laurent tavian thanks to contribution and helpful discussions with m. jimenez, v. parma, f....
TRANSCRIPT
Consequences of a hypothetical incident for different sectors
(with beam energy up to 5 TeV)
Laurent Tavian
Thanks to contribution and helpful discussions withM. Jimenez, V. Parma, F. Bertinelli, J.Ph. Tock,
R. van weelderen, S. Claudet, A. Perin, C. Garion, R. Schmidt
Chamonix 2011 LHC Performance Workshop,Session 04: Beam Energy
Content
• Introduction– Recall of the 19th Sept’08 fault tree– Recall of sector consolidation status for 2011/12
operation• Updated fault trees and consequences in case of:
– A hypothetical electrical arc in a cryo-magnet interconnect for beam energy up to 5 TeV
– A hypothetical electrical arc in a magnet cold-mass for beam energy up to 5 TeV
• Conclusion
Fault tree of 19 Sept 2008 incident at the LHC Cryogenic effects [1/2]
Electrical arc
Beam pipe perforation
He vessel perforation Soot
He discharge in insulation vacuum
Contamination by soot
Inadequate sizing of relief devices
(MCI)
Pressurization of vacuum enclosures
Mechanical damage to MLI
Contamination by MLI
ODH in tunnel
Blast
Trip AUG
Loss of beam vacuum
Break vent door
Ph. Lebrun
Fault tree of 19 Sept 2008 incident at the LHC Cryogenic effects [2/2]
Pressurization of vacuum enclosures
Pressure forces on vacuum barriers
Plastic deformation of shells
Buckling of bellows
Rupture of supports and ground anchors
Displacement of magnets
Mechanical damage to interconnects
Secondary electrical arcs
Damage to tunnel floor
Ph. Lebrun
Sub-sector inventory(Ref. CERN ATS Note 2010-057)
Q1_R Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L Q3_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q3_R Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L Q1_L
D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2
Q1_R Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q3_R Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L
D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2 D5
Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L
--> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L
D5 D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2
Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L Q3_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L Q1_L
D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2
Q1_R Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q3_R Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q8_L
D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D3
Q8_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L
--> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L
D4 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2 D5
Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L Q3_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L Q1_L
D5 D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2
Q1_R Q7_R Q11_R Q15_R Q19_R Q23_R Q27_R Q31_R Q33_R Q31_L Q27_L Q23_L Q19_L Q15_L Q11_L Q3_L
--> --> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Q3_R Q10_R Q14_R Q18_R Q22_R Q26_R Q30_R Q32_R Q32_L Q28_L Q24_L Q20_L Q16_L Q12_L Q7_L Q1_L
D1 A1 A1 A1 A1 A1 A2 A1 A1 A1 A1 A1 A1 D2
DF
BX
I2 M3 M1 M1 D6 D6 M4 I1
DF
BA
DF
BA
DF
BL
Q6_
L
Q5_
L
Q4D
2_L
S8-1
DF
BX
D1_
R
D2Q
4_R
DF
BM
DF
BM
Q5_
R
DF
BM
Q6_
R
DF
BX
M2 D7 M1 M3 I2
Q6_
L
DF
BM
Q5_
L
DF
BM
Q4D
2_L
D1_
L
S7-8
DF
BM
Q6_
R
DF
BA
DF
BA
DF
BA
DF
BM
Q6_
L
M1 M1 D6 M2
S6-7
DF
BM
Q4_
R
DF
BM
Q5_
R
DF
BA
I1 M4 D6 D6 M1 M1
DF
BA
DF
BA
DF
BM
Q5_
L
DF
BM
Q4_
L
S5-6
DF
BX
D2Q
4_R
Q5_
R
Q6_
R
DF
BL
I1M1 M3 M1 D6 D6 M4
DF
BA
DF
BL
Q6_
L
Q5_
L
Q4D
2_L
DF
BX
S4-5
DF
BM
D3_
R
D4Q
5_R
DF
BM
DF
BM
Q6_
R
DF
BA
D3_
L
M2 D8 D6 M1 M3 M1
DF
BA
DF
BM
Q6_
L
DF
BM
Q5D
4_L
DF
BM
S3-4
DF
BM
Q6_
R
DF
BLC
DS
LC
DF
BA
DF
BA
Q6_
L
DF
BM
I2 M3 M1 D7 M2
S2-3
DF
BX
D1_
R
D2Q
4_R
DF
BM
DF
BM
Q5_
R
Q6_
R
DF
BA
Q4D
2_L
D1_
L
DF
BX
I1 M4 D6 D7 M1 M3 I2
DF
BA
DF
BA
Q6_
L
DF
BM
Q5_
L
DF
BM
S1-2
DF
BX
D2Q
4_R
Q5_
R
Q6_
R
DF
BL
Inner tripletInner triplet Maching sectionDispersion suppressor
ArcDispersion suppressor
Matching section
MCI in case of electrical arc in an interconnect
080919 accident (~ 5 TeV)
With “smaller” electrical arc (i.e. lower magnetic stored energy and/or lower discharge time constant), perforation of the beam pipe can not be excluded with the present consolidation status. (Electrical insulation of the beam pipe interconnect foreseen in 2013/12)
Discharge conditions through safety devices vs beam energy
• Mass flow MCI flow (already at 3.5 TeV, an electrical arc is able to create the MCI breaches ( 2 x 60 cm2)), e.g. 30 kg/s in the continuous cryostat.
