Session 2 of ATC/ABOC Days 2008 Session 2 of ATC/ABOC Days 2008 - PowerPoint PPT Presentation

Session 2 of ATC/ABOC Days 2008 Session 2 of ATC/ABOC Days 2008 Doris Forkel-Wirth, SC-RP Doris Forkel-Wirth, SC-RP Pierre Bonnal, AB-SU Pierre Bonnal, AB-SU 1

� Radiation Protection Constraints for the Operation of CERN’s Beam Facilities H. Vincke, SC-RP � The ARCON-RAMSES Bridge D. Perrin, SC/RP � Radiation Issues of the PS and SPS accelerator G. Simone, AB/ABP � Are Radiation Constraints limiting the ISOLDE Operation in 2008 R. Catherall, AB/ATB � Towards a Modified n-TOF Facility to Increase Radiation Safety M. Brugger, AB/ATB � Ensuring Safe and Reliable Operation of CNGS as of 2008 E. Gschwendtner, AB/ATB 2

� Revised Safety code F (Radiation protection) was issued in November 2006 to bring CERN in line with European radiation protection legislations and regulations � CERN’s revised Radiation Protection rules and regulations were endorsed by the Swiss and French authorities � CERN Reference levels – an ambitious goal? ◦ The individual, effective dose of occupationally exposed persons should stay below 6 mSv per year 6 mSv per year ◦ The effective dose due to internal exposure should be less than 1 uSv per hour of stay 1 uSv per hour of stay ◦ The annual effective dose to members of the reference group should stay below 10 uSv per year 10 uSv per year 3

< 2007 <2.5 μ Sv h -1 <7.5 μ Sv h -1 Area Dose Am bient dose Am bient dose equivalent rate equivalent rate Classifica- tion lim it At In low occu- workplaces pancy areas Non-designated Radiological reassessment area 1 mSv / y < 0.5 μ Sv h -1 < 2.5 μ Sv h -1 of Supervised all CERN areas required radiation 6 mSv / y < 3 μ Sv h -1 < 15 μ Sv h -1 area New Area Simple Controlled 20 mSv/y < 10 μ Sv/h < 50 μ Sv/h Radiation area < 2007 <25 μ Sv h -1 <100 μ Sv h -1 Safety Instruction S3-GSI1, EDMS 810149 4

Additional concrete shielding Underground Simple controlled tunnel Supervised area < < 2006: 2006: ~160 uSv/h ~160 uSv/h on top of H6 beam line n top of H6 beam line 2007: 2007: ~ 20 20 uSv/h uSv/h due to addition ue to additional 6.4 al 6.4 m thic m thick iron k iron shielding in shielding in TCC2 TCC2 Courtesy: Lau Gatignon 5

ALARA procedures – 3 levels: most of the ALARA elements ◦ If the rad. risk is low low were already used all over a light procedure is sufficient CERN in the past ◦ If it is mediu medium since December 2006: an optimization effort is � systematic, formalized required approach ◦ If it is high high � requires “close collaboration” an optimization effort is between RP and the required, the procedure will be maintenance teams submitted to the ALARA committee 6

� First ALARA committee meeting was held 19/11/2007 (only part of class III works were discussed, the rest will be done in February 2008) � Conclusions and recommendations ◦ Many jobs are already optimized thanks to � experience � good co-ordination of the activities by machine superintendants � investment (e.g. SPS magnet repair: workshop in ECA5) ◦ Improvements are still possible � Remote radiation measurement device � Remote visual inspection device � Use of fluorescence tubes with double the life time � Switching off the light during beam operation � …… 7

Arcon-Ramses Bridge Arcon-Ramses Bridge ARCON-RAMSES interface Spare parts Beam interlocks Oracle Limited RAMSES deployment Compensatory measures already identified – to be translated into operational procedures

PS and SPS Radiation Issues PS bridge PS bridge problem cured by displacing beam losses from section 5 to 73 Final solution: MTE 9

PS and SPS Radiation Issues Radiation is caused by losses during injection – Radiation is caused by losses during injection – difficult to minimize more difficult to minimize more MTE will reduce the losses by about 50 % MTE will reduce the losses by about 50 % - might be not yet sufficient - might be not yet sufficient 10

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Waste disposal Actinide target testing Activated air release X-rays from REX-ISOLDE linac

Start Up 2007 Isotope Isotope Half life alf life O-14 71 sec 2.50E+03 2007 2006 2005 O-15 2 min chimney monitor kBq/m3 2.00E+03 N-13 10 min C-11 20 min 1.50E+03 Ar-41 1.83 h 1.00E+03 5.00E+02 0.00E+00 April to December Radiation monitor PMVG170C showing higher levels compared to 2 previous years Tunnel gate monitor alarms set off

