A Fusion Program Strategy forTimely Fusion Energy Deployment
By

Mickey Wade
Presented to

NAS Committee for a
Strategic Plan for U.S.
Burning Plasma Research

February 26, 2018
*With input from C. Greenfield, H. Guo, D. Hill, J. Menard, C. Petty, W.
Solomon, and T. Taylor and revised based on comments to accompanying
white paper by P. Ferguson, R. Hawyrluk, D. Whyte, and M. Zarnstorff
1

M.R. Wade / NAS Panel/ Feb 2018

General Comments• The strategic plan outlined here is my personal view on a potential
path forward to realize fusion energy in the next several decades– Takes onboard what I have learned from the community workshop but
does not represent a community perspective• The plan is based on my assessment of the opportunities andattempts to focus resources on areas that would provide distinctive
US leadership– It’s not comprehensive for what is required for fusion energy– It could be more aggressive

2

M.R. Wade / NAS Panel/ Feb 2018

Key Points for this Panel• Because of its unique positioning in the world program, the US has anopportunity to take a distinctive pathway to fusion energyØ Distinct opportunities for US leadership• Technically, the US is well positioned to extend world leadership in key
physics areas with continued investment:– Burning plasma science– High performance tokamak operation– Theory & computation• Additional investment is required to establish world leadership in key
technology areas going forward– Materials– HTS magnets• Success in these individual areas can converge in ~ 2040 time scale for aleadership-class next-step device beyond ITER
Ø Cost-attractive pilot plant/DEMO/FNSF
3

M.R. Wade / NAS Panel/ Feb 2018

Outline of Talk
• Introduction/Background• Heart of the Plan
• Other Considerations of Plan
– Blanket R&D Plan
– ‘Without ITER’ Plan
– Secondary Pathways– Reduced Funding Implications

4

M.R. Wade / NAS Panel/ Feb 2018

World is Moving Aggressively Forwardwith Fusion Energy• To date, worldwide fusion energy R&D has had the common goal ofdemonstrating the feasibility of fusion energy– ITER project embodies, at a grand scale, this partnership• World program is considering major facilities beyond ITER that are based on
existing or high-confidence approaches

EU
DEMO

KDEMO

Japan
DEMO

CFETR

• Looking beyond ITER, nations are likely to view fusion energy R&D quite
differently due to unique strategic needs for energy supply
U.S. program has an opportunity to take a distinctive
approach that significantly improves the cost-attractiveness ofboth the pathway to fusion energy AND the end product5

M.R. Wade / NAS Panel/ Feb 2018

Envisioned Strategy Leverages U.S. ScientificExcellence to Deliver Timely Fusion Energy

Foundation for
Tokamak Approachto Fusion

Ensure Successof ITERITER

Theory andComputation

MAST
NSTX-UJETASDEXUpgrade

US strategy for new
fusion facilities(materials, magnets,
blankets)

CFETR(China)WEST
KSTAR
JT-60 SA

DIII-D

EAST
SST-1

6

Cost-attractive
Pilot Plant/DEMO/FNSF

Major
upgrades or
new facilities
M.R. Wade / NAS Panel/ Feb 2018Play leadingrole
in international
fusion efforts

Underlying Features of the Strategy• This plan develops the U.S. pathway through the tokamak line
– Performance metrics and maturity level of physics basis
exceed all other lines– Enables leverage of significant investment worldwide in tokamaks– Requisite time scale demands urgency à next several decades• A strong theory, modeling, and computation program isfoundational to the plan
– Exascale and high-capacity computing are key enabling capabilities• Plan assumes U.S. remains a participant in ITER
• Required funding was not a significant consideration

7

M.R. Wade / NAS Panel/ Feb 2018

Key Objectives of the Plan
• Establish U.S. leadership in critical physics and technological areas
Ø Strategically position the U.S. with critical expertise that will be neededby other nations in their pursuit of fusion energy• Deliver world-class research platforms in a timely mannerØ Enable excellent science leading to key knowledge & breakthroughs• Utilize the most cost-attractive approaches to establish this leadershipØ Wisely invest available resources to enable broader set of pursuits• Broaden the constituency base to enable strengthened technical andpolitical support
Ø Promote pathways that broaden the required scientific disciplines andinstitutional engagement• Provide compelling 2040 goal for program direction and resourcing
Ø Identify the destination to clarify technical objectives

