NToF - Radiation Protection M. Brugger, P. Cennini, A. Ferrari, E. Lebbos, V. Vlachoudis CERN...

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nToF Collaboration Meeting - Radioprotection Constraints 3 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 Radio-Protection Issues Planification & Design

Transcript of NToF - Radiation Protection M. Brugger, P. Cennini, A. Ferrari, E. Lebbos, V. Vlachoudis CERN...

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 nToF Collaboration Meeting - Radioprotection Constraints 3 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 Radio-Protection Issues Planification & Design nToF Collaboration Meeting - Radioprotection Constraints 4 Installation/Operation Installation/Operation Shielding & Access Monitoring Activation of Air Cooling (Activation, Contamination) Handling & Related Procedures Handling & Related Procedures Residual Dose Rates Contamination Waste Disposal, Transport Waste Disposal, Transport Specific & Total Activity Residual Dose Rates Contamination Radio-Protection Issues nToF Collaboration Meeting - Radioprotection Constraints 5 FLUKA Calculations Handling Residual Dose Rates Intervnetion Procedures & Doses nToF Collaboration Meeting - Radioprotection Constraints 6 Detailed geometry Detailed geometry (1) Target only, (2) as well as with the surrounding structure (3) Including the downstream tunnel structure Residual dose rates 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 Activation of air folding of particle fluences with production cross sections Activation of target Activation of target specific activity and expression as multiple of the respective exemption limits FLUKA Calculations nToF Collaboration Meeting - Radioprotection Constraints 7 Geometry Details nToF Collaboration Meeting - Radioprotection Constraints 8 Target in the Pit Target Earth Pit filled (concrete) Beam Pipe Concrete Marble Beam nToF Collaboration Meeting - Radioprotection Constraints 9 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 Calculation of Residual Dose Rates nToF Collaboration Meeting - Radioprotection Constraints 10 Calculation of Residual Dose Rates Evaluation of calculated DR Evaluation of calculated DR Different levels of details Geometry (target only, in the pit, chemical properties) 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 Measurement Location Calculation of Residual Dose Rates 0% Co 0.01% Co 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 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 Removal of Sand nToF Collaboration Meeting - Radioprotection Constraints 16 Position for Sand Removal nToF Collaboration Meeting - Radioprotection Constraints 17 Taking Samples for Material Studies nToF Collaboration Meeting - Radioprotection Constraints 18 Estimates are available for all expected scenarios Target Displacement Sand Removal Taking Pictures Sample Taking Low Individual and Collective Doses 20 80 Sv Collective dose Optimized Procedures Well Planned Interventions Good News: no problem - straight foreward! Good News: no problem - straight foreward! Intervention Scenarios nToF Collaboration Meeting - Radioprotection Constraints 19 Air Activation Ventilation nToF Collaboration Meeting - Radioprotection Constraints 20 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) Air Activation & Ventilation nToF Collaboration Meeting - Radioprotection Constraints 21 Take a Look from Above nToF ALARA: As Low As Reasonably Possible Problem: The public often isnt very reasonable nToF Collaboration Meeting - Radioprotection Constraints 22 Air Activation & Ventilation Critical Group: Border Guards nToF Collaboration Meeting - Radioprotection Constraints 23 FLUKA isotope production yield FLUKA simulation in order to calculate the isotope production yield (39 different isotopes considered) Exposure of personnel Dose conversion coefficients Dose conversion coefficients based on the Swiss and French legislation Dose to the public Dose to the public Definition of critical groups (border guards) Calculation of dose conversion coefficients based on environmental models different ventilation scenarios Study of different ventilation scenarios and their impact on the respective dose estimate Dose Estimation nToF Collaboration Meeting - Radioprotection Constraints 24 Production term depends on tunnel layout: 1) no additional shielding closest to reality 2) eight meter shielding (closest to reality) 3) 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 Calculation Parameters nToF Collaboration Meeting - Radioprotection Constraints 25 Dose to Personnel & Critical Group Direct Exposure (Person inhaling the Air) Dose to public (critical group) nToF Collaboration Meeting - Radioprotection Constraints 26 Different Configurations Case 1 Dose to public: minimal (< 0.2 Sv) Ar 41 /Be 7 Dose to personnel: ~130 Sv/h (laminar flow, continuous ventilation) - Ar 41 ~500 Sv (enclosed configuration, per flush) - Be 7, P 32 No Ventilation Natural Flow 5 exch./day nToF Collaboration Meeting - Radioprotection Constraints 27 Different Configurations Case 2 Dose to public: ~1 Sv (laminar), 100) usual goal: be better than 1 sv/h additional dilution Enclosed scenario is conservative as air will mix before release (additional dilution) filters Be7 and P-32 capture very well on filters Enclosed case 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 What Ventilation System? Fortunately we dont need a crane for this! nToF Collaboration Meeting - Radioprotection Constraints 29 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 30 Nuclide Vector Waste Disposal nToF Collaboration Meeting - Radioprotection Constraints 31 Target Disposal Waste Study Specific actifity (Bq/g) Specific actifity (Multiples of LE) Nuclide Vector nToF Collaboration Meeting - Radioprotection Constraints 32 The FLUKA study is based on the entire period of nToF operation ( ) Several cooling times were calculated, results shown refer to Mai 2006 Preliminary as target assumed to be pure lead Nuclide Vector Stainless Steel Frame Lead Target (pure Pb) nToF Collaboration Meeting - Radioprotection Constraints 33 Characterization of the nuclide vector Characterization of the nuclide vector, specific activities, total activity, residual dose rate (for different cooling times) a too high concentration of -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 Class-A 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 Good News: disposal seems to become feasible with PSI Target Disposal Waste Study Question of Money nToF Collaboration Meeting - Radioprotection Constraints 34 and nToF Collaboration Meeting - Radioprotection Constraints 35 Old Target: ventilation layout/filtering/monitoring Decision on the ventilation layout/filtering/monitoring new calculations most probably not needed! Inspection of the target Inspection of the target -> otherwise we risk a lot final preparation of the intervention FLUKA calculations for the nuclide vector Refined FLUKA calculations for the nuclide vector waste disposal Decision on waste disposal New Target: Final design material constraints, size additional shielding needed? Handling Handling (Residual Dose Rates) Effect on air activation Waste characterization Big question mark Contamination of cooling circuit show stopper for operation? Whats Missing (for RP) Question of Time