hello and welcome to this ah css moocs course entitled fundamentals of nuclear power generation

which has been offered under the nptel online certification scheme i am ah dipankar n basu

assistant professor in the department of mechanical engineering iit guwahati and i am going to

be your instructor for the entire of this course now the as i have already mentioned

in the introduction video that the topic of nuclear power generation is a bit of advanced

level topic and ah therefore i would expect the entire audience of mine to be either at

the advance level of your analogy curriculum or may be during a post graduate that is you

must be at least at the six semester of your ug course or a may during a master specializing

in mechanical thermal or nuclear or power engineering so that you already have the fundamental

knowledge about fluid mechanics and heat transfer and also you are aware about the laws of thermodynamics

and also you are ah quite aware about the differential calculus or differential equations

rather because we need to make use of those concepts some of those concepts in different

sections of this particular course ah its quite a bit odd for me that there is

no audience in front of me and i am not a in a position to have direct interaction with

you or have eye contact with you face your questions directly but ah still i would like

to keep this course as much interacting as i can so that ah ah that means i would like

to follow a more questions as i kind of a pattern so and ah i am sure all of you are

going to respond that is ah whenever you have any query or any doubt or you need any clarification

dont hesitate to drop a mail to me i would try to respond to that at the earliest and

for that purpose while my contact details are already available on the course so you

should also know the friends that is my ts i have three phd students as my ts all of

them are quite senior phd scholar in the department of mechanical engineering iit guwahati

mister kiran saikia who is working in the field of boiling water reactors and therefore

his phd topic is quite relevant to the content of this course mister bhaskarjyoti sharma

is working on micro fluidics and heat transfer at microscale whereas ah mister milan sarkar

another senior ph student he is working on super critical ah boilers or super critical

nuclear reactors which is again an advanced level nuclear reactor and ah if possible would

like to mention about that sometimes in this course ah their contact details are also available

there so you can send mail to either of them as well regarding any kind of clarification

now it is already available the course outline on the course web page but still i would like

to repeat it here here ah this course ah we shall be starting from the very fundamentals

of nuclear power generation that is ah introducing the concept of atomic power generation ah

discussing about very briefly about the atomic structures and the source of nuclear energy

and from there gradually shall be moving to more complicated or more advanced topics accordingly

the entire content has been divided in to twelve modules and ah it is span for twelve

weeks so the objective is to cover one module in

every week accordingly each of the modules some of the modules rather it be covered in

two lectures some of them may require three or four lectures and each of the module will

be followed by one tutorial where the tutorial may contain ah multiple choice questions may

contain the numerical problems or may have slightly discrete one as well depending upon

the content of that particular module again as i mentioned ah hint towards the solution

of all this tutorials will be given and we shall be there for helping you while solving

this tutorials i would also like to solve some sample problems after ah every module

or after any relevant module and ah these are the text books that we shall be following

in this course where i shall mostly be following the book of ah remand murray but ah any of

you may not be having direct access to this one so you can ah follow either of the next

two the book on power planning engineering by professor p k nag i think the third edition

is the latest one and also the look by m m el wakil on power plant technology another

classical book both of them has a chapter on ah nuclear power generation which is very

much relevant and ah if i go back to the course outline ah both of this books will be ah sufficient

to cover up to module number eight or nine for this particular course

but of course the rest of three modules where we shall be discussing about ah several advanced

topics such as biological effects of radiation the reactor safety and security and also the

waste management these are ah more ah modern day topics and ah they may not be available

in the books you can ah refer to different materials available on internet and of course

the lectures will be there for your help now the topic of nuclear power generation has

a quite rich history of course i am in history point of view i am not talking about ah the

way other sources of power generations are invented and how they came into practice rather

it has a quite a way of checkered history because the term nuclear energy where introduced

to the man kind ah only after that at hiroshima in nineteen forty five and it is quite fascinating

to think that in just about six seven decades from that point we are discussing about nuclear

power as a possible source of power generation or is a possible solution for future energy

demands ah the term which came to the concept of or

came to the knowledge of common people there is something synonymous to greater destruction

ah it is only thanks to the contribution of several researches and several scientist who

kept on working on this and ah didnt just kept it limited to atomic energy do not kept

limited atomic energy to ah ah the open related options whether divert it to the commercial

power generation and ah because of that ah only nineteen fifties first commercial nuclear

power plant was established and gradually we moved on to get a good share of the global

energy production from the nuclear energy ah just to ah justify the need of knowing

the nuclear energy i would like to show you this couple of ah ah projection that i have

