power
plant’s first wall and vacuum vessel, which
achieving a self-sustaining reaction and means considerations need to be given to
converting that power to near inexhaustible radiation damage, biological shielding,
electricity will change humanity and our remote handling, and safety,” explained Ian
relationship with energy forever. As enticing Chapman, CEO of the United Kingdom
as this may sound, progress has not been easy Atomic Energy Authority.
or smooth. Technical challenges around the
structures, fuels and materials needed to hold Chief among engineers’ tasks is developing
such complex machines together remain only high-performance materials that are able
partially solved. to sustain high temperatures and the
intense neutron fluxes from the reaction.
Understanding the technical limits and gaps Understanding the impact of operating
of knowledge faced by fusion energy today conditions on the plasma-facing components
begins by looking inside the reactor itself. is also essential for the future of large-scale
fusion power plants.
Inside a tokamak reactor (see article, page 6),
a super-hot ionized gas or ‘plasma’ is heated
to over 100 million degrees Celsius (°C) to Materials built for extremes
induce fusion reactions. Confined by powerful Creating structural and plasma-facing
magnetic fields, the walls of the reactor are materials that can withstand degradation
protected from the volatile plasma. from neutrons is a priority for researchers.
These materials need safety characteristics
Plasma used in nuclear fusion is usually made such as low neutron-induced radioactivity
up of two heavy isotopes of hydrogen — to minimize the production of radioactive
deuterium and tritium — which then fuse to waste. Today, however, there is a lack of
The ‘He Ion Source and DiFU produce helium and neutrons. In fusion power specialized fusion irradiation facilities
Dual-Beam Facility’ was installed plants, engineers hope to ‘breed’ or create where radiation degradation mechanisms
with IAEA support in Croatia’s additional tritium from the reaction itself with can be tested and materials can be developed
Ruđer Bošković Institute. yet untested lithium blanket shielding that and qualified under the
(Photo: IAEA) reacts neutrons resulting from fusion. necessary conditions.
20 | IAEA Bulletin, May 2021Fusion Energy
The IAEA is helping to address issues plasmas with better energy confinement —
associated with fusion materials development a critical parameter for the performance of a
and research by coordinating the drafting fusion device — ensuring the plasma is hot
of guidelines for reference material testing enough for long enough so that sustained
techniques, and by bridging knowledge fusion reactions can take place.
gaps in designing facilities for testing fusion
reactor materials and components. In ITER, the world’s largest fusion
experiment, the divertor will be made up of
“Technologies like the dual-beam ion facility 54 ‘cassettes’, each weighing 10 tonnes. The
installed in 2019 at the Ruđer Bošković conditions placed on the cassettes will be
Institute in Croatia with IAEA support can very demanding; facing steady heat fluxes of
simulate the conditions that a material would 10 to 20 megawatts per square metre, with
be exposed to in a fusion reactor. These parts exposed to temperatures of between
conditions include product transmutation and 1000°C and 2000°C, the cassettes will need
simulating damage produced by energetic to be replaced by remote handling at least
fusion-generated neutrons and particles,” said once during the machine’s lifetime. To deal
Melissa Denecke, Director of the IAEA’s with the extreme heat and damaging particles,
Division of Physical and Chemical Sciences. the components facing the plasma will be
armoured with tungsten, a material that has
The main part of a reactor where plasma both low tritium absorption and the highest
comes into direct contact with the reactor melting temperature of any natural element.
vessel is known as the ‘divertor’, and
scientists and engineers are looking to “Although ITER’s divertor design
find its optimal configuration so that it reflects the state of the art of our current
better handles the heat fluxes it encounters. understanding and capabilities from a
Using knowledge and data acquired physics and technology point of view, further
from various irradiation experiments and developments will be required for future
simulation tools, they are also developing fusion power plants. Learning what these are
and verifying a framework of reactor is one of the many important missions of the
design criteria for all in-vessel components, ITER project,” said Richard Pitts, Leader of
divertors included. the Experiments & Plasma Operation Section
at the ITER Organization.
A very hot exhaust Designing and building future fusion reactors
Located at the very bottom of a reactor in will depend on the technical, technological
most designs, where impurities such as and material results of ITER and other
helium ‘ash’ are diverted, the divertor acts as well-established multinational coordinated
the ‘exhaust pipe’ of the fusion reactor and research and development activities, but the
is where any excessive heat is channelled to. distance between us and a fusion-powered
This configuration helps to produce ‘purer’ future continues to narrow every day.
IAEA Bulletin, May 2021 | 21You can also read
