Download Radio Isotopes - Radio Immuno Assay

RADIO ISOTOPES
Radionuclide or Radioisotopes
 Isotopes - Atoms with same number of protons but
a different number of neutrons in the nucleus
 An additional neutron or two may upset the
binding energy and cause the atom to become
unstable.
 In an unstable atom, the nucleus changes by giving
off a neutron to get back to a balanced state.
 As the unstable nucleus changes, it gives off
radiation and is said to be radioactive.
 Radioisotopes are isotopes that are unstable and
release radiation.
All isotopes are not radioisotopes.
ISOTOPES
Transmutation
 All elements with atomic numbers > 83 are radioisotopes
 Elements with atomic numbers < 83, have isotopes and
most have at least one radioisotope.
 As a radioisotope tries to stabilize, it may transform into a new
element in a process called transmutation.
 Nucleus of radioisotopes is characterized by excess
energy which is available to be imparted either to a
newly-created radiation particle within the nucleus, or
else to an atomic electron (internal conversion).
 Radioisotope thus undergoes radioactive decay, and
emits a gamma rays (s) and/or subatomic particles.
particles constitute ionizing radiation.
These
Radioisotopes occur naturally, and can also be artificially produced.
Radioactive decay
Alpha particles result from
the decay of relatively heavy
radioisotopes.
•
They consist of two neutrons
and two protons, bound
together.
Americium 241 (Am-241) is
a example, commonly found
in household smoke
detectors.
In beta decay, a neutron
converts to a proton emitting
a beta particle in the
process.
Beta particle is identical to an
ordinary electron.
Carbon-14 (C-14) is a
radioisotope of carbon, which
undergoes beta decay and is
used to establish the age of
ancient artifacts ("carbon
dating").
Gamma rays are emitted if a nucleus
still has excess energy following
decay and the emission of other
particles.
They are electromagnetic in nature
(called photons), with a discrete,
unique energy
This is used to identify different
radioisotopes.
Gamma rays are not physical
particles, but their interactions with
matter are described by assigning
them particle-like properties.
Naturally occurring radionuclides
 Primordial radionuclides:
Originate mainly from the interiors of stars.
Their half-lives are so long - not yet decayed.
 Secondary radionuclides:
Radiogenic isotopes derived from the decay of
primordial radionuclides.
Shorter half-lives than primordial radionuclides.
 Cosmogenic radionuclides:
Carbon-14 - continually formed in the atmosphere due
to cosmic rays.
Artificially produced radionuclides
Nuclear reactors:
• Produced with nuclear reactors.
• Neutrons activate elements placed within the reactor.
• Eg. Thallium-201 and iridium-192
Particle accelerators:
• Cyclotrons accelerate protons at a target to produce
positron emitting radioisotopes e.g. fluorine-18.
Radionuclide generators:
• Contain a parent isotope that decays to produce a
radioisotope.
• Parent is produced in a nuclear reactor – molybdenum99.
Nuclear explosions:
• Produced as an unavoidable side effect of nuclear and
thermonuclear explosions.
Uses
For their chemical properties
• Carbon can serve as tracers because they are
chemically very similar to the non-radioactive
nuclides.
• Result examined with a radiation detector, such
as a Geiger counter
• For example, one might culture plants in an
environment in which the carbon dioxide
contained radioactive carbon; then the parts of
the plant that had laid down atmospheric carbon
would be radioactive.
2. As sources of radiation:
• Used for diagnosis, treatment, and research.
• Radioactive chemical tracers emitting
gamma rays or positrons can provide
diagnostic information about a person's
internal anatomy and the functioning of
specific organs.
• This is used in some forms of tomography:
single photon emission computed
tomography and positron emission
tomography scanning.
• Medicines - promising method of treatment in hemopoietic
forms of tumors. Gamma sources sterilize syringes and other
medical equipment.
• In biochemistry and genetics, radionuclides label molecules
allow tracing chemical and physiological processes occurring
in living organisms, such as DNA replication or amino acid
transport.
• In food preservation, radiation is used to stop the sprouting of
root crops after harvesting, to kill parasites and pests, and to
control the ripening of stored fruit and vegetables.
• In agriculture and animal husbandry, radionuclides produce
high quality crops, disease and weather resistant varieties of
crops, to study how fertilisers and insecticides work, and to
improve the production and health of domestic animals.
• In industry and mining, radionuclides examine welds,
to detect leaks, to study the rate of wear, erosion and
corrosion of metals, and for on-stream analysis of a
wide range of minerals and fuels.
• Most household smoke detectors contain the
radionuclide americium formed in nuclear reactors,
saving many lives.
• Radionuclides trace and analyze pollutants, to study
the movement of surface water, and to measure
water runoffs from rain and snow, as well as the flow
rates of streams and rivers.
• Natural radionuclides are used in geology,
archeology, and paleontology to measure ages of
rocks, minerals, and fossil materials.
Dangers
• If radionuclides are released into the environment,
through accident, poor disposal, or other means, they
can potentially cause harmful effects of radioactive
contamination.
• They can also cause damage if they are excessively
used during treatment or in other ways applied to living
beings. This is called radiation poisoning.
• Radionuclides can also cause malfunction of some
electrical devices.