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Gas activation in the CNGS decay tunnel during AWAKE operation

Gas activation in the CNGS decay tunnel during AWAKE operation. Eduard Feldbaumer - CERN/RP AWAKE Collaboration Meeting 20 th – 21 st of June 2013. Contents. Current RP status of the CNGS facility ( C ERN N eutrinos to G ran S asso ) Gas activation studies in the CNGS decay tunnel

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Gas activation in the CNGS decay tunnel during AWAKE operation

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  1. Gas activation in the CNGS decay tunnel during AWAKE operation Eduard Feldbaumer - CERN/RP AWAKE Collaboration Meeting 20th – 21st of June 2013

  2. Contents • Current RP status of the CNGS facility ( CERN Neutrinos to Gran Sasso) • Gas activation studies in the CNGS decay tunnel • Outlook on required RP studies for AWAKE AWAKE Collaboration Meeting - Eduard Feldbaumer

  3. CNGS - Current RP status AWAKE Collaboration Meeting - Eduard Feldbaumer

  4. AWAKE experimental area @ CNGS TT41 AWAKE CNGS Decay tunnel TI8 LHC Hadron stopper AWAKE Collaboration Meeting - Eduard Feldbaumer

  5. CNGS area CNGS2011 - FLUKA geometry Awake Area Service gallery CNGS target chamber Protons AWAKE Collaboration Meeting - Eduard Feldbaumer

  6. CNGS area Hadron Stopper ~ 1 km CNGS2011 - FLUKA geometry Awake Area Service gallery Horn Reflector Protons Decay tunnel CNGS Target He Tube 1 He Tube 2 AWAKE Collaboration Meeting - Eduard Feldbaumer

  7. Calculated residual dose rate at CNGS • 10 m downstream from CNGS target after Horn • Proton Intensity: • 8x1012 s-1 • Beam Energy: • 400 GeV • Irradiation time: • 200 days • Cooling time: • 6 months High radiation area 14 0.7 3 70 0.5 M. L. Sentís, A. Ferrari, S. Roesler – Estimation of the Dose Equivalent Rate from Induced Radioactivity in the Region near the Fast Coupling System of the CNGS Magnetic Horn – EDMS No. 497224, 2004 AWAKE Collaboration Meeting - Eduard Feldbaumer

  8. CNGS - Radiation Survey • Survey data from March 2013 • Low occupancy radiation areas: • Non- designated • Supervised • Simple controlled • Limited stay (measured dose rates in µSv/h) AWAKE experimental area 0.1 20 10 16 0.8 0.1 0.6 1.3 55 4.5 15 Calculated values 5 3.5 65 CNGS target 22 20 16 42 0.5 80 120 7.5 Data: Courtesy of Heinz Vincke AWAKE Collaboration Meeting - Eduard Feldbaumer

  9. Required RP measures • 80 cm concrete shielding separating AWAKE from CNGS • dose reduction factor > 100 • Removal of activated equipment to make place for AWAKE installation • Decontamination campaign of AWAKE area  Should allow for classification as supervised radiation area during AWAKE installation phase AWAKE Collaboration Meeting - Eduard Feldbaumer

  10. Gas activation in decay tunnelFLUKA simulation AWAKE Collaboration Meeting - Eduard Feldbaumer

  11. CNGS decay tunnel • Dimensions: • Length = 998 m • Diameter = 2.45 m • Volume = 4705 m3 • Front cap: Ti • Thickness = 3 mm • CNGS operation: Vacuum in decay tunnel (1 mbar) • General safety issue! • Safety Shutter: 30 mm steel • Awake installation & operation: Decay tunnel filled with gas • Gas activation CNGS safety shutter in «closed» position K.Elsener, M. Grill, A. Masi, A. PardonsCNGS-2006-06 AWAKE Collaboration Meeting - Eduard Feldbaumer

  12. FLUKA simulation geometry CNGS target Air Beam position 1 He tube C - Rods CNGS target Beam position 2 Horn He tube 1 Reflector He tube 2 Decay tunnel ~ 1 km Iron dump Decay tunnel Carbon dump Hadron Stopper AWAKE Collaboration Meeting - Eduard Feldbaumer

  13. Material definition • Filling gas for decay tunnel • He: density = 1.786E-4 g/cm3 (0°C, 1 atm) • N2: density = 1.251E-3 g/cm3 (0°C, 1 atm) • Air: density = 1.225E-3 g/cm3 (20°C, 1 atm) 78% N2 , 21% O2 , 1% Ar • Material definitions for geometry from FLUKA input CNGS2011 (Alfredo Ferrari et al.) AWAKE Collaboration Meeting - Eduard Feldbaumer

