STUDY OF RADIOACTIVITY AND MEASUREMENT OF ABSORPTION COEFFICIENT OF GAMMA RAYS OF PHOTONS FOR ALANINE Submitted to Dr. Babasaheb Ambedkar Marathwada University, Aurangabad Submitted By Mr. Haqi Esmail Shareef Under the guidance of Dr. Pravina Pawar 1
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STUDY OF RADIOACTIVITY AND MEASUREMENT
OF ABSORPTION COEFFICIENT OF GAMMA RAYS
OF PHOTONS FOR ALANINE
Submitted to
Dr. Babasaheb Ambedkar Marathwada University,
Aurangabad
Submitted By Mr. Haqi Esmail Shareef
Under the guidance of Dr. Pravina Pawar
Department of Physics,Dr. Babasaheb Ambedkar Marathwada University,
Aurangabad
1
Certificate This is to certify that Mr. Haqi Esmail Shareef has successfully
completed the project intitled “Study of Radioactivity and Measurement
Of absorption Coefficient of Gamma Rays of Photons for Alanine”
under the guide of Dr. K.M. Jadhav and Pravina Pawar.
For partial fulfillment of requirement for a work of the degree of
Master of Science in Physics with specialization Nuclear Physical in the
Academics year 2011-2012.
2
Prof. (Dr) K.M. Jadhav
(Professor Incharge)
Dr. Pravina Pawar
(Asst. Professor)
Prof. (Dr) P.W. Khirade
Examiner
AcknowledgmentI express my first and for most thanks and gratitude to Prof. Dr.
K.M. Jadhav Sir for permitting me to undertake this project work and
giving valuable guidance. He has a source of inspiration for completion
and shaping of the assigned work in a proper way. If feel honored to
remain indebted to him forever…
It is also a pleasure to express my gratitude thanks to Dr. Pravina
Pawar mam, for giving a valuable guidance. Her affective concern,
proper guidance, and inspiring nature naturally turned me towards the
fulfillment of my project… I also express thanks to my father and mother
and wife and two sons who directly helped and supported me all time.
Haqi Esmail Shareef
M.Sc. Physics(Nuclear Physics)
3
INDEXSr. No. Chapter Name Sr. No.
I Introduction 5-32Historical Introduction 5
Radioactivity 5-6
Definition of Radioactivity 6
Natural Radioactivity 7
Artificial Radioactivity 7
Units of Radioactivity 7
Types of decay 10
Activity measurements 12
Mathematics of radioactive decay 12
Universal law of radioactive decay 13
One –decay process 13
Glossary 14
Application of radioactivity 17
Nuclear medicine 17
Radiotherapy 18
Radioactive tracers 18
Industry and the Home 18
Power Generation 20
Art Restoration 20
Fundamental Laws Of Radioactivity 24
Radioactive decay series 29
II Introduction to biomolecule 33-54
4
Biomolecules 33
Importance of Biomolecules 33
Type of Biomolecules 34
Biomolecule - Amino - Acids 35
Amino acid - General Structure 38
Functional Significance of Amino Acid R-Groups
38
General Properties 39
Peptide Bonds 39
Classification 40
Physical Properties 42
Optical Properties of the Amino Acids 45
Chemical Nature of the Amino Acids 45
Acid-Base Properties of the Amino Acids 48
Amino Acid Benefits 49
Amino acids and their functions in the body 50
III Cross section 55-69
Gamma radiation 57
Absorption coefficient of Gamma ray photons
59
interaction of gamma ray photon with matter 61
IV Result & Discussion 88
V Conclusions 88-89
References 90-91
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CHAPTER - I
INTRODUCTION
HISTORICAL INTRODUCTION
In attempting to discover a possible connection between X-rays
and luminescence observed in a discharge tube, H. Becquerel (1895)
found that after exposure to cathode rasy potassium suranyl sulfate
possessed the property of affecting a photographic plate wrapped in black
paper, indicating that the uranium salt was emitting a penetrating type of
radiation. In the same year he made surprising discovery that uranium
compounds alone, without any previous treatment, are capable of fogging
a photographic plate, and so emit rays spontaneously. In addition to their
photographic action, the radiations were foud, like X-rays, to be capable
of ionizing the year, so that the activity of a uranium compound could be
measured by the rate at which a known quantity caused the discharged of
an electroscope. The emission of rays capable of producing these effects
is a fundamental property of the uranium atom, as the rays are observed
with various uranium salts in different valence states as well as with the
element itself; further, the activity is found to be independent of the
temperature or previous history of the material. The spontaneous
emission of radiation of this type is now known as
Radioactivity:
A study of the subject has thrown much light on the structure of
matter.
When examining the ionizing activity of the mineral pitchblende,
one of the chief ores of uranium and consisting mainly of U3O8 Mme. M.
Curie and her husband, P Curie (1898) Noted that it had a greater activity
than was expected from the uranium it contained. This result indicated the
6
presence in the ore of compounds an element, or elements, even more
radioactive than uranium and by using ordinary chemical methods of
separation, two such substances were isolated. One of the elements was
precipitated as its sulfide with bismuth sulfide; it was called polonium, in
honor of Poland, the native country of Mme. Curie. The other elements
separated together with barium as their sulfates, which were subsequently
converted the bromides and separated by fraction crystallization. The
elements, obtained as the impure bromide by M. Curie, P. Curie and G.
Bemont (1898), was given the name Radium because of exceptional
activity. After wards, A Debierne (1899) and F. Giesel (1901) found the
new radioelement actinium in uranium minerals.
