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Burning Plasma Gap Between ITER and DEMO
Dale Meade
Fusion Innovation Research and Energy
US-Japan WorkshopFusion Power Plants and Related Advanced Technologies
March 5-7, 2008UCSD, San Diego, CA
Outline
Issues for DEMO (summary of FESAC Report)
Burning Plasma Issues
Gaps in Burning Plasma Issues
FESAC Planning Panel Report to FPA: December 5, 2007
Report on FESAC web site:
http://www.science.doe.gov/ofes/fesac.shtml
Full Greenwald presentation to FPA (Dec 5, 2007)
http://fire.pppl.gov/
Fusion Energy Sciences Advisory Committee Report
Priorities, Gaps and Opportunities: Towards a Long Range Strategic Plan for Magnetic Fusion Energy
October 2007
FESAC Planning Panel Report to FPA: December 5, 2007
● Importance: – Importance for the fusion energy mission and the degree
of extrapolation from the current state of knowledge● Urgency:
– Based on level of activity required now and in the near future.
● Generality: – Degree to which resolution of the issue would be generic
across different designs or approaches for Demo.
● After evaluation, the issues were grouped into three tiers. The tiers defined to suggest an overall judgment on:
– the state of knowledge
– the relative requirement and timeliness for more intense research for each issue.
Criteria For Prioritization of Issues for DEMO
FESAC Planning Panel Report to FPA: December 5, 2007
● Tier 1: solution not in hand, major extrapolation from current state of knowledge, need for qualitative improvements and substantial development for both short and long term – Plasma Facing Components– Materials
● Tier 2: solutions foreseen but not yet achieved, major extrapolation from current state of knowledge, need for qualitative improvements and substantial development for long term – Off-normal events– Fuel cycle– Plasma-wall interactions
Finding 3: Results of Prioritization of Issues for DEMO
● Tier 2: (Continued)
– Integrated, high-performance steady-state burning plasmas
– Power extraction
– Predictive modeling
– Measurement
● Tier 3: solutions foreseen but not yet achieved, moderate extrapolation from current state of knowledge, need for quantitative improvements and substantial development for long term – RF launchers/internal
components– Auxiliary systems– Control– Safety and environment– Magnets
Burning Plasma Issues and Metrics
1. Fusion Power Gain ( Pf => Qp => nE, Ti, Lawson)
2. Fusion Power Density (n => Pf/Vp => p2, p/B02, p/Bmax
2 )
3. Fusion Power Sustainment (duration=> dur /char , ) (Pcd/Pf => fBS, Te )
4. Fusion Power Control (Pmax, Pmin => nT/nD, Qp, Pheat,PCD ) (Ploss, loss Transient Events )
5. Fusion Plasma Interface• Hi Te for CD <=> Lo T for divertor, Hi Ti at edge pedestal
• materials - T retention, Impurity Rad to disperse Pexhaust
• self-conditioning of walls at long pulse, impact of hi Twall
• is existing confinement data base for C PFCs relevant?(These are sub-issues under Integrated High Performance Steady State Burning Plasma Issue in the FESAC Panel Report)
Fusion Power Source Gain Metric and Gap
Q Gap: Today to FPP ~ 50, ITER to FPP ~ 6
QFPP ≈ 30
Note: Duration Also
Economic Reactors Will Require Efficient Magnetic Utilization⟨p⟩
( )atm
0.1110301101001000TPXIGNITOR-ARIES AT2ASSTRH2 O Cu Coil ST Ops MaxBcoil2 (T2)ProjectedAchieved1 %βfusion = 2 %LN2 Cu Coil, Bitter Wedged Ops Max-ARIES ST0.5%NSTX-FIRE AT-ARIES RS-FIRE H- & -ITER H ITER ATTFTR-C Mod- C Mod AT- ( )Alc C OHJET -PBX M• “ ” , Attractive fusion systems require both high field highβ and efficient utilization.
