National Fusion Power Plant Studies ProgramAchievements and Recent Results

Prepared for Bill Dove

OFES Headquarters

June, 1999

National Power Plant Studies ProgramProvides a Vision for the Fusion Program

¬ Establish Goals and Requirements for Fusion Power:∗ Economics (power density, recirculating power, thermal

efficiency, availability, etc.);∗ Safety (no need for evacuation);∗ Environmental (low-level waste, minimize waste);∗ Provides a common basis for comparative assessment.

② Perform Self-Consistent Design & Analysis (both plasmacore & engineering components), for example:∗ Detailed analysis of MHD equilibrium and stability and

current drive subject to constraints on κ (vertical stabilityshell and coils), δ (divertor geometry), location of kink shell(blanket design), current-driver launcher (first wall design),core-plasma radiation (first wall and divertor design), etc.

National Power Plant Studies ProgramProvides a Vision for the Fusion Program

® Determine Potential of Confinement Concepts:∗ Concept potential as a power plant or a fusion development

device (benefits);∗ Degree of extrapolation from present data base (risk);∗ Identification of key issues for R&D program;∗ Identification of innovative solution to improve the concept.

④ Determine Potential of Enabling and Power Technologies:∗ As a candidate for a power plant;∗ As a vehicle to help fusion development;

Framework:Assessment Based on Attractiveness & Feasibility

Periodic Input fromEnergy Industry

Goals andRequirements

Scientific & TechnicalAchievements

Evaluation Based on Customer Attributes

Attractiveness

Characterizationof Critical Issues

Feasibility

Projections andDesign Options

Balanced Assessment ofAttractiveness & Feasibility

No: Redesign R&D Needs andDevelopment Plan

Yes

GOAL: Demonstrate that Fusion Power Can Bea Safe, Clean, & Economically Attractive Option

Requirements:

• Have an economically competitive life-cycle cost of electricity:∗ Low recirculating power;

∗ High power density;

∗ High thermal conversion efficiency.

• Gain Public acceptance by having excellent safety andenvironmental 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.

Conceptual Design of Magnetic Fusion PowerSystems Are Developed Based on a ReasonableExtrapolation of Physics & Technology

⇒ Visions for Fusion Power Systems Provide Essential Guidanceto Fusion Science & Technology R&D.

Power Plant Design and Analysis

R & D Program

What has been achieved: Credibility

What is important: Attractiveness

The ARIES Team Has Examined Several MagneticFusion Concept as Power Plants in the Past 10 Years

• TITAN reversed-field pinch (1988)

• ARIES-I first-stability tokamak (1990)

• ARIES-III D-3He-fueled tokamak (1991)

• ARIES-II and -IV second-stability tokamaks (1992)

• Pulsar pulsed-plasma tokamak (1993)

• SPPS stellarator (1994)

• Starlite study (1995) (goals & technical requirements for power plants & Demo)

• ARIES-RS reversed-shear tokamak (1996)

• ARIES-ST spherical torus (1999)

Power Plant Studies Program Has IdentifiedKey R&D Directions (selected physics areas)

• Trade-off of β and bootstrap fraction (recirculating power) which resultedin a fundamental shift in the direction of tokamak research andsignificantly influenced TPX design.

• Continuous interaction with tokamak program, resulting in the ARIES-RSdesign which represents the goal of the advanced tokamak program.

• The need to operate RFP with a highly radiative core and an efficientcurrent drive system so that a compact RFP can be realized.

• Development of new stellarator magnetic configuration to address thecritical issue of large size.

• Directions for optimization of spherical tokamak concept.

• Assessment of potential advanced fuels and pulsed-tokamak operation.

Power Plant Studies Program Has IdentifiedKey R&D Directions for Tokamak Optimization

• ARIES-I First Stability Steady-State:

∗ Demonstrated the trade-off of β (power density) and bootstrapfraction (recirculating power) which resulted in a fundamental shiftin the direction of tokamak research.

∗ High aspect ratio, low current with a high bootstrap currentfraction and intermediate elongation is optimum.

• ARIES-II Second Stability Steady-State:∗ Found that the true benefit of second-stability is to reduce current

drive requirement.

∗ High-β equilibria are not optimum because of bootstrapmisalignment and overdrive.

Power Plant Studies Program Has IdentifiedKey R&D Directions for Tokamak Optimization

• Pulsar, Pulsed Tokamak:

∗ Demonstrated that plasma β is limited by ohmic profile constraint.

∗ Feasibility issue of large and costly thermal energy storage wasremoved by an innovative thermal storage design.