8

M.R. Wade / NAS Panel/ Feb 2018

Strategic Plan Includes Community-Identified Elements
but Relative Emphasis Varies Significantly
Strategic Elements from recent
USMFRSD Community Workshops:

Relative Emphasis* in this Plan

• Burning plasma science

Burning
Plasmas• HTS magnets for fusion applications• Configuration researchHighperformance
tokamaks• Stellarators• Theory/computation

Materials

Stellarators• Plasma-material interactions & divertor

Configuration
R&D• Fusion nuclear materials

PMI &Divertor

Fuel Cycle

HTS
Magnets

Theory &Computation• Tritium fuel cycle• Sustained high performance*Relative emphasis denoted by size of label

9

M.R. Wade / NAS Panel/ Feb 2018

Timing of Transitions Must Balance Desire for Change andTime Scale Required to Implement Effective Change• Strong desire in the community
for a strategic plan that disrupts
the status quo– Sooner rather than later• Impactful, lasting change requires
deliberate thought and planning– Small changes in direction (small
rudder changes) will produce largechange in target/goal• This strategic plan attempts to address this tension by calling fordefinitive changes in program makeup but over a time scale in which
the implementation can realistically (and non-disruptively) be done10

M.R. Wade / NAS Panel/ Feb 2018

Outline of Talk
• Introduction/Background• Heart of the Plan
• Other Considerations of Plan
– Blanket R&D Plan
– ‘Without ITER’ Plan
– Secondary Pathways– Reduced Funding Implications

11

M.R. Wade / NAS Panel/ Feb 2018

Overall Objective of Strategic Plan is to Converge R&D
Elements in ~ 2040 for Design of Cost-Attractive Next Step
Produce, Understand,and Exploit
Burning Plasmas

Establish the feasibilityof high power density,
steady-state tokamak
operation

Technical Basisfor a Cost-Attractive
Pilot Plant/DEMO/FNSF
in 2040

Fabricate high-criticaltemperature magnets
for fusion purposes

12

Provide solutions to
extreme power exhaust
requirements in future
fusion energy systems

Develop and qualifymaterials for high heat
flux and 14-MeV
neutron fluence

M.R. Wade / NAS Panel/ Feb 2018

Overall Objective of Strategic Plan is to Converge R&D
Elements in ~ 2040 for Design of Cost-Attractive Next Step
Produce, Understand,and Exploit
Burning Plasmas•

Plan will likely require significantly increased funding• Tough choices will be required if these funding Provide
levels fall
solutions to
Establish the feasibility
Technical
Basisextreme power exhaust
short of these requirementsof high power density,
for a Costrequirements in future
steady-state tokamak
Attractive
Pilot
Plant and assumption
fusion energy• Choices depend on
expected
funding
on systems
operationor DEMO
in 2040 (e.g., first to fusion,
what is the most importantdeliverable
leadership in specific areas, …)
Ø Possibilities outlined at end of talkFabricate high-criticaltemperature magnets
for fusion purposes

13

Develop and qualifymaterials for high heat
flux and 14-MeV
neutron fluence

M.R. Wade / NAS Panel/ Feb 2018

Access and Understanding of Burning Plasmas isFoundational to Fusion Energy R&D – US Leads in This Effort
Produce, Understand,and Exploit
Burning Plasmas

Importance:• Fundamental building block of entire plan à
Motivates and enables all other areas

U.S status:• Key contributor to physics basis for ITER designand operation (ELM suppression, disruption
mitigation, scenarios,…)• DIII-D well positioned for future impact

International context:• All ITER partners have programs that
support burning plasma science• 100% of ITER R&D output will beavailable to the U.S. (if we remaina partner)

14

Integrated
Demonstration
Materials
Tritium Breeding
Heat Extraction

Burning Plasmas
Foundational Science & Technology

M.R. Wade / NAS Panel/ Feb 2018

Burning Plasma R&D Focused on Demonstrating ITER Q=10
Operation and Exploiting ITER for Future Aspirations
Key Elements of R&D Plan:• Establish credibility for cost-attractive Pilot plant/DEMO/FNSF– ITER achieves it technical mission (Q=10, 500 MW for 400 s)– Robust solutions for disruption and ELM control– Predictive understanding of the physics of burning plasmas• Inform design of Pilot plant/DEMO/FNSF– Identification/qualification of burning plasma operational scenarios thatoffer best integrated performance– ρ* (size) scaling of transport

