Recent Advances in Fusion:
The Energy Source for the XXI Century
Mohamed Abdou
Distinguished Professor, Mechanical and Aerospace Engineering Department
Director, Center for Energy Science and Technology Advanced Research (CESTAR)
Director, Fusion Science and Technology Center
University of California Los Angeles (UCLA)
The Second International Conference on Thermal Engineering Theory and Applications
January 3-6, 2006
Al Ain, United Arab Emirates
What is Nuclear Fusion?
•
•
Nuclear Fusion is the energy-producing process taking place in the core of
the Sun and stars
The core temperature of the Sun is about 15 million °C. At these
temperatures hydrogen nuclei fuse to give Helium and Energy. The
energy sustains life on Earth via sunlight
Fusion Reactions
• Deuterium – from water
(0.02% of all hydrogen is heavy hydrogen or
deuterium)
• Tritium – from lithium
(a light metal common in the Earth’s crust)
Deuterium + Lithium → Helium + Energy
This fusion cycle (which has the fastest
reaction rate) is of interest for Energy
Production
The World, particularly in developing
countries, needs a New Energy Source
• Growth in world population and growth in energy demand from
increased industrialisation/affluence will lead to an Energy Gap which will
be increasingly difficult to fill with fossil fuels
• Without improvements in efficiency we will need 80% more energy by 2020
• Even with efficiency improvements at the limit of technology we would still
need 40% more energy
World Energy Scene* (I)
1) The world uses a lot of energy
Average power consumption = 13.6 TWs, or 2.2 kWs per person
World energy market ~ $3 trillion/yr (electricity ~$1 trillion/yr)
- very unevenly (OECD 6.2 kW/person; Bangladesh
0.20 kW/person; China 1.3kW/person)
2) World energy use is expected to grow
- growth necessary to lift billions of people out of poverty
3) 80% is generated by burning fossil fuels
 climate change & debilitating pollution
- which won’t last for ever
Need major new (clean) energy sources
- requires new technology
*See Sir Chris Llewellyn-Smith, FPA, October 11, 2005
Future Energy Use
 The International Energy Agency (IEA) expects the
world’s energy use to increase 60% by 2030 (while
population expected to grow from 6.2B to 8.1B) driven largely by growth of energy use and population
in India (current use = 0.7 kWs/person, vs. OECD
average of 6.2 kWs/person) and China (current use =
1.3 kWs/person)
 Strong link between energy use and the Human
Development Index (HDI ~ life expectancy at birth +
adult literacy and school enrolment + gross national
product per capita at purchasing power parity) – need
increased energy use to lift billions out of poverty
Carbon dioxide levels over the last 60,000
years - we are provoking the atmosphere!
Source University of Berne and National Oceanic, and Atmospheric Administration
Meeting the Energy Challenge Requires:
Fiscal measures to change the behaviour of consumers,
and provide incentives to expand use of low carbon
technologies
Actions to improve efficiency (domestic, transport, …)
Use of renewables where appropriate (although locally
useful, not hugely significant globally)
BUT only four sources capable in principle of meeting a
large fraction of the world’s energy needs:
• Burning fossil fuels (currently 80%) - develop & deploy CO2 capture
and storage
• Solar - seek breakthroughs in production and storage
• Nuclear fission - hard to avoid if we are serious about reducing fossil
fuel burning (at least until fusion available)
• Fusion - with so few options, we must develop fusion as fast as
possible, even if success is not 100% certain
ITER
• The World is about to construct the next
step in fusion development, a device
called ITER
• ITER will demonstrate the scientific and
technological feasibility of fusion energy
for peaceful purposes
• ITER will produce 500 MW of fusion power
• Cost, including R&D, is 15 billion dollars
ITER Design - Main Features
Central
Solenoid
Outer Intercoil
Structure
Blanket
Module
Vacuum Vessel
Cryostat
Toroidal Field Coil
Port Plug (IC Heating)
Poloidal Field Coil
Divertor
Machine Gravity Supports
Torus Cryopump
ITER is a collaborative effort among Europe,
Japan, US, Russia, China, South Korea, and India
ITER Location
Caradache (France)
Rokkasho (Japan)
Cadarache was selected as the ITER construction site. There will be
some facilities in Rokassho under the “Broader Approach” agreement.
