tunnel to define length of restricted working areas Actual situation Evolution How to continue S etup of the spilling test How Where When Risks Ongoing work Conclusions 01112013 ID: 408877
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Helium Spill Test in LHC tunnelto define length of restricted working areas
Actual situationEvolutionHow to continueSet-up of the spilling testHowWhereWhenRisksOn-going workConclusions
01/11/2013
Johan BremerSlide3
Helium Spill Test in LHC tunnelActual situation
01/11/2013Johan Bremer
LHC Project Report 684*: header C average flow 1 kg/s
length helium jam 6 m
After discussion (HSE and DSO): make restricted work area of 3 m, centred around release point.
*SUMMARY
OF THE EXPERIMENTAL STUDIES OF COLD
HELIUM PROPAGATION
ALONG A SCALE MODEL OF THE LHC
TUNNEL (2003)Slide4
Helium Spill Test in LHC tunnelEvolution
01/11/2013Johan BremerNew proposal based on scale model
New proposal based on simulations
~100 m
Restricted
w
orking-area
50 + 30 m
(45 % of tunnel)
Vacuum barrier
Pressure relief
d
evice (w/o spring)
Ventilation
Jumper
Restricted
w
orking-area
6 + 6 m
(9 % of tunnel)Slide5
Helium Spill Test in LHC tunnelHow to continue
01/11/2013Johan BremerLarge difference between proposal based on scale model and proposal based on simulation workMake a representative spilling test in the tunnel to check the validity of the different models and calculations and base new access rules on these validated calculations:Liquid helium spill of 1 kg/sTotal spill per test 125 kg (= 1000 liquid liters)
Ventilation flow in access mode: 18000 m3/h, about 0.7 m/s in tunnelSlide6
Helium Spill Test in LHC tunnelSet-up of the spilling test: how
01/11/2013Johan Bremer
Pressurize
dewars
with warm helium gas taken from cylinder. The liquid mass flow will be measured by balances on which the
dewars
will be placed
1450 mm
DN 200
Dewar: Design pressure 2 bar
Safety valve 0.5 bar
Pressure drop system 0.1 barSlide7
Helium Spill Test in LHC tunnelSet-up of the spilling test: how
01/11/2013Johan BremerEquip the tunnel with measurement system25 Temperature sensors (Pt100)25 ODH (special development of fast reacting measurement head)6 cameras4 air velocity sensors2 mass balances (used for calculation of mass flow)
Equipment will be placed on 15 stands, 8 downstream (over 200 meter) and 7 upstream (over 100 meter) of ventilation
direction, at
places referenced to the simulation model
Most sensors will be placed at 1.75 m height, in passage
area
Total of two to three tests will be madeSlide8
Helium Spill Test in LHC tunnelSet-up of the spilling test: where / when
01/11/2013Johan Bremer Test should be made at a point where the ventilation flow is out-going (un-even point)Test should be made at the end of continuous cryostat section, to minimize effect on the chosen sectorTest should be made where there is least interference with on-going workThe ODH sensors have to be developed (fast reacting sensors not available on the market
)
Discussion with SMACC, VSC and coordination:
Test foreseen for end of January 2014 in sector 4-5, left of 5,
300 meter into arcSlide9
Helium Spill Test in LHC tunnelSet-up of the spilling test: risk
01/11/2013Johan Bremer Risk assessment based on LHC sector 3-4 experience and modelisation:Sector 3-4Estimate of situation during helium release*:first 40 sec helium flow: 15 to 26 kg/s (spill: 1 kg/s)helium mass released first 120 sec : 2000 kg (spill: 125 kg)
No explicit damage to tunnel structure, cable trays, electrical cabinets, cryogenic piping / valves
etc
,
directly
related to helium flow
Modelisation
helium spill in XFEL tunnel
**:
Modeled helium flow in the range of spill test;
Maximum temperature drop of mechanical equipment in the tunnel is not going over 40 degrees (if jet not directed onto equipment)
Conclusion: very confident that collateral damage is excluded, but…..
* CERN-ATS-2009-002: Task Force Report: Safety of Personnel in LHC underground areas following the accident of 19
th
September 2008
**Simulation
study of helium release in the XFEL tunnel, WUT-ref:#630333/I22-01Slide10
Helium Spill Test in LHC tunnelSet-up of the spilling test: risk
01/11/2013Johan BremerHelium spill tests will only be performed outside of normal working hours (no access in sector 4-5)Interconnects will be closed in area in which the spill test will find placeAll equipment owners in the area where the spill test will find place, are asked to protect their sensitive material (electronic cards, connectors etc.) against condensation of water during and directly after the spilling test* Simulation study of helium release in the XFEL tunnel, WUT-ref:#630333/I22-01Slide11
Helium Spill Test in LHC tunnelon-going work
01/11/2013Johan BremerPrototype of ODH system under testInstrumentation for test has been ordered, DAQ-chain being programmedFull instrumentation test by end of NovemberTesting of emptying by pressurization at this moment with LN2Discussion with LHC coordination
First discussion on how to implement future test results on “restricted working areas” will start shortlySlide12
Helium Spill Test in LHC tunnelConclusions
01/11/2013Johan BremerNo consistent data to support length of “restricted working areas” in LHC tunnelExisting models have to be verified with “real life” spilling testNecessary equipment and instrumentation has been identifiedPossibility of collateral damage has been classified as minimalEquipment owners have to be aware of eventual water condensation on their equipment
Cost of test: about 110
kCHF
, without helium (6000 CHF / test
)
Tests
will take place during last week of January in sector 4-5 left of 5, first 300 meter
into the continuous cryostatSlide13