Status of Fusion Research

Transcription

1 Status of Fusion Research Farrokh Najmabadi Prof. of Electrical Engineering Director of Center for Energy Research UC San Diego NCSU Seminar North Carolina September 2, 2010

2 World uses (& needs) a lot of energy! World Primary Energy consumption is 14 TW (2004) Equivalent to ~0.5 EJ or 11.2 Billion Ton of Oil Equivalent pa World energy [electricity] market ~ $4.5 trillion [$1.5 trillion] pa World energy use is expected to grow 50% by Growth is necessary in developing countries to lift billions of people out of poverty 80% of world energy is from burning fossil fuels Conditions for Sustainability/Growth: Large supply of the energy resource (TW scale) Acceptable land/resource usage Minimal by-product stream Economically feasible technology Fusion Engineering Grand Challenge

3 Brining a Star to Earth T D + T 4 He (3.5 MeV) + n (14 MeV) n + 6 Li 4 He (2 MeV) + T (2.7 MeV) n D + 6 Li 2 4 He MeV (Plasma) + 17 MeV (Blanket) DT fusion has the largest cross section and lowest temperature (~100M o C). But, it is still a high-temperature plasma! Plasma should be surrounded by a Li-containing blanket to generate T. Or, DT fusion turns its waste (neutrons) into fuel! Through careful design, only a small fraction of neutrons are absorbed in structure and induce radioactivity. For liquid coolant/breeders (e.g., Li, LiPb), most of fusion energy is directly deposited in the coolant simplifying energy recovery Practically no resource limit (10 11 TWy D; 10 4 (10 8 ) TWy 6 Li)

4 Fusion Energy Requirements: Confining the plasma so that alpha particles sustain fusion burn Lawson Criteria: nτ E ~ s/m 3 Heating the plasma for fusion reactions to occur to 100 Million o C (routinely done in present experiments) Optimizing plasma confinement device to minimize the cost Smaller devices Cheaper systems, e.g., lower-field magnets (MFE) or lowerpower lasers (IFE) Extracting the fusion power and breeding tritium Co-existence of a hot plasma with material interface Developing power extraction technology that can operate in fusion environment

5 Two Approaches to Fusion Power 1) Inertial Fusion Inertial Fusion Energy (IFE) Fast implosion of high-density DT capsules by laser or particle beams (~30 fold radial convergence, heating to fusion temperature). A DT burn front is generated, fusing ~1/3 of fuel (to be demonstrated in National Ignition Facility in Lawrence Livermore National Lab). Several ~300 MJ explosions per second with large gain (fusion power/input power).

6 Two Approaches to Fusion Power 2) Magnetic Fusion Magnetic Fusion Energy (MFE) Particles confined within a toroidal magnetic bottle for 10 s km and 100 s of collisions per fusion event. Strong magnetic pressure (100 s atm) to confine a low density but high pressure (10 s atm) plasma. At sufficient plasma pressure and confinement time, the 4 He power deposited in the plasma sustains fusion condition. Rest of the Talk is focused on MFE

7 Plasma behavior is dominated by collective effects Pressure balance (equilibrium) does not guaranty stability. Example: Interchange stability Fluid Interchange Instability Outside part of torus inside part of torus Impossible to design a toroidal magnetic bottle with good curvatures everywhere. Fortunately, because of high speed of particles, an averaged good curvature is sufficient.

8 Tokamak is the most successful concept for plasma confinement DIII-D, General Atomics Largest US tokamak R=1.7 m Many other configurations possible depending on the value and profile of q and how it is generated (internally or externally)

9 T3 Tokamak achieved the first high temperature (10 M o C) plasma 0.06 MA Plasma Current R=1 m

10 JET is currently the largest tokamak in the world ITER Burning plasma experiment (under construction) R=3 m R=6 m

11 Progress in plasma confinement has been impressive ITER Burning plasma experiment Fusion triple product n (10 21 m -3 ) τ(s) T(keV) 500 MW of fusion Power for 300s Construction has started in France

