FUSION
- Powering the World’s Future?
Andrew Borthwick
UKAEA Culham (JET)
EURATOM/UKAEA Fusion Association
Presented to the MAE on 16.02.06
SUMMARY
l Introduction - What is Nuclear Fusion?
l Advantages of Fusion as a power source &
the energy crisis
l Physics of Fusion
l Engineering Challenges
l Current Generation of Reactors
l Geo-Politics and Economics
l Conclusion
WHAT IS FUSION?
l Fusion is the process that produces energy
in the core of the Sun and stars.
l The temperature of the centre of the Sun is
15 million °C. At this temperature hydrogen
nuclei fuse to give Helium and Energy.
l On Earth we must use deuterium-tritium and
Deuterium
need at least 100 million °C
Helium
l We use a “magnetic bottle” called a tokamak
to keep the hot plasma away from the wall
l The challenge is to make an effective
“magnetic bottle” and a robust container
Tritium
neutron
Advantages
The world is facing an energy crisis. No
conventional power source is flawless
l Political security of supply - oil & gas
l Finite resources - oil & gas
l Pollution - all fossil fuels
l Long term liabilities - nuclear fission
l Political liabilities - nuclear fission
l Geographic dependencies - renewables
l Load following ability - renewables
Advantages - Fuel
Raw fuel of a fusion reactor is water and lithium*
l > 1000 years reserves of Lithium
l Near unlimited reserves of Deuterium
l Lithium in one laptop battery + half a bath-full of water (-> one egg cup
full of heavy water)
200,000 kW-hours
= (current UK electricity production)/(population of the UK) for 30 years
* deuterium/hydrogen = 1/6700
+ tritium from: neutron (from fusion) + lithium
tritium + helium
Advantages - Fuel (2)
Compare burning fossil fuel (oil, coal), wood or gas
Hydrocarbon + Oxygen + Energy (few electron volts - eV)
Ash + Carbon Dioxide + Water + More Energy (few eV)
1 GW for one day needs 10,000 tons of fossil fuel = 10 train loads of coal
With burning deuterium and tritium
Deuteron + Tritium + Energy (~10 keV)
Helium (‘ash’) + neutron + energy (17 MeV)
1 GW for one day needs 1 kg of deuterium* + tritium**
* extracted from (sea) water
** bred by: neutron + lithium (very abundant) ® tritium + helium
Advantages - Safety
Safety of Fusion Power Plants is Intrinsic
l Although temperature is very high inside a fusion reactor, the particle
density is very low
– density only about 1020 m-3 cf. 2 x1025 m-3 in atmospheric air
– pressure is only 1 to 2 atmospheres
l There is a very small amount of fuel inside the tokamak ( 0.5gram) at
any one time, enough for only 1 minute of power production
l There is not enough energy in the plant to lead to melting of the
structure even in the worst possible accident
Advantages - Pollution
No toxic or greenhouse gasses released to atmosphere. No
solid waste
l Reaction products helium
l Residual Radioactivity in structure
à Very small compared to Fission
à Will decay such that superstructure
could be recycled after ~ 100yrs
Potential hazard (ingestion)
à Harmless & a valuable commodity
1
0 .8
0 .6
0 .4
0 .2
0
0
5
10
15
Time after shutdown (years)
20
25
Advantages - Load Demand
Fusion best suited to GW conventional steam turbine
generation
l Geography only limited by cooling water supply
l Interfaces well with existing grid distribution architectures
l Suited to base load supply - peak lopping accommodated by mix of
generation sources - such as pumped storage
Advantages - Summary
l Political security of supply
à Not dependant on unsavoury regimes
l Finite resources
à Near endless supply
l Pollution
à No greenhouse gasses, or toxic emissions
l Long term liabilities
à Superstructures decommissioned & recycled within 100 years
à Inherently safe design
l Political liabilities
à No weapons proliferation consequences
l Geographic dependencies
à No special additional requirements
l Load following ability
à Interfaces well with existing distribution & supply systems
Disadvantages
Fusion is Bl**dy hard
FUSION REACTION IS DIFFICULT TO START!
• Large kinetic energy of
Deuterium and Tritium
nuclei required to
overcome the mutual
electrostatic repulsion
• Solution is to form a
high temperature
plasma in which
repeated collisions occur
• Some collisions achieve
close enough proximity
for the nuclear force to
take over - fusion then
occurs
e2
4peorm
Potential
Energy
rm
Nuclear separation distance
What conditions are needed for self-sustained fusion?
Fusion power = (Reaction rate) x (Energy release per reaction)
Reaction rate = (D-T collision frequency) x (Reaction probability)
Chance of mutual
encounters
Speed related
Kinetic energy
related
Fusion power µ Density2 x Temperature2
(or Pressure2)
Thermal losses = (Plasma Thermal Energy) / t
Optimum
temperature
100 -200M0C
= (Density x Temperature) / t
Fusion Power/Thermal losses Density.Temperature.
>>5
Plasma and Magnetic Bottles
At fusion temperatures the negative electrons are detached
from the positive nuclei to form a plasma which can be
manipulated by magnetic fields
Major progress in recent years
• Huge strides in physics,
engineering, technology - triple
product doubles every 1.8 yr
(comparable to Moores law)
• JET: 16 MW of fusion power ~
equal to heating power. 21 MJ of
fusion energy in one pulse
MAST
• Ready to build ITER - the next
generation, GigaWatt-scale
Extrapolation to the Next Step
• to get large fusion energy gain (Q » 10) about 2 x linear
dimensions of JET and 15MA plasma current
• key parameter is energy confinement time (describes
thermal insulation quality)
Cross section of present EU D-shape
tokamaks compared to the ITER project
JET operates the closest to ITER
A Fusion power plant would be like a conventional one,
but with different fuel and furnace
Lithium
compound
Not to
scale !
