ARIES-CS Radial Build Definition and

Nuclear System Characteristics

ARIES-CS Radial Build Definition and

Nuclear System Characteristics

L. El-Guebaly, P. Wilson, D. Henderson, T. Tautges,

M. Wang, C. Martin, J. Blanchardand the ARIES Team

Fusion Technology InstituteUW - Madison

US / Japan Workshop on Power Plant StudiesJanuary 24 - 25, 2006

UCSD

2

Nuclear Areas of Research

VV

Blanket

Shield

Magnet

Manifolds

Radial Build Definition:– Dimension of all components

– Optimal composition

High-performance shielding module at min

Neutron Wall Loading Profile:– Toroidal & poloidal distribution

– Peak & average values

Blanket Parameters:– Dimension– TBR, enrichment, Mn

– Nuclear heat load– Damage to FW– Service lifetime

Radiation Protection:– Shield dimension & optimal

composition– Damage profile at shield,

manifolds, VV, and magnets– Streaming issues

Activation Issues:– Activity and decay heat– Thermal response to

LOCA/LOFA events – Radwaste management

3

Nuclear Task Involves Active Interaction with many Disciplines

1-D Nuclear Analysis(∆min, TBR, Mn, damage, lifetime)

Activation Assessment(Activity, decay heat, LOCA/LOFA,

Radwaste classification)

3-D Neutronics(Overall TBR, Mn)

Radial Build Definition@ ∆min and elsewhere

(Optimal dimension and composition,blanket coverage, thermal loads )

NWL Profile( peak, average, ratio)

Prelim. Physics(R, a, Pf, ∆min, plasma contour, magnet CL)

DesignRequirements

no ∆min match

or insufficient breeding

Init. DivertorParameters

Init. MagnetParameters

Blanket Concept

Systems Code(R, a, Pf)

CAD Drawings

Safety Analysis

Blanket Design

4

Stellarators Offer Unique Engineering Features and Challenges

• Minimum radial standoff at min controls machine size and cost. Well optimized radial build particularly at min

• Sizable components with low shielding performance (such as blanket and He manifolds) should be avoided at min.

• Could design tolerate shield-only module (no blanket) at min? Impact on TBR, overall size, and economics?

• Compactness mandates all components should provide shielding function:– Blanket protects shield– Blanket and shield protect manifolds and VV– Blanket, shield, and VV protect magnets

• Highly complex geometry mandates developing new approach to directly couple CAD drawings with 3-D neutronics codes.

• Economics and safety constraints control design of all components from beginning.

5

ARIES-CS Requirements Guide In-vessel Components Design

Overall TBR 1.1 (for T self-sufficiency)

Damage to Structure 200 dpa - advanced FS (for structural integrity) 3% burn up - SiC

Helium Production @ Manifolds and VV 1 appm (for reweldability of FS)

S/C Magnet (@ 4 K): Fast n fluence to Nb3Sn (En > 0.1 MeV) 1019 n/cm2

Nuclear heating 2 mW/cm3 dpa to Cu stabilizer 6x10-3 dpa

Dose to electric insulator > 1011 rads

Machine Lifetime 40 FPY

Availability 85%

6

Reference Dual-cooled LiPb/FS Blanket Selected with Advanced LiPb/SiC as Backup

Breeder Multiplier Structure FW/Blanket Shield VVCoolant Coolant Coolant

Internal VV:

Flibe Be FS Flibe Flibe H2O

LiPb (backup) – SiC LiPb LiPb H2O

LiPb (reference) – FS He/LiPb He H2O

Li4SiO4 Be FS He He H2O

External VV:

LiPb – FS He/LiPb He or H2O He

Li – FS He/Li He He

7

FW Shape Varies Toroidally and Poloidally - a Challenging 3-D Modeling Problem

min

Beginning of FieldPeriod

Middle of FieldPeriod

= 0

= 60

3 FPR = 8.25 m

8

UW Developed CAD/MCNP Coupling Approach to Model ARIES-CS for Nuclear Assessment

• Only viable approach for ARIES-CS 3-D neutronics modeling.

• Geometry and ray tracing in CAD; radiation transport physics in MCNPX.

• This unique, superior approach gained international support.

• Ongoing effort to benchmark it against other approaches developed abroad

(in Germany, China, and Japan).

• DOE funded UW to apply it to ITER - relatively simple problem.

CAD geometry engine Monte Carlo

methodRay object intersection

CAD based Monte Carlo Method

CAD geometry file Neutronics

input file

9

3-D Neutron Wall Loading ProfileUsing CAD/MCNP Coupling Approach

IB OB

– R = 8.25 m design.– Neutrons tallied in discrete bins:

– Toroidal angle divided every 7.5o.– Vertical height divided into 0.5 m segments.

