Radiation Protection at the LHC Lessons Learned D. Forkel-Wirth, D. Perrin, S. Roesler, C. Theis, Heinz Vincke, Helmut Vincke, J. Vollaire CERN-SC-RP-SL 13 October 2006, ILC and LHC Forum

Lessons learnt about  RP involvement into a project  Choice of RP design parameters  Code development and benchmarking  Implementation of ALARA  Radiation monitoring system  Radioactive waste management

RP resources for LHC  LHC machine: senior RP physicists FTE x 12 years Fellows x 12 years  LHC experiments: RP “observer status”: providing guide lines RP link person (since 2003) By far not all lay-outs, lay-out modifications and their impact on the radiation levels can be followed up - nevertheless a lot was achieved

RP resources for LHC Conclusion:  Savings in RP man-power during the project phase will cause additional costs during the construction phase by last minute changes during operation by increased waiting times, limitation of access technical modifications higher personal and collective doses  RP has to be closely involved into the project (machine and experiment) and to be treated like all other sub-project groups with respect to staffing and budgeting – from the design phase onwards

RP Design Parameters for LHC Fortunately very conservative parameters were chosen in 1995 but still problems in 2006: Consequence: in some cases we had to abandon all safety margins with respect to calculations (a safety factor of two to three is normally applied) uSv/h3 uSv/h 50 mSv20 mSv 2.5 mSv1 mSv Internal exposure of the public: 2003)

RP Design Parameters  Difficult task to define design parameters for dose rates and dose for projects whose design and operation stretches over decades as the development of RP legislation over these decades must be anticipated  Apply very conservative RP parameters and “pessimistic” beam parameters (e.g. ultimate beam intensity for environmental impact).  In the worst case: adjust your parameters – it will pay off on long term

Code development and benchmarking Required by the Swiss and French Authorities:  Estimate of collective and personal dose during maintenance of the LHC  Characterization of the future radioactive waste (nuclide vector) -> Development and benchmarking of the Monte Carlo code was required

Personal and collective dose during maintenance dose estimates would have resulted in unrealistic high numbers

Personal and collective dose during maintenance  2003: FLUKA code development enables realistic, three dimensional dose rate maps: - detailed calculation of radioactive isotopes produced by spallation reaction in the various materials - transport of decay product (β, γ) through matter -> realistic dose rates become available in three dimensions -> maintenance scenario * dose rates = personal dose!

Benchmarking at CERN- High-Energy Reference Field (CERF) facility Location of Samples: Behind a 50 cm long, 7 cm diameter copper target, centered with the beam axis

Benchmarks - CERF  Different materials typical for the LHC  Measurments and simulations for a large number of cooling times  Very good agreement was found between the simulation and the experiment (disagreements less than 20 %)

SPS-LHC Injection Test cm 12.0 cm 26.0 cm Graphite Cu (reduced density) Steel8.0 cm 9.2 cm 8.2 cm  Full scale collimator test in the SPS-LHC transfer line (TT40)  Dose rates were measured at two different cooling times of one week and one month  Very good agreement within 10%  Confirmed the accuracy of the new simulation approach * H. Vincke

Results TT40 1st Measurement after two weeks of cooling Measured dose rate: 0.95 mSv/h Simulated dose rate: ~1.1 mSv/h 2nd Measurement after one month of cooling Measured dose rate: 0.4 mSv/h Simulated dose rate: ~0.4 mSv/h * H. Vincke

ALARA: Collimator Exchange LHC Point 7

ALARA  Use of plug-in system for collimators allowing short installation and replacement times.  Orientation of accelerator components in order to facilitate the access to the connection boxes at their less-radioactive end.  Flanges for vacuum pipes which allow for easy coupling/de-coupling.  Remote bake-out system for critical parts.  Patch-panels for cables allowing an easier replacement and the use of especially radiation- resistant cables in high-loss areas.  Use of cables with a radiation resistance of at least 500kGy.  Placement of ionization chambers (PMI) to monitor remotely residual dose rates at locations with the highest expected losses.  and….

