The Fusion Nuclear Regime, Our Next Step
What Does it Need to Do?
C. E. Kessel, ORNL

SOFE Town Hall on Fusion Energy, June 4, 2019

The Compact Pilot Plant (CPP)The Compact Pilot Plant is identified in the National Academy Study report
2nd Major Recommendation: the US should start a national program of interconnected science andtechnology research extending beyond what will be accomplished with ITER and leading toconstruction of a compact fusion pilot plant at the lowest possible capital cost
In first phase, pilot plant should be capable of demonstrating fusion electricity for periods lasting
minutes…..
In the second phase, the pilot plant should be capable of uninterrupted operation for many days
allowing fusion materials and component testing consistent with a commercial power plant……
What is compact? Size, cost, power……. Lowest possible cost, and leading to low COE?
Lower unit electric power plants as the end product?
Presumably fusion electricity is net electricity
Are two phases actually required? Do the two phases require different fusion cores?
Why is it called a Pilot Plant? Will this be a problem for the Office of Science?
What is the difference between a CPP and an FNSF?

What does a Compact Pilot Plant / Fusion Nuclear Science
Facility Need to do?
Strongly advance fusion neutron exposure of all fusion core, near-core and ex-core components towards power plantlevelsUtilize and advance fusion power plant relevant materials addressing radiation resistance, activation, operating
temperatures, chemical compatibility, and plasma material damage
Operate in fusion power plant relevant environmental conditions; temperatures, pressures/stresses, flow rates,hydrogen, B-field, neutrons, and gradientsProduce tritium in quantities that closely approaches or exceeds consumption from fusion reactions, plant losses anddecay
Extract, process, inject, and exhaust significant quantities of tritium in a manner that meets all safety criteria,requiring a high level of inventory prediction, control and accountancy

What does a Compact Pilot Plant / Fusion Nuclear Science
Facility Need to do?
Routinely operate plasmas for long durations…….generally considered to be days to weeks, and ultimately ~ 1 year fora power plant
Advance and demonstration enabling technologies that support the very long duration plasma operations with
sufficient performance and reliability to project to DEMO and power plants
Demonstrate safe and environmentally friendly plant operations, in particular with respect to tritium leakage, hot cell
operations, onsite radioactive material processing and storage, no evacuation plan and meet or exceed all regulatory
aspects
Develop power plant relevant subsystems for robust and high efficiency operation, including net electricity
production, heating and current drive, pumping, heat exchanger, cryo-plant, etc.
Advance toward high availability, including gains in subsystem and component reliability, progress in capabilities andefficiency of remote maintenance operations, accumulation of reliability and failure rate data that can be used toproject and design future systems

What is the Fusion Nuclear Regime?
ITER

CPP/FNSF

Power Plant (ACT1&2)

Fusion power, MW

500

518

1800-2600

Fusion power growing

Major radius, m

6.2

4.8

6.2-9.8

Devices getting larger?

Ave neutron wall load,
MW/m2

0.57
(0.76 peak)

1.2(1.75 peak)

1.5-2.5(2.3-3.8 peak)

Increasing rate of damage,He prod

Plasma pulse length, s500-3000

105 - 106

3x107

Ultra-long plasma durations

DT operation, years

20 (~ 1 FPY)

25 (7.8 FPY)

40 FPYHigh neutron exposure

Peak material damage, 3dpa

7, 20, 30, 40, 40-80

150-200

High damage, He and H
production

TBR

1.07

1.05

Tritium self-sufficiency

Materials

SS, CuCrZr, H2O, W

RAFM, W, SiC-c, He,PbLi, Li2TiO3RAFM, W, SiC-c, He,PbLi, Li2TiO3Transition to fusion nuclear
relevant materials

Operatingtemperatures

150-285 C

300-600 C

300-600 C

Power plant operating
environment

MaintenancePort based, small piece Radial, Full sector

Radial, Full sector

High availability

ITER DT
CPP/FNSF He/DD
CPP/FNSF DT

now
2015

2035

2025

ITER He/H, DD
DIII-D
NSTX-U

2045
ITER DT

Notional timeline to establish
2055

Pre-CPP/FNSF R&D
CPP/FNSF Design & Construct
CPP/FNSF Operation

Plasma Optimization

Worldwide short and long pulse plasma facilities
JET, ASDEX-U, WEST, JT-60SA, KSTAR, EAST
Design & Construction of Fusion
Nuclear Device

Fusion nuclear materials development

HFIR

Fusion Nuclear
DeviceFPNS

Plasma facing materials andcomponents

MPEX

BCTF

Blanket and fuel cycle development
Enabling Technologies (magnets, H/CD,fueling, diagnostics, etc.)