– Peak ~3 MW/m2 at OB midplane of = 0o – Peak to average = 1.52

= 0

= 60

Peak

10

Novel Shielding Approach Helps Achieve Compactness

Benefits:– Compact radial build at min – Small R and low Bmax

– Low COE.

Challenges:– Integration of shield-only and transition

zones with surrounding blanket.– Routing of coolants to shield-only zones.– Higher WC decay heat compared to FS.

WC Shield-only Zone(6.5% of FW area)

Transition Zone(13.5% of FW area)

11

Toroidal / Radial Cross Section(R = 8.25 m )

| | WC-Shield only Zone (~6.5%)

Transition Region (~13.5%)

Nominal Blanket/shieldZone (~80%)

Plasma

Magnet

Vacuum Vessel

WC-Shield-II

WC-Shield-I

Blanket

FS-Shield

FWSOL

Back Wall

Gap

Non-uniformBlanket

LiPb & He Manifolds

4

17

5

28

35

28

5438

8

13

38

28

min =

119

cm

5 cm

Divertor System(10% of FW area)

12

Radial Build Satisfies Design Requirements (3 MW/m2 peak )

||Thickness

(cm)

ShieldOnlyZone

@ min VV

Blanket

Shield

Magnet

WC

Shi

eld-

only

or

Tra

nsit

ion

Reg

ion

Manifolds

Thickness(cm)

Blanket/ShieldZone

> 181 cm

SO

L

Vac

uu

m V

esse

l

FS

Sh

ield

3.8

cm F

W

Gap

+ T

h. I

nsu

lato

r

Win

din

g P

ack

Pla

sma

5 >2 ≥228 312.228

Coi

l Cas

e &

In

sula

tor

5 cm

BW

Ext

ern

al S

tru

ctu

re

10

25 cmBreeding

Zone-I

25 cmBreeding Zone-II

0.5 cmSiC Insert

1.5 cm FS/He

1.5

cm F

S /H

e

63| | 35

Man

ifol

ds

SO

L

Vac

uu

m V

esse

l

Bac

k W

all

Gap

Gap

+ T

h. I

nsu

lato

r

Coi

l Cas

e &

In

sula

tor

Win

din

g P

ack

Pla

sma

5 17

|

5

FW

Ext

ern

al S

tru

ctu

re

1.5 cm FS/He

WC

Sh

ield

-I(r

epla

cea b

l e)

38

WC

Sh

ield

-II

(per

man

ent)

min = 119 cm

28 2

Gap

2

Replaceable | Permanent Components

13

Blanket Design Meets Breeding Requirement

• Local TBR approaches 1.3• 3-D analysis confirmed 1-D local TBR estimate for full blanket coverage.• Uniform and non-uniform blankets sized to provide 1.1 overall TBR based

on 1-D results combined with blanket coverage. To be confirmed with detailed 3-D model.

0.0

0.5

1.0

1.5

0 20 40 60 80

Thickness of Breeding Zone (cm)

3.8cm He-Cooled FWHe-Cooled FS-Shield

FullBlanket

14

Preliminary 3-D Results Using CAD/MCNP Coupling Approach

Model* 1-D 3-D

Local TBR 1.285 1.316 ± 0.61%

Energy multiplication (Mn) 1.14 1.143 ± 0.49%

Peak dpa rate (dpa/FPY) 40 39.4 ± 4.58%

FW/B lifetime (FPY) 5 5.08 ± 4.58%

Nuclear heating (MW):FW 156 145.03 ±1.33%Blanket 1572 1585.03 ±1.52%Back wall 13 9.75 ± 6.45%Shield 71 62.94 ± 2.73%Manifolds 18 19.16 ± 5.49%Total 1830 1821.9 ± 0.49%

____________________________* Homogenized components. Uniform blanket everywhere. No divertor. No penetrations. No gaps.

Future 3-D analysis will include blanket variation, divertor system and penetrations to confirm 1.1 overall TBR and Mn.

