FUSION - Powering the World s Future? Andrew Borthwick UKAEA Culham (JET) EURATOM/UKAEA Fusion Association

Transcription

1 FUSION - Powering the World s Future? Andrew Borthwick UKAEA Culham (JET) EURATOM/UKAEA Fusion Association Presented to the MAE on

2 SUMMARY Introduction - What is Nuclear Fusion? Advantages of Fusion as a power source & the energy crisis Physics of Fusion Engineering Challenges Current Generation of Reactors Geo-Politics and Economics Conclusion

3 WHAT IS FUSION? Fusion is the process that produces energy in the core of the Sun and stars. The temperature of the centre of the Sun is 15 million C. At this temperature hydrogen nuclei fuse to give Helium and Energy. On Earth we must use deuterium-tritium and need at least 100 million C We use a magnetic bottle called a tokamak to keep the hot plasma away from the wall The challenge is to make an effective magnetic bottle and a robust container Deuterium Tritium Helium neutron

4 Advantages The world is facing an energy crisis. No conventional power source is flawless Political security of supply - oil & gas Finite resources - oil & gas Pollution - all fossil fuels Long term liabilities - nuclear fission Political liabilities - nuclear fission Geographic dependencies - renewables Load following ability - renewables

5 Advantages - Fuel Raw fuel of a fusion reactor is water and lithium* > 1000 years reserves of Lithium Near unlimited reserves of Deuterium 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/ tritium from: neutron (from fusion) + lithium tritium + helium

6 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

7 Advantages - Safety Safety of Fusion Power Plants is Intrinsic Although temperature is very high inside a fusion reactor, the particle density is very low density only about m -3 cf. 2 x10 25 m -3 in atmospheric air pressure is only 1 to 2 atmospheres 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 There is not enough energy in the plant to lead to melting of the structure even in the worst possible accident

8 Advantages - Pollution No toxic or greenhouse gasses released to atmosphere. No solid waste Reaction products helium à Harmless & a valuable commodity Residual Radioactivity in structure à Very small compared to Fission à Will decay such that superstructure could be recycled after ~ 100yrs Potential hazard (ingestion) Time after shutdown (years)

9 Advantages - Load Demand Fusion best suited to GW conventional steam turbine generation Geography only limited by cooling water supply Interfaces well with existing grid distribution architectures Suited to base load supply - peak lopping accommodated by mix of generation sources - such as pumped storage

10 Political security of supply Advantages - Summary à Not dependant on unsavoury regimes Finite resources à Near endless supply Pollution à No greenhouse gasses, or toxic emissions Long term liabilities à Superstructures decommissioned & recycled within 100 years à Inherently safe design Political liabilities à No weapons proliferation consequences Geographic dependencies à No special additional requirements Load following ability à Interfaces well with existing distribution & supply systems

11 Disadvantages Fusion is Bl**dy hard

12

13 FUSION REACTION IS DIFFICULT TO START! Large kinetic energy of Deuterium and Tritium nuclei required to overcome the mutual electrostatic repulsion Potential Energy e 2 4pe o r m 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 r m Nuclear separation distance

14 What conditions are needed for self-sustained fusion? Fusion power Reaction rate = (Reaction rate) x (Energy release per reaction) = (D-T collision frequency) x (Reaction probability) Chance of mutual encounters Speed related Fusion power µ Density 2 x Temperature 2 Kinetic energy related (or Pressure 2) Thermal losses = (Plasma Thermal Energy) / t = (Density x Temperature) / t Fusion Power/Thermal losses > > 5 Optimum temperature M 0 C Density.Temperature.

15 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

16 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 Ready to build ITER - the next generation, GigaWatt-scale MAST

17 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

18 A Fusion power plant would be like a conventional one, but with different fuel and furnace Lithium compound Not to scale!

19 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 )

20 Vacuum Systems High vacuum must be maintained to minimise conduction, convection & contamination JET 200m 3 vacuum vessel - leak rate of 1x10-9 mbar.ltr/s per component ~ 1x10-8 mbar.ltr/s for the vessel Total pump rate of 15x10 6 ltr/s distributed between cryopumps & turbo pumps Only 0.5g of gas in plasma - very susceptible to contamination. Cleanliness paramount

21 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

22 Heating the Plasma

23 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

24 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!)

25 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

26 Diagnostics Many Diagnostics are required for plasma real time control & physics experiments LIDAR & Thomson scattering- Plasma density & velocity profiles CO2 Laser Interferometery - density profiles IR - Optical cameras Magnetics - plasma position 3D X-ray tomography And many others!!

27 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

28 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

29

30 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 Europe, Japan, Russia, US, China, South Korea & India Site in France (Cadarache) has been selected (June 2005) Basics design complete - on-site construction due to start 2007 ITER

31 THE WORLD NEEDS MORE/CLEANER ENERGY World need for power will increase Present annual consumption per person eg USA TCE (tons of coal equivalent) W Europe TCE China TCE India TCE Expect/hope Þ at least 3 TCE, while populations rising IEA expects world energy need to double by 2045

32 COST COMPARISONS Results from Shell Renewables + Fusion Power Plant Conceptual Studies

33 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

34 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

35 Conclusion Fusion is the process that drives the stars Terrestrial, man-made fusion offers near limitless supply of energy There are no environmental impacts nor safety issues Terrestrial Fusion is achieved by isolation within a magnetic bottle Engineering challenges exist - particularly for materials technology Geo-Politics and Economics are driving renewed interest - resulting in global collaboration & ITER