Evaluation of RHIC Safety Relief System in Response to the LHC Incident

1
Evaluation ofRHIC Safety Relief System in
Response to the LHC Incident

• K. C. Wu
• 1/28/09

2
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

3
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

4
Layout of LHC vs RHIC
LHC 27 km
RHIC 3.8 km
5
Tunnel Cross Section of LHC ( 3.8 m dia.) vs
RHIC ( 4.9 m)
RHIC
LHC
Sea level
100 m under ground, with small slopes
6
Cross Section of Arc Dipole Magnet for LHC (914
mm dia. Cryostat) vs RHIC (610 mm dia.)
LHC Dipole
RHIC Dipole
7
Comparison of Magnetic Stored Energy and Liquid
Helium Volume for Dipole and Quadrupole between
RHIC and LHC
LHC dipole magnet carries 20 times magnetic
stored energy of a RHIC dipole
8
Comparison of Magnetic Stored Energy and Liquid
Helium Volume Based on the Lattice of RHIC
(1D1Q) and LHC (6D2Q)
Energy per meter for LHC is 16 times that of
RHIC Energy per Liter liquid He for LHC is 10
times that of RHIC
9
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

10
L. Evans Talk
11
L. Evans Talk
12
CERN Interim Report - 10/15/08
https//edms.cern.ch/file/973073/1/Report_on_08091
9_incident_at_LHC__2_.pdf
13
CERN Interim Report - 10/15/08
14
CERN Interim Report - 10/15/08
15
CERN Report - 11/26/08
16
Interconnect Vaporized CERN Release 11/26/08
17
Inter-connect Between Two LHC Magnets CERN
Release 11/26/08
18
Faulty Electrical Connection Between Two LHC
Magnets CERN Release 10/16/08
19
Interconnections and Busbar Splice Between Two
LHC Magnets 11/26/08
20
Damaged Inter-connect (R. Aymar) 12/05/08 (NOT
the Vaporized interconnect) http//indico.cern.ch/
getFile.py/access?contribId12resId1materialId
slidesconfId44986
21
Damaged Support (R. Aymar) CERN 12/05/08
22
CERN Interim Report - 10/15/08
23
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

24
Schematic Layout of LHC ( 27 Km)
Failure Occurred in Sector 34
25
8 Sectors Cooled by 8 RefrigeratorsEach Sector
is 3.3 Km Comparable to RHIC
Failure location Sector 3-4
26
LHC - Magnet and Cryogenic Distribution Line in
Separate Cryostat
Separate Magnet Cryogenic Distribution
Line Safety Relief (in Jumper) is designed to
discharge helium from Magnet to D line Vacuum
Tank Relief to Tunnel
27
3 Relief Valve Systems

• To protect
• cryogenic process lines (main),
• cryostat and vacuum jacket (secondary, turns out
  major for LHC), and
• beam tube (not well defined)
• Process Relief lines associated with Magnet,
  Supply and Return etc.
• usually set slightly below design pressure of
  pipe, based on criteria such as magnet quench and
  loss of vacuum (by air or helium)
• helium is released eventually to outside tunnel
• Vacuum Tank Relief Magnet Cryostat and Vacuum
  Jacket
• usually set at low pressure ( 1.5 psi or 0.01
  MPa based on some less established criteria)
• release to tunnel (ODH study) and cryogenic
  safety
• Beam Tube
• typically low pressure and small capacity, not
  intend to manage large helium release
• release to tunnel

28
LHC Cooling Scheme - 3.3 Km Sector is Divided to
27 Cells (6D 2Q) in Parallel Except Shield,
107 m, 1.3 bar, 1.9 K
Cryogenic Dist. Line
Jumper
Magnets
29
LHC - Safety Relief Valves and Other Component in
a Sector ( 27 Cells)
RHIC pressure relief is discharged to ambient air
outside during an upset condition. Pressure
relief in LHC will be discharged to Cryogenic
Distributing Line.
30
LHC - Cold Mass and Vacuum Sub-sectorization in a
3.3 Km Sector
214m
Vacuum barriers 13 for Magnet Cryostat, 1 per
Jumper, 8 in Cryogenic Distribution Line,
Hydraulic restrictions 12 for Cold Mass RHIC
does not have vacuum barrier between magnets, the
vacuum barriers are on VJR - Warm/Cold Transition)
31
LHC - SSS (Quadrupole) with Jumper
3 SSS (quadrupole) have moved - over pressure on
vacuum barriers L. Evans
32
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

