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Advantages of gamma radiation in science and industry
Askari. Mohammadbagher: Dept.of Physics Azad University,North branch Tehran,Tehran,Iran
[email protected]
Tell:+989131990432
Abstract
Gamma radiation is one of the three types of natural radioactivity. Gamma rays are
electromagnetic radiation, like X-rays. The other two types of natural radioactivity are alpha
and beta radiation, which are in the form of particles. Gamma rays are the most energetic
form of electromagnetic radiation, with a very short wavelength of less than one-tenth of a
nanometer. Gamma radiation is the product of radioactive atoms. Depending upon the ratio of
neutrons to protons within its nucleus, an isotope of a particular element may be stable or
unstable. When the binding energy is not strong enough to hold the nucleus of an atom
together, the atom is said to be unstable. Atoms with unstable nuclei are constantly changing
as a result of the imbalance of energy within the nucleus. Over time, the nuclei of unstable
isotopes spontaneously disintegrate, or transform, in a process known as radioactive decay.
Various types of penetrating radiation may be emitted from the nucleus and/or its
surrounding electrons. Nuclides which undergo radioactive decay are called radionuclide's.
Any material which contains measurable amounts of one or more radionuclides is a
radioactive material. Gamma radiation a nucleus which is in an excited state may emit one or
more photons (packets of electromagnetic radiation) of discrete energies. The emission of
gamma rays does not alter the number of protons or neutrons in the nucleus but instead has
the effect of moving the nucleus from a higher to a lower energy state (unstable to stable).
Gamma ray emission frequently follows beta decay, alpha decay, and other nuclear decay
processes. In this article Our purpose is to investigate gamma-ray applications in science and
industry.
Figure 1 (chemistry.tutorvista.com)
Key words: Gamma ray, Medical science, food science, Agricultural, Genetics, cosmology,
ancient monuments
Introduction
The term gamma ray was coined by British physicist Ernest Rutherford in 1903 following
early studies of the emissions of radioactive nuclei. Just as atoms have discrete energy levels
associated with different configurations of the orbiting electrons, atomic nuclei have energy
level structures determined by the configurations of the protons and neutrons that constitute
the nuclei. While energy differences between atomic energy levels are typically in the 1- to
10-eV range, energy differences in nuclei usually fall in the 1-keV (thousand electron volts)
to 10-MeV (million electron volts) range. When a nucleus makes a transition from a highenergy level to a lower-energy level, a photon is emitted to carry off the excess energy;
nuclear energy-level differences correspond to photon wavelengths in the gamma-ray region.
When an unstable atomic nucleus decays into a more stable nucleus (see radioactivity), the
“daughter” nucleus is sometimes produced in an excited state. The subsequent relaxation of
the daughter nucleus to a lower-energy state results in the emission of a gamma-ray photon.
Gamma-ray spectroscopy, involving the precise measurement of gamma-ray photon energies
emitted by different nuclei, can establish nuclear energy-level structures and allows for the
identification of trace radioactive elements through their gamma-ray emissions. Gamma rays
are also produced in the important process of pair annihilation, in which an electron and its
antiparticle, a positron, vanish and two photons are created. The photons are emitted in
opposite directions and must each carry 511 keV of energy—the rest mass energy (see
relativistic mass) of the electron and positron. Gamma rays can also be generated in the decay
of some unstable subatomic particles, such as the neutral pion.Gamma-ray photons, like their
X-ray counterparts, are a form of ionizing radiation; when they pass through matter, they
usually deposit their energy by liberating electrons from atoms and molecules. At the lower
energy ranges, a gamma-ray photon is often completely absorbed by an atom and the gamma
rays energy transferred to a single ejected electron (see photoelectric effect). Higher-energy
gamma rays are more likely to scatter from the atomic electrons, depositing a fraction of their
energy in each scattering event (see Compton Effect). Standard methods for the detection of
gamma rays are based on the effects of the liberated atomic electrons in gases, crystals, and
semiconductors (see radiation measurement and scintillation counter).In this article we we
will investigate the use of gamma radiation in Medical Science, food science,Agricultural
Sciences, Genetics, cosmology Science, Conservation of ancient monuments and applications
in industry.
