Now, in a coming few lectures, we will discuss
about theNuclear Energy, Nuclear Power Plants
. So, before we start with the Nuclear Power
Plants, I will like to brush up the memory
of nuclearscience, starting from the Structure
of the Atoms, Chemical and Nuclear Reactions,
Nuclear Stability and Binding Energy, Radioactive
Decay Half Life, Nuclear Fission, Chain Reaction.
Because nowadays, our power generation is
mainly dependent on hydropower and thermal
power. We have sufficient reserves of coals;
coal ah, but the issue is related with the
emission of carbon . So, in future the power
demand will increase, our thermal plants can
meet out the power demands ; but the emission
of carbon which is which is going to the atmosphere
will lead to the coal mining. So, we cannot
use, though we have reserves of the coal,
we will not be able to use that coal for power
generation.
Now, the second is major source of power is
hydro power. Now, hydro power if you go for
the large day, the gestation period is quite
high; it goes up to 20 to 30 years and there
are environmental related issues also. Though,
we can go to the small head power plant, medium
or low head power plants. A highway cannot
be replaced by a number of small roads, similarly
a benefits of a high head dam cannot be replaced
by a benefits of fromthe low head dams .
So, but if you go for the high head dam, then
the submerged area is more and there I mean
environmental related issues. Now, third option
we are bulk of power is generated is left
us with, with us is a Nuclear Power right.
Nowadays, there is a lot of emphasis on the
solar power as well. But right now, it is
ok, but we do not do after down the 20-30
years when these solar panels will become,
I mean they will live their life. So, disposal
of solar panel may also become an issue. Now,
in solar power also by say localize heating,
we are also creating localized hotspots and
that may also change I mean change the environment
of a particular locality. I mean these studies
have to be carried out, I mean we are not
very sure about them .
But for nuclear power, we are very sure. There
are issues with related with the nuclear power
also I mean maybe it is the disposal of the
used fuel and a lot of work that research
work is going on regarding the disposal of
the used fuel. But still it can be considered
as a nuclear power because it does not add
carbon to the environment. Let us go back
to the topics to be covered here .
So, we will start with the structure of the
atom . So, we know the all the matter composed
of the unique particle that is known as atom
and you must have studied a lot about the
structure of the atom. I need not discuss.
There is a nucleus consisting of neutron and
proton surrounded by the electrons right and
when we talk about the material which is used
for the nuclear power plant, it is a radioactive
material . So, radioactive material we will
take up later on .
Let us talk about the size of the atom. Let
us have some physical idea about the size
. So, normally the radius of the nucleus is
the order of 10 to power minus 16 meters.
It is 10 to power minus 6 angstrom. Angstrom
will also a unit . So, it is 10 to power minus
16 angstrom and if you go for the radius of
the atom, then it is 10 to power minus 11
angstrom . So, there is a large gap between
this and this right.
Now, after this the radius of the nucleus
and the radius of the electron, the nucleus
consists of the neutrons, the mass of a neutron
is 1.674 into 10 to power minus 27 kgs. Mass
of a proton is 1.673, its approximately same;
10 to power minus 27 kg. But mass of the electron
is much much less 9.101 into 10 to power minus
31 kg. It is much much lesser than this .
And the elements which are same number of
protons have a same type of physical properties
right. There are other elements also ah, other
particles also which are known as positrons;
positron. Positron is positively charged electron,
that is known as positron. Neutrino, is the
tiny particles, they are rejected, they ejected
the beta particles; they are known as neutrinos.
Now, there are two types of reactions; chemical
reaction, nuclear reaction; the heat is also
liberated in chemical reaction .
Suppose, we take C plus O2, these very simple
I mean you are burning of carbon oxidation
of carbon CO2. Only 4 electron volt is released
right and 1 electron volt, it is worth to
move electronin 1 volt potential difference.
So, it comes out to be 1.6021 into 10 to power
minus 19 Joules is equal to 4.4 into 10 to
power minus 26 kilo Watt hour. Why I am giving
this figure because when we will do the calculations
regarding the nuclear power plants, these
figures have to be in our mind .
Now, when the size of the atom grows the number
of neutron and proton increases; neutron and
proton increases, at the same time number
of electron also increases. And at a certain
level, it becomes difficult to keep them close;
especially, neutron and protons to bind them
together . So, some energy is required, always
not only when the size is large, but for the
smaller atom also some energy is required
to keep the neutrons and protons together
and that is known as Binding Energy.
If binding energy is more that obvious stable;
when the binding energy is less, it is it
tends to disintegrate and those atoms which
tends to integrate are useful for nuclear
energy because when the disintegration takes
place, a lot of energies binding energy itself
is released right and a lot of energy is generated
.