15

M.R. Wade / NAS Panel/ Feb 2018

ITER is the Center Piece of Burning Plasma Science R&D,
Both Motivating and Enabling Cutting Edge Research• ITER capabilities are far beyond anything
the US could do on its own
Ø 500 MW for 400 s

JET

C-Mod

MAST

DIII-D

NSTX

TCV

Alpha-particle physics
Transport and MHD at low ρ*
Fusion burn stability, control, and propagation
Strong, non-linear coupling of heating, current
drive, turbulent transport, MHD stability andboundary plasma

M.R. Wade / NAS Panel/ Feb 2018

SST-1

EAST

KSTAR

Realization

ITER• ... and will enable new opportunities

16

JT-60SA

Physics Basis• ITER participation motivates vigorous R&D on
key challenges for fusion– Achieve necessary density/ temperature
confinement (n T τ)
– Operate safely at high plasma pressure– Handle concomitant heat/particle flux
– Minimize/Eliminate effect of transients––––

ASDEX-U

Exploitation

U.S. Domestic Facilities Are Essential to Prepare for
ITER Operation and Subsequent Exploitation
Facilities Plan:
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-UITER

RecoveryConstruction

2040

Construct

OperateLiquid Walls
1st Plasma

DD OpsDT Ops• Preparation for ITER
– Improved physics basis for robust solutions for disruption/ELM control– Improved ITER scenarios (Q = 10 at lower Ip)– Better predictive understanding• Exploitation of ITER
– Explore means for very high gain operation in ITER
– Detailed investigations of physics phenomena observed in ITER but
require enhanced diagnostic capabilities

17

M.R. Wade / NAS Panel/ Feb 2018

Targeting High Power Density, Steady-State Systems is aHallmark of US Program and Should Remain a Key Strength
Importance:• Cost attractiveness of future fusion systems
improved by power density and steady-state
capability

Establish the feasibilityof high power density,
steady-state tokamak
operation

U.S status:• World leader in developing physics basis of high-performance, steady-state• No long-pulse capability

International context:• New superconducting devices (EAST, KSTAR, JT-60SA) have advantage in
extending to true steady-state• Planned DIII-D/NSTX-U upgrades will maintain U.S. leadership in advancing
performance envelope and establishing physics basis

18

M.R. Wade / NAS Panel/ Feb 2018

R&D Plan Focused on Demonstrating and Providing thePhysics Basis for Design of Future Steady-State Devices
Key Elements of R&D Plan:• Establish credibility for cost-attractive Pilot plant/DEMO/FNSF– Demonstrated capability of fully non-inductive, high β operation– Physics/technology basis for high efficiency current drive tools• Inform design of Pilot plant/DEMO/FNSF– Quantification of performance limits for AT and ST along with optimalcurrent profile to achieve those limits– Impact of high toroidal field and density on confinement, current drive,and core-edge integration

19

M.R. Wade / NAS Panel/ Feb 2018

DIII-D/NSTX-U/HPDT/ITER Provide a Powerful Combination
for Developing Basis for High Power Density, Steady-State
Facilities Plan:
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-UITER

Recovery

2040

Construct

OperateLiquid Walls
1st Plasma

DD OpsDT Ops• Establish physics basis for high power density, steady-state– DIII-D/NSTX-U upgrades will provide access to steady-state regimes– HPDT enables exploration of unique operating space (see next slide)• Inform next steps– DIII-D/NSTX-U current profile sustainment à ITER H&CD upgrades for Q=5– DIII-D/NSTX-U performance limits à HPDT design (R/a, size, CD tools)– HPDT/ITER steady-state regimes à Pilot plant/DEMO/FNSF physics basis
and design

20

M.R. Wade / NAS Panel/ Feb 2018

Moderate Sized, High Field Device Needed to Test
Important Regime for Compact Tokamak Approach•

High βΝ is highly favorable for compact,high gain, high power density approach

Assumes constant ν*, β, qPtransport~ nT/τ(gyro-Bohm)

