Fusion Nuclear Science and Technology Development and the Roles of ITER and the Next Step Fusion Nuclear Facility, FNF (CTF/VNS) Plenary Talk at the 18th Topical Meeting on the Technology of Fusion Energy (TOFE), San Francisco, September 30, 2008 Mohamed Abdou With Input from:A. Ying, N. Morley, M. Sawan, S. Willms, D. Sze,C. Wong, S. Malang, R. Kurtz, R. Stoller and the FNST Community
Fusion Nuclear Science and Technology (FNST) Development and the Roles of ITER and the Next Step Fusion Nuclear Facility, FNF (CTF/VNS) Outline -R&D Tasks Prior to DEMO • FNST Issues • Framework for FNST Development & Requirements for Fusion Testing • ITER TBM Role and Limitations • Next Step Fusion Nuclear Facility (FNF) Role, Mission TBR Requirements, Base Blanket Options and Testing Strategy Design Options for the FNF Device • ISSUES that have Major Impact on FNST and Fusion Development: External Tritium Supply Reliability, Availability, Maintainability - Summary
Fusion Nuclear Science and Technology(FNST) Fusion Power & Fuel Cycle Technology FNST includes the scientific issues and technical disciplines as well as materials, engineering and development of fusion nuclear components: From the edge of Plasma to TF Coils: 1. Blanket Components (includ. FW) 2. Plasma Interactive and High Heat FluxComponents (divertor, limiter, rf/PFC element, etc) 3. Vacuum Vessel & Shield Components Other Systems / Components affected by the Nuclear Environment: 4. Tritium Processing Systems 5. Remote Maintenance Components 6. Heat Transport and Power Conversion Systems
Numerous technical studies were performed over the past 30 years in the US and worldwide to study issues, experiments, facilities, and pathways for FNST development These studies resulted in important conclusions and illuminated the pathways for FNST and fusion development • This presentation will utilize the results of previous studies, but will not provide details on the scientific and engineering basis for such conclusions. • These studies are documented in many scholarly journal publications and numerous topical reports. They can be viewed on the web site: www.fusion.ucla.edu • Studies of particular importance to this presentation: • FINESSE Study (1983-86, led by UCLA) • IEA Study on VNS/CTF (1994-96 US, EU, J, RF) • ITER TBM (1987-present) • US ITER TBM Planning and Costing (2003-2007) • Recent Workshop on FNST held August 12-14, 2008
R&D Tasks to Be Accomplished Prior to Demo 1) Plasma - Current Drive/Steady State - Confinement/Burn - Edge Control - Disruption Control 2) Plasma Support Systems - Superconducting Magnets - Fueling - Heating 3) Fusion Nuclear Science and Technology (FNST) • Blanket - Divertors - rf (PFC elements) - VV & Shield 4) Systems Integration Where Will These Tasks be Done?! • Burning Plasma Facility (ITER) and other plasma devices will address 1, 2, & much of 4 • TheBIG GAPis Fusion Nuclear Science and Technology (FNST) • Where, How, and When will it be done?
