Challenges and Strategy for Development of
FNST: Blanket/FW & Tritium Fuel Cycle

Mohamed Abdou
Distinguished Professor of Engineering and Applied Science, UCLA
with input from N. B. Morley, A. Ying, S. Smolentsev
and many US and worldwide collaborators over many years

Presentation at the meeting of the NAS Committee for a Strategic Planfor U.S. Burning Plasma Research
February 26, 2018 at the General Atomics facility in La Jolla, California

M. Abdou NAS Committee in La Jolla, CA 02-26-20181

This Talk:• Will not list detailed R&D items. We have done this many times. Many
documents available• The focus is on the critical go/no-go problems for which HOW and
WHERE to perform the R&D is a challenge, yet there is not acredible strategy being adopted, communicated, nor pursued• What is presented here is derived from Many comprehensive studies
performed over 3 decades. Efforts on these studies were hundreds ofman-years because of “free” participation by Aerospace, Nuclear, andother industries, internal funds from many national labs anduniversities, Japan and EU (plus much enthusiasm!). These studies
cannot be redone today. The results of these studies have beenreported in scholarly journals and comprehensive reports.
• Scientific bases and more details on the complex issues andstrategy elements addressed in this talk are provided in selectedreferences listed at the end of this presentation

M. Abdou NAS Committee in La Jolla, CA 02-26-20182

Outline
Introduction/Definitions
I. KEY Challenges/Issues and Required R&D

1. Multiple Effects/Multiple Interactions
2. RAMI (Reliability/Availability/Maintainability/Inspectability)
3. Tritium Fuel Cycle and Tritium Self-Sufficiency
4. External T Supply and Required T Startup Inventory

II. Scientific Framework and Strategy for Fusion Development

1. Role and Features of required non-fusion and fusion facilities
2. FNST Requirements on FNSF Parameters and Features
3. Timing and Stages of FNSF(s), How many FNSF(s) do we need?
4. Solving the paradox of short MTBF/long MTTR and what to do about dpa

III. More on a Plasma-Based Fusion Environment Test Facility (FNSF)

1. What type of facility should FNSF be and what main features andparameters should it have?
2. Options for FNSF Facility: Tokamaks (standard and low aspect ratios, typeof magnets), GDT/mirrors

Summary
M. Abdou NAS Committee in La Jolla, CA 02-26-20183

Fusion Nuclear Science & Technology (FNST)
FNST is the science, engineering, technology and materials
for the fusion nuclear components thatgenerate, control and utilize neutrons, energetic particles & tritium.

In-vessel Components (“Core”)
 Blanket and Integral First Wall Divertor/PFC
 Vacuum Vessel and Shield

Other Nuclear Systems
FNST Core Tritium Fuel Cycle
 Instrumentation & Control Systems
 Remote Maintenance Components
 Heat Transport & Power Conversion Systems
Tritium Fuel
Cycle pervades
entire fusion
system

T storage &management
Impurity separation,
Isotope separation
T wastetreatment

FuelingsystemDT
plasmaExhaustProcessing

PFC & Blanket
T processing
design dependent

PFCs
Blanket4

Neutrons (flux, spectrum, gradients, pulses)- Bulk (volumetric) Heating- Radiation Effects- Tritium Production- Activation and Decay Heat

Heat Sources (thermal gradients, pulses)- Bulk (neutrons)- Surface (particles, radiation)

Particle/Debris Fluxes (energy, density, gradients)
Magnetic Fields (3-components, gradients)- Steady and Time-Varying Field

Mechanical & Electromagnetic Forces- Normal (steady, cyclic) and Off-Normal (pulsed)

Multiple functions, materials,
and many interfaces in highly
constrained system

Fusion Nuclear Environment is Complex & Unique

Combined Loads, Multiple Environmental Effects- Thermal-chemical-mechanical-electrical-magnetic-gravitationalnuclear interactions and multiple/synergistic effects- Interactions among physical elements of components

5Blanket/FW systems are complex and have many
functional materials, joints, fluids, and interfaces
Li, PbLi,
Li-Salt flow

E.g. Ceramic Breeder Based

Neutron MultiplierBe, Be12Ti
Tritium Breeder
Li2TiO3 , Li4SiO4E.g. Liquid Breeder Based

Surface Heat Flux
Neutron Wall Load

First Wall
(RAFS, F82H)
or H
Coolants
Coolants: HeHe,
H202O,
or liquid metal or salt
6Key challenges that must be carefully considered in planning acredible pathway for FNST & Fusion Development• The Fusion Nuclear Environment: Multiple field environment(neutrons, heat/particle fluxes, magnetic field, etc.) with highmagnitude and steep gradients experienced by complex Blanket/FW- lead to yet undiscovered new phenomena due to multiple interactions
and synergistic effects- can not adequately simulate in laboratory facilities or fission reactors- full simulation to uncover phenomena and quantify behavior requires DT
Plasma-based facility (FNSF)• Nuclear heating in a large volume with steep gradients̶̶̶drives temperatures and most FNST phenomena
cannot simulate in laboratory facilities or fission reactors
can be simulated only in DT Plasma-based facility (FNSF)• Complex configuration with FW/Blanket/Divertor inside the vacuum
vessel. Makes the fusion system not fault tolerant and challenging tomaintain. RAMI is a central issue
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I. KEY Challenges/Issues and Required R&D
1. Multiple Effects/Multiple Interactions
2. RAMI (Reliability/Availability/Maintainability/Inspectability)
3. Tritium Fuel Cycle and Tritium Self-Sufficiency
4. External T Supply and Required T Startup Inventory

M. Abdou NAS Committee in La Jolla, CA 02-26-20188Moving forward with Multiple Effects/Multiple Interactions
Experiments and Modelling is NECESSARY to understand andlearn the behavior of blankets in the fusion environment

Example: MHD Thermofluids

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9

Fusion Researchers for 30 years studied Liquid Metal MHD Flow
Behavior in Blankets as if it were PURELY in the Presence of Magnetic
Field (i.e. separate effect). So, the common assumption has been:
Flow is Laminar: the flow velocity profile isstrongly altered by the action of the Lorentz
force leading to flat laminar core with verythin Hartmann and side layers