Ratio ~
nTτPalpha~ n2T2

21

M.R. Wade / NAS Panel/ Feb 2018

Moderate Sized, High Field Device Needed to Test
Important Regime for Compact Tokamak Approach•

High βΝ is highly favorable for compact,high gain, high power density approach– Decrease in βΝ increases device size andreduces nominal output power– fBS ~ q βΝ à reduced CD requirements

Ptransport~ nT/τReduceβNPalpha~ n2T2

22

M.R. Wade / NAS Panel/ Feb 2018

Moderate Sized, High Field Device Needed to Test
Important Regime for Compact Tokamak Approach
•

•

•

23

High βΝ is highly favorable for compact,high gain, high power density approach– Decrease in βΝ increases device size andreduces nominal output power– fBS ~ q βΝ à reduced CD requirements
Progressive set of new capabilities would
enable a detailed assessment of thisapproach. (example from the R/a ~ 3 path)– Presently planned upgrades of DIII-D– DIII-D scale device at 3 T, 40 MW– New device with increased size, field,
and power (could be a substantial
upgrade of an existing facility)
Resultant high power density device would
also enable exploration of:– High pressure pedestals– Power exhaust solutions (later in talk)

M.R. Wade / NAS Panel/ Feb 2018

Ptransport~ nT/τ

a = 0.75 m, 4 T,
50 MW
DIII-D, 3 T,
40 MW
DIII-D, 2.1 T,
25 MW

Palpha~ n2T2

DIII-D/NSTX-U/HPDT/ITER Provide a Powerful Combination
for Developing Basis for High Power Density, Steady-State
Facilities
TransitionPlan:
logic/timing depends on2020 and R&D progressavailable funding(perhaps one in ~ 2025, one in ~ 2030)
DIII-D

ITER

Recovery

2040
High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-U

2030

Construct

OperateLiquid Walls
1st Plasma

HPDT could be DT
a Ops
new facility ora substantial upgrade of
DIII-D or NSTX-U

DD Ops• Establish physics basis for high power density, steady-state– DIII-D/NSTX-U upgrades will provide access to steady-state regimes– HPDT enables exploration of unique operating space (see next slide)• Inform next steps– DIII-D/NSTX-U current profile sustainment à ITER H&CD upgrades for Q=5– DIII-D/NSTX-U performance limits à HPDT design (R/a, size, CD tools)– HPDT/ITER steady-state regimes à Pilot plant/DEMO/FNSF physics basis
and design

24

M.R. Wade / NAS Panel/ Feb 2018

DIII-D/NSTX-U/HPDT/ITER Provide a Powerful Combination
for Developing Basis for High Power Density, Steady-State
Facilities
TransitionPlan:
logic/timing depends on2020 and R&D progressavailable funding(perhaps one in ~ 2025, one in ~ 2030)
DIII-D

ITER

Recovery

2040
High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-U

2030

Construct

OperateLiquid Walls
1st Plasma

HPDT could be DT
a Ops
new facility ora substantial upgrade of
DIII-D or NSTX-U

DD Ops• Establish physics basis for high power density, steady-state
Decided through a community– process
DIII-D/NSTX-U
upgradesthat engages
all will provide access to steady-state regimes– HPDT
enablesand
explorationof unique operating space (see next slide)stakeholders
FES• Inform next steps– DIII-D/NSTX-U current profile sustainment à ITER H&CD upgrades for Q=5– DIII-D/NSTX-U performance limits à HPDT design (R/a, size, CD tools)– HPDT/ITER steady-state regimes à Pilot plant/DEMO/FNSF physics basis
and design

25

M.R. Wade / NAS Panel/ Feb 2018

Power Exhaust Solutions are Essential for High PowerDensity Systems – Recent Renewed Emphasis in R&D
Importance:• Fundamental limitation on achievable power
density of future fusion systems is handlingthe concomitant heat flux

U.S status:• World leader in divertor/SOL measurements• Wide range of capabilities to change divertor
geometry and conditions

International context:• Capabilities exceed those of US in important areas– Metal walls/divertors (AUG, JET, EAST, WEST)– Long pulse (EAST, KSTAR, WEST, JT-60SA)

