Materials Issues, Gaps and Materials Issues, Gaps and Research NeedsResearch NeedsMaterials Issues, Gaps and Materials Issues, Gaps and Research NeedsResearch Needs

RJ Kurtz1 and the ReNeW Materials Panel

1Pacific Northwest National Laboratory

Harnessing Fusion Power WorkshopLos Angeles, CAMarch 2 - 4, 2009

ReNeW Materials Panel MembersReNeW Materials Panel Members

Name Affiliation EmailRick Kurtz, Leader PNNL rj.kurtz@pnl.gov

Mike Mauel Columbia mauel@columbia.edu

Mike Nastasi LANL nasty@lanl.gov

Bob Odette UCSB odette@engineering.ucsb.edu

Shahram Sharafat UCLA shahrams@ucla.edu

Roger Stoller ORNL stollerre@ornl.gov

Steve Zinkle ORNL zinklesj@ornl.gov

Greenwald Panel Materials IssuesGreenwald Panel Materials Issues

Issue DescriptionMI-1 Constitutive mechanical properties of structural and breeding blanket materials after thermal and

irradiation exposure including joints and dissimilar material transition regions.

MI-2 Dimensional and phase stability of structural and breeding material systems due to neutron irradiation.

MI-3 Scientific basis for high-temperature design criteria.

MI-4 Quantitative predictive model for thermal conductivity degradation of neutron irradiated metals and ceramics.

MI-5 Physical mechanisms controlling the chemical dissolution of materials exposed to coolants, including mass transfer phenomena associated with surrounding dissimilar solid materials.

MI-6 Mechanisms responsible for radiation-induced changes in electrical resistance and optical properties in dielectric materials.

MI-7 Exploration of reduced-activation and reduced-decay-heat compositions that simultaneously provide high structural material performance.

Overarching Issue: Understand the basic materials science phenomena for fusion breeding blankets, structural components, plasma diagnostics, and heating components in high neutron areas.

Greenwald Panel Materials GapsGreenwald Panel Materials Gaps

Gap Description

GM-1 Predictive multiscale models of materials behavior in the fusion environment.

GM-2 Constitutive mechanical properties of structural and breeding blanket materials in the fusion environment.

GM-3 Dimensional and phase stability and physical property degradation in the fusion environment.

GM-4 Science basis for robust high-temperature design criteria.

GM-5 Chemical compatibility of materials in the fusion environment.

GM-6 Fabrication and joining of complex structures.

ReNeW Panel Materials IssuesReNeW Panel Materials Issues

Issues Systems ComponentsAlloy Development FW/Blanket/Shield, Vacuum

Vessel, Divertor/PFCStructural & HHF Materials

Chemical Compatibility FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC

Structural & HHF Materials, Tritium Breeding & Neutron Multiplier Materials, Tritium Extraction, HX & Piping

Design Criteria FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC, Magnets

Structural & HHF Materials, Neutron Shielding, Tritium Extraction, HX & Piping, Magnet Materials

Erosion Divertor/PFC HHF Materials

Fabrication & Joining FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC

Structural & HHF Materials, Neutron Shielding, Tritium Extraction, HX & Piping

Plasma-Material Interactions Divertor/PFC HHF Materials

Radiation Effects FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC, Magnets, Functional

Structural Materials, Tritium Breeding & Neutron Multiplier Materials, HHF Materials, Magnet Materials, Plasma Diagnostic Materials, Optical Materials, Mirrors

Safety, Licensing, RAMI FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC

Structural & HHF Materials

Thermal Creep & Fatigue FW/Blanket/Shield, Vacuum Vessel, Divertor/PFC

Structural & HHF Materials, Tritium Breeding & Neutron Multiplier Materials

Tritium Inventory FW/Blanket/Shield, Divertor/PFC Tritium Breeding & Neutron Multiplier Materials, Tritium Extraction, HX & Piping, HHF Materials

Tritium Permeation FW/Blanket/Shield Tritium Breeding & Neutron Multiplier Materials, Tritium Extraction, HX & Piping

Materials Research and the Path to Materials Research and the Path to Fusion PowerFusion Power

Materials research to identify candidate materials- Radiation damage- Activation- Mechanical & physical properties- Compatibility with coolants and tritium breeders- Large-scale fabrication & joining issues

Identify and demonstrate approaches to improve material performance

Identify concept specific issues and demonstrate proof-of-principle solutions, e.g.

- Design with ferromagnetic material- Methods for design of large, thermo-mechanically loaded

structures

Development of materials with acceptable performance and demonstrate to goal life (dpa, He)

Demonstrate solutions to concept specific issues on actual structural materials and prototypic components

Develop design data base, constitutive equations, and models to describe all aspects of material behavior required for design and licensing

Ion Accelerators

RTNS

Fission Reactors

IFMIF

Component Test Facilities

Actual Fusion Environment Test Results

Plasma Physics Confinement

Fusion Reactor Concept Definition

ITER

DEMO Conceptual

Designs

DEMO Final Design &

ConstructionKey need is close integration of materials science with the structural analysis-design process.

