Fusion Nuclear Science and
Technology Development
and
the Roles of ITER and the Next Step
Fusion Nuclear Facility, FNF (CTF/VNS)
Mohamed Abdou
With Input from: A. Ying, N. Morley, M. Sawan, S. Willms, D. Sze,
C. Wong, S. Malang, R. Kurtz, R. Stoller and the FNST Community
Plenary Talk at the 18th Topical Meeting on the Technology of
Fusion Energy (TOFE), San Francisco, September 30, 2008
1
Fusion Nuclear Science and Technology (FNST)
Development and the Roles of ITER and the Next Step
Fusion Nuclear Facility, FNF (CTF/VNS)
Outline
-
R&D Tasks Prior to DEMO
-
FNST Issues
Framework for FNST Development & Requirements for Fusion Testing
ITER TBM Role and Limitations
Next Step Fusion Nuclear Facility (FNF)
Role, Mission
TBR Requirements, Base Blanket Options and Testing Strategy
Design Options for the FNF Device
- ISSUES that have Major Impact on FNST and Fusion Development:
External Tritium Supply
Reliability, Availability, Maintainability
- Summary
2
Fusion Nuclear Science and Technology (FNST)
Fusion Power & Fuel Cycle Technology
FNST includes the scientific issues and
technical disciplines as well as materials,
engineering and development of fusion
nuclear components:
From the edge of Plasma to TF Coils:
1. Blanket Components (includ. FW)
2. Plasma Interactive and High Heat Flux
Components (divertor, limiter, rf/PFC element, etc)
3. Vacuum Vessel & Shield Components
Other Systems / Components affected
by the Nuclear Environment:
4. Tritium Processing Systems
5. Remote Maintenance Components
6. Heat Transport and Power Conversion
Systems
3
Numerous technical studies were performed over the past 30
years in the US and worldwide to study issues, experiments,
facilities, and pathways for FNST development
These studies resulted in important conclusions and
illuminated the pathways for FNST and fusion development
 This presentation will utilize the results of previous studies, but will
not provide details on the scientific and engineering basis for such
conclusions.
 These studies are documented in many scholarly journal
publications and numerous topical reports. They can be viewed on
the web site: www.fusion.ucla.edu
 Studies of particular importance to this presentation:
– FINESSE Study (1983-86, led by UCLA)
– IEA Study on VNS/CTF (1994-96 US, EU, J, RF)
– ITER TBM (1987-present)
– US ITER TBM Planning and Costing (2003-2007)
– Recent Workshop on FNST held August 12-14, 2008
4
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 Science and Technology (FNST)
-Blanket
- Divertors
- rf (PFC elements)
- VV & Shield
4) Systems Integration
Where Will These Tasks be Done?!
• Burning Plasma Facility (ITER) and other plasma devices will address 1, 2, & much of 4
• The BIG GAP is Fusion Nuclear Science and Technology (FNST)
• Where, How, and When will it be done?
5
Summary of Critical R&D Issues for
Fusion Nuclear Science and Technology (FNST)
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, internal coils, doubling time
2. Tritium extraction and inventory in the solid/liquid breeders
under actual operating conditions
3. Thermomechanical loadings and (MHD) Thermofluid response of
blanket and PFC components under normal and off-normal operation
4. Materials property changes, 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
6
Framework for FNST R&D involves modeling and
experiments in non-fusion and fusion facilities
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
• Experiments in non-fusion facilities are essential and are prerequisites to testing in
fusion facilities
• Testing in Fusion Facilities is NECESSARY to uncover new phenomena, validate the
science, establish engineering feasibility, and develop components
7
Three Stages of FNST Testing in Fusion Facilities
Are Required Prior to DEMO
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 fusion
environment
• Screen and narrow 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 burn
1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks
COT ~ 1-2 weeks
Modules
D
E
M
O
Modules/Sectors
• Establish engineering feasibility • Failure modes, effects, and rates and
mean time to replace/fix components
of blankets (satisfy basic
(for random failures and planned outage)
functions & performance, up to
10 to 20 % of lifetime)
• Iterative design / test / fail / analyze /
• Select 2 or 3 concepts for further improve programs aimed at reliability
growth and safety
development
• Verify design and predict availability
of FNT components in DEMO
Where to do Stages I, II, and III?