26

M.R. Wade / NAS Panel/ Feb 2018

Provide solutions to
extreme power exhaust
requirements in future
fusion energy systems

R&D Plan Focuses on Understanding, Predictive Capability
and Solutions, Then Extending to High Power Density
Key Elements of R&D Plan:• Establish credibility for cost-attractive Pilot plant/DEMO/FNSF– Scientific understanding and demonstrated capability to dissipate very
high heat flux without degrading core performance– Physics/technology basis for high accuracy divertor design• Inform design of Pilot plant/DEMO/FNSF– Validated predictive capability in highly dissipative conditions fordivertor/first wall design– Quantitative tradeoffs of impact of divertor design on core and divertor
performance

27

M.R. Wade / NAS Panel/ Feb 2018

HPDT Would Provide Research Platform for Resolving Power
Exhaust Solutions in High Power Density Systems•

Combination of high power and modest
size would naturally provide reactor-scaleheat fluxes into SOL– Higher that expected in ITER•

Headroom above L-H power thresholdenables development of core radiative
solutions to augment boundary solutions– As well as self consistency of thosesolutions•High field would enable decoupling of
density and collsiionality– n ~ ν*1/2 B/a1/2 (at constant β and q)– Providing improved test bed for coreedge integration

28

M.R. Wade / NAS Panel/ Feb 2018

a = 0.75 m,
3 MA, 4 T,
50 MW

Δλq = Δλq,Eich ~ 1/ Ip

R&D Plan Focuses on Developing Predictive Capability andPractical Solutions, Then Extending to High Power Density
Facilities Plan:
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-UITER

Recovery

2040

Construct

OperateLiquid Walls
1st Plasma

DD OpsDT Ops• Establish physics basis for dissipative divertor operation– Targeted upgrades/research on DIII-D/NSTX-U to close the predictive gapof dissipative divertor operation and assess impact of divertor geometry– ITER provides affirmation/test bed for physics basis established above• Extend to high power density– ITER/HPDT provide unique combination of facilities to assess full radiative
solutions (including both core and edge) at high power density

29

M.R. Wade / NAS Panel/ Feb 2018

High-Critical-Temperature Magnets Have Potential for
Improving Various Aspects of Fusion Magnet Systems
Importance:
Fabricate high-critical• Substantially increased operating spacetemperature magnets(critical field, operating temperature, current
for fusion purposes
density) offer potential for several advantages– Higher field operation– Jointed coils à potentially improved maintainability of system– Smaller radial build of coil à potentially smaller size system

U.S status:• Historically a world leader in magnet development for fusion; limited
expertise with large HTS magnets• Significant investment in other fields have led to rapid
development of HTS conductors

International context:• Due to the potential, many other countries pursuing this option also
• Due to competitiveness, openness of information not as readily available as
most fusion technologies
30

M.R. Wade / NAS Panel/ Feb 2018

R&D Plan Targets Development of Relevant Technology,
then Demonstration of Large-Bore HTS Magnets
Key Elements of R&D Plan:• Establish credibility for cost-attractive Pilot plant/DEMO/FNSF– Demonstrated capability to build large-bore HTS magnets• Inform design of Pilot plant/DEMO/FNSF– Ability to produce jointed HTS magnets– Performance variation of large-bore HTS magnets with:• Operating temperature (refrigeration costs)• Neutron fluence

31

M.R. Wade / NAS Panel/ Feb 2018

R&D Plan Targets Development of Relevant Technology,
then Demonstration of Large-Bore HTS Magnets
Facilities Plan:
2020

2030
HTS Coil
Facility

DesignConstruct

2040
Operate• HTS conductor/coil development– Develop relevant means to produce either/both:• High performance HTS conductor from strands to take advantage of ITER
cable-in-conduit-conductor (CICC) technology• High performance, large-bore HTS magnets using HTS tapes• HTS magnet construction/testing– Construct HTS magnet coil and quantify performance (possibly partnerwith China)• System studies with HTS– Benefit of technology needs full assessment, especially as desired net
electricity output increases above 500 MW
32

M.R. Wade / NAS Panel/ Feb 2018

Solutions that Lengthen Materials Lifetime are a
Critical R&D Need; Worldwide Effort is Modest
Importance:• Maximizing materials lifetime is critical tocost-attractiveness of future fusion systems