0
10
20
30
40
50
60
70
80
90
100
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
Dis
char
ged
heliu
m te
mpe
ratu
re [K
]
Stor
ed m
agne
tic e
nerg
y [M
J]
Beam energy [TeV]
Stored energy
Discharge temperature• Temperature of helium heated by
the electrical arc power and discharged through the safety devices depends on:• the stored magnetic energy• The current discharge time
constant• The heat transferred by
convection from the environment.
Maximum pressure build-upin vacuum enclosure
Q6R
2Li
nk Q
6R2
DFB
AM
id-a
rc su
b-se
ctor
DS
& D
FBA
DFB
AM
id-a
rc su
b-se
ctor
DS
& D
FBA
Link
Q6L
8Q
6L8
DFB
AM
id-a
rc su
b-se
ctor
DS
& D
FBA
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
S1-2 S2-3 S3-4 S4-5 S5-6 S6-7 S7-8 S8-1
Max
imum
vac
uum
-enc
losu
re p
ress
ure
[bar
]
3.5 TeV
5 TeV
Maximum pressure of re-enforced fixed points
Vacuum-enclosure design pressure
Off-design remaining cases
Vacuum sub-sectorP max [bar]
Remarks3.5 TeV 5 TeV
Link Q6R2 & Q6L8 5.1 5.1 Compatible with vacuum enclosure design margin (DN200 link)
Q6R2 & Q6L8 1.8 1.8 Compatible with vacuum enclosure design margin
Mid-arc S2-3, S7-8 & S8-1 1.8 2.3* Compatible with vacuum enclosure design margin and re-enforced fixed points on SSS
DFBA HCM R2, L3, R7 & L8 1.6 2.0 Compatible with vacuum enclosure design margin and re-enforced fixed points on DFBA
DFBA HCM R8 & L1 1.4 1.7 Compatible with vacuum enclosure design margin and re-enforced fixed points on DFBA
DS L3, L8 & L1 1.4 1.6 Compatible with vacuum enclosure design margin and re-enforced fixed points on SSS and DFBA
Conclusion: Up to 5 TeV, no longer mechanical collateral damages in adjacent sub-sectors!