this particular one which i am sure all of you are aware that presently we get the energy

needs our day to day energy needs mostly from the fossil fuels like coal petroleum or natural

gases however as per the considering the present energy reserves available and also the present

day consumption this talks are not infinite rather they depleting at a very very fast

rate and ah just going by this projection the stock of ah petroleum and natural gas

are not expected to last longer than twenty fifty or twenty sixty whereas coal may survive

for thirty forty years more but by the year ah twenty one hundred we are expected to run

dry if we keep on depending solely on this fossil fuels and ah

now if you compare that with the other projection that is where i am showing here the global

electricity consumption you can see here the electricity consumption is not only increasing

year by year but it is actually escalating at at a very very fast rate particularly in

ah ah asian and ah middle east related countries where we can see there is an accelerated growth

if we compare the figures say from nineteen ninety to two thousand ten over this ah period

of twenty years the consumption in the asian countries has become nearly double or at least

ah one point six seven times and ah in terms of the global figure if you compare this one

and nineteen eighty which was ah around six thousand turn or tower tera or tower we should

say in two thousand ten it was around eighteen thousand

so a three time increase in thirty years and ah this electricity consumption is only going

to increase at a even faster rate because of several ah quite well known reasons like

our ah fascinations towards ah electronic gadgets we are ah depending on ah heavier

machineries for solving every day to day needs of ours our fascination towards elimination

and ah so and so several reasons and therefore we need to find some other options ah without

instead of adjust continue to depending on the fossil fuels we have to find some other

options of electricity generation and ah thats where the renewal and nuclear power comes

into the here i have some numbers to the substantiate

the same ah point if you compare the figures from nineteen ninety to two thousand eight

we can see the global population has increased by about twenty seven percent over that period

where ah in ah european countries or a in some advanced nations the growth rate is quite

moderate china has done quite amical because their growth rate is only seventeen percent

in ah middle east and african countries the growth rate is quite high um um over fifty

percent and in fact india is also not far behind thirty four percent increase in the

population you can see in period of just eighteen years

now if you compare to the energy uses on the last set of data we can see ah china has seen

one forty six percent a staggering number really one forty six percent increase in their

energy uses well their population growth is only seventeen percent that leads to an hundred

eleven percent increase in their per capita energy consumption middle east is also not

far behind there the increase in energy consumption is ah even higher one seventy percent and

so about eight percent increase in the per capita energy consumption

india has seen ah the energy consumption becoming nearly doubled ah leading to a forty two percent

increase in the per capita of energy consumption for as the advanced countries has done ah

really good job like in a usa or in european countries we have seen ah it to be more or

less the same ah in this others this involves about ah countries like australia and others

here you can see that is in fact a reduction in the per capita energy consumption

but because of the contribution coming from ah asian and middle east countries we have

more than ten percent increase in the per capita energy consumption over this period

of eighteen years and that figure that actually that keeps on increasing and ah therefore

ah we have taken for some newer option to develop a commercial electricity and thats

where the renewal energy and nuclear energy both comes into picture

now renewable while conventionally renewable sources like solar wind biomass they definitely

have a great future there are several issues as well particularly they are intermittent

in nature like you know solar energy can ah supply electricity only during the day time

and not at ah night periods or periods of ah zero or insufficient solar energy solution

wind energy requires a particular wind velocity and so they are very much location specific

ah somewhat similar about biomass and ah because of all these factors the renewable energy

till date are ah restricted more ah towards local scale or they are ah more being thought

about peak load stations that is to meet the demand during the periods of the highest consumption

of course ah effort is on to have base load solar or wind power stations ah and ah they

are coming coming up in a different countries at different ah rate and that that is only

going to increase in future but there has still several issues to solve like ah in ah

whenever you talk about nuclear ah even without knowing anything people always keeps on complaining

about the possible effects on the environment etcetera but ah the conventional power sources

like a coal and can have ah as detrimental environmental effect as nuclear wind has ah

huge reservation from environmental protection point of view like station wind powers ah

in fact and ah thats where nuclear particularly about that point on base peak load station

nuclear course higher than renewable because it cant access act as a base load station

it can supply a continuous amount of electricity throughout the year without being bothered

about the surrounding or environment or any other demographic issues etcetera

ah and ah therefore we also need to focus on nuclear and ah thats why if you see the

global energy scenario i have the data of two thousand fourteen here nucleus still is

this quite small fraction only ten percent of the global energy consumption but this

percentage is actually increasing despite ah despite ah reservations from ah different

