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Fusion Nuclear Technology Develo

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					  Fusion Nuclear Technology
Development and the Role of CTF
       (and ITER TBM)

                      Mohamed Abdou
         Distinguished Professor of Engineering and Applied Science
       Director, Center for Energy Science and Technology (CESTAR)
   Director, Fusion Science and Technology Center (
               University of California, Los Angeles (UCLA)

     Presented at Workshop on CTF, Culham Conference Centre
              Culham, United Kingdom, May 22-23, 2007
Fusion Nuclear Technology Development
and the Role of CTF/VNS (and ITER TBM)
1. What is Fusion Nuclear Technology?
2. Brief Statement of Technical Issues and Role of Fusion Testing
3. Framework for FNT Development and Requirements
     -    Stages
     -    Parameters
4. Role of ITER TBM
5. Top Level Issues for FNT Development Facilities
     -    Reliability / Maintainability / Availability (and Reliability Growth
     -    Tritium Consumption and Supply
6. Technical Details on Parameters Required for VNS/CTF
     -    Wall Load
     -    Steady State Plasma
     -    Fluence
     -    Test Area
7. Issues yet to be resolved for CTF
         Fusion Nuclear Technology (FNT)
               Fusion Power & Fuel Cycle Technology
FNT Components from the edge of the
Plasma to TF Coils (Reactor “Core”)
1. Blanket Components (includ. FW)
2. Plasma Interactive and High Heat Flux
  a. divertor, limiter
  b. rf antennas, launchers, wave guides, etc.
3. Vacuum Vessel & Shield Components
Other Components affected by the
Nuclear Environment
4. Tritium Processing Systems
5. Instrumentation and Control Systems
6. Remote Maintenance Components
7. Heat Transport and Power Conversion
Notes on FNT:
• The Vacuum Vessel is outside the
  Blanket (/Shield). It is in a low-
  radiation field.
• Vacuum Vessel Development for
  DEMO should be in good shape
  from ITER experience.
• The Key Issues are for
  Blanket / PFC.
• Note that the first wall is an
  integral part of the blanket (ideas
  for a separate first wall were
  discarded in the 1980’s). The
  term “Blanket” now implicitly
  includes the first wall.
• Since the Blanket is inside of the
  vacuum vessel, many failures
  (e.g. coolant leak from module)
  require immediate shutdown and
  repair/replacement.                   Adaptation from ARIES-AT Design
          Pillars of a Fusion Energy System

1. Confined and Controlled
   Burning Plasma (feasibility)

2. Tritium Fuel Self-Sufficiency

3. Efficient Heat Extraction and
   Conversion (attractiveness)

4. Safe and Environmentally        The Blanket is THE
   Advantageous                    KEY component
   (feasibility/attractiveness)    and determines the
                                   critical path to
5. Reliable System Operation       DEMO

  Yet, No fusion blanket has ever been built or tested!
 R&D Tasks to be Accomplished Prior to Demo
  1) Plasma
    - Confinement/Burn              - Current Drive/Steady State
    - Disruption Control            - Edge Control
  2) Plasma Support Systems
    - Superconducting Magnets       - Fueling       - Heating
  3) Fusion Nuclear Technology Components and Materials
     [Blanket (including First Wall), Divertors, rf Launchers]
    - Materials combination selection and configuration optimization
    - Performance verification and concept validation
    - Show that the fuel cycle can be closed (tritium self-sufficiency)
    - Failure modes and effects
    - Remote maintenance demonstration
    - Reliability growth
    - Component lifetime
  4) Systems Integration

                    Where Will These Tasks be Done?!
• Burning Plasma Facility (ITER) and other plasma devices will address 1, 2, & much of 4
• How and Where Will Fusion Nuclear Technology (FNT) be developed?
         FNT Development Issues and Pathways
 Numerous technical studies were performed over the past 30 years in the US and
  worldwide to study issues, experiments, facilities, and pathways for FNT
  development. (This is probably the most studied subject in fusion development)
 This is an area where the US has played a major leadership role in the world program
  and provided major contributions such as engineering scaling laws for testing,
  VNS/CTF concept, and blanket designs
 These studies involved many organizations (universities, National Labs, Industry, and
  utilities) and many scientists, engineers, and plasma physicists. Industry participation
  was particularly very strong from Fission and Aerospace and they provided
  substantial contributions.
 Examples of Major Studies on FNT/Blanket
     –   Blanket Comparison and Selection Study (1982-84, led by ANL)
     –   FINESSE Study (1983-86, led by UCLA)
     –   IEA Study on VNS/CTF (1994-96 US, EU, J, RF)
     –   ITER TBM (1987-2007) , US ITER TBM (2003-2007)
 Other studies that provided important input: DEMO Study (led by ANL 1981-1983)
  and many Power Plant Studies (UWMAKs, STARFIRE, ARIES, others in EU,J,RF)
 Many Planning activities discussed FNT and provided input (TPA, FESAC, etc)

  These Studies resulted in important conclusions and illuminated the
               pathways for FNT and fusion development
 Summary of Critical R&D Issues for Fusion Nuclear Technology

1.   D-T fuel cycle tritium self-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, passive coils, doubling time
2. Tritium extraction and inventory in the solid/liquid breeders
   under actual operating conditions
3. Thermomechanical loadings and response of blanket and PFC
   components under normal and off-normal operation
4. Materials interactions and compatibility
5. Identification and characterization of failure modes, effects, and
   rates in blankets and PFC’s
6. 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
             Blanket systems are complex and have many
            integrated functions, materials, and interfaces
[18-54] mm/s                [0.5-1.5] mm/s
                                                                   Neutron Multiplier
                                                                   Be, Be12Ti (<2mm)

                                                           Tritium Breeder
                                                           Li2TiO3 (<2mm)
PbLi flow