12 Large amount of fusion power has also been produced ITER Burning plasma experiment DT Experiments DD Experiments

13 Fusion Energy Requirements: Confining the plasma so that alpha particles sustain fusion burn Lawson Criteria: nτ E ~ s/m 3 Heating the plasma for fusion reactions to occur to 100 Million o C (routinely done in present experiments) Optimizing plasma confinement device to minimize the cost Smaller devices Cheaper systems, e.g., lower-field magnets (MFE) or lowerpower lasers (IFE) Extracting the fusion power and breeding tritium ITER and Satellite tokamaks (e.g., JT60-SU in Japan) should demonstrate operation of a fusion plasma (and its support technologies) at the power plant scale. Developing power extraction technology that can operate in fusion environment Co-existence of a hot plasma with material interface

14 ITER Device History EU, Japan, USSR, and US conducted the Conceptual Design Activity 1992 Engineering Design Activity (EDA) Started 1998 Initial EDA ended. US urged rescoring to reduce cost 1998 US withdraws from ITER at Congressional Direction. EU, Japan, RF pursue a lower cost design 2001 EDA ends 2003 US, Korea, and China join ITER 2006 Agreement on ITER Site 2009 Construction of long-lead time components started 2017? First Plasma 2026? Full power DT experiments

15 We have made tremendous progress in optimizing fusion plasmas Substantial improvement in plasma performance though optimization of plasma shape, profiles, and feedback. Achieving plasma stability at high plasma pressure. Achieving improved plasma confinement through suppression of plasma turbulence, the transport barrier. Progress toward steady-state operation through minimization of power needed to maintain plasma current through profile control. Controlling the boundary layer between plasma and vessel wall to avoid localized particle and heat loads.

16 ITER and satellite tokamaks will provide the necessary data for a fusion power plant DIII-D DIII-D ITER Simultaneous Max Baseline ARIES-AT Major toroidal radius (m) Plasma Current (MA) Magnetic field (T) Electron temperature (kev) 7.5* 16* 8.9** 18** Ion Temperature (kev) 18* 27* 8.1** 18** Density (10 20 m -3 ) 1.0* 1.7* 1.0** 2.2** Confinement time (s) Normalized confinement, H β (plasma/magnetic pressure) 6.7% 13% 2.5% 9.2% Normalized β Fusion Power (MW) 500 1,755 Pulse length 300 S.S. * Peak value, **Average Value

17 Fusion Energy Requirements: Confining the plasma so that alpha particles sustain fusion burn Lawson Criteria: nτ E ~ s/m 3 Heating the plasma for fusion reactions to occur to 100 Million o C (routinely done in present experiments) Optimizing plasma confinement device to minimize the cost Smaller devices Cheaper systems, e.g., lower-field magnets (MFE) or lower-power lasers (IFE) Extracting the fusion power and breeding tritium Developing power extraction technology that can operate in fusion environment Co-existence of a hot plasma with material interface

18 First wall and blanket System is subject to a harsh environment Environment: Surface heat flux (due to X-ray and ions) First wall erosion by ions. Radiation damage by neutrons (e.g. structural material) Volumetric heating by neutrons in the blanket. MHD effects Functions: Tritium breeding management Maximize power recovery and coolant outlet temperature for maximum thermal efficiency Constraints: Simple manufacturing technique Safety (low afterheat and activity) Outboard blanket & first wall x ray Neutrons ions

19 New structural material should be developed for fusion application Fe-9Cr steels: builds upon 9Cr-1Mo industrial experience and materials database (9-12 Cr ODS steels are a higher temperature future option) SiC/SiC: High risk, high performance option (early in its development path) W alloys: High performance option for PFCs (early in its development path)

20 Irradiation leads to a operating temperature window for material Structural Material Operating Temperature Windows: dpa Radiation embrittlement η Carnot =1-T reject /T high Thermal creep Zinkle and Ghoniem, Fusion Engr. Des (2000) 709 Additional considerations such as He embrittlement and chemical compatibility may impose further restrictions on operating window

21 Flow configuration allows for a coolant outlet temperature to be higher than maximum structure temperature Several blanket Concepts have been developed Dual coolant with a self-cooled PbLi zone, He-cooled RAFS structure and SiC insert Simple, low pressure design with SiC structure and LiPb coolant and breeder. Innovative design leads to high LiPb outlet temperature (~1,100 o C) while keeping SiC structure temperature below 1,000 o C leading to a high thermal efficiency of ~ 60%.

