The Tore Supra tokamak at CEA Cadarache
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Transcript of The Tore Supra tokamak at CEA Cadarache
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 1
AssociationEuratom-CEA
PIONEERING SUPERCONDUCTING MAGNETS IN LARGE TOKAMAKS : EVALUATION AFTER 16
YEARS OF OPERATING EXPERIENCE IN TORE SUPRA
P. Libeyre, J.-L. Duchateau, B. Gravil,
D. Henry, J.Y. Journeaux, M. Tena, D. van Houtte
Association EURATOM-CEA, CEA/DSM/DRFC
CEA Cadarache (France)
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 2
AssociationEuratom-CEA
•The Tore Supra tokamak at CEA Cadarache
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 3
AssociationEuratom-CEA
1. Introduction
2. Status of the Tore Supra Toroidal Field (TF) system
3. Normal operation
4. Fast safety discharges
5. The cryogenic system
6. Can the magnet experience of Tore Supra be useful for ITER ?
7. Conclusion
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 4
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1. Introduction (1/4)
The Tore Supra TF magnet during assembly
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 5
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1. Introduction (2/4)
Tore Supra TF coil structure
Supercritical helium (4.5 K) in thick casing channels
Superfluid helium (1.8 K) in thin casing
bare conductorsin superfluid helium !
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 6
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1. Introduction (3/4)
one of the largest superconducting system in operation (600 MJ magnetic energy)
Relying on a refrigerator including for the first time industrial quantities of superfluid helium ( Claudet bath)
The Tore Supra TF system is :
Operated daily close to nominal conditions (1250 A)since November 1989.
Continuous toroidal field on the whole day
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 7
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1. Introduction (4/4)
The path to steady-state operation
Introduction of a new type of refrigeration for superconducting magnets on an industrial level :
Thousands of litres in TS (1988)Hundreds of thousands litres in LHC
(2007) !
the continuous toroidal field allows long duration plasma experiments to be performed
The revolution of
superfluid helium
The Tore Supra TF system contribution
J.L Duchateau et al. “Monitoring and controlling Tore Supra toroidal field system: status after a year of operating experience at nominal current“ 1991 IEEE Trans. On Magn. 27 2053
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 8
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2. Status of the Tore Supra TF system (1/3)
1982-1988coil manufacture and magnet assembly
all coils tested up to nominal current (1 400 A) at Saclay
1988 start of operation
short circuit in BT17 during a fast safety discharge
1989 replacement of BT17 by spare coil BT19
acceptance tests of TF coils up to 1450 A (9.3 T)
quench of BT13 during fast safety discharge (FSD)
limitation of operating current to 1250 A
temperature increase observed in BT13 during FSD
1995 disparition of defect on BT13
no more temperature increase in BT13 during FSD
2002 continuous data acquisition system
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 9
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2. Status of the Tore Supra TF system (2/3)
Similar behaviour ofBT13 compared to
the other coils
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
-500 1500 3500 5500 7500 9500
Time (s)
Co
il te
mp
era
ture
(K
)
4.4
4.6
4.8
5
5.2
5.4
5.6
5.8
6
6.2
6.4
Th
ick
ca
sin
g h
eliu
m t
em
pe
ratu
re (
K)
BT13 Temperature
BT16, BT17 Temperatures
Thick casing coil helium temperature
Green light for TF operation1.87 K
No more apparent defect on BT13
Temperature increase in coils during FSD (2003)
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 10
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1000
1100
1200
1300
1400
1500
1600
1700
1800
6 7 8 9 10 11 12 13Magnetic Field [T]
Cu
rre
nt
[A]
Coil Critical current at 1.8 K (except BT19)
Operation pointCritical point Large margin
(2.4 K)
reduced
nominal
Load line
Coil Critical current at 4.2 K (except BT19)
Safe operation of the TF magnet since 1989 at 1250 A, 8 T
2. Status of the Tore Supra TF system (3/3)
BT19
BT19
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3. Normal operation (1/4)
Tore SupraTF activitySince 1988
0
100
200
300
400
500
600
700
800
120/600 600/900 900/1200 >1200
Range of TF current (A)
Nu
mb
er o
f T
F c
ycle
sSince 1988 :
13 thermal cycles from room to LHe temperature
1 090 TF cycles
20 074 plasma discharges
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 12
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3. Normal operation (2/4)
Winding-pack temperature during one day of operation
0
0.2
0.4
0.6
0.8
1
1.2
5 7 9 11 13 15 17 19 21 23
Time ( h )
Pla
sm
a c
urr
en
t (M
A)
an
d
TF
cu
rre
nt
(kA
)
1.60
1.62
1.64
1.66
1.68
1.70
1.72
1.74
1.76
1.78
1.80
BT
15
co
il t
em
pe
ratu
re (
K)
TF system current
BT15 Temperature
Plasma discharges Long Plasma
discharges
Cleaning Plasma discharges
Temperature increase at current ramping-up and down (0.06 K)
Green light for TF operation1.87 K
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3. Normal operation (3/4)
0
0.2
0.4
0.6
0.8
1
1.2
5 7 9 11 13 15 17 19 21 23
Time ( h )
Pla
sm
a c
urr
en
t (M
A)
an
d
TF
c
urr
en
t(k
A)
4.40
4.50
4.60
4.70
4.80
4.90
5.00
Th
ick
ca
sin
g h
eli
um
te
mp
era
ture
(K
)
TF system current
Thick casinghelium temperature
Plasma discharges
Long Plasma discharges
Cleaning Plasma discharges
Thick casing helium temperature during one day of operation
Temperature increase linked to cleaning plasma discharges
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 14
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3. Normal operation (4/4)
Temperature increase due to a disruption from 1.7 MA
2.69 2.70 2.71 2.72 2.73 2.74 s
-400
-200
0
200
400
600
800
1000
1200
1400
1600 TS#31828
dIP/dt (MA/s)
IP (kA)
Plasma disruption
Thick casing : + 0.83 K4.5
4.6
4.7
4.8
4.9
5
5.1
5.2
5.3
5.4
5.5
-50 50 150 250 350 450
time (s)
Th
ick
ca
sin
g h
eli
um
te
mp
era
ture
(K
)
1.695
1.7
1.705
1.71
1.715
1.72
1.725
Co
il t
em
pe
ratu
re (
K)
Coil temperature
Thick casing helium temperature
Winding-pack : + 0.02 K
18/09/03
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 15
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4. Fast Safety Discharges (1/3)
FSD
Largest voltage at terminals (320 V at 1400 A)
Risk of short circuit
(bare conductors)To be
avoided !