But we just discovered that what weassumed for 30 years is wrong

M. Abdou NAS Committee in La Jolla, CA 02-26-201810

Discovery: Spatial gradients in nuclear heating & temperature in LM blanket combinedwith 𝒈𝒈 and 𝑩𝑩 lead to New Phenomena that fundamentally alter our understanding of
the MHD Thermofluid behavior, Tritium Transport/Permeation and Materials
Interactions in the blanket in the fusion nuclear environment
lead to Buoyant MHD interactions resulting in an unstable “Mixed Convection” flow regime
Base flow strongly altered leading to velocity
gradients, stagnant zones and even “flow reversal”
UPWARD FLOW

Vorticity Field shows new instabilities that
affect transport phenomena (Heat, T, Corrosion)

DOWNWARD FLOWVg
B

This result is from modeling at limited parameters in idealized geometry.
 Predictions from separate effect tests for the integrated fusion nuclear environment are wrong
 Blankets designed with current knowledge of phenomena and data will not work
M. Abdou NAS Committee in La Jolla, CA 02-26-201811

What do we need to do to investigate “MHD Buoyant
interactions/mixed convection flow” and other phenomena?
• Need to perform multiple effects experiments in which we can observe &characterize MHD mixed convection phenomena & discover new phenomena• Need major initiatives to perform more integrated phenomenological andcomputational modeling using high speed computation (e.g. solve
simultaneously Energy, Maxwell, and Navier-Stokes equations in a coupledmanner, push for high performance parameters e.g. Ha, Gr, Re)

Requirements in Experiments:
1)
2)
3)
4)
5)
6)

Simulation of volumetric heating and high temperature with steep gradients
Provide flexible orientation of the channel flow w.r.t. gravity
Provide sufficient volume inside the magnets to realistically simulate multi-channel flows withmulti-material and geometry representation
Include representative 3-component magnetic fields with gradients
Use Prototypic Materials (e.g. PbLi, RAFM, SiC) and operating conditions (e.g. high T)
Develop instrumentation techniques compatible with high-temperature liquid metals• Designing Laboratory Facilities that satisfy the above Requirements involves
Big challenges that we must confront. Examples are highlighted in the next 2
slides (from UCLA research)
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Multiple effects experiments will necessarily be at scaled down
conditions from blankets in DEMO. How do we preserve phenomena?
• By preserving ratios of forces through the use of relevant non-dimensional parameters
Non-Dimensional Parameters Reynolds Number, 𝑅𝑅𝑅𝑅 =𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝜌𝜌𝜌𝜌𝜌𝜌
=𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝜇𝜇 Hartmann Number, 𝐻𝐻𝐻𝐻 = Grashof Number,

𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓^0.5 = 𝐵𝐵𝐵𝐵̇ 4𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝑔𝑔𝛽𝛽∆𝑇𝑇𝐿𝐿3
𝑔𝑔𝛽𝛽𝑞𝑞𝐿𝐿
𝐺𝐺𝐺𝐺 == 𝜈𝜈2 = 𝜈𝜈2𝜅𝜅
𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓

𝜎𝜎𝜇𝜇• Need to consider these parameters in a coupled manner• What is the “right combinations” of these Dimensionless Parameters to preserve
phenomena? Discovery of the right combinations is R&D by itself.
• Examples of coupled parameters we should attempt to preserve in the experiments:o Ha/Re – determines transition to turbulence in Hartmann layerso𝑟𝑟 =𝐺𝐺𝐺𝐺�𝐻𝐻𝐻𝐻 𝑅𝑅𝑅𝑅

𝑎𝑎 2
- responsible for the shape of velocity and temperature profile𝑏𝑏

in steady mixed-convection flows
o 𝐻𝐻𝐻𝐻 ⁄ 𝐺𝐺𝐺𝐺 – determines transition from 3D to Q2D in MHD mixed-convection flows
M. Abdou NAS Committee in La Jolla, CA 02-26-201813Non-Linear LM MHD Phenomena is difficult to scalefrom experiment to DEMO
(Blanket scaling problem similar to plasma physics!)
DEMO BLANKET: Ha~104, Gr~1012, Re~105
EXPERIMENT:
Ha~103, Gr~109, Re~105
Grand Challenge
How do we scale results from experiments to predicting Blanket behavior in
DEMO?
• Non-linear phenomena (difficult to scale)• Higher Ha will suppress (or strongly modify) turbulence/instabilities• Higher Gr will enhance buoyancy/instabilities• So, what will be the real behavior in the real blanket where both Ha andGr are high?