8
ITER Provides Substantial Hardware Capabilities
for Testing of Blanket Systems
TBM System (TBM + T-Extrac,
Heat Transport/Exchange…)
ITER has allocated 3
equatorial ports (1.75 x
2.2 m2) for TBM testing
Each port can
accommodate only 2
modules (i.e. 6 TBMs max)
Bio-shield
He pipes to
TCWS
A PbLi loop
Transporter located in
the Port Cell Area
2.2 m
Equatorial Port
Plug Assy.
Vacuum Vessel
TBM
Assy
Fluence in ITER is limited to 0.3 MW-y/m2. ITER can
only do Stage I. ITER TBM is the most effective and
least expensive to do Stage I. But we need another
facility for Stages II & III.
Port
Frame
9
Fusion Nuclear Facility (FNF)
• The idea of FNF (also called VNS, CTF) is to build a small size, low
fusion power DT plasma-based device in which Fusion Nuclear
Science and Technology (FNST) experiments can be performed in the
relevant fusion environment:
1- at the smallest possible scale, cost, and risk, and
2- with practical strategy for solving the tritium consumption and
supply issues for FNST development.
In MFE: small-size, low fusion power can be obtained in a low-Q
(driven) plasma device, with normal conducting Cu magnets
- Equivalent in IFE: reduced target yield (and smaller chamber radius?)
• There are at least TWO classes of Design Options for FNF:
- Tokamak with Standard Aspect Ratio, A ~ 2.8 - 4
- ST with Small Aspect Ratio, A ~ 1.5
10
Critical Factors that have Major Impact on Fusion
Testing and Development Pathway for FNST
1. Tritium Consumption / Supply Issue
2. Reliability / Maintainability / Availability Issue
3. Cost, Risk, Schedule
 The idea of a Fusion Nuclear Facility, FNF (also called VNS, CTF,
etc.) dedicated to FNST testing was born out of the analyses of
these critical factors 20 years ago
 Today, these factors remain the key to defining details of FNF
mission, design, and testing strategy
11
The issue of external tritium supply is serious and has major
implications on FNST (and Fusion) Development Pathway
Tritium Consumption in Fusion is HUGE! Unprecedented!
55.6 kg per 1000 MW fusion power per year
Production in fission is much smaller & Cost is very high:
Fission reactors: 2–3 kg/year
$84M-$130M/kg (per DOE Inspector General*)
Tritium decays at
5.47% per year
CANDU
Supply
w/o Fusion
*www.ig.energy.gov/documents/CalendarYear2003/ig-0632.pdf
CANDU Reactors: 27 kg from over 40 years,
$30M/kg (current)
Tritium Decays at 5.4% per year
 A Successful ITER will exhaust most
of the world supply of tritium.
With ITER:
2016 1st Plasma,
4 yr. HH/DD
 FNST engineering development and
reliability growth stages must be done in
a small fusion power device (FNF) to
minimize tritium consumption (only stage I
fusion break-in can be done in ITER).
 Even FNF has to breed most, or all, of its
own tritium consumption.
Two Issues In Building A DEMO:
1 – Need Initial (startup) inventory of ~10 Kg per DEMO
(How many DEMOS will the world build? And where will startup tritium come from?)
2 – Need Verified Breeding Blanket Technology to install on DEMO
12
FNF has to breed tritium to:
a- supply most or all of its consumption
b- accumulate excess tritium sufficient to provide the tritium inventory required for startup of DEMO
2.0
Required TBR in FNF
Required TBR
1.5
10 kg T available after ITER and FNF
5 kg T available after ITER and FNF
1.0
FNF does not run out of T
0.5
2021 FNF start
From Sawan&Abdou 8/2008
0.0
50
100
150
200
250
300
350
400
Fusion Power of FNF (MW)
13
Situation we are running into with breeding blankets: What we want to
test (the breeding blanket) is by itself An ENABLING Technology
13
Base Breeding Blanket and Testing Strategy In FNF
(Conclusions Derived from FNST Workshop August 12-14, 2008)
 A Breeding Blanket should be installed as the “BASE”
Blanket on FNF from the beginning
– Needed to breed tritium.
– Switching from non-breeding to breeding blanket involves complexity and
long downtime, especially if coolant changes from water to Helium.
– There is no non-breeding blanket for which there is more confidence than a
breeding blanket (all involve risks, all will require development).