In the course of a study of the penetrating power of the radiations.
Rutherford (1899) Concluded that they could be divided in to two types,
which he referred to as α-rays and β-Rays, Respectively.
Shortly afterwards P Curie Founded that part of radiation was not
deflected in a magnetic field, and this was shown by P. Villard to have
exceptional penetrating power, these radiations were called the γ-rays.
Definition of Radioactivity:
The phenomenon of spontaneous disintegration of an unstable
atomic nucleus accompanied by emission of radiation is called
radioactivity.
Radioactivity was discovered by Henry Becquerel in 1896. He
found that photographic plate was affected when placed near uranium
salt. He concluded that the Uranium might have emitted highly entreating
and invisible radiation. Later Madam Curic was confirmed the same. The
substances showing this property are called radioactive substances.e.g. U,
Ra, Th.
7
Natural Radioactivity:
The phenomenon of spontaneous emission of highly penetrating
and invisible radiation from heavy element is called natural radioactivity.
It is generally shown by heavy element having atomic number 83 or more
than that.
Artificial Radioactivity:
The process of stable nucleus into unstable radioactive nucleus by
bombarding it with suitable projectile is called artificial radioactivity.
It is generally shown by light element having atomic number less
than 83.
Units of Radioactivity:
In general, radiation is in the form of an alpha- particle (i.e.,
ionized helium atom having two units of positive charge and four units of
mass), a beta-ray (a particle of mass equal to that of an electron and of
either positive or negative charge emitted from a nucleus due to the
proton or neutron decay), a gamma –ray an electromagnetic radiation
similar to X-rays but emanating from a nucleus) and neutrons. A
radioactive material is characterized by the type of radiation it emits, the
energy of the emitted radiation, and its half.
Half –life is the time required for reducing the number of
radioactive to one-half the initial value. Some of the naturally
occurring radioisotopes have a very long half- life [in the range of
thousands of years (yr), whereas some artificially produced radioisotopes
have a very short half- life [ in the range of milliseconds (msec) to
microseconds (sec) ] Thus it is essential that we define the activity or
8
disintegration rat e of a radioisotope since each disintegration emits an
energetic particle which interacts with the surrounding medium.
The fundamental unit of radioactivity is the curie (Ci). One curie
represents 3.7 × 1010 disintegrations per second (dis/sec) of any type of
radiation. This unit has now been replaced by an SI unit, called the
Becquerel (Bq), which represents one disintegration per second. As is
evident, the Becquerel is itself a small unit. The conventionally used
units, smaller than the curie, are known as milicurie (mCi; 1 mCi = 10 -3
Ci) and microcurie (µCi; 1µCi =10-6 Ci) Most sources handled in a
laboratory are either of microcurie or, at the most, few millicurie strength.
The radioisotopes used in food processing and medical therapy can be of
the order of several kilocurie (kCi) or even megacurie (MCi)
If N represents the number of atoms of a radioactive substance and
its disintegration rate constant or decay constant (ie., probability of
disintegrations per second per atom) hen the product N … represents the
activity of the substance. The disintegration rate constant is related to half
life T ½ as 0.693/ T1/2 since, at any time t,N(t) Noe-. Therefore, for a
given N, a substance with a long half – life will be less active than a
substance with a short half- life. Thus, an optimal choice of weight and
half –life is always desirable, depending on the situation. Some of
radioisotopes commonly used in the laboratory and their radiations are
indicated in Fig 1.1 and Table 1.1.
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Table 1.1 Some common laboratory radioactive sources
(a) Gamma –ray Sources
Isotope Half life Gamma –ray energy
(Mev)137 Cs60Co
22 Na
54Mn88 Y
30 yr
5.25 yr
2.6 yr
300d
108d
0.662 (93.5%)
1.173 (100%)
1.332(100%)
1.275 (100%)
0.511 (100%)
0.835 (100%)
0.898 (91%)
1.836%)
Table 1.1 Some common laboratory radioactive sources
(b)Beta-ray sources ( negative)
Isotope Half life Maximum energy
(Mev)99 Tc14C3H204 TI147 PM35S32P90Sr/ 90Y
2.12 × 105 yr
5730 yr
12.26 yr
3.81 yr
2.62 yr
87.9 d
14.28d
27.7yr /64 hr
0.292
0.156
0.0186
0.766
0.224
0.167
1.71
0.56/2.27
10
Example Calculate the activity of 1 gm of radium, 226 Ra, whose half life
is 1620 yr.
One gram of radium contains (6.203 × 1023)/226 atoms. The decay
constant of radium is.
0.693 0.693= yr -1 = 1620 1620 yr × 365 d/yr × 24 hr /d × 3600 s ec.3/ hr
Types of decay
As for types of radioactive radiation, it was found that an electric
or magnetic field could split such emissions into three types of beams.
For lack of better terms, the rays were given the alphabetic names alpha,
beta and gamma, still in use today. While alpha decay was seen only in
heavier elements (atomic number 52, tellurium and greater), the other two
types of decay were seen in all of the elements.
In analyzing the nature of the decay products, it was obvious from
the direction of electromagnetic forces produced upon the radiations by
external magnetic and electric fields that alpha rays carried a positive
charge, beta rays carried negative charge, and gamma rays were neutral.
From the magnitude of deflection, it was clear that alpha particles were
much more massive than beta particles. Passing alpha particles through a
very thin glass window and trapping them in a discharge tube allowed
researchers to study the emission spectrum of the resulting gas, and
ultimately prove that alpha particles are helium nuclei. Other experiments
showed the similarity between classical beta radiation and cathode rays.
