1 semmelweis university faculty of dentistry, budapest studium: radiation protection/strahlenschutz,...
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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
Committed dose: ∫ D(t) dtτ
0
According to regulation: τ = 50 y (adults), 70 y (children)
external internal (by intake of radioisotopes)
τ time˚
Dose rate
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Categories of Exposures(with respect to the regulation)
• Occupational exposures (Berufliche …)
• Public (incl.: Medical?) exposures
• (Non-human Biota exposures ?)
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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)
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Natural: Cosmogene and terrestrial radionuclides Univerzum (ions, α-, β-, n-, müon- … radiation)
γn
γ
Atmosphere
Earth Surface
Raindr.
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Terrestrial exposure: natural radioactive decay series (r. nuclides mainly in soil)
Pb-208stabile
Rn-22032 s
Th-232T=14 mrd y
. . . . . .
U-235T=0.72 mrd y
Actinium serie
Uranium serie
Thorium serie
Rn-2193,9 s
Pb-207stabile
U-238T=4.5 mrd y
Rn-2223,8 day
Pb-206stabile
. . .
. . .
. . .
. . .
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.
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Rn-222 concentrations indoor and outdoorIn winter: due to small ventilation, the Rn-gas accumulates indoor
Living room (indoor)
100-500 Bq/m3
soil
Rn-222 (noble gas)
Outdoor, air:
5-10 Bq/m3, to height of nearly 200-300 m
exhalation
ventilation
500-2000 Bq/m3 Rn-222
Ra-226 Rn-222
„cultural man”: 80 % indoor
α
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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
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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,…
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irrigationSource
Atmosph
Surface water
Soil
Vegetables
Feeding vegetation
Animals, anim. prod.
water plants, fishes
Man
Sediment
inhalation
•A radioaktív anyag migrációja a bioszférában és besugárzási útvonalak az ember esetén (szaggatott nyíl a sugárzás, folyamatos nyíl a radioaktív anyag terjedését jelöli)
Transport, migration of radionuclides discharged from NPP/isotope lab. Exposure pathways (Expositionspfaden).
external expos.
external expos.
intakes
intakes
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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)
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Averaged dose levels, inc. confidence ranges (natural sources)
Sources, pathways Mean values and ranges (mSv)
Cosmic rays, external, annual effective dose 0.38 (0.3-1.0)
Inhalation and ingestion of cosmogene radionuclides (internal, committed effective dose, annual)
0.012 (0.008– 0.02)
Terrestrial, external, annual effective dose, outdoor
, indoor
0.45 (0.3-0.6)
0.55 (0.4-0.8)
Terrestrial, annual internal, committed eff. dose (without Rn and daughters)
0.27 (0.2-0.5)
Terrestrial, annual internal, comitted eff. Dose from the Rn daughters 1.2 (0.5-5.0)
Terrestrial, annual internal, committed equivalent dose to lung, due to Rn daughters
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Technical Enhanced Natural Occurring Radioactive Material (TE-NORM): indoor (building material: Ra-226 content), …
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Averaged individual doses to public (artificial sources)
Sources, components Mean and range (mSv)
Medical, external (mainly X-ray diagn),annual effective dose 1.5 (0.1-5)
From NPP (1-5 km far), annual 0.01 ( - 0.1)
Atomic bombs (Hirosima, Nagaszaki, inside the city area) 100-5000
Nuclear tests, North hemisphere 0.1-2
, South < 0.01
Chernobyl accident, effective dose
within r ≈ 30 km circle 1-20
Central and West Europe 0.1-2
North America 0.01
Japan 0.01
South hemisphere < 0.01SE X-ray stations, eff. dose by films (-2009, last 3 years): ≈ 0.5 mSv / ySE dentist X-ray stations (last 3 years): < 0.3 mSv / ySE nuclear medic. labs (last 3 years): ≈ 0.7 mSv / év
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Medical exposure (patient dose per test)
0
2
4
6
8
10
12
14
16
18
20
Végtag
ok
Mell
kas f
elv.
Mam
mog
ráfia
Epeviz
sg.
Hasi C
T
Mell
kas-C
T
Érfesté
s
Inter
venc
pajzs
m (Tc-
99m)
máj-lép
-szc.(
Tc-99
m)
vese
-szc.
(Tc-9
9m)
mammo-
szc.(
Tc-99m
)
szívi
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rf. (T
c-99m
)
daga
nat (
PET)
szívi
zompe
rf.(T
l-201
)
E [
mS
v]
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Hírsugár (2007. júliusi száma), Sugárhumor/Déri Zsolt(Eötvös Loránd Fizikai Társulat Sugárvédelmi Szakcsoport)
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• 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 from measured 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)
Determination of exposures
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18„Rainpeaks”: due to intensive wash out to the surface, from atmosphere
Environmental monitoring, early warning system Continously (mainly by 2-10 minutes frequency) measured dose rates, usually 1 m heigh from the surface
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Personel monitoring, dose meters
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Whole body counter, determination incorporated radionuclides (geometries used)
Ív geometria
Szék geometria
Álló geometria (mozgó, vagy rögzített detektor)
Fekvő scanning geometria Fekvő ágy geometria
detector
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Scanning whole body counter with two detectors (Pb etc shielding to minimize the
effect of outside background)
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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
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90Sr contamination (pure β-emitter, sample measurements)
Sr-90 activities in teeth, in capital Budapest(Turai I.: Sugáreg. ismeretek, 1993)
0
20
40
60
80
100
120
140
1955 1960 1965 1970 1975 1980
év
mB
q/g
Ca Milky
tooth
Permanent tooth
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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.