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Summary of FNST Multiple Effects/Multiple Interactions
Issues and required R&D
Right now, we do not know and cannot predict how the blanket/FW will workin the fusion nuclear environment. This behavior cannot be predicted by synthesizing
results of separate effects; and predictions are wrong.
Pathway Issues and Needed R&D:
• Need to move forward with Multiple Effects/Multiple Interactions Experiments. We mustbuild a number of new laboratory facilities to do the best possible simulation of the
combined effects of the fusion nuclear environment and representative blanket mockups.
• A sequence of progressively more powerful facilities is needed ($5M, $20M, $50M). We
also need several such facilities with different approaches to simulation to be constructedaround the world.
Current status: No such facilities exist in the world. A first-of-a-kind facility is being
completed as an upgrade of the MaPLE (Magnetohydrodynamic PbLi Experiment) facility
at UCLA, in exemplary partnership with EUROfusion, to study MHD thermofluids multipleeffects, material interactions, and tritium transport & permeation.
• But full simulations in the Lab is impossible because volumetric heating can be simulated
only in DT Plasma-based facility. Need to build experimental FNSF
• Extrapolation from lab facilities to FNSF/DEMO is extremely problematic (non-linear
phenomena similar to plasma physics issues). Launching Major 3-D Modelling Initiative is a
MUST
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Reliability/Availability/Maintainability/Inspectability (RAMI) is a serious
challenge that has major impact on priorities and strategy for fusion R&D
Num Failurerequired
MTTR
Fractionof
OutageComponentAvailability
MTBF infor MTTR
each component
needs
tobe Riskhigh Component
berrate infor
for Minor failures that
Availability
years-1Component #failureMTBF
MTTR/type
Fraction
OutageComponenthr
Major
failure, hr are Major
rate
Major
Minor
Failures
Risk
Availability
failure,(1/hr)
(yrs)
(hrs)
(hrs)
Major
hr
16
5 x10-6
104
240
0.1
0.91
Toroidal
0.098
23
Coils
MTBF
– Meantime
between failures 0.97
8 parameters:
5 x10-6
5x103
240
0.1
Two key
Poloidal
23
0.025
MTTR
–
Mean
time
to
repairCoils
4
1 x10-4
72
10
0.1
0.99
Magnet0.007
1.14
supplies
2 x10-4
300
24
0.1
0.978
Cryogenics 2
0.57
0.022
100
1 x10-5
800
100
0.05
0.881
Blanket
11.4
0.135
32
2 x10-5
500
200
0.1
0.871
Divertor
5.7
0.147
-4
4
2 x10
500
20
0.3
0.884
Htg/CD
0.57
0.131
-5
of7250% requires:
1 DEMO
3 x10 availability
-1.0
0.998
Fueling
3.8
0.002
-4
Availability
1  Blanket/Divertor
1 x10
180
24 ~ 87%
0.1
0.995
Tritium
1.14
0.005
System Blanket MTBF >11 years
3
5 x10-5
6
0.1
0.998
Vacuum0.002
 MTTR < 2 2.28
weeks 72
Conventional equipment- instrumentation, cooling, turbines, electrical plant --0.952
0.05
0.615
(Due to unscheduled maintenances)
TOTAL SYSTEM
0.624

Extrapolation from other technologies shows expected MTBF for fusion
blankets/divertor is as short as ̴hours/days, and MTTR ~months
GRAND Challenge: Huge difference between Required and Expected!!

16

Fundamental Reasons why we have Serious Problems withshort MTBF, long MTTR, and very low expected availability
in current fusion “confinement” systems
 Location of Blanket/FW/Divertor inside* the vacuum vessel:
 low fault tolerance  short MTBF Because many failures (e.g. coolantleak) require immediate shutdown, also no redundancy possible.
 long MTTR Because repair & replacement requires breaking “vacuumseal” and many connects / disconnects, and many operations in thelimited access space of tokamaks, stellerators, and other “toroidal/closed”
configurations * The decision to put the blanket inside the vacuum vessel is necessary to protect the vacuum vessel, whichmust be robust and cannot be in high radiation/temperature/stress state facing the plasma.

 Large surface area of the first wall results in high failure rate for a given
unit failure rate per unit length of piping, welds, and joints  short MTBF
Results show: anticipated MTBF is hours/days (required is years), and MTTR is
3-4 months (required is days), and availability is very low < 5%Contrast this to fission reactors:•••

Can continue operation with ~2% of fuel rods with failures (MTBF ~ years)
An entire fuel bundle can be replaced in ~ 2 days (MTTR ~ 2 days).
Fission reactors have been able to achieve 90% availability
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Observations and Suggestions for improving thesituation with RAMI, the Achilles’ Heel issue for fusion
 MTBF/MTTR will be the key issue in determining thefeasibility of plasma confinement configurations andthe feasibility of blanket concepts and material
choices (structure, breeder, insulators, T barriers, etc.)
 Performance, Design Margin, Failure
Modes/Rates should be the focus of FNST R&D
Not a long dpa life
1. Setting goals for MTBF/MTTR is more important
NOW than dpa goals for lifetime of materials(RAFS with 10-20 dpa, 100 ppm He is sufficient for now)

2. R&D should Now focus on:– Scientific understanding of multiple effects, performance and failures so that functions,requirements & safety margins can be achieved, and designs simplified and improved– Subcomponent tests including non-nuclear tests– Understand that Reliability Growth takes very long time, Build FNSF early as“experimental” facility that focuses only on the FNST components inside the vacuum
vessel. Realistic understanding of MTBF/MTTR can be obtained in such FNSF
– Be prepared for surprises and be ready to change pathway.
M. Abdou NAS Committee in La Jolla, CA 02-26-201818

Tritium Fuel Cycle: Dynamic models have been developed to calculate
time-dependent tritium flow rates and inventories and required TBRThis work helped us make progress working with physicists and technologists
and now reveals more Serious R&D challenges ahead

Simplified Schematic of Fuel Cycle
to New
PlantsStartupInventory

T Storage andManagement

Isotope
Separation
SystemFueling
SystemFuel
CleanupDT Plasma

VacuumPumping
Coolant TProcessing

Water
Detritiation
SystemNeutronBlanketDivertor/
FW PFC
Coolant

T Processingfor Blanket
depends ondesign options

T WasteTreatment
M. Abdou NAS Committee in La Jolla, CA 02-26-201819

Tritium self-sufficiency condition:
TBRa ≥ TBRr
TBRa= Achievable tritium breeding ratio
TBRa is a function of design, technology, material and physics.

