Enabling Technologies – VLT Town Hall
Nuclear Reactor Compatibility Issues

D. Youchison
June 04, 201928th IEEE Symposium on Fusion EngineeringOutline• Objectives/Requirements for a nuclear reactor(compact pilot plant)• Major Critical Issues including Gap Metrics for a
Nuclear Reactor• Magnets• Heating• Fueling• PFCs and IVCs
• Blankets and Power Conversion (covered by C. Kessel)• Remote Handling• Potential Next Step Initiatives• Q&A with audience

28th IEEE Symposium on Fusion EngineeringPilot plant means long pulse, compact, highdensity, DT and blanket operations

from J. Rapp

The goal of such a device would be to provide fusion-relevant neutron wall loading Wn
1MW/m , neutron uence 6MW-yr/m , component testing area of 5-10m , and continuous
on-time (i.e. steady-state operation)for durations in the range of 10 s
2

2

2

6

28th IEEE Symposium on Fusion EngineeringInternational DEMO Concept Requirements
Mission

EU DEMONet electricity(Qeng > 1)

JA DEMONet electricity(Qeng > 1)

K-DEMONet electricity(Qeng > 1)

Tritium selfsufficiency

Tritium selfsufficiency

Tritium selfsufficiency

CFETR (Phase I)Materials & component
testing in fusion
environment
Full tritium fuel cycle

Materials andcomponent testingin fusion
environment
1,500 MW≥ 300 MW> 1.05
> 1.0
2 hr to steady state Steady state

KDEMO

Pfus
TBR
Pulse length

2000 MW> 1.0
2 hr

Duty factor
PelecTritium
breeding~ 70%
500 MWTo be determined– solid and PbLi
breeder underconsideration

Magnetic
configuration
MaintenanceTokamakTokamakTokamakTokamak

Remote handling

Remote handling

Remote handling

Remote handling200-300 MW (net) ≥ 150 MW (net)
Solid breeder, PWR Solid breeder, PWR
technology
technology

PILOT PLANT

50–200 MW≥ 1.01000 s to steady state
30–50%
N/A
Solid breeder, PWR
technology, close
tritium cycle at ~ 1/10
DEMO scale

Source: Kamendje, Richard et al, International Energy Agency’s Fusion Power Coordinating Committee, Paris,France, 2016.

28th IEEE Symposium on Fusion Engineering

HTS as an enabling technology for high field fusion magnets
Progress has been made in conductor & cableconcepts for high field magnets• Driven primarily by high energy physics community inUS but significant efforts• Focus particular in the field range of 10 T – 20 T were
REBCO and Bi-2212 are advantageous

Two private venture fusion efforts are pursuing thisenabling technology for their concepts• But many other national and international labs / universities
are pursuing HTS for fusion & high field magnets

Mumgaard NAS
comments 2018

28th IEEE Symposium on Fusion EngineeringPeter Lee, ASC/NHMFL

Conductor on Round Core cables

Path to fusion magnets over the next ten years could be interesting
CORC cable principle:

Winding many high-temperature superconducting YBCOIssues to consider

coated conductors from SuperPower in a helical fashion with
the YBCO under compression around a small former.

Conductor supply and cost?

Conductor and cable piece
lengths

400 A/mm2, 4.2
K, 20 T

Cable Stability and Quench
Protections Benefits:

80 kA, 4.2 K, 10.9
T

D.C. van der Laan, SUST 22, 065013 (2009).

- Very flexible
Radiation Degradation- Very high currents and current densities

HTS cab les: acceler -ator anveryd strong
ot her lar g e m ag n et s60 kA, 4.2 K
MechanicallyPrototype Large Coils- Minimum degradation from cabling (< 10 %)12 Tr eq uir e hig h cur r ent(10-20 k A)
- Current
sharingcab
betweenl es
tapes possible
Cryogenic Cooling (SCHe, H2,LN2?)
Easy p at h t o 2212
cab l est h r ou g h t he st an d ar dRu t her f or d cab le
REBCO cab l es ar e h ar d er
(Coat ed Con d u ct or i s asi ng l e f i lam ent ) b u tp ossi b le (IRL, KIT, CORC,t w i st ed st ack (MIT)2212 Strand 1000
A/mm2
4.2 K 27 T
BSCCO-2212 Rutherford cable
Bi-2212 Rut her f or d cables(Ar no Godek e LBNL) w it hm ullit e insulat ion sleeve

REBCO coated conductor
woundin
TSTC-Twisted cable
Stacked-TapeCable
manylayers helicallyon a roundform
28th IEEE
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on Fusion
Engineering
This CORC geom et r y (van6 kA 17
T 4.2 K

What the appropriate
performance metrics?
2000’s DOE Superconductivity
Program$25/kA-m @ 77 K

FusionDepends on who you ask andthe final applications
Current / Current Density (B,T)
50 -100 kA
1000 A/mm2 (CS ITER)
4.2 K, 20 K
10 T to 20 TStrategic investments could enable growth in fusion and other highfield areas
Prototype Cable Test Facility
Access to cable testing in general islimited by no. of facilities and time
available
SULTAN – split solenoid

Large Coil Demonstrations

Multi-coil demo facility

Which geometry and when (3-5years)?