Gamma radiation in medicine:
Gamma rays are electromagnetic radiation like X-rays, but they have higher energy. Gamma
rays are energetic photons or a light wave in the same electromagnetic family as light and xrays, but much more energetic and so, potentially harmful. These waves are generated by
radioactive atoms and by nuclear explosions. Gamma rays can be produced in labs through
the process of nuclear collision and also through the artificial radioactivity that accompanies
these interactions. The high-energy nuclei needed for the collisions are accelerated by devices
such as the cyclotron and synchrotron. By using these accelerators Gamma rays are produced
using Bremsstrahlung process. Gamma-rays can kill living cells, a fact which medicine uses
to its advantage, using gamma-rays to kill cancerous cells. Gamma rays can kill living cells;
they are used to kill cancer cells without having to resort to difficult surgery. This is called
"Radiotherapy" and works because cancer cells can't repair themselves like healthy cells can
when damaged by gamma rays. Getting the dose right is very important. There's also targeted
radiotherapy, where a radioactive substance is used to kill cancer cells - but it's a substance
that'll be taken up by a specific part of the body, so the rest of the body only gets a low dose.
An example would be using radioactive iodine to treat cancer in the thyroid gland.
Radioactivity is particularly damaging to rapidly dividing cells, such as cancer cells. This
also explains why damage is done by radiotherapy to other rapidly dividing cells in the body
such as the stomach lining (hence nausea), hair follicles (hair tends to fall out), and a growing
fetus (not because of mutations, but simply major damage to the baby's rapidly dividing
cells)[1].
Figure 2 (www.nrc.gov)
Doctors can put slightly radioactive substances into a patient's body, then scan the patient to
detect the gamma rays and build up a picture of what's going on inside the patient. This is
very useful because they can see the body processes actually working, rather than just
looking at still pictures. Example:the picture on is a "Scintigram", and shows an asthmatic
person's lungs.
The patient was given a slightly radioactive gas to breathe, and the picture was taken using a
gamma camera to detect the radiation. The colours show the air flow in the lungs.In industry,
radioactive "tracer" substances can be put into pipes and machinery, then we can detect where
the substances go. This is basically the same use as in medicine[2].
Figure 3 (www.darvill.clara.net)
Gamma rays kill microbes, and are used to sterilise food so that it will keep fresh for
longer.This is known as "irradiated" food.Gamma rays are also used to sterilise medical
equipmentGamma rays cause cell damage and can cause a variety of cancers.They cause
mutations in growing tissues, so unborn babies are especially vulnerable [3].
Gamma radiation in food science
Irradiation is a process in which food is exposed to high doses of radiation in the form of
gamma rays, X-rays or electron beams. Irradiation can kill bacteria in food, both good and
bad, but has no effect on the infectious agent that causes mad cow disease, or on viruses,such
as those that cause hepatitis. The long-term health consequences of eating irradiated food are
still unknown. Irradiation creates a complex series of reactions that alter the molecular
structure of food and create known carcinogens, including benzene, and other toxic
chemicals, including toluene. In addition, byproducts of irradiation, called 2-ACBs, which
do not occur naturally in any food, have been linked to tumor growth in rats and genetic
damage in human cells. Animals fed irradiated foods have died prematurely and suffered
mutations, stillbirths, organ damage and nutritional deficiencies. Irradiation can also change
the flavor, odor, texture, color and nutritional content of food. For example, yolks of
irradiated eggs are more watery and have less color and brightness than non-irradiated eggs.
Irradiation also destroys the niacin and vitamins in eggs, including up to 24 percent of
vitamin A, at just one-third the radiation level approved by the FDA. Irradiation is used to
create a false sense of security about food safety [4].
Figure 4 (people.chem.duke.edu)
It is promoted as a solution to the overcrowded and unsanitary conditions on factory farms
that make animals susceptible to disease, and to the filthy conditions in slaughterhouses that
contaminate meat with bacteria. However, since irradiation may not eliminate all bacteria
from foods, and since foods can be contaminated or re-contaminated after having been
irradiated, the process does not totally eliminate the possibility of foodborne illness. That is
why the USDA recommends the same food-handling practices for irradiated foods as for nonirradiated foods. Food is irradiated to extend its shelf life and kill pests like fruit flies. It uses
gamma rays with short wavelengths and high frequencies that penetrate food so rapidly that
little or no heat is produced. Microwaving, which uses longer wavelengths, causes foods to
heat rapidly. Currently, the US Food and Drug Administration has approved irradiation of
foods including meat and poultry, shell eggs, fruits and vegetables, herbs, spices and flour.