They are both streams of electrons. Likewise gamma radiation and x-rays
were found to be similar high – energy electromagnetic radiation.
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Although alpha, beta, and gamma were found most commonly,
other types of decay were eventually discovered. Shortly after the
discovery of the positron in cosmic ray products, it was realized that the
same process that operates in classical beta decay can also produce
positrons. (Positron emission). In an analogous process, instead of
emitting positrons and neutrinos, some proton-rich nuclides were found to
capture their own atomic electrons (electron capture) and emit only a
neutrino (and usually also a gamma ray). Each of these types of decay
involves the capture or emission of nuclear electrons or positrons, and
acts to move a nucleus toward the ratio. Some radionuclides may have
several different paths of decay. For example, approximately 36% of
bismuth decays, through alpha –emission, to thallium -208 while
approximately 64% of bismuth 212 decays, through beta – emission to
polonium -212. Both thallium-208 and the polonium-212 is radioactive
daughter of bismuth -212. And both decay directly to stable lead -208.
Constant quantities
The half –life – T ½, is the lime taken for the activity of a given
amount of a radioactive substance to decay to half of its initial
value.
The mean lifetime- T, “tau” the average lifetime of radioactive
particle before decay.
The decay constant - lambda” the inverse of the mean lifetime.
Although these are constants, they are associated with statistically
random behavior of populations of atoms. In consequence predictions
using these constants are less accurate for small number of atoms.
In principle the reciprocal of any number greater than one- half life,
third life or even a ( 1/2- life – can be used in exactly the same way as
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half –life , but the half – life t ½ is adopted as the standard time associated
with exponential decay.
Time- variable quantities:
Total activity – A is number of decays per unit time of a
radioactive sample.
Number of particles – N is the total number of particles in
the sample.
Specific activity – SA, number of decays per unit time per
amount of substance of the sample at time set to Zero (t=0)
Amount of substance can be the mass, volume or moles of the
initial sample.
These are related as follows
Where α0 is the initial amount of active substance- substance that has the
same percentage of unstable particles as when the substance was formed.
Activity measurements
The units in which activities are measured are becqurel (symbol
Bq) = one disintegration per second, curie (Ci) = 3.7×1010 Bq. Low
activities are also measured in disintegrations per minute (dpm).
Mathematics of radioactive decay
For the mathematical details of exponential decay in general
context, see exponential decay for related derivations with some further
details, see half –life.
For the analogous mathematics in 1st order chemical reactions, see
consecutive reactions.
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Universal law of radioactive decay
Radioactivity is one very frequent example of exponential decay.
The law however is only statistical – not exact. In the following
formalism, the number of nuclides or nuclide population N, is of course a
discrete variable ( a natural number) but for any physical sample N is so
large (amounts of L =1023 Avogadro’s constant) that it can be treated as
a continuous variable. Differential calculus to set up differential equations
for modeling the behavior of the nuclear decay.
One –decay process
Consider the case of a nuclide a decaying into another B by some
process A B (emission of other particles, like electron neutrinos V.
E and electrons e in beta decay are irrelevant in what follows). The
decay of an unstable nucleus is entirely random and it is impossible to
predict when a particular atom will decay. However it is equally likely to
decay at any time. Therefore, given a sample of a particular radioisotope,
the number of decay events – d/ N expected to occur in a small interval
of time d/ is proportional to the number of atoms present N that is.
Particular radionuclides decay at different rates, so each has its
own decay constant they probability of decay – dN/* N is proportional
to an increment of time df.
The negative sign indicates that N decrease as time increases, as
each decay event follows one after another. The solution to this first order
differential equation is the function.
Where N0 is the value of N at time t = 0
14
This equation is of particular interest; the behavior of numerous
important quantities can be found from it (see below). Although the
parent decay distribution follows an exponential, observations of decay
times will be limited by a finite integer number of N atoms and follow
Poisson statistics as a consequence of t he random nature of the process.
We have for all time t:
NA + NB = N total = N A0,
Where Ntotal is the constant number of particles throughout the
decay process, clearly equal to the initial number of nuclides since this is
the initial substance.
If the number of non –decayed A nuclei is: Then the number of
nuclei of B, i.e. number of decayed a nuclei, is
Glossary :
Important terms used in connection with radioactivity are given
below; the terms given do not necessarily appear in the present article.
Alpha particle: charged particles emitted from a radioactive atom.
Each charged particle consists of two protons and two neutrons. Atom:
This is the smallest unit of an element. It contains a nucleus with neutrons
and protons, surrounded by orbiting electrons. Atomic mass: the mass of
an atom usually expressed as atomic mass unit (amu).
Beta particle: (often designated beta rays) charged particles emitted from
a radioactive atom. These particles are identical except for their charge.
The charge is classified as positive (positron) or negative (electrons or
negatron).
15
Carbon 14: A naturally occurring radio isotope of carbon having a mass
number of 14 and half life 5780 years. Used in Radio carbon dating for
determination of age of ancient objects.
Cathode ray: Electrons originating at the cathodes of gaseous discharge
devices.3 these electrons are often focused in a small area such as a tube
and intensified on a surface. The most familiar form of a cathode- ray
tube is the television picture tube.
Conductivity: The ratio of electric current to the field in a material.
Passage of electric charger which can be occur a variety of ways such as
passage of electrons or ionized atoms.