• Advanced tokamaks offer the best combination of highβ .and achievable high field
NSTX≈ 5 MWm-3≈ 0.5 MWm-3 Nb SnCIC
3 CSCoil
Ops Max βfusion = ⟨p⟩ / Bcoil2 60JT U -DIII D Fusion Power Density Metric and Gap
Need to update and identify AT modes
Plasma Pressure Gap: from today ~ 6 and 106 in duration
from ITER ~ 3 and 103 in duration
Fusion Power Source Sustainment Metric and Gap
Need a metric for coupling of hi Q(alpha defined profile) and fBS
Also need high Te for high cd
Gap: Today to FPP is very large, ITER to FPP ~ 104
Contributions from EAST,KSTAR, JT-60SA for non-burning plasma
M Kikuchi - IAEA 2006
FPP
Fusion Power Source Control Metric and Gap
1. Operation must be on the thermally stable branch of PopCon• ITER will establish this for a modest AT regime with βN ≤ 3
and fBS ≈ 50%. Is this good enough for a 1st Demo?
2. Need to establish how far the AT regime (negative shear) can be pushed toward high bootstrap % with a pressure profile defined by strong alpha heating.
3. A highly reliable disruption avoidance system compatible with item 2 must be developed.
4. Develop techniques to eliminate large ELMs.
Fusion Power Source Interface Issues
• The AT regimes envisioned require high Te in the core for efficient current drive, and highish Ti at the plasma edge pedestal but low T in the divertor plasma to reduce erosion.
• Significant radiation is required near the plasma edge and on the divertor to spread the thermal exhaust power over a larger area.
• Impact of self-conditioning of PFCs at long pulses and impact of hi Twall on edge plasma and hence confinement.
• Are the existing confinement data base and associated scaling relations for Carbon PFCs relevant to DEMO or FPP?
The Gap from ITER to Tokamak Power PlantsITER-AT PPCS-C FIRE-AT ARIES-RS ASSTR-2
R (m), a (m) 6.35,1.85 7.5,2.5 2.14, 0.595 5.52, 1.38 6, 1.5κx , κa , κ95 -, 1.85,1.82 2.1, 1.9, 2.0, 1.85,1.82 1.9, - ,1.70 -, -, 1.8x , 95 0.55, 0.40 0.7, 0.47, 0.7, 0.55 0.77, 0.5 -, 0.4Div. Confi .g , material SN, C(W) SN, W DN, W DN, W SN,W(Ploss)/ (R MW/m) 15 ~70 16 80 ~100Bt(Ro) ( )T , Ip (MA) 5.1, 9 6, 20 6.5, 4.5 8, 11.3 11, 12q(0),qmin, q95 3.5, 2.2, 5.3 4, 2.7, 4.0 2.8, 2.49, 3.5 -, -, 4.8βt(%), βN , βp 2.8, 3.1, 1.5 5, 4 , 4, 4.1, 2.15 5, 4.8, 2.29 -, 3.7,-fbs (%) 48 63 77 88 80Current Driv e Tech NIB ,I ECF NBI ICFW, LHF ICFW, LHF NINBNon Inducti veCD. % 100 100 100 100 100n(0)/ ⟨n⟩vol, T(0)/ ⟨T⟩vol 1.3, 2.4 1.5,2.5 1.5, 3.0 1.5, 1.7 1.5, -n/nG, ⟨n⟩vol (10
20 m-3) 0.8 ,1.2 0.85, 2.4 1.7, 2.1 1.2, 2.1Ti(0), Te(0) 27, 25 25 14, 16 27, 28 ~35Zeff 2.1 2.2 2.3 1.7 1.6H98(y,2) 1.6 1.3 1.7 1.4E, ( )s 2.7 0.7 1.5Bur nDuration/cr , s 10, 3000 Steady-state 4, 32 Steady-state Steady-stateQ = Pfusion/(Paux + POH) 6 30 4.8 25 58Fusio nPo (wer MW) 360 3400 140 2160 3530Pfus/Vo l (MWm-3) 0.45 1.9 5.5 6.2 7.3 neutro (n MWm-2) 0.5 2.2 1.7 4 4.7
FESAC Planning Panel Report to FPA: December 5, 2007
● G-1 Sufficient understanding of all areas of the underlying plasma physics to predict
the performance and optimize the design and operation of future devices. Areas
likely to require additional research include turbulent transport and multi-scale, multi-
physics coupling.
● G-2 Demonstration of integrated, steady-state, high-performance (advanced) burning
plasmas, including first wall and divertor interactions. The main challenge is
combining high fusion gain with the strategies needed for steady-state operation.
● G-3 Diagnostic techniques suitable for control of steady-state advanced burning
plasmas that are compatible with the nuclear environment of a reactor. The principle
gap here is in developing measurement techniques that can be used in the hostile
environment of a fusion reactor.
