Advanced Manufacturing for Fusion PFC and Blanket Materials

Transcription

1 Advanced Manufacturing for Fusion PFC and Blanket Materials Y. Katoh 1,*, R.R. Dehoff 1, A. Sabau 1, L.M. Garrison 1, S.J. Zinkle 1,2 L.L. Snead 3, C.H. Henager 4, Jr., 1 Oak Ridge National Laboratory 2 University of Tennessee 3 Stony Brook University, 4 Pacific Northwest National Laboratory, *katohy@ornl.gov Prepared for discussion at FESAC-TEC PMI Workshop June 20-22, 2017, Chicago, IL ORNL is managed by UT-Battelle for the US Department of Energy

2 Main conclusions Advanced manufacturing, mainly a variety of additive manufacturing techniques, is a potential game changer for fusion. Advanced manufacturing is expected to enable previously inaccessible material and component technologies. Envisioned applications include: 1) Complex geometries examples: Enhanced heat removal for solid PFC Enhanced tritium recovery for solid breeding blanket 2) Novel composite FGM example: Transient structure for PFM Adoption of advanced manufacturing urges upgrade of fusion component engineering from empirical to modeling-driven, computational designbased approaches. 2 Y. Katoh, June 2017

3 Advanced manufacturing technologies - Examples Additive manufacturing Fused deposition modeling Powder bed, laser or electron beam Powder bed, binder jet Vapor precursor processes e.g. laser CVD Ultrasound bonding Rapid sintering Direct current, field-assisted, pulsed or flash, Hybrid Additive preforming 3 Y. Katoh, June 2017

4 Advanced manufacturing why important for fusion? Solid PFC s performances are limited by various factors: Heat removal to coolant: micro-engineered cooling geometries offer potential to significantly improve heat removal [Youchison et al.] Thermo-mechanical integrity: composite-based transition from PFM to structural and backend materials minimizes thermal stress and risk of unacceptable crack propagation Heat & particle resistance: novel refractory composite allows use of brittle materials as PFM constituents (attractive PFMs are brittle) [Henager et al.] Tritium fuel cycle feasibility is critical to fusion energy Solid breeder: engineered micro-porous structures present potential to achieve greatly improved tritium recovery for solid blankets. [e.g., Ultramet SBIR] 4 Y. Katoh, June 2017

5 Application of technology: 1) Graded transitional structures for PFC W Cu (water) Steel (He) Monoblock concept Crack Mismatch stress Functionally graded structure minimizes thermal mismatch stress (thus fatigue, too) Multiple interfaces in graded structure mitigate catastrophic crack penetration CMC research indicates orders of magnitude increase in SCC rupture life with multi-layer interfaces than monolayer interface W-Cu graded structures are relatively mature material technology where AM can largely expand design flexibility Graded monoblock concepts W-steel graded structures are difficult to realize with conventional processing routes 5 Y. Katoh, June 2017

6 Application of technology: 1) Graded transitional structures for PFC (cont ed) Garrison et al., 2017, SOFE W-steel graded laminate composite manufactured through conventional hot rolling Graded structure involving a large number of interfaces is fabricated Reaction limits flexibility and component properties in this approach W-steel bonded sheet fabricated through Ultrasound Bonding technique Clean, reaction-free interface is achieved in this room temperature fabrication process 6 Y. Katoh, June 2017

7 Application of technology: 2) Engineered refractory composites Composite with dispersed or semidetached refractory particles embedded in a ductile metal matrix (ductile phasetoughened = DPT composite) is a promising technology for PFC While W-Cu DPT composites have been commercially available for decades, choice of potential matrix materials is extremely limited with the conventional process AM may overcome this limitation. Among near-term possibilities are refractory ceramic steel cermets and their graded transitional structures. TiC/FM steel composite manufactured by binder jet AM (Levy et al., 2017, Mater. Des.) 7 Y. Katoh, June 2017

8 Advanced Manufacturing of HFIR Control Plate with Embedded Neutron Absorbers X-ray radiograph of embedded neutron absorbers (Courtesy K. Terrani) 8 Y. Katoh, June 2017

9 Application of technology: 3) Fabrication of complex geometries Non-AM microfinned Cu tubes for HVAC HX (Shabray and Cotton, 2015, Appliance Design) Capability of fabricating complex porous geometries is the primary advantage of AM. Immediate application opportunities include micro-engineered cooling channels where very significant benefit is anticipated for solid PFC and blanket. Factors increase in HTC with relatively simple microfinned channels Solid breeder with micro-engineered tritium extraction features presents another near-term development opportunity. Cellular solid breeder concept (Sharafat et al., 2016, Fusion Eng.& Design, US patent A1) 9 Y. Katoh, June 2017

