concept development of compact demo reactor

Concept development of compact DEMO reactor

Kenji Tobitafor DEMO Plant Design Team

Japan Atomic Energy Research Institute

Special thanks: F. Najmabadi (UCSD), C.P.C. Wong (GA), K. Okano(CRIEPI)

IEA/LT Workshop (W59) combined with DOE/JAERI Technical Planning of Tokamak Experiments (FP1-2) 'Shape and Aspect Ratio Optimization for High Beta Steady-State Tokamak'

OUTLINE

1. ABC of Fusion Reactor Study

2. Compact reactor study at JAERI

3. DEMO design study at JAERIStarted in 2003

Focus on the possibility of an economically attractive reactor in low-A (= 2-2.9), left behind in fusion reactor study previously

- 2 -

1. ABC of Fusion Reactor Study

• Direction of fusion reactor studies

• Necessity to pursue economic fusion energy

- 3 -

(A) Reactor study seeks for an economic reactor concept

Design Year1995 20001990

0

5

10

15

CO

E (¢

/kW

h)

SSTR (16 ¥/kWh)

ARIES-I

ARIES-RS

ARIES-AT

CREST (12.5 ¥/kWh)

Cost-of-Electricity of Fusion

COE of other sources

fission ~5¢/kWhcoal-fired ~6¢/kWh

[1992 JA price basis]

- 4 -

(B) In fusion energy, 60~70% of COE is capital cost

COE (¢/kWh) = Cc + CF + COM

Pe • 8760 (h/yr) • fav

Capital Fuel Operation & maintenance

Capital 53.87 B¥/yrFuel 0.04 B¥/yr

Operation 19.77 B¥/yrMaintenance 17.95 B¥/yr

Costs of CREST (discount rate 2%)

Availabilityoutput

To reduce COE 1) Capital cost 2) Thermal efficiency 3) Availability

- 5 -

(C) Much lower construction cost required for commercialization of FE

Const. Cost Electricity Share

SSTR ~4,500 $/kWARIES-RS 3,770 $/kW

Default 3,440 $/kW 0 ~ 6%

Low Cost 2,400 $/kW 4~11%

- 6 -

Fusion share assessment in 2100

4% ~ 1,500 plants

Share depends on • COE of other sources• CO2-emission standards, etc.

The estimated fusion cost may not be competitive in market

Tokimatsu (2003)

Exploration of compact reactor

USA

Najmabadi (2000) QuickTime˛ Ç∆TIFFÅiLZWÅj êLí£ÉvÉçÉOÉâÉÄ

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JAERI

SSTR (1990)

A-SSTR2 (1999)

Rp = 7 m

Rp = 6.2 m

- 7 -

How to compensate for reduced Vp in compact reactor

low recirculating power by high bootstrap higher thermal efficiency higher N

higher Bmax

ARIES

JAERIHigh to reduce Bmax

Moderate at high Bmax

- 8 -

2. Compact reactor study at JAERI

What led us to low-A compact reactor concept?

- 9 -

JAERI’s approach toward compact reactor

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Rp = 7 mBmax = 16.5 TN = 3.5

Rp = 6.2 mBmax = 23 TN = 4

A-SSTR2

VECTOR

SSTR

Higher Bmax and N

- 10 -

High BT can make it heavySSTR A-SSTR2

7.0 m Rp 6.2 m16.5 T Bmax 23 T136 GJ WTFC 181 GJ

11,200 tons TFC Weight 14,640 tons

TFC weight is significant part of reactor: ~ 45% in SSTR



- 11 -

JAERI’s approach toward compact reactor



Rp = 7 mBmax = 16.5 TN = 3.5

Rp = 6.2 mBmax = 23 TN = 4

Rp = 3.5 mBmax = 20 TN = 5.5

A-SSTR2

VECTOR

SSTR

High Bmax with slim TFC - 10 -

0 5 10R (m)

