Identification of key MHD thermofluid issues and associated R&D for the liquid breeder blankets

1. Identification of key MHD thermofluid issues and associated R&D for the liquid breeder blankets Presented by: Sergey Smolentsev (UCLA) With contribution from: - Mohamed Abdou, Neil Morley, Karim Messadek, Alice Ying (UCLA) - Clement Wong (GA) - Siegfried Malang (Consultant, Germany) - Ramakanth Munipalli (HyPerComp) - Rene Moreau (SIMAP, France) ReNeW Theme III and IV workshop UCLA March 2-6, 2009

2. MHD, Heat and Mass transfer are among the key phenomena affecting blanket operation • Traditionally, the major MHD thermofluid issues are pressure drop, flow balancing, electric and thermal insulation, 3-D effects, and electromagnetic coupling. But there are more…. • Tritium permeation is an issue – no solution has ever been developed • Corrosion severely limits the solid-liquid interface temperature and thus represents an obstacle to developing attractive blankets at high temperature operation • Both tritium permeation and corrosion limits are highly dependent on MHD flow dynamics and heat transfer • It is thus essential to address heat and mass transfer as important parts of MHD thermofluid. It has never been done systematically and should be initiated

3. Examples of key blanket feasability issues influenced by MHD Thermofluid • MHD thermofluid has a tremendous effect on blanket feasibility issues, among which are - MHD pressure drop - liquid-solid interface temperature - heat leakage into He (key element in success of DCLL) - secondary stresses in structural elements and insulating flow inserts - tritium permeation - corrosion / deposition - thermal blanket performance • Blankets are highly constrained by the above requirements, which are often competing • MHD thermofluid predictive capability is essential to studying and resolving the key blanket feasibility issues

4. Addressing MHD thermofluid issues in the past and recently For decades, we have designed blankets using very simple models and limited experimental data • Reduced models(slug flow, core flow approximation, fully-developed flow models, Q2D approximation) • Experimental facilities limited to surrogate liquids, low magnetic field, small magnet gaps, specific heating schemes (no volumetric heating), traditional or low-tech flow diagnostics Recent studies (APEX, ITER-TBM) have shown that the MHD phenomena in blankets are more complicated • these predictions are based on 2D and 3D approaches, whose capabilities are still limited to low Ha, Gr, Re and simplified flow geometry We really need much more to reach commonly accepted standards in other engineering branches

5. New trends in MHD thermofluid – recently started • New physical mechanisms, which were ignored in previous models: - convection and MHD turbulence - buoyancy effects - coupling - interfacial slip • Realistic geometrical models: - FCI and associated gaps - 3-D elements • Full magnetic field: - all 3 components - field gradients • Advanced experimental techniques: - ultrasound MHD mixed convection is an example of tight coupling between MHD and heat transfer

6. New trends in MHD thermofluid – recently started, cont. • New physical mechanisms, which were ignored in previous models: - convection and MHD turbulence - buoyancy effects - coupling - interfacial slip • Realistic geometrical models: - FCI and associated gaps - 3-D elements • Full magnetic field: - all 3 components - field gradients • Advanced experimental techniques: - ultrasound • Q2D MHD turbulent flow • Kelvin-Helmholtz instability • Interaction of bulk eddies with • boundary layers • Tritium permeation • Heat loss • Interfacial temperature

7. New trends in MHD thermofluid – recently started, cont. • New physical mechanisms, which were ignored in previous models: - convection and MHD turbulence - buoyancy effects - coupling - interfacial slip • Realistic geometrical models: - FCI and associated gaps - 3-D elements • Full magnetic field: - all 3 components - field gradients • Advanced experimental techniques: - ultrasound Temperature distribution in ITER TBM based on a 3-D MHD thermofluid model 3-D modeling of PbLi flow in the inlet manifold

8. A STRONG R&D program IS NEEDED • A strong R&D program on MHD thermofluid is essential to establishing the feasibility of liquid breeder blankets • This R&D program includes experiment, theory, and numerical modeling • The program culminates in verified/ validated predictive capability tools capable of addressing current conceptual designs, ITER TBM, CTF, and eventually DEMO

9. Experiment • To deliver necessary knowledge and to construct a physical database for formulation of proper boundary conditions and model closures • To validate new physical models and benchmark numerical codes • New experimental MHD facilities with advanced capabilities, including bigger space, stronger prototypical magnetic fields, and usage of surrogate liquids (KOH, GaInSn, Hg, Ga) as well as “real” liquids (Li, PbLi, Flibe, Flinabe). • In addition to the lab experiments, experimental testing in fully-integrated fusion environment, including volumetric nuclear heating and its gradients: in ITER and CTF

10. Theory & numerical modeling • To develop new adequate physical models for MHD thermofluid under blanket conditions that provide: - description of basic transport mechanism in the flow bulk as well as interfacial phenomena - full coupling between MHD fluid dynamics and heat & mass transfer - capability of addressing key blanket issues, including tritium permeation and corrosion • To develop validated high-efficiency computer codes suitable for: - computations in a wide parameter range, including Ha, Gr, Re, Pr - interpretation of the experimental data and planning new experiments in lab facilities, ITER-TBM and CTF - improvement of current conceptual blanket designs and development of new liquid breeder blankets