∗ Long pulse (1 hour or more) is essential for feasibility.

∗ High cost of current-drive system (PF coils) leads to optimumplasmas with high aspect ratio, low current, and high bootstrapfraction (same as first-stability steady state).

∗ Demonstrated that for the same physics and technologyextrapolation, pulsed tokamaks are substantially more costly thansteady-state one.

⇒ Pulsed Tokamak Operation is Not Attractive

Power Plant Studies Program Has IdentifiedKey R&D Directions for Tokamak Optimization

• ARIES-RS Reversed-Shear, Steady-State:∗ Excellent potential for power plant because of high bootstrap

fraction and high plasma beta.

∗ The tokamak program uses ARIES-RS parameters as the R&Dgoals.

• Starlite assessment:∗ Reversed-shear tokamak plasmas lead to attractive power plant

embodiments.

∗ First-stability steady-state tokamak plasmas (specially with high-field magnets) are acceptable fall back positions.

∗ Pulsed-tokamak plasmas are not attractive.

ARIES-RS is an attractive vision for fusion with areasonable extrapolation in physics & technology

∗ Competitive cost ofelectricity;

∗ Steady-state operation;

∗ Low level waste;

∗ Public & worker safety;

∗ High availability.

Key Performance Parameters of ARIES-RS

Requirements Design Feature Performance Level

Economics COE 7.5 c/kWh

Power Density Reversed-shear PlasmaLi-V blanket with insulating coatingRadiative divertor

Wall load:5.6/4.0 MW/m2

Surface heat flux:6.0/2.0 MW/m2

Efficiency 610o C outlet (including divertor)Low recirculating power

46% gross efficiency~90% bootstrap fraction

Lifetime Radiation-resistant V-alloy 200 dpa

Availability Full-sector maintenanceSimple, low-pressure design

1 month< 1 MPa

Safety Low afterheat V-alloyNo Be, no water, Inert atmosphere

< 1 rem worst-case off-sitedose (no evacuation plan)

Environmentalattractiveness

Low activation materialRadial segmentation of fusion core

Low-level waste (Class-A)Minimum waste volume

Our Vision of Magnetic Fusion Power Systems HasImproved Dramatically in the Last Decade, and Is DirectlyTied to Advances in Fusion Science & Technology

Estimated Cost of Electricity (c/kWh) Volume of Fusion Core (m3)

02468

101214

Mid 80'sPhysics

Early 90'sPhysics

Late 90's Physics

1 Gwe 2 Gwe

0

1000

2000

3000

4000

Mid 80's Pulsar

Early 90'sARIES-I

Late 90'sARIES-RS

1 Gwe 2 Gwe

• No current-drive (low recirculating power):

∗ Stellarators (SPPS): recent advances bring the size in-line withadvanced tokamaks. Needs coils and components withcomplicated geometry.

• No superconducting TF coils

∗ Spherical tokamaks (ARIES-ST): Potential for high performanceand small size devices for fusion research but requires high betaand perfect bootstrap alignment. Center-post is a challenge.

∗ RFP (TITAN): Simple magnets and potential for highperformance. Steady-state operation requires resolution of theconflict between current-drive and confinement.

Alternative Confinement Systems

Stellarator Power Plant Study focused the USStellarator Activity on Compact Stellarators

• Modular MHH configurationrepresented a factor of twoimprovement on previousstellarator configuration withattractive features for powerplants.

• Many critical physics andtechnology areas wereidentified.

The ARIES-ST Study Has Identified KeyDirections for Spherical Torus Research

• Substantial progress is madetowards optimization of high-performance ST equilibria,providing guidance for physicsresearch.

Assessment:

• 1000-MWe ST power plants arecomparable in size and cost toadvanced tokamak power plants.

• Spherical Torus geometry offersunique design features such assingle-piece maintenance.

• Modest size machines canproduce significant fusion power,leading to low-cost developmentpathway for fusion.

Power Plant Studies Program Has IdentifiedKey R&D Directions (selected technology areas)

• Introduction of SiC composites and associated blanket design (one of threelow-activation material under development world-wide);

• The emphasis on RF systems (especially fast waves) for current drive and therespective launchers (e.g., folded wave-guides);

• Innovative superconducting magnet designs using plates and a structural cap(later used in ITER);

• Segmentation of fusion core for ease of maintenance and reduction of waste.

• Innovative high-performance blanket design with ferritic steels;

• Introduction of advanced manufacturing techniques which reduce the unit costsof components drastically.

