ARIES-AT: Evolution of Vision for Advanced Tokamak Power Plants Farrokh Najmabadi University of California, San Diego, La Jolla, CA, United States of America.
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ARIES-AT: Evolution of Vision for Advanced Tokamak Power Plants
Farrokh NajmabadiUniversity of California, San Diego, La Jolla, CA, United States of America
Japan-US Workshop on Fusion Power Plants and Related Advanced Technologies with participation of EU March 29-31, 2001 The University of Tokyo, JAPAN
You can download a copy of the presentation from the ARIES Web Site:ARIES Web Site: http://aries.ucsd.edu/
The ARIES Team: Michael C. Billone2, Leslie Bromberg6, Tom H. Brown7, Vincent Chan4, Laila A. El-guebaly8, Phil Heitzenroeder7, Stephen C. Jardin7, Charles Kessel Jr. 7, Lang L. Lao4, Siegfried Malang10, Tak-kuen Mau1, Elsayed A. Mogahed9, Farrokh Najmabadi1, Tom Petrie4, Dave Petti5, Ronald Miller1, Rene Raffray1, Don Steiner8, Igor Sviatoslavsky9, Dai-kai Sze2, Mark Tillack1, Allan D. Turnbull4, Lester Waganer3, Xueren Wang1
1) University of California, San Diego, 2) Argonne National Laboratory, 3) Boeing High Energy Systems, 4) General Atomics, 5) Idaho National Engineering &
Environmental Lab.,6) Massachusetts Institute of Technology, 7) Princeton Plasma Physics Laboratory, 8) Rensselaer Polytechnic Institute, 9) University of Wisconsin - Madison,10) Forschungszentrum Karlsruhe
Public Acceptance:
• No public evacuation plan is required: total dose < 1 rem at site boundary;
• Generated waste can be returned to environment or recycled in less than a few hundred years (not geological time-scale);
• No disturbance of public’s day-to-day activities;
• No exposure of workers to a higher risk than other power plants;
Reliable Power Source:
• Closed tritium fuel cycle on site;
• Ability to operate at partial load conditions (50% of full power);
• Ability to maintain power core;
• Ability to operate reliably with less than 0.1 major unscheduled shut-down per year.
Top-Level Requirements for Commercial Fusion Power Plants
Above requirements must be achieved simultaneously and consistent with a competitive life-cycle cost of electricity goal.
Translation of Requirements to GOALS for Fusion Power Plants
Requirements:
Have an economically competitive life-cycle cost of electricity:
• Low recirculating power;
• High power density;
• High thermal conversion efficiency;
• Less-expensive systems.
Gain Public acceptance by having excellent safety and environmental characteristics:
• Use low-activation and low toxicity materials and care in design.
Have operational reliability and high availability:
• Ease of maintenance, design margins, and extensive R&D.
Acceptable cost of development.
Improvements “saturate”after a certain limit
Detailed Systems analysis from TITAN reversed-field pinch (1988 $)
There Is Little Economic Benefit for Operating Beyond ~ 5 MW/m2 of Wall Load
Simple analysis for a cylindrical plasma with length L:
r
What we pay for, VFPC
Hyperbolic dependence
Wall loading Iw 1/r
is set by neutron mfp
VFPC = L ( 2r2)
For r >> , VFPC 2 Lr1 / Iw
For r << , VFPC 2 L 2 const.
“Knee of the curve” is at r
High and cheap copper TF Helicity Injection (ohmic current
drive) Freedom of choice of aspect ratio Optimization driven by geometrical
constraints.
There Is Little Economic Benefit for Operating Beyond 5-10 MW/m2 of Wall Load
• ARIES-RS, ARIES-ST, and ARIES-AT have not optimized at the highest wall load (all operate at around 5 MW/m2 peak)
6
7
8
9
10
0 1 2 3 4 5
Avg. wall load (MW/m2)
CO
E (
c/kW
h)
ARIES-RS
Systems code
Hyperbolic dependence4
5
6
7
8
0 1 2 3 4 5
Avg. Wall Load (MW/m2)
CO
E (c
/kW
h)
ARIES-AT
Systems code
Hyperbolic dependence
• Physics & Engineering constraints cause departure from geometrical dependence e.g., high field needed for high load increases TF cost
• ARIES-AT optimizes at lower wall loading because of high efficiency.
ARIES-AT2 Was Launched to Assess the latest Developments in Advanced Tokamak Physics, Technology and Design Concepts
Advanced Tokamak High-performance reversed-shear
plasma Build upon ARIES-RS research; Include latest physics from the
R&D program; Include optimization techniques
devised in the ARIES-ST study; Perform detailed physics analysis
to enhance credibility.
Advanced Technology High-performance, very-low
activation blanket: High thermal conversion
efficiency; Smallest nuclear boundary.
High-temperature superconductors: High-field capability; Ease of operation.
Advanced Manufacturing Techniques Detailed analysis in support of:
Manufacturing; Maintainability; Reliability & availability.
