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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

zompe

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

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.