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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
Radiation exposure

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

= 1esu/cm3

Module IV

absorbed dose d
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
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
Equivalent dose (HT)

Accounts for biological effect

per unit dose

radiation weighting absorbed

factor ( WR) X dose (D)

HT= WRxD

X

Module IV

unit of equivalent d ose
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
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

projected and a vertable dose
Projected and avertable dose

Projected dose

Averted dose

Averted dose

Module IV

collective effective dose s
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

background radiation
Background radiation
  • Terrestrial radioactivity
  • Cosmic radiation
  • Internal radioactivity

Natural background radiation doses in Europe

Module IV

terrestrial r adiation external and internal exposure
Terrestrial radiation:external and internal exposure
  • U-238 Ra-222
  • Th-232 Ra-220

Module IV

internal r adioactivity
Internal radioactivity
  • Radioactivity in diet
    • lead-210
    • polonium-210
    • potassium-40

Module IV

av e rage ocupational radiation doses received during various types of work
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

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

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

basic p rinciples of r adi ation p rotection
Basicprinciples of radiationprotection
  • Justification of practice
  • Optimization of protection
  • Individual dose limits

Module IV

a l a r a
ALARA

Aslow as reasonably

achievable

Module IV

basic methods of protection against e xposure to ionizing radiation
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

distance
Distance

Module IV

inverse s quare l aw
Inverse square law

d=50cm

150 mSv/h

0.06 mSv/h

Module IV

shielding
Shielding

Module IV

inhalation
Inhalation

Module IV

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

Module IV

review points
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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