CRYOGENICS OPERATIONS 2008 Organized by CERN
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Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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CRYOGENICS OPERATIONS 2008
Organized by CERN
Design status of the cryogenic system of JT60-SA: optimization of the refrigeration
capacity for different operation modes
Christine Hoa, Frédéric MichelSBT, CEA Grenoble
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Outline
• Cryogenic system for the tokamak JT-60SA
• Operation modes and heat loads
• Optimization of the refrigeration capacity
» Thermal buffer operation during day» Liquid storage during night
• Perspectives and conclusions
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Cryogenic system for the tokamak JT-60SA
• Presentation of the tokamak JT-60SA» Superconductive tokamak in Naka, Japan» ITER Broader approach, joint project between
Japan and Europe» CEA in charge of the cryogenic system
procurement» D-D Plasma physics planned for 2015» 2008: Concept design phase
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Cryogenic system for the tokamak JT-60SA
Spherical Cryostat
Central Solenoid(4 modules) 4.4 K
2*9 Divertor
Cryopumps
4.4 K
26 HTS Current
Leads 50 K
Cryopumps baffles80 K
Vacuum VesselThermal Shield
80 K
18 Toroidal Field Coils
4.4 K
6 Equilibrium Field Coils 4.4
K
CryostatThermal Shield
80 K
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Cryogenic system for the tokamak JT-60SA
Cold Box 4.5KCold Box 80K
+ LHe tank
Auxiliary Cold Box
For Magnets and cryopumps
Coil Termination
Box
Coil Termination
Box
Coil Termination
Box
Coil Termination
Box
TF Magnets+Structures
EF 1-2 +CS 1-2
18
EF 5-6 +CS 3-4
EF 3-4-7
Tokamak hall
Storage Area
New compressor
building
Existing building
GH
e 300K
CPL
ML2ML1
ML: Magnet LineCPL: Cryopumps Cryogenic Line
ML3 ML5ML4
Limit of supply
Thermal Shields
HTS HTS
Thermal Shields
Thermal Shields
Thermal Shields
CryoPumps
Warm Compressor Station
Warm storage and gas management
JT-60SA Operation States
Long Term Maintenance
(LTM)
Baking Operation
State (BOS)
Holding Operation
State (HOS)
Plasma Operation
State (POS)
Duration >30 days ~ 7 days Night (12 h) or WE Day (10 h)
Temperature (K) 300 20 4.6 4.4
TF current OFF OFF OFF/ON ON Magnets
EF and CS current OFF OFF OFF/ON ON
Vacuum Vessel & Cryostat
Thermal Shield Temperature (K)
300 80/120 80/100 80/100
Vacuum Vessel Temp (K) 300 470 313 313
Divertor Cryopumps Temperature (K) 300 470 20-30 K
regeneration 4.4
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN,
Geneva, Switzerland6
Operation modes
• Yearly schedule
CRYOP08- 25/09, 15:30Baking scenarios studies,
V.Lamaison
JT-60SA will be operated 6 or 7 months / year
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Operation modes
• Daily schedule
00 08 09 19 20 24
Toroidal field
TF C
oil c
urr
en
t (k
A)
34
100 sec /3000 sec or
60 sec/1800 sec
00
Plasma Operation StateHolding Op. State Holding Op. State
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Heat loads
• Refrigerator Capacity of ~10 kW @4.5 K
Temperature levels Cryogenic subsystems units
POS 100/3000 sec
scenario HOS BOS4,5 K total CS coils W 475 0 0
total EF coils W 635 312,5 612,5total TF coils W 1444 1032,61 1837,5aux. Loads W 730 730 650
cryopump panel W 248 0 0cold circulators W 2201 1576,5 1
cold compressor W 734 390 0TOTAL 4,5 K W 6467 4042 3101
50K HTS Current leads flow@(50 K-300 K) g/s 23,8 23,03 0
80 K Thermal shields 80 K W 31962 31890 118500
4,5 K Equivalent refrigeration power kW 8,1 5,8 8,2
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Heat loads
• Direct Pulsed Heat loads
Averaged heat loads at 4.5 K: 6.5 kW
Pulsed Heat loads at 4,5 K
0
5000
10000
15000
20000
25000
30000
35000
40000
-40 960 1960 2960 3960 4960 5960
t(s)
P (
W)
TOTAL CS
TOTAL EF
TOTAL TF WP
TOTAL TF Structures
Cryopumps
Aux. Loads+circulators+CC
Needs of smoothing the pulsed heat loads
Christine Hoa, 22nd-26th September 2008
Heat loads into the Thermal Buffer at 4.3 K
0
2000
4000
6000
8000
10000
12000
14000
-40 460 960 1460 1960 2460 2960
t (s)
P (
W)
TOTAL TF WP
TOTAL TF Structures
TOTAL CS
TOTAL EF
Aux. Loads., circulators, CC
Cryo-pumps
TOTAL
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Heat loads• Pulsed heat loads: (POS: 100s plasma/3000 s)
13 kW Peak heat loads
A first smoothing in the CICC and in the cooling channels
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Heat loads• Pulsed heat loads: Comparison with other tokamaks
Tokamaks Equivalent Refrigeration
Power at 4.5 K
Averaged powerAt 4.5 K
Peak heat loads at 4.5 K
Ratio Peak/Averaged Power
Thermal buffer size
ITER [1] 2*30 kW 37 kW (magnets) 43 kW 1.2 4*2 m3
JT60-SA 10 kW (TBC) 6.5 kW (magnets+
cryo-pumps)
13 kW 2.2 6 m3
K-STAR [2]
9 kW 4.7 kW 6.2 KW 1.3 6 m3
TORE SUPRA [3]
800 WThick casing only
100 WThick casing only
17 kW Thick casing only
170 3*1.5 m3
References[1] Review of conceptual design of ITER cryoplant system, Sanmarti M., Kalinin V., Lässer R., Michel F, Murdoch D., Poncet J.-M., Roussel P., Serio L.[2] KSTAR Tokamak helium refrigeration System design and manufacturing, Pascal Dauguet, Air Liquid.[3] Thermal buffer made of He I at constant volume, JAGER B. ; MARDION G. B. ; CLAUDET G. ; DESMARIS M. ; Cryogenics 1985, vol. 25, no10, pp. 578-582 .