15

He Access Tubes Raise Streaming Concern

||Thickness

(cm)

ShieldOnlyZone

@ min VV

Blanket

Shield

Magnet

WC

Shi

eld-

only

or

Tra

nsit

ion

Reg

ion

Manifolds

Thickness(cm)

Blanket/ShieldZone

> 181 cm

SO

L

Vac

uu

m V

esse

l

FS

Sh

ield

3.8

cm F

W

Gap

+ T

h. I

nsu

lato

r

Win

din

g P

ack

Pla

sma

5 ? ≥228 302.228

Coi

l Cas

e &

In

sula

tor

5 cm

BW

Ext

ern

al S

tru

ctu

re

10

25 cmBreeding

Zone-I

25 cmBreeding Zone-II

0.5 cmSiC Insert

1.5 cm FS/He

1.5

cm F

S /H

e

63| | 35

Man

ifol

ds

Loc

al S

hie

ld

He Tube(32 cm ID)

SO

L

Vac

uu

m V

esse

l

Bac

k W

all

Gap

Gap

+ T

h. I

nsu

lato

r

Coi

l Cas

e &

In

sula

tor

Win

din

g P

ack

Pla

sma

5 17

|

5

FW

Ext

ern

al S

tru

ctu

re

1.5 cm FS/He

WC

Sh

ield

-I(r

epla

cea b

l e)

38

WC

Sh

ield

-II

(per

man

ent)

min = 119 cm

28 2

16

Local Shield Helps Solve Neutron Streaming Problem

Pla

s ma

Ba c

k W

all

FW

/Bla

nk

et Shie

ld

Man

ifol

ds

VV

Mag

ne t

He Access Tube

Loc

al S

hiel

d

0

10

20

30

40

No TubeI-D

Limit

2-D with 20 cm Local Shield

2-D

No Local Shield

with TubeOngoing 3-D analysis will optimize dimension of local shield

Hot spots at VV and magnet

17

Key Design Parameters for Economic Analysis

Integral system analysis will assess impact ofmin, Mn, and th on COE

LiPb/FS/He LiPb/SiC(reference) (backup)

min 1.19 1.14

Overall TBR 1.1 1.1

Energy Multiplication (Mn) 1.14 1.1

Thermal Efficiency (th) 40-45%* 55-63%*

FW Lifetime (FPY) 5 6

System Availability ~85% ~85%

__________* Depending on peak .

18

Activation Assessment

• Main concerns:

– Decay heat of FS and WC components.

– Thermal response of blanket/shield during LOCA/LOFA.

– Waste classification:- Low or high level waste?

-Any cleared metal?

– Radwaste stream.

19

Decay Heat

WC decay heat dominates at 3 h after shutdown

102

103

104

105

106

100 101 102 103 104 105 106 107

Time After Shutdown (s)

1h 1d 1w

FS of Blanket-I

FWWC Shield-I

LiPb

20

Thermal Response duringLOCA/LOFA Event

• 3-coolant system rare LOCA/LOFA event (< 10-8/y) • Severe accident scenario: He and LiPb LOCA in all blanket/shield modules

& water LOFA in VV.• For blanket, FW temperature remains below 740 oC limit.• WC shield modules may need to be replaced. More realistic accident scenario

will be assessed.

Nominal Blanket/ShieldTmax ~ 711 oC

Shield-only Zone

Tmax ~ 1060 oC

740 C temp limit

1 s 1 m 1 h 1 d 1 mo

740 C temp limit

1 s 1 m 1 h 1 d 1 mo

21

Waste Management Approach

• Options:– Disposal in LLW or HLW repositories– Recycling – reuse within nuclear facilities– Clearing – release to commercial market, if CI < 1.

• Repository capacity is limited:– Recycling should be top-level requirement for fusion

power plants– Transmute long-lived radioisotopes in special module– Clear majority of activated materials to minimize waste

volume.

22

ARIES-CS Generates Only Low-Level Waste

WDRReplaceable Components:

FW/Blanket-I 0.4WC-Shield-I 0.9

Permanent Components:WC-Shield-II 0.3FS Shield 0.7Vacuum Vessel 0.05Magnet < 1Confinement building << 0.1

LLW (WDR < 1) qualifies for near-surface disposal or, preferably, recycling

23

Majority of Waste (74%) can be Cleared from Regulatory Control

0

2000

4000

6000

8000

Blanket BuildingShield/VV Magnet

14%

5% 7%

74%

Dispose or Recycle

Clear10-1

101

103

105

107

109

1011

100 102 104 106 108 1010

Time After Shutdown (s)

1h 1d1y

Shield

Limit 100y

Blanket

Vacuum Vessel

Magnet

Building

In-vessel components cannot be cleared

24

Building Constituents can be Cleared 1-4 y after Plant Decommissioning

Building composition: 15% Mild Steel, 85% Concrete

10-4

10-2

100

102

104

100 102 104 106 108 1010

Time After Shutdown (s)

1h 1d

IAEA

Limit

100y

US

InnermostSegmentMild Steel

3.5 y

10-4

10-3

10-2

10-1

100

101

102

103

104

100 102 104 106 108 1010

Time After Shutdown (s)