sectors the nuclear energy is there to exist before you see the country wise scenario usa

is the largest contributor in fact if you see this figure this number that is production

from us nuclear energy produced from us in the year two thousand sixteen i s more than

combining the next three is france china and russia but us is the huge country and that

requires very large amount of electricity so despite such a large numbers actually nuclear

energy is a quite small portion of the total energy produced in us but there are certain

countries like ah france france gets a good share of their total energy from nuclear if

you see this figure nuclear consist of very large fraction in this ah particular case

which is well above forty five percent in france ah the principle reason being the absence

of ah fossil fuels sources in france like they are coal or oil reservoir quite limited

compared to other countries just compare that to that with their neighbor germany germany

has a very decent ah reserve of coal and thats why they are getting much larger fraction

of their energy from coal which is ah just about four point five percent in france it

is twenty four point five percent in case of germany and their nuclear share is quite

small but i would like to ah attract your attention

to another figure see the greenhouse gas emission ah in case of france was seven point eight

one whereas that for germany is eleven point four six i shall be coming back to this figure

after a few slides ah this is a global ah energy map slightly old data of two thousand

eleven you can see in europe and ah us in european countries and us there is a good

spread of nuclear energy and ah also in japan japan is a country that ah depends a lot on

nuclear energy despite that fukushima and ah associated effects

india and china has seen an increase in their total ah nuclear production over a last one

or two decades and ah therefore ah ah of course there are other areas like in africa or in

latin america there are very very few nuclear resources or in the eastern part of russia

but ah the feasible reason being the absence of ah corresponding ah uranium or other kind

of fuels now coming to the indian scenario ah by the year two thousand seventeen january

two thousand seventeen effect indian was getting only a small fraction of their total production

from nuclear just five seven eight zero if you compare that coming from thermal its extremely

small fraction but ah far about that i would like to again

ah draw your attention to this next figures where i have shown an year wise ah or the

increase in the consumption of the from different sources increasing the production from sources

over different five year plans and now if you see the ah numbers at the end of the eleventh

plan and also till january two thousand seventeen the increase in ah nuclear while it is only

about thousand megawatt ah actually ah by it is quite small covered to others but now

if we ah compare that from percentage over which period hydro energy production has seen

only an eleven percent increase whereas nuclear energy has seen twenty one percent increase

and as there are several nuclear power plants are planned in india it is expected to increase

even more in fact this twenty one percent has gone even

further because it is database ah till january two thousand seventeen but the latest indian

power nuclear power plant ah went operational in ah march two thousand seventeen which point

where which added another thousand megawatt capacity to this and these are the breakup

of union nuclear power plant started in as old as nineteen sixty nine from that tarapur

atomic power plant and that kept on increasing at a faster rate particularly see in two thousand

onwards you can see there are several plants coming on and the last one as i have mentioned

in march two thousand seventeen another thousand megahertz capacity was added which gives a

total six seven eight zero megawatt electrical of install capacity of nuclear power plant

in indian and there are several other plans ah proposed

like the map here shows quite a few such locations and ah by twenty twenty whereas several other

plans which are expected to becoming operational giving or ah giving a project data generation

capacity of eight thousand megawatt electrical or actually slightly more than that

therefore nuclear energy is here to stay and hence we need to have a detailed idea about

this now you must be aware that whenever there is a talk of setting up a new nuclear power

plant there will be lots and lots of deliberations and discussions and arguments compared to

any conventional power stations i personally feel that most of that can be

ascribed to the lack of knowledge about the technology people are not properly aware about

exactly about how this technology works exactly how energy is harnesses from the atoms exactly

how we use the fuel or on how we can ah protect the surrounding from radiation hazards exactly

what are the nature of this radiation hazards that we always keep on discussing how we ah

discovered the spent fuel or how we ah disposed the waste fuel ah if we have proper knowledge

about them then probably we shall be in a much better position to discuss whether we

should go for nuclear energy or not and i am sure that successfully completion of this

course will allow you to participate in those discussions and put on your own points for

this so let us ah start with very three basic principle

today we shall not be discussing too much about the nuclear power generation ah ah as

a topic whether we shall be discussing more about some introductory points about how energy

is produced what are the points where nuclear is separate from the conventional sources

what are the advantages and disadvantages of nuclear energy and also would like to plan

a very briefly into the history ah paying out homage to several great minds who have

contributed to the development of this particular field and finally shall we look into the atomic

structure so that we can prepare our self to though more in depth discussion on the

