ARC: A compact, high-field, fusion nuclear science facility and demonstration

power plant with demountable magnets Authors: B.N. Sorbom, J. Ball, T.R. Palmer, F.J. Mangiarotti, J.M. Sierchio, P. Bonoli, C. Kasten, D.A. Sutherland, H.S. Barnard, C.B. Haakonsen, J. Goh, C. Sung, and D.G. Whyte

Abstract

The Affordable, Robust, Compact (ARC) reactor conceptual design aims to reduce the size, cost, and complexity of a combined Fusion Nu-clear Science Facility (FNSF) and demonstration fusion pilot power plant. ARC is a 260 MWe tokamak reactor with a major radius of 3.3 m, a minor radius of 1.1 m, and an on-axis magnetic field of 9.2 T. ARC has Rare Earth Barium Copper Oxide (REBCO) superconducting toroidal field coils with joints to allow disassembly, allowing for removal and re-placement of the vacuum vessel as a single component. External cur-rent drive of 25 MW of inboard launched LHRF power and 13.6 MW of inboard launched ICRF power is used to provide a robust, steady state core plasma. ARC uses an all-liquid blanket, consisting of low pressure, slowly flowing Fluorine Lithium Beryllium (FLiBe) molten salt. The liquid blanket acts as a working fluid, coolant, and tritium breeder, and mini-mizes the solid material that can become activated. The large tempera-ture range over which FLiBe is liquid permits blanket operation at 800 K with single phase fluid cooling and a high-efficiency Brayton cycle.

Acknowledgements

References

56th Annual Meeting of the APS Division of Plasma Physics, October 27 - October 31, 2014 • New Orleans, Louisiana

We thank Leslie Bromberg, Charles Forsberg, Martin Greenwald, Amanda

Hubbard, Zach Hartwig, Brian LaBombard, Bruce Lipschultz, Earl Marmar,

Joseph Minervini, Geoff Olynyk, Michael Short, Peter Stahle, Makoto Taka-

yasu, Stephen Wolfe, and Stephen Wukitch for conversations and com-

ments that improved this work. BNS is supported by U.S. DOE Grant No.DE

-FG02-94ER54235 and Cooperative Agreement No. DE-FC02-99ER54512

This work originated from a MIT Nuclear Science and Engineering graduate

course. DGW acknowledges the support of the NSE Department and the

PSFC.

High Temperature Superconductors (HTS) open up

high field design space

HTS lack critical current degradation of traditional superconductors, al-

lowing for higher fields to be accessed

Structural analysis shows that stress, not critical current

limits the maximum achievable field

Design Parameter Value

Fusion Power 525 MW

Total Thermal Power 708 MW

Conversion Efficiency 0.40 – 0.50

Net Electric Power 190 – 261 MW

Power Multiplication Factor 3.0 – 3.8

Plasma Gain 13.6

LHCD Coupled Power 25 MW

ICRF Coupled Power 13.6 MW

Major Radius 3.3 m

Inverse Aspect Ratio 0.34

Toroidal Field 9.2 T

Plasma Current 7.8 MA

Bootstrap Fraction 63 %

Normalized Beta 2.59

Avg. Plasma Temperature 13.9 keV

Avg. Plasma Density 1.75 x 1020 m-3

Tritium Breeding Ratio 1.10

Magnet Lifetime 10 FPY

Simple cost analysis demonstrates economic feasibility

and motivates further study

Cost analysis based on Meade volumetric cost scaling [6] combined

with quotes obtained by manufacturers

Predicts total cost of ARC to be ~$5.5B

“Novel” material costs found to be small fraction of total cost (YBCO

tapes — $200M, FLiBe — $150M )

Vacuum vessel cost ($90M) low enough to be a replaceable component Tem

Technology High temperature superconductors enable demountable

magnets, replaceable vacuum vessel

Vertical maintenance scheme makes liquid immersion

blanket concept attractive

High field enables efficient RF current drive

High temperature superconductor opera-

tion allows for joints in magnets

Joints allow for disassembly of magnets

and vertical maintenance scheme

Demountable coils (combined with all-

liquid blanket) allow ARC vacuum vessel

to be a single, replaceable component

Replaceable vacuum vessel is attractive

from an FNSF viewpoint (allows multiple

materials/divertors to be tested) and a

DEMO viewpoint (vacuum vessel can be

replaced every few years to mitigate ra-

diation damage concerns)

Vacuum vessel fully immersed in

slowly flowing FLiBe molten salt

Low risk nuclear technology—no

‘cracks’ in fluid to allow neutron leaks

FLiBe has similar thermohydraulic

properties to water, but at a higher

temperature and temperature oper-

ating window [2]

FLiBe acts as neutron moderator,

tritium breeder, and coolant

MCNP5 simulations with ARC geome-

try show TBR of 1.10 and magnet life-

time of ~ 10 full power years

LHCD efficiency shown to scale as B2

[3], making high-field, high-field

launch LHCD attractive

ACCOME [4] simulations using ARC

parameters yield LHCD current drive

efficiency of 0.41 [1020A/W/m2]

Efficient LHCD, combined with fast-

wave ICRF allows for fully non-

inductive operation of ARC

COMSOL analysis of magnet structure

design shows that stress limits take

over before critical current limits in

superconductor

This motivates future investigation in-

to structural materials and structural

engineering to enable even higher

fields (and thus better performance)

ARC Highlights: A “JET-sized” FNSF/Pilot

High magnetic field enabled by high temperature,

Rare Earth Barium Copper Oxide (REBCO) super-

conductors

Compact design (same fusion power as ITER at 1/7

the volume)

All-liquid, molten salt (FLiBe) immersion blanket

Vertical maintenance scheme enabled by jointed

magnets

High-temperature, high-efficiency Brayton cycle

power generation

Margin to intrinsic limits of core plasma

Efficient, high-field side launch LHCD and fast-

wave ICRF provide current drive for fully non-

inductive operation

Sensitivity scan shows wide range of possible ARC

confinement space

ARC is stable to all disruptive limits while having high

fusion performance

High field allows ARC to be fully non-inductive and achieve

wall loading suitable for FNSF mission

ARC was designed to be within all

disruptive limits

Note that VDE limit is not a ‘hard’

limit but a conservative empirically

observed limit [5]

The high field in ARC provides a high

safety factor and a low βN route to

non-inductive scenarios with a mod-

est bootstrap fraction of 63%

A 0D scoping study was per-

formed in R-ε space, fixing fusion

power, plasma gain, and βN

The primary limit bounding the

solution space was the non-

inductive requirement, not intrin-

sic limits

While no explicit divertor design

was chosen, power density was

chosen to allow ARC to be used as

a divertor “test-bed” during its

FNSF stage

0D sensitivity scan was carried

out to assess ARC performance at

different achieved H factors

Scan performed by scaling the

volume-averaged pressure ob-

tained from the design point

External power is modified to

satisfy non-inductive requirement

Results show that the ARC design

achieves Qp>5 over a large range

of H factors

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6. 6. D. Meade, “A Comparison of Unit Costs for FIRE and ITER,” presented at ITER Cost Review Session July 9, 2002

7. This poster based on the paper, “ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets” Submitted to Fusion Engineering and Design, Sept. 2014. Preprint available at:

8. http://arxiv.org/abs/1409.3540

[1]

ITER

(NbSn, 5.3 T)

ARC

(HTS, 9.2 T)

*To Scale*

(Same fusion power)

R = 3.3 m Plasma Core Scenario

Higher fields enable smaller reactors