FAFNIR: Strategy and Risk Reduction in Accelerator Driven Neutron Sources for Fusion DataCCFE is the fusion research arm of the United Kingdom Atomic Energy Authority
FAFNIR: Facility for Fusion Neutron
Irradiation Research - Materials Strategy
and the European Fusion Roadmap Elizabeth Surreya, Mike Portona, Tristan Davenneb, David Findlayb, Alan Letchfordb, John Thomasonb, James Marrowc, Steve Robertsc, Andrei
Seryid, eBrian Connelly, fPaul Mummery, fHywel Owen
aEURATOM/CCFE, bSTFC Rutherford Appleton Laboratory cUniversity of Oxford, dJohn Adams Institute University of Oxford,
eUniversity of Birmingham, fUniversity of Manchester
The Lack of 14MeV Irradiation Data1,2 • Highest damage in 14MeV spectrum
< 0.1dpa at RTNS-II (1980-1986)
via fission spectrum
MeV and increases embrittlement
tailoring
properties
1 S Zinkle, Workshop on Advanced Computational Science:
Application to Fusion and Generation-IV Fission Reactors in
Washington DC, USA 31 March -2 April (2004) 2E Gaganidze et al. J Nucl Mat 386-388 349-352 (2009) & J
Nucl Mat 417 93-98 (2011)
The Fission Experience
reactors to generate a reliable data
base for fission core structural
materials…
0.1
1
10
100
1000
10000
displacement damage (dpa)
displacement damage (dpa)
€665M (2003)
>€1B (2012)
– Power ~10 times greater than existing cw systems
– Beam uniformity & profile pushed to extremes in order to provide target stability and
irradiation uniformity
• Liquid lithium target
– High flow velocity results in nozzle erosion and flow perturbation
– Real time Li purification needed
Schedule
Construction (2030-40)
IFMIF: Operational 2028 2 years of experimentation before DEMO construction
DEMO
5 5
– No long term irradiation data
– No nuclear design codes
Development of models - interpolation and extrapolation with confidence - understanding of effects of each variable and physical processes over the life of the device
• Result
• Lesson
Approach to licensing cascades into safety case & decisions on the scope of design criteria development in advance of plant build
Design criteria undertaken in close co-operation with dedicated materials experiments and modelling activities
Accelerated testing programmes in parallel to operations facilitate long term learning
Complete understanding of the environment is not needed, therefore end of life fusion neutron irradiation is not required before the design and build of DEMO. Instead only an insight into the effects is needed
with margin provided for the inevitable ‘unknown unknowns’ that will be revealed during the lifetime of the project.
WHAT DO WE NEED TO KNOW TO BUILD DEMO......
Operational characteristics for DEMO:
• 2MW/m2 neutron load • 3 year in-vessel life (2 yr divertor) • 33% availability
~20dpa Steels over 3 years3
~10dpa Cu alloys over 2 years3
~15dpa W over 3 years3
High dose rate source not necessary >50dpa/fpy >5dpa/fpy
Population of materials database Elimination of unsuitable materials
Assess reliability and lifetime
Validation/calibration of other irradiation techniques
Assess design threats and their potential mitigations
~10dpa most degradation
3 Materials Advisory Group Report, EFDA 2013
7 7
The need for an achievable strategy ……..AND WHEN DO WE NEED TO KNOW IT?
Limited time available - DEMO in H2020 Fusion Roadmap
Engineering design assessment starts 2020 Construction starts 2032
To mitigate major design risks need moderate dpa data mid to late 2020’s
IFMIF/EVEDA delayed – no realistic prospect of delivering before 2030
The Neutron Source solution must be:
Rapid construction Reliable for high availability
The Neutron Source solution can be:
Lower intensity than IFMIF/EVEDA lower dpa by 2030 more valuable
Low Technological Risk
FAFNIR: FAcility for Fusion Neutron Irradiation Research
is a solution
Energy (GeV) A
Energy (GeV) A
times existing operating systems
result of CW operation
accelerator
precedent - 2mA 1.3MW (PSI)5
upper limit – 30mA 1.2MW
655, 3 (2011)
difficulty for target
upper limit – 1.2MW 700GWm-3?