Curie: A unit of radioactivity, defined as that quantity of any radioactive
nuclide which has 3700 x 1010 disintegrations per second.
Deuterium: The isotope of element hydrogen with one neutron and one
proton in his nucleus.
Electrons: A negative charged particle that orbits the nucleus of an atom.
It is lighter in weight than a proton or neutron.
Elements: An element is a substance made up of atoms with the same
atomic number. 75% of the elements are metals and the others are
nonmetals. A few examples are oxygen, iron, gold, chlorine, and
uranium.
Fluorescence: Electrons absorb energetic radiation (for example
ultraviolet light) raising an electron to a higher “Bohr” orbit. The
energized electron soon drops down in a series of steps through lower
energy states and in the process release photons at lower energy stares
corresponding to visible light. The bright color occurs because the
photons are concentrated in a narrow range of wavelengths.
16
Geiger counter : A radiation counter that uses a Geiger – Muller tube in
appropriate circuits to detect and count ionizing particles , each particle
crossing the tube produces ionization of gas in the tube which is roughly
independent of the particle’s nature and energy resulting a uniform
discharge across the tube. Also knows as Geiger – Muller counter.
Geiger Muller tube: A radiation counter tube usually consisting of a gas
–filled cylindrical metal chamber containing a fine –wire anode at its
axis. Also knows as Geiger – Muller Counter tube.
Half –life: The period of time in takes for half the nuclei of a radioactive
element to undergo decay to another nuclear form.
Heavy water: A compound of hydrogen and oxygen containing a higher
proportion of the hydrogen isotope deuterium, than does naturally
occurring water.
Ionization chamber: A particle detector which measures the ionization
produced in the gas filling the chamber by the fast moving charged
particles as they pass through.
Isotope: Atoms having the same number of protons in its nucleus as other
varieties of the element but has a different number of neutrons.
Magnetic field: All magnetic fields are created by moving electric
charge. The single moving electron around a nucleus is a tiny electric
current. These orbiting electrons create magnetic fields and their net
effect is to provide the atom with a magnetic field.
Neutron: A particle with no charge that is located in the nucleus of an
atom.
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Nuclear physics: A branch of physics that includes the study of the
nuclei of atoms, their interactions with each other, and with constituent
particles.
Nucleus: The central part of every atom that contains protons and
neutrons.
Nuclide: A species of atom characterized by the number of protons,
number, and energy content in the nucleus, or alternatively by the atomic
number, mass number and atomic mass. To be regarded as a district
nuclide, the atom must be capable of existing for a measurable life time.
Also knows as nuclear species.
Application of radioactivity:
The principles of radioactivity and radioactivity decay have wide –
ranging applications in medicine, industry, the home, the arts and
sciences, and electric power generation.
Nuclear medicine:
Nuclear medicine is a branch of medicine and medical imaging that
uses the nuclear properties of matter in diagnosis and therapy. Many
procedures in nuclear medicine use pharmaceuticals that have been
labeled with radionuclides (radiopharmaceuticals). In diagnosis,
radioactive substances are administered to patients and the radiation
emitted is measured. The majority of these diagnostic tests involve the
formation of an image using a gamma camera. Imaging may also be
referred to as radionuclide imaging or nuclear scintigraphy. Other
diagnostic tests use probes to acquire measurements from parts of the
body, or counters for the measurement of samples taken from the patient.
In therapy, radionuclides are administered to treat disease or provide
18
palliative pain relief. For example, administration of Iodine -131 is often
used for the treatment of thyrotoxicosis and thyroid cancer.
Radiotherapy
Radiation therapy (or radiotherapy) is the medical use of ionizing
radiation as part of cancer treatment to control malignant cells. The
radiation may be given in the form of external beam radiotherapy of high
– energy electrons or X-rays or it may come from radioactive sources
placed inside the patient.
Radioactive tracers
Radioactive tracers are radioactive substances added in minute
amounts to the reacting elements or compounds in a chemical process and
traced through the process by appropriate detection methods, e.g. Geiger
counter. Compounds containing tracers are often said to be tagged or
labeled.
In medical applications, a radioactive atom can be attached to a
molecule or more complex substance, which can then be used to examine
a chemical reaction in a test tube, or it can be administered to a patient by
ingestion or injection and subsequently be incorporated into a
biochemical process. The radioactive emissions from the radioactive
atom can be used to track the behavior of the labeled molecule or
substance in biological process by means of medical imaging.
Industry and the Home
Radiation processing is the use of ionizing radiation to produce
beneficial physical chemical or biological effects on an industrial scale.
Examples include.
19
The isotope 252Cf (a neutron emitter) is used in neutron activation
analysis to inspect airline luggage for hidden explosives, to gauge
the moisture content of soil and other materials, in bore hole
logging in geology, and in human cervix cancer therapy.
In paper mills, the thickness of the paper can be controlled by
measuring how much beta radiation passes through the paper to a
Geiger counter. The counter controls the pressure of the rollers to
give the correct thickness.
Checking Welds. If a gamma source is placed on one side of the
welded metal, and a photographic film on the other side, weak
points or air bubbles will show up on the film.
Foodstuffs can be irradiated to extend shelf life or reduce the
numbers of harmful bacteria.
Improve material properties, particularly in polymers, curing
adhesives and resins, improvement of gemstones, wire and cable
jacket curing, tire manufacture.
Smoke alarms contain a weak source made of Americium -241.
Alpha particles are emitted that ionize the air, so that the air
conducts electricity and a small current flow. If smoke enters the
alarm, this absorbs the particles, the current reduces and the
alarm sounds.
