Neil Morley, UCLA 8/4/2010

1. FNSF Testing Strategy Discussions for PFC – PFC/FNSF Joint SessionChairs: Maingi, Menard, Morley Session Objectives and First Wall Testing Description Neil Morley, UCLA 8/4/2010

2. Starting Point for this session, a Fusion Nuclear Science Facility – FNSF (CTF, VNS, etc)… An FNSF facility is proposed as an test facility in which the impact of the integrated fusion environment • Combined plasma particle and heat flux; nuclear heating, damage, activation; magnetic field and forces; vacuum; and high temperature operation, … on the operation, performance, and reliability of in-vessel components and systems • Divertor, firstwall/blanket, shields, plasma facing features of fueling/heating/diagnostic systems, … can be tested, studied, improved and validated

3. Linkages of Main Thrust 13 Elements (Theme IV) The multiple Theme III thrusts also had a similar progression -- ending with testing in a integrated fusion environment Basic Properties / Separate Effects Testing Models and Theory Multiple / Partially-Integrated Effects Testing Test Facility Planning & Preparation Simulation Codes ITER-TBM / FNSF Facility and Test Article Planning, Preparation, Qualification Integrated Fusion Mockup/Comp Testing Integration, Benchmarking Demo ReadinessDatabase, Design Tools, Qualification / Licensing Increasing time, complexity, integration, cost Decreasing number of concepts and options

4. The classical fusion “bootstrap” problem… • To test in a fusion environment, one must be able to create and sustain a fusion environment • FNSF will to some/large degree require the successful operation of the very components it is supposed to test • How should the basic machine be built? • How to scale, design, instrument and perform relevant experiments in a reduced scale FNSF that tell us something/everything about DEMO and power plant conditions? • These questions have led to, in the FNST community meetings over the past 2 years, a discussion of a strategy for first wall / blanket components. We would like to broaden this discussion to include the divertor as well.

5. Agenda of this joint session • What divertor material, cooling and configuration options should be considered for FNSF? • What FNSF parameters and features are required for divertor/PMI testing? What is the PFC/PMI testing strategy in FNSF? • What R&D is required for the FNSF divertor?

6. “Base” vs. “Test” First Wall/Blanket • First wall is integrated into blanket – development, design, analysis and testing must be considered together • A functioning breeding blanket will be needed to breed tritium during DT operation • no practical or affordable external source is likely available (~1.6 kg/year burned per 100 MW at 30% availability) • Consider deployment of a base FW/blanket whose main mission is supply tritium, and port based test FW/blankets that are more easily removable and replaceable and instrumentable

7. A FW/Breeding Blanket Testing Strategy • Both port-based and base blanket have a testing mission • Base blanket • Are made largely using the same materials and designs as desired test blankets, optimized for reliability • Interaction with plasma and neutron field similar to testing blankets • Should be operated with more conservative temperature margins and smaller temperature gradients • Can still provide important statistical data on operations and failure modes/effects/rates in all phases DD thru DT operation • Port-based blankets • Are more highly instrumented and designed for specific scientific purposes and experimental missions • Can be operated with more aggressive and prototypic temperatures and gradients • Should be designed for fast replacement

8. What Material Options Exist to Use For Base First Wall / Breeding Blanket • FW and Structural Material: Ferritic/Martensitic steel • Austenitic steel is less suitable because of low thermal stress factor, high activation, and high swelling. It does not extrapolate to reactor. No reasons found to think that austenitic steel reduces risk. • Issue of FW armors have not yet been discussed in detail, need PFC/PMI input • Primary Coolant should be Helium, even for base blanket • Most generically reactor relevant, both for ceramic breeder and dual coolant blanket options • Keep operating temperature of the ferritic structure above 300°C to minimize the impact of neutron-induced damage. • Potential for chemical reactions between the coolant and the beryllium or liquid metal breeders can be avoided

9. A breeding blanket w/ integrated First Wall should be installed as a BASE Blanket on a FNSF from the beginning • Switching from non-breeding to breeding blanket involves complexity and long downtime, especially if coolant changes from water to helium • There is no non-breeding blanket for which there is more confidence than a breeding blanket (all involve risks, all will require development). • The actual wall conditions and materials used during the DT testing phase – e.g. high temperature and ferritic steel, should also be used during the HH/DD early operation phase in order to: • correctly optimize the plasma performance and pulse length and • obtain actual information on plasma-blanket interactions prior to DT operations (PMI, first wall heat flux, off-normal events…) Such information is needed for safety/licensing/availability of the DT phase

