1 radiation safety aspects of the linear collider b. racky, a. leuschner, n. tesch radiation...
TRANSCRIPT
1
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
2
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
3
Top view , route on map
4
Some data of TESLA :Some data of TESLA :
5
Side view with earth cover
6
Main locations of beam lossMain locations of beam loss
7
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)
8
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
9
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
10
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
11
Stray radiation fields due to myons
12
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)
13
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
14
Release of radioactive airRelease of radioactive air
Overview ventilation system S. II-251 TDR
Should it be operated as a closed or open system?
15
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
16
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
17
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
18
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
19
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
20
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
21
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
22
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% ?
23
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:
24
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
25
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)
26
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
27
Protection of the StaffProtection of the Staff
personal doses < 20 mSv / a
local dose rates < 3 mSv / hOnly
temporary access
ALARA
28
Residual RadioactivityResidual Radioactivity
Hot spotsHot spots
29
Radioactivity of the tunnel airRadioactivity of the tunnel air
30
ConclusionsConclusions