– Using base breeding blanket will provide very important information essential
to “reliability growth”. This makes full utilization of the “expensive” neutrons.
– Note that ~ 20m2 of testing area is required per concept. Two concepts need
40m2 which is almost the net surface area available on the outboard of FNF.
 What Material Options to Use For Base Breeding Blanket
– FW and Structural Material: Ferritic Steel only option available by 2030
• Austenitic steel is less suitable because of low thermal stress factor, high
activation, and high swelling above 60 dpa. It does not extrapolate to reactor. No
reasons found to think that austenitic steel reduces risk.
– Primary Coolant should be Helium.
• Only with this inert gas the potential for chemical reactions between the coolant
and the beryllium or liquid metal breeders can be avoided, and the operating
temperature of the ferritic structure can be kept above 300°C to minimize the
impact of neutron-induced damage.
14
Base Breeding Blanket and Testing Strategy In FNF (con’t)
 The Two Breeding Blanket Concepts preferred by the US are:
– The Dual Coolant Lithium Lead Concept (DCLL) with RAFS and SiC FCI
– The Helium Cooled Ceramic Breeder (HCCB) with RAFS
– These concepts are relatively more mature and provide a more promising
pathway toward attractiveness compared to other concepts.
 These two concepts are recommended for testing and for
Base Breeding Blanket on FNF
– US can not test many concepts because the cost of R&D, design and
analysis, and mockup testing for any given concept to qualify a test module
for testing is large (~ $80 million). (Screening of many concepts is better
done by the 7 international partners on ITER).
– The concepts for the Base Breeding Blanket should be the same as those
being tested, i.e. DCLL and HCCB, but run initially at reduced
parameters/performance.
– Provide important data on failure modes/effects/rates and speed up the
“reliability growth” phase which is very demanding and time consuming.
 Both port-based and base blanket can have “testing” missions, with
base blanket operating in a more conservative mode and port-based
blankets more highly instrumented and specialized for specific
experimental missions.
15
Example of Fusion Nuclear Facility (FNF) Device Design Option:
Standard Aspect Ratio (A=3.5) with demountable TF coils (GA design)
• High elongation, high
triangularity double
null plasma shape
for high gain, steadystate plasma
operation
Plate constructed copper TF Coils which enables…
•TF Coil joint for complete disassembly and maintenance
•OH Coil wound on the TF Coil to maximize Volt-seconds
16
Another Option for FNF Design: Small Aspect Ratio (ST)
Smallest power and size, Cu TF magnet, Center Post
(Example from Peng et al, ORNL) R=1.2m, A=1.5, Kappa=3, Pfusion=75MW
WL [MW/m2]
R0 [m]
1.20
A
1.50
Kappa
3.07
Qcyl
4.6
Bt [T]
1.13
Ip [MA]
3.4
3.7
2.0
3.0
2.18
8.2
3.8
Beta_N
10.1
5.9
Beta_T
0.14
0.18
0.28
ne [1020/m3]
0.43
1.05
1.28
fBS
0.58
0.49
0.50
Tavgi [keV]
5.4
10.3
13.3
Tavge [keV]
3.1
6.8
8.1
1.5
HH98
0.50
2.5
3.5
Paux-CD [MW]
15
31
43
ENB [keV]
100
239
294
PFusion [MW]
7.5
75
150
Q
T M height [m]
1.64
T M area [m2]
14
Blanket A [m2]
66
Fn-capture
ST-VNS Goals, Features, Issues, FNST Mtg, UCLA, 8/12-14/08
1.0
0.1
0.76
17
Reliability / Availability / Maintainability (RAM)
•
RAM, particularly for nuclear components, is one of the most challenging issues for
fusion.
A – A fusion device has many major components:
• Availability required for each component needs to be high
B – Blanket, divertor and other FNST components are located INSIDE the Vacuum Vessel:
• Many failures (e.g. coolant leak) require immediate shutdown (shorter MTBF)
• Repair/replacement takes long time (longer MTTR)
• Shorter MTBF and longer MTTR result in Lower Availability
Availability = MTBF / (MTBF+MTTR)
•
A primary goal of FNF is to solve the RAM issue by providing for “reliability growth”
testing and maintenance experience.