Reduce WTFC by small RTF

ITERBmax= 13TWTFC = 41 GJ

SSTRBmax= 16.5TWTFC = 140 GJ

VECTORBmax= 19TWTFC = 10 GJ

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High WTFC

Low WTFC

Massive TFC

Slender TFC

RTF

- 12 -

VECTOR

18.2m

Rp 3.2 m Ip 14 MAa 1.4 m N 5.5A 2.3 HH 1.3 2.35 n/nGW 0.9

Bmax 19 T qMHD 6.5BT 5 T Pfus 2.5 GW

Physical features CS-less

Low A (~2.3) high , high nGW, high q

- 13 -

Remove CS to shorten RTF and reduce WTFC

Concept of VECTOR

Slender CSLow-A

Difference between VECTOR and ST

conventional

VECTOR

ST

CS removed

Cu coil

SC coil

A ~ 2.5

A ~ 1.5

Power reactor

VNS

w. n-shield

w/o. n-shield

A = 3-4

- 14 -

VECTOR, likely to have economical and environmental advantages

Reactor weight (t)

Pow

er /

Wei

ght (

kWth/t)

Low const. costResource-saving

Economical

0

100

200

300

0 10,000 20,000 30,000

ITER

ARIES-RS

ARIES-STSSTR

A-SSTR2

DREAM

VECTOR

- 15 -

Radwaste of VECTOR, ~4,000 t• LLW, vulnerable point of fusion (usually, ≥ 10,000 t)

• PWR ~ 4,000 tClearance Clearance Clearance

Reinforced shield Reinforced shieldRecycle

ReuseCompactness

Res

ourc

es (t

)



Dis

posa

l was

te (t

) 0

10,000

10,000

20,000

20,000

Clearance

Low level

Medium level

SSTR DEMO2001 VECTOR

ReuseLiPbTiH2

RecycleBe12TiLi12TiO3

- 16 -

Remarks on VECTOR

VECTOR concept on TFC system breaks new ground of power reactor design in low-A

ST

1 2 3 4 52

4

6

8

ARIES-ST

ARIES-AT

ARIES-RS

ARIES-I

A-SSTR2

SSTRPPCS(B)PPCS(A)PPCS(C)

PPCS(D)

CREST

VECTOR

VECTOR-opt

conventional

A

N

What is sure

Open question Is the optimal design point for co

st-minimum really A ~ 2.3 for the VECTOR concept?

Assumed parametric dependence of N(A) is uncertain.

- 17 -

3. DEMO design study at JAERI

How to fit VECTOR concept to DEMO

Three DEMO options

- 18 -

JA Strategy for FE commercialization

IFMIF

Commercial.

DEMO

ITER

Tech.R&DNCT

1 GWe output Year-long continuous op.

Economical feasibility

• DEMO must be compact and have high power density

- 19 -

Tradeoff between size and feasibility

CL

small as possible to reduce WTFC

CSRemove Install

Compact Large Rp

More feasible

+

difficult +

Size

plasma

Based on roles of CS, three DEMO options are under consideration

VECTOR concept

- 20 -

Difficulties caused by CS-less

Ip rise/control

Ex) CS-less Ip ramp-up Exp. (JT-60U, etc)

will be resolved

Shaping triangularity is limited (x ~ 0.3) problematic in • confinement in high n/nGW • suppression of giant ELMs

0.6

0.5

0.4

0.3

0.2

0.1

03 4 5 6 7

q95

giant ELM

grassy ELMJT-60U

- 21 -

Best effort to raise w/o CS

Rp 5.1 m

a 2.1 mIp 17.5 MA

p 2.5

li 0.8

up 2.0

up 0.3

A far distance between plasma and PF coils makes the shaping difficult.