However, only a few of these approved foods are actually produced commercially; currently,
irradiated foods are limited to small amounts of ground beef, spices, and some imported fruit
such as papayas. Irradiated foods sold in grocery stores are required to be labeled.
Figure 5 (2012books.lardbucket.org)
Gamma radiation in Agricultural science
There are other existing practices currently being used that do not involve radiation to reduce
pathogens, increase shelf life, eliminate pests, increase juice yield, delay sprouting, and
improve re-hydration. Pathogens in foods could also be reduced by more sanitary and
stronger regulated agricultural practices [5]. However, such practices can only reduce the risk
to a limited degree, whereas processing by ionizing radiation could practically eliminate these
risks [6,7,8]. The United Nations Food and Agricultural Organization (FAO) has passed a
motion to commit member states to implement irradiation technology for their national
phytosanitary programs; the General assembly of the International Atomic Energy Agency
(IAEA) has urged wider use of the irradiation technology. European law dictates that no
foods other than dried aromatic herbs, spices and vegetable seasonings are permitted for the
application of irradiation [9] However, any Member State is permitted to maintain previously
granted clearances, add new clearance as granted in other Member States or add clearances
that the EC's Scientific Committee on Food (SCF) approved. Presently, Belgium, Czech
Republic, France, Italy, Netherlands, Poland, and the United Kingdom) have adopted such
provisions [10] It also states that irradiation shall not be used "as a substitute for hygiene or
health practices or good manufacturing or agricultural practice". These regulations only
govern food irradiation in consumer products to allow irradiation to be used for patients
requiring sterile diets.
Figure 6 (www. scialert.net)
(a) Plantlet ready to be transferred to soil, (b) Young Gerbera plantlets were transferred to
soil, (c) Gerbera plantlet after 8 weeks being transferred to soil and (d) Six- months-old
Gerbera plant successfully acclimatized
Gamma radiation in Genetics
The frequency of revertants induced by 60Co γ rays of the ochre allele, cyc1-9, has been
measured in radiation-sensitive strains carrying one of 19 nonallelic mutations and in wildtype strains. The results indicate that ionizing radiation mutagenesis depends on the activity
of the RAD6 group of genes and that the gene functions employed are very similar, but
probably not identical, to those that mediate UV mutagenesis. Repair activities dependent on
the functions of the RAD50 through RAD57 loci, the major pathway for the repair of damage
caused by ionizing radiation, do not appear to play any part in mutagenesis. A comparison
between the γ-ray data and those obtained previously with UV [11]and chemical mutagens
suggests that the RAD6 "mutagenic pathway" is in fact composed of a set of processes, some
of which are concerned with error-prone, and some with error-free, recovery activities [12].
Exposing plants to radiation is sometimes called radiation breeding and is a sub class of
mutagenic breeding. Radiation breeding was discovered in the 1920s when Lewis Stadler of
the University of Missouri used X-rays on barley seeds. The resulting plants were white,
yellow, pale yellow and some had white stripes [13].
Figure 7 (forum.spore.com)
Gamma radiation in cosmology Science
Gamma rays have the smallest wavelengths and the most energy of any wave in the
electromagnetic spectrum. They are produced by the hottest and most energetic objects in the
universe, such as neutron stars and pulsars, supernova explosions, and regions around black
holes. On Earth, gamma waves are generated by nuclear explosions, lightning, and the less
dramatic activity of radioactive decay. Unlike optical light and x-rays, gamma rays cannot be
captured and reflected by mirrors. Gamma-ray wavelengths are so short that they can pass
through the space within the atoms of a detector. Gamma-ray detectors typically contain
densely packed crystal blocks. As gamma rays pass through, they collide with electrons in the
crystal. This process is called Compton scattering, wherein a gamma ray strikes an electron
and loses energy, similar to what happens when a cue ball strikes an eight ball. These
collisions create charged particles that can be detected by the sensor.
Figure 8 (missionscience.nasa.gov)
If we could see gamma rays, the night sky would look strange and unfamiliar. The familiar
view of constantly shining constellations would be replaced by ever-changing bursts of highenergy gamma radiation that last fractions of a second to minutes, popping like cosmic
flashbulbs, momentarily dominating the gamma-ray sky and then fading.