TBRr = Required tritium breeding ratio
TBRr should exceed unity by a margin required to:1) Compensate for losses and radioactive decay (5.47% per year) oftritium between production and use2) Supply tritium inventory for start-up of other reactors (for a
specified doubling time)3) Provide a “reserve” storage inventory necessary for continued
reactor operation under certain conditions (e.g. a failure in a tritium
processing line)

TBRr depends on many system physics and technology
parameters. To determine TBRr, one must consider the“dynamics” of the entire T fuel cycle
M. Abdou NAS Committee in La Jolla, CA 02-26-201820

Need to Demonstrate T Self-Sufficiency early (fundamental requirement).
But there are large uncertainties and the required R&D is challenging
Doubling Time: 5 years

1.3

Max achievable
TBR ~ 1.15
Δ = uncertainty inpredicting achievable TBR

Tritium Processing Time
24 hours
12 hours
6 hours
1 hour

1.25

1.2

1.15

Δ,
uncertainty

1.1

1.05

Loarte & Baylor
Recent Proposal(2016)“Window”
for Tritium
self
sufficiency

1
0

1

2

3

Tritium Burnup Fraction x η f

4

5

(%)

State of the art (ITER: fb ~0.35%, ηf < 50%) achieving T self-sufficiency is Unlikely.
To Change this to likely, we must:• Lower Required TBR: R&D to achieve fb x ηf > 5% and tp< 6 hours (how do we get there?)• Reduce uncertainties in achievable TBR, Δ : R&D for blanket & conduct “full blanket” (or at least“full sector”) tests in DT Fusion Facility. ITER will not do it. So, Where and When? (need FNSF)
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EXTERNAL T Supply Issue: Tritium Consumption and Production
Tritium Physical constants
 Half life: 12.32 years; decay rate: 5.47 %/yr - Relatively short life
- Some of the T will be lost by radioactive decay during T flow, processing, and storage- T available now from non-fusion sources is totally irrelevant to evaluating availability of T forstartup of DEMO or FNSF constructed > 20 years from now

Tritium Consumption in Fusion Systems is Huge
55.8 kg per 1000 MW fusion power per year
Tritium Production in Fission Reactors* is much smaller (and cost is very high)
LWR (with special designs for T production): ̴ 0.5-1 kg/year($84M-$130M/kg per DOE Inspector General)

Typical CANDU produces ~ 130 g per year ( .2 Kg per GWe per full power year) (T is unintended by product)
CANDU Ontario: Current supply will be exhausted by ITER DT starting in 2036.
Future Supply from CANDU depends on whether current reactors can be licensed to extend life by
20 years after refurbishment.
There are many political, national policy, and practical issues with both CANDU and LWR••

Other non-fission sources (e.g. APT (proton-accelerator)) proved totally uneconomical
Start-up with D-D fuel would pose additional tokamak physics and technological problems, andwould delay power production by years and is not economically sensible* Note: Fission reactor operators do not really want to make tritium because of permeation and safety concerns. They want to minimize
tritium production if possible
M. Abdou NAS Committee in La Jolla, CA 02-26-201822

Issue: With ITER DT start in 2036, there will be no tritium left to provide“Start up” T inventory for any major DT Fusion facility beyond ITER
But the Required T Startup inventory is HUGE unless we do something
CANDU Supply
w/o Fusion

Start DT Dec 2035

With ITER:
Burn 0.9 kg/yr for 16 yr

Fusion Power = 3000 MW

40

tp: tritium processing time
Technology Advances

Tritium decays at
5.47% per year

Tritium Start-up Inventory (kg)50

tp=24 hrs30

tp=12 hrs
tp=6 hrs20
tp=1 hr

10

0
0

1

2

3

Tritium Burnup Fraction x η f

4

5

(%)

Physics x Technology Advances

M. Abdou NAS Committee in La Jolla, CA 02-26-201823

Confronting the Consequences of Fusion Tritium Consumption being large
and the lack of adequate external non-fusion supply of T to start any
fusion device other than ITER is critical for the development of fusion
The world fusion programs cannot depend on external non-fusion supply of T to:
1. Provide startup T inventory for 2 or 3 DEMOs plus other facilities such as FNSF and
CFETR
2. Provide replacement for any shortfall in satisfying T self-sufficiency in large power
fusion devices

Therefore, Fusion Development Pathway must develop a strategy that
confronts this problem. Examples of some key elements of such a strategy:• Every effort must be done to minimize the Required Startup T Inventory : e.g.
higher burn fraction, higher fueling efficiency, shorter T processing time,minimization of T inventory in all components• Minimize failures in tritium processing systems and required reserve time
• No DT fusion devices other than ITER can be operated without a full breedingblanket• Development of breeding blanket technology must be done in low fusion powerdevices• Use FNSF to accumulate excess tritium sufficient to provide the tritium inventory
required for startup of DEMO (See calculations in Supporting slides)
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II. Scientific Framework and Strategy for
Fusion Development

1. Role and Features of required non-fusion and fusion
facilities
2. FNST Requirements on FNSF Parameters and Features
3. Timing and Stages of FNSF(s), How many FNSF(s) do weneed?
4. Solving the paradox of short MTBF/long MTTR and what
to do about dpa

M. Abdou NAS Committee in La Jolla, CA 02-26-201825

Science-Based Framework for FNST/Blanket/FW R&D involves
modeling & experiments in non-fusion & fusion facilities.
V&V’d Predictive Capability,
Design Codes/Data

Theory/Modeling

Basic

Separate
Effects

Property
Measurement

Multiple Effect/
Interactions

Phenomena Exploration

Partially
Integrated

Integrated

Component

Engineering•Scientific Feasibility
Development &•Concept Screening•Performance Verification Reliability
Growth

Non-Fusion Facilities(laboratory facilities/experiments,
fission reactors and accelerator-based
neutron sources)

Testing in Fusion Facilities

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We are now in mostly “Separate Effects” stage. We Need to move to“multiple effects/multiple interactions” experiments and modelling
V&V’d Predictive Capability,
Design Codes/Data

Theory/Modeling

Basic

Separate
Effects

Now
Property
Measurement

Multiple Effect/
Interactions

Next 10
Years

Partially
Integrated

Integrated

Component

2 or more facilities will
be needed, plus TBM in
ITER/FNSF DD Phase

TBM in ITER &FNSF

in FNSF

Phenomena Exploration

Engineering•Scientific Feasibility
Development &•Concept Screening•Performance Verification Reliability
Growth

Non-Fusion Facilities(laboratory facilities/experiments,
fission reactors and accelerator-based
neutron sources)

Testing in Fusion Facilities
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27

Necessary R&D Stages of Testing FNST components in thefusion nuclear environment prior to DEMO
FNST Testing in Fusion Facilities

