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Advanced Tokamaks FIRE to ARIES. "Prospects for Fusion Energy" AST 558 Dale Meade February 21, 2005. http://fire.pppl.gov/ast558_2005.html. Elements and Issues for a Fusion Power Plant. Requirements for the Development of Fusion Power. • General issues understood very early
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Advanced Tokamaks FIRE to ARIES "Prospects for Fusion Energy" AST 558 Dale Meade February 21, 2005 http://fire.pppl.gov/ast558_2005.html
Requirements for the Development of Fusion Power • General issues understood very early • Reactor plasma conditions (ntE ≈ 3x1020m-3s, Ti ~ 20 keV, Q ≥ 25) - confinement (turbulence), plasma heating • Neutron Wall Loading ~ 4 MWm-2 (for economic attractiveness) - material damage ~ 40 dpa/yr with low radioactive waste - tritium breeding (TBR > 1) to complete the fuel cycle • Fusion Power Densities ( ~ 5 MWm-3, ––> p ~ 10 atm) b = 〈 p / Bc2, MHD stability and coil engineering • Plasma Wall Interaction - ~ 2 MW m-2 thermal load on wall low impurity levels, low tritium retention (< 0.5 kG-T) alpha ash removal • High-duty cycle, essentially steady-state
Modern Perspective on Fusion Electric Power Plants Advanced Reactor Innovation Evaluation Studies (ARIES) carried out ~ 10 studies over 15 years Farrokh Najmabadi University of California, San Diego, La Jolla, CA ARIES Web Site: http://aries.ucsd.edu/ARIES/
Increase Power Density Power density, 1/Vp What we pay for,VFPC High-Field Magnets • Little Gain Big Win • ARIES-I with 19 T at the coil (cryogenic). • Advanced SSTR-2 with 21 T at the coil (HTS). D r r > D r ~ D r < D High bootstrap, High b • 2nd Stability: ARIES-II/IV • Reverse-shear: ARIES-RS, ARIES-AT, A-SSRT2 Decrease Recirculating Power Fraction • Improvement “saturates” about Q ~ 40. • A steady-state, first stability device with Nb3Sn Tech. has a recirculating fraction about 1/2 of this goal. Directions for Improvement • Improvement “saturates” at ~5 MW/m2 peak wall loading (for a 1GWe plant). • A steady-state, first stability device with Nb3Sn technology has a power density about 1/3 of this goal.
A dramatic change occurred in 1990: Introduction of the Advanced Tokamak • Our vision of a fusion system in 1980s was a large pulsed device. • Non-inductive current drive is inefficient. • Some important achievements in 1980s: • Experimental demonstration of bootstrap current (TFTR); • Development of ideal MHD codes that agreed with experimental results. • Development of steady-state power plant concepts (ARIES-I and SSTR) based on the trade-off of bootstrap current fraction and plasma b (Kessel, Jardin) • ARIES-I was still too large and too expensive: Utilize advance technologies: • Utilized high field magnets to improve the power density • Introduced SiC composite to achieve excellent safety & environmental characteristics.
Reverse Shear Regime • Requires wall stabilization (Resistive-wall modes) • Excellent match between bootstrap & equilibrium current profile at high b. • Internal transport barrier • ARIES-RS (medium extrapolation): bN= 4.8, b=5%, Pcd=81 MW (achieves ~5 MW/m2 peak wall loading.) • ARIES-AT (aggressive extrapolation): bN= 5.4, b=9%, Pcd=36 MW (high b is used to reduce peak field at magnet) Reverse Shear Plasmas Lead to Attractive Tokamak Power Plants First Stability Regime • Does Not need wall stabilization (Resistive-wall modes) • Limited bootstrap current fraction (< 65%), limited bN= 3.2 and b=2%, • ARIES-I: Optimizes at high A and low I and high magnetic field.
Approaching COE insensitive of power density Approaching COE insensitive of current drive Evolution of ARIES Designs
ARIES Studies (1988-2003) have Defined the Plasma Requirements for an Attractive Fusion Power Plant Plasma Exhaust Pheat/Rx ~ 100MW/m Helium Pumping Tritium Retention High Gain Q ~ 25 - 50 ntET ~ 6x1021 m-3skeV Pa/Pheat = fa ≈ 90% Low rotation Plasma Control Fueling Current Drive RWM Stabilization High Power Density Pf/V~ 6 MWm-3 ~10 atm Gn ≈ 4 MWm-2 Steady-State ~ 90% Bootstrap Lets design the smallest (cheapest) experiment to test the “critical burning plasma physics” issues.