                                                                        First Wall
                                                                      (RAFS, F82H)
                                       Surface Heat Flux
                                       Neutron Wall Load
                 Fusion environment is unique and complex:
                   multi-component fields with gradients
    Neutrons (fluence, spectrum, temporal and                Particle Flux (energy and density,
     spatial gradients)                                        gradients)
      • Radiation Effects (at relevant temperatures,          Magnetic Field (3-component with
         stresses, loading conditions)
      • Bulk Heating
                                                                  • Steady Field
      • Tritium Production
                                                                  • Time-Varying Field
      • Activation
                                                              Mechanical Forces
    Heat Sources (magnitude, gradient)                           • Normal/Off-Normal
       •    Bulk (from neutrons and gammas)
       •    Surface
                                                              Thermal/Chemical/Mechanical/
    Synergistic Effects                                       Electrical/Magnetic Interactions
       •    Combined environmental loading conditions
       •    Interactions among physical elements of components

    Multi-function blanket in multi-component field environment leads to:
    - Multi-Physics, Multi-Scale Phenomena        Rich Science to Study
    - Synergistic effects that cannot be anticipated from simulations & separate effects
      tests. Even some key separate effects in the blanket can not be produced in non-fusion
     facilities (e.g. volumetric heating with gradients)

      A true fusion environment is ESSENTIAL to activate mechanisms that
           cause prototypical coupled phenomena and integrated behavior
    Types of experiments, facilities and modeling for FNT

                  Theory/Modeling                                    Design Codes

           Separate          Multiple          Partially
Basic                                                             Integrated          Component
            Effects        Interactions       Integrated

                                                           •Fusion Env. Exploration Design
                       Phenomena Exploration               •Concept Screening        Verification &
                                                           •Performance Verification Reliability Data

    Non-Fusion Facilities
     (non neutron test stands,
     fission reactors and accelerator-based
     neutron sources)

                                                  Testing in Fusion Facilities
• Non fusion facilities (e.g. non-neutron test stands, fission reactors and neutron
  sources) have important roles
• Testing in Fusion Facilities is NECESSARY for multiple interactions, partially
  integrated, integrated, and component tests
                           Stages of FNT Testing in Fusion Facilities
                                                  Engineering Feasibility
                                                                                             Component Engineering                     E
       Fusion “Break-in” &                                                                      Development &
                                                     & Performance                                                                     M
       Scientific Exploration                                                                  Reliability Growth

                Stage I                                   Stage II                                    Stage III
     0.1 – 0.3 MW-y/m2                                1 - 3 MW-y/m2                            > 4 - 6 MW-y/m2
                                                        1-2 MW/m2,                                  1-2 MW/m2,
     0.5 MW/m2, burn > 200 s
                                                 steady state or long pulse                  steady state or long burn
                                                     COT ~ 1-2 weeks                             COT ~ 1-2 weeks

      Sub-Modules/Modules                                  Modules                               Modules/Sectors

• Initial exploration of coupled            • Uncover unexpected synergistic            • Identify lifetime limiting failure modes
  phenomena in a fusion environment           effects coupled to radiation                and effects based on full environment
                                              interactions in materials, interfaces,      coupled interactions
• Uncover unexpected synergistic effects,
                                              and configurations
  Calibrate non-fusion tests                                                            • Failure rate data: Develop a data base
                                            • Verify performance beyond beginning         sufficient to predict mean-time-
• Impact of rapid property changes in
                                              of life and until changes in properties     between-failure with confidence
  early life
                                              become small (changes are substantial
                                                                     2                  • Iterative design / test / fail / analyze /
• Integrated environmental data for           up to ~ 1-2 MW · y/m )
                                                                                          improve programs aimed at reliability
  model improvement and simulation
                                            • Initial data on failure modes & effects     growth and safety
                                            • Establish engineering feasibility of      • Obtain data to predict mean-time-to-
• Develop experimental techniques and
                                              blankets (satisfy basic functions &         replace (MTTR) for both planned
  test instrumentation
                                              performance, up to 10 to 20 % of            outage and random failure
• Screen and narrow the many material         lifetime)
                                                                                        • Develop a database to predict overall
  combinations, design choices, and
                                            • Select 2 or 3 concepts for further          availability of FNT components in
  blanket design concepts
                                              development                                 DEMO
  Fusion “Break-in” & Scientific Exploration
                                 Stage I

            0.1 – 0.3 MW-y/m2,      0.5 MW/m2, burn > 200 s


 Initial exploration of coupled 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
     Engineering Feasibility & Performance
                               Stage II

1 - 3 MW-y/m2, 1-2 MW/m2, steady state or long pulse, COT ~ 1-2 weeks


 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
    Component Engineering Development &
            Reliability Growth
                               Stage III

> 4 - 6 MW-y/m2, 1-2 MW/m2, steady state or long burn, COT ~ 1-2 weeks

 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
FNT Requirements for Major Parameters for Testing in Fusion Facilities with
         Emphasis on Testing Needs to Construct DEMO Blanket
 - These requirements have been extensively studied over the past 20 years, and they have been agreed to internationally
   (FINESSE, ITER Testing Blanket Working Group, IEA-VNS, etc.)
 - Many Journal Papers published (>35), e.g. IEA-VNS Study Paper (Fusion Technology, Vol. 29, Jan 1996)

                                            Parameter                                                        Value
    Neutron wall load (MW/m2)                                                                                1 to 2
    Plasma mode of operation                                                                             Steady State
    Minimum COT (periods with 100% availability) (weeks)                                                     1 to 2

    Neutron fluence at test module (MW·y/m2)
     Stage IC: initial fusion break-in (less demanding requirements than II & III)                          ~0.1- 0.3
     Stage II: concept performance verification (engineering feasibility)                                    1 to 3
              d                                                                                                     d
     Stage III : component engineering development and reliability growth                                    4 to 6