The ARIES-RS Study Set the Goals and Direction of Research for ARIES-AT
Efficiency 610oC outlet (including divertor) Low recirculating power
> 1000 oC coolant outlet > 90% bootstrap fraction
ARIES-RS Performance ARIES-AT Goals Economics
Power Density Reversed-shear Plasma Radiative divertor Li-V blanket with insulating coatings
Higher performance RS Plasma, SiC composite blanket High Tc superconductors
Availability Full-sector maintenance Simple, low-pressure design
Same or better
Safety and Environmental attractiveness
Low afterheat V-alloy No Be, no water, Inert atmosphere Radial segmentation of fusion core to minimize waste quantity
SiC Composites Further attempts to minimize waste quantity
Manufacturing Advanced manufacturing techniques
Major Parameters of ARIES-RS and ARIES-AT
Cost of electricity (c/kWh) 7.5 4.7
ARIES-RS ARIES-ATAspect ratio 4.0 4.0Major toroidal radius (m) 5.5 5.2Plasma minor radius (m) 1.4 1.3Toroidal 5%* 9.2%*
Normalized 4.8* 5.4*
• Designs operate at 90% of maximum theoretical limit.
Plasma elongation (x) 1.9 2.2
Plasma current 11 13Peak field at TF coil (T) 16 11.1Peak/Avg. neutron wall load (MW/m2) 5.4/4 4.9/3.3Thermal efficiency 0.46 0.59Fusion power (MW) 2,170 1,760
Current-drive power to plasma (MW) 81 37Recirculating power fraction 0.17 0.145
Physics Analysis
Continuity of ARIES research has led to the progressive refinement of research
ARIES-I:
• Trade-off of with bootstrap
• High-field magnets to compensate for low
ARIES-II/IV (2nd Stability):
• High only with too much bootstrap
• Marginal reduction in current-drive power
ARIES-RS:
• Improvement in and current-drive power
• Approaching COE insensitive of power density
ARIES-AT:
• Approaching COE insensitive of current-drive
• High is used to reduce toroidal field
Need high equilibria with high bootstrap
Need high equilibria with aligned bootstrap
Better bootstrap alignment
More detailed physics
Impr
oved
Phy
sics
ARIES-AT2: Physics Highlights
Using > 99% flux surface from free-boundary plasma equilibria rather than 95% flux surface used in ARIES-RS leads to larger elongation and triangularity and higher stable
ARIES-AT blanket allows vertical stabilizing shell closer to the plasma, leading to higher elongation and higher
A kink stability shell ( = 10 ms), 1cm of tungsten behind the blanket, is utilized to keep the power requirements for n = 1 resistive wall mode feedback coil at a modest level.
We eliminated HHFW current drive and used only lower hybrid for off-axis current drive.
As a whole, we performed detailed, self-consistent analysis of plasma MHD, current drive, transport, fueling, and divertor.
The ARIES-AT Equilibrium is the Results of Extensive ideal MHD Stability Analysis – Elongation Scans Show an Optimum Elongation
Detailed Physics Modeling Has Been Performed for ARIES-AT
• High accuracy equilibria;• Large ideal MHD database over profiles, shape and aspect ratio;• RWM stable with wall/rotation or wall/feedback control;• NTM stable with LHCD;• Bootstrap current consistency using advanced bootstrap models;• External current drive;• Vertically stable and controllable with modest power (reactive);• Rough kinetic profile consistency with RS /ITB experiments, as
well GLF23 transport code;• Modest core radiation with radiative SOL/divertor;• Accessible fueling;• No ripple losses;• 0-D consistent startup;
Fusion Technologies
ARIES-AT Fusion Core
ARIES-I Introduced SiC Composites as A High-Performance Structural Material for Fusion
Excellent safety & environmental characteristics (very low activation and very low afterheat).
High performance due to high strength at high temperatures (>1000
oC).
Large world-wide program in SiC: New SiC composite fibers with proper
stoichiometry and small O content. New manufacturing techniques based
on polymer infiltration or CVI result in much improved performance and cheaper components.
Recent results show composite thermal conductivity (under irradiation) close to 15 W/mK which was used for ARIES-I.
Continuity of ARIES research has led to the progressive refinement of research
ARIES-I:
• SiC composite with solid breeders
• Advanced Rankine cycle
Starlite & ARIES-RS:
• Li-cooled vanadium
• Insulating coating
ARIES-ST:
• Dual-cooled ferritic steel with SiC inserts
• Advanced Brayton Cycle at 650 oC
ARIES-AT:
• LiPb-cooled SiC composite
• Advanced Brayton cycle with = 59%
Many issues with solid breeders; Rankine cycle efficiency saturated at high temperature
Max. coolant temperature limited by maximum structure temperature
High efficiency with Brayton cycle at high temperature
Impr
oved
Bla
nket
Tec
hnol
ogy
Outboard blanket & first wall
ARIES-AT2: SiC Composite Blankets
Simple, low pressure design with SiC structure and LiPb coolant and breeder.