Non-fusion
facilities

Scientific Feasibility

Engineering
Feasibility

Engineering
Development

Preparatory R&D

Stage I

Stage II

Stage III

Modeling andexperiments in nonfusion facilities

Fluence ~0.3 MW-y/m2

1 - 3 MW-y/m2> 4 - 6 MW-y/m2

NWL ≥ 0.5 MW/m2
Plasma burn > 200 s

1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks

1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks

Sub-Modules/Modules

Modules (10-20m2 )• Basic property
measurement• Understandissues throughmodeling andsingle andmultiple-effectexperiments• Discover and understand newsynergistic phenomena• Establish scientific feasibility ofbasic functions under prompt
responses and under the impact of
rapid property changes in early life

• Establish engineering feasibilityof blankets/PFC/materials(satisfy basic functions &performance, up to 10 to 20% of
MTBF and of lifetime)• Show basic RAMI feasibility

D
E
M
O

Modules/Sectors (20-30m2 )• RAMI: Failure modes, effects, andrates and mean time to replace/fix
components and reliability growth• Verify design and predict
availability of FNST components
in DEMO

None of the top leveltechnical issues can be
resolved before
testing in the fusion
environment
M. Abdou NAS Committee in La Jolla, CA 02-26-2018

28

Planning the Pathway to DEMO Must Account for Unexpected
Negative Results for Current Blanket/PFC and Confinement Concepts

Preparatory R&D

Scientific Feasibility
And Discovery

Engineering
Feasibility andValidation

I

II

Non-Fusion
Facilities

Engineering
Development

III

D
E
M
O

Fusion Facility(ies)

FNSF
FNSF-1OR

FNSF-2• Today, we do not know whether one facility will be sufficient to show scientificfeasibility, engineering feasibility, and carry out engineering development
OR if we will need two or more consecutive facilities.
May be multiple FNSF in parallel?! (2 or 3 around the world)

We will not know until we build one!!
• Only Laws of nature will tell us regardless of how creative we are. We may even find29
we must change “direction” (e.g. New Confinement Scheme)

Staged approach Strategy for FNSF and Design for Breeding
Blankets, Structural Materials, PFC & Vacuum Vessel• DD phase has important role : All in-vessel components, e.g. divertor, FW/Blanket
performance verification without neutrons before proceeding to the DT PhaseDay 1 Design
 Vacuum vessel – low dose environment, proven materials and technology
 Inside the VV – all is “experimental.” Understanding failure modes, rates,

effects and component maintainability is a crucial FNSF mission.
 Structural material - reduced activation ferritic steel for in-vessel components
 Base breeding blankets - conservative operating parameters, ferritic steel, 10 dpa design

life (acceptable projection, obtain confirming data ~10 dpa & 100 ppm He)

 Testing ports - well instrumented, higher performance blanket experiments(also special test module for testing of materials specimens)

After first stage, Upgrade Blanket (and P FC) Design , Bootstrap approach Extrapolate a factor of 2 (standard in fission, other development), 20 dpa, 200 appm He.
Then extrapolate next stage of 40 dpa…
 Conclusive results from FNSF (real environment) for testing structural & other materials:- no uncertainty in spectrum or other environmental effects- prototypical responses, e.g. gradients, materials interactions, joints

30III. More on a Plasma-Based Fusion Environment Test Facility
Fusion Nuclear Science Facility (FNSF)
1. What type of facility should FNSF be and what main featuresand parameters should it have?
“Now + 1”

OR“DEMO – 1”?

2. Options for FNSF Facility: Tokamaks (standard and low aspectratios, type of magnets), GDT/mirrors

M. Abdou NAS Committee in La Jolla, CA 02-26-201831

What should the next DT Fusion Facilities (Other than ITER) be?
Three key facts must be considered in deliberating on this question
1. Even with the aggressive R&D of computational simulation andexperiments in non-fusion facilities that we must do, we will still haveserious uncertainties in predicting the blanket behavior in the fusion
nuclear environment
Therefore, the primary goal of the next DT fusion facility (at least the 1ststage) is to perform FNST experiments to discover synergistic effects
and learn about blanket/PFC/Materials integrated behavior in the fusion
nuclear environment. Must plan to be surprised! The next DT fusion
facility cannot be for validation or demonstration.
2. RAMI is the “Achilles heel” for fusion. RAMI will be the key issue indetermining the feasibility of plasma confinement configurations andblanket concepts– Very Low Availability (a few percent) will be a dominant issue to be confronted by thenext DT fusion device (regardless of its name FNSF, CFETR, DEMO, etc.)– RAMI must be the most critical factor in any planning we do

3. External Tritium Supply is very limited and expensive AND achieving
tritium self-sufficiency in fusion devices has many uncertainties– Next DT fusion device must breed its own tritium and have low fusion power tominimize T startup inventory requirements and avoid risk of breeding short fall
M. Abdou NAS Committee in La Jolla, CA 02-26-2018

32

VNS/CTF/FNSF
Is this idea new?
No, it was first proposed in 1984 (in FINESSE) and studied and evolved overmany years/decades in many excellent studies, for example:- FINESSE (1983-86)- TASKA-M UW-KFK (1983-85)- IEA HVPNS Study (1995-96)- UCLA/GA/ORNL/Columbia Univ. joint study on FNSF (2009-2013)

What name for the facility?
The name was changed over the years VNS/CTF/FNSF. FNSF is thename adopted since 2007
(Not to be confused with “FNSF” in the recent FESS study that defined very different type of
facility with very different mission)

M. Abdou NAS Committee in La Jolla, CA 02-26-201833

Why FNSF should be low fusion power, small size
• To reduce risks associated with external T supply and internal breeding
shortfall• Reduce Capital, operating cost, and replacement time (note Blanket/FW/
Divertor will fail and get replaced many times)• Avoid accumulating “mountains” of Radwaste from failed FNST components• Satisfy FNST key requirement 1-2 MW/m2 on 10-20 m2 test area (or less if
cost is much lower)• Cost/risk/benefit analyses* led to recommendations for Tokamak FNSF:‒ Fusion Power < 100 MW‒ Size comparable to JET (R < 3 m)
‒ Low Q plasma (1-3) - and minimize extrapolation in physics from JET‒ Normal conducting TF coils (to reduce inboard B/S thickness, also
increase maintainability e.g. by using demountable coils).

