radioisotopes and its applications

1. RADIOISOTOPES
SUBMITTED TO:
Dr N. J. Patel
Associate Professor
Dept. of Biochemistry
B .A. College of Agriculture ,
Anand
SUBMITTED BY
Parmar Sneha Jayantilal
M. Sc 1st sem
Genetics and plant breeding
B. A. College of Agriculture
Anand.

2. WHAT IS RADIOISOTOPES ?
• Different isotopes of the same element have the same number of
protons in their atomic nuclei but differing numbers of neutrons.
• Radioisotopes are radioactive isotopes of an element. They can also
be defined as atoms that contain an unstable combination of neutrons
and protons, or excess energy in their nucleus.

3. HOW DO RADIOISOTOPES OCCUR?
• The unstable nucleus of a radioisotope can occur naturally, or as a result
of artificially altering the atom. In some cases a nuclear reactor is used
to produce radioisotopes, in others, a cyclotron. Nuclear reactors are
best-suited to producing neutron-rich radioisotopes, such as
molybdenum-99, while cyclotrons are best-suited to producing proton-
rich radioisotopes, such as fluorine-18.
• The best known example of a naturally-occurring radioisotope
is uranium. All but 0.7 per cent of naturally-occurring uranium is
uranium-238; the rest is the less stable, or more radioactive, uranium-
235, which has three fewer neutrons in its nucleus.

4. RADIOACTIVE DECAY
• Atoms with an unstable nucleus regain stability by shedding excess
particles and energy in the form of radiation. The process of shedding
the radiation is called radioactive decay. The radioactive decay
process for each radioisotope is unique and is measured with a time
period called a half-life. One half-life is the time it takes for half of the
unstable atoms to undergo radioactive decay.

5. EVOLUTION OF ISOTOPES
• In 1898, discovery of polonium by Pierre and Marie Curie introduced the term
"radioactive". Radium was discovered by the Curie six months after the
discovery of polonium with the collaboration of the chemist G. Bemont .
Radium played by far a more important role than polonium. Its separation in
significant amount opened the way to its medical and industrial application and
also its use in laboratories. Later 'uranic rays' was discovered by Henri
Becquerel in 1900 .
• Overall 1800 isotopes are present, but at present only up to 200 radioisotopes
are used on a regular basis, and most of them are produced artificially.
Radioisotopes can be manufactured in several ways.
• The most common is by neutron activation in a nuclear reactor. This involves
the capture of a neutron by the nucleus of an atom resulting in an excess of
neutrons (neutron rich) which leads to the production of desired radioisotope .

6. • Some radioisotopes are manufactured in a cyclotron, devised by
Lawrence and Livingston in 1932 in which charged particles such as
protons, deuterons and alpha particles are introduced to the nucleus
resulting in a deficiency of neutrons (proton rich). These particles are
accelerated to high energy levels and are allowed to impinge on the
target material. 11C, 13N, 18F, 123I, etc. are some of the isotopes that
can be produced in a cyclotron.

7. types of radioisotopes
Naturally occurring radioisotopes:
• 1. Primordial radioisotopes
• Primordial radioisotopes originate mainly from the interiors of stars. eg.
Uranium and Thorium. They are still present as their half-lives are so long
that they are not yet completely decayed.
• 2. Secondary radioisotopes
• Secondary radioisotopes are radiogenic isotopes derived from the decay of
primordial radioisotopes. They have shorter half-lives than primordial
radioisotopes.
• 3. Cosmogenic radioisotopes
• Cosmogenic isotopes are continually being formed in the atmosphere due to
cosmic rays. eg. Carbon-14

8. • Artificially produced radioisotopes:
• 1. Nuclear reactors
• The high flux of neutrons activate the elements placed within the nuclear
reactor to produce radioisotopes. eg. Thallium-201 and Iridium-192.
• 2. Particle accelerators
• Cyclotrons accelerate protons to bombard a target and produce positron
that emits radioisotopes. eg. Fluorine-18.
• 3. Radionuclide generators
• Radioisotopes generators contain a parent isotope produced in a nuclear
reactor, that decay to produce a radioisotope. e.g.Technetium-99
produced Molybdenum -99.
• 4. Nuclear explosions
• Radioisotopes produced as an unavoidable side effect of nuclear and
thermonuclear explosions.