33
1 Refrigerator 2 Parallel Cooling Circuits
(Blue and Yellow) each 6 Sextants in Series3.8
Km is divided into six 600 m Sextants
RHIC Cryogenic System
Process relief valves are located mostly on Valve
Box at the end of a Sextant
34
Cross Section of RHIC Tunnel Two Magnet Cryostats
with Cryogenic Lines inside
Safety Relief are located mostly on Valve Boxes
in Service Building Safety Relief on Q8 also
routed outside tunnel Vacuum Tank Relief to Tunnel
35
Cross Sectional View of a RHIC Dipole(to be
Cooled at 3.5 bar, 4.5 K, 120 g/s)Cryogenic
Lines inside Magnet Cryostat
Cryo lines M Magnet S Supply R Return U
Utility H Shield
36
Cryogenic Connection Containing Bus for a RHIC
Interconnect
Upper line 2.5 OD, t .083, bus 1 x 1, A
3.3 in2 21 cm2, Material for SS tube 4.2
cm3/cm Lower line 3.0 OD, t
.083, bus 1 x 1, A 5.3 in2 34 cm2,
Material for SS tube 5.0 cm3/cm In RHIC,
voltage taps have been installed on bus
connection for quench protection
37
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

38
1) RHIC Process Relief Valves for M, S, R, U H
39
Forced Cooling of RHIC Sextant 4/5 Process
Control Screen Display ( 600 m, 3.5 bar, 4.5 K
and 120g/s)
Valve Box ( Process Relief)
Valve Box ( Process Relief)
Add. Relief Valve for Magnet
See Next Page
40
Flow Schematic showing VJR, Triplet Q4
(Location of Vacuum Barrier)
VJR for section with warm bore Has vacuum
barrier At higher elevation than magnet cryostat
41
Relief Valves for M, S, R, U and H lines Located
on Valve Box
Relief Valves For 300 Sextant
Relief Valves For 500 Sextant
2 relief valve for S, R, U H per Sextant per
Ring 4 relief valves for M per Sextant per Ring
42
In RHIC Arc Region, Additional Relief Valve for M
line is Installed between D8 and Q8 (2 in a
Sextant 600 m)
43
Summary of Process Relief Valves in RHIC
Presently, relief valves are set 250 psig (265
psia). Relief valve calculation remains
applicable and M, S, R, U H lines are
adequately protected.
44
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

45
2) RHIC Vacuum Tank Relief Valves, Potential
Helium Release Rate for Oxygen Deficiency Hazard
Calculation and Cryogenic Safety Evaluation
46
RHIC Vacuum Tank Relief and Potential Helium
Release Rate for ODH Calculation

• In RHIC, each vacuum tank relief is sized to
  release all helium in the cold mass to insulating
  vacuum space while keeping pressure below 1.5 atm
  in a magnet cryostat.
• In 1995, Helium Release Rate is based on
  releasing all helium in the M line of a Sextant
  to RHIC tunnel as the most creditable (or worst)
  accident. It appears that a major LHC type
  failure, helium from neighboring sextants and
  refrigerator could flow into the failed region
  unless the sextant is isolated immediately after
  the incident.
• No one was at risk during the LHC incident is
  likely due to people is NOT allowed in the LHC
  tunnel during powering
• Before more accurate results for helium release,
  it is suggest to recalculate ODH based on present
  helium release rate as compare to that given in
  AD/RHIC/RD-79. Operation of refrigerator and
  valves as related to minimize helium release
  shall be investigated.