FIRE Physics Objectives Burning Plasma Physics (Conventional Inductively Driven H-Mode) Q ~10 as target, higher Q not precluded fa = Pa/Pheat ~ 66% as target, up to 83% @ Q = 25 TAE/EPM stable at nominal point, access to unstable alpha ash demonstrate alpha ash removal Advanced Toroidal Physics (100% Non-inductively Driven AT-Mode) Q ~ 5 as target, higher Q not precluded fbs = Ibs/Ip ~ 80% as target, ARIES-RS/AT≈90% bN ~ 4.0, n = 1 wall stabilized, RWM feedback Quasi-Stationary Burn Duration (use plasma time scales) Pressure profile evolution and burn control > 20 - 40 tE Alpha ash accumulation/pumping > 4 - 10 tHe Plasma current profile evolution ~ 2 to 5 tskin Divertor pumping and heat removal > 10 - 20 tdivertor First wall heat removal > 1 tfirst-wall
Fusion Ignition Research Experiment (FIRE) • R = 2.14 m, a = 0.595 m • B = 10 T, (~ 6.5 T, AT) • Ip = 7.7 MA, (~ 5 MA, AT) • PICRF = 20 MW • PLHCD ≤ 30 MW (Upgrade) • Pfusion ~ 150 MW • Q ≈ 10, (5 - 10, AT) • Burn time ≈ 20s (2 tCR - Hmode) • ≈ 40s (< 5 tCR - AT) • Tokamak Cost = $350M (FY02) • Total Project Cost = $1.2B (FY02) 1,400 tonne LN cooled coils Mission: to attain, explore, understand and optimize magnetically-confined fusion-dominated plasmas
FIRE is Based on ARIES-RS Vision • 40% scale model of ARIES-RS plasma • ARIES-like all metal PFCs • Actively cooled W divertor • Be tile FW, cooled between shots • Close fitting conducting structure • ARIES-level toroidal field • LN cooled BeCu/OFHC TF • ARIES-like current drive technology • • FWCD and LHCD (no NBI/ECCD) • • No momentum input • • Site needs comparable to previous • DT tokamaks (TFTR/JET). • • T required/pulse ~ TFTR ≤ 0.3g-T
ARIES-RS (Q = 25) Critical Issue #1- Plasma Energy Confinement: FIRE and ITER Require Modest (2.5 to 5) Extrapolation • Tokamaks have established a solid basis for confinement scaling of the diverted H-Mode. • BtE is the dimensionless metric for confinement time projection • ntET is the dimensional metric for fusion - ntET = bB2tE = bB . BtE • ARIES-RS Power Plants require BtE only slightly larger than FIRE due high b and B. • STs require extrapolation of 200
Significant Progress on Existing Tokamaks Improves FIRE (and ITER) Design Basis since FESAC and NRC Reviews • Extended H-Mode and AT operating ranges • Benefits of FIRE high triangularity, DN and moderate n/nG • Extended H-Mode Performance based ITPA scaling with reduced b degradation, and ITPA Two Term (pedestal and core) scaling (Q > 20). • Hybrid modes (AUG, DIII-D,JET) are excellent match to FIRE n/nG, and projects Q > 20. • Slightly peaked density profiles (n(0)/<n> = 1.25)enhance performance. • Elms mitigated by high triangularity, disruptions in new ITPA physics basis will be tempered somewhat.
New ITPA tE Scaling Opens Ignition Regime for FIRE Unstable side Stable side • Systematic scans of tE vs b on DIII-D and JET show little degradation with b in contrast to the ITER 98(y, 2) scaling which has tE ~b-0.66 • A new confinement scaling relation developed by ITPA has reduced adverse scaling with b see eq. 10 in IAEA-CN-116/IT/P3-32. Cordey et al. • A route to ignition is now available if high bN regime can be stabilized.
No He Pumping • Needs He pumping technology
FIRE, The Movie Simulation of a Standard H-mode in FIRE - TSC • CTM ≈ GLF23 • m = 1 sawtooth Model - Jardin et al • other effects to be added - Jardin et al FIRE, the Movie
= p2sv /T2 Note: total power requires a volume integral
Critical Issue #2 - High Power Densities: Requires Significant (x10) Extrapolation in Plasma Pressure
Modeling FIRE Burning Advanced Tokamak Ip = 4.5 MA BT = 6.5 T H-mode edge also simulated
“Steady-State” High-b Advanced Tokamak Discharge on FIRE Pf/V = 5.5 MWm-3 Gn ≈ 2 MWm-2 B = 6.5T bN = 4.1 fbs = 77% 100% non-inductive Q ≈ 5 H98 = 1.7 n/nGW = 0.85 Flat top Duration = 48 tE = 10 tHe = 4 tcr FT/P7-23
The proposed RWM Coils would be in the Front Assembly of Every 3rd Port Plug Assembly RWM coils wrapped on end of Port Plug
Q = 5 FIRE AT Mode is Limited by the First Wall and Vac Vess Nominal operating point • Q = 5 • Pf = 150 MW, • Pf/Vp = 5.5 MWm-3 (ARIES) • ≈ steady-state 4 to 5 tCR Physics basis improving (ITPA) • required confinement H factor and bN attained transiently • C-Mod LHCD experiments will be very important First Wall is the main limit • Improve cooling • revisit FW design Opportunity for additional improvement.
Note: ITER and FIRE first wall (Be to VV) cost/PFC area ≈ equal at $0.25M/m2
Cool 1st Wall OFHC TF (≤ 7 T) Additional Opportunities to Optimize FIRE for the Study of ARIES AT Physics and Plasma Technologies ARIES AT (bN ≈ 5.4, fbs ≈ 90%) 12
Steps to a Magnetic Fusion Power Plant FIRE ARIES-RS ITER
FIRE Status • Physics Validation Review successfully passed. March 30-31, 2004 • Pre-Conceptual Activities are completed. September 30, 2004 • Ready to begin Conceptual Design Activities. Now • FIRE is ready to be put forward as per Fusion Energy Sciences Advisory Committee recommendation • Informal international discussions are being held at the technical level • Time to begin reassessment as recommended by NRC Burning Plasma Panel
AST 558: Graduate Seminar - "Prospects for Fusion Energy" February 7 A Brief History of Fusion and Magnetic Fusion Basics - Meade February 14 Recent JET Experiments and Science Issues - Strachan February 21 Advanced Tokamaks FIRE to ARIES - Meade February 28 The ARIES Power Plant Studies – Jardin March 7 IFE basics and NIF - Mark Herrmann(LLNL) Midterms and Spring Break March 21 The FESAC Fusion Energy Plan - Goldston March 28 Fusion with High Power Lasers – Sethian(NRL) April 4 ITER Physics and Technology- Sauthoff April 11 Stellarator Physics and Technology - Zarnstorff April 18 “New” Mirror Approaches for Fusion - Fisch April 25 ST Science and Technology – Peng May 2 FRC Science and Technology - Cohen