Challenge toward Lower Aspect Ratio Challenge toward Lower Aspect - - PowerPoint PPT Presentation

• 1. Cover Page

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Challenge toward Lower Aspect Ratio Challenge toward Lower Aspect Ratio Tokamak Tokamak Power Reactor

• wer Reactor

S.NISHIO and Reactor Design Team

JAERI ; Naka Fusion Research Establishment Naka-machi, Naka-gun Ibaraki-ken 311-0193, JAPAN

Nishio@ naka.jaeri.go.jp

(1)ST Plasma, Its Higher Performance (2)Possible Reactor Concepts with ST Plasma (3)Super-conducting Ｔｏｒｏｉｄａｌ Ｆｉｅｌｄ Coil (4)Normal-conducting Ｔｏｒｏｉｄａｌ Ｆｉｅｌｄ Coil Contents

10th International Spherical Torus Workshop & US-Japan Exchange Meeting on the Spherical Torus

• Sept. 29 – Oct. 1, 2004 at Kyoto Univ, JAPAN

• 2. Why

Compact？

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Sensitive Parameters ？

Plasma Beta ＆ Toroidal Coil Neutron Wall Load ＆ Power Core Components

A Craving for Compact & Lightweight

• 3. CS-less

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Discard of Center Solenoid Coil Discard of Center Solenoid Coil

CS Coil Support Wheel

In due time, they fall into disuse !!

• 4. To VECTOR

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To VECTOR To VECTOR

( A~4 ) ( A~4 ) ( A~ 2 ) ( A~ 2 )

CS-less

Maximum Field, BMAX (T) Center Post Radius, RCP (m) Average Current Density, iAVE (A/mm2)

5 10 15 20 25 20 40 60 80 100 0.5 1 1.5 2 2.5

COIL

1.5 1 2 2 2 4 6 8 10 3 3 4 4 5 5 ST Region Conventional Region

Normalized Beta， βN Ellipticity, κ A s p e c t R a t i

• ，

， A

R.L. Miller et al.,

• Phys. Plasma 4(4), April 1997

PLASMA

Weight Power Density

VECTOR

• 5. This is

VECTOR

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This is the VECTOR. This is the VECTOR. Simple Vacuum Boundary

18.2 m Replacement Unit

Simple Maintenance Scheme

Plasma Major Radius : RP = 3.2 m Plasma Minor Radius : aP = 1.4 m Plasma Ellipticity : κ = 2.35 Plasma Current : IP = 14 MA Normalized Beta : βN = 5.7 Fusion Power : PF = 2.5 GW Neutron Wall Load : Pn = 5 MW/m2 Field on axis : B0 = 5 T Reactor Weight : W = 8800 Ton Weight Power Dens. : p = 280 kW/ton

• 6. Where is VECTOR

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Where is VECTOR ? Where is VECTOR ?

18.2m VECTOR

30 m

ITER 26m ARIES-RS

20 m

ARIES-ST

• 7. Light TFC

Why CS-less TFC is so lightweight ? Why CS-less TFC is so lightweight ?

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TFC weight is in proportion to the stored energy !

• 8. Tough

Structure

CS-less TFC Concept, Its characteristics. CS-less TFC Concept, Its characteristics.

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The “Solid” is stronger than the “Barrel” by 5 times.

σθ= -(RB/t)pB σr~0 σr= σθ= -pP Isotropic Support

p P 2R P p B 2R B t

Barrel Structure ( conventional ) Solid Post Structure ( Apple Shape ) Same Area : 2 πRBt= πRP2 Same Load : W = 2πRBpB= 2πRPpP Wedge Support

• 9. TFC Design

Flow

Design Flow of SC-ST TF Coil Design Flow of SC-ST TF Coil

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CP Area Superconducting Filament Area Design Current Density of Filament TFC Ampere-turns TFC Shape Stored Energy Terminal Voltage

• f TFC System

Conductor Current Electromagnetic Force Structural Material Area Allowable Current Decay Rate Joule Heating Stabilizer Area Cooling Channel Area Insulator Area Plasma Design Neutronics Design Area

Center Post One Sector

Cooling Channel Bi2212 Strands Pb Insulator Structural Material Conductor

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Optimization of TFC Material Compositon

• 10. Plasma Design Flow

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Plasma Design Flow Plasma Design Flow

1.5 1 2 2 2 4 6 8 10 3 3 4 4 5 5 ST Region Conventional Region

Normalized Beta， βN Ellipticity, κ Aspect Ratio，A

Shield Thickness, ∆ Ellipticity, κ Plasma Temp. Plasma Current, I

P

Radius of Center Post Current Density

• Max. Field, B

Max

Field on Axis, B Minor Radius, a

P

Plasma Power Balance Plasma Dens. MHD Safety Factor, q

Ψ

Confinement, HHy2=1.8 Plasma Dens., n/nGW =1.0 NO YES Plasma Major Radius, R

P

Where is optimum point?

• 11. Summary

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Summary Summary

(i) Heavy tokamak is caused by heavy TFC. (ii) CS-less leads to lightweight tokamak. (iii) ST power reactor with NC TFC is skeptical.

Urgent Issue

• High δ plasma equilibrium
• Break-down & Current ramp-up

Parameter Space

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