Helium Spill Test in LHC tunnel to 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 01/11/2013Johan Bremer

Helium Spill Test in LHC tunnel Actual 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)

Helium Spill Test in LHC tunnel Evolution 01/11/2013Johan Bremer New proposal based on scale model New proposal based on simulations ~100 m Restricted working-area m (45 % of tunnel) Vacuum barrier Pressure relief device (w/o spring) Ventilation Jumper Restricted working-area m (9 % of tunnel)

Helium Spill Test in LHC tunnel How to continue 01/11/2013Johan Bremer 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/s Total spill per test 125 kg (= 1000 liquid liters) Ventilation flow in access mode: m 3 /h, about 0.7 m/s in tunnel

Helium Spill Test in LHC tunnel Set-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 bar

Helium Spill Test in LHC tunnel Set-up of the spilling test: how 01/11/2013Johan Bremer  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

Helium Spill Test in LHC tunnel Set-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 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

Helium Spill Test in LHC tunnel Set-up of the spilling test: risk 01/11/2013Johan Bremer 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 : 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

Helium Spill Test in LHC tunnel Set-up of the spilling test: risk 01/11/2013Johan Bremer  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

Helium Spill Test in LHC tunnel on-going work 01/11/2013Johan Bremer  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

Helium Spill Test in LHC tunnel Conclusions 01/11/2013Johan Bremer  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