10. APPLICATIONS IN AGRICULTURE
• Application of Radioactive Tracers in Agricultural Chemistry
• The radioactive materials released by the accident have many direct harmful
effects on plants, animals and their environment . In the first two months after the
accident, this problem of direct deposition on plants is of the greatest concern
since radioactive iodine decomposes rapidly. After the initial stage of
sedimentation, a growing concern is the contamination of plants by absorbing
radioactive materials such as cesium and strontium from the soil to the roots of
the soil . In the first few years after the accident, due to factors such as
weathering and decay, the content of radioactive substances in agricultural
animals and plants declined rapidly, but the level of radioactivity continued to
decline afterwards, but at a slower rate . In order to restore the soil used for
cultivation, scientists and farmers are trying to find a way to eliminate radiation in
the soil. They used various expensive methods to find a solution to the
radioactive problem in areas with high planting rates . The solution is the
sunflower plant, which is a super-accumulating plant with an effective mechanism
to absorb nutrients, water, minerals and certain radioisotopes (such as strontium
and cesium) from the soil. Sunflower is also very attractive since it grows well and
can quickly produce large amounts of biomass . Compared with many other
crops, it can adapt too many different climates and can grow without much
management.

11. • Plant nutrition studies
• Fertilizers are very expensive and their efficient use is of great
importance to reduce the production cost of agricultural crops. It is
essential that a maximum amount of fertilizer used during cultivation
finds its way into the plant and that the minimum is lost. Radioisotopes
are very useful in estimating the amount of phosphorus and nitrogen
available in the soil. This estimation helps in determining the amount of
phosphate and nitrogen fertilizers that should be applied to soil.
Fertilizers labelled with radioactive isotopes such as phosphorus-32 and
nitrogen-15 have been used to study the uptake, retention and
utilization of fertilizers. Excessive use of fertilizers effects biodiversity
and damages the environment. These isotopes provide a means to
determine about amount of fertilizer taken and lost to the environment
by the plant

12. • . Nitrogen-15 also helps in assessment of nitrogen fixed by plants from
the atmosphere under field conditions. IAEA develops and transfers
techniques that use radioactive isotopes for measuring the nutrient
uptake from various fertilizer sources with an aim to achieve higher and
more stable grain yields by optimizing the uptake of nutrients from
applied fertilizers (Zapata and Hera, 1995). Only small amount of
fertilizer applied to the soil is taken up by the crop. The rest either
remains in the soil or is lost through several processes. FAO and IAEA
have jointly conducted several research programmes for the efficient use
of radioactive isotopes for fertilizer management practices in important
agricultural crops like wheat, rice and maize.

13. • Insect pest management
• Insect pests are responsible for significant reduction in production of
agricultural crops throughout the world (Alphey, 2007). Insect pests are
serious threat to agricultural productivity. They not only reduce crop
yields but also transmit disease to cultivated crops. Radiolabel pesticides
were used to monitor the persistence of their residues in food items,
soil, ground water and environment. These studies have helped to trace
and minimize the side effects of pesticides and insecticides. There are
concerns that continuous uses of pesticides have negative impacts on
the environment and it also results into development of resistance
against pesticides in many insect species (ANBP, 2005). Moreover,
pesticides not only kill target species but also many other beneficial pest
species responsible for maintaining natural ecological balance in the crop
fields.

14. • IAEA is using nuclear science to develop environmentally friendly
alternatives for pest control. FAO and IAEA division jointly sponsors
projects and conducts research on control of insects using ionizing
radiations. They have placed considerable emphasis on the Sterile
Insect Technique (SIT) proposed by Knipling in 1955 (Knipling, 1955).
This technique relies on application of ionizing radiation as a means to
effectively sterilize male insects without affecting their ability to
function in the field and successfully mate with wild female insects. This
technique involves release of large numbers of sterile male insects of
the target species in the field crop.