Radiation Monitoring System  Radiological survey of work places: Measurement of ambient dose equivalent H*(10) [Sv] in pulsed, high energy, mixed radiation fields  Challenge: Correct Reliable State-of-the-art Compliant with international standards and legal requirements  Radiation Monitoring System for the Environment and Safety for LHC (RAMSES): outsourced to a company strong technical collaboration with CERN

RAMSES with location ID Radiation Display Control box Radiation Monitor Controller Direct hardware connection Tap box Basic Area Controller with ID + local database RP Data Base long term storage RP User Interface Remote User Interface Internet LHC point (local Network) CERN Networks (Ethernet) RP User Interface Configuration and Supervision Manager ~ 400 detectors of various types ~ 6 Mill. CHF 5.5 FTE (CERN)

inside the tunnel behind shielding Particle fields

Air filled ionisation chamber (PMI) wall: C-H 2 volume: 3 l gas: air, 1 atm voltage: 400 V High-pressure ionisation chamber (IG5) volume: 5,2 l active gas: Ar or H (20 bar) high-voltage: 1200 V Comparison of Experiment and Simulations

SPS secondary hadron beam is hitting a copper target  irradiation of the PMI chambers with different radiation fields at various positions. Pos 1Pos 2Pos 3Pos 4Pos 5Pos 6 Hadron beam Cu target Beam parameters: Momentum: 120 GeV/c Intensity: 9*10 7 hadrons/ SPS cycle (16.8 s with 4.8 s continuous beam) Composition: 60.7%  %p 4.5%K + Set-up in the CERF Target Area air filled plastic chambers

Pos 6 Pos 5 Pos 4 Pos 3 Pos 2 Pos 1 beam Simulation of Particle Fluences

Pos 6 Pos 5 Pos 4 Pos 3 Pos 2 Pos 1 beam Simulation of Particle Fluences

Pos 6 Pos 5 Pos 4 Pos 3 Pos 2 Pos 1 beam Simulation of Particle Fluences

Simulation Counts/ prim. part. *10 -6 Simulation error *10 -6 Measurement Counts/ prim. part. *10 -6 Measurement error *10 -6 Simulation/ Measurement Error Pos 1 5,63 ± 0,125,64± 0, ± Pos 2 16,06 ± 0,4415,58± 1, ± Pos 3 67,46 ± 0,7367,25± 6, ± Pos 4 85,33 ± 0,6479,00± 8, ± Pos 5 96,20 ± 1,2689,39± 9, ± Pos 6 108,31 ± 0,82115,74± 17, ± Comparison of simulation and experiment

PS super-cycle 14.4 s BOOSTER 1.2 s SPS FIX TARGETS North & West areas East area ADEast area SPP SPN SPS (Machine Development) Time resolution of monitoring: 0.2 s + x * 0.1 s RAMSES LHC in future 0.9 s or 0.6 s

Read-Out Electronics For pulsed fields the read-out electronics has to be based on charge digitizers Range to be covered: A (background level) A Switching not permitted! Present CERN electronics covers 5 – 6 decades Newly developed: 9 – 10 decades First tests: electronics measures reliably up to 300 nC/pulse ~ 50 mGy/hour (LHC injection)

Conclusion  Outsourcing possible  Strong technical involvement of CERN-RP required  Resources are limited - but nevertheless: RAMSES: state of the art monitoring system

Radioactive waste management  Reduce radioactive waste already in the design phase – keep amount of material inside the tunnel and the experimental cave ALARA  Disposal of radioactive waste is expensive France: ~ 3 kEuro/m3 Switzerland: ~ 30 kCHF/m3  Conditioning center required (CERN: ~ 7 FTE)  Interim storage space needed

More ….  Workshops for radioactive material (try to group them)  State of the art operational dosimetres  Adequate RP training of workers  RP involvement comprises more than just RP issues (e.g. damage to material, High Level Dosimetry)

Conclusions  Don’t forget about RP resources and close RP involvement already in the design phase  Pool of Monte Carlo specialists required - allows cost- efficient design  Monte Carlo Code development might be required  Use very conservative RP design parameters  Radiation monitoring system needs to be designed  Radioactive workshops required  Radioactive waste to be minimised