Fusion Nuclear Technology
Development and the Role of CTF
(and ITER TBM)
Mohamed Abdou
(web: www.fusion.ucla.edu/abdou/)
Distinguished Professor of Engineering and Applied Science
Director, Center for Energy Science and Technology (CESTAR)
(www.cestar.seas.ucla.edu/)
Director, Fusion Science and Technology Center (www.fusion.ucla.edu/)
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)
Outline
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
Strategy)
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
Components
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
Systems
Notes on FNT:
• The Vacuum Vessel is outside the
Blanket (/Shield). It is in a lowradiation 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
(feasibility)
3. Efficient Heat Extraction and
Conversion (attractiveness)
4. Safe and Environmentally
Advantageous
(feasibility/attractiveness)
5. Reliable System Operation
(attractiveness)
The Blanket is THE
KEY component
and determines the
critical path to
DEMO
Yet, No fusion blanket has ever been built or tested!
R&D Tasks to be Accomplished Prior to Demo
1) Plasma
- Confinement/Burn
- Disruption Control
- Current Drive/Steady State
- 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
scheme
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

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
Synergistic Effects
•
•

Particle Flux (energy and density,
gradients)
Magnetic Field (3-component with
gradients)
• Steady Field
• Time-Varying Field
Mechanical Forces
• Normal/Off-Normal

Thermal/Chemical/Mechanical/
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
Basic
Separate
Effects
Property
Measurement
Multiple
Interactions
Design Codes
Partially
Integrated
Phenomena Exploration
Integrated
Component
•Fusion Env. Exploration Design
Verification &
•Concept Screening
•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
Fusion “Break-in” &
Scientific Exploration
Stage I
0.1 – 0.3 MW-y/m2
 0.5 MW/m2, burn > 200 s
Sub-Modules/Modules
• 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
Verification
Component Engineering
Development &
Reliability Growth
Stage II
Stage III
1 - 3 MW-y/m2
> 4 - 6 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
Modules
• 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
2
up to ~ 1-2 MW · y/m )
• 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
Modules/Sectors
• Identify lifetime limiting failure modes
and effects based on full environment
coupled interactions
• Failure rate data: Develop a data base
sufficient to predict mean-timebetween-failure with confidence
• Iterative design / test / fail / analyze /
improve programs aimed at reliability
growth and safety
• Obtain data to predict mean-time-toreplace (MTTR) for both planned
outage and random failure
• Develop a database to predict overall
availability of FNT components in
DEMO
D
E
M
O
Fusion “Break-in” & Scientific Exploration
Stage I
0.1 – 0.3 MW-y/m2,

0.5 MW/m2, burn > 200 s
Sub-Modules/Modules
 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
Verification
Stage II
1 - 3 MW-y/m2, 1-2 MW/m2, steady state or long pulse, COT ~ 1-2 weeks
Modules
 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
Modules/Sectors
 Identify lifetime limiting failure modes and effects based on full
environment coupled interactions
 Failure rate data: Develop a data base sufficient to predict meantime-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
a
Neutron wall load (MW/m2)
Plasma mode of operation
Minimum COT (periods with 100% availability) (weeks)
Neutron fluence at test module (MW·y/m2)
Stage IC: initial fusion break-in (less demanding requirements than II & III)
Stage II: concept performance verification (engineering feasibility)
d
Stage III : component engineering development and reliability growth
Total “cumulative” neutron fluence experience (MW·y/m2)
Total test area (m2)
Total test volume (m3)
Magnetic field strength (T)
Value
1 to 2
b
Steady State
1 to 2
~0.1- 0.3
1 to 3
d
4 to 6
>6
>10
>5
>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
Role of ITER TBM
Component Engineering
Development &
Reliability Growth
Fusion “Break-in” &
Scientific Exploration
Engineering Feasibility
& Performance
Verification
Stage I
Stage II
Stage III
1 - 3 MW-y/m2
> 4 - 6 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
0.1 – 0.3 MW-y/m2
 0.5
MW/m2,
burn > 200 s
Sub-Modules/Modules
• 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
Modules
• 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
2
up to ~ 1-2 MW · y/m )
• 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
Modules/Sectors
• Identify lifetime limiting failure modes
and effects based on full environment
coupled interactions
• Failure rate data: Develop a data base
sufficient to predict mean-timebetween-failure with confidence
• Iterative design / test / fail / analyze /
improve programs aimed at reliability
growth and safety
• Obtain data to predict mean-time-toreplace (MTTR) for both planned
outage and random failure
• Develop a database to predict overall
availability of FNT components in
DEMO
D
E
M
O
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
18
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
development.