*: Above 1.9 bar, plastic deformation of SSS vacuum barrier could occur(pressure test under preparation)
Updated fault tree up to 5 TeV
Electrical arc
Beam pipe perforation
He vessel perforation Soot
He discharge in insulation vacuum
Contamination by soot
Inadequate sizing of relief devices
(MCI)
Pressurization of vacuum enclosures
Mechanical damage to MLI
Contamination by MLI
ODH in tunnel
Blast
Trip AUG
Loss of beam vacuum
Break vent door
Ph. LebrunInstrumentation flange opening
on temporary consolidated sectors
Mechanical damage of instrumentation
cabling
Damages in case of a hypothetical electrical arc in an interconnect
(up to 5 TeV)• Sept’08 damages which are mitigated by the 2009 consolidations:
– Plastic deformation of shells– Buckling of bellows– Rupture of supports and ground anchors– Damage to tunnel floor– Mechanical damage to interconnects– Secondary electrical arcs
• Damages still present up to 5 TeV– He vessel and beam pipe perforation– Mechanical damage of MLI– Contamination by soot of MLI and beam pipes– Contamination by MLI of vacuum enclosure and beam pipes– Mechanical damage of BPM cabling
Expected damages in case of a hypothetical incident
PTQVQV QVQV SVSV
Cold-massVacuum vesselLine ECold support postWarm JackCompensator/BellowsVacuum barrier
Q D D QD D D QD D D QD D D QD
PTQVQV SV
Q D D QD D D QD
He vessel perforationMechanical damage of MLI
Contamination of MLI by soot & of vacuum enclosure by MLI
Contamination of beam pipe(s) by soot
BD
Contamination of beam pipe(s) by MLI(over the whole continuous cryostat length)Length to be removed and re-installed (~12 dipoles + ~4 SSS)
BDBD BD BD BD BD BD BD BD BD BD BD BD BD BD BD BD
PTQVQV QVQV SVSV
Q D D QD D D QD D D QD D D QD
PTQVQV SV
Q D D QD D D QD
He vessel perforation
Mechanical damage of MLI
Contamination of MLI by soot & of vacuum enclosure by MLIContamination of beam pipe(s) by soot
BD
Contamination of beam pipe(s) by MLI(over the whole continuous cryostat length) Length to be removed and re-installed (~14 dipoles + ~4 SSS)
BDBD BD BD BD BD BD BD BD BD BD BD BD BD BD BD BD
To be exchanged or repaired (surface) before operation restart
To be repaired in-situ before operation restart
Consolidation can wait the next long shut-down
Electrical arc position
Electrical arc in the middle of a subsector
Electrical arc closed to a vacuum barrier
Mechanical damage of instrumentation cabling
Mechanical damage of instrumentation cabling
Mechanical damage of MLI (1)• Without MLI, cold mass enclosure are not protected against pressure
build-up in case of break of the insulation vacuum with air.Heat transfer by condensation of air on cold wall
• From a calculation by Nusselt– h ≈ 0.943 (r2 g k3 Lv/h x DT)0.25
• Assimilating air to nitrogen– h ≈ 680 W/m2 K– heat flux h DT ≈ 50’000 W/m2
– average thickness of film ≈ 0.2 mm
• Multi-layer insulation– take e = 10 mm
• Conduction in solid nitrogen– conductivity integral from 77 to 4 K
≈ 50 W/m– Heat flux h DT ≈ 5’000 W/m2
LHeAir
Liquid air film, falling
x
Heat transport limited by conduction across falling film
LHeAir
Liquid air film, falling
Solid air trapped between MLI layers
e
Heat transport limited by conduction across solid air
Bare wall with MLI
Not compatible with the cold-mass pressure relief system !
Ph. Lebrun
Mechanical damage of MLI (2)Affected length?
• S3-4 incident: ~ 2/3 of the total affected length (22 cryo-magnets over 2 sub-sectors)
• New incident ?:– MLI damage goes with rv2 or m2/ r or m2T/P
• S3-4 incident 30 kg/s – 6 bar – 70 K• New incident 3.5 TeV: 30 kg/s – 1.1 to 1.3 bar – 40 K factor 3 to 2.6• New incident 5 TeV: 30 kg/s – 1.1 to 1.5 bar – 60 K factor 4.5 to 3.5
– But the distribution of the safety devices allows a faster decrease of the flow along the length
– Let’s assume the same damage ratio (2/3) for a new incident i.e.: • ~ 10/16 cryo-magnets to be repaired use of spares for dipoles re-cryostating of SSS (no spare)
– Question: Can we safely operate with only missing MLI on SSS? (if yes, the heavy SSS re-cryostating could wait the next long shutdown!)
Contamination by soot of beam pipes: Affected length?