47
Liquid Helium Volume for M, S, R, U and H Lines
in RHIC (Revised)
Amount of helium in the magnet line is 1.2 ton
per sextant Amount of helium in the supply line
is 0.35 ton per sextant
48
Vacuum Space and Barrier in RHIC

• There are 4 separate insulating vacuum in a RHIC
  Sextant
• 1 Q4 to Q4 in regular arc region Blue
• 1 Q4 to Q4 in regular arc region Yellow
• 2 (1 at each end of a Sextant) for the common
  vacuum of DX - Triplet - VJR Blue VJR Yellow
• 4 Vacuum Barriers are located on VJR (Triplet
  Q4) above Q4 and
• 4 Vacuum Barriers are located on VJR (Triplet -
  Valve Box) above Triplet
• Designed pressure is 1.5 atm external for Vacuum
  Jacket of VJR, including Barriers. VJR is
  designed according to B31.3

49
Illustration of Vacuum Barrier Flat plate with
holes and bellows that connect process pipes
50
Vacuum Barrier on VJR - Q4 to Triplet
IR region lt- -
- -gt arc region
DX
Triplet
Q4
VJR
End plate is 3/8 thick
51
Vacuum Tank Relief Valve in Arc Region (Q4 Q4)
on Every Interconnect ( 60 Total)
52
Vacuum Tank Relief Valve on Interconnect
4 x 1 holes at inlet to prevent relief being
plugged
1.875 ID
53
Interconnect showing with Superinsulation
Incorporate passages for leak check, also prevent
S.I. From damaged by helium flow should there is
a major spill.
Inlet 4 x 1 holes, tube 1.875 diameter
54
Flow Schematic in Insertion Region(1 Vacuum
Space for DX, Triplet and 2 Spools of VJR to Q4)
Vacuum Barrier above Triplet
Triplet
Vacuum Barrier above Q4
DX
VJR
55
RHIC IR Region VJR from Triplet to Q4 and to
Valve Box
To Valve Box Vacuum Barrier is above Triplet
To Q4 Vacuum Barrier is in Q4 side
56
10 Vacuum Relief Valves for Vacuum Space
Triplet, DX VJR
Vacuum Tank Relief is the same as other RHIC
magnets. 6 total for Triplet and DX
2 x 2 Commercial Pump Out Relief are installed
for each VJR to Q4, 4 total
57
Pump Out Relief on VJR Cryolab SV7-816-5W1 or
Cryocomp SV716-SW ID 2 inch
58
Vacuum Tank Relief

• 2 OD, 1.875 ID, Area 2.76 in2, square inch
• Installed on interconnect, Stainless Steel
• Set at 1.5 psi (on 3 bolts with springs)
• 2 3/8 from cryostat to flange
• From Q4 - Q4 per Ring in a RHIC arc region, 60
  relief. Total area for relief is gt 150 in2
• In each DX Triplet VJR region, 6 relief 4
  pump out relief. Total area for relief is 29
  in2

59
No Damage on Vacuum Barrier and Magnet Supports
is Expected for RHIC

• Due to ample vacuum tank relief valves, pressure
  in magnet cryostat will be below 1.5 atm even for
  a major helium release similar to the LHC
  incident.
• The vacuum barrier, internal supports for magnets
  and external support for cryostat are able to
  sustain a pressure difference of 0.5 atm to air
  and 1.5 atm to VJR. A more detailed study
  could be performed.
• Main concern is personal safety if large amount
  of cold helium is released into the tunnel, and
  not damage of magnets or equipments.

60
Helium Release Rate for ODH and Cryogenic Safety
Evaluation

• Also used in vacuum tank relief valve
• Unless failed region is isolated immediately
  after an incident. helium released into vacuum
  tank could come from
• that particular sextant,
• the depressurization of 3.5 to 1.5 bar in the
  entire ring or two rings and
• from helium refrigerator.
• Present study assumes the 2nd ring and the helium
  refrigerator are isolated. Amount of helium only
  from that in a sextant plus depressurization of
  the failed ring.

61
Illustration of Helium Flow During Steady State
Operation and Pipe Failure in M Line
62
4 Vacuum Space in a RHIC Sextant
When one M line fails, it effects only the region
of a vacuum space. Insulating vacuum remain
intact in all other regions. Once
helium enters the broken arc region, it quickly
spread over the entire length.
63
Estimation of Liquid Helium due to failure of M
line in the arc region (Q4-Q4) and in the
Insertion Region from the sum of liquid volume
and depressurization of M S lines in one RHIC
Ring
64
Potential Flow from Helium Refrigerator
discussion with R. Than

• Nominal flow from helium refrigerator to RHIC
  rings are 400 g/s.
• The Intermediate Pot in the cold end of the
  refrigerator has 2,000 gallon 8,000 L of
  liquid helium.
• Without operator interference, refrigerator could
  push 400 to 800 g/s of helium to RICH rings
  until liquid in Int. Pot exhausted.
• Based on simple minded assumption, 240 kg 480
  kg of additional helium could be pushed into RHIC
  in 10 min.
• Note Total compressor flow is 1,700 g/s at
  nominal operating condition. This flow is shared
  by upper turbines ( 500 g/s), lower turbines (
  600 g/s) and feed to RHIC rings.