  14. Operation scenarios *4 x 2 weeks per year AWAKE Collaboration Meeting - Eduard Feldbaumer

  15. Gas activation – Scenario 1 Relative statistic uncertainty of calculated activation ΔA < 5% … activation concentration of isotope i … Swiss limits for Air activation AWAKE Collaboration Meeting - Eduard Feldbaumer

  16. Gas activation – Scenario 2 • Main contributing isotopes: • N2, Air: • C-11, N-13 • Be-7 • H-3 • He: • H-3 Relative statistic uncertainty of calculated activation ΔA < 5% AWAKE Collaboration Meeting - Eduard Feldbaumer

  17. Gas activation - Awake proton beam • Proton beam for AWAKE operation on the CNGS target • Decay tube filled with N2 • CNGS beam: • 1 sigma = 0.05 mm  100 % p on target • Awake beam: • 1 sigma = 1.35 mm  85 % p on target AWAKE Collaboration Meeting - Eduard Feldbaumer

  18. Material ranking due to activation AWAKE Collaboration Meeting - Eduard Feldbaumer

  19. Accidental release of activated N2 (preliminary results) • Dose to persons inside CNGS area • Scenario 2 with cooling time: 1h • 1h stay inside gas cloud without further decay • Breathing rate for workers according to IAEA: 1.2 m3/h • Expected additional dose from inhalation: 17.1 µSv • Release to environment: • Awake • N2 activation in Scenario 2 • Cooling: 1h • CNGS • Air release studies* • Cooling: several hours * P. Vojtyla et al. – RADIOLOGICAL AND ENVIRONMENTAL IMPACTS OF AIR RELEASES FROM THE CNGS FACILITY - EDMS 685145, 2007 AWAKE Collaboration Meeting - Eduard Feldbaumer

  20. Conclusion • N2 filling of decay tunnel OK for RP - Slightly radioactive directly after Awake operation + No further corrosion of decay tunnel + Costs not too high + No safety issue due to low pressure • Required cooling time after nominal AWAKE operation: 1h • Radiological impact of accidental N2-release on workers acceptable • Optional low pressure inside decay tube to slow down release • Option: Keep vacuum and closed shutter (requires further studies) AWAKE Collaboration Meeting - Eduard Feldbaumer

  21. OutlookRP studies for AWAKE AWAKE Collaboration Meeting - Eduard Feldbaumer

  22. Airborne radioactivity • Expected air activation: • Low in Awake area due to low beam losses • higher downstream in CNGS area •  Separation of ventilation • Simulation scenarios: Air activation inside CNGS target chamber • with CNGS target in place • 85 % of remaining AWAKE proton beam impinging on CNGS target • CNGS target removed • Closed safety shutter of decay tube • Required for • ventilation system, ventilation modes • Access to AWAKE and CNGS area • Advantage: Current CNGS FLUKA geometry sufficient for preliminary studies AWAKE Collaboration Meeting - Eduard Feldbaumer

  23. Prompt dose rate • Access to AWAKE area during electron beam operation • Calculation of required shielding for operation • Worst case beam loss scenarios • Access during proton beam operation • Maximum beam intensity in case of accident • Beam loss scenarios in vicinity of openings Implementation of AWAKE setup in FLUKA geometry Picture: Courtesy of Ans Partons AWAKE Collaboration Meeting - Eduard Feldbaumer

  24. RP studies for AWAKE • Priorities due to expected impact AWAKE Collaboration Meeting - Eduard Feldbaumer

  25. Summary • Activation and Contamination inside AWAKE area from previous CNGS operation • Shielding wall between AWAKE & CNGS • Cleaning of area • Nitrogen filling of CNGS decay tube ok for RP • Final decision for AWAKE operation still pending • Optional: Vacuum with closed shutter (needs to be studied) • RP studies concentrating on air activation and prompt dose • Major impact on access and ventilation system • Low impact from Material, water and soil activation (CNGS studies) AWAKE Collaboration Meeting - Eduard Feldbaumer

  26. Thank you! AWAKE Collaboration Meeting - Eduard Feldbaumer

  27. CNGS vs. AWAKE beam parameters 1) Stefan Roesler, Doris Forkel-Wirth, Heinz Vincke - Summary of radiation protection studies for CNGS until the year 2005 – EDMS 805741 , 2006-12-04 2) Edda GSCHWENDTNER, Ans PARDONS, Chiara BRACCO et al. - The AWAKE Facility at CERN - Technical Study, Design and Comparison between the AWAKE Facility at CNGS and at the West Area - EDMS 1272163, 2013-02-21 AWAKE Collaboration Meeting - Eduard Feldbaumer

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