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Simulations des niveaux de radiations en arrêt machine

Simulations des niveaux de radiations en arrêt machine. M. Brugger, D. Forkel-Wirth, S. Roesler (SC/RP). IR7 Radiation Protection Issues. Impact on environment. activation and release of air activation and release of water activation of rock radioactive waste. Impact on personnel (direct)

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Simulations des niveaux de radiations en arrêt machine

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  1. Simulations des niveaux de radiations en arrêt machine M. Brugger, D. Forkel-Wirth, S. Roesler (SC/RP)

  2. IR7 Radiation Protection Issues Impact on environment • activation and release of air • activation and release of water • activation of rock • radioactive waste Impact on personnel (direct) (indirect) • remanent dose from radioactive • components during interventions • stray radiation • dose to components (cables, magnets, etc.) • production of ozone (corrosion!) Simulations des niveaux de radiations en arrêt machine

  3. FLUKA Simulation Parameters • Detailed model of IR7 • (two beamlines incl. dogleg, collimators, dipoles incl. magnetic field, quadrupoles, tunnel, etc.) • Layout corresponds to V 6.5 (status March/April 04) • Only Phase 1, No Absorbers,… • No local shielding (!) • Forced inelastic interactions of 7 TeV protons in collimator jaws according to loss distribution obtained from tracking code * • Uniform distribution along the jaw, 200 mm inside • Magnetic field • Dogleg fully implemented (incl. field) • Magnetic field in the quadrupoles not considered • Annual number of protons lost per year at IR7 • Environmental calculations(ultimate operation): 7.3 x 1016 ** • Maintenance calculations(nominal operation): 4.1 x 1016 ** * data provided by R.Assmann ** data provided by M.Lamont (two beams) Simulations des niveaux de radiations en arrêt machine

  4. FLUKA-calculations: Geometry IR7 Air duct D4 D3 Q5 Q4 Q4 Q5 Enclosed sections Dipole Collimator Quadrupole *Collimators were rotated and positioned in the geometry by using a modified script from Vasilis Vlachoudis Simulations des niveaux de radiations en arrêt machine

  5. Design Criterion2mSv/year/person/intervention Simulations des niveaux de radiations en arrêt machine

  6. Calculation Procedure • Detailed Geometry description including • Correct source terms • Loss distributions • Complete geometry • Tunnel structure • Collimator, magnets • Beamline, Dogleg separation • Monte-Carlo simulation to calculate the remanent dose rates in the entire geometry using the new “Explicit Method” • Calculation of dose rate maps for the entire geometry and various cooling times, including • Separate simulations for different contributors • Average and Maximum Values for relevant locations • Compilation of intervention scenarios together with the corresponding groups • Time, location and frequency of the intervention • Number of people involved • Calculation of individual and collective doses • Iteration and optimization Simulations des niveaux de radiations en arrêt machine

  7. Remanent Dose Rates: Contributions Contributions to total remanent dose rates(180 days of operation, 1 hour of cooling) TCP TCS D4 D3 Q5 collimators beampipes magnets Tunnel walland floor Nominal Intensity Simulations des niveaux de radiations en arrêt machine

  8. Remanent Dose Rates: Section between TCP and Q5 Remanent dose rates after 180 days of operation Nominal Intensity 1 day of cooling 4 months of cooling TCS ~1 mSv/h ~5 mSv/h • first secondary collimator (Phase 1) most radioactive component (in the absence of additional • absorbers) with over 90% caused by secondary particles from upstream cascades • further peaks of remanent dose rate close to upstream faces of magnets • dose rate maps allow a detailed calculation of intervention doses Simulations des niveaux de radiations en arrêt machine

  9. Dose Rate Maps for the Full Geometry Only Beam 1 Cooling Time of one Day Simulations des niveaux de radiations en arrêt machine

  10. Dose Rate Maps for the Different Cooling Times 1 hour 8 hours 1 day 1 week 1 month 4 months Simulations des niveaux de radiations en arrêt machine

  11. Dose Rate Maps for the Different Cooling Times 1 hour 8 hours 1 day 1 week 1 month 4 months Simulations des niveaux de radiations en arrêt machine

  12. Chosen Locations for 1st Estimates Cooling Time of one Day Simulations des niveaux de radiations en arrêt machine

  13. Dose Rate Distribution in the Aisle (Pos1) 2nd Beam mirrored and added Cooling Time of one Day Simulations des niveaux de radiations en arrêt machine

  14. Average and Maximum Dose Rates • Shows the MAXIMUMintervention time, in order to stay BELOWthe design constraint • Must NOT BE USED asoptimization criterion • Even at long coolingtimes long interventionswill become difficult Simulations des niveaux de radiations en arrêt machine

  15. Intervention Scenarios - Details • To study various maintenance scenarios in order to get a complete view of individual and collective doses at IR7 we need the following information: • Kind of intervention • Location of the intervention • Respective cooling time • Number of persons involved • Steps of the intervention • Time estimate for each step • Frequency of the intervention • Typical cooling period before intervention • In the moment the uncertainty lies in the estimates for the intervention(s), not in the calculation of the remanent dose rates! Simulations des niveaux de radiations en arrêt machine

  16. Intervention Scenarios The following scenarios have already been identified and/or studied in more detail. x Simulations des niveaux de radiations en arrêt machine

  17. Conclusion • Access to the collimation region will strongly depend on the exact location of the intervention as well as the time to be spent there • Next to “hot spots” (e.g. collimators, downstream magnets or absorbers) the occupancy time for maintenance operations will be rather short • During the first years of operation the situation will be slightly relaxed (factor of ~3) • Optimization of intervention scenarios should already begin now in order to be able to adopt last design changes and identify those intervention scenarios important for further improvement Simulations des niveaux de radiations en arrêt machine

  18. Backup Slides Simulations des niveaux de radiations en arrêt machine

  19. Radiation Protection Legislation:General Principles • Justification • any exposure of persons to ionizing radiation has to be justified • 2) Limitation • the individual doses have to be • kept below the legal limits • 3) Optimisation • the individual doses and collective doses have to be kept as low as reasonable achievable (ALARA) Simulations des niveaux de radiations en arrêt machine

  20. Radiation Protection Legislation:Optimisation • Radiological protection associated with justified activities shall be deemed to be optimized provided • the appropriatedifferent possible solutionsshall have been individually assessed andcompared with each other; • thesequence of decisionsthat led to the particular solution remainstraceable; • due consideration has been given to thepossible occurrence of failuresand the elimination of radioactive sources. • The principle of optimisation shall be regarded as satisfied for activities which under no circumstances lead to an effective dose of more that100mSv per yearfor occupationally exposed persons or more than10mSv per yearfor persons not occupationally exposed. • [Swiss Radiation Protection Legislation (22 June 1994), see also Council Directive 96/29/Euratom ]. Simulations des niveaux de radiations en arrêt machine

  21. Radiation Protection Legislation:Design Criterion Job dose estimates are legally requiredin order to optimize the design of the facility and to limit the exposure of personnel CERN design criterion :2 mSv/year/person Simulations des niveaux de radiations en arrêt machine

  22. Dose To Cables • Estimate of annual dose distribution assuming a loss rate of 1.1E16 particles per year. (H. Vincke) • A change of the cable tray location to the aisle would significantly improve the situation. • The plot to the right only includes one beam, thus the real distribution (worst case for the aisle side) would shift more to the left. • The expected reduction factor would then go down (from almost 10 as expected in the graph), to ~3-5. Simulations des niveaux de radiations en arrêt machine

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