65
Some Estimations on Helium Volume

• 1 ton 1,000 kg
• For liquid helium, 1 kg 8 L
• For helium gas at ambient condition, 1 kg 6,000
  Liter 210 Cubic Foot
• 1 ton ? 210,000 CF ? 6,000 m3
• Volume of a RHIC Sextant 300,000 CF (equivalent
  to 1.5 ton of helium gas)

66
Estimated helium release to RHIC Tunnel for ODH
and Cryogenic Safety Evaluation Assuming
Refrigerator and the 2nd Ring are Isolated 1
ton in 1 min. 1.5 ton in 2 min. (A more
realistic model is being developed, not complete
yet)
67
Possible Ways to Limit Helium Release

• Suggest to integrate insulating vacuum readout
  (Thermocouple or Cold Cathode) and O2 sensor to
  cryogenic process control.
• Establish criteria for identifying major failure
  based on vacuum reading, O2 value and pressure
  pattern in the ring.
• Suggest to interlock insulating vacuum and O2
  reading with sextant isolation valves to limit
  amount of helium released into RHIC tunnel during
  a major failure.

68
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

69
3) RHIC Beam Tube Vacuum Relief (Not intend for
large helium release)
70
Beam Tube Vacuum Relief (Burst Disc) in RHIC On
Two Ends of an Arc and on Every Triplet, 4 per
Sextant
71
Beam Tube Relief Line 1 almost 2.75 m long
from Interconnect to Burst Disc
72
Relief Burst Disc for RHIC Beam Tube
73
Relief Burst Disc for RHIC Beam Tube
Orifice for the relief valve is 3/8 or 0.95 cm
Orifice area 0.71 cm2 R. Todd In addition,
there are 8 1/8 holes (0.63 cm2 total) 1 line
( 2.75 m) is used to connect the beam tube to
relief burst disc
74
Overview

• Brief comparison between LHC and RHIC
• Brief description of LHC Incident few pages
  extraction from L. Evans talks, CERN report on
  Oct. 15 and Nov. 26
• LHC cryogenic and superconducting system
• RHIC cryogenic and superconducting system
• Safety relief valves for cryogenic lines in RHIC
• Vacuum tank relief valves for cryostat in RHIC,
  ODH and other Cryogenic Safety consideration
• Beam tube vacuum relief valves in RHIC
• Energy needed to burn a SS pipe or copper bus

75
4) Energy Needed to Burn a SS Pipe or Copper Bus
by Electric Heat

• Energy needed to melt SS304 and copper
• Damage of pipe by an electric arc

76
Some properties of stainless steel and copper
77
Energy in RHIC also at 1 kA and 500 A

• In an LHC sector (3.3 km), magnetic energy 1/2
  L I2 is 1 GJ (dipole circuit).
• One ring of RHIC dipole is 70 MJ.
• Assuming 50 of the energy is extracted as in
  the case for LHC, the remaining energy will be
  35 MJ.
• Since 35 MJ (RHIC) is small compared to 300 MJ
  (LHC), damage will be much less for RHIC if an
  incident ever occurs.
• However, it takes  10 KJ to melt 1 cc of ss
  which is equivalent to a 2.5 cm dia. hole on a
  .083 inch wall pipe. 35 MJ is still large. 
• Quench protection is essential.
• Note if person are allowed at 1 kA, the energy
  will be 1.4 MJ (1/25 that of 35 MJ). At 500 A,
  the energy is 350 KJ.
• Experience in Quench protection system of RHIC
  has been very good, and is best be reassured by
  the Electrical Group.

