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An Introduction to Ionizing An Introduction to Ionizing RadiationRadiation

H.L.Anil RanjithH.L.Anil RanjithHead-Div of Radiation ProtectionHead-Div of Radiation Protection

Atomic Energy AuthorityAtomic Energy Authority

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Composed of :Composed of :

Solid - Eg : gold, copper, common Solid - Eg : gold, copper, common saltsalt

Liquid - Eg : water, milk, mercuryLiquid - Eg : water, milk, mercuryGas - Eg : air, oxygenGas - Eg : air, oxygen

The Structure of Matter The Structure of Matter

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ELEMENTELEMENT AN ELEMENT IS A PURE SUBSTANCE AN ELEMENT IS A PURE SUBSTANCE

WHICH CAN NOT BE BROKEN IN TO WHICH CAN NOT BE BROKEN IN TO OTHER SUBSTANCES BY ANY OTHER OTHER SUBSTANCES BY ANY OTHER METHOD.METHOD.

ATOMATOM

SMALLEST PARTICLE OF AN ELEMENT THAT SMALLEST PARTICLE OF AN ELEMENT THAT HAS ALL THE CHEMICAL PROPERTIES OF THE HAS ALL THE CHEMICAL PROPERTIES OF THE GIVEN ELEMENT.GIVEN ELEMENT.

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COMPOUNDCOMPOUND A COMPOUND IS FORMED WHEN TWO OR MORE A COMPOUND IS FORMED WHEN TWO OR MORE

ELEMENTS COMBINE TOGETHER CHEMICALLY ELEMENTS COMBINE TOGETHER CHEMICALLY TO PROVIDE A MORE COMPLEX KIND OF TO PROVIDE A MORE COMPLEX KIND OF MATTER. MATTER.

MOLECULEMOLECULE SMALLEST PARTICLE OF ACOMPOUND THAT SMALLEST PARTICLE OF ACOMPOUND THAT

CAN EXIST WITHOUT LOOSING CHEMICAL CAN EXIST WITHOUT LOOSING CHEMICAL PROPERTIES OF THE COMPOUND.PROPERTIES OF THE COMPOUND.

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THE STRUCTURE OF THE ATOMTHE STRUCTURE OF THE ATOM BASICALLY CONSISTS OF TWO PARTSBASICALLY CONSISTS OF TWO PARTS::

NUCLEUS :NUCLEUS : CENTRAL CORE WHERE ALMOST ALL THE MASS OF THE ATOM CENTRAL CORE WHERE ALMOST ALL THE MASS OF THE ATOM

RESIDES. RESIDES.

CONSISTS OF: POSITIVELY CHARGED PROTONS AND CONSISTS OF: POSITIVELY CHARGED PROTONS AND ELECTRICALLY NEUTRAL NEUTRONS.ELECTRICALLY NEUTRAL NEUTRONS. (THESE TWO PARTICLES (THESE TWO PARTICLES ARE COMMONLY CALLED “NUCLEONS”) ARE COMMONLY CALLED “NUCLEONS”)

ELECTRON :ELECTRON :

LIGHT WEIGHT NEGATIVELY CHARGED PARTICLES ORBITING LIGHT WEIGHT NEGATIVELY CHARGED PARTICLES ORBITING THE NUCLEUS, A GREAT DISTANCE AWAY. THE NUCLEUS, A GREAT DISTANCE AWAY.

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Structure of the AtomStructure of the AtomProtons 1

1p(1.007276 amu)

Neutrons 10n

(1.008665 amu)Electrons(0.0005486 amu)

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ATOMIC NUMBER(Z)ATOMIC NUMBER(Z)

NO OF PROTONS IN THE NO OF PROTONS IN THE NUCLEUSNUCLEUS

THE ATOMIC NUMBER DETERMINES THE THE ATOMIC NUMBER DETERMINES THE CHEMICAL PROPERTIES OF THE CHEMICAL PROPERTIES OF THE ELEMENTELEMENT

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MASS NUMBER(A)MASS NUMBER(A)

TOTAL NUMBER OF PROTONS AND TOTAL NUMBER OF PROTONS AND NEUTRONS IN THE NUCLEUS.NEUTRONS IN THE NUCLEUS.

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An atom of element An atom of element having same number having same number of protons (z) and of protons (z) and different number of different number of neutrons (n) is called neutrons (n) is called an isotope of the an isotope of the element.element.