Radiation has many uses in agriculture. In plant research, radiation
is used to develop new plant types to speed up the process of developing
superior agricultural products. Insect control is another important
application; pest populations are drastically reduced and, in some cases,
eliminated by exposing male insects to sterilizing doses of radiation.
Fertilizer consumption has been reduced through research with
radioactive tracers. Radiation pellets are used is grain elevators to kill
20
insects and rodents. Irradiation prolongs the shelf- life of foods by
destroying bacteria, viruses and molds.
Radioactive dating
Radioactive dating or radiometric dating is a technique used to date
materials based on knowledge of the decay rates of naturally occurring
isotopes, and their current abundances. Many isotopes have been studied,
probing a wide range of time scales. Radioactive dating is the principal
source of information about the age of the Earth and rates of evolutionary
change and is used to estimate the age of once- living materials.
Power Generation
Nuclear power is a type of nuclear technology involving the
controlled used of nuclear fission to release energy for work including
propulsion, heat and the generation of electricity. Nuclear energy is
produced by a controlled nuclear chain reaction and creates heat which is
used to boil water, produce steam and drive a steam turbine. The turbine
can be used for mechanical work and also to generate electricity. As of
2007, nuclear power provided about 6% of the world’s energy and 16%
of the world’s electricity with the U.S. France, and Japan together
accounting for 57% of all nuclear generated electricity.
Art Restoration
Nuclear science plays an important role in the art world. A
technique known as X-ray fluorescence spectroscopy (or XRF) works by
irradiating samples of materials using X-rays without destroying the
analyzed material. At the same time, it can identify a vast number of
21
elements simultaneously, making it an excellent way to “fingerprint” all
kinds of materials. For example, XRF has been used to examine the tip of
David’s nose, analyzing dust and dirt before Michelango’s masterpiece
could be safely restored.
Restration work on Cellini’s bronze statue of Perseus at the Uffizi
Museum in Florence also benefited from insights gained using XRF.
Examinations of Perseus right knee showed that the bronze alloy was
composed of varying percentages of copper, tin lead, antimony, iron and
silver.
Clues from XRF results also can aid forensic scientists in solving
crimes; for example, by determining if a paint pigment matches the artist
original palette. Discovering the presence of a modern replacement for an
old traditional pigment known to be used by a particular artist can provide
evidence that a painting is a forgery.
Common Radioisotopes and Their Uses
Americium – 2141 : Used in many smoke detectors for homes and
business to measure levels of toxic lead in dried paint samples , to ensure
uniform thickness in rolling processes like steel and paper production,
and to help determine where oil wells should be drilled.
Cadmium 109: Used to analyze metal alloys for checking stock and
sorting scrap.
Californium -252: Used to measure the mineral content of coal ash and
to measure the moisture of materials stored in silos.
Carbon -14: Used in research to ensure that potential new drugs are
metabolized without forming harmful by products.
22
Cesium 137 : Used to treat cancers ; to calibrate the equipment used to
measure correct patient dosages of radioactive pharmaceuticals; to
measure and control the liquid flow in oil pipelines; to tell researchers
whether oil wells are plugged by sand; and to ensure the right fill level
for packages of food, drugs and other products. (The products in these
packages do not become radioactive).
Chromium -51: Used in research in red blood cell survival studies.
Cobalt -57: used in nuclear medicine to help physicians interpret
diagnostic scans of patients organs and to diagnose pernicious anemia.
Cobalt 60: Used to sterilize surgical instruments: to improve the safety
and reliability of industrial fuel oil burners: and to preserve poultry, fruits
sand spices.
Copper 67: When injected with monoclonal antibodies into a cancer
patient. Helps the antibodies bind to and destroy the tumor.
Curium 244: Used in mining to analyze material excavated from pits and
slurries from drilling operations.
Iodine 131: Used to diagnose and treat thyroid disorders.
Iridium 192: Used to test the integrity of pipeline welds boilers and
aircraft parts.
Iron 55: Used to analyze electroplating solutions.
Krypton 85 : Used in indicator lights in appliances like clothes of thin
plastics sheet metal washers and dryers, stereos and coffeemakers to
gauge the thickness of thin plastics, sheet metal, rubber, textiles and
paper and to measure dust and pollutant levels.
23
Nickel 63: Used to detect explosives and as voltage regulators and
current surge protectors in electronic devices
Phosphorus 32: Used in molecular biology and genetics research.
Sources
International Atomic Energy Agency, In Vienna‘s Art World
Nuclear Science Feeds a “Happy End” Accessed 27 August 2007.
McGraw Hill Dictionary of Scientific and Technical Terms Sci-
Tech Dictionary definition of radioactive tracer (New York,
McGraw – Hill Companies. Inc.2003)
Nuclear Management Company. Medical and industrial uses of
radioactive materials, Accessed 27 August 2007.
Wikipedia Contributors, Radiation therapy, Wikipedia the Free
Encyclopedia. Accessed 27 August 2007.
Wikipedia contributors, Nuclear power, Wikipedia the Free
Encyclopedia Accessed 27 August 2007.
Controlling Exposure to external radiation
Shielding:
There is a variety of shielding materials that can be placed between
you and source to absorb most of the radiation that would otherwise reach
you.
The choice of shielding material depends on the type of radiation
and other functions served by the shields (such as containment,
transparency or structural support).