22 Bottom Poloidal distance (m) 2 3 Top Design leads to a LiPb Outlet Temperature of 1,100 o C While Keeping SiC Temperature Below 1,000 o C PbLi Inlet Temp. = 764 C Radial distance (m) SiC/SiC Pb-17Li Max. SiC/SiC Temp. = 996 C Max. SiC/PbLi Interf. Temp. = 994 C First Wall Channel Two-pass PbLi flow, first pass to cool SiC f /SiC box second pass to superheat PbLi q'' plasma Poloidal Radial v FW q'' back v back Pb-17Li Inner Channel q''' LiPb PbLi Outlet Temp. = 1100 C SiC/SiC First Wall Out SiC/SiC Inner Wall

23 Managing the plasma material interface is challenging Alpha power and alpha ash has to eventually leave the plasma Particle and energy flux on the material surrounding the plasma Modern tokomaks use divertors: Closed flux surfaces containing hot core plasma Open flux surfaces containing cold plasma diverted away from the first wall. Particle flux on the first wall is reduced, heat flux on the first wall is mainly due to radiation (bremsstrahlung, synchrotron, etc.) Alpha ash is pumped out in the divertor region High heat and particle fluxes on the divertor plates. Confined plasma Separatrix Flux surface First Wall Edge Plasma Divertor plates

24 Several Gad-cooled W divertor Concepts has been produced. EU finger: 2.6 cm diameter Impinging multi-jet cooling Allowable heat flux >10 MW/m 2 ~535,000 units for a power plant Mass flow rate [g/s] Nu p / Nu P p * / P * Plate: 20 cm x 100 cm Impinging slot-jet cooling Allowable heat flux ~10 MW/m 2 ~750 units for a power plant Nominal operating condition Re (/10 4 ) Thermal hydraulic experiments confirm very high heat transfer for slot jet cooling H > 50 kw/(m 2 K) is possible

25 The ARIES-AT utilizes an efficient superconducting magnet design On-axis toroidal field: Peak field at TF coil: 6 T 11.4 T TF Structure: Caps and straps support loads without inter-coil structure; Superconducting Material Either LTC superconductor (Nb 3 Sn and NbTi) or HTC Structural Plates with grooves for winding only the conductor.

26 Modular sector maintenance enables high availability Full sectors removed horizontally on rails Transport through maintenance corridors to hot cells Estimated maintenance time < 4 weeks ARIES-AT elevation view

27 Fusion Core Is Segmented to Minimize the Rad-Waste Blanket 1 (replaceable) Blanket 2 (lifetime) Shield (lifetime) Only blanket-1 and divertors are replaced every 5 years

28 Radioactivity levels in fusion power plants are very low and decay rapidly after shutdown Activity (Ci/W th ) Vanadium 1 d ARIES-ST ARIES-RS Ferritic Steel 1 mo 1 y 100 y Time Following Shutdown (s) SiC composites lead to a very low activation and afterheat. All components of ARIES-AT qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste. After 100 years, only 10,000 Curies of radioactivity remain in the 585 tonne ARIES-RS fusion core. Level in Coal Ash

29 Waste volume is not large 1270 m 3 of Waste is generated after 40 full-power year (FPY) of operation. Coolant is reused in other power plants 29 m 3 every 4 years (component replacement), 993 m 3 at end of service Equivalent to ~ 30 m 3 of waste per FPY Effective annual waste can be reduced by increasing plant service life. Cumulative Compacted Waste Volume (m3) Blanket Shield Vacuum Vessel Magnets Structure Cryostat Cumulative Compacted Waste Volume (m3) Class A 90% of waste qualifies for Class A disposal Class C

30 Advances in fusion science & technology has dramatically improved our vision of fusion power plants Major radius (m) Estimated Cost of Electricity (c/kwh) Mid 80's Pulsar Early 90's ARIES-I Late 90's ARIES-RS 2000 ARIES-AT Mid 80's Physics Early 90's Physics Late 90's Physics Advanced Technology

31 In Summary,

32 Status of fusion power Over 15 MW of fusion power is generated (JET, 1997) establishing scientific feasibility of fusion power Although fusion power < input power. ITER will demonstrate technical feasibility of fusion power by generating copious amount of fusion power (500MW for 300s) with fusion power > 10 input power. Tremendous progress in understanding plasmas has helped optimize plasma performance considerably. Vision of attractive fusion power plants exists. Transformation of fusion into a power plant requires considerable R&D in material and fusion nuclear technologies (largely ignored or under-funded to date). This step, however, can be done in parallel with ITER Large synergy between fusion nuclear technology R&D and Gen-IV.

33 Thank You