- In MFE: small-size, low fusion power can be obtained in a low-Q plasma
device.
- 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.
Projected Ontario (OPG) Tritium
Inventory (kg)
Projections for World Tritium Supply Available to Fusion
Reveal Serious Problems
30
25
CANDU Supply
20
w/o Fusion
15
World Max. tritium supply is 27 kg
10
Tritium decays at a rate of 5.47% per year
5
0
2000
2010
2020
2030
2040
Year
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 www.ig.doe.gov/pdf/ig-0632.pdf
Projections for World Tritium Supply Available to Fusion for
Various Scenarios (Willms, et al)
Projected Ontario (OPG) Tritium Inventory (kg)
30
CTF
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
25
20
Candu Supply
w/o Fusion
15
1000 MW Fusion,
10% Avail, TBR 0.0
ITER-FEAT (2004
start) + CTF
10
5
0
1995
ITER-FEAT
(2004 start)
See calculation assumptions in
Table S/Z
2000
2005
2010
2015
2020
Year
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:
–
–
–
–
–
–
–
–
–
–
–
–
•
The results on the following figure show:
–
–
–
•
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.
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 +
burn
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
development.
Availability (Due to Unscheduled Events)
1
i represents a component
Availability: =
1   Outage Risk
i
(Outage Risk) i = (failure rate) i • (mean time to repair) i=
MTTR i
MTBFi
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
- Chamber Technology Capabilities
Need Low
Failure Rate
C  i  replacement cost  O & M
COE =
P fusion  Availability  M  h th
Energy
Multiplication
Need High Temp.
Energy Extraction
Need High Availability / Simpler Technological and Material Constraints
(1 / failure rate )
1 / failure rate  replacemen t time
 Need Low Failure Rate:
- Innovative Chamber Technology
 Need Short Maintenance 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
rate in
hr-1
MTBF in MTTR
for
years
Outage Risk Component
16
5 x10-6
23
Major
failure,
hr
104
MTTR
Fraction of
for Minor failures that
failure, hr are Major
240
0.1
0.098
0.91
8
5 x10-6
23
5x103
240
0.1
0.025
0.97
4
1 x10-4
1.14
72
10
0.1
0.007
0.99
2
100
32
4
1
1
2 x10-4
1 x10-5
2 x10-5
2 x10-4
3 x10-5
1 x10-4
0.57
11.4
5.7
0.57
3.8
1.14
300
800
500
500
72
180
24
100
200
20
-24
0.1
0.05
0.1
0.3
1.0
0.1
0.022
0.135
0.147
0.131
0.002
0.005
0.978
0.881
0.871
0.884
0.998
0.995
3
5 x10-5
72
6
0.1
2.28
Conventional equipment- instrumentation, cooling, turbines, electrical plant ---
0.002
0.05
0.624
0.998
0.952
0.615
ber
Toroidal
Coils
Poloidal
Coils
Magnet
supplies
Cryogenics
Blanket
Divertor
Htg/CD
Fueling
Tritium
System
Vacuum
TOTAL SYSTEM
Availability
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)
800
ed
(R
)
600
5
400
200
0
Expected
0
1
2
C
A
0
3
MTBF per Blanket Segment(FPY)
10
N
ee
d
MTBF per Blanket System(FPY)
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.
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)
MISSION
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:
R&D
ITER
CTF
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
TBM Preparation
TBM (Fusion “break-in”)
Exploration &
Decision
Engr.
Design
Construction
H-H
?? Extended Phase ??
FNT Testing
Engineering Feasibility and Reliability Growth
System Analysis / Design Studies
Demo
Engr. Design
 ITER TBM Provides Timely Information to CTF
 R&D Activities are critical to support effective FNT/Blanket
testing in ITER and CTF
Construction
Operation
Arrows indicate
major points of FNT
information flow
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
remains.
