Simulations des niveaux de radiations en arrêt machine M. Brugger, D. Forkel-Wirth, S. Roesler...

Simulations des niveaux de radiations

en arrêt machine

M. Brugger, D. Forkel-Wirth, S. Roesler (SC/RP)

10 Novembre 2004 Simulations des niveaux de radiations en arrêt machine

2

IR7 Radiation Protection Issues

Impact on environment • activation and release of air• activation and release of water• activation of rock• radioactive waste

Impact on personnel (direct) (indirect)

• remanent dose from radioactive components during interventions• stray radiation

• dose to components (cables, magnets, etc.)

• production of ozone (corrosion!)


3

Detailed model of IR7 (two beamlines incl. dogleg, collimators, dipoles incl. magnetic

field, quadrupoles, tunnel, etc.) Layout corresponds to V 6.5 (status March/April 04)

Only Phase 1, No Absorbers,… No local shielding (!) Forced inelastic interactions of 7 TeV protons in collimator jaws

according to loss distribution obtained from tracking code * Uniform distribution along the jaw, 200 m inside

Magnetic field Dogleg fully implemented (incl. field) Magnetic field in the quadrupoles not considered

Annual number of protons lost per year at IR7 Environmental calculations

(ultimate operation): 7.3 x 1016 ** Maintenance calculations

(nominal operation): 4.1 x 1016 **

FLUKA Simulation Parameters

* data provided by R.Assmann** data provided by M.Lamont (two beams)


4

FLUKA-calculations: Geometry IR7

Collimator Dipole Quadrupole

Air duct

Enclosed sections

D4 D3 Q5 Q4 Q4 Q5

*Collimators were rotated and positioned in the geometry by using a modified script from Vasilis Vlachoudis


5

Design Criterion 2mSv/year/person/interv

ention


6

Calculation Procedure Detailed Geometry description including

Correct source terms Loss distributions Complete geometry

Tunnel structure Collimator, magnets Beamline, Dogleg separation

Monte-Carlo simulation to calculate the remanent dose rates in the entire geometry using the new “Explicit Method”

Calculation of dose rate maps for the entire geometry and various cooling times, including Separate simulations for different contributors Average and Maximum Values for relevant locations

Compilation of intervention scenarios together with the corresponding groups Time, location and frequency of the intervention Number of people involved

Calculation of individual and collective doses Iteration and optimization


7

Remanent Dose Rates: ContributionsContributions to total remanent dose rates (180 days of operation, 1 hour of cooling)

collimators beampipes

TCP TCS

D4 D3 Q5

Nominal Intensity

magnets

Tunnel walland floor


8

Remanent Dose Rates: Section between TCP and Q5Remanent dose rates after 180 days of operation

1 day of cooling 4 months of cooling

TCS

~5 mSv/h ~1 mSv/h• first secondary collimator (Phase 1) most radioactive component (in the absence of additional

absorbers) with over 90% caused by secondary particles from upstream cascades• further peaks of remanent dose rate close to upstream faces of magnets• dose rate maps allow a detailed calculation of intervention doses

Nominal Intensity


9

Dose Rate Maps for the Full Geometry

Cooling Time of one Day

Only Beam 1


10

1 hour

Dose Rate Maps for the Different Cooling Times

8 hours

1 day 1 week

1 month 4 months


11

Dose Rate Maps for the Different Cooling Times

1 hour 8 hours

1 day 1 week

1 month 4 months


12

Chosen Locations for 1st Estimates



13

Dose Rate Distribution in the Aisle (Pos1)


2nd Beam mirrored and added


14

Average and Maximum Dose Rates

Shows the MAXIMUMintervention time, in order to stay BELOWthe design constraint

Must NOT BE USED asoptimization criterion

Even at long coolingtimes long interventionswill become difficult


15

Intervention Scenarios - Details To study various maintenance scenarios in order to get a

complete view of individual and collective doses at IR7 we need the following information: Kind of intervention Location of the intervention Respective cooling time Number of persons involved Steps of the intervention Time estimate for each step Frequency of the intervention Typical cooling period before intervention

In the moment the uncertainty lies in the estimates for the intervention(s), not in the calculation of the remanent dose rates!


16

Intervention ScenariosThe following scenarios have already been identified and/or studied in more detail.

x


17

Conclusion Access to the collimation region will strongly depend on

the exact location of the intervention as well as the time to be spent there

Next to “hot spots” (e.g. collimators, downstream magnets or absorbers) the occupancy time for maintenance operations will be rather short

During the first years of operation the situation will be slightly relaxed (factor of ~3)

Optimization of intervention scenarios should already begin now in order to be able to adopt last design changes and identify those intervention scenarios important for further improvement


18

Backup Slides


19

Radiation Protection Legislation: General Principles

Limits per 12-months period (mSv)

Exposed Workers

Public B A

EURATOM < 1 < 6 < 20

France < 1 < 6 < 20

CERN < 0.3 < 6 < 20

Switzerland < 1 < 20

1) Justification

any exposure of persons to ionizing radiation has to be justified

2) Limitation

the individual doses have to be

kept below the legal limits

3) Optimisation

the individual doses and collective doses have to be kept as low as reasonable achievable (ALARA)


20

Radiation Protection Legislation: Optimisation

Radiological protection associated with justified activities shall be deemed to be optimized provided

• the appropriate different possible solutions shall have been individually assessed and compared with each other;

• the sequence of decisions that led to the particular solution remains traceable;

• due consideration has been given to the possible occurrence of failures and the elimination of radioactive sources.

The principle of optimisation shall be regarded as satisfied for activities which under no circumstances lead to an effective dose of more that 100Sv per year for occupationally exposed persons or more than 10Sv per year for persons not occupationally exposed. [Swiss Radiation Protection Legislation (22 June 1994), see also Council Directive 96/29/Euratom ].


21

Radiation Protection Legislation: Design Criterion

Job dose estimates are legally required in order to optimize the design of the facility and to limit the exposure of personnel

CERN design criterion : 2 mSv/year/person


22

Dose To Cables Estimate of annual dose distribution

assuming a loss rate of 1.1E16 particles per year. (H. Vincke)

A change of the cable tray location to the aisle would significantly improve the situation.

The plot to the right only includes one beam, thus the real distribution (worst case for the aisle side) would shift more to the left.

The expected reduction factor would then go down (from almost 10 as expected in the graph), to ~3-5.

Simulations des niveaux de radiations en arrêt machine M. Brugger, D. Forkel-Wirth, S. Roesler...

Documents

Transcript of Simulations des niveaux de radiations en arrêt machine M. Brugger, D. Forkel-Wirth, S. Roesler...