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Magnet Design Considerations& Efficiency Advantages
of Magnetic Diversion Concept
W. Meier & N. MartovetskyLLNL
HAPL Program MeetingNRL
March 3-4, 2005
Work performed under the auspices of the U.S. Department of Energy by the University of California,Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.
UCRL-PRES-210109
Meier HAPL March 05 2
Many system trades need to be considered for magnetic diversion concept
• Costs
+ Chamber (smaller chamber lower cost first wall and blanket)
– Magnets, cryo refrigeration system, magnet structural support and shielding
– Ion dump (ion dump “first wall”, cooling, shielding)
• Performance
+ Lower first wall heat flux more options for FW coolant
+ Possible higher operating temp higher thermal conversion efficiency, but
- requires advanced materials higher costs, longer development time?
+ Possible direct conversion of ion energy possible higher conversion eff., but
- requires added equipment, cost and complexity
• Nuclear Considerations
– Small chamber shorter FW life for given fusion power
– Neutron leakage thru ion port reduced TBR, shielding issues
– Need to shield cryo magnets
+ Ion dump wall out of direct line of sight of neutrons less n damage
Meier HAPL March 05 3
ITER Central Solenoid (CS) Cable in Conduit Conductor (CICC)
Conductor consists of:• Nb3Sn superconducting strands• Pure copper strands• Multi-stage cable including wraps and central spiral• Jacket
– Extruded segments 4-8m long– Butt welded/inspected– Cable inserted and compacted
CICC(49 mm x 49mm)
Strand Nb3Sn
(0.83 mm diameter)
Conductor in winding pack:
1 mm per side insulation
1 mm axial shim
0.5 mm radial shim
Shims are used to compensate winding errors and keep winding pack tolerances
Meier HAPL March 05 4
CS CICC Construction
Conduit
Cable wrap (protects cable against damage during pull through)
Subcable wrap (to reduce AC losses)
Strand
Subcables Helium flow
Meier HAPL March 05 5
ITER PF Conductor (NbTi+Cu)
Strand (courtesy of EMI, 0.81 mm diameter, Ni plated)
CICC in 316 LN steel jacket, 1152 strands
Meier HAPL March 05 6
PF magnets for ITER are similar in size and complexity – possible prototype
12.5 m
PF2 is about same radius as our middle magnets
PF3 is about same radius as our deflector magnet
Meier HAPL March 05 7
Conceptual design of the magnet system
Meier HAPL March 05 8
Peak field is 5.4 T at inner edge of smaller radius (3.25 m) coils – allows NbTi CICC
Field, T
Field, T
Meier HAPL March 05 9
Forces and stored energy are significant, comparable to ITER PF coils
1 30.0 -14.02 29.3 14.83 24.2 83.04 7.2 31.65 20.4 -115.0
Mag Hoop Axial
Forces, 106 N
1
2
3
5
4
Stored energy in system = 2.9 GJ – very significant,
requires good quench detection and protection
system (dump resistors, fast circuit breakers).
Arrows indicate direction of forces. (Not to scale)
Meier HAPL March 05 10
ARIES is developing magnet costs and scaling for Compact Stellerator study
From L. Bromberg and J. Shultz, “ARIES CS Magnets” PPPL Meeting, 12/4/04
Meier HAPL March 05 11
Near-term, real world cost info is available from ITER
1 IUA = $1000 (1989$) ~ $1360 (2005$)** escalated using US producer prize index for manufacturing
~ $100M(2005$) forsix PF coils
PF5: I = 9.8 MA-turns, R = 8.4 m Cost ~ $19.6M (14.4M IUA)
IFE5: I = 9 MA-turns, R = 7.85 mIf Cost ~ Vol, then Cost ~ $17M
Meier HAPL March 05 12
Power flow diagram with direct conversion
Chamber:Target
gain (G)
Laser (d)
Blanket(x M)
Neutrons & x-rays(~70%) HGH
Steam orBrayton
cycle(t)
Charged particles& plasma (~30%)
HGH = High Grade Heat
DirectConverter
(i)
HGH
Laser poweron target
Pd = laser power
Pne = net electric power
Pte = thermal-electric
Pde = direct-electric
Adapted from A.E. Robson
Pe = gross electric
Meier HAPL March 05 13
Efficiency improvement using DC is easily implemented in systems code
Overall conversion efficiency for gross power
g t i Pe t i Pnx Pi
Driver power
Pd ERR
d
Net electric power
Pne t d Pe t d Pd
Overall conversion efficiency for net power
n t i Pe t i Pd
Pnx Pi
Fusion Power
Pf E G RR
Neutron + x-ray power including blanket multiplication
Pnx 0.7 Pf M
Ion/plasma power
Pi 0.3 Pf
Electric power from direct conversion
Pde i Pi i
Electric power from thermal conversion
Pte t i Pnx 1 i Pi t
Gross electric power
Pe t i Pde i Pte t i
E = driver energyG = Target gainRR = Rep-rateM = Blanket multiplication
d = driver efficiency
t = thermal-electric conversion efficiency
i = ion-electric conversion efficiency
Meier HAPL March 05 14
Net plant efficiency can be significantly higher with DC of ion energy
Net
eff
icie
ncy
Ion-to-electric efficiency
0 0.1 0.2 0.3 0.4 0.50.3
0.32
0.34
0.36
0.38
0.4 Assumes:• Gain = 140• Laser eff. = 7%• Thermal eff. = 40%• Ion dump heat also converted at 40%
50% DC = 38.9%No DC = 30.5%
Meier HAPL March 05 15
COE could be significantly lower depending on added costs of magnets and direct conversion
0 0.1 0.2 0.3 0.4 0.50.75
0.8
0.85
0.9
0.95
1
Ion-to-electric efficiency
Nor
mal
ized
CO
E
No added capital cost
10% higher capital cost
Assumes:• Same as previous• COE ~ (Capital cost)/Pne
Meier HAPL March 05 16
Next Steps?
• Next steps depends largely on level of detail desired for evaluation of magnetic diversion concept
• Need more info on
– Choice of FW and blanket for chamber
– Design of ion dumps and cooling method
– Direct conversion systems and costs
• Good start on basis for magnet design, costs and scaling
• Potential plant efficiency improvements are significant, but will be offset to some degree by added costs for magnets, ion dumps and conversion equipment.