Chapter 10
Section 10.1
Atomic nuclei are unstable and the isotopes that contain them are
radioactive. A radioactive isotope is called a radionuclide.
The picture above is a radionuclide speciation in the environment.
Radioactive decay is the transformation of the nucleus, a decaying
nucleus ejects small particles into space, or it may also emit a powerful radiation
like an X ray called a gamma ray. Transmutation is the conversion of one
isotope into another. A natural radiation is called alpha radiation, which
consists of a stream of particles called alpha particles that move with a velocity
about one-tenth of the speed of light.
The following is a picture of cosmic rays:
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Beta radiation is also a natural radiation that consists of particles called
beta particles, which are actually electrons.
The beta particles are produced in the nucleus and then emitted, they can
penetrate matter, including air, more easily than alpha particles. Gamma
radiation is the energy lost by the nucleus usually carried away by the moving
particles, like in X rays or ultraviolet rays, but with more energy.
Nuclear equations are different than chemical equations in the sense that
nuclear equations describe the changes is atomic numbers, mass numbers, and
identities of radionuclides.
Half-life is used to describe the differences between the more stable and the not
so stable radinuclides.
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There are three series still active in nature, called radioactive
disintegration series, and uranium-238 is head of one.
Section 10.2
There are two undesired effects of radiation and they are: acute and
latent. Acute effects show up fast and can be in the form of burns or radiation
sickness. Latent effects are effects that show up in time such as cancer,
especially leukemia, another example is the alteration of a gene. Cells do not
have the capacity for self-repair of radiation damage.
Atomic radiation is very dangerous because they generate unstable
reactive particles in living tissue. Alpha particles as well as beta particles, and
also X rays are called ionization radiations.
Any particle with an unpaired electron is called a radical, and they are
very reactive species. Ions and radicals react with stable substances around
them, altering them in ways to foreign metabolism. When this chemical reaction
happens in the genes and chromosomes, the cell’s genetic substances can lead
to cancer, tumor growth, or genetic mutation.
The first symptoms of radiation exposure usually happen in tissues whose
cells divide most frequently, like the cells in the bone marrow, or intestinal tract.
Radiation sickness, is the set of symptoms caused by non-lethal exposures to
radiation.
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The inverse-square law is the intensity of radiation inversely proportional
to the square of the distance from the source.
Radiation intensity, I** 1
d2
This law is strictly true only in a vacuum but is closely enough when the
condition is air to make good estimates. If we want to compare one location to
another we can use the following equation:
Background radiation, is the radiation given off by naturally occurring
radionuclides, by radioactive pollutants, cosmic rays, and medical X rays, and we
are always exposed to them.
Section 10.3
The becquerel, Bq, is the SI unit of activity and is used to describe how
active a sample is.
1 Bq = 1dps
One curie, Ci, is equal to 3.7 X 1010 dps, the number of radioactive
disintegrations that occur per second in a 1.0-g sample of radium.
1 Ci = 3.7 X 1010 dps = 3.7 X 1010 Bq
The roetgen is the older unit of X ray or gamma ray exposure, it serves to
figure out how intense the exposure to X-ray or gamma-ray is. The SI unit for
absorbed dose is the gray and it helps determine how much energy is absorbed
by a unit mass of tissue or other materials.
1 Gy = 1 J/kg
The rad is 1/100th of a gray:
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1 rad = 10-2 Gy
The sievert, Sv, is the SI unit that expresses dose equivalent that is
additive for different kinds of radiation and different target tissues.
H = DQN
The absorbed dose is multiplied by factor Q and by any other factor N
bearing on the net effect.
The electron-volt, eV, describes the energy of X rays or gamma rays.
1 eV = 1.602 X 10-19 J
A dosimeter is a device for measuring exposure, a common type is a film
badge that contains photographic film, and becomes fogged by radiation.
Section 10.5
X rays, gamma rays, and particle beams have been used in medicine for
diagnosis and for cancer treatment. A beam of 100 kilorads kills any insects that
remain after harvest and inhibits the sprouting of potatoes and onions during
storage. A medium dosage bean of radiation is 100 to 1000 kilorads can actually
reduce the populations of Salmonella bacteria in fish and other meats. High
dosage beams are 1000 to 10,000 kilorads sterilize poultry, fish and other meats.
Ionization radiation causes chemical reactions in foods or any insects or
microorganisms in them. When the primary products of irradiation react with
food molecules to give secondary substances is called radiolytic products.
Section 10.6
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Ionizing radiation has been used for diagnostic or therapeutic or
therapeutic medical uses. Radiation is used to locate a cancer or tumor or to
assess the function of some organ, like the thyroid gland. Exposing someone to
radiation includes some risks. To minimize these risks, the radiologist uses
radionuclides that have the following properties.
1) The radionuclide has to have a half-life that is short.
2) The product of the decay of the radionuclide should have little if any radiation
of its own.
3) The half-life of it should be long enough for it to be prepared and administered
to the patient before it all decays.
4) This is to be used for diagnosis, it should decay by penetrating radiation
entirely, which means gamma radiation.
5) In therapy as in cancer therapy, nonpenetrating radiation is preferred because
a radionuclide well placed in cancerous tissue should cause damage to such
issues.
6) The diseased tissue should concentrate the radionuclide, giving a “hot spot”
where the diseased area exists.
Section 10.7
Electrical power plants use the heat from the burning of some kind of fuel
to convert water into high-pressure steam, fission is the source of heat, and it
happens to a nuclear fuel inside a reactor. The disintegration of a large atomic
nucleus into small fragments following neutron capture is Fission.
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**Fission is the splitting of atoms into smaller pieces, caused by neutrons hitting
each other. These smaller pieces strike other atoms, releasing energy. When this
process continues, it is called a chain reaction.
A nuclear chain reaction is the mechanism of nuclear fission by which one
fission event makes enough fission neutrons to cause more than one additional
fission.
A nuclear reactor is a device to enable the control of nuclear fission at
the critical ratio so that heat generated is removed rapidly enough to prevent a
meltdown (Holum, 316). In a water reactor the water is kept under pressure so
that it can be heated above its normal boiling point.
One of the biggest problems of nuclear energy has been the permanent
storage of radioactive wastes. Power plants that use petroleum or coal are huge
emitters of carbon dioxide, a greenhouse gas.
Some options are the use of wind energy, solar energy, and other technologies.
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Bibliography
WWW.Google.images.com
Holum, John R. Fundamentals Of General, Organic, And Biological Chemistry.
Sixth Edition. Canada: John Wiley & Sons, INC., 1998
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