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Rpc Dosimetry 2


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Rpc Dosimetry 2

  1. 1. The CERN Dosimetry Service – Results of Monitoring and Status Report Thomas Otto, SC-RP, CERN and Personnel of the Individual Dosimetry Service EDMS No. 568 545 v.1
  2. 2. Overview <ul><li>Status of the Dosimetry Service at CERN </li></ul><ul><li>Technical characteristics of the CERN Dosimeter system </li></ul><ul><li>Monitoring Results </li></ul><ul><li>Resources of the Dosimetry Service </li></ul><ul><li>The LHC challenge </li></ul>
  3. 3. Personal Dosimetry at CERN <ul><li>A service of the Radiation Protection Group </li></ul><ul><li>Monitoring more than 6000 persons/year with passive personal dosimeters </li></ul><ul><li>4400 persons are professionally exposed, the rest on short visits to CERN (assimilated to members of the public, but monitored) </li></ul>
  4. 4. Dosimetry by photographic film <ul><li>CERN: the last Dosimetry Service in Switzerland to use film dosimetry </li></ul><ul><li>Film dosimeter failed to fulfil requirements of CH dosimetry ordinance (1999): </li></ul><ul><ul><li>linearity in dose, energy </li></ul></ul><ul><ul><li>detection threshold </li></ul></ul>
  5. 5. Film-Dose Relationship <ul><li>Direct relationship User-Film-Dose </li></ul><ul><li>An unused film generates a “0” dose record </li></ul>
  6. 6. Replacement of Film-Dosimetry <ul><li>CERN’s purchasing criteria for a new dosimetry system: </li></ul><ul><ul><li>A dosimetry system owned by CERN (no subscription) </li></ul></ul><ul><ul><li>No manpower-intensive technology, as for example in Film- or TLD-based dosimeters </li></ul></ul><ul><ul><li>Workload should be mainly administrative (assisted by a database) </li></ul></ul>
  7. 7. The CERN dosimeter <ul><li>Owned by CERN: </li></ul><ul><ul><li>5500 DIS-1 </li></ul></ul><ul><ul><li>41 DBR-1 readers </li></ul></ul><ul><ul><li>Software, computers </li></ul></ul><ul><li>Reader Maintenance </li></ul><ul><ul><li>Raditec AG </li></ul></ul><ul><li>Fast Neutron dosimeter </li></ul><ul><ul><li>annual delivery and evaluation by PSI </li></ul></ul>
  8. 8. Immediate Reading of Dosimeter <ul><li>The accumulated dose information in the DIS dosimeter can be read out at a reader station </li></ul><ul><li>Comparable to pocket ionisation chamber, but delivers dose–of-record </li></ul><ul><li>Information is immediately centralised in database </li></ul>
  9. 9. Distribution of 41 reader stations <ul><li>At accelerator access points </li></ul><ul><li>and places of large public frequentation </li></ul>
  10. 10. The CERN DIS Network
  11. 11. Connection of Databases
  12. 12. Monthly Dose Record <ul><li>Monthly Dose = first Read-out in following month minus first read-out in the month concerned </li></ul>May June July Monthly Dose May Monthly Dose June
  13. 13. The DIS-Dose relationship <ul><li>One DIS-1 dosimeter will deliver many dose values during its use. </li></ul><ul><li>An unused dosimeter generates no reading. </li></ul>
  14. 14. Reminders and Warnings <ul><li>Dosimeters which have not been read-out are filtered from database and reminder / warning e-mails are sent to the persons concerned </li></ul>June July August 1 st and 2 nd Reminder 1 st and 2 nd warning Last warning Access blocked, invoice
  15. 15. Readout “discipline”
  16. 16. How many persons are monitored ? End of LEP Introduction of DIS
  17. 17. Collective Personal Dose Gradual intro-duction of operational dosimeters Systematic application of optimisation measures Variations due to amount of shutdown-work