Beam D+ 40MeV, 250mA 40MeV, 2.5mA 40MeV, 5mA 40MeV, 30mA
Target 10MW
Liquid Li
Build accelerator for final foreseen current
Progressive increase of target power handling parallel programme 7 IFMIF CDR , IEA (2004)
FAcility for Fusion Neutron Irradiation Research
neutron spectrum of FAFNIR and other fusion sources
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
neutron energy (MeV)
No problem matching
30mA at 3MeV
8N Chauvin, et al., Proc IPAC2013, Shanghai, China (2013) THPWO006S. 9Virostek, et al, Proc IPAC 2012, New Orleans,
USA (2012) THPPC034, 10T Furukawa et al., IPAC’10, 76 (2010) , 11 Y Yuri et al., Uniform beam distribution by nonlinear
focusing forces, IPAC’10, 4149 (2010)
DTL
graphite - density 1850kgm-3
Multi-sliced target (5 x 1mm) - most deposition in final slice
Flat-topped circular beam radius 30mm Average power density is a function incident radius, R, of beam on target
R
13
no instabilities
creep (10-7cm.cm-1s-1) set
Thermal model – slices rotate inside cooling
stator (300K), emissivity 0.75
effects, no credit for increase in strength
Assume all beam power deposited in final slice
Temperature excursion as target passes under
beam
stress
Principal stress (MPa)
0
500
1000
1500
2000
2500
3000
target radius (m)
temperature limit 2000K
target radius (m)
0
500
1000
1500
2000
2500
3000
target radius (m)
Entry level 5mA beam current feasible
Upgrade programme
Forced helium cooling T~ 1945K principle stress 28.2MPa R=0.5m
Compression designed target – stress limit mitigation, compressive limit 90MPa
Other types of graphite/composite formulas
15
Strong dose gradient
raster scanning/beam spreading minimise in-plane variation
Strong temperature gradient
Remote handling necessary
16
16
Key to maximising the value of FAFNIR is exploitation of the volume by:
Using smaller specimen types than those proposed for IFMIF, where possible and where
valid data can be obtained.
Doubling-up use of specimens so that “dead zones” in “large” (millimetric) fracture or tensile
specimens can be used for other tests (e.g. nano-indentation testing, lift-out for TEM and APT
specimen preparation, measurement of thermal conductivity, electrical conductivity, and
swelling)
Maximising use of micromechanical test methods over a wide temperature range for
derivation of yield, work-hardening and where possible fracture data
Use of pre-made (electropolished) TEM foils to distinguish radiation damage from FIB
damage in lift-out specimens
mitigation of size issues providing sparse data in some areas
Carefully-planned use of test volume:
A series of FAFNIR test campaigns of about 1 year or more (to 1-2 dpa maximum)
Sufficient specimens to test fully most of the desired physical and mechanical properties of
materials proposed for a DEMO power plant in 100cm3
Test volume needed is ≥ 100cm3 at damage rate ≥1.5dpa/FPY
17
Tension-based fracture specimens
Type Size
Acceptance of small size sample testing by standards authorities (ASME, etc) essential
5
m
18
layer
bend
materials, (30 specimens each)
significant embrittlement expected
materials (30-40 specimens each)
materials (30-40 specimens each)
minimum dimension >> grain size
1x8 30-50 small-punch disc 3 materials (10-20
specimens each)
TEM 0.05x0.05 300 FIB machining of tensile,
creep ,bend specimens
creep , bend specimens
20
1.00E+09
2.00E+09
3.00E+09
4.00E+09
5.00E+09
6.00E+09
7.00E+09
Yi el
d St
re ss
(P a)
micro-cantilever testing of un-
irradiation dose 0.6dpa at 300 C
Dose rates: high 6 x 10-4 dpa/s low
3 x 10-5 dpa/s.
Schedule and cost
2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
Eng design Target 2
PIE
Buildings
Services
PIE
Target upgrade 1.2MW
Options available for flexible irradiation strategy if a decision is made soon
Cost estimates (2012 US)
Commissioning $41M
displacement damage (dpa)
Population of materials
Identification of unknown phenomena
potential mitigations
Acknowledgement
Programme under grant EP/I501045.
proven technology with:
– low beam losses to facilitate hands- on maintenance - need well- controlled, low-emittance beam in a generous aperture
– good heat removal compatible with CW operation – low power and accelerating gradient
– demonstrated high availability
• 1.2 MW of 40 MeV at 30mA CW
– ~1MW already at Los Alamos (NC linac), SNS (SC linac), PSI (cyclotron)
– beam dynamics to 40 MeV at ~30mA poses no particular problems
– 1.2 MW of 40 MeV at 30 mA CW is new but feasible
• Beam profile and current to be optimised with target design to achieve required irradiation volumes and uniformity
Off resonance ECR Source, DC accelerator ~90kV e.g. SILHI 140mA D+ for EVEDA8
8N Chauvin, et al., Proc IPAC2013, Shanghai, China (2013) THPWO006S. 9Virostek, et al, Proc IPAC 2012, New Orleans,
USA (2012) THPPC034, 10T Furukawa et al., IPAC’10, 76 (2010) , 11 Y Yuri et al., Uniform beam distribution by nonlinear
focusing forces, IPAC’10, 4149 (2010)
RFQ ~3MeV CW e.g. PXIE9 60kW/m DTL ~3-40MeV CW 1.5MV/m 50kW/m 100-200MHz and SC – larger structures
Higher beam energy (100s MeV), lower current (1-2mA mean)
Permanent or electromagnetic optics options
Non-linear optics AVF cyclotorn ±10%11 Raster scanning 6mA beam – PSI Gantry 2 HIMAC10
Super conducting option – TRL low
25
Adjustments for simplified infrastructure (lithium loop, tritium handling, power requirements)
Additional costs for post irradiation examination facilities, sample handling* & target programme
*assumed host contribution in IFMIF CDR
CAPITAL COSTS
Target facilities 51.4 12.5
20% Contingency 20% Manpower
Commissioning costs of FAFNIR US$41M (2012)