CPP/FNSF

HBMTF
RFTF

Utilize int’l collaborations where they
are better positioned to do R&D

Any Next Step Should be Fusion Nuclear, and Will Involve a
Critical Materials-Component Exploration à Optimization

DPA

plasmaEstablish the actual fusion in-service material and scientific/engineering
database on all components in the fusion core and near core

1 FPY

How do materials behave
How do components behave

The CPP/FNSF needs to push to high nuclear exposures in a systematic way
We must prepare for the CPP/FNSF with 1) fusion prototypic neutron source
material exposures, and 2) highly integrated non-nuclear component testing

plasmaSubject to high temperatures,
high stresses,
high neutron damage,high He and H production,hydrogen in material matrix (H, D, T)
multi-material interfaces
gradients in all these parameters

20 cm

L

appm HeHe, 8

Tritium, Making it, Retrieving it, Accounting for it, Controlling it
A CPP/FNSF will have to generate its own tritium, although it will have to start with an inventory
produced somewhere else (fission plant?)A CPP/FNSF will be the first complete tritium self-sufficient system
CPP/FNSF producing Pfusion = 518 MW
Tritium consumption = 28.8 kg /FPY (ITER lifetime consumption)
DT operation phases, plasma on-time (making neutrons):
Phase 3 – 274 days….21.6 kg Tritium consumed
4 – 460 days….36.3 kg
5 – 639 days….50.4 kg
6 – 894 days….70.5 kg
7 – 894 days….70.5 kg à 250 kg T consumed

Tritium breeding ratio = 1.07
Including all penetrations for H/CD,TBM, MTM, diagnostics

Tritium migration
modeling, tracking
movement and losses

Single plasma pulse is ~ 10 days long, requires 0.79 kg of T
9.14x10-7 kg/s of T is consumed (1.82x1020 tritons/s)

A power plant would consume ~ 4000-5000 kg T in its life

Humrickhouse, INL

Bohm, Davis, UW

A CPP/FNSF Will Have Major Plasma Challenges
The plasma pulse length must grow by ~300 times for a CPP/FNSF and ~104 times for a power plant,
beyond ITER
With plasma on-times per year advancing from 3x10-4 for present devices, to 0.05 for ITER, to 0.35 for
CPP/FNSF, and 0.85 for power plantsSuch long plasma durations raise many questions about the plasma operating point, and require major
improvements for plasma support systems
Plasma facing components are metal, we think
What beta to assume? Above the no wall limit?
How high an energy confinement is credible?
100% non-inductive plasma current
Strong plasma shaping, internal feedback coils
Mitigated disruptions? No runaway electrons
ELMs
Density relative to Greenwald density
Radiative divertor solutions, DN or SN?

βNHow Can We Take Full Advantage of aDD Phase on the CPP/FNSF?

Power Plant

6ACT1With wall βN limit

5KSTAR

43Presentfacili7es

2100

101

JT-60SAEASTFNSF

DEMO

No wall βN limit

ITER

Range ofpowerplants

ACT2Pulse length, s102

103

104

105

1 day106107

2 weeks 1 year

Plasma and Engineering Enabling Technologies, the Stuff ThatEC
Makes it Work
LH
Transitioning to new materials
Transitioning to high temperatures
Long pulse plasma loading
Continuous operation
Nuclear damage and gamma rays
Limited access and resolution
Diagnostics
Plasma Control

Heating and Current Drive
ICRF

Pellet Fueling and Continuous Cryo-pumping
TF coil, case and super-structureImproved LTSCHTSC Tape

Magnets

Remote MaintenanceHow Compact Can a CPP/FNSF Be?
Inboard build determines the device size for a tokamak
Magnet radiation limits dominate requirements for shielding
Breeding zone thickness determined by TBR requirement
Aspect ratio can drive need for inboard breeding