78
Thanks for the input and help of

• R. VanWeelderen, J. Wenninger (CERN)
• P. Wanderer, J. Sondericker, R. Felter
• J. Tuozzolo, R. Than, A. Warkentien, W. DeJong,
  E. Quimby, R. Karol
• D. Weiss, G. McIntyre, R. Todd, R. Davis,
  S. Seberg
• K. Brown, A. Arno

79
References

• Pressure Relief for RHIC Cryogenic System,
  AD/RHIC/RD-64, 1993
• Safety Relief for RHIC Vacuum Tank,
  AD/RHIC/RD-71, 1994
• Specification for RHIC Vacuum Jacketed Piping
  System, No. RHIC-CR-E-3201-0014, Rev. E, 9/1/95
• Estimation of Helium Discharge Rates for RHIC ODH
  Calculations, AD/RHIC/RD-79, 1995

80
Comparisons Between RHIC and LHC, p1

• LHC Sector (3.3 km)
• Tunnel radius 1.9 m, gt 100 m under ground
• 2 in 1 magnet
• Separate Cryogenic Distribution Lines with Magnet
  Cryostat
• 1 magnet cryostat 1 CDL in Tunnel
• 1 bar, 1.9 K
• Superfluid Helium II
• Magnet Cell Cooled in parallel
• Relief valves located in Jumper and to be vented
  through Cryogenic Distribution Line to recover /
  outside
• Vacuum tank Relief (2? per 214 m)
• Vacuum Tank Relief to Tunnel
• 13 vacuum barriers for Magnet in a Sector (13 in
  3.3 km)
• There are also barriers on jumpers

• RHIC Ring ( 3.8 km)
• Tunnel radius 2.4 m, Sea level
• 1 in 1 magnet
• Integrate Cryogenic Distribution Lines in Magnet
  Cryostat
• 2 magnet cryostat in Tunnel
• 3.5 bar, 4.5 K, 120 g/s
• Supercritical Forced Flow
• Magnet Cooled in Series
• Relief valves mostly located on Valve Box and to
  be vented directly to outside
• Vacuum Tank Relief (1 per magnet) installed
  mainly on Interconnect
• Vacuum Tank Relief to Tunnel
• 2 vacuum barriers in a sextant (on VJR, 12 in
  3.8 km Ring)

81
Comparisons Between RHIC and LHC, p2

• RHIC - Arc Dipole
• 5000 A, 3.5 T
• 350 kilo-joule magnetic stored energy
• RHIC - Sextant
• Stored energy 8.9 Mega-joule per sextant
  (excluding IR)
• 4 safety relief valves for Magnet in a sextant (
  600 m)
• Calculated capacity per sextant due to loss of
  vacuum 5,400 g/s
• 8,750 L liquid volume per sextant ( 15 L/m)
• 60 Vacuum tank relief in the arc region ( 500
  m)
• 6 Vacuum tank relief (16 in2 total) and 4
  commercial 2 pump out relief for DX - Triplet VJR

• LHC - Arc Dipole
• 11800 A, 8.4 T (failure occurred at 8,700 A,
  74 of 11800 A)
• 7,100 kilo-joule magnetic stored energy ( 20
  RHIC dipole) (failure occurred at 55 design
  energy)
• LHC - Cell
• Stored energy 44 Mega-joule per cell ( 6 D 2
  Q)
• 2 safety relief valves for Magnet in a cell (
  110 m)
• Calculated capacity per cell after magnet quench
  2,000 g/s?
• 2,200 L (assuming 20 L/m)
• Few vacuum tank relief in two cells ( 220 m) 2

82
Comparison Between RHIC and LHC on ODH

• LHC RHIC
• Tunnel 1.9 m radius 2.4 m radius
• Small cross section area Area 1.66 times
  larger
• More energy in magnets Much less energy
• ( 200 Mega Joules Estimate at 350
  Kilo-Joules
• Released into magnets at 500 A when people
  are
• at 8,700 A in the incident) allowed to
  tunnel
• 3.3 km tunnel underground 600 m sextant at
  ground level
• Longer walk to exit About 3 minutes walk to
  exit
• Fan capacity 21,000 SCF Fan capacity 60,000
  SCF
• Helium release 2 ton initially Expect 2 tons
  total
• total 6 ton for the incident
• Vacuum tank relief 2 in 210 m Vacuum tank
  relief 60 in 500 m.
• Magnet cryostat fails and ODH No over
  pressure in cryostat is expected
• More than 1 magnets failed and Under the
  hypothetical / worst situation,
• Helium is released from more than Helium is
  expected to come from
• One magnet only the failed magnet, no
  subsequent failure
• Valve Box between sextants,
• Failed sextant could be isolated