Overview of HAPL First Wall Materials Issues HAPL Materials and Design Team HAPL Average Power Laser Program Workshop Princeton 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

Problem with Swelling Under Fusion Neutron Irradiation? Y. Katoh et al., J. Nucl. Mater. 323 (2003) 251

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/m2 (MFE) = 10 4 MW/m2 (IFE)

Effect of Heat Flux on W-Armor Coated SiC 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 Metal Helium,or Salt Coolant? Development of Armor fabrication process and repair He management mech. & thermal fatigue testing Surface Roughening/Ablation thermal fatigue x-ray and ion irradiation effects Underlying Structure bonding (especially ODS) high cycle fatigue creep rupture Armor/Structure Thermomechanics design and armor thickness finite element modeling thermal fatigue and FCG Modeling Irradiation Effects swelling 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 /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

Minimum Dose for Helium Accumulation Is IFE Below Threshold? 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, W J/cm 2 MAP N R a < 0.5 µm SEM, W J/cm 2 MAP N R a ~ µm P - V ~ 35 µm Pulsed Ion Effects - Tungsten RHEPP Facility

Able to produce single-shot damage in tungsten; indicates a fluence >1 J/cm 2 See roughening of single-crystal & powder met. tungsten at 1 J/cm 2 See no change at 0.5 and 0.7 J/cm 2 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 response Relevant 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 response Relevant equilibrium temperature (High-temperature sample holder)

(Blanchard, talks next Snead, talk next session) Thermal Fatigue of Cladding ORNL Infrared Processing Facility S T R E S (Mpa) Depth (mm)

Development of Thermal Fatigue Facility for HAPL ORNL Infrared Processing Facility Upgrade IFE ~10  sec ~10 4 MW/m 2 ~0.4 MJ/m 2 300kW Upgrade ~200 MW/m 2 ~2 msec 300kW Current ~35 MW/m 2 ~20 msec ~0.1 MJ/m 2 750kW Current ~5 MW/m 2 ~20 msec ~0.7 MJ/m 2 ~0.1 MJ/m cm 2 Test Area

(Snead, talk next session) Thermal Stability of Cladding ORNL Infrared Processing Facility W FeW or Fe 7 W 6 F82H Steel 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

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