• Experience return from S3-4– V1 more representative (not burst disk opening)– In V1 about 600 m contaminated with soot– Pressurization: up to 3.5 bar
V1V2
~600 m
~400 m
• New incident expectation: Affected length is assumed to be proportional to the quantity of soot introduced:• For most sub-sectors, pressurization limited to 1.1-1.5 bar:
quantity of soot introduced in the beam pipes divided by 2.3 to 3 250 to 200 m of magnet could be affected
• For the specific mid-arc subsectors (3/8), pressurization limited to 1.8 -2.3 bar: quantity of soot introduced in the beam pipe divided by 2 to 1.5 300 to 400 m of magnet could be affected
M. Jimenez
Repair schedule following a hypothetical interconnect electrical arc
monthsweeks 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Sector warm-up (4 weeks)
Prepare spare dipoles (12 to 14) (1 week of preparation + 2 dipoles per week)
removal of SSS (4) (2 weeks of preparation + 2 SSS per week)
removal of dipole (12 to 14) (3 dipoles per week)
Recryostating of SSS for MLI(2 to 3) (4 weeks per SSS with overlap of 2 weeks)
Beam tube and BS cleaning of SSS (3 to 4) (1 SSS per week)
New SSS assembly (0 to 1) (2 weeks of preparation + 3 months)
Reinstallation (12-14 dipoles + 4 SSS) (3 months)
Opening of IC and PIMS (sector wide) (4 weeks)
BS MLI cleaning (1 shift) (3 months)
Reclosing of IC (sector wide) (4 weeks)
Sector recooldown (including cryo-tunning) (6 weeks)
Sector ELQA and HWC (4 weeks)
New DFBA assembly
7 81 2 3 4 5 6
Remark: In case of a hypothetical electrical arc in an Inner Triplet, soot contamination of the detector beam pipe cannot be excluded (Fast shutter valves installation only in 2013/12 long shutdown) Long and heavy repair work if NEG coatings are damaged! (4 to 6 months)
Fault tree of an electrical arc in magnet coil (caused by a short circuit or by a catastrophic beam loss)
Electrical arc in a magnet cold mass
Beam pipe perforation
Magnet quench Soot ?*
Pressurization of CM
Contamination by soot ?*
ODH in tunnel
Pressurization of beam vacuum
Beam pipe rupture disk
opening
Mechanical damage of bellows (Nested &
PIMs)*Not seen during the “Noell 4”Incident in SM18
Damage due to a hypothetical electrical arc in a magnet coil
Complementary solutions to improve the beam vacuum protection and to protect sensitive equipments (RF, kickers, experiments,…) J.M. Jimenez – LHC MAC April’10.
Mitigation solutionsRupture disks (3/4)
Max. pressure (quench valve)
Adjusted level at 10 bars (quench valve)
Nested bellows buckling
PIM bellows buckling
C. Garion
Maximum pressure following a dipole quench (measurements)
0
2
4
6
8
10
12
14
16
18
0 1 2 3 4 5
Max
imum
pre
ssur
e [b
ar]
Beam energy [TeV]
tc - 100 s
tc - 50 sNested bellows buckling
PIM bellows buckling
Working line ?
KC. WuR. van Weelderen
S. Claudet
Damages in case of a hypothetical electrical arc in a magnet coil
• Beam pipe perforation of a single magnet (Reminder: the downtime for a single dipole exchange is about 4 months)
• Plastic deformation (rupture ?) of nested & PIM bellows:– No damage at 3.5 TeV (with 50 s time constant)– Could become critical above 3.5 TeV especially if we
increase the discharge time constant.• PIMs can be repaired in-situ• Nested bellow repair requires magnet removal.
Conclusion• Electrical arc in an interconnect:
– The present consolidation, up to 5 TeV, will suppress mechanical collateral damages in adjacent sub-sectors.
– Nevertheless, mechanical damage of the MLI in the concerned sub-sector as well as contamination of the beam pipe(s) could require heavy repair work.
– With the present consolidation status, a new incident will still have big impact on the machine down time (8 to 12 months)
• Electrical arc in a dipole coil:– Limited impact at 3.5 TeV (but at least 4 months of downtime to exchange one
dipole)– Could be more critical above 3.5 TeV (damage of bellows over several sub-
sectors)
• A hypothetical incident caused by an electrical arc during the 2011/12 operation could seriously impact the LHC physics program: Corresponding risks must be carefully assessed.