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Universities1. UCSD2. Wisconsin3. Georgia Tech4. UCLA5. U Rochester6. PPPL7. UC Santa Barbara8. UNC9. DELFT

Industry1. General Atomics2. Titan/PSD3. Schafer Corp4. SAIC5. Commonwealth Tech6. Coherent7. Onyx8. DEI9. Mission Research Corp10. Northrup11. Ultramet, Inc12. Plasma Processes, Inc13. Optiswitch Technology14. Plasma Processing, Inc

IFE First Wall Survival Development and Testing of an Armored Ferritic

L L Snead, G. R. Romanoski, C. A. Blue, and J. Blanchard

Presented at the 16th TOFE, Madison Wisconsin September 16, 2004

HAPL IFE First Wall Materials

• Carbon and refractory metals (tungsten) considered - Reasonably high thermal conductivity at high temperature

(~100-200 W/m-K)

- Sublimation temperature of carbon ~ 3370°C

- Melting point of tungsten ~3410°C

• In addition, possibility of an engineered surface to provide better accommodation of high energy deposition is considered

- tungsten coated ferritic or SiC

- carbon brush structures

- tungsten foam

Unique Threats to IFE First Wall

• Intense cyclic heating

- stresses and sublimation due to pulse heating (Renk talk this session)

- cyclic stress induced debonding

- long-tem thermal stability

• Surface removal due to high energy ions.

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

0 1 2 3 4 5 6 7 8 9 10

Time (microseconds)

Raffray data

Fabrication Process : W/F82H

• 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

--> Plates of W/Fe (ORNL) have been produced and are being tested.

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

--> Plates of W/Fe (Plasma Processed Inc.) have been produced and are being tested.

Testing of Armored Ferritic : W/F82H

• The primary concern for armored materials is the survival of the interface:

--> CTE mismatch produced during processing--> Stressed induced during pulsed heating--> Stability of a “ductile” interfacial region on long-term annealing

Temperature (°C)

Spec

imen

Exp

ansi

on (

ppm

)

High Density Infrared (HDI) Plasma Arc Lamp Technology

Unique high density infrared plasma arc lamp Most powerful radiant arc

lamp in the world

Broad area processing with high radiant energies

Conservative heating rates 2,000C/s to 20,000C/s Allows controlled diffusion on nanometer scale

Able to melt Rhenium Melting point of 3180C

Thermal Fatigue Testing

Rep rate: 10HzMax. flux: 20.9MW/m2 (20ms)Min. flux: 0.5MW/m2(80ms)Duration: 1000 cyclesSubstrate temp. (bottom): 600 ºC

Substrate material: F82H steelCoating material: tungsten (100µm-thick)Specimen size: 25 x 25 x 5 (mm)

W coated specimen

Cooling table 0

5

10

15

20

25

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

Heat flux (MW/m

2)

Thermal Fatigue Testing

IR testing closely matches stress state at interface.

Flexural tests will be performed on samples that incorporate the W armor and substrate to quantify the mechanical strength of the interface at different cycle durations and following thermal aging.

-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

Stre

ss (

MP

a)

Depth (mm)

Blachard results

Thermal Fatigue Testing

Rep rate: 10HzMax. flux: 20.9MW/m2 (20ms)Min. flux: 0.5MW/m2(80ms)Duration: 1000 cyclesSubstrate temp. (bottom): 600 ºC

Substrate material: F82H steelCoating material: tungsten (100µm-thick)Specimen size: 25 x 25 x 5 (mm)

W coated specimen

Cooling table 0

5

10

15

20

25

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

Heat flux (MW/m

2)

QuickTime™ and aDV/DVCPRO - NTSC decompressorare needed to see this picture.

• No obvious degradation of adhesion of W to F82H following fatigue testing• For these fatigue tests, carbide dissolution indicating interface >900°C

As Deposited

DiffusionBonded

PlasmaSprayed

1000 shot, 20 MW/m2

W Coated F82H After Thermal Fatigue Testing

W Coated F82H After 10,000 Cycle Fatigue Testing

In interface over-temperature (>900°C) a W-Fe intermetallic forms.

Formation of W-Fe brittle phase will likely lead to interface fracture and coating failure.

Isothermal aging experiments will be performed on W / F82H samples to demonstrate the temperature and time limitations of the interface.