� Ventilation ◦ Studies performed by TS-CV, simulations going on - the situation will be improved before the start up of 2008 � REX-ISOLDE ◦ Lead collimator type shielding under study � Radioactive Waste Management ◦ Situation is progressing in terms of slightly radioactive non- actinide targets. � Agreement with PSI/Nagra, 3 rd campaign under way. ◦ Dismantling of actinide targets to be studied - pre-requisite for final disposal as waste � Off-line separator in Class A lab required to outgas actinide targets

Target Inspection � Pitting corrosion Pitting corrosion caused a hole at the proton impact location � Important surface oxidation surface oxidation due to rupture of protection layer when the drying (heating) was performed (flush) � Target shape didn’t allow for a correct water flow at the entrance face entrance face � Modular assembly lead to a mechanical mechanical instability instability and 21 st deformation Ja nu ATC/ABOC Days - Towards a ary modified n-TOF Facility to 20 15 Increase Radiation Safety 08

Residual Dose Rate Scan - Entry Face New FLUKA Comparison for Different Cobalt Contents 10000 Measurement / uSv/h FLUKA Co1 (0.01%) FLUKA Co2 (0.05%) FLUKA Co3 (0.075%) FLUKA Co4 (0.1%) Residual Dose Rates / μ Sv/h 1000 FLUKA SIMULATION 100 Target Entry Exit Face Face 21 st 10 Ja 400 900 1400 1900 2400 2900 nu ATC/ABOC Days - Towards a ary Distance from Target Face / mm modified n-TOF Facility to 20 16 Increase Radiation Safety 08

Residual Dose Rate ( μ Sv/h) as a function of the stainless steel Cobalt content (representative for location in front of the target support) 1.20 1.10 1.00 1.00 Using a stainless steel type 0.90 with low Co59 content will Residual Dose Rate ( μ Sv/h) 0.80 be important for the new 0.77 0.70 target design 0.60 0.52 Materials have to be chosen 0.50 Materials have to be chosen according to the radiation fields according to the radiation fields 0.40 they will be exposed to they will be exposed to 0.30 N-TOF: dominated by thermal N-TOF: dominated by thermal neutrons….. 0.20 neutrons….. LHC: mainly dominated by high LHC: mainly dominated by high 0.11 21 0.10 st energetic hadron fields energetic hadron fields Ja 0.00 nu 0 0.02 0.04 0.06 0.08 0.1 0.12 ATC/ABOC Days - Towards a ary modified n-TOF Facility to 20 Cobalt Content within Stainless Steel (%) 17 Increase Radiation Safety 08

New Target Design New Target Design Monorail Service Gallery Cooling Station � Cooling station equipped with a Double wall tubes closed retention vessel ISR Upper level � Double contained piping between the cooling station and Shielding Elements the target vessel Pit Cover � Water leak collection in the old Rectangular Connecting pit Section Area pool using the existing envelope Circular pit Section � The water collected in the pool is Quick 0 m 1 connections Envelope extracted by an externally First Shielding accessible closed collection Existing Pool Square pit vessel Section New Target Collection Assembly Vessel 21 st Ja nu ATC/ABOC Days - Towards a ary modified n-TOF Facility to 20 18 Increase Radiation Safety 08

First CNGS Neutrino Interaction inside an OPERA Brick Tue, 2 Oct, 17:04:25 ν μ CC interaction Muon 7GeV/c Event display E. Gschwendtner, AB/ATB/SBA ABOC-ATC days, 21 Jan 08 19

Strict access procedures: � Minimum 1day waiting time for access ◦ change to access mode in ventilation � reliable system! ◦ RP: air and dust probes, dose map, etc… � Any access to TCC4 and downstream part of TSG4: shielding plugs must be opened (~2hrs). � In case of horn/reflector/target exchange: remove entire shielding in TSG41 (1-2 weeks). � In case of transformer exchange: remove all shielding in TSG4 (1-3 days) E. Gschwendtner, AB/ATB/SBA ABOC-ATC days, 21 Jan 08 20

� RP Constraints ◦ RP constraints due to revised Safety Code F are respected by applying compensatory measures: � Reduction of beam losses � Shielding � Fencing � Access procedures ◦ Formalized ALARA approach introduced and first “retour d’experience” ◦ PS + SPS ◦ Radiation problems around PS and understood and solutions already implemented and/or foreseen or still under study � ARCON ◦ ARCON will be gradually transformed into RAMSES .