1h 1d1.3 y

IAEA

Limit

100y

US

InnermostSegmentConcrete

25

Stellarators Generate Large Radwaste Compared to Tokamaks

Means to reduce ARIES-CS radwaste are being pursued(more compact machine with less coil support and bucking structures)

FW

BackWall

Blanket

Shield

CoilStructure Manifolds

V V

WP

BuckingCylinder

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

ARIES - I III II IV RS ST ATSPPS CS

SiCSiC

SiC

V V

V

FS

FS(D-

3He)

FS

Stellarators not compacted, no replacements

26

Well Optimized Radial Build Contributed to Compactness of ARIES-CS

Over past 25 y, stellarator major radius more than halved by advanced physics and technology, dropping from 24 m for UWTOR-M to 7-8 m for ARIES-CS,

approaching R of advanced tokamaks.

UWTOR-M24 m

0 5 10 15 20 25

2

4

6

8

m

Average Major Radius (m)

ASRA-6C20 m

HSR-G18 m

SPPS14 mFFHR-J

10 m

ARIES-CS

ARIES-STSpherical Torus

3.2 m

ARIES-ATTokamak

5.2 m

Stellarators||

7 m 8.25 m

198219872000199620002005

27

Concluding Remarks

• Novel shielding approach developed for ARIES-CS. Ongoing study is assessing benefits and addressing challenges.

• CAD/MCNP coupling approach developed specifically for ARIES-CS 3-D neutronics modeling.

• Combination of shield-only zones and non-uniform blanket presents best option for ARIES-CS.

• Proposed radial build satisfies design requirements.

• No major activation problems identified for ARIES-CS.

• At present, ongoing ARIES-CS study is examining more compact design (R < 8 m) that needs further assessment.

28

ARIES-CS Publications

L. El-Guebaly, R. Raffray, S. Malang, J. Lyon, and L.P. Ku, “Benefits of Radial Build Minimization and Requirements Imposed on ARIES-CS Stellarator Design,” Fusion Science & Technology, 47, No. 3, 432 (2005).

L. El-Guebaly, P. Wilson, and D. Paige, “Initial Activation Assessment of ARIES Compact Stellarator Power Plant,” Fusion Science & Technology, 47, No. 3, 440 (2005).

M. Wang, D. Henderson, T. Tautges, L. El-Guebaly, and X. Wang, “Three -Dimensional Modeling of Complex Fusion Devices Using CAD-MCNP Interface,” Fusion Science & Technology, 47, No. 4, 1079 (2005).

L. El-Guebaly, P. Wilson, and D. Paige, “Status of US, EU, and IAEA Clearance Standards and Estimates of Fusion Radwaste Classifications,” University of Wisconsin Fusion Technology Institute Report, UWFDM-1231 (December 2004).

L. El-Guebaly, P. Wilson, and D. Paige, “Evolution of Clearance Standards and Implications for Radwaste Management of Fusion Power Plants,” Journal of Fusion Science & Technology, 49, 62-73 (2006).

M. Zucchetti, L. El-Guebaly, R. Forrest, T. Marshall, N. Taylor, K. Tobita, “The Feasibility of Recycling and Clearance of Active Materials from Fusion Power Plants,” Submitted to ICFRM-12 conference at Santa Barbara (Dec 4-9, 2005).

L. El-Guebaly, R. Forrest, T. Marshall, N. Taylor, K. Tobita, M. Zucchetti, “Current Challenges Facing Recycling and Clearance of Fusion Radioactive Materials,” University of Wisconsin Fusion Technology Institute Report, UWFDM-1285. Available at: http://fti.neep.wisc.edu/pdf/fdm1285.pdf

L. El-Guebaly, “Managing Fusion High Level Waste – a Strategy for Burning the Long-Lived Products in Fusion Devices,” Fusion Engineering and Design. Also, University of Wisconsin Fusion Technology Institute Report, UWFDM-1270. Available at: http://fti.neep.wisc.edu/pdf/fdm1270.pdf

R. Raffray, L. El-Guebaly, S. Malang, and X. Wang, “Attractive Design Approaches for a Compact Stellarator Power Plant” Fusion Science & Technology, 47, No. 3, 422 (2005).

J. Lyon, L.P. Ku, P. Garabedian, L. El-Guebaly, and L. Bromberg, “Optimization of Stellarator Reactor Parameters,” Fusion Science & Technology, 47, No. 3, 4414 (2005).

R. Raffray, S. Malang, L. El-Guebaly, and X. Wang, “Ceramic Breeder Blanket for ARIES-CS,” Fusion Science & Technology, 48, No. 3, 1068 (2005).