Radiological protection studies - PowerPoint Presentation

Slide1

Radiological protection studies

M. Casolino – H. Vincke – S. RoeslerHSE-RP

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11

th

SHiP Collaboration Meeting

7

th

June 2017

Outline

General considerations

Classification of the ventilation system

Tritium

productionAir activation

Activation and radioactive waste

Energy deposition for the coil

New model for the magnetSummary

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11

th

SHiP

Collaboration meeting

General considerations for the SHiP target complex

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High prompt dose

in SHiP target area calls for adequate shielding around the target

Only

absolute

necessary equipment

should be installed in

“hot” areas Depending on residual dose and tasks,

manual interventions

should partially/completely be

replaced

by remote maintenance/repair

Air volumes to be minimized in ‘hot’ areas or to be replaced by He/vacuum environmentStatic confinement of air by physical barriers to separate air in contaminated areas from outsideDynamic confinement by a ventilation system guaranteeing a pressure cascade from low to high contaminated areas

Water cooling circuits for highly radioactive elements should be closed and separated from othersActivation and contamination of ground water and earth to be avoided

The design must consider minimization, decommissioning and dismantling of radioactive waste

Water and

Ground activation

Radioactive waste

Air and He

activation

Prompt and residual radiation

Radiation Protection

11

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SHiP

Collaboration meeting

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11

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SHiP Collaboration meeting

Water and

Ground activation

Radioactive waste

Air and He

activation

Prompt and residual radiation

Radiation Protection

FLUKA was used to evaluate the radiation protection requirements for the

SHiP

target complex

Tritium production

5A simplified geometry was used:

Target: one section of Mo, one section of W. No water cooling, no Ta cladding

Region between target and proximity shielding filled by

He

Proximity shielding and passive shielding in

Cast Iron

2m concrete thick walls around passive shielding

11

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SHiP

Collaboration meeting

Air and He ActivationbeamH-3 has a very low radio-toxicity but it can be a radiation hazard when:inhaledingested via food or waterabsorbed through the skin

Tritium production

6Calculations performed assuming

5 years of operation  2*10

20

pot

11

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SHiP Collaboration meeting

Air and He Activation

H-3 activity

Mo

10 TBq

W

8 TBqHe0.9 GBqCast Iron1 TBqConcrete2 MBq95% of H-3 is produced in the target, but most probably no outgassing into the helium vessel. Absorbed by the water (HTO form) and circulated in the water cooling system.While for the iron and concrete shielding outgassing calculation are in progress.

Air activation

7Geometry (v21) used:

Still

120cm long target

No Ta cladding, no gaps between He vessel and concrete

Scored particle fluence for air activation in the following regions:

Internal Helium volume

Middle Helium volumeExternal Helium volumeFirst Air volumeSecond Air volume

11

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SHiP

Collaboration meeting

Air and He Activation

beamyz

Closed loop for purificationClosed loop for ventilation plus leaks? from He circuit

Air activation

8Calculations performed assuming

5 years operation

 2 * 1020

pot

99.9% He purity

from He purification system 

assumed 0.1% air contaminationFor the CA1 calculation:

Assumed a standard breathing rate (1.2 m

3

/h)

For the moment no leakage term

11

th SHiP Collaboration meetingAir and He ActivationActivity (

Bq)after 60 s coolingMultiple of CAAir in inner He5.6*1077.5*105Air in middle He7.8*105

1.3*103Air in external He1.5*1022*10-2First air volume1.7*10

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0.7Second air volume8.3*1046.7*10-3Inner He

2.8*1090.42Middle He4.1*1078.7*10-4

External He9*1031.5*10-81 Person working 40h/w, 50w/y with standard breathing rate in air contaminated environment with CA = 1 receives 20 mSv.

Classification of the ventilation system

9The ventilation system requirements ( e.g. pressure cascades) are defined in the

ISO 17873:2004

Four classifications are possible

Accident case analysed



breakdown of He vessel

CA values calculated mixing the helium and the air of the closed loop

CA for accident ~ 2.6

Classification for the ventilation system:

C2

For flexibility for future installations could be classified as C3

Check on the inhaled dose ongoing

11th SHiP Collaboration meetingAir and He Activation

ClassificationDepression valuesDAC1 valuespermanent (accident)C1<60 Pa0 (<1)C280 to 100 Pa

<1 (<80)C3120 to 140 Pa<1 (<4000)C4220 to 300 Pa >1 (any)

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Slightly different definition compared to CA

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11

th

SHiP Collaboration meeting

Water and

Ground activation

Radioactive waste

Air and He

activation

Prompt and residual radiation

Radiation Protection

Waste production

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Using geometry v21 with some modifications:

Including Ta cladding

Extended target to 150cm

Calculations performed assuming

5 years operation

 2 * 1020

pot

Results presented in terms of

Design

Limits

(DL)

If DL > 1 the waste is radioactiveAfter 10 years of cooling DL > 1 for proximity and passive shielding in the He-vessel

11th SHiP Collaboration meetingRadioactive waste1 day of cooling1 month of cooling1 year of cooling10 years of cooling

DLDLDLDL

Waste production

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Using geometry v21 with some modifications:

Including Ta cladding

Extended target to 150cm

Calculations performed assuming

5 years operation

 2 * 1020

pot

Results presented in terms of

Design

Limits

(DL)

If DL > 1 the waste is radioactiveFloor below the target slightly radioactive, possibility to use movable blocks of concrete or iron.

11th SHiP Collaboration meetingRadioactive waste1 day of cooling1 month of cooling1 year of cooling10 years of cooling

DLDLDL

DL

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Energy deposition for the coil

11

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SHiP

Collaboration meeting

Using same geometry as for waste productionCalculations performed assuming 5 years operation  2 * 1020

pot

Beginning of the magnet assumed at the position y[150:180] – z [152.5-158]

Maximum dose ~50KGy

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Integration of new SHiP magnet

11

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SHiP

Collaboration meeting

GDML file imported in FlukaImproving the importing phase

Checks between Geant4 and Fluka

model ongoing

Some volumes in

Fluka

are approximated

Differences in volume can go up to 80% Magnetic field in place alreadyEven if with the above mentioned caveats particles are bent10 primaries on target

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SummaryMany studies ongoing for the

radiation protection aspects for the SHiP experiment:

He and Air activation:

~95%

of H-3 is produced

into the target

outgassing studies for the shielding are in progressAir activation drives the classification of the ventilation system to C2

according to ISO17873:2004

Possibility to use C3 to have

flexibility

f

or future installations

after SHiP Waste production: Proximity and passive shielding will have DL > 1 even after 10y of coolingFloor below the target radioactive  dismountable floor (iron or concrete) neededEnergy deposition:Maximum dose

received by the magnet in the new position ~50kGyIntegration of the new magnet ongoing:Improving GDML import11th SHiP

Collaboration meeting

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Thank you for your attention

11

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SHiP

Collaboration meeting

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Backup

11

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SHiP

Collaboration meeting