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External and Internal Radiation Dose

Semmelweis University Faculty of Dentistry, Budapest Studium: Radiation Protection/Strahlenschutz, 2011/2012 PUBLIC EXPOSURES (Strahlendosen für die Bevölkerung) 26 . October, 2011 , 16:00-17:10 Room: Árkövy Béla Kanyár hab. PhD, Semmelweis Univ., Radiation Protection Service.

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External and Internal Radiation Dose

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  1. Semmelweis University Faculty of Dentistry, BudapestStudium: Radiation Protection/Strahlenschutz, 2011/2012PUBLIC EXPOSURES (Strahlendosen für die Bevölkerung)26. October, 2011, 16:00-17:10Room: ÁrkövyBéla Kanyár hab. PhD, Semmelweis Univ., Radiation Protection Service

  2. External and Internal Radiation Dose external internal (by intake of radioisotopes) Dose rate Committed dose: ∫ D(t) dt τ ˚ τ time 0 According to regulation: τ = 50 y (adults), 70 y (children)

  3. Categories of Exposures(with respect to the regulation) • Occupational exposures (Berufliche …) • Public (incl.: Medical?) exposures • (Non-human Biota exposures ?)

  4. Sources of Public Exposures • Natural Exposure (Natürliche…) annual impact:  2.5 mSv effective dose (external + internal) • Artificial Exposure (Künstliche …) annual impact:  1.7 mSv effective dose (mainly due to medical, X-ray diagnostics)

  5. Natural: Cosmogene and terrestrial radionuclides Univerzum (ions, α-, β-, n-, müon- … radiation) Atmosphere n γ Raindr. Earth Surface γ

  6. Terrestrial exposure: natural radioactive decay series (r. nuclides mainly in soil) Thorium serie Th-232 T=14 mrd y . . . Rn-220 32 s . . . Pb-208 stabile Actinium serie U-235 T=0.72 mrd y . . . Rn-219 3,9 s . . . Pb-207 stabile Uranium serie U-238 T=4.5 mrd y . . . Rn-222 3,8 day . . . Pb-206 stabile Main processes: Rn-emanation: deliberation of Rn molecules from chem.-phys.binding in solid phase of soil (to gas form in soil) Rn-exhalation: outflow of Rn gas from soil to atmosphere.

  7. Rn-222 concentrations indoor and outdoor „cultural man”: 80 % indoor In winter: due to small ventilation, the Rn-gas accumulates indoor Living room (indoor) 100-500 Bq/m3 Outdoor, air: 5-10 Bq/m3, to height of nearly 200-300 m ventilation Rn-222 (noble gas) α Ra-226 Rn-222 exhalation 500-2000 Bq/m3 Rn-222 soil

  8. Rn-conc. due to periodic ventilation, for short (minutes) time intervals • CRn (Bq/m3) 300 200 100 Short and periodic ventilations, 5-6 hourly 6 h 9 h 12 h 15 h 18 h

  9. Artificial exposures • The main sources of the impact are: • - contamination of air, soil, vegetation etc. in the close environment of: nuclear power plants (NPP) and isotope labs, due to discharges of radionuclides • - contamination of spring waters in the close environment of Radioactive Repositories • Medical patient: X-ray diagnostic tests,…

  10. Transport, migration of radionuclides discharged from NPP/isotope lab. Exposure pathways (Expositionspfaden). external expos. inhalation Vegetables Atmosph Soil intakes Feeding vegetation Source irrigation Man Animals, anim. prod. Surface water Sediment intakes water plants, fishes external expos. • A radioaktív anyag migrációja a bioszférában és besugárzási útvonalak az ember esetén (szaggatott nyíl a sugárzás, folyamatos nyíl a radioaktív anyag terjedését jelöli)

  11. Atmospheric dispersion near to the source • In „normal practice”, 2-3 km far from the NPP no contamination are detected, only assessments are provided from the discharges and meteorological parameters (fequently used: Gaussian plume model)

  12. Table 10.Worldwide average annual doses in the environment (dose to the human body). The ranges correspond to about a 90% confidence interval Averaged dose levels, inc. confidence ranges (natural sources) Technical Enhanced Natural Occurring Radioactive Material (TE-NORM): indoor (building material: Ra-226 content), …

  13. Table 10.Worldwide average annual doses in the environment (dose to the human body). The ranges correspond to about a 90% confidence interval Averaged individual doses to public (artificial sources) SE X-ray stations, eff. dose by films (-2009, last 3 years): ≈ 0.5 mSv / y SE dentist X-ray stations (last 3 years): < 0.3 mSv / y SE nuclear medic. labs (last 3 years): ≈ 0.7 mSv / év

  14. Medical exposure (patient dose per test)

  15. Hírsugár (2007. júliusi száma), Sugárhumor/Déri Zsolt(Eötvös Loránd Fizikai Társulat Sugárvédelmi Szakcsoport)

  16. Determination of exposures • External dose: nearly 100 % in medical, dental praxis - X-ray diagn., Radiation therapy - Meassurement of X-rays (≈ 60 keV 20-150 keV): mainly by ionization chamber (energy dependency) • Internal dose: Radioactive isotopes: used as tracers to test the metabolic systems (nuclear medicine), and in internal radioisotope therapy (I-131 to thyroid) Dose assessment: Calculation frommeasured radionuclide concentration of air and food samples (inhalation and ingestion dose). - α-, β- and γ-ray contamination of whole body, surfaces, samples etc.: special sample processing, detectors: NaI(Tl), semiconducter ones (Ge, Si)

  17. Environmental monitoring, early warning system Continously (mainly by 2-10 minutes frequency) measured dose rates, usually 1 m heigh from the surface „Rainpeaks”: due to intensive wash out to the surface, from atmosphere

  18. Personel monitoring, dose meters

  19. Whole body counter, determination incorporated radionuclides (geometries used) detector

  20. Scanning whole body counter with two detectors (Pb etc shielding to minimize the effect of outside background)

  21. A Cs-137 in the inhabitans of capital Budapest (measured by: Andrási, A., …(KFKI)) Atmospheric nuclear tests (SU-USA: 1945-1964), later on by less intensity: Fr, GrB, China,…) Activ./body weight

  22. 90Sr contamination (pure β-emitter, sample measurements) Permanent tooth Milky tooth

  23. Literature:Basic safety standards. IAEA Safety Series No. 115, Vienna, 1996)Kanyár, B., G. J. Köteles: Dosimetry and Biological Effects of Ionizing Radiation, Chapter 10, in: Vértes, A., Z. Klencsar (eds): Handbook of Nuclear Chemistry, Springer, 2010 UNSCEAR Reports (2-4 yearly, UN NewYork, …)EU Radiation Protection No. 136, 2004. European guidelines on radiation protection in dental radiologyICRP (Intern. Comm. on Radiol. Prot.) Public. No 103, Pergamon P., NewYork, London, 2007.

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