Central solenoid

LTSC TF Coil in FNSF

Bucking cylinder

Radial build for FNSF

Material choices for shielding, breeding, structure
He vs H2O, WC vs Borated-Fe, Cu vs SC
Actual TF/CS magnet builds (winding pack andstructural), B and <j>Burning out components or protecting for plant life
Assumptions for qdivpeak, bN, H98, B

The FNSF Can Actually Provide Both Missions Described in theNAS report for the Pilot Plant
The FNSF design reference operating point for the plasma, was constructed to reflect
the power plant regime, but many operating points are available to the device
FNSFref
Plasma gain (Pfus/Paux) Q

45678

9

Engr gain (Pelec/Prec)

Qengr

0.77

0.98

1.12

1.26

1.40

1.53

Beta

2.5

2.5 - 3.3

2.5 - 3.3

2.8 - 3.3

2.8 - 3.3

3.0 - 3.5

Energy confinementbNH98

1.0

1.2 - 1.6

1.3 - 1.6

1.4 - 1.6

1.4 - 1.6

1.5 - 1.6

Density/density limit

n/nGr

0.9

0.45 - 0.9 0.6 - 0.9

0.7 - 0.9

0.7 - 0.9

0.8 - 0.9

Net electric power

Pnet,elec,
MWe

-80

-10 - 1745 - 60

54 - 95

87 - 114

14 - 27

A facility like the FNSF can produce net electricity by being somewhat more aggressive on plasma physics

Any Compact Pilot Plant will be very similar to the FNSF
Net electricity can be produced with somewhat more aggressive plasma physics thanassumed for the reference operating point in the FNSF, in the same device with thesame fusion core
The NEXT step in the US fusion development path MUST be Nuclear, but is not a power
plant……whatever you want to call it, a CPP, a FNSF
Establishing the strongly fusion nuclear & plasma in-service environment for the first time, andoptimizing the fusion core material-components
Establishing the first tritium self-sufficient facility
Establishing the first sustained ultra-long pulse plasmas and the multiple enabling technologies thatsupport these
Provide the first integrated operation of a strongly fusion nuclear plant with all relevant subsystems

Backup Slides

A nearer term facility like the FNSF requires a numberof technical philosophies/approaches to be
defined/explored
Pre-FNSF R&D – how do we see the R&D evolution to prepare us for the FNSF, design and operation
Facility missions and metrics – what progress does the facility make on the pathway to a power plant
Physics strategy – how do we choose plasma parameters, what’s their impact
Long term power plant relevance and engineering strategy – design choices are made to keep thescientific/technology development on track, avoid diversions that do not contribute to the power
plant vision
Minimal, Moderate, and Maximal FNSF
Qualification requirements to install a component/material in the FNSF – fusion neutron exposure to
the dpa level, highly integrated non-nuclear testing…..plasma-vacuum systems are not consistent
with “cook and look” approach to FNS, remote-maintenance
FNSF program plan – phases, material/temperature/dpa evolution, operation and maintenanceBlanket (divertor/launchers) choices and testing strategy – provide the process by which we test andadvance fusion core components, and backups
Hot Cell – how do we access and process the information from the FNSF operation

Pre-FNSF: Fusion Core Components, Evolu7on to Integrated
Component Tes7ng (Blanket, Divertor, RF Launcher)
2030

2020

2050

2040

DT FNSF

He/DD

DCLL RAFM 350-550 C

7 dpa

2060

20 dpaUS DEMO

30 dpa40 dpa40-80 dpa

(including MTM, TBM, Diag, RF penetra7ons)

Tri7umLiquid Metal
Integrated
blanket testFW à
Linear plasma
Tokamak
HHF

DCLL CNA/RAFM 400-600 C

Breeding blanket(including MTM, TBM, Diag, RF penetra7ons)DCLL CNA and/or ODS 450-650 C(including MTM, TBM, Diag, RF penetra7ons)

VV

Vacuum Vessel Baini7c Steel

Integrated blanket test

Tungsten-1 Divertor
Divertor

Tungsten-2 Divertor
RAFM/Cu coated RF

RF launchers

RAFM/W coated RF

Linear plasma
Tokamak
HHF
Linear plasma
Tokamak
HHF
RF test standIntegrated blanket testPhase