    Total “cumulative” neutron fluence experience (MW·y/m2)                                                    >6
    Total test area (m2)                                                                                       >10
    Total test volume (m3)                                                                                     >5
    Magnetic field strength (T)                                                                                >4
    a - Prototypical surface heat flux (exposure of first wall to plasma is critical)
    b - For stages II & III. If steady state is unattainable, the alternative is long plasma burn with plasma duty cycle >80%
    c - Initial fusion break-in has less demanding requirements than stages II & III
    d - Note that the fluence is not an accumulated fluence on “the same test article”; rather it is derived from testing “time”
    on “successive” test articles dictated by “reliability growth” requirements
                ITER TBM is a Necessary First Step in Fusion Environment
                   Testing to enable future Engineering Development                                                                    D
      Role of ITER TBM
                                                  Engineering Feasibility
                                                                                             Component Engineering                     E
                                                                                                Development &
       Fusion “Break-in” &                           & Performance                             Reliability Growth                      M
       Scientific Exploration                          Verification
                Stage I                                   Stage II                                    Stage III
     0.1 – 0.3 MW-y/m2                               1 - 3 MW-y/m2                             > 4 - 6 MW-y/m2
                                                        1-2 MW/m2,                                  1-2 MW/m2,
     0.5   MW/m2,   burn > 200 s                steady state or long pulse                  steady state or long burn
                                                     COT ~ 1-2 weeks                             COT ~ 1-2 weeks
      Sub-Modules/Modules                                  Modules                               Modules/Sectors
• Initial exploration of coupled            • Uncover unexpected synergistic            • Identify lifetime limiting failure modes
  phenomena in a fusion environment           effects coupled to radiation                and effects based on full environment
                                              interactions in materials, interfaces,      coupled interactions
• Uncover unexpected synergistic effects,
                                              and configurations
  Calibrate non-fusion tests                                                            • Failure rate data: Develop a data base
                                            • Verify performance beyond beginning         sufficient to predict mean-time-
• Impact of rapid property changes in
                                              of life and until changes in properties     between-failure with confidence
  early life
                                              become small (changes are substantial
                                                                     2                  • Iterative design / test / fail / analyze /
• Integrated environmental data for           up to ~ 1-2 MW · y/m )
                                                                                          improve programs aimed at reliability
  model improvement and simulation
                                            • Initial data on failure modes & effects     growth and safety
                                            • Establish engineering feasibility of      • Obtain data to predict mean-time-to-
• Develop experimental techniques and
                                              blankets (satisfy basic functions &         replace (MTTR) for both planned
  test instrumentation
                                              performance, up to 10 to 20 % of            outage and random failure
• Screen and narrow the many material         lifetime)
                                                                                        • Develop a database to predict overall
  combinations, design choices, and
                                            • Select 2 or 3 concepts for further          availability of FNT components in
  blanket design concepts
                                              development                                 DEMO
Critical Factors in Deciding where to
   do Blanket / FNT Fusion Testing
 • Tritium Consumption / Supply Issue
 • Reliability / Maintainability / Availability Issue
 • Cost, Risk, Schedule

 • The Key FNT Testing Requirements are :
    - Fusion Power only 20-30 MW
    - Over about 10m2 of surface area (with exposure to plasma)
    - With Steady State Plasma Operation (or plasma cycle >80%)
    - Testing Time on successive test articles equivalent to neutron
    fluence “experience” of ~ 6 MW • y/m2
              What is CTF (VNS)?
• The idea of CTF is to build a small size, low fusion power
  DT plasma-based device in which Fusion Nuclear
  Technology 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 FNT
    - In MFE: small-size, low fusion power can be obtained in a low-Q plasma

    - Equivalent in IFE: reduced target yield and smaller chamber radius.

• This is a faster, much less expensive approach than
  testing in a large, ignited/high Q plasma device for which
  tritium consumption, and cost of operating to high fluence
  are very high (unaffordable!, not practical).
Tritium Consumption in Large and Small Power DT Devices
                        AND Tritium Supply Issue
        AND Impact on the Path to FNT Development

  Note: Projections of world tritium supply available to fusion for various scenarios were
        generated by Scott Willms, including information from Paul Rutherford’s 1998 memo
        on “Tritium Window”, and input from M. Abdou and D. Sze.
Projections for World Tritium Supply Available to Fusion
                Reveal Serious Problems
  Projected Ontario (OPG) Tritium


                                                                                                              CANDU Supply
                                    20                                                                        w/o Fusion
  Inventory (kg)

                                                    World Max. tritium supply is 27 kg
                                                Tritium decays at a rate of 5.47% per year

                                         2000     2010               2020                  2030                   2040

Tritium Consumption in Fusion is HUGE! Unprecedented!
       55.8 kg per 1000 MW fusion power per year
Production & Cost:
CANDU Reactors: 27 kg from over 40 years, $30M/kg (current)
Fission reactors: 2–3 kg per year, at a cost of ~$200M/kg
It takes tens of fission reactors to supply one fusion reactor.
$84M-$130M per kg, per DOE Inspector General*
*DOE Inspector General’s Audit Report, “Modernization of Tritium Requirements Systems”, Report DOE/IG-0632, December 2003,
available at
             Projections for World Tritium Supply Available to Fusion for
                           Various Scenarios (Willms, et al)
                                                                    5 yr, 100 MW, 20% Avail, TBR 0.6
                                                                    5 yr, 120 MW, 30% Avail, TBR 1.15
                                                                    10 yr, 150 MW, 30% Avail, TBR 1.3
   Projected Ontario (OPG) Tritium Inventory (kg)


                                                                                                                                            Candu Supply
                                                                                                                                            w/o Fusion

                                                                                              1000 MW Fusion,                          ITER-FEAT (2004
                                                                                              10% Avail, TBR 0.0                       start) + CTF


                                                            See calculation assumptions in
                                                                                                                             (2004 start)

                                                            Table S/Z
                                                     1995    2000       2005       2010      2015       2020       2025   2030    2035      2040     2045
• World Tritium Supply would be Exhausted by 2025 if ITER were to run at 1000 MW fusion power
  with 10% availability
• Large Power DT Fusion Devices are not practical for blanket/PFC development.
• We need 5-10 kg of tritium as “start-up” inventory for DEMO (can be provided from CTF operating with
  TBR > 1 at later stage of operation)
• Blanket/PFC must be developed in the near term prior to DEMO (and we cannot wait
  very long for blanket/PFC development even if we want to delay DEMO).
                                                                                 Canadian + Korean
                                                                                 Inventory without
                                                                                 supply to fusion