NASA's Swift satellite recorded the gamma-ray blast caused by a black hole being born 12.8
billion light years away (below). This object is among the most distant objects ever detected.
Scientists can use gamma rays to determine the elements on other planets. The Mercury
Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) Gamma-Ray
Spectrometer (GRS) can measure gamma rays emitted by the nuclei of atoms on planet
Mercury's surface that are struck by cosmic rays. When struck by cosmic rays, chemical
elements in soils and rocks emit uniquely identifiable signatures of energy in the form of
gamma rays. These data can help scientists look for geologically important elements such as
hydrogen, magnesium, silicon, oxygen, iron, titanium, sodium, and calcium.
The gamma-ray spectrometer on NASA's Mars Odyssey Orbiter detects and maps these
signatures, such as this map (below) showing hydrogen concentrations of Martian surface
soils. Gamma rays also stream from stars, supernovas, pulsars, and black hole accretion disks
to wash our sky with gamma-ray light. These gamma-ray streams were imaged using NASA's
Fermi gamma-ray space telescope to map out the Milky Way galaxy by creating a full 360degree view of the galaxy from our perspective here on Earth.
Figure 9 (news.discovery.com)
Gamma-ray bursts are the most energetic and luminous electromagnetic events since the Big
Bang and can release more energy in 10 seconds than our Sun will emit in its entire 10billion-year expected lifetime! Gamma-ray astronomy presents unique opportunities to
explore these exotic objects. By exploring the universe at these high energies, scientists can
search for new physics, testing theories and performing experiments that are not possible in
Earth-bound laboratories.
Gamma radiation in Conservation of ancient monuments
The application of gamma rays in conservation science dates back to the 1960s, when the
radio-resistance of significant mould fungi from goods of cultural value was tested [14].
High-energy electromagnetic radiation is deeply penetrating and biocidal through the
denaturation and cleavage of nucleic acids, which leads to a simultaneous and indiscriminate
devitalisation of all living organisms [15]. Gamma irradiation is successfully used to sterilize
laboratory and hospital utensils and food, but it can have unwanted side effects when applied
in paper conservation where high irradiation doses, which are often required in repeated
doses, can result in cumulative depolymerization of the underlying cellulose in the paper.
Severe aging characteristics, such as lowered folding endurance and tear resistance, increased
yellowing, and general embrittlement, have been reported in paper treated with gamma rays
[16], whereas more recent studies have suggested that the damage in terms of mechanical–
physical properties is not significant [17]. The observed effects of gamma rays on fungi from
paper have confirmed that radiation treatment of books and documents is effective, as there
was no fungal growth detectable in cultivation studies.
Figure 10 (ktork46.blogspot.com)
Radiation can bring about physical and chemical changes in the cells of microorganisms [14].
The use of x-rays, gamma rays and electron beam radiation has been employed to eliminate
microorganisms in mummies; the most famous instance was the treatment of the mummy of
Ramesses II in Grenoble, France
Fungi are among the most degradative organisms inducing biodeterioration of paper-based
items of cultural heritage. Appropriate conservation measures and restoration treatments to
deal with fungal infections include mechanical, chemical, and biological methods, which
entail effects on the paper itself and health hazards for humans. Three different conservation
treatments, namely freeze-drying, gamma rays, and ethylene oxide fumigation, were
compared and monitored to assess their short- (one month, T1) and long-term (one year, T2)
effectiveness to inhibit fungal growth. After the inoculation with fungi possessing cellulose
hydrolysis ability — Chaetomium globosum, Trichoderma viride, and Cladosporium
cladosporioides — as single strains or as a mixture, different quality paper samples were
treated and screened for fungal viability by culture-dependent and -independent techniques.
Results derived from both strategies were contradictory. Both gamma irradiation and EtO
fumigation showed full efficacy as disinfecting agents when evaluated with cultivation
techniques. However, when using molecular analyses, the application of gamma rays showed
a short-term reduction in DNA recovery and DNA fragmentation; the latter phenomenon was
also. When RNA was used as an indicator of long-term fungal viability, differences in the
RNA recovery from samples treated with freeze-drying or gamma rays could be observed in
samples inoculated with the mixed culture.
