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Nuclear Chemistry and nuclear reactions in nature
1. Nuclear Chemistry
•The study of the changes some atomic nuclei undergo.
•A nuclear reaction may result in one or more of the following:
•conversion of an atom to its isotope or an atom of another
element,
•conversion of mass into energy or vice versa, and
•release of nuclear radiations.
2. Importance of nuclear reaction
• Although nuclear reactions are less numerous than chemical
reactions, they are essential in many aspects
• they are the source of energy in the sun and stars and the synthesis of
elements in the universe.
• Nuclear reactions are becoming essential in human life:
• electricity production from nuclear power plants,
• a source of radioisotopes for medical imaging to visualize organs and
diagnose diseases, to treat tumors, and cancerous cells,
3. Nuclear nomenclature and symbols
Nucleoid
• Nucleoid is another name for the nucleus of an atom, that is often used in
nuclear chemistry.
• The composition of a nucleoid is represented by the same symbol that
represents the isotopes of elements, as Z
A
X ,
• where X is the element symbol, Z is the number of protons (atomic #, P+, and A is the
number of protons and neutron in the nucleus (mass# P+ and n0).
• For example, carbon exists as a mixture of , 6
12
C and 6
13
C isotopes.
• Similarly, hydrogen exists as a mixture of 1
1
H , 1
2
H and 1
3
H , that can also be
represented as hydrogen-1, hydrogen-2, and hydrogen-3, respectively.
4. Importance of nuclear reaction
Spectrum of medical imaging (left) and radiation therapy of the pelvis. (right).
5. Nuclear nomenclature and symbols
Nucleons
• The protons and neutrons are also called nucleons.
Nuclear reaction
• A nuclear reaction is a process in which two nuclei, or a nucleus and an
external subatomic particle, collide to produce one or more new nuclides.
• The reactant nucleoid, called the parent nucleoid, usually transforms into a
different nucleoid called the daughter nucleoid.
• The daughter nucleoid may be an isotope of the parent nucleoid, or it may be
a different element.
• The conversion of an isotope to another isotope of the same or a different
element is a nuclear reaction that is called transmutation or a nuclear
transformation,
6. Nuclear reaction
• A nuclear fission reaction in which a parent nucleoid 92
235
U absorbs a
neutron and transforms to a daughter nucleoid 92
236
U, which later on
transforms to two daughter nucleoids 56
144
Ba and 36
89
Kr along with
emission three protons.
7. • Unstable Isotopes - Atoms that spontaneously release protons and
neutrons from the nucleus.
• Stable Isotopes -Atoms that do not release protons or neutrons from
the nucleus and ARE NOT RADIOACTIVE
• These isotopes ARE RADIOACTIVE.
Radioactive Isotopes
8. Mass Defect
• Some of the mass can be converted into energy
• Shown by a very famous equation!
E=mc2
Energy
Mass
Speed of light
9. Nuclear radiation
• Nuclear radiation or radioactivity is the particles and energy emitted by the
nucleus during a nuclear reaction.
• The nuclear reaction is accompanied by the emission of nuclear radiations.
• The nuclear radiations include gamma-rays (γ-rays), alpha-particles α-particles), beta-
particle ( β-particles), neutrons (n), and positron ( β+-particles).
• Nuclear radiations are ionizing radiations, i.e., they can knock off electrons
from the atoms they come in contact with.
10. Nuclear radiation
Gamm-rays
• The gamma-rays are electromagnetic radiations that have no mass and have energy higher
than that of X-rays. The symbol , γ, 0
0
γ or γ-ray represents a gamma-ray.
Alpha-particles
• The alpha-particles (α-particles ) are helium nuclei with two protons, two neutrons, and
without electrons, i.e., 2
4
He2+.
• The α-particles are also represented as 2
4
He or Helium-4.
Beta-particles
• The beta-particles (β-particles) are fast-moving electrons that have atomic number -1,
charge -1, and negligible mass. The symbol, β−, −1
0
β , −1
0
e or also represents a β-particle.
Positrons
• Positrons are anti-particle of electron, i.e., they have the same mass but opposite charge
than that of an electron.
• The symbol +β, β+ , +1
0
β, or +1
0
e represents a positron.