24
Dense materials with high atomic numbers, such as lead, form the
most effective and compact shields for small sources of penetrating
radiation. Because beta rays are less penetrating than other rays, pure beta
ray emitters can be effectively shielded by lighter materials such as glass,
water or Lucite.
When high ener4gy beta rays are emitted and absorbed secondary
X-ray and bremsstrahlung radiation are generated. The intensity of his
secondary radiation increases if the beta rays are absorbed in high atomic
number shielding material. This secondary radiation is more penetrating
than the beta rays when large quantities (ie. Greater than 100 mCi, or 3.7
GBq) of a pure beta emitter like 32 p are used, the quantity of secondary
radiation may be excessive unless shielded. The best shielding
configuration in this case4 is to use a ½ inch-thick Lucite acrylic sheet or
similar material, adjacent to the 32 p to absorb the beta rays, while
minimizing the creation of secondary radiation. Use sheets of lead foil
outside the shields of Lucite to absorb the more penetrating
bremsstrahlung and x rays.
Fundamental Laws of Radioactivity:
1) Soddy Fajan’s Displacement Law:
When a radioactive disintegration occurs with the emission of
and particles the original atom called the parent atom changes
into same thing else called the daughter. In 1913 Soddy and Fajan
discovered a simple law known as the displacement law of
radioactivity, can be stated as follows.
(a) When a radioactive atom emits and particles (mass 4 and
charge 2e) it is converted into another element of atomic number
25
two less than that of the parent element and the place of the new
atom is shifted two groups lowers in the periodic table.
+
(b) When a radioactive atom emits a particles ( mass approximately
Zero and charge –e) it is converted into another element of atomic
number one greater than that of the parent element but of the same
atomic weight and the place of the new atom is shifted one group
higher in the periodic table.
-1eo
Now a day these rules are stated as follows
a) Algebraic sum of the electric changes before disintegration must be
equal to the total charge disintegration.
b) The sum of mass numbers of the initial particles must be equal to
the sum of mass numbers of the final particles.
2) Law of radioactive disintegration
This law was established expectably in 1902 by Rutherford and
Soddy in Great Britain. They found that the rate at which a particular
radioactive material disintegrates or decays was independent of
physical and chemical condition and was dependent of physical and
chemical condition and was dependent of number of atom present at
that time. Since disintegration is taking place continuously the number
of atoms present is changing hence the rate of disintegration will
change with time.
Let N be the number of atoms present in a particular radio element
at a given instant t. The number of dN that will decay during the time
26
interval dt (from t to t +dt) must be proportional to N and also
proportional to dt.
Thus we have
dN N dt
Or
dN = -l Ndt
Where is constant is known as disintegration constant of the
radioactive element. Negative sign indicates that number of atom of the
radioactive element decreases with time.
On rearranging and integrating equation (1)
We get,
N= No ------------ (2)
Where No is the initial number of atom of the radioactive nuclide.
Here we have assumed that the probability of disintegration per second
is independent of the age of that atom and is the same for all atoms of the
species. For a nuclide having several modes of decay is the probability
of decay and is sum of the probabilities 1, 2 of the individual modes
of decay.
3) Law of Successive Transformation:
In general one radioactive substance decays into another that is
also radioactive. The first is called the parent (or mother) substance, the
second the daughter substance. This relation is not limited to parent and
27
daughter but extends over many generations, until a stable and product is
reached. It was found experimentally that the naturally occurring
radioactive nuclides from three series. In the study of radioactive series it
is important to know the number of atoms of each member of the series as
a function of time.
If a time t = 0 we have N1 (0), N2 (0) …atoms of radioactive
substance 1, 2 …etc.
Respectively Now we have to find the number of atoms N1 (t) N2
(t) …. Present at any subsequent time‘t’
Substance first decays according to the law given by equation (1)
dN1/dt = - N1 1 …………………… (8)
The number of atoms of substance 2 decreases because substance 2
decays and increases because of the decay of substance.
dN2/dt = N1 – N2
From equation (8) the number of atoms N1 can be written as,
N1 = N1(0) ……..(10)
Inserting this value of n1 in equation (9)
We have,
dN2/dt = N1 (0) - N2
Or
dN2/dt + N2 = N1 (0)
28
Multiplying it throughout by and then integrating we have,
N2 = / N1 (0)
Where is a constant of integration
Since N2 = N2 (0) when t = 0 hence we have.
C- N2 (0) - / N1 (0)
N2= / N1 (0)
= / N1 (0) (N2 (0) –N1 / ------------ (11)
This treatment can be extended to a chain of any number of radioactive
products. The procedure is similar to that of the special case already
discussed except that the mathematics becomes more tedious as the
length of the chain increase. The differential equations representing the
number of atoms each member of the series are given as
dN1 /dt = N1
dn2/dt = N1- N2……………………..(12)
- - -
- - -
- - -
dNn /dt = n-1 – n Nn……(13)
The family of differential can be solved by Putting.
N1 = C11 e ………………(14)
29
--- --- ---
--- --- ---
--- --- ---
N2=C2 e +Cn2e +Cnn ------------- (16)
The constants C11, C21, C22 ….Cnn were determined by Bateman under the
assumption that at t = only the parent.
l.e. at t = 0, N1 = N1 (0), N2= N3= N4 = ….=0
from equation (14) we get C11= N1 =(0)
N1= N1 (0)
From equation (12) and (15) we get
0 = C11 e0 + C22 e0 or C21 = -C21
And
C11 = -C22 = N1 (0) – ( C21=- C21)
And
C21 = and
C22 =
N2 = N1 (0)
The number of atoms of the nth member of the chain is obtained by
equation (16) where constants are having values.