FESAC - Finding 6: Assessment of Gaps (1)
FESAC Planning Panel Report to FPA: December 5, 2007
● G-4 Control strategies for high-performance burning plasmas, running near operating
limits, with auxiliary systems providing only a small fraction of the heating power and
current drive. Innovative strategies will be required to implement control in high-Q
burning plasma where almost all of the power and the current drive is generated by
the plasma itself.
● G-5 Ability to predict and avoid, or detect and mitigate, off-normal plasma events in
tokamaks that could challenge the integrity of fusion devices.
● G-6 Sufficient understanding of alternative magnetic configurations that have the
ability to operate in steady-state without off-normal plasma events. These must
demonstrate, through theory and experiment, that they can meet the performance
requirements to extrapolate to a reactor and that they are free from off-normal events
or other phenomena that would lower their availability or suitability for fusion power
applications.
FESAC - Finding 6: Assessment of Gaps (2)
FESAC Planning Panel Report to FPA: December 5, 2007
● G-7. Integrated understanding of RF launching structures and wave coupling for
scenarios suitable for Demo and compatible with the nuclear and plasma
environment. The stresses on launching structures for ICRH or LHCD in a high
radiation, high heat-flux environment will require designs that are less than optimal
from the point of view of wave physics and that may require development of new RF
techniques, new materials and new cooling strategies
● G-8. The knowledge base required to model and build low and high-temperature
superconducting magnet systems that provide robust, cost-effective magnets (at
higher fields if required).
● G-9. Sufficient understanding of all plasma-wall interactions necessary to predict the
environment for, and behavior of, plasma facing and other internal components for
Demo conditions. The science underlying the interaction of plasma and material
needs to be significantly strengthened to allow prediction of erosion and re-deposition
rates, tritium retention, dust production and damage to the first wall.
FESAC - Finding 6: Assessment of Gaps (3)
FESAC Planning Panel Report to FPA: December 5, 2007
● G-10. Understanding of the use of low activation solid and liquid materials,
joining technologies and cooling strategies sufficient to design robust first-
wall and divertor components in a high heat flux, steady-state nuclear
environment. Particularly challenging issues will include tritium permeation
and retention, embrittlement and loss of heat conduction.
● G-11 Understanding the elements of the complete fuel cycle, particularly
efficient tritium breeding, retention, recovery and separation in vessel
components.
● G-12 An engineering science base for the effective removal of heat at high
temperatures from first wall and breeding components in the fusion
environment.
FESAC - Finding 6: Assessment of Gaps (4)
FESAC Planning Panel Report to FPA: December 5, 2007
● G-13 Understanding the evolving properties of low activation materials in the fusion
environment relevant for structural and first wall components. This will include the
effects of materials chemistry and tritium permeation at high-temperatures. Important
properties like dimensional stability, phase stability, thermal conductivity, fracture
toughness, yield strength and ductility must be characterized as a function of neutron
bombardment at very high levels of atomic displacement with concomitant high levels
of transmutant helium and hydrogen.
● G-14 The knowledge base for fusion systems sufficient to guarantee safety over the
plant life cycle - including licensing and commissioning, normal operation, off-normal
events and decommissioning/disposal.
● G-15 The knowledge base for efficient maintainability of in-vessel components to
guarantee the availability goals of Demo are achievable.
FESAC - Finding 6: Assessment of Gaps (5)
,fbs, 65% ,68% , 88% , 91%
A Range of Advanced Tokamak Power Plants is Possible
• Is ARIES-I’ an acceptable 1st generation Fusion Power Plant? The physics can evolve continuously to ARIES-RS and then to ARIES-AT
Summary of Burning Plasma Issues
• First D-T experiments on TFTR and JET confirmed expectations for weakly burning plasmas with fractional alpha heating ~ 10%
• ITER is expected to confirm “steady-state” burning plasma (Q = 5) with 50 % alpha heating and 50% bootstrap fraction. Increases in performance are limited by the power handling capability of first wall and neutron heating of TF conductor.
• Significant gap will still exist between ITER and DEMO • control of hi-gain Q > 20 (f > 80%) and hi-bootstrap fraction fbs > 70%
• Possibilities to Bridge the Gap• Simulations of alpha heating in DD long pulse AT tokamaks • Additional advanced burning plasma experiment• Upgrade ITER• Start with ARIES-1 like DEMO and evolve to ARIES-RS, AT