•
•
•
•
(For Wall Load = 1 MW/m2 availability needs to be 30% to get 6 MW-y/m2 in 20 calendar years)
But achieving a reasonable Availability in the FNF device is by itself a challenge.
•
•
•
Reliability Growth testing requires high fluence (> 6 MW-y/m2)
Fluence = Wall Load x calendar time x availability
This requires that FNF itself has reasonably high availability
Important Consideration for FNF Device Design and R&D
R&D for both Base and Test Breeding blankets for FNF is critical
RAM is a complex topic for which the fusion field does not have an R&D program or
dedicated experts. A number of fusion engineers tried over the past 3 decades to
study it and derive important guidelines for FNST and Fusion development.
18
DEMO Availability of 50% Requires Blanket Availability ~88%
(Table based on information from J. Sheffield’s memo to the Dev Path Panel)
Fraction of
Outage Risk Component
Component Num Failure
MTBF in MTTR MTTR
ber
rate in
for
for Minor failures that
Availability
years
-1
hr
16
5 x10-6
23
Major
failure,
hr
104
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
Toroidal
Coils
Poloidal
Coils
Magnet
supplies
Cryogenics
Blanket
Divertor
Htg/CD
Fueling
Tritium
System
Vacuum
TOTAL SYSTEM
failure, hr are Major
240
0.1
0.098
0.91
Assuming 0.2 as a fraction of year scheduled for regular maintenance.
Demo Availability = 0.8* [1/(1+0.624)] = 0.49 (Blanket Availability must be .88
and blanket MTBF must be > 11 years!)
19
Obtainable Blanket System Availability (%)
Obtainable Blanket System Availability for Different Testing
Fluences and Test Areas (using standard reliability growth methodology)
70
6 MW.yr/m2
60
MTTR = 1 month
1 failure during the test
80 blanket modules in
blanket system
Experience factor = 0.8
Confidence Level = 50%
3 MW.yr/m2
50
40
Test area per test article =
0.5 m2
30
Neutron wall load = 2 MW/m2
1 MW.yr/m2
20
10
0
0
2
4
6
Test Area (m2)
Test Area (m2)
(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.
It is a challenge to do enough “reliability growth” testing to ensure 88% Blanket Availability:
1- “Cumulative” testing fluence of > 6 MW∙y/m2
2- Number of test modules per concept ~ 10-20 (two concepts require ~ 20 – 40 m2)
20
An optimal pathway for FNST development involves ITER and FNF
Role of FNF (CTF/VNS)
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
Modules
D
E
M
O
Modules/Sectors
 FNF is needed to do Stages II (Engineering Feasibility) and III (Reliability Growth)
– FNF must be small-size, low fusion power (< 150 MW), hence,
a driven plasma with Cu magnets.
 ITER can do only Stage I, so Why do ITER TBM?
– Screening/scoping better done with international partners. Cost of R&D
prior to fusion testing is high. US can not do more than 2 concepts.
– US will gain information from all parties programs (for six other concepts).
This information can not practically be generated any other way.
– Operating cost of ITER already paid for. To do scoping on FNF would take
3-4 years of operation at operating cost of ~ $200 Million/yr.
21
The most Challenging Phase of Fusion Development
still lies ahead – the development of Fusion Nuclear
Science and Technology is the Biggest GAP
 Achieving high availability is a challenge for Magnetic Fusion Concepts
•
•
Device has many components
Blanket/PFC are located inside the vacuum vessel
 Tritium available for fusion development other than ITER is rapidly diminishing
•
•
Any DT fusion development facility other than ITER must breed its own tritium, making the
Breeding Blanket an Enabling Technology
Where will the initial inventory for the world DEMOs (~ 10 kg per DEMO) come from?
How many DEMOs in the world?
 FNF is a Required and Exciting Step in Fusion Development.
(Building FNF in the US, parallel to ITER, is a most important element in restoring
US leadership in the world fusion program.)
•
Each country aspiring to build a DEMO will most likely need to build its own FNF —
not only to have verified breeding blanket technology, but also to generate the initial tritium
inventory required for the startup of DEMO.
 We must start now the R&D modeling and testing in non-fusion facilities for US
Selected Blanket Concepts.
•
This R&D is needed prior to testing in ANY fusion facility. What is needed to qualify a
test module for ITER is the same as that required for a test module, or a base
22
breeding blanket, on FNF. Such R&D takes > 10 years.