SiC Composites as High-performanceStructural Material

• Excellent safety & environmentalcharacteristics (very low activationand very low afterheat)

• High performance due to highstrength at high temperatures(1000

oC)

• Excellent candidate for coupling toa closed gas cycle drasticallysimplifying balance of plant.

High-Performance Ferritic Steels Blanket

• Typically, the coolant outlettemperature is limited to themax. operating temperature ofstructural material (550

oC for

ferritic steels)

• By using a coolant/breeder(LiPb), cooling the structureby He gas, and SiC insulators,a coolant outlet temperatureof 700

oC is achieved for

ARIES-ST increasing thethermal conversion efficiencysubstantially.

• A laser or plasma-arc deposits alayer of metal (from powder) on ablank to begin the material buildup

• The laser head is directed to laydown the material in accordancewith a CAD part specification

Beam and PowderInteraction Region

Z-Axis Positioningof Focusing Lensand Nozzle

High PowerLaser

PowderDeliveryNozzle

PositioningTable

Preform

Formed Part

Schematic of Laser Forming Process

AeroMet has produced avariety of titanium partsas seen in attached photo.Some are in as-builtcondition and othersmachined to final shape.Also see Penn State foradditional information.

Laser or Plasma Arc Forming

Schematic of Spray Casting Process

Support Table

T-Bars orSows

MeltingFurnace

HoldingFurnace

LowPressureTransfer

Pump

Track-MountedSpray Robot

w/High PressurePump (1 of 4)

Cove rGas Shie ld

Launde rDis t rib u t io n

Pump

AnodeUppe rS h e ll

Molten Metal Furnace, Courtesy ofSECO/WARWICK, Inc

National Power Plant Studies ProgramIs a High-Leverage Research Effort

National Power Plant Studies ProgramIs a High-Leverage Research Effort

Maximize useof resources

Maximize useof resources

Community input and consensus

Community input and consensus

Unique in the worldUnique in the world

Visions for the national fusion program A high-leverage niche on the international program

Visions for the national fusion program A high-leverage niche on the international program

High-qualityscientific research

High-qualityscientific research

National Power Plant Studies Program Is aHigh-Leverage Research Effort

• High-quality scientific research through in-depth analysis andintegration ensures that innovation, assessment, and design solutionsare credible, meet all applicable requirements and accepted by thescientific community.

• Maximize use of resources by focusing on high-leverage issues,continuity of team core groups, and benefiting from the participationof team members in national or international projects.

• Community input and consensus are actively sought. The teamcomprises key members from major fusion centers. Decisions aremade by consensus in order to obtain the best technical solutionwithout institutional bias. Team is flexible and expert groups andadvocates are brought in as needed. Workshop and “Town meeting”are held for direct discussion and dissemination of the results.

National Power Plant Studies Program Is aHigh-Leverage Research Effort

• Unique in the world in the ability to provide a fully integratedanalysis of power plant options including plasma physics, fusiontechnology, economics, safety, etc.

• A high-leverage niche on the international fusion program.US power plant studies program has provided visions of safe,environmentally benign, and economically competitive power plantfor the international fusion program.

∗ It is recognized internationally as a credible driving forcetowards an attractive end product (goal of US program);

∗ As such, our vision is having an impact on international fusionprogram plans and scientists;

∗ This is witnessed by the number of international collaborationsin this area, especially long-term visits ( a few months to ayear) by international scientists to work with us.

Advances in Physics and Technology Are Helping toReduce the Cost of Fusion Systems Substantially.Continued Improvements Can Reasonably Be Expected.Examples:• Higher performance plasmas (e.g, advanced tokamak, ST);

• High-Temperature Superconductors:∗ Operation at higher fields;

∗ Operation at higher temperatures and decreased sensitivity to nuclearheating simplifies cryogenics.

• Advanced Manufacturing Techniques:∗ Manufacturing cost can be more than 20 times the raw material costs;

∗ New “Rapid Prototyping” techniques aim at producing near-finishedproducts directly from raw material (powder or bars). Results:

low-cost, accurate, and reliable components.

⇒ Advance ARIES-RS study is exploring the impact of improvedphysics and advanced technologies.

Summary

• Marketplace and customer requirements establish designrequirements and attractive features for a competitive commercialfusion power product.

• Progress in plasma physics understanding and engineering andtechnology are the key elements in achieving the goals of fusion.

• Power plant studies marry the marketplace and customerrequirements (attractiveness) to R&D (credibility) in order toprovide essential guidance to R&D directions of the program.

• The National US power plant studies program has been verysuccessful in shaping future R&D.

• The key ingredient of this success is detailed and self-consistentdesign work which underlines the credibility of this activity for thefusion scientists.