Fusion Power Station Schematic
Fusion Nuclear Technology (FNT)
Fusion Power & Fuel Cycle Technology
FNT Components from the edge of the
Plasma to TF Coils (Reactor “Core”)
1. Blanket Components
2. Plasma Interactive and High Heat Flux
Components
a. Divertor, limiter
b. RF antennas, launchers, wave guides, etc.
3. Vacuum Vessel & Shield Components
Other Components affected by the
Nuclear Environment
4. Tritium Processing Systems
5. Instrumentation and Control Systems
6. Remote Maintenance Components
7. Heat Transport and Power Conversion
Systems
Shield
Blanket
Vacuum vessel
Radiation
Plasma
Neutrons
First Wall
Tritium breeding zone
Coolant for energy
conversion
Magnets
Blanket (including first wall)
Blanket Functions:
A. Power Extraction
–
Convert kinetic energy of neutrons and secondary gamma rays into heat
–
Absorb plasma radiation on the first wall
–
Extract the heat (at high temperature, for energy conversion)
B. Tritium Breeding
–
Tritium breeding, extraction, and control
–
Must have lithium in some form for tritium breeding
C. Physical Boundary for the Plasma
–
Physical boundary surrounding the plasma, inside the vacuum vessel
–
Provide access for plasma heating, fueling
–
Must be compatible with plasma operation
–
Innovative blanket concepts can improve plasma stability and confinement
D. Radiation Shielding of the Vacuum Vessel
Blanket Materials
1.
Tritium Breeding Material (Lithium in some form)
Liquid: Li, LiPb (83Pb 17Li), lithium-containing molten salts
Solid: Li2O, Li4SiO4, Li2TiO3, Li2ZrO3
2.
Neutron Multiplier (for most blanket concepts)
Beryllium (Be, Be12Ti)
Lead (in LiPb)
3.
Coolant
– Li, LiPb
4.
– Molten Salt
– Helium
– Water
Structural Material
–
Ferritic Steel (accepted worldwide as the reference for DEMO)
–
Long-term: Vanadium alloy (compatible only with Li), and SiC/SiC
5.
MHD insulators (for concepts with self-cooled liquid metals)
6.
Thermal insulators (only in some concepts with dual coolants)
7.
Tritium Permeation Barriers (in some concepts)
8.
Neutron Attenuators and Reflectors
A Helium-Cooled Li-Ceramic Breeder Concept: Example
Material Functions
• Beryllium (pebble bed) for
neutron multiplication
• Ceramic breeder (Li4SiO4,
Li2TiO3, Li2O, etc.) for tritium
breeding
• Helium purge (low pressure)
to remove tritium through
the “interconnected
porosity” in ceramic breeder
• High pressure Helium
cooling in structure (ferritic
steel)
Several configurations exist (e.g. wall parallel or “head on”
breeder/Be arrangements)
Li/Vanadium Blanket Concept
Vanadium structure
Li
Lithium
Secondary Shield
Li
Primary Shield
Li
Reflector
Breeding Zone
(Li flow)
Primary shield
(Tenelon)
Secondary shield
(B4C)
Reflector
Vanadium structure
Lithium
Pathway Toward Higher Temperature Through Innovative
Designs with Current Structural Material (Ferritic Steel):
Dual Coolant Lead-Lithium (DCLL) FW/Blanket Concept
 First wall and ferritic steel structure
cooled with helium
 Breeding zone is self-cooled
 Structure and Breeding zone are
separated by SiCf/SiC composite
flow channel inserts (FCIs) that
 Provide thermal insulation to
decouple PbLi bulk flow
temperature from ferritic steel
wall
 Provide electrical insulation to
reduce MHD pressure drop in
the flowing breeding zone
DCLL Typical Unit Cell
Pb-17Li exit temperature can be significantly higher than the
operating temperature of the steel structure  High Efficiency
Flows of electrically conducting
coolants will experience complicated
magnetohydrodynamic (MHD) effects
What is magnetohydrodynamics (MHD)?