• 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
Concept:
- 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
results)
- 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
Importance
• 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
1.5
2
2.5
50%
33%
25%
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, www.fusion.ucla.edu/abdou)
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
desired
– 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”
terminology)
- 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
recognized:
- 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
requirements.
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).
1.0 Results are given for different numbers of failures.
Number of Failures 0
Confidence Level
0.8
TYPICAL
TEST
SCENARIO
Example,
1
To get 80% confidence
in achieving a particular
value for MTBF, the
total test time needed
is about 3 MTBF (for
case with only one
failure occurring during
the test).
2
0.6
3
0.4
4
0.2
0.0
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-Betw een-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 (%)
Obtainable Blanket System Availability with 50%
Confidence for Different Testing Fluences and Test Areas
MTTR = 1 month
1 failure during the test
80 blanket modules in
blanket system
70
60
6 MW.yr/m2
Experience factor =0.8
3 MW.yr/m2
50
40
30
1 MW.yr/m2
20
Neutron wall load = 2 MW/m2
10
0
0
2
4
6
Test Area (m2)
8
10
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
(m2)
0.5
1
5
10
# of Test Articles
1
2
10
20
Test Fluences =
1 MWyr/m2
0 failure
1 failure
during the
during the
test
test
1.5%
~0%
3.6%
~0%
10.9%
0.7%
17.8%
1.7%
Test Fluences =
3 MWyr/m2
0 failure
1 failure
during the
during the
test
test
5%
~0%
9.5%
0.5%
30%
5.5%
47%
14%
Test Fluences =
6 MWyr/m2
0 failure
1 failure
during the
during the
test
test
10%
0.5%
17%
1.5%
51.5%
16%
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)
Note
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
heating, vacuum vessel, blanket,
divertor, tritium system, fueling,
etc.)
 All components except the reactor
core (FW/blanket) will have
reliability data from ITER and other
facilities
 The reliability requirements on the
FW/Blanket are most challenging
and pose critical concerns (due to a
large number of modules). These
must be seriously addressed as an
integral part of the R&D pathway to
DEMO.
 Predicting Achievable MTBF
(mean-time-between-failure)
requires real data from integrated
tests in the fusion environment.
CTF base machine avaialbility =30% (MTTR blanket = 2 weeks)
Demo base machine availability =30% (MTTR blanket = 2 weeks)
Demo base machine availability 50% (MTTR blanket = 2 weeks)
Demo base machince availability 50% (MTTR blanket= 1 week)
0.4
The base machine includes 10 major components.
CTF FW area 100 m2 with 64 blanket modules
Demo (ITER like FW area 680 m2 and 440
blanket modules)
0.35
Availability decreases
due to the number of
module increases
0.3
1
0.25
2
0.2
1
0.15
Availability increases due to
improved base machine
availability
3 Availability increases due to a
shortened MTTR for blanket
2
0.1
0.05
0
Lifetime of Demo FW/blanket
3
 10 years
2
4
6
Blanket Module MTBF (year)
8
10
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
BACKUP SLIDES
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
Required TBR
td = doubling time
td=1 yr
td=5 yr
Fusion power
1.5GW
Reserve time
2 days
Waste removal efficiency 0.9
(See paper for details)
Max achievable
TBR ≤ 1.15
td=10 yr
“Window” for
Tritium self
sufficiency
Fractional burn-up [%]
Tritium Consumption in ITER
 Here is from a summary of the final design report.
Link is:
http://fusion.gat.com/iter/iter-ga/images/pdfs/cost_estimates.pdf
 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
break-in
– 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
environment
 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 earlylife radiation damage effects in ceramics
 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
FCI temperature, stress
and deformation
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
Power
Fluence
(MW·y/m2)
Tritium
Consumption
(TBR = 0)
Tritium
Consumption
(TBR = 0.6)
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
major modifications (double the
capital cost)
>1
910 MW
>6
>305 kg
>122 kg
Two Device Scenario
1) Burning Plasma (ITER)
FACTS
- 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.
Conclusion:
- 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