So, if you look at the some of the neutron
and proton, some of the mass of the neutron
and mass of the proton, it exceeds because
because mass now we consider the mass can
be converted to energy and energy can be converted
into the mass . So, we need binding energy.
So, mass of the proton and mass of the neutron
if you look at, it exceeds the total mass
of the electron and we are from the delta
E that is known as binding energy delta m
C square.
Suppose, there is a 1 gram of metal . So,
delta E is going to be equal to 10 to power
minus 3 because we are converting into kilograms.
3 into 10 to power 8, this is speed of light
m C squared. It is 9 into 10 to power 13 joules.
It is 9 into 10 to power 7 mega Joules. Its
quite high right. So, only fraction of this
mass in neutron and proton which is used for
converting which is converted into the binding
energy and which puts together neutron and
proton.
Now, there is anotheryou need which is known
as atomic mass unit amu . Now, atomic mass
unit, we say we take carbon; atomic weight
of carbon divided by 12 and if we take a 1
kg of carbon, it will contain as per the this
is Avogadro hypothesis 6.023 into 10 to power
26 atoms of carbon right and this divided
by 12, we will give 1.66 into 10 to power
minus 12 ah, sorry not 12 sorry it is 27 ok.
This is atomic mass unit . So, all the value
related with the mass of particles of of of
an atom like neutron, proton, electron is
always expressed in terms of amu. Suppose,
this atomic mass unit, I want to convert into
the energy . So, it is going to be 1.66 into
10 to power minus 27 into 3 into 10 to power
8 square it is going to be equal to 1.49 into
10 to power minus 10 Joules . Now, this four
point 1.49 next .
This 1.49 into 10 to power minus 10 joules,
if I want to convert this into the electron
volt, then 1 electron volt is 1.6 into 10
to power minus 19 right. So, when I convert
this into the electron volt, we get 931 million
electron volt . So, one amu can generate 931
million electron volts, that is quite high
energy. We can take one example of helium.
Helium has atomic mass 4, atomic number 2
.
So, it has 2 electrons, 2 neutrons, 2 protons
and 2 electrons. Mass is when we do the mass
spectroscopy of helium of helium, we get a
mass of the helium and then, we get the value
4.00277 amu. When you calculate the mass by
analytical means, we get 4.03314 amu . So,
there is the difference and this difference
goes in the form of a binding energy . So,
delta m is equal to if you take the difference
it is 0.03037 amu and if you multiply this
by 931, you will get 28.2 million electron
volt.
So, this is the binding energy which is available
for helium. Now, helium is nucleus which has
2 neutrons and 2 protons . So, binding energy
per particle is 282 sorry 28.2 divided by
4 7.05 million electron volt . It is a stable;
7 is good, good enough. I mean more is the
binding energy, more is the stability of the
atom. It goes up to say for iron, it is a
maximum, close to the iron it goes up to eight
eight point something it more than 8.5 right.
The moment this binding energy reduces for
heavy metals, for this radioactive materials,
it goes down that is why slight with the slight
excitation, the nuclear disintegrate or the
emission of the particles takes place. For
example, for deuterium, the binding energy
is only 1.115 and million electron volts per
neutron per or nucleons. It is so low. So,
So, for example, we can take uranium, 238.
Atomic number 92, atomic mass 238.
It is 92 protons and 146 neutrons and same
92 electrons. It is quite a stable right,
but if you take uranium 235, it is quietly
unstable, due to the fact that it has much
lower binding energy than this one ok . Now,
if you look at the if you are draw a curve
for different mass number and this is negative
binding energy .
So, you will get a curve like this and iron
is somewhere here and it is approximately
approximately 60 and this is 9 and this is
8 . So, iron is somewhere here . So, it is
the most stable that is why I said it is the
most stableelement right.
Now, when radioactive decay happens, I mean
disintegration of disintegration happens,
then there is a life for every substance right.
We normally consider in the nuclear engineering,
we are normally considered with the Half life;
half life of a substance .
So, half life is when the mass of the substances
reduced to half, that is half life andyou
will find some of the isotopeswhich have low
mass. For example, krypton 40 ; sorry potassium
40. Potassium 40 is it is naturally radioactive,
there is a normal perception that a heavy
those who have elements those who have very
high mass are radioactive, like some of the
examples are like this potassium 40 or rubidium
87, this is also a radioactive . Indium 115,
this is also radioactive.
And during radioactivity, alpha, beta and
gamma rays, they come out of the substance.
Alpha is I mean like helium, as you and you
may be doing all these things. Now, gamma
is a high frequency, low wavelength electromagnetic
radiation. So, gamma penetration power of
gamma is very high . Even a thin foil of say
one mm thickness can you stop the alpha particles,
but not the gamma particle, gamma rays. Gamma
rays even can penetrate the ceiling of the
house; I mean their penetration power or the
energy level is quite high.
Now, I will give you an example of alpha decay.
