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nToF - Radiation Protection

nToF - Radiation Protection. M. Brugger, P. Cennini, A. Ferrari, E. Lebbos, V. Vlachoudis CERN AB/ATB/EET. The Safest of all Operations is no Operation!. BUT…. Radio-Protection Issues. Installation/Operation Shielding & Access Monitoring Activation of Air

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nToF - Radiation Protection

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  1. nToF - Radiation Protection M. Brugger, P. Cennini, A. Ferrari, E. Lebbos, V. VlachoudisCERN AB/ATB/EET

  2. The Safest of all Operations is no Operation! BUT…

  3. Radio-Protection Issues • Installation/Operation • Shielding & Access • Monitoring • Activation of Air • Cooling (Activation, Contamination) • Handling & Related Procedures • Residual Dose Rates • Contamination • Waste Disposal, Transport • Specific & Total Activity • Residual Dose Rates • Contamination Planification & Design nToF Collaboration Meeting - Radioprotection Constraints

  4. Radio-Protection Issues • Installation/Operation • Shielding & Access • Monitoring • Activation of Air • Cooling (Activation, Contamination) • Handling & Related Procedures • Residual Dose Rates • Contamination • Waste Disposal, Transport • Specific & Total Activity • Residual Dose Rates • Contamination nToF Collaboration Meeting - Radioprotection Constraints

  5. FLUKA CalculationsHandling – Residual Dose RatesIntervnetion Procedures & Doses nToF Collaboration Meeting - Radioprotection Constraints

  6. FLUKA Calculations • Detailed geometry • (1) Target only, (2) as well as with the surrounding structure • (3) Including the downstream tunnel structure • Residual dose rates • two methods: single-step & two-step (well benchmarked) • detailed 3D dose rate maps • various cooling times: 1y 8m, 2y, 2y 5m, 3y, 10y • Individual & collective dose estimates • Activation of air • folding of particle fluences with production cross sections • Activation of target • specific activity and expression as multiple of the respective exemption limits nToF Collaboration Meeting - Radioprotection Constraints

  7. Geometry Details nToF Collaboration Meeting - Radioprotection Constraints

  8. Target in the Pit Earth Target Pit filled(concrete) Beam Marble Beam Pipe Concrete nToF Collaboration Meeting - Radioprotection Constraints

  9. Calculation of Residual Dose Rates • Evaluation of calculated DR • Different levels of details • Geometry (target only, in the pit, chemical properties) • Comparison with performed measurements • Preparation of the intervention • Calculation of residual dose rates (DR) • 3D DR maps for dose planning • Planning, procedures, optimization • Inspection, Interventions • Visual control, taking pictures from various angles • Taking samples for analysis nToF Collaboration Meeting - Radioprotection Constraints

  10. Calculation of Residual Dose Rates • Evaluation of calculated DR • Different levels of details • Geometry (target only, in the pit, chemical properties) • Comparison with performed measurements • Preparation of the intervention • Calculation of residual dose rates (DR) • 3D DR maps for dose planning • Planning, procedures, optimization • Inspection • Visual control, taking pictures from various angles • Taking samples for analysis nToF Collaboration Meeting - Radioprotection Constraints

  11. Calculation of Residual Dose Rates 0.01% Co 0% Co 0.01% Co Measurement Location nToF Collaboration Meeting - Radioprotection Constraints

  12. Calculation of Residual Dose Rates Measured Dose Rate: ~15mSv/h Considered Cobald Content: 0.01% nToF Collaboration Meeting - Radioprotection Constraints

  13. Calculation of Residual Dose Rates • Evaluation of calculated DR • Different levels of details • Geometry (target only, in the pit, chemical properties) • Comparison with performed measurements • Preparation • Calculation of residual dose rates (DR) • 3D DR maps for dose planning • Planning, Procedures, Optimization • Inspection • Visual, pictures from various angles • Taking samples for analysis nToF Collaboration Meeting - Radioprotection Constraints

  14. Residual Dose Rate Maps nToF Collaboration Meeting - Radioprotection Constraints

  15. Taking Samples for Material Studies nToF Collaboration Meeting - Radioprotection Constraints

  16. Intervention Scenarios • Estimates are available for all expected scenarios • Target Displacement • Sand Removal • Taking Pictures • Sample Taking • Low Individual and Collective Doses • 20 – 80 mSv Collective dose • Optimized Procedures • Well Planned Interventions • Good News: no problem - straight foreward! nToF Collaboration Meeting - Radioprotection Constraints

  17. Air ActivationVentilation nToF Collaboration Meeting - Radioprotection Constraints

  18. Air Activation & Ventilation • Installation layout (air flow, release point(s)) • FLUKA simulation • Isotope production yield (particle fluences folded with respective isotope production cross sections) • Possible ventilation layout • Release values • Dose calculations • Direct exposure (personnel) • Long/Short-term exposure (public: critical group) nToF Collaboration Meeting - Radioprotection Constraints

