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 isn’t 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), <0.1  Sv (enclosed) Dose to personnel:  ~86  Sv/h (laminar flow, continuous ventilation)  ~15  Sv (enclosed configuration, per flush) - Be 7 Standard Ventilation

nToF Collaboration Meeting - Radioprotection Constraints 28 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  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 don’t 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? What’s Missing (for RP) Question of Time