1. Materials Science and Development in Support of Inertial Fusion Energy Lance Snead Steven Zinkle Timothy Burchell Oak Ridge National Laboratory Presented at the Laser IFE Program Workshop Naval Research Laboratory, February 6,7 2001 Research Areas Briefly Covered : Thermal Conductivity Modeling (SiC, graphite and composites) Characterizing and Reducing Radiation Induced Dimensional Changes in CFC’s (IFE Funded, 50k$/yr, 3 year) Advanced Composites and Low Tritium Retaining Materials (For IFE Proposal) NRL IFE 2/2001

2. Present-Day High Thermal Conductivity Materials NRL IFE 2/2001

3. Thermal Conductivity Modeling (SiC, graphite and composites) Irradiation-induced thermal conductivity degradation in ceramics and graphite is dominated by defect-phonon scattering. Understanding this interaction allows accurate modeling and prediction. The defect resistance term, 1/Krd, is a simple, intrinsic material property. NRL IFE 2/2001

4. Thermal Conductivity Modeling (SiC, graphite and composites) - data on defect resistance - NRL IFE 2/2001 HFIR Irradiation Snead/Burchell

5. Thermal Conductivity (W/cm-K) Irradiation Temperature (°C) unirradiated irradiated DPA=displacement per atom Predicting Thermal Conductivity Degradation of Advanced CFC’s NRL IFE 2/2001 - combining theroetical model and measured data - MKC-1PH High Conductivity CFC

6. Irradiation Induced Dimensional Change in Advanced CFC’s 1000°C, 10 dpa Interstitials created during irradiation form new graphitic basal planes leading to highly anisotropic dimensional changes. Engineering composites can “balance” and minimize such dimensional changes There are no very high temperature data on advanced CFC’s. NRL IFE 2/2001 Oku Data

7. NRL IFE 2/2001

8. SiC/Graphite System: Engineering Low T-3 retention, High Conductivity Material Why SiC/Graphite fiber Combines Advantages of SiC composite : Low tritium retention With Advantages of Graphite fibers : Very high thermal conductivity Where we are First attempt at manufacture completed --> thermal conductivity promising --> mechanical properties similar to SiC/SiC composites --> tritium retention measurements underway (Causey) Drawbacks --> New material system -->Unknown mechanical performance -->Unknown radiation performance NRL IFE 2/2001

9. 1 10 100 1000 200400600800100012001400 T-3 Retention (appm) Irradiation / T-3 Loading Temperature (C) Non-irradiated, infinite charge time Non-Irradiated 1 hr Charge Time High Quality Irradiated CFC (Causey, Snead) Intermediate Quality Irradiated Graphite (Causey, Snead) Tritium Retention in Graphite NRL IFE 2/2001 T-3 attaches to basal plane edges and highly defected structure. More perfect material and/or high temperature allows less retention.

10. First High Thermal Conductivity SiC/G Composite Matrix : CVI SiC Fibers : Z-direction either Amoco P55 or Thornel K-1100 fiber X-Y direction P-55 fiber. Volume Fraction 44%. Architecture : Unbalanced 1-1-6 weave 6 tows in Z-direction FiberK-1100 P-55 Nicalon Type-S Kth (W/m-K@RT) ~950 120 15 Diameter (micron) 10 10 13 Tensile Strength (GPa) 3.1 1.9 2.6 Tensile Modulus (GPa) 965 379 420 Density (g/cc) 2.2 2.0 3.2 P55 fiber K-1100 fiber NRL IFE 2/2001

11. High Thermal Conductivity SiC/G Composites Mechanical performance comparable to that of SiC/SiC composites. Further development will likely yield improved properties. Total of 9 tests on CVI SiC/K1100 fiber Ultimate Bend Strength 283 ± 30 MPa Macroscopic Matrix Microcracking ~130 MPa NRL IFE 2/2001

12. High Thermal Conductivity SiC/G Composite - infiltration - Good inter-bundle infiltration (5-8% void) Large intra-bundle porosity (13% void) P55 P55 tow NRL IFE 2/2001

13. High Thermal Conductivity SiC/G Composites - tritium retention - Tritium retention, non-irradiated and irradiated, is highly dependent on graphite perfection. K-1100 type fibers are nearly perfect. Atsumi data T irr =600°C Tload=1000°C T irr =200°C Tload=1000°C NRL IFE 2/2001 Causey/Snead data

14. High Thermal Conductivity SiC/G Composites - thermal conductivity - 0 50 100 150 200 250 300 350 400 0200400600800 Thermal Conductivity (W/m-K) Temperature (C) SiC/SiC Composite (transverse) P55 Graphite/CVI SiC (high TC) Morton CVD SiC K1100 Graphite/ CVI SiC (high TC) At IFE-relevant temp., SiC matrix / graphite fiber : --> conductivity exceeds present SiC/SiC --> conductivity exceeds SiC theoretical max imum --> exceeds SOMBRERO assumptions NRL IFE 2/2001

15. 0 50 100 150 200 250 300 350 400 02004006008001000 Thermal Conductivity (W/m-K) Temperature (C) CVD SiC/K1100 Non-Irradiated CVD SiC/K1100 Irradiated CVD SiC Non-Irradiated CVD SiC Irradiated High Thermal Conductivity SiC/G Composites - thermal conductivity - At IFE-relevant temp., SiC matrix / graphite fiber : --> irradiated TC exceeds maximum for SiC --> exceeds SOMBRERO assumptions irradiated values are empirically determined NRL IFE 2/2001

16. Future Efforts in Area of IFE Materials Continue and complete METS experiment to define high temperature swelling and thermal conductivity of advanced CFC’s. Expand work to include tritium retention and second generation materials. Develop data-base for designers. Complete thermal defect model for conductivity prediction. Continue low-level development of SiC/graphite system. Include piggy-back irradiation experiment and tritium retention measurement. Offer collaborative irradiation-effects study in HFIR low-dose, low-cost rabbit facility. Leverage current MFE modeling effort and ceramic/diagnostic programs. NRL IFE 2/2001