15. • Sterile male insects compete with the regular male population during
sexual reproduction and the eggs produced from their mating are
infertile so they produce no offspring (Morrison et al., 2010). It is highly
specific form of "birth control which reduces and eliminates the insect
population after two or three generations. It has been effectively
utilized in elimination of Mediterranean fruit fly from US, Mexico and
Chile and screw worm infestation in the US and Mexico (Klassen and
Curtis, 2005; Wyss, 2000; Lindquist et al., 1992). It has been successfully
used to eradicate several insect pests of agricultural significance
throughout the world.

16. • Crop improvement
• Plant breeding requires genetic variation of useful traits for crop
improvement. Different types of radiation can be used to induce
mutations to develop desired mutants line that are resistant to
disease, are of higher quality, allow earlier ripening, and produce a
higher yield. An initial attempt to induce mutations in plants was
demonstrated by American Scientist L.J. Stadler in 1930 using X-rays.
Later on, gamma and neutron radiation were employed as ionizing
radiations. This technique of utilizing radiation energy for inducing
mutation in plants has been widely used to obtain desired or
improved characters in number of plant varieties. It offers the
possibility of inducing desired characters that either cannot be found
in nature or have been lost during evolution. A proper selection of
mutant varieties can lead to improved quality and productivity.

17. • During last two decades, radiation-induced mutations have increasingly
contributed to the improvement of crop plant varieties and it has become
an established part of plant breeding methods. Radiation induced
mutation experiments are showing promising results for improvement of
cultivated crop varieties in many countries. Bhabha Atomic Research
Centre (BARC) has developed number of high yielding varieties of tur,
green gram, black gram, groundnut, jute and rice by using radiation energy
for inducing mutation (Sood et al., 2010). Crop varieties developed by
using induced mutations have been found valuable by many national
authorities so they have been released and approved for commercial
production. Most of the groundnut and black gram grown in India are from
mutant varieties developed at BARC. There are many similar successful
mutants in use in other countries, for example, high yielding mutant
barleys which can utilize higher doses of fertilizer for increased grain
production. Improved pearl millet line showing resistance to downy
mildew disease was developed using irradiation treatment in India and is
now grown over an area of several million hectares.

18. • Disinfestation of stored foodgrains:
• For improving productivity as well as for protection of crop plants
against various diseases , different types of agro-chemicals and
other sources are used. In these days, radiation from
radioisotopes are employed in crop protection. Ionizing
radiations are inestimatable value for obtaining an insight into
ecological habits of insects. With the aid of radioisotopes we can
find out population density, the maturity rate during different
stages of the life cycle, modes of dispersal, movement and
migration, flight range hibernating places, egg laying sites,
relation to predators.

19. • Mutation Breeding:
• Mutation breeding involves the use induced beneficial
practical plant breeding purpose both directly and
create a new characteristics, such as drought resistance or
crops. It has been observed that irradiation of crop with
Co60 can lead to changes due to its deep penetrating rays
the plants which are inherited. Radioisotope and radiation
induction. Mutation is sudden heritable changes of the
chromosomes of the organisms. The employment of
hereditary variant is an useful tool of potential value in
been able to show conclusively that with radiation, changes
about in the organization and general morphological
plant improvement.

20. • New varieties of crops:
• When seeds of wheat, rice maize, sugarcane tobacco,
flowers are exposed to a measured dose of gamma rays,
profound genetic changes with the result that on sowing,
give a variety of plants, some of which are high yielding
Successful breeding of new varieties of cereals and cash
reported from many countries and there is no doubt that
from radiation-induced mutants promise a revolutionary
breeders all over the world

21. • Increasing Animal Production and Health:
• To enhance livestock productivity, radio-immunoassays of
hormones have been performed and using the information
supplementation strategies for milk producing animals in
subtropical environments have been developed through
techniques. The quantity and quantity is the principal
throughout a wide spectrum of animal species and
based on isotopic methods have led to dramatic increases
production and/or reproductive efficiency by improving the
livestock through supplemental feeding with locally
urea, molasses, palm kernel cake, rice polishing and