FNS related activities in the ARIES program

1. FNS related activitiesin the ARIES program M. S. Tillack Fusion Nuclear Science and Technology Annual Meeting 3 August 2010 UCLA

2. Topics • Design and analysis of plasma-facing components: pushing the limits of performance • A new systems analysis technique – VASST • Evaluation of R&D pathways using “Technology Readiness”

3. Several W-He divertor designs have been studied and evolved in ARIES Tapered T-tube Pin-fin cooling Finger/plate combinations Fingers without W/FS joints

4. Tapering reduces temperature and increases stress The T-tube divertor is limited by W temperature more than stress, so tapering is helpful

5. Pin-fin experiments demonstrated very high heat removal 5 2 mm Bare  2 mm Pins 0.5 mm Bare 0.5 mm Pins For plate divertor, pin-fin array qmax[MW/m2] • Increases qmax to 18 MW/m2 at expected Re, and to 19 MW/m2 at higher Re • Allows operation at lower Re for a given qmax  lower pressure drop Re (/104)

6. Fabrication to failure (birth to death) analysis Fabrication Cycle • Time-dependent analysis including fabrication, shakedown, cycling (warm or cold shutdown), off-normal events. • Development of reference scenarios for power plants: ELM’s, disruptions, VDE’s Operation Cycle, warm shutdown

7. Pushing the limits: beyond 3Sm ASME code (3Sm) ½ eue (necking) • Self-relieving thermal stress is a large portion of the total stress in HHF components. • Accounting for inelastic behavior (yielding) can expand the design window considerably. • Our goal is steady-state divertor heat fluxes >10 MW/m2 (>1 MW/m2 for FW’s) and accommodation of transients. creep, crack growth, irradiation effects past present future

8. Elastic-plastic analysis allows for higher performance in the first wall stress-free-temperature is 1050 ºC

9. A modified first wall concept has been examined • W pins are brazed into ODS steel plate, which is attached to ferritic steel cooling channels • Pins help resist thermal transients and erosion • Minor impact on neutronics • 1 MW/m2 normal, 2 MW/m2 transient applied • 1 mm FW leads to ratchetting, 2 mm is stable F82H F82H ODS steel ODS steel W W

10. External transition joints help alleviate one of the most challenging aspects of HHFC’s 2D plane strain analysis • elastic/plastic, bilinear isotropic hardening • 1050 ºC stress-free (brazing) temperature • 100 cycles 20–700˚C • 3D analysis will be performed next • mat’l ε2dεallowable • ODS 0.77% ~1% • Ta 0.54% 5-15% • W ~0 % ~1%

11. Future plans on HHFC (tentative) • Full elastic/plastic analysis of plate and finger concepts • 3D analysis of joint • Design integration of pin fins in the plate concept • Come see us at TOFE: • “Optimization of ARIES T-tube divertorconcept,” J. A. Burke, X. R. Wang, M. S. Tillack • “Elastic-plastic analysis of the transition joint for high performance divertor target plate,” D. Navaei, X. R. Wang, M. S. Tillack, S. Malang • “High performance divertor target concept for a power plant: a combination of plate and finger concepts,” X.R. Wang, S. Malang, M. S. Tillack • “Innovative first wall concept providing additional armor at high heat flux regions,” X.R. Wang, S. Malang, M. S. Tillack • “Ratchetting models for fusion component design,” J. P. Blanchard, C. J. Martin, M. S. Tillack, and X. R. Wang • “Developing a new visualization tool for the ARIES systems code,” L. C. Carlson, F. Najmabadi, M. S. Tillack

12. Systems analysis in ARIES has evolved during the past 2 years Fusion Eng. & Design, 85 (2), 243-265, 2010. ASC VASST Determination of an optimum design point. Single-parameter scans around the design point. Difficult to use, maintain and modify. Non-interactive tool for self-consistency and costing. Multi-dimensional parameter space scans. Large database of physics operating points stored. Graphical user interface. Interactive tool for concept exploration.

13. Systems analysis flow physics engineering build out & costing Inboard radial build and engineering limits Top and outboard build, costing Plasmas that satisfy power and particle balance Scan several plasma parameters to generate large database of physics operating points Screen physics operating points thru physics filters, engineering feasibility, and engineering filters Surviving feasible operating points are built out and costed, graphical display of parameters (e.g. COE) Filters include e.g. Toroidal magnetic fields Heat flux to divertor Neutron wall load Net electric power

14. Number of points in database (Visual ARIES Systems Scanning Tool) VASST GUI v.2 Blanket database used Auto-labeling Pull-down menus for common parameters Color bar scale Constraint parameter can restrict database Correlation coefficient Save plot as TIFF, JPEG, BMP, PNG… Turn on ARIES-AT point design for reference Edit plotting properties

15. The code has multiple applications scan parameter space, explore tradeoffs (e.g. conservative vs. aggressive), describe a design point, and even evaluate research facilities We are currently exploring the 4 corners of tokamak design space to better understand tradeoffs Example: optimum size and bN in the aggressive/aggressive corner

16. We adopted “technology readiness levels” as the basis for the evaluation of progress Fusion Science & Tech 56 (2) August 2009. TRL’s express increasing levels of integration and environmental relevance, terms which must be defined for each technology application

17. Utility Advisory Committee“Criteria for practical fusion power systems” J. Fusion Energy 13 (2/3) 1994. • Have an economically competitive life-cycle cost of electricity • Gain public acceptance by having excellent safety and environmental characteristics • No disturbance of public’s day-to-day activities • No local or global atmospheric impact • No need for evacuation plan • No high-level waste • Ease of licensing • Operate as a reliable, available, and stable electrical power source • Have operational reliability and high availability • Closed, on-site fuel cycle • High fuel availability • Capable of partial load operation • Available in a range of unit sizes

18. These criteria for practical fusion suggest three categories of technology readiness • Power management for economic fusion energy • Plasma power distribution • Heat and particle flux management • High temperature operation and power conversion • Power core fabrication • Power core lifetime • Safety and environmental attractiveness • Tritium control and confinement • Activation product control and confinement • Radioactive waste management • Reliable and stable plant operations • Plasma control • Plant integrated control • Fuel cycle control • Maintenance 12 top-level issues cf. GNEP issues: • LWR spent fuel processing • Waste form development • Fast reactor spent fuel processing • Fuel fabrication • Fuel performance

19. Example TRL table: Heat & particle flux handling

20. The level of readiness depends on the design concept Power plant relevant high-temperature gas-cooled PFC’s Low-temperature water-cooled PFC’s

21. The current status was evaluated for a reference ARIES power plant • For the sake of illustration, we considered a Demo based on the ARIES advanced tokamak DCLL power plant design concept • He-cooled W divertor, DCLL blanket @700˚C, Brayton cycle, plant availability=70%, 3-4 FPY in-vessel, waste recycling or clearance

22. The ITER program contributes in some areas, very little in others • ITER promotes to level 6 issues related to plasma and safety • ITER helps incrementally with some issues, such as blankets, PMI, fuel cycle • The absence of reactor-relevant technologies severely limits its contribution in several areas

23. Major gaps remain for several of the key issues for practical fusion energy • A range of nuclear and non-nuclear facilities are required to advance from the current status to TRL6 • One or more test facilities such as CTF are required before Demo to verify performance in an operating environment