- 22 -

Three DEMO optionsshaping Ip rampCSsize

“Full CS” 1.5 m (dia.)~30 Vsec x ~ 0.45 15 MAlarge

Option C

“CS-less” small x ~ 0.3 Option A

0.7m (dia.)~10 Vsec“Slim CS” x ~ 0.4 ~ 5 MAmedium

Option B

challenging

conservative- 23 -

Preliminary design parametersCS-less Slim CS Full CS

Rp (m) 5.1 5.5 6.5

a (m) 2.15 2.1 2.1A 2.4 2.6 3.1 2.08 2.0 1.9 ~0.3 0.4 0.45

BT /Bmax (T) 5.4 / 18.2 6.0 / 16.4 6.8 / 14.6

Ip (MA) 18.1 16.7 15.0

q95 5.7 5.4 5.3

N 4.6 4.3 4.1

HH 1.3 1.3 1.3fBS 0.76 0.77 0.79

n/nGW 0.95 0.98 1.0

Pfus (GW) 3.1 3.0 3.0

Pn (MW/m2) 3.6 3.5 3.0

Q 49 52 54Weight (tons) 15,700 17,500 23,900

- 24 -

Comparison of Options

0

100

200

300

0 10,000 20,000 30,000

ITER

ARIES-RS

ARIES-STSSTR

A-SSTR2

DREAM

VECTOREconomical

Low const. costP fus

/ w

eigh

t (kW

/t)

Reactor weight (t)

Option A

CS-lessRp~5.1m

Full CSRp~6.4m

Option C

shaping, Ip ramp

Slim CSRp~ 5.5m

Option B

shaping

Higher Bmax

, N margin Adv. n-shield

- 25 -

Key parameters in reactor design

inboard SOLGapBLKn-shieldVVth-insulator

B

R

CL

Rp

RTF

Bmax

TF

TF 1.3 m Rule of thumb

TFCCS

Minimum shield thickness enough to protect TFC from neutron damage

Four key parameters : Rp, Bmax, RTF, TF

To use BT effectively, the inboard SOL width should be small

- 27 -

SOLin, expected to increase with A

SOLin usually assumed to be 10 cm

but expected to decrease with A.

SOLout ~

€

SOL in

SOL out

~A+ 1

21+ 1

A

⎛ ⎝ ⎜

⎞ ⎠ ⎟L

A−12

1−1A

⎛ ⎝ ⎜

⎞ ⎠ ⎟L~1+

L2A

1− L2A

L=ln8A+p +li2−1

Roughly,

defined by the width of heat flux in SOL (assumed to be 3 cm)

- 28 -

Low-A requires a wide inboard clearance, especially for “CS-less”

For A~3 SOL

in ~ 10 cm, good approx.

For A < 2.5 must be careful about SOL

in

without CS

25

20

15

102 2.5 3.0

A

SOL

(cm )

inp = 2.5

βpp = 2.5 = 2.5

with CS

Determined from the flux surface corresponding to SOLout = 3cm

- 29 -

RCS

RTFTF a

RP

0

5

10

15

20

0 1 2 3 4RTF (m)

Bmax (T)

Rcs = 0.7m

Rcs = 0 m

Rcs = 1.5 m

Separate TFC design

Bmax

CSTFC

Selection of 　　 design parameterｓ

- 30 -

N, BT


RCS

RTFTF a

RP

0

5

10

15

20

0 1 2 3 4RTF (m)

Bmax (T)

Rcs = 0.7m

Rcs = 0 m

Rcs = 1.5 m

Separate TFC design

Bmax

CSTFC

75% of

78% of N

2 3 41.5

2.0

2.5

3

4

5

A

NWong’s formula (, N)

- 30 -


N, BT

RCS

RTFTF a

RP

0

5

10

15

20

0 1 2 3 4RTF (m)

Bmax (T)

Rcs = 0.7m

Rcs = 0 m

Rcs = 1.5 m

Separate TFC design

Bmax

CSTFC

2 3 41.5

2.0

2.5

3

4

5

A

N

75% of

78% of NWong’s formula (, N)

HH (=1.3)

IP, q VP, Pfus, PCD, fGW, ….