Summary of Critical R&D Issues for Fusion Nuclear Science and Technology (FNST) • D-T fuel cycle tritiumself-sufficiency in a practical system depends on many physics and engineering parameters/details: e.g. fractional burn-up in plasma, tritium inventories, FW thickness, penetrations, internal coils, doubling time 2. Tritium extraction and inventory in the solid/liquid breeders under actual operating conditions 3.Thermomechanicalloadings and (MHD) Thermofluid response of blanket and PFC components under normal and off-normal operation 4. Materials property changes, interactionsand compatibility 5. Identification and characterization of failure modes, effects, and rates in blankets and PFC’s • Engineering feasibility and reliability of electric (MHD) insulators and tritium permeation barriers under thermal/mechanical/electrical/magnetic/nuclear loadings with high temperature and stress gradients 7. Tritium permeation, control and inventory in blanket and PFC 8. Remote maintenance with acceptable machine shutdown time 9. Lifetime of blanket, PFC, and other FNT components
Framework for FNST R&D involves modeling and experiments in non-fusion and fusion facilities Theory/Modeling Design Codes Basic Separate Effects Multiple Interactions Partially Integrated Integrated Component Design Verification & Reliability Data • Fusion Env. Exploration Property Measurement Phenomena Exploration • Concept Screening • Performance Verification Non-Fusion Facilities (non neutron test stands, fission reactors and accelerator-based neutron sources) Testing in Fusion Facilities • Experiments in non-fusion facilities are essential and are prerequisites to testing in fusion facilities • Testing in Fusion Facilities is NECESSARY to uncover new phenomena, validate the science, establish engineering feasibility, and develop components
D E M O Component Engineering Development & Reliability Growth Engineering Feasibility & Performance Verification Fusion “Break-in” & Scientific Exploration Stage I Stage II Stage III 1 - 3 MW-y/m2 0.1 - 0.3 MW-y/m2 > 4 - 6 MW-y/m2 1-2 MW/m2 steady state or long burn COT ~ 1-2 weeks 1-2 MW/m2 steady state or long burn COT ~ 1-2 weeks 0.5 MW/m2, burn > 200 s Sub-Modules/Modules Modules Modules/Sectors • Failure modes, effects, and rates and mean time to replace/fix components (for random failures and planned outage) • Iterative design / test / fail / analyze / improve programs aimed at reliability growth and safety • Verify design and predict availability of FNT components in DEMO • Establish engineering feasibility of blankets (satisfy basic functions & performance, up to 10 to 20 % of lifetime) • Select 2 or 3 concepts for further development • Initial exploration of coupled phenomena in fusion environment • Screen and narrow blanket design concepts Three Stages of FNST Testing in Fusion FacilitiesAre Required Prior to DEMO Where to do Stages I, II, and III?
Equatorial Port Plug Assy. Port Frame TBM Assy ITER Provides Substantial Hardware Capabilities for Testing of Blanket Systems He pipes to TCWS TBM System (TBM + T-Extrac, Heat Transport/Exchange…) Bio-shield • ITER has allocated 3 equatorial ports (1.75 x 2.2 m2) for TBM testing • Each port can accommodate only 2 modules (i.e. 6 TBMs max) A PbLi loop Transporter located in the Port Cell Area 2.2 m Vacuum Vessel Fluence in ITER is limited to 0.3 MW-y/m2. ITER can only do Stage I. ITER TBM is the most effective and least expensive to do Stage I. But we need another facility for Stages II & III.
Fusion Nuclear Facility (FNF) • The idea of FNF (also called VNS, CTF) is to build a small size, low fusion power DT plasma-based device in which Fusion Nuclear Science and Technology (FNST) experiments can be performed in the relevant fusion environment: 1- at the smallest possible scale, cost, and risk, and 2- with practical strategy for solving the tritium consumption and supply issues for FNST development. In MFE: small-size, low fusion power can be obtained in a low-Q (driven) plasma device, with normal conducting Cu magnets • Equivalent in IFE: reduced target yield (and smaller chamber radius?) • There are at least TWO classes of Design Options for FNF: - Tokamak with Standard Aspect Ratio, A ~ 2.8 - 4 - ST with Small Aspect Ratio, A ~ 1.5
