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…

05.12.2006 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 IssuesRadio-Protection Issues

Planification & Design


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


FLUKA CalculationsFLUKA CalculationsHandling – Residual Dose Handling – Residual Dose RatesRatesIntervnetion Procedures & Intervnetion Procedures & DosesDoses


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


Geometry DetailsGeometry Details


Target in the PitTarget in the PitTargetEarth

Pit filled(concrete)

Beam Pipe

Concrete

Marble

Beam


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


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


Measurement Location

Calculation of Residual Calculation of Residual Dose RatesDose Rates0% Co

0.01% Co0.01% Co


0

10

20

30

40

50

60

70

80

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Cobalt Content / %

Re

sid

ua

l Do

se

Ra

te /

mS

v/h

No Concrete Structure Including Concrete Structure

Calculation of Residual Calculation of Residual Dose RatesDose RatesMeasured Dose Rate: ~15mSv/h

Considered Cobald Content: 0.01%


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


Residual Dose Rate MapsResidual Dose Rate Maps


Taking Samples for Material Taking Samples for Material StudiesStudies


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


Air Air ActivationActivationVentilatioVentilationn


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


Take a Look from AboveTake a Look from Above

nToF

ALARA:As Low As

Reasonably Possible

Problem:The public often isn’t

very reasonable


Air Activation & VentilationAir Activation & VentilationCritical Group:Border Guards


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


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


Dose to Personnel & Critical Dose to Personnel & Critical GroupGroupDirect Exposure (Person inhaling the Air)Dose to public (critical group)


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


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


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!


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


Nuclide Nuclide VectorVectorWaste Waste DisposalDisposal


Target Disposal – Waste Target Disposal – Waste StudyStudy

Specific actifity (Bq/g) Specific actifity (Multiples of LE)

Nuclide Vector


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)


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


and…and…


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

ntof - radiation protection

Documents

dose planningplanning

15075sheet1no concrete

various anglestaking

chemical propertiescomparison

msvhconsidered cobald

ntof radiation protectionm

interventionsvisual

particle fluences