ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS

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ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS
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Historical background
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Humans have evolved in an environment of ionizing
radiation
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Discovery of X rays (1895)
Wilhelm Conrad Roentgen
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Discovery of uraniums natural radioactivity
(1896)

Antoine Henri Becquerel
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Discovery of polonium and radium (1898)

Marie Curie
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Discovery of harmful effects of ionizing radiation

• First report about local radiation injuries
  (1896) and radiation-induced skin cancer (1902)
• First report about radiation-induced sterility
  (1903) and radiation-induced leukemia (1911)

• 1920s bone cancer among radium dial painters
• 1930s liver cancer and leukemia due to
  Throtrast administration
• 1940s excess leukemia among first radiologists

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Discovery of A-bombs effect in Japan (1945)
Hiroshima, 6.08.1945 Nagasaki, 9.08.1945
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Discovery of radiation accidents consequences
Chernobyl, USSR (1986)
Coiania, Brazil (1987)
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After September 11th, growing apprehension that
by shrouding a core of conventional explosives
around a radioactive source.
Terrorist can use of radioactive material
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..contamination could be spread over a wide area


and terror created!!
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What is radiation?
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Origin of ionizing radiation
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Ionizing radiation
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Origin of radiation is from atom anatomy
Proton
Neutron
Electron
Nucleons
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Atomic symbols
MASS NUMBER (the number of protons and
neutrons)
A
XN
SYMBOL OF ELEMENT
Z
The number of neutrons
ATOMIC NUMBER (the number of protons)
Example
131
53I78
131I or I-131
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Isotopes
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Why are some nuclides radioactive?
The stable isotopes of elements have very
definite ratios of neutrons to protons in their
nuclei. As the atomic mass number increases,
the ratio of neutrons to protons increases
according to a definite pattern. If isotopes vary
from this pattern, they are relatively unstable.
The most stable state of a nucleus is called
the ground state. In an unstable nucleus the
nucleons are in an exited state and must
release energy to reach the ground state. In
the transformation of an unstable nucleus to a
more stable nucleus, energy is emitted in the
form of particles such as alpha and beta
particles, and in some cases photons (gamma
rays). This is the process of radioactive decay.
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Alpha (a) decay
AZX A-4Z-2Y 42He e.g. 23892U
23490Th 42He
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Beta (?-) decay

• n p e- ?
• AZX?AZ1 Y e- ? e.g. 13153 I ? 13154
  Xee-?

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Positron (?) decay
p n e ? AZX?AZ-1 Ye ?
e.g. 189 F? 188Oe?
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Electron capture
p e- ?n ? AZX? AZ-1 Y ? 12553 I ?
12552 Te?
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Gamma (?) emission
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Nuclear energy levelsgamma radiation
SIMPLIFIED NUCLEAR MODEL
Gamma ray
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Activity

Radioactivity is the number of decaying nuclei
per unit of time The System International (SI)
unit of radioactivity is the Becquerel (Bq) 1 Bq
one disintegration per second Non-SI unit of
radioactivity is the Curie (Ci) 1 Ci 3,7 x 1010
radioactive disintegration per second 1 Bq 2.7
x 10-11 Ci 1 Ci 3.7 x 1010 Bq
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Time of half-life

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Electric generators of ionizing radiation

• Ionizing radiation can also be obtained by
  subjecting matter to a sufficient amount of
  energy. This is the principle of X-ray generators
  and particle accelerators
• X-rays can have two sources
• electron rearrangement their energy is then
  specific to the element considered but not to the
  isotope
• the phenomenon of incident electron retardation
  (Bremsstrahlung effect) their energy is non
  specific and varies between zero and the maximum
  energy as a direct function of the initial energy
  of the electron.

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Comparison of the risks from radioactive sources
and electric generators

• The emission of ionizing radiation by a
  radioactive source behaves a law of decay
  governing the time in which work can be done
• Electric generators obey an On/Off effect which
  is tied to the presence or absence of the
  electricity supply

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Forms of ionizing radiation and its abilities
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Excitation of atom or molecules by ionizing
radiation
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Ionization of atom or moleculesby ionizing
radiation
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Forms of ionizing radiation
Particulate radiation
Directly ionizing
consisting of atomic or subatomic particles
(electrons, protons, etc.) which carry energy in
the form of kinetic energy of mass in motion
Indirectly ionizing
Electromagnetic radiation
in which energy is carried by oscillating
electrical and magnetic fields traveling through
space at speed of light
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Specific ionization andlinear energy transfer
(LET)
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Penetrating power of radiation
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Alpha particle interaction
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Interaction of alpha radiation with living
matter external deposition

• Alpha radiation is not external hazard
• The maximum range in tissue is lt 0.1 mm
• All alpha radiation is absorbed in stratum
  corneum

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Interaction of alpha radiation with living
matter internal deposition
Prime danger is inhalation and ingestion of alpha
emitter
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Beta interaction with matter
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Interaction of beta radiation with living matter
Cell nucleus
Cell diameter
100 cell diameter
alpha
1.7 MeV beta
0.15 MeV beta
beta
5.3 MeV alpha
Auger
I I I I
I i
0.001 0.01 0.1 1
10 100
mm
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Interaction of beta radiation with living matter
external and internal deposition

• Beta radiation damages epithelial basal stratum.
  High energy ß-radiation may affect vascular layer
  of derma, with lesion like thermal burn
• Danger is inhalation and ingestion of beta
  emitter
• Danger is external ß-irradiation whole body

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Neutron interaction
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Interaction of neutron radiation with living
matter
Neutron radiation is only external hazard high
danger of external irradiation whole body
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Interaction of gamma radiation with matter
In terms of ionization, gamma radiation interacts
with matter in three main ways 1. Photoelectric
effect 2. Compton scattering 3. Pair production
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Gamma interaction by photoelectric effect
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Gamma interaction by Compton scattering
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Pair production
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Difference between X-rays and gamma rays
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Interaction of gamma radiation with living
matter external and internal deposition

• Gamma radiation is very external hazard
• - high danger of external irradiation whole body
• - danger of external irradiation of skin
• Danger is inhalation and ingestion of gamma
  emitter

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Risk due to radiation exposure
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Summary of lecture

• Ionizing radiation is radiation with enough
  energy so that during an interaction with an
  atom, it can remove tightly bound electrons from
  their orbits, causing the atom to become
  excitated or ionized.
• Ionizing radiation occurs in two forms
  particles or waves.
• Alpha particles is not external hazard and can
  bee shielded against by clothing. Internal
  deposition of alpha particles is of importance on
  a long-term basis in terms of causing radiation
  injury.
• Beta irradiation causes damage to the epithelial
  basal stratum. The lesion is similar to a
  superficial thermal burn. Beta particles
  shielding requires solid materials, like a wall.
• Gamma and neutron radiation are the most
  biologically active, and required lead equivalent
  shielding for protection.
• Fission products are the major radiation hazard,
  because a large number emit penetrating gamma
  radiation. This can result in whole body
  injuries, even at great distance.

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Lecture is ended
THANKS FOR ATTENTION
In lecture materials of the International Atomic
Energy Agency (IAEA), kindly given by doctor
Elena Buglova, were used