Magnetic Bottle
Special magnetic field configurations are necessary for
stable plasma confinement and good thermal insulation
• Toroidal (ring
shaped) systems
have no ‘ends’, so
losses can only
occur by slow
diffusion across
the magnetic field
• Most successful is
the TOKAMAK
(Russian for
‘Toroidal
Magnetic
Chamber’)
Vacuum Systems
High vacuum must be maintained to minimise conduction,
convection & contamination
• JET 200m3 vacuum vessel - leak rate of 1x10-9 mbar.ltr/s per
component ~ 1x10-8 mbar.ltr/s for the vessel
• Total pump rate of 15x106 ltr/s distributed between cryopumps &
turbo pumps
• Only 0.5g of gas in plasma - very susceptible to contamination.
Cleanliness paramount
First Wall
First wall of reactors have significant engineering challenges - Weight,
Strength, Shielding, Austenetic, Radiation hardness
• Subjected to bombardment of 2 MW m-2 from 14
MeV neutrons Þ 20 displacements per atom
per year
• Note: 14 MeV Þ much bigger cascades than in
fission + new effects as helium is generated in
materials
• Plasma facing material subjected to an additional
500 kW m-2 in form of particles + electromagnetic
radiation
• Materials must be lightweight to minimise plasma
contamination
• Beryllium & Carbon composites currently used.
Moving toward Tungsten & SiC composites
Heating the Plasma
Heating the Plasma (2)
• JET PINI Positive Ion
Deuterium / Tritium
accelerator. Same principle
as Ion engine.
• JET has 16 ~ 25MW plasma
heating.
• Modern designs use negative
ions
• RF Antenna RF waves
couple to plasma species by
exciting resonances.
• Most Efficient heating
system, but “temperamental”
Exhaust
Plasma shaping & exhaust provided by the diverter
• Diverter coils induce X-point in
plasma - draws boundary layers on
to a limiter
• Limiter vacuum & plasma facing,
subject to up to 20 MW m-2 D/He
ion & radiation flux
• Exhaust removed by cryopump extremes of temperature (3K 100MK in 2m!)
Remote Handling
Structure becomes activated & contaminated. Manned access is
minimised or not possible
• All first wall components designed for robotic installation
• Significant planning & simulation required to prove assembly
Diagnostics
Many Diagnostics are required for plasma real time control
& physics experiments
• LIDAR & Thomson scatteringPlasma density & velocity profiles
• CO2 Laser Interferometery density profiles
• IR - Optical cameras
• Magnetics - plasma position
• 3D X-ray tomography
• And many others!!
MAST - centrepiece of the UK’s own programme
Based on a promising more compact, but less developed, configuration than
JET
Þ interesting new information
Þ could play vital role as a “Component Test Facility” in the
medium-term
Þ could, in long-run, be basis for (smaller and simpler) power
stations
JOINT EUROPEAN TORUS [JET]
Currently the world’s largest magnetic fusion device
The only magnetic fusion device with real deuterium-tritium
fusion fuel capability and remote in-vessel remote handling
4Tesla magnetic field; 5MA plasma current; >30MW heating
ITER
•
Aim is to demonstrate integrated
physics and engineering on the
scale of a power station
•
Key ITER technologies fabricated
and tested by industry
e.g. Superconducting magnet
coils
•
•
4.5 Billion Euro construction cost
•
Site in France (Cadarache) has
been selected (June 2005)
•
Basics design complete - on-site
construction due to start 2007
Europe, Japan, Russia, US, China,
South Korea & India
THE WORLD NEEDS MORE/CLEANER ENERGY
• World need for power will increase
Present annual consumption per person
eg
USA
12.5 TCE (tons of coal equivalent)
W Europe 6.0 TCE
Expect/hope Þ at least 3
China
1.4 TCE
TCE, while populations rising
India
0.7 TCE
•
IEA expects world energy need to double by 2045
COST COMPARISONS
Results from Shell Renewables + Fusion Power Plant Conceptual
Studies
The UK Government (Lord Sainsbury, Professor Sir David King) advocate a “Fast Track” Fusion
Programme Strategy
MAST
25 years from now design of PPP finalised using
results from ITER and IFMIF
FUSION FAST TRACK: WHAT IS NEEDED
• proceed to ITER construction without delay
• during ITER construction ® operate JET ® speed up/improve ITER
operation
• continue configuration optimisation (MAST, . . .)
• intensify materials work (® test facilities in parallel with ITER)
• move from ITER directly to Prototype Power Plant
and generally ® greater focus and co-ordination of fusion work
Europe/world-wide means:
Fusion a reality in our lifetimes
Conclusion
l Fusion is the process that drives the stars
l Terrestrial, man-made fusion offers near
limitless supply of energy
l There are no environmental impacts nor safety
issues
l Terrestrial Fusion is achieved by isolation
within a magnetic bottle
l Engineering challenges exist - particularly for
materials technology
l Geo-Politics and Economics are driving
renewed interest - resulting in global
collaboration & ITER