1He/H
1-2

2

45

6

7

DT
2.75

DT
4.5

DT
5.0

DT
6.5

DT
6.5

PP40 FPY

1.75

1.75

1.75

1.75

1.75

2.25

1525

3535358555 d91 d128 d128 d128 d

310 d

Plasma duty
cycle, %(pulse/dwell)

33

67

91

9595

100%

(1d/2d)(2d/1d)(5d/.5d)(10d/.5d)(10d/.5d)

Total
maintenancetime, days

550 d

1131 d1120 d1495 d1495 d2585 d200 d/yr

229 d/yr

224 d/yr

230 d/yr

230 d/yr

55 d/yr

Peak dpa

7.2

19.7

30.6

39.8

39.8/79.6

150-200
650/500

years

DD
2-3

3

peak

Nw ,
MW/m2
Plasma ontime, %/year

15-50

Max/minblanketstructure opotemp, C

< 550

< 550

550/400

550/400

600/450

650/500

650/500

Blanket
Structurematerial

RAFM
Gen1RAFM
Gen1RAFM
Gen1

RAFM
Gen1

RAFMCNA

RAFMCNA &ODS

RAFMODS

25.3 years DT, 7.8 years neutrons, 650 plasma pulses

Components in fusion
core would be evolved
and tested in the FNSF
We concentrate on the blankets, butthere are others that may have a testing
sequence…..materials, temperatures,design, etc.

Divertor

IB and OB
Blankets

RF Launchers, TBMs,Diagnostics

Blanket Layout andTesting
There are several DIFFERENT blanket
geometries due to multiple functions inthe FNSF

Nuclear analysis of different sectors
Step 11
2 NBI added, 4sectors

Step 12
1 IC added, 1sector

DCLL 550/400C RAFM (some are taken for autopsy)

4

DCLL 550/400C RAFM/ LH
DCLL 550/400C RAFM/ EC
DCLL 550/400C RAFM/ NB
DCLL 550/400C RAFM/ IC

102
1combined diag

DCLL 600/450C RAFM CNA (next phase T and RAFM)DCLL 550/400C RAFM/ MTM
DCLL 550/400C RAFM/ TBM-HCLL
DCLL 550/400C RAFM/ TBM-HCCB(PB)
DCLL 550/400C RAFM/ Diagnostic

Step 10
3 Diagnostics added, 3sectors

Step 13
1 LH added, 1sector

Step 94 TBM added, 4sectors

Step 141 EC added, 1sector

A. Davis, UW

211
1
3___
16

Top view

Divertor Testing, must fit into
the allocated envelope
What will be the preferred W or other divertor
material?
W or W-alloy
W/X composites
Wf/Wm composites???
Will there be variants like RAFM?
Structure & armor design

Flat plat fully detach
Fdiv,rad ~ 100%

Magnetic geometries
Structure Temperature ranges
Taken from Snead, 2016

W/RAF laminate(Garrison)

FZJ

X-divertor, KDEMO
Covelle, Univ Texas

WC in Fe matrix (Álvarezet al., 2015)

ITER-like tilted plate
Fdiv,rad ~ 75%

What do we do with the Sectors: Blankets,Divertors, Launchers in the Hot Cells?
Inspect
Decontaminate (clean off)
Inspect
Dismantle
Inspect
Examine untreated surfaces
Examine mounts/connectors
Cut samples
FW
Side wall
Grid plates
Mounting hardware
SRDiv armor
Div structure
FCI
W stabilizer…...
Material examinations (PIE, mech prop tests, He bubbles, etc.)

From ARIES-AT

Also examine the test specimens in the material test module & surveillance samples

Hot Cell
We are anticipating a hot cell sequence from large intact sectors
progressively down to small material samples, requiring a transferfrom hot cell 1 to hot cell 2, etc….we want information quickly
Robotic and computer controlled systems would dominate theprocessing
10,000 Sv/hr dose at FW vs 6 mSv/year background
Issues include 1) high dose and hardened equipment, 2) complex
processing (tritium, surface materials), 3) decay heat, and 4) need for
rapid turnaroundFull Sector Maintenance is Pursued to Provide
Fast, Flexible and Reliable Approach
Possible Test Blanket Module (TBM, RF) maintenanceInspection
Minor Maintenance
Major MaintenanceHow much time does
it take?

Maintenance Cask

Maintenance Corridor