11. Radioactivity
• Radioactivity is the process of emission of particles or energy from an
atomic nucleus by a spontaneous disintegration of radioactive
nucleoids.
• Radioactive decay is the spontaneous disintegration or
decomposition of a nucleus.
12. Radioactivity
• Stability of nucleus is determined by the difference between
coulombic repulsion and attraction.
• If repulsion > attraction nucleus disintegrates, emitting particles
and/or radiation.
• Determining factor is n/p ratio.
13. Nuclear vs chemical Reactions
Chemical
Reactions
Mass is
conserved
(doesn’t
change)
Small
energy
changes
•Atoms rearrange
by breaking and
making of bonds.
•No changes in
the nuclei;
involve ONLY
valence electrons.
•Balance atoms in
chemical
equations.
•Reaction rate is
affected by
temperature and
catalyst.
Nuclear
Reactions
Small
changes
in mass
Huge
energy
changes
•Elements
convert into other
elements.
.Protons, neutrons,
electrons and
gamma rays can
be lost or gained.
•Balance mass and
atomic numbers in
nuclear equations,
•Reaction rate is
not affected by
temp. and catalyst.
14. Types of Radiation
• The effect of an electric field on three types of
radiation is shown.
• Positively charged alpha particles are deflected
toward the negatively charged plate.
15. Types of Radioactive Decay
Alpha emission (expulsion of an alpha particle)
.Two protons & two neutrons, like helium.
.Shoot out at high speed but slow down quickly in air, stopped by skin or paper
• For example 92
238
U → 90
234
Th + 2
4
He
• Some times the -decay is accompanied by -emission, e.g.:
84
210
Po → 82
206
Pb + 2
4
He + γ
• Note that the γ-rays have zero mass, so they do not change the atomic number and mass
number of the parent nucleoid.
• Smoke detectors used in homes need -particles for their function.
• Americium-241 is the -decay-emitter used in the smoke detectors.
16. Steps in balancing nuclear reaction equation
1. Write the symbols of the known nucleoids, particles, and radiations
in the reactants and products, separated by an arrow. Leave a
question mark for the unknown pieces of information.
2. Balance the mass number on the two sides of the equation.
3. Balance the atomic number on the two sides of the equation.
4. Write the symbols of the unknown nucleoid or particles by finding
them in the periodic table, based on the atomic numbers.
17. Example
Write the nuclear reaction equation for the α-decay of americium-241.
Solution
• Step 1. The symbol and the atomic number of americium in the periodic table are Am and 95,
respectively. So the initial equation is:
95
241
Am → ?
?
?+ 2
4
He
• Step 2. Balance the mass number on the two sides of the equation, i.e., the mass number of
unknown nucleoid is 241-4 = 237:
95
241
Am → ?
237
?+ 2
4
He
• Step 3. Balance the atomic number on the two sides of the equation, i.e., the atomic number
of the unknown nucleoid is 95-2 = 93:
95
241
Am → 93
237
?+ 2
4
He
• Step 4. Find the symbol of the unknown nucleoid from the periodic table of elements, i.e.,
the element at atomic number 93 is neptunium symbol Np:
95
241
Am → 93
237
Np + 2
4
He
This is the balanced nuclear equation for the -decay of americium-241 in smoke detectors.
18. Practice exercise
• Radium-226, present in many types of rocks and soils, is an α-emitter
producing radon-222 in the process. The radon-222 is also an α-emitter
that can diffuse into houses from the rocks and soil underneath the
buildings. Radon is an environmental health issue in the buildings when
its concentration becomes above a certain level. The nuclear equation for
the α-decay of radon-222 is the following.
86
222
𝑅𝑛 → 84
218
𝑃𝑜 + 2
4
He
Write the nuclear equation for the α-decay of radium-226
19. Types of Radioactive Decay
Beta Emission (emission of a beta particle)
• a beta particle is an electron that is ejected from the nucleus (from a neutron).
• Can pass through skin and sheets of metal
• The nucleoids have more neutrons than needed for stability. They usually
stabilize them by converting one of the neutrons (n) into a proton (p) and an
electron (e) by the following nuclear process:
e
p
n 0
1
1
1
1
0 −
+
→
20. Types of Radioactive Decay
• An example of β-decay is the transformation of nitrogen-16 to
oxygen-17:
7
16
N → 8
16
O + −1
0
e
Uses of some beta-emitters
• Iodine-131 is used for radiation therapy of an overactive thyroid
gland.
