applications of nuclear technology 2_2

8/12/2019 Applications of Nuclear Technology 2_2

1/28

Applications of nuclear technology


2/28

CONTENTS

1 INTRODUCTION 5 1.1. Introduction ....................................................................................................... 51.2. History And Scientific Background ................................................................... 5

2. APPLICATIONS IN DIFFERENT FIELDS 7 2.1. Scientific Analysis Techniques .. . .7

2.1.1. Nuclear Magnetic Resonance (NMR) ................................................... ....72.1.2. Tracers .................................................................................................... 10

2.2. Electric Power Generation ................................................................................. 112.2.1. Fission Reactor ....................................................................................... 112.2.2. Fusion Reactor ... ...........12

2.3. Medicical .............................................................................................................. 132.3.1. Diagnosis ................................................................................................ 132.3.2. Therapy ................................................................................................... 142.3.3. Sterilisation ............................................................................................ 15

2.4. Food and Agriculture........................................................................................... 152.4.1. Fertilisers ............................................................................................... 152.4.2. Increasing Genetic Variability ............................................................... 162.4.3. Insect Control ......................................................................................... 162.4.4. Food Preservation ................................................................................... 172.4.5. Water Resources ..................................................................................... 19

2.5. Industry ............................................................................................................... 192.5.1. Gamma Radiography.............................................................................. 202.5.2. Measurement and Industrial Analysis .................................................. 212.5.3. Sample Power Sources ........................................................................... 212.5.4. Environmental Monitoring .................................................................... 222.5.5. Other Industrial Uses ............................................................................ 22

2.6. Household Uses of Radiation .............................................................................. 232.6.1. Smoke Detector ...................................................................................... 232.6.2. Other Uses of Radionuclides in Houses ................................................. 24

2.7. Archaology and Geology ...................................................................................... 242.7.1. Radioactive Dating ................................................................................. 252.7.2. Geology and Element Identification ...................................................... 27

2.8. Space Mission ...................................................................................................... 28

3 CONCLUSION 29

4 REFERENCES 30


3/28

3

1 INTRODUCTION

1.1 INTRODUCTION

Nuclear Technology is the technology that involves the reactions of atomic nuclei. In our

daily life we need food, water and good health. This Technology can be used in diversified fields

for peaceful purposes such as electricity generation, medicinal purposes, reducing pollution, etc .

Radioisotopes play an important part in technologies that provide us with these basic needs. The

International Atomic Energy Agency (IAEA) is a base for international cooperation in hundreds

of development projects.

Nuclear Technology is all around us. We'll find aspects of nuclear Technology

everywhere we go. Everywhere from power generation to medicine to daily life, most people

will encounter some form of nuclear Technology in action, making their lives easier.

1.2 HISTORY AND SCIENTIFIC BACKGROUND

The vast majority of common, natural phenomena on Earth only involve gravity and

electromagnetism, and not nuclear reactions. This is because atomic nuclei are generally kept

apart because they contain positive electrical charges and therefore repel each other.

In 1896, Henri Becquerel was investigating phosphorescence in uranium salts when he

discovered a new phenomenon which came to be called radioactivity. He, Pierre Curie and Marie

Curie began investigating the phenomenon. In the process, they isolated the element radium,

which is highly radioactive. They discovered that radioactive materials produce intense,

penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the

Greek letters. Some of these kinds of radiation could pass through ordinary matter, and all of

them could be harmful in large amounts. All of the early researchers received various radiation

burns, much like sunburn, and thought little of it.


4/28

4

The new phenomenon of radioactivity was seized upon by the manufacturers of a number

of patent medicines and treatments involving radioactivity were put forward. Gradually it was

realized that the radiation produced by radioactive decay was ionizing radiation, and that even

quantities too small to burn could pose a severe long-term hazard. Many of the scientists working

on radioactivity died of cancer as a result of their exposure.

As the atom came to be better understood, the nature of radioactivity became clearer.

Some larger atomic nuclei are unstable, and so decay (release matter or energy) after a random

interval. The three forms of radiation that Becquerel and the Curies discovered are also more

fully understood. Alpha decay is when a nucleus releases an alpha particle, which is two protons

and two neutrons, equivalent to a helium nucleus. Beta decay is the release of a beta particle, a

high-energy electron. Gamma decay releases gamma rays, which unlike alpha and beta radiationare not matter but electromagnetic radiation of very high frequency, and therefore energy. This

type of radiation is the most dangerous and most difficult to block. All three types of radiation

occur naturally in certain elements.

It has also become clear that the ultimate source of most terrestrial energy is nuclear,

either through radiation from the Sun caused by stellar thermonuclear reactions or by radioactive

decay of uranium within the Earth, the principal source of geothermal energy.


5/28

5

2 APPLICATIONS IN DIFFERENT FIELDS

2 1 SCIENTIFIC ANALYSIS TECHNIQUES

2 1 1 Nuclear Magnetic Resonance (NMR)

Nuclear magnetic resonance (NMR) was a phenomenon first discovered in 1946, and was

refined in the 1950s by the Swiss-born United States physicist Felix Bloch. Since then, it has

been applied in sciences ranging from physics to biochemistry, as well as applications such as

medicine and forensic science. It is a technique used for analysis of various substances.

Nuclear magnetic resonance is the vibration or resonance of a nucleus, when it is placedin a magnetic field - hence the name nuclear magnetic resonance. Particularly in medicine, it is

also known as magnetic resonance imaging . The word 'nuclear' in a medical procedure

frightens some people, hence the alternative name! However, nuclear magnetic resonance has

nothing to do with radiation or radioactivity.

Nuclei begin to resonate when placed in strong magnetic fields and targeted with specific

radio waves. (Energy of the radio waves is absorbed by the nuclei, making it resonate.) This

resonance occurs because at certain radio frequencies nuclei will absorb the wave energy,

becoming excited from a low energy state to a higher energy state. These different energy states

are called magnetic moments . Without the magnetic field, nuclei do not have the magnetic

moments: they cannot exist in different energy states, and will therefore not be able to absorb

any energy from the radio waves. This is why a magnetic field is used.

The energy the hydrogen nucleus can be split into two different levels in the presence of a

magnetic field. The change between the levels (moments) requires a certain amount of energy.

The energy of radio waves (E) is equal to a constant h (Planck's constant, 6.626 10 -34)

multiplied by the frequency of the wave f ,

E = hf


6/28

6

Thus, for the frequencies at which a nucleus will resonate, the corresponding energy can

be calculated to give relative values for the magnetic moments.

The specific frequencies at which nuclei resonate can be used to identify them - as a type

of "fingerprint". Measurements have been taken by scientists for the frequencies and magnetic

moments of many atoms - forming a database that can be used to identify unknown samples.

Fig.2.1: MRI Scanner

NMR SPECTOSCOPY

Spectroscopy is the analysis of different compounds. Scientists use NMR spectroscopy to

study the bonds and structures of molecules.

Hydrogen atoms not bonded to other atoms are called free hydrogen atoms . These

absorb energy at the radio wave frequency 42.58 MHz (in the presence of a magnetic field).

However, this frequency varies slightly if the hydrogen atom is bonded to other atoms. This

variance can be used to determine the structure of an unknown compound.

The atoms surrounding the hydrogen atom in a molecule are collectively called the

neighbourhood of atoms . Different neighbourhoods affect the absorbed frequency of the


7/28

7

hydrogen atom in different ways, giving rise to a fingerprint for each neighbourhood. Variations

in the frequency absorbed due to different neighbourhoods are called chemical shifts . Because

of this variation, shifts can be used to identify a given neighbourhood.

The specific hydrogen atom analysed with this technique is 1H, because it is the most

abundant (over 99% of all hydrogen atoms in existence are of the 1H isotope) and it can take on

different magnetic moments. However, 13C can also be analysed although this is not common

since the abundance of it is very small, and equipment sensitivity to it is about 10,000 weaker

than for 1H.

NMR spectroscopy produces a graph which is then analysed to identify the compound

tested. The technique is used to identify unknown compounds, analysing samples obtained from

oil exploration, and forensic science. It is a widely used technique in organic chemistry, and has

also been used to help establish the chemical structure of benzene - a structure that had eluded

scientists for many years.

Fig.2.2: NMR Spectroscopy


8/28


9/28

9

As the radioisotope passes through the body, the trail of radiation that is emitted can be

recorded using networks of detectors to show how the radioisotope is consumed.

Alternatively, in a process called autoradiography used often in studying plants, the plant is

exposed to a radioactive isotope (for example, placed in an atmosphere filled with carbon

dioxide containing the carbon-14 radioisotope). After absorbing the radioactive carbon dioxide,

the plant has some of the radioisotope within it. It is then placed on a photographic film. The

regions of the plant where the radioisotope has mostly concentrated darkens the film; the regions

where the radioisotope does not exist does not affect the film. Overall a map of the location of

the radioisotopes is generated. This technique is useful in the study of how plants absorb

nutrients, and also has been used by scientists to study DNA replication.

2 2 ELECTRIC POWER GENERATION

2 2 1 Fission Reactor

In a fission reaction, an atom such as 235 U is bombarded with a neutron. The 235 U atom

then absorbs the neutron to form 236U. However, this is unstable, and it breaks up into two

roughly equal sized atoms, releasing some neutrons and a lot of energy.

Fig.2.4: Fission reaction of U-235

Regardless of what the products may be, the neutrons released can continue on to break

up more 235 U atoms. Thus, if a chain reaction can be created and sustained, there will be a lot of


10/28

10

energy released. In 1942, scientists at the University of Chicago in USA achieved such a self-

sustaining chain reaction. They did this in the operation of the world's first ever nuclear reactor.

235U atoms will only absorb slow moving neutrons. The neutrons produced from the

breaking up of a 235U atom move at very high speed. Thus it is difficult to achieve a sustained

chain reaction unless the produced neutrons can be slowed down. The slowing down is done by a

moderator .

Nuclear Reactors produce electricity by boiling water into steam.

This steam then turns turbines to produce electricity.

The difference is that nuclear Reactors do not burn anything.

Instead, they use uranium fuel, consisting of solid ceramic pellets, to produceelectricity through a process called fission.

Fig.2.5: General working of Nuclear Power Plant

2 2 2 Fusion Reactor

It is called 'fusion' because it is based on fusing light nuclei such as hydrogen isotopes to

release energy, similar to that which powers the sun and other stars.

Nuclei of two isotopes of hydrogen, deuterium(D) and tritium(T) react to produce a

helium(He) nucleus and a neutron(n). In each reaction, 17.6 MeVof energy is liberated:


11/28

11

D + T 4He (3.5 MeV) + n (14.1 MeV)

Fig.2.6: Fusion Process

2 3 MEDICAL

Radiation and radioisotopes are used in medicine particularly for diagnosis and

therapy of various medical conditions. In developed countries 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. The use of

radiopharmaceuticals in diagnosis is growing at over 10% per year.

2 3 1 Diagnosis

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.


12/28

12

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 tumors 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 99Mo,

with a half-life of 66 hours, which progressively decays to 99Tc. The 99Tc is washed out of the

lead pot by saline solution when it is required. After two weeks or less the generator is returned

for recharging. Tc-99 is employed in some 30 million diagnostic procedures per year

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.

2 3 2 Therapy

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 60Co source, or internal - using a small gamma or beta radiation source.

131I is commonly used to treat thyroid cancer, probably the most successful kind of cancer

treatment, and also for non-malignant thyroid disorders. 192 Ir 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 uses153

Sm complexed with organic phosphate to relieve the pain of secondary cancerslodged in bone.


13/28

13

2 3 3 Sterilisation

Many medical products today are sterilised by gamma rays from a 60Co 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.

2 4 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 Organization (FAO) works with the IAEA on

programs to improve food sustainability assisted by nuclear and related biotechnologies.

2 4 1 Fertilisers

Fertilisers are expensive and if not properly used can damage the environment. It is

important that as much of the fertiliser as possible finds its way into plants and that a minimum is

lost to the environment.


14/28


15/28

15

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

export industries.

Three UN organizations - the IAEA, the FAO, the World Health Organisation (WHO),

with the governments concerned, are promoting new SIT programs in many countries.

2 4 4 Food Preservation

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.

Radiation is also used to sterilise food packaging. In the Netherlands, for example, milk

cartons are freed from bacteria by irradiation.

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 irradiation.

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


16/28

16

Fig.2.7: Irradiating process

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 radioactive!

Table 2.1: Food Irradiation Applications

Radiati on dose (ki lograys,

kGy)

Purpose

"low" up to 1 kGy inhibits fruit and vegetable ripening

controls some bacteria in meats

controls insects in grains


17/28

17

2 4 5 Water Resources

Adequate potable water is essential for life. 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 with IAEA.

Neutron probes can measure soil moisture very accurately, enabling better management

of land affected by salinity, particularly in respect to irrigation.

2 5 INDUSTRY

Radiation is used widely throughout industry for various tasks including quality control,

maintenance work and assessment of the environment.

"medium" 1-10 kGy destroys bacteria in meat including salmonella, shigella,

campylobacter and yersinia

inhibits mold growth on fruit

"high" more than 10 kGy destroys insects and bacteria in spices

sterilises food to the same extent achieved by high heat


18/28


19/28

19

happens, the radiation passes through any cracks that may exist, onto the photographic film taped

on the outside. This film is then developed and checked for cracks or welding deterioration.

Some industrial machinery contains parts that have small amounts of radioactive

materials. This allows easy observation and detection of wear and tear.

2 5 2 Measurement and Industrial Analysis

Radioisotopes are commonly used for measuring viscosity, density and thickness in

conditions where other methods would be difficult or impossible to apply. Since radiation does

not require direct contact it is used where high heat or corrosive chemicals may exist.

Radiation is reduced in intensity when it passes through many materials. Therefore the

amount of stuff between a radiation detector and emitter can be determined by calculating the

difference between the intensity of emitted radiation and the intensity of the received radiation.

This concept is applied in the manufacture of thin plastic films. The produced film is passed

through a radioisotope gauge - the thicker the film, the lower the detected radiation. Changes in

the detected level of radiation correspond to a change in thickness of the plastic, so this is a form

of quality control.

Radioisotopes can also be used to calculate the efficiency of large mixers, or the flow of

materials through blast furnaces. Leaks and other defects can also be detected in building cooling

towers and power station heat exchangers.

2 5 3 Sample Power Sources

Radioisotopes are used as power sources for applications requiring small amounts of portable energy, such as for remote weather stations and weather balloons, and navigation

beacons and buoys. They are more environmentally friendly than batteries because once all the

energy from radioactivity is used, there are few left-over wastes except for the stable atoms

formed, whereas used batteries will always contain toxic heavy metals that are hazardous to the

environment.


20/28


21/28

21

Table 2.2: List of Some Common Radioisotopes used in Industry

Radioisotope Industrial Uses

Hydrogen-3 Water age measurement, study of sewage

carbon-14 Water age measurement

Chlorine-36 Water age measurement

Scandium-40 Study of blast furnace efficiency

Manganese-54 Study of environmental impact of mining

Chromium-57 Study of coastal erosion

Cobalt-60 Sterilisation

Zinc-65 Study of environmental impact of mining

Cesium-137 soil erosion monitoring

Iridium-192 Study of coastal erosion, checking of aircraft welding faults

Gold-198 Study of sewage and sources of water pollution, monitoring of sand movements

in ocean floors and river beds, coastal erosion, study of blast furnace efficiency

Lead-210 soil and sand age measurement

2 6 HOUSEHOLD USES OF RADIATION

2 6 1 Smoke Detector

One of the commonest uses of radioisotopes today is in household smoke detectors.

These contain a small amount of 241 Am which is a decay product of 241 Pu originating in nuclear

reactors. The 241 Am 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 alarm.


22/28

22

Fig.2.9: Smoke Detector

2 6 2 Other Uses of Radionuclides in Houses

Other items that contain radiation are collectors and those who acquire antiques are

watches and clocks; glassware (canary or Vaseline glass), tile, and ceramics; gas lantern mantles;

and camera lenses. Some old watches and clocks have dials that were painted with a radiation-

emitting compound to make them visible in the dark. Old glassware, tile, and ceramics that

contain radioactivity generally have enhanced naturally occurring radionuclides (such asuranium, thorium, or potassium) incorporated right into the glass or into the glaze. An older-style

gas lantern mantle with thorium in its silk threads is often used by radiation safety offices as a

source to check the operation of their radiation-detection instruments. Old camera lenses also

might contain some thorium, which was believed to create a better image on the film.

2 7 ARCHEOLOGY AND GEOLOGY

The principals of radioactive decay are employed widely in many fields of archeology

and geology to determine the nature and age of materials, artifacts and rocks.


23/28

23

2 7 1 Radioactive Dating

The principals of radioactive decay are applied in the technique of radioactive dating , a

process widely used by geologists and archaeologists to determine the age of materials and

artifacts.

Radioactive 14C atoms exist naturally. They are everywhere around us: in our clothes, in

the food we eat, even in the air we breathe. However, there are not many of these 1.310 -12

percent of all carbon atoms are the 14C isotope. This is why they do not pose danger to us - there

are so few of them.

The ratio of radioactive 14C atoms to stable 12C atoms in the atmosphere has remained

constant over thousands of years. 14C atoms are formed when neutrons from the sun's cosmic

radiation collide with 14 N atoms in the atmosphere

Thus the decay of 14 C is reasonably balanced with its production, resulting in a constant

ratio of 14 C to 12 C .

Fig.2.10: Production of Carbon - 14

Carbon dioxide (CO 2) molecules in the air can contain either isotope of carbon. This CO 2

is continually used by plants to grow. Because the ratio of 14C to 14C in atmospheric CO 2 is

constant, the intake of CO 2 by a plant results in a constant ratio of the two isotopes in the plant's


24/28

24

body while it is alive. However, when the plant dies it will no longer take in CO 2. As a result, the14C decaying in the dead plant will not be replenished by a "fresh supply" of more CO 2, resulting

in the ratio of 14C to 12C decreasing over time.

Because animals eat plants, the ratio of 14C to 12C in them also decreases once they die,

since the 14C cannot be replenished.

This process of dating using 14C is used by paleontologists. Paleontologists burn a small

sample of a fossil to react the carbon in it with oxygen, to form CO 2. The CO 2 that contains 14C

will be radioactive, and the amount can be easily measured using a radiation counter. Burning is

done to facilitate measuring the level of 14C.

14C has a half life of about 5730 years. This means that in a given sample of a carbon-

containing substance, the ratio of 14C to 12C will decrease by half every 5730 years. Suppose for

example, some archaeologists uncovered ancient manuscripts and found that the ratio of 14C to12C in the paper was half of that found in living trees. This would mean that the manuscripts

would be about 5730 years old.

The use of radioactive 14C for dating was first done by William Libby, an academic at the

University of Chigaco, USA, in 1947.

The relatively short half-life of 14C (5730 years) means that the amount of 14C remaining

in materials and objects older than about 80,000 years is too small to be measured with today's

equipment. Thus carbon dating is limited to objects which are not older than this. However, the

abundance of other atoms with longer half-lives, such as 238U (half-life 4.5 10 9 years) can be

measured in place of 14C. Geologists measure the amounts of other radioactive metal isotopes

such as 238 U, 84Rb and 40P found in rocks to determine their age. Measurements show that the

oldest rocks on Earth are about 4.6 billion years old - which is a reasonably accurate estimate of

the Earth's age. Similarly, analysis of fossilised plants shows that they first occurred on Earth

about 3 billion years ago.

The major problem using radiocarbon dating is the chance of getting carbon from the

samples mixed up with "fresh" carbon.


25/28

25

As well as using 14C to 12C decay, geologists also measure the decay of 40P to argon in

dating rocks. This method is not accurate for rocks that have been heated above 120c (250f)

because the argon diffuses out from the rock at these temperatures. The decay of 87Rb to 87Sr is

used to check potassium-argon dates, and is much more accurate because neither isotope is

diffused by heat. This rubidium technique was used by scientists to determine the age of the

moon. Measurements using 238 U were used to determine the age of the Earth.

2 7 2 Geology and Element Identification

Radioactivity is also used to identify the location of deposits of uranium and other

radioactive minerals. This is useful in mining exploration. The intensity of detected radiation

also is an indication of the amount of uranium that may be located there.

The mining industry employs radioactivity in its routines. One example is identification

of rocks and minerals. X-rays from a radioactive material can induce other materials to emit

fluorescent X-rays. These subsequent X-rays can have their energies measured, and then this

gives an indication of the elements present in the original material. The intensity of these X-rays

also is an indicator of the amount of the element present.

This technique is done by placing probes into the slurry - water that contains sediments of

minerals, etc. The probes contain a radioisotope and a detector. The radiation from the isotope

causes metals in the slurry to emit fluorescent X-rays - these are identified by the detector also

located on the probe. The probe's input is then analysed to give an indication of the types and

amount of metals present in the slurry. Metals that are detected this way include lead, copper, tin,

zinc, nickel and iron.

Elements that can absorb neutrons will release gamma rays. These gamma rays can be

analysed for their energies. Specific energies correspond to specific elements - thus this isanother way of identifying the metals and minerals that may be present.


26/28

26

2 8 SPACE MISSIONS

Radioisotope thermal generators are used in space missions. The heat generated by the

decay of a radioactive source, often 238Pu, is used to generate electricity. The Voyager space

probes, the Cassini mission to Saturn, the Galileo mission to Jupiter and the New Horizons

mission to Pluto all are powered by RTGs. A typical RTG produces about 300 watts of

electricity and will operate unattended for many years. The Spirit and Opportunity Mars rovers

have used a mix of solar panels for electricity and RTGs for heat. The latest Mars rover,

Curiosity, is much bigger and uses RTGs for heat and electricity as solar panels would not be

able to supply enough electricity.

In the future electricity or heat from nuclear power plants could be used to make hydrogen.

Hydrogen can be used in fuel cells to power cars, or can be burnt to provide heat in place of gas,

without producing emissions that would cause climate change.

Fig.2.11: Space crafts


27/28


28/28

applications of nuclear technology 2_2

Documents