10. Fundamental FNST Research Gradient region • An example -- 3D MHD simulation of LM coolant streamlines in a pipe disturbed by a magnetic field gradient • Formation of instabilities and recirculating regions can strongly influence both heat and tritium transport behavior and generate strong flow resistance. • MHD forces generally exceed viscous and inertial forces by 5 orders of magnitude in fusion blankets. • An intensive program of laboratory scale experiments and model development addressing gaps in understanding and database Example areas: • PbLi alloy tritium chemistry, transport characteristics, isotope / impurity control • PbLi compatibility with SiC flow channel insert material and ferritic/martensitic steel • Liquid metal MHD interactions that dominate liquid metal blankets and free surface divertors flow and transport • Heat transfer and enhancement in high-temperature helium-cooled divertor concepts. • Tritium chemistry, transport and removal techniques from high temperature helium • Ceramic-breeder pebble-bed response to thermomechanical load and cycling • Interaction database of beryllium and liquid metal alloys with water and air

11. Fundamental FNST Research (2) Past tritium solubility measurements in PbLi have a wide discrepancy, by orders of magnitude. New experiments must provide better accuracy and help identify sensitivities that can drastically change the results • Scope • Functions and Elements of the Blanket, FW, Divertor, heat transport and tritium systems (mainline and alternates) • Database, basic phenomena exploration, model development in: • Thermofluid/Heat transfer properties • Chemistry and reaction rates • Thermomechanical properties • Diagnostic capabilities • Multiple university/lab research programs • Time scale • Consistent 10 year effort • Other Benefits • Innovation, invention, discovery • Basic validation of existing designs and models • Reinvigoration of FNST in the US

12. Objectives of this PFC/FNSF session Similar to first wall/blanket, discuss FNSF objectives, strategy and requirements for testing PFC components • What type of divertors are we considering for DEMO and power plants? • Are they good candidates for testing in FNSF • How many variations, how should they be tested? • What needs to be shown/observed/measured in divertor testing in FNSF • What are the possible testing strategies for divertor in FNSF • Can base/test divertors be included (partial toroidal, or upper/lower splits) • Use DD phase for extensive divertor and FW testing • What PMI specific testing is envisioned (maybe independent of first wall or divertor heat sink design) • What are the requirements on FNSF • Heating power, access for diagnostics, replacement speed, flexibility in PF coil positioning?? • Accommodate significant quantities of lithium • For these strategies, what is the R&D required in advance of an FNSF

13. Keep an open mind… • We asked some people to supply a perspective on some of these questions • We likely won’t arrive at a definite conclusion today • Try to understand the assumptions and concerns of experts from PFC and plasma edge • Try to understand how divertor operation and testing can be done in FNSF • Try to identify the features or parameters of an FNSF that might be required

14. Linkages of Main Thrust 13 Elements (Theme IV) The multiple Theme III thrusts also had a similar progression -- ending with testing in a integrated fusion environment Basic Properties / Separate Effects Testing Models and Theory Multiple / Partially-Integrated Effects Testing Test Facility Planning & Preparation Simulation Codes ITER-TBM / FNSF Facility and Test Article Planning, Preparation, Qualification Integrated Fusion Mockup/Comp Testing Integration, Benchmarking Demo ReadinessDatabase, Design Tools, Qualification / Licensing Increasing time, complexity, integration, cost Decreasing number of concepts and options

15. Multiple-Effects, Synergistic Phenomena PMTF-1200 high heat flux facility MTOR Thermofluid/MHD facility • Synergistic phenomena will dominate the behavior, failure modes and reliability of first designs and prototypes. Examples… • LM Thermofluid/MHD + FCI Thermomechanics • Neutron irradiation driven heating and breeding in blanket unit cells • Multiple effect tritium/thermal/chemical effects • Utilize test facilities to • explore multiple-effect phenomena, • investigate specific design and material combinations • uncover synergistic failure modes • Partially-integrated thermal, nuclear, electromagnetic, and plasma loading conditions • Magnetic/Thermal, • Plasma/Thermal, Tritium/Thermal, • Neutron/Thermal/Tritium that can accommodate prototypic sizes and materials (Be, Li, PbLi, T) • Sufficient single effects database a prerequisite

16. Multiple-Effects, Synergistic Phenomena (2) TPE, in the STAR Tritium Lab HFIR and ATR Test Reactors • Scope • Mockups of the Blanket, First Wall, Divertor, heat transport and tritium systems (mainline and alternates) • Upgrade and construction of needed user test facilities (3-4 total) • Time scale • Planning and scoping - Immediate • Operations, Consistent 10 yr effort • Additional Benefits • Model validation in more complex operational regimes • Testing fabrication and diagnostic capability • Initial reliability growth and qualification information • Enabling continuous powerand tritium extraction