Radiation Protection at the LHC Lessons Learned D. Forkel-Wirth, D. - PowerPoint PPT Presentation

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: � 1 - 2 senior RP physicists FTE x 12 years 1 - 2 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 Dose rate constraints for areas accessible during beam operation Total beam loss “Normal” beam loss Ambient Dose Equivalent in Ambient Dose Equivalent Rate mSv in uSv/h Simple Controlled Area 50 10 Supervised Area 2.5 1 Non-designated Area 0.3 0.1 Fortunately very conservative parameters were chosen in 1995 but still problems in 2006: 1995 2006 Internal exposure of the public: 10 uSv/h 3 uSv/h < 10 uSv per year to the critical group (> 2003) 50 mSv 20 mSv 2.5 mSv 1 mSv 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)

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 < 2003: Monte Carlo codes could not provide three dimensional dose rate maps – only dose rates on “infinite” surfaces were available -> dose estimates would have resulted in unrealistic high numbers Consignes à appliquer lors des activités de maintenance en fonction des débits de doses ambiants. Niveau de référence du débit Consignes à appliquer lors des activités de maintenance de doses ambiant Tous les travaux doivent être soigneusement planifiés et optimisés. > 100 µ Sv/h > 2 mSv/h Tous les travaux doivent être soigneusement planifiés ; la durée de l’intervention dans la zone doit être strictement limitée ; la télémanipulation des composants est à envisager sérieusement. > 20 mSv/h Aucun travail n’est autorisé dans les endroits où les débits de doses sont supérieurs à cette valeur, car les limites de dose seraient trop facilement atteintes voir dépassées. La télémanipulation des objets est essentielle.

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 C ERN- High-Energy R eference F ield (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 F ull 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 8.2 cm Very good agreement � within 10% 9.2 cm Confirmed the accuracy � of the new simulation 26.0 cm Steel 8.0 cm 12.0 cm approach 121.6 cm Cu (reduced Graphite density) * H. Vincke Vincke * H.

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 cm cm 1.0E+03 1.0E+03 4.6E+02 4.6E+02 2.2E+02 2.2E+02 20 20 1.0E+02 1.0E+02 4.6E+01 4.6E+01 2.2E+01 2.2E+01 1.0E+01 1.0E+01 10 10 4.6E+00 4.6E+00 2.2E+00 2.2E+00 1.0E+00 1.0E+00 4.6E-01 4.6E-01 0 2.2E-01 2.2E-01 0 1.0E-01 1.0E-01 4.6E-02 4.6E-02 2.2E-02 2.2E-02 1.0E-02 1.0E-02 -10 -10 4.6E-03 4.6E-03 2.2E-03 2.2E-03 1.0E-03 1.0E-03 4.6E-04 4.6E-04 -20 -20 2.2E-04 2.2E-04 1.0E-04 1.0E-04 * H. Vincke Vincke * H. -20 -10 0 10 20 -20 -10 0 10 20 cm cm

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

1.E-01 kaons pion+ Particle pion- neutrons 1.E-02 protons photons electrons 1.E-03 d Φ / d ln(E) [1/cm 2 ] fields 1.E-04 1.E-05 inside 1.E-06 the 1.E-07 tunnel 1.E-08 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 Energy [GeV] 1.E-04 kaons pion+ pion- neutrons protons photons 1.E-05 d Φ / d ln(E) [1/cm 2 ] 1.E-06 1.E-07 behind 1.E-08 shielding 1.E-09 1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 Energy [GeV]

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

Set-up in the CERF Target Area SPS secondary hadron beam is hitting a copper target � irradiation of the PMI chambers with different radiation fields at various positions. Pos 1 Pos 2 Pos 3 Pos 4 Pos 5 Pos 6 Beam parameters: •Momentum: 120 GeV/c •Intensity: 9*10 7 hadrons/ SPS cycle (16.8 s with 4.8 s continuous beam) Hadron beam Cu target •Composition: 60.7% π + air filled plastic 34.8% p 4.5% K + chambers

Simulation of Particle Fluences 0.1 neutrons Position 2 photons Pos 6 0.01 ch. hadrons + /e - e 1E-3 Pos 5 1E-4 d Φ /dln(E) 1E-5 Pos 4 1E-6 Pos 3 1E-7 Pos 2 1E-8 Pos 1 1E-9 beam 1E-4 1E-3 0.01 0.1 1 10 100 Energy (GeV)

Simulation of Particle Fluences 0.1 neutrons Position 4 Pos 6 photons 0.01 ch. hadrons + /e - e Pos 5 1E-3 1E-4 d Φ /dln(E) Pos 4 1E-5 1E-6 Pos 3 1E-7 Pos 2 1E-8 Pos 1 1E-9 beam 1E-4 1E-3 0.01 0.1 1 10 100 Energy (GeV)

Simulation of Particle Fluences 0.1 neutrons Position 6 Pos 6 photons 0.01 ch. hadrons + /e - e Pos 5 1E-3 1E-4 d Φ /dln(E) Pos 4 1E-5 1E-6 Pos 3 1E-7 Pos 2 1E-8 Pos 1 1E-9 beam 1E-4 1E-3 0.01 0.1 1 10 100 Energy (GeV)