  19. ALARA: As Low As Reasonably Possible Take a Look from Above Problem: The public often isn’t very reasonable  nToF nToF Collaboration Meeting - Radioprotection Constraints

  20. Air Activation & Ventilation Critical Group: Border Guards nToF Collaboration Meeting - Radioprotection Constraints

  21. Dose Estimation • FLUKA simulation in order to calculate the isotope production yield (39 different isotopes considered) • Exposure of personnel • Dose conversion coefficientsbased on the Swiss and French legislation • Dose to the public • Definition of critical groups (border guards) • Calculation of dose conversion coefficients based on environmental models • Study of different ventilation scenariosand their impact on the respective dose estimate nToF Collaboration Meeting - Radioprotection Constraints

  22. Calculation Parameters • Production term – depends on tunnel layout: • no additional shielding • eight meter shielding (closest to reality) • fourteen meter shielding • Ventilation Flow (critical parameters) • Laminar (continuous) • assumed volumes: active region, decay • ventilation speed • operation time • Enclosed Case (Flush before Access) • ventilation speed • waiting time nToF Collaboration Meeting - Radioprotection Constraints

  23. Dose to Personnel & Critical Group Direct Exposure (Person inhaling the Air) Dose to public (critical group) nToF Collaboration Meeting - Radioprotection Constraints

  24. Different Configurations Case 1 • Dose to public: minimal (< 0.2 mSv) – Ar41/Be7 • Dose to personnel: • ~130 mSv/h (laminar flow, continuous ventilation) - Ar41 • ~500 mSv (enclosed configuration, per flush) - Be7, P32 No Ventilation“Natural Flow” 5 exch./day nToF Collaboration Meeting - Radioprotection Constraints

  25. Different Configurations Case 2 • Dose to public: ~1 mSv (laminar), <0.1 mSv (enclosed) • Dose to personnel: • ~86 mSv/h (laminar flow, continuous ventilation) • ~15 mSv (enclosed configuration, per flush) - Be7 StandardVentilation nToF Collaboration Meeting - Radioprotection Constraints

  26. What Ventilation System? • Estimate for ‘dose to personnel’ is a very conservative assumption (Safety Report #19: unknown situation  a factor of ¼, usually  dilution>100) • usual goal: be better than 1 msv/h • Enclosed scenario is conservative as air will mix before release (additional dilution) • Be7 and P-32 capture very well on filters • Enclosed case has to be favored, ideally including an installed filter unit (in operation before flush) • To be discussed together with RP and evaluated with respect to costs involved and maximum efficiency • Good News: solution seems to be straight forward Fortunately we don’t need a crane for this!  nToF Collaboration Meeting - Radioprotection Constraints

  27. How Could it Look Like Continuous operation in order to filter Be7 and P32 Flush before access with highest possible speed nToF Collaboration Meeting - Radioprotection Constraints

  28. Nuclide VectorWaste Disposal nToF Collaboration Meeting - Radioprotection Constraints

  29. Target Disposal – Waste Study • Specific actifity (Bq/g) • Specific actifity (Multiples of LE) Nuclide Vector nToF Collaboration Meeting - Radioprotection Constraints

  30. Nuclide Vector Lead Target (pure Pb) • The FLUKA study is based on the entire period of nToF operation (2001-2004) • Several cooling times were calculated, results shown refer to Mai 2006 • Preliminary as target assumed to be pure lead Stainless Steel Frame nToF Collaboration Meeting - Radioprotection Constraints

  31. Target Disposal – Waste Study • Characterization of the nuclide vector, specific activities, total activity, residual dose rate (for different cooling times) • a too high concentration of a-emitters can be a show stopper (~1MBq/200l of ‘treated’ volume) – to be investigated! • Storage possibilities (coordinated by NAGRA) • PSI (now, soon) • Final Swiss depository (not yet built/decided) • @ CERN (temporary) • Transport • can be well shielded, thus transport will be Class-A • most probably no CASTOR like overkill (to be verified) • Costs • ~100kCHF per cubic meter • 7kCHF for the container • XXX CHF for transport • Study needs to be refined with proper the chemical composition • Good News: disposal seems to become feasible with PSI Question of Money  nToF Collaboration Meeting - Radioprotection Constraints

  32. and… nToF Collaboration Meeting - Radioprotection Constraints

  33. What’s Missing (for RP) • Old Target: • Decision on the ventilation layout/filtering/monitoring • new calculations most probably not needed! • Inspection of the target -> otherwise we risk a lot • final preparation of the intervention • Refined FLUKA calculations for the nuclide vector • Decision on waste disposal • New Target: • Final design • material constraints, size • additional shielding needed? • Handling (Residual Dose Rates) • Effect on air activation • Waste characterization • Big question mark • Contamination of cooling circuit – show stopper for operation? Question of Time  nToF Collaboration Meeting - Radioprotection Constraints

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