30
Cn1=
Cn2=
= exp - 0.766
Table (1-1): Radioactive decay series
Series First Isotopes Half-Life [Y] Last IsotopesUranium 238U 4.49x109 206Pb
Actinium 235U 7.10x108 207Pb
Thorium 232Th 1.39x1010 208Pb
Neptunium 237Np 2.17x106 209Bi
There are three natural radioactive series, called uranium, thorium
and actinium series. Neptunium series is included in this table too, which
does not occur in nature because it’s half life “2.1x106 y” is much smaller
than the age of the universe “3x109 y” [46].
1.2. a: U-238 Series
This series begins with U-238 nuclei (half-life 4.49x109y) and
gradually converted to the Pb-206 which is a stable element through
sequences of the emission of alpha and beta particles. All nuclides in this
31
series are solid elements except Rn-222 nuclei, which is gas. The
elements of this series which are represented in Table (1-2) are arranged
according to the mass number indicated in (4n+2) system.
Table (1-2): U-238 Decay Series [47, 78]
1.2. b: U-235 Series
This series begins with U-235 nuclei (half life 7.10x108 y), which
is the longest half life comparing to other elements in this series and ends
with Pb-207, which is a stable element. The elements of this series which
are represented in Table (1-3) are arranged according to the mass number
indicated in (4n+3) system.
Nuclide Half-life Type of decay
U-238 4.49x109y Alpha
Th-23 24.1 d Beta
Pa-234m 1.18 min Beta
U-234 2.48x105 y Alpha
Th-230 7.52x104 y Alpha
Ra-226 1600 y Alpha
Rn-222 3.825 d Alpha
Po-218 3.05 min Alpha
Pb-214 26.8 min Beta,
Bi-214 19.7 min Beta
Po-214 1.6x10-4s Alpha
Pb-210 22 y Beta
Bi-210 5.01 d Beta
Po-210 138.4 d Alpha
Pb-206
32
Table (1-2): U-238 Decay Series [47, 78]
1.2. c : Th-232 Series
Thorium was discovered by “Berzelius”, which is derived from the
Scandinavian god “Thor”. This series begin with Th-232 nuclei (half life
1.39x1010 y) and end with Pb-208 isotope. The elements of this series
which are represented in Table (1-4) are arranged according to the mass
number indicated in (4n) system.
Table (1-4): Th-232 Decay Series [47-48]
Nuclide Half-life Type of decay
Nuclide Half-life Type of decay
U-235 7.10x108 y Alpha
Th-231 25.6 h Beta
Pa-231 3.98x104 y Alpha
Ac-227 22 y Beta
Th 227 or Fr-233
18.17 d
22 min
Alpha
Beta
Ra-223 11.7 d Alpha
Rn-219 3.92 s Alpha
Po-215 1.83x10-3 s Alpha
Pb-211 36.1 min Beta,
Bi-211 2.15 min Alpha
Po-211 0.52 sec Alpha
Ti-207 4.79 min Beta
Pb-207 Stable ---
33
Th-232 1.39x1010 y Alpha
Ra-228 6.7 y Beta
Ac-228 6.13 h Beta
Th-228 1.9 y Alpha
Ra-224 3.64 d Alpha
Rn-220 54.5 s Alpha
Po-216 0.158 s Alpha
Pb-212 10.6 h Beta
Bi-212 60.0 min Beta
Ti-208or
Po-212
3.1 min
3.0x10-7 s
Beta
Alpha
1.2. d: Np-237 Series
Np-237 which a half-life (2.14x106 y), which is much shorter than
the geological age of the earth. Virtually all neptunium decayed within
the first 50 millions of years after the earth was formed [45]. So 237Np
did not find in nature but it discovered in some` stars spectrum [49].
CHAPTER - II
34
INTRODUCTION TO BIOMOLECULE
Biomolecules:
A biomolecule is defined as an organic compound which is found
in almost all the living organisms. These are the molecules that are
composed of carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus and
sometimes some other elements to a very small extent.
Importance of Biomolecule:
Biomolecule play a very important role in the functioning of living
organization and therefore these are considered as the building blocks of
life.
Biomolecule are essential for life to exist. These molecules make
up and control a living organism’s body. These play a vital role in the
development of living organization. An organism needs each and every
biomolecule in a proper amount for the functioning and well being of his
body. Each biomolecule has a certain task and duty that keeps the body
healthy and control it.
Biomolecule are necessary for the existence of all known forms of
life. For example, humans possess skin and hair. The main component of
hair is keratin, an agglomeration of proteins which are themselves
polymers built from amino acids. Amino acids are some of the most
important building blacks used, in nature, to construct larger molecules.
Another type of building block is the nucleotides, each of which consists
of three components; a Purina or pyramiding base, a pentose sugar or a
phosphate group these nucleotides, mainly, from the nucleic acids.
35
Beside the polymeric biomolecule, numerous small organic
molecules are absorbed or synthesized by living systems. Many
biomolecule may be useful or important drugs.
Type of Biomolecule:
Biomolecule ranges from a small molecule to large polymers.
A. Small Molecules mainly include molecules like :
Lipids such as phospholipids, glycolipids, sterols, and
glyceroliopids: - are the main components or biological membranes
and as function as the highest energy providing molecules.
Carbohydrates such as sugars also provide energy and act as
energy storage molecules.