Eg:Eg:

191191Ir, Ir, 192192Ir, Ir, 193193IrIr (Z=77)(Z=77)

5858Co Co 5959Co Co 6060CoCo

(Z=27)(Z=27)

An IsotopeAn Isotope

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An IsotopeAn Isotope

Hydrogen Deuterium Tritium

Hydrogen, deuterium, and tritium all have the same atomic number Z: Their chemical properties are the

same, but their mass numbers are different.

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Nuclear StabilityNuclear Stability

Impairs by presence of too many or too Impairs by presence of too many or too few neutrons in the nucleusfew neutrons in the nucleus

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Too many or too few neutronsToo many or too few neutrons in the nucleus cause in the nucleus cause UNSTABILITYUNSTABILITY of the atom of the atom

Unstable atom seeks to become stable by breaking and Unstable atom seeks to become stable by breaking and emits energy asemits energy as RADIATION. RADIATION. The process is calledThe process is called RADIOACTIVITY RADIOACTIVITY and the Atom is said to be and the Atom is said to be RadioactiveRadioactive

Isotopes of elements which are radioactive are called RADIONUCLIDERADIONUCLIDESS

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Unstable Nuclides

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Radioactivity Radioactivity The process of rearrangements of nuclei by The process of rearrangements of nuclei by

changing the relative no. of neutrons and changing the relative no. of neutrons and protons in the nuclei of unstable atoms protons in the nuclei of unstable atoms

The rearrangements will cause release of The rearrangements will cause release of energy in the form of particles or energy in the form of particles or electromagnetic radiation (commonly called electromagnetic radiation (commonly called radiation)radiation)

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Discovery of RadioactivityDiscovery of Radioactivity

Maria Curie 1867-1934

Henri Becquerel 1852-1908

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Radiation DecayRadiation Decay Half-life is the time it Half-life is the time it

takes for half of the nuclei takes for half of the nuclei in a substance to undergo in a substance to undergo radio-active decayradio-active decay

Isotopes found in nature Isotopes found in nature typically have long half-typically have long half-lives; medical isotopes lives; medical isotopes typically have short half-typically have short half-liveslives

Typically the shorter the Typically the shorter the half-live the more half-live the more radioactive the materialradioactive the material

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Radioactive Decay (Radioactive Radioactive Decay (Radioactive DisintegrationDisintegration

Time taken to decay half of the atoms in a sample at certain time.

Half-life (THalf-life (T1/21/2))

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RADIATIONRADIATION

Ionising radiationIonising radiation

Alpha radiationAlpha radiation Beta radiationBeta radiation Gamma radiationGamma radiation X- radiation etcX- radiation etc

Neutron radiationNeutron radiation

Non ionising radiationNon ionising radiation

Micro wavesMicro waves Radio wavesRadio waves Lasers etc.Lasers etc.

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Non Ionizing RadiationNon Ionizing Radiation SourcesSources

Ultraviolet lightUltraviolet light Visible lightVisible light Infrared radiationInfrared radiation MicrowavesMicrowaves Radio & TVRadio & TV Power transmissionPower transmission

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Non Ionizing RadiationNon Ionizing Radiation

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Ionizing RadiationIonizing RadiationWhen radiation has enough energy to alter

the matter that it collides with or passes through it is referred to as ionizing radiation

Since humans are made up of matter, ionizing radiation can affect us adversely

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Ionizing Radiation (cont’d)Ionizing Radiation (cont’d)

There are 2 types of ionizing radiation:There are 2 types of ionizing radiation:

electromagnetic waveselectromagnetic waves sub-atomic particles sub-atomic particles

Typically, particles are parts of atomsTypically, particles are parts of atoms alpha (helium nucleus)alpha (helium nucleus) beta (electron)beta (electron) positron (positive anti-electron)positron (positive anti-electron) neutron (component of nucleus)neutron (component of nucleus)

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““Radioactive” versus Radioactive” versus “Radiation”“Radiation”

The terms “radioactive” and “radiation” are The terms “radioactive” and “radiation” are often confusedoften confused

By keeping the following relationship in By keeping the following relationship in mind, these two terms can be mind, these two terms can be distinguished:distinguished:

Radioactive atoms emit radiationRadioactive atoms emit radiation

Radioactive atoms emit radiationRadioactive atoms emit radiation

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RadiationRadiation is particles or waves of is particles or waves of energy emitted from unstable atomsenergy emitted from unstable atoms

Radioactive ContaminationRadioactive Contamination is is radioactive material usually in any radioactive material usually in any location you do not want itlocation you do not want it

