Pilot Plant Study Hutch Neilson Princeton Plasma Physics Laboratory ARIES Project Meeting 19 May 2010

1. Pilot Plant StudyHutch NeilsonPrinceton Plasma Physics LaboratoryARIES Project Meeting19 May 2010

2. Motivation and Goals - 1 • There is growing interest in a nuclear facility as the next major step for U.S. fusion. Missions for fusion nuclear facilities include: • Burning plasmas (e.g., ITER) • Component testing (e.g., CTF, FDF, FNSF) • Net electricity production (pilot plant, Demo) • Pilot plant working definition: produces net electricity (QENG ≥ 1) at scale small enough (smaller than ITER) as to be flexible and affordable in the near term. Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

3. Motivation and Goals - 2 • Pilot plant study was undertaken to contribute to the planning for a potential nuclear next step. We are examining two aspects that have not received adequate attention: • Net-electricity mission could convincingly demonstrate fusion’s viability to the public. Could we be ready for such a mission by the mid-2020’s? Would it be a useful focus for fusion R&D? What other missions could be accomplished? What role could it play in closing S&T gaps to DEMO? • Risk and risk tolerance are important factors in readiness assessment. What are the risks for a pilot plant? What R&D would be most useful for reducing the risks? What risks would remain? Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

4. Study Questions • Value: What missions, besides Qeng > 1, could be accomplished? What role could it play in closing S&T gaps to DEMO? • Readiness/Risk: What R&D is needed to satisfy readiness conditions for pilot plant construction in, e.g., 2025? What are those conditions? What would be the risks? • Best Value: What R&D, going beyond minimum readiness, would be most useful for making the pilot plant more capable, more attractive, less risky? Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

5. What is Qeng ≈ 1 where th is thermal conversion efficiency, Mn is neutron energy multiplier, Pn is the neutron power from fusion, P is the alpha power from fusion, Paux is the injected power (heat + CD + control), Ppump is the coolant pumping power, auxis the injected power wall plug efficiency, Psub is subsystems power, Pcoils is power lost in coils (Cu), and Pcontrol is the power used in plasma or plant control that is not included in Pinj. Pextra = Ppump + Psub + Pcoils + Pcontrol Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

6. Pilot Plant Mission Gives Interesting Perspectives • Identified a range of design points for AT, ST, and CS: • Implications of QENG ≥ 1 mission for development priorities • ηth: thermal conversion efficiency. • ηaux: auxiliary power wall-plug efficiency. • QPlasma: Pfus/Paux • Priorities for pilot plant size andavailability • Magnet current density • Blanket thickness • Divertor/first wall heat flux limits • Maintainable configuration • Technology advances offer the most benefit. • What advances could we reasonably expect to achieve by ~2025? Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

7. A Maintainable Configuration is a Prerequisite for Adequate Availability and Flexibility • Configuration studies are performed for all configurations to understand criteria for maintainability. (Example: compact stellarator) 7 Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

8. Study Plan Understand the technology issues, at a strategic level • Current state of risk / readiness? • R&D activities to support pilot plant readiness by ~2025? • What risks would be mitigated? What risks would remain? What would be the consequences to the pilot mission of accepting those risks? • What is a reasonable range of assumptions for pilot plant design? Get help from experts in the wider community to understand how these issues inter-relate for pilot plants. Outputs: • Interim report, July • Open workshop, September • IAEA paper, October • Final report, December Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

9. Interim Report Contents / Assignments 0. Our definition of a pilot plant. 1. Characteristics and issues of possible pilot plant designs 1.1. Advanced tokamak (R. Hawryluk) 1.2. Spherical tokamak (J. Menard) 1.3. Compact stellarator (M. Zarnstorff) 2. Required advances, R&D possibilities, and residual risks in key technologies 2.1. Magnets (H. Neilson, L. Bromberg) 2.2. Blankets (C. Kessel) 2.3. Divertor / First Wall (R. Goldston) 2.4. Configuration Maintainability / Availability (T. Brown) 3. Risk Assessment (t.b.d.) 4. Plans for completing the study (all) Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010

10. What Might Come of It? • A framework for including risk assessment as part of fusion program planning (not just for pilot plants). • What level of risk is acceptable? • Do the benefits (i.e. reduced risk) of risk mitigation R&D outweigh its costs in delay and money? • A compelling basis for ordering of R&D priorities. • What R&D provides the most risk reduction benefit for its cost? • A debate on what the next step needs to accomplish. • What is the value of a given mission to fusion R&D? to the public? • What is “good enough” to be ready to take the next step? Ready Ready Pilot Plant Study / H. Neilson / ARIES Project Meeting, 19 May 2010