Vitamins though not synthesized by organisms, are important
biomolecule, which are necessary for the survival and health of
organization.
Hormones, neurotransmitters and metabolites: hormones regulate
the metabolic processes and many other functions of organisms.
B. Monomers include :
Amino acids: buildings blocks of proteins function as genetic code
and as biomolecule that assist in other processes such as lipid
transport.
Nucleotides: They are the source of chemical energy (ATP, GTP),
assist in cellular signaling, and participate in important enzymatic
reaction (coenzyme A, flavin) adenine dinucleotide, flavin
The following observations are made from Eqs. (17), (18) and (19) :
i) eσ, eσs, and eσa (cm/electron) are independent of the properties of the
absorber while µσ, µσs, and µσa are functions of the atomic umber of the
material, i.e., the scattering is proportional to Z.
ii) The mass absorption coefficient µσ/ρ given by
σ/ρ =NA (Z/A) eσ (20)
Because for light elements Z/A ~ ½, Eq. (20) implies that the mass
absorption coefficient for a given photon energy is practically constant
for light elements.
iii) The decrease of the total scattering coefficient per electron, eσ, is
slow for photon energies up to 0.5 Mev, but beyond that the decrease is
roughly proportional 1hv.
C) Pair production (P.P.): (possible only when energy is above 1.02
Mev.)
The third most important process by which photons lose there is
electron-positron pair formation. The threshold energy for this process is
2m0c2. It is found that if a photon of energy greater than 1.02 Mev strikes
a foil of high Z, the photon disappears and in its place an electron
positron pair is formed (Fig. 3). If a pair is produced in cloud chamber
and a magnetic field is applied, the electrons and positrons are deflected
in the opposite direction which equal curvature.
70
The conservation of momentum requires the presence of a heavy
body. Actually the pair formation takes place in the filed of the nucleus
and the conservation of energy gives
hv=2m0c2+E++E_+Enuc (21)
where hv=energy of the incident photon,
2m0c2 = energy of the equivalent to the reset mass of the electron
and the positron;
E+, E_, Enuc = the kinetic energies of the positron, electron, and the
recoiling nucleus, respectively.
Because the mass of the nucleus is very large, it takes away a very
small amount of kinetic energy, and so Enuc am be neglected. Thus Eq.
(21) takes the form
hv = 2m0c2 + E++E (22)
which clearly shows that the threshold for pair formation is 2m0c2 or 1.02
Mev.
Fig. 3 Electron-positron pair formation,
Pair production is also possible in the field of light particles, but
the threshold is such cases are higher. The theoretical calculation has
been accomplished by H. Bethe and W. Heilter. The absorption
coefficient aK per atom increase with increasing energy of the photon and
also increase with Z2.
71
CHAPTER - IV
RESULT & DISCUSSION
Table 1 Counts per 60 second for Alanine at 0.662 MeV.
I0 = 6683
Back ground counts: 58
Source used Cs 137
Photo Peak 5.3
Sr. No. Thickness (g/cm2)
Trial I Trial II Mean I/ I I0/I
1
2
3
4
5
0.474
0.548
1.423
1.897
2.371
6678
6300
5969
5860
5778
6670
6306
5975
5878
5760
6674
6303
5972
5869
5769
6616
6245
5914
5811
5711
1.01
1.07
1.13
1.15
1.17
72
Figure 1.Plot of I0/I Vs thickness t for Alanine at 0.662 MeV.
73
Table 2 Counts per 60 second for Alanine at 1.17 MeV.
I0 = 1988
Back ground counts: 38
Source used Co 60
Photo Peak 6.1
Sr. No. Thickness (g/cm2)
Trial I Trial II Mean I/ I I0/I
1
2
3
4
5
0.474
0.548
1.423
1.897
2.371
1976
1932
1860
1816
1780
1960
1830
1862
1810
1782
1968
1931
1861
1813
1781
1930
1893
1823
1775
1743
1.03
1.05
1.09
1.12
1.14
74
Figure 2.Plot of I0/I Vs thickness t for Alanine at 1.17 MeV
75
Table 3 Counts per 60 second for Alanine at 1.280 MeV.
I0 = 17022
Back ground counts 58
Source used : Na22
Photo Peak 9.1
Sr. No Thickness (g/cm2)
Trial I Trial II Mean I/ I I0/I
1
2
3
4
5
0.474
0.548
1.423
1.897
2.371
16752
16420
16122
15670
14993
16740
16430
16110
15678
14985
16746
16425
16116
15674
14989
16688
16367
16058
15616
14931
1.02
1.04
1.06
1.09
1.14
76
Figure 3 .Plot of I0/I Vs thickness t for Alanine at 1.280 MeV.
77
Table 4 Counts per 60 second for Alanine at 1.33 MeV.
I0 = 2536
B. C Background count: 40
Source used: Co60
Photo peak: 7.8
Sr No Thickness (g/cm2)
Trial I Trial II Mean I/ I I0/I
1
2
3
4
5
0.474
0.548
1.423
1.897
2.371
2532
2430
2415
2300
2288
2520
2434
2405
2308
2280
2526
2432
2410
2304
2284
2486
2392
2370
2264
2244
1.02
1.06
1.07
1.12
1.13
78
Figure 4.Plot of I0/I Vs thickness t for Alanine at 1.33 MeV.
79
Table 5: Linear attenuation coefficient μ (cm-1) and mass attenuation coefficient μ/ρ (cm2/g) of Alanine absorber at Photon energies 0.662, 1.170, 1.280 and 1.330 MeV