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ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS

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ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS Historical background Humans have evolved in an environment of ionizing radiation Discovery of X rays (1895) Discovery ... – PowerPoint PPT presentation

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Title: ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS


1
ORIGIN OF IONIZING RADIATION AND RADIONUCLIDS
2
Historical background
3
Humans have evolved in an environment of ionizing
radiation
4
Discovery of X rays (1895)
Wilhelm Conrad Roentgen
5
Discovery of uraniums natural radioactivity
(1896)

Antoine Henri Becquerel
6
Discovery of polonium and radium (1898)

Marie Curie
7
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

8
Discovery of A-bombs effect in Japan (1945)
Hiroshima, 6.08.1945 Nagasaki, 9.08.1945
9
Discovery of radiation accidents consequences
Chernobyl, USSR (1986)
Coiania, Brazil (1987)
10
After September 11th, growing apprehension that
by shrouding a core of conventional explosives
around a radioactive source.
Terrorist can use of radioactive material
11
..contamination could be spread over a wide area


and terror created!!
12
What is radiation?
13
Origin of ionizing radiation
14
Ionizing radiation
15
Origin of radiation is from atom anatomy
Proton
Neutron
Electron
Nucleons
16
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
17
Isotopes
18
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.
19
Alpha (a) decay
AZX A-4Z-2Y 42He e.g. 23892U
23490Th 42He
20
Beta (?-) decay
  • n p e- ?
  • AZX?AZ1 Y e- ? e.g. 13153 I ? 13154
    Xee-?

21
Positron (?) decay
p n e ? AZX?AZ-1 Ye ?
e.g. 189 F? 188Oe?
22
Electron capture
p e- ?n ? AZX? AZ-1 Y ? 12553 I ?
12552 Te?
23
Gamma (?) emission
24
Nuclear energy levelsgamma radiation
SIMPLIFIED NUCLEAR MODEL
Gamma ray
25
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
26
Time of half-life

27
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.

28
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

29
Forms of ionizing radiation and its abilities
30
Excitation of atom or molecules by ionizing
radiation
31
Ionization of atom or moleculesby ionizing
radiation
32
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
33
Specific ionization andlinear energy transfer
(LET)
34
Penetrating power of radiation
35
Alpha particle interaction
36
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

37
Interaction of alpha radiation with living
matter internal deposition
Prime danger is inhalation and ingestion of alpha
emitter
38
Beta interaction with matter
39
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
40
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

41
Neutron interaction
42
Interaction of neutron radiation with living
matter
Neutron radiation is only external hazard high
danger of external irradiation whole body
43
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
44
Gamma interaction by photoelectric effect
45
Gamma interaction by Compton scattering
46
Pair production
47
Difference between X-rays and gamma rays
48
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

49
Risk due to radiation exposure
50
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.

51
Lecture is ended
THANKS FOR ATTENTION
In lecture materials of the International Atomic
Energy Agency (IAEA), kindly given by doctor
Elena Buglova, were used
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