Gas activation in the CNGS decay tunnel during AWAKE operation
Eduard Feldbaumer - CERN/RP
AWAKE Collaboration Meeting 20th – 21st of June 2013
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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
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CNGS - Current RP status
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AWAKE experimental area @ CNGS
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AWAKE
CNGS
Decay tunnel
Hadron stopper
TI8
LHC
TT41
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CNGS area
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Awake AreaCNGS target chamber
CNGS2011 - FLUKA geometry
Service gallery
Protons
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CNGS area
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~ 1 km
Awake Area
Decay tunnel
Hadron Stopper
CNGS2011 - FLUKA geometry
Horn
CNGS Target
Reflector
He Tube 1 He Tube 2
Service gallery
Protons
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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
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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
0.7 3
14
0.570
High radiation area
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CNGS - Radiation Survey Survey data from March 2013
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1.30.1 0.8
0.1
0.6
0.5
3.5
42 16
4.5
16
807.5
2022
10
120
55
5
15
20
65
Low occupancy radiation areas:• Non- designated• Supervised• Simple controlled• Limited stay
Data: Courtesy of Heinz Vincke
(measured dose rates in µSv/h)
CNGS target
Calculated values
AWAKE experimental area
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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
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Gas activation in decay tunnelFLUKA simulation
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CNGS decay tunnel
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CNGS operation: Vacuum in decay tunnel (1 mbar)General safety issue!
Safety Shutter: 30 mm steel
Awake installation & operation: Decay tunnel filled with gasGas activation
Dimensions:• Length = 998 m• Diameter = 2.45 m• Volume = 4705 m3
Front cap: Ti • Thickness = 3 mm
CNGS safety shutter in «closed» positionK.Elsener, M. Grill, A. Masi, A. Pardons CNGS-2006-06
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FLUKA simulation geometry
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Air
C - Rods He tube
Horn He tube 1 He tube 2 Reflector Decay tunnel
Decay tunnel Carbon dump Iron dump
~ 1 km
CNGS target
CNGS target
Beam position 1
Beam position 2
Hadron Stopper
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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.)
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Operation scenarios
*4 x 2 weeks per year
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Beam parameter Scenario 1 Scenario 2
Operation 4 years* nominal 4 years* ultimate
Energy 400 GeV
Intensity 3.E11 p/bunch 3.5E11 p/bunch
Repetition 1/30 Hz 0.14 Hz
Total 4.84E16 p/year 2.37E17 p/year
Beam start in front of CNGS target Decay tunnel
Beam size (1 sigma) 0.5 mm (CNGS beam)
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Cooling TimeA (Bq/cm3) Σ(A/CA)
He N2 Air He N2 Air0 s 7.71E-03 2.94E-01 3.36E-01 0.03 2.40 3.081 min 5.14E-03 1.74E-01 1.98E-01 0.03 2.29 2.781 h 4.92E-03 3.85E-02 4.03E-02 0.03 0.39 0.591 d 4.88E-03 2.78E-02 2.68E-02 0.03 0.24 0.397 d 4.87E-03 2.65E-02 2.53E-02 0.03 0.23 0.331 m 4.80E-03 2.22E-02 2.11E-02 0.02 0.18 0.22
Gas activation – Scenario 1
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Relative statistic uncertainty of calculated activation ΔA < 5%
∑𝑖
𝐴𝑖
𝐶𝐴𝑖
<1
… activation concentration of isotope i
… Swiss limits for Air activation
Cooling TimeA (Bq/cm3)
He N2 Air0 s 7.71E-03 2.94E-01 3.36E-011 min 5.14E-03 1.74E-01 1.98E-011 h 4.92E-03 3.85E-02 4.03E-021 d 4.88E-03 2.78E-02 2.68E-027 d 4.87E-03 2.65E-02 2.53E-021 m 4.80E-03 2.22E-02 2.11E-02
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Gas activation – Scenario 2
Main contributing isotopes:
N2, Air: C-11, N-13 Be-7 H-3
He: H-3
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Cooling TimeA (Bq/cm3) Σ(A/CA)
He N2 Air He N2 Air0 s 2.89E-02 2.95E+00 3.44E+00 0.13 22.40 29.771 min 2.44E-02 1.64E+00 1.93E+00 0.13 21.44 26.931 h 2.40E-02 4.09E-01 4.27E-01 0.12 4.17 5.951 d 2.39E-02 2.98E-01 2.89E-01 0.12 2.59 3.917 d 2.39E-02 2.83E-01 2.72E-01 0.12 2.43 3.421 m 2.37E-02 2.35E-01 2.25E-01 0.12 1.96 2.31
1 y 2.18E-02 9.09E-02 8.56E-02 0.11 0.55 0.61Relative statistic uncertainty of calculated activation ΔA < 5%
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Gas activation - Awake proton beam Proton beam for AWAKE operation on the CNGS target
Decay tube filled with N2
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CNGS beam: 1 sigma = 0.05 mm 100 % p on target
Awake beam: 1 sigma = 1.35 mm 85 % p on target
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Material ranking due to activation
Material RP ranking Explanation Objections
Vacuum Best No activation General safety issue
He Very good Not radioactive after 4y operation High costs
N2 Ok Slightly radioactive after 4y operation 1 h cooling for nominal beam
Air Ok Slightly radioactive after 4y operation 1 h cooling for nominal beam
Further corrosion of the decay tube
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Material RP ranking Explanation
Vacuum Best No activation
He Very good Not radioactive after 4y operation
N2 Ok Slightly radioactive after 4y operation 1 h cooling for nominal beam
Air Ok Slightly radioactive after 4y operation 1 h cooling for nominal beam
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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
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Nuclides Awake N2
A (Bq)CNGS Air
A (Bq)
H-3 4.58E+08 6.02E+09
Be-7 9.50E+08 1.54E+11
Be-10 3.23E+02 7.83E+03
C-10 4.67E+08 1.53E+09
C-11 4.73E+06 1.08E+09
N-13 4.50E+07 1.35E+07
F-18 7.55E+05 1.34E+09
Na-22 3.80E+04 1.05E+07
Na-24 2.34E+05 9.35E+09
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
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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)20/06/201
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OutlookRP studies for AWAKE
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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 studies20/06/201
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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
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Picture: Courtesy of Ans Partons
Implementation of AWAKE setup in FLUKA geometry
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Priorities due to expected impact
RP studies for AWAKE
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Task Impact Impact on Status
Gas activation in Decay Tunnel High Choice of gas
Access to CNGS area Done
Airborne radioactivity in CNGS area High
Access to CNGS areaVentilation system Air release to environment
On-going, using existing FLUKA geometry
Prompt dose rates High Access to AWAKE during electron beam operation
Requires implementation of AWAKE geometry in FLUKA
Material activation and residual dose rates Medium Access to AWAKE
Safety shutter of DT Pending
Activation of cooling water Low No major impact expected
Cooling of hadron stopper(?) Pending
Activation of ground water and soil Low No major impact expected Pending,
Compare to CNGS operation
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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)
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Thank you!
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CNGS vs. AWAKE beam parameters
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Beam parameter CNGS1 AWAKE2
Beam momentum 400GeV/c 400GeV/c
Annual periods of operation 3 x 67 days 4 x 14 days
Total expected period of operation 10 years 4 years
Annual number of p.o.t. (nominal)(maximum)
4.5 x 1019 protons7.6 x 1019 protons
4.9 x 1016 protons2.4 x 1017 protons
Average beam intensity (nominal)(maximum)
2.6 x 1012 protons/s4.4 x 1012 protons/s
1.0 x 1010 protons/s4.9 x 1010 protons/s
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