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Personal Dosimetry in a RIB Facility

Personal Dosimetry in a RIB Facility. External Exposure Internal Exposure Biokinetic Models Dosimetry Threshold Measurements Particularities of a RIB facility Thomas Otto, CERN, TIS-RP. Dosimetry: basic concept. Absorbed dose:

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Personal Dosimetry in a RIB Facility

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  1. Personal Dosimetry in a RIB Facility External Exposure Internal Exposure Biokinetic Models Dosimetry Threshold Measurements Particularities of a RIB facility Thomas Otto, CERN, TIS-RP

  2. Dosimetry: basic concept • Absorbed dose: • together with suitable weighting or quality factors: dose equivalent H • radiation detriment is assumed to be proportional to dose equivalentin the low dose, low doserate regime • dose equivalent H key quantity for radiological risk assessment Personal Dosimetry in RIB facilities

  3. External vs. Internal Exposure Personal Dosimetry in RIB facilities

  4. ICRP 60: Risk-related quantityeffective Dose E Tissue weighting factors wT for 13 organs (“tissues”) Legal limits expressed in E E is one dose equivalent quantity Effective Dose Personal Dosimetry in RIB facilities

  5. “Dose measurement” Organs inaccessible for measurement Effective Dose cannot be measured directly Operational quantity “Personal dose equivalent” for protection purposes H > E Measure H with calibrated dosimeter on representative part of body Dosimetry of External Exposure Personal Dosimetry in RIB facilities

  6. Gamma/Beta: mature technology TLD or OSL Neutrons: Wide range of relevant energies Dosimeters only for partial energy range Albedo, Track-etch Personal Dosimeters Personal Dosimetry in RIB facilities

  7. Penetration of radioisotopes into the body inhalation via respiratory tract ingestion via Gastro-Intestinal tract by wounds description by biokinetic models Internal Exposure Personal Dosimetry in RIB facilities

  8. Describe: deposition in airways clearance into blood compartment model 1st order rate equations Particle size spectrum 1 um: 51 %deposition 5 um: 82 %deposition Clearance type: Fast, Medium, Slow 10 min , 140 days, 20 years Respiratory Tract Model Personal Dosimetry in RIB facilities

  9. Activity in target organs from biokinetic models Sum over 50 years: all decays in one organ all organs Committed dose E(50) Result of Calculations: ICRP publications dose coefficients “dose per activity” (Sv/Bq) for workers and members of public for different particle sizes and clearance types for large range of isotopes Dose Calculation Personal Dosimetry in RIB facilities

  10. “Dose measurement” Organs inaccessible for measurement Effective Dose cannot be measured directly Calculation of dose from incorporated activity Need to estimate incorporated activity Dosimetry Personal Dosimetry in RIB facilities

  11. Direct Measurement whole-body: whole-body counters “Anthropogammametry” body part: thyroid measurement for g-emitters Excretion Analysis urine feces chemical preparation nuclear counting techniques (AMS) for a/b-emitters Incorporation Measurements Personal Dosimetry in RIB facilities

  12. Whole-Body Counters Personal Dosimetry in RIB facilities

  13. Relation of excreted activity to incorporated activity: biokinetic models experiments on volunteers experience from accidents Excretion Analysis Personal Dosimetry in RIB facilities

  14. Reference data for “standard” isotopes ICRP Publ. 78 3H, 59Fe 57,58,60Co 85,89,90Sr, 106Ru 125,129,131I 134,137Cs, 226,228Ra, 228,232Th 234,235,238U, 37Np 7 Transuranium isotopes Excretion Analysis (2) Personal Dosimetry in RIB facilities

  15. Swiss Ordinance for Dosimetry: documented measurement of aerosol concentration at workplace with threshold for full internal dosimetry threshold:E(50)  1 mSv Isotope-specific thresholds Guidance only for few isotopes Difficult Isotope discrimination Workplace Measurement Personal Dosimetry in RIB facilities

  16. Wide range of isotopes Prototype-like installation without large body of experience (as e.g. NPP) “Experimental” (vs. industrial) way of operation Characteristics of a RIB facility Personal Dosimetry in RIB facilities

  17. External Dosimetry in RIB Facility • Full-body gamma dosimeters • Electronic dosimeter upon access to activated area (front-end, separator, reactor, storage) for immediate dose control • Extremity g/b –dosimeters for specific work • during operation, neutron dosimeter(type depending on driver: reactor vs. accelerator) Personal Dosimetry in RIB facilities

  18. Workplace Monitoring in RIB Facility • Regular checks for volatile contamination • Activity-in–air measurements • Look for representative “tracer” nuclides and estimate total contamination from their concentration • Identify such tracers • Determine best measurement practice(Instrument sensitivities, sample preparation…) Personal Dosimetry in RIB facilities

  19. Internal Dosimetry in RIB Facilities • Periodic whole-body scans for gamma emitters are simple, low-cost and reassuring for emplyer and staff • Periodicity has to be reviewed • Extra-scans after incidents • Excretion analysis needs identification of “tracers “ and development of specific sample preparation/detection methods • Use of automated equipment and personal protective equipment to raise threshold for “real” internal dosimetry Personal Dosimetry in RIB facilities

  20. Summary • Personal dosimetry key element of radiological protection programme • External vs. internal dosimetry • Specific challenges of RIB-facilities: • non-standard character of installation • range of isotopes • Development work for implementation of full dosimetry programme is still necessary Personal Dosimetry in RIB facilities

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