nuclear energy generation so now here we have the principle of electrical

power generation ah which ah i am sure all of you are aware about ah the electricity

production is achieved when a group of electron is availed to move through a conductor by

some that some desire direction and ah that movement of electron is generally achieved

by spinning a conductor in a magnetic field now up to that part ah more or less all power

stations or conventional power stations ah have the same kind of working principle but

how to create this motion of the conductor there is a difference in most of the common

power stations you will find a turbine which has several blades and mountains on it and

the turbine itself is mountain and on a shaft ah we create the rotary motion of the turbine

by heating the turbine blades with some high velocity fluid stream so that the kinetic

energy of the fluid steam is transferred to the blades and ah subsequently to the shaft

and alternator is mounted on the same shaft which gives us the electricity as the output

now the difference between different kinds of power stations is the way of producing

that high velocity fluids stream like in case of a coal based thermal power plant we have

thermal energy to kinetic energy conversion in the nozzle

basically coal or such kind of fuel like any gas etcetera is burnt in a boiler so that

the heat of combustion is used to ah generate stream by supplying that to water we get a

high energy or high enthalpy ah stream of ah steam that is taken through a nozzle and

it pass through the nozzle the thermal energy is converted to kinetic energy which is subsequently

taken into the turbine whereas in case of ah hydroelectric power stations here we know

that water from a higher energy ah elevation is allowed to fall through there by converting

its potential energy to the kinetic energy and when this high velocity water jet strikes

the blades of the hydraulic turbine then waste is the same and this ah kinetic energy is

readily available in case of wind turbine because the we need a certain velocity of

wind so which we will be avail to move the turbine blades by a certain ah magnitude and

certain rpm rather and that we will subsequently lead to the production of electricity

now ah there can be two types of ah this high stream energy or high velocity energy generation

we can divide in two categories one like this hyrdoller wind where we either directly get

the kinetic energy or convert potential energy into kinetic energy the other where thermal

energy involved like coal where we generate thermal energy by burning some fuel or by

some other means and that thermal energy is used to raise stream and then raised through

the nozzle and the turbine and nuclear is in this letter category that is it is quite

similar to the coal based power stations ah in both the cases ah several components are

same like you will be having the same kind of nozzels and turbines a stream generator

where ah energy is is supplied from some fuel to produce stream then you may have a condenser

and boiler keep on and all those associated accessories but their difference is how we

supply the energy to the stream in that stream generator like in case of ah coal based power

stations we have chemical energy of fuel converted to the thermal energy

now there we have basically a chemical reaction and any chemical reaction means rearrangement

of electrons inside the molecules so that ah the number of atoms are conserved but atoms

combine in different way to form different kinds of molecules so the total number of

molecules may not be conserved but total number of atoms and electrons will be conserved

but in case of a nuclear we have conversion of nuclear energy to the thermal energy where

not electrons or we are not at all talking about atoms and molecules whether we are going

inside the atoms and we are into the nucleus where the protons and neutrons they will be

rearranged to form a new nucleus giving ah words to a new atom and therefore total number

of the sub atomic particles that is protons and neutrons will be conserved but total number

atoms may not be conserved yes we shall be discussing about this in more detail then

ah i have to justify why should we go for nuclear power ah and here i have dotted out

a few points some of those will be discussed in more detail later on

the first one is no combustion of course ah in case of incase of coal based power stations

we bound the fuel and the ah exhaust gases are ah ah allowed to escape to the surrounding

leading to environmental pollution and ah such kind of greenhouse emission is absent

in case of nuclear because there is no chemical reaction involved whatever happens that is

happening at the atomic level only and ah green house emission will therefore be ah

significantly lesser i have a shown you couple of numbers for france and germany earlier

if you remember in case of germany the amount of greenhouse gas emission was ah at least

fifty percent more compare to france and one primary reason being this because germany

depends a lot on coal based power stations or power generation and ah similarly oil based

that is ah combustion related technologies whereas france gets the significant share

from nuclear so nuclear definitely is in much cleaner technology compared to coal

the operating cost is generally much lesser then lesser volume of operating zone per reactor

or higher energy density this point i shall be discussing in more detail during the next

lecture it is also highly reliable compare to wind and solar as i have mentioned they

the amount of electricity or energy that we get from nuclear plant is independent of the

surrounding condition and the demographic details and therefore they are excellent as

based load power stations ah they are not suffered too much by the fluctuations in the

environmental conditions and therefore ah they are easier to control in a way also

next point may raise some eye brows renewable now renewable conventional we attach this

