DDOSE CONCEPTS, QUANTOSE CONCEPTS, QUANTIITTIIES AND UNES AND UNIITSTS,, BASBASIIC PRC PRIINCNCIIPLES AND PLES AND PRIMARY PRIMARY

METHODS OF RADMETHODS OF RADIIATATIION PROTECTON PROTECTIIONON

DDOSE CONCEPTS, QUANTOSE CONCEPTS, QUANTIITTIIES AND UNES AND UNIITSTS,, BASBASIIC PRC PRIINCNCIIPLES AND PLES AND PRIMARY PRIMARY

METHODS OF RADMETHODS OF RADIIATATIION PROTECTON PROTECTIIONON

Module IVModule IV

Module IV - 2

Radiation Radiation exposureexposure

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

= 1esu/cm3

Module IV - 3

Absorbed dose (D)Absorbed dose (D)

Energy imparted to matter from any type of radiation

D: absorbed dose

E: energy absorbed by material of mass ‘m’

Module IV - 4

Units of Units of aabsorbed bsorbed ddoseose

The SI unit: gray (Gy)

1 Gy = 1 joule/kilogram

Old unit : rad

1 Gy=100 rad

Module IV - 5

Equivalent dose Equivalent dose (H(HTT))

Accounts for biological effect

per unit dose

radiation weighting absorbed

factor ( WR ) X dose (D)

HT = WR x D

X

Module IV - 6

Radiation weighting factorsRadiation weighting factors (W (WRR))

ICRP 60 (1991)

 

Radiation type and energy range

WR

Photons (X-rays and gamma-rays) all energies Electrons, all energies Neutrons <10 keV 10-100 keV >100 kev to 2 MeV 2-20 MeV >20 MeV Protons >20MeV Alpha-particles, fission fragments

1 1 5 10 20 10 5 5 20

Module IV - 7

Unit of Unit of equivalent equivalent ddose ose

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 - 8

Effective dose (E)Effective dose (E)

Risk related parameter, taking relative radiosensitivity of each 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 - 9

Tissue and organ Tissue and organ weighting factorsweighting factors

Organ or tissue Tissue weightingfactor (WT)

GonadsRed bone marrowColonLungStomachBladderBreastLiverOesophagusThyroidSkinBone surfaceRemainder

Total

0.20.120.120.120.120.050.050.050.050.050.010.010.05

1.0

Module IV - 10

Conversion between units Conversion between units used in radiation protectionused in radiation protection

Physicalquantity

SI unit Non-SIunit

Relationship

Activity

Exposure

AbsorbeddoseEquivalentdose

becquerel

coulomb/kg

gray (=J/kg)

sievert

curie (Ci)

roentgen ®

rad

rem

1 Bq=2.7x10-11 Ci1 Ci=3.7x1010Bq1 mCi=37 MBq1 R=2.58x10-4 C/kg1C/kg=3876 R1 Gy=100 rad1 rad=1 cGy1 Sv=100 rem1 rem=10 mSv

Module IV - 11

Committed equivalentCommitted equivalent ddose ose HHTT(t)(t)

and cand committed ommitted eeffective ffective ddose E(t)ose E(t)

Module IV - 12

Averted dose

Averted dose

Projected dose

Projected Projected and aand avertablevertable dose dose

Module IV - 13

Collective effective dose Collective effective dose ((SS))

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)

i

ii NES .

Module IV - 14

Sources and Sources and llevels of evels of rradiation adiation eexposure to xposure to

ppopulationopulation

Module IV - 15

Sources of Sources of rradiation adiation ddose to ose to ggeneral eneral ppopulationopulation

Module IV - 16

Background Background radiationradiation

•Terrestrial radioactivity

•Cosmic radiation

•Internal radioactivity

Natural background radiation doses in Europe

Module IV - 17

Terrestrial Terrestrial rradiationadiation::external and internal exposureexternal and internal exposure

U-238 Ra-222

Th-232 Ra-220

Module IV - 18

Cosmic Cosmic rradiationadiation

Module IV - 19

Internal Internal rradioactivityadioactivity

•Radioactivity in diet

•lead-210

•polonium-210

•potassium-40

Module IV - 20

AvAveerage ocupational radiation doses rage ocupational radiation doses received received duringduring various various types of types of workwork

‘Non-coal’

mining

16.3

mili

siev

erts

Dos

e in

mili

siev

erts

Module IV - 21

Dose Dose llimits imits rrecomended by ICRP ecomended by ICRP (1991)(1991) -- wwhole hole bbodyody

Occupationalexposure

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

Module IV - 22

Dose Dose llimits imits rrecomended by ecomended by ICRP (1991)ICRP (1991) -- t tissuesissues

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  

Module IV - 23

RRadadiiatatiion protecton protectiionon

Basic Basic pprinciples rinciples and and

primary methodsprimary methods

Module IV - 24

BasicBasic pprinciples of rinciples of rradiadiationation pprotectionrotection

Justification of practice

Optimization of protection

Individual dose limits

Module IV - 25

AALLAARRAA

As low as reasonablyachievable

Module IV - 26

Three basic factorsTimeDistanceShielding

Basic methods of protection against Basic methods of protection against

eexposurexposure to ionizing radiationto ionizing radiation

Module IV - 27

TimeTime

Exposure rate =10mGy/h

X Time = Total dose

1 hour = 10 mGy

2 hours = 20 mGy

Module IV - 28

DistanceDistance

Module IV - 29

Inverse Inverse ssquare quare llawaw

150 mSv/h0.06 mSv/h

d=50cm

Module IV - 30

ShieldingShielding

Module IV - 31

Shielding Shielding pphotonshotons

Module IV - 32

HalfHalf valuevalue layerlayer (HVL) (HVL)

Module IV - 33

Internal Internal eexposure xposure

Module IV - 34

InhalationInhalation

Module IV - 35

Ingestion/AbsorptionIngestion/Absorption

Module IV - 36

Protective clothingProtective clothing and and hand washinghand washing

Module IV - 37

Medical Medical eexposurexposureRelative effective dose and equivalent period of Relative effective dose and equivalent period of

exposure to natural background radiationexposure to natural background radiationEffective dose (mSv)

Equivalent period of natural radiation

Radiography

Chest 0.02 3 days

Pelvis 1.0 6 months

IVP 4.6 2.5 years

Barium studies 9.0 4.5 years

CT (Chest, Abdomen)

8.0 4 years

Nuclear Medicine

Thyroid imaging 1.0 6 months

Bone imaging 3.6 1.8 years

Module IV - 38

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)