Develop and qualifymaterials for high heat
flux and 14-MeV
neutron fluence

U.S status:• Very limited US effort• Beginning new initiatives on plasma-material interaction (MPEX)International context:• Several plasma-material and high heat flux facilities worldwide, each withvarying degrees of capability• Little experimental effort worldwide on materials effects of 14-MeV neutrons

33

M.R. Wade / NAS Panel/ Feb 2018

R&D Plan Targets Development/Qualification of Materials
that Offer Long-Lifetime to Erosion and Neutron Damage
Key Elements of R&D Plan:• Establish credibility for cost-attractive Pilot plant/DEMO/FNSF– Qualified long-lifetime materials for plasma facing and structuralcomponents• Inform design of Pilot plant/DEMO/FNSF– Anticipated lifetime of materials à scheduled maintenance requirements– Performance limits of materials after exposure à engineering constraints
on stresses, heat flux, …

34

M.R. Wade / NAS Panel/ Feb 2018

14-MeV Neutron Source Critically Needed to Fill
Knowledge Gap on Impact of Neutron Damage• Evaluation of fusion radiation effects requires
simultaneous displacement damage and He
generation– With He % above ~100 appm
• Limited data available at He concentrations
above 10 appm
Ø Facility critically needed to fill this gap??

• Proposed int’l facilities focus on small sample
sizes for material exposure (e.g., IFMIF, DONES)• U.S. developed capability to expose moderatesize samples would be world-leading– Enabling tests of joints, welds, composites
not possible in small samples• Recent developments in Gas Dynamic Traps
may provide potential lower-cost option– Eg.. Combining GDT with HTS magnet

35

M.R. Wade / NAS Panel/ Feb 2018

GDT-Based
Volumetric Neutron
SourceR&D Plan Focused on Science-Driven Developmentof Materials for Fusion Application
Facilities Plan:
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-U

2040

Construct

OperateLiquid Walls

RecoveryLinear PMI Design
Facility

Pilot Plant/
DEMO/FNSF
OperateConstruct

Volumetric
DesignNeutron Source

Construct

Operate• Identification of best candidate materials– Utilize theory and basic facilities to develop new materials that meetrequirements– Asessmaterial evolution in dedicated test facilities (lifetime to erosion andneutron damage)– Followed by deployment in fusion systems for compatibility• Qualification of materials– Utilize HPDT and VNS to test materials at near-reactor-level conditions
36

M.R. Wade / NAS Panel/ Feb 2018

Plan Envisions Multiple Facilities Transitions,Culminating with Three World-Class US Facilities
Facilities Plan:
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-U

2040

Construct

OperatePilot Plant/
DEMO/FNSF

Liquid Walls

RecoveryITER

1st Plasma

Linear PMI Design
Facility

OperateConstruct

Volumetric
DesignNeutron Source
HTS Coil
Facility

DT OpsDD OpsDesignOperateConstruct
Construct

OperateVolumetric
NeutronSourceITER

HPDT
Produce,
Understand,and Exploit
Burning Plasmas

37

Establish the feasibilityof high power density,
steady-state tokamak
operation

Provide solutions to
extreme power
exhaust requirements
in future fusion energy
systems

M.R. Wade / NAS Panel/ Feb 2018

Develop and qualifymaterials for highheat flux and 14MeV neutron fluenceOutline of Talk
• Introduction/Background• Heart of the Plan
• Other Considerations of Plan
– Blanket R&D Plan
– ‘Without ITER’ Plan
– Secondary Pathways– Reduced Funding Implications

38

M.R. Wade / NAS Panel/ Feb 2018

Blanket R&D Plan Relies on International Partnerships toMaintain Level of Expertise Required for Future Efforts• Efficient tritium breeding and power conversion is key requirement forcost-attractive fusion systems• Demonstrative progress requires having a facility capable of both highneutron flux and power flow
– Likely requires a device with non-trivial fusion power

Ø U.S. should invest sufficiently to leverage worldwide R&D while
simultaneously developing U.S.-specific approaches that would benefit
high-power density fusion systems. Program elements should include:- Partnership with CFETR for blanket development/testing- High thermal efficiency blankets (e.g., He-cooled PbLi)

