1 Radiation Safety Aspects of the Linear Collider B. Racky, A. Leuschner, N. Tesch Radiation Protection Group TeV Superconducting Linear Accelerator

2 Radiation 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 :

5 Side view with earth cover

6 Main locations of beam loss

7 Calculations of doses and activities MC code FLUKA99 fluence/ dose conversion: ICRP Neutron and Gamma fields Muon fields Activity concentrations MC code FLUKA99 (option resnuclei) analytical model (1- dimenional transport)

8 Protection of the Public (local population and environment) Stray radiation fields Radioactivity of released tunnel air Radioactivity of drinking water Activation of soil

9 Protection 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 < natural activity

10 Stray radiation fields due to neutrons

11 Stray radiation fields due to myons

12 Release of radioactive air Produced Nuclei Main air activation zone in the tunnel, near IP: 100 kW beam loss (collimators)

13 Release 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 : ratio < 0.1

14 Release of radioactive air Overview ventilation system S. II-251 TDR Should it be operated as a closed or open system?

15 Release of radioactive air Open system : Tunnel ventilation rate : 0,8 m/s, 6*10 4 m 3 /h length of collimator section : 100 m volume of activation zone :2000 m 3 distance to exhaust station :5 km delay time :1.4 h Closed system : 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 air Closed system Sum of all ratios = << 1.0 and << 0.1

17 Release of radioactive air Open system Sum of all ratios =

18 Release 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 water wet soil (27% water) concrete shielding (3 m) in the vicinity of a main dump dump TESLA lumi run: Operation time: 5000 h (1 year) Energy: 250 GeV power: 12 MW

20 Activity concentration of wet soil Most relevant nuclei Sum of all activity concentrations: Bq/g rings of 50 cm thickness

21 Activation of Soil and Groundwater region of 50 cm around a main dump after 5000 h of operation sandwater 7 Be 3 H 22 Na Silicon 32 % Oxygen 53 % Aluminium 4 % Oxygen 89 % 100 % 15 % natural activity: Bq/g Dose, consuming 800 l/a 2.5 mSv (?% 22 Na) 3 H : 2.60 Bq/g 22 Na : 0.45 Bq/g 7 Be : ? Bq/g 22 Na : ? Bq/g

22 Transport of ground water Ground water flow: (expert‘s report) area north dump south dump descent 1m / 750m 1m/ 900m permeability 5* m/s 5* m/s filter velocity 6.7* m/s 5.6* m/s distance velocity 2.2* m/s 1.9* m/s distance velocity 6.9 m/ year 6.0 m/ year error about 80% ?

23 Transport of activated ground water activation 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 ? Distance calculations for the dominant nuclide Na-22 After activation:

24 Zones of activated ground water Distance A c for 30 µSv/a after velocity distance time (m/s) (m) (a) 5.0 * * * * * * * *

25 Protection 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 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 Staff personal doses < 20 mSv / a local dose rates < 3 mSv / h Only temporary access ALARA

28 Residual Radioactivity Hot spots

29 Radioactivity of the tunnel air

30 Conclusions