• Yttrium-90 is used to treat cancer and is also injected into large joints
to relieve the pain due to arthritis.
• Phosphorous-32 is used to treat leukemia and other blood disorders.
• Carbon-14 is used to determine the age of a fossil or an old object.
21. Write the nuclear equation for the β-decay of iodine-131.
• Solution
• Step 1. The symbol and the atomic number of iodine in the periodic table are I and 53,
respectively. So the initial equation is:
53
131
I → ?
?
? + −1
0
e
• Step 2. Balance the mass number on the two sides of the equation, i.e., the mass number of
unknown nucleoid is 131-0 = 131:
• 53
131
I → ?
131
? + −1
0
e
• Step 3. Balance the atomic number on the two sides of the equation, i.e., the atomic
number of the unknown nucleoid is 53-(-1) = 54:
53
131
I → 54
131
? + −1
0
e
• Step 4. Find the symbol of the unknown nucleoid from the periodic table of elements, i.e.,
the element at atomic number 54 is xenon symbol Xe:
53
131
I → 54
131
Xe + −1
0
e
This is the balanced nuclear equation for the -decay of iodine β-131 that is used to treat over-
active thyroid glands.
23. Types of Radioactive Decay
Gamma (γ) emission
• Can pass deep into the body. Can pass through sheets of metal. Only stopped
by lead.
• Gamma rays are high-energy (short wavelength) electromagnetic radiation.
• They are denoted by the symbol 0
0
γ .
• The emission of gamma rays does not change the atomic number or mass
number of a nucleus (both the subscript and superscript are zero).
• Does not result in transmutation, simply the nucleoid changes from a more unstable
state, called a metastable state, to a relatively stable state,
• Gamma rays almost always accompany alpha and beta radiation, as they
account for most of the energy loss that occurs as a nucleus decays
24. Gamma (γ) emission
• A symbol m or * next to the mass number as a superscript to the right
indicates the metastable state of the parent nucleoid.
• For example, technetium-99m is a γ-emitter widely used in medical imaging:
43
99𝑚
Tc → 43
99
Tc + γ
• Similarly, boron-11m is a γ-emitter:
4
11𝑚
B → 4
11
B + γ
• Note that the nucleoid remains the same after -emission, except for the
change form metastable to a more stable state indicated by m.
25. Gamma (γ) emission
• Often, the γ-emission accompanies α-emission or β-emission. For example, polonium-
210 decays by a simultaneous α-emission and γ-emissions.
84
210
Po → 82
206
Pb + 2
4
He + γ
• Similarly, iridium-192 used in implants to treat breast cancer, and cobalt-60 used as an
external radiation source for cancer treatment, simultaneously emit β and γ-rays.
• Iodine-131 decays to β-particle and xenon-131m that is rapidly followed by a γ-decay of
xenon-131m.
26. Types of Radioactive Decay
Positron (conversion of proton to neutron, mostly in artificial radiation)
• Occurs when nucleoids have more protons than needed for stability.
• They usually stabilize them by converting one of the protons (p) into a neutron (n)
and a positron β+ by the following nuclear process:
1
1
P → 0
1
n + +1
0
e
• Emission occurs as nuclei try to obtain a balance between nuclear attractions,
electromagnetic repulsions, and a low quantum of nuclear shell energy.
• The neutron stays in the nucleus, but the positron emits from the nucleus.
27. Types of Radioactive Decay
1
1
P → 0
1
n + +1
0
e
• Note that the positron has a +1 mass number that balances the +1 atomic number
of the proton on the other side of the equation.
• The positron has a +1 charge that also balances the +1 charge of the proton on the
other side of the equation.
• The mass number of a positron is zero as it has negligible mass compared to the
mass of a proton or a neutron.
• Carbon-11 is an example of positron-emitter: 6
11
C → 5
11
B + +1
0
e
• Note that in the positron-emission process, the mass number remains the same, but
the atomic number decreases by one in the daughter nucleus.