39

M.R. Wade / NAS Panel/ Feb 2018‘Without ITER Plan’: HPDT Mission Would be
Expanded to Include Burning Plasma Science• Only significant change in the plan is to add DT capability to HPDT
2020
DIII-D

2030

High Power Density Tokamak (HPDT)Divertor, H&CD Upgrades
DesignNSTX-UITER

Recovery

2040

Construct

DD OpsDTDT
OpsOpsLiquid Walls
1st Plasma

DD Ops• With further increases in field, HPDT-DT should be capable of Q = 5-10
– e.g., FIRE-AT: a = 0.6 m, B = 6.5 T, P = 50 MW• Impact on Plan:– ê Costs more, takes more time, much shorter pulse length– é High β, burning plasmas could be assessed– é Logic of remainder of program would not change; however, costdifference would have to absorbed
A potential serious impact that is not taken into account here is the political
impact (e.g., reduced funding, response of partners) of withdrawal.
40

M.R. Wade / NAS Panel/ Feb 2018

Given Sufficient Funding, U.S. Should Strive to Develop A NonTokamak Configuration to Sufficient Maturity for Evaluation• Alternate configurations have long been a strength of the US program– Scientific opportunities are abundant in this area

• Furthermore, significant challenges remain for the tokamak (e.g., current
sustainment, plasma disruptions)Ø Compelling secondary pathways should be developed to reduce risk

• Personal view: Quasi-symmetric stellarator represents the mostcompelling US option- Based on emerging theoretical basis and recent results from LHD and W7-X

• Proof-of-principle-scale quasi-symmetric facility would assess predictions of
turbulence-driven ion thermal transport and energetic particle confinement– Possibly in partnership with other countries
2020
Proof-of-Principle
Quasi-Symmetric Stellarator

41

2030
DesignConstruct

M.R. Wade / NAS Panel/ Feb 2018

2040
OperateITER

High PowerDensity
Tokamak

Linear PMI
Facility

Volumetric
Neutron Source

Magnet Test
Facility

Inability to Attract Increased Funding Will Necessitate
Tough Choices; Priorities Will Depend on Objective

Be the first to fusion

A

B

B

A

C

Distinctive path to fusion

B

A

C

A

B

Establish U.S. industrial leadership in key
technologies

B

C

B

A

A

Establish U.S. leadership in physics design

B

A

A

B

C

Leverage international investment

A

C

C

A

B

Facility Priorities Based on
Underlying Strategic Objective
Strategic Objective

42

M.R. Wade / NAS Panel/ Feb 2018

Summary• With targeted investment, physics advances can continue to accelerate the
US path to fusion energyØ Aggressively pursue burning plasmas, high performance tokamaks, andpower exhaust solutions• Technology will ultimately be the mechanism through which world leadershipis demonstrated in attractive fusion energy
Ø Lay down the foundations now to lead in distinctive technologies (e.g., neutronresistant materials, HTS magnets, …)• Strategic plan outlined here simultaneously:a) Enables resolution of critical issues for fusion developmentb) Provides compelling scientific opportunities to carry out cutting edge researchc) Develops world-leading technical capabilities in fusion physics & technologyd) Enables a pathway to a cost-attractive Pilot plant/DEMO/FNSF in ~ 2040

43

M.R. Wade / NAS Panel/ Feb 2018

Summary• With targeted investment, physics advances can continue to accelerate the
US path to fusion energyØ Aggressively pursue burning plasmas, high performance tokamaks, andpower exhaust solutions• Technology will ultimately be the mechanism through which world leadershipis demonstrated in attractive fusion energy
Ø Lay down the foundations now to lead in distinctive technologies (e.g., neutronresistant materials, HTS magnets, …)• Strategic plan outlined here simultaneously:a) Enables resolution of critical issues for fusion developmentb) Provides compelling scientific opportunities to carry out cutting edge researchc) Develops world-leading technical capabilities in fusion physics & technologyd) Enables a pathway to a cost-attractive Pilot plant/DEMO/FNSF in ~ 2040

Good luck on the development of the Final Report. Your task is
not an easy one, but one that will have a lasting impact on the futureof fusion research in the US and the world.
44

M.R. Wade / NAS Panel/ Feb 2018