Transcript Nuclear Radiation

Nuclear Radiation
By: Abijith Singh
Brian Carrion
Sikender Shahid
Qaim Ali
Tony Lawrence
What is Radioactivity?
• Radioactivity is a process in which
unstable atomic nuclei become more
stable by spontaneously emitting
highly energetic particles and or
energy.
http://10.200.10.53/videos/25514/sec18850_700k.asf
Discovery
• Roentgen “photographed” his wife’s hand using cathode
rays. He discovered x-rays, a form of radiation.
• Becquerel discovered that uranium crystals left in sealed
cabinets emitted their own energy, discovering natural
radioactivity.
• Marie Curie and her husband Pierre measured the ability
of emanations from various elements. They introduced
“radio-active” when they realized that a pitchblende
uranium formed 300 times current stronger than pure
uranium.
Radioactive Decay
Radioactive decay occurs when the nucleus is not
stable. This process does not require energy and the
reaction is spontaneous. It involves the spontaneous
transformation of one element into another.
For example..
Alpha Decay
• Alpha decay is a type of radioactive decay in
which an atomic nucleus emits an alpha particle
and transforms into an atom
• Alpha decay occurs because the nucleus has
too many protons which cause excessive
repulsion. In an attempt to reduce the repulsion,
a Helium nucleus is emitted.
Beta Decay
• A beta particle is an electron. It emerges from a weak decay
process in which one of the neutrons inside an atom decays to
produce a proton, the beta electron and an anti-electron-type
neutrino. Some nuclei instead undergo beta plus decay, in
which a proton decays to become a neutron plus a positron and
an electron-type neutrino.
http://library.thinkquest.org/C0126323/beta_decay.htm
Gamma Decay
• Gamma decay is one of the three radioactive
decay modes available to atomic nuclei.
• The nucleus in an excited energy state decays
to a lower-energy state by emitting a highenergy photon.
• The decay process is very similar to the
absorption and emission of light by atoms in the
ultraviolet, visible, and infrared spectrums.
Radioactive Elements
• Elements which either have no stable
isotopes or have at least one naturally
occurring isotope, are radioactive.
• http://www.theodoregray.com/PeriodicTabl
e/Elements/Radioactives.html
Smoke Detector
• The particles generated by americium are able
to ionize the oxygen and nitrogen atoms of the
air in the chamber.
• After ionizing an electron, you end up with a free
electron and an atom missing one electron.
• The electronics in the smoke detector sense the
amount of electrical current that these electrons
and ions moving toward the plates represent.
• When smoke enters the ionization chamber, it
disrupts this current. The smoke detector senses
the drop and sets off the horn.
Radiation Units
• The basic unit of radiation dose used to be the ``rad,'' defined in terms of
the energy deposited by ionizing radiation per unit mass of exposed matter
(e.g. flesh or bone):
• The RBEs of -rays, X-rays and -rays (fast electrons) are all 1 by definition;
thermal neutrons have an average RBE of 3; fast neutrons, protons and rays (4He nuclei) all have RBEs of 10; and fast heavy ions have an RBE of
20.9 A new unit was then constructed by combining the RBE with the
dosage in rads, namely the rem (rntgen equivalent to man), defined by
• The ``R'' in the preceding paragraph stands for rem and the ``mR'' for
millirem - one thousandth of a rem. Today the standard international unit
for measuring ``effective dosage'' is the seivert. Converting between rem
and seivert is just like converting between rad and gray:
Radiation Exposure
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Nuclear fallout of an atomic weapon
Exposure in a nuclear power plant
Cosmic and Ground Radiation
House construction material
Medical and dental X-rays
Radiation Effects
• Less than a 100 REM: temporary
impairment of immune system
• 100-150 REM: mild “radiation sickness”;
bone growth…
• 150-650 REM: “radiation sickness”; …
• 650-8000 REM: delayed death in a week
• Above 8000 REM: death immediately or
in a day
Geiger Counter
• Geiger counters are devices that detect
radioactivity
• The Geiger Counter contains gas which is
around a high-voltage electrode.
• When a particle or wave strikes one of the
gas molecules, it triggers an avalanche
effect that causes all the gas to ionize and
to conduct electrical current.
Use of Geiger Counters
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Everyday Uses
Medicine
Astronomy
Geology
Half-life
Half-life: length of time during which half of a given number of atoms of
a radioactive nuclide decays.
Half Life Equation
Example
• If you originally had 157 grams of carbon14 and the half-life of carbon-14 is 5730
years, how much would there be after
2000 years?
The answer is that there would be 123 grams left.
Overall
• Nuclear radiation is basically radioactivity
which is a process in which unstable
atomic nuclei become more stable by
spontaneously emitting highly
energetic particles and or energy.
Exposure to much radiation can result
tin death.