Why is the study of FW/Blanket/Divertor Components Reliability and Lifetime a DEMO R&D Gap?

1. Neutron Multiplier Be, Be12Ti (<2mm) Tritium Breeder Li2TiO3 (<2mm) High-P, High-T He coolant Surface Heat Flux Neutron Wall Load First Wall (RAFS) Why is the study of FW/Blanket/Divertor Components Reliability and Lifetimea DEMO R&D Gap? NCT Discussion Group, FNT-7: Alice Ying, Neil Morley (UCLA) • What is the Broad Issue? • FW/blanket/divertor components performance, reliability, and lifetime must lead to DEMO availability goal ~50-70%, tritium self-sufficiency, high grade heat generation for electricity production, and sufficient radiation shielding for components and personnel. • What Is the R&D gap? • No FW/blanket module or system has ever been built or tested – potential interdependent and synergistic phenomena and failure mechanisms have not necessarily been identified or understood. • Plasma facing components that are capable of withstanding continuous high surface heat load of ~10 MW/m2 are yet to be tested at the Demo-level materials, high temperature, transients,and irradiation. • Blanket example: Typical vision of a ceramic-breeder–based blanket module. FW/Blanket systems are complex and have many integrated functions, materials, and interfaces

2. Summary of R&D Issues for FW/Blanket/Divertor • D-T fuel cycle tritiumself-sufficiency in a practical system(from El-Guebaly and Sawan, UW) • depends on many physics and engineering parameters / details: e.g. fractional burn-up in plasma, tritium inventories, FW thickness, penetrations, passive coils, doubling time • Tritium production, extraction and inventory in the solid/liquid breeders under actual operating conditions • Tritium permeation, control and inventory in blanket and PFC • Identification and characterization of performance, failure modes, effects, and rates in blankets and PFC’s • Thermo-magnetic-mechanical-vibration loadings and response of blanket and PFC components under normal and off-normal operation • Materials interactions, compatibility, and chemistry • Radiation damage and Plasma drivensynergistic effects • Lifetime of blanket, PFC, and other fusion nuclear components • 3. Remote maintenance with acceptable machine shutdown time.

3. Experiments in non-fusion simulation facilities are essential to establishing FW/Blanket/Divertor scientific foundations … Theory/Modeling Design Codes Basic Separate Effects Multiple Interactions Partially Integrated Integrated Component • Fusion Env. Exploration Design Verification & Reliability Data Property Measurement Phenomena Exploration • Concept Screening • Performance Verification •  Thermo-mechanical  Tritium • High Heat Flux  Magnetic • Plasma/Tokamak  … Non-Fusion Facilities (various non neutron test stands, fission reactors and accelerator-based neutron sources) Testing in Fusion Facilities … and critical to understand & interpretcomplex, synergistic experiments in the integrated fusion environment

4. He pipes to TCWS Visionof TBM System Bio-shield A PbLi loop Transporter located in the Port Cell Area 2.2 m Vacuum Vessel ITER will provide the first opportunity, through the test blanket module (TBM) program, to perform low fluence integrated environment and phenomena experiments ITER has allocated 3 ITER equatorial ports (1.75 x 2.2 m2) for TBM testing, and space in the reactor hall and TCWS building for support systems • ITER will test and develop the knowledge base for low temperature, water-cooled copper FW and divertor designs. However, DEMO will require different materials, designs, and temperatures. • ITER-TBM can be used tostudy synergistic effects among FW/blanket phenomena and provide data to improve models and benchmark simulation codes. • TBM experiments in ITER can provide a bridge between laboratory and NCT experiments. • There is currently no ITER program for testing advanced divertor designs

5. 30 CANDU Supply w/o Fusion 25 20 Projected Ontario (OPG) Tritium Inventory (kg) 15 1000 MW Fusion 10% Avail, TBR 0.0 10 ITER-FEAT (2004 start) 5 0 1995 2000 2010 2015 2020 2025 2030 2035 2040 2045 2005 Year A NCT Facility Is Unique in Filling the FW/Blanket/Divertor Reliability and LifetimeGap in the Following Ways • Provide a true fusion environment ESSENTIAL to activate mechanisms that drive coupled phenomena, integrated behavior, and prototypical failure modes; and thus allow development of engineering performance and growth of reliability. The requirements for testing nuclear components are estimated as: • NWL 1-2 MW/m2, ~ 6 MW.y/m2, ~ 10 m2 test area, and high surface heat load (SHF ~0.5 / 10 MW/m2 for FW / divertor). • Long pulse / continuous plasma operation • Large module to sector size tests for prototypic geometry • Meet testing needs with practical machine and cost: • reasonable fusion power / tritium consumption • high base availability and capacity for fast replacement of failed test components Performing these tests in large fusion device (e.g. ITER, early DEMO) leads to large tritium consumption and cost • e.g., A 1000 MW fusion power facility, even at a low availability will consume the projected CANDU tritium supply in just a few years • THEREFORE, NCT should be done at low power, <150MW (hence driven plasma), or breed/recover much of its own T

