1 radiation safety aspects of the linear collider b. racky, a. leuschner, n. tesch radiation...

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Radiation Safety Aspects of Radiation Safety Aspects of the Linear Colliderthe Linear Collider

B. Racky, A. Leuschner, N. Tesch

Radiation Protection Group

TeV Superconducting Linear Accelerator

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Radiation Safety Aspects of TESLARadiation Safety Aspects of TESLA

Overview TESLA

Locations of beam loss

Protection of the public

• exposure limits

• exposure paths

Protection of the staff

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Top view , route on map

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Some data of TESLA :Some data of TESLA :

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Side view with earth cover

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Main locations of beam lossMain locations of beam loss

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Calculations of doses and activitiesCalculations of doses and activities

• MC code FLUKA99

• fluence/ dose conversion: ICRP

Neutron and Gamma fieldsNeutron and Gamma fields

Muon fieldsMuon fields

Activity concentrationsActivity concentrations

• MC code FLUKA99

(option resnuclei)

• analytical model

(1- dimenional transport)

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Protection of the PublicProtection of the Public(local population and environment)(local population and environment)

• Stray radiation fields

• Radioactivity of released tunnel air

• Radioactivity of drinking water

• Activation of soil

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Protection of the PublicProtection of the Public

Sum of all exposures

Release of radioactive air

Activation of groundwater

Activation of soil

1 mSv/a 0,1 mSv/a

0,3 mSv/a

0,3 mSv/a ?

?

0,03 mSv/a

0,03 mSv/a

< natural activity

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Stray radiation fields due to neutrons

1,0E-07

1,0E-06

1,0E-05

1,0E-04

1,0E-03

1,0E-02

1,0E-01

1,0E+00

1,0E+01

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E+06

1,0E+07

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Thickness of the sand cover [m]

An

nu

al d

ose

[µS

v]

natural exposure

minimum cover average cover

intranuclear cascadeneutrons

giant resonanceneutrons

electromagnetic cascade photons

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Stray radiation fields due to myons

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Release of radioactive airRelease of radioactive air

Nuclide half life3 H 12 a

7 Be 53 d11 C 20 m14 C 6 ka13 N 10 m15 O 2 m38 Cl 27 m39 Cl 56 m37 Ar 35 d41 Ar 1.8 h

Produced Nuclei

Main air activation zone

in the tunnel, near IP:

100 kW beam loss

(collimators)

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Release of radioactive airRelease of radioactive air

Radioactive air can be released

without any permission,

if the mean annual

activity concentration

is below given nuclide specific limits.

(leading to a dose < 0,3 mSv/a

for the worst case of exposure)

§§§§§

For a mixture of nuclei :

0.11

n

iCL

Ci

A

A

ratio < 0.1

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Release of radioactive airRelease of radioactive air

Overview ventilation system S. II-251 TDR

Should it be operated as a closed or open system?

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Release of radioactive airRelease of radioactive air

Open system :

Open system :

Tunnel ventilation rate : 0,8 m/s, 6*104 m3/h

length of collimator section : 100 m

volume of activation zone : 2000 m3

distance to exhaust station : 5 km

delay time : 1.4 h

Closed system :

Closed system :

data :data :

Ventilation switched off during 1 month operation,

air blown out on each monthly maintenance day

Ventilation switched on during operation,

air blown out permanently

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Release of radioactive airRelease of radioactive air

Nuclide half lifelimit: Ac L

(Bq/m3)Ac max outlet

(Bq/m3)ann. Ac mean

(Bq/m3)ratio

Ac mean/ Ac L

3 H 12 a 5.0* 102 1.67* 103 4.61* 10-2 9.2* 10-5

7 Be 53 d 3.0* 103 1.27* 104 3.51* 10-1 1.2* 10-4

11 C 20 m 1.5* 104 4.29* 103 1.19* 10-1 7.9* 10-6

14 C 6 ka 4.0* 103 2.87* 102 7.96* 10-3 2.0* 10-6

13 N 10 m 1.0* 104 5.68* 102 1.57* 10-2 1.6* 10-6

15 O 2 m 5.0* 103 3.40* 10-8 9,43* 10-13 1.9* 10-16

38 Cl 27 m 2.5* 103 9.81* 102 2.72* 10-2 1.1* 10-5

39 Cl 56 m 3.0* 103 1.37* 103 3.80* 10-2 1.3* 10-5

37 Ar 35 d 1.0* 109 2.01* 109 5.58* 10-2 5.6* 10-11

41 Ar 1.8 h 1.0* 103 3.07* 103 8.51* 10-1 8.5* 10-4

Closed systemClosed system

Sum of all ratios = 0.0011 << 1.0 and << 0.1

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Release of radioactive airRelease of radioactive air