terms to solar wind and biomass but here i am using that on renewably nuclear also well

i shall be coming back to this ah after a few lectures but ah in certain situations

nuclear energy can also be termed as renewable and ah then possibility of mere infinity energy

generation through fusion reaction again i shall be coming back to this later on but

just into the perspective ah a projection shows that while the reserve of coal and ah

other kind of fossil fuels may not last for more than fifty sixty years common nuclear

fuels like uranium and thorium they also may not last more than hundred years but if we

use ah the fusion reaction and if you are able to master this technology that can ah

provide energy for about three hundred thousand years

so how that of course we shall be discussing later on but ah everything is not rosy about

this nuclear power because there are several factors that we need to be mindful of like

the environmental effect that everyone discusses about it is particularly with the handling

of radioactive fuels mining refining and transportation of the same there is possibility of radiation

hazards in ah module number ten we shall be discussing about this radioactivity and radioactive

hazardous and possible ways of ah getting us protected from that the radioactive waste

disposal the topic of the last module and another very highly devoted topic the high

capital cost involvement nuclear power plant as that requires ah several layers of protection

to ah protects us from the contentment and other kind of radiation related issues generally

the capital cost involvement is much higher than fossil fossil fuel based plants

the possible implication of nuclear accidents while ah so far in the history there are only

three incidents where a accidents happened in some nuclear power plant the three mile

island in us in nineteen seventy nine the chernobyl incident i think in nineteen eighty

five or eight six in the farmer soviet union and the very recent one at fukushima power

stations ah we shall be try to discuss a bit about the details of each of them and try

to see how or they happened on whatever reasons behind each of those accidents and what are

the factors we need to be careful ah learning from them ah the finite nature of uranium

and other fuels that is similar to the fossil fuels that can also be a concern

so with this factors in mind let us now try to the see a bit about historical development

of the nuclear power generation these ah being a fundamental ah portion of physics there

are contributions from several great minds and i am going to mention only a very few

of them which without mentioning this actually we cant proceed with any discussion on nuclear

power and ah the first homo we must pay to sir albert einstein because this entire concept

of ah nuclear energy generation or mass to energy conversion etcetera they all started

probably in nineteen hundred five while the topic of radio activity was already ah identified

and ah proved before that but it was only in this years nineteen hundred five which

is often refer as the annus mirabalis that is the miraculous year of sir albert einstein

that everything related to the nuclear power generation that started

because this is the year when he published four research papers and totally changed the

concepts of ah space time mass and energy and basically ah the entire ah journey of

modern physics started from that year onwards all of his papers where published in this

particular general annalen der physic which is one of the oldest publishing researcher

general which is still active now i cant remember probably i think it started its journey in

nineteen ah sorry seventeen hundred nineteen nine and it is a still a very popular one

ah on this particular journal in the year nineteen hundred five he published four papers

the paper one was on photoelectric effects which lead to the development of the quantum

mechanics later on it may be a surprise ah to many of you and

the noble prize that sir albert einstein received later on was actually related to his work

on photo electric effect or not because of the much celebrated theory of relativity in

his section paper he discussed about the brownian molecular motion which ah undoubtedly proved

the existence of atoms and the third paper special theory of relativity nothing to mention

about in ah a later year probably in nineteen hundred twelve or thirteen he published the

ah generalized theory of relativity and the paper four which is related to this mass energy

equivalence and that gave to this ah widely used and very very popular relation e equal

to m c square where m is mass and c is the velocity of light in vacuum and e is the corresponding

energy so c being generally a constant this particular one gives the mass to energy conversion

or vice versa emest rutherford was the person which is often

referred as the father of nuclear physics he proposed the atomic structure to give the

first ah feasible modular of atomic structure in nineteen hundred eleven which is quite

similar to the solar structure that we have over solar system where ah we have a heavier

mass at the center and all the electrons are orbiting around that in ah elliptical or hemispherical

or i should now say hemispherical semicircular kind of orbits the heavier nucleus ah was

identified to be positively charged and the mass of the nucleus was found to be much much

larger compared to the electrons ah the it was followed by the interpretation

of news board following the quantum physics well ah quantum physics and therefore this

mode is often referred as the rutherford more model of atoms ah there work established that

inside the atoms there is a huge amount empty space because the average radius of nucleus

was measured to be in the range of ten to the power minus sixteen meter whereas that

average radius of atom is ah of the order of ten to the power of minus eleven meter

and these huge amount of space inside was occupied only by very very tiny electrons

