Overview of HAPL First Wall Materials Issues

HAPL Materials and Design Team

HAPL Average Power Laser Program WorkshopPrinceton Plasma Physics Laboratory

October 27-28, 2004

Leveraging and Focus of Program

Selection of structural materials is leveraging past and planned development carried out by the international MFE and other nuclear materials program assuming a “near term” time horizon.

Swelling resistant alloys have been developed via international collaborations

• Lowest swelling is observed in body-centered cubic alloys (V alloys, ferritic steel)

• A key issue regarding BCC alloys is radiation embrittlement

0

2

4

6

8

10

12

14

0 50 100 150 200Damage Level (dpa)

Ferritic steel

Ti-modified 316 stainless steel

316 stainless steel

Tirr=400-500˚C

Problem with Swelling Under Fusion Neutron Irradiation?

0

0.5

1

1.5

2

2.5

3

3.5

4

0 10 20 30 40 50 60 70 80

Fluence (dpa)

Swelling (%)

Fe-20N-15Cr600C / 15He

316F600C / 15He

316F600C / 0He

JLF-1470C / 15He

JLS-1470C / 15He

JLF-1470C / 0He

7~10Cr SteelNeutron data663~703K

Dual-ion irradiation

Y. Katoh et al., J. Nucl. Mater. 323 (2003) 251

Temporal Distribution of Heat Flux

Debris Ions

10ns 0.2s 1s 2.5s

FastIons

Ph

oton

sEnergyDeposition

Instantaneous Heat Flux10 MW/m2 (MFE) = 104 MW/m2 (IFE)

Effect of Heat Flux on W-Armor Coated SiC

200

600

1000

1400

1800

2200

2600

3000

Surface

1 micron

5 microns

10 microns

100 microns

Time (s)

3-mm Tungsten slab

Density = 19350 kg/m3

Coolant Temp. = 500°C

h =10 kW/m2-K154 MJ DD Target Spectra

Raffray, et al.

Porous W StructureMonolithic W

Candidate First Wall Structure W/LAF (W/SiC Backup)

LAF(~600°C max) or ODS(~800°C) structure, possibly both.

Liquid MetalHelium,or

Salt Coolant?

Development of Armor fabrication process and repair

He management mech. & thermal fatigue testing

Surface Roughening/Ablationthermal fatiguex-ray and ion irradiation effects

Underlying Structurebonding (especially ODS)high cycle fatiguecreep rupture

Armor/Structure Thermomechanicsdesign and armor thicknessfinite element modelingthermal fatigue and FCG

Modeling Irradiation Effectsswelling and embrittlement

• It is assumed that MFE program will develop and qualify a low activation ferritic for fusion application.

Fabrication Process : W/F82H(ORNL, Snead talk this session)

• Two processes for bonding low activation ferritic to tungsten are considered: Diffusion Bonding and Plasma Spray:

I. Diffusion-bonded tungsten foil (.1 mm thickness) - Allows the best possible mechanical properties and surface integrity - Tungsten will remain in the un-recrystallized state - No porosity

II. Plasma-sprayed tungsten transition coatings - Allows for a graded transition structure by blending tungsten and steel powders in an intermediate layer to accommodate CTE mismatch. - Resulting microstructure is recrystallized but small grain size - May be spayed in vacuum or under a cover gas (wall repair) - Variable porosity

Micro-Engineered Structural Materials (UCLA, Ghoneim talk next session)

Develop Micro-engineered FW Concepts: Continue development (with ULTRAMET)of engineered W-foam armor bonded to a ODS steels. Foam has nano-grains.

Thermo-mechanical fatigue of engineered FW:2-D and 3-D fatigue modeling..

Thermomechanical deformation of engineered FW:Investigate the effects of foam structure on global 3-D deformation and failure.

Model Helium and Hydrogen retention in engineered FW:Complete 1-D diffusion/ clustering model for helium bubbles.

Model Irradiation Experiments of engineered FW:Compare model to experiments at UW & UNC.

Develop interface fracture mechanics criteria:Determine experiments for the critical stress/ fracture toughness of interface cracks.

Helium Management(IEC Radel Talk, this session

Snead Talk next session_

At room temp. growth of He bubbles beneath the surface causes blistering at ~3 x 1021/m2 and surface exfoliation at ~1022/m2.

For IFE power plant, MeV He dose >>> 1022/m2 .

MeV Helium

MeV Helium

First Wall Armor

200

600

1000

1400

1800

2200

2600

3000

Surface

1 micron

5 microns

10 microns

100 microns

Time (s)

3-mm Tungsten slab

Density = 19350 kg/m3

Coolant Temp. = 500°C

h =10 kW/m2-K154 MJ DD Target Spectra

vacancy

0 1 2 3 4 5 6 7 8 9 10

Time of microseconds

Minimum Dose for Helium AccumulationIs IFE Below Threshold?