Nuclide half lifelimit: Ac L

(Bq/m3)Ac max outlet

(Bq/m3)ann. Ac mean

(Bq/m3)ratio

Ac mean/ Ac L

3 H 12 a 5.0* 102 8.00* 10-2 4.57* 10-2 9.1* 10-5

7 Be 53 d 3.0* 103 7.37* 10-1 4.21* 10-1 1.4* 10-4

11 C 20 m 1.5* 104 3.04* 102 1.73* 102 1.2* 10-2

14 C 6 ka 4.0* 103 1.38* 10-2 7.90* 10-3 2.0* 10-6

13 N 10 m 1.0* 104 8.20* 101 4.67* 101 4.7* 10-3

15 O 2 m 5.0* 103 2.42* 10-8 1.38* 10-8 2.8* 10-12

38 Cl 27 m 2.5* 103 3.81* 101 2.17* 101 8.7* 10-3

39 Cl 56 m 3.0* 103 3.56* 101 2.04* 101 6.8* 10-3

37 Ar 35 d 1.0* 109 1.29* 10-1 7.34* 10-2 7.3* 10-11

41 Ar 1.8 h 1.0* 103 4.04* 102 2.31* 102 2.3* 10-1

Open systemOpen system

Sum of all ratios = 0.26 < 1.0 but > 0.1

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Release of radioactive airRelease of radioactive air

Conclusions A closed ventilation system leads to much

smaller release of radioactivity

Also an open system would fulfill

the legal requirements

Compromise ?

open system with bypassed release stations closed to

loss points

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Activation of soil and ground waterActivation of soil and ground water

wet soil (27% water)

concrete shielding (3 m)

in the vicinity of a main dump

dump

TESLA lumi run:TESLA lumi run:

Operation time: 5000 h (1 year)

Energy: 250 GeV

power: 12 MW

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Activity concentration of wet soilActivity concentration of wet soil

Most relevant nuclei Sum of all activity concentrations:

Nuclide half life3 H 12 a

7 Be 53 d18 F 110 m

22 Na 2.6 a24 Na 15 h28 Mg 21 h

32 P 14 d33 P 25 d35 S 88 d

37 Ar 35 d42 K 12 h43 K 22 h48 V 16 d49 V 330 d

51 Cr 28 d54 Mn 312 d55 Fe 2.7 a

0

10

20

30

40

50

60

70

80

90

ring1 ring2 ring3 ring4 ring5

saturation values5000 h operation

Bq/g

rings of 50 cm thickness

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Activation of Soil and GroundwaterActivation of Soil and Groundwaterregion of 50 cm around a main dump after 5000 h of

operation

sandsand waterwater

7 Be

7 Be

3 H

3 H

22 Na

Silicon 32 %

Oxygen 53 %

Aluminium 4 %

Oxygen 89 %

100 %

100 %

15 %

natural activity:

0.3 -1 Bq/g

Dose, consuming 800 l/a

2.5 mSv (?% 22Na)

3H : 2.60 Bq/g

22Na : 0.45 Bq/g

7Be : ? Bq/g

22Na : ? Bq/g

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Transport of ground waterTransport of ground water

Ground water flow: (expert‘s report)

area north dump south dump

descent 1m / 750m 1m/ 900m

permeability 5* 10-5 m/s 5* 10-5 m/s

filter velocity 6.7* 10-8 m/s 5.6* 10-8 m/s

distance velocity 2.2* 10-7 m/s 1.9* 10-7 m/s

distance velocity 6.9 m/ year 6.0 m/ year

error about 80% ?

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Transport of activated ground waterTransport of activated ground wateractivation zone: north dump 12 m

south dump 18 m

At what distance is the activity concentration

so low, that drinking 800 l /a results in a dose of 30 µSv/a ?

vd

edilfdcAdcA )

0()(

Distance calculations for the dominant nuclide Na-22

After activation:

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Zones of activated ground waterZones of activated ground water Distance Ac for 30 µSv/a after

velocity distance time

(m/s) (m) (a)

5.0 * 10-6 42 0.3

2.0 * 10-6 230 3.6

2.2 * 10-7 78 11

1.0 * 10-7 42 13

5.0 * 10-6 280 1.8

3.0 * 10-6 340 3.6

1.9 * 10-7 76 13

1.0 * 10-7 44 14

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Protection of the StaffProtection of the Staff

accelerator operation:

• stray radiation fields

(shielding , interlocks)

maintenance time:

• residual radioactivity

(choice of material, shielding)

• radioactive air

(ventilation concept)

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Protection of the StaffProtection of the Staff

personal doses < 6 mSv / a

(2000 h working time)

local doses < 15 mSv / a

(5000 h operation time) =

local doses < 1,5 mSv / a

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Protection of the StaffProtection of the Staff

personal doses < 20 mSv / a

local dose rates < 3 mSv / hOnly

temporary access

ALARA

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Residual RadioactivityResidual Radioactivity

Hot spotsHot spots

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Radioactivity of the tunnel airRadioactivity of the tunnel air

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ConclusionsConclusions