The Many Uses of Nuclear Technology
The first power station to produce electricity by using heat
from the splitting of uranium atoms began operating in the 1950s.
Today most people are aware of the important contribution nuclear
energy makes in providing almost 14% of the world's electricity, -
more than all electricity produced worldwide in
Not so well known are the many other ways the peaceful atom
has slipped quietly into our lives, often unannounced and in many
Radioisotopes and radiation have many applications in
agriculture, medicine, industry and research. They greatly improve
the day to day quality of our lives.
What is a radioisotope?
different forms of an atom of the same chemical element. They have
identical chemical properties but a different relative atomic mass.
While the number of protons is the same, the number of neutrons in
the nucleus differs.
Some isotopes are referred to as
'stable' and others as 'unstable' or 'radioactive'. It is the
radioactive nature of these unstable atoms, usually referred to
as 'radioisotopes', which gives them so many
applications in modern science and technology. Their radioactivity
means that they can be used as a tag to follow the movement of some
material incorporating them.
The first practical application of a
radioisotope was made by George de Hevesy in 1911. At the time de
Hevesy was a young Hungarian student working in Manchester with
naturally radioactive materials. Not having much money he lived in
modest accommodation and took his meals with his landlady. He began
to suspect that some of the meals that appeared regularly might be
made from leftovers from the preceding days or even weeks, but he
could never be sure. To try and confirm his suspicions de Hevesy
put a small amount of radioactive material into the remains of a
meal. Several days later when the same dish was served again he
used a simple radiation detection instrument - a gold leaf
electroscope - to check if the food was radioactive. It was, and de
Hevesy's suspicions were confirmed.
History has forgotten the landlady, but
George de Hevesy went on to win the Nobel prize in 1943 and the
Atoms for Peace award in 1959. His was the first use of radioactive
tracers - now routine in environmental science.
Scientists continue to find new and
beneficial ways of using nuclear technology to improve our lives.
In our daily life we need food, water and good health.
Radioisotopes play an important part in technologies that provide
us with these basic needs. The UN's International Atomic Energy
Agency (IAEA) is a base for international cooperation in hundreds
of development projects.
Food and Agriculture
At least 800 million of the world's
seven billion inhabitants are chronically malnourished, and tens of
thousands die daily from hunger and hunger-related causes.
Radioisotopes and radiation used in food and agriculture are
helping to reduce these tragic figures.
As well as directly improving food
production, agriculture needs to be sustainable over the longer
term. The UN's Food and Agriculture Organisation (FAO) works with
the IAEA on programs to improve food sustainability assisted by
nuclear and related biotechnologies.
Fertilisers are expensive and if not
properly used can damage the environment. Efficient use of
fertilisers is therefore of concern to both developing and
developed countries. It is important that as much of the fertiliser
as possible finds its way into plants and that a minimum is lost to
Fertilisers 'labelled' with a
particular isotope, such as nitrogen-15 and phosphorus-32 provide a
means of finding out how much is taken up by the plant and how much
is lost, allowing better management of fertiliser application.
Using N-15 also enables assessment of how much nitrogen is fixed
from the air by soil and by root bacteria in legumes.
Ionising radiation to induce mutations in plant breeding has been
used for several decades, and some 1800 crop varieties have been
developed in this way. Gamma or neutron irradiation is often used
in conjunction with other techniques, to produce new genetic lines
of root and tuber crops, cereals and oil seed crops.
New kinds of sorghum, garlic, wheat,
bananas, beans and peppers are more resistant to pests and more
adaptable to harsh climatic conditions. In Mali, irradiation of
sorghum and rice seeds has produced more productive and marketable
Crop losses caused by insects may
amount to more than 10% of the total harvest worldwide, - in
developing countries the estimate is 25-35%. Stock losses due to
tsetse in Africa and screwworm in Mexico have also been sizeable.
Chemical insecticides have for many years been the main weapon in
trying to reduce these losses, but they have not always been
effective. Some insects have become resistant to the chemicals
used, and some insecticides leave poisonous residues on the crops.
One solution has been the use of sterile insects.
The Sterile Insect Technique (SIT)
involves rearing large numbers of insects then irradiating their
eggs with gamma radiation before hatching, to sterilise them. The
sterile males are then released in large numbers in the infested
areas. When they mate with females, no offspring are produced. With
repeated releases of sterilised males, the population of the insect
pest in the project area is drastically reduced.
Major SIT operations have been
conducted in Mexico, Argentina and northern Chile against the
Medfly (Mediterranean fruit fly) and in 1981 this was declared a
complete success in Mexico. In 1994-95 eradication was achieved in
two fruit-growing areas of Argentina and 95% success in another, as
well as in Chile. The program has been extended to all of southern
South America and to Africa. Meanwhile the EU is financing a 'fly
factory' on Portugal's Madeira island to produce up to 100 million
sterile male Medflies per week.
A very successful SIT campaign was
screwworm eradication in southern USA, Mexico and nearby. By 1991
the screwworm eradication had yielded some US$ 3 billion in
economic benefits due to healthier livestock, not to mention
humans. The Mexican plants and equipment were then applied to
infestations in Libya, Jamaica and Central America, providing 20
million sterile pupae per week.
SIT has been effective on the Medfly in
southern Africa and is now being applied to Codling Moths which
damage citrus crops. The IAEA and FAO are assessing the potential
of using SIT against Sugarcane Borers on sugarcane, as well as
consolidating Codling Moth management to support the apple and pear
A number of the most fertile parts of
Africa cannot be farmed because of the tsetse fly which carries the
parasite trypanosome that causes the African sleeping sickness
disease and the cattle disease Nagana. Economic losses due to this
are estimated by FAO at US$ 4 billion per year. However, SIT in
conjunction with conventional pest controls is starting to change
all this. Zanzibar was declared tsetse-free in 1997 and Nigeria has
also benefited. In southern Ethiopia a major tsetse SIT program is
under way, with a million sterile males per month being produced in
a 'fly factory' at Addis Ababa and then released.
Screwworm flies are major pests in some
parts of the world. Females lay eggs into animal wounds and on soft
tissues, the larvae then burrow through the flesh creating serious
bacterial infections that attract more egg-laying females and are
often fatal. Using SIT, screwworm has been eradicated from North
and Central America, and also Libya. South America, most of Africa,
and south Asia through to Melanesia remain a challenge.
Three UN organizations - the IAEA, the
FAO, the World Health Organisation (WHO), with the governments
concerned, are promoting new SIT programs in many
Some 25-30% of the food harvested in
many countries is lost as a result of spoilage by microbes and
pests. In a hungry world we cannot afford this. The reduction of
spoilage due to infestation and contamination is of the utmost
importance. This is especially so in countries which have hot and
humid climates and where an extension of the storage life of
certain foods, even by a few days, is often enough to save them
from spoiling before they can be consumed. Some countries lose a
high proportion of harvested grain due to moulds and insects.
In all parts of the world there is
growing use of irradiation technology to preserve food. In over 40
countries health and safety authorities have approved irradiation
of more than 60 kinds of food, ranging from spices, grains and
grain products to fruit, vegetables and meat. It can replace
potentially harmful chemical fumigants to eliminate insects from
dried fruit and grain, legumes, and spices.
Following three decades of testing, a
worldwide standard was adopted in 1983 by a joint committee of WHO,
FAO and IAEA. In 1997 another such joint committee said there was
no need for the earlier recommended upper limit on radiation dose
As well as reducing spoilage after
harvesting, increased use of food irradiation is driven by concerns
about food-borne diseases as well as growing international trade in
foodstuffs which must meet stringent standards of quality. On their
trips into space, astronauts eat foods preserved by
Food irradiation means that raw foods
are exposed to high levels of gamma radiation which kills bacteria
and other harmful organisms without affecting the nutritional value
of food itself or leaving any residue. It is the only means of
killing bacterial pathogens in raw and frozen food. Of course,
irradiation of food does not make it
|Low dose (up to 1 kGy)
||Inhibition of sprouting
||Potatoes, onions, garlic, ginger, yam
||Insect and parasite disinfestation
||Cereals, fresh fruit, dried foods
||Fresh fruit, vegetables
|Medium dose (1-10 kGy)
||Extend shelf life
||Fish, strawberries, mushrooms
||Halt spoilage, kill pathogens
||Seafood, poultry, meat
|High dose (10-50 Gy)
||Meat, poultry, seafood, prepared foods
Radiation is also used to sterilise
food packaging. In the Netherlands, for example, milk cartons are
freed from bacteria by irradiation.
Adequate potable water is essential for
life. Yet in many parts of the world water has always been scarce
and in others it is becoming scarcer. Yet for any new development,
whether agricultural, industrial or human settlement, a sustainable
supply of good water is vital.
Isotope hydrology techniques
enable accurate tracing and measurement of the extent of
underground water resources. Such techniques provide important
analytical tools in the management and conservation of existing
supplies of water and in the identification of new, renewable
sources of water. They provide answers to questions about origin,
age and distribution of groundwater, as well as the
interconnections between ground and surface water and aquifer
recharge systems. The results permit planning and sustainable
management of these water resources.
For surface waters they can give
information about leakages through dams and irrigation channels,
the dynamics of lakes and reservoirs, flow rates, river discharges
and sedimentation rates. From Afghanistan to Zaire there some 60
countries, developed and developing, that have used isotope
techniques to investigate their water resources in collaboration
Neutron probes can measure soil
moisture very accurately, enabling better management of land
affected by salinity, particularly in respect to irrigation.
Many of us are aware of the wide use of
radiation and radioisotopes in medicine particularly
for diagnosis (identification)
andtherapy (treatment) of various medical
conditions. In developed countries (a quarter of the world
population) the frequency of diagnostic nuclear medicine is 1.9% of
the population per year, and the frequency of therapy with
radioisotopes is about one tenth of this.
Over 10,000 hospitals worldwide use
radioisotopes in medicine. In the USA there are some 18 million
nuclear medicine procedures per year among 311 million people, and
in Europe about 10 million among 500 million people. The use of
radiopharmaceuticals in diagnosis is growing at over 10% per
Radioisotopes are an essential part of
diagnostic treatment. In combination with imaging devices which
register the gamma rays emitted from within, they can study the
dynamic processes taking place in various parts of the body. An
advantage of nuclear over x-ray techniques is that both bone and
soft tissue can be imaged very successfully.
In using radiopharmaceuticals for
diagnosis, a radioactive dose is given to the patient and the
activity in the organ can then be studied either as a two
dimensional picture or, with a special technique called tomography,
as a three dimensional picture.
The most widely used diagnostic
radioisotope is technetium-99m*, with a half-life of six hours, and
which gives the patient a very low radiation dose. Such isotopes
are ideal for tracing many bodily processes with the minimum of
discomfort for the patient. They are widely used to indicate
tumours and to study the heart, lungs, liver, kidneys, blood
circulation and volume, and bone structure.
* Technetium generators, a lead
pot enclosing a glass tube containing the radioisotope, are
supplied to hospitals from the nuclear reactor where the isotopes
are made. They contain molybdenum-99, with a half-life of 66 hours,
which progressively decays to technetium-99. The Tc-99 is washed
out of the lead pot by saline solution when it is required. After
two weeks or less the generator is returned for
Technetium (Tc-99) is employed in some
30 million diagnostic procedures per year, of which 6-7 million are
in Europe, 15 million in North America, 6-8 million in Asia/Pacific
(particularly Japan), and 0.5 million in other regions. The
chemistry of technetium is so versatile it can form tracers by
being incorporated into a range of biologically-active substances
to ensure that it concentrates in the tissue or organ of
Another major use of radioisotopes
for diagnosis is in radio-immuno-assays for biochemical analysis in
a laboratory. They can be used to measure very low concentrations
of hormones, enzymes, hepatitis virus, some drugs and a range of
other substances in a sample of the patient's blood. The patient
never comes in contact with the radioisotopes used in the
diagnostic tests. In the USA alone it is estimated that some 40
million such tests are carried out each year, and in Europe, about
The uses of radioisotopes in therapy are
comparatively few, but important. Cancerous growths are sensitive
to damage by radiation, which may be external - using a gamma beam
from a cobalt-60 source, or internal - using a small gamma or beta
Iodine-131 is commonly used to treat
thyroid cancer, probably the most successful kind of cancer
treatment, and also for non-malignant thyroid disorders.
