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

1. The assessment of individual and collective intervention doses for the LHC beam cleaning insertions M. Brugger, D. Forkel-Wirth, H. G. Menzel, S. Roesler (SC/RP)

2. Objectives • Raise awareness about the necessity to begin optimization already now - the respective groups of concern will need time to define their needs in order to implement the optimizations before the startup of the machine • Identify critical interventions in order to suggest improvements and perform possible optimizations • Prepare the staged machine installation (collimator upgrade, vacuum, kickers, etc…) during the first years of LHC • Prepare contracts in time: external companies intervening in high radiation areas have to be certified (i.e. respective constraints will have to be included in market surveys) • Collect input for documentation (INB reports) which has to be soon submitted to the French authorities for LHC approval. They will include estimates for individual and collective doses (one of the major concerns of the authorities!) • Detailed Monte Carlo simulations are available for IR7 (arbitrary locations, different cooling times) • Applying a new method (developed by RP) to calculate remanent dose rates based on the explicit production of radionuclides and the simulation of their decay particles. This overcomes the old limitations due to conversion coefficients only valid at contact to large surfaces. The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

3. You have to look close… Not to miss the details… The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

4. To Avoid Surprises… The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

5. To Be Prepared… The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

6. LHC Goal:Critical individual and collective doses for the LHC (including experiments) Regions with low losses (e.g. due to residual gas) Regions of point losses (e.g. Collimators,…) *picture by T. Wijnands The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

7. Beam Operation Expected Intensities/Losses • First Year (2007): Start with low intensities, 1.3x1016 particles lost at IR7 (both beams) • Second Year (2008): 25ns Operation, still limited intensities, 2.1x1016 particles lost at IR7 (both beams) • Third Year (2009): Install MKBs, Upgrade to phase 2, Pushing up the intensity, Probably at ‘Nominal’ around the end of the year -> 2.1x1016 – 4.1x1016 particles lost at IR7 (both beams) • Fourth year (2010) – xxx (20xx): Operate at around ‘Nominal’ intensity-> 4.1x1016 particles lost at IR7 (both beams) • xxx year (20xx): Push the machine to its maximum and operate at around ‘Ultimate’ intensity, unlikely without further changes of the machine layout-> 7.3x1016 particles lost at IR7 Possible Operational Periods • Breakdown of a year into shutdown and operational periods (e.g. 4 months / 8 months) • Breakdown of operational periods into beam-on and beam-off periods (e.g. 25 day beam run / 3 days off) • Breakdown of beam periods into physics and other runs (e.g. 1 day setting up, 4 days MD and 20 days physics * M. Lamont * R. Bailey The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

8. Beam Operation - Consequences • As compared to nominal operation one can assume the following scaling factors with respect to losses during the first years of operation: • 1st year: 1/3 • 2nd year: 1/2 • 4th - xxx year: 1 • Afterwards (???): 2 • With respect to expected operational periods of the machine access due to interventions might be necessary at the following cooling times: • Urgent repairs when LHC is operating: 1 - 8 hours • Repairs during beam-off period: 8 hours – 3 days • Interventions during shutdown: 1 day – 4 months The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

9. Which are the Constraints? The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

10. Radiation Protection Legislation:General Principles • 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) Optimization • Dynamic Process:the individual doses and collective doses have to be kept “As Low As Reasonably Achievable” (ALARA), i.e. iterations are necessary between the intervening groups and RP in order to reduce individual and collective doses to a reasonable minimum The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

11. Corresponding Constraints The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

12. Monte Carlo Calculations(FLUKA) The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

13. Calculation Procedure • Detailed Geometry description including • Correct source terms including primary loss distribution • Complete geometry • Tunnel structure, Collimator, magnets • Beamline, Dogleg separation • Monte-Carlo simulation using the new “Explicit Method” to calculate dose rate maps for the entire geometry and various cooling times, including • Successfully benchmarked method: at CERF and during the TT40 tests • Extensive set of simulations (several thousands NCU days!) • Separate simulations for different contributors • Average and Maximum Values for relevant locations • Results are calculated per lost proton and can be scaled with the respective losses • Typical operational period of 180 days and cooling times ranging from one hour to four months • Compilation of intervention scenarios together with the corresponding groups • Time, location and frequency of the intervention • Number of persons involved • Calculation of individual and collective doses • Iteration and optimization The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

14. Dose Rate Maps for the Different Cooling Times Aisle: 1-4mSv/h Close: 2-20mSv/h Aisle: 0.5-2mSv/h Close: 2-20mSv/h 1 hour 8 hours Aisle: 0.1-0.5mSv/h Close: 0.5-5mSv/h Aisle: 0.1-1mSv/h Close: 1-10mSv/h 1 day 1 week Aisle: 0.05-0,3mSv/h Close: 0.1-3mSv/h Aisle: 0.01-0.1mSv/h Close: 0.1-1mSv/h 4 months 1 month Results are normalized for one LHC year (180 days) running at nominal intensity. The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

15. Intervention Scenarios - IR7 only The following scenarios have already been identified and/or studied in more detail. The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

