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11. Cover Page
S. NISHIO Japan Atomic Energy Agency, Naka Fusion Institute, Naka-shi, Ibaraki-ken 311-0193, Japan
US - Japan Workshop on Power Plant Studies and Related Advanced Technologies with EU Participation, 24-25 January , 2006 at UC San Diego, 584 EBU-II
Magnets of Tokamak Reactor :the indispensable & (but) burdensome existence
2
Contents
● TFC Cost is Major Part of Total Cost ● Lightweight TFC leads to Low Cost Tokamak● 1st step lightening : Reactor Concept Modification ● 2nd step lightening : Coil Concept Improvement
Having an Eye on Low Cost Tokamak Reactor
3
Reactor Concept Modification
Pf = 3 GW, Pn = 5 MW/m2
21 3 4 652
6
4
8
10
12
7Aspect Ratio, A
Nor
mal
ized
Bet
a,
N
Pf t2B0
4 N2B0
2 8 8
Wt ~ 3500 tonWt ~ 3500 ton
MassiveLightweightWc < 2000 ton Wc > 15000 ton
Low A Concept Leads to Lightweight TFC
4Reactor Weight & TFC Bmax , CSC Bore
1
2
34
10 15 2050
1
2
TF Coil Maximum Field (T)
CS
Co
ilB
ore
(m)
VECTOR
ITER
SSTR
J-DEMO
ARIES-ST
● CS-less & high field TFC leads to lightweight Tokamak
Contour Map of Reactor Weight
5Empirical Scaling for Magnet Weight
100
101
102
103
104
105
10-2
10-1
100
101
102
103
EQ
M
M : Structure Weight: Mass Weight DensityE : Stored EnergyQ : Geometry Factor (1～3): Design Stress
Virial Theorem
=7900kg/m3
Q=3=400MPa
XX
Vi r i alAct MeanI TERCST- 7TRI AM- 1MNCTCSCYi n- Yang
I TERCSMCLHDLCT60SUCSCNCTTFC60SUTFCI TERTFCSSTRASSTR2
VECTOR
ARIES-RS
Mag
net
Wei
gh
t (T
on
)
Stored Energy (GJ)
ARIES-RS TFC, Why SO LIGHTWEIGHT ?
6Coil Concept Improvement
Indirect (Conduction) Cooling
&
TFCs, PFCs Integrated Structure
7
Cooling Methods
R. T. curedreinforced resin
Layer to layerGFRP spacer3.5 mm
Al stabilizedNbTi/Cu compositesuperconductor
Turn to turnGFRP spacer2.0 mm
Pool Boiling
● Low Tech. ● Poor Mech. Strength● Low Insulation Voltage
Forced Cooling Conduction Cooling
● Good Heat Removal ● High Insulation Voltage● Severe Pressure Drop
● Excellent Mech. Strength● poor Heat Removal
8Windings of Forced Cooling System
Current path and coolant path are not independent each other.
9For Poor Heat Removal of Conduction Cooling
Stabilization of High Temp. Super-Conductor (YBCO)
is designed to be done with the enthalpy of the YBCO material itself, rather than by cooling with supercritical helium against the disturbances such as movement etc.
Heat capacity :
500 mJ/cm3 for the temperature range between 33 and 35 K
10Structure of Winding
Higher field Middle field Lower field
Size of winding pack 478 mm x
174 mm
398 mm x
150 mm
272 mm x
127.2 mm
No of pancakes 4 4 4
No of turns 104 88 52
Thickness of cooling plate 10 mm 10 mm 10 mm
Current density 50 A/mm2 59 A/mm2 60 A/mm2
Parameters of winding packs
Each coil has three (higher, middle and lower field) winding packs installed into the coil case..
To reduce stress (or strain) on the winding and to control the occurrence of flux jumps, three slots are machined into the coil case in which each winding pack is installed.
Ground insulator
Cooling Plate
Welding Conductor
Case
Lower field winding pack
Middle field winding pack
Higher field winding pack
11Structure of TF coil
Pancake insulator Turn insulator
Cooling plate
Ground insulator
Side plate
Iron core
Case
Case Lower field winding pack
Higher field winding pack
Side plates
I ron core
Middle field winding pack
12For Quick Response for IP Control
1
2
34
10 15 2050
1
2
TF Coil Maximum Field (T)
CS
Co
ilB
ore
(m)
VECTOR
ITER
SSTR
J-DEMO
ARIES-ST
Slim CS Iron CoreSolenoid Free
Flux supply & Mechanical toughness
13Summary
● CS-less (Low A) concept leads to lightweight Tokamak.
● Conduction cooling method leads to lightweight TFC.
● High temp. superconductor meets conduction cooling.
● Cs-less & iron core concept may meet the requirements for quick Ip control and TFC mechanical strength.