Suppose alpha decay is plutonium 239 94. If
alpha decay is done, then plutonium 235, here
92 plus helium right. Beta decay suppose led
214 and 82, it causes this with 214 83 plus
electrons 0 minus 1 plus neutrino and gamma
radiation, this is for not for the beta, but
this is for the gamma radiation . So, if you
open a book on any any book on the nuclear
science, you will find a n number of equationshow
the , I mean radioactive decay takes place
in different substances.
There is a positron decay also, there is a
that is very interesting positron decay . So,
in this what happens? Excess protons 
converted into the neutrons right. For example,
nickel [inaudible] 13 7 C 13 6 plus e 0 plus
1 or P 30 15 is convert to silicon 30 14 plus
. So, these type of reaction also takes place.
Sometimes inhalation process takes place.
This positive electron it it it combines with
them negative, it combines positron will combines
with the electron and enormous an amount of
energy is liberated that is known as Inhalation.
And suppose, there are 2 electrons. So, 2
into their atomic mass unit is 00055 and 931,
it is going to be 1.024 million electron volts
are liberated when inhalation of electrons
takes place. Now, we will discuss about the
half life right .
Now, radioactive decay of any substance is
a first order reaction. So, dN by dt is equal
to minus lambda N right. So, here we can take
dN by N is equal to minus lambda dt or natural
if we integrate both the sides. Integrate
both the sides dN by N is equal to minus integrate
lambda d t to 0 to t. This is initial and
this is after time t.
We will get natural log N by N o is equal
to minus lambda t or N by N o is equal to
e to power minus lambda t or N is equal to
N o e to power minus lambda t . Now, half
life when N is when N is N o by 2 that is
known as half life .
So, when N is N o by 2, in that case N o by
2 is equal to N o e to power minus lambda
t . So, t half is going to be equal tothis
is half; natural log of half minus natural
log of half divided by lambda right and it
is going to be equal to a 0.693 by lambda
right. Now, in this case for example, krypton;
if you take krypton 87. Half life is 76 minutes.
If you take radioactive this uranium 235,
half life is 71 point into 10 to power 8 years
.
So, radioactivity is also having a unit . So,
1 unit is curie that is equal to 3.651 into
10 to power 10 disintegration per second and
another unit is q u e r; Becquerel, it is
equal to 1 disintegration per second .
Now, similarly if you take the half life,
it can be half life can be polonium 214 can
be 170 micro seconds as well. Carbon 14 half
life is 5100 years. Thorium, it it goes up
to 10 to power 10 . So, it can vary from a
few seconds or milliseconds or microseconds
to millions of years . So, if you comes the
average life.
What is the average life of a radioactive
material? Average life? Now, in order to find
the average life that is T, we will integrate
0 to infinity minus t dN by N o and this will
give lambda N o 0 to infinity t e rise to
power minus lambda t divided by N o . So,
average life T is equal to if we integrate
this and with this N o will be canceled out
minus t e rise to power minus t lambda minus
e raise to power minus t lambda divided by
lambda 0 to infinity .
Now, if you are putting infinity here, at
t they will become 0. Now, we are putting
0 and they are becoming equal to 1 by lambda
. So, average life is 1 by lambda; half life
is 0.693 by lambda . So, average life of any
radioactive material is 1.445 times the half
life . Now, for the power generation, a chain
reaction is required; chain reaction, chain
reaction.
In chain reaction, what happens? For low energy
neutron, strike the heavy nucleus right, then
disintegration or decay of this nucleus takes
place and enormous heat is liberated and at
the same time, when suppose when neutron is
striking this nucleus more; more than 1 neutron
will leave this after disintegration, more
than 1 neutron will leave this nucleus, suppose
they are 3 neutrons, 1 neutron low velocity.
It is a high energy neutron, then it will
penetrate . So, low energy neutron will go
and strike the nucleus. Now, radioactive decay
will take place which will contain 3 neutrons
also and these 3 neutrons will again this
strike another 3. This is how the chain reaction
takes place. It will again strike again next
3 nucleus and in the next 3 nucleus again
3 neutrons and this chain will continue in
GP. It is a fast reaction; it continues in
GP andthat is why there is a term K which
is neutrons in any generation. This is first
generation and so, this is second generation.
So, neutron in any generation divided by the
neutron in previous generation; if it is more
than 1, the chain will continue; otherwise,
the chain will die out. And through this process
and this is the basic of a nuclear power generation
and nuclear power plants and in nuclear power
plants for the reduction of the speed of the
neutrals, moderators are provided. So,moderators
are provided and these moderators, they retired
or the reduce the the the kinetic energy of
these neutrons. So, that proper fission or
or the chain reaction can take place .
So, further on this regarding the power generation
in the nuclear power plant, we will discuss
in the next lecture. This is all for today.
Thank you very much.