Innovative design leads to high LiPb outlet temperature (~1,100oC) while keeping SiC structure temperature below 1,000oC leading to a high thermal efficiency of ~ 60%.
Simple manufacturing technique. Very low afterheat.
Class C waste by a wide margin.
LiPb-cooled SiC composite divertor is capable of 5 MW/m2 of heat load.
Innovative Design Results in a LiPb Outlet Temperature of 1,100oC While Keeping SiC Temperature Below 1,000oC
• Two-pass PbLi flow, first pass to cool SiCf/SiC box second pass to superheat PbLi
q''plasma
Pb-17Li
q'''LiPb
Out
q''back
vback
vFW
Poloidal
Radial
Inner Channel
First Wall Channel
SiC/SiCFirst Wall SiC/SiC Inner Wall
700
800
900
1000
1100
1200800
900
1000
1100
1200
1
2
3
4
5
6
00.020.040.060.080.1
00.020.040.060.080.1
Radial distance (m)
Poloidaldistance(m)
SiC/SiC
Pb-17Li
Bottom
Top
PbLi Outlet Temp. = 1100 °C
Max. SiC/PbLi Interf. Temp. = 994 °C
Max. SiC/SiC Temp. = 996°C
PbLi Inlet Temp. = 764 °C
Advanced Brayton Cycle Parameters Based on Present or Near Term Technology Evolved with Expert Input from General Atomics
Key improvement is the development of cheap, high-efficiency recuperators.
RecuperatorIntercooler 1Intercooler 2
Compressor 1
Compressor 2Compressor 3
HeatRejection
HX
Wnet
Turbine
Blanket
IntermediateHX
5'
1
22'
38
9
4
7'9'
10
6
T
S
1
2
3
4
5 6 7 8
9 10
Divertor
LiPbBlanketCoolant
He DivertorCoolant
11
11
Multi-Dimensional Neutronics Analysis was Performed to Calculate TBR, activities, & Heat Generation Profiles
Very low activation and afterheat Lead to excellent safety and environmental characteristics.
All components qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste.
On-line removal of Po and Hg from LiPb coolant greatly improves the safety aspect of the system and is relatively straight forward.
Use of High-Temperature Superconductors Simplifies the Magnet Systems
Inconel strip
YBCO Superconductor Strip Packs (20 layers each)
8.5 430 mm
CeO2 + YSZ insulating coating(on slot & between YBCO layers)
HTS does not offer significant superconducting property advantages over low temperature superconductors due to the low field and low overall current density in ARIES-AT
HTS does offer operational advantages: Higher temperature operation (even
77K), or dry magnets Wide tapes deposited directly on the
structure (less chance of energy dissipating events)
Reduced magnet protection concerns
and potential significant cost advantages Because of ease of fabrication using advanced manufacturing techniques
ARIES-AT Also Uses A Full-Sector Maintenance Scheme
Impact of Advanced Technologies on Fusion Power Plant Characteristics
Impact
Dramatic impact on cost and attractiveness of power plant: Reduces fusion plasma size; Reduces unit cost and enhanced
public acceptance.
Detailed analysis in support of: Manufacturing; Maintainability; Reliability & availability.
Simpler magnet systems Not utilized; Simple conductor, coil, & cryo-
plant. Utilized for High Tc superconductors. High availability of 80-90%
Sector maintenance leads to short schedule down time;
Low-pressure design as well as engineering margins enhance reliability.
Technologies
High-performance, very-low activation blanket: High thermal conversion
efficiency; Smallest nuclear boundary.
High-temperature superconductors: High-field capability; Ease of operation.
Advanced Manufacturing Techniques
Our Vision of Magnetic Fusion Power Systems Has Improved Dramatically in the Last Decade, and Is Directly Tied to Advances in Fusion Science & Technology
Estimated Cost of Electricity (c/kWh)
0
2
4
6
8
10
12
14
Mid 80'sPhysics
Early 90'sPhysics
Late 90's Physics
AdvancedTechnology
Major radius (m)
0
1
2
3
4
5
6
7
8
9
10
Mid 80's Pulsar
Early 90'sARIES-I
Late 90'sARIES-RS
2000 ARIES-AT
ARIES-AT parameters:Major radius: 5.2 m Fusion Power 1,760 MWToroidal : 9.2% Net Electric 1,000 MWAvg. Wall Loading: 3.3 MW/m2 COE 4.7
c/kWh
Summary
• Identification of top-level requirements are essential in developing conceptual designs of fusion power plants.
• ARIES designs have explored the wide range of advanced tokamak power plants:
* ARIES-I: First Stability * ARIES-RS: Nominal reversed shear
* ARIES-II: Second Stability * ARIES-AT: Aggressive reversed shear
• Combination of advanced tokamak physics and advanced technologies lead to attractive fusion systems.
• Achieving full safety and environmental potential of fusion is an absolute necessity (but it is not sufficient).
• The goal of the US program in power plant studies is to guide fusion R&D. It strives for a balance between attractiveness (extrapolation in data base) and creditability. Past history indicates that we have been typically projecting only 10 years ahead!
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