this empty space is very very important which we shall be discussing later on ah there are

several sub atomic particles which are present inside the nucleus particularly in the present

age of gravitational wave we um should mention about positrons and neutrinos but here i am

not not going to mention about those because in this particular course we shall be restricting

ourselves only to this three well known ah sub atomic particles proton neutron and for

course electron ah electron was discovered by j j thompson in eighteen ninety seven during

his cathode ray experiments and the complete description of electron ah particular the

measurement of idea about its mass and energy was given by r millikan in around nineteen

hundred six golfstein was the researcher how discovered

the existence of positively charge particle inside the matter ah it was around eighteen

ninety six but he failed to reveal the nature or completely he was not able to completely

describe the nature of this positively charged particle rutherford prove the e existence

of protons through his gold foil experiment in nineteen hundred eleven and also he gave

the name proton but it has also identified that nuclears doesnt constitute only a protons

but there it is possible to have some other heavy subatomic particle which probably is

neutral and from ah the ah discovery of that neutron element was done by james chadwick

in nineteen thirty two and it was name neutron and this particularly discovery has far reaching

implication on a development of nuclear physics a henry becquerel was the person who first

discovered the concept the radioactivity around the eighteen ninety six when he identified

that uranium salt can emit ah rays with penetrating power which are quite similar to x rays but

they dont need any kind of external power to produce that rather that was found to be

coming out more spontaneously from the salt ah simultaneous experiments were also done

by the curie family that is the madame curie and pierre curie they identified the existence

of much more reactive elements they were the persons who coined the term radioactivity

and they also identified two reactive elements which are found to be much more reactive compared

to uranium and they gave the name polonium and radium ah radium was discovered around

eighteen ninety eight the name polonium actually refers to poland which was ah the birth place

of madam curie both becquerel and curie family together received the noble prize in nineteen

hundred three for the discovery of ah the radioactivity or spontaneous disintegration

of mater ah but ah this was only the natural phenomenon

or spontaneous disintegration ah natural transmutation of ah atoms that is conversation of one atom

to the other that was first observed by rutherford and frederick soddy in nineteen hundred one

ah rutherford repeatedly was ah reportedly rutherford was the first person to ah achieve

artificial transmutation of nitrogen to oxygen around nineteen nineteen but ah fully artificial

transmutation was achieved in nineteen thirty two by john cockcroft and emest walton when

they were able to convert lithium to two helium atoms ah which ah lead to ah several groups

actively working on this topic of transmutation that is converting one atom to another and

ah there by releasing the energy stored in the atom

ah envico fermi there his coworkers where the group who first claim to have developed

ah atoms heaver then uranium in nineteen thirty four because till that time uranium was ah

the atom ah known as to was ah identified as the atom with the ah heavier the mass or

the highest amount of mass but fermi claimed that they have discovered atoms higher then

this ah by bombarding uranium with neutrons their claim was neutron has absorbed the uranium

or sorry uranium has absorbed the neutron there by converting it to much heavier atom

and ah developing a newer atom but ah their claim was ah doubted by that the same time

itself but ah that failed to attract proper attention ah his claim ah ah led to led to

the noble prize in nineteen thirty but later on it was proved that fermis experiment were

wrong or rather fermi interpretation of experimental observation was wrong

ah the experiments otto hohn lise meitner they aided to the um they for contributed

or they continue to work on this particular field for several years and they were the

first group added by the theoretical explanation provided by fritz strassman and oto frisch

they successfully interpreted the observations from all earlier experiments including that

from fermi and their coworkers and were able to achieve a proper nuclear reaction under

control condition and ah also liberate the energy that is stored in the atom

ah their work led to the noble of prize of otto hahn in nineteen forty four which was

given under quite controversial circumstances because this noble prize was awarded or announced

in the later part of nineteen forty five post the second world war where the atom bomb at

hiroshima and nagasaki was already history and otto hahn was also um under the ah locker

or i should say ah he was ah in jail and ah that ah it is also quite un fair to give the

noble prize only to the otto hahn because ah meitner and strassman contributed equally

to experiment but still hahn was the person who received the noble prize for this and

ah the result of their interpretation led to the manhattan project then chicago pile

one the first ever nuclear reactor develop by mankind and then the unmentionable at the

hiroshima in nineteen forty five thank fully scientist did not stop their rather

they continued working on this and in an restrict nuclear energy only to the weapons whether

started thinking about using this huge amount of energy source for the benefits of the man

kind and ah there by producing commercial electricity from that the first commercial

