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D OSE CONCEPTS, QUANT I T I ES AND UN I TS , BAS I C PR I NC I PLES AND PRIMARY METHODS OF RAD I AT I ON PROTECT I ON. Module IV. Radiation exposure. Traditional unit: Roentgen (R) = 2.58x10 -4 coulomb/kg = 1esu/cm 3. Absorbed dose (D). Energy imparted to matter

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DOSE CONCEPTS, QUANTITIES AND UNITS,BASIC PRINCIPLES AND PRIMARY METHODS OF RADIATION PROTECTION

Module IV


Radiation exposure l.jpg
Radiation exposure

Traditional unit: Roentgen (R) = 2.58x10-4 coulomb/kg

= 1esu/cm3

Module IV


Absorbed dose d l.jpg
Absorbed dose (D)

Energy imparted to matter

from any type of radiation

D = E/m

D:absorbed dose

E: energy absorbed by material of mass ‘m’

Module IV


Units of a bsorbed d ose l.jpg
Units of absorbed dose

The SI unit: gray (Gy)

1 Gy = 1 joule/kilogram

Old unit : rad

1 Gy=100 rad

Module IV


Equivalent dose h t l.jpg
Equivalent dose (HT)

Accounts for biological effect

per unit dose

radiation weighting absorbed

factor ( WR) X dose (D)

HT= WRxD

X

Module IV


Radiation weighting factors w r icrp 60 1991 l.jpg
Radiation weighting factors (WR)ICRP 60 (1991)

Module IV


Unit of equivalent d ose l.jpg
Unit of equivalent dose

SI unit: sievert (Sv)

HT (Sv) = WR x D (Gy)

Old unit: rem

(roentgen equivalent man)

HT (rem) =( WR) x D (rad)

1 Sv = 100 rems

Module IV


Effective dose e l.jpg
Effective dose (E)

Risk related parameter, takingrelative radiosensitivity ofeach organ and tissue into account

E(Sv)= ΣT WT x HT

WT: tissue weighting factor for organ T

HT: equivalent dose received by organ or tissue T

Module IV


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Tissue and organ weighting factors

Module IV


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Conversion between units used in radiation protection

Module IV


Committed equivalent d ose h t t and c ommitted e ffective d ose e t l.jpg
Committed equivalentdose HT(t)and committed effective dose E(t)

Module IV


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Projected and avertable dose

Projected dose

Averted dose

Averted dose

Module IV


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Collective effective dose (S)

Total radiation dose incurred by population

Ei:average effective dose in the population subgroup i

Ni: number of individuals in subgroup i

Unit:man-sievert (man.Sv)

Module IV


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Sources and levels of radiation exposure to population

Module IV


Sources of r adiation d ose to g eneral p opulation l.jpg
Sources of radiation dose to general population

Module IV


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Background radiation

  • Terrestrial radioactivity

  • Cosmic radiation

  • Internal radioactivity

Natural background radiation doses in Europe

Module IV


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Terrestrial radiation:external and internal exposure

  • U-238 Ra-222

  • Th-232 Ra-220

Module IV


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Cosmic radiation

Module IV


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Internal radioactivity

  • Radioactivity in diet

    • lead-210

    • polonium-210

    • potassium-40

Module IV


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Average ocupational radiation doses received during various types of work

‘Non-coal’

mining

16.3 milisieverts

Dose in milisieverts

Module IV


Dose l imits r ecomended by icrp 1991 w hole b ody l.jpg

Occupational

exposure

Public exposure

50 mSv maximum in any 1 year

100 mSv in

5 years

5 mSv in any 5 consecutive years

(Working figure 20 mSv per year)

(Working figure

1 mSv per year

Dose limits recomended by ICRP (1991)-whole body

Module IV


Dose l imits r ecomended by icrp 1991 t issues l.jpg

Annual doses to tissues

Occupational

Public

Lens of the eye

150 mSv

15 mSv

Skin (1cm2)

500 mSv

50 mSv

Hands and feet or individual organ

500 mSv

Dose limits recomended by ICRP (1991)- tissues

Module IV


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Radiation protection

Basic principles

and

primary methods

Module IV


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Basicprinciples of radiationprotection

  • Justification of practice

  • Optimization of protection

  • Individual dose limits

Module IV


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ALARA

Aslow as reasonably

achievable

Module IV


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Basic methods of protection against exposureto ionizing radiation

  • Three basic factors

    • Time

    • Distance

    • Shielding

Module IV


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Time

Exposure rate

=10mGy/h

Time = Total dose

X

1 hour = 10 mGy

2 hours = 20 mGy

Module IV


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Distance

Module IV


Inverse s quare l aw l.jpg
Inverse square law

d=50cm

150 mSv/h

0.06 mSv/h

Module IV


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Shielding

Module IV


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Shielding photons

Module IV


Half value layer hvl l.jpg
Halfvaluelayer (HVL)

Module IV


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Internal exposure

Module IV


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Inhalation

Module IV



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Protective clothing and hand washing

Module IV


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Medical exposureRelative effective dose and equivalent period of exposure to natural background radiation

Module IV


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Review points

  • Becquerel, coulomb per kilogram, gray, and sievert are part of International System of Units (SI).

  • Absorbed dose of radiation in SI units is expressed in gray. Ability of some types of radiation to cause more significant levels of biological damage taken into account with radiation weighting factor used to determine equivalent dose, expressed in sieverts

  • Goal of radiation safety: keep radiation exposure as low as reasonably achievable (ALARA)

Module IV


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