16. 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 • Typical cooling period before intervention • Number of persons involved • Steps of the intervention • Time estimate for each step (including location) • Annual frequency of the intervention • Are external contractors involved • At the moment the uncertainty lies in the estimates for the intervention(s), not in the calculation of the remanent dose rates! The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

17. Example: Exchange of Collimators(Collimator, Vacuum, RP, Beam Instrumentation?,…) The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

18. Vacuum pump Quick-connect flanges Beam 2 Collimator tank Interconnect support Collimator support Survey reference points Motorization/sensors How will it look like ? Narrow, thus difficult access e.g. Exchange of motor on the tunnel side position in case of a tilted collimator *R. Perret et al The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

19. Individual Doses The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

20. Exchange of Collimator *Scenario O. Aberle Reminder: CERN Design criterion - 2 mSv/person/intervention The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

21. Collimator Exchange -Vacuum System Vacuum: Collimator exchange - Summary of different scenarios Total accumulated dose per person in mSv *Scenario M. Jimenez using chain clamps reduces the individual dose to 2/3 dismounting the second beam-line would almost double it Reminder: CERN Design criterion - 2 mSv/person/intervention The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

22. BakeOut/NEG Coating - Vacuum *Scenario M. Jimenez permanent bakeout equipment would gain about a factor of 5 with respect to the individual and collective dose Reminder: CERN Design criterion - 2 mSv/person/intervention The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

23. Collective Dose The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

24. Collimator Exchange – All Steps The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

25. Collimator Exchange – Collective Dose The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

26. Collimator, Exchange – Prel. Conclusions • Values refer the most radioactive collimator (1st secondary) and to “nominal” intensity not to be reached during phase 1. They can be scaled by a factor of two for the first years of operation • However, collimator supports and additional material not included in the simulation will however increase individual and collective doses • In addition, after installation of phase 2 even higher doses have to be anticipated due to the hybrid collimators (e.g., copper jaws) • The results and scenarios have to be further discussed and refined in order to become as realistic as possible • Without improvements long down times will have to be accepted (at least for those collimators showing the highest remanent dose rates) • Chain clamps and permanent bakeout equipment will certainly improve the situation (the latter will have to be radiation hard) The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

27. How do these values compare to current interventions at CERN and the SPS? The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

28. Comparable Interventions As compared to the values above, we do face significantly higher individual and collective doses at IR7 (e.g., collimator exchange: 1d – 1w cooling: 6-25 mSv) The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

29. How to obtain to a realistic annual dose estimate? The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

30. The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

31. Annual Doses – SPS, CERN 100-700mSv/year SPS - tendency to lower doses during the last years - future major contributors: CNGS, LHC (not only IR7),… - future increase of intensities will also result in higher annual doses of the PS and SPS C E R N 300-1500mSv/year * J. C. Gaborit, G. Grobon, E. Cennini The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

32. Annual Doses – Prel. Conclusions • Phase 2 installation will become a critical intervention • Details need to be clarified • For a complete assessment of annual doses to be expected at IR7 iterations are still necessary with the respective groups • receive missing information • discuss the available results • refine the scenarios (locations, time) • clarify expected frequency of interventions • For the LHC we suggest to develop scenarios for • the first years of operation • phase 2 installation • “good” years • after 5-10 years of operation • “bad” year • When compared to current annual doses for the SPS and CERN it is obvious that further optimization is important The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

33. Important Issues & Conclusions • Optimization: what has been achieved so far for IR7: • No local heavy shielding (not remotely removable) • Reorientation of magnets • Plug-in system for collimators (fast exchange), Fast connect flanges for vacuum,… ? • What is currently being done: • Identify most critical scenarios, calculate individual and collective doses • Get a first impression about annual doses • Important issues • INB reports for LHC approval (including provisional estimates for individual and collective doses) • Mock-up installations and precise intervention planning, the latter is legally required • In case of critical interventions in high radiation areas external companies have to be certified (i.e., constraints will have to be included in market surveys) • What will have to be done: • Before startup: further optimization, improvements, development of work procedures, iteration with calculations, mock-ups • During the first years: validation using measurements, scaling of simulations, detailed maintenance planning, dose evaluation The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

34. What we would like to avoid: waiting too long and then have to use detours… The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

35. ‘Cause this would lead to: Uuups bad and certainly dangerous surprises: And not only authorities would… …get angry The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

36. Conclusions • Optimization: what has been achieved so far for IR7: • No local heavy shielding (not remotely removable) • Reorientation of magnets • Plug-in system for collimators (fast exchange) • Fast connect flanges for vacuum • What is currently being done: • Identify most critical scenarios, calculate individual and collective doses • Get a first impression about annual doses • Iteration with groups of concern, identify possible improvements • What will have to be done: • Before startup: further optimization, improvements, development of work procedures, iteration with calculations, mock-ups • During the first years: validation using measurements, scaling of simulations, detailed maintenance planning, dose evaluation The assessment of individual and collective intervention doses for the LHC beam cleaning insertions

37. Thank You… The assessment of individual and collective intervention doses for the LHC beam cleaning insertions