Multiple effects for HT DCLL Presented by Neil Morley University of California, Los Angeles US-EU DCLL Workshop November 14-15, 2014 Slides from my colleagues S. Smolentsev and M. Abdou gratefully acknowledged

Next 10 Years We are now in mostly “Separate Effects” stage. We need to move to “multiple effects/multiple interactions” to discover new phenomena and enable future integrated tests in ITER TBM and FNSF Now TBMs in ITER & FNSF in FNSF Property Measurement Phenomena Exploration Model Validation Non-Fusion Facilities: 2 Theory/Modeling Basic Separate Effects Multiple Effect/ Interactions Partially Integrated Design Codes/Data Component Multiple Effects / Multiple Interactions – bringing together different combinations of multiple physical loads, multiple materials and complex configurations that can drive new interacting and synergistic phenomena Testing in Fusion Facilities

Consider a representative FW/blanket system: “Dual Coolant Lead Lithium” - DCLL 3 FW Armor RAFS Structure SiC Flow Channel Inserts Shield He Flow ARIES-ST DCLL blanket  This is considered as a leading FW/Blanket system in the US  EU and China have similar version  Features and R&D issues are typical of a family of PbLi and/or helium cooled FW/blankets –Molten PbLi and helium coolants / breeders and circulation systems –Thermomechanical response of helium cooled RAFS structures –Tritium transport and control –Corrosion and activation –Reliability over long operation and transient events

Features of the High Temperature DCLL  Allow high temperature PbLi flow inside FCI while keeping the RAFM steel operating in acceptable range for both structural and PbLi compatibility  Keep MHD pressure drop under control in a practical way that results in acceptable inboard dP and overall flow distribution  High temperature condition can be intentional for better power conversion or as a safety margin for temperature excursion protection 4 FCI PbLi He

5 Thermofluid Multiple Effect / Multiple Interactions Combined MHD/heat/mass transfer behavior in a DCLL unit cell PbLi Flow distribution in a complex collection of parallel channels Corrosion and tritium mass transfer in a non- isothermal PbLi flow system PbLi/He accident scenario evaluation Helium heat transfer and stability in strongly heated complex flow configurations What do we think we need to know about DCLL MHD thermofluid multiple effects / multiple interactions

Combined MHD/heat/mass transfer behavior in a DCLL unit cell Given a inflow conditions, non-uniform B-field and heating in typical DCLL unit cells, what will be the:  Material interface temperatures, temperature gradients, thermal stresses  Mass loss rates and corrosion product concentrations  Tritium transport rates and tritium concentrations  FCI performance and MHD Pressure drop What science needs to be studied  What combination of phenomena controls flow regime / stability of the channel. What is the sensitivity?  How does the flow regime impact the heat and scalar transport –E.g. Hot spots, corrosion product source terms, tritium leakage to helium,  How does the FCI material properties and component integrity evolve over time due to interfacial effects 6 FCI PbLi He

Spatial Gradients in Nuclear Heating and Temperature in LM Blanket Lead to New Phenomena that fundamentally alter our understanding of the behavior of the blanket in the fusion nuclear environment 7 B g V UPWARD FLOW DOWNWARD FLOW Vorticity Field shows unstable velocity affecting all transport phenomena Base flow strongly altered possibly leading to stagnant zones and “flow reversal” Buoyant MHD interactions result in “Mixed Convection” flow regime with substantial impact on flow dynamics, heat transfer, corrosion/tritium transport

The mixed-convection flow requires new rules for predicting transition. Bottom: Flow map showing stable laminar (s) and two turbulent regimes (wt and st) in the Ha – Re plane for Gr = 5x10 7. Top: Predictions of the critical Ha number with the linear theory. Linear stability analysis DNS  UCLA (Smolentsev) built flow maps (Ha-Re-Gr) and determined critical Ha number to predict transitions and specify turbulence mode. These results suggest that in DCLL blanket (DEMO, Gr~10 12 ) poloidal flows are turbulent.  These predictions are so far limited to computations and analytical studies. Experiments are needed. We are planning such experiments. Pre- experimental analysis has been completed showing that anticipated flow regimes can be reproduced in the MTOR Lab.

Flow distribution in a complex, multi-material configuration of parallel channels What design, flow conditions, and FCI behavior leads to highly unbalanced flow and channel overheating?  Complex conducting structures, manifold designs and partial FCI insulation  Magnetic fields not aligned with walls and will vary front-to-back, side-to-side and over time in large modules  Heating varies strongly back to front and vary over time  FCIs motion and property changes over time  Unsteady flows that may cause pressure oscillations 9 DCLL blankets modules have 4-8 multiple channels fed from common supply and return pipes FW Armor RAFS Structure SiC Flow Channel Inserts Shield He Flow

The current paths in complex flow elements are difficult to understand and predict, and will strongly impact flow distribution 10 In MHD one must always always be prepared to consider the complete electromagnetic field. The current and magnetic fluxes must have complete paths which may extend outside the region of fluid-mechanical interest into locations whose exact position may be crucial -- J A Shercliff UCLA current flow simulation in a 3 channel manifold, cut along symmetry plane down middle channel