                                                                          Canadian + Korean
                                                                          Inventory with ITER

Updated projections of Canadian + Korean tritium supply and consumption using ITER current schedule. (From
                 Scott Willms [March 2007]). Notes & assumptions given on a separate slide.
    ITER Impact on Canadian/Korean Candu Tritium Inventory (March 2007)
                                                     (from Scott Willms, LANL)
•    Following the methodology developed for the Snowmass and 35-year fusion development plan exercises, the impact
     of ITER (the seven party agreement signed 11/07) on tritium available from both Canada and Korea was analyzed.
•    The assumptions were:
      –   Use the same assumption for Canadian tritium as was used for the 35-yr development plan
      –   In addition to the Canadian tritium, Korean tritium is available for fusion (about a 25% additional amount of tritium)
      –   ITER has a 2 kg tritium working inventory which is built up over two years beginning in 2018
      –   ITER first plasma is 2016 with 3 yr HH, 1 yr DD following by tritium operations
      –   ITER tritium operations are 6 yr followed by 1 year maintenance (no tritium burned) followed by 10 year tritium
      –   The first 10 year campaign includes three yr HH, 1 yr DD and then builds to 1.08 kg tritium burned per year over a five year period,
          then remains flat to the end of the first 10 years (modification of scenario communicated by Janeschitz at Snowmass 2002)
      –   The second 10 years burns 1.43 kg tritium per year for each of the 10 years. This builds the wall irradiation to 0.3 MW-yr/m2
          (neutrons) average over a 680 m2 wall
      –   Between the two 10-yr campaigns there is a one year maintenance phase which presumably includes a first wall replacement. The
          first 10 year would not irradiate the first wall to 0.3 MW-yr/m2. The new first wall installed at the beginning of the second 10-yr
          increases from 0 to 0.3 MW-yr/m2 linearly over the second 10 yr.
      –   At the end of ITER a total of 1 kg of tritium is lost to waste and 1 kg of tritium is returned to Canada/Korea
      –   The only demand on the Canadian/Korean tritium is 0.1 kg/yr for sales and ITER. That is, there is no accounting for other demands
          on this tritium such as CTF or Demo.
      –   There is no tritium breeding in ITER
      –   Note: There has been no signaling from Korea that they will supply tritium to ITER. They are only recovering tritium to get it out of
          their heavy water. Canada assisted Korea with the installation of their tritium recovery system, and it is not known what contractual
          agreements they may have. Korean tritium sales, if they took place, would be in competition with Canada.

•    The results on the following figure show:
      –   Upper Curve: The Canadian/Korean tritium inventory without fusion. This assumes the only demand on this tritium is decay and 0.1
          kg/yr sales.
      –   Middle Curve: The Canadian/Korean tritium inventory with the above + ITER
      –   Lower Curve: The yearly ITER transactions with the Canadian/Korean tritium due to ITER tritium inventory build up (down) + decay +

•    Observations:
      – With these assumptions there is enough tritium for ITER, and about 5 kg of tritium would remain at the end of ITER
      – The tritium supply would not accommodate any significant extension of ITER, loss of tritium or significant fusion
         experiment requiring tritium
      – There is a marginal amount of tritium remaining to startup one Demo, and tritium breeding on that one machine would
         have to work “out of the box”
             Reliability / Maintainability / Availability
                   Critical Development Issues

    Unavailability = U(total) = U(scheduled) + U(unscheduled)

                      This you design for   This can kill your DEMO and your future

Scheduled Outage:
  Planned outage (e.g. scheduled maintenance of components, scheduled
  replacement of components, e.g. first wall at the end of life, etc.).
  This tends to be manageable because you can plan scheduled maintenance /
  replacement operations to occur simultaneously in the same time period.

Unscheduled Outage: (This is a very challenging problem)
  Failures do occur in any engineering system. Since they are random they tend
  to have the most serious impact on availability.

This is why “reliability/availability analysis,” reliability testing, and
“reliability growth” programs are key elements in any engineering
             Availability (Due to Unscheduled Events)
  Availability: =                           i represents a component
                  1   Outage Risk
     (Outage Risk) i = (failure rate) i • (mean time to repair) i=
               MTBF = mean time between failures = 1/failure rate
               MTTR = mean time to repair

• A Practical Engineering System must have:
 1. Long MTBF: have sufficient reliability
     - MTBF depends on reliability of components.
            One can estimate what MTBF is NEEDED from “availability allocation
            models” for a given availability goal and for given (assumed) MTTR.
            But predicting what MTBF is ACHIEVEABLE requires real data
            from integrated tests in the fusion environment.

 2. Short MTTR: be able to recover from failure in a short time
     - MTTR depends on the complexity and characteristics of the system (e.g.
       confinement configurations, component blanket design and configuration,
       nature of failure). Can estimate, but need to demonstrate MTTR in fusion
       test facility.
Reliability/Maintainability/Availability is one of the remaining
     “Grand Challenges” to Fusion Energy Development.
    FNT R&D is necessary to meet this Grand Challenge.

