REALIZATION OF FUSION AS THE ULTIMATE
ENERGY SOURCE FOR HUMANITY
Mohamed Abdou
Distinguished Professor of Engineering and Applied Science
Director, Center for Energy Science and Technology (CESTAR)
Director, Fusion Science and Technology Center
University of California, Los Angeles (UCLA)
web: http://www.fusion.ucla.edu/abdou/
Invited Keynote Lecture in ExHFT-7:
7th World Conference on
Experimental Heat Transfer, Fluid Mechanics and Thermodynamics
Krakow, Poland June 28-July 3, 2009
REALIZATION OF FUSION AS THE ULTIMATE
ENGERGY SOURCE FOR HUMANITY
OUTLINE
•
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•
•
•
•
•
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Fusion Research Transition and DEMO Goal
ITER
Blanket Principles and Interactions
MHD Thermofluid Issues
Blanket Types and Issues
Science-based framework for FNST Development
Blanket Testing in ITER
Need for a New Fusion Nuclear Facility
Summary
2
What is fusion?
 Fusion powers the Sun and Stars. Two light nuclei combine to form a
heavier nuclei (the opposite of nuclear fission).
Deuterium
mc2
E=
17.6 MeV
Tritium
Neutron
80% of energy
release
(14.1 MeV)
Used to breed
tritium and close
the DT fuel cycle
Li + n → T + He
Li in some form must be
used in the fusion
system
Helium
20% of energy release
(3.5 MeV)
Illustration from DOE brochure
 Deuterium and tritium is the easiest,
attainable at lower plasma temperature,
because it has the largest reaction
rate and high Q value.
 The World Program is focused
on the D-T Cycle
3
077-05/rs
Incentives for Developing Fusion
 Sustainable energy source
(for DT cycle: provided that Breeding Blankets are
successfully developed and tritium self sufficiency
conditions are satisfied)
 No emission of Greenhouse or other polluting gases
 No risk of a severe accident
 No long-lived radioactive waste
Fusion energy can be used to produce electricity
and hydrogen, and for desalination.
Fusion Research is about to transition from Plasma
Physics to Fusion Science and Engineering
• 1950-2010
– The Physics of Plasmas
• 2010-2035
– The Physics of Fusion
– Fusion Plasmas-heated and sustained
• Q = (Ef / Einput )~10
• ITER (magnetic fusion) and NIF (inertial fusion)
• 2010-2040 ?
– Fusion Nuclear Science and Technology for Fusion
– DEMO by 2040?
• > 2050 ?
– Large scale deployment!
5
The World Fusion Program has a Goal for a
Demonstration Power Plant (DEMO) by ~2040(?)
Plans for DEMO are based on Tokamaks
Poloidal Ring Coil
Cryostat
Coil Gap
Rib Panel
Blanket
Maint.
Port
Plasma
Vacuum
Vessel
Center Solenoid Coil
Toroidal Coil
(illustration is from JAEA DEMO Design)
ITER
• The World has started construction of 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 is a collaborative effort among Europe, Japan,
US, Russia, China, South Korea, and India. ITER
construction site is Cadarache, France.
• ITER will begin operation in hydrogen in ~2019. First D-T
7
Burning Plasma in ITER in ~ 2026
ITER is a reactor-grade tokamak plasma physics
experiment - a huge step toward fusion energy






Will use D-T and produce neutrons
500MW fusion power, Q=10
Burn times of 400s
Reactor scale dimensions
Actively cooled PFCs
Superconducting magnets
~29 m
~15 m
By Comparison,
JET
 ~10 MW
 ~1 sec
 Passively
Cooled
JET
ITER
Magnet System in Tokamak (e.g. ITER) has 4 sets of coils
• 18 Toroidal Field (TF) coils
produce the toroidal magnetic
field to confine and stabilize
the plasma
− Superconducting,
Nb3Sn/Cu/SS
− Max. field: 11.8T
• 6 Poloidal Field (PF) coils
position and shape the
plasma
− Superconducting,
NbTi/Cu/SS
− Max. field: 6T
• Central Solenoid (CS)
coil induces current in
the plasma
• 18 Correction coils correct error fields
− Superconducting, NbTi/Cu/SS
− Max. field < 6T
TF coil case provides main
structure of the magnet
system and machine core
Stored energy in ITER magnetic field is large ~ 1200 MJ
Equivalent to a fully loaded 747 moving at take off speed 265 km/h
− Superconducting,
Nb3Sn/Cu/alloy908
−Max. field: 13.5T
9
New Long-Pulse Confinement and Other Facilities
Worldwide will Complement ITER
Japan (w/EU)
China
EAST
JT-60SA
(also LHD)
Europe
South Korea
W7-X
(also
JT-60SA)
India
SST-1
ITER Operations:
34% Europe
13% Japan
13% U.S.
