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RADIOACTIVITY

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RADIOACTIVITY NUCLEAR MEDICINE NUCLEAR ENERGY FISSION Splitting the Uranium Atom: Uranium is the principle element used in nuclear reactors and in certain types of ... – PowerPoint PPT presentation

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Title: RADIOACTIVITY


1
RADIOACTIVITY
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RADIOACTIVITY ?
The atoms making up matter are generally stable,
but some of them are spontaneously transformed by
emitting radiations which release energy. This is
called radioactivity.
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There are three types of radiations corresponding
to three types of radioactivity. alpha
radioactivity corresponds to the emission of a
helium nucleus, a particularly stable structure
consisting of two protons and two neutrons,
called an a particle. beta radioactivity
corresponds to the transformation, in the
nucleus - either of a neutron into a proton,
beta- radioactivity, characterised by the
emission of an electron e- - or of a proton into
a neutron, beta radioactivity, characterised by
the emission of an anti-electron or positron e.
It only appears in artificial radioactive nuclei
produced by nuclear reactions. gamma
radioactivity, unlike the other two, is not
related to a transmutation of the nucleus. It
results in the emission, by the nucleus, of an
electromagnetic radiation, like visible light or
X-rays, but more energetic. gamma radioactivity
can occur by itself or together with alpha or
beta radioactivity
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When we talk about the alpha decay then it means
that a twice positive charged heliumion (helium
atomic nucleus) is emited from the atomic
nucleus. Then we find two protons ans two
neutrons less in this atomic nucleus, so it is
lighter. The alpha radiation is the most
dangerous of the three types of radiation, but a
sheet of paper is enough to protect oneself. The
skin protects us also from alpha radiation
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There are two types of the beta decay. The one is
the beta minus decay and the other is the beta
plus decay. When we talk about the beta minus
decay a neutron decays into a proton, an electron
and an antineutrino. The electron and the
antineutrino are emited. The radioactive particle
is the electron. The number of nucleons do not
change, but we have got one proton more than
before the decay. 2 or 3 cm of wood are enough to
protect oneself.
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When we talk about the beta plus decay a proton
decays into a neutron, a positron (the
antiparticle of the electron) and a neutrino. The
positron and the neutrino are emited. The
radioactive particle is the positron
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When we talk about the gamma decay high-energy
electromagnetic waves are emited from the atomic
nucleus. This waves are photons, which have got a
higher frequency and less wave long than light. A
gamma decay can happen after an alpha decay or a
beta decay, because the atomic nucleus is very
energitic.
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X-rays come from
ELECTRON CLOUD
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DIFFERENCE BETWEEN X-RAYS GAMMA RAYS
ORIGIN!!!
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RADIATION ITS ORIGIN
RADIATION TYPE
ORIGIN
  • ALPHA
  • BETA-
  • BETA
  • GAMMA
  • X-RAYS
  • NUCLEUS
  • NUCLEUS
  • NUCLEUS
  • NUCLEUS
  • ELECTRON CLOUD
  • (SPACE CHARGE)

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RADIATION AND ITS CHARGE
--
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RADIATION AND ITS CHARGE
  • ALPHA
  • BETA
  • BETA
  • GAMMA
  • X-RAYS
  • 2
  • -1
  • 1
  • 0
  • 0

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RADIATION PENETRATION
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                                                 A
lpha particles can usually be stopped by a very
thin barrier. Radioisotopes emitting alpha
particles are usually not hazardous outside the
body, but they can cause damage if
ingested. Betas (streams of electrons) can pass
through a hand, but are usually stopped by a
modest barrier such as a few millimeters of
aluminum, or even a layer of clothing. As with
alphas, beta particles are more hazardous if
inhaled or ingested. Gammas can be very
penetrating and can pass through thick barriers.
Several feet of concrete would be needed to stop
some of the more energetic gammas. A natural
gamma source found in the environment (and in the
human body) is 40K, an isotope of
potassium. Neutrons are also very penetrating.
Some elements, like hydrogen, capture and scatter
neutrons. Water is commonly used as a neutron
radiation shield.
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HALF-LIFE
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DECAY CHAIN
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HALF-LIFE AND RADIOACTIVITY REMAINING
HALF-LIFE
RADIOACTIVITY REMAINING
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 50
  • 25
  • 12.5
  • 6.25
  • 3.12
  • 1.56
  • 0.78

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USES FOR RADIOACTIVITY
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CARBON DATING
The rate at which 14C decays is absolutely
constant. Given any set of 14C atoms, half of
them will decay in 5730 years. Since this rate is
slow relative to the movement of carbon through
food chains (from plants to animals to bacteria)
all carbon in biomass at earth's surface contains
atmospheric levels of 14C. However, as soon as
any carbon drops out of the cycle of biological
processes - for example, through burial in mud or
soil - the abundance of 14C begins to decline.
After 5730 years only half remains. After another
5730 years only a quarter remains. This process,
which continues until no 14C remains, is the
basis of carbon dating
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NUCLEAR MEDICINE
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NUCLEAR ENERGY FISSION
Splitting the Uranium Atom Uranium is the
principle element used in nuclear reactors and in
certain types of atomic bombs. The specific
isotope used is 235U. When a stray neutron
strikes a 235U nucleus, it is at first absorbed
into it. This creates 236U. 236U is unstable and
this causes the atom to fission
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CHAIN REACTION
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NUCLEAR-ENERGY POWER PLANTS
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In a nuclear reactor, however, the last thing you
(and the rest of the world) want is all your
atoms splitting at once. But the reactor core
needs to be slightly supercritical so that plant
operators can raise and lower the temperature of
the reactor. The control rods give the operators
a way to absorb free neutrons so operators can
maintain the reactor at a critical level.To turn
nuclear fission into electrical energy, the first
step for nuclear power plant operators is to be
able to control the energy given off by the
enriched uranium and allow it to heat water into
steam
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