Design Study of Fusion DEMO Plant at JAERI

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Design Study of Fusion DEMO Plant at JAERI
S6-14-O-02
ISFNT7, Tokyo, May 23-27, 2005

• Japan Atomic Energy Research Institute

K. Tobita, S. Nishio, M. Enoeda, M. Sato, T.
Isono, S. Sakurai, H. Nakamura,S. Sato, S.
Suzuki, M. Ando, K. Ezato, T. Hayashi, T.
Hayashi, T. Hirose, T. Inoue, Y. Kawamura, N.
Koizumi, Y. Kudo, R. Kurihara, T. Kuroda, K.
Mouri, Y. Nakamura, M. Nishi, Y. Nomoto, J.
Ohmori, N. Oyama, K. Sakamoto, T. Suzuki, M.
Takechi, H. Tanigawa, K. Tsuchiya, D. Tsuru (
Kawasaki Heavy Industries)
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OUTLINE

1. Background
2. Concept of DEMO
3. Features of DEMO plant
4. Next steps in design study

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1. Background
Situation of JA strategy for FE commercialization
JA strategy still argued in AEC, not settled
Point of argument ONE or TWO steps to
commercialization?
1 step?
Commercial.
Technology Economy
ITER
Middle of this century
2 steps?
Economy
Technology
Satellite tokamaks
IFMIF
Tech.RD
DEMO stage
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Place of DEMO
Technology
advanced
conservative
expensive
competitive
Economy
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Philosophy for DEMO design
Design compromise of VECTOR, based
on foreseeable technologies
Technology
advanced
VECTOR (2001)
Modify VECTOR concept to reduce tech.
requirements without losing compactness
Comparable in tech. level
Low-A DEMO
(Exp. in low-A scarce. Needs support by satellite
tokamak)
conservative
ex. NCT
SSTR (1991)
expensive
Economy
competitive
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VECTOR concept superconducting low-A
w/o CS coils
Remove CS
Aspect ratio
RTFC giving Bmax
A 2-2.5
(elongation )
( magnetic energy )
Slender TFC system
High ?
Compact, low-A high ??with slender TFC
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2. Concept of DEMO
VECTOR
CS-less
Advantage
very compact (light)
Difficulties
plasma shape control
triangularity (HH, ELM contr) positions
(null point, div. hit point)
plasma current ramp-up
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2. Concept of DEMO
DEMO(J05)
VECTOR
Slim CS
CS-less
compromise
Rcs 0.7m, ?cs 38 Vsec
Advantage
very compact (light)
reduced but still compact
Difficulties
plasma shape control
resolved
triangularity (HH, ELM contr) positions
Ics 10 MA/m
(null point, div. hit point)
improved but still limited
plasma current ramp-up
induce 3.8 MA
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Impact of CS on reactor weight
Systems code analysis
weight gt constr. cost
to find the minimum reactor weight of the
following cases
Considering tech. feasibility and weight, Slim
CS is a good compromise.
Rcs shaping Ip-ramp
CS-less - limited -
Slim CS 0.7m good 3.8 MA
Full CS 1.5m good flattop
DEMO
40Wb
170Wb
DEMO(J05)
Conditions
TFC stress 800 MPa same ?, ?N margins,
fusion output 3 GW, etc.
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3. Features of DEMO plant

• Nb3Al S.C.
• 12 TF coils, Bmax 16.4 T

Rp 5.5m, a 2.1m, A 2.6 BT 6T, Ip
16.7MA, ?N 4.3, Pfus 3 GW

• Blanket
• Li2TiO3 / Be12Ti (pebble)
• F82H / pressurized water

Extrapolation of TBM(JA)

• Divertor
• W monoblock / F82H cooling tube

• Current drive
• NBI 1.5 MeV
• ECRF 170-190 GHz

• Maintenance
• Sector maintenance

Firm support of BLK / high availability
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(1) Light reactor weight, leading to a
reduction of construction cost
Reactor weight
DEMO(J05) 17,500 tons
ARIES-RS, ARIES-ST SSTR,A-SSTR2, ITER gt 22,000 tons
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(2) Seemingly ?N (4.3) is high,
but likely to have a large ?N margin

• Theoretically, higher ?N expected in lower A

ex., Lin-Liu / Stambaugh formulation
?N limit for 100 BS-driven plasma
Tough constraint
Margin to LL-S ?N
Margin designs
0 A-SSTR2
10 SSTR, PPCS(D)
20 DEMO(J05), PPCS(C)
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(3) DEMO requires technologies comparable to SSTR
Magnet
Maximum field
TFC magnetic energy
Plasma
Vertical stability
Density
ballooning stability
Confinement
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4. Next steps in design study

• Refine divertor concept
• consistent solution of shape control (?),
  radial build and
• heat/particle control
• study startup and shutdown scenarios
• overdrive in startup / shutdown by
  impurity gas puff
• Provide feasible maintenance scheme
• sector transport / hot cell maintenance
• Assess supercritical CO2 as alternative coolant
• Advantages Compact turbines, compatible
  with Be,
• easy separation
  of T, etc.
• Disadvantage organic compounds by COT2
  reaction

Major change from the ITER scheme
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Presentations on DEMO
MAY 23 (MON) M. Nishi S1-01-0-01 Tritium accountancy
MAY 24 (TUE) H. Nakamura P2-20 Tritium penetration
MAY 26 (THU) T. Isono P5-27 Magnet design
MAY 26 (THU) M. Sato P5-30 Core and divertor concept
MAY 26 (THU) S. Nishio P5-29 Reactor structure
MAY 26 (THU) T. Inoue P5-32 NBI system
MAY 26 (THU) K. Sakamoto P5-28 ECRF system
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Summary

• A compact low-A (A 2.6) reactor is under
  consideration at JAERI as a DEMO concept.
• DEMO has a slim CS for plasma shape control as a
  compromise of the CS-less VECTOR concept. Yet,
  the reactor weight is still light compared with
  other tokamak designs.
• Required technologies seem comparable in
  difficulty level to those for SSTR.

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