10% China
10% India
10% Russia
10% S. Korea
KSTAR
U.S.
Being planned
Fusion Nuclear Science
&Technology Testing
Facility
(FNSF/CTF/VNS)
The primary functions of the blanket are to provide for:
Power Extraction & Tritium Breeding
Shield
Blanket
Vacuum vessel
Radiation
DT
Plasma
Neutrons
First Wall
Tritium breeding zone
Coolant for energy
extraction
Magnets
Lithium-containing Liquid metals (Li, PbLi) are strong candidates as
breeder/coolant
11
Fusion Nuclear Science and Technology (FNST)
Fusion Power & Fuel Cycle Technology
FNST includes the scientific issues and
technical disciplines as well as materials,
engineering and development of fusion
nuclear components:
From the edge of Plasma to TF Coils:
1. Blanket Components (includ. FW)
2. Plasma Interactive and High Heat Flux
Components (divertor, limiter, rf/PFC element, etc)
3. Vacuum Vessel & Shield Components
The location of the Blanket inside the
vacuum vessel is necessary but has
major consequences:
a- many failures (e.g. coolant leak)
require immediate shutdown
b- repair/replacement take long time
12
Fusion environment is unique and complex:
multi-component fields with gradients
•Neutron and Gamma fluxes
•Particle fluxes
•Heat sources (magnitude and gradient)
– Surface (from plasma radiation)
– Bulk (from neutrons and gammas)
• Magnetic Field (3-component)
– Steady field
– Time varying field
• With gradients in magnitude and direction
Plasma
Width
B
0
(for ST)
BT
Inner
Edge
Bp
Outer
Edge
R
Multi-function blanket in multi-component field environment leads to:
- Multi-Physics, Multi-Scale Phenomena
Rich Science to Study
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- Synergistic effects that cannot be anticipated from simulations & separate effects
tests. Modeling and Experiments are challenging
Challenging
Fusion Nuclear Science & Technology Issues
1. Tritium Supply &
Tritium Self-Sufficiency
2. High Power Density
3. High Temperature
4. MHD for Liquid Breeders / Coolants
5. Tritium Control (Extraction and Permeation)
6. Reliability / Maintainability / Availability
7. Testing in Fusion Facilities
15
Flows of electrically conducting coolants will experience
complicated MHD effects in the magnetic fusion environment
3-component magnetic field and complex geometry
– 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.
Dominant impact on LM design.
Challenging Numerical/Computational/Experimental Issues
16
MHD Characteristics of Fusion
Liquid Breeder Blanket Systems
A perfectly insulated “WALL”
can solve the problem, but is it
practical?
Self-Cooled liquid Metal
Blankets are NOT feasible now
because of MHD Pressure Drop
Conducting walls
Insulated walls
Lines of current enter the low
resistance wall – leads to very
high induced current and high
pressure drop
1
0.8
0.6
0.4
1
0.8
0.6
0.4
0.2
0.2
0
0
-0.2
-0.2
All current must close in the
liquid near the wall – net drag
from jxB force is zero
-0.4
-0.6
-0.8
-0.4
-0.6
-0.8
-1
-1
-1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Net JxB body force
p = VB2 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
•
-
•
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Perfect insulators make the net
MHD body force zero
But insulator coating crack
tolerance is very low (~10-7).
–
•
-0.8
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)
18
Impact of MHD and no practical Insulators :No self-cooled blanket option
Separately-cooled LM Blanket
Example: PbLi Breeder/ helium Coolant with RAFM
Module box
 EU mainline blanket design
(container & surface
 All energy removed by separate
heat flux extraction)
Helium coolant
 The idea is to avoid MHD issues.