NAS report suggested that perhaps
an updated version of the 80’s
international Large Coil Test (LCT)TF PF CS Helical

Six Coils, 8 T, 11 kA, NbTi

11T – 1% over 300 mm, 100 kA

EDIPO – in repair
12 T – 1% over 1 m

NHMFL14.5 T, 160 mm bore
NIFS (Japan)
13 T, 700mm bore, 50 kA

NIFS-FFHR-d1

It should be thought about the process (time, funds) it took to get to LTS cables
28th IEEE
Symposium
Fusionthatare currentlyon
being
used Engineering
for current fusion magnets.

ICRF Issues and Gaps

ITER Antenna• Plasma heating and current drive using the Ion Cyclotron
Range of Frequencies (ICRF) are important elements for thesuccess of fusion1,2• Most DEMO concepts identify ICRF as a main heating system• Launching structures for ICRH or LHCD must operate in a highradiation, high heat-flux environment• The exposed antenna surfaces must be resistive to high heat (1-10MW/m2) and neutron fluxes with acceptable levels of impurity
production• Many reactor concepts will require operating at ~700 °C• The issues and gaps with creating reliable ICRF operation cut
across the disciplines of plasma theory and simulation, RFtechnology, materials, diagnostics, and reactor engineering(reliability and maintenance)
1Greenwald Panel FESAC Report(http://science.energy.gov/~/media/fes/fesac/pdf/2007/Fesac_planning_report.pdf)
2Research Needs for Magnetic Fusion Energy Sciences Final Report(https://www.burningplasma.org/web/ReNeW/ReNeW.report.press1.pdf)

28th IEEE Symposium on Fusion Engineering

ITER Faraday ShieldFNFS

Antennas operate in a harsh environment• Physics issues: antenna near-field interactions with the plasma in the scrape
off layer (SOL) are not well understood:

Hot spots on Tore Supra antenna• The formation of the RF plasma sheath: enhanced particle and energy fluxes on
the antenna and on surfaces intersected by the magnetic field lines connected
to/near the antenna• The parasitic RF losses in SOL region• RF breakdown/arcing, which is one of the main power-limiting issues operating in
the plasma environment• Material issues: antenna-compatible materials operating in a CW highheat/neutron flux environment are not validated:• Thermal and neutron-induced stresses at joints/grain boundaries (antennastructural stability)• Cracking due to void formation (possible arc initiation)• Erosion of coatings and dust production (possible arc initiation)• Reliability issues: Long pulse operation of the antenna and source• Solving these problems will likely require an approach that combinesmodeling/design with validation of the models on dedicated RF CouplingExperiments/Test Stands and Confinement Devices

28th IEEE Symposium on Fusion Engineering

RF breakdown/arcing

Surface changes from PMIS Lindig et al., T145 (2011)014039Y Ueda et al., Fus. Sci.
Technol. 52 (2007) 513

ECH challenges• Steady state, 1 MW+ gyrotrons, high frequencies and lifetimes• Cooled, high power miter bends, switches and polarizers
Problem: too many ports!
• Window development• Neutron damage to mirrors• HFS launch, integration of antennas
and WGs into blankets necessary fora nuclear facility.

28th IEEE Symposium on Fusion EngineeringFuel Throughput in Fusion Plasmas
Needs Dramatic Extension from Previous Experiments
Fuel Throughput (Pa-m3)

Pure Tritium Extrusion

DT*Requires

DEMO

recirculation
NFPP

ITER-DT
ITER-1
W7-X LHD
Tore Supra
TRIAM-1M

JT60
JET
ATF
TFTR
DIII-D

1 Min

1 Hr

1 Day

ST

Hydrogen, Deuterium and Tritium Pellets

Plasma Duration (s)• DT fuel throughput for ITER and beyond is well beyond what has
been achieved in previous devices. Recirculation of DT within thepellet system makes the design much more complicated.

28th IEEE Symposium on Fusion Engineering

Pure Tritium Pellet

Fusion Exhaust Pumping Schemes
Efficient tritium compatible pumping is needed
to remove the exhaust gases from the plasma(transport losses and burn byproducts).

• Batch Cryopumps – ITER Method T2 inventory, Deflagration limit,
Thermal cycling, Valve cycling, He pumping• Continuous Cryopump – Snail pump prototype developed and tested by
Foster at ORNL

- Mechanical scraper- Cryo separation- Helium compression for conventional pumping- Pellet formation from exhaust concept tested• Liquid Metal Pumps (KIT): – Diffusion pump and liquid metal ringroughing pump

- Needs separation of impurities and helium to provide direct
recirculation to fueling system- Super permeable membrane separation?

