1. Update on Helium Management and Tungsten Bonded Ferritic
Presented by Lance Snead
Oak Ridge National Laboratory
HAPL e-meeting
June 6, 2003

2. Helium Management - Strategy Review
this year
next year
Understand Trapping
and Diffusion
Effects of
Thermal Cycling
Modeling
Structure
Testing
Engineered Structure
function of
function of
Single X
CVD X
Powder Met
Initial Dose
Temperature
Material :
Temperature
Concentration

3. Helium Management - Results Update
Previous Result
Repeat of Experiment
CVD produced 238 counts
Polycrystalline produced 82 counts
Single crystal produced no counts
CVD produced 480 counts
Polycrystalline produced 355 counts
Single crystal produced 303 counts

4. Helium Management - Results Update
• The error in the original data was confirmed by a third test. While there is a dependence of microstructure on retained helium is not dramatic.
• Work to be completed this year:
- Implantation system to be automated for
continual irradiation/anneal, simulating IFE
implantation dose, temperature and thermal
spike.
Samples of CVD W, powder met W, and single crystal tungsten were implanted at 1013, 1014, and 1015 /cm2 at room temperature and shipped to DELFT for thermal desorption studies (underway.)
Elevated dose/annealing and TEM microstructural analysis continues.
Trapping sites and diffusion coefficients by end of year for modeling…..

5. First Wall Armor - Strategy Review
this year
next year(s)
FW Paper
Process Armor Systems
Model Interface Stress
Determine Thermal
Stability of Interface
Evaluate Properties
Prototype
W on SiC (complete)
underway
Monolithic W on LAF
Plasma Spray
Transient Melt (IR melt)
Diffusion Bonded
Engineered W on LAF
Tungsten Foams
Functionally Graded

6. First Wall Armor - Plasma Spray
• The potential for failure of a tungsten cladding on F82H steel is driven by strain mismatch at the coating interface. This strain mismatch arises from the cladding process as well as nominal and transient operating conditions. The CTE of F82H Steel at 600C is 11 ppm/K compared to 4.7 ppm/K for tungsten. In addition, the alpha and gamma iron phase transformations must be considered for F82H Steel at temperatures associated with cladding.
• Plasma spraying under inert gas and vacuum allow for the deposition of pure tungsten and tungsten/steel composite microstructures. Graded layers can mitigate concentrated strain mismatches.
• Plasma spraying of preheated substrates can be used to manage the magnitude and direction of interfacial stress.
--> Samples have been sprayed at various substrate temperatures.
--> Metallography has been carried out. X-ray diffraction and annealing pending.
• Transient powder melt may allow porosity near surface.
--> Metallography has been carried out.
• Diffusion bonding of tungsten foil as the top layer would result in the highest surface integrity if strain mismatch could be managed by plasma sprayed, composite inter-layers.

7. Examples of Two Techniques
Plasma Sprayed W on F83H LAF
600°C Substrate Temperature
Transient Powder Melt W on F83H LAF
Ambient Substrate Temperature
100
microns
• cleaner interface
• martensite formation(brittle)
• phase separation at interface