Unlike its roles in medical sterilization or food disinfestation, gamma irradiation remains far
from the frontline of treatments in the field of book conservation. Although it can be used for
the same purpose—to kill mold and other fungi, as well as bacteria, in damaged documents—
the practice of exposing valued papers to ionizing radiation is recommended only in certain,
desperate circumstances. That said, irradiation is a young, promising, and relatively untested
treatment in the preservation field—and as such is both scorned and lauded Intermittent
studies performed over the past three decades have identified the damage that irradiation can
impart to paper—or, more specifically. Although can be produced using anything from
animal furs to metal, most paper is produced from cellulosic plant fibers,and principally those
obtained from wood pulp, cotton, and linen. During irradiation, free radicals can be unleashed
in the cellulose and quickly react with oxygen to break cellulose molecules and degrade the
paper.
Gamma radiation in industry
Radioisotopes have very useful properties: radioactive emissions are easily detected and can
be tracked until they disappear leaving no trace. Alpha, beta and gamma radiation, like xrays, can penetrate seemingly solid objects, but are gradually absorbed by them. The extent of
penetration depends upon several factors including the energy of the radiation, the mass of
the particle and the density of the solid. These properties lead to many applications for
radioisotopes in the scientific, medical, forensic and industrial fields [18].Many process
industries utilise fixed gauges to monitor and control the flow of materials in pipes,
distillation columns, etc, usually with gamma rays. The height of the coal in a hopper can be
determined by placing high energy gamma sources at various heights along one side with
focusing collimators directing beams across the load. Detectors placed opposite the sources
register the breaking of the beam and hence the level of coal in the hopper. Such level gauges
are among the most common industrial uses of radioisotopes. When the intensity of radiation
from a radioisotope is being reduced by matter in the beam, some radiation is scattered back
towards the radiation source. The amount of 'backscattered' radiation is related to the amount
of material in the beam, and this can be used to measure characteristics of the material. This
principle is used to measure different types of coating thicknesses. Industries utilise
radioactive sources for a wide range of applications. When the radioactive sources used by
industry no longer emit enough penetrating radiation for them to be of use, they are treated as
radioactive waste. Sources used in industry are generally short-lived and any waste generated
can be disposed of in near-surface facilities.
Figure 11 (www.accent.ro)
Gamma rays are used in industry to inspect castings and welds. The gamma rays are passed
through the object being inspected onto photographic film. The image formed on the film can
reveal defects that are invisible to the eye or hidden from direct observation.
Result and Discussion
Gamma ray, electromagnetic radiation of the shortest wavelength and highest energy.Gamma
rays are produced in the disintegration of radioactive atomic nuclei and in the decay of
certain subatomic particles. The commonly accepted definitions of the gamma-ray and X-ray
regions of the electromagnetic spectrum include some wavelength overlap, with gamma-ray
radiation having wavelengths that are generally shorter than a few tenths of an angstrom
(10−10 metre) and gamma-ray photons having energies that are greater than tens of
thousands of electron volts (eV). There is no theoretical upper limit to the energies of
gamma-ray photons and no lower limit to gamma-ray wavelengths; observed energies
presently extend up to a few trillion electron volts—these extremely high-energy photons are
produced in astronomical sources through currently unidentified mechanisms. The possibility
of gamma ray optical systems introduces a whole new way of looking at the universe. For
example, the introduction of x-rays in the early 1900s created an entirely new way to see
inside the human body, never before possible. It’s unclear what gamma ray optics or a G-ray
machine will do for medicine or human health but it’s certain that such devices will be better
able to “see” processes and objects impossible to detect today,One item of interest was the
promise that someday, gamma ray optics will be able to render harmless, radioactive isotopes
such as nuclear waste. Somehow a focused gamma ray beam at the proper (neutron binding
energy) wavelength could be used to “evaporate” or remove neutrons from an atomic nucleus
and by doing so render it less lethal. How this works on Kg of material versus a single atom
is another question.[18] Also, gamma ray optics could be used in the future to potentially
create designer radioactive isotopes for medical diagnostics and therapy. Even higher
resolution nuclear spectroscopy is envisioned by using gamma ray optics. Gamma ray optics
could transmute lead into gold, we might have something. This probably means that
someday, gamma ray optics will be able to store information in an atomic nucleus and that
would certainly take data density out of the magnetic domain altogether.
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[19]:http://silvertonconsulting.com/blog/2012/05/10/gamma-ray-optics-promise-nuclear-wastemitigation/#sthash.C6TRLNzf.dpuf