Iridium-192 wire implants are used especially in the head and
breast to give precise doses of beta rays to limited areas, then
removed. A new treatment uses samarium-153 complexed with organic
phosphate to relieve the pain of secondary cancers lodged in
(See also information paper Radioisotopes
Many medical products today are
sterilised by gamma rays from a cobalt-60 source, a technique which
generally is much cheaper and more effective than steam heat
sterilisation. The disposable syringe is an example of a product
sterilised by gamma rays. Because it is a 'cold' process radiation
can be used to sterilise a range of heat-sensitive items such as
powders, ointments and solutions and biological preparations such
as bone, nerve, skin, etc, used in tissue grafts.
The benefit to humanity of
sterilisation by radiation is tremendous. It is safer and cheaper
because it can be done after the item is packaged. The sterile
shelf life of the item is then practically indefinite provided the
package is not broken open. Apart from syringes, medical products
sterilised by radiation include cotton wool, burn dressings,
surgical gloves, heart valves, bandages, plastic and rubber sheets
and surgical instruments.
One of the commonest uses of
radioisotopes today is in household smoke detectors. These contain
a small amount of americium-241 which is a decay product of
plutonium-241 originating in nuclear reactors. The Am-241 emits
alpha particles which ionise the air and allow a current between
two electrodes. If smoke enters the detector it absorbs the alpha
particles and interrupts the current, setting off the
(See also information paper Smoke Detectors
Radioisotopes also play an important
role in detecting and analysing pollutants, since even very small
amounts of a radioisotope can easily be detected, and the decay of
short-lived isotopes means that no residues remain in the
Nuclear techniques have been applied to
a range of pollution problems including smog formation, sulphur
dioxide contamination of the atmosphere, sewage dispersal from
ocean outfalls and oil spills.
The ability to measure radioactivity in minute amounts has given
radioisotopes a wide range of applications in industry as
'tracers'. By adding small amounts of radioactive substances to
materials used in various processes it is possible to study the
mixing and flow rates of a wide range of materials, including
liquids, powders and gases and to locate leaks.
Tracers added to lubricating oils can
help measure the rate of wear of engines and plant and equipment.
Tracer techniques have been used in plant operations to check the
performance of equipment and improve its efficiency, resulting in
savings in energy and the better use of raw materials.
Gauges containing radioactive sources
are in wide use in all industries where levels of gases, liquids
and solids must be checked. These gauges are most useful where
heat, pressure or corrosive substances, such as molten glass or
molten metal, make it impossible or difficult to use direct contact
Radioisotope thickness gauges are
used in the making of continuous sheets of material including
paper, plastic film, metal, glass, etc, when it is desirable to
avoid contact between the gauge and the material.
Density gauges are used where automatic
control of a liquid, powder or solid is important, for example, in
Radioisotope instruments have three
- measurements can be made without physical contact with the
material or product being measured.
- Very little maintenance of the isotope source is
- The cost/benefit ratio is excellent - many instruments pay for
themselves within a few months through the savings they allow.
Radioisotopes which emit gamma rays are more portable than x-ray
machines, and may give higher-energy radiation, so can be used to
check welds of new gas and oil pipeline systems, with the
radioactive source being placed inside the pipe and the film
outside the welds.
Other forms of radiography (neutron
radiography/ autoradiography), based on different principles, can
be used to gauge the thickness and density of materials or locate
components that are not visible by other means.
(See also information paper Radioisotopes
Some radioisotopes emit a lot of energy
as they decay. Such energy can be harnessed for heart pacemakers
and to power navigation beacons and satellites. The decay heat of
plutonium-238 has powered many US space vehicles. It enabled the
Cassini space probe to investigate Saturn, and it powers the
Mars Science Laboratory, the
Analysis of radioisotopes is of vital
importance in determining the age of rocks and other materials that
are of interest to geologists, anthropologists and
From the moment we get up in the
morning, until we go to sleep, we benefit unknowingly from many
ingenious applications of radioisotopes and radiation. The water we
wash with (origin, supply assurance), the textiles we wear
(manufacture control gauging), the breakfast we eat (improved
grains, water analysis), our transport to work (thickness gauges
for checking steels and coatings on vehicles and assessing the
effects of corrosion and wear on motor engines), the bridges we
cross (neutron radiography), the paper we use (gauging, mixing
during production processes), the drugs we take (analysis) not to
mention medical tests (radioimmunoassay, perhaps
radiopharmaceuticals), or the environment which radioisotope
techniques help to keep clean, are all examples that we sometimes
take for granted.