Need High Power Density/Physics-Technology Partnership
            - High-Performance Plasma                                   Need Low
            - Chamber Technology Capabilities                           Failure Rate

                C  i  replacement cost  O & M
          COE =
                  P fusion  Availability  M  h th
                                              Energy            Need High Temp.
                                              Multiplication    Energy Extraction

          Need High Availability / Simpler Technological and Material Constraints
                                             Need Low Failure Rate:
                                                - Innovative Chamber Technology
                 (1 / failure rate )         Need Short Maintenance Time:
     1 / failure rate  replacemen t time       - Simple Configuration Confinement
                                                - Easier to Maintain Chamber Technology
An Example Illustration of Achieving a Demo Availability of 49%
 (Table based on information from J. Sheffield’s memo to the Dev Path Panel)

Component Num            Failure      MTBF in MTTR             MTTR        Fraction of   Outage Risk Component
                 ber     rate in      years   for              for Minor failures that               Availability
                         hr-1                       Major      failure, hr are Major
Toroidal         16      5 x10-6      23            104        240          0.1          0.098       0.91
Poloidal         8       5 x10-6      23            5x103      240          0.1          0.025       0.97
Magnet           4       1 x10-4      1.14          72         10           0.1          0.007       0.99
Cryogenics       2       2 x10-4      0.57          300        24           0.1          0.022       0.978
Blanket          100     1 x10-5      11.4          800        100          0.05         0.135       0.881
Divertor         32      2 x10-5      5.7           500        200          0.1          0.147       0.871
Htg/CD           4       2 x10-4      0.57          500        20           0.3          0.131       0.884
Fueling          1       3 x10-5      3.8           72         --           1.0          0.002       0.998
Tritium          1       1 x10-4      1.14          180        24           0.1          0.005       0.995
Vacuum          3      5 x10-5     2.28           72          6            0.1           0.002       0.998
Conventional equipment- instrumentation, cooling, turbines, electrical plant ---         0.05        0.952
TOTAL SYSTEM                                                                             0.624       0.615

   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)
 The reliability requirements on the Blanket/FW (in current confinement concepts that
have long MTTR > 1 week) are most challenging and pose critical concerns. These must
  be seriously addressed as an integral part of the R&D pathway to DEMO. Impact on
      ITER is predicted to be serious. It is one of the key DRIVERS for CTF/VNS.

                                                                                          MTBF per Blanket Segment(FPY)
                   MTBF per Blanket System(FPY)   10                                800


                                                   5                                400


                                                                            A         0
                                                       0    1          2        3
                                                           MTTR (Months )

      A = Expected with extensive R&D (based on mature technology and no fusion-specific failure modes
      C = Potential improvements with aggressive R&D
    Reliability/Availability is a challenge to fusion,
        particularly blanket/PFC, development
• Fusion System has many major components (TFC, PFC, plasma heating,
  vacuum vessel, blanket, divertor, tritium system, fueling, etc.)
  - Each component is required to have high availability
• All systems except the reactor core (blanket/PFC) will have reliability data
  from ITER and other facilities
• There is NO data for blanket/PFC (we do not even know if any present blanket
  concept is feasible)
• Estimates using available data from fission and aerospace for unit failure rates
  and using the surface area of a tokamak show:
                 PROBABLE MTBF for Blanket ~ 0.01 to 0.2 yr
                 compared to REQUIRED MTBF of many years

                Need Aggressive “Reliability Growth” Program
          We must have an aggressive “reliability growth” program for the
           blanket / PFC (beyond demonstrating engineering feasibility)
     1) All new technologies go through a reliability growth program
     2) Must be “aggressive” because extrapolation from other technologies
        (e.g. fission) strongly indicates we have a serious CHALLENGE
   Component Technology Facility (CTF)
The mission of CTF is to test, develop, and qualify Fusion
Nuclear Technology Components (fusion power and fuel cycle
technologies) in prototypical fusion power conditions.

The CTF facility will provide the necessary integrated testing
environment of high neutron and surface fluxes, steady state
plasma (or long pulse with short dwell time), electromagnetic
fields, large test area and volume, and high neutron fluence.

The testing program and CTF operation will demonstrate the
engineering feasibility, provide data on reliability /
maintainability / availability, and enable a “reliability growth”
development program sufficient to design, construct, and
operate blankets, plasma facing and other FNT components
for DEMO.
         Major Activities and Example Timeline for
         Fusion Nuclear Technology Development
 YEAR:   07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

         Experiments in Non-Fusion Facilities: Thermal, MHD, Tritium, Fission, Accelerator Neutron Sources, etc.
         Theory, Modeling and Computer Simulation

             Machine Construction                 Phase I: H-H/D-D/D-T                 ?? Extended Phase ??
                 TBM Preparation                  TBM (Fusion “break-in”)

                   Exploration &          Engr.                                               FNT Testing
CTF                  Decision            Design
                                                       Construction     H-H
                                                                               Engineering Feasibility and Reliability Growth

                             System Analysis / Design Studies

Demo                                                                           Engr. Design          Construction      Operation

 ITER TBM Provides Timely Information to CTF                                                                 Arrows indicate
                                                                                                              major points of FNT
 R&D Activities are critical to support effective FNT/Blanket                                                information flow
  testing in ITER and CTF
           Quantification of Test Requirements
              General Observations of FINESSE Study Results

• In many cases, a true integrated test in the strictest sense cannot be performed
  under significantly scaled-down conditions for certain parameters (e.g., power
  density, surface heat load, geometry)
• Under scaled-down environmental conditions, the function of an integrated test
  module has to be divided into two or more “act-alike” tests. Each act-alike test
  emphasizes a group of issues/phenomena.
• While an overlap among the various act-alike tests can be included to account
  for certain interfaces, a concern about possibly missing some phenomena
• Perfect quantitative engineering scaling is not possible because it requires
  complete quantitative models for all (including interactive) phenomena.
• If fusion testing will have to be carried out under scaled-down conditions, then:
    - Engineering scaling needs to continue to be nourished as a key technical
      discipline in fusion.
    - The need for a more thorough understanding of phenomena and more
      analytical modeling will become more critical.
How Many Modules/Submodules Need to Be Tested For Any
            Given One Blanket Concept?
•   Never assume one module, because engineering science for testing shows
    the need to account for:
    1. Engineering Scaling           2. Statistics
    3. Variations required to test operational limits and
    design/configuration/material options
•   US detailed analysis indicates that a prudent medium risk
    approach is to test the following test articles for any given One Blanket
     - One Look-Alike Test Module
     - Two Act-Alike Test Modules
     - (Engineering Scaling laws show that at least two modules are required,
        with each module simulating a group of phenomena)
     - Four supporting submodules (two supporting submodules
         for each act-alike module to help understand/analyze test
     - Two variation submodules (material/configuration/design variations and
        operation limits)
     These requirements are based on “functional” and engineering
       scaling requirements. There are other more demanding
       requirements for “Reliability Growth” (See separate section on this)
            Neutron Wall Load Requirements
• Neutron wall load is a primary source of both heating and nuclear
  reactions in the blanket
    –   Bulking heating
    –   Surface heating
    –   Reaction rate (e.g., tritium production)
    –   Fluence

