nToF - Radiation Protection
description
Transcript of nToF - Radiation Protection
nToF - Radiation nToF - Radiation ProtectionProtection
M. Brugger, P. Cennini, A. Ferrari, M. Brugger, P. Cennini, A. Ferrari, E. Lebbos, V. VlachoudisE. Lebbos, V. Vlachoudis
CERN AB/ATB/EETCERN AB/ATB/EET
The Safest of The Safest of all Operations all Operations is no is no Operation!Operation!
BUT… BUT…
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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 IssuesRadio-Protection Issues
Planification & Design
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Installation/OperationInstallation/Operation Shielding & Access Monitoring Activation of AirActivation of Air Cooling (Activation, Contamination)
Handling & Related ProceduresHandling & Related Procedures Residual Dose RatesResidual Dose Rates Contamination
Waste Disposal, TransportWaste Disposal, Transport Specific & Total ActivitySpecific & Total Activity Residual Dose RatesResidual Dose Rates Contamination
Radio-Protection IssuesRadio-Protection Issues
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FLUKA CalculationsFLUKA CalculationsHandling – Residual Dose Handling – Residual Dose RatesRatesIntervnetion Procedures & Intervnetion Procedures & DosesDoses
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Detailed geometryDetailed geometry (1) Target only, (2) as well as with the surrounding
structure (3) Including the downstream tunnel structure
Residual dose ratesResidual 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 airActivation of air folding of particle fluences with production cross sections
Activation of targetActivation of target specific activity and expression as multiple of the
respective exemption limits
FLUKA CalculationsFLUKA Calculations
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Geometry DetailsGeometry Details
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Target in the PitTarget in the PitTargetEarth
Pit filled(concrete)
Beam Pipe
Concrete
Marble
Beam
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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 Calculation of Residual Dose RatesRates
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Calculation of Residual Calculation of Residual Dose RatesDose Rates Evaluation of calculated DREvaluation of calculated DR
Different levels of details Different levels of details Geometry (target only, in the pit, chemical Geometry (target only, in the pit, chemical
properties)properties) Comparison with performed measurementsComparison 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
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Measurement Location
Calculation of Residual Calculation of Residual Dose RatesDose Rates0% Co
0.01% Co0.01% Co
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0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
Cobalt Content / %
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No Concrete Structure Including Concrete Structure
Calculation of Residual Calculation of Residual Dose RatesDose RatesMeasured Dose Rate: ~15mSv/h
Considered Cobald Content: 0.01%
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Calculation of Residual Calculation of Residual Dose RatesDose Rates Evaluation of calculated DR
Different levels of details Geometry (target only, in the pit, chemical properties)
Comparison with performed measurements PreparationPreparation
Calculation of residual dose rates (DR)Calculation of residual dose rates (DR) 3D DR maps for dose planning3D DR maps for dose planning Planning, Procedures, OptimizationPlanning, Procedures, Optimization
Inspection Visual, pictures from various angles Taking samples for analysis
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Residual Dose Rate MapsResidual Dose Rate Maps
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Taking Samples for Material Taking Samples for Material StudiesStudies
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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 ScenariosIntervention Scenarios
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Air Air ActivationActivationVentilatioVentilationn
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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 & VentilationAir Activation & Ventilation
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Take a Look from AboveTake a Look from Above
nToF
ALARA:As Low As
Reasonably Possible
Problem:The public often isn’t
very reasonable
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Air Activation & VentilationAir Activation & VentilationCritical Group:Border Guards
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FLUKAFLUKA simulation in order to calculate the isotope production yieldisotope production yield (39 different isotopes considered)
Exposure of personnel Dose conversion coefficientsDose conversion coefficients based on the
Swiss and French legislation Dose to the publicDose to the public
Definition of critical groups (border guards) Calculation of dose conversion coefficients based
on environmental models Study of different ventilation scenariosdifferent ventilation scenarios and
their impact on the respective dose estimate
Dose EstimationDose Estimation
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Production term – depends on tunnel layout:1) no additional shielding
2) eight meter shielding (closest to realityclosest to reality)
3) fourteen meter shielding Ventilation Flow (critical parameters)
Laminar (continuous)Laminar (continuous) assumed volumes: active region, decay ventilation speed operation time
Enclosed Case (Flush before Access)Enclosed Case (Flush before Access) ventilation speed waiting time
Calculation ParametersCalculation Parameters
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Dose to Personnel & Critical Dose to Personnel & Critical GroupGroupDirect Exposure (Person inhaling the Air)Dose to public (critical group)
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Different Configurations Different Configurations Case 1Case 1
Dose to public: minimal (< 0.2 Sv) – Ar41/Be7
Dose to personnel: ~130 Sv/h (laminar flow, continuous ventilation) - Ar41
~500 Sv (enclosed configuration, per flush) - Be7, P32
No Ventilation“Natural Flow” 5 exch./day
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Different Configurations Different Configurations Case 2Case 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) - Be7
StandardVentilation
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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 usual goal: be better than 1 sv/hsv/h
Enclosed scenario is conservative as air will mix before release (additional dilutionadditional dilution)
Be7 and P-32 capture very well on filtersfilters 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?What Ventilation System?
Fortunately we don’t need a crane for this!
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How Could it Look LikeHow Could it Look Like
Continuous operation in order to filter Be7 and P32
Flush before access with highest possible speed
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Nuclide Nuclide VectorVectorWaste Waste DisposalDisposal
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Target Disposal – Waste Target Disposal – Waste StudyStudy
Specific actifity (Bq/g) Specific actifity (Multiples of LE)
Nuclide Vector
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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
Nuclide VectorNuclide Vector
Stainless Steel Frame
Lead Target (pure Pb)
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Characterization of the nuclide vectorCharacterization 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)PSI (now, soon) Final Swiss depository (not yet built/decided) @ CERN (temporary)
Transport can be well shielded, thus transport will be Class-AClass-A most probably no CASTOR like overkill (to be verified)
Costs ~100kCHF per cubic meter~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 PSIGood News: disposal seems to become feasible with PSI
Target Disposal – Waste Target Disposal – Waste StudyStudy
Question of Money
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and…and…
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Old Target: Decision on the ventilation layout/filtering/monitoringventilation 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 Refined FLUKA calculations for the nuclide vectorFLUKA calculations for the nuclide vector Decision on waste disposalwaste disposal
New Target: Final designFinal design
material constraints, size additional shielding needed?
HandlingHandling (Residual Dose Rates) Effect on air activation Waste characterization
Big question mark Contamination of cooling circuit – show stopper for operation?Contamination of cooling circuit – show stopper for operation?
What’s Missing (for RP)What’s Missing (for RP)
Question of Time