10 Application of technology: 3) Fabrication of complex geometries Refractory, high thermal conductivity, and reactive materials are more challenging for AM. Powder-bed AM tungsten was demonstrated only recently. Tungsten gear component fabricated by femtosecond fiber laser AM (Bai et al., 2016, Proc. SPIE) Tungsten microengineered mesh article fabricated by electron beam AM (Wright et al., 2016) 10 Y. Katoh, June 2017

11 Critical and design variables Material or material system More limited methods and conditions for refractory materials and reactive material systems Dimensions Limited by instrument capacity in most cases Length scale of geometrical features Minimum length scale for engineered features typically hundreds micron. This limits as-am ed surface finish quality. Method of manufacturing Chosen from various options May be combined with other manufacturing techniques in hybrid processes Processing parameters Need optimization for desired microstructures and properties Scientific foundation is generally not strong Non-uniform properties tailoring Properties may be tailored to meet location-specific requirements within single article 11 Y. Katoh, June 2017

12 Risks, uncertainties, maturity A wide variation of AM technologies are becoming increasingly available. Inherent technical limitations are method-specific AM. Material properties currently achieved via AM are highly technique- and material-specific and are in general inferior to conventional wrought material. This makes it challenging to achieve desired properties for known materials. AM demonstration of fabrication of small tungsten objects is only recent. While forming tungsten components like the EU HEMJ finger divertor tile is now feasible with AM, achieving adequate thermomechanical properties remains to be demonstrated. PIM tungsten tile for EU HEMJ divertor (KIT) AM is often combined with more conventional processing technologies. In these hybrid approaches the limitations associated with conventional processes often limit attractiveness and final properties. AM is among the most rapidly developing technologies and the trend is expected to accelerate over the next decades. Applications of metal AM are currently concentrated on the aerospace and biomedical sectors due to high cost of capital equipment and feedstock. As AM acceptance increases, it is anticipated that decreasing costs will open application space in other sectors. Improvements in surface finish and part quality are also keys to making inroads to other AM applications. 12 Y. Katoh, June 2017

13 Technology development examples for fusion applications Tungsten-steel composite FGM Tungsten parts for HEMJ divertor with advanced cooling features Ceramic breeder blocks with microporous features AM Method Ultrasonic welding Electron beam AM Laser beam AM Estimated Current TRL Advances required to achieve TRL6 Feasibility of welding W to steel needs to be addressed. Prototypical element may be developed with moderate investment. TRL6 requires nuclear test facility. Material and component may be developed with moderate investment. Computational design scheme needs to be developed. TRL6 requires nuclear test facility. Suitable breeding material and methods need to be identified, developed, optimized. Tritium transport needs to be understood. TRL6 requires nuclear test Time horizon to achieve goal for application 1 yr from TRL 2 to 3 2 yrs to TRL4 2 yrs to TRL5 Then nuclear test 2 yrs to TRL3 to 4 2 yrs to TRL5 Then nuclear test 1 yr from TRL 2 to 3 2 yrs to TRL4 2 yrs to TRL5 Then nuclear tes Available resources Leverage Facility resources are available in US industry. Significant facility and personnel resources are available in DOE labs and industry. Significant leverage can be expected. Significant facility and personnel resources are available in DOE labs and industry. Leverage can be expected. International status vs. US opportunity? 13 Y. Katoh, June 2017 Key industrial partners in US industry. Limited work in UK and US. Leadership opportunity for US. Leadership opportunity for US.

14 Summary of the key points and concluding remarks Advanced manufacturing is attractive because it Can bring technical break-through to fusion Involves a variety of technical approaches and is rapidly expanding and advancing Presents ability to micro-engineer porous structure as the primary strength For fusion, for example, it presents potential for: Dramatic increase in heat transfer for PFC Dramatic increase in tritium recovery for solid breeding blanket Dramatic improvement in PFM thermomechanical performance 14 Y. Katoh, June 2017 But be careful Used to be called rapid prototyping Easy to lose focus Metal AM is generally immature technology AM is not almighty However, it is of limited use: Unless coupled with strong computational studies Unless coupled with tritium materials science, thermofluid dynamics and computational modeling Unless coupled with thermomechanical modeling and computational materials design