Neutron wall load requirements determined by:
• Engineering scaling requirements (conclusion: should not scale down by
  more than a factor of 2-3
• Tradeoffs between device availability and wall load for a given testing
  fluence and testing time
               Wall Load and Availability Required to Reach 6 MW•y/m2
                         Goal Fluence in 12 Calendar Years

                 Wall Load (MW/m2)                                  Availability
                            1                                           50%
                            1.5                                         33%
                            2                                           25%
                            2.5                                         20%
         For pulsed plasma operation, this becomes the product of availability and plasma duty cycle. Therefore,
         at any given wall load, higher availability would be required.
 Importance of Steady State Operation for
                   Nuclear Testing

• To substantially increase the capability for
  meaningful nuclear technology testing
• To reduce the failure rate and improve the
  availability of the testing device

- Many papers and presentations on this topic from
 the last 20 years. It is well understood and accepted
 (see, for example,
       Effects of Pulsed Plasma Operation on
                Nuclear Technology Testing

• Time-Dependent Changes in Environmental Conditions for Testing
   –   Nuclear (volumetric) heating
   –   Surface heating
   –   Poloidal magnetic field
   –   Tritium production rate

• Result in Time-Dependent Changes and Effects in Response of Test
  Elements that:
   – Can be more dominant than the steady-state effects for which testing is
   – Can complicate tests and make results difficult to model and understand

Examples of Effects
   –   Thermal conditions
   –   Tritium concentration profiles
   –   Failure modes/fracture mechanism
   –   Time to reach equilibrium
                       COT Requirements

•   Test Schedule Issues

       – It is desirable to complete a test campaign before the machine is shut
         down for a significant period of time

       – The objective of design/test/fix iterative program requires timely data
         acquisition as input to redesign and construction of new test
         modules. It is therefore desirable to complete test campaigns as
         quickly as possible.

•   Requirements on Environmental Control

       – The level of control over conditions within test modules and ancillary
         systems during shutdown is uncertain.

                       Recommended COT for FNT:
                                1-2 weeks
       Device Fluence vs Test Module Fluence
• Must make a distinction between:
    - Fluence achievable at test module ( modules will fail and will be
      replaced. Module Fluence is the “cumulative” experience
      accumulated on successive test articles, in “reliability growth”
    - Test facility “lifetime fluence” (The device itself will need to have a
      longer lifetime than the test articles. The blanket is an exception
      because it is the “object of testing”, depending on testing strategy)
• Benefits to FNT testing as a function of neutron fluence have been
    - Many issues show continuous increase in benefits at higher fluences
    - Some issues show distinct fluence regions of highest benefit
• There is inevitably a long period of fail/replace/fix for test modules
• Time required to perform the three testing stages: The reliability
  growth testing phase is the most demanding on fluence
                          Testing Fluence

• In this study, we derive fluence directly for each of the three stages of
  fusion testing

    Stage I: Scoping (~ 0.1 - 0.3 MW • y/m2)
    Just enough time to explore environment, develop instrumentation, and get
    initial data

    Stage II: Concept Verification (1-3 MW • y/m2)
    1 MW • y/m2 is barely enough to establish engineering feasibility (~10% of
    minimum life)

    Stage III: Engineering Development & Reliability Growth (4-6 MW • y/m2)
    This fluence is derived from detailed analysis of reliability growth testing
                                                      “Reliability Growth”
    Upper statistical confidence level as a function of test time in
    multiples of MTBF for time terminated reliability tests (Poisson

   distribution). Results are given for different numbers of failures.
                                               Number of Failures     0

                                     0.8      TYPICAL                                                             Example,
                                              TEST                         1
                                              SCENARIO                                                            To get 80% confidence
                                                                                                                  in achieving a particular
                  Confidence Level

                                     0.6                                        2                                 value for MTBF, the
                                                                                                                  total test time needed
                                                                                      3                           is about 3 MTBF (for
                                     0.4                                                                          case with only one
                                                                                            4                     failure occurring during
                                                                                                                  the test).

                                        0.0     0.5   1.0   1.5     2.0   2.5   3.0       3.5   4.0   4.5   5.0

                                      Test Time in Multiplies of Mean-Time-Between-Failure (MTBF)
Reference: M. Abdou et. al., "FINESSE: A Study of the Issues, Experiments and Facilities for Fusion Nuclear
Technology Research & Development, Chapter 15 (Figure 15.2-2.) Reliability Development Testing Impact on Fusion
Reactor Availability", Interim Report, Vol. IV, PPG-821, UCLA,1984. It originated from A. Coppola, "Bayesian
Reliability Tests are Practical", RADC-TR-81-106, July 1981.
Achievable DEMO Reactor and Blanket System Availabilities
(for a given confidence level) depend on:
   • Testing Fluence at the Blanket Test Module & No. of test modules
   • Achievable Mean Time to Replace (MTTR) for Blankets
  Findings of Testing Fluence Requirements on
    Achievable Reactor Availability Analyses

