A methodology for evaluating progress toward an attractive fusion energy source

1. A methodology for evaluating progress toward an attractive fusion energy source M. S. Tillack, L. M. Waganer US/Japan Workshop on Fusion Power Plant Studies 5-7 March 2008

2. Why do we need a methodology for evaluating progress? • Metrics are needed to quantify progress and the value of fusion facilities • In addition to individual facilities, a method is needed to compare alternative pathways (using cost, risk,benefit) in an objective and quantitative manner • DOE and the Greenwald subpanel of FESAC (”Priorities, gaps and opportunities: towards a long-range strategic plan for magnetic fusion energy”) also recognizes the need for metrics (http://www.ofes.fusion.doe.gov/fesac.shtml) ?

3. The EU is also pursuing an approach to evaluate current technology readiness

4. The US Government Accountability Office (GAO) encourages “a disciplined and consistent approach for measuring technology readiness” • Technology Readiness Levels represent a systematic methodology that provides an objective measure to convey the maturity of a particular technology. • They were originally developed by NASA, but with minor modification, they can be used to express the readiness level of just about any technology element. • The Department of Defense has adopted this metric to evaluate the readiness levels of new technologies and guide their development to the state where they are considered “Operationally Ready”. • The Department of Energy has adopted the use of TRL’s in their evaluation of the GNEP program. • Can fusion energy benefit from this approach to develop the technologies needed for Demo?

5. Generic description of readiness levels

6. Characteristics of TRL’s

7. Characteristics of TRL’s, cont’d. GAO recommendation: “Direct DOE Acquisition Executives to ensure that projects with critical technologies reach a level of readiness commensurate with acceptable risk – analogous to TRL 7 – before deciding to approve the preliminary design and commit to definitive cost and schedule estimates, and at least TRL 7 or, if possible, TRL 8 before committing to construction expenses.

8. Example of TRL’s for GNEP*:fast reactor spent fuel processing

9. Example of TRL’s for GNEP*, continued:fast reactor spent fuel processing *Global Nuclear Energy Partnership

10. How can we apply this to fusion energy? • Use criteria from utility advisory committee to derive issues (roll back) • Connect the criteria to fusion-specific (design independent) technical issues and R&D needs • Describe Technology Readiness Levels for the key issues • Define the end goal (design) in enough detail to evaluate progress • Evaluate status, gaps, facilities and pathways

11. 1 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, high availability • Closed, on-site fuel cycle • High fuel availability • Capable of partial load operation • Available in a range of unit sizes End-user (Customer) Pathways Power plant requirements Demo R&D needs R&D and facilities definition Power plant designs

12. 2 The criteria for attractive fusion suggest three categories of technology readiness • Economic Power Production • Control of plasma power flows • Heat and particle flux handling • High temperature operation and power conversion • Power core fabrication • Power core lifetime • Safety and Environmental Attractiveness • Tritium inventory and control • Activation product inventory and control • Waste management • Reliable Plant Operations • Plasma diagnosis and control • Plant integrated control • Fuel cycle control • Maintenance 12 top-level issues

13. The intent is to be comprehensive based on functions rather than physical elements • Economic Power Production • Control of plasma power flows • Heat and particle flux handling • High temperature operation and power conversion • Power core fabrication • Power core lifetime Power deposition Power flows Power conversion

14. 3 Example: High Temperature Operation

15. 4 An evaluation of readiness requires identification of an end goal • For the sake of illustration, we are considering Demo’s based on mid-term and long-term ARIES power plant design concepts, e.g. • Diverted, high confinement mode, tokamak burning plasma • Low-temperature or high-temperature superconducting magnets • He-cooled W or PbLi-cooled SiC divertors • PbLi-cooled SiC or dual-cooled He/PbLi/ferritic steel blankets • 800˚C (or higher) coolant outlet temperature with high-efficiency Brayton cycle • Advanced power core fabrication processes • Efficient autonomous maintenance

16. 5 Example evaluation: High temperature operation and power conversion (DCLL) • Concept development is largely completed. Limited data on ex-vessel parts of power conversion system (e.g., HX) • To achieve TRL4: Need full loop operation at high temperature in a laboratory environment • This is typical of many issues; some are more advanced, but most are stuck at TRL=3

17. Summary • The TRL approach has significant advantages • Objective metrics for entire range of development • Systematic for all plant elements • Integrated approach • Widely accepted (within the US government) • We have shown that the TRL approach can be applied to fusion energy • The ARIES pathways study will develop a complete methodology and evaluate example concepts • TRL’s have been defined for all of the key issues • We are preparing to run through an example evaluation of Demo concepts • Analysis of facilities will follow