• The nuclear equation is balanced because the mass number is the same (11 = 11+0), and the
atomic number is also the same (6 = 5+1) on the two sides of the equation.
28. Uses of some positron-emitters
• Positron emission is used in positron emission tomography (PET) which is a medical imaging
technique. Short-lived positron-emitting isotopes C11, N13, O15, and F18 used for positron
emission tomography are typically produced by proton irradiation of natural or enriched
targets described in a later section.
• Fluorine-18 in fluorodeoxyglucose, abbreviated as [18F]FDG is a positron-emitter commonly
used to detect cancer,
• Fluorine-18 in [18F]NaF is widely used for detecting bone formation.
• Other examples are oxygen-15 [15O]H2O used to measure blood flow.
• Nitrogen-13 used to tag ammonia molecules for myocardial perfusion imaging.
8
15
O → 7
15
N + +1
0
e
7
13
N → 6
13
C + +1
0
e
29. Example: Write the nuclear equation for the positron-emission of fluorine-18
• Solution
• Step 1. The symbol and the atomic number of fluorine in the periodic table are F and 9,
respectively. So the initial equation is:
9
18
F → ?
?
? + +1
0
e
• Step 2. Balance the mass number on the two sides of the equation, i.e., the mass number of
• unknown nucleoid is 18-0 = 18:
9
18
F → ?
18
? + +1
0
e
• Step 3. Balance the atomic number on the two sides of the equation, i.e., the atomic number
of the unknown nucleoid is 9-(+1) = 8:
9
18
F → 8
18
? + +1
0
e
• Step 4. Find the symbol of the unknown nucleoid from the periodic table of elements, i.e.,
the element at atomic number 8 is oxygen symbol O:
9
18
F → 8
18
O + +1
0
e
• This is the balanced nuclear equation for the positron-emission of fluorine-18.
30. Less common forms of radioactivity
Several relatively less common forms of radioactivity are known. Some examples are the following.
1. Neutron-emission is a mode of radioactive decay in which one or more neutrons are ejected from a
nucleus.
2. Proton-emission is a rare form of radioactivity in which a proton emits from a nucleoid.
3. Spontaneous fission is a radioactive process in which a more massive nucleoid breaks into smaller
nucleoids, often along with the emission of smaller nuclear particles.
4. In electron-capture, an external electron is captured to react with proton and produce a neutron in the
nucleus.
• For example, beryllium-7 decays by electron capture, as shown in the following equation.
4
7
𝐵𝑒 + −1
0
e→ 3
7
Li + γ
• Note that the mass number remains the same, but the atomic number decreases by one in the electron-
capture process.
• Chromium-51, which is used for imaging the spleen, decays by the electron capture and -emission.
24
51
𝐶𝑟 + −1
0
e→ 23
51
V + γ
32. Band of Stability
• The region on a
graph which
indicates all stable
nuclei when the
number of
neutrons are
compared to the
number of protons
for all stable nuclei
33. We can predict the stability of a nucleus by using some simple rules
•All isotopes heavier than atomic number 83 have an unstable nucleus.
(technetium, Tc, z=43 & promethium, Pm, z=61 are also radioactive)
•Isotopes with 2, 8, 20, 28, 50, 82, or 126 protons or neutrons in their nucleus
occur in the most stable isotopes (magic numbers).
•Nuclei are the most stable with pairs of protons and neutrons, so those with
all protons and all neutrons paired up are the most stable.
•Isotopes with an atomic number less than 83 are most stable when the ratio
of protons to neutrons is 1:1.
34. Stability of Nuclei
Protons Neutrons # of stable
isotopes
Stability
Odd Odd 4 Least stable See below
Odd Even 50
Even Odd 57
Even Even 168 Most stable
Stable odd proton odd neutron
nuclei: H-2, z=1; Li-6, z=3;
B-10, z=5; N-14, z=7
35. • The dots indicate stable
nuclei, which group in a
band of stability
according to their
neutron-to-proton ratio.
• As the size of nuclei
increases, so does the
neutron-to-proton ratio
that affects stability.
• Nuclei outside this band
of stability are
radioactive.
36. Type of decay depends, in general, on
neutron to proton ratio.