• Achieving a “ cumulative” fluence of ~ 5-6 MW • y/m2 at the test
  modules with ~ 6-12 test modules is crucial to achieving DEMO
  reactor availability on the 40% to 50% range with 90% confidence,
• Achieving DEMO reactor availability of 60% with 90% confidence may
  not be possible for any practical blanket test program,
• The mean downtime (MTTR) to recover (or replace) from a random
  failure in the blanket must be on the order of one week or less in order
  to achieve the required blanket and reactor system availabilities, and
• Determining (and shortening) the length of the MTTR (how long it
  takes to replace a failed blanket module) must be by itself one of
  the critical objectives for testing in fusion facilities (e.g. in CTF).
        Obtainable Blanket System Availability with 50%
    Confidence for Different Testing Fluences and Test Areas
                                                               MTTR = 1 month
                                                      70       1 failure during the test
                                                                                            6 MW.yr/m2
                                                               80 blanket modules in
         Obtainable Blanket System Availability (%)

                                                               blanket system
                                                      60       Experience factor =0.8
                                                                                            3 MW.yr/m2


                                                      30                                     1 MW.yr/m2


                                                                                                     Neutron wall load = 2 MW/m2

                                                           0            2            4          6            8         10
                                                                                    Test Area (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.
            Device Surface Area Requirements

• No. of Modules per Specific Design Concept
    – Need for Engineering Scaling and Statistics.
    – A large number of test modules lead to a faster reliability growth and a higher
      precision level.

• Full scale test preferable
    – There are many problems that were solved only after setting up a full scale test.
    – There are also many problems that surfaced only in the full scale test but did not
      show in the reduced scale.
    – Account for neutron flux spatial variation in poloidal direction.

• If each module first wall area is about 1 m2
    – Test area required = (6 – 12) x A (for engineering scaling) m2 per concept.

• If test 3 concepts, use 6 modules per concept; or 2 concepts use 12 modules
  per concept.

            Total test area at the first wall required: > 10 m2
                  Level of Confidence Obtainable for
                     Different Testing Scenarios

    Test Area     # of Test Articles          Test Fluences =              Test Fluences =              Test Fluences =
    (m2)                                        1 MWyr/m2                    3 MWyr/m2                    6 MWyr/m2
                                         0 failure       1 failure    0 failure       1 failure    0 failure       1 failure
                                        during the      during the   during the      during the   during the      during the
                                            test            test         test            test         test            test
        0.5                 1             1.5%             ~0%           5%             ~0%          10%            0.5%
         1                  2             3.6%             ~0%         9.5%            0.5%          17%            1.5%
         5                 10             10.9%           0.7%          30%            5.5%         51.5%            16%
        10                 20             17.8%           1.7%          47%             14%          72%             36%

Neutron wall load = 2 MW/m2
MTBF per module = 26 years
Experience factor = 0.8
(*test fluence of 0.1 MWyr/m2 is too low to consider)

1) Assuming that the reactor has 16 sectors, 80 blanket modules (each module is about 1(toroidal) x 8 (poloida) m2).
     “Engineering scaling” is applied to the test article design in order to have meaningful data extrapolated from a 0.5 m2
2) The irradiation effects on material properties are not considered in the estimation.
3) 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.
     Reliability/Availability is a challenge to fusion, particularly
                      FW/blanket, development
• Fusion System has many major
  components (TFC, PFC, plasma                      CTF base machine avaialbility =30% (MTTR blanket = 2 weeks)
                                                    Demo base machine availability =30% (MTTR blanket = 2 weeks)
  heating, vacuum vessel, blanket,                  Demo base machine availability 50% (MTTR blanket = 2 weeks)
                                                    Demo base machince availability 50% (MTTR blanket= 1 week)
  divertor, tritium system, fueling,
  etc.)                                   0.4
                                                    The base machine includes 10 major components.
 All components except the reactor                 CTF FW area 100 m2 with 64 blanket modules
  core (FW/blanket) will have            0.35       Demo (ITER like FW area 680 m2 and 440
                                                    blanket modules)
  reliability data from ITER and other                                                                       3
  facilities                              0.3        1Availability decreases
 The reliability requirements on the               due to the number of
                                                    module increases
  FW/Blanket are most challenging        0.25
  and pose critical concerns (due to a                                                                        2
  large number of modules). These
  must be seriously addressed as an
  integral part of the R&D pathway to                     1
 Predicting Achievable MTBF                                                   2  Availability increases due to
                                                                                      improved base machine
  (mean-time-between-failure)             0.1                                                        availability
                                                                              3 Availability increases due to a
  requires real data from integrated                                              shortened MTTR for blanket
  tests in the fusion environment.       0.05
                                                0             2           4             6           8             10
      Lifetime of Demo FW/blanket    10 years                    Blanket Module MTBF (year)
Conclusions on Blanket and PFC Reliability Growth

 • Blanket and PFC tests in ITER alone cannot demonstrate DEMO
   availability higher than 4%

 • Blanket and PFC testing in VNS (CTF) allows DEMO blanket system
   and PFC system availability of > 50%, corresponding to DEMO
   availability > 30%

  Recommendations on Availability/Reliability Growth Strategy and Goals

 - Set availability goal for initial operation of DEMO of ~ 30% (i.e. defer some risk)
 - Operate CTF and ITER in parallel, together with other facilities, as
   aggressively as possible
 - Realize that there is a serious decision point with serious consequences
   based on results from ITER and CTF
      • If results are positive proceed with DEMO
      • If not, then we have to go back to the drawing board
       Examples of possible Failure Modes in Blanket/First Wall
           (for solid and liquid breeder blanket concepts)
•     Cracking around a discontinuity/weld
•     Crack on shutdown (with cooling)
•     Solid breeder loses functional capability due to extensive cracking
•     Cracks in electrical insulators (for liquid metal blankets)
•     Cracks, thermal shock, vaporization, and melting during disruptions
•     First wall/breeder structure swelling and creep leading to excessive
      deformation or first wall/coolant tube failure
•     Environmentally assisted cracking
•     Excessive tritium permeation to worker or public areas
•     Cracks in electrical connections between modules
    Our concern is that failure rates may be much higher in fusion blankets because they appear
      to be much more complex than steam generators and the core of fission reactors because
      of the following points:
    • Larger numbers of subcomponents and interactions (tubes, welds, breeder, multiplier,
      coolant, structure, insulators, tritium recovery, etc.).
    • More damaging, higher energy neutrons.
    • Other environmental conditions: magnetic field, vacuum, tritium, etc. (for example, a leak
      from the first wall or blanket module walls into the vacuum system results in failure, while in
      steam generators and fission reactors, continued operation with leaks is often possible).
    • Reactor components must penetrate each other; many penetrations have to be provided
      through the blanket for plasma heating, fueling, exhaust, etc.
    • Ability to have redundancy inside the blanket / first wall system is practically impossible.
                Current physics and technology concepts lead to a
               “narrow window” for attaining Tritium self-sufficiency