6. Backups…

9. Stages of FW/Blanket/Divertor Testing in Fusion Facilities D E M O Gap? Role of ITER TBM Component Engineering Development & Reliability Growth Engineering Feasibility & Performance Verification Fusion “Break-in” & Scientific Exploration Stage III Stage I Stage II 1 - 3 MW-y/m2 > 4 - 6 MW-y/m2 0.1 – 0.3 MW-y/m2 Fluence 1-2 MW/m2, steady state or long pulse COT ~ 1-2 weeks 1-2 MW/m2, steady state or long burn COT ~ 1-2 weeks 0.5 MW/m2, burn > 200 s NWL Sub-Modules/Modules Modules/Sectors Modules Exp type • Initial exploration of coupled, prompt phenomena in a fusion environment • Uncover unexpected synergistic effects, Calibrate non-fusion tests • Impact of rapid property changes in early life • Integrated environmental data for model improvement and simulation benchmarking • Develop experimental techniques and test instrumentation • Screen and narrow the many material combinations, design choices, and blanket design concepts • Uncover unexpected synergistic effects coupled to radiation interactions in materials, interfaces, and configurations • Verify performance beyond beginning of life and until changes in properties become small (changes are substantial up to ~ 1-2 MW · y/m2) • Initial data on failure modes & effects • Establish engineering feasibility of blankets (satisfy basic functions & performance, up to 10 to 20 % of lifetime) • Select 2 or 3 concepts for further development • Identify lifetime limiting failure modes and effects based on full environment coupled interactions • Failure rate data: Develop a data base sufficient to predict mean-time-between-failure with confidence • Iterative design / test / fail / analyze / improve programs aimed at reliability growth and safety • Obtain data to predict mean-time-to-replace (MTTR) for both planned outage and random failure • Develop a database to predict overall availability of FNT components in DEMO

10. Blanket Functions (including first wall) Power Extraction Convert energy of neutrons and secondary gamma rays into heat Absorb plasma radiation on the first wall Systems to Extract the heat (at high temperature, for energy conversion) Tritium Fuel Replacement Tritium breeding, must have lithium in some form Tritium extraction and control systems Radiation Shielding of the Vacuum Vessel Physical Boundary for the Plasma Physical boundary surrounding (surface facing) the plasma, inside the vacuum vessel Share space with / Provide access for plasma heating, fueling Part of greater electomagnetic environment – conducting materials, ferromagnetic materials, induced currents 10

11. Fusion environment is unique and complex:multiple fields and varied environments Neutrons (fluence, spectrum, temporal and spatial gradients) Radiation Effects (at relevant temperatures, stresses, loading conditions) Bulk Heating Tritium Production Activation Heat Sources (magnitude, gradient) Bulk (from neutrons and gammas) Surface Heat Flux (steady, MARF, Disruption) Particle Flux (energy and density, gradients) Steady/Blobs Unsteady • Magnetic Field (3-component with gradients) • MHD from Steady Fields with and without Plasma Current • Currents from unsteady fields/disruptions • Mechanical Forces • Pressurization • Thermal stresses • EM forces • Weight • Vibrations • Chemical Environment • Hydrogen, Transmutation, Corrosion • Multi-function, multi-material, multi-interface blanket in multi-component field environment leads to: • Multi-Physics, Multi-Scale Phenomena • Synergistic effects

12. [0.5-1.5] mm/s [18-54] mm/s Neutron Multiplier Be, Be12Ti (<2mm) Tritium Breeder Li2TiO3 (<2mm) PbLi flow scheme First Wall (RAFS, F82H) Surface Heat Flux Neutron Wall Load Blanket systems are complex and have many integrated functions, materials, and interfaces

13. There are Many Blanket Concepts Proposed Worldwide They all have feasibility issues and attractive features

14. Tritium breeding blankets are complex, integrated systems critical to the feasibility of D-T fusion energy Poloidal flow PbLi channel • The Blanket provides the mechanisms by which: • tritium is generated for fuel self-sufficiency • high grade heat is extracted for efficient energy production • Breeding blankets are complex, heterogeneous, highly integrated systems, with: • Multiple functions, materials and material interfaces • Integrated Plasma facing FW, tritium breeder, neutron multiplier, specialized insulators and permeation barriers, structure, and high temperature coolant Dual-Coolant PbLi Liquid Breeder Module Purge gas pipe He-cooled RAFS FW SiC FCIs Ceramic breeder pebbles Helium-Cooled Li2TiO3 Ceramic Breeder Module • All blanket concepts have feasibility issues! Yet, no fusion blanket has ever been built or tested. ITER has always been planned as the facility to begin blanket testing. Be Pebbles He-cooled RAFS FW

15. Simulation capabilities continue to advance and can play a larger role • Example – 3D MHD PbLi flow through and expansion maniflold • 17-44% flow mismatch between center and side channels (controlled by MHD) Electric current Ha = 929, Re = 1500, N = 575 (based on Parallel Channel Half-Width) Velocity profiles Stream lines

16. DEMO Availability of 50% Requires Blanket Availability >85% (Table based on information from J. Sheffield’s memo to the Dev Path Panel) Assuming 0.2 as a fraction of year scheduled for regular maintenance. Demo Availability = 0.8* [1/(1+0.624)] = 0.49 (Blanket Availability must be .88)