– Motion of a conductor in a magnetic field produces an EMF that can
induce current in the liquid. This must be added to Ohm’s law:
j   (E  V  B )
– Any induced current in the liquid results in an additional body force
in the liquid that usually opposes the motion. This body force must
be included in the Navier-Stokes equation of motion:
V
1
1
 (V  )V   p   2 V  g  j  B
t


– For liquid metal coolant, this body force can have dramatic impact
on the flow: e.g. enormous MHD drag, highly distorted velocity
profiles, non-uniform flow distribution, modified or suppressed
turbulent fluctuations
Large MHD drag results in large
MHD pressure drop
Conducting walls
Insulated wall
Lines of current enter the low
resistance wall – leads to very
high induced current and high
pressure drop
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0.6
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All current must close in the
liquid near the wall – net drag
from jxB force is zero
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Net JxB body force p = cVB2
where c = (tw w)/(a )
For high magnetic field and high
speed (self-cooled LM concepts
in inboard region) the pressure
drop is large
The resulting stresses on the
wall exceed the allowable stress
for candidate structural
materials
•
•
Perfect insulators make the net
MHD body force zero
But insulator coating crack
tolerance is very low (~10-7).
–
•
It appears impossible to develop
practical insulators under fusion
environment conditions with large
temperature, stress, and radiation
gradients
Self-healing coatings have been
proposed but none has yet been
found (research is on-going)
Many liquid wall reactor concepts for high power
density were conceived & analyzed in APEX
 Many candidate liquids were studied: Li,
Sn-Li, Sn, Flibe and Flinabe
 Several liquid wall flow schemes were
conceived:
–
–
–
–
Thick liquid walls
Thin fast flowing protection layer (CLIFF)
Inertial or EM assisted wall adhesion
Integrated or stand-alone divertors Surface
 Concept performance was
analyzed from many perspectives
Fast Flow
Cassette
Inboard
Fast
Flow
Outboard
Fast Flow
Divertor
Cassette
Renewal
– Liquid wall flow MHD and heat transfer
– Breeding, shielding and activation potential
– Simplicity of system design, maintenance
 Interactions of liquid walls with plasma
operation were emphasized
Bottom Drain
Flow
– Plasma edge effects, impurities & recycling
– Liquid metal motion coupling to plasma
Thin liquid wall concept (blanket
modes
region behind LW not shown)
New simulation tools and experimental facilities
used to address flowing liquid metals in NSTX
divertor fields – now being applied to DCLL-TBM
 New phenomenon observed in both experiments and
numerical simulation for film flows in NSTX divertor: the
liquid film tends to ‘pinch in’ away from the wall under a
positive surface normal magnetic field gradient.
PbLi
FCI
‘Pinching in’
Gallium flow experiment at UCLA M-TOR facility
HIMAG simulation of the above experiment
Flow Velocity : 3 m/s
 Simulation with MHD research
code (at UCLA) shows tendency
for strong reversed flow jets near
slot or crack in flow channel
insert (MTOR experiments in
development)
Average surface normal field gradient: 0.6 T/m
Summary
• The D-T Fusion process offers the promise of:
– Virtually unlimited energy source from cheap abundant fuels;
– No atmospheric pollution of greenhouse and acid rain gases;
– Low radioactive burden from waste for future generations.
• Tremendous Progress has been achieved over the past
decades in plasma physics and fusion technology.
• Fusion R&D involves many challenging areas of physics
and technologies and is carried out through extensive
international collaboration
• EU, JA, USA, RF, PRC, Korea, and India are about to
construct ITER to demonstrate the scientific and
technological feasibility of fusion energy (ITER will
produce 500MW of fusion power )