Plan FNSF scope, mission, power, and size such that we can build it
the soonest (parallel to ITER). Avoid planning FNSF to be very
ambitious since this has the risk of ever rising costs and very
lengthy schedule delays (learn the lesson of ITER)*References IEA study: M. Abdou et al., Fusion Technology 23:1-57 (1996); also UCLA/GA/ORNL studies 2010-2013; see www.fusion.ucla.edu

34

Imagine We had a facility today in which the fusion nuclear environment
is simulated and had enough test volume to do experiments on thefusion nuclear components (in-vessel components: Blanket/FW,
T system, remote maintenance)
What would have happened?
- We would have resolved most of these critical go/no-go issues- We would have had real assessment whether the path we are on now leads topractical fusion- We would be in a better position to address “fusion is always 40 years away”
What kind of facility is needed?
- The only way to simulate the fusion nuclear environment with sufficient volume isto have DT plasma based facility. But plasma performance requirements aremodest: driven, Q ~1-3, fusion power < 100 MW, size comparable to JET
Why do we not have this facility today? Why a fusion program with a mission
to build a large, high performance powerful DT plasma with very high Q has
not yet built a modest small-size low power DT plasma device? Mystery!!
- Physicists need to think of driven DT plasma for FNSF as ENABLER of
Fusion Nuclear Science and Technology Development (think of “ENABLING
Plasma”. Do not burden FNSF with ambitious physics or superconducting
magnet mission).
M. Abdou NAS Committee in La Jolla, CA 02-26-2018

35

Degree of “prototypicality” between FNSF and DEMO?
•

•

•
•

Some researchers have recently advocated that FNSF should be as close as possible to
DEMO in order to minimize the gap between FNSF and DEMO
– But our analysis in comprehensive studies over 30 years provides different conclusion
The major issue in fusion development now is that
– We don’t know how FNST components will behave in the fusion nuclear environment– R&D to test and qualify the FNST components is likely to require long time withsuccess not assured (we do not even have scientific feasibility yet!)– The seriousness of the RAMI issue makes the risks very highOur concern now should be how to build a practical FNSF with minimum extrapolation ofphysics and technology (Be technically credible!)
The focus of FNSF should be on prototypical “in-vessel” fusion nuclear components which
are missing from ITER-•

Components outside the vacuum vessel (e.g. S.C. magnets) are already prototypical and tested
in ITER at almost the same scale as DEMO - no need to be prototypical in FNSF

An approach that makes FNSF close to DEMO will have:– Much larger size than needed for FNSF testing mission– Much larger capital and operating costs– Longer replacement time and accumulation of much Radwaste– Unacceptable risk

Think of:

“Now + 1”

NOT“DEMO – 1”

M. Abdou NAS Committee in La Jolla, CA 02-26-2018

36

Options for FNSF
Different Confinement concepts were studied as options for FNSF overdecades in the studies mentioned previously Mirrors
Were highly favored in the 1980’s because of (a) “decoupling” of fusion power and power density
which allows high wall load with no need for large fusion power, and (b) other features such as
easier accessibility/maintainability. But interest declined because of difficulties obtaining highelectron temperature Standard Aspect Ratio Tokamak with driven plasma, low fusion power
Example of design led by GA : Standard Aspect Ratio (A~3.5) with demountable TF coils,
R ~2.5 m, Pfusion=125 MW at PNW=1 MW/m2

 Small Aspect Ratio (ST)
Example of design by M. Peng et al., ORNL; R=1.2m, A=1.5, κ=3, Pfusion=75MW, PNW=1 MW/m2

 GDT
Several studies, several variants. One studied in IEA HVPNS study had only 0.5 m2 test area andhad issue of too steep gradients in the test space. But improvements were made in subsequentstudies

M. Abdou NAS Committee in La Jolla, CA 02-26-201837

Example of Fusion Nuclear Science Facility (FNSF) Design Option:
Standard Aspect Ratio (A~3.5) (GA design)
demountable normal TF coils, R=2.5m, Pfusion =125 MW, PNW = 1 MW/m2• High elongation, hightriangularity double
null plasma shape
Challenges for Material/Magnet Researchers:
for high gain,
steady-state plasma • Development of practical “demountable” joint in Normal Cu Magnets
operation• Development of inorganic insulators (to reduce inboard shield and size of device)Another Option for FNSF Design: Small Aspect Ratio (ST) (Peng et al, ORNL)
Smallest power and size, Cu TF magnet, Center Post
R=1.2m, A=1.5, κ=3, Pfusion= 75MW, PNW = 1 MW/m2

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

M. Abdou NAS Committee in La Jolla, CA 02-26-2018

1.0

0.1

Q

0.50

2.5

3.5

Paux-CD [MW]

15

31

43

ENB [keV]

100

239

294

PFusion [MW]

7.5

75

150

T M height [m]1.64

T M area [m2]14

Blanket A [m2]66

Fn-capture

0.76

39

GDT-based neutron source for subcomponent and material testing*• Mirror-to-mirror length 15 m
• Mirror magnetic field 15 T
• Mirror ratio 20 (4 for the testzones)• NBI power (trapped) 30 MW• Neutron power 2.5 MW overthe surface of 2 test zones (1 mlong, 20 cm ID each)• Tritium consumption 140 g for
CW operation of one year (i.e.,
the fluence 2MWa/m2)• No tritium breeding (but theblanket cassettes can be tested)
Plasma parameters in: D. D. Ryutov et al., J. Fusion Energy, 17, 253,
1998; P. A.Bagryansky et al., Fusion Eng. Des., 70, 13 2004; P. A.
Bagryansky et al., PRL, 114, 205001,2015; Test-zone design in: U.
Fischer et al., Jan. 1999. Fusion Technol. 35-1T, 160, 1999 Generalreview in: A.W. Molvik et al., Fusion Sci. Tech. 57, 369, 2010