Current Development Status of Current Development Status of Fusion Structural MaterialsFusion Structural Materials

UnirradiatedIrradiated

RAF/M Steels

V Alloys

NFA Steels

SiC/SiC

W Alloys

UnirradiatedIrradiated

UnirradiatedIrradiated

UnirradiatedIrradiated

UnirradiatedIrradiated

ConceptExploration

Proof ofPrinciple

PerformanceExtension

Feasibility Tech. maturation

Low-Activation Structural Materials Low-Activation Structural Materials for Fusionfor Fusion

None of the current reduced or low-activation fusion materials existed 15 years ago.

Low-activation is a must!!

IFMIF

Spallationneutrons

Fusionreactor

ITER

10

15

10

16

10

17

10

18

10

19

10

20

10

21

10

5

10

6

10

7

10

8

10

9

Magnetic

Inertial

( )Ion Temperature K

1955

1960

1965

1970-75

1975-80

1980s

1990s

Breakeven

Ignition

Extrapolation to fusion regime is much larger for the fusion materials than for plasma physics program.Lack of an intense neutron source emphasizes the need for a coordinated scientific effort combining experiment, modeling and theory to a develop a fundamental understanding of radiation damage.

Fusion Materials Relies Heavily on Modeling due Fusion Materials Relies Heavily on Modeling due to Inaccessibility of Fusion Operating Regimeto Inaccessibility of Fusion Operating Regime

He and Displacement Damage Levels

Steels

Impact of He-Rich Environment on Impact of He-Rich Environment on Neutron Irradiated MaterialsNeutron Irradiated Materials

A unique aspect of the DT fusion environment is substantial production of gaseous transmutants such as He and H.

Accumulation of He can have major implications for the integrity of fusion structures such as:- Loss of high-temperature creep strength.

- Increased swelling and irradiation creep at intermediate temperatures.

- Potential for loss of ductility and fracture toughness at low temperatures.

Grain boundary

1

10

100

1000

Un-implanted 200 appm He

316 SS @ 750°C & 100 MPa

Science-Based High-Temperature Science-Based High-Temperature Design CriteriaDesign Criteria

Current high-temperature design methods are largely empirical.

Cyclic plastic loading is far more damaging than monotonic loading.

New models of high-temperature deformation and fracture are needed for:• Creep-fatigue interaction.• Elastic-plastic, time-dependent fracture mechanics.• Materials with low ductility, pronounced anisotropy,

composites and multilayers.

10 100 800600

1000

1500

2000

2500

3000

COMPRESSION HOLD-TIME

SYMMETRICAL HOLD-TIME

TENSION HOLD-TIMEZEROHOLD-TIME

EUROFER 97 T=550°C Δεt=1.0%

, NUMBER OF CYCLES TO FAILURE N

f

TIME PER CYCLE, S

J. Aktaa & R. Schmitt, FZK, 2004

Breaking the High Strength-Low Breaking the High Strength-Low Toughness/Ductility ParadigmToughness/Ductility Paradigm

Increased strength is accompanied by reduced toughness (cracking resistance) and ductility.

Strength is increased by alloying, processing and radiation damage.

Low toughness and ductility reduce failure margins.

The benefits of simultaneously achieving high-strength and high ductility/ toughness would be enormous.

Toughness or Ductility

Stre

ngth

Theoretical Strength ~E/50

Future Materials

Current Engineering Materials

Fundamentals of Material-Coolant Chemical Fundamentals of Material-Coolant Chemical Compatibility in the Fusion EnvironmentCompatibility in the Fusion Environment

The traditional approach to corrosion is empirical.

Correlations do not capture basic physics and have limited predictive capability.

Opportunities: Controlled experiments

combined with physical models utilizing advanced thermodynamics & kinetics codes.

Integrated experiments using sophisticated in situ diagnostic and sensor technologies.

M. Zmitko / US-EU Material and Breeding Blanket Experts Meeting (2005)J. Konys et al./ ICFRM-12 (2005)

Theory and Modeling of Materials Theory and Modeling of Materials Performance Under Fusion ConditionsPerformance Under Fusion Conditions

Integration of modeling-theory-experiments-database development is a critical challenge in bridging the multi-physics-length-time scales.

• Microstructural evolution in a high-energy neutron, He-rich environment.

• Resulting in degradation of performance sustaining properties and stability.

• Effects of He are critical.

• Success - simulations and experiments show high-energy fusion damage events are similar to multiple, lower-energy events - provides fission-fusions dpa damage scaling.

