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 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

20/06/2013

AWAKE Collaboration Meeting - Eduard Feldbaumer


3

CNGS - Current RP status

20/06/2013

4

AWAKE experimental area @ CNGS

20/06/2013


AWAKE

CNGS

Decay tunnel

Hadron stopper

TI8

LHC

TT41


5

CNGS area

20/06/2013

Awake AreaCNGS target chamber

CNGS2011 - FLUKA geometry

Service gallery

Protons


6

CNGS area

20/06/2013

~ 1 km

Awake Area

Decay tunnel

Hadron Stopper

CNGS2011 - FLUKA geometry

Horn

CNGS Target

Reflector

He Tube 1 He Tube 2

Service gallery

Protons


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

20/06/2013

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


8

CNGS - Radiation Survey Survey data from March 2013

20/06/2013

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


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

20/06/2013


10

Gas activation in decay tunnelFLUKA simulation

20/06/2013


11

CNGS decay tunnel

20/06/2013

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


12

FLUKA simulation geometry

20/06/2013

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


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.)

20/06/2013


14

Operation scenarios

*4 x 2 weeks per year

20/06/2013

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)


15

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

20/06/2013

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


Gas activation – Scenario 2

Main contributing isotopes:

N2, Air: C-11, N-13 Be-7 H-3

He: H-3

20/06/2013

16

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%


17

Gas activation - Awake proton beam Proton beam for AWAKE operation on the CNGS target

Decay tube filled with N2

20/06/2013

CNGS beam: 1 sigma = 0.05 mm 100 % p on target

Awake beam: 1 sigma = 1.35 mm 85 % p on target


18

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

20/06/2013

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


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

20/06/2013

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


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)20/06/201

3


21

OutlookRP studies for AWAKE

20/06/2013


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 studies20/06/201

3


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

20/06/2013

Picture: Courtesy of Ans Partons

Implementation of AWAKE setup in FLUKA geometry


24

Priorities due to expected impact

RP studies for AWAKE

20/06/2013

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


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)

20/06/2013


26

Thank you!

20/06/2013


CNGS vs. AWAKE beam parameters

20/06/2013

27

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

Documents

Gas activation in the CNGS decay tunnel during AWAKE operation