Radiation protection issues in the LHC experimental areas

1. Radiation protection issues in the LHC experimental areas Doris Forkel-Wirth and Marco Silari SC/RP M. Silari – LAAWG – 17 September 2007

2. Contacts LHC experiments – SC/RP • Meetings between RP group representatives and the RSOs of the LHC experiments started in 2004 and now take place monthly to discuss RP open issues following the review organized by TS on 14.02.2007 • List of topics at various stages of discussion: • Buffer zones and RP controls • Local/centralized workshops for repair of radioactive components • Gate monitors for PAD/MAD • Traceability (for material leaving the site) • Access to the underground experimental areas during short machine stops • RGE and Operational radiation protection • RAMSES • RP training • Individual dosimetry and operational dosimetry • Classification of areas and of personnel • Dose objectives, dose limits, optimization, ALARA M. Silari – LAAWG – 17 September 2007

3. Safety code F • Safety code F – Radiation protection and the radiation safety instructions are equivalent to current French and Swiss legislation and regulation. • Safety code F and the radiation safety instructions together are equivalent to the 1996 radiation safety manual (still valid for an interim period until all safety instructions are reviewed). • They can be complemented by area- or work-specific procedures M. Silari – LAAWG – 17 September 2007

4. Removal of radioactive material and buffer zones • Material removed from beam areas will be temporary placed in a “buffer zone” to be checked for induced radioactivity before it can leave the site • Regular checks will be performed by an SC/RP technician • Dismantling and transport of heavy components from the detectors will have to be planned in advance and will not require an intermediate storage in a buffer zone • Traceability must be guaranteed This is similar to what is planned for the LHC machine M. Silari – LAAWG – 17 September 2007

5. Classification of areas • Service areas (USA15, PX24, USC55, UX85) • during beam operation: supervised areas • during shut-down: possible declassification into non-designated areas? • USC55 fulfills the requirements of a non-designated area during beam on and beam off • Experimental caverns: • before 2007: simple controlled areas (Radiation Safety Manual 1996) • as of 2007: partition of the areas into supervised and simple controlled areas (Safety Code F 2006) • CERN reference levels: • annual, individual dose below 6 mSv/year • effective dose due to internal exposure below 1 μSv per hour of stay -> possibly waiting time to be respected before access into beam areas can be granted • Radiological classification essential to discuss access procedures, job and dose planning… M. Silari – LAAWG – 17 September 2007

6. Classification of workers • Occupationally exposed : • Class A > 6 mSv / 12 months • Class B < 6 mSv / 12 months • Short term visitors:< 1 mSv / 12 months (not classified as occupationally exposed) • Non occupationally exposed:< 1 mSv / 12 months M. Silari – LAAWG – 17 September 2007

7. Individual monitoring • All individuals working in supervised and controlled radiation areas must wear a CERN individual passive dosimeter to be read at least once per month at one of the reader stations available at various locations on the CERN sites. • Only individuals classified as occupationally exposed (i.e., VCT are excluded) may work in controlled radiation areas. They must wear an additional, operational dosimeter with direct dose reading (and in given circumstances alarm capabilities). M. Silari – LAAWG – 17 September 2007

8. Most of the ALARA elementswere already used at CERN in the past Since December 2006 systematic, formalized approach Same for LHC machine and experiments ALARA at CERN Slides on ALARA courtesy of P. Bonnal M. Silari – LAAWG – 17 September 2007

9. ALARA at CERN M. Silari – LAAWG – 17 September 2007

10. ALARA procedures – 3 levels: If the rad. risk/hazard is low very light procedure If it is medium  an optimization effort is required If it is high  an optimization effort is required, the procedure will be submitted to the ALARA committee ALARA at CERN – 3 levels M. Silari – LAAWG – 17 September 2007

11. ALARA criteria M. Silari – LAAWG – 17 September 2007

12. ALARA criteria M. Silari – LAAWG – 17 September 2007

13. RSOs, RP Experts (RPE) and RP Assistants • As long as human resources in the RP group are not sufficient to follow-up properly ALL RP issues related to the LHC machine and experiments, it is intended to delegate part of the RP tasks to the experiments for low risk maintenancejobs • High risk maintenance jobs need the presence of SC/RP • This approach requires: • the appointment of a number of RP experts and RP assistants in each experiment • for each experiment, the identification of the perimeter (“operational zoning” vs “waste zoning”) inside which RP tasks can be delegated to the RPEs and assistants • well-established intervention scenarios and working procedures • This approach should guarantee radiation safety allowing at the same time some flexibility This approach is presently under discussion between PH and SC M. Silari – LAAWG – 17 September 2007

14. RSOs, RP Experts (RPE) and RP Assistants • The delegation of RP duties to the experiments requires a number of properly trained radiation protection experts (RPE) and RP assistants in the experiments. These are people in the Collaborations (the present idea is that they should be CERN staff) who on top of their normal duties take up part-time job in radiation protection • RPEs must have a technical RP background certified by a national authorization body • Specific RP training can possibly be given at CERN (two-week training) by an external, certified institution • Pool of RP assistants with lower-level RP training • Required number of RPEs and assistants to be defined by each experiment • The line of responsibility and the interlink between RSO, RPEs, RP assistants and the SC/RP group is under discussion • The SC/RP group will perform random, spot checks M. Silari – LAAWG – 17 September 2007

15. General RP training for all CERN staff and users One-day radiation protection training course under revision (pilot session to be given soon to the RSOs). The course will be compulsory for ALL staff and users (not just people in the LHC Collaborations) • The course is addressed to occupationally exposed workers, that is people who work at CERN in the presence of ionising radiation (work in supervised or controlled radiation areas, or with radioactive sources) • The course is mandatory because: • national legislations impose that people working with ionising radiation are informed of the risks incurred, and are aware of the rules to be followed in order to minimise exposure • CERN must guarantee that staff and users work safely The course will be divided in three sections and will be followed by an evaluation session (multiple choice questionnaire) M. Silari – LAAWG – 17 September 2007

16. General RP training: content (provisional) • Part I: Fundamentals • Risk perception • Sources of ionising radiation at CERN • Biological effects of radiation • Quantities and units • Operational radiation protection • Radiation shielding • Induced radioactivity and external exposure • Part II: Radiation protection at CERN • CERN safety structure • Code F, classification of areas and personnel • Individual dosimetry • Radiation monitoring • Use of radioactive sources • Industrial radiographies and potential, serious accidents • Radioactive waste • Transport of radioactive material • Part III: Area-specific risks, rules, access and protection means • Access into radiation areas of PS and SPS • INB approach for SPS-LHC-CNGS • Radiation areas in the LHC machine • Access into LHC experimental areas M. Silari – LAAWG – 17 September 2007

17. Operational radiation protection for LHC experiments A document to be revised every year, following evolution of the extension of radioactive areas, types of intervention, etc • Organisation of RP for the experiments (a common section containing information pertaining to all experiments, plus experiment-specific sections) • RP classifications for LHC experiments, including classification of areas under the various beam conditions and for the various intervention scenarios • Material zoning for maintenance, operational zoning, traceability, classification of workers • Protection of workers and the public • Required RP training • RP risk analysis for work places and activities, job and dose planning, radiation survey and radiation veto • Scenarios for short accesses and for long shutdowns • Control of material removed from the LHC experimental areas • Handling of activated material from the LHC experiments outside the experimental cavern • Dose objectives, dose limits, optimization, ALARA M. Silari – LAAWG – 17 September 2007