28th IEEE Symposium on Fusion EngineeringITER

Transient Mitigation using Pellet Technology

SPI-II with Gas Manifold• Disruption Mitigation• Shattered pellet injector (SPI) experiments on DIII-D deliver deep
penetration and assimilation to maximize dispersal of plasmaenergy into radiation to spread out the heat over greatest areapossible• Large High-Z (Ar, Ne) pellets developed for thermal mitigation andrunaway electron dissipation• SPI experiments on JET and KSTAR are planned in support of ITERDMS• ELM Pacing• Experiments on DIII-D demonstrated peak heat flux deposited incryogenically cooled barrels
the divertor per ELM decreases with increasing injection frequencyThreeinside
the guard vacuum
28th IEEE Symposium on Fusion Engineering

Plasma Facing Components
New challenges in a nuclear facility:• Higher q” and temperatures from compact plasmas• Long pulse or steady state operation• Active cooling required (high pressure, high temperature, chemistry). Water is
not coolant of choice.
• Corrosion, transport and fouling (crud activation)• Modularity compatible with blanket and divertor concepts – (affects manifolds, RH,••
•
•
••
•
•
•
•

shielding, ports, part count, connections, bake-out)

Integral FW/blanket and advanced divertors
Manifolding and welding
Remote handling and repair
EM loads particularly during disruptions
Joining and additive mfg.
Engineering Diagnostics, Performance monitoring & RAMI
Neutron irradiation -> activation
Tritium absorption and permeation
Disruption/ELM melting
Erosion and dust formation*A nuclear reactor cannot be a versatile plasma research platform

28th IEEE Symposium on Fusion Engineering

PFC development path from PMI Workshop Report• armor• heatsink• coolant

actively cooledX

W & RAFM

X
X

28th IEEE Symposium on Fusion Engineering••••

multi-channel
manifolding
mountsdiagnostics

TRL3
CVD Nb Sleeve (0.065” wall)
CVD W Tube (0.060” wall)

W Foam
1.25”
0.75”

TRL2

2.0”
6.0”
8.5”

0.62”
0.75” (for Swagelok)
0.50”All-tungsten porous media heat sink (left), all-copper
porous media heat sink (middle), all-moly porous
foam tee-tube heat sink (right)

U.S. can no longer fabricate or test advanced helium-cooled PFCs

TRL4

TRL4
Multi-channel helium-cooled TZM/Moly heatsink with moly foam: 3D CAD (left panel) andfabricated test device (right panel)
TRL2
1990

TRL22020

New Initiative in Advanced Helium Cooling• Helium cooling for FW/Blanket and divertor• PFCs and power conversion HXs• RAFM and W materials – additive manufacturing• Manifold development• Closed helium flow loop, 10 MPa, 1 kg/s
• E-beam HHF facility with microwave and induction heating
In-vessel Components

28th IEEE Symposium on Fusion EngineeringLM PFCs

Remote Handling Technology••••

Reactor systems must incorporate RH designs from the very beginning
Large Hot Cell repair bays and shielded transport systems are required
Large component assembly/disassembly with precision
Sealing of large faces to maintain vacuum – how many making and breaking
can a surface take? Are there better methods for sealing components to ensure
vacuum?
• For large component replacement with very high radiation (Tritium and otherairborne contamination), how to design an effective hot cell? Is an overheadbridge crane system still the best option?
• What is the best design for an airlock that enables robotic transfers?
RemoteControlled
Servomanipulator

Advanced Human–Machine Interfaces
Target28th IEEE Symposium on Fusion Engineering

Remote HandlingControl Room

Remote Handling Sensor/Actuators• How to disconnect and reconnect myriads of fluid and vacuum lines?
Are there better ways than cutting and welding?
• Develop radiation tolerant cameras that can withstand radiationlevels of >107 Gy. Vacuum tube (Vidicon & Chalnicon) cameras canwithstand 106 Gy, but have poor resolution. Rad resistant fiber optics.
• Do LiDAR and ultrasonic offer possibilities for some areas ofdiagnostics? Need improved synthetic vision and VR simulation.
• Do electronics need to go to vacuum tubes or can CMOS withshielding still be a viable option? What about GaAs rad hard chips?
• Large component placement – hydraulic, air, or electric actuation.
Non organic based hydraulic system?

ITER casksCassette manipulators

Some New Initiatives:• Advanced helium cooling for PFCs & HHF test facility- could be part of a larger blanket test facility• RH as part of FESS system studies• HTSC joint development – SC magnet test stand• HFS launch RF heating initiative• Steady-state pellet fueling

Q&A

28th IEEE Symposium on Fusion Engineering