Check consistency

- 30 -

0.5 1.0 1.5 2.0 2.5 3.04

5

6

7

18000 t

15000 t

Pfus= 3 GW

2 GW

RTF (m)

Rp (m)

A = 2 A = 2.5

A = 3

18 T0 T 15 T

Pn = 4 MW/m2

3 MW/m2

N = 5

TFC inoar with (m)

0.5 1.0 1.5 2.00.0

N = 4

Optimal design point (“Slim CS”)

Pfus = 3GW　 ← Pe

net = 1 GWe

Weight minimum

Optimal range, rather wideoptimal

–– less dependent on A (or RTF)

fat TFC & high-A

slender TFC & low-A

- 31 -

Breakdown of weight

A= 2.2

A= 2.8

0.5 1.0 1.5 2.0 2.5 3.04

5

6

7

18000 t

15000 t

Pfus= 3 GW

2 GW

RTF (m)

Rp (m)

A = 2 A = 2.5

A = 3

18 T0 T 15 T

Pn = 4 MW/m2

3 MW/m2

N = 5

N = 4

Weight (t)

light heavy

Higher ATorus comp.

PFC TFC

Lower A TFCTorus comp.

PFC

5,000 10,000 15,000 20,0000

TFCPFCBLK

Div

Shld

VV

CryoOther

- 32 -

Problem in parameter selection: N (A) is not sure

Kessel (ARIES-AT, -RS)Wong (based on Miller’s stab.DB)

A (A)

N(A,)-dependence hidden

N vs curve, depends on

N, less dependent on in our conditions

Our conditions

A = 2.0

2.5 3.0 3.5

8

7

6

5

4

N

2.0 3.0

100% BS-driven plasma

Our systems code uses this

- 33 -

How does the optimal design point change when N is independent on ?

Original assumption

2

3

1

1.5 2.0 2.5 3.0 3.5 4.00

2

4

6

N

A1.5 2.0 2.5 3.0 3.5 4.0

2

3

1

0

2

4

6

A

N

Alternative assumption to check an impact of N()

Based on Wong’s formula Kessel-like (but not incl. dependence of N on A)

- 34 -

RTF (m)0.5 1.0 1.5 2.00.0

1.5 2.0 2.5 3.0 3.5 4.0

2

3

1

0

2

4

6

A

N

TF inoar with (m)

0.5 1.0 1.5 2.0 2.5 3.04

5

6

7

18000 t

15000 t

A = 2 A = 2.5 A = 3

18 T0 T 15 T

4 MW/m2

Pn = 3 MW/m2

Pfus = 3 GW

2 GW

0.5 1.0 1.5 2.0 2.5 3.04

5

6

7

18000 t

15000 t

Pfus = 3 GW

2 GW

RTF (m)

Rp (m)

A = 2A = 2.5

A = 3

18 T0 T 15 T

Pn = 4 MW/m2

3 MW/m2

N = 4

TFC inoar with (m)0.5 1.0 1.5 2.00.0

1.5 2.0 2.5 3.0 3.5 4.0

2

3

1

0

2

4

6

N

A

N = 5

A ~ 3 optimum when N(A,) = const Original design Constant N

N = 4

optimal

OptimalSlight increase in Rp

- 35 -

Present understanding on DEMO• With slim CS, DEMO seems to su

cceed in adopting the VECTOR concept with plasma shaping capability.

• At the optimum design point, DEMO can have low-A (= 2.5-3) which is unexplored A in previous power reactor study before VECTOR.

ST

1 2 3 4 52

4

6

8

ARIES-ST

ARIES-AT

ARIES-RS

ARIES-I

A-SSTR2

SSTRPPCS(B)PPCS(A)PPCS(C)

PPCS(D)

CREST

VECTOR

VECTOR-opt

conventional

A

N

DEMO

- 36 -

SummaryVECTOR concept Removes CS to shorten RTF and reduce WTFC ,

leading to slim TFC system compatible with high Bmax

Suggests a possibility of power reactor with A = 2-3

DEMO • CS will be necessary for shaping.

• “Slim CS”, i.e., modified VECTOR concept, enables us to envision DEMO with A = 2.5-3

To make the proper footing of DEMO, dependence of N on A and should be investigated in the range of A = 2.5-4, hopefully through international cooperation

- 37 -

concept development of compact demo reactor

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