37. Types of decay
e
p
n 0
1
1
1
1
0 −
+
→
Above band of stability (neutron rich, n>p)
Below band of stability (neutron poor, n<p)
Positrons combine with electrons in 10-9 seconds to
give gamma radiation
38. Exercises
1. Radon-222 is an alpha emitter. Write a balanced
equation for the reaction.
2. Predict whether or not the following nuclei are
radioactive (unstable):
Sn-120, z=50; Fr-213, z=87; O-16, z=8; O-15, z=8
3. Rank the following in order of increasing nuclear
stability:
Ca-40, z=20; Ca-39, z=20; B-11, z=5
4. With respect to band of stability state modes of
decay expected for the following:
N-13, z=7; Al-26, z=13
39. Radioactive Decay Series
• Radioactive decay produces a simpler
and more stable nucleus.
• A radioactive decay series occurs as a
nucleus disintegrates and achieves a
more stable nuclei
• There are 3 naturally occurring
radioactive decay series.
• Thorium 232 ending in lead 208
• Uranium 235 ending in lead 207
• Uranium 238 ending in lead 206
40. The radioactive decay series for uranium-238.
This is one of three naturally occurring series.
42. Rate of nuclear decay
• First order kinetics
• Decay rate = #of atoms disintegrating per unit time
• When there are a large number of nuclei the ratio of the
rate of nuclear decay per unit time to the total number
of radioactive nuclei will be a constant
• K = rate; rate = Kn
n
• The radioactive decay constant is specific for each
isotope
43. Half life
• The rate of radioactive decay is expressed in terms of half-
life
• The half-life of an element is the time required
for one-half of its unstable nuclei to decay
• The half-life of an element is related to the
ratio of 0.693 to its radioactive decay constant
• t ½ = 0.693/k
• The decay constant for U238 is 4.87 X 10-18/s
• The half life is therefore
• t ½ = 0.693/4.87 X 10-18/s = 1.42 X 1017s =
4.5 X109 years
• The half-life of U238 is 4.5 billion years.
44. Decay Rate
• Log(N0/N) = Kt/2.30 = 0.301(t)/t1/2 where N = # of isotopes after time
t has elapsed, No is initial # of isotopes.
• t = (t1/2/0.301)(logN0/N) OR (1/K)logN0/N
• N/N0 = (1/2)n where n = # of half lives = period/t1/2
• Current mass = (initial mass)(1/2)(period/half life).
• Rates not affected by temperature or catalyst.
45. Transmutation or Induced nuclear reactions
(natural or artificial)
1. bombardment by other nuclei or alpha particles.
2. Electron capture
One of innermost electrons of an atom is absorbed by nucleus and a
proton is converted to a neutron.
195 0 195
Au + e → Pt occurs in nuclei with z>80
79 -1 78
3. Neutron capture
6 1 3 4
Li + n → H + He
3 0 1 2
46. Induced Nuclear Reactions
• Scientists can also force ( = induce) nuclear reactions by
smashing nuclei with alpha, beta and gamma radiation to
make the nuclei unstable
• Using alpha particle
4 14 17 1
2 7 8 1
He + N O + H
→
4 14 17 1
2 7 8 1
+ N O + p
→
or
47. Induced nuclear Reactions
• Using neutrons
37 1 38
Cl + n → CL
17 0 17
• Neutron capture by stable nuclei leads to higher n/p ratio, so nuclei
decay to produce beta particle.
38 38 0
Cl → Ar + e-
17 18 -1
48. Nuclear Reactions
• Two types:
• Fission = the splitting of nuclei
• Fusion = the joining of nuclei (they fuse together)
• Both reactions involve extremely large amounts of energy
Albert Einstein’s
equation E = mc2
illustrates the energy
found in even small
amounts of matter
49. Nuclear Fission:
• Is the splitting of one heavy nucleus into two or more
smaller nuclei, as well as some sub-atomic particles and
energy.
• A heavy nucleus is usually unstable, due to many
positive protons pushing apart.
• When fission occurs:
1.Energy is produced.
2.More neutrons are given off.
50. Nuclear Fission
• Neutrons are used to make nuclei unstable
• It is much easier to crash a neutral neutron than a positive proton
in a nucleus to release energy.