But, PbLi must still be circulated to extract
tritium
Breeder cooling
unit (heat extraction
from PbLi)
 ISSUES:
– Low velocity of PbLi leads to high
tritium partial pressure , which leads to
tritium permeation (Serious Problem)
– Tout limited by PbLi compatibility with
RAFM steel structure ~ 470 C
(and also by limit on Ferritic, ~550 C)
 Possible MHD Issues :
– MHD pressure drop in the inlet
manifolds
– B- Effect of MHD buoyancy-driven flows
on tritium transport
Stiffening structure
Drawbacks: Tritium
Permeation and limited
thermal efficiency
(resistance to accidental in-box
pressurization i.e He leakage)
He collector system
(back)
19
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
FCI does not serve structural function
Pb-17Li exit temperature can be significantly higher than the
operating temperature of the steel structure  High Efficiency
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High pressure drop is only one of the MHD issues for LM
blankets; MHD heat and mass transfer are also of great
importance!
Instabilities and 3D MHD effects in complex
detailed geometry and configuration with
magnetic and nuclear fields gradients
have major impact.
FCI overlap gaps act
as conducting breaks
in FCI insulation
• Unbalanced pressure drops (e.g. from
insulator cracks) leading to flow control and
channel stagnation issues
• Unique MHD velocity profiles and instabilities
affecting transport of mass and energy
Accurate Prediction of MHD Heat &Mass
Transfer is essential to addressing
important issues such as:
• thermal stresses,
• temperature limits,
• failure modes for structural and
functional materials,
• thermal efficiency, and
• tritium permeation.
and hence disturb current
flow and velocity, and
redistribute energy
Courtesy of Munipalli et al.
(Ha=1000; Re=1000; =5 S/m,
cross-sectional dimension expanded 10x)
21
077-05/rs
Buoyancy effects in DCLL blanket
DCLL DEMO blanket, US
 Exp(r )
q(r )  qmax
 a 2
qmax
and associated T 
~ 103 K
k
Caused by
Can be 2-3 times stronger than
forced flows. Forced flow: 10 cm/s.
Buoyant flow: 25-30 cm/s
 exp{ r}
q(r ) ~ qmax
In buoyancy-assisted (upward)
flows, buoyancy effects may play a
positive role due to the velocity jet
near the “hot” wall, reducing the
FCI T
In buoyancy-opposed (downward)
flows, the effect may be negative
due to recirculation flows
Effect on the interface T, FCI T,
heat losses, tritium transport
Vorticity distribution in the buoyancy-assisted
(upward) poloidal flow
22
Corrosion Is A Serious Issue For LM Blankets
•
At present, the interface temperature between PbLi and Ferritic Steel (FS) is
limited to < 470 C because of corrosion
– This is very restrictive and does not allow higher temperature operation with FS or
advanced ODS.
•
Data available are from corrosion experiments with no magnetic field. They
are static or dynamic.
– Results show strong dependence on temperature and on the velocity of PbLi.
– Therefore, corrosion should be expected to experience MHD effects due to sharp
changes in the velocity and temperature profiles.
– There is experimental evidence of the effect of magnetic field.
•
Criteria for determining the allowable interface temperature :
a) thinning of the walls (in the “hot” section) due to corrosion
b) deposition of the corrosion products transported in the heat transport loop to the Heat
Exchanger (“cold” section) causing radioactive “CRUD” that hampers HX maintenance.
c) corrosion products deposition in the “cold” section causing clogging small orifices,
valves, etc.
Usually the criterion c) is applied with the assumption, that the corrosion rate has to be limited to 20
micron/year in order to avoid clogging. This leads to an allowable interface temperature of ~ 470 C as
measured in experiments with turbulent flow without magnetic fields
•
Experiments with sodium loops have shown that deposits in the "cold"
sections is more limiting than thinning of the "hot" walls
Hence, in addition to corrosion rates, it is important to predict the behavior of the
corrosion products in the entire heat transport loop, particularly “deposition”. 23
Experiments in Riga (funded by Euratom)
Show Strong Effect of the Magnetic Field on Corrosion
(Results for PbLi in Ferritic Steel)
Macrostructure of the washed samples
after contact with the PbLi flow
B=0 T
B=1.8 T
From: F. Muktepavela et al. EXPERIMENTAL STUDIES
OF THE STRONG MAGNETIC FIELD ACTION ON
THE CORROSION OF RAFM STEELS IN Pb17Li MELT
FLOWS, PAMIR 7, 2008
Strong experimental evidence of
significant effect of the applied magnetic
field on corrosion rate. The underlying
physical mechanism has not been fully
24
understood yet
Need R&D on Corrosion: Modelling and Experiments in
MHD Flows Relevant to the Fusion System Environment
•
Corrosion includes many physical mechanisms that are currently not well
understood (dissolution of the metals in the liquid phase, chemical reactions of dissolved
non-metallic impurities with solid material, transfer of corrosion products due to convection
and thermal and concentration gradients, etc.).