thermal load on cryogenic system 2h30 to recover
0
2
4
6
8
10
12N
umbe
r of
Fas
t saf
ety
disc
harg
es
Since 1989 : 75 Fast Safety Discharges of the TF magnet (on 1090 TF cycles)
0
20
40
60
80
100
120
140
160
Num
ber o
f TF
curr
ent c
ycle
s
FSD TF cycles
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 16
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4. Fast Safety Discharges (2/3)
0 2 4 6 8 10 12 14 16
electric interference
cryogenic system
detection system
power supply
control software
quench
Origin of Fast Safety Discharges since 1994
No FSD due to a quench !
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 17
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4. Fast Safety Discharges (3/3)
Remedies to Fast Safety Discharges
Increase of trigger delays on alarms as much as possible without affecting the protection of the coil in case of a real quench
Sensor conditioning to decrease sensitivity to electric interference
Optimisation of the protection
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 18
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5. The cryogenic system (1/2)
Availability
sources of unavailability
0 20 40 60 80 100
2002
2003
% of time
control
magnet safetysystemHeII coldcompressor
Manpower : 12 persons
Electric power : 1.1 MW
Cost : 0.5 M€/year
(excluding staff and energy)
92
97
0 10 20 30 40 50 60 70 80 90 100
2003 : 97 %
2002 : 92%
availability
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 19
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5. The cryogenic system (2/2)
The major tendencies of the cryoplant ageing
loss of electrical insulation of many temperature sensors located in the depth of the cryostats.
drift of adjustment of the electronic components dedicated to the magnetic bearings of the cold compressors.
Preventive maintenance of compressor units
Good availability of the refrigerator
Nevertheless, ageing signs are visible :
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 20
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TF system Tore Supra ITER
Magnetic energy 0.6 GJ 40 GJ
Superconductor NbTi Nb3Sn
Conductor type monolithic bare conductor
2.8 mm x 5.6 mm
Cable-in-conduit
TFMC (40.7 mm Ø)
Conductor current 1.4 kA 68 kA
Discharge voltage 0.5 kV 10 kV
Cooling system Superfluid helium bath
Supercritical helium forced flow
Cryogenic power 1.1 MW ~ 35 MW
6. Can the TF magnet experience of Tore Supra be useful for ITER ? (1/4)
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 21
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0
10
20
30
40
50
60
70
80
90
100
6 7 8 9 10 11 12 13 14 15 16
Magnetic Field (T)
Cri
tica
l ca
ble
cu
rren
t d
ensi
ty
(A/m
m2)
NbTi, 1.8 K
NbTi, 4.5 K
Nb3Sn,TFMC
-0.65%, 4.5 K
Tore SupraITER
6. Can the TF magnet experience of Tore Supra be useful for ITER ? (2/4)
Operation of ITER TF at 11.8 T doesn’t allow NbTi to be used
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 22
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6. Can the TF magnet experience of Tore Supra be useful for ITER ? (3/4)
Extrapolation of the operation of the TF magnet
from Tore Supra to ITER is not straightforward
Forced flow cooling Very high voltage monitoring
Fast safety discharge
Tore Supra : no quench
ITER : quench of all coils
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 23
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6. Can the TF magnet experience of Tore Supra be useful for ITER ? (4/4)
experience of the CEA magnet team in conductor and coil design
16 years of reliable plasma operation with a TF superconducting magnet
Decision to build ITER is possible
ITER magnet R&D programme
Still to be doneExperience in TS can help :
Design of protection and monitoring system Impact on cryoplant
Detailed magnet operation
Impact on scenarios
P. Libeyre Pioneering superconductivity 23rd SOFT, Venice 21 September 2004 24
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7. Conclusion
The Tore Supra tokamak is the first important meeting between Superconductivity and Plasma Physics.
Superconducting magnets can be operated successfully with plasma physics on the long term
Continuous operation of the toroidal field simplifies plasma discharge preparation
No significant heat load is associated to long shots
Continuous operation limits fatigue degradation
The Tore Supra TF magnet is a useful tool to prepare ITER construction and operation