Radiation vs. Radioactive Radiation vs. Radioactive ContaminationContamination

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RF wave infrared visible uv x-ray -ray cosmic

low energylow energy high energyhigh energy

ionizing radiationionizing radiationnon-ionizingnon-ionizing

Electromagnetic SpectrumElectromagnetic Spectrum

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Alpha particle

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ALPHA PARTICLEALPHA PARTICLE EMISION OF TWO PROTONS AND TWO NEUTRONS EMISION OF TWO PROTONS AND TWO NEUTRONS

FROM THE NUCLEUSFROM THE NUCLEUS

2382389292UU-------------->>234 234

9090Th +Th +4422He (Alpha)He (Alpha)

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Beta Particle

P

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BETA RADIATIONBETA RADIATION

EMISION OF AN ELECTRON OR A POSITRONEMISION OF AN ELECTRON OR A POSITRON FROM A NUCLEUS FROM A NUCLEUS

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MECHANISUM OF BETA MECHANISUM OF BETA EMISSIONEMISSION

ELECTRON EMISSIONELECTRON EMISSION

0011n n 11

11P + -P + -1100e + ve + v

POSITRON EMISSIONPOSITRON EMISSION

1111P 1 P 1

00n + 0 n + 0

11e + v e + v

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Phosphorous –32 beta spectrum

0.5 1.0 1.50

E = 0.70 MeV

Beta particle energy,MeV

Emax = 1.71 MeV

RELATIVE

NUMBER

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ELECTRON EMISSIONELECTRON EMISSIONAN EXAMPLEAN EXAMPLE

32321515P P 3232

1616S + S + 00-1-1 e + 1.71 MeV e + 1.71 MeV

POSITRON EMISSIONPOSITRON EMISSION AN EXAMPLEAN EXAMPLE

22221111Na Na 2222

1010Ne + Ne + 0011e + ve + v

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ORBITAL ELECTRON CAPTUREORBITAL ELECTRON CAPTURE

INSTEAD OF CONVERTING A PROTON TO A INSTEAD OF CONVERTING A PROTON TO A NEUTRON AND A POSITRON,IN SOME NEUTRON AND A POSITRON,IN SOME RADIOACTIVE TRANSFORMATION ONE OF RADIOACTIVE TRANSFORMATION ONE OF THE EXTRA- NUCLEAR ELECTRON IS THE EXTRA- NUCLEAR ELECTRON IS CAPTURED BY THE NUCLEUS, AND UNITS CAPTURED BY THE NUCLEUS, AND UNITS WITH AN INTRA-NUCLEAR PROTRON TO WITH AN INTRA-NUCLEAR PROTRON TO FORM A NEUTRON ACCORDING TO THE FORM A NEUTRON ACCORDING TO THE FOLLOWING EQUATIONFOLLOWING EQUATION

00

-1-1 e + e + 1111 H H 11

00 n +v n +v

ORBITAL ELECTRON CAPTURE

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Gamma Rays

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22Na

Ec 10.2% e + 89.8% , 0.544 MeV

Gamma , 1.277 MeV

22 Ne

Sodium-22 decay scheme

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Neutrons

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NEUTRON RADIATIONNEUTRON RADIATION CAN MAKE THE MATERIAL THROUGH CAN MAKE THE MATERIAL THROUGH

WHICH THEY PASS RADIOACTIVE BY BEING WHICH THEY PASS RADIOACTIVE BY BEING ABSORBED BY NUCLEI ( THIS PROCESS IS ABSORBED BY NUCLEI ( THIS PROCESS IS CALLED NEUTRON ACTIVATION)CALLED NEUTRON ACTIVATION)

HAS NO CHARGEHAS NO CHARGE CAN CAUSE SIGNIFICANT CELL DAMAGE BY CAN CAUSE SIGNIFICANT CELL DAMAGE BY

INDIRECT IONISATION AND OTHER INDIRECT IONISATION AND OTHER PROCESSES PROCESSES

CAN CAUSE FISSION IN HEAVY ISOTOPES CAN CAUSE FISSION IN HEAVY ISOTOPES SUCH AS SUCH AS 235235U OR U OR 239239Pu Pu

X-ray productionX-ray production

BremsstrahlungBremsstrahlung

Photon

Electron

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ShieldingShielding………………

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ALPHA RADIATION is stopped by your skin;

it is only a hazard when inside your body

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BETA RADIATION can penetrate the skin;

therefore, it can be a skin or eye hazard

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X- and GAMMA RADIATION can penetrate into

your body delivering a deep dose

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NEUTRONS are very penetrating;

therefore, they can affect all organs