•
•
We need to better understand corrosion process, including transport and
deposition.
We need new models that can predict corrosion rates and transport and
deposition of corrosion products throughout the heat transport system.
– These models need to account for MHD velocity profiles and heat transfer in the
blanket and the temperature gradients and complex geometry in the entire heat
transport systems.
•
More comprehensive experiments are needed.
– Need to simulate MHD velocity profiles
– Need to simulate the temperature field and temperature gradients in the “hot” and
“cold” sections.
– Better instrumentation
•
•
R&D to develop corrosion resistant “barriers” will have high pay off.
Highest interest is in PbLi systems with both ferritic steel and SiC (FCI).
25
Illustration of Coupling between MHD and heat
and mass transfer in blanket flows
MHD Flow
Heat Transfer
Convection
He
Bubbles
formation
and their
transport
Mass Transfer
Buoyanoydriven flows
Diffusion
Dissolution, convection,
and diffusion through
the liquid
Tritium
transport
Dissolution and
diffusion through the
solid
Tritium Permeation
Corrosion
Transport of
corrosion
products
Deposition and
aggregation
Interfacial
phenomena
26
Coupling through the source / sink term, boundary conditions, and transport coefficients
Science-Based Framework for FNST R&D involves modeling
and experiments in non-fusion and fusion facilities
Theory/Modeling/Data
Basic
Separate
Effects
Property
Measurement
Multiple
Interactions
Design Codes
Partially
Integrated
Phenomena Exploration
Integrated
Component
•Fusion Env. Exploration Design
Verification &
•Concept Screening
•Performance Verification Reliability Data
Non-Fusion Facilities
(non neutron test stands,
fission reactors and accelerator-based
neutron sources)
Testing in Fusion Facilities
• Experiments in non-fusion facilities are essential and are prerequisites to testing in
fusion facilities
• Testing in Fusion Facilities is NECESSARY to uncover new phenomena, validate the
science, establish engineering feasibility, and develop components
27
MHD flows in fusion context are characterized by very
unique effects not seen in ordinary fluid dynamics
•
•
High interaction parameter ~103 to 105
(ratio Magnetic / Inertial Forces)
– Inertia forces are small compared
with electromagnetic forces,
except in some thin layers
Result: Joule dissipation associated
with the strong magnetic field induces
a strong flow anisotropy, ultimately
leading to a quasi-2D state.
MTOR Thermofluid/MHD facility
at UCLA
Liquid metal free surface flow experiment
Magnetic field suppresses short
wavelength surface oscillations and
consolidates them into larger surface
disturbances aligned with the field
1 m/s flow, B = 0
B = 1.2 T
Ying (UCLA)
Fusion plasma facing components must survive for long
operating time with severe heat fluxes
PMTF-1200 high heat flux facility at SNL
•
•
Fusion heat flux requirements rival that of
rocket engines, but must operate for long
periods of time
Effects of thermal cycling are particularly
worrisome for ITER operation, where many
pulses of the burning plasma are required
High heat flux experiments
Repeated high heat flux and thermal cycle
survivability tests on mockups of the first
wall for ITER, both EU (right column) and
US (left column) samples survived 12,000
cycles at 0.875 MW/m2 and 1000 cycles
at 1.4 MW/m2
(Ulrickson,
Slide SNL)
29
Irradiation experiments in fission reactors to test
tritium release/retention in lithium ceramics
•
Using lithium bearing
ceramics is one option,
often in the form of
small pebble beds
•
But this material must
release tritium and
resist damage by
neutrons and extreme
thermal conditions
•
Fission experiments are
being used to explore
this behavior prior to
testing in fusion
Ceramic breeder irradiation
experiments
Unit cells of Beryllium and Li4SO4
have been tested in the NRG
reactor in Petten, Netherlands to
investigate tritium release
characteristics and combine
neutron and thermomechanical
damage to ceramic breeder and
beryllium pebble beds
Testing Blankets in the fusion environment is Necessary: Combined effects of
Radiation, Surface Heat flux, Nuclear Heating & gradients, Magnetic field &
gradients, etc can be reproduced only in a fusion facility.
Example: MHD flow & FCI behavior are highly coupled in a complex fusion environment
 PbLi flow is strongly influenced by MHD interaction
with plasma confinement field and buoyancy-driven
convection driven by spatially non-uniform
volumetric nuclear heating
 This MHD flow and convective heat
transport processes determine the
temperature and thermal stress of SiC FCI
 The FCI temperature and thermal stress coupled
with early-life radiation damage effects in ceramics
affect deformation, cracking, and properties of the
FCI
Courtesy of S.