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Optimization of the refrigeration capacity
• Smoothing the heat loads with a thermal buffer
» Optimization of the refrigeration capacity for an averaged power over a plasma scenario (6.5 kW)
» Stable interface with the refrigerator: constant mass flow rate
» Drawbacks• Large volume for the thermal
buffer• T variations in the buffer
constraint on the magnets• P variations in the buffer
constraints on the cold compressor
Heat loadsdeposited into the saturated bath Qheat exchanger (t)
Extracted heat loadsQrefrigerator (t)
Vbath volume of the saturated bath with a liquidlevel, Pbath, Tbath
mtotal constant
with
mliq=(1-x)mtotal
mtotal constant
with mvap=mtotal
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
13
Heat loads
• How to smooth the pulsed heat loads?» Practical solution, but not economical: regulation with a heater
immersed into the saturated bath. • Installed power for the cryoplant: peak heat loads • JT60-SA: 13 kW at 4.5 K
» Optimized solutions with a thermal buffer• Installed power for the cryoplant: averaged heat loads• JT60-SA: 6.5 kW at 4.5 K• Technical challenges and compromises
– Cryodistribution: to ensure a stable operation of the refrigeration
– Cryoplant: new developments for adapted refrigerator that can cope with mass flow rate variation?
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Optimization of the refrigeration capacity
• Baseline solution for a thermal buffer operation
• T, P variations in the thermal buffer» 4.3 to 5.0 K» 1.09 to 1.96 bars
• Regulation on the mass flow rate: » Cold compressor speed, » Control valve » By-pass valve…
HX2HX1
P2
CSWP
Cold Box
JT valveCC
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
15
Optimization of the refrigeration capacity
• Other solution for a thermal buffer operation: a refrigeration box immersed into the thermal buffer
• Advantages» Decoupling of the refrigerator
interface and the thermal buffer• Thermal buffer at constant
volume• Regulation on a constant pressure
in the refrigeration box
» Easier operation
• Drawbacks» Refrigeration box: a supplementary
component to design and connect
HX2HX1
P2
CSWP
CC
Cold Box
JT valve
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
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Optimization of the refrigeration capacity
• Day/night operation» Heat loads at 4.5 K during HOS and
POS are significantly different • 6.5 kW at Plasma Operation Scenario• 4.0 kW at Holding Operation Scenario
» HOS: to store Liquid Helium into a tank using a liquefaction mode for the cryoplant
» POS: to supply supplementary Liquid Helium from the storage to cope with higher loads, using an “economiser” mode for the cryoplant.
Cold Box 4.5KCold Box 80K
Warm Compressor Station
Warm storage and gas management
Thermal buffer tank
Liquid HeliumTank
Auxiliary Cold Box
TF, Stuctures, CS and EF + Cryopumps
Variable heat loads
HOS operation: LHe storage
POS operation: « economiser »
Christine Hoa, 22nd-26th September 2008
Cryogenics Operations 2008, CERN, Geneva, Switzerland
17
Optimization of the refrigeration capacity
• Day/night operation» Hypothesis
• Heat loads: 6.5 kW at POS, 4.0 kW at HOS• The expected efficiency for the cryoplant to produce LHe: 120 W needs to produce 1g/s.• The expected efficiency for the cryoplant to convert LHe into
refrigeration power: 1g/s could give 80 W.• All the liquid stored during HOS is used during POS.
» Results• Installed power at 4.5 K ~ 5.5 kW• The active liquid helium volume : 4.3 m3
Christine Hoa, 22nd-26th September 2008
Perspectives and Conclusions
• Operation under pulsed heat loads» New challenges for the cryogenic system (cryoplant and
cryodistribution)» Different concepts for smoothing the heat loads with a thermal buffer» Optimization of the refrigerator capacity:
• Plasma Operation Scenario• Holding Operation Scenario
• Investigations» Process modeling (Vincenta, HYSYS,…)» Experimental mock up» Analysis of the available cryogenic components under pulsed heat
loads» Feedbacks from other tokamaks operations ( TORA SUPRA, KSTAR…)» Other abnormal operation modes: disruption, fast discharge…
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
Thank you for your attention!
Christine Hoa, 22nd-26th September 2008Cryogenics Operations 2008, CERN, Geneva, Switzerland
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