                                                          Fusion power             1.5GW
                                                          Reserve time             2 days
                                                          Waste removal efficiency 0.9
                                                          (See paper for details)
                                     td = doubling time
Required TBR

                                           td=1 yr
                                                               Max achievable
                                 td=5 yr                         TBR ≤ 1.15

                      td=10 yr

                                                                  “Window” for
                                                                  Tritium self

                        Fractional burn-up [%]
              Tritium Consumption in ITER

 Here is from a summary of the final design report.
  Link is:

 9.4.3 Fuel Costs
  The ITER plant must be operated, taking into account the available
  tritium externally supplied. The net tritium consumption is 0.4
  g/plasma pulse at 500 MW burn with a flat top of 400 s
 “The total tritium received on site during the first 10 years of
  operation, amounts to 6.7 kg.”
 “whereas the total consumption of tritium during the plant life time
  may be up to 16 kg to provide a fluence of 0.3 MWa/m2 in average
  on the first wall”
 “This corresponds, due to tritium decay, to a purchase of about 17.5
  kg of tritium. This will be well within, for instance, the available
  Canadian reserves.”
  ITER TBM is also of great benefit to CTF/VNS
 Exactly the same R&D and qualification testing for ITER TBM will be
  needed for CTF
    –   Ferritic steel, Ceramic FCI and Breeder, Be development
    –   MHD flow and heat transfer simulation capabilities
    –   Tritium permeation and control technologies
    –   Other safety, fabrication, and instrumentation R&D

   But in ITER costs can be shared with international partners

 ITER should be used for Concept screening and fusion environment
    – Spending years doing screening in CTF will cost hundreds of millions in
      operation. ITER operation costs are already paid for, and shared internationally
    – CTF should be used for engineering development and reliability growth on the
      one or two concepts that look most promising following screening in ITER

 TBM tests in ITER will have prototypical Interactions between the
  FW/Blanket and Plasma, thus complementing tests in CTF (if CTF plasma
  and environment are not exactly prototypical, e.g. highly driven with different
  sensitivity to field ripple, low outboard field with different gradients)
International studies and experts have concluded that
  extensive testing of fusion nuclear components in
 FUSION testing facilities is REQUIRED prior to DEMO

- Non-fusion facilities can and should be used to narrow
  material and design concept options and to reduce the
  costs and risks of the more costly and complex tests in the
  fusion environment. Extensive R&D programs on non-fusion
  facilities should start now.
- However, non-fusion facilities cannot fully resolve any of the
  critical issues for blankets
- There are critical issues for which no significant information
  can be obtained from testing in non-fusion facilities (An
 example is identification and characterization of failure modes, effects and
 rates). Even some key separate effects in the blanket can not be
 produced in non-fusion facilities (e.g. volumetric heating with gradients)

- The Feasibility of Blanket Concepts can NOT be established
  prior to testing in fusion facilities
        Example: Interactions between MHD flow and FCI
         behavior are highly coupled and require fusion
 PbLi flow is strongly influenced by MHD interaction with
  plasma confinement field and buoyancy-driven
  convection driven by spatially non-uniform
  volumetric nuclear heating

 Temperature and thermal stress of
  SiC FCI are determined by this MHD flow
  and convective heat transport processes

 Deformation and cracking of the FCI depend on
  FCI temperature and thermal stress coupled with early-
  life radiation damage effects in ceramics
                                                             FCI temperature, stress
                                                             and deformation
 Cracking and movement of the FCIs will strongly
  influence MHD flow behavior by opening up new
  conduction paths that change electric current profiles

    Similarly, coupled phenomena in tritium
    permeation, corrosion, ceramic breeder
      thermomechanics, and many other
        blanket and material behaviors
 Separate Devices for Burning Plasma and FNT Development, i.e.
  ITER + CTF are more Cost Effective and Faster than a Single
                       Combined Device
    (to change ITER design to satisfy FNT testing requirements is very
       expensive and not practical. To do it in “DEMO” is impossible)

                                  NWL     Fusion     Fluence      Tritium        Tritium
                                          Power     (MW·y/m2)   Consumption   Consumption
                                                                 (TBR = 0)     (TBR = 0.6)
Two Device Scenario
1) Burning Plasma (ITER)          0.55   500 MW        0.1         5 kg          2 kg
2) FNT Testing (CTF)              >1     < 100 MW      >6          33 kg         13 kg
Single Device Scenario
(Combined Burning Plasma +
FNT Testing), e.g. ITER with      >1     910 MW        >6        >305 kg        >122 kg
major modifications (double the
capital cost)

- World Maximum Tritium Supply (mainly CANDU) available for Fusion is 27 kg
- Tritium decays at 5.47% per year
- Tritium cost now is $30M / kg. More tritium will cost $200M / kg.
- There is no external tritium supply to do FNT testing development in a large power
  DT fusion device. FNT development must be in a small fusion power device.
       Engineering Scaling in “Act-Alike” Test
               Modules has Limitations

Engineering scaling laws must be followed
   •    Preserve important Phenomena

Not all parameters can be scaled down simultaneously
   •    Simulation is never perfect
   •    Trade-offs among parameters results

Complex engineering issues are involved
   •    Large uncertainties in individual issues
   •    Value judgements on relative importance of different
        issues and environmental conditions