Smolentsev
FCI temperature, stress and
deformation
 Cracking and movement of the FCIs will strongly
influence MHD flow behavior by opening up new
conduction paths that change electric current
profiles
Resulting temperature field also strongly couples to phenomena
such as tritium transport and permeation, and corrosion
31
31
077-05/rs
ITER Provides Substantial Hardware Capabilities
for Testing of Blanket System
TBM System (TBM + T-Extrac,
Heat Transport/Exchange…)
Bio-shield
A PbLi loop
Transporter located in
the Port Cell Area
2.2 m
ITER has allocated 3
ITER equatorial ports
(1.75 x 2.2 m2) for TBM
testing
Each port can
accommodate only 2
modules (i.e. 6 TBMs max)
He pipes to
TCWS
Equatorial Port
Plug Assy.
Vacuum Vessel
TBM
Assy
Port
Frame
Fluence in ITER is limited to 0.3MW-y/m2 . We have to
build another facility, for FNST development
32
THREE Stages of FNST Testing in Fusion Facilities
are Required Prior to DEMO
Role of FNF (CTF/VNS)
Role of ITER TBM
Component Engineering
Development &
Reliability Growth
Fusion “Break-in” &
Scientific Exploration
Engineering Feasibility
& Performance
Verification
Stage I
Stage II
Stage III
1 - 3 MW-y/m2
> 4 - 6 MW-y/m2
1-2 MW/m2,
steady state or long pulse
COT ~ 1-2 weeks
1-2 MW/m2,
steady state or long burn
COT ~ 1-2 weeks
0.1 - 0.3 MW-y/m2
 0.5
MW/m2,
burn > 200 s
Sub-Modules/Modules
Modules
D
E
M
O
Modules/Sectors
 ITER is designed to fluence < 0.3MW-y/m2. ITER can do only Stage I
 A Fusion Nuclear Facility, FNF is needed , in addition to ITER, to do Stages II
(Engineering Feasibility) and III (Reliability Growth)
 FNF must be small-size, low fusion power (< 150 MW), hence,
a driven plasma with Cu magnets.
33
Example of Fusion Nuclear Facility (FNF) Device Design Option :
Standard Aspect Ratio (A=3.5) with demountable TF coils (GA design)
• High elongation, high
triangularity double
null plasma shape
for high gain, steady- Challenges for Material/Magnet Researchers:
• Development of practical “demountable” joint in Normal Cu Magnets
state plasma
operation
• Development of Inorganic Insulators (to reduce inboard shield and size of device)
Lessons learned:
The most challenging problems in FNST
are at the INTERFACES
• Examples:
– MHD insulators
– Thermal insulators
– Corrosion (liquid/structure interface temperature limit)
– Tritium permeation
• Research on these interfaces must integrate the many
technical disciplines of fluid dynamics, heat transfer, mass
transfer, thermodynamics and material properties in the
presence of the multi-component fusion environment
(must be done jointly by blanket and materials researchers)
35
Summary
• Fusion is the most promising long-term energy option
– renewable fuel, no emission of greenhouse gases, inherent safety
• The blanket must simultaneously achieve tritium breeding and power
extraction at high temperature in a multi-component fusion environment
(magnetic field, radiation field, surface heat flux, bulk heating) with strong
gradients. This results in new phenomena and synergistic effects that can
not be anticipated from simulations and separate-effect tests.
• Fluid dynamics, heat & mass transfer play important role in R&D for
blankets and other plasma-facing components. Other important disciplines
are neutronics, radiation effects, structural mechanics.
• LM Blankets are most promising, but their potential is limited by MHD effects.
Innovative concepts must continue to be proposed and investigated
• Modeling and experiments for blanket and PFC are challenging because
of complex geometry, multi component fields with gradients, and the
inability to simulate bulk heating in the lab without neutrons. Significant
progress has been made in 3-D modeling and in laboratory experiments.
• 7 nations started construction of ITER to demonstrate the scientific and
technological feasibility of fusion energy. ITER will have first DT plasma in ~2026
• The most challenging Phase of Fusion development still lies
ahead. It is the development of Fusion Nuclear Science and
Technology (FNST)
– ITER, limited fluence, addresses only initial Stage of FNST testing
– In addition to ITER, a Fusion Nuclear Facility (FNSF) is required to develop FNST.
36