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.