Government Labs 1.NRL 2.LLNL 3.SNL 4.LANL 5.ORNL 6.PPPL Universities 1.UCSD 2.Wisconsin 3.Georgia Tech 4.UCLA 5.U Rochester 6.PPPL 7.UC Santa Barbara 8.UNC 9.DELFT Industry 1.General Atomics 2.Titan/PSD 3.Schafer Corp 4.SAIC 5.Commonwealth Tech 6.Coherent 7.Onyx 8.DEI 9.Mission Research Corp 10.Northrup 11.Ultramet, Inc 12.Plasma Processes, Inc 13.Optiswitch Technology 14.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 (~ 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 0.2  s 1s1s 2.5  s Fast Ions Photons Energy Deposition Instantaneous Heat Flux 10 MW/m 2 (MFE) = 10 4 MW/m 2 (IFE)

Effect of Heat Flux on W-Armor Coated SiC 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) Specimen Expansion (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  2,000  C/s to 20,000  C/s  Allows controlled diffusion on nanometer scale  Able to melt Rhenium  Melting point of 3180  C

Thermal Fatigue Testing Rep rate: 10Hz Max. flux: 20.9MW/m 2 (20ms) Min. flux: 0.5MW/m 2 (80ms) Duration: 1000 cycles Substrate temp. (bottom): 600 ºC Substrate material: F82H steel Coating material: tungsten (100µm-thick) Specimen size: 25 x 25 x 5 (mm) W coated specimen Cooling table

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. Stress (MPa) Depth (mm) Blachard results

Thermal Fatigue Testing Rep rate: 10Hz Max. flux: 20.9MW/m 2 (20ms) Min. flux: 0.5MW/m 2 (80ms) Duration: 1000 cycles Substrate temp. (bottom): 600 ºC Substrate material: F82H steel Coating material: tungsten (100µm-thick) Specimen size: 25 x 25 x 5 (mm) W coated specimen Cooling table

No obvious degradation of adhesion of W to F82H following fatigue testing For these fatigue tests, carbide dissolution indicating interface >900°C As Deposited Diffusion Bonded Plasma Sprayed 1000 shot, 20 MW/m 2 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. W FeW F82H Steel

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 Management At room temp. growth of He bubbles beneath the surface causes blistering at ~3 x /m 2 and surface exfoliation at ~10 22 /m 2. For IFE power plant, MeV He dose >>> /m 2. MeV Helium First Wall Armor vacancy Time of microseconds

Effect of Iterative Implant/Anneal on Retained Helium 1.3 MeV He implantation Poly-X tungsten target Resistive Heating A series of implantation to He/m 2 for 1, 10, 100 and 1000 cycles has been completed

Effect of Iterative Implant/Anneal on Retained Helium 1.3 MeV He implantation Poly-X tungsten target Resistive Heating Implantation to He/m 2 for 1, 10, 100 and 1000 cycles

Total 3 He dose (10 19 He/m 2 ) Proton Yield (  10%) Determination of critical step size  For Single-X W critical step size ~3·10 16  Helium doses implanted at 850°C and flash-annealed at 2000°C in 1000 cycles

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 II Validate science & technology Phase III Engineering Test Facility operating  2020  Full size laser: 2.4 MJ, 60 laser lines  Optimize targets for high yield  Develop materials and components.   MW net electricity  Resolve basic issues by 2028 Phase I Basic fusion science & technology 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 windows Establishing Chamber operating windows is a multidisciplinary, simulation intensive, process Here is an example for a 154 MJ target. UCSD Wisconsin LLNL GA 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) Tungsten first wall temperature stays below melting point (tungsten melts at 3410  C) Temperature (  C) 154 MJ target No gas 6.5 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/m 2 (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 Metal Helium,or Salt Coolant? Development of Armor fabrication process and repair He management mech. & thermal fatigue testing Surface Roughening/Ablation Underlying Structure bonding (especially ODS) high cycle fatigue creep rupture Armor/Structure Thermomechanics design and armor thickness finite element modeling thermal fatigue and FCG Structure/Coolant Interface corrosion/mass transfer coating at high temperature? Modeling Irradiation Effects swelling and embrittlement

Helium Management (ORNL, Delft, UNC) Parametric Study Variables Techniques Data Materials Temp. Dose Single-XIrrad. Temp Total DoseNuclear Reaction Analysis N He, % retention Poly-XAnneal Temp Dose IncrementThermal Desorption Diffusivity/Activation Energy CVDAnneal RateTEM/SEM Defect size and distribution Foam weak dependence on material type strong dependence on implantation temperature annealing from °C diffuses significant helium ----> there are knobs to turn that delay exfoliation in W