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12

Critical Step Size

Normalized Accumulation

1016

He/m2

0

500

1000

1500

2000

2500

0 1 2 3 4 5

Minutes

0

2

4

6

8

10

Simulated IFE He Implant/Anneal

(Sandia, Renk talk next session)

FIB/XTEM of 1000-pulse W, showing deep cracks evidently caused by fatigue, no surface melt

SEM, W250 pulses @2.5 J/cm2 MAP NRa < 0.5 µm

SEM, W1000 pulses @2.5 J/cm2 MAP NRa ~ 4 - 5 µmP - V ~ 35 µm

Pulsed Ion Effects - Tungsten

RHEPPFacility

• Able to produce single-shot damage in tungsten; indicates a fluence >1 J/cm2

• See roughening of single-crystal & powder met. tungsten at 1 J/cm2

• See no change at0.5 and 0.7 J/cm2

XAPPER : High Cycle X-ray Surface Irradiation Facility Developed for HAPL

(Latkowski talk, next session)

UCLA Dragonfire: High Cycle Laser Thermomechanical Testing Facility Developed for HAPL

Laser pulse simulates temperature evolution.

Capability to simulate a variety of wall temperature profiles.

Repeatable and well-characterized source.

Clean environment for careful measurements

Laser pulse simulates temperature evolution.

Capability to simulate a variety of wall temperature profiles.

Repeatable and well-characterized source.

Clean environment for careful measurements

A suite of diagnostics: Real-time temperature (High-speed

Optical Thermometer) Per-shot ejecta mass and constituents

(QMS & RGA) High rep-rate experiments to simulate

fatigue and material responseRelevant equilibrium temperature

(High-temperature sample holder)

A suite of diagnostics: Real-time temperature (High-speed

Optical Thermometer) Per-shot ejecta mass and constituents

(QMS & RGA) High rep-rate experiments to simulate

fatigue and material responseRelevant equilibrium temperature

(High-temperature sample holder)

(Blanchard, talks nextSnead, talk next session)

Thermal Fatigue of Cladding

ORNL Infrared Processing Facility

0

5

10

15

20

25

-200 0 200 400 600 800 1000Time (ms)

Heat flux (MW/m

2)

-200

-100

0

100

200

0 0.5 1 1.5 2 2.5 3 3.5

HAPL baseline

Infrared heating

Stress (MPa)

depth (mm)

Armor interface S T R E S S(Mpa)

Depth (mm)

Development of Thermal Fatigue Facility for HAPL

ORNL Infrared Processing Facility Upgrade

HeatLoad(MW/m

2)

Time (milliseconds)

10

100

1000

104

105

0.001 0.01 0.1 1.0 10 1001

IFE

~10 sec~104 MW/m2

~0.4 MJ/m2

300kW Upgrade~200 MW/m2

~2 msec 300kW Current~35 MW/m2

~20 msec

~0.1

MJ/m2

750kW Current~5 MW/m2

~20 msec~0.7 MJ/m2

~0.1 MJ/m2

300 cm2 Test Area

(Snead, talk next session)

Thermal Stability of Cladding

ORNL Infrared Processing Facility

W

FeW orFe7W6

F82HSteel

For cyclic heating studied, coating appears to me mechanically stable, however thermal stability of interface need further improvement.

Discussion and HAPL Materials Near-Term Goals

• Fabrication of W/LAF appears to be feasible and mature. Prototype armor and recommended materials for “engineered” material to be made this FY.

• Thermal fatigue of actively cooled tungsten armored LAF component to be fatigue tested to >10,000 cycles for IFE relevant interface stress. (ORNL IR Thermal Fatigue Facility.)

• For IFE-relevant dose and temperature, diffusion of helium appears promising. Very high dose and kinetic information still required for modeling. (IEC -v- UNC)

• Results of the RHEPP pulsed ion work suggests sub-surface fatigue cracking not predicted by elastic-plastic modeling. Experiments incorporating varied materials and grain structures will be carried out.

• Tools are now in place (xapper, dragonfire, RHEPP) to compare the effects of x-ray, laser and ion fatigue on cyclically heated surfaces. Coordinated experimentation and modeling to determine potential “subthreshold” and thermomechanical fatigue effects is focus of this years effort.

Ferritic/martensitic Steels with Reduced Radioactivity and Superior Properties Compared to Commercial Steels have

been Developed by Fusion

Developmental reduced activation steels

IEA fusion reduced activation steel

Commercial ferritic steel (HT9)

Fusion-developed steels also have superior tensile strength, irradiated fracture toughness, and thermal conductivity

Comparison of thermal creep-rupture strengths

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1 10 100 1000 104

Comparison of Fission and Fusion Radioactivity after Shutdown

Years After Shutdown

Fission: Light Water Reactor

Fusion: Conventional Ferritic steel

Fusion: Reduced Activation

Ferritic Steel

Coal AshBelow Regulatory Concern

Modified Thermomechanical Treatment Procedure for New 9Cr Ferritic/Martensitic Steel Produced High

Strength

• Strength and ductility in tensile test are comparable to high-strength experimental ODS steel

R.L. Klueh, to be published