Comparison of 10 and 50 Comparison of 10 and 50 keV displacement keV displacement cascades in ironcascades in iron

100K, iron

50 keV

10 keV

5 nm

Coupling of Modeling and Experiment Coupling of Modeling and Experiment to Determine He Transport and Fateto Determine He Transport and Fate

0.0001

0.001

0.01

0.1

1

0 0.02 0.04 0.06 0.08 0.1

dΣ/dΩ [(cm•ster)

-1]

q2 (Å-2)

SANS/ASAXS PAS

LMC: NuclearLMC: Nuc + Mag

SANS: NucSANS: N+Mag

0.001

0. 01

0.1

1

0 0.01 0.02 0.03 0.04 0.05 0.06

dS/d W

(cm

-1•s

ter

-1)

q2 (Å- 2)

feature‘signals’

Multiscale modelingTEM, SANS, Positron theory

predictfeatures

simulateobservables

self-consistent ‘understanding’of He effects

Experimental characterizationTEM THDS

HeFe

GR Odette, UCSB & BD Wirth, UCB

Compelling Scientific Needs - ICompelling Scientific Needs - I

Recent fusion materials R&D efforts have led to the development of high-performance reduced-activation structural materials with good radiation resistance for doses ~30 dpa and ~300 appm He.

The overarching scientific challenge facing structural materials for DEMO is microstructural evolution and property changes (mechanical and physical) that may occur for neutron doses up to ~200 dpa and ~2000 appm He.

Development of high-performance alloys and ceramics including large-scale fabrication and joining technologies is needed.

Current understanding of strength-ductility/toughness relationships is inadequate to simultaneously achieve high-strength and high-ductility and toughness.

Compelling Scientific Needs - IICompelling Scientific Needs - II

Better mechanistic physical models of thermo-mechanical degradation are needed for development of advanced materials and science-based high-temperature structural design criteria.

The mechanisms controlling chemical compatibility of materials exposed to coolants and erosion of materials due to interaction with the plasma are poorly understood.

Better understanding of radiation-induced and thermo-mechanical property changes in high-heat flux materials (tungsten), magnet, and a host of functional materials is required.

Critical Resource Needs - ICritical Resource Needs - I

Research Scientists and Engineers• Many specialized skills will be needed – physical metallurgists, ceramists,

electron microscopists, mechanical property specialists, fracture mechanics, materials evaluation specialists (SANS, PAS, APT, etc.), corrosion scientists, nondestructive evaluation specialists, theory and modeling experts (multiscale materials modeling).

• 2003 FESAC Development Plan estimated ~60 FTE/y at peak activity.• Existing talent pool rapidly shrinking!

Materials Science Facilities• Materials evaluation equipment – TEM, SEM, FIB, Auger, APT, etc.• High-temperature materials testing – creep, fatigue, fracture, thermal-shock and

fatigue.• Compatibility testing – flow loops for corrosion testing, oxidation.• Physical property measurements – thermal, electrical, optical, etc.• Material fabrication and joining of small to large-scale components.• Hot cells for handling and testing of activated materials.

Critical Resource Needs - IICritical Resource Needs - II

Non-Nuclear Structural Integrity Benchmarking Facilities• Facilities for testing various components such as blanket modules are needed to

investigate the potential for synergistic effects that are not revealed in simpler single-variable experiments or limited multiple-variable studies.

• Provides data to refine predictive models of materials behavior.• Gives reliability and failure rate data on materials, components and structures to

valid codes for designing intermediate step nuclear devices and DEMO.• Test bed to test and evaluate nondestructive inspection techniques and

procedures. Other Facilities

• Extensive computational resources will be needed at all phases of fusion materials development to support model development but, in particular, large-scale structural damage mechanics computational capability will be needed to guide and interpret data obtained from component-level test facilities.

Critical Resource Needs - IIICritical Resource Needs - III

Fission Reactors• The capability to perform irradiation experiments in fission reactors is essential

for identifying the most promising materials and specimen geometries for irradiation in an intense neutron source.

Intense Neutron Source• Overcoming radiation damage degradation is the rate-controlling step in fusion

materials development.• Evaluation of radiation effects requires simultaneous displacement damage

(~200 dpa) and He generation (~2000 appm).• International assessments have concluded that an intense neutron source with ≥

0.5 liter volume with ≥ 2 MW/m2 equivalent 14 MeV neutron flux to enable testing up to a least 10 MW-y/m2, availability > 70%, and flux gradients ≤ 20%/cm is essential to develop and qualify radiation resistant structural materials for DEMO.

Critical Resource Needs - IVCritical Resource Needs - IV

Component Test Facility• Nuclear facility to explore the potential for synergistic effects in a fully integrated

fusion neutron environment. Data and models generated from non-nuclear structural test facilities, fission reactor studies and the intense neutron source will be needed to design this facility.