51. Example of Fision reaction
235 1 141 92 1
U + n → Ba + Kr + 3 n
92 0 56 36 0
• OR
235 1 137 96 1
U + n → Te + Zr + 2 n
92 0 52 40 0
Energy released is about 2x1011 J/mole.
54. Nuclear Fusion
• joining of two light nuclei into one
heavier nucleus.
• In the core of the Sun, two hydrogen
nuclei join under tremendous heat and
pressure to form a helium nucleus.
• When the helium atom is formed, huge
amounts of energy are released.
The
fusion of
hydroge
n nuclei
55. Fusion at the sun
Sun has about 90% H and 9% He atoms.
1 4 0
4 H → He + 2 e stepwise reaction
1 2 +1
Energy produced is about 2.6x109 KJ
Temp of interior of the sun is about 15 million oC.
Release more energy the fision.
56. Complete the following nuclear equations, thought to be the source
of the energy of some stars.
(a) 1H + 12C ?
(b) 13N 13C + ?
(c) 13C + 1H ?
(d) 1H + 14N ?
(e) 15O 15N + ?
(f) 15N + 1H 12C + ?
Nuclear Fusion
57. Measurement of Radiation
- Film badges
•The film is exposed and the optical density of the
film shows the workers exposure levels during
the time the film badge was worn.
•Ionization counter.
•Measure ions that are produced by radiation
58. Measurement of Radiation
- Scintillation counter.
• Measures the flashes of light that occur when radiation
strikes a phosphor.
• Geiger counter
• Measures pulses of electrons released from the
ionization of gas molecules in a metal cylinder
• Each pulse of electrons is heard as a pop or click
59. This is a beta-gamma probe, which can measure beta
and gamma radiation in millirems per unit of time.
60. Harmfulness of radioactivity
• Small dose → leukemia and cancer
• Large dose → radiation sickness (vomitting, feeling tired, loss of
appetite, gum bleeding hair fallout, eventual death)
• Very large dose → burn skin black → death in minutes
61. Applications
• Archaeology.
• Medicine
• Chemotherapy (cancer treatment)
• Power pacemakers
• Diagnostic tracers (e.g iodine nutrition problems, checking lungs)
• Agriculture
• Sterilising food (Irradiate food)
• Pesticide
• Environment
• Energy
• Fission
• Fusion
• Nuclear power and atomic bombs
62. Archaeology
• A wide range of nuclear techniques are used by archaeologists to
determine the age of items
• Artefacts such as the Shroud of Turin, the Dead Sea Scrolls and
Charlemagne’s Crown can be dated, and their authenticity verified,
using nuclear techniques.
63. Archaeology
• During its life, a plant or animal is exchanging carbon with its
surroundings, so the carbon it contains will have the same proportion
of 14C as the atmosphere.
• Once it dies, it ceases to acquire 14C, but the 14C within its biological
material at that time will continue to decay, and so the ratio of 14
C to 12C in its remains will gradually decrease.
• Because 14C decays at a known rate, the proportion of radiocarbon
can be used to determine how long it has been since a given sample
stopped exchanging carbon – the older the sample, the less 14
C will be left.
64. Carbon dating
where N0 is the number of atoms of the isotope in the original sample
(at time t = 0, when the organism from which the sample was taken died),
and N is the number of atoms left after time t. λ is a constant that
depends on the particular isotope; for a given isotope it is equal to the
reciprocal of the mean-life – i.e. the average or expected time a given
atom will survive before undergoing radioactive decay. The mean-life,
denoted by τ, of 14
The equation above can be rewritten as
66. Sterilisation and irradiation
• Sterilisation is one of the most beneficial uses of radiation.
• Gamma rays are used to sterilise hospital equipment,
especially plastic syringes (which would be damaged if
heated), dressings, surgical gloves and instruments, and
heart valves. These can be sterilised after packaging by
using radiation.
• Radiation sterilisation can be used where more traditional
methods, such as heat treatment, cannot be used, such as
in the sterilisation of powders and ointments and in
biological preparations like tissue grafts.
67. Food and agriculture
• Nuclear techniques are used in farming and agricultural communities
to combat disease and provide other benefits.