WFeW

F82HSteel

10

100

1000

104

0.001 0.01 0.1 1 10 100

Time (milliseconds)

IFE

~104 MW/m2

~ 10 sec

2005 IR upgrade ~100 / 2MW m ~ 1 msec

IR ThermalFatigueFacility~20 / 2MW m ~ 20 msec

> 0.1 / 2MJ m

~ 0.2 / 2MJ m

~ 0.2 / 2MJ m

2heat flux

Thermal Fatigue Facility Upgrades for Prototype Testing (complete 2005)

• Continuous operation: 1 msec, 5 Hz at 100 MW/m2

• 300 cm2 surface area irradiation

• Front surface temperature monitoring

• Fabrication of cooled prototype plasma spray tungsten armored low-activation ferritic

Helium ManagementAt 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

0

500

1000

1500

2000

2500

0 1 2 3 4 5

Minutes

0

2

4

6

8

10

Effect of Iterative Implant/Anneal on Retained Helium

1.3 MeV He implantationPoly-X tungsten targetResistive Heating

A series of implantation to 1019 He/m2 for1, 10, 100 and 1000 cycles has been completed

Effect of Iterative Implant/Anneal on Retained Helium

1.3 MeV He implantationPoly-X tungsten targetResistive Heating

Implantation to 1019 He/m2 for1, 10, 100 and 1000 cycles

Total 3He dose

(1019 He/m2)

Proton Yield

(10%)

1 10

2 13

3 70

5 2000

10 7100

Determination of critical step size

For Single-X W critical step size ~3·1016 Helium doses implanted at 850°C and flash-annealed at

2000°C in 1000 cycles

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

50

100

150

200

250

300

350

400

12.8 12.9 13 13.1 13.2 13.3 13.4 13.5

Energy (MeV)

Proton Yield

1000 steps (850/2000)

1 step as-implanted (850)

1 step annealed (850/2000)

100 steps (850/2500)

Update on Effect of Peak Annealing Temperature

• Single x annealed at 2500°C shows significantly less He retention than 2000°C anneal.

• Annealing temperature plays a significant role in retained He and critical dose. As part of the chambers study we need to make precise assessment of implantation and annealing temperatures to focus experiment.

2500°C

2000°C

Concluding Remarks

• The HAPL program has selected refractory armored low-activation ferritic steel as it’s prime candidate first wall.

• Currently, optimization of the plasma-sprayed W/F82H steel in near completion and mechanical testing underway.

• IFE-unique critical-issues are being pursued- X-ray and ion ablation and roughening (Renk and Latkowski)- thermal fatigue of tungsten ferritic interface- long-term thermal stability- helium management

Special issue of Journal of Nuclear Materials on subject of HAPL chamber currently being assembled.

SiC without coating

SiC

W coating

IR processing

10µm

Interface

SiC was removed by sublimation of the surface of the SiC prior to ordering the W powder melt. Rough interface was formed.

Fabrication Process : W/SiC

Tungsten Powder

The Path to Develop Laser Fusion Energy

Phase IIValidatescience &technology2006 - 2014

Phase IIIEngineeringTest Facilityoperating 2020

Full size laser: 2.4 MJ, 60 laser lines Optimize targets for high yield Develop materials and components. 300-700 MW net electricity Resolve basic issues by 2028

Phase IBasic fusionscience &technology1999- 2005

Ignition Physics Validation•MJ target implosions•Calibrated 3D simulations

Target Design & Physics

•2D/3D simulations•1-30 kJ laser-target expts

Full Scale Components

•Power plant laser beamline •Target fab/injection facility •Power Plant design

Scalable Technologies

•Krypton fluoride laser•Diode pumped solid state laser•Target fabrication & injection•Final optics•Chambers materials/design

Chamber Progress -1 Operating windowsEstablishing Chamber operating windows is a multidisciplinary, simulation intensive, process...........Here is an example for a 154 MJ target.

UCSDWisconsinLLNLGA

Target Physics:gives target emissions(neutrons, x-rays, ions)

Chamber Physics:What hits wall: "threat spectra"

Materials:How wall responds to"threat spectra"

Target Injection Survival:allowed chamber conditions(gas, wall temperature)

0 2 4 6 8 10time (? )sec

Surface1 micron5 microns10 microns100 microns

Surface1 micron5 microns10 microns100 microns

3000

2600

2200

1800

1600

1200

600

200

Tungsten first wall temperature staysbelow melting point (tungsten melts at 3410 C)

Tem

per

atu

re (C

)

154 MJ targetNo gas6.5 m radius

Summary of Thermal Fatigue Experiment

•Thermal fatigue experiments were carried out successfully using IR processing facility. Preliminary results showed tungsten coating was stable following the heat load (10Hz, 23.5MW/m2 (10ms), 1000cycles).

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/Ablation

Underlying Structurebonding (especially ODS)high cycle fatiguecreep rupture

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

Structure/Coolant Interfacecorrosion/mass transfercoating at high temperature?

Modeling Irradiation Effectsswelling and embrittlement

Helium Management (ORNL, Delft, UNC)

Parametric Study

Variables Techniques Data

Materials Temp. Dose

Single-X Irrad. Temp Total Dose Nuclear Reaction Analysis N He,% retention

Poly-X Anneal Temp Dose Increment Thermal Desorption Diffusivity/Activation Energy

CVD Anneal Rate TEM/SEM Defect size and distribution

Foam

• weak dependence on material type

• strong dependence on implantation temperature

• annealing from 800-2000°C diffuses significant helium

----> there are knobs to turn that delay exfoliation in W