• Both normal conductor andcombined solenoids will be
used*Information provided by Dmitri Ryutov

M. Abdou NAS Committee in La Jolla, CA 02-26-201840

Need New Approach to International Collaboration• Any DT device which will be built going forward in which the fusion nuclear
components are exposed to the fusion nuclear environment for the first time
will serve the function of FNSF regardless of name DEMO or CFETR or FNSF.
Therefore, there is worldwide common interest in FNST challenges and R&D
addressed in this talk regardless of the publicly stated strategy• We should think of a new more effective approach to international
collaboration much different from the ITER model. For example:– 2 or 3 countries each build its own FNSF and share results and experience– Other countries can contribute more to R&D for FNSF and DEMO
– Each Major Country builds its own DEMO when there is enough data,experience, testing, and qualification of fusion nuclear components in thefusion nuclear environment (from FNSF)• It is a mistake that US does not have its own TBM in ITER (we are paying forthe cost but not getting the full benefits of ITER!). We recommend that the US
at least for now maintain collaboration with other parties leading TBM (e.g.
Korea, EU, China, Japan)
M. Abdou NAS Committee in La Jolla, CA 02-26-201841

Summary (1 of 3)
Overall Problem:

There are critical go/no-go problems for which HOW and WHERE to perform the R&D are achallenge, yet there is not a credible strategy being adopted, communicated, nor pursued

Major Go/No-Go Issues
-

-

-

-

The fusion Nuclear environment is multiple-field, with steep gradients in volumetricheating, that result in many multiple effects/synergistic phenomena many of which are
yet unknown. Can not adequately simulate in laboratory or other existing facilities,
neither predict using existing models
FNST components (Blanket/FW/Divertor) are inside the VACCUM Vessel in complex“closed” toroidal geometry, making RAMI the “Achilles’ heel” for fusion, which together
with multiple effects/large surface area, result in predicted extremely low “availability”
for any DT device we build (FNSF, CFETR, DEMO, etc.)
There are Large uncertainties in achieving Tritium Self Sufficiency because of low plasmaburn fraction and fueling efficiency, in addition to the inability to narrow the current
uncertainties in the achievable TBR without testing a full blanket sector in a plasma-based
deviceThere are no non-fusion sources to provide the “Start Up” inventory for DEMO, which iscurrently estimated to be huge

M. Abdou NAS Committee in La Jolla, CA 02-26-201842

Summary (2 of 3)

What to do about these issues (Key elements of a prudent strategy)
1. Build a number of multiple-effect Laboratory facilities with maximum possible
simulation of the fusion nuclear environment. These will be only partially effectivein uncovering all the key multiple-effect/synergistic phenomena in blankets/FW. In
parallel, undertake a Major Modelling initiative taking advantage of recent
advances of massively parallel computation.
2. Build a Fusion Nuclear Science Facility (FNSF) to learn behavior of
blankets/FW/Divertor in the fusion nuclear environment, learn about
multiple/synergistic-effects phenomena, quantify the potential to attain T selfsufficiency, and possibly produce excess tritium to supply the Required Start up
inventory for DEMO; and understand failure modes, rates, effects (RAMI). Select a
version of FNSF that can make it near term (operation parallel to ITER). Make itsmall volume, low fusion power, with small requirements for external T supply,
simplest, most reliable, driven plasma with current physics basis to enable the
FNST mission. Requirements are well defined, but which concept and options for
FNSF need a well-led study.
3. Use Tokamaks (and stellerators) as intermediate step in fusion development(continue participation in ITER), but in parallel, search for other new plasma
confinement schemes that may have better potential for commercialization. In
particular, simplicity of configuration, better maintainability, and moremanageable RAMI problems. High power density is also desired.
M. Abdou NAS Committee in La Jolla, CA 02-26-2018

43

Summary (3 of 3)
What to do about these issues (Key elements of a prudent strategy) (Cont’d)
4. Seek a more effective international cooperation model which is more efficient andreduces redundancy. Need an international cooperation strategy in which thecritical R&D facilities, modelling, and research is “distributed” (rather thanduplicated) among countries based on mutual benefits even if the development
strategy varies among countries.
5. Time has come to ask for a more effective, more agile management and leadershipof the fusion program with clear roles and effective interactions for universities,
national Labs, and industry -- all pursuing a credible strategy for fusion
development.
6. Include in the fusion strategy clear elements that enable successful renewal of“human resources”, while preserving “corporate memory/knowledge” represented
by senior researchers and multi-decade literature. Crucial for a program that istaking several human generations.

M. Abdou NAS Committee in La Jolla, CA 02-26-2018

44

Thank You!
Extra Slides follow

M. Abdou NAS Committee in La Jolla, CA 02-26-201845

Selected References with more detailed information about issues,recommended R&D, and strategy elements in this presentation
Abdou, M., Morley, N.B., Smolentsev, S., Ying, A., Malang, S., Rowcliffe, A., Ulrickson, M., "Blanket/First
wall challenges and required R&D on the pathway to DEMO", Fusion Engineering and Design, 100:2-43(2015).
M. Abdou, S. Berk, A. Ying, M. Peng, S. Sharafat, J. Galambos, G. Hollenberg, S. Malang, E. Proust, S.
Booth, L. Giancarli, P. Lorenzetto, Y. Seki, V. Filatov, G. Shatalov, A. Sidorenkov, "Results of an International
Study on a High-Volume Plasma-Based Neutron Source for Fusion Blanket Development", Fusion
Technology, 29: 1-57 (1996).
M. Abdou, E. Vold, C. Gung, M. Youssef, K. Shin, "Deuterium-Tritium Fuel Self-Sufficiency in Fusion
Reactors", Fusion Technology, 9: 250-285 (1986).
M. Abdou, P. Gierszewski, M. Tillack, K. Taghavi, K. Kleefeldt, G. Bell, H. Madarame, Y. Oyama, D. Berwald,
J. Garner, R. Whitley, J. Straalsund, R. Burke, J. Grover, E. Opperman, R. Puigh, J. Davis, G. Morgan, G. Deis,
M. Billone, K. Thomassen, D. Jassby, "A Study of the Issues and Experiments for Fusion Nuclear
Technology," Fusion Technology, 8: 2595-2645 (1985).
M. Abdou, P. Gierszewski, M. Tillack, M. Nakagawa, J. Reimann, D. Sze, J. Bartlit, J. Grover, R. Puigh, R.
McGrath, "Technical Issues and Requirements of Experiments and Facilities for Fusion Nuclear
Technology", Nuclear Fusion, 27(4): 619-688 (1987).
A.M. Garofalo, M.A. Abdou, J.M Canik, V.S. Chan, A.W. Hyatt, D.N. Hill, N.B. Morley, G.A. Navratil, M.E.
Sawan, T.S. Taylor, C.P. C. Wong, W. Wu, A. Ying, “A Fusion Nuclear Science Facility for a fast-track path to
DEMO,” Fusion Engineering and Design, 89: 876-881 (2014).
M. Abdou and The APEX Team, "Exploring Novel High Power Density Concepts for Attractive Fusion
Systems", Fusion Engineering & Design, 45, No.1: 145-167 (1999).
M. Abdou NAS Committee in La Jolla, CA 02-26-201846