nuclear power plant started working in early fifties in the soviet union whom followed

by united states and other countries started slowly following that ah which ah has gived

us a good platform about nuclear power generation standing at this point and there are several

generations of nuclear reactors that has been ah designed and ah used by the mankind starting

form first generation moving to second and third and presently you are leaving in the

ah mod of four generation nuclear reactors and looking for a bright future of nuclear

power generation ah i would like just touch upon briefly on

the atomic structure before closing the shot today ah as per the bohr rutherford model

any atom of comprises of a heavy nucleus which is generally positively charged and electrons

tiny electrons orbiting around that in hemispherical or electrical orbits the electrons are ah

extreme small in terms of their mass as you can see here their mass is of the order of

ten to the power minus thirty one kgs whereas the nucleus comprises of ah proton and neutrons

who are having nearly similar mass and ah the it that is of the order of ten to the

power of minus twenty seven kg which is ten to the power of four kg higher then electrons

and therefore whenever we shall be doing any calculation from now onwards using the mass

of proton and neutron the mass of the electron will invariably will neglected

neutron is positively charged whereas proton is having equal amount of charge as the electron

which is one point six zero two into ten top the power minus nineteen coulomb but the charge

of proton and electron are of opposite sense and therefore ah they are given opposite signs

conventional proton is called positively charge whereas electron is called negatively charged

and proton and neutron as both of them comprise the nucleus they together are often called

nucleons now there are several conventions by which

we can represent a nucleus or an atom in the present course we shall be following this

particular concept is it x or a exist here is z is the atomic umber which is equal to

the number of protons present in the nucleus so atomic number is the number of protons

present in the nucleus which of course is equal to the number of electrons ah rotated

in the orbits to keep an atom electrically neutral and it is the proton which it generally

determines the chemical properties of any particular nucleus and therefore atomic number

is associated with the chemical properties a on the other hand is the mass number which

is the total number of nucleons that is number of protons plus neutrons present together

inside the nucleus it determines the nuclear characteristics which we shall be repeatedly

discussing in this course so the atomic number we can write that the mass number is related

to the atomic number plus the number of neutrons is often represented by the symbol n

now the size of the nucleons is extremely small as i have mentioned it is of the order

of ten to the power of minus sixteen meter whereas the size of the atom ranges from ten

to the power of minus nineteen ten to the power of thirteen meter leaving plenty of

voice inside the atom quite often the radius of an atom is correlated to the mass number

by a very much empirical relation like this one point four into ten to the power of minus

thirteen into a to the power one third but this an empirical nature ah nature relation

of empirical nature and the radius that we get from atom that ah is in centimeter so

please be careful about the unit of this radius now both the as we have seen in the previous

slide here we are talking about extremely small mass of the order of ten to the power

of minus twenty seven kgs or ten to the power of minus thirty one kgs ah which are quite

ah odd to ah discuss about ah using from a point of view of our ah day to day life and

then therefore a new unit of mas is ah required to be proposed and that unit is called atomic

mass unit or amu which is defined as one twelfth of the mass of the common carbon atom

proper measurements says that one amu is equal to one point six six zero five into ten to

the power of minus twenty seven kgs which subsequently gives the mass of electron proton

and neutron as like this so from now onwards we shall be using amu as the mass per energy

while amu is the commonly used unit for this but in some books you will also find this

small u is used to define the mass of ah ah this ah atomic sub atomic elements

we shall also be ah proposing an unit for energy which is electron volt it is defined

as the amount of energy gained or lost by a single electron as it passes through an

electoral potential barrier of one volt one electron passing through a potential barrier

of one volt then the amount of energy gained by the electron are amount of energy required

to make to move is called one electron volt so corresponding amount of energy you will

be one electronic charge multiplied by one volt giving one point six zero two into ten

to the power nineteen joule and electron volt generally being a small unit on mev is ah

mega electro volt which is one point six zero two into ten to the power of minus thirteen

joule we have to repeatedly make use of this particular one so from now onwards we shall

be using amu as the unit for mass and mev as the unit for energy unless ah otherwise

required this is a structure of modern periodic table

where ah means this particular one shows ah elements up to an atomic number of one one

eight but ah truly speaking up to atomic number of ninety two which is uranium ah beyond that

basically all of them are artificial that is produced in the laboratory via some kind

of nuclear experiments or nuclear reactions but till ninety two all the elements are naturally

available hydrogen is the smallest one or with the first one in the series which is

having an atomic number of one and also a mass number of one because ah its nucleus