Critical Factors that have Major Impact on Fusion Testing and Development Pathway for FNST • Tritium Consumption / Supply Issue • Reliability / Maintainability / Availability Issue • Cost, Risk, Schedule The idea of a Fusion Nuclear Facility, FNF (also called VNS, CTF, etc.) dedicated to FNST testing was born out of the analyses of these critical factors 20 years ago Today, these factors remain the key to defining details of FNF mission, design, and testing strategy
The issue of external tritium supply is serious and has major implications on FNST (and Fusion) Development Pathway A Successful ITER will exhaust most of the world supply of tritium. FNST engineering development and reliability growth stages must be done ina small fusion power device (FNF) to minimize tritium consumption (only stage I fusion break-in can be done in ITER). Even FNF has to breed most, or all, of its own tritium consumption. Tritium Consumption in Fusion is HUGE! Unprecedented! 55.6 kg per 1000 MW fusion power per year Production in fission is much smaller & Cost is very high: Fission reactors:2–3 kg/year $84M-$130M/kg(per DOE Inspector General*) Tritium decays at 5.47% per year CANDU Supply w/o Fusion *www.ig.energy.gov/documents/CalendarYear2003/ig-0632.pdf CANDU Reactors:27 kgfrom over 40 years,$30M/kg (current) Tritium Decays at 5.4% per year With ITER: 2016 1st Plasma, 4 yr. HH/DD Two Issues In Building A DEMO: 1 – Need Initial (startup) inventory of ~10 Kg per DEMO (How many DEMOS will the world build? And where will startup tritium come from?) 2 – Need Verified Breeding Blanket Technology to install on DEMO
FNF has to breed tritium to:a- supply most or all of its consumptionb- accumulate excess tritium sufficient to provide the tritium inventory required for startup of DEMO 2.0 1.5 1.0 0.5 0.0 50 100 150 200 250 300 350 400 Required TBR in FNF 10 kg T available after ITER and FNF 5 kg T available after ITER and FNF Required TBR FNF does not run out of T 2021 FNF start From Sawan&Abdou 8/2008 Fusion Power of FNF (MW) Situation we are running into with breeding blankets: What we want to test (the breeding blanket) is by itself An ENABLING Technology 13
Base Breeding Blanket and Testing Strategy In FNF(Conclusions Derived from FNST Workshop August 12-14, 2008) A Breeding Blanket should be installed as the “BASE” Blanket on FNF from the beginning Needed to breed tritium. 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). Using base breeding blanket will provide very important information essential to “reliability growth”. This makes full utilization of the “expensive” neutrons. Note that ~ 20m2 of testing area is required per concept. Two concepts need 40m2which is almost the net surface area available on the outboard of FNF. What Material Options to Use For Base Breeding Blanket FW and Structural Material: Ferritic Steel only option available by 2030 Austenitic steel is less suitable because of low thermal stress factor, high activation, and high swelling above 60 dpa. It does not extrapolate to reactor. No reasons found to think that austenitic steel reduces risk. Primary Coolant should be Helium. Only with this inert gas the potential for chemical reactions between the coolant and the beryllium or liquid metal breeders can be avoided, and the operating temperature of the ferritic structure can be kept above 300°C to minimize the impact of neutron-induced damage.
Base Breeding Blanket and Testing Strategy In FNF (con’t) • The Two Breeding Blanket Concepts preferred by the US are: • The Dual Coolant Lithium Lead Concept (DCLL) with RAFS and SiC FCI • The Helium Cooled Ceramic Breeder (HCCB) with RAFS • These concepts are relatively more mature and provide a more promising pathway toward attractiveness compared to other concepts. • These two concepts are recommended for testing and for Base Breeding Blanket on FNF • US can not test many concepts because the cost of R&D, design and analysis, and mockup testing for any given concept to qualify a test module for testing is large (~ $80 million). (Screening of many concepts is better done by the 7 international partners on ITER). • The concepts for the Base Breeding Blanket should be the same as those being tested, i.e. DCLL and HCCB, but run initially at reduced parameters/performance. • Provide important data on failure modes/effects/rates and speed up the “reliability growth” phase which is very demanding and time consuming. • Both port-based and base blanket can have “testing” missions, with base blanket operating in a more conservative mode and port-based blankets more highly instrumented and specialized for specific experimental missions.