• In agriculture, radioactive materials are used to improve food crops,
preserve food, and control insect pests. They are also used to
measure soil moisture content, erosion rates, salinity, and the
efficiency of fertiliser uptake in the soil.
• The process of treating food with radiant energy isn't new. The sun's
energy, for example, has been used for centuries to preserve meat,
fruits, vegetables and fish.
68. Food Irradiation
•Food can be irradiated with g rays from 60Co or
137Cs.
•Even after ithas been packaged, gamma rays can
be used to kill bacteria, moulds and insects in
food. (taste may be affected in some cases)
•Irradiated milk has a shelf life of 3 mo. without
refrigeration.
•USDA has approved irradiation of meats and
eggs.
69. Applications in medicine
• Perhaps the most important use of radioactive materials is in medicine.
Radiopharmaceuticals—drugs that contain radioactive material—are
important in the diagnosis and treatment of many diseases. They can be
injected into the body, inhaled, or taken orally as medicines or to enable
imaging of internal organs and bodily processes.
• e.g. thyroid gland.- overactive thyroid gland produces too much iodine
containing hormones which results in increase in heart rate. Diagnosis of this
condition, or other thyroid problems involves the use of I-123, with a half life
of 13 hours.
Radioactive iodine concentrates in the thyroid gland and in the hormone
molecules. Radiation released is detected from outside the body using a
special camera. The resulting scan enables doctors to make an accurate
diagnosis and recommend appropriate treatment.
Technetium -99 is now preferred to iodine isotopes. It only emits gamma
radiation, so it is safe
71. Lung function
• Krypton-81 is used to check lung function.
• A small amount is breathed in, it decays in the lungs and the radiation
can be watched on a tv screen where it shows up as bright spots.
• Dark patches imply the lung is not well.
73. Cancer treatment
• Powerful gamma rays are dangerous but weak beam gamma rays cure
cancer.
• Can be tricky because radiation kills both healthy and cancerous cells.
The dose of radiation has to be carefully calculated and a narrow
beam is applied
• Cobolt-60 is used as a source of gamma radiation
75. Industry
1. Industry uses radioactive materials in a
variety of ways to improve productivity
and safety and to obtain information that
could not be obtained in other ways.
2. Radioactive sources are used in non-
destructive testing of pipeline blockages
and welds, cracks and leakages (Irridium-192).
3. In measuring rate of wear in machinery
and density of material being drilled
through.
76. Smoke detection and Thickness control
Smoke detectors.
• Alarm with Americium-241, half life 460 years; emits alpha particles
which ionise the air. Air then conducts electricity, current flows.
if smoke enters the alarm, it absorbs the alpha particles, current
decreases and the alarm sounds.
Thickness control.
• Measuring how much beta radiation passes through the paper to a
geiger counter (GR). GR controls the pressure of the rollers to give
correct thickness.
77. Environment
• Radioactive materials are used as tracers to measure environmental
processes, including the monitoring of silt, water and pollutants. They
are used to measure and map effluent and pollution discharges from
factories and sewerage plants, and the movement of sand around
harbours, rivers and bays. Radioactive materials used for such
purposes have short half-lives and decay to background levels within
days.
•
Nuclear science plays a valuable role in helping
us understand the history of our environment.
79. Atomic Bomb
• Uranium-235 explosive reaction.
• Chain reaction that grows with time, very fast, in only a fraction of a
second. Enormous energy is produced.
• When the chain reaction is in fixed volume container the tremendous
amounts of energy produced cause an explosion.
• Explosion has immediate and residual effects.
80. Nuclear Energy
• Chain reaction used to create electricity.
• Reaction tank is called a reactor.
• Reaction is controlled by using boron rods which absorb neutrons.
• Boron rods are placed above the reactor.
• They are lowered into it to slow down the reaction, and raised again
to speed it up.
• Heat from the reaction is used to change water into steam, which
drives turbines and these drive generators. The result is electricity.
85. • Hazardous wastes produced by nuclear reactions are
problematic.
• Some waste products, like fuel rods, can be re-used
• Some products are very radioactive, and must be stored away
from living things.
• Most of this waste is buried underground, or stored in concrete
• It takes 20 half-lives (thousands of years) before the material is safe.
Challenges of Nuclear Power
»Disposal of waste products