  18. 18. Distribution of Doses
  19. 19. Comparison with other sectors of activity in Switzerland Data averaged 2005- 2007
  20. 20. Duration of Dosimeter Use <ul><li>80 dosimeters sufficient for 100 monitored persons (including turnover-time) </li></ul><ul><li>Try to identify and recuperate “convenience” dosimeters, implication of Department Heads, Group Leaders, … </li></ul><ul><li>Implies higher personnel cost for additional administrative work </li></ul>
  21. 21. Infrastructure, Consumables and Personnel <ul><li>Film Dosimetry </li></ul><ul><li>Infrastructure </li></ul><ul><ul><li>Photo laboratory </li></ul></ul><ul><ul><li>Densitometers </li></ul></ul><ul><li>Consumables </li></ul><ul><ul><li>Films </li></ul></ul><ul><ul><li>Chemicals </li></ul></ul><ul><li>Personnel </li></ul><ul><ul><li>Mostly technical training </li></ul></ul><ul><li>DIS Dosimetry </li></ul><ul><li>Infrastructure </li></ul><ul><ul><li>Reader stations </li></ul></ul><ul><ul><li>Server computer </li></ul></ul><ul><ul><li>Workstations </li></ul></ul><ul><li>Consumables </li></ul><ul><ul><li>Neutron detectors </li></ul></ul><ul><ul><li>(DIS) </li></ul></ul><ul><li>Personnel </li></ul><ul><ul><li>Mostly administrative training </li></ul></ul><ul><li>Administrative work is similar (although today stricter procedures) </li></ul><ul><li>Technical work for DIS is performed on computers and in calibration lab, in similar volume as previously in photographic lab </li></ul><ul><li>Less manual work , but comparatively more (and more complex) administrative and data processing work </li></ul>
  22. 22. Service’s HR requirements <ul><li>Baseline: 6000 clients, 500 dosimeter exchanges / month </li></ul><ul><li>Customer reception </li></ul><ul><ul><li>Open on workdays from 8:00 – 12:00 </li></ul></ul><ul><ul><li>2 persons, obligation of presence </li></ul></ul><ul><li>Customer and Supplier Relations </li></ul><ul><ul><li>Reporting, enquiries, dose records, chasing unduly used dosimeters </li></ul></ul><ul><ul><li>Purchasing, supply and maintenance contract management </li></ul></ul><ul><li>Dosimeter Maintenance and Support </li></ul><ul><ul><li>Calibration and reset of used dosimeters </li></ul></ul><ul><ul><li>Preparation of 500 dosimeters for following month </li></ul></ul><ul><ul><li>Repair of simple malfunctions </li></ul></ul>
  23. 23. LHC: forthcoming challenge <ul><li>The experimental collaborations estimate 1500 additional persons to become professionally exposed in the first year(s) of LHC operation </li></ul><ul><ul><li>+25% </li></ul></ul><ul><li>Administer 25 % more clients </li></ul><ul><ul><li>Reception, check prerequisites, assignment, communication, revocation, dose records </li></ul></ul><ul><li>Increase number of dosimeters, +22 % </li></ul><ul><ul><li>Calibrations, maintenance, reset </li></ul></ul><ul><li>Equip LHC access points with reader stations, +38% </li></ul><ul><ul><li>First-line interventions, Distances(!), maintenance, repair </li></ul></ul>
  24. 24. How to cope with the finite dosimeter lifetime ?
  25. 25. Summary <ul><li>The CERN Dosimeter (DIS-1 and CR-39) is adapted to the needs for personal dosimetry of a research centre </li></ul><ul><li>After overcoming some startup difficulties, the service is running stable for about 6000 users per year </li></ul><ul><li>The annual collective Dose of persons working at CERN is situated between 250 and 500 mSv, depending mainly on the amount of work in the shut-down. Steps have been taken to rationalise the use of dosimeters </li></ul><ul><li>The LHC challenge with many additional occupationally exposed persons lies ahead of us </li></ul>