PbLi ingress in SiC FCI can dramatically change conductivity, increase drag in that channel and lead to severe flow redardation 15 vol% dense, 85% porosity filled with aerogel

12 Thermofluid Multiple Effect / Multiple Interactions Combined MHD/heat/mass transfer behavior in a DCLL unit cell PbLi Flow distribution in a complex collection of parallel channels Corrosion and tritium mass transfer in a non- isothermal PbLi flow system PbLi/He accident scenario evaluation Helium heat transfer and stability in strongly heated complex flow configurations What do we think we need to know about DCLL thermofluid multiple effects / multiple interactions

Next 10 Years So how do we explore, discover, understand and accurately model multiple effect multiple interactions phenomena? Now TBMs in ITER & FNSF in FNSF Property Measurement Phenomena Exploration Model Validation Non-Fusion Facilities: 13 Theory/Modeling Basic Separate Effects Multiple Effect/ Interactions Partially Integrated Design Codes/Data Component Testing in Fusion Facilities Use real materials, prototypic temperatures Simulate surface and bulk heating and gradients Provide large volume and use multiple channels Have more prototypic Ha, Gr, N, Re, etc. A handful of upgraded/new experimental facilities will be needed that:

We envision two thermofluid MHD facilities beyond near term upgrades of existing facilities  Multiple Effect/Multiple Interactions Blanket Facility Role: Address near full size DCLL unit cell thermofluid flow and transport issues and reduced scale multi- channel flow control  Partially Integrated Blanket Facility Role: bring together all simulated conditions affecting thermofluid/thermomechanical blanket/FW performance to the maximal practical degree prior to FNSF 14 These are both non-nuclear facilities that can be flexibly operated and instrumented to investigate both prompt and long time scale DCLL blanket phenomena in a controlled and well characterized fashion

Blanket MHD thermofluid test facilities Multiple Effect/Multiple Interactions Blanket Facility. Role: Address near full size DCLL unit cell thermofluid flow and transport issues and reduced scale multi-channel flow control –strong magnetic field, ~5T –Magnetic volume capable to accommodate full single channel size, ~0.3 x 1.5 m) –controlled orientation with respect to gravity and channel walls –simulated volumetric heating and gradients –PbLi and He flow loops at prototypic temperatures (~1/2 TBM scale) 15 $20M class facility, can be a gradual extension of MTOR/MaPLE facilities at UCLA

Possible upgrades for MaPLE and BOB magnet Flexible B orientation Higher flowrate and temperature PbLi Simulated volumetric heating Online PbLi purification Instrumentation System to switch from Horizontal to Vertical oriented “BOB” magnet gap

Possible upgrades for MaPLE and BOB magnet Flexible B orientation Higher flowrate and temperature PbLi Simulated volumetric heating Online PbLi purification Instrumentation Secondary He coolant Higher magnetic field Larger magnetic volume System to switch from Horizontal to Vertical oriented “BOB” magnet gap Evolve into the Multiple Effect Multiple Interaction facility just described

Blanket MHD thermofluid test facilities Partially Integrated Blanket Facility. Role: bring together all simulated conditions affecting thermofluid/thermomechanical blanket/FW performance to the maximal practical degree prior to FNSF –Simulated toroidal and poloidal magnetic field –Up to full size FW/blanket test modules in multiple poloidal orientations with respect to gravity –Simulated surface and volumetric heating and gradients –PbLi and He flow loop of ~full DEMO module size –Prototypic temperatures, pressures, materials 18 $50-80M class National Laboratory facility to really prepare for FNSF – requires significant design and construction effort

What are the principal challenges in simulating the fusion nuclear environment?  Nuclear heating in a large volume with strong gradients, not possible to reproduce in simulation facility. Use various techniques Embedded heaters in LM, on walls or in flow channel inserts. Must be careful about changing the flow, FCI behavior, etc. Integration into multiple experiments required Inlet temperature control (e.g. flow in hot, let cool)  Complex magnetic field with toroidal field / poloidal field fidelity or transient fields during disruptions Requires complex magnet systems, very important for LM blankets Or utilization of modules in long pulse confinement devices  Complex mockup configuration with prototypic size and scale Not possible in fission reactors 19 Can not bring together all conditions in one test or adequately simulate nuclear heating

Study on Blanket/FW Multiple Effect/Multiple Interaction and Partially Integrated Test Strategy and Facilities 20 Why the Study is Needed The subject of multiple effect/multiple interactions is very complex and requires experienced blanket R&D experts But the cost of the facility for full simulation can be very expensive Therefore, tradeoffs between the capabilities incorporated in the facility and COST are needed. Developing cost estimates require mechanical design for a given set of specified parameters Requires Blanket R&D experts as well as mechanical engineers and magnet designers and cost professionals. There are several US institutions interested in developing proposals to construct blanket facilities The study could be “international” and a good mechanism for collaboration