Selected References with more detailed information about issues,recommended R&D, and strategy elements in this presentation (Cont.)
M. Abdou, The APEX TEAM, A. Ying, N. Morley, K. Gulec, S. Smolentsev, M. Kotschenreuther, S.
Malang, S. Zinkle, T. Rognlien, P. Fogarty, B. Nelson, R. Nygren, K. McCarthy, M. Youssef, N.
Ghoniem, D. Sze, C. Wong, M. Sawan, H. Khater, R. Woolley, R. Mattas, R. Moir, S. Sharafat, J.
Brooks, A. Hassanein, D. Petti, M. Tillack, M. Ulrickson, T. Uchimoto, "On the Exploration of
Innovative Concepts for Fusion Chamber Technology", Fusion Engineering and Design, 54: 181-247(2001).
“Tritium Fuel Cycle, Tritium Inventories, and Physics and Technology R & D Challenges for: 1)
Enabling the startup of DEMO and future Power Plants AND 2) Attaining Tritium Self-sufficiency in
Fusion Reactors”, M. Abdou Keynote Presentation at International Symposium on Fusion Nuclear
Technology (ISFNT-13), Kyoto, Japan, September 25-29, 2017. [PDF]
W.R. Meier, A.R. Raffray, R.J. Kurtz, N.B. Morley, W.T. Reiersen, P. Sharpe, S. Willms, “Findings of the
US research needs workshop on the topic of fusion power,” Fusion Engineering and Design, 85:
969-973 (2010).
M. Kovari, M. Coleman,I. Cristescu, R. Smith, «Tritium resources available for fusion reactors” 2018
Nucl. Fusion 58 026010

General References
Broader references on FNST are available upon request
Many references are provided already in the Selected References on theprevious slides
M. Abdou NAS Committee in La Jolla, CA 02-26-2018

47

FNSF should be designed to breed tritium to:a) Achieve T self sufficiency, ANDb) Accumulate excess tritium sufficient to provide the tritium inventory required for startup of DEMO

Required TBR in FNSF
10 kg T available after ITER and FNSF

5 kg T available after ITER and FNSF
FNSF does not run out of T2018 ITER start
2026 FNSF start

Impose a newrequirement not
originally in the
mission of
FNSF when it
was first
proposed in1984 and in
subsequentstudies in the
1980’s and 90’s

From Sawan & Abdou

Situation we are running into with breeding blankets: What we want totest (the breeding blanket) is by itself An ENABLING Technology
M. Abdou, Keynote ISFNT-13, 9-25-201724

FNST embodies most of the remaining Feasibility andAttractiveness Issues in Fusion Energy Development.
FNST R&D is essential to confront Grand Challenges
Need High Power Density/Physics-Technology Partnership-High-Performance Plasma- Blanket/FW/divertor Technology Capabilities

Need Low
Failure RateC ⋅ i + replacement cost + O & M
COE =P fusion ⋅ Availability ⋅ M ⋅ η th
EnergyMultiplication

Need High Temp.
Energy Extraction Blanket

Need High Availability / Simpler Technological and Material Constraints(1 / failure rate )1 / failure rate + replacement time

• Need Low Failure Rate:- Innovative Chamber Technology• Need Short Maintenance Time:- Simple Configuration Confinement- Easier to Maintain Chamber Technology
49

M. Abdou NAS Committee in La Jolla, CA 02-26-2018

Need for High Power Density Capability
To improve potential attractiveness of fusion powercompared to other energy sources (e.g. fission)

Average core power
density (MW/m3)

PWR

BWR LMFBR ITER-Type

96

56

240

0.4

50

There are strong GRADIENTS in the multi-component fields of thefusion environment
Magnetic Field
Volumetric Heating(for ST)

3.0 10 -8

103
Radial Distribution of Damage Rate

2.5 10 -8

2.0 10 -8

Radial Distributionof Tritium
RadialvariationofProduction
tritiumin LiPb Breeder
production rate in PbLi in 2
Neutron Wall Loading 0.78 MW/m
DCLL

1.5 10 -8

DCLL TBM
LiPb/He/FS
90% Li-6

1.0 10 -8

5.0 10 -9

0.0 10 00

Front
Channel5
1020

Radial Distance from FW (cm)2ferritic
steel
structure(DCLL)
NeutronWall Loading
0.78 MW/m

102

DCLL TBM
LiPb/He/FS
90% Li-6
101

100
dpa/FPY
He appm/FPY
H appm/FPY

Back Channel
15

in Steel
Structure
Damageparametersin...........................

Damage Rate in Steel Structure per FPY

Tritium Production Rate (kg/m3.s)

Tritium

25

30

10-1
0

5

10

15

20

25

30

35

40

Depth in Blanket (cm)These gradients play a major role in the behavior of fusion nuclear components.
51
Simulating these gradients in experiments is challenging but Essential.