Johan Bremer

Helium Spill Test in LHC tunnelto define length of restricted working areas

Actual situation Evolution How to continue Set-up of the spilling test

How Where When Risks

On-going work Conclusions

01/11/2013

Johan Bremer

Helium Spill Test in LHC tunnelActual situation

01/11/2013

LHC Project Report 684*: header Caverage flow 1 kg/slength 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)

Johan Bremer

Helium Spill Test in LHC tunnelEvolution

01/11/2013

New proposal based on scale model

New proposal based on simulations

~100 m

Restrictedworking-area

50 + 30 m(45 % of tunnel)

Vacuum barrier Pressure reliefdevice (w/o spring)

VentilationJumper

Restrictedworking-area

6 + 6 m(9 % of tunnel)

Johan Bremer

Helium Spill Test in LHC tunnelHow to continue

01/11/2013

Large difference between proposal based on scale model and proposal based on simulation work

Make 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 tunnel

Johan Bremer

Helium Spill Test in LHC tunnelSet-up of the spilling test: how

01/11/2013

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 barSafety valve 0.5 barPressure drop system 0.1 bar

Johan Bremer

Helium Spill Test in LHC tunnelSet-up of the spilling test: how

01/11/2013

Equip the tunnel with measurement system 25 Temperature sensors (Pt100) 25 ODH (special development of fast reacting measurement head) 6 cameras 4 air velocity sensors 2 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 made

Johan Bremer

Helium Spill Test in LHC tunnelSet-up of the spilling test: where / when

01/11/2013

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 sector

Test should be made where there is least interference with on-going work

The 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 arc

Johan Bremer

Helium Spill Test in LHC tunnelSet-up of the spilling test: risk

01/11/2013

Risk assessment based on LHC sector 3-4 experience and modelisation:

Sector 3-4 Estimate 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/I22-01

Johan Bremer

Helium Spill Test in LHC tunnelSet-up of the spilling test: risk

01/11/2013

Helium 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 place

All 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/I22-01

Johan Bremer

Helium Spill Test in LHC tunnelon-going work

01/11/2013

Prototype of ODH system under test

Instrumentation for test has been ordered, DAQ-chain being programmed

Full instrumentation test by end of November

Testing of emptying by pressurization at this moment with LN2

Discussion with LHC coordination

First discussion on how to implement future test results on “restricted working areas” will start shortly

Johan Bremer

Helium Spill Test in LHC tunnelConclusions

01/11/2013

No consistent data to support length of “restricted working areas” in LHC tunnel

Existing models have to be verified with “real life” spilling test

Necessary equipment and instrumentation has been identified

Possibility of collateral damage has been classified as minimal

Equipment 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 cryostat