contains only a single proton and no neutron the next one is helium which contains two

which contains protons and two neurons and ah that goes on this way ah as we are discussing

about radioactivity and nuclear reaction in this course are interest will mostly be starting

from the elements after lead lead is more or less ah in ah nuclear ah i should say it

is neutral from nuclear experiments point of view but all those elements after that

like this ah polonium and radon and radium uranium thorium plutonium they all are ah

highly radioactive of of course their radioactive level varies

but ah generally our discussion ah at least in the first part of this course will mostly

be ah ah around mostly be around this ah materials after lead but ah that is ah means ah here

of course we are showing the ah means you can see here each of this symbols are followed

by one number like if you take say oxygen ah here below the symbol we are presenting

the mass number of common oxygen nucleus in terms of amu which is fifteen point nine nine

nine but this is only the common nucleus but a any atom can have multiple nucleus which

we call as isotopes an isotopes are atoms which of the same atomic

number but may have different mass number that is they have the same number of proton

in the nucleus but may have varying number of neutrons and as we have already seen that

protons are related to the chemical nature so their chemical properties will be even

more already the same but the number of neutrons or number of nucleons that decides the nuclear

nature and therefore ah different isotopes of the same element may have different nuclear

nature while they are expected to have more or less the same chemical nature

so in an nutshell by varying the number of neutron in the nucleus we can produce different

isotopes of ah the same element and can vary their nuclear properties like here you can

see three different isotopes of hydrogen the first one which is a common one which has

only a single proton and therefore one electron orbiting around that no neutron in a nucleus

but in the second one which is called deuterium it has one neutron and one proton so the atomic

number remains one but the mass number is two in this case and the third one which has

atomic number of one again but a mass number of three because it has three neutrons

in all the cases there is only a single proton in the nucleus there will be only a single

electron in the orbits also ah these are some further examples of ah a some isotopes like

carbon can have three common isotopes c twelve thirteen and fourteen in all the cases we

are having six protons in the nucleus but number of neutrons varies respectively six

seven and eight and ah as a result of that it is also possible to have the nucleus of

ah two different elements which are having different atomic number but the same mass

number for example just compare tritium which is

the third isotope of hydrogen having one proton and two neutron it is having ah mass number

of three now you compare that with three helium or three h e it is having an atomic number

of two because there are two protons but a single neutron it is also therefore having

a mass number of three so both tritium and three h e they are having the same as number

but different atomic numbers of course the common isotope of helium is ah helium four

which has ah two protons and two neutrons mostly all natural elements can have several

isotopes like i have listed here some of them boron can have two lithium can have two some

of the substances such as the beryllium or gold they are ah having just one known isotopes

we can artificially produce several others in the laboratory but in nature we generally

found only one of them whereas some of the elements can have several like you can see

here for teen ah it has several isotopes starting from mass number of hundred twelve to one

twenty four and ah all of them are quite prevalent in nature because you can see where s n one

twenty appears about thirty two percent this is also appearing twenty four percent and

this appears fourteen percent so all of them are quite prevalent in nature

and primary interest here is uranium uranium commonly has three isotopes u two thirty four

u two thirty five and u two thirty eight all of them are having the same atomic number

which is ninety two but the number of neutrons have is u two thirty eight is the most common

one which comprises ninety nine point three percent about ah the ah of the uranium ore

that we extract form iron but it also contains ah very small amount about point seven percent

of u two thirty five and very little amount of two thirty four very little amount of two

thirty four so ah different isotopes of the same element

can have different number of neutrons and accordingly their nuclear characteristics

can be completely different like we shall be seeing later on while the difference between

u two thirty five and u two thirty eight is only the presence of three extra neutrons

in the nucleus for u a two thirty eight their nuclear nature is completely different while

u two thirty five can be used as a nuclear fuel u two thirty eight cant

ah we shall be ah taking this discussion forward in the next class ah so i would like to summarize

whatever we have discussed today today you have got a brief introduction to the course

so where discussed about the course content we ah planned a little bit in the history

by paying homage to the some of the scientist and very briefly we have discussed about the

topic of atomic structure and isotopes and ah the measure completion that we are having

from ah todays lecture is that ah most of the natural elements can have several isotopes

because of the presence of different number of neutrons and the nucleus and accordingly

with the nuclear characteristics may vary i would like to stop here for the day we shall

be starting in the next class by seeing different kinds of nuclear reaction and discussing the

source of nuclear energy and ah ah the mode of harnessing that one so

thank you bye for the day