Example of Fusion Nuclear Facility (FNF) Device Design Option:Standard Aspect Ratio (A=3.5) with demountable TF coils (GA design) • High elongation, high triangularity double null plasma shape for high gain, steady-state plasma operation Plate constructed copper TF Coils which enables… • TF Coil joint for complete disassembly and maintenance • OH Coil wound on the TF Coil to maximize Volt-seconds
Another Option for FNF Design: Small Aspect Ratio (ST) Smallest power and size, Cu TF magnet, Center Post (Example from Peng et al, ORNL) R=1.2m, A=1.5, Kappa=3, Pfusion=75MW ST-VNS Goals, Features, Issues, FNST Mtg, UCLA, 8/12-14/08
Reliability / Availability / Maintainability (RAM) RAM, particularly for nuclear components, is one of the most challenging issues for fusion. A – A fusion device has many major components: Availability required for each component needs to be high B – Blanket, divertor and other FNST components are located INSIDE the Vacuum Vessel: Many failures (e.g. coolant leak) require immediate shutdown (shorter MTBF) Repair/replacement takes long time (longer MTTR) Shorter MTBF and longer MTTR result in Lower Availability Availability = MTBF / (MTBF+MTTR) A primary goal of FNF is to solve the RAM issue by providing for “reliability growth” testing and maintenance experience. Reliability Growth testing requires high fluence (> 6 MW-y/m2) Fluence = Wall Load x calendar time x availability This requires that FNF itself has reasonably high availability (For Wall Load = 1 MW/m2 availability needs to be 30% to get 6 MW-y/m2 in 20 calendar years) But achieving a reasonable Availability in the FNF device is by itself a challenge. Important Consideration for FNF Device Design and R&D R&D for both Base and Test Breeding blankets for FNF is critical RAM is a complex topic for which the fusion field does not have an R&D program or dedicated experts. A number of fusion engineers tried over the past 3 decades to study it and derive important guidelines for FNST and Fusion development.
DEMO Availability of 50% Requires Blanket Availability ~88% (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 and blanket MTBF must be > 11 years!)
Obtainable Blanket System Availability for Different Testing Fluences and Test Areas(using standard reliability growth methodology) MTTR = 1 month 1 failure during the test 80 blanket modules in blanket system Experience factor = 0.8Confidence Level = 50% Test area per test article = 0.5 m2 Neutron wall load = 2 MW/m2 Test Area (m2) (m2) Level of Confidence based on Figure 15-2.2 in "FINESSE: A Study of the Issues, experiments and Facilities for Fusion Nuclear Technology Research & Development, Chapter 15 Reliability Development Testing Impact on Fusion Reactor Availability", Interim report, Vol. IV, PPG-821, UCLA, 1984. It is a challenge to do enough “reliability growth” testing to ensure 88% Blanket Availability: 1- “Cumulative” testing fluence of > 6 MW∙y/m2 2- Number of test modules per concept ~ 10-20 (two concepts require ~ 20 – 40 m2)
An optimal pathway for FNST development involves ITER and FNF D E M O Role of FNF (CTF/VNS) 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 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 Sub-Modules/Modules Modules/Sectors Modules • FNF is needed to do Stages II (Engineering Feasibility) and III (Reliability Growth) • FNF must be small-size, low fusion power (< 150 MW), hence, a driven plasma with Cu magnets. • ITER can do only Stage I, so Why do ITER TBM? • Screening/scoping better done with international partners. Cost of R&D prior to fusion testing is high. US can not do more than 2 concepts. • US will gain information from all parties programs (for six other concepts). This information can not practically be generated any other way. • Operating cost of ITER already paid for. To do scoping on FNF would take 3-4 years of operation at operating cost of ~ $200 Million/yr.
The most Challenging Phase of Fusion Development still lies ahead – the development of Fusion Nuclear Science and Technology is the Biggest GAP Achieving high availability is a challenge for Magnetic Fusion Concepts Device has many components Blanket/PFC are located inside the vacuum vessel Tritium available for fusion development other than ITER is rapidly diminishing Any DT fusion development facility other than ITER must breed its own tritium, making the Breeding Blanket an Enabling Technology Where will the initial inventory for the world DEMOs (~ 10 kg per DEMO) come from? How many DEMOs in the world? FNF is a Required and Exciting Step in Fusion Development. (Building FNF in the US, parallel to ITER, is a most important element in restoring US leadership in the world fusion program.) Each country aspiring to build a DEMO will most likely need to build its own FNF — not only to have verified breeding blanket technology, but also to generate the initial tritium inventory required for the startup of DEMO. We must start now the R&D modeling and testing in non-fusion facilities for US Selected Blanket Concepts. This R&D is needed prior to testing in ANY fusion facility. What is needed to qualify a test module for ITER is the same as that required for a test module, or a base breeding blanket, on FNF. Such R&D takes > 10 years.